Inkjet recording method and inkjet recording apparatus

Abstract

To provide an inkjet recording method capable of recording an image having good scratch resistance by using an aqueous ink and a reaction liquid.SOLUTION: In the inkjet recording method, an aqueous ink containing resin particles and a reaction liquid containing a reactant for flocculating a component in the aqueous ink are applied to a recording medium by being discharged from a recording head of an inkjet system. The reaction liquid contains a compound represented by the following general formula (1) (where n represents an integer of 0-3). At least one of the aqueous ink and the reaction liquid contains a surfactant having an HLB value of 15 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to an inkjet recording method and an inkjet recording apparatus. [Background technology]

[0002] In recent years, inkjet recording methods have been increasingly used in the signage and display field, such as for recording posters and large advertisements. In this field, polyvinyl chloride sheets and polyethylene terephthalate (PET) sheets are often used as recording media due to considerations such as durability and cost. These are recording media that do not have or have almost no water-based ink absorption layer on the recording surface, and are called so-called non-absorbent recording media (recording media that do not absorb water-based ink) or low-absorbent recording media (recording media with low water-based ink absorption). There is a need for inkjet recording methods that can record directly onto these recording media.

[0003] As a method for recording images on the aforementioned non-absorbent or low-absorbent recording media (hereinafter collectively referred to as "non-absorbent recording media"), recording methods using non-aqueous inks mainly composed of organic solvents or inks that harden with energy rays such as UV light are known. However, non-aqueous inks use volatile organic solvents and therefore have an odor, and UV-curing inks require the use of polymerizable monomers and UV irradiation during fixing, so these recording methods have many challenges in terms of environmental impact and odor. In addition, recordings made using these methods leave behind decomposition products such as organic solvents and polymerizable monomers within the image, and depending on the usage environment of the recording, such as when the recording is displayed indoors, the odor can become a major problem.

[0004] For these reasons, recording methods that can record on non-absorbent recording media using water-based inks are being investigated. Non-absorbent recording media have little to no ink absorption layer, making it difficult to achieve high-definition image quality. As a method for improving image quality on non-absorbent recording media, an inkjet recording method has been proposed in which a reaction solution containing a coagulant that aggregates components in the ink is applied to the recording media, and then water-based ink is applied (see Patent Document 1).

[0005] Furthermore, when displaying materials in the sign and display field, they are subjected to strong rubbing of the surface with tools such as scrapers when displayed on walls, or are touched by many people when displayed outdoors. This requires higher abrasion resistance than conventional inkjet-recorded photographs and graphic art. As a method to improve the abrasion resistance of images recorded on non-absorbent recording media, a method has been proposed that uses a reaction solution and an aqueous ink containing resin particles, and further incorporates a nitrogen-containing solvent into the aqueous ink (see Patent Document 2).

[0006] Furthermore, a method has been proposed in which an image such as white is recorded by applying the reaction solution to the recording medium and then applying an ink containing an inorganic oxide colloid to the recording medium (see Patent Document 3). Patent Document 3 states that the reaction solution may contain a nitrogen-containing solvent. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-138353 [Patent Document 2] Japanese Patent Publication No. 2018-154805 [Patent Document 3] Japanese Patent Publication No. 2002-103783 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Images in the fields as described above are required to have a higher level of abrasion resistance than ever before. As a result of the study by the present inventors, it has been found that in the inkjet recording method using aqueous ink and a reaction liquid in the prior art, the abrasion resistance of the image does not reach a sufficiently high level, and there is room for improvement.

[0009] Therefore, an object of the present invention is to provide an inkjet recording method capable of recording an image with good abrasion resistance using an aqueous ink and a reaction liquid. Another object of the present invention is to provide an inkjet recording apparatus that can be used in the above inkjet recording method.

Means for Solving the Problems

[0010] The above object is achieved by the following present invention. That is, according to the present invention, there is provided an inkjet recording method in which an aqueous ink containing resin particles and a reaction liquid containing a reactant for aggregating components in the aqueous ink are ejected from an inkjet recording head and applied to a recording medium, wherein the reaction liquid contains a compound represented by the following general formula (1), and at least one of the aqueous ink and the reaction liquid contains a surfactant having an HLB value of 15 or less.

[0011] TIFF0007871129000001.tif33170(In the general formula (1), n represents an integer of 0 to 3.)

Effects of the Invention

[0012] According to the present invention, it is possible to provide an inkjet recording method capable of recording an image with good abrasion resistance using an aqueous ink and a reaction liquid. Further, according to the present invention, it is possible to provide an inkjet recording apparatus that can be used in the above inkjet recording method.

Brief Description of the Drawings

[0013] [Figure 1]This is a schematic perspective view showing one embodiment of the inkjet recording apparatus of the present invention. [Figure 2] This is a schematic side view showing one embodiment of the inkjet recording apparatus of the present invention. [Modes for carrying out the invention]

[0014] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when a compound is a salt, the salt exists in the ink dissociated into ions, but for convenience, it will be expressed as "contains a salt." Also, water-based ink for inkjet printers may be simply referred to as "ink." Unless otherwise specified, the physical properties are values ​​at room temperature (25°C).

[0015] The inventors investigated a method for obtaining an image with good scratch resistance in an inkjet recording method using an aqueous ink containing resin particles and a reaction solution containing a reactant that agglomerates the components in the ink. As a result, it was found that the desired image can be obtained by including a compound represented by general formula (1), described later, in the reaction solution, and by including a surfactant with an HLB value of 15 or less in at least one of the ink and the reaction solution. The inventors believe that the reason why an image with good scratch resistance can be obtained by the above means is as follows.

[0016] First, when we observed solid images recorded using ink containing resin particles and a reaction solution, we found many areas on the recording medium that were not colored by the ink's pigments, resulting in white areas (white spots). On the other hand, when we recorded images using only the ink, no white spots were observed. The reaction solution contains a reactant that agglomerates the pigments and resin particles in the ink, and it works to fix the ink when the ink and reaction solution react on the recording medium. Therefore, when using both ink and reaction solution, the ink does not wet and spread as easily as when using only ink without the reaction solution. As a result, it is presumed that white spots are more likely to occur when using both ink and reaction solution.

[0017] The inventors hypothesized that the reduced contact area between the ink dots and the recording medium due to whiteouts might decrease the adhesion of the ink dots to the recording medium, resulting in an inability to obtain an image with good scratch resistance. Therefore, they considered whether it would be possible to improve scratch resistance by lowering the surface tension of the ink by incorporating a surfactant with a low HLB value into the ink, thereby increasing the wettability of the ink to the recording medium. As a result of their investigation, they were able to slightly improve scratch resistance by increasing the wettability of the ink and suppressing the occurrence of whiteouts, but it did not reach a sufficiently high level. Therefore, they conducted a detailed observation of the image surface on the recorded material and found that the film-forming ability of the resin particles was insufficient. It is thought that if the film-forming ability of the resin particles is low, the fusion force between the resin particles will be low, and the strength of the image formed when the ink dries will not be achieved.

[0018] Heating a recording medium coated with ink can improve the film-forming properties of resin particles. However, this would necessitate additional heating methods and increased power consumption. Therefore, to improve the film-forming properties of resin particles without heating, 2-pyrrolidone, a water-soluble organic solvent with high solubility for resin particles, was added to the ink. However, no improvement in image abrasion resistance was observed. Detailed observation of the image surface on the recording material revealed that while the film-forming properties of the resin particles had improved, white spots had occurred. The reason for this is thought to be as follows: 2-pyrrolidone has a high affinity for surfactants with low HLB values, and these surfactants suppress orientation at the interface between the ink dots and the recording medium, and at the interface between the air layer and the ink dots (hereinafter, these will be collectively referred to simply as "interfaces"). As a result, the wettability of the ink on the recording medium did not improve, and white spots occurred, thus preventing an improvement in image abrasion resistance.

[0019] Based on the above findings, the inventors hypothesized that the scratch resistance of images could be improved by lowering the affinity between the water-soluble organic solvent and the surfactant, and conducted various studies. As a result, they found that the scratch resistance of images could be dramatically improved by including a surfactant with an HLB value of 15 or less in the ink and / or reaction solution, and by including a compound represented by general formula (1) as the water-soluble organic solvent in the reaction solution. The compound represented by general formula (1) has a pyrrolidone skeleton that can increase the solubility of resin particles. In addition, the compound represented by general formula (1) has a hydrophilic group, which is a hydroxyl group (when n in general formula (1) is 0) or a hydroxyalkyl group (when n in general formula (1) is an integer from 1 to 3). Therefore, because the compound has an HLB value of 15 or less, it has low affinity with highly hydrophobic surfactants. As a result, it is presumed that the surfactant is more easily oriented at the interface, improving the wettability of the ink to the recording medium.

