Inkjet recording method and inkjet recording apparatus

Abstract

In an inkjet recording device that uses a tube pump to deliver aqueous ink, the present invention provides an inkjet recording method that ensures good ink adhesion recovery on the recording head even if the recording head is left uncapped for a long period of time. [Solution] An inkjet recording method using an inkjet recording device equipped with a tube pump capable of flowing water-based ink, which is provided in a flow path connecting a first ink storage section for storing water-based ink and a second ink storage section for temporarily storing water-based ink, and which performs forward and reverse liquid delivery through the same flow path by means of the tube pump. The water-based ink contains a pigment, an acetylene-based surfactant, a silicone-based surfactant, and a urethane resin, and the relationship between the dynamic surface tension γ10 at a lifespan of 10 milliseconds and the dynamic surface tension γ100 at a lifespan of 100 milliseconds is γ10-γ100≦4.0mN / m.

Description

Technical Field

[0001] The present invention relates to an inkjet recording method and an inkjet recording apparatus.

Background Art

[0002] In recent years, a recording method of applying ink to a recording medium by an inkjet method when outputting text or charts has been widely used. Inkjet recording apparatuses are also utilized in business fields such as office use. In the business field, compatibility between high-speed printing and the optical density of printed matter is required. Therefore, considerations such as enhancing the penetrability of ink into the recording medium and increasing the concentration of pigments contained in the ink have been made. In an inkjet recording apparatus, a tube pump may be provided in an ink flow path for the purpose of maintaining the discharge performance of a recording head and filling the recording head with ink. In such an inkjet recording apparatus, the ink in the ink flow path flows due to the operation of the tube pump provided in the ink flow path. However, when pigment ink is used as the ink in an inkjet recording apparatus equipped with a tube pump, pigment particles contained in the pigment ink may aggregate inside the tube of the tube pump, inside the recording head, or near the discharge port, affecting the discharge performance of the recording head. In Patent Document 1, studies have been made to maintain the discharge stability of a recording head by containing an amide compound in the pigment ink used in an inkjet recording apparatus equipped with a tube pump. Also, in Patent Document 2, studies have been made to maintain the discharge stability of a recording head by containing two types of urethane resins in the pigment ink.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] Some inkjet recording devices equipped with a tube pump have the tube pump in the flow path connecting the main tank (first ink storage section) and the sub-tank (second ink storage section). Such inkjet recording devices have a configuration that allows ink to be supplied from the main tank to the sub-tank and ink to be recovered from the sub-tank to the main tank by rotating the tube pump in the forward and reverse directions. The present inventors investigated whether ink clogging caused by ink hardening near the ejection port of the recording head after being left unused for a long period of time can be resolved by a recovery operation, that is, the ink hardening recovery property, using the ink proposed in Patent Document 1 and the ink proposed in Patent Document 2. As a result, it was found that the hardening recovery property was insufficient, and in cases where the power to the device is cut off while the recording head is not capped, it is difficult to perform normal printing by performing only the normal recovery operation.

[0005] The object of the present invention is to provide an inkjet recording method in which an inkjet recording apparatus uses a tube pump to deliver aqueous ink, and even if the recording head is left uncapped for a long period of time, the ink adhesion recovery on the recording head is good. Another object of the present invention is to provide an inkjet recording apparatus used in the above-mentioned inkjet recording method. [Means for solving the problem]

[0006] The above objective is achieved by the present invention as follows. Specifically, according to the present invention, the device comprises a first ink storage section for storing aqueous ink, a second ink storage section for temporarily storing the aqueous ink, a recording head for discharging the aqueous ink, and a tube pump provided in a flow path connecting the first ink storage section and the second ink storage section, capable of flowing the aqueous ink from the first ink storage section to the second ink storage section and from the second ink storage section to the first ink storage section, wherein the first ink storage section, the tube pump, the second ink storage section, and the recording head are arranged in this order, and the tube pump flows the aqueous ink to the first ink storage section An inkjet recording method is provided, which uses an inkjet recording apparatus that performs forward liquid delivery from a section to the second ink storage section and reverse liquid delivery from the second ink storage section to the first ink storage section via the same flow path, and records an image by ejecting the aqueous ink from the recording head, wherein the aqueous ink contains a pigment, an acetylene-based surfactant, a silicone-based surfactant, and a urethane resin, and the relationship between the dynamic surface tension γ10 of the aqueous ink at a lifetime of 10 milliseconds and the dynamic surface tension γ100 at a lifetime of 100 milliseconds, as measured by the maximum bubble pressure method, is γ10 - γ100 ≤ 4.0 mN / m. [Effects of the Invention]

[0007] According to the present invention, in an inkjet recording apparatus that uses a tube pump to deliver aqueous ink, it is possible to provide an inkjet recording method in which the ink on the recording head recovers well even if the recording head is left uncapped for a long period of time. Furthermore, according to the present invention, it is possible to provide an inkjet recording apparatus for use in the above-mentioned inkjet recording method. [Brief explanation of the drawing]

[0008] [Figure 1]This is a schematic perspective view showing one embodiment of an inkjet recording apparatus used in the inkjet recording method of the present invention. [Figure 2] This is a schematic diagram showing an example of an ink supply system. [Figure 3] This is a schematic diagram showing the configuration of a tube pump. [Modes for carrying out the invention]

[0009] The present invention will be described in more detail below with reference to preferred embodiments. Furthermore, water-based ink for inkjet printing may be simply referred to as "ink." Unless otherwise specified, physical properties are given at room temperature (25°C). In the present invention, a "unit" constituting the resin means a repeating unit derived from one monomer.

[0010] Furthermore, in this invention, the maximum bubble pressure method is a method for determining the surface tension of a liquid by measuring the maximum pressure required to release bubbles generated at the tip of a probe (a thin tube) immersed in the liquid to be measured, and then calculating the surface tension of the liquid from the measured maximum pressure. Specifically, the maximum pressure is measured while continuously generating bubbles at the tip of the probe. The time from the moment a new bubble surface is generated at the tip of the probe until the maximum bubble pressure (the moment when the radius of curvature of the bubble is equal to the radius of the probe tip) is reached is called the "lifetime". In other words, the maximum bubble pressure method is a method for measuring the surface tension of a liquid in a moving state.

