Inkjet recording method, inkjet recording device, and ink set

Abstract

To provide an inkjet recording method that can record a high quality image with reduced positional deviation of ruled lines and reduced variation of line widths recorded by a plurality of inks using a circulation serial head.SOLUTION: An inkjet recording method discharges ink from a recording head having a plurality of discharge ports, discharge elements, and first flow channels and second flow channels each of which communicate with each other between the discharge ports and the discharge elements and allow ink to distribute therein, and records an image. The method includes: a discharge step of discharging ink from the discharge ports; a flowing step of causing the ink to flow in the first flow channel different from the discharge step to the second flow channel; and a step of heating the ink in the recording head. The recording head is a serial system that comprises a plurality of discharge port arrays in which the plurality of discharge ports are arrayed in a predetermined direction, and that scans in a direction crossing an array direction of the discharge port arrays. The first flow channel and the second flow channel are arranged in parallel with the direction in which the recording head scans, and the ink flowing directions thereof are the same. The plurality of discharge port arrays include a first discharge port array for discharging first ink upstream of the ink flowing direction, and a second discharge port array for discharging second ink downstream thereof. Static surface tension γs1 of the first ink and static surface tension γs2 of the second ink satisfy a relation of γs1<γs2.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an inkjet recording method, an inkjet recording apparatus, and an ink set. [Background technology]

[0002] Inkjet recording methods make it possible to record images such as photographs and documents on various recording media. In addition, various inks have been proposed depending on the application, such as inks suitable for recording photographic quality images on glossy paper and inks suitable for recording documents on plain paper.

[0003] In recent years, inkjet recording methods have been used to record business documents, including characters and charts, on recording media such as plain paper, and the frequency of use for such applications has increased dramatically. There is a demand for the ability to record documents at higher speeds than before. In addition, there is a strong demand for inkjet recording devices to be more compact due to restrictions on installation space, etc.

[0004] There are two types of print head systems for inkjet printing devices: serial and line. From the viewpoint of miniaturization, serial print heads (serial heads) are advantageous. In order to improve the printing speed using a serial head, it is necessary to increase the scanning speed of the print head. It is also necessary to reduce the frequency of so-called preliminary ejection operations, which are a type of recovery process performed between scans of the print head, and to perform one-pass printing, in which multiple inks are applied to a unit area in one relative scan of the print head and the print medium.

[0005] As a method for reducing the frequency of the preliminary ejection operation, for example, a liquid ejection head that can suppress the accumulation of solids in the liquid near the periphery of the ejection port even after the ejection operation is stopped for a certain period of time has been proposed (Patent Document 1). Also, as a method for recording a plurality of inks in one pass, a method has been proposed in which an image is recorded by applying a second black ink with the same surface tension as the color ink to the boundary between the black ink and the color ink (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-124608 A [Patent Document 2] JP 2008-126619 A Summary of the Invention [Problem to be solved by the invention]

[0007] In order to achieve both high-speed printing and compact printing apparatus, the present inventors have studied printing an image in one pass using a serial type print head (circulating serial head) that employs a mechanism for flowing ink near the ejection port, as proposed in Patent Document 1. As a result, the ink ejection stability has improved even after the ejection operation has been stopped for a certain period of time, and the frequency of preliminary ejection operations performed during scanning of the print head has been reduced. Next, the inventors have studied printing an image in one pass using a circulating serial head that is equipped with multiple inks with uniform surface tension, as proposed in Patent Document 2. As a result, they have found that new problems arise, such as the occurrence of misalignment of the positions of ruled lines printed with multiple inks and variations in line width under certain scanning conditions.

[0008] Therefore, an object of the present invention is to provide an inkjet recording method capable of recording high-quality images with reduced misalignment of the ruled lines and reduced variation in line widths recorded with a plurality of inks using a circulation serial head. Another object of the present invention is to provide an inkjet recording apparatus and an ink set for use in the inkjet recording method. [Means for solving the problem]

[0009] That is, according to the present invention, there is provided an inkjet recording method for recording an image by ejecting ink from a recording head having a plurality of ejection ports for ejecting ink, ejection elements for generating energy for ejecting the ink, and a first flow path and a second flow path communicating between the ejection ports and the ejection elements and through which the ink flows, the method comprising: an ejection step of ejecting the ink from the ejection ports; and a flow step, separate from the ejection step, of causing the ink in the first flow path to flow into the second flow path, the recording head comprising an ejection element substrate having a plurality of ejection port arrays in which the plurality of ejection ports are arranged in a predetermined direction, The inkjet recording method includes a serial type recording head that scans in a direction intersecting an arrangement direction of the nozzle array, the first flow path and the second flow path are arranged parallel to the scanning direction of the recording head, and the ink flow direction is the same, the multiple nozzle arrays include a first nozzle array that ejects a first ink and a second nozzle array that ejects a second ink, the first nozzle array is arranged upstream and the second nozzle array is arranged downstream with respect to the ink flow direction, and a static surface tension γs1 of the first ink and a static surface tension γs2 of the second ink satisfy a relationship of γs1<γs2. Effect of the Invention

[0010] According to the present invention, it is possible to provide an inkjet recording method capable of recording high-quality images with reduced misalignment of ruled lines and reduced variation in line widths recorded with a plurality of inks using a circulation serial head. Also, according to the present invention, it is possible to provide an inkjet recording apparatus and an ink set used in the inkjet recording method. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic diagram showing a state in the vicinity of an ejection port of a print head. [Diagram 2] 1 is a perspective view illustrating an embodiment of an inkjet recording apparatus. [Diagram 3] FIG. 1 is a schematic diagram illustrating an internal configuration of an inkjet recording apparatus. [Figure 4] 3A and 3B are schematic diagrams showing an example of the arrangement of ejection port arrays in a print head and an example of the circulating flow direction of ink. [Diagram 5] 5A and 5B are schematic diagrams illustrating the flow state of ink within a print head when the print head is scanning. [Figure 6] 1A and 1B are schematic diagrams illustrating dot-on-dot ruled line recording. [Figure 7] FIG. 2 is a perspective view showing a cross section of a discharge element substrate. [Figure 8] FIG. 2 is a schematic diagram showing an ink supply system. [Figure 9] 5A and 5B are schematic diagrams illustrating the flow state of ink in the vicinity of an ejection port. [Figure 10] FIG. 2 is a cross-sectional view partially illustrating an example of a recording head. [Figure 11] 5A to 5C are schematic diagrams illustrating image patterns recorded in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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 dissociated into ions in the ink, but for convenience, it is expressed as "containing salt". In addition, the aqueous ink for inkjet may be simply referred to as "ink". The first flow path and the second flow path may be collectively referred to as "flow path". Similarly, the first ink and the second ink may be collectively referred to as "ink". The secondary color ruled line recorded with the two inks may be simply referred to as "ruled line". In the present invention, the ejection accuracy is evaluated using "ruled line" because it is easy to recognize the state in which the deposition position of the ink droplet is shifted from the target position, but the image recorded by the inkjet recording method, inkjet recording device, and ink set of the present invention is not limited to the ruled line. The physical property values ​​are values ​​at room temperature (25°C) unless otherwise specified.

[0013] <Inkjet recording method and inkjet recording apparatus> The inkjet recording apparatus of the present invention includes a recording head having a plurality of orifices for ejecting ink, an ejection element that generates energy for ejecting the ink, and a first flow path and a second flow path through which ink flows by communicating between the orifices and the ejection element. The recording head includes an ejection element substrate having a plurality of ejection orifice rows in which a plurality of ejection orifices are arranged in a predetermined direction, and is a serial type recording head (serial head) that scans in a direction intersecting the arrangement direction of the ejection orifice rows. The inkjet recording apparatus of the present invention further includes a flow means, separate from the ejection element, for causing the ink in the first flow path to flow to the second flow path. The inkjet recording method of the present invention is, for example, a method of recording an image by ejecting ink from the recording head using the inkjet recording apparatus described above. That is, the inkjet recording method of the present invention includes an ejection step of ejecting ink from the orifices, and a flow step, separate from the ejection step, of causing the ink in the first flow path to flow to the second flow path. The inkset of the present invention includes a first ink and a second ink used in the inkjet recording method described above.

[0014] FIG. 1 is a schematic diagram showing the state near the ejection port of a recording head. The recording head shown in FIG. 1 includes an ejection port 1 for ejecting ink, an ejection element 4 for generating energy for ejecting ink, and a first flow path 17 and a second flow path 18 that communicate between the ejection port 1 and the ejection element 4 and through which ink flows. As will be described later in the description of the ejection element substrate in the recording head, the ejection port 1 is formed in an ejection port forming member 5, and the ejection element 4 is disposed on a substrate 3. The ink flows from the first flow path 17 to the second flow path 18 (in the direction of the arrow in FIG. 1) through between the ejection port 1 and the ejection element 4. If the ink does not flow, evaporation of water from the ink meniscus 12 at the ejection port 1 progresses, and the ink present between the ejection port 1 and the ejection element 4 gradually thickens. For this reason, if the ejection pause time is long, the fluid resistance of the ink increases at the time of the next ejection operation, and ejection may become difficult. In contrast, if the ink flows in the direction of the arrow in Figure 1, even if water evaporates from the meniscus 12, ink will be continuously supplied between the ejection port 1 and the ejection element 4 due to the circulating flow, thereby suppressing the ink from thickening and making it less likely to become difficult to eject.

