Ink set for inkjet recording, inkjet recording method, maintenance method, and inkjet recording apparatus

Abstract

The present invention addresses the problem of providing an ink set for inkjet recording, an inkjet recording method, a maintenance method, and an inkjet recording apparatus with which harmful effects caused by pretreatment liquid components are reduced and maintainability is improved.　This ink set for inkjet recording includes an ink composition, a pretreatment liquid, and a maintenance liquid, the ink set being characterized in that the pretreatment liquid contains a polyvalent metal salt and the maintenance liquid contains an acidic component.

Description

Technical Field

[0001] The present invention relates to an ink set for inkjet recording, an inkjet recording method, a maintenance method, and an inkjet recording apparatus. More specifically, the present invention relates to an ink set for inkjet recording and the like, which reduces the adverse effects caused by the pretreatment liquid component and improves the maintainability.

Background Art

[0002] The inkjet recording (also referred to as "printing") method is a recording method in which droplets of ink are ejected from an inkjet head and landed on a substrate such as paper. With this method, it is possible to print high-resolution and high-quality images at high speed with a relatively inexpensive apparatus.

[0003] In inkjet printing, particularly when using aqueous ink, when printing a pattern of characters or images on a substrate, after the liquid component of the ink penetrates into the substrate, it dries and the ink is fixed. When using a highly permeable material such as plain paper, special paper, or high-quality paper or recycled paper as the substrate, the ink can be fixed to provide a high-quality image. However, when using a low-permeability material such as coated paper, art paper, lightly coated paper, or a film substrate as the substrate, the ink droplets after landing are difficult to penetrate into the substrate, so drying due to penetration does not occur, bleeding occurs between the droplets, and the image quality is impaired.

[0004] To address this problem, a pretreatment step of applying a pretreatment liquid to a low-permeability substrate is known. As the pretreatment liquid (also referred to as "reaction liquid" or "treatment liquid"), there are two types: one that forms a layer (ink receiving layer) that absorbs the liquid component of the ink and improves the drying property, and one that forms a layer (ink aggregation layer) that aggregates solid components and intentionally causes thickening of the ink to prevent bleeding and color unevenness between the ink droplets.

[0005] The pretreatment liquid for forming the ink aggregation layer contains a flocculant for the purpose of aggregating the solid components of the ink and thickening the ink. As such a flocculant, organic acids, cationic polymers, polyvalent metal salts, etc. are used. However, since organic acids may accelerate deterioration depending on the members of the ejection device, the devices that can be used are limited. Also, inks using cationic polymers are less likely to obtain stable droplet ejection due to the viscosity and the properties of the polymer itself. In addition to such a viewpoint, from the viewpoint of having high reactivity with the solid components of the ink, it is preferable to use a polyvalent metal salt as the flocculant. On the other hand, when the pretreatment liquid is applied from the inkjet head, the dried matter of the pretreatment liquid deposits on the nozzles of the inkjet head, resulting in poor ejection of the pretreatment liquid due to nozzle clogging. Therefore, when using a polyvalent metal salt as the flocculant, it is necessary to clean the nozzles, and a technique of using it together with a maintenance liquid is known.

[0006] Patent Document 1 discloses a technique of a maintenance liquid containing a water-soluble organic solvent having a boiling point of 280°C or lower and water. In this maintenance liquid, when the polyvalent metal salt itself precipitates due to evaporation of water, it can be removed, but it was difficult to remove the carbonate formed by the reaction of carbon dioxide in the air and metal ions.

[0007] Patent Document 2 discloses a technique of a maintenance liquid containing a chelating agent and a surfactant. In this maintenance liquid, by containing a surfactant, aggregation of the ink on the nozzle surface can be suppressed. Also, by containing a chelating agent, the metal ions in the aggregate can be chelated and the aggregate can be redispersed, but it was difficult to remove the carbonate.

[0008] Patent Document 3 discloses a technique of a maintenance liquid containing an organic solvent and water. However, this maintenance liquid is for improving clogging of the ink caused by evaporation and solidification of the moisture of the ink, and is not for the purpose of removing the dried matter of the pretreatment liquid.

[0009] Thus, the maintenance liquids in Patent Documents 1 to 3 are not intended to remove carbonates formed by the reaction of metal ions with carbon dioxide in the air when the pretreatment liquid contains a polyvalent metal salt. In fact, it was difficult to remove the carbonates.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been made in view of the above problems and situations, and the problem to be solved is to provide an inkjet recording ink set, an inkjet recording method, a maintenance method, and an inkjet recording apparatus that reduce the adverse effects caused by the pretreatment liquid components and improve the maintainability.

Means for Solving the Problems

[0012] In order to solve the above problems, the present inventor studied the causes of the above problems and found that when a polyvalent metal salt is used as a flocculant for the pretreatment liquid, dried matter of the pretreatment liquid precipitates on the nozzles of the inkjet head, so maintenance is required. However, in the conventionally known technology, there is still room for further improvement in maintainability. Through repeated studies, it was found that the maintainability is improved by including an acidic component in the maintenance liquid. That is, the above problems according to the present invention are solved by the following means.

[0013] 1. An inkjet recording ink set including an ink composition, a pretreatment liquid, and a maintenance liquid, wherein the pretreatment liquid contains a polyvalent metal salt, The pretreatment liquid contains at least either an inorganic acid or an organic acid. The maintenance liquid contains at least one of citric acid or acetic acid and a salt thereof, and an inkjet recording ink set characterized by this.

[0014] 2. An inkjet recording ink set including an ink composition, a pretreatment liquid, and a maintenance liquid, wherein the pretreatment liquid contains a polyvalent metal salt, the maintenance liquid contains at least either citric acid or acetic acid and its salt, and the pH value of the maintenance liquid is in the range of 5.0 to 6.4 at 25°C. An inkjet recording ink set. 3. The inkjet recording ink set according to claim 1, wherein the pH value of the maintenance liquid is in the range of 5.0 to 6.4 at 25°C.

[0015] 4 . The polyvalent metal salt contains at least one metal element of calcium or magnesium, and the inkjet recording ink set according to claim 1. from Item 3 Item any one of The inkjet recording ink set described in.

[0016] 5 . The pretreatment liquid contains at least one of citric acid, acetic acid, or glycolic acid, and the inkjet recording ink set according to any one of claims 1 to 4 The item described in any one of the items up to.

[0020] 6 . An inkjet recording method of recording using the inkjet recording ink set according to any one of claims 1 to 5 The item, including a step of applying the pretreatment liquid simultaneously with or immediately before the step of ejecting the ink composition. An inkjet recording method characterized by this.

[0021] 7 . The inkjet recording method according to claim 6 The item, including a step of cleaning the pretreatment liquid head using the maintenance liquid.

[0022] 8 . The inkjet recording method according to claim 7The inkjet recording method according to the item.

[0023] 9 . A maintenance method for an inkjet recording apparatus, characterized by using an ink set for inkjet recording according to any one of claims 1 to 5 claim.

[0024] 10 . From the 6 item to the 8 item, an inkjet recording apparatus characterized by using the inkjet recording method according to any one of claims.

Advantages of the Invention

[0025] By the above means of the present invention, it is possible to provide an ink set for inkjet recording, an inkjet recording method, a maintenance method, and an inkjet recording apparatus that reduce the adverse effects caused by the pretreatment liquid components and improve the maintainability.

[0026] Although the mechanism of manifestation or the mechanism of action of the effects of the present invention is not clear, it is speculated as follows.

[0027] When a pretreatment liquid using a polyvalent metal salt as a flocculant is applied from an inkjet head, dried matter of the pretreatment liquid is deposited on the nozzles of the inkjet head, and poor discharge of the pretreatment liquid due to nozzle clogging occurs. Therefore, it is necessary to perform maintenance on the nozzles, but in the conventionally known maintenance techniques, the removal of the dried matter of the pretreatment liquid deposited on the nozzles was insufficient.

[0028] As a result of repeated studies by the present inventor, it was found that the dried matter of the pretreatment liquid contains carbonates formed by the reaction of carbon dioxide in the air with metal ions. Further, it was found that this carbonate is difficult to remove by conventionally known maintenance techniques, and the removal of the carbonate becomes possible by containing an acidic component in the maintenance liquid.

[0029] That is, a carbonate is a salt composed of carbonate ions and metal ions, and carbonic acid is an extremely weak acid (weak acid) among acids. Therefore, in many acidic components, the carbonate dissolves, carbonic acid is released, and carbon dioxide gas is generated. Accordingly, it is presumed that the removal of the carbonate has become possible by such a reaction mechanism.

Brief Description of the Drawings

[0030]

Figure 1

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Figure 8

Embodiments for Carrying Out the Invention

[0031] The ink set for inkjet recording of the present invention is an ink set for inkjet recording including an ink composition, a pretreatment liquid, and a maintenance liquid, wherein the pretreatment liquid contains a polyvalent metal salt, The pretreatment liquid contains at least either an inorganic acid or an organic acid. The maintenance liquid is characterized by containing at least one of citric acid or acetic acid and a salt thereof. The inkjet recording ink set of the present invention is an inkjet recording ink set including an ink composition, a pretreatment liquid, and a maintenance liquid, wherein the pretreatment liquid contains a polyvalent metal salt, the maintenance liquid contains at least either citric acid or acetic acid and its salt, and the pH value of the maintenance liquid is in the range of 5.0 to 6.4 at 25°C. Th these These features are technical features common to or corresponding to the following embodiments.

[0032] As an embodiment of the present invention, from the viewpoint of suppressing the formation of carbonate, it is preferable that the pretreatment liquid contains an acidic component.

[0033] From the viewpoint of suppressing a decrease in image chroma, it is preferable that the polyvalent metal salt contains at least one metal element of calcium or magnesium.

[0034] From the viewpoint of suppressing the formation of carbonate, it is preferable that the pretreatment liquid contains at least one of citric acid, acetic acid, or glycolic acid.

[0035] From the viewpoint of efficiently removing carbonate, it is preferable that the maintenance liquid contains at least one of citric acid, acetic acid, or glycolic acid.

[0036] From the viewpoint of keeping the pH value of the maintenance liquid constant, it is preferable that the maintenance liquid contains at least one of citric acid or acetic acid and also contains its salt.

[0037] From the viewpoint of suppressing the deterioration of the water-repellent film on the surface of the inkjet head, it is preferable that the pH value of the maintenance liquid is in the range of 5.0 to 6.4 at 25°C.

[0038] Furthermore, from the viewpoint of obtaining a high-quality image, the inkjet recording method of the present invention more preferably includes a step of applying the pretreatment liquid simultaneously with or immediately before the step of discharging the ink composition.

[0039] From the viewpoint of preventing poor discharge of the pretreatment liquid, the inkjet recording method preferably includes a step of cleaning the pretreatment liquid head with the maintenance liquid, and more preferably cleaning with a wiping member.

[0040] Hereinafter, the present invention, its components, and embodiments and modes for carrying out the present invention will be described in detail. In the present application, "~" is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value.

[0041] ≪Overview of Ink Set for Inkjet Recording≫ The ink set for inkjet recording of the present invention is an ink set for inkjet recording including an ink composition, a pretreatment liquid, and a maintenance liquid, wherein the pretreatment liquid contains a polyvalent metal salt, The pretreatment liquid contains at least either an inorganic acid or an organic acid. and the maintenance liquid is characterized by containing at least one of citric acid and acetic acid and a salt thereof. The inkjet recording ink set of the present invention is an inkjet recording ink set including an ink composition, a pretreatment liquid, and a maintenance liquid, wherein the pretreatment liquid contains a polyvalent metal salt, the maintenance liquid contains at least either citric acid or acetic acid and its salt, and the pH value of the maintenance liquid is in the range of 5.0 to 6.4 at 25°C.

