Inkjet recording method, inkjet recording device, and set of aqueous ink and cleaning liquid

Abstract

To provide an inkjet recording method which suppresses fixation of aqueous ink to a liquid contact member, and is excellent in fixation recoverability.SOLUTION: An inkjet recording method discharges aqueous ink from a recording head of an inkjet recording device, and records an image on a recording medium. An inkjet recording method includes an ink application step of applying aqueous ink onto a recording medium, and a cleaning step of cleaning a liquid contact member with which the aqueous ink is brought into contact in an inkjet recording device using an aqueous cleaning liquid. The cleaning liquid contains a surface active agent, a first water-soluble organic solvent having a vapor pressure lower than that of water, a second water-soluble organic solvent having an SP value by Fedors method of 9.8 or more and 14.2 or less, and a third water-soluble organic solvent having water retention of 50% or less. A content (mass%) of the third water-soluble organic solvent in the cleaning liquid is 0.70 time or more in a mass ratio of the water-soluble organic solvent to the total content (mass%), and a pH of the cleaning liquid is 8.5 or more.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In recent years, inkjet recording methods have been increasingly used in the field of sign and display, such as printing posters and large-format advertisements. In this field, inkjet recording devices are characterized by a larger recording area than home inkjet recording devices. In addition, since images need to be eye-catching, inks that exhibit high color development and can record images with excellent strength and fastness of the color material layer are required.

[0003] As an inkjet recording method that satisfies the above-mentioned characteristics, a method is known in which an ink containing resin particles is applied and then fixed by heating, etc. However, the use of ink containing resin particles may cause adhesion at the points where the aqueous ink comes into contact with the ink (hereinafter, also referred to as liquid-contacting members) in the inkjet recording device.

[0004] In general, by using a water-soluble organic solvent with a low vapor pressure such as glycerin, evaporation of the liquid component is reduced, and therefore the adhesion of the water-based ink to the liquid-contacting member can be suppressed. However, while the water-based ink containing resin particles can record an image with excellent robustness, even if a water-soluble organic solvent with a low vapor pressure is used, the ink is likely to adhere to the liquid-contacting member. For example, if the water-based ink adheres to the vicinity of the nozzle of the recording head, it leads to a decrease in ejection performance. In addition, if the water-based ink adheres to a unit (hereinafter also referred to as a recovery unit) including a recovery member (cap, absorber, etc.) on the surface where the nozzle of the recording head is formed, the accumulated adherent material will eventually come into contact with the recording medium, causing problems such as image smearing.

[0005] To address the above-mentioned problems, a method of cleaning a member using a cleaning liquid is known. An inkjet recording method using an ink containing resin particles and a water-soluble organic solvent with a high vapor pressure such as tripropylene glycol monomethyl ether, and a maintenance liquid has been proposed (see Patent Document 1). Also, an inkjet recording method using an ink containing urethane resin particles and a water-soluble organic solvent with a high vapor pressure such as 1,2-propanediol, and a cleaning liquid has been proposed (see Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2010-184429 A [Patent Document 2] JP 2018-144300 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present inventors have investigated various characteristics of the inkjet recording method using the aqueous ink and cleaning solution described in Patent Document 1 and Patent Document 2. As a result, it has been found that even when cleaning is performed using a cleaning solution, some areas still contain residual aqueous ink, and the ink sticks to such areas, and even when cleaning is performed, the ink cannot be restored from the stuck state to a state where it can be ejected normally, resulting in poor recovery from the stuck state.

[0008] Therefore, an object of the present invention is to provide an inkjet recording method in which the adhesion of the aqueous ink to the liquid-contacting member is suppressed and the adhesion recovery property is excellent even when recording is performed continuously using an ink that is prone to adhesion. Another object of the present invention is to provide an inkjet recording apparatus used in the inkjet recording method, and a set of the aqueous ink and the cleaning liquid. [Means for solving the problem]

[0009] That is, according to the present invention, there is provided an inkjet recording method for ejecting an aqueous ink from a recording head of an inkjet recording device to record an image on a recording medium, the inkjet recording method comprising: an ink application step of applying the aqueous ink to a recording medium; and a cleaning step of cleaning a liquid-contacting member in the inkjet recording device with which the aqueous ink comes into contact, using an aqueous cleaning liquid, wherein the inkjet recording device has a cleaning liquid supply path for supplying the cleaning liquid to the liquid-contacting member, the aqueous ink contains a pigment and resin particles, the cleaning liquid contains a surfactant, a first water-soluble organic solvent having a vapor pressure lower than that of water, a second water-soluble organic solvent having an SP value according to the Fedors method of 9.8 or more and 14.2 or less, and a third water-soluble organic solvent having a water retention ability of 50% or less, the content (mass%) of the third water-soluble organic solvent in the cleaning liquid is 0.7 times or more in terms of mass ratio to the total content (mass%) of the water-soluble organic solvents, and the pH of the cleaning liquid is 8.5 or more.

[0010] Moisture retention: 10.0 g of a 20% by weight aqueous solution of a water-soluble organic solvent is placed in a petri dish and placed in an environment with a temperature of 30°C and a relative humidity of 10%. When the mass no longer changes, the mass of the components is measured and calculated using the following formula (i). Moisture retention (%) = [mass of component remaining in dish (g) - 2.0(g)] / 2.0(g) (i) Effect of the Invention

[0011] According to the present invention, it is possible to provide an inkjet recording method in which the adhesion of the aqueous ink to the liquid-contacting member is suppressed and the adhesion recovery property is excellent even when recording is performed continuously using an ink that is prone to adhesion. Furthermore, according to the present invention, it is possible to provide an inkjet recording apparatus used in the inkjet recording method, and a set of the aqueous ink and the cleaning liquid. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view illustrating an embodiment of an inkjet recording apparatus of the present invention. [Diagram 2] 1 is a side view diagrammatically illustrating an embodiment of an inkjet recording apparatus of the present invention. [Diagram 3] FIG. 2 is a schematic diagram illustrating an embodiment of a recovery unit of an inkjet recording apparatus of the present invention. [Figure 4] FIG. 2 is a schematic diagram illustrating an embodiment of an ink supply configuration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the ink in the form of dissociation into ions, but for convenience, it is expressed as "containing a salt." In addition, the aqueous ink and reaction liquid for inkjet printing may be simply referred to as "ink" and "reaction liquid." Unless otherwise specified, the physical property values ​​are values ​​at room temperature (25°C), normal pressure (1 atm = 101.325 kPa), and normal humidity (relative humidity 50%).

[0014] The present inventors have studied the cause of adhesion of the liquid contacting member with which the ink comes in contact in an inkjet recording apparatus. First, the members of the recovery unit with which the ink comes in contact during the cleaning operation (recovery operation) of the recording head will be described. The members of the recovery unit include a cap that covers the surface of the recording head on which the ejection ports are formed (hereinafter, sometimes referred to as the ejection port surface), an absorber provided inside the cap, and an ink discharge path. When the recovery operation of the recording head is performed, the components of the ink and cleaning liquid are attached to each of the above-mentioned members. Thereafter, the water contained in the attached matter evaporates, and the viscosity increases. At this time, the viscosity of the attached matter further increases because the water-soluble organic solvent with a low vapor pressure is difficult to evaporate. As a result, even if the recovery operation of the recording head is performed, the ejection state does not recover to a normal state.

[0015] As described in Patent Documents 1 and 2, by using an ink containing a water-soluble organic solvent with a high vapor pressure, the increase in viscosity is suppressed, but the water-soluble organic solvent is likely to remain in the pigment layer formed by the ink applied to the recording medium. As a result, a problem occurs in which the fastness of the image cannot be obtained. In other words, it has not been possible to improve the adhesion recovery while maintaining the fastness of the image.

[0016] Inks used in the sign and display field are not only used on "absorbent recording media" that can absorb ink, but also on low-absorbent recording media that have low ink absorption and non-absorbent recording media that do not absorb ink. For this reason, inks containing water-soluble organic solvents with a higher vapor pressure than water are often used. Water-soluble organic solvents with a higher vapor pressure than water are prone to cause an increase in viscosity. In addition, in the case of inks containing water-soluble organic solvents with a low relative dielectric constant, the relative concentration of the water-soluble organic solvent increases with the evaporation of water, destabilizing the dispersion state of the components present in the ink in a dispersed state, such as pigments and resin particles. These factors combine to create a situation in which the recovery unit is prone to the formation of highly viscous, hard-to-remove solidified matter. If solidification occurs in the tube connected to the suction pump, it becomes impossible to generate negative pressure in the cap that covers the ejection port surface. As a result, it is considered that even if a recovery operation is performed, the ejection state will not be restored to a normal state.

[0017] In this situation, the present inventors have considered that, for example, in order to perform a recovery operation of the recording head normally, it is necessary to efficiently clean the liquid-contacting members of the recovery unit using a cleaning liquid containing a surfactant for exerting cleaning power. Therefore, the present inventors have further studied the composition of the cleaning liquid. As a result, they have found that the recovery operation of the recording head can be performed normally and the adhesion recovery can be improved by using a cleaning liquid characterized by containing a surfactant and a specific water-soluble organic solvent in a predetermined ratio.

[0018] That is, the inkjet recording method of the present invention has the following features. First, the inkjet recording device has a cleaning liquid supply path that supplies a cleaning liquid to a liquid-contacting member of the aqueous ink. The aqueous ink contains a pigment and resin particles. The cleaning liquid contains a surfactant, a first water-soluble organic solvent having a vapor pressure lower than that of water, a second water-soluble organic solvent having an SP value of 9.8 to 14.2 according to the Fedors method, and a third water-soluble organic solvent having a water retention capacity of 50% or less.

