Ink set and recording head inspection method

Abstract

To provide an ink set that facilitates introduction of a recording head filling liquid into an ink flow channel within a recording head, effectively inhibits agglomeration of pigment components of inkjet ink within the recording head, and enables the recording head filling liquid to be purged stably.SOLUTION: An ink set includes an inkjet ink and a recording head filling liquid. The inkjet ink contains a pigment, a pigment coating resin, an aqueous medium, a polymeric nonionic surfactant, and a specific glycol ether. The specific glycol ether is triethylene glycol monobutyl ether or diethylene glycol monobutyl ether. The polymeric nonionic surfactant has a mass average molecular weight of 6,500 or more and 10,500 or less. The recording head filling liquid contains a specific moisturizing agent and water. The specific moisturizing agent is a compound represented by general formula (1).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an ink set and a method for inspecting a recording head. [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 components) 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 an ink set which allows the print head filler liquid to be easily introduced into the ink flow paths in the print head, can effectively suppress aggregation of the pigment components in the inkjet ink in the print head, and can stably purge the print head filler liquid. Another object of the present invention is to provide a method for inspecting a print head using the above ink set. [Means for solving the problem]

[0010] The ink set according to the present invention comprises an inkjet ink and a recording head filling liquid. The inkjet ink contains a pigment, a pigment-coated resin, an aqueous solvent, a polymeric nonionic surfactant, and a specific glycol ether. The specific glycol ether is triethylene glycol monobutyl ether or diethylene glycol monobutyl ether. The mass average molecular weight of the polymeric nonionic surfactant is 6,500 or more and 10,500 or less. The recording head filling liquid contains a specific humectant and water. The specific humectant is a compound represented by the following general formula (1).

[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 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

[0014] According to the ink set of the present invention, the print head filler liquid can be easily introduced into the ink flow path in the print head, and the pigment components in the inkjet ink can be effectively prevented from coagulating in the print head, and the print head filler 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

[0015] 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.

[0016] 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.

[0017] In this specification, acrylic and methacrylic may be collectively referred to as "(meth)acrylic." Additionally, "at least one of A and B" means "A and / or B."

[0018] <First embodiment: Ink set> An ink set according to a first embodiment of the present invention will be described below. The ink set of this embodiment includes an inkjet ink (hereinafter, sometimes simply referred to as ink) and a recording head filling liquid (hereinafter, sometimes simply referred to as filling liquid). The ink contains a pigment, a pigment-coated resin, an aqueous solvent, a polymeric nonionic surfactant, and a specific glycol ether. The specific glycol ether is triethylene glycol monobutyl ether or diethylene glycol monobutyl ether. The mass average molecular weight of the polymeric nonionic surfactant is 6500 or more and 10500 or less. The recording head filling liquid contains a specific moisturizing agent and water. The specific moisturizing agent is a compound represented by the following general formula (1).

[0019] [ka]

[0020] 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.

[0021] In the ink set of this embodiment, the filling liquid is used by filling a recording head in which ink remains. For example, when the recording head is left unused for a while for some reason after ink is ejected by the recording head, the filling liquid is filled into the recording head for use. Specifically, the filling liquid is filled into the recording head for use when the recording head is shipped, stored for a long period of time, or transported. The ink set of this embodiment is suitable as an ink set for use in the recording head inspection method according to the second embodiment.

[0022] The ink set of the present embodiment has the above-mentioned configuration, which makes it easy for the filling liquid to be introduced into the ink flow path in the recording head, and can effectively suppress the aggregation of the pigment components (pigment and pigment-coated resin) in the ink in the recording head. In addition, even when the filling liquid is purged from the recording head after the recording head is left unused, the filling liquid can be stably purged. The reason for this is presumed to be as follows. The ink set of the present embodiment includes ink and a filling liquid. The filling liquid enters the ink flow path of the recording head and dilutes the ink remaining in the ink flow path. As a result, the solid content of the ink remaining in the ink flow path is less likely to aggregate. In particular, the ink set of the present embodiment contains a specific moisturizing agent with low viscosity in the filling liquid. By containing the specific moisturizing agent in the filling liquid, the viscosity of the filling liquid can be prevented from increasing even when the moisture in the filling liquid evaporates. As a result, the filling liquid can effectively suppress the aggregation of the pigment components (pigment and pigment-coated resin) in the ink in the recording head. In addition, the pressure (purge pressure) of the recording head when purging the filling liquid does not increase, and the filling liquid can be stably purged from the recording head after the recording head is left unused. In addition, the ink set of this embodiment contains a polymeric nonionic surfactant in the ink. The polymeric nonionic surfactant can effectively suppress the aggregation of the pigment components (pigment and pigment-coated resin) in the ink. In particular, the ink set of this embodiment can effectively suppress the aggregation of the pigment components in the ink when the ink and the filling liquid are mixed, and can impart introductory properties to the filling liquid. Furthermore, the ink set of this embodiment contains a specific glycol ether in the ink. The specific glycol ether has high hydrophobicity and good wettability, and therefore can impart introductory properties to the filling liquid when the ink and the filling liquid are mixed.