[0042] "Ink set" refers to a set composed of a combination of materials used for inkjet recording. The ink set of the present invention is a set having a configuration including at least "ink composition", "pretreatment liquid", and "maintenance liquid". In addition to these, the ink set may include an overcoat liquid. "Overcoat liquid" is a liquid for coating an ink composition layer formed by ink landing on a substrate, and the type is not particularly limited. Also, as will be described in detail later, the ink composition according to the present invention is aqueous, and in this specification, "ink composition" is also simply referred to as "ink".

[0043] The ink composition according to the present invention has a fast drying speed and is preferably used for a substrate with low permeability. Examples of substrates with low permeability include those that are non-absorbent or low-absorbent to ink. The ink composition according to the present invention preferably contains an aqueous solvent. As used in this specification, "permeability" and "absorbency" refer to properties with respect to ink.

[0044] Examples of the ink non-absorbent base material include a plastic film having no ink absorption layer, a material coated with plastic, a material adhered with a plastic film, and the like. Examples of the plastic herein include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, and the like.

[0045] As materials coated with plastic or adhered with a plastic film, in order to impart gas barrier properties, moisture-proof properties, fragrance retention properties, etc., a material coated with polyvinylidene chloride on one or both sides of the film, or a film vapor-deposited with a metal oxide can also be preferably used.

[0046] The film can be preferably used whether it is an unstretched film or a stretched film. In the case of a plastic film, the thickness of the base material is preferably in the range of 10 to 120 μm, and more preferably in the range of 12 to 60 μm.

[0047] In addition, as the ink non-absorbent base material, metal base materials such as tin plates and tin-free steel plates (TFS plates, thickness 0.1 to 0.6 μm) for three-piece can applications are also preferably used, and can be suitably used, for example, in packaging materials for canned foods provided with a thermosetting resin as a coating layer. The packaging material for canned foods, for example, blocks air, moisture, and light and seals the internal food, so an epoxy-phenol-based paint or a polyester-based laminating agent is used on the food side, and a polyester-based or acrylic-based thermosetting paint is generally used on the outside.

[0048] Examples of the ink low-absorbent base material include a base material provided with a coating layer for receiving ink on the surface, such as printing paper such as art paper, coated paper, and matte paper, a plastic film surface coated with a hydrophilic polymer, and a material coated with particles such as silica and titanium together with a binder.

[0049] The ink set for inkjet recording of the present invention contains a pretreatment liquid, and thus can prevent bleeding even when printed on a substrate with low permeability. Further, by containing a maintenance liquid, it is possible to prevent poor discharge of the pretreatment liquid due to nozzle clogging.

[0050] <1.1 Pretreatment liquid> The pretreatment liquid according to the present invention is characterized by containing a polyvalent metal salt.

[0051] In inkjet printing using aqueous ink, when a substrate with low permeability is used, the ink droplets after landing hardly penetrate into the substrate, so drying by penetration does not occur, bleeding occurs between the droplets, and the image quality is easily impaired. Therefore, a pretreatment step of applying a pretreatment liquid to a substrate with low permeability is known.

[0052] As the pretreatment liquid (also referred to as "reaction liquid" or "treatment liquid"), there are two types: one that forms a layer (ink receiving layer) that absorbs the liquid components of the ink and improves the drying property, and one that forms a layer (ink aggregation layer) that aggregates the solid components and intentionally causes thickening of the ink to prevent bleeding and color unevenness between the ink droplets.

[0053] The pretreatment liquid according to the present invention forms an ink aggregation layer and contains a polyvalent metal salt as a flocculant. Further, from the viewpoint of suppressing the formation of carbonate composed of polyvalent metal ions and carbon dioxide in the air, it is preferable to contain an acidic component. Furthermore, it is preferable to contain water as a solvent.

[0054] <1.1.1 Polyvalent metal salt> The pretreatment liquid according to the present invention is characterized by containing a polyvalent metal salt. The polyvalent metal salt can aggregate anionic components (usually a dispersant or a colorant, etc.) in the ink composition by salting out. Further, since the polyvalent metal salt has a low molecular weight, it easily diffuses into the aqueous ink and can aggregate the dispersant or colorant in the aqueous ink at a higher speed.

[0055] The "polyvalent metal salt" according to the present invention is a compound composed of polyvalent metal ions with a valence of two or more and anions bonded to these polyvalent metal ions, and is soluble in water. Since the flocculant is a polyvalent metal salt, it can interact instantaneously with the dispersant, suppress bleeding, and obtain a clear image without color unevenness.

[0056] Specific examples of polyvalent metal ions include divalent metal ions such as Ca 2+ , Cu 2+ , Ni 2+ , Mg 2+ , Zn 2+ , Ba 2+ ; trivalent metal ions such as Al 3+ , Fe 3+ , Cr 3+ , Y 3+ ; and tetravalent metal ions such as Zr 4+ . The polyvalent metal ions may be used alone or in combination of two or more. From the viewpoint of obtaining a high flocculation effect because of a large ionization tendency and easy generation of cations, it is preferably any one of the metal ions of Ca 2+ , Mg 2+ , Zn 2+ or Al 3+ . Further, these metal ions produce colorless and water-soluble salts and can suppress a decrease in image chroma. Furthermore, from the viewpoint of a small ionic radius and easy movement in the ink flocculation layer and in the ink droplets, it is preferably Ca 2+ , Mg 2+ .

[0057] Examples of the anion include Cl - , I - , Br - , SO4 2- , ClO 3- , NO 3- , HCOO - , CH3COO - and the like.

[0058] The type of salt constituting the polyvalent metal salt is not particularly limited. For example, known salts such as water-soluble carbonates, sulfates, nitrates, hydrochlorides, organic acid salts, borates, and phosphates that do not inhibit the effects of the present invention can be used. Specific examples of particularly preferred polyvalent metal salts include calcium salts or magnesium salts of carboxylic acids such as calcium chloride, magnesium chloride, calcium nitrate, magnesium nitrate, calcium acetate, and magnesium lactate.

[0059] The content of the polyvalent metal salt should be such that it can effectively aggregate the anionic components in the ink composition. From the perspective of achieving both image quality and heat-resistant water resistance, it is preferably contained in the range of 5% by mass or less, more preferably in the range of 1 - 4% by mass, and even more preferably in the range of 2 - 3% by mass with respect to the pretreatment liquid.

[0060] The content of the polyvalent metal salt in the pretreatment liquid can be measured by known methods. For example, it can be measured by ICP emission spectrometry.

[0061] <1.1.2 Acidic Component> The pretreatment liquid according to the present invention preferably contains an acidic component. By containing an acidic component in the pretreatment liquid, the dissolution of carbon dioxide in the air to generate carbonate ions is suppressed.

[0062] The acidic component is not particularly limited and may be an inorganic acid or an organic acid. Also, the acidic component may be used alone or in combination of two or more. Examples of inorganic acids include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, etc. Examples of organic acids include formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid, lactic acid, sulfonic acid derivatives, glycolic acid, sulfamic acid, pyrophosphoric acid, etc.

[0063] Among them, the acidic component is preferably citric acid, acetic acid, or glycolic acid, and more preferably citric acid and acetic acid.

[0064] The content of the acidic component is preferably in the range of 0 to 2% by mass, more preferably in the range of 0 to 1.5% by mass, and even more preferably in the range of 0 to 1% by mass with respect to the total mass of the pretreatment liquid.

[0065] Although the water-repellent film on the surface of the inkjet head has characteristics that are likely to deteriorate due to the acidic component, by using the acidic component contained in the pretreatment liquid as a relatively weak acid and setting the content within the above range, deterioration of the water-repellent film can be suppressed.

[0066] Further, the content of the acidic component is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less with respect to the mass of the polyvalent metal salt. The acidic component also functions as a flocculant in the pretreatment liquid, but from the viewpoint of having a high reactivity with the solid components of the ink, it is preferable that the polyvalent metal salt functions as a flocculant. When within the above range, since the polyvalent metal salt preferentially functions as a flocculant, higher-quality images can be obtained.

[0067] The content of the acidic component in the pretreatment liquid can be measured by a known method. For example, it can be measured by high-performance liquid chromatography (HPLC).

[0068] <1.1.3 Water and Other Additives> From the viewpoint of evaporating and dispersing by drying after being applied on the substrate, the pretreatment liquid according to the present invention preferably uses water as the main solvent. As the water, it is preferably pure water or ultrapure water such as ion-exchanged water, ultrafiltration water, reverse osmosis permeated water, distilled water, etc., from which ionic impurities have been removed as much as possible. Also, using water sterilized by ultraviolet irradiation or hydrogen peroxide addition is suitable because it can prevent the generation of mold and bacteria when the pretreatment liquid is stored for a long time.

[0069] The water content in the pretreatment liquid is preferably 30% by mass or more, more preferably 35% by mass or more, still more preferably 40% by mass or more, and particularly preferably 45% by mass or more, based on the total mass of the pretreatment liquid.

[0070] The pretreatment liquid according to the present invention may further contain a water-soluble organic solvent. By adding an organic solvent, the wettability of the pretreatment liquid with respect to the substrate can be improved. As the organic solvent, the same ones as those exemplified in the ink composition described below can be used. The content of the organic solvent contained in the pretreatment liquid is preferably in the range of 1 to 60% by mass based on the total mass of the pretreatment liquid.

[0071] The pretreatment liquid according to the present invention can be appropriately blended with other components such as surfactants, crosslinking agents, fungicides, bactericides, resin fine particles, etc., as long as the effects of the present invention are not impaired.

[0072] For example, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, anti-fading agents described in JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, and JP-A-3-13376, various anionic, cationic, or nonionic surfactants, fluorescent brighteners described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-242871, and JP-A-4-219266, defoaming agents, lubricants such as diethylene glycol, preservatives, thickeners, antistatic agents, etc., and various known additives can also be contained.

[0073] <1.1.4 Physical properties of the pretreatment liquid> When the pretreatment liquid according to the present invention is ejected (applied) onto a substrate by an inkjet head, the surface tension of the pretreatment liquid at 25°C is preferably in the range of 20 to 40 mN / m, and more preferably in the range of 20 to 35 mN / m. The surface tension can be measured, for example, by using an automatic surface tension meter CBVP-Z (trade name, manufactured by Kyowa Interface Science Co., Ltd.) to check the surface tension when a platinum plate is wetted with the ink in an environment of 25°C.

[0074] From the same perspective, the viscosity of the pretreatment liquid at 25°C is preferably in the range of 3 to 12 mPa·s, and more preferably in the range of 3 to 10 mPa·s. The viscosity can be measured, for example, by using a viscoelasticity tester MCR-300 (trade name, manufactured by Pysica) to measure the viscosity in an environment of 25°C.

[0075] <1.1.5 Preparation method of pretreatment liquid> The pretreatment liquid according to the present invention can be prepared by dispersing and mixing the above components by a conventionally known method. Further, after sufficiently stirring the above components, filtration can remove coarse particles and foreign matters that cause clogging.

[0076] <1.2 Maintenance liquid> The maintenance liquid according to the present invention is characterized by containing an acidic component.

[0077] In inkjet printing using aqueous ink, when a pretreatment liquid is used, dried matter of the pretreatment liquid deposits on the nozzles of the inkjet head, resulting in poor ejection of the pretreatment liquid due to nozzle clogging. Therefore, it is necessary to maintain the nozzles. The dried matter of the pretreatment liquid includes the polyvalent metal salt itself deposited by evaporation of moisture, and carbonates formed by the reaction of carbon dioxide in the air with metal ions. The carbonates include bicarbonates.

[0078] In the conventionally known maintenance technology, it was possible to remove the polyvalent metal salt itself contained in the dried product of the pretreatment liquid, but it was difficult to remove the carbonate. The maintenance liquid according to the present invention contains an acidic component, so that not only the polyvalent metal salt but also the carbonate can be removed. Note that the removable dried product is not limited to the polyvalent metal salt and the carbonate.

