JP2011084643A - Composite self-dispersible polymer aqueous dispersion, process for producing the same, aqueous ink composition, ink set and image-forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous ink composition having excellent ink stability, discharge stability, and good fixing properties. <P>SOLUTION: The aqueous ink composition is constituted of a composite self-dispersible polymer aqueous dispersion which is obtained from a mixed solution including a first water-insoluble polymer having an acidic group and a second water-insoluble polymer having an acidic group and an acid value different from the acid value of the first water-insoluble polymer by 8 or more and water, contains the first water-insoluble polymer and the second water-insoluble polymer, and includes composite particles having a volume average particle diameter of 0.1-80 nm and a coloring agent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an aqueous composite self-dispersing polymer dispersion and a method for producing the same, an aqueous ink composition, an ink set, and an image forming method.

  The ink jet recording method performs recording by ejecting ink droplets from a large number of nozzles formed on an ink jet head, and the noise during the recording operation is low, the running cost is low, and various recording media are used. On the other hand, it is widely used because it can record high-quality images.

  By the way, carbon black pigment is used for black ink in inkjet ink, but water-soluble dye is central in color ink, and weather resistance (for example, light resistance, ozone resistance, water resistance) is improved. Is required. In particular, when considering application to the printing field, improvement in weather resistance is particularly important. The pigment is inherently high in fastness due to its high crystallinity, and has excellent light resistance and water resistance compared to dyes. However, there are problems such as dischargeability due to clogging of the nozzle part, storage stability such as coagulation sedimentation, and further fixing of printed matter such as abrasion resistance and glossiness due to particles remaining on the surface of the recording medium. It is left.

  As a fixability improving technique, a self-dispersible copolymer obtained by copolymerizing an unsaturated monomer having an aliphatic hydrocarbon group having 14 to 20 carbon atoms, a benzyl methacrylate monomer, and a styrene monomer. An aqueous inkjet recording liquid in which a polymer is used in the form of a hydrosol or an emulsion in an aqueous inkjet recording liquid is disclosed (for example, see Patent Document 1). This recording liquid has good storage stability, maintains a high printing density and printing quality even when it is given quick drying by osmotic drying, and is also excellent in friction resistance and water resistance.

  In addition, a water-based ink for ink jet recording containing self-dispersing pigments and self-emulsifying polymer particles containing a structural unit derived from an aromatic group-containing monomer is disclosed (for example, see Patent Document 2). The ink is said to be excellent in gloss when printed on special paper while satisfying a high printing density.

JP 2002-88285 A JP 2006-283003 A

  However, although the aqueous dispersion-containing inks described in Patent Document 1 and Patent Document 2 have a certain degree of fixability improvement effect, it may be difficult to obtain a stable aqueous dispersion. Even when a stable aqueous dispersion is obtained, the viscosity of the aqueous dispersion may be high, and for example, it is difficult to apply to an inkjet ink.

  The present invention relates to a composite self-dispersing polymer aqueous dispersion excellent in dispersion stability and a method for producing the same, an aqueous ink composition excellent in ink stability and fixability, an ink set including the aqueous ink composition, and an image. It is an object to provide a forming method.

Specific means for solving the above problems are as follows.
<1> a mixed solution containing a first water-insoluble polymer having an acidic group and a second water-insoluble polymer having an acidic group and an acid value different from that of the first water-insoluble polymer by 8 or more A self-dispersing polymer aqueous dispersion containing composite particles obtained from water and containing the first water-insoluble polymer and the second water-insoluble polymer and having a volume average particle size of 0.1 nm to 80 nm .
<2> The composite self-dispersing polymer aqueous dispersion according to <1>, wherein both the first water-insoluble polymer and the second water-insoluble polymer are vinyl polymers.
<3> The composite self-dispersing polymer aqueous dispersion according to <1> or <2>, wherein the composite self-dispersing polymer aqueous dispersion aggregates due to a change in pH environment.
<4> The composite self-dispersing polymer aqueous dispersion according to any one of <1> to <3>, wherein the acidic groups in the first water-insoluble polymer and the second water-insoluble polymer are both carboxyl groups. object.
<5> Both the first water-insoluble polymer and the second water-insoluble polymer contain a hydrophobic constituent unit, and at least one of the hydrophobic constituent units is at least one of an acrylate monomer and a methacrylic ester monomer. The composite self-dispersing polymer aqueous dispersion according to any one of <1> to <4>, which is a structural unit derived from a seed.

<6> An aqueous ink composition comprising the composite self-dispersing polymer aqueous dispersion described in any one of the above items <1> to <5> and a colorant.

<7> A mixed solution of a first water-insoluble polymer having an acidic group and a second water-insoluble polymer having an acidic group and an acid value different from that of the first polymer by 8 or more and water A composite self-dispersing polymer aqueous dispersion comprising a step of obtaining composite particles containing the first water-insoluble polymer and the second water-insoluble polymer, wherein the composite particles have a volume average particle size of 0.1 nm to 80 nm. Manufacturing method.
<8> An ink set comprising the water-based ink composition according to <6> and a treatment liquid capable of forming an aggregate by contact with the water-based ink composition.

<9> An ink application step for applying the aqueous ink composition according to <6> to a recording medium, and a heat fixing step for fixing the image by heating the recording medium to which the aqueous ink composition has been applied. An image forming method.
<10> The image formation according to <9>, further including a treatment liquid application step of applying a treatment liquid capable of forming an aggregate by contact with the aqueous ink composition according to <6> to a recording medium. Method.

  According to the present invention, a composite self-dispersing polymer aqueous dispersion excellent in dispersion stability and a method for producing the same, an aqueous ink composition excellent in ink stability and fixability, an ink set including the aqueous ink composition, and An image forming method can be provided.

<Composite self-dispersing polymer aqueous dispersion>
The aqueous dispersion of the composite self-dispersing polymer of the present invention has a first water-insoluble polymer having acidic groups and a second water-insoluble polymer having acidic groups and an acid number different from that of the first water-insoluble polymer by 8 or more. A composite particle obtained from a mixed solution containing the water-insoluble polymer and water and containing the first water-insoluble polymer and the second water-insoluble polymer and having a volume average particle size of 0.1 nm to 80 nm. An aqueous dispersion of a composite self-dispersing polymer.
The composite self-dispersing polymer is configured to include composite particles containing two kinds of water-insoluble polymers having a difference in acid value of 8 or more, so that the volume average particle diameter is 0.1 nm or more and 80 nm or less, An aqueous dispersion of a composite self-dispersing polymer having excellent dispersion stability can be formed. This is because, for example, a polymer having a low acid value is arranged inside the composite self-dispersing polymer particle and a polymer having a high acid value is arranged outside, so that a structure suitable for dispersion can be obtained. It can be considered that the stability of the particle shape of the particles and the dispersion stability are compatible at a high level.

  In the present invention, the composite self-dispersing polymer is an acid having at least one kind of the first water-insoluble polymer having an acidic group and an acid group having a difference of 8 or more from the acid value of the first water-insoluble polymer. And at least one second water-insoluble polymer exhibiting a value, and other polymers as necessary. The composite self-dispersing polymer is a composite of two or more water-insoluble polymers, and is a polymer having self-dispersibility as a composite (hereinafter sometimes referred to as “self-dispersing polymer”).

The self-dispersing polymer in the present invention refers to a water-insoluble polymer that can be dispersed in an aqueous medium by a hydrophilic functional group (preferably a dissociable group or a salt thereof) of the polymer itself. The dispersed state here refers to an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in an aqueous medium and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in a solid state in an aqueous medium. It includes both states.
The self-dispersing polymer is preferably a self-dispersing polymer that can be in a dispersed state in which a water-insoluble polymer is dispersed in a solid state, for example, from the viewpoint of ink fixability when contained in an aqueous ink composition.

  In the present invention, the dispersion state of the self-dispersing polymer means a solution in which 30 g of a water-insoluble polymer is dissolved in 70 g of an organic solvent (for example, methyl ethyl ketone), a neutralizing agent that can neutralize 100% of the dissociable group of the water-insoluble polymer ( After the salt-forming group is anionic, sodium hydroxide, acetic acid if it is cationic) and 200 g of water are mixed and stirred (apparatus: stirring apparatus with stirring blades, rotation speed 200 rpm, 30 minutes, 25 ° C.) It means a state in which even after removing the organic solvent from the mixed solution, it can be visually confirmed that the dispersed state exists stably at 25 ° C. for at least one week.

  The water-insoluble polymer means a polymer having a dissolution amount of 10 g or less when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., and the dissolution amount is preferable. Is 5 g or less, more preferably 1 g or less. The dissolution amount is the dissolution amount when neutralized with sodium hydroxide or acetic acid 100% according to the type of dissociable group of the water-insoluble polymer.

The aqueous dispersion of the composite self-dispersing polymer of the present invention (hereinafter sometimes referred to as “composite particles”) has a first water-insoluble polymer (hereinafter referred to as “the composite particle”) having both acidic groups and having an acid value difference of 8 or more. Manufactured from a solution containing a second water-insoluble polymer (hereinafter sometimes simply referred to as “second polymer”) and water. The dispersion stability of the composite particles thus improved is improved. For example, the ink stability and the ejection stability of the aqueous ink composition containing the composite particles are improved.
In the present invention, the composite self-dispersing polymer aqueous dispersion includes a first polymer and a second polymer having an acid value (mgKOH / g) difference of 8 or more, but the acid value difference is 8 or more and 80 or less. More preferably, it is 20 or more and 80 or less. If the difference between the acid value of the first polymer and the acid value of the second polymer is less than 8, sufficient ink stability and ejection stability may not be obtained.
In addition, the acid value in this invention is measured by the method as described in JIS specification (JISK0070: 1992).
Hereinafter, among the first polymer and the second polymer, a polymer having a larger acid value may be referred to as a high acid value polymer, and a polymer having a smaller acid value may be referred to as a low acid value polymer.

  The acid values of the first polymer and the second polymer contained in the composite self-dispersing polymer aqueous dispersion are determined according to the self-dispersibility, the content of the water-soluble component, and the fixability when the aqueous ink composition is constituted. From the viewpoint of promoting the aggregation reaction by changing the pH environment (for example, contact with an acidic treatment solution), it is preferably 20 or more and 200 or less independently, more preferably 22 or more and 150 or less. preferable. When the acid value is 20 or more, the particles can be more stably dispersed, and when the acid value is 200 or less, water-soluble components can be reduced, and a stable dispersion state can be easily maintained.

