JP2012144644A - Ink composition and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink composition which excels in dischargeability when an image is recorded by an inkjet method, and which is excellent in solvent resistance and fixability of a recorded image.SOLUTION: The ink composition includes: a nonionic polymer (a) which contains a repeating unit (a1) having a group shown by formula (1), and a repeating unit (a2) having a hydrophilic group; water (b); and a color material (c). In the formula (1), Rand Reach independently denote a 1-4C alkyl group, and Rand Rmay mutually bond to form a 4-6 membered ring.

Description

  The present invention relates to an ink composition and an image forming method.

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 ink jet method, the active energy ray-curable water-based ink is used for image printing, pretreatment for imparting printability to the recording medium, and protection / decoration of the printed image. Many excellent features and possibilities, such as being suitable for post-processing, etc., and being excellent in safety because it contains water as the main component, and being able to be applied to high-density inkjet recording due to low viscosity. This technology has
Examples of basic constituent materials of the active energy ray-curable water-based ink 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). it can. Among these, the polymerizable substance and the polymerization initiator may be prepared in an emulsion state, or may be present in a solution state with water solubility provided by appropriate substituents.
Examples of the water-soluble polymerizable substance and the polymerization initiator include those described in Patent Document 1, for example. An ink composition for ink jet recording in which a film having excellent adhesion and the like can be obtained by light irradiation. Are listed.
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, Patent Document 1, which is a technique using a polymerization initiator, has an adverse effect on film properties and printed matter due to the degradation product and unreacted residue of the added polymerization initiator remaining in the cured film, and printed images. Insufficient fixability and solvent resistance. Further, there is room for further improvement in the dischargeability of the ink composition.
In Patent Document 2, no study is made regarding solvent resistance, and there is still room for improvement in terms of fixability and solvent resistance. Therefore, an aqueous ink composition having good fixability, solvent resistance, and ejection properties is desired.

  In light of the above circumstances, the problem to be solved by the present invention is excellent in dischargeability when recording an image by the ink jet method, solvent resistance that is durability against a solvent of the recorded image, and difficulty in sticking the image. An object of the present invention is to provide an ink composition having excellent fixing properties.

Specific means for solving the above problems are as follows.
Item 1. (A) Nonionic polymer having a repeating unit (a1) having a group represented by the following formula (1) and a repeating unit (a2) having a hydrophilic group, (b) water, and (c) color An ink composition having a material.

(In Formula (1), R ^a and R ^b each independently represents an alkyl group having 1 to 4 carbon atoms, and R ^a and R ^b may be bonded to each other to form a 4- to 6-membered ring. )
Item 2. The hydrophilic group in the repeating unit (a2) in the polymer (a) is at least one selected from the group consisting of an amide group, a carbamoyl group, an alkyl-substituted carbamoyl group, an alcoholic hydroxyl group, and a group having a polyalkyleneoxy structure. Item 2. The ink composition according to Item 1, which is a group of
Item 3. Item 3. The ink composition according to Item 2, wherein the amide group is a group represented by Formula (11).

Formula (11)

(In (Formula 11), R ^1a and R ^1b each independently represent a hydrogen atom or an alkyl group. R ^1a and R ^1b may combine with each other to form a 4- to 6-membered ring. * Indicates the bonding position.)
Item 4. Item 3. The ink composition according to Item 2, wherein the alkyl-substituted carbamoyl group is a group represented by Formula (12).

Formula (12)

(In (Formula 12), R ^2a and R ^2b each independently represents a hydrogen atom or an alkyl group. R ^2a and R ^2b may be bonded to each other to form a 4- to 6-membered ring. Indicates the bonding position.)
Item 5. Item 3. The ink composition according to Item 2, wherein the group having a polyalkyleneoxy structure is a group represented by Formula (13).

Formula (13)

(In Formula (13), R ^3a represents an alkylene group, R ^3b represents a hydrogen atom or an alkyl group. N3 represents an integer of 4 to 50. Plural R ^{3a s} may be the same or different. (* Indicates a bonding position.)
Item 6. Item 6. The ink composition according to any one of Items 1 to 5, which has 8 or more groups represented by Formula (1) in one molecule of the polymer (a).
Item 7. Item 7. The ink composition according to any one of Items 1 to 6, wherein the repeating unit (a1) has a structure represented by the following general formula (1 ′).

(In the general formula (1 ′), R ^a and R ^b each independently represents an alkyl group having 1 to 4 carbon atoms, and R ^a and R ^b may be bonded to each other to form a 4- to 6-membered ring. Good.
Z represents a single bond, —COO— * or —CONR ^d — *, and R ^d represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. In addition, * represents the position couple | bonded with X.
X represents an alkylene group. R ^c represents a hydrogen atom or a methyl group. )
Item 8. Item 8. The ink composition according to any one of Items 1 to 7, further comprising (d) a water-soluble organic solvent.
Item 9. Item 10. The ink composition according to any one of Items 1 to 8, wherein the content of water (b) is 10% by mass to 97% by mass with respect to the total amount of the ink composition.
Item 10. Item 10. The ink composition according to any one of Items 1 to 9, wherein the copolymer ratio of the repeating unit having a hydrophilic group in the polymer (a) is 30 or more and 90 or less.
Item 11. Item 11. The ink composition according to any one of Items 1 to 10, wherein the repeating unit (a2) has a structure represented by the following general formula (2).

(In the formula (2), 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 having 1 to 4 carbon atoms. It represents a group. Incidentally, * is .A representative of the group .R ^y that represents a position bonded with R ^y selected from the group consisting of a single bond, an alkylene group, an arylene group and aralkylene group represents a hydrophilic group.)
Item 12. Item 12. The ink composition according to any one of Items 1 to 11, further comprising a surfactant.
Item 13. Item 13. An image forming method comprising: an ink application step of applying the ink composition according to any one of Items 1 to 12 onto a recording medium; and an irradiation step of irradiating the applied ink composition with active energy rays.

  According to the present invention, it is possible to provide an ink composition that is excellent in dischargeability when an image is recorded by an ink jet method and excellent in solvent resistance and fixability of the recorded image.

<Ink composition>
The ink composition of the present invention comprises (a) a nonionic polymer having a repeating unit (a1) having a group represented by the following formula (1) and a repeating unit (a2) having a hydrophilic group (hereinafter, referred to as “nonionic polymer”). It is also characterized by simply containing “(a) polymer”), (b) water, and (c) a coloring material.

(In Formula (1), R ^a and R ^b each independently represents an alkyl group having 1 to 4 carbon atoms, and R ^a and R ^b may be bonded to each other to form a 4- to 6-membered ring. )
In addition, the wavy line in Formula (1) in this specification represents the bonding position in (a) polymer.
In the present specification, “to” is used in the sense of including the numerical values described before and after the lower limit value and the upper limit value.

Hereinafter, the ink composition of the present invention (hereinafter also simply referred to as “ink composition”) will be described in detail.
<(A) Nonionic polymer having a repeating unit (a1) having a group represented by the formula (1) and a repeating unit (a2) having a hydrophilic group>

  The polymer (a) used in the present invention may be a nonionic polymer having a repeating unit (a1) having a group represented by the formula (1) and a repeating unit (a2) having a hydrophilic group. Can be used without limitation. By using the compound having a group represented by the formula (1), the crosslinking reaction of the ink composition can be advanced. The nonionic polymer of the present invention refers to a non-dissociable (non-ionic) polymer that does not have a dissociable (ionic) group in the ink composition.

  Hereinafter, the repeating unit (a1) having a group represented by the above formula (1) and the repeating unit (a2) having a hydrophilic group in the polymer (a) will be described in detail.

-Repeating unit (a1) having a group represented by formula (1)-
The polymer (a) of the present invention has a repeating unit having a group represented by the following formula (1) as an essential component.

(In Formula (1), R ^a and R ^b each independently represents an alkyl group having 1 to 4 carbon atoms, and R ^a and R ^b may be bonded to each other to form a 4- to 6-membered ring.)
In the formula (1), R ^a and R ^b may have a substituent or may not have a substituent, but preferably have no substituent.

