JP5579768B2 - Ink composition, image forming method and printed matter - Google Patents

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 aqueous ink composition is used for image printing, pretreatment for imparting printability to the recording medium, and protection of the printed image. -It can be used suitably for decoration post-processing, etc., and since it has water as the main component, it has excellent safety, such as being able to be applied to high-density inkjet recording due to its low viscosity, It is a technology with potential.
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. Particularly in the case of outdoor advertising, high water resistance is required. In addition, when a large area print or a large number of prints is formed continuously, a process for removing stains on the printing apparatus with an organic solvent is required, but the organic solvent used for cleaning is scattered and formed. If the ink is attached to an ink image, if the image has low solvent resistance, the portion where the solvent has adhered is dissolved and removed, and image defects such as white spots can be caused. Therefore, the image has a high level of water resistance and solvent resistance. There is a need for an ink composition that can form.

  Examples of basic constituent materials of the active energy ray-curable water-based ink composition include water, a polymerizable substance, a polymerization initiator that generates radicals by active energy rays and starts polymerization, and a coloring material (pigment or dye). be able to. Among these, a polymerizable substance and a polymerization initiator may be prepared in an emulsion state, or may be present in a solution state given water solubility by an appropriate substituent.

Examples of the active energy ray-curable aqueous ink composition in which the polymerizable substance and the polymerization initiator are water-soluble include, for example, the ink composition described in Patent Document 1, and according to the ink composition, It is said that an ink composition for ink jet recording can be obtained in which a film having excellent adhesion and the like can be obtained by light irradiation.
Patent Document 2 describes an ink composition containing an active energy ray polymerizable substance having a specific maleimide structure.

JP 2005-307199 A JP 2007-119449 A

However, in the technique described in Patent Document 1 using a water-soluble polymerization initiator, the degradation of the added polymerization initiator and the unreacted residue remain in the cured film, which adversely affects the film properties and the printed matter. Therefore, there is room for further improvement in the blocking resistance and water resistance of the printed image.
In Patent Document 2, no study is made regarding solvent resistance, and there is room for improvement in solvent resistance.
Accordingly, a water-based ink composition that forms an image having good blocking resistance, water resistance, and solvent resistance has been eagerly desired, but has not yet been provided.

The present invention has been made in light of the above circumstances, and can provide an image excellent in both water resistance and solvent resistance and improved in high-temperature blocking properties, and is suitable for image formation using an inkjet method. It is an object of the present invention to provide an ink composition having excellent ink storage stability.
In addition, the present invention provides an image recording method capable of forming an image excellent in both water resistance and solvent resistance and improved in high temperature blocking properties, and is excellent in both water resistance and solvent resistance and high temperature blocking. It is an object of the present invention to provide a print having an image with improved properties.

Specific means for solving the above problems are as follows.
<1> (a) The repeating unit (a-1) having a partial structure represented by the following general formula (1) and the repeating unit (a-2) having a hydrophilic group are based on the total mass of the polymer compound. 8% by mass to 25% by mass and a repeating unit (a-3) having a partial structure represented by the following general formula (2), and the solubility parameter in an unneutralized state is 20.7 to 23.23. An ink composition comprising a high molecular compound of 0 MPa ^1/2 and (b) water.

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

In General Formula (2), Y represents an n + 1 valent substituent, and n represents an integer of 2 to 5.

<2> The ink composition according to <1>, wherein Y in the general formula (2) is an n + 1 valent substituent formed by removing n hydrogen atoms from a linear or cyclic alkyl group.
<3> The repeating unit (a-1) having a partial structure represented by the general formula (1) is a repeating unit represented by the following general formula (3), described in <1> or <2>. Ink composition.

In General Formula (3), R ^a and R ^b each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and at least one of R ^a and R ^b represents an alkyl group having 1 to 4 carbon atoms. Represent. R ^a and R ^b may be bonded to each other to form a 4- to 6-membered alicyclic structure. 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.

<4> The repeating unit (a-2) having a partial structure represented by the general formula (2) is a repeating unit represented by the following general formula (4), described in <1> or <2>. Ink composition.

In the general formula (4), R ^{c ′} represents a hydrogen atom or a methyl group. Z ′ is the same as Z in the general formula (3), and Y ′ and n ′ are the same as Y and n in the general formula (2), respectively.

<5> The ink composition according to any one of <1> to <4>, wherein the weight average molecular weight of the polymer compound (a) is 5,000 to 150,000.
<6> The repeating unit (a-2) having the hydrophilic group has at least one hydrophilic group selected from alcoholic hydroxyl groups, alkyl-substituted carbamoyl groups, carboxyl groups, sulfo groups, and salts thereof. The ink composition according to any one of <1> to <5>, which is (a-2).
<7> The repeating unit (a-2) having a hydrophilic group is a repeating unit (a-2) having at least one hydrophilic group selected from a carboxyl group and a salt thereof <1> to <6> The ink composition according to any one of the above.
<8> The ink composition according to any one of <1> to <7>, further comprising (c) a water-soluble organic solvent.
<9> The ink composition according to any one of <1> to <8>, further comprising (d) a colorant.
<10> The ink composition according to any one of <1> to <9>, which is for inkjet recording.
<11> An ink application step of applying the ink composition according to any one of <1> to <10> onto a recording medium;
An irradiation step of irradiating the ink composition applied on the recording medium with active energy rays;
An image forming method comprising:
<12> an ink application step of applying the ink composition according to any one of <1> to <10> onto a recording medium;
An ink drying step of drying and removing at least part of (b) water and (c) water-soluble organic solvent contained in the ink composition applied on the recording medium;
An irradiation step of irradiating the ink composition applied and dried on the recording medium with active energy rays;
An image forming method comprising:
<13> An image recording medium formed with the ink composition according to any one of <1> to <10> or recorded by the image forming method according to <11> or <12>. Printed image with an image.