  The mass ratio of the first polymer to the second polymer (high acid value polymer / low acid value polymer) in the composite self-dispersing polymer is preferably 1/99 to 99/1, and preferably 5/95 to 95 /. 5 is more preferable, and 1/9 to 9/1 is still more preferable. When the mass ratio between the first polymer and the second polymer is in the above range, formation of more stable composite particles is promoted more effectively.

  In the composite self-dispersing polymer in the present invention, the first polymer and the second polymer, both having an acid value of 20 or more and 200 or less and a difference in acid value of 8 or more and 80 or less, are converted into The polymer mass ratio (high acid value polymer / low acid value polymer) is preferably 1/99 to 99/1, the acid values are both 22 or more and 150 or less, and the acid value difference is 20 or more and 80 or less. It is more preferable that the 1st polymer and 2nd polymer which are these are 5 / 95-5 / 95 by mass ratio of the high acid value polymer with respect to a low acid value polymer.

In the present invention, the first polymer and the second polymer constituting the composite self-dispersing polymer are not particularly limited in structure as long as the acid value difference is 8 or more and is water-insoluble.
The first and second polymers are preferably vinyl polymers from the viewpoint of dispersion stability, and the first and second polymers are each composed of at least one hydrophilic constituent unit and hydrophobic. A vinyl polymer containing at least one of the structural units is more preferable. The hydrophilic structural unit and the hydrophobic structural unit may be the same or different in the first polymer and the second polymer, respectively.
Furthermore, at least one of the hydrophobic structural units is preferably a structural unit derived from a monomer having an ethylenically unsaturated bond from the viewpoint of dispersion stability, and is preferably an acrylate monomer or a methacrylate ester. More preferably, it is a structural unit derived from at least one selected from monomers.

  Specific examples of the monomer constituting the hydrophobic structural unit include styrene, α-methylstyrene, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert- Butyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, tert-octyl acrylate, 2-chloroethyl acrylate, 2-bromoethyl acrylate, 4-chlorobutyl acrylate, cyanoethyl acrylate, 2-acetoxyethyl acrylate, benzyl Acrylate, methoxybenzyl acrylate, 2-chlorocyclohexyl acrylate, cyclohexyl acrylic , Furfuryl acrylate, tetrahydrofurfuryl acrylate, phenyl acrylate, 2-phenoxyethyl acrylate, 5-hydroxypentyl acrylate, 2,2-dimethyl-3-hydroxypropyl acrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, 2- (2-methoxyethoxy) ethyl acrylate, 2- (2-butoxyethoxy) ethyl acrylate, glycidyl acrylate, 1-bromo-2-methoxyethyl acrylate, 1, 1-dichloro-2-ethoxyethyl acrylate, 2,2,2-tetrafluoroethyl acrylate, 1H, 1H, 2H, 2H-perfluorodecyl acrylate, methyl meta Acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, amyl methacrylate, hexyl methacrylate, benzyl methacrylate, chlorobenzyl methacrylate, octyl methacrylate, stearyl methacrylate, 2- (3-phenylpropyloxy) ethyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate, phenyl methacrylate, 2-phenoxyethyl methacrylate, cresyl methacrylate, naphthyl methacrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl methacrylate, tri ethylene Recall monomethacrylate, dipropylene glycol monomethacrylate, 2-methoxyethyl methacrylate, 3-methoxybutyl methacrylate, 2-ethoxyethyl methacrylate, methoxydiethylene glycol methacrylate, 2-iso-propoxyethyl methacrylate, 2-butoxyethyl methacrylate, 2- (2 -Methoxyethoxy) ethyl methacrylate, 2- (2-ethoxyethoxy) ethyl methacrylate, 2- (2-butoxyethoxy) ethyl methacrylate, 2-acetoxyethyl methacrylate, 2-acetoacetoxyethyl methacrylate, allyl methacrylate, glycidyl methacrylate, 2, 2,2-tetrafluoroethyl methacrylate, 1H, 1H, 2H, 2H-perfluorodecylmeta Relate and the like.

  Furthermore, other specific examples of the monomer constituting the hydrophobic structural unit include ester derivatives of acrylic acid and methacrylic acid having a cyclic aliphatic group. Specific examples of the cycloaliphatic group include cyclohexyl, cyclohexylmethyl, 3-cyclohexenylmethyl, 4-isopropylcyclohexyl, 1-methylcyclohexyl, 2-methylcyclohexyl, 3-methylcyclohexyl, 4-methylcyclohexyl, and 1-ethyl. Cyclohexyl, 4-ethylcyclohexyl, 2-tert-butylcyclohexyl, 4-tert-butylcyclohexyl, menthyl, 3,3,5-trimethylcyclohexyl, cycloheptyl, cyclooctyl, nonyl, cyclodecyl, 2-norbornyl, isobornyl, 3- Methyl-2-norbornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl, adamantane-1-yl, adamantane-2-yl, 2-methyladamantane 2-yl, 1-ethyl-2-yl and 3,5-dimethyl adamantane-yl, such as 1,1'-bis adamantan-3-yl.

  In the present invention, the content of the hydrophobic structural unit contained in the first polymer and the second polymer is preferably independently 30 to 96% by mass, and preferably 40 to 96% by mass. More preferred.

Both the first polymer and the second polymer in the present invention have at least one acidic group. Examples of the acidic group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group, and among them, a carboxyl group is preferable from the viewpoint of fixability when an aqueous ink composition is formed.
In addition, the acidic groups contained in the first polymer and the second polymer may each be a single type or a combination of two or more types. Furthermore, the acidic groups in the first polymer and the second polymer may be the same or different.

The acidic group is preferably contained in the first polymer and the second polymer as part of a hydrophilic structural unit, and the hydrophilic structural unit is derived from a monomer having an ethylenically unsaturated bond and an acidic group. More preferably.
Examples of the monomer having an ethylenically unsaturated bond and an acidic group (hereinafter sometimes referred to as “acidic group-containing monomer”) include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer. Can be mentioned.

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

  The content ratio of the structural unit derived from the acidic group-containing monomer in the first polymer and the second polymer corresponds to the preferred acid value range and acid value difference of the first polymer and the second polymer described above. It can be set as the content rate to do. Specifically, for example, 4 to 30% by mass is preferable, and 4 to 23% by mass is more preferable.

Moreover, the 1st polymer and 2nd polymer in this invention may contain at least 1 sort (s) of the hydrophilic structural unit which does not have an acidic group, respectively. As a hydrophilic structural unit which does not have an acidic group, the hydrophilic structural unit containing a nonionic group can be mentioned, for example. Moreover, as a nonionic group, a hydroxyl group, an alkyleneoxy group, its polymer, etc. can be mentioned, for example.
As a content rate of the hydrophilic structural unit which does not have an acidic group in a said 1st polymer and a 2nd polymer, it is preferable that it is 0-40 mass% from a viewpoint of dispersion stability, respectively, and 0-30 mass%. It is more preferable that

The molecular weight ranges of the first polymer and the second polymer in the present invention are each a weight average molecular weight, preferably 3000 to 200,000, more preferably 5000 to 150,000, and 10,000 to 100,000. More preferably. By setting the weight average molecular weight to 3000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-emulsification stability can be improved by making a weight average molecular weight or less into 200,000.
The weight average molecular weight can be measured by gel permeation chromatography (GPC).

  Specific examples of the first and second polymers in the present invention are exemplified compounds B-01 to B-19, but the present invention is not limited to these. In addition, the parenthesis represents the mass ratio of the copolymerization component.

B-01: Methyl methacrylate / methoxyethyl acrylate / benzyl methacrylate / methacrylic acid copolymer (44/15/35/6) Acid value 38.9
B-02: Methyl methacrylate / benzyl acrylate / phenoxyethyl methacrylate / acrylic acid copolymer (50/15/30/5) Acid value 38.9
B-03: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/50/5) Acid value 38.9
B-04: Isobutyl methacrylate / phenoxyethyl acrylate / benzyl methacrylate / methacrylic acid copolymer (43/16/35/6) Acid value 38.9
B-05: Methyl methacrylate / phenoxyethyl methacrylate / benzyl methacrylate / methacrylic acid copolymer (45/23/26/6) Acid value 38.9
B-06: Methyl methacrylate / benzyl methacrylate / methacrylic acid copolymer (39/55/6) Acid value 38.9
B-07: benzyl acrylate / methyl methacrylate / acrylic acid copolymer (55/40/5) Acid value 38.9
B-08: Phenoxyethyl methacrylate / benzyl acrylate / methacrylic acid copolymer (45/47/8) Acid value 51.8
B-09: Styrene / phenoxyethyl acrylate / butyl methacrylate / acrylic acid copolymer (5/48/40/7) Acid value 54.5
B-10: benzyl methacrylate / isobutyl methacrylate / cyclohexyl methacrylate / methacrylic acid copolymer (35/30/30/5) Acid value 32.4
B-11: Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (38/52/10) Acid value 64.8
B-12: Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (40/52/8) Acid value 51.8
B-13: Methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (34/52/14) Acid value 90.8
B-14: Methyl methacrylate / methoxyethyl acrylate / benzyl methacrylate / methacrylic acid copolymer (44/13/35/8) Acid value 51.8
B-15: Methyl methacrylate / methoxyethyl acrylate / benzyl methacrylate / methacrylic acid copolymer (38/13/35/14) Acid value 90.8
B-16: Methyl methacrylate / methoxyethyl acrylate / benzyl methacrylate / methacrylic acid copolymer (36/13/35/16) Acid value 103.6
B-17: Methyl methacrylate / benzyl methacrylate / methacrylic acid copolymer (58/35/7) Acid value 45.4
B-18: Isobutyl methacrylate / phenoxyethyl acrylate / benzyl methacrylate / methacrylic acid copolymer (17/16/35/32) Acid value 207.4
B-19: Methyl methacrylate / benzyl methacrylate / methacrylic acid copolymer (48/50/2) Acid value 13.0

  In the present invention, examples of the combination of the first polymer and the second polymer include, for example, those configured by appropriately selecting from the above exemplary compounds so that the difference in acid value is 8 or more.

  There is no restriction | limiting in particular as the synthesis | combining method of the 1st and 2nd polymer in this invention, It can synthesize | combine by copolymerizing a monomer mixture by well-known polymerization methods, such as a solution polymerization method and a block polymerization method. Among these polymerization methods, the solution polymerization method is preferable from the viewpoint of droplet ejection stability when an aqueous ink composition is used. For example, the first and second polymers can be synthesized by copolymerizing a monomer mixture and, if necessary, a mixture containing an organic solvent and a radical polymerization initiator in an inert gas atmosphere. .

