Ink filling method, inkjet recording method, inkjet recording device, and aqueous ink

Abstract

To provide an ink filling method capable of preparing an inkjet recording device excellent in discharge stability of ink, while having an ink circulation type recording head.SOLUTION: An ink filling method initially fills an ink supply system having a recording head 1 having a discharge port 13, a pressure chamber 12 communicating with the discharge port 13, a discharge element 15, and a first flow channel 130 and a second flow channel 140 connected to a pressure chamber 13 in an inkjet recording device, with aqueous ink having an amount of dissolved oxygen of 3.0 mg / L or less, from an ink storage body storing the aqueous ink. A layer contacting the aqueous ink of the ink storage body is formed of a resin, a difference between an average SP value of a water-soluble organic solvent in the aqueous ink and an SP value of a resin forming the layer of the ink storage body is 6.5 (cal / cm3)1 / 2 or less, and surface tension at 25°C of the aqueous ink is 25 mN / m or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, the use of inkjet recording devices has been increasing in the fields of office recording and commercial recording. Also, in order to cope with the trend of high ink viscosity, there is a demand for technology to further improve the ink ejection stability. However, in conventional inkjet recording devices, when the period during which ink is not ejected from the ejection ports (non-use period) becomes long, the ink gradually solidifies, which can affect the ink ejection properties.

[0003] In order to address these issues, an inkjet recording device equipped with a recording head of a so-called ink circulation system has been proposed. For example, an ink circulation type recording head has been proposed that has ejection ports, ejection elements, and first and second flow paths that communicate between the ejection ports and the ejection elements and through which ink flows (Patent Document 1). This recording head has a flow means that is separate from the ejection elements and that causes the ink in the first flow path to flow to the second flow path.

[0004] In addition, in conventional inkjet recording devices, when ink is initially filled from an ink container such as an ink bottle or ink cartridge at the start of use, air bubbles are generated in the filled ink and tend to adhere to the inner surfaces of the ink container and the components in the ink supply system. If these air bubbles circulate through the ink supply system and are supplied to the recording head, this causes irregular or non-ejection of the ink. In order to suppress the generation of air bubbles due to such initial filling, it is effective to use an ink container that contains ink in which the amount of dissolved gas has been reduced as much as possible in advance by performing a degassing process such as heating or reducing pressure. For example, a method has been proposed in which dissolved gas in ink is removed by using a gas-permeable membrane (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-014238 A [Patent Document 2] Japanese Patent Application Publication No. 5-017712 Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors prepared an inkjet recording apparatus in which an ink supply system having an ink circulation type recording head proposed in Patent Document 1 was initially filled with degassed ink, and investigated its characteristics. As a result, it was found that, despite the initial filling with degassed ink, air bubbles were generated in the ink supply system, and the generated air bubbles reached the ejection orifices, causing new problems such as ink non-ejection.

[0007] Therefore, an object of the present invention is to provide an ink filling method capable of preparing an inkjet recording device having excellent ink ejection stability even while having an ink circulation type recording head. Another object of the present invention is to provide an inkjet recording method having excellent ink ejection stability even while using an inkjet recording device having an ink circulation type recording head. Still another object of the present invention is to provide an inkjet recording device and an aqueous ink for use in this inkjet recording method. [Means for solving the problem]

[0008] That is, according to the present invention, there is provided an ink filling method for initially filling an ink supply system of an inkjet recording apparatus having a recording head including: an ejection port for ejecting an inkjet water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; a first flow path connecting with the pressure chamber; and a second flow path connecting with the pressure chamber at a position opposite to the first flow path with the ejection element therebetween, the ink supply system comprising: an ink container containing the water-based ink having a dissolved oxygen content of 3.0 mg / L; the water-based ink contains a pigment and a water-soluble organic solvent; a layer of the ink container that comes into contact with the water-based ink is formed of a resin; and the difference between an average SP value of the water-soluble organic solvent and an SP value of the resin forming the layer of the ink container is 6.5 (cal / cm 3 ) 1 / 2 and the surface tension of the water-based ink at 25° C. is 25 mN / m or more. Effect of the Invention

[0009] According to the present invention, it is possible to provide an ink filling method that makes it possible to prepare an inkjet recording device that has excellent ink ejection stability even while having an ink circulation type recording head. Also, according to the present invention, it is possible to provide an inkjet recording method that has excellent ink ejection stability even while using an inkjet recording device that has an ink circulation type recording head. Furthermore, according to the present invention, it is possible to provide an inkjet recording device and an aqueous ink used in this inkjet recording method. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram illustrating an example of a recording head. [Diagram 2] 1 is a perspective view illustrating an embodiment of an inkjet recording apparatus of the present invention. [Diagram 3]1 is a schematic diagram illustrating an internal configuration of an embodiment of an inkjet recording apparatus of the present invention. [Figure 4] 5A and 5B are schematic diagrams illustrating an example of the state of ink in an ink container and an ink supply system. [Diagram 5] 5A and 5B are schematic diagrams illustrating an example of the state of ink in an ink container and an ink supply system. [Figure 6] FIG. 2 is a cross-sectional view illustrating an example of an ink container. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the aqueous ink in the form of dissociation into ions, but for convenience, it is expressed as "containing a salt." In addition, aqueous ink for inkjet printing may be simply referred to as "ink." Physical property values ​​are values ​​at room temperature (25°C) unless otherwise specified.

[0012] When ink that has been degassed and has a low dissolved oxygen content is used, even if air bubbles are generated in the ink during initial filling, the generated air bubbles are easily absorbed by the ink. In the case of a non-ink circulation type recording head, as shown in FIG. 4(a), most of the air bubbles 34 that grow on the surface of the resin member 32 that forms the layer of the ink container are absorbed by the ink 30 that has a low dissolved oxygen content. For this reason, ink non-ejection is unlikely to occur, and the ink ejection stability is unlikely to decrease. In contrast, in the case of an ink circulation type recording head, as shown in FIG. 4(b), among the air bubbles that grow on the surface of the resin member 32, some of the air bubbles 44 that are not absorbed by the ink reach the ink flow path 40 that communicates with the ejection port. Then, while the ink circulates in the ink flow path 38 of the recording head, the air bubbles 44 accumulate in the ink flow path 40, which greatly affects the ink ejection stability. Thus, when an inkjet recording device equipped with an ink circulation type recording head is used, it is considered that ink non-ejection is likely to occur even if ink that has been degassed and has a low dissolved oxygen content is used.

[0013] The present inventors have conducted research to improve the ejection stability of ink by suppressing the generation of air bubbles when ink is initially filled from an ink container into an ink supply system. As a result, they have found that it is important to satisfy the following requirements (i) to (v), and have arrived at the present invention. (i) The ink supply system is initially filled with water-based ink from an ink container that contains water-based ink with a dissolved oxygen content of 3.0 mg / L or less. (ii) The water-based ink contains a pigment and a water-soluble organic solvent. (iii) The layer of the ink container that comes into contact with the water-based ink is made of a resin. (iv) The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the layer of the ink container is 6.5 (cal / cm 3 ) 1 / 2 The following is the result. (v) The surface tension of the water-based ink at 25°C is 25 mN / m or more.

[0014] The SP value is a physical property value generally used as an index of compatibility of a two-component solution. The smaller the difference in SP value between the components, the greater the mutual solubility (affinity). When the above relationship (iv) is satisfied, the mutual affinity is good, and the wettability of the ink to the resin forming the innermost layer (contact surface with the ink) of the ink container is increased. For this reason, as shown in FIG. 5(a), air bubbles 34 formed by air that has permeated into the ink container are less likely to adhere to the resin member 32, and the air bubbles 34 do not grow and are absorbed into the ink 30, which has a small amount of dissolved oxygen. As a result, as shown in FIG. 5(b), even if the ink circulates in the ink flow path 38 of the recording head, air bubbles are less likely to accumulate in the ink flow path 40, and the ink ejection stability is improved.

[0015] Generally, the greater the surface tension (interfacial tension) of the components that make up the ink supply system, the faster the ink will wet those components. When the ink wets the components of the ink supply system faster, air bubbles formed by the air that has permeated those components are less likely to adhere to the inner surfaces of those components. For this reason, the air bubbles do not grow but are detached and are absorbed by the ink with a low amount of dissolved oxygen. As a result, it is believed that the generation of air bubbles in the ink supply system during initial filling is suppressed, improving the ink ejection stability.