According to the present invention, an image excellent in both water resistance and solvent resistance and improved in high-temperature blocking properties can be obtained, suitable for image formation using an inkjet method, and excellent in storage stability of ink. Ink compositions can be provided.
In addition, the present invention is an image recording method capable of forming an image excellent in both water resistance and solvent resistance and improved in high temperature blocking properties, and is excellent in both water resistance and solvent resistance and high temperature blocking properties. It is possible to provide a print having an improved image.

Hereinafter, the ink composition, the image forming 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 limited to an independent process, and is included in the term if the intended action of the process is achieved even when it cannot be clearly distinguished from other processes.

[Ink composition]
The ink composition of the present invention comprises (a) a polymer compound comprising a repeating unit (a-1) having a partial structure represented by the following general formula (1) and a repeating unit (a-2) having a hydrophilic group. And a repeating unit (a-3) having a partial structure represented by the following general formula (2), the solubility parameter in an unneutralized state is 20 It is an ink composition containing a polymer compound having a molecular weight of 7 to 23.0 MPa ^1/2 and (b) water.

(In General Formula (1), R ^a and R ^b each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and at least one of R ^a and R ^b is an alkyl group having 1 to 4 carbon atoms. R ^a and R ^b may be bonded to each other to form a 4- to 6-membered alicyclic structure, and * represents a bonding site with a main chain or a side chain in the polymer compound.

(In General Formula (2), Y represents an n + 1 valent substituent, and n represents an integer of 2 to 5.)

  Hereinafter, the repeating unit (a-1) having a partial structure represented by the general formula (1), the repeating unit (a-2) having a hydrophilic group, and the general formula (2) are used. A polymer compound having a repeating unit (a-3) having a partial structure is also referred to as “(a) polymer compound”.

The ink composition of the present invention can form an image excellent in both water resistance and solvent resistance and improved in high temperature blocking property by containing each of the above components.
Here, in the present invention, the water resistance and solvent resistance of the image mean the durability of the formed image with respect to water and solvent.
Further, the high-temperature blocking property of an image is desired for an adjacent printed material when the printed material on which an image is formed on a recording medium is stored repeatedly in a temperature atmosphere higher than room temperature of 30 ° C. to 50 ° C. This means that image sticking and transfer that are not considered to be suppressed are suppressed.
In general, thermoplastic resins have a problem that they are easily blocked when stored at high temperatures. However, since the ink composition of the present invention contains the above-described components, an image formed using the ink composition of the present invention has improved high-temperature blocking properties.

Although the mechanism of the present invention is not yet clear, the present inventors presume as follows.
That is, (a) the polymer compound comprises a repeating unit (a-1) having a partial structure represented by the general formula (1) and a repeating unit (a-2) having a specific amount of a hydrophilic group. By containing, (a) the polarity of the polymer compound itself is increased, the hydrophilicity is improved and the affinity for the aqueous solvent is increased, and it is considered that the water resistance and solvent resistance of the image can be improved.
In addition to the above two types of repeating units, a bulky group having a branched chain is added to the main chain by including the repeating unit (a-3) having a partial structure represented by the general formula (2). When introduced, the glass transition temperature (Tg) is increased. Thereby, it is considered that the softening of the printing screen is suppressed even in a high temperature state and the high temperature blocking property can be improved.
Furthermore, it is considered that the storage stability of the ink could be improved because the interaction with the pigment and the pigment dispersant was suppressed by controlling the polarity of the polymer compound within a specific range.

  The ink composition of the present invention may contain various liquid or solid compounds as additives as required, as long as the effects of the present invention are not impaired, in addition to (a) the polymer compound and (b) water. Good. For example, from the viewpoint of improving solubility, in addition to (b) water, (c) a water-soluble organic solvent may be included. Moreover, a colored image can be obtained by including (d) a colorant. Moreover, you may contain the other component suitably.

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

[(A) polymer compound]
The ink composition of the present invention comprises (a) a polymer compound comprising a repeating unit (a-1) having a partial structure represented by the following general formula (1) and a repeating unit (a-2) having a hydrophilic group. And a repeating unit (a-3) having a partial structure represented by the following general formula (2), the solubility parameter in an unneutralized state is 20 0.7-23.0 MPa ^1/2 of a polymer compound (hereinafter, also simply referred to as “(a) polymer compound”).
Hereinafter, the physical properties of (a) each repeating unit contained in the polymer compound and (a) the polymer compound will be described in detail.

(Repeating unit (a-1) having a partial structure represented by the general formula (1))
(A) The polymer compound 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 represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and at least one of R ^a and R ^b represents an alkyl group having 1 to 4 carbon atoms. Represent. R ^a and R ^b may be bonded to each other to form a 4- to 6-membered alicyclic structure. * Indicates a binding site to the main chain or side chain in the polymer compound.

