Inkjet recording method, inkjet recording device, and aqueous ink

Abstract

To provide an inkjet recording method which can suppress deterioration in discharge stability of ink due to bubbles, while using an inkjet recording device having an ink circulation type recording head.SOLUTION: An inkjet recording method imparts aqueous ink discharged from a discharge port 13 to a recording medium, using an inkjet recording device having a recording head 1 having the discharge port 13, a pressure chamber 12 communicating with the discharge port 13, a discharge element 15, and a first flow channel 130 and a second flow channel 140 connected to a pressure chamber 13, and records an image. The recording head 1 is configured to be capable of supplying aqueous ink to the pressure chamber 12 from any one of the first flow channel 130 and the second flow channel 140, dynamic surface tension at life time of 0 millisecond of the aqueous ink is 60 mN / m or less, and a contact angle of the inner wall surfaces of the first flow channel 130 and the second flow channel 140 with the aqueous ink is 60° or less.SELECTED DRAWING: Figure 1

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] Ink circulation type inkjet recording devices are known that circulate ink between a recording head that ejects ink and an ink storage section, thereby discharging air bubbles in the flow path and suppressing thickening of the ink near the ejection ports. Among ink circulation type inkjet recording devices, there are types that circulate ink using a pump provided outside the recording head and types that circulate ink using a pump provided inside the recording head.

[0003] For example, an inkjet recording apparatus has been proposed that includes an ink circulation type recording head in which ink is circulated within the recording head by a piezoelectric circulation pump mounted within the recording head (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-195932 A Summary of the Invention [Problem to be solved by the invention]

[0005] In an inkjet recording device equipped with an ink circulation type recording head proposed in Patent Document 1, ink supplied from a circulation pump to a pressure control mechanism is supplied to an ejection port via a supply flow path, and ink that is not ejected is recovered by the circulation pump via a recovery flow path. However, when the amount of ink ejected within a predetermined period increases, such as when recording a solid image, the amount of ink supplied to the ejection port gradually decreases, which can result in blank areas in the image.

[0006] In order to suppress the occurrence of blank areas in an image when using an inkjet recording device equipped with an ink circulation type recording head, the inventors of the present invention have investigated the adoption of various configurations. However, it has been found that bubbles are likely to be generated in the ink flow path near the ejection port, and the generated bubbles may cause ink non-ejection, which may lead to a decrease in the ejection stability of the ink.

[0007] It is therefore an object of the present invention to provide an inkjet recording method that can suppress deterioration in ink ejection stability caused by bubbles even when using an inkjet recording device equipped with an ink circulation type recording head. It is also an object of the present invention to provide an inkjet recording device 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 using an inkjet recording device including a recording head having an ejection port for ejecting water-based ink, a pressure chamber communicating with the ejection port, an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port, a first flow path connected to the pressure chamber, and a second flow path connected to the pressure chamber at a position opposite the first flow path with the ejection element therebetween, and applying the water-based ink ejected from the ejection port to a recording medium to record an image, wherein the recording head is configured to be able to supply the water-based ink to the pressure chamber from both the first flow path and the second flow path, and the dynamic surface tension of the water-based ink at a lifetime of 0 milliseconds is 60 mN / m or less, and the contact angle between the water-based ink and inner wall surfaces of the first flow path and the second flow path is 60° or less. Effect of the Invention

[0009] According to the present invention, it is possible to provide an inkjet recording method that can suppress a decrease in ink ejection stability caused by bubbles even when using an inkjet recording device equipped with an ink circulation type recording head. Also, according to the present invention, it is possible to provide an inkjet recording device and a water-based ink for use in the inkjet recording method. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram illustrating an example of a recording head. [Diagram 2] 1 is a perspective view illustrating an embodiment of an inkjet recording apparatus of the present invention. [Diagram 3] 1 is a schematic diagram illustrating an internal configuration of an embodiment of an inkjet recording apparatus of the present invention. [Figure 4] FIG. 4 is a plan view showing a schematic view of the vicinity of a heater of the recording element substrate. [Diagram 5] 5 is a cross-sectional view showing the recording element substrate in a state where it is cut vertically along the XY line in FIG. 4. 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." In addition, 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.

[0012] The present inventors have conducted various studies to suppress the deterioration of ink ejection stability due to bubbles when using an inkjet recording device equipped with an ink circulation type recording head. Specifically, first, a recording head was prepared that includes an ink ejection port, a pressure chamber communicating with the ejection port, an ejection element disposed in the pressure chamber, a first flow path connected to the pressure chamber, and a second flow path connected to the pressure chamber at a position opposite to the first flow path with the ejection element sandwiched therebetween. Next, this recording head was configured to be capable of supplying ink to the pressure chamber from both the first flow path and the second flow path, and was then mounted on an inkjet recording device. Then, when an image was recorded using this inkjet recording device, the following was found. That is, when the amount of ink ejected within a predetermined period increases, bubbles are likely to be generated in the ink flow path (pressure chamber) near the ejection port, and the generated bubbles are likely to cause non-ejection of ink, thereby decreasing the ejection stability of the ink. When configured to be capable of supplying ink to the pressure chamber from both the first flow path and the second flow path, the amount of ink supplied from the second flow path, which also functions as a recovery flow path, varies depending on the amount of ink supplied from the first flow path. For this reason, it is believed that bubbles become more likely to occur because the flow direction of the ink changes successively depending on the amount of ink ejected from the ejection port, thereby reducing the ejection stability of the ink.

[0013] As a result of further investigation, the inventors discovered that by satisfying the following requirements (i) and (ii), bubbles are less likely to occur even when the ink flow direction changes successively, and the ink ejection stability is improved, thereby arriving at the present invention. (i) The dynamic surface tension of the ink at a life time of 0 milliseconds is 60 mN / m or less. (ii) The contact angle between the ink and the inner wall surfaces of the first flow path and the second flow path is 60° or less.

[0014] If the dynamic surface tension of the ink at a life time of 0 milliseconds exceeds 60 mN / m, the ink will not instantly fit the inner wall surfaces of the first flow path and the second flow path insufficiently, and bubbles will easily form in the pressure chamber. Also, if the contact angle between the ink and the inner wall surfaces of the first flow path and the second flow path exceeds 60°, bubbles formed in the pressure chamber will easily adhere to the inner wall surfaces of the first flow path and the second flow path.

[0015] <Inkjet recording method, inkjet recording apparatus, and water-based ink> The inkjet recording method of the present invention uses an inkjet recording device equipped with a recording head having a specific configuration, and records an image by applying aqueous ink ejected from an ejection port of the recording head to a recording medium. The recording head includes an ejection port for ejecting the aqueous ink, a pressure chamber communicating with the ejection port, an ejection element, a first flow path, and a second flow path. The ejection element is an element disposed in the pressure chamber and generates energy for ejecting the aqueous ink from the ejection port. The first flow path is a flow path for the aqueous ink that is connected to the pressure chamber. The second flow path is a flow path for the aqueous ink that is connected to the pressure chamber at a position opposite to the first flow path with the ejection element therebetween. The recording head is configured to be able to supply the aqueous ink to the pressure chamber from both the first flow path and the second flow path. The dynamic surface tension of the aqueous ink at a life time of 0 milliseconds is 60 mN / m or less, and the contact angle between the aqueous ink and the inner wall surfaces of the first flow path and the second flow path is 60° or less.

[0016] The inkjet recording device of the present invention is a device equipped with a recording head having a specific configuration, and the recording head includes an ejection port for ejecting water-based ink, a pressure chamber communicating with the ejection port, an ejection element, a first flow path, and a second flow path. The ejection element is an element disposed in the pressure chamber and generates energy for ejecting the water-based ink from the ejection port. The first flow path is a flow path for water-based ink connected to the pressure chamber. The second flow path is a flow path for water-based ink connected to the pressure chamber at a position opposite to the first flow path with the ejection element therebetween. The recording head is configured to be able to supply water-based ink to the pressure chamber from both the first flow path and the second flow path. The dynamic surface tension of the water-based ink at a life time of 0 milliseconds is 60 mN / m or less, and the contact angle between the water-based ink and the inner wall surfaces of the first flow path and the second flow path is 60° or less.

[0017] The water-based ink of the present invention is used in an inkjet recording method in which an inkjet recording device having a recording head with a specific configuration is used, and the water-based ink is applied to a recording medium from an ejection port of the recording head to record an image. The recording head includes an ejection port for ejecting the water-based ink, a pressure chamber communicating with the ejection port, an ejection element, a first flow path, and a second flow path. The ejection element is an element disposed in the pressure chamber and generates energy for ejecting the water-based ink from the ejection port. The first flow path is a flow path for the water-based ink that is connected to the pressure chamber. The second flow path is a flow path for the water-based ink that is connected to the pressure chamber at a position opposite to the first flow path with the ejection element therebetween. The recording head is configured to be able to supply the water-based ink to the pressure chamber from both the first flow path and the second flow path. The dynamic surface tension of the water-based ink at a life time of 0 milliseconds is 60 mN / m or less, and the contact angle between the water-based ink and the inner wall surfaces of the first flow path and the second flow path is 60° or less.

[0018] (Inkjet recording device) FIG. 2 is a perspective view showing a schematic diagram of an embodiment of an inkjet recording apparatus according to the present invention. As shown in FIG. 2, a feeding unit 20 of a recording apparatus 1000 can hold a plurality of recording media, and feeds the recording media by a feeding roller (not shown). A recording medium 601 (FIG. 3) is described as a cut sheet cut to a predetermined size, but the present invention is not limited to this, and can also be applied to a form in which recording is performed on rolled paper. The recording medium fed by the feeding unit 20 is transported in the Y direction (transport direction) by a transport unit including a transport roller (not shown), and moves to a recording position facing a recording head 200 (FIG. 3(b)) that ejects ink. A carriage 100 carries the recording head 200, and is driven by a carriage motor 4 to reciprocate along a guide shaft 3 via a timing belt 2 in an X direction (main scanning direction) that intersects with the Y direction.

[0019] When an image for a unit area is recorded by the movement of the carriage 100 in the X direction and the ink ejection operation of the print head 200, the print medium is transported in the Y direction by the transport unit. The unit area can be arbitrarily set, such as the arrangement width of the ejection port array arranged along the Y direction in the print head 200, "one band" that can be recorded by one movement of the print head 200 in the X direction, or "one pixel" corresponding to the resolution of the print head. In the serial method, an image can be recorded over the entire print medium by a printing operation that repeats the ink ejection operation for one band and the intermittent transport operation of the print medium. In this embodiment, the X direction and the Y direction are perpendicular to each other.

