Cleaning liquid

Abstract

To provide a cleaning liquid capable of removing even white ink after fixing and improving discharge failure of an inkjet printer.SOLUTION: A cleaning liquid comprising: a first surfactant; a second surfactant; and a basic compound, wherein the first surfactant is an amphoteric surfactant, and the second surfactant is an anionic surfactant that is a sulfonate and / or a nonionic surfactant that has a branched structure and has an HLB of 7 to 14.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cleaning solution. [Background technology]

[0002] Inkjet printing is a method in which ink droplets are ejected onto a printing substrate from extremely fine nozzles using an inkjet printer to form colored images such as letters and designs. In recent years, methods for lowering the viscosity of ink have been investigated in order to achieve high-speed printing and quick-drying ink.

[0003] However, when inkjet printers are left without ink ejection for long periods of time, a dried film of ink forms on the head (near the nozzle opening) and inside the nozzles. This dried film can cause the ink to deflect and clog the nozzles, which can be problematic.

[0004] Therefore, a method has been proposed in which an ink cleaning liquid is used to remove the dried ink film that has accumulated inside the head and nozzles.

[0005] For example, Patent Document 1 discloses a cleaning liquid for cleaning sites on which the ejected aqueous inkjet ink adheres in an inkjet printer that ejects the aqueous inkjet ink containing a pigment and an alkali-soluble resin having an acid group in the molecule, the cleaning liquid containing an amphoteric surfactant, a basic compound, and water and having a pH of 9 to 12, the amphoteric surfactant being at least one selected from the group consisting of lauryl dimethylamine oxide, lauryl dimethylaminoacetic acid betaine, and 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, and the amphoteric surfactant is contained in an amount of 0.1 to 3 mass % relative to the total amount of the cleaning liquid. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-060156 Summary of the Invention [Problem to be solved by the invention]

[0007] However, with the method described in Patent Document 1, it is difficult to remove the ink after it has solidified, and in the case of white ink, it is particularly difficult to remove the solidified white ink, leaving room for further improvement.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a cleaning liquid that can remove even solidified white ink and improve ejection defects in inkjet printers. [Means for solving the problem]

[0009] The present inventors have conducted extensive research in light of the above-mentioned problems and have found that all of the above problems can be solved by using a cleaning solution containing a first surfactant, a second surfactant, and a basic compound, in which the first surfactant is an amphoteric surfactant and the second surfactant is a specific anionic surfactant and / or nonionic surfactant, thereby completing the present invention.

[0010] That is, the present invention provides a cleaning liquid containing a first surfactant, a second surfactant, and a basic compound, wherein the first surfactant is an amphoteric surfactant, and the second surfactant is an anionic surfactant that is a sulfonate salt and / or a nonionic surfactant that has a branched structure and an HLB value of 7 to 14.

[0011] In the cleaning liquid of the present invention, the first surfactant is preferably at least one selected from the group consisting of lauryl dimethylamine oxide, lauryl dimethyl aminoacetic acid betaine, and 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine. The first surfactant is preferably contained in an amount of 0.1 to 3% by mass relative to the total amount of the cleaning liquid. The second surfactant is preferably sodium alkyl sulfate sulfonate and / or polyoxyethylene isotridecyl ether (5EO). The second surfactant is preferably contained in an amount of 0.1 to 3% by mass relative to the total amount of the cleaning liquid. The basic compound is preferably sodium hydroxide and / or potassium hydroxide. The cleaning solution of the present invention preferably has a pH of 9-12. The cleaning solution of the present invention preferably further contains a preservative and water. The cleaning liquid of the present invention is a cleaning liquid for cleaning an aqueous ink composition for inkjet printing, and the aqueous ink composition for inkjet printing preferably contains a pigment and an alkali-soluble resin having an acid group in the molecule. The pigment is preferably contained in an amount of 3 to 12 mass % relative to the total amount of the aqueous inkjet printing ink composition, and the alkali-soluble resin having an acid group in the molecule preferably has an acid value of 100 to 200 mgKOH / g. [Effects of the Invention]

[0012] The present invention can provide a cleaning liquid that can remove even solidified white ink and can improve ejection defects in inkjet printers. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention relates to a cleaning liquid containing a first surfactant, a second surfactant, and a basic compound, wherein the first surfactant is an amphoteric surfactant, and the second surfactant is an anionic surfactant that is a sulfonate salt and / or a nonionic surfactant that has a branched structure and an HLB value of 7 to 14.