In the general formula (1), the alkyl group having 1 to 4 carbon atoms represented by R ^a or R ^b 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. 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- to 6-membered alicyclic structure.

As R ^a and R ^b , an aspect in which both are alkyl groups having 1 to 4 carbon atoms, or R ^a and R ^b are bonded to each other to form a 4- to 6-membered alicyclic structure. It is more preferable that both R ^a and R ^b are alkyl groups having 1 to 2 carbon atoms, and it is still more preferable that both R ^a and R ^b are alkyl groups having 1 carbon atom.

  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 polymer compound may have an aspect 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 (3).

In General Formula (3), R ^a and R ^b each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and at least one of R ^a and R ^b represents an alkyl group having 1 to 4 carbon atoms. Represent. R ^a and R ^b may be bonded to each other to form a 4- to 6-membered alicyclic structure. 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.

In General Formula (3), R ^a and R ^b each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and at least one of R ^a and R ^b represents an alkyl group having 1 to 4 carbon atoms. Represent. R ^a and R ^b may combine with each other to form a 4- to 6-membered ring structure.

^{R a} and ^{R b} in the general formula (3) has 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 (3), R ^c represents a hydrogen atom or a methyl group. R ^c is preferably a methyl group.

In General Formula (3), 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 X Represents the binding position. 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 the general formula (3), 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 carbon number 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 polymer compound is improved. The effect of the 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 (3), 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 content of the repeating unit (a-1) having a partial structure represented by the general formula (1) contained in the polymer compound (preferably the repeating unit represented by the general formula (3)) is the ink content. The cured film (image) formed by the composition is appropriately selected according to the intended properties. That is, the content of the repeating unit (a-1) represented by the general formula (1) may be increased if a strong ink image is obtained, and may be decreased if a flexible cured film is obtained. There is a tendency.
In consideration of these, the content of the repeating unit (a-1) represented by the general formula (1) is preferably 5% by mass to 90% by mass with respect to the total mass of the polymer compound (a). More preferably, it is 20 mass%-70 mass%, and it is especially preferable that it is 30 mass%-65 mass%.
(A) The polymer compound 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 (a) the polymer compound. When the repeating unit (a-1) represented by the general formula (1) is a repeating unit represented by the general formula (3), a monomer represented by the following general formula (3 ′) is used. Can do.
The partial structure (a-1) 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 ^{(3 '), R a,} R b, R c, Z and X, ^R a in the formula ^{(3), R b, R} c, are respectively the Z and X synonymous, preferable ranges It is the same.

  Preferable examples of the monomer represented by the general formula (3 ′) include monomers (3′-1) to (3′-11) shown below. It is not limited.

  Monomers containing a partial structure represented by the general formula (1) represented by the monomers (3′-1) to (3′-11) are disclosed in, for example, JP-A-52-988, It can be produced with reference to the method described in JP-A-4-251258.

(Repeating unit having a hydrophilic group (a-2))
The (a) polymer compound in the present invention contains a specific amount of the repeating unit (a-2) 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 polymer compound (a), and may be a nonionic hydrophilic group or an ionic hydrophilic group (for example, An anionic hydrophilic group or a cationic hydrophilic group).

  Nonionic hydrophilic groups include, but are not particularly limited to, for example, residues obtained by removing one hydrogen atom from a heterocyclic structure containing a nitrogen atom or oxygen atom, an amide group, a carbamoyl group, an alkyl-substituted carbamoyl group, an alcohol Nonionic hydrophilic groups such as a functional hydroxyl group or 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, And cyclic carbonates such as propylene carbonate, and cyclic ethers such as tetrahydrofuran and 1,4-dioxane;

  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. Most preferred are carboxyl groups and salts thereof.

  The repeating unit (a-2) having a hydrophilic group is preferably a repeating unit represented by the following general formula (5).

In general formula (5), 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 .

In the general formula (5), the ^{Z 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 the general formula (5), 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 (5), 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 (5) include the hydrophilic groups described above, and preferred ranges thereof are also the same.

(A) The content of the repeating unit represented by the general formula (5) in the polymer compound needs to be 8% by mass to 25% by mass, and preferably 10% by mass to 23% by mass. More preferably, it is 20 mass%-20 mass%.
(A) The polymer compound may contain only one type of repeating unit (a-2) having a hydrophilic group, or may contain two or more types.

  The repeating unit represented by the general formula (5) is derived from the monomer represented by the following general formula (5 ′), and (a) high by including these monomers as a copolymerization component. The repeating unit (a-2) is introduced into the molecular compound.

In the general formula ^{(5 '), R cy,} Z y, R y, and A, ^R cy in the general formula ^{(5), 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 (5 ′) include the following monomer compounds, but the present invention is not limited to these.

  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 (5 ′), a commercially available compound can be used, and it can be produced by a generally known method.

  In the present invention, in addition to the monomer represented by the general formula (5 ′), 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 number of hydrophilic groups contained in the polymer compound is not limited, and the number is appropriately selected according to the type of the hydrophilic group, (a) the molecular weight of the polymer compound, and the like.

  The content of the hydrophilic group in the polymer compound (a) is preferably included in such a number that the polymer compound is water-soluble. Here, (a) that the polymer compound is water-soluble means that (a) the polymer compound can be dissolved by 3% by mass or more in water at 25 ° C.

