JP5915847B2 - Inkjet ink set and cleaning method - Google Patents

Description

  The present invention relates to an inkjet ink set and an ink flow path cleaning method.

  2. Description of the Related Art Conventionally, so-called inkjet recording apparatuses are known that record images and characters with fine ink droplets ejected from nozzles of an inkjet recording head. In an ink jet recording apparatus, for example, a flow path for supplying ink from an ink receiving portion for storing ink to an ink jet recording head, or for causing ink to flow to a nozzle opening (nozzle hole) in the ink jet recording head. An ink flow path for distributing ink, such as a flow path, is provided. Since such an ink flow path often has a fine structure, there is a problem that the ink flow path is likely to be clogged with ink for ink jet recording.

  For example, in Patent Documents 1 to 8, a cleaning liquid or a maintenance liquid is used to keep the nozzle surface moisturized or circulate in the ink flow path. It describes that clogging, nozzle clogging, and the like are eliminated.

Japanese Patent Publication No. 06-8437 Japanese Patent Publication No. 08-30200 Japanese Patent Laid-Open No. 04-261476 Japanese Patent Application Laid-Open No. 11-263021 Japanese Patent Laid-Open No. 11-263022 JP 2000-109733 A JP 2000-328093 A JP 2002-105500 A

  However, when a recording ink containing a bright pigment, a metal oxide, or the like is used as a color material, the color material (the bright pigment, the metal oxide, etc.) contained in the ink is a color material of a conventional ink ( For example, since the ink settles more easily than the inorganic pigment, organic pigment, dye, etc.), the ink channel may be clogged.

  In such a case, even if the ink flow path is cleaned using the cleaning liquid or maintenance liquid described above, the clogging of the ink flow path or the clogging of the nozzles cannot be sufficiently eliminated, and the ejection failure of the recording ink composition may occur. It may occur.

  One of the objects according to some embodiments of the present invention is to provide an ink set that is excellent in cleaning properties of the ink flow path and excellent in ejection stability.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the ink set for inkjet according to the present invention is as follows:
A recording ink composition that is used by being supplied to an ink flow path and contains at least one of a luster pigment and a metal oxide as a coloring material;
An auxiliary ink composition used for cleaning the ink flow path,
The viscosity of the recording ink composition at 20 ° C. is η ₁ (mPa · s), and the surface tension at 20 ° C. is γ ₁ (mN / m).
When the viscosity at 20 ° C. of the auxiliary ink composition is η ₂ (mPa · s) and the surface tension at 20 ° C. is γ ₂ (mN / m),
The following formula (1) and the following formula (2) are simultaneously satisfied.

η ₁ ≦ η ₂ (1)

γ ₁ ≧ γ ₂ (2)

  According to the ink jet ink set of Application Example 1, even when the recording ink composition containing a color material that easily settles is circulated through the ink flow path, the recording ink composition is used as the auxiliary ink. Since the composition can be washed away favorably, the ink flow path is excellent in cleaning properties and the recording ink composition is excellent in ejection stability.

[Application Example 2]
In application example 1,
The η ₂ is 3 mPa · s or more and 10 mPa · s or less,
The γ ₂ may be 15 mN / m or more and 35 mN / m or less.

[Application Example 3]
In application example 1 or application example 2,
The auxiliary ink composition may contain a defoaming surfactant.

[Application Example 4]
In any one of Application Examples 1 to 3,
The recording ink composition substantially does not contain alkyl polyols having a normal boiling point of 280 ° C. or higher, and contains alkyl polyols having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower,
The auxiliary ink composition may contain alkyl polyols having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower.

[Application Example 5]
In any one of Application Examples 1 to 4,
The auxiliary ink composition contains a coloring material,
The content of the color material in the auxiliary ink composition may be 0.5% by mass or less.

[Application Example 6]
In any one of Application Examples 1 to 5,
The auxiliary ink composition can have a freezing temperature under −1 atm of −15 ° C. or lower.

[Application Example 7]
One aspect of the cleaning method according to the present invention is:
A cleaning method for cleaning an ink flow path of an ink jet recording apparatus,
The auxiliary ink composition described in any one of Application Examples 1 to 6 is circulated through the ink flow path.

[Application Example 8]
In Application Example 7,
When the recording ink composition according to any one of claims 1 to 6 is present in the ink flow path, the ink flow path has a flow rate of 0.1 ml / (second · mm ² ) or more. The auxiliary ink composition can be distributed.

FIG. 2 is a perspective view illustrating a configuration of a printer according to an embodiment of the invention.

  Hereinafter, preferred embodiments of the present invention will be described. The embodiment described below describes an example of the present invention. In addition, the present invention is not limited to the following embodiments, and includes various modifications that are implemented within a range that does not change the gist of the present invention.

1. Ink-jet ink set An ink-jet ink set according to an embodiment of the present invention (hereinafter, also simply referred to as “ink set”) is used by being supplied to an ink flow path, and a bright pigment and a metal oxide are used as coloring materials. A recording ink composition containing at least one of the above and an auxiliary ink composition used for cleaning the ink flow path, wherein the viscosity of the recording ink composition at 20 ° C. is η ₁ (mPa · s). The surface tension at 20 ° C. was γ ₁ (mN / m), the viscosity of the auxiliary ink composition at 20 ° C. was η ₂ (mPa · s), and the surface tension at 20 ° C. was γ ₂ (mN / m). In this case, the following formula (1) and the following formula (2) are simultaneously satisfied.

η ₁ ≦ η ₂ (1)

γ ₂ ≦ γ ₁ (2)

  The function of washing the recording ink composition provided in the auxiliary ink composition by simultaneously satisfying the above formula (1) and the above formula (2) in the relationship between the viscosity and the surface tension of the recording ink composition and the auxiliary ink composition. Is significantly improved. The reason for this is as follows.

  That is, when the viscosity of the auxiliary ink composition becomes equal to or higher than the viscosity of the recording ink composition (Equation (1)), the force of the auxiliary ink composition that extrudes the recording ink composition and the precipitate derived therefrom increases. Further, when the surface tension of the auxiliary ink composition is equal to or lower than the surface tension of the recording ink composition (formula (2)), the auxiliary ink composition is easily mixed with the recording ink composition, and sedimentation derived therefrom. It becomes easy to penetrate into things. Then, the recording ink composition in the ink flow path and the precipitate derived therefrom are easily washed away efficiently by the auxiliary ink composition.