R ^a and R ^b each represent an alkyl group having 1 to 4 carbon atoms, preferably 1 to 2 carbon atoms, and most preferably 1 carbon atom. These groups 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, a t-butyl group, or the like. R ^a and R ^b may combine with each other to form a 4- to 6-membered ring. Moreover, when forming a 4-6 membered ring, it is preferable to have an alicyclic structure.

  The polymer (a) of the present invention is water-soluble or water-dispersible, and (a) 1 g of the polymer is preferably dissolved or dispersible in less than 30 ml of water, and dissolved in less than 20 ml of water. Or it is more preferable that it can be dispersed, and it is particularly preferable that it can be dissolved or dispersed with less than 10 ml of water. From the viewpoint of ejection stability in ink jet drawing and storage stability of the ink composition, the polymer (a) is preferably water-soluble.

  Specific examples of the structure represented by the formula (1) in the polymer (a) of the present invention are shown in the following (A-1) to (A-3).

(A-1) (A-2)

(A-3)

  (A) The polymer is not limited to repeating units other than the repeating unit (a1) represented by the formula (1) and the repeating unit (a2) having a hydrophilic group, such as polyacrylate, polyester, polyethyleneimine, polystyrene, etc. Can be used. It is preferable that the polymer (a) is a vinyl polymer from the viewpoint of dischargeability and production suitability of the ink composition.

  Moreover, it is preferable that the repeating unit (a1) which has group represented by Formula (1) is a structure represented by following formula (1 ').

(In Formula (1 ′), R ^a and R ^b each independently represents an alkyl group having 1 to 4 carbon atoms, and R ^a and R ^b may be bonded to each other to form a 4- to 6-membered ring. .
Z represents a single bond, —COO— * or —CONR ^d — *, and R ^d represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. In addition, * represents the position couple | bonded with X.
X represents an alkylene group. R ^c represents a hydrogen atom or a methyl group. )

In Formula (1 ′), R ^a and R ^b each independently represent an alkyl group having 1 to 4 carbon atoms, and R ^a and R ^b may be bonded to each other to form a 4- to 6-membered ring. R ^a and R ^b in formula (1 ′) are the same as those exemplified as R ^a and R ^b in formula (1) described above (including preferred examples).

In the formula (1 ′), R ^c represents a hydrogen atom or a methyl group. R ^c is preferably a methyl group.

In the formula (1 ′), Z represents —COO— * or —CONR ^d — *. Z is preferably -COO- *. In addition, * is a position couple | bonded with X.
R ^d 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 ^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. R ^d may have a substituent or may not have a substituent, but preferably has no substituent.

  In the formula (1 ′), X represents an alkylene group, and is preferably an alkylene group having 2 to 20 carbon atoms. The alkylene group may have a linear structure, a branched structure, or a cyclic structure. In the alkylene group, an ether bond, an ester bond, an amide bond, a urethane bond, or an arylene group may exist. In the case where X is an alkylene group, the number of carbon atoms is preferably 2 to 20, more preferably 2 to 12, and still more preferably 2 to 8.

In Formula (1 ′), R ^a and R ^b are each independently an alkyl group having 1 to 2 carbon atoms, R ^c is a methyl group, Z is —COO—, and X is 2 carbon atoms. It is preferably an alkylene group having 12 carbon atoms.

  (A) When the polymer includes a structure represented by the above formula (1 ′), (a) the polymer is a polymer obtained by polymerizing a monomer represented by the following general formula (1′-1). It is preferably a coalescence.

  The copolymerization ratio of the repeating unit of the formula (1 ′) in the polymer (a) is, for example, 5 to 60, preferably 10 to 50, and preferably 10 to 40 on a mass basis with respect to the polymer (a). Further preferred.

R ^a , R ^b , R ^c , Z and X in the general formula (1′-1) are the same as those in the formula (1 ′) described above (including preferred examples).

  Preferred examples of the monomer represented by the formula (1′-1) include the following compounds (1-1-1) to (1-1-11), but the present invention is limited to these. Not.

  Monomers (1-1-1) to (1-1-11) that give the repeating unit represented by the general formula (1′-1) in the present invention are, for example, JP-A-52-988, It can be produced with reference to the method described in JP-A-4-251258.

-Repeating unit (a2) having a hydrophilic group-
The (a) polymer of the present invention has a repeating unit (a2) having a hydrophilic group.
The hydrophilic group in the repeating unit (a2) is not limited as long as it is a group that increases the hydrophilicity of the polymer (a) and is a non-dissociable group.

  The number of the hydrophilic groups in the repeating unit (a2) having a hydrophilic group is not limited. For example, one or more hydrophilic groups may be used, and the number depends on the type of hydrophilic group, the molecular weight, and the like. Accordingly, it is appropriately selected.

  Examples of the hydrophilic group include, but are not limited to, for example, a residue obtained by removing one hydrogen atom from a heterocyclic ring containing a nitrogen atom or an oxygen atom as a hetero atom, an amide group, a carbamoyl group, an alkyl-substituted carbamoyl group, an alcoholic group Examples thereof include a hydroxyl group and a group having a polyalkyleneoxy structure. Among these, an amide group, a carbamoyl group, an alkyl-substituted carbamoyl group, an alcoholic hydroxyl group and a group having a polyalkyleneoxy structure are preferable, and a carbamoyl group, an alkyl-substituted carbamoyl group, a group having a polyalkyleneoxy structure, and an alcoholic hydroxyl group are more preferable. A carbamoyl group, an alkyl-substituted carbamoyl group, and an alcoholic hydroxyl group are particularly preferable.

As the heterocycle in the residue obtained by removing one hydrogen atom from a heterocycle containing a nitrogen atom or an oxygen atom as the heteroatom,
lactones such as γ-butyrolactone,
Cyclic ureas such as 2-pyrrolidone and ethylene urea;
Cyclic carbonates such as ethylene carbonate and propylene carbonate;
Cyclic ethers such as tetrahydrofuran and 1,4-dioxane;
And crown ethers such as 12-crown-4.

  Although it does not limit as said amide group, For example, group represented by following formula (11) is mentioned preferably.

Formula (11)

(In (Formula 11), R ^1a and R ^1b each independently represent a hydrogen atom or an alkyl group. R ^1a and R ^1b may combine with each other to form a 4- to 6-membered ring. * Indicates the bonding position.)

R ^1a and R ^1b in the formula (11) each independently represent a hydrogen atom or an alkyl group. The alkyl group in R ^1a and R ^1b represents a linear or branched alkyl group, and may include a —COO— bond, —O— bond, and —NH— bond. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and most preferably 1 to 3 carbon atoms. R ^1a and R ^1b may be bonded to each other to form a 4- to 6-membered ring. These groups may or may not have a substituent, but preferably do not have a substituent. Specific examples of the alkyl group represented by R ^1a and R ^1b include a methyl group and a t-butyl group.

In the formula (11), the substituent that R ^1a and R ^1b may have is preferably a hydroxyl group, an alkoxy group having 1 to 2 carbon atoms, or the like.

  The alkyl-substituted carbamoyl group includes a monoalkylcarbamoyl group in which the hydrogen atom bonded to N of the carbamoyl group is substituted with an alkyl group, or a dialkyl in which two hydrogen atoms bonded to N of the carbamoyl group are substituted with an alkyl group A carbamoyl group may be mentioned. Specifically, a group represented by the following formula (12) is preferably exemplified.

Formula (12)

(In (Formula 12), R ^2a and R ^2b each independently represents a hydrogen atom or an alkyl group. R ^2a and R ^2b may be bonded to each other to form a 4- to 6-membered ring. Indicates the bonding position.)

R ^2a and R ^2b in the formula (12) each independently represent a hydrogen atom or an alkyl group. The alkyl group in R ^2a and R ^2b represents a linear or branched alkyl group, and may include an —O— bond, —COO— bond, and —C (═O) — bond. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and most preferably 1 to 3 carbon atoms. R ^2a and R ^2b may be bonded to each other to form a 4- to 6-membered ring. Specific examples of the alkyl group represented by R ^2a and R ^2b include, but are not limited to, a methylene group, an ethylene group, and the like. These groups may or may not have a substituent, but preferably do not have a substituent.

