Inkjet recording apparatus and maintenance method

Abstract

To provide an inkjet recording device that is excellent in cleaning performance and can provide a recording object with high friction-fastness and cleaning-fastness, and a maintenance method for the same.SOLUTION: The inkjet recording device comprises: a recording head that has a nozzle for discharging an ink composition and a nozzle formation surface having a discharge port of the nozzle; and a pressurizing / cleaning mechanism that applies pressure to the inside of the recording head to perform cleaning operation of ejecting the ink composition from the nozzle. The ink composition contains resin particles, organic solvents whose normal boiling point is 280°C or higher, at least either of organic alkali and inorganic alkali, and at least either of betaine and cold-solid polyalcohol, where glass transfer temperatures of the resin particles are in a range from -30 to -50°C.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an inkjet recording apparatus and a maintenance method. [Background technology]

[0002] Inkjet recording methods are capable of recording high-definition images with a relatively simple device, and have been rapidly developed in various fields. In the meantime, various studies have been conducted on cleaning methods for inkjet recording devices. For example, Patent Document 1 discloses a liquid ejection device that can appropriately perform maintenance on an ejection head having nozzles while suppressing wasteful consumption of liquid, and discloses that the device is used to increase the pressure of the liquid in the nozzles for cleaning. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-013301 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, ink compositions that contain solids such as resin particles to improve friction fastness may have poor cleaning properties (ability to recover from clogging) when subjected to pressure cleaning, and there is a demand for both providing recorded matter with excellent friction fastness and ensuring good cleaning properties (ability to recover from clogging). [Means for solving the problem]

[0005] The inkjet recording apparatus of the present invention comprises a recording head having a nozzle for ejecting an ink composition and a nozzle forming surface having an ejection port of the nozzle, and a pressure cleaning mechanism that applies pressure to the inside of the recording head and performs a cleaning operation to eject the ink composition from the nozzle. The ink composition used contains resin particles, an organic solvent having a normal boiling point of 280°C or higher, at least one of an organic alkali and an inorganic alkali, and at least one of betaine and a polyhydric alcohol that is solid at room temperature, and the glass transition temperature of the resin particles is -30 to 50°C.

[0006] The resin particles in the ink composition used in the inkjet recording device preferably contain a crosslinkable group.

[0007] The resin particles in the ink composition used in the inkjet recording device preferably contain urethane resin particles.

[0008] The content of the resin particles in the ink composition used in the inkjet recording device is preferably 3.0 to 8.0% by mass with respect to the total amount of the ink composition.

[0009] The total content of the organic alkali and inorganic alkali in the ink composition used in the inkjet recording device is preferably 0.10 to 0.60 in terms of mass ratio relative to the total content of the polyhydric alcohol and betaine.

[0010] The content of the resin particles in the ink composition used in the inkjet recording device is preferably 1.0 to 2.0 in terms of mass ratio to the total amount of the polyhydric alcohol and betaine.

[0011] The inkjet recording apparatus preferably includes a wiping cleaning mechanism that wipes the nozzle surface with an absorbent member.

[0012] The absorbent member of the inkjet recording apparatus is impregnated with a cleaning liquid, and the ratio of the surface tension of the cleaning liquid to the surface tension of the ink composition is preferably 0.75 to 1.25.

[0013] The cleaning liquid used in the inkjet recording apparatus preferably has a contact angle with respect to the nozzle formation surface that is 1.3 to 1.7 times the contact angle of the ink composition with respect to the nozzle formation surface.

[0014] The maintenance method of the present invention is a maintenance method for the inkjet recording apparatus, and includes a pressure cleaning step of applying pressure to the inside of the recording head to discharge the ink composition from the nozzles. [Brief description of the drawings]

[0015] [Figure 1] 2 is a diagram illustrating an example of the configuration of a print head, an ink supply mechanism, and a pressure cleaning mechanism; FIG. [Diagram 2] 4A and 4B are diagrams illustrating an example of the configuration of a wiping cleaning mechanism; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the gist of the present invention. In the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings, unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0017] 1. Inkjet recording device The inkjet recording apparatus of the present embodiment is equipped with a recording head having nozzles for ejecting an ink composition and a nozzle forming surface having an ejection port of the nozzle, and a pressure cleaning mechanism that applies pressure to the inside of the recording head and performs a cleaning operation to eject the ink composition from the nozzle. The ink composition used contains resin particles, an organic solvent having a normal boiling point of 280°C or higher, at least one of an organic alkali and an inorganic alkali, and at least one of betaine and a polyhydric alcohol that is solid at room temperature, and the glass transition temperature of the resin particles is -30 to 50°C.

[0018] In an inkjet recording apparatus that ejects an ink composition from a nozzle, cleaning is performed periodically to discharge the ink composition from inside the nozzle in order to prevent the ink composition from clogging the nozzle, etc. Cleaning can be broadly classified according to the method of applying pressure to the ink composition inside the nozzle, and is divided into pressurized cleaning and reduced pressure cleaning.

[0019] Pressurized cleaning is a cleaning method in which a positive pressure is continuously applied to the ink composition in the nozzle from the upstream side of the ink supply flow path toward the nozzle on the downstream side, thereby discharging the ink composition from the nozzle, whereas reduced pressure cleaning is a cleaning method in which the nozzle forming surface is covered with a cap and negative pressure is applied to the covered space by a suction pump or a negative pressure generating mechanism, thereby discharging the ink composition from the nozzle.

[0020] The ink composition discharged by cleaning contains various components such as resin particles in addition to coloring materials. When such resin particles are contained, aggregates may easily occur in the nozzle, or the viscosity may easily increase depending on the drying state of the ink composition in the nozzle. In particular, when resin particles having a glass transition temperature of -30 to 50°C are used, it has been revealed that while the abrasion fastness of the resulting recorded matter can be improved, aggregates are easily generated.

[0021] In general, pressure cleaning tends to be more difficult to discharge the ink composition than vacuum cleaning, and therefore pressure cleaning has the problem of deteriorating the cleaning ability of a recording device that uses an ink composition that contains resin particles with a glass transition temperature of -30 to 50°C.

