JP7534836B2 - Cleaning solution and method for cleaning inkjet printer - Google Patents

Description

The present invention relates to a cleaning liquid, in particular a cleaning liquid used for cleaning inkjet printers, and a method for cleaning an inkjet printer using the same.

The printing method using an inkjet printer (inkjet printing method) is a method of printing by generating small droplets of ink and depositing them on a recording medium such as paper.

In recent years, the inkjet printing method has been increasingly applied to industrial applications. The colorants contained in inkjet inks are broadly divided into water-soluble colorants and water-insoluble colorants. Of these, water-insoluble colorants such as pigments generally have superior fastness properties in various respects compared to water-soluble colorants. For this reason, inkjet inks for industrial use often contain water-insoluble colorants.

Recording media used for industrial applications are diversified, including various types of paper, fiber, and film, and there are many recording media that are ink-nonabsorbent, such as resin films, and recording media that are ink-poorly absorbent, such as coated paper. Non-aqueous solvent inks and curable inks are known as inks used for printing on such ink-nonabsorbent or ink-poorly absorbent recording media. However, from the viewpoint of safety to the natural environment and living organisms, there is a strong demand for aqueous inks to replace these inks. Such aqueous inks contain water-insoluble colorants and dispersants, and also generally contain polymers, waxes, etc., for the purpose of improving abrasion resistance, solvent resistance, etc. For this reason, such aqueous inks have a high solid content and are extremely easy to dry. Drying of the ink causes the formation of solids in the nozzles and ink flow paths of the inkjet head during long-term storage, storage in high temperature or low humidity environments, etc., and is prone to clogging. When clogging occurs in the inkjet head in this way, ink cannot be ejected stably, and problems such as deterioration of print image quality and reduction in image density occur. For this reason, industrial inkjet heads are generally equipped with a cap member on the nozzle to prevent the ink from drying out, etc. However, when the environment in which the inkjet printer operates is harsh, it is difficult to completely prevent the ink from drying out.

In light of the above situation, there is a strong demand for a cleaning liquid (also called a cleaning liquid, maintenance liquid, etc.) that can dissolve and remove ink that dries and solidifies and clogs the inkjet head. Patent documents 1 to 6 disclose cleaning liquids used to clean inkjet printers.

Patent No. 5027444 Patent No. 4649823 Patent No. 4397220 Patent No. 5618250 Patent No. 5819206 Patent No. 5819205

The objective of the present invention is to provide a cleaning liquid that can dissolve and remove solid matter even when colored ink dries and solids are produced, and a method for cleaning an inkjet printer using the same.

［式（１）中、Ｒ^１は直鎖状又は分岐鎖状のＣ１－Ｃ３０アルキル基を表す。ＥＯはエチレンオキシ基を表し、ＰＯはプロピレンオキシ基を表す。ＥＯとＰＯとが結合する順序は任意である。ｍ及びｎはそれぞれ独立に１～５の整数を表す。ｍとｎとの比であるｍ：ｎは１：２以上かつ３：２より小さい。］

［式（２）中、ＥＯはエチレンオキシ基を表し、ＰＯはプロピレンオキシ基を表す。ＥＯとＰＯとが結合する順序は任意である。ｍ１、ｎ１、及びＬ１はそれぞれ独立に１以上の整数を表す。ただし、ｍ１、ｎ１、及びＬ１は｛（ｍ１＋Ｌ１）／（ｍ１＋ｎ１＋Ｌ１）｝×１００＞２７の条件を満たす。］
２）
上記式（２）で表される化合物の含有率が０．４質量％～２質量％である上記１）に記載の洗浄液。
３）
さらに、有機溶剤を含有する上記１）又は２）に記載の洗浄液。
４）
上記有機溶剤がグリコールエーテルである上記３）に記載の洗浄液。
５）
上記１）～４）のいずれか１項に記載の洗浄液の、インクジェットプリンタの洗浄における使用。
６）
インクジェットプリンタに付着したインクジェットインクの固形物に対して上記１）～４）のいずれか１項に記載の洗浄液を接触させることにより、前記固形物を溶解除去するインクジェットプリンタの洗浄方法。
７）
インクジェットヘッドに上記洗浄液を充填し、インク流路内に上記洗浄液を通液することにより、上記インク流路内に付着した上記固形物を溶解除去する上記６）に記載の洗浄方法。
８）
インクジェットヘッドのノズルを上記洗浄液に浸漬することにより、上記ノズルに付着した上記固形物を溶解除去する上記６）に記載の洗浄方法。 Specific means for solving the above problems include the following embodiments.
1)
A cleaning solution containing a compound represented by the following formula (1), a compound represented by the following formula (2), and water, wherein the content of the compound represented by the formula (2) is 0.2 mass % to 2 mass %.