In the formula (12), the substituent that R ^2a and R ^2b may have is preferably a hydroxyl group, an alkoxy group having 1 to 2 carbon atoms, or the like.

  Although it does not limit as group which has the said polyalkylene oxy structure, For example, group represented by following formula (13) is mentioned preferably.

Formula (13)
(In Formula (13), R ^3a represents an alkylene group, R ^3b represents a hydrogen atom or an alkyl group. N3 represents an integer of 4 to 50. Plural R ^{3a s} may be the same or different. May be.)

R ^3a in the formula (13) represents an alkylene group. The alkylene group represented by R ^3a represents a linear, branched or cyclic alkylene group, and may include an —O— bond or a —COO— bond. The alkylene group preferably has 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, and most preferably 1 to 3 carbon atoms. A plurality of R ^3a present in the group of formula (13) may be the same or different, and are preferably the same. These groups may or may not have a substituent, but preferably do not have a substituent. Specific examples of the alkylene group represented by R ^3a include an ethylene group.

As the substituent that R ^3a in Formula (13) may have, a hydroxyl group, an alkoxy group having 1 to 2 carbon atoms, or the like is preferable.

R ^3b in the formula (13) represents a hydrogen atom or an alkyl group. The alkyl group represented by R ^3b represents a linear, branched or cyclic alkyl group, preferably has 1 to 10 carbon atoms, more preferably has 1 to 6 carbon atoms, and most preferably has 1 to 3 carbon atoms. Specific examples of the alkyl group represented by R ^3b include a methyl group and an ethyl group.

  N3 in the formula (13) represents an integer of 4 to 50, more preferably 4 to 40, and still more preferably 5 to 30.

  (A) The repeating unit (a2) in the polymer preferably further has a structure represented by the following general formula (2).

(In the general formula (2), 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 a carbon atom having 1 to 4 carbon atoms. represents an alkyl group. Here, * is .A representative of the group .R ^y representing the position at which the group bonds to R ^y is selected from the group consisting of a single bond, an alkylene group, an arylene group and aralkylene group represents a hydrophilic group. )

In the general formula (2), R ^cy represents a hydrogen atom or a methyl group.
In the general formula (2), ^{Z y} is ^{-COO - *, - CONR dy -} * or a single bond, is preferably -COO- *. In addition, * is a position couple ^| bonded with ^Ry . 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 alkoxy group having 1 to 4 carbon atoms and a hydroxyl group.

In the general formula (2), 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, and an alkylene group having 1 to 20 carbon atoms, an arylene group having 6 to 20 carbon atoms, or carbon. An aralkylene group of several 7 to 20 is preferable. These groups may have a substituent or may not have a substituent. In these groups, an ether bond, an ester bond, an amide bond, and a urethane bond may exist. In the general formula (2), R ^y is preferably a single bond.

Examples of the substituent that R ^y may have include an alkoxy group having 1 to 4 carbon atoms and a hydroxyl group.

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 2} H 4 -CONH -, - C 4 H 8 -OCONH-C 6 H 12 -, - CH 2 -OCONHC 10 H 20 -, - CH 2 C (OH) CH 2 - or the like Can be mentioned.

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 most preferably 6 to 10 carbon atoms. . Specific examples of the arylene group for R ^y include a phenylene group and —C ₆ H ₄ —CO—C ₆ H ₄ —.

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 most preferably 7 to 10 carbon atoms. . Specific examples of the aralkylene _{group, -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 include, but are not limited to, a residue obtained by removing one hydrogen atom from a heterocyclic ring containing a nitrogen atom or an oxygen atom as a hetero atom, an amide group, a carbamoyl group, an alkyl-substituted carbamoyl group A group having an alcoholic hydroxyl group and a polyalkyleneoxy structure is preferred, an amide group, a carbamoyl group, an alkyl-substituted carbamoyl group, a group having an alcoholic hydroxyl group and a polyalkyleneoxy structure are preferred, a carbamoyl group, an alkyl-substituted carbamoyl group, an alcohol A functional hydroxyl group is particularly preferred.

As the heterocycle in the residue obtained by removing one hydrogen atom from a heterocycle containing a nitrogen atom or an oxygen atom as the heteroatom,
lactones such as γ-butyrolactone,
Cyclic ureas such as 2-pyrrolidone and ethylene urea;
Cyclic carbonates such as ethylene carbonate and propylene carbonate;
Cyclic ethers such as tetrahydrofuran and 1,4-dioxane;
And crown ethers such as 12-crown-4.

  Although it does not limit as said amide group, For example, group represented by following formula (11) is mentioned preferably.

Formula (11)

(In (Formula 11), R ^1a and R ^1b each independently represent a hydrogen atom or an alkyl group. R ^1a and R ^1b may combine with each other to form a 4- to 6-membered ring. * Indicates the bonding position.)

R ^1a and R ^1b in the formula (11) each independently represent a hydrogen atom or an alkyl group. The alkyl group in R ^1a and R ^1b represents a linear or branched alkyl group, and may include a —COO— bond, —O— bond, and —NH— bond. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and most preferably 1 to 3 carbon atoms. R ^1a and R ^1b may be bonded to each other to form a 4- to 6-membered ring. These groups may or may not have a substituent, but preferably do not have a substituent. Specific examples of the alkyl group represented by R ^1a and R ^1b include a methyl group and a t-butyl group.

In the formula (11), the substituent that R ^1a and R ^1b may have is preferably a hydroxyl group, an alkoxy group having 1 to 2 carbon atoms, or the like.

  The alkyl-substituted carbamoyl group includes a monoalkylcarbamoyl group in which the hydrogen atom bonded to N of the carbamoyl group is substituted with an alkyl group, or a dialkyl in which two hydrogen atoms bonded to N of the carbamoyl group are substituted with an alkyl group A carbamoyl group may be mentioned. Specifically, a group represented by the following formula (12) is preferably exemplified.

Formula (12)

(In (Formula 12), R ^2a and R ^2b each independently represents a hydrogen atom or an alkyl group. R ^2a and R ^2b may be bonded to each other to form a 4- to 6-membered ring. Indicates the bonding position.)

R ^2a and R ^2b in the formula (12) each independently represent a hydrogen atom or an alkyl group. The alkyl group in R ^2a and R ^2b represents a linear or branched alkyl group, and may include an —O— bond, —COO— bond, and —C (═O) — bond. The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and most preferably 1 to 3 carbon atoms. R ^2a and R ^2b may be bonded to each other to form a 4- to 6-membered ring. Specific examples of the alkyl group represented by R ^2a and R ^2b include, but are not limited to, a methylene group, an ethylene group, and the like. These groups may or may not have a substituent, but preferably do not have a substituent.

In the formula (12), the substituent that R ^2a and R ^2b may have is preferably a hydroxyl group, an alkoxy group having 1 to 2 carbon atoms, or the like.

  Although it does not limit as group which has the said polyalkylene oxy structure, For example, group represented by following formula (13) is mentioned preferably.

Formula (13)

(In Formula (13), R ^3a represents an alkylene group, R ^3b represents a hydrogen atom or an alkyl group. N3 represents an integer of 4 to 50. Plural R ^{3a s} may be the same or different. May be.)

R ^3a in the formula (13) represents an alkylene group. The alkylene group represented by R ^3a represents a linear, branched or cyclic alkylene group, and may include an —O— bond or a —COO— bond. The alkylene group preferably has 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, and most preferably 1 to 3 carbon atoms. A plurality of R ^3a present in the group of formula (13) may be the same or different, and are preferably the same. These groups may or may not have a substituent, but preferably do not have a substituent. Specific examples of the alkylene group represented by R ^3a include an ethylene group.

As the substituent that R ^3a in Formula (13) may have, a hydroxyl group, an alkoxy group having 1 to 2 carbon atoms, or the like is preferable.

R ^3b in the formula (13) represents a hydrogen atom or an alkyl group. The alkyl group represented by R ^3b represents a linear, branched or cyclic alkyl group, preferably has 1 to 10 carbon atoms, more preferably has 1 to 6 carbon atoms, and most preferably has 1 to 3 carbon atoms. Specific examples of the alkyl group represented by R ^3b include a methyl group and an ethyl group.

