JP2014198747A - Ink composition, image recording method and printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink composition which has an extremely low content of a low molecular weight component in a film after curing, can provide an image excellent in blocking resistance without bleeding and is an excellent in ejection restoring property.SOLUTION: There is provided an ink composition which comprises: (a) a polymer compound containing a repeating unit (a-1) having a partial structure represented by the general formula (1) and a repeating unit (a-2) having a partial structure represented by the general formula (2); and (b) an organic solvent. In the general formula (1), Rand Reach independently represent an alkyl group having 1 to 6 carbon atoms and may bond to each other to form a 4- to 6-membered alicyclic structure. In the general formula (2), Rrepresents a hydrogen atom or a methyl group, X represents a divalent linking group containing one or more selected from -OC(=O)-, -NHC(=O)- and -O-, and *s individually represent a binding site with the main chain or the side chain in the polymer compound.

Description

  The present invention relates to an ink composition that can be applied for ink jet recording, image formation using the ink composition, and a print formed by the ink composition.

As an image recording method for forming an image on a recording medium such as paper based on an image data signal, there are an electrophotographic method, a sublimation type and a melt type thermal transfer method, an ink jet method and the like.
The electrophotographic system requires a process of forming an electrostatic latent image on a photosensitive drum by charging and exposure, and there is a problem that the system becomes complicated and consequently the manufacturing cost becomes high. In addition, although the thermal transfer system is inexpensive, there are problems such as high running costs and waste materials due to the use of ink ribbons.
On the other hand, the ink-jet method has an advantage that the ink can be used efficiently and the running cost is low because the ink is ejected only on the required image portion and the image is directly formed on the recording medium. In addition, it has less noise and is excellent as an image recording method.

Among the ink compositions used for image recording by the inkjet method, the active energy ray-curable ink composition is used for image printing, pretreatment for imparting printability to a recording medium, and protection of the printed image. It can be used suitably for decorative post-processing, etc., and can also be used for recording media that do not absorb ink, such as coated paper, or recording media that do not absorb ink, such as plastic film. It is a technology that has many excellent features and possibilities.
In recent years, an ink image formed on a resin recording medium by an ink composition has been increasingly used for applications such as large-area advertisements and outdoor advertisements. When used in such advertising applications, high-quality images are required, and high productivity is also required.

  Examples of the basic constituent material of the active energy ray-curable ink composition include a polymerizable compound, a polymerization initiator that generates radicals and the like by an active energy ray, and a colorant (pigment or dye). . In particular, as a method for obtaining high curability (blocking resistance), there is a method of introducing an initiator group having a function of a polymerization initiator into the polymerizable compound itself. However, when the concentration of the initiating group in the polymerizable compound is increased, the discharge is reduced due to insufficient solubility of the initiating group. In addition, low molecular weight components such as decomposition products of the polymerization initiator remain in the cured film and volatilize, thereby causing problems such as odor. For these reasons, there is a need for an extremely small amount of ink composition that has high blocking resistance, excellent ejection properties, and does not contain or contains residual low molecular weight components.

As an active energy ray-curable ink composition in which an initiation group is introduced into a polymerizable compound for the purpose of improving curability, for example, Patent Document 1 discloses a decomposition with a polymer compound having a radical generating group and a polymerizable group. It is described that a polymerizable polymerization initiator is used.
Patent Document 2 describes the use of two types of polymer compounds having different polymerizable groups and a low-molecular polymerization initiator.

JP 2008-274077 A JP 2009-212281 A

However, in the technique described in Patent Document 1 using a degradable polymerization initiator, a low molecular weight component may remain in the cured film, and the reactive low molecular weight component may volatilize or may be deposited on the surface of the ink image. There is room for improvement because it may leach out and cause blocking.
Also, the technique described in Patent Document 2 uses a low molecular weight polymerization initiator and has the same problems due to the inclusion of a low molecular weight component, so that a low molecular weight reactive component is reduced without lowering the sensitivity. There is a need for reduced ink compositions.

The present invention has been made in light of the above circumstances, the content of low molecular weight components in the cured film is extremely low, excellent discharge recovery when applied to inkjet, and the formed image It is an object of the present invention to provide an ink composition having good blocking resistance.
In addition, the present invention suppresses the content of low molecular weight components in the cured film to a low level, and an image recording method capable of forming an image excellent in blocking resistance, and the content of low molecular weight components in the film to a low level. Another object of the present invention is to provide a print having an image excellent in blocking resistance.

Specific means for solving the above problems are as follows.
<1> (a) Repeating unit (a-1) having a partial structure represented by the following general formula (1) and repeating unit (a-2) having a partial structure represented by the following general formula (2) And the molar concentration (I) of the maleimide group in the partial structure represented by the general formula (1) is 0.5 mmol / g to 2.0 mmol / g, and the general formula (2) And (b) an ink composition containing a high molecular compound having an unsaturated double bond mass molar concentration (II) in the partial structure represented by formula (II) of 1.0 mmol / g to 2.5 mmol / g, and (b) an organic solvent.

[In General Formula (1), R ^a and R ^b each independently represents an alkyl group having 1 to 6 carbon atoms, and R ^a and R ^b are bonded to each other to form 4 to 6 members together with adjacent carbon atoms. The alicyclic structure may be formed. * Indicates a binding site to the main chain or side chain in the polymer compound.
In General Formula (2), R ¹ represents a hydrogen atom or a methyl group, and X represents —OC (═O) —, —NHC (═O) —, —O—, —OCH ₂ —, an arylene group, and an alkylene group. , A nitrogen-containing heterocycle in which a nitrogen atom is bonded to a C═C double bond in the general formula (2), or a divalent linking group composed of a combination of two or more thereof. * Indicates a binding site to the main chain or side chain in the polymer compound. ]
<2> The ink composition according to <1>, wherein both R ^a and R ^{b in} the general formula (1) are methyl groups.
<3> X in the general formula (2) is a divalent linking group containing one or more selected from —OC (═O) —, —NHC (═O) —, and —O— <1> or The ink composition according to <2>.
<4> The ink composition according to any one of <1> to <3>, wherein the polymer compound (a) has a weight average molecular weight of 5,000 to 100,000.
<5> The ink composition according to any one of <1> to <4>, wherein the content of the polymer compound (a) is 5% by mass to 30% by mass with respect to the total mass of the ink composition. .

<6> Maleimide in the partial structure represented by the general formula (1) is the molar concentration (II) of the unsaturated double bond in the partial structure represented by the general formula (2) in the polymer compound (a) The ink composition according to any one of <1> to <5>, wherein the value [(II) / (I)] divided by the molar mass concentration (I) of the group is represented by 0.5 to 4.
<7> (a) The ink composition according to any one of <1> to <6>, wherein the polymer compound is a vinyl polymer.
<8> The ink composition according to any one of <1> to <7>, wherein (a) the polymer compound is a vinyl polymer having a main chain formed of a copolymer containing (meth) acrylates.
<9> The ink composition according to any one of <1> to <8>, further including (c) water.
<10> The ink composition according to <9>, wherein the polymer compound (a) is a polymer compound further including a repeating unit (a-3) having a hydrophilic group.
<11> The ink composition according to any one of <1> to <10>, which has a viscosity at 25 ° C. of 2 mPa · s to 30 mPa · s and is for inkjet recording.
<12> The ink according to any one of <1> to <11>, wherein the content of the compound having a boiling point of 280 ° C. or more and a molecular weight of 300 or less is less than 1% by mass with respect to the total mass of the ink composition. Composition.
<13> A step of applying the ink composition according to <11> onto a recording medium using an ink jet recording apparatus to form an ink image, and a liquid component containing an organic solvent contained in the formed ink image And a step of irradiating the dried ink image with active energy rays.
<14> The image recording method according to claim 13, wherein a recording medium having a surface temperature heated to 40 ° C. or higher and 100 ° C. or lower is used.
<15> The image recording medium is formed of the ink composition according to any one of <1> to <12>, or is recorded by the image recording method according to <13> or <14>. Printed image with an image.

According to the present invention, an ink composition in which the content of a low molecular weight component in a film after curing is extremely low, discharge recovery is excellent when applied to an inkjet, and blocking resistance of a formed image is good. Can be provided.
In addition, the present invention suppresses the content of low molecular weight components in the cured film to a low level, and an image recording method capable of forming an image excellent in blocking resistance, and the content of low molecular weight components in the film to a low level. A printed matter having an image excellent in blocking resistance can be provided.

Hereinafter, the ink composition, the image recording method, and the printed material of the present invention will be described.
In addition, in this specification, when mentioning the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, the present in the composition unless otherwise specified. It means the total amount of multiple substances.
In the ink composition of the present invention, the solid content means the total mass of all components excluding the solvent among the components contained in the ink composition at 25 ° C. The solid content in the present specification includes liquid components such as low molecular weight components other than the solvent.
In the present specification, a numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In this specification, the term “process” is not only an independent process, but is included in this term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes.

[Ink composition]
The ink composition of the present invention includes (a) a repeating unit (a-1) having a partial structure represented by the following general formula (1) and a repeating unit having a partial structure represented by the following general formula (2). (A-2), and the molar molar concentration (I) of the maleimide group in the partial structure represented by the general formula (1) is 0.5 mmol / g to 2.0 mmol / g, and Contains a polymer compound having an unsaturated double bond mass molar concentration (II) in the partial structure represented by the general formula (2) of 1.0 mmol / g to 2.5 mmol / g, and (b) an organic solvent. An ink composition.

(In the general formula (1), R ^a and R ^b each independently represents an alkyl group having 1 to 6 carbon atoms. R ^a and R ^b are bonded to each other and have 4 to 6 members together with adjacent carbon atoms. The alicyclic structure may be formed as follows. * Represents a binding site with the main chain or side chain in the polymer compound.)

(In General Formula (2), R ¹ represents hydrogen or a methyl group, and X represents —OC (═O) —, —NHC (═O) —, —O—, —OCH ₂ —, an arylene group, and an alkylene group. Represents a nitrogen-containing heterocycle in which a nitrogen atom is bonded to a C═C double bond in the general formula (2) or a divalent linking group composed of a combination of two or more thereof, * represents a main chain in the polymer compound Or the binding site with a side chain is shown.)

In the present specification, the repeating unit (a-1) having a partial structure represented by the general formula (1) and the repeating unit (a-) having a partial structure represented by the general formula (2) are used. 2) and the above-mentioned (a) polymer compound according to the present invention in a specific amount described later may be referred to as “(a) specific copolymer”.
Further, the maleimide group in the partial structure represented by the general formula (1) is referred to as “MI”, and the unsaturated double bond in the partial structure represented by the general formula (2) is referred to as “C═C”. There is.

  The ink composition of the present invention contains each of the components described above, so that the ink composition is excellent in dischargeability when used for inkjet recording, and does not contain a low molecular weight component in the cured film. , The content thereof is extremely small, and it is possible to form an image having excellent blocking resistance and no bleeding.

Although the action mechanism of the present invention is not clear, the present inventors presume as follows.
Usually, when a large amount of initiating groups (reactive groups) are introduced into the polymerizable compound, the curability is improved, but the solubility tends to decrease. When such a polymerizable compound is used, the ink composition The discharge performance of the ink drops.
In the present invention, the partial structure represented by the general formula (1) included in the specific copolymer (a) used as the polymerizable compound is a cross-linked cross-link between the partial structures represented by the general formula (1). Is a starting group capable of initiating radical polymerization of the partial structure represented by the general formula (2), and by including this partial structure in the molecule, (a) dissolution of the specific copolymer in the solvent The property becomes better. Further, since the partial structure represented by the general formula (2) which is a polymerizable group coexists in the molecule, even if a large amount of these partial structures are present in the specific copolymer (a). As compared with the case where a polymerizable compound having a general reactive group is used, it is presumed that the dischargeability of the ink composition is hardly lowered and both the curability and the dischargeability are improved. Further, the ink composition of the present invention does not contain or contains a low molecular weight component in the cured film, and the content can be suppressed to a very low level. It is thought that a number of problems have been solved, such as the problem of odor due to volatilization of water and blocking due to leaching to the ink image surface.