  Thus, by satisfying the above formulas (1) and (2) simultaneously, the function of the auxiliary ink composition for washing out the recording ink composition is remarkably enhanced. Therefore, when the ink set according to the present embodiment is used, even when the recording ink composition containing a color material that easily settles is supplied to the ink flow path, the auxiliary ink composition sufficiently covers the ink flow path. Can be washed. Thereby, the clogging of the ink flow path and the clogging of the nozzle can be reduced, and the ejection stability of the recording ink composition ejected from the nozzle can be improved thereafter.

  The relationship between the viscosity and surface tension of the recording ink composition and the auxiliary ink composition is expressed by the following formula (1-1) and the following formula (2-) from the viewpoint of easy handling and fluidity of the auxiliary ink composition. It is more preferable to satisfy 1) at the same time.

0 ≦ η ₂ −η ₁ ≦ 5 (1-1)

−5 ≦ γ ₂ −γ ₁ ≦ 0 (2-1)

A more preferable range of the above formula (1-1) is 0 ≦ η ₂ −η ₁ ≦ 3.

  Hereinafter, the recording ink composition and the auxiliary ink composition constituting the ink set according to the present embodiment will be described in detail.

1.1. Recording ink composition The recording ink composition constituting the ink set according to this embodiment is supplied to an ink flow path (described later) of an ink jet recording apparatus, and is discharged from a nozzle hole through the ink flow path. By doing so, an image is recorded on the recording medium.

  Hereinafter, each component contained in the recording ink composition will be described.

1.1.1. Colorant The recording ink composition according to the present embodiment contains at least one of a luster pigment and a metal oxide as a colorant.

  Examples of the metal oxide include titanium dioxide, zinc oxide, silica, alumina, magnesium oxide and the like. These metal oxides can be used as white pigments. In this case, it is preferable to use titanium dioxide from the viewpoint of particularly excellent whiteness and abrasion resistance.

  When a metal oxide is used as a white pigment, the volume-based average particle size (hereinafter referred to as “average particle size”) is preferably 200 nm or more, and more preferably 200 nm or more and 400 nm or less. preferable. When the average particle diameter of the white pigment is within the above range, particularly not below the lower limit, an image having good whiteness can be recorded. In addition, when the average particle diameter of the white pigment is within the above range, particularly without exceeding the upper limit, a white ink having excellent ejection stability can be obtained.

  The average particle diameter of the white pigment can be measured by a particle size distribution measuring apparatus using a laser diffraction scattering method as a measurement principle. Examples of the particle size distribution measuring apparatus include a particle size distribution meter (for example, “Microtrack UPA” manufactured by Nikkiso Co., Ltd.) having a dynamic light scattering method as a measurement principle.

  The glitter pigment is not particularly limited as long as it can exhibit glitter when attached to a medium. For example, aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium And one or more alloys (also referred to as metal pigments) selected from the group consisting of copper and pearl pigments having pearly luster. Representative examples of pearl pigments include pigments having pearly luster and interference gloss such as titanium dioxide-coated mica, fish scale foil, and bismuth oxychloride. Further, the glitter pigment may be subjected to a surface treatment for suppressing reaction with water. By including a glitter pigment in the ink, an image having excellent glitter can be formed.

  The said color material may be used individually by 1 type, and may be used in mixture of 2 or more types.

  The content of the color material can be appropriately selected depending on the application, but is preferably 1% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 20% by mass with respect to the total mass of the recording ink composition. It is below mass%.

1.1.2. Alkyl polyols The recording ink composition according to this embodiment may contain alkyl polyols having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower. The recording ink composition according to this embodiment may contain an alkyl polyol having a boiling point within the above range, thereby making it easier to control the wet-spreading property and drying property of the recording ink composition. . This is preferable because clogging of the nozzle can be reduced.

  The alkyl polyols have a normal boiling point of 180 ° C. or higher and 250 ° C. or lower, and preferably 188 ° C. or higher and 230 ° C. or lower. It is preferable that the standard boiling point of the alkyl polyol is within the above range, particularly not lower than the lower limit, because the moisture retention of the recording ink composition is good and the occurrence of nozzle clogging is easily suppressed. When the standard boiling point of the alkyl polyols is within the above range, particularly without exceeding the upper limit, the occurrence of unevenness in the density of the image and the decrease in the fixing property of the image are achieved without greatly reducing the drying property of the recording ink composition. Can be suppressed.

  Examples of alkyl polyols having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower include propylene glycol [189 ° C.], dipropylene glycol [230 ° C.], 1,2-butanediol [192 ° C.], and 1,3-butylene glycol. [208 ° C], 1,2-pentanediol [210 ° C], 1,2-hexanediol [224 ° C], 1,2-heptanediol [227 ° C], 3-methyl-1,3-butanediol [203 ° C], 2-ethyl-2-methyl-1,3-propanediol [226 ° C], 2-methyl-1,3-propanediol [214 ° C], 2-methyl-2-propyl-1,3-propane Examples include diol [230 ° C.], 2,2-dimethyl-1,3-propanediol [210 ° C.] and 2-methylpentane-2,4-diol [197 ° C.]. In addition, the numerical value in a parenthesis represents a normal boiling point.

  Alkyl polyols having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower may be used singly or in combination of two or more.

  The content of the alkyl polyols is a recording ink from the viewpoint of improving the wet spreading property to the recording medium and reducing density unevenness, and ensuring the storage stability and ejection reliability of the recording ink composition. It is preferably contained in the range of 8% by mass or more and 25% by mass or less with respect to the total mass of the composition.

  The recording ink composition according to this embodiment preferably does not contain alkyl polyols having a normal boiling point of 280 ° C. or higher. By including an alkyl polyol having a standard boiling point of 280 ° C. or higher, the drying property of the recording ink composition may be significantly reduced. As a result, not only the shading unevenness of the image is noticeable, but also the fixing property of the image may be lowered. Examples of the alkyl polyols having a normal boiling point of 280 ° C. or higher include glycerin (standard boiling point 290 ° C.).

  In the present invention, “substantially free of A” means that it is not added in excess of an amount that sufficiently achieves the significance of adding A. Specific examples of “substantially free” include, for example, 1.0% by mass or more, preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and still more preferably 0% by mass. 0.05% by mass or less, particularly preferably 0.01% by mass or less, more preferably 0.001% by mass or less.

1.1.3. Other Components The recording ink composition according to the present embodiment further comprises water, a resin dispersant, a resin, glycol ethers, wax, pyrrolidones, a surfactant, a pH adjuster, an antiseptic / fungicide, A rusting agent, a chelating agent, etc. can be contained. When the recording ink composition according to this embodiment contains these components, the characteristics may be further improved.