[0079] <1.2.1 Acidic Component> The maintenance liquid according to the present invention is characterized by containing an acidic component. When the maintenance liquid contains an acidic component, the carbonate dissolves in the maintenance liquid, carbonic acid is released, and carbon dioxide gas is generated.

[0080] The acidic component is not particularly limited and may be an inorganic acid or an organic acid. Further, the acidic component may be used alone or in combination of two or more. Examples of the inorganic acid include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, and the like. Examples of the organic acid include formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid, lactic acid, sulfonic acid derivatives, glycolic acid, sulfamic acid, pyrophosphoric acid, and the like.

[0081] Among them, the acidic component is preferably any one of citric acid, acetic acid, or glycolic acid, and more preferably citric acid and acetic acid.

[0082] Further, from the viewpoint of keeping the pH value of the maintenance liquid constant, it is preferable that the acidic component contains at least one of citric acid or acetic acid and also contains its salt. Citric acid and acetic acid are weak acids, and a mixed solution containing their salts functions as a buffer solution, so that the pH value can be kept constant.

[0083] The content of the acidic component is preferably in the range of 0.1 to 5% by mass, more preferably in the range of 0.3 to 4.5% by mass, and still more preferably in the range of 0.5 to 4.0% by mass with respect to the total mass of the maintenance liquid.

[0084] <1.2.2 Water and Other Additives> From the viewpoint of exerting the moisturizing power of the maintenance liquid, the maintenance liquid according to the present invention preferably has water as a main component. The water content is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more based on the total mass of the maintenance liquid.

[0085] The maintenance liquid according to the present invention may further contain a water-soluble organic solvent. By adding an organic solvent, the surface tension becomes smaller compared to a maintenance liquid composed only of water. Therefore, the wettability to the tube for supplying the maintenance liquid to the cap device is increased, and the supplyability is improved. Also, the wettability to the nozzles of the inkjet head is increased, and the dried matter of the flocculant can be effectively removed.

[0086] As the organic solvent, the same ones as those exemplified for the organic solvent in the ink composition described below can be used. By making the organic solvent contained in the maintenance liquid common with the organic solvents contained in the pretreatment liquid and the ink composition, the compatibility is enhanced, and the detergency is further excellent.

[0087] The content of the organic solvent contained in the maintenance liquid is preferably in the range of 3 to 49% by mass, more preferably in the range of 4 to 40% by mass, and still more preferably in the range of 5 to 30% by mass based on the total mass of the maintenance liquid.

[0088] The maintenance liquid according to the present invention may, if necessary, be added with a surfactant, a preservative, a fungicide, a rust inhibitor, a colorant, a chelating agent, etc. By adding a surfactant, the surface tension of the maintenance liquid is reduced, and the removal ability of the flocculant is improved. Examples of the surfactant include acetylene glycol-based surfactants, silicone-based surfactants, and fluorine-based surfactants.

[0089] <1.2.3 Physical Properties of Maintenance Liquid> In the present invention, the "pH value" refers to the physical property measured as follows. That is, at 25°C, it is the value measured in accordance with JIS Z8802:2011 using a pH meter with a glass electrode calibrated with neutral phosphate standard solution and borate standard solution as pH standard solutions. Examples of such pH meters include "HM-41X" manufactured by Toa DKK Corporation and "D-51" manufactured by Horiba, Ltd.

[0090] From the viewpoint of suppressing the deterioration of the water-repellent film on the surface of the inkjet head, the pH value of the maintenance liquid according to the present invention at 25°C is preferably in the range of 5.0 to 6.4, and more preferably a value close to 6.4. Further, by controlling the pH value within the above range, in addition to the water-repellent film, corrosion of the members constituting the cap device can be prevented.

[0091] By providing a water-repellent film on the surface of the inkjet head, the residue of ink and pretreatment liquid and the adhesion of foreign substances to the nozzle opening surface can be suppressed. The water-repellent film contains, for example, water-repellent substances such as fluororesin particles. Although the reason is not clear, these water-repellent substances may deteriorate in water-repellency over time due to the adhesion of acidic solutions, but since the maintenance liquid is in the state of a weakly acidic buffer solution, the deterioration of water-repellency can be suppressed.

[0092] <1.2.4 Preparation method of maintenance liquid> The maintenance liquid according to the present invention can be prepared by dispersing and mixing the above components by a conventionally known method. Further, after sufficiently stirring the above components, filtration can remove coarse particles and foreign substances that cause clogging.

[0093] <1.3 Ink composition> The "ink composition (also simply referred to as 'ink')" according to the present invention preferably contains at least a coloring material, an organic solvent, and water.

[0094] <1.3.1 Coloring material> The ink composition according to the present invention is characterized by containing a coloring material. A coloring material is a material used for coloring. Among them, those soluble in water or oil are called dyes, and those insoluble are called pigments. Although not particularly limited, from the viewpoint of having a property of being difficult to fade against light, gas, etc., it is preferable to use a pigment as the coloring material.

[0095] (Pigment) Since pigments are difficult to fade against light, gas, etc., an image formed on a substrate such as plastic using a pigment is excellent in water resistance, gas resistance, light resistance, etc., and has good storage properties. The pigment is not particularly limited, and conventionally known ones can be used. For example, inorganic pigments such as titanium oxide, iron oxide, carbon black, and organic pigments such as insoluble pigments and lake pigments can be preferably used.

[0096] Titanium oxide has three crystal forms: anatase type, rutile type, and brookite type. Generally, it can be roughly classified into anatase type and rutile type. Although not particularly limited, the rutile type with a large refractive index and high hiding power is preferable. Specifically, examples include the TR series manufactured by Fuji Titanium Industry Co., Ltd., the JR series manufactured by Tayca Corporation, and Taypeak (registered trademark) manufactured by Ishihara Sangyo Co., Ltd.

[0097] Carbon black can be used, for example, those manufactured by conventionally known methods such as the contact method, furnace method, and thermal method.

[0098] The insoluble pigment is not particularly limited. For example, azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole, etc. are preferable.

[0099] Specific organic pigments that can be preferably used include the following pigments.

[0100] Examples of pigments for magenta or red include, for example, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 202, C.I. Pigment Red 222, C.I. Pigment Violet 19, and the like.

[0101] Examples of pigments for orange or yellow include, for example, C.I. Pigment Orange 31, C.I. Pigment Orange 43, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 15, C.I. Pigment Yellow 15:3, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 93, C.I. Pigment Yellow 128, C.I. Pigment Yellow 94, C.I. Pigment Yellow 138, C.I. Pigment Yellow 155, and the like. Particularly in terms of the balance between color tone and lightfastness, C.I. Pigment Yellow 155 is preferred.

[0102] Examples of pigments for green or cyan include, for example, C.I. Pigment Blue 15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, C.I. Pigment Blue 60, C.I. Pigment Green 7, and the like.

[0103] Examples of pigments for black include, for example, C.I. Pigment Black 1, C.I. Pigment Black 6, C.I. Pigment Black 7, and the like.

[0104] In addition, the pigments used in the white ink are not particularly limited. For example, white inorganic pigments such as C.I. Pigment White 6, 18, 21, titanium oxide, zinc oxide, zinc sulfide, antimony oxide, magnesium oxide, and zirconium oxide can be mentioned. In addition to the white inorganic pigments, white organic pigments such as white hollow resin fine particles and polymer particles can also be used.

[0105] The content of the pigment in the ink is not particularly limited, but for inorganic pigments, it is preferably in the range of 7 to 18% by mass, and for organic pigments, it is preferably in the range of 0.5 to 7% by mass.

[0106] From the viewpoint of stable dispersion of the pigment and improvement of the storage stability of the ink composition, the average particle size of the dispersion state of the pigment in the ink is preferably 50 nm or more and less than 200 nm. The particle size measurement of the pigment can be determined by a commercially available particle size measuring instrument using the dynamic light scattering method, electrophoresis method, etc. Among them, the measurement by the dynamic light scattering method is simple and can accurately measure the particle size region.

[0107] The pigment can be dispersed and used by a dispersing machine together with a dispersant and additives necessary according to other desired purposes.

[0108] As the dispersing machine, conventionally known ball mills, sand mills, line mills, high-pressure homogenizers, etc. can be used. Among them, it is preferable to disperse the pigment by a sand mill because the particle size distribution becomes sharp. In addition, the material of the beads used for sand mill dispersion is not particularly limited, but from the viewpoint of preventing the generation of bead fragments and contamination of ionic components, it is preferably zirconia or zircon. Furthermore, the bead diameter is preferably in the range of 0.3 to 3 mm.

[0109] <1.3.2 Organic Solvent> From the viewpoint of accelerating the drying speed, the ink composition according to the present invention preferably contains an organic solvent, and more preferably contains a water-soluble organic solvent. Examples of the water-soluble organic solvent include alcohols, polyhydric alcohols, amines, amides, glycol ethers, 1,2-alkanediols having 4 or more carbon atoms, and the like.

[0110] Examples of the alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, t-butanol, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, 1-octanol, 2-octanol, n-nonyl alcohol, tridecyl alcohol, n-undecyl alcohol, stearyl alcohol, oleyl alcohol, benzyl alcohol, and the like.

[0111] Examples of the polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol having 5 or more ethylene oxide groups, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol having 4 or more propylene oxide groups, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, and the like.

[0112] Examples of the amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, and the like.

[0113] Examples of the amides include formamide, N,N-dimethylformamide, N,N-dimethylacetamide, and the like.

[0114] Examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, and the like.

[0115] Examples of 1,2-alkanediols having 4 or more carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and the like.

[0116] Particularly preferred organic solvents are polyhydric alcohols, which can preferably suppress bleeding during high-speed printing. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol are preferred.

[0117] The ink composition can contain one or a combination of two or more selected from these organic solvents.

[0118] The content of the organic solvent in the ink composition is not particularly limited, but is preferably in the range of 10 to 60% by mass.

[0119] <1.3.3 Water> From the viewpoint of evaporation and scattering due to drying, the ink composition according to the present invention preferably contains water and preferably uses water as the main solvent. The water is preferably pure water or ultrapure water such as ion-exchanged water, ultrafiltration water, reverse osmosis permeated water, distilled water, etc., with ionic impurities removed as much as possible. In addition, using water sterilized by ultraviolet irradiation or hydrogen peroxide addition is suitable because it can prevent the generation of mold and bacteria when the ink composition is stored for a long time.

[0120] The water content in the ink composition is preferably 40% by mass or more, more preferably 49% by mass or more, still more preferably 55% by mass or more, and particularly preferably 65% by mass or more based on the total mass of the ink composition.

[0121] <1.3.4 Pigment Dispersant> For the purpose of dispersing pigments insoluble in water or oil in the ink composition, a pigment dispersant may be contained. Examples of such pigment dispersants include a method of dispersing with a polymer dispersant such as a water-soluble polymer and / or a water-dispersible polymer, a method of dispersing with a surfactant such as a water-soluble surfactant and / or a water-dispersible surfactant, and a method of dispersing and / or dissolving a surface-treated pigment in which a hydrophilic functional group is chemically and physically introduced on the surface of pigment particles in water.

[0122] As the polymer dispersant, a polymer dispersant having an anionic group is preferable, and those having a molecular weight in the range of 4000 to 200000 can be preferably used.

[0123] Examples of the polymer dispersant include block copolymers, random copolymers having a structure derived from two or more monomers selected from styrene, styrene derivatives, vinylnaphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives, and salts thereof, polyoxyalkylene, polyoxyalkylene alkyl ether, and the like.

[0124] The polymer dispersant preferably has an acryloyl group and is preferably added after being neutralized with a neutralizing base. Here, the neutralizing base is not particularly limited, but an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, and morpholine is preferable. In particular, when the pigment is titanium oxide, it is preferable that the titanium oxide is dispersed with a polymer dispersant having an acryloyl group.