[0023] The ink set of this embodiment will be described in more detail below. Each of the components described below may be used alone or in combination of two or more.

[0024] [ink] The ink contains a pigment, a pigment-coated resin, an aqueous solvent, a polymeric nonionic surfactant, and a specific glycol ether. In the ink, the pigment forms pigment particles together with the pigment-coated resin. The pigment particles are dispersed in the solvent. From the viewpoint of optimizing the color density, hue, or stability of the ink, the D of the pigment particles is adjusted. 50 The thickness is preferably 30 nm or more and 200 nm or less, and more preferably 70 nm or more and 130 nm or less.

[0025] (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).

[0026] In the ink, the pigment content is preferably 2.0% by mass or more and 15.0% by mass or less, and more preferably 5.0% by mass or more and 10.0% by mass or less. By making the pigment content 2.0% by mass or more, it becomes easier to form an image having a desired image density. In addition, by making the pigment content 15.0% by mass or less, the fluidity of the ink can be ensured.

[0027] (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.

[0028] 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 can be mentioned. 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).

[0029] In the total repeating units contained in the copolymer (X), the content of repeating units derived from styrene is preferably 10.0% by mass or more and 20.0% 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 10.0% by mass or more and 20.0% 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 35.0% by mass or more and 45.0% 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 25.0% by mass or more and 35.0% by mass or less.

[0030] In the ink, the content of the pigment coating resin is preferably from 0.7% to 6.0% by mass, and more preferably from 2.0% to 4.0% by mass. By setting the content of the pigment coating resin to be from 0.7% to 6.0% by mass, the ejection stability of the ink can be optimized.

[0031] The acid value of the pigment coating resin is preferably from 30 mgKOH / g to 300 mgKOH / g, and more preferably from 80 mgKOH / g to 180 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.

[0032] 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.

[0033] The Mw of the pigment coating resin is preferably from 10,000 to 50,000, and more preferably from 15,000 to 25,000. By setting the Mw of the pigment coating resin to be from 10,000 to 50,000, it is possible to optimize the image density of the formed image and the ejection stability of the ink while suppressing an increase in the viscosity of the ink.

[0034] 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.).

[0035] 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 is preferably neutralized with an equal amount of a basic compound before being used as a raw material for the ink. The basic compound is preferably a hydroxide of an alkali metal ion (e.g., potassium hydroxide or sodium hydroxide).

[0036] (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.

[0037] The content of the aqueous medium in the ink is preferably from 70.0% by mass to 96.0% by mass, and more preferably from 80.0% by mass to 92.0% by mass.

[0038] (water) Water is the main solvent of the ink. The content of water in the ink is, for example, preferably from 20.0% by mass to 93.0% by mass, and more preferably from 50.0% by mass to 87.0% by mass.

[0039] (Water-soluble organic solvent) The ink preferably further contains a water-soluble organic solvent, such as a glycol compound, a glycol ether compound other than the specific glycol ether, a lactam compound, a nitrogen-containing compound, an acetate compound, thiodiglycol, glycerin, or dimethyl sulfoxide.

[0040] 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.

[0041] Examples of glycol ether compounds other than the specific glycol ethers 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, and propylene glycol monomethyl ether.

[0042] Lactam compounds include, for example, 2-pyrrolidone and N-methyl-2-pyrrolidone.

[0043] Examples of nitrogen-containing compounds include 1,3-dimethylimidazolidinone, formamide, and dimethylformamide.

[0044] An example of the acetate compound is diethylene glycol monoethyl ether acetate.

[0045] The water-soluble organic solvent in the ink is preferably 2-pyrrolidone or glycerin.

[0046] The content of the water-soluble organic solvent in the ink is preferably from 8.0% to 60.0% by mass, and more preferably from 20.0% to 45.0% by mass. By setting the content of the water-soluble organic solvent to be from 8.0% to 60.0% by mass, the ejection stability of the ink can be optimized.

[0047] When the ink contains 2-pyrrolidone as the water-soluble organic solvent, the content of 2-pyrrolidone in the ink is preferably from 1.5% by mass to 12.5% ​​by mass, and more preferably from 4.0% by mass to 9.0% by mass.

