JP7301639B2 - Cleaning liquid and cleaning method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cleaning liquid, particularly a cleaning liquid used for cleaning an inkjet printer, and a cleaning method using the cleaning liquid.

A printing method using an inkjet printer (inkjet printing method) is a method of printing by generating ink droplets and adhering them to a recording medium such as paper. In recent years, the inkjet printing method has been applied to industrial applications. Colorants contained in inkjet ink are roughly classified into water-soluble colorants and water-insoluble colorants. Among these, water-insoluble colorants such as pigments are generally superior in various fastnesses to water-soluble colorants. For this reason, industrial inkjet inks often contain water-insoluble colorants.

Recording media used for industrial applications are diversifying into various types of paper, fibers, films, and the like. Among recording media, there are many non-ink-absorbing media such as resin films and non-ink-absorbing media such as coated paper. Non-aqueous solvent inks, curable inks, and the like are known as inks used for printing on such recording media. However, there is a strong demand for water-based inks to replace these inks, for example, from the viewpoint of safety to the natural environment and living organisms. Such water-based inks contain a water-insoluble colorant and a dispersant, and generally contain polymers, waxes, and the like for the purpose of improving abrasion resistance, solvent resistance, and the like. Therefore, such water-based inks have a high solids content and are very prone to drying. Drying of the ink causes formation of solid matter in the nozzle portion of the inkjet head and in the ink flow path during long-term storage, storage in a high-temperature, low-humidity environment, etc., and clogging is likely to occur. When the ink jet head is clogged in this manner, the ink cannot be discharged stably. As a result, problems such as deterioration of print quality and reduction in image density occur. Therefore, in general, industrial inkjet heads are devised such as by equipping nozzle portions with cap members to prevent drying of the ink. However, when the environment in which the inkjet printer operates is severe, it is difficult to completely avoid the drying of the ink.

In view of the above situation, there is a strong demand for a cleaning liquid (also referred to as a cleaning liquid or maintenance liquid) that can clean the inkjet head even if it is clogged due to the formation of solid matter when the ink dries. Patent Documents 1 to 6 disclose cleaning liquids used for cleaning an inkjet recording apparatus.
Patent No. 5027444 Patent No. 4649823 Patent No. 4397220 Patent No. 5618250 Patent No. 5819206 Patent No. 5819205

SUMMARY OF THE INVENTION An object of the present invention is to provide a cleaning liquid capable of cleaning solids even when colored ink dries to produce solids.

As a result of intensive studies aimed at solving the above-described problems, the inventors of the present invention have found that the above-described problems can be solved by a cleaning liquid containing two specific compounds and water, and have completed the present invention. let me
That is, the present invention relates to the following 1) to 6).

1)
A cleaning liquid containing a compound represented by the following formula (1), a compound represented by the following formula (2), and water.

[In formula (1), R ¹ represents a linear or branched C1-C30 alkyl group. OP represents an oxypropylene group, and OE represents an oxyethylene group. m represents an integer of 1-2, and n represents an integer of 1-15. Also, the order in which OP and OE are combined is arbitrary. ]

[In formula (2), R ² represents a linear or branched C1-C30 alkyl group or aryl group. EO represents an ethyleneoxy group. L represents an integer of 10 or more. ]
2)
The cleaning liquid according to 1) above, wherein the total content of the compound represented by the above formula (2) is 0.2% by mass to 2% by mass in the total mass of the cleaning liquid.
3)
The cleaning liquid according to 1) or 2) above, which further contains an organic solvent.
4)
3) above, wherein the organic solvent is glycol ether.
5)
Use of the cleaning solution according to any one of 1) to 4) above for cleaning an inkjet printer.
6)
A cleaning method for an inkjet printer, comprising cleaning the inkjet ink adhering to the inkjet printer with the cleaning liquid described in any one of 1) to 4) above.

ADVANTAGE OF THE INVENTION According to the present invention, even when colored ink dries to produce solids, it is possible to provide a washing liquid capable of washing the solids.

In this specification, both "%" and "parts" are expressed on a mass basis unless otherwise specified.