[0020] A platen 10 that supports the recording medium from below in the vertical direction is disposed in a position facing the recording head 200 and in a recording area where recording is performed by the recording head 200. The platen 10 maintains a predetermined distance between the recording surface of the recording medium and the ejection port surface of the recording head 200, on which the ejection ports for ejecting ink are arranged.

[0021] Fig. 3 is a schematic diagram showing the internal configuration of an embodiment of an inkjet recording apparatus 1000 of the present invention. Fig. 3(a) is a schematic top view of the recording apparatus 1000 (Fig. 2) seen from above, and Fig. 3(b) is a schematic side view of the recording apparatus 1000 (Fig. 2) seen from the front. The carriage 100 removably mounts ink cartridges that contain ink to be supplied to the recording head 200. The ink cartridges 211 to 214 supply ink to their respective ejection port rows.

[0022] Furthermore, within the movement area of ​​the carriage 100, outside the area (printing area) through which the printing medium 601 passes, a cap 302 for capping the ejection port surface of the print head 200 is disposed. The position of the carriage 100 (print head 200) where the ejection port surface of the print head 200 faces the cap 302 is also referred to as the home position 301. The cap 302 is connected to suction means (not shown), and ink is sucked from the print head 200 by driving the suction means with the ejection port surface capped.

[0023] (Recording head) The circulation of ink in the recording head 1 will be described with reference to FIG. 1. In one circulation unit 54 corresponding to one type of ink applied to the recording apparatus of this embodiment, a filter 110, a first pressure adjustment means 120, a second pressure adjustment means 150, and a circulation pump 500 are arranged. These components are connected by respective flow paths as shown in FIG. 1, and constitute a circulation path for supplying and recovering ink to the ejection module 300 in the recording head 1. FIG. 1 shows a schematic diagram of the flow of ink during a recording operation in which ink is ejected from an ejection port 13 provided at a position opposite to an ejection element 15 arranged in a pressure chamber 12 to record an image. The arrows in the figure indicate the flow of ink. In this embodiment, when a recording operation is performed, both an external pump (not shown) and a circulation pump 500 start to operate. The external pump and the circulation pump 500 may be operated regardless of the recording operation. The external pump and the circulation pump 500 may not be operated in conjunction with each other, and may be operated independently.

[0024] The first pressure adjustment means 120 is disposed in connection with the first flow path 130, and is a means for adjusting the pressure applied to supply ink from the first flow path 130 to the pressure chamber 12. The circulation pump 500 is a pump capable of supplying ink from the first pressure adjustment means 120 through the first flow path 130 into the pressure chamber 12, and of pumping ink so as to recover the ink in the pressure chamber 12 through the second flow path 140. The bypass flow path 160 is an ink flow path that connects the first flow path 130 and the second flow path 140 without passing through the pressure chamber 12. The second pressure adjustment means 150 is disposed in connection with the second flow path 140. The first pressure adjustment means 120 has a first valve chamber 121 and a first pressure control chamber 122, and the first valve chamber 121 is in communication with the first pressure control chamber 122 through a communication port 191A that can be opened and closed by a valve 190A.

[0025] During the recording operation, the circulation pump 500 is in an ON state (driving state). The inkjet recording device includes an ink storage unit (not shown), such as an ink cartridge, that stores ink. The ink supplied from the ink storage unit flows into the first valve chamber 121 and the first pressure control chamber 122 of the first pressure adjustment means 120 through the filter 110. Then, the ink flowing out from the first pressure control chamber 122 flows into the first flow path 130 and the bypass flow path 160. A part of the ink that flows into the first flow path 130 is discharged from the discharge port 13 when passing through the discharge module 300. The remaining ink that is not discharged from the discharge port 13 flows into the second flow path 140 and is then supplied to the second pressure control chamber 152. Then, the ink supplied to the second pressure control chamber 152 circulates to the first flow path 130 via the circulation pump 500.

[0026] 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. Therefore, the ink in the first pressure control chamber 122 is supplied to the ejection module 300 again via the first 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 second 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 is completed within the recording head 1.

[0027] Furthermore, the ink consumed during recording is supplied to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121 from an ink storage unit (not shown) such as an ink cartridge.

[0028] Below, it will be explained that when continuing to print a high "duty" such as a solid image, the negative pressure in the pressure chamber increases, and as a result, ink is supplied to the pressure chamber 12 from both the first flow path 130 side and the second flow path 140 side. The definition of duty can change depending on various conditions. As an example, an image printed by applying one ink droplet with a volume of 4 pL per droplet to a unit area of ​​1,200 dpi x 1,200 dpi will be treated as having a printing duty of 100%. Printing with a high duty is, for example, printing performed at a duty of 100%.

[0029] When recording at a high duty is continued, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the second flow path 140 decreases. On the other hand, since the circulation pump 500 causes ink to flow out at a constant rate, 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 in a state where the inflow and outflow are balanced. As a result, the negative pressure in the second pressure control chamber 152 becomes stronger according to the recording duty. In addition, when the circulation pump 500 is driven, in a configuration in which the communication port 191B is in a closed state, the communication port 191B opens in response to the printing duty, and ink flows from the bypass flow path 160 into the second pressure control chamber 152.

[0030] Then, when recording at a higher duty is continued, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the second flow path 140 decreases, and instead the amount of ink flowing into the second pressure control chamber 152 from the communication port 191B via the bypass flow path 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 second flow path 140 becomes zero, and all the ink flowing out to the circulation pump 500 becomes ink flowing in from the communication port 191B. If this state progresses further, ink flows back from the second pressure control chamber 152 into the pressure chamber 12 through the second flow path 140 (FIG. 1(b)). 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 communication port 191B through the bypass flow path 160. In this case, ink from the first flow path 130 and ink from the second flow path 140 are supplied to the pressure chamber 12, and the ink is ejected from the ejection port 13.

[0031] This backflow of ink that occurs when the printing 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 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 communication port 191B in the second pressure adjustment means is open. Even in a configuration that does not include the second pressure adjustment means, the provision of the bypass flow path 160 may cause the above-mentioned backflow of ink.

[0032] As described above, the inkjet recording method of the present embodiment preferably includes the following steps. That is, ink supplied from an ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120 and the first flow path 130. Then, ink not discharged from the discharge port 13 is circulated to the first flow path 130 via the second flow path 140 and the circulation pump 500. In addition, the inkjet recording method of the present embodiment preferably further includes the following steps. That is, ink supplied from an ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120 and the first flow path 130. In addition, ink supplied from an ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120, the bypass flow path 160, and the second flow path 140.

[0033] In addition, in the case where the recording head 1 further includes the second pressure adjustment means 150, the inkjet recording method of the present embodiment preferably includes the following steps. That is, the ink supplied from the ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120 and the first flow path 130. Then, the ink not discharged from the discharge port 13 is circulated to the first flow path 130 via the second flow path 140, the second pressure adjustment means 150, and the circulation pump 500. In addition, the inkjet recording method of the present embodiment preferably includes the following steps. That is, the ink supplied from the ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120 and the first flow path 130. In addition, the ink supplied from the ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120, the bypass flow path 160, the second pressure adjustment means 150, and the second flow path 140.

[0034] The first flow path and the second flow path are preferably formed of a resin. Examples of the resin forming the first flow path and the second flow path include an epoxy resin and an acrylic resin. Among these resins, it is preferable to use a resin having photosensitivity because it is easy to form the first flow path and the second flow path having a complex structure.

[0035] The ejection element 15 may be either a piezoelectric element (piezo) or a heating element such as a heater. In particular, the ejection element is preferably a heating element. The recording head is preferably a thermal type recording head that heats the ink with a heating element and generates bubbles in the water-based ink to eject the ink.

[0036] In the inkjet recording method of the present embodiment, it is preferable to heat the ink in the recording head to a temperature higher than the recording environment temperature (for example, around 25° C.). Heating means for heating the ink in the recording head to a temperature higher than the recording environment temperature can include, for example, a heater for adjusting the ink temperature arranged in contact with the recording head, a heater for ink ejection, and other heating elements (electrothermal conversion elements). To heat the ink using a heater for ink ejection, for example, it is sufficient to repeatedly pass a current that is not enough to eject the ink. By heating the ink in the recording head, the viscosity of the ink is reduced. This makes it easier to supply (refill) the ink, and enables stable continuous ejection. It is more preferable to heat the ink using a heater for adjusting the ink temperature arranged in contact with the recording head, since it is possible to reduce the temperature variation of the ink supplied to the multiple ejection ports and uniformly heat it, effectively suppressing unevenness in the image.

[0037] When the ink in the recording head is heated to a temperature higher than the recording environment temperature and ejected, the ink is preferably heated to 30° C. or higher and 80° C. or lower before being ejected, and more preferably heated to 35° C. or higher and 70° C. or lower before being ejected. The temperature of the ink during ejection, i.e., the temperature Ta (° C.) of the ink after heating, is preferably 30° C. or higher and 80° C. or lower, and more preferably 35° C. or higher and 70° C. or lower.

[0038] [Recording element board] In the inkjet recording method of this embodiment, it is preferable to use a recording device having the following configuration and apply voltage control to the heating elements via the aqueous ink. The recording head in the recording device has a first protective layer arranged at a position corresponding to the heating elements to block contact between the heating elements and the aqueous ink in the pressure chamber, and a second protective layer formed of a metal material arranged at a position corresponding to the heating elements and in contact with the aqueous ink. The recording device also preferably has a voltage application means that uses the second protective layer as a cathode and a portion that is conductive via the aqueous ink as an anode. This prevents the accumulation of burnt material on the heating elements and effectively prevents image unevenness.

[0039] Fig. 4 is a plan view showing the vicinity of the heater of the recording element substrate, and Fig. 5 is a cross-sectional view showing the recording element substrate cut vertically along the XY line in Fig. 4.

