Inkjet recording method, inkjet recording device and aqueous ink

Abstract

To provide an inkjet recording method capable of recording an image excellent in scratch resistance while enhancing intermittent discharge stability of ink.SOLUTION: An inkjet recording method records an image on a storage medium through discharging of an aqueous ink from a discharge port of a recording head including: a discharge unit having the discharge port configured to discharge the aqueous ink, a pressure chamber communicating with the discharge port, and a discharge element arranged at the pressure chamber and configured to generate energy to discharge the aqueous ink from the discharge port; and a circulation unit having a supply channel configured to supply the aqueous ink to the pressure chamber, and a recovery channel configured to recover the aqueous ink from the pressure chamber. The aqueous ink includes a pigment and a wax particle. The circulation unit further has a circulation pump configured to flow the aqueous ink in the supply channel into the recovery channel.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an inkjet recording method, an inkjet recording apparatus, and a water-based ink. [Background technology]

[0002] In recent years, inkjet recording methods have been increasingly used in the field of sign and display, such as printing posters and giant advertisements. In this field, polyvinyl chloride sheets and polyethylene terephthalate (PET) sheets are often used as recording media from the viewpoints of the durability and cost of the recording media. These recording media have no or almost no water-based ink absorbing layer on the recording surface of the recording media, and are called non-absorbent recording media (recording media that have no water-based ink absorbing properties) and low-absorbent recording media (recording media that have low water-based ink absorbing properties). Hereinafter, recording media whose surfaces have almost no ink absorbing properties will also be referred to as "non- or poorly absorbent recording media". When recording images not only on absorbent recording media but also on non- or poorly absorbent recording media, solvent-based inks and curable inks have been used in the past. However, from the viewpoints of reducing environmental loads and odors, there is an increasing need for water-based inks using water-based media.

[0003] Recorded matter obtained by recording an image on a non- or poorly absorbent recording medium is often used for car wrapping, wall construction, etc. For this reason, images recorded on non- or poorly absorbent recording media are required to have abrasion resistance that can withstand the construction process. In order to meet such requirements, for example, a recording method has been proposed in which an image is recorded using a water-based clear ink containing wax together with color inks (Patent Document 1).

[0004] Meanwhile, in order to stably record high-quality images over a long period of time, an ink ejection device has been proposed that includes a recording head having an ink inflow passage and an ink outflow passage, and a circulation means for circulating ink from the outflow passage to the inflow passage (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-024150 [Patent Document 2] JP 2018-075751 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors have studied a method of recording an image by applying a water-based pigment ink containing wax to a recording medium using a so-called ink circulation type inkjet recording device proposed in Patent Document 2. The "ink circulation type" refers to a method in which ink is circulated from an ink tank to the original ink tank by passing through the vicinity of the nozzles of the recording head. As a result of the study, it was found that a new problem occurred, such as the difficulty of achieving both intermittent ink ejection stability and abrasion resistance of the recorded image. "Insufficient intermittent ink ejection stability" means that when a state in which ink is not ejected for a certain period of time continues, the liquid components in the ink evaporate from some of the ejection ports, and the ejection state of the ink from those ejection ports gradually becomes unstable. In other words, intermittent ejection stability refers to a property in which the ejection of the ink does not become unstable or non-ejection occurs even in such a case, and the recorded image is unlikely to be disturbed.

[0007] It is therefore an object of the present invention to provide an inkjet recording method capable of recording images having excellent abrasion resistance while improving the intermittent ejection stability of the ink. It is also an object of the present invention to provide an inkjet recording apparatus and a water-based ink for use in the inkjet recording method. [Means for solving the problem]

[0008] That is, according to the present invention, there is provided an inkjet recording method in which the water-based ink is ejected from the ejection port of a recording head, the recording head including: an ejection unit having an ejection port for ejecting the water-based ink, a pressure chamber communicating with the ejection port, and an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; and a circulation unit having a supply flow path for supplying the water-based ink to the pressure chamber, and a recovery flow path for recovering the water-based ink from the pressure chamber, the inkjet recording method being characterized in that the water-based ink contains a pigment, wax particles, and a water-soluble organic solvent, and the circulation unit further includes a circulation pump for causing the water-based ink from the supply flow path to flow into the recovery flow path. Effect of the Invention

[0009] According to the present invention, it is possible to provide an inkjet recording method capable of recording an image having excellent abrasion resistance while improving intermittent ejection stability of the ink. Also, according to the present invention, it is possible to provide an inkjet recording apparatus and a water-based ink used in the inkjet recording method. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an inkjet recording apparatus. [Diagram 2] FIG. 2 is an exploded perspective view of the recording head. [Diagram 3] 3A and 3B are longitudinal and enlarged sectional views of a recording head and a discharge module, respectively. [Figure 4] FIG. 2 is a schematic view showing the appearance of a circulation unit. [Diagram 5] FIG. [Figure 6] FIG. 4 is a block diagram showing a schematic diagram of a circulation path. [Figure 7] FIG. 4 is a cross-sectional view showing an example of a pressure adjusting means. [Figure 8] FIG. 2 is an external perspective view of a circulation pump. [Figure 9]9 is a cross-sectional view of the circulating pump shown in FIG. 8(a) taken along line IX-IX. [Figure 10] FIG. 2 is a diagram illustrating the flow of ink in a print head. [Figure 11] FIG. 4 is a schematic diagram showing a circulation path in the discharge unit. [Figure 12] FIG. 3 shows an aperture plate 330. [Figure 13] FIG. 2 is a diagram showing an example of a discharge element substrate. [Figure 14] 5A and 5B are cross-sectional views showing the ink flow in the ejection unit. [Figure 15] FIG. 4 is a cross-sectional view showing an example of the vicinity of a discharge port. [Figure 16] FIG. 11 is a cross-sectional view showing another example of the vicinity of the discharge port. [Figure 17] 11A and 11B are diagrams showing other examples of the ejection element substrate. [Figure 18] FIG. 2 is a diagram showing a flow path configuration of a recording head. [Figure 19] FIG. 2 is a diagram showing a connection state between a main body of the inkjet printing apparatus and a print head. [Figure 20] FIG. 2 is a perspective view of a line-shaped recording head. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the ink in the form of dissociation into ions, but for convenience, it is expressed as "containing a salt". Titanium oxide and titanium oxide particles may be simply referred to as "pigment". Furthermore, water-based ink for inkjet printing may be simply referred to as "ink". Physical property values ​​are values ​​at room temperature (25°C) unless otherwise specified. When "(meth)acrylic acid" and "(meth)acrylate" are written, they mean "acrylic acid, methacrylic acid" and "acrylate, methacrylate", respectively.

[0012] For aqueous inks applied not only to absorbent recording media but also to non-absorbent recording media, it is required that the ink can record images having strong abrasion resistance that can withstand application as wrapping films or wallpapers. It is known that inks capable of recording images with improved abrasion resistance can be obtained by incorporating wax particles. As a result of the study by the present inventors, it was found that it is preferable to design the ink so that wax particles are present on the surface of the image from the viewpoint of efficiently improving the abrasion resistance of the image. In general, wax particles have a high hydrophobicity and tend to gather at the gas-liquid interface. It was found that inks containing wax particles tend to remain near the meniscus at the ejection port of the recording head because the wax tends to gather at the gas-liquid interface, and the intermittent ejection stability is likely to decrease due to drying of the ink. The present inventors consider the cause as follows. Wax particles that tend to gather at the gas-liquid interface interact with the hydrophobic part of the pigment and inhibit the pigment present near the meniscus from moving (retreating) into the ink flow path. It is considered that the wax and pigment solidify and adhere near the ejection port as the moisture evaporates from the meniscus, thereby decreasing the intermittent ejection stability of the ink.

[0013] Therefore, in order to improve the intermittent ejection stability of the ink, the present inventors have investigated using an ink circulation type inkjet recording device as proposed in Patent Document 2 to eject an aqueous ink containing wax to record an image. However, in addition to easily hindering the above-mentioned pigment retraction, wax particles have properties such as easily adhering to the inner wall surface of the ink flow path and easily separating in the ink. For this reason, when using an ink circulation type inkjet recording device in which the ink flow path of the recording head is likely to be long, the amount of circulated ink is large, and wax particles adhere to the inner wall surface, which may easily cause variation in the distribution of wax particles in the ink. As a result, it has been found that it is difficult to stably improve the scratch resistance of the recorded image.

[0014] As a result of further investigations, the inventors have provided a circulation unit having a supply flow path for supplying ink to a pressure chamber communicating with an ejection port, and a recovery flow path for recovering ink from the pressure chamber, with a pump configured to cause the ink in the supply flow path to flow into the recovery flow path. They have then found that it is effective to use an inkjet recording device equipped with such a circulation unit and a recording head that circulates the ink therein to record an image using a water-based pigment ink containing wax particles, and have arrived at the present invention.

[0015] That is, the inkjet recording method of the present invention has the following features. First, the recording head includes a discharge unit having a discharge port for discharging water-based ink, a pressure chamber communicating with the discharge port, and a discharge element disposed in the pressure chamber and generating energy for discharging the water-based ink from the discharge port, as well as a circulation unit having a supply flow path for supplying water-based ink to the pressure chamber, and a recovery flow path for recovering the water-based ink from the pressure chamber. The circulation unit further includes a circulation pump for causing the water-based ink from the supply flow path to flow into the recovery flow path. The water-based ink also contains pigment and wax particles. Then, the water-based ink is discharged from the discharge port of the recording head to record an image.

[0016] The present inventors speculate that the mechanism by which the above-mentioned configuration can improve the intermittent ejection stability of the ink and the abrasion resistance of the image is as follows. In the present invention, a pump configured to make the ink in the supply flow path flow into the recovery flow path is further provided in a circulation unit having a supply flow path that supplies ink to a pressure chamber communicating with an ejection port and a recovery flow path that recovers the ink from the pressure chamber. Then, an inkjet recording device is used that includes a recording head that has such a circulation unit and circulates the ink therein. With this configuration, unlike the case where a pump is provided at a location separate from the recording head, the ink circulation range is substantially limited within the recording head, so that the amount of circulated ink can be reduced. As a result, it is possible to effectively suppress separation of wax in the ink circulation flow path, and it is considered that it is possible to achieve both intermittent ejection stability of the ink and abrasion resistance of the recorded image.

[0017] The ink contains a pigment and wax particles. By containing wax particles, it is possible to impart slipperiness to a recording medium and improve abrasion resistance. With an ink that does not contain wax particles, intermittent ejection stability is obtained, but abrasion resistance of the image is not obtained. In other words, the problem of intermittent ejection stability is a problem that occurs significantly when wax particles are used to improve abrasion resistance.

[0018] <Inkjet recording method, inkjet recording apparatus, and water-based ink> The inkjet recording method of the present invention is a method for recording an image by ejecting water-based ink from an inkjet recording head by the action of thermal energy and applying the ink to a recording medium. The recording head includes an ejection unit and a circulation unit. The ejection unit has a plurality of ejection ports for ejecting the water-based ink, a pressure chamber communicating with the ejection ports, and an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the plurality of ejection ports. The circulation unit has a supply flow path for supplying the aqueous ink to the pressure chamber of the ejection unit, and a recovery flow path for recovering the aqueous ink from the pressure chamber of the ejection unit. The aqueous ink contains a pigment and wax particles. The circulation unit further has a pump configured to cause the aqueous ink from the supply flow path to flow into the recovery flow path. Note that in the present invention, it is not necessary to provide a step of curing the image by irradiating with active energy rays or the like.

[0019] The inkjet recording apparatus of the present invention is an apparatus used in an inkjet recording method in which a water-based ink is ejected from an inkjet recording head by the action of thermal energy and applied to a recording medium to record an image. The inkjet recording apparatus of the present invention is an apparatus that is suitably used in the above-mentioned recording method.

[0020] The aqueous ink of the present invention is an aqueous ink used in an inkjet recording method in which the ink is ejected from an inkjet recording head and applied to a recording medium to record an image, and is an aqueous ink that is suitably used in the above recording method.

[0021] The inkjet recording method and inkjet recording apparatus (hereinafter, simply referred to as "recording method and recording apparatus") of the present invention will be described in detail below. Here, in the following preferred embodiment, an example will be described in which a thermal method is adopted in which an electrothermal conversion element is used as an ejection element for ejecting ink to generate air bubbles, but the present invention is not limited to this. For example, the present invention can also be applied to a recording head that employs an ejection method that ejects ink using a piezoelectric element (piezo), or another ejection method. Furthermore, the pump and pressure adjustment means described below are not limited to the configurations shown in the preferred embodiment and drawings.

[0022] (Inkjet recording device) FIG. 1 is a diagram for explaining an inkjet recording apparatus, and is an enlarged view of a recording head of the inkjet recording apparatus and its surroundings. First, a schematic configuration of an inkjet recording apparatus 50 in this embodiment will be described with reference to FIG. 1. FIG. 1(a) is a perspective view that shows a schematic inkjet recording apparatus that uses a recording head 1. The inkjet recording apparatus 50 in this embodiment constitutes a serial type inkjet recording apparatus that performs recording on a recording medium P by ejecting ink as a liquid while scanning a serial type recording head 1. It is preferable that the recording head 1 be a serial type recording head.

[0023] The recording head 1 is mounted on a carriage 60. The carriage 60 reciprocates along a guide shaft 51 in a main scanning direction (X direction). The recording medium P is transported by transport rollers 55, 56, 57, and 58 in a sub-scanning direction (Y direction) that intersects (orthogonal in this example) the main scanning direction. In each of the figures referred to below, the Z direction indicates the vertical direction, and intersects (orthogonal in this example) 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.

[0024] The recording head 1 includes a circulation unit 54 and a discharge unit 3 (see FIG. 2) described later. The specific configuration will be described later, but the discharge unit 3 is provided with a plurality of discharge ports and energy generating elements (hereinafter referred to as discharge elements) that generate discharge energy for discharging ink from each discharge port.

[0025] The inkjet recording device 50 is also provided with an ink tank 2, which is an ink supply source, and an external pump 21, and the ink stored in the ink tank 2 is supplied to a circulation unit 54 via an ink supply tube 59 by the driving force of the external pump 21.

[0026] The inkjet recording device 50 records a predetermined image on the recording medium P by repeating a recording scan in which the recording head 1 mounted on the carriage 60 moves in the main scanning direction while ejecting ink to perform recording, and a transport operation in which the recording medium P is transported in the sub-scanning direction. That is, the recording method of the present invention preferably records an image by ejecting water-based ink in a unit area of ​​the recording medium by multiple reciprocating scans while scanning the recording head 1 back and forth in a direction intersecting the transport direction of the recording medium. Here, the unit area can be set as any area such as one pixel or one band. Note that the recording head 1 in this embodiment is capable of ejecting four types of ink, namely black (K), cyan (C), magenta (M), and yellow (Y), and is capable of recording a full-color image by 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. The present disclosure is also applicable to a recording head for ejecting other types of ink. That is, the types and the number of inks ejected from the recording head are not limited.

