Inkjet recording apparatus and maintenance method

Abstract

To provide an inkjet recording device that can achieve both a recording matter excellent in friction fastness and excellent water repellency / durability (nozzle durability).SOLUTION: An inkjet recording device according to the present invention comprises: a recording head which has a nozzle that discharges an ink composition and a nozzle formation surface having a discharge port of the nozzle; a cleaning mechanism that performs cleaning operation of making the nozzle discharge the ink composition; and a wiping / cleaning mechanism that wipes the nozzle formation surface with an absorption member including cellulose. The ink composition contains pigment, cross-linking component, a surfactant and water. A contact angle of the ink composition relative to the nozzle formation surface is 50° or more, and the cleaning mechanism performs pressure-cleaning in which pressure is applied to the inside of the recording head to perform cleaning.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Inkjet recording apparatuses are relatively simple devices that are capable of recording high-resolution images, and have been rapidly developing in various fields. In the midst of this, various investigations have been conducted into cleaning methods for inkjet recording apparatuses.

[0003] For example, Patent Document 1 describes a method for cleaning the nozzle surface of a recording head, in which an absorbent sheet is pressed against the nozzle surface to remove droplets adhering to the nozzle surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-188858 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the cleaning method described in Patent Document 1, when an ink composition containing a crosslinkable component for improving abrasion resistance is used, the liquid repellency durability (nozzle durability) of the nozzle formation surface of the inkjet head may decrease. Therefore, there is a demand for providing recorded matter with excellent abrasion resistance and good liquid repellency durability (nozzle durability) at the same time. [Means for solving the problem]

[0006] One aspect of the inkjet recording apparatus according to the present invention is a recording head having nozzles for ejecting an ink composition and a nozzle forming surface having ejection openings for the nozzles; a cleaning mechanism that performs a cleaning operation to discharge the ink composition from the nozzle; a wiping cleaning mechanism that wipes the nozzle forming surface with an absorbent member containing cellulose, the ink composition contains a pigment, a crosslinkable component, a surfactant, and water; the contact angle of the ink composition with respect to the nozzle forming surface is 50° or more; The cleaning mechanism is a pressure cleaning mechanism that applies pressure to the inside of the recording head to perform cleaning.

[0007] One aspect of the maintenance method according to the present invention is to A maintenance method for the inkjet recording apparatus of the above aspect, comprising: a cleaning step of performing pressure cleaning by applying pressure to the inside of the recording head to discharge the ink composition from the nozzles; and a wiping and cleaning step of wiping the nozzle forming surface with the absorbing member containing cellulose. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram schematically illustrating an inkjet recording apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram schematically illustrating an example of the configuration of a print head, an ink supply mechanism, and pressure cleaning. [Figure 3] FIG. 2 is a schematic view showing a nozzle formation surface of the inkjet recording apparatus according to the present embodiment. [Figure 4] FIG. 2 is a diagram schematically illustrating an example of the configuration of a wiping cleaning mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described. The embodiments described below are examples of the present invention. The present invention is not limited to the following embodiments, and includes various modified forms that are implemented within the scope of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0010] 1. Inkjet recording device An inkjet recording apparatus according to one embodiment of the present invention comprises a recording head having nozzles for ejecting an ink composition and a nozzle forming surface having ejection openings for the nozzles; a cleaning mechanism for performing a cleaning operation to eject the ink composition from the nozzles; and a wiping cleaning mechanism for wiping the nozzle forming surface with an absorbent member containing cellulose, wherein the ink composition contains a pigment, a crosslinkable component, a surfactant, and water, and the contact angle of the ink composition with respect to the nozzle forming surface is 50° or greater, and the cleaning mechanism is a pressure cleaning mechanism that applies pressure to the inside of the recording head to perform cleaning.

[0011] In an inkjet recording apparatus that ejects an ink composition from nozzles, the recording head is periodically cleaned to ensure stable ejection of the ink composition. Examples of such cleaning include a cleaning method that forcibly ejects the ink composition from the nozzles, and a wiping cleaning method that wipes the nozzle surface with an absorbing member to remove ink droplets remaining on the nozzle surface after the ejection.

[0012] However, when the ink composition used in the inkjet recording device contains a pigment and / or a crosslinkable component that exhibits reactivity with OH groups in the resin or recording medium in order to improve the abrasion resistance of the recorded matter, cleaning the recording head can sometimes reduce the durability of the liquid repellency of the nozzle formation surface, making it impossible to ensure good ejection stability.

[0013] It has been confirmed that such a decrease in the durability of the liquid repellency of the nozzle-forming surface is caused by physical and chemical damage to the nozzle-forming surface when the ink composition described above is used. That is, it is believed that the nozzle-forming surface is damaged when the pigment contained in the ink composition is rubbed against the nozzle-forming surface during wipe-cleaning, in which the nozzle-forming surface is wiped with an absorbing member. It is also believed that the chemical composition of the nozzle-forming surface changes when the nozzle-forming surface reacts with the crosslinkable component in the ink composition that remains on the nozzle-forming surface.

[0014] Therefore, in ink compositions containing pigments and crosslinkable components, improving the friction resistance of recorded material and maintaining the durability of the liquid repellency of the nozzle formation surface of the recording head are in a contradictory relationship, and achieving both friction resistance and durability of the liquid repellency has been a challenge.

[0015] In contrast, the inkjet recording apparatus according to this embodiment sets the contact angle of the ink composition with the nozzle-forming surface at a certain level or greater and uses a wipe-off cleaning method in which the ink droplets are wiped off with an absorbent member containing cellulose. This reduces physical damage to the nozzle-forming surface and also reduces the likelihood of ink droplets remaining on the nozzle-forming surface, thereby reducing chemical damage to the nozzle-forming surface caused by the crosslinkable components in the ink droplets reacting with the nozzle-forming surface. Furthermore, pressurized cleaning, a cleaning method that forcibly ejects the ink composition from the nozzles, prevents the ink composition from being suddenly ejected from the nozzles, further reducing physical damage to the nozzle-forming surface. Therefore, even when the ink composition used in the inkjet recording apparatus contains a pigment or a crosslinkable component, it is possible to reduce physical and chemical damage to the nozzle-forming surface when cleaning the recording head, thereby achieving both friction resistance and durability of liquid-repellent properties. In this specification, "liquid-repellent properties" refers to the property or ability of a solid (nozzle-forming surface) and a liquid (ink composition) to have a large contact angle and thus be less likely to wet.

[0016] An example of the configuration of the inkjet recording apparatus according to this embodiment, and an ink composition (hereinafter simply referred to as "ink composition") used in the inkjet recording apparatus according to this embodiment will be described in detail below.

[0017] 1.1.Device configuration Fig. 1 is a diagram schematically illustrating an inkjet recording apparatus according to this embodiment. As shown in Fig. 1, the inkjet recording apparatus 1 has a recording head 6 for ejecting an ink composition, a maintenance unit 55, and a pressure cleaning device (not shown). In other words, the inkjet recording apparatus 1 shown in Fig. 1 is a configuration in which the maintenance unit 55 and the pressure cleaning device are incorporated into the configuration of a known inkjet printer.

[0018] 1.1.1. Recording head Fig. 2 is a diagram schematically illustrating an example of the configuration of a recording head 6 and an ink supply unit 61 that supplies an ink composition (described later) to the recording head 6. As shown in Fig. 2, the recording head 6 has a nozzle 601 that ejects the ink composition and a nozzle forming surface 600 that has an ejection port 606 (not shown) of the nozzle.

[0019] The recording head 6 has a nozzle 601 opening in a nozzle forming surface 600, a reservoir 602 that temporarily stores an ink composition, and a cavity 603 that connects the nozzle 601 and the reservoir 602, and the ink composition is supplied from the reservoir 602 to the nozzle 601 via the cavity 603. During recording, the cavity 603 applies pressure to the ink composition, causing the ink composition to be ejected from the nozzle 601.

[0020] 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, each ink supply unit 61 includes 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 composition 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, when the liquid feed pump 64 rotates in the forward direction, the ink composition circulates through the circulation path 66. In other words, the ink composition stored in the tank 62 is supplied by the liquid feed pump 64 to the recording head 6 via the supply flow path 63 (outward path) and recovered from the recording head 6 to the tank 62 via the recovery flow path 65 (return path).

[0021] Furthermore, the ink supply unit 61 has an ink refill mechanism 67 that refills the ink composition into the tank 62, and a pressure adjustment mechanism 68 that adjusts the pressure inside the tank 62. The ink refill mechanism 67 has a replaceable or refillable ink reservoir 671 such as an ink cartridge or an ink pack, a refill flow path 672 (refill pipe) that connects the ink reservoir 671 and the tank 62, and a refill pump 673 provided in the refill flow path 672. When the refill pump 673 rotates in the forward direction, the ink composition inside the ink reservoir 671 is refilled into the tank 62 via the refill flow path 672.

[0022] 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.

[0023] 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. The recording medium is then moved in the sub-scanning direction (the longitudinal 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.

[0024] In the serial method using a serial head, for example, the inkjet head is mounted on a carriage that can move in the width direction of the recording medium. The carriage is then moved in the main scanning direction (the lateral or width direction of the recording medium), 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.

[0025] 1.1.2.Nozzle forming surface 3 is a schematic diagram showing a nozzle forming surface 600 when the recording head 6 is viewed from the recording medium P side. As shown in FIG. 3, the nozzle forming surface 600 is provided with a plurality of nozzle outlets 606 that eject the ink composition. A plurality of outlets 606 are arranged in a predetermined direction to form a nozzle row 604. As shown in FIG. 3, the nozzle forming surface 600 may be provided with a plurality of nozzle rows 604.

[0026] The nozzle-forming surface 600 may contain a fluorine compound bonded via a hydrolyzable bond. This can further improve the liquid repellency of the nozzle-forming surface 600, making it easier to adjust the contact angle of the ink composition (described later) with respect to the nozzle-forming surface 600 to a certain range or greater, and also tends to improve ejection stability. On the other hand, if the nozzle-forming surface 600 contains a fluorine compound bonded via a hydrolyzable bond, the hydrolyzable bond may react with a crosslinking component contained in the ink composition when cleaved by hydrolysis. Such a reaction may change the chemical composition on the nozzle-forming surface 600, thereby affecting the durability of the liquid repellency and the ejection stability. However, with the inkjet recording apparatus according to this embodiment, the contact angle of the ink composition with respect to the nozzle-forming surface is set to a certain range or greater, and wipe-cleaning is performed using a cellulose-containing absorbent member, followed by pressurized cleaning, thereby ensuring the durability of the liquid repellency and the ejection stability.

