Inkjet recording method, inkjet recording device, and water-based ink

Abstract

This invention provides an inkjet recording method that exhibits excellent suction recovery and ink ejection stability, even when using ink containing resin particles. [Solution] An inkjet recording method comprising the steps of applying aqueous ink to a recording medium to record an image, and then heating the recording medium, using an inkjet recording device equipped with a recording head comprising a discharge port 13 for discharging aqueous ink, a pressure chamber 12 communicating with the discharge port, a discharge element disposed in the pressure chamber, a liquid storage chamber capable of supplying aqueous ink to the pressure chamber, a foam reservoir chamber 520 communicating with the liquid storage chamber, a depressurization chamber disposed adjacent to the foam reservoir chamber, and a gas permeable membrane disposed at the boundary between the foam reservoir chamber and the depressurization chamber, wherein the aqueous ink contains resin particles, and the glass transition temperature T of the resin particles g (°C), Maximum temperature of water-based ink in the foam chamber T i (°C), and the heating temperature T of the recording medium. fix (°C) satisfies the relationship in equation (1) below. T i <T g ≦T fix ...(1)

Description

[Technical Field]

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

[0002] Inkjet recording devices can record high-resolution images such as photographs, documents, and posters by ejecting fine droplets of liquid from the recording head's ejection port and applying them to the recording medium. In recent years, in addition to high resolution, recorded images are required to have properties such as scratch resistance. In particular, for applications such as poster printing, where wiping with a wet cloth is anticipated, water-resistant and scratch-resistant images are also required. To record images with improved water-resistant and scratch-resistant properties, inks containing resin particles are used, and inkjet recording devices that heat the recording medium after image recording are employed.

[0003] When using an inkjet recording device, bubbles may enter the ink channels in the ink storage section, such as ink cartridges and ink storage bags, or when replacing the recording head. If these bubbles enter the pressure chamber of the recording head, the pressure required to eject the ink may become insufficient, affecting the ink ejection performance. Furthermore, if bubbles remain in the ink channels of the recording head, changes in the external environment, such as a rise in the installation environment, may cause the remaining bubbles to expand, potentially leading to ink leakage. Therefore, to ensure stable operation of the recording device and recording head, it is preferable to design the recording head to allow bubbles that have entered the interior to be discharged to the outside.

[0004] If the amount of foam that has entered the recording head increases, a suction recovery process is performed to restore the condition by sucking out the foam along with the ink through the discharge port. If the amount of foam mixed in increases due to continuous use of the recording device or leaving it unused for a long period of time, it may be necessary to perform the suction recovery process multiple times. However, since the suction recovery process leads to a decrease in productivity due to the occurrence of recording downtime, it is preferable to avoid it as much as possible.

[0005] As a technology to address foaming, recording devices have been proposed that include a degassing section equipped with a hollow fiber module in the path supplying ink from the ink reservoir to the recording head (Patent Documents 1 and 2). On the other hand, recording devices have been proposed that incorporate a degasser including a partition made of a hollow fiber membrane inside the recording head (Patent Document 3). Furthermore, a liquid injection device has been proposed that captures gas (foam) mixed in the liquid along the ink flow path in a filter chamber, and recovers the gas by depressurizing a gas recovery section provided adjacent to the filter chamber via a permeable compartment wall (Patent Document 4). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-058544 [Patent Document 2] Japanese Patent Publication No. 2013-223980 [Patent Document 3] Japanese Patent Publication No. 2011-173428 [Patent Document 4] Japanese Patent Publication No. 2008-173961 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present inventors investigated the characteristics of the devices proposed in Patent Documents 1 to 4. The methods proposed in Patent Documents 1 and 2 had the problem of the devices becoming large. Furthermore, it was found that in the liquid injection devices proposed in Patent Documents 3 and 4, when ink containing resin particles was used, the foam discharge effect was insufficient, and dispensing failures were likely to occur.

[0008] Therefore, an object of the present invention is to provide an inkjet recording method that exhibits excellent suction recovery and ink ejection stability, even when using an ink containing resin particles. Another object of the present invention is to provide an inkjet recording apparatus and an aqueous ink used in this inkjet recording method. [Means for solving the problem]

[0009] In other words, according to the present invention, an inkjet recording method is used which an inkjet recording device is equipped with a recording head comprising: an ejection port for ejecting aqueous ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the aqueous ink from the ejection port; a liquid storage chamber capable of supplying the aqueous ink to the pressure chamber; a foam storage chamber communicating with the liquid storage chamber and configured to retain foam inside; a depressurization chamber disposed adjacent to the foam storage chamber and configured to reduce the pressure inside; and a gas permeable membrane disposed at the boundary between the foam storage chamber and the depressurization chamber; an inkjet recording method comprising the steps of applying the aqueous ink ejected from the ejection port to a recording medium to record an image, and then heating the recording medium, wherein the aqueous ink contains resin particles and the glass transition temperature T of the resin particles g (°C), the maximum temperature T of the aqueous ink in the foam reservoir chamber. i (°C), and the heating temperature T of the recording medium in the above step. fix An inkjet recording method is provided characterized in that (°C) satisfies the relationship of the following formula (1). T i <T g ≦T fix ...(1) [Effects of the Invention]

[0010] According to the present invention, even when using an ink containing resin particles, it is possible to provide an inkjet recording method that exhibits excellent suction recovery and ink ejection stability. Furthermore, according to the present invention, it is possible to provide an inkjet recording apparatus and an aqueous ink used in this inkjet recording method. [Brief explanation of the drawing]

[0011] [Figure 1A] This is a schematic perspective view showing one embodiment of the inkjet recording apparatus of the present invention. [Figure 1B] This is a schematic side view showing one embodiment of the inkjet recording apparatus of the present invention. [Figure 2] This diagram schematically shows an example of a recording unit. [Figure 3] This is a schematic diagram showing an example of the flow path in the ink supply section. [Figure 4] This is a schematic diagram illustrating an example of a de-aeration and depressurization process. [Figure 5] This is an exploded perspective view showing an example of a recording head. [Figure 6] This is a longitudinal cross-sectional view showing an example of a circulation pathway. [Figure 7] This is a schematic diagram showing an example of a de-foaming unit. [Figure 8] This diagram schematically shows a first example of the ink path configuration. [Figure 9] This diagram schematically shows the first modified example of the circulation pathway. [Figure 10] This diagram schematically shows a second example of the ink path configuration. [Figure 11] This diagram schematically shows a second modified example of the circulation pathway. [Modes for carrying out the invention]

[0012] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when a compound is a salt, the salt exists in the ink dissociated into ions, but for convenience, it will be expressed as "contains a salt." Also, water-based ink for inkjet printers may be simply referred to as "ink." Unless otherwise specified, physical properties are values ​​at room temperature (25°C) and normal pressure (1 atm). When "(meth)acrylic acid" or "(meth)acrylate" is written, it means "acrylic acid, methacrylic acid" and "acrylate, methacrylate," respectively.

[0013] The present inventors have investigated the reason why the effect of discharging bubbles becomes insufficient when an ink containing resin particles is used. Specifically, first, the present inventors analyzed a recording head in which the bubble discharging effect was insufficient. As a result, it was found that resin particles adhered to the gas permeable membrane and clogged fine pores of the membrane, resulting in insufficient bubble discharging effect. Furthermore, it was also found that the occurrence of defective bubble discharge caused by clogging of resin particles is limited to specific situations, and is more likely to occur when the apparatus is restarted after being stopped for a long period of time.

[0014] The present inventors speculate as follows on the reason why defective bubble discharge is likely to occur when the apparatus is restarted after being stopped for a long period of time. In order to record an image with improved scratch resistance, it is effective to use an ink containing a relatively large amount of resin particles. On the other hand, the liquid component in the ink tends to evaporate easily in the bubble storage chamber. Therefore, the resin particles become concentrated near the liquid surface of the ink that is left standing in the bubble storage chamber. When the apparatus is restarted in this state, it is thought that the resin particles are likely to fuse together as the temperature rises, clogging the fine pores of the gas permeable membrane and causing defective bubble discharge.

[0015] Next, in order to suppress the fusion of resin particles, the present inventors investigated the use of resin particles whose glass transition temperature T g is higher than the temperature of the ink that rises during use. As a result, while it became possible to sufficiently suppress clogging of the fine pores of the gas permeable membrane, there arose a problem that the scratch resistance of the image decreased. Under such circumstances, the present inventors determined that the glass transition temperature T of the resin particles g (°C), the maximum temperature T of the ink in the bubble storage chamber i (°C), and the heating temperature T of the recording medium fix (°C) were studied for controlling them so as to satisfy the relationship of the following formula (1). As a result, the inventors found that clogging of fine pores in the gas permeable membrane due to fusion of resin particles is suppressed, ink ejection stability is improved, and it becomes possible to sufficiently fuse resin particles on the recording medium, which led to the completion of the present invention. T i <T g ≦T fix...(1)

[0016] <Inkjet recording method, inkjet recording device, and water-based ink> The present invention relates to an inkjet recording method that uses an inkjet recording apparatus equipped with a predetermined recording head, applies aqueous ink ejected from the ejection port of the recording head to a recording medium to record an image, and then heats the recording medium. The recording head comprises an ejection port for ejecting aqueous ink, a pressure chamber communicating with the ejection port, an ejection element, a liquid storage chamber capable of supplying aqueous ink to the pressure chamber, a foam reservoir, a depressurization chamber, and a gas permeable membrane arranged at the boundary between the foam reservoir and the depressurization chamber. The ejection element is located in the pressure chamber and is the part that generates energy for ejecting aqueous ink from the ejection port. The foam reservoir is a part that communicates with the liquid storage chamber and is configured to retain foam inside. The depressurization chamber is located adjacent to the foam reservoir and is configured to allow depressurization inside. The aqueous ink contains resin particles, and the glass transition temperature of the resin particles is T g (°C), Maximum temperature of water-based ink in the foam chamber T i (°C), and the heating temperature T of the recording medium in the above-mentioned process. fix (°C) satisfies the relationship in equation (1) below. T i <T g ≦T fix ...(1)

[0017] Furthermore, the inkjet recording apparatus of the present invention is an apparatus used in an inkjet recording method that includes a predetermined recording head, an application of aqueous ink ejected from the ejection port of the recording head to a recording medium to record an image, and then a step of heating the recording medium. The recording head comprises an ejection port for ejecting aqueous ink, a pressure chamber communicating with the ejection port, an ejection element, a liquid storage chamber capable of supplying aqueous ink to the pressure chamber, a foam reservoir, a depressurization chamber, and a gas permeable membrane arranged at the boundary between the foam reservoir and the depressurization chamber. The ejection element is located in the pressure chamber and is the part that generates energy for ejecting aqueous ink from the ejection port. The foam reservoir is a part that communicates with the liquid storage chamber and is configured to hold foam inside. The depressurization chamber is a part located adjacent to the foam reservoir and is configured to allow depressurization inside. The aqueous ink contains resin particles, and the glass transition temperature T of the resin particles g (°C), Maximum temperature of water-based ink in the foam chamber T i (°C), and the heating temperature T of the recording medium in the above-mentioned process. fix (°C) satisfies the relationship in equation (1) below. T i <T g ≦T fix ...(1)

[0018] Furthermore, the aqueous ink of the present invention is an inkjet recording method that uses an inkjet recording apparatus equipped with a predetermined recording head, and includes the steps of recording an image by applying aqueous ink ejected from the ejection port of the recording head to a recording medium, and then heating the recording medium. The recording head comprises an ejection port for ejecting aqueous ink, a pressure chamber communicating with the ejection port, an ejection element, a liquid storage chamber capable of supplying aqueous ink to the pressure chamber, a foam reservoir chamber, a depressurization chamber, and a gas permeable membrane arranged at the boundary between the foam reservoir chamber and the depressurization chamber. The ejection element is located in the pressure chamber and is the part that generates energy for ejecting aqueous ink from the ejection port. The foam reservoir chamber is a part that communicates with the liquid storage chamber and is configured to retain foam inside. The depressurization chamber is a part located adjacent to the foam reservoir chamber and is configured to allow depressurization inside. The aqueous ink contains resin particles, and the glass transition temperature T of the resin particles g (°C), Maximum temperature of water-based ink in the foam chamber Ti (°C), and the heating temperature T of the recording medium in the above-mentioned process. fix (°C) satisfies the relationship in equation (1) below. T i <T g ≦T fix ...(1)

[0019] (Inkjet recording device) Figure 1A is a schematic perspective view showing one embodiment of the inkjet recording apparatus of the present invention. Figure 1B is a schematic side view showing one embodiment of the inkjet recording apparatus of the present invention. As shown in Figures 1A and 1B, the recording apparatus of this embodiment includes an inkjet recording head 1 that ejects ink. Examples of recording heads include recording heads that eject ink by the action of mechanical energy and recording heads that eject ink by the action of thermal energy. Among these, recording heads that eject ink by the action of thermal energy are preferred. A recording head that ejects ink by the action of thermal energy is a thermal recording head that imparts thermal energy to the ink by applying an electric pulse to an electrothermal conversion element and ejects the ink from the ejection port. This thermal recording head preferably includes a mechanism (temperature control mechanism) that heats the aqueous ink ejected from the recording head and applied to the recording medium to a predetermined temperature. When a temperature control mechanism is included, the heating temperature of the ink ejected from the recording head is preferably 35°C or higher and 70°C or lower.

[0020] [Heating process] The recording method of the present invention includes a step of heating (heat treatment) a recording medium to which ink has been applied. Heating the recording medium to which ink has been applied can accelerate drying or increase the intensity of the image. Examples of means for heating the recording medium include known heating means such as heaters, air blowing means such as hair dryers, and means combining these. Examples of heat treatment methods include applying heat from the opposite side (back side) of the recording medium (ink-applied side) with a heater, applying warm air or hot air to the recording surface of the recording medium, and heating from the recording surface or back side using an infrared heater. A combination of these methods may also be used.

[0021] Because the scratch resistance of the image can be improved, the heating temperature T of the ink-coated recording medium can be increased. fix The temperature (°C) is preferably between 70°C and 90°C. The heating temperature of the ink-coated recording medium may be read by a sensor incorporated at a position corresponding to the heating means of the recording device, or it may be determined from the relationship between the amount of heat and the temperature of the recording medium, which is determined according to the type of ink and recording medium.