The ink composition of the present invention contains (a) a specific copolymer and (b) a solvent (dispersion medium) containing an organic solvent. The specific copolymer (a) may further contain a repeating unit (a-3) having a hydrophilic group. Furthermore, as long as the effects of the present invention are not impaired, for example, (c) water and (d) a colorant may be included as additives. (D) By including a colorant, a colored image can be obtained by the ink composition of the present invention. As will be described later, other components may be included as additives for various purposes.
The additive preferably has a content of a compound having a boiling point of 280 ° C. or more and a molecular weight of 300 or less of less than 1% by mass with respect to the total mass of the ink composition.

  Hereinafter, the ink composition of the present invention (hereinafter also simply referred to as “ink composition”) will be described in detail.

[(A) Specific copolymer]
Each repeating unit contained in the specific copolymer (a) and the physical properties of the specific copolymer (a) contained in the ink composition of the present invention will be described in detail.

(Repeating unit (a-1) having a partial structure represented by the general formula (1))
(A) The specific copolymer includes a repeating unit (a-1) having a partial structure represented by the following general formula (1).

In General Formula (1), R ^a and R ^b each independently represents an alkyl group having 1 to 6 carbon atoms. R ^a and R ^b may be bonded to each other to form a 4-membered to 6-membered alicyclic structure with adjacent carbon atoms. * Indicates a binding site to the main chain or side chain in the polymer compound.

In general formula (1), the C1-C6 alkyl group represented by R ^<a> or R ^<b > may be a linear structure or a branched structure. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, and a t-butyl group. Among these alkyl groups, an alkyl group having 1 to 2 carbon atoms (methyl group and ethyl group) is preferable, and an alkyl group having 1 carbon atom (methyl group) is particularly preferable.

In general formula (1), the alkyl group represented by R ^a or R ^b may or may not have a substituent, but preferably does not have a substituent.

R ^a and R ^b may be bonded to each other to form a 4-membered to 6-membered alicyclic structure together with adjacent carbon atoms.

As R ^a and R ^b , an embodiment in which both are alkyl groups having 1 to 6 carbon atoms, or a 4-membered to 6-membered alicyclic structure together with adjacent carbon atoms when R ^a and R ^b are bonded to each other, Preferably, R ^a and R ^b are both alkyl groups having 1 to 2 carbon atoms, and both R ^a and R ^b are both alkyl groups having 1 carbon atom. preferable.

  Specific examples of the partial structure represented by the general formula (1) are shown below, but the present invention is not limited to these.

  (A) The specific copolymer may be an embodiment having a plurality of partial structures represented by the general formula (1) in the side chain.

  The repeating unit (a-1) having a partial structure represented by the general formula (1) is preferably a repeating unit represented by the following general formula (1-1).

In General Formula (1-1), R ^a and R ^b each independently represent an alkyl group having 1 to 6 carbon atoms. R ^a and R ^b may be bonded to each other to form a 4-membered to 6-membered alicyclic structure with adjacent carbon atoms. R ^c represents a hydrogen atom or a methyl group. Z represents a single bond, —COO — **, or —CONR ^d — **, R ^d represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and ** represents a bonding position with X. X represents a divalent organic group.

^{R a} and ^{R b} in the general formula (1-1), the have each the same meaning as ^{R a} and ^{R b} in the general formula (1), and preferred ranges are also the same.

In the general formula (1-1), R ^c represents a hydrogen atom or a methyl group. R ^c is preferably a methyl group.
In General Formula (1-1), Z represents a single bond, —COO — **, or —CONR ^d — **, R ^d represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and ** Represents a bonding position with X. Z is preferably -COO-**.

Further, R ^d in the —CONR ^d — ** represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The alkyl group having 1 to 4 carbon atoms represented by R ^d may have a linear structure or a branched structure. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, and a t-butyl group. R ^d is preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, that is, a methyl group or an ethyl group, and particularly preferably a hydrogen atom. If R ^d represents an alkyl group, the alkyl group may have a substituent, may not have a substituent, but preferably does not have a substituent.

  In General Formula (1-1), X represents a divalent organic group. Examples of the divalent organic group include an alkylene group or an aralkylene group, and an alkylene group having 2 to 20 carbon atoms or an aralkylene group having 6 to 12 carbon atoms is preferable. X is more preferably an alkylene group.

  When X represents an alkylene group, the alkylene group preferably has 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, and still more preferably 2 to 8 carbon atoms. When the number of carbon atoms of the alkylene group represented by X is within this range, (a) the mobility of the partial structure represented by the general formula (1) existing at the end of the side chain in the specific copolymer is improved, The effect of the present invention is further improved.

  The alkylene group represented by X may have a linear structure, a branched chain in the alkylene chain, or a cyclic structure. In addition, the alkylene group may contain a bond selected from —O—, —COO—, —OC (═O) —, and —CONH— in the alkylene chain. The alkylene group may be substituted with an alkyl group having 4 or less carbon atoms, a hydroxyl group, or a chlorine atom.

As the repeating unit represented by the general formula (1-1), R ^a and R ^b are each independently an alkyl group having 1 to 2 carbon atoms, R ^c is a methyl group, and Z is —COO— *. * And X is preferably an alkylene group having 2 to 12 carbon atoms.

(A) The molar mass concentration (I) of the maleimide group in the partial structure represented by the general formula (1) contained in the specific copolymer is 0.5 mmol / g to 2.0 mmol / g, and 0.6 mmol / G to 1.6 mmol / g is preferable, and 0.8 mmol / g to 1.5 mmol / g is more preferable.
If the mass molar concentration is too large or too small, the image strength tends to decrease. In addition, when forming an ink image excellent in flexibility, it is preferable that the molar concentration in the above range is small.
The mass molar concentration (I) of the maleimide group in the partial structure represented by the general formula (1) contained in the specific copolymer (a) is measured by, for example, ¹ H NMR measurement or FT-IR measurement. be able to.

(A) Content of the repeating unit (a-1) having a partial structure represented by the general formula (1) contained in the specific copolymer (preferably the repeating unit represented by the general formula (1-1)) Is appropriately selected according to the intended properties of the cured film (image) formed of the ink composition. That is, the content of the repeating unit (a-1) having a partial structure represented by the general formula (1) is determined from the viewpoint of the strength of the formed image and the flexibility of the (a) specific copolymer. The mass is preferably 10% by mass to 40% by mass, more preferably 15% by mass to 40% by mass, and still more preferably 20% by mass to 35% by mass.
(A) The specific copolymer may contain only one type of repeating unit (a-1) having a partial structure represented by the general formula (1), or may contain two or more types.

The repeating unit (a-1) having a partial structure represented by the general formula (1) is copolymerized using a monomer having a partial structure represented by the general formula (1) as one of the copolymerization components. By doing so, it can be introduced into the specific copolymer (a). When the repeating unit (a-1) having a partial structure represented by the general formula (1) is a repeating unit represented by the general formula (1-1), (a) for the synthesis of the specific copolymer A monomer represented by the following general formula (1-1 ′) can be used.
The partial structure represented by the general formula (1) can also be introduced by a method using a polymer reaction. Examples of such a method include a method obtained by reacting a prepolymer having a primary amino group with a corresponding anhydride, a functional group that reacts with a functional group in the prepolymer to form a bond and a general formula ( Examples thereof include a method of reacting a compound having a partial structure represented by 1) with a prepolymer.

In the general formula ^{(1-1 '), R a,} R b, R c, Z and X, ^R a in the general formula ^{(1-1), R b, R} c, are respectively the Z and X synonymous The preferable range is also the same.

  Preferable examples of the monomer represented by the general formula (1-1 ′) include monomers (1-1′-1) to (1-1′-12) shown below. However, the present invention is not limited to these.

  Monomers containing a partial structure represented by the general formula (1) represented by the monomers (1-1′-1) to (1-1′-12) are disclosed in, for example, JP-A 52- It can be produced with reference to the methods described in JP-A-988, JP-A-4-251258 and the like.

(Repeating unit (a-2) having a partial structure represented by formula (2))
The specific copolymer (a) in the present invention contains a specific amount of the repeating unit (a-2) having a partial structure represented by the general formula (2).

In General Formula (2), R ¹ represents hydrogen or a methyl group, X represents —OC (═O) —, —NHC (═O) —, —O—, —OCH ₂ —, an arylene group, an alkylene group, A divalent linking group comprising a combination of two or more selected from nitrogen-containing heterocycles in which the nitrogen atom is bonded to the C═C double bond in the general formula (2), represents —OC (═O) —, —NHC (═O) — and —O— are preferably included, and —NHC (═O) — and —O— are more preferably included. * Indicates a binding site to the main chain or side chain in the polymer compound.

  In order to introduce the partial structure represented by the general formula (2) into the specific copolymer (a) of the present invention, a known method can be used. For example, a repeating unit having a structure represented by the general formula (2) and a precursor having any of an epoxy group, an oxazoline group, a hydroxyl group or an amino group, and a partial structure represented by the general formula (1) (a- 1) A method obtained by reacting a polymer compound having both a repeating unit having a carboxyl group, a structure represented by the general formula (2), a carboxyl group, and a partial structure represented by the general formula (1) A method of reacting a repeating unit (a-1) having a polymer compound having both a repeating unit having an epoxy group, an oxazoline group, a hydroxyl group or an amino group, a structure represented by the general formula (2) and an isocyanate A polymer having both a precursor having a group, a repeating unit (a-1) having a partial structure represented by the general formula (1), and a repeating unit having a hydroxyl group or an amino group; A method obtained by reaction, a polymer compound having both a structure represented by the general formula (2), a formyl group, a repeating unit having a partial structure represented by the general formula (1) and a repeating unit having an amino group; A polymer compound having both a structure represented by the general formula (2), an amino group, a repeating unit having a partial structure represented by the general formula (1), and a repeating unit having a formyl group Examples include a reaction method.

(A) The molar mass concentration (II) of the unsaturated double bond in the partial structure represented by the general formula (2) in the specific copolymer is 1.0 mmol / g to 2.5 mmol / g, and 1.3 mmol / G to 2.5 mmol / g is preferable, and 1.5 mmol / g to 2.5 mmol / g is more preferable.
When the molar concentration (II) of the unsaturated double bond in the partial structure represented by the general formula (2) is in the above range, the (a) specific copolymer according to the present invention is excellent in curability and suitable. Blocking resistance is obtained.

(A) The content of the repeating unit (a-2) in the specific copolymer is preferably 20% by mass to 65% by mass, more preferably 25% by mass to 60% by mass, and 30% by mass to More preferably, it is 50 mass%.
(A) The specific copolymer may contain only one type of repeating unit (a-2) having a partial structure represented by the general formula (2), or may contain two or more types.
In addition, the mass molar concentration (II) of the unsaturated double bond in the partial structure represented by the general formula (2) contained in (a) the specific copolymer is, for example, ¹ H NMR measurement or FT-IR measurement. Can be measured.

