Inkjet ink and inkjet recording method

Abstract

The present invention pertains to an inkjet ink that contains water, an organic solvent, a dye, a pigment, and a polymeric dispersant. The content of the dye is 5-25 mass% with respect to the total content of the pigment and the dye. The weighted average value of solubility parameters of the organic solvent is 26.0-31.0 MPa1 / 2. The present invention also pertains to an image recording method using the inkjet ink.<sp / >

Description

Inkjet ink and inkjet recording method

[0001] The present disclosure relates to an inkjet ink and an inkjet recording method.

[0002] Various studies have been conducted on inkjet inks and inkjet recording methods. For example, Patent Document 1 discloses the following pigment ink for inkjet recording, which is a pigment ink for inkjet recording that provides a printed matter with high optical density and does not cause non-ejection due to aggregation of pigment even when brought into contact with a dye ink before printing. The pigment ink for inkjet recording described in Patent Document 1 is a pigment ink for inkjet recording containing a pigment and water, further contains a water-soluble dye, and is characterized in that when 10 parts by weight of an aqueous sodium chloride solution is added to 100 parts by weight of the ink, the pigment maintains dispersion when 1.0% by weight aqueous sodium chloride solution is added, and the pigment aggregates when 2.0% by weight aqueous sodium chloride solution is added.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-065111

[0004] However, there are cases where further improvement in image density is required for images recorded by an inkjet recording method. For example, in a high-speed inkjet recording method (e.g., an inkjet recording method in which inkjet ink is applied onto a substrate conveyed at a conveyance speed of 200 m / min or more), the drying time is shortened, which tends to cause uneven image density and easily reduce image density. For this reason, further improvement in image density is required. In order to improve image density, in addition to a pigment, means of incorporating a dye is conceivable, for example, like the ink in Patent Document 1, but in this case, the light resistance of the image may be reduced.

[0005] This disclosure has been made in view of these circumstances. One embodiment of this disclosure aims to solve the problem of an inkjet ink capable of recording images with excellent density and lightfastness, and an inkjet recording method that applies inkjet ink to a substrate being transported at a transport speed of 200 m / min or more, while still being capable of recording images with excellent density and lightfastness.

[0006] This disclosure includes the following embodiments: <1> A solution containing water, an organic solvent, a dye, a pigment, and a polymeric dispersant, wherein the dye content is 5% to 25% by mass relative to the total content of the pigment and the dye, and the weighted average value of the solubility parameter of the organic solvent is 26.0 MPa １／２ ~31.0 MPa １／２ The inkjet ink described in <1>. <2> The total content of pigments and dyes is 6% by mass or more of the total amount of inkjet ink. <3> The inkjet ink described in <1> or <2>, which contains colored resin particles comprising a dye and a resin, wherein the dye comprises at least one selected from the group consisting of oil-soluble dyes, disperse dyes and vat dyes, and the resin comprises a chain polymer, the chain polymer comprising a structure represented by the following formula (G), a cyclic structure, and a hydrophilic group.

[0007]

[0008] In formula (G), Rg represents a hydrogen atom or substituent, and Lg represents -O-, -S-, or -NRz-. Rz represents a hydrogen atom or substituent. * indicates a bond position.

[0009] <4> An inkjet ink according to any one of <1> to <3>, wherein the polymer dispersant has a crosslinked structure. <5> An inkjet ink according to any one of <1> to <4>, used as an ink in an inkjet recording method that includes applying ink to a substrate being transported at a transport speed of 200 m / min or more by an inkjet method to record an image. <6> An inkjet recording method that includes applying an inkjet ink according to any one of <1> to <5> to a substrate being transported at a transport speed of 200 m / min or more by an inkjet method to record an image.

[0010] According to one embodiment of the present disclosure, an inkjet ink capable of recording images with excellent density and lightfastness is provided, as well as an inkjet recording method that applies the inkjet ink onto a substrate being transported at a transport speed of 200 m / min or more, while still being capable of recording images with excellent density and lightfastness.

[0011] This figure conceptually illustrates an example of an inkjet recording apparatus used in the inkjet recording method of this disclosure.

[0012] In this specification, numerical ranges indicated using "~" mean a range that includes the numbers 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. Also, in numerical ranges described in this specification, the upper or lower limit stated in one numerical range may be replaced with the value shown in the example. In this specification, the amount of each component in a composition means the total amount of multiple substances present in the composition if there are multiple substances corresponding to each component in the composition, unless otherwise specified. 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.

[0013] In this specification, “image” means any film formed by applying ink, and “image recording” means the formation of an image (i.e., a film). The concept of “image” in this specification also includes solid images. In this specification, “(meth)acryloyl group” is a concept that includes both acryloyl group and methacryloyl, “(meth)acrylate” is a concept that includes both acrylate and methacrylate, and “(meth)acrylic” is a concept that includes both acrylic and methacrylic. In this specification, the term “dispersant” simply means a polymeric dispersant, and the term “solvent” simply means an organic solvent.

[0014] <Inkjet Ink> The inkjet ink of this disclosure (hereinafter also simply referred to as "ink") contains water, an organic solvent, a dye, a pigment, and a polymeric dispersant, wherein the dye content is 5% to 25% by mass relative to the total content of the pigment and dye, and the weighted average value of the solubility parameter of the organic solvent is 26.0 MPa. １／２ ~31.0 MPa １／２ It is inkjet ink.

