JP2009126931A - Water-based ink composition, ink set and image recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition having a nonconventional and extremely high aggregation reaction rate and high stability of ink with time and an ink set. <P>SOLUTION: The water-based ink composition comprises a water-insoluble colored particle (A) and a water-insoluble particle (B) coated with a carboxy group-containing copolymer. The ink set comprises at least one kind of the water-based ink composition and a treatment solution for changing the pH of the water-based ink composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water-based ink composition, an ink set, and an image recording method, and more particularly to a technique for speeding up the aggregation reaction rate of the water-based ink composition.

  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.

Among ink-jet recording methods, there is known an ink-jet head that forms an image on an intermediate transfer member by performing ink droplets onto the intermediate transfer member and then transfers the image onto a recording medium. . According to this transfer type recording method, it is possible to transfer the image onto the recording medium after removing the ink solvent (for example, water) on the intermediate transfer member by means such as a solvent removing roller. Since there are no problems such as image blurring, back-through, and deformation of the recording medium (so-called cockling), a high-quality image can be obtained.
As an ink jet recording method, there is known a two-liquid reaction method that promotes fixing of an ink by causing two liquids of an ink and a treatment liquid that aggregates the ink to react to cause the ink to aggregate.

  When this two-component reaction method is applied to a transfer-type ink jet recording method, in order to reduce the size of the apparatus, the time until the ink aggregates after the ink is brought into contact with the treatment liquid on the intermediate transfer member is shortened. There is a need to. In other words, the solvent in the aggregate that agglomerates due to contact between the ink and the processing liquid is transported to the solvent removal roller and removed, but if the aggregation reaction rate is slow, a long distance from the droplet ejection nozzle to the solvent removal roller is secured. It must be done, and the equipment becomes larger.

  As a conventional technique in which the two-component reaction method is applied to a transfer type inkjet recording method, for example, a recording liquid containing at least a colorant and the other reactivity capable of reacting with at least one reactive component in the recording liquid There is known a method including a step of mixing a treatment liquid containing components on a transfer body and a step of transferring the mixture to a recording material (for example, see Patent Document 1). Furthermore, it is known to use a recording liquid containing at least a resin emulsion having an ionic group on the surface of the resin particles as the reactive component in the recording liquid that reacts with a reactive component in the processing liquid. According to this recording method, even when recording is performed quickly, the image on the transfer body is not blurred and a high transfer rate can be obtained.

Further, as a method for synthesizing a resin emulsion, in addition to an emulsion polymerization method using a low molecular surfactant, for example, a hydrophobic vinyl monomer mixture containing an α, β-unsaturated carboxylic acid is polymerized in an organic solvent. In the presence of a vinyl-based aqueous emulsion polymer obtained by removing an organic solvent from the resulting polymer-containing solution and then adding water and a basic substance, a radically polymerizable aliphatic vinyl-based monomer A method of producing a resin emulsion for polymerizing a body is known (for example, see Patent Document 2).
JP 2003-82265 A JP 53-39387 A

  However, the ink composition and the treatment liquid described in Patent Document 1 have a slow aggregation reaction rate, and after the ink composition is ejected from the nozzle onto the intermediate transfer body to which the treatment liquid is applied, the treatment liquid and There is a problem in that it takes a long time for the ink composition that has come into contact to aggregate. That is, when the ink composition is used, in an ink jet recording apparatus that requires quick recording, it is inevitable that the entire recording apparatus is enlarged. Further, even when the two-liquid reaction method is applied to a method of directly aggregating on a recording medium not via an intermediate transfer member, if the aggregation reaction rate between the ink composition and the treatment liquid is slow, There is a problem that the coloring material penetrates together with the permeating solvent, the fixing property on the recording medium is deteriorated, and the recording density and the sharpness are lowered. Therefore, speeding up the agglomeration reaction rate between the ink composition and the treatment liquid is an important issue in ordinary inkjet recording methods other than the transfer type.

  On the other hand, when the aliphatic resin emulsion obtained by the production method described in Patent Document 2 is applied to the above-described two-component reaction method, a weak acid such as a safe organic carboxylic acid has insufficient cohesion, and the image There is a problem that the transferability and fixability of the toner are inferior, and the abrasion resistance of the image is poor.

  The present invention has been made in view of such circumstances, and provides an ink composition and an ink set having an unprecedented extremely high agglomeration reaction rate and high stability over time of the ink. It is an object of the present invention to provide a used image recording method.

Specific means for solving the above problems are as follows.
<1> An aqueous ink composition comprising water-insoluble colored particles (A) containing a colorant and water-insoluble particles (B) coated with a carboxyl group-containing copolymer.
<2> The water-based ink composition according to <1>, wherein the water-insoluble particles (B) coated with the carboxyl group-containing copolymer have a property of aggregating due to a change in pH environment.

<3> The water-insoluble particles (B) coated with the carboxyl group-containing copolymer include a water-insoluble polymer having a glass transition temperature of 15 ° C. to 120 ° C. <1> or <2 > The water-based ink composition as described in>.
<4> The water-based ink composition according to <3>, wherein the water-insoluble polymer has an acid value of less than 30.

<5> The water-insoluble particles (B) coated with the carboxyl group-containing copolymer are obtained by emulsion polymerization in the presence of an aqueous solution or emulsion of the carboxyl group-containing copolymer. <1 The water-based ink composition according to any one of> to <4>.
<6> The aqueous ink composition according to <5>, wherein the aqueous solution or emulsion of the carboxyl group-containing copolymer further contains a basic compound.

<7> The water-based ink composition according to any one of <1> to <6>, wherein the carboxyl group-containing copolymer has an acid value of 30 or more and 500 or less.

<8> An ink set comprising at least one of the water-based ink compositions according to any one of <1> to <7>, and a treatment liquid that changes the pH of the water-based ink composition.

<9> A treatment liquid application step of applying a treatment liquid contained in the ink set according to <8> onto a recording medium; and at least one of the water-based ink composition contained in the ink set according to <8>. A seed is applied on the recording medium to which the treatment liquid is applied, and the water-insoluble colored particles (A) and the water-insoluble particles (B) in the aqueous ink composition are aggregated to form an image on the recording medium. An image recording method comprising: an aggregating step to be formed.
<10> The image recording method according to <9>, further comprising a solvent removal step of removing at least part of the solvent of the aqueous ink composition and the treatment liquid after the aggregation step.

<11> A treatment liquid application step of applying the treatment liquid contained in the ink set according to <8> onto the intermediate transfer member, and at least a water-based ink composition contained in the ink set according to <8>. One type is applied onto the intermediate transfer body to which the treatment liquid has been applied, and the water-insoluble colored particles (A) and the water-insoluble particles (B) in the aqueous ink composition are aggregated to form the surface on the intermediate transfer body. An aggregating step for forming an image on the substrate, a solvent removing step for removing at least part of the solvent of the aqueous ink composition and the treatment liquid from the intermediate transfer body after the aggregating step, and the intermediate step after the solvent removing step. A transfer step of transferring an image formed on the transfer body to a recording medium.

<12> The image recording method according to any one of <9> to <11>, wherein the aggregation step includes a step of applying the water-based ink composition by an inkjet method.

  According to the present invention, it is possible to provide an ink composition and an ink set having an unprecedented extremely high agglomeration reaction rate and high ink stability over time, and an image recording method using the ink set. it can.

  Hereinafter, the water-based ink composition, the ink set, and the image recording method according to the present invention will be described in detail. First, the aqueous ink composition of the present invention (hereinafter sometimes simply referred to as “ink”) and the ink set of the present invention will be described.

<Water-based ink composition>
The aqueous ink composition of the present invention contains at least one kind of water-insoluble colored particles (A) containing a colorant and at least one kind of water-insoluble particles (B) coated with a carboxyl group-containing copolymer. To do. The water-insoluble particles (B) preferably have a property of aggregating due to a change in pH environment.
Since the water-insoluble particles (B) are coated with a carboxyl group-containing copolymer, an extremely fast aggregation rate can be achieved, and the time-dependent stability of the aqueous ink composition containing the water-insoluble particles (B) can be improved. Can be high. Further, the water-insoluble particles (B) can take in the water-insoluble colored particles (A) during aggregation to form aggregates.

The aggregate of the water-insoluble particles (B) and the water-insoluble colored particles (A) can be suitably used for image formation, for example.
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 method for recording an image using the water-based ink composition of the present invention is not particularly limited, and a known image recording method can be used. For example, the image is coated by means such as an inkjet method, a copying method, a printing method, and the like. Examples thereof include a method of applying a water-based ink composition to a recording medium. Among these, an image recording method including a step of applying the water-based ink composition of the present invention by an inkjet method is preferable from the viewpoint of compactness of the recording apparatus and high-speed recording properties.

  Hereinafter, the water-based ink composition of the present invention will be described in detail. The water-insoluble particles (B) coated with a carboxyl group-containing copolymer, which is a characteristic component of the water-based ink composition of the present invention, will be described below. .