[0040] The configuration of the recording element substrate 101 of the recording head 100 will be described. The recording element substrate 101 is composed of a silicon substrate 102, a heat storage layer 103, a heating resistor layer 104, and an electric wiring layer 105. The heat storage layer 103 is formed of materials such as a thermally oxidized silicon film, a silicon oxide film, and a silicon nitride film. The electric wiring layer 105 is a wiring formed of a metal material such as aluminum, aluminum-silicon, and aluminum-copper. The heating portion 104a as an electrothermal conversion element is formed by removing a part of the electric wiring layer 105 to form a gap and exposing the heating resistor layer 104 at that part. The electric wiring layer 105 is connected to a driving element circuit (not shown) or an external power supply terminal (not shown) and receives power from the outside. In the illustrated example, the electric wiring layer 105 is disposed as a layer adjacent to the heating resistor layer 104. However, the present invention is not limited to this configuration. The electrical wiring layer 105 may be formed as a layer adjacent to the silicon substrate 102, a part of which may be partially removed to form a gap in which the heating resistor layer 104 is disposed.

[0041] The first protective layer 106 is made of materials such as silicon oxide and silicon nitride, and is provided adjacent to the heat generating portion 104a and the electrical wiring layer 105 with the electrical wiring layer 105 partially interposed therebetween. The first protective layer 106 also functions as an insulating layer that blocks contact between the heat generating portion 104a and the ink in the ink flow path.

[0042] The second protective layer 107 is the outermost layer that comes into contact with the ink in the ink flow path. The area of ​​the second protective layer 107 that is located on the ink flow path side of the heat generating portion 104a and that applies the heat generated by the heat generating portion 104a to the ink corresponds to the heater 108. The second protective layer 107 must protect the heater 108 from chemical and physical shocks that occur as the heat is generated by the heat generating portion 104a, and must also function as an electrode. In order to achieve both of these characteristics, the second protective layer 107 is made of a metal material.

[0043] It is preferable to use a metal material containing at least one metal element selected from the group consisting of iridium, ruthenium, and tantalum, since it can become a protective layer that is strong against physical effects such as impacts due to cavitation and chemical effects due to ink. Examples of such metal materials include alloys of these metal elements with other metals. In the case of alloys, the higher the ratio of the above metal elements, the stronger the protective layer is likely to be against physical and chemical effects. It is preferable to use iridium, ruthenium, or tantalum, rather than alloys. It is particularly preferable to use iridium or ruthenium from the viewpoint of easy removal of anionic components attached to the electrode, since it is difficult to form a strong oxide film even when heated and the potential can be generated more uniformly. In addition, the surface of the second protective layer is heated to about 300°C or more and 600°C or less by the heat generated by the heater 108, but it is more preferable to use iridium, since iridium does not form an oxide film up to 800°C, even in the atmosphere, which is a condition in which oxygen is more abundant than in the ink.

[0044] The second protective layer 107 can be made of a metal material containing at least one metal element selected from the group consisting of iridium, ruthenium, and tantalum. However, such metal materials have poor adhesion. For this reason, an adhesion layer 109 is disposed between the first protective layer 106 and the second protective layer 107 to improve the adhesion of the second protective layer 107 to the first protective layer 106. The adhesion layer 109 is made of a material having electrical conductivity.

[0045] The second protective layer 107 is inserted into the through hole 115 and is electrically connected to the electrical wiring layer 105 via the adhesive layer 109. The electrical wiring layer 105 extends to an end of the recording element substrate 101, and its tip becomes an external electrode 111 for electrical connection to the outside.

[0046] A flow path forming member 112 is bonded to the recording element substrate 101 having the above-mentioned configuration. The flow path forming member 112 has ejection ports 113 at positions corresponding to the heaters 108, and forms an ink flow path that communicates with the ejection ports 113 from ink supply ports (116) provided penetrating the recording element substrate 101 via the heaters 108. The arrows in Fig. 5 indicate the flow of ink when the ink in the first flow path 130 and the ink supplied from the second flow path 140 (both shown in Fig. 1(b)) are ejected from the ejection ports 113.

[0047] A method of controlling the voltage in the above-mentioned recording head will be described. The second protective layer 107 is composed of two regions, a region (heater side region 107a) including the heater 108 formed at a position corresponding to the heat generating portion 104a, and the other region (counter electrode side region 107b), and each region is electrically connected. When there is no ink in the ink flow path, there is no electrical connection between the heater side region 107a and the counter electrode side region 107b. However, the ink usually contains electrolytes such as coloring material (its dispersant) and resin. The electrolyte is ionically dissociated to generate anionic components and cationic components. Therefore, when the ink flow path is filled with ink, the heater side region 107a and the counter electrode side region 107b, which is a portion that is electrically connected via the ink, are electrically connected via the ink.

[0048] In this state, when electricity is applied to the heater side region 107a as a cathode and the counter electrode side region 107b as an anode, a potential difference is generated between these electrodes. When ionic dissociation of the electrolyte in the ink occurs, the anionic components are electrically repelled against the heater side region 107a, and the cationic components are electrically repelled against the counter electrode side region 107b, respectively, so that the distribution state of each component changes according to the charging state of each electrode. Since the heater side region 107a is negatively charged, the anionic components move away from the vicinity of the heater 108 due to electrical repulsion and are less likely to adhere to the heater, thereby suppressing unevenness in the image. Since the counter electrode side region 107b is positively charged, the anionic components move in a direction approaching it, and some of them temporarily adhere to the counter electrode side region 107b. However, the anionic components can be removed by soluble metal ions that may be present in the vicinity. In this way, the behavior of the heater side area 107a and the counter electrode side area 107b cooperate to suppress a decrease in the ejection performance when voltage control of the print head is performed.

[0049] [Voltage control procedure] The procedure for performing voltage control will be described. When the recording device receives image data, the image data is developed as data suitable for the recording device. Next, a potential difference is generated between the heater side area 107a and the counter electrode side area 107b of the second protective layer 107 in the recording head 100. At this time, a voltage is applied from the voltage application means of the recording device through the recording element substrate 101 of the recording head 100, with the heater side area 107a of the second protective layer 107 as a cathode and the counter electrode side area 107b as an anode. Then, recording is started by ejecting ink. After the recording is completed, the application of the voltage between the heater side area 107a and the counter electrode side area 107b of the second protective layer 107 is stopped, and the potential difference generated between them is released. In this embodiment, the recording operation by ejecting ink includes not only the period during which the recording head ejects ink to perform recording, but also the period from when a recording start command is received to when the ejection of ink is completed.

[0050] The voltage control is performed to suppress the adhesion of substances that cause scorching to the heater. Therefore, it is preferable to perform the voltage control continuously from a certain time before to a certain time after the ink ejection operation based on the recording data, the preliminary ejection data, etc. In this case, the period during which the voltage control is continued may be appropriately set in consideration of the power consumption, etc. Considering that the voltage control is performed in the presence of aqueous ink containing an electrolyte, it is preferable to set the voltage to about 1 V or more and 4 V or less, at which electrolysis of water does not occur.

[0051] (Water-based ink) The inkjet recording method of the present invention is a recording method in which an image is recorded by applying an aqueous ink having a dynamic surface tension of 60 mN / m or less at a life time of 0 milliseconds ejected from an ejection port of a recording head to a recording medium using the aqueous ink. The components constituting the ink and the physical properties of the ink are described below.

[0052] [Colorant] The ink may contain a coloring material. Pigments and dyes can be used as the coloring material. Among them, pigments are preferred. The content (mass%) of the coloring material in the ink is preferably 0.10% by mass or more and 15.00% by mass or less, and more preferably 1.00% by mass or more and 10.00% by mass or less, based on the total mass of the ink.

[0053] 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. Of these, carbon black and organic pigments such as azo and quinacridone are preferred.

[0054] The pigment dispersion method is not particularly limited. For example, resin-dispersed pigments dispersed with a resin dispersant, pigments dispersed with a surfactant, and microencapsulated pigments in which at least a part of the pigment particle surface is coated with a resin or the like can be used. Self-dispersed pigments in which a functional group containing a hydrophilic group such as an anionic group is bonded to the pigment particle surface, and pigments in which an organic group containing a polymer is chemically bonded to the pigment particle surface (resin-bonded self-dispersed pigments) can also be used. Pigments with different dispersion methods may be used in combination. Among them, resin-dispersed pigments dispersed with a resin dispersant are preferred.

[0055] As the resin dispersant, it is preferable to use a water-soluble resin that can disperse the pigment in an aqueous medium by the action of anionic groups. The content (mass%) of the pigment in the ink is preferably 0.3 to 10.0 times the content of the resin dispersant in terms of mass ratio.

[0056] The resin dispersant may be an acrylic resin, a urethane resin, etc. Among them, an acrylic resin is preferred, and an acrylic resin composed of a unit derived from (meth)acrylic acid or a (meth)acrylic acid ester is more preferred.

[0057] The acrylic resin is preferably one having a hydrophilic unit and a hydrophobic unit as a segment. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer is preferable. 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 styrene and α-methylstyrene is preferable. These resins easily interact with pigments, and are therefore suitable as resin dispersants for dispersing pigments.

[0058] 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. 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; anionic monomers such as anhydrides and salts of these acidic monomers; and the like. Examples of the cations constituting the salts of the 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 by polymerizing a hydrophobic monomer not having a hydrophilic group such as an anionic group. Examples of the hydrophobic monomer include monomers having an aromatic group such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid esters such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0059] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic 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 anionic group is a salt type, examples of the cation that serves 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. In addition, it may be a group that is a combination of these groups.

[0060] It is preferable to use a dye having an anionic group, and examples of the dye include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone dyes.

[0061] [Urethane resin] The ink preferably contains a urethane resin. The urethane resin is preferably a water-soluble urethane resin. By using an ink containing a urethane resin such as a water-soluble urethane resin, it is possible to further suppress the decrease in ink ejection stability caused by bubbles. The content (mass %) of the urethane resin in the ink is preferably 0.10 mass % or more and 20.00 mass % or less, and more preferably 1.00 mass % or more and 10.00 mass % or less, based on the total mass of the ink.

[0062] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, it exists in an aqueous medium in a state in which it does not form particles whose particle size can be measured by dynamic light scattering. 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 dynamic light scattering, if particles having a particle size are not measured, the resin can be determined to be water-soluble. On the other hand, if particles having a particle size are measured, the resin can be determined to be "resin particles" (i.e., "water-dispersible resin"). The measurement conditions at this time can be, for example, as follows. [Measurement conditions] SetZero: 30 seconds Number of measurements: 3 Measurement time: 180 seconds

[0063] As the particle size distribution measuring device, a particle size analyzer using a dynamic light scattering method (for example, the product name "UPA-EX150" manufactured by Nikkiso Co., Ltd.) can be used. Of course, the particle size distribution measuring device and the measurement conditions to be used are not limited to those described above.