[0015] The inks of this disclosure enable the recording of images with excellent density and lightfastness. The effect of improving image density is due to the inclusion of dyes in addition to pigments, the fact that the dye content relative to the total content of pigments and dyes is 5% by mass or more, and the weighted average value of the solubility parameter (hereinafter also referred to as the SP value) of the organic solvent (hereinafter also referred to as the average SP value) being 26.0 MPa. １／２ ~31.0 MPa １／２ This is considered to be the effect obtained by having such an average SP value of 26.0 MPa. １／２ As a result, ink penetration into the substrate and the resulting decrease in image density are suppressed. In particular, the average SP value of the organic solvent is 31.0 MPa. １／２ As a result of the following, ink impact interference is suppressed, image density unevenness is suppressed, and image density reduction caused by image density unevenness is suppressed.

[0016] The effect of improving the light fastness of an image is an effect obtained when the content of the dye relative to the total content of the pigment and the dye is 25% by mass or less. When the content of the dye relative to the total content of the pigment and the dye is 25% by mass or less, a decrease in light fastness caused by the dye is suppressed.

[0017] By the way, generally, in a high-speed inkjet recording method (for example, an inkjet recording method of applying inkjet ink onto a substrate conveyed at a conveyance speed of 200 m / min or more), the drying time is shortened, and as a result, density unevenness of an image is likely to occur, and the density of the image is likely to decrease. For this reason, in high-speed inkjet recording methods, there is a demand for further improvement in image density. According to the ink of the present disclosure, even when used in a high-speed inkjet recording method (for example, an inkjet recording method of applying inkjet ink onto a substrate conveyed at a conveyance speed of 200 m / min or more), a decrease in image density can be effectively suppressed.

[0018] Hereinafter, the ink of the present disclosure will be described in more detail.

[0019] <Water> The ink of the present disclosure contains water. The content of water is preferably 20% by mass or more, more preferably 30% by mass or more, and still more preferably 40% by mass or more, relative to the total mass of the ink. The upper limit of the water content depends on the amounts of other components. The upper limit of the water content relative to the total mass of the ink is, for example, 90% by mass or 80% by mass.

[0020] <Organic Solvent> The ink of the present disclosure contains at least one organic solvent. The weighted average value of the solubility parameters (i.e., the average SP value) of the organic solvent contained in the ink of the present disclosure is 26.0 MPa １／２ ~ 31.0 MPa １／２ .

[0021] In this disclosure, if the ink contains only one type of organic solvent, the average SP value of the organic solvent means the SP value of that single type of organic solvent. In this disclosure, if the ink contains two or more types of organic solvents, the average SP value of the organic solvents means the weighted average value of the SP values ​​of each individual organic solvent contained (hereinafter also referred to as the average SP value).

[0022] For example, if the ink of this disclosure contains only two types of organic solvents, organic solvent type A and organic solvent type B, the average SP value can be calculated using the following formula: Average SP value = (Mass content of organic solvent type A / (Total mass content of organic solvent type A and organic solvent type B)) × SP value of organic solvent type A + (Mass content of organic solvent type B / (Total mass content of organic solvent type A and organic solvent type B)) × SP value of organic solvent type B

[0023] In this disclosure, the solubility parameter (SP value) of each organic solvent species refers to the Hansen solubility parameter calculated using the software "Hansen Solubility Parameter in Practice" (HSPiP Ver.6.0.04).

[0024] The organic solvent is preferably a water-soluble organic solvent.

[0025] In this disclosure, "water-soluble" in "water-soluble organic solvent" means the property of dissolving 1 g or more in 100 g of water at 25°C.

[0026] The organic solvent in the ink of this disclosure is more preferably composed of an alkanediol having 4 or fewer carbon atoms and at least one selected from the group consisting of monoalkylene glycol monoalkyl ethers and 1,2-alkanediols having 5 or more carbon atoms, from the viewpoint of improving optical density by improving the ink discharge stability. In this case, the total amount of the alkanediol having 4 or fewer carbon atoms and at least one selected from the group consisting of monoalkylene glycol monoalkyl ethers and 1,2-alkanediols having 5 or more carbon atoms is preferably 5% to 50% by mass, more preferably 10% to 40% by mass, and even more preferably 15% to 35% by mass, based on the total amount of ink.

[0027] Examples of alkanediols having four or fewer carbon atoms include ethylene glycol, propylene glycol (PG) (also known as 1,2-propanediol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butanediol. Propylene glycol is particularly preferred as an alkanediol having four or fewer carbon atoms. Examples of monoalkylene glycol monoalkyl ethers include propylene glycol monomethyl ether (PGmME), propylene glycol monoethyl ether, propylene glycol monopropyl ether (PGmPE), propylene glycol monobutyl ether (PGmBE), ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether (EGiPE), ethylene glycol monoisobutyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol monohexyl ether (EGmHE), and the like.

[0028] Examples of 1,2-alkanediols having five or more carbon atoms include 1,2-pentanediol, 1,2-hexanediol (1,2-HDO), 1,2-heptanediol, 1,2-octanediol, and the like.

[0029] The organic solvent preferably contains propylene glycol and at least one selected from the group consisting of ethylene glycol monohexyl ether, propylene glycol monobutyl ether, and diethylene glycol monoethyl ether (DEGmEE). In this case, the total amount of propylene glycol and at least one selected from the group consisting of ethylene glycol monohexyl ether, propylene glycol monobutyl ether, and diethylene glycol monoethyl ether is preferably 5% to 50% by mass, more preferably 10% to 40% by mass, and even more preferably 15% to 35% by mass, based on the total amount of ink.

[0030] The organic solvent may include other solvent species besides the preferred solvent species described above. Examples of other solvent species include diethylene glycol (DEG), dipropylene glycol (DPG), polypropylene glycol (PPG) (molecular weight for example 200 to 600), diethylene glycol monoethyl ether (DEGmEE), triethylene glycol monobutyl ether (TEGmBE), diethylene glycol monoisopropyl ether (DEGiPE), diethylene glycol monoisobutyl ether (DEGiBE), glycerin (GL), and the like.