[0027] In the present invention, the term "fluorine compound bonded via a hydrolyzable bond" refers to a compound having a long-chain polymer group containing fluorine bonded to the surface of the nozzle-forming surface 600 by a bond that can undergo a hydrolysis reaction. Such a hydrolyzable bond is formed, for example, by a dehydration condensation reaction between a compound in which a hydroxy group is directly bonded to a metal atom, which is generated by hydrolysis of an alkoxy group in a metal alkoxide, and the hydroxyl groups on the surface of the nozzle-forming surface 600. Specifically, when the metal alkoxide is a silane coupling agent or the like, the alkoxy group on the silicon atom is hydrolyzed to generate silanol (Si-OH), which then undergoes a dehydration condensation reaction with the hydroxyl groups on the surface of the nozzle-forming surface 600 to form a hydrolyzable bond (Si-O bond).

[0028] One method for applying a "fluorine compound bonded via a hydrolyzable bond" to the nozzle-forming surface 600 is to form a molecular film of a metal alkoxide having a long-chain polymer group containing fluorine, followed by a drying process, an annealing process, etc. The film thus formed on the nozzle-forming surface 600 from a fluorine compound bonded via a hydrolyzable bond is also referred to below as a liquid-repellent film.

[0029] The metal alkoxide is not particularly limited, but examples of the metal species commonly used include silicon, titanium, aluminum, and zirconium. Examples of the fluorine-containing long-chain polymer group include perfluoroalkyl chains and perfluoropolyether chains. Examples of the alkoxysilane having this fluorine-containing long-chain polymer group include silane coupling agents having a fluorine-containing long-chain polymer group. The liquid-repellent film is not particularly limited, and examples include SCA (silane coupling agent) films and those described in Japanese Patent Publication No. 4424954.

[0030] The liquid-repellent film can be formed on a conductive film formed on the substrate (nozzle plate) on which the nozzles are formed, or it can be formed on a base film (PPSi (Plasma Polymerized Silicone) film) formed first by plasma polymerizing a silicon material. The use of this base film allows the silicon material of the nozzle plate and the liquid-repellent film to blend together.

[0031] The thickness of the liquid-repellent film is preferably 1 nm or more and 30 nm or less, more preferably 1 nm or more and 20 nm or less, and particularly preferably 1 nm or more and 15 nm or less. When the thickness of the liquid-repellent film is within the above range, the nozzle forming surface 600 tends to have better liquid repellency, the film deteriorates relatively slowly, 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.

[0032] The nozzle forming surface 600 may be provided with a nozzle plate cover 605 that covers at least a portion of the nozzle forming surface 600. In the example of Fig. 3, the nozzle plate cover 605 is provided so as to surround all of the nozzle rows 604 (discharge ports 606). The nozzle plate cover 605 is provided to fulfill at least one of the following roles: fixing a plurality of nozzle chips (hereinafter simply referred to as "chips") in the nozzle forming surface 600 of the head formed by combining the chips; and preventing the recording medium from floating up and coming into direct contact with the nozzles.

[0033] 1.1.3.Pressure cleaning The inkjet recording apparatus according to this embodiment is equipped with a pressure cleaning mechanism that applies pressure to the interior of the recording head 6 to perform cleaning, thereby discharging the ink composition from the nozzles 601. Pressure cleaning is a cleaning method in which the ink composition is continuously discharged from the nozzles 601 by pressurizing the interior of the tank 62 that supplies the ink composition to the recording head 6, which ejects the ink composition. In contrast, discharging the ink composition by so-called flushing (blank ejection) is a method in which a drive signal unrelated to recording is applied to a piezoelectric element in the recording head 6, causing the piezoelectric element to deform and pressurize the cavity 603, thereby intermittently discharging the ink composition from the nozzles 601. Therefore, pressure cleaning enables cleaning in which a constant applied pressure is maintained and a large amount of ink composition is continuously discharged.

[0034] Furthermore, pressurized cleaning can further reduce physical damage to the nozzle forming surface 600 compared to reduced-pressure cleaning. Reduced-pressure cleaning is a cleaning method in which the nozzle forming surface 600 is covered with a cap, negative pressure is generated by a suction pump or a negative pressure generating mechanism, and then a valve is opened to reduce the pressure in the covered space, thereby discharging the ink composition from the nozzles 601. In this type of reduced-pressure cleaning, the pressure change in the space is large, particularly immediately after the valve is opened, and the ink composition is suddenly discharged. In contrast, in pressurized cleaning, the pressure in the tank 62 is likely to be kept below a certain level, and the ink composition is less likely to be suddenly discharged. In this way, cleaning by pressurized cleaning can further reduce physical damage to the nozzle forming surface 600, further improve the durability of the liquid repellency of the nozzle forming surface 600, and improve ejection stability.

[0035] 2, the pressure adjustment mechanism 68 has a pressurization path (pressurization piping) 681 that connects a pressurization buffer tank 81 (described later) and the tank 62, and a three-way valve 682 that is provided in the pressurization path 681. The three-way valve 682 is actuated to adjust the pressure inside the tank 62. That is, the three-way valve 682 has a function of switching between a path from the pressurization buffer tank 81 (described later) to the tank 62 and a path that introduces air into the tank 62, and is capable of selecting either path. For example, when the path is switched from the pressurization buffer tank 81 to the tank 62, the positive pressure accumulated in the pressurization buffer tank 81 is applied to the tank 62, increasing the pressure inside the tank 62. Conversely, when the path is switched to the path that introduces air into the tank 62, the inside of the tank 62 is opened to the atmosphere and returned to atmospheric pressure.

[0036] When the positive pressure accumulated in the pressurized buffer tank 81 is applied to the tank 62 to increase the pressure inside the tank 62, the pressure (pressurizing force) inside the tank 62 is preferably 38 kPa or less, more preferably 37 kPa or less, and particularly preferably 36 kPa or less. When the pressure (pressurizing force) inside the tank 62 is within the above range, the ink composition is prevented from being suddenly discharged and physical damage to the nozzle forming surface 600 is further reduced, thereby further improving the durability of the liquid repellency of the nozzle forming surface 600 and improving the ejection stability.

[0037] The pressurized buffer tank 81 has, for example, a cylindrical shape, and is capable of accumulating positive pressure in its internal space. The pressurized buffer tank 81 is connected to the pressurized pump 8 by a positive pressure introduction path (piping) 82. A three-way valve 83 is provided in the positive pressure introduction path 82. The three-way valve 83 has the function of switching between a path from the pressurized buffer tank 81 to the pressurized pump 8 and a path that introduces air into the pressurized pump 8, and is capable of selecting either path. For example, when the path is switched from the pressurized buffer tank 81 to the pressurized pump 8, the pressurized buffer tank 8 is pressurized by the pressurized pump 8, and the pressure in the internal space of the pressurized buffer tank 81 increases. By continuing to drive the pressurized pump 8 and continuing to pressurize, positive pressure accumulates in the pressurized buffer tank 81, and the accumulated positive pressure is stored. On the other hand, when the pressurized pump 8 is switched to a path that introduces air, the pressurized buffer tank 8 stops pressurizing the pressurized buffer tank 81. A pressure sensor 84 is provided to measure the pressure inside the pressurized buffer tank 81.

[0038] One end of a common pressurization path (pipe) 85 is connected to the pressurization buffer tank 81. The other end of this common pressurization path 85 branches into six paths, and each branch path functions as a pressurization path 681. Furthermore, a three-way valve 86 is provided in the common pressurization path 85, and has the function of switching between a path from the pressurization buffer tank 81 to each ink supply unit 61 and a path that releases pressurization from the pressurization buffer tank 81 to the atmosphere, making it possible to select either path. For example, when the path is switched from the pressurization buffer tank 81 to each ink supply unit 61, the positive pressure in the pressurization buffer tank 81 pressurizes each part of each ink supply unit 61. On the other hand, when the path is switched to the path that releases air from the pressurization buffer tank 81 to the atmosphere, the pressurized supply to each ink supply unit 61 by the positive pressure in the pressurization buffer tank 81 is stopped.

[0039] 1.1.4. Wiping Cleaning Mechanism The inkjet recording apparatus according to this embodiment includes a wiping-cleaning mechanism that wipes the nozzle-forming surface 600 with an absorbing member containing cellulose. The wiping-cleaning mechanism moves at least one of the absorbing member 701 and the recording head 6 relative to the other, and removes ink droplets adhering to the nozzle-forming surface 600 with the absorbing member 701. That is, the ink composition that has been ejected from the nozzle orifices 606 and adhered to the nozzle-forming surface 600 by pressure cleaning or a recording operation is wiped away with the absorbing member 701. This reduces the amount of ink composition remaining on the nozzle-forming surface 600, thereby reducing chemical damage to the nozzle-forming surface 600 caused by crosslinking components contained in the ink composition. Therefore, wiping-cleaning can further improve the durability of the liquid repellency of the nozzle-forming surface 600 and improve ejection stability.

[0040] 4 shows an outline of a wiping cleaning mechanism, which is an example of the maintenance unit 55. The wiping cleaning mechanism has an absorbing member 701 and a driving mechanism 702 that moves the absorbing member 701 along the nozzle forming surface 600, and also has a cleaning liquid supply pipe (not shown) that sprays cleaning liquid as needed.

[0041] The absorbing member 701 is not particularly limited as long as it is liquid-absorbent, and examples thereof include fabrics (woven, knitted, nonwoven, etc.), sponges, pulp, etc. Among these, fabrics are preferred. Fabrics are flexible and can more easily wipe off ink adhering to the nozzle-forming surface 600, especially when the nozzle plate cover 605 is provided. The absorbing member 701 used in this embodiment is formed of fibers containing cellulose. More preferably, the absorbing member 701 is formed of fibers made of cellulose. Use of such an absorbing member 701 can reduce physical damage to the nozzle-forming surface 600 compared to wiping with a rubber wiper or the like. Therefore, even in the inkjet recording apparatus according to this embodiment, which uses an ink composition containing a pigment, it is possible to prevent a decrease in the liquid-repellent durability of the nozzle-forming surface 600 and ensure ejection stability.

[0042] The thickness of the absorbing member 701 can be set appropriately as desired, for example, to 0.1 mm or more and 3 mm or less. A thickness of 0.1 mm or more increases the amount of ink composition that can be absorbed, and further reduces the amount of ink composition that remains on the nozzle forming surface 600. A thickness of 3 mm or less results in a compact absorbing member 701, allowing the entire maintenance unit 55 to be miniaturized and making mechanical transport of the absorbing member 701 easier.