  N3 in the formula (13) represents an integer of 4 to 50, more preferably 4 to 40, and still more preferably 5 to 30.

  The copolymerization ratio of the repeating unit of the formula (2) in the polymer (a) is preferably 40 to 95, more preferably 50 to 90, and more preferably 60 to 90 on a mass basis with respect to the polymer (a). 90 is most preferred.

  The structure represented by the general formula (2) can be obtained by polymerizing a monomer represented by the following general formula (2-1).

In the general formula ^{(2-1), R cy, Z} y, R y, A , said ^R in the general formula ^{(2) cy, Z y,} R y, and A, respectively, similarly, including preferred ranges and definition It is.

  Preferable examples of the monomer represented by the general formula (2-1) include, but are not limited to, the following exemplary compounds (2-1-1) to (2-1-12). Can do. Exemplary compounds (2-1-1) to (2-1-2) are monomers capable of forming a repeating unit having an amide group. (2-1-3) is a monomer capable of forming a repeating unit having a carbamoyl group. (2-1-4) to (2-1-6) are monomers that can form a repeating unit having an alkyl-substituted carbamoyl group. (2-1-7) to (2-1-9) are monomers that can form a repeating unit having a group having a polyalkyleneoxy structure. (2-1-10) is a monomer capable of forming a repeating unit having a residue obtained by removing one hydrogen atom from a heterocyclic ring containing a nitrogen atom or an oxygen atom as a hetero atom. (2-1-11) to (2-1-12) are monomers capable of forming a repeating unit having an alcoholic hydroxyl group. In addition, this invention is not limited to these exemplary compounds.

  The monomer represented by the formula (2-1) can be produced by a commercially available compound or a generally known method that is generally known.

  Furthermore, the monomer represented by the formula (2-1) may be subjected to a polymerization reaction using a monomer that gives a repeating unit in which a hydrophilic group is protected with a protective group. The polymer (a) of the present invention may be synthesized by polymerizing the monomer to form a polymer compound and then removing the protective group. For example, in order to introduce a repeating unit of polyvinyl alcohol as a hydrophilic group, use a method of polymerizing vinyl acetate and vinyl benzoate as monomers, performing a polymer reaction, and then hydrolyzing with alkali or acid. Can do.

  In the (a) polymer of the present invention, other monomer components can be used as the polymer in addition to the above-mentioned compounds. Examples of the other monomer that can be copolymerized with the monomer represented by the formula (1′-1) and the monomer represented by the formula (2-1) include styrene and p-methoxystyrene. , Methyl (meth) acrylate, ethyl (meth) acrylate, allyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate , Stearyl (meth) acrylate, cyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, 2-ethylhexylglycol (meth) acrylate, butoxyethyl (meth) acrylate, butoxymethyl (Meta) acryle 3-methoxybutyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) acrylate, 2- (2-butoxyethoxy) ethyl (meth) acrylate, 2,2,2-tetrafluoroethyl (meth) ) Acrylate, 1H, 1H, 2H, 2H-perfluorodecyl (meth) acrylate, 4-butylphenyl (meth) acrylate, phenyl (meth) acrylate, 2,4,5-tetramethylphenyl (meth) acrylate, 4- Chlorophenyl (meth) acrylate, phenoxymethyl (meth) acrylate, phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) acrylate, glycidyloxypropyl (meth) Acry Rate, butoxydiethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, p-sulfamoylphenyl (meth) acrylamide It is done. Monomers that can be copolymerized with the monomer represented by the formula (1′-1) include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2 -Alkyl (meth) acrylates having 1 to 8 carbon atoms such as ethylhexyl (meth) acrylate are preferred. In addition, well-known monomers other than the above can be used as necessary.

  (A) The polymer preferably has a structure represented by the following general formula (A ′).

(A ')

R ^a , R ^b , R ^c , Z and X in the general formula (A ′) are the same including the definition and preferred range in the formula (1 ′).
R ^cy , Z ^y , R ^y and A in the general formula (A ′) are the same including the definition and preferred range in the general formula (2).

The sum of a and b in the general formula (A ′) is 100.
In the general formula (A ′), a and b represent a copolymerization ratio in the polymer (a), and the sum of a and b is 100 (note that the copolymerization ratio is based on mass). A in the copolymerization ratio represents a copolymerization ratio of the repeating unit (a1) having a group represented by the formula (1), and b represents a copolymerization ratio of the repeating unit (a2) having a hydrophilic group. To express. Preferably 5 ≦ a ≦ 60 and 40 ≦ b ≦ 95, more preferably 10 ≦ a ≦ 50 and 50 ≦ b ≦ 90.

  The polymer (a) is not limited, but examples thereof include the following exemplary compounds (A-1) to (A-8), and (A-1) to (A-4) are preferable.

  (A) The polymer preferably has a weight average molecular weight of 2,000 to 100,000, more preferably a weight average molecular weight of 2,000 to 80,000, and most preferably 2,000 to 50,000.

The polymer (a) preferably has 8 or more groups represented by the formula (1) in one molecule of the polymer (a), more preferably 8 to 200, more preferably 10 It is more preferable to have ~ 150 or more, and most preferable to have 10 to 120. The polymer (a) preferably has 8 or more groups represented by the formula (1) from the viewpoint of fixability.
The number of the group represented by the formula (1) in the polymer can be determined from (a) the weight average molecular weight of the polymer and the copolymerization ratio. For example, it is a binary copolymer, and the copolymerization ratio of the repeating unit having a molecular weight M _{A to} the repeating unit having a molecular weight M _B is X ^A : X ^B , and the weight average molecular weight of the polymer When M is M _X , (a) the number of groups contained in the polymer can be calculated as {M _X * [X ^A / (X ^A + X ^B )]} / M _A (pieces).

The weight average molecular weight is measured by gel permeation chromatography (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation) and TSKgel Sup as the column.
erHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (4.6 mm ID × 15 cm, manufactured by Tosoh Corporation) and THF (tetrahydrofuran) as an eluent.

  As the exemplary compounds (A-1) to (A-8) in the present invention, the (a) polymer is known as a precursor represented by the above formula (1′-1) or (2-1). 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. Can be manufactured.

  (A) As content in the ink composition of a polymer, 1-40 mass% is preferable, 2-30 mass% is more preferable, 3-20 mass% is further more preferable.

In this invention, it discovered that the effect of this invention was acquired by using the said (a) polymer, (b) water, and (c) coloring material in an ink composition. Although the mechanism of the present invention is not clear, the present inventors infer as follows. It is inferred that the colorant and the pigment dispersant that disperses the colorant have improved dispersibility by utilizing charge repulsion. Since the hydrophilic group in the polymer (a) of the present invention hardly affects the dissociation of the ionic groups of the colorant and the pigment dispersant, it is considered difficult to reduce the charge repulsion of the colorant and the pigment. As a result, it is considered that the pigment dispersibility during ink preparation and ink storage can be kept good, and the ejection properties and the like are improved. Furthermore, it is considered that (a) the maleimide group in the polymer allows the crosslinking reaction to proceed efficiently and the effect of the present application is obtained.
The present invention is not limited to the above estimation mechanism.

<(C) Color material>
The ink composition of the present invention contains (c) a color material.
There is no restriction | limiting in particular as a color material which can be used for this invention, It can select from well-known color materials, such as a pigment, a water-soluble dye, a disperse dye, and can use it. Among these, as a coloring material, it is more preferable that a pigment is included.

(Pigment)
The pigment is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include known organic pigments and inorganic pigments. Resin particles dyed with dyes, commercially available pigment dispersions and surfaces Treated pigments (for example, pigments dispersed in water, liquid organic compounds or insoluble resins, and pigment surfaces treated with resins, pigment derivatives, etc.) are also included. Examples of the pigment include, for example, “The Pigment Dictionary” edited by Seijiro Ito (2000, published by Asakura Shoten), Isao Hashimoto “Organic Pigment Handbook” (2006, published by Color Office), Herbst, K.M. Hunger, “Industrial Organic Pigments” (published by Wiley-VHC in 1992), JP 2002-12607, JP 2002-188025, JP 2003-26978, JP 2003-342503, JP Examples described in Japanese Unexamined Patent Publication No. 2009-235370.