(water)
The recording ink composition according to this embodiment may contain water. Water is a main medium of the recording ink composition and is a component that evaporates and scatters when dried. The water is preferably water from which ionic impurities such as pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water or ultrapure water are removed as much as possible. Further, when water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is used, it is preferable because generation of mold and bacteria can be prevented when the pigment dispersion and the recording ink composition using the same are stored for a long period of time. It is.

(Resin dispersant)
The recording ink composition according to this embodiment may contain a resin dispersant from the viewpoint of improving the dispersibility of the coloring material in the recording ink composition. As the resin dispersant, any of water-soluble and water-insoluble types may be used.

  Specific examples of the resin dispersant include polyvinyl alcohols, polyacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, styrene- Acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic Acid ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-maleic acid ester copolymer , Vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer, etc. And salts thereof.

  Examples of the salt include basic compounds such as ammonia, ethylamine, diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, diethanolamine, triethanolamine, triisopropanolamine, aminomethylpropanol, and morpholine. Of the salt.

(resin)
A resin may be added to the recording ink composition according to this embodiment from the viewpoint of improving the fixability to the recording medium. Examples of the resin include acrylic resin, styrene acrylic resin, rosin modified resin, phenol resin, terpene resin, polyester resin, polyamide resin, epoxy resin, polyurethane resin, vinyl chloride vinyl acetate copolymer resin, and cellulose acetate butyrate. Examples thereof include fiber-based resins and vinyltoluene-α-methylstyrene copolymer resins. These resins may be used alone or in combination of two or more.

(Glycol ethers)
The recording ink composition according to this embodiment may contain glycol ethers. Glycol ethers can improve the wetting and spreading properties of the recording ink composition and improve the fixing properties of the recording ink composition.

  Specific examples of such glycol ethers include ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoisohexyl ether, diethylene glycol monohexyl ether, triethylene glycol monohexyl ether, diethylene glycol monoisohexyl ether, triethylene glycol Ethylene glycol monoisohexyl ether, ethylene glycol monoisoheptyl ether, diethylene glycol monoisoheptyl ether, triethylene glycol monoisoheptyl ether, ethylene glycol monooctyl ether, ethylene glycol monoisooctyl ether, diethylene glycol monoisooctyl ether, triethylene glycol Monoisooctylate , Ethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylhexyl ether, triethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylpentyl ether, ethylene glycol mono-2-ethylpentyl ether, ethylene glycol mono -2-methylpentyl ether, diethylene glycol mono-2-methylpentyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monomethyl Examples include ether. These can be used individually by 1 type or in mixture of 2 or more types.

(wax)
The recording ink composition according to this embodiment may contain a wax. The wax imparts lubricity to the surface of the recorded image. As a result, the occurrence of image peeling and rubbing can be suppressed, and the image fixing property is improved.

  Examples of the components constituting the wax include plant and animal waxes such as carnauba wax, candeli wax, beeswax, rice wax, and lanolin; petroleum oils such as paraffin wax, microcrystalline wax, polyethylene wax, oxidized polyethylene wax, and petrolatum. Wax; Mineral waxes such as montan wax and ozokerite; synthetic waxes such as carbon wax, Hoechst wax, polyolefin wax, stearamide, natural / synthetic wax emulsions such as α-olefin / maleic anhydride copolymer and blended wax Etc. can be used alone or in admixture of plural kinds.

  As the wax, commercially available products can be used as they are. For example, Nopcoat PEM-17 (trade name, manufactured by San Nopco), Chemipearl W4005 (trade name, manufactured by Mitsui Chemicals), AQUACER 515, AQUACER 539, AQUACER 593 (above products) Name, manufactured by Big Chemie Japan Co., Ltd.).

(Pyrrolidones)
Pyrrolidones can be used from the viewpoint of improving the fixability of the recording ink composition. Examples of pyrrolidones include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-pyrrolidone, N-butyl-2-pyrrolidone, and 5-methyl-2-pyrrolidone. Is mentioned.

(Surfactant)
The surfactant has an action of uniformly wetting and spreading the recording ink composition on the recording medium. The surfactant is not particularly limited, but is preferably a nonionic surfactant. Among the nonionic surfactants, silicone surfactants and / or acetylene glycol surfactants are more preferable. More preferably, a silicone surfactant and an acetylene glycol surfactant are used in combination.

  As the silicone surfactant, a polysiloxane compound or the like is preferably used, and examples thereof include polyether-modified organosiloxane. More specifically, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 (above trade name, manufactured by BYK Japan Japan Co., Ltd.) ), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22 4515, KF-6011, KF-6012, KF-6015, KF-6017 (above trade names, manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

  The acetylene glycol-based surfactant is superior to other nonionic surfactants in its ability to keep the surface tension and the interfacial tension properly, and has almost no foaming property. As a result, the ink composition containing the acetylene glycol surfactant can appropriately maintain the surface tension and the interfacial tension with the printer member in contact with the recording ink composition such as the head nozzle surface. When applied to an ink jet recording system, ejection stability can be improved. As acetylene glycol surfactants, for example, Surfinol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37 CT111, CT121, CT131, CT136, TG, GA, DF-110D, 82 (all trade names, manufactured by Air Products and Chemicals Inc.), Olfin B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP. 4001, EXP. 4036, EXP. 4051, AF-103, AF-104, AK-02, SK-14, AE-3 (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.), acetylenol E00, E00P, E40, E100 (all trade names, Kawaken Fine Chemical Co., Ltd.).

(Other)
Examples of the pH adjuster include potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, diethanolamine, triethanolamine, triisopropanolamine, potassium carbonate, sodium carbonate, Examples thereof include sodium hydrogen carbonate.

  Examples of antiseptics and fungicides include sodium benzoate, sodium pentachlorophenol, 2-pyridinethiol-1-oxide sodium, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazoline-3-one Etc. Examples of commercially available products include Proxel XL2, Proxel GXL (above trade name, manufactured by Avicia), Denside CSA, NS-500W (above trade name, manufactured by Nagase ChemteX Corporation), and the like.

  Examples of the rust inhibitor include benzotriazole.

  Examples of the chelating agent include ethylenediaminetetraacetic acid and salts thereof (such as ethylenediaminetetraacetic acid dihydrogen disodium salt), iminodisuccinic acid and salts thereof, and the like.

