Inkjet ink and image recording method

Abstract

An inkjet ink containing water, a pigment, and at least one of a resin particle and a wax particle and having a pH of 7.2 to 11, and satisfying the following inequality (X). In the following inequality (X), ORPi represents the oxidation-reduction potential of the inkjet ink in mV measured under a device condition in which the oxidation-reduction potential of water at pH 6.2 reaches 310 mV, and pHi represents the pH of the inkjet ink. ORPi - [285 - 59 x (pHi - 6.2)] ≥ 0 Inequality (X).

Description

Technical Field

[0001] This invention relates to an inkjet ink and an image recording method. Background Technology

[0002] In the past, various studies have been conducted on inkjet-based image recording (i.e., image recording in which ink is ejected from the recording head of an inkjet recording device and applied to a recording medium) and the ink used for such image recording (hereinafter also referred to as "inkjet ink").

[0003] For example, Japanese Patent Application Publication No. 2015-063574 discloses an ink that, when used in an inkjet recording apparatus having a recording head with a protective layer and a resin component in contact with the ink, provides an ink in which the thickness of the protective layer is not easily reduced and the resin component is not easily degraded. The inkjet recording apparatus includes: a recording head (i.e., an inkjet head) in which at least a portion of the component in contact with the ink is formed of at least one material selected from the group consisting of silicon, silicon oxide, silicon nitride, and silicon carbide; and a resin component in contact with the ink. The ink contains: pigment; soluble copper ions; and a specific compound containing a bipyridine structure.

[0004] Furthermore, in Japanese Patent Application Publication No. 2003-165936, an inkjet ink with excellent dispersion and dissolution stability was disclosed, which does not produce changes in droplet size or droplet ejection speed, or ejection defects. This ink is used in inkjet printers where at least a portion of the part in contact with the ink is formed of silicon, glass, or a film on which oxides, nitrides, metals, or organic compounds are disposed, and it is an inkjet ink with a pH of 6.5 to 11.5 and an interfacial potential of 0 to -50 mV between the part and the colorant.

[0005] Furthermore, Japanese Patent Application Publication No. 2016-044236 discloses an ink that contains a resin for effectively improving the robustness of the recorded image and can suppress the dissolution of silicon compounds from the recording head (i.e., inkjet head) while exhibiting good ejection stability and preservation stability, and is capable of recording images with high optical density. This ink is used in an inkjet recording method that uses a recording head, at least a portion of which is made of silicon or a silicon compound, to eject ink from the recording head and record an image on a recording medium. The ink contains a self-dispersing pigment with phosphonic acid groups directly or via other atomic groups bonded to the particle surface, a resin having anionic groups, and a specific compound having amino groups.

[0006] Furthermore, in Japanese Patent Application Publication No. 2011-063000, an image forming method is disclosed that, when forming an image through an inkjet head having an ink circulation system, it can suppress the deterioration of printhead components (especially the printhead plate and ink flow path) and can form a high-definition image stably for a long time. The method includes: a step of ejecting an ink composition containing at least one selected from silica compounds from an inkjet head, wherein the inkjet head includes: a plurality of droplet ejection elements; and an ink circulation device having a common flow path that is connected to the plurality of droplet ejection elements via a supply channel and a common circulation path that is connected to the plurality of droplet ejection elements via a return channel, and the ink composition is circulated in the common circulation path while being supplied to the plurality of droplet ejection elements from the common flow path.

[0007] Furthermore, in Japanese Patent Application Publication No. 2011-111527, an aqueous ink composition was disclosed as having excellent long-term ejection properties and being able to suppress shape deformation of inkjet head components and decrease in liquid repellency. The composition contains: a colorant comprising at least one of an azo pigment with a specific structure and its tautomers, as well as their salts and hydrates; a dispersant; and colloidal silica. Summary of the Invention

[0008] The technical problem to be solved by the invention

[0009] When using alkaline inkjet ink (e.g., pH 7.2 or higher) and an inkjet head containing silicon in the ink flow path wall to record images, the inkjet ink is sometimes used to etch the silicon-containing ink flow path wall.

[0010] From the perspective of inkjet ink ejection properties, it is sometimes necessary to suppress the etching of the ink flow path walls.

[0011] One aspect of the present invention is to provide an inkjet ink and an image recording method using the inkjet ink, wherein the inkjet ink is ink ejected from an inkjet head containing silicon in the ink flow path wall, and is capable of suppressing the etching of the ink flow path wall.

[0012] means for solving technical problems

[0013] The specific solutions used to address the problem include the following methods.

[0014] <1> An inkjet ink, which is an inkjet ink ejected from an inkjet head containing silicon in the ink flow path wall, wherein,

[0015] The inkjet ink contains water, pigment, and at least one selected from resin particles and wax particles.

[0016] pH ranges from 7.2 to 11.

[0017] And it satisfies the following inequality (X).

[0018] ORPi - [285 - 59 × (pHi - 6.2)] ≥ 0 …… Inequality (X)

[0019] In inequality (X), ORPi represents the redox potential of the inkjet ink measured in mV under device conditions where the redox potential of water at pH 6.2 reaches 310 mV, and pHi represents the pH of the inkjet ink.

[0020] <2> The inkjet ink described in <1> also contains an oxidizing agent.

[0021] <3> According to the inkjet ink described in <2>, wherein,

[0022] The oxidant contains at least one selected from the group consisting of hydrogen peroxide and peroxides.

[0023] <4> The inkjet ink according to <2> or <3>, wherein,

[0024] The oxidant contains at least one selected from the group consisting of hydrogen peroxide, peracetic acid, sodium percarbonate, and urea peroxide.

[0025] <5> The inkjet ink according to any one of <2> to <4>, wherein,

[0026] The content of oxidant relative to the total content of resin particles and wax particles is 0.02% to 6% by mass.

[0027] <6> The inkjet ink according to any one of <1> to <5> further contains colloidal silica.

[0028] <7> The inkjet ink according to any one of <1> to <6> further contains an organic solvent with a ClogP value of 1.0 to 3.5.

[0029] <8> The inkjet ink according to <7>, wherein the organic solvent with a ClogP value of 1.0 to 3.5 is selected from at least one of the compounds represented by Formula 1 and Formula 2 below.

[0030] [Chemical Formula 1]

[0031]

[0032] In Equation 1 or Equation 2, R 1 Each can be used independently to represent a hydrogen atom or a methyl group, R 2Each group independently represents a straight-chain or branched hydrocarbon group with 4 to 9 carbon atoms, or an aryl group with 6 to 10 carbon atoms, where n represents an integer from 1 to 3.

[0033] <9> The inkjet ink according to any one of <1> to <8> further contains a dispersant, and the dispersant is cross-linked.

[0034] <10> The inkjet ink according to any one of <1> to <9>, wherein,

[0035] The resin particles contain resin comprising the structural units represented by Formula 3 below.

[0036] [Chemical Formula 2]

[0037]

[0038] In Equation 3, R 3 X represents an alkyl group having 1 to 4 hydrogen atoms or carbon atoms. 1 Y represents a divalent linker group. 1 Indicating anionic groups, in X 1 and Y 1 In the middle, the atom furthest from the main chain is 4 to 27 atoms away from the main chain.

[0039] <11> The inkjet ink according to any one of <1> to <10> further contains cellulose nanofibers.

[0040] <12> According to the inkjet ink described in <11>, wherein,

[0041] The average fiber width of cellulose nanofibers is greater than 1 nm and less than 10 nm.

[0042] <13> The inkjet ink according to <11> or <12>, wherein,

[0043] The average fiber length of cellulose nanofibers is greater than 10 nm and less than 1000 nm.

[0044] <14> The inkjet ink according to any one of <11> to <13>, wherein,

[0045] The cellulose nanofibers are TEMPO oxidized cellulose nanofibers.

[0046] <15> The inkjet ink according to any one of <11> to <14>, wherein,

[0047] The mass ratio of cellulose nanofiber content to the total content of resin particles and wax particles is 1.00% to 10.00% by mass.

[0048] <16> The inkjet ink according to any one of <11> to <15>, wherein,

[0049] The content of cellulose nanofibers is 0.01% to 1.00% by mass relative to the total amount of inkjet ink.

[0050] <17> The inkjet ink according to any one of <11> to <16> has a viscosity of 3.8 mPa·s to 6.0 mPa·s when measured at 30°C and 100 rpm.

[0051] <18> An image recording method, comprising:

[0052] The process of ejecting inkjet ink, any one of <1> to <17>, from an inkjet head containing silicon in the ink flow path and applying it to a recording medium.

[0053] Invention Effects

[0054] According to one aspect of the present invention, an inkjet ink and an image recording method using the inkjet ink are provided, wherein the inkjet ink is inkjet ink ejected from an inkjet head containing silicon in the ink flow path wall, and is capable of suppressing the etching of the ink flow path wall. Detailed Implementation

[0055] In this invention, the numerical range represented by “~” refers to the range included by taking the values ​​recorded before and after “~” as the lower limit and upper limit values.

[0056] In this invention, regarding the amount of each component in the composition, when multiple substances corresponding to each component are present in the composition, unless otherwise specified, the amount of each component in the composition represents the total amount of the multiple substances present in the composition.

[0057] In the numerical ranges recorded in stages in this invention, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges recorded in stages, and can also be replaced with the value shown in the embodiment.

[0058] In this invention, the term "process" includes not only independent processes, but also processes that can be clearly distinguished from other processes, as long as the intended purpose of the process can be achieved.

[0059] In this invention, the combination of preferred methods is a more preferred method.

[0060] In this invention, "(meth)acrylic acid" is a concept that includes both acrylic acid and methacrylic acid, and "(meth)acrylate" is a concept that includes both acrylate and methacrylate.

[0061] [Inkjet ink]

[0062] The inkjet ink of this invention (hereinafter, also simply referred to as "ink") is...

[0063] Inkjet ink ejected from an inkjet head containing silicon (Si) in the ink flow path walls.

[0064] It contains water, pigments, and at least one of resin particles and wax particles (hereinafter also referred to as "resin particles and / or wax particles").

[0065] pH ranges from 7.2 to 11.

[0066] The following inequality (X) is satisfied.

[0067] ORPi - [285 - 59 × (pHi - 6.2)] ≥ 0 …… Inequality (X)

[0068] In inequality (X), ORPi represents the redox potential of the inkjet ink measured in mV under device conditions where the redox potential of water at pH 6.2 reaches 310 mV, and pHi represents the pH of the inkjet ink.

[0069] As described above, when using conventional alkaline (e.g., pH 7.2 or higher) inkjet ink and an inkjet head containing silicon in the ink flow path wall to eject the inkjet ink from the inkjet head to record images, sometimes the silicon-containing ink flow path wall is etched by the alkaline inkjet ink.

[0070] When the ink flow path walls are etched, the ejection of ink from the inkjet head can sometimes be impaired, so it is desirable to suppress the etching of the ink flow path walls.

[0071] Although the ink of the present invention is an alkaline ink, it is able to suppress the etching of the silicon-containing ink flow path walls of the inkjet head.

[0072] In detail, in the ink of the present invention,

[0073] The ink contains at least one of resin particles and wax particles, and

[0074] The ink satisfies inequality (X) (i.e., the redox potential ORPi of the ink is greater than "285-59×(pHi-6.2)").

[0075] Therefore, it is possible to suppress the etching of the silicon-containing ink flow path walls of the inkjet head.

[0076] The reasons for this effect are speculated as follows.

[0077] It is believed that in the ink of the present invention, since the ink satisfies inequality (X), the formation of an oxide film (i.e., a silicon oxide film) on the surface of the ink flow path wall containing silicon can be promoted, and the ink flow path wall can be protected by the silicon oxide film, thereby suppressing the etching of the ink flow path wall.

[0078] Furthermore, it is believed that in the ink of the present invention, the resin particles and / or wax particles in the ink act as buffering materials, which can suppress the wear of the ink flow path walls by the pigments in the ink, thereby suppressing the etching caused by the wear of the ink flow path walls.

[0079] <pH>

[0080] The pH of the ink of the present invention (i.e., pHi in inequality (X)) is 7.2 to 11.

[0081] That is, the ink of the present invention is an alkaline ink.

[0082] As mentioned above, in conventional alkaline inks, etching of the ink flow path walls may occur, but in the ink of the present invention, the problem of etching of the ink flow path walls can be solved.

[0083] A pH of 7.2–11 is beneficial for the storage stability of ink.

[0084] The pH of the ink is preferably 7.5 to 10, and more preferably 8.0 to 9.5.

[0085] In this invention, pH refers to the value measured using a pH meter (e.g., the product name "WM-50EG" manufactured by DKK-TOA CORPORATION) at a temperature of 25°C.

[0086] <Inequality (X)>

[0087] The ink of the present invention satisfies the following inequality (X).

[0088] ORPi - [285 - 59 × (pHi - 6.2)] ≥ 0 …… Inequality (X)

[0089] In inequality (X), ORPi represents the redox potential of the inkjet ink measured in mV under device conditions where the redox potential of water at pH 6.2 reaches 310 mV, and pHi represents the pH of the inkjet ink.

[0090] In this invention, ORPi refers to the value measured using a redox potential measuring device (e.g., the ORP Tester 10 manufactured by Eutech Instruments), which is calibrated to have a redox potential of 310 mV for water at pH 6.2.