[0020] Furthermore, detailed observation of the image surface on the recorded material revealed a significant improvement in the film-forming properties of the resin particles. The reason for this is thought to be as follows: As mentioned above, the compound represented by general formula (1) easily increases the solubility of resin particles. In addition, due to the low affinity between the surfactant and the compound represented by general formula (1), the surfactant orients not only at the interface but also at the resin particles. As a result, it is presumed that the surfactant penetrates into the interior of the molecular chains of the resin forming the resin particles, loosening the entanglement of the molecular chains and thereby improving the film-forming properties of the resin particles. Thus, by using the compound represented by general formula (1), the surfactant can be efficiently oriented at the interface and at the resin particles, thereby improving the wettability of the ink on the recording medium and the film-forming properties of the resin particles, and consequently, the scratch resistance of the image is thought to have dramatically improved.

[0021] It was found that even when the compound represented by general formula (1) is included in the ink rather than the reaction solution, the effect of improving scratch resistance is less pronounced compared to when it is included in the reaction solution. The inventors speculate on the reason for this as follows: When the compound represented by general formula (1) is present only in the ink, the resin particles in the ink tend to incorporate the compound represented by general formula (1) into the molecular chains of the resin, causing the resin particles to swell in the ink. As a result, the rapid dissolution of the resin particles that should occur when they come into contact with the compound represented by general formula (1) from the reaction solution on the recording medium becomes less likely to occur, and thus the effect of improving scratch resistance is not obtained. As described above, it is important to include the compound represented by general formula (1) in the reaction solution.

[0022] <Inkjet recording method and inkjet recording device> The present invention relates to an inkjet recording method that includes the step of applying an aqueous ink containing resin particles and a reaction solution that aggregates the components in the aqueous ink to a recording medium by ejecting them from an inkjet recording head. The present invention also relates to an inkjet recording apparatus that comprises the above-mentioned aqueous ink, the above-mentioned reaction solution, and an inkjet recording head that ejects them and applies them to a recording medium. It is not necessary to perform a step of curing the image by irradiation with active energy rays or the like. The present invention relates to an inkjet recording method and an inkjet recording apparatus that will be described in detail below. The present invention is not limited to the following description unless it exceeds the gist of the invention.

[0023] [Water-based ink] The inkjet recording method and inkjet recording apparatus of the present invention use an aqueous ink containing resin particles. The resin particles form a film by creating a film, which provides physical strength to the image. The components that make up the ink will be described in detail below.

[0024] (Resin particles) The ink contains resin particles. In this specification, "resin particles" refers to resin that exists in an insoluble state in the aqueous medium constituting the ink, and specifically means resin that can exist in the aqueous medium in a state in which particles whose particle size can be measured by dynamic light scattering are formed. On the other hand, "water-soluble resin" refers to resin that exists in a dissolved state in the aqueous medium constituting the ink, and specifically means resin that can exist in the aqueous medium in a state in which particles whose particle size can not be measured by dynamic light scattering are not formed. When resin particles are expressed in contrast to "water-soluble resin," they become "water-dispersible resin (water-insoluble resin)."

[0025] Whether a resin falls under the definition of "resin particles" as described above can be determined by the following method. First, prepare a liquid containing the resin to be judged (resin content: 10% by mass). Next, prepare a sample by diluting this liquid 10 times (by volume) with pure water. Then, measure the particle size of the resin in the sample using dynamic light scattering. If particles with a particle size are measured, the resin can be determined to be "resin particles" (i.e., "water-dispersible resin"). On the other hand, if particles with a particle size are not measured, the resin can be determined to be not "resin particles" (i.e., "water-soluble resin"). As a particle size analyzer for dynamic light scattering, a particle size analyzer (for example, product name "UPA-EX150", manufactured by Nikkiso) can be used. The measurement conditions in this case can be, for example, SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, shape: perfectly spherical, refractive index: 1.59. Of course, the particle size analyzer and measurement conditions are not limited to those described above.

[0026] Examples of resin materials that form resin particles include acrylic resins, urethane resins, polyester resins, olefin resins, and styrene resins. Among these, acrylic resins, urethane resins, and polyester resins are preferred. In the following description, "(meth)acrylic acid" refers to "acrylic acid, methacrylic acid," and "(meth)acrylate" refers to "acrylate, methacrylate."

[0027] [Acrylic resin] The acrylic resins used herein are resins that contain units derived from at least one acrylic monomer selected from (meth)acrylic acid and (meth)acrylic acid ester monomers, and are obtained by (co)polymerizing monomer components containing acrylic monomers. Preferably, the acrylic resin used is a resin composed of units having acid groups and units not having acid groups, obtained by copolymerizing a monomer having an acid group and a monomer not having an acid group.

[0028] Examples of monomers having acidic groups that can be polymerized to form units having acidic groups include monomers having carboxylic acid groups such as (meth)acrylic acid, maleic acid, itaconic acid, and fumaric acid; monomers having sulfonic acid groups such as styrene sulfonic acid; monomers having phosphonic acid groups such as ethyl 2-phosphonate (meth)acrylic acid; and anhydrides and salts of these monomers. Examples of salts include alkali metal salts such as lithium, sodium, and potassium, ammonium salts, and organic ammonium salts. Among these, alkali metal salts such as lithium, sodium, and potassium are preferred. Among the monomers having acidic groups, monomers having carboxylic acid groups are preferred, and (meth)acrylic acid is even more preferred.

[0029] Examples of monomers that do not have acid groups and can be polymerized to form units without acid groups include monomers having hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 3-methyl-5-hydroxypentyl (meth)acrylate; monomers having aromatic groups such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Monomers without acid groups that have aromatic groups and alkyl (meth)acrylates are preferred, and monomers having aromatic groups are even more preferred.

[0030] [Urethane resin] Urethane resins are resins synthesized using at least a polyisocyanate and a component that reacts with it (such as a polyol or polyamine), and optionally a crosslinking agent or chain extender. Preferably, urethane resins obtained by polymerizing a polyisocyanate, a polyol without acid groups, and a polyol with acid groups are used.

[0031] Polyisocyanates are compounds having two or more isocyanate groups in their molecular structure. Examples of polyisocyanates include aliphatic polyisocyanates and aromatic polyisocyanates. Examples of aliphatic polyisocyanates include polyisocyanates having a chain structure such as tetramethylene diisocyanate and hexamethylene diisocyanate; and polyisocyanates having a cyclic structure such as isophorone diisocyanate and hydrogenated xylylene diisocyanate. Examples of aromatic polyisocyanates include tolylene diisocyanate and 1,5-naphthylene diisocyanate. Among these, isophorone diisocyanate is preferred.

[0032] Polyols are compounds having two or more hydroxyl groups in their molecular structure. Examples of polyols include polyether polyols, polyester polyols, and polycarbonate polyols, which are polyols without acid groups; and polyols with acid groups. Polyamines are compounds having two or more amino or imino groups in their molecular structure. Examples of polyether polyols include addition polymers of alkylene oxides and polyols; and glycols such as (poly)alkylene glycols. Examples of polyester polyols include acid esters. Examples of polycarbonate polyols include alkanediol-based polycarbonate diols. The number-average molecular weight of polyols without acid groups is preferably between 400 and 4,500.

[0033] Examples of polyols having acidic groups include those having acidic groups such as carboxylic acid groups, sulfonic acid groups, phosphoric acid groups, and phosphonic acid groups. The acidic groups may also form salts, and examples of salts include alkali metal salts such as lithium, sodium, and potassium, ammonium salts, and organic ammonium salts. Among these, alkali metal salts such as lithium, sodium, and potassium are preferred. As monomers having acidic groups, polyols having carboxylic acid groups such as dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, and dimethylolbutyric acid are preferred, with dimethylolpropionic acid and dimethylolbutanoic acid being even more preferred.

[0034] Examples of polyamines include monoamines having multiple hydroxyl groups, such as dimethylolethylamine and diethanolmethylamine; bifunctional polyamines, such as ethylenediamine and propylenediamine; and polyamines with three or more functions, such as diethylenetriamine and triethylenetetramine. For convenience, compounds having multiple hydroxyl groups and one amino or imino group are also listed as "polyamines."

[0035] When synthesizing urethane resins, crosslinking agents and chain extenders can be used. Typically, crosslinking agents are used in the synthesis of prepolymers, while chain extenders are used to perform chain extension reactions on pre-synthesized prepolymers. Basically, depending on the purpose, such as crosslinking or chain extension, water, polyisocyanates, polyols, and polyamines can be appropriately selected and used as crosslinking agents and chain extenders.