[0015] The inventors combined multiple inks in a serial type recording head (circulating serial head) that generates a circulating flow as shown in FIG. 1, and discharged the inks from the discharge ports to record an image. As a result, the ink discharge stability was improved even after the discharge operation was stopped for a certain period of time, and the frequency of the preliminary discharge operation performed during the scan of the recording head could be reduced. However, it was found that under certain scanning conditions, a new problem occurred in that the position of the secondary color ruled lines recorded with multiple inks may shift or the line width may vary. A detailed investigation into the reasons for the shift in the position of the ruled lines and the variation in the line width was found to occur as follows.

[0016] First, an inkjet recording device equipped with a circulating serial head will be described. Fig. 2 is a perspective view that shows a schematic diagram of an embodiment of an inkjet recording device 1000. A feeding unit 200 can hold a plurality of recording media, and feeds the recording media by a feeding roller (not shown). The recording medium P (see Fig. 3) of this embodiment will be described using a cut sheet of paper cut to a predetermined size as an example, but is not limited to this and can also be used in a form in which recording is performed on rolled paper.

[0017] The recording medium fed by the feeding unit 200 is transported in the Y direction (transport direction) by a transport unit including a transport roller (not shown) to a recording position facing an ejection unit (recording head) 300 (see FIG. 3(b)) that ejects ink. The carriage 100 is equipped with the ejection unit (recording head) 300, and is driven by a carriage motor 400 to reciprocate along a guide shaft 700 via a timing belt 600 in an X direction (main scanning direction) that intersects with the Y direction.

[0018] When an image for a unit area is recorded by the movement of the carriage 100 in the X direction and the ink discharge operation by the discharge unit (recording head) 300, the recording 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 discharge port array arranged along the Y direction in the discharge unit 300, "one band" that can be recorded by one movement of the discharge unit 300 in the X direction, or "one" pixel corresponding to the resolution of the recording head. In the serial method, an image can be recorded over the entire recording medium by a recording operation that repeats the ink discharge operation for one band and intermittent transport operation. In this embodiment, the X direction and the Y direction are orthogonal to each other.

[0019] A platen 500 that supports the recording medium from below in the vertical direction is disposed in a recording area facing the discharge unit (recording head) 300 where recording is performed by the discharge unit (recording head) 300. The platen 500 maintains a predetermined distance between the recording surface of the recording medium and a discharge port surface 2 (FIG. 3) of the discharge unit (recording head) 300 on which discharge ports for discharging ink are arranged.

[0020] 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 when viewed from above, and FIG. 3(b) is a schematic side view of the recording apparatus 1000 when viewed from the front. The carriage 100 detachably mounts an ink cartridge that contains ink to be supplied to the discharge unit (recording head) 300. A plurality of ink cartridges 111, 112, 113, and 114 correspond to the discharge port arrays 21, 22, 23, and 24 (see FIG. 4), respectively, and supply ink to each discharge port array. For example, discharge port arrays and ink cartridges corresponding to each of the inks of cyan, magenta, yellow, and black (CMYK) are provided.

[0021] Furthermore, within the movement area of ​​the carriage 100, outside the area (printing area) through which the recording medium P passes, a cap 302 for capping the discharge port surface 2 of the discharge unit (printing head) 300 is disposed. The position of the carriage 100 (discharge unit (printing head) 300) where the discharge port surface 2 of the discharge unit (printing head) 300 faces the cap 302 is also referred to as the home position 301. The cap 302 is connected to suction means (not shown), and by driving the suction means with the discharge port surface 2 capped, ink is sucked from the discharge unit (printing head) 300.

[0022] FIG. 4 is a schematic diagram showing an example of the arrangement of the ejection port arrays in the ejection unit (recording head) 300 and an example of the circulating flow direction, which is the flow direction of the ink. FIG. 4 shows the ejection unit (recording head) 300 shown in FIG. 3(b) as viewed from the recording medium P side. As shown in FIG. 4, the ejection unit (recording head) 300 is a serial type recording head that includes an ejection element substrate 10 having four ejection port arrays 21, 22, 23, and 24, and scans in the X direction intersecting the arrangement direction of the ejection port arrays 21 to 24. The circulating flow directions of the four ejection port arrays 21 to 24 are all the same direction from right to left, and are parallel to the X direction (scanning direction). The ejection unit (recording head) 300 reciprocates in the forward direction from left to right and the return direction from right to left, so that the scanning direction and the circulating flow direction are the same direction in the return direction, and are opposite directions in the forward direction.

[0023] Next, the locations where the positional deviation of the ruled lines and the variation in the line width occurred and the reasons for the occurrence will be described. Using the above-mentioned inkjet recording device and the ejection port array 24 on the most upstream side and the ejection port array 21 on the most downstream side with respect to the ink flow direction in the ejection unit (recording head) 300 thereof, secondary color ruled lines were recorded in one pass recording at the center and both ends of the width direction (X direction) of the recording medium. Specifically, after the secondary color ruled lines were recorded at three locations at the center and both ends of the recording medium in the forward direction in the X direction, the recording medium was transported by one band in the Y direction, and the secondary color ruled lines were recorded at three locations at the center and both ends of the recording medium in the return direction in the X direction. As a result, it was found that the ruled lines recorded at the end of the recording medium on the home position side immediately after the ejection unit (recording head) 300 was switched from the return direction to the forward direction were thicker than the other ruled lines. It was also found that the phenomenon occurred in which the position of the ruled lines moved outward (toward the home position) more than expected.

[0024] The inventors of the present invention closely observed the ruled line on the home position side recorded on the recording medium. As a result, among the dots constituting the ruled line, the dots formed by the ink droplets discharged from the discharge port array 24 moved toward the home position side more than the dots formed by the ink droplets discharged from the discharge port array 21. Furthermore, when the other discharge port arrays were used for verification, the degree to which the positions of the dots formed by the ink droplets moved toward the home position side increased in the order of the discharge port arrays 21, 22, 23, and 24. In other words, it was found that the deviation of the dots formed by the ink droplets of the discharge port array 24 that were discharged first immediately after switching from the backward direction to the forward direction was the largest. The inventors of the present invention speculate as follows about the reason for the occurrence of such a phenomenon.

[0025] Figure 5 is a schematic diagram explaining the flow state of ink inside the print head when the print head scans. When printing is started using a circulating serial head, when the print head scans in the forward direction from the home position and then switches from the forward direction to the backward direction and scans the print medium, the meniscus 12 at the ejection port 1 is stable, as shown in Figure 5(a). At this time, it is considered that ink droplets 30 are normally formed from the stable meniscus 12 and are ejected in a direction perpendicular to the ejection port face of the print head. Therefore, deviation in the position of the dots formed by the ink droplets 30 is unlikely to occur.

[0026] Thereafter, immediately after the print head switches from the backward direction to the forward direction, that is, when the print head stops instantaneously near the home position, an inertial force acts on the ink near the ejection port 1. At that time, as shown in FIG. 5(b), the inventors speculate that the meniscus at the ejection port 1 is destroyed, causing the ink to overflow downstream of the circulating flow. If ink is ejected in this state, the ink droplets 30 are ejected not perpendicular to the ejection port face of the print head, but bent slightly downstream of the circulating flow. Even if the ink overflows, it is quickly drawn into the ejection port 1 and the meniscus 12 is reformed, so that the influence becomes smaller as the ejection port array moves downstream of the circulating flow, and it is speculated that the position of the dots formed by the ink droplets 30 is unlikely to shift in parts other than the end. From the above, the inventors speculate that the above-mentioned phenomenon is caused by the inertial force acting when the ink circulating flow direction and the print head scanning direction are the same and the print head stops instantaneously after that.

[0027] The present inventors have studied a method for improving the ejection accuracy and suppressing the above-mentioned shift in the position of the ruled lines and the variation in line width. Specifically, they have studied the requirements for suppressing the shift in the position of the ruled lines and the variation in line width even if ink overflows from the ejection ports due to inertial force. As a result, they have found that the shift in the position of the ruled lines and the variation in line width can be suppressed by making the static surface tension of the ink ejected from the ejection port array on the upstream side lower than the static surface tension of the ink ejected from the ejection port array on the downstream side in the ink flow direction.

[0028] In this specification, of the multiple ejection port arrays in a print head, the ejection port array on the upstream side with respect to the ink flow direction may be referred to as the "first ejection port array," and the ink ejected from the first ejection port array may be referred to as the "first ink." Also, the ejection port array on the downstream side with respect to the ink flow direction may be referred to as the "second ejection port array," and the ink ejected from the second ejection port array may be referred to as the "second ink." In multiple ejection port arrays, the "upstream side" and "downstream side" with respect to the ink flow direction refer to the relative relationship between the two ejection port arrays being compared.

[0029] As described above, the inventors speculate as follows about the reason why it is possible to print high-quality images with reduced misalignment of ruled lines and variation in line width by satisfying the relationship of static surface tension γs1 of the first ink < static surface tension γs2 of the second ink.

[0030] Hereinafter, an example of recording a ruled line so that dots formed by ink droplets of a plurality of inks overlap (dot-on-dot) will be described with reference to FIG. 6. The dashed line in FIG. 6 indicates the center line of the position targeted by the ink droplets. In a state where there is no ink overflow, when recording in the forward direction, ink droplets 31 of the first ink and ink droplets 32 of the second ink (see FIG. 6(a1)) adhere and settle to overlap at the targeted position on the recording medium P as shown in FIGS. 6(a2) and (a3), and a ruled line is recorded. In contrast, in a state where there is ink overflow, the ink droplets 31 of the first ink are ejected downstream of the circulating flow (to the right in FIG. 6(b1)) from the ink droplets 32 of the second ink, and therefore adhere adjacent to each other on the recording medium P as shown in FIGS. 6(b2-1) and (b2-2).