[0031] Regarding organic solvents, you may refer to publicly available documents such as International Publication No. 2024 / 241860 as appropriate.

[0032] In the inks of this disclosure, the content of the organic solvent is preferably 10% to 60% by mass, more preferably 13% to 60% by mass, even more preferably 15% to 40% by mass, and even more preferably 20% to 35% by mass, based on the total amount of ink.

[0033] <Dyes> The inks of this disclosure contain at least one dye.

[0034] The dye may be contained in the ink in a dissolved form, or in the form of colored resin particles containing the dye and resin.

[0035] Regardless of the form in which the dye is contained in the ink, the dye content is 5% to 25% by mass relative to the total content of pigment and dye. Preferably, the dye content is 5% to 22% by mass, and more preferably 7% to 22% by mass, relative to the total content of pigment and dye.

[0036] Regardless of the form in which the dye is contained in the ink, the total content of pigment and dye is preferably 4% by mass or more, more preferably 4.5% by mass or more, even more preferably 5% by mass or more, even more preferably 5.5% by mass or more, and even more preferably 6% by mass or more, based on the total amount of ink. The upper limit of the total content of pigment and dye is, for example, 10% by mass or less, preferably 8% by mass or less, based on the total amount of ink.

[0037] The dye content relative to the total amount of ink is preferably 0.1% to 4% by mass, more preferably 0.1% to 3% by mass, and even more preferably 0.2% to 2% by mass.

[0038] Examples of dyes contained in ink in a dissolved form include water-soluble dyes such as direct dyes, acid dyes, food dyes, basic dyes, and reactive dyes. For direct dyes, refer to publicly available documents such as Japanese Patent Publication No. 2006-160817, Japanese Patent Publication No. 2009-512737, and Japanese Patent Publication No. 2024-122332. Direct dyes are dyes designated as "C.I. Direct," where "C.I." is an abbreviation for "Color Index."

[0039] As direct dyes, for example; C.I. Direct Red 2, 4, 9, 11, 23, 26, 31, 37, 39, 62, 63, 72, 75, 76, 79, 80, 81, 83, 84, 87, 89, 92, 95, 111, 173, 184, 207, 211, 212, 214, 218, 219, 223, 224, 225, 226, 227, 232, 233, 240, 241, 242, 243, 247, 254; C.I. Direct Violet 7, 9, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100, 101; C.I. Direct Yellow 4, 8, 9, 11, 12, 27, 28, 29, 33, 35, 39, 41, 44, 50, 53, 58, 59, 68, 86, 87, 93, 95, 96, 98, 100, 106, 108, 109, 110, 120, 130, 132, 142, 144, 157, 161, 163; C.I. Direct Blue 1, 10, 15, 22, 25, 55, 67, 68, 71, 76, 77, 78, 80, 84, 86, 87, 90, 98, 106, 108, 109, 151, 156, 158, 159, 160, 168, 189, 192, 193, 194, 199, 200, 201, 202, 203, 207, 211, 213, 214, 218, 225, 229, 236, 237, 244, 248, 249, 251, 252, 264, 270, 280, 288, 289, 290, 291; C.I. Examples include Direct Black 9, 17, 19, 22, 32, 51, 56, 62, 69, 77, 80, 91, 94, 97, 108, 112, 113, 114, 117, 118, 121, 122, 125, 132, 146, 154, 166, 168, 173, 199; and so on.

[0040] Examples of acid dyes include: C.I. Acid Red 1, 8, 35, 42, 52, 57, 62, 80, 81, 82, 87, 94, 111, 114, 115, 118, 119, 127, 128, 131, 143, 144, 151, 152, 154, 158, 186, 245, 249, 254, 257, 261, 263, 266, 289, 299, 301, 305, 336, 337, 361, 396, 397; and so on.

[0041] (Colored resin particles containing dye and resin) The ink of this disclosure preferably contains colored resin particles containing dye and resin. That is, the ink of this disclosure preferably contains the dye in the form of colored resin particles containing dye and resin. This further improves the density of the image. In particular, it is believed that by the ink containing colored resin particles containing dye and resin, the ink ejection stability is improved, unevenness in image density is suppressed, and consequently the density of the image is improved.

[0042] For colored resin particles containing dyes and resins, you may refer to publicly available documents such as International Publication No. 2020 / 022192 and International Publication No. 2021 / 065250.

[0043] -Specific Dyes- In colored resin particles, the dye preferably contains at least one selected from the group consisting of oil-soluble dyes, disperse dyes, and vat dyes (hereinafter also referred to as "specific dyes"). The following dyes are preferred as specific dyes. In the following, "Disperse" refers to disperse dyes, "Solvent" refers to oil-soluble dyes, and "vat" refers to construction dyes.

[0044] C.I.Disperse Yellow 3,7,8,23,39,51,54,60,71,86、 C.I.Solvent Yellow 2,14,16,21,33,43,44,56,82,85,93,98,114,131,135,157,160,163,167,176,179,185,189、 C.I.Disperse Red 11,50,53,55,55:1,59,60,65,70,75,93,146,158,190,190:1,207,239,240、 C.I.Solvent Red 8,23,24,25,49,52,109,111,119,122,124,135,146,149,150,168,169,172,179,195,196,197,207,222,227,312,313、 C.I.Disperse Blue 3,5,19,26,26:1,35,55,56,58,64,64:1,72,72:1,81,81:1,91,95,108,131,141,145,359,360、 C.I.Solvent Blue 3,4,5,35,36,38,44,45,59,63,67,68,70,78,83,97,101,102,104,105,111,122、 C.I.Disperse Orange 1,1:1,5,7,20,23,25,25:1,33,56,76、 C.I.Solvent Orange 3,14,54,60,62,63,67,86,107、 C.I.Disperse Violet 8,11,17,23,26,27,28,29,36,57、 C.I.Solvent Violet 8,9,11,13,14,26,28,31,36,59、 C.I.Solvent Green 3,5,7,28、 C.I.Disperse Brown 2、 C.I.Solvent Brown 53、 C.I.Solvent Black 3,5,7,27,28,29,34