[0048] When the ink contains glycerin as the water-soluble organic solvent, the content of glycerin in the ink is preferably from 6.0% by mass to 50.0% by mass, and more preferably from 16.0% by mass to 36.0% by mass.

[0049] (Polymer nonionic surfactant) The mass average molecular weight of the polymeric nonionic surfactant is from 6,500 to 10,500, and preferably from 7,000 to 9,000. By setting the mass average molecular weight of the polymeric nonionic surfactant to be from 6,500 to 10,500, aggregation of the pigment components in the ink (pigment and pigment-coating resin) can be effectively suppressed (in other words, aggregation suppression performance can be optimized).

[0050] Examples of polymeric nonionic surfactants include copolymers having a repeating unit derived from a polyalkylene glycol alkyl ether (meth)acrylate and a repeating unit derived from an alkyl (meth)acrylate (hereinafter, sometimes referred to as copolymer (α)).

[0051] Examples of the polyalkylene glycol alkyl ether (meth)acrylate include polyethylene glycol methyl ether (meth)acrylate and polypropylene glycol methyl ether (meth)acrylate. In the polyethylene glycol methyl ether (meth)acrylate, the molecular weight of the polyethylene glycol portion is, for example, 100 or more and 300 or less. In the polypropylene glycol methyl ether (meth)acrylate, the molecular weight of the polypropylene portion is, for example, 80 or more and 150 or less. As the polyalkylene glycol alkyl ether (meth)acrylate, polyethylene glycol methyl ether acrylate (PEGA) or polypropylene glycol methyl ether acrylate (PPGA) is preferred.

[0052] The content of repeating units derived from polyalkylene glycol alkyl ether (meth)acrylate relative to all repeating units contained in the copolymer (α) is preferably 50.0 mass % or more and 90.0 mass % or less, more preferably 60.0 mass % or more and 80.0 mass % or less.

[0053] Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate. The (meth)acrylic acid alkyl ester is preferably methyl acrylate (MMA), lauryl acrylate (LA), butyl acrylate (BA), ethyl acrylate (EA), or lauryl methacrylate (LMA).

[0054] The content of repeating units derived from an alkyl (meth)acrylate relative to all repeating units in the copolymer (α) is preferably from 10.0 to 50.0% by mass, more preferably from 20.0 to 40.0% by mass.

[0055] The copolymer (α) is preferably a copolymer having a repeating unit derived from monomers of the following combination (1) or a copolymer having a repeating unit derived from monomers of the following combination (2). Combination (1): PEGA, BA, PPGA, LA and MMA Combination (2): PEGA, EA, PPGA, LMA and MMA

[0056] Copolymer (α) preferably has any one of combinations 1 and 2 of repeating units derived from monomers shown in Table 1 below. In Table 1 below, "proportion" indicates the preferred numerical range of the content ratio [mass %] of the repeating units derived from each monomer. For example, "50.0-70.0", which is the proportion of "PEGA" in composition 1, indicates that PEGA is contained in an amount of 50.0 mass % or more and 70.0 mass % or less.

[0057] [Table 1]

[0058] The content of the polymeric nonionic surfactant in the ink is preferably from 0.2% to 0.9% by mass, and more preferably from 0.2% to 0.4% by mass. By setting the content of the polymeric nonionic surfactant to from 0.2% to 0.9% by mass, the aggregation suppression performance can be further optimized.

[0059] (Specific glycol ether) The specific glycol ether contained in the ink is triethylene glycol monobutyl ether or diethylene glycol monobutyl ether.

[0060] The specific glycol ether has high hydrophobicity and good wettability, and therefore can impart introductory properties to the filler liquid when the ink and the filler liquid are mixed.

[0061] The content of the specific glycol ether in the ink is preferably from 1.0% to 6.0% by mass, and more preferably from 3.0% to 5.0% by mass. By setting the content of the specific glycol ether to be from 1.0% to 6.0% by mass, the introduceability of the filling liquid when the ink and the filling liquid are mixed can be optimized.

[0062] (Low molecular weight surfactant) The ink may contain only a polymeric nonionic surfactant as a surfactant, but may further contain a surfactant having a smaller molecular weight than the polymeric nonionic surfactant (hereinafter, referred to as another low molecular weight surfactant). The content of the polymeric nonionic surfactant in the surfactant is preferably 40.0% by mass or more, and more preferably 50.0% by mass or more.