[0091] There are no particular limitations on the specific method used to make the ink satisfy inequality (X).

[0092] For example, by adjusting the types and amounts of the components contained in the ink, it is possible to adjust the ink to satisfy inequality (X).

[0093] As shown in inequality (X), the value of “ORPi-[285-59×(pHi-6.2)]” is greater than 0.

[0094] From the viewpoint of further suppressing the etching of the ink flow path walls, the value of "ORPi-[285-59×(pHi-6.2)]" is preferably 5.0 or more, and more preferably 10 or more.

[0095] There is no particular upper limit to the value of “ORPi-[285-59×(pHi-6.2)]”, but 30 can be given as an example of an upper limit.

[0096] <Inkjet head>

[0097] The ink of the present invention is ejected from an inkjet head containing silicon in the ink flow path wall.

[0098] As an inkjet head, the ink flow path wall is preferably formed of a silicon-containing component.

[0099] There are no particular limitations on such inkjet heads, but reference can be made to inkjet heads described in publicly available documents such as Japanese Patent Application Publication No. 2015-063574, Japanese Patent Application Publication No. 2003-165936, Japanese Patent Application Publication No. 2016-044236, Japanese Patent Application Publication No. 2011-063000, Japanese Patent Application Publication No. 2011-111527, and Japanese Patent No. 4902711.

[0100] <Water>

[0101] The ink of this invention contains water.

[0102] The water content relative to the total amount of ink of the present invention is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and even more preferably 60% by mass or more.

[0103] The upper limit of the water content relative to the total amount of ink of the present invention also depends on the content of other components, such as 99% by mass, 90% by mass, 80% by mass, etc.

[0104] <Pigment>

[0105] The ink of this invention contains pigments.

[0106] The type of pigment is not particularly limited; it can be either organic or inorganic pigment.

[0107] As for pigments, examples include those described in Seishiro Itō's "Encyclopedia of Pigments" (2000), W. Herbst and K. Hunger's "Industrial Organic Pigments", Japanese Patent Application Publication Nos. 2002-12607, 2002-188025, 2003-26978, and 2003-342503.

[0108] From the viewpoint of ink ejectibility, the pigment content is preferably 0.5% to 15% by mass relative to the total amount of ink, and more preferably 1% to 10% by mass.

[0109] <Resin particles and / or wax particles>

[0110] The ink of this invention contains resin particles and / or wax particles.

[0111] When the ink of the present invention contains resin particles, the resin particles may be of only one type or of two or more types. Furthermore, when the ink of the present invention contains resin particles, the resin particles can be dispersed in the ink using a dispersant.

[0112] When the ink of the present invention contains wax particles, the wax particles may be of only one type or of two or more types. Furthermore, when the ink of the present invention contains wax particles, the wax particles can be dispersed in the ink using a dispersant.

[0113] Relative to the total amount of ink, the total content of resin particles and wax particles in the ink of the present invention is preferably 0.5% to 20% by mass, more preferably 1% to 10% by mass, and even more preferably 1.5% to 8% by mass.

[0114] (Resin particles)

[0115] The resin particles contain resin, and may also contain core materials other than resin, but resin particles consisting only of resin are preferred.

[0116] -Structural Unit (c1)-

[0117] The resin particles preferably contain a resin comprising the structural unit represented by Formula 3 below (hereinafter also referred to as "structural unit (c1)").

[0118] [Chemical Formula 3]

[0119]

[0120] In Equation 3, R 3X represents an alkyl group having 1 to 4 hydrogen atoms or carbon atoms. 1 Y represents a divalent linker group. 1 Indicating anionic groups, in X 1 and Y 1 In this process, the atom furthest from the main chain is 4 to 27 atoms away from the main chain. If the distance between the atom furthest from the main chain and the main chain is more than 4 atoms, the hydrophobicity of structural unit c1 increases, and the overall hydrophobicity of the resin particles increases. Therefore, after the ink droplet lands on the recording medium, the resin particles contained in the ink droplet are easily fixed on the recording medium, suppressing landing interference. Therefore, it is believed that if the ink of this invention is used, an image with excellent graininess can be obtained. Furthermore, it is believed that because the resin particles are highly hydrophobic overall, they are less prone to swelling, resulting in excellent ejectibility of the ink according to this invention.

[0121] On the other hand, it is believed that if the distance between the atom farthest from the main chain and the main chain is less than 27 atoms, the overall hydrophobicity of the resin particles will not be too high and the ejectibility will be excellent. Furthermore, from the viewpoint of ease of obtaining raw materials and suitability for manufacturing, in X1 and Y1, the distance between the atom farthest from the main chain and the main chain is preferably less than 27 atoms.

[0122] In Equation 3, R 3 Preferably, it contains hydrogen atoms or methyl groups.

[0123] In Equation 3, X 1 Preferably, the free radicals -C(=O)O- and -C(=O)NR are selected. 4 - A divalent group composed of alkylene and arylene groups, or a combination of two or more of these groups, more preferably a divalent group selected from -C(=O)O- or -C(=O)NR. 4 - A group consisting of alkylene groups having 6 to 22 carbon atoms and arylene groups having 6 to 20 carbon atoms, or a divalent group consisting of two or more of these groups.

[0124] When X 1 Contains -C(=O)O- or -C(=O)NR 4 - When, R in preferred formula 3 3 The bonded carbon atom is with -C(=O)O- or -C(=O)NR 4 - carbon atoms (R) 4 (Except for the carbon atoms contained in it) Direct bonding.

[0125] R 4 The alkyl group represents 1 to 4 carbon atoms, preferably hydrogen atoms or methyl groups, and more preferably hydrogen atoms.

[0126] In Equation 3, Y 1Preferably, it is -C(=O)OM, -S(=O)2OM or -OP(=O)(OM)2, more preferably -C(=O)OM.

[0127] M represents a hydrogen atom, an alkali metal, or a quaternary ammonium. M can be bonded or dissociated. From the viewpoint of the dispersion stability of resin particles in the ink, M is preferably an alkali metal. Examples of alkali metals include sodium and potassium. For example, when using Y... 1 In the process of synthesizing resin particles from monomers of -C(=O)OH, resin particles with M being an alkali metal can be obtained by replacing hydrogen atoms with alkali metal bicarbonates, alkali metal carbonates, sodium hydroxide, potassium hydroxide, etc.

[0128] In Equation 3, from the viewpoint of improving ink ejectibility and obtaining images with better graininess, X 1 and Y 1 In this process, the atom furthest from the main chain is preferably 10 to 23 atoms away from the main chain, and more preferably 12 to 20 atoms away from the main chain.

[0129] Structural unit c1 is preferably the structural unit represented by Equation 4 or Equation 5 below, and more preferably the structural unit represented by Equation 4.

[0130] [Chemical Formula 4]

[0131]

[0132] In equation 4 or equation 5, R 3 A represents either a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, respectively. 1 These can be used to independently represent single bonds, -C(=O)O-, or -C(=O)NR. 4 -, R 4 L represents an alkyl group having 1 to 4 hydrogen atoms or carbon atoms. 1 Y represents a divalent linker group with 6 to 22 carbon atoms, respectively. 1 L represents an anionic group. 1 and Y 1 In the middle, the atom furthest from the main chain is 4 to 27 atoms away from the main chain.

[0133] In equation 4 or equation 5, R 3 The meaning of R is the same as in Equation 3 above. 3 The meanings are the same, and the preferred methods are also the same.

[0134] In Equation 4, A 1 Preferably -C(=O)O- or -C(=O)NR 4 - In Equation 5, A 1 Single bonds are preferred.

[0135] In equation 4 or 5, -C(=O)O- or -C(=O)NR 4 The orientation of the - bond is not particularly limited, but -C(=O)O- or -C(=O)NR is preferred. 4 - The carbon atom in - and R in formula 4 or 5 3 The carbon atoms that are bonded are directly bonded.

[0136] R 4 Preferably, it is a hydrogen atom or a methyl group, more preferably a hydrogen atom.

[0137] In Equation 4, L 1 Preferably, the alkylene group has 6 to 22 carbon atoms. The alkylene group can be linear or branched, but from the viewpoint of ink ejectibility, a linear form is preferred. 1 Preferably, it is an alkylene group having 8 to 22 carbon atoms, more preferably an alkylene group having 8 to 16 carbon atoms, and even more preferably an alkylene group having 10 to 12 carbon atoms.

[0138] In Equation 5, L 1 Preferably, the linker group has 6 to 20 carbon atoms. The linker group is not particularly limited, but from the viewpoint of synthetic applicability, -C(=O)NR is preferred. 4 -(CH2) n -or -C(=O)O-(CH2) n -, more preferably -C(=O)NR 4 -(CH2) n -. R 4 The alkyl group represents 1 to 4 hydrogen atoms or carbon atoms, preferably hydrogen atoms or methyl groups, more preferably hydrogen atoms. Furthermore, n represents an integer from 5 to 18, more preferably 7 to 15, and even more preferably 10 to 12.

[0139] In equation 4 or 5, Y 1 The preferred options are -C(=O)OM, -S(=O)2OM or -OP(=O)(OM)2, and the preferred option is -C(=O)OM.

[0140] M represents a hydrogen atom, an alkali metal, or a quaternary ammonium. M can be bonded or dissociated. From the viewpoint of the dispersion stability of resin particles in the ink, M is preferably an alkali metal. Examples of alkali metals include sodium and potassium.

[0141] In Equation 4 or Equation 5, from the viewpoint of improving ink ejectibility and obtaining images with better graininess, L 1 and Y 1 In this process, the atom furthest from the main chain is preferably 10 to 23 atoms away from the main chain, and more preferably 12 to 20 atoms away from the main chain.

[0142] The following shows a preferred example of structural unit c1, but structural unit c1 is not limited to this specific example. In the specific example, n represents the number of repetitions, and R represents an alkyl group having 1 to 4 hydrogen atoms or carbon atoms.

[0143] [Chemical Formula 5]

[0144]

[0145] The content of structural unit c1 relative to the total mass of the resin is 1% to 20% by mass, and from the viewpoint of ink ejectibility, it is preferably 1.5% to 18% by mass, and more preferably 2% to 12% by mass.

[0146] In this invention, the resin may contain only one type of structural unit c1, or it may contain two or more types of structural units c1. When the resin contains two or more structural units c1, the above-mentioned content refers to the total content of the two or more structural units c1.

[0147] Structural unit c1 is derived from a monomer containing anionic groups and has a relatively long side chain, thus exhibiting high hydrophobicity. If the structural unit derived from the monomer containing anionic groups has high hydrophobicity, the overall hydrophobicity of the resin particles increases. Therefore, after the ink droplet lands on the recording medium, the resin particles contained within the ink droplet are rapidly fixed, and landing interference is suppressed. Therefore, it is believed that if the ink of the present invention is used, an image with excellent graininess can be obtained. Furthermore, it is believed that because the resin particles have high overall hydrophobicity, they are less prone to swelling, resulting in excellent ejectibility of the ink according to the present invention.

[0148] In this invention, the content of structural unit c1 is 1% to 20% by mass relative to the total mass of the resin, but the types of structural units other than structural unit c1 are not particularly limited. It is generally believed that the overall physical properties of the resin change depending on the types of structural units constituting the resin. However, the inventors have discovered that structural unit c1 is derived from monomers containing anionic groups, thereby improving the ink ejectibility and obtaining images with excellent particle texture, as described above.

[0149] -Structural unit c2-

[0150] The resin preferably also contains structural unit c2 (hereinafter also simply referred to as "structural unit c2") derived from an olefinic unsaturated compound having an aromatic ring structure or an alicyclic structure as a structural unit other than structural unit c1.

[0151] Examples of rings contained in structural unit c2 include benzene rings, naphthalene rings, anthracene rings, and aliphatic hydrocarbon rings with 5 to 20 carbon atoms. Preferably, the rings contained in structural unit c2 are benzene rings or aliphatic hydrocarbon rings with 6 to 10 carbon atoms. These rings may have substituents on them.

[0152] The olefinic unsaturated compound having an aromatic ring structure or an alicyclic structure is preferably an olefinic unsaturated compound having an olefinic unsaturated group at the end of the compound, more preferably styrene, styrene with substituents, (meth)acrylate compounds or (meth)acrylamide compounds, and even more preferably styrene, styrene with substituents or (meth)acrylate compounds.

[0153] From the viewpoint of improving the abrasion resistance of the obtained image, structural unit c2 is preferably selected from at least one of the group consisting of structural units represented by the following formulas A to F. Furthermore, from the viewpoint of further improving the ink ejectibility, structural unit c2 is more preferably composed of structural units represented by the following formula A.

[0154] [Chemical Formula 6]

[0155]

[0156] In equations A through F, R 11 and R 12 Each can be used independently to represent a hydrogen atom or a methyl group. R 13 Each alkyl group can be independently represented as a linear or branched alkyl group with 1 to 10 carbon atoms. n can be an independent integer from 0 to 5. L 2 Each of these groups independently represents a divalent group selected from the group consisting of alkylene groups with 1 to 18 carbon atoms, aryl groups with 6 to 18 carbon atoms, -O-, -NH-, -S-, and -C(=O)-, or a divalent group or single bond formed by combining two or more of these groups.

[0157] In formula A, R 11 Hydrogen atoms are preferred.

[0158] In equations B to F, R 12 Methyl is preferred.