[0022] In the recording apparatus shown in Figures 1A and 1B, a heater 25 supported by a frame (not shown) is positioned downstream in the sub-scanning direction A from the position where the recording head 1 reciprocates in the main scanning direction B. The recording medium P to which the ink has been applied can be heated by the heater 25. Specific examples of the heater 25 include sheath heaters and halogen heaters. The heater 25 is covered by a heater cover 26. The heater cover 26 is a component that efficiently irradiates the recording medium P with the heat generated from the heater 25. Furthermore, the heater cover 26 also serves as a component that protects the heater 25. The recording medium P to which the ink ejected from the recording head 1 has been applied is wound up by a take-up spool 27 to form a roll-shaped winding medium 24.

[0023] [Recording media] Any recording medium may be used. For example, recording media without a coating layer, such as plain paper, uncoated paper, and synthetic paper; recording media with a coating layer, such as recording paper, glossy paper, and art paper; and other recording media with ink absorption (permeability) can be used. In addition, non-permeable recording media such as films and sheets made of resin materials such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET) can also be used.

[0024] [Records Department] Figure 2 is a schematic diagram showing an example of a recording unit, and is an enlarged view of the recording head and its surroundings. First, the general configuration of the recording unit 50 will be explained with reference to Figure 2. Figure 2(a) is a schematic perspective view showing a recording unit 50 on which a recording head 1 can be mounted. The recording unit 50 constitutes a serial inkjet recording device that records onto a recording medium P by scanning the recording head 1 and ejecting ink.

[0025] The recording head 1 is mounted on the carriage 60. The carriage 60 reciprocates along the guide axis 51 in the main scanning direction (X direction). The recording medium P is transported by the upstream transport rollers 55, 56 and the downstream transport rollers 57, 58 in the sub-scanning direction (Y direction) which intersects (in this example, is perpendicular to) the main scanning direction. In the figures referenced below, the Z direction represents the vertical direction and intersects (in this example, is perpendicular to) the XY plane defined by the X and Y directions. The recording head 1 is configured to be removable and attachable to the carriage 60 by the user.

[0026] The recording head 1 is composed of a circulation unit 54 (see Figure 5), which will be described later, and an ejection unit 3 (see Figure 5). The specific configuration will be described later, but the ejection unit 3 is provided with multiple ejection ports and an energy generating element (hereinafter referred to as an ejection element) that generates ejection energy for ejecting ink from each ejection port.

[0027] Furthermore, the recording unit 50 is equipped with an ink storage unit 2 and an ink supply unit 400, which are ink supply sources. The ink stored in the ink storage unit 2 is supplied to the recording head 1 by the ink supply unit 400 via the first supply passage 111 and the second supply passage 112. In addition, any gases such as bubbles generated in the recording head 1 are discharged to the outside of the recording head 1 via the third air passage 113 by the ink supply unit 400.

[0028] The recording unit 50 records a predetermined image on the recording medium P by repeatedly performing a recording scan, in which the recording head 1 mounted on the carriage 60 moves in the main scanning direction and ejects ink to record, and a transport operation, in which the recording medium P is transported in the sub-scanning direction. The recording head 1 is capable of ejecting four types of ink: black (K), cyan (C), magenta (M), and yellow (Y), and it is possible to record a full-color image using these inks. However, the inks that can be ejected from the recording head 1 are not limited to the above four types of ink. This disclosure is also applicable to recording heads for ejecting other types of ink. In other words, the type and number of inks ejected from the recording head are not limited. For example, the number of inks ejected from the recording head may be one type or two or more types. In addition, inks that do not contain colorants (clear inks) or reaction solutions containing a reactant that reacts with the ink can also be used as inks.

[0029] Furthermore, the recording unit 50 is provided with a control unit 100 and a cap member (not shown) capable of covering the discharge port surface where the discharge port of the recording head 1 is formed. The cap member is positioned in the recording unit 50 away from the transport path of the recording medium P in the X direction. The cap member covers the discharge port surface of the recording head 1 when not recording and is used to suppress drying of ink near the discharge port, protect the recording head, and perform ink suction operations from the discharge port. Signals output from the control unit 100 are transmitted to the recording head 1 and the like via signal line 109.

[0030] Figure 2(b) is a block diagram showing the control system of the recording unit 50. The control unit 100 of the recording unit 50 includes a CPU 103, RAM 102, ROM 101, a head driver 1A, motor drivers 104A and 105A, and pump drivers 404A and 500A. The CPU 103 functions as a control means that controls the operation of each part of the recording unit 50 based on a program such as a processing procedure stored in the ROM 101. The RAM 102 is used as a work area when the CPU 103 executes processing. The CPU 103 receives image data from an external host device 900 to control the head driver 1A and controls the driving of the ejection element provided in the ejection unit 3. The CPU 103 also controls the drivers of various actuators provided in the recording unit. For example, the CPU 103 controls the motor driver 104A that drives the transport motor 104 for transporting the recording medium P. The CPU 103 controls the motor driver 105A, which drives the carriage motor 105 for moving the carriage 60. The CPU 103 controls the pump driver 500A, which drives the circulation pump 500. The CPU 103 controls the pump driver 404A, which drives the unidirectional pump 404, which will be described later. The control unit 100 also receives signals output from various sensors, such as a volume sensor, a pressure sensor 409, and a liquid sensor 416. Figure 2(b) shows a configuration in which image data received from the host device 900 is processed, but processing may be performed in the recording unit 50 without relying on data from the host device 900.

[0031] [Ink supply unit] Figure 3 is a schematic diagram showing an example of the flow path of the ink supply unit. The ink supply unit 400 shown in Figure 3 has an intermediate storage unit 401 that temporarily stores ink supplied from an ink storage unit 2, which is detachably configured to be attached to the recording unit 50, through a first supply path 111. A first check valve 222 is provided in the middle of the first supply path 111, and the first check valve 222 restricts the backflow of ink from the intermediate storage unit 401 to the ink storage unit 2. At least one surface of the intermediate storage unit 401 is formed of a flexible membrane 402, and the volume of the intermediate storage unit 401 can be changed. A volume sensor (not shown) is provided in the intermediate storage unit 401. The volume sensor can detect the volume of the intermediate storage unit 401 by measuring the displacement of the flexible membrane 402. From the volume sensor's detection result of the intermediate storage unit 401's volume, it is possible to estimate the amount of ink in the intermediate storage unit 401. The amount of ink in the intermediate storage section 401 may be estimated from the volume detection result of the volume sensor and the amount of ink consumed by the formation of an image on the recording medium and the suction of ink from the cap member.

[0032] The intermediate storage section 401 is in contact with an air-filled pressure chamber via a flexible membrane 402. Hereafter, the pressure chamber of the intermediate storage section 401 will be referred to as the intermediate pressure chamber 403. By changing the pressure of the gas (air) in the intermediate pressure chamber 403, it is possible to change the pressure of the ink stored in the intermediate storage section 401. The ink stored in the intermediate storage section 401 is supplied to the recording head 1 through a second supply passage 112 connected to the intermediate storage section 401 and the filter 110 of the recording head 1. A second check valve 223 is provided in the middle of the second supply passage 112, and the second check valve 223 restricts the backflow of ink from the recording head 1 to the intermediate storage section 401. The ink supply section 400 has a one-way pump 404 driven by a pump driver 404A. The one-way pump 404 is configured using, for example, a diaphragm pump, and is capable of sucking in and discharging air in one direction when driven by the pump driver 404A.

[0033] The intermediate pressure chamber 403 and the suction side of the one-way pump 404 are connected via a first air passage 414. A first on-off valve 408 is provided in the middle of the first air passage 414, and the opening and closing operation of the first on-off valve 408 makes it possible to switch between opening and closing the first air passage 414. The first air passage 414 is provided with a first branch air passage 418 that branches off between the first on-off valve 408 and the one-way pump 404, with one end communicating with the atmosphere. A third on-off valve 407 is provided in the first branch air passage 418, and the opening and closing operation of the third on-off valve 407 makes it possible to switch between sealing and opening the suction side of the one-way pump 404 to the atmosphere.

[0034] Furthermore, the intermediate pressure chamber 403 and the ejection side of the one-way pump 404 are connected via a second air passage 415. A second on-off valve 405 is provided in the middle of the second air passage 415, and the opening and closing operation of the second on-off valve 405 makes it possible to switch between opening and closing the second air passage 415. The second air passage 415 is provided with a second branch air passage 419 that branches off between the second on-off valve 405 and the one-way pump 404, with one end communicating with the atmosphere. A fourth on-off valve 406 is provided in the second branch air passage 419, and the opening and closing operation of the fourth on-off valve 406 makes it possible to switch between sealing and opening the ejection side of the one-way pump 404 with the atmosphere. A liquid sensor 416 is provided at the end of the second branch air passage 419 that is open to the atmosphere. The liquid sensor 416 is capable of detecting ink that has entered the air passage. A pressure sensor 409 is provided at one of the positions that communicates with the intermediate pressure chamber 403. The pressure sensor 409 is capable of detecting the pressure of the gas (air) in the intermediate pressure chamber 403. The one-way pump 404 and the depressurization chamber 760 of the de-bubbling unit 770 in the recording head 1 are connected via the third air passage 113. A third check valve 213 is provided in the middle of the third air passage 113, and the third check valve 213 restricts the backflow of gas (air) from the ink supply unit 400 to the depressurization chamber 760. In Figure 3, reference numerals 121, 151, and 152 indicate the first valve chamber, the second valve chamber, and the second pressure control chamber, respectively.

[0035] To record an image on the recording medium P, the ink supply unit 400 performs four main operations: pressurizing the pressure chamber, maintaining pressure, replenishing ink, and de-bubbling / de-pressurizing. Based on detection results from a volume sensor (not shown) and a pressure sensor 409, the CPU 103 controls the unidirectional pump 404 and the first to fourth on-off valves to perform the pressurizing, pressure maintenance, ink replenishment, and de-bubbling / de-pressurizing operations.

[0036] [Bubble removal and depressurization operation] Figure 4 is a schematic diagram illustrating an example of a de-bubbling and de-pressurization operation. The de-bubbling and de-pressurization operation is an operation to reduce the pressure inside the de-pressurization chamber 760. The speed at which gas moves from the foam reservoir chamber 520 of the de-bubbling unit 770 in the recording head 1 to the de-pressurization chamber 760 through the gas permeable membrane 710 is proportional to the difference between the pressure inside the foam reservoir chamber 520 and the pressure inside the de-pressurization chamber 760. For this reason, it is preferable to maintain a low pressure inside the de-pressurization chamber 760. A third check valve 213, installed in the middle of the third air passage 113, restricts the inflow of gas from the third air passage 113 to the de-pressurization chamber 760. However, due to the inflow of gas from the foam reservoir chamber 520 through the gas permeable membrane 710 and the inflow of gas that slightly permeates through the components constituting the de-pressurization chamber 760, the pressure inside the de-pressurization chamber 760 gradually increases over time. When the pressure in the depressurization chamber 760 gradually increases over time, a de-bubbling depressurization operation is required to reduce the pressure in the depressurization chamber 760. If it is estimated that the pressure in the depressurization chamber 760 exceeds a predetermined pressure based on the time elapsed since the last de-bubbling depressurization operation, the ink supply unit 400 performs the de-bubbling depressurization operation. During the de-bubbling depressurization operation, the ink supply unit 400 closes the first on-off valve 408, closes the second on-off valve 405, closes the third on-off valve 407, and opens the fourth on-off valve 406, while driving the one-way pump 404 to reduce the pressure in the depressurization chamber 760. If a predetermined time has elapsed since the one-way pump 404 was driven and it is estimated that the pressure in the depressurization chamber 760 is below the predetermined pressure, the ink supply unit 400 stops driving the one-way pump 404. During this time, since the first on-off valve 408 and the second on-off valve 405 are closed, the gas pressure in the intermediate pressure chamber 403 is maintained at a positive pressure. Even if the pressure in the intermediate pressure chamber 403 and the first to third air passages fluctuates due to the aforementioned pressure chamber pressurization operation, pressurization maintenance operation, ink replenishment operation, etc., after the de-bubbling and de-pressurization operation, the pressure in the de-pressurization chamber 760 is maintained at a low pressure (negative pressure) because the third check valve 213 is closed. For example, the frequency of the de-bubbling and de-pressurization operation may be increased in situations where bubbles are likely to form, such as at the start of initial use or after cleaning. The frequency of the de-bubbling and de-pressurization operation may be decreased as time passes after the start of initial use or after cleaning.Furthermore, the frequency of the de-aeration and depressurization operation may be varied depending on the temperature, operating conditions, etc.

[0037] [Recording head] Figure 5 is an exploded perspective view showing an example of a recording head. The basic configuration of the recording head will be explained below, mainly using Figure 5 and referring to Figure 2 as appropriate. An example including a circulation unit is shown here, but the circulation unit is not required. As shown in Figure 5, the recording head 1 is composed of a circulation unit 54 and an ejection unit 3 for ejecting ink supplied from the circulation unit 54 onto the recording medium P. The recording head 1 is fixedly supported on the carriage 60 of the recording unit 50 by positioning means (not shown) and electrical contacts provided on the carriage 60. The recording head 1 ejects ink while moving together with the carriage 60 in the main scanning direction (X direction) shown in Figure 2, and records onto the recording medium P.

[0038] A second support member 7, having an opening 7a through which the ejection module 300 is inserted, is adhesively fixed to one side of the first support member 4. The second support member 7 holds an electrical wiring member 5 that is electrically connected to the ejection module 300. The electrical wiring member 5 applies an electrical signal to the ejection module 300 for ejecting ink. The electrical connection between the ejection module 300 and the electrical wiring member 5 is sealed with a sealing material (not shown) to protect it from corrosion by ink and external impacts. In addition, an electrical contact substrate 6 is heat-pressed to the end 5a of the electrical wiring member 5 using an anisotropic conductive film (not shown), and the electrical wiring member 5 and the electrical contact substrate 6 are electrically connected. The electrical contact substrate 6 has an external signal input terminal (not shown) for receiving electrical signals from the recording unit 50.