(B) Water-insoluble particles The water-insoluble particles (B) in the present invention are characterized by being coated with a carboxyl group-containing copolymer. The water-insoluble particles (B) in the present invention are preferably those obtained by emulsion polymerization in the presence of an aqueous solution or emulsion of a carboxyl group-containing copolymer. Thereby, the coating of the water-insoluble particles (B) with the carboxyl group-containing copolymer can be made more efficient, and the aggregation reaction rate due to the change in pH environment can be improved more effectively.

-Carboxyl group-containing copolymer-
The carboxyl group-containing copolymer in the present invention functions as an emulsifier component. The carboxyl group-containing copolymer forms a micelle having droplets of an emulsified component containing an ethylenically unsaturated monomer described later, which can be a constituent of water-insoluble particles, and incorporates a radical polymerization initiator into the micelle. The polymerization can be started in the state. In other words, the carboxyl group-containing copolymer can provide a field for polymerization in water to an ethylenically unsaturated monomer that is insoluble or hardly soluble in water.

In general, an emulsifier in emulsion polymerization plays a role of emulsifying a hydrophobic component in an aqueous medium. Therefore, it is preferable to have a hydrophilic component and a hydrophobic component. Therefore, it is also important that the carboxyl group-containing copolymer in the present invention has a carboxyl group as a hydrophilic component and further has a hydrophobic portion.
As said hydrophobic part, an aromatic group, an aralkyl group, an alkyl group etc. can be mentioned, for example. Among them, the hydrophobic part preferably contains at least one selected from an aromatic group, an aralkyl group, and an alkyl group having 4 or more carbon atoms.

  There is no restriction | limiting in particular as a carboxyl group-containing copolymer, For example, a vinyl polymer and a condensation type polymer (Epoxy resin, polyester, polyurethane, polyamide, cellulose, polyether, polyurea, polyimide, polycarbonate etc.) can be used.

The carboxyl group-containing copolymer in the present invention is particularly preferably a vinyl polymer from the viewpoint of dispersion stability of water-insoluble particles. Preferable examples of the vinyl polymer and the monomer constituting the vinyl polymer include those described in JP-A Nos. 2001-181549 and 2002-88294. In addition, radical transfer of vinyl monomers using dissociable groups (or substituents that can be induced to dissociable groups), polymerization initiators, and iniferters, or dissociable groups on either initiators or terminators A vinyl polymer in which a dissociable group is introduced at the end of a polymer chain by ionic polymerization using a compound having (or a substituent that can be derived from a dissociable group) can also be used.
Moreover, as a suitable example of the monomer which comprises a condensation type polymer and a condensation type polymer, what is described in Unexamined-Japanese-Patent No. 2001-247787 can be mentioned.

The carboxyl group-containing copolymer can be composed of, for example, an ethylenically unsaturated monomer having a carboxyl group and other components.
Examples of the ethylenically unsaturated monomer having a carboxyl group that is a copolymerization component of the carboxyl group-containing copolymer include (meth) acrylic acid, (anhydrous) itaconic acid, and (anhydrous) maleic acid. In addition, when the carboxyl group-containing copolymer has no crosslinkable functional group other than the carboxyl group, the carboxyl group-containing copolymer can be synthesized by bulk polymerization without using an organic solvent.

Moreover, as an example of components other than the ethylenically unsaturated monomer having a carboxyl group that can constitute a carboxyl group-containing copolymer,
Methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl ( Alkyl (meth) acrylates such as (meth) acrylate and ethylhexyl (meth) acrylate;
Hydroxyl groups such as hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, and hydroxyhexyl (meth) acrylate Ethylenically unsaturated monomers having aralkyl; aralkyl (meth) acrylates such as benzyl (meth) acrylate; dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate; aromatic monomers such as styrene and methylstyrene; N -N-hydroxyalkyl (meth) acrylamide such as hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide; -Methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N- (n-, iso) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, And (meth) acrylamides such as N-alkoxyalkyl (meth) acrylamides such as N- (n-, iso) butoxyethyl (meth) acrylamide.

  The carboxyl group-containing copolymer in the present invention is composed of (meth) acrylic acid, aromatic monomer, aralkyl (meth) acrylate, dialkylaminoalkyl (meth) acrylate and alkyl (meth) from the viewpoint of emulsion polymerization stability. It is preferably composed of at least one selected from acrylates, and more preferably composed of (meth) acrylic acid, an aromatic monomer, and alkyl (meth) acrylate.

  The acid value (KOHmg / g) of the carboxyl group-containing copolymer in the present invention is a viewpoint that promotes the aggregation reaction by a change in pH environment (for example, contact with an acidic treatment solution) and a viewpoint that stabilizes emulsion polymerization. Therefore, it is preferably 30 or more and 500 or less. More preferably, it is 30 or more and 400 or less, More preferably, it is 30 or more and 200 or less. When the acid value is 30 or more, the emulsifying power in radical polymerization is improved, and emulsion polymerization can be performed more stably. Moreover, aggregation reactivity can be improved more because an acid value is 500 or less.

The molecular weight range of the carboxyl group-containing copolymer is preferably 5000 to 200,000 in terms of weight average molecular weight, more preferably 10,000 to 150,000, and still more preferably 30,000 to 70,000. By setting the weight average molecular weight to 5000 or more, the polymerization stability is further improved, and aggregation during the polymerization can be more effectively suppressed. Moreover, when the weight average molecular weight is 200,000 or less, it is possible to suppress the viscosity of the aqueous solution or emulsion of the carboxyl group-containing copolymer from becoming too high, and the emulsion polymer can be more uniformly performed. In addition, it is possible to more effectively suppress the deterioration of ejection properties when the aqueous ink composition is configured.
The weight average molecular weight can be measured by gel permeation chromatography (GPC).

  The carboxyl group-containing copolymer in the present invention can be obtained by a usual method such as solution polymerization in a solvent, for example. If possible, synthesis by polymerization in an aqueous medium or synthesis by bulk polymerization can also be performed. Is possible.

In general, emulsion polymerization is often performed in the absence of an organic solvent, and even when an organic solvent is present, it is often preferable that the proportion of the organic solvent in the entire system is not so large. Therefore, when the carboxyl group-containing copolymer obtained by solution polymerization is used as an emulsifier when radically polymerizing the component to be emulsified, the organic solvent used when preparing the carboxyl group-containing copolymer is removed. It is preferable to keep it. By reducing the ratio of the organic solvent, the polymerization conversion rate becomes better, and the physical properties of the coating film become better.
As a method for removing the organic solvent, for example, a solvent removal method using a normal decompression method can be used.

  Specific examples of the carboxyl group-containing copolymer are exemplified compounds C-01 to C-10, but the present invention is not limited thereto. In addition, the parenthesis represents the mass ratio of the copolymer component.

C-01: Styrene / butyl acrylate / acrylic acid copolymer (48/27/25)
C-02: Methyl methacrylate / ethyl acrylate / methacrylic acid copolymer (60/30/10)
C-03: benzyl methacrylate / ethyl acrylate / methacrylic acid / dimethylaminoethyl methacrylate copolymer (60/30/6/4)
C-04: Methyl methacrylate / benzyl methacrylate / acrylic acid copolymer (70/27/3)
C-05: Styrene / butyl methacrylate / methacrylic acid / dimethylaminoethyl methacrylate copolymer (55/24/15/6)
C-06: Styrene / t-butyl metallate / acrylic acid copolymer (53/27/20)
C-07: benzyl methacrylate / butyl methacrylate / methacrylic acid copolymer (55/30/15)
C-08: benzyl methacrylate / cyclohexyl methacrylate / methacrylic acid / dimethylaminoethyl acrylate copolymer (70/15/10/5)
C-09: benzyl methacrylate / dodecyl methacrylate / N-vinyl pyrrolidone copolymer / acrylic acid (50/25/5/20)
C-10: benzyl methacrylate / methyl methacrylate / hydroxyethyl methacrylate / acrylic acid copolymer (55/15/10/20)

-Water-insoluble polymer-
The water-insoluble particles (B) in the present invention preferably contain at least one water-insoluble polymer having a glass transition temperature of 15 ° C to 120 ° C. Thereby, good transferability can be imparted to the aggregate formed by the water-insoluble particles (B).
The acid value of the water-insoluble polymer is preferably less than 30. Thereby, the aggregation reactivity by the change of pH environment of a water-insoluble particle | grain (B) improves more effectively.

The water-insoluble polymer in the present invention may be used alone or in combination of two or more different in structure, copolymerization ratio, molecular weight and the like.
There is no restriction | limiting in particular as said water-insoluble polymer, For example, a vinyl polymer and a condensation type polymer (Epoxy resin, polyester, polyurethane, polyamide, a cellulose, polyether, polyurea, a polyimide, a polycarbonate etc.) can be used.

