Cleaning solution

Abstract

The present invention provides a cleaning solution that can safely and efficiently remove dried ink containing binder resin. [Solution] The cleaning solution comprises an organic solvent having a ClogP value of -1.0 or less, an amphoteric surfactant having a betaine structure, a polycarboxylic acid polymer having an average molecular weight of 2000 to 50000, and water, wherein the content of the organic solvent is 10 parts by mass or more, the content of the polycarboxylic acid polymer is 0.1 parts by mass or more and 1 part by mass or less, the content of the water is 30 parts by mass or more, and the percentage of the content of the amphoteric surfactant relative to the content of the organic solvent is 0.5% to 1.5%.

Description

Technical Field

[0001] The present invention relates to a cleaning liquid.

Background Art

[0002] Conventionally, an ink containing a binder resin, which is excellent in fixing properties and the like for ink poorly absorbent recording media (poorly absorbent media), is known. Such an ink containing a binder resin firmly adheres to a substrate by drying. Therefore, when the above ink adheres to the nozzle plate of an inkjet head and dries, it becomes difficult to remove the dried product of the ink.

[0003] Various cleaning liquids have been proposed to remove the dried ink deposits formed by adhering and drying on the nozzle plate and the like. For example, Patent Document 1 discloses a maintenance liquid containing an alkane-1,2-diol monoalkyl ether having a ClogP value of 0.6 or more and 1.0 or less, and Patent Document 2 discloses a cleaning liquid containing an amphoteric surfactant, a basic compound, and water, not containing an aromatic hydrocarbon compound and a ketone compound which are organic solvents, having a pH of 9 to 12, wherein the amphoteric surfactant is at least one selected from the group consisting of dimethyllaurylamine oxide, lauryldimethylaminoacetic acid betaine, and 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, and being contained in an amount of 0.1 to 3% by mass based on the total amount of the cleaning liquid.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the maintenance fluid disclosed in Patent Document 1 contains a highly hydrophobic solvent, as described above, which may damage materials that make up the inkjet printer, posing a safety problem. Furthermore, the cleaning fluid disclosed in Patent Document 2 has a single cleaning component, resulting in poor cleaning performance against inks containing binder resins as described above.

[0006] In view of the above circumstances, the object of the present invention is to provide a cleaning solution that can safely and efficiently remove dried ink containing binder resin. [Means for solving the problem]

[0007] To achieve the above objective, a cleaning solution according to one embodiment of the present invention comprises an organic solvent having a ClogP value of -1.0 or less, an amphoteric surfactant having a betaine structure, a polycarboxylic acid polymer having an average molecular weight of 2000 to 50000, and water. The above organic solvent content is 10 parts by mass or more, the above polycarboxylic acid polymer content is 0.1 parts by mass or more and 1 part by mass or less, and the above water content is 30 parts by mass or more. The percentage of the amphoteric surfactant content relative to the content of the organic solvent is 0.5% or more and 1.5% or less.

[0008] The above cleaning solution, by containing appropriate amounts of a suitable organic solvent, appropriate cleaning components, and water, can safely and efficiently remove dried ink containing binder resin.

[0009] The above cleaning solution may have a viscosity of 8.0 mPa·s or less at 25°C.

[0010] The above cleaning solution may have a static surface tension of 20 mN / m or more and less than 40 mN / m.

[0011] The above organic solvent may be selected from the group consisting of 1,2-propanediol, 1,3-propanediol, and glycerin.

[0012] The above organic solvent may also be 1,3-propanediol.

[0013] The above-mentioned amphoteric surfactant may also be an amphoteric surfactant having a coconut oil fatty acid amidopropyl dimethyl acetate betaine structure. [Effects of the Invention]

[0014] As described above, the present invention provides a cleaning solution that can safely and efficiently remove dried ink containing binder resin. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below.

[0016] [Embodiment: Cleaning solution] (Overall structure) The following describes a cleaning solution according to one embodiment of the present invention. The cleaning solution according to this embodiment comprises an organic solvent, a cleaning component, and water.

[0017] First, the formation process of the ink-dried material that is to be cleaned with the cleaning solution according to this embodiment will be described.