[0016] "Initial filling" means filling the ink supply system with ink when a user first uses an inkjet recording device after manufacture. In other words, by satisfying the above requirements (i) to (v) under the condition where ink first comes into contact with the ink supply system (from the ink container to the recording head) of the inkjet recording device, the effect of improving the ejection stability of the ink can be obtained. In other words, the above requirements (i) to (v) are particularly effective conditions for initial filling. If the ink supply system is not initially filled with ink, the amount of dissolved oxygen in the ink gradually increases as air permeates through the members constituting the ink supply system and mixes with the ink. Then, a part of the air that is not absorbed by the ink forms air bubbles 44 and reaches the ink flow path 40 that communicates with the ejection port. Then, while the ink circulates in the ink flow path 38 of the recording head, the air bubbles 44 accumulate in the ink flow path 40, which greatly affects the ejection stability of the ink. In this way, if the ink supply system is not initially filled with ink, it is considered that ink non-ejection is likely to occur even if the above requirements (i) to (v) are satisfied.

[0017] <Ink filling method, inkjet recording method, inkjet recording apparatus, and water-based ink> The ink filling method of the present invention is a method for initially filling an ink supply system of an inkjet recording device having an ink supply system with a recording head having a specific configuration with water-based ink from an ink container that contains water-based ink with a dissolved oxygen content of 3.0 mg / L or less. The recording head is equipped with an ejection port for ejecting the water-based ink, a pressure chamber communicating with the ejection port, an ejection element, a first flow path, and a second flow path. The ejection element is an element that is disposed in the pressure chamber and generates energy for ejecting the water-based ink from the ejection port. The first flow path is a flow path for the water-based ink that is connected to the pressure chamber. The second flow path is a flow path for the water-based ink that is connected to the pressure chamber at a position opposite to the first flow path with the ejection element in between. The water-based ink contains a pigment and a water-soluble organic solvent, and the layer of the ink container that comes into contact with the water-based ink is formed of a resin. The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin that forms the innermost layer of the ink container is 6.5 (cal / cm 3 ) 1 / 2 and the surface tension of the water-based ink at 25° C. is 25 mN / m or more.

[0018] The inkjet recording method of the present invention uses an inkjet recording device that includes an ink supply system having a recording head with a specific configuration, and the ink supply system is initially filled with water-based ink. The inkjet recording method then records an image by applying the water-based ink ejected from the ejection ports to a recording medium. The ink supply system is initially filled with water-based ink from an ink container that contains water-based ink having a dissolved oxygen content of 3.0 mg / L or less. The water-based ink contains a pigment and a water-soluble organic solvent, and the layer of the ink container that comes into contact with the water-based ink is formed of a resin. The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin that forms the innermost layer of the ink container is 6.5 (cal / cm 3 ) 1 / 2 and the surface tension of the water-based ink at 25° C. is 25 mN / m or more.

[0019] Furthermore, the inkjet recording device of the present invention is a device equipped with an ink supply system having a recording head with a specific configuration, and in which the supply system is initially filled with water-based ink from an ink container that contains water-based ink with a dissolved oxygen content of 3.0 mg / L or less. The recording head is equipped with an ejection port for ejecting the water-based ink, a pressure chamber communicating with the ejection port, an ejection element, a first flow path, and a second flow path. The ejection element is an element that is disposed in the pressure chamber and generates energy for ejecting the water-based ink from the ejection port. The first flow path is a flow path for the water-based ink that is connected to the pressure chamber. The second flow path is a flow path for the water-based ink that is connected to the pressure chamber at a position opposite to the first flow path across the ejection element. The water-based ink contains a pigment and a water-soluble organic solvent, and the layer of the ink container that comes into contact with the water-based ink is formed of a resin. The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin that forms the innermost layer of the ink container is 6.5 (cal / cm 3 ) 1 / 2 and the surface tension of the water-based ink at 25° C. is 25 mN / m or more.

[0020] The water-based ink of the present invention is used in an inkjet recording method using an inkjet recording device having an ink supply system with a recording head having a specific configuration, the ink supply system of which is initially filled with the water-based ink. The inkjet recording method is a method for recording an image by applying water-based ink ejected from an ejection port to a recording medium. The ink supply system is initially filled with the water-based ink from an ink container that contains the water-based ink having a dissolved oxygen content of 3.0 mg / L or less. The water-based ink contains a pigment and a water-soluble organic solvent, and the layer of the ink container that comes into contact with the water-based ink is formed of a resin. The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin that forms the innermost layer of the ink container is 6.5 (cal / cm 3 ) 1 / 2 and the surface tension of the water-based ink at 25° C. is 25 mN / m or more.

[0021] (Inkjet recording device) FIG. 2 is a perspective view showing a schematic diagram of an embodiment of an inkjet recording apparatus according to the present invention. As shown in FIG. 2, a feeding unit 20 of a recording apparatus 1000 can hold a plurality of recording media, and feeds the recording media by a feeding roller (not shown). A recording medium 601 (FIG. 3) is described as a cut sheet cut to a predetermined size, but the present invention is not limited to this, and can also be applied to a form in which recording is performed on rolled paper. The recording medium fed by the feeding unit 20 is transported in the Y direction (transport direction) by a transport unit including a transport roller (not shown), and moves to a recording position facing a recording head 200 (FIG. 3(b)) that ejects ink. A carriage 100 carries the recording head 200, and is driven by a carriage motor 4 to reciprocate along a guide shaft 3 via a timing belt 2 in an X direction (main scanning direction) that intersects with the Y direction.

[0022] When an image for a unit area is recorded by the movement of the carriage 100 in the X direction and the ink ejection operation of the print head 200, the print medium is transported in the Y direction by the transport unit. The unit area can be arbitrarily set, such as the arrangement width of the ejection port array arranged along the Y direction in the print head 200, "one band" that can be recorded by one movement of the print head 200 in the X direction, or "one pixel" corresponding to the resolution of the print head. In the serial method, an image can be recorded over the entire print medium by a printing operation that repeats the ink ejection operation for one band and the intermittent transport operation of the print medium. In this embodiment, the X direction and the Y direction are perpendicular to each other.

[0023] A platen 10 that supports the recording medium from below in the vertical direction is disposed in a position facing the recording head 200 and in a recording area where recording is performed by the recording head 200. The platen 10 maintains a predetermined distance between the recording surface of the recording medium and the ejection port surface of the recording head 200, on which the ejection ports for ejecting ink are arranged.

[0024] Fig. 3 is a schematic diagram showing the internal configuration of an embodiment of an inkjet recording apparatus 1000 of the present invention. Fig. 3(a) is a schematic top view of the recording apparatus 1000 (Fig. 2) seen from above, and Fig. 3(b) is a schematic side view of the recording apparatus 1000 (Fig. 2) seen from the front. The carriage 100 removably mounts ink cartridges that contain ink to be supplied to the recording head 200. The ink cartridges 211 to 214 supply ink to their respective ejection port rows.

[0025] Furthermore, within the movement area of ​​the carriage 100, outside the area (printing area) through which the printing medium 601 passes, a cap 302 for capping the ejection port surface of the print head 200 is disposed. The position of the carriage 100 (print head 200) where the ejection port surface of the print head 200 faces the cap 302 is also referred to as the home position 301. The cap 302 is connected to suction means (not shown), and ink is sucked from the print head 200 by driving the suction means with the ejection port surface capped.

[0026] (Recording head) The circulation of ink in the recording head 1 will be described with reference to FIG. 1. In one circulation unit 54 corresponding to one type of ink applied to the recording apparatus of this embodiment, a filter 110, a first pressure adjustment means 120, a second pressure adjustment means 150, and a circulation pump 500 are arranged. These components are connected by respective flow paths as shown in FIG. 1, and constitute a circulation path for supplying and recovering ink to the ejection module 300 in the recording head 1. FIG. 1 shows a schematic diagram of the flow of ink during a recording operation in which ink is ejected from an ejection port 13 provided at a position opposite to an ejection element 15 arranged in a pressure chamber 12 to record an image. The arrows in the figure indicate the flow of ink. In this embodiment, when a recording operation is performed, both an external pump (not shown) and a circulation pump 500 start to operate. The external pump and the circulation pump 500 may be operated regardless of the recording operation. The external pump and the circulation pump 500 may not be operated in conjunction with each other, and may be operated independently.

[0027] The first pressure adjustment means 120 is disposed in connection with the first flow path 130, and is a means for adjusting the pressure applied to supply ink from the first flow path 130 to the pressure chamber 12. The circulation pump 500 is a pump capable of supplying ink from the first pressure adjustment means 120 into the pressure chamber 12 via the first flow path 130, and of pumping ink so as to recover the ink in the pressure chamber 12 via the second flow path 140. The bypass flow path is an ink flow path that connects the first flow path 130 and the second flow path 140 without passing through the pressure chamber 12. The second pressure adjustment means 150 is disposed in connection with the second flow path 140. The first pressure adjustment means 120 has a first valve chamber 121 and a first pressure control chamber 122, and the first valve chamber 121 is communicated with the first pressure control chamber 122 via a communication port 191A that can be opened and closed by a valve 190A.