Examples of the organic pigment and the inorganic pigment include a yellow pigment, a red pigment, a magenta pigment, a blue pigment, a cyan pigment, a green pigment, an orange pigment, a purple pigment, a brown pigment, a black pigment, and a white pigment.
Examples of the yellow pigment include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 10, 65, 73, 74, 75, 97, 98, 111, 116, 130, 167, 205 and other monoazo pigments, 61, 62, 100, 168, 169, Monoazo lake pigments such as 183, 191, 206, 209, 212, 12, 13, 14, 16, 17, 55, 63, 77, 81, 83, 106, 124, 126, 127, 152, 155, 170, 172, Disazo pigments such as 174, 176, 214 and 219, anthraquinone pigments such as 24, 99, 108, 193 and 199, monoazopyrazolone pigments such as 60, condensed azo pigments such as 93, 95, 128 and 166, 109, 110, 139, 173, 185 and other isoindoline pigments, 120, 151, 154, 175, 180, 181, 194 and other benz Midazoron pigments, azomethine metal complex pigments such as 117,129,150,153, quinophthalone pigments such as 138, quinoxaline pigments 213 are preferred.

  Examples of the red or magenta pigment include C.I. I. Pigment Red 193 and other monoazo lake pigments, 38 and other disazo pigments, 2, 5, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 22, 23, 31, 32, 112, 114, Naphthol AS pigments such as 146, 147, 150, 170, 184, 187, 188, 210, 213, 238, 245, 253, 256, 258, 266, 268, 269, etc. β-naphthol pigments such as 3, 4, 6, etc. , 49, 53, 68 etc. β-naphthol lake pigments, 237, 239, 247 etc. naphthol AS lake pigments, 41 etc. pyrazolone pigments, 48, 52, 57, 58, 63, 64: 1, 200 etc. BONA Lake pigments, xanthene lake pigments such as 81: 1, 169, 172, thioindigo pigments such as 88, 181, 279, 123, 149, 17 8, 179, 190, 224 etc. perylene pigment, 144, 166, 214, 220, 221, 242, 262 etc. condensed azo pigment, 168, 177, 182, 226, 263 etc. anthraquinone pigment, 83 etc. anthraquinone lake Pigments, benzimidazolone pigments such as 171, 175, 176, 185, 208, quinacridone pigments such as 122, 202 (including mixtures with CI Pigment Violet 19), 207, 209, 254, 255, 264, Diketopyrrolopyrrole pigments such as 270 and 272 are preferred, and azomethine metal complex pigments such as 257 and 271 are preferred.

Examples of the blue or cyan pigment include C.I. I. Naphthol AS pigments such as CI Pigment Blue 25 and 26, phthalocyanine pigments such as 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17: 1, 75, and 79 Dye lake pigments such as 1:56, 61, 62, anthraquinone pigments such as 60, indigo pigments such as 63, and dioxazine pigments such as 80 are preferable.
Examples of the green pigment include C.I. I. Dye lake pigments such as CI Pigment Green 1, 4, 58, phthalocyanine pigments such as 7, 36, and azomethine metal complex pigments such as 8 are preferable.
Examples of the orange pigment include C.I. I. Monoazo pigments such as CI Pigment Orange 1, β-naphthol pigments such as 2, 3, 5 and the like, naphthol AS pigments such as 4, 24, 38 and 74, pyrazolone pigments such as 13, 34, 36, 60, 62, 64 and 72 Benzimidazolone pigments such as 15 and 16, disazo pigments such as 15 and 16, β-naphthol lake pigments such as 17 and 46, naphthalene sulfonic acid lake pigments such as 19; perinone pigments such as 43, quinacridone pigments such as 48 and 49, 51 Anthraquinone pigments such as 61, isoindolinone pigments such as 61, isoindoline pigments such as 66, azomethine metal complex pigments such as 68, and diketopyrrolopyrrole pigments such as 71, 73 and 81 are preferred.

Examples of the brown pigment include C.I. I. BONA lake pigments such as CI Pigment Brown 5, condensed azo pigments such as 23, 41 and 42, and benzimidazolone pigments such as 25 and 32 are preferred.
Examples of the purple pigment include C.I. I. Pigment violet 1, 2, 3, 27, etc. dyed lake pigments, 13, 17, 25, 50 etc. naphthol AS pigments, 5: 1 etc. anthraquinone lake pigments, 19 etc. quinacridone pigments, 23, 37 etc. dioxazine pigments A perylene pigment such as No. 29, benzimidazolone pigment such as No. 32, and a thioindigo pigment such as No. 38 are preferred.
Examples of the black pigment include C.I. I. Indazine pigments such as CI pigment black 1, carbon black as 7, graphite as 10, magnetite as 11, anthraquinone pigment as 20 and perylene pigment as 31 and 32 are preferable.
Examples of the white pigment include C.I. I. Pigment White 4 Zinc Oxide, 6 Titanium Oxide, 7 Zinc Sulfide, 12 Zirconium Oxide (Zirconium White), 18 Calcium Carbonate, 19 Aluminum Oxide / Silicon Oxide (Kaolin clay), 21 Or the barium sulfate which is 22, the aluminum hydroxide (alumina white) which is 23, the silicon oxide which is 27, and the calcium silicate which is 28 are preferable.
The inorganic particles used in the white pigment may be simple substances, or may be oxides such as silicon, aluminum, zirconium, and titanium, organometallic compounds, and composite particles with organic compounds.
Of these, the titanium oxide is preferably used. In addition to the titanium oxide, another white pigment (may be other than the above-described white pigment) may be used in combination.

Pigment particles, dispersants, and media so that the volume average particle diameter of the pigment particles is preferably 0.005 to 0.5 μm, more preferably 0.01 to 0.45 μm, and still more preferably 0.015 to 0.4 μm. Selection, dispersion conditions, and filtration conditions are preferably set.
In the present invention, the average particle size and particle size distribution of the particles are determined by dynamic light scattering using a commercially available particle size measuring device such as Nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.). It is obtained by measuring the volume average particle diameter by the method.

(Water-soluble dye)
Examples of water-soluble dyes that can be used in the present invention include acid dyes and direct dyes. Acid dyes and direct dyes have a structure having an acid group as a solubilizing group. Examples of the acidic group include a sulfonic acid group and a salt thereof, a carboxylic acid group and a salt thereof, and a phosphoric acid group and a salt thereof. The number of acidic groups may be one, multiple, or a combination. The chemical structure of the chromophore contained in the water-soluble dye includes azo, phthalocyanine, triphenylmethane, xanthene, pyrazolone, nitro, stilbene, quinoline, methine, thiazole, quinoneimine, and indigoid. Type, rhodamine type, anthraquinone type, anthraquinone type and the like.
Although not limited to the following, specific examples of preferable oil-soluble dyes include C.I. I. Acid Yellow 19, C.I. I. Acid Red 37, C.I. I. Acid Blue 62, C.I. I. Acid Orange 10, C.I. I. Acid Blue 83, C.I. I. Acid Black 01, C.I. I. Direct Yellow 44, C.I. I. Direct Yellow 142, C.I. I. Direct Yellow 12, C.I. I. Direct Blue 15, C.I. I. Direct Blue 25, C.I. I. Direct Blue 249, C.I. I. Direct Red 81, C.I. I. Direct Red 9, C.I. I. Direct Red 31, C.I. I. Direct black 154, C.I. I. Direct black 17 etc. are mentioned.

(Disperse dye)
In the present invention, a disperse dye can also be used.
Preferable specific examples of the disperse dye include C.I. I. Disperse Yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184: 1, 186, 198, 199, 201, 204, 224 and 237 C. I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; C.I. I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1, 177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse violet 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225 257, 266, 267, 287, 354, 358, 365 and 368; I. Disperse Green 6: 1 and 9 etc. are mentioned.

  Color materials that can be used in the present invention may be used alone or in combination of two or more.

  (C) The content of the color material in the ink composition is appropriately selected depending on the physical properties of the color material (specific gravity, coloring power, color, etc.), and how many colors of the ink composition are combined to produce a printed material. However, it is preferably 0.1 to 30% by mass and more preferably 0.5 to 20% by mass with respect to the mass of the entire ink composition.