[0063] Examples of low molecular weight surfactants include nonionic surfactants such as acetylene glycol surfactants (surfactants containing acetylene glycol compounds), silicone surfactants (surfactants containing silicone compounds), and fluorine surfactants (surfactants containing fluorine resins or fluorine-containing compounds). Examples of acetylene glycol surfactants include ethylene oxide adducts of acetylene glycol and propylene oxide adducts of acetylene glycol. More specifically, examples of acetylene glycol surfactants include "Olfine (registered trademark) E1010" (manufactured by Nissin Chemical Industry Co., Ltd., ethylene oxide adducts of acetylene glycol).

[0064] When the ink contains a low molecular weight surfactant, the content of the low molecular weight surfactant in the ink is preferably from 0.1% to 0.5% by mass, and more preferably from 0.1% to 0.3% by mass.

[0065] (Other ingredients) 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.

[0066] (Preferred composition) The ink preferably has any one of compositions 1 to 7 shown in Table 2 below. In Table 2 below, "ratio" indicates a numerical range of a preferred content ratio [mass %]. For example, "5.0-7.0" which is the pigment ratio of composition 1 indicates that the pigment is contained in an amount of 5.0 mass % or more and 7.0 mass % or less. "S-1", "S-3", "S-4" and "S-6" of the types of polymeric nonionic surfactants respectively indicate the surfactants (S-1), (S-3), (S-4) and (S-6) used in the examples. In addition, BTG indicates triethylene glycol mono-n-butyl ether, and BDG indicates diethylene glycol mono-n-butyl ether.

[0067] [Table 2]

[0068] In addition, in compositions 1 to 7 shown in Table 2, the water-soluble organic solvent preferably has the composition shown in Table 3 below. In Table 3 below, "ratio" indicates a preferable numerical range of the content ratio [mass %]. For example, "3.0-7.0" indicating the ratio of 2-pyrrolidone indicates that 2-pyrrolidone is contained in an amount of 3.0 mass % or more and 7.0 mass % or less.

[0069] [Table 3]

[0070] (Ink manufacturing method) The ink can be produced, for example, by uniformly mixing a pigment dispersion containing a pigment, an aqueous solvent, a polymeric nonionic surfactant, and a specific glycol ether with a stirrer. In the production of the ink, after the components are uniformly mixed, foreign matter and coarse particles may be removed with a filter (for example, a filter with a pore size of 5 μm or less). The pigment dispersion contains a pigment, a pigment-coated resin, and an aqueous solvent. The pigment dispersion may further contain a low-molecular surfactant. The pigment-coated resin is prepared, for example, by neutralizing an equal amount of an alkali-soluble resin with a basic compound (for example, potassium hydroxide or 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 with a filter (for example, a filter with a pore size of 5 μm or less) after the dispersion treatment.

[0071] [Filling liquid] The filling liquid contains a specific moisturizing agent and water. The filling liquid may further contain a surfactant.

[0072] (Specific moisturizer) The specific moisturizing agent is a compound represented by the above-mentioned general formula (I). In the general formula (I), a+b+c preferably represents an integer of 6 or more and 18 or less, more preferably an integer of 6 or more and 15 or less, and even more preferably an integer of 6 or more and 9 or less. By containing 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), the filling liquid can prevent the filling liquid from thickening even when the water in the filling liquid evaporates. As a result, the filling liquid can effectively suppress the pigment components (pigment and pigment-coated resin) in the ink from coagulating in the recording head. In addition, the filling liquid can be stably purged from the recording head after the recording head is left standing. However, if the viscosity of the specific moisturizing agent is too low, the filling liquid may actually reduce the dispersibility of the pigment components in the recording head. In the general formula (I), if a+b+c is 4 or more and 20 or less, the pigment components in the ink can be effectively suppressed from coagulating in the recording head. In general formula (I), by adjusting a+b+c to be 6 or more and 18 or less, aggregation of the pigment components in the ink can be more effectively prevented within the recording head.

[0073] The viscosity of the specific moisturizing agent at 25°C is preferably 260 mPa·s or more and 450 mPa·s or less, more preferably 330 mPa·s or more and 450 mPa·s or less, and even more preferably 380 mPa·s or more and 440 mPa·s or less. By having the viscosity of the specific moisturizing agent be 260 mPa·s or more and 450 mPa·s or less, it is possible to effectively suppress aggregation of the pigment components in the ink in the recording head. In addition, it is possible to stably purge the filling liquid from the recording head after the recording head is left standing. The measured value of the viscosity of the specific moisturizing agent is a value measured at 25°C using a falling ball viscometer (for example, Anton Paar's "Lovis2000").