[0027] The moving speed of the recording head during reciprocating scanning (scanning speed, inches / s) is preferably 25 inches / s or more. More specifically, the speed at which the recording head moves relative to the recording medium P during recording is preferably 25 inches / s or more. The scanning speed is preferably 100 inches / s or less, and more preferably 80 inches / s or less. If the scanning speed exceeds 100 inches / s, ink foaming is likely to become noticeable, and sufficient intermittent ejection stability may not be obtained.

[0028] Furthermore, the inkjet recording device 50 is provided with a cap member (not shown) capable of covering the ejection port surface on which the ejection ports of the recording head are formed, at a position offset in the X direction from the transport path of the recording medium P. The cap member covers the ejection port surface of the recording head 1 during non-recording operations, and is used to prevent the ejection ports from drying, to protect the ejection ports, and to suck ink from the ejection ports.

[0029] The recording head 1 shown in Fig. 1(a) shows an example in which the recording head 1 is provided with four circulation units 54 corresponding to four types of ink, but it is sufficient that the recording head 1 is provided with a circulation unit 54 corresponding to the type of ink to be ejected. Also, multiple circulation units 54 may be provided for the same type of ink. In other words, the recording head 1 can be configured to include one or more circulation units. It is also possible to have a configuration in which at least one ink is circulated rather than circulating all four types of ink.

[0030] FIG. 1B is a block diagram showing a control system of the inkjet recording apparatus 50. The CPU 103 functions as a control means for controlling the operation of each part of the inkjet recording apparatus 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 a host device 400 outside the inkjet recording apparatus 50, controls the head driver 1A, and controls the driving of the discharge elements provided in the discharge unit 3. The CPU 103 also controls the drivers of various actuators provided in the inkjet recording apparatus. For example, the CPU 103 controls a motor driver 105A of a carriage motor 105 for moving the carriage 60, and a motor driver 104A of a conveying motor 104 for conveying the recording medium P. The CPU 103 also controls a pump driver 500A for driving a circulation pump 500 described later, a pump driver 21A of an external pump 21, and the like. Although FIG. 1B shows a form in which processing is performed when image data is received from the host device 400, processing may be performed in the inkjet recording apparatus 50 independently of data from the host device 400.

[0031] [Basic configuration of recording head] Fig. 2 is an exploded perspective view of the recording head 1 of this embodiment. Fig. 3 is a cross-sectional view of the recording head 1 shown in Fig. 2 taken along line IIIa-IIIa. Fig. 3(a) is an overall vertical cross-sectional view of the recording head 1, and Fig. 3(b) is an enlarged view of the ejection module shown in Fig. 3(a). The basic configuration of the recording head 1 of this embodiment will be described below, mainly with reference to Fig. 2 and Fig. 3, and with appropriate reference to Fig. 1.

[0032] 2, the recording head 1 includes a circulation unit 54 and an ejection unit 3 for ejecting ink supplied from the circulation unit 54 onto a recording medium P. The recording head 1 in this embodiment is fixedly supported on a carriage 60 of an inkjet recording device 50 by positioning means and electrical contacts (not shown) 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 FIG. 1, and performs recording on the recording medium P.

[0033] An ink supply tube 59 is provided on the external pump 21 connected to the ink tank 2 serving as the ink supply source (see FIG. 1). A liquid connector (not shown) is provided on the tip of the ink supply tube 59. When the recording head 1 is mounted on the inkjet recording device 50, the liquid connector provided on the tip of the ink supply tube 59 is airtightly connected to a liquid connector insertion port 53a, which is an ink inlet port provided on the head housing 53 of the recording head 1. As a result, an ink supply path is formed from the ink tank 2 to the recording head 1 via the external pump 21. In this embodiment, since four types of ink are used, four sets of the ink tank 2, the external pump 21, the ink supply tube 59, and the circulation unit 54 are provided corresponding to each ink, and four ink supply paths corresponding to each ink are independently formed. In this way, the inkjet recording device 50 of this embodiment is provided with an ink supply system to which ink is supplied from the ink tank 2 provided outside the recording head 1. Note that the inkjet recording device 50 of this embodiment is not provided with an ink recovery system that recovers the ink in the recording head 1 to the ink tank 2. Therefore, the recording head 1 is provided with a liquid connector insertion port 53a for connecting an ink supply tube 59 of the ink tank 2, but is not provided with a connector insertion port for connecting a tube for recovering the ink of the recording head 1 to the ink tank 2. A liquid connector insertion port 53a is provided for each ink.

[0034] 3, 54B indicates a circulation unit for black ink, 54C indicates a circulation unit for cyan ink, 54M indicates a circulation unit for magenta ink, and 54Y indicates an ink circulation unit for yellow ink. Each circulation unit has substantially the same configuration, and in this embodiment, when there is no need to distinguish between the circulation units, they are all referred to as circulation unit 54.

[0035] 2 and 3(a), the discharge unit 3 includes two discharge modules 300, a first support member 4, a second support member 7, an electric wiring member (electric wiring tape) 5, and an electric contact substrate 6. As shown in FIG. 3(b), the discharge module 300 includes a silicon substrate 310 having a thickness of 0.5 to 1 mm, and a plurality of discharge elements 15 provided on one side of the silicon substrate 310. In this embodiment, the discharge elements 15 are configured by electrothermal conversion elements (heaters) that generate thermal energy as discharge energy for discharging ink. Electric power is supplied to each ejection element 15 via electrical wiring formed on a silicon substrate 310 by a film formation technique.

[0036] Further, an ejection port forming member 320 is formed on the surface (lower surface in FIG. 3(b)) of the silicon substrate 310. In the ejection port forming member 320, a plurality of pressure chambers 12 corresponding to a plurality of ejection elements 15 and a plurality of ejection ports 13 for ejecting ink are formed by photolithography. Furthermore, a common supply flow path 18 and a common recovery flow path 19 are formed in the silicon substrate 310. Further, in the silicon substrate 310, a supply connection flow path 323 that communicates the common supply flow path 18 with each pressure chamber 12, and a recovery connection flow path 324 that communicates the common recovery flow path 19 with each pressure chamber 12 are formed. In this embodiment, one ejection module 300 is configured to eject two types of ink. That is, of the two ejection modules shown in FIG. 3(a), the ejection module 300 located on the left side of the figure ejects black ink and cyan ink, and the ejection module 300 located on the right side of the figure ejects magenta ink and yellow ink. Note that this combination is an example, and any combination of inks may be used. One ejection module may be configured to eject one type of ink, or may be configured to eject three or more types of ink. The two ejection modules 300 do not have to eject the same number of types of ink. One ejection module 300 may be provided, or may be configured to include three or more ejection modules 300. Furthermore, in the example shown in FIG. 3, two ejection port arrays extending in the Y direction are formed for one color of ink. A pressure chamber 12, a common supply flow path 18, and a common recovery flow path 19 are formed for each of the multiple ejection ports 13 that constitute each ejection port array.

[0037] An ink supply port and an ink recovery port, which will be described later, are formed on the back surface (upper surface in FIG. 3(b)) of the silicon substrate 310. The ink supply port supplies ink from an ink supply flow path 48 to the multiple common supply flow paths 18, and the ink recovery port recovers ink from the multiple common recovery flow paths 19 to an ink recovery flow path 49.

[0038] The ink supply port and ink recovery port referred to here refer to openings that supply and recover ink during forward ink circulation, which will be described later. That is, during forward ink circulation, ink is supplied from the ink supply port to each common supply flow path 18, and ink is recovered from each common recovery flow path 19 to the ink recovery port. However, ink may also be circulated in the reverse direction. In this case, ink is supplied from the ink recovery port described above to the common recovery flow path 19, and ink is recovered from the common supply flow path 18 to the ink supply port.

[0039] As shown in FIG. 3(a), the discharge module 300 has its back surface (upper surface in FIG. 3(a)) adhesively fixed to one surface of the first support member 4 (lower surface in FIG. 3(a)). An ink supply flow path 48 and an ink recovery flow path 49 are formed in the first support member 4, penetrating from one surface to the other surface. One opening of the ink supply flow path 48 is connected to the ink supply port in the silicon substrate 310, and one opening of the ink recovery flow path 49 is connected to the ink recovery port in the silicon substrate 310. The ink supply flow path 48 and the ink recovery flow path 49 are provided independently for each type of ink.

[0040] Moreover, a second support member 7 having an opening 7a (see FIG. 2) through which the discharge module 300 is inserted is adhesively fixed to one surface of the first support member 4 (the upper surface in FIG. 3(a)). The second support member 7 holds an electric wiring member 5 that is electrically connected to the ejection module 300. The electric wiring member 5 is a member for applying an electric signal for ejecting ink to the ejection module 300. The electric connection portion between the ejection module 300 and the electric wiring member 5 is sealed with a sealant (not shown) and is protected from corrosion by ink and external impacts.

[0041] In addition, an electrical contact board 6 is thermocompression-bonded to an end 5a (see FIG. 2) of the electrical wiring member 5 using an anisotropic conductive film (not shown), and the electrical wiring member 5 and the electrical contact board 6 are electrically connected. The electrical contact board 6 has an external signal input terminal (not shown) for receiving an electrical signal from the inkjet recording device 50.

[0042] Furthermore, a joint member 8 (FIG. 3(a)) is provided between the first support member 4 and the circulation unit 54. A supply port 88 and a recovery port 89 are formed in the joint member 8 for each type of ink. The supply port 88 and the recovery port 89 communicate the ink supply flow path 48 and the ink recovery flow path 49 of the first support member 4 with the flow paths formed in the circulation unit 54. In FIG. 3(a), the supply port 88B and the recovery port 89B correspond to black ink, and the supply port 88C and the recovery port 89C correspond to cyan ink. Furthermore, the supply port 88M and the recovery port 89M correspond to magenta ink, and the supply port 88Y and the recovery port 89Y correspond to yellow ink.

[0043] The openings at one end of each of the ink supply flow passage 48 and the ink recovery flow passage 49 of the first support member 4 have a small opening area that matches the ink supply port and the ink recovery port in the silicon substrate 310. In contrast, the openings at the other end of each of the ink supply flow passage 48 and the ink recovery flow passage 49 of the first support member 4 have a shape that is expanded to the same opening area as the large opening area of ​​the joint member 8 formed to match the flow passage of the circulation unit 54. By adopting such a configuration, it is possible to suppress an increase in flow passage resistance to the ink collected from each recovery flow passage. However, the shapes of the openings at one end and the other end of each of the ink supply flow passage 48 and the ink recovery flow passage 49 are not limited to the above example.

[0044] In the recording head 1 having the above configuration, ink supplied to the circulation unit 54 passes through the supply port 88 of the joint member 8 and the ink supply flow path 48 of the first support member 4, and flows from the ink supply port of the ejection module 300 into the common supply flow path 18. The ink then flows from the common supply flow path 18 into the pressure chamber 12 through the supply connection flow path 323, and a portion of the ink that has flowed into the pressure chamber is ejected from the ejection port 13 by driving the ejection element 15. The remaining ink that has not been ejected passes from the pressure chamber 12 through the recovery connection flow path 324 and the common recovery flow path 19, and flows from the ink recovery port into the ink recovery flow path 49 of the first support member 4. The ink that has flowed into the ink recovery flow path 49 then flows into the circulation unit 54 through the recovery port 89 of the joint member 8, and is recovered.

[0045] [Components of the circulation unit] 4 is a schematic external view of one circulation unit 54 corresponding to one type of ink applied to the recording apparatus of this embodiment. In addition to the circulation pump 500, the circulation unit 54 preferably has a filter 110, a first pressure adjustment means 120, and a second pressure adjustment means 150. These components are connected by respective flow paths as shown in FIG. 5 and FIG. 6, and constitute a circulation path that supplies and recovers ink to and from the ejection module 300 in the recording head 1. The recording head 1 has a circulation pump 500 that causes ink from a recovery flow path to flow into a supply flow path. In other words, the recording head 1 having the circulation pump is fixed and supported on the carriage 60.

[0046] [Circulation path inside the recording head] FIG. 5 is a vertical cross-sectional view showing a circulation path of one type of ink (one color ink) in the recording head 1. In order to explain the circulation path more clearly, the relative positions of each component (first pressure adjustment means 120, second pressure adjustment means 150, circulation pump 500, etc.) in FIG. 5 are simplified. Therefore, the relative positions of each component are different from the configuration in FIG. 19 described later. FIG. 6 is a block diagram showing the circulation path shown in FIG. 5. As shown in FIG. 5 and FIG. 6, 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. In this embodiment, the two pressure adjustment means 120 and 150 are used to achieve circulation within a certain pressure range in the circulation path. Also, the ink is configured to flow through the pressure chamber 12 (ejection element 15) at a flow rate according to the pressure difference between the first pressure adjustment means 120 and the second pressure adjustment means 150. Below, the circulation path in the recording head 1 and the flow of ink within the circulation path will be described with reference to Figures 5 and 6. The arrows in each figure indicate the direction of ink flow.

[0047] First, we will explain the connection state of each component in the recording head 1. An external pump 21 that sends ink contained in an ink tank 2 (FIG. 6) provided outside the recording head 1 to the recording head 1 is connected to a circulation unit 54 via an ink supply tube 59 (FIG. 1). An ink flow path (inflow flow path) located upstream of the circulation unit 54 is provided with a filter 110. An ink supply path (inflow flow path) located downstream of the filter 110 is connected to a first valve chamber 121 of a first pressure adjustment means 120. The first valve chamber 121 is connected to a first pressure control chamber 122 via a first communication port 191A that can be opened and closed by a first valve 190A shown in FIG. 5. The inflow flow path is a flow path through which ink in an ink tank 2 provided outside the recording head 1 flows into the recording head 1 to be supplied to the pressure chamber 12.

[0048] The first pressure control chamber 122 is connected to the supply flow path 130, the bypass flow path 160, and the pump outlet flow path 180 of the circulation pump 500. The supply flow path 130 is connected to the common supply flow path 18 via the ink supply port provided in the ejection module 300. The bypass flow path 160 is connected to a second valve chamber 151 provided in the second pressure adjustment means 150. The second valve chamber 151 is connected to the second pressure control chamber 152 via a second communication port 191B that is opened and closed by a second valve 190B shown in FIG. 5. FIGS. 5 and 6 show an example in which one end of the bypass flow path 160 is connected to the first pressure control chamber 122 of the first pressure adjustment means 120, and the other end of the bypass flow path 160 is connected to the second valve chamber 151 of the second pressure adjustment means 150. One end of the bypass flow path 160 may be connected to the supply flow path 130, and the other end of the bypass flow path may be connected to the second valve chamber 151.

[0049] The second pressure control chamber 152 is connected to the recovery flow path 140. The recovery flow path 140 is connected to the common recovery flow path 19 via the ink recovery port provided in the ejection module 300. Furthermore, the second pressure control chamber 152 is connected to the circulation pump 500 via a pump inlet flow path 170. In FIG. 5, 170a denotes the inlet of the pump inlet flow path 170.

[0050] Next, a description will be given of the flow of ink in the recording head 1 having the above configuration. As shown in Fig. 6, the ink contained in the ink tank 2 is pressurized by an external pump 21 provided in the inkjet recording device 50, and is supplied to the circulation unit 54 of the recording head 1 as a positive pressure ink flow.