[0045] The following dyes are particularly preferred as vat dyes: C.I. Vat Yellow 2, 4, 10, 20, 33; C.I. Vat Orange 1, 2, 3, 5, 7, 9, 13, 15; C.I. Vat Red 1, 2, 10, 13, 15, 16, 41, 61; C.I. Vat Blue 1, 3, 4, 5, 6, 8, 12, 14, 18, 19, 20, 29, 35, 41; C.I. Vat Black 1, 8, 9, 13, 14, 20, 25, 27, 29, 36, 56, 57, 59, 60

[0046] In colored resin particles, oil-soluble dyes are preferred as dyes. Oil-soluble dyes may be oil-soluble dyes obtained by modifying a water-soluble reactive dye with an alkyl group having 4 or more carbon atoms, or oil-soluble dyes obtained by replacing the countercation in an acid dye with an organic cation containing an alkyl group having 4 or more carbon atoms.

[0047] In this disclosure, "water-soluble" in the context of water-soluble reactive dyes means that the amount that dissolves in 100 g of distilled water at 25°C is greater than 1 g.

[0048] In this disclosure, "oil-soluble dye" means a dye having a solubility in methyl ethyl ketone at 20°C (hereinafter also referred to as "MEK solubility") of 5% by mass or more.

[0049] As for oil-soluble dyes, dyes that are insoluble in water, that is, dyes whose solubility in 100 g of distilled water at 20°C is 1 g or less, are preferred.

[0050] The oil-soluble dye may also be a dye having two azo groups.

[0051] Examples of oil-soluble dyes include those described in paragraphs 0089 to 0106 of International Publication No. 2020 / 022192.

[0052] The dye content in the colored resin particles is preferably 10% to 90% by mass, more preferably 15% to 80% by mass, even more preferably 20% to 75% by mass, and even more preferably 25% to 70% by mass, relative to the solid content of the colored resin particles.

[0053] -Resin- In colored resin particles, the resin preferably contains a chain-like polymer. Here, "chain-like polymer" means a polymer that includes a main chain in which each structural unit forming the polymer is linked together in a chain-like manner. The chain-like polymer may have side chains branching from the main chain. That is, the chain-like polymer may have a branched structure.

[0054] The chain polymer preferably contains a structure represented by the following formula (G), a cyclic structure, and a hydrophilic group.

[0055]

[0056] In formula (G), Rg represents a hydrogen atom or substituent, and Lg represents -O-, -S-, or -NRz-. Rz represents a hydrogen atom or substituent. * indicates a bond position.

[0057] The substituent represented by Rg is preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 6 carbon atoms, and even more preferably a hydrocarbon group having 1 to 3 carbon atoms. Preferred hydrocarbon groups include alkyl groups and aryl groups. Rg preferably represents a hydrogen atom.

[0058] Lg represents -O-, -S-, or -NRz-. Rz represents a hydrogen atom or substituent. The preferred range for Rz is the same as the preferred range for Rg described above. Lg is preferably -O- or -NRz-, and more preferably -O-.

[0059] The chain polymer preferably has a structure represented by formula (G) in its main chain. The structure represented by formula (G) preferably represents a urethane bond, a thiourethane bond (-NH-C(=O)-S-), or a urea bond. That is, the chain polymer is preferably polyurethane, polythiourethane, or polyurea. Polyurethane can typically be synthesized by reacting a diisocyanate compound with a diol compound. Polyurethane may further have thiourethane bonds and / or urea bonds. Polythiourethane can typically be synthesized by reacting a diisocyanate compound with a dithiol compound. Polythiourethane may further have urethane bonds and / or urea bonds. Polyurea can typically be synthesized by reacting a diisocyanate compound with a diamine compound. Polyurea may further have urethane bonds and / or thiourethane bonds.

[0060] The chain polymer may be synthesized by known methods (for example, the method described in International Publication No. 2018 / 042916, etc.) or a commercially available product may be used.

[0061] The cyclic structure that may be included in the chain polymer is a monovalent or greater (preferably monovalent or divalent) group obtained by removing one or more (preferably one or two) arbitrary hydrogen atoms from a cyclic compound. The cyclic structure is preferably included in the main chain of the chain polymer. The ring included in the cyclic structure (hereinafter also referred to as "ring X") may be an aliphatic ring or an aromatic ring. Ring X may also be a hydrocarbon ring or a heterocycle. Ring X is preferably a ring with 3 to 30 carbon atoms in its ring members, and more preferably a ring with 3 to 20 carbon atoms in its ring members. The hydrocarbon ring may be an aliphatic ring or an aromatic ring. Preferably, it is a hydrocarbon ring with 5 to 15 carbon atoms in its ring members, and more preferably a hydrocarbon ring with 6 to 12 carbon atoms in its ring members. Specific examples of hydrocarbon rings include a cyclohexane ring, a norbornane ring (bicyclo[2.2.1]heptane ring), and an octahydro-4,7-methano-1H-indene ring (tricyclo[5.2.1.0 ２，６Examples include decane rings, benzene rings, naphthalene rings, and fluorene rings. The heterocycle is preferably a ring with 3 to 12 carbon atoms in its ring members, containing at least one nitrogen atom, oxygen atom, and sulfur atom. Ring X may have substituents. If ring X has substituents, the substituent is denoted as substituent Z. Substituents Z are not particularly limited, but examples include alkyl groups, alkoxy groups, halogen atoms, alkyl halides, and heteroatom-containing groups. As halogen atoms for substituent Z, fluorine atoms, chlorine atoms, bromine atoms, or iodine atoms are preferred, and fluorine atoms, chlorine atoms, or bromine atoms are more preferred. As alkyl halides for substituent Z, alkyl groups with 1 to 6 carbon atoms having at least one halogen atom are preferred. The preferred range for halogen atoms in alkyl halides is the same as the preferred range for halogen atoms as substituent Z. As alkyl groups for substituent Z, alkyl groups with 1 to 6 carbon atoms are preferred. Examples of heteroatom-containing groups as substituent Z include alkoxy groups, acyloxy groups, and (meth)acryloyloxy groups, with alkoxy groups having 1 to 6 carbon atoms being preferred, methoxy or ethoxy groups being more preferred, and methoxy groups being particularly preferred.