(Dispersant)
When a pigment is used as a coloring material, a pigment dispersant may be used as necessary when preparing 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, styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, Le 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 of dissolving the pigment described in Japanese Patent Application Nos. 2000-377068, 2001-1495, and 2001-234966 in a solvent together with a pigment derivative, and crystallizing in a poor 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.

  As a method for dispersing the pigment, for example, various dispersing machines such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used. It is also preferable to use a centrifugal separator or a filter for the purpose of removing the coarse particles of the pigment dispersion.

  The preferred addition amount of the dispersant in the ink composition is such that the mass ratio (D / P) is P, where P is the mass of the pigment in the ink composition, and D is the mass of the polymer dispersant in the ink composition. 0.01 ≦ D / P ≦ 2.0 is preferable, 0.03 ≦ D / P ≦ 1.5 is more preferable, and 0.05 ≦ D / P ≦ 0.6 is satisfied. Is more preferable.

  Further, at the time of dispersion, in addition to the dispersing agent, a dispersing aid generally called synergist (for example, SOLPERSE series 5000, 12000, 22000, commercially available from Lubrizol, EFKA 6745, etc., commercially available from BASF Japan) It is also preferred to improve the dispersibility and wettability of the pigment by adding various surfactants and antifoaming agents.

In the present invention, when the pigment is dispersed, the pigment and the dispersant are mixed and then added to the polar organic solvent and dispersed, or the polar organic solvent and the dispersant are mixed and then the pigment is added. And dispersing. For the dispersion, for example, dispersion devices such as a ball mill, a bead mill, a sand mill, a salt mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used. Among these, a bead mill dispersing device is preferable because of its excellent dispersibility.
The beads used for the bead mill dispersion are preferably those having a volume average diameter of 0.01 to 3.0 mm, more preferably 0.05 to 1.5 mm, and still more preferably 0.1 to 1.0 mm. By using it, a pigment dispersion excellent in stability can be obtained.

<(B) Water>
The ink composition of the present invention contains water as a main solvent.
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 to 97% by mass, and in the case of the ink composition, it is preferably 30 to 95% by mass, and 35 to 93% by mass. % Is more preferable.

<Other additives>
In addition to the essential components (a) polymer, (b) water, and (c) coloring material, the ink composition of the present invention is used with known additives as long as the effects of the present invention are not impaired. can do. Hereinafter, additives that can be used in the ink composition will be described.

<Water-soluble organic solvent>
The ink composition of the present invention contains water as a main solvent, but it is preferable to further use a water-soluble organic solvent 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.),

-Amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentane Methyldiethylenetriamine, tetramethylpropylenediamine, etc.),
Amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.),
Heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, etc.)
・ Sulphoxides (for example, dimethyl sulfoxide),
-Sulfones (for example, sulfolane),
・ Others (urea, acetonitrile, acetone, etc.)

  Preferable water-soluble organic solvents include polyhydric alcohol ethers 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 and the like are preferable, and 2-pyrrolidone is particularly preferable. A solvent having a particularly 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 addition amount of the water-soluble organic solvent with respect to the total amount of the ink composition is not limited, but is preferably 1 to 60% by mass, and more preferably 2 to 35% 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. Polymer, 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.

(latex)
Latex can be added to the ink composition of the present invention. Examples of the latex that can be used in the present invention include styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylic acid ester copolymer, polyurethane, silicon-acrylic copolymer, and acrylic-modified fluorine-fatting. Latex. The latex may be a polymer particle dispersed using an emulsifier, or a so-called soap-free latex dispersed without using an emulsifier. A surfactant is often used as an emulsifier, but a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a single group having a solubilizing group) It is also preferable to use a polymer obtained from a monomer and a monomer having an insoluble part.

  The volume average particle size of the polymer particles in the latex used in the ink composition of the present invention is preferably 10 nm or more and 300 nm or less, and more preferably 10 nm or more and 100 nm or less. The average particle size of the polymer particles in the latex can be determined by a commercially available particle size measuring instrument using a light scattering method, an electrophoresis method, or a laser Doppler method.

  In the ink composition of the present invention, when latex is used, the addition amount is preferably 0.1% by mass to 20% by mass with respect to the total amount of the ink composition, and 0.5% by mass. It is still more preferable to set it as% -10 mass%.

(Aqueous polymer)
An aqueous polymer different from (a) the polymer can be added to the ink composition of the present invention. Preferable examples of the aqueous polymer include natural polymers, and specific examples thereof include proteins such as glue, gelatin, casein, or albumin, natural rubbers such as gum arabic or gum tragacanth, and glucosides such as saponin. And alginic acid and propylene glycol alginate, triethanolamine alginate, or alginic acid derivatives such as ammonium alginate, and cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, or ethylhydroxylcellulose.

  Other preferable examples of the aqueous polymer include synthetic polymers such as polyvinyl alcohols, polyvinylpyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, Acrylic resin such as vinyl acetate-acrylic acid ester copolymer or acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester Styrene acrylic resin such as copolymer, styrene-α-methylstyrene-acrylic acid copolymer, or styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene -Maleic anhydride copolymer, vinyl naphth Talen-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-croton Examples include acid copolymers, vinyl acetate copolymers such as vinyl acetate-acrylic acid copolymers, and salts thereof. Of these, nonionic aqueous polymers are preferred, and particularly preferred examples include polyvinylpyrrolidones.

The molecular weight of the aqueous polymer that can be used in the present invention is preferably 1,000 or more and 200,000 or less. Furthermore, 3,000 or more and 20,000 or less are more preferable.
The addition amount of the aqueous polymer is preferably 10% by mass or more and 1,000% by mass or less with respect to the dissolved pigment. Furthermore, 50 mass% or more and 200 mass% or less are more preferable.

(Polymerization initiator)
The ink composition of the present invention may contain a polymerization initiator as long as the effects of the present invention are not impaired. The polymerization initiator is preferably water-soluble, and the degree of water solubility is preferably 0.5% by mass or more, preferably 1% by mass or more, preferably 3% by mass in distilled water at 25 ° C. It is particularly preferable to dissolve the above. Moreover, it can be used even in a state where a non-aqueous polymerization initiator is dispersed.
In the present invention, it is preferable to use a polymerization initiator selected from the group consisting of α-hydroxyketones, α-aminoketones and acylphosphine oxides. Specifically, 1- [4- (2-hydroxyethyl) -phenyl] -2-hydroxy-2-methyl] -1-propan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2- A water-soluble polymerization initiator such as methyl-1-phenylpropan-1-one or a non-aqueous polymerization initiator of [bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide] can also be used. .

(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, particularly preferably 3% by mass or more, with respect to distilled water at room temperature. As the sensitizing dye, a polymerization 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. Further, a sensitizing dye described in JP 2010-24276 A and a sensitizing dye described in JP 6-107718 A can be suitably used.

(Polymerizable compound)
The ink composition of the present invention may contain a polymerizable compound. The polymerizable compound may be any water-soluble compound having at least one ethylenically unsaturated bond capable of radical polymerization in the molecule, and has a chemical form such as a monomer, oligomer or polymer. included. Only one type of the specific polymerizable compound may be used, or two or more types may be used in combination at an arbitrary ratio in order to improve the target characteristics. Preferably, two or more kinds are used in combination.

  The polymerizable compound used in the present invention dissolves at least 2% by mass or more in distilled water at room temperature, but preferably dissolves by 15% by mass or more, and particularly those that uniformly mix with water at an arbitrary ratio. preferable.

  Examples of the polymerizable compound include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and other unsaturated carboxylic acids and esters thereof, and salts thereof, anhydrous having an ethylenically unsaturated group. Products, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, unsaturated urethanes, vinyl ethers, allyl ethers, and the like, and acrylic acid, methacrylic acid and esters and salts thereof are preferred. These polymerizable compounds may be used alone or in combination of two or more.

  The polymerizable compound that can be used in the present invention may have a poly (ethyleneoxy) chain, a poly (propyleneoxy) chain, or an ionic group (for example, a carboxyl group, a sulfo group, etc.) in order to impart water solubility. preferable. In the case of having a poly (ethyleneoxy) chain and a poly (propyleneoxy) chain, the number of units of ethyleneoxy and propyleneoxy is preferably in the range of 1 to 10, more preferably in the range of 1 to 5.