[0051] The ink supplied to the circulation unit 54 passes through the filter 110 to remove foreign matter such as dust and air bubbles, and then flows into the first valve chamber 121 provided in the first pressure adjustment means 120. The ink pressure decreases due to pressure loss when passing through the filter 110, but the ink pressure at this stage is positive. The ink that has flowed into the first valve chamber 121 then passes through the first communication port 191A and flows into the first pressure control chamber 122 when the first valve 190A is in the open state. Due to pressure loss when passing through the first communication port 191A, the ink that has flowed into the first pressure control chamber 122 switches from positive pressure to negative pressure.

[0052] Here, the pore size (μm) of the filter 110 is preferably 1 μm or more and 10 μm or less. If the pore size is less than 1 μm, particles such as coloring materials in the ink with a particle diameter of 1 μm or less will also be collected, and a stable supply of the ink may not be sufficiently maintained. As a result, sufficient intermittent ejection stability may not be obtained. On the other hand, if the pore size exceeds 10 μm, it becomes difficult to remove impurities such as coarse particles in the ink. As a result, the above-mentioned impurities are likely to enter the ink flow path, and sufficient intermittent ejection stability may not be obtained.

[0053] Next, the flow of ink in the circulation path will be described. The circulation pump 500 operates to pump ink sucked from the pump inlet flow path 170 on the upstream side to the pump outlet flow path 180 on the downstream side. Therefore, when the pump is driven, the ink supplied to the first pressure control chamber 122 flows into the supply flow path 130 and the bypass flow path 160 together with the ink sent from the pump outlet flow path 180. Although details will be described later, in this embodiment, a piezoelectric diaphragm pump using a piezoelectric element attached to a diaphragm as a drive source is used as a circulation pump capable of sending liquid. The piezoelectric diaphragm pump is a pump that changes the volume of the pump chamber by inputting a drive voltage to a piezoelectric element, and sends liquid by alternately moving two check valves due to pressure fluctuations.

[0054] The ink that has flowed into the supply flow channel 130 flows from the ink supply port of the ejection module 300 through the common supply flow channel 18 into the pressure chamber 12, and some of the ink is ejected from the ejection port 13 by driving (heat generation) the ejection element 15. The remaining ink that has not been used for ejection flows through the pressure chamber 12, passes through the common recovery flow channel 19, and then flows into the recovery flow channel 140 connected to the ejection module 300. The ink that has flowed into the recovery flow channel 140 flows into the second pressure control chamber 152 of the second pressure adjustment means 150.

[0055] On the other hand, the ink that has flowed from the first pressure control chamber 122 into the bypass flow path 160 flows into the second valve chamber 151, and then passes through the second communication port 191B and flows into the second pressure control chamber 152. The ink that has flowed into the second pressure control chamber 152 via the bypass flow path 160 and the ink that has been recovered from the recovery flow path 140 are sucked into the circulation pump 500 via the pump inlet flow path 170 by the operation of the circulation pump 500. Then, the ink that has been sucked into the circulation pump 500 is sent to the pump outlet flow path 180 and flows into the first pressure control chamber 122 again. Thereafter, the ink that has flowed into the second pressure control chamber 152 from the first pressure control chamber 122 via the supply flow path 130 through the ejection module 300 and the ink that has flowed into the second pressure control chamber 152 via the bypass flow path 160 flows into the circulation pump 500. Then, the ink is sent from the circulation pump 500 to the first pressure control chamber 122. In this manner, the ink is circulated in the circulation path.

[0056] As described above, in this embodiment, the circulation pump 500 can circulate the ink along the circulation path formed in the recording head 1. This makes it possible to suppress thickening of the ink and accumulation of ink sedimentation components (solid components) such as coloring materials in the ejection module 300, and makes it possible to maintain good ink fluidity in the ejection module 300 and ejection characteristics at the ejection ports.

[0057] The circulation path in this embodiment is configured to be completed within the print head 1, and therefore, as described above, the length of the circulation path can be significantly shortened compared to when ink is circulated between the ink tank 2 provided outside the print head and the print head 1. This makes it possible to circulate the ink with a small circulation pump.

[0058] Furthermore, the connection flow path between the recording head 1 and the ink tank 2 is configured to include only a flow path for supplying ink. In other words, a flow path for recovering ink from the recording head 1 to the ink tank 2 is not required. Therefore, only a tube for supplying ink needs to be provided to connect the ink tank 2 and the recording head 1, and no tube for recovering ink needs to be provided. Therefore, the inside of the inkjet recording device 50 can be simplified in configuration with a reduced number of tubes, and the device as a whole can be made more compact. Furthermore, by reducing the number of tubes, it is possible to reduce the pressure fluctuation of the ink caused by the oscillation of the tubes accompanying the main scanning of the recording head 1. Furthermore, the oscillation of the tubes during the main scanning of the recording head 1 becomes a driving load of the carriage motor that drives the carriage 60. Therefore, by reducing the number of tubes, the driving load of the carriage motor is reduced, and it is possible to simplify the main scanning mechanism including the carriage motor and the like. Furthermore, since it is not necessary to collect ink from the recording head to an ink tank, it is also possible to reduce the size of the external pump 21. Thus, according to this embodiment, it is possible to realize a reduction in size and cost of the inkjet recording device 50.

[0059] [Pressure adjustment means] FIG. 7 is a diagram showing an example of a pressure adjusting means. The configuration and operation of the pressure adjusting means (first pressure adjusting means 120, second pressure adjusting means 150) built into the above-mentioned recording head 1 will be described in more detail with reference to FIG. 7. The first pressure adjusting means 120 and the second pressure adjusting means 150 have substantially the same configuration. For this reason, the first pressure adjusting means 120 will be described below as an example, and the second pressure adjusting means 150 will only be described with the reference numerals of the parts corresponding to the first pressure adjusting means in FIG. 7. In the case of the second pressure adjusting means 150, the first valve chamber 121 described below will be read as the second valve chamber 151, and the first pressure control chamber 122 will be read as the second pressure control chamber 152.

[0060] The first pressure adjustment means 120 has a first valve chamber 121 and a first pressure control chamber 122 formed in a cylindrical housing 125. The first valve chamber 121 and the first pressure control chamber 122 are separated by a partition wall 123 provided in the cylindrical housing 125. However, the first valve chamber 121 communicates with the first pressure control chamber 122 through a communication port 191 formed in the partition wall 123. The first valve chamber 121 is provided with a valve 190 that switches between communication and blocking between the first valve chamber 121 and the first pressure control chamber 122 at the communication port 191. The valve 190 is held at a position facing the communication port 191 by a valve spring 200, and has a configuration that allows it to come into close contact with the partition wall 123 by the biasing force of the valve spring 200. When the valve 190 comes into close contact with the partition wall 123, the flow of ink through the communication port 191 is blocked. To increase the close contact with the partition 123, it is preferable that the portion of the valve 190 that comes into contact with the partition 123 is made of an elastic material. Furthermore, a valve shaft 190a that is inserted into the communication port 191 protrudes from the center of the valve 190. By pressing this valve shaft 190a against the biasing force of a valve spring 200, the valve 190 moves away from the partition 123, allowing ink to flow through the communication port 191. Hereinafter, the state in which the valve 190 blocks the flow of ink through the communication port 191 is referred to as the "closed state," and the state in which ink can flow through the communication port 191 is referred to as the "open state."

[0061] The opening of the cylindrical housing 125 is closed by the flexible member 230 and the pressure plate 210. The first pressure control chamber 122 is formed by the flexible member 230, the pressure plate 210, the peripheral wall of the housing 125, and the partition wall 123. The pressure plate 210 is configured to be displaceable in accordance with the displacement of the flexible member 230. The materials of the pressure plate 210 and the flexible member 230 are not particularly limited, but for example, the pressure plate 210 can be configured from a resin molded part, and the flexible member 230 can be configured from a resin film. In this case, the pressure plate 210 can be fixed to the flexible member 230 by thermal welding.

[0062] A pressure adjustment spring 220 (biasing member) is provided between the pressure plate 210 and the partition wall 123. Due to the biasing force of the pressure adjustment spring 220, the pressure plate 210 and the flexible member 230 are biased in a direction in which the internal volume of the first pressure control chamber 122 expands, as shown in FIG. Furthermore, when the pressure in the first pressure control chamber 122 decreases, the pressure plate 210 and the flexible member 230 are displaced in a direction that reduces the internal volume of the first pressure control chamber 122 against the pressure of the pressure adjustment spring 220. Then, when the internal volume of the first pressure control chamber 122 decreases to a certain amount, the pressure plate 210 abuts against the valve shaft 190a of the valve 190. Thereafter, when the internal volume of the first pressure control chamber 122 further decreases, the valve 190 moves together with the valve shaft 190a against the biasing force of the valve spring 200 and moves away from the partition wall 123. This causes the communication port 191 to be in an open state (the state of FIG. 7(b)).

[0063] In this embodiment, the connections within the circulation path are set so that the pressure in the first valve chamber 121 is higher than the pressure in the first pressure control chamber 122 when the communication port 191 is in the open state. As a result, when the communication port 191 is in an open state, ink flows from the first valve chamber 121 into the first pressure control chamber 122. This ink inflow displaces the flexible member 230 and the pressure plate 210 in a direction increasing the internal volume of the first pressure control chamber 122. As a result, the pressure plate 210 moves away from the valve shaft 190a of the valve 190, and the valve 190 is brought into close contact with the partition wall 123 by the biasing force of the valve spring 200, and the communication port 191 becomes in a closed state (the state of FIG. 7(c)).

[0064] In this manner, in the first pressure adjustment means 120 of this embodiment, when the pressure in the first pressure control chamber 122 decreases to a certain pressure or below (for example, when the negative pressure becomes stronger), ink flows in from the first valve chamber 121 via the communication port 191. This prevents the pressure in the first pressure control chamber 122 from decreasing any further. Therefore, the pressure in the first pressure control chamber 122 is controlled to be kept within a certain range.

[0065] Next, the pressure in the first pressure control chamber 122 will be described in more detail. As described above, the flexible member 230 and the pressure plate 210 are displaced in response to the pressure in the first pressure control chamber 122, and the pressure plate 210 comes into contact with the valve shaft 190a, opening the communication port 191 (as shown in FIG. 7(b)). At this time, the relationship of the forces acting on the pressure plate 210 is expressed by the following formula 1.

[0066] P2×S2+F2+(P1-P2)×S1+F1=0...Equation 1

[0067] Furthermore, when equation 1 is rearranged for P2, it becomes as follows. P2=-(F1+F2+P1×S1) / (S2-S1)...Equation 2 P1: Pressure (gauge pressure) of the first valve chamber 121 P2: Pressure (gauge pressure) of the first pressure control chamber 122 F1: Valve spring force 200 F2: Spring force of the pressure adjusting spring 220 S1: Pressure receiving area of ​​valve 190 S2: Pressure receiving area of ​​the pressure plate 210

[0068] Here, the spring force F1 of the valve spring 200 and the spring force F2 of the pressure adjustment spring 220 are positive (leftward in FIG. 7) in the direction pressing the valve 190 and the pressure plate 210. In addition, the pressure P1 in the first valve chamber 121 and the pressure P2 in the first pressure control chamber 122 are configured so that P1 satisfies the relationship P1≧P2.

[0069] The pressure P2 in the first pressure control chamber 122 when the communication port 191 is open is determined by formula 2, and when the communication port 191 is open, due to the relationship P1≧P2, ink flows from the first valve chamber 121 into the first pressure control chamber 122. As a result, the pressure P2 in the first pressure control chamber 122 does not decrease any further, and P2 is maintained within a certain pressure range.

[0070] On the other hand, as shown in FIG. 7(c), when the pressure plate 210 is not in contact with the valve shaft 190a and the communication port 191 is closed, the relationship of the forces acting on the pressure plate 210 is expressed by Equation 3.

[0071] P3×S3+F3=0...Equation 3

[0072] Here, if we rearrange Equation 3 for P3, we get the following: P3 = -F3 / S3 Equation 4 F3: The spring force of the pressure adjusting spring 220 when the pressure plate 210 and the valve shaft 190a are not in contact with each other P3: pressure (gauge pressure) in the first pressure control chamber 122 when the pressure plate 210 and the valve shaft 190a are not in contact with each other S3: The pressure-receiving area of ​​the pressure plate 210 when the pressure plate 210 and the valve 190 are not in contact with each other

[0073] Here, FIG. 7(c) shows a state in which the pressure plate 210 and the flexible member 230 are displaced to the right side of the figure to the limit of their displacement. The pressure P3 in the first pressure control chamber 122, the spring force F3 of the pressure adjustment spring 220, and the pressure receiving area S3 of the pressure plate 210 change according to the amount of displacement while the pressure plate 210 and the flexible member 230 are displaced to the state of FIG. 7(c). Specifically, when the pressure plate 210 and the flexible member 230 are in the right direction in FIG. 7 compared to FIG. 7(c), the pressure receiving area S3 of the pressure plate 210 becomes smaller, and the spring force F3 of the pressure adjustment spring 220 becomes larger. As a result, the pressure P3 in the first pressure control chamber 122 becomes smaller according to the relationship of Equation 4. Therefore, according to Equation 2 and Equation 4, the pressure in the first pressure control chamber 122 gradually increases from the state of FIG. 7(b) to the state of FIG. 7(c) (i.e., the negative pressure becomes weaker and approaches the positive pressure side). That is, from a state in which the communication port 191 is open, the pressure plate 210 and the flexible member 230 gradually displace to the left, and the pressure in the first pressure control chamber 122 gradually increases until the internal volume of the first pressure control chamber 122 finally reaches its limit of displacement. In other words, the negative pressure weakens.

[0074] [Circulation pump] Next, the configuration and operation of the circulation pump 500 built into the above-mentioned recording head 1 will be described in detail with reference to FIGS.

[0075] Fig. 8 is an external perspective view of the circulation pump 500. Fig. 8(a) is an external perspective view showing the front side of the circulation pump 500, and Fig. 8(b) is an external perspective view showing the rear side of the circulation pump 500. The outer shell of the circulation pump 500 is composed of a pump housing 505 and a cover 507 fixed to the pump housing 505. The pump housing 505 is composed of a housing body 505a and a flow path connecting member 505b adhesively fixed to the outer surface of the housing body 505a. The housing body 505a and the flow path connecting member 505b are each provided with a pair of through holes communicating with each other at two different positions. The pair of through holes provided at one position forms a pump supply hole 501, and the pair of through holes provided at the other position forms a pump discharge hole 502. The pump supply hole 501 is connected to a pump inlet flow path 170 connected to the second pressure control chamber 152, and the pump discharge hole 502 is connected to a pump outlet flow path 180 connected to the first pressure control chamber 122. The ink supplied from the pump supply hole 501 passes through a pump chamber 503 (see FIG. 9) described later and is discharged from the pump discharge hole 502.

