Recording head filling liquid, ink set, and recording head inspection method

Abstract

To provide a recording head filling liquid that facilitates introduction into an ink flow channel within a recording head, effectively inhibits agglomeration of pigment components of inkjet ink within the recording head, and enables stable purging.SOLUTION: A recording head filling liquid contains a specific moisturizing agent, a monovalent alkali, and water. The specific moisturizing agent is a compound represented by general formula (1). The specific moisturizing agent has a percentage content of 19.00 mass% or more and 42.00 mass% or less. The recording head filling liquid has a static surface tension at 25°C of 20.0 mN / m or more and 29.0 mN / m or less. In general formula (1), a, b, and c each represent, independently of one another, an integer of 1 or greater, and a+b+c is 4 or greater and 20 or smaller.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a printhead filling fluid, an ink set, and a method for inspecting a printhead. [Background technology]

[0002] An inkjet recording device is equipped with a recording head that ejects inkjet ink. Generally, the recording head is thoroughly inspected for ejection performance before being shipped. To inspect the ejection performance of the recording head, an ejection test is performed by actually filling the recording head with inkjet ink.

[0003] However, if the recording head is shipped with ink-jet ink remaining in the ink flow path, the solvent of the ink-jet ink may evaporate during transportation or storage, causing the solids (particularly the pigment) of the ink-jet ink to aggregate and produce aggregates. The above-mentioned aggregates may cause ejection defects in the recording head after shipment.

[0004] Therefore, in some cases, recording head manufacturers ship recording heads filled with a solution that does not contain pigment components (hereinafter, sometimes referred to as recording head filling fluid). The recording head filling fluid is required to be able to be purged from a recording head that has been left unused for a while.

[0005] Furthermore, the print head filler fluid enters the ink flow paths of the print head and dilutes the ink-jet ink remaining in the ink flow paths, so the print head filler fluid is required to be easily introduced into the ink flow paths in the print head.

[0006] As the recording head filling liquid, for example, a recording head filling liquid containing silicone oil has been proposed (Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-227729 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, Patent Document 1 cannot meet the above-mentioned requirements.

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to provide a filler liquid for a recording head which is easily introduced into an ink flow path in a recording head, which can effectively suppress aggregation of pigment components in an ink-jet ink in the recording head, and which can be purged stably. Another object of the present invention is to provide an ink set and a method for inspecting a recording head which use the above filler liquid for a recording head. [Means for solving the problem]

[0010] The recording head filling liquid according to the present invention contains a specific moisturizing agent, a monovalent alkali, and water. The specific moisturizing agent is a compound represented by the following general formula (1). The content of the specific moisturizing agent is 19.00% by mass or more and 42.00% by mass or less. The static surface tension of the recording head filling liquid at 25° C. is 20.0 mN / m or more and 29.0 mN / m or less.

[0011] [ka]

[0012] In the general formula (1), a, b, and c each independently represent an integer of 1 or more, and a+b+c is 4 or more and 20 or less.

[0013] The ink set according to the present invention comprises an inkjet ink and the above-mentioned recording head filling liquid.

[0014] The method for inspecting a recording head according to the present invention is a method for inspecting a recording head using the ink set described above, and includes an inspection step of inspecting the ejection performance of the recording head, and a filling step of filling the recording head with the recording head filler liquid after the inspection step. In the inspection step, the ejection performance of the recording head is inspected by ejecting the inkjet ink from the recording head. Effect of the Invention

[0015] According to the print head filling liquid and ink set of the present invention, the print head filling liquid can be easily introduced into the ink flow path in the print head, the pigment components in the inkjet ink can be effectively prevented from coagulating in the print head, and the print head filling liquid can be stably purged. According to the print head inspection method of the present invention, the occurrence of ejection defects in the inspected print head can be prevented. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described. In the following, the volume median diameter (D 50 ) is a value measured using a dynamic light scattering particle size distribution analyzer (for example, Zetasizer (registered trademark) Nano ZS manufactured by Malvern Instruments) unless otherwise specified.

[0017] In the following, unless otherwise specified, the measured acid value is a value measured according to "JIS (Japanese Industrial Standards) K0070-1992". Furthermore, unless otherwise specified, the measured mass average molecular weight (Mw) is a value measured using gel permeation chromatography.

[0018] In the following, unless otherwise specified, the measured value of static surface tension is a value measured at 25°C according to the Wilhelmy method (plate method) using a surface tension meter (for example, "Automatic Surface Tensiometer DY-300" manufactured by Kyowa Interface Science Co., Ltd.).

[0019] In the following, unless otherwise specified, the measured viscosity values ​​are values ​​measured at 25°C using a falling ball viscometer (for example, "Lovis2000" manufactured by Anton Paar).

[0020] In the following, unless otherwise specified, the measured pH value is a value measured at 25° C. using a pH meter (for example, “D-51” manufactured by Horiba, Ltd.).

[0021] In this specification, acrylic and methacrylic may be collectively referred to as "(meth)acrylic". Each component described in this specification may be used alone or in combination of two or more. "At least one of A and B" means "A and / or B".

[0022] [First embodiment: recording head filling liquid] The recording head filling liquid (hereinafter, sometimes simply referred to as filling liquid) according to the first embodiment of the present invention will be described below. The filling liquid according to this embodiment contains a specific moisturizing agent, a monovalent alkali, and water. The specific moisturizing agent is a compound represented by the following general formula (1). The content ratio of the specific moisturizing agent is 19.00 mass % or more and 42.00 mass % or less. The static surface tension of the filling liquid according to this embodiment at 25°C is 20.0 mN / m or more and 29.0 mN / m or less.

[0023] [ka]

[0024] In the general formula (1), a, b, and c each independently represent an integer of 1 or more, and a+b+c is 4 or more and 20 or less.

[0025] The filling liquid according to the present embodiment is used by filling a recording head in which inkjet ink (hereinafter sometimes simply referred to as ink) remains. Specifically, the filling liquid according to the present embodiment is used by filling a recording head when the recording head is shipped, when the recording head is stored for a long period of time, or when the recording head is transported. The filling liquid according to the present embodiment is suitable as a filling liquid used in the ink set according to the second embodiment, or the method for inspecting a recording head according to the third embodiment.

