Image recording method

Abstract

This image recording method includes a step for recording an image on a substrate by discharging an inkjet ink which contains no fluorine-based surfactant or contains 0.001 mass% or less of a fluorine-based surfactant from a nozzle using an inkjet recording device equipped with a nozzle substrate on which the nozzle is formed. The nozzle substrate has a liquid-repellent layer on a discharge surface. The liquid-repellent layer has a partial structure represented by formula (1). Formula (1): (L-Y-)kSi-(O-*)4-k In formula (1), L is a hydrocarbon group, Y is a single bond or a divalent linking group containing no fluorine atom, k is an integer between 1 and 3, and ＊ denotes a position of a bond to another structure.

Description

Image recording method

[0001] The present disclosure relates to an image recording method.

[0002] Conventionally, various studies have been conducted on image recording methods using ink. For example, Japanese Patent Application Laid-Open No. 2003-277664 discloses an inkjet recording apparatus including an inkjet recording ink containing a coloring material, a humectant, water, and a water-soluble substance that undergoes a polycondensation reaction in a water-free state, and recording is performed by ejecting the ink onto a recording medium. The water-soluble substance contains an alkyl fluoride group.

[0003] By the way, in recent years, regulations on PFAS (perfluoroalkyl compounds, polyfluoroalkyl compounds) have been strengthened. Therefore, there is a need for an image recording method that suppresses ink repellency while complying with PFAS regulations.

[0004] An object of one aspect of the present disclosure is to provide an image recording method that suppresses ink repellency.

[0005] The present disclosure includes the following aspects. <1> Using an inkjet recording apparatus including a nozzle substrate on which nozzles are formed, ejecting an inkjet ink that does not contain a fluorosurfactant or has a fluorosurfactant content of 0.001% by mass or less from the nozzles to record an image on a substrate, the nozzle substrate has a liquid-repellent layer on the ejection surface, and the liquid-repellent layer has a partial structure represented by the following formula (1). (L-Y-) ｋ Si-(O-*) ４－ｋ…(1) In formula (1), L is a hydrocarbon group, Y is a single bond or a divalent linking group that does not contain a fluorine atom, k is an integer from 1 to 3, and * indicates the position of bonding with other structures. <2> The image recording method according to <1>, wherein the nozzle substrate has a layer containing silicon oxide and a liquid-repellent layer on the ejection surface in that order. <3> The image recording method according to <1>, wherein the nozzle substrate has a layer containing a compound containing elements of groups 3 to 6, a layer containing silicon oxide, and a liquid-repellent layer on the ejection surface in that order. <4> The image recording method according to any one of <1> to <3>, wherein the thickness of the liquid-repellent layer is 50 nm or less. <5> The image recording method according to any one of <1> to <4>, wherein the inkjet ink has a Si concentration of 0.05% by mass or more. <6> The image recording method according to any one of <1> to <5>, wherein the inkjet ink contains a silicone-based surfactant. <7> A silicone-based surfactant is represented by the following formula (2), the image recording method described in <6>. In formula (2), R １ Each of these independently represents an alkyl group or hydroxyl group having 1 to 3 carbon atoms, R ２ R represents an alkanediyl group with 2 to 5 carbon atoms. ３ <8> The image recording method according to any one of <1> to <7>, wherein k is 3 in formula (1). <9> The image recording method according to <6>, wherein the inkjet ink further comprises at least one selected from the group consisting of acetylene glycol-based surfactants and polyoxyethylene-based surfactants.

[0006] According to one aspect of this disclosure, an image recording method is provided in which ink repellency is suppressed.

[0007] In this specification, a numerical range indicated using "~" means a range that includes the numbers listed before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described in this specification, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0008] In this specification, the amount of each component in a composition means the total amount of multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. In this specification, the term "process" is included not only in the sense of an independent process, but also in the sense of a process that cannot be clearly distinguished from other processes, as long as the intended purpose of that process is achieved.

[0009] In this specification, "image" refers to membranes in general, and "image recording" refers to the formation of an image (i.e., a membrane). Furthermore, the concept of "image" in this specification also includes solid images.

[0010] [Image recording method]

[0011] The image recording method of this disclosure includes the step of recording an image by ejecting an inkjet ink from a nozzle using an inkjet recording apparatus equipped with a nozzle substrate on which a nozzle is formed, wherein the inkjet ink does not contain a fluorine-based surfactant or contains 0.001% by mass or less of a fluorine-based surfactant, and the nozzle substrate has a liquid-repellent layer on the ejection surface, and the liquid-repellent layer has a substructure represented by the following formula (1): (L-Y-) ｋ Si-(O-*) ４－ｋ …(1) In formula (1), L is a hydrocarbon group, Y is a single bond or a divalent linking group that does not contain a fluorine atom, k is an integer from 1 to 3, and * indicates the bond position with other structures.

[0012] The inventors of the present invention have found that when a fluorosurfactant is contained in an inkjet ink, ink repellency occurs when the fluorosurfactant adheres to various members inside the inkjet recording apparatus.

[0013] According to the image recording method of the present disclosure, inkjet ink that does not contain a fluorosurfactant or has a fluorosurfactant content of 0.001% by mass or less is ejected using an inkjet recording apparatus including a nozzle substrate having a specific liquid-repellent layer, thereby suppressing ink repellency. Further, in the image recording method of the present disclosure, the content of the fluorosurfactant in the inkjet ink is 0.001% by mass or less, and the liquid-repellent layer substantially does not contain fluorine atoms, so that it is possible to comply with PFAS regulations.

[0014] The ink described in JP-A-2003-277664 is considered to cause repellency because it contains a water-soluble substance containing an alkyl fluoride group. Further, a water-repellent film is formed on the ejection-side surface of the nozzle plate for inkjet recording described in JP-A-2003-277664, and the water-repellent film contains an alkyl fluoride group and cannot comply with PFAS regulations.

[0015] Hereinafter, the image recording method of the present disclosure will be described in detail.

[0016] <Inkjet recording apparatus> The inkjet recording apparatus used in the image recording method of the present disclosure includes a nozzle substrate on which nozzles are formed. The nozzle substrate has a liquid-repellent layer on the ejection surface, and the liquid-repellent layer has a partial structure represented by the following formula (1). (L-Y-) ｋ Si-(O-*) ４－ｋ ...(1) In formula (1), L is a hydrocarbon group, Y is a single bond or a divalent linking group not containing a fluorine atom, k is an integer of 1 to 3, and * means a bonding position with another structure.

[0017] Other layers other than the liquid-repellent layer may be provided on the nozzle substrate. The liquid-repellent layer is preferably located on the outermost surface of the nozzle substrate. That is, the liquid-repellent layer is the outermost layer among the layers provided on the nozzle substrate.

[0018] In the image recording method disclosed herein, an image can be recorded by ejecting fine ink droplets from a nozzle onto a substrate.

[0019] The nozzle substrate is, for example, a substrate made of silicon, and may be a single-crystal silicon substrate or a polycrystalline silicon substrate. A nozzle for ejecting ink is formed on the nozzle substrate.

[0020] A nozzle is a hole that penetrates the nozzle substrate and is formed, for example, by dry etching. Preferably, multiple nozzles are formed on the nozzle substrate. The shape of the nozzle is not particularly limited, but from the viewpoint of controlling the direction of ink discharge, it is preferable that it be tapered, with the diameter decreasing in the direction in which the ink is discharged. The diameter of the hole on the side of the nozzle from which the liquid is discharged, i.e., the diameter of the nozzle opening, can be adjusted as appropriate. The diameter of the nozzle opening is, for example, 10 μm to 30 μm.

[0021] The thickness of the nozzle substrate corresponds to the length of the nozzle and is preferably 10 μm to 100 μm, and more preferably 20 μm to 60 μm.