[0036] [Polyester resin] Polyester resins are resins composed of units derived from polyhydric alcohols and units derived from polyhydric carboxylic acids. Examples of polyhydric alcohols that constitute the units of polyester resins include dihydric to tetrahydric alcohols. Examples of polyhydric alcohol structures include polyhydric alcohols with aliphatic groups, polyhydric alcohols with aromatic groups, and sugar alcohols. Specific examples of polyhydric alcohols include dihydric alcohols such as ethylene glycol (also known as 1,2-ethanediol), neopentyl glycol (also known as 2,2-dimethyl-1,3-propanediol), 1,3-propanediol, 1,4-butanediol, benzenediol, and 2,2-bis(4-hydroxyphenyl)propane (also known as bisphenol A); trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane; and tetrahydric alcohols such as pentaerythritol. Furthermore, oligomers (low-molecular-weight polymers with a molecular weight of 1,000 or less) can also be used as polyhydric alcohols.

[0037] It is preferable to use divalent or trivalent polyhydric alcohols because the weight-average molecular weight of the polyester resin can be easily adjusted. Furthermore, from a structural standpoint, it is preferable to use polyhydric alcohols having aliphatic groups or polyhydric alcohols having aromatic groups. Among the polyhydric alcohols having aliphatic groups, those having a linear or branched aliphatic group with 1 to 6 carbon atoms are even more preferable. In particular, ethylene glycol, neopentyl glycol, bisphenol A, and glycerin are preferred, and it is also preferable to use two or more of these in combination.

[0038] Polycarboxylic acids that form units constituting polyester resins through reactions include divalent to tetravalent polycarboxylic acids. Examples of polycarboxylic acid structures include polycarboxylic acids with aliphatic groups, polycarboxylic acids with aromatic groups, and nitrogen-containing polycarboxylic acids. Specific examples of polycarboxylic acids include divalent carboxylic acids such as glutaric acid, adipic acid, terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid; trivalent carboxylic acids such as trimellitic acid; and tetravalent carboxylic acids such as ethylenediaminetetraacetic acid. Furthermore, oligomers (low-molecular-weight polymers with a molecular weight of 1,000 or less) can also be used as polycarboxylic acids.

[0039] It is preferable to use divalent or trivalent polycarboxylic acids because the weight-average molecular weight and acid value of polyester resins can be easily adjusted. Furthermore, from a structural standpoint, it is preferable to use polycarboxylic acids having aliphatic groups or polycarboxylic acids having aromatic groups. In particular, it is preferable to use adipic acid, terephthalic acid, isophthalic acid, and trimellitic acid, and it is also preferable to use two or more of these in combination.

[0040] [Analysis method] Analysis of resin particles is preferably performed by analyzing the constituent units of the resin that forms the resin particles. Examples of methods for analyzing the constituent units of a resin include the following: First, the resin particles are dissolved in an organic solvent capable of dissolving them (e.g., tetrahydrofuran) to prepare a sample. The resin particles used at this time may be in an aqueous dispersion or a dry state. The obtained sample is analyzed by nuclear magnetic resonance (NMR) spectroscopy, matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS), etc. This makes it possible to determine the types and proportions of the units (monomers) that make up the resin. Alternatively, the resin particles themselves can be analyzed by pyrolysis gas chromatography to detect the constituent units (monomers) of the resin. Furthermore, if insoluble matter that does not dissolve in the organic solvent is produced when preparing the above sample, this insoluble matter can be analyzed by pyrolysis gas chromatography to detect the constituent units (monomers) of the resin.

[0041] [Physical properties] The amount of anionic groups in the resin particles is preferably 350 μmol / g or less. By using resin particles with such an amount of anionic groups, surfactants with an HLB value of 15 or less are more easily oriented to the resin particles, improving the film-forming properties of the resin particles and making it easier to improve the scratch resistance of the image. The amount of anionic groups in the resin particles is preferably 50 μmol / g or more. Anionic groups are groups contained in the unit derived from the monomer described above, and examples include carboxylic acid groups, sulfonic acid groups, and phosphonic acid groups. The amount of anionic groups in the resin particles can be determined by colloidal titration. In the examples described later, a potentiometric automatic titrator (product name "AT-510", manufactured by Kyoto Electronics Manufacturing Co., Ltd.) equipped with a flow potentiometric titration unit (PCD-500) was used to measure the amount of anionic groups in the resin particles by colloidal titration using potentiometry. Methyl glycol chitosan was used as the titration reagent. Furthermore, the glass transition temperature (Tg) of the resin particles is preferably between 0°C and 100°C, and more preferably between 20°C and 90°C. The glass transition temperature of the resin particles can be determined for the resin particles themselves using a differential scanning calorimeter.

[0042] [Content] The resin particle content (mass%) in the ink is preferably 1.0% to 20.0% by mass, and more preferably 2.0% to 15.0% by mass, based on the total mass of the ink. In particular, it is even more preferably 5.0% to 10.0% by mass.

[0043] (Other resins) The ink may further contain resins other than the resin particles mentioned above (other resins). The type and form of the other resins are acceptable as long as they can be stably present in the aqueous ink. Examples of other resins include acrylic resins, urethane resins, polyester resins, olefin resins, polyamide resins, polyvinyl alcohol resins, and styrene resins. These resins preferably have salt-type anionic groups to improve their solubility. Examples of cations that form salts of anionic groups include organic amine cations such as monoethanolamine, diethanolamine, triethanolamine, aminemethylpropanol, and N,N-dimethylethanolamine; and alkali metal ions such as potassium and sodium. Among these, alkali metal ions are preferred. Furthermore, the other resins are preferably water-soluble resins.

[0044] (aqueous medium) The ink is an aqueous ink containing at least water as an aqueous medium. The ink may contain an aqueous medium which is a mixed solvent of water and a water-soluble organic solvent. From the viewpoint of odor and other factors, it is preferable that the ink contains 50.0% by mass or more of water as the aqueous medium. It is preferable to use deionized water or ion-exchanged water as the water. The water content (by mass) in the ink is more preferably 50.0% by mass or more and 90.0% by mass or less, based on the total mass of the ink.

[0045] As the water-soluble organic solvent, any of the following can be used for inkjet inks: alcohols, polyols, (poly)alkylene glycols, glycol ethers, other nitrogen-containing compounds, and sulfur-containing compounds. Furthermore, one or more of these water-soluble organic solvents can be included in the ink. The content (by mass) of the water-soluble organic solvent in the ink is preferably 5.0% to 40.0% by mass, and more preferably 15.0% to 30.0% by mass, based on the total mass of the ink. Maintaining a water-soluble organic solvent content within the above range ensures stable ink discharge. This water-soluble organic solvent content includes the content of compounds represented by general formula (1) that can be included in the ink as needed.

[0046] Preferably, the ink further contains a compound represented by general formula (1). In an ink containing a compound represented by general formula (1), resin particles tend to incorporate the compound represented by general formula (1) into the molecular chains of the resin, causing the resin particles to swell in the ink. When the swollen resin particles come into contact with the compound represented by general formula (1) in the reaction solution on the recording medium, the resin particles dissolve rapidly, resulting in improved film-forming properties and further enhanced scratch resistance of the image. Preferably, the content (mass%) of the compound represented by general formula (1) in the ink is 1.0% by mass or more and 20.0% by mass or less, based on the total mass of the ink. When the ink contains a compound represented by general formula (1), it is also preferable to contain a water-soluble organic solvent other than the compound represented by general formula (1).

[0047] (Colorants) Ink does not necessarily have to contain colorants, but colorants such as pigments and dyes can be included in the ink. When colorants are included in the ink, the colorant content (mass%) in the ink is preferably 0.1% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink.

[0048] When using pigments as colorants, the type of pigment is not particularly limited. Specific examples of pigments include inorganic pigments such as carbon black and titanium dioxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolon, diketopyrrolopyrrole, and dioxazine. The ink may contain one or more types of pigments. Among these, carbon black and organic pigments are preferred. Inks containing these pigments have a black or color hue.

[0049] When using pigments as colorants, various dispersion methods can be used, including resin-dispersed pigments using a resin (resin dispersant) as a dispersant, and self-dispersing pigments in which hydrophilic groups are bonded to the surface of the pigment particles. Additionally, resin-bonded pigments, in which organic groups containing resin are chemically bonded to the surface of the pigment particles, and microcapsule pigments, in which the surface of the pigment particles is coated with resin, can also be used. It is also possible to use pigments with different dispersion methods in combination. From the viewpoint of achieving better image scratch resistance, the use of resin-dispersed pigments is preferable.

[0050] When using dyes as colorants, the type of dye is not particularly limited. Specific examples of dyes include direct dyes, acid dyes, basic dyes, disperse dyes, and food dyes. Specific examples of dye skeletons include azo, triphenylmethane, phthalocyanine, azaphthalocyanine, xanthene, and anthrapyridone. Inks may contain one or more types of dyes.