[0026] The filler liquid according to the present embodiment, having the above-mentioned configuration, is easily introduced into the ink flow path in the recording head, and can effectively suppress aggregation of the pigment components in the ink in the recording head, and can be purged stably. The reason why the filler liquid according to the present embodiment exhibits the above-mentioned effects is presumed to be as follows.

[0027] The filling liquid according to the present embodiment contains a specific moisturizing agent, a monovalent alkali, and water. The filling liquid according to the present embodiment enters the ink flow path of the recording head and dilutes the ink remaining in the ink flow path. This makes it difficult for the solid content of the ink remaining in the ink flow path to aggregate. In particular, the filling liquid according to the present embodiment contains a specific moisturizing agent represented by general formula (1). The specific moisturizing agent in which a+b+c in general formula (1) is 4 or more has a low viscosity, and the pressure (purge pressure) of the recording head when purging the filling liquid according to the present embodiment does not increase. Therefore, the filling liquid according to the present embodiment can be stably purged from the recording head even after the recording head is left standing. In addition, although the reason is unclear, according to the study by the inventors of the present application, a moisturizing agent in which a+b+c in general formula (1) is more than 20 cannot sufficiently suppress the aggregation of the pigment component in the ink in the recording head. The filling liquid according to this embodiment can sufficiently suppress aggregation of the pigment components in the ink in the recording head and can stably purge the ink by containing a specific humectant in general formula (1) where a+b+c is 4 or more and 20 or less. In particular, the filling liquid according to this embodiment can effectively suppress aggregation of the pigment components in the ink in the recording head by containing the specific humectant represented by general formula (1) in a proportion of 19.00% by mass or more and 42.00% by mass or less.

[0028] Furthermore, the filler liquid according to the present embodiment contains a monovalent alkali, which can effectively suppress aggregation of the pigment components in the ink, and can maintain high dispersion stability of the pigment components. According to the studies of the present inventors, a filler that does not contain an alkali cannot sufficiently suppress aggregation of the pigment components in the ink in the recording head. Furthermore, a filler liquid that contains a divalent alkali instead of a monovalent alkali cannot ensure dispersion stability of the pigment components, and cannot sufficiently suppress aggregation of the pigment components in the ink in the recording head.

[0029] The filling liquid according to the present embodiment has a static surface tension of 20.0 mN / m or more and 29.0 mN / m or less at 25° C. The filling liquid according to the present embodiment has a low static surface tension and is easily introduced into the ink flow path in the recording head. The filling liquid according to the present embodiment will be described in more detail below.

[0030] The static surface tension of the filling liquid according to the present embodiment at 25° C. may be 20.0 mN / m or more and 29.0 mN / m or less, preferably 27.0 mN / m or more and 29.0 mN / m or less, and more preferably 28.0 mN / m or more and 29.0 mN / m or less. If the static surface tension of the filling liquid according to the present embodiment at 25° C. is 27.0 mN / m or more and 29.0 mN / m or less, the filling liquid according to the present embodiment can be more reliably introduced into the ink flow path in the recording head.

[0031] The pH of the filler liquid according to the present embodiment is preferably from 7 to 10, and more preferably from 8 to 9. By setting the pH of the filler liquid according to the present embodiment to from 7 to 10, the filler liquid according to the present embodiment can more effectively suppress aggregation of the pigment components in the ink inside the recording head.

[0032] (Specific moisturizer) The specific moisturizing agent according to the present embodiment is a compound represented by the above-mentioned general formula (I). In the general formula (I), a+b+c may be an integer of 4 or more and 20 or less, but preferably represents an integer of 6 or more and 18 or less, more preferably represents an integer of 6 or more and 15 or less, and even more preferably represents an integer of 6 or more and 9 or less. The filling liquid according to the present embodiment contains a specific moisturizing agent having a low viscosity (for example, a specific moisturizing agent having a viscosity of 450 mPa·s or less at 25° C.), so that the filling liquid according to the present embodiment can be stably purged from the recording head even after the recording head is left standing. In addition, in the general formula (I), if a+b+c is an integer of 4 or more and 20 or less, the dispersion stability of the pigment component in the ink can be kept high, and the pigment component in the ink can be effectively suppressed from aggregating in the recording head. In addition, in the general formula (I), by making a+b+c 6 or more and 18 or less, the pigment component in the ink can be more effectively suppressed from aggregating in the recording head.

[0033] The viscosity of the specific moisturizer at 25°C is preferably 260 mPa·s or more and 450 mPa·s or less, and more preferably 330 mPa·s or more and 450 mPa·s or less. By making the viscosity of the specific moisturizer 260 mPa·s or more and 450 mPa·s or less, aggregation of the pigment components in the ink inside the recording head can be effectively suppressed. In addition, the filling liquid according to this embodiment can be stably purged from the recording head after the recording head is left unused.

[0034] The content of the specific moisturizing agent in the filling liquid according to the present embodiment may be 19.00% by mass or more and 42.00% by mass or less, but is preferably 27.00% by mass or more and 38.00% by mass or less, and more preferably 27.00% by mass or more and 33.00% by mass or less. By setting the content of the specific moisturizing agent in the filling liquid according to the present embodiment to 19.00% by mass or more and 42.00% by mass or less, it is possible to effectively suppress the aggregation of the pigment component in the ink in the recording head. In addition, by setting the content of the specific moisturizing agent in the filling liquid according to the present embodiment to 27.00% by mass or more and 38.00% by mass or less, it is possible to more effectively suppress the aggregation of the pigment component in the ink in the recording head.

[0035] (Monovalent alkali) Examples of monovalent alkalis include sodium compounds, potassium compounds, lithium compounds, cesium compounds, and rubidium compounds. Examples of these monovalent alkalis include hydroxides, carbonates, and hydrogen carbonates with an alkali metal ion as the cation. Examples of sodium compounds include sodium hydroxide (NaOH), sodium carbonate (Na 2 CO 3 ), sodium bicarbonate (NaHCO 3 ) Examples of potassium compounds include potassium hydroxide (KOH), potassium carbonate (K 2 CO 3 ), potassium bicarbonate (KHCO 3 Examples of lithium compounds include lithium hydroxide (LiOH), lithium carbonate (Li 2 CO 3 ), lithium bicarbonate (LiHCO 3 Examples of cesium compounds include cesium hydroxide (CsOH) and cesium carbonate (Cs 2 CO 3 ), Cesium bicarbonate (CsHCO 3 Examples of rubidium compounds include rubidium hydroxide (RbOH), rubidium carbonate (Rb 2 CO 3 ), rubidium bicarbonate (RbHCO3 ) Monovalent alkali dissolves in water, dissociates into an alkali metal ion and a counter ion, and exhibits basicity (pH ≧ 7). As the monovalent alkali, hydroxides are preferred, and among them, sodium hydroxide is particularly preferred.