1.1.4. Method for Preparing Recording Ink Composition The recording ink composition according to this embodiment can be obtained by mixing the components described above in an arbitrary order and removing impurities by filtering or the like as necessary. As a method for mixing the components, a method in which materials are sequentially added to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer and stirred and mixed is suitably used. As a filtration method, centrifugal filtration, filter filtration, or the like can be performed as necessary.

1.1.5. Physical Properties of Recording Ink Composition The recording ink composition according to this embodiment has a surface tension at 20 ° C. of 20 mN / m or more and 50 mN from the viewpoint of a balance between image quality and reliability as an ink composition for inkjet recording. / M or less, more preferably 20 mN / m or more and 40 mN / m or less. The surface tension is measured, for example, by using an automatic surface tension meter CBVP-Z (trade name, manufactured by Kyowa Interface Science Co., Ltd.) and the surface when the platinum plate is wetted with the ink composition in an environment of 20 ° C. It can be measured by checking the tension.

  From the same viewpoint, the viscosity at 20 ° C. of the recording ink composition according to this embodiment is preferably 2 mPa · s or more and 8 mPa · s or less, and preferably 2 mPa · s or more and 5 mPa · s or less. More preferred. The viscosity can be measured, for example, by using a viscoelasticity tester MCR-300 (trade name, manufactured by Pysica) under a 20 ° C. environment.

  The pH of the recording ink composition is preferably neutral or alkaline, and more preferably in the range of 7.0 or more and 10.0 or less in an environment of 20 ° C. When the pH is within the above range, the storage stability and dispersion stability of the recording ink composition are improved. Further, when metal parts are used in the ink flow path of the ink jet recording apparatus, the occurrence of corrosion or the like can be suppressed.

1.2. Auxiliary Ink Composition The auxiliary ink composition according to this embodiment is used for cleaning an ink flow path in an ink jet recording apparatus. Hereinafter, components contained in the auxiliary ink composition according to the present embodiment will be described.

1.2.1. Surfactant The auxiliary ink composition according to the present embodiment preferably contains a surfactant. The surfactant can increase the wettability of the auxiliary ink composition with respect to the ink flow path and can improve the cleaning performance of the ink flow path. Further, the surfactant can reduce the surface tension of the auxiliary ink composition, and can increase the permeability of the auxiliary ink composition to the recording ink composition and the sediment in the ink flow path. Thereby, the washability of the ink flow path can be improved.

  As the surfactant, any surfactant may be used, but a nonionic surfactant is preferable. Among the nonionic surfactants, silicone surfactants and / or acetylene glycol surfactants are more preferable. More preferably, a silicone surfactant and an acetylene glycol surfactant are used in combination.

  As the silicone surfactant, a polysiloxane compound or the like is preferably used, and examples thereof include polyether-modified organosiloxane. More specifically, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 (above trade name, manufactured by BYK Japan Japan Co., Ltd.) ), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22 4515, KF-6011, KF-6012, KF-6015, KF-6017 (above trade names, manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

  The acetylene glycol-based surfactant is superior to other nonionic surfactants in its ability to keep the surface tension and the interfacial tension properly, and has almost no foaming property. As a result, the ink composition containing the acetylene glycol surfactant can appropriately maintain the surface tension and the interfacial tension with the printer member in contact with the ink composition such as the head nozzle surface. When applied to the method, the discharge stability can be improved. As acetylene glycol surfactants, for example, Surfinol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37 CT111, CT121, CT131, CT136, TG, GA, DF-110D, 82 (all trade names, manufactured by Air Products and Chemicals Inc.), Olfin B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP. 4001, EXP. 4036, EXP. 4051, AF-103, AF-104, AK-02, SK-14, AE-3 (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.), acetylenol E00, E00P, E40, E100 (all trade names, Kawaken Fine Chemical Co., Ltd.).

  Among the surfactants described above, the auxiliary ink composition is preferably a surfactant having a defoaming property (antifoaming agent). Examples of suitable antifoaming agents include silicone antifoaming agents, polyether antifoaming agents, fatty acid ester antifoaming agents, and acetylene-based antifoaming agents. These may be used individually by 1 type and may use 2 or more types together. Among these, a silicone antifoaming agent and an acetylene-based antifoaming agent are preferable from the viewpoint of excellent foam breaking effect.

  The surfactant having the antifoaming property described above preferably has an HLB value based on the Griffin method of 6 or less, and more preferably 5 or less. A surfactant having an HLB value of 6 or less can suppress the generation of bubbles in the ink flow path during cleaning, and thus can reduce ejection failure of the recording ink composition due to mixing of bubbles. In particular, when a piezo-type ink jet recording apparatus is used, ejection defects are likely to occur due to the generation of bubbles in the ink flow path. Therefore, a surfactant having an HLB value of 5 or less should be added to the auxiliary ink composition. Is preferred.

  Here, the HLB value of the surfactant used in the present embodiment is a value for evaluating the hydrophilicity of the compound proposed by Griffin, and is a value calculated by the following formula (3). The HLB value according to the Griffin method shows a value in the range of 0 to 20, and the larger the value, the more hydrophilic the compound.

  HLB value = 20 × (mass% of hydrophilic group) = 20 × (sum of formula weight of hydrophilic group / molecular weight of surfactant) (3)

  Specific examples of surfactants having an HLB value of 6 or less include Surfynol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, DF-110D, 82 (all trade names Manufactured by Air Products and Chemicals Inc.), BYK-011, BYK-012, BYK-017, BYK-018, BYK-019, BYK-020, BYK-021, BYK-022, BYK-023, BYK-023 024, BYK-025, BYK-028, BYK-038, BYK-044, BYK-080A, BYK-094, BYK-1610, BYK-1615, BYK-1650, BYK-1730, BYK-1770 , Big Chemie Japan Co., Ltd.) and the like.

  When these surfactants are contained, the content thereof is preferably 0.01% by weight or more and 1% by weight or less based on the total weight of the auxiliary ink composition.

1.2.2. Alkyl polyols The auxiliary ink composition according to this embodiment may contain alkyl polyols having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower. By adding an alkyl polyol having a boiling point within the above range, it can be preferably used in that the viscosity of the auxiliary ink composition can be easily adjusted. Further, when the ink flow path is filled with the auxiliary ink composition and the ink jet recording apparatus is stored for a long period of time, drying of the ink flow path can be further suppressed. This is preferable because clogging of the nozzle can be reduced.