  From the viewpoint of expressing the solubility of the polymer compound in water, the content of the repeating unit (a-2) having a hydrophilic group in the polymer compound (a) needs to be 8% by mass to 25% by mass. The content is preferably 10% by mass to 23% by mass, and more preferably 10% by mass to 20% by mass.

(Repeating unit (a-3) having a partial structure represented by formula (2))
(A) The polymer compound includes a repeating unit (a-3) having a partial structure represented by the following general formula (2). By introducing a bulky group into the main chain, the glass transition temperature (Tg) of the ink composition is increased, the diffusibility of the ink composition itself can be controlled within an appropriate range, and high temperature blocking properties are improved. can do.

  In General Formula (2), Y represents an n + 1 valent substituent, and n represents an integer of 2 to 5.

Y represents an n + 1 valent substituent obtained by removing n hydrogen atoms from a linear or cyclic alkyl group. The n + 1 valent substituent is preferably a group obtained by removing n hydrogen atoms from an alkyl group.
As the alkyl group, a linear alkyl group having 1 to 7 carbon atoms is preferable. From the viewpoint of reducing rigidity, a linear alkyl group having 1 to 4 carbon atoms is more preferable, and a linear alkyl group having 1 to 2 carbon atoms is preferable. More preferred is an alkyl group.
Moreover, as an alkyl group, a C3-C7 cyclic alkyl group is also preferable. From the viewpoint of bulkiness and high rigidity, the cyclic alkyl group is more preferably a cyclic alkyl group having 6 to 7 carbon atoms. Moreover, bridge structures, such as bicyclo, may be sufficient.

The alkyl group may have a substituent. Examples of the substituent include a hydroxyl group and a halogen atom.
The alkyl group may have a carbonyl group in the alkyl chain.
In the general formula (2), Y may be an n + 1 valent substituent in which at least two selected from the group consisting of linear and cyclic alkyl groups are combined.

  Although the specific example of the partial structure represented by General formula (2) below is shown, this invention is not limited to this.

  In general formula (2), n represents an integer of 2 to 5. n is preferably an integer of 2 to 4, and n is more preferably 2 or 3.

  The repeating unit (a-3) having a partial structure represented by the general formula (2) is preferably a repeating unit represented by the following general formula (4).

In formula (4), R ^{c ′} represents a hydrogen atom or a methyl group, and a methyl group is more preferable from the viewpoint of high-temperature blocking properties. Z ′ is the same as Z in the general formula (3), and the preferred range is also the same. Y ′ and n ′ are the same as Y and n in the general formula (2), respectively, and the preferable ranges are also the same.

In the present invention, the content of the repeating unit (a-3) having a partial structure represented by the general formula (2) is 5% by mass to 70% by mass with respect to the total mass of the polymer compound (a). The range of 5 mass% to 60 mass% is more preferable, and 5 mass% to 50 mass% is most preferable.
(A) The polymer compound may contain only one type of repeating unit (a-3) having a partial structure represented by the general formula (2), or may contain two or more types.

  The specific polymer (a) of the present invention includes a repeating unit (a-1) having a partial structure represented by the general formula (1), which is a highly polar component, and a repeating unit (a-2) having a hydrophilic group. By containing the repeating unit (a-3) having a partial structure represented by the general formula (2), which is a low-polarity component, in an appropriate composition ratio, it can be adjusted within the range of the SP value described later.

(Repeating unit having a hydrophobic group (a-4))
The (a) polymer compound according to the present invention includes (a) a repeating unit (a-1) having a partial structure represented by the general formula (1), a repeating unit (a-2) having a hydrophilic group, And a repeating unit (a-3) having a partial structure represented by the general formula (2), and if necessary, a repeating unit (a-4 having a hydrophobic group which is a low polar component) ) May be included.
Thereby, the adjustment of the SP value described later becomes easier.

  As the repeating unit (a-4) having a hydrophobic group, the homopolymer may have a repeating unit derived from a water-insoluble vinyl monomer. Among them, any (meth) acrylic acid alkyl ester or aralkyl ester structure may be used as long as it has a partial structure different from the partial structure represented by the general formula (2).

Among them, as the repeating unit (a-4) having a hydrophobic group, (a) from the viewpoint of adjusting the polarity of the polymer compound, those having 5 to 22 total carbon atoms are preferable, and those having 8 to 22 are more preferable. 8 to 14 are 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. Also, aralkyl esters such as benzyl group and phenoxyethyl group may be used.

The repeating unit (a-4) having a hydrophobic group that can be contained in the polymer compound (a) according to the present invention is exemplified below, but (a-4) of the present invention is not limited thereto.
Specific examples of the repeating unit (a-4) having a hydrophobic group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl methacrylate, n-butyl (meth) acrylate, n-hexyl (meta ) Acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl methacrylate, 2-boronyl methacrylate, benzyl methacrylate, phenoxyethyl ( (Meth) acrylates such as (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, acetoacetoxyethyl (meth) acrylate, styrene, α-methylstyrene, 4-methylstyrene, etc. Examples include, but are not limited to, methyl ether, ethyl methacrylate, n-propyl methacrylate, n-butyl (meth) acrylate, n-hexyl (meth) acrylate, and the like. -Ethylhexyl (meth) acrylate, octyl (meth) acrylate, benzyl methacrylate, phenoxyethyl (meth) acrylate and the like are preferable. Moreover, n-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, and phenoxyethyl (meth) acrylate are more preferable.

