JP7330800B2 - AQUEOUS INK, INK CARTRIDGE, AND INKJET RECORDING METHOD - Google Patents

Description

The present invention relates to an aqueous ink, an ink cartridge, and an inkjet recording method.

2. Description of the Related Art In recent years, there has been an increasing need to record images not only on ink-absorbent recording media but also on non-absorbent recording media using water-based inks by an inkjet recording method. Furthermore, as the image recording speed increases, there is a demand for quickly fixing the coloring material and resin contained in the ink onto the recording medium. Further, images displayed outdoors, such as posters, panels, signs, and pop advertisements, are required to have much higher abrasion resistance and water resistance than ever before.

A water-based ink containing a compound (polymerizable compound) that undergoes a reaction upon irradiation with an active energy ray has been studied in order to record an image excellent in fixability at high speed. For example, a photocurable ink using a reaction product of an aromatic diamine having an acid group and maleimidecarboxylic acid as a polymerizable compound has been proposed (Patent Document 1). Further, a photocurable recording liquid containing a block polymer having a hydrophobic block and a hydrophilic block with a radically polymerizable group and a hydrophobic photopolymerization initiator has been proposed (Patent Document 2).

JP 2009-132812 A Japanese Unexamined Patent Application Publication No. 2011-201973

However, even if the inks proposed in Patent Documents 1 and 2 are used, it is difficult to record an image having sufficient abrasion resistance to withstand outdoor display due to the influence of radical polymerization inhibition by atmospheric oxygen. there were. In addition, the polymerizable compounds used in the inks proposed in Patent Documents 1 and 2 are highly hydrophilic, making it difficult to record images with sufficient water resistance.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a water-based ink capable of recording an image excellent in abrasion resistance and water resistance. Another object of the present invention is to provide an ink cartridge and an ink jet recording method using the water-based ink.

The above objects are achieved by the present invention described below. That is, according to the present invention, there is provided an active energy ray-curable water-based inkjet ink containing resin particles and a photoacid generator, wherein the resin particles are a group consisting of an epoxy group, an oxetanyl group, and a vinyl ether group. a reactive group-containing resin having at least one cationic polymerizable reactive group selected from the The unit is a (meth)acrylate-derived unit having the cationic polymerizable reactive group, and the second unit is an inorganic group composed of an organic group containing the cationic polymerizable reactive group and a siloxane unit. A unit containing a silsesquioxane structure, wherein the content (% by mass) of the photoacid generator is the content (% by mass) of the first unit and the organic group in the second unit A water-based ink characterized by a mass ratio of 0.05 times or more and 0.50 times or less with respect to the total content (% by mass) is provided.

According to the present invention, it is possible to provide a water-based ink capable of recording an image excellent in abrasion resistance and water resistance. Further, according to the present invention, it is possible to provide an ink cartridge and an inkjet recording method using this water-based ink.

1 is a cross-sectional view schematically showing one embodiment of an ink cartridge of the present invention; FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing an example of an inkjet recording apparatus used in the inkjet recording method of the present invention, where (a) is a perspective view of main parts of the inkjet recording apparatus and (b) is a perspective view of a head cartridge;

The present invention will be further described in detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is dissociated into ions in the ink, but for convenience, it is expressed as "containing the salt." In addition, water-based ink for inkjet is sometimes simply referred to as "ink". Unless otherwise specified, physical property values are values at normal temperature (25° C.) and normal pressure (1 atm). A "unit" of a resin means a repeating unit derived from one monomer or one unit structure, unless otherwise specified. In addition, "(meth)acrylic acid" and "(meth)acrylate" mean "acrylic acid, methacrylic acid" and "acrylate, methacrylate", respectively.

The present inventors have investigated an active energy ray-curable water-based ink capable of recording an image that satisfies the level of scratch resistance and water resistance required in recent years, which exceeds the level achieved in the past. did. As a result, the polymerizable compounds used in conventional inks tend to hinder the progress of the polymerization reaction and are highly hydrophilic, resulting in insufficient scratch resistance and water resistance of the recorded images. There was found.

As a result of further studies based on the above findings, it was found that water-based ink containing a resin particle formed of a reactive group-containing resin having a specific reactive group and a photoacid generator has excellent scratch resistance and It has been found that an image having remarkably improved water resistance can be formed. The reactive group incorporated in the reactive group-containing resin constituting the resin particles is at least one selected from the group consisting of an epoxy group, an oxetanyl group, and a vinyl ether group. Then, a photoacid generator is used to induce a reaction by these reactive groups, ie, cationic polymerizable groups, by irradiation with active energy rays. The reason why the composition of the present invention improves the scratch resistance and water resistance of the recorded image is presumed as follows.

The resin particles used as the polymerizable compound are made of a reactive group-containing resin having at least one reactive group selected from the group consisting of epoxy groups, oxetanyl groups, and vinyl ether groups. When the photo-acid generator generates an acid by irradiation with active energy rays, the reactive group causes a cationic polymerization reaction using the generated acid as a polymerization initiator. Unlike the radical polymerization reaction used in Patent Documents 1 and 2, the cationic polymerization reaction used in the present invention is less susceptible to polymerization inhibition by oxygen, so that a cured product with a high degree of polymerization is easily formed even in the atmosphere. Further, unlike the highly hydrophilic polymerizable compounds used in Patent Documents 1 and 2, the polymerizable compound contained in the ink of the present invention has the shape of resin particles. Therefore, for example, even when an ink-absorbing recording medium is used, the polymerizable compound is less likely to sink into the interior of the recording medium, and the amount of the polymerizable compound present on the surface increases. As a result, when the ink applied to the recording medium is irradiated with active energy rays, the cationic polymerization reaction occurs efficiently, forming a resin film with a higher density of cross-linking, and the abrasion resistance of the image is remarkable. improve to

In addition, the polymerizable compound used in the curable inks described in Patent Documents 1 and 2 is a low-molecular-weight compound having an acid group or a polymer having a hydrophilic block, and thus is hydrophilic. expensive. When such a polymerizable compound is used, the resin film formed by polymerization maintains high hydrophilicity, and when the image comes into contact with water, the resin softens, and the water resistance of the image tends to be impaired. On the other hand, the resin particles, which are the polymerizable compounds used in the present invention, have lower hydrophilicity than low-molecular-weight compounds or polymers having hydrophilic blocks due to their particle shape, and the resin film formed by polymerization is also hydrophilic. can be kept low, the water resistance of the image is remarkably improved.

<Ink>
The ink of the present invention is an active energy ray-curable water-based inkjet ink containing resin particles and a photoacid generator. The resin particles contain a reactive group-containing resin having at least one reactive group selected from the group consisting of epoxy groups, oxetanyl groups, and vinyl ether groups. Each component constituting the ink will be described below.