Preferred examples of the vinyl polymer and the monomer constituting the vinyl polymer, and the condensation polymer and the monomer constituting the condensation polymer include the vinyl polymer and the monomer constituting the vinyl polymer mentioned in the description of the carboxyl group-containing copolymer, In addition, the condensation polymer and the monomer constituting the condensation polymer can be similarly exemplified.
The water-insoluble polymer in the present invention is preferably a vinyl polymer from the viewpoint of aggregation reactivity and transferability, more preferably a vinyl polymer composed of an aromatic monomer and another vinyl monomer, and an aromatic monomer. And a vinyl polymer comprising at least one selected from alkyl (meth) acrylate, dialkylaminoalkyl (meth) acrylate and (meth) acrylic acid.

  In the present invention, the glass transition temperature (Tg) of the water-insoluble polymer constituting the water-insoluble particles (B) is in the range of 15 to 120 ° C. from the viewpoint of ink droplet ejection properties and ink fixing properties in the ink jet system. It is preferable that 30-100 degreeC is more preferable, and 40-90 degreeC is further more preferable. When the Tg of the water-insoluble polymer is equal to or higher than the above temperature, the ink droplet ejection property becomes better. Further, the fixing property of the ink becomes better when the temperature is equal to or lower than the above temperature.

The water-insoluble polymer can contain a dissociable group or a nonionic dispersible group.
When the water-insoluble polymer contains an anionic dissociable group, the content of the anionic dissociable group is determined from the viewpoint of promoting the aggregation reaction due to a change in pH environment (for example, contact with an acidic treatment solution). (KOHmg / g) is preferably less than 30, more preferably 20 or less, and particularly preferably 10 or less. In addition, about the anionic dissociation group, the description about the anionic group in the dispersing agent mentioned later can be applied as it is.

  Further, when a nonionic dispersible group is included, from the viewpoint of aggregation reactivity, the content of the nonionic dispersible group is preferably 10 or less as the number of functional groups (mmol / g), and may not be contained. More preferred. In addition, as a nonionic dispersible group, the description about the nonionic group in the dispersing agent mentioned later can be applied as it is.

  On the other hand, when the water-insoluble polymer contains a cationic dissociable group, the content of the cationic group is preferably 0 to 100, more preferably 0 to 70, and particularly preferably 10 to 60, as the number of functional groups (mmol / g). preferable. Since the water-insoluble polymer contains a cationic dissociable group, the pH of the ink is lowered, so that the particle charge of the water-insoluble particles (B) can be changed from minus to plus, and the aggregation reaction rate is further improved. Can be made.

The cationic dissociable group is not particularly limited as long as it has a positive charge, but is preferably a cationic organic dissociable group, and is a cationic organic dissociative group containing a nitrogen atom or a phosphorus atom. More preferably, it is a group. Among these, a pyridinium cation or an ammonium cation is more preferable.
Specific examples of the monomer containing a cationic dissociable group include N, N-dialkylaminoethyl (meth) acrylate, N, N-dialkylaminopropyl (meth) acrylate, and N, N-dialkylaminopropyl (meth) acrylamide. And monomers having a tertiary amino group such as vinyl imidazole and vinyl pyridine.

  The molecular weight of the water-insoluble polymer in the present invention is 3,000 to 2,000,000 in terms of weight average molecular weight, preferably 5,000 to 1,000,000, more preferably 10,000 to 1,000,000 from the viewpoints of aggregation and ink transfer properties. is there.

Hereinafter, exemplary compounds PL-01 to PL-22 are listed as examples of the water-insoluble polymer compound. The value in parentheses represents the mass ratio of the copolymer component.
PL-01: Styrene / 2-ethylhexyl methacrylate copolymer (90/10)
PL-02: Styrene / butyl acrylate copolymer (80/20)
PL-03: Styrene / butyl acrylate / dimethylaminoethyl methacrylate copolymer (68/22/10)
PL-04: Styrene / butyl methacrylate / acrylic acid copolymer (70/27/3)
PL-05: Styrene / butyl methacrylate / acrylic acid / dimethylaminoethyl methacrylate copolymer (67/24/3/6)
PL-06: Styrene / t-butyl metallate copolymer (50/50)
PL-07: benzyl methacrylate / butyl methacrylate / methacrylic acid copolymer (80/17/3)
PL-08: benzyl methacrylate / cyclohexyl methacrylate / dimethylaminoethyl acrylate copolymer (70/20/10)
PL-09: benzyl methacrylate / dodecyl methacrylate / N-vinylpyrrolidone copolymer (77/15/8)
PL-10: benzyl methacrylate / methyl methacrylate / hydroxyethyl methacrylate copolymer (80/10/10)
PL-11: benzyl methacrylate / dimethylaminopropyl acrylate copolymer (92/8)
PL-12: Styrene / hexyl acrylate / dimethylaminopropylacrylamide copolymer (80/15/5)
PL-13: Styrene / benzyl methacrylate / N-vinylimidazole copolymer (60/35/5)
PL-14: benzyl methacrylate / butyl methacrylate / N-acryloylmorpholine copolymer (80/10/10)
PL-15: benzyl methacrylate / t-octylacrylamide / acrylic acid copolymer (80/17/3)
PL-16: Styrene / butyl methacrylate / glycidyl methacrylate copolymer (75/15/10)
PL-17: Styrene / butyl methacrylate / 2-carboxyethyl acrylate copolymer (70/25/5)
PL-18: Styrene / butyl methacrylate / 4-vinylpyridine copolymer (70/25/5)
PL-19: Styrene / 4-phenoxyethyl acrylate / dimethylaminopropyl methacrylate copolymer (70/23/7)
PL-20: Styrene / butyl methacrylate copolymer (65/35)
PL-21: Styrene / butyl acrylate / ethylene glycol diacrylate copolymer (65/30/5)
PL-22: Styrene / 3-chloro-2-hydroxypropyl methacrylate copolymer (80/20)

-Preparation method of water-insoluble particles (B)-
As a method for producing the water-insoluble particles (B) coated with the carboxyl group-containing copolymer in the present invention, known methods can be used without any particular limitation. For example, 1) emulsion polymerization, 2) emulsion dispersion, etc. Can be mentioned.
In the present invention, water-insoluble particles (B) can be obtained by carrying out emulsion polymerization and emulsion dispersion in the presence of an aqueous solution or emulsion of the carboxyl group-containing copolymer. In addition, a carboxylate emulsifier can be used in combination as long as the effects of the present invention are not impaired.

  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, various fatty acid soaps such as beef tallow fatty acid soap, coconut oil fatty acid soap, rosin acid soap, stearates and oleates, alkenyl succinates, N-acyl sarcosine salts such as sodium N-lauroyl sarcosine, etc. Is mentioned. Among them, alkenyl succinate is preferable from the viewpoint of stability against shearing force. Moreover, as a suitable example of a reactive carboxylate emulsifier, what is described in Unexamined-Japanese-Patent No. 9-302007 etc. can be mentioned.

-Basic compounds-
In the present invention, the aqueous solution or emulsion of the carboxyl group-containing copolymer preferably further contains a basic compound. By further containing a basic compound, some or all of the carboxyl groups in the carboxyl group-containing copolymer are neutralized, and the aqueous solution or emulsion of the carboxyl group-containing copolymer can be made more stable. Thus, emulsion formation using this can be performed more efficiently.

  Examples of the basic compound used in the present invention include organic amine compounds, ammonia, alkali metal hydroxides, and the like. 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. These basic compounds are preferably used in an amount of 20 to 300 mol% with respect to 100 mol% of the carboxyl groups in the carboxyl group-containing copolymer.

-1) Emulsion polymerization
Emulsion polymerization includes, for example, a monomer, a polymerization initiator, an emulsifier (including a polymer emulsifier, hereinafter may be simply referred to as an emulsifier), and, if necessary, a water-soluble polymerization chain in an aqueous medium (eg, water). It can be carried out by polymerizing an emulsion prepared by adding a transfer agent or the like.
The monomer is not particularly limited, and a monomer that can constitute the water-insoluble polymer can be suitably used.

The polymerization initiator is not particularly limited, and may be an inorganic persulfate (for example, potassium persulfate, sodium persulfate, ammonium persulfate, etc.), an azo initiator (for example, 2,2′-azobis (2- Amidinopropane) dihydrochloride, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], etc.), organic peroxides (eg peroxypivalic acid-t-butyl, t- Butyl hydroperoxide and the like) can be used. These can be used alone or in combination of two or more.
Among these, it is preferable to use an azo-based initiator and an organic peroxide from the viewpoint of aggregation of water-insoluble particles.
The amount of the polymerization initiator used in the present invention is usually 0.01 to 2% by mass, preferably 0.2 to 1% by mass, based on all monomers.