[0074] The content of the specific moisturizing agent in the filling liquid is preferably 16.0% by mass or more and 41.0% by mass or less, and more preferably 25.0% by mass or more and 35.0% by mass or less. By making the content of the specific moisturizing agent in the filling liquid 16.0% by mass or more and 41.0% by mass or less, it is possible to effectively suppress aggregation of the pigment component in the ink in the recording head. In addition, it is possible to stably purge the filling liquid from the recording head after the recording head is left standing.

[0075] (Surfactant) The surfactant contained in the filling liquid may be the same as the surfactant exemplified as the low molecular surfactant in the ink. The surfactant contained in the filling liquid is preferably an acetylene glycol surfactant. The acetylene glycol surfactant has an effect of improving the wettability of the filling liquid to stainless steel, 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 becomes more easily introduced into the ink flow path in the recording head. An example of the acetylene glycol surfactant contained in the filling liquid is "Surfynol (registered trademark) 420" (manufactured by Nissin Chemical Industry Co., Ltd.).

[0076] The content of the surfactant in the filling liquid is preferably 0.1% by mass or more and 0.5% by mass or less, and more preferably 0.1% by mass or more and 0.3% by mass or less. By making the content of the surfactant in the filling liquid 0.1% by mass or more, the filling liquid can be more easily introduced into the ink flow path in the recording head, and the pigment components 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 dispersibility of the pigment components. Therefore, by making the content of the surfactant in the filling liquid 0.5% by mass or less, the filling liquid can more effectively prevent the pigment components in the ink from coagulating in the recording head.

[0077] (water) Water is the main solvent of the filling liquid. The content of water in the filling liquid is, for example, preferably from 45.0% by mass to 95.0% by mass, and more preferably from 65.0% by mass to 85.0% by mass.

[0078] (Other ingredients) The filling liquid 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.

[0079] (Preferred composition) The filling liquid preferably has any one of compositions 1 to 7 shown in Table 4 below. In Table 4 below, "ratio" indicates a preferred numerical range of the content ratio [mass %]. For example, "27.0-33.0", which is the ratio of the specific moisturizing agent in composition 1, indicates that the specific moisturizing agent is contained in an amount of 27.0 mass % or more and 33.0 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.

[0080] [Table 4]

[0081] (Method of manufacturing the filling liquid) The filling solution can be produced, for example, by mixing the specific moisturizing agent, water, and components added as necessary (for example, surfactants). The specific moisturizing agent can be produced by reacting polyethylene glycol with glycerin at 180 to 220°C for etherification.

[0082] [Second embodiment: recording head inspection method] The following describes a method for inspecting a printhead according to a second embodiment of the present invention. The printhead inspection method of the present invention is a method for inspecting a printhead using the ink set according to the first embodiment, and includes an inspection step for inspecting the ejection performance of the printhead, and a filling step for filling the printhead with a filling liquid after the inspection step. In the inspection step, the ejection performance of the printhead is inspected by ejecting ink from the printhead.

[0083] The printhead inspection method of this embodiment uses the ink set according to the first embodiment, and therefore can suppress ejection defects from occurring in the inspected printhead. The printhead inspection method of this embodiment is performed, for example, before the printhead manufacturer ships the printhead. The printhead inspected by the printhead inspection method of this embodiment is not particularly limited, but examples include piezo type printheads and thermal type printheads. The printhead may be, for example, a line type printhead.

[0084] [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.

[0085] 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.

[0086] [Filling process] In this process, the recording head is filled with the filling liquid. 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 can be discharged from the recording head by ejecting the filling liquid from the recording head. EXAMPLES

[0087] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0088] In the examples, the Mw of the alkali-soluble resin and polymeric nonionic surfactant were measured using gel permeation chromatography ("HLC-8020GPC" manufactured by Tosoh Corporation) under the following conditions. 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.

[0089] (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

[0090] [Study 1: Types of moisturizers used in print head filling fluid] First, the type of humectant used in the recording head filling liquid was examined. The preparation methods of each raw material used in the production of the ink are described below.

[0091] [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.

[0092] (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 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. Thus, the pigment dispersion resin (R-1) was neutralized with an equal amount (strictly speaking, 105% amount) of NaOH, thereby obtaining a pigment-coated resin solution containing the pigment-coated resin (R) (neutralized alkali-soluble resin) and water.

[0093] (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 5 below.

[0094] The "water" content in Table 5 below indicates the total content of the ion-exchanged water charged into the vessel and the water contained in the pigment-coated resin solution (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" (an ethylene oxide adduct of acetylene glycol), an acetylene glycol surfactant manufactured by Nissin Chemical Industry Co., Ltd.