[0036] The filling liquid according to the present embodiment contains a monovalent alkali, which effectively suppresses aggregation of the pigment component in the ink, and maintains high dispersion stability of the pigment component. In particular, the filling liquid according to the present embodiment contains the specific moisturizing agent described above as a moisturizing agent, which provides high dispersion stability of the pigment component in the ink. Therefore, the filling liquid according to the present embodiment has a high degree of freedom in the selection of anions that can be used as counter ions of the alkali metal ions.

[0037] (water) Water is a main solvent of the filling liquid according to the present embodiment. The water content in the filling liquid according to the present embodiment is, for example, preferably 45.00 mass % or more and 80.00 mass % or less, and more preferably 60.00 mass % or more and 75.00 mass % or less.

[0038] (Surfactant) The filling liquid according to the present embodiment preferably further contains a surfactant. The surfactant reduces the static surface tension of the filler according to the present embodiment at 25° C., and makes it easier for the filling liquid according to the present embodiment to be introduced into the ink flow path in the recording head. The surfactant in the filler according to the present embodiment is preferably a nonionic surfactant. The nonionic surfactant contained in the filling liquid according to the present embodiment is preferably an acetylene glycol surfactant. The acetylene glycol surfactant has the effect of optimizing the wettability of the filling liquid according to the present embodiment to stainless steel material, which is often used as the material for the flow path of the recording head. Therefore, by containing an acetylene glycol surfactant, the filling liquid according to the present embodiment becomes more easily introduced into the ink flow path in the recording head. As an acetylene glycol surfactant contained in the filling liquid according to the present embodiment, for example, "Olfine (registered trademark) E1010" (manufactured by Nissin Chemical Industry Co., Ltd., an ethylene oxide adduct of acetylene glycol) can be mentioned.

[0039] The surfactant content in the filling liquid according to the present embodiment is preferably 0.05% by mass or more and 0.10% by mass or less, and more preferably 0.05% by mass or more and 0.07% by mass or less. By making the surfactant content in the filling liquid according to the present embodiment 0.05% by mass or more, the filling liquid according to the present embodiment can be more easily introduced into the ink flow path in the recording head, and the pigment component in the ink can be more effectively prevented from coagulating in the recording head. On the other hand, a large amount of surfactant may actually reduce the dispersion stability of the pigment component in the ink. Therefore, by making the surfactant content in the filling liquid according to the present embodiment 0.10% by mass or less, the filling liquid according to the present embodiment can more effectively prevent the pigment component in the ink from coagulating in the recording head.

[0040] (Other ingredients) The filling liquid according to the present embodiment may further contain known additives (for example, a dissolution stabilizer, a drying inhibitor, an antioxidant, a viscosity adjuster, a pH adjuster, and an anti-mold agent) as necessary.

[0041] (Preferred composition) The filling liquid according to the present embodiment preferably has any one of compositions 1 to 13 shown in Table 1 below. In Table 1 below, "ratio" indicates a preferred numerical range of the content ratio [mass %]. For example, "27.00-33.00", which is the ratio of the specific moisturizing agent in composition 1, indicates that the specific moisturizing agent is contained in an amount of 27.00 mass % or more and 33.00 mass % or less. The types of specific moisturizing agents "M-2", "M-3", "M-4" and "M-5" respectively indicate the specific moisturizing agents (M-2), (M-3), (M-4) and (M-5) used in the examples.

[0042] [Table 1]

[0043] (Method of manufacturing the filling liquid) The filling liquid according to the present embodiment can be produced, for example, by mixing a specific moisturizing agent, a monovalent alkali, water, and a component (for example, a surfactant) that is added as required. The specific moisturizing agent can be produced by reacting polyethylene glycol with glycerin at 180 to 220°C to etherify the mixture.

[0044] [Second embodiment: ink set] An ink set according to a second embodiment of the present invention will be described below. The ink set according to this embodiment includes ink and the filler liquid according to the first embodiment. Details of the filler liquid have already been described in the first embodiment, so they will be omitted.

[0045] The ink set according to this embodiment uses the filling liquid according to the first embodiment as the filling liquid, and therefore the filling liquid can be easily introduced into the ink flow path inside the recording head, effectively preventing the pigment components in the ink from agglomerating inside the recording head, and can stably purge the filling liquid.

[0046] [ink] The ink preferably contains a pigment, a pigment-coated resin, and water. In the ink, the pigment forms, for example, pigment particles together with the pigment-coated resin. The pigment particles are present in a dispersed state in a solvent. From the viewpoint of optimizing the color density, hue, or stability of the ink, the D of the pigment particles is preferably adjusted. 50 The thickness is preferably 30 nm or more and 250 nm or less, and more preferably 70 nm or more and 130 nm or less.

[0047] (Pigments) Examples of pigments contained in the ink include yellow pigments, orange pigments, red pigments, blue pigments, purple pigments, and black pigments. Examples of yellow pigments include CI Pigment Yellow (74, 93, 95, 109, 110, 120, 128, 138, 139, 151, 154, 155, 173, 180, 185, and 193). Examples of orange pigments include CI Pigment Orange (34, 36, 43, 61, 63, and 71). Examples of red pigments include CI Pigment Red (122 and 202). Examples of blue pigments include CI Pigment Blue (15, more specifically 15:3). Examples of purple pigments include CI Pigment Violet (19, 23, and 33). Examples of black pigments include CI Pigment Black (7).

[0048] In the ink, the pigment content is preferably 2.00% by mass or more and 15.00% by mass or less, and more preferably 5.00% by mass or more and 10.00% by mass or less. By making the pigment content 2.00% by mass or more, it becomes easier to form an image having a desired image density. In addition, by making the pigment content 15.00% by mass or less, the fluidity of the ink can be ensured.

[0049] (pigment coated resin) The pigment coating resin is a resin that is soluble in the ink. A part of the pigment coating resin is present, for example, on the surface of the pigment particle to impart dispersibility to the pigment particle. A part of the pigment coating resin is present, for example, in a dissolved state in the ink.