  Further, the volume average particle size of the composite self-dispersing polymer in the present invention is in the range of 0.1 to 80 nm, more preferably 0.2 to 60 nm, and further preferably 0.3 to 40 nm. When the volume average particle size is 0.1 nm or more, the production suitability is improved and the viscosity of the aqueous dispersion can be suppressed. Moreover, storage stability improves by setting it as the volume average particle diameter of 80 nm or less. On the other hand, when it is less than 0.1 nm, the interaction between particles is greatly increased, the viscosity of the aqueous polymer dispersion is increased, and the production efficiency may be lowered. On the other hand, if it exceeds 80 nm, the fusion of polymer particles and the number of micron-sized coarse particles increase, and it becomes difficult to maintain a stable dispersion state.

The particle size distribution of the composite self-dispersing polymer is not particularly limited, and may be a wide particle size distribution or a monodispersed particle size distribution.
The volume average particle size and particle size distribution of the composite self-dispersing polymer can be measured using, for example, a dynamic light scattering method.
When the aqueous ink composition is constituted using the aqueous composite self-dispersing polymer of the present invention, the composite self-dispersing polymer may be used alone or in combination of two or more.

Moreover, it is preferable that the composite self-dispersing polymer in the present invention has a property of aggregating due to a change in pH environment. By having such characteristics, for example, it is possible to achieve both stability over time and high-speed recording properties when an ink composition is used. For example, when the composite self-dispersing polymer contains at least one polymer having a dissociable group, the composite self-dispersing polymer can be configured to aggregate due to a change in pH environment.
In addition, the composite self-dispersing polymer can form an aggregate by, for example, incorporating a colorant (for example, water-insoluble colored particles) during aggregation. The aggregate containing the composite self-dispersing polymer and the colorant can be suitably used for image formation, for example.

<Method for producing composite self-dispersing polymer aqueous dispersion>
In the present invention, the composite self-dispersing polymer aqueous dispersion uses a mixed solution of the first polymer and the second polymer (hereinafter sometimes simply referred to as “polymer solution”) and water, and the first polymer and It is manufactured by a manufacturing method including a step of obtaining composite self-dispersing polymer particles (hereinafter, sometimes simply referred to as “composite particles”) containing a second polymer.

  The polymer solution includes at least one first polymer, at least one second polymer, and at least one solvent that dissolves the first polymer and the second polymer. The polymer solution can be obtained by dissolving the first polymer and the second polymer in a solvent that dissolves the first polymer and the second polymer. There is no restriction | limiting in particular as a method of melt | dissolution, The melt | dissolution method used normally can be applied.

  The solvent is not particularly limited as long as it can dissolve the first polymer and the second polymer. For example, an organic solvent (hereinafter sometimes referred to as “organic good solvent”) in which the solubility (25 ° C.) of the first polymer and the second polymer is 10% by mass or more can be given.

Examples of the organic good solvent in the present invention include ketone solvents such as methyl ethyl ketone and acetone, ether solvents such as 1,3-dioxane, 1,4-dioxane, 1,3-oxolane and tetrahydrofuran, and esters such as ethyl acetate. And amide solvents such as dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and the like. In the present invention, at least one selected from ketone solvents, ether solvents, and ester solvents is preferable, and at least one selected from ketone solvents, ether solvents, and ester solvents having a boiling point of 100 ° C. or less. It is more preferable that it is at least one selected from methyl ethyl ketone, acetone, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran and ethyl acetate.
The organic good solvents may be used alone or in combination of two or more.

  Moreover, as a solvent which melt | dissolves the 1st polymer and 2nd polymer in this invention, the said organic good solvent and the solvent (henceforth "an organic poor solvent") with low solubility of the 1st polymer and the 2nd polymer. May be used in combination. Here, the organic poor solvent in which the solubility of the first polymer and the second polymer is small means an organic solvent in which the solubility (25 ° C.) of the first polymer and the second polymer is less than 10% by mass, respectively. .

Examples of the organic poor solvent in the present invention include alcohol solvents such as ethanol, isopropyl alcohol, n-butanol, s-butanol, t-butanol, and 2-ethylhexanol. Especially, it is preferable that it is an alcohol solvent whose boiling point is 100 degrees C or less, and it is more preferable that it is at least 1 sort (s) chosen from ethanol, isopropyl alcohol, and t-butanol.
In addition, an organic poor solvent may be used individually by 1 type, or may be used in combination of 2 or more type.

  When using the organic poor solvent in the present invention, from the viewpoint of dispersion stability of the aqueous polymer dispersion, the content of the organic poor solvent in the solvent dissolving the first polymer and the second polymer is 30 to 70% by mass. It is preferable that it is 30 to 60% by mass.

In the present invention, the polymer solution may further contain at least one neutralizing agent.
The neutralizing agent neutralizes part or all of the acidic groups of the first polymer and the second polymer, so that the first polymer and the second polymer form a stable dispersion state in the aqueous medium. Used for.

  Examples of the neutralizing agent used in the present invention include basic compounds such as organic amine compounds, ammonia, and alkali metal hydroxides. Examples of organic amine compounds include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dipropylamine, monoethanolamine, diethanolamine, triethanolamine, N, N-dimethyl-ethanolamine, N, N-diethyl-ethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, N-methyldiethanolamine, N-ethyldiethanolanine, monoisopropanolamine, di Examples include isopropanolamine and triisopropanolamine. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Among these, sodium hydroxide, potassium hydroxide, triethylamine, and triethanolamine are preferable from the viewpoint of stabilizing the dispersion of the first polymer and the second polymer in water.

  These neutralizing agents (preferably basic compounds) are preferably used in an amount of 5 to 120 mol%, more preferably 10 to 110 mol%, more preferably 15 to 100 mol, based on 100 mol% of the acidic group. % Is more preferable. By making it 5 mol% or more, the effect of stabilizing the dispersion of particles in water is remarkably exhibited, and by making it 120 mol% or less, water-soluble components in the dispersed state are remarkably reduced, There is an effect of suppressing an increase in viscosity.

  The step of obtaining a composite self-dispersing polymer aqueous dispersion of the first polymer and the second polymer (hereinafter sometimes referred to as “dispersing step”) is performed at least in a mixed solution of the first polymer and the second polymer. It is preferably a step of preparing an aqueous dispersion by mixing and stirring while adding water. By adding water to the polymer solution dissolved in the solvent as described above, an aqueous polymer dispersion having more excellent dispersion stability can be obtained without requiring a strong shearing force.

In the present invention, the method of mixing and stirring is not particularly limited, and a commonly used mixing and stirring device, and a dispersing machine such as an ultrasonic dispersing machine or a high-pressure homogenizer can be used as necessary.
In the present invention, at least water is added to the polymer solution, but in addition to water, a neutralizing agent or an organic solvent (preferably an organic poor solvent) may be further added.

The method for producing a composite self-dispersing polymer aqueous dispersion in the present invention preferably includes a solvent removal step after the dispersion step. The solvent removal step is not particularly limited as long as at least a part of the solvent can be removed, and a commonly used method such as distillation, distillation under reduced pressure, or the like can be applied.
In the present invention, by including a solvent removal step, an aqueous polymer dispersion having more excellent dispersion stability can be obtained.

In the solvent removal step of the present invention, at least part of the solvent is removed, but part of the water may be removed together with the solvent.
In the present invention, in the solvent removal step, the solvent content in the composite self-dispersing polymer aqueous dispersion is 0.05% by mass or more and 10% by mass or less of the total solid mass of the first polymer and the second polymer. Thus, the step of removing the solvent is preferred, and it is more preferably 0.08% by mass or more and 8% by mass or less.

  In addition, in this invention, an emulsifier can be used together in the range which does not impair the effect of this invention. Examples of the emulsifiers that can be used in combination include carboxylate emulsifiers, sulfonate emulsifiers, and the like, and carboxylate emulsifiers are preferred from the viewpoint of aggregation of composite particles.

  The carboxylate emulsifier that can be used in the present invention is not particularly limited as long as it is an emulsifier having a carboxyl group in the molecule. For example, beef tallow fatty acid soap, coconut oil fatty acid soap, rosin acid soap, various purified fatty acid soaps such as stearate and oleate, alkenyl succinate, and N-acyl sarcosine salts such as N-lauroyl sarcosine sodium Is mentioned. Among them, alkenyl succinate is preferable from the viewpoint of stability against shearing force.

  The amount of the emulsifier used in the present invention is 0.01% by mass or less, preferably 0.005% by mass or less, based on the aggregation properties of the composite particles, and is substantially 0.005% by mass or less. More preferably not.

<Water-based ink composition>
The aqueous ink composition of the present invention (hereinafter sometimes simply referred to as “ink composition”) comprises at least one colorant and two polymers formed by a specific production method and having an acid value of 8 or more different. Containing at least one kind of composite self-dispersing polymer, and further containing a water-soluble organic solvent and other additives as required. The composite self-dispersing polymer can be used as an aqueous dispersion.

  The water-based ink composition of the present invention can be used not only for monochromatic image formation but also for full-color image formation. In order to form a full color image, a magenta color ink, a cyan color ink, and a yellow color ink can be used, and a black color ink may be further used to adjust the color tone. Further, red, green, blue, and white inks other than yellow, magenta, and cyan color inks, and so-called special color inks (for example, colorless) in the printing field can be used.

The composite self-dispersing polymer preferably has a property of aggregating with a change in pH environment. By having such characteristics, it is possible to achieve both the stability over time of the ink composition and the high-speed recording property. Since the composite self-dispersing polymer contains at least two kinds of water-insoluble polymers having acidic groups, the composite self-dispersing polymer can be configured to aggregate due to a change in pH environment.
In addition, the composite self-dispersing polymer can form an aggregate by, for example, incorporating a colorant (for example, water-insoluble colored particles) during aggregation. Aggregates containing a composite self-dispersing polymer and a colorant can be suitably used for image formation, for example.

The content of the composite self-dispersing polymer in the aqueous ink composition of the present invention is preferably 1 to 30% by mass, and preferably 5 to 15% by mass with respect to the aqueous ink composition from the viewpoint of image glossiness and the like. % Is more preferable.
The mass ratio of the colorant to the composite self-dispersing polymer (colorant / composite self-dispersing polymer) in the water-based ink composition of the present invention is 1 / 0.5 to 1 / from the viewpoint of image scratch resistance. 10 is preferable, and 1/1 to 1/4 is more preferable.

[Colorant]
As the colorant, known dyes, pigments and the like can be used without particular limitation. Among these, from the viewpoint of ink colorability, a colorant that is almost insoluble or hardly soluble in water is preferable. Specific examples include various pigments, disperse dyes, oil-soluble dyes, dyes forming J aggregates, and the like, and pigments are more preferable.
In the present invention, the water-insoluble pigment itself or the pigment itself surface-treated with a dispersant can be used as the colorant.