[0031] In this case, if the static surface tension γs1 of the first ink on the upstream side is greater than or equal to the static surface tension γs2 of the second ink on the downstream side, a force that tries to pull the first ink dots 33 toward the second ink dots 34 that are attached closer to the targeted position is unlikely to occur. Figures 6(b2-1) and (b3-1) are schematic diagrams showing a case where the static surface tension γs1 of the first ink is greater than the static surface tension γs2 of the second ink. In this case, the position of the printed ruled line moves toward the first ink on the upstream side (see the dashed line in Figure 6(b3-1)), and the line width also becomes thicker than in the case of Figure 6(a3).

[0032] Here, by making the static surface tension γs1 of the first ink < the static surface tension γs2 of the second ink, it becomes possible to pull the dots 33 of the first ink toward the dots 34 of the second ink that are attached closer to the targeted position, as shown in FIG. 6(b2-2). As a result, as shown in FIG. 6(b3-2), the positional deviation and line width of the ruled line can be made closer to that in the case of printing without ink overflow, as shown in FIG. 6(a3) (see the two-dot chain line in FIG. 6(b3-2)). As a result, the inventors speculate that it becomes possible to print ruled lines with reduced variation in the center and both ends of the print medium, even when ink overflows from the ejection openings due to inertial force, which is a phenomenon unique to the circulation serial head.

[0033] FIG. 7 is a perspective view showing a cross section of the discharge element substrate. As shown in FIG. 7, the discharge element substrate 10 includes a discharge port forming member 5 in which a discharge port 1 is formed, and a substrate 3 in which a discharge element (not shown) is arranged. The discharge port forming member 5 and the substrate 3 are laminated to form a first flow path 17 and a second flow path 18 through which ink flows. The first flow path 17 is a region from an inlet 8 through which ink flows in the inflow path 6 to a portion between the discharge port 1 and the discharge element (liquid chamber 213 in FIG. 8). The second flow path 18 is a region from a portion between the discharge port 1 and the discharge element (liquid chamber 213 in FIG. 8) to an outlet 9 through which ink flows out to the outlet path 7. For example, if a pressure difference is provided between the inlet 8 and the outlet 9, such as the inlet 8 having a high pressure and the outlet 9 having a low pressure, the ink can flow from the high pressure side to the low pressure side (in the direction of the arrow in FIG. 7). The ink that has passed through the inflow path 6 and the inlet 8 enters the first flow path 17. Then, the ink that has passed through the portion between the ejection port 1 and the ejection element (the liquid chamber 213 in FIG. 8) passes through the second flow path 18 and the outlet port 9, and flows into the outlet path 7.

[0034] The flowing step of causing the ink in the first flow path to flow to the second flow path is a separate step (different step) from the ejection step of ejecting ink from the ejection port. In addition, the flow of ink from the first flow path to the second flow path in the flowing step is preferably performed separately from filling the space between the ejection port and the ejection element with ink. The flowing step is preferably a step of causing the ink in the first flow path to flow to the second flow path without discharging the ink from the ejection port. Discharging the ink from the ejection port includes a recovery operation such as preliminary ejection or suction. During a recovery operation of the recording head, the flow of ink from the first flow path to the second flow path may be stopped. In addition, in the flowing step, it is preferable to cause the ink to flow from the first flow path to the second flow path by a flowing means other than the ejection element.

[0035] Hereinafter, the inkjet recording method and the inkjet recording apparatus of the present invention will be described in further detail, taking as an example a thermal type recording head that uses a discharge element that generates thermal energy to generate bubbles to discharge ink. However, the inkjet recording method and the inkjet recording apparatus of the present invention can be applied to a piezo type recording head or a recording head that employs another discharge method. Here, an example in which ink is circulated between an ink storage section and a recording head will be described, but other forms may also be used. For example, a form in which two ink storage sections are provided on the upstream side and downstream side of a recording head, and ink flows from one ink storage section to the other ink storage section may also be used. Furthermore, an example in which a recording head incorporating a discharge element substrate in which four discharge port rows capable of discharging four colors of ink, CMYK, are arranged will be described, but a recording head having discharge port rows capable of discharging two or more types of ink may also be used. In the present invention, it is particularly preferable to use a recording head that discharges ink by a thermal method.

[0036] In the flow process, it is preferable to flow the ink continuously or intermittently. Hereinafter, the method of flowing the ink continuously and the method of flowing the ink intermittently will be described in detail. First, the method of flowing the ink continuously will be described with reference to FIG. 8. FIG. 8 is a schematic diagram showing an ink supply system. The discharge unit (recording head) 300 shown in FIG. 8 is connected to a first circulation pump (high pressure side) 1001, a first circulation pump (low pressure side) 1002, a sub-tank 1003, a second circulation pump 1004, and the like. For the sake of simplicity, FIG. 8 shows only a path through which ink of one color flows, but in reality, flow paths for four colors of CMYK are provided in each of the discharge units (recording heads) 300.

[0037] The sub-tank 1003, which is connected to the main tank 1006 that is an ink storage section, has an air communication port (not shown) and is capable of discharging air bubbles mixed in the ink to the outside. The sub-tank 1003 is also connected to a refill pump 1005. Ink is consumed in the discharge unit (print head) 300 by discharging (discharging) ink from the discharge port for image recording, suction recovery, etc. The refill pump 1005 transfers an amount of ink corresponding to the consumed amount from the main tank 1006 to the sub-tank 1003.

[0038] The first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 cause the ink in the discharge unit (recording head) 300, which has flowed out from the connection part 1110, to flow into the sub tank 1003. As the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002, it is preferable to use a positive displacement pump having a quantitative liquid delivery capability. Specific examples of such a positive displacement pump include a tube pump, a gear pump, a diaphragm pump, and a syringe pump. When the discharge unit 300 is driven, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 can cause the ink to flow into the common inflow channel 211 and the common outflow channel 212.

[0039] The negative pressure control unit 230 includes two pressure adjustment mechanisms with mutually different control pressures set thereto. The pressure adjustment mechanism (high pressure side) H and the pressure adjustment mechanism (low pressure side) L are respectively connected to a common inflow channel 211 and a common outflow channel 212 in the ejection unit 300 via a supply unit 220 provided with a filter 221 that removes foreign matter from the ink.

[0040] The supply unit 220 and the discharge unit (recording head) 300 are connected by an ink supply tube (not shown) which is an ink supply path. Since the discharge unit (recording head) 300 scans back and forth inside the inkjet recording device, the ink supply tube is made of a resin material having flexibility that can withstand the back and forth scanning.

[0041] The discharge unit 300 is provided with a common inflow path 211, a common outflow path 212, and an inflow path 6 and an outflow path 7 which communicate with a liquid chamber 213 which is a portion between the discharge port 1 and the discharge element (not shown). Since the inflow path 6 and the outflow path 7 communicate with the common inflow path 211 and the common outflow path 212, a flow (arrow in FIG. 8) occurs in which part of the ink flows from the common inflow path 211 through the inside of the liquid chamber 213 to the common outflow path 212. The arrow in FIG. 7 indicates the flow of ink inside the liquid chamber 213. That is, as shown in FIG. 7, the ink in the first flow path 17 flows to the second flow path 18 through between the discharge port 1 and the discharge element.

[0042] As shown in FIG. 8, a pressure adjustment mechanism H is connected to the common inflow channel 211, and a pressure adjustment mechanism L is connected to the common outflow channel 212, so that a pressure difference occurs between the inflow channel 6 and the outflow channel 7. As a result, a pressure difference also occurs between the inflow port 8 (FIG. 7) communicating with the inflow channel 6 and the outflow port 9 (FIG. 7) communicating with the outflow channel 7. When the ink is made to flow by the pressure difference between the inflow port and the outflow port, it is preferable to control the flow velocity (mm / s) of the ink when it flows to 1.0 mm / s or more and 100.0 mm / s or less. When the ink flow velocity is 1.0 mm / s or more, the increase in the viscosity of the ink near the ejection port when the ejection operation is stopped for a certain period of time is suppressed, and the ejection stability of the ink is likely to be improved. On the other hand, when the ink flow velocity is 100.0 mm / s or less, the stability of the meniscus of the ejection port is likely to be improved, the occurrence of ink overflow from the ejection port due to inertial force is easily suppressed, and the shift in the position of the ruled lines and the variation in the line width are easily suppressed.

[0043] In the inkjet recording method of the present invention, the ink in the first flow path may be caused to flow to the second flow path even during a recovery operation of the recording head. When the ink flows during a recovery operation of the recording head, the ink flows steadily. When the ink flows steadily, water is more likely to evaporate, and the concentration of the circulating ink is more likely to increase. In order to suppress the increase in the ink concentration, it is preferable to provide the inkjet recording device with a mechanism that adds water to the ink after a certain period of time has elapsed. Furthermore, it is preferable to provide the inkjet recording device with a detector that detects the ink concentration, and add water to the ink in conjunction with the detected increase in the ink concentration.

[0044] FIG. 9 is a schematic diagram for explaining the flow state of ink in the vicinity of the ejection port. The flow state of ink in the vicinity of the ejection port is roughly divided into two types. The first type is a flow state in which no circulating flow occurs in the vicinity of the meniscus 12 of the ejection port 1 as shown in FIG. 9(a). The second type is a flow state in which a circulating flow occurs in the vicinity of the meniscus 12 of the ejection port 1 as shown in FIG. 9(b). Even if the flow speed of the ink in the flow path is the same, the flow state of the ink in the vicinity of the meniscus 12 may not be constant. It is considered that which flow state the ink will be in depends on the thickness (c) of the ejection port forming member 5, the height (d) of the flow path (first flow path 17 and second flow path 18), and the diameter (e) of the ejection port 1, rather than the flow speed of the ink in the flow path. For example, when the height (d) of the flow path and the diameter (e) of the ejection port 1 are the same, if the thickness (c) of the ejection port forming member 5 is large, a circulating flow is likely to occur in the vicinity of the meniscus 12 as shown in FIG. 9(b).