[0011] The present inventors investigated the ink adhesion recovery properties in a recording head using the ink proposed in Patent Document 1 and the ink proposed in Patent Document 2. Specifically, first, each ink was filled into an inkjet recording device equipped with a tube pump in a flow path connecting the main tank and the sub-tank, and printing was performed for a certain period of time. After that, the appearance of the printed materials was observed using the following methods (1) and (2). (1) After confirming that the recording head was covered with the cap, the power was turned off and the device was left for 5 days. After 5 days, the power to the device was turned on again, the recording head suction recovery operation was performed once, and then printing was performed. (2) On the other hand, as described above, after printing for a certain period of time, the power cord of the device was unplugged while the recording head was moving back and forth to cut off the power. After that, the device was left for 5 days with the recording head not covered by the cap and the ejection port exposed. After 5 days, the power to the device was turned on again, the recording head's suction recovery operation was performed once, and then printing was performed.

[0012] Observation of printed materials produced by methods (1) and (2) revealed that, even when using the inks proposed in Patent Document 1 and Patent Document 2, no dot defects were observed in the printed materials produced by method (1). However, dot defects were observed in the printed materials produced by method (2).

[0013] The inventors analyzed the mechanism by which this result occurred.

[0014] First, we investigated the mechanism by which the ink adhesion recovery performance in the recording head deteriorated with the inks described in Patent Documents 1 and 2.

[0015] Although the pigment is dispersed in the ink, when the ink is pumped through the tube by a tube pump, high shear forces are applied to the pigment in the ink at the points where the tube is pressed by components such as rollers inside the tube pump. This is thought to cause instability in the dispersion of the pigment in the ink.

[0016] When ink is delivered only in the forward direction, even if unstable pigment dispersion occurs, it is unlikely that the unstable pigment will form aggregates and be delivered to the recording head all at once, as these aggregates will remain in stagnant areas in the ink flow path. On the other hand, when a tube pump delivers water-based ink in both the forward direction (from the main tank to the sub-tank) and the reverse direction (from the sub-tank to the main tank) through the same flow path, turbulence occurs when the ink flow reverses from reverse to forward. This is thought to release stagnant areas, causing aggregates of unstable pigment dispersion to be delivered to the recording head all at once.

[0017] Here, for the pigment whose generated dispersion has become unstable, during normal use, since the recording head is capped, it remains in the ink and the pigment does not adhere inside the nozzle near the discharge port of the recording head, and is regularly discharged by printing or recovery operations. On the other hand, when the inkjet recording apparatus abnormally stops due to a power failure or the like and is left in a state where the recording head is not capped, drying progresses from the nozzle. As a result, the inventors推测 that the pigment adheres firmly directly inside the nozzle or strong aggregates are formed among the pigments, making it difficult for the ink discharge state to return to the original state even after a recovery operation and resulting in non-discharge.

[0018] In order to solve such problems of fixing and recovery properties, the inventors have examined surfactants, additives contained in the ink to be used, and ink physical property values. As a result of the examination, it has been found that by satisfying the requirements (i) and (ii) shown below, the fixing and recovery properties of the ink are good even after being left for a long time without capping the recording head. (i) The aqueous ink contains a pigment, an acetylene-based surfactant, a silicone-based surfactant, and a urethane resin. (ii) The relationship between the dynamic surface tension γ10 at a lifetime of 10 milliseconds and the dynamic surface tension γ100 at a lifetime of 100 milliseconds of the aqueous ink measured by the maximum bubble pressure method is γ10 - γ100 ≦ 4.0 mN / m.

[0019] Although the mechanism by which the fixing and recovery properties of the ink are improved by using the ink with the above configuration is not clear, the inventors推测 as follows.

[0020] First, the inventors investigated various surfactants contained in ink and found that using an ink containing a silicone-based surfactant with low surface energy improved the ink's adhesion recovery properties. This is presumed to be because the presence of the silicone-based surfactant made the ink flow more smoothly within the tube, reducing stagnation and retention, which in turn reduced the accumulation of dispersed and unstable pigments inside the nozzle, thus improving adhesion recovery properties. However, when the recording head was left uncapped for a long period of time, simply including a silicone-based surfactant in the ink was not sufficient to adequately improve the ink's adhesion recovery properties.

[0021] Here, the inventors investigated various additives and ink properties in conjunction with silicone-based surfactants. Through this investigation, they found that when the ink further contains an acetylene-based surfactant and a urethane resin, and the initial fluctuation of the ink's dynamic surface tension is small, the ink's ability to recover its adhesion after being left for a long period of time is good.

[0022] This is presumed to be because the deposits inside the nozzle become a mixture of pigment, acetylene-based surfactant, and urethane resin, resulting in improved pigment redispersibility during the recovery process.

[0023] Urethane resins generally consist of a soft segment and a hard segment. The soft segment is mainly composed of polyether, polyester, or polycarbonate polyol, and contains ether, ester, and carbonate bonds, giving it hydrophilic properties. The urethane bonds, on the other hand, are polar. Therefore, interaction with the highly hydrophobic pigment surface is low, and when fresh ink is supplied to the recording head during the recovery operation, the urethane resin present between the pigments relatively easily separates from the pigments. This is thought to result in good pigment redispersibility.

[0024] Furthermore, it is believed that acetylene-based surfactants adsorb to the pigment surface before slow-orienting silicone-based surfactants, improving the redispersibility of the pigment and inhibiting the subsequent adsorption of silicone-based surfactants to the pigment surface. Silicone-based surfactants have low surface energy relative to urethane resin, and if they adsorb to the pigment first, they repel the urethane resin, making it difficult for the urethane resin to mix between pigments. In contrast, it is believed that acetylene-based surfactants orient themselves to the pigment first and inhibit the adsorption of silicone-based surfactants, thereby enabling the urethane resin to effectively mix between pigments. As a result, it is thought that a solidified mixture of pigment, acetylene-based surfactant, and urethane resin can be formed. It is speculated that the urethane resin, which has little interaction with the pigment, mixes between the pigments, and the acetylene-based surfactant is adsorbed, improving the redispersibility of the pigment during recovery and improving the ink's adhesion recovery.