[0018] When forming an image using an inkjet recording device, inkjet recording ink (hereinafter simply referred to as "ink") is ejected from the ejection surface of the recording head onto the recording medium. Specifically, the ink is ejected toward the recording medium from a number of ejection ports formed on the ejection surface. At this time, the ejected ink may adhere to the ejection surface. When ink adheres to the ejection surface, the adhered ink comes into contact with air and dries. In this way, dried ink material is formed.

[0019] Such ink dry matter is particularly likely to occur when using an ink that is excellent in terms of fixing properties and the like with respect to a recording medium having poor ink absorbency (poor absorption medium). This is because such inks contain a relatively large amount of binder resin.

[0020] Ink dry matter causes poor ink ejection. Depending on the formation position of the ink dry matter, the ink dry matter may block the ejection port. Specifically, when the ink dry matter blocks part or all of the ejection port, it becomes difficult to eject the ink, and the ink is ejected in a direction different from the desired ejection direction.

[0021] When poor ink ejection occurs, the quality of the formed image deteriorates. Therefore, it is desirable to remove the ink dry matter to prevent the occurrence of poor ink ejection. However, it has been difficult to remove the dry matter of inks containing a binder resin, especially with conventional cleaning liquids. Also, when the cleaning liquid contains a highly hydrophobic solvent, the cleaning liquid may attack materials constituting the inkjet printer, posing a problem in terms of safety.

[0022] On the other hand, the cleaning liquid according to this embodiment contains an organic solvent, an amphoteric surfactant and a polycarboxylic acid polymer as cleaning components, and water. The above organic solvent has a ClogP value of -1.0 or less. The above amphoteric surfactant has a betaine structure. The above polycarboxylic acid polymer has an average molecular weight of 2000 or more and 50000 or less. The content of the above organic solvent is 10 parts by mass or more, the content of the above polycarboxylic acid polymer is 0.1 parts by mass or more and 1 part by mass or less, and the content of the above water is 30 parts by mass or more. Also, the percentage of the content of the above amphoteric surfactant with respect to the content of the above organic solvent is 0.5% or more and 1.5% or less.

[0023] By including an organic solvent with a ClogP value of -1.0 or less as an organic solvent, high detergency and safety can be ensured as follows. Since the above organic solvent has a ClogP value of -1.0 or less, it has low hydrophobicity, making it difficult to dry the cleaning liquid. Thereby, it is possible to suppress the decrease in detergency due to the drying of the cleaning liquid. Also, because of its low hydrophobicity, the possibility of invading materials constituting an inkjet printer, etc. is low, and safety can be enhanced. Therefore, by including the above organic solvent in the cleaning liquid, the effect of enhancing safety while ensuring high detergency can be obtained.

[0024] Also, by including both the above amphoteric surfactant and the above polycarboxylic acid-based polymer as cleaning components, the cleaning liquid becomes likely to penetrate into the ink dried matter. In order for the cleaning liquid to remove the ink dried matter, it is necessary to penetrate into the ink dried matter, cause a chemical reaction with the ink dried matter, and dissolve or disperse the ink dried matter. That is, the cleaning effect of the cleaning liquid is exerted by the cleaning liquid dissolving the ink dried matter, etc. The cleaning liquid according to the present embodiment can penetrate into the ink dried matter and exhibit a high cleaning effect by including the above cleaning components. Therefore, by including the above cleaning components in the cleaning liquid, the effect of penetrating into the ink dried matter and enhancing the removability of the ink dried matter can be obtained.

[0025] Furthermore, by setting the percentage of the content of the above amphoteric surfactant with respect to the content of the above organic solvent to 0.5% or more and 1.5% or less, both can exert the above actions in a well-balanced manner, and higher removability of the ink dried matter due to the synergistic effect of both can be obtained.

[0026] The cleaning liquid according to the present embodiment can easily penetrate into the ink dried matter by including the above organic solvent and cleaning components. Therefore, the ink dried matter swells and is dissolved by the cleaning liquid according to the present embodiment. Thereby, the ink dried matter can be easily removed by a wiping operation using a rubber blade or the like.