[0062] The chain polymer preferably has at least one structural unit (repeating unit) selected from the structural unit represented by the following formula (1) (also called structural unit (1)) and the structural unit represented by the following formula (2) (also called structural unit (2)).

[0063]

[0064] In equations (1) and (2), Cy １ and Cy ２ Each of these independently represents a divalent organic group containing a cyclic structure, Y １ and Y ２ Each of these independently represents -O-, -S-, or -NRz-, where Rz represents a hydrogen atom or substituent. *1 and *2 each independently represent a bond position.

[0065] Structural unit (1) is preferably a structural unit derived from a diisocyanate compound, and structural unit (2) is preferably a structural unit derived from a diol compound, a dithiol compound, or a diamine compound.

[0066] *1 preferably indicates a bonding position with structural units other than structural unit (1). Examples of structural units other than structural unit (1) include structural unit (2) or structural unit (3) described later. *2 preferably indicates a bonding position with structural units other than structural unit (2). Examples of structural units other than structural unit (2) include structural unit (1).

[0067] Y １ and Y ２ Each of these independently represents an oxygen atom, a sulfur atom, or -NRz-, while Rz represents a hydrogen atom or a substituent. The Rz in this case is the same as the Rz in formula (G) described earlier. １ and Y ２ Each of these is preferably -O- or -NRz-, and more preferably -O-.

[0068] Cy １ and Cy ２ Each of these independently represents a divalent organic group containing a cyclic structure.

[0069] Cy １ and Cy ２ Preferably, each of these independently represents a group represented by the following formula (RA1) or (RA2).

[0070]

[0071] Formula (RA １ ) Medium, M １ Each of the following independently represents a ring which may have substituents, Lc represents a divalent linking group, k represents an integer of 0 or more, and LA １ and LA ２ Each of these independently represents a single bond or a divalent linking group. １If there are multiple Lc, they may be different or the same. If there are multiple Lc, they may be different or the same. * indicates a bonding position. Formula (RA ２ ) Medium, M ２ represents a ring which may have substituents, LA ３ * represents a trivalent linking group. * represents the bond position.

[0072] Formula (RA １ ) M １ and formula (RA ２ ) M ２ This is the same as the ring X mentioned above. Equation (RA １ ) M １ and formula (RA ２ ) M ２ The substituents that may be present are the same as those of substituent Z described above.

[0073] Formula (RA １ In this formula, Lc represents a divalent linking group. Examples of Lc include alkylene groups, alkylene oxy groups, sulfonyl groups, carbonyl groups, ether groups (-O-), ester groups (-COO-), spiro ring groups, or groups formed by combinations thereof, with alkylene groups or sulfonyl groups having 1 to 10 carbon atoms being preferred. Lc may have substituents, and examples of substituents include the substituent Z described above.

[0074] Formula (RA １ In this expression, k represents an integer greater than or equal to 0, preferably an integer between 0 and 2, and more preferably 0 or 1.

[0075] Formula (RA １ ) Middle, LA １ and LA ２ Each of these independently represents a single bond or a divalent linking group. LA １ and LA ２ Examples of divalent linking groups include those similar to Lc described earlier. LA １ and LA ２ It is particularly preferable that represent a single bond or an alkylene group having 1 to 10 carbon atoms. LA １ and LA ２ It may have substituents, and examples of substituents include substituent Z described above.

[0076] Formula (RA ２ ) Middle, LA ３ represents a trivalent linking group. LA ３ Examples include trivalent hydrocarbon groups having 1 to 10 carbon atoms, or trivalent linking groups formed by combining a hydrocarbon group having 1 to 10 carbon atoms with at least one divalent linking group selected from a sulfonyl group, carbonyl group, ether group (-O-), ester group (-COO-), and spiro ring group. ３ It may have substituents, and examples of substituents include substituent Z described above.

[0077] From the perspective of making chain polymers more hydrophobic and rigid, and improving various properties, Cy １ and Cy ２ Preferably, at least one of them contains two or more rings, and more preferably three or more.

[0078] In this specification, the number of rings refers to the number of single rings. Therefore, the concept of "containing two or more rings" includes not only containing two or more single rings that are not part of a fused ring, a bridging ring, or a spiro ring, but also containing one fused ring, one bridging ring, and one spiro ring.

[0079] Also, Cy １ and Cy ２ Preferably, at least one of the rings includes a five-membered or six-membered ring. Here, the concept of "including a five-membered or six-membered ring" also includes fused rings containing a five-membered or six-membered monoring, bridging rings containing a five-membered or six-membered monoring, and spirorings containing a five-membered or six-membered monoring. １ A specific example of this is the structure described in paragraph

[0060] of International Publication No. 2018 / 042916. ２ A specific example of this is the structure described in paragraph

[0064] of International Publication No. 2018 / 042916. From the viewpoint of further improving the properties by making the chain polymer more hydrophobic and rigid, it is preferable that the chain polymer has both structural unit (1) and structural unit (2).