[Compound represented by formula (1)]
In the above formula (1), OP represents a linear or branched oxypropylene group, and OE represents an oxyethylene group.
R ¹ is a linear or branched chain usually C1-C30, preferably C7-C13, more preferably C7-C10, more preferably C8-C10, particularly preferably C9 alkyl group. Among them, straight-chain alkyl groups are preferred.
m represents an integer of 1-2, and n usually represents an integer of 1-15, preferably 2-8. More preferably, the m:n ratio is 1:4 or 2:4.
Both m and n are average values. Therefore, in this specification, when m and n have numerical values below the decimal point, the numerical values obtained by rounding off the first decimal place are used as the values of m and n.
The content of the compound represented by formula (1) is generally 0.1% to 2%, preferably 0.5% to 1%, in the total mass of the cleaning liquid.
A compound represented by Formula (1) can be synthesized by a known method. Moreover, it is also available as a commercial product. Specific examples of commercially available products include Lutensol XL40 manufactured by BASF.
Moreover, the order in which OP and OE in the above formula (1) are combined is arbitrary, and the order represented by the formula (1) is not specified. Preferably, it is the order represented by Formula (1).

[Compound represented by formula (2)]
^R2 is an alkyl group or an aryl group.
The alkyl group for R ² is a linear or branched chain, usually C1-C30, preferably C10-C28, more preferably C10-C26, still more preferably C10-C24, optionally preferably C12-C24, particularly preferably C13-C22 alkyl groups are included. A linear alkyl group is preferable among the alkyl groups.
Aryl groups for R ² include C6-C14 aryl groups, preferably C6-C10 aryl groups, and more preferably phenyl groups.
The aryl group in R ² can have further substituents. The number of substituents is generally 1 to 5, preferably 1 to 4, more preferably 1 to 3, still more preferably 1 or 2, particularly preferably 2.
Substituents include arylalkyl groups, preferably C6-C14 aryl C1-C6 alkyl groups; more preferably C6-C10 aryl C1-C4 alkyl groups; more preferably C6-C10 aryl C1-C3 alkyl groups; C6-C10 aryl C1-C2 alkyl group is more preferred; phenethyl group (phenylethyl group) is particularly preferred.
EO represents an ethyleneoxy group.
L is an integer of 10 or more, preferably 10 to 30, more preferably 10 to 26, even more preferably 10 to 22, optionally preferably 10 to 20, particularly preferably 13 to 18. Since L is an average value, it may not be an integer and may have decimal numbers. In this specification, in such a case, the value of L is a numerical value obtained by rounding off the first decimal place to an integer.
The content of the compound represented by the above formula (2) is 0.2% to 2% in the total mass of the cleaning liquid.
A compound represented by formula (2) can be synthesized by a known method. Moreover, it is also available as a commercial product. Specific examples of commercially available products include GENAPOL X150 manufactured by Clariant and Emulgen A90 manufactured by Kao Corporation.

By using the compounds represented by the above formulas (1) and (2) together, the washing liquid can be made into a uniform solution. Further, by making the cleaning liquid a uniform solution, it is possible to stably obtain a cleaning liquid having a high cleaning ability.

[Organic solvent]
The above cleaning liquid may further contain an organic solvent. There are no particular restrictions on the organic solvent.
Examples of organic solvents include C1-C6 alkanols having one hydroxy group, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, and tert-butanol; N,N-dimethylformamide, and N , N-dimethylacetamide and the like; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidin-2-one; 1,3-dimethylimidazolidin-2-one, and 1, cyclic ureas such as 3-dimethylhexahydropyrimid-2-one; ketones or ketoalcohols such as acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate; cyclics such as tetrahydrofuran and dioxane ether; ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexylene glycol, 1,2-hexanediol, 1,2-pentanediol, 4-methyl-1,2-pentanediol, 3,3-dimethyl-1,2-butanediol, 1,2-octanediol, 5-methyl-1,2-hexanediol, 4-methyl-1,2- Hexanediol, 4,4-dimethyl-1,2-pentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol or polypropylene glycol having a molecular weight of 400 or more, thiodiglycol or dithiodiglycol, etc. , mono-, oligo- or polyalkylene glycols or thioglycols having C2-C8 alkylene units; polyols (triols) such as glycerin, diglycerin, hexane-1,2,6-triol, trimethylolpropane; γ-butyrolactone, and dimethyl sulfoxide; and glycol ether. Among these, glycol ethers are preferred.
Preferred glycol ethers are monoalkyl ethers of di- or tri-C2-C4 alkylene glycols.
C2-C4 alkylene glycol moieties include ethylene glycol, propylene glycol, and butylene glycol. Among these, ethylene glycol and propylene glycol are preferred, and ethylene glycol is more preferred.
The range of carbon number of alkyl in the monoalkyl ether moiety is usually C1-C6, preferably C1-C5, more preferably C2-C4, still more preferably C3-C4, particularly preferably C4.
Specific examples include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether (butyl diglycol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether. , ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, propylene glycol monopropyl ether, triethylene glycol monobutyl ether and the like. Among these, butyl diglycol is preferred.
The total content of the organic solvent in the total mass of the cleaning liquid is usually 0-60%, preferably 0.1-50%, more preferably 0.2-40%, still more preferably 0.5-30%. . Further, when at least glycol ether is contained as an organic solvent, the total content of glycol ether is usually 0 to 15%, preferably 0.1 to 15%, more preferably 0.2 to 13%, still more preferably 0.2%. 5 to 10%.
When a glycol ether and another organic solvent are used together, the sum of the total content of these is the total content of the organic solvent in the total mass of the cleaning liquid. Again, the total glycol ether content is as described above.