[0050] Examples of pigment coating resins include copolymers of at least one monomer selected from the group consisting of (meth)acrylic acid alkyl esters, styrene, and vinyl naphthalene, and at least one monomer selected from the group consisting of (meth)acrylic acid and maleic acid.

[0051] As the pigment coating resin, styrene-(meth)acrylic resin is preferred. The styrene-(meth)acrylic resin has a repeating unit derived from at least one monomer selected from among (meth)acrylic acid alkyl esters and (meth)acrylic acid, and a styrene unit. As the (meth)acrylic acid alkyl esters, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate are listed. As the styrene-(meth)acrylic resin, a copolymer (X) of styrene, methyl methacrylate, methacrylic acid, and butyl acrylate is preferred. The copolymer (X) is preferably neutralized with an equal amount of a basic compound (e.g., potassium hydroxide or sodium hydroxide).

[0052] In the total repeating units contained in the copolymer (X), the content of repeating units derived from styrene is preferably 10.00% by mass or more and 20.00% by mass or less. In the total repeating units contained in the copolymer (X), the content of repeating units derived from methyl methacrylate is preferably 10.00% by mass or more and 20.00% by mass or less. In the total repeating units contained in the copolymer (X), the content of repeating units derived from methacrylic acid is preferably 35.00% by mass or more and 45.00% by mass or less. In the total repeating units contained in the copolymer (X), the content of repeating units derived from butyl acrylate is preferably 25.00% by mass or more and 35.00% by mass or less.

[0053] In the ink, the content of the pigment coating resin is preferably 0.70% by mass to 6.00% by mass, and more preferably 2.00% by mass to 4.00% by mass. By setting the content of the pigment coating resin to 0.70% by mass to 6.00% by mass, it is possible to prevent the ink from clogging the nozzles.

[0054] The acid value of the pigment coating resin is preferably from 30 mgKOH / g to 300 mgKOH / g, and more preferably from 50 mgKOH / g to 150 mgKOH / g. By setting the acid value of the pigment coating resin to be from 30 mgKOH / g to 300 mgKOH / g, it is possible to optimize the storage stability of the ink while optimizing the dispersibility of the pigment.

[0055] The acid value of the pigment coating resin can be adjusted by changing the amount of monomer used in synthesizing the pigment coating resin. For example, the acid value of the pigment coating resin can be increased by using a monomer (more specifically, acrylic acid, methacrylic acid, etc.) having an acidic functional group (e.g., a carboxyl group) in synthesizing the pigment coating resin.

[0056] The Mw of the pigment coating resin is, for example, from 10,000 to 50,000. By setting the Mw of the pigment coating resin to from 10,000 to 50,000, it is possible to suppress an increase in the viscosity of the ink while achieving a desired image density of the image formed by the ink.

[0057] The Mw of the pigment coating resin can be adjusted by changing the polymerization conditions for the pigment coating resin (more specifically, the amount of polymerization initiator used, polymerization temperature, polymerization time, etc.).

[0058] In the polymerization of the pigment-coated resin, the amount of the polymerization initiator used is preferably 0.001 to 5 moles, more preferably 0.01 to 2 moles, per mole of the monomer mixture. In the polymerization of the pigment-coated resin, for example, the polymerization temperature can be 50° C. to 70° C., and the polymerization time can be 10 to 24 hours. The polymerized pigment-coated resin may be used as it is as a raw material for the ink, or may be neutralized with an equivalent amount of a basic compound before use as a raw material for the ink. The basic compound is preferably a hydroxide of an alkali metal ion (e.g., NaOH).

[0059] (aqueous medium) The aqueous medium contained in the ink is a medium containing water. The aqueous medium may function as a solvent or as a dispersion medium. Specific examples of the aqueous medium include aqueous media containing water and a water-soluble organic solvent.

[0060] The content of the aqueous medium in the ink is preferably from 30.00% by mass to 95.00% by mass, and more preferably from 70.00% by mass to 95.00% by mass.

[0061] (water) Water is the main solvent of the ink. The content of water in the ink is, for example, preferably from 20.00% by mass to 90.00% by mass, and more preferably from 50.00% by mass to 80.00% by mass.

[0062] (Water-soluble organic solvent) The ink preferably further contains a water-soluble organic solvent, such as a glycol compound, a glycol ether compound, a lactam compound, a nitrogen-containing compound, an acetate compound, thiodiglycol, glycerin, or dimethyl sulfoxide.

[0063] Examples of glycol compounds include ethylene glycol, 1,3-propanediol, propylene glycol, 1,5-pentanediol, 1,2-octanediol, 1,8-octanediol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, and tetraethylene glycol.

[0064] Examples of glycol ether compounds include diethylene glycol diethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether and propylene glycol monomethyl ether.

[0065] Lactam compounds include, for example, 2-pyrrolidone and N-methyl-2-pyrrolidone.

[0066] Examples of nitrogen-containing compounds include 1,3-dimethylimidazolidinone, formamide, and dimethylformamide.

[0067] An example of the acetate compound is diethylene glycol monoethyl ether acetate.

[0068] The water-soluble organic solvent in the ink is preferably triethylene glycol monobutyl ether, 2-pyrrolidone or glycerin.

[0069] The content of the water-soluble organic solvent in the ink is preferably from 10.00% to 80.00% by mass, and more preferably from 20.00% to 40.00% by mass. By setting the content of the water-soluble organic solvent to be from 10.00% to 80.00% by mass, the ejection stability of the ink can be optimized.

[0070] (Surfactant) The ink preferably further contains a surfactant. The surfactant optimizes the compatibility and dispersion stability of each component contained in the ink. The surfactant also imparts wettability to the recording medium to the ink. The surfactant in the ink is preferably a nonionic surfactant.

[0071] Examples of the nonionic surfactant in the ink include acetylene glycol surfactants (surfactants containing an acetylene glycol compound), silicone surfactants (surfactants containing a silicone compound), and fluorine surfactants (surfactants containing a fluorine resin or a fluorine-containing compound). Examples of the acetylene glycol surfactant include an ethylene oxide adduct of acetylene glycol and a propylene oxide adduct of acetylene glycol.

[0072] When the ink contains a surfactant, the content of the surfactant in the ink is preferably from 0.10% by mass to 1.00% by mass, and more preferably from 0.20% by mass to 0.40% by mass.