Unless the effect of this invention is impaired, (a) specific copolymer which concerns on this invention contains repeating units other than the said repeating unit (a-1) and repeating unit (a-2) according to the objective. May be. Hereinafter, the repeating unit other than the repeating unit (a-1) and the repeating unit (a-2) that can be included in the specific copolymer (a) according to the present invention will be described.
(Repeating unit having hydrophilic group (a-3))
The specific copolymer (a) in the present invention may contain a repeating unit (a-3) having a hydrophilic group.
The hydrophilic group is not particularly limited as long as it is a group having a function of enhancing the hydrophilicity of the specific copolymer (a), and may be a nonionic hydrophilic group or an ionic hydrophilic group (for example, , An anionic hydrophilic group or a cationic hydrophilic group).

  The nonionic hydrophilic group is not particularly limited. For example, a residue obtained by removing one hydrogen atom from a heterocyclic structure containing a nitrogen atom or an oxygen atom, an amide group, a carbamoyl group, an alkyl-substituted carbamoyl group, an alcoholic hydroxyl group Or a nonionic hydrophilic group such as a group having a polyalkyleneoxy structure.

  Examples of the heterocyclic structure in the residue obtained by removing one hydrogen atom from a heterocyclic structure containing a nitrogen atom or an oxygen atom include lactones such as γ-butyrolactone; cyclic ureas such as 2-pyrrolidone and ethylene urea; ethylene carbonate , Cyclic carbonates such as propylene carbonate, cyclic ethers such as tetrahydrofuran and 1,4-dioxane; and the like.

  As the amide group, an amide group having 2 to 10 carbon atoms is preferable, and a hydrogen atom is preferably bonded to a nitrogen atom in the amide group.

  The alkyl-substituted carbamoyl group is a monoalkylcarbamoyl group in which a hydrogen atom bonded to a nitrogen atom of a carbamoyl group is substituted with an alkyl group, or two hydrogen atoms bonded to a nitrogen atom of a carbamoyl group are substituted with an alkyl group And a dialkylcarbamoyl group formed. The alkyl group may further have a substituent such as a hydroxyl group. Among these alkyl-substituted carbamoyl groups, a monoalkylcarbamoyl group substituted with an alkyl group having 1 to 8 carbon atoms or an alkyl group having 1 to 4 carbon atoms substituted with a hydroxyl group is preferable.

  Although it does not specifically limit as group which has a polyalkyleneoxy structure, The polyalkyleneoxy structure which has a C1-C4 alkyleneoxy group in a repeating unit is preferable. One type of alkyleneoxy group in the polyalkyleneoxy structure may be used, or a plurality of types of alkyleneoxy groups may be combined. The terminal group of the polyalkyleneoxy structure is preferably a hydroxyl group or an alkoxy group, more preferably a hydroxyl group or a methoxy group.

  Although it does not specifically limit as an ionic hydrophilic group, For example, ionic hydrophilic groups, such as a carboxyl group, a sulfo group, a phosphoric acid group, a phosphonic acid group, a phenolic hydroxyl group, or a quaternary ammonium group, are mentioned. The ionic hydrophilic group may form a salt.

  When the ionic hydrophilic group forms a salt, examples of the counter salt include onium salts such as alkali metal salts (Li, Na, K, etc.), ammonium salts, pyridinium salts, and phosphonium salts. Among these, alkali metal salts (Li, Na, K, etc.) or ammonium salts are preferable.

  Among these hydrophilic groups, an amide group, a carbamoyl group, an alkyl-substituted carbamoyl group, an alcoholic hydroxyl group, a group having a polyalkyleneoxy structure, a carboxyl group, a sulfo group, and a salt thereof are preferable. A carbamoyl group, a carboxyl group, a sulfo group, and salts thereof are more preferable. Particularly preferred are carboxyl groups and salts thereof.

The repeating unit (a-3) having a hydrophilic group is preferably a repeating unit represented by the following general formula (3).
When the specific copolymer (a) in the present invention further includes a repeating unit having a hydrophilic group, the repeating unit having the hydrophilic group is a repeating unit represented by the following general formula (3). Is preferred.

In general formula (3), R ^cy represents a hydrogen atom or a methyl group. Z ^y represents —COO — ***, —CONR ^dy — ***, or a single bond, and R ^dy represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ^y represents a group selected from the group consisting of a single bond, an alkylene group, an arylene group, and an aralkylene group. A represents a hydrophilic group. *** represents a position where Z ^y is bonded to R ^y .

The general formula (3) will be described in detail.
In general formula (3), R ^cy represents a hydrogen atom or a methyl group.

In the general formula ^{(3), Z} y ^{is, -COO - ***, - CONR dy} - ***, or a single bond, -COO - is preferably ***. Incidentally, *** is a position ^{where Z y} is bonded to ^{R y.}

R ^dy represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The alkyl group having 1 to 4 carbon atoms may have a linear structure or a branched structure. Specifically, it represents a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, or a t-butyl group. R ^dy is preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms (that is, a methyl group or an ethyl group), and particularly preferably a hydrogen atom.

R ^dy may or may not have a substituent, but preferably does not have a substituent. Examples of the substituent that R ^dy may have include an aryl group having 6 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a hydroxyl group, a carboxyl group, and a halogen atom (F, Cl, Br, I, etc.). Etc.

In General Formula (3), R ^y represents a single bond or a group selected from the group consisting of an alkylene group, an arylene group, and an aralkylene group, an alkylene group having 1 to 20 carbon atoms, and an arylene having 6 to 20 carbon atoms. It is preferably a group or an aralkylene group having 7 to 20 carbon atoms.
When ^Ry is a group selected from the group consisting of an alkylene group, an arylene group, and an aralkylene group, these groups may or may not have a substituent. The alkylene group, arylene group, and aralkylene group represented by R ^y may have an ether bond, an ester bond, an amide bond, or a urethane bond in the structure.
In the general formula (3), R ^y is preferably a single bond.

When ^Ry is a group selected from the group consisting of an alkylene group, an arylene group, and an aralkylene group, these groups may further have a substituent. Examples of the substituent include an aryl group having 6 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a hydroxyl group, a carboxyl group, a halogen atom (F, Cl, Br, I, etc.) and the like.

When ^Ry is an alkylene group having 1 to 20 carbon atoms, the alkylene group may have a linear structure, a branched structure, or a cyclic structure. When ^Ry is an alkylene group, the number of carbon atoms is more preferably 2 to 12, and further preferably 2 to 8. Specific examples of the alkylene group for R ^y include —CH ₂ —, —C ₂ H ₄ —, —C (CH ₃ ) ₂ —CH ₂ —, —CH ₂ C (CH ₃ ) ₂ CH ₂ —, —C. _{6 H 12 -, - C 4} H 7 (C 4 H 9) C 4 H 8 -, C 18 H 36 -, 1,4-trans- cyclohexylene _{group, -C 2 H 4 -OCO-C} 2 H 4 _{-, - C 2 H 4 -OCO} -, - C 2 H 4 -O-C 5 H 10 -, - CH 2 -O-C 5 H 9 (C 5 H 11) -, - C 2 H 4 -CONH _{-C 2 H 4 -, - C} 4 H 8 -OCONH-C 6 H 12 -, - CH 2 -OCONHC 10 H 20 -, - CH 2 CH (OH) CH 2 -, and the like.

When ^Ry is an arylene group having 6 to 20 carbon atoms, the arylene group preferably has 6 to 18 carbon atoms, more preferably 6 to 14 carbon atoms, and particularly preferably 6 to 10 carbon atoms. . Specific examples of the arylene group represented by R ^y include a phenylene group, a biphenylene group, —C ₆ H ₄ —CO—C ₆ H ₄ —, a naphthylene group, and the like.

When ^Ry is an aralkylene group having 7 to 20 carbon atoms, the aralkylene group preferably has 7 to 18 carbon atoms, more preferably 7 to 14 carbon atoms, and particularly preferably 7 to 10 carbon atoms. . Specific examples of the aralkylene group represented by R ^y _{is, -C 3 H 6 -C 6 H} 4 -, - C 2 H 4 -C 6 H 4 -C 6 H 4 -, - CH 2 -C 6 H _{4 -C 6 H 4 -C 2 H} 4 -, - C 2 H 4 -OCO-C 6 H 4 - , and the like.

  Examples of the hydrophilic group represented by A in the general formula (3) include the hydrophilic groups described above, and preferred ranges thereof are also the same.

(A) When specific copolymer has a repeating unit represented by General formula (3), (a) Content of the repeating unit represented by General formula (3) in a specific copolymer is as follows. It is.
When the hydrophilic group A in the general formula (3) is an ionic hydrophilic group, the content of the repeating unit represented by the general formula (3) is 5% by mass to 50% in the specific copolymer (a). The content is preferably 5% by mass, more preferably 5% by mass to 40% by mass, and particularly preferably 1% by mass to 20% by mass.
When the hydrophilic group A in the general formula (3) is a nonionic hydrophilic group, it is preferably 20% by mass to 95% by mass in the specific copolymer (a), and 30% by mass to 80% by mass. More preferably, 30 mass%-70 mass% is especially preferable.

  The repeating unit represented by the general formula (3) is derived from the monomer represented by the following general formula (3 ′), and (a) specific by including these monomers as a copolymerization component. The repeating unit (a-3) is introduced into the copolymer.

In the general formula ^{(3 '), R cy,} Z y, R y, and A, ^R cy in Formula ^{(3), Z y, R} y, and A and have the same meanings, the preferred range is also the same is there.

  Preferable examples of the monomer represented by the general formula (3 ′) include the following monomer compounds, but the present invention is not limited thereto.

  Methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, poly (ethylene glycol-co-propylene glycol) (meth) acrylate, 2-hydroxyethyl (meth) acrylate, glycerol (meth) Acrylate (meth) acryloyloxyethyl ethylene urea, vinylpyrrolidone, 3- (meth) acryloyloxy-γ-butyrolactone, acrylamide, tert-butylacrylamide, N, N-dimethyl (meth) acrylamide, diacetone acrylamide, (meth) Sodium acrylate, potassium (meth) acrylate, tetrabutylammonium (meth) acrylate, mono (meth) acryloyloxyethyl succinic acid, Sodium (meth) acryloyloxyethyl succinate, sodium mono (meth) acryloyloxyethyl phthalate, (meth) acryloyloxyethyl acid phosphate, sodium 2-acrylamido-2-methylpropanesulfonate, 2-acrylamide- Examples include 2-methylpropane sulfonic acid, styrene sulfonic acid, sodium styrene sulfonate, and vinyl benzoic acid.

  As the monomer represented by the general formula (3 ′), a commercially available compound can be used, and it can be produced by a generally known and commonly used method.

  In the present invention, in addition to the monomer represented by the general formula (3 ′), unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, and fumaric acid, and anhydrides thereof, and further derived therefrom. Dicarboxylic acid salts can also be preferably used.

(A) The content of the repeating unit having a hydrophilic group in the specific copolymer differs depending on the type of the hydrophilic group, but (a) the specific copolymer is water-soluble. Is preferred.
Here, (a) the specific copolymer being water-soluble means that (a) the specific copolymer can be dissolved in 3% by mass or more in water at 25 ° C.

(A) When the specific copolymer contains the repeating unit (a-3), the content of the repeating unit (a-3) is preferably 5% by mass to 30% by mass, and 5% by mass to 25%. More preferably, the content is 10% by mass to 20% by mass.
(A) The specific copolymer may contain only one type of repeating unit (a-3) having a hydrophilic group, or may contain two or more types.