[0045] Next, a method for intermittently flowing ink will be described with reference to FIG. 10. FIG. 10 is a cross-sectional view partially showing an example of a recording head. As shown in FIG. 10, ink flowing in from an inlet 210 flows in the direction of the arrow by the action of a circulation pump 206, which is an ink flow means, and flows out from an outlet 214. The circulation pump 206 is a pump that can intermittently flow ink. Therefore, by driving the circulation pump 206, ink can be intermittently flowed between the ejection port 1 and the ejection element 4.

[0046] The inkjet recording apparatus of the present invention preferably includes a means for adjusting the temperature of the ink in the recording head. The inkjet recording method of the present invention may further include a step of heating the ink in the recording head. The temperature of the ink in the recording head can be adjusted, for example, by a means for controlling the temperature of the recording head. Examples of the means for controlling the temperature of the recording head include a heater for temperature adjustment provided in direct contact with the recording head and a heater for ink ejection. In order to control (heat or warm) the temperature of the recording head by the heater for ink ejection, for example, it is sufficient to repeatedly pass a current that does not eject ink. The temperature of the recording head and the ink in the recording head can be read, for example, by a temperature sensor provided in the recording head. The temperature of the ink in the recording head is preferably adjusted to a range of 40°C to 60°C.

[0047] When heating the inks, if the static surface tension γs1 of the first ink and the static surface tension γs2 of the second ink do not satisfy the relationship γs1<γs2, the viscosity of the ink decreases, which may slightly reduce the stability of the meniscus. This makes it easier for the ink to overflow from the ejection orifices due to inertia, which makes it easier for the position of the ruled lines to shift and the line width to vary. In contrast, if the static surface tension γs1 of the first ink and the static surface tension γs2 of the second ink satisfy the relationship γs1<γs2, the position of the ruled lines can be prevented from shifting and the line width can be prevented from varying.

[0048] In the inkjet recording method of the present invention, the scanning speed of the recording head when recording an image, i.e., the moving speed when the recording head scans, can be preferably 30 inches / second or more, more preferably 35 inches / second or more, from the viewpoint of increasing the recording speed. In addition, the moving speed when the recording head scans is preferably 70 inches / second or less. By making the moving speed when the recording head scans 70 inches / second or less, the inertial force when the recording head stops is suppressed, and ink is less likely to overflow from the ejection openings. As a result, it becomes easier to suppress the occurrence of misalignment of the ruled lines and variation in line width.

[0049] In the recording head used in the inkjet recording method of the present invention, the distance between the first and second ejection port arrays can be 1.8 mm or less. Another ejection port array may be arranged between the first and second ejection port arrays, or the first and second ejection port arrays may be adjacent to each other. If the distance between the ejection port arrays is short, the ejection port arrays can be arranged densely, which makes it easier to achieve miniaturization and high image quality. On the other hand, if the distance between the first and second ejection port arrays is 1.8 mm or less, the second ink ejected from the second ejection port array is easily affected by ink overflow from the ejection port due to inertial force. As a result, it is thought that the position of the ruled lines is easily shifted and the line width is easily varied, but the static surface tension γs1 of the first ink and the static surface tension γs2 of the second ink satisfy the relationship γs1<γs2, so that the position of the ruled lines is easily shifted and the line width is easily varied. The distance between the first and second ejection port rows is preferably 0.1 mm or more, and more preferably 0.5 mm or more.

[0050] The inkjet recording method of the present invention includes a step of recording an image using the inkjet recording device (recording step). Specifically, in the recording step, ink discharged from the discharge port of a recording head is applied to a recording medium to record an image. Any recording medium may be used as the target for recording an image. In particular, it is preferable to use permeable paper such as a recording medium without a coating layer, such as plain paper or uncoated paper, or a recording medium with a coating layer, such as glossy paper or art paper.

[0051] The inkjet recording method of the present invention may not have a step (heating step) of heating the recording medium to which the ink has been applied in the recording step. When the recording medium to which the ink has been applied is heated, the temperature inside the device body increases with the heating step, and it is considered that the evaporation of water from the meniscus of the recording head is likely to proceed. Therefore, the above heating step may not be performed in order to easily suppress the occurrence of misalignment of the ruled lines and variation in line width by reducing the influence of the temperature rise.

[0052] <Ink> The inkjet recording method and inkjet recording apparatus of the present invention include a process for recording an image by using a plurality of inks and applying the inks ejected from the ejection openings of a recording head to a recording medium. The plurality of inks (ink set) include a first ink ejected from an ejection opening array (first ejection opening array) on the upstream side in the ink flow direction, and a second ink ejected from an ejection opening array (second ejection opening array) on the downstream side. Furthermore, the static surface tension γs1 of the first ink and the static surface tension γs2 of the second ink satisfy the relationship γs1<γs2.

[0053] The static surface tension of the ink can be appropriately controlled by adjusting the type and amount of the surfactant and water-soluble organic solvent contained in the ink, which will be described later. The static surface tension of the ink may be adjusted by using a surfactant and a water-soluble organic solvent in combination. The static surface tension of the ink can be measured by a plate method using a platinum plate. In the examples described later, the static surface tension of the ink at 25° C. was measured using an automatic surface tensiometer (product name "CBVP-Z type", manufactured by Kyowa Interface Science Co., Ltd.).

[0054] In the range in which the static surface tension γs1 of the first ink and the static surface tension γs2 of the second ink satisfy the relationship γs1<γs2, the values ​​of γs1 and γs2 are preferably 24 mN / m or more and 42 mN / m or less. The difference between the static surface tensions of the first ink and the second ink (γs2-γs1) is preferably 3 mN / m or less, more preferably 2 mN / m or less, and more preferably exceeds 0 mN / m.

[0055] The components constituting the first ink and the second ink and the physical properties of the inks will be described in detail below.

[0056] (Colorant) The coloring material contained in the ink may be a pigment or a dye. Among them, a pigment is preferable. The content (mass %) of the coloring material in the ink is preferably 0.10 mass % or more and 15.00 mass % or less, and more preferably 0.30 mass % or more and 10.00 mass % or less, based on the total mass of the ink.

[0057] Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide, and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, dioxazine, etc. Of these, carbon black and organic pigments are preferred.

[0058] As a pigment dispersion method, resin-dispersed pigments using a resin as a dispersant, self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface, etc. can be used. In addition, resin-bonded pigments in which organic groups containing a resin are chemically bonded to the pigment particle surface, and microcapsule pigments in which the pigment particle surface is coated with a resin, etc. can be used. Among them, resin-dispersed pigments are more preferable from the viewpoint of ejection properties.

[0059] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin as described below, particularly a water-soluble resin, can be used. The content (mass%) of the pigment in the ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the content of the resin dispersant.

[0060] 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. Specific 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.

[0061] It is preferable to use a dye having an anionic group. Specific examples of the dye include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone dyes.

[0062] (resin) The ink may contain a resin. The content (mass %) of the resin in the ink is preferably from 0.10% to 20.00% by mass, and more preferably from 0.50% to 15.00% by mass, based on the total mass of the ink.

[0063] The 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, the resin can be added to the ink (ii) to improve various properties of the recorded image. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be resin particles that are dispersed in an aqueous medium. The resin particles do not need to encapsulate a colorant. When a resin is used as a dispersant for dispersing the pigment, it is preferable to further contain another resin in addition to the resin as the dispersant.

[0064] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali of equimolar amount 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. 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

[0065] 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.

[0066] The acid value of the water-soluble resin is preferably 100 mgKOH / g or more and 250 mgKOH / g or less. The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. In this specification, the acid value of the resin can be a value measured by a potentiometric titration device using a potassium hydroxide-methanol titrant. The weight average molecular weight of the water-soluble resin is preferably 3,000 or more and 15,000 or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 2,000,000 or less. In this specification, the weight average molecular weight of the resin can be measured as a polystyrene-equivalent value measured by gel permeation chromatography (GPC). The volume average particle diameter of the resin particles measured by dynamic light scattering is preferably 100 nm or more and 500 nm or less.

[0067] Examples of the resin include acrylic resins, urethane resins, olefin resins, etc. Among these, acrylic resins and urethane resins are preferred.

[0068] The acrylic resin preferably has a hydrophilic unit and a hydrophobic unit as constituent units. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer is preferred. In particular, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one of styrene and α-methylstyrene is preferred. These resins are easily interacted with pigments, and therefore can be suitably used as a resin dispersant for dispersing pigments.

[0069] The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of the hydrophilic monomer having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Examples of cations constituting the salts of acidic monomers include ions of lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit not having a hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer not having a hydrophilic group such as an anionic group. Specific examples of the hydrophobic monomer include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0070] The urethane resin can be obtained, for example, by reacting a polyisocyanate with a component that reacts with it (such as a polyol or a polyamine). In addition, it may be obtained by further reacting a crosslinking agent or a chain extender.

[0071] Polyisocyanates are compounds that have two or more isocyanate groups in their molecular structure. Examples of polyisocyanates that can be used include aliphatic polyisocyanates and aromatic polyisocyanates. Specific examples of aliphatic polyisocyanates include polyisocyanates having a chain structure such as tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene 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.

[0072] Specific 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.

[0073] A polyol can be used as a component that becomes a unit constituting a urethane resin by reacting with the above-mentioned polyisocyanate. In the present invention, the term "polyol" means a compound having two or more hydroxyl groups in the molecule. Specifically, polyols having no acid group, such as polyether polyol, polyester polyol, and polycarbonate polyol; polyols having an acid group; and the like can be mentioned.