[0014] The present inventors have conducted extensive research to solve the above problems and have come to the following findings. That is, the inventors speculated that because air is hydrophobic, the dried ink film (ink composition after solidification) has a structure in which many hydrophobic sites of the pigment and binder resin (including alkali-soluble resins having acid groups in the molecule) are exposed on the surface, and the acid groups of the binder resin face inward of the dried ink film. A white ink composition with low coloring power requires a higher pigment concentration than other colors to achieve high color density. Furthermore, a large amount of binder resin must be included to impart high resistance to the dried white ink film. Therefore, we hypothesized that the number of sites (e.g., acid groups) on the surface of the dried film that can act to redissolve the white ink inevitably decreases, making it even more difficult to clean. In order to quickly dissolve and remove (wash away) the dried white ink film, it is necessary to quickly form a salt between the acid groups of the binder resin and the basic compound contained in the washing solution. Therefore, according to the above speculation, it is presumed that the important function of the washing solution is to penetrate (or adsorb) into the binder resin and form a salt while many of the hydrophobic sites of the pigment and binder resin are exposed on the surface.

[0015] In conventional cleaning solutions, amphoteric surfactants were considered effective among compounds that have a hydrophobic portion (generally a long-chain alkyl group or an aromatic ring) and a hydrophilic portion (generally an ionic group or a polyethylene chain) in the molecule, as they have a stronger adsorption power with the hydrophobic portion of the binder resin and can collect more water molecules in the hydrophilic portion. However, they did not have sufficient cleaning properties for the dried film of white ink described above.

[0016] The cleaning liquid of the present invention contains, in addition to the amphoteric surfactant as the first surfactant, an anionic surfactant which is a sulfonate salt and / or a nonionic surfactant which has a branched structure and an HLB value of 7 to 14 as the second surfactant. The above-mentioned sulfonate anionic surfactant has high penetration power and can quickly form a salt with the acid groups of the binder resin that face inward in the dried film of the white ink, while the above-mentioned nonionic surfactant with a branched structure and an HLB of 7 to 14 can more efficiently and strongly adsorb to the hydrophobic parts of the binder resin. It was discovered that by including this second surfactant in addition to the first surfactant, an amphoteric surfactant, the product has excellent cleaning properties even under harsh cleaning conditions, such as when cleaning white ink. However, the present invention should not be construed as being limited to the above mechanism.

[0017] The above-mentioned excellent washability means that the ink has excellent resolubility in a dried film, redispersibility after strong shaking, and redispersibility after change with time, which will be described later.

[0018] (First surfactant) The cleaning liquid of the present invention contains a first surfactant, and the first surfactant is an amphoteric surfactant. The first surfactant and the second surfactant described below are materials that serve to reduce the surface tension of the cleaning liquid and increase the wettability of the dried ink film with a hydrophobic surface.

[0019] The first surfactant is preferably at least one selected from the group consisting of lauryl dimethylamine oxide, lauryl dimethylaminoacetic acid betaine, and 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, and from the viewpoint of improving cleaning properties, lauryl dimethylamine oxide is more preferable.

[0020] The first surfactants may be used alone or in combination.

[0021] From the viewpoint of improving cleaning performance, the first surfactant is preferably contained in an amount of 0.1 to 3 mass % relative to the total amount of the cleaning liquid, and more preferably 0.5 to 1.5 mass %.

[0022] (Second surfactant) The cleaning liquid of the present invention contains a second surfactant, and the second surfactant is an anionic surfactant that is a sulfonate salt and / or a nonionic surfactant that has a branched structure and an HLB value of 14 or less.

[0023] The cleaning solution of the present invention contains the anionic surfactant, which increases the penetration power of the cleaning solution and allows it to quickly form a salt with the acid groups of the binder resin (alkali-soluble resin described below) facing inward in the dried ink film. Furthermore, the cleaning solution of the present invention contains the nonionic surfactant, which allows the cleaning solution to more efficiently and strongly adsorb to the hydrophobic moieties of the binder resin (alkali-soluble resin described below) that constitutes the aqueous inkjet printing ink composition. Therefore, the cleaning solution of the present invention can remove even solidified white ink, and can improve ejection defects in inkjet printers.