(Repeating unit having a hydrophobic group (a-4))
(A) The specific copolymer may include a repeating unit (a-4) having a hydrophobic group. By including a repeating unit having a hydrophobic functional group, (a) the polarity of the specific copolymer is appropriately maintained, and the ink image formed by the ink composition is excellent in water resistance and non-absorbing. The adhesiveness to the recording medium is excellent.
As the repeating unit (a-4) having a hydrophobic group, a homopolymer having only a repeating unit (a-4) having a weight average molecular weight of 10,000 or more has a solubility in water at 25 ° C. of 1. Any repeating unit derived from a vinyl monomer that is less than 0% by mass can be used without limitation, and among them, a repeating unit derived from a monomer selected from alkyl esters of (meth) acrylic acid and aralkyl esters is preferably used.
Especially, from the viewpoint of adjusting the polarity of the specific copolymer to an appropriate range, the hydrophobic group is preferably an alkyl group having 5 to 22 carbon atoms, and an alkyl group having 8 to 22 carbon atoms. Is more preferable, and an alkyl group having 8 to 14 carbon atoms is more preferable. That is, in the case of alkyl acrylate, it is an ester having an alkyl group having 4 to 19 carbon atoms, and an ester having an alkyl group having 4 to 13 carbon atoms is preferred. In the case of alkyl methacrylate, it is an ester having an alkyl group having 4 to 18 carbon atoms, and an ester having an alkyl group having 4 to 10 carbon atoms is preferred.
The alkyl group may be linear or branched, and may be cyclic. Further, aralkyl esters such as benzyl group and phenoxyethyl group may be used.

  Although the repeating unit (a-4) which (a) specific copolymer based on this invention can contain is illustrated below, (a-4) of this invention is not limited to these. Specific examples of (a-4) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) ) Acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate And cyclohexyl methacrylate, among others, n-propyl methacrylate, isopropyl methacrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, benzyl methacrylate, phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, acetoacetoxyethyl (meth) acrylate and the like ( (Meth) acrylic acid esters, styrenes such as styrene, α-methylstyrene, 4-methylstyrene, vinyl ethers such as chloroethyl vinyl ether, etc., among others, substituted with an alkyl group having 5 to 22 carbon atoms. (Meth) acrylic acid esters, n-propyl methacrylate, isopropyl methacrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, n-hex Sil (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl methacrylate, etc. are preferred, n-propyl methacrylate, isopropyl Methacrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, benzyl methacrylate, phenoxy More preferred is ethyl (meth) acrylate. Further, n-butyl methacrylate, isobutyl methacrylate, tert-butyl (meth) acrylate, cyclohexyl methacrylate, isobornyl methacrylate, 2-ethylhexyl methacrylate, and phenoxyethyl (meth) acrylate are particularly preferable.

(A) The specific copolymer may contain only one type of repeating unit (a-4), or may contain two or more types.
(A) The specific copolymer may not contain the repeating unit (a-4) (0% by mass), but when it is contained, the content of the repeating unit (a-4) having a hydrophobic group is From the viewpoint of reducing the polarity of the polymer, (a) in the specific copolymer, a range of more than 0% by mass and 40% by mass or less is preferable, more than 0% by mass and 30% by mass or less are more preferable, Most preferably, it is in the range of more than 25% by mass.

The weight average molecular weight of the specific copolymer (a) contained in the ink composition of the present invention is preferably in the range of 5,000 or more and 100,000 or less. From 10,000 to 80,000 is more preferable.
The weight average molecular weight is measured by gel permeation chromatography (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (4.6 mm ID × 15 cm, Tosoh Corporation) as columns and THF (tetrahydrofuran) as an eluent. And the column oven was set at a set temperature of 40 ° C. Standard polystyrene was used for calculation of molecular weight.

  Maleimide in the partial structure represented by the general formula (1) is represented by the molar concentration (II) of the unsaturated double bond in the partial structure represented by the general formula (2) in the specific copolymer (a) in the present invention. A value obtained by dividing the mass molar concentration (I) of the group is preferably from 0.5 to 4, more preferably from 1 to 3, from the viewpoint of further improving the curability.

  In the present invention, the content of the specific copolymer (a) is preferably 5% by mass to 30% by mass, and more preferably 5% by mass to 25% by mass with respect to the total mass of the ink composition. More preferably, it is 5 mass%-20 mass%.

  The specific copolymer (a) contained in the ink composition of the present invention is preferably a vinyl polymer, more preferably a vinyl polymer whose main chain is composed of a copolymer containing (meth) acrylates. .

  The specific copolymer (a) according to the present invention includes, for example, a monomer for forming the repeating unit (a-1) having a partial structure represented by the general formula (1), and the general formula (2). And a monomer for forming a repeating unit (a-2) having a partial structure represented by the formula (1) and a repeating unit (a-3) having a hydrophilic group, if desired, The monomer for forming and the monomer for forming the repeating unit (a-4) having a hydrophobic group are polymerized by a known polymerization method, and an acidic group is made of an alkali metal as necessary. It can be obtained by neutralization with a hydroxide or the like. Specifically, for example, JP 2008-24830 A, JP 2009-221281 A, JP 52-988 A, JP 55-154970 A, Langmuir Vol. 18, No. 14, pages 5414-5421. (A) The specific copolymer can be produced by a method according to the polymerization method described in (2002).

[(B) Organic solvent]
The ink composition of the present invention contains an organic solvent.
Here, the organic solvent refers to a low molecular weight liquid having no polymerizable group such as an ethylenic double bond, and has a molecular weight of 220 or less and a boiling point from the viewpoint of reducing the content of the organic solvent in the ink cured film. It is preferable to use a liquid of 280 ° C. or lower.

Examples of the organic solvent that can be used in the present invention include the following.
Alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.),
Polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, 2-methylpropane Diols),
・ Polyhydric alcohol ethers (for example, ethylene glycol monoalkyl ether such as ethylene glycol monoalkyl ethers having 1 to 4 carbon atoms, diethylene glycol such as diethylene glycol dimethyl ether alkyl ethers having 1 to 4 carbon atoms, triethylene glycol monomethyl ether, etc. Alkyl ethers of 1 to 4 carbon atoms of triethylene glycol, alkyl ethers of 1 to 4 carbon atoms of propylene glycol such as propylene glycol monomethyl ether, alkyl ethers of 1 to 4 carbon atoms of dipropylene glycol, tripropylene glycol Methyl ether),

Amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), methoxypropionamide, N-methylmethoxypropionamide, N, N-dimethylmethoxypropionamide, n-butoxypropionamide, N-methyl n-butoxypropionamide, N, N-dimethyl n-butoxypropionamide, etc.)
Heterocycles (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, propylene carbonate, ethylene carbonate, ethylene urea etc),
Ketones (for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.),
-Sulfones (for example, sulfolane),
-Esters (for example, acetate such as ethyl acetate and butyl acetate, alkyl lactate such as ethyl lactate, etc.)
・ Others (urea, acetonitrile, etc.)

  Preferable organic solvents include polyhydric alcohols, polyhydric alcohol ethers, and heterocyclic rings, and these may be used in combination.

Of the polyhydric alcohols, 2-methylpropanediol is preferred.
Among the polyhydric alcohol ethers, so-called glycol ethers are preferable, and specifically, tripropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, and diethylene glycol dimethyl ether are preferable, and dipropylene glycol dimethyl ether is more preferable.
As the heterocyclic ring, 2-pyrrolidone, γ-butyrolactone, propylene carbonate, ethylene urea and the like are preferable, and 2-pyrrolidone and γ-butyrolactone are particularly preferable.

  The organic solvent may be used alone or in combination. The amount of the organic solvent added in the ink composition is preferably 60% by mass to 95% by mass, more preferably 70% by mass to 90% by mass, in the case of an ink having a water content of less than 5%. In addition, in an ink having a water content of 5% or more, the total amount is preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 30% by mass.

[(C) water]
The ink composition of the present invention may contain water.
As water, it is preferable to use ion-exchanged water, distilled water or the like that does not contain impurities.
When water is contained in the ink composition of the present invention, the content is preferably 10% by mass to 97% by mass, more preferably 30% by mass to 95% by mass, and 50% by mass to 85% by mass. % Is more preferable.

(D) Colorant The ink composition of the present invention may contain a colorant, and becomes a colored ink composition by containing a colorant.
Examples of the colorant include dyes and pigments, and pigments are preferable from the viewpoint of durability such as heat resistance, light resistance, and water resistance.

  When a pigment is used as the colorant, the pigment can be contained in the ink composition as a pigment dispersion. Use of a pigment dispersion as a colorant is preferable from the viewpoint of improving solvent resistance. As the pigment dispersion, a self-dispersed pigment can be used in addition to a pigment dispersed with a pigment dispersant.

(Pigment)
As a pigment used as a colorant, generally used organic pigments, inorganic pigments, and the like can be used. Usually, any commercially available pigment can be used, and further, a pigment pretreated with a commercially available pigment dispersion or surface treatment agent, for example, a pigment dispersed in an insoluble resin or the like as a dispersion medium, Or what grafted resin to the pigment surface etc. can be used unless the effect of this invention is impaired.
Examples of these pigments include, for example, “Pigment Dictionary” (2000), edited by Seijiro Ito. Herbst, K.M. Hunger “Industrial Organic Pigments”, JP 2002-12607 A, JP 2002-188025 A, JP 2003-26978 A, and JP 2003-342503 A3.

  Examples of organic pigments and inorganic pigments that can be used in the present invention include C.I. I. Pigment Yellow 1 (Fast Yellow G, etc.), C.I. I. A monoazo pigment such as C.I. Pigment Yellow 74; I. Pigment Yellow 12 (disaji yellow, etc.), C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 155, C.I. I. Disazo pigments such as C.I. Pigment Yellow 219; I. Azo lake pigments such as C.I. Pigment Yellow 100 (eg Tartrazine Yellow Lake); I. Pigment yellow 95 (condensed azo yellow, etc.), C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Condensed azo pigments such as C.I. Pigment Yellow 166; I. Acidic dye lake pigments such as C.I. Pigment Yellow 115 (such as quinoline yellow lake); I. Basic dye lake pigments such as C.I. Pigment Yellow 18 (Thioflavin Lake, etc.); I. Anthraquinone pigments such as CI Pigment Yellow 24 (Flavantrone Yellow), isoindolinone pigments such as Isoindolinone Yellow 3RLT (Y-110), C.I. I. Quinophthalone pigments such as C.I. Pigment Yellow 138 (Kinophthalone Yellow); I. An isoindoline pigment such as C.I. Pigment Yellow 139 (isoindoline yellow); I. Nitroso pigments such as C.I. Pigment Yellow 153 (nickel nitroso yellow, etc.); I. Metal complex salt azomethine pigments such as C.I. Pigment Yellow 117 (copper azomethine yellow, etc.); I. Pigment yellow 120 (benzimidazolone yellow) C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 175, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 181, C.I. I. An acetolone pigment such as C.I. Pigment Yellow 194; I. And nickel azo pigments such as CI Pigment Yellow 150. Among these, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 150, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 155, C.I. I. Pigment Yellow 180 or the like is preferably used.

  Examples of those exhibiting red or magenta color include C.I. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Pigment red 1, C.I. I. Pigment red 4, C.I. I. B-naphthol pigments such as C.I. Pigment Red 6; I. Disazo pigments such as C.I. Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Pigment Red 57: 1 (Brilliant Carmine 6B etc.), C.I. I. Pigment red 52: 1, C.I. I. Azo lake pigments such as C.I. Pigment Red 48 (B-oxynaphthoic acid lake, etc.); I. Pigment red 144 (condensed azo red, etc.), C.I. I. Pigment red 166, C.I. I. Pigment red 220, C.I. I. Pigment red 214, C.I. I. Pigment red 221, C.I. I. Condensed azo pigments such as C.I. Pigment Red 242, C.I. I. Pigment Red 174 (Phloxine B lake, etc.), C.I. I. Acidic dye lake pigments such as C.I. Pigment Red 172 (Erythrosin Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Red 81 (Rhodamine 6G 'lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Red 177 (eg, dianthraquinonyl red); I. Thioindigo pigments such as C.I. Pigment Red 88 (Thioindigo Bordeaux, etc.); I. Perinone pigments such as CI Pigment Red 194 (perinone red, etc.)