[0039] As shown in Figure 2, the ink supply unit 400, which is connected to the ink storage unit 2 that serves as the ink supply source, is provided with a first supply path 111 and a second supply path 112. A main body-side connecting member is provided at the end of the second supply path 112. When the recording head 1 is mounted on the recording unit 50, the main body-side connecting member provided at the end of the second supply path 112 is detachably connected to the head-side connecting member 800 provided on the head housing 53 of the recording head 1. This forms an ink supply path (first supply path 111 and second supply path 112) from the ink storage unit 2 through the ink supply unit 400 to the recording head 1. Since the recording head 1 uses four types of ink, four sets of ink storage units 2, first supply path 111, second supply path 112, and circulation unit 54 are provided, each corresponding to a different ink, and four independent ink supply paths corresponding to each ink are formed. In this way, the recording unit 50 is equipped with an ink supply system that supplies ink from the ink storage unit 2 located outside the recording head 1.

[0040] [Configuration of the bubble removal unit] Figure 7 is a schematic diagram showing an example of a de-foaming unit. Figure 7(a) is a cross-sectional view of the de-foaming unit 770. Figure 7(b) is a schematic diagram of the deformation suppression member 720 in the de-foaming unit 770. The second de-foaming unit 770B has the same configuration as the first de-foaming unit 770A. The second foam accumulation chamber 520B has the same configuration as the first foam accumulation chamber 520A. Hereafter, the first de-foaming unit 770A and the second de-foaming unit 770B may be described collectively as the de-foaming unit 770. Also, the first foam accumulation chamber 520A and the second foam accumulation chamber 520B may be described collectively as the foam accumulation chamber 520. As shown in Figure 7(a), the bubble removal unit 770 (first bubble removal unit 770A and second bubble removal unit 770B) has a bubble reservoir chamber 520 (first bubble reservoir chamber 520A and second bubble reservoir chamber 520B) and a pressure reduction chamber 760. Furthermore, the bubble removal unit 770 has a gas permeable membrane 710, a deformation suppression member 720, a first communication port 751 for connecting the bubble reservoir chamber 520 to the ink flow path or liquid chamber, and a second communication port 761 for connecting the pressure reduction chamber 760 to the ink supply unit 400.

[0041] The bubble removal unit 770 (first bubble removal unit 770A and second bubble removal unit 770B) communicates with the ink supply unit 400 provided in the main body of the recording unit 50, and the pressure is reduced by the operation of the ink supply unit 400. Furthermore, a third check valve 213 (Figures 3 and 4) is provided between the bubble removal unit 770 and the ink supply unit 400, so that the pressure reduction state is maintained even when the recording unit 50 is not operating, thereby enabling the bubble removal operation. The third check valve 213 may be provided at the branched portions of the third air passage 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B. The third check valve 213 may be provided at the concentrated portion of the third air passage 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B.

[0042] Figure 6 is a longitudinal cross-sectional view showing an example of a circulation path. As shown in Figure 6(a), the first de-foaming unit 770A is provided above the supply channel 130 in the vertical direction, and the second de-foaming unit 770B is provided above the first recovery channel 140 in the vertical direction, but is not limited to this. The de-foaming unit 770 (first de-foaming unit 770A) may be provided only in the supply channel 130. The de-foaming unit 770 may be provided above the ink storage section 2, the first supply channel 111, the second supply channel 112, the third supply channel 910, the filter 110, the pump inlet channel 170, the pump outlet channel 180, the bypass channel 160, and the pressure chamber 12 in the vertical direction. Also, as shown in Figure 6(b), the first foam reservoir chamber 520A may communicate with the side surface of the supply channel 130, and the first de-foaming unit 770A may be formed extending to the side of the first foam reservoir chamber 520A. The second foam accumulation chamber 520B may communicate with the side of the first recovery channel 140, and the second foam removal unit 770B may be formed extending laterally from the second foam accumulation chamber 520B. The foam accumulation chamber 520 may communicate with the side of a communication section other than the supply channel 130 and the first recovery channel 140, and the foam removal unit 770 may be formed extending laterally from the foam accumulation chamber 520, as long as the configuration allows for capturing bubbles and bringing them into contact with the gas permeable membrane 710. In other words, the foam removal unit 770 may be formed extending horizontally from the foam accumulation chamber 520, rather than being above the foam accumulation chamber in the vertical direction. From the viewpoint of foam removal efficiency, it is preferable that the depressurization chamber be located adjacent to the foam accumulation chamber above it in the vertical direction.

[0043] A pressure chamber 12, a common supply channel 18, and a common recovery channel 19 are formed for each of the multiple discharge ports 13 that constitute the discharge port row. The first pressure adjustment means 120 includes a first valve chamber 121 and a first pressure control chamber 122. The second pressure adjustment means 150 includes a second valve chamber 151 and a second pressure control chamber 152. The first pressure adjustment means 120 is configured to have a relatively higher control pressure than the second pressure adjustment means 150. The first valve chamber 121 communicates with the first pressure control chamber 122 via a communication port 191A that can be opened and closed by a valve 190A shown in Figure 6. A valve shaft 190s is provided protruding from the center of the valve 190, which is inserted into the communication port 191A. By pressing this valve shaft 190s against the biasing force of the valve spring 200, the valve 190 is separated from the partition wall (not shown), and ink can flow through the communication port 191. The second valve chamber 151 communicates with the second pressure control chamber 152 via a communication port 191B, which is opened and closed by a valve 190B shown in Figure 6. A pressure regulating spring 220 is provided between the pressure plate 210 and a partition wall (not shown) as a biasing member. The biasing force of the pressure regulating spring 220 biases the pressure plate 210 and the flexible member 230 in a direction that expands the internal volume of the first pressure control chamber 122. Furthermore, when the pressure inside the first pressure control chamber 122 decreases, the pressure plate 210 and the flexible member 230 are displaced against the pressure of the pressure regulating spring 220 in a direction that decreases the internal volume of the first pressure control chamber 122.

[0044] [Gas permeable membrane] As shown in Figure 7(a), the gas permeable membrane 710 is provided on the housing of the circulation unit 54 that forms the foam reservoir chamber 520, so as to separate the foam reservoir chamber 520 from the depressurization chamber 760. Hereafter, the housing of the circulation unit 54 that forms the foam reservoir chamber 520 will be referred to as the unit housing 540. The gas permeable membrane 710 is bonded to the unit housing 540 by bonding methods such as heat welding, ultrasonic welding, and laser welding. Any of the bonding methods such as heat welding, ultrasonic welding, and laser welding can be used as long as the foam reservoir chamber 520 is sealed so that the ink inside does not leak into the depressurization chamber 760.

[0045] The gas permeable membrane 710 is a flexible member and is preferably planar. The gas permeable membrane 710 is made of a material that has a free volume or pores sufficient to allow air, which is a mixed gas such as oxygen gas and nitrogen gas, specifically oxygen molecules, nitrogen molecules, or mixtures thereof (hereinafter collectively referred to as "gas") to permeate. When using a gas permeable membrane made of a pore-containing material, the pore diameter (diameter) should be sufficient to allow the above-mentioned gas to permeate without allowing ink to permeate, and is preferably 100 nm or less, and more preferably 0.01 nm or more. The material of the gas permeable membrane 710 is preferably resin. Specifically, examples of materials for the gas permeable membrane 710 include polypropylene (PP), polyethylene (PE), polymethylpentene (TPX), and polytetrafluoroethylene (PTFE). To improve the de-bubbling efficiency, the material of the gas permeable membrane 710 is preferably highly gas permeable. Furthermore, the material of the gas permeable membrane 710 is required to be easily bonded to the unit housing 540 by heat welding and to not tear or peel off. In addition, the gas permeable membrane 710 is required to be reliable as a wetted material. Thus, it is preferable to select the material of the gas permeable membrane 710 from the viewpoints of gas permeability, manufacturing method (productivity), and reliability. The material of the gas permeable membrane is preferably polypropylene or polyethylene, and more preferably polypropylene, because it has excellent gas permeability and can further improve discharge stability.

[0046] The foam flowing into the foam reservoir chamber 520 includes initial foam (approximately 0.2 mL) remaining after initial filling at the start of initial use, foam from replacing the storage compartment that flows in during normal use (approximately 0.015 mL per month), and permeate foam that permeates from the outside (approximately 0.001 mL / day). To deal with this foam, it is preferable to perform a defoaming operation when the amount of foam permeation is 0.01 mL / day or more. As specified in "JIS K7126-1", the amount of gas permeation through the gas permeable membrane 710 can be verified by methods such as the pressure sensor method. The pressure sensor method is a method of measuring gas permeability by keeping one side (low-pressure side) separated by a test piece under vacuum, introducing a test gas to the other side (high-pressure side), and measuring the increase in pressure on the low-pressure side. According to the pressure sensor method, it is possible to calculate the gas permeability coefficient from the gas permeability and the thickness of the test piece. In the pressure sensor method, the amount of gas permeation through the gas permeable membrane can be verified by measuring the gas permeability using the test piece as a gas permeable membrane. Ink is filled into the recording head 1 by suction, the bubbles in the bubble reservoir chamber 520 are brought into contact with the entire gas permeable membrane 710, and the gas pressure in the depressurization chamber 760 is maintained at a negative pressure of approximately 50 kPa by the ink supply unit 400, and the device is left in an environment such as room temperature (25°C) and atmospheric pressure (1 atm). In this series of operations, the amount of bubbles in the bubble reservoir chamber 520 can be measured over time using computed tomography (CT) or the like, making it possible to verify the amount of bubbles (gas) that permeate through the gas permeable membrane 710.

[0047] Since the gas permeable membrane 710 is welded to the unit housing 540 to seal the foam reservoir chamber 520, the material of the gas permeable membrane 710 is preferably one that offers high reliability in welding and as a wetted material. To achieve a foam permeation rate of 0.01 mL / day or more, the thickness of the gas permeable membrane 710 is preferably 0.10 mm or less, more preferably less than 0.10 mm, and particularly preferably 0.90 mm or less. A thickness of 0.10 mm or less allows foam to escape more easily, further improving discharge stability. Furthermore, the thickness of the gas permeable membrane 710 is preferably 0.01 mm or more. A thickness of 0.01 mm or more provides sufficient strength for the gas permeable membrane to efficiently remove foam, further improving discharge stability.

[0048] [Bubble Collection Room] Figure 6 is a longitudinal cross-sectional view showing an example of a circulation path. As shown in Figure 6(a), the first foam reservoir chamber 520A is provided above the supply channel 130 in the vertical direction so as to communicate with the supply channel 130 via the first communication port 751. The second foam reservoir chamber 520B is provided above the first recovery channel 140 in the vertical direction so as to communicate with the first recovery channel 140 via the first communication port 751. As a result, foam mixed in with the ink in the first pressure adjustment means 120, the second pressure adjustment means 150, the supply channel 130, and the first recovery channel 140, etc., due to circulation and discharge operations, can be captured and held in the foam reservoir chamber 520 and discharged from the ink by a de-foaming operation. Examples of foam mixed with the ink include upstream foam that enters the recording head due to replacement of the ink storage unit 2, eluted foam generated in the recording head due to environmental changes, and unexpected foam generated in the recording head. The types of foam discharged by the de-foaming operation are not limited to these. If the amount of foam is such that it can be captured and held in the foam reservoir chamber 520, and a sufficient foam removal speed can be obtained, the foam mixed in the ink can be discharged to the outside of the recording head 1.

[0049] Maximum ink temperature in the foam reservoir: T iThe temperature (°C) can be controlled, for example, by a heater installed in the recording head. The temperature of the ink in the foam reservoir can also be measured, for example, by a temperature sensor installed inside the foam reservoir. This further improves ejection stability, thus reducing the maximum ink temperature T in the foam reservoir. i It is preferable that the temperature (°C) be between 30°C and 50°C.

[0050] Examples of materials for the unit housing 540 that forms the foam reservoir chamber 520 include polypropylene (PP) and polyethylene (PE). Polypropylene is preferred for the unit housing 540 because it offers reliability in welding the gas permeable membrane 710, ease of handling, and further improves discharge stability.

[0051] [Decompression chamber] As shown in Figure 7(a), the depressurization chamber 760 has an opening in which the gas permeable membrane 710 is placed, an opening opposite this opening for welding the gas permeable membrane 710, and a second communication port 761. The depressurization chamber 760 is formed by being surrounded by the unit housing 540, the gas permeable membrane 710, and the cover member 730. The second communication port 761 is formed through the side of the unit housing 540 and connects the depressurization chamber 760 to the degassing channel. The opening for welding the gas permeable membrane 710 is sealed by bonding a separate cover member 730 to the unit housing 540. Methods for bonding the cover member 730 include heat welding, ultrasonic welding, and laser welding. Examples of materials for the cover member 730 include polypropylene (PP) and polyethylene (PE). From the viewpoint of reliability of welding the cover member 730 and ease of handling, it is preferable that the material of the cover member 730 is the same as the material of the unit housing 540 that forms the foam reservoir chamber 520.

[0052] [The principle of removing bubbles] During the de-bubbling operation, the depressurization chamber 760 is reduced in pressure, causing the bubbles to permeate the gas permeable membrane 710 due to the pressure difference between the pressure of the bubbles in the bubble reservoir chamber 520 and the pressure of the gas in the depressurization chamber 760. The amount of permeation during the de-bubbling operation is expressed by the following equation (X). In equation (X), Q is the amount of gas permeation, P is the permeation coefficient, p is the degree of depressurization (gauge pressure), S is the bubble contact area, t is time, and L is the thickness of the gas permeable membrane 710. Q = P × p × S × t / L ... (X)

[0053] The gas permeation rate, represented by Q, is the amount of gas permeating through the bubbles during the de-bubbling operation. The permeation coefficient, represented by P, is a value determined by the material properties of the gas permeable membrane 710 and represents the basic speed of the de-bubbling operation. The degree of depressurization, represented by p, is the degree of depressurization (gauge pressure) of the depressurization chamber 760. The bubble contact area, represented by S, is the area in contact with the gas permeable membrane 710. The value represented by L is the thickness of the gas permeable membrane 710. Since the amount of bubble permeation increases with increasing degree of depressurization, it is preferable to set the degree of depressurization to 10 kPa or higher in order to ensure a sufficient amount of bubble permeation to handle the bubbles generated during normal use and to further improve discharge stability. It is preferable that the degree of depressurization be 70 kPa or lower.