[0024] The anionic surfactant that is a sulfonate is preferably a sodium alkyl sulfate sulfonate and / or a polyoxyethylene alkyl ether sulfonate, and more preferably a sodium salt of sodium alkyl sulfate sulfonic acid or sodium polyoxyethylene alkyl ether sulfate.

[0025] From the viewpoint of improving detergency, the alkyl sodium sulfate sulfonate is preferably a linear or branched alkyl sodium sulfate sulfonate having 10 to 20 carbon atoms, and more preferably a linear alkyl sodium sulfate sulfonate having 12 to 14 carbon atoms.

[0026] The sodium polyoxyethylene alkyl ether sulfate may be one to which ethylene oxide (EO) has been added, for example, one to which an average of 7 moles have been added (also referred to as 7EO). Polyoxyethylene alkyl ether (7EO) sodium sulfate is preferred from the viewpoint of excellent cleaning properties even after aging (for example, after being left in an open oven at 50°C for 3 months).

[0027] The nonionic surfactant having a branched structure and an HLB value of 7 to 14 is preferably a polyalkylene glycol fatty acid ester or polyoxyethylene alkyl ether having a branched structure.

[0028] As the polyalkylene glycol fatty acid ester, those in which an average of 5 moles of ethylene oxide (EO) are added to isotridecyl alcohol (also referred to as 5EO) or those in which an average of 8 moles of ethylene oxide (EO) are added to isotridecyl alcohol (also referred to as 8EO) are more preferred.

[0029] The polyoxyethylene alkyl ether is preferably an EO or PO adduct of polyalkylene glycol 2-ethylhexyl ether.

[0030] The second surfactants may be used alone or in combination.

[0031] The nonionic surfactant having a branched structure and an HLB of 7 to 14 has an HLB of 7 to 14. When the HLB is within the above range, the cleaning properties that the present invention aims to achieve can be imparted. The nonionic surfactant having a branched structure and an HLB value of 7 to 14 preferably has an HLB value of 8 to 13.

[0032] In this specification, the HLB value is defined as 20 for a hypothetical compound with an infinitely long hydrophilic group attached to the lipophilic group of the surfactant, which has the highest hydrophilicity, and 0 for a lipophilic compound with no hydrophilic group at all. The HLB value is a value calculated for each surfactant as a relative value to these values, and can generally be calculated using the Griffin formula. The Griffin formula used to calculate the HLB value is shown below. HLB value = 20 × Mw / M M: molecular weight of nonionic surfactant, Mw: molecular weight of hydrophilic part

[0033] From the viewpoint of improving cleaning performance, the second surfactant is preferably contained in an amount of 0.1 to 3 mass % relative to the total amount of the cleaning liquid, more preferably 0.2 to 2.5 mass %, and even more preferably 0.5 to 1.5 mass %.

[0034] From the viewpoint of ease of handling due to foaming, the amount of the second surfactant is preferably 0.2 to 2.5 parts by mass, and more preferably 0.5 to 1.5 parts by mass, per part by mass of the first surfactant.

[0035] (basic compounds) The cleaning liquid of the present invention contains a basic compound.

[0036] Examples of the basic compound include sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia. Among these, alkali metal hydroxides are preferred, sodium hydroxide and potassium hydroxide are more preferred, and potassium hydroxide is more preferred, as they are strong bases and can sufficiently enhance the cleaning effect.

[0037] The content of the basic compound may be any amount necessary to adjust the pH of the cleaning solution to the range described below, and may vary depending on the basicity of the basic compound itself, the presence of an acid component or a base component in other materials, and other factors.

[0038] (preservatives) The cleaning solution of the present invention preferably contains a preservative.

[0039] The preservative is not particularly limited, and any known preservative that can be used in the field of cleaning solutions can be appropriately selected and used. Specific examples include PROXEL GXL (manufactured by Lonza Japan) and KORDEK MLX (manufactured by DuPont).

[0040] From the viewpoint of antiseptic effect, the preservative is preferably contained in an amount of 0.01 to 1% by mass, and more preferably 0.05 to 0.5% by mass, based on the total amount of the cleaning liquid.

[0041] (water) The cleaning solution of the present invention comprises water. As the water, commercially available purified water, ion-exchanged water, etc. can be used.