(resin particles)
The ink of the present invention contains resin particles containing a reactive group-containing resin having a reactive group. The reactive group is at least one of an epoxy group, an oxetanyl group, and a vinyl ether group. These reactive groups (hereinafter also referred to as "cationically polymerizable reactive groups") are functional groups that cause cationic polymerization. The reactive group of the reactive group-containing resin may contain a radically polymerizable reactive group. However, the ratio (mol%) of the cationic polymerizable reactive group to all the reactive groups in the reactive group-containing resin is preferably 95.0 mol% or more, and is 100.0 mol%. is preferred.

Examples of the reactive group-containing resin that constitutes the resin particles include the following. (1) resins having a unit derived from a monomer (compound) having a cationic polymerizable reactive group and an ethylenically unsaturated bond, (2) resins in which cationic polymerizable reactive groups are incorporated into various resins, (3) A combination of the above (1) and (2), and the like can be mentioned. When multiple types of resins are used as the reactive group-containing resin, each resin is a mixture of resin particles composed of a single resin, a resin particle composed of a plurality of resins in combination, or a combination thereof. Either can be used. The reactive group-containing resin may have a hydroxy group, a phenyl group, an ethylene oxide group, an anionic group, or the like as long as the effects of the present invention are not impaired. However, hydrophilic groups such as anionic groups, ethylene oxide groups, and hydroxy groups may be present in a small amount if necessary for stably presenting the resin particles in the water-based ink. From the viewpoint of water resistance, it is preferable not to use too much. Above all, since even a small amount of anionic groups tends to increase the hydrophilicity of the resin particles, when using a resin having anionic groups, the acid value is preferably 5 mgKOH/g or less.

The "ethylenically unsaturated bond" in the monomer (compound) of (1) is a radically polymerizable reactive group, and examples thereof include a vinyl group, an allyl group, and a (meth)acryloyl group.

Examples of compounds having a cationic polymerizable reactive group and a vinyl group include 1,3-butadiene monoepoxide, 1,2-epoxy-4-vinylcyclohexane, glycidyl vinyl ether, 1,4-butanediol monovinyl monoglycidyl ether, and the like. be able to.

Examples of compounds having a cationic polymerizable reactive group and an allyl group include allyl vinyl ether, allyl glycidyl ether, o-allylphenyl glycidyl ether, 3-allyloxymethyl-3-ethyloxetane, and 3-allyloxyoxetane. can.

A compound having a cationic polymerizable reactive group and a (meth)acryloyl group is a "(meth)acrylate having a cationic polymerizable reactive group". Specifically, glycidyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate glycidyl ether, 3,4-epoxycyclohexylmethyl (meth) acrylate, (3-ethyl-3-oxetanyl) methyl (meth) acrylate, ( 2-(2-vinyloxyethoxy)ethyl meth)acrylate and the like can be mentioned.

Examples of resins (including oligomers) of (2) include polyconjugated dienes; polyethers; urethanes; polydimethylsiloxanes; can be used.

Examples of polyconjugated dienes having cationic polymerizable reactive groups include polybutadiene type epoxy resins. Commercially available products such as DENALEX: R-15EPT, FCA-061L, FCA-061M (all trade names, manufactured by Nagase ChemteX Corporation) may be used.

Examples of polyethers having cationic polymerizable reactive groups include bisphenol A type epoxy resins and bisphenol F type epoxy resins. Commercially available products such as EPICLON: 830, 1050 (both trade names, manufactured by DIC) may be used.

As urethanes having a cationic polymerizable reactive group, urethane-modified epoxy resins and the like can be given. Adeka Resin: Commercially available products such as EPU-6, EPU-7N, EPU-11F, EPU-15F (all trade names, manufactured by Adeka) may be used.

Examples of polydimethylsiloxanes having cationic polymerizable reactive groups include epoxy-modified silicone oils. Commercially available products such as KF-101, KF-105, X-22-163, X-22-173BX, and X-22-9002 (all trade names, manufactured by Shin-Etsu Silicone Co., Ltd.) may also be used.

Silsesquioxanes having a cationic polymerizable reactive group incorporate a cationic polymerizable reactive group into the organic group R in the structure (silsesquioxane structure) represented by the composition formula of R—SiO _1.5 . It is a chemical compound and sometimes treated as an oligomer or resin. A silsesquioxane compound has an organic group containing a cationic polymerizable reactive group and an inorganic group composed of siloxane units, so it has both the properties of an organic compound and the properties of an inorganic substance, resulting in a recorded image. can further improve the scratch resistance and water resistance. An alkyl group, an aryl group, etc. can be mentioned as an organic group. The cationically polymerizable reactive group may be incorporated into at least one of the organic groups in the silsesquioxane compound, or may be incorporated into all of the organic groups. Furthermore, silsesquioxane compounds incorporating polydimethylsiloxane units are also preferred. Due to the water repellency and the reduction of the coefficient of friction due to the polydimethylsiloxane unit, the scratch resistance and water resistance of the recorded image can be further improved.

Examples of the silsesquioxane compound having a cationic polymerizable reactive group include silsesquioxane compounds having an oxetanyl group (OX-SQ: TX-100, OX-SQ HDX, SI-20 (trade name, Toagosei (manufactured by Arakawa Chemical); silsesquioxane compounds having an epoxy group (Compoceran: SQ506, SQ511, SQ502-8, SQ508, SQ510 (trade names, manufactured by Arakawa Chemical)). The above "OX-SQ SI-20" is a silsesquioxane compound having a dimethylsiloxane unit and an oxetanyl group.

The ratio (% by mass) of units having a cationically polymerizable reactive group in the resin particles is preferably 50.00% by mass or more and 100.00% by mass or less based on the total mass of the resin particles. Since the above ratio is used as an index indicating the amount of the structure that reacts, for a silsesquioxane compound having a cationic polymerizable reactive group, it is the ratio of the organic group (the above-mentioned "organic group R"). shall be Within the above range, the cationic polymerization reaction of the resin particles proceeds sufficiently, and the scratch resistance and water resistance of the image can be further improved.

The reactive group-containing resin preferably contains at least one of the following first unit and second unit because it can further improve the scratch resistance and water resistance of the recorded image. Even more preferred are those that have both of the second units. The first unit is a (meth)acrylate-derived unit having a cationic polymerizable reactive group. The second unit is a unit containing a silsesquioxane structure having an organic group containing a cationic polymerizable reactive group and an inorganic group composed of siloxane units.

The reactive group-containing resin may have a unit derived from a monomer having no cationic polymerizable reactive group for the purpose of adjusting physical properties. Monomers having no cationically polymerizable reactive group include monomers having an ethylenically unsaturated bond. Specifically, aromatic group-containing monomers such as styrene, α-methylstyrene, and benzyl (meth)acrylate; alkyl (meth)acrylates such as methyl (meth)acrylate and 2-ethylhexyl (meth)acrylate; cycloalkyl Cycloalkyl (meth)acrylates such as (meth)acrylate; amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; vinyl acetate; acid group-containing monomers such as (meth)acrylic acid; can be mentioned. Moreover, the reactive group-containing resin may have a unit derived from a surfactant or the like having a radically polymerizable reactive group.