[0022] From the viewpoint of maintaining alkali resistance of the discharge surface, it is preferable that the nozzle substrate has a silicon dioxide-containing layer and a liquid-repellent layer on the discharge surface in that order. When alkaline liquid penetrates into the liquid-repellent layer on the discharge surface of the nozzle substrate due to prolonged use, the presence of the intermediate layer (i.e., the silicon dioxide-containing layer) helps to maintain alkali resistance of the discharge surface.

[0023] The thickness of the silicon dioxide-containing layer is preferably 0.3 nm to 120 nm, and more preferably 0.3 nm to 3 nm, or 10 nm to 100 nm. In particular, when the thickness of the silicon dioxide-containing layer is 0.3 nm to 3 nm, or 10 nm to 100 nm, the adhesion between the silicon dioxide-containing layer and the liquid-repellent layer is increased, resulting in superior wipe resistance and alkali resistance of the dispensing surface.

[0024] Furthermore, from the viewpoint of improving alkali resistance of the discharge surface, it is preferable that the nozzle substrate has, in this order, a layer containing a compound containing elements from groups 3 to 6, a layer containing silicon dioxide, and a liquid-repellent layer on the discharge surface.

[0025] Examples of compounds containing elements from Groups 3 to 6 include tantalum oxide, zirconium oxide, titanium oxide, and hafnium oxide, with tantalum oxide, zirconium oxide, or hafnium oxide being preferred.

[0026] The thickness of the layer containing the compound with elements from groups 3 to 6 is preferably 3 nm to 70 nm, and more preferably 10 nm to 50 nm. The thickness of the layer containing silicon dioxide is preferably 0.3 nm to 120 nm, and more preferably 0.3 nm to 3 nm, or 10 nm to 100 nm.

[0027] The liquid-repellent layer is preferably a layer with a contact angle of 60° or more with respect to water. More preferably, the contact angle of the liquid-repellent layer with respect to water is 70° or more, and even more preferably 80° or more. Since the liquid-repellent layer is provided on the outermost surface of the nozzle substrate 10, the discharge surface has excellent wipe resistance.

[0028] The liquid-repellent layer has a substructure represented by the following formula (1): (L-Y-) ｋ Si-(O-*) ４－ｋ …(1) In formula (1), L is a hydrocarbon group, Y is a single bond or a divalent linking group that does not contain a fluorine atom, k is an integer from 1 to 3, and * indicates the bond position with other structures.

[0029] In formula (1), the hydrocarbon group represented by L may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. Of these, the hydrocarbon group is preferably an aliphatic hydrocarbon group, and more preferably an alkyl group. The alkyl group may be a linear alkyl group, a branched alkyl group, or a cyclic alkyl group. The number of carbon atoms in the hydrocarbon group is preferably 1 to 30, and more preferably 1 to 20. The hydrocarbon group may have substituents, but it is preferable that the substituents do not contain fluorine atoms.

[0030] In formula (1), the divalent linking group Y, which does not contain a fluorine atom, can be, for example, a combination of at least one selected from the group consisting of -O-, -C(=O)-, and NR-, and a hydrocarbon group. R represents a hydrogen atom or a hydrocarbon group. However, the linking portion of Y to L is not a hydrocarbon group.

[0031] If Y is a divalent linking group, Y can be, for example, * １ -O-C(=O)-(hydrocarbon group)-C(=O)-O-(hydrocarbon group)-* ２ * １ -O-(hydrocarbon group)-O-(hydrocarbon group)-* ２ * １ -C(=O)-NH-(hydrocarbon group)-* ２ * １ -NH-C(=O)-NH-(hydrocarbon group)-* ２ * １ -O-C(=O)-NH-(hydrocarbon group)-* ２ This includes: * １ * indicates the bonding position with L. ２ This indicates the bonding position with Si.

[0032] The hydrocarbon group contained in the divalent linking group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. Among these, an aliphatic hydrocarbon group is preferred, and an alkylene group is more preferred. The alkylene group may be a linear alkylene group, a branched alkylene group, or a cyclic alkylene group, but a linear alkylene group is preferred.

[0033] From the viewpoint of improving the durability of the liquid-repellent layer by further agglomerating the hydrocarbon groups, it is preferable that Y is a single bond.

[0034] Furthermore, from the viewpoint of discharge reliability, it is preferable that k is 3.

[0035] The liquid-repellent layer is preferably formed using a compound represented by formula (11) or formula (12) below.

[0036] L-Y-Six ３ ...(11) LY-SiNR １１NSi-Y-L …(12) In formula (11), L is a hydrocarbon group. Y is a single bond or a divalent linking group that does not contain a fluorine atom. X is independently a hydrolyzable group. In formula (12), L is independently a hydrocarbon group. Y is independently a single bond or a divalent linking group that does not contain a fluorine atom. R １１ This is either a hydrogen atom or a methyl group.

[0037] The preferred embodiment of the hydrocarbon group L is as described above. The preferred embodiment of the divalent linking group represented by Y, which does not contain a fluorine atom, is as described above. Y is preferably a single bond.

[0038] Examples of hydrolyzable groups represented by X include halogen atoms, alkoxy groups, and acyloxy groups. The hydrolyzable group is preferably a halogen atom or an alkoxy group, and more preferably an alkoxy group. Examples of halogen atoms include chlorine atoms, bromine atoms, and iodine atoms, with chlorine atoms being preferred. The alkoxy group is preferably an alkoxy group having 1 to 6 carbon atoms, and more preferably an alkoxy group having 1 to 3 carbon atoms. When the hydrolyzable group is an alkoxy group, the density of the liquid-repellent layer is improved and alkali resistance is improved.

[0039] For example, by using a compound represented by formula (11) or formula (12), a liquid-repellent layer having the substructure represented by formula (1) can be obtained. The liquid-repellent layer may contain a hydrolysate of the compound represented by formula (11) or formula (12). The hydrolysate of the compound represented by formula (11) or formula (12) has Si-O-Si bonds, which improves the durability of the liquid-repellent layer.

[0040] Examples of compounds represented by formula (11) include methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, and hexadecyltrimethoxysilane.

[0041] Examples of compounds represented by formula (12) include hexamethyldisilazane, 1,3-bis(chloromethyl)tetramethyldisilazane, 1,3-dimethyl-1,1,3,3-tetraphenyldisilazane, 1,3-diphenyltetramethyldisilazane, 1,3-divinyl-1,1,3,3-tetraphenyldisilazane, and heptamethyldisilazane.

[0042] The thickness of the liquid-repellent layer is preferably 50 nm or less, and more preferably 0.5 nm to 40 nm. When the thickness of the liquid-repellent layer is 50 nm or less, the curvature of the discharge is suppressed and the straightness of the discharge is improved.

[0043] In an inkjet recording device, components other than the nozzle substrate can be those of a commonly known inkjet recording device. The nozzle substrate is, for example, configured as part of the inkjet head. The inkjet head includes, for example, the nozzle substrate and a channel substrate in which ink channels communicating with the nozzles are formed. Preferably, the nozzle substrate and the channel substrate are joined together by adhesive or the like.

[0044] The inkjet recording device may include an inkjet head, a transport means for transporting a substrate, and a drying means for drying the ink ejected onto the substrate.

[0045] An inkjet recording device includes, for example, a plurality of inkjet heads, one for each ink color; an ink supply unit for storing the ink supplied to each inkjet head; a paper supply unit for supplying a substrate (recording paper); a decal processing unit for removing curls from the recording paper; a transport unit positioned opposite the ejection surface of each inkjet head for transporting the recording paper; a drying unit for drying the ink ejected onto the substrate; an image detection unit for reading the image recording result; and a paper discharge unit for discharging the recorded image to the outside. Furthermore, it is preferable that the inkjet recording device has a liquid circulation mechanism for circulating ink between the inkjet heads and the ink supply unit.