[0043] The surface density of the absorbing member 701 is preferably 0.005 g / cm 2 More than 0.15g / cm 2 or less, more preferably 0.02 g / cm 2 More than 0.13g / cm 2 When the amount is within the above range, the ink composition remaining on the nozzle forming surface 600 is more easily absorbed.

[0044] The absorbing member 701 may hold the impregnating liquid described below at the time of shipment. This allows the nozzle-forming surface 600 to be wiped immediately, and eliminates the need for a mechanism for spraying or applying the impregnating liquid to the nozzle-forming surface 600. Here, "holding the impregnating liquid at the time of shipment" refers to a state in which the absorbing member 701 already holds the impregnating liquid when an inkjet recording apparatus equipped with the absorbing member 701 is installed, a state in which the absorbing member 701 already holds the impregnating liquid when the absorbing member 701 is installed in the inkjet recording apparatus, or a state in which a replacement absorbing member 701 holds the impregnating liquid. Here, "installing the inkjet recording apparatus" refers to preparing the inkjet recording apparatus for initial use, and "installing the absorbing member" refers to preparing the absorbing member 701 for initial use. In this embodiment, wiping the nozzle-forming surface 600 using the absorbing member 701 is sufficient as long as at least the nozzle-forming surface 600 is wiped with the absorbing member 701. It is preferable that the wiping remove at least a portion of the deposits adhering to the nozzle-forming surface 600.

[0045] The driving mechanism 702 is a means for moving at least one of the absorbing member 701 and the recording head 6 relative to the other, causing the absorbing member 701 to perform wiping cleaning, which removes deposits from the nozzle forming surface 600. The driving mechanism 702 preferably has a pressing member (not shown) that presses the absorbing member 701 and the nozzle forming surface 600 relatively with a pressure of 50 gf to 500 gf (preferably 75 gf to 300 gf). A pressing force of 50 gf or more improves cleaning performance. Furthermore, even if there is a step between the nozzle plate (not shown) and the nozzle plate cover 605, the mechanism is excellent at preventing ink from adhering or accumulating in the gap, or at removing ink from the gap. Furthermore, a pressing force of 500 gf or less improves the preservation of the liquid-repellent film. The drive mechanism 702 is not particularly limited, but can, for example, press the absorbing member 701 from the side opposite to the side that contacts the nozzle forming surface 600, thereby bringing the absorbing member 701 into contact with the nozzle forming surface 600. Alternatively, the recording head 6 can be driven to bring the absorbing member 701 into contact with the nozzle forming surface 600. Note that the load referred to here is the total sum of loads applied to the nozzle forming surface 600 by the entire drive mechanism 702.

[0046] Furthermore, it is preferable that the driving mechanism 702 moves the absorbing member 701 and the recording head 6 relative to each other at a speed of 0.2 inch / s or more and 1.5 inch / s or less. By keeping the speed within the above range, the durability of the liquid repellency tends to be further improved. The wiping speed is typically about one-fifth to one-twentieth of the speed at which the recording head 6 moves when recording an image, but is not limited to this speed relationship.

[0047] The pressing member is not particularly limited, but is preferably covered with an elastic member, for example. The Shore A hardness of the elastic member is preferably 10 or more and 60 or less, and more preferably 10 or more and 50 or less. This allows the pressing member and absorbing member 701 to bend when pressed, and allows the absorbing member 701 to be pushed deep into the uneven surface of the nozzle forming surface 600. As a result, cleaning performance is further improved.

[0048] 1.1.5. Impregnation solution An impregnating liquid may be used in the inkjet recording apparatus according to this embodiment. The impregnating liquid is supplied to the nozzle-forming surface and / or the absorbing member at least when the wiping-cleaning step described below is performed. Specifically, the impregnating liquid may be supplied to and adhered to the nozzle-forming surface and / or the absorbing member using a known spray device or the like when the wiping-cleaning step is performed, or the impregnating liquid may be held in the absorbing member in advance when the wiping-cleaning step is performed, so that the impregnating liquid adheres to the nozzle-forming surface. When the absorbing member contains the impregnating liquid, the pigment can more easily migrate from the surface to the interior of the absorbing member. This can further reduce physical damage to the nozzle-forming surface, and tends to further improve the durability of the liquid repellency and the ejection stability.

[0049] The amount of the impregnation liquid impregnated into the absorbing member is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 10 parts by mass or more and 120 parts by mass or less, and particularly preferably 30 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the absorbing member. When the amount of impregnation is within this range, the ink composition can easily penetrate into the inside of the absorbing member, and damage to the nozzle surface can be further reduced.

[0050] Components that can be contained in the impregnation liquid will be described below.

[0051] The impregnation liquid preferably contains an organic solvent and / or water, a surfactant, etc. This allows the ink composition described below to be more easily absorbed into the absorbing member. The impregnation liquid is not particularly limited as long as it can move the pigment from the surface of the absorbing member to the inside.

[0052] The organic solvent contained in the impregnation 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.

[0053] The content of the organic solvent is preferably 1 to 10% by mass, more preferably 3 to 7% by mass, based on the total amount of the impregnation liquid. The content of water is preferably 85 to 99% by mass, more preferably 90 to 98% by mass, based on the total amount of the impregnation liquid. When the contents of the organic solvent and water are each within the above ranges, cleaning properties tend to be further improved.

[0054] The surfactant contained in the impregnation liquid is not particularly limited, but for example, the same surfactants as those exemplified in the ink composition described below can be used. The content of the surfactant is preferably 0.05 to 1.0 mass % relative to the total amount of the impregnation liquid.

[0055] 1.2. Ink composition The ink composition used in the inkjet recording apparatus according to this embodiment contains a pigment, a crosslinkable component, a surfactant, and water. Each component contained in the ink composition used in the inkjet recording apparatus according to this embodiment will be described below.

[0056] 1.2.1.Pigments The ink composition used in the inkjet recording apparatus according to this embodiment contains a pigment. Any pigment that is commonly used in aqueous pigment inks can be used without any particular limitation.

[0057] Examples of the pigment that can be used include organic pigments such as azo pigments, phthalocyanine pigments, dye pigments, condensed polycyclic pigments, nitro pigments, and nitroso pigments (Brilliant Carmine 6B, Lake Red C, Watching Red, Disazo Yellow, Hansa Yellow, Phthalocyanine Blue, Phthalocyanine Green, Alkali Blue, and Aniline Black); metals such as cobalt, iron, chromium, copper, zinc, lead, titanium, vanadium, manganese, and nickel; metal oxides and sulfides; carbon blacks (CI Pigment Black 7) such as furnace carbon black, lamp black, acetylene black, and channel black; and inorganic pigments such as ochre, ultramarine, and Prussian blue.

[0058] More specifically, examples of carbon black used as black pigments include No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (all trade names, manufactured by Mitsubishi Chemical Corporation), Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Pretex 35, U, V, 140U, Special Black, etc. 6, 5, 4A, 4, 250, etc. (all trade names, manufactured by Degussa), Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, 700, etc. (all trade names, manufactured by Columbia Carbon), Rigal 400R, 330R, 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400, Elftex 12, etc. (all trade names, manufactured by Cabot Corporation).

[0059] Examples of yellow pigments include CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 167, 172, and 180.

[0060] Magenta pigments include CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48(Ca), 48(Mn), 57(Ca), 57:1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, and CI Pigment Violet 19, 23, 32, 33, 36, 38, 43, 50, etc.

[0061] Cyan pigments include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:34, 15:4, 16, 18, 22, 25, 60, 65, 66, and CI Vat Blue 4 and 60.

[0062] Examples of pigments other than black, yellow, magenta, and cyan include CI Pigment Green 7, 10, CI Pigment Brown 3, 5, 25, 26, and CI Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63, and the like.

[0063] The above-mentioned pigments may be used alone or in combination of two or more.

[0064] The lower limit of the pigment (solid content) content in the ink composition is preferably 1% by mass or more, more preferably 3% by mass or more, and particularly preferably 4% by mass or more, relative to the total mass of the ink composition. The upper limit of the pigment (solid content) content is preferably 30% by mass or less, more preferably 15% by mass or less, and particularly preferably 12% by mass or less, relative to the total mass of the ink composition. A pigment (solid content) content within this range tends to ensure good abrasion resistance of the recorded matter.

[0065] 1.2.2. Crosslinking component The ink composition used in the inkjet recording apparatus according to this embodiment contains a crosslinkable component. In the present invention, the term "crosslinkable component" refers to a compound capable of reacting with a reactive group such as a hydroxyl group to form a crosslinked structure. By including a crosslinkable component in the ink composition, the crosslinkable component reacts with a reactive group such as a hydroxyl group possessed by the recording medium or resin particles (described below), thereby making it possible to further improve the abrasion resistance of the recorded material. Examples of such a crosslinkable component include, but are not limited to, a urethane-based resin having a crosslinkable group and a crosslinking agent. The urethane-based resin having a crosslinkable group and the crosslinking agent will be described below.

[0066] The recording medium is not particularly limited, but may include various types of fabrics. The material constituting the fabric is not particularly limited, and examples thereof include natural fibers such as cotton, linen, wool, and silk; synthetic fibers such as polypropylene, polyester, acetate, triacetate, polyamide, and polyurethane; and biodegradable fibers such as polylactic acid, and may also be blends of these fibers. The fabric may be any of the above-mentioned fibers in the form of woven fabric, knitted fabric, nonwoven fabric, etc.

[0067] 1.2.2.1. Urethane resin with crosslinkable groups The crosslinkable component contained in the ink composition may be, for example, a urethane resin having a crosslinkable group. In this case, the "crosslinkable group" refers to a group capable of forming a crosslinked structure upon reaction, and does not include the terminal group of the urethane resin. When the ink composition contains a urethane resin having a crosslinkable group, a crosslinked structure is formed with a reactive group such as a hydroxyl group of the recording medium, thereby improving the fixability of the ink composition to the recording medium and providing superior abrasion resistance. The crosslinkable group is not particularly limited as long as it is capable of reacting with an active hydrogen-containing group containing active hydrogen, such as a hydroxyl group, of the recording medium to form a bond. Specific examples of the crosslinkable group include an isocyanate group and a silanol group. The isocyanate group, which is a crosslinkable group, may be a blocked isocyanate group that has been chemically protected by, for example, capping or blocking. The blocked isocyanate group is deprotected and activated by heating, and the activated isocyanate reacts with an active hydrogen-containing group, such as a hydroxyl group, of the recording medium to form a bond, such as a urethane bond, a urea bond, or an allophanate bond.