[0074] Examples of polyols having no acid group include long-chain polyols having a number average molecular weight of about 450 to 4,000, such as polyether polyols, polyester polyols, and polycarbonate polyols.

[0075] Examples of polyols having an acid group include polyols containing an acid group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group in the structure. In particular, it is preferable to use a water-soluble urethane resin synthesized by further using a polyol having an acid group such as dimethylolpropionic acid or dimethylolbutanoic acid in addition to a polyol having no acid group. The acid group may be in the form of a salt. Examples of cations constituting the salt include ions of lithium, sodium, potassium, ammonium, and organic ammonium. When the water-soluble urethane resin has an acid group, it usually exhibits water solubility by neutralizing the acid group with a neutralizing agent such as a hydroxide of an alkali metal (lithium, sodium, potassium, etc.) or ammonia water.

[0076] 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".

[0077] 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.

[0078] Examples of olefin-based resins include α-olefin polymers such as polyethylene and polypropylene. The α-olefin polymers have α-olefin units such as ethylene units and propylene units as main constituent units. The α-olefin polymers may be homopolymers of ethylene or propylene, or may be copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene. Examples of copolymers include random copolymers, block copolymers, graft copolymers, and combinations of these copolymers.

[0079] [Resin particles] The ink preferably contains resin particles. By using an ink containing resin particles, the meniscus can be more stabilized. Resin particles have less entanglement between molecules, unlike water-soluble resins, and therefore tend to move quickly to the vicinity of the meniscus along with the flow of the ink. It is considered that the meniscus is stabilized by the interaction between the resin particles oriented in the vicinity of the meniscus, making it easier to suppress the overflow of ink from the ejection port due to inertial force, and easier to suppress the misalignment of the ruled lines and the variation in line width. Examples of the resin particles include acrylic resin particles, olefin resin particles, and urethane resin particles.

[0080] [Water-soluble urethane resin] The ink preferably contains a water-soluble urethane resin. Among water-soluble resins, water-soluble urethane resins rapidly interact with each other in the vicinity of the meniscus and form a stable molecular film. Therefore, by using an ink containing a water-soluble urethane resin, it becomes easier to prevent the ink from overflowing from the ejection port due to inertial force, and it becomes easier to prevent the positional deviation of the ruled lines and the variation in the line width.

[0081] [Block copolymer] The ink preferably contains a block copolymer. A block copolymer usually has a structure in which a plurality of blocks derived from monomers having the same or similar properties are arranged. Block copolymers generally used in aqueous inkjet inks have the following structures. For example, there is an AB block structure having a hydrophobic block (A block) and an ionic hydrophilic block (B block); an ABC block structure in which a nonionic hydrophilic block (C block) is further added to this AB block structure; and the like. That is, since the block copolymer has a structure in which the hydrophilic block and the hydrophobic block are each localized, it has high surface activity and is quickly oriented in the vicinity of the meniscus. For this reason, when an ink containing a block copolymer is used, the meniscus is stabilized, and it becomes easier to suppress the occurrence of ink overflowing from the ejection port due to inertial force, and it is easy to suppress the misalignment of the ruled lines and the variation in line width.

[0082] The block copolymer can be synthesized by a conventional synthesis method such as anionic living polymerization, cationic living polymerization, group transfer polymerization, atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization, etc. The block copolymer is preferably a water-soluble resin rather than a resin particle.

[0083] (Surfactant) The ink preferably contains a surfactant. The surfactant is oriented at the gas-liquid interface with the hydrophobic group facing the atmosphere and the hydrophilic group facing the ink, so that the meniscus can be further stabilized. Examples of the surfactant include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Among them, it is preferable to use a nonionic surfactant from the viewpoint of the reliability of the ink.

[0084] Examples of the nonionic surfactant include hydrocarbon surfactants such as ethylene oxide adducts of acetylene glycol and polyoxyethylene alkyl ethers, fluorine-based surfactants such as perfluoroalkyl ethylene oxide adducts, silicone surfactants such as polyether-modified siloxane compounds, etc. Among these, hydrocarbon surfactants are preferred, and ethylene oxide adducts of acetylene glycol are more preferred.

[0085] Among the ethylene oxide adducts of acetylene glycol, it is particularly preferable to use a compound represented by the following general formula (1). The first ink preferably contains a compound represented by the following general formula (1). The second ink may also contain a compound represented by the following general formula (1).

[0086] TIFF2024178107000001.tif63170 (in the general formula (1), x and y each independently represent a number of 0 or more, and x+y is 0 or more and 50 or less)

[0087] The compound represented by general formula (1) has a high orientation speed to the interface and can be quickly oriented to the meniscus. Therefore, even under conditions where the meniscus is likely to be drawn in, such as when the ink flow speed is high or the meniscus is greatly vibrated due to ejection, the meniscus can be stabilized. Therefore, it is easy to suppress the misalignment of the ruled line position and the variation in the line width. In general formula (1), x and y each independently represent a number of 0 or more, and are preferably 1 or more. In addition, in general formula (1), x+y is 0 or more and 50 or less, preferably 1 or more and 50 or less, and more preferably 1.3 or more and 10 or less. The content (mass %) of the compound represented by general formula (1) in the ink is preferably 0.05% by mass or more and 5.00% by mass or less, and more preferably 0.10% by mass or more and 3.00% by mass or less, based on the total mass of the ink.

[0088] (aqueous medium) The ink used in the inkjet recording method of the present invention is preferably an aqueous ink containing at least water as an aqueous medium. The ink may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As the water, deionized water or ion-exchanged water is preferably used. The content (mass%) of water in the aqueous ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink. In addition, the content (mass%) of the water-soluble organic solvent in the aqueous ink is preferably 3.00% by mass or more and 48.00% 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, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds, can be used.

[0089] The ink may contain a first water-soluble organic solvent having a relative dielectric constant of 15.0 or less at a temperature of 25° C. as the water-soluble organic solvent. The mass ratio of the content (mass%) of the first water-soluble organic solvent to the content (mass%) of all water-soluble organic solvents in the first ink is S1. The mass ratio of the content (mass%) of the first water-soluble organic solvent to the content (mass%) of all water-soluble organic solvents in the second ink is S2. In this case, it is preferable that the above ratios S1 and S2 of the first ink and the second ink satisfy the relationship S1>S2. The lower the relative dielectric constant of a water-soluble organic solvent, the higher its hydrophobicity tends to be. Therefore, the solubility and dispersion stability of the coloring material (pigment or dye) contained in the ink is likely to decrease in the water-soluble organic solvent with a lower relative dielectric constant. By satisfying S1>S2, when the first ink and the second ink are attached to a recording medium so that at least a part of them overlap, the coloring material in the upstream first ink is more likely to move to the dot side formed by the ink droplets of the downstream second ink, which has a lower ratio of the first water-soluble organic solvent. As a result, deviation in the position of the ruled lines and variation in line width can be further suppressed.

[0090] The relative dielectric constant of a water-soluble organic solvent or water can be measured using a dielectric constant meter (for example, a product name "BI-870" (manufactured by BROOKHAVEN INSTRUMENTS CORPORATION)) at a frequency of 10 kHz. In this specification, the relative dielectric constant is a value measured at 25°C. In the examples described later, the relative dielectric constant of a water-soluble organic solvent at 25°C was measured using the dielectric constant meter. The relative dielectric constant of a water-soluble organic solvent that is solid at 25°C is a value calculated from the following formula (2) by measuring the relative dielectric constant of a 50% by mass aqueous solution. Usually, the term "water-soluble organic solvent" refers to a liquid, but in the present invention, water-soluble organic solvents that are solid at 25°C (room temperature) are also included. ε sol =2ε 50% -ε water (2) ε sol : Dielectric constant of solid water-soluble organic solvent at 25℃ ε 50% : Relative dielectric constant of a 50% by mass aqueous solution of a solid water-soluble organic solvent at 25°C εwater : relative dielectric constant of water

[0091] Here, the reason for determining the relative permittivity of the water-soluble organic solvent that is solid at 25°C from the relative permittivity of a 50% by mass aqueous solution is as follows. Among the water-soluble organic solvents that are solid at 25°C and can be used as components of aqueous ink, there are some for which it is difficult to prepare a high-concentration aqueous solution exceeding 50% by mass. On the other hand, in an aqueous solution of a low concentration such as 10% by mass or less, the relative permittivity of water becomes dominant, and it is difficult to obtain a reliable (effective) value of the relative permittivity of the water-soluble organic solvent. As a result of the inventors' investigation, it was found that, among the water-soluble organic solvents that are solid at 25°C and can be used in ink, the aqueous solution to be measured can be prepared with almost any of them, and the obtained relative permittivity is consistent with the effect of the present invention. For these reasons, it was decided to use a 50% by mass aqueous solution. For water-soluble organic solvents that are solid at 25°C and cannot be prepared into a 50% by mass aqueous solution due to their low solubility in water, an aqueous solution of the saturated concentration is used, and the above ε sol For convenience, the value of the relative dielectric constant calculated in accordance with the case of determining

[0092] Examples of water-soluble organic solvents that are commonly used in aqueous inks and are solid at 25° C. include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol having a number average molecular weight of 1,000.

[0093] Specific examples of the first water-soluble organic solvent having a relative dielectric constant of 15.0 or less, with the relative dielectric constant at 25°C shown in parentheses, include 1,2-hexanediol (14.8), propylene glycol monomethyl ether (12.4), n-propanol (12.0), diethylene glycol monobutyl ether (11.0), triethylene glycol monobutyl ether (9.8), tetraethylene glycol monobutyl ether (9.4), ethylene glycol monobutyl ether (9.4), tripropylene glycol monomethyl ether (8.5), 1,6-hexanediol (7.1), and polyethylene glycol having a number average molecular weight of 600 or 1,000 (11.4, 4.6, respectively). The relative dielectric constant of the first water-soluble organic solvent is preferably 3.0 or more. These first water-soluble organic solvents having a relative dielectric constant of 15.0 or less can be used alone or in combination of two or more. In the present invention, the content of 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 ink is generally quite small, and the effect of the relative dielectric constant is also small.