[0019] The content (mass%) of the third water-soluble organic solvent in the cleaning liquid is 0.7 times or more the mass ratio of the total content (mass%) of the water-soluble organic solvents. The moisture retention will be described in detail later. The pH of the cleaning liquid is 8.5 or more. The method includes a step of applying the water-based ink to the recording medium, and a cleaning step of cleaning the water-based ink contacting member with the cleaning liquid. The present inventors speculate as follows about the mechanism by which the above configuration enables the recovery operation of the recording head to be performed normally and improves adhesion recovery.

[0020] The ink contains a pigment and resin particles. When such ink is discharged for a long period of time, it may become strongly fixed to the liquid-contacting member. By using a cleaning liquid containing a second water-soluble organic solvent having an SP value of 9.8 to 14.2 by the Fedors method, even if the ink is fixed, the fixed matter can be efficiently dissolved and the ink can be returned to a normal state in which the fixation to the liquid-contacting member is eliminated. This is thought to be because a water-soluble organic solvent having an SP value within the above range has a high affinity with general-purpose resin particles in water-based inkjet inks and can efficiently dissolve attached matter. If the SP value is outside the above range (less than 9.8 or more than 14.2), the affinity with the resin particles is low and the dissolution of the fixed matter is difficult to proceed. As a result, the fixation cannot be eliminated by the recovery operation, and the fixation recovery cannot be obtained. In addition, if the SP value is less than 9.8, the liquid-contacting member may be corroded.

[0021] However, even when the second water-soluble organic solvent is used, there are cases where the stuck matter is generated and the stuck matter recovery is not obtained. As a result of the study by the present inventors, it was found that the stuck matter can be reliably dissolved and the stuck matter recovery is improved by setting the pH of the cleaning liquid to 8.5 or more. The pH of a typical aqueous ink for inkjet printing is over 7.0, and the pigment and resin particles are designed to be kept dispersed in an alkaline liquid. The higher the pH of the cleaning liquid, the easier it is to dissolve the stuck matter and redisperse the pigment and resin particles, and it was found that the pH of the cleaning liquid should be 8.5 or more for this purpose.

[0022] The cleaning liquid must contain a first water-soluble organic solvent with a vapor pressure lower than that of water. Since the first water-soluble organic solvent has a vapor pressure lower than that of water, for example, even if water evaporates from the ink and cleaning liquid adhering to the liquid-contacting member of the recovery unit, the first water-soluble organic solvent does not evaporate easily. Therefore, a sudden increase in viscosity is unlikely to occur. As a result, the cleaning effect of the cleaning liquid is exerted. If the water-soluble organic solvent in the cleaning liquid is only a water-soluble organic solvent with a vapor pressure similar to that of water, the liquid remaining on the liquid-contacting member after cleaning will dry up and become solidified as before cleaning, and therefore the fixation recovery property cannot be obtained.

[0023] However, it has been found that even if the above-mentioned cleaning liquid is used, there are cases where the adhesion of ink to the liquid-contacting member cannot be suppressed. The cap for protecting the recording head that ejects ink is likely to become attached to the ink due to preliminary ejection or the like. Therefore, the liquid-contacting member of the recovery unit including the cap is cleaned. The cap for protecting the recording head is in a state of contact with the ejection port surface (capping state). By being in the capping state, the evaporation of ink from the ejection port can be suppressed. The water-soluble organic solvent of the cleaning liquid remains inside the cap in the capping state after the inside of the cap is cleaned. Since an opening is provided in the closed space between the cap and the ejection port surface, a large amount of the first water-soluble organic solvent remains inside the cap as the water evaporates.

[0024] When the ink is left in the above state, depending on the equilibrium state between the water-soluble organic solvent in the ink near the ejection port, the water-soluble organic solvent remaining inside the cap (mainly the first water-soluble organic solvent), and water, the ink may be particularly likely to stick. Specifically, when the equilibrium is biased in the direction of moisture absorption by the water-soluble organic solvent remaining inside the cap, the water in the ink near the ejection port is absorbed, and as a result, the components in the ink are likely to precipitate. As a result of the study by the present inventors, the following was found. In the ink containing components present in a dispersed state such as pigments and resin particles, the ink exhibits a behavior of diffusing in the direction where there is more water, so the above phenomenon is not noticeable. However, in the ink containing components present in a dissolved state such as water-soluble resins, the above phenomenon is noticeable, and it was found that the ink cannot be restored to its sticking state. When such precipitation occurs, a strong recovery operation is required, which consumes a large amount of ink and cleaning liquid. Furthermore, if the recovery operation is not performed, the image quality will be reduced.

[0025] Therefore, in order to suppress the above-mentioned precipitation, the present inventors further studied and found that it is useful to control the composition of the ink using the water retention of the water-soluble organic solvent as an index. That is, the ink contains a third water-soluble organic solvent having a "water retention (%)" of 50% or less, which will be described later. Furthermore, by setting the content (mass%) of the third water-soluble organic solvent in the cleaning solution to 0.7 times or more in mass ratio to the total content (mass%) of the water-soluble organic solvents, the water equilibrium state can be made uniform. If the mass ratio is less than 0.7 times, the water equilibrium state is biased, and the water-soluble organic solvent remaining inside the cap tends to absorb water. As a result, adhesion recovery cannot be obtained.

[0026] In this specification, the water retention capacity is a value calculated by the following method. Specifically, 10.0 g of a 20% by mass aqueous solution of a water-soluble organic solvent is placed in a petri dish and placed in an environment with a temperature of 30° C. and a relative humidity of 10%. When the mass no longer changes, the mass of the components is measured and the water retention capacity is calculated by the following formula (i). Moisture retention (%) = [mass of component remaining in dish (g) - 2.0(g)] / 2.0(g) (i) <Inkjet recording method, inkjet recording apparatus, and set of water-based ink and cleaning liquid> The inkjet recording method of the present invention (hereinafter also simply referred to as "recording method") is a method in which an aqueous ink is ejected from an inkjet recording head of an inkjet recording apparatus by the action of thermal energy and applied to a recording medium to record an image. The inkjet recording apparatus has a cleaning liquid supply path that supplies a cleaning liquid to a member that contacts the aqueous ink. The recording method of the present invention has an ink application step of applying the aqueous ink to the recording medium, and a cleaning step of cleaning the member that contacts the aqueous ink in the inkjet recording apparatus with an aqueous cleaning liquid.

[0027] The water-based ink contains a pigment and resin particles. The cleaning solution contains a surfactant, a first water-soluble organic solvent having a vapor pressure lower than that of water, a second water-soluble organic solvent having an SP value of 9.8 to 14.2 by the Fedors method, and a third water-soluble organic solvent having a water retention capacity of 50% or less. The content (mass%) of the third water-soluble organic solvent in the cleaning solution is 0.7 times or more the total content (mass%) of the water-soluble organic solvents.

[0028] The inkjet recording apparatus of the present invention (hereinafter, also simply referred to as "recording apparatus") is an apparatus used in an inkjet recording method in which an aqueous ink and an aqueous reaction liquid are ejected from an inkjet recording head by the action of thermal energy and applied to a recording medium to record an image. The recording apparatus of the present invention is an apparatus that is suitably used in the above-mentioned recording method. In the present invention, it is not necessary to provide a step of curing the image by irradiation with active energy rays or the like.

[0029] The set of water-based ink and cleaning liquid of the present invention is a set used in an inkjet recording method in which water-based ink is ejected from a recording head to record an image on a recording medium. The set is preferably used in the above-mentioned recording method. The form of the set includes a set of multiple ink cartridges each containing multiple inks and cleaning liquids independently, and an ink cartridge formed integrally by combining multiple ink containing sections each containing multiple inks and cleaning liquids. The set of the present invention is not limited to the above form and may be in any form as long as it is configured so that the inks and cleaning liquids can be used in combination.

[0030] The inkjet recording method and inkjet recording apparatus (hereinafter, also simply referred to as "recording method and recording apparatus") of the present invention will be described in detail below.

[0031] FIG. 1 is a perspective view that illustrates an ink jet recording apparatus according to an embodiment of the present invention.

[0032] FIG. 2 is a side view showing an embodiment of the inkjet recording apparatus of the present invention. As shown in FIGS. 1 and 2, the recording apparatus of this embodiment includes an inkjet recording head 22 that ejects ink. The recording head 22 is a recording head that ejects ink by the action of thermal energy. A recording head that ejects ink by the action of thermal energy applies thermal energy to the ink by applying an electric pulse to an electrothermal conversion element, and ejects the ink from the ejection port. Although a recording head that ejects ink by the action of thermal energy is exemplified here, a recording head that ejects ink by the action of mechanical energy may be adopted. The recording head may include a mechanism (temperature control mechanism) that heats the water-based ink ejected from the recording head. When the temperature control mechanism is included, the temperature of the ink ejected from the recording head is preferably 35° C. or higher and 70° C. or lower.

[0033] [Heating process] The recording method of the present invention may include a step of heating (heat treatment) the recording medium to which the ink has been applied. By heating the recording medium to which the ink has been applied, it is possible to promote drying and increase the strength of the image. Examples of the means for heating the recording medium include known heating means such as a heater, air blowing means using air blowing such as a dryer, and heating means such as a combination of these. Examples of the heating means include the above heating means, air blowing means, and a combination of these. Examples of the heat treatment method include a method of applying heat from the opposite side (back side) of the recording surface (ink application surface) of the recording medium using a heater, a method of applying warm or hot air to the recording surface of the recording medium, and a method of heating from the recording surface or back side using an infrared heater. A combination of these methods may also be used.

[0034] In order to enhance the abrasion resistance of the image, the heating temperature of the recording medium to which the ink and reaction liquid have been applied is preferably 50° C. or more and 90° C. or less. The heating temperature of the recording medium to which the ink has been applied may be read by a sensor incorporated in a position corresponding to the heating means of the recording device, or may be determined from the relationship between the amount of heat and the temperature of the recording medium, which is determined according to the type of ink and recording medium.

