Cleaning composition for inkjet head

Abstract

The present invention relates to: [1] a cleaning composition for an inkjet head, the cleaning composition containing a solvent (A) and water, the dipole moment of the solvent (A) at 25 DEG C as determined by a density pan-function method being 5.0 D or more, and the water content in the cleaning composition being 30 mass% or more; [2] The use of a composition as an inkjet head cleaning agent, said composition containing: a solvent (A) having a dipole moment of 5.0 D or more at 25 DEG C as determined by a density pan-function method, and a water content of 30 mass% or more; [3] A method for cleaning an inkjet head using a composition containing a solvent (A) and water, the dipole moment of the solvent (A) at 25 DEG C as determined by a density pan-function method being 5.0 D or more, and the content of the water being 30 mass% or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a cleaning composition for an inkjet head. BACKGROUND

[0002] For a cleaning composition, its composition is adjusted in various ways in consideration of its cleaning effect, and required properties corresponding to the kind of the object to be cleaned, the form of the composition, the method of use, and the like, and it has been widely used. As the object of such a cleaning composition, there is an article using a pigment dispersion.

[0003] A pigment dispersion is composed of a pigment having various functionalities, and a medium in which the pigment is dispersed. The pigment dispersion is made by mixing a pigment as a solid and a medium as a liquid, and in order to disperse the pigment in the medium, a polymer is used in most cases. In addition, in order to impart various properties, a polymer different from the polymer for dispersing the pigment is sometimes used. Therefore, the pigment dispersion is a stable dispersion even immediately after manufacture, but sometimes the settling of the pigment or the aggregation of the pigment, the adhesion of the pigment to a member to which the pigment dispersion is attached, and the drying of the pigment and the sticking due to the presence of the above-mentioned polymer, and the like occur with the passage of time or by heating, and the like, and the dispersion state of the pigment becomes an irreversible state. Such an irreversible change in state is sometimes actively utilized as a function of the pigment dispersion, but on the other hand, it often brings about a side effect beyond the intention of the designer of the pigment dispersion, and thus there are not a few examples of loss in industrial use.

[0004] As one example thereof, an ink for inkjet recording can be cited. The ink for inkjet recording, if left standing, aggregation of ink components occurs at the ejection nozzle, and adhesion of solid components in the vicinity of the ejection nozzle occurs. The adhesion of the solid components not only causes ejection defects such as ejection deviation, but sometimes clogging of the ejection nozzle occurs at the time of standing, and it is necessary to replace the inkjet head which is expensive.

[0005] As a reason for the specific aggregation of the ink components, there are many factors including settling due to high specific gravity of the pigment, and increase in ink concentration due to drying of the ink medium, but when the ink for inkjet recording is applied to various industrial fields, the adhesion of the solid components of the ink in the vicinity of the ejection nozzle and the clogging of the ejection nozzle affect the reduction of the production speed and the increase in the running cost of the printer, and this becomes one of the obstacles to the spread of the ink for inkjet recording.

[0006] Therefore, in view of such a problem, various studies have been made on a cleaning liquid for an inkjet head.

[0007] For example, in Japanese Patent Application Publication No. 2018-104637 (Patent Literature 1), in order to provide a cleaning liquid for an aqueous ink containing a pigment and a water-insoluble polymer, which is excellent in cleaning property of the aqueous ink, and a cleaning method of the aqueous ink using the cleaning liquid, a cleaning liquid for an aqueous ink containing a pigment and a water-insoluble polymer, and a cleaning method of the aqueous ink using the cleaning liquid are described, the cleaning liquid containing a surfactant, a water-soluble organic solvent containing diethylene glycol monoisopropyl ether, and water, the surfactant containing one or more selected from an alkyne diol or an ethylene oxide adduct thereof, and a polyethylene glycol alkyl ether having an alkyl group with a carbon number of 8 or more or a polyethylene glycol aryl ether having an aryl group with a carbon number of 6 or more, the content of the water-soluble organic solvent in the cleaning liquid being in a prescribed range. SUMMARY

[0008] The present application relates to a cleaning composition for an inkjet head, the cleaning composition containing: a solvent (A) having a dipole moment at 25°C of 5.0 D or more calculated using the method of density functional theory, and water, the content of water in the cleaning composition being 30% by mass or more. DETAILED DESCRIPTION

[0009] In the technology of Patent Literature 1, it is attempted to improve the cleaning property of the ink in the inkjet head by applying a cleaning liquid containing a surfactant and an amphiphilic organic solvent. However, in such a technology, as a characteristic in trade-off relationship with the cleaning property of the ink, there is the component resistance of the inkjet head. The component resistance of the inkjet head means that the constituent components of the inkjet head such as an adhesive or a seal are deformed due to swelling or dissolution or the like by the action of the surfactant or the amphiphilic organic solvent, and thus the shape of the inkjet head is disordered or the constituent components of the inkjet head are peeled off. In the case where a cleaning liquid of the ink having low adaptability to such a component resistance is applied, the inkjet head can become unusable in a much shorter time than expected. Therefore, it is required to take into account both the excellent cleaning property of the coating film derived from the ink adhered to the components of the inkjet head and the excellent component adaptability.

[0010] The present application provides a cleaning composition which is excellent in coating film cleaning property, and thus is excellent in ejection recovery property of an inkjet head, and is also excellent in component adaptability.

[0011] The present inventors have found that the above technical problems can be solved by a cleaning composition for an inkjet head containing: a solvent having a dipole moment at 25°C of 5.0 D or more calculated using the method of density functional theory, and water, the content of water in the cleaning composition being 30% by mass or more.

[0012] That is, the present application provides a cleaning composition for an inkjet head, wherein the cleaning composition for an inkjet head contains: a solvent (A) and water,

[0013] The solvent (A) has a dipole moment of 5.0 D or more at 25°C calculated using a density functional method,

[0014] The content of water in the cleaning composition is 30% by mass or more.

[0015] [Cleaning composition]

[0016] The cleaning composition of the present application is a cleaning composition containing a solvent (A) and water, the solvent (A) having a dipole moment of 5.0 D or more at 25°C calculated using a density functional method, and the content of water in the cleaning composition being 30% by mass or more.

[0017] The cleaning composition of the present application is preferably a cleaning composition for an inkjet head.

[0018] The cleaning composition of the present application has excellent film cleaning properties, and also has excellent component adaptability. The reason is not certain, but it can be considered as follows.

[0019] The solvent (A) contained in the cleaning composition of the present application has a dipole moment of 5.0 D or more at 25°C calculated using a density functional method, and has a large charge shift within the molecule, and thus is easily oriented toward the hydrophilic functional group in the polymer constituting the film, and thus it is considered that the wettability of the cleaning composition of the present application to the polymer can be improved.

[0020] Further, the solvent (A) is easily stabilized in a state where the intermolecular distance between the solvent (A) molecules is short due to the charge shift within the molecule. Thus, it is considered that the solvent (A) molecules oriented toward the hydrophilic functional group of the polymer constituting the film are taken as a starting point, and a chain between the solvent (A) molecules is formed, and thus the solvent (A) is aggregated around the hydrophilic functional group. Further, it is considered that since the solvent (A) has a dipole moment of 5.0 D or more at 25°C, the water solubility is high, and thus after being aggregated around the hydrophilic functional group of the polymer, water is easily introduced to move the polymer in water, and thus the peelability of the film from the object to be cleaned is improved, and the excellent cleaning properties of the film are improved.

[0021] Further, since the content of water in the cleaning composition of the present application is 30% by mass or more, the content of organic solvent can be suppressed, and thus the component adaptability is also excellent.

[0022] Further, even if the film is a film containing a pigment, since the cleaning composition of the present application can act on the polymer constituting the film as described above, it is considered that the peelability of the film containing a pigment from the object to be cleaned can be improved, and the excellent cleaning properties of the film containing a pigment can be improved.

[0023] As such an effect, it can be considered that by applying the cleaning composition of the present application to the coating film adhered to the inkjet head, both excellent cleaning-based ejection recovery and excellent component suitability can be achieved.

[0024] <Solvent (A)>

[0025] Regarding the cleaning composition of the present application, from the viewpoint of improving the peelability of the coating film to improve the cleaning property, a solvent (A) (hereinafter also referred to as "solvent (A)") having a dipole moment of 5.0 D or more at 25°C calculated using the density functional method is contained.

[0026] In the present application, the dipole moment is a value at 25°C. As described in the examples, the dipole moment is calculated using the quantum chemical calculation software TURBOMOLE Ver. 7.7, using BP86 as the functional and def-TZVP as the basis function, by calculation using the density functional method. In addition, the unit of the dipole moment is "D (Debye)".

[0027] Regarding the dipole moment of the solvent (A), from the viewpoint of improving the peelability of the coating film to improve the cleaning property and the viewpoint of improving the component suitability, it is preferably 5.2 D or more, more preferably 5.4 D or more, and further preferably 5.6 D or more, and from the same viewpoints described above, it is preferably 6.5 D or less, more preferably 6.3 D or less, and further preferably 6.1 D or less. That is, the dipole moment of the solvent (A) is preferably 5.2 D or more and 6.5 D or less, more preferably 5.4 D or more and 6.3 D or less, and further preferably 5.6 D or more and 6.1 D or less.

[0028] The solvent (A) can be used alone or two or more kinds can be used in combination.

[0029] Regarding the solvent (A), from the viewpoint of improving the peelability of the coating film to improve the cleaning property, it is preferably one or more selected from cyclic carbonates and cyclic sulfones, and more preferably one or more selected from propylene carbonate (dipole moment: 5.64 D), ethylene carbonate (dipole moment: 5.41 D), and sulfolane (dipole moment: 5.39 D).

[0030] The propylene carbonate, ethylene carbonate, and sulfolane which the cleaning composition of the present application is suitably used for are cyclic organic solvents having a dipole moment of 5.0 D or more, and thus it can be considered that they easily penetrate into the gaps of the polymer constituting the coating film, and an effect of improving the swelling property of the polymer can be obtained. On the other hand, the propylene carbonate, ethylene carbonate, and sulfolane are water-soluble, and thus it can be considered that after entering into the gaps of the polymer, water is easily introduced, and thus the peelability of the coating film from the object to be cleaned is improved to improve the excellent cleaning property of the coating film.