[0054] The de-aeration unit 770 (first de-aeration unit 770A and second de-aeration unit 770B) has a foam accumulation chamber 520 (first foam accumulation chamber 520A and second foam accumulation chamber 520B). The depressurization chamber 760 is adjacent to the foam accumulation chamber 520 via a gas permeable membrane 710.

[0055] The configuration of the circulation path is not limited to the configuration described above. Below, we will describe other configurations of the circulation path, including the first and second configuration examples of the ink path, as well as various modifications of the circulation path.

[0056] [First example of ink path configuration] Figure 8 is a schematic diagram showing a first configuration example of the ink path. The first configuration example of the ink path is an example in which the second pressure adjustment means 150, the second foam reservoir chamber 520B, the circulation pump 500, the bypass flow path 160, and the first recovery flow path 140 shown in Figure 6 are not arranged. In the first configuration example of the ink path, ink is not circulated, and the ink supplied from the second supply path 112 flows in the order of the first pressure adjustment means 120, the supply flow path 130, and the pressure chamber 12, and is discharged from the discharge port 13. The first pressure control chamber 122, the supply flow path 130, and the pressure chamber 12 are pressure-controlled by the first pressure adjustment means 120, thus achieving stable ink discharge.

[0057] The first foam reservoir chamber 520A is located above the supply channel 130 in the vertical direction so as to communicate with the supply channel 130, and the first foam removal unit 770A is formed extending vertically above the first foam reservoir chamber 520A. This allows foam mixed into the ink in the first pressure adjustment means 120 or the supply channel 130, etc., by circulation or discharge operations to be captured in the first foam reservoir chamber 520A and discharged from the ink by a foam removal operation. The foam mixed into the ink includes the aforementioned upstream foam, eluted foam, and unintended foam, but is not limited to these. Any amount of foam that can be captured in the foam reservoir chamber 520 and that is sufficient to achieve a sufficient foam removal speed can be discharged from the ink. Therefore, the possibility of foam entering the ink channel communicating with the discharge port 13 can be greatly reduced.

[0058] The first bubble removal unit 770A communicates with the ink supply unit 400 of the main body of the recording unit 50 and is depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, so that the depressurized state is maintained even when the main body of the recording unit 50 is not constantly operating, thereby enabling the bubble removal operation. The third check valve 213 may also be provided in the third air passage 113 between the first bubble removal unit 770A and the ink supply unit 400.

[0059] There may be two or more foam retention chambers 520 and foam removal units 770. Furthermore, the foam retention chambers 520 and foam removal units 770 do not necessarily have to be located in the supply passage 130. For example, the foam retention chambers 520 and foam removal units 770 may be located vertically above the ink storage section 2, the first supply passage 111, the second supply passage 112, the third supply passage 910, the filter 110, and the pressure chamber 12. Also, the foam retention chambers 520 and foam removal units 770 do not necessarily have to be located vertically above the communication section such as the supply passage 130. As long as the configuration allows for capturing bubbles and bringing them into contact with the gas permeable membrane, the foam retention chambers 520 may communicate with the side of the communication section, and the foam removal units 770 may extend laterally from the foam retention chambers 520. This is also true when foam accumulation chambers 520 and foam removal units 770 are provided in multiple parts of the communication section other than the supply channel 130 and the first recovery channel 140.

[0060] [First variation of the circulation path] Figure 9 is a schematic diagram showing the first modified circulation path. Figure 9 shows the circulation path when circulation is performed without discharge. The first modified circulation path is an example in which the second pressure adjustment means 150 in Figure 6 is not arranged and the bypass flow path 160 and the first recovery flow path 140 are directly connected.

[0061] In the first modified example of the circulation path, the flow resistance of the ink flow path from the bypass flow path 160 to the first recovery flow path 140 is denoted as R1, and the flow resistance of the ink flow path from the supply flow path 130 to the first recovery flow path 140 via the discharge module 300 is denoted as R2. Since the flow rate of ink flowing through each flow path is inversely proportional to the flow resistance, the ratio of the flow rate of ink in the flow path via the bypass flow path 160 to the flow rate of ink in the flow path via the discharge module 300 is R2 to R1. In accordance with this relationship, the flow resistance of each flow path is set so that the circulation amount is such that the viscosity of the ink near the discharge port 13 in the discharge module 300 is suppressed. That is, the flow resistance of each flow path is set so that the flow velocity of the ink in the pressure chamber 12 is greater than or equal to a predetermined flow velocity. The flow resistance R1 of the flow path via the bypass flow path 160 is controlled by changing the cross-sectional area or length of the flow path, or by providing a throttling in the flow path.

[0062] The first foam reservoir chamber 520A is located above the supply channel 130 in the vertical direction so as to communicate with the supply channel 130, and the first foam removal unit 770A extends vertically upward from the first foam reservoir chamber 520A. The second foam reservoir chamber 520B is located above the first recovery channel 140 in the vertical direction so as to communicate with the first recovery channel 140, and the second foam removal unit 770B extends vertically upward from the second foam reservoir chamber 520B. As a result, foam mixed in with the ink in the first pressure adjustment means 120, the supply channel 130, and the first recovery channel 140, etc., through circulation and discharge operations, is captured in the foam reservoir chamber 520 and discharged from the ink through a foam removal operation. The bubbles that mix with the ink include the aforementioned upstream bubbles, eluted bubbles, and unintended bubbles, but are not limited to these. It is possible to discharge from the ink a quantity of bubbles that can be captured in the bubble reservoir chamber 520 and that are sufficient to achieve a sufficient de-bubbling speed. Therefore, the possibility of bubbles entering the ink channel connected to the discharge port 13 can be greatly reduced.

[0063] The first bubble removal unit 770A and the second bubble removal unit 770B are in communication with the ink supply unit 400 of the main body of the recording unit 50, and are depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, so that the depressurized state is maintained even when the main body of the recording unit 50 is not constantly operating, thereby enabling the bubble removal operation. The third check valve 213 may be provided at the branched portions of the third air passage 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B. The third check valve 213 may be provided at the concentrated portion of the third air passage 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B.

[0064] The foam reservoir 520 and the foam removal unit 770 do not need to be provided in both the supply channel 130 and the first recovery channel 140; they may be provided only in the supply channel 130 or only in the first recovery channel 140. Furthermore, three or more foam reservoirs 520 and foam removal units 770 may be provided. The foam reservoir 520 and foam removal unit 770 do not need to be provided in both the supply channel 130 and the first recovery channel 140. For example, the foam reservoir 520 and foam removal unit 770 may be provided vertically above the ink storage section 2, the first supply channel 111, the second supply channel 112, and the third supply channel 910. The foam reservoir 520 and foam removal unit 770 may also be provided vertically above the filter 110, the pump outlet channel 180, the bypass channel 160, and the pressure chamber 12. Furthermore, the foam accumulation chamber 520 and the foam removal unit 770 do not necessarily need to be located above the vertical direction of the communication section, such as the supply channel 130. As long as the configuration allows for capturing foam and bringing it into contact with the gas permeable membrane, the foam accumulation chamber 520 may communicate with the side of the communication section, and the foam removal unit 770 may be formed extending laterally from the foam accumulation chamber 520. This is also true when the foam accumulation chamber 520 and the foam removal unit 770 are provided in multiple parts of the communication section other than the supply channel 130 and the first recovery channel 140.

[0065] [Second example of ink path configuration] Figure 10 is a schematic diagram showing a second configuration example of the ink path. The second configuration example of the ink path is an example in which the first pressure adjustment means 120 and the second pressure adjustment means 150, the second foam reservoir chamber 520B, the circulation pump 500, the bypass passage 160, and the first recovery passage 140 shown in Figure 6 are not arranged. Furthermore, the second configuration example of the ink path is an example in which a third pressure adjustment means 902 communicating with the second supply passage 112 is arranged instead of the first pressure adjustment means 120 and the second pressure adjustment means 150, etc. In the second configuration example of the ink path, ink is not circulated, and the ink supplied from the second supply passage 112 flows in the order of supply passage 130 and pressure chamber 12, and is discharged from the discharge port 13. Since the second supply passage 112, the third supply passage 910, the supply passage 130, and the pressure chamber 12 are pressure controlled by the third pressure adjustment means 902, stable ink discharge is achieved.

[0066] The third pressure adjustment means 902 is located outside the recording head 1 and communicates with the third supply path 910 of the recording head 1 via the second supply path 112. The third pressure adjustment means 902 can be, for example, a head-based system utilizing head difference, but any method is applicable. This modified version is applicable to ink supply methods such as an ink cartridge system, where the ink cartridge is replaced when the ink stored in the ink reservoir is consumed, or the so-called CISS system (continuous ink supply system), where ink is injected from an inlet.

[0067] The first foam reservoir chamber 520A is located above the supply channel 130 in the vertical direction so as to communicate with the supply channel 130, and the first foam removal unit 770A is formed extending vertically above the first foam reservoir chamber 520A. This allows foam mixed into the ink in the supply channel 130, etc., by circulation and discharge operations to be captured in the foam reservoir chamber 520A and discharged from the ink by the foam removal operation. The foam mixed into the ink includes the aforementioned upstream foam, eluted foam, and unintended foam, but is not limited to these. It is possible to discharge from the ink any amount of foam that can be captured in the foam reservoir chamber 520 and that is sufficient to achieve a sufficient foam removal speed. Therefore, the possibility of foam entering the ink channel communicating with the discharge port 13 can be greatly reduced.

[0068] The first bubble removal unit 770A communicates with the ink supply unit 400 of the main body of the recording unit 50 and is depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, so that the depressurized state is maintained even when the main body of the recording unit 50 is not constantly operating, thereby enabling the bubble removal operation. The third check valve 213 may also be provided in the third air passage 113 between the first bubble removal unit 770A and the ink supply unit 400.

[0069] There may be two or more foam retention chambers 520 and foam removal units 770. Furthermore, the foam retention chambers 520 and foam removal units 770 do not necessarily have to be located in the supply passage 130. For example, the foam retention chambers 520 and foam removal units 770 may be located vertically above the ink storage section 2, the first supply passage 111, the second supply passage 112, the third supply passage 910, the filter 110, and the pressure chamber 12. Also, the foam retention chambers 520 and foam removal units 770 do not necessarily have to be located vertically above the communication section such as the supply passage 130. As long as the configuration allows for capturing bubbles and bringing them into contact with the gas permeable membrane, the foam retention chambers 520 may communicate with the side of the communication section, and the foam removal units 770 may extend laterally from the foam retention chambers 520. This is also true when foam accumulation chambers 520 and foam removal units 770 are provided in multiple parts of the communication section other than the supply channel 130 and the first recovery channel 140.

[0070] [Second variation of the circulation pathway] Figure 11 schematically shows a second modified example of the circulation path. Figure 11 shows the circulation path when circulation is performed without discharge. The second modified example of the circulation path is an example in which the first pressure regulating means 120 and the second pressure regulating means 150 in Figure 6 are not arranged, and the bypass passage 160 and the first recovery passage 140 are directly connected.

[0071] In the second modified example of the circulation path, the flow resistance of the ink flow path from the bypass flow path 160 to the first recovery flow path 140 is denoted as R1, and the flow resistance of the ink flow path from the supply flow path 130 to the first recovery flow path 140 via the discharge module 300 is denoted as R2. Since the flow rate of ink flowing through each flow path is inversely proportional to the flow resistance, the ratio of the flow rate of ink in the flow path via the bypass flow path 160 to the flow rate of ink in the flow path via the discharge module 300 is R2 to R1. In accordance with this relationship, the flow resistance of each flow path is set so that the circulation amount is such that the viscosity of the ink near the discharge port 13 in the discharge module 300 is suppressed. That is, the flow resistance of each flow path is set so that the flow velocity of the ink in the pressure chamber 12 is equal to or greater than a predetermined flow velocity. The flow resistance R1 of the flow path via the bypass flow path 160 is controlled by changing the cross-sectional area or length of the flow path, or by providing a throttling in the flow path.

[0072] The third pressure adjustment means 902 is located outside the recording head 1 and communicates with the third supply path 910 of the recording head 1 via the second supply path 112. The third pressure adjustment means 902 can be, for example, a head-based system utilizing head difference, but any method is applicable. This modified example is applicable to both the ink cartridge system described above and ink supply systems such as the CISS system.

[0073] The first foam reservoir chamber 520A is located above the supply channel 130 in the vertical direction so as to communicate with the supply channel 130, and the first de-foaming unit 770A extends vertically upward from the first foam reservoir chamber 520A. The second foam reservoir chamber 520B is located above the first recovery channel 140 in the vertical direction so as to communicate with the first recovery channel 140, and the second de-foaming unit 770B extends vertically upward from the second foam reservoir chamber 520B. As a result, foam mixed in with the ink in the supply channel 130, the first recovery channel 140, the pump inlet channel 170, and the pump outlet channel 180, etc., due to circulation and discharge operations, is captured in the foam reservoir chamber 520 and discharged from the ink by de-foaming operations. The bubbles that mix with the ink include the aforementioned upstream bubbles, eluted bubbles, and unintended bubbles, but are not limited to these. It is possible to discharge from the ink a quantity of bubbles that can be captured in the bubble reservoir chamber 520 and that are sufficient to achieve a sufficient de-bubbling speed. Therefore, the possibility of bubbles entering the ink channel connected to the discharge port 13 can be greatly reduced.

[0074] The first bubble removal unit 770A and the second bubble removal unit 770B are in communication with the ink supply unit 400 of the main body of the recording unit 50, and are depressurized by the operation of the ink supply unit 400. Furthermore, a third check valve 213 is provided between the bubble removal unit 770 and the ink supply unit 400, so that the depressurized state is maintained even when the main body of the recording unit 50 is not constantly operating, thereby enabling the bubble removal operation. The third check valve 213 may be provided at the branched portions of the third air passage 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B. The third check valve 213 may be provided at the concentrated portion of the third air passage 113 between the ink supply unit 400 and the first bubble removal unit 770A and the second bubble removal unit 770B.