C. I. Pigment red 149 (perylene scarlet, etc.), C.I. I. Pigment red 179, C.I. I. Pigment red 178, C.I. I. Pigment red 190, C.I. I. Pigment red 224, C.I. I. Pigment red 123, C.I. I. Perylene pigments such as C.I. Pigment Red 224; I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Pigment red 122 (quinacridone magenta, etc.), C.I. I. Pigment red 262, C.I. I. Pigment red 207, C.I. I. Quinacridone pigments such as CI Pigment Red 209, and quinacridone pigments which are solid solutions of the plurality of quinacridone pigments; I. Isoindolinone pigments such as CI Pigment Red 180 (isoindolinone red 2BLT, etc.); I. Alizarin lake pigments such as C.I. Pigment Red 83 (Madalake, etc.); I. Pigment red 171, C.I. I. Pigment red 175, C.I. I. Pigment red 176, C.I. I. Pigment red 185, C.I. I. Naphtholone pigments such as C.I. Pigment Red 208; I. Naphthol AS lake pigments such as C.I. Pigment Red 247; I. Pigment red 2, C.I. I. Pigment red 5, C.I. I. Pigment red 21, C.I. I. Pigment red 170, C.I. I. Pigment red 187, C.I. I. Pigment red 256, C.I. I. Pigment red 268, C.I. I. Naphthol AS pigments such as C.I. Pigment Red 269; I. Pigment red 254, C.I. I. Pigment red 255, C.I. I. Pigment red 264, C.I. I. And diketopyrrolopyrrole pigments such as CI Pigment Red 27. Among these, C.I. I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Pigment red 122 (quinacridone magenta, etc.), C.I. I. Pigment red 262, C.I. I. Pigment red 207, C.I. I. A quinacridone pigment such as CI Pigment Red 209 and a quinacridone pigment which is a solid solution containing a plurality of these quinacridone pigments are preferred.

  Examples of pigments exhibiting blue or cyan colors include C.I. I. Disazo pigments such as C.I. Pigment Blue 25 (Dianisidine Blue, etc.); I. Pigment blue 15, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 15: 6, C.I. I. Phthalocyanine pigments such as C.I. Pigment Blue 16 (phthalocyanine blue, etc.); I. Acidic dye lake pigments such as C.I. Pigment Blue 24 (Peacock Blue Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Blue 1 (Viclotia Pure Blue BO Lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkali blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1). Among these, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Copper phthalocyanine pigments such as CI Pigment Blue 15: 6 are preferred.

Examples of the pigment exhibiting green include C.I. I. Pigment green 7 (phthalocyanine green), C.I. I. Phthalocyanine pigments such as C.I. Pigment Green 36 (phthalocyanine green); I. Pigment green 8 (nitroso green), C.I. I. And azo metal complex pigments such as CI Pigment Green 10.
Examples of orange pigments include C.I. I. An isoindoline pigment such as C.I. Pigment Orange 66 (isoindoline orange); I. Anthraquinone pigments such as C.I. Pigment Orange 51 (dichloropyrantron orange); I. Pigment orange 2, C.I. I. Pigment orange 3, C.I. I. Β-naphthol pigments such as C.I. Pigment Orange 5; I. Pigment orange 4, C.I. I. Pigment orange 22, C.I. I. Pigment orange 24, C.I. I. Pigment orange 38, C.I. I. Naphthol AS pigments such as CI Pigment Orange 74; I. Isoindolinone pigments such as CI Pigment Orange 61; I. Perinone pigments such as C.I. Pigment Orange 43; I. Pigment orange 15, C.I. I. Disazo pigments such as CI Pigment Orange 16; I. Pigment orange 48, C.I. I. Quinacridone pigments such as CI Pigment Orange 49; I. Pigment orange 36, C.I. I. Pigment orange 62, C.I. I. Pigment orange 60, C.I. I. Pigment orange 64, C.I. I. An acetolone pigment such as C.I. Pigment Orange 72; I. Pigment orange 13, C.I. I. And pyrazolone pigments such as CI Pigment Orange 34.
Examples of the pigment exhibiting brown include C.I. I. Pigment brown 25, C.I. I. And naphthron pigments such as CI Pigment Brown 32.

Examples of pigments exhibiting black color include carbon black, titanium black, C.I. I. Indazine pigments such as CI Pigment Black 1 (aniline black); I. Pigment black 31, C.I. I. And perylene pigments such as CI Pigment Black 32. Among these, C.I. I. Pigment Black 7 is preferable.
Examples of the white pigment include basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , so-called silver white), zinc oxide (ZnO, so-called zinc white), titanium oxide (TiO ₂ , so-called titanium white), and titanium. Strontium acid (SrTiO ₃ , so-called titanium strontium white) and the like can be used, and among these, titanium oxide is preferable. The inorganic particles used for the white pigment may be a simple substance or, for example, oxides such as silicon, aluminum, zirconium and titanium, organometallic compounds, and composite particles with organic compounds.

  Here, titanium oxide has a smaller specific gravity than other white pigments, a large refractive index, and is chemically and physically stable, so that it has a large hiding power and coloring power as a pigment. Excellent durability against other environments. Therefore, it is preferable to use titanium oxide as the white pigment. Of course, other white pigments (may be other than the listed white pigments) may be used as necessary.

Since the non-white pigment has a better color developability as the average particle size is smaller, if the pigment dispersion is applied to a pigment dispersion other than white, the average particle size of the pigment contained in the pigment dispersion is: The thickness is preferably about 0.01 μm to 0.4 μm, more preferably 0.02 μm to 0.3 μm.
The maximum particle diameter of the pigment is 3 μm or less, preferably 1 μm or less. The particle size of the pigment can be adjusted by selecting a pigment, a dispersant, a dispersion medium, setting dispersion conditions, and filtering conditions. Further, when the ink composition of the present invention is prepared as a white ink composition, the average particle size of the pigment contained in the pigment dispersion is 0.05 μm to The thickness is preferably about 1.0 μm, more preferably about 0.1 μm to 0.4 μm. Also when it is set as a white pigment dispersion, it is preferable that the maximum particle diameter of a pigment is 3 micrometers or less, Preferably it is 1 micrometer or less.

(Dispersant)
When a pigment is used as the colorant, a pigment dispersant may be used as necessary when preparing the pigment particles. Examples of the pigment dispersant that can be used include higher fatty acid salts and alkyl sulfates. , Alkyl ester sulfate, alkyl sulfonate, sulfosuccinate, naphthalene sulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin Activators such as esters, sorbitan esters, polyoxyethylene fatty acid amides, amine oxides, or styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, Mar acids, block copolymers of two or more monomers selected from fumaric acid derivatives include random copolymers and salts thereof.

  A self-dispersing pigment can also be used in the ink composition of the present invention. The self-dispersing pigment as used in the present invention refers to a pigment that can be dispersed without a dispersant, and particularly preferably pigment particles having a polar group on the surface.

The pigment particles having a polar group on the surface as used in the present invention are a pigment whose surface is directly modified with a polar group, or an organic substance having an organic pigment mother nucleus, which is bonded directly or via a joint. (Hereinafter referred to as pigment derivative).
Examples of the polar group include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a boric acid group, and a hydroxyl group, preferably a sulfonic acid group and a carboxylic acid group, and more preferably a sulfonic acid group.

  Examples of a method for obtaining pigment particles having a polar group on the surface include, for example, WO 97/48769, JP-A-10-110129, JP-A-11-246807, JP-A-11-57458, 11-189739, JP-A-11-323232, JP-A-2000-265094, etc. are oxidized with an appropriate oxidizing agent to oxidize a sulfonic acid group or at least part of the pigment surface. The method of introduce | transducing polar groups, such as the salt, is mentioned. Specifically, it is prepared by oxidizing carbon black with concentrated nitric acid or, in the case of color pigments, by oxidizing with sulfamic acid, sulfonated pyridine salt, amidosulfuric acid, etc. in sulfolane or N-methyl-2-pyrrolidone. can do. In these reactions, the pigment dispersion can be obtained by removing and purifying the substance that has been excessively oxidized and becomes water-soluble. Moreover, when a sulfonic acid group is introduced onto the surface by oxidation, the acidic group may be neutralized with a basic compound as necessary.

  As other methods for obtaining pigment particles having polar groups on the surface, the pigment derivatives described in JP-A-11-49974, JP-A-2000-273383, JP-A-2000-303014, etc. may be treated by milling or the like. Examples include a method of adsorbing to the pigment particle surface, a method of crystallization in a poor solvent after dissolving the pigment described in Japanese Patent Application Nos. 2000-377068, 2001-1495, and 2001-234966 together with a pigment derivative. In any method, pigment particles having a polar group on the surface can be easily obtained.

  The polar group on the pigment surface may be free or in a salt state, or may have a counter cation. Examples of the counter cation include inorganic salts (lithium, sodium, potassium, magnesium, calcium, aluminum, nickel, ammonium) and organic salts (triethylammonium, diethylammonium, pyridinium, triethanolammonium, etc.), preferably 1 A counter cation having a valence.

  The content of the colorant with respect to the total amount of the ink composition in the invention is preferably 0.5% by mass to 10% by mass, and more preferably 0.5% by mass to 8% by mass.

[Other additives]
In the ink composition of the present invention, in addition to the above-mentioned (a) specific copolymer and (b) organic solvent which are essential components, the above preferred additive components may be used depending on the purpose as long as the effects of the present invention are not impaired. (C) water, (d) colorant, and further known additives used in the ink composition can be used in combination. Hereinafter, additives other than (c) water and (d) colorant that can be used in the ink composition will be described.

(Resin particles)
The ink composition of the present invention may contain at least one resin particle. By containing the resin particles, the adhesion of the image to the recording medium can be further improved.

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

  Among the above, as the resin particles, acrylic resin, urethane resin, polyether resin, polyester resin, and polyolefin resin particles are preferable, having flexibility and strength, and excellent adhesion to the recording medium. From the viewpoint that an image can be formed, particles of urethane resin are particularly preferable.

(Surfactant)
A surfactant can be added to the ink composition of the present invention.
As surfactants preferably used, anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, Nonionic surfactants such as polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

In the present invention, a polymer surfactant can also be used, and the following water-soluble resins are mentioned as preferred polymer surfactants. As the water-soluble resin, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer are preferably used. Styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer Etc.
In the present invention, a silicone surfactant having a polyalkylsiloxane and a fluorine surfactant having a fluorinated alkyl group can also be preferably used.

  In the ink composition of the present invention, when a surfactant is used, the addition amount is preferably 0.1% by mass or more and 5% by mass or less in terms of solid content. It is particularly preferable that the solid content addition amount be 0.5 mass% or more and 2 mass% or less.

(Sensitizing dye)
In the present invention, a known sensitizing dye can be used in combination, and a sensitizing dye is preferably used in combination. The solubility is preferably 0.5% by mass or more, more preferably 1% by mass or more, at room temperature in distilled water. Those that dissolve 3% by mass or more are particularly preferable. Further, as the sensitizing dye, a photopolymerization initiator in which a water-insoluble polymerization initiator is dispersed can also be used.