[0022] In contrast, in the inkjet recording device of this embodiment, the ink composition contains an organic solvent having a normal boiling point of 280°C or higher, at least one of an organic alkali and an inorganic alkali, and at least one of betaine and a polyhydric alcohol that is solid at room temperature, thereby ensuring the redispersibility of stuck components that may occur in an ink composition containing resin particles, and thereby improving the cleaning properties of pressurized cleaning.

[0023] In addition, by making it possible to use pressurized cleaning with an ink composition containing resin particles in this way, it is possible to suppress the generation of ink bubbles that tend to occur during reduced pressure cleaning, and also to suppress adhesion of a portion of the ink composition discharged during cleaning to the nozzle formation surface. This makes it possible to avoid the phenomenon in which additional cleaning becomes necessary due to cleaning, and also makes it possible to shorten the overall cleaning time compared to reduced pressure cleaning. The inkjet recording apparatus of this embodiment will be described in detail below.

[0024] 1.1. Ink composition First, the ink composition will be described in detail. The ink composition used in the inkjet recording device of this embodiment contains resin particles having a glass transition temperature of -30 to 50°C, an organic solvent having a normal boiling point of 280°C or higher, at least one of an organic alkali and an inorganic alkali, and at least one of betaine and a polyhydric alcohol that is solid at room temperature.

[0025] 1.1.1.Resin particles The glass transition temperature of the resin particles is -30 to 50°C, preferably -25 to 45°C, more preferably -20 to 45°C, and even more preferably 10 to 45°C. When the glass transition temperature of the resin particles is 50°C or less, it becomes possible to form a film at a lower temperature, and the fixability of the obtained recorded matter tends to be improved. In addition, the texture can be made good. From the viewpoint of improving the texture, the glass transition temperature of the resin particles is more preferably 0°C or less. In addition, when the glass transition temperature of the resin particles is -30°C or more, the robustness of the obtained coating film tends to be further improved. The glass transition temperature of the resin particles can be measured using differential scanning calorimetry (DSC) in accordance with JIS K7121:1987. An example of a differential scanning calorimeter is "DSC6220" (product name, manufactured by Seiko Electronics Co., Ltd.).

[0026] The resin particles are not particularly limited, but may be, for example, urethane resin particles or (meth)acrylic resin particles. Among these, urethane resin particles are preferred. By using such resin particles, the bleeding of the obtained image is more suppressed, and the abrasion resistance tends to be more improved. The resin particles may be used alone or in combination of two or more kinds.

[0027] The urethane resin particles are not particularly limited as long as they are resin particles having urethane bonds in the molecule, and include polyether type urethane resins having ether bonds in the main chain, polyester type urethane resins having ester bonds in the main chain, and polycarbonate type urethane resins having carbonate bonds in the main chain.Among these, polyether type urethane resins or polycarbonate type urethane resins are preferred, and polycarbonate type urethane resins are more preferred.In addition, from the viewpoint of improving dispersion stability, anionic urethane resin particles having carboxyl group, sulfo group, hydroxyl group, etc. are preferred.

[0028] The acrylic resin particles are not particularly limited, but examples thereof include those obtained by polymerizing (meth)acrylic monomers such as (meth)acrylic acid and (meth)acrylic acid esters, and those obtained by copolymerizing (meth)acrylic monomers with other monomers. Among these, anionic acrylic resin particles are preferred.

[0029] The resin particles preferably contain a crosslinkable group. The crosslinkable group may be one that reacts with the crosslinkable group to form a crosslinked structure, and may be one that reacts with a functional group different from the crosslinkable group to form a crosslinked structure. By using resin particles having such a crosslinkable group, the fastness of the coating film obtained tends to be improved. On the other hand, since such resin particles are easily crosslinked, they tend to reduce clogging and cleaning properties, so the present invention is particularly useful.

[0030] The crosslinkable group as described above is not particularly limited, but examples thereof include a blocked isocyanate group, a silanol group, or these groups protected by a protective group. The silanol group is not particularly limited, but examples thereof include a triethoxysilyl group, a trimethoxysilyl group, and a tris(2-methoxyethoxy)silyl group. In terms of storage stability and reactivity, the crosslinkable group is preferably a blocked isocyanate group. A blocked isocyanate is an isocyanate group blocked by a blocking agent. The blocking agent blocks and inactivates the isocyanate group, while regenerating or activating the isocyanate group after deblocking. Examples of blocking agents include imidazole compounds, imidazoline compounds, pyrimidine compounds, guanidine compounds, alcohol compounds, phenol compounds, active methylene compounds, amine compounds, imine compounds, oxime compounds, carbamic acid compounds, urea compounds, acid amide (lactam) compounds, acid imide compounds, triazole compounds, pyrazole compounds, mercaptan compounds, bisulfites, etc. When the resin has a crosslinkable group, a crosslinked structure is formed between the resins, etc., and the friction fastness can be improved.

[0031] Commercially available dispersions of crosslinkable group-containing urethane resin particles are not particularly limited, but examples thereof include "Takelac WS-6021" (product name, manufactured by Mitsui Chemicals, Inc., emulsion of polyether-based polyurethane resin having a polyether-derived skeleton), "Takelac WS-5100" (product name, manufactured by Mitsui Chemicals, Inc., emulsion of polycarbonate-based polyurethane resin having a polycarbonate-derived skeleton), "Elastron" series "H-38", "BAP", "C-52", "F-29", and "W-11P" (all product names, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), "Elastron" series "E-37" and "H-3" (all product names, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., emulsion of polyester-based polyurethane resin having a polyester-derived skeleton), "Superflex" series "870", "800", "150", "420", "460", "470", and "610", Examples of such emulsions include "700" (product name, Daiichi Kogyo Seiyaku Co., Ltd., urethane resin emulsion), "Permarine UA-150" (product name, Sanyo Chemical Industries, Ltd., urethane resin emulsion), "Suncure 2710" (product name, Lubrizol Japan, urethane resin emulsion), "NeoRez" series' "R-9660", "R-9637", and "R-940" (product names, Kusumoto Chemical Industries, Ltd., urethane resin emulsion), "Adeka Bonditer" series' "HUX-380" and "290K" (product names, ADEKA Corporation, urethane resin emulsion), and "ETERNACOLL UW-1501F" (product name, Ube Industries, Ltd., urethane resin emulsion).