[0035] In the recording device shown in FIGS. 1 and 2, a heater 25 supported by a frame (not shown) is disposed downstream in the sub-scanning direction A from the position where the recording head 22 reciprocates in the main scanning direction B. The recording medium 1 to which ink has been applied is heated by the heater 25. Examples of the heater 25 include a sheath heater and a halogen heater. The heater 25 is covered by a heater cover 26. The heater cover 26 is a member for efficiently irradiating the heat generated by the heater 25 to the recording medium 1. Furthermore, the heater cover 26 is also a member for protecting the heater 25. The recording medium 1 to which ink has been applied ejected from the recording head 22 is wound by a take-up spool 27 to form a roll-shaped wound medium 24.

[0036] The following describes the main parts of the inkjet recording device shown in Figures 1 and 2: [1] a cleaning liquid supplying method, [2] cleaning liquid, [3] a recovery mechanism for supplying cleaning liquid, and [4] an ink supplying mechanism for supplying cleaning liquid.

[0037] (How to supply cleaning fluid) The cleaning liquid can be used to clean ink contacting members such as the recovery mechanism of the recording head and the ink supply flow path, etc. In addition, at a predetermined timing (such as when reusing after a long period of non-use), the cleaning liquid can be passed from the liquid storage unit to the recording head in the same way as the ink and reaction liquid to clean the entire liquid supply system.

[0038] A method of supplying the cleaning liquid will be described with reference to FIG. 3. FIG. 3 is a schematic diagram showing one embodiment of the recovery unit. A cap 501 constituting the recovery unit 111 is supported by an elevation mechanism (not shown) so as to be able to ascend and descend, and moves between an ascending position and a descending position. At the ascending position, the cap 501 abuts against the print head 110 and covers (caps) the ejection port surface of the print head 110. By covering the ejection port surface of the print head 110, the cap 501 prevents ink from evaporating and drying from the ejection port surface of the print head 110 during non-printing operations, and drives a suction pump 502 described later to suck ink from the print head.

[0039] Tubes 105 and 505 are connected to the cap 501, and the tube 105 is connected to a cleaning liquid storage unit (not shown) provided inside or outside the inkjet recording device in order to clean the cap 501 and the recording head 110. The cleaning liquid is supplied into the cap 501 through the tube 105 by a pressure unit (not shown) in order to dilute the ink remaining in the cap 501 and suppress adhesion. The cleaning liquid may be supplied at least at a timing after the preliminary ejection or suction operation, but may be configured to be supplied at regular intervals to maintain a wet state. The tube 505 is connected to a drainage liquid storage unit (not shown), and uses a suction pump 502 to discharge the ink and cleaning liquid held in the cap 501. The tube 105 can also function as an air communication port, that is, as an opening. In addition, absorbers 506 and 507 are arranged inside the cap 501, and can hold a certain amount of ink discharged during preliminary ejection or suction recovery, and cleaning liquid supplied from the cleaning liquid storage unit.

[0040] During a printing operation, the cap 501 retreats to a lowered position to avoid interference with the print head 110 that moves together with the carriage 102. With the cap 501 retreated to the lowered position, the print head 110 can perform preliminary ejection toward the cap 501 when the print head 110 moves to a position opposite the cap 501.

[0041] The supply of the cleaning liquid to the tube 105 can be performed by generating negative pressure in the closed space between the print head 110 and the cap 501 in contact with it by driving the suction pump 502. However, the method of supplying the cleaning liquid is not limited to the above method. For example, the cleaning liquid can also be supplied by pressurizing using a pump connected to an externally provided cleaning liquid storage unit.

[0042] (Ink contact parts) Examples of liquid-contacting members that come into contact with ink in an inkjet recording apparatus include a recovery mechanism, an ink supply mechanism, etc. Specific examples of liquid-contacting members in the recovery mechanism include a cap 501, a waste liquid tube 505 of the suction mechanism, and absorbers 506 and 507 arranged in the cap 501. These liquid-contacting members can perform a cleaning operation by supplying a cleaning liquid from a cleaning liquid supply tube 105 to the cap 501 and then discharging it by a suction pump 502. If necessary, the cleaning operation can be performed multiple times.

[0043] FIG. 4 is a schematic diagram showing an ink supply configuration. A pressure pump 412 is used to pressurize the supply flow path 410, and ink is supplied from an ink storage unit 413 to the recording head 110. Usually, when an inkjet recording device is transported, the ink in the supply flow path 410 is drained to prevent ink leakage. However, when using an ink containing a water-soluble organic solvent with a higher vapor pressure than water, the ink remaining in the supply flow path 410 may dry and become hardened depending on the transport conditions after the ink is drained. Therefore, it is preferable to supply a cleaning liquid into the supply flow path and clean the supply flow path. In particular, ink is likely to remain in places having a complex flow path shape such as the buffer unit 411 and the pressure pump 412. Therefore, it is preferable to perform cleaning multiple times.

[0044] The cleaning can be performed in the same manner as the ink supply, by replacing the ink containing section 413 with a cleaning liquid containing section. The cleaning is not limited to the above method, and for example, the ink supply tube may be connected to a containing section other than the ink containing section.

[0045] (Recording medium) In the recording method and recording device of the present invention, it is preferable to use a low-absorbency or non-absorbency recording medium (low to non-absorbency recording medium). 1 / 2 Water absorption up to 0mL / m 2 More than 10mL / m 2The recording medium is as follows. The Bristow method is described in JAPAN TAPPI Paper Pulp Test Method No. 51 "Testing Method for Liquid Absorbency of Paper and Paperboard". In the present invention, a recording medium that satisfies the above-mentioned condition of water absorption is defined as a "low to non-absorbent recording medium". Recording media for inkjet recording having a coating layer (ink receiving layer) formed of inorganic particles (glossy paper, matte paper, etc.) and plain paper having no coating layer have a water absorption of 10 mL / m or more. 2 It is an "absorbent recording medium" that exceeds this.

[0046] Examples of low to non-absorbent recording media that can be used include plastic films, recording media having a plastic film attached to the recording surface side of a substrate, recording media having a resin coating layer provided on the recording surface of a substrate containing cellulose pulp, etc. Among these, plastic films are preferred, and recording media having a resin coating layer provided on the recording surface of a substrate containing cellulose pulp are also preferred.

[0047] When the ink containing resin particles is applied to a recording medium having low to non-absorbent properties, the water, water-soluble organic solvent, and other components are evaporated, and the resin particles are concentrated. The fusion between the concentrated resin particles is promoted, and the strength of the recorded image is improved. In contrast, even if the ink is applied to a recording medium having high absorbency of liquid components, the fusion between the resin particles is not promoted, and the strength of the image is not improved. In this specification, the recording medium does not mean a transfer body, but means a recording medium on which an image as a recorded matter is recorded.

[0048] <Cleaning solution> The cleaning liquid used in the recording method of the present invention is an aqueous cleaning liquid containing a surfactant and a specific water-soluble organic solvent. Each component used in the cleaning liquid will be described in detail below.

[0049] [Surfactants] The cleaning liquid contains a surfactant. A surfactant is a substance that is composed of a hydrophobic portion (such as a hydrocarbon chain, a perfluoroalkyl group, or a siloxane structure) and a hydrophilic portion (such as an ethylene oxide group or an ionic group). Examples of the surfactant include various surfactants such as anionic, cationic, amphoteric, and nonionic. Of these, it is preferable to use a nonionic surfactant. Examples of the nonionic surfactant include hydrocarbon-based, silicone-based, and fluorine-based surfactants. Of these, it is preferable to use a hydrocarbon-based surfactant.

[0050] It is preferable to use a cleaning liquid containing a large amount of surfactant, since this provides excellent cleaning properties and better adhesion recovery. The content (mass %) of the surfactant in the cleaning liquid is preferably 0.1 mass % or more and 5.0 mass % or less, and more preferably 1.0 mass % or more and 5.0 mass % or less, based on the total mass of the cleaning liquid.

[0051] Moreover, the content (mass%) of the surfactant in the cleaning solution is preferably 2.0 times or more the critical micelle concentration of the surfactant. Usually, surfactants are used to reduce the surface tension of the liquid and improve the wettability of the target object. In the case of aqueous pigment ink for inkjet, the content is often made larger than the content (critical micelle concentration) of the surfactant at which the reduction in surface tension is saturated. As a result of the study by the present inventors, it was found that by adding a surfactant to the cleaning solution at a content equal to or greater than the critical micelle concentration, the cleaning power can be significantly increased while maintaining the surface tension at a certain level. The critical micelle concentration is the minimum concentration required for surfactants to gather together in water to form micelles. The critical micelle concentration can be simply measured by measuring the surface tension of a liquid in which the content of the surfactant in water is changed stepwise, and measuring the minimum amount of surfactant at which no change in surface tension is observed even if the amount of surfactant is increased further.

[0052] In addition, the HLB value of the hydrocarbon nonionic surfactant according to the Griffin method is preferably 17 or less, since it has good cleaning properties and can further improve adhesion recovery. The "HLB value" of the surfactant in this specification is a value determined by the Griffin method, and is calculated based on the formula: HLB value = 20 x (formula weight of hydrophilic group of surfactant) / (molecular weight of surfactant). The HLB value determined by the Griffin method is a physical property value that indicates the degree of hydrophilicity or lipophilicity of the surfactant, and takes a value of 0 to 20. The smaller the HLB value, the higher the lipophilicity, and the larger the HLB value, the higher the hydrophilicity. The HLB value of the surfactant is preferably 4 or more, and more preferably 10 or more.