There is no restriction | limiting in particular as a pigment in this invention, A conventionally well-known organic and inorganic pigment can be used. For example, polycyclic pigments such as azo lakes, azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, diketopyrrolopyrrole pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, basic Examples include dye lakes such as dye-type lakes and acid dye-type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as titanium oxide, iron oxide, and carbon black. Any pigment not described in the color index can be used as long as it can be dispersed in the aqueous phase. Further, it is of course possible to use a pigment obtained by surface-treating the above pigment with a surfactant, a polymer dispersing agent or the like, or graft carbon. Among the above pigments, it is particularly preferable to use an azo pigment, a phthalocyanine pigment, an anthraquinone pigment, a quinacridone pigment, or a carbon black pigment.
Specific examples of the pigment that can be used in the present invention include pigments described in paragraph numbers [0142] to [0145] of JP-A-2007-100071.

(Dispersant)
When the colorant in the present invention is a pigment, it is preferably dispersed in an aqueous solvent by a dispersant. The dispersant may be a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.
The low molecular surfactant type dispersant (hereinafter sometimes referred to as “low molecular dispersant”) may be added for the purpose of stably dispersing the organic pigment in an aqueous solvent while keeping the ink at a low viscosity. it can. The low molecular dispersant herein is a low molecular dispersant having a molecular weight of 2000 or less. Moreover, 100-2000 are preferable and, as for the molecular weight of a low molecular dispersing agent, 200-2000 are more preferable.

  The low molecular weight dispersant has a structure including a hydrophilic group and a hydrophobic group. In addition, the hydrophilic group and the hydrophobic group may be independently contained in one molecule or more, and may have a plurality of types of hydrophilic groups and hydrophobic groups. In addition, a linking group for linking a hydrophilic group and a hydrophobic group can be appropriately included.

Examples of the hydrophilic group include an anionic group, a cationic group, a nonionic group, and a betaine type combining these.
The anionic group is not particularly limited as long as it has a negative charge, but may be a phosphate group, phosphonic acid group, phosphinic acid group, sulfuric acid group, sulfonic acid group, sulfinic acid group or carboxylic acid group. Preferably, it is a phosphoric acid group or a carboxylic acid group, more preferably a carboxylic acid group.

The cationic group is not particularly limited as long as it has a positive charge, but is preferably an organic cationic substituent, more preferably a cationic group containing nitrogen or phosphorus, and nitrogen. More preferably, it is a cationic group. Among these, a pyridinium cation or an ammonium cation is particularly preferable.
The nonionic group is not particularly limited as long as it has no negative or positive charge. For example, a polyalkylene oxide, polyglycerin, a part of sugar unit, etc. are mentioned.

In the present invention, the hydrophilic group is preferably an anionic group from the viewpoint of dispersion stability and aggregation of the pigment.
Moreover, when a low molecular weight dispersing agent has an anionic hydrophilic group, it is preferable that the pKa is 3 or more from a viewpoint of making it contact with an acidic process liquid and promoting aggregation reaction. The pKa of the low molecular dispersant in the present invention is determined experimentally from a titration curve by titrating a solution of 1 mol / L of the low molecular dispersant in tetrahydrofuran-water = 3: 2 (V / V) solution with an acid or alkaline aqueous solution. It is the calculated value.
Theoretically, if the pKa of the low molecular dispersant is 3 or more, 50% or more of the anionic groups are in a non-dissociated state when in contact with a treatment solution having a pH of about 3. Accordingly, the water solubility of the low molecular weight dispersant is remarkably lowered, and an agglomeration reaction occurs. That is, the aggregation reactivity is improved. From this viewpoint, it is preferable that the low molecular dispersant has a carboxylic acid group as an anionic group.

  On the other hand, the hydrophobic group may have any structure such as hydrocarbon-based, fluorocarbon-based, and silicone-based, but is particularly preferably hydrocarbon-based. Further, these hydrophobic groups may have a linear structure or a branched structure. The hydrophobic group may have a single chain structure or two or more chain structures, and may have a plurality of types of hydrophobic groups in the case of a structure having two or more chains.

  The hydrophobic group is preferably a hydrocarbon group having 2 to 24 carbon atoms, more preferably a hydrocarbon group having 4 to 24 carbon atoms, and further preferably a hydrocarbon group having 6 to 20 carbon atoms.

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

  In addition, as hydrophilic polymer compounds chemically modified from natural products, fiber polymers such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, sodium starch glycolate, sodium starch phosphate, etc. And seaweed polymers such as alginic acid propylene glycol ester.

  Synthetic water-soluble polymer compounds include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, acrylic polymers such as polyacrylamide, polyacrylic acid or alkali metal salts thereof, and water-soluble styrene acrylic resins. Resin, water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salt of β-naphthalene sulfonic acid formalin condensate, quaternary ammonium, amino group, etc. And a polymer compound having a cationic functional group salt in the side chain.

  Among these, from the viewpoint of pigment dispersion stability and aggregation, a polymer compound containing a carboxyl group is preferable. For example, an acrylic resin such as a water-soluble styrene acrylic resin, a water-soluble styrene maleic resin, and a water-soluble vinyl naphthalene. High molecular compounds containing a carboxyl group such as an acrylic resin and a water-soluble vinyl naphthalene maleic resin are particularly preferred.

  As the water-insoluble dispersant among the polymer dispersants, a polymer having both a hydrophobic part and a hydrophilic part can be used. For example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol ( Examples thereof include a meth) acrylate- (meth) acrylic acid copolymer and a styrene-maleic acid copolymer.

The weight average molecular weight of the polymer dispersant in the present invention is preferably 3,000 to 200,000, more preferably 5,000 to 100,000, still more preferably 5,000 to 80,000, and particularly preferably 10,000. 000-60,000.
In addition, a weight average molecular weight can be measured by a gel permeation chromatograph (GPC), for example.

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

In the present invention, when a dye is used as a colorant, a dye held on a water-insoluble carrier can be used. As the dye, known dyes can be used without particular limitation. For example, the dyes described in JP-A-2001-115066, JP-A-2001-335714, JP-A-2002-249677 and the like can be used in the present invention. It can be used suitably. The carrier is not particularly limited as long as it is insoluble in water or hardly soluble in water, and inorganic materials, organic materials, and composite materials thereof can be used. Specifically, the carriers described in JP-A-2001-181549, JP-A-2007-169418, etc. can be suitably used in the present invention.
The carrier holding the dye (coloring agent) can be used as an aqueous dispersion using a dispersant. As the dispersant, the above-described dispersants can be suitably used.

  The colorant in the present invention preferably contains a pigment and a dispersant, more preferably contains an organic pigment and a polymer dispersant, and a polymer containing an organic pigment and a carboxyl group, from the viewpoint of light resistance and quality of the image. It is particularly preferable to contain a dispersant.

In the present invention, the volume average particle diameter of the colorant is preferably 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. When the volume average particle size is 200 nm or less, the color reproducibility is good, and in the case of the ink jet method, the droplet ejection characteristics are good. Moreover, light resistance becomes favorable because a volume average particle diameter is 10 nm or more.
Further, the particle size distribution of the colorant is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more colorants having a monodispersed particle size distribution may be used in combination.
The volume average particle size and particle size distribution of the colorant can be measured using, for example, a light scattering method.

In the present invention, the colorants may be used alone or in combination of two or more.
The content of the colorant is preferably 1 to 25% by mass, more preferably 2 to 20% by mass, and 5 to 20% by mass with respect to the aqueous ink composition from the viewpoint of image density. More preferably, 5-15 mass% is especially preferable.

[Water-soluble organic solvent]
The aqueous ink composition of the present invention contains water as a solvent, but can further contain a water-soluble organic solvent. The water-soluble organic solvent can be contained, for example, as a drying inhibitor or a penetration accelerator.
The anti-drying agent can effectively prevent nozzle clogging that may occur due to drying of ink at the ink ejection port, particularly when the aqueous ink composition of the present invention is applied to an image forming method using an inkjet method. .

  The drying inhibitor is preferably a water-soluble organic solvent having a vapor pressure lower than that of water. Specific examples of the drying inhibitor include ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6-hexanetriol, Polyvalent alcohols typified by acetylene glycol derivatives, glycerin, trimethylolpropane, etc., polyvalent alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monoethyl (or butyl) ether Lower alkyl ethers of alcohols, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, heterocyclic rings such as N-ethylmorpholine, sulfolane, dimethyls Sulfoxide, sulfur-containing compounds such as sulfolane, diacetone alcohol, polyfunctional compounds such as diethanolamine, and urea derivatives. Of these, polyhydric alcohols such as glycerin and diethylene glycol are preferred as the drying inhibitor. Moreover, said drying inhibitor may be used independently or may be used together 2 or more types. These drying inhibitors are preferably contained in the ink in an amount of 10 to 50% by mass.

  Further, the penetration accelerator is preferably used for the purpose of allowing the ink to permeate the recording medium (for example, printing paper) better. Specific examples of penetration enhancers include alcohols such as ethanol, isopropanol, butanol, di (tri) ethylene glycol monobutyl ether, 1,2-hexanediol, sodium lauryl sulfate, sodium oleate, and nonionic surfactants. Etc. can be used suitably. These penetration enhancers exhibit a sufficient effect when contained in the ink composition in an amount of 5 to 30% by mass. Further, it is preferable that the penetration enhancer is used within a range of an addition amount that does not cause bleeding of prints and paper loss (print through).

In addition to the above, the water-soluble organic solvent can be used for adjusting the viscosity. Specific examples of water-soluble organic solvents that can be used to adjust the viscosity include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol, pentanol, hexanol, Cyclohexanol, benzyl alcohol), 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), glycol derivatives (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether) Ter, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, Triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine) Ethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine) and other polar solvents (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, sulfolane, 2-pyrrolidone, N -Methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone).
In addition, a water-soluble organic solvent may be used independently and may use 2 or more types together.

[Other additives]
Examples of other additives in the present invention include, for example, antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, antifungal agents, pH adjusters, surface tension adjusters, antifoaming agents, and viscosity adjusters. Well-known additives, such as an agent, a dispersing agent, a dispersion stabilizer, a rust preventive agent, and a chelating agent, are mentioned. These various additives may be added directly after the aqueous ink composition is prepared, or may be added when the aqueous ink composition is prepared.

  Examples of ultraviolet absorbers include benzotriazole compounds, benzophenone compounds, cinnamic acid compounds, triazine compounds, Research Disclosure No. 1; The compounds described in No. 24239, and compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds can also be used.

  As the antifading agent, various organic and metal complex antifading agents can be used. Organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc. Complex, zinc complex and the like.

Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof. These are preferably used in the water-based ink composition in an amount of 0.02 to 1.00% by mass.
As the pH adjuster, a neutralizer (organic base, inorganic alkali) can be used. For the purpose of improving the storage stability of the aqueous ink composition, the pH adjuster is preferably added so that the aqueous ink composition has a pH of 6 to 10, and more preferably added to have a pH of 7 to 10. .

Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like.
Moreover, the addition amount of the surface tension adjusting agent is preferably an addition amount for adjusting the surface tension of the water-based ink composition to 20 to 60 mN / m in order to achieve good droplet ejection by the ink jet method, and is adjusted to 20 to 45 mN / m. The addition amount to be adjusted is more preferable, and the addition amount adjusted to 25 to 40 mN / m is more preferable. On the other hand, when ink is applied by a method other than the inkjet method, a range of 20 to 60 mN / m is preferable, and a range of 30 to 50 mN / m is more preferable.
The surface tension (25 ° C.) of the water-based ink composition can be measured using, for example, a plate method.

Specific examples of surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensation in hydrocarbons. Products, anionic surfactants such as polyoxyethylene alkyl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxy Nonionic surfactants such as ethylene alkylamine, glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals) and Olfine (manufactured by Nissin Chemical Industry Co., Ltd.), which are acetylene-based polyoxyethylene oxide surfactants, are also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.
Furthermore, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used.
Also, fluorine (fluorinated alkyl) surfactants, silicone surfactants, and the like described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are disclosed. By using, the abrasion resistance can be improved.
These surface tension modifiers can also be used as an antifoaming agent, and fluorine compounds, silicone compounds, chelating agents represented by EDTA, and the like can also be used.

The viscosity of the aqueous ink composition of the present invention is preferably in the range of 1 to 30 mPa · s, and in the range of 1 to 20 mPa · s, from the viewpoint of droplet ejection stability and agglomeration speed when ink is applied by an inkjet method. Is more preferable, the range of 2 to 15 mPa · s is more preferable, and the range of 2 to 10 mPa · s is particularly preferable.
In addition, when ink is applied by a method other than the inkjet method, a range of 1 to 40 mPa · s is preferable, and a range of 5 to 20 mPa · s is more preferable.
The viscosity (20 ° C.) of the water-based ink composition can be measured using, for example, a Brookfield viscometer.

<Ink set>
The ink set of the present invention comprises at least one aqueous ink composition of the present invention described above and at least one treatment liquid capable of forming an aggregate by contact with the aqueous ink composition. It has been done.
Details of the water-based ink composition are as described above.

  In the present invention, the composite self-dispersing polymer constituting the water-based ink composition contains two types of polymers having different acid values of 8 or more, so that the formed image has good anti-blocking property, fixing property and ejection stability. become.

[Treatment solution]
The treatment liquid in the present invention is configured so as to be able to form an aggregate by contact with the above-described aqueous ink composition. Specifically, the treatment liquid preferably includes at least an aggregating component capable of aggregating dispersed particles such as a colorant (pigment) in the ink composition to form an aggregate. It can be constructed using components. By using the treatment liquid together with the water-based ink composition, for example, it is possible to increase the speed of inkjet recording, and an image with excellent density and resolution can be obtained even when recording at high speed (for example, reproducibility of fine lines and fine portions). .

(Aggregating component)
The treatment liquid can contain at least one aggregation component capable of forming an aggregate upon contact with the ink composition. When the water-based ink composition applied to the recording medium comes into contact with the aggregation component in the treatment liquid, aggregation of pigments and the like stably dispersed in the ink composition is promoted.

Examples of the treatment liquid include a liquid capable of generating an aggregate by changing the pH of the ink composition. At this time, the pH (25 ° C. ± 1 ° C.) of the treatment liquid is preferably 1 to 6, more preferably 1.2 to 5, more preferably 1.5 from the viewpoint of the aggregation rate of the ink composition. More preferably, it is ~ 4. In this case, the pH (25 ± 1 ° C.) of the ink composition used in the ejection process is preferably 7.5 to 9.5 (more preferably 8.0 to 9.0).
Among these, in the present invention, from the viewpoint of image density, resolution, and speedup of inkjet recording, the pH (25 ° C. ± 1 ° C.) of the ink composition is 7.5 or more, and the pH of the treatment liquid (25 (° C. ± 1 ° C.) is preferably 1.5 to 3.
The aggregating components can be used alone or in combination of two or more.

  The treatment liquid can be configured using at least one acidic compound as an aggregation component. As the acidic compound, a compound having a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, or a carboxyl group, or a salt thereof (for example, a polyvalent metal salt) may be used. it can. Among these, from the viewpoint of the aggregation rate of the ink composition, a compound having a phosphate group or a carboxyl group is more preferable, and a compound having a carboxyl group is still more preferable.

  The compound having a carboxyl group includes polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid. , Pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof (for example, polyvalent metal salts), etc. It is preferable to be selected from among These compounds may be used alone or in combination of two or more.

The treatment liquid in the present invention can be configured to further contain an aqueous solvent (for example, water) in addition to the acidic compound and the like.
As content in the processing liquid of an acidic compound, it is preferable that it is 5-95 mass% with respect to the total mass of a processing liquid from a viewpoint of the aggregation effect, and it is more preferable that it is 10-80 mass%. More preferably, it is 15-50 mass%, Most preferably, it is 18-30%.

  Examples of the treatment liquid include a treatment liquid containing at least one polyvalent metal salt as an aggregating component. By including a polyvalent metal salt, high-speed cohesion can be improved. Examples of the polyvalent metal salt include alkaline earth metals belonging to Group 2 of the periodic table (eg, magnesium, calcium), transition metals belonging to Group 3 of the periodic table (eg, lanthanum), and cations from Group 13 of the periodic table. (For example, aluminum) and the salt of lanthanides (for example, neodymium) can be mentioned. As the metal salt, carboxylate (formic acid, acetic acid, benzoate, etc.), nitrate, chloride, and thiocyanate are suitable. Among them, preferred are calcium salts or magnesium salts of carboxylic acids (formic acid, acetic acid, benzoates, etc.), calcium salts or magnesium salts of nitric acid, calcium chloride, magnesium chloride, and calcium salts or magnesium salts of thiocyanic acid.

  As content in the process liquid of a polyvalent metal salt, 1-10 mass% is preferable from a viewpoint of the aggregation effect, More preferably, it is 1.5-7 mass%, More preferably, it is 2-6 mass%. It is a range.

  Further, the treatment liquid may be configured using at least one cationic organic compound as an aggregation component. Examples of the cationic organic compound include poly (vinyl pyridine) salt, polyalkylaminoethyl acrylate, polyalkylaminoethyl methacrylate, poly (vinyl imidazole), polyethyleneimine, polybiguanide, polyguanide, and polyallylamine and derivatives thereof. Mention may be made of cationic polymers.

  The weight average molecular weight of the cationic polymer is preferably smaller in terms of the viscosity of the treatment liquid. When the treatment liquid is applied to the recording medium by an ink jet method, the range of 1,000 to 500,000 is preferable, the range of 1,500 to 200,000 is more preferable, and still more preferably 2,000 to 100,000. Range. When the weight average molecular weight is 1000 or more, it is advantageous from the viewpoint of the aggregation rate, and when it is 500,000 or less, it is advantageous from the viewpoint of ejection reliability. However, this is not the case when the treatment liquid is applied to the recording medium by a method other than inkjet.

Furthermore, as the cationic organic compound, for example, a primary, secondary, or tertiary amine salt type compound is preferable. Examples of the amine salt type compounds include compounds such as hydrochloride or acetate (for example, laurylamine, cocoamine, stearylamine, rosinamine), quaternary ammonium salt type compounds (for example, lauryltrimethylammonium chloride, cetyltrimethyl). Ammonium chloride, lauryldimethylbenzylammonium chloride, benzyltributylammonium chloride, benzalkonium chloride, etc.), pyridinium salt type compounds (eg, cetylpyridinium chloride, cetylpyridinium bromide, etc.), imidazoline type cationic compounds (eg, 2-heptadecenyl- Hydroxyethyl imidazoline etc.), ethylene oxide adducts of higher alkylamines (eg dihydroxyethyl stearylamine etc.), etc. And cationic compounds, for example, amino acid type amphoteric _{surfactants, R-NH-CH 2 CH} 2 -COOH type compounds (R represents an alkyl group), carboxylic acid salt type amphoteric surfactants (e.g., Stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, etc.), amphoteric surfactants exhibiting a cationic property in a desired pH range, such as amphoteric surfactants such as sulfate ester type, sulfonic acid type, and phosphate ester type.
Of these, divalent or higher cationic organic compounds are preferred.

  As content in the processing liquid of a cationic organic compound, 1-50 mass% is preferable from a viewpoint of the aggregation effect, More preferably, it is 2-30 mass%.

  Among the above, the aggregating component is preferably a divalent or higher carboxylic acid or a divalent or higher cationic organic compound, and more preferably a divalent or higher carboxylic acid in terms of aggregability and image scratch resistance.

(Other ingredients)
The treatment liquid in the present invention can generally contain a water-soluble organic solvent in addition to the aggregating component, and can be constituted using other various additives within a range not impairing the effects of the present invention. The details of the water-soluble organic solvent are the same as those in the ink composition described above.

  Examples of the other additives include a drying inhibitor (wetting agent), an antifading agent, an emulsion stabilizer, a penetration accelerator, an ultraviolet absorber, an antiseptic, an antifungal agent, a pH adjuster, a surface tension adjuster, Known additives such as antifoaming agents, viscosity modifiers, dispersants, dispersion stabilizers, rust preventives, chelating agents are listed, and specific examples of other additives included in the ink composition described above The listed ones are applicable.

The viscosity of the treatment liquid is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, still more preferably in the range of 2 to 15 mPa · s, from the viewpoint of the aggregation rate of the ink composition. The range of 10 mPa · s is particularly preferable.
The viscosity is measured under a condition of 20 ° C. using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD).

The surface tension of the treatment liquid is preferably 20 to 60 mN / m, more preferably 20 to 45 mN / m, and more preferably 25 to 40 mN / m from the viewpoint of the aggregation rate of the ink composition. More preferably.
In addition, surface tension is measured on 25 degreeC conditions using Automatic Surface Tensiometer CBVP-Z (made by Kyowa Interface Science Co., Ltd.).

<Image forming method>
The image forming method of the present invention includes an ink application step for applying the aqueous ink composition to a recording medium, and a heat fixing step for fixing the image by heating the recording medium to which the aqueous ink composition has been applied. However, other steps can be further provided as necessary.
Examples of other steps include a treatment liquid application step for applying a treatment liquid capable of forming an aggregate by contact with the aqueous ink composition to the recording medium, a heat drying step, and the like.