[0027] The cleaning solution according to this embodiment has the high removal properties described above, and is particularly effective in removing dried ink residues that have excellent adhesion to poorly absorbent media. Furthermore, the cleaning solution according to this embodiment has a low possibility of damaging materials that make up an inkjet printer, and is superior to conventional cleaning solutions in terms of safety. In other words, the cleaning solution according to this embodiment can safely and efficiently remove dried ink residues that contain a large amount of binder resin and are difficult to dissolve or disperse.

[0028] As described above, the cleaning solution according to this embodiment can suitably remove dried ink. However, the cleaning solution according to this embodiment can suitably remove not only dried ink but also undried ink.

[0029] Next, we will describe the components that make up the cleaning solution according to this embodiment.

[0030] (Organic solvents) The organic solvent contained in the cleaning solution according to this embodiment has a ClogP value of -1.0 or less. ClogP is a predicted value of the octanol / water partition coefficient logP (more specifically, the 1-octanol / water partition coefficient logP), which is a numerical value indicating the hydrophilicity and hydrophobicity of the compound. The octanol / water partition coefficient logP is the logarithm of the octanol / water partition coefficient. ClogP can be calculated, for example, using "ChemDraw" from PerkinElmer. A larger ClogP value indicates higher hydrophobicity of the compound.

[0031] Examples of organic solvents included in the cleaning solution according to this embodiment include glycol compounds, glycol ether compounds, lactam compounds, nitrogen-containing compounds, acetate compounds, thiodiglycols, glycerin, and dimethyl sulfoxides, all of which have a ClogP value of -1.0 or less.

[0032] Examples of glycol compounds with a ClogP value of -1.0 or less include 1,2-propanediol and 1,3-propanediol.

[0033] Glycol compounds and glycerin are preferred organic solvents, and 1,3-propanediol is more preferred.

[0034] The content of the organic solvent in the cleaning solution according to this embodiment is preferably 5% by mass or more and 70% by mass or less, and more preferably 10% by mass or more and 65% by mass or less, based on the total mass of the cleaning solution.

[0035] (Cleansing ingredients) The cleaning solution according to this embodiment contains a surfactant and a polycarboxylic acid polymer.

[0036] (Surfactants) The surfactant in the cleaning solution according to this embodiment is an amphoteric surfactant having a betaine structure. Betaine refers to an intramolecular salt having a cationic structure (e.g., a quaternary ammonium ion structure) and an anionic structure (e.g., an anionic structure of an acid such as a carboxylic acid) in a single molecule. Examples of amphoteric surfactants having a betaine structure include coconut oil fatty acid amidopropyl dimethyl acetate betaine, coconut oil fatty acid amidopropyl betaine, lauric acid amidopropyl betaine, palm kernel fatty acid amidopropyl betaine, isostearic acid amidopropyl betaine, and linolenic acid amidopropyl. Among the amphoteric surfactants having a betaine structure, amphoteric surfactants having a coconut oil fatty acid amidopropyl dimethyl acetate betaine structure are preferred. Amphoteric surfactants having a betaine structure have excellent properties of adhering to the surface of dried ink and releasing the dried ink, and dispersing the dried ink in the cleaning solution.

[0037] The content of the amphoteric surfactant having a betaine structure in the cleaning solution according to this embodiment is preferably 0.1% to 5% by mass, more preferably 0.3% to 1.5% by mass, and particularly preferably 0.3 parts by mass to 1.0 part by mass, based on the total mass of the cleaning solution. Furthermore, the percentage of the amphoteric surfactant content relative to the content of the organic solvent is preferably 0.5% to 1.5%.

[0038] Furthermore, one type of surfactant may be used alone, or a mixture of two or more surfactants may be used. In addition, the above-mentioned surfactant may be used in combination with other surfactants described below.

[0039] (Other surfactants) The cleaning solution according to this embodiment may contain other surfactants. Examples of other surfactants include cationic surfactants, anionic surfactants, amphoteric surfactants other than those mentioned above, and nonionic surfactants. Nonionic surfactants are preferred among the other surfactants.