  The alkyl polyols have a normal boiling point of 180 ° C. or higher and 250 ° C. or lower, and preferably 188 ° C. or higher and 230 ° C. or lower. It is preferable for the standard boiling point of the alkyl polyols to be in the above range because the auxiliary ink composition has good moisture retention and can easily prevent nozzle clogging.

  Specific examples of the alkyl polyols having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower are the same as the substances exemplified in the recording ink composition, and thus the description thereof is omitted. Alkyl polyols having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower may be used singly or in combination of two or more.

  As the alkyl polyol having a standard boiling point of 180 ° C. or higher and 250 ° C. or lower added to the auxiliary ink composition, the same alkyl polyols contained in the recording ink composition can be preferably used. When the alkyl polyols contained in the auxiliary ink composition and the alkyl polyols contained in the recording ink composition are used in common, it is preferable in terms of efficient replacement of the auxiliary ink composition and the recording ink composition. .

  The content of the alkyl polyol is 20 with respect to the total mass of the auxiliary ink composition from the viewpoint of ensuring the viscosity of the auxiliary ink composition within an appropriate range and ensuring the storage stability of the auxiliary ink composition. The mass is preferably from 50% by mass to 50% by mass, and more preferably from 30% by mass to 50% by mass.

  Further, the auxiliary ink composition preferably contains substantially no alkyl polyol having a standard boiling point of 280 ° C. or higher when it is necessary to balance the drying property with the recording ink composition. Here, “substantially not contained” means that it is not contained in an amount that sufficiently exhibits the significance of addition. Specific examples of “substantially free” of the above alkyl polyol include, for example, 1.0% by mass or more, preferably 0.5% by mass or less, more preferably 0.1% by mass or less, More preferably 0.05% by mass or less, particularly preferably 0.01% by mass or less, and most preferably 0.001% by mass or less.

1.2.3. Colorant The auxiliary ink composition according to the present embodiment may contain a colorant. By coloring the auxiliary ink composition, it can also be used as inspection ink used for inspecting normal ejection of the head before shipment. Thereby, complicated steps such as replacement of the ink flow path with the auxiliary ink composition again at the time of shipment can be omitted.

  Examples of the color material include pigments and dyes.

  Specifically, known inorganic pigments, organic pigments, and carbon black can be used as the pigment. For example, azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelate azo pigments, phthalocyanine pigments, perylene, and perinone pigments. Polycyclic pigments such as anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, dye chelates, dye lakes, nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments Can do. The above pigments can be used alone or in combination of two or more.

  Examples of the dye include various dyes used for normal inkjet recording such as direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, and reactive disperse dyes. Can be used. The above dyes can be used alone or in combination of two or more.

  When a coloring material is added, the content thereof is preferably 0.5% by mass or less, and 0.01% by mass to 0.5% by mass with respect to the total mass of the auxiliary ink composition. More preferably. When the content of the color material is 0.5% by mass or less, it is possible to secure a recording density sufficient to use the auxiliary ink composition as it is as a test liquid for confirming ejection of an inkjet printer head. It is preferable that the ink composition for recording is replaced with the recording ink composition in this step because problems due to ink color mixture are unlikely to occur.

  When a pigment is used as the color material, it is preferable that the pigment can be stably dispersed and held in water. As the method, a method of dispersing with a resin dispersant such as a water-soluble resin and / or a water-dispersible resin (hereinafter, the pigment treated by this method is referred to as “resin-dispersed pigment”), water-soluble surfactant A method of dispersing with a surfactant of an agent and / or a water-dispersible surfactant (hereinafter, the pigment treated by this method is referred to as “surfactant-dispersed pigment”), and hydrophilic functional groups on the pigment particle surface In which water is dispersed and / or dissolved in water without a dispersant such as the above-described resin or surfactant (hereinafter, the pigment treated by this method is referred to as “surface-treated pigment”). And the like). As the auxiliary ink composition according to the present embodiment, any of the resin-dispersed pigments, surfactant-dispersed pigments, and surface-treated pigments can be used. It preferably contains a resin dispersed pigment.

  Examples of the resin dispersant used for the resin dispersion pigment include polyvinyl alcohols, polyacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, and styrene. -Acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid- Acrylate ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-maleic acid ester copolymer Polymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic Examples include acid copolymers and salts thereof. Among these, a copolymer of a monomer having a hydrophobic functional group and a monomer having a hydrophilic functional group, and a polymer composed of a monomer having both a hydrophobic functional group and a hydrophilic functional group are preferable. As the form of the copolymer, any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer can be used.

  Examples of the salt include basic compounds such as ammonia, ethylamine, diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, diethanolamine, triethanolamine, triisopropanolamine, aminomethylpropanol, and morpholine. Of the salt. The addition amount of these basic compounds is not particularly limited as long as it is 50 mol% or more with respect to the neutralization equivalent of the resin dispersant.

  The molecular weight of the resin dispersant is preferably in the range of 1,000 to 100,000 as a weight average molecular weight. When the molecular weight is in the above range, the pigment is stably dispersed in water, and viscosity control when applied to the auxiliary ink composition is easy.

  Moreover, it is preferable that it is the range of 30-300 as an acid value, and it is more preferable that it is the range of 50-150. When the acid value is within this range, the dispersibility of the pigment particles in water can be stably secured.

  The surfactant used in the surfactant-dispersed pigment includes alkane sulfonate, α-olefin sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, acylmethyl taurate, and dialkyl sulfo oxalate. Anionic surfactants such as alkyl sulfate ester salts, sulfated olefins, polyoxyethylene alkyl ether sulfate ester salts, alkyl phosphate ester salts, polyoxyethylene alkyl ether phosphate ester salts, monoglycerite phosphate ester salts, Amphoteric surfactants such as alkyl pyridium salts, alkyl amino acid salts, alkyl dimethyl betaines, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polyoxyethylenes Alkylamide, glycerol alkyl esters, nonionic surfactants such as sorbitan alkyl esters.

  The amount of the resin dispersant or the surfactant added to the pigment is preferably 1 part by mass or more and 100 parts by mass or less, and more preferably 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the pigment. By being in this range, the dispersion stability of the pigment in water is further improved.

  The resin-dispersed pigment, surfactant-dispersed pigment, and surface-treated pigment described above are dispersed in water as follows: for resin-dispersed pigment, pigment, water, and resin dispersant; for surfactant-dispersed pigment, pigment and water. For surfactants and surface-treated pigments, add surface-treated pigment and water, and water-soluble organic solvents / neutralizers, etc., as necessary, ball mill, sand mill, attritor, roll mill, agitator mill, Henschel mixer, It can be performed by a conventionally used disperser such as a colloid mill, an ultrasonic homogenizer, a jet mill, or an ang mill. In this case, as the particle diameter of the pigment, it is possible to disperse until the average particle diameter is 20 nm or more and 500 nm or less, more preferably 50 nm or more and 180 nm or less, in order to ensure dispersion stability of the pigment in water. preferable.