[0075] The foam reservoir 520 and the foam removal unit 770 do not need to be provided in both the supply channel 130 and the first recovery channel 140; they may be provided only in the supply channel 130 or only in the first recovery channel 140. Furthermore, three or more foam reservoirs 520 and foam removal units 770 may be provided. The foam reservoir 520 and foam removal unit 770 do not need to be provided in both the supply channel 130 and the first recovery channel 140. For example, the foam reservoir 520 and foam removal unit 770 may be provided vertically above the ink storage section 2, the first supply channel 111, the second supply channel 112, and the third supply channel 910. The foam reservoir 520 and foam removal unit 770 may also be provided vertically above the filter 110, the pump inlet channel 170, the pump outlet channel 180, the bypass channel 160, and the pressure chamber 12. Furthermore, the foam accumulation chamber 520 and the foam removal unit 770 do not necessarily need to be located above the vertical direction of the communication section, such as the supply channel 130. As long as the configuration allows for capturing foam and bringing it into contact with the gas permeable membrane, the foam accumulation chamber 520 may communicate with the side of the communication section, and the foam removal unit 770 may be formed extending laterally from the foam accumulation chamber 520. This is also true when the foam accumulation chamber 520 and the foam removal unit 770 are provided in multiple parts of the communication section other than the supply channel 130 and the first recovery channel 140.

[0076] (Reaction solution) The recording method of the present invention may include a reaction solution application step of applying an aqueous reaction solution containing a reactant that reacts with aqueous ink to a recording medium. The components used in the reaction solution will be described in detail below.

[0077] [Reactive agent] The reaction solution reacts with the ink upon contact, causing the components in the ink (components with anionic groups, such as resins, surfactants, and self-dispersing pigments) to aggregate, and contains a reactant. The presence of the reactant destabilizes the state of the components with anionic groups in the ink when the ink and reactant come into contact on the recording medium, thereby promoting ink aggregation. Examples of reactants include polyvalent metal ions, cationic components such as cationic resins, and organic acids. The reactant may be used alone or in combination of two or more types.

[0078] Examples of polyvalent metal ions that make up polyvalent metal salts include Ca 2+ Cu 2+ Ni 2+ Mg 2+ Sr 2+ Ba 2+ , and Zn 2+ Divalent metal ions such as Fe 3+ , Cr 3+ , Y 3+ , and Al 3+ Examples of trivalent metal ions include the following. To include polyvalent metal ions in the reaction solution, a water-soluble polyvalent metal salt (which may also be a hydrate) composed of a polyvalent metal ion and an anion can be used. Examples of anions include Cl - , Br - , I - , - ClO2 - ClO3 - ClO4 - NO2 - NO3 - SO4 2- CO3 2- , HCO3 - , PO4 3- HPO4 2- , and H2PO4 - Inorganic anions such as HCOO - , (COO - )2, COOH(COO - ), CH3COO - CH3CH(OH)COO -, C2H4(COO - )2, C6H5COO - , C6H4(COO - )2, and CH3SO3 - Examples of organic anions include the following. When polyvalent metal ions are used as a reactant, the content (mass%) of the polyvalent metal salt in the reaction solution is preferably 1.0% by mass or more and 20.0% by mass or less, based on the total mass of the reaction solution. In this specification, when the polyvalent metal salt is a hydrate, the "content (mass%) of polyvalent metal salt" in the reaction solution means the "content (mass%) of the anhydrous polyvalent metal salt" excluding water as the hydrate.

[0079] The reaction solution containing an organic acid has buffering capacity in the acidic range (pH less than 7.0, preferably pH 2.0 to 5.0), which efficiently converts the anionic groups of components present in the ink into acidic forms and aggregates them. Examples of organic acids include monocarboxylic acids and their salts such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrole carboxylic acid, furanic acid, picolinic acid, nicotinic acid, thiophene carboxylic acid, levulinic acid, and coumaric acid; dicarboxylic acids and their salts or hydrogen salts such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid, and tartaric acid; tricarboxylic acids and their salts or hydrogen salts such as citric acid and trimellitic acid; and tetracarboxylic acids and their salts or hydrogen salts such as pyromellitic acid. When using an organic acid as a reactant, the content (by mass) of the organic acid in the reaction solution is preferably 1.0% by mass or more and 50.0% by mass or less, based on the total mass of the reaction solution.

[0080] Examples of cationic resins include resins having the structure of primary to tertiary amines and resins having the structure of quaternary ammonium salts. Specifically, examples include resins having the structures of vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, guanidine, diallyldimethylammonium chloride, and alkylamine-epichlorohydrin condensates. To improve solubility in the reaction solution, cationic resins can be used in combination with acidic compounds, or cationic resins can be subjected to quaternization treatment. When a cationic resin is used as a reactant, the content (mass%) of the cationic resin in the reaction solution is preferably 0.1% by mass or more and 10.0% by mass or less, based on the total mass of the reaction solution.

[0081] [Aqueous medium] The reaction solution is an aqueous reaction solution containing at least water as an aqueous medium. Examples of aqueous mediums used in the reaction solution include those similar to those that can be incorporated into inks, as described later. The aqueous medium used in the reaction solution may contain water-soluble organic solvents, as described later, that can be incorporated into inks. The content (mass%) of the water-soluble organic solvent in the reaction solution is preferably 1.0% by mass or more and 45.0% by mass or less, based on the total mass of the reaction solution. The water-soluble organic solvent preferably contains specific water-soluble hydrocarbon compounds, as described later. The content (mass%) of the water-soluble hydrocarbon compounds in the reaction solution is preferably 1.0% by mass or more and 20.0% by mass or less, based on the total mass of the reaction solution. Furthermore, the water content (mass%) in the reaction solution is preferably 50.0% by mass or more and 95.0% by mass or less, based on the total mass of the reaction solution.

[0082] [Other ingredients] The reaction solution may contain various other components as needed. These other components are similar to those that can be included in the ink, as described later.

[0083] [Physical properties of the reaction solution] The reaction solution is an aqueous reaction solution applied to an inkjet system. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical properties. Specifically, the surface tension of the reaction solution at 25°C is preferably 20 mN / m or more and 60 mN / m or less. The viscosity of the reaction solution at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the reaction solution at 25°C is preferably 5.0 or more and 9.5 or less, and more preferably 6.0 or more and 9.0 or less.

[0084] (ink) The ink used in the recording method of the present invention is an aqueous inkjet ink containing resin particles. The glass transition temperature T of the resin particles. g (°C), Maximum ink temperature in the foam reservoir T i (°C), and the heating temperature T of the recording medium in the process of heating the recording medium. fix The temperature (°C) satisfies the relationship shown in formula (1) below. Note that the ink of the present invention does not need to be a so-called "curable ink." Therefore, the ink of the present invention does not need to contain polymerizable monomers or other compounds that can polymerize by the application of external energy. The components used in the ink will be described in detail below. T i <T g ≦T fix ...(1)

[0085] [Colorants] The ink preferably contains a colorant. Pigments and dyes can be used as the colorant. The colorant content (by mass) in the ink is preferably 0.50% by mass or more and 15.00% by mass or less, and more preferably 1.00% by mass or more and 10.00% by mass or less, based on the total mass of the ink.

[0086] Specific examples of pigments include inorganic pigments such as carbon black and titanium dioxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolon, diketopyrrolopyrrole, and dioxazine. Pigments may be used individually or in combination of two or more.

[0087] As for the dispersion method of the pigment, resin-dispersed pigments using a resin as a dispersant, and self-dispersing pigments in which hydrophilic groups are bonded to the surface of the pigment particles can be used. In addition, resin-bonded pigments in which organic groups containing resin are chemically bonded to the surface of the pigment particles, and microcapsule pigments in which the surface of the pigment particles is coated with resin or the like can be used. It is also possible to use a combination of pigments with different dispersion methods from among these. In particular, it is preferable to use resin-dispersed pigments in which the resin as a dispersant is physically adsorbed to the surface of the pigment particles, rather than resin-bonded pigments or microcapsule pigments.

[0088] For the resin dispersant used to disperse the pigment in an aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium through the action of anionic groups. As the resin dispersant, a resin having anionic groups can be used, and it is preferable to use a resin such as those described later, and among them, a water-soluble resin. The pigment content (mass%) in the ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the resin dispersant content (mass%).

[0089] Self-dispersing pigments can be those in which anionic groups such as carboxylic acid groups, sulfonic acid groups, and phosphonic acid groups are bonded directly to the particle surface of the pigment or via other atomic groups (-R-). The anionic group may be either acidic or salt-type, and if it is salt-type, it may be in a partially dissociated state or a fully dissociated state. When the anionic group is salt-type, examples of cations that become counterions include alkali metal cations, ammonium, and organic ammonium. Specific examples of other atomic groups (-R-) include linear or branched alkylene groups with 1 to 12 carbon atoms; arylene groups such as phenylene and naphthylene groups; carbonyl groups; imino groups; amide groups; sulfonyl groups; ester groups; and ether groups. Combinations of these groups may also be used.

[0090] It is preferable to use dyes that have anionic groups. Specific examples of dyes include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone. Dyes may be used individually or in combination of two or more. It is even more preferable that the colorant be a resin-dispersed pigment in which a resin acting as a dispersant is physically adsorbed onto the surface of the pigment particles, or a self-dispersing pigment in which anionic groups are directly or via other atomic groups (-R-) to the surface of the pigment particles.

[0091] The ink preferably contains a pigment. The inclusion of a pigment makes it easier to physically inhibit and suppress the fusion of resin particles, thereby further improving the discharge stability. Since it is easier to obtain such an effect of suppressing the fusion of resin particles and further improve the discharge stability, the pigment content (mass%) in the ink is preferably 0.10 times or more in mass ratio to the resin particle content (mass%). The aforementioned mass ratio is preferably 2.00 times or less, and more preferably 1.00 times or less.

[0092] [Resin particles] The ink contains resin particles. Using ink containing resin particles can improve the scratch resistance of recorded images.

[0093] Examples of resins that constitute the resin particles include acrylic resins, urethane resins, olefin resins, and polyester resins. Among these, acrylic resins and urethane resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid and (meth)acrylate are preferred. By using acrylic resins, the effect of suppressing fusion can be further improved, and the discharge stability can be further improved. The content (mass%) of resin particles in the ink is preferably 0.10% by mass or more and 20.00% by mass or less, and more preferably 6.00% by mass or more and 15.00% by mass or less, based on the total mass of the ink. If the resin particle content is less than 6.00% by mass, the scratch resistance of the image may be slightly reduced. On the other hand, if the resin particle content is more than 15.00% by mass, fusion in the foam chamber is more likely to occur, and the discharge stability may be slightly reduced. The resin particles exist in the ink in a dispersed state, that is, in the form of a resin emulsion.

[0094] As for acrylic resins, those having hydrophilic units and hydrophobic units as constituent units are preferred. In particular, resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from at least one of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer are preferred. Especially preferred are resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from a (meth)acrylic acid ester monomer.

[0095] Hydrophilic units are units that have hydrophilic groups, such as anionic groups. Hydrophilic units can be formed, for example, by polymerizing hydrophilic monomers that have hydrophilic groups. Specific examples of hydrophilic monomers that have hydrophilic groups include acidic monomers having carboxylic acid groups, such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Cations that constitute salts of acidic monomers include ions such as lithium, sodium, potassium, ammonium, and organic ammonium. Hydrophobic units are units that do not have hydrophilic groups, such as anionic groups. Hydrophobic units can be formed, for example, by polymerizing hydrophobic monomers that do not have hydrophilic groups, such as anionic groups. Specific examples of hydrophobic monomers include aromatic ring monomers such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0096] The resin that constitutes the resin particles is preferably a resin having a cross-linked structure. Resin particles formed from a resin with a cross-linked structure are less prone to fusing and can firmly maintain their shape. Therefore, by using an ink containing resin particles formed from a resin with a cross-linked structure, the discharge stability can be further improved.

[0097] The resin constituting the resin particles preferably contains units derived from crosslinkable monomers. Examples of crosslinkable monomers include monomers having two or more ethylenically unsaturated bonds. Specifically, examples include dienes such as butadiene and isoprene; difunctional alkyl(meth)acrylates such as 1,4-butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate; trifunctional alkyl(meth)acrylates such as trimethylolpropane tri(meth)acrylate and ethylene oxide-modified trimethylolpropane tri(meth)acrylate; and divinylbenzene. Among these, from the viewpoint of further improving discharge stability, it is preferable that the crosslinkable monomer is at least one selected from the group consisting of ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate.

[0098] The content (by mass%) of crosslinkable units in the resin constituting the resin particles is preferably 0.5% by mass or more and 3.0% by mass or less, based on the total mass of the resin. If the content of crosslinkable units is less than 0.5% by mass, the effect of improving discharge stability may decrease. On the other hand, if the content of crosslinkable units exceeds 3.0% by mass, the resin particles may not fuse well on the recording medium, and the effect of improving abrasion resistance may decrease.

[0099] Urethane resins can be obtained, for example, by reacting polyisocyanate with a polyol. Alternatively, they may be obtained by further reacting with a chain extender. Examples of olefin resins include polyethylene and polypropylene. Polyester resins can be obtained, for example, by dehydration condensation of a polycarboxylic acid with a polyol.

[0100] In this specification, "resin particles" refers to a resin that, when neutralized with an equimolar amount of alkali equivalent to its acid value, forms particles whose particle size can be measured by dynamic light scattering and exists in an aqueous medium. Whether a resin is water-soluble or water-dispersible (resin particles) can be determined according to the following method. First, a liquid containing resin neutralized with an alkali equivalent to its acid value (such as sodium hydroxide or potassium hydroxide) is prepared (resin solids content: 10% by mass). Next, the prepared liquid is diluted 10 times (by volume) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by dynamic light scattering, if particles with a particle size are measured, the resin can be determined to be resin particles. The measurement conditions in this case can be, for example, SetZero: 30 seconds, Number of measurements: 3, Measurement time: 180 seconds. As a particle size distribution analyzer, a particle size analyzer using dynamic light scattering (for example, product name "UPA-EX150", manufactured by Nikkiso) can be used. Of course, the particle size distribution measuring devices and measurement conditions used are not limited to those mentioned above.