[0028] During the recording operation, the circulation pump 500 is in an ON state (driving state). The inkjet recording device includes an ink storage unit (not shown), such as an ink cartridge, that stores ink. The ink supplied from the ink storage unit flows into the first valve chamber 121 and the first pressure control chamber 122 of the first pressure adjustment means 120 through the filter 110. Then, the ink flowing out from the first pressure control chamber 122 flows into the first flow path 130 and the bypass flow path 160. A part of the ink that flows into the first flow path 130 is discharged from the discharge port 13 when passing through the discharge module 300. The remaining ink that is not discharged from the discharge port 13 flows into the second flow path 140 and is then supplied to the second pressure control chamber 152. Then, the ink supplied to the second pressure control chamber 152 circulates to the first flow path 130 via the circulation pump 500.

[0029] On the other hand, the ink that has flowed from the first pressure control chamber 122 into the bypass flow path 160 flows into the second pressure control chamber 152 via the second valve chamber 151. The ink that has flowed into the second pressure control chamber 152 passes through the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows into the first pressure control chamber 122 again. At this time, the control pressure by the first valve chamber 121 is set higher than the control pressure of the first pressure control chamber 122. Therefore, the ink in the first pressure control chamber 122 is supplied to the ejection module 300 again via the first flow path 130 without flowing into the first valve chamber 121. The ink that has flowed into the ejection module 300 flows into the first pressure control chamber 122 again via the second flow path 140, the second pressure control chamber 152, the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180. In this manner, the ink circulation is completed within the recording head 1.

[0030] Furthermore, the ink consumed during recording is supplied to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121 from an ink storage unit (not shown) such as an ink cartridge.

[0031] Below, it will be explained that when continuing to print a high "duty" such as a solid image, the negative pressure in the pressure chamber increases, and as a result, ink is supplied to the pressure chamber 12 from both the first flow path 130 side and the second flow path 140 side. The definition of duty can change depending on various conditions. As an example, an image printed by applying one ink droplet with a volume of 4 pL per droplet to a unit area of ​​1,200 dpi x 1,200 dpi will be treated as having a printing duty of 100%. Printing with a high duty is, for example, printing performed at a duty of 100%.

[0032] When recording at a high duty is continued, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the second flow path 140 decreases. On the other hand, since the circulation pump 500 causes ink to flow out at a constant rate, the balance between the inflow and outflow in the second pressure control chamber 152 is lost, the ink in the second pressure control chamber 152 decreases, the negative pressure in the second pressure control chamber 152 becomes stronger, and the second pressure control chamber 152 shrinks. Then, as the negative pressure in the second pressure control chamber 152 becomes stronger, the inflow amount of ink flowing into the second pressure control chamber 152 through the bypass flow path 160 increases, and the second pressure control chamber 152 becomes stable in a state where the inflow and outflow are balanced. As a result, the negative pressure in the second pressure control chamber 152 becomes stronger according to the recording duty. In addition, when the circulation pump 500 is driven, in a configuration in which the communication port 191B is in a closed state, the communication port 191B opens in response to the printing duty, and ink flows from the bypass flow path 160 into the second pressure control chamber 152.

[0033] Then, when recording at a higher duty is continued, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the second flow path 140 decreases, and instead the amount of ink flowing into the second pressure control chamber 152 from the communication port 191B via the bypass flow path 160 increases. If this state progresses further, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the second flow path 140 becomes zero, and all the ink flowing out to the circulation pump 500 becomes ink flowing in from the communication port 191B. If this state progresses further, ink flows back from the second pressure control chamber 152 into the pressure chamber 12 through the second flow path 140 (FIG. 1(b)). In this state, the ink flowing out from the second pressure control chamber 152 to the circulation pump 500 and the ink flowing out to the pressure chamber 12 flow into the second pressure control chamber 152 from the communication port 191B through the bypass flow path 160. In this case, ink from the first flow path 130 and ink from the second flow path 140 are supplied to the pressure chamber 12, and the ink is ejected from the ejection port 13.

[0034] This backflow of ink that occurs when the printing duty is high is a phenomenon that occurs due to the provision of the bypass flow path 160. In addition, in the above, an example has been described in which the communication port 191B in the second pressure adjustment means is opened in response to the backflow of ink, but backflow of ink may also occur when the communication port 191B in the second pressure adjustment means is open. Even in a configuration that does not include the second pressure adjustment means, the provision of the bypass flow path 160 may cause the above-mentioned backflow of ink.

[0035] As described above, the inkjet recording method of the present embodiment preferably includes the following steps. That is, ink supplied from an ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120 and the first flow path 130. Then, ink not discharged from the discharge port 13 is circulated to the first flow path 130 via the second flow path 140 and the circulation pump 500. In addition, the inkjet recording method of the present embodiment preferably further includes the following steps. That is, ink supplied from an ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120 and the first flow path 130. In addition, ink supplied from an ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120, the bypass flow path 160, and the second flow path 140.

[0036] In addition, in the case where the recording head 1 further includes the second pressure adjustment means 150, the inkjet recording method of the present embodiment preferably includes the following steps. That is, the ink supplied from the ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120 and the first flow path 130. Then, the ink not discharged from the discharge port 13 is circulated to the first flow path 130 via the second flow path 140, the second pressure adjustment means 150, and the circulation pump 500. In addition, the inkjet recording method of the present embodiment preferably includes the following steps. That is, the ink supplied from the ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120 and the first flow path 130. In addition, the ink supplied from the ink storage unit (not shown) is discharged from the discharge port 13 via the first pressure adjustment means 120, the bypass flow path 160, the second pressure adjustment means 150, and the second flow path 140.

[0037] The ejection element 15 may be either a piezoelectric element (piezo) or a heating element such as a heater. In particular, the ejection element is preferably a heating element. The recording head is preferably a thermal type recording head that heats ink with a heating element to generate air bubbles in the ink and eject the ink.

[0038] (Ink container) Fig. 6 is a cross-sectional view showing a schematic example of an ink container. The ink container 50 shown in Fig. 6 has a bag-like shape and includes a bag 55 and ink 45 contained in the bag 55. The bag 55 has a layer that comes into contact with the ink 45. The innermost layer is a layer made of resin, such as a film layer 47. The bag 55 has a metal layer 52 as a layer other than the layer that comes into contact with the ink 45.

[0039] The ink 45 contained in the bag 55 is a so-called degassed ink, in which the amount of dissolved oxygen is reduced. Ink with a reduced amount of dissolved oxygen (degassed ink) can be produced by degassing ink prepared according to a conventional method. For example, a degassing module using hollow fibers can be used for the degassing process.

[0040] The amount of dissolved oxygen in the ink 45 contained in the bag 55 is 3.0 mg / L or less, and preferably 0.1 mg / L or more and 2.8 mg / L or less. If the amount of dissolved oxygen in the ink exceeds 3.0 mg / L, air bubbles generated during initial filling are not sufficiently absorbed by the ink, and the unabsorbed air bubbles are likely to reach the ink flow path communicating with the ejection port, making it difficult to improve the ejection stability of the ink. The amount of dissolved oxygen in the ink in the ink container can be measured by a dissolved oxygen meter using the galvanic cell method (diaphragm electrode method) or the like. In the present invention, the amount of dissolved "oxygen" is used to represent the gas (air) dissolved in the ink.

[0041] The difference between the average SP value of the water-soluble organic solvent in the ink and the SP value of the resin forming the layer of the ink container that comes into contact with the ink is 6.5 (cal / cm 3 ) 1 / 2 The characteristics of the resin that forms the innermost layer of the ink container can be verified according to the method described below. The innermost layer (resin layer) of the ink container is cut to an appropriate size and used as a measurement sample, which is then analyzed by pyrolysis gas chromatography / mass spectrometry (Py-GC / MS). This makes it possible to confirm the types of units that make up the resin. Furthermore, the composition ratio of the units can be determined from the confirmed unit types and the nuclear magnetic resonance (NMR) chemical shift. The SP value of the resin can then be determined by the determined resin units and their composition ratio using the Fedors method. For example, the SP value of polyethylene is 8.6 (cal / cm 3 ) 1 / 2 The SP value of polypropylene is 8.0 (cal / cm 3 ) 1 / 2 The SP value of polyvinyl chloride is 11.0 (cal / cm 3 ) 1 / 2 The SP value of the resin that makes up the ink storage bag is 5.0 (cal / cm 3 ) 1 / 2 More than 15.0(cal / cm 3 ) 1 / 2 It is preferable that the calorie content is 7.0 (cal / cm 3 ) 1 / 2More than 10.0(cal / cm 3 ) 1 / 2 It is even more preferable that:

[0042] To initially fill the ink supply system of an inkjet recording device equipped with an ink supply system having a recording head with ink, for example, the ink supply port 60 of the ink container 50 shown in Fig. 6 is connected to one end of the ink supply system. Then, the ink container 50 is appropriately pressurized and the contained ink 45 is injected into the ink supply system, thereby initially filling the ink supply system with ink.