[0042] From the viewpoint of dissolving the above-mentioned materials, the water content is preferably 70 to 99 mass %, and more preferably 90 to 97 mass %. The water content is the total amount of water contained in the various components.

[0043] (others) The cleaning liquid of the present invention may contain an organic solvent, a surfactant other than the first surfactant and the second surfactant, an antifoaming agent, and the like, as needed.

[0044] (pH of cleaning solution) The cleaning solution of the present invention preferably has a pH of 9 to 12. If the pH of the cleaning solution is less than 9, the cleaning power is likely to decrease, and if the pH of the cleaning solution is more than 12, it is likely to cause occupational health problems and corrode the area where it is attached (such as the head components). The pH value is measured in accordance with JIS K6221.

[0045] (Cleaning solution manufacturing method) The method for producing the detergent of the present invention is not particularly limited, and the above-mentioned various materials may be stirred and mixed by a known method.

[0046] (Aqueous ink composition for inkjet printing) Next, the aqueous ink composition for ink jet printing, which is a preferred target for cleaning with the cleaning liquid of the present invention, will be described. The aqueous ink composition for ink jet printing contains a pigment and an alkali-soluble resin having an acid group in the molecule.

[0047] The pigment is not particularly limited, and examples thereof include known inorganic pigments and organic pigments. Examples of the inorganic pigment include carbon black, titanium oxide, red iron oxide, graphite, iron black, chromium oxide green, and aluminum hydroxide. Examples of the organic pigment include dye lake pigments, azo-based, benzimidazolone-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigo-based, thioindigo-based, perylene-based, perinone-based, diketopyrrolopyrrole-based, isoindolinone-based, nitro-based, nitrone-based, anthraquinone-based, flavanthrone-based, quinophthalone-based, pyranthrone-based, and indanthrone-based pigments. The above pigments may be used in combination.

[0048] The content of the pigment in the aqueous ink composition for inkjet printing is not particularly limited. When the aqueous inkjet printing ink composition contains a large amount of the pigment, the color density can be maintained even when printing with a smaller amount of droplets of the aqueous inkjet printing ink composition, which results in less transfer of liquid components to the printing paper, which is advantageous for quick drying and suppression of penetration of coloring components into the paper. On the other hand, maintaining a low viscosity of the ink requires that the total amount of solids in the aqueous ink jet printing ink composition be kept constant. Therefore, if the content of the pigment, which is an insoluble component, increases, the content of the alkali-soluble resin, which is a soluble component, must be reduced instead. These factors combined make such aqueous inkjet printing ink compositions prone to forming dried films that are poorly resolubilized, and prone to ejection defects. However, the cleaning liquid of the present invention has sufficient cleaning properties to be able to clean and remove even the dried film of such an ink containing a large amount of pigment. Specifically, the cleaning liquid of the present invention can sufficiently clean and remove even a dried film containing 3 to 12 mass % of the pigment based on the total amount of the aqueous inkjet printing ink composition.

[0049] Examples of the alkali-soluble resin include alkali-soluble resins obtained by copolymerizing a carboxyl group-containing monomer such as acrylic acid, methacrylic acid, or (anhydrous) maleic acid (monoalkyl ester) with a hydrophobic group-containing monomer such as an alkyl group-containing monomer having 8 or more carbon atoms such as 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, or 2-hydroxystearyl (meth)acrylate, an alkyl vinyl ether having 8 or more carbon atoms such as dodecyl vinyl ether, an alkyl vinyl ester having 8 or more carbon atoms such as vinyl 2-ethylhexanoate, vinyl laurate, or vinyl stearate, an alicyclic hydrocarbon group-containing monomer such as cyclohexyl (meth)acrylate, or an aromatic hydrocarbon group-containing monomer such as benzyl (meth)acrylate, styrene, α-styrene, or vinyl toluene.

[0050] The content of the alkali-soluble resin is, for example, 10 to 60 parts by mass relative to 100 parts by mass of the pigment.