[0051] (Other ingredients) In addition to the components mentioned above, the ink may also contain, as needed, water-soluble organic compounds that are solid at room temperature (25°C), such as urea and its derivatives, trimethylolpropane, and trimethylolethane. Furthermore, the ink may contain various additives such as other surfactants, pH adjusters, defoamers, rust inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, evaporation accelerators, chelating agents, and water-soluble resins.

[0052] [Reaction solution] The inkjet recording method and inkjet recording apparatus of the present invention use a reaction solution containing a reactant that agglomerates components in the ink and a compound represented by general formula (1). The reaction solution is preferably colorless and does not need to contain a colorant. Furthermore, it is preferable that the reaction solution does not contain resin (water-soluble resin, resin particles).

[0053] (Reactive agent) The reactant is not particularly limited and can include, for example, polyvalent metal ions, cationic resins, and acidic organic carboxylic acids, and one or more of these can be used. These reactants react with the anionic groups of the ink components to cause them to aggregate. Examples of components having anionic groups that react with the reactant include resin dispersants for dispersing pigments, self-dispersing pigments in which anionic groups are directly or via other atomic groups bonded to the particle surface, resin particles, and water-soluble resins.

[0054] Examples of polyvalent metal ions include calcium, magnesium, copper, nickel, zinc, barium, aluminum, titanium, strontium, chromium, cobalt, and iron. Examples of cationic resins include polyallylamine hydrochloride, polyamine sulfone hydrochloride, polyvinylamine hydrochloride, and chitosan acetate.

[0055] Examples of acidic organic carboxylic acids, with pKa values ​​in parentheses (for compounds with multiple pKa values, the pKa of the first dissociation step where hydrogen ions are released from the acid), include: monocarboxylic acids such as formic acid (3.8), acetic acid (4.8), propionic acid (4.9), butyric acid (4.8), benzoic acid (4.2), glycolic acid (3.8), lactic acid (3.9), salicylic acid (3.0), pyrrole carboxylic acid (4.6), furoic acid (3.2), nicotinic acid (4.9), levulinic acid (4.4), and coumaric acid (2.8); malonic acid (2.7), succinic acid (4.0), glutaric acid (4.3), adipyl phosphate. Examples include dicarboxylic acids such as nic acid (4.4), maleic acid (1.8), fumaric acid (2.9), itaconic acid (3.9), sebacic acid (4.6), phthalic acid (2.9), malic acid (3.2), and tartaric acid (3.0); tricarboxylic acids such as citric acid (2.8), trimellitic acid (2.5), and 1,2,3-propanetricarboxylic acid (3.5); and tetracarboxylic acids such as pyromellitic acid (1.9).

[0056] Acidic organic carboxylic acids are compact molecules among the reactants, making them prone to precipitation (bleed-out) on the image surface. When organic carboxylic acids precipitate on the image surface, a rough texture is created, which may make the image appear less scratch-resistant. In this case, using a reaction solution containing the compound represented by general formula (1) can suppress the decrease in scratch resistance due to the precipitation of organic carboxylic acids. The reason for this is thought to be as follows: The compound represented by general formula (1) not only has an affinity for resin particles, but its hydroxyl group also forms hydrogen bonds with the carboxylic acid group of the organic carboxylic acid. Furthermore, the compound represented by general formula (1) has a sufficiently high boiling point and low vapor pressure among water-soluble organic solvents used in water-based inkjet inks, so it does not evaporate as quickly as water. Therefore, the resin particles and organic carboxylic acids tend to exist in close proximity to each other via the compound represented by general formula (1), making it less likely for the organic carboxylic acid to precipitate on the image surface, and thus suppressing the decrease in the image's scratch resistance.

[0057] Among the reactants, it is preferable to use an acidic organic carboxylic acid with a pKa of 1.8 or higher. Acidic organic carboxylic acids cause the components to aggregate by reducing the hydrophilicity of the components by changing the anionic groups of the ink components from the ionic dissociation type to the H type. In this case, acidic organic carboxylic acids with a pKa of 1.8 or higher tend to react slowly. In addition, compared to polyvalent metal ions and cationic resins, acidic organic carboxylic acids have fewer reaction sites with anionic groups, so the aggregates produced by the reaction tend to be smaller. Furthermore, because the reaction proceeds slowly and the aggregates produced by the reaction tend to be small, the surface of the image tends to become smoother, thus improving the scratch resistance of the image. Here, pKa represents the ease with which the protons of the acid dissociate, and is the negative common logarithm of the acid dissociation constant (Ka) (pKa = -log10Ka). The amount of acid that dissociates in the reaction solution mainly depends on the pKa of the first-step dissociation reaction in which hydrogen ions are released from the acid. Therefore, in the present invention, the pKa of the acidic organic carboxylic acid refers to the pKa of the first dissociation reaction in which hydrogen ions are released from the acid, in the case of a compound having multiple pKas. The pKa of the above acidic organic carboxylic acid is preferably 4.9 or less.

[0058] Among the organic carboxylic acids mentioned above, polycarboxylic acids having multiple (two or more) carboxylic acid groups are preferred because they are more likely to improve the scratch resistance of the image. Since polycarboxylic acids generally have higher water solubility than monocarboxylic acids, it is thought that precipitation due to evaporation of the aqueous medium or evaporation of the acid is less likely to occur before they are applied to the recording medium, and as a result, the function as an acid is less likely to deteriorate. Furthermore, because polycarboxylic acids have two or more carboxylic acid groups, the hydrogen bonding with the compound represented by general formula (1) is strengthened. As a result, polycarboxylic acids are more likely to exist in the vicinity of the compound represented by general formula (1), so the bleed-out of organic carboxylic acids to the image surface is further suppressed, and the scratch resistance of the image is further improved. It is preferable that the number of carboxylic acid groups in the polycarboxylic acid is four or less.

[0059] The amount of reactant in the reaction solution (mass%) is preferably 0.1% to 5.0% by mass, more preferably 0.5% to 5.0% by mass, and even more preferably 1.0% to 5.0% by mass, based on the total mass of the reaction solution.

[0060] (aqueous medium) From the viewpoint of odor and other factors, the reaction solution is preferably an aqueous reaction solution containing water, and it is even more preferable that it contains 50.0% by mass or more of water as the aqueous medium. Deionized water or ion-exchanged water is preferred as the water. The water content (by mass) in the reaction solution is more preferably 50.0% by mass or more and 90.0% by mass or less, based on the total mass of the reaction solution.

[0061] Furthermore, the reaction solution may also contain a water-soluble organic solvent as an aqueous medium. The water-soluble organic solvents mentioned in the description of the ink above can be used as the water-soluble organic solvents to be included in the reaction solution. The content (mass%) of the water-soluble organic solvent in the reaction solution is preferably 5.0% by mass or more and 40.0% by mass or less, and more preferably 15.0% by mass or more and 30.0% by mass or less, based on the total mass of the reaction solution. By keeping the content of the water-soluble organic solvent in the reaction solution within the above range, it is possible to reduce the likelihood of discharge problems with the reaction solution.

[0062] The reaction solution contains a compound represented by the following general formula (1) as a water-soluble organic solvent.

[0063] TIFF0007871129000002.tif33170

[0064] In general formula (1), n ​​represents an integer from 0 to 3. When n is 0, it represents a single bond, indicating that the hydroxyl group is directly bonded to the nitrogen atom. Compounds represented by general formula (1) have a structure that combines a pyrrolidone skeleton and an N-substituted site with a hydroxyl group. The number of carbon atoms in the N-substituted site with a hydroxyl group in compounds represented by general formula (1) is 0 to 3. Specifically, N-hydroxy-2-pyrrolidone, N-hydroxymethyl-2-pyrrolidone, N-(2-hydroxyethyl)-2-pyrrolidone, and N-(3-hydroxypropyl)-2-pyrrolidone can be used as compounds represented by general formula (1).

[0065] When a compound equivalent to the compound represented by general formula (1) but without the N-substituent, i.e., 2-pyrrolidone, is used instead, the effect of improving the scratch resistance of the image is not obtained. On the other hand, when a compound in general formula (1) where n is 4 or more is used instead of the compound represented by general formula (1), the hydrophobicity of the hydroxyalkyl moiety increases, and the affinity with surfactants with an HLB value of 15 or less decreases. As a result, the surfactant has difficulty oriented at the interface or resin particles, and therefore the effect of improving the scratch resistance of the image is not obtained.

[0066] The content (mass%) of the compound represented by general formula (1) in the reaction solution is preferably 7.0% by mass or more and 31.0% by mass or less, and more preferably 10.0% by mass or more and 30.0% by mass or less, based on the total mass of the reaction solution.

[0067] (Other ingredients) In addition to the components mentioned above, the reaction solution may contain various additives as needed, such as other surfactants, pH adjusters, rust inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, evaporation accelerators, chelating agents, and water-soluble resins.