[0032] The content of the resin particles is preferably 2.0 to 10% by mass, more preferably 3.0 to 8.0% by mass, and even more preferably 3.0 to 6.0% by mass, based on the total amount of the ink composition. When the content of the resin particles is 2.0% by mass or more, the fastness of the resulting coating film tends to be improved. Also, when the content of the resin particles is 10% by mass or less, the clogging resistance tends to be improved.

[0033] The content of the resin particles is, in terms of mass ratio relative to the total amount of the polyhydric alcohol and the betaine, 0.6 to 3.0, more preferably 1.0 to 2.0, and even more preferably 1.2 to 1.8. When the content of the resin particles is within the above range, the fastness and cleanability of the resulting coating film tend to be further improved.

[0034] 1.1.2. Organic solvents with normal boiling points of 280°C or higher The organic solvent having a normal boiling point of 280°C or more is not particularly limited, but may be, for example, glycerin. It is preferably a compound composed of carbon atoms, hydrogen atoms, and oxygen atoms. It is also preferably a compound that is liquid at room temperature. Here, "room temperature" means room temperature, i.e., 25°C.

[0035] The content of the organic solvent having a normal boiling point of 280° C. or higher is preferably 3.5 to 17.5 mass %, more preferably 5.0 to 15 mass %, and even more preferably 7.5 to 12.5 mass %, relative to the total amount of the ink composition. When the content of the organic solvent having a normal boiling point of 280° C. or higher is within the above range, the ink composition tends to have good moisture retention, and further improved clogging resistance and cleaning properties.

[0036] 1.1.3. Organic and inorganic alkalis The organic alkali is preferably an alkanolamine. Such organic alkali is not particularly limited, but examples thereof include triethanolamine, diethanolamine, monoethanolamine, and tripropanolamine. Furthermore, the inorganic alkali is not particularly limited, but examples thereof include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Among these, it is preferable to use an organic alkali. By using such an alkali, the dispersion stability of the ink components, particularly the dispersion stability of the resin particles, is further improved, so that clogging resistance and cleaning properties tend to be further improved.

[0037] The content of the organic alkali is preferably 0.05 to 3.0% by mass, more preferably 0.10 to 2.5% by mass, even more preferably 0.20 to 2.0% by mass, and even more preferably 0.20 to 0.75% by mass, relative to the total amount of the ink composition. By having the content of the organic alkali within the above range, the dispersion stability of the ink components is further improved, and therefore clogging resistance and cleaning properties tend to be further improved.

[0038] The content of the inorganic alkali is preferably 0.05 to 0.75% by mass, more preferably 0.05 to 0.50% by mass, and even more preferably 0.05 to 0.30% by mass, relative to the total amount of the ink composition. By having the content of the inorganic alkali within the above range, the dispersion stability of the ink components, particularly the dispersion stability of the resin particles, is improved, and therefore clogging resistance and cleaning properties tend to be improved.

[0039] The total content of the organic alkali and inorganic alkali is preferably 0.05 to 3.0% by mass, more preferably 0.10 to 2.5% by mass, even more preferably 0.20 to 2.0% by mass, and even more preferably 0.20 to 0.75% by mass. When the total content of the organic alkali and inorganic alkali is within the above range, the dispersion stability of the ink components, in particular the dispersion stability of the resin particles, is improved, and therefore clogging resistance and cleaning properties tend to be improved.

[0040] The total content of the organic alkali and inorganic alkali is preferably 0.05 to 0.90, more preferably 0.10 to 0.60, and even more preferably 0.10 to 0.40, in terms of mass ratio relative to the total content of the betaine and the polyhydric alcohol that is solid at room temperature described below. By having the total content of the organic alkali and inorganic alkali within the above range, the dispersion stability of the ink components is improved, and therefore clogging resistance and cleaning properties tend to be improved. In addition, the content of the organic alkali and inorganic alkali remaining in the recorded matter can be reduced, and the abrasion fastness can be improved.

[0041] 1.1.4. Polyhydric alcohols that are solid at room temperature The polyhydric alcohol that is solid at room temperature is not particularly limited, but examples thereof include polyhydric alcohols such as trimethylolpropane and neopentyl glycol, as well as sugars such as glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose. Among these, trimethylolpropane is preferred. Here, "room temperature" means room temperature, 25°C.

[0042] The content of the polyhydric alcohol that is solid at room temperature is preferably 0.5 to 7.5 mass %, more preferably 1.0 to 6.0 mass %, and even more preferably 1.5 to 4.0 mass %, relative to the total amount of the ink composition. When the content of the polyhydric alcohol that is solid at room temperature is within the above range, the ink composition tends to have good moisture retention and moisture absorption properties, and further improved clogging resistance and cleaning properties.

[0043] 1.1.5. Betaine In the present embodiment, betaine refers to a compound having both amino and carboxyl functional groups. From the viewpoint of stability, the amino group is preferably a tertiary amino group or a quaternary amino group. Such betaines are not particularly limited, and examples thereof include tertiary betaines such as dimethylglycine, dimethylalanine, dimethylglutamic acid, and diethylglycine; and quaternary betaines such as trimethylglycine, trimethylalanine, trimethylglutamic acid, and triethylglycine. Among these, quaternary betaines are preferred, and trimethylglycine is more preferred. By using such betaines, the ink composition tends to have good moisture retention and moisture absorption properties, and cleaning recovery is more improved. Note that one type of betaine may be used alone, or two or more types may be used in combination.

[0044] The number of carbon atoms constituting the betaine is preferably 3 to 12, more preferably 3 to 7, and further preferably 4 to 6. When the number of carbon atoms of the betaine is within the above range, stability against disturbances such as the inclusion of charged foreign matter tends to be further improved.

[0045] The content of betaine is preferably 0.5 to 7.5% by mass, more preferably 1.0 to 5.0% by mass, and even more preferably 1.5 to 3.0% by mass, relative to the total amount of the ink composition. When the content of betaine is within the above range, clogging resistance and cleaning properties tend to be further improved.