[0101] It is preferable that the resin particles have electrically charged functional groups on their surface. Examples of electrically charged functional groups include carboxylic acid groups, sulfonic acid groups, and sulfate ester groups. Having such functional groups generates electrical repulsion between the particles, making them less likely to fuse together and further improving the discharge stability.

[0102] The amount of anionic groups in the resin particles is preferably between 50 μmol / g and 200 μmol / g. If the amount of anionic groups is less than 50 μmol / g, the particles may become more prone to fusing, which may reduce the effect of improving discharge stability. On the other hand, if the amount of anionic groups exceeds 200 μmol / g, the water solubility of the resin particles may improve, which may reduce the effect of improving abrasion resistance.

[0103] The amount of anionic groups in resin particles can be measured and calculated according to the following method. First, hydrochloric acid is added to an aqueous dispersion of resin particles until the pH becomes 2 or less, and the mixture is stirred for 24 hours. Then, the precipitate is separated by centrifugation and dried to obtain the resin. 1 g of the obtained resin is pulverized, and 30 g of 0.1 mol / L sodium bicarbonate aqueous solution is added and the mixture is stirred for 15 hours. Then, the supernatant is separated by centrifugation. Pure water is added to 1 g of the separated supernatant to obtain a 15 g sample. The obtained sample is titrated with 0.1 mol / L hydrochloric acid, and the amount of anionic groups per unit mass of resin particles is calculated from the measured value. Note that the various analyses described above may also be performed using resin extracted from ink by an appropriate method.

[0104] Glass transition temperature T of resin particles g (°C) and the maximum ink temperature T in the foam reservoir. i (°C) preferably satisfies the following formula (2): Glass transition temperature T of resin particles g (°C) and the maximum ink temperature T in the foam chamber i The ink ejection stability can be further improved if (°C) satisfies the relationship in equation (2) below. g (℃) and T i The difference from (°C) is preferably 50°C or less. T g -T i ≥10 ···(2)

[0105] Glass transition temperature T of resin particles g (°C), and the heating temperature T of the recording medium in the process of heating the recording medium after image recording. fix(°C) preferably satisfies the relationship represented by the following formula (3). Glass transition temperature T of the resin particles g (°C) and heating temperature T of the recording medium fix (°C) satisfies the relationship represented by the following formula (3), the abrasion resistance of the recorded image can be further improved. T fix (°C) and T g (°C) is preferably 40°C or less. T fix -T g ≧5 ···(3)

[0106] Glass transition temperature T of the resin particles g (°C) is preferably 50°C or more and 80°C or less. Glass transition temperature T of the resin particles g If it is lower than 50°C, fusion may easily occur, and the effect of improving ejection stability may be reduced. On the other hand, if the glass transition temperature of the resin particles exceeds 80°C, the effect of improving abrasion resistance may be reduced. The glass transition temperature of the resin particles can be measured using a differential scanning calorimeter (for example, product name "DSC Q1000", manufactured by TA instruments).

[0107] The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 2,000,000 or less. Cumulative 50% particle diameter based on volume of the resin particles measured by dynamic light scattering method (D 50 ) is preferably 50 nm or more and 500 nm or less. The cumulative 50% particle diameter based on volume of the resin particles is the diameter of particles that reaches 50% when accumulated from the small particle diameter side, based on the total volume of the measured particles in the particle diameter integration curve. The cumulative 50% particle diameter based on volume of the resin particles can be measured with a dynamic light scattering particle size analyzer and under measurement conditions described later. The resin particles do not need to encapsulate a coloring material.

[0108] [Water-soluble resin] The ink may contain a water-soluble resin. Whether the resin is water-soluble or water-dispersible (resin particles) can be determined by the method described above. The acid value of the water-soluble resin is preferably 50 mg KOH / g or more and 200 mg KOH / g or less, and more preferably 100 mg KOH / g or more and 150 mg KOH / g or less. The weight-average molecular weight of the water-soluble resin is preferably 3,000 or more and 15,000 or less.

[0109] The content (by mass) of the water-soluble resin in the ink is preferably 0.10% by mass or more and 10.00% by mass or less, and more preferably 0.50% by mass or more and 5.00% by mass or less, based on the total mass of the ink. Examples of the form of the water-soluble resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be used alone or in combination of two or more types.

[0110] [Composition of water-soluble resin] Examples of water-soluble resins include acrylic resins, urethane resins, olefin resins, and polyester resins. Among these, acrylic resins and urethane resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylate are even more preferred.

[0111] As for acrylic resins, those having hydrophilic units and hydrophobic units as constituent units are preferred. Among these, resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from at least one of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer are preferred. In particular, resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from at least one of a monomer of styrene and α-methylstyrene are preferred. Because these resins readily interact with pigments, they can be suitably used as resin dispersants for dispersing pigments.

[0112] Hydrophilic units are units that have hydrophilic groups, such as anionic groups. Hydrophilic units can be formed, for example, by polymerizing hydrophilic monomers that have hydrophilic groups. Specific examples of hydrophilic monomers that have hydrophilic groups include acidic monomers having carboxylic acid groups, such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Cations that constitute salts of acidic monomers include ions such as lithium, sodium, potassium, ammonium, and organic ammonium. Hydrophobic units are units that do not have hydrophilic groups, such as anionic groups. Hydrophobic units can be formed, for example, by polymerizing hydrophobic monomers that do not have hydrophilic groups, such as anionic groups. Specific examples of hydrophobic monomers include aromatic ring monomers such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0113] Urethane resins can be obtained, for example, by reacting polyisocyanate with a polyol. Alternatively, they may be obtained by further reacting with a chain extender. Examples of olefin resins include polyethylene and polypropylene. Polyester resins can be obtained, for example, by dehydration condensation of a polycarboxylic acid with a polyol.

[0114] [wax particles] The ink may contain wax particles formed from wax. The wax in this specification may be a composition containing other components, or it may be wax itself. The wax particles may be dispersed by a dispersant such as a surfactant or resin. One type of wax may be used alone, or two or more types may be used in combination. The content (mass%) of wax particles in the ink is preferably 0.50% by mass or more and 2.00% by mass or less, based on the total mass of the ink.

[0115] In the narrow sense, wax is an ester of a higher monohydric or dihydric alcohol that is insoluble in water and a fatty acid, and includes animal waxes and plant waxes, but does not include oils and fats. In the broad sense, it includes high-melting-point fats, mineral waxes, petroleum waxes, and various wax formulations and modified products. In this invention, any wax in the broad sense can be used without particular limitation. Wax in the broad sense can be classified into natural waxes, synthetic waxes, formulations thereof (blended waxes), and modified products thereof (modified waxes).

[0116] Examples of natural waxes include animal-based waxes such as beeswax, whale wax, and wool wax (lanolin); plant-based waxes such as wood wax, carnauba wax, sugarcane wax, palm wax, candelilla wax, and rice wax; mineral waxes such as montane wax; and petroleum-based waxes such as paraffin wax, microcrystalline wax, and petrolatum. Examples of synthetic waxes include hydrocarbon waxes such as Fischer-Tropsch wax and polyolefin wax (e.g., polyethylene wax, polypropylene wax). Blended wax is a mixture of the above-mentioned waxes. Modified wax is obtained by modifying the above-mentioned waxes through oxidation, hydrogenation, alcohol modification, acrylic modification, urethane modification, etc. One of the above waxes may be used alone, or two or more may be used in combination. Preferably, the wax is at least one selected from the group consisting of microcrystalline wax, Fischer-Tropsch wax, polyolefin wax, paraffin wax, and modified or blended products thereof. In particular, it is even more preferable that the mixture be a blend of multiple types of waxes, and especially preferable that it be a blend of petroleum-based waxes and synthetic waxes.

[0117] Furthermore, it is preferable that the wax particles are made of wax containing oxidized wax. Since the surface of wax particles made of oxidized wax is more hydrophilic, using wax particles made of oxidized wax can further enhance the fusion suppression effect.

[0118] The wax particles are preferably solid at ordinary temperature (25°C). The melting point Tw (°C) of the wax particles is preferably 120°C or lower, more preferably 100°C or lower. The melting point of the wax particles can be measured in accordance with the test method described in 5.3.1 (Melting point test method) of JIS K2235:1991 (Petroleum waxes). In the case of microcrystalline wax, petrolatum, or a mixture of a plurality of types of wax, more accurate measurement can be obtained by using the test method described in 5.3.2. The melting point of wax particles is easily affected by characteristics such as the molecular weight of the wax (higher molecular weight results in higher melting point), molecular structure (linear structure results in higher melting point, branching lowers the melting point), crystallinity (higher crystallinity results in higher melting point), and density (higher density results in higher melting point). Therefore, by controlling these characteristics, wax particles having a desired melting point can be obtained. The melting point of the wax particles in the ink can be measured, for example, in accordance with the above test method after washing and drying the wax particles separated by ultracentrifugation of the ink.

[0119] The volume-based 50% cumulative particle diameter of wax particles (D 50 ) is preferably 150 nm or more. The volume-based 50% cumulative particle diameter of the wax particles can be measured by the same method as that for the volume-based 50% cumulative particle diameter of the resin particles described above. If the volume-based 50% cumulative particle diameter of the wax particles is less than 150 nm, the effect of suppressing fusion of the wax particles may be slightly reduced. The volume-based 50% cumulative particle diameter of wax particles (D 50 ) is preferably 250 nm or less, more preferably 200 nm or less. The volume-based 50% cumulative particle diameter of wax particles (D 50 ) can be measured by a dynamic light scattering method, and the measurement conditions and apparatus can be the same as those for the measurement method for the resin described above.

[0120] [Aqueous medium] The ink used in the recording method of the present invention is an aqueous ink containing at least water as an aqueous medium. The ink may contain an aqueous medium which is water or a mixed solvent of water and a water-soluble organic solvent. Deionized water or ion-exchanged water is preferably used as the water. The water content (mass%) in the aqueous ink is preferably 50.00% by mass or more and 95.00% by mass or less, based on the total mass of the ink. The water-soluble organic solvent content (mass%) in the aqueous ink is preferably 2.00% by mass or more and 40.00% by mass or less, based on the total mass of the ink. As the water-soluble organic solvent, any of those usable in inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing solvents, and sulfur-containing solvents, can be used. One type of water-soluble organic solvent may be used alone, or two or more types may be used in combination.

[0121] [Water-soluble hydrocarbon compounds] The water-soluble organic solvent preferably contains a specific water-soluble hydrocarbon compound. This water-soluble hydrocarbon compound is a compound having a hydrocarbon chain with 3 or more carbon atoms, substituted with two or more hydrophilic groups selected from the group consisting of hydroxyl groups, amino groups, and anionic groups. However, the hydrocarbon chain may be interrupted by a sulfonyl group or an ether group. If the hydrocarbon chain has 3 or 4 carbon atoms, the hydrophilic group includes an anionic group, or the hydrocarbon chain is interrupted by a sulfonyl group.

[0122] In this invention, a hydrocarbon compound that is dissolved in water at 25°C at a concentration equal to the amount of the compound in the ink is defined as "water-soluble." That is, the solubility in water at 25°C is greater than the amount contained in the ink. The fact that the hydrocarbon chain is interrupted by a sulfonyl group or an ether group means that a sulfonyl group (-S(=O)2-) or an ether group (-O-) is present in the middle of the hydrocarbon chain. Water-soluble hydrocarbon compounds have hydrogen-bonding groups such as hydroxyl groups, amino groups, anionic groups, sulfonyl groups, and ether groups. Therefore, by using an ink containing this hydrocarbon compound, cockling and curling of recording media on which images are recorded can be suppressed. General hydrocarbon compounds having hydrocarbon chains with a relatively small number of carbon atoms (3 or 4) tend to have a small molecular weight and a low vapor pressure. However, the above-mentioned water-soluble hydrocarbon compounds have hydrogen-bonding anionic groups or their hydrocarbon chains are interrupted by sulfonyl groups, so they are less likely to evaporate due to intermolecular or intramolecular interactions and remain between fibers, exhibiting an effect of suppressing cockling and curling. The content (by mass) of water-soluble hydrocarbon compounds in the ink is preferably 1.00% by mass or more and 20.00% by mass or less, based on the total mass of the ink.

[0123] The number of carbon atoms in the hydrocarbon chain constituting the water-soluble hydrocarbon compound is preferably 3 to 50, and more preferably 3 to 10. Examples of anionic groups include sulfonic acid groups and carboxylic acid groups. Specific examples of water-soluble hydrocarbon compounds include alkanediols such as 1,5-pentanediol and 1,6-hexanediol; alanine, β-alanine, trimethylglycine, amidosulfuric acid (also known as sulfamic acid), aminomethanesulfonic acid, taurine (also known as 2-aminoethanesulfonic acid), carbamic acid, glycine, aspartic acid, glutamic acid, sulfanilic acid, or salts of the above-mentioned acids; amino acids such as phenylalanine, leucine, isoleucine, threonine, tryptophan, valine, methionine, lysine, and arginine; sulfonyl compounds such as bis(2-hydroxyethyl)sulfone; alkylene glycols such as triethylene glycol, tetraethylene glycol, tripropylene glycol, and polyethylene glycol with a number average molecular weight of about 200 to 1,000; and sugars such as sorbitol, D-sorbitol, xylitol, trehalose, fructose, and D(+)-xylose. Water-soluble hydrocarbon compounds may be used individually or in combination of two or more.

[0124] [Surfactants] The ink preferably further contains a nonionic surfactant. Since nonionic surfactants readily adsorb to the surface of resin particles, they can further suppress the fusion of resin particles and improve discharge stability. Because this effect of suppressing the fusion of resin particles is easily obtained and discharge stability can be further improved, the content (mass%) of the nonionic surfactant in the ink is preferably 0.10 times or more by mass ratio to the content (mass%) of resin particles. Furthermore, the above mass ratio is preferably 1.00 times or less, and more preferably 0.30 times or less.

[0125] [Other ingredients] The ink may contain various other components as needed. Examples of other components include various additives such as defoamers, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, fungicides, antioxidants, and reduction inhibitors.

[0126] [Ink properties] The ink is a water-based ink for use in inkjet systems. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical properties. The viscosity of the ink at 25°C is preferably between 1.0 mPa·s and 10.0 mPa·s. The viscosity of the ink at 25°C can be measured with a rotational viscometer. The viscosity of the ink can be adjusted, for example, using water-soluble organic solvents, resins, and surfactants.