[0051] The acid value of the alkali-soluble resin is not particularly limited. When the acid value of the alkali-soluble resin is low, the aqueous medium is more likely to separate from the system, resulting in excellent drying properties. On the other hand, such an aqueous ink composition for inkjet printing is more likely to have fewer sites that act to redissolve the dried film. However, the cleaning solution of the present invention has a high ability to efficiently cause the basic groups of the basic compound contained in the cleaning solution to react with the acid groups contained in the molecules of the alkali-soluble resin to form a salt, and therefore can clean away even such a dried film of the aqueous ink composition for inkjet printing. Specifically, the cleaning solution of the present invention can sufficiently clean and remove even a dried film of an aqueous ink composition for inkjet printing that contains an alkali-soluble resin with an acid value of 100 to 200 mgKOH / g.

[0052] The aqueous ink composition for inkjet printing may contain a water-dispersible resin, a surfactant, and the like, as needed. These materials can be appropriately selected from known materials used in aqueous ink compositions for ink jet printing.

[0053] The pigment is mixed with an aqueous resin varnish in which an alkali-soluble resin is dissolved in water in the presence of a basic compound, and the mixture is kneaded in a disperser. Thereafter, the pigment is used after being prepared into a resin-coated pigment in which the alkali-soluble resin is precipitated on the pigment surface by an acid precipitation method, an ion exchange method, or the like.

[0054] On the other hand, such aqueous ink jet printing ink compositions are prone to deflection of ink jets and nozzle clogging when dried and solidified, particularly when they contain a high concentration of pigment or a small amount of an alkali-soluble resin with a low acid value. However, the cleaning solution of the present invention is less likely to cause occupational hygiene problems, is less likely to corrode the area where it is attached (such as head components), and can thoroughly clean the area where it is attached, dissolving the dried ink film and improving ejection defects. As a result, even in a state in which the aqueous ink jet printing ink composition adheres to the adhesion site and causes ejection defects in an ink jet printer that has been left without ejecting the aqueous ink jet printing ink composition for a long period of time, the cleaning liquid of the present invention can remove a dried film of the aqueous ink jet printing ink composition from the adhesion site. Therefore, an ink jet printer that has been cleaned with the cleaning solution of the present invention can then eject the aqueous ink composition for ink jet printing normally. [Example]

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

[0056] The materials used in the examples and comparative examples are as follows.

[0057] <Production of aqueous ink composition for inkjet printing> An aqueous inkjet ink composition was produced using the following raw materials. (white pigment) Product name: JR-809 (product name "JR-809", titanium oxide treated with silica and alumina, average particle size 0.23 μm, DBP oil supply amount 24 ml / 100 g, manufactured by Teika Co., Ltd.) (alkali-soluble resin) Weight average molecular weight 15800, acid value 144mgKOH / g, copolymer of styrene / lauryl acrylate / acrylic acid = 51 / 30 / 19 (Water dispersible resin) Neo Rez R-966 (DSM) (polyether polyurethane resin (active ingredient content 33% by weight)) (surfactant) Ethylene oxide adduct of acetylene glycol, product name: Acetylenol E100, manufactured by Kawaken Fine Chemicals Co., Ltd. (High-pressure emulsifying and dispersing equipment) Gaulin homogenizer, manufactured by APV Gaulin Inc.

[0058] 25 parts by mass of alkali-soluble resin was mixed with sodium hydroxide to a neutralization equivalent of 100% and purified water to make 100 parts by mass, and the mixture was heated and stirred at 90°C to dissolve, thereby preparing an alkali-soluble resin varnish. 40 parts by mass of the obtained aqueous resin varnish, 10 parts by mass of water, and 50 parts by mass of white pigment were mixed with stirring and milled in a wet circulation mill to obtain an aqueous inkjet base ink.

[0059] (Aqueous inkjet ink composition 1) 20 parts by mass of the obtained aqueous inkjet base ink, 24.2 parts by mass of water-dispersible resin, 20 parts by mass of glycerin, 10 parts by mass of propylene glycol, 1 part by mass of surfactant, and 4 parts by mass of water were stirred and mixed to obtain aqueous inkjet ink composition 1 with a pigment concentration of 10% by mass and a pigment / alkali-soluble resin (by mass) ratio of 10 / 2.

[0060] (Aqueous inkjet ink composition 2) 6 parts by mass of the obtained aqueous inkjet base ink, 24.2 parts by mass of water-dispersible resin, 25 parts by mass of glycerin, 10 parts by mass of propylene glycol, 1 part by mass of surfactant, and 9 parts by mass of water were stirred and mixed to obtain aqueous inkjet ink composition 2 with a pigment concentration of 3% by mass and a pigment / alkali-soluble resin (mass) ratio of 10 / 2.