[In formula (1), ^R1 represents a linear or branched C1-C30 alkyl group. EO represents an ethyleneoxy group, and PO represents a propyleneoxy group. EO and PO may be bonded in any order. m and n each independently represent an integer of 1 to 5. The ratio of m to n, m:n, is 1:2 or more and less than 3:2.]

[In formula (2), EO represents an ethyleneoxy group, and PO represents a propyleneoxy group. The order in which EO and PO are bonded is arbitrary. m1, n1, and L1 each independently represent an integer of 1 or more. However, m1, n1, and L1 satisfy the condition {(m1+L1)/(m1+n1+L1)}×100>27.]
2)
The cleaning solution according to the above 1), wherein the content of the compound represented by the above formula (2) is 0.4% by mass to 2% by mass.
3)
The cleaning solution according to 1) or 2) above, further comprising an organic solvent.
4)
The cleaning solution according to the above 3), wherein the organic solvent is a glycol ether.
5)
Use of the cleaning solution according to any one of 1) to 4) above in cleaning an inkjet printer.
6)
A method for cleaning an inkjet printer, comprising contacting a solid matter of inkjet ink adhering to the inkjet printer with the cleaning liquid according to any one of 1) to 4) above, thereby dissolving and removing the solid matter.
7)
The cleaning method according to 6) above, further comprising filling an inkjet head with the cleaning liquid and passing the cleaning liquid through an ink flow path to dissolve and remove the solid matter adhering to the ink flow path.
8)
The cleaning method according to 6) above, wherein the solid matter adhering to the nozzle of the inkjet head is dissolved and removed by immersing the nozzle in the cleaning liquid.

According to the present invention, it is possible to provide a cleaning liquid that can dissolve and remove solid matter even when colored ink dries and produces solid matter, and a method for cleaning an inkjet printer using the same.

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

<Cleaning solution>
The cleaning solution according to this embodiment contains a compound represented by the above formula (1), a compound represented by the above formula (2), and water, and the content of the compound represented by the formula (2) is 0.2% by mass to 2% by mass. By using the compounds represented by the above formulas (1) and (2) in combination and appropriately adjusting the content of the compound represented by the above formula (2), a cleaning solution that is a homogeneous solution can be obtained. Furthermore, by making the cleaning solution a homogeneous solution, it becomes possible to stably exhibit high cleaning ability.

The components contained in the cleaning solution according to this embodiment are described in detail below. Note that each of the components described below may be used alone or in combination of two or more.

[Compound represented by formula (1)]
In the above formula (1), ^R1 represents a linear or branched C1-C30 alkyl group, preferably a C10-C18 alkyl group, and more preferably a C12-C15 alkyl group. Of these, linear alkyl groups are preferred.

In the above formula (1), EO represents an ethyleneoxy group, and PO represents a propyleneoxy group. The order in which EO and PO are bonded is arbitrary and is not limited to the order shown in the above formula (1), but the order shown in the above formula (1) is preferred.

In the above formula (1), m and n each independently represent an integer from 1 to 5. The ratio of m:n is in the range of 1:2 or more and less than 3:2. Preferred combinations of m and n (m:n) are 1:2, 2:3, 3:4, 4:5, 5:5, 4:4, 3:3, 2:2, 1:1, 5:4, and 4:3, with 4:4 being more preferred.