[0125] Commercially available products can be used as the polymer dispersant. For example, Joncryl (registered trademark) 67 (weight average molecular weight: 12,500, acid value: 213), Joncryl 678 (weight average molecular weight: 8,500, acid value: 215), Joncryl 586 (weight average molecular weight: 4,600, acid value: 108), Joncryl 611 (weight average molecular weight: 8,100, acid value: 53), Joncryl 680 (weight average molecular weight: 4,900, acid value: 215), Joncryl 683 (weight average molecular weight: 8,000, acid value: 160), Joncryl 819 (weight average molecular weight: 14,500, acid value 75), Joncryl 690 (weight average molecular weight: 16,500, acid value: 240) (the above are trade names, manufactured by BASF Japan Ltd.), etc. can be mentioned.

[0126] Also, the addition amount of the polymer dispersant is preferably in the range of 10 to 100% by mass, more preferably in the range of 10 to 40% by mass, based on the pigment.

[0127] The pigment particularly preferably has a form of a so-called capsule pigment in which the pigment is coated with a polymer dispersant. As the method for coating the pigment with a polymer dispersant, various known methods can be used. For example, a phase inversion emulsification method, an acid precipitation method, or a method in which the pigment is dispersed with a polymerizable surfactant, a monomer is supplied thereto, and the coating is performed while polymerizing, etc. can be mentioned.

[0128] As a particularly preferred method, a water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone, and after the acidic groups in the resin are partially or completely neutralized with a base, the pigment and ion-exchanged water are added, dispersed, and then the organic solvent is removed, and water is added as necessary for preparation.

[0129] Examples of the surfactant include anionic surfactants such as alkane sulfonates, α-olefin sulfonates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, acylmethyl taurates, dialkyl sulfosuccinates, alkyl sulfate esters, sulfated olefins, polyoxyethylene alkyl ether sulfate esters, alkyl phosphate esters, polyoxyethylene alkyl ether phosphate esters, and monoglycerite phosphate esters; amphoteric surfactants such as alkylpyridinium salts, alkyl amino acid salts, and alkyldimethyl betaines; and nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkyl amides, glycerin alkyl esters, and sorbitan alkyl esters.

[0130] The addition amount of the polymer dispersant and the surfactant to the pigment is preferably in the range of 1 to 100% by mass, more preferably in the range of 5 to 50% by mass, based on the total mass of the pigment. When within the above range, the pigment can be stably dispersed in water.

[0131] Examples of the surface-treated pigment include, as hydrophilic functional groups, -OM, -COOM, -CO-, -SO3M, -SO2NH3, -RSO3M, -PO3HM, -PO3M3, -SO3NHCOR, -NH3, -NR3 (wherein M represents a hydrogen atom, an alkali metal, ammonium, or an organic ammonium, and R represents an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a naphthyl group which may have a substituent). These functional groups are physically and / or chemically introduced by being grafted directly onto the pigment particle surface and / or via another group. Examples of the polyvalent group include an alkylene group having 1 to 12 carbon atoms, a phenylene group which may have a substituent, or a naphthylene group which may have a substituent.

[0132] In addition, as the surface-treated pigment, it is preferable that the surface of the pigment particles is surface-treated with a treating agent containing sulfur so that -SO3M and / or -RSO3M (where M is a counter ion representing a hydrogen ion, an alkali metal ion, an ammonium ion, or an organic ammonium ion) are chemically bonded thereto. That is, in a solvent in which the pigment has no active protons, has no reactivity with sulfonic acid, and the pigment is insoluble or hardly soluble, the pigment is dispersed, and then -SO3M and / or -RSO3M are chemically bonded to the particle surface by amidosulfuric acid or a complex of sulfur trioxide and a tertiary amine, and it is preferably one that can be dispersed and / or dissolved in water.

[0133] As surface treatment means for grafting a functional group or its salt directly or via a polyvalent group onto the surface of pigment particles, various known surface treatment means can be applied. For example, ozone or a sodium hypochlorite solution is allowed to act on commercially available carbon black, and the carbon black is further oxidized to hydrophilize its surface (for example, JP-A-7-258578, JP-A-8-3498, JP-A-10-120958, JP-A-10-195331, JP-A-10-237349), means for treating carbon black with 3-amino-N-alkyl-substituted pyridinium bromide (for example, JP-A-10-195360, JP-A-10-330665), means for dispersing an organic pigment in a solvent in which the organic pigment is insoluble or hardly soluble and introducing a sulfonic group onto the pigment particle surface with a sulfonating agent (for example, JP-A-8-283596, JP-A-10-110110, JP-A-10-110111), means for dispersing an organic pigment in a basic solvent that forms a complex with sulfur trioxide, adding sulfur trioxide to treat the surface of the organic pigment, and introducing a sulfonic group or a sulfonamino group (for example, JP-A-10-110114), etc. The functional groups grafted onto one pigment particle may be single or of multiple types.

[0134] <1.3.5 Resin> From the perspective of solidifying the ink composition and firmly fixing it on the substrate, the ink composition according to the present invention may contain a water-soluble and / or water-insoluble resin. Further, the resin may be in a state dissolved in the ink composition or in a state dispersed in the ink composition. As the resin in the dissolved state, the above-mentioned polymer dispersant can be used.

[0135] (Water-insoluble resin fine particles) The resin used in the ink composition according to the present invention is preferably in the form of fine particles and dispersed in the ink composition, and more preferably water-insoluble resin fine particles. The water-insoluble resin fine particles used in the present invention are a fine particle dispersion of a water-insoluble resin that can accept the ink composition and exhibits solubility or affinity for the ink composition.

[0136] The water-insoluble resin fine particles are those that are inherently water-insoluble but have a form in which the resin is dispersed in an aqueous medium as microscopic fine particles, and are non-water-soluble resins dispersed in water by forced emulsification using an emulsifier or the like, or non-water-soluble resins that can self-emulsify to form a stable aqueous dispersion by introducing a hydrophilic functional group into the molecule without using an emulsifier or a dispersion stabilizer. These resins are usually used in a state of being emulsified and dispersed in water or a water / alcohol mixed solvent.

[0137] The resin to be used is preferably at least a polyester-based resin, a polyurethane-based resin, a polyacrylic-based resin, or a composite resin of a polyurethane-based resin and a polyacrylic-based resin.

[0138] For example, when the pretreatment liquid contains resin fine particles, the ionicity of the resin fine particles in the pretreatment liquid is nonionic or cationic, and the ionicity of the resin fine particles in the ink composition composed of the above-mentioned polyester-based resin, polyurethane-based resin, polyacrylic-based resin, or a composite resin of a polyurethane-based resin and a polyacrylic-based resin is preferably nonionic or anionic.

[0139] Among them, the resin fine particles used in the ink composition preferably contain an acid structure. Even when the addition amount of the surfactant is small, they can be dispersed in water, and the water resistance of the ink composition layer is improved. This is called a self-emulsifying type, which means that the urethane resin can be dispersed and stabilized in water only by molecular ionic properties without using a surfactant. Examples of the acid structure include acid groups such as carboxy group (-COOH) and sulfonic acid group (-SO3H). The acid structure may be present in the side chain or at the end of the resin.

[0140] Preferably, some or all of the above acid structures are neutralized. By neutralizing the acid structure, the water dispersibility of the resin can be improved. Examples of the neutralizing agent for neutralizing the acid structure preferably include organic amines, and it is preferable to use organic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine, and triethanolamine.

[0141] Commercially available products may be used as the resin fine particles used in the ink composition. Examples of commercially available products of resin fine particles are listed below according to the type of resin.

[0142] <Polyester> Pesresin A-110F, A-520, A-613D, A-615GE, A-640, A-645GH, A-647GEX manufactured by Takamatsu Yushi Co., Ltd., Elite (registered trademark) KA-5034, KA-5071S, KA-1449, KA-0134, KA-3556, KA-6137, KZA-6034, KT-8803, KT-8701, KT-9204, KT-8904, KT-0507, KT-9511 manufactured by Unitika Ltd.

[0143] <Urethane type> NeoRez (registered trademark) R-967, R-600, R-9671 manufactured by Kusumoto Kasei Co., Ltd., W-6061, W-5661, WS-4000 manufactured by Mitsui Chemicals, Inc.

[0144] <Acrylic type> NeoCryl (registered trademark) A-1127 manufactured by Kusumoto Chemicals, Ltd., Mowinyl (registered trademark) 6899D, 6969D, 6800, 6810 manufactured by Japan Coating Resin Co., Ltd., TOCRYL (registered trademark) W-7146, W-7150, W-7152 manufactured by Toyochem Co., Ltd.

[0145] From the viewpoint of ensuring the storage stability and ejection stability of the ink composition, the average particle size of the resin fine particles is preferably in the range of 5 to 400 nm, more preferably in the range of 50 to 200 nm.

[0146] The content of the resin fine particles in the ink is not particularly limited, but is preferably in the range of 2 to 10% by mass, more preferably in the range of 2 to 5% by mass.

[0147] <1.3.6 Other Additives> The ink composition according to the present invention can contain various known additives as required for the purpose of improving surfactant, ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances.

[0148] In addition, a surfactant can also be contained in the ink composition. Thereby, the ink ejection stability can be improved, and the spread (dot diameter) of the droplets landing on the recording medium can be controlled.

[0149] The surfactant that can be used in the ink composition according to the present invention can be used without particular limitation. However, when the other components of the ink composition contain an anionic compound, the ionic property of the surfactant is preferably anionic, nonionic or betaine type. In particular, in the present invention, when an alkaline component is contained in the surfactant such as an anionic surfactant, the aggregability of the pigment is reduced, and the resin fine particles themselves are likely to aggregate. Therefore, a nonionic surfactant is preferred.

[0150] In the present invention, preferably, a fluorine-based or silicone-based surfactant having a high ability to reduce static surface tension, an anionic surfactant such as dioctyl sulfosuccinate having a high ability to reduce dynamic surface tension, a relatively low molecular weight polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, acetylene glycols, Pluronic (registered trademark) type surfactants, nonionic surfactants such as sorbitan derivatives are preferably used. It is also preferable to use a fluorine-based or silicone-based surfactant in combination with a surfactant having a high ability to reduce dynamic surface tension.

[0151] The content of the surfactant in the ink composition is not particularly limited, but is preferably in the range of 0.1 to 5.0% by mass.

[0152] In the ink composition used in the present invention, in addition to the above description, if necessary, for the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances, various known additives, for example, pH adjusters, polyolefin waxes, preservatives, fungicides, rust inhibitors, chelating agents, polysaccharides, viscosity adjusters, specific resistance adjusters, film formers, ultraviolet absorbers, antioxidants, anti-fading agents, anti-moth agents, etc. can be appropriately selected and used. For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, 57-87988, 62-261476, etc., anti-fading agents described in JP-A-57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091, 3-13376, etc., fluorescent brightening agents described in JP-A-59-42993, 59-52689, 62-280069, 61-242871, JP-A-4-219266, etc. can be mentioned.

[0153] Examples of the pH adjuster include potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, diethanolamine, triethanolamine, triisopropanolamine, potassium carbonate, sodium carbonate, sodium hydrogen carbonate, and the like.

[0154] Examples of the polyolefin wax include waxes produced from olefins such as ethylene, propylene, and butylene or their derivatives and their copolymers. Specifically, polyethylene-based waxes, polypropylene-based waxes, polybutylene-based waxes, and the like can be mentioned. As the polyolefin wax, commercially available products can be used. Specifically, examples include Nopcoat PEM17 (trade name, manufactured by San Nopco Ltd.), ChemPearl (registered trademark) W4005 (trade name, manufactured by Mitsui Chemicals, Inc.), AQUACER (registered trademark) 515, AQUACER (registered trademark) 593 (above trade names, manufactured by BYK-Chemie Japan Co., Ltd.), and the like.

[0155] Adding polyolefin wax is preferable because it can improve the slipperiness of the image formed on a substrate with low permeability against physical contact and can improve the rubbing resistance of the image. The content of the polyolefin wax is preferably in the range of 0.01 to 10% by mass, more preferably in the range of 0.05 to 1% by mass, based on the total mass of the ink composition.