(A) The polymer compound may contain only one type of repeating unit (a-4) having a hydrophobic group, or may contain two or more types.
From the viewpoint of reducing the polarity of the copolymer, the repeating unit (a-4) having a hydrophobic group is preferably in the range of 0 to 72% by mass in the total mass of the polymer compound (0) to 45% by mass. %, More preferably 0 to 35% by mass.

The polymer compound (a) used in the present invention includes a repeating unit (a-1) having a partial structure represented by the general formula (1), a repeating unit (a-2) having a hydrophilic group, and a general formula. From each group of each repeating unit consisting of the repeating unit (a-3) having the partial structure represented by (2), at least one kind of repeating unit is contained in the preferred content range, and the SP value is within the above range. Selected to be within range.
(A) In the polymer compound, the repeating unit (a-1) having a partial structure represented by the general formula (1), the repeating unit (a-2) having a hydrophilic group, and the general formula (2) As a preferable ratio of the repeating unit (a-3) having the partial structure represented, the (a-1): (a-2): (a-3) is 20% by mass to 75% by mass: 8% by mass to 25% by mass: preferably 5% by mass to 70% by mass, more preferably 25% by mass to 70% by mass: 10% by mass to 23% by mass: 7% by mass to 65% by mass. 30% by mass to 65% by mass: 10% by mass to 20% by mass: 15% by mass to 60% by mass is most preferable. However, the ratio is selected so that the sum of (a-1), (a-2) and (a-3) is 100% by mass.

When the polymer compound (a) used in the present invention contains a repeating unit (a-4) having a hydrophobic group, the repeating unit (a-1) having a partial structure represented by the general formula (1), hydrophilic Each repeating unit comprising a repeating unit (a-2) having a functional group, a repeating unit (a-3) having a partial structure represented by the general formula (2), and a repeating unit (a-4) having a hydrophobic group From each group of units, at least one or more repeating units are selected such that the SP value falls within the above range within the preferable content range.
(A) As a preferred ratio of (a-1), (a-2), (a-3) and (a-4) in the polymer compound, (a-1): (a- 2): (a-3): (a-4) is 20% by mass to 75% by mass: 8% by mass to 25% by mass: 5% by mass to 70% by mass: 1% by mass to 67% by mass. % Range is preferable, 25% by mass to 70% by mass: 10% by mass to 23% by mass: 7% by mass to 63% by mass: 2% by mass to 58% by mass is more preferable, and 30% by mass to 65% by mass: 10%. Most preferably, 20% by mass to 20% by mass: 8% to 55% by mass: 5% to 52% by mass. However, the ratio is selected so that the sum of (a-1), (a-2), (a-3) and (a-4) is 100% by mass.

((A) Physical property value of polymer compound)
The (a) polymer compound according to the present invention has an SP value of 20.7 to 23.0 MPa ^1/2 . With a view to expressing the solvent resistance and water resistance at a high level, SP value is more preferably 21.2~22.8MPa ^1/2, 21.5~22.5MPa ^1/2 is particularly preferred.
In the present invention, the SP value is a solubility parameter calculated by the Okitsu method (Adhesion 38, No. 6, page 6 (1994) Polymer publication society), and the molar attractive constant, molar volume for each unit in the molecular structure. The estimated value proposed by Okitsu is given.
When calculating the SP value of the polymer, the carboxylic acid in (meth) acrylic acid is calculated in an unneutralized state.

The SP values of typical monomer units used in the present invention are described below. The numerical value described in parentheses after the monomer name is the SP value, and the unit is MPa ^1/2 .
The following monomer 1 (24.41), the following monomer 2 (23.22), the following monomer 3 (22.75), methacrylic acid (24.02), 2-hydroxyethyl methacrylate (22.89), 2-hydroxyethyl Acrylamide (32.87) methyl methacrylate (19.5), n-butyl methacrylate (18.33), isobutyl methacrylate (17.76), tert-butyl methacrylate (17.97), 2-ethylhexyl methacrylate (17.30) ), Stearyl methacrylate (17.08), 2-hydroxyethyl methacrylate (22.89), tetrahydrofurfuryl methacrylate (21.29), cyclohexyl methacrylate (18.79), benzyl methacrylate (20.21), 2-phenoxy Echi Methacrylate (20.23), isobornyl methacrylate (18.09)

The ink composition of the present invention is excellent in both water resistance and solvent resistance because it contains the polymer compound (a) exhibiting an SP value in a specific range.
(A) When using a non-crosslinkable polymer in which the polymer compound does not have the repeating unit (a-1) having the partial structure represented by the general formula (1), water resistance and solvent resistance by adjusting the polarity It is difficult to balance sex. However, since the ink composition of the present invention includes the repeating unit (a-1) having the partial structure represented by the general formula (1) in the polymer compound (a), the crosslinking effect and the insolubilizing effect due to the polarity. Can play together. Therefore, both effects of water resistance and solvent resistance can be achieved.

The weight average molecular weight of the polymer compound (a) contained in the ink composition of the present invention is preferably in the range of 5,000 to 150,000 from the viewpoint of water resistance. From the viewpoint of enhancing dischargeability, the weight average molecular weight of the polymer compound (a) is more preferably in the range of 5,000 to 100,000, and still more preferably in the range of 10,000 to 90, 0000. .
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.