  As the usage-amount of the carboxyl group-containing copolymer as an emulsifier in this invention, it is preferable that it is 2-300 mass% with respect to all the monomers from a cohesive viewpoint of water-insoluble particle | grains, and 5-100 mass%. It is more preferable that When the amount of the carboxyl group-containing copolymer used is 2% by mass or more, the monomer can be emulsified more efficiently. Moreover, the aggregation property of the water-insoluble particle | grains (B) obtained can be made more favorable because it is 300 mass% or less.

  Examples of the water-soluble polymerization chain transfer agent include mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-lauryl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, tetramethylthiuram disulfide, and tetraethylthiuram disulfide. And disulfides, halogenated derivatives such as carbon tetrachloride, carbon tetrabromide, 2-ethylhexyl thioglycolate, α-methylstyrene dimer and sodium phosphinate as a water-soluble chain transfer agent. More than seeds can be used.

-2) Emulsification dispersion-
As the emulsification dispersion in the present invention, a known emulsification dispersion method can be used without particular limitation. For example, a forced emulsification method in which a polymer solution or a molten polymer is emulsified and dispersed in an aqueous medium containing an emulsifier, the emulsifier is dissolved in the polymer solution and the aqueous medium is added, or the aqueous medium solution of the emulsifier is gradually added to the polymer solution. Any method of phase inversion emulsification that is added and phase inversion may be used.
The water-insoluble polymer can be used as the polymer solution and the molten polymer. The emulsifier is as described above.

In the present invention, from the viewpoint of dispersion stability and aggregation of the water-insoluble particles (B), the water-insoluble polymer is prepared by emulsion polymerization in the presence of an aqueous solution or emulsion of a carboxyl group-containing copolymer. It is preferable to constitute insoluble particles (B).
Further, the water-insoluble particles (B) in the present invention are selected from (meth) acrylic acid, aromatic monomers, aralkyl (meth) acrylates, dialkylaminoalkyl (meth) acrylates and alkyl (meth) acrylates from the same viewpoint. Selected from aromatic monomers and (meth) acrylic acid, aralkyl (meth) acrylates, dialkylaminoalkyl (meth) acrylates and alkyl (meth) acrylates. Water-insoluble particles (B) containing at least one water-insoluble polymer are preferable.

The average particle size of the water-insoluble particles (B) in the present invention is preferably in the range of 20 to 400 nm, more preferably 20 to 200 nm, and even more preferably 20 to 100 nm. Aggregation characteristics are improved by having an average particle diameter of 20 nm or more. Further, by setting the average particle diameter to 400 nm or less, ink droplet ejection properties are improved.
Further, the particle size distribution of the water-insoluble particles (B) is not particularly limited, and may be any having a wide particle size distribution or a monodispersed particle size distribution. Further, two or more kinds of water-insoluble particles may be mixed and used.
The average particle size and particle size distribution of the water-insoluble particles (B) can be measured using, for example, a light scattering method.

The content of the water-insoluble particles (B) in the present invention is preferably 1 to 30% by mass and 5 to 15% by mass with respect to the aqueous ink composition from the viewpoint of image glossiness and the like. It is more preferable.
In addition, the content ratio of the water-insoluble colored particles to the water-insoluble particles (water-insoluble colored particles / water-insoluble particles) in the water-based ink composition of the present invention is 1 / 0.5 to from the viewpoint of image scratch resistance. 1/10 is preferable, and 1/1 to 1/4 is more preferable.

(A) Water-insoluble colored particles The water-insoluble colored particles (A) in the present invention contain at least one 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 surface-treated with a dispersant can be used as water-insoluble colored particles.

  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, quinophthaloni 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 organic pigment used in the present invention are shown below.
Examples of organic pigments for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Examples of organic pigments for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 222C. I. Pigment violet 19 and the like.

Examples of organic pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment Green 7 and siloxane-crosslinked aluminum phthalocyanine described in U.S. Pat. No. 4,311,775.
Examples of organic pigments for black include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

-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 the colorant, a water-insoluble carrier can be used as a water-insoluble colored particle. 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 (water-insoluble colored particles) can be used as an aqueous dispersion using a dispersant. As the dispersant, the above-described dispersants can be suitably used.

  The water-insoluble colored particles in the present invention preferably contain a pigment and a dispersant, more preferably contain an organic pigment and a polymer dispersant, from the viewpoint of light resistance and quality of the image, and the organic pigment and the carboxyl group. It is particularly preferable to include a polymer dispersant.

In the present invention, the average particle size of the water-insoluble colored particles is preferably 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. When the 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 an average particle diameter is 10 nm or more.
The particle size distribution of the water-insoluble colored particles is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Further, two or more kinds of water-insoluble colored particles having a monodisperse particle size distribution may be mixed and used.
The average particle size and particle size distribution of the water-insoluble colored particles can be measured using, for example, a light scattering method.

In the present invention, the water-insoluble colored particles may be used alone or in combination of two or more.
Further, the content of the water-insoluble colored particles is preferably 1 to 25% by mass, more preferably 2 to 20% by mass, and more preferably 5 to 20% by mass with respect to the aqueous ink composition from the viewpoint of image density. % Is more preferable, and 5 to 15% by mass is particularly preferable.

-Water-soluble organic solvent-
The aqueous ink composition of the present invention contains water as a main solvent, but can further contain a water-soluble organic solvent. The water-soluble organic solvent can be contained as a drying inhibitor and a penetration enhancer.
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 recording method using an ink jet 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, Polyhydric alcohols represented 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 penetrate better into the recording medium (printing paper). 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 printing bleeding 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), amine (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, Tylenediamine, 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, 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.

  The ultraviolet absorber is used for the purpose of improving image storability. Examples of ultraviolet absorbers include benzotriazoles described in JP-A Nos. 58-185677, 61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492, 56-211141, Cinnamic acid compounds described in, for example, Kaihei 10-88106, JP-A-4-298503, 8-53427, 8-239368, 10-182621, JP-A-8- No. 501291, etc., triazine compounds, Research Disclosure No. Compounds described in No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene-based and benzoxazole-based compounds, so-called fluorescent brighteners, can also be used.

  The anti-fading agent is used for the purpose of improving image storage stability. 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. More specifically, Research Disclosure No. No. 17643, Nos. VII to I, J; 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in Japanese Patent No. 15162 and the compounds included in the general formulas and compound examples of typical compounds described on pages 127 to 137 of JP-A-62-215272 can be used.

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.
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 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), which is an acetylene-based polyoxyethylene oxide surfactant, is 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 antifoaming agents, 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 of the water-based ink composition can be measured using, for example, a Brookfield viscometer.

<Ink set>
The ink set of the present invention includes at least one water-based ink composition and at least one treatment liquid that changes the pH environment of the water-based ink composition. By bringing the aqueous ink composition and the treatment liquid into contact with each other, the dispersion stability of the water-insoluble particles is changed, and the water-insoluble colored particles and the water-insoluble particles can be rapidly aggregated.

  The pH of the treatment liquid in the present invention is preferably 1 to 6, more preferably 2 to 5, and further preferably 3 to 5, from the viewpoint of the aggregation rate of the aqueous ink composition. The treatment liquid in the present invention can be configured to contain at least one acidic compound. 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 can be used. Among these, from the viewpoint of the aggregation rate of the aqueous ink composition, a compound having a phosphate group or a carboxyl group is more preferable, and a compound having a carboxyl group is more preferable.

As the compound having a carboxyl group in the present invention, for example, a compound having a furan, pyrrole, pyrroline, pyrrolidone, pyrone, pyrrole, thiophene, indole, pyridine, quinoline structure and further having a carboxyl group as a functional group is preferable. Can be mentioned. Specifically, 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, etc. A treatment liquid can be constituted.
Among the compounds having a carboxyl group, pyrrolidone carboxylic acid, pyrone carboxylic acid, furan carboxylic acid, coumaric acid, or a compound derivative thereof, or a salt thereof is preferable from the viewpoint of safety and low corrosivity. In addition, these compounds may be used individually by 1 type, and may be used together 2 or more types.

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.
As content of the acidic compound of a processing liquid, 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%.

  Further, the treatment liquid may contain other additives within a range that does not impair the effects of the present invention. Other additives include, for example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension adjusters, Known additives such as foaming agents, viscosity modifiers, dispersants, dispersion stabilizers, rust preventives, chelating agents can be mentioned, and are shown as specific examples of other additives contained in the above-mentioned aqueous ink composition. Can be applied.

The viscosity of the treatment liquid in the present invention is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, and in the range of 2 to 15 mPa · s from the viewpoint of the aggregation rate of the aqueous ink composition. Further preferred is a range of 2 to 10 mPa · s.
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 speed of the aqueous ink composition. More preferably it is.
Next, an image recording method using the ink set of the present invention will be described.