[0159] In equations A through C, R 13 Preferably, each is an alkyl group having 1 to 4 carbon atoms, either linear or branched, and more preferably methyl or ethyl.

[0160] In formulas A to C, n is preferably an integer from 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0161] In formula B, L 2Preferably, the carbon atom bonded to the carbonyl group described in Formula B contains at least a -O- or -NH- divalent linker group. More preferably, the carbon atom bonded to the carbonyl group contains at least -O- or -NH- and contains a straight-chain or branched alkylene group with 1 to 18 carbon atoms that may have a ring structure. Further preferred are -OCH2- or -NHCH2-, and particularly preferred are -OCH2-.

[0162] In equations C to E, L 2 Preferably, the carbon atom bonded to the carbonyl group described in Formulas C to F contains at least a divalent linker group of -O- or -NH-, more preferably -O- or -NH-, and even more preferably -O-.

[0163] The following are specific examples of the structural unit represented by Equation A, but the structural unit represented by Equation A is not limited to the following specific examples.

[0164] [Chemical Formula 7]

[0165]

[0166] The following are specific examples of the structural unit represented by Equation B, but the structural unit represented by Equation B is not limited to the following specific examples.

[0167] [Chemical Formula 8]

[0168]

[0169] The following are specific examples of the structural unit represented by Equation C, but the structural unit represented by Equation C is not limited to the following specific examples.

[0170] [Chemical Formula 9]

[0171]

[0172] The following are specific examples of the structural unit represented by Equation D, but the structural unit represented by Equation D is not limited to the following specific examples.

[0173] [Chemical Formula 10]

[0174]

[0175] The following are specific examples of the structural unit represented by Equation E, but the structural unit represented by Equation E is not limited to the following specific examples.

[0176] [Chemical Formula 11]

[0177]

[0178] The following are specific examples of the structural unit represented by Equation F, but the structural unit represented by Equation F is not limited to the following specific examples.

[0179] [Chemical Formula 12]

[0180]

[0181] From the viewpoint of improving the ink ejectibility, the content of structural unit c2 is preferably 5% to 90% by mass, more preferably 10% to 50% by mass, relative to the total mass of the resin.

[0182] The resin may contain only one type of structural unit c2, or it may contain two or more types of structural units c2. When the resin contains two or more structural units c2, the above content refers to the total content of the two or more structural units c2.

[0183] -Other structural units c3-

[0184] The resin may contain structural unit c1 and other structural units c3 (hereinafter also referred to as "structural unit c3") besides structural unit c2.

[0185] Structural unit c3 is not particularly limited, but is preferably a structural unit derived from (meth)acrylamide compounds or (meth)acrylate compounds, more preferably a structural unit derived from (meth)acrylate compounds. Furthermore, structural unit c3 preferably does not contain anionic groups.

[0186] Structural unit c3 is preferably a structural unit derived from an alkyl group of an alkyl (meth)acrylate compound having 1 to 10 carbon atoms. The alkyl group can be linear, branched, or have a cyclic structure.

[0187] The resin may or may not contain structural unit c3. When the resin contains structural unit c3, from the viewpoint of improving the ink ejectibility, the content of structural unit c3 relative to the total mass of the resin is preferably 10% to 90% by mass, more preferably 30% to 85% by mass, and even more preferably 50% to 80% by mass.

[0188] The resin may contain only one type of structural unit c3, or it may contain two or more types of structural units c3. When the resin contains two or more structural units c3, the above content refers to the total content of the two or more structural units c3.

[0189] (Properties of resin particles)

[0190] From the viewpoint of the dispersibility of resin particles, the content of anionic groups in the resin contained in the resin particles relative to the total mass of the resin is preferably 0.05 mmol / g to 0.7 mmol / g, more preferably 0.1 mmol / g to 0.4 mmol / g.

[0191] The weight-average molecular weight (Mw) of the resin is preferably 10,000 to 1,000,000, more preferably 20,000 to 500,000.

[0192] In this invention, unless otherwise stated, weight-average molecular weight (Mw) refers to the value measured by gel permeation chromatography (GPC). In the GPC-based measurement, an HLC (registered trademark)-8020GPC (Tosoh Corporation) was used as the measuring apparatus, three TSKgel (registered trademark) Super Multipore HZ-H (4.6mm ID × 15cm, Tosoh Corporation) columns were used, and THF (tetrahydrofuran) was used as the eluent. An RI detector was used for the measurement, with the sample concentration set at 0.45% by mass, the flow rate at 0.35 ml / min, the sample injection volume at 10 μl, and the measurement temperature at 40°C. Calibration curves were prepared using eight samples manufactured by Tosoh Corporation: “Standard Samples TSK Standard, Polystyrene”: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, “A-2500”, “A-1000”, and “n-propylbenzene”.

[0193] From the viewpoint of improving the abrasion resistance of the image, the glass transition temperature (Tg) of the resin is preferably 30°C to 120°C, more preferably 50°C to 100°C, and even more preferably 70°C to 100°C.

[0194] The glass transition temperature (Tg) is the measured Tg obtained through actual measurement. Tg is measured using a differential scanning calorimeter, such as the one manufactured by SII NanoTechnology Inc. (product name "EXSTAR6220"), under normal measurement conditions. When measurement is difficult due to material decomposition, a calculated Tg is used, calculated using the following formula. The calculated Tg is the value obtained from Formula 1 below.

[0195] 1 / Tg=Σ(Xi / Tgi)……(1)

[0196] Here, the polymer to be calculated is assumed to be a copolymer of n monomer components from i=1 to n. Xi is the mass fraction of the i-th monomer (ΣXi=1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. Σ is the sum of all components from i=1 to n. Furthermore, the values ​​of the glass transition temperatures (Tgi) of the homopolymers of each monomer are adopted from the Polymer Handbook (3rd edition) (J. Brandrup, E. Himmergut, Wiley-Interscience, 1989).

[0197] From the viewpoint of ink ejectibility, the volume average particle size of the resin particles is preferably 1 nm to 200 nm, more preferably 5 nm to 100 nm, and most preferably 10 nm to 50 nm.

[0198] Volume average particle size was measured using a light-scattering particle size distribution measuring device, such as the particle size distribution measuring device manufactured by Nikkiso Co., Ltd. (product name "MICROTRAC UPA (registered trademark) EX150").

[0199] -Methods for manufacturing resin particles-

[0200] The method for manufacturing resin particles is not particularly limited, but emulsion polymerization is preferred. Emulsion polymerization is a method of polymerizing an emulsion by adding monomers, polymerization initiators, emulsifiers, and additives such as chain transfer agents as needed to an aqueous medium (e.g., water). When emulsion polymerization is applied to the preparation of resin particles, the monomers that form the aforementioned structural unit c1 also function as emulsifiers. Therefore, no additional emulsifier is needed besides the monomers that form structural unit c1; however, known emulsifiers may be added as long as they do not reduce the ink's printability and image quality.

[0201] The polymerization initiator used in the method for manufacturing resin particles is not particularly limited. Examples include inorganic persulfates (e.g., potassium persulfate, sodium persulfate, ammonium persulfate, etc.), azo initiators (e.g., 2,2'-azobis(2-amidinylpropane) dihydrochloride, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], etc.), organic peroxides (e.g., tert-butyl peroxypentanoate, tert-butyl hydroperoxide, etc.), and their salts. One polymerization initiator may be used, or two or more may be used in combination. Preferably, an azo initiator or an organic peroxide is used.

[0202] The amount of polymerization initiator used relative to the total mass of monomers is preferably 0.01% to 2% by mass, more preferably 0.2% to 1% by mass.

[0203] Chain transfer agents used in the manufacturing process of resin particles include, for example, known compounds such as carbon tetrahalides, styrene dimers, (meth)acrylate dimers, thiols, and thioethers. Among these, styrene dimers or thiols as described in Japanese Patent Application Publication No. 5-17510 are preferred as chain transfer agents.

[0204] The resin particles are preferably dispersed in the ink.

[0205] Furthermore, the resin particles are preferably self-dispersible resin particles. Self-dispersible resin particles refer to resin particles composed of water-insoluble resin, which, in the absence of surfactants, can be dispersed in an aqueous medium through the functional groups (e.g., anionic groups) inherent in the resin itself when in a dispersed state by phase inversion emulsification.

[0206] The dispersion state includes two states: the emulsion state (emulsion) in which water-insoluble resin is dispersed in a liquid state in an aqueous medium, and the dispersion state (suspension) in which water-insoluble resin is dispersed in a solid state in an aqueous medium.

[0207] Furthermore, "water insoluble" means that the amount of water that can be dissolved in 100 parts by mass of water at 25°C is less than 5.0 parts by mass.

[0208] The resin particles do not function as a dispersant for the pigment. Furthermore, the resin particles exist in the ink in particle form. Therefore, they differ from the dispersants used in this invention.

[0209] From the viewpoint of ink preservation stability and the abrasion resistance of the obtained image, the content of resin particles relative to the total mass of ink is preferably 0.5% to 20% by mass, more preferably 1% to 10% by mass, and even more preferably 1.5% to 8% by mass.

[0210] The following examples illustrate specific examples of resin contained in resin particles, but the present invention is not limited thereto. In the following examples, n represents the number of repetitions, and the percentage by mass refers to the content of each structural unit.

[0211] The resin particles are preferably resin particles composed of the resins shown in the specific examples below. Furthermore, in the specific examples below, anionic groups are described in an acidic state, but some or all of the acid may be a salt.

[0212] [Chemical Formula 13]

[0213]

[0214] [Chemical Formula 14]

[0215]

[0216] [Chemical Formula 15]

[0217]

[0218] [Chemical Formula 16]

[0219]

[0220] When the ink of the present invention contains resin particles, the ink of the present invention can be prepared using commercially available resin emulsions (i.e., aqueous dispersions of resin particles).

[0221] Commercially available resin emulsions include, for example, A-810 (SANSUI Co., Ltd.), A-995 (SANSUI Co., Ltd.), HIROS-X•NE-2186 (SEIKO PMC CORPORATION), HIROS-X•TE-1048 (SEIKO PMC CORPORATION), Cybinol SK-202 (SAIDEN CHEMICAL INDUSTRY CO.,LTD.), TOCRYLW-1048 (TOYOCHEM CO., LTD.), WC-M-1217 (ARAKAWA CHEMICAL INDUSTRIES, LTD.), WC-M-1219 (ARAKAWA CHEMICAL INDUSTRIES, LTD.), N985(A)-1 (Emulsion Technology Co., Ltd.), Neocryl A-1105 (DSM coating resin), Acryte SE-810A, and Acryte... SE-953A-2, Acryte SE-1658F, Acryte SE-2974F, Acryte SE-2978F (TAISEI FINE CHEMICAL CO,.LTD.), LuckStar 7132-C (DIC), ST200 (NIPPON SHOKUBAI CO.,LTD.), Mowinyl 972 (Japan CoatingResin co.,ltd.), etc.

[0222] (Wax particles)

[0223] The ink of this invention may contain wax particles.

[0224] The melting point of the wax constituting the wax particles is preferably 40°C or higher and 140°C or lower, more preferably 45°C or higher and 100°C or lower, and even more preferably 50°C or higher and 95°C or lower.

[0225] As components of wax particles, waxes include both natural and synthetic waxes.

[0226] As natural waxes, examples include petroleum-based waxes, plant-based waxes, and animal-based waxes.

[0227] Examples of petroleum-based waxes include paraffin wax, microcrystalline wax, and petrolatum.

[0228] Examples of plant-based waxes include carnauba wax, candelilla wax, rice bran wax, and wood wax.

[0229] Examples of animal-derived waxes include lanolin and beeswax.

[0230] Examples of synthetic waxes include synthetic hydrocarbon waxes and modified waxes.

[0231] Examples of synthetic hydrocarbon waxes include polyethylene wax and Fischer-Tropsch wax.

[0232] Examples of modified waxes include paraffin wax derivatives, lignite wax derivatives, microcrystalline wax derivatives, and their derivatives.

[0233] From the viewpoint of further improving the abrasion resistance of images, carnauba wax is particularly preferred as the wax constituting the wax particles.

[0234] Commercially available wax particles include Cellosol 524, Trasol CN, Trasol PF60, polylon L-787, polylon P-502 (all manufactured by CHUKYO YUSHI CO.,LTD.), ITOHWAX E-210 (manufactured by ITOH OILCHEMICALS CO.,LTD.), Nopcote PEM17 (manufactured by SAN NOPCO LIMITED), and AQUACER 515 (manufactured by BYK Japan KK).

[0235] Furthermore, as a wax particle, ester A described in paragraph 0254 of Japanese Patent Application Publication No. 2011-162692 can also be cited.

[0236] Among these, carnauba waxes are Cellosol524 and Trasol CN.

[0237] Furthermore, regarding preferred methods for dispersing wax particles (such as organic solvents or dispersion stabilizers that can be used when dispersing wax particles), one can appropriately refer to paragraphs 0154 to 0170 of Japanese Patent Application Publication No. 2011-162692.

[0238] <Oxidizing Agent>

[0239] The ink of the present invention preferably contains at least one oxidizing agent.

[0240] This further suppresses the etching of the ink flow path walls.

[0241] As an oxidizing agent, at least one can be selected from the group consisting of hydrogen peroxide and peroxides.

[0242] Examples of peroxides include peracetic acid, sodium percarbonate, and urea peroxide.