Note that m and n are both average values. Therefore, in this specification, when m and n have decimal values, the values are rounded off to one decimal place to an integer, and the values of m and n are the values of m and n.

The compound represented by the above formula (1) can be synthesized by a known method. It is also available as a commercially available product. Specific examples of commercially available products include GENAPOL EP2424 and EP2544 manufactured by Clariant.

The total content of the compounds represented by the above formula (1) in the total mass of the cleaning solution is typically 0.1% to 2%, preferably 0.5% to 1%.

[Compound represented by formula (2)]
In the above formula (2), EO represents an ethyleneoxy group, and PO represents a propyleneoxy group. The order in which EO and PO are bonded is arbitrary and is not limited to the order shown in the above formula (2), but the order shown in the above formula (2) is preferred.

In the above formula (2), m1, n1, and L1 each independently represent an integer of 1 or more. The ranges of m1, n1, and L1 are not particularly limited. Usually, m1 is 11 or more and 40 or less, n1 is 25 or more and 58 or less, and L1 is 11 or more and 40 or less, preferably, m1 is 11 or more and 39 or less, n1 is 27 or more and 58 or less, and L1 is 11 or more and 39 or less, more preferably, m1 is 13 or more and 37 or less, n1 is 29 or more and 56 or less, and L1 is 13 or more and 37 or less.

However, m1, n1, and L1 satisfy the condition {(m1+L1)/(m1+n1+L1)}×100>27. The lower limit of the value of {(m1+L1)/(m1+n1+L1)}×100 is preferably 28 or more. The upper limit of the value of {(m1+L1)/(m1+n1+L1)}×100 is usually 76 or less, preferably 71 or less, and more preferably 62 or less. The range of the value of {(m1+L1)/(m1+n1+L1)}×100 is usually greater than 27 and less than 76, preferably 28 or more and less than 71, more preferably 35 or more and less than 62, even more preferably 40 or more and less than 60, particularly preferably 45 or more and less than 60, and extremely preferably 47 or more and less than 57.

Note that m1, n1, and L1 are all average values. Therefore, in this specification, when m1, n1, and L1 have decimal values, the values of m1, n1, and L1 are rounded to the nearest integer.

In addition, in this specification, when the calculation result of {(m1+L1)/(m1+n1+L1)} x 100 has a decimal value, the calculation result will be rounded to one decimal place.

The compound represented by the above formula (2) can be synthesized by a known method. It is also available as a commercially available product. Specific examples of commercially available products include GENAPOL PF40 manufactured by Clariant and EPAN U-105 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

The total content of the compounds represented by the above formula (2) in the total mass of the cleaning solution is 0.2% to 2%, preferably 0.4% to 2%.

[water]
The cleaning solution according to the present embodiment contains water as a solvent. The water used is preferably ion-exchanged water, distilled water, or the like, in order to reduce ionic impurities as much as possible.

The water content of the cleaning solution in its total mass is typically 60% to 80%, preferably 65% to 80%.

[Organic solvent]
The cleaning solution according to the present embodiment may further contain an organic solvent. Examples of the organic solvent include C1-C6 alkanols having one hydroxyl group, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, and tertiary butanol; amides, such as N,N-dimethylformamide and N,N-dimethylacetamide; lactams, such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidin-2-one; cyclic ureas, such as 1,3-dimethylimidazolidin-2-one and 1,3-dimethylhexahydropyrimid-2-one; ketones or ketoalcohols, such as acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate; cyclic ethers, such as tetrahydrofuran and dioxane; ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexylene glycol, and 1,2-dimethylpropane glycol. , 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, dithiodiglycol, or other mono-, oligo-, or polyalkylene glycols or thioglycols having a C2-C8 alkylene unit; polyols (triols) such as glycerin, diglycerin, hexane-1,2,6-triol, and trimethylolpropane; γ-butyrolactone, dimethyl sulfoxide; and glycol ethers. Among these, glycol ethers are preferred.