[0046] The total content of the polyhydric alcohol and betaine that are solid at room temperature is preferably 0.5 to 7.5 mass %, more preferably 1.0 to 6.0 mass %, and even more preferably 1.5 to 4.0 mass %, relative to the total amount of the ink composition. When the total content of the polyhydric alcohol and betaine that are solid at room temperature is within the above range, the ink composition tends to have good moisture retention and moisture absorption properties, and further improved clogging resistance and cleaning properties.

[0047] 1.1.6.Pigments The ink composition of the present embodiment may further contain a pigment. The pigment is not particularly limited, but examples thereof include organic pigments such as azo pigments (e.g., azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, etc.), polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), nitro pigments, nitroso pigments, and aniline black; inorganic pigments such as carbon black (e.g., furnace black, thermal lamp black, acetylene black, channel black, etc.), metal oxides, metal sulfides, and metal chlorides; and extender pigments such as silica, calcium carbonate, and talc.

[0048] The above-mentioned pigment is preferably added to the ink as a pigment dispersion obtained by dispersing the pigment in water with a dispersant, or as a pigment dispersion obtained by dispersing a self-dispersing surface-treated pigment in which hydrophilic groups have been introduced onto the pigment particle surfaces by utilizing a chemical reaction, or as a pigment dispersion obtained by dispersing a pigment coated with a polymer in water.

[0049] The pigment and the dispersant constituting the pigment dispersion may each be used alone or in combination of two or more kinds.

[0050] The content of the pigment, as solid content, relative to the total amount of the ink composition is preferably 1.0 to 12 mass %, more preferably 2.0 to 10 mass %, and even more preferably 3.0 to 7.5 mass %.

[0051] 1.1.7 Water The ink composition of this embodiment may further contain water. The content of water is preferably 50 to 80 mass %, more preferably 60 to 80 mass %, and even more preferably 65 to 75 mass %, based on the total amount of the ink composition.

[0052] Surfactants The ink composition of the present embodiment may further contain a surfactant. The surfactant is not particularly limited, but examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants. Among these, acetylene glycol surfactants are preferred from the viewpoint of clogging recovery.

[0053] The acetylene glycol surfactant is not particularly limited, but for example, one or more selected from 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alkylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and 2,4-dimethyl-5-decyne-4-ol and alkylene oxide adduct of 2,4-dimethyl-5-decyne-4-ol are preferred. Commercially available acetylene glycol surfactants are not particularly limited, but for example, E series such as Olfin 104 series and Olfin E1010 (product names manufactured by Air Products Co., Ltd.), Surfynol 61, 104, 465 (product names manufactured by Nissin Chemical Industry Co., Ltd.), etc. The acetylene glycol surfactant may be used alone or in combination of two or more types.

[0054] The fluorosurfactant is not particularly limited, but examples thereof include perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, and perfluoroalkyl amine oxide compound. The commercially available fluorosurfactant is not particularly limited, but examples thereof include S-144, S-145 (manufactured by Asahi Glass Co., Ltd.); FC-170C, FC-430, and Fluorad-FC4430 (manufactured by Sumitomo 3M Co., Ltd.); FSO, FSO-100, FSN, FSN-100, and FS-300 (manufactured by Dupont Co., Ltd.); and FT-250 and 251 (manufactured by Neos Co., Ltd.). The fluorosurfactant may be used alone or in combination of two or more kinds.

[0055] Examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes. Examples of commercially available silicone surfactants include, but are not limited to, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, and BYK-349 (all product names, manufactured by BYK Japan Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (all product names, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0056] The content of the surfactant is preferably 0.1 to 5.0% by mass, and more preferably 0.1 to 3.0% by mass, based on the total mass of the ink composition. When the content of the surfactant is within the above range, clogging recovery properties tend to be further improved.

[0057] 1.1.9 Method for producing ink composition The method for producing the ink composition of this embodiment is not particularly limited, and examples thereof include a method of mixing resin particles, an organic solvent having a normal boiling point of 280° C. or higher, at least one of an organic alkali and an inorganic alkali, at least one of betaine and a polyhydric alcohol that is solid at room temperature, and other components as necessary. When a pigment is used, the components may be mixed in the form of a pigment dispersion.

[0058] 1.2. Recording head The recording head has nozzles for ejecting an ink composition and a nozzle forming surface having ejection openings for the nozzles. Fig. 1 shows a schematic configuration example of the recording head and an ink supply mechanism to the recording head.

[0059] The recording head 6 has a nozzle 601 opening in a nozzle forming surface 600, a reservoir 602 for temporarily storing an ink composition, and a cavity 603 that connects the nozzle 601 and the reservoir 602, and ink is supplied from the reservoir 602 to the nozzle 601 via the cavity 603. During recording, the cavity 603 applies pressure to the ink, causing the ink to be ejected from the nozzle 601.

[0060] A liquid-repellent film (not shown) may be provided on the nozzle forming surface 600. The liquid-repellent film is not particularly limited as long as it is a film having liquid repellency, and can be formed, for example, by forming a molecular film of a metal alkoxide having liquid repellency, and then performing a drying process, an annealing process, or the like. The molecular film of the metal alkoxide may be any film as long as it has liquid repellency, but it is preferable that it is a monomolecular film of a metal alkoxide having a long-chain polymer group containing fluorine, or a monomolecular film of a metal acid salt having a liquid repellent group such as a long-chain polymer group containing fluorine.

[0061] The metal alkoxide is not particularly limited, but the metal species generally used are, for example, silicon, titanium, aluminum, and zirconium. Examples of the long-chain RF group include perfluoroalkyl chains and perfluoropolyether chains. Examples of the alkoxysilane having this long-chain RF group include silane coupling agents having long-chain RF groups. The liquid-repellent film is not particularly limited, and for example, SCA (silane coupling agent) film and those described in Japanese Patent No. 4424954 can also be used. Note that a film that has water repellency in particular is called a water-repellent film.

[0062] Alternatively, a silicone material may be plasma-polymerized to form a base film, and then the liquid-repellent film may be formed on the base film. By using such a base film, the silicone material of the nozzle plate and the liquid-repellent film can be made to blend well with each other.