[0046] The components of the inkjet recording device, other than the inkjet head, are the same as those of conventionally known configurations; for example, refer to International Publication No. 2017 / 073526 and Japanese Patent Publication No. 2022-049414.

[0047] <Substrate> The substrate used in the image recording method of this disclosure is not particularly limited, and examples include so-called coated paper used in general offset printing. Coated paper is obtained by applying a coating material to the surface of a generally untreated fine paper, neutral paper, etc., which is mainly composed of cellulose, to provide a coating layer.

[0048] Coated paper may be one that is generally available on the market. For example, general-purpose coated paper for printing can be used as the coated paper. Specifically, examples include coated papers (A2, B2) such as "OK Topcoat+" from Oji Paper Co., Ltd., "Aurora Coat" and "U-Light" from Nippon Paper Industries Co., Ltd., and art paper (A1) such as "Tokuryo Art" from Mitsubishi Paper Mills Ltd.

[0049] The substrate may be a low-water-absorbent substrate or a non-water-absorbent substrate. In this disclosure, a low-water-absorbent recording medium is defined as a recording medium with a water absorption coefficient Ka of 0.05 mL / m³. ２ ms １／２ ~0.5 mL / m ２ ms １／２ This refers to something that is 0.1 mL / m³ ２ ms １／２ ~0.4 mL / m² ２ ms １／２ Preferably, it is 0.2 mL / m² ２ ms １／２ ~0.3 mL / m² ２ ms １／２ It is more preferable that this is the case. Furthermore, a non-absorbent substrate is defined as having a water absorption coefficient Ka of 0.05 mL / m³. ２ ms １／２This refers to values ​​less than [a certain value]. The water absorption coefficient Ka is synonymous with that described in JAPAN TAPPI Paper and Pulp Test Method No. 51:2000 (published by the Japan Paper and Pulp Technology Association). Specifically, the absorption coefficient Ka is calculated using an automatic scanning liquid absorber KM500Win (manufactured by Kumagai Riki Co., Ltd.) from the difference in the amount of water transferred at contact times of 100 ms and 900 ms.

[0050] The non-absorbent substrate is preferably a resin substrate. Examples of resin substrates include substrates formed from thermoplastic resin into a sheet. The resin substrate preferably contains polypropylene, polyethylene terephthalate, nylon, polyethylene, or polyimide. The resin substrate may be transparent, colored, or at least a portion of it may be subjected to metal vapor deposition treatment. The shape of the resin substrate is not particularly limited, but it is preferably a sheet-shaped resin substrate, and from the viewpoint of the productivity of printed materials, it is more preferably a resin substrate that can be wound into a roll.

[0051] <Ink ejection> Ink ejection is preferably performed using an inkjet head having a resolution of 300 dpi or higher (more preferably 600 dpi or higher, and even more preferably 800 dpi or higher). Here, dpi is an abbreviation for dots per inch, and 1 inch is equal to 2.54 cm.

[0052] From the viewpoint of obtaining a high-resolution image, the amount of ink droplets is preferably 1 pL (picoliters) to 10 pL, and more preferably 1.5 pL to 6 pL.

[0053] The ink ejected may be one type or two or more types. By combining multiple inks, it is possible to record images with high color reproduction.

[0054] <Other steps> The image recording method of the present disclosure may include other steps besides the step of ejecting ink. Examples of other steps include a step of preheating the substrate and a step of drying the substrate to which the ink has been applied.

[0055] <Ink> The ink used in the image recording method of this disclosure does not contain a fluorine-based surfactant, or the content of a fluorine-based surfactant is 0.001% by mass or less.

[0056] Because the ink contains virtually no fluorine-based surfactants, ink repellency is suppressed.

[0057] In this disclosure, a fluorinated surfactant means a compound that contains a fluorine atom and has surfactant properties.

[0058] Examples of commercially available fluorine-based surfactants include the Megafac series from DIC Corporation, the Florard series from Sumitomo 3M Limited, the Surflon series from AGC Inc., the PolyFox series from OMNOVA, the Futergent series from Neos Corporation, and the Capstone series from DuPont.

[0059] The ink preferably has a Si concentration of 0.05% by mass or more, and more preferably 0.1% by mass or more. The upper limit of the Si concentration is, for example, 3% by mass.

[0060] Repeated ink ejection tends to cause hydrolysis of the nozzle substrate due to hydroxide ions in the ink, leading to a decrease in water repellency. When the Si concentration in the ink is 0.05% by mass or higher, hydrolysis of the nozzle substrate is reduced, extending the lifespan of the liquid-repellent layer. As a result, the frequency of nozzle substrate maintenance can be reduced. Methods for achieving a Si concentration of 0.05% by mass or higher include, for example, incorporating a silicone-based surfactant (described later) into the ink. Alternatively, the Si concentration may be adjusted by adding Si-containing compounds such as colloidal silica, sodium silicate, or potassium silicate to the ink.

[0061] In this disclosure, the Si concentration is measured using inorganic elemental analysis.

[0062] (Water) The ink preferably contains water. That is, the ink is preferably an aqueous ink. The water content is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, based on the total amount of ink. The upper limit of the water content also depends on the amounts of other components. The upper limit of the water content relative to the total amount of ink is, for example, 90% by mass or 80% by mass.

[0063] (Pigments) The ink preferably contains at least one pigment. The pigment may be an organic pigment or an inorganic pigment.

[0064] Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments or polycyclic pigments are preferred. Examples of azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelated azo pigments. Examples of polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples of dye chelates include basic dye-type chelates and acid dye-type chelates.

[0065] Examples of inorganic pigments include titanium dioxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chromium yellow, and carbon black.

[0066] Examples of pigments include those described in "Dictionary of Pigments" edited by Seijiro Ito (published in 2000), "Industrial Organic Pigments" by W. Herbst and K. Hunger, Japanese Patent Publication No. 2002-12607, Japanese Patent Publication No. 2002-188025, Japanese Patent Publication No. 2003-26978, and Japanese Patent Publication No. 2003-342503.

[0067] In particular, when recording images using black ink, it is preferable to use carbon black as the black pigment. If the carbon black has a high volatile content (i.e., the carbon black surface is oxidized), the liquid-repellent layer formed on the nozzle substrate's ejection surface is less likely to wear off. Therefore, the volatile content of the carbon black is preferably 1% or more, and more preferably 2% or more. The upper limit for the volatile content is, for example, 22%.

[0068] The volatile content of carbon black is measured, for example, as the volatile content at 950°C using the method described in DIN 53552.

[0069] The volume-average particle size of the pigment is preferably 10 nm to 200 nm, more preferably 10 nm to 180 nm, and even more preferably 10 nm to 150 nm. When the volume-average particle size is 200 nm or less, color reproducibility is good and ejection performance is improved when recording images using an inkjet recording method. Furthermore, when the volume-average particle size is 10 nm or more, lightfastness is good.

[0070] Furthermore, the particle size distribution of the pigment is not particularly limited and may be either a broad particle size distribution or a monodisperse particle size distribution. Alternatively, two or more pigments with monodisperse particle size distributions may be mixed and used.

[0071] The volume-average particle size and particle size distribution of the pigment are values ​​measured by a particle size distribution analyzer (for example, the Microtrac UPA® EX150 manufactured by Nikkiso Co., Ltd.).

[0072] The pigment content is preferably 1% to 20% by mass, and more preferably 3% to 10% by mass, relative to the total amount of ink.

[0073] (Organic Solvents) The ink preferably contains at least one organic solvent.