In addition to the components described above, the cleaning liquid may further contain various preparation agents as necessary. Examples of such preparation agents include surfactants, preservatives, antifungal agents, pH adjusters, chelating reagents, antirust agents, water-soluble ultraviolet absorbers, antioxidants, and the like.
The total content of the preparation agent is usually about 0% to 30%, preferably 0% to 20%, and more preferably about 0% to 10%, relative to the total mass of the cleaning liquid.

The cleaning liquid is substantially free of colorants. As used herein, "substantially" means that no coloring agent is intentionally added to the cleaning liquid.

[Surfactant]
Surfactants include anionic, cationic, nonionic, amphoteric, silicon-based, and fluorine-based surfactants. Among these, nonionic surfactants are preferred.

Examples of anionic surfactants include alkylsulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acyl amino acids or salts thereof, N-acyl methyl taurine salts, Alkyl sulfate polyoxyalkyl ether sulfate, alkyl sulfate polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate, lauryl alcohol sulfate, alkylphenol type phosphate, alkyl type phosphate, alkylaryl sulfone acid salts, diethylsulfosuccinate, diethylhexylsulfosuccinate, dioctylsulfosuccinate, and the like.

Cationic surfactants include 2-vinylpyridine derivatives, poly-4-vinylpyridine derivatives and the like.

Nonionic surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyethylene di Styrenated phenyl ether, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1- Hexyn-3-ol and the like can be mentioned.

Examples of amphoteric surfactants include betaine lauryldimethylaminoacetate, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, betaine coconut oil fatty acid amidopropyldimethylaminoacetate, polyoctylpolyaminoethylglycine, imidazoline derivatives and the like. mentioned.

Examples of silicone-based surfactants include polyether-modified siloxane and polyether-modified polydimethylsiloxane.

Examples of fluorine-based surfactants include perfluoroalkylsulfonic acid compounds, perfluoroalkylcarboxylic acid compounds, perfluoroalkylphosphoric acid ester compounds, perfluoroalkylethylene oxide adducts, and perfluoroalkyl ether groups having side chains. and polyoxyalkylene ether polymer compounds having

Examples of preservatives include organic sulfur, organic nitrogen sulfur, organic halogen, haloarylsulfone, iodopropargyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, and benzothiazole. , isothiazolines, dithiols, pyridine oxides, nitropropanes, organic tins, phenols, quaternary ammonium salts, triazines, thiazines, anilides, adamantanes, dithiocarbamates, brominated indanones, benzyl Compounds such as bromoacetate-based compounds and inorganic salt-based compounds are included.

Specific examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one and salts thereof. .

Any substance can be used as the pH adjuster as long as it can adjust the pH to 5 to 11 without adversely affecting the ink composition to be prepared.
Specific examples thereof include alkanolamines such as diethanolamine, triethanolamine and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonium hydroxide (ammonia water). or alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium hydrogencarbonate and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

Specific examples of chelating agents include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracil diacetate.

Specific examples of rust inhibitors include acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

Examples of water-soluble ultraviolet absorbers include sulfonated benzophenone-based compounds, benzotriazole-based compounds, salicylic acid-based compounds, cinnamic acid-based compounds, and triazine-based compounds.

Examples of antioxidants that can be used include various organic and metal complex anti-fading agents. Examples of the organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. be done.

The cleaning liquid can be obtained by adding the components described above and, if necessary, an ink preparation agent, and mixing them thoroughly.
The method for cleaning the inkjet printer is not particularly limited as long as it is a method for cleaning the solid matter of the inkjet ink adhering to the inkjet printer. A typical cleaning method includes, for example, a method of wiping off stains on the portion to which the colored ink has adhered by absorbing the cleaning liquid with a sponge or the like. On the other hand, for example, when the colored ink dries on the inkjet head and the inkjet head is heavily soiled, the inkjet head can be cleaned by filling the inkjet head with a cleaning liquid instead of the colored ink.
When the inkjet head is filled with the cleaning liquid for cleaning, it is preferable to subject the cleaning liquid to microfiltration.
For precision filtration, a membrane filter and/or glass filter paper or the like can be used. The pore size of a filter or the like for microfiltration is usually 0.5 μm to 20 μm, preferably 0.5 μm to 10 μm.