[0243] The oxidant preferably contains at least one selected from the group consisting of hydrogen peroxide, peracetic acid, sodium percarbonate and urea peroxide.

[0244] This further suppresses the etching of the ink flow path walls.

[0245] The mass ratio of the oxidant content to the total content of resin particles and wax particles is preferably 0.02% to 6% by mass, more preferably 0.05% to 4% by mass, and even more preferably 0.1% to 2% by mass.

[0246] When the content of oxidant relative to the total content of resin particles and wax particles is 0.02% by mass or more, the etching of the ink flow path wall is further suppressed.

[0247] When the content of oxidant relative to the total content of resin particles and wax particles is less than 6% by mass, the stability of the ink is further improved.

[0248] The content of oxidant relative to the total amount of ink is preferably 0.001% to 1% by mass, more preferably 0.01% to 0.1% by mass.

[0249] When the content of oxidant relative to the total amount of ink is 0.001% by mass or more, the etching of the ink flow path wall is further suppressed.

[0250] When the content of oxidant relative to the total amount of ink is less than 1% by mass, the stability of the ink is further improved.

[0251] Colloidal silica

[0252] The ink of the present invention preferably contains at least one type of colloidal silica.

[0253] As a result, the etching of the ink flow path walls is further suppressed.

[0254] Colloidal silica is a colloid composed of particles of inorganic oxides containing silicon.

[0255] Colloidal silica may contain silica (including its hydrates) as the main component and may contain aluminates as a small component.

[0256] Examples of aluminates that are sometimes present in small amounts include sodium aluminate and potassium aluminate.

[0257] Furthermore, colloidal silica may contain inorganic salts such as sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonium hydroxide, or organic salts such as tetramethylammonium hydroxide. These inorganic and organic salts, for example, function as stabilizers of the colloid.

[0258] There are no particular limitations on the dispersion medium used in colloidal silica; it can be any of water, organic solvents, or mixtures thereof.

[0259] The organic solvent can be a water-soluble organic solvent or a non-water-soluble organic solvent, but a water-soluble organic solvent is preferred.

[0260] As water-soluble organic solvents, examples include methanol, ethanol, isopropanol, and n-propanol.

[0261] There are no particular limitations on the manufacturing method of colloidal silica; it can be produced using commonly used methods. For example, it can be produced by the synthesis of aerosil through the thermal decomposition of silicon tetrachloride or by water glass.

[0262] Alternatively, it can also be manufactured by liquid-phase synthesis methods such as hydrolysis of alkoxides (see, for example, "Fibers and Industry", Vol. 60, No. 7 (2004) P376).

[0263] The volume average particle size of colloidal silica only needs to meet the requirement that the particle size ratio (colloidal silica / titanium dioxide particles) is below 0.04.

[0264] From the viewpoint of more effectively suppressing the wear and deterioration of the inkjet head, the volume average particle size of colloidal silica is preferably 200 nm or less, more preferably 100 nm or less, even more preferably 50 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less.

[0265] As a lower limit for the volume average particle size of colloidal silica, examples include 1 nm, 3 nm, etc.

[0266] The volume-average particle size of colloidal silica was determined by dynamic light scattering.

[0267] As a measurement device for volume average particle size based on dynamic light scattering, for example, the NANOTRAC UPA manufactured by MICROTRAC Corporation is used.

[0268] The shape of colloidal silica is not particularly limited as long as it does not impede the ink's ejection performance. For example, it can be any of the following: spherical, strip-shaped, needle-shaped, or beaded. Among these, from the viewpoint of ink ejectibility, a spherical shape is preferred.

[0269] Colloidal silica can be manufactured colloidal silica or commercially available products.

[0270] As a specific example of a commercially available product, for example:

[0271] Ludox AM, Ludox AS, Ludox LS, Ludox TM, Ludox HS, etc. (all manufactured by EI Du Pont deNemours & Company); SNOWTEX S, SNOWTEX XS, SNOWTEX 20, SNOWTEX 30, SNOWTEX 40, SNOWTEX N, SNOWTEX C, SNOWTEX O, etc. (all manufactured by Nissan Chemical Corporation);

[0272] Syton C-30, SytonZOO, etc. (all manufactured by Mons anto Company);

[0273] Nalcoag-1060, Nalcoag-ID21~64 (the above are manufactured by Nalco Chem Co).

[0274] Methanol sol, IPA sol, MEK sol and toluene sol (all manufactured by FUSO CHEMICAL CO., LTD.);

[0275] Catoloid-S, Catoloid-F120, CatoloidSI-350, ColloidSI-500, ColloidSI-30, ColloidS-20L, CatoloidS-20H, CatoloidS-30L, CatoloidS-30H, CatoloidSI-40, OSCAL-1432 (isopropanol sol), etc. (all manufactured by JGC Catalysts and Chemicals Ltd.);

[0276] Adelite (manufactured by Asahi Denka Co., Ltd.); etc.

[0277] Furthermore, as bead-like colloidal silica, examples include commercially available colloidal silica under trade names such as SNOWTEX ST-UP, SNOWTEX PS-S, SNOWTEX PS-M, SNOWTEX ST-OUP, SNOWTEX PS-SO, and SNOWTEX PS-MO (all manufactured by Nissan Chemical Corporation).

[0278] From the viewpoint of further suppressing the etching of the ink flow path wall, the content of the solid component of colloidal silica is preferably 0.01% to 5% by mass, more preferably 0.01% to 2% by mass, and even more preferably 0.01% to 1% by mass, relative to the total amount of ink.

[0279] <Organic Solvents>

[0280] From the viewpoint of ink ejectibility, the ink of the present invention preferably contains an organic solvent.

[0281] From the viewpoint of ink ejectibility, the content of organic solvent is preferably 2.5% by mass or more relative to the total amount of ink.

[0282] The upper limit of the organic solvent content is not particularly limited, but from the viewpoint of ink drying properties, 30% by mass is preferred.

[0283] As an organic solvent, an organic solvent with a ClogP value of 1.0 to 3.5 is preferred.

[0284] If the ClogP value of the organic solvent is 1.0 or higher, the hydrophobicity will not be too low, and therefore it is preferred from the viewpoint of suppressing ink drying and improving image graininess.

[0285] If the ClogP value of the organic solvent is below 3.5, the hydrophobicity will not be too high, thus resulting in excellent sprayability.

[0286] As an organic solvent

[0287] Preferably, at least one compound is selected from the group consisting of compounds represented by Formula 1 and compounds represented by Formula 2.

[0288] More preferably, it is an organic solvent of at least one of the above-mentioned types with a ClogP value of 1.0 to 3.5.

[0289] [Chemical Formula 17]

[0290]

[0291] In Equation 1 or Equation 2, R 1 Each can be used independently to represent a hydrogen atom or a methyl group, R 2Each group independently represents a straight-chain or branched hydrocarbon group with 4 to 9 carbon atoms, or an aryl group with 6 to 10 carbon atoms, where n represents an integer from 1 to 3.

[0292] In Equation 1, from the perspective of reducing the surface tension of the ink, R 1 Hydrogen atoms are preferred.

[0293] In Formula 1, from the viewpoint of reducing the surface tension of the ink, n is preferably 1 or 2.

[0294] In Equations 1 and 2, R is used as... 2 The hydrocarbon group represented by 4 to 9 carbon atoms is either straight-chain or branched, for example, n-butyl, tert-butyl, n-pentyl, n-hexyl and 2-ethylhexyl.

[0295] In Equations 1 and 2, R is used as... 2 The aryl group represented by carbon atoms with 6 to 10 carbon atoms can be exemplified by phenyl, p-toluyl, m-toluyl, 2,6-dimethylphenyl, 4-tert-butylphenyl, 4-methoxyphenyl, 4-butoxyphenyl, 2-chlorophenyl, and naphthyl.

[0296] Organic solvents represented by Formula 1 or Formula 2 and having a ClogP value of 1.0 to 3.5 can be cited as examples:

[0297] Ethylene glycol monopentyl ether, ethylene glycol monohexyl ether, ethylene glycol monoheptyl ether, ethylene glycol monooctyl ether, ethylene glycol monononyl ether, ethylene glycol mono-2-ethylhexyl ether, and other ethylene glycol monoalkyl ethers;

[0298] Diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, diethylene glycol monoheptyl ether, diethylene glycol monooctyl ether, diethylene glycol monononyl ether, diethylene glycol mono-2-ethylhexyl ether, and other diethylene glycol monoalkyl ethers;

[0299] Triethylene glycol monopentyl ether, triethylene glycol monohexyl ether, triethylene glycol monoheptyl ether, triethylene glycol monooctyl ether, triethylene glycol monononyl ether, triethylene glycol mono-2-ethylhexyl ether, and other triethylene glycol monoalkyl ethers;

[0300] Propylene glycol monobutyl ether, propylene glycol monopentyl ether, propylene glycol monohexyl ether, propylene glycol monoheptyl ether, propylene glycol monooctyl ether, propylene glycol mono-2-ethylhexyl ether, and other propylene glycol monoalkyl ethers;

[0301] Dipropylene glycol monobutyl ether, dipropylene glycol monopentyl ether, dipropylene glycol monohexyl ether, dipropylene glycol monoheptyl ether, dipropylene glycol monooctyl ether, dipropylene glycol mono-2-ethylhexyl ether and other dipropylene glycol monoalkyl ethers;

[0302] Tripropylene glycol monobutyl ether, tripropylene glycol monopentyl ether, tripropylene glycol monohexyl ether, tripropylene glycol monoheptyl ether, tripropylene glycol monooctyl ether, tripropylene glycol mono-2-ethylhexyl ether, and other tripropylene glycol monoalkyl ethers; and

[0303] Alkanediols such as 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, and 1,2-decanediol.

[0304] The organic solvents that may be contained in the ink are preferably ethylene glycol monoalkyl ethers, diethylene glycol monoalkyl ethers or alkanediols, and more preferably ethylene glycol monohexyl ether, diethylene glycol monohexyl ether (hexyl diethylene glycol), diethylene glycol mono-2-ethylhexyl ether or 1,2-octanediol.

[0305] Furthermore, as organic solvents that may be contained in the ink of the present invention, examples include those described in paragraphs 0142 to 0154 of Japanese Patent Application Publication No. 2015-180710.

[0306] <Dispersant>

[0307] The ink of the present invention may contain at least one dispersant.

[0308] In this invention, the dispersant has the function of dispersing pigments. By adsorbing onto the surface of the pigment and coating at least a portion of the pigment surface, the pigment is more easily dispersed in a dispersion medium (e.g., water, a mixture of water and organic solvents, etc.).

[0309] From the viewpoint of improving the ejectibility of ink, the dispersant is preferably cross-linked.

[0310] It is believed that part of the dispersant is adsorbed onto the surface of the pigment, while part detaches from the surface of the pigment and exists in the ink.

[0311] It is believed that when the dispersant is cross-linked, it is less likely to detach from the surface of the pigment, thus improving the ink's sprayability.

[0312] Whether the dispersant is crosslinked can be determined, for example, by the following methods.

[0313] After centrifuging the ink at 10,000 rpm for 30 minutes, the precipitated pigment dispersion was extracted using a highly polar organic solvent. The composition was then analyzed by spectrophotometry or nuclear magnetic resonance (NMR) to determine the structure of the dispersant and the content ratio of its constituent monomers. The highly polar organic solvent used was appropriately selected based on the type of polymer for which extraction was intended.

[0314] From the perspective of ink dispersion stability, polymers are preferred as dispersants.

[0315] The structure of the dispersant is not particularly limited and can be any of random polymers, block polymers, and graft polymers.

[0316] The dispersant is more preferably a cross-linked polymer (hereinafter also referred to as "cross-linked polymer").

[0317] Crosslinked polymers are formed, for example, by using a crosslinking agent to crosslink an uncrosslinked polymer.

[0318] At this point, it is preferable to first prepare a pigment dispersion containing uncrosslinked polymer and pigment, and then form a crosslinked polymer by crosslinking the uncrosslinked polymer in the uncrosslinked pigment dispersion using a crosslinking agent (i.e., to obtain a pigment dispersion containing crosslinked polymer and pigment).

[0319] The uncrosslinked polymer is preferably a water-soluble polymer.

[0320] In this invention, "water-soluble" in "water-soluble polymer" refers to the property of dissolving at least 2% by mass in distilled water at 25°C. Preferably, the water-soluble resin dissolves at least 5% by mass in distilled water at 25°C, and more preferably at least 10% by mass.

[0321] Examples of uncrosslinked polymers include polyethylene, polyurethane, and polyester. Among these, polyethylene is preferred.

[0322] The uncrosslinked polymer is preferably a polymer having functional groups that can be crosslinked using a crosslinking agent. Examples of crosslinkable functional groups include carboxyl groups or their salts, isocyanate groups, and epoxy groups. From the viewpoint of improving the dispersibility of pigments, crosslinkable functional groups are preferably carboxyl groups or their salts, and particularly preferably carboxyl groups.

[0323] Polymers containing carboxyl groups are preferably copolymers comprising structural units derived from carboxyl-containing monomers (hereinafter referred to as "carboxyl-containing monomers"). The copolymer may contain only one type of structural unit derived from a carboxyl-containing monomer, or it may contain two or more types. The copolymer may be a random copolymer or a block copolymer.