[0031] As the solvent (A), from the viewpoint of improving the peeling property of the coating film to improve the cleanability, it is further preferred to select one or more of propylene carbonate and ethylene carbonate, and it is more further preferred to be propylene carbonate or a mixture of propylene carbonate and ethylene carbonate.

[0032] In the case where the solvent (A) is a mixture of propylene carbonate and ethylene carbonate, the mass ratio of the content of ethylene carbonate to the content of propylene carbonate [ethylene carbonate / propylene carbonate] in the cleaning composition of the present application is preferably greater than 0, and is preferably 5 or less, more preferably 4 or less, further preferably 3 or less, more further preferably 2 or less, more further preferably 1 or less, more further preferably 0.7 or less, more further preferably 0.5 or less, and more further preferably 0.3 or less, from the viewpoint of balancing the cleanability and the component adaptability.

[0033] The content of the solvent (A) in the cleaning composition of the present application is preferably 5% by mass or more, more preferably 8% by mass or more, further preferably 10% by mass or more, more further preferably 15% by mass or more, and more further preferably 17% by mass or more, from the viewpoint of improving the peeling property of the coating film to improve the cleanability, and is preferably 65% by mass or less, more preferably 60% by mass or less, further preferably 55% by mass or less, more further preferably 45% by mass or less, more further preferably 40% by mass or less, more further preferably 30% by mass or less, and more further preferably 20% by mass or less, from the viewpoint of improving the component adaptability. That is, the content of the solvent (A) in the cleaning composition is preferably 5% by mass or more and 65% by mass or less, more preferably 5% by mass or more and 60% by mass or less, further preferably 8% by mass or more and 55% by mass or less, more further preferably 8% by mass or more and 45% by mass or less, more further preferably 10% by mass or more and 40% by mass or less, more further preferably 15% by mass or more and 30% by mass or less, and more further preferably 17% by mass or more and 20% by mass or less.

[0034] <Solvent (B)>

[0035] As the cleaning composition of the present application, from the viewpoint of improving the dispersibility of the coating film peeled off from the object to be cleaned to improve the cleanability, it is preferred to contain an organic solvent (B) having one or more groups selected from a hydroxyl group and a polyoxyalkylene group (hereinafter also referred to as "solvent (B)") in addition to the solvent (A).

[0036] The solvent (B) can be used alone or two or more kinds can be used in combination.

[0037] As the solvent (B), specific examples can include ethylene glycol, diethylene glycol, polyoxyalkylene phenyl ether, and polyoxyalkylene benzyl ether.

[0038] The solvent (B) preferably contains one or more solvents (B1) (hereinafter sometimes referred to simply as "solvents (B1)") selected from the group consisting of ethylene glycol, diethylene glycol, polyoxyalkylene phenyl ether, and polyoxyalkylene benzyl ether.

[0039] In the case where the cleaning composition of the present application contains the solvent (B1) in addition to the solvent (A), it can be considered that the solvent (A) has a function of dispersing the coating film peeled off from the object to be cleaned in the cleaning composition of the present application containing water due to the strong polarity of the alkylene group of the solvent (B1) and the oxygen atoms present at both ends or in the middle of the alkylene group, and as a result, the cleaning property of the coating film is further improved.

[0040] Among these, the solvent (B1) is preferably one or more selected from the group consisting of polyoxyalkylene phenyl ether and polyoxyalkylene benzyl ether from the viewpoint of improving the dispersibility of the coating film peeled off from the object to be cleaned to improve the cleaning property.

[0041] With respect to the polyoxyalkylene group of the polyoxyalkylene phenyl ether, it is preferable to contain a unit derived from alkylene oxide having 2 to 4 carbon atoms from the viewpoint of improving the dispersibility of the coating film peeled off from the object to be cleaned to improve the cleaning property. As the above alkylene oxide, ethylene oxide, propylene oxide, butylene oxide, and the like can be mentioned, and it is preferably one or more selected from the group consisting of ethylene oxide and propylene oxide, more preferably contains at least ethylene oxide, and further preferably is ethylene oxide. That is, the polyoxyalkylene group of the polyoxyalkylene phenyl ether more preferably contains at least polyoxyethylene, and further preferably is polyoxyethylene.

[0042] Specifically, as the polyoxyalkylene phenyl ether, one or more selected from the group consisting of polyoxyethylene phenyl ether and polyoxypropylene phenyl ether is preferable. Among these, polyoxyethylene phenyl ether is more preferable.

[0043] With respect to the average addition mole number of the alkylene oxide in the polyoxyalkylene group of the polyoxyalkylene phenyl ether, it is preferably 2 or more, more preferably greater than 2, further preferably 3 or more, and preferably 10 or less, more preferably 8 or less, and further preferably 6 or less from the viewpoint of improving the dispersibility of the coating film peeled off from the object to be cleaned to improve the cleaning property. That is, the average addition mole number of the alkylene oxide in the polyoxyalkylene group of the polyoxyalkylene phenyl ether is preferably 2 or more and 10 or less, more preferably greater than 2 and 8 or less, and further preferably 3 or more and 6 or less.

[0044] As the polyoxyalkylene group of the polyoxyalkylenebenzyl ether, from the viewpoint of improving the dispersibility of the coating film peeled off from the object to be cleaned to improve the cleaning properties, it is preferable to contain a unit derived from an alkylene oxide having 2 or more and 4 or less carbon atoms. As the above alkylene oxide, ethylene oxide, propylene oxide, butylene oxide, and the like can be exemplified, and it is preferable to contain one or more selected from the group consisting of ethylene oxide and propylene oxide, more preferably to contain at least ethylene oxide, and further preferably to be ethylene oxide. That is, the polyoxyalkylene group of the polyoxyalkylenebenzyl ether more preferably contains at least a polyoxyethylene group, and further preferably is a polyoxyethylene group.

[0045] As the polyoxyalkylenebenzyl ether, specifically, it is preferable to exemplify one or more selected from the group consisting of a polyoxyethylenebenzyl ether and a polyoxypropylenebenzyl ether. Among these, a polyoxyethylenebenzyl ether is more preferable.

[0046] As the average addition mole number of the alkylene oxide in the polyoxyalkylene group of the polyoxyalkylenebenzyl ether, from the viewpoint of improving the dispersibility of the coating film peeled off from the object to be cleaned to improve the cleaning properties, it is preferable to be 2 or more, and it is preferable to be 10 or less, more preferably 8 or less, and further preferably 6 or less.

[0047] As the content of the solvent (B1) in the component (B), from the viewpoint of improving the dispersibility of the coating film peeled off from the object to be cleaned to improve the cleaning properties, it is preferable to be 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, more further preferably 95% by mass or more, and more further preferably 97% by mass or more, and it is preferable to be 100% by mass or less, more further preferably 100% by mass.

[0048] As the content of the component (B) in the cleaning composition of the present application, from the viewpoint of improving the dispersibility of the coating film peeled off from the object to be cleaned to improve the cleaning properties, it is preferable to be 0.5% by mass or more, more preferably 1% by mass or more, and further preferably 2% by mass or more, and from the viewpoint of improving the component adaptability, it is preferable to be 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, more further preferably 20% by mass or less, and more further preferably 10% by mass or less. That is, the content of the component (B) in the cleaning composition is preferably 0.5% by mass or more and 50% by mass or less, more preferably 0.5% by mass or more and 40% by mass or less, further preferably 1% by mass or more and 30% by mass or less, more further preferably 1% by mass or more and 20% by mass or less, and more further preferably 2% by mass or more and 10% by mass or less.

[0049] The content of the solvent (B1) in the cleaning composition of the present application is preferably 0.5% by mass or more, more preferably 1% by mass or more, and further preferably 2% by mass or more, from the viewpoint of improving the dispersibility of the coating film peeled off from the object to be cleaned to improve the cleaning property, and is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, more further preferably 20% by mass or less, and more further preferably 10% by mass or less, from the viewpoint of improving the component adaptability. That is, the content of the solvent (B1) in the cleaning composition is preferably 0.5% by mass or more and 50% by mass or less, more preferably 0.5% by mass or more and 40% by mass or less, further preferably 1% by mass or more and 30% by mass or less, more further preferably 1% by mass or more and 20% by mass or less, and more further preferably 2% by mass or more and 10% by mass or less.

[0050] The content of the solvent (B) in the cleaning composition of the present application relative to the content of the solvent (A) in terms of the mass ratio [solvent (B) / solvent (A)] is preferably 0.05 or more, more preferably 0.07 or more, and further preferably 0.10 or more, from the viewpoint of improving the cleaning property of the coating film, and is preferably 3.0 or less, more preferably 2.5 or less, further preferably 2.0 or less, more further preferably 1.5 or less, more further preferably 1.0 or less, more further preferably 0.9 or less, more further preferably 0.7 or less, more further preferably 0.5 or less, and more further preferably 0.3 or less. That is, the mass ratio [solvent (B) / solvent (A)] is preferably 0.05 or more and 3.0 or less, more preferably 0.05 or more and 2.5 or less, further preferably 0.05 or more and 2.0 or less, more further preferably 0.07 or more and 1.5 or less, more further preferably 0.07 or more and 1.0 or less, more further preferably 0.07 or more and 0.9 or less, more further preferably 0.10 or more and 0.7 or less, more further preferably 0.10 or more and 0.5 or less, and more further preferably 0.10 or more and 0.3 or less.

[0051] (Other solvents)

[0052] The cleaning composition of the present application can also contain other solvents than the solvents (A) and (B) within a range not impairing the effects of the present application. As such other solvents, for example, γ-butyrolactone (dipole moment: 4.69 D), 2-pyrrolidone (dipole moment: 4.16 D), dimethyl sulfoxide (dipole moment: 4.10 D), dimethylformamide (dipole moment: 4.06 D), N-methylpyrrolidone (dipole moment: 3.99 D), tetrahydrofuran (dipole moment: 1.92 D), cyclohexane (dipole moment: 0.00 D), and benzene (dipole moment: 0.00 D) can be exemplified.