[0095] [Table 5]

[0096] 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.

[0097] 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.

[0098] [Preparation of polymeric nonionic surfactants] A polymeric nonionic surfactant (S-1) was prepared for use in the preparation of ink. A copolymer (mass average molecular weight (Mw) 8000) having a repeating unit (PEGA unit) derived from polyethylene glycol methyl ether acrylate (molecular weight of polyethylene glycol portion: 200), a repeating unit (BA unit) derived from butyl acrylate, a repeating unit (PPGA unit) derived from polypropylene glycol methyl ether acrylate (molecular weight of polypropylene glycol portion: 100), a repeating unit (LA unit) derived from lauryl acrylate, and a repeating unit (MMA unit) derived from methyl methacrylate was prepared. This copolymer was designated as polymeric nonionic surfactant (S-1). The mass ratio of each repeating unit in the polymeric nonionic surfactant (S-1) was "PEGA unit:BA unit:PPGA unit:LA unit:MMA unit=60:10:10:12:8". The polymeric nonionic surfactant (S-1) was soluble in water.

[0099] [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 stirrer (stirring speed: 400 rpm), the pigment dispersion liquid (D-1), polymeric nonionic surfactant (S-1), triethylene glycol mono-n-butyl ether, 2-pyrrolidone, and glycerin were added in this order. The ratio of the amounts of each raw material added was as shown in Table 6 below.

[0100] [Table 6]

[0101] [Preparation of filling solution] Filling solutions (F-1) to (F-6) were prepared by the following method. First, the details of the humectants (M-1) to (M-6) used in the preparation of the filling solutions are shown below.

[0102] [Moisturizers (M-1)~(M-6)] The compounds shown in Table 7 below were prepared by the method described below, and these were designated as moisturizers (M-1) to (M-6). The viscosity of each moisturizer was measured at 25°C using a falling ball viscometer ("Lovis2000" manufactured by Anton Paar).

[0103] [Preparation of moisturizers (M-2) to (M-6)] Polyethylene glycol and glycerin were reacted at 200°C for etherification. In this way, compounds as moisturizers (M-2) to (M-6) shown in Table 7 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. - HPLC equipment: Hitachi High-Tech Science Corporation "HITACHI D-7000" ·Flow rate: 1.0mL / min Detector: ESA Biosciences "Corona CAD Detector"

[0104] (Glycerin analysis conditions) Column: Tosoh Corporation "TSK-GEL Amide-80" (5 μm, 4.6 × 250 mm) Solution: 50% by volume acetonitrile / water (distilled water)

[0105] (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% to 98% by volume, after which the volume ratio of acetonitrile was kept at 98% by volume.

[0106] [Preparation of moisturizer (M-1)] A compound as moisturizer (M-1) shown in Table 7 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 in the same manner as moisturizers (M-2) to (M-6).

[0107] [Table 7]

[0108] [Preparation of filling solution (F-1)] A mixed solution was obtained by mixing 30.0 parts by mass of moisturizer (M-1), 0.2 parts by mass of "Surfynol (registered trademark) 420" (ethylene oxide adduct of acetylene glycol) manufactured by Nissin Chemical Industry Co., Ltd., which is an acetylene glycol surfactant, and ion-exchanged water. The amount of ion-exchanged water added was such that the total amount of the mixed solution was 100.0 parts by mass. This mixed solution was used as filling solution (F-1).

[0109] [Preparation of filling solutions (F-2) to (F-6)] Filling solutions (F-2) to (F-6) were prepared in the same manner as in the preparation of filling solution (F-1), except that the types and amounts of each component were changed as shown in Table 8. Note that surfactant B in the following Table 8 represents the above-mentioned "Surfynol (registered trademark) 420."

[0110] [Table 8]

[0111] [Ink set preparation] As shown in the following Table 9, the ink (I-1) was combined with any one of the filling liquids (F-1) to (F-6), thereby preparing the ink sets of Examples 1 to 4 and Comparative Examples 1 and 2.

[0112] [Rating 1] The ink sets of Examples 1 to 4 and Comparative Examples 1 and 2 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 Table 9 below.

[0113] (Aggregation suppression performance (open system)) 1.0 part by mass of the ink (ink (I-1) in Study 1) included in the ink set to be evaluated and 50.0 parts by mass of the filling liquid (any of filling liquids (F-1) to (F-6)) 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").

[0114] 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 1.0 part by mass of ink: 50.0 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.

[0115] (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.

[0116] (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.

[0117] (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).