  Specific examples of the (a) polymer compound that can be used in the present invention will be shown below by describing the repeating unit contained in the (a) polymer compound, its mass-based content, and the weight average molecular weight. The present invention is not limited to this. In addition, the following "SP" shows the SP value of a copolymer and has each described the value obtained by the measuring method mentioned above.

In Table 1,
MAA: Methacrylic acid (Wako Pure Chemical Industries, Ltd.)
MAA-Na: sodium methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.)
iBMA: Isobutyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.)
IBOMA: Isoboronyl methacrylate (Wako Pure Chemical Industries, Ltd.)
tBMA: tert-butyl methacrylate (Wako Pure Chemical Industries, Ltd.)
BMA: n-butyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.)
C18MA: Octadecyl methacrylate (Wako Pure Chemical Industries, Ltd.)
PEMA: Phenoxyethyl methacrylate (NK ester PHE-1G, manufactured by Shin-Nakamura Chemical Co., Ltd.)
EHMA: 2-ethylhexyl methacrylate (Wako Pure Chemical Industries, Ltd.)

  The polymer compound (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 a repeating group having a hydrophilic group. A monomer for forming the unit (a-2) and a monomer for forming the repeating unit (a-3) having a partial structure represented by the general formula (2) It can be obtained by polymerizing by a method and neutralizing an acidic group with an alkali metal hydroxide or the like as required. Specifically, for example, a method according to the polymerization method described in JP-A-52-988, JP-A-55-154970, Langmuir Vol. 18, No. 14, pages 5414-5421 (2002), etc. a) A polymer compound can be produced.

[(B) Water]
The ink composition of the present invention contains water.
(B) As water, it is preferable to use ion-exchanged water, distilled water or the like that does not contain impurities.
The water content in the ink composition of the present invention 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. More preferred.

[Other additives]
In the ink composition of the present invention, in addition to the essential components (a) polymer compound and (b) water, known additives can be used in combination as long as the effects of the present invention are not impaired. Hereinafter, additives that can be used in the ink composition will be described.

(C) Water-soluble organic solvent The ink composition of the present invention contains water as a main solvent, but a water-soluble organic solvent may be further used in the solvent depending on the purpose.
Here, the water-soluble organic solvent means an organic solvent having a solubility in water at 25 ° C. of 10% by mass or more.

Examples of water-soluble organic solvents 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, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, 2- Methylpropanediol, etc.)
Polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, tripropylene Glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol Monophenyl ether, propylene glycol monophenyl ether, etc.),

Amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, 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),
・ Sulphoxides (for example, dimethyl sulfoxide),
-Sulfones (for example, sulfolane),
・ Others (urea, acetonitrile, acetone, etc.)

  Preferable water-soluble organic solvents include polyhydric alcohol ethers, amides, and heterocyclic rings, and these are preferably used in combination.

Among the polyhydric alcohol ethers, so-called glycol ethers are preferable, specifically, tripropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol dimethyl ether are preferable, and 2-dipropylene glycol monomethyl 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.
In particular, a solvent having a high boiling point can be preferably used, and the boiling point at normal pressure is preferably 120 ° C. or higher, more preferably 150 ° C. or higher.

  One or more water-soluble organic solvents may be used in combination. The total amount of the water-soluble organic solvent added to the ink composition is preferably 1% by mass to 60% by mass, and more preferably 2% by mass to 35% by mass.

(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 the pigment used as the colorant, generally used organic pigments, inorganic pigments, and those obtained by dyeing resin particles with a dye 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 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 black pigments include C.I. I. Pigment black 7 (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) can be used. 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 an organic compound. Among these, titanium oxide (TiO ₂ , so-called titanium white) is preferable.

  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, random copolymers and can be exemplified 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., oxidize the pigment particle surface with an appropriate oxidizing agent, so that at least a part of the pigment surface has a sulfonic acid group or 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 particles described in JP-A-11-49974, JP-A-2000-273383, JP-A-2000-303014, etc. are treated with a treatment such as milling. Examples include a method of adsorbing to the surface, a method described in Japanese Patent Application Nos. 2000-377068, 2001-1495, and 2001-234966, and a method of crystallizing in a poor solvent after dissolving the pigment derivative together with a solvent. In any method, pigment particles having a polar group on the surface can be easily obtained.

  The polar group on the surface of the pigment may be free or in a salt state, or may have a counter salt. Examples of the counter salt include inorganic salts (lithium, sodium, potassium, magnesium, calcium, aluminum, nickel, ammonium) and organic salts (triethylammonium, diethylammonium, pyridinium, triethanolammonium, etc.), preferably 1 A counter salt 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 5% by mass.

(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 above-described components, the ink according to the present invention is used for the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. According to various known additives, for example, viscosity modifiers, surface tension modifiers, specific resistance modifiers, film forming agents, preservatives, dispersants, surfactants, UV absorbers, antioxidants, anti-fading agents. , Antibacterial agent, rust preventive agent, solid wetting agent, silica fine particles and the like can be appropriately selected and used. For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicon oil, JP-A-57-74193, JP-A-57-87988 and JP-A-62-261476, UV-absorbers described in JP-A-57-74192, JP-A-57-8798. Japanese Patent Laid-Open No. 60-72785, Japanese Patent Laid-Open No. 61-146591, Japanese Patent Laid-Open No. 1-95091, Japanese Patent Laid-Open No. 3-13376, etc. No. 42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, etc. , PH adjusting agents such as phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate and the like.