  Examples of known sensitizing dyes that can be used in combination include N- [2-hydroxy-3- (3,4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy) propyl] -N, N, N. -Trimethylaluminum chloride, benzophenone, thioxanthone, anthraquinone derivatives and 3-acylcoumarin derivatives, terphenyl, styryl ketone and 3- (aroylmethylene) thiazoline, camphorquinone, eosin, rhodamine and erythrosine, and their modified forms And dispersions thereof. Moreover, the compound represented by the general formula (i) described in JP-A 2010-24276 and the compound represented by the general formula (I) described in JP-A-6-107718 can also be suitably used. .

  In addition to the components described above, the ink composition according to the present invention can improve ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. Depending on the purpose, various known additives such as viscosity modifiers, surface tension modifiers, specific resistance modifiers, film forming agents, preservatives, dispersants, surfactants, ultraviolet absorbers, antioxidants, fading Inhibitors, anticorrosives, rust inhibitors, solid wetting agents, silica fine particles and the like can be appropriately selected and used. For example, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil and other oil droplet fine particles, UV absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, JP-A-57-8 No. 989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, JP-A-3-13376, etc. No. 42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266 and the like, Examples include pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, and potassium carbonate.

(Photopolymerization initiator)
Since the ink composition of the present invention can reduce the content of low molecular weight compounds in the ink cured film, it can provide an ink excellent in odor. For this reason, in the present invention, a polymerizable monomer generally used in an active energy ray-curable ink composition other than a low molecular weight component that can be removed in a drying step such as water or a volatile organic solvent, It is preferable not to contain an initiator and a compound that decomposes upon irradiation with active energy rays and generates a low molecular weight component.
Examples of the polymerizable monomer include (meth) acrylates, (meth) acrylamides, and N-vinyl compounds. Hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, diethylene glycol di ( (Meth) acrylate, dipropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, PO modified Bifunctional acrylates such as neopentyl glycol diacrylate, trifunctional acrylates such as trimethylolpropane triacrylate, EO-modified trimethylolpropane triacrylate, Le acrylamides, acrylamides such as methylene bisacrylamide, such as N- vinyl compounds such as N- vinyl caprolactam.
Examples of the polymerization initiator and the compound that generates a low molecular weight component include acetophenones, benzophenones, acylphosphine oxides, biimidazoles, benzoin ethers, oxime esters, thioxanthones, titanocenes, sulfonium salts, iodonium salts Known polymerization initiators such as 2-hydroxy-2-methylpropiophenone, pt-butyltrichloroacetophenone, p-dimethylaminoacetophenone, benzophenone, Michler's ketone, 4-chlorobenzophenone, Michler's ketone, o-benzoylbenzoic acid, 4-4′-dialkylaminobenzophenone, and thioxanthone series include thioxanthone, 2-chlorothioxanthone, 2-alkylthioxanthone, 2-hydroxy-2-methyl Tilpropiophenone, 2-hydroxy-2-methyl-4′-isopropylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, isopropyl benzoin ether, isobutyl benzoin ether, 2,2-dimethoxy-2-phenylacetophenone, camphorquinone, 2-Methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2- (dimethyl Amino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2- (o-chlorophenyl) -4,4 ′, 5,5′- Tetraphenyl-1,2'-biimidazole, 2-hydroxy-1- {4- [4- (2-hydroxy) -2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane- 1-one, iodonium, (4-methylphenyl) [4- (2-methylpropyl) phenyl] -hexafluorophosphate (1-), ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (0-acetyloxime), 1.2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], bis (η5 -2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) titanium, bis (2,4,6-trime Rubenzoiru) - phenyl phosphine oxide, 2,4,6-trimethylbenzoyl - diphenyl - phosphine oxide, and the like phenylglyoxylate butyric acid methyl ester.
Among these, a polymerizable monomer, a polymerization initiator, and a compound that decomposes upon irradiation with active energy rays and generates a low molecular weight component, has a molecular weight in the range of 100 to 500 and a boiling point of 280 ° C. or higher. It is preferable that the content of the liquid or the solid compound at room temperature is less than 1%.

<Method for Preparing Ink Composition>
The method for preparing the ink composition according to the present invention is not particularly limited, and each component may be a medium such as a ball driving machine mill such as a ball mill, a centrifugal mill or a planetary ball mill, a high speed rotating mill such as a sand mill, or a stirring tank mill. It can be prepared by stirring, mixing, and dispersing with a simple dispersing machine such as a stirring mill or a disper. About the addition order of each component, it is arbitrary. Preferably, the azo pigment, the polymer dispersant and the organic solvent are premixed and then subjected to a dispersion treatment, and the obtained dispersion is mixed with the resin and the organic solvent. In this case, at the time of addition or after addition, the mixture is uniformly mixed with a simple stirrer such as a three-one motor, a magnetic stirrer, a disper, or a homogenizer. You may mix using mixers, such as a line mixer. Further, in order to make the dispersed particles finer, they may be mixed using a dispersing machine such as a bead mill or a high-pressure jet mill. Depending on the type of pigment or polymer dispersant, a resin may be added during premixing before pigment dispersion.

  The ink composition of the present invention preferably has a surface tension at 25 ° C. of 40 mN / m to 200 mN / m. The surface tension is measured under the condition of 25 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.). The viscosity at 25 ° C. is preferably 2 mPa · s to 30 mPa · s, and more preferably 3 mPa · s to 30 mPa · s. The viscosity of the ink composition is measured under conditions of 25 ° C. using VISCOMETER TV-22 (manufactured by TOKI SANGYOCO. LTD).

[Image recording method]
The image recording method of the present invention includes an ink application step of applying the ink composition onto a recording medium, and an irradiation step of irradiating the applied ink composition with active energy rays. By performing these steps, an image of the ink composition fixed on the recording medium is formed.

(Ink application process)
Hereinafter, the ink application process in the image recording method of the present invention will be described.
The ink application process in the present invention is not limited as long as it is a process of applying the ink composition onto a recording medium.

  As an embodiment of applying the ink composition of the present invention on a recording medium, an embodiment of applying an ink composition by an inkjet method onto a recording medium is particularly preferable.

  In the image recording method of the present invention, the ink jet recording apparatus used when the ink jet method is applied in the ink application process is not particularly limited, and a known ink jet recording apparatus capable of achieving the target resolution is arbitrarily selected. Can be used. That is, any known inkjet recording apparatus including a commercially available product can discharge the ink composition onto the recording medium in the image recording method of the present invention.

Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and a heating unit.
Examples of the ink supply system include an original tank containing the ink composition of the present invention, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, a piezo-type inkjet head, and the like. The piezo-type inkjet head preferably has a multi-size dot of 1 pl to 100 pl, more preferably 8 pl to 30 pl, preferably 320 × 320 dpi to 4,000 × 4,000 dpi (dot per inch), more preferably 400 × 400 dpi. ˜1,600 × 1,600 dpi, more preferably 720 × 720 dpi. The dpi referred to in the present invention represents the number of dots per 2.54 cm (1 inch).

In the ink application step, it is desirable that the discharged ink composition has a constant temperature. Therefore, the ink jet recording apparatus preferably includes a means for stabilizing the ink composition temperature. The parts to be kept at a constant temperature are all the piping systems and members from the ink tank (intermediate tank if there is an intermediate tank) to the nozzle ejection surface. That is, heat insulation and heating can be performed from the ink supply tank to the inkjet head portion.
The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the flow rate of the ink composition and the environmental temperature. The temperature sensor can be provided near the ink supply tank and the nozzle of the inkjet head. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

  The ink composition is discharged using the ink jet recording apparatus, and the ink composition is preferably heated to 25 ° C. to 80 ° C., more preferably 25 ° C. to 50 ° C., and the viscosity of the ink composition is preferably 2 mPa · It is preferable to carry out after lowering to s to 30 mPa · s, more preferably 3 mPa · s to 13 mPa · s. In particular, it is preferable to use an ink composition having a viscosity of 2 mPa · s to 30 mPa · s at 25 ° C. as the ink composition of the present invention, since it can be discharged satisfactorily. By using this method, high ejection stability can be realized.

  The temperature of the ink composition during ejection is preferably constant, and the control range of the temperature of the ink composition is more preferably ± 5 ° C. of the set temperature, more preferably ± 2 ° C. of the set temperature, and most preferably set. A temperature of ± 1 ° C. is appropriate.

In the present invention, the recording medium is not particularly limited, and a known recording medium can be used as a support or a recording material. Examples of the recording medium include paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, polyvinyl chloride resin, two Cellulose acetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), paper or plastic laminated or vapor-deposited with the above metals A film etc. are mentioned.
Among them, since the ink composition of the present invention is excellent in adhesiveness, it can be suitably used as a recording medium for non-absorbent recording media, and plastic recording media such as polyvinyl chloride, polyethylene terephthalate, and polyethylene are preferable, A polyvinyl chloride resin recording medium is more preferable, and a polyvinyl chloride resin sheet or film is more preferable.

The recording medium is preferably heated before applying ink from the viewpoint of suppressing bleeding. “Before applying ink” means before applying an ink composition onto a recording medium by coating or discharging.
The heating condition of the recording medium is preferably such that the surface temperature of the recording medium is 40 ° C. or higher and 100 ° C. or lower when the ink composition is applied, and more preferably 40 ° C. or higher and 80 ° C. or lower. More preferably, the temperature is 40 ° C. or higher and 70 ° C. or lower.
In the present invention, the surface temperature of the recording medium refers to the measured temperature 5 cm before the landing point.
The method for measuring the surface temperature is not particularly limited, but a thermocouple, a radiation thermometer, a resistance thermometer, a metal thermometer, a thermolabel, etc. can be used. In this specification, the temperature measured with a thermocouple Is adopted.
The means for heating the recording medium is not particularly limited, and known ones can be used as appropriate. Examples of the heating means include a heat drum, warm air, an infrared lamp, a heat oven, and a platen heater.

(Irradiation process)
Hereinafter, the irradiation step in the image recording method of the present invention will be described.
The irradiation step in the present invention is not limited as long as it is a step of irradiating the ink composition applied on the recording medium with active energy rays.

  Examples of active energy rays that can be used in the irradiation step include ultraviolet rays (hereinafter also referred to as UV light), visible rays, and electron beams, and it is preferable to use UV light.

  Although the peak wavelength of UV light depends on the absorption characteristics of the sensitizing dye used as necessary, it is preferably, for example, 200 nm to 405 nm, more preferably 220 nm to 390 nm, and 220 nm to 350 nm. More preferably. In this invention, when not using a sensitizing dye and a photoinitiator together, it is preferable that it is 200 nm-310 nm, and 200 nm-280 nm are more preferable.

UV light is the illumination intensity on the exposed surface is, for ^{example, 10mW / cm 2 ~2,000mW / cm} 2, ^is preferably a suitably be irradiated with ^{20mW / cm 2 ~1,000mW / cm 2} .

  As the UV light source, a mercury lamp, a gas / solid laser or the like is mainly used, and a mercury lamp, a metal halide lamp and a UV fluorescent lamp are widely known. In addition, replacement with GaN-based semiconductor ultraviolet light-emitting devices is very useful industrially and environmentally. LED (UV-LED) and LD (UV-LD) are small, have long life, high efficiency, and low cost. Yes, it is expected as a UV light source. In the present invention, when a sensitizing dye and a photopolymerization initiator are used in combination, a metal halide lamp, a high-pressure mercury lamp, a medium-pressure mercury lamp, a low-pressure mercury lamp, and a UV-LED are preferable. If not, a medium pressure mercury lamp or a low pressure mercury lamp is preferred, and a low pressure mercury lamp is particularly preferred.