[0025] Furthermore, we believe that the initial fluctuation in the dynamic surface tension of the ink affects the ink's penetration behavior when fresh ink contacts the contaminated material during the recovery process. If the initial fluctuation in dynamic surface tension is large and not constant, the degree of decrease in surface tension will differ depending on the location at the interface between the ink and the pigment contaminated material when fresh ink contacts the contaminated material during the recovery process. If the surface tension of the ink is partially high, ink penetration will be suppressed in that area, while if the surface tension is partially low, ink will penetrate from that area, resulting in uneven penetration of fresh ink into the pigment contaminated material. We hypothesize that this uneven penetration of ink reduces the ink's ability to recover from adhesion. On the other hand, if the initial fluctuation in dynamic surface tension is small (γ10-γ100 ≤ 4.0 mN / m or less) and the surface tension is uniform regardless of location at the interface between the ink and the pigment contaminated material, the fresh ink will penetrate uniformly into the pigment contaminated material during the recovery process. We hypothesize that this allows the pigment to be effectively redispersed with fewer recovery operations, enabling a return to a normal discharge state.

[0026] (Inkjet recording device) Figure 1 is a schematic perspective view showing one embodiment of the inkjet recording apparatus of the present invention. Figure 2 is a schematic diagram of the ink supply system within the inkjet recording apparatus. The inkjet recording apparatus of this embodiment is a so-called serial type inkjet recording apparatus that performs recording operations by reciprocating the recording head in the X direction (main scanning direction). The recording medium 101 is intermittently transported in the Y direction (sub-scanning direction) by transport rollers 107. The recording head 102 mounted on the carriage 103 is reciprocated in the X direction (main scanning direction), which is perpendicular to the Y direction, which is the transport direction of the recording medium 101. Recording operations are performed by the transport of the recording medium 101 in the Y direction and the reciprocating scanning of the recording head 102 in the X direction, and an image is recorded on the recording medium. As shown in Figure 2, the recording head 102 consists of an inkjet type recording element substrate 205 that ejects ink from a plurality of ejection ports, and a sub-tank 203 connected to the recording element substrate 205 as a second ink storage unit that supplies ink to the ejection ports. The recording head 102 is mounted on the carriage 103. The sub-tank 203 does not necessarily have to be mounted on the recording head 102, and may be fixed inside the inkjet recording device. The carriage 103 is supported so as to be movable along a guide rail 105 arranged along the X direction and is fixed to an endless belt 106 that moves parallel to the guide rail 105. The endless belt 106 reciprocates by the driving force of a motor (not shown), thereby causing the carriage 103 to reciprocate and scan in the X direction.

[0027] Methods for ejecting ink from the recording head include methods that impart mechanical energy to the ink and methods that impart thermal energy to the ink. Among these, the method of imparting mechanical energy to the ink to eject it is particularly preferable.

[0028] Furthermore, it is preferable to use an ink-absorbing recording medium. Specific examples of ink-absorbing recording media include paper-based recording media such as glossy paper, art paper, and plain paper.

[0029] The main tank housing 108 houses multiple main tanks 201 according to the ink color. The recording head 102 is equipped with multiple sub-tanks 203 according to the ink color, similar to the main tanks 201, and each main tank 201 and each sub-tank 203 is connected by an ink supply tube 104. The following describes the supply path for one color of ink, but the same mechanism can be applied to any color of ink. The ink stored in the main tank 201 is supplied via the ink supply tube 104 by the drive of the tube pump 202, which is a liquid transfer pump, and is temporarily stored in the sub-tank 203. Furthermore, the ink is supplied from the sub-tank 203 to the recording element substrate 205 and discharged from the discharge port.

[0030] Figure 3 is a schematic diagram showing the configuration of a tube pump. The tube pump 30 comprises a central rotating part (not shown) and a plurality of pump rotors 31 arranged around the rotating part. The rotating part rotates clockwise and counterclockwise in Figure 3 by the drive of a motor (not shown). An ink supply tube 104 runs through the inside of the tube pump 30, and each of the pump rotors 31 contacts the ink supply tube 104 by crushing it. Driven by a motor (not shown), the pump rotors 31 arranged around the rotating part rotate while crushing the ink supply tube, and ink flows in the ink supply tube 104 according to the direction of rotation. Specifically, when the pump rotor 31 rotates in the forward direction (counterclockwise) in Figure 3, ink flows from the main tank 201 to the sub-tank 203. Conversely, when the pump rotor 31 rotates in the reverse direction (clockwise) in Figure 3, ink flows from the sub-tank 203 to the main tank 201. In this invention, the rotation direction of the pump rotor 31 of the tube pump 202 is controlled by controlling the motor drive according to the measurement value of a pressure gauge (not shown) that measures the pressure in the sub-tank 203. For example, if the measurement value of the pressure gauge is below a certain value, the pump rotor 31 is rotated forward to supply ink from the main tank 201 to the sub-tank 203. If the measurement value of the pressure gauge is above a certain value, the tube pump 30 is rotated in reverse to recover ink from the sub-tank 203 to the main tank 201. This maintains the pressure in the sub-tank 203 near a certain value and stabilizes the discharge of ink from the discharge port of the recording element substrate 205. This control is performed continuously when the recording element substrate 205 is performing a recording operation. Note that the switching between forward and reverse rotation of the pump rotor 31 may be performed by user instruction.

[0031] <ink> The inkjet recording method of the present invention uses an aqueous ink. The aqueous ink contains a pigment, a silicone-based surfactant, an acetylene-based surfactant, and a urethane resin. Furthermore, the relationship between the dynamic surface tension γ10 at a lifetime of 10 milliseconds and the dynamic surface tension γ100 at a lifetime of 100 milliseconds, as measured by the maximum bubble pressure method, is γ10 - γ100 ≤ 4.0 mN / m.

[0032] The following describes in detail the components of the ink used in the inkjet recording method of the present invention.

[0033] (Pigment) Ink contains pigments as colorants. Specific examples of pigments include inorganic pigments such as carbon black and titanium dioxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolon, diketopyrrolopyrrole, and dioxazine.

[0034] As for the dispersion method of the pigment, resin-dispersed pigments using a resin as a dispersant, and self-dispersing pigments in which hydrophilic groups are bonded to the surface of the pigment particles can be used. In addition, resin-bonded pigments in which organic groups containing resin are chemically bonded to the surface of the pigment particles, and microcapsule pigments in which the surface of the pigment particles is coated with resin or the like can be used.