[0076] FIG. 9 is a cross-sectional view of the circulating pump 500 shown in FIG. 8(a) taken along line IX-IX. A diaphragm 506 is joined to the inner surface of a pump housing 505, and a pump chamber 503 is formed between the diaphragm 506 and a recess formed on the inner surface of the pump housing 505. The pump chamber 503 is connected to a pump supply hole 501 and a pump discharge hole 502 formed in the pump housing 505. A check valve 504a is provided in the middle of the pump supply hole 501, and a check valve 504b is provided in the middle of the pump discharge hole 502. Specifically, the check valve 504a is arranged so that a part of the check valve 504a can move leftward in the figure in a space 512a formed in the middle of the pump supply hole 501. A part of the check valve 504b is arranged so that a part of the check valve 504b can move rightward in the figure in a space 512b formed in the middle of the pump discharge hole 502.

[0077] When diaphragm 506 is displaced to increase the volume of pump chamber 503 and reduce the pressure in pump chamber 503, check valve 504a moves away from the opening of pump supply hole 501 in space 512a (i.e., moves to the left in the figure). When check valve 504a moves away from the opening of pump supply hole 501 in space 512a, the check valve 504a enters an open state that allows the flow of ink through pump supply hole 501. When diaphragm 506 is displaced to decrease the volume of pump chamber 503 and reduce the pressure in pump chamber 503, check valve 504a comes into close contact with the wall surface surrounding the opening of pump supply hole 501. As a result, the check valve 504a enters a closed state that blocks the flow of ink through pump supply hole 501.

[0078] On the other hand, when the pump chamber 503 is depressurized, the check valve 504b comes into close contact with the wall surface surrounding the opening of the pump housing 505 and enters a closed state in which it blocks the flow of ink through the pump discharge hole 502. When the pump chamber 503 is pressurized, the check valve 504b moves away from the opening of the pump housing 505 toward the space 512b (i.e., moves to the right in the figure), allowing the flow of ink through the pump discharge hole 502.

[0079] The material of each check valve 504a, 504b may be any material that can deform in response to the pressure in the pump chamber 503, and may be made of, for example, an elastic material such as EPDM (ethylene propylene rubber) or elastomer, or a film or thin plate such as polypropylene, but is not limited to these.

[0080] As described above, pump chamber 503 is formed by joining pump housing 505 and diaphragm 506. Therefore, the pressure in pump chamber 503 changes as diaphragm 506 deforms. For example, when diaphragm 506 is displaced toward pump housing 505 (displaced to the right in the figure) and the volume of pump chamber 503 decreases, the pressure in pump chamber 503 increases. As a result, check valve 504b arranged opposite pump discharge hole 502 opens, and ink in pump chamber 503 is discharged. At this time, check valve 504a arranged opposite pump supply hole 501 is in close contact with the wall surface surrounding pump supply hole 501, so that the backflow of ink from pump chamber 503 to pump supply hole 501 is suppressed.

[0081] Furthermore, when the diaphragm 506 is displaced in a direction in which the pump chamber 503 widens, the pressure in the pump chamber 503 decreases. As a result, the check valve 504a arranged opposite the pump supply hole 501 opens, and ink is supplied to the pump chamber 503. At this time, the check valve 504b arranged at the pump discharge hole 502 comes into close contact with the wall surface surrounding the opening formed in the pump housing 505 to close the opening. As a result, the backflow of ink from the pump discharge hole 502 to the pump chamber 503 is suppressed.

[0082] In this way, in the circulation pump 500, the diaphragm 506 deforms to change the pressure in the pump chamber 503, thereby sucking in and discharging ink. At this time, if bubbles get into the pump chamber 503, even if the diaphragm 506 is displaced, the pressure change in the pump chamber 503 is reduced due to the expansion and contraction of the bubbles, and the amount of liquid delivered decreases. Therefore, the pump chamber 503 is arranged parallel to gravity to make it easier for bubbles that get into the pump chamber 503 to gather above the pump chamber 503, and the pump discharge hole 502 is arranged above the center of the pump chamber 503. This makes it possible to improve the discharge of bubbles in the pump and stabilize the flow rate.

[0083] [Ink flow inside the recording head] FIG. 10 is a diagram for explaining the flow of ink in the recording head. The circulation of ink in the recording head 1 will be explained with reference to FIG. 10. In order to more clearly explain the ink circulation path, the relative positions of each component (such as the first pressure adjustment means 120, the second pressure adjustment means 150, and the circulation pump 500) in FIG. 10 are simplified. Therefore, the relative positions of each component are different from the configuration in FIG. 19 described later. FIG. 10(a) is a schematic diagram showing the flow of ink when a recording operation is performed in which ink is discharged from the discharge port 13 to perform recording. The arrows in the figure indicate the flow of ink. In this embodiment, when a recording operation is performed, both the external pump 21 and the circulation pump 500 start to be driven. Regardless of the recording operation, the external pump 21 and the circulation pump 500 may be driven. In addition, the external pump 21 and the circulation pump 500 do not need to be driven in conjunction with each other, and may be driven independently.

[0084] During the recording operation, the circulation pump 500 is ON (driven), and the ink flowing out from the first pressure control chamber 122 flows into the supply flow path 130 and the bypass flow path 160. The ink that flows into the supply flow path 130 passes through the ejection module 300, then flows into the recovery flow path 140, and is then supplied to the second pressure control chamber 152.

[0085] On the other hand, the ink that has flowed from the first pressure control chamber 122 into the bypass flow path 160 flows into the second pressure control chamber 152 via the second valve chamber 151. The ink that has flowed into the second pressure control chamber 152 passes through the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows into the first pressure control chamber 122 again. At this time, the control pressure by the first valve chamber 121 is set higher than the control pressure of the first pressure control chamber 122 based on the relationship of the above-mentioned formula 2. Therefore, the ink in the first pressure control chamber 122 is supplied to the ejection module 300 again via the supply flow path 130 without flowing into the first valve chamber 121. The ink that has flowed into the ejection module 300 flows into the first pressure control chamber 122 again via the recovery flow path 140, the second pressure control chamber 152, the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180. In this manner, the ink circulation that is completed within the recording head 1 is performed.

[0086] In the above ink circulation, the amount of ink circulating (flow rate) in the ejection module 300 is determined by the difference in the control pressure between the first pressure control chamber 122 and the second pressure control chamber 152. This pressure difference is set so as to be a circulation amount capable of suppressing thickening of ink near the ejection port in the ejection module 300. In addition, the ink consumed by the recording is supplied from the ink tank 2 to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121. The mechanism by which the consumed ink is supplied will be described in detail. By reducing the ink from the circulation path by the amount of ink consumed by the recording, the pressure in the first pressure control chamber is reduced, and as a result, the ink in the first pressure control chamber 122 is also reduced. As the ink in the first pressure control chamber 122 is reduced, the internal volume of the first pressure control chamber 122 is reduced. Due to this reduction in the internal volume of the first pressure control chamber 122, the first communication port 191A is opened, and ink is supplied from the first valve chamber 121 to the first pressure control chamber 122. This supplied ink experiences a pressure loss when passing from first valve chamber 121 through first communication port 191A, and as it flows into first pressure control chamber 122, the ink changes from a positive pressure state to a negative pressure state. As ink flows from first valve chamber 121 into first pressure control chamber 122, the pressure inside the first pressure control chamber increases, increasing the internal volume of the first pressure control chamber and closing first communication port 191A. In this way, first communication port 191A alternates between an open state and a closed state depending on the consumption of ink. Furthermore, if no ink is consumed, first communication port 191A is maintained in a closed state.

[0087] FIG. 10B is a schematic diagram showing the flow of ink immediately after the recording operation is completed and the circulation pump 500 is turned off (stopped). When the recording operation is completed and the circulation pump 500 is turned off, the pressures of the first pressure control chamber 122 and the second pressure control chamber 152 are both at the control pressure during the recording operation. Therefore, the ink moves as shown in FIG. 10B according to the pressure difference between the pressures of the first pressure control chamber 122 and the second pressure control chamber 152. Specifically, the ink continues to flow from the first pressure control chamber 122 to the ejection module 300 via the supply flow path 130, and then to the second pressure control chamber 152 via the recovery flow path 140. The ink also continues to flow from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151.

[0088] The amount of ink that has moved from the first pressure control chamber 122 to the second pressure control chamber 152 by these ink flows is supplied to the first pressure control chamber 122 from the ink tank 2 via the filter 110 and the first valve chamber 121. Therefore, the content volume in the first pressure control chamber 122 is kept constant. From the relationship of the above-mentioned formula 2, if the content volume of the first pressure control chamber 122 is constant, the spring force F1 of the valve spring 200, the spring force F2 of the pressure adjustment spring 220, the pressure receiving area S1 of the valve 190, and the pressure receiving area S2 of the pressure plate 210 are kept constant. Therefore, the pressure in the first pressure control chamber 122 is determined according to the change in the pressure (gauge pressure) P1 in the first valve chamber 121. Therefore, if there is no change in the pressure P1 in the first valve chamber 121, the pressure P2 in the first pressure control chamber 122 is kept at the same pressure as the control pressure during the recording operation.

[0089] On the other hand, the pressure of the second pressure control chamber 152 changes over time according to the change in the content volume caused by the inflow of ink from the first pressure control chamber 122. Specifically, from the state of FIG. 10(b) until the communication port 191 is closed and the second valve chamber 151 and the second pressure control chamber 152 are not in communication with each other as shown in FIG. 10(c), the pressure of the second pressure control chamber 152 changes according to Equation 2. Thereafter, the pressure plate 210 and the valve shaft 190a are not in contact with each other and the communication port 191 is closed. Then, as shown in FIG. 10(d), ink flows from the recovery passage 140 into the second pressure control chamber 152. This ink inflow displaces the pressure plate 210 and the flexible member 230, and the pressure of the second pressure control chamber 152 changes according to Equation 4 until the internal volume of the second pressure control chamber 152 reaches its maximum. That is, it rises.

[0090] 10(c), no flow of ink occurs from the first pressure control chamber 122 through the bypass flow path 160 and the second valve chamber 151 to the second pressure control chamber 152. Therefore, after the ink in the first pressure control chamber 122 is supplied to the ejection module 300 through the supply flow path 130, only a flow occurs through the recovery flow path 140 to the second pressure control chamber 152. As described above, the movement of ink from the first pressure control chamber 122 to the second pressure control chamber 152 occurs in response to the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 . Therefore, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the movement of the ink stops.

[0091] In addition, in a state where the pressure in the second pressure control chamber 152 is equal to the pressure in the first pressure control chamber 122, the second pressure control chamber 152 expands to a state shown in FIG. 10(d). When the second pressure control chamber 152 expands as shown in FIG. 10(d), a storage portion capable of storing ink is formed in the second pressure control chamber 152. The time from when the circulation pump 500 is stopped to when the state shown in FIG. 10(d) is transitioned to is about 1 to 2 minutes, which may vary depending on the shape and size of the flow path and the properties of the ink. When the circulation pump 500 is driven from the state shown in FIG. 10(d) where ink is stored in the storage portion, the ink in the storage portion is supplied to the first pressure control chamber 122 by the circulation pump 500. As a result, the amount of ink in the first pressure control chamber 122 increases as shown in FIG. 10(e), and the flexible member 230 and the pressure plate 210 are displaced in the expansion direction. Then, when the circulation pump 500 continues to be driven, the state inside the circulation path changes as shown in FIG. 10(a).

[0092] 10(a) is an example of the ink circulation during the printing operation, but as described above, the ink may be circulated without the printing operation. Even in this case, the ink flows as shown in FIGS. 10(a) to 10(e) according to the driving and stopping of the circulating pump 500.

[0093] As described above, in this embodiment, the second communication port 191B in the second pressure adjustment means 150 is in an open state when the circulation pump 500 is driven to circulate ink, and is in a closed state when the circulation of ink stops, but this is not limited to the above example. The control pressure may be set so that the second communication port 191B in the second pressure adjustment means 150 is in a closed state even when the circulation pump 500 is driven to circulate ink. The role of the bypass flow path 160 will be specifically described below.

[0094] The bypass flow path 160 connecting the first pressure adjustment means 120 and the second pressure adjustment means 150 is provided to prevent the negative pressure generated in the circulation path from being affected by the discharge module 300 when the negative pressure exceeds a predetermined value. The bypass flow path 160 is also provided to supply ink to the pressure chamber 12 from both sides of the supply flow path 130 and the recovery flow path 140.

[0095] First, an example will be described in which the bypass flow path 160 is provided to prevent the negative pressure from being influenced by the discharge module 300 when the negative pressure becomes stronger than a preset value. For example, the ink characteristics (e.g., viscosity) may change due to a change in the environmental temperature. When the ink viscosity changes, the pressure loss in the circulation path also changes. For example, when the ink viscosity decreases, the pressure loss in the circulation path decreases. As a result, the flow rate of the circulation pump 500 driven at a constant drive amount increases, and the flow rate through the discharge module 300 increases. On the other hand, since the discharge module 300 is kept at a constant temperature by a temperature adjustment mechanism (not shown), the viscosity of the ink in the discharge module 300 is maintained constant even if the environmental temperature changes. While the viscosity of the ink in the discharge module 300 does not change, the flow rate of the ink flowing through the discharge module 300 increases, and the negative pressure in the discharge module 300 is strengthened due to flow resistance. In this way, if the negative pressure in the discharge module 300 becomes stronger than the default value, the meniscus of the discharge port 13 may be destroyed, and external air may be drawn into the circulation path, preventing normal discharge. Even if the meniscus is not destroyed, the negative pressure in the pressure chamber 12 may become stronger than the default value, affecting discharge.

[0096] For this reason, in this embodiment, the bypass flow path 160 is formed in the circulation path. By providing the bypass flow path 160, when the negative pressure becomes stronger than a preset value, ink also flows through the bypass flow path 160, so that the pressure of the ejection module 300 can be kept constant. Therefore, for example, the second communication port 191B in the second pressure adjustment means 150 may be configured with a control pressure that maintains the closed state even when the circulation pump 500 is being driven. Then, the control pressure in the second pressure adjustment means may be set so that the communication port 191 in the second pressure adjustment means 150 is in an open state when the negative pressure becomes stronger than a preset value. In other words, if the meniscus does not collapse even when the flow rate of the pump is changed due to a viscosity change such as an environmental change, or if a predetermined negative pressure is maintained, the second communication port 191B may be in a closed state when the circulation pump 500 is driven.

[0097] Next, an example will be described in which the bypass flow path 160 is provided to supply ink to the pressure chamber 12 from both the supply flow path 130 and the recovery flow path 140. Pressure fluctuations in the circulation path can also be caused by the ejection operation of the ejection element 15. This is because a force that draws ink into the pressure chamber is generated by the ejection operation.

[0098] Hereinafter, it will be described that when high duty recording is continued, the ink supplied to the pressure chamber 12 is supplied to both the supply flow path 130 side and the recovery flow path 140 side. The definition of duty can change depending on various conditions. As an example, an image recorded under the condition that one ink droplet with a volume of 4 pL per droplet is applied to a unit area of ​​1,200 dpi x 1,200 dpi will be treated as having a recording duty of 100%. High duty recording means, for example, recording performed at a duty of 100%.