[0063] The liquid-repellent film has a thickness of preferably 1 nm or more and 30 nm or less, more preferably 1 nm or more and 20 nm or less, and even more preferably 1 nm or more and 15 nm or less. By being in the above range, the nozzle surface tends to have better liquid repellency, the deterioration of the film is relatively slow, and the liquid repellency can be maintained for a longer period of time. In addition, the film is easier to form in terms of cost.

[0064] In the ink supply mechanism, an ink supply unit 61 is provided for each recording head 6, and supplies an ink composition to the recording head 6. As an example, the ink supply unit 61 has a tank 62 for storing the ink composition, a supply flow path 63 connecting the tank 62 to a reservoir 602 of the recording head 6, a liquid feed pump 64 provided in the supply flow path 63, and a recovery flow path 65 connecting the reservoir 602 of the recording head 6 to the tank 62. In this way, a circulation path 66 is formed in which the ink flows through the tank 62, the supply flow path 63, the reservoir 602 of the recording head 6, the recovery flow path 65, and the tank 62 in this order. Therefore, the ink circulates through the circulation path 66 by rotating the liquid feed pump 64 in the forward direction. That is, the ink stored in the tank 62 is supplied to the recording head 6 through the supply flow path 63 (outward path) by the liquid feed pump 64, and is recovered from the recording head 6 to the tank 62 through the recovery flow path 65 (return path).

[0065] Furthermore, the ink supply unit 61 has an ink supply mechanism 67 that supplies ink to the tank 62, and a pressure adjustment mechanism 68 that adjusts the pressure inside the tank 62. The ink supply mechanism 67 has a replaceable or refillable ink reservoir 671 such as an ink cartridge or an ink pack, a supply flow path 672 (supply pipe) that connects the ink reservoir 671 and the tank 62, and a supply pump 673 provided in the supply flow path 672. When the supply pump 673 rotates in the forward direction, the ink composition inside the ink reservoir 671 is supplied to the tank 62 via the supply flow path 672.

[0066] The recording head 6 may be a line head that performs recording by a line method, or a serial head that performs recording by a serial method.

[0067] In the line method using a line head, for example, an inkjet head having a width equal to or greater than the recording width of the recording medium is fixed to the recording device. Then, the recording medium is moved in the sub-scanning direction (the vertical direction of the recording medium, the transport direction), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement, thereby recording an image on the recording medium.

[0068] In the serial method using a serial head, for example, an inkjet head is mounted on a carriage that can move in the width direction of the recording medium. The carriage is then moved along the main scanning direction (the lateral direction or width direction of the recording medium), and ink droplets are ejected from the nozzle openings of the head in conjunction with this movement, thereby recording an image on the recording medium.

[0069] 1.2.Pressurized cleaning mechanism The pressurized cleaning mechanism applies pressure to the inside of the recording head to perform pressurized cleaning to discharge the ink composition from the nozzle. The pressurized cleaning mechanism continuously discharges the ink composition. This allows for better cleaning performance than intermittent discharge of the ink composition as droplets. In addition, since the applied pressure is easy to adjust, it is preferable to have a pressure adjustment mechanism 68 separate from the ink composition discharge mechanism used in the normal recording process, such as the cavity 603. In the pressurized cleaning, it is preferable to apply a pressure higher than that of the discharge mechanism when forming an image. By applying a pressure higher than that when ejecting the ink, it is possible to improve the cleaning performance. The pressurized cleaning mechanism described below is an example, and is not limited to the following.

[0070] The pressure adjustment mechanism 68 has a pressurizing path (pressurizing piping) 681 that connects the pressurized buffer tank 81 and the tank 62, and a three-way valve 682 that is provided in the pressurizing path 681. The three-way valve 682 operates to adjust the pressure in the tank 62. That is, the three-way valve 682 has a function of switching between a path from the pressurized buffer tank 81 to the tank 62 and a path that introduces the atmosphere into the tank 62, and each path can be selected. For example, when the path is switched from the pressurized buffer tank 81 to the tank 62, the pressure in the tank 62 is increased by the pressurized buffer tank 81. Conversely, when the path is switched to the path that introduces the atmosphere into the tank 62, the inside of the tank 62 is opened to the atmosphere and returned to atmospheric pressure.

[0071] In the pressurized cleaning, the recording head 6 is positioned above the maintenance unit 55. Then, the rotation speed of the liquid supply pump 64 is accelerated in the forward direction to a constant pressurized speed. This pressurized speed is faster than the normal speed during the recording operation. Then, the maintenance unit 55 caps the nozzle forming surface 600, and the tank 62 is pressurized by the pressurized buffer tank 81, which pressurizes the nozzle 601 from the tank 62 via the recovery flow path 65. After that, the capping is released, and the ink in the nozzle 601 is ejected to the maintenance unit 55. Also, air bubbles and the like in the nozzle 601 are discharged from the nozzle 601 along with the ink ejected from the nozzle 601.

[0072] 1.3. Wipe cleaning mechanism The inkjet recording apparatus of this embodiment may further include a wipe-cleaning mechanism that wipes the nozzle forming surface with an absorbent member. This allows ink discharged from the nozzles 601 and attached to the nozzle forming surface 600 to be wiped off by pressure cleaning or recording operation. This makes it possible to suppress ejection defects caused by the ink composition attached to the nozzle forming surface. Since the absorbent member absorbs the ink composition, the ink composition is less likely to be pushed back into the nozzles when wiping it off, making it possible to improve cleaning properties.

[0073] An outline of the wiping cleaning mechanism is shown in Fig. 2. The wiping cleaning mechanism has an absorbent member 701, a drive mechanism 702 that moves the absorbent member 701 along the nozzle forming surface 600, and a cleaning liquid supply pipe 73 that sprays cleaning liquid as necessary.

[0074] The driving mechanism 702 moves at least one of the absorbent member and the recording head 6 relative to the other, and performs a cleaning operation in which the absorbent member removes the ink composition adhering to the nozzle formation surface.