[0064] The acid value of the urethane resin is preferably 30 mgKOH / g or more and 100 mgKOH / g or less. If the acid value of the urethane resin is less than 30 mgKOH / g, the hydrophilicity is low, so the ink does not easily fit the inner wall surfaces of the first flow path and the second flow path, and the foam-suppressing ability may be slightly reduced. On the other hand, if the acid value of the urethane resin is more than 100 mgKOH / g, the hydrophilicity is high, so the ink does not easily adsorb to the bubble interface in the ink, and the foam-suppressing ability may be slightly reduced.

[0065] The weight-average molecular weight of the urethane resin is preferably 5,000 or more and 20,000 or less. If the weight-average molecular weight of the urethane resin is less than 5,000, the foaming property of the ink may be somewhat high. On the other hand, if the weight-average molecular weight of the urethane resin is more than 20,000, the ink may not easily fit the inner wall surfaces of the first flow path and the second flow path due to low hydrophilicity, and the foam suppression property may be somewhat reduced.

[0066] As the urethane resin, for example, urethane resins having units derived from polyisocyanate, polyol having no acid group, polyol having an acid group, amine, or the like can be used.

[0067] [Polyisocyanate] Polyisocyanate is a compound having two or more isocyanate groups in its molecular structure. Examples of polyisocyanate include aliphatic polyisocyanate and aromatic polyisocyanate. The ratio (mol%) of the unit derived from polyisocyanate in the urethane resin is preferably 10.0 mol% or more and 80.0 mol% or less, more preferably 20.0 mol% or more and 60.0 mol% or less.

[0068] Examples of the aliphatic polyisocyanate include polyisocyanates having a chain structure such as tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate; and polyisocyanates having a cyclic structure such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatemethyl)cyclohexane.

[0069] Examples of aromatic polyisocyanates include tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, and α,α,α',α'-tetramethylxylylene diisocyanate.

[0070] Among the above polyisocyanates, it is preferable to use a polyisocyanate having a cyclic structure. Furthermore, among the polyisocyanates having a cyclic structure, it is more preferable to use isophorone diisocyanate.

[0071] [Polyols, polyamines] A polyol is a compound having two or more hydroxyl groups in its molecular structure. Examples of polyols include polyols without acid groups, such as polyether polyols, polyester polyols, and polycarbonate polyols; polyols with acid groups; and the like. A polyamine is a compound having two or more "amino groups, imino groups" in its molecular structure. The ratio (mol%) of units derived from polyols and polyamines in the urethane resin is preferably 10.0 mol% or more and 80.0 mol% or less, and more preferably 20.0 mol% or more and 60.0 mol% or less.

[0072] (1) Polyols without acid groups Examples of the polyether polyol include addition polymers of alkylene oxides and polyols, glycols such as (poly)alkylene glycol, etc. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, α-olefin oxide, etc. Examples of polyols to be addition polymerized with alkylene oxide include diols such as 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 4,4-dihydroxyphenylpropane, 4,4-dihydroxyphenylmethane, hydrogenated bisphenol A, dimethylol urea and derivatives thereof; and triols such as glycerin, trimethylolpropane, 1,2,5-hexanetriol, 1,2,6-hexanetriol, pentaerythritol, trimethylolmelamine and derivatives thereof, and polyoxypropylenetriol. Examples of glycols include (poly)alkylene glycols such as tetramethylene glycol, hexamethylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, (poly)tetramethylene glycol, and neopentyl glycol; ethylene glycol-propylene glycol copolymers; and the like.

[0073] Examples of polyester polyols include acid esters. Examples of acid components constituting the acid esters include aromatic dicarboxylic acids such as phthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and tetrahydrophthalic acid; alicyclic dicarboxylic acids such as hydrogenated products of these aromatic dicarboxylic acids; and aliphatic dicarboxylic acids such as malonic acid, succinic acid, tartaric acid, oxalic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, alkyl succinic acid, linoleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, and itaconic acid. Anhydrides, salts, and derivatives (alkyl esters, acid halides) of these can also be used as the acid component. Examples of components that form esters with the acid component include polyols such as diols and triols; and glycols such as (poly)alkylene glycols. Examples of polyols and glycols include those exemplified as components constituting the above polyether polyols.

[0074] The polycarbonate polyol may be a polycarbonate polyol produced by a known method.Specific examples include alkanediol-based polycarbonate diols such as polyhexamethylene carbonate diol.Furthermore, examples include polycarbonate diols obtained by reacting a carbonate component such as alkylene carbonate, diaryl carbonate, or dialkyl carbonate, or phosgene with an aliphatic diol component.

[0075] The ratio (mol %) of the units derived from a polyol having no acid group to the total amount of the units derived from a polyol in the urethane resin is preferably as follows: preferably from 5.0 mol % to 50.0 mol %, and more preferably from 10.0 mol % to 30.0 mol %.

[0076] It is preferable to use polypropylene glycol as the polyol having no acid group. That is, it is preferable that the urethane resin contained in the ink is a urethane resin having a unit derived from polypropylene glycol. Since the urethane resin having a unit derived from polypropylene glycol is highly hydrophilic, the ink becomes more compatible with the inner wall surfaces of the first flow path and the second flow path, and bubbles generated in the ink are less likely to adhere to the inner wall surfaces of the first flow path and the second flow path.

[0077] (2) Polyol having an acid group Examples of polyols having an acid group include polyols having an acid group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group. The acid group is preferably a carboxylic acid group. Examples of polyols having a carboxylic acid group include dimethylol acetic acid, dimethylol propionic acid, dimethylol butanoic acid, and dimethylol butyric acid. Among these, dimethylol propionic acid and dimethylol butanoic acid are preferred.

[0078] The acid group of the polyol having an acid group may be in the form of a salt. Examples of cations that form salts include ions of alkali metals such as lithium, sodium, and potassium; ammonium ions, and cations of organic amines such as dimethylamine. Since the molecular weight of a general-purpose polyol having an acid group is at most about 400, the unit derived from the polyol having an acid group basically becomes the hard segment of the urethane resin. The acid value of the urethane resin can be adjusted, for example, by the amount of the polyol having an acid group used.

[0079] The ratio (mol %) of the units derived from a polyol having an acid group to the total amount of the units derived from a polyol in the urethane resin is preferably as follows: preferably from 30.0 mol % to 90.0 mol %, and more preferably from 50.0 mol % to 90.0 mol %.

[0080] (3) Polyamines Examples of polyamines include monoamines having multiple hydroxyl groups, such as dimethylolethylamine, diethanolmethylamine, dipropanolethylamine, and dibutanolmethylamine; bifunctional polyamines, such as ethylenediamine, propylenediamine, hexylenediamine, isophoronediamine, xylylenediamine, diphenylmethanediamine, hydrogenated diphenylmethanediamine, and hydrazine; and trifunctional or higher polyamines, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyamidepolyamine, and polyethylenepolyimine. For convenience, compounds having multiple hydroxyl groups and one "amino group, imino group" are also listed as "polyamines". Since the molecular weight of polyamines is at most about 400, the units derived from polyamines basically become the hard segments of urethane resins. The ratio (mol%) of the units derived from polyamines in the urethane resin is preferably 10.0 mol% or less, and more preferably 5.0 mol% or less. The proportion (mol %) of the polyamine-derived units in the urethane resin may be 0.0 mol %.

[0081] The urethane resin preferably has a unit derived from polyamine. The ratio of urethane bonds to the total of urethane bonds in the urethane resin and urea bonds derived from polyamine is preferably 85 mol% or more and 99 mol% or less. When the ratio of urethane bonds is 85 mol% or more, the hydrophilicity of the urethane resin is improved, and the wettability with materials such as resins forming the first flow path and the second flow path is improved, and foaming properties can be further suppressed. When the ratio of urethane bonds is less than 85 mol%, ink deposits tend to accumulate around the ejection port, and ejection stability during recording may be slightly reduced. On the other hand, when the ratio of urethane bonds is more than 99 mol%, the hydrophilicity is high, and it is difficult to adsorb to the bubble interface in the ink, and the foaming suppression property may be slightly reduced.

[0082] [Cross-linking agents, chain extenders] When synthesizing a urethane resin, a crosslinking agent or a chain extender can be used. Usually, a crosslinking agent is used when synthesizing a prepolymer, and a chain extender is used when carrying out a chain extension reaction on a prepolymer that has been synthesized in advance. Basically, the crosslinking agent or the chain extender can be appropriately selected from water, polyisocyanate, polyol, polyamine, etc. depending on the purpose, such as crosslinking or chain extension. As the chain extender, one that can crosslink the urethane resin can also be used.

[0083] [Analysis method] (1) Urethane resin composition The composition of the urethane resin can be analyzed by the following method. First, a method for extracting the urethane resin from the ink will be described. To extract the urethane resin from the ink, the ink is centrifuged at 80,000 rpm, and an excess of acid (such as hydrochloric acid) is added to the supernatant liquid separated to precipitate the resin. When chloroform is added to the precipitated resin, the urethane resin dissolves, so that the urethane resin can be extracted from the liquid phase. Furthermore, in addition to chloroform, an organic solvent such as hexane, which does not dissolve pigments or other resins but dissolves the urethane resin, may be used. Although the urethane resin can be analyzed in the ink state, it is preferable to analyze the urethane resin extracted from the ink, since the measurement accuracy can be improved.

[0084] The urethane resin was dissolved in deuterated dimethyl sulfoxide (DMSO) and analyzed by proton nuclear magnetic resonance ( 1 The urethane resin is analyzed by H-NMR. From the positions of the peaks obtained, the types of polyisocyanate, polyol without acid groups, polyol with acid groups, and polyamine can be identified. The dried urethane resin is also analyzed by pyrolysis gas chromatography to identify the types of polyisocyanate, polyol without acid groups, polyol with acid groups, and polyamine. Furthermore, the composition ratio can be calculated from the ratio of the integrated values ​​of each peak.

[0085] (2) Proportion of urethane bonds The ratio of urethane bonds to the total of urethane bonds and urea bonds derived from polyamines in the urethane resin can be measured as follows. That is, the urethane resin is dissolved in deuterated dimethyl sulfoxide to prepare a measurement sample. Then, the measurement sample is analyzed by carbon nuclear magnetic resonance ( 13 The prepared sample is analyzed by C-NMR, and the percentage of urethane bonds in the urethane resin can be calculated from the integrated values ​​of the peaks of the urethane bonds and the urea bonds derived from polyamines. However, the positions of the peaks of the urethane bonds and the urea bonds derived from polyamines differ depending on the type of compound used in the synthesis of the urethane resin. For this reason, it is necessary to examine the positions of the peaks of the urethane bonds and the urea bonds derived from polyamines for each compound used in the synthesis of the urethane resin. The method is described below.