[0074] The type of organic solvent is not limited, and includes, for example: monoalcohols with 1 to 4 carbon atoms; alkylene glycols (also known as diols) such as ethylene glycol, propylene glycol (also known as 1,2-propanediol), 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, and 4-methyl-1,2-pentanediol; triols such as glycerin, 1,2,6-hexanetriol, and trimethylolpropane; alkylene glycol monoalkyl ethers such as ethylene glycol monoalkyl ether and propylene glycol monoalkyl ether; polyalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, and polyoxyethylene polyoxypropylene glycol; Examples include polyalkylene glycol ethers such as diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tripropylene glycol monoalkyl ether, and polyoxypropylene glyceryl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone; and the like.

[0075] In particular, from the viewpoint of discharge stability, the organic solvent preferably contains a diol having 2 to 4 carbon atoms. Furthermore, from the viewpoint of ink discharge stability, the organic solvent preferably contains, along with a diol having 2 to 4 carbon atoms, at least one selected from the group consisting of a glycol ether containing an alkyl group having 1 to 6 carbon atoms and a diol having 5 to 7 carbon atoms.

[0076] Preferred glycol ethers include ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monoisopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether. Preferred diols include propylene glycol, 1,2-butanediol, 1,2-pentanol, and 1,2-hexanol.

[0077] From the viewpoint of discharge stability, the mass ratio of the content of diols having 2 to 4 carbon atoms to the content of glycol ethers containing alkyl groups having 1 to 6 carbon atoms is preferably 20:1 to 1:1, and more preferably 10:1 to 2:1.

[0078] From the viewpoint of discharge stability, the mass ratio of the content of diols having 2 to 4 carbon atoms to the content of diols having 5 to 7 carbon atoms is preferably 20:1 to 1:1, and more preferably 10:1 to 2:1.

[0079] Furthermore, from the viewpoint of ink ejection stability, it is preferable that the organic solvent includes at least one selected from the group consisting of alkylene glycols and alkylene glycol monoalkyl ethers.

[0080] The content of the organic solvent is preferably 10% to 40% by mass, and more preferably 15% to 30% by mass, based on the total amount of ink.

[0081] (Resin) The ink preferably contains at least one type of resin.

[0082] Examples of resins include pigment-dispersed resins, resin particles, and water-soluble resins.

[0083] - Pigment Dispersion Resin - The resin may contain at least one pigment dispersion resin. In this disclosure, the pigment dispersion resin is a resin having the function of dispersing pigments.

[0084] The form of the pigment dispersion resin is not particularly limited and may be a random resin, a block resin, or a graft resin. Preferably, the pigment dispersion resin is a resin having a crosslinked structure.

[0085] It is preferable that the pigment contained in the ink is coated with at least a portion of a resin having a cross-linked structure. When the pigment dispersion resin is a resin having a cross-linked structure and at least a portion of the pigment is coated with the pigment dispersion resin, the pigment dispersion resin is less likely to detach from the surface of the pigment, resulting in high dispersion stability of the pigment.

[0086] For example, by mixing a pigment with an uncrosslinked resin and then crosslinking it with a crosslinking agent, at least a portion of the pigment can be coated with a resin having a crosslinked structure.

[0087] In this disclosure, "resin" refers to a compound having a weight-average molecular weight (Mw) of 1000 or more.

[0088] In this disclosure, weight-average molecular weight (Mw) refers to the value measured by gel permeation chromatography (GPC). The GPC measurement is performed using an HLC®-8020GPC (manufactured by Tosoh Corporation) as the measuring instrument, with three TSKgel® Super Multipore HZ-H columns (4.6 mm ID × 15 cm, manufactured by Tosoh Corporation) and THF (tetrahydrofuran) as the eluent. The measurement is performed with a sample concentration of 0.45% by mass, a flow rate of 0.35 mL / min, a sample injection volume of 10 μL, and a measurement temperature of 40°C, using an RI detector. The calibration curve will be prepared from eight samples of "Standard Samples TSK standard, polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0089] The resin having a cross-linked structure is not particularly limited as long as it has at least one cross-linked structure within its molecule.

[0090] Whether or not the resin contained in the ink has a cross-linked structure can be determined, for example, by the following method. First, the resin is separated from the ink using a separation method such as solvent extraction. The separated resin can then be analyzed using various analytical methods such as nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and thermal analysis to comprehensively determine whether or not it has a cross-linked structure.

[0091] In preparing the inks of this disclosure, a pigment dispersion in which the pigment is dispersed in a resin having a cross-linked structure may be used. The pigment dispersion may be a commercially available product. Examples of commercially available products include Projet Yellow APD1000, Projet Magenta APD1000, Projet Cyan APD1000, and Projet Black APD1000 (manufactured by FUJIFILM Imaging Colorants).

[0092] -Resin Particles- From the viewpoint of improving abrasion resistance, it is preferable that the resin contains at least one type of resin particle. The resin particles may contain resin and other core materials, but it is preferable that the resin particles consist only of resin.

[0093] The type of resin that constitutes the resin particles is not particularly limited. Examples of resin particles include particles made of acrylic resin, particles made of polyester resin, particles made of polyurethane resin, and particles made of polyolefin resin.

[0094] In this disclosure, acrylic resin means a resin comprising at least one of structural units derived from (meth)acrylic acid and structural units derived from (meth)acrylic acid esters.

[0095] For resin particles, you may refer to, for example, paragraphs 0038 to 0114 of International Publication No. 2021 / 192720, paragraphs 0109 to 0120 of Japanese Patent Publication No. 2015-25076, etc.

[0096] If the ink contains resin particles, the resin particle content is preferably 0.3% to 10% by mass, more preferably 1% to 6% by mass, and even more preferably 1.5% to 5% by mass, relative to the total amount of ink.

[0097] (Surfactants) The ink preferably contains at least one type of silicone-based surfactant. Repeated ink ejection tends to wear down the liquid-repellent layer on the ejection surface of the nozzle substrate. When the ink contains a silicone-based surfactant, the liquid-repellent layer is repaired by the silicone-based surfactant, thereby extending the life of the liquid-repellent layer. As a result, the frequency of maintenance of the nozzle substrate can be reduced.

[0098] The silicone-based surfactant is preferably a polyether-modified silicone compound.

[0099] Specifically, the silicone-based surfactant is preferably represented by the following formula (2).

[0100]

[0101] In formula (2), R １ Each of these independently represents an alkyl group or hydroxyl group having 1 to 3 carbon atoms, R ２ R represents an alkanediyl group with 2 to 5 carbon atoms. ３ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a hydroxyl group, where m is 1 to 20, n is 1 to 20, a is 0 to 20, and b is 0 to 20.

[0102] Note that m, n, a, and b represent the average number of moles added for each unit. (C ２ H ４ The constituent units represented by (O) and (C ３ H ６ The constituent units represented by O) may be joined randomly or in blocks. The constituent units with subscript m and the constituent units with subscript n may be joined randomly or in blocks. (C ３ H ６ The constituent unit represented by O is (CH(CH ３ ) - CH２ It is preferable to represent it as O).

[0103] R １ R is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group. ２ R is preferably an alkanediyl group having 3 or 4 carbon atoms, and more preferably a trimethylene group. ３ It is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group.

[0104] It is more preferable that a is 1 to 15, b is 0, m is 1 to 10, and n is 1 to 5. Furthermore, it is even more preferable that a is 3 to 10, b is 0, m is 1 to 3, and n is 1 to 3.

[0105] The silicone-based surfactant is preferably represented by the following formula (2A).

[0106] In equation (2A), m is between 2 and 3, n is between 1 and 2, and a is between 1 and 23.

[0107] Furthermore, the silicone-based surfactant is preferably represented by the following formula (2B).