In the present invention, the content of "units" and "organic groups" in the resin particles in the ink is a value indicating the amount of predetermined units and organic groups present in the ink. These contents can be calculated by multiplying the content (% by mass) of the resin particles in the ink by the ratio (% by mass) of the predetermined unit or the predetermined organic group in the resin particles.

The content (% by mass) of units derived from a monomer having a cationic polymerizable reactive group in the ink is preferably 0.10% by mass or more based on the total mass of the ink. Since the above content is used as an index indicating the content of the reacting structure, the unit derived from the silsesquioxane compound having a cationic polymerizable reactive group is the organic group (the above-mentioned "organic group R" ) shall be the content. When the above content is less than 0.10% by mass, the cationic polymerization reaction of the resin particles does not sufficiently proceed, and the scratch resistance and water resistance of the image may slightly decrease. The content (% by mass) of units derived from a monomer having a cationic polymerizable reactive group in the ink is preferably 20.00% by mass or less, and 5.00% by mass, based on the total mass of the ink. It is more preferable that the content is not less than 15.00% by mass.

The cationically polymerizable reactive groups of the resin particles preferably contain both epoxy groups and oxetanyl groups. In addition to this, the resin particles are preferably resin particles formed of a reactive group-containing resin having at least one of the above-described first unit and second unit. In this case, in the first unit and the second unit, when the content of the unit having an epoxy group is C _E (% by mass) and the content of the unit having an oxetanyl group is C _O (% by mass), C _E and C It is preferable that _O satisfies the relationship of the following formula (1). When the relationship of the following formula (1) is satisfied, the scratch resistance of the recorded image can be further improved. The presence of an epoxy group, which easily causes an initiation reaction, and an oxetanyl group, which easily causes an elongation reaction of a polymer chain, in a predetermined ratio allows the cationic polymerization reaction to be efficiently initiated and progressed quickly. The degree of cross-linking tends to be high. As a result, the scratch resistance of the recorded image can be further improved.
0.10≦ _CE /( _CE + _CO )≦0.65 (1)

Resin particles formed from a reactive group-containing resin can be synthesized by a known synthesis method such as emulsion polymerization. In the synthesis, a conventionally known surfactant (non-reactive surfactant) or the like can be used in order to assist the emulsifying ability or assist the dispersion stability of the resin particles.

As used herein, the phrase "the resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, it is water-soluble in a state in which particles whose particle size can be measured by a dynamic light scattering method are not formed. means present in the medium. Whether or not the resin is water-soluble can be determined according to the method described below. First, a liquid (resin solid content: 10% by mass) containing a resin neutralized with an acid value equivalent alkali (sodium hydroxide, potassium hydroxide, etc.) is prepared. Next, the prepared liquid is diluted 10-fold (by volume) with pure water to prepare a sample solution. Then, the particle size of the resin in the sample solution is measured by a dynamic light scattering method, and if particles having a particle size are not measured, it can be determined that the resin is water-soluble. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, shape: spherical, refractive index: 1.59. As the particle size distribution analyzer, a particle size analyzer using dynamic light scattering (for example, trade name “UPA-EX150” manufactured by Nikkiso Co., Ltd.) can be used. Of course, the particle size distribution measuring device and measurement conditions to be used are not limited to those described above.

As used herein, "the resin is water-dispersible", i.e., "resin particles", means that it exists in an aqueous medium in the form of particles whose particle diameter can be measured by a dynamic light scattering method. means In other words, the resin particles exist in a state of being dispersed in the ink, that is, in a state of a resin emulsion. The content (% by mass) of the resin particles in the ink is preferably 2.00% by mass or more and 20.00% by mass or less based on the total mass of the ink. If the content of the resin particles is less than 2.00% by mass, the resulting resin film tends to be insufficiently cured, and the scratch resistance and water resistance of the image may be slightly reduced. On the other hand, when the content of the resin particles exceeds 20.00% by mass, the ejection stability of the ink may deteriorate.

Whether or not a certain resin is a "resin particle" can be determined according to the method described below. First, a liquid (resin content: 10% by mass) containing a resin neutralized with an acid value equivalent alkali (sodium hydroxide, potassium hydroxide, etc.) is prepared. Next, the prepared liquid is diluted 10-fold (by volume) with pure water to prepare a sample solution. Then, the particle size of the resin in the sample solution is measured by the dynamic light scattering method, and when particles having the particle size are measured, the resin can be determined to be "resin particles". The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, shape: spherical, refractive index: 1.59. As the particle size distribution analyzer, a particle size analyzer using dynamic light scattering (for example, trade name “UPA-EX150” manufactured by Nikkiso Co., Ltd.) can be used. Of course, the particle size distribution measuring device and measurement conditions to be used are not limited to those described above. The reason why the particle size is measured using the neutralized resin is to confirm that particles are formed even in a state where it is difficult to form particles due to sufficient neutralization. However, a resin that takes the form of particles exists in the form of particles even in water-based ink.

The average particle diameter (D50) of the resin particles is preferably 50 nm or more and 300 nm or less, more preferably 50 nm or more and 200 nm or less. In the present specification, the average particle size of various particles including resin particles means the 50% cumulative value (D50) of the volume-based particle size distribution. The average particle diameter (D50) of various particles including resin particles can be measured under similar conditions using, for example, the above-described dynamic light scattering particle size distribution analyzer.

(Photoacid generator)
The ink of the present invention contains a photoacid generator. A photoacid generator is a compound that absorbs light and generates an acid. The generated acid binds to the oxygen atoms of the cationic polymerizable reactive groups of the resin particles to generate cationic species, thereby initiating cationic polymerization. As the photoacid generator, both water-soluble and water-dispersible photoacid generators can be used. Furthermore, the photoacid generator may be contained in the ink in a state of being encapsulated in the resin particles described above. In this case, the photoacid generator is preferably water-dispersible, since the encapsulation state of the resin particles can be stably maintained. Among them, the photoacid generator is either (1) water-dispersible or (2) water-dispersible and contained in the ink in a state of being encapsulated in resin particles. is preferred. This is because a large amount of the photoacid generator tends to exist on the surface of the recording medium together with the resin particles after the ink is applied to the recording medium, so that the cationic polymerization reaction proceeds efficiently. In addition to this, since the hydrophilicity of the photoacid generator is low, it is difficult to lower the water resistance of the image.