As the glycol ether, a monoalkyl ether of a di- or tri-C2-C4 alkylene glycol is preferred. Examples of the C2-C4 alkylene glycol moiety include ethylene glycol, propylene glycol, and butylene glycol. Of these, ethylene glycol and propylene glycol are preferred, and ethylene glycol is more preferred. The range of carbon numbers of the alkyl in the monoalkyl ether moiety is usually C1-C6, preferably C1-C5, more preferably C2-C4, even more preferably C3-C4, and particularly preferably C4.

Specific examples of glycol ethers 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, etc. Of these, butyl diglycol is preferred.

The total content of organic solvents in the total mass of the cleaning solution is usually 0 to 60%, preferably 0.1 to 50%, more preferably 0.2 to 40%, and even more preferably 0.5 to 30%. When the cleaning solution contains at least glycol ether 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%, and even more preferably 0.5 to 10%.

When glycol ethers are used in combination with other organic solvents, the sum of their respective contents is the total content of the organic solvents in the total mass of the cleaning solution. In this case, the total content of glycol ethers is as described above.

[Preparation Agents]
The cleaning solution according to the present embodiment may further contain various additives, if necessary, in addition to the above-mentioned components, such as surfactants (excluding the compounds represented by the above formula (1) and the compounds represented by the above formula (2)), preservatives, antifungal agents, pH adjusters, chelating agents, rust inhibitors, water-soluble ultraviolet absorbers, antioxidants, etc.

The total content of the preparation agents in the total mass of the cleaning solution is usually 0% to 30%, preferably 0% to 20%, and more preferably 0% to 10%.

The cleaning solution of this embodiment does not substantially contain any colorant. In this specification, "substantially" means that no colorant is intentionally added to the cleaning solution.

Surfactants include anionic, cationic, nonionic, amphoteric, silicone-based, and fluorine-based surfactants. Of these, nonionic surfactants are preferred.

Examples of anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acylamino acids or salts thereof, N-acyl methyl taurines, alkyl sulfates polyoxyalkyl ether sulfates, alkyl sulfates polyoxyethylene alkyl ether phosphates, rosin acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol phosphates, alkyl phosphates, alkylaryl sulfonates, diethyl sulfosuccinates, diethylhexyl sulfosuccinates, dioctyl sulfosuccinates, etc.

Examples of cationic surfactants include 2-vinylpyridine derivatives, poly-4-vinylpyridine derivatives, etc.

Examples of nonionic surfactants include ether-based surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, and polyoxyethylene distyrenated phenyl ether; ester-based surfactants such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; and acetylene glycol (alcohol)-based surfactants such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 3,5-dimethyl-1-hexyne-3-ol.

Examples of amphoteric surfactants include lauryl dimethylaminoacetate betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, coconut oil fatty acid amidopropyl dimethylaminoacetate betaine, polyoctyl polyaminoethyl glycine, imidazoline derivatives, etc.

Examples of silicone surfactants include polyether-modified siloxane, polyether-modified polydimethylsiloxane, etc.

Examples of fluorine-based surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains.

Examples of preservatives include organic sulfur, organic nitrogen sulfur, organic halogen, haloarylsulfone, iodopropargyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, benzothiazole, isothiazolinone, dithiol, pyridine oxide, nitropropane, organic tin, phenol, quaternary ammonium salt, triazine, thiazine, anilide, adamantane, dithiocarbamate, brominated indanone, benzyl bromoacetate, inorganic salt, and other compounds.

Examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and its salts.

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

Examples of chelating agents include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracildiacetate.

Examples of rust inhibitors include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, etc.

Examples of water-soluble UV absorbers include sulfonated benzophenone compounds, benzotriazole compounds, salicylic acid compounds, cinnamic acid compounds, triazine compounds, etc.

As the antioxidant, for example, various organic and metal complex-based anti-fading agents can be used. Examples of organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc.