[0073] (Additives) The ink may further contain known additives (for example, a dissolution stabilizer, a drying inhibitor, an antioxidant, a viscosity adjuster, a pH adjuster, and an anti-mold agent) as necessary.

[0074] (Preferred composition) The ink preferably has the composition shown in Table 2 below. In Table 2, the pigment ratio of composition 1, "5.40-6.60", indicates that the pigment is contained in an amount of 5.40% by mass or more and 6.60% by mass or less. The same applies to the other columns. "Resin" indicates pigment-coated resin. "TGBE" indicates triethylene glycol mono-n-butyl ether.

[0075] [Table 2]

[0076] (Ink manufacturing method) The ink can be produced, for example, by mixing a pigment dispersion containing a pigment, an aqueous solvent, and a component (e.g., a surfactant) that is added as needed. The pigment dispersion contains a pigment, a pigment-coated resin, and water. The pigment-coated resin is prepared, for example, by neutralizing an equal amount of an alkali-soluble resin with a basic compound (e.g., sodium hydroxide). The pigment dispersion can be prepared by adding a pigment to an aqueous solution containing a pigment-coated resin, and then performing a dispersion treatment. An example of the device used for the dispersion treatment is a bead mill. In the production of the ink, foreign matter and coarse particles may be removed by a filter (e.g., a filter with a pore size of 5 μm or less) after the dispersion treatment.

[0077] [Third embodiment: recording head inspection method] A method for inspecting a printhead according to a third embodiment of the present invention will be described below. The method for inspecting a printhead according to the present invention is a method for inspecting a printhead using an ink set according to the second embodiment, and includes an inspection step for inspecting the ejection performance of the printhead, and a filling step for filling the printhead after the inspection step with the filling liquid according to the first embodiment. In the inspection step, the ejection performance of the printhead is inspected by ejecting ink using the printhead. The ink set used in the method for inspecting a printhead according to this embodiment can be the same as the ink set described in the second embodiment. Also, the filling liquid used in the method for inspecting a printhead according to this embodiment can be the same as the filling liquid described in the first embodiment. Therefore, a duplicated description will be omitted.

[0078] The printhead inspection method according to the present embodiment uses the ink set according to the second embodiment, and therefore can suppress ejection defects from occurring in the printhead after inspection. The printhead inspection method according to the present embodiment is carried out, for example, before a printhead manufacturer ships the printhead. The printhead inspected by the printhead inspection method according to the present embodiment is not particularly limited, and examples thereof include a piezoelectric printhead and a thermal printhead. The printhead may be, for example, a line printhead.

[0079] [Inspection process] In this process, the ejection performance of the print head is inspected. Specifically, in this process, the ejection performance of the print head is inspected by ejecting ink from the print head. In the print head inspected in this process, ink remains in the ink flow path.

[0080] In this step, the recording head after the inspection step may be washed. The method for washing the recording head is not particularly limited, but for example, a method of filling the recording head with a cleaning liquid and then discharging the cleaning liquid from the recording head can be mentioned. For example, the cleaning liquid can be a cleaning liquid containing water or a water-soluble organic solvent. In this step, even if the recording head is washed, it is difficult to completely remove the ink in the ink flow path.

[0081] [Filling process] In this process, the recording head is filled with the filling liquid according to the first embodiment. After this process, the recording head is, for example, stored in preparation for shipment, or transported for shipment. After the recording head is delivered to the user, the filling liquid according to the first embodiment can be discharged from the recording head by ejecting the filling liquid according to the first embodiment from the recording head. EXAMPLES

[0082] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0083] In the examples, the Mw of the alkali-soluble resin and the surfactant were measured under the following conditions using gel permeation chromatography ("HLC-8020GPC" manufactured by Tosoh Corporation). Calibration curves were prepared using TSKgel standard polystyrenes F-40, F-20, F-4, F-1, A-5000, A-2500, and A-1000 manufactured by Tosoh Corporation, and n-propylbenzene. The pH of the filling solution was measured at 25°C using a pH meter ("D-51" manufactured by Horiba, Ltd.).

[0084] (Conditions for measuring mass average molecular weight) Column: Tosoh Corporation's "TSKgel SuperMultiporeHZ-H" (4.6mm I.D. x 15cm semi-microcolumn) Number of columns: 3 Eluent: Tetrahydrofuran ·Flow rate: 0.35mL / min Sample injection volume: 10μL ·Measurement temperature: 40℃ Detector: IR detector

[0085] [Study 1: Type of moisturizer in filling fluid] First, we investigated the type of humectant to be used in the filling liquid. The preparation methods of each raw material used in the production of the ink are shown below.

[0086] [Preparation of pigment dispersion] A pigment dispersion (D-1) for use in preparing an ink was prepared. In preparing the pigment dispersion (D-1), first, a pigment coating resin solution containing the pigment coating resin (R) and water was prepared.

[0087] (Preparation of pigment coated resin solution) An alkali-soluble resin having a repeating unit derived from methacrylic acid (MAA unit), a repeating unit derived from methyl methacrylate (MMA unit), a repeating unit derived from butyl acrylate (BA unit), and a repeating unit derived from styrene (ST unit) was prepared. This alkali-soluble resin had a mass average molecular weight (Mw) of 20,000 and an acid value of 100 mgKOH / g. The mass ratio of each repeating unit in this alkali-soluble resin was "MAA unit: MMA unit: BA unit: ST unit = 40: 15: 30: 15". This alkali-soluble resin was mixed with an aqueous sodium hydroxide solution (neutralization treatment). The alkali-soluble resin was neutralized with sodium hydroxide (NaOH) by the neutralization treatment. In the neutralization treatment, the amount of the aqueous sodium hydroxide solution used was 1.05 times the theoretical amount of the aqueous sodium hydroxide solution required to neutralize the alkali-soluble resin. In this way, the alkali-soluble resin was neutralized with an equal amount (strictly speaking, 105% amount) of sodium hydroxide, thereby obtaining a pigment-coated resin solution containing the pigment-coated resin (R) (neutralized alkali-soluble resin) and water.

[0088] (Distributed Processing) A magenta pigment (CI Pigment Red 122), the above-mentioned pigment-coated resin solution containing the pigment-coated resin (R), surfactant A, and ion-exchanged water were added to the vessel of a media-type wet disperser (DYNO (registered trademark)-MILL manufactured by WAB) so as to obtain the composition shown in Table 3 below.