[0040] The content of other surfactants in the cleaning solution according to this embodiment is preferably 0.1% to 5% by mass, and more preferably 0.3% to 5% by mass, based on the total mass of the cleaning solution.

[0041] Furthermore, as for other surfactants, one type of surfactant may be used alone, or a mixture of two or more surfactants may be used.

[0042] (Polycarboxylic acid polymers) The polycarboxylic acid polymer in the cleaning solution according to this embodiment is a polycarboxylic acid polymer having an average molecular weight of 2,000 to 50,000. Examples of polycarboxylic acid polymers include polyacrylic acid and its salts, polymaleic acid and its salts, acrylic acid-maleic acid copolymers and their salts, acrylic acid-sulfonic acid monomer copolymers and their salts, acrylic acid-methacrylic acid copolymers and their salts, and the like.

[0043] The polycarboxylic acid polymer in the cleaning solution according to this embodiment has an average molecular weight of 2,000 to 50,000, as described above. The molecular weight is measured, for example, using gel permeation chromatography. When the molecular weight of the polycarboxylic acid polymer is within this range, the cleaning solution containing the polycarboxylic acid polymer easily penetrates the ink-dried material, which is preferable from the viewpoint of the removal of the ink-dried material.

[0044] The content of the polycarboxylic acid polymer in the cleaning solution according to this embodiment is preferably 0.02% by mass or more and 1% by mass or less, more preferably 0.04% by mass or more and 1% by mass or less, and particularly preferably 0.1 parts by mass or more and 1 part by mass or less, based on the total mass of the cleaning solution.

[0045] (water) Examples of the water contained in the cleaning solution according to this embodiment include commercially available purified water and ion-exchanged water. Ion-exchanged water is more preferred as the above water.

[0046] The water content is preferably 20% to 99% by mass, and more preferably 30% to 99% by mass, relative to the total mass of the cleaning solution. When the water content is within this range, for example, the viscosity of the cleaning solution containing the water can be set to a viscosity that is favorable for removing dried ink.

[0047] The cleaning solution according to this embodiment, by containing the above-mentioned organic solvent, cleaning components, and water, easily penetrates the dried ink material, suppresses the decrease in cleaning performance due to the drying of the cleaning solution, and enhances safety by reducing hydrophobicity. Therefore, the cleaning solution according to this embodiment can safely and efficiently remove dried ink material that contains a large amount of binder resin and is difficult to dissolve or disperse.

[0048] (others) The cleaning solution according to this embodiment may further contain known additives (e.g., dissolution stabilizers, drying inhibitors, antioxidants, viscosity modifiers, pH adjusters, and antifungal agents) as needed.

[0049] (Physical properties of the cleaning solution) Next, the physical properties of the cleaning solution according to this embodiment will be described.

[0050] ·Static surface tension The static surface tension of the cleaning solution according to this embodiment is less than 40 mN / m. Specifically, the static surface tension of the cleaning solution at 25°C is preferably 20 mN / m or more and less than 40 mN / m, and more preferably 22 mN / m or more and less than 30 mN / m. When the static surface tension of the cleaning solution is within this range, the wettability of the cleaning solution increases, and the cleaning solution quickly penetrates into gaps between the ink and the nozzle plate, which is preferable from the viewpoint of removing dried ink.

[0051] • Viscosity and pH The viscosity of the cleaning solution according to this embodiment is not particularly limited, but is preferably 1 mPa·s to 10 mPa·s, and more preferably 1 mPa·s to 8 mPa·s. Similarly, the pH of the cleaning solution according to this embodiment is not particularly limited, but is preferably 7 to 14, and more preferably 9 to 10, considering the balance between chemical damage to the inkjet head and cleaning performance.

[0052] (Method for removing dried ink) The method for removing dried ink using the cleaning solution according to this embodiment is not particularly limited, but for example, the dried ink can be removed as follows.

[0053] First, the cleaning solution according to this embodiment is supplied to the ejection surface of the recording head to which dried ink has adhered. Methods for supplying the cleaning solution to the ejection surface include, for example, supplying it using a sponge or sheet impregnated with the cleaning solution, ejecting the cleaning solution by an inkjet method, applying the cleaning solution using a roller, and spraying the cleaning solution. After that, a wiping action is performed on the ejection surface using a wiping blade or the like. This makes it possible to easily remove the dried ink that has adhered to the ejection surface.