[0324] Examples of carboxyl-containing monomers include (meth)acrylic acid, β-carboxyethyl acrylate, fumaric acid, itaconic acid, maleic acid, and crotonic acid.

[0325] From the viewpoint of crosslinking and dispersibility, the carboxyl-containing monomer is preferably (meth)acrylic acid or β-carboxyethyl acrylate, more preferably (meth)acrylic acid.

[0326] In addition to structural units derived from carboxyl-containing monomers, the copolymer preferably contains structural units derived from hydrophobic monomers. The copolymer may contain only one type of structural unit derived from hydrophobic monomers or more than two types.

[0327] Examples of hydrophobic monomers include (meth)acrylates having alkyl groups with 1 to 20 carbon atoms and (meth)acrylates having aromatic rings.

[0328] The polymer containing a carboxyl group is preferably a copolymer containing at least one of the following: structural units derived from a carboxyl-containing monomer and structural units selected from the group consisting of structural units derived from alkyl groups having 1 to 20 carbon atoms and structural units derived from methyl methacrylates having an aromatic ring; more preferably, a copolymer containing structural units derived from methyl methacrylates and structural units derived from methyl methacrylates having an aromatic ring; and particularly preferably, a copolymer containing structural units derived from methyl methacrylates and structural units derived from benzyl methacrylates.

[0329] From the viewpoint of pigment dispersibility, the acid value of the uncrosslinked polymer is preferably 67 mg KOH / g to 200 mg KOH / g, more preferably 67 mg KOH / g to 150 mg KOH / g.

[0330] Furthermore, from the viewpoint of pigment dispersibility, the acid value of the crosslinked polymer is preferably 55 mg KOH / g to 100 mg KOH / g.

[0331] The weight-average molecular weight (Mw) of the uncrosslinked polymer is not particularly limited, but from the viewpoint of pigment dispersibility, it is preferably 3,000 to 100,000, more preferably 5,000 to 80,000, and even more preferably 10,000 to 60,000.

[0332] The preferred range of weight-average molecular weight of the crosslinked polymer is the same as that of the uncrosslinked polymer.

[0333] When crosslinking an uncrosslinked polymer, the crosslinking agent used is preferably a compound having two or more reaction sites with the uncrosslinked polymer (e.g., a polymer with carboxyl groups). Only one crosslinking agent may be used, or two or more may be used.

[0334] A preferred combination of a crosslinking agent and an uncrosslinked polymer is a combination of a compound having two or more epoxy groups (i.e., an epoxy compound with two or more functional groups) and a polymer having carboxyl groups. In this combination, a crosslinked structure is formed by the reaction of epoxy groups and carboxyl groups. This forms a crosslinked polymer. The formation of the crosslinked structure using the crosslinking agent is preferably carried out after dispersing the pigment using the uncrosslinked polymer.

[0335] Examples of epoxide compounds with two or more functions include, for example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether.

[0336] Among them, epoxy compounds with two or more functions are preferably polyethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, or trimethylolpropane triglycidyl ether.

[0337] Crosslinking agents can be commercially available products.

[0338] Commercially available products include, for example, Denacol EX-321, EX-821, EX-830, EX-850 and EX-851 (manufactured by Nagase ChemteX Corporation).

[0339] From the viewpoint of crosslinking reaction rate and dispersion stability after crosslinking, the molar ratio of the reactive site (e.g., epoxy group) in the crosslinking agent to the reactive site (e.g., carboxyl group) in the uncrosslinked polymer is preferably 1:1.1 to 1:10, more preferably 1:1.1 to 1:5, and even more preferably 1:1.1 to 1:3.

[0340] Based on mass, the mixing ratio of pigment to dispersant is preferably 1:0.06 to 1:3, more preferably 1:0.125 to 1:2, and even more preferably 1:0.125 to 1:1.5.

[0341] <Silicone-based surfactants>

[0342] The ink of the present invention may contain at least one silicone-based surfactant.

[0343] Silicone-based surfactants are preferably compounds with a polysiloxane structure in their molecules. The presence of silicone-based surfactants in the ink improves its ejectibility. This is believed to be because the ink is less likely to adhere to the nozzle from which it is ejected.

[0344] Examples of silicone-based surfactants include compounds in which organic groups are introduced into a portion of dimethylpolysiloxane.

[0345] Organic groups are introduced into the side chain, single end, double end, or both the side chain and the end of the dimethylpolysiloxane.

[0346] Examples of dimethyl polysiloxanes with introduced organic groups include, for example, modified silicone compounds such as amino-modified silicone, alcohol-modified silicone, polyether-modified silicone, and long-chain alkyl-modified silicone.

[0347] From the perspective of improving the ink's ejectibility, polyether-modified silicone surfactants are preferred.

[0348] Silicone-based surfactants are preferably compounds with a molecular weight of 200 to 2000 and having the structure represented by Formula 4 below.

[0349] [Chemical Formula 18]

[0350]

[0351] In Equation 4, R 4 It represents an alkyl group with 1 to 4 hydrogen atoms or carbon atoms, and x, y and z each independently represent an integer greater than 1. Indicates the bonding position with other structures in the molecule.

[0352] In Equation 4, R 4 Preferably, it contains hydrogen atoms or methyl groups.

[0353] The molecular weight of silicone-based surfactants is 200–2000, preferably 400–1800. Silicone-based surfactants with a molecular weight of 200–2000 tend to orient at the interface, thus improving sprayability.

[0354] The content of silicone surfactant relative to the total mass of ink is preferably 0.03% to 0.8% by mass, more preferably 0.04% to 0.5% by mass, and even more preferably 0.05% to 0.3% by mass.

[0355] <Ethynediol-based surfactants>

[0356] The ink of the present invention may contain at least one acetylene glycol-based surfactant.

[0357] As an acetylenic diol-based surfactant, the acetylenic diol-based surfactant represented by the following formula 6 can be cited as an example.

[0358] [Chemical Formula 19]

[0359]

[0360] In Equation 6, R 52 R 53 R 54 and R 55 Each can independently represent a straight-chain, branched, or cyclic alkyl group having 1 to 8 hydrogen atoms or carbon atoms. 2 and Y 3 Each of the following groups independently represents an alkylene group with 2 to 6 carbon atoms. x and y represent the average number of moles added, and satisfy 1 ≤ x + y ≤ 85.

[0361] As R 52 and R 54 The alkyl group represented is a straight-chain, branched, or cyclic alkyl group having 1 to 8 carbon atoms. Examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, 2-butyl, tert-butyl, hexyl, cyclohexyl, and octyl. When R... 52 and R 54When representing a cyclic alkyl group, the alkyl group preferably has 3 to 8 carbon atoms. 52 and R 54 Preferably, it is an alkyl group having 1 to 3 carbon atoms, and most preferably, it is a methyl group.

[0362] As R 53 and R 55 The alkyl group represented is a straight-chain, branched, or cyclic alkyl group having 1 to 8 carbon atoms. Examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, 2-butyl, tert-butyl, hexyl, cyclohexyl, and octyl. When R... 53 and R 55 When representing a cyclic alkyl group, the alkyl group preferably has 3 to 8 carbon atoms. 53 and R 55 Preferably, it is a straight-chain, branched, or cyclic alkyl group having 3 to 8 carbon atoms, and is particularly preferred to be isobutyl.

[0363] The sum of x and y is 1 to 85 (1 ≤ x + y ≤ 85), preferably 3 to 50, more preferably 3 to 30, and even more preferably 5 to 30.

[0364] If the sum of x and y is 3 or more, the solubility is further improved and the cloud point becomes higher. This further suppresses separation and precipitation when the moisturizing liquid is heated to above 30°C. On the other hand, if the sum of x and y is less than 30, the effect of reducing surface tension and improving wettability is more effective. Therefore, when the filled ink is sprayed after being filled with the moisturizing liquid, the sprayability of the sprayed ink is further improved.

[0365] Y 2 and Y 3 Alkylenes with 2 to 4 carbon atoms are preferred, alkylenes with 2 or 3 carbon atoms are preferred, and alkylenes with 2 carbon atoms (vinylenes) are particularly preferred.

[0366] That is, among the compounds represented by Formula 6, the acetylene glycol surfactant represented by Formula 7 below is more preferred.

[0367] [Chemical Formula 20]

[0368]

[0369] In Equation 7, R 52 R 53 R 54 R 55 The meanings of x and y are respectively the same as R in Equation 6. 52 R 53 R 54 R 55 The meanings of x and y are the same, and their preferred ranges are also the same.

[0370] Examples of acetylenic diol-based surfactants represented by Formula 6 include 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 3,6-dimethyl-4-octylen-3,6-diol, 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol, and 2,5-dimethyl-3-hexyn-2,5-diol, among other alkyl oxide adducts (preferably ethylene oxide adducts).

[0371] In particular, the acetylenic diol surfactant represented by Formula 6 is preferably an ethylene oxide adduct of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (3≤x+y≤30, preferably 5≤x+y≤30).

[0372] The acetylene glycol surfactant represented by Formula 6 can be a commercially available product.

[0373] Commercially available products include the Surfynol series (e.g., Surfynol 420, Surfynol 440, Surfynol 465, and Surfynol 485), OLFINE series (e.g., OLFINE E1010 and OLFINE E1020), DYNOL series (e.g., DYNOL 604) manufactured by Air Products Ltd. or Nissin Chemical Co., Ltd., and ACETYLENOL manufactured by Kawaken Fine Chemicals Co., Ltd. Additionally, commercially available products are also supplied by The Dow Chemical Company, General Aniline Co., Ltd., and others.

[0374] The content of acetylene glycol surfactant relative to the total mass of ink is preferably 0.03% to 5% by mass, more preferably 0.04% to 4% by mass, and even more preferably 0.05% to 3% by mass.

[0375] <Cellulose Nanofibers>

[0376] The ink of the present invention preferably contains at least one type of cellulose nanofiber.

[0377] The ink of this invention contains cellulose nanofibers, which effectively increases the viscosity of the ink. Therefore, improved ink ejectibility is expected.

[0378] Cellulose nanofibers are nanocellulose extracted from cellulose raw materials (e.g., wood).

[0379] Methods for extracting cellulose nanofibers include, for example, mechanical processing (e.g., pulverization using a bead mill) and chemical processing (e.g., TEMPO catalytic oxidation, carboxymethylation, cationization, etc.).

[0380] From the viewpoint of further improving the filter applicability of the ink (i.e., the anti-clogging performance of the filter when the ink passes through the filter. The same applies below.), the cellulose nanofibers that may be contained in the ink of the present invention preferably include TEMPO oxidized cellulose nanofibers (i.e., nanofibers extracted by TEMPO catalytic oxidation treatment).

[0381] Here, TEMPO refers to 2,2,6,6-tetramethylpiperidine 1-oxy radical.

[0382] Commercially available products can be used as cellulose nanofibers.

[0383] Commercially available products as cellulose nanofibers include, for example:

[0384] "RHEOCRYSTA" (registered trademark) manufactured by DKS Co. Ltd.

[0385] "CELLENPIA" (registered trademark) manufactured by NIPPON PAPER INDUSTRIES CO., LTD.

[0386] SUGINO MACHINE LIMITED manufactures IMa-10002, BMa-10002, WMa-10002, AMa-10002, and FMa-10002.

[0387] "ELEX" manufactured by Daio Paper Corporation;

[0388] "AUROVISCO" (registered trademark) manufactured by Oji Paper Co., Ltd.; etc.

[0389] The average fiber width of the cellulose nanofibers is preferably 1 nm or more and 20 nm or less, more preferably 1 nm or more and 10 nm or less. When the average fiber width of the cellulose nanofibers is 20 nm or less, the filter applicability of the ink is further improved.

[0390] In this invention, the fiber width of 10 cellulose nanofibers is measured by observing them with a scanning electron microscope, and the average fiber width of the 10 fiber widths is obtained by arithmetic averaging.

[0391] The average fiber length of the cellulose nanofibers is preferably 10 nm or more and 1000 nm or less, more preferably 100 nm or more and 900 nm or less, even more preferably 100 nm or more and 600 nm or less, and even more preferably 200 nm or more and 400 nm or less. When the average fiber length of the cellulose nanofibers is 1000 nm or less, the filter applicability of the ink is further improved.

[0392] In this invention, the fiber length of 10 cellulose nanofibers is measured by observing them with a scanning electron microscope, and the average fiber length of the 10 fiber lengths is obtained by arithmetic averaging.

[0393] From the viewpoint of further improving the viscosity increase of ink and the filterability of ink, the average aspect ratio of cellulose nanofibers is preferably 100 or more and 400 or less, more preferably 100 or more and 300 or less.

[0394] In this invention, the aspect ratio (i.e., fiber length / fiber width) of 10 cellulose nanofibers is measured by observing them with a scanning electron microscope, and the average aspect ratio of the 10 fibers is calculated by arithmetically averaging the measured aspect ratios of the cellulose nanofibers.

[0395] The mass ratio of the cellulose nanofiber content to the total content of resin particles and wax particles is preferably 1.00% to 10.00% by mass, more preferably 2.00% to 8.00% by mass, and even more preferably 3.00% to 6.00% by mass.

[0396] When the content of cellulose nanofibers relative to the total content of resin particles and wax particles is 1.00% by mass or more, the viscosity of the ink can be increased more effectively.