[Preparation method of cleaning solution, etc.]
The cleaning solution according to the present embodiment can be obtained by adding the compound represented by the above formula (1), the compound represented by the above formula (2), water, and, if necessary, an organic solvent and/or a modifier, and thoroughly mixing them. The obtained cleaning solution may be subjected to microfiltration to remove impurities. In particular, when the cleaning solution is filled into an inkjet head, it is preferable to microfilter the cleaning solution. For the microfiltration, a membrane filter, glass filter paper, or the like can be used. The pore size of the filter or the like used for microfiltration is usually 0.5 μm to 20 μm, and preferably 0.5 μm to 10 μm.

The pH of the cleaning liquid according to this embodiment at 25° C. is usually 5 to 11, and preferably 7 to 10.5, so as not to corrode the components of the inkjet printer.
The surface tension of the cleaning liquid according to this embodiment at 25° C. is usually 10 mN/m to 50 mN/m, and preferably 20 mN/m to 40 mN/m.
The viscosity of the cleaning liquid according to this embodiment at 25° C. is usually 30 mPa·s or less, preferably 20 mPa·s or less, with the lower limit being about 0.1 mPa·s.

[Uses of cleaning fluid]
The cleaning liquid according to the present embodiment can be used to dissolve and remove solid matter solidified from water-based inks containing various colorants. Examples of water-based inks include water-based inks containing water-soluble dyes such as acid dyes, direct dyes, and reactive dyes; water-based inks containing water-insoluble colorants such as disperse dyes and pigments; and the like. The cleaning liquid according to the present embodiment has a high cleaning power, so it is preferably used to dissolve and remove solid matter solidified from water-based inks containing water-insoluble colorants, particularly pigments. In addition, the cleaning liquid according to the present embodiment has a high cleaning power, and therefore exhibits extremely high performance as a cleaning liquid when dissolving and removing solid matter solidified from water-based inks containing various resins together with pigments.

<How to clean an inkjet printer>
The method for cleaning an inkjet printer according to this embodiment involves bringing the cleaning liquid according to this embodiment described above into contact with solid matter of inkjet ink adhering to the inkjet printer, thereby dissolving and removing the solid matter.

Examples of inkjet inks include water-based inks containing water-soluble dyes such as acid dyes, direct dyes, and reactive dyes; water-based inks containing water-insoluble colorants such as disperse dyes and pigments; and the like. In particular, the cleaning solution according to this embodiment has a high cleaning power, making it possible to dissolve and remove solid matter that has solidified from water-based inks containing water-insoluble colorants, particularly pigments.

The method of contacting the inkjet ink solids with the cleaning solution according to this embodiment is not particularly limited. For example, the cleaning solution may be absorbed into a sponge, cloth, or the like, and the dirt on the part where the solid colored ink is attached may be wiped off. In addition, when the colored ink dries on the inkjet head and the inkjet head is severely dirty, the inkjet head may be filled with a cleaning solution instead of the colored ink, and the cleaning solution may be passed through the ink flow path. By passing the cleaning solution in this way, the solid colored ink attached to the inkjet head, the ink flow path, the nozzle, etc. can be dissolved and removed. Alternatively, when the nozzle of the inkjet head is clogged by the solid colored ink, the nozzle may be immersed in the cleaning solution. By immersing the nozzle in the cleaning solution in this way, the solid colored ink attached to the nozzle can be dissolved and removed.

For all of the above, combinations of preferred items are more preferred, and combinations of more preferred items are even more preferred. The same applies to combinations of preferred items and more preferred items, more preferred items and even more preferred items, etc.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. The cleaning solution and colored ink were prepared under stirring unless otherwise specified. The "water" used in the examples is ion-exchanged water.

[Examples 1 to 3: Preparation of cleaning solution]
The components shown in Table 1 below were mixed to obtain 100 parts of each cleaning liquid. The resulting liquid was filtered through a membrane filter having a pore size of 3 μm to obtain the cleaning liquids of Examples 1 to 3.

[Comparative Examples 1 to 11: Preparation of comparative cleaning solutions]
Comparative cleaning solutions of Comparative Examples 1 to 11 were obtained in the same manner as in Examples 1 to 3, except that the components shown in Table 1 below were used.