[0156] Examples of the preservative and fungicide include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one, and the like. Commercially available products include Proxel XL2, Proxel GXL (above trade names, manufactured by Avecia), and Denicide (registered trademark) CSA, NS-500W (above trade names, manufactured by Nagase ChemteX Corporation), and the like.

[0157] Examples of the rust inhibitor include benzotriazole and the like.

[0158] Examples of the chelating agent include ethylenediaminetetraacetic acid and its salts (such as sodium dihydrogen ethylenediaminetetraacetate).

[0159] <1.3.7 Physical properties of the ink composition> From the viewpoint of image quality, the surface tension of the ink composition according to the present invention at 25°C is preferably in the range of 20 to 40 mN / m, and more preferably in the range of 20 to 35 mN / m. The surface tension can be measured, for example, by using an automatic surface tension meter CBVP-Z (trade name, manufactured by Kyowa Interface Science Co., Ltd.) to confirm the surface tension when a platinum plate is wetted with the ink in an environment of 25°C.

[0160] Similarly, from the viewpoint of image quality, the viscosity of the ink composition according to the present invention at 25°C is preferably in the range of 1 to 40 mPa·s, and more preferably in the range of 2 to 10 mPa·s. The viscosity can be measured, for example, by using a viscoelasticity tester MCR-300 (trade name, manufactured by Pysica).

[0161] ≪2 Inkjet recording method≫ The inkjet recording method of the present invention is an inkjet recording method for recording using the inkjet recording ink set of the present invention, and is characterized by including a step of applying a pretreatment liquid simultaneously with or immediately before the step of discharging the ink composition.

[0162] By having a step of applying a pretreatment liquid immediately before the step of discharging the ink composition, bleeding can be prevented even when printing on a substrate with low permeability, and high-quality images can be obtained. In addition, by using the inkjet recording ink set, for example, using a single inkjet printer, the step of applying a pretreatment liquid and the step of discharging the ink composition can be continuously and efficiently performed on the surface of a substrate with low permeability.

[0163] Specifically, the inkjet recording method of the present invention preferably comprises a step of applying a pretreatment liquid to the surface of a low-permeability substrate (also referred to as the "pretreatment liquid application step"), a step of drying the pretreatment liquid to form a pretreatment layer (also referred to as the "pretreatment liquid drying step"), a step of ejecting an ink composition onto the pretreatment layer by an inkjet method (also referred to as the "ink composition ejection step"), and a step of drying the ink composition to form an ink layer (also referred to as the "ink composition drying step"). Here, the step of applying the pretreatment liquid and the step of ejecting the ink composition may be performed simultaneously, or the step of applying the pretreatment liquid may be performed immediately before the step of ejecting the ink composition. However, from the viewpoint of obtaining a high-quality image, it is preferable that they are performed simultaneously.

[0164] Further, when using the pretreatment liquid according to the present invention, since a dried product of the pretreatment liquid deposits on the nozzles of the inkjet head and ejection failure of the pretreatment liquid due to nozzle clogging occurs, it is necessary to maintain the nozzles. Therefore, the inkjet recording method of the present invention preferably includes a step of cleaning the pretreatment liquid head for applying the pretreatment liquid using the maintenance liquid according to the present invention (also referred to as the "maintenance step").

[0165] The step of cleaning using the maintenance liquid means applying the maintenance liquid according to the present invention to the pretreatment liquid head to remove dirt, foreign matters, dried products, etc. caused by the pretreatment liquid. Further, the pretreatment liquid head refers to a head that ejects the pretreatment liquid and is a head that ejects only the pretreatment liquid.

[0166] <2.1 Pretreatment Liquid Application Step> The pretreatment liquid application step is a step of applying the above-mentioned pretreatment liquid onto a recording medium of a low-absorbency substrate or a non-absorbency substrate. The method of applying the pretreatment liquid onto the recording medium is not particularly limited, but it is preferably the inkjet method described below. Since the inkjet method can apply the pretreatment liquid only to the ink application area, it is possible to prevent cloudiness caused by applying the pretreatment liquid to the non-ink application area. Further, as will be described later, when the substrate to be used is a metal substrate or the like, it is also preferable to arrange the metal substrate on a conveyance belt and apply and form a pretreatment layer while conveying the belt, or to use a flatbed type printer for fixing the substrate for forming the pretreatment layer.

[0167] <2.2 Pretreatment Liquid Drying Step> The pretreatment liquid drying step is a step of drying the pretreatment liquid applied onto a recording medium of a low-absorbency substrate or a non-absorbency substrate to form a pretreatment layer. However, this step can be omitted, and the ink composition ejection step may be continuously performed immediately after the pretreatment liquid application step. Further, when the ink composition ejection step is continuously performed in this way, or when the ink composition ejection step is performed simultaneously with the pretreatment liquid application step, the drying of the pretreatment liquid is performed together with the drying of the ink composition.

[0168] It is preferable to perform the drying of the pretreatment liquid under conditions such as removing water or a water-soluble organic solvent, which is a solvent component of the pretreatment liquid. The drying temperature of the pretreatment liquid is preferably, for example, within the range of 50 to 100°C. The drying time of the pretreatment liquid is preferably, for example, within the range of 3 to 30 seconds.

[0169] The drying of the pretreatment liquid may be performed, for example, using a non-contact heating type drying device such as a drying furnace or a hot air blower, or using a contact heating type drying device such as a hot plate or a heat roller.

[0170] The drying temperature can be obtained by measuring any one selected from (a) the ambient temperature such as the furnace temperature or the hot air temperature when using a non-contact heating type drying device such as a drying furnace or a hot air blower, (b) the temperature of the contact heating part when using a contact heating type drying device such as a hot plate or a hot roller, or (c) the surface temperature of the surface to be dried, during the entire period of drying the pretreatment liquid. As the measurement location, it is more preferable to measure (c) the surface temperature of the surface to be dried.

[0171] The thickness of the obtained pretreatment layer is preferably in the range of 0.3 to 3.0 μm, and more preferably in the range of 0.5 to 2 μm. When it is 0.3 μm or more, it is easy to enhance the adhesion of the image and the lamination strength while suppressing the bleeding of the ink. Also, when it is 3.0 μm or less, the deformation stress due to moisture and heat can be reduced, so the adhesion of the image and the strength in the case of performing lamination processing are less likely to be impaired.

[0172] <2.3 Ink Composition Discharge Step> The ink composition discharge step is a step of discharging the ink composition by an inkjet method simultaneously with or immediately after forming a pretreatment layer on a recording medium of a low-absorbency substrate or a non-absorbency substrate.

[0173] The inkjet method is not particularly limited, and a printer equipped with an inkjet head filled with the ink composition can be used. Specifically, based on a digital signal, the ink composition can be discharged as droplets from the nozzles of the inkjet head and landed on the pretreatment layer of the substrate to perform printing.

[0174] The inkjet head may be any of an on-demand type and a continuous type inkjet head. Examples of on-demand type inkjet heads include electro-mechanical conversion types such as single cavity type, double cavity type, vender type, piston type, share mode type and shared wall type, and electro-thermal conversion types such as thermal inkjet type and bubble jet (where "bubble jet" is a registered trademark of Canon Kabushiki Kaisha) type, etc.

[0175] Among the above inkjet heads, it is preferable that the inkjet head uses a piezoelectric element as an electro-mechanical conversion element used in the electro-mechanical conversion method (also referred to as a piezo type inkjet head).

[0176] Also, the inkjet head may be any of a scan type and a single pass type inkjet head, but a single pass type is preferable. In the case of the single pass type, it is preferable to use an inkjet head of a line head type.

[0177] The line head type inkjet head refers to an inkjet head having a length equal to or greater than the width of the printing range. As the line head type inkjet head, one head having a length equal to or greater than the width of the printing range may be used, or a plurality of heads may be combined to have a length equal to or greater than the width of the printing range.

[0178] Also, a plurality of heads may be arranged side by side such that their nozzles are staggered, so as to increase the resolution of the entire heads.

[0179] The conveyance speed of the recording medium of a low absorbent substrate or a non-absorbent substrate can be set, for example, within the range of 1 to 120 m / min. The higher the conveyance speed, the faster the image forming speed. According to the present invention, a high-definition image with high ink fixability can be obtained even at a very high line speed of 50 to 120 m / min applicable to the single pass type inkjet image forming method.

[0180] <2.4 Ink Composition Drying Process> The ink composition drying process is a process of drying the ink composition landed on a recording medium of a low-absorbency substrate or a non-absorbency substrate. When the pretreatment liquid drying process is omitted, in this ink composition drying process, the pretreatment liquid is also dried together.

[0181] The drying of the ink composition mainly removes water, water-soluble organic solvents, etc., which are the solvent components of the ink composition, and at the same time, the polyvalent metal salt according to the present invention is dried at a temperature equal to or higher than the thermal decomposition temperature and thermally decomposed. The upper limit of the drying temperature is preferably carried out at a temperature of 220 °C or lower from the viewpoint of achieving both the thermal decomposability of the aggregating agent and the stability of the ink composition. The drying time of the ink is controlled by at least the time for the polyvalent metal salt to thermally decompose. The decomposition time is appropriately selected according to the type of polyvalent metal salt to be selected, and can be appropriately determined from the viewpoint of the degree of thermal decomposition and productivity for obtaining the effects of the present invention.

[0182] The drying of the ink composition can be carried out in the same manner as the drying of the aforementioned pretreatment liquid.

[0183] <2.5 Maintenance Process> The maintenance process (method) is a process of cleaning the pretreatment liquid head for applying the pretreatment liquid with the maintenance liquid according to the present invention. The maintenance method is not particularly limited, and known methods can be used. For example, a method of removing the dried matter on the nozzle surface of the head with a wiping member, a method of covering and moisturizing the nozzle surface of the head with a head moisturizing cap (also referred to as a "cap") supplied with the maintenance liquid to remove the dried matter, a method of immersing the nozzle portion of the head in the maintenance liquid, a method of circulating the maintenance liquid in the head for cleaning, etc. can be mentioned. These methods can be used alone or in combination.

[0184] <2.5.1 Maintenance Process by Wiping> Among the above methods, a method of cleaning using a wiping member is preferable. In the present invention, "wiping" means removing dried matter deposited on the nozzle surface by applying some force, either in contact or non-contact, and "wiping member" means a part, device, etc. itself used for wiping or the material constituting these.

[0185] As such a cleaning method, for example, an absorber containing a maintenance liquid is used as the wiping member, and the wiping member is pressed against the nozzle surface of the head by pressing means or the like to apply a pressing load, thereby wiping the nozzle surface. At this time, the wiping member may or may not be in direct contact with the head. Also, after spraying the maintenance liquid onto the nozzle surface by spraying means such as an inkjet recording head, the above wiping means may be performed. In addition, the nozzle surface of the head may be covered with a cap supplied with the maintenance liquid, the dried matter may be softened, and then the above wiping means may be performed.

[0186] As a wiping member that directly contacts the head, it is preferable that it easily absorbs the maintenance liquid, has a hardness lower than at least the nozzle surface of the head, and is less likely to damage the water-repellent film. Examples of such members include polyester, acrylic, polyamide, polyurethane, etc. These members can form a woven fabric or a non-woven fabric. In particular, those with high water absorbency and that can easily absorb liquid even with a low pressing force during contact are more preferable. The shape is not particularly limited, and known ones can be used.

[0187] Also, from the viewpoint of being less likely to damage the nozzle, a method of wiping without directly contacting the nozzle is more preferable. Examples of such a method include a method of forming a maintenance liquid layer in the gap between the nozzle surface and the wiping member and cleaning by the movement of the maintenance liquid layer (Japanese Patent Laid-Open No. 10-315487).