[0068] [Surfactants] At least one of the aqueous ink and the reaction solution contains a surfactant with an HLB value of 15 or less. If neither the aqueous ink nor the reaction solution contains a surfactant, white areas will occur in the resulting image, reducing the adhesion between the recording film and the recording medium, and thus the effect of improving the image's scratch resistance will not be obtained. The surfactant only needs to be oriented at the interface in the ink dots where the ink and reaction solution are mixed, so it is sufficient if it is contained in either the ink or the reaction solution, or it may be contained in both. If the HLB value of the surfactant is greater than 15, it will dissolve in water, and the surfactant will not be able to oriented at the interface or resin particles, so the effect of improving the image's scratch resistance will not be obtained. It is more preferable that the HLB value of the surfactant is 12 or less. By using a surfactant with an HLB value of 12 or less, the surfactant is more likely to oriented at the interface or resin particles, and the effect of improving the image's scratch resistance is more easily obtained. It is preferable that the HLB value of the surfactant is 10 or more.

[0069] In this specification, the HLB value is the value obtained by the Griffin method. The HLB value obtained by the Griffin method can be determined from the formula weight of the hydrophilic group and the molecular weight of the surfactant using the following formula (A). The HLB value obtained by the Griffin method represents the degree of hydrophilicity or lipophilicity of the surfactant and takes a value from 0 to 20. A lower HLB value indicates that the surfactant is more lipophilic, and a higher HLB value indicates that it is more hydrophilic. HLB value = 20 × formula weight of hydrophilic group of surfactant / molecular weight of surfactant ... (A)

[0070] Surfactants with an HLB value are nonionic surfactants. Examples of surfactants with an HLB value of 15 or less include hydrocarbon surfactants such as polyoxyethylene alkyl ethers and ethylene oxide adducts of acetylene glycol; fluorine-based surfactants such as perfluoroalkyl ethylene oxide adducts; and silicone-based surfactants such as polyether-modified siloxane compounds. One or more surfactants with an HLB value of 15 or less can be used.

[0071] As the surfactant, it is preferable to contain a hydrocarbon-based surfactant, and among them, it is more preferable to contain a polyoxyethylene alkyl ether. In the polyoxyethylene alkyl ether, the ethylene oxide group as a hydrophilic group and the long-chain alkyl group as a hydrophobic group are clearly separated, and the long-chain alkyl group portion is likely to be oriented on the resin particles, and the scratch resistance of the image is more likely to be improved.

[0072] The content (% by mass) of the surfactant having an HLB value of 15 or less is preferably 1.0% by mass or less based on the total mass of the ink or the reaction solution containing the surfactant. Thereby, since it is difficult to form micelles due to the aggregation of surfactants in the ink or the reaction solution, the surfactant is likely to be oriented on the interface or the resin particles, and the scratch resistance of the image is more likely to be improved. Further, the content (% by mass) of the surfactant having an HLB value of 15 or less is preferably 0.1% by mass or more, and more preferably 0.2% by mass or more.

[0073] [ΔSP value] The resin particles, the compound represented by the general formula (1), and the surfactant having an HLB value of 15 or less are preferably used so as to satisfy the relationships described below with respect to their respective SP values. The SP value (δ: solubility parameter) in this specification is a value (unit: (cal / cm 3 )) calculated by the Fedors method based on the following formula (B). When converting to the SI unit system, the relationship of "(cal / cm 1 / 2 )) = 2.046×10 3 (J / m 1 / 2 ))" may be used. In the following description, the unit ((cal / cm 3 )) of the SP value may be omitted. 3 )) 1 / 2 」The relationship of "may be used. In the following description, the unit ((cal / cm 3 )) of the SP value may be omitted. 1 / 2 )) δ = (ΔE vap / V) 1 / 2 ···(B) (In the formula (B), ΔE vap represents the molar heat of vaporization (cal / mol) of the compound, and V represents the molar volume (cm3 (Represents / mol).

[0074] (ΔSP values ​​of the compound represented by general formula (1) and resin particles) The difference (ΔSP value) between the SP value of the compound represented by general formula (1) and the SP value of the resin particles is 5.0 (cal / cm³). 3 ) 1 / 2 The following is preferable: When the ΔSP value of the compound represented by general formula (1) and the resin particles is 5.0 or less, the film-forming properties of the resin particles are easily improved, and the effect of improving the scratch resistance of the image is easily obtained. The ΔSP value of the compound represented by general formula (1) and the resin particles can be determined by subtracting the SP value of the resin particles from the SP value of the compound represented by general formula (1). The ΔSP value of the compound represented by general formula (1) and the resin particles is preferably 1.0 or more, and more preferably 1.5 or more.

[0075] (ΔSP values ​​of resin particles and surfactants with an HLB value of 15 or less) The difference (ΔSP value) between the SP value of resin particles and the SP value of surfactants with an HLB value of 15 or less is 3.0 (cal / cm³). 3 ) 1 / 2 The following is preferable: When the ΔSP value of the resin particles and the surfactant with an HLB value of 15 or less is 3.0 or less, the film-forming properties of the resin particles are easily improved, and the effect of improving the scratch resistance of the image is easily obtained. The ΔSP value of the resin particles and the surfactant with an HLB value of 15 or less can be determined by subtracting the SP value of the surfactant from the SP value of the resin particles. The ΔSP value of the resin particles and the surfactant with an HLB value of 15 or less is preferably 0.5 or more, and more preferably 1.0 or more.

[0076] [Mass ratio of each component] With respect to the aqueous ink and the specific components in the reaction solution, it is preferable that the following relationships are satisfied.

[0077] (Mass ratio of resin particles to surfactants with an HLB value of 15 or less) The resin particle content (mass%) in the aqueous ink is preferably 5.0 to 40.0 times the mass ratio of the surfactant content (mass%) in the aqueous ink or reaction solution containing a surfactant with an HLB value of 15 or less. When this mass ratio is 40.0 times or less, the amount of surfactant on the recording medium is sufficient relative to the resin particles, which makes it easier to improve the film-forming properties of the resin particles and to obtain an effect of improving the scratch resistance of the image. On the other hand, when this mass ratio is 5.0 times or more, the amount of surfactant remaining in the resin film after recording is small or less, which makes it easier to increase the intensity of the image and thus to obtain an effect of improving the scratch resistance of the image.

[0078] (Mass ratio of the compound represented by general formula (1) to the surfactant with an HLB value of 15 or less) The content (mass%) of the compound represented by general formula (1) in the reaction solution is preferably 60.0 times or less in mass ratio to the content (mass%) of the surfactant in the aqueous ink or reaction solution, which contains a surfactant with an HLB value of 15 or less. By having a mass ratio of 60.0 times or less, the dissolution of the surfactant into the compound represented by general formula (1) is suppressed, and the surfactant is more likely to orient itself to the interface and resin particles, thus making it easier to obtain the effect of improving the scratch resistance of the image. The mass ratio is preferably 10.0 times or more.

[0079] (Mass ratio of the compound represented by general formula (1) to the resin particles) The content (mass%) of the compound represented by general formula (1) in the reaction solution is preferably 1.0 to 5.0 times the mass ratio of the resin particle content (mass%) in the aqueous ink. When this mass ratio is 1.0 or more, the amount of the compound represented by general formula (1) is sufficient relative to the resin particles, making it easier to improve the film-forming properties of the resin particles and thus easier to obtain the effect of improving the scratch resistance of the image. On the other hand, when this mass ratio is 5.0 or less, the amount of the compound represented by general formula (1) that remains in the resin film after recording is less, making it easier to increase the intensity of the image and thus easier to obtain the effect of improving the scratch resistance of the image.

[0080] [Recording medium] The recording medium used in the inkjet recording method and inkjet recording apparatus of the present invention is not particularly limited, but it is preferable to use a non-absorbent recording medium. A non-absorbent recording medium is defined as the recording medium used in the Bristow test described in JAPAN TAPPI Paper and Pulp Test Method No. 51, "Test Method for Liquid Absorption of Paper and Paperboard," from the start of contact for 30 msec. 1 / 2 Up to 10 mL / m² of water absorption capacity 2 The recording medium is as follows. In this invention, a recording medium that satisfies the above water absorption amount condition is defined as a "non-absorbent recording medium". Inkjet recording mediums having an ink-receiving layer formed of inorganic particles (glossy paper, matte paper, etc.) and plain paper without a coating layer have a water absorption amount of 10 mL / m². 2 It is an "absorbent recording medium" that exceeds [a certain limit]. When recording media other than non-absorbent recording media are used, liquid components are easily absorbed by those recording media. On the other hand, when non-absorbent recording media are used, the absorption of liquid components is suppressed, and surfactants are more likely to orient themselves at the interface and resin particles, thus making it easier to improve the scratch resistance of images.