[0053] [Water-soluble organic solvent] The cleaning solution contains a first water-soluble organic solvent having a vapor pressure lower than that of water, a second water-soluble organic solvent having an SP value of 9.8 to 14.2 by the Fedors method, and a third water-soluble organic solvent having a water retention capacity of 50% or less. The content (mass%) of the third water-soluble organic solvent in the cleaning solution is 0.7 times or more in mass ratio to the total content (mass%) of the water-soluble organic solvents. In this specification, the definitions of each water-soluble organic solvent are not exclusive, and a water-soluble organic solvent may satisfy multiple definitions. Even in such a case, the mechanism described above is expressed without any impairment, and the effect of the present invention can be obtained. Each water-soluble organic solvent will be described in detail below.

[0054] [First water-soluble organic solvent] The cleaning solution contains a first water-soluble organic solvent with a lower vapor pressure than water. Many of the vapor pressures of water-soluble organic solvents are described in literature, such as "Chemical Handbook: Basics, Revised 5th Edition" (edited by the Chemical Society of Japan and Maruzen Co., Ltd.). For those not described in literature, values ​​calculated using calculation software (for example, "ACD / PhysChem Suite Version 12.00" manufactured by ACD / Labs) can be used. As mentioned above, the first water-soluble organic solvent is likely to remain on the liquid-contacting member after cleaning. The phenomenon that occurs on the liquid-contacting member after cleaning is mainly the evaporation of water contained in the ink and cleaning solution in the early stages. The evaporation rate gradually slows down, and the deposit is mainly composed of the water-soluble organic solvent and solids (pigments and resin particles). In this process, if the water-soluble organic solvent contained in the cleaning solution has a vapor pressure similar to that of water, the deposit is mainly composed of solids such as resin particles, and dries up to become a solidified matter. When the ink dries up, it becomes difficult to dissolve the ink if the ink contains a large amount of resin particles, and even if a recovery operation is performed, the ejection state does not return to a normal state.

[0055] However, even if the deposit is mainly composed of the first water-soluble organic solvent and the solid content in the ink, if the second water-soluble organic solvent described later also serves as the first water-soluble organic solvent, the remaining second water-soluble organic solvent may easily suppress redispersion of the pigment and resin particles. As a result, the solubility of the adhered matter may be slightly reduced. In order to facilitate redispersion of the pigment and resin particles, the first water-soluble organic solvent preferably has a relative dielectric constant of 20.0 or more. Examples of water-soluble organic solvents that have a relative dielectric constant of 20.0 or more at 25°C and a vapor pressure lower than that of water include triethylene glycol (22.7), 2-pyrrolidone (28.0), 1-(2-hydroxyethyl)-2-pyrrolidone (37.6), and glycerin (42.3). Here, the numbers in parentheses are the measured values ​​of the relative dielectric constant at 25°C.

[0056] The relative dielectric constant of the first water-soluble organic solvent can be measured using a dielectric constant meter (for example, product name "BI-870" manufactured by BROOKHAVEN INSTRUMENTS CORPORATION, etc.) at a frequency of 10 kHz. When the cleaning solution contains a plurality of first water-soluble organic solvents, the relative dielectric constant is treated as an average relative dielectric constant. Here, the average relative dielectric constant is a value calculated by multiplying the relative dielectric constant of each first water-soluble organic solvent by the ratio (mass %) of each first water-soluble organic solvent in the total amount of the first water-soluble organic solvent in the cleaning solution, and integrating the values. For example, the average relative dielectric constant of a cleaning solution containing 1,2-butanediol (22.2): 10.0 mass % and 1,2-propanediol (28.8): 5.0 mass % can be calculated as follows. Here, the number in parentheses is the relative dielectric constant at 25°C. (Average dielectric constant)=22.2×10.0 / 15.0+28.8×5.0 / 15.0=24.4 The relative dielectric constant of a water-soluble organic solvent that is a solid at 25° C. is a value calculated from the relative dielectric constant of a 50% by mass aqueous solution measured using the following formula (1). Although the term "water-soluble organic solvent" usually refers to a liquid, in the present invention, water-soluble organic solvents that are solid at 25° C. are also included in the water-soluble organic solvents. ε sol =2ε 50% -ε water (1) ε sol : Dielectric constant of solid water-soluble organic solvent at 25℃ ε 50% : Relative dielectric constant of a 50% by mass aqueous solution of a solid water-soluble organic solvent at 25°C ε water : relative dielectric constant of water Examples of water-soluble organic solvents that are generally used in aqueous inks and cleaning solutions and are solid at 25°C include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol with a number-average molecular weight of 1,000. The reason for determining the dielectric constant of a water-soluble organic solvent that is solid at 25°C from the dielectric constant of a 50% by mass aqueous solution is as follows. Among water-soluble organic solvents that are solid at 25°C and can be used as components of aqueous inks, it is difficult to prepare a high-concentration aqueous solution of more than 50% by mass. On the other hand, in a low-concentration aqueous solution of 10% by mass or less, the dielectric constant of water becomes dominant, and it is not possible to obtain a reliable (effective) dielectric constant value of the water-soluble organic solvent. As a result of the inventors' investigation, it was found that the aqueous solution to be measured can be prepared from almost all of the water-soluble organic solvents that are solid at 25°C and can be used in inks and cleaning solutions, and the dielectric constant to be determined is consistent with the effect of the present invention. For these reasons, it was decided to use a 50% by mass aqueous solution. For water-soluble organic solvents that are solid at 25°C and cannot be prepared as a 50% aqueous solution due to their low solubility in water, use an aqueous solution of the saturated concentration and use the above ε sol For convenience, the value of the relative dielectric constant calculated in accordance with the case of determining

[0057] The content (mass%) of the first water-soluble organic solvent in the cleaning solution is preferably 5.0% by mass or more and 50.0% by mass or less, more preferably 20.0% by mass or more and 40.0% by mass or less, based on the total mass of the cleaning solution. The second water-soluble organic solvent described later may also serve as the first water-soluble organic solvent, but the content (mass%) of the second water-soluble organic solvent that satisfies the definition of the first water-soluble organic solvent is preferably 10.0 mass or less, based on the total mass of the cleaning solution. This is because it may suppress redispersion of pigments and resin particles in the ink, making it difficult to dissolve solidified substances.

[0058] [Second water-soluble organic solvent] The cleaning liquid contains a second water-soluble organic solvent having an SP value of 9.8 to 14.2, both inclusive, as determined by the Fedors method. The SP value (δ) is a value calculated by the Fedors method based on the following formula. The SP value is also called the "solubility parameter," and the smaller the difference between the SP value of the solute and the SP value of the solvent, the greater the affinity of the solute to the solvent tends to be. For this reason, the SP value can be used as an index for measuring the strength of the interaction between two substances. By ensuring that the SP value is within the above range, sufficient affinity with the resin particles in the ink can be obtained. Although units are omitted in the present specification, the unit of the SP value (δ) is ((cal / cm 3 ) 1 / 2 ). δ = (ΔE vap / V) 1 / 2 (In the formula, ΔE vap represents the molar heat of vaporization (cal / mol), and V represents the molar volume (cc / mol) at 25°C. Specific examples of the water-soluble organic solvent having an SP value of 9.8 or more and 14.2 or less, that is, the second water-soluble organic solvent, are 1,5-pentanediol (14.2), methanol (13.8), triethylene glycol (13.6), 1,6-hexanediol (13.5), 3-methyl-1,5-pentanediol (13.4), 2-methylpentane-2,4-diol (13.1), tetraethylene glycol (12.8), number average molecular weight 200 polyethylene glycol (12.8), 1,2-butanediol (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), 2-methyl-2-hydroxypentan-4-one (11.7), isopropanol (11.6), N- Examples of such polyethers include methyl-2-pyrrolidone (11.5), ethylene glycol monoethyl ether (11.5), 1,3-dimethyl-2-imidazolidinone (11.4), n-butanol (11.3), diethylene glycol monomethyl ether (11.2), 2-butanol (11.1), diethylene glycol monoethyl ether (10.9), tert-butanol (10.9), triethylene glycol monoethyl ether (10.6), polyethylene glycol having a number average molecular weight of 600 (10.5), diethylene glycol monobutyl ether (10.5), 3-methoxy-3-methylbutanol (10.5), triethylene glycol monobutyl ether (10.3), tetraethylene glycol monobutyl ether (10.2), and polyethylene glycol having a number average molecular weight of 1,000 (10.1) (the numbers in parentheses indicate the SP values).

[0059] The second water-soluble organic solvent is preferably at least one selected from the group consisting of monohydric alcohols, dihydric alcohols, and glycol ethers. Among them, it is more preferable that the second water-soluble organic solvent is at least one selected from the group consisting of monohydric alcohols and dihydric alcohols. The alkyl group constituting the monohydric and dihydric alcohols may be either linear or branched, and may be substituted with an alkoxy group having 1 to 3 carbon atoms. Examples of the monohydric alcohol include methanol (13.8), ethanol (12.6), n-propanol (11.8), isopropanol (11.6), n-butanol (11.3), 2-butanol (11.1), tert-butanol (10.9), and 3-methoxy-3-methylbutanol (10.5). Specific examples of dihydric alcohols include 1,5-pentanediol (14.2), 1,6-hexanediol (13.5), 3-methyl-1,5-pentanediol (13.4), 2-methylpentane-2,4-diol (13.1), 1,2-butanediol (12.8), 1,2-pentanediol (12.2), and 1,2-hexanediol (11.8).

[0060] Among them, as the second water-soluble organic solvent, 1,2-butanediol (26.1), 1,2-pentanediol (25.0), and 1,2-hexanediol (24.1) are preferable, and 1,2-hexanediol is particularly preferable. By using these water-soluble organic solvents, the wettability of the cleaning liquid can be easily increased, and the cleaning property can be further improved.