As used herein, the term "water-soluble" as used in the photoacid generator means that the photoacid generator dissolves in an aqueous medium and can exist in the aqueous medium without forming particles whose particle size can be measured. means. On the other hand, when the photo-acid generator is "water-dispersible", it means that the photo-acid generator exists in the aqueous medium in a dispersed state and forms particles whose particle size can be measured in the aqueous medium. It means you can. Whether the photo-acid generator is water-soluble or water-dispersible can be determined by measuring the particle size under the same conditions as the determination method for the resin particles described above. That is, the particle size of a sample solution containing a photoacid generator (photoacid generator content: 1% by mass) is measured by a dynamic light scattering method, and when particles having a particle size are measured, the light Acid generators can be judged to be "water-dispersible". On the other hand, if particles with a particle size are not measured, it can be determined to be "water soluble".

As the photoacid generator, a known photoacid generator such as a salt of an onium ion and an anion can be used. Onium ions include sulfonium ions, iodonium ions, selenium ions, ammonium ions, and phosphonium ions.

Sulfonium ions include triphenylsulfonium ion, tri-p-tolylsulfonium ion, tri-o-tolylsulfonium ion, tris(4-methoxyphenyl)sulfonium ion, 1-naphthyldiphenylsulfonium ion, diphenylphenacylsulfonium ion, phenyl Arylsulfonium ions such as methylbenzylsulfonium ion, 4-hydroxyphenylmethylbenzylsulfonium ion, dimethylphenacylsulfonium ion, and phenacyltetrahydrothiophenium ion can be mentioned.

The iodonium ion includes aryl such as diphenyliodonium ion, di-p-tolyliodonium ion, bis(4-dodecylphenyl)iodonium ion, bis(4-methoxyphenyl)iodonium ion, and (4-octyloxyphenyl)phenyliodonium ion. Mention may be made of iodonium ions.

Selenium ions include triphenylselenium ion, tri-p-tolylselenium ion, tri-o-tolylselenium ion, tris(4-methoxyphenyl)selenium ion, 1-naphthyldiphenylselenium ion, tris(4-fluorophenyl) Aryl selenium ions such as selenium ions, tri-1-naphthyl selenium ions and tri-2-naphthyl selenium ions can be mentioned.

Ammonium ions include tetramethylammonium ion, ethyltrimethylammonium ion, diethyldimethylammonium ion, triethylmethylammonium ion, tetraethylammonium ion, trimethyl-n-propylammonium ion, trimethylisopropylammonium ion, trimethyl-n-butylammonium ion, Mention may be made of alkylammonium ions such as trimethylisobutylammonium ion.

Phosphonium ions include tetraphenylphosphonium ion, tetra-p-tolylphosphonium ion, tetrakis(2-methoxyphenyl)phosphonium ion, triphenylbenzylphosphonium ion, triphenylphenacylphosphonium ion, triphenylmethylphosphonium ion, and triethylbenzylphosphonium ion. ions, arylphosphonium ions such as tetraethylphosphonium ions.

Examples of anions include halide ions, various acids such as sulfonic acid, nitric acid, boric acid, phosphoric acid, carboxylic acid, trifluoromethanesulfonic acid, tetrafluoroboric acid, hexafluorophosphoric acid, and fluoroantimonic acid, and of these acids. Derivative anions and the like can be mentioned.

Water-soluble photoacid generators include diphenyl-o-methylphenylsulfonium p-toluenesulfonate, diphenyl-m-methylphenylsulfonium p-toluenesulfonate, diphenyl-2,4,6-trimethylphenylsulfonium p-toluenesulfonate, Diphenyl-2,4-dimethylphenylsulfonium p-toluenesulfonate, diphenyl-o-methylphenylsulfonium benzenesulfonate, diphenyl-o-ethylphenylsulfonium p-toluenesulfonate, diphenyliodonium chloride, diphenyliodonium tetrafluoroborate, diphenyliodonium trifluoride Examples include romethanesulfonate, diphenyliodonium p-toluenesulfonate, and the like.

Water-dispersible photoacid generators include 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyl-p-methylphenylsulfonium trifluoromethanesulfonate, and diphenyl(4-methoxyphenyl)sulfonium trifluoromethane. sulfonate, diphenyl-p-methylphenylsulfonium nonafluorobutanesulfonate, tri-p-tolylsulfonium nonafluorobutanesulfonate, and the like. When preparing an aqueous ink using a water-dispersible photoacid generator, it is preferable to use an aqueous dispersion prepared as follows. A solution obtained by dissolving a photoacid generator in an organic solvent and water to which a component that assists dispersion is added are mixed and dispersed using a dispersing machine, and then the organic solvent is distilled off under reduced pressure to obtain an aqueous dispersion. get Known surfactants, emulsifiers and the like can be given as components that aid dispersion. As the disperser, it is preferable to use an ultrasonic homogenizer, a high-pressure homogenizer, or the like, since the particle size can be easily adjusted.

Photoacid generators are excellent in thermal stability and photosensitivity, and can efficiently generate acid, facilitating the cationic polymerization reaction, and further improving the scratch resistance of recorded images. Arylsulfonium salts are preferred because they can be Commercially available arylsulfonium salts include trade name “WPAG-367” (manufactured by Wako Pure Chemical Industries), trade name “CPI-410S” (manufactured by San-Apro), trade name “Irgacure 290” (manufactured by BASF), and the like. can be done.

The content (% by mass) of the photoacid generator in the ink is preferably 0.10% by mass or more and 10.00% by mass or less, based on the total mass of the ink, and 0.30% by mass or more and 5.00% by mass. % by mass or less is more preferable. If the content of the photoacid generator is less than 0.10% by mass, the resulting resin film tends to be insufficiently cured, and the scratch resistance and water resistance of the image may be slightly reduced. On the other hand, if the content of the photo-acid generator exceeds 10.00% by mass, the ejection stability of the ink may slightly deteriorate.

When the resin particles have at least one of the above first unit and second unit, it is preferable that the following relationship is satisfied. That is, the content (% by mass) of the photoacid generator in the ink is the mass ratio to the sum of the content (% by mass) of the first unit and the content (% by mass) of the organic group in the second unit. , 0.05 times or more and 0.50 times or less. When the above mass ratio is less than 0.05 times, the amount of cations generated upon irradiation with active energy rays is reduced. For this reason, the cationic polymerization reaction does not proceed efficiently, and the effect of further improving the scratch resistance and water resistance of the image may not be sufficiently obtained. On the other hand, when the mass ratio is more than 0.50 times, the amount of cationic polymerizable groups involved in cross-linking is reduced. For this reason, the cationic polymerization reaction does not proceed efficiently, and the effect of further improving the scratch resistance and water resistance of the image may not be sufficiently obtained.

Components such as the photoacid generator to be contained in the ink can be confirmed as follows. Of course, the invention is not limited to the methods described below. A method of extracting and analyzing components from ink will be described below, but components extracted from dispersions, aqueous solutions, etc. can also be analyzed in the same manner.