[0035] For resin dispersants used to disperse pigments in an aqueous medium, those that can disperse pigments in the aqueous medium through the action of carboxylic acid groups are preferred.

[0036] The resin dispersant is preferably a resin having hydrophilic units and hydrophobic units as constituent units. Furthermore, the resin dispersant is preferably an acrylic resin having at least acrylic components such as units derived from (meth)acrylic acid or units derived from (meth)acrylic esters, and is even more preferably a water-soluble acrylic resin. In particular, a water-soluble acrylic resin in the form of a random copolymer is preferred. In the following description, "(meth)acrylic" means "acrylic" and "methacrylic," and "(meth)acrylate" means "acrylate" and "methacrylate."

[0037] Hydrophilic units are units having hydrophilic groups such as acidic groups and hydroxyl groups. Hydrophilic units can be formed, for example, by polymerizing monomers having hydrophilic groups. Specific examples of monomers having hydrophilic groups include acidic monomers having carboxyl groups such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid; acidic monomers having sulfonic acid groups such as styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 3-sulfopropyl (meth)acrylate; and anionic monomers such as anhydrides and salts of these acidic monomers; monomers having hydroxyl groups such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate; and monomers having ethylene oxide groups such as methoxy(mono, di, tri, poly)ethylene glycol (meth)acrylate. Cationic ions that constitute salts of anionic monomers include lithium, sodium, potassium, ammonium, and organic ammonium ions. The acid value of the resin is preferably 50 mg KOH / g or more and 200 mg KOH / g or less.

[0038] As a self-dispersing pigment, oxidized self-dispersing carbon black (oxidized carbon black) can be used. Furthermore, pigments in which anionic groups such as carboxylic acid groups, sulfonic acid groups, and phosphonic acid groups are directly bonded to the particle surface of the pigment or via other atomic groups (-R-) can also be used. Oxidized carbon black can be obtained by oxidizing carbon black particles. Methods for oxidizing carbon black include, for example, treating the surface of the raw material carbon black with ozone, hypochlorous acid and its salts, and persulfuric acid and its salts to oxidize the carbon black. The anionic group may be of the acid type or salt type, and in the case of the salt type, it may be in a partially dissociated state or a fully dissociated state. When the anionic group is of the salt type, examples of cations that become counterions include alkali metal cations, ammonium, and organic ammonium. Other specific examples of atomic groups (-R-) include linear or branched alkylene groups with 1 to 12 carbon atoms; arylene groups such as phenylene and naphthylene groups; carbonyl groups; imino groups; amide groups; sulfonyl groups; ester groups; and ether groups. Combinations of these groups are also possible.

[0039] (Silicone-based surfactant) The ink contains a silicone-based surfactant.

[0040] Preferably, the silicone-based surfactant is a silicone-based surfactant represented by the following formula (1) or formula (2). In formulas (1) and (2), (C2H4O) represents an ethylene oxide unit and (C3H6O) represents a propylene oxide unit. In each silicone-based surfactant, the ethylene oxide unit and propylene oxide unit may exist in any state within its structure, such as in a random form or in a block form. Here, the existence of each unit in a random state means that the ethylene oxide unit and propylene oxide unit are arranged irregularly. Furthermore, the existence of each unit in a block state means that each block is composed of several of the above units, and these blocks are arranged regularly.

[0041] [ka]

[0042] In the general formula (1) above, R1 represents an alkylene group, R2 represents a hydrogen atom or an alkyl group, m and n independently represent integers of 1 or more, a represents an integer of 1 or more, and b represents an integer of 0 or more.

[0043] [ka]

[0044] (In the above general formula (2), R 3、 R6 represents a hydrogen atom or an alkyl group, 4、 R5 represents an alkylene group, p represents an integer greater than or equal to 1, c and e represent integers greater than or equal to 1, and d and f represent integers greater than or equal to 0.

[0045] (Acetylene-based surfactant) The ink contains an acetylene-based surfactant. The acetylene-based surfactant is preferably an acetylene glycol-based surfactant. An acetylene glycol-based surfactant is a surfactant in which multiple hydroxyl groups are substituted on an acetylene skeleton, and an ethylene oxide chain may be present between the acetylene skeleton and the hydroxyl groups.

[0046] Specific examples include the following product names: Acetylenel E60 and Acetylenel E100 (both manufactured by Kawaken Fine Chemicals); and Surfinol 104E, Surfinol 465, and Surfinol 485 (all manufactured by Nisshin Chemical Industry).

[0047] It is preferable that the ratio A / S of the acetylene-based surfactant content to the silicone-based surfactant content S (mass%) is 0.5 or more and 10.0 or less. When A / S is 0.5 or more and 10.0 or less, the effect of improving adhesion recovery is further enhanced.

[0048] (urethane resin) The ink contains a urethane resin. The urethane resin can be obtained, for example, by reacting a polyisocyanate with a component that reacts with it (such as a polyol or polyamine). Alternatively, it may be obtained by further reacting it with a crosslinking agent or a chain extender.

[0049] [Polyisocyanate] Polyisocyanates are compounds having two or more isocyanate groups in their molecular structure. Examples of polyisocyanates include aliphatic polyisocyanates and aromatic polyisocyanates. Specific examples of aliphatic polyisocyanates include chain-like polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate; and cyclic polyisocyanates such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatemethyl)cyclohexane.

[0050] Specific examples of aromatic polyisocyanates include tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dibenzyle diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, and α,α,α',α'-tetramethylxylylene diisocyanate.

[0051] [Polyol] Polyols can be used as components that form units constituting the urethane resin through the reaction with the polyisocyanate described above. In this invention, "polyol" means a compound having two or more hydroxyl groups in its molecule. Specifically, examples include polyols without acid groups such as polyether polyols, polyester polyols, and polycarbonate polyols; polyols with acid groups; and so on.

[0052] Examples of polyols that do not have acid groups include long-chain polyols such as polyether polyols, polyester polyols, and polycarbonate polyols, which have a number-average molecular weight of approximately 450 to 4,000.