[0061] The content (mass%) of the second water-soluble organic solvent in the cleaning liquid is preferably 10.0% by mass or more based on the total mass of the cleaning liquid. If the content is less than 10.0% by mass, the effect of penetrating into the interface between the fixed object and the liquid-contacting member may not be sufficient, and the fixation recovery may not be sufficient. The content (mass%) of the second water-soluble organic solvent in the cleaning liquid is preferably 35.0% by mass or less. If the amount of the second water-soluble organic solvent is too large, in the case of a resin-dispersed pigment, it may act on the resin dispersant used to disperse the pigment, making the dispersion state of the pigment somewhat unstable, and the fixation recovery may not be sufficient. When a water-soluble organic solvent (fourth water-soluble organic solvent) having an SP value of 9.8 to 12.2 is used among the second water-soluble organic solvents, the content (mass%) of the fourth water-soluble organic solvent in the cleaning liquid is preferably 10.0% by mass or less based on the total mass of the cleaning liquid. Among them, it is more preferable that the content is 5.0% by mass or less. The content of the fourth water-soluble organic solvent in the cleaning solution may be 0.0% by mass, that is, the cleaning solution may be substantially free of the fourth water-soluble organic solvent.

[0062] [Third water-soluble organic solvent] The above-mentioned precipitation is a phenomenon that occurs with drying, and when the nozzle surface of the recording head is covered with a cap, it is unlikely to occur near the nozzles of the recording head or on the nozzle surface. However, when the recording device is stored without being used for a long period of time, the ink gradually dries out even if the cap is on, causing precipitation on the nozzle surface, which hinders the recording head from coming into contact with the cap. As a result, negative pressure cannot be generated in the cap during the suction operation performed with the recording head and cap in close contact, and adhesion recovery may be reduced.

[0063] The cleaning liquid contains a third water-soluble organic solvent having a water retention capacity of 50% or less, and the content (mass%) of the third water-soluble organic solvent in the cleaning liquid is 0.7 times or more in mass ratio to the total content (mass%) of the water-soluble organic solvents. The above mass ratio is preferably 0.9 times or more. Among them, the above mass ratio is more preferably 1.0 times. In other words, it is particularly preferable that all the water-soluble organic solvents in the cleaning liquid are composed only of the third water-soluble organic solvent having a water retention capacity of 50% or less, and the cleaning liquid does not substantially contain a water-soluble organic solvent having a water retention capacity of more than 50%. By setting the mass ratio of the third water-soluble organic solvent in the above range, as described above, the water equilibrium state can be made uniform and adhesion after cleaning can be suppressed. The water retention capacity of the third water-soluble organic solvent is preferably 30% or more. By setting it in the above range, the fluctuation of the water equilibrium state can be more effectively suppressed and adhesion after cleaning can be efficiently suppressed.

[0064] The third water-soluble organic solvent may be one having a water retention capacity of 50% or less among the above-mentioned first water-soluble organic solvent and second water-soluble organic solvent. Of course, a third water-soluble organic solvent that does not meet the definition of the first water-soluble organic solvent and the second water-soluble organic solvent, that is, that is, that is not the first water-soluble organic solvent and the second water-soluble organic solvent, may be used. As long as the effects of the present invention are obtained, other water-soluble organic solvents that do not meet the definition of any of the first water-soluble organic solvent, the second water-soluble organic solvent, and the third water-soluble organic solvent may be contained.

[0065] The vapor pressure (kPa) of the water-soluble organic solvent with the highest content in the aqueous ink is preferably higher than the vapor pressure (kPa) of the water-soluble organic solvent with the highest content in the cleaning solution. With such a composition, even if the mixture of the aqueous ink and the cleaning solution remains on the liquid-contacting member, the vapor pressure of the water-soluble organic solvent in the cleaning solution, which is the main component of the mixture, is low, so that adhesion is suppressed and the adhesion recovery is further improved. In addition, the cleaning solution preferably contains a water-soluble organic solvent with a content (mass%) of 10.0 mass% or more. Even if the cleaning solution contains multiple types of water-soluble organic solvents, the component with the highest content is 10.0 mass% or more, so that the main water-soluble organic solvent of the mixture remaining on the liquid-contacting member after cleaning is easily derived from the cleaning solution. As a result, the adhesion recovery is further improved.

[0066] [Other ingredients] The cleaning liquid may contain other components as necessary. Examples of other components include the same components as those described below that can be contained in the ink. In the present invention, these additives are not considered as water-soluble organic solvents, and are not included in the calculation of the SP value, vapor pressure, and water retention. It is preferable that the cleaning liquid does not contain a reactant to be contained in the reaction liquid.

[0067] [Physical properties of cleaning solution] The surface tension of the cleaning liquid at 25°C is preferably 65 mN / m or less, more preferably 40 mN / m or less. If the surface tension exceeds 65 mN / m, it may be difficult for the cleaning liquid to penetrate into the interface between the fixed object and the liquid-contacting member, and sufficient adhesion recovery may not be obtained. The surface tension of the cleaning liquid at 25°C is preferably 20 mN / m or more. The surface tension of the cleaning liquid is a "static" surface tension, and can be measured using a plate method or the like. The pH of the cleaning liquid at 25°C must be 8.5 or more. In particular, it is more preferable that it is 9.0 or more, and it is preferably 9.5 or less. The pH of the cleaning liquid can be measured using a pH meter using a glass electrode or the like. The viscosity of the cleaning liquid is preferably 15.0 mPa·s or less, more preferably 5.0 mPa·s or less. It is also preferable that it is 1.0 mPa·s or more. If the viscosity is within the above range, it is easy to penetrate into the interface between the fixed object and the liquid-contacting member, and therefore cleaning properties can be further improved. The viscosity of the cleaning liquid can be measured using a rotational viscometer or the like.

[0068] <Ink> The ink used in the recording method of the present invention is a water-based ink for ink-jet recording, which contains a pigment and resin particles. Each component of the ink will be described in detail below.

[0069] (Colorant) The ink contains a pigment. The content (mass %) of the pigment in the ink is preferably from 0.5 to 15.0% by mass, and more preferably from 1.0 to 10.0% by mass, based on the total mass of the ink.

[0070] Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, and dioxazine.

[0071] As a pigment dispersion method, resin-dispersed pigments using a resin as a dispersant, self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface, etc. can be used. In addition, resin-bonded pigments in which organic groups containing a resin are chemically bonded to the pigment particle surface, and microcapsule pigments in which the pigment particle surface is coated with a resin, etc. can be used. Among them, it is preferable to use resin-dispersed pigments in which a resin as a dispersant is physically adsorbed onto the pigment particle surface, rather than resin-bonded pigments or microcapsule pigments.

[0072] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin as described below, particularly a water-soluble resin, can be used. The content (mass%) of the pigment in the ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the content of the resin dispersant.

[0073] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the anionic group is a salt type, examples of the cation that serves as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Specific examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. In addition, it may be a group that is a combination of these groups.

[0074] (resin) The ink contains resin particles. By using an ink containing resin particles, an image with improved image fastness such as abrasion resistance can be recorded. The resin particles are preferably formed of an acrylic resin. The ink may further contain a water-soluble resin that can be dissolved in an aqueous medium. The water-soluble resin can be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary. Also, it can be added to the ink (ii) to improve various properties of the recorded image.

[0075] The content (mass%) of the resin in the ink is preferably 0.1% by mass or more and 20.0% by mass or less, more preferably 0.5% by mass or more and 15.0% by mass or less, based on the total mass of the ink. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be used alone or in combination of two or more kinds.

[0076] [Resin Composition] Examples of the resin include acrylic resins, urethane resins, and olefin resins. Among them, acrylic resins and urethane resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylate are more preferred. In this specification, the terms "(meth)acrylic acid" and "(meth)acrylate" mean "acrylic acid, methacrylic acid" and "acrylate, methacrylate", respectively.

[0077] From the viewpoint of affinity with the second water-soluble organic solvent, it is preferable that the SP value of the resin particles and the SP value of the second water-soluble organic solvent, as determined by the Fedors method, are close to each other.

[0078] The acrylic resin preferably has a hydrophilic unit and a hydrophobic unit as constituent units. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer is preferred. In particular, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of styrene and α-methylstyrene is preferred. These resins are likely to interact with pigments, and therefore can be suitably used as a resin dispersant for dispersing pigments.

[0079] The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of the hydrophilic monomer having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Examples of cations constituting the salts of acidic monomers include ions of lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit not having a hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer not having a hydrophilic group such as an anionic group. Specific examples of the hydrophobic monomer include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0080] The urethane resin can be obtained by reacting, for example, polyisocyanate with a polyol. In addition, a chain extender may be further reacted with the urethane resin. Examples of the olefin resin include polyethylene and polypropylene.

[0081] [Resin properties] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, 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.

[0082] When the particle size of the resin in the sample solution is measured by dynamic light scattering, if no particles having a particle size are measured, the resin can be determined to be water-soluble. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3, and measurement time: 180 seconds. In addition, a particle size analyzer using dynamic light scattering (for example, the product name "UPA-EX150", manufactured by Nikkiso) can be used as the particle size distribution measuring device.

[0083] Of course, the particle size distribution measuring device and the measurement conditions are not limited to those described above.

[0084] The acid value of the water-soluble resin is preferably 100 mgKOH / g or more and 250 mgKOH / g or less, and the weight average molecular weight of the water-soluble resin is preferably 3,000 or more and 15,000 or less.