[0089] The "water" content in Table 3 below indicates the total content of the ion-exchanged water charged into the vessel and the water contained in the pigment-coated resin solution (more specifically, the water contained in the aqueous sodium hydroxide solution used to neutralize the alkali-soluble resin, and the water generated by the neutralization reaction of the alkali-soluble resin and sodium hydroxide). Surfactant A indicates "Olfine (registered trademark) E1010" (ethylene oxide adduct of acetylene glycol), an acetylene glycol surfactant (nonionic surfactant) manufactured by Nissin Chemical Industry Co., Ltd.

[0090] [Table 3]

[0091] Next, the contents of the vessel were wet-dispersed. Zirconia beads (particle diameter 1.0 mm) were used as media. The amount of media put in was 70 volume % of the capacity of the vessel. The dispersion conditions were a temperature of 10°C and a peripheral speed of 8 m / sec. As a result, a pigment dispersion liquid was obtained.

[0092] The volume median diameter (D 50 ) was measured. Specifically, the obtained pigment dispersion (D-1) was diluted 300 times with ion-exchanged water, and this was used as a measurement sample. The D of the pigment particles in the measurement sample was measured using a dynamic light scattering particle size distribution measurement device ("Zetasizer (registered trademark) Nano ZS" manufactured by Malvern Instruments). 50 The D of the pigment particles in the measurement sample was 50 of the pigment particles contained in the pigment dispersion (D-1) 50 The measurement was carried out 10 times, and the average of the measurement results was taken as the D of the pigment particles. 50 The D of the pigment particles contained in the pigment dispersion (D-1) was adopted. 50 was 100 nm.

[0093] [Ink preparation] [Preparation of Ink (I-1)] Ion-exchanged water was added to a flask equipped with a stirrer ("Three-One Motor (registered trademark) BL-600" manufactured by Shinto Scientific Co., Ltd.). While stirring the contents with the above-mentioned stirrer (stirring speed: 400 rpm), the pigment dispersion liquid (D-1), surfactant B, triethylene glycol mono-n-butyl ether, 2-pyrrolidone, and glycerin were added in this order. The ratio of the amount of each raw material added was as shown in Table 4 below. Surfactant B refers to "Surfynol (registered trademark) 420" (ethylene oxide adduct of acetylene glycol), which is an acetylene glycol surfactant (nonionic surfactant) manufactured by Nissin Chemical Industry Co., Ltd.

[0094] [Table 4]

[0095] [Preparation of filling solution] Filling solutions (F-1) to (F-12) were prepared by the following method. First, the details of the moisturizers (M-1) to (M-6) used in the preparation of filling solutions (F-1) to (F-6) and (F-8) to (F-12) are shown below.

[0096] [Moisturizers (M-1)~(M-6)] The compounds shown in Table 5 below were prepared by the method described below, and these were designated as moisturizers (M-1) to (M-6). The viscosity of moisturizers (M-1) to (M-6) was measured at 25°C using a falling-ball viscometer ("Lovis2000" manufactured by Anton Paar).

[0097] [Preparation of moisturizers (M-2) to (M-6)] Polyethylene glycol and glycerin were reacted at 200°C for etherification. As a result, compounds as moisturizers (M-2) to (M-6) shown in Table 5 were synthesized. It was confirmed by high performance liquid chromatography (HPLC) that the peaks of glycerin and polyethylene glycol of the obtained compounds were 99% or more. In detail, acetonitrile and water were added to the obtained compounds and mixed, and quantitative analysis was performed by HPLC under the following conditions. The moisturizers (M-2) to (M-6) were specific moisturizers. - HPLC equipment: Hitachi High-Tech Science Corporation "HITACHI D-7000" ·Flow rate: 1.0mL / min Detector: ESA Biosciences "Corona CAD Detector"

[0098] (Glycerin analysis conditions) Column: Tosoh Corporation "TSK-GEL Amide-80" (5 μm, 4.6 × 250 mm) Solution: 50% by volume acetonitrile / water (distilled water)

[0099] (Polyethylene glycol analysis conditions) Column: GL Science "Inertsil C8-3" (5 μm, 4.6 × 150 mm) Solution: Acetonitrile / water (distilled water) The volume ratio of acetonitrile in the solution was kept at 45% by volume for 3 minutes, and then a linear gradient was run for 9 minutes from 45% by volume to 98% by volume, after which the volume ratio of acetonitrile was kept at 98% by volume.

[0100] [Preparation of moisturizer (M-1)] A compound as moisturizer (M-1) shown in Table 5 was synthesized in the same manner as moisturizers (M-2) to (M-6), except that ethylene glycol was used instead of polyethylene glycol. The obtained compound was confirmed to have glycerin and ethylene glycol peaks of 99% or more by the same method as moisturizers (M-2) to (M-6).

[0101] [Table 5]

[0102] [Preparation of filling solution (F-1)] A mixed liquid was obtained by mixing 30.00 parts by mass of moisturizer (M-1), 0.06 parts by mass of surfactant C, sodium hydroxide, and ion-exchanged water. The amount of sodium hydroxide added was an amount (trace amount) that made the pH of the mixed liquid 8 to 9. The amount of ion-exchanged water added was an amount that made the total amount of the mixed liquid 100.00 parts by mass. This mixed liquid was used as a filling liquid (F-1). The surfactant C is "Olfine (registered trademark) Exp4300" manufactured by Nissin Chemical Industry Co., Ltd., which is an acetylene glycol surfactant (nonionic surfactant).

[0103] [Preparation of filling solutions (F-2) to (F-7)] Filling solutions (F-2) to (F-12) were prepared in the same manner as filling solution (F-1), except that the types and amounts of each component were changed as shown in Tables 6 to 7.

[0104] The static surface tension of the filling liquids (F-1) to (F-12) was measured at 25° C. according to the Wilhelmy method (plate method) using a surface tension meter ("Automatic Surface Tensiometer DY-300" manufactured by Kyowa Interface Science Co., Ltd.) The measurement results are shown in Tables 6 and 7 below.

[0105] [Table 6]

[0106] [Table 7]

[0107] [Ink set preparation] As shown in the following Tables 8 to 9, the ink (I-1) was combined with any one of the filling liquids (F-1) to (F-12), thereby preparing the ink sets of Examples 1 to 6 and Comparative Examples 1 to 6.