<Image recording method>
The first image recording method of the present invention includes a treatment liquid application step of applying a treatment liquid contained in the ink set onto a recording medium, and a treatment of at least one of the aqueous ink compositions contained in the ink set. An aggregating step of applying the liquid onto the recording medium and aggregating the water-insoluble colored particles (A) and the water-insoluble particles (B) in the aqueous ink composition to form an image on the recording medium. And an image recording method.
By using the ink set, the aqueous ink composition can be rapidly aggregated.

  The first image recording method of the present invention preferably further includes a solvent removal step of removing at least a part of the solvent of the water-based ink composition and the treatment liquid after the aggregation step. As a result, it is possible to suppress bleeding, show-through, deformation of the recording medium, and the like of the formed image.

Further, the second image recording method of the present invention includes at least one of a treatment liquid application step for applying a treatment liquid contained in the ink set onto an intermediate transfer member, and an aqueous ink composition contained in the ink set. Then, it is applied onto the intermediate transfer body to which the treatment liquid has been applied, and the water-insoluble colored particles (A) and the water-insoluble particles (B) in the aqueous ink composition are aggregated to form an image on the intermediate transfer body. An aggregation step to be formed; a solvent removal step of removing at least part of the solvent of the ink composition and the treatment liquid from the intermediate transfer member after the aggregation step; and a step of removing the solvent on the intermediate transfer member after the solvent removal step. A transfer step of transferring the formed image to a recording medium.
By using the ink set of the present invention, the water-based ink composition can be rapidly aggregated, and an image composed of aggregates having good transferability can be obtained.

  In the image recording method of the present invention, as a method for applying the treatment liquid to the recording medium or the intermediate transfer member, a known liquid applying method can be used without any particular limitation. Examples of the liquid application method include application using an inkjet method, application using a coating roller, and the like.

  In addition, as a method for applying the water-based ink composition to the recording medium or the intermediate transfer body to which the treatment liquid is applied, a known liquid application method can be used without any particular limitation. Examples of the liquid application method include application by an inkjet method. In the present invention, from the viewpoint of rapid recording properties, it is preferable that the water-based ink composition is applied by an ink jet method.

  Hereinafter, as an example of the image recording method of the present invention, an image recording method using an inkjet method and an apparatus for carrying out the method will be described in detail with reference to the drawings.

[Inkjet recording apparatus]
FIG. 1 is an example of the overall configuration of a transfer type inkjet recording apparatus for carrying out an inkjet recording method using the ink set of the present invention.
As shown in FIG. 1, the inkjet recording apparatus 10 mainly includes an intermediate transfer body 12, a treatment liquid application unit 14, an ink discharge unit 16, and a transfer unit 18, and further includes a solvent removal unit 20 and a cleaning unit 22. I have. Although not shown in the figure, an image fixing unit for fixing the image transferred to the recording medium 34 can be further provided.

The intermediate transfer body 12 is composed of an endless belt having a predetermined width, and is wound around a plurality of rollers 26. In the present embodiment, four rollers 26A to 26D are used as an example. The intermediate transfer member 12 is not limited to an endless belt, and a method of conveying a sheet-like intermediate transfer member with a conveyor belt or a drum-like member can also be used.
The power of a motor (not shown) is transmitted to at least one of the plurality of rollers 26, and the intermediate transfer body 12 is driven counterclockwise in FIG. 1 outside each roller 26 (26A to 26D) by driving the motor. (Hereinafter referred to as “transfer body rotation direction”).

  The processing liquid application unit 14 is provided with a recording head (processing liquid head) 30S corresponding to the processing liquid. The processing liquid head 30 </ b> S discharges the processing liquid from the discharge surface facing the intermediate transfer body 12. Thereby, the treatment liquid is applied onto the recording surface 12 a of the intermediate transfer body 12. In addition, the process liquid provision part 14 can also employ | adopt the application | coating system which used the application roller not only the system discharged from nozzle-shaped bend. This coating method can easily apply the treatment liquid to almost the entire surface including the image area on which the ink droplets on the intermediate transfer body 12 land. In this case, it is preferable that the thickness of the treatment liquid on the intermediate transfer body 12 is 1 to 5 μm. A means for making the thickness of the treatment liquid on the intermediate transfer body 12 constant may be further provided. For example, there are a method using an air knife, and a method in which a member having a sharp corner is provided with a gap having a prescribed amount of processing solution thickness between the intermediate transfer member 12.

The ink discharge unit 16 is disposed downstream of the treatment liquid application unit 14 in the intermediate transfer member rotation direction. The ink ejection unit 16 is provided with recording heads (ink heads) 30K, 30C, 30M, and 30Y corresponding to black (K), cyan (C), magenta (M), and yellow (Y) inks. Yes. Then, each ink that satisfies the water-based ink composition condition of the present invention is stored in each ink storage section (not shown) corresponding to each color ink, and is supplied to each recording head 30K, 30C, 30M, 30Y.
Each of the ink heads 30K, 30C, 30M, and 30Y ejects the corresponding color ink from the ejection surface facing the intermediate transfer body 12. As a result, each color ink is applied onto the recording surface 12 a of the intermediate transfer body 12.

  Each of the treatment liquid head 30S and the ink heads 30K, 30C, 30M, and 30Y has a large number of ejection ports (nozzles) over the maximum recording width (maximum recording width) of the image formed on the intermediate transfer body 12. It is a full line head formed. Compared to a serial type that performs recording while reciprocating a short shuttle head in the width direction of the intermediate transfer body 12 (front and back in FIG. 1), image recording is performed on the intermediate transfer body 12 at a higher speed. Can do. Of course, the present invention is also suitable for a method capable of relatively high-speed recording even in the serial type, for example, a one-pass recording method in which one line is formed by one scan.

In the present embodiment, the recording heads (the treatment liquid head 30S and the ink heads 30K, 30C, 30M, and 30Y) all have the same structure, and in the following, the recording head is represented by reference numeral 30. And
When the processing liquid is ejected from the processing liquid head 30 </ b> S toward the intermediate transfer body 12, the area of the intermediate transfer body 12 to which the processing liquid is applied is associated with the rotation of the intermediate transfer body 12. The ink moves sequentially under 30K, 30C, 30M, and 30Y, and each corresponding color ink is ejected from each of the ink heads 30K, 30C, 30M, and 30Y.
The treatment liquid application amount and the ink application amount are preferably adjusted as necessary. For example, the application amount of the treatment liquid may be changed according to the recording medium to be transferred in order to adjust physical properties such as viscoelasticity of the aggregate formed by mixing the treatment liquid and the ink.

  The solvent removal unit 20 is disposed downstream of the ink discharge unit 16 in the intermediate transfer body rotation direction. In the solvent removal unit 20, a solvent removal roller 32 is provided at a position facing the roller 26 </ b> A across the intermediate transfer body 12. The solvent removal roller 32 is composed of a roller-like porous body and is disposed so as to contact the recording surface 12 a of the intermediate transfer body 12. As other modes, there are a method of removing excess solvent from the intermediate transfer body 12 with an air knife, a method of heating and evaporating the solvent, and the like. Any solvent removal method may be used, but it is preferable to use a method that does not rely on heat. By means of heating the surface of the transfer body or applying heat to the aggregate on the transfer body to evaporate the solvent, it is not possible to maintain the preferred viscoelasticity of the aggregate during transfer by removing the solvent excessively due to overheating of the aggregate. On the contrary, transferability may be reduced. There is also a concern about the influence of the heat of the intermediate transfer member on the ink discharge performance from the ink jet head.

  In the solvent removal unit 20, the solvent on the recording surface 12 a of the intermediate transfer body 12 is removed by the solvent removal roller 32. For this reason, even when a large amount of processing liquid is applied to the recording surface 12a of the intermediate transfer body 12, the solvent is removed by the solvent removal unit 20, so that a large amount of solvent (dispersed in the recording medium 34 by the transfer unit 18). Medium) is not transferred. Therefore, even when paper is used as the recording medium 34, there is no problem characteristic to the aqueous solvent such as curl and cockle.

By removing the excess solvent from the aggregate by the solvent removing unit 20, the aggregate can be concentrated and the internal cohesive force can be further increased. Thereby, fusion of the resin particles contained in the aggregate is effectively promoted, and a stronger internal cohesive force can be imparted to the aggregate until the transfer step. Furthermore, the effective concentration of the aggregates by removing the solvent can impart good fixability and gloss to the image even after transfer to the recording medium.
Note that it is not always necessary to remove all the solvent by the solvent removing unit 20. If the ink aggregates are excessively removed by excessively removing them, the adhesion of the aggregates to the transfer body becomes too strong, and an excessive pressure is required for the transfer, which is not preferable. Rather, in order to maintain viscoelasticity suitable for transferability, it is desirable to leave a small amount. As an effect obtained by leaving a small amount of solvent, the aggregate is hydrophobic, and solvent components that are difficult to volatilize (mainly organic solvents such as glycerin) are hydrophilic, so the aggregate and residual solvent components are removed by solvent. After the separation, a thin liquid layer composed of residual solvent components is formed between the aggregate and the intermediate transfer member. Therefore, the adhesive force of the aggregate to the transfer body is weakened, which is advantageous for improving transferability.