[0043] Specific examples of the resin forming the innermost layer of the ink container include the following: thermoplastic resins such as polyolefins, such as polyethylene and polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate; mixtures and modified products of these thermoplastic resins; thermosetting resins; and the like. Among these, it is preferable that the resin forming the innermost layer of the ink container is polyethylene or polypropylene. Polyethylene and polypropylene have good wettability with ink, so that an air layer is unlikely to form in the ink container, and the generation of air bubbles during initial filling can be further suppressed.

[0044] Examples of the shape of the ink container include a box shape and a bag shape. Among them, the ink container is preferably shaped like a bag. When the ink container is shaped like a bag, it shrinks as the ink supply system is filled with ink, making it difficult for an air layer to form inside the ink container, and thus making it possible to further suppress the generation of air bubbles during initial filling.

[0045] As shown in Fig. 6, the ink container 50 preferably has a metal layer 52 as a layer other than the layer that comes into contact with the ink 45. Examples of metals that form the metal layer include metals such as aluminum, silver, and copper; metal compounds such as silicon oxide and alumina; and the like. The presence of a metal layer improves gas barrier properties, making it difficult for air to pass through the ink container. This makes it difficult for an air layer to form, and can further suppress the generation of air bubbles during initial filling.

[0046] (Water-based ink) In the ink filling method and ink jet recording method of the present invention, a water-based ink containing a pigment and a water-soluble organic solvent is used. The components constituting the ink and the physical properties of the ink will be described below.

[0047] [Pigment] The ink contains a pigment. The content (mass %) of the pigment in the ink is preferably from 0.1% to 15.0% by mass, and more preferably from 1.0% to 10.0% by mass, based on the total mass of the ink.

[0048] Examples of the pigment include inorganic pigments such as carbon black and titanium oxide, and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, dioxazine, and perinone. A dye may be used in combination to improve the color tone of the ink or the dispersibility of the pigment.

[0049] The pigment dispersion method is not particularly limited. For example, resin-dispersed pigments dispersed with a resin dispersant, pigments dispersed with a surfactant, and microencapsulated pigments in which at least a part of the pigment particle surface is coated with a resin or the like can be used. Self-dispersed pigments in which a functional group containing a hydrophilic group such as an anionic group is bonded to the pigment particle surface, and pigments in which an organic group containing a polymer is chemically bonded to the pigment particle surface (resin-bonded self-dispersed pigments) can also be used. Pigments with different dispersion methods may be used in combination. Among them, resin-dispersed pigments dispersed with a resin dispersant are preferred.

[0050] As the resin dispersant, it is preferable to use a water-soluble resin that can disperse the pigment in an aqueous medium by the action of anionic groups. The content (mass%) of the pigment in the ink is preferably 0.3 to 10.0 times the content of the resin dispersant in terms of mass ratio.

[0051] The resin dispersant may be an acrylic resin, a urethane resin, etc. Among them, an acrylic resin is preferred, and an acrylic resin composed of a unit derived from (meth)acrylic acid or a (meth)acrylic acid ester is more preferred.

[0052] The acrylic resin is preferably one having a hydrophilic unit and a hydrophobic unit as a segment. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer is preferable. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of styrene and α-methylstyrene is preferable. These resins easily interact with pigments, and are therefore suitable as resin dispersants for dispersing pigments.

[0053] The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Examples of the hydrophilic monomer having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid; anionic monomers such as anhydrides and salts of these acidic monomers; and the like. Examples of the cations constituting the salts of the acidic monomers include ions of lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit not having a hydrophilic group such as an anionic group. The hydrophobic unit can be formed by polymerizing a hydrophobic monomer not having a hydrophilic group such as an anionic group. Examples of the hydrophobic monomer include monomers having an aromatic group such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid esters such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0054] The weight average molecular weight of the resin dispersant is preferably from 1,000 to 30,000, and more preferably from 3,000 to 15,000. The acid value of the resin dispersant is preferably from 80 mgKOH / g to 250 mgKOH / g.

[0055] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the anionic group is a salt type, examples of the cation that serves as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. In addition, it may be a group that is a combination of these groups.

[0056] [Aqueous medium] The ink is an aqueous ink containing an aqueous medium which is a mixed solvent of water and a water-soluble organic solvent. As the water, deionized water (ion-exchanged water) is preferably used. The content (mass%) of water in the ink is preferably 10.0% by mass or more and 90.0% by mass or less, more preferably 50.0% by mass or more and 90.0% by mass or less, based on the total mass of the ink. As the water-soluble organic solvent, any of those usable for inkjet inks, such as alcohols, glycols, (poly)alkylene glycols, nitrogen-containing compounds, and sulfur-containing compounds, can be used. The content (mass%) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less, based on the total mass of the ink. Usually, a "water-soluble organic solvent" is a liquid, but in the present invention, for convenience, those which are solid at 25°C (room temperature) are also included in the water-soluble organic solvent. 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.

[0057] The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin that forms the innermost layer of the ink container is 6.5 (cal / cm 3 ) 1 / 2 It is preferably 3.0 (cal / cm 3 ) 1 / 2 More than 6.0(cal / cm 3 ) 1 / 2 The following is the result.

[0058] The SP value (δ: solubility parameter) in this specification is a value calculated by the Fedors method based on the following formula (A) (unit: (cal / cm 3 ) 1 / 2 ) when converting to the SI system of units, use the unit "(cal / cm 3 ) 1 / 2 =2.046×10 3 (J / m 3 ) 1 / 2 " relationship can be used. Note that the ΔE vap For V, the values ​​described in, for example, Coating Times, No. 193 (1992) can be used. δ = (ΔE vap / V) 1 / 2 (A) (In formula (A), ΔE vap represents the molar heat of vaporization of the compound (cal / mol), and V is the molar volume of the compound at 25°C (cm 3 / mol)

[0059] Aqueous inkjet inks usually contain multiple types of water-soluble organic solvents. For this reason, it is appropriate to consider the SP value of the water-soluble organic solvent in the ink in terms of the concept of "average SP value". The average SP value means a value calculated for each water-soluble organic solvent by multiplying the SP value specific to the water-soluble organic solvent by the proportion (mass%) of the water-soluble organic solvent in the total amount of the water-soluble organic solvent in the ink, and then integrating the calculated values. When the ink contains only one type of water-soluble organic solvent, the SP value of that water-soluble organic solvent is the "average SP value". For example, in the case of "Ink 1" prepared in the "Examples" described later, the composition of the water-soluble organic solvent (total 20.0 parts by mass) is as follows. The numbers in parentheses are the SP values ​​(units omitted) of each water-soluble organic solvent. Glycerin (16.4): 10.0 parts by weight Polyethylene glycol (10.5) having a number average molecular weight of 600: 10.0 parts by weight

[0060] The average SP value of the water-soluble organic solvent in this "ink 1" can be calculated according to the following formula (B). Average SP value = (16.4 × 10.0 / 20.0) + (10.5 × 10.0 / 20.0) = 13.5 (B)

[0061] The Fedors method SP value of a general-purpose water-soluble organic solvent for water-based inkjet ink is calculated in units (cal / cm 3 ) 1 / 2The following are the abbreviated names: Glycerin (16.4), 1,3-propanediol (16.1), trimethylolpropane (15.9), 1,4-butanediol (15.0), diethylene glycol (15.0), ethylene glycol (14.8), 1,3-butanediol (14.8), 2-methyl-1,3-propanediol (14.8), 1,2,6-hexanetriol (14.5), urea (14.4), ethyleneurea (14.2), 1,5-pentanediol (14.2), triethanolamine (13.7), methanol. (13.8), triethylene glycol (13.6), 1,6-hexanediol (13.5), 3-methyl-1,5-pentanediol (13.4), tetraethylene glycol (12.8), polyethylene glycol with a number average molecular weight of 200 (12.8), 2-pyrrolidone (12.6), ethanol (12.6), 1,2-pentanediol (12.2), ethylene glycol monomethyl ether (12.0), n-propanol (11.8), 1,2-hexanediol (11.8), isopropanol (11.6), N-methyl-2-pyrrolidone (11.5), ethylene glycol monoethyl ether (12.0), 1,3-dimethyl-2-imidazolidinone (11.4), n-butanol (11.3), diethylene glycol monomethyl ether (11.2), 2-butanol (11.1), isobutanol (11.1), diethylene glycol monoethyl ether (10.9), tert-butanol (10.9), triethylene glycol monoethyl ether (10.6), poly(ethylene glycol) with a number average molecular weight of 600. Ethylene glycol (10.5), diethylene glycol monobutyl ether (10.5), triethylene glycol monobutyl ether (10.3), tetraethylene glycol monobutyl ether (10.2), polyethylene glycol with a number average molecular weight of 1,000 (10.1), acetone (9.1), methyl ethyl ketone (9.0), tetraethylene glycol dimethyl ether (8.5), triethylene glycol butyl methyl ether (8.4), ethylene glycol dimethyl ether (7.6).