The pH of the cleaning liquid is generally pH 5 to 11, preferably pH 7 to 10.5, for the purpose of not corroding ink jet printer members.
The surface tension of the cleaning liquid is usually 10 mN/m to 50 mN/m, preferably 20 mN/m to 40 mN/m.
The viscosity of the cleaning liquid is usually 30 mPa·s or less, preferably 20 mPa·s or less, and the lower limit is about 0.1 mPa·s.

The above cleaning liquid can be used for cleaning water-based inks containing various colorants. Examples of colorants include water-based dye inks containing water-soluble dyes such as acid dyes, direct dyes, and reactive dyes; water-based inks containing water-insoluble colorants containing disperse dyes and pigments; be done.
Since the cleaning liquid has a high cleaning power, it is preferably used for cleaning water-based inks containing water-insoluble colorants, particularly pigments. In addition, because of its high detergency, the cleaning liquid exhibits extremely high performance as a cleaning liquid for water-based inks containing various resins together with pigments.

One of all the above components can be used alone. Moreover, two or more types can also be used together.
In addition, with respect to all of the above items, a combination of preferable items is more preferable, and a combination of more preferable items is even more preferable. The same applies to combinations of preferable and more preferable items, combinations of more preferable and more preferable items, and the like.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples. In addition, cleaning liquids and colored inks were prepared with stirring unless otherwise specified.
"Water" used in the examples is deionized water.

[Examples 1 and 2]: Preparation of cleaning solutions.
Each component shown in Table 1 below was mixed to obtain a total amount of 100 parts of cleaning solution. The resulting liquid was filtered through a 3 μm membrane filter to obtain cleaning liquids of Examples 1 and 2 for evaluation test.
“XL40” used in Examples 1 and 2 is a compound corresponding to formula (1) above.

[Comparative Examples 1 to 6]: Preparation of cleaning solutions for comparison.
Cleaning liquids for comparison in Comparative Examples 1 to 6 were obtained in the same manner as in Examples 1 and 2, except that each component shown in Table 1 below was used. "SN465", "EP7025" and "LS106" used in Comparative Examples 1 to 6 are all compounds that do not correspond to the above formula (1).

The abbreviations and the like in Table 1 below have the following meanings. Further, the numerical values in Table 1 are "parts".
Gly: glycerin 2Py: 2-pyrrolidone.
BDG: butyl diglycol.
XL40: Lutensol XL40 manufactured by BASF.
SN465: Surfynol 465, a nonionic surfactant manufactured by Nisshin Kagaku Co., Ltd.
EP7025: Softanol EP-7025, a nonionic surfactant manufactured by Nippon Shokubai Co., Ltd.
LS106: Emulgen LS-106, a nonionic surfactant manufactured by Kao Corporation.
A90: Emulgen A90, a nonionic surfactant manufactured by Kao Corporation.
X150: GENAPOL X150, a nonionic surfactant manufactured by Clariant.
TEA: triethanolamine.
GXL(S): Proxel GXL(S) manufactured by Lonza.

XL40 is a compound in which R ¹ is a 4-nonyl group, m is 1, and n is 4 in the above formula (1).
Since SN465 is acetylene glycol, it is a compound not included in the above formula (1).
EP7025 is a compound not included in the above formula (1) because R ¹ is a C12-C15 branched chain alkyl group, m is 2.5, and n is 7 in the above formula (1).
LS106 has an alkyl group as R ¹ and an oxyethylene group, but does not have an oxypropylene group (that is, m is 0), so it is a compound not included in the above formula (1).
A90 is a compound in which R ² is a phenyl group substituted with two 1-phenylethyl groups and L is 18 in the above formula (2).
X150 is a compound in which R ² is a C13 alkyl group and L is 13-16 in the above formula (2).

[Preparation Example 1]: Preparation of Resin A.
25 parts of Joncryl 678 (MW: 8500) and 14.3 parts of triethanolamine were dissolved in 60.7 parts of deionized water and stirred for 1 hour to obtain a solution. The resulting solution is referred to as Resin A.