[0188] In the above method, the wiping member is preferably an elastic member having absorbency for the maintenance liquid, and a member having elasticity and a member having absorbency for the maintenance liquid may be bonded together.

[0189] As the member having absorbency for the maintenance liquid, a porous polymer is preferable, and a foamed formal resin or a thermally sintered type porous polymer is more preferable. For example, low density polyethylene, high density polyethylene, polypropylene, polymethyl methacrylate, polystyrene, acrylonitrile-based polymer, ethylene-vinyl acetate copolymer, fluororesin, phenol resin, etc. may be mentioned. As long as it has absorbency, leatherette, non-woven fabric, etc. may be used. As the elastic member, rubber etc. are preferable, and a leaf spring or an elastic plastic may be used.

[0190] In addition to this, as a method of wiping without directly contacting the nozzle, there are a method of spraying the maintenance liquid on the nozzle surface and then injecting air for cleaning (Japanese Patent No. 4937785), a method of removing the maintenance liquid on the nozzle surface by suction, etc.

[0191] ≪3 Inkjet recording apparatus≫ The inkjet recording apparatus of the present invention is characterized by using the inkjet recording method of the present invention. FIG. 1 is a schematic diagram showing a preferable example of the inkjet recording apparatus of the present invention. However, the present invention is not limited to this. For example, in the inkjet recording apparatus 1 shown in FIG. 1, the first drying unit 14 may be omitted, and the inkjet head 11 and the inkjet head 21 may be adjacent to each other.

[0192] The inkjet recording apparatus 1 mainly comprises a pretreatment liquid application unit 10 and an ink composition discharge unit 20. In the pretreatment liquid application unit 10, a pretreatment layer C is formed on the base material F, and an ink composition layer R is formed by the ink composition discharge unit 20.

[0193] Specifically, pretreatment liquid droplets 12 are ejected from the inkjet head 11 onto the base material F fed out from the feed roller 30, and a pretreatment layer C is formed. Subsequently, the pretreatment layer C is dried by the first drying unit 14. Note that, although the pretreatment liquid application unit 10 shown in FIG. 1 uses an inkjet head 11, it is not limited thereto, and a roll coater or the like may be used instead.

[0194] Next, ink composition droplets 22 are ejected from the inkjet head 21 onto the pretreatment layer C, an ink layer R is formed, and after drying at a temperature equal to or higher than the thermal decomposition temperature of the aggregating agent according to the present invention by the second drying unit 23, the base material F on which the pretreatment layer C and the ink composition layer R are formed is wound up by the winding roller 40 to obtain an image recording material.

[0195] In FIG. 1, the case where the base material F is a film base material is shown. However, in the case of a metal base material or the like, the metal base material is arranged on the conveyor belt, and the pretreatment layer C and the ink composition layer R can be applied and formed in one pass while conveying the belt.

[0196] As an apparatus other than the inkjet recording apparatus shown in FIG. 1, it is also preferable to use a flatbed type printer for applying the pretreatment liquid and ejecting the ink composition. In a flatbed type printer, the base material is fixed, and the inkjet head can be moved in the main scanning direction and the sub-scanning direction intersecting the main scanning direction, and printing can be performed without conveying the base material. In the case of a metal base material such as tinplate, since roll-to-roll conveyance is not possible like resin film equipment, it is preferable to use a flatbed type printer that does not require conveyance of the base material.

[0197] As such a flatbed type printer, the printers described in FIG. 1 of JP-A-2015-74161 and FIG. 1 of JP-A-2017-177578 can be cited as an example.

[0198] In addition, in FIG. 1, the apparatus is configured such that the pretreatment liquid is applied onto the base material and then the ink composition is ejected. However, the apparatus may be configured to apply the pretreatment liquid and eject the ink composition simultaneously, and a two-liquid type inkjet recording apparatus may also be used.

[0199] The two-liquid type is a method provided with a droplet ejection means having one or more ejection ports for ejecting the ink composition and one or more ejection ports for ejecting the pretreatment liquid. The two-liquid type inkjet recording apparatus is a recording apparatus that forms an image by applying droplets of the ink composition and droplets of the pretreatment liquid onto the surface of the recording medium from the droplet ejection means and causing them to merge. By using such an apparatus, the application of the pretreatment liquid and the ejection of the ink composition can be performed simultaneously.

[0200] The two-liquid type inkjet recording apparatus can be used without particular limitation, and further, for example, it may have a control unit that controls the amount of ink applied and the amount of treatment liquid applied in the droplet ejection means.

[0201] As the inkjet recording apparatus of the present invention, the droplet ejection means may be either a scanning method or a line method. FIG. 2 shows a preferred example of the droplet ejection means of the scanning method. The droplet ejection means 120 has a head 1Pr for the pretreatment liquid and heads 1Y, 1M, 1C, 1K corresponding to the ink compositions of each color, and each head has a plurality of nozzles (displayed as 121 in FIG. 3). In the droplet ejection means 120, the nozzles correspond to ejection ports, and by appropriately applying pressure to the ink composition and the pretreatment liquid, minute droplets are ejected from these nozzles.

[0202] When the droplet ejection means is of the line type, the droplet ejection means has a length equal to or greater than the printing area width PW of the entire printing area P with respect to the recording medium M, and the head 1Pr for the pretreatment liquid and the heads 1Y, 1M, 1C, 1K corresponding to the ink compositions of each color are arranged in order along the conveyance direction Y so as to be parallel to the printing area width PW. The head 1Pr for the pretreatment liquid may be arranged before or after the heads of the ink compositions of each color.

[0203] In the line-type droplet ejection means, one head unit 101 (a set of head 1Pr and heads 1Y, 1M, 1C, 1K) having a width equal to or greater than the printing area width PW may be used, or a plurality of head units 101 may be combined so as to have a width equal to or greater than the printing area width PW.

[0204] Also, a plurality of head units may be arranged side by side such that their nozzles are staggered, so as to increase the resolution of the droplet ejection means as a whole. Further, a plurality of such droplet ejection means may be arranged side by side along the conveyance direction Y of the recording medium.

[0205] The inkjet recording apparatus of the present invention preferably further includes an apparatus for cleaning the pretreatment liquid head using the maintenance liquid according to the present invention. Such an apparatus is not particularly limited, and a conventionally known maintenance apparatus can be used. Among them, an apparatus having a wiping member is preferable. The wiping member is not particularly limited, and it is preferable to use the wiping member used in the above-described maintenance step by wiping.

[0206] The maintenance method of the inkjet recording apparatus of the present invention refers to a method of cleaning the pretreatment liquid head in the inkjet recording apparatus using the maintenance liquid according to the present invention. The method of cleaning is not particularly limited, and the method described in the above-mentioned "maintenance step" can be used.

[0207] FIG. 4 shows a preferred example of an inkjet recording apparatus including an apparatus for cleaning using a maintenance liquid. The inkjet recording apparatus 201 includes a conveyance unit 210, head units 220Y, 220M, 220C, 220K (hereinafter also referred to as head unit 220 when not distinguished from each other), a maintenance unit 230 (wiping unit), a control unit 240, and the like.

[0208] The conveying unit 210 includes a conveying belt 211 and a pair of conveying rollers 212. The conveying rollers 212 rotate about a rotation axis parallel to the X direction in FIG. 4 by the drive of a conveying motor (not shown). The conveying belt 211 is an annular belt whose inner side is supported by the pair of conveying rollers 212, and moves in a circular motion as the conveying rollers 212 rotate. The inkjet recording apparatus 201 performs a conveying operation of conveying the recording medium M in the moving direction (conveying direction: Y direction in FIG. 4) of the conveying belt 211 by the conveying belt 211 moving in a circular motion at a speed corresponding to the rotation speed of the conveying rollers 212 with the recording medium M placed on the conveying belt 211. As the recording medium M, various media such as paper, metal, film, and fabric can be used.

[0209] The head unit 220 ejects ink from nozzles based on image data onto the recording medium M being conveyed by the conveying belt 211 to record an image on the recording medium M. In the inkjet recording apparatus 201 of the present embodiment, four head units 220Y, 220M, 220C, and 220K corresponding to four colors of ink, namely yellow (Y), magenta (M), cyan (C), and black (K), are arranged in order at predetermined intervals from the upstream side in the conveying direction of the recording medium M. Note that the number of head units 220 may be three or less or five or more.

[0210] As shown in FIG. 4, each of the head units 220 is individually movable in the X direction. Thereby, when image formation is not being performed, the nozzle opening surface 221a (not shown) can be moved to a position facing the maintenance unit 230. In FIG. 4, a state is shown in which the head unit 220K has moved in the X direction and faces the maintenance unit 230. Hereinafter, the position of the head unit 220 when ejecting the ink composition for image formation is also referred to as the ink composition ejection position, and the position facing the maintenance unit 230 is also referred to as the maintenance position.

[0211] When the head unit 220 moves in the X direction, the maintenance unit 230 positions the nozzle opening surface 221a at a position where it can be maintained. The maintenance unit 230 may be provided separately for each head unit 220, or the maintenance of all the head units 220 may be performed by moving a single maintenance unit 230 in the Y direction.

[0212] FIG. 5 shows a preferred example of the maintenance unit 230. The maintenance unit 230 includes a maintenance liquid tank 231 that stores a maintenance liquid 260. The maintenance liquid tank 231 is connected to a first waste liquid flow path 232. The maintenance unit 230 includes a sheet-like wiper member 235, a supply roller 236, a take-up roller 237, two guide rollers 238, and a pressing member 239. The member used as the wiper member 235 is not particularly limited, and the above wiping member can be used, but it is preferably a porous sheet or the like. The wiper member 235 is supplied by being unwound from the supply roller 236, and is wound up by the take-up roller 237 via the guide roller 238. The supply roller 236 is immersed in the maintenance liquid 260 in the maintenance liquid tank 231, and thereby the maintenance liquid 260 is supplied so as to adhere to the wiper member 235. In this way, the maintenance liquid tank 231 functions as a maintenance liquid supply means for storing the maintenance liquid 260 and supplying the maintenance liquid 260 to the wiper member 235. Also, the take-up roller 237 is immersed in the maintenance liquid 260 in the maintenance liquid tank 231. Therefore, the maintenance liquid tank 231 may contain waste liquid of the maintenance liquid 260. The pressing member 239 is configured to be movable above the two guide rollers 238. Therefore, the maintenance unit 230 is a winding type maintenance device using a sheet-like wiper member 235. Also, as the maintenance liquid 260, the maintenance liquid according to the present invention is used.

[0213] In FIG. 5, both the supply roller 236 and the take-up roller 237 are disposed in the maintenance liquid tank 231. However, a configuration may also be adopted in which only the supply roller 236 is disposed in the maintenance liquid tank 231, and the take-up roller 237 is disposed in a separately prepared waste liquid tank or above the waste liquid tank. Further, instead of the maintenance liquid tank 231, a waste liquid tank may be prepared, at least the take-up roller 237 is disposed outside the waste liquid tank, and the maintenance liquid 260 is supplied to the wiper member 235 by a separately prepared maintenance liquid application device or maintenance liquid discharge device.

[0214] As shown in FIG. 6, the carriage 226 is configured to be slidable along the guide rail 216 and is movable in the X direction. The carriage 226 is mounted with an inkjet head 250. Therefore, the inkjet head 250 is movable in the X direction. A maintenance unit 230 is disposed below the carriage 226.

[0215] When the carriage 226 moves from the home position HP to the left direction X1, the pressing member 239 of the maintenance unit 230 moves upward. As a result, the nozzle surface 252 of the inkjet head 250 and the wiper member 235 come into contact with each other. At this time, as the inkjet head 250 moves, a wiping operation of the nozzle surface 252 is performed. Alternatively, as the supply roller 236 and the take-up roller 237 rotate, the wiper member 235 moves to perform a wiping operation. Note that the wiping operation is not limited to this, and it is sufficient that the inkjet head 250 and the wiper member 235 of the maintenance unit 230 move relative to each other. For example, a configuration in which the maintenance unit 230 moves may be adopted.