[0062] The average SP value of the water-soluble organic solvent in the ink is 8.0 (cal / cm3 ) 1 / 2 More than 15.5(cal / cm 3 ) 1 / 2 It is preferable that the calorie content is 12.0 (cal / cm 3 ) 1 / 2 More than 15.0(cal / cm 3 ) 1 / 2 It is even more preferable that:

[0063] The properties of the water-soluble organic solvent can be verified according to the method shown below. The type of water-soluble organic solvent can be confirmed by diluting an appropriate amount of ink with methanol and performing a qualitative analysis by gas chromatography / mass spectrometry (GC / MS). Furthermore, the content of the water-soluble organic solvent can be confirmed by an absolute calibration curve method using a standard solution of the component to be analyzed. Then, the average SP value of the water-soluble organic solvent in the ink can be calculated from the confirmed type and content of the water-soluble organic solvent.

[0064] The water-soluble organic solvent in the ink preferably contains a first water-soluble organic solvent having a relative dielectric constant of 28.0 or less. When an ink containing a first water-soluble organic solvent having a relative dielectric constant of 28.0 or less is used, the ink has high wettability with the resin constituting the innermost layer of the ink container, so that an air layer is further unlikely to be formed in the container, and the generation of air bubbles due to initial filling can be further suppressed. If the relative dielectric constant of the first water-soluble organic solvent is more than 28.0, the ejection stability of the ink may be slightly reduced. It is more preferable that the relative dielectric constant of the first water-soluble organic solvent is 3.0 or more and 20.0 or less.

[0065] The relative dielectric constant of the water-soluble organic solvent can be measured using a dielectric constant meter (e.g., trade name "BI-870" manufactured by BROOKHAVEN INSTRUMENTS CORPORATION) at a frequency of 10 kHz. The relative dielectric constant of a water-soluble organic solvent that is solid at 25°C is determined by measuring the relative dielectric constant of a 50% by mass aqueous solution and calculating the value from the following formula (1). ε sol =2ε 50% -ε water (1) εsol : Dielectric constant of solid water-soluble organic solvent at 25℃ ε 50% : Relative dielectric constant of a 50% by mass aqueous solution of a solid water-soluble organic solvent at 25°C ε water : relative dielectric constant of water

[0066] 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 an aqueous solution with a high concentration exceeding 50% by mass. On the other hand, in an aqueous solution with a low concentration of 10% by mass or less, the relative permittivity of water becomes dominant, and it is not possible to obtain a reliable (effective) value of the relative permittivity of the water-soluble organic solvent. As a result of the investigation conducted by the present inventors, 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 all 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 with a 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

[0067] Among the water-soluble organic solvents generally used in water-based inkjet inks, specific examples of water-soluble organic solvents having a relative dielectric constant of 28.0 or less include 2-pyrrolidone (28.0), 1,5-pentanediol (27.0), 3-methyl-1,3-butanediol (24.0), 3-methyl-1,5-pentanediol (23.9), ethanol (23.8), 1-(hydroxymethyl)-5,5-dimethylhydantoin (23.7), triethylene glycol (22.7), tetraethylene glycol (20.8), polyethylene glycol with a number average molecular weight of 200 (18.9), 2-ethyl-1 Examples of dielectric constants include 1,3-hexanediol (18.5), isopropanol (18.3), 1,2-hexanediol (14.8), n-propanol (12.0), polyethylene glycol with a number average molecular weight of 600 (11.4), triethylene glycol monobutyl ether (9.8), tetraethylene glycol monobutyl ether (9.4), tripropylene glycol monomethyl ether (8.5), 1,6-hexanediol (7.1), and polyethylene glycol with a number average molecular weight of 1,000 (4.6) (the numbers in parentheses are the dielectric constants at 25°C).

[0068] Other specific examples of water-soluble organic solvents (water-soluble organic solvents with a dielectric constant of more than 28.0) commonly used in water-based inkjet inks include urea (110.3), ethyl isopropyl sulfone (59.0), ethylene urea (49.7), dimethyl sulfoxide (48.9), glycerin (42.3), γ-butyrolactone (41.9), ethylene glycol (40.4), 1-(2-hydroxyethyl)-2-pyrrolidone (37.6), trimethylolpropane ( 33.7), methanol (33.1), N-methyl-2-pyrrolidone (32.0), triethanolamine (31.9), diethylene glycol (31.7), 1,4-butanediol (31.1), 1,3-butanediol (30.0), 3-methylsulfolane (29.0), 1,2-propanediol (28.8), 1,2,6-hexanetriol (28.5), 2-methyl-1,3-propanediol (28.3), etc.

[0069] The content (mass%) of the first water-soluble organic solvent in the ink is preferably 0.25 times or more, more preferably 0.35 times or more, and particularly preferably 0.35 times or more and 0.70 times or less, in terms of mass ratio to the content (mass%) of the water-soluble organic solvent. If the mass ratio is less than 0.25 times, the effect of improving the ejection stability of the ink may be slightly reduced. The content (mass%) of the first water-soluble organic solvent in the ink is preferably 1.0 mass% or more and 20.0 mass% or less, and more preferably 3.0 mass% or more and 15.0 mass% or less, based on the total mass of the ink.

[0070] The first water-soluble organic solvent preferably contains polyethylene glycol, and more preferably is polyethylene glycol. The polyethylene glycol as the first water-soluble organic solvent is represented by the formula: HO-(CH2-CH2-O) n -H" (wherein "n" is a number equal to or greater than 3). When the resin forming the innermost layer of the ink container is polyethylene or polypropylene, polyethylene glycol has high wettability with respect to polyethylene or polypropylene. For this reason, by using ink containing polyethylene glycol, it becomes even more difficult for an air layer to form within the container, and the generation of air bubbles due to initial filling can be further suppressed.

[0071] The number average molecular weight of polyethylene glycol is preferably 200 or more, more preferably 200 to 1,000. If the number average molecular weight of polyethylene glycol is less than 200, the effect of suppressing bubble generation may be slightly reduced. The number average molecular weight of polyethylene glycol is a value calculated in terms of polystyrene measured by gel permeation chromatography (GPC) using tetrahydrofuran as the mobile phase.

[0072] [Urethane resin] The ink preferably contains a urethane resin. More preferably, the urethane resin is a water-soluble urethane resin. By using an ink containing a urethane resin such as a water-soluble urethane resin, the ejection stability of the ink can be further improved. The content (mass %) of the water-soluble urethane resin in the ink is preferably 0.1 mass % or more and 10.0 mass % or less, and more preferably 0.3 mass % or more and 1.0 mass % or less, based on the total mass of the ink.

[0073] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, it exists in an aqueous medium in a state in which it does not form particles whose particle size can be measured by dynamic light scattering. Whether or not a resin is water-soluble can be determined according to the following method. First, a liquid (resin solid content: 10 mass%) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by dynamic light scattering, if particles having a particle size are not measured, the resin can be determined to be water-soluble. On the other hand, if particles having a particle size are measured, the resin can be determined to be "resin particles" (i.e., "water-dispersible resin"). The measurement conditions at this time can be, for example, as follows. [Measurement conditions] SetZero: 30 seconds Number of measurements: 3 Measurement time: 180 seconds

[0074] 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.

[0075] As the urethane resin, for example, urethane resins having units derived from polyisocyanate, polyol having no acid group, polyol having an acid group, polyamine, etc. can be used.

[0076] [Polyisocyanate] Polyisocyanate is a compound having two or more isocyanate groups in its molecular structure. Examples of polyisocyanate include aliphatic polyisocyanate and aromatic polyisocyanate. The ratio (mol%) of the unit derived from polyisocyanate in the urethane resin is preferably 10.0 mol% or more and 80.0 mol% or less, more preferably 20.0 mol% or more and 60.0 mol% or less.

[0077] Examples of the aliphatic polyisocyanate include polyisocyanates having a chain structure such as tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate; and polyisocyanates having a cyclic structure such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatemethyl)cyclohexane.

[0078] 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.

[0079] Among the above polyisocyanates, it is preferable to use a polyisocyanate having a cyclic structure. Furthermore, among the polyisocyanates having a cyclic structure, it is more preferable to use isophorone diisocyanate.

[0080] [Polyols, polyamines] A polyol is a compound having two or more hydroxyl groups in its molecular structure. Examples of polyols include polyols without acid groups, such as polyether polyols, polyester polyols, and polycarbonate polyols; polyols with acid groups; and the like. A polyamine is a compound having two or more "amino groups, imino groups" in its molecular structure. The ratio (mol%) of units derived from polyols and polyamines in the urethane resin is preferably 10.0 mol% or more and 80.0 mol% or less, and more preferably 20.0 mol% or more and 60.0 mol% or less.