[0053] Examples of polyols having acidic groups include polyols containing acidic groups such as carboxylic acid groups, sulfonic acid groups, and phosphonic acid groups in their structure. In particular, it is preferable to use urethane resins synthesized using polyols having acidic groups such as dimethylolpropionic acid and dimethylolbutanoic acid in addition to polyols without acidic groups, and it is even more preferable to use water-soluble urethane resins. The acidic groups may be in the form of salts. Examples of cations constituting the salts include ions such as lithium, sodium, potassium, ammonium, and organic ammonium. When a water-soluble urethane resin has acidic groups, it usually exhibits water solubility by neutralizing the acidic groups with neutralizing agents such as alkali metal hydroxides (lithium, sodium, potassium, etc.) or ammonia water.

[0054] [Polyamines] Examples of polyamines include monoamines having multiple hydroxyl groups, such as dimethylolethylamine, diethanolmethylamine, dipropanolethylamine, and dibutanolmethylamine; bifunctional polyamines such as ethylenediamine, propylenediamine, hexylenediamine, isophoronediamine, xylylenediamine, diphenylmethanediamine, hydrogenated diphenylmethanediamine, and hydrazine; and polyamines with three or more functions, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyamide polyamine, and polyethylenepolyimine. For convenience, compounds having multiple hydroxyl groups and one amino or imino group are also listed as "polyamines."

[0055] [Crosslinking agents, chain extenders] When synthesizing urethane resins, crosslinking agents and chain extenders can be used. Typically, crosslinking agents are used in the synthesis of prepolymers, while chain extenders are used to perform chain extension reactions on pre-synthesized prepolymers. Basically, depending on the purpose, such as crosslinking or chain extension, water, polyisocyanates, polyols, and polyamines can be appropriately selected and used as crosslinking agents or chain extenders. Chain extenders that can crosslink urethane resins can also be used.

[0056] The ratio of the urethane resin content (U, mass%) to the pigment content (P, mass%) is preferably 0.05 to 1.00. A U / P ratio of 0.05 to 1.00 improves adhesion recovery. This is because the urethane resin, which has little interaction with the pigment, is present in an appropriate amount between the pigments, thereby inhibiting the formation of strong pigment aggregation.

[0057] (Alkanediol) The ink preferably contains an alkanediol. The inclusion of an alkanediol improves the ink's adhesion recovery. This is because the inclusion of an alkanediol, which has high compatibility with silicone-based surfactants in water, allows the silicone-based surfactant to spread uniformly within the tube, resulting in smoother ink flow. This is thought to reduce the accumulation of dispersed and unstable pigments, thereby improving the ink's adhesion recovery.

[0058] Examples of alkanediols that can be used in inks include the following: for example, 1,3-butanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexanediol, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,2-butanediol, 1,4-butanediol, 2,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, triethylene glycol, 1,2,6-hexanetriol, etc.

[0059] The ink more preferably contains 1,3-butanediol, 3-methyl-1,3-butanediol, and 2-ethyl-1,3-hexanediol among the alkanediols.

[0060] It is preferable that the ratio D / T of the alkanediol content D (mass%) in the aqueous ink to the total content T (mass%) of all components excluding pigments and resins in the aqueous ink is 0.2 or more and 0.4 or less. A D / T of 0.2 or more and 0.4 or less improves adhesion recovery. It is hypothesized that by adjusting the content ratio of alkanediols, which have high compatibility with silicone-based surfactants, to within the above range, pigment aggregation is suppressed, the flow of the ink in the tube becomes smoother, the accumulation of dispersed and unstable pigments decreases, and adhesion recovery is improved.

[0061] (aqueous medium) The ink contains an aqueous medium, which is water or a mixed solvent of water and a water-soluble organic solvent. Deionized water (ion-exchanged water) is preferred as the water. The water-soluble organic compound is not particularly limited; any alcohols, glycol ethers, and nitrogen-containing compounds suitable for use in aqueous inks can be used. Furthermore, one or more of these water-soluble organic compounds can be included in the ink.

[0062] The water content (mass%) in the ink is preferably 50.00 to 95.00 based on the total mass of the ink. Furthermore, the water-soluble organic solvent content (mass%) in the ink is preferably 3.00 to 50.00 based on the total mass of the ink. A water-soluble organic solvent content of 3.00 or higher ensures sufficient reliability, such as adhesion resistance, when the ink is used in an inkjet recording device. Additionally, a water-soluble organic solvent content of 50.00 or lower prevents an increase in ink viscosity, reducing the likelihood of ink supply problems.

[0063] (Other additives) In addition to the components mentioned above, the ink may contain various additives as needed, such as surfactants, pH adjusters, rust inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, evaporation accelerators, chelating agents, and other polymers. The ink may also contain colorants such as pigments and dyes, but it is usually not necessary to include such colorants.

[0064] (Ink properties) It is important that the relationship between the dynamic surface tension γ10 at a lifespan of 10 milliseconds and the dynamic surface tension γ100 at a lifespan of 100 milliseconds, as measured by the maximum bubble pressure method, is γ10 - γ100 ≤ 4.0 mN / m. Furthermore, it is preferable that γ10 - γ100 ≤ 3.0 mN / m.

[0065] Since the ink is an aqueous ink used in inkjet systems, it is preferable to appropriately control its physical properties. Specifically, the static surface tension of the ink at 25°C, as measured by the plate method, is preferably between 20.0 mN / m and 60.0 mN / m, and more preferably between 20.0 mN / m and 45.0 mN / m.

[0066] Furthermore, the viscosity of the ink at 25°C is preferably between 1.0 mPa·s and 10.0 mPa·s. Also, the pH of the ink at 25°C is preferably between 7.0 and 10.0. [Examples]

[0067] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way by the following examples unless it exceeds the gist of the invention. Unless otherwise specified, amounts of components indicated in "parts" and "%" are based on mass.