[0086] First, compounds (polyisocyanate, polyol, polyamine) that are the raw materials for urethane resin are prepared. Then, (i) a reaction product of polyisocyanate and polyol, (ii) a reaction product of polyisocyanate and polyamine, (iii) a reaction product of polyisocyanate and polyol having an acid group, and (iv) a reaction product of polyisocyanate and water are prepared. The prepared reaction products are dried and dissolved in deuterated DMSO, and the carbon nuclear magnetic resonance ( 13 Analyze by C-NMR.

[0087] In the above example, the chemical shift of the urethane bond is confirmed from the reactant (i) and the reactant (iii), and the chemical shift of the urea bond derived from the polyamine is confirmed from the reactant (ii) and the reactant (iv). From each of the confirmed chemical shifts, the peak of the urethane bond and the peak of the urea bond are identified, and the ratio of the integrated values ​​of these peaks is used to calculate the proportion of the urethane bond in the total of the urethane bond and the urea bond derived from the polyamine in the urethane resin. For example, in the case of a urethane resin obtained using isophorone diisocyanate, the peak of the urethane bond is detected at about 155 ppm, although there is some deviation depending on the measurement conditions and the composition of the urethane resin. In addition, the peak of the urea bond derived from the polyamine is detected at about 159 ppm. The peak of the urea bond derived from water is detected at about 158 ​​ppm.

[0088] (3) Acid value of urethane resin The acid value of the urethane resin can be measured by dissolving the urethane resin in tetrahydrofuran (THF) and performing potentiometric titration with a potassium hydroxide ethanol titrant using an automatic potentiometric titrator (product name "AT510", manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0089] (4) Weight average molecular weight of urethane resin The weight average molecular weight of the urethane resin can be measured by gel permeation chromatography (GPC). In the examples described later, the urethane resin dissolved in THF was used as a measurement sample and measured by GPC. The measurement conditions for GPC are as follows.

[0090] Equipment: Alliance GPC 2695 (Waters) Column: Shodex KF-806M 4-column (Showa Denko) Mobile phase: Tetrahydrofuran (special grade) ·Flow rate: 1.0mL / min Oven temperature: 40.0℃ -Amount of sample solution injected: 0.1mL Detector: RI (Refractive Index) Polystyrene standard samples: PS-1 and PS-2 (Polymer Laboratories, molecular weights: 7,500,000, 2,560,000, 841,700, 377,400, 320,000, 210,500, 148,000, 96,000, 59,500, 50,400, 28,500, 20,650, 10,850, 5,460, 2,930, 1,300, 580, 17 types)

[0091] [Other resins] The ink can further contain a resin (other resin) other than the above-mentioned urethane resin. The other resin can be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary. Also, (ii) to improve various properties of the recorded image. Examples of the form of the resin include a block copolymer, a random copolymer, a graft copolymer, and a combination thereof. The resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be a resin particle that is dispersed in an aqueous medium. The resin particle does not need to contain a coloring material. The content (mass %) of the other resin in the ink is preferably 0.10 mass % or more and 20.00 mass % or less, and more preferably 1.00 mass % or more and 10.00 mass % or less, based on the total mass of the ink.

[0092] The other resin is preferably a resin having an acid group. Specific examples of the other resin include acrylic resins, polyester resins, urea resins, polysaccharides, and polypeptides. Among them, acrylic resins are preferred because they are easy to ensure the ejection stability of the ink.

[0093] The acid value of the other resin is preferably 30 mgKOH / g or more and 350 mgKOH / g or less. The weight average molecular weight of the other resin, measured by gel permeation chromatography (GPC) in terms of polystyrene, is preferably 1,000 or more and 100,000 or less, and more preferably 5,000 or more and 50,000 or less.

[0094] [Aqueous medium] The ink is an aqueous ink containing an aqueous medium which is water or a mixed solvent of water and a water-soluble organic solvent. As the water, deionized water (ion-exchanged water) is preferably used. The content (mass%) of water in the ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink. 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. The content (mass%) of the water-soluble organic solvent in the ink is preferably 3.00% by mass or more and 50.00% by mass or less based on the total mass of the ink. The water-soluble organic solvent in this specification includes those which are generally used in aqueous inks and are solid at 25°C. Examples of such water-soluble organic solvents include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol having a number average molecular weight of 1,000.

[0095] The ink preferably contains a first water-soluble organic solvent whose SP value is 15.0 or less. In general, the smaller the SP value of a water-soluble organic solvent, the more hydrophobic it is, and the more quickly it is adsorbed to the interface of bubbles formed by air. Therefore, by containing a first water-soluble organic solvent whose SP value is 15.0 or less, the foam suppression property of the ink can be further improved. The SP value of the first water-soluble organic solvent is preferably 14.0 or less, more preferably 13.0 or less, and more preferably 5.0 or more. The content (mass %) of the first water-soluble organic solvent in the ink is preferably 0.10 mass % or more and 50.00 mass % or less based on the total mass of the ink. In addition, it is more preferable that it is 0.50 mass % or more and 35.0 mass % or less, and particularly preferable that it is 1.00 mass % or more and 25.00 mass % or less.

[0096] The SP value (δ: solubility parameter) in this specification is a value calculated by the Fedors method based on the following formula (A) (unit: (cal / cm 3 )1 / 2 ) when converting to the SI system of units, use the unit "(cal / cm 3 ) 1 / 2 =2.046×10 3 (J / m 3 ) 1 / 2 " relationship can be utilized. δ = (ΔE vap / V) 1 / 2 (A) (In formula (A), ΔE vap represents the molar heat of vaporization of the compound (cal / mol), and V is the molar volume of the compound at 25°C (cm 3 / mol)

[0097] Specific examples of the first water-soluble organic solvent having an SP value of 15.0 or less, with the SP value shown in parentheses, are 1,4-butanediol (15.0), diethylene glycol (15.0), ethylene glycol (14.8), 1,3-butanediol (14.8), 2-methyl-1,3-propanediol (14.8), 1,2,6-hexanetriol (14.5), urea (14.4), ethyleneurea (14.2), 1,5-pentanediol (14.2), N-(hydroxymethyl)-2-pyrrolidone (14.2), 1,2,7-heptanetriol (13.9), Triethanolamine (13.7), triethylene glycol (13.6), 1,6-hexanediol (13.5), 1,2-propanediol (13.5), N-(2-hydroxyethyl)-2-pyrrolidone (13.5), 3-methyl-1,5-pentanediol (13.4), 2-ethylpropane-1,3-diol (13.2), 2-methylpentane-2,4-diol (13.1), N-(3-hydroxypropyl)-2-pyrrolidone (12.9), tetraethylene glycol (12.8), polyethylene glycol with a number average molecular weight of 200. (12.8), 1,2-butanediol (12.8), 2-pyrrolidone (12.6), N-(4-hydroxybutyl)-2-pyrrolidone (12.5), 1,2-pentanediol (12.2), ethylene glycol monomethyl ether (12.0), 1,2-hexanediol (11.8), N-methyl-2-pyrrolidone (11.5), ethylene glycol monoethyl ether (11.5), 1,3-dimethyl-2-imidazolidinone (11.4), diethylene glycol monomethyl ether (11.2), diethylene glycol monoethyl ether (10.9), triethylene glycol monoethyl ether (10.6), polyethylene glycol having a number average molecular weight of 600 (10.5), diethylene glycol monobutyl ether (10.5), triethylene glycol monobutyl ether (10.3), tetraethylene glycol monobutyl ether (10.2), polyethylene glycol having a number average molecular weight of 1,000 (10.1), tetraethylene glycol dimethyl ether (8.5), triethylene glycol butyl methyl ether (8.4), and ethylene glycol dimethyl ether (7.6). It is preferable to use a first water-soluble organic solvent having a lower vapor pressure than water. The SP value of the first water-soluble organic solvent is preferably 5.0 or more. These first water-soluble organic solvents having an SP value of 15.0 or less can be used alone or in combination of two or more. In the present invention, the first water-soluble organic solvent does not include surfactants or additives as described below. This is because the content of surfactants and additives in aqueous inks is generally quite small, and they have little effect on the effects of the present invention.

[0098] The first water-soluble organic solvent is preferably an alkylene glycol. In this specification, the alkylene glycol used as the water-soluble organic solvent is a compound having a structure in which one hydroxyl group is bonded to each of two different carbon atoms of an aliphatic hydrocarbon having two or more carbon atoms. In addition, the ink preferably contains a nonionic surfactant and an alkylene glycol as the first water-soluble organic solvent. The alkylene glycol has a structure similar to that of the nonionic surfactant. For this reason, when the nonionic surfactant and the alkylene glycol are used in combination, the alkylene glycol is easily compatible with the nonionic surfactant oriented at the interface of bubbles generated in the ink, and the defoaming property of the nonionic surfactant can be further improved. Among the alkylene glycols, 1,2-alkanediol is preferable, and 1,2-hexanediol is particularly preferable.

[0099] In addition to the first water-soluble organic solvent, "other water-soluble organic solvents" having an SP value of more than 15.0 may be used. Examples of the "other water-soluble organic solvents" include bis(2-hydroxyethyl)sulfone (20.5), glycerin (16.4), N-hydroxy-2-pyrrolidone (16.4), 1,3-propanediol (16.1), and trimethylolpropane (15.9).