[0075] The absorbent member 701 is not particularly limited, but examples thereof include fabric, sponge, and the like. Among these, fabric is preferable. Fabric is flexible, and ink adhering to the nozzle surface is easier to wipe off, particularly when a nozzle plate cover is provided. In addition, the fabric is not particularly limited, but examples thereof include fabrics made of cotton, cupra, polyester, polyethylene, polypropylene, lyocell, rayon, and the like. It is also preferable to use nonwoven fabric made of these fibers.

[0076] It is preferable that the absorbent member 701 is impregnated with a cleaning liquid. By using the cleaning liquid, the ink composition attached to the nozzle forming surface 600 tends to be more easily removed. In addition, the pigment particles tend to move from the surface of the absorbent member to the inside, and the resin particles tend not to remain on the surface of the absorbent member. This is particularly effective when the absorbent member contains resin particles with a glass transition temperature of -30 to 50°C. Resin particles with a glass transition temperature of -30 to 50°C may melt due to frictional heat generated between the absorbent member and the nozzle forming surface when wiping, and may adhere to the nozzle forming surface. However, by impregnating the absorbent member with a cleaning liquid, it is possible to effectively suppress the adhesion of such resin particles.

[0077] The cleaning liquid preferably contains a water-soluble organic solvent or water used in the ink composition, a surfactant, etc. This allows the resin particles to be more easily absorbed into the absorbing member. The impregnation liquid is not particularly limited as long as it can move the inorganic pigment particles from the surface of the absorbing member to the inside.

[0078] The water-soluble organic solvent contained in the cleaning solution is not particularly limited, and examples thereof include glycerin; glycols such as ethylene glycol, triethylene glycol, propylene glycol, tripropylene glycol, propanediol, butanediol, pentanediol, and hexylene glycol; and lower alkyl ethers of glycols such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether.

[0079] The content of the water-soluble organic solvent is preferably 1 to 10 mass %, more preferably 3 to 7 mass %, based on the total amount of the cleaning liquid. The content of water is preferably 85 to 99 mass %, more preferably 90 to 98 mass %, based on the total amount of the cleaning liquid. By having the contents of the water-soluble organic solvent and water within the above ranges, respectively, cleaning properties tend to be further improved.

[0080] The surfactant contained in the cleaning liquid is not particularly limited, but may be, for example, the same as those exemplified in the ink composition. The content of the surfactant is preferably 0.05 to 1.0 mass % based on the total amount of the cleaning liquid.

[0081] The ratio of the surface tension S2 of the cleaning liquid to the surface tension S1 of the ink composition is preferably 0.75 to 1.25, more preferably 0.9 to 1.25, and even more preferably 1.1 to 1.25. When the surface tension ratio is within the above range, the ink composition and the cleaning liquid tend to become more compatible with each other, and cleaning properties tend to be further improved.

[0082] The surface tension S1 of the ink composition is preferably 20 to 40 mN / m, and more preferably 25 to 35 mN / m. When the surface tension S1 is within the above range, the cleaning properties tend to be further improved.

[0083] The surface tension S2 of the cleaning liquid is preferably 25 to 50 mN / m, and more preferably 30 to 42 mN / m. When the surface tension S2 is within the above range, the cleaning properties tend to be further improved.

[0084] Both surface tensions S1 and S2 are surface tensions at 25° C. The surface tensions can be measured by the method described in the Examples.

[0085] Furthermore, the contact angle C2 of the cleaning liquid with respect to the nozzle surface is preferably 1.1 to 2.0 times, more preferably 1.3 to 1.7 times, and even more preferably 1.5 to 1.7 times, the contact angle C1 of the ink composition with respect to the nozzle surface. When the contact angle ratio is within the above range, resin particles are less likely to remain on the nozzle surface, and cleaning properties tend to be further improved.

[0086] The contact angle C1 of the ink composition is preferably 50 to 80°, more preferably 55 to 75°, and even more preferably 60 to 70°. When the contact angle C1 is within the above range, resin particles are less likely to remain on the nozzle formation surface, and cleaning properties tend to be further improved.

[0087] The contact angle C2 of the cleaning liquid is preferably 80 to 130°, more preferably 90 to 120°, and further preferably 100 to 110°. When the contact angle C2 is within the above range, the cleaning property tends to be further improved.

[0088] Both of the contact angles C1 and C2 are contact angles at 25° C. The contact angles can be measured by the method described in the Examples.

[0089] The surface tensions S1 and S2 and the contact angles C1 and C2 can be appropriately adjusted depending on the type and amount of the surfactant contained in the ink composition and the cleaning liquid, and the type and amount of the organic solvent used.

[0090] 2. Maintenance Method The maintenance method of the present embodiment is a maintenance method for the inkjet recording device using the ink composition, and includes a pressurized cleaning step of applying pressure to the inside of the recording head to eject the ink composition from the nozzles, thereby making it possible to further improve clogging prevention reliability and cleaning performance even when an ink composition having abrasion fastness and washing fastness is used.

[0091] Furthermore, the maintenance method of this embodiment may include a wiping-cleaning step of wiping the nozzle forming surface with an absorbent member before or after the pressure cleaning, thereby making it possible to remove the ink composition that has adhered to the nozzle forming surface during the pressure cleaning step or the recording step. EXAMPLES

[0092] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0093] 1. Preparation of Ink Composition Each component was placed in a mixing tank, mixed and stirred, and filtered through a membrane filter with a pore size of 5 μm to obtain the ink composition of each example, as shown in Table 1. The numerical values ​​of each component shown in each example in the table represent mass % unless otherwise specified. In addition, in the table, the numerical values ​​of the pigment dispersion and the resin particles represent mass % of the solid content.