1.2.4. Other Components The auxiliary ink composition according to the present embodiment can further contain water, a resin, glycol ethers, a pH adjuster, an antiseptic / fungicide, a rust inhibitor, a chelating agent, and the like. When the ink composition according to this embodiment contains these components, the characteristics may be further improved. Specific examples of these components are the same as the components exemplified in the recording ink composition, and thus the description thereof is omitted.

1.2.5. Method for Preparing Auxiliary Ink Composition The auxiliary ink composition according to the present embodiment is obtained by mixing the components described above in an arbitrary order, and removing impurities by filtering or the like as necessary. As a method for mixing the components, a method in which materials are sequentially added to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer and stirred and mixed is suitably used. As a filtration method, centrifugal filtration, filter filtration, or the like can be performed as necessary.

1.2.6. Physical Properties of Auxiliary Ink Composition The auxiliary ink composition according to this embodiment has a surface tension at 20 ° C. of 15 mN / m or more and 35 mN / m from the viewpoint of easy washing of the recording ink composition in the ink flow path. It is more preferable that it is 15 mN / m or more and 30 mN / m or less. The surface tension can be measured by a method similar to the method shown for the recording ink composition.

  From the same viewpoint, the viscosity at 20 ° C. of the auxiliary ink composition according to this embodiment is preferably 3 mPa · s to 10 mPa · s, and more preferably 3 mPa · s to 6 mPa · s. preferable. The viscosity can be measured by a method similar to the method shown for the recording ink composition.

  The pH of the auxiliary ink composition is preferably neutral or alkaline, and more preferably in the range of 7.0 to 10.0. When the pH is within the above range, the storage stability of the auxiliary ink composition is improved. Further, when metal parts are used in the ink flow path of the ink jet recording apparatus, the occurrence of corrosion or the like can be suppressed.

Further, from the viewpoint of suppressing the aggregation of the recording ink composition and the auxiliary ink composition or increasing the compatibility of the two ink compositions, the pH (pH ₁ ) of the recording ink composition, the auxiliary ink composition, and the like. It is preferable that the relationship with pH (pH ₂ ) satisfies the following formula (4). Thereby, the auxiliary ink composition can easily wash out the recording ink composition, and the storage stability of the recording ink composition may be improved.

pH ₁ ≦ pH ₂ +1 (4)

  In the auxiliary ink composition according to this embodiment, the freezing temperature corresponding to one atmospheric pressure is preferably −15 ° C. or lower, and more preferably −20 ° C. or lower. As a result, the auxiliary ink composition according to the present embodiment can be used as a transport liquid that is used by filling the ink flow path in order to prevent destruction of the ink flow path of the ink jet recording apparatus during transportation.

2. Inkjet recording apparatus The recording ink according to this embodiment is discharged as a droplet from the nozzles of an inkjet recording head (hereinafter, also simply referred to as “head”) through an ink flow path and adheres to a recording medium. To do. In this way, a recorded matter in which an image made of recording ink is recorded on the recording medium is obtained.

  Hereinafter, an ink jet recording apparatus including a head capable of ejecting recording ink according to the present embodiment will be described with reference to FIG. In each drawing used for the following description, the scale of each member is appropriately changed in order to make each member a recognizable size. In the present embodiment, an inkjet printer (hereinafter simply referred to as “printer”) is illustrated as an inkjet recording apparatus. The present invention is not limited to this apparatus configuration.

  FIG. 1 is a perspective view illustrating a configuration of a printer 1 according to the present embodiment. A printer 1 shown in FIG. 1 is a serial printer. A serial printer is a printer in which a head is mounted on a carriage that moves in a predetermined direction, and droplets are ejected onto a recording medium by moving the head as the carriage moves.

  As shown in FIG. 1, a printer 1 includes a carriage 3 on which a head 2 is mounted, a carriage moving mechanism 4 that moves the carriage 3 in the medium width direction of the recording medium P, and a medium that conveys the recording medium P in the medium feeding direction. A feed mechanism 5 is provided. The printer 1 also has a control unit 6 that controls the operation of the entire printer 1. The medium width direction is the main scanning direction (head scanning direction). The medium feeding direction is a sub-scanning direction (a direction orthogonal to the main scanning direction).

  As shown in FIG. 1, the head 2 is connected via an ink supply tube 20 to an ink storage unit 10 that individually stores a recording ink composition and an auxiliary ink composition. The recording ink composition and the auxiliary ink composition are configured such that each ink can be supplied to the head 2 by a known switching means.

  As the printer 1 according to the present embodiment, a so-called off-carriage type printer in which the ink storage unit 10 is mounted on the housing of the printer 1 and the ink is supplied to the head 2 via the ink supply pipe 20 is exemplified. However, the present invention is not limited to this. For example, a so-called on-carriage type printer in which an ink cartridge is mounted on a carriage may be used. Further, it may be used for a line head type printer having no carriage.

  In addition, a home position serving as a scanning start point of the head 2 is set outside the area in which the recording medium P is conveyed in the moving range of the head 2. A maintenance unit 7 including a cap member 17 is provided at the home position.

  The maintenance unit 7 is configured to perform a moisturizing operation, a flushing operation, a head cleaning operation, and the like. Specifically, the moisturizing operation is for capping the head 2 with the cap member 17 other than the recording operation to suppress drying of nozzle holes (not shown) of the head 2. The flushing operation is to prevent the nozzle holes from being clogged by preliminarily discharging the recording ink composition from the nozzle holes of the head 2 to the cap member 17. In the head cleaning operation, after the head 2 is capped by the cap member 17, a suction pump (not shown) is driven to discharge the recording ink composition from each nozzle hole, and the ink flow path is replaced with the auxiliary ink composition. Is.

  In the present specification, the ink flow path refers to a flow path through which the liquid that has flowed out of the ink container passes through the nozzles of the head 2. For example, in the printer 1, the ink supply pipe 20 and the ink circulation path inside the head 2 correspond to the ink flow path.

3. Cleaning Method The cleaning method according to the present embodiment is a cleaning method for cleaning the ink flow path of the above-described ink jet recording apparatus, and distributes the above-described auxiliary ink composition through the ink flow path.