[0053] The content of other solvents than the solvents (A) and (B) in the cleaning composition of the present application is preferably 10 mass% or less, more preferably 5 mass% or less, further preferably 3 mass% or less, and still further preferably 0 mass% from the viewpoint of improving the cleanability of the coating film and the viewpoint of improving the part suitability.

[0054] < Water >

[0055] The cleaning composition of the present application contains water from the viewpoint of improving the cleanability of the coating film and the viewpoint of improving the part suitability. The water can be any one of tap water, ion-exchanged water, ultrafiltration water, RO water, and distilled water, and is preferably one or more selected from the group consisting of ion-exchanged water, ultrafiltration water, RO water, and distilled water from the viewpoint of improving the cleanability of the coating film.

[0056] The content of water in the cleaning composition of the present application is 30 mass% or more, preferably 35 mass% or more, more preferably 40 mass% or more, further preferably 45 mass% or more, still further preferably 50 mass% or more, yet further preferably 55 mass% or more, and yet further preferably 60 mass% or more, and is preferably 90 mass% or less, more preferably 85 mass% or less, and further preferably 80 mass% or less. That is, the content of water in the cleaning composition is 30 mass% or more, preferably 35 mass% or more and 90 mass% or less, more preferably 40 mass% or more and 90 mass% or less, further preferably 45 mass% or more and 85 mass% or less, still further preferably 50 mass% or more and 85 mass% or less, yet further preferably 55 mass% or more and 80 mass% or less, and yet further preferably 60 mass% or more and 80 mass% or less.

[0057] The mass ratio of the content of the solvent (A) to the content of water in the cleaning composition of the present application [solvent (A) / water] is preferably 0.05 or more, more preferably 0.07 or more, further preferably 0.10 or more, more further preferably 0.15 or more, more further preferably 0.20 or more, from the viewpoint of improving the cleanability of the coating film, and is preferably 3.0 or less, more preferably 2.0 or less, further preferably 1.5 or less, more further preferably 1.0 or less, more further preferably 0.70 or less, more further preferably 0.50 or less, more further preferably 0.30 or less, from the viewpoint of improving the component adaptability. That is, the mass ratio of [solvent (A) / water] is preferably 0.05 or more and 3.0 or less, more preferably 0.05 or more and 2.0 or less, further preferably 0.07 or more and 1.5 or less, more further preferably 0.07 or more and 1.0 or less, more further preferably 0.10 or more and 0.70 or less, more further preferably 0.15 or more and 0.50 or less, and more further preferably 0.20 or more and 0.30 or less.

[0058] In addition to the above-mentioned components, various additives such as a pH adjuster, an antifoaming agent, a preservative, a mold inhibitor, a rust preventive, and the like can be added to the cleaning composition of the present application.

[0059] In addition, the cleaning composition of the present application does not contain a pigment and a polymer.

[0060] Further, from the viewpoint of the dispersibility of the pigment and the polymer, the cleaning composition of the present application preferably does not contain an acid and an oxidizing agent.

[0061] The cleaning composition of the present application can be obtained by mixing and stirring the solvent (A), water, and, as necessary, the solvent (B), the other solvents described above, and the additives described above.

[0062] (Cleaning method)

[0063] The cleaning composition of the present application is preferably used for the cleaning of a coating film attached to an object to be cleaned. The object to be cleaned is preferably an inkjet head. That is, the cleaning method using the cleaning composition of the present application is preferably a method of cleaning an inkjet head using the cleaning composition.

[0064] As the cleaning method using the cleaning composition of the present application, a method in which the cleaning composition is brought into contact with a coating film attached to an object to be cleaned is preferred. As the method of contact, for example, a dipping method, a spraying method, a coating method, and a stirring method can be listed. In addition, a method in which the cleaning composition of the present application is impregnated into a liquid-absorbing wiping member such as a nonwoven fabric and the surface of an object to be cleaned is wiped and cleaned is preferred as a method of removing a stubbornly adhered coating film.

[0065] [Use of the cleaning composition of the present application]

[0066] Since the coating film cleanability of the cleaning composition of the present application is excellent, and the part adaptability is also excellent, it is preferably used as a cleaner for, for example, an aqueous ink containing a polymer. In the present application, "aqueous" means that, in a medium in which a polymer is dispersed, water accounts for the largest proportion on a mass basis. At this time, even if the above-mentioned polymer is a water-insoluble polymer, it can be cleaned well.

[0067] In the present application, "water-insoluble polymer" means that, when a polymer is dissolved in 100 g of water at 25°C until saturated after being dried at 105°C for 2 hours so that the weight becomes constant, the amount of dissolution is 10 g or less, and the amount of dissolution is preferably 5 g or less, more preferably 1 g or less. In the case where the water-insoluble polymer is an anionic polymer, the amount of dissolution is that when 100% of the anionic group of the polymer is neutralized with sodium hydroxide. In the case where the water-insoluble polymer is a cationic polymer, the amount of dissolution is that when 100% of the cationic group of the polymer is neutralized with hydrochloric acid.

[0068] In the case where the cleaning composition of the present application is used as a cleaner for an aqueous ink containing a polymer and water (hereinafter also sometimes referred to simply as "aqueous ink"), it is preferably used as a cleaner for an aqueous ink for flexographic printing, for gravure printing, or for inkjet recording, and more preferably used as a cleaner for an aqueous ink for inkjet recording.

[0069] Among them, "recording" is a concept including printing and lettering that record characters and images. In the case where the cleaning composition of the present application is used as a cleaner for removing a coating film of an aqueous ink for inkjet recording attached to an inkjet head, the effect of the cleaning property of the cleaning composition of the present application can be exerted, and the ejection recovery property can be improved.

[0070] In the case where the cleaning composition of the present application is used as a cleaner for an aqueous ink for inkjet recording, it can also be used for cleaning of an inkjet recording apparatus using an aqueous ink for inkjet recording, an implement for maintenance of the recording apparatus, and the like. Among them, cleaning applied to an inkjet recording apparatus is preferred, and cleaning applied to an inkjet head is more preferred. Specifically, it can be used for cleaning of an ink ejection port of an inkjet head, a portion near the ink ejection port, an ink supply path of an inkjet recording apparatus from an ink tank or an ink cartridge to the ink ejection port, and the like. More specifically, it is suitable as a cleaner (spray liquid, wiping liquid) for an aqueous ink for inkjet recording attached to a nozzle plate provided with a plurality of ejection nozzle holes of an inkjet head for each color ink. That is, the cleaning composition of the present application is preferably used as a cleaning composition for an inkjet head.

[0071] Aqueous Ink

[0072] The aqueous ink which is the object of the cleaning composition of the present application contains a polymer and water. The aqueous ink can be a so-called primer liquid and / or a topcoat liquid. The aqueous ink can contain a pigment in addition to the polymer and water. That is, the coating film which is cleaned with the cleaning composition of the present application contains at least a component from the polymer derived from the aqueous ink, and preferably contains a component from the polymer and a component from the pigment.

[0073] 〔Polymer〕

[0074] The polymer contained in the aqueous ink which is the object of the cleaning composition of the present application preferably contains at least one of a function as a pigment dispersant which exerts a pigment dispersing action, or a function as a fixing agent to a printing medium.

[0075] As to the polymer which exerts a function as a pigment dispersant (hereinafter also referred to as "pigment dispersing polymer"), from the viewpoint of dispersion stability and ejection recovery of the ink, a water-insoluble polymer is preferred.

[0076] As a preferred example of the pigment dispersing polymer, from the viewpoint of dispersion stability and ejection recovery of the ink, one or more selected from the group consisting of a polyester resin, a polyurethane resin, and a vinyl-based resin can be exemplified. Among these, one or more selected from the group consisting of a polyester resin and a vinyl-based resin is more preferred, and a polyester resin is further preferred.

[0077] The polyester resin can be obtained by polycondensation of an alcohol component and a carboxylic acid component. As the alcohol component, an aromatic or aliphatic polyhydric alcohol, preferably an aromatic dihydric alcohol such as a bisphenol A oxyalkylene adduct, can be exemplified. As the carboxylic acid component, for example, an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, a polybasic carboxylic acid of three or more, preferably an aliphatic dicarboxylic acid containing fumaric acid or the like can be exemplified.

[0078] The vinyl-based resin can be obtained by polyaddition of a monomer mixture containing an ionic monomer such as acrylic acid or methacrylic acid, and one or more selected from the group consisting of a hydrophobic monomer such as an (meth)acrylamino ester, an aromatic group-containing monomer, and a hydrophilic nonionic monomer such as a polyalkylene glycol (meth)acrylate, using a known method.

[0079] Among these, from the viewpoint of dispersion stability and ejection recovery of the ink, the aqueous ink is preferably an ink in which a pigment is dispersed using a water-insoluble polymer having an anionic group such as a carboxyl group.

[0080] In the water-based ink, from the viewpoint of dispersion stability and ejection recovery of the ink, the pigment is preferably contained in the form of a water-insoluble polymer particle containing a pigment (hereinafter also sometimes referred to simply as "pigment-containing polymer particle") using the above-described water-insoluble polymer as a pigment dispersing polymer. The pigment-containing polymer particle is formed by adsorbing the water-insoluble polymer on the pigment in the water-based ink. As the form of the particle, there are included, for example, a particle form in which the pigment is enclosed in the polymer, a particle form in which the pigment is uniformly dispersed in the polymer, a particle form in which the pigment is exposed on the surface of the polymer particle, and the like, and also included are mixtures thereof.

[0081] As for the polymer having a function as a fixing agent to a printing medium (hereinafter also referred to as "fixing aid polymer"), from the viewpoint of imparting higher fixability to a printed matter, it is preferable to be a water-insoluble polymer.

[0082] As a preferable example of the fixing aid polymer, from the viewpoint of imparting higher fixability to a printed matter, it is preferable to cite one or more selected from the group consisting of a polyester resin, an acrylic resin, a styrene / (meth)acrylic resin, a styrene-based resin, a styrene / butadiene-based resin, a butadiene-based resin, a vinyl chloride-based resin, a vinyl acetate-based resin, and a polyurethane-based resin. Among these, it is more preferable to be one or more selected from the group consisting of a polyester resin, an acrylic resin, and a styrene / acrylic resin, and it is further preferable to be a polyester resin.