[0216] ≪4 Image recording material≫ An image recording material recorded by the ink for inkjet recording and the inkjet recording method of the present invention preferably has a substrate, a pretreatment layer formed on the substrate using the pretreatment liquid, and an ink composition layer formed on the pretreatment layer using the ink composition.

[0217] As shown in FIG. 7, on the base material F, the pretreatment liquid according to the present invention is applied by a roll coater or discharged from an inkjet head to form a pretreatment layer C. At the position where the pretreatment layer C is fixed, the ink composition is discharged from the inkjet head and fixed to form an ink composition layer R.

[0218] The above configuration shows the minimum configuration, and other functional layers may be formed between the base material and the pretreatment layer. Also, on the upper layer of the ink composition layer, for example, a non-absorbent film base material or the like may be laminated via a laminate adhesive layer. At least, the configuration in which the pretreatment layer and the ink composition layer are in contact is essential.

[0219] As an example of the image recording material in the present invention, it is an image recording material using at least the pretreatment liquid and the water ink composition according to the present invention. The recording medium is not particularly limited, but is preferably a recording medium made of a non-absorbent material (hereinafter, also referred to as a "non-absorbent recording medium").

[0220] In the present invention, the thickness of the recording medium is appropriately selected according to the type of the recording medium. When the recording medium is a plastic film, the thickness of the recording medium is preferably in the range of 10 to 120 μm, more preferably in the range of 12 to 60 μm. When the recording medium is a metal recording medium, the thickness of the recording medium is preferably in the range of 0.05 to 0.5 mm, more preferably in the range of 0.1 to 0.3 mm. When the recording medium is a leather base material, the thickness of the recording medium is preferably in the range of 1 to 5 mm, more preferably in the range of 1 to 3 mm.

[0221] As an example of a non-absorbent recording medium, known plastic films can be used. Specific examples include polyester films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide-based films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, biodegradable films such as polylactic acid films, and the like. In addition, in order to impart gas barrier properties, moisture-proof properties, fragrance retention properties, etc., films coated with polyvinylidene chloride on one or both sides of the film, or films vapor-deposited with metal oxides can also be preferably used. The non-absorbent film can be preferably used whether it is an unstretched film or a stretched film.

[0222] In addition, examples of the non-absorbent recording medium include leather substrates. Leather used for printing purposes is generally cowhide. Cowhide is usually tanned using a chromium compound to add durability. It is common to apply an acrylic-based or urethane-based white pigment paint to the tanned leather to make a recording medium.

[0223] In addition to these, examples of the non-absorbent recording medium include recording media made of inorganic compounds such as metals and glass. For example, it can also be preferably used for packaging materials for retort foods, etc., in which a thermosetting resin is provided as a coating layer on a metal recording medium. Such packaging materials for retort foods block air, moisture, and light and seal the internal food. For example, they are composed of films obtained by laminating (laminating) thermoplastic resin layers or aluminum foil layers such as polypropylene on the food side and polyester on the outside to block air, moisture, and light and seal the internal food.

[0224] FIG. 8 shows a cross-sectional view of a packaging material for canned foods, which is an example of the image recording product of the present invention. A thermosetting resin (e.g., TW-1407 series, manufactured by T&K TOKA) is roller-coated onto a tin base material 351 to form a thermosetting resin layer (base coat) 352. An image is formed thereon by a pretreatment layer 353 and an ink composition layer 354. Next, a thermosetting resin (e.g., AX-10 series, manufactured by T&K TOKA) is roller-coated to form a thermosetting resin layer (top coat) 355, and then heat-cured and dried to obtain a packaging material 350 for canned foods.

Example

[0225] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the unit “part” or “%” is used, and unless otherwise specified, it represents “part by mass” or “mass %”.

[0226] [Example 1] As shown below, an inkjet recording ink set including an ink composition, a pretreatment liquid, and a maintenance liquid was prepared.

[0227] [Preparation of Ink]

[0228] [Preparation of Cyan Ink] A pigment (PB15:3, manufactured by DIC Corporation, TGR-SD) was added to 20% by mass, a pigment dispersant (an acrylic dispersant having a carboxy group neutralized with dimethylaminoethanol, “Joncryl 819” manufactured by BASF, acid value 75 mgKOH / g, solid content 20% by mass) was added to 6% by mass, propylene glycol was added to 22% by mass, a fungicide Proxel GXL(S) was added to 0.1%, and ion-exchanged water (the remainder; an amount such that the total amount is 100% by mass) was added. After premixing the resulting mixture, it was dispersed using a bead mill filled with 50% by volume of 0.5 mm zirconia beads to prepare a pigment dispersion liquid A having a pigment content of 20% by mass. The average particle size of the pigment particles contained in this pigment dispersion liquid was 120 nm. The measurement of the average particle size was performed using “Zetasizer 1000HS” manufactured by Malvern Corporation.

[0229] To 15% by mass of the above pigment dispersion (3% by mass as solids), a resin fine particle dispersion (the addition amount is adjusted so that the resin fine particles (solids) are 5% by mass in the ink), 22% by mass of propylene glycol, 5% by mass of glycerin, 0.2% by mass of surfactant KF351A (Shin-Etsu Silicone Co., Ltd.), 1% by mass of surfactant E1010 (Nisshin Chemical Industry Co., Ltd.), 0.1% by mass of fungicide Proxel GXL(S), and ion-exchanged water (the balance; in an amount such that the total amount is 100% by mass) were added while stirring, and the resulting mixture was filtered through a 1-μm filter. There was no substantial compositional change before and after filtration.

[0230] <Preparation of Yellow Ink> To 20% by mass of a pigment (PY155, 3GP-CT: manufactured by Clariant), 6% by mass of a pigment dispersant (an acrylic dispersant having a carboxy group neutralized with dimethylaminoethanol, "Joncryl 819" manufactured by BASF, acid value 75 mgKOH / g, solids 20% by mass), 22% by mass of propylene glycol, 0.1% of fungicide Proxel GXL(S), and ion-exchanged water (the balance; in an amount such that the total amount is 100% by mass) were added to prepare a premixed solution. After that, it was dispersed using a bead mill filled with 50% by volume of 0.5-mm zirconia beads to prepare a pigment dispersion A having a pigment content of 20% by mass. The average particle size of the pigment particles contained in this pigment dispersion was 120 nm. The measurement of the average particle size was performed using "Zetasizer 1000HS" manufactured by Malvern.

[0231] To 15% by mass of the above pigment dispersion (3% by mass as solids), a resin fine particle dispersion (the addition amount is adjusted so that the resin fine particles (solids) are 5% by mass in the ink), 22% by mass of propylene glycol, 5% by mass of glycerin, 0.2% by mass of surfactant KF351A (Shin-Etsu Silicone Co., Ltd.), 1% by mass of surfactant E1010 (Nisshin Chemical Industry Co., Ltd.), 0.1% by mass of fungicide Proxel GXL(S), and ion-exchanged water (the balance; in an amount such that the total amount is 100% by mass) were added while stirring, and the resulting mixture was filtered through a 1-μm filter. There was no substantial compositional change before and after filtration.

[0232] <Preparation of Black Ink> 20% by mass of a pigment (PB7, REGAL 330R; manufactured by Cabot), 6% by mass of a pigment dispersant (an acrylic dispersant having a carboxy group neutralized with dimethylaminoethanol, "Joncryl 819" manufactured by BASF, acid value 75 mgKOH / g, solid content 20% by mass), 22% by mass of propylene glycol, 0.1% of a mildewproof agent Proxel GXL(S), and ion-exchanged water (the remainder; in an amount such that the total amount is 100% by mass) were premixed, and then dispersed using a bead mill filled with zirconia beads with a diameter of 0.5 mm at a volume ratio of 50% to prepare a pigment dispersion A having a pigment content of 20% by mass. The average particle diameter of the pigment particles contained in this pigment dispersion was 120 nm. The average particle diameter was measured using a "Zetasizer 1000HS" manufactured by Malvern.

[0233] To 15% by mass of the above pigment dispersion (3% by mass as solid content), a resin fine particle dispersion (the addition amount was adjusted so that the resin fine particles (solid content) were 5% by mass in the ink), 22% by mass of propylene glycol, 5% by mass of glycerin, 0.2% by mass of a surfactant KF351A (Shin-Etsu Silicone), 1% by mass of a surfactant E1010 (Nisshin Chemical Industry Co., Ltd.), 0.1% by mass of a mildewproof agent Proxel GXL(S), and ion-exchanged water (the remainder; in an amount such that the total amount was 100% by mass) were added while stirring, and the resulting mixture was filtered through a 1-μm filter. There was no substantial compositional change before and after filtration.

[0234] <Preparation of Magenta Ink> 20% by mass of pigments (PR122, PV19, RY: manufactured by DIC Corporation), 8% by mass of a pigment dispersant (an acrylic dispersant having a carboxy group neutralized with dimethylaminoethanol, "Joncryl 819" manufactured by BASF, acid value 75 mgKOH / g, solid content 20% by mass), 22% by mass of propylene glycol, 0.1% of the fungicide Proxel GXL(S), and ion-exchanged water (the remainder; in an amount such that the total amount is 100% by mass) were premixed, and then dispersed using a bead mill filled with 50% by volume of 0.5 mm zirconia beads to prepare a pigment dispersion A having a pigment content of 20% by mass. The average particle size of the pigment particles contained in this pigment dispersion was 140 nm. The average particle size was measured using "Zetasizer 1000HS" manufactured by Malvern.

[0235] To 20% by mass (4% by mass as solid content) of the above pigment dispersion, the commercially available resin fine particle dispersion B1 (the addition amount was adjusted so that the resin fine particles (solid content) were 5% by mass in the ink), 21% by mass of propylene glycol, 5% by mass of glycerin, 0.2% by mass of the surfactant KF351A (Shin-Etsu Silicone Co., Ltd.), 1% by mass of the surfactant E1010 (Nisshin Chemical Industry Co., Ltd.), 0.1% by mass of the fungicide Proxel GXL(S), and ion-exchanged water (the remainder; in an amount such that the total amount was 100% by mass) were added while stirring, and the resulting mixture was filtered through a 1 μm filter. There was no substantial compositional change before and after filtration.

[0236] [Preparation of Pretreatment Liquids 1, 4, and 5] After mixing and stirring the following components, they were filtered through a 5 μm membrane filter to obtain Pretreatment Liquid 1.

[0237] 66 parts by mass of ion-exchanged water 30 parts by mass of propylene glycol 3 parts by mass of a flocculant (calcium acetate: manufactured by Kanto Chemical Co., Inc.) Silicone-based surfactant (BYK® 3450: manufactured by Big Chemie Japan Co., Ltd.) 1 part by mass

[0238] The pretreatment solutions 4 and 5 were prepared in the same manner except that the flocculants in the pretreatment solution 1 were changed to magnesium acetate tetrahydrate (manufactured by Kanto Chemical Co., Inc.) and aluminum nitrate nonahydrate (manufactured by Fujifilm Wako Pure Chemical Corporation), respectively.

[0239] 〔Preparation of Maintenance Solutions 1 to 20〕 After mixing and stirring the components described in Tables I and II, the mixture was filtered through a 5-μm membrane filter to obtain maintenance solutions 1 to 20 (also referred to as "maintenance solutions"). Note that the numerical values in Tables I and II represent all parts by mass except for the pH value. Ion-exchanged water was added so that the total mass of the maintenance solution was 100 parts by mass. Also, the blank spaces for the compounds in the tables indicate that they were not added. For the blank spaces of the pH value, no measurement was performed, so they were left blank.