<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 agitator 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 200 mN / m to 40 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 is preferably 1 mPa · s to 40 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 forming method>
The image forming method of the present invention includes an ink applying 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 forming 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 forming method of the present invention, the ink jet recording apparatus used when the ink applying process ink jet method is applied is not particularly limited, and a known ink jet recording apparatus capable of achieving a 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 forming 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 to 100 pl, more preferably 8 to 30 pl, preferably 320 × 320 to 4,000 × 4,000 dpi (dot per inch), more preferably 400 × 400. ˜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 to 80 ° C., more preferably 25 to 50 ° C., and the viscosity of the ink composition is preferably 3 mPa · s to It is preferable to carry out after lowering to 15 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 50 mPa · s or less 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 adhesion, it can be suitably used for a non-absorbent recording medium as a recording medium, and a plastic substrate such as polyvinyl chloride, polyethylene terephthalate, polyethylene is preferable, A polyvinyl chloride resin base material is more preferable, and a polyvinyl chloride resin sheet or film is more preferable.

(Irradiation process)
Hereinafter, the irradiation step in the image forming 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 light glands, electron beams, and the like, and UV light is preferably used.

  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. It 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 light source is provided on both sides of the head unit including the ink ejection device, and the head unit and the light source are scanned by a so-called shuttle method, or another light source that is not driven and driven is used. Is preferred. 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 forming 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, the ink composition discharged onto the recording medium is preferably fixed by evaporating (b) water and a water-soluble organic solvent used in combination as necessary.

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 (b) water and a water-soluble organic solvent used in combination can be dried, if necessary. Heat drum, hot air, infrared lamp, heat oven, 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 with the ink composition of the present invention or an image recorded by the image forming method of the present invention. The printed matter of the present invention is a printed matter excellent in both water resistance and solvent resistance of a recorded image and excellent in high-temperature blocking properties.

  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 to 15, Comparative Examples 1 to 3]
[Preparation of ink composition]
(A) Polymer compound, (b) Water, (c) Water-soluble organic solvent, (d) Pigment dispersion and surfactant are mixed with a mixer (L4R manufactured by Silverson) so as to have the composition shown in Table 2 below. ) Were mixed and stirred at 500 revolutions / minute to prepare crude ink compositions, respectively.
Each obtained crude ink composition is packed into 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 3 were obtained.
The compounds A-1 to A-7, A-17 and compounds B-1 to B-3, which are polymer compounds, were synthesized in accordance with the matters described in JP-A-52-988. It was.
Each polymer compound synthesized was re-precipitated in a large amount of hexane, and then dissolved in an aqueous solution of sodium hydrogen carbonate (Wako Pure Chemical Industries, Ltd.).
Table 2 shows the compositions of the ink compositions 1 to 18 according to this example and the comparative example.

  The structures, molecular weights (MW) and SP values of (a) polymer compounds and comparative polymer compounds shown in Table 2 are as shown below. In addition, the composition ratio of each structural unit described in the polymer compound is based on mass.

(B) Ion exchange water was used as water.
(C) As a water-soluble organic solvent, 2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.), MPD (2-methyl-1,3-propanediol, manufactured by Tokyo Kasei Kogyo Co., Ltd.) as a surfactant, ZONYL FSN (fluorine surfactant Aldrich) was used.
(D) The pigment dispersion is a magenta pigment dispersion Projet Magenta APD 1000 (manufactured by Fuji Film Imaging Colorant Co., Ltd.) as a M dispersion, and a cyan pigment dispersion Projet Cyan APD 1000 (Fuji Film) as a C dispersion. Manufactured by Imaging Colorant Co., Ltd.), black pigment dispersion as K dispersion Projet Black APD 1000 (manufactured by Fujifilm Imaging Colorant Co., Ltd.), yellow pigment dispersion as Y dispersion Projet Yellow APD 1000 (Fuji Film Imaging) Colorant Co., Ltd.) was used.
The viscosity of the ink composition thus prepared was in the range of 4 mPa · s to 10 mPa · s at room temperature.

<Evaluation>
The obtained ink compositions 1 to 18 were subjected to No. of K hand coater manufactured by RK PRINT COAT INSTRUMENTS. Using 2 bars, it was applied to an 8 cm square vinyl chloride sheet (Avery 400 GLOSS WHITE PERMANENT, manufactured by Avery Dennison Co., Ltd.) with a thickness of 12 μm.
Further, after moisture was dried at 60 ° C. for 3 minutes, exposure was performed with a low-pressure mercury lamp under the condition of an energy of 1000 mJ / cm ² to obtain a printed matter having a cured film (solid image) on the vinyl chloride sheet.
The following evaluation was performed using the obtained printed matter. The evaluation results are shown in Table 3.

<Water resistance evaluation>
The surface on the side having the cured film in the obtained printed matter was rubbed with a cotton swab impregnated with ion-exchanged water and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3. 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.