The abbreviations in Table 1 below have the following meanings. The numerical values in Table 1 are in parts.
Gly: glycerin 2Py: 2-pyrrolidone BDG: butyl diglycol EP2424: Clariant nonionic surfactant, GENAPOL EP2424
EP2544: Clariant nonionic surfactant, GENAPOL EP2544
EP2564: Clariant nonionic surfactant, GENAPOL EP2564
EP2584: Clariant nonionic surfactant, GENAPOL EP2584
PF20: Clariant nonionic surfactant, GENAPOL PF20
PF40: Clariant nonionic surfactant, GENAPOL PF40
U105: Nonionic surfactant manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Epan U-105
TEA: triethanolamine GXL(S): Proxel GXL(S), manufactured by Lonza.

Incidentally, EP2424 is a compound in which, in the above formula (1), R ¹ is a C12-C14 alkyl group, m is 2, n is 4, and m:n is 1:2.
EP2544 is a compound represented by the above formula (1), in which R ¹ is a C12-C15 alkyl group, m is 4, n is 4, and m:n is 1:1.
EP2564 is a compound in which, in the above formula (1), R ¹ is a C12-C15 alkyl group, m is 6, n is 4, and m:n is 3:2, and is not included in the above formula (1).
EP2584 is a compound in which, in the above formula (1), R ¹ is a C12-C15 alkyl group, m is 8, n is 4, and m:n is 2:1, and is not included in the above formula (1).
PF20 is a compound in which m1 is 5, n1 is 30, L1 is 5, and {(m1+L1)/(m1+n1+L1)}×100=25 in the above formula (2), and is a compound not included in the above formula (2).
PF40 is a compound represented by the above formula (2), in which m1 is 13, n1 is 29, L1 is 13, and {(m1+L1)/(m1+n1+L1)}×100=47.
U105 is a compound represented by the above formula (2), in which m1 is 37, n1 is 56, L1 is 37, and {(m1+L1)/(m1+n1+L1)}×100=57.

[Preparation Example 1: Preparation of Resin A]
Joncryl 678 (weight average molecular weight: 8500) (25 parts) and triethanolamine (14.3 parts) were dissolved in ion-exchanged water (60.7 parts) and stirred for 1 hour to obtain a solution. The obtained solution is designated as "Resin A".

[Preparation Example 2: Preparation of colored dispersion]
The block copolymer described in Synthesis Example 3 of WO 2013/115071 was prepared, and the obtained polymer dispersant (5 parts) was dissolved in 2-butanone (20 parts) to obtain a uniform solution. A solution in which sodium hydroxide (0.4 parts) was dissolved in water (50.6 parts) was added to this solution, and then resin A (4 parts) was added, followed by stirring for 1 hour to obtain an emulsion. C.I. Pigment Yellow 74 (20 parts, Clariant HANSA YELLOW 5GX 01-JP) was added to this emulsion, and the dispersion treatment was carried out in a sand grinder under conditions of 1500 rpm to obtain a liquid. Water (100 parts) was dropped into the obtained liquid, and the liquid was filtered to obtain a filtrate. A colored dispersion having a pigment content of 12.4% was obtained by distilling off 2-butanone and a part of the water from the obtained filtrate under reduced pressure using an evaporator.
The pigment content in the color dispersion was determined by a dry weight method using MS-70 manufactured by A&D Co., Ltd., as a converted value of only the pigment from the total solid content in the liquid.

[Preparation Example 3: Preparation of Resin B]
By following up on Preparation Example 4 of WO 2015/147192, a resin emulsion having an acid value of 6 KOHmg/g, a glass transition temperature of 0° C., and a solid content of 25% was prepared. This resin emulsion is referred to as “Resin B”.

Preparation Example 4: Preparation of colored ink
The components shown in Table 2 below were mixed to obtain a total of 100 parts of a liquid, and the obtained liquid was filtered through a membrane filter having a pore size of 3 μm to obtain a colored ink to be used for evaluating the cleaning liquid.