[0061] <Examples 1 to 15 and Comparative Examples 1 to 4> According to the formulations shown in Table 1 below, the raw materials were charged into a beaker and mixed by stirring with a stirring device to prepare cleaning solutions of Examples 1 to 15 and Comparative Examples 1 to 4, respectively. Using the prepared cleaning liquid, the resolubility evaluation, redispersibility evaluation under strong shaking, and redispersibility evaluation over time for the dried films of aqueous inkjet ink compositions 1 and 2 were performed according to the following evaluation methods. The results are shown in Table 1. Note that a score of 4 or higher in all of the resolubility evaluation, redispersibility evaluation under strong shaking, and redispersibility evaluation over time was determined to be acceptable. The pH of the prepared cleaning solution was measured in accordance with JIS K6221.

[0062] The various materials used to prepare the cleaning solution are as follows: <First surfactant> Amphitol 20N (lauryl dimethylamine oxide, active ingredient 35% by mass, manufactured by Kao Corporation) Ankhitol 24B (lauryl dimethylaminoacetic acid betaine, active ingredient 26% by mass, manufactured by Kao Corporation) Amphitol 20Y-B (2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, active ingredient 40% by mass, manufactured by Kao Corporation) <Second surfactant> (anionic surfactants) Emulsogen EPA073 (polyoxyethylene alkyl ether (7EO) sodium sulfate, active ingredient 30% by mass, manufactured by Clariant) Latemul E-118B (sodium polyoxyethylene alkyl ether sulfonate, active ingredient 26% by mass, manufactured by Kao Corporation) (nonionic surfactant) Genapol X050 (polyoxyethylene isotridecyl ether (5EO), active ingredient 100% by mass, HLB10, manufactured by Clariant) Genapol X080 (polyoxyethylene isotridecyl ether (8EO), active ingredient 100% by mass, HLB 13, manufactured by Clariant) Tergitol EH-3 (EO / PO polyalkylene glycol 2-ethylhexyl ether, active ingredient 95% by mass, HLB 7.9, manufactured by Dow) Tergitol EH-9 (EO / PO polyalkylene glycol 2-ethylhexyl ether, active ingredient 90% by mass, HLB 12.5, manufactured by Dow) (Other surfactants) Triton H-55 (anionic surfactant, phosphate ester, active ingredient 50% by mass, manufactured by Dow) Genapol X150 (nonionic surfactant, polyoxyethylene isotridecyl ether (15EO), active ingredient 100% by mass, HLB15, manufactured by Clariant) Tergitol SA-9 (nonionic surfactant, linear EO / PO polyalkylene glycol natural alcohol ether, active ingredient 95% by mass, HLB 11.1, manufactured by Dow) <Basic compounds> Potassium hydroxide <Preservatives> PROXEL GXL (manufactured by Lonza Japan) <Water> purified water

[0063] <Redissolution evaluation> 0.2 g of the aqueous inkjet ink composition was dropped onto a glass plate and left for 1 minute in an oven at 40° C. 0.03 g of each of the cleaning solutions from the Examples and Comparative Examples was dropped onto the resulting dried film, and the solubility of the dried film was evaluated according to the following evaluation criteria. (Evaluation criteria) 5: The dried coating began to dissolve immediately after the cleaning solution was added dropwise, and was completely dissolved. 4: The dried film began to dissolve immediately after the cleaning solution was added, and more than 70% of it dissolved, but a small amount of dried film remained. 3: The dried coating began to dissolve immediately after the cleaning solution was dropped on it, and more than 40% but less than 70% dissolved. 2: The dried coating began to dissolve immediately after the cleaning solution was dropped onto it, and more than 20% but less than 40% dissolved. 1: Less than 20% of the dried film was dissolved when the cleaning solution was dropped onto it.