[0100] In addition, water-based inkjet inks usually contain multiple types of water-soluble organic solvents. For this reason, it is appropriate to consider the SP value of the water-soluble organic solvent in the ink in terms of the concept of "average SP value". The average SP value means a value calculated for each water-soluble organic solvent by multiplying the SP value specific to the water-soluble organic solvent by the proportion (mass %) of the water-soluble organic solvent in the total amount of the water-soluble organic solvent in the ink, and integrating the calculated values. When the ink contains only one type of water-soluble organic solvent, the SP value of that water-soluble organic solvent is the "average SP value". For example, in the case of "Ink 1" prepared in the "Examples" described later, the composition of the water-soluble organic solvent (total 21.00 parts by mass) is as follows. The numbers in parentheses are the SP values ​​(units omitted) of each water-soluble organic solvent. Glycerin (16.4): 10.00 parts by weight 1,2-Hexanediol (11.8): 1.00 parts by mass Polyethylene glycol (10.5) having a number average molecular weight of 600: 10.00 parts by weight

[0101] The average SP value of the water-soluble organic solvent in this "ink 1" can be calculated according to the following formula (B). Average SP value = (16.4 × 10.00 / 21.00) + (10.5 × 10.00 / 21.00) + (11.8 × 1.00 / 21.00) = 13.4 ... (B)

[0102] When the first flow path and the second flow path of the recording head are each formed of a resin, the difference between the average SP value of the water-soluble organic solvent in the ink and the SP value of the resin forming the first flow path and the second flow path is preferably 4.0 or less. It is more preferably 3.0 or less, and particularly preferably 2.0 to 3.0. It is empirically known that the smaller the absolute value of the difference in the SP values ​​of the two components, the higher the solubility. By setting the difference between the average SP value of the water-soluble organic solvent in the ink and the SP value of the resin forming the first flow path and the second flow path to 4.0 or less, the ink becomes more compatible with the first flow path and the second flow path, and bubbles are less likely to adhere to the inner wall surfaces of the first flow path and the second flow path.

[0103] [Surfactants] The ink preferably contains a surfactant. Examples of the surfactant include cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants. Among them, the use of an ink containing a nonionic surfactant is preferable because it can further improve the effect of improving the ejection stability.

[0104] Examples of the nonionic surfactant include hydrocarbon-based, fluorine-based, and silicone-based nonionic surfactants. Among them, acetylene glycol-based nonionic surfactants are preferable. When an acetylene glycol-based nonionic surfactant is used, bubbles in the ink are more likely to disappear, and the ejection stability of the ink can be further improved. The content (mass%) of the surfactant (total of the nonionic surfactant and other surfactants) in the ink is preferably 0.10% by mass or more and 5.00% by mass or less, and more preferably 0.20% by mass or more and 1.50% by mass or less, based on the total mass of the ink.

[0105] [Other ingredients] In addition to the above components, the ink may contain various additives, such as antifoaming agents, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors, as necessary. These additives are not included in the consideration of the SP value.

[0106] [Ink properties] The dynamic surface tension of the ink at 0 milliseconds of life is 60 mN / m or less, preferably 30 mN / m or more and 60 mN / m or less. If the dynamic surface tension of the ink at 0 milliseconds of life is less than 30 mN / m, the ink may easily foam and may easily lose its bubble breaking ability. The dynamic surface tension of the ink at 0 milliseconds of life can be measured as follows. First, a liquid is prepared that has the same composition as the ink, except that it does not contain coloring materials such as pigments, resins, surfactants, and additives. That is, a liquid is prepared that has a composition equivalent to the water (coloring materials such as pigments, resins, surfactants, and additives) and water-soluble organic solvents in the ink. Next, the static surface tension of the prepared liquid is measured using a surface tensiometer using the plate method, and the obtained value is taken as the "dynamic surface tension (mN / m) of the ink at 0 milliseconds of life". The reason for grasping the characteristics of the ink using such a liquid, that is, the "static surface tension of the aqueous medium in the ink" is that it is not necessary to consider the effects of coloring materials such as pigments, resins, surfactants, and additives when the ink is moving significantly.

[0107] The dynamic surface tension of ink with unknown composition at a life time of 0 milliseconds may be measured as follows. After performing a general composition analysis to determine the constituent components of the ink and their contents, an aqueous medium consisting of water and a water-soluble organic solvent may be prepared, and the static surface tension may be measured in the same manner as above. The dynamic surface tension of the ink at a life time of 0 milliseconds may be adjusted by the type and content of the water-soluble organic solvent. The static surface tension of water is 72 mN / m, and the dynamic surface tension of the ink at a life time of 0 milliseconds may be reduced by using a water-soluble organic solvent that easily breaks the hydrogen bonds between water molecules.

[0108] The contact angle (static contact angle) between the ink and the inner wall surfaces of the first flow path and the second flow path is 60° or less, preferably 40° or less, and more preferably 10° to 40°. If the contact angle between the ink and the inner wall surfaces of the first flow path and the second flow path is less than 10°, the contact angle between the ink and the inner wall surfaces of the first flow path and the second flow path and bubbles generated in the ink becomes large, which may reduce the ability to break bubbles and make it easier for bubbles to remain in the ink.

[0109] 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

[0110] 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.

[0111] <Production of pigment dispersion> (Pigment dispersion 1) A self-dispersing pigment (product name "Cab-O-Jet 300", manufactured by Cabot) in which benzene carboxylic acid groups are bonded to the surface of carbon black particles was prepared. The prepared self-dispersing pigment was diluted with water and thoroughly stirred to obtain pigment dispersion 1 with a pigment content of 15.00%.

[0112] (Pigment dispersion 2) A self-dispersing pigment (product name "CAB-O-JET250C", manufactured by Cabot) with -C6H3-(COONa)2 groups bonded to the particle surface of CI Pigment Blue 15:4 was prepared. The prepared self-dispersing pigment was diluted with water and thoroughly stirred to obtain pigment dispersion 2 with a pigment content of 15.00%.

[0113] (Pigment dispersion 3) 15.0 parts of pigment, 30.0 parts of aqueous solution of resin dispersant, and 55.0 parts of water were mixed, dispersed with a sand grinder for 1 hour, and then centrifuged to remove non-dispersed matter including coarse particles. Carbon black (trade name "Printex85", manufactured by Orion Engineered Carbons) was used as the pigment. As the aqueous solution of the resin dispersant, an aqueous solution was used in which a resin (solid content) content of 20.0% was obtained by neutralizing a styrene-acrylic acid copolymer with an equimolar amount of 10% aqueous potassium hydroxide solution with the acid value, and adding an appropriate amount of ion-exchanged water. The acid value of the styrene-acrylic acid copolymer was 150 mg KOH / g, and the weight average molecular weight was 8,000. After pressure filtration with a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm, an appropriate amount of ion-exchanged water was added to prepare pigment dispersion 3. The pigment content in pigment dispersion 3 was 15.00%, and the resin content was 3.00%.

[0114] (Pigment Dispersion 4) Except for using CI Pigment Blue 15:6 as the pigment, Pigment Dispersion Liquid 4 was obtained in the same manner as for Pigment Dispersion Liquid 3 described above. The pigment content in Pigment Dispersion Liquid 4 was 15.00%, and the resin content was 3.00%.

[0115] (Pigment Dispersion 5) Pigment dispersion 5 was obtained in the same manner as for Pigment dispersion 3, except that CI Pigment Red 122 was used as the pigment. The pigment content in Pigment dispersion 5 was 15.00%, and the resin content was 3.00%.

[0116] (Pigment Dispersion 6) Pigment dispersion 6 was obtained in the same manner as for the above-mentioned pigment dispersion 3, except that CI Pigment Red 122 was used as the pigment. The pigment content in pigment dispersion 6 was 15.00%, and the resin content was 3.00%.

[0117] <Preparation of dye solution> A dye (CI Direct Yellow 132) was dissolved in pure water, and then excess acid was added to precipitate the dye. The precipitated dye was filtered and separated to obtain a wet cake in which the anionic groups were converted to an acid form. The wet cake was added to pure water, and an aqueous solution of sodium hydroxide in an equimolar amount to the anionic groups of the dye was added to neutralize the anionic groups and dissolve the dye. An appropriate amount of pure water was then added to obtain an aqueous dye solution with a dye content of 15.00%.

[0118] <Synthesis of urethane resin> A four-neck flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a reflux tube was prepared. Into this four-neck flask, isophorone diisocyanate (IPDI), polypropylene glycol (PPG, number average molecular weight 2,000), dimethylolpropionic acid (DMPA), and 300.0 parts of methyl ethyl ketone, the types and amounts of which are shown in Table 1, were placed. Then, the mixture was reacted at 80°C for 6 hours under a nitrogen gas atmosphere. Next, ethylenediamine (EDA) in the amount shown in Table 1 was added, and the reaction was carried out at 80°C until the product reached a predetermined weight average molecular weight to obtain a reaction liquid. After the obtained reaction liquid was cooled to 40°C, ion-exchanged water was added, and an aqueous potassium hydroxide solution was added while stirring at high speed with a homomixer to obtain a liquid. The obtained liquid was heated and reduced pressure to distill off methyl ethyl ketone, and liquids containing urethane resins 1 to 5, each of which had a urethane resin (solid content) content of 30.00%, were obtained. The obtained urethane resins 1 to 5 were all water-soluble, had an acid value of 65 mgKOH / g, and a weight average molecular weight of 15,000 in terms of polystyrene. The acid value of the urethane resin was measured by potentiometric titration using a potassium hydroxide-methanol titrant. The weight average molecular weight of the urethane resin was measured by GPC. The proportion (mol %) of the urethane bond in the total of the urethane bond and the urea bond in the urethane resin was: 13The molecular weight was measured and calculated by C-NMR (shown as "Ratio of urethane bonds (mol %)" in Table 1).

[0119] TIFF2024178116000002.tif55170

[0120] <Other resins> (Acrylic Resin 1) A styrene-acrylic acid copolymer (water-soluble resin) having an acid value of 120 mgKOH / g and a weight average molecular weight of 8,000 was neutralized with an aqueous sodium hydroxide solution to obtain a liquid containing acrylic resin 1 with a resin (solid content) content of 20.00%.

[0121] (Resin particles 1) In a four-neck flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 18.0 parts of butyl methacrylate, 0.35 parts of methacrylic acid, 2.0 parts of a polymerization initiator (2,2'-azobis(2-methylbutyronitrile)), and 2.0 parts of n-hexadecane were placed. Nitrogen gas was introduced into the reaction system, and the mixture was stirred for 0.5 hours. 78.0 parts of a 6.0% aqueous solution of an emulsifier (trade name "NIKKOL BC15", manufactured by Nikko Chemicals) was dropped into the reaction system, and the mixture was stirred for 0.5 hours to obtain a mixture. After emulsifying the mixture by irradiating it with ultrasonic waves for 3 hours using an ultrasonic irradiator, a polymerization reaction was carried out for 4 hours at 80°C under a nitrogen atmosphere. After cooling the reaction system to 25°C, it was filtered, and an appropriate amount of pure water was added to obtain a liquid containing resin particles 1 with a resin particle (solid content) content of 20.00%.