[0094] [Table 1]

[0095] [Table 2]

[0096] The abbreviations and product ingredients used in the table are as follows:

[0097] [Pigment Dispersion] Cyan Pigment: The pigment dispersion used was prepared by mixing 65 parts of CI Pigment Blue 15:3 with 35 parts of Joncryl 611 (product name: manufactured by BASF Japan Ltd.), a styrene-acrylic acid-based dispersion resin, 1.70 parts of potassium hydroxide, and 250 parts of ultrapure water purified by ion exchange and reverse osmosis, dispersing the mixture in a ball mill using zirconia beads for 10 hours, filtering the mixture through glass fiber filter paper GA-100 (product name: manufactured by Advantec Toyo Co., Ltd.) to remove coarse particles, and adjusting the pigment concentration to 15% by mass. [Resin particles] Resin particle A (Takelac WS-6021, manufactured by Mitsui Chemicals, self-crosslinking group: yes, glass transition temperature 40°C) Resin particles B (Takelac W-6110, manufactured by Mitsui Chemicals, self-crosslinking group: none, glass transition temperature -20°C) Resin particles C (Takelac W-605, manufactured by Mitsui Chemicals, self-crosslinking group: none, glass transition temperature 100°C) [Organic solvents with normal boiling points of 280°C or higher] Glycerin [Polyhydric alcohols that are solid at room temperature] Trimethylolpropane Trehalose [Betaine] Trimethylglycine (betaine anhydrous, manufactured by Tokyo Chemical Industry Co., Ltd.) [Organic alkali] 2-Aminoethanol [Inorganic alkali] Potassium hydroxide [Surfactant] Surfactant A (BYK348, BYK, silicone surfactant) Surfactant B (Surfynol 465, product name of Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant)

[0098] In the table, "ratio of organic alkali and inorganic alkali to the total amount of polyhydric alcohol and betaine in the room temperature solid" represents the ratio of the total mass of organic alkali and inorganic alkali to the total mass of polyhydric alcohol and betaine in the room temperature solid. In the table, "ratio of resin particles to the total amount of polyhydric alcohol and betaine in the room temperature solid" represents the ratio of the total mass of resin particles to the total mass of polyhydric alcohol and betaine in the room temperature solid.

[0099] 1.1. Surface tension and surface tension ratio The surface tensions shown in the table were measured by the Wilhelmy method using a surface tensiometer (such as the CBVP-Z surface tensiometer manufactured by Kyowa Interface Science Co., Ltd.) at a liquid temperature of 25° C. The surface tension ratio (S2 / S1) was calculated from the surface tension S1 of the ink composition and the surface tension S2 of the cleaning liquid.

[0100] 1.2. Contact angle and contact angle ratio The contact angles listed in the table were measured at 25°C using a portable contact angle meter PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.). The nozzle formation surface used when measuring the contact angles was a silicon nozzle plate with a water-repellent film made of single crystal silicon. A silicon oxide film (SiO2 film) was formed by the chemical vapor deposition (CVD) method on the surface of the plate on the ink ejection side by introducing SiCl4 and water vapor into a CVD reactor. The thickness of the SiO2 film was 50 nm. Further oxygen plasma treatment was performed, and then the nozzle was heated to 300°C for 10 min. The ... 17 A water-repellent film was formed on the SiO2 film by chemical vapor deposition (CVD) using C2H4SiCl3, to obtain a silicon nozzle plate with a water-repellent film. The contact angle ratio (C2 / C1) was calculated from the contact angle C1 of the ink composition and the contact angle C2 of the cleaning solution.

[0101] 2. Preparation of Washing Solutions The cleaning solution shown in the table was prepared by mixing 5% by mass of glycerin, 0.1% by mass of Surfynol 465, and 94.9% by mass of water.

[0102] 3. Inkjet recording device An inkjet recording device equipped with a pressure cleaning mechanism and a wiping cleaning mechanism was prepared. Specifically, an inkjet recording device using an absorbent member impregnated with a cleaning liquid as the wiping cleaning mechanism, an inkjet recording device using an absorbent member impregnated with water as the wiping cleaning mechanism, and an inkjet recording device equipped with a rubber wiping blade instead of an absorbent member as the wiping cleaning mechanism were prepared. In addition, as Reference Example 1, an inkjet recording device having a reduced pressure cleaning mechanism instead of a pressure cleaning mechanism was prepared. Note that the table describes the configuration of the inkjet recording device used in each example.

[0103] 4. Evaluation Methodology 4.1. Evaluation of clogging resistance For each ink composition listed in Table 1, printing was performed continuously for one hour using SC-F2000 under the condition of a fabric surface temperature of 25°C (normal temperature), and after printing, one nozzle row (360 nozzles) was inspected for ejection abnormalities (non-ejection). Note that all nozzles were in a normal state before recording began, and evaluation was performed based on the following criteria. A: The number of nozzles with abnormal discharge is 0. B: The number of nozzles with abnormal discharge is 1 to 5. C: The number of nozzles with abnormal discharge is 6 or more.

[0104] 4.2.Cleaning ability (cleaning ability) evaluation Each ink composition was filled into all the rows of the head of an inkjet printer ("PX-S840" manufactured by Seiko Epson Corporation), and it was confirmed that all the rows were ejected normally. Thereafter, the print head was shifted from the standby position and stopped in the printing area, and left for 3 days in a 40°C, 20% RH environment. After being left as it was, the print head was returned to the standby position, and a pressurized cleaning operation was performed, and then a wiping operation was performed. A cotton nonwoven fabric was used as the absorbing member used for wiping. This was considered as a series of cleaning operations, and the number of cleanings required until ejection was restored was counted. The inkjet printer used for the evaluation was one that had been modified to include the above-mentioned pressurized cleaning mechanism and wiping cleaning mechanism. A: All nozzles were restored after three cleanings or less. B: All nozzles recovered after 4 to 10 cleanings. C: No recovery even after 11 cleanings

[0105] 4.3. Evaluation of friction durability The ink composition prepared above was applied to a cotton fabric by an inkjet method using an inkjet printer (manufactured by Seiko Epson Corporation, product name "PX-G930"). The recording conditions were a recording resolution of 1440 dpi x 720 dpi, a recording range of A4 size, and four solid pattern images were overlaid. In this way, inkjet printing was performed. Here, "solid pattern image" means an image in which dots are recorded in all pixels, which are the minimum recording unit area defined by the recording resolution.

[0106] Thereafter, the ink composition was fixed to the recording medium by performing a heat treatment at 165° C. for 5 minutes using a heat press machine. In this manner, a printed item in which an image was formed on the recording medium (ink was printed) was produced.