[0064] <Evaluation of redispersibility after strong shaking> 10 g of the aqueous inkjet ink composition was placed in a container and centrifuged at 720 G for 20 minutes using a centrifuge (Sigma 3-30KS). The supernatant was removed and the mixture was left in an open oven at 50° C. for 3 months. 1 g of the resulting dried ink film was immersed in 10 g of each of the cleaning solutions of the Examples and Comparative Examples, and the container was shaken three times, after which the redispersibility of the dried film was evaluated according to the following evaluation criteria. (Evaluation criteria) 5: The dried coating began to redisperse immediately after immersion in the cleaning solution, and was completely redispersed after shaking. 4: The dried coating began to redisperse immediately after immersion in the cleaning solution, and after shaking, all but a small portion of the coating redispersed. 3: After the dried coating was immersed in the cleaning solution, it began to redisperse when shaken, and most of it was redispersed. 2: After the dried coating was immersed in the cleaning solution, it began to redisperse upon shaking, and some of it redispersed. 1: The dried coating did not redisperse even after being immersed in the cleaning solution and then shaken.

[0065] <Evaluation of redispersibility over time> 10 g of the aqueous inkjet ink composition was placed in a container and centrifuged at 720 G for 20 minutes using a centrifuge (Sigma 3-30KS). The supernatant was removed and the mixture was left in an open oven at 50° C. for 3 months. 1 g of each of the cleaning solutions from the Examples and Comparative Examples was dropped onto 1 g of the dried ink film obtained, and the change over time and redispersibility of the dried film was evaluated according to the following evaluation criteria. (Evaluation criteria) 5: The dried film began to redisperse immediately after the cleaning solution was added, and after 2 hours, more than 80% of the dried film had redispersed. 4: The dried coating began to redisperse immediately after the cleaning solution was added, and after 2 hours, 50% to less than 80% of the dried coating had redispersed. 3: The dried coating began to redisperse immediately after the cleaning solution was added, and after 2 hours, 30% to less than 50% of the dried coating had redispersed. 2: The dried coating did not redisperse immediately after the cleaning solution was added, but after 2 hours, more than 10% but less than 30% of the dried coating had redispersed. 1: The dried coating did not redisperse even when the washing liquid was added dropwise.

[0066] [Table 1]

[0067] The cleaning solution of the example, which contained a specific anionic surfactant and / or nonionic surfactant as the second surfactant in addition to the first surfactant, was excellent in all evaluations, including the resolubility evaluation, the redispersibility evaluation with strong shaking, and the redispersibility evaluation over time. On the other hand, Comparative Example 1, which did not contain a second surfactant, Comparative Example 2, which contained an anionic surfactant that was a phosphate ester, Comparative Example 3, which contained a nonionic surfactant with an HLB value of more than 14, and Comparative Example 4, which contained a nonionic surfactant with a linear structure, did not have sufficient cleaning properties. [Industrial Applicability]

[0068] It is possible to provide a cleaning liquid that can remove even solidified white ink and improve ejection defects in inkjet printers.

Claims

1. The composition contains a first surfactant, a second surfactant, and a basic compound, the first surfactant is lauryl dimethylamine oxide; the second surfactant is an anionic surfactant which is a sulfonate salt and / or a nonionic surfactant which has a branched structure and an HLB of 7 to 14; A cleaning solution used for cleaning an aqueous ink composition for ink jet printing.

2. 2. The cleaning solution according to claim 1, wherein the first surfactant is contained in an amount of 0.1 to 3% by mass based on the total amount of the cleaning solution.

3. 3. The cleaning solution according to claim 1, wherein the second surfactant is sodium alkyl sulfate sulfonate and / or polyoxyethylene isotridecyl ether (5EO).

4. 4. The cleaning solution according to claim 1, wherein the second surfactant is contained in an amount of 0.1 to 3% by mass based on the total amount of the cleaning solution.

5. 5. The cleaning solution according to claim 1, wherein the basic compound is sodium hydroxide and / or potassium hydroxide.

6. 6. The cleaning solution according to claim 1, which has a pH of 9 to 12.

7. The cleaning solution according to any one of claims 1 to 6, further comprising a preservative and water.

8. A cleaning solution for cleaning an aqueous ink jet printing ink composition, comprising:

8. The cleaning liquid according to claim 1, wherein the aqueous ink composition for inkjet printing contains a pigment and an alkali-soluble resin having an acid group in the molecule.

9. the pigment is contained in an amount of 3 to 12% by mass based on the total amount of the aqueous ink composition for inkjet printing, The alkali-soluble resin having an acid group in the molecule has an acid value of 100 to 200 mgKOH / g. The cleaning solution according to claim 8.

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