[0081] Among non-absorbent recording media, those having a resin layer are preferred. The compound represented by general formula (1) has affinity not only for the resin particles contained in the ink, but also for the general constituent materials of the resin layer of non-absorbent recording media used to record images by applying water-based inkjet ink. Therefore, adhesion between the resin particles and the recording media is easily improved, and the scratch resistance of the image can be further enhanced.

[0082] Any non-absorbent recording medium having a resin layer may be used as long as it satisfies this condition. For example, a plastic film; a recording medium in which a plastic film is bonded to the recording surface side of a substrate; a recording medium in which an organic resin coating layer is provided on the recording surface side of a substrate containing cellulose pulp; and so on can be used. Among these, a plastic film is preferred, and a recording medium in which an organic resin coating layer is provided on the recording surface side of a substrate containing cellulose pulp is also preferred. For the organic resin layer such as the plastic film and the organic resin coating layer, for example, organic resins such as polyvinyl chloride, polyester such as PET, polyethylene, polypropylene, and polycarbonate can be used.

[0083] [Discharge method] Methods for ejecting ink and reaction fluid from the recording head include methods that impart mechanical energy to the ink and reaction fluid, and methods that impart thermal energy to the ink and reaction fluid. Among these, it is preferable to employ a method that imparts thermal energy to the ink and reaction fluid to eject it. As for the recording head, examples include a recording head that ejects ink and reaction fluid by the action of mechanical energy, and a recording head that ejects ink and reaction fluid by the action of thermal energy. Among these, a recording head that ejects ink and reaction fluid by the action of thermal energy is preferred. The order in which the ink and reaction fluid are applied to the recording medium is not particularly limited, but it is preferable to apply the reaction fluid first, followed by the ink.

[0084] [Heating process] By applying ink and reaction solution to the recording medium and then heating the recording medium, resin particles are formed, thereby increasing the intensity of the image and further improving the scratch resistance of the image.

[0085] The means of heating are not particularly limited and can be used by heating with a heater, blowing hot air with a dryer, or a combination of these. The inkjet recording device may be equipped with the above-mentioned heater, dryer, or a combination of these as heating means. Examples of heating methods include applying heat from the side (back side) of the recording medium opposite to the recording surface (ink application surface) with a heater, applying hot air or hot air to the recording surface (front side) of the recording medium, or applying heat from the recording surface or back side with an infrared heater. A combination of these methods may also be used. The heating temperature (image temperature) is preferably 60°C to 120°C, and more preferably 70°C to 100°C.

[0086] The difference (T-Tg) between the heating temperature T (°C) of the recording medium and the glass transition temperature Tg (°C) of the resin particles is preferably -10°C or higher (heating temperature ≥ resin particle Tg - 10°C), and more preferably 0°C or higher (i.e., above the resin particle Tg). A difference (T-Tg) of -10°C or higher makes it easier for the resin particles to fuse together, thus improving the scratch resistance of the image. Furthermore, the difference (T-Tg) between the heating temperature T (°C) and the glass transition temperature Tg (°C) is preferably +30°C or lower, and more preferably +20°C or lower.

[0087] [An example of an inkjet recording device] Figure 1 is a schematic perspective view showing one embodiment of the inkjet recording apparatus of the present invention. Figure 2 is a schematic side view showing one embodiment of the inkjet recording apparatus of the present invention. In the recording apparatus shown in Figures 1 and 2, a heater 25 supported by a frame (not shown) is positioned downstream in the sub-scanning direction A from the position where the recording head 22 reciprocates in the main scanning direction B. The recording medium 1 to which the reaction solution and ink have been applied can be heated by the heater 25. The heater 25 is covered by a heater cover 26. The heater cover 26 is a component for efficiently irradiating the recording medium 1 with the heat generated from the heater 25. Furthermore, the heater cover 26 also serves as a component to protect the heater 25. The recording medium 1 to which the ink ejected from the recording head 22 has been applied is wound up by a take-up spool 27 to form a roll-shaped winding medium 24. [Examples]

[0088] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way by the following examples unless it exceeds the gist of the invention. Unless otherwise specified, amounts of components indicated in "parts" and "%" are based on mass.

[0089] <Preparation of Pigment Dispersion> A water-soluble resin, a styrene / acrylic acid copolymer (composition (molar) ratio = 84.6 / 15.4, acid value 120 mg KOH / g), was dissolved in deionized water using sodium hydroxide equimolar to the acid value to prepare an aqueous solution of resin dispersant with a resin content of 20.0%. A mixture of 30.0 parts pigment (carbon black), 30.0 parts of the resin dispersant aqueous solution, and 40.0 parts water was placed in a sand grinder and dispersed for 1 hour. After that, coarse particles were removed by centrifugation, and the mixture was pressure filtered through a 3.0 μm pore size microfilter (manufactured by Fujifilm). An appropriate amount of deionized water was added to obtain a pigment dispersion. The pigment content in the pigment dispersion was 30.0%, and the resin content was 6.0%.

[0090] <Physical properties of resin particles> A water dispersion of resin particles was dried at 60°C to obtain solid resin particles. Two mg of the obtained resin particles were placed in an aluminum container and sealed to prepare a sample for measurement. A differential scanning calorimeter (product name "Q1000", manufactured by TA instruments) was used to perform thermal analysis on the prepared sample according to the temperature program shown below, and a heating curve was created. The temperature at the intersection of a straight line extending from two points on the low-temperature side of the created heating curve (horizontal axis: temperature, vertical axis: heat quantity) to the high-temperature side, and a tangent line drawn at the point where the slope of the step-like change in the curve is maximum, was defined as the "glass transition temperature (Tg) of the resin (particles)". [Temperature Program]: (1) Heat up to 200℃ at a rate of 10℃ / min (2) Defrost from 200°C to -50°C at a rate of 5°C / min (3) Heat from -50°C to 200°C at a rate of 10°C / min.

[0091] The amount of anionic groups in the resin particles was determined by colloidal titration. Using a potentiometric automatic titrator (product name "AT-510", manufactured by Kyoto Electronics Manufacturing Co., Ltd.) equipped with a flow potentiometric titration unit (PCD-500), the amount of anionic groups (μmol / g) in the resin particles was measured by colloidal titration utilizing potentiometry. Methyl glycol chitosan was used as the titration reagent. The SP value ((cal / cm²)) of the resin particles was also determined. 3 ) 1 / 2 The SP value for the units constituting the resin and the mass ratio of those units were used to calculate it.

[0092] <Synthesis of resin particles> (Resin particle 1) Approximately 1160 mL of water was heated to 90°C in the reactor. Additionally, 1.39 g of potassium persulfate was mixed with 160 mL of water as a polymerization initiator to prepare a solution. First, 32 mL of this initiator solution was added to the reactor and stirred. Separately, a monomer mixture was prepared by mixing 183 g of styrene, 80 g of benzyl acrylate, 1.5 g of methacrylic acid, 1.6 g of isooctyl thioglycolate as a chain transfer agent, and 9.98 g of a 30% aqueous solution of emulsifier with 159.4 mL of water. The emulsifier used was "Rhodafac RS 710" (manufactured by Rhodia Novecare). The monomer mixture was added dropwise to the reactor over 30 minutes, and simultaneously, 129.4 g of the initiator solution was added dropwise over the same period and stirred. The resulting reaction mixture was stirred and maintained at 90°C for 3 hours. The reaction mixture was then cooled to 50°C. Subsequently, potassium hydroxide was added to adjust the pH of the solution to 8.5. After cooling the solution to 25°C, the solution was filtered using a 200-mesh filter, and an appropriate amount of deionized water was added to adjust the resin particle content to 30.0%. In this way, an aqueous dispersion of resin particle 1, which is resin particle formed from acrylic resin, was obtained. The amount of anionic groups in resin particle 1 was 71 μmol / g, the Tg was 67°C, and the SP value was 10.8.

[0093] (Resin particles 2) A 1 L separable flask equipped with a stirrer, thermometer, and reflux tubing was prepared. A mixture of 100 g of polycarbonate diol, 4.2 g of 2,2-bis(hydroxymethyl)propionic acid, 41 g of 4,4'-dicyclohexylmethane diisocyanate, 2.2 g of triethylamine, and 80 g of acetone (solvent) was prepared. The polycarbonate diol used was "T-5650E," manufactured by Asahi Kasei. Under a nitrogen atmosphere, this mixture was placed in the flask, one drop of catalyst (di(2-ethylhexanoate) tin(II)) was added, and the mixture was reacted at 80°C for 15 hours. After cooling to 40°C, water was added to the flask while stirring at 300 rpm to form urethane resin particles. After stirring at 40°C for 30 minutes, 1.2 g of diethylenetriamine was added, and the mixture was stirred at 40°C for 6 hours. After removing the solvent by distillation, deionized water was added to adjust the resin content to 30.0%. In this way, an aqueous dispersion of resin particles 2, which are resin particles formed from a urethane resin, was obtained. The amount of anionic groups in resin particles 2 was 125 μmol / g, the Tg was 64°C, and the SP value was 11.5.