  The transfer unit 18 is disposed downstream of the solvent removal unit 20 in the intermediate transfer member rotation direction. The transfer unit 18 is provided with a pressure roller 36 at a position facing the roller 26B with the intermediate transfer body 12 interposed therebetween. A heater 37 is provided inside the pressure roller 36, and the temperature of the outer peripheral surface of the pressure roller 36 is increased by the heater 37. The recording medium 34 is conveyed from the left side to the right side in FIG. 1 so as to pass between the intermediate transfer body 12 and the pressure roller 36. When passing between the intermediate transfer body 12 and the pressure roller 36, the surface side of the recording medium 34 is brought into contact with the recording surface 12 a of the intermediate transfer body 12, and pressure is applied by the pressure roller 36 from the back surface side of the recording medium 34. Thus, the image formed on the recording surface 12 a of the intermediate transfer body 12 is transferred and formed on the recording medium 34. Thus, in the present invention, a structure in which the heating part is limited to only the transfer part of the transfer body is desirable. With this structure, it is possible to prevent excessive heat load and excessive removal of the solvent component contained in the aggregate due to heating of the entire surface of the transfer member. Further, when the aggregate is heated at the transfer portion 18, most of the solvent contained in the aggregate is removed, and the resin fusion promoted in combination with the physical aggregate concentration effect by pressurization. In a region where the transfer body is in contact with the pressure heating roller, a stronger internal cohesive force can be imparted to the aggregate during a short period from immediately before the transfer process to when the transfer is performed.

Note that even if the solvent removal step is not performed before the solution transfer, the solvent can be removed in a short time by heating, so there is not much problem with the transfer rate. Since the absolute amount of the solvent to be evaporated is small, this concentration effect is not only more effective, but also the heat load during transfer can be reduced. In addition, due to effective concentration of the ink aggregates by heating at the transfer portion, it is possible to impart good fixability and glossiness to the image even after transfer to the recording medium.
Furthermore, the temperature and pressure during transfer may be freely adjusted to suitable conditions depending on the recording medium, printing conditions, and the like.

Further, the surface of the intermediate transfer body 12 may have a structure having a releasable surface layer as necessary. Since the surface of the releasability imparting transfer body has the property of low surface energy and high releasability, it is possible to realize a high transfer rate. In the present invention, a sufficient transfer rate can be obtained without particularly providing releasability, but there is no problem if releasability is imparted to the surface of the intermediate transfer member from the viewpoint of cleaning load and the like. Here, the releasable surface described in the present invention refers to a surface having a critical surface tension of 30 mN / m or less or a contact angle with water of 75 ° or more.
Preferred materials used for the surface layer of the intermediate transfer body 12 include, for example, polyurethane resins, polyester resins, polystyrene resins, polyolefin resins, polybutadiene resins, polyamide resins, polyvinyl chloride resins, polyethylene resins. , Known materials such as fluorine-based resins and polyimide-based resins.

The cleaning unit 22 is disposed downstream of the transfer unit 18 in the rotation direction of the transfer body and upstream of the treatment liquid application unit 14 in the rotation direction of the transfer body. In the cleaning unit 22, a cleaning roller 38 is provided at a position facing the roller 26 </ b> C across the intermediate transfer body 12, and is disposed so as to contact the recording surface 12 a of the intermediate transfer body 12. Residues after transfer on the surface 12a are removed.
The cleaning roller 38 is made of a flexible porous member, and has a system for cleaning the surface of the intermediate transfer body (recording surface 12a) while soaking the cleaning liquid in the cleaning liquid applying means. The surface is provided with a brush, and the cleaning liquid is applied to the surface of the intermediate transfer body. There are a method of removing dust on the surface of the intermediate transfer member with a brush while applying to the surface, and a method of scraping off the residue on the surface of the intermediate transfer member by providing a flexible blade on the roller surface. The removal rate of the residue can be increased by setting the linear velocity on the surface of the cleaning roller 38 to be slower or faster than the linear velocity on the surface of the intermediate transfer member. A shearing force is generated on the surface of the intermediate transfer member according to the speed difference between the surface of the cleaning roller 38 and the surface of the intermediate transfer member, and the residue can be efficiently removed.

In the present invention, after transferring the aggregate, an image fixing unit may be separately provided as needed in order to give a strong fixing property to the recording medium.
The image fixing unit is disposed on the recording medium discharge side (right side in FIG. 1) of the transfer unit 18. In the image fixing unit, two fixing rollers can be provided on the front and back surfaces of the recording medium. By fixing and heating the image transferred and formed on the recording medium 34 with these fixing rollers, the fixability of the recorded image on the recording medium 34 can be improved. In addition, as a fixing roller, although a pair of roller which consists of one pressure roller and one heating roller is preferable, it is not limited to this.

In the present invention, it is also possible to provide means (not shown) for heating the recording medium 34 before the recording medium is conveyed to the transfer unit 18.
Since the recording medium 34 that is in direct contact with the aggregate has already reached the desired transfer temperature, heat transfer can be efficiently performed in a shorter time during the transfer nip. Further, as compared with the case where heating is performed only at the transfer nip, the ink aggregate and the surface of the recording medium are brought into contact with each other by previously setting the recording medium at a desired transfer temperature. This temperature can be freely adjusted according to the type of the recording medium 34, and the viscoelasticity of the ink aggregate can be controlled by this temperature control.

When the recording medium 34 has many irregularities due to pulp fibers on the surface of plain paper or fine paper, and an anchor effect can be expected between the aggregate and the surface of the recording medium, the viscoelasticity of the aggregate is transferred to the transfer portion. By controlling and adjusting not only the heating temperature of the media but also the heating temperature of the media surface that is in direct contact with the transfer, it is possible to give good fixability to plain paper and fine paper with the optimal viscoelasticity of the aggregates .
In addition, when the recording medium 34 is a recording medium having a smooth surface such as coated paper, the agglomerates are better after the transfer by controlling the viscoelasticity than the recording medium having irregularities on the surface. It is also possible to impart fixing properties.

[Inkjet recording method]
Next, the ink jet recording method of the present invention for recording an image using the ink set of the present invention on the ink jet recording apparatus configured as described above will be described. In the description of the recording method, the ink aggregation reaction mechanism in the present invention will be described.
FIG. 2 is a conceptual diagram showing only the part necessary for the description of the present invention in the ink jet recording apparatus of FIG. 1, a method of applying a treatment liquid to the intermediate transfer member by a coating method, and the intermediate transfer member as a belt. It is shown by a method of transporting by the conveyor 13.

In order to perform the ink jet recording method of the present invention, first, the treatment liquid 40 discharged from the application head 14A is supplied to the application roller 14B, and is applied onto the intermediate transfer body 12 in a thin film form via the application roller 14B (treatment liquid). Application step).
Next, the intermediate transfer body 12 to which the processing liquid 40 has been applied is conveyed to the position of the recording head 16 by the belt conveyor 13, the ink 42 of the present invention is ejected, and the processing liquid 40 and the ink 42 come into contact with each other. . As a result, the water-insoluble colored particles (A) and the water-insoluble particles (B) in the ink quickly aggregate to form an aggregate 44 (aggregation step). Aggregation is caused by a decrease in dispersion stability of the water-insoluble particles (B) due to a change in pH environment.

  In this embodiment, the example in which the ink set of the present invention is applied to a transfer type ink jet recording method has been described. However, the present invention can also be applied to a recording method in which recording is directly performed on a recording medium. It can be done promptly.

  Next, an example using the ink set of the present invention comprising the ink of the present invention and the treatment liquid will be described, but the present invention is not limited to this example. Unless otherwise specified, “part” and “%” are based on mass.

[Preparation of carboxyl group-containing copolymer]
-Synthesis Example 1
Into a 5 liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 400.0 g of isopropanol was charged and heated to 75 ° C. While maintaining the temperature in the reaction vessel at 75 ° C., 192.0 g of styrene, 108.0 g of n-butyl acrylate, 100.0 g of acrylic acid, 80.0 g of isopropanol, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) 1 A mixed solution consisting of .6 g was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, a solution consisting of 1.6 g of “V-601” and 80.0 g of isopropanol was added, stirred at 75 ° C. for 2 hours, and then a solution consisting of 0.8 g of “V-601” and 40.0 g of isopropanol was added. After stirring at 75 ° C. for 2 hours, the temperature was raised to 85 ° C., and stirring was further continued for 2 hours. The weight average molecular weight (Mw) of the obtained copolymer was 48000 (calculated in terms of polystyrene by gel permeation chromatography (GPC), the columns used were TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200 (manufactured by Tosoh Corporation)), The acid value was 195 (mgKOH / g).
Next, after adding 105.3 g of triethylamine and stirring for 10 minutes, 1800 g of distilled water was added to disperse in water. Thereafter, a total of 680 g of isopropanol and distilled water was distilled off under reduced pressure at a temperature in the reaction vessel of 70 ° C., and a carboxyl group-containing copolymer (aqueous acrylic copolymer) having a solid content concentration of 19.1% (C-1) An aqueous dispersion (emulsion) was obtained.