[0122] <Ink> The components shown in the upper part of Tables 2-1 to 2-4 were mixed and thoroughly stirred, and then pressure filtered using a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to prepare each ink. In Tables 2-1 to 2-4, the values ​​in parentheses next to the water-soluble organic solvents are the SP values ​​of each water-soluble organic solvent. The coloring material, resin, and surfactant were removed from each ink, and liquids were prepared by replacing these with water, and the dynamic surface tension (γ0 (mN / m)) at a life time of 0 milliseconds was measured using an automatic surface tensiometer (trade name "CBVP-Z type", manufactured by Kyowa Interface Science). The static surface tension (γ S (mN / m)) was measured. The measurement results are shown in the lower part of Tables 2-1 to 2-4. Details of the surfactants in Tables 2-1 to 2-4 are shown below. Acetylenol E60: Ethylene oxide adduct of acetylene glycol (nonionic surfactant, manufactured by Kawaken Fine Chemicals) Pluronic(R) L31: Polyoxyethylene polyoxypropylene block polymer (nonionic surfactant, manufactured by BASF) NIKKOL BC-20: Polyethylene glycol (20) monocetyl ether (nonionic surfactant, manufactured by Nikko Chemicals) Zonyl FSO: Perfluoroalkyl ethylene oxide adduct (nonionic surfactant, manufactured by DuPont) BYK348: Polyether modified siloxane compound (nonionic surfactant, manufactured by BYK) · NIKKOL SCS: Sodium cetyl sulfate (anionic surfactant, manufactured by Nikko Chemicals)

[0123] TIFF2024178116000003.tif206170

[0124] TIFF2024178116000004.tif205170

[0125] TIFF2024178116000005.tif205170

[0126] TIFF2024178116000006.tif220170

[0127] <Recording head> Recording heads 1 to 7 having the following configuration were prepared. The characteristics of the prepared recording heads are shown in Table 3. Table 3 also shows the characteristics of recording head 8 used in Reference Example 4. (recording head 1) A recording head 1 having the configuration shown in Fig. 1 was prepared. The first flow path and the second flow path were both made of a material containing a photosensitive epoxy resin.

[0128] (Recording head 2) A recording head 2 was prepared, which had the same configuration as the above-mentioned "recording head 1" except that it did not have the first pressure adjusting means (a member denoted by reference numeral 120 in FIG. 1).

[0129] (recording head 3) A recording head 3 was prepared, which had the same configuration as the above-mentioned "recording head 1" except that it did not have the second pressure adjusting means (a member denoted by reference numeral 150 in FIG. 1).

[0130] (recording head 4) A recording head 4 was prepared, which had the same configuration as the above-mentioned "recording head 1" except that the ejection elements were piezoelectric elements (piezo).

[0131] (recording head 5) A recording head 5 having the configuration shown in FIG. 1 and including a recording element substrate having the configuration shown in FIG. 4 and FIG. 5 was prepared. Iridium was used as the material of the second protective layer. The recording head 5 has the same configuration as the above-mentioned "recording head 1" except that it has a voltage application means (configuration shown in FIG. 4 and FIG. 5). When evaluating each item described later using the recording head 5, ink was discharged while maintaining a voltage controlled state. Specifically, each ink was filled in the ink flow path of the recording head, and the heater side region 107a of the second protective layer 107, which serves as a cathode, and the counter electrode side region 107b of the second protective layer 107, which serves as an anode, were made conductive (FIG. 4). In this state, voltage control was performed to charge the heater side region 107a of the second protective layer 107 negatively and the counter electrode side region 107b positively. Then, a DC voltage of +2 V was applied to the external electrode 111 connected to the counter electrode side region 107b of the second protective layer 107, and while maintaining the voltage controlled state, a voltage for ejecting ink was applied to the heat generating portion 104a. After the ejection of ink for recording was completed, the voltage control was stopped.

[0132] (Recording head 6) A recording head 6 having the configuration shown in Fig. 1 was prepared. The first flow path and the second flow path were both made of a material containing a photosensitive acrylic resin.

[0133] (recording head 7) A recording head 7 was prepared, which has the same configuration as the "recording head 1" except that it does not have the second flow path, the first pressure adjustment means (the member represented by the reference numeral 120 in FIG. 1), and the second pressure adjustment means (the member represented by the reference numeral 150 in FIG. 1). The first flow path is formed of a material containing a photosensitive epoxy resin.

[0134] (recording head 8) A recording head 8 was prepared, which has the same configuration as the "recording head 1", except that it does not have the circulation path in the recording head, the second flow path, the first pressure adjustment means (the member represented by the reference numeral 120 in FIG. 1), and the second pressure adjustment means (the member represented by the reference numeral 150 in FIG. 1). The first flow path is formed of a material containing a photosensitive epoxy resin.

[0135] The characteristics of each recording head (whether or not circulation is present, and the form of supply), and the SP value ((cal / cm 3 ) 1 / 2 ) are shown in Table 3.

[0136] TIFF2024178116000007.tif75170

[0137] <Contact angle measurement> Using an automatic contact angle meter (product name "DropMaster700", Kyowa Interface Science Co., Ltd.), the contact angles (static contact angles (°)) between the inner wall surfaces of the first flow path and the second flow path of the prepared recording head and each ink were measured. The results are shown in Table 4.

[0138] <Evaluation> In the examples other than Reference Example 4, an inkjet recording device (product name "WG7350", manufactured by Canon) incorporating a serial type recording head (FIG. 3) was used. In Reference Example 4, an inkjet recording device (product name "GX6030" manufactured by Canon) equipped with a recording head 8 shown in Table 3 was used. The combination of recording head and ink shown in Table 4 was incorporated into the prepared inkjet recording device. In the evaluation, a heater arranged in contact with the recording head was used to keep the ink in the recording head heated to a temperature of 40°C. However, in Example 38, the ink in the recording head was not heated. The evaluation results are shown in Table 4. 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 unacceptable levels.

[0139] (Discharge stability) The following evaluation was performed in an environment of 15°C temperature and 10% relative humidity. Using the above-mentioned inkjet recording device, a pattern ("WG7350" or "GX6030" nozzle check pattern) for checking the ejection state of each ejection port was recorded on a recording medium (product name "Canon Photo Paper Gloss Gold", manufactured by Canon). In this example, the recording duty of a solid image recorded under the condition that two ink droplets with a mass of 4 ng per droplet are applied to a unit area of ​​1 / 1,200 inch x 1 / 1,200 inch is defined as 100%. The recorded nozzle check pattern was visually confirmed, and the ejection stability of the ink was evaluated according to the following evaluation criteria. AA: The ratio of ejection ports where ejection failure occurred was 1% or less of all ejection ports. A: The percentage of ejection ports where ejection failure occurred was more than 1% and 5% or less of all ejection ports. B: The ratio of the ejection ports where ejection failure occurred was more than 5% and 8% or less of all the ejection ports. C: The ratio of ejection ports where ejection failure occurred exceeded 8% of all ejection ports.

[0140] (Image unevenness) The following evaluations were carried out in an environment with a temperature of 25°C and a relative humidity of 50%. Using the above-mentioned inkjet recording device, three solid images with a recording duty of 100% were recorded on the entire surface of an A4-sized recording medium (product name "High-quality dedicated paper HR-101S", manufactured by Canon) in one pass recording. One pass recording means that ink is applied to a unit area (one band: an area that can be recorded in one main scan of the recording head) in one relative scan of the recording head and recording medium. The first solid image and the third solid image were visually compared and evaluated for image unevenness according to the evaluation criteria shown below. AA: No unevenness was observed in any part of the solid image. A: Unevenness occurred in an area of ​​3 cm or less of one band area at the beginning of ejection (edge ​​of the recording medium). B: Within one band of the area at the beginning of ejection (the edge of the recording medium), unevenness occurred in an area exceeding 3 cm and not exceeding 10 cm. C: Unevenness occurred in an area exceeding 10 cm in one band area from the beginning of ejection (edge ​​of the recording medium).

[0141] TIFF2024178116000008.tif152170

[0142] In Reference Examples 1 to 3 using the recording head 7 without the second flow path, no deterioration in ejection stability due to bubbles was observed, but evaluation of image unevenness showed blank spots in some of the recorded solid images.