[0080] Examples of compounds for forming structural unit (1) (hereinafter also referred to as "unit (1) forming compound" or "unit (1) compound") include diisocyanate compounds. In addition to isocyanate groups, unit (1) forming compounds may also have polymerizable groups other than isocyanate groups. Specific examples of unit (1) forming compounds include those described in paragraph 0067 of International Publication No. 2018 / 042916.

[0081] Examples of compounds for forming structural unit (2) (hereinafter also referred to as "unit (2) forming compounds" or "unit (2) compounds") include diol compounds, dithiol compounds, and diamine compounds. Unit (2) forming compounds may have polymerizable groups other than hydroxyl groups or amino groups. Specific examples of unit (2) forming compounds include those described in paragraphs 0069 to 0070 of International Publication No. 2018 / 042916.

[0082] The total amount of at least one structural unit selected from structural unit (1) and structural unit (2) relative to the total amount of the chain polymer is preferably 15% by mass or more, more preferably 30% by mass or more, even more preferably 45% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more. This increases the proportion of cyclic structures in the chain polymer. "Total amount of at least one structural unit selected from structural unit (1) and structural unit (2)" refers to the sum of the amount of structural unit (1) and the amount of structural unit (2).

[0083] There is no particular upper limit to the total amount of structural unit (1) and structural unit (2) relative to the total amount of the chain polymer, but for example it is 98% by mass or less, and preferably 95% by mass or less.

[0084] When the total amount of cyclic structures in 1 g of the chain polymer is defined as the ring value of the chain polymer, the ring value of the chain polymer is preferably 0.7 mmol / g or more. More preferably, the ring value of the chain polymer is 4.00 mmol / g or more. There is no particular upper limit to the ring value of the chain polymer, but for example, it is 9.00 mmol / g or less. When the cyclic structures contained in the chain polymer consist only of structural unit (1) and structural unit (2), the ring value of the chain polymer can also be determined by the following formula.

[0085] The cyclic value (moles / g) of a chain polymer = (((Content of structural unit (1) relative to the total amount of chain polymer (mass%) / 100) × Number of cyclic structures in structural unit (1) / Molecular weight of structural unit (1)) + ((Content of structural unit (2) relative to the total amount of chain polymer (mass%) / 100) × Number of cyclic structures in structural unit (2) / Molecular weight of structural unit (2))) × 1000

[0086] (Hydrophilic Groups) Chain polymers preferably contain hydrophilic groups. Hydrophilic groups contained in chain polymers contribute to the dispersion stability of colored resin particles. As hydrophilic groups, anionic groups or nonionic groups are preferred, and anionic groups are preferred because they are superior in their effect of improving dispersion stability. For example, when comparing anionic and nonionic groups of the same molecular weight, anionic groups are superior in their effect of improving dispersion stability. That is, anionic groups (particularly preferably at least one selected from the group consisting of carboxyl groups and salts of carboxyl groups) can fully exert their effect of improving dispersion stability even when their molecular weight is small.

[0087] The anionic group may be an unneutralized anionic group or a neutralized anionic group. Examples of unneutralized anionic groups include carboxyl groups, sulfol groups, sulfate groups, phosphonic acid groups, and phosphate groups. Examples of neutralized anionic groups include salts of carboxyl groups, sulfol groups, sulfate groups, phosphonic acid groups, and phosphate groups.

[0088] In this specification, "carboxyl group is neutralized" means that the carboxyl group as an anionic group is in the form of a "salt" (e.g., "-COONa"). The same applies to sulfo groups, sulfate groups, phosphonic acid groups, and phosphate groups as anionic groups. Neutralization can be carried out, for example, using alkali metal hydroxides (e.g., sodium hydroxide, potassium hydroxide, etc.) or organic amines (e.g., triethylamine, etc.).

[0089] From the viewpoint of dispersion stability, the anionic group that may be included in the chain polymer is preferably at least one selected from the group consisting of carboxyl group, salt of carboxyl group, sulfo group, salt of sulfo group, sulfate group, salt of sulfate group, phosphonic acid group, salt of phosphonic acid group, phosphate group, and salt of phosphate group, and more preferably at least one selected from the group consisting of carboxyl group and salt of carboxyl group. As for the "salt" in the above-mentioned salt of carboxyl group, salt of sulfo group, salt of sulfate group, salt of phosphonic acid group, and salt of phosphate group, alkali metal salts or organic amine salts are preferred, and alkali metal salts are more preferred. As the alkali metal in alkali metal salts, K or Na is preferred.

[0090] Furthermore, when the chain polymer contains anionic groups as hydrophilic groups, and the total amount of anionic groups in 1 g of the chain polymer is taken as the acid value of the chain polymer, the acid value of the chain polymer is preferably 0.10 mmol / g to 2.00 mmol / g, and more preferably 0.30 mmol / g to 1.50 mmol / g, from the viewpoint of dispersion stability. In particular, the total amount of carboxyl groups and carboxyl group salts in 1 g of the chain polymer is preferably 0.30 mmol / g to 1.50 mmol / g.

[0091] Furthermore, if the chain polymer has anionic groups as hydrophilic groups, the degree of neutralization of the anionic groups of the chain polymer is preferably 50% to 100%, and more preferably 70% to 90%. Here, the degree of neutralization refers to the ratio (i.e., ratio [number of neutralized anionic groups / (number of unneutralized anionic groups + number of neutralized anionic groups)]) of the chain polymer contained in the ink to the sum of the number of unneutralized anionic groups (e.g., carboxyl groups) and the number of neutralized anionic groups (e.g., salts of carboxyl groups). The degree of neutralization (%) of the chain polymer is measured by neutralization titration.