[0085] The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 3,000,000 or less, more preferably 100,000 or more and 3,000,000 or less. The volume-based cumulative 50% particle diameter (D50) of the resin particles measured by dynamic light scattering is preferably 50 nm or more and 500 nm or less. The volume-based cumulative 50% particle diameter of the resin particles is the diameter of the particles that is 50% of the total volume of the measured particles when integrated from the small particle diameter side in the particle diameter integration curve. The volume-based cumulative 50% particle diameter of the resin particles can be measured using the particle size analyzer and measurement conditions using the dynamic light scattering method described above. The glass transition temperature of the resin particles is preferably 40°C or more and 120°C or less, more preferably 50°C or more and 100°C or less. The glass transition temperature (° C.) of the resin particles can be measured using a differential scanning calorimeter (DSC). The resin particles do not necessarily contain a coloring material.

[0086] [Aqueous medium] The ink is an aqueous ink containing water as an aqueous medium. The ink may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As the water, deionized water or ion-exchanged water is preferably used. The content (mass%) of water in the aqueous ink is preferably 50.0 mass% or more and 95.0 mass% or less based on the total mass of the ink. The content (mass%) of the water-soluble organic solvent in the aqueous ink is preferably 3.0 mass% or more and 50.0 mass% or less based on the total mass of the ink. As the water-soluble organic solvent, any of those usable for inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing solvents, and sulfur-containing solvents, can be used. The ink preferably contains a water-soluble organic solvent having a higher vapor pressure than water. The ink may also contain a water-soluble organic solvent having a lower vapor pressure than water. The water-soluble organic solvent may be used alone or in combination of two or more.

[0087] [Other ingredients] The ink may contain various other components as necessary. Examples of other components include various additives such as defoamers, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors. However, it is preferable that the ink does not contain a reactant to be contained in the reaction liquid. In the present invention, these additives are not considered as water-soluble organic solvents, and are not included in the calculation of the SP value, vapor pressure, and water retention capacity.

[0088] [Ink properties] The ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less.

[0089] (Reaction solution) The recording method of the present invention preferably includes a reaction liquid applying step of applying an aqueous reaction liquid containing a reactant that reacts with the aqueous ink to a recording medium. In particular, it is preferable to include a reaction liquid applying step before an ink applying step of applying the aqueous ink to a recording medium, or to perform the ink applying step and the reaction liquid applying step in parallel. Each component used in the reaction liquid will be described in detail below.

[0090] The reaction liquid reacts with the ink when it comes into contact with the ink, and aggregates the components in the ink (components having anionic groups, such as resins, surfactants, and self-dispersing pigments), and contains a reactant. The presence of the reactant can destabilize the state of the components having anionic groups in the ink when the ink and the reactant come into contact with each other on the recording medium, and promote the aggregation of the ink. Examples of the reactant include cationic components such as polyvalent metal ions and cationic resins, and organic acids. The reactant may be used alone or in combination of two or more.

[0091] Examples of polyvalent metal ions constituting polyvalent metal salts include Ca. 2+ , Cu 2+ , Ni 2+ , Mg 2+ , Sr 2+ , B.A. 2+ , and Zn 2+ Divalent metal ions such as Fe 3+ , Cr 3+ , Y 3+ , and Al 3+ In order to add a polyvalent metal ion to the reaction solution, a water-soluble polyvalent metal salt (which may be a hydrate) formed by combining a polyvalent metal ion with an anion can be used. Examples of the anion include Cl. - , Br - , I - , ClO - , ClO2 - , ClO3 - , ClO4 - , NO2 - , NO3 - , SO4 2- , CO3 2- , HCO3 - , PO4 3- , HPO4 2- , and H2PO4 - Inorganic anions such as HCOO - , (COO - )2, COOH(COO - ), CH3COO - , CH3CH(OH)COO -, C2H4(COO - )2, C6H5COO - , C6H4(COO - )2, and CH3SO3 - In the case where a polyvalent metal ion is used as a reactant, the content (mass%) of the polyvalent metal salt in the reaction solution is preferably 1.0 mass% or more and 20.0 mass% or less based on the total mass of the reaction solution. In this specification, when the polyvalent metal salt is a hydrate, the "content (mass%) of the polyvalent metal salt" in the reaction solution means the "content (mass%) of the anhydride of the polyvalent metal salt" excluding water as the hydrate.

[0092] The reaction liquid containing an organic acid has a buffering ability in the acidic range (less than pH 7.0, preferably pH 2.0 to 5.0), and thus efficiently converts the anionic groups of the components present in the ink into an acid form and causes them to aggregate. Examples of the organic acid include monocarboxylic acids and salts thereof, such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrole carboxylic acid, furan carboxylic acid, picolinic acid, nicotinic acid, thiophene carboxylic acid, levulinic acid, and coumaric acid; dicarboxylic acids and salts and hydrogen salts thereof, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid, and tartaric acid; tricarboxylic acids and salts and hydrogen salts thereof, such as citric acid and trimellitic acid; and tetracarboxylic acids and salts and hydrogen salts thereof, such as pyromellitic acid. When an organic acid is used as the reactant, the content (mass %) of the organic acid in the reaction liquid is preferably 1.0 mass % or more and 50.0 mass % or less based on the total mass of the reaction liquid.

[0093] Examples of cationic resins include resins having a structure of primary to tertiary amines and resins having a structure of quaternary ammonium salts. Specific examples include resins having a structure of vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, guanidine, diallyldimethylammonium chloride, and alkylamine-epichlorohydrin condensate. In order to increase the solubility in the reaction solution, the cationic resin may be used in combination with an acidic compound or the cationic resin may be subjected to a quaternary treatment. When a cationic resin is used as a reactant, the content (mass%) of the cationic resin in the reaction solution is preferably 0.1 mass% or more and 10.0 mass% or less based on the total mass of the reaction solution.

[0094] [Aqueous medium] The reaction liquid is an aqueous reaction liquid containing at least water as an aqueous medium. The aqueous medium used in the reaction liquid may contain a water-soluble organic solvent that can be contained in the ink, as described below.

[0095] [Other ingredients] The reaction liquid may contain various other components as necessary. Examples of the other components include the same components as those that can be contained in the ink described above.

[0096] [Physical properties of reaction solution] The reaction liquid is an aqueous reaction liquid applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the reaction liquid at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the reaction liquid at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the reaction liquid at 25°C is preferably 5.0 or more and 9.5 or less, and more preferably 6.0 or more and 9.0 or less. EXAMPLES

[0097] 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.

[0098] <Physical properties of water-soluble organic solvents> The physical properties of the water-soluble organic solvents were measured as follows. The vapor pressure was a literature value or a value calculated using calculation software, and the SP value was a value calculated by the Fedors method. The physical properties of the water-soluble organic solvents are shown in Table 1. Below, the numerical value attached to polyethylene glycol indicates the number average molecular weight.

[0099] (moisture retention capacity) The water retention of the water-soluble organic solvent was measured by the following method. Specifically, 2.0 g of the water-soluble organic solvent and 8.0 g of ion-exchanged water were mixed to prepare an aqueous solution with a water-soluble organic solvent content of 20%. 10.0 g of the aqueous solution was placed in a petri dish and left to stand in an environment with a temperature of 30° C. and a relative humidity of 10%. After confirming that no mass change occurred by leaving it to stand for 24 hours, the mass of the components remaining in the petri dish in this environment was measured, and the water retention was calculated according to the formula (i) described above. For 1,2-butanediol, 1,5-pentanediol, 2-propanol, and 3-methoxy-3-methylbutanol, it was not possible to calculate a water retention that was commensurate with their molecular structures. This is thought to be due to the effect of evaporation of the water-soluble organic solvent. Such water-soluble organic solvents were not included in the third water-soluble organic solvent. In addition, in Table 1, the column for "water retention" for these water-soluble organic solvents is marked with "-".

[0100] (Dielectric constant) The relative dielectric constant of the water-soluble organic solvent was measured using a dielectric constant meter (product name "BI-870", manufactured by BROOKHAVEN INSTRUMENTS CORPORATION) at a frequency of 10 kHz.

[0101] [Table 1]

[0102] <Preparation of reaction solution> The components (unit: %) shown in Table 2 were mixed and thoroughly stirred, and then pressure filtered using a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare a reaction solution. "Cation Master PDT-2" is the trade name of a cationic resin solution "Poly-2-hydroxypropyldimethylammonium chloride aqueous solution" manufactured by Yokkaichi Chemical, with a resin content of 60.0%. "Acetylenol E100" is the trade name of a hydrocarbon-based nonionic surfactant manufactured by Kawaken Fine Chemical.

[0103] [Table 2]

[0104] <Preparation of pigment dispersion> (Pigment dispersion 1) A styrene-ethyl acrylate-acrylic acid copolymer (resin 1) with an acid value of 150 mgKOH / g and a weight average molecular weight of 8,000 was prepared. 20.0 parts of resin 1 were neutralized with potassium hydroxide in an amount equimolar to the acid value, and then an appropriate amount of pure water was added to prepare an aqueous solution of resin 1 with a resin (solid content) content of 20.0%. 10.0 parts of pigment (CI Pigment Blue 15:3), 15.0 parts of the aqueous solution of resin 1, and 75.0 parts of pure water were mixed to obtain a mixture. The obtained mixture and 200 parts of zirconia beads with a diameter of 0.3 mm were placed in a batch-type vertical sand mill (manufactured by Imex) and dispersed for 5 hours while cooling with water. After centrifuging to remove coarse particles, the mixture was pressure-filtered with a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare pigment dispersion 1 with a pigment content of 10.0% and a resin dispersant (resin 1) content of 3.0%.

[0105] (Pigment dispersion 2) Pigment dispersion 2 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Red 122. The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0106] (Pigment dispersion 3) Pigment dispersion 3 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Yellow 74. The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0107] (Pigment Dispersion 4) Pigment dispersion 4 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to carbon black. The pigment dispersion 4 had a pigment content of 10.0% and a resin dispersant (resin 1) content of 3.0%.