[0108] [Rating 1] The ink sets of Examples 1 to 6 and Comparative Examples 1 to 6 were evaluated by the following methods for the ink aggregation suppression performance (ability to suppress aggregation of pigment components in the ink) in an open system (with evaporation) and a closed system (without evaporation), the purging property of the filling liquid (whether the filling liquid can be purged after being left as it is) and the introduction property of the filling liquid (the tendency of the filling liquid to be easily introduced into the ink flow path in the recording head). The evaluation results are shown in Tables 8 to 9 below.

[0109] (Aggregation suppression performance (open system)) 1.00 parts by mass of the ink (ink (I-1) in Study 1) included in the ink set to be evaluated and 50.00 parts by mass of the filling liquid (any of filling liquids (F-1) to (F-12)) were mixed in a beaker. Next, the beaker containing the mixed liquid was stored in a thermostatic bath at 40°C for one month without sealing (storage treatment). The mixed liquid after the treatment was analyzed for the presence or absence of aggregates with a particle diameter of 3 μm or more using a particle shape image analyzer (Malvern Panatical's "FPIA (registered trademark)-3000").

[0110] In addition, when the recording head is filled with filling liquid after inspecting the recording head, the residual ink and filling liquid are mixed inside the recording head. The mixing ratio of the residual ink and filling liquid (amount of ink / amount of filling liquid) varies depending on the part of the recording head, but is expected to be about 1 / 50 at most. Therefore, the mixing ratio of the ink and filling liquid is set to 1.00 parts by mass of ink: 50.00 parts by mass of filling liquid. In addition, aggregates with a particle diameter of 3 μm or more generated inside the recording head may clog the filter arranged inside the recording head and cause ink discharge failure. Therefore, whether or not aggregates with a particle diameter of 3 μm or more are generated after the storage process is used as the criterion for determining whether or not ink aggregation can be suppressed.

[0111] (Agglomeration suppression performance (closed system)) "Flocculation inhibition performance (closed system)" was evaluated in the same manner as the evaluation of "Flocculation inhibition performance (open system)" above, except for the following changes. When evaluating "Flocculation inhibition performance (closed system)", the beaker was sealed with parafilm during storage processing to prevent evaporation. "Flocculation inhibition performance (closed system)" is evaluated under milder conditions than "Flocculation inhibition performance (open system)" because there is no concentration of pigment components due to evaporation of the solvent.

[0112] (Criteria for evaluating aggregation inhibition performance) A (Pass): In both open and closed systems, no aggregates with particle diameters of 3 μm or more were generated after storage and processing. B (Fail): Aggregates with particle diameters of 3 μm or more were generated in at least one of the open and closed systems after storage treatment.

[0113] (Purgeability) When filling liquid is purged from a recording head that has been left in a high-temperature environment, the water-soluble organic solvent and moisture in the filling liquid inside the recording head evaporate, causing the viscosity of the filling liquid around the nozzles to increase. If the viscosity of the filling liquid increases, the pressure (purge pressure) of the recording head when purging the filling liquid increases, destroying the recording head. According to the study by the present inventors, if the viscosity of the moisturizing agent at 25°C is 450 mPa·s or less, the filling liquid can be purged without problems without increasing the purge pressure, and there is no risk of destroying the recording head. Therefore, whether the viscosity of the moisturizing agent at 25°C is 450 mPa·s or less is used as a criterion for purging the filling liquid (whether the filling liquid can be purged after being left alone).

[0114] (Criteria for judging purgeability) A (Pass): Viscosity of moisturizer at 25°C is 450 mPa s or less B (Fail): Viscosity of moisturizer at 25°C exceeds 450 mPa s (Easy to introduce) First, an unused recording head (Kyocera Corporation's "KJ4B-QA", total number of nozzles: 2656) was filled with ink and discharged. Ink (I-1) was used as the ink. Next, the recording head was washed with pure water and then thoroughly dried. Next, 25 mL of the filling liquid (any of filling liquids (F-1) to (F-12)) included in the ink set to be evaluated was filled into the recording head. Then, the filling liquid was discharged from the recording head by discharging the filling liquid from the recording head. This operation was performed a total of 10 times (total of 250 mL filled). Then, the filling liquid was filled again into the recording head. Then, a nozzle check pattern was printed on a glass plate using the recording head filled with the filling liquid. As a result, a nozzle check pattern was formed on the glass plate using the filling liquid. Next, the above-mentioned glass plate was read by a scanner to count the number of discharge nozzles that could discharge the filling liquid (number of discharge nozzles). The ratio [%] (introduction rate) of the number of ejection nozzles to the total number of nozzles (2656) of the recording head was calculated using the following formula. The introductory property of the filling liquid was judged according to the following criteria. Adoption rate = 100 x number of discharge nozzles / total number of nozzles

[0115] (Criteria for determining introductory properties) A (Pass): Adoption rate is 90% or higher B (Fail): Adoption rate is less than 90%

[0116] [Table 8]

[0117] [Table 9]

[0118] As shown in Tables 3 to 9, if a+b+c in the general formula (1) of the moisturizer is less than 4, the purging property of the filling liquid will be unacceptable. On the other hand, if a+b+c in the general formula (1) of the moisturizer is more than 20, sufficient ink aggregation suppression performance will not be obtained. For this reason, it was found that a+b+c in the general formula (1) of the moisturizer is good when it is 4 or more and 20 or less.

[0119] Furthermore, as shown in Tables 3 to 9, if the content of the specific moisturizer in the filling liquid is less than 19.00% by mass or more than 42.00% by mass, sufficient ink aggregation suppression performance cannot be obtained. Therefore, it was found that the content of the specific moisturizer in the filling liquid is preferably 19.00% by mass or more and 42.00% by mass or less.

[0120] Furthermore, as shown in Tables 5 and 7, it was found that when the filling liquid does not contain an alkali, sufficient ink aggregation suppression performance cannot be obtained.

[0121] [Study 2: Types of alkali in the filling fluid] Next, the type of alkali contained in the filling liquid was examined.