[0108] In equation (2B), m is 2 to 3, n is 1 to 2, a is 1 to 23, b is 0 to 24, R ３ This is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a hydroxyl group.

[0109] The silicone-based surfactant may be a commercially available product. Examples of commercially available silicone-based surfactants include BYK-302, BYK-307, BYK-331, BYK-333, BYK-345, BYK-347, BYK-348, BYK-349, BYK-378, BYK-3400, BYK-3450, BYK-3451, BYK-3455, BYK-3760 (all manufactured by Bic Chemie Japan); KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, K Examples include F-644, KF-6011, KF-6012, KF-6015, KF-6017, KF-6020 (all manufactured by Shin-Etsu Chemical Co., Ltd.); Silface SAG002, Silface SAG005, Silface SAG008, Silface SAG503A (all manufactured by Nisshin Chemical Co., Ltd.); and TEGOWet KL245, TEGOWet 240, TEGOWet 250, TEGOWet 260, TEGOWet 270, TEGOWet 280 (all manufactured by Evonik).

[0110] The content of the silicone-based surfactant is preferably 0.01% to 3% by mass, more preferably 0.1% to 2% by mass, and even more preferably 0.2% to 1.5% by mass, based on the total amount of ink.

[0111] The ink preferably further contains, in addition to a silicone-based surfactant, at least one selected from the group consisting of acetylene glycol-based surfactants and polyoxyethylene-based surfactants. Including at least one selected from the group consisting of acetylene glycol-based surfactants and polyoxyethylene-based surfactants further suppresses ink repellency.

[0112] Examples of acetylene glycol-based surfactants include acetylene glycol and polyalkylene oxide adducts of acetylene glycol.

[0113] Examples of acetylene glycol-based surfactants include 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, 2,5,6,11-tetramethyl-6-dodecine-5,8-diol, 2,5-dimethyl-3-hexyn-2,5-diol, and 2,5,8,11-tetramethyl-6-dodecine-5,8-diol, as well as their ethylene oxide adducts.

[0114] Acetylene glycol-based surfactants may be commercially available products. Examples of commercially available acetylene glycol-based surfactants include Surfinol 104, Surfinol 104E, Surfinol 104H, Surfinol 104A, Surfinol 104PA, Surfinol 104PG-50, Surfinol 104S, Surfinol 420, Surfinol 440, Surfinol 46, Surfinol 485, Surfinol SE, Surfinol SE-F, Surfinol 61, and Surfinol 8. 2. Examples include Surfinol DF110D, Dynol 604, Dynol 607, Surfinol 2502 (HLB value 8), Surfinol TG, Orphine E1004, Orphine E1010 (all manufactured by Evonik Industries); Acetyleneol E00, Acetyleneol E13T, Acetyleneol E40, Acetyleneol E60, Acetyleneol E100, Acetyleneol E200 (all manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0115] When the ink contains an acetylene glycol-based surfactant, the content of the acetylene glycol-based surfactant is preferably 0.01% to 3% by mass, more preferably 0.1% to 2.5% by mass, and even more preferably 0.2% to 2% by mass, based on the total amount of ink.

[0116] Examples of polyoxyethylene-based surfactants include polyoxyethylene alkyl ethers. Polyoxyethylene alkyl ethers are R ２０ -O-(CH ２ CH ２ O) ｎ１ It is preferable to represent it as -H.２０ is a hydrocarbon group, and n1 is 1 to 40.

[0117] R ２０ The hydrocarbon group represented may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. Among these, an aliphatic hydrocarbon group is preferred, and an alkyl group is more preferred. The alkyl group may be a linear alkyl group, a branched alkyl group, or a cyclic alkyl group, but a branched alkyl group is preferred. The number of carbon atoms in the hydrocarbon group is preferably 6 to 20, and more preferably 10 to 18.

[0118] Polyoxyethylene surfactants may be commercially available products. Examples of commercially available polyoxyethylene surfactants include: NOVEL 6-3, NOVEL 6-6 (both manufactured by Novel Co., Ltd.); TAKESURF D-1004, TAKESURF D-1006EH, TAKESURF D-1007, TAKESURF D-1715-N, TAKESURF D-1105, TAKESURF D-1110 (all manufactured by Takemoto Oil Co., Ltd.); CAFLON NE0400, CAFLON NE0500, CAFLON NE0800, CAFLON TD0500, CAFLON TD0800, CAFLON Examples include TD1000 (manufactured by UNIVAR); Synperonic 13 / 7-85-L (manufactured by CRODA); Emulgen 104P, Emulgen 106, Emulgen 108, Emulgen 709, Emulgen 120, Emulgen 210, Emulgen 220 (all manufactured by Kao Corporation); TERGITOL 15-S-7, TRITON (registered trademark) HW-1000 (manufactured by Dow); Neodol 25 / 7 (manufactured by Shell Chemicals), etc.

[0119] When the ink contains a polyoxyethylene-based surfactant, the content of the polyoxyethylene-based surfactant is preferably 0.01% to 3% by mass, more preferably 0.1% to 2.5% by mass, and even more preferably 0.2% to 2% by mass, based on the total amount of ink.

[0120] (Other Components) The ink may contain other components besides those listed above, as needed. Examples of other components include wax, colloidal silica, inorganic salts, solid wetting agents (such as urea), fade inhibitors, emulsifying stabilizers, penetration enhancers, UV absorbers, preservatives, fungicides, pH adjusters, defoamers, viscosity modifiers, dispersion stabilizers, rust inhibitors, chelating agents, water-soluble polymer compounds, and the like.

[0121] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure.

[0122] <<Preparation of Ink>> [Ink 1] <Preparation of Aqueous Dispersion of Resin Particles> In a three-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, water (250 g), 12-methacrylamide dodecanoic acid (6.7 g), potassium bicarbonate (0.17 g), and isopropanol (20 g) were charged and heated to 85°C under a nitrogen atmosphere. A mixed solution consisting of 4,4'-azobis(4-cyanovaleric acid) (radical polymerization initiator, product name "V-501", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (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 three-necked flask at a constant rate so that the addition would be completed in 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: immediately after the start of the addition of the monomer solution and 1.5 hours after the start of the addition of the monomer solution. After the addition of the monomer solution was completed, the mixture was stirred for 1 hour. Subsequently, a mixed solution consisting of V-501 (0.06 g), potassium bicarbonate (0.04 g), and water (6 g) was added to the resulting reaction mixture, and the mixture was stirred for a further 3 hours. The resulting reaction mixture was filtered through a 50 μm mesh to obtain an aqueous dispersion of resin particles.

[0123] <Preparation of Black Ink> The following components were mixed to obtain a mixture. Then, coarse particles were removed from the mixture using a 1 μm filter to obtain black ink.

[0124] (Pigments) ・Black pigment dispersion: Product name "ProJet Black APD4000": Pigment dispersion containing carbon black, pigment concentration 14.3% by mass, manufactured by FujiFilm Imaging Colorants Ltd... Amount that results in a pigment content of 4.0 parts by mass in the ink. ・Cyan pigment dispersion: Product name "ProJet Cyan APD1000": Pigment dispersion containing pigment blue 15:3, pigment concentration 14.1% by mass, manufactured by FujiFilm Imaging Colorants Ltd... Amount that results in a pigment content of 1.0 part by mass in the ink. ・Magenta pigment dispersion: Product name "Pro-Jet Magenta APD1000: Pigment dispersion containing Pigment Red 122, pigment concentration 14.0%, manufactured by FujiFilm Imaging Colorants Ltd. ... The amount of pigment in the ink is 2.0 parts by mass.