[0068] <Preparation of resin> (Preparation of urethane resin) [Preparation of aqueous dispersions of urethane resins 1-4] The aqueous dispersions of urethane resin particles shown below were used as aqueous dispersions of urethane resins 1-4. • Aqueous dispersion of urethane resin 1: Product name "Takelac W5661" (manufactured by Mitsui Chemicals, polyether urethane resin particles, resin particle content 35%). • Aqueous dispersion of urethane resin 2: Product name "Hydran APX-101H" (manufactured by DIC, polyurethane emulsion, resin particle content 45%) • Aqueous dispersion of urethane resin 3: Product name "Superflex 420" (manufactured by Daiichi Kogyo Seiyaku, polyurethane dispersion, resin particle content 32%) • Aqueous dispersion of urethane resin 4: Product name "Superflex 170" (manufactured by Daiichi Kogyo Seiyaku, polyurethane dispersion, resin particle content 33%)

[0069] [Preparation of aqueous solution of urethane resin 5] A four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube, and reflux tube was prepared. 41.7 parts of polyisocyanate (isophorone diisocyanate), 40.1 parts of long-chain polyol without acid groups (polypropylene glycol / number average molecular weight 2,000), 13.2 parts of a portion of polyol with acid groups (dimethylolpropionic acid), and 200.0 parts of methyl ethyl ketone were added to this four-necked flask. The mixture was then reacted at 80°C for 6 hours under a nitrogen atmosphere. Next, 0.6 parts of a chain extender (ethylenediamine), 2.0 parts of a stopping agent (methanol), 2.4 parts of the remaining polyol with acid groups (dimethylolpropionic acid), and 100.0 parts of methyl ethyl ketone were added. The remaining isocyanate group percentage was confirmed by FT-IR, and the reaction was continued at 80°C until the desired percentage was reached to obtain the reaction solution. After cooling the resulting reaction solution to 40°C, deionized water was added, and potassium hydroxide aqueous solution was added while stirring at high speed with a homomixer to obtain a liquid. Methyl ethyl ketone was removed from the obtained liquid by heating and reducing the pressure, and an aqueous solution of urethane resin 5 with a urethane resin (solids) content of 20.0% was prepared.

[0070] <Resins other than urethane resin> (Aqueous dispersion of acrylic resin particles) In a flask equipped with a stirrer, nitrogen inlet tube, reflux condenser, and thermometer, 18.0 parts butyl methacrylate, 0.35 parts methacrylic acid, 2.0 parts polymerization initiator, and 2.0 parts n-hexadecane were added and stirred for 30 minutes while introducing nitrogen gas. 2,2'-azobis(2-methylbutylnitrile) was used as the polymerization initiator. Next, 78.0 parts of a 6.0% aqueous solution of polyoxyethylene cetyl ether (trade name "NIKKOLBC-20", manufactured by Nikko Chemicals) was added dropwise and stirred for 30 minutes to obtain a mixture. The mixture was emulsified by irradiating it with ultrasound for 3 hours using an ultrasonic irradiator, and then the polymerization reaction was carried out at 80°C for 4 hours under a nitrogen atmosphere. After cooling to 25°C and filtering, an appropriate amount of pure water was added to prepare an aqueous dispersion of acrylic resin particles with a polymer particle content of 20.0% by mass.

[0071] (Aqueous dispersion of polyester resin particles) In a reaction vessel set up inside an autoclave, 60.0 parts ethylene glycol, 40.0 parts neopentyl glycol, 54.5 parts terephthalic acid, and 54.5 parts isophthalic acid were added and heated at 220°C for 4 hours to carry out the esterification reaction. Next, the temperature was raised to 240°C, and the pressure inside the autoclave was reduced to 13 Pa over 90 minutes. The esterification (dehydration condensation) reaction was continued by maintaining the reduced pressure of 240°C and 13 Pa for 5 hours, after which nitrogen gas was introduced into the autoclave to return to atmospheric pressure (1 atm). The temperature inside the reaction vessel was lowered to 220°C, and a catalyst (tetra-n-butyl titanate) and 1.0 part trimetic acid were added and heated at 220°C for 2 hours to carry out the transesterification reaction. The amount of catalyst used (mol) was 3 × 10⁻⁶ -4 The formula was multiplied by (total amount of polycarboxylic acid used (mol)). Then, nitrogen gas was introduced into the autoclave to create a pressurized state, and the sheet-like resin was removed. After cooling this resin to 25°C, it was crushed in a crusher to obtain polyester resin particles.

[0072] A stirrer (product name "Tornado Stirrer Standard SM-104", manufactured by AS ONE) was set up in a 2L beaker. 200g of the above-mentioned polyester resin and methyl ethyl ketone (MEK) were placed in this beaker and the polyester was dissolved by stirring at 30°C. Next, 15.9g of 5% potassium hydroxide aqueous solution was added and stirred for 30 minutes. 500g of deionized water was added dropwise at a rate of 20mL / min while stirring at 30°C. After that, the temperature was raised to 60°C, the MEK was removed by distillation, and then some of the water was also removed by distillation. After cooling to 25°C, the solution was filtered through a 150-mesh wire mesh (a filter with 150 stainless steel wires woven vertically and horizontally per 1-inch square), and the concentration of the resin particles was adjusted to 25.0% with deionized water to prepare an aqueous dispersion of polyester resin particles.

[0073] <Preparation of Pigment Dispersion> (Pigment dispersion 1) A mixture was obtained by mixing 12.0 parts of carbon black (product name "Black Pearls 880", manufactured by Cabot), 24.0 parts of an aqueous solution of a resin dispersant, and 64.0 parts of deionized water. The aqueous solution of the resin dispersant was obtained by neutralizing a styrene-acrylic acid copolymer with an acid value of 170 mg KOH / g and a weight-average molecular weight of 8,000 with a 10.0% aqueous sodium hydroxide solution, resulting in an aqueous solution with a resin (solids) content of 20.0%. The obtained mixture was charged into a batch-type vertical sand mill (manufactured by Imex), filled with 85 parts of 0.3 mm zirconia beads, and dispersed for 3 hours while cooling with water. After that, non-dispersed material including coarse particles was removed by centrifugation. Furthermore, the mixture was pressure filtered through a cellulose acetate filter with a pore size of 3.0 μm (manufactured by Advantec) to prepare pigment dispersion 1 with a pigment content (solids) of 10.0% and a resin content of 4.0%.

[0074] (Pigment dispersion 2) Pigment dispersion 2 was prepared in the same manner as for pigment dispersion 1 described above, except that the type of pigment was changed to CI Pigment Blue 15:3 (product name "Hosta Palm Blue B2G," manufactured by Heubach). The pigment content in pigment dispersion 2 was 10.0%, and the resin content was 4.0%.