  In the present invention, when the aqueous ink composition contains a colorant and the composite self-dispersing polymer, an image having both blocking resistance and good fixability can be formed.

[Ink application process]
In the ink application step, the aqueous ink composition of the present invention described above is applied to a recording medium to form an image. In this step, a water-based ink composition can be selectively applied on the recording medium, and a desired visible image can be formed. Examples of the application method of the water-based ink composition include an ink jet method, a copying method, and a printing method. Among these, from the viewpoint of downsizing the recording apparatus and high-speed recording properties, a step of applying the aqueous ink composition by an ink jet method is preferable.
The details of each component in the water-based ink composition of the present invention and the details of preferred embodiments are as described above.

  Specifically, the image recording using the ink-jet method is performed by supplying energy to obtain a desired recording medium, that is, plain paper, resin-coated paper, for example, JP-A-8-169172 and JP-A-8-27693. Publication No. 2-276670, No. 7-276789, No. 9-323475, No. JP-A-62-238783, JP-A-10-153898, No. 10-217473, No. 10- No. 235995, No. 10-337947, No. 10-217597, No. 10-337947, etc. Liquid composition for ink jet paper, film, electrophotographic co-paper, fabric, glass, metal, ceramics, etc. This can be done by discharging an object. As a preferable ink jet recording method for the present invention, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that discharges ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezo element, and an electric method. An acoustic ink jet system that converts a signal into an acoustic beam, irradiates the ink by using ink and ejects the ink by using radiation pressure, and a thermal ink jet (Bubble Jet (registered trademark)) that heats the ink to form bubbles and uses the generated pressure. )) Any method may be used.
The ink jet method includes a method of ejecting many low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method using is included.
There are no particular restrictions on the ink nozzles used when recording by the inkjet method, and they can be appropriately selected according to the purpose.

  As an ink jet method, a short-type serial head is used, and a shuttle system that performs recording while scanning the head in the width direction of the recording medium, and a line head in which recording elements are arranged corresponding to the entire area of one side of the recording medium There is a line system using. In the line method, an image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, and a carriage system such as a carriage for scanning a short head is not necessary. Further, since complicated scanning control of the carriage movement and the recording medium is not required, and only the recording medium is moved, the recording speed can be increased as compared with the shuttle system. The ink jet recording method of the present invention can be applied to any of these, but generally, when applied to a line system in which no dummy jet is performed, the effect of improving ejection accuracy and image scratch resistance is great.

  Furthermore, in the ink application process in the present invention, in the case of the line method, not only one type of ink composition is used but also two or more types of ink compositions are used, and an ink composition (nth color ( n ≧ 1), for example, the second color), and the ink composition (n + 1th color, for example, the third color) to be ejected subsequently is set to a discharge (droplet ejection) interval of 1 second or less, and recording is preferably performed. be able to. In the present invention, an ejection interval of 1 second or less in the line method prevents bleeding and color mixing between ink droplets, and has excellent scratch resistance under high-speed recording higher than that of the prior art, and occurrence of blocking. A suppressed image can be obtained. In addition, an image having excellent hue and drawability (reproducibility of fine lines and fine portions in the image) can be obtained.

  The amount of ink droplets ejected from the inkjet head is preferably 0.5 to 6 pl (picoliter), more preferably 1 to 5 pl, and still more preferably 2 to 4 pl from the viewpoint of obtaining a high-definition image. .

[Heat fixing process]
The image forming method of the present invention includes, after the ink application step, a heating and fixing step of fixing the image by bringing a heating surface into contact with the ink image formed by applying the ink composition and heating it. By performing the heat fixing process, the image on the recording medium is fixed, and the resistance to image abrasion can be further improved. Moreover, it can suppress effectively that the image formed by using the water-based ink composition of this invention is transcribe | transferred to the said heating surface.

  The heating is preferably performed at a temperature equal to or higher than at least one glass transition temperature (Tg) of the polymer contained in the composite self-dispersing polymer in the image. Since it is heated to Tg or more, it becomes a film and the image is strengthened. The heating temperature is preferably a temperature range of Tg + 10 ° C. or higher. Specifically, the heating temperature is preferably in the range of 40 to 150 ° C, more preferably in the range of 50 ° C to 100 ° C, and still more preferably in the range of 60 ° C to 90 ° C.

  The pressure at the time of pressurizing with heating is preferably in the range of 0.1 to 3.0 MPa, more preferably in the range of 0.1 to 1.0 MPa, and still more preferably 0.1 in terms of surface smoothing. It is the range of -0.5MPa.

  The method of heating is not particularly limited, but a non-contact drying method such as a method of heating with a heating element such as a nichrome wire heater, a method of supplying warm air or hot air, a method of heating with a halogen lamp, an infrared lamp, etc. Preferably, it can be mentioned. The heating and pressing method is not particularly limited. For example, a method of pressing a hot plate against the image forming surface of a recording medium, a pair of heating and pressing rollers, a pair of heating and pressing belts, or a recording medium Using a heating and pressing device equipped with a heating and pressing belt arranged on the image recording surface side and a holding roller arranged on the opposite side, heat fixing by bringing them into contact, such as a method of passing a pair of rollers, etc. The method to perform is mentioned suitably.

  In the case of heating and pressing, a preferable nip time is 1 to 10 seconds, more preferably 2 to 1 second, and further preferably 4 to 100 milliseconds. Moreover, a preferable nip width is 0.1 mm to 100 mm, more preferably 0.5 mm to 50 mm, and still more preferably 1 to 10 mm.

  The heat and pressure roller may be a metal metal roller, or a metal core bar provided with a coating layer made of an elastic body and, if necessary, a surface layer (also referred to as a release layer). Good. The latter metal core can be formed of, for example, a cylindrical body made of iron, aluminum, SUS, or the like, and the surface of the metal core is preferably at least partially covered with a coating layer. The coating layer is particularly preferably formed of a silicone resin or fluororesin having releasability. Further, it is preferable that a heating element is built in one core metal of the heat and pressure roller, and heat treatment and pressure treatment are performed simultaneously or necessary by passing a recording medium between the rollers. Accordingly, the recording medium may be sandwiched and heated using two heating rollers. As the heating element, for example, a halogen lamp heater, a ceramic heater, a nichrome wire or the like is preferable.

  As a belt base material constituting the heat and pressure belt used in the heat and pressure apparatus, seamless nickel brass is preferable, and the thickness of the base material is preferably 10 to 100 μm. Further, as the material of the belt base material, aluminum, iron, polyethylene or the like can be used in addition to nickel. When silicone resin or fluororesin is provided, the thickness of the layer formed using these resins is preferably 1 to 50 μm, more preferably 10 to 30 μm.

  Further, in order to realize the pressure (nip pressure), for example, an elastic member such as a spring having tension so that a desired nip pressure can be obtained in consideration of the nip gap at both ends of a roller such as a heat and pressure roller. Select and install.

  The conveyance speed of the recording medium when using a heat and pressure roller or a heat and pressure belt is preferably in the range of 200 to 700 mm / second, more preferably 300 to 650 mm / second, and still more preferably 400 to 600 mm / second. It is.

[Processing liquid application process]
The image forming method of the present invention preferably includes a treatment liquid application step in addition to the ink application step and the heat fixing step from the viewpoint of high-speed image formation.
In the treatment liquid application step, a treatment liquid capable of forming an aggregate by contact with the ink composition is applied to the recording medium, and the treatment liquid is contacted with the ink composition to form an aggregate containing a colorant. To form an image. In this case, dispersed particles such as a composite self-dispersing polymer and a colorant in the ink composition aggregate to fix the image on the recording medium. The details and preferred embodiments of each component in the treatment liquid are as described above.

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

The treatment liquid application step may be provided either before or after the ink application step using the ink composition.
In the present invention, an embodiment in which the ink application step is provided after the treatment liquid is applied in the treatment liquid application step is preferable. That is, before applying the ink composition to the recording medium, a processing liquid for aggregating the colorant in the ink composition is applied in advance so that the processing liquid applied on the recording medium comes into contact. An embodiment in which an ink composition is applied to an image to form an image is preferable. Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

The application amount of the treatment liquid is not particularly limited as long as the ink composition can be aggregated. Preferably, the application amount of the aggregation component (for example, a divalent or higher carboxylic acid or a cationic organic compound) is 0.1 g. / M ² or more. Especially, the quantity from which the provision amount of an aggregation component will be 0.1-1.0 g / m < ² > is preferable, More preferably, it is 0.2-0.8 g / m < ² >. When the amount of the aggregating component is 0.1 g / m ² or more, the agglomeration reaction proceeds favorably, and when it is 1.0 g / m ² or less, the glossiness is not excessively increased.

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

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

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

  As the recording medium, commercially available media can be used. For example, “OK Prince fine quality” manufactured by Oji Paper Co., Ltd., “Shiorai” manufactured by Nippon Paper Industries Co., Ltd., and Nippon Paper Industries ( Fine coated paper such as “New NPI fine quality” manufactured by Co., Ltd., “OK Everlight Coat” manufactured by Oji Paper Co., Ltd., and “Aurora S” manufactured by Nippon Paper Industries Co., Ltd., Oji Lightweight coated paper (A3) such as “OK Coat L” manufactured by Paper Industries Co., Ltd. and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd. “OK Top Coat +” manufactured by Oji Paper Co., Ltd. and Nippon Paper Industries Co., Ltd. ) Coated paper (A2, B2) such as “Aurora Coat” manufactured by Oji Paper Co., Ltd. Art paper (A1) such as “OK Kanfuji +” manufactured by Oji Paper Co., Ltd. Is mentioned. It is also possible to use various photographic papers for ink jet recording.

Among the above, from the viewpoint of obtaining a high-quality image having a large color material movement suppressing effect and better color density and hue than before, the water absorption coefficient Ka is preferably 0.05 to 0.5. a recording medium mL ^/ m 2 ^{· ms 1/2,} more preferably recording medium 0.1~0.4mL ^/ m 2 ^{· ms 1/2,} more preferably 0.2-0.3 ml / It is a recording medium of m ² · ms ^1/2 .

  The water absorption coefficient Ka is synonymous with that described in JAPAN TAPPI paper pulp test method No. 51: 2000 (issued by Japan Paper Pulp Technology Association). Specifically, the absorption coefficient Ka is an automatic scanning absorption meter. It is calculated from the difference in the amount of water transferred between the contact time of 100 ms and the contact time of 900 ms using KM500Win (manufactured by Kumagai Riki Co., Ltd.).