[0083] The fixing aid polymer can be used alone or in a mixture of two or more.

[0084] From the viewpoints of fixability to a printing medium and rub resistance of a printed matter, the fixing aid polymer is preferably a water-insoluble polymer particle not containing a pigment, and more preferably a polyester resin particle not containing a pigment.

[0085] The polyester resin constituting the polyester resin particle not containing a pigment can be obtained by polycondensation of an alcohol component and a carboxylic acid component. As the above-described alcohol component, there can be cited a polyhydric alcohol of aromatic or aliphatic, and an aromatic dihydric alcohol such as an oxyalkylene adduct of bisphenol A is preferable. As the above-described carboxylic acid component, there can be cited an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, a polybasic carboxylic acid of three or more, and the like, and it is preferable to contain an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and a polybasic carboxylic acid of three or more.

[0086] From the viewpoint of handling, the water-insoluble polymer particles not containing pigments are preferably used in the form of a dispersion, and either a commercially available product or a product synthesized by emulsion polymerization or the like can be used. As a commercially available product of the dispersion of the water-insoluble polymer particles not containing pigments, for example, acryl-based resins such as "Neocryl A1127" (manufactured by DSM NeoResins Co., Ltd., anionic self-crosslinking water-based acrylic resin), "JONCRYL 390" (manufactured by BASF JAPAN LTD.), and the like; styrene / acryl-based resins such as "JONCRYL 7100", "JONCRYL 734", "JONCRYL 538" (all of which are manufactured by BASF JAPAN LTD.); styrene / butadiene-based resins such as "SR-100", "SR102" (both of which are manufactured by NIPPON A&L INC.); and vinyl chloride-based resins such as "VINYBLAN 701" (manufactured by NISSIN CHEMICAL CO., LTD.); polyurethane-based resins such as "WBR-2018", "WBR-2000U" (both of which are manufactured by TAISEI FINE CHEMICAL CO., LTD.); and the like can be listed.

[0087] In the case where the water-based ink contains the pigment-containing polymer particles, the weight average molecular weight of the water-insoluble polymer constituting the particles is preferably 5,000 or more, more preferably 7,000 or more, and further preferably 10,000 or more, and is preferably 100,000 or less, more preferably 50,000 or less, and further preferably 30,000 or less. That is, in the case where the water-based ink contains the pigment-containing polymer particles, the weight average molecular weight of the water-insoluble polymer constituting the particles is preferably 5,000 or more and 100,000 or less, more preferably 7,000 or more and 50,000 or less, and further preferably 10,000 or more and 30,000 or less.

[0088] In the case where the water-based ink contains the water-insoluble polymer particles not containing pigments, the weight average molecular weight of the water-insoluble polymer constituting the particles is preferably 5,000 or more, more preferably 7,000 or more, and further preferably 10,000 or more, and is preferably 100,000 or less, more preferably 50,000 or less, and further preferably 30,000 or less. That is, in the case where the water-based ink contains the water-insoluble polymer particles not containing pigments, the weight average molecular weight of the water-insoluble polymer constituting the particles is preferably 5,000 or more and 100,000 or less, more preferably 7,000 or more and 50,000 or less, and further preferably 10,000 or more and 30,000 or less.

[0089] The weight average molecular weight of the above water-insoluble polymer can be measured by gel permeation chromatography, and the specific measurement method can use the method described in the examples.

[0090] As for the acid value of the polymer, from the viewpoint of improving the peelability of the coating film to further improve the cleanability, it is preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, and further preferably 20 mgKOH / g or more. The higher the acid value of the polymer, the more the peelability of the coating film achieved by the cleaner of the present application is improved, and thus the upper limit of the acid value of the polymer is not particularly limited.

[0091] 〔Pigment〕

[0092] The pigment contained in the water-based ink which becomes the object of the cleaning composition of the present application can be any pigment among inorganic pigments and organic pigments, and these pigments are used in combination with extender pigments as needed.

[0093] As the inorganic pigment, for example, carbon black, metal oxides, etc. can be listed. In black ink, carbon black is preferred. As carbon black, for example, furnace black, lamp black, acetylene black, channel black can be listed. In white ink, for example, metal oxides such as titanium dioxide, zinc oxide, silicon dioxide, aluminum oxide, magnesium oxide, etc. can be listed.

[0094] As the organic pigment, for example, azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments can be listed.

[0095] In non-color ink, any non-color pigment such as white, black, gray, etc. can be used; in color ink, any color pigment such as yellow, magenta, cyan, red, blue, orange, green, etc. can be used.

[0096] As the extender pigment, for example, silicon dioxide, calcium carbonate, talc can be listed.

[0097] The pigment can be used alone as one kind or in combination with two or more kinds.

[0098] The pigment can be contained in the water-based ink in the form of a self-dispersed pigment, a pigment dispersed with a dispersant, or a water-insoluble polymer particle containing the pigment.

[0099] In the water-based ink, as components other than the polymer and water, and the pigment, a neutralizing agent, an organic solvent, a surfactant can be further contained as needed. Also, in the water-based ink, as optional components, various additives such as a humectant, a wetting agent, a penetrant, a dispersant, a surfactant, a viscosity modifier, an antifoaming agent, a preservative, a mildew preventive, a rust preventive, etc. can be contained.

[0100] The water-based ink can be obtained by mixing and stirring a pigment, a water-insoluble polymer, water, a neutralizing agent as necessary, an organic solvent, a surfactant, and the like.

[0101] In the case where the water-based ink contains the pigment-containing polymer particles, the pigment-containing polymer particles can be incorporated into the water-based ink after a dispersion of the pigment-containing polymer particles is obtained by dispersing treatment of a pigment, a water-insoluble polymer, a neutralizing agent as necessary, a surfactant, and the like using a publicly known method.

[0102] The content of the water-insoluble polymer in the water-based ink is preferably 1% by mass or more, more preferably 3% by mass or more, and further preferably 5% by mass or more from the viewpoints of dispersion stability and ejection recovery of the ink, and fixability to a printing medium and rub resistance of a printed matter, and is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less from the viewpoint of viscosity of the ink. That is, the content of the water-insoluble polymer in the water-based ink is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, and further preferably 5% by mass or more and 10% by mass or less.

[0103] The content of the pigment in the water-based ink is preferably 1% by mass or more, more preferably 2% by mass or more, and further preferably 3% by mass or more from the viewpoint of letter density of a printed matter, and is preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 8% by mass or less, and more further preferably 6% by mass or less from the viewpoints of viscosity of the ink and rub resistance of a printed matter. That is, the content of the pigment in the water-based ink is preferably 1% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass or less, further preferably 2% by mass or more and 8% by mass or less, and more further preferably 3% by mass or more and 6% by mass or less.

[0104] In the case where the water-based ink contains the pigment-containing polymer particles and the polymer particles not containing a pigment, the content of the water-insoluble polymer is the total amount of the water-insoluble polymers contained in the pigment-containing polymer particles and the polymer particles not containing a pigment.

[0105] The content of water in the water-based ink is preferably 35% by mass or more, more preferably 40% by mass or more, and further preferably 45% by mass or more from the viewpoints of dispersion stability of the ink and rub resistance of a printed matter, and is preferably 80% by mass or less, more preferably 75% by mass or less, and further preferably 70% by mass or less. That is, the content of water in the water-based ink is preferably 35% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 75% by mass or less, and further preferably 45% by mass or more and 70% by mass or less.

[0106] The cleaning method using the cleaning composition of the present application as a cleaning agent for water-based ink is preferably a method in which the above cleaning composition is brought into contact with a coating film of an object to be cleaned to which a water-based ink is adhered. As the method of contact, the same as above, dipping method, spraying method, coating method, stirring method, etc. can be exemplified.

[0107] As the above cleaning method, a method in which the cleaning composition of the present application is impregnated into a liquid-absorbing wiping member such as nonwoven fabric, and a coating film adhered to the ink ejection nozzle face or ink ejection nozzle outlet of an inkjet head is wiped off; a method in which, when different kinds of ink are used, the ink path in a printer is cleaned by repeatedly supplying the cleaning composition from an ink cartridge containing the cleaning composition to the ink path using the supply mechanism and discharge mechanism of the printer before and after the ink is replaced; a method in which, in the case where an inkjet head is not used for a long period of time, the coating film is removed from the inkjet head, the cleaning composition is filled in, and sealing and storage are performed, etc. can be exemplified. As the wiping member, there is no particular limitation as long as it has liquid-absorbing property, and woven fabric, knitted fabric, nonwoven fabric, sponge, pulp, etc. can be exemplified.

[0108] In the above cleaning method, from the viewpoint of exerting more excellent cleaning power, when the above cleaning composition is brought into contact, it is preferable to perform cleaning at 0°C or higher, more preferably 10°C or higher, further preferably 20°C or higher, and from the viewpoint of energy reduction, it is preferable to perform cleaning at lower than 100°C, more preferably 80°C or lower, further preferably 70°C or lower, more further preferably 50°C or lower. That is, in the above cleaning method, it is preferable to perform cleaning at 0°C or higher and lower than 100°C, more preferably 0°C or higher and 80°C or lower, further preferably 10°C or higher and 70°C or lower, more further preferably 20°C or higher and 50°C or lower.

[0109] The present application can provide a cleaning composition which is excellent in cleaning property of a coating film and also excellent in component adaptability.

[0110] The present application also includes the following modes of <1> to <53>.

[0111] <1> A cleaning composition, wherein the cleaning composition contains: a solvent (A) and water,

[0112] The solvent (A) has a dipole moment at 25°C of 5.0 D or more, which is calculated using the density functional method,

[0113] The content of water in the cleaning composition is 30% by mass or more.

[0114] <2> The cleaning composition according to <1> above, wherein the above solvent (A) is one or more selected from the group consisting of propylene carbonate, ethylene carbonate, and sulfolane.

[0115] ​The cleaning composition according to any one of <1> to <8> above, wherein the cleaning composition further contains an organic solvent (B) having one or more groups selected from a hydroxyl group and a polyoxyalkylene group.