[0099] If recording at a high duty continues, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the recovery flow path 140 decreases. On the other hand, since the circulation pump 500 causes a constant amount of ink to flow out, the balance between the inflow and outflow in the second pressure control chamber 152 is lost, the ink in the second pressure control chamber 152 decreases, the negative pressure in the second pressure control chamber 152 becomes stronger, and the second pressure control chamber 152 shrinks. Then, as the negative pressure in the second pressure control chamber 152 becomes stronger, the inflow amount of ink flowing into the second pressure control chamber 152 through the bypass flow path 160 increases, and the second pressure control chamber 152 becomes stable with the outflow and inflow balanced. As a result, the negative pressure in the second pressure control chamber 152 becomes stronger according to the duty. Furthermore, as described above, when the circulation pump 500 is driven, in a configuration in which the second communication port 191B is in a closed state, the second communication port 191B opens depending on the duty, and ink flows from the bypass flow path 160 into the second pressure control chamber 152.

[0100] Then, when recording at an even higher duty is continued, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the recovery flow passage 140 decreases, and instead the amount of ink flowing into the second pressure control chamber 152 from the second communication port 191B via the bypass flow passage 160 increases. If this state progresses further, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the recovery flow passage 140 becomes zero, and all ink flowing out to the circulation pump 500 becomes ink flowing in from the second communication port 191B. If this state progresses further, ink now flows back from the second pressure control chamber 152 into the pressure chamber 12 through the recovery flow passage 140. In this state, the ink flowing out from the second pressure control chamber 152 to the circulation pump 500 and the ink flowing out to the pressure chamber 12 flow into the second pressure control chamber 152 from the second communication port 191B through the bypass flow passage 160. In this case, the pressure chamber 12 is filled with ink from the supply flow passage 130 and ink from the recovery flow passage 140, and is ejected.

[0101] This backflow of ink that occurs when the recording duty is high is a phenomenon that occurs due to the provision of the bypass flow path 160. In addition, in the above, an example has been described in which the second communication port 191B in the second pressure adjustment means is opened in response to the backflow of ink, but backflow of ink may also occur when the second communication port 191B in the second pressure adjustment means is in the open state. Even in a configuration that does not include a second pressure adjustment means, the provision of the bypass flow path 160 may cause the above-mentioned backflow of ink.

[0102] The circulation flow rate (mL / min) of the ink circulating in the circulation unit including the supply flow path 130, the recovery flow path 140, and the circulation pump 500 is preferably 1.0 mL / min or more and 10.0 mL / min or less. It is more preferably 1.5 mL / min or more and 8.0 mL / min or less, and particularly preferably 2.0 mL / min or more and 5.0 mL / min or less. If the circulation flow rate of the ink in the circulation unit is less than 1.0 mL / min, the ink circulation is too slow, so the ink is likely to dry out from the meniscus, and the effect of improving the intermittent ejection stability of the ink may not be sufficiently obtained. On the other hand, if the circulation flow rate of the ink in the circulation unit is more than 10.0 mL / min, air bubbles are likely to be generated in the ink, and the effect of improving the intermittent ejection stability of the ink may not be sufficiently obtained.

[0103] In order to suppress localized evaporation of the ink, the flow rate of the aqueous ink in the circulation path (circulation flow rate, mm / s) is preferably 10 mm / s or more and 30 mm / s or less. The circulation flow rate refers to the flow rate of the aqueous ink circulating in the circulation path. The circulation path refers to the region from the supply flow path to the recovery flow path. In the examples described later, the flow rate of the aqueous ink in the circulation path did not change even near the meniscus of the ejection port. If the circulation flow rate is less than 10 mm / s, the ejection stability may not be sufficiently obtained due to the influence of localized evaporation of the ink. On the other hand, if the circulation speed is 30 mm / s or more, the change in the ejection amount of the ink becomes large during continuous ejection, and normal ejection may not be performed. As a result, the ejection stability may not be sufficiently obtained. The circulation flow rate and the circulation flow rate can be simply controlled by adjusting the difference between the pressure in the supply flow path and the pressure in the recovery flow path.

[0104] [Configuration of the discharge unit] FIG. 11 is a schematic diagram showing a circulation path for one color of ink in the discharge unit 3 of this embodiment. FIG. 11(a) is an exploded perspective view of the discharge unit 3 seen from the first support member 4 side, and FIG. 11(b) is an exploded perspective view of the discharge unit 3 seen from the discharge module 300 side. The arrows indicated by IN and OUT in the figure indicate the flow of ink, and the flow of ink for only one color will be described, but the other colors flow in the same manner. In addition, the second support member 7 and the electric wiring member 5 are omitted in FIG. 11, and are also omitted in the following description of the configuration of the discharge unit. In addition, the first support member 4 in FIG. 11(a) shows a cross section taken along line XI-XI in FIG. 3. The discharge module 300 includes a discharge element substrate 340 and an aperture plate 330. FIG. 12 is a diagram showing the aperture plate 330, and FIG. 13 is a diagram showing an example of the discharge element substrate 340.

[0105] Ink is supplied to the discharge unit 3 from the circulation unit 54 via a joint member 8 (see FIG. 3). The route of the ink from after the ink passes through the joint member 8 until it returns to the joint member 8 will be described. In the following drawings, the joint member 8 will be omitted from illustration.

[0106] The ejection module 300 includes an ejection element substrate 340, which is a silicon substrate 310, and an aperture plate 330, and further includes an ejection port forming member 320. The ejection element substrate 340, the aperture plate 330, and the ejection port forming member 320 are overlapped and joined together so that the flow paths of the inks communicate with each other, thereby forming the ejection module 300, which is supported by a first support member 4. The ejection module 300 is supported by the first support member 4 to form an ejection unit 3. The ejection element substrate 340 includes an ejection port forming member 320, which includes a plurality of ejection port rows in which a plurality of ejection ports 13 are arranged, and ejects a portion of the ink supplied via an ink flow path in the ejection module 300 from the ejection port 13. Ink that is not ejected is collected via the ink flow path in the ejection module 300.

[0107] As shown in Figs. 11 and 12, the opening plate 330 has a plurality of arranged ink supply ports 311 and a plurality of arranged ink recovery ports 312. As shown in Figs. 13 and 14, the ejection element substrate 340 has a plurality of arranged supply connection channels 323 and a plurality of arranged recovery connection channels 324. Furthermore, the ejection element substrate 340 has a common supply channel 18 communicating with the plurality of supply connection channels 323 and a common recovery channel 19 communicating with the plurality of recovery connection channels 324. The ink flow channels in the ejection unit 3 are formed by communicating an ink supply channel 48 and an ink recovery channel 49 (see Fig. 3) provided in the first support member 4 with a flow channel provided in the ejection module 300. The support member supply port 211 is a cross-sectional opening that forms the ink supply channel 48, and the support member recovery port 212 is a cross-sectional opening that forms the ink recovery channel 49.

[0108] Ink supplied to the ejection unit 3 is supplied from the circulation unit 54 (see FIG. 3(a)) side to the ink supply flow path 48 (see FIG. 3(a)) of the first support member 4. The ink flowing through the support member supply port 211 in the ink supply flow path 48 is supplied to the common supply flow path 18 of the ejection element substrate 340 via the ink supply flow path 48 (see FIG. 3(a)) and the ink supply port 311 of the opening plate 330, and enters the supply connection flow path 323. This is the supply side flow path. After that, the ink flows through the pressure chamber 12 (see FIG. 3(b)) of the ejection port forming member 320 to the recovery connection flow path 324 of the recovery side flow path. The flow of ink in the pressure chamber 12 will be described in detail later.

[0109] In the recovery side flow path, the ink that has entered the recovery connection flow path 324 flows into the common recovery flow path 19. After that, the ink flows from the common recovery flow path 19 through the ink recovery port 312 of the opening plate 330 to the ink recovery flow path 49 of the first support member 4, and then through the support member recovery port 212 to be recovered in the circulation unit 54.

[0110] The area of ​​the opening plate 330 without the ink supply port 311 or the ink recovery port 312 corresponds to the area for separating the support member supply port 211 and the support member recovery port 212 in the first support member 4. Moreover, this area does not have an opening in the first support member 4 either. Such an area is used as an adhesion area when the ejection module 300 and the first support member 4 are adhered to each other.

[0111] In FIG. 12, the aperture plate 330 has a plurality of rows of apertures arranged in the X direction, and the supply (IN) apertures and the recovery (OUT) apertures are arranged alternately in the Y direction so as to be shifted by half a pitch in the X direction. In FIG. 13, the ejection element substrate 340 has a common supply flow path 18 communicating with a plurality of supply connection flow paths 323 arranged in the Y direction, and a common recovery flow path 19 communicating with a plurality of recovery connection flow paths 324 arranged in the Y direction, arranged alternately in the X direction. The common supply flow paths 18 and the common recovery flow path 19 are separated by type of ink, and further, the number of common supply flow paths 18 and common recovery flow paths 19 is determined according to the number of ejection port rows of each color. In addition, the supply connection flow paths 323 and the recovery connection flow paths 324 are also arranged in the number corresponding to the ejection ports 13. It is not necessarily required that they correspond one-to-one, and one supply connection flow path 323 and one recovery connection flow path 324 may correspond to a plurality of ejection ports 13.

[0112] Such an opening plate 330 and an ejection element substrate 340 are overlapped and joined so that the flow paths of each ink are connected to form an ejection module 300, and by being supported by the first support member 4, an ink flow path is formed that has the above-mentioned supply flow path and recovery flow path.

[0113] Fig. 14(a) to (c) are cross-sectional views showing ink flows in different parts of the discharge unit 3. Fig. 14(a) is a cross-section shown by XIVa-XIVa in Fig. 11(a) and shows a cross-section of a part where the ink supply flow path 48 and the ink supply port 311 in the discharge unit 3 communicate with each other. Fig. 14(b) is a cross-section shown by XIVb-XIVb in Fig. 11(a) and shows a cross-section of a part where the ink recovery flow path 49 and the ink recovery port 312 in the discharge unit 3 communicate with each other. Fig. 14(c) is a cross-section shown by XIVc-XIVc in Fig. 11(a) and shows a cross-section of a part where the ink supply port 311 and the ink recovery port 312 do not communicate with the flow path of the first support member 4.

[0114] In the supply flow path for supplying ink, as shown in FIG. 14(a), ink is supplied from a portion where the ink supply flow path 48 of the first support member 4 and the ink supply port 311 of the opening plate 330 overlap and communicate with each other. In the recovery flow path for recovering ink, as shown in FIG. 14(b), ink is recovered from a portion where the ink recovery flow path 49 of the first support member 4 and the ink recovery port 312 of the opening plate 330 overlap and communicate with each other. In addition, as shown in FIG. 14(c), in the ejection unit 3, there is also an area where the opening plate 330 does not have an opening. In such an area, ink is not supplied or recovered between the ejection element substrate 340 and the first support member 4. As shown in FIG. 14(a), ink is supplied in an area where the ink supply port 311 is provided, and as shown in FIG. 14(b), ink is recovered in an area where the ink recovery port 312 is provided. In the present embodiment, the configuration using the opening plate 330 has been described as an example, but a configuration without using the opening plate 330 may be used. For example, a configuration may be used in which flow paths corresponding to the ink supply flow path 48 and the ink recovery flow path 49 are formed in the first support member 4, and the ejection element substrate 340 is joined to the first support member 4.

[0115] 15(a) and (b) are cross-sectional views showing an example of the vicinity of the ejection port 13 in the ejection module 300, and FIG. 16 is a cross-sectional view showing an ejection module configured with the common supply flow path 18 and the common recovery flow path 19 expanded in the X direction. The thick arrows shown in the common supply flow path 18 and the common recovery flow path 19 in FIG. 15 and FIG. 16 indicate the oscillation of ink in a configuration using a serial type inkjet recording device 50. The ink supplied to the pressure chamber 12 via the common supply flow path 18 and the supply connection flow path 323 is ejected from the ejection port 13 by driving the ejection element 15. When the ejection element 15 is not driven, the ink is recovered from the pressure chamber 12 to the common recovery flow path 19 via the recovery connection flow path 324, which is a recovery flow path.

[0116] In the case of using the serial type inkjet recording device 50, when ink is discharged from the circulating ink, the ink discharge is influenced by the ink oscillation in the ink flow path caused by the main scanning of the recording head 1. Specifically, the influence of the ink oscillation in the ink flow path may appear as a difference in the ink discharge amount or a deviation in the discharge direction. As shown in FIG. 16, when the common supply flow path 18 and the common recovery flow path 19 have a cross-sectional shape that is wide in the X direction, which is the main scanning direction, the ink in the common supply flow path 18 and the common recovery flow path 19 is easily subjected to an inertial force in the main scanning direction, and the ink undergoes a large oscillation. As a result, the ink oscillation may affect the ink discharge from the discharge port 13. In addition, if the common supply flow path 18 and the common recovery flow path 19 are widened in the X direction, the distance between the colors will be increased, which may reduce the recording efficiency.

[0117] Therefore, in the cross section shown in FIG. 15, the common supply flow path 18 and the common recovery flow path 19 of this embodiment both extend in the Y direction, but are also configured to extend in the Z direction perpendicular to the X direction, which is the main scanning direction. With this configuration, the width of each flow path in the main scanning direction of the common supply flow path 18 and the common recovery flow path 19 can be reduced. By reducing the width of each flow path in the main scanning direction of the common supply flow path 18 and the common recovery flow path 19, the ink oscillation caused by the inertial force (indicated by the thick black arrow in the figure) acting on the ink in the common supply flow path 18 and the common recovery flow path 19 in the opposite direction to the main scanning direction during the main scanning is reduced. This makes it possible to suppress the effect of the ink oscillation on the ink ejection. In addition, the cross-sectional area is increased by extending the common supply flow path 18 and the common recovery flow path 19 in the Z direction, thereby reducing the flow path pressure loss.

[0118] As described above, by reducing the width of each of the common supply flow path 18 and the common recovery flow path 19 in the main scanning direction, the oscillation of ink in the common supply flow path 18 and the common recovery flow path 19 during main scanning is reduced, but the oscillation is not eliminated. Therefore, in order to suppress the occurrence of differences in ejection for each ink type that may still occur even with the reduced oscillation, in this embodiment, the common supply flow path 18 and the common recovery flow path 19 are configured to be disposed at positions that overlap with each other in the X direction.

[0119] As described above, in this embodiment, the supply connection flow path 323 and the recovery connection flow path 324 are provided corresponding to the ejection port 13, and the supply connection flow path 323 and the recovery connection flow path 324 are arranged side by side in the X direction with the ejection port 13 in between. Therefore, there are portions where the common supply flow path 18 and the common recovery flow path 19 do not overlap in the X direction, and if the corresponding relationship in the X direction between the supply connection flow path 323 and the recovery connection flow path 324 is lost, this will affect the flow and ejection of ink in the X direction in the pressure chamber 12. When the influence of ink fluctuation is added to this, it may further affect the ejection of ink from each ejection port.