[0094] (Resin particles 3-9) A mixture of the components (in parts) listed under "Esterification Reaction" in Table 1 was placed in a reaction vessel set up inside an autoclave, and the mixture was heated at 220°C for 4 hours to carry out the esterification reaction. The abbreviations for the components in Table 1 are as follows: EG: ethylene glycol, NPG: neopentyl glycol, BPA: bisphenol A, tPA: terephthalic acid, iPA: isophthalic acid, and BTA: trimellitic acid. Next, the temperature was raised to 240°C, and the pressure inside the autoclave was reduced to 13 Pa over 90 minutes. The esterification (dehydration condensation) reaction was continued by maintaining the reduced pressure of 240°C and 13 Pa for 5 hours, after which nitrogen gas was introduced into the autoclave to return to atmospheric pressure. The temperature inside the reaction vessel was lowered to 220°C, and the catalyst (tetra-n-butyl titanate) and the components (in parts) listed under "Transesterification Reaction" in Table 1 were added, and the mixture was heated at 220°C for 2 hours to carry out the transesterification reaction. The amount of catalyst used (moles) is 3 × 10 -4The total amount of polycarboxylic acid used (moles) was used. Then, nitrogen gas was introduced into the autoclave to create a pressurized state, and the sheet-like resin was extracted. After cooling this resin to 25°C, it was crushed in a crusher to obtain the final resin.

[0095] A stirrer (product name "Tornado Stirrer Standard SM-104", manufactured by AS ONE) was set up in a 2L beaker. 210g of the resin obtained above and methyl ethyl ketone were added to this beaker, and the resin was dissolved by stirring at 30°C. Next, a 5% potassium hydroxide aqueous solution was added in an amount corresponding to the neutralization rate (mol%) based on the acid value corresponding to the acid group of the resin, and the mixture was stirred for 30 minutes. 500g of deionized water was added dropwise at a rate of 20mL / min while stirring at 30°C. After raising the temperature to 60°C, the methyl ethyl ketone was removed by distillation, and then some of the water was also removed by distillation. After cooling to 25°C, the mixture was filtered through a 150-mesh wire mesh, and the resin content was adjusted to 30.0% with deionized water. In this way, aqueous dispersions of resin particles 3-9, which are resin particles formed from polyester resin, were obtained. The properties of resin particles 3-9 are shown in the "Properties" column of Table 1.

[0096] TIFF0007871129000003.tif58170

[0097] <SP value of water-soluble organic solvents> The SP values ​​of the water-soluble organic solvents used in the preparation of the ink and reaction solution are shown below. ·N-(2-hydroxyethyl)-2-pyrrolidone:14.3 • N-hydroxymethyl-2-pyrrolidone: 15.2 • N-(3-hydroxypropyl)-2-pyrrolidone: 13.7 • N-hydroxy-2-pyrrolidone: 16.4 • N-(4-hydroxybutyl)-2-pyrrolidone: 13.2 2-Pyrrolidone: 12.6 • N-methyl-2-pyrrolidone: 11.5 ·3-Methoxy-N,N-dimethylpropionamide:9.2 ·γ-Butyrolactone:9.9 • 1,2-Butanediol: 12.8

[0098] <Surfactants> The following commercially available surfactants were used to prepare the ink and reaction solution, as described later. • NIKKOL BL-4.2 (manufactured by Nikko Chemicals): HLB value 10, SP value 9.6 • EMALEX 1615 (manufactured by Nippon Emulsion): HLB value 15, SP value 9.4 • TERGITOL 15-S-7 (manufactured by Dow Chemical): HLB value 11, SP value 9.4 • TERGITOL 15-S-9 (manufactured by Dow Chemical): HLB value 12, SP value 9.4 NIKKOL BC-10 (Nikko Chemicals): HLB value 13, SP value 9.4 • Zonyl FS-3100 (Chemours): HLB value 10, SP value 8.7 • Acetyleneol E60 (manufactured by Kawaken Fine Chemical): HLB value 11, SP value 9.9 NIKKOL BC-20 (Nikko Chemicals): HLB value 16, SP value 9.4 Of the surfactants listed above, "Zonyl FS-3100" is a fluorine-based surfactant, "Acetylenel E60" is an ethylene oxide adduct of acetylene glycol, and the others are polyoxyethylene alkyl ethers.

[0099] <Ink preparation> Each ink was prepared by mixing the components (in %) shown in the upper row of Table 2 (Tables 2-1 and 2-2), stirring thoroughly, and then pressure filtering through a cellulose acetate filter with a pore size of 1.2 μm (product name "Minisart", manufactured by Sartorius). "Proxel GXL(S)" in Table 2 is a commercially available preservative (product name; manufactured by Arch Chemicals) and was also used in the preparation of the reaction solution described later.

[0100] TIFF0007871129000004.tif117170

[0101] TIFF0007871129000005.tif117170

[0102] <Preparation of reaction solution> Each component (in %) shown in the upper row of Table 3 (Tables 3-1 to 3-5) was mixed and thoroughly stirred. The mixture was then pressure filtered through a cellulose acetate filter with a pore size of 1.2 μm (product name "Minisart", manufactured by Sartorius) to prepare each reaction solution. In Table 3, "PDT-2" is the product name of an aqueous solution of dimethylamine-epichlorohydrin condensate (60% purity) manufactured by Yokkaichi Synthetic Co., Ltd. "PAS-92" is the product name of an aqueous solution of diallylamine hydrochloride-sulfur dioxide copolymer (20% purity) manufactured by Nitto Boseki Medical Co., Ltd.

[0103] TIFF0007871129000006.tif181170

[0104] TIFF0007871129000007.tif179170

[0105] TIFF0007871129000008.tif179170

[0106] TIFF0007871129000009.tif183170

[0107] TIFF0007871129000010.tif176170

[0108] <Rating> The following recording media were used for image recording. "Water absorption amount" was recorded from the start of contact in the Bristow method for 30 msec. 1 / 2 This indicates the amount of water absorbed up to that point. • Recording medium 1 (product name "Scotchcal Graphic Film IJ1220", manufactured by 3M, material: polyvinyl chloride, water absorption capacity: 10 mL / m²) 2 below) • Recording medium 2 (Product name: Canon Photo Paper Glossy Pro [Platinum Grade] PT-201, manufactured by Canon, no resin layer, water absorption capacity: 10 mL / m²) 2 super) • Recording medium 3 (product name "LX Gloss Coat 157 LXGC54", manufactured by Sakurai, no resin layer, water absorption capacity: 10 mL / m²) 2 below)

[0109] The following evaluation was performed using an inkjet recording device (product name "imagePROGRAF PRO-2000", manufactured by Canon) with an infrared heater incorporated into the position of the recording medium facing the recording medium on the downstream side of the recording head in the direction of transport of the recording medium. In the above inkjet recording device, an image recorded under the condition of applying one drop of 4 ng of ink to a unit area of ​​1 / 1200 inch × 1 / 1200 inch is defined as having a recording duty cycle of 100%. Each ink prepared above was filled into an ink cartridge. The recording conditions were an environment of 25°C and 50% relative humidity. Using the above recording device, the reaction solution (recording duty cycle 30%) and ink (recording duty cycle 120%) were applied to the recording medium in the order shown in Table 4 (Tables 4-1 and 4-2), using the combinations of reaction solution, ink, and recording medium. Subsequently, the areas of the recording medium to which the reaction solution and ink were applied were heated with an infrared heater so that the image reached the temperature shown in Table 4, and a solid image was recorded.

[0110] The abbreviations in Tables 2-4 represent the following: ·R I : Percentage of resin particles in the ink ·S I : Content of surfactants with an HLB value of 15 or less in the ink (%) ·L R : Content (%) of the compound represented by general formula (1) in the reaction solution ·S R : Content (%) of surfactants with an HLB value of 15 or less in the reaction solution ·S:S I or S R That is, the surfactant content (%) in the ink or reaction solution.

[0111] The "mass ratio" column in Table 4 represents the mass ratio of each component. The "ΔSP value" column in Table 4 represents the difference in SP values ​​of each component. Within this column, "resin particle-surfactant" represents the difference between the SP value of the resin particle and the SP value of the surfactant, and "general formula (1)-resin particle" represents the difference between the SP value of the compound represented by general formula (1) and the SP value of the resin particle.