[0125] (Organic solvents) ・Propylene glycol (PG) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) ... 20.0 parts by mass ・Diethylene glycol monoethyl ether (DEGmEE) (manufactured by Daicel Corporation) ... 8.0 parts by mass

[0126] (Resin particles) - Dispersion of the resin particles prepared above (solid content concentration 25% by mass) ... an amount in which the resin particle content is 1.0 part by mass

[0127] (Wax) - "AQUACER 531" (PE wax emulsion) manufactured by BIC CHEMI JAPAN (45% solids by mass) ... amount that results in a wax content of 1.0 part by mass.

[0128] (Surfactants) ・Silicone-based surfactant 1 (described later) ... 1.0 part by mass

[0129] (Additives) ・Colloidal silica... "Snowtex XS" manufactured by Nissan Chemical Industries... The amount required to bring the Si concentration in the ink to the values ​​listed in Table 1.

[0130] • Water… an amount that totals 100 parts by mass.

[0131] [Ink 2 to Ink 7, Ink A] <Preparation of Black Pigment Dispersion> A monomer supply composition was prepared by mixing methacrylic acid (172 parts by mass), benzyl methacrylate (828 parts by mass), and isopropanol (375 parts by mass). An initiator supply composition was prepared by mixing 2,2-azobis(2-methylbutyronitrile) (22.05 parts by mass) and isopropanol (187.5 parts by mass). Next, isopropanol (187.5 parts by mass) was heated to 80°C under a nitrogen atmosphere, and the mixture of the monomer supply composition and the initiator supply composition was added dropwise over 2 hours. After the dropwise addition was complete, the obtained solution was kept at 80°C for a further 4 hours, and then cooled to 25°C. After cooling, the solvent was removed under reduced pressure to obtain a water-soluble polymer (methacrylic acid / benzyl methacrylate copolymer). The water-soluble polymer had a weight-average molecular weight of approximately 30,000 and an acid value of 112 mgKOH / g.

[0132] 0.8 equivalents of methacrylic acid in the obtained water-soluble polymer (150 parts by mass) were neutralized with an aqueous potassium hydroxide solution. Then, deionized water was added to adjust the concentration to 25% by mass, and an aqueous solution of polymer dispersant Q-1 was obtained.

[0133] An aqueous solution of polymer dispersant Q-1 (124 parts by mass), black pigment (carbon black, product name "XPB721", manufactured by Orion: 20% volatile content) (48 parts by mass), a 5% by mass aqueous solution of potassium hydroxide (70 parts by mass), and ion-exchanged water (5 parts by mass) were mixed and dispersed using a bead mill (bead diameter 0.1 mmφ, zirconia beads) until the desired volume-average particle size was obtained, thereby obtaining a dispersion (uncrosslinked dispersion) in which the black pigment was dispersed by polymer dispersant Q-1. The pigment concentration of the black pigment was 15% by mass.

[0134] To this uncrosslinked dispersion (136 parts by mass), 1.3 parts by mass of trimethylolpropane polyglycidyl ether (product name "Denacol EX-321", manufactured by Nagase ChemteX Corporation), which is a crosslinking agent, and 14.3 parts by mass of an aqueous boric acid solution (boric acid concentration: 4% by mass) were added. The mixture was reacted at 50°C for 6.5 hours, and then cooled to 25°C, thereby crosslinking the polymer dispersant Q-1 with the crosslinking agent. This resulted in a dispersion (crosslinked dispersion) in which the black pigment was dispersed by the crosslinked resin 1. Note that the crosslinked resin 1 is a crosslinked product of the resin dispersant Q-1.

[0135] Next, ion-exchanged water was added to the obtained crosslinked dispersion, and ultrafiltration was performed using an ultrafilter (SARTOCON SLICE 200, manufactured by SARTORIUS) and an ultrafiltration filter (SARTOCO SLICE CASSETTE, manufactured by SARTORIUS, molecular weight cutoff 30,000, 3051443902E--SG). After purification to reduce the dipropylene glycol concentration in the crosslinked dispersion to 0.1% by mass or less, the dispersion was concentrated until the pigment concentration reached 15% by mass, thereby obtaining a black pigment dispersion A (black pigment concentration 15% by mass) in which the black pigment was dispersed by the crosslinked resin 1.

[0136] <Preparation of Black Ink> Using the black pigment dispersion A prepared above, black ink was obtained in the same manner as for ink 1, except that the type and content of the surfactant were changed to those shown in Tables 1 to 3. The pigment concentration in inks 2 to 7 and ink A was 4% by mass.

[0137] [Ink 8] Black ink was obtained in the same manner as Ink 7, except that the following component was added instead of colloidal silica: • Sodium silicate… "Sodium silicate aqueous solution (solid content concentration 52% to 57% by mass)" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. … The amount required to achieve the Si concentration in the ink as shown in Table 3.

[0138] [Ink 9] Black ink was obtained in the same manner as ink 8, except that the amount of sodium silicate was adjusted so that the Si concentration in the ink was as shown in Table 3. The pigment concentration in the ink was 4% by mass.

[0139] [Ink 10] <Preparation of Black Pigment Dispersion> Black ink was obtained in the same manner as for ink 5, except that the black pigment (carbon black, product name "FW182", manufactured by Orion: volatile content 20%) was changed. The pigment concentration in the ink was 4% by mass.

[0140] [Ink 11] <Preparation of Black Pigment Dispersion> Black pigment dispersion B was obtained in the same manner as ink 2, except that when preparing the uncrosslinked dispersion, an aqueous solution of polymer dispersant Q-1 (124 parts by mass), black pigment (carbon black, product name "Special Black 5", manufactured by Orion: volatile content 15%) (48 parts by mass), a 5% by mass potassium hydroxide aqueous solution (60 parts by mass), and ion-exchanged water (15 parts by mass) were mixed.

[0141] <Preparation of Black Ink> Black ink was obtained in the same manner as for ink 5, except that the black pigment dispersion B prepared above was used. The pigment concentration in the ink was 4% by mass.

[0142] [Ink 12] <Preparation of Black Pigment Dispersion> Except that when preparing the uncrosslinked dispersion, an aqueous solution of polymer dispersant Q-1 (124 parts by mass), black pigment (carbon black, product name "Nipex 170IQ", manufactured by Orion: 5% volatile content) (48 parts by mass), a 5% by mass aqueous solution of potassium hydroxide (7 parts by mass), and ion-exchanged water (68 parts by mass) were mixed together, the same method as for Ink 2 was used to obtain Black Pigment Dispersion C.

[0143] <Preparation of Black Ink> Black ink was obtained in the same manner as ink 5, except that the black pigment dispersion C prepared above was used. The pigment concentration in the ink was 4% by mass.

[0144] [Ink 13] <Preparation of Black Pigment Dispersion> Except that when preparing the uncrosslinked dispersion, an aqueous solution of polymer dispersant Q-1 (124 parts by mass), black pigment (carbon black, product name "#2600", manufactured by Mitsubishi Chemical Corporation: 4% volatile content) (48 parts by mass), a 5% by mass aqueous solution of potassium hydroxide (7 parts by mass), and ion-exchanged water (68 parts by mass) were mixed together, the same method as for Ink 2 was used to obtain Black Pigment Dispersion D.

[0145] <Preparation of Black Ink> Black ink was obtained in the same manner as for ink 5, except that the black pigment dispersion D prepared above was used. The pigment concentration in the ink was 4% by mass.

[0146] [Inks 14-16] Black ink was obtained in the same manner as ink 7, except that the type and content of the organic solvent were changed to those listed in Table 4. The pigment concentration in the ink was 4% by mass. The details of the organic solvent are as follows: ・1,2-HD …1,2-Hexanediol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) ・TEA …Triethanolamine (manufactured by Tokyo Chemical Industries, Ltd.) ・EGmHE …Ethylene glycol monohexyl ether (manufactured by Nisshin Chemical Industry Co., Ltd.) ・PGmBE …Propylene glycol monobutyl ether (manufactured by Tokyo Chemical Industries, Ltd.)