[0116] The cleaning composition according to any one of <1> to <3> above, wherein the organic solvent (B) comprises one or more solvents (Bl) selected from ethylene glycol, diethylene glycol, a polyoxyalkylene phenyl ether, and a polyoxyalkylene benzyl ether.

[0117] The cleaning composition according to <4> above, wherein the polyoxyalkylene of the polyoxyalkylene phenyl ether or the polyoxyalkylene benzyl ether is a polyoxyethylene.

[0118] The cleaning composition according to <5> above, wherein the average addition mole number of ethylene oxide of the polyoxyethylene is 2 or more and 6 or less.

[0119] The cleaning composition according to any one of <1> to <6> above, wherein the content of water in the cleaning composition is 30 mass% or more and 90 mass% or less.

[0120] A cleaning composition, wherein the cleaning composition contains a solvent (A), an organic solvent (B), and water,

[0121] the solvent (A) has a dipole moment of 5.0 D or more at 25°C calculated using a density functional method,

[0122] the content of water in the cleaning composition is 30 mass% or more and 90 mass% or less,

[0123] the solvent (A) is propylene carbonate,

[0124] the organic solvent (B) is a polyoxyethylene phenyl ether.

[0125] A cleaning composition, wherein the cleaning composition contains a solvent (A), an organic solvent (B), and water,

[0126] the solvent (A) has a dipole moment of 5.0 D or more at 25°C calculated using a density functional method,

[0127] the content of water in the cleaning composition is 30 mass% or more and 90 mass% or less,

[0128] the solvent (A) is propylene carbonate,

[0129] the organic solvent (B) is a polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of the polyoxyethylene of 2.

[0130] The cleaning composition according to any one of <1> to <9> above, wherein the content of the propylene carbonate in the cleaning composition is 5 mass% or more and 60 mass% or less,

[0131] The content of the polyoxyethylene phenyl ether having an average addition mole number of 2 of the oxyethylene groups in the cleaning composition is 0.5 mass% or more and 50 mass% or less.

[0132] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the content of the water in the cleaning composition for inkjet head is 30 mass% or more.

[0133] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the solvent (A) is one or more selected from the group consisting of propylene carbonate, ethylene carbonate, and sulfolane.

[0134] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the content of the water in the cleaning composition for inkjet head is 30 mass% or more.

[0135] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the solvent (A) is one or more selected from the group consisting of propylene carbonate, ethylene carbonate, and sulfolane.

[0136] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the cleaning composition for inkjet head further contains an organic solvent (B) having one or more groups selected from the group consisting of a hydroxyl group and a polyoxyalkylene group.

[0137] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the organic solvent (B) contains one or more solvents (B1) selected from the group consisting of ethylene glycol, diethylene glycol, polyoxyalkylene phenyl ether, and polyoxyalkylene benzyl ether.

[0138] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the polyoxyalkylene of the polyoxyalkylene phenyl ether or the polyoxyalkylene benzyl ether is polyoxyethylene.

[0139] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the average addition mole number of the oxyethylene groups of the polyoxyethylene is 2 or more and 6 or less.

[0140] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the content of the water in the cleaning composition for inkjet head is 30 mass% or more and 90 mass% or less.

[0141] The cleaning composition for inkjet head according to any one of <11> to <20> above, wherein the cleaning composition for inkjet head contains a solvent (A), an organic solvent (B), and water,

[0142] The solvent (A) has a dipole moment of 5.0 D or more at 25°C calculated using a density functional method,

[0143] The water content in the cleaning composition for an inkjet head is 30% by mass or more and 90% by mass or less,

[0144] The solvent (A) is propylene carbonate,

[0145] The organic solvent (B) is a polyoxyethylene phenyl ether.

[0146] The cleaning composition for an inkjet head contains a solvent (A), an organic solvent (B), and water,

[0147] The solvent (A) has a dipole moment of 5.0 D or more at 25°C calculated using a density functional method,

[0148] The water content in the cleaning composition for an inkjet head is 30% by mass or more and 90% by mass or less,

[0149] The solvent (A) is propylene carbonate,

[0150] The organic solvent (B) is a polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2.

[0151] The cleaning composition for an inkjet head contains a solvent (A), an organic solvent (B), and water,

[0152] The cleaning composition for an inkjet head contains a solvent (A), an organic solvent (B), and water,

[0153] The cleaning composition for an inkjet head contains a solvent (A) and water,

[0154] The solvent (A) has a dipole moment of 5.0 D or more at 25°C calculated using a density functional method,

[0155] The water content in the cleaning composition for an inkjet head is 30% by mass or more,

[0156] The water-based ink for inkjet recording contains a polymer having an acid value of 5 mgKOH / g or more and water.

[0157] The cleaning composition for an inkjet head contains a solvent (A), an organic solvent (B), and water,

[0158] The cleaning composition according to any one of <21> to <23> above, wherein the solvent (A) is one or more selected from the group consisting of propylene carbonate, ethylene carbonate, and sulfolane.

[0159] The cleaning composition according to any one of <21> to <23> above, wherein the cleaning composition further contains an organic solvent (B) having one or more groups selected from the group consisting of a hydroxyl group and a polyoxyalkylene group.

[0160] The cleaning composition according to any one of <21> to <24> above, wherein the organic solvent (B) comprises one or more solvents (Bl) selected from the group consisting of ethylene glycol, diethylene glycol, a polyoxyalkylene phenyl ether, and a polyoxyalkylene benzyl ether.

[0161] The cleaning composition according to <25> above, wherein the polyoxyalkylene of the polyoxyalkylene phenyl ether or the polyoxyalkylene benzyl ether is a polyoxyethylene.

[0162] The cleaning composition according to <26> above, wherein the average addition mole number of ethylene oxide of the polyoxyethylene is 2 or more and 6 or less.

[0163] The cleaning composition according to any one of <21> to <27> above, wherein the content of water in the cleaning composition for an inkjet head is 30 mass% or more and 90 mass% or less.

[0164] A cleaning composition for an inkjet head, wherein the cleaning composition for an inkjet head is used for an inkjet head that ejects an aqueous ink for ink recording, and contains a solvent (A), an organic solvent (B), and water,

[0165] The solvent (A) has a dipole moment at 25°C of 5.0 D or more calculated using a density functional method,

[0166] The content of water in the cleaning composition for an inkjet head is 30 mass% or more and 90 mass% or less,

[0167] The solvent (A) is propylene carbonate,

[0168] The content of the propylene carbonate in the cleaning composition for an inkjet head is 5 mass% or more and 60 mass% or less,

[0169] The organic solvent (B) is a polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of the polyoxyethylene of 2,

[0170] The content of the polyoxyethylene phenyl ether having an average addition mole number of 2 of oxyethylene groups in the cleaning composition for an inkjet head is 0.5 mass% or more and 50 mass% or less,

[0171] The water-based ink for inkjet recording contains a polymer having an acid value of 5 mgKOH / g or more and 300 mgKOH / g or less, and water,

[0172] The polymer is a vinyl-based polymer having a weight average molecular weight of 5,000 or more and 100,000 or less,

[0173] The content of the vinyl-based polymer in the water-based ink for inkjet recording is 1 mass% or more and 20 mass% or less.

[0174] <30> The cleaning composition for an inkjet head according to <29> above, wherein the vinyl-based polymer has an acid value of 60 mgKOH / g or more and 300 mgKOH / g or less.

[0175] <31> The cleaning composition for an inkjet head according to <29> or <30> above, wherein the water-based ink for inkjet recording further contains a pigment,

[0176] The content of the pigment in the water-based ink for inkjet recording is 1 mass% or more and 15 mass% or less.

[0177] <32> A cleaning composition for an inkjet head, wherein the cleaning composition for an inkjet head is used for an inkjet head that has ejected a water-based ink for inkjet recording, and contains a solvent (A), an organic solvent (B), and water,

[0178] The solvent (A) has a dipole moment at 25°C of 5.0 D or more, which is calculated using a density functional method,

[0179] The content of the water in the cleaning composition for an inkjet head is 30 mass% or more and 90 mass% or less,

[0180] The solvent (A) is propylene carbonate,

[0181] The content of the propylene carbonate in the cleaning composition for an inkjet head is 5 mass% or more and 60 mass% or less,

[0182] The organic solvent (B) is a polyoxyethylene phenyl ether having an average addition mole number of 2 of oxyethylene groups,

[0183] The content of the polyoxyethylene phenyl ether having an average addition mole number of 2 of oxyethylene groups in the cleaning composition for an inkjet head is 0.5 mass% or more and 50 mass% or less,

[0184] The aqueous ink for inkjet recording contains: a polymer having an acid value of 5 mgKOH / g or more and 300 mgKOH / g or less, and water,

[0185] The polymer is a polyester having a weight average molecular weight of 5,000 or more and 100,000 or less,

[0186] The content of the polyester in the aqueous ink for inkjet recording is 1 mass% or more and 20 mass% or less.

[0187] <33> The cleaning composition for an inkjet head according to <32> above, wherein the polyester has an acid value of 5 mgKOH / g or more and 50 mgKOH / g or less.

[0188] <34> The cleaning composition for an inkjet head according to <32> or <33> above, wherein the aqueous ink for inkjet recording further contains a pigment,

[0189] The content of the pigment in the aqueous ink for inkjet recording is 1 mass% or more and 15 mass% or less.

[0190] <35> Use of a cleaning composition as an inkjet head cleaner, wherein the cleaning composition contains: a solvent (A) and water,

[0191] The solvent (A) has a dipole moment at 25°C of 5.0 D or more calculated using the density functional method,

[0192] The content of the water is 30 mass% or more.

[0193] <36> The use according to <35> above, wherein the solvent (A) is one or more selected from the group consisting of propylene carbonate, ethylene carbonate, and sulfolane.

[0194] <37> The use according to <35> or <36> above, wherein the cleaning composition further contains: an organic solvent (B) having one or more groups selected from the group consisting of a hydroxyl group and a polyoxyalkylene group.