[0094] Specific examples of the water-soluble organic solvent, including the first water-soluble organic solvent having a relative dielectric constant of 15.0 or less, include the following (the numbers in parentheses indicate the relative dielectric constant at 25°C): monohydric alcohols having 1 to 4 carbon atoms, such as methanol (33.1), ethanol (23.8), n-propanol (12.0), isopropanol (18.3), n-butanol, sec-butanol, and tert-butanol. Dihydric alcohols such as 1,2-propanediol (28.8), 1,2-butanediol (22.2), 1,3-butanediol (30.0), 1,4-butanediol (31.1), 1,5-pentanediol (27.0), 1,2-hexanediol (14.8), 1,6-hexanediol (7.1), 2-methyl-1,3-propanediol (28.3), 3-methyl-1,3-butanediol (24.0), 3-methyl-1,5-pentanediol (23.9), 2-ethyl-1,3-hexanediol (18.5), etc. Polyhydric alcohols such as 1,2,6-hexanetriol (28.5), glycerin (42.3), trimethylolpropane (33.7), trimethylolethane, etc. Alkylene glycols such as ethylene glycol (40.4), diethylene glycol (31.7), triethylene glycol (22.7), tetraethylene glycol (20.8), dipropylene glycol (19.7), butylene glycol, hexylene glycol, thiodiglycol, etc. Glycol ethers such as ethylene glycol monobutyl ether (9.4), diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (11.0), triethylene glycol monoethyl ether, triethylene glycol monobutyl ether (9.8), tetraethylene glycol monobutyl ether (9.4), propylene glycol monomethyl ether (12.4), tripropylene glycol monomethyl ether (8.5), etc. Polyalkylene glycols having a number average molecular weight of 200 to 1,000 such as polyethylene glycol having a number average molecular weight of 200 (18.9), polyethylene glycol having a number average molecular weight of 600 (11.5), polyethylene glycol having a number average molecular weight of 1,000 (4.6), polypropylene glycol, etc.Nitrogen-containing compounds such as 2-pyrrolidone (28.0), N-methyl-2-pyrrolidone (32.0), 1-(2-hydroxyethyl)-2-pyrrolidone (37.6), 1,3-dimethyl-2-imidazolidinone, N-methylmorpholine, 1-(hydroxymethyl)-5,5-dimethylhydantoin (23.7), 1,3-bis(2-hydroxyethyl)-5,5-dimethylhydantoin (16.0), urea (110.3), ethyleneurea (49.7), and triethanolamine (31.9). Sulfur-containing compounds such as dimethyl sulfoxide (48.9) and bis(2-hydroxyethylsulfone). As the water-soluble organic solvent to be contained in the ink, it is preferable to use one having a relative dielectric constant of 3.0 or more, 120.0 or less, and a vapor pressure at 25°C lower than that of water.

[0095] (Other additives) In addition to the above components, the ink may contain various additives, such as an antifoaming agent, other surfactants, a pH adjuster, a viscosity adjuster, an antirust agent, an antiseptic, an antifungal agent, an antioxidant, and an antireducing agent, as necessary.

[0096] (dynamic surface tension) Of the inks used in the inkjet recording method of the present invention, the first ink preferably has a dynamic surface tension of 36 mN / m or more at 10 milliseconds. By setting the dynamic surface tension of the first ink at 36 mN / m or more at 10 milliseconds, a sufficiently stable meniscus can be formed by capillary force. In addition, it is possible to reduce overflow of ink due to the inertial force acting when the recording head stops instantaneously when the circulating flow direction and the scanning direction are the same. This makes it possible to further suppress the shift in the position of the ruled lines and the variation in the line width. It is preferable that the dynamic surface tension of the first ink and the second ink at 10 milliseconds is 48 mN / m or less. By setting the dynamic surface tension at 10 milliseconds to 48 mN / m or less, the bleeding rate is unlikely to decrease, the droplets of the first ink and the second ink are likely to come into contact with each other on the recording medium, and it is easy to suppress the shift in the position of the ruled lines and the variation in the line width.

[0097] The dynamic surface tension of ink is measured by the maximum bubble pressure method. The maximum bubble pressure method measures the maximum pressure required to release bubbles generated at the tip of a probe (thin tube) immersed in the liquid to be measured, and calculates the surface tension of the liquid from the measured maximum pressure. Specifically, the maximum pressure is measured while continuously generating bubbles at the tip of the probe. The time from when a new bubble surface is generated at the tip of the probe to when the maximum bubble pressure (the point when the radius of curvature of the bubble is equal to the radius of the tip of the probe) is called the "lifetime". In other words, the maximum bubble pressure method is a method for measuring the surface tension of a liquid in a moving state. The dynamic surface tension of ink at 10 milliseconds can be easily adjusted by the type and content of the water-soluble organic solvent and surfactant.

[0098] (viscosity) The viscosity of the ink is preferably 3.0 mPa·s or more, and preferably 10.0 mPa·s or less. By making the ink viscosity 3.0 mPa·s or more, a stable meniscus can be formed, which makes it easier to prevent ink from overflowing from the ejection port due to inertial force, and makes it easier to suppress deviations in the position of the ruled lines and variations in line width. The viscosity of the ink can be measured using a rotational viscometer or the like.

[0099] The viscosity η1 of the first ink and the viscosity η2 of the second ink preferably satisfy the relationship η1<η2. By making the viscosity relationship between the first ink and the second ink η1<η2, the first ink on the upstream side can be more easily drawn into the dots formed by the ink droplets of the second ink on the downstream side, thereby further suppressing misalignment of the ruled lines and variations in line width. The difference in viscosity between the first ink and the second ink (η2-η1) is preferably 7.0 mPa s or less, and more preferably 4.0 mPa s or less. EXAMPLES

[0100] 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.

[0101] <Resin preparation> (Resin Dispersant) A styrene-ethyl acrylate-acrylic acid copolymer (water-soluble resin) with an acid value of 150 mgKOH / g and a weight-average molecular weight of 8,000 was prepared for use as a resin dispersant. 20.0 parts of the resin were neutralized with potassium hydroxide in an amount equal to the acid value, and an appropriate amount of pure water was added to prepare an aqueous solution of the resin dispersant with a resin (solid content) content of 20.00%.

[0102] (Acrylic resin) A water-soluble resin, styrene / acrylic acid copolymer (acid value 120 mgKOH / g, weight average molecular weight 8,000), was dissolved in ion-exchanged water containing potassium hydroxide in an amount equimolar to the acid value to prepare an aqueous solution of acrylic resin with a resin (solid content) content of 20.00%.

[0103] (urethane resin) A four-neck flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux tube was prepared. 29 parts of isophorone diisocyanate, 39 parts of polypropylene glycol having a number average molecular weight of 2,000, 12 parts of dimethylolpropionic acid, 0.02 parts of dibutyltin dilaurate, and 120 parts of methyl ethyl ketone were added to the flask. Then, the mixture was reacted at 80°C for 6 hours under a nitrogen gas atmosphere. Then, an appropriate amount of methanol was added, and the mixture was reacted at 80°C until the weight average molecular weight reached 12,000. After the reaction, the mixture 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. Methyl ethyl ketone was distilled off from the resin solution under heating and reduced pressure to prepare an aqueous solution of urethane resin having a resin (solid content) content of 20.00%.

[0104] (Aqueous dispersion of resin particles) 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. The mixture was emulsified by irradiating ultrasonic waves with an ultrasonic irradiator for 3 hours, and then polymerization reaction was carried out at 80°C for 4 hours under a nitrogen atmosphere. The reaction system was cooled to 25°C, filtered, and an appropriate amount of pure water was added to obtain an aqueous dispersion of resin particles with a resin particle content of 20.00%.

[0105] <Preparation of pigment dispersion> (Pigment dispersion 1) A mixture was obtained by mixing 10.0 parts of pigment (CI Pigment Blue 15:3), 15.0 parts of the aqueous solution of the resin dispersant prepared earlier, and 75.0 parts of pure water. The obtained mixture and 200 parts of zirconia beads with a diameter of 0.3 mm were placed in a batch-type vertical sand mill (manufactured by Imex), dispersed for 5 hours while cooling with water, and then centrifuged to remove coarse particles. The mixture was filtered under pressure with a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare pigment dispersion 1 with a pigment content of 10.00% and a resin dispersant (resin) content of 3.00%.

[0106] (Pigment dispersion 2) Except for changing the type of pigment to CI Pigment Red 122, the same procedure as for the above-mentioned Pigment Dispersion 1 was used to obtain Pigment Dispersion 2 having a pigment content of 10.00% and a resin dispersant (resin) content of 3.00%.

[0107] (Pigment dispersion 3) Except for changing the type of pigment to CI Pigment Yellow 74, the same procedure as for the above-mentioned Pigment Dispersion 1 was used to obtain Pigment Dispersion 3 having a pigment content of 10.00% and a resin dispersant (resin) content of 3.00%.

[0108] (Pigment Dispersion 4) The pigment type is carbon black (specific surface area 220 m 2 Pigment dispersion 4 with a pigment content of 10.00% and a resin dispersant (resin) content of 3.00% was obtained in the same manner as in Pigment Dispersion 1 described above, except that the DBP oil absorption was changed to 10.00% (10.00 mL / 100 g, and DBP oil absorption was 105 mL / 100 g).