[0120] Therefore, by arranging the common supply flow path 18 and the common recovery flow path 19 at positions where they overlap in the X direction, the ink oscillation during main scanning in the common supply flow path 18 and the common recovery flow path 19 becomes approximately equal at any position in the Y direction where the ejection ports 13 are arranged. As a result, the pressure difference between the common supply flow path 18 side and the common recovery flow path 19 side generated in the pressure chamber 12 does not vary greatly, and stable ejection can be performed.

[0121] In addition, in some recording heads that circulate ink, the flow path that supplies ink to the recording head and the flow path that recovers ink are configured as the same flow path, but in this embodiment, the common supply flow path 18 and the common recovery flow path 19 are configured as separate flow paths. The supply connection flow path 323 and the pressure chamber 12 are connected to each other, and the pressure chamber 12 and the recovery connection flow path 324 are connected to each other, and ink is discharged from the ejection port 13 of the pressure chamber 12. In other words, the pressure chamber 12, which is a path that connects the supply connection flow path 323 and the recovery connection flow path 324, is configured to have the ejection port 13. Therefore, an ink flow that flows from the supply connection flow path 323 side to the recovery connection flow path 324 side is generated in the pressure chamber 12, and the ink in the pressure chamber 12 is efficiently circulated. By efficiently circulating the ink in the pressure chamber 12, the ink in the pressure chamber 12, which is easily affected by the evaporation of ink from the ejection port 13, can be kept fresh.

[0122] Furthermore, since the two flow paths, the common supply flow path 18 and the common recovery flow path 19, are connected to the pressure chamber 12, if it becomes necessary to eject ink at a high flow rate, it is possible to supply ink from both flow paths. In other words, compared to a configuration in which ink supply and recovery are configured using only one flow path, the configuration of this embodiment has the advantage of not only being able to circulate ink efficiently, but also being able to handle ejection at a high flow rate.

[0123] Furthermore, the common supply flow path 18 and the common recovery flow path 19 are less susceptible to the influence of ink fluctuations when they are disposed close to each other in the X direction. Preferably, the distance between the flow paths is 75 μm or more and 100 μm or less.

[0124] Fig. 17 is a diagram showing another example of the ejection element substrate 340. In Fig. 17, the supply connection flow path 323 and the recovery connection flow path 324 are omitted. Since ink that has received thermal energy from the ejection elements 15 in the pressure chambers 12 flows into the common recovery flow path 19, ink with a relatively high temperature flows compared to the temperature of the ink in the common supply flow path 18. At this time, as shown in the α portion surrounded by the dashed line in Fig. 17, there is a portion in the X direction of the ejection element substrate 340 where only the common recovery flow path 19 exists. In this case, the temperature locally increases in that portion, causing temperature unevenness in the ejection module 300, which may affect ejection.

[0125] In the common supply flow path 18, ink flows that is at a relatively low temperature relative to the common recovery flow path 19. Therefore, when the common supply flow path 18 and the common recovery flow path 19 are adjacent to each other, the temperatures in the common supply flow path 18 and the common recovery flow path 19 are partially offset in the vicinity thereof, suppressing a rise in temperature. Therefore, it is preferable that the common supply flow path 18 and the common recovery flow path 19 are adjacent to each other and have approximately the same length, and are positioned so as to overlap each other in the X direction.

[0126] 18(a) and (b) are diagrams showing the flow path configuration of the recording head 1 corresponding to three colors of ink: cyan (C), magenta (M), and yellow (Y). As shown in FIG. 18(a), the recording head 1 is provided with a circulation flow path for each type of ink. The pressure chambers 12 are provided along the X direction, which is the main scanning direction of the recording head 1. As shown in FIG. 18(b), the common supply flow path 18 and the common recovery flow path 19 are provided along the ejection port row in which the ejection ports 13 are arranged, and are provided extending in the Y direction so as to sandwich the ejection port row between the common supply flow path 18 and the common recovery flow path 19.

[0127] [Connection between the main body and the recording head] 19 is a schematic diagram showing in more detail the connection state between the ink tank 2 and external pump 21 provided in the main body of the inkjet recording device 50 of this embodiment and the recording head 1, and the arrangement of the circulation pump, etc. The inkjet recording device 50 of this embodiment is configured so that when a problem occurs in the recording head 1, only the recording head 1 can be easily replaced. Specifically, it has a liquid connection part 700 that can easily connect and disconnect the ink supply tube 59 connected to the external pump 21 and the recording head 1. This makes it possible to easily attach and detach only the recording head 1 to and from the inkjet recording device 50.

[0128] 19, the liquid connection part 700 has a liquid connector insertion port 53a protruding from the head housing 53 of the recording head 1, and a cylindrical liquid connector 59a into which the liquid connector insertion port 53a can be inserted. The liquid connector insertion port 53a is fluidly connected to an ink supply flow path (inflow flow path) formed in the recording head 1, and is connected to the first pressure adjustment means 120 via the above-mentioned filter 110. In addition, the liquid connector 59a is provided at the tip of an ink supply tube 59 connected to an external pump 21 that pressurizes and supplies ink from the ink tank 2 to the recording head 1.

[0129] 19, the recording head 1 can be easily attached, detached, and replaced by the liquid connection part 700. However, if the sealing performance between the liquid connector insertion port 53a and the liquid connector 59a is reduced, ink supplied under pressure by the external pump 21 may leak from the liquid connection part 700. If the leaked ink adheres to the circulation pump 500 or the like, a malfunction may occur in the electrical system. Therefore, in this embodiment, the circulation pump and the like are arranged as follows.

[0130] [Placement of circulation pumps, etc.] 19, in this embodiment, in order to prevent ink leaking from the liquid connection part 700 from adhering to the circulation pump 500, the circulation pump 500 is disposed above the liquid connection part 700 in the direction of gravity. In other words, the circulation pump 500 is disposed above the liquid connector insertion port 53a, which is the ink introduction port of the recording head 1, in the direction of gravity. Furthermore, the circulation pump 500 is disposed in a position where it is not in contact with the members that constitute the liquid connection part 700. As a result, even if ink leaks from the liquid connection part 700, the ink flows horizontally in the opening direction of the liquid connector 59a or downward in the direction of gravity, preventing the ink from reaching the circulation pump 500 located above in the direction of gravity. In addition, since the circulation pump 500 is disposed at a position away from the liquid connection part 700, the possibility of ink reaching the circulation pump 500 by running down a member is also reduced.

[0131] Furthermore, the electrical connection part 515, which electrically connects the circulation pump 500 and the electrical contact board 6 via a flexible wiring member 514, is provided above the liquid connection part 700 in the direction of gravity. This makes it possible to reduce the possibility of electrical trouble caused by ink from the liquid connection part 700.

[0132] Furthermore, in this embodiment, since the wall portion 52b of the head housing 53 is provided, even if ink is ejected from the opening 59b of the liquid connection portion 700, the ink can be blocked, reducing the possibility of the ink reaching the circulation pump 500 or the electrical connection portion 515.

[0133] (Heating process) The recording method of the present invention may include a step of heating (heat treatment) the recording medium to which the ink has been applied. By heating the recording medium to which the ink has been applied, it is possible to promote drying and increase the strength of the image.

[0134] Examples of the means for heating the recording medium include known heating means such as a heater, air blowing means using air blowing such as a dryer, and a combination of these. Examples of the heating means include the above heating means, air blowing means, and a combination of these. Examples of the heat treatment method include a method of applying heat from the opposite side (back side) of the recording surface (ink application surface) of the recording medium using a heater, a method of applying warm or hot air to the recording surface of the recording medium, and a method of heating from the recording surface or back side using an infrared heater. A combination of these methods may also be used.

[0135] In order to enhance the abrasion resistance of the image, the heating temperature of the recording medium to which the ink and reaction liquid have been applied is preferably 50° C. or more and 90° C. or less. The heating temperature of the recording medium to which the ink has been applied may be read by a sensor incorporated in a position corresponding to the heating means of the recording device, or 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.

[0136] (Recording medium) In the recording method and recording apparatus of the present invention, it is preferable to use a non- or poorly absorbent recording medium. The non- or poorly absorbent recording medium is a recording medium that is absorbed within 30 msec from the start of contact in the Bristow method. 1 / 2 Water absorption up to 0mL / m 2 More than 10mL / m 2 The following recording media are used. The Bristow method is described in JAPAN TAPPI Paper and Pulp Test Method No. 51, "Testing Method for Liquid Absorbency of Paper and Paperboard." In the present invention, a "non-absorbent" recording medium that satisfies the above-mentioned condition for water absorption amount and has no ink absorbency, and a "poorly absorbent" recording medium that has almost no ink absorbency are defined as "non- to poorly absorbent recording media." Recording media for inkjet recording (glossy paper, matte paper, etc.) having a coating layer (ink receiving layer) formed of inorganic particles, and plain paper having no coating layer, have a water absorption amount of 10 mL / m2 or more. 2It is an "absorbent recording medium" exceeding 100%. As non- to poorly absorbent recording media, a plastic film; a recording medium in which a plastic film is adhered to the recording surface of a substrate; a recording medium in which a resin coating layer is provided on the recording surface of a substrate containing cellulose pulp; and the like can be used. Among these, a plastic film is preferred, and a recording medium in which a resin coating layer is provided on the recording surface of a substrate containing cellulose pulp is also preferred.

[0137] (Water-based ink) The ink used in the recording method of the present invention is a water-based ink for ink-jet recording, which contains a pigment and wax particles. The components constituting the ink and the physical properties of the ink will be described below.

[0138] [Pigment] The ink contains a pigment as a coloring material. The content (mass %) of the pigment in the ink is preferably from 0.1 to 15.0% by mass, and more preferably from 1.0 to 10.0% by mass, based on the total mass of the ink.

[0139] Examples of the pigment include inorganic pigments such as carbon black and titanium oxide, and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, dioxazine, and perinone. Among them, the pigment is preferably at least one selected from the group consisting of carbon black and organic pigments.

[0140] As a method for dispersing pigments, resin-dispersed pigments using a resin (resin dispersant) as a dispersant, self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface, etc. can be used. In addition, resin-bonded pigments in which organic groups containing a resin are chemically bonded to the pigment particle surface, and microcapsule pigments in which the pigment particle surface is coated with a resin, etc. can be used. Among them, it is preferable to use resin-dispersed pigments in which a resin as a dispersant is physically adsorbed onto the pigment particle surface, rather than resin-bonded pigments or microcapsule pigments. In other words, it is preferable that the pigment is a pigment that is dispersed by the action of a resin dispersant.

[0141] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin described below, especially a water-soluble resin, can be used. The content (mass%) of the pigment in the ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the content of the resin dispersant.

[0142] As the self-dispersing pigment, a pigment having an acid group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group bonded directly or via another atomic group (-R-) to the particle surface of the pigment can be used. The acid group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the acid group is a salt type, examples of the cation serving as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. The pigment may also be a group formed by combining these groups.

[0143] [Wax particles] The ink contains particles (wax particles) formed of wax. The wax may be a composition containing components other than wax, or may be wax itself. The wax exists in the form of wax particles dispersed in the ink. In a narrow sense, wax is an ester of a water-insoluble higher monohydric or dihydric alcohol and a fatty acid, and includes animal wax and vegetable wax, but does not include oils and fats. In a broad sense, wax includes high-melting fats, mineral wax, petroleum wax, and blends and modified products of various waxes. In the recording method of the present invention, any wax in the broad sense can be used without particular restrictions. Wax in the broad sense can be classified into natural wax, synthetic wax, blends thereof (blended wax), and modified products thereof (modified wax).

[0144] Examples of natural waxes include petroleum wax, vegetable wax, and animal and vegetable wax. Examples of petroleum wax include paraffin wax, microcrystalline wax, and petrolatum. Examples of vegetable wax include carnauba wax, candelilla wax, rice wax, sugarcane wax, palm wax, and wood wax. Examples of animal and vegetable wax include lanolin, spermaceti, and beeswax.

[0145] Examples of synthetic waxes include hydrocarbon waxes such as Fischer-Tropsch wax and polyolefin wax (e.g., polyethylene wax and polypropylene wax). The blended wax is a mixture of the above-mentioned various waxes. The modified wax is a wax obtained by subjecting the above-mentioned various waxes to a modification treatment such as oxidation, hydrogenation, alcohol modification, acrylic modification, or urethane modification. The wax is preferably at least one selected from the group consisting of microcrystalline wax, Fischer-Tropsch wax, polyolefin wax, paraffin wax, and modified or blended products thereof. Among these, a blend of multiple types of wax is more preferable, and a blend of petroleum wax and synthetic wax is particularly preferable.

[0146] The wax is preferably solid at room temperature (25° C.). From the viewpoint of abrasion resistance, the melting point T M (°C) is preferably 40°C or more and 120°C or less, and more preferably 50°C or more and 100°C or less. The melting point of the wax can be measured in accordance with the test method described in 5.3.1 (melting point test method) of JIS K2235:1991 (petroleum wax). In the case of microcrystalline wax, petrolatum, and a mixture of multiple types of wax, the test method described in 5.3.2 can be used to measure more accurately. The melting point of the wax is easily affected by characteristics such as molecular weight (the higher the molecular weight, the higher the melting point), molecular structure (the higher the melting point if it is linear, and the lower the melting point if it is branched), crystallinity (the higher the crystallinity, the higher the melting point), and density (the higher the crystallinity, the higher the melting point). Therefore, by controlling these characteristics, a wax having a desired melting point can be obtained.

[0147] The content (mass %) of wax particles in the ink is preferably 0.8% by mass or more and 5.0% by mass or less based on the total mass of the ink. If the content of wax particles is less than 0.8% by mass, the wax particles are too few, and the effect of improving the scratch resistance of the image may not be sufficiently obtained. On the other hand, if the content of wax particles is more than 5.0% by mass, the wax particles are too many, and the separation of the wax cannot be sufficiently suppressed even by the circulation action, and the effect of improving the intermittent ejection stability of the ink may not be sufficiently obtained. The content of the wax particles is the total content of the wax and the dispersant that disperses the wax.

[0148] The amount of anions (μmol / g) of the wax particles is preferably equal to or less than the amount of anions (μmol / g) of the pigment. If the amount of anions of the wax particles is greater than the amount of anions of the pigment, the pigment in the ink is less likely to retreat from the vicinity of the meniscus, and the pigment is more likely to adhere, which may result in insufficient improvement in the intermittent ejection stability of the ink. In addition, the pigment is more likely to be exposed to the surface of the image than the wax, so that the effect of improving the scratch resistance of the image may not be sufficiently obtained. The amount of anions (μmol / g) of the wax particles is preferably 0.9 times or less, more preferably 0.5 times or less, and more preferably 0.05 times or more, in terms of the ratio to the amount of anions (μmol / g) of the pigment.