[0107] The printed fabrics of each example were subjected to a color fastness test against rubbing using a type I (crock meter) tester in accordance with the method specified in ISO-105 X12. Dry rubbing was tested according to the dry test specified in ISO-105 X12 and evaluated using a staining gray scale. The evaluation criteria were as follows: A: Abrasion resistance is grade 4 or higher. B: Friction fastness is between grade 2 and grade 4 C: Friction fastness is less than grade 2

[0108] 4.4. Washing fastness evaluation A washing fastness test was carried out on each printed fabric in accordance with the A-2 method of JIS L 0844 (test method for color fastness to washing). Specifically, after washing, rinsing, spin-drying, and drying, the discoloration of the printed part of the test piece was judged. Discoloration was evaluated based on the degree of discoloration according to the JIS L0804:2004 (ISO 105-A02:1993) discoloration gray scale, and the following criteria were used to evaluate the degree of discoloration. A: Washing fastness is grade 4 or higher. B: Washing fastness is grade 2 or higher but less than grade 4. C: Washing fastness is less than grade 2.

[0109] 4.5.Texture The feel of each printed material was evaluated. A: The feel of the printed item is almost unchanged compared to the original fabric. B: The texture of the printed item feels a little stiffer than the original fabric. C: The print feels harder than the original fabric. D: The feel of the printed item is clearly harder than that of the original fabric.

[0110] 3. Evaluation results The composition of the ink composition used in each example, the configuration of the inkjet recording device, and the evaluation results are shown in Table 1. It can be seen from the table that by using an ink composition containing resin particles having a glass transition temperature of -30 to 50°C, an organic solvent having a normal boiling point of 280°C or higher, at least one of an organic alkali and an inorganic alkali, and at least one of betaine and a polyhydric alcohol that is solid at room temperature, in an inkjet recording device having a pressurized cleaning mechanism, it is possible to provide recorded matter having excellent resistance to friction while ensuring good cleaning properties (ability to recover from clogging).

[0111] In detail, when comparing each of the Examples with Comparative Examples 1 and 2, it can be seen that by using resin particles having a glass transition temperature of -30 to 50°C, the obtained recorded matter has excellent friction fastness, washing fastness, and texture.

[0112] In addition, when comparing each Example with Comparative Example 3, it is found that the use of an organic solvent having a normal boiling point of 280° C. or more results in excellent clogging resistance and cleaning properties. Furthermore, when comparing each Example with Comparative Examples 4 and 5, it is found that the combined use of at least one of an organic alkali and an inorganic alkali, or at least one of betaine and a polyhydric alcohol that is solid at room temperature results in excellent clogging resistance and cleaning properties. In particular, it is found that the absence of any of an organic solvent having a normal boiling point of 280° C. or more, at least one of an organic alkali and an inorganic alkali, and at least one of betaine and a polyhydric alcohol that is solid at room temperature reduces clogging resistance and cleaning properties.

[0113] Furthermore, according to Reference Example 1, by adopting reduced pressure cleaning, no problems occurred in terms of cleaning performance, but the cleaning time was longer than when pressurized cleaning was adopted. This longer cleaning time includes the time required to remove air bubbles in the ink composition induced by reduced pressure cleaning that adhere to the nozzle formation surface. Furthermore, when the cleaning performance evaluation was repeatedly performed, the occurrence of nozzle missing due to cleaning was also observed.

[0114] Furthermore, when Examples 1 to 3 are compared, it is found that the cleaning ability is further improved by impregnating the absorbing member with the cleaning liquid. [Explanation of symbols]

[0115] 6... recording head, 55... maintenance unit, 61... ink supply section, 62... tank, 63... supply flow path, 64... liquid delivery pump, 65... recovery flow path, 66... ​​circulation path, 67... ink supply mechanism, 68... pressure adjustment mechanism, 73... cleaning liquid supply pipe, 81... pressurized buffer tank, 600... nozzle formation surface, 601... nozzle, 602... reservoir, 603... cavity, 671... ink storage body, 672... supply flow path, 673... supply pump, 681... pressurized path, 682... three-way valve, 701... absorbent member, 702... drive mechanism

Claims

1. a recording head having a nozzle for ejecting an ink composition and a nozzle forming surface having an ejection port of the nozzle; a pressure cleaning mechanism that applies pressure to the inside of the recording head to perform a cleaning operation of discharging the ink composition from the nozzles; a wipe-cleaning mechanism that wipes the nozzle forming surface with an absorbent member, the ink composition contains resin particles, an organic solvent having a normal boiling point of 280° C. or higher, at least one of an organic alkali and an inorganic alkali, and at least one of betaine and a polyhydric alcohol that is solid at room temperature; The glass transition temperature of the resin particles is −30 to 50° C., The absorbent member is impregnated with a cleaning liquid, a ratio of a surface tension of the cleaning liquid to a surface tension of the ink composition is 1.1 to 1.25; a total content of the organic alkali and the inorganic alkali is 0.10 or more in terms of mass ratio to a total content of the polyhydric alcohol and the betaine; The content of the resin particles is 1.0 to 2.0 in terms of mass ratio with respect to the total amount of the polyhydric alcohol and the betaine. Inkjet recording device.

2. The resin particles contain a crosslinkable group. The inkjet recording apparatus according to claim 1 .

3. The resin particles include urethane resin particles.

3. The inkjet recording apparatus according to claim 1 or 2.

4. The content of the resin particles is 3.0 to 8.0% by mass with respect to the total amount of the ink composition. The inkjet recording apparatus according to any one of claims 1 to 3.

5. The total content of the organic alkali and the inorganic alkali is 0.10 to 0.60 in terms of mass ratio relative to the total content of the polyhydric alcohol and the betaine. The inkjet recording apparatus according to any one of claims 1 to 4.

6. a contact angle of the cleaning liquid with respect to the nozzle forming surface is 1.3 to 1.7 times a contact angle of the ink composition with respect to the nozzle forming surface; The inkjet recording apparatus according to any one of claims 1 to 5.

7. A maintenance method for the inkjet recording apparatus according to any one of claims 1 to 6, comprising the steps of: a pressure cleaning step of applying pressure to the inside of the recording head and discharging the ink composition from the nozzles; Maintenance methods.

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