[0122] [Preparation of filling solutions (F-13) to (F-18)] Filling liquids (F-13) to (F-18) were prepared in the same manner as filling liquid (F-1), except that the type and amount of each component was changed as shown in Tables 10 to 11. The static surface tensions of filling liquids (F-13) to (F-18) were measured using the same method as that used to measure the static surface tensions of filling liquids (F-1) to (F-12). The measurement results are shown in Tables 10 to 11 below.

[0123] [Table 10]

[0124] [Table 11]

[0125] [Ink set preparation] As shown in the following Table 12, the ink (I-1) was combined with any one of the filling liquids (F-13) to (F-18), thereby preparing the ink sets of Examples 7 to 11 and Comparative Example 7.

[0126] [Rating 2] The ink sets of Examples 7 to 11 and Comparative Example 7 were evaluated for the ink aggregation suppression performance, the purging performance of the filler liquid, and the introduceability of the filler liquid by the same method as that described in [Evaluation 1]. The evaluation results are shown in Table 12 below.

[0127] [Table 12]

[0128] As shown in Tables 10 to 12, it was found that by containing monovalent alkali in the filler liquids (F-13) to (F-17), aggregates with particle diameters of 3 μm or more were not generated after storage treatment of the mixture of the ink (I-1) and the filler liquids (F-13) to (F-17). On the other hand, since the filler liquid (F-18) contains a divalent alkali, the dispersion stability of the pigment component could not be guaranteed, and the generation of aggregates with particle diameters of 3 μm or more after storage treatment could not be suppressed. Therefore, it was found that by containing a monovalent alkali in the filler liquid, aggregation of the pigment component in the ink can be effectively suppressed, and the dispersion stability of the pigment component can be maintained at a high level.

[0129] [Study 3: Static surface tension of filling liquid] Next, the static surface tension of the filling liquid was examined.

[0130] [Preparation of filling solutions (F-19) to (F-23)] Filling liquids (F-19) to (F-23) were prepared in the same manner as filling liquid (F-1), except that the type and amount of each component was changed as shown in Table 13. The static surface tensions of filling liquids (F-19) to (F-23) were measured using the same method as that used to measure the static surface tensions of filling liquids (F-1) to (F-18). The measurement results are also shown in Table 13 below.

[0131] [Table 13]

[0132] [Ink set preparation] As shown in the following Table 14, the ink (I-1) was combined with any one of the filling liquids (F-19) to (F-23), thereby preparing the ink sets of Examples 12 to 13 and Comparative Examples 8 to 10.

[0133] [Rating 3] For the ink sets of Examples 12 to 13 and Comparative Examples 8 to 10, the ink aggregation suppression performance, the purging property of the filler liquid, and the introduceability of the filler liquid were evaluated by the same method as that described in [Evaluation 1]. The evaluation results are shown in Table 14 below.

[0134] [Table 14]

[0135] As shown in Tables 13 to 14, the filling liquids (F-22) to (F-23) used in Examples 12 to 13 had a static surface tension of 20.0 mN / m or more and 29.0 mN / m or less at 25°C. In the ink sets of Examples 12 to 13, the filling liquid was easily introduced into the ink flow path in the recording head. On the other hand, the filling liquids (F-19) to (F-21) used in Comparative Examples 8 to 10 had a static surface tension of more than 29.0 mN / m at 25°C. As a result, in the ink sets of Comparative Examples 8 to 10, the filling liquid was difficult to introduce into the ink flow path in the recording head. For this reason, it was found that good introduction properties could be imparted to the filling liquid by setting the static surface tension of the filling liquid at 25°C to 20.0 mN / m or more and 29.0 mN / m or less.

[0136] Furthermore, as shown in Tables 13 and 14, the static surface tension of the filling liquid at 25°C can be adjusted by changing the content of the nonionic surfactant (surfactant C in Study 3). The nonionic surfactant reduces the static surface tension of the filling liquid at 25°C, making it easier for the filling liquid to be introduced into the ink flow path in the recording head. As shown in Table 13, when the content of the nonionic surfactant in the filling liquid is set to 0.05% by mass or more and 0.10% by mass or less, the static surface tension of the filling liquid can be easily adjusted to a range of 20.0 mN / m or more and 29.0 mN / m or less. [Industrial Applicability]

[0137] The recording head filling liquid, the ink set, and the recording head inspection method of the present invention can be used in the manufacture of recording heads.

Claims

1. The composition contains a specific moisturizing agent, a monovalent alkali, and water, The specific moisturizing agent is a compound represented by the following general formula (1): The content of the specific moisturizing agent is 19.00% by mass or more and 42.00% by mass or less, A recording head filling liquid having a static surface tension at 25° C. of 20.0 mN / m or more and 29.0 mN / m or less. 【Chemistry 1】 (In the general formula (1), a, b, and c each independently represent an integer of 1 or more, and a+b+c is 4 or more and 20 or less.)

2. 2. The recording head filling liquid according to claim 1, wherein the viscosity of the specific moisturizing agent at 25[deg.] C. is from 260 mPa.s to 450 mPa.s.

3. 3. The printhead filling liquid according to claim 1, wherein the monovalent alkali contains at least one of a sodium compound, a potassium compound, a lithium compound, a cesium compound, and a rubidium compound.

4. 3. The recording head filling liquid according to claim 1, wherein in said general formula (1), a+b+c is 6 or more and 18 or less.

5. Further containing a nonionic surfactant, 3. The recording head filling liquid according to claim 1, wherein the nonionic surfactant includes an acetylene glycol surfactant.

6. 6. The recording head filling liquid according to claim 5, wherein the content of said nonionic surfactant is 0.05% by mass or more and 0.10% by mass or less.

7. 3. The recording head filling liquid according to claim 1, wherein the pH is from 7 to 10.

8. 3. The recording head filling liquid according to claim 1, which is used by filling a recording head in which ink-jet ink remains.

9. An ink set comprising an inkjet ink and the recording head filling liquid according to claim 1 or 2.

10. The ink set according to claim 9 , wherein the ink-jet ink comprises a pigment, a pigment-coated resin, and an aqueous medium.

11. A method for inspecting a recording head using the ink set according to claim 9, comprising the steps of: an inspection step of inspecting the ejection performance of the recording head; a filling step of filling the recording head with the recording head filler liquid after the inspection step, In the inspection step, the ejection performance of the recording head is inspected by ejecting the inkjet ink from the recording head.

12. 12. The method of inspecting a recording head according to claim 11, wherein the recording head is a line type recording head.

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