[0112] (Abrasion resistance) The obtained recordings were subjected to a friction test using a Japan Society for the Promotion of Science (JSPS) type abrasion resistance tester (manufactured by Tester Sangyo Co., Ltd.) conforming to JIS L0849, with a white friction cloth (cotton) specified in JIS L0803. The recorded images were subjected to a friction test with a load of 500g for 20 back-and-forth cycles. The images after the friction test were visually inspected, and the abrasion resistance of the images was evaluated according to the evaluation criteria shown below. In this invention, "A+", "A", and "B" were considered acceptable levels, and "C" was considered an unacceptable level. The evaluation results are shown in Table 4. A+: No abrasions were observed in the image after 10 treatments. A: Abrasions were visible in the image taken after 10 treatments, but not in the image taken after 5 treatments. B: Scratch marks were visible in the image taken 5 times, but the white background of the recording medium was not visible. C: Scratch marks were visible in the image taken 5 times, and the white background of the recording medium was visible.

[0113] TIFF0007871129000011.tif249170

[0114] TIFF0007871129000012.tif77170

[0115] Furthermore, the disclosure of this embodiment includes the following methods and configurations. (Method 1) An inkjet recording method comprising dispensing an aqueous ink containing resin particles and a reaction solution containing a reactant that agglomerates the components in the aqueous ink from an inkjet recording head and applying them to a recording medium, The reaction solution contains a compound represented by the following general formula (1): An inkjet recording method characterized in that at least one of the aqueous ink and the reaction solution contains a surfactant with an HLB value of 15 or less.

[0116] TIFF0007871129000013.tif33170 (In the general formula (1) above, n represents an integer from 0 to 3.)

[0117] (Method 2) The inkjet recording method according to Method 1, wherein the content (mass%) of the resin particles in the aqueous ink is 5.0 times or more and 40.0 times or less in mass ratio to the content (mass%) of the surfactant in the aqueous ink or reaction solution containing the surfactant. (Method 3) The inkjet recording method according to Method 1 or 2, wherein the content (mass%) of the compound represented by the general formula (1) in the reaction solution is 60.0 times or less in mass ratio to the content (mass%) of the surfactant in the aqueous ink or the reaction solution containing the surfactant. (Method 4) The inkjet recording method according to any one of Methods 1 to 3, wherein the content (mass%) of the compound represented by the general formula (1) in the reaction solution is 1.0 times or more and 5.0 times or less in mass ratio to the content (mass%) of the resin particles in the aqueous ink. (Method 5) The inkjet recording method according to any one of Methods 1 to 4, wherein the content (mass%) of the surfactant is 1.0% by mass or less, based on the total mass of the aqueous ink or reaction solution containing the surfactant. (Method 6) The inkjet recording method according to any one of Methods 1 to 5, wherein the HLB value of the surfactant is 12 or less. (Method 7) An inkjet recording method according to any one of Methods 1 to 6, wherein the surfactant comprises a polyoxyethylene alkyl ether. (Method 8) The difference between the SP value of the resin particles and the SP value of the surfactant is 3.0 (cal / cm²). 3 ) 1 / 2 The inkjet recording method described in any one of the following methods 1 to 7. (Method 9) The difference between the SP value of the compound represented by the general formula (1) and the SP value of the resin particles is 5.0 (cal / cm³). 3 ) 1 / 2 The inkjet recording method described in any one of the following methods 1 to 8. (Method 10) An inkjet recording method according to any one of Methods 1 to 9, wherein the amount of anionic groups in the resin particles is 350 μmol / g or less. (Method 11) An inkjet recording method according to any one of Methods 1 to 10, wherein the aqueous ink further contains a compound represented by the general formula (1). (Method 12) The inkjet recording method according to any one of Methods 1 to 11, wherein the reactant is an acidic organic carboxylic acid and has a pKa of 1.8 or higher. (Method 13) The inkjet recording method according to Method 12, wherein the acid-type organic carboxylic acid has a plurality of carboxylic acid groups. (Method 14) The recording medium, from the start of contact in the Bristow method for 30 msec 1 / 2 The amount of water absorbed up to 10 mL / m² is 2 The inkjet recording method according to any one of the following methods 1 to 13. (Method 15) The inkjet recording method according to Method 14, wherein the recording medium has a resin layer. (Method 16) An inkjet recording method according to any one of Methods 1 to 15, wherein the aqueous ink and the reaction solution are applied to the recording medium, and then the recording medium is heated. (Method 17) The inkjet recording method according to Method 16, wherein the difference (T-Tg) between the heating temperature T (°C) of the recording medium and the glass transition temperature Tg (°C) of the resin particles is -10°C or higher. (Configuration 1) comprising an aqueous ink containing resin particles, a reaction solution containing a reactant that agglomerates the components in the aqueous ink, and an inkjet recording head that ejects the aqueous ink and the reaction solution and applies them to a recording medium, The reaction solution contains a compound represented by the following general formula (1): An inkjet recording apparatus characterized in that at least one of the aqueous ink and the reaction solution contains a surfactant with an HLB value of 15 or less.

[0118] TIFF0007871129000014.tif33170 (In the general formula (1) above, n represents an integer from 0 to 3.)

Claims

1. An inkjet recording method comprising dispensing an aqueous ink containing resin particles and a reaction solution containing a reactant that agglomerates the components in the aqueous ink from an inkjet recording head and applying them to a recording medium, The reaction solution contains a compound represented by the following general formula (1): An inkjet recording method characterized in that at least one of the aqueous ink and the reaction solution contains a surfactant with an HLB value of 15 or less. (In the general formula (1) above, n represents an integer between 0 and 3.)

2. The inkjet recording method according to claim 1, wherein the content (mass%) of the resin particles in the aqueous ink is 5.0 times or more and 40.0 times or less in mass ratio to the content (mass%) of the surfactant in the aqueous ink or reaction solution containing the surfactant.

3. The inkjet recording method according to claim 1, wherein the content (mass%) of the compound represented by the general formula (1) in the reaction solution is 60.0 times or less in mass ratio to the content (mass%) of the surfactant in the aqueous ink or the reaction solution containing the surfactant.

4. The inkjet recording method according to claim 1, wherein the content (mass%) of the compound represented by the general formula (1) in the reaction solution is 1.0 times or more and 5.0 times or less in mass ratio to the content (mass%) of the resin particles in the aqueous ink.

5. The inkjet recording method according to any one of claims 1 to 4, wherein the content (mass%) of the surfactant is 1.0% by mass or less, based on the total mass of the aqueous ink or reaction solution containing the surfactant.

6. The inkjet recording method according to any one of claims 1 to 4, wherein the HLB value of the surfactant is 12 or less.

7. The inkjet recording method according to any one of claims 1 to 4, wherein the surfactant comprises a polyoxyethylene alkyl ether.

8. The difference between the SP value of the resin particles and the SP value of the surfactant is 3.0 (cal / cm²). ３ ) １／２ The inkjet recording method according to any one of claims 1 to 4 below.

9. The difference between the SP value of the compound represented by the general formula (1) and the SP value of the resin particles is 5.0 (cal / cm²). ３ ) １／２ The inkjet recording method according to any one of claims 1 to 4 below.

10. The inkjet recording method according to any one of claims 1 to 4, wherein the amount of anionic groups in the resin particles is 350 μmol / g or less.

11. The inkjet recording method according to any one of claims 1 to 4, wherein the resin forming the resin particles is at least one selected from the group consisting of acrylic resins, urethane resins, and polyester resins.

12. The inkjet recording method according to any one of claims 1 to 4, wherein the compound represented by the general formula (1) in the reaction solution and the resin particles in the aqueous ink come into contact with the recording medium for the first time.

13. The inkjet recording method according to any one of claims 1 to 4, wherein the aqueous ink further contains a compound represented by the general formula (1).

14. The inkjet recording method according to any one of claims 1 to 4, wherein the reactant is an acidic organic carboxylic acid and has a pKa of 1.8 or higher.

15. The inkjet recording method according to claim 14, wherein the acid-type organic carboxylic acid has a plurality of carboxylic acid groups.

16. The recording medium, from the start of contact in the Bristow method, 30 msec １／２ The water absorption capacity up to 10 mL / m² is 10 mL / m². ２ The inkjet recording method according to any one of claims 1 to 4 below.

17. The inkjet recording method according to claim 16, wherein the recording medium has a resin layer.

18. The inkjet recording method according to any one of claims 1 to 4, wherein the aqueous ink and the reaction solution are applied to the recording medium, and then the recording medium is heated.

19. The inkjet recording method according to claim 18, wherein the difference (T - Tg) between the heating temperature T (°C) of the recording medium and the glass transition temperature Tg (°C) of the resin particles is -10°C or higher.

20. The system comprises an aqueous ink containing resin particles, a reaction solution containing a reactant that agglomerates the components in the aqueous ink, and an inkjet recording head that ejects the aqueous ink and the reaction solution and applies them to a recording medium. The reaction solution contains a compound represented by the following general formula (1): An inkjet recording apparatus characterized in that at least one of the aqueous ink and the reaction solution contains a surfactant with an HLB value of 15 or less. (In the general formula (1) above, n represents an integer between 0 and 3.)

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