[0054] Furthermore, the cleaning solution according to this embodiment can also be used to remove dried ink residue adhering to components of the inkjet recording device other than the recording head.

[0055] [Other embodiments] Although embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the embodiments described above and can be modified in various ways.

[0056] [Examples and Comparative Examples] The following describes examples of the present invention, but the present invention is not limited to these examples.

[0057] (Preparation of cleaning solution) In each example and comparative example, the materials listed in Tables 1 and 2 were placed in beakers in the proportions listed in Tables 1 and 2. The mixture in the beakers was stirred for 30 minutes at a rotation speed of 400 rpm using a stirrer (Shinto Kagaku Co., Ltd. "Three One Motor BL-600") to prepare the washing solutions for each example and comparative example.

[0058] [Table 1]

[0059] [Table 2]

[0060] As shown in Table 1, the cleaning solutions in Examples 1 to 16 contain Amogen CB-H as a surfactant. Amogen CB-H is an amphoteric surfactant containing a coconut oil fatty acid amidopropyl dimethyl acetate betaine structure. Note that Silface SAG503A and Orphine EXP4300 are both surfactants that do not contain a coconut oil fatty acid amidopropyl dimethyl acetate betaine structure.

[0061] Furthermore, as shown in Table 1, the cleaning solutions for Examples 1 to 16 contain 1,2-propanediol, 1,3-propanediol, or glycerin as an organic solvent, and Aqualic DL-40, Aqualic DL-453, or Aqualic TL-37 as a polycarboxylic acid polymer. The average molecular weight of Aqualic DL-40 is 3500, the average molecular weight of Aqualic DL-453 is 50000, and the average molecular weight of Aqualic TL-37 is 5000, all within the range of 2000 to 50000. The average molecular weight of Aqualic DL-522 is 170000, which is outside the range of 2000 to 50000. In all examples, the content of the organic solvent is 10 parts by mass or more, the content of the polycarboxylic acid polymer is 0.1 parts by mass or more and 1 part by mass or less, the content of water is 30 parts by mass or more, and the percentage of the amphoteric surfactant content relative to the organic solvent content is 0.5% to 1.5%.

[0062] As shown in Table 2, Comparative Example 1 differs from Example 1 in that it does not contain Aqualic DL-40. The mass percentage of deionized water was increased by the same amount as the mass percentage (0.5 mass%) of Aqualic DL-40 in Example 1.

[0063] Comparative Example 2 differs from Example 1 in that it does not contain Amogen CB-H. Furthermore, the mass percentage of deionized water is increased by the same amount as the mass percentage (0.3 mass%) of Amogen CB-H in Example 1.

[0064] Comparative Example 3 differs from Example 1 in that it contains triethylene glycol monobutyl ether as the organic solvent instead of 1,3-propanediol.

[0065] Comparative Example 4 differs from Example 1 in that it contains diethylene glycol monobutyl ether instead of 1,3-propanediol as the organic solvent.

[0066] In Comparative Example 5, the mass percentage of Amogen CB-H is less than in Example 1, and the mass percentage of ion-exchanged water is higher by the same amount (0.2 mass%). As a result, the percentage of amphoteric surfactant content relative to the organic solvent content is 0.33% (rounded to three decimal places), which is outside the range of 0.5% to 1.5%.

[0067] In Comparative Example 6, the mass percentage of Amogen CB-H was higher than in Example 1, and consequently, the mass percentage of ion-exchanged water was lower by the same amount (0.2% by mass). As a result, the percentage of amphoteric surfactant content relative to the organic solvent content was 1.67% (rounded to three decimal places), which is outside the range of 0.5% to 1.5%.

[0068] In Comparative Example 7, the mass percentage of Aqualic DL-40 is less than in Example 1, and by that amount (0.45 mass%), the mass percentage of ion-exchanged water is greater than in Example 1. As a result, the polycarboxylic acid polymer content is 0.05 parts by mass, which is outside the range of 0.1 parts by mass to 1 part by mass.