[0397] When the content of cellulose nanofibers relative to the total content of resin particles and wax particles is 10.00% by mass, the filter applicability of the ink can be further improved.

[0398] The mass ratio of cellulose nanofiber content to the total amount of ink is preferably 0.01% to 1.00% by mass, more preferably 0.03% to 0.50% by mass, and even more preferably 0.05% to 0.40% by mass.

[0399] When the content of cellulose nanofibers relative to the total amount of ink is 0.01% by mass or more, the viscosity of the ink can be increased more effectively.

[0400] When the content of cellulose nanofibers relative to the total amount of ink is less than 1.00% by mass, the filter applicability of the ink can be further improved.

[0401] <Other Ingredients>

[0402] The ink of the present invention may also contain other components besides those described above.

[0403] Other surfactants besides silicone-based and acetylene glycol-based surfactants can be cited as examples.

[0404] Furthermore, other components may include preservatives, ultraviolet absorbers, anti-fading agents, mildew inhibitors, pH adjusters, rust inhibitors, antioxidants, emulsion stabilizers, antifoaming agents (e.g., the defoaming agent described in paragraph 0159 of Japanese Patent Application Publication No. 2015-180710), viscosity modifiers, dispersion stabilizers, chelating agents, solid wetting agents (e.g., urea), and water-soluble polymers (e.g., the water-soluble polymer described in paragraph 0139 of Japanese Patent Application Publication No. 2015-180710).

[0405] <Physical Properties of Inks>

[0406] (Dynamic surface tension)

[0407] The ink of the present invention preferably has a dynamic surface tension of 35 mN / m or less at 10 milliseconds.

[0408] As a result, the image quality of images recorded with ink is improved. This is believed to be because the dynamic surface tension at 10 milliseconds is below 35 mN / m, which reduces the surface tension of the ink, suppresses landing interference, and improves the wetting and spreading properties of the ink.

[0409] The lower limit of the dynamic surface tension at 10 ms is not particularly limited, but from the viewpoint of ink preservation stability, it is preferably 15 mN / m.

[0410] In this invention, the dynamic surface tension at 10 milliseconds is measured using the maximum bubble pressure method at an environment of 23°C and 55% relative humidity.

[0411] The dynamic surface tension at 10 milliseconds can be measured, for example, using a bubble pressure dynamic surface tension meter (product name "BP100", manufactured by KRUSS).

[0412] The dynamic surface tension at 10 milliseconds refers to the surface tension calculated from the maximum bubble pressure when bubbles are continuously ejected from the probe cap inserted into the ink and a new interface is formed in the tip of the probe cap (0 milliseconds) until the maximum bubble pressure is reached in 10 milliseconds.

[0413] The dynamic surface tension of ink ejected from the nozzle decreases from the moment of ejection and gradually decreases after landing on the recording medium, eventually converging to the value of the ink's static surface tension. The rate of decrease in dynamic surface tension is greatest immediately after ejection and gradually decreases over time. Therefore, if an ink droplet A lands on the recording medium, and then another ink droplet B lands on the medium, at the moment of ink droplet B's landing, the dynamic surface tension of ink droplet A is lower than that of ink droplet B. If the dynamic surface tensions of the two ink droplets are different, landing interference can easily occur between the first landing ink droplet A and the second landing ink droplet B. Specifically, ink droplet A, with its relatively lower dynamic surface tension, is attracted to ink droplet B, which has a relatively higher dynamic surface tension, resulting in uneven image density. Uneven image density leads to a coarser image, i.e., poor image graininess.

[0414] The dynamic surface tension at 10 milliseconds is the closest value to the dynamic surface tension at the instant the ink droplet falls onto the recording medium.

[0415] If the dynamic surface tension at 10 milliseconds is below 35 mN / m, the ink droplets diffuse on the recording medium, suppressing landing interference. This reduces the likelihood of uneven image density and results in images with excellent graininess.

[0416] (Viscosity)

[0417] In the ink of the present invention, from the viewpoint of ink ejectibility, the viscosity measured at 30°C and 100 rpm (revolutionsperminute) is preferably 1.2 mPa·s to 15.0 mPa·s, more preferably 2.0 mPa·s to 13.0 mPa·s, even more preferably 2.5 mPa·s to 10.0 mPa·s, and even more preferably 3.8 mPa·s to 6.0 mPa·s.

[0418] The viscosity values ​​mentioned above were measured using a rotational viscometer.

[0419] As a rotational viscometer, for example, the "VISCOMETER TV-22" (manufactured by TOKI SANGYO CO.LTD) is used for measurement.

[0420] [Image recording method]

[0421] The image recording method of the present invention includes a step of ejecting the ink of the present invention described above from an inkjet head containing silicon in the ink flow path wall and applying it to a recording medium (hereinafter also referred to as the "ink application step").

[0422] The image recording method of the present invention uses the ink of the present invention and the inkjet head described above. Therefore, according to the image recording method of the present invention, etching of the silicon-containing ink flow path walls of the inkjet head can be suppressed.

[0423] The image recording method of the present invention may, as needed, include: a step of drying the water and organic solvent contained in the ink applied to the recording medium (hereinafter also referred to as the "ink drying step"), a step of melting the resin particles contained in the ink and fixing them (hereinafter also referred to as the "heat fixing step"), and other steps.

[0424] The image recording method of the present invention is preferably a method of recording images by directly applying the ink of the present invention to a recording medium. That is, the image recording method of the present invention is preferably a so-called single-liquid system.

[0425] <Ink application process>

[0426] In the ink application process, the ink of the present invention is ejected from an inkjet head containing silicon in the ink flow path walls and applied to a recording medium. Thus, an image is recorded using the ink of the present invention.

[0427] The recording medium is not particularly limited; for example, coated paper used in common offset printing can be cited.

[0428] Coated paper is a type of paper in which a coating material is applied to the surface of high-quality paper, neutral paper, or other paper that is primarily composed of cellulose and is typically untreated.

[0429] Coated paper is available as a commercially available product. Examples of coated paper include "OK TOP COAT+" manufactured by Oji Paper Co., Ltd., "AURORACOAT" and "U-LITE" (A2, B2) manufactured by NIPPON PAPER INDUSTRIES CO., LTD., and "Tokubishi Art" (A1) coated paper manufactured by MITSUBISHI PAPER MILLS LIMITED.

[0430] The ink ejection and application to the recording medium can be performed using conventional inkjet recording methods.

[0431] Examples of inkjet recording methods include: charge control methods that use electrostatic attraction to eject ink; on-demand inkjet methods (pressure pulse methods) that use the vibration pressure of piezoelectric elements; acoustic inkjet methods that convert electrical signals into sound beams and irradiate the ink, then use radiation pressure to eject the ink; and thermal inkjet methods that heat the ink to form bubbles and utilize the resulting pressure.

[0432] Typically, image recording methods using inkjet recording devices include: shuttle scanning (also known as "serial head method") which records images using a short serial head, and single-pass method (also known as "line head method") which records images using a line head that arranges recording elements corresponding to the entire area of ​​the recording medium in the width direction.

[0433] In shuttle scanning, an image is recorded while the serial head scans along the width of the recording medium.

[0434] In contrast, in the single-pass scanning method, by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, images can be recorded on the entire surface of the recording medium. Therefore, unlike the shuttle scanning method, the single-pass scanning method does not require a transport system such as a carriage for the scanning serial head. Furthermore, the single-pass scanning method eliminates the need for complex scanning control between the carriage movement and the recording medium; only the recording medium moves, thus increasing the recording speed compared to the shuttle scanning method.

[0435] From the viewpoint of ensuring image quality, the ink ejected from the inkjet head is preferably 1 pL (picoli) to 10 pL, more preferably 1.5 pL to 6 pL. Furthermore, the ejection volume refers to the volume of ink ejected from one nozzle in one stroke using an inkjet recording method.

[0436] When an inkjet head has a nozzle surface configured with nozzles that eject ink, it can have a moisturizing cap that covers the nozzle surface and forms a moisturizing space between the cap and the nozzle surface. Storing a moisturizing liquid inside the moisturizing cap can increase the humidity of the moisturizing space.

[0437] Moisturizing lotions may contain acetylene glycol-based surfactants, water, and preservatives.

[0438] <Ink Drying Process>

[0439] The image recording method of the present invention may include an ink drying process as needed.

[0440] The ink drying process is the process of drying the water and organic solvents contained in the ink applied to the recording medium.

[0441] Heating components are not particularly limited as long as they can dry the water and organic solvents contained in the ink. Examples include heating drums, warm air, infrared lamps, heating ovens, and heating plates.

[0442] The heating temperature and heating time can be adjusted appropriately according to the water and organic solvent content in the ink.

[0443] <Thermal Fixing Process>

[0444] The image recording method of the present invention may include a heat fixing process after the ink application process, as needed.

[0445] The thermal fixing process is a process of melting and fixing the resin particles contained in the ink. Through the thermal fixing process, images on the recording medium can be fixed, thereby improving the abrasion resistance of the image. For example, the thermal fixing process described in paragraphs 0112 to 0120 of Japanese Patent Application Publication No. 2010-221415 can be used as the thermal fixing process.

[0446] <Processing fluid application process>

[0447] The image recording method of the present invention may include a treatment liquid application step, which involves applying a treatment liquid containing water and a flocculant to the surface of the recording medium to which the ink is to be applied before the ink application step. During this process, the ink of the present invention is applied to the area of ​​the recording medium to which the treatment liquid was applied.

[0448] Therefore, the components in the ink can be coagulated by using the flocculant in the pre-applied treatment liquid, which is advantageous in terms of the image quality (e.g., detail) of the obtained image.

[0449] (treatment solution)

[0450] Regarding the treatment solution, you can refer appropriately to paragraphs 0176 to 0198 of Japanese Patent Application Publication No. 2015-180710.

[0451] From the viewpoint of ink coagulation rate, the pH of the treatment solution at 25°C is preferably 0.1 to 4.0, more preferably 0.2 to 2.0.

[0452] The treatment solution contains water.

[0453] The water content relative to the total amount of the treatment liquid is preferably 50% by mass or more, and more preferably 60% by mass or more.

[0454] The upper limit of water content relative to the total amount of the treated liquid also depends on the amount of other components such as flocculants, but is, for example, 90% by mass, 80% by mass, etc.

[0455] The treatment solution contains flocculants.

[0456] As a flocculant, the treated liquid preferably contains at least one of the acidic compounds.

[0457] Acidic compounds used as flocculants can be any one of organic acidic compounds and inorganic acidic compounds, or two or more organic acidic compounds and inorganic acidic compounds can be used together.

[0458] As organic acidic compounds, examples include organic compounds with acidic groups.

[0459] Examples of acidic groups include phosphate groups, phosphonic acid groups, phosphonic acid groups, sulfate groups, sulfonic acid groups, sulfinic acid groups, and carboxyl groups. Among these, phosphate groups or carboxyl groups are preferred, and carboxyl groups are more preferred.

[0460] As organic compounds (organic carboxylic acids) having a carboxyl group, preferred compounds include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid (preferably DL-malic acid), maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, phthalic acid, 4-methylphthalic acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone carboxylic acid, pyranone carboxylic acid, pyrrolic carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, or derivatives of these compounds or their salts (e.g., polyvalent metal salts). One or more of these compounds may be used.

[0461] The organic carboxylic acid is preferably a divalent or higher carboxylic acid (hereinafter also called a polycarboxylic acid), more preferably at least one of the following groups: free malonic acid, malic acid, maleic acid, succinic acid, glutaric acid, fumaric acid, tartaric acid, 4-methylphthalic acid and citric acid, and particularly preferably at least one of the following groups: free malonic acid, malic acid, tartaric acid and citric acid.

[0462] Examples of inorganic acidic compounds include phosphoric acid, nitric acid, nitrous acid, sulfuric acid, and hydrochloric acid, with phosphoric acid being particularly preferred.

[0463] The total amount of acidic compounds contained in the treatment solution is not particularly limited, but from the viewpoint of ink coagulation rate, it is preferably 5% to 40% by mass, more preferably 10% to 30% by mass.

[0464] Regarding the ratio of organic acidic compounds to inorganic acidic compounds, the content of inorganic acidic compounds relative to the content of organic acidic compounds is preferably 5 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and even more preferably 15 mol% to 35 mol%.

[0465] Instead of acidic compounds, or in addition to acidic compounds, the treatment solution can also be used with other coagulating components such as polyvalent metal salts or cationic polymers as flocculants.

[0466] Regarding polyvalent metal salts or cationic polymers, for example, the polyvalent metal salts or cationic polymers described in paragraphs 0155 to 0156 of Japanese Patent Application Publication No. 2011-042150 can be used.

[0467] -Water-soluble polymers-

[0468] The treatment solution preferably contains at least one water-soluble polymer compound.

[0469] There are no particular limitations on the water-soluble polymer compound used; known water-soluble polymer compounds such as polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, and polyethylene glycol can be used.

[0470] Furthermore, as a water-soluble polymer compound, the specific polymer compound described later or the water-soluble polymer compound described in paragraphs 0026 to 0080 of Japanese Patent Application Publication No. 2013-001854 is preferred.

[0471] The weight-average molecular weight of water-soluble polymers is not particularly limited, for example, it can be set to 10,000 to 100,000, preferably 20,000 to 80,000, and more preferably 30,000 to 80,000.