A water-dispersible component is separated from the resin particle-containing ink by density gradient centrifugation. A water-dispersible component can be separated and extracted as a precipitate by the difference in sedimentation coefficient of the components in the density gradient sedimentation velocity method and by the difference in the density of the components in the density gradient sedimentation equilibrium method. Resin particles are included in the sediment. If the photoacid generator is water-dispersible, it is contained in the precipitate, and if it is water-soluble, it is contained in the supernatant liquid.

A water-soluble photoacid generator can be analyzed as follows. The supernatant liquid is aliquoted to prepare a sample (aqueous solution or dried solid) suitable for subsequent analytical procedures. Next, component analysis is performed, and if the sample contains a photo-acid generator, the ink to be analyzed contains a "water-soluble photo-acid generator". Component analysis methods include gel permeation chromatography, liquid chromatography mass spectrometry, ion chromatography, nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption ionization mass spectrometry, inductively coupled plasma atomic emission spectrometry, inductive coupling Plasma mass spectroscopy, ultraviolet-visible spectroscopy, infrared spectroscopy, X-ray crystal structure analysis and the like can be mentioned.

Analysis of precipitates can be carried out as follows. In the density gradient centrifugation method, the components are separated into layers, so after appropriately aliquoting and washing if necessary, prepare a sample (aqueous solution or dried solid) suitable for the subsequent analysis method. . Qualitative analysis and quantitative analysis are performed on the components in the sample by the above component analysis method. The composition of the resin constituting the resin particles can also be specified by analyzing the monomer after depolymerization by pyrolysis gas chromatography. If the sample contains a photoacid generator and a reactive group-containing resin, the ink to be analyzed contains "resin particles encapsulating a water-dispersible photoacid generator". In addition, when the sample contains a photoacid generator but does not contain a reactive group-containing resin, the ink to be analyzed is a “water-dispersible photoacid-generating agent (not encapsulated in resin particles) agent".

(colorant)
A pigment or a dye can be used as the coloring material to be contained in the ink. The content (% by mass) of the coloring material in the ink is preferably 0.10% by mass or more and 15.00% by mass or less, and 1.00% by mass or more and 10.00% by mass or less based on the total mass of the ink. is more preferable.

Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole and dioxazine.

As a method of dispersing the pigment, a resin-dispersed pigment using a resin as a dispersing agent, or a self-dispersing pigment having a hydrophilic group bonded to the particle surface of the pigment can be used. Further, a resin-bonded pigment in which an organic group containing a resin is chemically bonded to the surface of a pigment particle, or a microcapsule pigment in which the surface of a pigment particle is coated with a resin or the like can be used. Among them, it is preferable to use a resin-dispersed pigment in which a resin as a dispersant is physically adsorbed on the particle surface of the pigment instead of a resin-bonded pigment or a microcapsule pigment.

As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use a resin capable of dispersing the pigment in the aqueous medium by the action of an anionic group. Examples of resin dispersants include acrylic resins and urethane resins. Among them, acrylic resins are preferable, and acrylic resins having a hydrophilic unit and a hydrophobic unit as constituent units are more preferable.

A hydrophilic unit is a unit having a hydrophilic group such as an anionic group, a hydroxy group, or an ethylene oxide group. A hydrophilic unit can be formed, for example, by polymerizing a monomer having a hydrophilic group. Specific examples of monomers having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. ; monomers having a hydroxy group such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate; monomers having an ethylene oxide group such as methoxy (mono, di, tri, poly)ethylene glycol (meth)acrylate etc. can be mentioned. Examples of cations constituting salts of acidic monomers include ions such as lithium, sodium, potassium, ammonium and organic ammonium.

A hydrophobic unit is a unit that does not have a hydrophilic group such as an anionic group, a hydroxy group, or an ethylene oxide group. A hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer having no hydrophilic group. Specific examples of hydrophobic monomers include monomers having aromatic groups such as styrene, α-methylstyrene, and benzyl (meth)acrylate; ethyl (meth)acrylate, methyl (meth)acrylate, (iso-)propyl (meth) Monomers having an aliphatic group such as acrylate, (n-, iso-, t-)butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate can be mentioned.

The resin dispersant preferably has a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from a monomer having an aliphatic group or an aromatic group. These resinous dispersants are preferred because they are particularly susceptible to interaction with pigments.

The weight average molecular weight of the resin dispersant is preferably 1,000 or more and 30,000 or less, more preferably 3,000 or more and 15,000 or less. The weight average molecular weight of the resin dispersant is a polystyrene-equivalent value measured by gel permeation chromatography (GPC). The acid value of the resin dispersant is preferably 80 mgKOH/g or more and 250 mgKOH/g or less, more preferably 100 mgKOH/g or more and 200 mgKOH/g or less. The content (% by mass) of the resin dispersant in the ink is preferably 0.50% by mass or more and 1.00% by mass or less based on the total mass of the ink. Further, the content (% by mass) of the resin dispersant in the ink is preferably 0.10 times or more and 0.30 times or less as a mass ratio to the content (% by mass) of the pigment.

(aqueous medium)
The ink of the present invention is an aqueous ink containing an aqueous medium which is a mixed solvent of water and a water-soluble organic solvent. It is preferable to use deionized water (ion-exchanged water) as water. The content (% by mass) of water in the ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink.

As the water-soluble organic solvent, any known water-soluble organic solvent generally used for aqueous ink for inkjet can be used. Examples of water-soluble organic solvents include monohydric alcohols, polyhydric alcohols, alkylene glycols having an alkylene group having about 1 to 4 carbon atoms, polyethylene glycols having a number average molecular weight of about 200 to 2,000, glycol ethers, Nitrogen-containing compounds and the like can be used. The content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.00% by mass or more and 50.00% by mass or less based on the total mass of the ink.

(other ingredients)
In addition to the above components, the ink may optionally contain surfactants, pH adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, reducing agents, evaporation accelerators, chelating agents, and various additives such as water-soluble resins.

<Ink cartridge>
The ink cartridge of the present invention includes ink and an ink containing portion that contains the ink. The ink contained in this ink container is the ink of the present invention described above. FIG. 1 is a cross-sectional view schematically showing one embodiment of the ink cartridge of the present invention. As shown in FIG. 1, the bottom surface of the ink cartridge is provided with an ink supply port 12 for supplying ink to the recording head. The interior of the ink cartridge serves as an ink containing portion for containing ink. The ink storage section is composed of an ink storage chamber 14 and an absorber storage chamber 16 which communicate with each other through a communication port 18 . Also, the absorber storage chamber 16 communicates with the ink supply port 12 . The ink containing chamber 14 contains liquid ink 20 , and the absorber containing chamber 16 contains absorbers 22 and 24 that hold the ink in an impregnated state. The ink storage section may have a configuration in which the absorber retains the total amount of the stored ink without having an ink storage chamber for storing liquid ink. Further, the ink containing portion may have a form in which the ink is contained in a liquid state without having an absorber. Further, the ink cartridge may be configured to have an ink containing portion and a recording head.