The abbreviations in Table 2 below have the following meanings. The numerical values in Table 2 below are in parts. The parts of Resin B and AQ515 in Table 2 are solid content equivalents.
Dp1: Colored dispersion obtained in Preparation Example 2 TEG: Triethylene glycol 1,2 HD: 1,2-hexanediol SN465: Nonionic surfactant manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 465
AQ515: Polyethylene wax manufactured by BYK-Chemie, AQUACER 515 (solid content 35.0%)

[Stability test]
After each of the cleaning solutions obtained in Examples 1 to 3 and Comparative Examples 1 to 11 was allowed to stand at room temperature for 12 hours, the state of the cleaning solution was visually observed and its stability was evaluated. The evaluation criteria were the following two stages. The evaluation results are shown in Table 3 below.
-Evaluation criteria-
A: There was no change in the condition of the cleaning solution.
C: A liquid component separated from the cleaning solution was observed floating on the surface of the cleaning solution.

In addition, the cleaning test described below was conducted using only the cleaning solution rated "A" in the stability test.

[Washability test]
20 μL of the colored ink obtained in Preparation Example 4 was dropped onto a glass petri dish and allowed to stand in a thermostatic chamber at 60° C. for 1 hour to dry, thereby obtaining a solid matter in which the colored ink had solidified. 10 mL of each of the cleaning solutions of Examples 1 to 3 and Comparative Examples 2 to 4, 7, 8, and 11 was dropped onto the obtained solid matter, and it was visually evaluated whether or not the solid matter could be dissolved. The evaluation criteria were the following four levels. The evaluation results are shown in Table 3 below. In Table 3, "-" indicates that the cleaning property test was not performed.
-Evaluation criteria-
A: No remaining solid matter was observed, and the liquid was homogeneous.
B: The liquid became almost homogeneous, but a small amount of solid matter remained.
C: Solid matter clearly remained, and the liquid was not recognized as a homogeneous liquid.
D: The shape of the solid matter did not change at all or changed very little.

However, even a small amount of solid matter remaining means that there is a possibility that clogging of the inkjet head cannot be cleared. For this reason, cleaning solutions that are not rated "A" for cleaning ability are not practical.

As is clear from the above results, it was confirmed that the cleaning solutions of Examples 1 to 3 were excellent in stability and cleaning properties.

Claims (5)

A cleaning liquid for an inkjet printer comprising a compound represented by the following formula (1), a compound represented by the following formula (2) , water, and a glycol ether , wherein the content of the compound represented by formula (2) is 0.2% by mass to 2% by mass.

[In formula (1), ^R1 represents a linear or branched C1-C30 alkyl group. EO represents an ethyleneoxy group, and PO represents a propyleneoxy group. EO and PO may be bonded in any order. m and n each independently represent an integer of 1 to 5. The ratio of m to n, m:n, is 1:2 or more and less than 3:2.]

[In formula (2), EO represents an ethyleneoxy group, and PO represents a propyleneoxy group. The order in which EO and PO are bonded together is arbitrary. m1, n1, and L1 each independently represent an integer of 1 or more. However, m1, n1, and L1 satisfy the condition {(m1+L1)/(m1+n1+L1)}×100>27.] The inkjet printer cleaning solution according to claim 1, wherein the content of the compound represented by formula (2) is 0.4% by mass to 2% by mass. 3. A method for cleaning an inkjet printer, comprising contacting solid matter of inkjet ink adhering to an inkjet printer with the inkjet printer cleaning liquid according to claim 1 or 2 , thereby dissolving and removing said solid matter. 4. The cleaning method according to claim 3, further comprising filling an inkjet head with the inkjet printer cleaning liquid and passing the cleaning liquid through an ink flow path to dissolve and remove the solid matter adhering to the ink flow path. 4. The cleaning method according to claim 3 , wherein the solid matter adhering to the nozzles of an inkjet head is dissolved and removed by immersing the nozzles in the inkjet printer cleaning liquid.