  Among the recording media, so-called coated paper used for general offset printing is preferable. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not generally surface-treated. The coated paper tends to cause quality problems such as image gloss and scratch resistance in image formation by ordinary aqueous inkjet, but in the inkjet recording method of the present invention, gloss unevenness is suppressed and gloss and resistance are reduced. An image having good rubbing properties can be obtained. In particular, it is preferable to use a coated paper having a base paper and a coat layer containing kaolin and / or calcium bicarbonate. More specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is more preferable.

  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.

(Synthesis Example 1)
-Synthesis of Polymer B-12-
In a 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 560.0 g of methyl ethyl ketone was charged and heated to 87 ° C. in a nitrogen atmosphere. While maintaining the reflux state in the reaction vessel (hereinafter referred to as reflux until the end of the reaction), 232.0 g of methyl methacrylate, 301.6 g of isobornyl methacrylate, 46.4 g of methacrylic acid, 108 g of methyl ethyl ketone, and “V-601” (Wako Pure) A mixed solution consisting of 2.32 g (manufactured by Yakuhin Co., Ltd.) was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, the mixture was stirred for 1 hour, (1) a solution consisting of 1.16 g of “V-601” and 6.4 g of methyl ethyl ketone was added, and the mixture was stirred for 2 hours. Subsequently, the process of (1) was repeated four times, and a solution consisting of 1.16 g of “V-601” and 6.4 g of methyl ethyl ketone was added and stirring was continued for 3 hours to obtain a solution of water-insoluble polymer B-12. . The weight average molecular weight (Mw) of the obtained polymer is 58000 (calculated in terms of polystyrene by gel permeation chromatography (GPC), and the columns used are TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (manufactured by Tosoh Corporation)), The acid value was 38.9 (mgKOH / g).

-Synthesis of polymer B-13-
In the synthesis of the polymer B-12, instead of methyl methacrylate 232.0 g, isobornyl methacrylate 301.6 g, and methacrylic acid 46.4 g, the monomer was charged so as to have the structure and mass ratio shown in the following polymer B-13. A solution of water-insoluble polymer B-13 was obtained in the same manner as in the synthesis of polymer B-12 except that the amount was changed. The weight average molecular weight (Mw) of the obtained polymer was 57000, and the acid value was 90.8.

(Preparation Example 1)
-Preparation of composite self-dispersing polymer aqueous dispersion PL-01-
Next, 145.7 g (solid content concentration 44.6%) of the polymer B-12 obtained above and 145.7 g (solid content concentration 44.6%) of the polymer B-13 were weighed to obtain isopropanol. 82.5 g and 40.77 g of a 2 mol / L NaOH aqueous solution were added, and the temperature in the reaction vessel was raised to 87 ° C. Next, 380 g of distilled water was added dropwise at a rate of 10 ml / min to disperse in water (dispersing step). Thereafter, the temperature in the reaction vessel was kept at 87 ° C. for 1 hour, 91 ° C. for 1 hour, and 95 ° C. for 30 minutes under atmospheric pressure, and then the reaction vessel was depressurized, and isopropanol, methyl ethyl ketone, and distilled water totaled 287. 0 g was distilled off (solvent removal step) to obtain a composite self-dispersing polymer aqueous dispersion PL-01 having a solid content concentration of 26.5%. Table 1 shows the physical properties of the obtained aqueous dispersion PL-01.

(Synthesis Example 2)
In the synthesis of Polymer B-12 of Synthesis Example 1, instead of methyl methacrylate 232.0 g, isobornyl methacrylate 301.6 g, and methacrylic acid 46.4 g, the types of monomers and Except having changed charge amount, it carried out similarly to the synthesis | combination of polymer B-12, and obtained polymer B-01, B-03, B-04, B-06, B-11, B-13, and B-19. It was. The physical properties of the obtained polymer are shown in Table 1.
In addition, the number of each structural unit of the following compound example represents mass ratio.

(Preparation Example 2)
In the preparation of the composite self-dispersing polymer aqueous dispersion PL-01 of Preparation Example 1, the types and mixing ratios of the two polymers used were changed as shown in Table 1, and the neutralization degree of the mixed polymers was the same. Composite self-dispersing polymer aqueous dispersions (PL-02) to (PL-12) were obtained in the same manner as in Preparation Example 1 except that the addition amount of the aqueous NaOH solution was changed so as to be. The physical properties of the obtained composite self-dispersing polymer aqueous dispersions (PL-02) to (PL-12) are shown in Table 1.

(Comparative Preparation Example 1)
According to the production example of self-emulsifying polymer particles described in paragraph No. [0041] of JP-A-2006-283003, an aqueous dispersion PLH-01 of the following exemplary compound BH-01 was obtained. In the following exemplified compounds, AS-6S is a trade name of styrene macromer (manufactured by Toagosei Co., Ltd.), and NK ESTER EH-4G is a trade name of polyethylene glycol methacrylate 2-ethylhexyl ether (Shin Nakamura Chemical Co., Ltd.). ). The physical properties of the obtained (PLH-01) are shown in Table 1.

(Comparative Preparation Example 2)
An aqueous dispersion PLH-02 of the following exemplary compound BH-02 was obtained according to the production example of the copolymer resin liquid described in paragraph No. [0098] of JP-A-2002-88285. The physical properties of the obtained (PLH-02) are shown in Table 1.

(Comparative Preparation Example 3)
In the preparation of the aqueous dispersion (PL-01) of Preparation Example 1, the types and mixing ratios of the two polymers used were changed as described in Table 1, and the neutralization degree of the mixed polymers became the same. Thus, composite self-dispersing polymer aqueous dispersions PLH-03 and PLH-05 were obtained in the same manner as in Preparation Example 1 except that the addition amount of the NaOH aqueous solution was changed. The physical properties of the resulting aqueous dispersions PLH-03 and PLH-05 are shown in Table 1.

(Comparative Preparation Example 4)
In the preparation of the composite self-dispersing polymer aqueous dispersion PL-01 of Preparation Example 1, instead of using a mixed solution of two polymers B-12 and B-13 having different acid values, a solution 291 containing only the polymer B-06 0.5 g (solid content concentration 44.6%), and the amount of the aqueous NaOH solution was changed so that the degree of neutralization of the polymer would be the same. A dispersion polymer aqueous dispersion PLH-04 was obtained. The physical properties of the obtained PLH-04 are shown in Table 1.

(Comparative Preparation Example 5)
An aqueous dispersion of the polymer B-06 alone obtained in Comparative Preparation Example 4 and an aqueous dispersion of the polymer B-12 alone obtained in the same manner as in Comparative Preparation Example 4 are B-06 / B-12 = The mixture was mixed at a ratio of 8/1 to obtain a self-dispersing polymer aqueous dispersion PLH-06 containing polymer B-06 and polymer B-12. Table 1 shows the physical properties of PLH-06 obtained.

  The particle diameters in Table 1 are volume average particle diameters measured using the dynamic light scattering method within 24 hours after preparing the composite self-dispersing polymer aqueous dispersion. Microtrac UPA EX-150 (Nikkiso ( It is the value measured by the usual method using the product made by Co., Ltd. “First / second polymer (w / w)” means the mass ratio of the first polymer to the second polymer.

The composite self-dispersing polymer aqueous dispersion obtained above was evaluated for stability as follows.
Each 10 mL of the aqueous dispersion was sealed in a 15 mL glass bottle and allowed to stand at 60 ° C. for 14 days, and then the volume average particle diameter was measured. The rate of change in volume average particle size before and after standing [volume average particle size after leaving-volume average particle size before leaving) / volume average particle size before standing] (%) was calculated and evaluated as follows: Evaluation was made according to criteria. The results are shown in Table 1.
In addition, the measurement before standing was performed within 24 hours at room temperature after preparing the composite self-dispersing polymer aqueous dispersion.
~Evaluation criteria~
A: The rate of change of the volume average particle diameter was less than 10%.
Δ: The rate of change of the volume average particle diameter was 10% or more and less than 50%.
X: The rate of change of the volume average particle diameter was 50% or more.

<Example 1>
[Preparation of water-based ink composition]
<< Preparation of Cyan Ink C-1 >>
(Preparation of cyan dispersion as colorant)
In a reaction vessel, 6 parts of styrene, 11 parts of stearyl methacrylate, 4 parts of styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.), 5 parts of Blenmer PP-500 (manufactured by NOF Corporation), 5 parts of methacrylic acid, 2-mercaptoethanol A mixed solution of 0.05 part and 24 parts of methyl ethyl ketone was prepared.
On the other hand, 14 parts of styrene, 24 parts of stearyl methacrylate, 9 parts of styrene macromer AS-6 (manufactured by Toa Gosei), 9 parts of Blenmer PP-500 (manufactured by NOF Corporation), 10 parts of methacrylic acid, 2-mercaptoethanol A mixed solution consisting of 13 parts, 56 parts of methyl ethyl ketone and 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) was prepared and placed in a dropping funnel.

  Next, under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 75 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped over 1 hour. After 2 hours from the end of dropping, a solution prepared by dissolving 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12 parts of methyl ethyl ketone was added dropwise over 3 hours, and further at 75 ° C. for 2 hours, Aging was performed at 80 ° C. for 2 hours to obtain a polymer dispersant solution.

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

  Moreover, 5.0 g of the obtained polymer dispersant solution in terms of solid content, 10.0 g of cyan pigment pigment blue 15: 3 (manufactured by Dainichi Seika), 40.0 g of methyl ethyl ketone, 8.0 g of 1 mol / L sodium hydroxide, Ion-exchanged water 82.0 g and 0.1 mm zirconia beads 300 g were supplied to the vessel and dispersed with a ready mill disperser (manufactured by Imex) at 1000 rpm for 6 hours. The obtained dispersion was concentrated under reduced pressure using an evaporator until methyl ethyl ketone was sufficiently distilled off, and concentrated until the pigment concentration was 10%, and a cyan dispersion C1 as a colorant was prepared. The resulting cyan dispersion C1 had a volume average particle size of 77 nm.

  Then, using cyan dispersion C1 as a colorant and PL-01 as a composite self-dispersing polymer aqueous dispersion, each component was mixed so as to have the following ink composition, and then coarse particles were removed with a 5 μm filter. Cyan ink C-1 was prepared as an aqueous ink composition.