<Inkjet recording method>
The inkjet recording method of the present invention has an ink application step and an irradiation step. The ink applying step is a step of applying the ink of the present invention to a recording medium by ejecting it from an inkjet recording head. The irradiation step is a step of irradiating the ink applied to the recording medium with an active energy ray, causing polymerization between the resin particles by reaction of the reactive groups of the resin particles. In the inkjet recording method of the present invention, the irradiation step is carried out after the ink application step. Furthermore, a drying step of heating and drying the ink applied to the recording medium may be added. Either the irradiation step or the drying step may be performed first, or may be performed in multiple steps.

Methods for ejecting ink include a method of applying mechanical energy to ink and a method of applying thermal energy to ink. In the present invention, it is preferable to adopt a method of applying thermal energy to the ink to eject the ink.

Examples of active energy rays that are used to cure the ink include electron beams, ultraviolet rays, visible rays, and X-rays. Among them, it is preferable to irradiate ultraviolet rays. Examples of ultraviolet light sources include mercury lamps, metal halide lamps, excimer lasers, ultraviolet lasers, cold cathode tubes, hot cathode tubes, black lights, and LEDs (Light Emitting Diodes). It is preferable that the irradiation dose of ultraviolet rays is 10 mJ/cm ² or more and 5,000 mJ/cm ² or less. Also, the irradiation time is preferably set to 1 second or more and 60 seconds or less.

Techniques for drying the ink include heating, air drying, a combination thereof, and the like, and can be carried out by known means. The heating temperature is preferably 30° C. or higher and 100° C. or lower. Moreover, it is preferable that the wind speed in air drying is 1 m/sec or more and 10 m/sec or less. The drying time is preferably 1 second or more and 60 seconds or less.

FIG. 2 is a diagram schematically showing an example of an inkjet recording apparatus used in the inkjet recording method of the present invention, (a) is a perspective view of the main part of the inkjet recording apparatus, and (b) is a perspective view of a head cartridge. is. The inkjet recording apparatus is provided with transport means (not shown) for transporting the recording medium 32 and a carriage shaft 34 . A head cartridge 36 can be mounted on the carriage shaft 34 . The head cartridge 36 has recording heads 38 and 40, and is constructed so that an ink cartridge 42 is set therein. While the head cartridge 36 is conveyed along the carriage shaft 34 in the main scanning direction, ink (not shown) is ejected from the recording heads 38 and 40 toward the recording medium 32 . An image is recorded on the recording medium 32 by conveying the recording medium 32 in the sub-scanning direction by conveying means (not shown). As the recording medium, it is possible to use non-ink-absorbing materials such as glass and plastic sheets, and ink-absorbing (non-absorbing or easy-absorbing) materials such as paper. Among them, it is preferable to use an ink-absorbing recording medium such as a recording medium having no coat layer such as plain paper; and a recording medium having a coat layer such as glossy paper, matte paper, and lightly coated paper.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited by the following examples as long as the gist thereof is not exceeded. "Parts" and "%" regarding component amounts are based on mass unless otherwise specified.

<Conditions for measuring particle size>
The particle size of the particles (dispersed particles of the photo-acid generator, resin particles) prepared below is the 50% cumulative value (D50) of the volume-based particle size distribution. D50 is determined using a particle size analyzer (trade name “UPA-EX150”, manufactured by Nikkiso) using a dynamic light scattering method, SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, shape: spherical, Refractive index: Measured under the condition of 1.59.

<Preparation of pigment dispersion>
(Pigment dispersion liquid 1)
Pigment (carbon black) 16.0 parts, 50.0 parts of an aqueous solution obtained by neutralizing a styrene-acrylic acid copolymer with a 10% sodium hydroxide aqueous solution (resin content: 20.0%), and ions 35.0 parts of exchanged water were mixed. A styrene-acrylic acid copolymer having an acid value of 100 mgKOH/g and a weight average molecular weight of 10,000 was used. After dispersion for 2 hours using a batch-type vertical sand mill, coarse particles were removed by centrifugation. A pigment dispersion liquid 1 was obtained by pressure filtration through a microfilter having a pore size of 3.0 μm (manufactured by FUJIFILM Corporation). The pigment content in Pigment Dispersion Liquid 1 was 16.0%, and the resin content was 10.0%.

(Pigment dispersion liquid 2)
C.I. I. Pigment Dispersion 2 was obtained in the same manner as Pigment Dispersion 1 described above, except that Pigment Blue was changed to 15:3. The pigment content in the pigment dispersion liquid 2 was 16.0%, and the resin content was 10.0%.

(Pigment dispersion liquid 3)
C.I. I. Pigment Dispersion 3 was obtained in the same manner as Pigment Dispersion 1 described above, except that Pigment Red 122 was used. The content of the pigment in the pigment dispersion 3 was 16.0%, and the content of the resin was 10.0%.

(Pigment dispersion liquid 4)
C.I. I. Pigment Dispersion 4 was obtained in the same manner as Pigment Dispersion 1 described above, except that Pigment Yellow 74 was used. The content of the pigment in the pigment dispersion liquid 4 was 16.0%, and the content of the resin was 10.0%.

<Preparation of photoacid generator dispersion>
(Dispersion of photoacid generator 1)
A solution A was obtained by dissolving 3.00 parts of a photoacid generator 1 (a water-dispersible arylsulfonium salt, trade name “CPI-410S”, manufactured by San-Apro) in 47.00 parts of ethyl acetate. Further, 0.30 parts of a nonionic surfactant (polyoxyalkylene branched decyl ether, trade name "Noigen XL-1000", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is dissolved in 100.00 parts of pure water to obtain a solution B. Ta. After adding solution B to solution A and stirring well, the components were emulsified by ultrasonic treatment using an ultrasonic homogenizer (trade name “Digital Sonifier 450DA”, manufactured by Branson) to obtain an emulsion. The conditions at this time were amplitude: 76 μm, output: 50 W, frequency: 20 kHz, time: 30 minutes. Ethyl acetate was distilled off from the resulting emulsion under reduced pressure, and the water content was adjusted to obtain a dispersion of photoacid generator 1 containing 10.0% of photoacid generator 1. . The particle size of the photoacid generator 1 in the dispersion was 120 nm.

(Dispersion of photoacid generator 2)
The content of the photo-acid generator 2 is 10.0% in the same procedure as the dispersion liquid of the photo-acid generator 1 described above, except that the photo-acid generator 1 is changed to the photo-acid generator 2. A dispersion of photoacid generator 2 was obtained. As the photoacid generator 2, a water-dispersible arylsulfonium salt (trade name “Irgacure 290”, manufactured by BASF) was used. The particle size of the photoacid generator 2 in the dispersion was 145 nm.