[0143] The disclosure of this embodiment includes the following methods and configurations. (Method 1) An inkjet recording method using an inkjet recording device including a recording head including: an ejection port for ejecting water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; a first flow path connecting with the pressure chamber; and a second flow path connecting with the pressure chamber at a position opposite to the first flow path with the ejection element in between, the inkjet recording method comprising the steps of: applying the water-based ink ejected from the ejection port to a recording medium to record an image, the recording head is configured to be able to supply the water-based ink to the pressure chamber from both the first flow path and the second flow path, The dynamic surface tension of the water-based ink at a life time of 0 milliseconds is 60 mN / m or less; The inkjet recording method according to claim 1, wherein a contact angle between the water-based ink and inner wall surfaces of the first flow path and the second flow path is 60° or less. (Method 2) The inkjet recording method according to Method 1, wherein the water-based ink has a dynamic surface tension of 30 mN / m or more at a lifetime of 0 milliseconds. (Method 3) The inkjet recording method according to Method 1 or 2, wherein a contact angle between the inner wall surface and the water-based ink is 40° or less. (Method 4) The inkjet recording method according to any one of Methods 1 to 3, wherein a contact angle between the inner wall surface and the water-based ink is 10° or more. (Method 5) The inkjet recording method according to any one of Methods 1 to 4, wherein the aqueous ink contains a nonionic surfactant. (Method 6) The ink-jet recording method according to Method 5, wherein the nonionic surfactant is an acetylene glycol-based nonionic surfactant. (Method 7) The inkjet recording method according to any one of Methods 1 to 6, wherein the water-based ink contains a first water-soluble organic solvent having an SP value of 15.0 or less. (Method 8) The inkjet recording method according to Method 7, wherein the first water-soluble organic solvent is an alkylene glycol. (Method 9) The aqueous ink contains a nonionic surfactant and a first water-soluble organic solvent having an SP value of 15.0 or less, 5. The inkjet recording method according to any one of Methods 1 to 4, wherein the first water-soluble organic solvent is an alkylene glycol. (Method 10) The first flow path and the second flow path are each formed of a resin, 10. The inkjet recording method according to any one of Methods 1 to 9, wherein the difference between the average SP value of the water-soluble organic solvent in the aqueous ink and the SP value of the resin is 4.0 or less. (Method 11) The inkjet recording method according to any one of Methods 1 to 10, wherein the water-based ink contains a urethane resin. (Method 12) The urethane resin has a unit derived from a polyamine, 12. The ink-jet recording method according to Method 11, wherein the proportion of urethane bonds in the urethane resin relative to the total of urethane bonds and urea bonds derived from the polyamine is 85 mol % or more and 99 mol % or less. (Method 13) The inkjet recording method according to any one of Methods 1 to 12, wherein the static surface tension of the water-based ink is 25 mN / m or more. (Method 14) The recording head further includes a first pressure adjusting means arranged to be connected to the first flow path, the first pressure adjusting means adjusting a pressure applied to the water-based ink supplied from the first flow path to the pressure chamber; a circulation pump that supplies the water-based ink from the first pressure adjustment means to the pressure chamber via the first flow path and is capable of pumping the water-based ink so as to recover the water-based ink in the pressure chamber via the second flow path; a bypass flow path that connects the first flow path and the second flow path without passing through the pressure chamber, the inkjet recording apparatus further comprises an ink storage unit that stores the water-based ink, the water-based ink supplied from the ink storage unit is discharged from the ejection port via the first pressure adjustment means and the first flow path, and the water-based ink not discharged from the ejection port is circulated to the first flow path via the second flow path and the circulation pump; The inkjet recording method described in any one of Methods 1 to 13, further comprising a step of ejecting the water-based ink supplied from the ink storage section from the ejection port via the first pressure adjustment means and the first flow path, and ejecting the water-based ink from the ejection port via the first pressure adjustment means, the bypass flow path, and the second flow path. (Method 15) The recording head further includes a second pressure adjusting means connected to the second flow path, the water-based ink supplied from the ink storage unit is ejected from the ejection port via the first pressure adjustment means and the first flow path, and the water-based ink not ejected from the ejection port is circulated to the first flow path via the second flow path, the second pressure adjustment means, and the circulation pump; The inkjet recording method described in any one of Methods 1 to 14, further comprising a step of ejecting the water-based ink supplied from the ink storage section from the ejection port via the first pressure adjustment means and the first flow path, and ejecting the water-based ink from the ejection port via the first pressure adjustment means, the bypass flow path, the second pressure adjustment means, and the second flow path. (Method 16) The ejection element is a heating element, 16. The inkjet recording method according to any one of Methods 1 to 15, wherein the recording head is a thermal type recording head that heats the water-based ink using the heating element, generates air bubbles in the water-based ink, and ejects the water-based ink. (Method 17) 17. The inkjet recording method according to any one of Methods 1 to 16, wherein the recording head further comprises a heating means for heating the water-based ink in the recording head. (Method 18) The recording head further includes a first protective layer disposed at a position corresponding to the heating element, the first protective layer blocking contact between the heating element and the water-based ink in the pressure chamber; a second protective layer made of a metal material, the second protective layer being disposed in a position corresponding to the heating element and in contact with the water-based ink; 18. The ink-jet recording method according to Method 16 or 17, further comprising: a voltage application means for applying a voltage to the second protective layer as a cathode and to an area electrically connected via the water-based ink as an anode. (Configuration 1) An inkjet recording device comprising a recording head including: an ejection port for ejecting water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; a first flow path connecting with the pressure chamber; and a second flow path connecting with the pressure chamber at a position opposite to the first flow path across the ejection element, the recording head is configured to be able to supply the water-based ink to the pressure chamber from both the first flow path and the second flow path, The dynamic surface tension of the water-based ink at a life time of 0 milliseconds is 60 mN / m or less; an ink jet recording device, wherein a contact angle between the water-based ink and inner wall surfaces of the first flow path and the second flow path is 60° or less; (Configuration 2) A water-based ink for use in an inkjet recording method, which uses an inkjet recording device including a recording head including: an ejection port for ejecting water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; a first flow path connecting with the pressure chamber; and a second flow path connecting with the pressure chamber at a position opposite to the first flow path with the ejection element in between, and which records an image by applying the water-based ink ejected from the ejection port to a recording medium, the recording head is configured to be able to supply the water-based ink to the pressure chamber from both the first flow path and the second flow path, The dynamic surface tension at a lifetime of 0 milliseconds is 60 mN / m or less. A water-based ink, wherein a contact angle between the water-based ink and inner wall surfaces of the first flow path and the second flow path is 60° or less.

Claims

1. an inkjet recording method using an inkjet recording device including a recording head including: an ejection port for ejecting water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; a first flow path connecting with the pressure chamber; and a second flow path connecting with the pressure chamber at a position opposite to the first flow path with the ejection element therebetween, the inkjet recording method comprising the steps of: applying the water-based ink ejected from the ejection port to a recording medium to record an image, the method comprising: the recording head is configured to be able to supply the water-based ink to the pressure chamber from both the first flow path and the second flow path, The dynamic surface tension of the water-based ink at a life time of 0 milliseconds is 60 mN / m or less; a contact angle between the water-based ink and inner wall surfaces of the first flow path and the second flow path is 60° or less.

2. 2. The ink jet recording method according to claim 1, wherein the water-based ink has a dynamic surface tension of 30 mN / m or more at a life time of 0 milliseconds.

3. 2. The ink-jet recording method according to claim 1, wherein a contact angle between the inner wall surface and the water-based ink is 40[deg.] or less.

4. 2. The ink-jet recording method according to claim 1, wherein a contact angle between the inner wall surface and the water-based ink is 10[deg.] or more.

5. 2. The ink-jet recording method according to claim 1, wherein the water-based ink contains a nonionic surfactant.

6. 6. The ink-jet recording method according to claim 5, wherein the nonionic surfactant is an acetylene glycol-based nonionic surfactant.

7. 2. The ink jet recording method according to claim 1, wherein the water-based ink contains a first water-soluble organic solvent having an SP value of 15.0 or less.

8. 8. The ink jet recording method according to claim 7, wherein the first water-soluble organic solvent is an alkylene glycol.

9. the aqueous ink contains a nonionic surfactant and a first water-soluble organic solvent having an SP value of 15.0 or less; 2. The ink jet recording method according to claim 1, wherein the first water-soluble organic solvent is an alkylene glycol.

10. the first flow path and the second flow path are each formed of a resin, 2. The ink jet recording method according to claim 1, wherein a difference between an average SP value of the water-soluble organic solvent in the aqueous ink and an SP value of the resin is 4.0 or less.

11. The ink-jet recording method according to claim 1 , wherein the water-based ink contains a urethane resin.

12. the urethane resin has a unit derived from a polyamine, The ink jet recording method according to claim 11, wherein a ratio of urethane bonds to a total of urethane bonds in the urethane resin and urea bonds derived from the polyamine is 85 mol % or more and 99 mol % or less.

13. 2. The ink-jet recording method according to claim 1, wherein the water-based ink has a static surface tension of 25 mN / m or more.

14. the recording head further comprises a first pressure adjusting means arranged to be connected to the first flow path, the first pressure adjusting means adjusting a pressure applied to the water-based ink supplied from the first flow path to the pressure chamber; a circulation pump that supplies the water-based ink from the first pressure adjustment means through the first flow path into the pressure chamber and that is capable of pumping the water-based ink so as to recover the water-based ink in the pressure chamber through the second flow path; a bypass flow path that connects the first flow path and the second flow path without passing through the pressure chamber, the inkjet recording apparatus further comprises an ink storage unit that stores the water-based ink, the water-based ink supplied from the ink storage unit is discharged from the ejection port via the first pressure adjustment means and the first flow path, and the water-based ink not discharged from the ejection port is circulated to the first flow path via the second flow path and the circulation pump; 14. The inkjet recording method according to claim 1, further comprising a step of ejecting the water-based ink supplied from the ink storage section from the ejection port via the first pressure adjustment means and the first flow path, and ejecting the water-based ink from the ejection port via the first pressure adjustment means, the bypass flow path, and the second flow path.

15. the recording head further includes a second pressure adjusting means connected to the second flow path, the water-based ink supplied from the ink storage unit is ejected from the ejection port via the first pressure adjustment means and the first flow path, and the water-based ink not ejected from the ejection port is circulated to the first flow path via the second flow path, the second pressure adjustment means, and the circulation pump; 15. The inkjet recording method according to claim 14, further comprising a step of ejecting the water-based ink supplied from the ink storage unit from the ejection port via the first pressure adjustment means and the first flow path, and ejecting the water-based ink from the ejection port via the first pressure adjustment means, the bypass flow path, the second pressure adjustment means, and the second flow path.

16. the ejection element is a heating element, 2. The ink jet recording method according to claim 1, wherein the recording head is a thermal type recording head that heats the water-based ink with the heating elements to generate air bubbles in the water-based ink and ejects the water-based ink.

17. 2. The ink jet recording method according to claim 1, wherein said recording head further comprises a heating means for heating said water-based ink in said recording head.

18. the recording head further includes a first protective layer disposed at a position corresponding to the heating element, the first protective layer blocking contact between the heating element and the water-based ink in the pressure chamber; a second protective layer made of a metal material, the second protective layer being disposed in a position corresponding to the heating element and in contact with the water-based ink; The ink-jet recording method according to claim 16, further comprising: a voltage application means for applying a voltage to the second protective layer as a cathode and to an area electrically connected via the water-based ink as an anode.

19. an inkjet recording device including a recording head including: an ejection port for ejecting a water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; a first flow path connected to the pressure chamber; and a second flow path connected to the pressure chamber at a position opposite to the first flow path with the ejection element therebetween, the recording head is configured to be able to supply the water-based ink to the pressure chamber from both the first flow path and the second flow path, The dynamic surface tension of the water-based ink at a life time of 0 milliseconds is 60 mN / m or less; a contact angle between the water-based ink and inner wall surfaces of the first flow path and the second flow path is 60° or less.

20. an ink jet recording device including a recording head including: an ejection port for ejecting the water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; a first flow path connecting the pressure chamber; and a second flow path connecting the pressure chamber at a position opposite to the first flow path with the ejection element therebetween; and an ink jet recording method for recording an image by applying the water-based ink ejected from the ejection port to a recording medium, the recording head is configured to be able to supply the water-based ink to the pressure chamber from both the first flow path and the second flow path, The dynamic surface tension at a lifetime of 0 milliseconds is 60 mN / m or less; A water-based ink, wherein a contact angle between the water-based ink and inner wall surfaces of the first flow path and the second flow path is 60° or less.

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