[0069] In Comparative Example 8, the mass percentage of Aqualic DL-40 is higher than in Example 1, and by that same amount (1.0 mass%), the mass percentage of ion-exchanged water is also higher than in Example 1. As a result, the polycarboxylic acid polymer content is 1.5 parts by mass, which is outside the range of 0.1 parts by mass to 1 part by mass.

[0070] In Comparative Example 9, the mass percentages of 1,3-propanediol and amogen CB-H are lower than in Example 1, and the mass percentage of deionized water is higher by the same amount (25 + 0.25 = 25.25 mass%). As a result, the organic solvent content is 5 parts by mass, which is outside the range of 10 parts by mass or more.

[0071] In Comparative Example 10, 1,2-propanediol was used instead of 1,3-propanediol as the organic solvent. The mass percentage of the organic solvent and the mass percentage of Amogen CB-H were lower than in Example 1, and the mass percentage of deionized water was higher by the same amount (25 + 0.25 = 25.25 mass%). As a result, the organic solvent content was 5 parts by mass, which is outside the range of 10 parts by mass or more.

[0072] In Comparative Example 11, glycerin was used instead of 1,3-propanediol as the organic solvent. The mass percentage of the organic solvent and the mass percentage of Amogen CB-H were lower than in Example 1, and the mass percentage of deionized water was higher by the same amount (25 + 0.25 = 25.25 mass%). As a result, the organic solvent content was 5 parts by mass, which is outside the range of 10 parts by mass or more.

[0073] In Comparative Example 12, the mass percentages of 1,3-propanediol and amogen CB-H are higher than in Example 1, and the mass percentage of deionized water is lower by the same amount (40 + 0.4 = 40.4 mass%). As a result, the water content is 28.5 parts by mass, which is outside the range of 30 parts by mass or more.

[0074] In Comparative Example 13, 1,2-propanediol was used instead of 1,3-propanediol as the organic solvent. The mass percentage of the organic solvent and the mass percentage of Amogen CB-H were higher than in Example 1, and the mass percentage of deionized water was lower by the same amount (40 + 0.4 = 40.4 mass%). As a result, the water content was 28.5 parts by mass, which is outside the range of 30 parts by mass or more.

[0075] In Comparative Example 14, glycerin was used instead of 1,3-propanediol as the organic solvent. The mass percentage of the organic solvent and the mass percentage of Amogen CB-H were higher than in Example 1, and the mass percentage of deionized water was lower by the same amount (40 + 0.4 = 40.4 mass%). As a result, the water content was 28.5 parts by mass, which is outside the range of 30 parts by mass or more.

[0076] Comparative Example 15 uses Aqualic DL-522 instead of Aqualic DL-40 as the polycarboxylic acid polymer, and the mass percentage of the polycarboxylic acid polymer is higher than in Example 1, and the mass percentage of ion-exchanged water is lower by the same amount (0.17 mass%).

[0077] (Preparation of ink-dried materials) 7 parts by mass of Bk dispersion, 5 parts by mass of urethane-based binder resin, 0.5 parts by mass of acetylene glycol-based surfactant, 10 parts by mass of glycol ether, 3 parts by mass of polyhydric alcohol, and 74.5 parts by mass of water were placed in a beaker. The mixture in the beaker was stirred using a stirrer (Shinto Kagaku Co., Ltd. "Three One Motor BL-600") to obtain ink (I-1). Similarly, 7 parts by mass of Bk dispersion, 5 parts by mass of styrene-acrylic-based binder resin, 0.5 parts by mass of acetylene glycol-based surfactant, 10 parts by mass of glycol ether, 3 parts by mass of polyhydric alcohol, and 74.5 parts by mass of water were placed in a beaker and mixed using a stirrer to obtain ink (I-2). Using these inks (I-1) and (I-2), multiple ink droplets with a diameter of 20 μm were attached to the nozzle plate of an inkjet head KJ4B-1200 manufactured by Kyocera Document Solutions Inc. Ink-dried material was prepared by drying the attached ink droplets at a temperature of 30°C for 72 hours.