[0108] <Preparation of resin particles> (Resin particles 1) In a four-neck flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 74.0 parts of ion-exchanged water and 0.2 parts of potassium persulfate were mixed. Also, 24.0 parts of ethyl methacrylate, 1.5 parts of methacrylic acid, and 0.3 parts of a reactive surfactant were mixed to prepare an emulsion. As the reactive surfactant, "ADEKA REASOAP ER20" (manufactured by ADEKA, nonionic surfactant, number of moles of ethylene oxide group added: 20) was used.

[0109] The prepared emulsion was added dropwise to the four-neck flask over 1 hour under a nitrogen atmosphere, and a polymerization reaction was carried out for 2 hours with stirring at 80° C. After cooling to 25° C., ion-exchanged water and an aqueous solution containing potassium hydroxide in an amount equimolar to the acid value of the resin particles were added to prepare an aqueous dispersion of resin particles 1 with a resin particle (solid content) content of 25.0%.

[0110] (Resin particles 2) In a four-neck flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 81.8 parts of ion-exchanged water and 0.2 parts of potassium persulfate were mixed. In addition, 16.1 parts of ethyl methacrylate, 1.6 parts of methoxypolyethylene glycol methacrylate, and 0.3 parts of the above reactive surfactant were mixed to prepare an emulsion. As the methoxypolyethylene glycol methacrylate, a product name "Blenmer PME1000" (manufactured by NOF Corp., the number of moles of ethylene oxide groups added is about 23) was used. Under a nitrogen atmosphere, the prepared emulsion was dropped into the four-neck flask over 1 hour, and a polymerization reaction was carried out for 2 hours while stirring at 80°C. After cooling to 25°C, ion-exchanged water was added to prepare an aqueous dispersion of resin particles 2 with a resin particle (solid content) content of 25.0%.

[0111] <Ink Preparation> Each ink was prepared by mixing the components (unit: %) shown in Table 3, thoroughly stirring, and then filtering under pressure using a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm. "Acetylenol E60" is the trade name of a hydrocarbon-based nonionic surfactant manufactured by Kawaken Fine Chemicals.

[0112] [Table 3]

[0113] <Preparation of cleaning solution> Each cleaning solution was prepared by mixing the components (unit: %) shown in the upper rows of Tables 4 to 6, thoroughly stirring, and then filtering under pressure using a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm. The properties of the cleaning solutions are shown in the lower rows of Tables 4 to 6.

[0114] The following surfactants were used to prepare the cleaning solution. The numbers in parentheses at the end of the surfactants in Tables 4 to 6 are HLB values ​​according to the Griffin method. "EO" in formulas (2) and (3) represents an ethylene oxide group (-CH2-CH2-O-). Product name: Acetylenol E60, manufactured by Kawaken Fine Chemicals, a hydrocarbon-based nonionic surfactant Product name: Acetylenol E100, manufactured by Kawaken Fine Chemicals, a hydrocarbon-based nonionic surfactant Product name: "NIKKOL BC-20", manufactured by Nikko Chemicals, a hydrocarbon-based nonionic surfactant Product name: "NIKKOL BC-30", manufactured by Nikko Chemicals, a hydrocarbon-based nonionic surfactant Product name: "NIKKOL BC-40", manufactured by Nikko Chemicals, a hydrocarbon-based nonionic surfactant "Silicone surfactants", compounds represented by the following formula (2) (nonionic surfactants) "Fluorosurfactant": a compound represented by the following formula (3) (nonionic surfactant)

[0115] [ka]

[0116] [Table 4]

[0117] [Table 5]

[0118] [Table 6]

[0119] <Preparing the recording medium> The following recording media were prepared. Recording medium 1: Polyethylene terephthalate (PET) film (product name "PETWH50 PAT8LK", manufactured by Lintec, 30 msec from the start of contact in the Bristow method) 1 / 2 Water absorption up to 2.5mL / m 2 ) Recording medium 2: Art paper (product name "Art PW8K", manufactured by Lintec, 30 msec from the start of contact in the Bristow method) 1 / 2Water absorption rate up to 10 mL / m 2 ) Recording medium 3: High-quality paper (product name "55PW8KCOC", manufactured by Lintec, 30 msec from the start of contact in the Bristow method 1 / 2 Water absorption rate up to 12 mL / m 2 ).

[0120] <Evaluation of adhesion recovery> In order to evaluate the adhesion recovery property, the reaction liquid, ink, and cleaning liquid obtained above were used to carry out the following evaluations of the performance of the cleaning liquid and the performance in the recovery operation. In the present invention, in the evaluation criteria for each of the following items, "AA", "A", and "B" were defined as acceptable levels, and "C" was defined as an unacceptable level. The evaluation results are shown in Table 7.

[0121] (Cleaning solution performance) [1] Solubility of the adherent 0.5 g of the ink shown in Table 7 was placed in a glass petri dish with an inner diameter of 5 cm, and the ink was allowed to stand for 120 hours in an environment of 30°C and 10% relative humidity to fix the ink. Then, 3 g of the cleaning solution shown in Table 7 was placed in the petri dish, and the solution was allowed to blend with the ink-fixed matter, and the petri dish was covered and left to stand for 15 hours. Then, the coloring of the contents of the petri dish due to the pigment in the ink was measured as the integral value (x) of absorbance in the wavelength range of 200 to 800 nm. In addition, the integral value (y) of absorbance of the cleaning solution was measured under the same conditions. A spectrophotometer (trade name "U-3011", manufactured by Hitachi High-Tech Science) was used to measure the absorbance. From the obtained values ​​of (x) and (y), the cleaning degree was calculated based on the following formula (ii), and the solubility of the fixed matter was evaluated according to the evaluation criteria shown below. The higher the cleaning degree, the higher the cleaning solution's ability to dissolve the fixed matter and the better the recovery from the fixed matter. Cleanliness = integrated value of absorbance after cleaning (x) / integrated value of absorbance of cleaning solution (y) (ii) AA: Cleanliness was 100 or higher A: The cleaning level was 20 or more and less than 100. B: Cleanliness was 10 or more but less than 20 C: The cleaning level was less than 10. [2] Suppression of viscosity increase A mixed liquid was prepared by mixing the ink and cleaning liquid shown in Table 7 at a volume ratio of 1:3, and the viscosity was measured (viscosity before storage (x)). The mixed liquid was placed in a container, left uncovered at a temperature of 30°C and a relative humidity of 10% for 15 hours, and then returned to 25°C and the viscosity was measured again (viscosity after storage (y)). A viscometer (product name "RE80 type viscometer", manufactured by Toki Sangyo Co., Ltd.) was used to measure the viscosity. The difference in viscosity before and after storage was calculated, and the inhibition of viscosity increase was evaluated according to the evaluation criteria shown below. The smaller the difference in viscosity before and after storage, the more the viscosity increase is inhibited even if the liquid evaporates, and the less likely it is that adhesion due to viscosity increase will occur even if the liquid evaporates on the liquid-contacting member, and the better the cleaning properties and the better the adhesion recovery properties. AA: The difference in viscosity (yx) was 15 mPa·s or less. A: The difference in viscosity (yx) was greater than 15 mPa s and less than 50 mPa s. B: The difference in viscosity (yx) was greater than 50 mPa·s and less than 100 mPa / s. C: The difference in viscosity (yx) exceeded 100 mPa s, or the mixture was solid after storage and the viscosity could not be measured.

[0122] [3] Suppression of precipitation A mixed solution was prepared by mixing the reaction solution and the cleaning solution shown in Table 7 at a ratio of 1:3 (volume ratio), and 5 g was placed in a glass petri dish with an inner diameter of 5 cm. After leaving the mixture uncovered for 120 hours in an environment with a temperature of 30°C and a relative humidity of 10%, the presence or absence of precipitates was visually confirmed. If precipitates were confirmed, operation (1) of vibrating the petri dish for 1 minute was performed, and the presence or absence of precipitates was visually confirmed. If precipitates were still confirmed at this point, operation (2) of adding 3 g of the reaction solution and vibrating the petri dish for 1 minute was performed, and the presence or absence of precipitates was visually confirmed. The precipitation inhibition was evaluated according to the evaluation criteria shown below. The presence or absence of precipitates was judged by whether the mixed solution was transparent or not. If precipitates were not generated, it means that the components are unlikely to precipitate even if the liquid evaporates, and the fixed substances are easily removed by the recovery operation using the cleaning solution, and therefore the fixation recovery property is excellent. In order to make it easier to confirm the presence or absence of precipitates in the mixture, the evaluation was performed using the reaction solution instead of ink. AA: No precipitate was observed A: Precipitates were observed, but after operation (1) the precipitates were no longer observed. B: Precipitates were observed, and they remained after operation (1), but no precipitates were observed after operation (2). C: Precipitates were observed, and the precipitates remained even after operations (1) and (2).

[0123] (Performance in recovery operations) The reaction liquid, ink, and cleaning liquid shown in Table 7 were filled in cartridges, and the cartridges were set in an inkjet recording device having a configuration shown in FIG. 1. The recording environment was set at a temperature of 25° C. and a relative humidity of 50%. In this example, an image recorded under the condition that one drop of 4.0 ng of liquid is applied to a unit area of ​​1 / 1,200 inch×1 / 1,200 inch is defined as having a recording duty of 100%. The reaction liquid and ink shown in Table 7 were applied to the recording medium in this order, with the recording duty of the reaction liquid being 50% and the recording duty of the ink being 160%, and a solid image of 2 cm×2 cm was recorded. As the recording medium, the above-mentioned recording medium 1 was used for Examples 1 to 27 and Comparative Examples 1 to 6. Recording medium 2 was used in Example 28, and recording medium 3 was used in Example 29. Evaluation using the inkjet recording device was performed by dividing the evaluation into [1] recovery unit and [2] supply flow path.