[0109] (Pigment Dispersion 5) An appropriate amount of ion-exchanged water was added to a commercially available pigment dispersion (product name "CAB-O-JET250C", manufactured by Cabot) to prepare Pigment Dispersion 5 with a pigment content of 10.00%. The pigment in Pigment Dispersion 5 is a self-dispersing pigment in which sulfonic acid groups are bonded to the particle surface of the pigment (CI Pigment Blue 15:4) via benzene rings.

[0110] (Pigment Dispersion 6) An appropriate amount of ion-exchanged water was added to a commercially available pigment dispersion (product name "CAB-O-JET265M", manufactured by Cabot) to prepare Pigment Dispersion 6 with a pigment content of 10.00%. The pigment in Pigment Dispersion 6 is a self-dispersing pigment in which sulfonic acid groups are bonded to the particle surface of the pigment (CI Pigment Red 122) via benzene rings.

[0111] (Pigment Dispersion 7) An appropriate amount of ion-exchanged water was added to a commercially available pigment dispersion (product name "CAB-O-JET270Y", manufactured by Cabot) to prepare Pigment Dispersion 7 with a pigment content of 10.00%. The pigment in Pigment Dispersion 7 is a self-dispersing pigment in which sulfonic acid groups are bonded to the particle surface of the pigment (CI Pigment Yellow 74) via benzene rings.

[0112] (Pigment Dispersion 8) An appropriate amount of ion-exchanged water was added to a commercially available pigment dispersion (product name "CAB-O-JET200", manufactured by Cabot) to prepare pigment dispersion 8 with a pigment content of 10.00%. The pigment in pigment dispersion 8 is a self-dispersing pigment in which sulfonic acid groups are bonded to the particle surface of the pigment (carbon black) via benzene rings.

[0113] <Ink Preparation> Each ink was prepared by mixing the components (unit: %) shown in the upper part of Table 1 (Table 1-1 to Table 1-4), thoroughly stirring, and then filtering under pressure with a cellulose acetate filter (Advantec) with a pore size of 3.0 μm. "Acetylenol E60", "Acetylenol E100", and "Acetylenol E40" are the product names of surfactants manufactured by Kawaken Fine Chemicals, and the values ​​of "x+y" in the general formula (1) are "6", "10", and "4", respectively. "Zonyl FS-3100" is the product name of a fluorine-based nonionic surfactant manufactured by DuPont. The lower part of Table 1 shows the static surface tension (mN / m), dynamic surface tension at 10 milliseconds (mN / m), and viscosity η (mPa·s) of the ink. The lower part of Table 1 shows the content F (%) of the water-soluble organic solvent in the ink having a relative dielectric constant of 15.0 or less at a temperature of 25° C. (content of the first water-soluble organic solvent), the content T (%) of all water-soluble organic solvents, and the value of F / T (times). The static surface tension of the ink was measured at 25° C. using an automatic surface tensiometer (product name "CBVP-Z type", manufactured by Kyowa Interface Science Co., Ltd.). The dynamic surface tension of the ink was measured at 25° C. using a dynamic surface tensiometer (product name "BUBBLE PRESSURE TENSIOMETER BP-2", manufactured by KRUSS Co., Ltd.) using a maximum bubble pressure method. The viscosity of the ink was measured at 25° C. using an E-type viscometer (product name "RE-85L", manufactured by Toki Sangyo Co., Ltd.).

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[0118] <Evaluation> Using an inkjet recording device having the main parts shown in Fig. 2 and Fig. 3, the ink cartridge shown in Fig. 3 was filled with ink, and the following evaluations were performed in an environment of 25°C temperature and 50% relative humidity. A serial type recording head (circulating serial head) having the configuration shown in Fig. 4 was used as the recording head. This recording head has a first flow path and a second flow path that communicate between the ejection port and the ejection element for each ejection port, and uses a pump to make the ink in the first flow path flow to the second flow path. The number of ejection ports per ejection port array is 256, the ejection port density is 600 dpi, and the ink ejection amount per ejection port is 8 ng. The ruled lines recorded in the following evaluations were recorded using two ejection port arrays under the condition that ink droplets were applied dot-on-dot from each ejection port array in an area of ​​1 / 600 inch x 1 / 600 inch. The inks (ink set of the first ink and the second ink) and the nozzle rows (symbols in FIG. 4) used were recorded under the conditions described in Table 2 (Table 2-1 and Table 2-2). The presence or absence of a flow process (circulation flow) in the recording head, the ink flow speed, the scanning method, the scanning speed, the distance between the nozzle rows, and the presence or absence of heating of the ink in the recording head were recorded under the conditions described in Table 3 (Table 3-1 and Table 3-2). The ink in the recording head was heated so that the temperature of the ink was 40° C. Furthermore, a preliminary ejection operation was not performed outside the recording medium area of ​​the recording head. Furthermore, a heating process was not performed on the recording medium to which the ink was applied. Table 2 also shows the magnitude relationship between the static surface tension γs1 of the first ink and the static surface tension γs2 of the second ink, and the magnitude relationship between the viscosity η1 of the first ink and the viscosity η2 of the second ink. In addition, Table 2 also shows the magnitude relationship between the ratio S1 of the content of the first water-soluble organic solvent to the total content of water-soluble organic solvents in the first ink and the ratio S2 of the content of the first water-soluble organic solvent to the total content of water-soluble organic solvents in the second ink.

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[0123] (Line stability) Using the above inkjet recording device, the recording head was scanned back and forth to record "Pattern 1" shown in FIG. 11, which has ruled lines in the same direction as the nozzle row direction at both ends of the recording medium and a solid area in the center, using the first and second inks in one pass. The solid area was recorded using two nozzle rows, with one ink droplet applied from each nozzle row to a unit area of ​​1 / 600 inch x 1 / 600 inch. The recording medium used was "High-quality dedicated paper HR-101SA4" (Canon). One day after recording, the line widths of the ruled lines recorded at the end of the recording medium on the home position side by the third return pass of the recording head and the ruled lines recorded at the end of the recording medium on the home position side by the forward pass immediately thereafter were measured using an image evaluation device. The image evaluation device used was "Personal IAS" (QEA, product name). From the measured line widths of the ruled lines, the line width ratio = (line width of the ruled line recorded in the forward direction) / (line width of the ruled line recorded in the reverse direction) was calculated. The calculated line width ratio and the positions of the ruled lines recorded in the forward direction and the ruled lines recorded in the reverse direction were visually confirmed to evaluate the ruled line stability according to the evaluation criteria shown below. In the present invention, in the evaluation criteria shown below, "AA", "A", and "B" were defined as acceptable levels, and "C" and "D" were defined as unacceptable levels. The results are shown in Table 4. The AA:linewidth ratio was less than 1.05. A: The line width ratio was 1.05 or more and less than 1.10. B: The line width ratio was 1.10 or more and less than 1.15. C: The line width ratio was 1.10 or more and less than 1.15, and a misalignment between the ruled lines recorded in the forward direction and the ruled lines recorded in the backward direction was visually confirmed. D: The line width ratio was 1.15 or more, and the positional deviation between the ruled lines recorded in the forward direction and the ruled lines recorded in the backward direction was visually confirmed.

[0124] (Discharge stability) Using the above inkjet recording device, the recording head was scanned back and forth to record "Pattern 2" having ruled lines in the same direction as the ejection port array direction at both ends of the recording medium shown in FIG. 11 using the first and second inks in one pass. As the recording medium, "High-quality dedicated paper HR-101SA4" (manufactured by Canon) was used. The recorded ruled lines were visually confirmed and the ejection stability was evaluated according to the following evaluation criteria. In the present invention, in the following evaluation criteria, "A" and "B" were defined as acceptable levels and "C" was defined as unacceptable levels. The results are shown in Table 4. A: There was no irregularity or non-discharge in any of the ruled lines. B: The ruled lines at the bottom edge of the recording medium were slightly disturbed, but there was no non-ejection. C: Disorders or non-ejection occurred in the ruled lines below halfway across the recording medium.

[0125] TIFF2024178107000010.tif157170

[0126] In the evaluation of the ruled line stability, it was visually confirmed that the ruled lines recorded in the forward direction were misaligned toward the home position with respect to the ruled lines recorded in the backward direction in Comparative Examples 1 to 4. Moreover, in all the Examples and Comparative Examples, no misalignment occurred in the ruled lines on the side opposite the home position.

[0127] Comparative Examples 5 to 7 are examples in which recording was performed under conditions in which a flow process, separate from the ejection process, in which the ink in the first flow path is caused to flow to the second flow path is not performed. In this case, since there is no reference ink flow direction, "first" and "second" are not defined for the ejection port array and the ink, but for convenience, the ejection port array and the ink are assigned as shown in Table 2. In Comparative Examples 5 to 7, since the ink is not circulated, it is considered that even if the recording head is reciprocated to record an image, no deviation in the position of the ruled line at the end of the recording medium or variation in the line width does not occur. However, the ejection stability was insufficient, and a preliminary ejection operation was required. Reference Example 1 is an example in which a line-type recording head equivalent to the width of the recording medium is used as the recording head. In Reference Example 1, since an image is recorded without reciprocating the recording head, it is considered that no deviation in the position of the ruled line at the end of the recording medium or variation in the line width does not occur. In Reference Example 1, the recording head is larger than a serial-type recording head, and the recording device cannot be made smaller.