[0068] Among these, the crosslinkable group is preferably one or more of a blocked isocyanate group and a silanol group from the viewpoint of further improving the fastness to rubbing under wet conditions, and more preferably a blocked isocyanate group from the viewpoint of further improving the fastness to rubbing under wet conditions.

[0069] In this specification, urethane resin refers to a resin containing a urethane bond, urea bond, or allophanate bond formed by reaction of an isocyanate group with an active hydrogen-containing group such as a hydroxyl group, an amino group, a urethane-bonding group, a carboxyl group, etc. Preferred urethane resins are polyether-skeleton urethane resins containing ether bonds in the main chain in addition to urethane bonds, polyester-type urethane resins containing a polyester skeleton, and polycarbonate-type urethane resins containing a polycarbonate skeleton.

[0070] A blocked isocyanate (chemically protected isocyanate) contains a latent isocyanate group in which the isocyanate group is blocked with a blocking agent, and can be obtained, for example, by reacting a polyisocyanate compound with a blocking agent.

[0071] Examples of polyisocyanate compounds include polyisocyanate monomers and polyisocyanate derivatives. Examples of polyisocyanate monomers include polyisocyanates such as aromatic polyisocyanates, araliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. These polyisocyanate monomers can be used alone or in combination of two or more.

[0072] Examples of the polyisocyanate derivatives include polymers of the above-mentioned polyisocyanate monomers (for example, dimers, trimers (for example, isocyanurate-modified products, iminooxadiazinedione-modified products), pentamers, heptamers, etc.), allophanate-modified products (for example, allophanate-modified products produced by the reaction of the above-mentioned polyisocyanate monomers with low-molecular-weight polyols described below), polyol-modified products (for example, polyol-modified products (alcohol adducts) produced by the reaction of polyisocyanate monomers with low-molecular-weight polyols described below), biuret-modified products (for example, Examples of such a modified polyisocyanate include biuret modified polyisocyanates produced by the reaction of the polyisocyanate monomers with water or amines, urea modified polyisocyanates produced by the reaction of the polyisocyanate monomers with diamines, oxadiazinetrione modified polyisocyanates produced by the reaction of the polyisocyanate monomers with carbon dioxide, carbodiimide modified polyisocyanates produced by the decarboxylation condensation reaction of the polyisocyanate monomers, uretdione modified polyisocyanates, and uretonimine modified polyisocyanates.

[0073] When two or more types of polyisocyanate compounds are used in combination, for example, when producing a blocked isocyanate, two or more types of polyisocyanate compounds may be reacted simultaneously, or blocked isocyanates obtained by using each polyisocyanate compound individually may be mixed.

[0074] The blocking agent blocks and inactivates the isocyanate group, while regenerating or activating the isocyanate group after deblocking. The blocking agent also has a catalytic action that activates the isocyanate group in both the blocked and deblocked states.

[0075] 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, and bisulfites.

[0076] Examples of imidazole compounds include imidazole (dissociation temperature 100°C), benzimidazole (dissociation temperature 120°C), 2-methylimidazole (dissociation temperature 70°C), 4-methylimidazole (dissociation temperature 100°C), 2-ethylimidazole (dissociation temperature 70°C), 2-isopropylimidazole, 2,4-dimethylimidazole, and 2-ethyl-4-methylimidazole.

[0077] Examples of imidazoline compounds include 2-methylimidazoline (dissociation temperature: 110° C.) and 2-phenylimidazoline.

[0078] Examples of pyrimidine compounds include 2-methyl-1,4,5,6-tetrahydropyrimidine.

[0079] Examples of guanidine compounds include 3,3-dialkylguanidines such as 3,3-dimethylguanidine, 1,1,3,3-tetraalkylguanidines such as 1,1,3,3-tetramethylguanidine (dissociation temperature 120° C.), and 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0080] Examples of alcohol compounds include methanol, ethanol, 2-propanol, n-butanol, s-butanol, 2-ethylhexyl alcohol, 1- or 2-octanol, cyclohexyl alcohol, ethylene glycol, benzyl alcohol, 2,2,2-trifluoroethanol, 2,2,2-trichloroethanol, 2-(hydroxymethyl)furan, 2-methoxyethanol, methoxypropanol, 2-ethoxyethanol, n-propoxyethanol, 2-butoxyethanol, and 2-ethoxyethoxyethanol. , 2-ethoxybutoxyethanol, butoxyethoxyethanol, 2-butoxyethylethanol, 2-butoxyethoxyethanol, N,N-dibutyl-2-hydroxyacetamide, N-hydroxysuccinimide, N-morpholineethanol, 2,2-dimethyl-1,3-dioxolane-4-methanol, 3-oxazolidineethanol, 2-hydroxymethylpyridine (dissociation temperature 140°C), furfuryl alcohol, 12-hydroxystearic acid, triphenylsilanol, 2-hydroxyethyl methacrylate, and the like.

[0081] Examples of phenolic compounds include phenol, cresol, ethylphenol, n-propylphenol, isopropylphenol, n-butylphenol, s-butylphenol, t-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n-octylphenol, n-nonylphenol, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol, di-s-butylphenol, di-t-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, and di-n-nonylphenol. Examples of suitable phenols include phenol, nitrophenol, bromophenol, chlorophenol, fluorophenol, dimethylphenol, styrenated phenol, methyl salicylate, methyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, 2-ethylhexyl hydroxybenzoate, 4-[(dimethylamino)methyl]phenol, 4-[(dimethylamino)methyl]nonylphenol, bis(4-hydroxyphenyl)acetic acid, 2-hydroxypyridine (dissociation temperature 80°C), 2- or 8-hydroxyquinoline, 2-chloro-3-pyridinol, and pyridine-2-thiol (dissociation temperature 70°C).

[0082] Examples of active methylene compounds include Meldrum's acid, dialkyl malonates (e.g., dimethyl malonate, diethyl malonate, di-n-butyl malonate, di-t-butyl malonate, di-2-ethylhexyl malonate, methyl n-butyl malonate, ethyl n-butyl malonate, methyl s-butyl malonate, ethyl s-butyl malonate, methyl t-butyl malonate, ethyl t-butyl malonate, diethyl methylmalonate, dibenzyl malonate, diphenyl malonate, benzylmethyl malonate, ethylphenyl malonate, t-butylphenyl malonate, isopropylidene malonate, etc.), alkyl acetoacetates (e.g., methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, t-butyl acetoacetate, benzyl acetoacetate, phenyl acetoacetate, etc.), 2-acetoacetoxyethyl methacrylate, acetylacetone, and ethyl cyanoacetate.

[0083] Examples of the amine compounds include dibutylamine, diphenylamine, aniline, N-methylaniline, carbazole, bis(2,2,6,6-tetramethylpiperidinyl)amine, di-n-propylamine, diisopropylamine (dissociation temperature 130°C), isopropylethylamine, 2,2,4- or 2,2,5-trimethylhexamethyleneamine, N-isopropylcyclohexylamine (dissociation temperature 140°C), dicyclohexylamine (dissociation temperature 130°C), bis(3,5,5-trimethylcyclohexyl)amine, piperidine, 2, Examples include 6-dimethylpiperidine (dissociation temperature 130°C), t-butylmethylamine, t-butylethylamine (dissociation temperature 120°C), t-butylpropylamine, t-butylbutylamine, t-butylbenzylamine (dissociation temperature 120°C), t-butylphenylamine, 2,2,6-trimethylpiperidine, 2,2,6,6-tetramethylpiperidine (dissociation temperature 80°C), (dimethylamino)-2,2,6,6-tetramethylpiperidine, 2,2,6,6-tetramethyl-4-piperidine, 6-methyl-2-piperidine, and 6-aminocaproic acid.

[0084] Examples of imine compounds include ethyleneimine, polyethyleneimine, 1,4,5,6-tetrahydropyrimidine, and guanidine.

[0085] Examples of oxime compounds include formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime (dissociation temperature 130°C), cyclohexanone oxime, diacetyl monooxime, benzophenone oxime, 2,2,6,6-tetramethylcyclohexanone oxime, diisopropyl ketone oxime, methyl t-butyl ketone oxime, diisobutyl ketone oxime, methyl isobutyl ketone oxime, methyl isopropyl ketone oxime, methyl 2,4-dimethylpentyl ketone oxime, methyl 3-ethylheptyl ketone oxime, methyl isoamyl ketone oxime, n-amyl ketone oxime, 2,2,4,4-tetramethyl-1,3-cyclobutanedione monooxime, 4,4'-dimethoxybenzophenone oxime, and 2-heptanone oxime.

[0086] Examples of carbamic acid compounds include N-phenylcarbamate phenyl.

[0087] Examples of urea compounds include urea, thiourea, and ethyleneurea.

[0088] Examples of acid amide (lactam) compounds include acetanilide, N-methylacetamide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, pyrrolidone, 2,5-piperazinedione, and laurolactam.

[0089] Examples of the acid imide compounds include succinimide, maleimide, and phthalimide.

[0090] Examples of triazole compounds include 1,2,4-triazole and benzotriazole.

[0091] Examples of pyrazole compounds include pyrazole, 3,5-dimethylpyrazole (dissociation temperature 120°C), 3,5-diisopropylpyrazole, 3,5-diphenylpyrazole, 3,5-di-t-butylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole.

[0092] Examples of the mercaptan compounds include butyl mercaptan, dodecyl mercaptan, and hexyl mercaptan.

[0093] The bisulfite salts include, for example, sodium bisulfite.

[0094] Furthermore, the blocking agent is not limited to the above, and other blocking agents such as benzoxazolone, isatoic anhydride, and tetrabutylphosphonium acetate may also be used.

[0095] For some of the compounds exemplified above, the dissociation temperature is also listed as the temperature at which the isocyanate group is regenerated.

[0096] Such blocking agents can be used alone or in combination of two or more. The dissociation temperature of the blocking agent can be selected appropriately. The dissociation temperature is, for example, from 60°C to 230°C, preferably from 80°C to 200°C, more preferably from 100°C to 180°C, and even more preferably from 110°C to 160°C. Within this temperature range, the pot life of the ink composition can be sufficiently extended.

[0097] The main chain of the urethane resin having a crosslinkable group may be any of a polyether type containing an ether bond, a polyester type containing an ester bond, a polycarbonate type containing a carbonate bond, etc. The elongation at break and 100% modulus of the crosslinked urethane resin (crosslinked product) can be adjusted by changing the density of crosslinking points and the type of main chain. Among these, urethane resins having a crosslinkable group with a polycarbonate skeleton or a polyether skeleton are more preferred because they have a good balance between elongation at break and 100% modulus and can easily improve the friction resistance and texture of printed materials. In particular, urethane resins having a polycarbonate skeleton are preferred because they tend to have good friction resistance.