[0075] (Pigment dispersion 3) Pigment dispersion 3 was prepared in the same manner as for pigment dispersion 1 described above, except that the type of pigment was changed to a solid solution of CI Pigment Red 202 and CI Pigment Violet 19 (product name "Syncassia Magenta D4500J", manufactured by Sun Chemical). The pigment content in pigment dispersion 3 was 10.0%, and the resin content was 4.0%.

[0076] (Pigment dispersion 4) Pigment dispersion 4 was prepared in the same manner as for pigment dispersion 1 described above, except that the type of pigment was changed to CI Pigment Yellow 74 (product name "Fast Yellow 011", manufactured by Dainichi Seika Kogyo Co., Ltd.). The pigment content in pigment dispersion 4 was 10.0%, and the resin content was 4.0%.

[0077] (Pigment dispersion 5) A solution was prepared by dissolving 5.0g of concentrated hydrochloric acid in 5.5g of water and cooled to 5°C. 1.6g of 4-aminophthalic acid (treatment agent) was then added. The container of this solution was placed in an ice bath and stirred to maintain the solution temperature below 10°C. A solution prepared by dissolving 1.8g of sodium nitrite in 9.0g of ion-exchanged water at 5°C was then added. After stirring for 15 minutes, carbon black (specific surface area 260m²) was added. 2 6.0 g of ( / g) was added under stirring, and the mixture was stirred for a further 15 minutes to obtain a slurry. The obtained slurry was filtered through filter paper (product name "Standard Filter Paper No. 2", manufactured by Advantec), the particles were thoroughly washed with water, and the mixture was dried in an oven at 110°C. After replacing the counterions from sodium ions to potassium ions by ion exchange, an appropriate amount of ion-exchanged water was added to adjust the pigment content. In this way, a pigment dispersion 5 was prepared containing a self-dispersing pigment with a pigment content of 10.0%, in which phthalate groups with potassium ions as counterions were bonded to the surface of carbon black particles.

[0078] <Ink preparation> Each ink was prepared by mixing the components (unit: %) shown in the upper row of Tables 1-3, stirring thoroughly, and then pressure filtering through a 1.0 μm pore size polypropylene filter (manufactured by Advantec). The lower row of the table shows the ink properties (γ10-γ100 (mN / m), urethane resin content U (%), pigment content P (%), alkanediol content D (%), amount of components excluding pigment and resin T (%), acetylene-based surfactant content A (%), silicone-based surfactant content S (%), U / P, D / T, A / S). Here, U / P means urethane resin content U (%) / pigment content P (%), D / T means alkanediol content D (%) / amount of components excluding pigment and resin T (%), and A / S means acetylene-based surfactant content A (%) / silicone-based surfactant content S (%). The dynamic surface tensions γ10 and γ100 were measured at 25°C using a dynamic surface tensimeter (product name "BUBBLE PRESSURE TENSIOMETER BP-2", manufactured by KRUSS) based on the maximum bubble pressure method. The pH of all prepared inks was adjusted using a 0.5 N sulfuric acid aqueous solution to be within the range of 8.5 to 9.0. Details of the components listed in Tables 1 to 3 are as follows. • Product name: "Silface SAG008" (manufactured by Nisshin Chemical Industry Co., Ltd., silicone-based surfactant, corresponds to the compound represented by formula (1)) • Product name: "Silface SAG002" (manufactured by Nisshin Chemical Industry Co., Ltd., silicone-based surfactant, corresponds to the compound represented by formula (1)) • Product name "KF-643" (manufactured by Shin-Etsu Chemical Co., Ltd., silicone-based surfactant, corresponds to the compound represented by formula (1)) • Product name: "Silface SAG503A" (manufactured by Nisshin Chemical Industry Co., Ltd., silicone-based surfactant, corresponds to the compound represented by formula (1)) • Product name: "Silface SAG005" (manufactured by Nisshin Chemical Industry Co., Ltd., silicone-based surfactant, corresponds to the compound represented by formula (2)) • Product name: "Acetylenel E100" (manufactured by Kawaken Fine Chemicals, acetylene-based surfactant) • Product name: "Equamid M-100" (manufactured by Idemitsu Kosan, amide compound)

[0079] [Table 1]

[0080] [Table 2]

[0081] [Table 3]

[0082] <Rating> An inkjet recording device was prepared, having the main components shown in Figure 1, an ink supply system as shown in Figure 2, and a tube pump as shown in Figure 3. This recording device uses a tube pump to deliver aqueous ink in both the forward direction (from the main tank to the sub-tank) and the reverse direction (from the sub-tank to the main tank) through the same flow path. The ink obtained above was filled into the main tank of this recording device.

[0083] In this invention, the following evaluation criteria were used, with "AA," "A," and "B" representing acceptable levels and "C" representing an unacceptable level.

[0084] (Adhesion recovery) During the recording operation of the inkjet recorder, the power cable was disconnected while the carriage was moving, resulting in a state where the recording head was not capped. In this state, the inkjet recorder was left in an environment with a temperature of 30°C and a relative humidity of 10% for 5 days. After that, a recovery operation (cleaning) of the inkjet recorder was performed, and a nozzle check pattern was recorded. The recorded nozzle check pattern was visually observed, and the ink adhesion recovery performance was evaluated according to the evaluation criteria shown below. AA: After 1-2 recovery operations, it was able to record normally. A: After 3 to 5 recovery operations, it was possible to record normally again. B: After 6 to 10 recovery operations, it was able to record normally. C: After performing recovery operations 11 times, the system was not able to record properly.

[0085] [Table 4]

[0086] Furthermore, the disclosure of embodiments of the present invention includes the following methods and configurations.

[0087] (Method 1) A first ink storage section for water-based ink, A second ink storage section for temporarily storing the aforementioned water-based ink, A recording head that ejects the aforementioned aqueous ink, The device comprises a tube pump provided in a flow path connecting the first ink storage section and the second ink storage section, which is capable of flowing the aqueous ink from the first ink storage section to the second ink storage section and from the second ink storage section to the first ink storage section, An inkjet recording apparatus is used in which the first ink storage section, the tube pump, the second ink storage section, and the recording head are arranged in this order, and the tube pump performs forward liquid delivery of the aqueous ink from the first ink storage section to the second ink storage section and reverse liquid delivery from the second ink storage section to the first ink storage section via the same flow path. An inkjet recording method for recording an image by ejecting the aqueous ink from the recording head, An inkjet recording method characterized in that the aqueous ink contains a pigment, an acetylene-based surfactant, a silicone-based surfactant, and a urethane resin, and the relationship between the dynamic surface tension γ10 of the aqueous ink at a lifetime of 10 milliseconds, measured by the maximum foam pressure method, and the dynamic surface tension γ100 at a lifetime of 100 milliseconds is γ10 - γ100 ≤ 4.0 mN / m.