[0078] (Method for evaluating the ink removal performance of cleaning solutions) In each example and comparative example, 0.1 ml of cleaning solution was dropped using a pipette onto an area of ​​the inkjet head on a thin stainless steel plate where no ink droplets were present. The inkjet head was then wiped twice with a rubber blade at 20-second intervals. The linear pressure was kept constant at 10 N / m and the wipe speed at 20 mm / s.

[0079] The ink removal performance of each cleaning solution was evaluated by the ink droplet removal rate. The removal rate was defined as the ratio of the number of ink droplets removed after the wiping operation to the number of ink droplets formed in the area where the rubber blade made contact during the wiping operation.

[0080] (Measurement of static surface tension) The static surface tension of each cleaning solution was measured using a surface tension meter (Kyowa Interface Science Co., Ltd. "Automatic Surface Tension Meter DY-300") in accordance with the Wilhelmy method (plate method). In all of Examples 1 to 16, the static surface tension at 25°C was between 23 and 36, and within the range of 20 mN / m to less than 40 mN / m.

[0081] (Calculation of ClogP value) The ClogP values ​​of the organic solvents used were calculated using PerkinElmer's "ChemDraw" software. The results of the ClogP calculations are as follows:

[0082] [Table 3]

[0083] As shown in Tables 1 and 3, the organic solvents contained in the cleaning solutions of Examples 1 to 16 all had a ClogP value of -1.0 or less.

[0084] (Evaluation of the Examples and Comparative Examples) As shown in Table 1, the cleaning solutions from Examples 1 to 16 all showed a high removal rate of 80% or more. This is thought to be because the appropriate amount of suitable organic solvent, suitable cleaning component, and water allowed for a synergistic effect that resulted in higher removal efficiency of dried ink.

[0085] As shown in Table 2, the cleaning solution related to Comparative Example 1 had a low removal rate of 20%. This is thought to be because it did not contain a polycarboxylic acid polymer with an average molecular weight of 2000 to 50000, and therefore did not penetrate the ink-dried material, thus failing to provide the effect of improving the removal of the ink-dried material.

[0086] As shown in Table 2, the cleaning solution related to Comparative Example 2 had a low removal rate of 10%. This is thought to be because, since it did not contain an amphoteric surfactant with a betaine structure, it remained highly wettable and could not sufficiently penetrate into the gaps between the dried ink and the nozzle plate, resulting in insufficient removal of the dried ink.

[0087] As shown in Table 2, the cleaning solution related to Comparative Example 3 had a low removal rate of 25%. This is thought to be because, since it did not contain an organic solvent with a ClogP value of -1.0 or less, the cleaning components were incorporated into the organic solvent, and sufficient removal of dried ink was not achieved.

[0088] As shown in Table 2, the cleaning solution related to Comparative Example 4 had a low removal rate of 30%. This is thought to be because, since it did not contain an organic solvent with a ClogP value of -1.0 or less, the cleaning components were incorporated into the organic solvent, and sufficient removal of dried ink was not achieved.

[0089] As shown in Table 2, the cleaning solution related to Comparative Example 5 had a slightly lower removal rate of 75%. This is thought to be because the percentage of amphoteric surfactants having a betaine structure relative to the content of organic solvents with a ClogP value of -1.0 or less was outside the range of 0.5% to 1.5%, so the two could not exert the above effects in a balanced manner, and a higher removal rate of dried ink due to the synergistic effect of the two could not be obtained.

[0090] As shown in Table 2, the cleaning solution related to Comparative Example 6 had a slightly lower removal rate of 75%. This is thought to be because the percentage of amphoteric surfactants having a betaine structure relative to the content of organic solvents with a ClogP value of -1.0 or less was outside the range of 0.5% to 1.5%, so the two could not exert the above effects in a balanced manner, and a higher removal rate of dried ink due to the synergistic effect of the two could not be obtained.

[0091] As shown in Table 2, the cleaning solution related to Comparative Example 7 had a slightly low removal rate of 65%. This is thought to be because the content of polycarboxylic acid polymers having an average molecular weight of 2000 to 50000 was outside the range of 0.1 parts by mass to 1 part by mass, and therefore the effect of penetrating the ink-dried material and improving the removal of the ink-dried material was not sufficiently obtained.