[0472] Furthermore, the content of water-soluble polymers in the treatment liquid of the present invention is not particularly limited, but is preferably 0.1% to 10% by mass relative to the total amount of the treatment liquid, more preferably 0.1% to 4% by mass, even more preferably 0.1% to 2% by mass, and particularly preferably 0.1% to 1% by mass.

[0473] If the content is 0.1% by mass or more, it can further promote the expansion of ink droplets; if the content is 10% by mass or less, it can further suppress the thickening of the treatment solution. Furthermore, if the content is 10% by mass or less, it can further suppress the uneven coating of the treatment solution caused by air bubbles in the treatment solution.

[0474] As a water-soluble polymer compound, a polymer compound containing hydrophilic structural units having ionic groups (preferably anionic groups) is preferred (hereinafter also referred to as "specific polymer compound"). This further promotes the spread of ink droplets imparted to the recording medium, thereby further suppressing image roughness.

[0475] Examples of ionic groups in specific polymer compounds include carboxyl groups, sulfonic acid groups, phosphate groups, borate groups, amino groups, ammonium groups, or their salts. Among these, carboxyl groups, sulfonic acid groups, phosphate groups, or their salts are preferred, more preferably carboxyl groups, sulfonic acid groups, or their salts, and even more preferably sulfonic acid groups or their salts.

[0476] As a hydrophilic structural unit having an ionic group (preferably an anionic group), it is preferred to have a structural unit derived from a (meth)acrylamide compound having an ionic group (preferably an anionic group).

[0477] The content of hydrophilic structural units having ionic groups (preferably anionic groups) in the water-soluble polymer compound can be set to, for example, 10% to 100% by mass, preferably 10% to 90% by mass, more preferably 10% to 70% by mass, even more preferably 10% to 50% by mass, and particularly preferably 20% to 40% by mass in the total mass of the water-soluble polymer compound.

[0478] As a specific polymer compound, in addition to at least one of the hydrophilic structural units having ionic groups (preferably anionic groups, particularly sulfonic acid groups) mentioned above, it more preferably also contains at least one of the hydrophobic structural units. By containing hydrophobic structural units, the specific polymer compound is more likely to exist on the surface of the processing liquid, thus further promoting the spread of ink droplets imparted to the recording medium and further suppressing image roughness.

[0479] As a hydrophobic structural unit, a structural unit derived from (meth)acrylate (preferably an alkyl ester of (meth)acrylate with 1 to 4 carbon atoms) is preferred.

[0480] The content of hydrophobic structural units in a specific polymer compound can be set to 10% to 90% by mass, preferably 30% to 90% by mass, more preferably 50% to 90% by mass, and particularly preferably 60% to 80% by mass, in the total mass of the specific polymer compound.

[0481] -Water-soluble organic solvents-

[0482] The treatment solution preferably contains at least one water-soluble organic solvent.

[0483] As a water-soluble organic solvent, there are no particular limitations as long as the organic solvent can dissolve 5g or more in 100g of water at 20°C. Specifically, the water-soluble organic solvent contained in the ink composition described later can be used in the processing liquid in the same way. Among them, from the viewpoint of suppressing curling, polyalkylene glycol or its derivatives are preferred, and more preferably at least one selected from diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, dipropylene glycol, tripropylene glycol monoalkyl ether, polyoxypropylene glycerol ether, and polyoxyethylene polyoxypropylene glycol.

[0484] From the viewpoint of coating properties, the content of water-soluble organic solvent in the treatment liquid is preferably 3% to 20% by mass, and more preferably 5% to 15% by mass, relative to the overall treatment liquid.

[0485] -surfactant-

[0486] The processing liquid may contain at least one surfactant. The surfactant can be used as a surface tension modifier. Examples of surface tension modifiers include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants. From the viewpoint of reducing the coagulation rate of the ink composition, nonionic or anionic surfactants are preferred.

[0487] Compounds cited as surfactants in Japanese Patent Application Publication No. 59-157636 (pages 37-38) and Research Disclosure No. 308119 (1989) can also be cited. Furthermore, fluorinated (fluorinated alkyl) surfactants or silicone surfactants described in Japanese Patent Application Publication Nos. 2003-322926, 2004-325707, and 2004-309806 can also be cited.

[0488] The treatment solution may contain other components.

[0489] As for other components that may be contained in the processing solution, appropriate reference can be made to the other components in the aforementioned ink.

[0490] Example

[0491] The following are embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0492] The following uses "part" as the quality standard.

[0493] The “weight percentage (%)” in Tables 1 to 4 represents “mass %”.

[0494] In this embodiment, the volume average particle size was measured using a particle size distribution measuring device (product name "MICROTRAC UPA (registered trademark) EX150") manufactured by Nikkiso Co., Ltd.

[0495] Regarding the weight-average molecular weight, the measurement was performed using an HLC (registered trademark)-8020GPC (manufactured by Tosoh Corporation) as the measuring device, three TSKgel (registered trademark) Super Multipore HZ-H (4.6mm ID × 15cm, manufactured by Tosoh Corporation) columns as the column, and THF (tetrahydrofuran) as the eluent.

[0496] Furthermore, measurements were performed using an RI detector, with the sample concentration set at 0.45% by mass, the flow rate at 0.35 mL / min, the sample injection volume at 10 μL, and the measurement temperature at 40 °C. Calibration curves were prepared using eight samples manufactured by Tosoh Corporation: “TSK Standard, Polystyrene”, namely “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, “A-2500”, “A-1000”, and “n-propylbenzene”.

[0497] The glass transition temperature was measured using a differential scanning calorimeter (product name "EXSTAR6220") manufactured by SII NanoTechnology Inc.

[0498] The dynamic surface tension at 10 milliseconds was measured using a bubble pressure dynamic surface tension meter (product name "BP100", manufactured by KRUSS).

[0499] [Preparation of resin particles]

[0500] <Preparation of Resin Particles C-29>

[0501] The resin particles C-29 in the specific example of the aforementioned resin particles were prepared as follows.

[0502] A three-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet was filled with water (250 g), 12-methacrylamide dodecanoic acid (6.7 g), potassium bicarbonate (0.17 g), and isopropanol (20 g), and heated to 85°C under a nitrogen atmosphere. A mixed solution consisting of 4,4'-azobis(4-cyanopentanoic acid) (free radical polymerization initiator, product name "V-501", manufactured by FUJIFILM Wako Pure Chemical Corporation) (0.11 g), potassium bicarbonate (0.08 g), and water (9 g) was added and stirred for 10 minutes. Next, a monomer solution consisting of styrene (14 g), benzyl methacrylate (14 g), methyl methacrylate (48 g), butyl methacrylate (3.3 g), and hydroxyethyl methacrylate (14 g) was added dropwise to the flask at a constant rate over 3 hours. Furthermore, a mixed solution consisting of V-501 (0.06 g), potassium bicarbonate (0.04 g), and water (6 g) was added in two portions, one immediately after the initial addition of the monomer solution and the other 1.5 hours later. After the addition of the monomer solution was completed, the mixture was stirred for 1 hour. Then, the mixed solution of V-501 (0.06 g), potassium bicarbonate (0.04 g), and water (6 g) was added to the obtained reaction mixture, and the mixture was stirred for another 3 hours. The reaction mixture was filtered through a 50 μm mesh to obtain an aqueous dispersion of resin particles C-29.

[0503] <Preparation of resin particles C-30, C-23 and C-24>

[0504] In the preparation of resin particles C-29, by appropriately changing the type and amount of monomers used, aqueous dispersions of resin particles C-30, C-23 and C-24 in the specific examples of the aforementioned resin particles were prepared.

[0505] <Resin Particle D>

[0506] An aqueous dispersion of resin particles D was obtained with reference to sections 0240 and 0241 of Japanese Patent Application Publication No. 2015-180710.

[0507] The resin in resin particle D is a copolymer of methyl methacrylate units / isoborneol methacrylate units / methacrylic acid units / sodium methacrylate units (=70 / 20 / 5 / 5 [mass ratio]).

[0508] [Preparation of pigment dispersions with cross-linked dispersants]

[0509] A pigment dispersion was prepared using Projet CyanAPD1000 (manufactured by FUJIFILM Imaging Colorants Inc., cyan pigment dispersion, pigment concentration in the pigment dispersion: 12% by mass) as a dispersant and crosslinked (more specifically, crosslinked polymer).

[0510] [Preparation of pigment dispersions in which the dispersant is not cross-linked]

[0511] As a pigment dispersion in which the dispersant is not cross-linked, FUJI SP BLUE 6633 (manufactured by Fuji Pigment Co.,LTD., cyan pigment dispersion, pigment concentration in the pigment dispersion: 17% by mass) was prepared.

[0512] [Examples 1-27, Comparative Examples 1-4]

[0513] <Ink Preparation>

[0514] The effective components of the inks shown in Tables 1 to 3 are mixed with water, and coarse particles are removed from the resulting mixture to obtain the ink.

[0515] The total amount of effective components and water in the inks shown in Tables 1 to 3 is 100 parts by mass.

[0516] The detailed information for the following components in Tables 1 to 3 is as follows.

[0517] •SANNIX GP250……polyoxypropyl glycerin manufactured by SANYO CHEMICAL INDUSTRIES, LTD.

[0518] ·PEG200……Polyethylene glycol 200 manufactured by SANYO CHEMICAL INDUSTRIES, LTD.

[0519] PVP K-15... Polyvinylpyrrolidone manufactured by Ashland Corporation

[0520] • SNOWTEX XS…Colloidal silica manufactured by Nissan Chemical Corporation

[0521] Mowinyl 972……An aqueous dispersion of styrene / acrylic resin particles manufactured by Japan Coating Resin Co., Ltd.

[0522] Trasol CN……Wax particles manufactured by CHUKYO YUSHI CO., LTD.

[0523] •Cellosol 524D…wax particles manufactured by CHUKYO YUSHI CO., LTD.

[0524] • Hitec E6314……Wax particles manufactured by Toho Chemical Industry Co., Ltd.

[0525] BYK-347...A silicone-based surfactant manufactured by BYK Corporation.

[0526] BYK-024...A silicone-based surfactant manufactured by BYK Corporation.

[0527] • OLFINE E1010……An acetylene glycol-based surfactant manufactured by Nissin Chemical Co., Ltd.

[0528] • OLFINE E1020……An acetylene glycol-based surfactant manufactured by Nissin Chemical Co., Ltd.

[0529] <Ink Measurement>

[0530] For the inks of the examples and comparative examples, pH and redox potential were measured and used as pHi and ORPi, respectively.

[0531] The values ​​on the left side of inequality (X) were calculated using these values.

[0532] The results are shown in Tables 1-3.

[0533] Furthermore, the dynamic surface tension of the inks in the examples and comparative examples was measured at 10 milliseconds.

[0534] The results are shown in Tables 1-3.

[0535] <Preparation of Treatment Solution 1 and Treatment Solution 2>

[0536] The following components were mixed to obtain treatment solution 1 and treatment solution 2, respectively.

[0537] -Composition of Treatment Solution 1-

[0538] DEGmBE (diethylene glycol monobutyl ether)

[0539] ...6.0% of quality

[0540] ·Malondiic acid

[0541] ...5.6% of mass

[0542] Malic acid

[0543] ...3.83% of mass

[0544] • 85% by mass aqueous solution of phosphoric acid

[0545] ...3.37% of mass

[0546] • The following water-soluble polymer 1 (in the following water-soluble polymer 1, the numbers in the lower right corner of each constituent unit indicate the mass ratio (mass%), and Mw indicates the weight-average molecular weight.)

[0547] ...0.4% of mass

[0548] • Defoamer (TSA-739 (15%) manufactured by Momentive Performance Materials Japan LLC.; emulsion-type silicone defoamer)

[0549] ...the amount of silicone oil was 0.0083% by mass.

[0550] ·benzotriazole

[0551] ...1.0% of quality

[0552] • Tayca Power BN2070M (a surfactant manufactured by Tayca Corporation)

[0553] ...the amount of the active ingredient is 0.42% by mass.

[0554] · Ion-exchange water

[0555] ...totaling to a margin of 100% by mass

[0556] [Chemical Formula 21]

[0557]

[0558] -Composition of Treatment Fluid 2-

[0559] DEGmBE (diethylene glycol monobutyl ether)

[0560] ...7.2% of mass

[0561] ·Malondiic acid

[0562] ...11.2% of mass

[0563] Malic acid

[0564] ...7.66% of mass

[0565] · 85% by mass aqueous solution of phosphoric acid

[0566] ...6.73% of mass

[0567] • The above-mentioned water-soluble polymer 1

[0568] ...0.8% of mass

[0569] • Defoamer (TSA-739 (15%) manufactured by Momentive Performance Materials Japan LLC.; emulsion-type silicone defoamer)

[0570] ...the amount of silicone oil is 0.01% by mass.

[0571] ·benzotriazole

[0572] ...1.2% of mass

[0573] ·Tayca Power BN2070M

[0574] ...the amount of the active ingredient is 0.5% by mass.

[0575] · Ion-exchange water

[0576] ...totaling to a margin of 100% by mass

[0577] <Image Recording>

[0578] The image was recorded using coated paper (trade name "OK TOP COAT+", manufactured by Oji Paper Co., Ltd.) as the recording medium, the above-mentioned processing liquid 1 as the processing liquid, the ink of each embodiment or comparative example as the ink, and the image was recorded using Jet Press 750S (manufactured by FUJIFILM Corporation) as the inkjet recording device.