[0124] [Recovery performance of recovery units] [1] Fixation recovery property After recording 100 solid images, the recovery unit (the absorbent in the cap) had some adhesion. 1 mL of cleaning solution was supplied from the cartridge into the cap, and then the cleaning operation was performed up to four times by sucking the solution with a suction pump. The recovery unit after cleaning was visually inspected, and the adhesion recovery in the recovery unit was evaluated according to the following evaluation criteria. AA: The deposits were removed in the first wash. A: After the first wash, some adhesion was found, but it was possible to remove it by washing again once. B: After the second wash, some residue was found, but it was removed within three washes. C: After the third wash, adhesions were observed and could not be removed even after three re-washes.

[0125] [2] Attraction With the ejection port surface of the recording head covered with a suction cap, the flow path was blocked upstream of the recording head, the air release valve of the suction cap was closed, and the suction pump was driven to perform suction. The suction performance of the recovery unit was evaluated according to the evaluation criteria shown below from the time required for the difference between the negative pressure (x) before suction and the negative pressure (y) to be within 5 kPa. The shorter the time to reach the specified negative pressure, the less the stuck material remains in the recovery unit, meaning that the sticking recovery performance is excellent. AA: The time required for the negative pressure difference (yx) before and after suction to reach within 5 kPa was within 1 minute. A: The time required for the negative pressure difference (yx) before and after suction to reach within 5 kPa was more than 1 minute but less than 5 minutes. B: Even after continuing suction for 5 minutes, the difference in negative pressure before and after suction (yx) did not reach within 5 kPa. C: Even when suction was performed with the suction pump, the suction cap did not become sealed and negative pressure was not created.

[0126] [Recovery performance in ink supply flow path] [1] Fixation recovery property The adhesion recovery property in the supply flow path was evaluated as follows. This evaluation was performed on the assumption that the ink supply system was cleaned when the inkjet recording device was taken out of use, and then refilled with ink in order to resume use. Specifically, after recording the above solid image, ink was removed from the ink supply system from the ink storage unit to the recording head. Next, a cleaning liquid was circulated through the ink supply system to clean it, and then the cleaning liquid was removed. This operation resulted in the ink supply system being in a state where no liquid was filled. In this state, the recording device was placed in an environment with a temperature of 60°C and a relative humidity of 50% for 48 hours as an accelerated test assuming a long period of suspension of use. After that, 50 g of ink was supplied from the ink storage unit to fill the flow path from the ink storage unit to the recording head with ink. This flow path has a capacity to be filled with 50 g of ink. From the 50 g of ink supplied to the ink storage section (supplied amount x = 50 (g)), the ink flow path was filled with ink (consumed amount y (g)), and the non-filling rate (%) = y / x x 100 was calculated, and the adhesion recovery property was evaluated according to the following evaluation criteria. The smaller the non-filling rate, the less ink remained in the flow path before the suspension of use, indicating excellent adhesion recovery property. AA: The non-filling rate was 10% or less. A: The non-filling rate was more than 10% and less than 15%. B: The non-filling rate was more than 15% and less than 30%. C: The non-filling rate exceeded 30%, or the ink supply stopped midway.

[0127] [Table 7]

Claims

1. 1. An inkjet recording method for recording an image on a recording medium by ejecting a water-based ink from a recording head of an inkjet recording apparatus, comprising: an ink applying step of applying the water-based ink to a recording medium; a cleaning step of cleaning a liquid-contacting member that comes into contact with the aqueous ink in the inkjet recording apparatus with an aqueous cleaning liquid, the inkjet recording apparatus has a cleaning liquid supply path that supplies the cleaning liquid to the liquid contact member, The water-based ink contains a pigment and resin particles, the cleaning solution contains a surfactant, a first water-soluble organic solvent having a vapor pressure lower than that of water, a second water-soluble organic solvent having an SP value according to the Fedors method of 9.8 to 14.2, and a third water-soluble organic solvent having a water retention capacity of 50% or less; the content (mass%) of the third water-soluble organic solvent in the cleaning solution is 0.7 times or more in terms of mass ratio to the total content (mass%) of the water-soluble organic solvents; The ink-jet recording method according to claim 1, wherein the cleaning solution has a pH of 8.5 or more. Moisture retention: 10.0 g of a 20% by mass aqueous solution of a water-soluble organic solvent is placed in a petri dish and placed in an environment at a temperature of 30° C. and a relative humidity of 10%. When the mass no longer changes, the mass of the components is measured and calculated using the following formula (i). Water retention capacity (%)=[mass of component remaining in petri dish (g)−2.0 (g)] / 2.0 (g) (i)

2. 2. The ink jet recording method according to claim 1, wherein the water retention capacity of the third water-soluble organic solvent is 30% or more.

3. The inkjet recording method according to claim 1 , wherein the content (mass %) of the third water-soluble organic solvent in the cleaning liquid is 0.9 times or more in mass ratio to the total content (mass %) of the water-soluble organic solvents.

4. 2. The ink jet recording method according to claim 1, wherein the liquid contact member includes a recovery mechanism for the recording head.

5. The ink jet recording method according to claim 1 , wherein the liquid contact member includes a supply mechanism for the water-based ink.

6. 2. The inkjet recording method according to claim 1, wherein the vapor pressure (kPa) of the water-soluble organic solvent having the highest content (mass %) in the aqueous ink is higher than the vapor pressure (kPa) of the water-soluble organic solvent having the highest content (mass %) in the cleaning liquid.

7. 2. The ink jet recording method according to claim 1, wherein the first water-soluble organic solvent in the cleaning liquid has a relative dielectric constant of 20.0 or more.

8. 2. The ink jet recording method according to claim 1, wherein the cleaning liquid contains a water-soluble organic solvent in an amount (mass %) of 10.0 mass % or more based on the total mass of the cleaning liquid.

9. 2. The inkjet recording method according to claim 1, wherein the cleaning liquid contains a fourth water-soluble organic solvent having an SP value of 9.8 to 12.2 as measured by the Fedors method, and the content (mass %) of the fourth water-soluble organic solvent in the cleaning liquid is 10.0 mass % or less.

10. 2. The ink jet recording method according to claim 1, wherein the surfactant in the cleaning liquid is a hydrocarbon-based nonionic surfactant having an HLB value of 17 or less according to the Griffin method.

11. 2. The ink jet recording method according to claim 1, wherein the cleaning liquid has a pH of 9.0 or more.

12. The ink jet recording method according to claim 1, further comprising a step of applying an aqueous reaction liquid containing a reactant that reacts with the aqueous ink to the recording medium.

13. The recording medium was subjected to the Bristow method for 30 msec from the start of contact. １／２ The amount of water absorbed is 10 mL / m ２ The ink jet recording method according to claim 1, wherein:

14. An inkjet recording apparatus used to record an image on a recording medium by ejecting water-based ink from a recording head, comprising: an ink applying means for applying the water-based ink to a recording medium; a cleaning unit that cleans a liquid-contacting member that comes into contact with the aqueous ink in the inkjet recording apparatus by using an aqueous cleaning liquid, the inkjet recording apparatus has a cleaning liquid supply path that supplies the cleaning liquid to a member that contacts the aqueous ink, the water-based ink contains a pigment and a water-soluble organic solvent having a vapor pressure higher than that of water, the cleaning solution is an aqueous cleaning solution containing a surfactant, a first water-soluble organic solvent having a vapor pressure lower than that of water, a second water-soluble organic solvent having an SP value according to the Fedors method of 9.8 to 14.2, and a third water-soluble organic solvent having a water retention capacity of 50% or less; an ink jet recording apparatus, wherein a content (mass %) of the third water-soluble organic solvent in the cleaning liquid is 0.7 times or more in mass ratio to a total content (mass %) of the water-soluble organic solvents. Moisture retention: 10.0 g of a 20% by mass aqueous solution of a water-soluble organic solvent is placed in a petri dish and placed in an environment at a temperature of 30° C. and a relative humidity of 10%. When the mass no longer changes, the mass of the components is measured and calculated using the following formula (i). Water retention capacity (%)=[mass of component remaining in petri dish (g)−2.0 (g)] / 2.0 (g) (i)

15. A set of an aqueous ink and a cleaning liquid for use in an inkjet recording method in which an aqueous ink is ejected from a recording head of an inkjet recording apparatus to record an image on a recording medium, comprising: The inkjet recording method includes: an ink applying step of applying the water-based ink to a recording medium; a cleaning step of cleaning a liquid-contacting member that comes into contact with the aqueous ink in the inkjet recording apparatus with an aqueous cleaning liquid, the inkjet recording apparatus has a cleaning liquid supply path that supplies the cleaning liquid to the liquid contact member, The water-based ink contains a pigment and resin particles, the cleaning solution contains a surfactant, a first water-soluble organic solvent having a vapor pressure lower than that of water, a second water-soluble organic solvent having an SP value according to the Fedors method of 9.8 to 14.2, and a third water-soluble organic solvent having a water retention capacity of 50% or less; A set of an aqueous ink and a cleaning solution, characterized in that the content (mass %) of the third water-soluble organic solvent in the cleaning solution is 0.7 times or more by mass relative to the total content (mass %) of the water-soluble organic solvents. Moisture retention: 10.0 g of a 20% by mass aqueous solution of a water-soluble organic solvent is placed in a petri dish and placed in an environment at a temperature of 30° C. and a relative humidity of 10%. When the mass no longer changes, the mass of the components is measured and calculated using the following formula (i). Water retention capacity (%)=[mass of component remaining in petri dish (g)−2.0 (g)] / 2.0 (g) (i)

Images