(Dispersion of photoacid generator 3)
The content of the photo-acid generator 3 is 10.0% in the same procedure as the dispersion liquid of the photo-acid generator 1 described above, except that the photo-acid generator 1 is changed to the photo-acid generator 3. A dispersion of photoacid generator 3 was obtained. As the photoacid generator 3, a water-dispersible aryliodonium salt (4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate, manufactured by Tokyo Chemical Industry Co., Ltd.) was used. The average particle size of the photoacid generator 3 in the dispersion was 133 nm.

<Synthesis of resin particles>
(Resin particles 1 to 7, 10 to 17, 19)
Ethyl acetate (solvent) 25.00 parts, each component shown in the upper row of Tables 1-1 and 1-2 (unit: parts), and a radical polymerization initiator (azobisisobutyronitrile, manufactured by Fujifilm Wako Pure Chemical Industries) 0.10 part was placed in a beaker and stirred well. Separately, a solution was prepared by dissolving 0.75 parts of a surfactant (sodium dodecyl sulfate, manufactured by Tokyo Kasei Kogyo Co., Ltd.) in 100.00 parts of ion-exchanged water, and the solution was dropped into the beaker and thoroughly stirred. . The contents of the beaker were subjected to ultrasonic treatment for 15 minutes using an ultrasonic homogenizer under the conditions of an amplitude of 76 μm, an output of 55 W, and a frequency of 20 kHz to emulsify the components to obtain an emulsion. The organic solvent was distilled off from the resulting emulsion under reduced pressure to obtain a mixture. The resulting mixture was placed in a flask equipped with a stirrer, a nitrogen inlet tube, a reflux condenser, and a thermometer, heated to 75°C under a nitrogen atmosphere, and subjected to a radical polymerization reaction under stirring for 2 hours to obtain a resin. Particles were synthesized. Thereafter, the dispersion was cooled to 25° C., and the content of water was adjusted so that the content of the resin particles in the dispersion was 20.00% to obtain dispersions of each resin particle. In the lower part of Tables 1-1 and 1-2, the particle size of the resin particles, the resin particles, the photoacid generator, the organic group of the first unit and the second unit, the unit having an epoxy group, and the oxetanyl group unit, each content. The photoacid generators 1 to 3 used in the synthesis of the resin particles are the same as those used in the preparation of the photoacid generator dispersion.

The details of the components forming the first unit used to synthesize the resin particles are as follows.
・3,4-epoxycyclohexylmethyl methacrylate: trade name “Cyclomer M100”, manufactured by Daicel ・4-hydroxybutyl acrylate glycidyl ether: trade name “4-HBAGE”, manufactured by Mitsubishi Chemical ・(3-ethyl-3-oxetanyl) Methyl acrylate: Product name “OXE-10”, manufactured by Osaka Organic Chemical Industry 2-(2-vinyloxyethoxy) ethyl acrylate: Product name “VEEA”, manufactured by Nippon Shokubai)

The details of the components forming the second unit used to synthesize the resin particles are as follows.
・Silsesquioxane compound 1: silsesquioxane having an oxetanyl group, trade name “OX-SQ SI-20”, functional group equivalent 262 g / mol, manufactured by Toagosei ・Silsesquioxane compound 2: having an oxetanyl group Silsesquioxane, trade name “OX-SQ TX-100”, functional group equivalent 209 g/mol, manufactured by Toagosei ・Silsesquioxane compound 3: 1-butoxy-2-propanol of silsesquioxane having an oxetanyl group Solution (solid content 50%), trade name “OX-SQ HDX”, functional group equivalent 287 g / mol, manufactured by Toagosei ・Silsesquioxane compound 4: isopropanol / toluene solution of silsesquioxane having an epoxy group (solid content 72%), organic content 65%, inorganic content 35%, trade name "Compoceran SQ502-8", manufactured by Arakawa Chemical

The organic group content of the second unit (that is, the oxetanyl group content) in the resin particle dispersions prepared using the silsesquioxane compounds 1 to 3 was calculated based on the following formula. The organic group of silsesquioxane compounds 1 to 3 is "2-(3-ethyl-3-oxetanyl)methoxyethyl group", and the molecular weight is 157.23 g/mol.
Organic group content (%) in the second unit = resin particle content (%) x molecular weight of organic group R (g/mol)/functional group equivalent (g/mol)

In addition, the content of the organic group of the second unit (that is, the content of the epoxy group) in the resin particle dispersion prepared using the silsesquioxane compound 4 was calculated based on the following formula. In addition, the "organic content" in the silsesquioxane compound 4 means the mass ratio (%) of the organic group in the compound.
Content (%) of organic groups in the second unit = content (%) of resin particles x organic content (%)/100 (%)

(Resin particles 8, 9, 18)
37.50 parts of ethyl acetate (solvent) and each component (unit: part) shown in the upper part of Table 2 were placed in a beaker and thoroughly stirred. As the epoxy resin, a bisphenol A type epoxy resin (trade name “EPICLON 1050” manufactured by DIC) was used. Separately, a solution was prepared by dissolving 0.50 parts of a surfactant (sodium dodecyl sulfate, manufactured by Tokyo Kasei Kogyo Co., Ltd.) in 100.00 parts of ion-exchanged water, and the solution was dropped into the beaker and thoroughly stirred. . The contents of the beaker were subjected to ultrasonic treatment for 30 minutes using an ultrasonic homogenizer under the conditions of an amplitude of 76 μm, an output of 55 W, and a frequency of 20 kHz to emulsify the components to obtain an emulsion. The organic solvent was distilled off from the resulting emulsion under reduced pressure to prepare resin particles. After that, the content of water was adjusted so that the content of the resin particles in the dispersion liquid was 20.00%, and a dispersion liquid of each resin particle was obtained. In the lower part of Table 2, the particle diameter of the resin particles, and the contents of the resin particles, the photoacid generator, the organic group of the first unit and the second unit, the unit having an epoxy group, and the unit having an oxetanyl group. indicate quantity.

(Resin 20)
A “photoradical polymerizable polymer micelle liquid” was prepared according to the description of Synthesis Example 1 of Patent Document 2, and this was used as a liquid containing the resin 20 . The resin 20 contains a photopolymerization initiator (radical polymerization initiator) with micelles of poly(ethylene glycol)-poly(benzyl methacrylate-co-acryloyl glycidyl methacrylate). The resin 20 (micelle) had a particle diameter of 220 nm, a resin content of 16.50%, and a photoinitiator content of 0.83%.

<Ink preparation>
(Inks 1-28, 30)
After mixing and sufficiently stirring each component (unit: %) shown in the upper row of Tables 3-1 to 3-3, pressure filtration was performed with a microfilter (manufactured by Fujifilm) with a pore size of 0.45 μm. Inks were prepared. In Tables 3-1 to 3-3, photoacid generator 4 is a water-soluble arylsulfonium salt, diphenyl-2,4,6-trimethylphenylsulfonium-p-toluenesulfonate (trade name “WPAG-367”). , manufactured by Wako Pure Chemical Industries). The numbers given for polyethylene glycol are number average molecular weights. In addition, "acetylenol E60" is a trade name of a nonionic surfactant (ethylene oxide adduct of acetylene glycol) manufactured by Kawaken Fine Chemicals.