[0127] The surface tension of the ink at 25°C is preferably between 20 mN / m and 60 mN / m. The surface tension of the ink at 25°C can be measured by methods such as the plate method. Furthermore, the pH of the ink at 25°C is preferably between 7.0 and 9.5, and more preferably between 8.0 and 9.5. The pH of the ink can be measured using a general pH meter equipped with a glass electrode or the like. [Examples]

[0128] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way by the following examples unless it exceeds the gist of the invention. Unless otherwise specified, amounts of components indicated in "parts" and "%" are based on mass.

[0129] <Preparation of Pigment Dispersion> (Pigment dispersion 1) 15.0 parts pigment, 15.0 parts aqueous solution of resin dispersant, and 70.0 parts water were mixed and dispersed in a sand grinder for 1 hour, after which undispersed material containing coarse particles was removed by centrifugation. Carbon black (product name "Printex85", manufactured by Orion Engineered Carbons) was used as the pigment. As the aqueous solution of resin dispersant, an aqueous solution with a resin (solids) content of 20.0% was used, obtained by neutralizing a styrene-acrylic acid copolymer with an equimolar amount of 10% potassium hydroxide aqueous solution equal to the acid value, and adding an appropriate amount of ion-exchanged water. The acid value of the styrene-acrylic acid copolymer was 150 mgKOH / g, and the weight-average molecular weight was 8,000. After pressure filtration through a pore size 3.0 μm microfilter (manufactured by Fujifilm), an appropriate amount of ion-exchanged water was added to prepare pigment dispersion 1. The pigment content in pigment dispersion 1 was 15.00%, and the resin content was 3.00%.

[0130] (Pigment dispersion 2) Pigment dispersion 2 was obtained in the same manner as for pigment dispersion 1 described above, except that CI pigment blue in a 15:3 ratio was used as the pigment. The pigment content in the obtained pigment dispersion 2 was 15.00%, and the resin content was 3.00%.

[0131] (Pigment dispersion 3) Pigment dispersion 3 was obtained in the same manner as for pigment dispersion 1 described above, except that CI Pigment Red 122 was used as the pigment. The pigment content in the obtained pigment dispersion 3 was 15.00%, and the resin content was 3.00%.

[0132] (Pigment dispersion 4) Pigment dispersion 4 was obtained in the same manner as for pigment dispersion 1 described above, except that CI Pigment Yellow 74 was used as the pigment. The pigment content in the obtained pigment dispersion 4 was 15.00%, and the resin content was 3.00%.

[0133] (Pigment dispersion 5) A self-dispersing pigment (product name "Cab-O-Jet300", manufactured by Cabot) was prepared, in which benzenecarboxylic acid groups were bonded to the surface of carbon black particles. The prepared self-dispersing pigment was diluted with water and thoroughly stirred to obtain a pigment dispersion 5 with a pigment content of 15.00%.

[0134] <Preparation of water-soluble resins> 100.0 parts of ethylene glycol monobutyl ether were placed in a four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux tube. Nitrogen gas was then introduced into the flask, and the temperature was raised to 110°C while stirring. A monomer solution was prepared by dissolving 50 parts of styrene, 32 parts of n-butyl acrylate, 18 parts of methacrylic acid, and 1.3 parts of polymerization initiator (t-butyl peroxide) in ethylene glycol monobutyl ether. The prepared monomer solution was added dropwise to the flask over 3 hours. After stirring for 2 hours, the ethylene glycol monobutyl ether was removed by reducing the pressure to obtain a water-soluble resin. The obtained water-soluble resin was neutralized with potassium hydroxide at a concentration of 1.0 times its acid value (molar ratio), and then dissolved at 80°C with an appropriate amount of deionized water to obtain an aqueous solution of the water-soluble resin with a resin content of 15.00%.

[0135] <Preparation of resin particles> (Resin particles 1-5, 8-19) A four-necked flask equipped with a stirrer, reflux condenser, and nitrogen gas inlet tube was filled with the amounts of potassium persulfate and deionized water shown in Table 1, and nitrogen gas was introduced. The monomers of the types and amounts shown in Table 1 were then mixed to obtain the mixture. The meanings of the abbreviations in Table 1 are explained below. BMA: n-butyl methacrylate • EMA: Ethyl methacrylate • CHMA: Cyclohexyl methacrylate • MAA: Methacrylic acid • EDMA: Ethylene glycol dimethacrylate BDDA: 1,4-butanediol diacrylate • PEGDMA: Polyethylene glycol dimethacrylate (n=4) • Aqualon KH-05 (product name, manufactured by Daiichi Kogyo Seiyaku): Anionic reactive surfactant • Bremmer PME1000: Nonionic reactive surfactant

[0136] The resulting mixture was added dropwise to a four-necked flask over 1 hour with stirring, and then reacted at 80°C for 2 hours. Afterward, the contents were cooled to room temperature, and potassium hydroxide and an appropriate amount of deionized water were added to adjust the pH of the liquid to 8.5. In this way, an aqueous dispersion containing 40.0% resin particles was obtained. The properties of the obtained resin particles are shown in Table 2.

[0137] The amount of anionic groups in the resin particles was measured and calculated as follows: Hydrochloric acid was added to an aqueous dispersion of resin particles until the pH was 2 or less, and the mixture was stirred for 24 hours. The precipitate was then separated by centrifugation and dried to obtain the resin. 1 g of the obtained resin was pulverized, and 30 g of 0.1 mol / L sodium bicarbonate aqueous solution was added and the mixture was stirred for 15 hours. The supernatant was then separated by centrifugation. 1 g of the separated supernatant was mixed with pure water to prepare a 15 g sample. The obtained sample was titrated with 0.1 mol / L hydrochloric acid using a potentiometric automatic titrator (product name "AT510", manufactured by Kyoto Electronics Manufacturing Co., Ltd.), and the amount of anionic groups per unit mass of resin particles was calculated from the measured values.

[0138] The glass transition temperature of the resin particles was measured according to the following procedure. First, an aqueous dispersion of resin particles was heated to 60°C and dried, then sealed in an aluminum container to prepare the sample. Next, using a differential scanning calorimetry system (product name "DSC Q1000", manufactured by TA Instruments), the sample was heated to 200°C at a rate of 10°C / min, cooled to -50°C at a rate of 5°C / min, and then heated to 200°C at a rate of 10°C / min to determine the glass transition temperature T g The temperature (°C) was measured.

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[0140] TIFF2026139580000003.tif135170

[0141] (Resin particles 6) A stirrer (product name "Tornado Stirrer Standard SM-104", manufactured by AS ONE) was set up in a 300 mL beaker. 100 g of an aqueous dispersion of polyester resin particles and 0.5 g of a crosslinking agent were added to this beaker and stirred at 80°C for 6 hours. The aqueous dispersion of polyester resin particles used was "Vyronal MD-1245" (manufactured by Toyobo, with a resin particle content of 30.0%). Ethylene glycol glycidyl ether (product name "Denacol EX-810", manufactured by Nagase ChemteX) was used as the crosslinking agent. Subsequently, pressure filtration was performed using a 3.0 μm pore size microfilter (manufactured by Fujifilm). Next, an appropriate amount of deionized water was added to adjust the resin particle content, obtaining an aqueous dispersion of resin particles 6 with a polyester resin particle content of 25.0%. The amount of anionic groups in the obtained resin particles 6 was 53 μmol / g, and the glass transition temperature T g The temperature was 60°C, and the proportion of cross-linked units was 1.5%.

[0142] (Resin particles 7) A 1 L separable flask equipped with a stirrer, thermometer, and reflux tubing was prepared. A mixture of 100 g of polycarbonate diol, 4.2 g of 2,2-bis(hydroxymethyl)propionic acid, 41 g of 4,4'-dicyclohexylmethane diisocyanate, 2.2 g of triethylamine, and 80 g of acetone was prepared. The polycarbonate diol used was "T-5650E," manufactured by Asahi Kasei. Under a nitrogen atmosphere, this mixture was placed in the flask, one drop of catalyst (di(2-ethylhexanoate) tin(II)) was added, and the mixture was reacted at 80°C for 15 hours. After cooling to 40°C, water was added to the flask while stirring at 300 rpm to prepare particulate urethane resin. After stirring at 40°C for 30 minutes, 1.2 g of diethylenetriamine was added, and the mixture was stirred at 40°C for 6 hours. After removing the acetone by distillation, deionized water was added to adjust the resin content to 30.0%. In this way, an aqueous dispersion of resin particles 7, which are resin particles formed from a urethane resin, was obtained. The amount of anionic groups in the obtained resin particles 7 was 125 μmol / g, and the glass transition temperature Tg The temperature was 64°C, and the proportion of crosslinked units was 0.8%.

[0143] <Ink preparation> Each ink was prepared by mixing the components (in %) shown in the middle section of Tables 3-1 to 3-5, stirring thoroughly, and then pressure filtering through a 3.0 μm pore size cellulose acetate filter (manufactured by Advantec). The physical properties of each prepared ink are shown in the lower section of Tables 3-1 to 3-5. The nonionic surfactants indicated by their trade names in Tables 3-1 to 3-5 are as follows: • Acetylenel E100: Ethylene oxide adduct of acetylene glycol (manufactured by Kawaken Fine Chemicals) • BYK348: Silicone-based surfactant (manufactured by Bic Chemie) • Surfinol 420: Ethylene oxide adduct of acetylene glycol (manufactured by Nisshin Chemical Industry Co., Ltd.) • Capstone FS-3100: Fluorine-based surfactant (manufactured by Chemour)

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[0149] <Preparation of reaction solution> 74.5 parts water, 5.0 parts magnesium sulfate heptahydrate, 19.0 parts 1,2-butanediol, 1.0 part 1,2-hexanediol, and 0.5 parts nonionic surfactant (product name "Acetylenel E100", manufactured by Kawaken Fine Chemicals) were mixed and thoroughly stirred. Then, the reaction solution was prepared by pressure filtration through a 3.0 μm pore size cellulose acetate filter (manufactured by Advantec).

[0150] <Recording head> Recording heads with the configurations shown in Table 4 were manufactured. In Table 4, abbreviations indicate the following: PP: polypropylene, PE: polyethylene, FEP: fluorinated ethylene hexafluoropropylene copolymer, and PS: polystyrene. Recording heads with the depressurization chamber positioned above the liquid storage chamber in the vertical direction (Figure 6(a)) and recording heads with the depressurization chamber positioned to the side of the liquid storage chamber (Figure 6(b)) are indicated as "upper" and "side" respectively in the "Position of depressurization chamber relative to liquid storage chamber" column of Table 4.

[0151] TIFF2026139580000009.tif138170

[0152] <Rating> An inkjet recording device (product name "imagePROGRAF PRO-2000", manufactured by Canon) was prepared with the recording heads of the types shown in Tables 5-1 and 5-2. In this example, the recording duty cycle of a solid image recorded under the condition that one drop of ink with a mass of 4.0 ng per drop is applied to a unit area of ​​1 / 1,200 inch × 1 / 1,200 inch is defined as 100%. The prepared reaction solution and each ink were filled into ink cartridges and set in the inkjet recording device with the combination of recording head and ink shown in Tables 5-1 and 5-2, and the following items were evaluated. In this invention, in the evaluation criteria for each item below, "AA", "A", and "B" were defined as acceptable levels, and "C" as an unacceptable level. The evaluation results are shown in Tables 5-1 and 5-2.

[0153] In Comparative Examples 7 and 8, an inkjet recording apparatus was used that, based on the description in Patent Document 1, had a degassing section equipped with a hollow fiber module in the path that supplies ink from the ink reservoir to the recording head. In Reference Example 1, an inkjet recording apparatus was used that, based on the description in Patent Document 2, had a filter for capturing bubbles in the path that supplies ink from the ink reservoir to the recording head. In Reference Example 2, an inkjet recording apparatus was used that, based on the description in Patent Document 3, had a degasser inside the recording head that included a partition formed of a hollow fiber membrane. In Reference Example 3, an inkjet recording apparatus was used that, based on the description in Patent Document 4, had a permeable partition wall with a thickness of 1.00 mm inside the recording head instead of a gas permeable membrane.

[0154] (Discharge stability) To replicate the conditions after a certain period of use, 0.3 mL of air was injected into the foam reservoir chamber. The foam reservoir chamber, which is connected to the liquid storage chamber, has a volume of 0.5 mL. The maximum ink temperature T in the foam reservoir chamber was measured using a heater installed in the recording head. i The temperature (°C) was controlled to the temperatures shown in Tables 5-1 and 5-2, and the depressurized chamber was depressurized to the degree of depressurization shown in Tables 5-1 and 5-2 for 10 days, allowing air from the bubble reservoir chamber to be transferred to the depressurized chamber via a gas permeable membrane. Subsequently, to reproduce the conditions after a certain period of use, 0.3 mL of air was injected into the bubble reservoir chamber, and then 100 solid images of 15 cm x 25 cm were recorded on an A4-sized recording medium. In the case without depressurization, 0.3 mL of air was injected into the liquid storage chamber, and the maximum ink temperature T in the liquid storage chamber was recorded. i The evaluation was performed using the same procedure as shown in Tables 5-1 and 5-2, except that the temperature (°C) was set to the temperature shown in Tables 5-1 and 5-2 and the device was left undisturbed for 10 days. The recording medium used was "Scotchcal Graphic Film IJ1220-10" (manufactured by 3M, material: polyvinyl chloride). Subsequently, the nozzle check pattern of the imagePROGRAF PRO-2000 was recorded, and the recorded nozzle check pattern was visually inspected to evaluate the ink ejection stability according to the evaluation criteria shown below. AA: The number of discharge ports that stopped discharging was 5 or less. A: The number of discharge ports that failed to discharge was between 6 and 10. B: The number of discharge ports that failed to dispense was between 11 and 15. C: The number of discharge ports that failed to dispense was 16 or more.