<Solvent resistance evaluation>
The surface on the side having the cured film in the obtained printed material was rubbed with a cotton swab impregnated with isopropyl alcohol and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3. 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.
<Bleeding evaluation>
As an ink jet recording apparatus, a commercially available ink jet printer (DMP-2831 manufactured by Fuji Film Dimatics) was prepared. Each obtained ink composition was loaded into the above-mentioned ink jet printer and heated at 40 degrees to a polyvinyl chloride substrate (Avery Dennison, AVERY 400 GLOSS WHITE PERMANENT) with a 2 cm wide thin line 5 cm long Recorded in. After the discharge was stopped, the obtained fine lines were visually evaluated for bleeding.
When the ink compositions 1 to 14 containing the pigment dispersion described in the examples were used, none of the ink compositions was almost blurred and the fine lines were good in a straight line state.

<High temperature blocking evaluation>
A solid image having an average film thickness of 1.2 μm of an image portion after drying of 5 cm × 5 cm was drawn using the ink jet recording method applied to the above-described evaluation of bleeding. The obtained two printed materials were overlapped so that the coating surfaces were matched, and further pressed at 40 ° C. for 1 hour at a pressure of 1 kg / cm ² . Thereafter, the state when the two coated surfaces were peeled was observed. The evaluation results are shown in Table 3.
-Evaluation criteria-
A: There is no peeling in the coating film, and no sound is produced when peeling off.
B: Although there is no peeling in a coating film, a sound is produced when peeling off.
C: Although there is no peeling in the coating film, some transfer is seen in the coating film.
D: The coating film is peeled off.
<Ink stability>
After the ink composition is stored at 60 ° C. for 1 week, the dispersion state of the pigment in each composition is visually evaluated, and the viscosity of each composition is measured to measure the rate of change from the viscosity before storage. The ranking was based on the following criteria. The evaluation results are shown in Table 3.
-Evaluation criteria-
A: There is no generation of precipitates, and the level of increase in viscosity is less than 10% and the stability is high.
B: No precipitate is generated, and the increase in viscosity is 10% or more and less than 20%, and there is no problem with discharge performance. , A practically problematic level

  As shown in Table 3, (a) the ink composition of each Example containing a polymer compound has water resistance, solvent resistance, and high-temperature blocking property in comparison with the ink composition of Comparative Example. It can be seen that an excellent image can be obtained and an ink composition excellent in storage stability can be obtained.

Claims (13)

(A) 8 mass of the repeating unit (a-1) having a partial structure represented by the following general formula (1) and the repeating unit (a-2) having a hydrophilic group with respect to the total mass of the polymer compound % To 25% by mass and a repeating unit (a-3) having a partial structure represented by the following general formula (2), the solubility parameter in an unneutralized state is 20.7 to 23.0 MPa ^{1 / 2.} An ink composition comprising a polymer compound which is ² and (b) water.

(In General Formula (1), R ^a and R ^b each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and at least one of R ^a and R ^b is an alkyl group having 1 to 4 carbon atoms. R ^a and R ^b may be bonded to each other to form a 4- to 6-membered alicyclic structure, and * represents a bonding site with a main chain or a side chain in the polymer compound.

(In General Formula (2), Y represents an n + 1 valent substituent, and n represents an integer of 2 to 5.)   The ink composition according to claim 1, wherein Y in the general formula (2) is an n + 1 valent substituent formed by removing n hydrogen atoms from a linear or cyclic alkyl group. The ink composition according to claim 1 or 2, wherein the repeating unit (a-1) having a partial structure represented by the general formula (1) is a repeating unit represented by the following general formula (3). .

(In General Formula (3), R ^a and R ^b each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and at least one of R ^a and R ^b is an alkyl group having 1 to 4 carbon atoms. R ^a and R ^b may combine with each other to form a 4- to 6-membered alicyclic structure, 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. ) The ink composition according to claim 1 or 2, wherein the repeating unit (a-2) having a partial structure represented by the general formula (2) is a repeating unit represented by the following general formula (4). .

(In the general formula (4), R ^{c ′} represents a hydrogen atom or a methyl group. Z ′ is the same as Z in the general formula (3), and Y ′ and n ′ are each the general formula (2 The same as Y and n in).   The ink composition according to any one of claims 1 to 4, wherein the polymer compound (a) has a weight average molecular weight of 5,000 to 150,000.   The repeating unit (a-2) having a hydrophilic group has a repeating unit (a-) having at least one hydrophilic group selected from alcoholic hydroxyl groups, alkyl-substituted carbamoyl groups, carboxyl groups, sulfo groups, and salts thereof. The ink composition according to any one of claims 1 to 5, which is 2).   The repeating unit (a-2) having the hydrophilic group is a repeating unit (a-2) having at least one hydrophilic group selected from a carboxyl group and a salt thereof. 2. The ink composition according to item 1.   The ink composition according to any one of claims 1 to 7, further comprising (c) a water-soluble organic solvent.   The ink composition according to any one of claims 1 to 8, further comprising (d) a colorant.   The ink composition according to any one of claims 1 to 9, which is for inkjet recording. An ink application step of applying the ink composition according to any one of claims 1 to 10 onto a recording medium;
An irradiation step of irradiating the ink composition applied on the recording medium with active energy rays;
An image forming method comprising: An ink application step of applying the ink composition according to any one of claims 1 to 10 onto a recording medium;
An ink drying step of drying and removing at least part of (b) water and (c) water-soluble organic solvent contained in the ink composition applied on the recording medium;
An irradiation step of irradiating the ink composition applied and dried on the recording medium with active energy rays;
An image forming method comprising:   An image formed on the image recording medium by the ink composition according to any one of claims 1 to 10 or recorded by the image forming method according to claim 11 or 12. Prints that have.