[0128] The disclosure of this embodiment includes the following methods and configurations. (Method 1) An inkjet recording method for recording an image by ejecting ink from a recording head including a plurality of ejection ports for ejecting ink, ejection elements for generating energy for ejecting the ink, and first and second flow paths communicating between the ejection ports and the ejection elements and through which the ink flows, comprising: a discharge step of discharging the ink from the discharge port; a flowing step, separate from the ejection step, for causing the ink in the first flow path to flow into the second flow path, the print head is a serial print head that includes an ejection element substrate having a plurality of ejection port arrays in which the plurality of ejection ports are arranged in a predetermined direction, and that scans in a direction intersecting the arrangement direction of the ejection port arrays, the first flow path and the second flow path are arranged parallel to a scanning direction of the recording head, and the ink flows in the same direction; the plurality of ejection port arrays include a first ejection port array that ejects a first ink and a second ejection port array that ejects a second ink, the first ejection port array being disposed on an upstream side and the second ejection port array being disposed on a downstream side with respect to a flow direction of the ink, an ink jet recording method, wherein a static surface tension γs1 of the first ink and a static surface tension γs2 of the second ink satisfy the relationship γs1<γs2; (Method 2) The inkjet recording method according to Method 1, wherein the first ink has a dynamic surface tension of 36 mN / m or more at 10 milliseconds. (Method 3) The ink jet recording method according to Method 1 or 2, in which the viscosity η1 of the first ink and the viscosity η2 of the second ink satisfy the relationship η1<η2. (Method 4) The inkjet recording method according to any one of Methods 1 to 3, wherein the first ink contains a compound represented by the following general formula (1):

[0129] TIFF2024178107000011.tif63170 (In the general formula (1), x and y each independently represent a number of 0 or more, and x+y is 0 or more and 50 or less.)

[0130] (Method 5) The ink contains a first water-soluble organic solvent having a relative dielectric constant of 15.0 or less at a temperature of 25° C., The inkjet recording method according to any one of Methods 1 to 4, wherein a ratio S1 of the content (mass%) of the first water-soluble organic solvent to the content (mass%) of all water-soluble organic solvents in the first ink and a ratio S2 of the content (mass%) of the first water-soluble organic solvent to the content (mass%) of all water-soluble organic solvents in the second ink satisfy the relationship S1>S2. (Method 6) The inkjet recording method according to any one of Methods 1 to 5, further comprising the step of heating the ink in the recording head. (Method 7) The inkjet recording method according to any one of Methods 1 to 6, wherein the moving speed of the recording head during the scanning is 70 inches / second or less. (Method 8) The inkjet recording method according to any one of Methods 1 to 7, wherein the flow velocity of the ink during the flow is 1.0 mm / s or more and 100.0 mm / s or less. (Method 9) The inkjet recording method according to any one of Methods 1 to 8, wherein the distance between the first ejection port row and the second ejection port row is 1.8 mm or less. (Configuration 1) An inkjet recording device including a recording head having a plurality of ejection ports for ejecting ink, ejection elements for generating energy for ejecting the ink, and first and second flow paths communicating between the ejection ports and the ejection elements and through which the ink flows, a flow means for causing the ink in the first flow path to flow into the second flow path, the flow means being separate from the ejection element; the print head is a serial print head that includes an ejection element substrate having a plurality of ejection port arrays in which the plurality of ejection ports are arranged in a predetermined direction, and that scans in a direction intersecting the arrangement direction of the ejection port arrays, the first flow path and the second flow path are arranged parallel to a scanning direction of the recording head, and the ink flows in the same direction; the plurality of ejection port arrays include a first ejection port array that ejects a first ink and a second ejection port array that ejects a second ink, the first ejection port array being disposed on an upstream side and the second ejection port array being disposed on a downstream side with respect to a flow direction of the ink, The static surface tension γs1 of the first ink and the static surface tension γs2 of the second ink are γs1 <γs2の関係を満たすことを特徴とするインクジェット記録装置。(Configuration 2) An ink set including a first ink and a second ink for use in an inkjet recording method for recording an image by ejecting the ink from a recording head including a plurality of ejection ports for ejecting ink, an ejection element for generating energy for ejecting the ink, and a first flow path and a second flow path communicating between the ejection ports and the ejection elements and through which the ink flows, the inkjet recording method includes a discharge step of discharging the ink from the discharge port, and a flow step, which is separate from the discharge step, of causing the ink in the first flow path to flow into the second flow path, the print head is a serial print head that includes an ejection element substrate having a plurality of ejection port arrays in which the plurality of ejection ports are arranged in a predetermined direction, and that scans in a direction intersecting the arrangement direction of the ejection port arrays, the first flow path and the second flow path are arranged parallel to a scanning direction of the recording head, and the ink flows in the same direction; the plurality of ejection opening arrays include a first ejection opening array that ejects the first ink and a second ejection opening array that ejects the second ink, the first ejection opening array being disposed on an upstream side and the second ejection opening array being disposed on a downstream side with respect to a flow direction of the ink, The static surface tension γs1 of the first ink and the static surface tension γs2 of the second ink are γs1

Claims

1. An inkjet recording method for recording an image by ejecting ink from a recording head including a plurality of ejection ports for ejecting ink, ejection elements for generating energy for ejecting the ink, and first and second flow paths communicating between the ejection ports and the ejection elements and through which the ink flows, comprising: a discharge step of discharging the ink from the discharge port; a flowing step, separate from the ejection step, for causing the ink in the first flow path to flow into the second flow path, the print head is a serial print head that includes an ejection element substrate having a plurality of ejection port arrays in which the plurality of ejection ports are arranged in a predetermined direction, and that scans in a direction intersecting the arrangement direction of the ejection port arrays, the first flow path and the second flow path are arranged parallel to a scanning direction of the recording head, and the ink flows in the same direction; the plurality of ejection opening arrays include a first ejection opening array that ejects a first ink and a second ejection opening array that ejects a second ink, the first ejection opening array being disposed on an upstream side and the second ejection opening array being disposed on a downstream side with respect to a flow direction of the ink, The static surface tension γs of the first ink １ and the static surface tension γs of the second ink ２ But, γs １ <γs ２ The ink jet recording method according to the present invention is characterized in that the above relationship is satisfied.

2. 2. The ink jet recording method according to claim 1, wherein the first ink has a dynamic surface tension of 36 mN / m or more at 10 milliseconds.

3. The viscosity η of the first ink １ and the viscosity η of the second ink ２ And, η １ <η ２ The ink jet recording method according to claim 1 , wherein the following relationship is satisfied:

4. The inkjet recording method according to claim 1 , wherein the first ink contains a compound represented by the following general formula (1): (In the general formula (1), x and y each independently represent a number of 0 or more, and x+y is 0 or more and 50 or less.)

5. the ink contains a first water-soluble organic solvent having a relative dielectric constant of 15.0 or less at a temperature of 25° C.; The ratio S of the content (mass%) of the first water-soluble organic solvent to the content (mass%) of the entire water-soluble organic solvent in the first ink １ and a ratio S of the content (mass%) of the first water-soluble organic solvent to the content (mass%) of the entire water-soluble organic solvent in the second ink. ２ But, S １ >S ２ The ink jet recording method according to claim 1 , wherein the following relationship is satisfied:

6. 2. The ink jet recording method according to claim 1, further comprising the step of heating the ink in the recording head.

7. 2. The ink jet recording method according to claim 1, wherein the moving speed of the recording head during the scanning is 70 inches / second or less.

8. 2. The ink jet recording method according to claim 1, wherein the flow velocity of the ink during the flow is 1.0 mm / s or more and 100.0 mm / s or less.

9. 2. The ink jet recording method according to claim 1, wherein the distance between the first ejection port array and the second ejection port array is 1.8 mm or less.

10. An inkjet recording apparatus including a recording head having a plurality of ejection ports for ejecting ink, ejection elements for generating energy for ejecting the ink, and first and second flow paths communicating between the ejection ports and the ejection elements and through which the ink flows, a flow means for causing the ink in the first flow path to flow into the second flow path, the flow means being separate from the ejection element; the print head is a serial print head that includes an ejection element substrate having a plurality of ejection port arrays in which the plurality of ejection ports are arranged in a predetermined direction, and that scans in a direction intersecting the arrangement direction of the ejection port arrays, the first flow path and the second flow path are arranged parallel to a scanning direction of the recording head, and the ink flows in the same direction; the plurality of ejection opening arrays include a first ejection opening array that ejects a first ink and a second ejection opening array that ejects a second ink, the first ejection opening array being disposed on an upstream side and the second ejection opening array being disposed on a downstream side with respect to a flow direction of the ink, The static surface tension γs of the first ink １ and the static surface tension γs of the second ink ２ But, γs １ <γs ２ The ink jet recording apparatus is characterized in that the above relationship is satisfied.

11. an ink set including a first ink and a second ink for use in an inkjet recording method, which records an image by ejecting the ink from a recording head including a plurality of ejection ports for ejecting ink, ejection elements for generating energy for ejecting the ink, and first and second flow paths communicating between the ejection ports and the ejection elements and through which the ink flows, the ink jet recording method includes a discharge step of discharging the ink from the discharge port, and a flow step, which is separate from the discharge step, of causing the ink in the first flow path to flow into the second flow path, the print head is a serial print head that includes an ejection element substrate having a plurality of ejection port arrays in which the plurality of ejection ports are arranged in a predetermined direction, and that scans in a direction intersecting the arrangement direction of the ejection port arrays, the first flow path and the second flow path are arranged parallel to a scanning direction of the recording head, and the ink flows in the same direction; the plurality of ejection opening arrays include a first ejection opening array that ejects the first ink and a second ejection opening array that ejects the second ink, the first ejection opening array being disposed on an upstream side and the second ejection opening array being disposed on a downstream side with respect to a flow direction of the ink, The static surface tension γs of the first ink １ and the static surface tension γs of the second ink ２ But, γs １ <γs ２ The ink set is characterized in that the following relationship is satisfied:

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