[0092] As shown in Table 2, the cleaning solution related to Comparative Example 8 had a slightly low removal rate of 70%. This is thought to be because the content of polycarboxylic acid polymers having an average molecular weight of 2000 to 50000 was outside the range of 0.1 parts by mass to 1 part by mass, and therefore the effect of penetrating the ink-dried material and improving the removal of the ink-dried material was not sufficiently obtained.

[0093] As shown in Table 2, the cleaning solution related to Comparative Example 9 had a slightly lower removal rate of 70%. This is thought to be because the content of organic solvents with a ClogP value of -1.0 or less was outside the range of 10 parts by mass or more, and therefore the decrease in cleaning performance due to drying of the cleaning solution could not be suppressed.

[0094] As shown in Table 2, the cleaning solution related to Comparative Example 10 had a slightly low removal rate of 60%. This is thought to be because the content of organic solvents with a ClogP value of -1.0 or less was outside the range of 10 parts by mass or more, and therefore the decrease in cleaning performance due to drying of the cleaning solution could not be suppressed.

[0095] As shown in Table 2, the cleaning solution related to Comparative Example 11 had a slightly low removal rate of 55%. This is thought to be because the content of organic solvents with a ClogP value of -1.0 or less was outside the range of 10 parts by mass or more, and therefore the decrease in cleaning performance due to drying of the cleaning solution could not be suppressed.

[0096] As shown in Table 2, the cleaning solution used in Comparative Example 12 had a low removal rate of 30%. This is thought to be because the water content was outside the range of 30 parts by mass or more, resulting in a high viscosity of the cleaning solution, which prevented the cleaning solution from sufficiently penetrating the ink-dried material, and thus insufficient removal of the ink-dried material was achieved.

[0097] As shown in Table 2, the cleaning solution related to Comparative Example 13 had a low removal rate of 20%. This is thought to be because the water content was outside the range of 30 parts by mass or more, resulting in a high viscosity of the cleaning solution, which prevented the cleaning solution from sufficiently penetrating the ink-dried material, and thus insufficient removal of the ink-dried material was achieved.

[0098] As shown in Table 2, the cleaning solution related to Comparative Example 14 had a low removal rate of 0%. This is thought to be because the water content was outside the range of 30 parts by mass or more, resulting in a high viscosity of the cleaning solution, which prevented the cleaning solution from sufficiently penetrating the ink-dried material, and thus insufficient removal of the ink-dried material was achieved.

[0099] As shown in Table 2, the cleaning solution related to Comparative Example 15 had a slightly low removal rate of 75%. This is thought to be because it did not contain a polycarboxylic acid polymer with an average molecular weight of 2000 to 50000, and therefore did not sufficiently penetrate the ink-dried material and improve its removal efficiency.

Claims

1. Organic solvents with a ClogP value of -1.0 or less, amphoteric surfactant having a betaine structure, A polycarboxylic acid polymer having an average molecular weight of 2000 to 50000, Water and Includes, The content of the organic solvent is 10 parts by mass or more, the content of the polycarboxylic acid polymer is 0.1 parts by mass or more and 1 part by mass or less, and the content of water is 30 parts by mass or more. The percentage of the content of the amphoteric surfactant relative to the content of the organic solvent is 0.5% or more and 1.5% or less. Cleaning solution.

2. A cleaning solution according to claim 1, The viscosity at 25°C is 8.0 mPa·s or less. Cleaning solution.

3. A cleaning solution according to claim 1 or 2, The static surface tension is 20 mN / m or more and less than 40 mN / m. Cleaning solution.

4. A cleaning solution according to claim 1 or 2, The organic solvent is selected from the group consisting of 1,2-propanediol, 1,3-propanediol, and glycerin. Cleaning solution.

5. The cleaning solution according to claim 4, The organic solvent is 1,3-propanediol. Cleaning solution.

6. A cleaning solution according to claim 1 or 2, The aforementioned amphoteric surfactant is an amphoteric surfactant having a coconut oil fatty acid amidopropyl dimethyl acetate betaine structure. Cleaning solution.

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