  In addition to the above-described components, the ink according to the present invention includes various known additives, for example, a viscosity adjuster, a surface tension adjuster, a specific resistance adjuster, a film forming agent, and a dispersant as necessary. , Surfactants, ultraviolet absorbers, antioxidants, anti-fading agents, anti-corrosive agents, rust preventives, solid wetting agents, silica fine particles and the like can be appropriately selected and used, for example, liquid paraffin, dioctyl phthalate, Oil droplet fine particles such as tricresyl phosphate and silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, and 57- No. 878989, 60-72785, 61-146591, JP-A-1-95091, JP-A-3-13376, etc., JP-A-59-42993 , 59-52689, 62-280069, 61-242871, and JP-A-4-219266, etc., sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, hydroxide Examples thereof include pH adjusters such as potassium and potassium carbonate.

<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 resulting dispersion is mixed with the resin and the organic solvent. In this case, at the time of addition or after addition, the mixture is uniformly mixed with a simple stirrer such as a three-one motor, a magnetic stirrer, a disper, or a homogenizer. You may mix using mixers, such as a line mixer. Further, in order to make the dispersed particles finer, they may be mixed using a dispersing machine such as a bead mill or a high-pressure jet mill. Depending on the type of pigment or polymer dispersant, a resin may be added during premixing before pigment dispersion.

  The ink composition of the present invention preferably has a surface tension at 25 ° C. of 20 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.). Moreover, 1-40 mPa * s is preferable and, as for a viscosity, 3-30 mPa * s is more preferable. 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 application step of applying the ink composition onto a recording medium, and an irradiation step of irradiating the 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.

  There is no restriction | limiting in particular as an inkjet recording device used for the image forming method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and 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.
The ink supply system includes, for example, 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, and a piezo-type inkjet head. 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. In the present invention, dpi represents the number of dots per 2.54 cm.

In the ink composition of the present invention, it is desirable that the ejected ink composition is kept at a constant temperature. Therefore, the ink jet recording apparatus is preferably provided with 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 thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

  Using the above-described ink jet recording apparatus, the ink composition is ejected by heating the ink composition to preferably 25 to 80 ° C., more preferably 25 to 50 ° C., so that the viscosity of the ink composition is preferably 3 to 15 mPa. It is preferable to carry out after lowering to s, more preferably 3 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 well. 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 on which the above metals are laminated or deposited 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. By irradiating the ink composition of the present invention with active energy rays, the crosslinking reaction of the compound in the ink composition proceeds to fix the image and to improve the solvent resistance of the printed matter. By this irradiation step, (a) a crosslinking reaction of the polymer occurs, and a crosslinked structure of the following general formula (5) is formed in the ink composition.

In formula (5), R ^a , R ^b , R ^c and R ^d each independently represents an alkyl group having 1 to 4 carbon atoms, and R ^a and R ^b are bonded to each other to form a 4- to 6-membered ring. May be. R ^c and R ^d may combine with each other to form a 4- to 6-membered ring. R ^a and R ^b are the same as those described in formula (1), including the preferred range. R ^c is the same as R ^a described in formula (1), including a preferred range. R ^d is the same as R ^b described in formula (1), including a preferred range.

  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.

  The peak wavelength of UV light depends on the absorption characteristics of the sensitizing dye used as necessary, but is preferably 200 to 405 nm, more preferably 250 to 405 nm, and 250 to 390 nm, for example. More preferably.

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.

The ink composition of the present invention is suitably irradiated with such UV light, for example, for 0.01 seconds to 120 seconds, preferably 0.1 seconds to 90 seconds.
Irradiation conditions and basic irradiation methods are disclosed in JP-A-60-132767. 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. Irradiation with active energy rays is performed for a certain period of time after ink landing and thermal fixing (for example, 0.01 seconds to 60 seconds, preferably 0.01 seconds to 30 seconds, more preferably 0.01 seconds to 15 seconds). It will be done after.

(Heat drying process)
The ink composition ejected on the recording medium is preferably fixed by evaporating (b) water and a water-soluble organic solvent used in combination as required by the heating means. A process of fixing by applying heat to the discharged ink composition of the present invention 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 such that (b) water present in the ink composition and the water-soluble organic solvent used in combination as needed evaporate, and (a) a polymer and a polymer binder film added as necessary If it can form, there will be no restriction | limiting in particular, The effect will be acquired if it is 40 degreeC or more, About 40 to 150 degreeC is preferable, More preferably, it is about 40 to 80 degreeC.
The drying / heating time is not particularly limited as long as (b) water present in the ink composition and the water-soluble organic solvent used in combination as needed can be evaporated and a film of the resin agent can be formed. The ink composition can be set as appropriate in consideration of the composition and printing speed of the ink composition to be used.
The solvent-type ink composition fixed by heating can be further photofixed by irradiating with active energy rays, if necessary.

  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.

  The pigment dispersion and ink composition material used in Examples and Comparative Examples are shown below.

<Synthesis of Polymer Dispersant D-1>
To a 500 ml three-necked flask equipped with a stirrer and a condenser tube, 44 g of methyl ethyl ketone was added and heated to 72 ° C. in a nitrogen atmosphere. Here, 25 g of methyl ethyl ketone was mixed with 0.43 g of dimethyl 2,2′-azobisisobutyrate and 30 g of benzyl methacrylate. Then, a solution in which 5 g of methacrylic acid and 15 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.21 g of dimethyl 2,2′-azobisisobutyrate dissolved in 1 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess amount of hexane, and the deposited resin was dried to obtain 43 g of polymer dispersant D-1.
The composition of the obtained resin was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) determined by GPC was 42,000. Furthermore, when the acid value was calculated | required by the method as described in JIS specification (JISK0070: 1992), it was 65.4 mgKOH / g.

<Preparation of dispersion of resin-coated pigment>
(Resin-coated cyan pigment dispersion (C))
Pigment Blue 15: 3 (phthalocyanine blue A220, manufactured by Dainichi Seika Co., Ltd.), 5 parts of the above polymer dispersant D-1, 42 parts of methyl ethyl ketone, 5.5 parts of 1 mol / L NaOH aqueous solution, Then, 87.2 parts of ion-exchanged water was mixed and dispersed with a bead mill using 0.1 mmφ zirconia beads for 2 to 6 hours.
Methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion (C) of a resin-coated cyan pigment having a pigment concentration of 10.2% by mass. .

(Resin-coated magenta pigment dispersion (M))
In the preparation of the resin-coated cyan pigment dispersion, the resin coating was carried out in the same manner as above except that Chromathal Jet Magenta DMQ (Pigment Red 122, manufactured by BASF Japan Ltd.) was used instead of phthalocyanine blue A220 used as the pigment. A magenta pigment dispersion (M) was obtained.

(Resin-coated yellow pigment dispersion (Y))
Resin-coated yellow was prepared in the same manner as described above except that Irgalite Yellow GS (Pigment Yellow 74, manufactured by BASF Japan Ltd.) was used instead of phthalocyanine blue A220 used as a pigment in the preparation of the resin-coated cyan pigment dispersion. A pigment dispersion (Y) was obtained.

(Resin-coated black pigment dispersion (K))
In the preparation of the resin-coated cyan pigment dispersion, a resin was obtained in the same manner as above except that the pigment dispersion CAB-O-JETTM 200 (carbon black, manufactured by CABOT) was used instead of the phthalocyanine blue A220 used as the pigment. A dispersion (K) of coated black pigment was obtained.

<(A) Polymer>
The polymer (a) was synthesized with reference to JP-A-52-988. (A) Each structure of the polymer is shown below.

<Water-soluble organic solvent>
・ 2-Pyrrolidone (manufactured by Sigma-Aldrich Japan)
・ Dipropylene glycol monomethyl ether (Sigma Aldrich Japan Co., Ltd.)

<Comparative compound>
Comparative compounds (P-1) and (P-2) were synthesized with reference to JP-A 52-988, and (P-3) was synthesized with reference to JP-A 2007-119449.