[0098] Furthermore, the urethane resin having a crosslinkable group preferably has an elongation at break of 150% or more, preferably 170% or more, more preferably 200% or more, and even more preferably 300% or more after crosslinking (crosslinked product). By selecting the density of crosslinking points and the type of main chain so as to obtain such an elongation at break, the texture of the recorded matter can be improved.

[0099] Here, the elongation at break can be measured, for example, by curing a urethane resin emulsion having crosslinkable groups to prepare a film having a thickness of about 60 μm, and measuring the elongation under conditions of a tensile test gauge length of 20 mm and a pulling speed of 100 mm / min. The 100% modulus can be measured by measuring the tensile stress when the film is stretched 100% of its original length in the tensile test. The film to be measured may be formed using a urethane resin emulsion having crosslinkable groups, or may be formed by molding using the same type of resin, but it is preferable to form the film using an emulsion resin.

[0100] The urethane resin having a crosslinkable group may be blended in the form of an emulsion. Such a resin emulsion is a so-called self-reactive urethane resin emulsion, and a commercially available urethane resin emulsion having an isocyanate group blocked with a blocking agent having a hydrophilic group can be used.

[0101] Commercially available urethane resins having crosslinkable groups include "ETERNACOLL UW-1501F" manufactured by Ube Industries, Ltd., the "Trixene series" such as "Trixene BI7986" and "Trixene BI7987" manufactured by Baxenden, "Bayhydur BL2781" manufactured by Bayer, the "Takenate WB series" manufactured by Mitsui Chemicals, Inc., "Duranate WM44-L70G" manufactured by Asahi Kasei Corporation, "Turboset TM2025" manufactured by Lubrizol, and the "Takelac WS series" such as "Takelac WS-4022," "Takelac WS-5984," and "Takelac WS-5100" manufactured by Mitsui Chemicals, Inc. Examples of polycarbonate-type urethane resins include "ETERNACOLL UW-1501F" and "Takelac WS-5100" manufactured by Ube Industries, Ltd., and examples of polyester-type urethane resins include "Takelac WS-4022" and "Takelac WS-5984." Examples of resins having a blocked isocyanate group as a crosslinkable group include "ETERNACOLL UW-1501F" manufactured by Ube Industries, Ltd., the "Trixene series" such as "Trixene BI7986" and "Trixene BI7987" manufactured by Baxenden, "Bayhydur BL2781" manufactured by Bayer, "Takenate WB series" manufactured by Mitsui Chemicals, Inc., "Duranate WM44-L70G" manufactured by Asahi Kasei Corporation, and "Turboset TM2025" manufactured by Lubrizol. Examples of resins having a silanol group as a crosslinkable group include "Takelac WS-4022," "Takelac WS-5984," and "Takelac WS-5100" manufactured by Mitsui Chemicals, Inc.

[0102] These urethane resins having a crosslinkable group may be used alone or in combination of two or more.

[0103] In this embodiment, the solids concentration of the urethane resin containing a crosslinkable group may be from 1.0% to 10.0% by mass, preferably from 3.0% to 9.0% by mass, and more preferably from 4.0% to 8.0% by mass, relative to the total mass of the ink composition. When the solids concentration of the urethane resin containing a crosslinkable group is within the above range, the abrasion resistance of the recorded matter tends to be further improved.

[0104] The glass transition temperature (Tg) of the urethane resin containing a crosslinkable group is preferably -10°C or lower, more preferably -15°C or lower, and particularly preferably -20°C or lower. When the glass transition temperature is within this range, the particles are in a soft state at room temperature (25°C), which further reduces physical damage to the nozzle surface and tends to result in better liquid repellency durability and ejection stability. On the other hand, in order to ensure the abrasion resistance of the printed matter, the glass transition temperature of the resin is preferably -50°C or higher, more preferably -40°C or higher, and particularly preferably -30°C or higher. The glass transition temperature (Tg) of the resin can be confirmed by a standard method such as differential scanning calorimetry (DSC).

[0105] 1.2.2.2. Crosslinking Agents The crosslinkable component contained in the ink composition may be, for example, a crosslinking agent. When the ink composition contains resin particles described below, the crosslinking agent reacts with reactive groups such as hydroxyl groups of the resin particles by heating at a temperature equal to or higher than the crosslinking reaction initiation temperature to form a strong coating, thereby further improving the abrasion resistance of the recorded material.

[0106] As the crosslinking agent, it is preferable to use at least one of a blocked isocyanate compound and a carbodiimide compound. These compounds are reactive with the functional groups of the resin particles described below, facilitating the formation of a network structure through a crosslinking reaction. For example, when a blocked isocyanate compound is heated at a temperature equal to or higher than the crosslinking reaction initiation temperature, it reacts with the hydroxyl groups of the resin particles described below to form urethane bonds. This is because the blocking agent that inactivated the isocyanate groups of the blocked isocyanate dissociates upon heating to a predetermined temperature, activating the isocyanate groups and allowing the crosslinking reaction to proceed. Furthermore, when a carbodiimide compound is heated at a temperature equal to or higher than the crosslinking reaction initiation temperature, it reacts with the carboxyl groups of the resin particles described below to form amide bonds.

[0107] Specific examples of the crosslinking agent include blocked isocyanate compounds obtained by blocking HDI (hexamethylene diisocyanate), H6XDI (hydrogenated xylylene diisocyanate), IPDI (isophorone diisocyanate), or H12MDI (dicyclohexylmethane diisocyanate) with TMP (trimethylolpropane) adducts or isocyanurates, such as SU-268A (manufactured by Myojo Chemical Industry Co., Ltd.) and MF-B60B (manufactured by Asahi Kasei Corporation). The carbodiimide compound is preferably a polypropylcarbodiimide compound having multiple carbodiimide groups in the molecule. For example, Carbodilite V-02 (manufactured by Nisshinbo) is one example.

[0108] When a blocked isocyanate compound or a carbodiimide compound is used as the crosslinking agent, it is preferable to use a urethane resin as the resin particles described below, since this allows the crosslinking reaction to proceed more smoothly.

[0109] The types of crosslinking agents are not limited to the above two types, and polyallylamine, oxazoline, etc. may also be used. In some cases, a catalyst may be added to promote crosslinking. Examples of catalysts include organic peroxides and azo compounds.

[0110] The amount of crosslinking agent added is preferably 0.1% by mass to 15% by mass, more preferably 0.1% by mass to 10% by mass, and even more preferably 5% by mass to 8% by mass. When the amount is 10% by mass or less, the texture of the recorded material is good, and when the amount is 5% by mass or more, the abrasion resistance is good.

[0111] Surfactants The ink composition used in the inkjet recording apparatus according to this embodiment contains a surfactant. The surfactant is not particularly limited, but examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants. Furthermore, from the viewpoint of facilitating adjustment of the contact angle of the ink composition with respect to the nozzle forming surface 600 within a certain range, the surfactant is preferably an acetylene glycol surfactant.

[0112] The acetylene glycol surfactant is not particularly limited, but examples thereof include Surfynol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA, and DF110D (all trade names, manufactured by Air Products & Chemicals Co.). , Olfine B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP.4001, EXP.4036, EXP.4051, AF-103, AF-104, AK-02, SK-14, AE-3 (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.), Acetylenol E00, E00P, E40, E100 (all trade names, manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0113] As the fluorine-based surfactant, it is preferable to use a fluorine-modified polymer, and specific examples include BYK-3440 (manufactured by BYK Japan), Surflon S-241, S-242, S-243 (all trade names, manufactured by AGC Seimi Chemical Co., Ltd.), and Futergent 215M (manufactured by Neos Corporation).

[0114] The silicone surfactant is not particularly limited, but a polysiloxane compound is preferred. The polysiloxane compound is not particularly limited, but for example, a polyether-modified organosiloxane is exemplified. Commercially available polyether-modified organosiloxanes include, for example, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, and BYK-348 (all trade names, manufactured by BYK-Chemie Japan), 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 trade names, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0115] The content of the surfactant is preferably 0.1% by mass to 1.0% by mass, more preferably 0.15% by mass to 0.5% by mass, and particularly preferably 0.2% by mass to 0.4% by mass, relative to the total mass of the ink composition. If the content of the surfactant is within this range, the contact angle of the ink composition with respect to the nozzle surface can be suitably adjusted within a certain range, which tends to result in better liquid repellency durability and ejection stability.

[0116] 1.2.4.Water The ink composition used in the inkjet recording apparatus according to this embodiment contains water as a main solvent. As the water, it is preferable to use pure water or ultrapure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, or distilled water. It is particularly preferable to use water that has been sterilized by ultraviolet irradiation or the addition of hydrogen peroxide, as this prevents the growth of mold and bacteria and allows the ink composition to be stored for a long period of time.

[0117] 1.2.5.Other Ingredients The ink composition used in the inkjet recording apparatus according to this embodiment may contain components other than those described above. Examples of such components are shown below.

[0118] <Resin particles> The ink composition used in the inkjet recording apparatus according to this embodiment preferably contains resin particles for the purpose of further improving the abrasion resistance of the recorded material.

[0119] Examples of such resin particles include resin particles made of urethane resin, acrylic resin, fluorene resin, polyolefin resin, rosin-modified resin, terpene resin, polyester resin, polyamide resin, epoxy resin, vinyl chloride resin, ethylene vinyl acetate resin, etc. These resin particles are often handled in the form of an emulsion, but may also be in the form of a powder. Furthermore, the resin particles can be used alone or in combination of two or more types.

[0120] Urethane resin is a general term for resins having urethane bonds. In addition to urethane bonds, the urethane resin may be a polyether-type urethane resin containing an ether bond in the main chain, a polyester-type urethane resin containing an ester bond in the main chain, or a polycarbonate-type urethane resin containing a carbonate bond in the main chain. The urethane resin may also include a urethane-based resin having a crosslinkable group contained in the ink composition described above.

[0121] The urethane resin may be a commercially available product, and may be selected from commercially available products such as Superflex 210, 460, 460s, 840, and E-4000 (trade names, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), Rezamin D-1060, D-2020, D-4080, D-4200, D-6300, and D-6455 (trade names, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), Takelac WS-6020, WS-6021, and W-512-A-6 (trade names, manufactured by Mitsui Chemicals Polyurethanes Inc.), Sancure 2710 (trade name, manufactured by Lubrizol), and Parmarin UA-150 (trade name, manufactured by Sanyo Chemical Industries, Ltd.).