[0155] (Abrasion resistance) Friction tests were conducted using a friction resistance tester (product name "AB-301", manufactured by Tester Sangyo Co., Ltd.), which is a friction tester II (JSPS type) compliant with JIS L 0849. Specifically, the surface of the solid image recorded in the above discharge stability evaluation was subjected to friction tests using a white friction cloth (cotton) specified in JIS L 0803, with 1g of water added, under a load of 500g for 30 and 50 reciprocating cycles. The image after the friction test was visually inspected, and the abrasion resistance of the image was evaluated according to the evaluation criteria shown below. A: No abrasion was observed in either the image after 30 round trips or the image after 50 round trips. B: Abrasion was observed in the image after 50 round trips, but not in the image after 30 round trips. C: Abrasion was observed in the image after 30 round trips.

[0156] (Suction recovery) Five days after refilling the ink, a normal suction recovery operation was performed using the printer driver. Then, the nozzle check pattern of the imagePROGRAF PRO-2000 was recorded on a recording medium. Plain paper (product name "CS-068 A4", Canon) was used as the recording medium. The recorded nozzle check pattern was visually inspected, and the suction recovery performance was evaluated according to the evaluation criteria shown below. A: The number of discharge ports that failed to discharge was 15 or less. C: The number of discharge ports that failed to dispense was 16 or more.

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[0158] TIFF2026139580000011.tif255164

[0159] Reference Example 1 exhibited excellent dispensing stability and suction recovery, but the device was large.

[0160] This embodiment includes the following methods and configurations. (Method 1) An inkjet recording method comprising using an inkjet recording apparatus equipped with a recording head comprising: an ejection port for ejecting aqueous ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the aqueous ink from the ejection port; a liquid storage chamber capable of supplying the aqueous ink to the pressure chamber; a foam storage chamber communicating with the liquid storage chamber and configured to retain foam inside; a depressurization chamber disposed adjacent to the foam storage chamber and configured to reduce the pressure inside; and a gas permeable membrane disposed at the boundary between the foam storage chamber and the depressurization chamber, wherein the aqueous ink ejected from the ejection port is applied to a recording medium to record an image, and the recording medium is then heated, The aforementioned water-based ink contains resin particles, Glass transition temperature T of the resin particles g (°C), the maximum temperature T of the aqueous ink in the foam reservoir chamber. i (°C), and the heating temperature T of the recording medium in the above step. fix An inkjet recording method characterized in that (°C) satisfies the relationship of the following formula (1). T i <T g ≦T fix ...(1) (Method 2) The inkjet recording method according to Method 1, wherein the aqueous ink further contains a pigment. (Method 3) The inkjet recording method according to Method 2, wherein the content (mass%) of the pigment in the aqueous ink is 0.10 times or more in mass ratio to the content (mass%) of the resin particles. (Method 4) The inkjet recording method according to any one of methods 1 to 3, wherein the aqueous ink further contains a nonionic surfactant. (Method 5) The inkjet recording method according to Method 4, wherein the content (mass%) of the nonionic surfactant in the aqueous ink is 0.10 times or more in mass ratio to the content (mass%) of the resin particles. (Method 6) Maximum temperature T of the water-based ink in the foam chamber i An inkjet recording method according to any one of methods 1 to 5, wherein (°C) is 30°C or more and 50°C or less. (Method 7) Glass transition temperature T of the resin particles g An inkjet recording method according to any one of methods 1 to 6, wherein (°C) is 50°C or higher and 80°C or lower. (Method 8) Heating temperature of the recording medium in the above step T fix An inkjet recording method according to any one of methods 1 to 7, wherein (°C) is 70°C or higher and 90°C or lower. (Method 9) Glass transition temperature T of the resin particles g (°C) and the maximum temperature T of the aqueous ink in the foam chamber. i The inkjet recording method described in any one of methods 1 to 8, wherein (°C) satisfies the relationship in formula (2) below. T g -T i ≥10 ···(2) (Method 10) Glass transition temperature T of the resin particles g (°C) and the heating temperature T of the recording medium in the above step. fix The inkjet recording method described in any one of methods 1 to 9, wherein (°C) satisfies the relationship in formula (3) below. T fix -T g ≥5 ···(3) (Method 11) The inkjet recording method according to any one of Methods 1 to 10, wherein the content (mass%) of the resin particles in the aqueous ink is 6.00% by mass or more and 15.00% by mass or less, based on the total mass of the ink. (Method 12) The inkjet recording method according to any one of Methods 1 to 11, wherein the resin constituting the resin particles is an acrylic resin. (Method 13) The inkjet recording method according to any one of Methods 1 to 12, wherein the resin particles have anionic groups. (Method 14) The inkjet recording method according to any one of Methods 1 to 13, wherein the amount of anionic groups in the resin particles is 50 μmol / g or more and 200 μmol / g or less. (Method 15) The inkjet recording method according to any one of Methods 1 to 14, wherein the resin constituting the resin particles has a crosslinked structure. (Method 16) The resin comprises a crosslinkable unit derived from a crosslinkable monomer, The inkjet recording method according to method 15, wherein the content (mass%) of the crosslinkable unit in the resin is 0.5% by mass or more and 3.0% by mass or less, based on the total mass of the resin. (Method 17) The inkjet recording method according to Method 16, wherein the crosslinkable monomer is at least one selected from the group consisting of ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate. (Method 18) The inkjet recording method according to any one of Methods 1 to 17, wherein the depressurization chamber is located adjacent to the liquid storage chamber in the vertical direction. (Method 19) The inkjet recording method according to any one of Methods 1 to 18, wherein the thickness of the gas permeable film is 0.10 mm or less. (Method 20) The inkjet recording method according to any one of Methods 1 to 19, wherein the thickness of the gas permeable film is 0.01 mm or more. (Method 21) The inkjet recording method according to any one of Methods 1 to 20, wherein the material of the gas permeable membrane is polypropylene. (Method 22) The inkjet recording method according to any one of Methods 1 to 21, wherein the degree of depressurization of the depressurization chamber is 10 kPa or more. (Configuration 1) An inkjet recording apparatus used in an inkjet recording method which includes a recording head comprising: a discharge port for discharging aqueous ink; a pressure chamber communicating with the discharge port; a discharge element disposed in the pressure chamber and generating energy for discharging the aqueous ink from the discharge port; a liquid storage chamber capable of supplying the aqueous ink to the pressure chamber; a foam storage chamber communicating with the liquid storage chamber and configured to retain foam inside; a depressurization chamber disposed adjacent to the foam storage chamber and configured to reduce the pressure inside; and a gas permeable membrane disposed at the boundary between the foam storage chamber and the depressurization chamber, wherein the inkjet recording apparatus is used in an inkjet recording method which includes the step of applying the aqueous ink discharged from the discharge port to a recording medium to record an image, and then heating the recording medium, The aforementioned water-based ink contains resin particles, Glass transition temperature T of the resin particles g (°C), the maximum temperature T of the aqueous ink in the foam reservoir chamber. i (°C), and the heating temperature T of the recording medium in the above step. fix An inkjet recording apparatus characterized in that (°C) satisfies the relationship of the following formula (1). T i <T g ≦T fix ...(1) (Configuration 2) An inkjet recording device equipped with a recording head comprising: an ejection port for ejecting water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; a liquid storage chamber capable of supplying the water-based ink to the pressure chamber; a foam storage chamber communicating with the liquid storage chamber and configured to retain foam inside; a depressurization chamber disposed adjacent to the foam storage chamber and configured to reduce the pressure inside; and a gas permeable membrane disposed at the boundary between the foam storage chamber and the depressurization chamber; the water-based ink used in an inkjet recording method comprising the steps of: applying the water-based ink ejected from the ejection port to a recording medium to record an image; and then heating the recording medium. Contains resin particles, Glass transition temperature T of the resin particles g(°C), the maximum temperature T of the aqueous ink in the foam reservoir chamber. i (°C), and the heating temperature T of the recording medium in the above step. fix A water-based ink characterized in that (°C) satisfies the relationship of formula (1) below. T i <T g ≦T fix ...(1)

Claims

1. An inkjet recording method is provided using an inkjet recording apparatus equipped with a recording head comprising: an ejection port for ejecting aqueous ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the aqueous ink from the ejection port; a liquid storage chamber capable of supplying the aqueous ink to the pressure chamber; a foam storage chamber communicating with the liquid storage chamber and configured to retain foam inside; a depressurization chamber disposed adjacent to the foam storage chamber and configured to reduce the pressure inside; and a gas permeable membrane disposed at the boundary between the foam storage chamber and the depressurization chamber; wherein the aqueous ink ejected from the ejection port is applied to a recording medium to record an image, and the recording medium is then heated. The aforementioned water-based ink contains resin particles, Glass transition temperature T of the resin particles ｇ (°C), the maximum temperature T of the aqueous ink in the foam reservoir chamber. ｉ (°C), and the heating temperature T of the recording medium in the above step. ｆｉｘ An inkjet recording method characterized in that (°C) satisfies the relationship of the following formula (1). T ｉ <T ｇ ≦T ｆｉｘ ・・・(1)

2. The inkjet recording method according to claim 1, wherein the aqueous ink further contains a pigment.

3. The inkjet recording method according to claim 2, wherein the content (mass%) of the pigment in the aqueous ink is 0.10 times or more in mass ratio to the content (mass%) of the resin particles.

4. The inkjet recording method according to claim 1, wherein the aqueous ink further contains a nonionic surfactant.

5. The inkjet recording method according to claim 4, wherein the content (mass%) of the nonionic surfactant in the aqueous ink is 0.10 times or more by mass ratio to the content (mass%) of the resin particles.

6. The maximum temperature T of the aqueous ink in the foam reservoir chamber. ｉ The inkjet recording method according to claim 1, wherein (°C) is 30°C or more and 50°C or less.

7. Glass transition temperature T of the resin particles ｇ The inkjet recording method according to claim 1, wherein (°C) is 50°C or more and 80°C or less.

8. The heating temperature T of said recording medium in said step ｆｉｘ (°C) is 70°C or higher and 90°C or lower. The inkjet recording method according to claim 1.

9. Glass transition temperature T of the resin particles ｇ (°C) and the maximum temperature T of the aqueous ink in the foam reservoir chamber. ｉ The inkjet recording method according to claim 1, wherein (°C) satisfies the relationship of formula (2) below. T ｇ -T ｉ ≧10 ・・・(2)

10. Glass transition temperature T of the resin particles ｇ (°C) and the heating temperature T of the recording medium in the above step. ｆｉｘ The inkjet recording method according to claim 1, wherein (°C) satisfies the relationship of formula (3) below. T ｆｉｘ -T ｇ ≧5 ・・・(3)

11. In the aqueous ink, the content (mass%) of the resin particles is, based on the total mass of the ink, The inkjet recording method according to claim 1, wherein the amount is 6.00% by mass or more and 15.00% by mass or less.

12. The inkjet recording method according to claim 1, wherein the resin constituting the resin particles is an acrylic resin.

13. The inkjet recording method according to claim 1, wherein the resin particles have anionic groups.

14. The inkjet recording method according to claim 1, wherein the amount of anionic groups in the resin particles is 50 μmol / g or more and 200 μmol / g or less.

15. The inkjet recording method according to claim 1, wherein the resin constituting the resin particles has a crosslinked structure.

16. The resin comprises a crosslinkable unit derived from a crosslinkable monomer, The inkjet recording method according to claim 15, wherein the content (mass%) of the crosslinkable unit in the resin is 0.5% by mass or more and 3.0% by mass or less, based on the total mass of the resin.

17. The inkjet recording method according to claim 16, wherein the crosslinkable monomer is at least one selected from the group consisting of ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate.

18. The inkjet recording method according to any one of claims 1 to 17, wherein the depressurization chamber is located adjacent to the foam reservoir chamber in the vertical direction, above it.

19. The inkjet recording method according to any one of claims 1 to 17, wherein the thickness of the gas permeable film is 0.10 mm or less.

20. The inkjet recording method according to any one of claims 1 to 17, wherein the thickness of the gas permeable film is 0.01 mm or more.

21. The inkjet recording method according to any one of claims 1 to 17, wherein the material of the gas permeable membrane is polypropylene.

22. The inkjet recording method according to any one of claims 1 to 17, wherein the degree of depressurization of the depressurization chamber is 10 kPa or more.

23. An inkjet recording apparatus used in an inkjet recording method which includes a recording head comprising: an ejection port for ejecting aqueous ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the aqueous ink from the ejection port; a liquid storage chamber capable of supplying the aqueous ink to the pressure chamber; a foam storage chamber communicating with the liquid storage chamber and configured to retain foam inside; a depressurization chamber disposed adjacent to the foam storage chamber and configured to reduce the pressure inside; and a gas permeable membrane disposed at the boundary between the foam storage chamber and the depressurization chamber, wherein the inkjet recording apparatus is used in an inkjet recording method which includes the step of applying the aqueous ink ejected from the ejection port to a recording medium to record an image, and then heating the recording medium, The aforementioned water-based ink contains resin particles, Glass transition temperature T of the resin particles ｇ (°C), the maximum temperature T of the aqueous ink in the foam reservoir chamber. ｉ (°C), and the heating temperature T of the recording medium in the above step. ｆｉｘ An inkjet recording apparatus characterized in that (°C) satisfies the relationship of the following formula (1). Ti<T ｇ ≦T ｆｉｘ ・・・(1)

24. The aqueous ink used in an inkjet recording method that uses an inkjet recording device equipped with a recording head comprising: an ejection port for ejecting aqueous ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the aqueous ink from the ejection port; a liquid storage chamber capable of supplying the aqueous ink to the pressure chamber; a foam storage chamber communicating with the liquid storage chamber and configured to retain foam inside; a depressurization chamber disposed adjacent to the foam storage chamber and configured to reduce the pressure inside; and a gas permeable membrane disposed at the boundary between the foam storage chamber and the depressurization chamber, wherein the aqueous ink ejected from the ejection port is applied to a recording medium to record an image, and the recording medium is then heated. Contains resin particles, Glass transition temperature T of the resin particles ｇ (°C), the maximum temperature T of the aqueous ink in the foam reservoir chamber. ｉ (°C), and the heating temperature T of the recording medium in the above step. ｆｉｘ A water-based ink characterized in that (°C) satisfies the relationship shown in the following formula (1). T ｉ <T ｇ ≦T ｆｉｘ ・・・(1)

Images