In the irradiation step, the ink composition of the present invention applied on the recording medium is irradiated with such UV light, for example, for 0.01 seconds to 120 seconds, preferably 0.1 seconds to 90 seconds. Is appropriate.
As the irradiation conditions and the basic irradiation method, the irradiation conditions and the irradiation method disclosed in JP-A-60-132767 can be similarly applied to the present invention. Specifically, a method in which a light source is provided on both sides of a head unit including an ink ejection device and the head unit and the light source are scanned by a so-called shuttle method, or a method in which a separate light source without driving is used is preferable. The irradiation with the active energy ray is performed after a certain period of time (for example, 0.01 seconds to 120 seconds, preferably 0.01 seconds to 60 seconds) after ink landing and heat drying.

(Ink drying process)
The image recording method of the present invention preferably further includes an ink drying step (also referred to as “heat drying step”) after the ink application step and before the irradiation step.
In the heat drying step, it is preferable that the ink composition discharged onto the recording medium is fixed by (b) an organic solvent and (c) water that is used together as necessary by the heating means.

A process of heating and drying and fixing the discharged ink composition of the present invention (heat drying process) will be described.
The heating means is not limited as long as it can dry (b) an organic solvent and (c) water that is used in combination as necessary, and includes, but is not limited to, a heat drum, hot air, an infrared lamp, a heat oven, a heat plate heating, etc. Can be used.
The heating temperature is preferably 40 ° C or higher, more preferably about 40 ° C to 150 ° C, and still more preferably about 40 ° C to 80 ° C. The drying / heating time can be appropriately set in consideration of the composition and printing speed of the ink composition to be used.

  The ink composition fixed by heating is irradiated with an active energy ray in an irradiation step as necessary, and further photofixed. As described above, in the irradiation step, fixing with UV light is preferable.

[Printed matter]
The printed matter of the present invention is characterized by having an image formed by the ink composition of the present invention or an image recorded by the image recording method of the present invention. In the printed matter of the present invention, the content of the low molecular weight component in the film after curing of the recorded image is extremely low, and the printed matter is excellent in blocking resistance.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” are based on mass.

[Examples 1-15, Comparative Examples 1-6]
1. Preparation of Ink Composition (a) Specific copolymer or comparative polymer compound, (b) organic solvent, (c) water, (d) colorant (pigment dispersion), and surfactant are shown in Table 1 below. The indicated amount was placed in a stainless steel beaker, and mixed and stirred at 250 rpm with a mixer (Silverson L4R) to prepare a crude ink composition. The specific copolymer and the comparative polymer compound contain (b) an organic solvent and / or (c) water in order to prepare a solution as described later. The pigment dispersion used as the colorant (d) also contains (b) an organic solvent and / or (c) water.
Each obtained crude ink composition is packed in a plastic disposable syringe and filtered through a polyvinylidene fluoride (PVDF) pore size 5 μm filter (Millex-SV, Millipore, diameter 25 mm) to obtain a finished product. Ink compositions of Examples 1 to 15 and Comparative Examples 1 to 6 were obtained.

Specific copolymers P-1 to P-5 and P-11 to P-15 and comparative compounds B-1 to B-6 used in the examples were synthesized as follows.
In addition, (a) specific copolymer is a compound mentioned above as an exemplary compound of (a) specific copolymer.

[Synthesis Example: Synthesis of Specific Copolymers P-1 to P-5 and P-11 to P-15]
<Synthesis of Monomer 1>
Toluene 75 g and dimethylmaleic anhydride 42.0 g (manufactured by Sigma-Aldrich Japan) were introduced into a 500 ml three-necked flask equipped with a Dean-Stark distillation tube and stirred with a stirrer (Shinto Kagaku Co., Ltd .: Three-One Motor). While heating, the temperature was raised to 50 ° C. 2-Amino-1-propanol (25.0 g) was added dropwise over 30 minutes, followed by stirring for 4 hours. After the temperature was lowered to 60 ° C., 0.042 g of p-methoxyphenol (Wako Pure Chemical Industries, Ltd.) and 6.2 g of sulfuric acid (Wako Pure Chemical Industries, Ltd.) were added, and further 43.0 g of methacrylic acid (Wako Pure Chemical). Kogyo Co., Ltd.) was added dropwise in 30 minutes. After completion of the dropwise addition, the temperature was raised until the solvent was refluxed, and the reaction was performed for 3 hours. The reaction solution was neutralized with 29 g of 50 w / v% sodium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.), and 200 ml of toluene and 100 ml of water were added to separate the solution. The organic layer was washed twice with saturated brine, 30 mg of p-methoxyphenol was added to the organic layer, and the solvent was distilled off under vacuum to obtain 64.5 g of monomer 1. The formation of the target product was confirmed by ¹ H NMR.
In addition, B-2 refine | purified and synthesize | combined the liquid before carrying out condensation reaction with methacrylic acid.

<Synthesis of Monomer 2 and Monomer 3>
In the synthesis of monomer 1, instead of dimethylmaleic anhydride, 1-cyclohexene-1,2-dicarboxylic acid anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) was used, and the amount of reagent and reaction time were adjusted as appropriate. 2 was obtained. In the synthesis of monomer 1, 6-amino-1-hexanol was used in place of 3-amino-1-propanol, and the amount of reagent and reaction time were appropriately adjusted to obtain monomer 3.

<Synthesis of Specific Copolymer P-11>
2-Pyrrolidone (14.4 g, manufactured by Wako Pure Chemical Industries, Ltd.) was added to a three-necked flask equipped with 200 mL of the stirrer substituted with nitrogen. After raising the temperature to 80 ° C. in a nitrogen stream, 14.4 g of 2-pyrrolidone, 6.0 g of the monomer 1, 5.4 g of methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.), 3 g of methyl methacrylate (stock of Wako Pure Chemical Industries, Ltd.) Company), 6-mercaptohexanol 0.05 g (manufactured by Aldrich Japan) and 2,2′-azobisisobutyric acid dimethyl 0.018 g (manufactured by Wako Pure Chemical Industries, Ltd.) were added dropwise over 3 hours. After the dropwise addition, 2 hours and 4 hours later, 0.018 g of dimethyl 2,2′-azobisisobutyrate was added, and the reaction was further performed for 2 hours. Next, 11.2 g of 2-pyrrolidone, 0.1 g of tetramethylammonium bromide (manufactured by Wako Pure Chemical Industries, Ltd.), 0.05 g of 4-hydroxy1,1,6,6-tetramethylpiperidineoxy free radical (Tokyo Chemical Industry) Co., Ltd.) and 5.6 g of 4-glycidyloxybutyl acrylate (manufactured by Nippon Kasei Co., Ltd.) were added and heated at 100 ° C. for 5 hours while bubbling air. After adjusting the solid content concentration to 33%, 30 g of the obtained solution, 0.88 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) and 20 g of water were added to a 200 ml eggplant-shaped flask and stirred at 60 ° C. After dissolution of the polymer, the solid content was adjusted to 20% by addition of water to obtain an aqueous solution of the specific copolymer P-11. Further, the solution after the addition reaction was measured by GPC, and it was confirmed that the weight average molecular weight was 58,000.

<Synthesis of Specific Copolymer P-12>
2-Pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.) 15.8 g was added to a three-necked flask equipped with 200 mL of the stirrer substituted with nitrogen. After heating to 80 ° C. under a nitrogen stream, 15.8 g of 2-pyrrolidone, 6.0 g of the monomer 1, 3.84 g of 2-hydroxyethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.), tert-butyl methacrylate 3 0.0 g (manufactured by Wako Pure Chemical Industries, Ltd.), 3.0 g of methacrylic acid, 0.058 g of 3-mercaptopropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.025 g of dimethyl 2,2′-azobisisobutyrate The solution was added dropwise over 3 hours. After dropping, 2 hours and 4 hours later, 0.025 g of dimethyl 2,2′-azobisisobutyrate was added, and the reaction was further performed for 2 hours. Next, 0.03 g of organic bismuth catalyst (trade name Neostan U-600, manufactured by Nitto Kasei Kogyo Co., Ltd.), 4-hydroxy 1,1,6,6-tetramethylpiperidineoxy free radical 0.05 g (manufactured by Tokyo Chemical Industry Co., Ltd.) ), 4.17 g of 2-isocyanatoethyl acrylate (trade name, Karenz AOI, Showa Denko KK) was added and heated at 70 ° C. for 5 hours while bubbling dry air. After adjusting the solid content concentration to 33%, 30 g of the obtained solution, 0.88 g of sodium hydrogen carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) and 20 g of water were added to a 200 ml eggplant-shaped flask and stirred at 60 ° C. After dissolution of the polymer, the solid content was adjusted to 20% by addition of water to obtain an aqueous solution of the specific copolymer P-12. Further, the solution after the addition reaction was measured by GPC, and it was confirmed that the weight average molecular weight was 40,000.

<Synthesis of Specific Copolymer P-13 to P-15>
The amount of the reagent used for the synthesis of the specific copolymer P-11 was appropriately changed, and the aqueous solution of the specific copolymer P-13 was appropriately changed for the amount of the reagent used for the synthesis of the specific copolymer P-12. An aqueous solution of the specific copolymers P-14 and P-15 was obtained. For P-15, cyclohexyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of tert-butyl methacrylate.
The aqueous solutions of the specific copolymers P-11 to P-15 are aqueous solutions having a specific copolymer concentration of 20% and a 2-pyrrolidone concentration of 40%.

<Synthesis of Specific Copolymers P-1 to P-5>
In the synthesis of the specific copolymer P-11, γ-butyrolactone (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a solvent instead of 2-pyrrolidone, and glycidyl methacrylate (Wako Pure Chemical Industries) was used instead of 4-glycidyloxybutyl acrylate. Kogyo Co., Ltd.) was used, and the amounts of other reagents were changed as appropriate until the addition reaction of 4-glycidyloxybutylacrylate. About 33% of the resulting polymer solution was adjusted to a concentration of 30% by adding γ-butyrolactone to obtain a solution of the specific copolymer P-1.
In addition, in the synthesis of the specific copolymer P-12, γ-butyrolactone was used instead of 2-pyrrolidone as a solvent, and the amount of other reagents was changed as appropriate until the addition reaction of 2-isocyanatoethyl methacrylate. About 33% of the resulting polymer solution was adjusted to a concentration of 30% by adding γ-butyrolactone to obtain solutions of specific copolymers P-2 to P-5. For P-5, n-butyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of tert-butyl methacrylate.
The solutions of the specific copolymers P-1 to P-5 are solutions containing 30% specific copolymer and 70% γ-butyrolactone.

<Synthesis of Monomer 4>
100 ml of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) was added to a three-necked flask equipped with 200 mL of the agitator. Further, 11.2 g of 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (trade name: Irgacure 2959 manufactured by BASF Japan Ltd.) and 5.3 g of triethylamine (Wako Pure Chemical Industries, Ltd.) was added and cooled in an ice bath. Thereafter, 4.2 g of methacrylic acid chloride (manufactured by Wako Pure Chemical Industries, Ltd.) was dropped while adjusting the temperature so as not to exceed 10 ° C. After completion of dropping, the mixture was stirred at room temperature for 5.0 hours. The obtained reaction solution was poured into 200 mL of water prepared in a 500 mL beaker, extracted by adding ethyl acetate, and the oil phase was dried over magnesium sulfate (manufactured by Wako Pure Chemical Industries, Ltd.). After filtering off magnesium sulfate, 0.01 g of 4-methoxyphenol (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the solution, the solvent was distilled off under reduced pressure, and the residue was purified by column chromatography to give 1- [4- (2-methacryloyl). 7.8 g of (oxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (monomer 4) were obtained.