The lower part of Tables 3-1 to 3-3 shows the content (%) of each component in the prepared ink. That is, the resin particles (R), the photoacid generator (P), the first unit (U1), the organic group (U2) of the second unit, the unit having an epoxy group (E), and the unit having an oxetanyl group (O ), each content is shown. In addition, the values of C _P /(C _U1 +C _U2 ) and C _E /(C _E +C _O ) are also shown at the bottom of Tables 3-1 to 3-3. The resin particle content C _R (%) includes resin particles 1 to 19, resin 20, and 1,4-butanediol diglycidyl ether, but does not include the pigment resin dispersant.

(Ink 29)
Ink 29 was prepared according to Example 1 of Patent Document 1. The ink 29 contains a radical polymerizable compound having a maleimide structure and a photopolymerization initiator (radical polymerization initiator).

<Evaluation>
An on-demand type ink jet recording apparatus was prepared, which was equipped with a recording head that applies heat energy according to a recording signal to ink and ejects the ink. A heating device provided with a near-infrared heater and a blower was incorporated at a position adjacent to the recording head so as to heat the image immediately after recording with hot air. The heating temperature was adjusted to 60° C., the wind speed was adjusted to 9 m/sec, and the drying time was 5 seconds. Also, an LED-UV lamp (wavelength range: 270 to 310 nm, center wavelength: 290 nm) was incorporated at a position adjacent to the heating device. The UV illuminance was adjusted to 70 mW/cm ² and the irradiation time was 20 seconds. Furthermore, in order to heat after irradiation with ultraviolet rays, the same heating device as described above was incorporated at a position adjacent to the LED-UV lamp. The heating temperature of this heating device was adjusted to 60° C., the wind speed was adjusted to 9 m/sec, and the drying time was adjusted to 5 seconds. However, in Reference Example 1, ultraviolet rays were not irradiated.

In this embodiment, an image printed under the condition that about 16 ng of ink is applied to a unit area (1 pixel) of 1/600 inch×1/600 inch is defined as having a print duty of 100%. In the present invention, in the evaluation criteria for each evaluation item shown below, "A" and "B" were defined as acceptable levels, and "C" was defined as unacceptable levels. Table 4 shows the evaluation results.

(Scratch resistance)
Using the inkjet recording apparatus described above, a solid image (200 mm×200 mm) with a recording duty of 100% was recorded on a recording medium (trade name “OK Topcoat”, basis weight 127.9 g, manufactured by Oji Paper Co., Ltd.). One hour after the recording, using a Gakushin type testing machine (abrasion resistance tester, manufactured by Imoto Seisakusho Co., Ltd.) in accordance with JIS L 0849:2013, a friction test was performed by rubbing the solid image under the conditions of a load of 500 g and 10 reciprocations. Ta. After the test, the state of the solid image was visually confirmed, and the scratch resistance of the image was evaluated according to the evaluation criteria shown below.
A: No scratch marks were visible on the solid image.
B: Scratches were found on the solid image, but the white background of the recording medium was not visible.
C: Scratches were found on the solid image, and the white background of the recording medium was visible.

(water resistance)
Using the inkjet recording apparatus described above, a solid image (200 mm×200 mm) with a recording duty of 100% was recorded on a recording medium (trade name “OK Topcoat”, basis weight 127.9 g, manufactured by Oji Paper Co., Ltd.). One hour after recording, one drop of pure water was dropped on the center of the solid image using a dropper. After being left for 1 minute, a silbon paper and a weight having a surface pressure of 40 g/cm ² were placed on the solid image, and the solid image and the silbon paper were rubbed together. After one day, the state of the solid image was visually observed, and the water resistance of the image was evaluated according to the evaluation criteria shown below.
A: No scratch marks were visible on the solid image.
B: Scratches were found on the solid image, but the white background of the recording medium was not visible.
C: Scratches were found on the solid image, and the white background of the recording medium was visible.

Claims (12)

An active energy ray-curable aqueous inkjet ink containing resin particles and a photoacid generator,
The resin particles contain a reactive group-containing resin having at least one cationic polymerizable reactive group selected from the group consisting of an epoxy group, an oxetanyl group, and a vinyl ether group ,
The reactive group-containing resin has at least one of a first unit and a second unit,
The first unit is a (meth)acrylate-derived unit having the cationic polymerizable reactive group,
The second unit is a unit containing a silsesquioxane structure, which has an inorganic group composed of an organic group containing the cationic polymerizable reactive group and a siloxane unit,
The content (% by mass) of the photoacid generator is a mass ratio to the sum of the content (% by mass) of the first unit and the content (% by mass) of the organic group in the second unit, and is 0 0.05 times or more and 0.50 times or less . The water-based ink according to claim 1, wherein the photoacid generator is water-dispersible. 2. The water-based ink according to claim 1, wherein the photoacid generator is water-dispersible and contained in a state of being encapsulated in the resin particles. 4. The aqueous ink according to any one of claims 1 to 3, wherein the photoacid generator is an arylsulfonium salt. 5. The water-based ink according to any one of claims 1 to 4, wherein the reactive group-containing resin has both the first unit and the second unit. 6. The ratio (mol %) of the cationically polymerizable reactive group to all the reactive groups of the reactive group-containing resin is 95.0 mol % or more and 100.0 mol % or less. The water-based ink according to any one of items 1 to 3. the cationically polymerizable reactive group comprises the epoxy group and the oxetanyl group;
Among the first unit and the second unit, the content C _E (% by mass) of the unit having the epoxy group and the content C _O (% by mass) of the unit having the oxetanyl group are represented by the following formula (1) The water-based ink according to any one of claims 1 to 6, which satisfies the relationship:
0.10≦ _CE /( _CE + _CO )≦0.65 (1) 1 to 1, wherein the ratio (% by mass) of the unit having the cationic polymerizable reactive group in the resin particles is 50.00% by mass or more and 100.00% by mass or less based on the total mass of the resin particles. 8. The water-based ink according to any one of 7. 9. The content (% by mass) of the unit derived from the monomer having a cationic polymerizable reactive group is 0.10% by mass or more and 20.00% by mass or less based on the total mass of the ink. The water-based ink according to any one of items 1 to 3. The aqueous ink according to any one of claims 1 to 9, wherein the content (% by mass) of the photoacid generator is 0.10% by mass or more and 10.00% by mass or less based on the total mass of the ink. . An ink cartridge comprising ink and an ink containing portion containing the ink,
An ink cartridge, wherein the ink is the water-based ink according to any one of claims 1 to 10 . A step of ejecting the water-based ink according to any one of claims 1 to 10 from an inkjet recording head and applying it to a recording medium;
and a step of irradiating the water-based ink applied to the recording medium with an active energy ray.

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