[0147] Details of the surfactants used in inks 1 to 16 and ink A are as follows: • Silicone-based surfactant 1: Product name "BYK-345", manufactured by BYK, having the structure represented by formula (2), where m is 1.8, n is 1, a is 5.9, b is 0, R ３ is a hydrogen atom or -C ３ H ７ The silicone-based surfactant and silicone-based surfactant 2: Product name "TEGOwet280", manufactured by Evonik, having a structure represented by formula (2), where m is 2 or 3, n is 1 or 2, a is 1 to 23, b is 0 to 24, R ２ R is an alkanediyl group having 2 to 5 carbon atoms. ３ R is a hydrogen atom, a C1-C3 alkyl group or a hydroxyl group. Silicone surfactant 3: Product name "TEGOwet270", manufactured by Evonik, has a structure represented by formula (2), where m is 2 or 3, n is 1 or 2, a is 1-23, b is 0-24, R ２ R is an alkanediyl group having 2 to 5 carbon atoms. ３Silicone-based surfactants and acetylene glycol-based surfactants containing a hydrogen atom, an alkyl group with 1 to 3 carbon atoms, or a hydroxyl group: Product name "Surfinol 104", manufactured by Nisshin Chemical Industry Co., Ltd. Polyoxyethylene-based surfactants: Product name "TRITON (registered trademark) HW-1000", manufactured by Dow Chemical Company Fluorine-based surfactants: Product name "Capstone FS-63", manufactured by Chemours

[0148] <<Fabrication of the inkjet head>> A nozzle substrate with nozzles formed on it and a channel substrate with ink channels formed on it were joined together to prepare a joint measuring 25 mm x 35 mm.

[0149] Step (a1): The bonded body was placed in a surface treatment vacuum chamber. After creating a vacuum in the vacuum chamber, the air was replaced with oxygen to generate oxygen plasma. The oxygen plasma irradiation conditions were 30 W output, 100 mL / min flow rate, and 30 seconds irradiation time.

[0150] Step (b1): The bonded body after the silicon oxide film formation step (a1) is placed in an ALD (Atomic Layer Deposition) chamber, H ２ O gas was introduced to form hydroxyl groups on the surface of the joint. Next, tris(dimethylamino)silane (TDMAS) gas was introduced to react the hydroxyl groups formed on the surface of the joint with the TDMAS. After that, the excess gas was exhausted. Next, H ２ O gas is introduced, and the TDMA bonded to the hydroxyl group in the previous reaction and H ２ O was reacted with H. After that, the excess gas was exhausted. Then, TDMA gas was introduced, exhausted, and H was added. ２ The introduction and exhaust of O gas constituted one cycle, and this process was repeated until a predetermined thickness (30 nm) was reached, thereby forming a silicon oxide layer.

[0151] Step (c1): Hydrophilization Treatment Next, the bonded body after step (b1) was placed in a vacuum chamber. After creating a vacuum in the vacuum chamber, it was replaced with oxygen to generate oxygen plasma. The irradiation conditions for the oxygen plasma were an output of 100 W, a flow rate of 100 mL / min, and an irradiation time of 1 minute.

[0152] Step (d1): Silane coupling agent deposition Next, the bonded structure after step (c1) was placed in the deposition chamber. The silane coupling agents listed in Tables 1-3 were added to the tungsten boat. When the temperature of the tungsten boat reached 70°C, the shutter was opened, and while monitoring the film thickness with a quartz crystal oscillator, the shutter was closed when the film thickness reached 3 nm, and the silane coupling agent was deposited.

[0153] Process (e1): Storage in a high-temperature, high-humidity environment. Next, in order to promote the hydrolysis reaction of the silane coupling agent and the condensation reaction between the joint after process (d1) and the silane coupling agent, the mixture was left for 12 hours at a temperature of 60°C and a humidity of 90%.

[0154] Step (f1): Removal of the liquid-repellent layer formed on the inner wall of the nozzle and the inner wall of the ink channel. Next, tape was applied to the surface of the nozzle substrate in the bonded body after step (e1), and oxygen plasma treatment was performed on the nozzle and ink channel from the side of the channel substrate opposite to the side bonded to the nozzle substrate. This removed the liquid-repellent layer formed on the inner wall of the nozzle and the inner wall of the ink channel, and an inkjet head was obtained.

[0155] Details of the silane coupling agents listed in Tables 1-3 are as follows.

[0156] Compound 1: Methyltrimethoxysilane (CH ３ -Si(OMe) ３ Compound 2: n-propyltrimethoxysilane (C ３ H ７ -Si(OMe) ３ Compound 3: Hexyltrimethoxysilane (C ６ H １５ -Si(OMe) ３ Compound 4: Octyltrimethoxysilane (C ８ H １７ -Si(OMe) ３ Compound 5: Hexadecyltrimethoxysilane (C １６ H ３３ -Si(OMe) ３ )

[0157] Compound 6: Hexamethyldisilazane

[0158]

[0159] Compound 7: 1,3-bis(chloromethyl)tetramethyldisilazane

[0160]

[0161] Compound 8: 1,3-dimethyl-1,1,3,3-tetraphenyldisilazane

[0162]

[0163] Compound 9: 1,3-diphenyltetramethyldisilazane

[0164]

[0165] Compound 10: 1,3-divinyl-1,1,3,3-tetramethyldisilazane

[0166]

[0167] Compound 11: Heptamethyldisilazane

[0168]

[0169] It was confirmed that all of the liquid-repellent layers have a substructure represented by formula (1).

[0170] <<Image Recording>> Image recording was performed using an inkjet recording device equipped with the inkjet head prepared above. The prepared ink was ejected from the nozzle of the inkjet head. The ink applied to the substrate was dried while the substrate was being transported. After recording an image on one side of the substrate, the substrate was inverted using an inversion device. Then, an image was recorded on the other side of the substrate. The detailed conditions for image recording are as follows.

[0171] • Base material: Product name "OK Topcoat", manufactured by Oji Paper Co., Ltd. (Water absorption capacity: 4.9 g / m²) ２) • Substrate transport mechanism: Roll to roll • Inkjet head temperature: 32°C • Inkjet head resolution: 1200 dpi x 1200 dpi • Ink droplet volume: 3.0 pL • Environment around inkjet head: Temperature 25°C ± 1°C, relative humidity 25°C ± 5% • Substrate transport speed: 80 m / min • Substrate tension during transport: 60 N

[0172] The substrate was dried by blowing 80°C hot air onto it using a pre-drying device before ink application. After applying black ink, within 3.0 seconds, the substrate was dried by radiant heating with an infrared heater and blowing 140°C hot air onto it using a drying device. Using the drying device, the mass of ink per unit area on the ink-applied surface of the substrate was 200 μg / cm². ２ The substrate was dried in the following manner. After that, the substrate was brought into contact with a cooling roller. The cooling roller had an adhesion work of 68.3 mN / m at the contact surface with the ink-applied surface, and a Vickers hardness of 450 Hv at the contact surface. Furthermore, the ink-applied surface of the substrate was brought into contact with a heating drum and dried. The outer surface of the heating drum had a maximum static friction coefficient of 0.49 and an arithmetic mean roughness of 2.07 μm.

[0173] [Examples 1 to 25, Comparative Example 1] Images were recorded using the above-prepared ink and an inkjet recording device equipped with the above-prepared ink head. Evaluations were performed on ink ejection curvature, the lifespan of the liquid-repellent layer, and ink repellency. The evaluation method is as follows.