[0092] Furthermore, the nonionic group acting as a hydrophilic group is preferably a group having a polyether structure, and more preferably a group containing a polyalkylene oxy group.

[0093] The chain polymer preferably contains structural units having hydrophilic groups. The structural units having hydrophilic groups are preferably formed using hydrophilic group-introducing compounds, which will be described later, as raw materials. Particularly preferred as the structural units having hydrophilic groups is the structural unit represented by the following formula (3) (also called structural unit (3)), which has an anionic group.

[0094]

[0095] In structural unit (3), RX1 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, A represents an anionic group, and *3 represents the bond position with structural units other than structural unit (3).

[0096] Here, "*3 represents the bonding position with structural units other than structural unit (3)" means that in a chain polymer, structural units (3) do not directly bond with each other. The structural units other than structural unit (3) that bond to the *3 position in structural unit (3) may be one type or two or more types. There are no particular restrictions on the structural units other than structural unit (3), but for example, a structural unit derived from a diisocyanate compound (for example, structural unit (1) above) can be used, and it is preferable that a urethane bond is formed by bonding with structural unit (3).

[0097] Examples of anionic groups represented by A are the same as those described above. A carboxyl group or a salt of a carboxyl group is preferred as the anionic group represented by A. The chain polymer may contain structural unit (3) in an embodiment where A is a carboxyl group, and structural unit (3) in an embodiment where A is a salt of a carboxyl group. The content of hydrophilic structural units (e.g., structural unit (3)) relative to the total amount of the chain polymer is preferably 3% to 30% by mass, and more preferably 5% to 20% by mass. The content of structural units having anionic groups relative to the total amount of the chain polymer may be adjusted considering the acid value of the chain polymer.

[0098] The introduction of hydrophilic groups into chain polymers can be carried out using hydrophilic group-introducing compounds. Among the hydrophilic group-introducing compounds, 2,2-dimethylolpropanoic acid and 2,2-dimethylolbutanoic acid are examples of compounds for forming structural unit (3) (hereinafter also referred to as "unit (3) forming compounds" or "unit (3) compounds"). Among the hydrophilic group-introducing compounds, amino acids such as α-amino acids (specifically, lysine, alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine) are examples of compounds for introducing anionic groups. In addition to the above α-amino acids, hydroxyl groups, thiol groups, and -NHR are also examples of compounds for introducing anionic groups. Ｎ１ Group (R Ｎ１ Compounds having at least one (preferably one or two) selected from (wherein represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms), and having a carboxyl group, a sulfo group, a sulfate group, a phosphonic acid group, or a phosphate group as the anionic group. The compound for introducing the anionic group may have a betaine structure (intramolecular salt structure). Specific examples include the compounds described in paragraph

[0114] of International Publication No. 2018 / 042916.

[0099] Compounds for introducing anionic groups may be used after neutralizing at least a portion of the anionic group by using inorganic bases such as sodium hydroxide or potassium hydroxide, or organic bases such as triethylamine.

[0100] Among the compounds for introducing hydrophilic groups, compounds having a polyether structure are preferred as compounds for introducing nonionic groups, and compounds having a polyoxyalkylene group are more preferred.

[0101] The chain polymer may contain polymerizable groups. These polymerizable groups contribute to the curing of images by light, heat, infrared radiation, etc. That is, when an image formed with an ink containing a dispersion of colored resin particles is cured, the colored resin particles are bonded together by the polymerizable groups, and as a result, the hydrophobicity and rigidity of the image are thought to improve. Furthermore, when the chain polymer contains polymerizable groups, the resulting cured film has a higher glass transition temperature (gelling), which suppresses cohesive failure of the film and further improves adhesion and film quality. When the chain polymer contains polymerizable groups, these polymerizable groups may be contained in at least one of structural unit (1) and structural unit (2) within the chain polymer, for example, or in parts other than structural unit (1) and structural unit (2). The parts other than structural unit (1) and structural unit (2) include structural units other than structural unit (1) that are derived from diisocyanate compounds, structural units other than structural unit (2) that are derived from diol compounds, dithiol compounds, or diamine compounds, structural unit (3), and so on.

[0102] As polymerizable groups, photopolymerizable groups or thermal polymerizable groups are preferred. As photopolymerizable groups, radical polymerizable groups are preferred, groups containing an ethylenically double bond are more preferred, and groups containing at least one of a vinyl group and a 1-methylvinyl group are even more preferred. As radical polymerizable groups, (meth)acryloyl groups are particularly preferred from the viewpoint of radical polymerization reactivity and the hardness of the formed film. As thermal polymerizable groups, epoxy groups, oxetanyl groups, azilidinyl groups, azetidinyl groups, ketone groups, aldehyde groups, or blocked isocyanate groups are preferred. The chain polymer may contain only one polymerizable group or two or more. The presence of polymerizable groups in a chain polymer can be confirmed, for example, by Fourier transform infrared spectroscopy (FT-IR) analysis. To introduce polymerizable groups into a chain polymer, one method is to use a polymerizable group introduction compound when synthesizing the chain polymer. For compounds used to introduce polymerizable groups, refer to paragraphs

[0117] to

[0124] of International Publication No. 2018 / 042916.

[0103] When a linear polymer has polymerizable groups, adding a radical polymerization initiator makes it easier to thermoset, thus enabling the production of a particularly hard cured film. Examples of radical polymerization initiators include peroxides and azo compounds. From the viewpoint of storage stability, a 10-hour half-life of the radical polymerization initiator at 100°C or higher is desirable. There are no particular restrictions on the radical polymerization initiator, but examples include Perbutyl A, Perhexa 22, Perbutyl Z, Perhexa V, Perbutyl P, Permil D, Perhexyl D, Perhexa 25B, Perbutyl C, Perbutyl D, Permenta H, Perhexyn 25B, Permil P, Perocta H, Permil H, Perbutyl H, and Nofmer BC, all manufactured by NOF Corporation. The amount of radical polymerization initiator used is preferably 0.1 to 20% by mass relative to the linear polymer, and more preferably 0.1 to 10% by mass. The radical polymerization initiator may be included in the colored resin particles together with a specific dye and linear polymer, or it may be included in a dispersion of colored resin particles separately from the colored resin particles.