[0081] (1) Polyols without acid groups Examples of the polyether polyol include addition polymers of alkylene oxides and polyols, glycols such as (poly)alkylene glycol, etc. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, α-olefin oxide, etc. Examples of polyols to be addition polymerized with alkylene oxide include diols such as 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 4,4-dihydroxyphenylpropane, 4,4-dihydroxyphenylmethane, hydrogenated bisphenol A, dimethylol urea and derivatives thereof; and triols such as glycerin, trimethylolpropane, 1,2,5-hexanetriol, 1,2,6-hexanetriol, pentaerythritol, trimethylolmelamine and derivatives thereof, and polyoxypropylenetriol. Examples of glycols include (poly)alkylene glycols such as tetramethylene glycol, hexamethylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, (poly)tetramethylene glycol, and neopentyl glycol; ethylene glycol-propylene glycol copolymers; and the like.

[0082] Examples of polyester polyols include acid esters. Examples of acid components constituting the acid esters include aromatic dicarboxylic acids such as phthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and tetrahydrophthalic acid; alicyclic dicarboxylic acids such as hydrogenated products of these aromatic dicarboxylic acids; and aliphatic dicarboxylic acids such as malonic acid, succinic acid, tartaric acid, oxalic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, alkyl succinic acid, linoleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, and itaconic acid. Anhydrides, salts, and derivatives (alkyl esters, acid halides) of these can also be used as the acid component. Examples of components that form esters with the acid component include polyols such as diols and triols; and glycols such as (poly)alkylene glycols. Examples of polyols and glycols include those exemplified as components constituting the above polyether polyols.

[0083] The polycarbonate polyol may be a polycarbonate polyol produced by a known method.Specific examples include alkanediol-based polycarbonate diols such as polyhexamethylene carbonate diol.Furthermore, examples include polycarbonate diols obtained by reacting a carbonate component such as alkylene carbonate, diaryl carbonate, or dialkyl carbonate, or phosgene with an aliphatic diol component.

[0084] The ratio (mol %) of the units derived from a polyol having no acid group to the total amount of the units derived from a polyol in the urethane resin is preferably as follows: preferably from 5.0 mol % to 50.0 mol %, and more preferably from 10.0 mol % to 30.0 mol %.

[0085] It is preferable to use polypropylene glycol as the polyol having no acid group. That is, it is preferable that the urethane resin contained in the ink is a water-soluble urethane resin having a unit derived from polypropylene glycol. Since the water-soluble urethane resin having a unit derived from polypropylene glycol is highly hydrophilic, the ink becomes more compatible with the inner surface of the ink supply system, and the generated air bubbles are less likely to adhere to the inner surface of the ink supply system.

[0086] (2) Polyol having an acid group Examples of polyols having an acid group include polyols having an acid group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group. The acid group is preferably a carboxylic acid group. Examples of polyols having a carboxylic acid group include dimethylol acetic acid, dimethylol propionic acid, dimethylol butanoic acid, and dimethylol butyric acid. Among these, dimethylol propionic acid and dimethylol butanoic acid are preferred.

[0087] The acid group of the polyol having an acid group may be in the form of a salt. Examples of cations that form salts include ions of alkali metals such as lithium, sodium, and potassium; ammonium ions, and cations of organic amines such as dimethylamine. Since the molecular weight of a general-purpose polyol having an acid group is at most about 400, the unit derived from the polyol having an acid group basically becomes the hard segment of the urethane resin. The acid value of the urethane resin can be adjusted, for example, by the amount of the polyol having an acid group used.

[0088] The ratio (mol %) of the units derived from a polyol having an acid group to the total amount of the units derived from a polyol in the urethane resin is preferably as follows: preferably from 30.0 mol % to 90.0 mol %, and more preferably from 50.0 mol % to 90.0 mol %.

[0089] (3) Polyamines Examples of polyamines include monoamines having multiple hydroxyl groups, such as dimethylolethylamine, diethanolmethylamine, dipropanolethylamine, and dibutanolmethylamine; bifunctional polyamines, such as ethylenediamine, propylenediamine, hexylenediamine, isophoronediamine, xylylenediamine, diphenylmethanediamine, hydrogenated diphenylmethanediamine, and hydrazine; and trifunctional or higher polyamines, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyamidepolyamine, and polyethylenepolyimine. For convenience, compounds having multiple hydroxyl groups and one "amino group, imino group" are also listed as "polyamines". Since the molecular weight of polyamines is at most about 400, the units derived from polyamines basically become the hard segments of urethane resins. The ratio (mol%) of the units derived from polyamines in the urethane resin is preferably 10.0 mol% or less, and more preferably 5.0 mol% or less. The proportion (mol %) of the polyamine-derived units in the urethane resin may be 0.0 mol %.

[0090] The water-soluble urethane resin preferably has a unit derived from polyamine. The ratio of urethane bonds to the total of urethane bonds and urea bonds derived from polyamine in the water-soluble urethane resin is preferably 85.0 mol % or more and 99.0 mol % or less. When the ratio of urethane bonds is within the above range, the hydrophilicity of the water-soluble urethane resin is appropriately improved, and the hydrophilicity of the ink is appropriately increased. This makes it easier for the ink to wet the innermost layer of the ink container and the inner surface of the ink supply system, making it difficult for an air layer to be formed, and further improving the ink ejection stability. On the other hand, when the ratio of urethane bonds is outside the above range, the hydrophilicity of the water-soluble urethane resin is out of the appropriate range, and the ink ejection stability may be slightly reduced.

[0091] [Cross-linking agents, chain extenders] When synthesizing a urethane resin, a crosslinking agent or a chain extender can be used. Usually, a crosslinking agent is used when synthesizing a prepolymer, and a chain extender is used when carrying out a chain extension reaction on a prepolymer that has been synthesized in advance. Basically, the crosslinking agent or the chain extender can be appropriately selected from water, polyisocyanate, polyol, polyamine, etc. depending on the purpose, such as crosslinking or chain extension. As the chain extender, one that can crosslink the urethane resin can also be used.

[0092] [Analysis method] (1) Urethane resin composition The composition of the urethane resin can be analyzed by the following method. First, a method for extracting the urethane resin from the ink will be described. To extract the urethane resin from the ink, the ink is centrifuged at 80,000 rpm, and an excess of acid (such as hydrochloric acid) is added to the supernatant liquid separated to precipitate the resin. When chloroform is added to the precipitated resin, the urethane resin dissolves, so that the urethane resin can be extracted from the liquid phase. Furthermore, in addition to chloroform, an organic solvent such as hexane, which does not dissolve pigments or other resins but dissolves the urethane resin, may be used. Although the urethane resin can be analyzed in the ink state, it is preferable to analyze the urethane resin extracted from the ink, since the measurement accuracy can be improved.

[0093] The urethane resin was dissolved in deuterated dimethyl sulfoxide (DMSO) and analyzed by proton nuclear magnetic resonance ( 1 The urethane resin is analyzed by H-NMR. From the positions of the peaks obtained, the types of polyisocyanate, polyol without acid groups, polyol with acid groups, and polyamine can be identified. The dried urethane resin is also analyzed by pyrolysis gas chromatography to identify the types of polyisocyanate, polyol without acid groups, polyol with acid groups, and polyamine. Furthermore, the composition ratio can be calculated from the ratio of the integrated values ​​of each peak.

[0094] (2) Proportion of urethane bonds The ratio of urethane bonds to the total of urethane bonds and urea bonds derived from polyamines in the urethane resin can be measured as follows. That is, the urethane resin is dissolved in deuterated dimethyl sulfoxide to prepare a measurement sample. Then, the measurement sample is analyzed by carbon nuclear magnetic resonance ( 13 The prepared sample is analyzed by C-NMR, and the percentage of urethane bonds in the urethane resin can be calculated from the integrated values ​​of the peaks of the urethane bonds and the urea bonds derived from polyamines. However, the positions of the peaks of the urethane bonds and the urea bonds derived from polyamines differ depending on the type of compound used in the synthesis of the urethane resin. For this reason, it is necessary to examine the positions of the peaks of the urethane bonds and the urea bonds derived from polyamines for each compound used in the synthesis of the urethane resin. The method is described below.

[0095] First, compounds (polyisocyanate, polyol, polyamine) that are the raw materials for urethane resin are prepared. Then, (i) a reaction product of polyisocyanate and polyol, (ii) a reaction product of polyisocyanate and polyamine, (iii) a reaction product of polyisocyanate and polyol having an acid group, and (iv) a reaction product of polyisocyanate and water are prepared. The prepared reaction products are dried and dissolved in deuterated DMSO, and the carbon nuclear magnetic resonance ( 13 Analyze by C-NMR.