[0174] <Ejection Curvature> Using the above inkjet recording device and ink, a solid image with 100% duty cycle was continuously recorded over a 10 m length of substrate (single-sided printing only). The last 5-6 m of the image recording section was cut, and the number of streaks in the solid image section equivalent to one head width (42.69 mm) was visually observed. Ejection curvature was evaluated based on the total number of white and black streaks. The evaluation criteria are as follows. "White streaks" are caused by the ejected ink curving or not being ejected, and refer to the lighter areas of color in the solid image. "Black streaks" are caused by the ejected ink curving and overlapping, and refer to the darker areas of color. AA: No white or black streaks. A: The total number of white and black streaks is 1 to 5. B: The total number of white and black streaks is 6 to 10. C: The total number of white and black streaks is 10 to 20. D: The total number of white and black stripes is 21 or more.

[0175] <Liquid-Repellent Layer Lifespan> Using the above-mentioned inkjet recording device and ink, the ink was purged under pressure for 3 seconds to cause the ink to overflow from the nozzle discharge surface. Afterwards, the ink adhering to the inkjet head was wiped off by hand with a Bencot (manufactured by Asahi Kasei Corporation) impregnated with deionized water. This series of operations constituted one maintenance cycle. Every 10 maintenance cycles, the contact angle of the liquid-repellent layer surface on the discharge surface of the nozzle substrate was measured using deionized water. If the contact angle was 80° or higher, another 10 maintenance cycles were performed. If the contact angle was less than 80°, the operation was terminated. The number of maintenance cycles at the time the operation was terminated was determined to be the lifespan of the liquid-repellent layer. The evaluation criteria are as follows. The contact angle with water was measured under conditions of 25°C using a fully automatic contact angle meter (product name "DM-701", manufactured by Kyowa Interface Science Co., Ltd.). AA: The number of maintenance cycles was 80 or more. A: The number of maintenance cycles was 60 or 70. B: The number of maintenance cycles was 40 or 50. C: The number of maintenance cycles was 20 or 30. D: The number of maintenance cycles was 10.

[0176] <Repelling> Using the above inkjet recording device and ink, a solid image with a duty cycle of 100% was continuously recorded over a 1000m length of substrate (double-sided printing). The last 999-1000m of the image recording section was cut off, and the repelling of the solid image on the back side (the second printed side) of the single-head equivalent width (42.69mm) was visually observed. The total number of repellings was calculated. Note that "repelling" refers to an image defect with a diameter of less than 3mm, which occurs in the solid image and results in an area where the ink has been repelled and the density is reduced. AA: No repellings were observed. A: The total number of repellings is 1 to 3. B: The total number of repellings is 4 to 6. C: The total number of repellings is 7 to 10. D: The total number of repellings is 11 or more.

[0177] Tables 1 to 3 show the evaluation results. In Example 1, the ink was prepared using a commercially available pigment dispersion, so "-" is written in the Pigment Type column.

[0178]

[0179]

[0180]

[0181]

[0182] As shown in Tables 1 to 4, Examples 1 to 25 included a step of recording an image on a substrate by ejecting ink that does not contain a fluorine-based surfactant from a nozzle substrate using an inkjet recording apparatus equipped with a nozzle substrate on which a nozzle is formed, and it was found that ink repellency is suppressed because the nozzle substrate has a liquid-repellent layer on the ejection surface, and the liquid-repellent layer has a substructure represented by the following formula (1). On the other hand, in Comparative Example 1, it was found that the ink contained a fluorine-based surfactant, and ink repellency occurred.

[0183] Next, another inkjet head was fabricated.

[0184] (Fabrication of Inkjet Head A) Similarly to the fabrication of the above inkjet head, a nozzle substrate with nozzles formed thereon and a flow path substrate with ink flow paths formed thereon were joined to prepare a joined body with dimensions of 25 mm × 35 mm. Surface treatment was performed in the same manner as in the above step (a1).

[0185] The joined body after step (a1) was placed in an ALD (Atomic Layer Deposition) chamber, and H ２ O gas was introduced to form hydroxyl groups on the surface of the joined body. Next, tetrakis(dimethylamino)hafnium (TDMAHf) gas was introduced to react the hydroxyl groups formed on the surface of the joined body with TDMAHf. Thereafter, the excess gas was exhausted. Next, H ２ O gas was introduced to react TDMAHf, which had been bonded to the hydroxyl groups in the previous reaction, with H ２ O. Thereafter, the excess gas was exhausted. Then, the introduction and exhaustion of TDMAHf gas and the introduction and exhaustion of H ２ O gas were taken as one cycle, and the process was repeated until a predetermined thickness (30 nm) was reached to form a hafnium oxide layer.

[0186] Steps (b1) to (f1) were performed using the joined body on which the hafnium oxide layer was formed to obtain an inkjet head A.

[0187] (Fabrication of Inkjet Head B) An inkjet head B was obtained in the same manner as the fabrication of inkjet head A, except that tert-butylimino tri(diethylamino)tantalum (TBDTET) gas was used instead of the above TDMAHf gas.

[0188] (Fabrication of Inkjet Head C) An inkjet head C was obtained in the same manner as the fabrication of inkjet head A, except that tetrakis(N-ethylmethylamino)zirconium (TEMAZ) gas was used instead of the above TDMAHf gas.

[0189] Using an inkjet recording apparatus equipped with inkjet head A, inkjet head B, and inkjet head C respectively, the ink of Example 1 was ejected. Evaluation results similar to those of Example 1 were obtained.

[0190] Furthermore, the disclosure of Japanese Patent Application No. 2024-166627, filed on September 25, 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated as being incorporated by reference.

Claims

1. An image recording method comprising the step of recording an image on a substrate by ejecting an inkjet ink, which does not contain a fluorine-based surfactant or contains 0.001% by mass or less of a fluorine-based surfactant, from a nozzle substrate, using an inkjet recording apparatus equipped with a nozzle substrate on which a nozzle is formed, wherein the nozzle substrate has a liquid-repellent layer on its ejection surface, and the liquid-repellent layer has a substructure represented by the following formula (1): (L-Y-) ｋ Si-(O-*) ４－ｋ …(1) In formula (1), L is a hydrocarbon group, Y is a single bond or a divalent linking group that does not contain a fluorine atom, k is an integer from 1 to 3, and * indicates the bond position with other structures.

2. The image recording method according to claim 1, wherein the nozzle substrate has a layer containing silicon oxide and the liquid-repellent layer on the discharge surface in that order.

3. The image recording method according to claim 1, wherein the nozzle substrate has, in this order, a layer containing a compound containing elements of Group 3 to Group 6, a layer containing silicon dioxide, and the liquid-repellent layer on the discharge surface.

4. The image recording method according to any one of claims 1 to 3, wherein the thickness of the liquid-repellent layer is 50 nm or less.

5. The image recording method according to any one of claims 1 to 3, wherein the inkjet ink has a Si concentration of 0.05% by mass or more.

6. The image recording method according to any one of claims 1 to 3, wherein the inkjet ink comprises a silicone-based surfactant.

7. The image recording method according to claim 6, wherein the silicone-based surfactant is represented by the following formula (2). In formula (2), R １ Each of these independently represents an alkyl group or hydroxyl group having 1 to 3 carbon atoms, R ２ R represents an alkanediyl group with 2 to 5 carbon atoms. ３ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a hydroxyl group, where m is 1 to 20, n is 1 to 20, a is 0 to 20, and b is 0 to 20.

8. The image recording method according to any one of claims 1 to 3, wherein k is 3 in formula (1).

9. The image recording method according to claim 6, wherein the inkjet ink further comprises at least one selected from the group consisting of acetylene glycol-based surfactants and polyoxyethylene-based surfactants.

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