[0240]

Table 1

[0241]

Table 2

[0242] Note that the compounds (chemicals) and products (trade names) used are shown below. (Acidic Component) Citric acid monohydrate: Manufactured by Kanto Chemical Co., Inc. Sodium citrate dihydrate: Manufactured by Kanto Chemical Co., Inc. Acetic acid: Manufactured by Kanto Chemical Co., Inc. Sodium acetate: Manufactured by Kanto Chemical Co., Inc. Sulfamic acid: Manufactured by Fujifilm Wako Pure Chemical Corporation Glycolic acid: Manufactured by Kanto Chemical Co., Inc. Pyrophosphoric acid: Manufactured by Kanto Chemical Co., Inc.

[0243] (Chelating Agent) EDTA (ethylenediaminetetraacetic acid): Manufactured by Kanto Chemical Co., Inc. HIDA (hydroxyiminodiacetic acid): Manufactured by Fujifilm Wako Pure Chemical Corporation EDTA·4Na (Ethylenediaminetetraacetic acid·tetrasodium): Kirest (registered trademark) 3D: manufactured by Kirest GLDA·4Na (L-Glutamic acid diacetic acid·tetrasodium): Kirest (registered trademark) CMG-40: manufactured by Kirest DHEG·Na (Dihydroxyethylglycine·sodium): Kirest (registered trademark) G-50: manufactured by Kirest

[0244] (Surfactant) Surfactant 1: Pegnol (registered trademark)-005: manufactured by Toho Chemical Industry Co., Ltd. Surfactant 2: Sodium oleate: manufactured by Fujifilm Wako Pure Chemical Corporation Surfactant 3: BYK (registered trademark) 348: manufactured by Big Chemie Japan

[0245] (Organic solvent) Propylene glycol: manufactured by Kanto Chemical Co., Inc. 1,2-Hexanediol: manufactured by Kanto Chemical Co., Inc. 1,3-Butanediol: manufactured by Kanto Chemical Co., Inc. DEGBE: Diethylene glycol monobutyl ether: manufactured by Fujifilm Wako Pure Chemical Corporation

[0246] Sodium hydrogen carbonate: manufactured by Fujifilm Wako Pure Chemical Corporation Triethanolamine: manufactured by Kanto Chemical Co., Inc.

[0247] Also, regarding the pH value at 25°C, it was measured using "HM-41X" manufactured by Toa DKK Corporation.

[0248] 〔Evaluation〕 For the prepared maintenance liquids 1 to 20 and pretreatment liquids 1, 4, and 5, evaluations were conducted with the following combinations. The results are shown in Table III Note that Examples 4, 6 to 9, 11 to 15, and 17 to 21 are for reference.

[0249] (Preparation of liquid ejection device) In a liquid ejection device equipped with an independently driven inkjet head (360 dpi, ejection volume: small droplet 7 pL, medium droplet 15 pL, large droplet 23 pL) manufactured by Konica Minolta, a cap covering the inkjet head and the bottom of the cap are configured to be able to supply a maintenance liquid. Further, means for spraying the maintenance liquid on the nozzle surface and means for wiping (wiping member) are also attached. As the wiping member, a head for Rubicel stick (polyurethane) manufactured by AS ONE Corporation was used.

[0250] (1) Maintainability The inkjet head of the above liquid ejection device was filled with the prepared pretreatment liquids 1, 4, and 5 respectively, left at room temperature (25 °C) for one week without a cap, and it was confirmed that dried substances of the pretreatment liquids were deposited on the nozzle surface of the head. The wiping member was immersed in maintenance liquids 1 to 20 respectively, the nozzle surface was wiped, and purge maintenance was performed. Then, the presence or absence of non-ejecting nozzles and deflecting nozzles was evaluated based on the following evaluation criteria. However, purge maintenance is a maintenance operation to prevent nozzle clogging by discharging unused ink that has not been ejected onto the substrate from the liquid supplied to the inkjet head. Also, the maintenance work in the following evaluation criteria refers to a series of operations of wiping the nozzle surface and then performing purge maintenance, and this work was repeated.

[0251] ◎: Nozzle recovery within 3 or fewer maintenance operations. 〇: Nozzle recovery within 4 to 7 maintenance operations. △: Nozzle recovery within 8 to 10 maintenance operations. ×: Nozzle cannot be recovered even after 11 or more maintenance operations. 〇 or above was considered a pass.

[0252] (2) Head member resistance After filling the inkjet head of the above liquid ejection device with the prepared pretreatment liquids 1, 4, and 5 respectively, immersing the maintenance liquids 1 to 20 in the wiping member respectively, and wiping the nozzle surface multiple times, purge maintenance was performed. Then, the presence or absence of defective ejection nozzles such as non-ejecting nozzles or flying deviation was evaluated based on the following evaluation criteria.

[0253] ◎: No defective ejection even after wiping 800 times or more 〇: No defective ejection even after wiping 650 times or more △: No defective ejection even after wiping 400 times or more ×: Defective ejection occurs after wiping less than 400 times Those with 〇 or above were considered qualified.

[0254]

Table 3

[0255] From Table III, in the ink set for inkjet recording of the present invention, it can be seen that the maintenance property is improved by the pretreatment liquid containing a polyvalent metal salt as a flocculant and the maintenance liquid containing an acidic component. Also, it can be seen that suppressing the deterioration of the members of the inkjet head by making the pH approach neutral.

[0256] [Example 2] In order to clarify the difference in effects due to the difference in the composition of various pretreatment liquids, using maintenance liquid 3 as a common maintenance liquid, first the difference in effects of ejection stability and head member resistance was evaluated, and further the difference in effects of maintenance property was evaluated as follows by the same method as in Example 1.

[0257] [Preparation of Pretreatment Liquids 2, 3, and 6 to 16] After mixing and stirring the components described in Tables IV and V, the mixture was filtered through a 5-μm membrane filter to obtain a pretreatment liquid. The numerical values in Tables IV and V represent all parts by mass except for the pH value and the acidic component content ratio. Ion-exchanged water was added so that the total mass of the pretreatment liquid was 100 parts by mass. In addition, the blank spaces for the compounds in the table indicate that they were not added. For the blank spaces of the acidic component content ratio, since it could not be calculated without containing an acidic component, they were left blank.

[0258] Next, the following evaluations were performed using Pretreatment Liquids 1 to 16 and Maintenance Liquid 3. The products (trade names) used were the same as those in Example 1. In addition, the acidic component content ratio in the table represents the ratio (%) of the mass of the acidic component to the mass of the polyvalent metal salt in the pretreatment liquid.

[0259] [Table 4]

[0260] [Table 5]

[0261] 〔Evaluation〕 The following evaluations were performed on the prepared Pretreatment Liquids 1 to 16. The results are shown in Table VI. For the liquid ejection device, the one described in Example 1 was used.

[0262] (3) Head Member Resistance After filling the inkjet head of the above liquid ejection device with each of the prepared Pretreatment Liquids 1 to 16, the pretreatment liquid was continuously ejected from the nozzles. Then, the presence or absence of defective ejection nozzles such as non-ejecting nozzles or flying deviations was evaluated based on the following evaluation criteria.

[0263] ◎: No defective ejection even after 2 weeks or more have passed 〇: Defective ejection occurred between 1 week or more and less than 2 weeks ×: Defective ejection occurred within less than 1 week 〇 or above was considered qualified.

[0264] (4) Ejection stability The inkjet heads of the above liquid ejection device are each filled with the prepared pretreatment liquids 1 to 16 and left at room temperature (25°C). The period until non-ejecting nozzles or deflecting nozzles are confirmed was evaluated based on the following evaluation criteria.

[0265] ◎: 2 weeks or more. 〇: 1 week or more and less than 2 weeks. ×: Less than 1 week. 〇 or above was considered qualified.

[0266] (5) Maintainability After the evaluation of the above ejection stability, the maintenance work described in the above maintainability evaluation in Example 1 was performed, and when the same evaluation was carried out, it was ◎ for all of the pretreatment liquids 1 to 16.

[0267]

Table 6

[0268] From Table VI, it can be seen that in the pretreatment liquid contained in the ink set for inkjet recording of the present invention, by further containing an acidic component, it becomes difficult to deposit the dried product of the pretreatment liquid containing carbonate. Also, it can be seen that by bringing the pH closer to neutral, deterioration of the members of the inkjet head is suppressed.

[0269] From the above results, when a polyvalent metal salt is used as the flocculant of the pretreatment liquid, by containing an acidic component in the maintenance liquid, the dried product of the pretreatment liquid containing carbonate deposited on the nozzles of the inkjet head can be removed. Also, by containing an acidic component in the pretreatment liquid, it becomes difficult for the dried product of the pretreatment liquid containing carbonate to deposit. That is, it is possible to provide an ink set for inkjet recording that reduces the adverse effects caused by the pretreatment liquid components and improves maintainability.

Industrial Applicability

[0270] The present invention can be used in an inkjet recording ink set, an inkjet recording method, a maintenance method, and an inkjet recording apparatus that reduce the adverse effects caused by the pretreatment liquid component and improve the maintainability.

Explanation of Signs

[0271] 1 Inkjet recording apparatus 10 Pretreatment liquid application section 11 Inkjet head 12 Pretreatment liquid droplet 14 First drying section 20 Ink composition discharge section 21 Inkjet head 22 Ink composition droplet 23 Second drying section 101 Head unit 120 Droplet discharge means 121 Nozzle M Recording medium W Width in the direction Y orthogonal to the scanning direction X of the head unit 1 PL Length in the Y direction of the entire printing area P, printing area length 130 Scanning section Im Image formation area A1~A6 Printing areas P Entire printing area 201 Inkjet recording apparatus 210 Conveying section 220K Head unit 216 Guide rail 226 Carriage 230 Maintenance section 231 Maintenance liquid layer 235 Wiper member 239 Pressing member 260 Maintenance liquid C Pretreatment layer F Substrate P Image recording object R Ink composition layer 350 Packaging material for canned food 351 Tin substrate 352 Thermosetting resin layer (base coat) 353 Pretreatment layer 354 Ink composition layer 355 Thermosetting resin layer (top coat)

Claims

1. An ink set for inkjet recording, comprising an ink composition, a pretreatment liquid, and a maintenance liquid, wherein the pretreatment liquid contains a polyvalent metal salt, wherein the pretreatment liquid contains at least one of an inorganic acid or an organic acid, wherein the maintenance liquid contains at least one of citric acid or acetic acid and a salt thereof An ink set for inkjet recording, characterized by the above.

2. An ink set for inkjet recording, comprising an ink composition, a pretreatment liquid, and a maintenance liquid, wherein the pretreatment liquid contains a polyvalent metal salt, wherein the maintenance liquid contains at least one of citric acid or acetic acid and a salt thereof, and the pH value of the maintenance liquid is in the range of 5.0 to 6.4 at 25°C An ink set for inkjet recording, characterized by the above.

3. The pH value of the maintenance liquid is in the range of 5.0 to 6.4 at 25°C The ink set for inkjet recording according to claim 1, characterized by the above.

4. The polyvalent metal salt contains at least one metal element of calcium or magnesium The ink set for inkjet recording according to any one of claims 1 to 3, characterized by the above.

5. The pretreatment liquid contains at least one of citric acid, acetic acid, or glycolic acid The ink set for inkjet recording according to any one of claims 1 to 4, characterized by the above.

6. An inkjet recording method of recording using the ink set for inkjet recording according to any one of claims 1 to 5, including a step of applying the pretreatment liquid simultaneously with or immediately before the step of discharging the ink composition A method for inkjet recording, characterized in that.

7. including a step of cleaning the pretreatment liquid head for applying the pretreatment liquid using the maintenance liquid The inkjet recording method according to claim 6, characterized in that.

8. including a step of cleaning the pretreatment liquid head using a wiping member The inkjet recording method according to claim 7, characterized in that.

9. A method for maintaining an inkjet recording apparatus, comprising: using the ink set for inkjet recording according to any one of claims 1 to 5 A maintenance method, characterized in that.

10. using the inkjet recording method according to any one of claims 6 to 8 An inkjet recording apparatus, characterized in that.

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