  Specifically, in the cleaning of the ink flow path, the auxiliary ink composition is caused to flow into the ink flow path to which the recording ink composition is supplied, and the recording ink composition in the ink flow path is changed to the auxiliary ink composition. It is done by replacing. By doing so, sediment or the like in the ink flow path is discharged from the nozzle together with the recording ink composition, and the ink flow path can be cleaned. The replacement of ink in the ink flow path can be performed, for example, by the above-described head cleaning operation.

  After the ink flow path has been washed, if the image recording using the ink jet recording apparatus is not performed for a long period of time, the ink flow path can be left filled with the auxiliary ink composition. Thereby, generation | occurrence | production of the sediment resulting from the ink composition for recording can be prevented.

  On the other hand, when recording an image using an ink jet recording apparatus, the recording ink composition is caused to flow into the ink flow path filled with the auxiliary ink composition, and the auxiliary ink composition is discharged from the nozzle. The ink channel may be filled again with the recording ink composition.

  The cleaning method according to this embodiment uses the auxiliary ink composition described above. For this reason, the occurrence of problems such as nozzle clogging and clogging of the ink flow path due to the above-described recording ink composition can be suppressed, so that the cleaning performance of the ink flow path through which the recording ink composition is distributed is excellent.

In the cleaning method according to the present embodiment, when the recording ink composition is present in the ink channel, the auxiliary ink composition is applied to the ink channel at a flow rate of 0.1 ml / (second · mm ² ) or more. It is preferable to circulate. This makes it easier for the auxiliary ink composition to wash away the recording ink composition present in the ink flow path, and the cleaning performance of the ink flow path is significantly improved. The above flow rate is more preferably 0.4 ml / (second · mm ² ).

4). Examples Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

4.1. Preparation of recording ink composition 4.1.1. Preparation of Metal Oxide Dispersion In the recording ink composition according to the present invention, white titanium oxide, which is a metal oxide, was used as a coloring material. When the metal oxide is added to the recording ink composition, a resin-dispersed metal oxide in which the metal oxide is dispersed in advance with a resin dispersion is used, and this is formed into a form of a water-based metal oxide dispersion. In the ink composition for recording.

  Specifically, the metal oxide dispersion was prepared as follows. First, an acrylic acid-acrylate copolymer (weight average molecular weight: 25,000, acid value) as a resin dispersant was added to 75 parts by mass of ion-exchanged water in which 1 part by mass of a 30% aqueous ammonia solution (neutralizing agent) was dissolved. : 180) 4 parts by mass was added and dissolved. Thereto, 20 parts by mass of titanium oxide (CI Pigment White 6) was added as a metal oxide, and dispersion treatment was performed for 10 hours by a ball mill using zirconia beads. Thereafter, centrifugal filtration using a centrifugal separator was performed to remove impurities such as coarse particles and dust, and the metal oxide concentration was adjusted to 20% by mass. The particle diameter of the metal oxide at that time was 350 nm as an average particle diameter.

4.1.2. Preparation of recording ink composition White recording ink composition having the material composition shown in Table 1 using the metal oxide dispersion prepared in “4.1.1. Preparation of metal oxide dispersion”. 1 was obtained. For the recording ink composition 1, the materials shown in Table 1 are put in a container, mixed by stirring with a magnetic stirrer for 2 hours, and then filtered through a membrane filter having a pore size of 5 μm to remove impurities such as dust and coarse particles. It was prepared by doing. The numerical values in Table 1 all indicate mass%, and ion exchange water was added so that the total mass of the recording ink composition was 100 mass%.

4.2. Preparation of auxiliary ink composition 4.2.1. Preparation of Color Material Dispersion Carbon black, which is a black pigment, was used as a color material for a part of the auxiliary ink composition used in this example. When an auxiliary ink composition is added using a pigment as a coloring material, a pigment dispersion in which the coloring material is previously dispersed with a resin dispersant is used, and the auxiliary ink composition in the state of a water-based pigment dispersion is used. Included.

  Specifically, the pigment dispersion was prepared as follows. First, an acrylic acid-acrylic acid ester copolymer (weight average molecular weight: 25,000, as a resin dispersant) was added to 76 parts by mass of ion-exchanged water in which 1.5 parts by mass of a 30% aqueous ammonia solution (neutralizing agent) was dissolved. Acid value: 180) 7.5 parts by mass was added and dissolved. Thereto, 15 parts by mass of pigment carbon black (CI Pigment Black 7) was added as a coloring material, and dispersion treatment was performed for 10 hours by a ball mill using zirconia beads. Thereafter, centrifugal filtration using a centrifugal separator was performed to remove impurities such as coarse particles and dust, and the pigment concentration was adjusted to 15% by mass.

4.2.2. Preparation of Auxiliary Ink Composition Auxiliary ink compositions 1 to 7 having different material compositions with the material compositions shown in Table 1 were obtained. In each auxiliary ink composition, the materials shown in Table 1 are put in a container, mixed with stirring with a magnetic stirrer for 2 hours, and then filtered with a membrane filter having a pore size of 5 μm to remove impurities such as dust and coarse particles. It was prepared by. The numerical values in Table 1 all represent mass%, and ion exchange water was added so that the total mass of the auxiliary ink composition was 100 mass%.

In Table 1, the components described by trade names are as follows.
・ JONCRYL352J (trade name, manufactured by BASF Japan Ltd., styrene-acrylic acid copolymer emulsion)
・ AQUACER 515 (trade name, manufactured by Big Chemie Japan KK, polyethylene wax emulsion)
・ BYK-348 (trade name, manufactured by BYK Japan, Inc., silicone surfactant)
Surfynol DF-110D (trade name, manufactured by Air Products and Chemicals Inc., acetylene glycol surfactant, HLB value: 3)

4.3. Evaluation test 4.3.1. Evaluation of detergency In performing this evaluation, an inkjet printer PX-G930 (trade name, manufactured by Seiko Epson Corporation, nozzle resolution: 180 dpi), which is an inkjet recording type printer, is used, and a head suction cap for cleaning the printer is used. A rotary pump that can change the number of rotations was modified for evaluation. Moreover, this evaluation was performed under the conditions of 20 ° C. to 25 ° C./RH 40% to 60%.