[0195] <38> Use of a cleaning composition as an inkjet head cleaner, wherein the cleaning composition contains: a solvent (A), an organic solvent (B), and water,

[0196] The solvent (A) has a dipole moment at 25°C of 5.0 D or more calculated using the density functional method,

[0197] The content of the water is 30 mass% or more and 90 mass% or less,

[0198] The solvent (A) is propylene carbonate,

[0199] The content of the propylene carbonate in the cleaning composition is 5 mass% or more and 60 mass% or less,

[0200] The organic solvent (B) is a polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2,

[0201] The content of the polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2 in the cleaning composition is 0.5 mass% or more and 50 mass% or less.

[0202] The use of the cleaning composition as a cleaner for an inkjet head that ejects an aqueous ink for inkjet recording, wherein the cleaning composition contains a solvent (A), an organic solvent (B), and water,

[0203] The solvent (A) has a dipole moment at 25°C of 5.0 D or more, which is calculated using a density functional method,

[0204] The content of the water in the cleaning composition is 30 mass% or more and 90 mass% or less,

[0205] The solvent (A) is propylene carbonate,

[0206] The content of the propylene carbonate in the cleaning composition is 5 mass% or more and 60 mass% or less,

[0207] The organic solvent (B) is a polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2,

[0208] The content of the polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2 in the cleaning composition is 0.5 mass% or more and 50 mass% or less,

[0209] The aqueous ink for inkjet recording contains a polymer having an acid value of 5 mgKOH / g or more and 300 mgKOH / g or less, and water,

[0210] The polymer is a vinyl-based polymer having a weight average molecular weight of 5,000 or more and 100,000 or less,

[0211] The content of the vinyl-based polymer in the aqueous ink for inkjet recording is 1 mass% or more and 20 mass% or less.

[0212] The use according to <39> above, wherein the vinyl-based polymer has an acid value of 60 mgKOH / g or more and 300 mgKOH / g or less.

[0213] The use according to <39> or <40> above, wherein the aqueous ink for inkjet recording further contains a pigment,

[0214] The content of the pigment in the aqueous ink for inkjet recording is 1 mass% or more and 15 mass% or less.

[0215] <42> Use of a cleaning composition as a cleaner for an inkjet head that ejects an aqueous ink for inkjet recording, wherein the cleaning composition contains: a solvent (A), an organic solvent (B), and water,

[0216] The solvent (A) has a dipole moment at 25°C of 5.0 D or more, calculated using the density functional method,

[0217] The content of water in the cleaning composition is 30 mass% or more and 90 mass% or less,

[0218] The solvent (A) is propylene carbonate,

[0219] The content of the propylene carbonate in the cleaning composition is 5 mass% or more and 60 mass% or less,

[0220] The organic solvent (B) is a polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2,

[0221] The content of the polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2 in the cleaning composition is 0.5 mass% or more and 50 mass% or less,

[0222] The aqueous ink for inkjet recording contains: a polymer having an acid value of 5 mgKOH / g or more and 300 mgKOH / g or less, and water,

[0223] The polymer is a polyester having a weight average molecular weight of 5,000 or more and 100,000 or less,

[0224] The content of the polyester in the aqueous ink for inkjet recording is 1 mass% or more and 20 mass% or less.

[0225] <43> The use according to <42> above, wherein the polyester has an acid value of 5 mgKOH / g or more and 50 mgKOH / g or less.

[0226] <44> The use according to <42> or <43> above, wherein the aqueous ink for inkjet recording further contains a pigment,

[0227] The content of the pigment in the aqueous ink for inkjet recording is 1 mass% or more and 15 mass% or less.

[0228] <45> A method for cleaning an inkjet head using a cleaning composition, wherein the cleaning composition contains: a solvent (A) and water,

[0229] The solvent (A) has a dipole moment of 5.0 D or more at 25°C calculated using a density functional method.

[0230] The water content is 30 mass% or more.

[0231] <46> The method according to <45> above, wherein the solvent (A) is one or more selected from the group consisting of propylene carbonate, ethylene carbonate, and sulfolane.

[0232] <47> The method according to <45> or <46> above, wherein the cleaning composition further contains an organic solvent (B) having one or more groups selected from the group consisting of a hydroxyl group and a polyoxyalkylene group.

[0233] <48> A method of cleaning an inkjet head that ejects an aqueous ink for inkjet recording using a cleaning composition, wherein the cleaning composition contains a solvent (A), an organic solvent (B), and water,

[0234] The solvent (A) has a dipole moment of 5.0 D or more at 25°C calculated using a density functional method.

[0235] The water content in the cleaning composition is 30 mass% or more and 90 mass% or less,

[0236] The solvent (A) is propylene carbonate.

[0237] The propylene carbonate content in the cleaning composition is 5 mass% or more and 60 mass% or less.

[0238] The organic solvent (B) is a polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2.

[0239] The polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2 in the cleaning composition has a content of 0.5 mass% or more and 50 mass% or less.

[0240] The aqueous ink for inkjet recording contains a polymer having an acid value of 5 mgKOH / g or more and 300 mgKOH / g or less, and water.

[0241] The polymer is a vinyl-based polymer having a weight average molecular weight of 5,000 or more and 100,000 or less.

[0242] The vinyl-based polymer content in the aqueous ink for inkjet recording is 1 mass% or more and 20 mass% or less.

[0243] <49> The method according to <48> above, wherein the vinyl-based polymer has an acid value of 60 mgKOH / g or more and 300 mgKOH / g or less.

[0244] The method according to <48> or <49> above, wherein the aqueous ink for ink-jet recording further contains a pigment,

[0245] The content of the pigment in the aqueous ink for ink-jet recording is 1 mass% or more and 15 mass% or less.

[0246] A method for cleaning an ink-jet head that ejects an aqueous ink for ink-jet recording, using a cleaning composition, wherein the cleaning composition contains: a solvent (A), an organic solvent (B), and water,

[0247] The content of water in the cleaning composition is 30 mass% or more and 90 mass% or less,

[0248] The solvent (A) is propylene carbonate,

[0249] The content of propylene carbonate in the cleaning composition is 5 mass% or more and 60 mass% or less,

[0250] The organic solvent (B) is a polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2,

[0251] The content of the polyoxyethylene phenyl ether having an average addition mole number of ethylene oxide of 2 in the cleaning composition is 0.5 mass% or more and 50 mass% or less,

[0252] The aqueous ink for ink-jet recording contains: a polymer having an acid value of 5 mgKOH / g or more and 300 mgKOH / g or less, and water,

[0253] The polymer is a polyester having a weight average molecular weight of 5,000 or more and 100,000 or less,

[0254] The content of the polyester in the aqueous ink for ink-jet recording is 1 mass% or more and 20 mass% or less.

[0255] The method according to <51> above, wherein the polyester has an acid value of 5 mgKOH / g or more and 50 mgKOH / g or less.

[0256] The method according to <51> or <52> above, wherein the aqueous ink for ink-jet recording further contains a pigment,

[0257] The content of the pigment in the aqueous ink for ink-jet recording is 1 mass% or more and 15 mass% or less.

[0258] Example

[0259] In the following production examples, examples, and comparative examples, "parts" and "%" are "mass parts" and "mass %" as long as there is no particular regulation. In addition, the measurement method or calculation method of each property and the like is as follows.

[0260] [Dielectric moment at 25°C of solvent]

[0261] As for the calculation of the dielectric moment at 25°C of the solvent, as a quantum chemistry calculation software, TURBOMOLE Ver. 7.7 developed by Karlsruhe Research Center in cooperation with the University of Karlsruhe was used, and was calculated using the density functional method. BP86 was used as the functional and def-TZVP was used as the basis function. In addition, for a substance having a plurality of conformations, the most stable conformation in a vacuum was used, and the calculation was performed in a single conformation.

[0262] [Softening point of polyester resin]

[0263] Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), 1 g of a sample was heated at a temperature rise rate of 6°C / min while a load of 1.96 MPa was applied with a plunger, and was extruded from a nozzle having a diameter of 1 mm and a length of 1 mm. The amount of lowering of the plunger of the flow tester with respect to the temperature was plotted, and the temperature at which the sample flowed out by half the amount was taken as the softening point.

[0264] [Glass transition temperature of polyester resin]

[0265] Using a differential scanning calorimeter "Pyris 6 DSC" (manufactured by Perkin Elmer Corporation), 5 mg of a sample was weighed on an aluminum tray, and was heated to 200°C, and was cooled from the temperature to 0°C at a temperature lowering rate of 10°C / min. Subsequently, the sample was heated at a temperature rise rate of 10°C / min. The temperature at which the intersection point between the extension line of the baseline below the temperature of the maximum endothermic peak and the tangent line showing the maximum slope from the rising portion of the peak to the peak vertex was taken as the glass transition temperature.

[0266] In addition, in the case of an aqueous dispersion, a freeze dryer "FDU-2100" manufactured by Tokyo Rikakikai Co., Ltd. was used, and the aqueous dispersion was freeze-dried at -10°C for 9 hours, and the obtained product was used as a sample.

[0267] [Acid value of polyester resin]

[0268] It was measured by the neutralization titration method described in JIS K 0070:1992. However, only the measurement solvent was changed from a mixed solvent of ethanol and ether to a mixed solvent of acetone and toluene [acetone:toluene = 1:1 (volume ratio)].

[0269] [Weight average molecular weight (Mw) of polyester resin]

[0270] The following gel permeation chromatography was used for the measurement.

[0271] (1) Preparation of a sample solution

[0272] The polyester resin was dissolved in chloroform to a concentration of 0.5 g / 100 mL, and the resulting solution was filtered with a fluororesin filter "FP-200" (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 2 μm to remove insoluble components, thereby preparing a sample solution.

[0273] (2) Measurement of molecular weight

[0274] The following measuring apparatus and analysis column were used, and tetrahydrofuran was circulated as a dissolving solution at a flow rate of 1 mL / min, and the column was stabilized in a thermostat at 40°C. 100 μL of the sample solution was injected thereinto to perform the measurement. The following monodisperse polystyrene [monodisperse polystyrene manufactured by Tosoh Corporation, 2.63 x 10 3 , 2.06 x 10 4 , 1.02 x 10 5 (molecular weight (Mw)), monodisperse polystyrene manufactured by GL Sciences Inc., 2.10 x 10 3 , 7.00 x 10 3 , 5.04 x 10 4 (molecular weight (Mw))] were used as standard samples, and the weight average molecular weight of the sample was calculated based on a calibration curve prepared in advance.