<Synthesis of Comparative Polymer Compounds B-1 and B-3 to B-5>
The amount of reagents used for the synthesis of the specific copolymers P-1 to P-5 and P-11 to 15, the reaction temperature, and the reaction time were appropriately changed, and a solution of comparative polymer compound B-1 and B- An aqueous solution of 3 to B-5 was obtained. The synthesized monomer 4 was used for B-5. The comparative polymer compound B-1 solution is a solution having a solid content concentration of 30% and a γ-butyrolactone concentration of 70%, and the comparative polymer compound B-3 to B-5 solution is a solid content of 20%, 2-pyrrolidone. An aqueous solution having a concentration of 40%.

<(A) Specific copolymer and comparative polymer compound>
The structures of typical (a) specific copolymers and comparative polymer compounds are shown below. In addition, the composition ratio of each structural unit described in each polymer compound below is based on mass. MI represents (a) the molar molar concentration (I) of the maleimide group in the partial structure represented by the general formula (1) in the specific copolymer and the comparative polymer compound, and C = C represents (a) The molar concentration (II) of the unsaturated double bond in the partial structure represented by the general formula (2) in the specific copolymer is shown. The same applies to MI and C = C in Table 1. However, for MI and C = C in Comparative Examples 1 to 6 in Table 1, the compound having the partial structure represented by the general formula (1) used in each of Comparative Examples 1 to 6 and the general formula ( 2) The molar concentration (I) of the maleimide group in the partial structure represented by the general formula (1) and the part represented by the general formula (2) with respect to the total amount of the compound having the partial structure represented by 2) The molar mass (II) of unsaturated double bonds in the structure is described.

<(B) Organic solvent>
2-methyl-1,3-propanediol (described as “MPD” in Table 1, manufactured by Tokyo Chemical Industry Co., Ltd.)
Dipropylene glycol dimethyl ether (described in Table 1 as “DPGDME”, manufactured by Wako Pure Chemical Industries, Ltd.)
<(C) Water>
(C) Ion exchange water was used as water.

<(D) Colorant (Pigment Dispersion)>
-M Dispersion 1 put CINQUASIA MAGENTA RT-355D 20.0 g, SOLPERSE 39000 9.0 g (manufactured by Nihon Lubrizol Corporation), and 71.0 g of γ-butyrolactone in a 200 mL beaker and stirred for 30 minutes with a stirrer. The liquid after stirring was dispersed with an Eiger motor mill (M-50, manufactured by Eiger Japan) for 3 hours to obtain an M dispersion 1 having a pigment concentration of 20%.
The M dispersion 2 was a magenta pigment dispersion (pigment concentration 15%, trade name: Projet Magenta APD 1000, manufactured by Fuji Film Imaging Colorant Co., Ltd.).
C dispersion was a cyan pigment dispersion (pigment concentration 15%, trade name: Projet Cyan APD 1000 (manufactured by Fuji Film Imaging Colorant Co., Ltd.)).

<Surfactant>
・ ZONYL FSN (trade name) (fluorine surfactant, manufactured by Aldrich)

When the viscosity of the ink composition of each obtained Example was measured using VISCOMETER TV-22 (made by TOKI SANGYOCO.LTD), all were in the range of 4 mPa * s-10 mPa * s at room temperature (25 degreeC). there were.
Moreover, when the surface tension of the obtained ink composition of each Example was measured using Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.), all were 20 mN / m at room temperature (25 ° C.). The range was ˜40 mN / m.

<Photopolymerization initiator>
Irgacure 29595 (trade name) (1- [4- (2-hydroxyethyl) -phenyl] -2-hydroxy-2-methyl] -1-propan-1-one, manufactured by BASF Japan Ltd.)
Irgacure 2959 (trade name) (abbreviated as Irg2959, described in Table 1, 2-hydroxy-1- [4- (2-hydroxyethoxy) phenyl] -2-methylpropan-1-one, manufactured by BASF Japan Ltd.)
・ TPO-L (trade name) (2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, manufactured by BASF Japan Ltd.)
<Polymerizable compound>
A-400 (trade name) (polyethylene glycol diacrylate (molecular weight 508) manufactured by Shin-Nakamura Chemical Co., Ltd.)

2. Evaluation The following evaluations were performed using the ink compositions obtained in Examples and Comparative Examples.
Each ink composition was manufactured by RK PRINT COAT INSTRUMENTS K Hand Coater No. Using 2 bars, it was applied to an 8 cm square recording medium with a thickness of 12 μm.
Furthermore, after moisture was dried at 60 ° C. for 3 minutes, exposure was performed with a low-pressure mercury lamp under the condition of energy of 1000 mJ / cm ² to obtain a printed matter having a cured film (solid image) on the recording medium. Unless otherwise specified, the recording medium is a vinyl chloride sheet (Avery 400 GLOSS WHITE PERMANENT, manufactured by Avery Dennison).
The following evaluation was performed using the obtained printed matter. The evaluation results are shown in Table 2.

<Blocking resistance evaluation>
Curability was confirmed by evaluation of blocking resistance. Two prints obtained in the same manner as in the water resistance test were used, and the prints were overlapped so that the surface on the side having the cured film faced, and an iron plate of the same size as the print was used. / Cm < ² >, 30 degreeC, and pressurized for 1 hour. Then, the state at the time of peeling off two coating-film surfaces was observed visually, and the following evaluation criteria evaluated. The evaluation results are shown in Table 2. In addition, A and B are levels with no practical problem.
-Evaluation criteria-
A: The cured film does not peel off, and no sound is produced when peeling off.
B: Although there is no peeling in the cured film, a sound is produced when peeling off.
C: Although there is no peeling in the cured film, some transfer is observed in the cured film.
D: Peeling occurs on the cured film.

<Water resistance evaluation>
The surface on the side having the cured film (image) in the obtained printed matter was rubbed with a cotton swab impregnated with distilled water and evaluated according to the following evaluation criteria. In addition, A and B are levels with no practical problem.
-Evaluation criteria-
A: No change was observed in the image even after rubbing 50 times or more.
B: The image density decreased after rubbing 10 to 49 times.
C: The image density was remarkably lowered after 0 to 9 rubbing.

<Bludge suppression evaluation>
A commercially available inkjet printer (manufactured by Fuji Film Dimatics, product name: DMP-2831) was prepared as an inkjet recording apparatus.
Each obtained ink composition was loaded into the above-mentioned ink jet printer, and heated at 40 ° C. using an attached platen heater, and 100 μm wide and 1 cm long in the direction perpendicular to the head scanning direction on the polyvinyl chloride recording medium. 20 lines were printed at an interval of 100 μm. The shape of the obtained straight line was visually observed and evaluated according to the following criteria. Note that the levels of A and B are levels that have no practical problem.
-Evaluation criteria-
A: High linearity and almost no disturbance at the edge B: The edge of the straight line is slightly disturbed but not mixed with the adjacent straight line C: The blur is large and mixed with the adjacent straight line There are some places

<Glossiness evaluation>
A monochromatic solid image of 5 cm × 5 cm was produced on the polyvinyl chloride recording medium heated at 40 ° C. using the inkjet printer. The produced printed matter was dried at 60 ° C. for 3 minutes, and then exposed with a low-pressure mercury lamp under the condition of energy of 1000 mJ / cm ² . About the obtained solid image, the glossiness was measured at a measurement angle of 60 ° using a gloss meter manufactured by Sheen Instruments, based on JIS Z8741. Evaluation was made according to the following evaluation criteria.
-Evaluation criteria-
A: Glossiness of 90 or more B: Glossiness of 80 or more and less than 90 C: Glossiness of less than 80

<Ejection recovery evaluation>
After the ink compositions of Examples 4 to 15 and Comparative Examples 4 to 7 were ejected by the ink jet printer, they were left for 10 minutes without maintenance. Thereafter, the ejection performance when ejection was resumed was evaluated by the number of nozzles (nozzle missing) from which the ink composition was not ejected.
A No nozzle missing B Nozzle missing 1 to 3 C Nozzle missing 4 or more

  As shown in Table 2, the repeating unit (a-1) having a partial structure represented by the general formula (1) and the repeating unit (a-2) having a partial structure represented by the general formula (2) (A) Each of the examples containing the specific copolymer has no odor, and each comparative example containing a photodegradable compound or a low molecular weight compound, that is, a low molecular weight component in the cured film. In comparison with each comparative example, it can be seen that any of them can form an image excellent in blocking resistance, water resistance, blur and glossiness. From the above evaluation, it was confirmed that the ink compositions of the examples were excellent in ejection recoverability.

Claims (15)

(A) A repeating unit (a-1) having a partial structure represented by the following general formula (1) and a repeating unit (a-2) having a partial structure represented by the following general formula (2): And the molar molar concentration (I) of the maleimide group in the partial structure represented by the general formula (1) is 0.5 mmol / g to 2.0 mmol / g, and is represented by the general formula (2). (B) an ink composition containing a high molecular compound having an unsaturated double bond mass molar concentration (II) in a partial structure of 1.0 mmol / g to 2.5 mmol / g, and (b) an organic solvent.

[In General Formula (1), R ^a and R ^b each independently represents an alkyl group having 1 to 6 carbon atoms, and R ^a and R ^b are bonded to each other to form 4 to 6 members together with adjacent carbon atoms. The alicyclic structure may be formed. * Indicates a binding site to the main chain or side chain in the polymer compound.
In General Formula (2), R ¹ represents a hydrogen atom or a methyl group, and X represents —OC (═O) —, —NHC (═O) —, —O—, —OCH ₂ —, an arylene group, and an alkylene group. , A nitrogen-containing heterocycle in which a nitrogen atom is bonded to a C═C double bond in the general formula (2), or a divalent linking group composed of a combination of two or more thereof. * Indicates a binding site to the main chain or side chain in the polymer compound. ] The ink composition according to claim 1, wherein both R ^a and R ^{b in} the general formula (1) are methyl groups.   The X in the general formula (2) is a divalent linking group containing one or more selected from -OC (= O)-, -NHC (= O)-and -O-. The ink composition according to 2.   The ink composition according to any one of claims 1 to 3, wherein the polymer compound (a) has a weight average molecular weight of 5,000 to 100,000.   The ink composition according to any one of claims 1 to 4, wherein the content of the polymer compound (a) is 5% by mass to 30% by mass with respect to the total mass of the ink composition.   The molar concentration (II) of the unsaturated double bond in the partial structure represented by the general formula (2) in the polymer compound (a) is changed to the maleimide group in the partial structure represented by the general formula (1). The ink composition according to any one of claims 1 to 5, wherein a value [(II) / (I)] divided by the molar mass concentration (I) is 0.5 to 4. The ink composition according to claim 1, wherein (a) the polymer compound is a vinyl polymer. The ink composition according to any one of claims 1 to 7, wherein the polymer compound (a) is a vinyl polymer having a main chain made of a copolymer containing (meth) acrylates.   The ink composition according to claim 1, further comprising (c) water.   The ink composition according to claim 9, wherein (a) the polymer compound is a polymer compound further comprising a repeating unit (a-3) having a hydrophilic group.   The ink composition according to any one of claims 1 to 10, which has a viscosity at 25 ° C of 2 mPa · s to 30 mPa · s and is for inkjet recording.   12. The ink composition according to claim 1, wherein the content of the compound having a boiling point of 280 ° C. or more and a molecular weight of 300 or less is less than 1% by mass with respect to the total mass of the ink composition.   A step of applying an ink composition according to claim 11 onto a recording medium using an ink jet recording apparatus to form an ink image, and drying to reduce a liquid component containing an organic solvent contained in the formed ink image. And a step of irradiating the dried ink image with active energy rays.   The image recording method according to claim 13, wherein a recording medium having a surface temperature of 40 ° C. or higher and 100 ° C. or lower is used.   An image formed by the ink composition according to any one of claims 1 to 12 or recorded by the image recording method according to claim 13 or 14 on an image recording medium. Prints that have.