[0122] Acrylic resin is a general term for polymers obtained by polymerizing at least an acrylic monomer such as (meth)acrylic acid or a (meth)acrylic acid ester as one component. Examples include resins obtained from acrylic monomers and copolymers of acrylic monomers with other monomers. Examples include acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers. Further examples include copolymers with vinyl monomers such as styrene. Acrylic monomers that can be used include acrylamide and acrylonitrile.

[0123] Commercially available resin particles made from acrylic resin may be used, and may be selected from, for example, FK-854, Mowinyl 952B, 718A (trade names, manufactured by Japan Coating Resins Co., Ltd.), Nipol LX852, LX874 (trade names, manufactured by Nippon Zeon Co., Ltd.), Polysol AT860 (manufactured by Showa Denko K.K.), Boncoat AN-1190S, YG-651, AC-501, AN-1170, 4001 (trade names, manufactured by DIC Corporation, acrylic resin emulsion), and the like.

[0124] In this specification, the acrylic resin may be a styrene-acrylic resin as described above. In addition, in this specification, the term "(meth)acrylic" means at least one of acrylic and methacrylic.

[0125] Styrene-acrylic resins are copolymers obtained from styrene monomers and acrylic monomers, and examples thereof include styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylate copolymers, styrene-α-methylstyrene-acrylic acid copolymers, and styrene-α-methylstyrene-acrylic acid-acrylate copolymers.

[0126] As the styrene-acrylic resin, commercially available products may be used, and examples thereof include JONCRYL 62J, 7100, 390, 711, 511, 7001, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, and 7610 (trade names, manufactured by BASF), and Mowinyl 966A, 975N, and 6960 (trade names, manufactured by Japan Coating Resins Co., Ltd.).

[0127] The vinyl chloride resin may be a vinyl chloride-vinyl acetate copolymer.

[0128] The polyolefin resin has an olefin such as ethylene, propylene, or butylene in its structural skeleton, and known polyolefin resins can be appropriately selected and used. Commercially available olefin resins can be used, such as Arrowbase CB-1200 and CD-1200 (trade names, manufactured by Unitika Ltd.).

[0129] The resin particles may also be supplied in the form of an emulsion. Examples of commercially available resin emulsions include Microgel E-1002 and E-5002 (product names of Nippon Paint Co., Ltd., styrene-acrylic resin emulsions), Boncoat AN-1190S, YG-651, AC-501, AN-1170, 4001, and 5454 (product names of DIC Corporation, styrene-acrylic resin emulsions), Polysol AM-710, AM-920, AM-2300, AP-4735, AT-860, and PSASE-4210E (acrylic resin emulsions), and Polyzo Polysol AP-7020 (styrene-acrylic resin emulsion), Polysol SH-502 (vinyl acetate resin emulsion), Polysol AD-13, AD-2, AD-10, AD-96, AD-17, AD-70 (ethylene-vinyl acetate resin emulsion), Polysol PSASE-6010 (ethylene-vinyl acetate resin emulsion) (trade name, manufactured by Showa Denko K.K.), Polysol SAE1014 (trade name, styrene-acrylic resin emulsion, manufactured by Zeon Co., Ltd.), Saivinol SK-200 (trade name, acrylic resin emulsion, manufactured by Saiden Chemical Co., Ltd.), AE -120A (trade name of JSR Corporation, acrylic resin emulsion), AE373D (trade name of E-Tech Corporation, carboxy-modified styrene-acrylic resin emulsion), Seikadyne 1900W (trade name of Dainichiseika Color & Chemicals Mfg. Co., Ltd., ethylene-vinyl acetate resin emulsion), Vinyblan 2682 (acrylic resin emulsion), Vinyblan 2886 (vinyl acetate-acrylic resin emulsion), Vinyblan 5202 (acetic acid acrylic resin emulsion) (trade name of Nissin Chemical Industry Co., Ltd.), Vinyblan 700, 2586 (Nissin Chemical Industry Co., Ltd.), Elitel KA-5071S, K T-8803, KT-9204, KT-8701, KT-8904, KT-0507 (trade name of Unitika Ltd., polyester resin emulsion), Hi-Tec SN-2002 (trade name of Toho Chemical Co., Ltd., polyester resin emulsion), Takelac W-6020, W-635, W-6061, W-605, W-635, W-6021 (trade name of Mitsui Chemicals Polyurethanes, urethane resin emulsion), Superflex 870, 800, 150, 420, 460, 470, 610, 620, 700 (trade name of Daiichi Kogyo Seiyaku Co., Ltd., urethane resin emulsion),Permarin UA-150 (Sanyo Chemical Industries, Ltd., urethane resin emulsion), Sancure 2710 (Lubrizol Japan, urethane resin emulsion), NeoRez R-9660, R-9637, R-940 (Kusumoto Chemicals Co., Ltd., urethane resin emulsion), Adeka Bontitor HUX-380, 290K (ADEKA Corporation, urethane resin emulsion), Mowinyl 966A, Mowinyl 7320 (Japan Coating Resins Co., Ltd.), Joncryl 7100, 390, 711, 511, 7001, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX The binder may be selected from the group consisting of PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, and 7610 (all manufactured by BASF), NK Binder R-5HN (manufactured by Shin-Nakamura Chemical Co., Ltd.), Hydran WLS-210 (non-crosslinked polyurethane manufactured by DIC Corporation), and Joncryl 7610 (manufactured by BASF).

[0130] When resin particles are contained in the ink composition, the content thereof is, relative to the total mass of the ink composition, 0.1% by mass to 20% by mass, preferably 1.0% by mass to 15.0% by mass, more preferably 2.0% by mass to 10.0% by mass, and even more preferably 3.0% by mass to 8.0% by mass, in terms of solid content.

[0131] Among the resin particles, urethane resin is preferred in that it provides a recording material with superior abrasion resistance.

[0132] The glass transition temperature (Tg) of the resin particles is preferably -10°C or lower, more preferably -15°C or lower, and particularly preferably -20°C or lower. When the glass transition temperature of the resin particles is within this range, the resin particles are in a soft state at room temperature (25°C), which further reduces physical damage to the nozzle formation surface and tends to result in better liquid repellency durability and ejection stability. On the other hand, in order to ensure the abrasion resistance of the recorded material, the glass transition temperature of the resin particles is preferably -50°C or higher, more preferably -40°C or higher, and particularly preferably -30°C or higher. The glass transition temperature (Tg) of the resin particles can be confirmed by a standard method using differential scanning calorimetry (DSC) or the like.

[0133] <Wetting agent> The ink composition used in the inkjet recording apparatus according to this embodiment preferably contains an organic solvent with a wetting effect in order to prevent clogging in the vicinity of the nozzles of the recording head.

[0134] Examples of humectants include polyhydric alcohols such as glycerin, 1,2,6-hexanetriol, trimethylolpropane, pentamethylene glycol, trimethylene glycol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, polyethylene glycols having a number average molecular weight of 2000 or less, dipropylene glycol, tripropylene glycol, isobutylene glycol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, mesoerythritol, and pentaerythritol, as well as glucose, mannose, fructooligosaccharides, and the like. Examples of suitable wetting agents include sugars such as sucrose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose, sugar alcohols, hyaluronic acids, and ureas; alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, and isopropanol; and 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, acetamide, dimethyl sulfoxide, sorbitol, sorbitan, acetin, diacetin, triacetin, and sulfolane.

[0135] The wetting agent may be used alone or in combination of two or more.

[0136] The content of the humectant is preferably 2.0% by mass or more and 20.0% by mass or less, and more preferably 5.0% by mass or more and 15.0% by mass or less, relative to the total mass of the ink composition. When the content of the humectant is within this range, appropriate physical properties (viscosity, etc.) of the ink composition can be ensured, and recording quality and reliability can be ensured.

[0137] <Dispersant> The ink composition used in the inkjet recording apparatus according to this embodiment preferably contains a dispersant for dispersing the pigment. The ink composition contains a pigment, and it is preferable that the pigment be stably dispersed and maintained in the dispersion medium. Examples of methods for achieving this include dispersing the pigment using a dispersant such as a water-soluble resin and / or a water-dispersible resin, or chemically or physically introducing hydrophilic functional groups onto the pigment particle surface to enable dispersion and / or solubility in water without the need for a dispersant. Among these, dispersing the pigment using a dispersant is preferred because it provides excellent pigment dispersion stability in the ink composition, ejection stability from the nozzle holes of the inkjet head when used in an inkjet method, and durability, such as adhesion and abrasion resistance, of the resulting image.

[0138] Examples of dispersants include polyvinyl alcohols, polyacrylic acid, acrylic acid-acrylonitrile copolymers, vinyl acetate-acrylic acid ester copolymers, acrylic acid-acrylic acid ester copolymers, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid ester copolymers, styrene-α-methylstyrene-acrylic acid copolymers, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymers, styrene-maleic acid copolymers, styrene-maleic anhydride copolymers, vinylnaphthalene-acrylic acid copolymers, vinylnaphthalene-maleic acid copolymers, vinyl acetate-maleic acid ester copolymers, vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acid copolymers, and salts thereof. Among these, copolymers of monomers having hydrophobic functional groups and monomers having hydrophilic functional groups, and polymers composed of monomers having both hydrophobic and hydrophilic functional groups are preferred. The copolymers can be in the form of random copolymers, block copolymers, alternating copolymers, or graft copolymers.

[0139] The content of the dispersant is preferably 5 parts by mass or more and 200 parts by mass or less, and more preferably 20 parts by mass or more and 120 parts by mass or less, relative to 100 parts by mass of the pigment content in the ink composition.

[0140] <Inorganic alkaline compounds> The ink composition used in the inkjet recording apparatus according to this embodiment preferably contains an inorganic alkali compound (an inorganic base compound). The inorganic alkali compound has the property of increasing the pH of the ink composition. The inorganic alkali compound also has at least the function of increasing the dispersion stability of the crosslinkable component and / or the function of improving the redispersibility of the crosslinkable component.

[0141] Examples of inorganic alkaline compounds include alkali metal hydroxides or alkaline earth metal hydroxides, alkali metal carbonates or alkaline earth metal carbonates, alkali metal phosphates or alkaline earth metal phosphates, and the like.

[0142] Examples of the hydroxides of alkali metals include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. Examples of the hydroxides of alkaline earth metals include calcium hydroxide, magnesium hydroxide, etc.