[0275] <Measurement Conditions>

[0276] Measuring apparatus: "HLC-8220 GPC" (manufactured by Tosoh Corporation)

[0277] Analysis column: "TSKgel GMHXL" + "TSKgel G3000HXL" (manufactured by Tosoh Corporation)

[0278] [Concentration of solid content]

[0279] In a 30-mL polypropylene container (inner diameter: 40 mm, height: 30 mm), 10.0 g of sodium sulfate, which had been constant-weighted in a desiccator, was weighed, and 1.0 g of the sample was added thereto, and they were mixed to obtain a mixture. Thereafter, the mixture was weighed, and held at 105°C for 2 hours to remove volatile components, and then left in a desiccator for 15 minutes, and the mass of the mixture after removal of the volatile components was measured. The mass of the mixture after removal of the volatile components was subtracted from the mass of the sodium sulfate, and the solid content of the sample after removal of the volatile components was divided by the mass of the sample before removal of the volatile components, to obtain the concentration of the solid content (%).

[0280] [average particle diameter of the pigment-containing water-insoluble polymer particles and the pigment-free water-insoluble polymer particles]

[0281] The cumulative average particle diameter measured using a laser particle analysis system "ELS-8000" (cumulative amount analysis) manufactured by Otsuka Electronics Co., Ltd. was used as the average particle diameter of the pigment-containing polymer particles or the pigment-free polymer particles. The measurement conditions were: temperature 25°C, angle of incident light to detector 90°, number of accumulations 100 times, and the refractive index of water (1.333) was input as the refractive index of the dispersion medium. The measurement concentration was 5 x 10 -3 % was performed.

[0282] Production Examples 1-1 to 1-2 (production of polyester resins P-1 to P-2)

[0283] Each of the raw material monomers (alcohol component and carboxylic acid component) shown in Table 1, an esterification catalyst, and an esterification catalyst aid were mixed in the amounts shown in Table 1, and were added to a four-necked flask having a content volume of 10 L equipped with a thermometer, a stirring device, a flow-type condenser, and a nitrogen gas introduction tube, and were reacted at 210°C for 10 hours in a mantle heater under a nitrogen atmosphere, and then were further reacted at -8.3 kPa (G) until the softening point reached the temperature shown in Table 1, to obtain polyester resins P-1 to P-2, respectively. The physical properties of the obtained polyester resins are shown in Table 1.

[0284] [Table 1]

[0285]

[0286] Production Example 2-1 (production of an aqueous dispersion D-1 of pigment-containing polyester resin particles)

[0287] (1) Pigment dispersion step

[0288] In a container having a content volume of 2 L, 66.7 g of the polyester resin P-1 as a pigment dispersion polymer was dissolved in methyl ethyl ketone (hereinafter referred to as "MEK") 156.4 g, 5.36 g of a 5N sodium hydroxide aqueous solution as a neutralizing agent, and 430.0 g of ion exchange water were added thereto, and the acid value of the polyester resin P-1 was adjusted to a neutralization degree of 85 mol% using sodium hydroxide, and the mixture was stirred at 2,000 r / min for 15 minutes using a dispersing paddle at 10°C or higher and 15°C or lower.

[0289] Next, 100.0 g of a magenta pigment was added, and the mixture was stirred at 7,000 r / min using a dispersing blade at 10°C or higher and 15°C or lower for 2 hours. The resulting pre-dispersion was filtered through a 150-mesh screen, diluted with 36.1 g of ion exchange water, and then dispersed using a microfluidizer "M-110EH-30XP" (Microfluidics Corp.) at a pressure of 150 MPa for 15 cycles to obtain a dispersion of pigment-containing polyester resin particles.

[0290] (2) Concentration Step

[0291] The dispersion of pigment-containing polyester resin particles was added to a 2-L round-bottom flask, and ion exchange water was added to adjust the solid content to 16.0%. The organic solvent was removed by using a rotary evaporator "Rotary Evaporator N-1000S" (Tokyo Rikakikai Co., Ltd.) at a rotation speed of 50 r / min and a bath temperature of 32°C under a pressure of 0.09 MPa (abs) for 3 hours. The bath temperature was then adjusted to 62°C, and the pressure was reduced to 0.07 MPa (abs) to concentrate the dispersion to a solid content of 25.0% to obtain a concentrate.

[0292] The concentrate was added to a 500-mL angular rotor, and centrifugation was performed at 3,660 r / min for 20 minutes using a high-speed cooling centrifuge "himac CR22G" (Hitachi-Koki Co., Ltd., set temperature 20°C). The liquid layer was filtered through a membrane filter "Minisart" (Sartorius Co., Ltd.) having a pore size of 5 μm to obtain an aqueous dispersion 1 of pigment-containing polyester resin particles.

[0293] The solid content of the obtained aqueous dispersion 1 was adjusted to 22.0% by adding ion exchange water, and 0.76 g of "Proxel (registered trademark) LV (S)" (Lonza Japan Co., Ltd.: preservative, active ingredient 20%) was added. The mixture was stirred at 70°C for 2 hours. After cooling to 25°C, the mixture was filtered through a filter having a pore size of 5 μm, and ion exchange water was added to obtain an aqueous dispersion D-1 of pigment-containing polyester resin particles (solid content 22.0%). The average particle diameter of the pigment-containing polyester resin particles in the aqueous dispersion D-1 was 130 nm.

[0294] Production Example 3-1 (Production of Aqueous Dispersion D-1 of Pigment-Free Polyester Resin Particles)

[0295] A four-necked flask equipped with a nitrogen inlet tube, a reflux cooling tube, a stirrer, and a thermocouple was charged with the polyester resin P-2 as a fixing aid polymer and methyl ethyl ketone (MEK) as an organic solvent in the proportions shown in Table 2, and the mixture was dissolved in the MEK at 25°C.

[0296] Next, 5N sodium hydroxide aqueous solution as a neutralizing agent was added in accordance with the compounding shown in Table 2, and ion exchange water was further added with stirring to obtain a dispersion liquid of the pigment-free polyester resin particles.

[0297] The obtained dispersion liquid was added to a four-necked flask, and in this state, while maintaining stirring, the temperature was maintained at 60°C and MEK was distilled off under reduced pressure. Next, after cooling to room temperature, ion exchange water was added, and filtered using a 200-mesh metal net to obtain an aqueous dispersion d-1 of the pigment-free polyester resin particles (solid content concentration 40.0%). The average particle diameter of the pigment-free polyester resin particles of the aqueous dispersion d-1 was 115 nm.

[0298] [Table 2]

[0299]

[0300] Ink Production Example 1

[0301] An aqueous ink X1 was obtained by mixing the compounding components of the aqueous ink shown in Table 3, and filtering the obtained mixture using a membrane filter "Minisart" (manufactured by Sartorius) having a pore size of 1.2 μm. The organic solvents, surfactants, and pH adjustors shown in Table 3 are as follows.

[0302] [Organic Solvent]

[0303] • BDG: diethylene glycol monobutyl ether (manufactured by Fuji Photo Film Co., Ltd. and Wako Pure Chemical Industries, Ltd., reagent)

[0304] • PG: propylene glycol (manufactured by Fuji Photo Film Co., Ltd. and Wako Pure Chemical Industries, Ltd., reagent)

[0305] [Surfactant]

[0306] • KF6011: alkylene glycol-modified polydimethylsiloxane (trade name "KF-6011", manufactured by Shin-Etsu Chemical Co., Ltd., nonionic surfactant)

[0307] [pH Adjustor]

[0308] • MDEA: N-methyldiethanolamine (manufactured by Fuji Photo Film Co., Ltd. and Wako Pure Chemical Industries, Ltd., reagent)

[0309] [Table 3]

[0310]

[0311] Examples A1 to A8, B1 to B6, C1 to C6, D1 to D6, Comparative Examples 1 to 4

[0312] Each ingredient was warmed to 45°C and mixed, and then cooled to 35°C, to prepare each cleaning composition in accordance with the compounding composition of the cleaning compositions shown in Tables 4 to 7. The evaluations shown below were performed using each cleaning composition. The results are shown in Tables 4 to 7.

[0313] Each ingredient shown in Tables 4 to 7 is as follows.

[0314] [Solvent (A)]

[0315] • Propylene carbonate (Dipole moment: 5.64 D): manufactured by FUJIFILM and KANTO CHEMICAL CO., INC. Reagent

[0316] • Ethylene carbonate (Dipole moment: 5.41 D): manufactured by FUJIFILM and KANTO CHEMICAL CO., INC. Reagent

[0317] [Solvent (B)]

[0318] (Solvent (B1))

[0319] • Polyoxyethylene phenyl ether (Average addition mole number of EO: 2.0): manufactured by NIKKAKI CHEMICAL CO., LTD.

[0320] • Polyoxyethylene phenyl ether (Average addition mole number of EO: 2.3): manufactured by NIKKAKI CHEMICAL CO., LTD.

[0321] • Polyoxyethylene phenyl ether (Average addition mole number of EO: 3.0): manufactured by AOKI OIL & FAT CO., LTD. "BLAUNON PH-3"

[0322] • Polyoxyethylene phenyl ether (Average addition mole number of EO: 4.0): manufactured by AOKI OIL & FAT CO., LTD. "BLAUNON PH-4"

[0323] • Polyoxyethylene phenyl ether (Average addition mole number of EO: 5.0): manufactured by AOKI OIL & FAT CO., LTD. "BLAUNON PH-5"

[0324] • Polyoxyethylene phenyl ether (Average addition mole number of EO: 5.5): manufactured by NIKKAKI CHEMICAL CO., LTD.