[0118] (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

[0119] (Easy to introduce) First, an unused recording head (Kyocera Corporation's "KJ4B-QA", total number of nozzles: 2656) was filled with ink and discharged. The ink used was cyan ink for Kyocera Document Solutions Corporation's inkjet color production printer "TASKalfa Pro 15000c". 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-6)) 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 into the recording head again. 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 with 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

[0120] (Criteria for determining introductory properties) A (Pass): Adoption rate is 90% or higher B (Fail): Adoption rate is less than 90%

[0121] [Table 9]

[0122] As shown in Tables 1 to 9, it was found that a+b+c in the general formula (1) of the moisturizing agent is favorable when it is 4 or more and 20 or less.

[0123] [Study 2: Mass average molecular weight of polymeric nonionic surfactants] Next, the weight average molecular weight of the polymeric nonionic surfactant was examined. The preparation methods of each raw material used in the production of the ink are shown below.

[0124] (Polymer nonionic surfactants (S-2)~(S-6)) As shown in Table 10 below, copolymers having repeating units and mass average molecular weights different from those of the polymeric nonionic surfactant (S-1) were prepared, and these were designated polymeric nonionic surfactants (S-2) to (S-6). All of the polymeric nonionic surfactants (S-2) to (S-6) were soluble in water. In Table 10 below, the repeating unit column indicates that the repeating unit is derived from the corresponding monomer (polyethylene glycol methyl ether acrylate (PEGA), butyl acrylate (BA), polypropylene glycol methyl ether acrylate (PPGA), lauryl acrylate (LA), methyl methacrylate (MMA), ethyl acrylate (EA), and lauryl methacrylate (LMA)). In addition, in Table 10 below, the mass ratio of each repeating unit in the polymeric nonionic surfactant is shown to be, for example, in the case of the polymeric nonionic surfactant (S-1), 60% repeating units derived from PEGA, 10% repeating units derived from BA, 10% repeating units derived from PPGA, 12% repeating units derived from LA, and 8% repeating units derived from MMA, by mass.

[0125] [Table 10]

[0126] [Preparation of Inks (I-2) to (I-8)] Inks (I-2) to (I-8) were prepared in the same manner as for the preparation of ink (I-1), except that the types and amounts of each raw material were changed as shown in Table 11. In addition, BTG in Table 11 below represents triethylene glycol mono-n-butyl ether.

[0127] [Table 11]

[0128] [Preparation of filling solution (F-7)] Filling solution (F-7) was prepared in the same manner as filling solutions (F-1) to (F-6), except that the type of moisturizer and the amount of moisturizer and water were changed as shown in Table 12.

[0129] [Table 12]

[0130] [Ink set preparation] As shown in Table 13 below, any one of the inks (I-1) to (I-8) was combined with the filling liquid (F-7), thereby preparing the ink sets of Examples 5 to 9 and Comparative Examples 3 to 5.

[0131] [Rating 2] The ink sets of Examples 5 to 9 and Comparative Examples 3 to 5 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 13 below.

[0132] [Table 13]

[0133] As shown in Tables 10 to 13, it was found that by including a polymeric nonionic surfactant in the ink, aggregation of the pigment components in the ink can be effectively suppressed when the ink is mixed with the filler liquid, and that the filler liquid can be provided with introductory properties. Also, as shown in Tables 10 to 13, if the mass average molecular weight of the polymeric nonionic surfactant is less than 6500 or more than 10500, dispersion stability cannot be guaranteed, and aggregates with a particle size of 3 μm or more are generated after storage treatment. On the other hand, it was found that if the mass average molecular weight of the polymeric nonionic surfactant is within the range of 6500 to 10500, aggregates with a particle size of 3 μm or more are not generated after storage treatment.

[0134] [Study 3: Types of glycol ether] Next, the type of glycol ether was examined.

[0135] [Preparation of Inks (I-9) to (I-13)] Inks (I-9) to (I-13) were prepared in the same manner as inks (I-1) to (I-8), except that the types and amounts of each raw material were changed as shown in Table 14. In Table 14, BTG represents triethylene glycol mono-n-butyl ether, BDG represents diethylene glycol mono-n-butyl ether, BEG represents ethylene glycol mono-n-butyl ether, and iPDG represents diethylene glycol isopropyl ether.

[0136] [Table 14]

[0137] [Ink set preparation] As shown in the following Table 15, any one of the inks (I-9) to (I-12) was combined with the filling liquid (F-7), thereby preparing the ink sets of Examples 10 to 12 and Comparative Examples 4 to 6.

[0138] [Rating 3] For the ink sets of Examples 10 to 12 and Comparative Examples 4 to 6, the ink aggregation suppression performance, the purging performance 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 15 below.