-Synthesis Example 2-
In the synthesis of Synthesis Example 1 (C-1), instead of 192.0 g of styrene, 108.0 g of n-butyl acrylate, and 100 g of acrylic acid, structures shown in the following compound examples (C-2) and (C-3) The amount of the monomer and the charged amount were changed so that the molar ratio was changed, and the amount of triethylamine was changed so that the degree of neutralization was the same. In the same manner as in the synthesis, an aqueous dispersion of carboxyl group-containing copolymers (C-2) and (C-3) was obtained. In addition, the weight average molecular weights (Mw) of the obtained carboxyl group-containing copolymers (C-2) and (C-3) were 62000 and 38000, respectively.

[Preparation of water-insoluble particles (B)]
-Synthesis Example 3-
A 1 liter three-necked flask equipped with a stirrer and a reflux condenser is charged with 62.8 g of C-1 obtained in Synthesis Example 1, 12.4 g of distilled water and 0.5 g of triethylamine, and heated to 70 ° C. under a nitrogen stream. Stir. An aqueous solution composed of 0.4 g of 2,2′-azobis (2-amidinopropane) dihydrochloride and 80 g of distilled water was added thereto, stirred for 30 minutes, and then a monomer solution composed of 39 g of styrene and 21 g of n-butyl acrylate. Was dropped at a constant speed so that the dropping was completed in 2 hours. After completion of the dropwise addition, an aqueous solution consisting of 0.2 g of 2,2′-azobis (2-amidinopropane) dihydrochloride and 20 g of distilled water was added, stirred at 70 ° C. for 4 hours, then heated to 85 ° C. and further heated Stirring was continued for 2 hours. The reaction solution was cooled and filtered to obtain 236 g of the desired latex (PL-02A). The obtained latex had a solid content concentration of 30.5%, an average particle size of 88 nm (particle size was measured with a Coulter submicron analyzer (manufactured by Beckman Coulter, Inc.)), and a weight average molecular weight (Mw) of 22. It was 80,000.

-Synthesis Example 4-
Latex PL-02B was synthesized in the same manner as PL-02A except that the amount of C-1 used was increased 2.5 times in the synthesis of PL-02A of Synthesis Example 3. Table 1 shows the physical properties of the obtained latex PL-02B.

-Synthesis Example 5-
Latex PL-02C was synthesized in the same manner as PL-02A except that in the synthesis of PL-02A of Synthesis Example 3, the amount of C-1 used was increased by 5 times. Table 1 shows the physical properties of the obtained latex PL-02C.

-Synthesis Example 6
In the synthesis of PL-02A of Synthesis Example 3, instead of 39 g of styrene and 21 g of n-butyl acrylate, the structures and molar ratios shown in the following compound examples (PL-02D, PL-03, PL-04, PL-20) As in the synthesis of PL-02A, except that the monomer type and the charge amount were changed, and the carboxyl group-containing copolymer was changed to the type and addition amount shown in Table 1, respectively. PL-02D, PL-02E, PL-02F, PL-03, PL-04, and PL-20 were respectively synthesized. Table 1 shows the physical properties of the obtained latexes PL-02D, PL-02E, PL-02F, PL-03, PL-04, and PL-20. In addition, PL-02E and PL-02F were prepared by synthesizing PL-02D except that carboxyl group-containing copolymers C-2 and C-3 were used in place of carboxyl group-containing copolymer C-1. Each was synthesized in the same manner as -02D.

-Synthesis Example 7-
In a 1 liter three-necked flask equipped with a stirrer and a reflux condenser, 62.8 g of C-1 obtained in Synthesis Example 1, Latemulu ASK (manufactured by Kao Corporation, carboxylate emulsifier) 17.2 g, triethylamine 0.5 g was added and heated and stirred at 70 ° C. under a nitrogen stream. An aqueous solution composed of 0.4 g of 2,2′-azobis (2-amidinopropane) dihydrochloride and 80 g of distilled water was added thereto, stirred for 30 minutes, and then a monomer solution composed of 39 g of styrene and 21 g of n-butyl acrylate. Was dropped at a constant speed so that the dropping was completed in 2 hours. After completion of the dropwise addition, an aqueous solution consisting of 0.2 g of 2,2′-azobis (2-amidinopropane) dihydrochloride and 20 g of distilled water was added, stirred at 70 ° C. for 4 hours, then heated to 85 ° C. and further heated Stirring was continued for 2 hours. The reaction solution was cooled and filtered to obtain 240 g of the desired latex of the present invention (PL-02A-2). The obtained latex had a solid content concentration of 31.6%, an average particle size of 68 nm, and a weight average molecular weight of 261,000.

-Synthesis Example 8-
In a 1 liter three-necked flask equipped with a stirrer and a reflux condenser, 2.4 g of a sulfonic acid surfactant Pionein A-43s (manufactured by Takemoto Yushi Co., Ltd.), 63.2 g of distilled water, and 0.5 g of triethylamine are added. The mixture was heated and stirred at 70 ° C. under a nitrogen stream. Thereto was added an aqueous solution consisting of 0.4 g of 2,2′-azobis (2-amidinopropane) dihydrochloride and 80 g of distilled water, and after stirring for 30 minutes, a monomer solution consisting of 42 g of styrene and 18 g of n-butyl acrylate. Was dropped at a constant speed so that the dropping was completed in 2 hours. After completion of the dropwise addition, an aqueous solution consisting of 0.2 g of 2,2′-azobis (2-amidinopropane) dihydrochloride and 20 g of distilled water was added, stirred at 70 ° C. for 4 hours, then heated to 85 ° C. and further heated Stirring was continued for 2 hours. The reaction solution was cooled and filtered to obtain 226 g of the desired latex of the present invention (PL-02A-H). The resulting latex had a solid content concentration of 27.1%, an average particle size of 71 nm, and a weight average molecular weight of 285,000.

[Preparation of water-based ink composition]
<< Preparation of Cyan Ink C1-1 >>
(Preparation of cyan dispersion as water-insoluble colored particles (A))
In a reaction vessel, 6 parts by mass of styrene, 11 parts by mass of stearyl methacrylate, 4 parts by mass of styrene macromer AS-6 (manufactured by Toa Gosei), 5 parts by mass of Plenmer PP-500 (manufactured by NOF Corporation), 5 parts by mass of methacrylic acid, 2- A mixed solution of 0.05 part by mass of mercaptoethanol and 24 parts by mass of methyl ethyl ketone was prepared.
On the other hand, 14 parts by mass of styrene, 24 parts by mass of stearyl methacrylate, 9 parts by mass of styrene macromer AS-6 (manufactured by Toa Gosei), 9 parts by mass of Plenmer PP-500 (manufactured by NOF Corporation), 10 parts by mass of methacrylic acid, 2-mercaptoethanol A mixed solution consisting of 0.13 parts by weight, 56 parts by weight of methyl ethyl ketone and 1.2 parts by weight 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. Two hours after the completion of the dropwise addition, a solution prepared by dissolving 1.2 parts by mass of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12 parts by mass of methyl ethyl ketone was added dropwise over 3 hours. Aged 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% by mass 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 could be sufficiently distilled off, and concentrated until the pigment concentration became 10%, and a cyan dispersion C1 as water-insoluble colored particles (A) was prepared. The average particle diameter of the obtained cyan dispersion liquid C1 was 77 nm.

  Then, using cyan dispersion C1 as water-insoluble colored particles (A) and PL-02A as water-insoluble particles (B), ink was prepared so as to have the following ink composition. After the preparation, coarse particles were removed with a 5 μm filter to prepare cyan ink C1-1 as an aqueous ink composition.

<Ink composition of cyan ink C1-1>
・ Cyan pigment (Pigment Blue 15: 3) manufactured by Dainichi Seika Co., Ltd. 4%
・ Polymer dispersant 2%
・ PL-02A (solid content conversion) 8%
・ Diethylene glycol (Wako Pure Chemical Industries) 10%
・ Glycerin 20%
・ Orphine E1010 (Nisshin Chemical) 1%
・ Ion-exchanged water added so that the total is 100% by mass
[Preparation of treatment solution]
The following composition was mixed to prepare a treatment liquid T-1.
<Composition of treatment liquid T-1>
・ 2-pyrrolidone-5-carboxylic acid (manufactured by Tokyo Chemical Industry) 10 parts ・ lithium hydroxide monohydrate (manufactured by Wako Pure Chemical Industries) 2 parts ・ glycerin (manufactured by Wako Pure Chemical Industries) 13 parts ・ diethylene glycol (manufactured by Wako Pure Chemical Industries) 10 parts, Olfine E1010 (Nisshin Chemical) 1.5 parts, 1,4-bis (1H, 1H, 2H, 2H-perfluoroheptyloxycarbonyl) ethanesulfonic acid Na 0.1 part, ion-exchanged water 100 mass in total % To be added

  And as a result of measuring the physical-property value of the obtained process liquid T-1, they were pH3.6, surface tension 28.0mN / m, and viscosity 3.1mPa * s.