  First, the printer modified as described above was filled with the white recording ink composition 1 to confirm the ejection, and it was confirmed that the recording ink composition 1 was sufficiently filled in the inside of the head and in all the nozzles. After that, the apparatus was stopped and allowed to stand for 3 days. After standing, a silicon tube provided with a container was attached to the ink supply port portion of the head, and the auxiliary ink compositions 1 to 7 were filled in the container. Then, by adjusting the number of rotations of the rotary pump so as to obtain a desired flow rate, the auxiliary ink compositions 1 to 7 that are three times the amount of the filled recording ink composition 1 are passed through, thereby recording inside the head. Ink composition 1 was washed. Thereafter, the recording ink composition 1 of the auxiliary ink composition was recorded by directly recording on a PET film (trade name “PET50A PL Thin”, manufactured by Lintec Corporation) and visually observing the white state of the recorded matter. Detergency was evaluated. As a print pattern, a fill pattern that can be printed at a resolution of 720 dpi in width and 720 dpi in length and 100% duty was used.

The evaluation criteria are shown below. The evaluation is performed at each flow rate [0.05 ml / (second · mm ² ), 0.1 ml / (second · mm ² ), 0.5 ml / (second · mm ² ), 1 ml / (second · mm ² )]. Went to.

A: The recording ink composition is not mixed at all.
B: The recording ink composition is slightly mixed, but is hardly visible.
C: The recording ink composition is a little mixed and easily visible.
D: A large amount of the recording ink composition is mixed and can hardly be washed.

4.3.2. Refillability evaluation The auxiliary ink compositions 1 to 7 were filled in the head of the ink jet printer PX-G930. Then, by performing a head cleaning operation, the auxiliary ink composition inside the head was replaced with the recording ink composition 1. After that, it is recorded as it is on a PET film (trade name “PET50A PL Thin”, manufactured by Lintec Co., Ltd.), and the discharge state of the recorded matter (confirmation of nozzle missing / bent state, etc.) and the color mixture of the recorded matter are visually observed. Thus, the refillability of the recording ink composition 1 for each of the auxiliary ink compositions 1 to 7 was evaluated. As a recording pattern used for confirmation, the head nozzle check pattern attached to the printer driver is used as it is for confirmation of refillability, and in a mixed color situation, recording can be performed at a resolution of 720 dpi × 720 dpi and 100% duty. A filled pattern was prepared and used.

  The evaluation criteria are shown below.

<Dischargeability>
A: In one head cleaning operation, all the nozzles were free from defects such as nozzle omission and bending, and the recording ink composition was ejected normally.
B: With the head cleaning operation of 2 to 5 times, there was no problem such as nozzle omission or bending at all nozzles, and the recording ink composition was ejected normally.
C: In 6 to 10 head cleaning operations, all the nozzles were free of defects such as nozzle omission and bending, and the recording ink composition was ejected normally.
D: Even when the head cleaning operation was performed 10 times or more, there were defects such as nozzle missing and bending, and there were nozzles that could not normally eject the recording ink composition.

<Color mixing status>
A: The auxiliary ink composition is not mixed at all.
B: Although the auxiliary ink composition is slightly mixed, it is hardly visible.
C: The auxiliary ink composition is slightly mixed and can be easily visually recognized.
D: A lot of auxiliary ink composition is mixed, or there are many missing nozzles / bents, so that almost no filling is possible.

4.3.3. Evaluation results The results of the above evaluation tests are also shown in Table 2.

  As shown in Table 2, when the ink set according to the example is used, the cleaning property of the recording ink composition by the auxiliary ink composition is excellent, and the refilling property of the recording ink composition is also excellent. It was done. As described above, the relationship between the viscosity and the surface tension between the auxiliary ink composition and the recording ink composition satisfies the above formulas (1) and (2) at the same time, so that the ink channel has excellent detergency and It was shown that the discharge stability is excellent.

  On the other hand, in the ink set according to Comparative Example 1, the relationship between the viscosity of the auxiliary ink composition and the recording ink composition does not satisfy the above formula (1). Therefore, the cleaning property of the recording ink composition by the auxiliary ink composition and the refilling property of the recording ink composition were lowered.

  In the ink set according to Comparative Example 2, the relationship between the surface tensions of the auxiliary ink composition and the recording ink composition does not satisfy the above formula (2). Therefore, the cleaning property of the recording ink composition by the auxiliary ink composition and the refilling property of the recording ink composition were lowered.

  In the ink set according to Example 5, the auxiliary ink composition 5 to which a coloring material was added was used. Using the auxiliary ink composition 5, the nozzle check pattern attached to the printer driver was used as it was, recorded on PPC paper, and the nozzle check was performed. As a result, the nozzle discharge status (that is, the inside of the head of the auxiliary ink composition 5) The state of filling in) was easily confirmed visually. Therefore, it is shown that by adding a small amount of color material (0.5% by mass or less in terms of color material solid content) to the auxiliary ink composition of the present invention, it can be suitably used as a test liquid for an inkjet printer head. It was done.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Head, 3 ... Carriage, 4 ... Carriage moving mechanism, 5 ... Medium feed mechanism, 6 ... Control part, 7 ... Maintenance unit, 10 ... Ink storage part, 17 ... Cap member, 20 ... Ink flow path

Claims (3)

A recording ink composition that is used by being supplied to an ink flow path and contains at least one of a luster pigment and a metal oxide as a coloring material;
An auxiliary ink composition used for cleaning the ink flow path,
The viscosity of the recording ink composition at 20 ° C. is η ₁ (mPa · s), and the surface tension at 20 ° C. is γ ₁ (mN / m).
When the viscosity at 20 ° C. of the auxiliary ink composition is η ₂ (mPa · s) and the surface tension at 20 ° C. is γ ₂ (mN / m),
Formula (1) and the following equation (2) meets at the same time,
η ₁ ≦ η ₂ (1)
γ ₁ ≧ γ ₂ (2)
The recording ink composition contains alkyl polyols having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower in the range of 8% by mass or more and 25% by mass or less, and alkyl polyols having a standard boiling point of 280 ° C. or higher in the range of 0. Do not contain more than 5% by mass,
The auxiliary ink composition contains an alkyl polyol having a normal boiling point of 180 ° C. or higher and 250 ° C. or lower in an amount of 20% by mass to 50% by mass, and an alkyl polyol having a standard boiling point of 280 ° C. or higher in an amount of 0.5% by mass or higher. Does not contain,
Inkjet ink set, characterized in that. In claim 1,
The η ₂ is 3 mPa · s or more and 10 mPa · s or less,
Inkjet ink set wherein the gamma ₂ is not more than 15 mN / m or more 35 mN / m. In claim 1 or claim 2,
The auxiliary ink composition contains an antifoaming surfactant, and is an ink jet ink set.

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