[0149] The amount of anions (anion amount per unit mass, unit: μmol / g) of wax particles and pigment can be measured by colloid titration. In the examples described below, a potential difference-based colloid titration was performed using an automatic potentiometric titrator (product name "AT-510", manufactured by Kyoto Electronics Co., Ltd.) equipped with a streaming potential titration unit (PCD-500). By this colloid titration, the amount of anions (μmol / g) per unit mass of the pigment in the pigment dispersion and the amount of anions (μmol / g) per unit mass of the wax particles in the wax water dispersion were measured. More specifically, the sample was diluted about 300 times (by mass) with pure water, and the pH was adjusted to about 10 with potassium hydroxide as necessary, and potentiometric titration was performed using 5 mmol / L methyl glycol chitosan as a titration reagent. It is of course possible to measure the amount of anions using particles extracted from the ink by an appropriate method.

[0150] Cumulative 50% particle size D of wax particles based on volume 50(nm) is preferably 100 nm or more and 300 nm or less. Among them, it is more preferably 150 nm or more and 300 nm or less, and particularly preferably 200 nm or more and 300 nm or less. The volume-based cumulative 50% particle diameter of the wax particles is the diameter of the particles that is 50% of the total volume of the measured particles when integrated from the small particle diameter side in the particle diameter integration curve. The volume-based cumulative 50% particle diameter of the wax particles can be measured under the same measurement conditions using a particle size analyzer by the dynamic light scattering method described in the resin section.

[0151] [Dispersant] The ink preferably further contains a dispersant that disperses the wax particles in the ink. That is, the wax is preferably dispersed in the ink in a particulate form by the action of the dispersant. When the wax is dispersed in the ink by the dispersant, the "wax particles" include the components dispersed in the ink, that is, the wax and the dispersant. Examples of the dispersant include a surfactant; a resin having a hydrophilic group such as a sulfonic acid group or a carboxylic acid group; and the like. Examples of the resin having a hydrophilic group include a resin to which a hydrophilic group is graft-bonded; a resin having units derived from a monomer having hydrophilicity and a monomer having a hydrophobic portion; and the like.

[0152] The dispersant preferably contains an anionic dispersant and a nonionic dispersant. That is, it is preferable to disperse wax particles in the ink by using an anionic dispersant and a nonionic dispersant in combination. By using an anionic dispersant, the retraction of the pigment from the vicinity of the meniscus is promoted, and the effect of improving the intermittent ejection stability of the ink can be further enhanced. And, by using an anionic dispersant and a nonionic dispersant in combination, the wax particles can be dispersed and stabilized by two repulsive forces, namely, the electrostatic repulsive force by the anionic group of the anionic dispersant and the steric repulsive force by the nonionic dispersant. By stabilizing the dispersion of the wax particles, the wax is uniformly distributed on the image surface even in image formation, and the effect of improving the scratch resistance of the image can be further enhanced. If the dispersant is only an anionic dispersant, the wax becomes more compatible with water and is less likely to be uniformly exposed on the image surface, and the scratch resistance of the image may not be sufficiently obtained. If the dispersant is only a nonionic dispersant, the pigment may be less likely to retract from the vicinity of the meniscus, and the intermittent ejection stability of the ink may not be sufficiently obtained.

[0153] Examples of the anionic dispersant include anionic surfactants; resins having an anionic group, such as acrylic resins; and the like. Examples of the anionic surfactant include alkylbenzene sulfonates, polyoxyethylene alkyl ether sulfates, and polyoxyethylene alkyl ether sulfonates. Examples of the resins having an anionic group include acrylic resins having units derived from (meth)acrylic acid. Among these, ethylene-acrylic acid copolymers are preferred.

[0154] The content (mass %) of the nonionic dispersant in the ink is preferably from 0.1 to 10.0% by mass, and more preferably from 1.0 to 7.5% by mass, based on the total mass of the ink.

[0155] The content (mass%) of the anionic dispersant in the ink is preferably 0.01 to 0.20 times the content (mass%) of the wax in the wax particles. If the mass ratio is less than 0.01, the pigment may not easily retreat from the vicinity of the meniscus, and the effect of improving the intermittent ejection stability of the ink may not be sufficiently obtained. On the other hand, if the mass ratio is more than 0.20, the wax may easily become compatible with water and may not be easily exposed uniformly on the image surface, and the effect of improving the scratch resistance of the image may not be sufficiently obtained.

[0156] Examples of the nonionic dispersant include compounds having an ethylene oxide structure, such as nonionic surfactants. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether; ethylene oxide adducts of acetylene glycol; and the like.

[0157] The content (mass%) of the nonionic dispersant in the ink is preferably 0.10 times or more and 0.30 times or less in mass ratio to the content (mass%) of the wax in the wax particles. If the mass ratio is less than 0.10 times, the wax may not be uniformly exposed on the image surface, and the effect of improving the scratch resistance of the image may not be sufficiently obtained. On the other hand, if the mass ratio is more than 0.30 times, the pigment may not easily retreat from the vicinity of the meniscus, and the effect of improving the intermittent ejection stability of the ink may not be sufficiently obtained.

[0158] [Aqueous medium] The ink is an aqueous ink containing an aqueous medium, which is a mixed solvent of water and a water-soluble organic solvent. Deionized water (ion-exchanged water) is preferably used as the water. The content (mass%) of water in the ink is preferably 50.0% by mass or more and 95.0% by mass or less, based on the total mass of the ink.

[0159] As the water-soluble organic solvent, any of those usable for inkjet inks, such as alcohols, glycols, (poly)alkylene glycols, nitrogen-containing compounds, and sulfur-containing compounds, can be used. As the water-soluble organic solvent, it is preferable to use one having a lower vapor pressure than water. The content (mass%) of the water-soluble organic solvent in the ink is preferably 25.0 mass% or less based on the total mass of the ink. If the content of the water-soluble organic solvent in the ink exceeds 25.0 mass%, the ink may be difficult to dry after being applied to the recording medium, and the effect of improving the abrasion resistance of the image may not be sufficiently obtained. The content (mass%) of the water-soluble organic solvent in the ink is preferably 3.0 mass% or more based on the total mass of the ink.

[0160] The water-soluble organic solvent preferably includes a first water-soluble organic solvent having a relative dielectric constant of 30.0 or less. When water evaporates during the drying process of the ink, the first water-soluble organic solvent increases near the meniscus, making it difficult for the pigment to stably exist near the meniscus. This makes it easier for the pigment to retreat from the vicinity of the meniscus, and the effect of improving the intermittent ejection stability of the ink can be further enhanced. The content (mass%) of the first water-soluble organic solvent in the ink is preferably 3.0 mass% or more and 25.0 mass% or less based on the total mass of the ink. In addition, the ratio of the content (mass%) of the first water-soluble organic solvent to the content (mass%) of the water-soluble organic solvent in the ink is preferably 50.0 mass% or more. In particular, it is preferably 80.0 mass% or more, and may be 100.0 mass%.

[0161] The relative dielectric constant of a water-soluble organic solvent can be measured using a dielectric constant meter (for example, trade name "BI-870" manufactured by BROOKHAVEN INSTRUMENTS CORPORATION) at a frequency of 10 kHz. The relative dielectric constant of a water-soluble organic solvent that is solid at 25°C is a value calculated from the relative dielectric constant of a 50% by mass aqueous solution measured using the following formula (A). Usually, "water-soluble organic solvents" are liquids, but in the present invention, for the sake of convenience, those that are solid at 25°C (room temperature) are also included in the water-soluble organic solvent. εsol =2ε 50% -ε water (A) ε sol : Dielectric constant of solid water-soluble organic solvent at 25℃ ε 50% : Relative dielectric constant of a 50% by mass aqueous solution of a solid water-soluble organic solvent at 25°C ε water : relative dielectric constant of water

[0162] Examples of water-soluble organic solvents that are generally used in aqueous inks and are solid at 25°C include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol with a number-average molecular weight of 1,000. The reason for determining the dielectric constant of a water-soluble organic solvent that is solid at 25°C from the dielectric constant of a 50% by mass aqueous solution is as follows. Among water-soluble organic solvents that are solid at 25°C and can be used as components of aqueous inks, it is difficult to prepare a high-concentration aqueous solution of more than 50% by mass. On the other hand, in a low-concentration aqueous solution of 10% by mass or less, the dielectric constant of water becomes dominant, and it is not possible to obtain a reliable (effective) dielectric constant value of the water-soluble organic solvent. Therefore, as a result of the study conducted by the present inventors, it was found that the aqueous solution to be measured can be prepared from almost all of the water-soluble organic solvents that are solid at 25°C and can be used in inks, and the dielectric constant to be obtained is consistent with the effect of the present invention. For these reasons, it was decided to use a 50% by mass aqueous solution. For water-soluble organic solvents that are solid at 25°C and cannot be prepared as a 50% aqueous solution due to their low solubility in water, use an aqueous solution of the saturated concentration and use the above ε sol For convenience, the value of the relative dielectric constant calculated in accordance with the case of determining

[0163] Specific examples of water-soluble organic solvents (first water-soluble organic solvents) having a relative dielectric constant of 30.0 or less among water-soluble organic solvents generally used in water-based inkjet inks include triethylene glycol (22.7), 2-methyl-1,3-propanediol (28.3), 1,2-butanediol (22.2), 1,3-butanediol (30.0), 3-methylsulfolane (29.0), 1,2-propanediol (28.8), 1,2,6-hexanetriol (28.5), 2-methyl-1,3-propanediol (28.3), 2-pyrrolidone (28.0), 1,5-pentanediol (27.0), 3-methyl-1,3-butanediol (24.0), 3-methyl-1,5-pentanediol (23.9), ethanol (23.8), 1-(hydroxymethyl)-5,5-dimethyl Examples of dielectric constants include ruhydantoin (23.7), triethylene glycol (22.7), tetraethylene glycol (20.8), polyethylene glycol having a number average molecular weight of 200 (18.9), 2-ethyl-1,3-hexanediol (18.5), isopropanol (18.3), 1,2-hexanediol (14.8), n-propanol (12.0), polyethylene glycol having a number average molecular weight of 600 (11.4), triethylene glycol monobutyl ether (9.8), tetraethylene glycol monobutyl ether (9.4), tripropylene glycol monomethyl ether (8.5), 1,6-hexanediol (7.1), and polyethylene glycol having a number average molecular weight of 1,000 (4.6) (the numbers in parentheses are the relative dielectric constants at 25°C).

[0164] The first water-soluble organic solvent may be used alone or in combination of two or more. The ink may further contain a water-soluble organic solvent (other water-soluble organic solvent) having a relative dielectric constant of more than 30.0. Specific examples of other water-soluble organic solvents commonly used in water-based inkjet inks include urea (110.3), ethyl isopropyl sulfone (59.0), ethylene urea (49.7), dimethyl sulfoxide (48.9), glycerin (42.3), γ-butyrolactone (41.9), ethylene glycol (40.4), 1-(2-hydroxyethyl)-2-pyrrolidone (37.6), trimethylolpropane (33.7), methanol (33.1), N-methyl-2-pyrrolidone (32.0), triethanolamine (31.9), diethylene glycol (31.7), and 1,4-butanediol (31.1).

[0165] [resin] The ink may further contain a resin (other resin) other than the above-mentioned resin dispersant. The other resin may be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary. Also, the other resin may be added to the ink (ii) to improve various properties of the recorded image. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. The other resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be resin particles that are dispersed in an aqueous medium. The resin particles do not need to contain a coloring material. The content (mass%) of the other resin in the ink is preferably 0.1% by mass or more and 20.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink.

[0166] [Resin Composition] Examples of other resins include acrylic resins, urethane resins, olefin resins, etc. Among these, acrylic resins and urethane resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylate are more preferred.

[0167] The acrylic resin preferably has a hydrophilic unit and a hydrophobic unit as constituent units. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer is preferred. In particular, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of styrene and α-methylstyrene is preferred. These resins are likely to interact with pigments, and therefore can be suitably used as a resin dispersant for dispersing pigments.

[0168] The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of the hydrophilic monomer having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Examples of cations constituting the salts of acidic monomers include ions of lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit not having a hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer not having a hydrophilic group such as an anionic group. Specific examples of the hydrophobic monomer include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0169] The urethane resin can be obtained by reacting, for example, polyisocyanate with a polyol. In addition, a chain extender may be further reacted with the urethane resin. Examples of the olefin resin include polyethylene and polypropylene.

[0170] [Resin properties] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, the resin is present in an aqueous medium in a state in which it does not form particles whose particle size can be measured by a dynamic light scattering method. Whether or not a resin is water-soluble can be determined according to the following method. First, a liquid (resin solid content: 10 mass%) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by a dynamic light scattering method, if no particles having a particle size are measured, the resin can be determined to be water-soluble. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3 times, and measurement time: 180 seconds. In addition, a particle size analyzer using a dynamic light scattering method (for example, the product name "UPA-EX150", manufactured by Nikkiso) can be used as a particle size distribution measuring device. Of course, the particle size distribution measuring device and the measurement conditions are not limited to those described above.

[0171] The acid value of the water-soluble resin is preferably 100 mgKOH / g or more and 250 mgKOH / g or less, and the weight average molecular weight of the water-soluble resin is preferably 3,000 or more and 15,000 or less.

[0172] The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 3,000,000 or less, and more preferably 100,000 or more and 3,000,000 or less. The volume-based cumulative 50% particle diameter (D 50) is preferably 50 nm or more and 500 nm or less. The volume-based cumulative 50% particle diameter of the resin particles is the diameter of the particles that is 50% of the total volume of the measured particles when integrated from the small particle diameter side in a particle diameter integration curve. The volume-based cumulative 50% particle diameter of the resin particles can be measured under the same measurement conditions using a particle size analyzer using the dynamic light scattering method described later. In addition, whether or not a certain resin is a resin particle can be determined by whether or not the particle diameter is measured when measured under the same measurement conditions using a particle size analyzer using the dynamic light scattering method. The glass transition temperature of the resin particles is preferably 40° C. or more and 120° C. or less, and more preferably 50° C. or more and 100° C. or less. The glass transition temperature (° C.) of the resin particles can be measured using a differential scanning calorimeter (DSC). The resin particles do not need to contain a coloring material.

[0173] [Other ingredients] In addition to the above components, the ink may contain various additives, such as antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors, as necessary.

[0174] [Ink properties] The ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the static surface tension of the ink at 25°C is preferably 25 mN / m or more, and more preferably 30 mN / m to 60 mN / m. The viscosity of the ink at 25°C is preferably 1.0 mPa·s to 10.0 mPa·s, and more preferably 1.0 mPa·s to 5.0 mPa·s. The pH of the ink at 25°C is preferably 5.0 to 10.0, and more preferably 7.0 to 9.5. EXAMPLES

[0175] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples without departing from the gist of the invention. "Parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0176] <Preparation of pigment dispersion> (Pigment dispersion 1) A styrene-ethyl acrylate-acrylic acid copolymer (resin 1) with an acid value of 150 mgKOH / g and a weight average molecular weight of 8,000 was prepared. 20.0 parts of resin 1 were neutralized with potassium hydroxide in an amount equimolar to the acid value, and an appropriate amount of pure water was added to prepare an aqueous solution of resin 1 with a resin (solid content) content of 20.0%. 20.0 parts of carbon black (trade name "MCF88", manufactured by Mitsubishi Chemical), 30.0 parts of the aqueous solution of resin 1, and 50.0 parts of ion-exchanged water were mixed to obtain a mixture. The obtained mixture was subjected to 50 passes of dispersion treatment at a pressure of 150 MPa using a Nanomizer (manufactured by Yoshida Machinery Co., Ltd.). After that, the mixture was centrifuged at a rotation speed of 5,000 rpm for 30 minutes to remove coarse particles. After pressure filtration using a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm, the mixture was diluted with ion-exchanged water to prepare Pigment Dispersion 1 with a pigment content of 15.0% and a resin dispersant (Resin 1) content of 4.5%. The amount of anions in the pigment in Pigment Dispersion 1 was 397.5 μmol / g.