<Ink composition of cyan ink C-1>
・ Cyan pigment (Pigment Blue 15: 3, manufactured by Dainichi Seika) 4%
・ The above polymer dispersant (solid content conversion) 2%
・ PL-01 (solid content conversion) 8%
・ Diethylene glycol monoethyl ether: 10%
(Water-soluble organic solvent, Wako Pure Chemical Industries)
・ Sanix GP250 ... 5%
(Water-soluble organic solvent, manufactured by Sanyo Chemical Industries, Ltd.)
・ Orphine E1010 (Nisshin Chemical)… 1%
・ Ion-exchanged water: added so that the total is 100%

<< Preparation of Cyan Inks C-2 to C-11, CH-1 to CH-7 >>
In the same manner as in the cyan ink C-1, except that the composite self-dispersing polymer aqueous dispersion shown in Table 2 below was used instead of the aqueous dispersion PL-01 of the composite particles in the cyan ink C-1. Cyan inks C-2 to 11 and CH-1 to 7 of the water-based ink composition were prepared, respectively. For CH-5, a cyan ink was prepared without using a composite self-dispersing polymer aqueous dispersion.
Table 2 shows the physical property values of the cyan ink obtained above immediately after preparation (within 24 hours).

In Table 2, the term of viscosity is described according to the following evaluation criteria.
~Evaluation criteria~
○ ... Less than 6.5 mPa · s Δ… 6.5 mPa · s or more and less than 10 mPa · s ×… 10 mPa · s or more

[Preparation of treatment solution]
Each component was mixed so that it might become the following composition, and the process liquid was prepared. The physical properties of the treatment liquid were a viscosity of 2.6 mPa · s, a surface tension of 37.3 mN / m, and a pH of 1.6 (25 ° C.).
~ Composition of treatment liquid ~
Malonic acid: 15.0%
(Divalent carboxylic acid, manufactured by Wako Pure Chemical Industries, Ltd.)
・ Diethylene glycol monomethyl ether: 20.0%
(Wako Pure Chemical Industries, Ltd.)
-N-oleoyl-N-methyl taurine sodium: 1.0%
(Surfactant)
・ Ion exchange water: 64.0%

[Evaluation]
Each cyan ink prepared as described above (hereinafter sometimes referred to simply as “ink”) was subjected to an ink stability test, a droplet ejection stability test, a discharge accuracy test, and an image fixability test. The ink aging stability test is an evaluation of the stability of the particle size and viscosity before ink is ejected, that is, when the ink is stored in the ink storage tank (or cartridge). When discharging from the droplet ejection nozzle of the ink jet apparatus, problems such as clogging of the droplet ejection nozzle occur. Further, the droplet ejection test is an evaluation relating to the ejection directionality. When the ink viscosity is high, the nozzles are clogged, resulting in a directionality defect. The ejection accuracy test is an evaluation of the stability in the ejection direction, and the ejection accuracy decreases when the dispersion stability of the water-based ink composition is poor.

(Aging stability test)
Each 10 mL of ink was sealed in a 15 mL glass bottle, and the volume average particle diameter and viscosity were measured after (1) leaving at 60 ° C. for 14 days and (2) leaving at 40 ° C. for 3 months. Volume average particle size change rate before and after standing [(Volume average particle size after leaving-Volume average particle size before leaving) / Volume average particle size before standing] (%) and Viscosity change rate [( Viscosity after standing-viscosity before standing) / viscosity before standing] (%) was calculated respectively. The evaluation criteria are as follows.
The measurement before standing was performed within 24 hours at room temperature after the ink composition was prepared.
~Evaluation criteria~
○: The rate of change in volume average particle size or the rate of change in viscosity was less than 5%.
Δ: The rate of change in volume average particle diameter or the rate of change in viscosity was 5% or more and less than 10%.
X: The change rate of the volume average particle diameter or the change rate of the viscosity was 10% or more.
And evaluation of x was judged to be unusable. The results are shown in Table 3.

(Drip droplet stability test)
The droplet ejection stability test was conducted as follows. Using a GELJET G717 printer head manufactured by Ricoh, droplets were ejected onto Tokuhishi Double-sided Art N (Mitsubishi Paper Co., Ltd.) so that the resolution was 1200 × 600 dpi and the ink ejection amount was 12 pL. The droplet ejection stability was evaluated by observing the state after 5 hours of continuous hitting. Table 3 shows the droplet ejection stability test results. The evaluation criteria for the droplet ejection stability test in Table 3 are as follows. In addition, it was judged that evaluation of x was unusable.
~Evaluation criteria~
○: No discharge failure and no direction failure.
○ △: There was no discharge failure and a little direction failure occurred.
Δ: Almost no ejection failure and some direction failure occurred.
X: There were many ejection defects.

(Discharge accuracy test)
-Initial pitch evaluation-
Sixteen 1-dot lines (length 120 mm) were printed under the following conditions. Next, the distance between lines at a position 50 mm from the droplet ejection start portion of the print sample was measured with a dot analyzer DA-6000 manufactured by Oji Scientific Instruments. The standard deviation of the measured distance between the lines was calculated as the discharge deviation, and this was used as an index of the discharge directionality, and the discharge accuracy was evaluated according to the following evaluation criteria. The results are shown in Table 3.

-Printing conditions-
Printer: Dimatix, DMP-2831
Ink amount: 10 pl
Image resolution: Nozzle arrangement direction 100 dpi
Transport direction 3200dpi
Discharge frequency: 24KHz
Recording medium: Fuji Film Co., Ltd.

~Evaluation criteria~
○: It was less than 5 μm.
Δ: 5 μm or more and less than 10 μm.
×: 10 μm or more.

(Fixability test)
A GELJET GX5000 printer head (manufactured by Ricoh) was prepared, and the storage tank connected thereto was refilled with the cyan ink obtained above. Tokishi Art Double Sided N (Mitsubishi Paper Co., Ltd.) as a recording medium is fixed on a stage that can move in a predetermined linear direction at 500 mm / second, and the stage temperature is kept at 30 ° C. The treated liquid was applied with a bar coater to a thickness of about 1.2 μm, and dried immediately at 50 ° C. for 2 seconds immediately after the application.
After that, the GELJET GX5000 printer head is fixedly arranged so that the direction of the line head in which the nozzles are arranged (main scanning direction) is inclined by 75.7 degrees with respect to the direction orthogonal to the moving direction of the stage (sub scanning direction). Then, while moving the recording medium at a constant speed in the sub-scanning direction, the ink was ejected by a line method under an ink droplet amount of 2.4 pL, an ejection frequency of 24 kHz, and a resolution of 1200 dpi × 1200 dpi, and a cyan solid image was printed.
Immediately after printing, the film was dried at 60 ° C. for 3 seconds, passed between a pair of fixing rollers heated to 60 ° C., and subjected to heat fixing treatment with a nip pressure of 0.25 MPa and a nip width of 4 mm, thereby obtaining an evaluation sample. .
After the cellophane tape (manufactured by Nichiban Co., Ltd.) and the mending tape (manufactured by 3M Co.) were attached to the evaluation sample so that the entire surface of the tape was adhered to the solid image part of the obtained evaluation sample, it was immediately peeled off, and the tape was peeled off. The color transfer was evaluated according to the following evaluation criteria.

~Evaluation criteria~
○ ... No color transfer was observed for both cellophane tape and mending tape.
Δ: Slight color transfer was observed on at least one of cellophane tape or mending tape.
X: Color transfer was observed on both the cellophane tape and the mending tape.

As can be seen from Table 3, the aqueous ink composition of the present invention is excellent in stability over time. On the other hand, cyan inks CH-1 and CH-2 had low dispersion stability and high ink viscosity. Furthermore, the viscosity and particle size tended to increase over time.
In addition, the water-based ink composition of the present invention has low ink viscosity and excellent ejection stability without causing defective discharge, whereas cyan inks CH-1 and CH-2 have high ink viscosity and are dispersed. The stability was low, and the droplet ejection stability was low.
Further, CH-3 containing a composite self-dispersing polymer having a difference in acid value of the polymer to be mixed of less than 8 tended to increase in viscosity and particle size over time. Also, cyan ink CH-4 prepared using an aqueous dispersion of a single polymer alone tended to be inferior in ejection accuracy.
Further, the cyan inks C-1 to C-11 containing the composite self-dispersing polymer aqueous dispersion of the present invention in the aqueous ink composition have good fixability, whereas the aqueous ink composition contains The fixability of the cyan ink CH-5 that does not contain the composite self-dispersing polymer aqueous dispersion is greatly inferior.
As described above, by using an ink composition containing a composite self-dispersing polymer aqueous dispersion produced by a specific production method, an ink having high unprecedented ink stability, stable ejection properties, and good fixing properties. It can be seen that the composition could be provided.

Claims (10)

A mixed solution comprising a first water-insoluble polymer having an acidic group and a second water-insoluble polymer having an acidic group and having an acid value different from the acid value of the first water-insoluble polymer by at least 8; Obtained from
A composite self-dispersing polymer aqueous dispersion containing composite particles containing the first water-insoluble polymer and the second water-insoluble polymer and having a volume average particle size of 0.1 nm to 80 nm.   The composite self-dispersing polymer aqueous dispersion according to claim 1, wherein the first water-insoluble polymer and the second water-insoluble polymer are both vinyl polymers.   The composite self-dispersing polymer aqueous dispersion according to claim 1 or 2, wherein the composite self-dispersing polymer aqueous dispersion aggregates due to a change in pH environment.   The composite self-dispersing polymer aqueous dispersion according to any one of claims 1 to 3, wherein the acidic groups in the first polymer and the second polymer are both carboxyl groups.   The first water-insoluble polymer and the second water-insoluble polymer both contain a hydrophobic constituent unit, and the hydrophobic constituent unit is derived from at least one selected from an acrylate ester monomer and a methacrylate ester monomer. The composite self-dispersing polymer aqueous dispersion according to any one of claims 1 to 4, which is a unit.   An aqueous ink composition comprising the composite self-dispersing polymer aqueous dispersion according to any one of claims 1 to 5 and a colorant. Using a first water-insoluble polymer having an acidic group and a second water-insoluble polymer mixed solution having an acidic group and an acid value different from the acid value of the first polymer by 8 or more and water, Obtaining composite particles comprising the first water-insoluble polymer and the second water-insoluble polymer,
The manufacturing method of the composite self-dispersing polymer aqueous dispersion whose volume average particle diameter of the said composite particle is 0.1 to 80 nm.   An ink set comprising the aqueous ink composition according to claim 6 and a treatment liquid capable of forming an aggregate by contact with the aqueous ink composition. An ink application step of applying the aqueous ink composition according to claim 6 to a recording medium;
A heat fixing step of fixing the image by heating the recording medium to which the water-based ink composition has been applied.   The image forming method according to claim 9, further comprising a treatment liquid application step of applying a treatment liquid capable of forming an aggregate by contact with the aqueous ink composition according to claim 6 to a recording medium.