[0139] [Table 15]

[0140] As shown in Tables 14 to 15, it was found that triethylene glycol mono-n-butyl ether and diethylene glycol mono-n-butyl ether could impart good introductory properties to the filling liquid. This is believed to be due to the high hydrophobicity and good wettability of the specific glycol ether. On the other hand, ethylene glycol mono-n-butyl ether has a smaller number of ethers (-O-) than the specific glycol ether, and therefore exhibits higher hydrophilicity than the specific glycol ether. In addition, diethylene glycol isopropyl ether has a shorter alkyl chain length than the specific glycol ether, and therefore exhibits higher hydrophilicity than the specific glycol ether. For this reason, these ethylene glycol mono-n-butyl ether and diethylene glycol isopropyl ether were insufficient in wettability and could not impart sufficient introductory properties to the filling liquid.

[0141] [Study 4: Content of moisturizer in print head filling fluid] Next, the content of the humectant used in the recording head filling liquid was examined.

[0142] [Preparation of filling solutions (F-8) to (F-9)] Filling solutions (F-8) to (F-9) were prepared in the same manner as for preparing filling solutions (F-1) to (F-6), except that the type and amount of each component was changed as shown in Table 16. Note that surfactant B in the following Table 16 represents the aforementioned "Surfynol (registered trademark) 420."

[0143] [Table 16]

[0144] [Ink set preparation] As shown in the following Table 17, the ink (I-1) was combined with any one of the filling liquids (F-8) to (F-9), thereby preparing the ink sets of Examples 13 and 14.

[0145] [Rating 4] For the ink sets of Examples 13 and 14, 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 17 below. For reference, Table 17 below also shows the evaluation results of the ink set of Example 1.

[0146] [Table 17]

[0147] As shown in Tables 16 and 17, whether the content of the specific moisturizer in the filling liquid was 20.0 mass% or 40.0 mass%, good results were obtained in terms of the ink aggregation inhibition performance, the purging property of the filling liquid, and the introduceability of the filling liquid, similar to Example 1. [Industrial Applicability]

[0148] The ink set and recording head inspection method of the present invention can be used in the manufacture of recording heads.

Claims

1. An ink set comprising an inkjet ink and a recording head filling liquid, The inkjet ink contains a pigment, a pigment-coated resin, an aqueous solvent, a polymeric nonionic surfactant, and a specific glycol ether, The specific glycol ether is triethylene glycol monobutyl ether or diethylene glycol monobutyl ether, The mass average molecular weight of the polymeric nonionic surfactant is 6,500 or more and 10,500 or less, The recording head filling liquid contains a specific moisturizing agent and water, The specific moisturizing agent is a compound represented by the following general formula (1): [Formula 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 ink set according to claim 1, wherein a content of the polymeric nonionic surfactant in the inkjet ink is from 0.2% by mass to 0.9% by mass.

3. The ink set according to claim 1 , wherein the content of the specific glycol ether in the inkjet ink is from 1.0% by mass to 6.0% by mass.

4. 3. The ink set according to claim 1, wherein the content of the specific humectant in the recording head filling liquid is 16.0% by mass or more and 41.0% by mass or less.

5. 3. The ink set according to claim 1, wherein the viscosity of the specific humectant at 25° C. is from 260 mPa·s to 450 mPa·s.

6. 3. The ink set according to claim 1, wherein the polymeric nonionic surfactant is a copolymer having a repeating unit derived from a polyalkylene glycol alkyl ether (meth)acrylate and a repeating unit derived from an alkyl (meth)acrylate.

7. The polymeric nonionic surfactant is a copolymer having a repeating unit derived from polyethylene glycol methyl ether acrylate, a repeating unit derived from butyl acrylate, a repeating unit derived from polypropylene glycol methyl ether acrylate, a repeating unit derived from lauryl acrylate, and a repeating unit derived from methyl methacrylate, or 7. The ink set according to claim 6, which is a copolymer having a repeating unit derived from polyethylene glycol methyl ether acrylate, a repeating unit derived from ethyl acrylate, a repeating unit derived from polypropylene glycol methyl ether acrylate, a repeating unit derived from lauryl methacrylate, and a repeating unit derived from methyl methacrylate.

8. The ink set according to claim 1 or 2, wherein in the general formula (1), a+b+c is 6 or more and 18 or less.

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

10. 3. A method for inspecting a recording head using the ink set according to claim 1, 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.

11. 11. The method of inspecting a recording head according to claim 10, wherein the recording head is a line type recording head.

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