(Comparative Compound P-1)

(Comparative Compound P-2)

(Comparative compound P-3, molecular weight 370)

<Polymerization initiator>
The polymerization initiator in Table 1 represents Irgacure 2959 (manufactured by BASF Japan).

<Polymerizable compound>
The polymerizable compound in Table 1 represents NK ester A-400 (poly (ethylene glycol) diacrylate, Mn400, manufactured by Shin-Nakamura Chemical Co., Ltd.).
<Surfactant>
The surfactant in Table 1 represents Glide 100 (manufactured by Tego Chemical Service).
<Sensitizer>
The sensitizers in Table 1 are N- [hydroxy-3- (3,4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy) propyl] -N, N, N-trimethylaminium chloride ( Sigma Aldrich Japan).

  Of the compounds used in Examples and Comparative Examples, compounds not described by the manufacturer were synthesized by applying known methods or known methods.

<Preparation of ink composition>
Using the obtained dispersions (C dispersion, M dispersion, Y dispersion, K dispersion), the ink compositions of Examples 1 to 9 and Comparative Examples 1 to 4 having the compositions shown in Table 1 below were used. The mixture was stirred at 2,500 rpm using a mixer (Silverson L4R) to prepare each.
The obtained ink composition was packed in a plastic disposable syringe and filtered through a 5 μm pore size filter made of polyvinylidene fluoride (PVDF) (Millex-SV, Millipore, diameter 25 mm) to obtain a finished ink.

The obtained ink was used as a K hand coater manufactured by RK PRINT COAT INSTRUMENTS No. Using 2 bars, it was applied to a vinyl chloride sheet (Avery 400 GLOSS WHITE PERMANENT, manufactured by Avery Dennison) at a thickness of 12 μm. Further, the moisture was dried at 60 ° C. for 3 minutes.
Using the obtained coating film, the following fixability was evaluated. The evaluation results are shown in Table 1.

<Fixability evaluation>
The obtained coating film was exposed with a Deep UV lamp (US-7, SP-7) under the condition of energy of 1000 mJ / cm ² . The degree of fixation on the film surface was evaluated by palpation. When the stickiness remained, the exposure was repeated until the stickiness disappeared, and the fixability was evaluated by the exposure amount until the stickiness disappeared.
A: No stickiness after 2 exposures B: No stickiness after 2 to 3 exposures C: No stickiness after 4-5 exposures D: No stickiness after 6 or more exposures

  Each ink composition obtained and the printed matter produced by the evaluation of the fixing property were used, and the solvent resistance was evaluated. The evaluation results are shown in Table 1.

<Solvent resistance evaluation>
A coating film similar to the coating film used in the evaluation of the fixing property was formed, and further exposed with a Deep UV lamp (US-7, SP-7) under an energy condition of 8000 mJ / cm ² . The surface of the printed material exposed under an energy condition of 8000 mJ / cm ² was rubbed with a cotton swab impregnated with isopropyl alcohol and evaluated according to the following criteria.
A: Even after rubbing 10 times or more, no change was observed in the image.
B: Image density decreased after 5 to 9 rubbing.
C: Image density decreased after 2-4 rubbing.
D: Image density was significantly reduced by just rubbing once.

<Ejection evaluation>
A commercially available inkjet printer (SP-300V manufactured by Roland DG Inc.) was prepared as an inkjet recording apparatus. Each obtained ink composition was loaded into the above-mentioned ink jet printer, and ejected from a head to a vinyl chloride sheet (Avery 400 GLOSS WHITE PERMANENT, manufactured by Avery Dennison Co., Ltd.) for 30 minutes in a standard printing mode. Recorded. After stopping the discharge, the obtained image was left for 5 minutes. Thereafter, an image (5 cm × 5 cm) obtained by recording a solid image and a fine line again in the standard printing mode was observed. The observed images were visually evaluated according to the following evaluation criteria.
A: The occurrence of missing dots due to the occurrence of missing or the like was not recognized, and a good image was obtained.
B: Although the occurrence of missing dots due to the occurrence of omission was slightly observed, it was of a level that would not cause any practical problems.
C: The image lacked practical use due to the occurrence of missing dots due to the occurrence of omission.
D: Unable to discharge.

<Storage stability evaluation>
The obtained ink composition was sealed in a container and allowed to elapse for 2 weeks at 60 ° C., and then the same evaluation as the above-described dischargeability evaluation was performed, and the evaluation was performed based on the same criteria.

  As represented by Example 3 and Example 4 in Table 1 above, the ink composition containing the water-soluble organic solvent had excellent effects of the present application. Further, as can be seen from Example 7 and Example 8 and the like, the effect of the present application was further improved by having a sensitizer. Further, as shown in Table 1, in the examples of the present invention, excellent effects were obtained in any of the fixing property, solvent resistance, ejection property and storage stability.

Claims (13)

(A) a nonionic polymer having a repeating unit (a1) having a group represented by the following formula (1) and a repeating unit (a2) having a hydrophilic group;
(B) water, and (c) an ink composition having a coloring material.

(In Formula (1), R ^a and R ^b each independently represents an alkyl group having 1 to 4 carbon atoms, and R ^a and R ^b may be bonded to each other to form a 4- to 6-membered ring. )   The hydrophilic group in the repeating unit (a2) in the polymer (a) is at least one selected from the group consisting of an amide group, a carbamoyl group, an alkyl-substituted carbamoyl group, an alcoholic hydroxyl group, and a group having a polyalkyleneoxy structure. The ink composition according to claim 1, wherein The ink composition according to claim 2, wherein the amide group is a group represented by the following formula (11).

Formula (11)
(In (Formula 11), R ^1a and R ^1b each independently represent a hydrogen atom or an alkyl group. R ^1a and R ^1b may combine with each other to form a 4- to 6-membered ring. * Indicates the bonding position.) The ink composition according to claim 2, wherein the alkyl-substituted carbamoyl group is a group represented by Formula (12).

Formula (12)
(In (Formula 12), R ^2a and R ^2b each independently represents a hydrogen atom or an alkyl group. R ^2a and R ^2b may be bonded to each other to form a 4- to 6-membered ring. Indicates the bonding position.) The ink composition according to claim 2, wherein the group having the polyalkyleneoxy structure is a group represented by the formula (13).

Formula (13)
(In Formula (13), R ^3a represents an alkylene group, R ^3b represents a hydrogen atom or an alkyl group. N3 represents an integer of 4 to 50. Plural R ^{3a s} may be the same or different. (* Indicates a bonding position.)   The ink composition according to any one of claims 1 to 5, which has 8 or more groups represented by the formula (1) in one molecule of the polymer (a). The ink composition according to claim 1, wherein the repeating unit (a1) has a structure represented by the following general formula (1 ′).

(In the general formula (1 ′), R ^a and R ^b each independently represents an alkyl group having 1 to 4 carbon atoms, and R ^a and R ^b may be bonded to each other to form a 4- to 6-membered ring. Good.
Z represents a single bond, —COO— * or —CONR ^d — *, and R ^d represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. In addition, * represents the position couple | bonded with X.
X represents an alkylene group. R ^c represents a hydrogen atom or a methyl group. )   The ink composition according to any one of claims 1 to 7, further comprising (d) a water-soluble organic solvent.   The ink composition according to any one of claims 1 to 8, wherein the content of the water (b) is 10% by mass to 97% by mass with respect to the total amount of the ink composition.   The ink composition according to any one of claims 1 to 9, wherein a copolymerization ratio of the repeating unit having a hydrophilic group in the (a) polymer is 30 or more and 90 or less. The ink composition according to claim 1, wherein the repeating unit (a2) has a structure represented by the following general formula (2).

(In the formula (2), 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 having 1 to 4 carbon atoms. It represents a group. Incidentally, * is .A representative of the group .R ^y that represents a position bonded with R ^y selected from the group consisting of a single bond, an alkylene group, an arylene group and aralkylene group represents a hydrophilic group.)   The ink composition according to any one of claims 1 to 11, further comprising a surfactant. An ink application step of applying the ink composition according to any one of claims 1 to 12 onto a recording medium;
An irradiation step of irradiating the applied ink composition with active energy rays.