[0096] In the above example, the chemical shift of the urethane bond is confirmed from the reactant (i) and the reactant (iii), and the chemical shift of the urea bond derived from the polyamine is confirmed from the reactant (ii) and the reactant (iv). From each of the confirmed chemical shifts, the peak of the urethane bond and the peak of the urea bond are identified, and the ratio of the integrated values ​​of these peaks is used to calculate the proportion of the urethane bond in the total of the urethane bond and the urea bond derived from the polyamine in the urethane resin. For example, in the case of a urethane resin obtained using isophorone diisocyanate, the peak of the urethane bond is detected at about 155 ppm, although there is some deviation depending on the measurement conditions and the composition of the urethane resin. In addition, the peak of the urea bond derived from the polyamine is detected at about 159 ppm. The peak of the urea bond derived from water is detected at about 158 ​​ppm.

[0097] [Surfactants] The ink preferably contains a surfactant. Examples of the surfactant include cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants. Among them, the use of an ink containing a nonionic surfactant is preferable because it can further enhance the effect of improving the ejection stability.

[0098] Examples of the nonionic surfactant include a hydrocarbon-based nonionic surfactant, a fluorine-based nonionic surfactant, and a silicone-based nonionic surfactant. Among them, the nonionic surfactant is preferably an acetylene glycol-based nonionic surfactant, and more preferably an acetylene glycol-based nonionic surfactant having 4 or more moles of ethylene oxide groups added. When the number of moles of ethylene oxide groups added is 4 or more, the compatibility with polyethylene glycol having a large molecular weight is increased, making it difficult for an air layer to form in the ink container, and the generation of bubbles at the time of initial filling can be further suppressed. On the other hand, when the number of moles of ethylene oxide groups added is less than 4, the effect of improving the ejection stability of the ink may be slightly reduced. Note that, when a surfactant other than a nonionic surfactant is used, the ejection accuracy of the ink may be slightly reduced, and the effect of improving the ejection stability of the ink may be slightly reduced. The number of moles of ethylene oxide groups added in the acetylene glycol-based nonionic surfactant is preferably 20 or less.

[0099] The content (mass %) of the surfactant in the ink is preferably from 0.1 to 5.0% by mass, and more preferably from 0.3 to 1.5% by mass, based on the total mass of the ink.

[0100] [Other ingredients] In addition to the above components, the ink may contain various additives, such as antifoaming agents, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors, as necessary.

[0101] [Ink properties] The surface tension of the ink at 25°C is 25 mN / m or more, preferably 45 mN / m or less, and more preferably 30 mN / m to 40 mN / m. If the surface tension of the ink is less than 25 mN / m, an air layer is likely to form in the ink supply system, and the ink ejection stability is reduced. In this specification, the surface tension of the ink is the "static surface tension" measured by the plate method under a temperature condition of 25°C. The surface tension of the ink can be adjusted, for example, by using a surfactant or a water-soluble organic solvent.

[0102] The ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less, and more preferably 1.0 mPa·s or more and 5.0 mPa·s or less. The pH of the ink at 25°C is preferably 5.0 or more and 10.0 or less, and more preferably 7.0 or more and 9.5 or less. EXAMPLES

[0103] 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.

[0104] <Production of pigment dispersion> (Pigment dispersion 1) A water-soluble resin was neutralized with a 10% potassium hydroxide aqueous solution with a neutralization equivalent of 1 and dissolved in ion-exchanged water to prepare an aqueous solution of a resin dispersant with a resin content of 10.0%. As the water-soluble resin, a styrene / acrylic acid copolymer (acid value 160 mgKOH / g, weight average molecular weight 10,000) was used. A mixture was obtained by mixing 10.0 parts of a pigment (CI Pigment Yellow 74), 50.0 parts of an aqueous solution of a resin dispersant, and 40.0 parts of water. The mixture obtained was dispersed for 1 hour using a sand grinder, and then centrifuged to remove coarse particles. After pressure filtration with a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm, an appropriate amount of ion-exchanged water was added to obtain a pigment dispersion liquid 1. The pigment content in the obtained pigment dispersion liquid 1 was 10.0%, and the resin dispersant content was 5.0%.

[0105] (Pigment dispersion 2) Pigment dispersion 2 was obtained in the same manner as for the above-mentioned pigment dispersion 1, except that CI Pigment Red 122 was used as the pigment. The pigment content in the obtained pigment dispersion 2 was 10.0%, and the resin dispersant content was 5.0%.

[0106] (Pigment dispersion 3) Except for using CI Pigment Blue 15:3 as the pigment, Pigment Dispersion Liquid 3 was obtained in the same manner as for Pigment Dispersion Liquid 1 described above. The pigment content in the obtained Pigment Dispersion Liquid 3 was 10.0%, and the resin dispersant content was 5.0%.

[0107] (Pigment Dispersion 4) Carbon black (specific surface area 210 m) as a pigment 2 Pigment dispersion 4 was obtained in the same manner as for pigment dispersion 1, except that a 10.0% polyaniline stearate dispersion was used (DBP oil absorption 74 mL / 100 g, DBP oil absorption 76 mL / 100 g). The pigment content in the obtained pigment dispersion 4 was 10.0%, and the resin dispersant content was 5.0%.

[0108] (Pigment Dispersion 5) A solution of 5.0 g of concentrated hydrochloric acid in 5.5 g of water was cooled to 5°C, and 1.6 g of 4-aminophthalic acid (treatment agent) was added. The container containing this solution was placed in an ice bath and the solution was stirred. While maintaining the liquid temperature below 10°C, a solution obtained by dissolving 1.8 g of sodium nitrite in 9.0 g of 5°C water was added. After stirring for 15 minutes, carbon black (specific surface area 220 m 2 6.0 g of 1,2-dichlorophenyl phthalate (1.0 g / g, DBP oil absorption 105 mL / 100 g) was added under stirring. After stirring for another 15 minutes, the resulting slurry was filtered with filter paper (product name "Standard Filter Paper No. 2", manufactured by Advantec) to obtain particles. The resulting particles were thoroughly washed with water and then dried in an oven at 110°C. After the counter ion was replaced by a potassium ion from a sodium ion by an ion exchange method, an appropriate amount of ion-exchanged water was added to adjust the pigment content. In this way, a pigment dispersion liquid 5 was obtained, which contains a self-dispersing pigment in which a phthalic acid group, the counter ion of which is a potassium ion, is bonded to the particle surface of carbon black. The pigment content in the resulting pigment dispersion liquid 5 was 10.0%.

[0109] <Synthesis of urethane resin> (Urethane resin 1~5) A four-neck flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a reflux tube was prepared. The types and amounts of polyisocyanate, polyol without an acid group, polyol with an acid group, and 300.0 parts of methyl ethyl ketone shown in Table 1 were placed in this four-neck flask. Then, the mixture was reacted at 80°C for 6 hours under a nitrogen gas atmosphere. Next, the amount of polyamine shown in Table 1 was added, and the mixture was reacted at 80°C to obtain a reaction liquid. After the reaction liquid obtained was cooled to 40°C, ion-exchanged water was added, and an aqueous potassium hydroxide solution was added while stirring at high speed with a homomixer to obtain a liquid. Methyl ethyl ketone was distilled off from the liquid obtained by heating and reducing the pressure, and liquids containing urethane resins 1 to 5 with a urethane resin (solid content) content of 20.0% were obtained. The properties of the urethane resins are shown in Table 1. The ratio (mol%) of the urethane bond to the total of the urethane bond and urea bond in the urethane resin was: 13The content was measured and calculated by C-NMR (shown as "Ratio of urethane bonds (mol %)" in Table 1). Details of each component in Table 1 are shown below. IPDI: Isophorone diisocyanate PPG: Polypropylene glycol DMPA: Dimethylolpropionic acid EDA: Ethylenediamine

[0110] The ratio of urethane bonds to the total of urethane bonds and urea bonds derived from polyamine in the obtained urethane resin was measured as follows. First, hydrochloric acid was added to a liquid containing the urethane resin to precipitate the urethane resin. The dried resin was dissolved in deuterated DMSO to prepare a measurement sample. Then, 13 The prepared sample was analyzed by C-NMR (apparatus name "Avance500", manufactured by BRUKER Bio Spin) to obtain the integrated values ​​of the peaks of the urethane bond and the urea bond derived from the polyamine. From each of the obtained integrated values, the proportion (mol%) of the urethane bond in the total of the urethane bond and the urea bond derived from the polyamine in the urethane resin was calculated.

[0111] TIFF2024178117000002.tif62170

[0112] <Synthesis of acrylic resin> (Acrylic Resin 1) 81.0 parts of styrene and 19.0 parts of acrylic acid were copolymerized by a conventional method to synthesize acrylic resin 1. After neutralizing the carboxylic acid groups in acrylic resin 1 with potassium hydroxide in an amount equimolar to the acid value, an appropriate amount of pure water was added to obtain a liquid containing acrylic resin 1 with a resin content of 20.0%.