[0088] (Method 2) The inkjet recording method according to Method 1, wherein the ratio U / P of the content of the urethane resin to the content P (mass%) of the pigment is 0.05 or more and 1.00 or less.

[0089] (Method 3) The aforementioned aqueous ink contains an alkanediol.

[0090] (Method 4) The inkjet recording method according to Method 3, wherein the ratio D / T of the content D (mass%) of the alkanediol in the aqueous ink to the content T (mass%) of all components excluding the pigment and resin in the aqueous ink is 0.2 or more and 0.4 or less.

[0091] (Method 5) The inkjet recording method according to any one of methods 1 to 4, wherein the ratio A / S of the content A (mass%) of the acetylene-based surfactant to the content S (mass%) of the silicone-based surfactant is 0.5 or more and 10.0 or less.

[0092] (Method 6) The inkjet recording method according to any one of methods 1 to 5, wherein the relationship between the dynamic surface tension γ10 of the aqueous ink at a lifetime of 10 milliseconds and the dynamic surface tension γ100 at a lifetime of 100 milliseconds is γ10 - γ100 ≤ 3.0 mN / m.

[0093] (Composition 1) An inkjet recording apparatus used in the inkjet recording method described in any one of methods 1 to 6, A first ink storage section for water-based ink, A second ink storage section for temporarily storing the aforementioned water-based ink, A recording head that ejects the aforementioned aqueous ink, The device comprises a tube pump provided in a flow path connecting the first ink storage section and the second ink storage section, which is capable of flowing the aqueous ink from the first ink storage section to the second ink storage section and from the second ink storage section to the first ink storage section, The first ink storage section, the tube pump, the second ink storage section, and the recording head are arranged in this order, and the tube pump performs forward transfer of the aqueous ink from the first ink storage section to the second ink storage section and reverse transfer of the aqueous ink from the second ink storage section to the first ink storage section via the same flow path. An inkjet recording apparatus characterized in that the aqueous ink contains a pigment, an acetylene-based surfactant, a silicone-based surfactant, and a urethane resin, and the relationship between the dynamic surface tension γ10 of the aqueous ink at a lifetime of 10 milliseconds, measured by the maximum foam pressure method, and the dynamic surface tension γ100 at a lifetime of 100 milliseconds is γ10 - γ100 ≤ 4.0 mN / m. [Explanation of symbols]

[0094] 201 Main Tank 202 Tube pump 203 Sub-tank 205 Recording element substrate

Claims

1. A first ink storage section for water-based ink, A second ink storage section for temporarily storing the aforementioned water-based ink, A recording head that ejects the aforementioned aqueous ink, It is provided in the flow path connecting the first ink storage section and the second ink storage section, and is used to flow the aqueous ink from the first ink storage section to the second ink storage section, The device comprises a tube pump capable of flowing the aqueous ink from the second ink storage section to the first ink storage section, An inkjet recording apparatus is used in which the first ink storage section, the tube pump, the second ink storage section, and the recording head are arranged in this order, and the tube pump performs forward liquid delivery of the aqueous ink from the first ink storage section to the second ink storage section and reverse liquid delivery from the second ink storage section to the first ink storage section via the same flow path. An inkjet recording method for recording an image by ejecting the aqueous ink from the recording head, An inkjet recording method characterized in that the aqueous ink contains a pigment, an acetylene-based surfactant, a silicone-based surfactant, and a urethane resin, and the relationship between the dynamic surface tension γ10 of the aqueous ink at a lifetime of 10 milliseconds and the dynamic surface tension γ100 at a lifetime of 100 milliseconds, as measured by the maximum foam pressure method, is γ10 - γ100 ≤ 4.0 mN / m.

2. The inkjet recording method according to claim 1, wherein the ratio U / P of the content of the urethane resin to the content P (mass%) of the pigment is 0.05 or more and 1.00 or less.

3. The inkjet recording method according to claim 1, wherein the aqueous ink contains an alkanediol.

4. The inkjet recording method according to claim 3, wherein the ratio D / T of the content D (mass%) of the alkanediol in the aqueous ink to the content T (mass%) of all components excluding the pigment and resin in the aqueous ink is 0.2 or more and 0.4 or less.

5. The inkjet recording method according to claim 1, wherein the ratio A / S of the content A (mass%) of the acetylene-based surfactant to the content S (mass%) of the silicone-based surfactant is 0.5 or more and 10.0 or less.

6. The inkjet recording method according to claim 1, wherein the relationship between the dynamic surface tension γ10 of the aqueous ink at a lifetime of 10 milliseconds and the dynamic surface tension γ100 at a lifetime of 100 milliseconds is γ10 - γ100 ≤ 3.0 mN / m.

7. An inkjet recording apparatus used in the inkjet recording method according to any one of claims 1 to 6, A first ink storage section for water-based ink, A second ink storage section for temporarily storing the aforementioned water-based ink, A recording head that ejects the aforementioned aqueous ink, It is provided in the flow path connecting the first ink storage section and the second ink storage section, and is used to flow the aqueous ink from the first ink storage section to the second ink storage section, The device comprises a tube pump capable of flowing the aqueous ink from the second ink storage section to the first ink storage section, The first ink storage section, the tube pump, the second ink storage section, and the recording head are arranged in this order, and the tube pump performs forward transfer of the aqueous ink from the first ink storage section to the second ink storage section and reverse transfer of the aqueous ink from the second ink storage section to the first ink storage section via the same flow path. An inkjet recording apparatus characterized in that the aqueous ink contains a pigment, an acetylene-based surfactant, a silicone-based surfactant, and a urethane resin, and the relationship between the dynamic surface tension γ10 of the aqueous ink at a lifetime of 10 milliseconds and the dynamic surface tension γ100 at a lifetime of 100 milliseconds, as measured by the maximum foam pressure method, is γ10 - γ100 ≤ 4.0 mN / m.

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