[0143] Examples of carbonates of alkali metals include lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, etc. Examples of carbonates of alkaline earth metals include calcium carbonate, etc.

[0144] Examples of alkali metal phosphates include lithium phosphate, potassium phosphate, trisodium phosphate, disodium hydrogen phosphate, etc. Examples of alkaline earth metal phosphates include calcium phosphate, calcium hydrogen phosphate, etc.

[0145] The ink composition used in the inkjet recording apparatus according to this embodiment may contain multiple types of the inorganic alkali compounds listed above. The total content of the inorganic alkali compounds is, relative to the total amount of the ink composition, from 0.01% to 0.8% by mass, preferably from 0.02% to 0.6% by mass, more preferably from 0.03% to 0.4% by mass, even more preferably from 0.04% to 0.3% by mass, particularly preferably from 0.05% to 0.2% by mass, and even more preferably from 0.05% to 0.1% by mass.

[0146] When the amount of the inorganic alkali compound is within this range, the pH of the ink composition can be sufficiently increased, and the function of increasing the dispersion stability of the crosslinkable component and / or the function of improving the redispersibility of the crosslinkable component can be exhibited.

[0147] <Other> The ink composition used in the inkjet recording apparatus according to this embodiment may contain, in addition to the above components, wax, preservatives, antifungal agents, rust inhibitors, chelating agents, viscosity modifiers, antioxidants, ureas, amines, sugars, etc.

[0148] 1.2.6. Method for preparing ink composition The ink composition used in the inkjet recording apparatus according to this embodiment can be obtained by mixing the components in any order and, if necessary, removing impurities by filtration, etc. A suitable method for mixing the components is to add the materials sequentially to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer, and stir and mix them.

[0149] Physical Properties The contact angle of the ink composition used in the inkjet recording apparatus according to this embodiment with respect to the nozzle-forming surface is 50° or greater, preferably 55° or greater, more preferably 58° or greater, and particularly preferably 60° or greater. When the contact angle between the ink composition and the nozzle-forming surface is within this range, droplets of the ink composition are less likely to remain on the nozzle-forming surface when the wipe-cleaning mechanism is used. This reduces chemical damage to the nozzle-forming surface caused by the crosslinkable components in the ink droplets reacting with the nozzle-forming surface, thereby further improving the durability of the liquid repellency and the ejection stability. Note that, in the present invention, "contact angle" refers to a static contact angle. Furthermore, the contact angle in the present invention is measured in accordance with the sessile drop method of JIS R 3257 (Test Method for Wettability of Substrate Glass Surfaces), except that the nozzle-forming surface is replaced by a glass substrate and pure water is used as the ink composition. Specifically, the contact angle can be measured using the Sessile Drop method (sessile drop method) using an automatic contact angle measuring device such as the OCAH200 (product name, manufactured by Data Physics).

[0150] The surface tension of the ink composition is preferably 20 to 40 mN / m, and more preferably 25 to 35 mN / m. When the surface tension is within the above range, cleaning properties tend to be further improved.

[0151] 2. Maintenance method A maintenance method according to one embodiment of the present invention is a maintenance method for the inkjet recording apparatus described above, and includes a cleaning step of applying pressure to the interior of the recording head to perform pressure cleaning, thereby discharging the ink composition from the nozzles, and a wiping cleaning step of wiping the nozzle surface with the absorbing member containing cellulose. This makes it possible to clean the nozzle surface while ensuring durable liquid repellency and ejection stability, even when a pigment ink having friction resistance is used.

[0152] The cleaning step and the wiping cleaning step of the maintenance method according to this embodiment will be described in detail below.

[0153] 2.1. Cleaning Step An example of the cleaning step of performing pressure cleaning in the maintenance method according to this embodiment will be described in detail with reference to FIGS.

[0154] During maintenance, as shown in FIG. 2, 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 pressurization speed. Note that the pressurization speed is faster than the normal speed during printing operations. Then, the maintenance unit 55 caps the nozzle forming surface 600, and the pressure adjustment mechanism 68 pressurizes the tank 62 to a positive pressure. More specifically, pressurized cleaning is performed as follows.

[0155] A three-way valve 86 is inserted in a common pressurization path 85 that connects the pressure adjustment mechanism 68 and the pressurization buffer tank 81. In this three-way valve 86, the port connected to the pressurization buffer tank 81 is a common port, and of the remaining ports, the port connected to the atmosphere is normally closed, while the port connected to the three-way valve 682 of the pressure adjustment mechanism 68 is normally open. During pressurized cleaning, the three-way valve 86 is maintained in its normal state, and positive pressure is supplied from the pressurization buffer tank 81 to the three-way valve 682 of the pressure adjustment mechanism 68.

[0156] In the three-way valve 682 of the pressure adjustment mechanism 68, the port connected to the tank 62 is a common port, and of the remaining ports, an atmosphere release port connected to the atmosphere is normally open, while the port connected to the three-way valve 86 is normally closed. During pressurized cleaning, the atmosphere release port closes and the port connected to the three-way valve 682 of the pressure adjustment mechanism 68 opens, and the tank 62 is pressurized by the positive pressure in the pressurized buffer tank 81.

[0157] When the tank 62 is pressurized in this manner by the positive pressure in the pressurized buffer tank 81, the pressure in the pressurized buffer tank 81 drops. If the pressure drops below a certain value, it becomes difficult to continue the pressurized cleaning. Therefore, in this embodiment, when the pressurization sensor 84 detects a pressure drop, the pressurization pump 8 is activated, and then the positive pressure side atmosphere release port of the three-way valve 83 is closed and the positive pressure side open / close port is opened to pressurize the pressurized buffer tank 81. At this time, the intake port of the pressurization pump 8 is open to the atmosphere. When the pressure value in the pressurized buffer tank 81 eventually exceeds a certain value, the pressurization pump 8 stops, and the positive pressure side atmosphere release port and the positive pressure side open / close port are opened and closed, respectively.

[0158] In this way, the internal pressure of the pressurized buffer tank 81 is always maintained at a constant value or higher, and the tank 62 is pressurized by the positive pressure in the pressurized buffer tank 81. As a result, the nozzle 601 is pressurized from the tank 62 via the recovery flow path 65. By then removing the cap, the ink composition in the nozzle 601 is ejected into the maintenance unit 55. In addition, air bubbles and the like in the nozzle 601 are expelled from the nozzle 601 along with the ink composition ejected from the nozzle 601.

[0159] Following this, a wiping cleaning step, which will be described later, is performed on the nozzle forming surface 600. This wipes off the ink composition that has been ejected from the nozzles 601 and adhered to the nozzle forming surface 600. Next, the rotation speed (circulation speed) of the liquid feed pump 64 is reduced to a normal speed, and flushing is performed, filling all the nozzles 601 with ink. When flushing is thus completed, the pressurized cleaning is terminated.

[0160] 2.2. Wipe-cleaning step In the wiping cleaning step of the maintenance method according to this embodiment, the nozzle forming surface 600 of the recording head 6 is wiped with an absorbing member 701 containing cellulose.

[0161] More specifically, in the wiping-cleaning step, a pressing member (not shown) of the drive mechanism 702 presses the absorbing member 701 containing cellulose against the nozzle forming surface 600 of the recording head 6 to apply a pressing load, thereby wiping the nozzle forming surface 600. Note that while the ink composition is being ejected onto the recording medium P, the absorbing member 701 impregnated with an impregnation liquid containing an organic solvent is kept on standby, and the wiping-cleaning step is performed after ejection of the ink composition has been completed.

[0162] In the maintenance method according to this embodiment, a wiping cleaning step may be performed before or after the pressure cleaning step, in which the nozzle forming surface 600 is wiped with an absorbing member 701 containing cellulose. This makes it possible to remove the ink composition that has adhered to the nozzle forming surface 600 during the pressure cleaning step or when the ink composition is ejected onto the recording medium P.

[0163] 3. Working Example The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" below is based on mass.

[0164] 3.1. Preparation of ink composition Each ink composition was obtained by mixing the components in the amounts shown in Tables 1 and 2 below, stirring at room temperature for 2 hours, and then filtering through a membrane filter with a pore size of 5 μm. The contents of the ink components shown in Tables 1 and 2 below are in mass %, and ion-exchanged water was added so that the total mass of the composition was 100 mass %. In Tables 1 and 2 below, the pigment content and resin content are expressed in terms of solid content.

[0165] The pigment used in preparing the ink composition was previously mixed with ion-exchanged water in a mass ratio of 2:1 (pigment:pigment dispersant) and a pigment dispersant (not shown in the table), which was a water-soluble styrene-acrylic resin, and then thoroughly stirred to prepare a pigment dispersion, which was then used in preparing the ink composition.

[0166] [Table 1]

[0167] [Table 2]

[0168] The following provides additional explanations for each component and term shown in Tables 1 and 2 above. <Pigments> Carbon Black: Product name "MA 100", manufactured by Mitsubishi Chemical Corporation <Resin> UW-1501F: Ube Industries, Ltd., product name "ETERNACOLL UW-1501F", cross-linked urethane resin, Tg=-20℃ Takelac W-6061: Mitsui Chemicals Polyurethanes product name, non-crosslinkable urethane resin, Tg = 25°C Movinyl 6960: Trade name of Nippon Synthetic Chemical Industry Co., Ltd., non-crosslinked acrylic resin, Tg = -20°C <Crosslinking agent> SU-268A: A product name manufactured by Meisei Chemical Industry Co., Ltd., an isocyanate in which the isocyanate group is protected with a blocking agent <Surfactant> Olfine E1010: Product name of Nissin Chemical Industry Co., Ltd., acetylene glycol-based BYK348: BYK Japan product name, silicone-based

[0169] In Tables 1 and 2 above, "crosslinkable urethane resin" refers to a urethane resin having a crosslinkable group as a crosslinkable component. Furthermore, "non-crosslinkable urethane resin" and "non-crosslinkable acrylic resin" refer to a urethane resin and an acrylic resin that are not crosslinkable components. In other words, "non-crosslinkable urethane resin" and "non-crosslinkable acrylic resin" refer to compounds that are not capable of forming a crosslinked structure by reacting with a reactive group such as a hydroxyl group.

[0170] In Tables 1 and 2 above, "nozzle contact angle" refers to the contact angle of the ink composition with the nozzle-forming surface. In other words, "nozzle contact angle" refers to the angle formed between the ink composition and the nozzle-forming surface at the location where the ink composition comes into contact with the nozzle-forming surface.