[0579] Before applying ink, a preconditioning solution is applied to the surface of the recording medium that will be inked.

[0580] The ink is applied to the surface of the recording medium that has been treated with the ink.

[0581] Set the resolution of the image using ink to 1200dpi×1200dpi and the image recording speed to 3600sph.

[0582] Here, dpi is short for dots per inch, and sph is short for sheets per hour.

[0583] <Evaluation>

[0584] The inks used in the examples and comparative examples were evaluated for suppressing the etching of silicon-containing ink flow path walls.

[0585] The evaluation results are shown in Tables 1 to 3.

[0586] The evaluation method is as follows.

[0587] <Etching Inhibition of Silicon-Containing Ink Flow Path Walls>

[0588] The following are evaluation samples of the silicon-containing ink flow path walls in the inkjet head.

[0589] A 1cm × 1cm chip was prepared on a silicon substrate (research high-purity silicon wafer 6-P-25, model: 2-960-59). Polyimide tape (KAPTON TAPE) was attached to a portion of the chip (i.e., the silicon substrate), and a silicon-exposed portion in contact with ink and a masked portion with polyimide tape attached were set, which was used as an evaluation sample.

[0590] The inks of each embodiment and each comparative example were placed in a covered container, and then the evaluation samples were immersed in the ink. Here, a stirring plate was pre-placed in the covered container, and the evaluation samples were immersed in the ink while the ink was being stirred.

[0591] The covered container containing the ink and the evaluation sample was placed in an evaluation oven set at 60°C and stirred for 8 days.

[0592] After a period of time, the evaluation samples were removed from the container, cleaned and dried, and the masking tape was removed.

[0593] The height difference between the exposed silicon portion and the masked portion (i.e., the height difference generated by etching) was measured using a height difference measuring instrument (SURFCORDER SE-500A manufactured by Kosaka Laboratory Ltd.).

[0594] The etching inhibition of silicon-containing ink flow path walls was evaluated based on the height difference and according to the following evaluation criteria.

[0595] In the following evaluation criteria, the higher the score, the better the etch inhibition of the silicon-containing ink flow path wall (i.e., etch is inhibited).

[0596] -Evaluation Criteria-

[0597] 5……No height difference caused by etching was detected.

[0598] 4.5… An elevation difference caused by etching was detected, but it was less than 0.2 μm.

[0599] 4……The height difference caused by etching is greater than 0.2μm and less than 0.5μm.

[0600] 3.5… The height difference caused by etching is greater than 0.5μm and less than 1.0μm.

[0601] 3……The height difference caused by etching is greater than 1.0μm and less than 2.0μm.

[0602] 2……The height difference caused by etching is greater than 2.0μm and less than 3.0μm.

[0603] 1……The height difference caused by etching is greater than 3.0μm.

[0604] <Image density maintenance>

[0605] As an evaluation corresponding to the etching suppression of the ink flow path walls, the image density maintenance was evaluated as follows. When the ink flow path walls have been etched, poor ink ejection from the inkjet head is prone to occur, which easily leads to image density fluctuations (i.e., the image density maintenance is prone to decrease).

[0606] First, ink was loaded into the inkjet recording device shown in the above-described "image recording" operation, and a solid image was recorded within 3 hours from the start of loading. The density of the obtained solid image was measured using a density meter (FD-5, manufactured by Konica Minolta, Inc.), and the result was used as the "initial density".

[0607] Next, the ink was placed in the inkjet recording device and left for 3 days. Then, a solid image was recorded in the same manner as described above, and the density of the solid image was measured. The obtained result is referred to as the "density after 3 days".

[0608] The percentage (%) of the concentration after 3 days relative to the initial concentration was calculated and used as the concentration maintenance rate.

[0609] The image's concentration maintenance was evaluated based on the obtained concentration variation rate and according to the following evaluation criteria.

[0610] In the following evaluation criteria, the level of maximum suppression of ink flow path wall etching is A.

[0611] -Evaluation Criteria-

[0612] A... The concentration maintenance rate is over 95%.

[0613] B...concentration maintenance rate is above 70% and less than 95%.

[0614] C...concentration maintenance rate is less than 70%.

[0615] [Table 1]

[0616]

[0617]

[0618] [Table 2]

[0619]

[0620]

[0621] [Table 3]

[0622]

[0623] As shown in Tables 1 to 3, in Examples 1 to 27, which contain at least one of water, pigment, resin particles, and wax particles and have a pH (i.e., pHi in inequality (X)) of 7.2 to 11 and satisfy inequality (X) "ORPi - [285 - 59 × (pHi - 6.2)] ≥ 0", the etching of the ink flow path walls containing silicon was suppressed.

[0624] In contrast, in Comparative Examples 1 to 4, which do not satisfy inequality (X), the etching inhibition of the ink flow path walls containing silicon is insufficient.

[0625] The results of Examples 1-3 show that when the ink contains an oxidant (Example 1), the etching inhibition is further improved.

[0626] The results of Examples 2 and 3 show that when the ink contains colloidal silica (Example 2), the etching inhibition is further improved.

[0627] Next, the recording medium was changed to coated paper (trade name "FLO GlossText") manufactured by Sappi Limited, and the evaluation was conducted in the same manner as the evaluation described above. The results obtained were the same as the evaluation results described above (i.e., the results shown in Tables 1 to 3).

[0628] Furthermore, the recording medium was changed to coated paper (trade name "Condat Gloss") manufactured by LECTA Corporation, and the evaluation was conducted in the same manner as described above. The results obtained were the same as those described above (i.e., the results shown in Tables 1 to 3).

[0629] Furthermore, the treatment solution was changed to treatment solution 2, and the evaluation was conducted in the same manner as the evaluation described above. As a result, the same evaluation results as those described above (i.e., the results shown in Tables 1 to 3) were obtained.

[0630] Furthermore, the image recording speed was changed to 5400 sph and no processing fluid was used, and the resolution was changed to 1200 dpi × 600 dpi. Otherwise, the evaluation was conducted in the same manner as the evaluation described above, and the results were the same as those described above (i.e., the results shown in Tables 1 to 3).

[0631] [Example 101]

[0632] Except for the addition of the ink viscosity measurement and ink filter suitability evaluation shown below, the same operations as in Example 24 were performed.

[0633] That is, the composition of the ink in Example 101 is the same as that of the ink in Example 24.

[0634] The results are shown in Table 4.

[0635] <Ink Viscosity Measurement>

[0636] The viscosity (mPa•s) of the ink was measured using a rotational viscometer “VI SCOMETER TV-22” (manufactured by TOKI SANGYO CO.LTD) at 30°C and 100 rpm (revolutionsperminute).

[0637] <Ink Filter Suitability Evaluation>

[0638] An Isopore membrane filter (manufactured by Merck Millipore Ltd.) with a pore size of 2 μm was placed into a syringe, and flexible tubes that would form ink flow paths were connected to both ends of the syringe.

[0639] Ink is supplied to a hose connected to one end of the syringe, and the ink is extruded by pressing at 75 kPa to allow the ink to pass through the Isopore membrane filter inside the syringe.

[0640] The amount of ink passing through (g) from the start of ink extrusion up to 100 seconds was measured.

[0641] Based on the measurement results and in accordance with the following evaluation criteria, the filter suitability of the ink was evaluated.

[0642] In the following evaluation criteria, the highest grade for ink filter suitability is "5".

[0643] -Evaluation Criteria for Ink Filter Suitability Evaluation-

[0644] 5... The ink throughput is 80g or more.

[0645] 4... The ink throughput is 60g or more but less than 80g.

[0646] 3... The ink throughput is 40g or more but less than 60g.

[0647] 2... The ink throughput is more than 20g and less than 40g.

[0648] 1. The ink throughput is less than 20g.

[0649] [Examples 102-107]

[0650] As shown in Table 4, the active ingredients of the ink were changed, but otherwise the same operations as in Example 101 were performed.

[0651] The results are shown in Table 4.

[0652] In each of the inks in Examples 102 to 107, for the ink of Example 101, cellulose nanofibers of the types and amounts (mass %) shown in Table 4 were added.

[0653] Here, CELLENPIA TC-02X, CELLENPIA TC-01A and CELLENPIA CS-01 are all cellulose nanofibers manufactured by NIPPONPAPER INDUSTRIES CO., LTD.

[0654] Among these cellulose nanofibers, CELLENPIA TC-02X and CELLENPIA TC-01A are TEMPO oxidized cellulose nanofibers.

[0655] The average fiber diameter of CELLENPIA TC-02X is 3.5nm, and the average fiber length is 350nm.

[0656] The average fiber diameter of CELLENPIA TC-01A is 3.5nm, and the average fiber length is 750nm.

[0657] The average fiber diameter of CELLENPIA CS-01 is 13.5nm, and the average fiber length is over 1500nm.

[0658] [Table 4]

[0659]

[0660] As shown in Table 4, in Examples 101 to 107, as in Examples 1 to 27, the etching of the silicon-containing ink flow path walls was suppressed.

[0661] In Examples 101-107, and in Examples 102-107 where the ink contained cellulose nanofibers, the ink viscosity increased effectively. Therefore, further improvement in the ink's ejectibility is expected.

[0662] The results of Examples 102-104 show that when the cellulose nanofibers include TEMPO oxidized cellulose nanofibers (Examples 102 and 103), the filter applicability of the ink is further improved.

[0663] All disclosures of Japanese Patent Application No. 2021-157230, filed September 27, 2021, and Japanese Patent Application No. 2022-050285, filed March 25, 2022, are incorporated herein by reference. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as those specifically and separately described and incorporated herein by reference.

Claims

1. An inkjet ink, which is an inkjet ink ejected from an inkjet head containing silicon in the ink flow path wall, wherein, The inkjet ink contains water, pigment, oxidant, and at least one selected from resin particles and wax particles. pH ranges from 7.2 to 11. The content of the oxidant relative to the total content of the resin particles and the wax particles is 0.02% to 6% by mass. And it satisfies the following inequality (X). ORPi - [285 - 59 × (pHi - 6.2)] ≥ 0 Inequality (X) In inequality (X), ORPi represents the redox potential of the inkjet ink measured in mV under device conditions where the redox potential of water at pH 6.2 reaches 310 mV, and pHi represents the pH of the inkjet ink.

2. The inkjet ink according to claim 1, wherein, The oxidant contains at least one selected from peroxides.

3. The inkjet ink according to claim 1, wherein, The oxidant contains at least one selected from the group consisting of hydrogen peroxide, peracetic acid, sodium percarbonate, and urea peroxide.

4. The inkjet ink according to claim 1 or 2, wherein, The oxidant contains hydrogen peroxide.

5. The inkjet ink according to any one of claims 1 to 3, wherein, The inkjet ink also contains colloidal silicon dioxide.

6. The inkjet ink according to any one of claims 1 to 3, wherein, The inkjet ink also contains an organic solvent with a ClogP value of 1.0 to 3.

5.

7. The inkjet ink according to claim 6, wherein, The organic solvent with a ClogP value of 1.0 to 3.5 is selected from at least one compound chosen from the group consisting of compounds represented by Formula 1 and compounds represented by Formula 2. In Equation 1 or Equation 2, R 1 Each can be used independently to represent a hydrogen atom or a methyl group, R 2 Each group independently represents a straight-chain or branched hydrocarbon group with 4 to 9 carbon atoms, or an aryl group with 6 to 10 carbon atoms, where n represents an integer from 1 to 3.

8. The inkjet ink according to any one of claims 1 to 3, wherein, The inkjet ink also contains a dispersant, and the dispersant is cross-linked.

9. The inkjet ink according to any one of claims 1 to 3, wherein, The resin particles contain a resin comprising the structural unit represented by Formula 3 below. In Equation 3, R 3 X represents an alkyl group having 1 to 4 hydrogen atoms or carbon atoms. 1 Y represents a divalent linker group. 1 Indicating anionic groups, in X 1 and Y 1 In the middle, the atom furthest from the main chain is 4 to 27 atoms away from the main chain.

10. The inkjet ink according to any one of claims 1 to 3, wherein, The inkjet ink also contains cellulose nanofibers.

11. The inkjet ink according to claim 10, wherein, The average fiber width of the cellulose nanofibers is greater than 1 nm and less than 10 nm.

12. The inkjet ink according to claim 10, wherein, The average fiber length of the cellulose nanofibers is greater than 10 nm and less than 1000 nm.

13. The inkjet ink according to claim 10, wherein, The cellulose nanofibers include TEMPO oxidized cellulose nanofibers.

14. The inkjet ink according to claim 10, wherein, The content of the cellulose nanofibers relative to the total content of the resin particles and the wax particles is 1.00% to 10.00% by mass.

15. The inkjet ink according to claim 10, wherein, The content of the cellulose nanofibers is 0.01% to 1.00% by mass relative to the total amount of inkjet ink.

16. The inkjet ink according to claim 10, wherein, The viscosity of the inkjet ink, measured at 30°C and 100 rpm, is 3.8 mPa·s to 6.0 mPa·s.

17. An image recording method, comprising: The process of ejecting inkjet ink as described in any one of claims 1 to 16 from an inkjet head containing silicon in the ink flow path wall and applying it to a recording medium.

Images