[0113] <Ink Preparation> Each component (unit: %) shown in the upper part of Tables 2-1 to 2-3 was mixed, thoroughly stirred and dispersed, and then pressure filtered through a polypropylene filter (Pall) with a pore size of 2.5 μm to prepare each ink. In Tables 2-1 to 2-3, "Acetylenol E60", "Acetylenol E100", "Acetylenol E40", and "Acetylenol E00" are all trade names of nonionic surfactants manufactured by Kawaken Fine Chemicals. The numbers in parentheses attached to the trade names of these nonionic surfactants are the number of moles of ethylene oxide groups added. "NIKKOL SCS" is the trade name of anionic surfactants manufactured by Nikko Chemicals. The numbers in parentheses attached to the water-soluble organic solvents are the relative dielectric constants at 25°C. The properties of the inks are shown in the lower part of Tables 2-1 to 2-3. The surface tension of the ink was measured at 25° C. using an automatic surface tensiometer (product name "DY-300", manufactured by Kyowa Interface Science Co., Ltd.).

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[0117] <Ink container> An ink container was manufactured having the configuration shown in Table 3. The meanings of the abbreviations in Table 3 are as follows. PE: Polyethylene PP: Polypropylene PVC: Polyvinyl chloride

[0118] TIFF2024178117000006.tif61170

[0119] <Evaluation> Each prepared ink was degassed using a degassing module (trade name "jet ink degassing module SEPAREL EF-G4", manufactured by DIC) until the dissolved oxygen amount (mg / L) shown in Table 4 was reached. The dissolved oxygen amount of the ink after degassing was measured using a dissolved oxygen meter (trade name "portable dissolved oxygen meter OM-71-L1", manufactured by HORIBA). Then, the ink container shown in Table 4 was initially filled with the degassed ink, and the ink ejection stability was evaluated at a temperature of 25°C and a relative humidity of 50%. However, in Reference Examples 3 and 4, the ink initially filled was used up, and the ink was newly filled with the degassed ink, and then the ink was evaluated. As the recording head, an ink circulation type line type recording head having the configuration shown in FIG. 1 was used, and the ink in the recording head was heated to a temperature of 40°C and ejected. The ejection port density was 600 dpi, and the ink ejection amount per ejection port was 5 ng.

[0120] Using two rows of ejection openings, and under the condition that three ink droplets are applied to a unit area of ​​1 / 600 inch x 1 / 600 inch, the recording medium is conveyed at a speed of 15 inches / second, and 10 solid images are recorded on the entire surface of the A4 size recording medium. Plain paper (product name "CS-064F A4", manufactured by Canon) was used as the recording medium. The recorded solid image on the 10th sheet was visually confirmed. If the solid image was disturbed, the recording head was observed with an optical microscope, the number of ejection openings where ejection failure occurred due to air bubbles was counted, and the ejection stability of the ink was evaluated according to the following evaluation criteria. In the present invention, in the evaluation criteria shown below, "AAA", "AA", "A", and "B" were defined as acceptable levels, and "C" was defined as unacceptable levels. The evaluation conditions are shown in Table 4, and the evaluation results are shown in Table 5. AAA: The solid image was not disturbed, and no non-ejection due to air bubbles occurred. AA: The number of ejection ports where ejection failure occurred due to air bubbles was 1 to 9. A: The number of ejection ports where ejection failure occurred due to air bubbles was 10 to 49. B: The number of ejection ports where ejection failure occurred due to air bubbles was 50 to 99. C: The number of ejection ports where ejection failure occurred due to air bubbles was 100 or more.

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[0122] TIFF2024178117000008.tif167170

[0123] Reference Examples 1 and 2 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 flows to the second flow path was not performed. In both examples, the level of ejection stability caused by bubbles was acceptable, but the ink was prone to sticking.

Claims

1. an ink supply system for an ink jet recording apparatus, the ink supply system having a recording head including: an ejection port for ejecting an ink jet water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the ink jet water-based ink from the ejection port; a first flow path connected to the pressure chamber; and a second flow path connected to the pressure chamber at a position opposite to the first flow path with the ejection element therebetween; 1. An ink filling method for initially filling an ink tank with water-based ink from an ink container that contains the water-based ink having a dissolved oxygen content of 3.0 mg / L or less, comprising the steps of: the water-based ink contains a pigment and a water-soluble organic solvent; a layer of the ink container that comes into contact with the water-based ink is made of a resin; The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the layer of the ink container is 6.5 (cal / cm ３ ) １／２ is as follows: The ink filling method is characterized in that the surface tension of the water-based ink at 25° C. is 25 mN / m or more.

2. 2. The ink filling method according to claim 1, wherein the resin is polyethylene or polypropylene.

3. 2. The ink filling method according to claim 1, wherein the ink container is shaped like a bag.

4. The ink filling method according to claim 1 , wherein the ink container has a metal layer.

5. 2. The ink filling method according to claim 1, wherein the water-soluble organic solvent includes a first water-soluble organic solvent whose relative dielectric constant is 28.0 or less.

6. The ink filling method according to claim 5 , wherein the content (mass %) of the first water-soluble organic solvent in the aqueous ink is 0.25 or more times the content (mass %) of the water-soluble organic solvent.

7. The ink filling method according to claim 5 , wherein the content (mass %) of the first water-soluble organic solvent in the aqueous ink is 0.35 or more times the content (mass %) of the water-soluble organic solvent.

8. 6. The ink filling method according to claim 5, wherein the first water-soluble organic solvent includes polyethylene glycol.

9. 9. The ink filling method according to claim 8, wherein the number average molecular weight of the polyethylene glycol is 200 or more.

10. 2. The ink filling method according to claim 1, wherein the water-based ink further contains a nonionic surfactant.

11. 11. The ink filling method according to claim 10, wherein the nonionic surfactant is an acetylene glycol-based nonionic surfactant having an added mole number of ethylene oxide groups of 4 or more.

12. The ink filling method according to claim 1 , wherein the water-based ink further contains a water-soluble urethane resin.

13. the water-soluble urethane resin has a unit derived from a polyamine, 13. The ink filling method according to claim 12, wherein a ratio of the urethane bonds to a total of the urethane bonds in the water-soluble urethane resin and the urea bonds derived from the polyamine is 85.0 mol % or more and 99.0 mol % or less.

14. an ink supply system for an ink jet recording apparatus, the ink supply system having a recording head including: an ejection port for ejecting an ink jet water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the ink jet water-based ink from the ejection port; a first flow path connected to the pressure chamber; and a second flow path connected to the pressure chamber at a position opposite to the first flow path with the ejection element therebetween; using the ink jet recording device initially filled with the water-based ink from an ink container that contains the water-based ink having a dissolved oxygen content of 3.0 mg / L or less; An inkjet recording method for recording an image by applying the water-based ink ejected from the ejection orifice to a recording medium, comprising: the water-based ink contains a pigment and a water-soluble organic solvent; a layer of the ink container that comes into contact with the water-based ink is made of a resin; The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the layer of the ink container is 6.5 (cal / cm ３ ) １／２ is as follows: The ink-jet recording method according to the present invention, wherein the surface tension of the water-based ink at 25° C. is 25 mN / m or more.

15. an ink supply system having a recording head including: an ejection port for ejecting an ink-jet water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the water-based ink from the ejection port; a first flow path connected to the pressure chamber; and a second flow path connected to the pressure chamber at a position opposite to the first flow path across the ejection element; an inkjet recording apparatus in which the supply system is initially filled with the water-based ink from an ink container that contains the water-based ink having a dissolved oxygen content of 3.0 mg / L or less, the water-based ink contains a pigment and a water-soluble organic solvent; a layer of the ink container that comes into contact with the water-based ink is made of a resin; The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the layer of the ink container is 6.5 (cal / cm ３ ) １／２ is as follows: The inkjet recording apparatus is characterized in that the surface tension of the water-based ink at 25° C. is 25 mN / m or more.

16. an ink supply system for an ink jet recording apparatus, the ink supply system having a recording head including: an ejection port for ejecting an ink jet water-based ink; a pressure chamber communicating with the ejection port; an ejection element disposed in the pressure chamber and generating energy for ejecting the ink jet water-based ink from the ejection port; a first flow path connected to the pressure chamber; and a second flow path connected to the pressure chamber at a position opposite to the first flow path with the ejection element therebetween; using the ink jet recording device initially filled with the water-based ink from an ink container that contains the water-based ink having a dissolved oxygen content of 3.0 mg / L or less; A water-based ink for use in an inkjet recording method in which the water-based ink is discharged from the discharge port and applied to a recording medium to record an image, the water-based ink contains a pigment and a water-soluble organic solvent; a layer of the ink container that comes into contact with the water-based ink is made of a resin; The difference between the average SP value of the water-soluble organic solvent and the SP value of the resin forming the layer of the ink container is 6.5 (cal / cm ３ ) １／２ is as follows: The water-based ink has a surface tension of 25 mN / m or more at 25° C.

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