[0171] In Tables 1 and 2 above, "pressurization" means performing pressurized cleaning. "Suction" means performing vacuum cleaning. "Pressurized CL subtank pressure" means the pressure inside the tank that stores the ink composition when performing pressurized cleaning. "Wipe speed" means the speed at which at least one of the absorbing member and the recording head is moved relative to the other.

[0172] In Tables 1 and 2 above, "cloth wiper conditions" refers to the fiber material from which the absorbing member of the wiping cleaning mechanism is made. The fiber materials used are marked with a "●" in the tables. Bemliese: Asahi Kasei Corporation product name, nonwoven fabric made from cellulose Toraysee: Toray Industries, Inc. product name, polyester or polyester and nylon fabric

[0173] 3.1.1.Surface tension The surface tensions shown in Tables 1 and 2 above were measured at a liquid temperature of 25°C by the Wilhelmy method using a surface tensiometer (such as the CBVP-Z surface tensiometer manufactured by Kyowa Interface Science Co., Ltd.).

[0174] 3.1.2.Contact angle The contact angles shown in Tables 1 and 2 above are the contact angles of the ink composition obtained above with respect to the nozzle-forming surface, and were measured at 25°C using a portable contact angle meter PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.). The nozzle-forming surface used in measuring the contact angles was a silicon nozzle plate with a liquid-repellent film made of single-crystal silicon. On the ink-ejecting surface of the plate, a silicon oxide film (SiO2 film) was formed by the chemical vapor deposition (CVD) method by introducing SiCl4 and water vapor into a CVD reactor. The SiO2 film had a thickness of 50 nm. Further, oxygen plasma treatment was performed, and then CF 17 A liquid-repellent film was formed on the SiO2 film by chemical vapor deposition (CVD) using C2H4SiCl3, creating a silicon nozzle plate with a liquid-repellent film.

[0175] 3.2.Evaluation Method 3.2.1.Nozzle durability evaluation The inkjet recording device used was a Seiko Epson Corporation printer (product name "SC-F2000") modified to include a cleaning mechanism that applies pressure to the inside of a tank storing the ink composition to perform pressure cleaning, and a wiping cleaning mechanism that wipes with a cellulose-derived absorbent member (a modified version of the product name "SC-F2000"). In Comparative Example 3, a device modified to include a reduced pressure (suction) cleaning mechanism instead of the pressure cleaning mechanism was used. In Comparative Example 5, a device modified to include a wiping cleaning mechanism that wipes with a synthetic fiber-derived absorbent member instead of the cellulose-derived absorbent member was used.

[0176] Each ink composition listed in Tables 1 and 2 above was filled into the cartridge of the modified SC-F2000. Next, a nozzle check pattern was printed using the inkjet recording device described above in a printing environment of 35°C and 20% RH. Subsequently, a cycle of pressurized cleaning followed by a wiping cleaning was performed 5,000 times with a one-minute interval under the evaluation conditions listed in Tables 1 and 2 above. A nozzle check pattern was then printed again, and the amount of misalignment of the ink dot with the greatest impact position misalignment between the initial and post-cycle operations was measured. The misalignment amount was measured using a SmartScope ZIP250 (manufactured by OGP) by setting the initial dot to 0, measuring the position of each dot, and calculating the amount of misalignment in the Y-axis direction (media feed direction) between the initial and post-cycle dot positions. The distance between the media and head A was 1.2 mm (platen gap). The evaluation criteria were as follows: (Evaluation criteria) S: The deviation in the landing position is within 1 μm. A: The deviation in the impact position is between 1 μm and 5 μm. B: The deviation in the impact position is more than 5 μm and less than 10 μm. C: The impact position deviation is more than 10 μm.

[0177] 3.2.2. Evaluation of ejection stability For each of the ink compositions listed in Tables 1 and 2, printing was carried out continuously for one hour using the SC-F2000 at a fabric surface temperature of 25°C (room temperature), and after printing was completed, one nozzle row (360 nozzles) was inspected for ejection abnormalities (non-ejection). Note that all nozzles were in a normal state before recording began. The evaluation criteria are as follows: (Evaluation criteria) S: The number of nozzles with abnormal discharge is 0. A: The number of nozzles with abnormal discharge is 1 to 2. B: The number of nozzles with abnormal discharge is 3 to 5. C: The number of nozzles with abnormal discharge is 6 or more.

[0178] 3.2.3. 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 "PXG930"). The recording conditions were a recording resolution of 1440 dpi x 720 dpi, a recording area of ​​A4 size, and four layers of solid pattern images were overcoated. 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.

[0179] Thereafter, the ink composition was fixed to the recording medium by heat treatment at 165°C for 5 minutes using a heat press machine. In this way, a printed item in which an image was formed on the recording medium (ink printed) was produced.

[0180] The printed fabrics of each example were subjected to a color fastness test against rubbing using a type I (Crockmeter) tester in accordance with the method specified in ISO-105 X12. Dry rubbing was tested in accordance with the dry test specified in ISO-105 X12 and evaluated using the stain gray scale. The evaluation criteria were as follows: (Evaluation criteria) A: Abrasion resistance is grade 4 or higher. B: Rub fastness is grade 2 or more but less than grade 4 C: Rub fastness is less than grade 2

[0181] 3.3.Evaluation Results The results of the evaluation test are shown in Tables 1 and 2 above.

[0182] The above evaluation results show that in Examples 1 to 10, the ink compositions containing a crosslinkable component provided excellent friction resistance to the recorded material, and even when such an ink composition was used, by setting the contact angle of the ink composition with the nozzle formation surface to a certain level or more and using an inkjet recording device equipped with a wiping cleaning mechanism that wipes the ink with an absorbent member containing cellulose and pressure cleaning, it was possible to achieve both good liquid repellency durability (nozzle durability).

[0183] In contrast, in Comparative Examples 1 and 2, which used ink compositions that did not contain a crosslinkable component, the abrasion resistance of the recorded material was poor. Furthermore, in Comparative Examples 3 to 5, when an ink composition containing a crosslinkable component was used, if the contact angle of the ink composition with the nozzle surface was not at least a certain level, or if an inkjet recording apparatus was used that was not equipped with a wiping cleaning mechanism that wipes with an absorbent member containing cellulose or pressure cleaning, the liquid repellency durability (nozzle durability) was poor.

[0184] The following can be derived from the above-described embodiment.

[0185] One aspect of the inkjet recording apparatus is a recording head having nozzles for ejecting an ink composition and a nozzle forming surface having ejection openings for the nozzles; a cleaning mechanism that performs a cleaning operation to discharge the ink composition from the nozzle; a wiping cleaning mechanism that wipes the nozzle forming surface with an absorbent member containing cellulose, the ink composition contains a pigment, a crosslinkable component, a surfactant, and water; the contact angle of the ink composition with respect to the nozzle forming surface is 50° or more; The cleaning mechanism is a pressure cleaning mechanism that applies pressure to the inside of the recording head to perform cleaning.

[0186] In one aspect of the inkjet recording apparatus, The surfactant may be an acetylene glycol surfactant.

[0187] In any one of the above inkjet recording apparatuses, The pressure applied in the pressure cleaning may be 38 kPa or less.

[0188] In any one of the above inkjet recording apparatuses, The nozzle forming surface may have a fluorine compound bonded via a hydrolyzable bond.

[0189] In any one of the above inkjet recording apparatuses, The ink composition may further contain resin particles.

[0190] In any one of the above inkjet recording apparatuses, The resin particles may be a urethane resin.

[0191] In any one of the above inkjet recording apparatuses, The resin particles may have a glass transition temperature (Tg) of −10° C. or lower.

[0192] One aspect of the maintenance method includes: A maintenance method for the inkjet recording apparatus of the above aspect, comprising: a cleaning step of performing pressure cleaning by applying pressure to the inside of the recording head to discharge the ink composition from the nozzles; and a wiping and cleaning step of wiping the nozzle forming surface with the absorbing member containing cellulose.

[0193] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments, such as configurations with the same functions, methods, and results, or configurations with the same purpose and effects. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects or purposes as the configurations described in the embodiments. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments. [Explanation of symbols]

[0194] P... recording medium, HP..., home position, 1... inkjet recording device, 12... frame, 6... recording head, 8... pressure pump, 55... maintenance unit, 61... ink supply unit, 62... tank, 63... supply flow path, 64... liquid feed pump, 65... recovery flow path, 66... ​​circulation path, 67... ink supply mechanism, 68... pressure adjustment mechanism, 81... pressure buffer tank, 82... positive pressure introduction path, 83... three-way valve, 84... pressure sensor, 85... common pressure path, 86... three-way valve, 600... nozzle formation surface, 601... nozzle, 602... reservoir, 603... cavity, 604... nozzle row, 605... nozzle plate cover, 606... ejection port, 671... ink reservoir, 672... supply flow path, 673... supply pump, 681... pressure path, 682... three-way valve, 701... absorbing member, 702... drive mechanism

Claims

1. A nozzle for ejecting an ink composition and a nozzle forming surface having an ejection opening of the nozzle. a recording head; a cleaning device that performs a cleaning operation to discharge the ink composition from the nozzle; Structure and a wiping cleaning mechanism that wipes the nozzle forming surface with an absorbent member containing cellulose; , and the ink composition contains a pigment, a crosslinkable component, a surfactant, and water; the crosslinkable component contains a curable urethane resin or a crosslinking agent having a crosslinkable group, a contact angle of the ink composition with respect to the nozzle forming surface is 50° or more; The cleaning mechanism applies pressure to the inside of the recording head to perform cleaning. It is cleaning, The pressure applied in the pressure cleaning is 38 kPa or less. Place.

2. 2. The ink composition according to claim 1, wherein the surfactant is an acetylene glycol surfactant. Kujet recording device.

3. The nozzle forming surface has a fluorine compound bonded via a hydrolyzable bond. The inkjet recording apparatus according to claim 1 or 2.

4. 4. The ink composition according to claim 1, further comprising resin particles.

10. The inkjet recording apparatus according to claim 1 .

5. 5. The ink jet recording apparatus according to claim 4, wherein the resin particles are made of a urethane resin.

6. 5. The resin particles according to claim 4, wherein the glass transition temperature (Tg) of the resin particles is −10° C. or lower.

6. The inkjet recording apparatus according to claim 5.

7. 7. The ink jet recording apparatus according to claim 1, wherein the ink jet recording medium is a A maintenance method comprising: Before applying pressure to the inside of the recording head to eject the ink composition from the nozzle a cleaning step of performing the pressurized cleaning; A wiping cleaning step of wiping the nozzle forming surface with the absorbing member containing cellulose. A maintenance method including:

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