[0325] • Polyoxyethylene benzyl ether (Average addition mole number of EO: 2.0): manufactured by TOKYO KASEI INDUSTRIES, LTD. Reagent

[0326] • Ethylene glycol (Dipole moment: 2.43 D): manufactured by FUJIFILM and KANTO CHEMICAL CO., INC. Reagent

[0327] • Diethylene glycol (Dipole moment: 1.66 D): manufactured by FUJIFILM and KANTO CHEMICAL CO., INC. Reagent

[0328] (Other solvents)

[0329] • γ-butyrolactone (dipole moment: 4.69 D): manufactured by FUJIFILM and light pure pharmaceutical co., ltd. reagent

[0330] <cleaning property>

[0331] (printing dot imparting)

[0332] Using the water-based ink X1 obtained in the ink manufacturing example 1, the ink was imparted dropwise (amount of ink droplet per 1 drop: 0.5 nL) at 5 mm intervals on a glass-made culture dish using a dispensing printer to form a grid-shaped printed image having printing dots of 5 dots in the longitudinal direction and 5 dots in the lateral direction. As the dispensing printer, a piezoelectric jet dispenser "PICO Pμlse Valve SD" (manufactured by NOSINEFD Co., Ltd.) was used; as the liquid agent fluid assembly, "FLUID ASSY Pμlse MST 3.0S F0 E05" (opening part 50 μm, ball valve size 3.0S) was used. In addition, the movement of the dispenser was performed using "PRO4" manufactured by NOSIN Co., Ltd.

[0333] (cleaning test)

[0334] Next, 2 g of each cleaning composition of the examples and comparative examples was added to the grid-shaped printed image on the culture dish, and after standing at normal temperature for 5 minutes, the culture dish was shaken for 60 seconds at 100 rpm using a shaker, and the cleaning composition was removed from the culture dish by tilting the culture dish at 120 degrees. Next, 2 g of ion exchange water was injected into the culture dish, and after standing at normal temperature for 1 minute, the culture dish was shaken for 60 seconds at 100 rpm using a shaker, and the ion exchange water was removed by tilting the culture dish at 120 degrees.

[0335] (cleaning property evaluation)

[0336] The printing dots of the grid-shaped printed image were observed for 25 dots, and the case where all the printing dots were removed was rated as 4 points, the case where a thin transparent film remained was rated as 3 points, the case where a thin colored film remained was rated as 2 points, the case where the printing dots were partially peeled but partially remained as they were was rated as 1 point, and the case where the printing dots had no visible change was rated as 0 point, and the score with respect to the total score of 100 points (cleaning property total score P) was evaluated for the cleaning property. The cleaning property total score P was 80 or more, and the cleaning property was excellent.

[0337] <component adaptability>

[0338] As the resin member, an O-ring "BS007 Viton 5 / 32 inch" (material: fluorocarbon elastomer) (manufactured by RS-Components K.K.) was weighed at a mass of about 0.08 g (M0), and immersed in each of the cleaning compositions of the examples and comparative examples for 1 month at 60°C. Next, the resin member was taken out, and immersed in ion exchange water 50 g at normal temperature for 1 hour. Next, the resin member was taken out, and dried in an environment at a temperature of 60°C and a relative humidity of 10% or less for one night, and then, after cooling at normal temperature for 1 hour in an environment at a relative humidity of 50±10%, the mass (Ml) was measured. Using the mass (M0) and the mass (Ml) thus obtained, the swelling ratio was calculated from the following formula. When the swelling ratio was less than 20%, the member was excellent in suitability.

[0339] Swelling ratio (%) = [(Ml - M0) / M0] x 100

[0340] <Discharge recovery>

[0341] (Continuous printing test before cleaning)

[0342] An inkjet head "KJ4B-QA06NTB" (manufactured by KYOCERA Corporation) was attached to an inkjet printer "OnePassJet" (manufactured by TRITEK CO., LTD.), and the aqueous ink Xl obtained in Production Example 1 was filled in the inkjet printer, and printing was performed at a temperature of 25±1°C and a relative humidity of 10±5%.

[0343] As the printing conditions, the following were set: inkjet head voltage 26 V, frequency 30 kHz, ejection liquid volume 7 pL, inkjet head temperature 32°C, pre-ejection purging number 200, and negative pressure -4.0 kPa.

[0344] Next, after printing was continuously performed for 3 hours under the above printing conditions without maintenance, the printing nozzles were checked for a pattern, and the number of nozzles in which discharge deviation or discharge clogging had occurred (the number of missing nozzles N0 before cleaning) was confirmed. As for the confirmation of discharge deviation, when the deviation from the prescribed ink landing intended position was 50 μm or more, it was judged that discharge deviation had occurred.

[0345] (Cleaning test)

[0346] Next, 50 mL of each of the cleaning compositions of Examples and Comparative Examples was injected and filled in the inkjet head, and the cleaning composition was overflowed from the nozzle side while being continuously flowed to clean. Next, the ink injection portion of the inkjet head was capped, and each of the cleaning compositions was left to stand in the inkjet head for 5 minutes. Thereafter, 50 mL of the same cleaning composition as the one left to stand in the inkjet head was injected and filled in the inkjet head again, and the cleaning composition was overflowed from the nozzle side while being continuously flowed to clean. Finally, 1 L of ion exchange water was injected and filled in the inkjet head, and the ion exchange water was overflowed from the nozzle side while being continuously flowed to clean.

[0347] (Printing test after cleaning)

[0348] In an environment at a temperature of 25±1°C and a relative humidity of 10±5%, an ink printing evaluation device "OnePassJet" (manufactured by TRITEK CO., LTD.) equipped with an inkjet head "KJ4B-QA06NTB" (manufactured by KYOCERA Corporation) was filled with the ink X1 obtained in Ink Production Example 1.

[0349] As the printing conditions, the inkjet head voltage was set to 26 V, the frequency was set to 30 kHz, the ejection liquid volume was set to 7 pL, the inkjet head temperature was set to 32°C, the number of pre-ejection purges was set to 200, and the negative pressure was set to -4.0 kPa.

[0350] Next, the nozzle check pattern was printed under the above printing conditions, and the number of nozzles in which ejection deviation or ejection clogging had occurred (the number of missing nozzles after cleaning N1) was confirmed. As for the confirmation of ejection deviation, when the deviation from the prescribed ink landing intended position was 50 μm or more, it was judged that ejection deviation had occurred.

[0351] (Nozzle recovery rate)

[0352] The nozzle recovery rate was calculated from the number of missing nozzles before cleaning N0 and the number of missing nozzles after cleaning N1 by the following equation. When the nozzle recovery rate was 90% or more, the ejection recovery property was excellent, and when the nozzle recovery rate was 95% or more, the ejection recovery property was particularly excellent.

[0353] Nozzle recovery rate (%) = 〔(N0-N1) / N0〕x 100

[0354] [Table 4]

[0355]

[0356] [Table 5]

[0357]

[0358] [Table 6]

[0359]

[0360] [Table 7]

[0361]

[0362] As is apparent from Tables 4 to 7, the cleaning compositions of the examples are excellent in cleaning property and part adaptability compared with the cleaning compositions of the comparative examples, and further, when used as a cleaner for an inkjet head that ejects an aqueous ink for inkjet recording, the inkjet head is excellent in ejection recovery.

Claims

1. A cleaning composition for an inkjet head, wherein the cleaning composition for an inkjet head contains: a solvent (A) and water, the solvent (A) has a dipole moment at 25°C of 5.0 D or more calculated using a density functional method, the content of the water in the cleaning composition is 30 mass% or more.

2. The cleaning composition for an inkjet head according to claim 1, wherein the solvent (A) is one or more selected from the group consisting of propylene carbonate, ethylene carbonate and sulfolane.

3. The cleaning composition for an inkjet head according to claim 1 or 2, wherein the cleaning composition for an inkjet head further contains: an organic solvent (B) having one or more groups selected from the group consisting of a hydroxyl group and a polyoxyalkylene group.

4. The cleaning composition for an inkjet head according to claim 3, wherein the organic solvent (B) contains one or more solvents (Bl) selected from the group consisting of ethylene glycol, diethylene glycol, a polyoxyalkylene phenyl ether and a polyoxyalkylene benzyl ether.

5. The cleaning composition for an inkjet head according to claim 4, wherein the polyoxyalkylene of the polyoxyalkylene phenyl ether or the polyoxyalkylene benzyl ether is a polyoxyethylene.

6. The cleaning composition for an inkjet head according to claim 4, wherein the polyoxyalkylene of the polyoxyalkylene phenyl ether or the polyoxyalkylene benzyl ether is a polyoxyethylene, and the average addition mole number of ethylene oxide of the polyoxyethylene is 2 or more and 6 or less.

7. The cleaning composition for an inkjet head according to any one of claims 1 to 6, wherein the cleaning composition for an inkjet head is used for an inkjet head which ejects an aqueous ink for inkjet recording, the aqueous ink for inkjet recording contains: a polymer having an acid value of 5 mgKOH / g or more and water.

8. Use of a cleaning composition as a cleaner for an inkjet head, wherein the cleaning composition contains: a solvent (A) and water, the solvent (A) has a dipole moment at 25°C of 5.0 D or more calculated using a density functional method, the content of the water is 30 mass% or more.

9. The use according to claim 8, wherein the solvent (A) is one or more selected from the group consisting of propylene carbonate, ethylene carbonate and sulfolane.

10. The use according to claim 8 or 9, wherein the cleaning composition further contains: an organic solvent (B) having one or more groups selected from the group consisting of a hydroxyl group and a polyoxyalkylene group.

11. The use according to any one of claims 8 to 10, wherein the use is for an inkjet head which ejects an aqueous ink for inkjet recording, the aqueous ink for inkjet recording contains: a polymer having an acid value of 5 mgKOH / g or more and water.

12. A method of cleaning an inkjet head using a cleaning composition, wherein the cleaning composition contains: a solvent (A) and water, the solvent (A) has a dipole moment at 25°C of 5.0 D or more calculated using a density functional method, the content of the water is 30 mass% or more.

13. The method according to claim 11, wherein the solvent (A) is one or more selected from the group consisting of propylene carbonate, ethylene carbonate and sulfolane.

14. The method according to claim 11 or 12, wherein The composition used in the method also contains an organic solvent (B) having one or more groups selected from hydroxyl groups and polyoxyalkylene groups.

15. The method according to any one of claims 12 to 14, wherein The inkjet head is an inkjet head that ejects an aqueous ink for inkjet recording, The aqueous ink for inkjet recording contains a pigment, a polymer having an acid value of 5 mgKOH / g or more, and water.

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