[Preparation Example 2]: Preparation of colored dispersion.
A block copolymer described in Synthesis Example 3 of WO 2013/115071 was prepared, and 5 parts of the obtained polymer dispersant was dissolved in 20 parts of 2-butanone to obtain a uniform solution. A solution obtained by dissolving sodium hydroxide (0.4 parts) in water (50.6 parts) was added to this solution, and after adding resin solution A (4 parts), the mixture was stirred for 1 hour to obtain a solution. C.I. I. Pigment Yellow 74 (20 parts, Clariant HANSA YELLOW 5GX 01-JP) was added, and dispersion treatment was performed in a sand grinder at 1500 rpm for 15 hours to obtain a liquid. After water (100 parts) was added dropwise to the obtained liquid, this liquid was filtered to obtain filtrate. From the resulting filtrate, 2-butanone and part of water were distilled off under reduced pressure using an evaporator to obtain a colored dispersion having a pigment content of 12.4%.
The pigment content in the colored dispersion was obtained as a conversion value of only the pigment from the total solid content in the liquid by the dry weight method using MS-70 manufactured by A&D Co., Ltd.

[Preparation Example 3] Preparation of Resin B.
A resin emulsion having an acid value of 6 KOH mg/g, a Tg of 0° C., and a solid content of 25% was prepared by replicating Preparation Example 4 of WO 2015/147192 Gazette. This is referred to as "Resin B".

[Preparation Example 4]: Preparation of colored ink.
After mixing each component shown in Table 2 below to obtain a total amount of 100 parts of a liquid, the resulting liquid was filtered through a 3 μm membrane filter to obtain a colored ink used for evaluation of the cleaning liquid.

The abbreviations and the like in Table 2 below have the following meanings. In addition, the numerical values in Table 2 below are "parts".
Dp1: Colored dispersion obtained in Preparation Example 2.
TEG: triethylene glycol.
1,2HD: 1,2-hexanediol.
SN465: Surfynol 465, a nonionic surfactant manufactured by Nisshin Kagaku Co., Ltd.
AQ515: AQUACER 515 (solid content: 35.0%), polyethylene wax manufactured by BYK-Chemie.
The parts of resin B and AQ515 in Table 2 are solid content conversion values.

[Stability test]
After the cleaning solutions obtained in each example and comparative example were allowed to stand at room temperature for 12 hours, the conditions of the cleaning solutions were visually observed to evaluate their stability. The following two grades were used as the evaluation criteria. The evaluation results are shown in Table 3 below.
In the stability test, using only the "A"-evaluated cleaning solution, the following detergency test was performed.
[Evaluation criteria]
A: There was no change in the state of the washing liquid.
C: A liquid component separated from the cleaning liquid was observed to float on the surface of the cleaning liquid.

[Detergency test]
20 microliters of the colored ink obtained in Preparation Example 4 was dropped onto a glass petri dish, and left to stand in a constant temperature bath at 60° C. for 1 hour to dry, thereby obtaining a solid matter in which the colored ink was solidified.
10 ml of each of the washing liquids of Examples and Comparative Examples was added dropwise to the obtained solids, and whether or not the solids could be washed was visually evaluated. The following four grades were used as the evaluation criteria. The evaluation results are shown in Table 3 below. In addition, "-" in Table 3 indicates that the detergency test was not performed.
[Evaluation criteria]
A: No residual solid matter was observed, and a uniform liquid was obtained.
B: A substantially uniform liquid was obtained, although a small amount of solid matter remained.
C: Clearly solid matter remained, and it was not recognized as a uniform liquid.
D: The shape of the solid did not change at all, or hardly changed.

As is clear from the above results, it was confirmed that the cleaning solutions of Examples are excellent in stability and cleaning properties.

The cleaning liquid of the present invention can clean the solid matter even when the colored ink, especially the water-based ink containing a water-insoluble colorant, dries to produce a solid matter. It is extremely useful as a cleaning liquid for

Claims (5)

A cleaning liquid for an inkjet printer, containing a compound represented by the following formula (1), a compound represented by the following formula (2), and water.

[In formula (1), R ¹ represents a linear or branched C1-C30 alkyl group. OP represents an oxypropylene group, and OE represents an oxyethylene group. m represents an integer of 1-2, and n represents an integer of 1-15. Also, the order in which OP and OE are combined is arbitrary. ]

[In formula (2), R ² represents a linear or branched C1-C30 alkyl group or aryl group.
EO represents an ethyleneoxy group. L represents an integer of 10 or more. ] 2. The cleaning liquid for inkjet printers according to claim 1, wherein the total content of the compound represented by the formula (2) is 0.2% by mass to 2% by mass in the total mass of the cleaning liquid. 3. The cleaning liquid for inkjet printers according to claim 1, further comprising an organic solvent. 4. The cleaning liquid for inkjet printers according to claim 3, wherein the organic solvent is glycol ether. A cleaning method for an inkjet printer, comprising cleaning inkjet ink adhering to the inkjet printer with the inkjet printer cleaning liquid according to any one of claims 1 to 4.