[0177] (Pigment dispersion 2) Pigment dispersion 2 was prepared with a pigment content of 15.0% and a resin dispersant (resin 1) content of 1.5% in the same manner as in the case of pigment dispersion 1, except that the aqueous solution of resin 1 was 10.0 parts and the ion-exchanged water was 70.0 parts. The amount of anions in the pigment in pigment dispersion 2 was 132.5 μmol / g.

[0178] (Pigment dispersion 3) 1.5 g of 4-amino-1,2-benzenedicarboxylic acid was added to a solution of 5 g of concentrated hydrochloric acid in 5.5 g of water while cooling it to 5°C. Next, the container containing this solution was placed in an ice bath to keep the solution at a constant temperature of 10°C or less, and a solution of 1.8 g of sodium nitrite dissolved in 9 g of water at 5°C was added to this solution. After stirring this solution for an additional 15 minutes, it was found to have a BET specific surface area of ​​220 m 2 6 g of carbon black having a DBP oil absorption of 105 mL / 100 g and an average particle size (cumulative 50% particle size on a volume basis) of 100 nm was added under stirring. After that, the mixture was stirred for another 15 minutes, and the obtained slurry was filtered with filter paper (product name "Standard Filter Paper No. 2", manufactured by Advantec), and the particles were thoroughly washed with water. This was dried in an oven at 110 ° C to prepare self-dispersed carbon black. Water was added to the obtained self-dispersed carbon black to disperse it so that the pigment content was 15.0%. As a result, a pigment dispersion liquid was obtained in which self-dispersed carbon black with -C6H3-(COONa)2 groups introduced on the particle surfaces of the carbon black was dispersed in water. The sodium ions in the pigment dispersion liquid were replaced with potassium ions by ion exchange to obtain pigment dispersion liquid 3 in which self-dispersed carbon black with -C6H3-(COOK)2 groups introduced on the surface of the carbon black was dispersed. The amount of anions of the pigment in pigment dispersion liquid 3 was 230 μmol / g.

[0179] <Preparation of wax particles> Ethylene and acrylic acid were copolymerized according to a conventional method, and then neutralized with a neutralizing agent in an amount equimolar to the acid value. An appropriate amount of ion-exchanged water was added to prepare an aqueous solution of dispersant 1 with a copolymer (solid content) content of 20.0%. Dispersant 1 had an acid value of 120 mg KOH / g and a weight average molecular weight of 8,000.

[0180] After mixing the types and amounts of each component shown in Table 1-1, the temperature and pressure were appropriately adjusted to disperse the wax. An appropriate amount of pure water was added to obtain aqueous dispersions of wax particles 1 to 16, in which the content of wax particles formed from wax and dispersant was 25.0%. Details of the waxes 1 to 4 and dispersants 1 to 4 used are shown below. The anion amount, melting point, and cumulative 50% particle diameter D on a volume basis of the wax particles were 50 was measured by the method described above. The properties of the wax particles are shown in Table 1-2. Wax 1: Polyethylene wax Wax 2: Paraffin wax Wax 3: Fischer-Tropsch wax Wax 4: Oxidized polyethylene wax Dispersant 1: Anionic dispersant, ethylene-acrylic acid copolymer prepared above (20.0% aqueous solution) Dispersant 2: Anionic dispersant, potassium montanate Dispersant 3: Nonionic dispersant, polyoxyethylene cetyl ether (number of moles of ethylene oxide group added: 10) Dispersant 4: Nonionic dispersant, polyoxyethylene oleyl ether (number of moles of ethylene oxide group added: 30)

[0181] TIFF2024178126000001.tif151170

[0182] TIFF2024178126000002.tif142170

[0183] <Ink Preparation> Each ink was prepared by mixing the components (unit: %) shown in Tables 2-1 to 2-3, thoroughly stirring, and then filtering under pressure with a cellulose acetate filter (manufactured by Advantec) with a pore size of 0.8 μm. In Tables 2-1 to 2-3, the numbers in parentheses next to the water-soluble organic solvents are the relative dielectric constants of the water-soluble organic solvents at 25° C. Details of each component in Tables 2-1 to 2-3 are shown below. Acetylenol E60: A nonionic hydrocarbon surfactant (manufactured by Kawaken Fine Chemicals) BYK348: Silicone-based nonionic surfactant (manufactured by BYK) Capstone FS-3100: Fluorine-based nonionic surfactant (manufactured by Chemours) Proxel GXL(S): preservative (manufactured by Arch Chemicals)

[0184] TIFF2024178126000003.tif229170

[0185] TIFF2024178126000004.tif246170

[0186] TIFF2024178126000005.tif246170

[0187] <Evaluation> The inks obtained above were evaluated for the following items. Each prepared ink was filled into an ink tank of an inkjet recording device having a recording head shown on the left side of Table 3. In Table 3, for the example with "1" in the recording head column, the ink was filled into the ink storage section of an inkjet recording device having the main part shown in Figure 1 (the recording head scans back and forth in a direction intersecting the arrangement direction of the ejection port array, and the recording head has the configuration shown in Figure 5).

[0188] In the example indicated by "2" in the "Recording head" column in Table 3, a recording head was used in which the ink circulation configuration shown in FIG. 5 was incorporated into the line head 800 shown in FIG. 20. This recording head was incorporated into an inkjet recording device so that the nozzle array crossed the recording medium transport direction, and the ink storage section was filled with ink. The line head 800 has a nozzle array that extends to the widest area of ​​the recording medium P that can be recorded by the recording device 50, and records an image while its position relative to the recording medium P transported in the sub-scanning direction is fixed. Therefore, when recording an image on the recording medium P, the line head 800 does not move relative to the recording medium P.

[0189] In the example indicated by "3" in the "Recording Head" column in Table 3, an inkjet recording device was used that was equipped with a serial type recording head and circulated ink in an ink supply system from an ink storage unit to the recording head. Ink was then filled into the ink storage unit of the recording head of this inkjet recording device. The inkjet recording device used in this example was provided with a circulation pump for circulating ink, separate from the recording head.

[0190] In the example indicated by "4" in the "Recording head" column in Table 3, a recording head was prepared that had a supply flow path that communicated between the ejection elements and through which ink circulated, but did not have a recovery flow path, and the ink storage section of this recording head was filled with ink.

[0191] In the example indicated by "5" in the "Recording head" column in Table 3, an inkjet recording device was used that was equipped with a line head 800 shown in FIG. 20 and circulated ink in an ink supply system from an ink storage unit to the recording head. Then, the ink storage unit of the recording head of this inkjet recording device was filled with ink. The inkjet recording device used in this example is provided with a circulation pump for circulating ink separately from the recording head. FIG. 20 is a perspective view of a line-shaped recording head. The line head 800 shown in FIG. 20 is a line head in which ejection element substrates 810, on which ejection port arrays are arranged, are linearly arranged.

[0192] Using the inkjet recording device having the above configuration, a 10 cm x 10 cm solid image with an ink recording duty of 120% was recorded under the conditions shown on the left side of Table 3. The recording environment was a temperature of 25°C and a relative humidity of 50%. When recording a solid image, the surface of the recording medium after the ink was applied was heated to 80°C, fixed, and then the following evaluation of abrasion resistance was performed. In this example, an image recorded under the condition of applying one drop of 4.0 pL of ink to a unit area of ​​1 / 1,200 inch x 1 / 1,200 inch is defined as having a recording duty of 100%. In Comparative Example 2, an image was recorded without operating the circulation pump 500 shown in FIG. 5. That is, in the examples and comparative examples other than Comparative Examples 1 and 2, the ink was circulated in the recording head. In the present invention, in the evaluation criteria for each item shown below, "AA", "A", and "B" were considered to be acceptable levels, and "C" was considered to be an unacceptable level. The evaluation results are shown on the right side of Table 3.

[0193] The recording media used are as follows: Recording medium 1: Product name "Scotchcal Graphic Film IJ1220N", manufactured by 3M, material = polyvinyl chloride, 30 msec from the start of contact in the Bristow method 1 / 2 Water absorption up to = 0 mL / m 2 More than 10mL / m 2 below Recording medium 2: High-quality paper, product name "HR-101S", Canon, 30 msec from the start of contact in the Bristow method 1 / 2 Water absorption rate up to 10 mL / m 2 super

[0194] (Intermittent discharge stability) First, ink was ejected from one ejection port of the recording head to record a ruled line having a length of 5 mm. Next, ruled lines were recorded under the same conditions as above, except that one drop of ink was ejected at 1.5 second intervals, 3.5 second intervals, and 5.0 second intervals. The three types of ruled lines recorded at predetermined intervals were visually confirmed, and the intermittent ejection stability of the ink was evaluated according to the following evaluation criteria. In Comparative Example 2, the ruled lines were recorded with the ink circulation stopped. The recorded ruled lines were visually confirmed, and the intermittent ejection stability of the ink was evaluated according to the following evaluation criteria. AA: No non-ejection or disturbance of the lines was observed even when ejected at 5.0 second intervals. A: When ejection was performed at 5.0 second intervals, non-ejection and irregularities in the ruled lines were observed, but when ejection was performed at 3.5 second intervals, no irregularities in the ruled lines were observed. B: When ejection was performed at 5.0 second intervals and 3.5 second intervals, non-ejection and disturbance of the ruled lines were observed, but when ejection was performed at 1.5 second intervals, no disturbance of the ruled lines was observed. C: Even when ejection was performed at 1.5 second intervals, non-ejection and irregular lines were observed.

[0195] (Abrasion resistance) A friction test was conducted using a JIS L0849-compliant friction tester II (Gakushin type) (product name "Wear Resistance Tester", manufactured by Tester Sangyo) and a white rubbing cloth (cotton) specified in JIS L0803, by reciprocating five times on the surface of the recorded image with a load of 250 g. After the friction test, the state of the scratches on the image and the ink adhering to the white rubbing cloth were visually confirmed, and the abrasion resistance of the image was evaluated according to the following evaluation criteria. A: Neither ink adhesion to the white rubbing cloth nor scratches on the image were observed. B: Ink adhesion to the white rubbing cloth was observed, but no abrasion marks were observed on the image. C: Both ink adhesion to the white rubbing cloth and scratches on the image were observed.

[0196] TIFF2024178126000006.tif255159

Claims

1. an ejection unit including an ejection port for ejecting water-based ink, a pressure chamber communicating with the ejection port, and an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; an inkjet recording method for recording an image on a recording medium by ejecting the water-based ink from the ejection port of a recording head including a circulation unit having a supply flow path for supplying the water-based ink to the pressure chamber and a recovery flow path for recovering the water-based ink from the pressure chamber, the method comprising: The water-based ink contains a pigment and wax particles, The inkjet recording method according to claim 1, wherein the circulation unit further comprises a circulation pump for causing the aqueous ink in the supply flow path to flow into the recovery flow path.

2. 2. The ink jet recording method according to claim 1, wherein a circulation flow rate (mL / min) of the aqueous ink in the circulation unit is 1.0 mL / min or more and 10.0 mL / min or less.

3. 2. The ink-jet recording method according to claim 1, wherein the pigment is at least one selected from the group consisting of carbon black and organic pigments.

4. 2. The ink jet recording method according to claim 1, wherein the amount of anions (μmol / g) of the wax particles is equal to or less than the amount of anions (μmol / g) of the pigment.

5. the water-based ink further contains a water-soluble organic solvent, The ink jet recording method according to claim 1 , wherein the water-soluble organic solvent comprises a first water-soluble organic solvent having a relative dielectric constant of 30.0 or less.

6. The inkjet recording method according to claim 5, wherein the content (mass %) of the water-soluble organic solvent in the aqueous ink is 25.0 mass % or less based on the total mass of the ink.

7. the water-based ink further contains a dispersant for dispersing the wax particles in the water-based ink; The ink jet recording method according to claim 1, wherein the dispersant comprises an anionic dispersant and a nonionic dispersant.

8. 8. The inkjet recording method according to claim 7, wherein the content (mass %) of the anionic dispersant in the aqueous ink is 0.01 to 0.20 times the content (mass %) of the wax in the wax particles in terms of a mass ratio.

9. 8. The inkjet recording method according to claim 7, wherein the content (mass %) of the nonionic dispersant in the aqueous ink is 0.10 to 0.30 times the content (mass %) of the wax in the wax particles.

10. 2. The ink jet recording method according to claim 1, wherein the recording head is a serial type recording head.

11. the circulation unit has a first pressure adjusting means for adjusting the pressure in the supply flow path, the first pressure adjustment means has a first valve chamber, a first pressure control chamber, and a first communication port that communicates the first valve chamber and the first pressure control chamber, 2. The ink jet recording method according to claim 1, wherein the first valve chamber includes a first valve that opens and closes the first communication port in response to a pressure change in the first pressure control chamber.

12. the circulation unit further has a second pressure adjusting means for adjusting the pressure in the recovery flow path, the second pressure adjustment means has a second valve chamber, a second pressure control chamber, and a second communication port that communicates the second valve chamber and the second pressure control chamber, The ink jet recording method according to claim 11, wherein the second valve chamber includes a second valve that opens and closes the second communication port in response to a pressure change in the second pressure control chamber.

13. The recording medium is １／２ The amount of water absorbed is 10 mL / m ２ The inkjet recording method according to any one of claims 1 to 12, wherein:

14. an ejection unit including an ejection port for ejecting water-based ink, a pressure chamber communicating with the ejection port, and an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; an inkjet recording device used to record an image on a recording medium by ejecting the water-based ink from the ejection openings of a recording head including a circulation unit having a supply flow path that supplies the water-based ink to the pressure chamber and a recovery flow path that recovers the water-based ink from the pressure chamber, The water-based ink contains a pigment and wax particles, The inkjet recording apparatus according to claim 1, wherein the circulation unit further comprises a circulation pump for causing the aqueous ink in the supply flow path to flow into the recovery flow path.

15. an ejection unit including an ejection port for ejecting water-based ink, a pressure chamber communicating with the ejection port, and an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; The ink jet recording method includes discharging the water-based ink from the discharge port of a recording head including a circulation unit having a supply flow path for supplying the water-based ink to the pressure chamber and a recovery flow path for recovering the water-based ink from the pressure chamber, and recording an image on a recording medium. A water-based ink comprising: The water-based ink contains a pigment and wax particles, The water-based ink according to claim 1, wherein the circulation unit further comprises a circulation pump that causes the water-based ink in the supply flow path to flow into the recovery flow path.

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