In the above, the average particle diameter was measured by appropriately diluting the dispersion to a concentration suitable for measurement with Microtrac UPA EX-150 (manufactured by Nikkiso Co., Ltd.), and the measurement conditions were all the same. That is, particle permeability: transmission, particle refractive index: 1.51, particle shape: non-spherical, density: 1.2 g / cm ³ , solvent: water, cell temperature: 18-25 ° C. It was measured. Moreover, the viscosity was measured with DV-II + VISCOMETER manufactured by BROOKFIELD. The surface tension was measured by a platinum plate method using CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.

<< Preparation of Cyan Inks C1-2-10, C1-H1, C1-H2 >>
The cyan ink of the water-based ink composition was the same as the cyan ink C-1, except that the water-insoluble particles (B) shown in Table 2 below were used instead of the latex PL-02A in the cyan ink C1-1. C1-2-10, C1-H1, and C1-H2 were prepared, respectively.

  Table 2 shows the physical property values of the cyan ink obtained above immediately after preparation.

[Evaluation]
Each cyan ink prepared as described above (hereinafter sometimes simply referred to as “ink”) was subjected to an ink stability test and a droplet ejection 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.
In addition, by the droplet ejection test, the agglomeration reaction rate until the agglomeration after the ink and the treatment liquid were deposited and contacted was examined.

(Ink stability test over time)
10 mL of each ink was sealed in a 15 mL glass bottle, and the average particle size and viscosity were measured after (1) leaving at 60 ° C. for 14 days and (2) leaving at 40 ° C. for 3 months. Change rate of average particle size before and after standing [(average particle size after leaving-average particle size before leaving) / average particle size before leaving] and change rate of viscosity [(viscosity after leaving-before leaving) Viscosity) / viscosity before standing] was calculated. The evaluation criteria are as follows.
~Evaluation criteria~
A: The change rate of the average particle diameter or the change rate of the viscosity was less than 5%.
Δ: The change rate of the average particle diameter or the change rate of the viscosity was 5% or more and less than 10%.
X: The change rate of the 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.

(Image formation test)
The image formation test was performed as follows. That is, on the intermediate transfer body of the silicone rubber sheet SR series 0.5 mm film thickness (manufactured by Tigers Polymer Co., Ltd.), the treatment liquid is applied to a film thickness of about 5 μm by a wire bar coater (wire bar type coating coater). Applied. Further, using a GELJETG717 printer head manufactured by Ricoh Co., Ltd., the intermediate transfer member was ejected with a resolution of 1200 × 600 dpi and an ink ejection amount of 12 pL. The ink was ejected, and after a predetermined time (1 second, 2 seconds, 10 seconds, 15 seconds) had elapsed, the solvent was removed with a solvent removal roller wrapped with Cressia's silica dry. Then, the aggregation reaction rate was evaluated by observing the adhesion of the coloring material to the silica dry.

Table 3 shows the results of the image formation test. In the image forming test shown in Table 3, the evaluation criteria for the color material adhesion to the silica dry after a lapse of a predetermined time are as follows.
~Evaluation criteria~
○… Color material adhesion could not be confirmed.
○ △: Slight adhesion of coloring material was confirmed.
Δ: Slight adhesion of coloring material occurred.
X ... There was much coloring material adhesion.
And evaluation of x was judged that the aggregation reaction was not complete | finished.

(Image transfer test)
The image transfer test was performed as follows. Art paper was placed on the image formed on the intermediate transfer member after the image fixing test, and heated at 100 ° C. for 1 minute. The image transfer was evaluated by observing image adhesion on the art paper after peeling. Table 3 shows the image transfer results. The evaluation criteria for the image transfer test in Table 3 are as follows.
~Evaluation criteria~
○: Almost transferred.
○ △: Slight transfer failure was observed.
Δ: Transfer defect occurred.
×: There were many defective transfer portions.
And evaluation of x was judged to be unusable.

(Drip droplet stability test)
The droplet ejection stability test was conducted as follows. The droplets are ejected under the same conditions on the intermediate transfer member processed in the same manner as in the image formation test. 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.
~Evaluation criteria~
○: No discharge failure and no direction failure.
○ △: There was no ejection failure and a little direction failure occurred.
Δ: Almost no ejection failure and some direction failure occurred.
×: There were many ejection failures.

As can be seen from Table 3, it was confirmed that the temporal stability of the ink of the present invention was equivalent to that of the conventional ink.
In addition, the stability over time of the ink C1-H1 of the comparative example using latex PL-02A-H using a sulfonate surfactant as an emulsifier is greatly reduced after long-term storage. It can be seen that the ink of the invention is excellent in long-term stability over time. This is because, for example, since the present invention uses a polymer emulsifier, adsorption / desorption from the surface of water-insoluble fine particles is less likely to occur than when a low molecular surfactant is used, so that the particles are stable even after a long period of time. It can be considered that it can exist.
In addition, when the ink of the present invention is used, it can be seen that the aggregation rate is high, the image forming property is good, and the image transfer property is good. On the other hand, Comparative Example Ink C1-H1 using Latex PL-02A-H using a sulfonate surfactant as an emulsifier, and Ink C1-H2 without adding latex have image forming properties and image transfer properties. It turns out that it is greatly inferior in the point.

1 is an overall configuration diagram illustrating an example of an ink jet recording apparatus that performs an image recording method of the present invention. It is a conceptual diagram for demonstrating the image recording method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12 ... Intermediate transfer body, 14 ... Processing liquid application part, 16 ... Ink discharge part, 18 ... Transfer part, 20 ... Solvent removal part, 22 ... Cleaning part, 26 ... Roller, 30 ... Recording head, 30S ... recording head (processing liquid head), 30K, 30C, 30M, 30Y ... recording head (ink head), 34 ... recording medium, 36 ... pressure roller, 38 ... cleaning roller, 40 ... processing liquid, 42 ... Ink, 44 ... agglomerate

Claims (12)

  An aqueous ink composition comprising water-insoluble colored particles (A) containing a colorant and water-insoluble particles (B) coated with a carboxyl group-containing copolymer.   The water-based ink composition according to claim 1, wherein the water-insoluble particles (B) coated with the carboxyl group-containing copolymer have a property of aggregating due to a change in pH environment.   The water-insoluble particles (B) coated with the carboxyl group-containing copolymer include a water-insoluble polymer having a glass transition temperature of 15 ° C to 120 ° C. A water-based ink composition.   The aqueous ink composition according to claim 3, wherein the acid value of the water-insoluble polymer is less than 30. 5.   The water-insoluble particles (B) coated with the carboxyl group-containing copolymer are obtained by emulsion polymerization in the presence of an aqueous solution or emulsion of the carboxyl group-containing copolymer. 5. The aqueous ink composition according to any one of 4 above.   The aqueous ink composition according to claim 5, wherein the aqueous solution or emulsion of the carboxyl group-containing copolymer further contains a basic compound.   The water-based ink composition according to claim 1, wherein an acid value of the carboxyl group-containing copolymer is 30 or more and 500 or less.   An ink set comprising at least one water-based ink composition according to any one of claims 1 to 7, and a treatment liquid that changes the pH of the water-based ink composition. A treatment liquid application step for applying the treatment liquid contained in the ink set according to claim 8 onto a recording medium;
At least one water-based ink composition contained in the ink set according to claim 8 is applied onto the recording medium to which a treatment liquid is applied, and the water-insoluble colored particles (A) in the water-based ink composition and An aggregating step of aggregating the water-insoluble particles (B) to form an image on the recording medium.   The image recording method according to claim 9, further comprising a solvent removal step of removing at least a part of the solvent of the water-based ink composition and the treatment liquid after the aggregation step. A treatment liquid application step of applying the treatment liquid contained in the ink set according to claim 8 onto the intermediate transfer member;
At least one water-based ink composition contained in the ink set according to claim 8 is applied onto the intermediate transfer body to which a treatment liquid has been applied, and the water-insoluble colored particles (A) in the water-based ink composition are applied. An aggregating step of aggregating the water-insoluble particles (B) to form an image on the intermediate transfer member;
After the aggregation step, a solvent removal step of removing at least a part of the aqueous ink composition and the solvent of the treatment liquid from the intermediate transfer member;
An image recording method comprising: a transfer step of transferring an image formed on the intermediate transfer member to a recording medium after the solvent removing step.   The image recording method according to claim 9, wherein the aggregation step includes a step of applying the water-based ink composition by an ink jet method.

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