[0104] When synthesizing a chain polymer, diisocyanate compounds (aliphatic diisocyanate compounds) other than the unit (1) forming compound, diol compounds (aliphatic diol compounds) other than the unit (2) forming compound, dithiol compounds (aliphatic dithiol compounds), or diamine compounds (aliphatic diamine compounds) can also be used. The above-mentioned diisocyanate compounds, diol compounds, dithiol compounds, and diamine compounds may contain heteroatoms in their molecules, for example, at least one selected from -O-, -CO-, -COO-, -OCOO-, -S-, and -SO2-. They may also have substituents, and the substituent Z mentioned above is an example of such substituent.

[0105] The weight-average molecular weight of the chain polymer is preferably 5,000 to 100,000, more preferably 8,000 to 70,000, and even more preferably 10,000 to 50,000, from the viewpoint of the dispersion stability of the ink (i.e., the dispersion stability of the colored resin particles).

[0106] In this specification, weight-average molecular weight (Mw) refers to the value measured by gel permeation chromatography (GPC). For the measurement of Mw by gel permeation chromatography (GPC), an HLC®-8020GPC (Tosoh Corporation) is used as the measuring instrument, three TSKgel® Super Multipore HZ-H columns (4.6 mm ID × 15 cm, Tosoh Corporation) are used as the columns, and THF (tetrahydrofuran) is used as the eluent. The measurement conditions are 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, and the measurement is performed using an RI detector. The calibration curve will be prepared from eight samples of Tosoh Corporation's "Standard Samples TSK standard, polystyrenee": "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0107] The resin content (e.g., a chain polymer; the same applies hereinafter) is preferably 10% by mass or more, and more preferably 20% by mass or more, relative to the solid content of the colored resin particles. When the resin content is 10% by mass or more relative to the solid content of the colored resin particles, the dispersion stability of the ink (i.e., the dispersion stability of the colored resin particles) is further improved. The resin content is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, particularly preferably 50% by mass or less, and most preferably 40% by mass or less, relative to the solid content of the colored resin particles.

[0108] Furthermore, the mass ratio of the content of the chain polymer to the content of at least one dye selected from the group consisting of oil-soluble dyes, disperse dyes, and vat dyes is preferably 0.1 to 2.5, more preferably 0.1 to 1, and even more preferably 0.1 to 0.7.

[0109] The colored resin particles may contain polymers other than chain polymers. Examples of other polymers include polymers having a three-dimensional crosslinked structure. The proportion of chain polymers in the total polymer components of the colored resin particles is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, even more preferably 95% to 100% by mass, and ideally 100% by mass.

[0110] <Pigments> The inks of this disclosure contain at least one pigment. There are no particular restrictions on the pigments, and they may be either organic or inorganic pigments. Examples of pigments include those described in the following public documents: Seijiro Ito (ed.), "Dictionary of Pigments" (published in 2000); W. Herbst, K. Hunger, "Industrial Organic Pigments"; Japanese Patent Publication No. 2002-12607; Japanese Patent Publication No. 2002-188025; Japanese Patent Publication No. 2003-26978; Japanese Patent Publication No. 2003-342503; Japanese Patent Publication No. 2015-193729; and others.

[0111] Examples of pigments include polycyclic pigments such as azo lake pigments, azo pigments, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, diketopyrrolopyrrole pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments; and inorganic pigments such as titanium dioxide, iron oxide-based pigments, and carbon black-based pigments. Preferably, the pigment is an azo pigment, phthalocyanine pigment, anthraquinone pigment, quinacridone pigment, or carbon black pigment. Regarding pigments, reference may be made to known documents such as Japanese Patent Publication No. 5404669 as appropriate.

[0112] Examples of pigments from a hue perspective include cyan pigment, magenta pigment, yellow pigment, black pigment, and white pigment.

[0113] The pigment content relative to the total amount of ink is preferably 1% to 10% by mass, more preferably 1.5% to 10% by mass, even more preferably 2% to 8% by mass, and even more preferably 3% to 6% by mass, from the viewpoint of image color density and ink ejection performance.

[0114] <Polymer Dispersant> The ink of this disclosure contains at least one polymer dispersant. The polymer dispersant functions as a pigment dispersant for dispersing pigments. The form of the polymer dispersant is not particularly limited and may be a random polymer, a block polymer, or a graft polymer.

[0115] The polymer dispersant preferably has a cross-linked structure. This further improves the image density.

[0116] Preferably, the pigments contained in the ink are coated with at least a portion of a polymer dispersant having a cross-linked structure. This is thought to prevent the polymer dispersant from detaching from the surface of the pigment. As a result, the ink ejection stability is improved, density unevenness in the image is suppressed, and consequently, the image density is improved.

[0117] For example, by mixing a pigment with an uncrosslinked polymer dispersant and then crosslinking it with a crosslinking agent, at least a portion of the pigment can be coated with a polymer dispersant having a crosslinked structure.

[0118] The polymeric dispersant having a crosslinked structure is not particularly limited as long as it is a polymeric dispersant having at least one crosslinked structure within its molecule.

[0119] Whether or not the polymer dispersant contained in the ink has a cross-linked structure can be determined, for example, by the following method. First, the polymer dispersant is separated from the ink using a separation method such as solvent extraction. The separated polymer dispersant 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.

[0120] A polymer dispersant having a crosslinked structure is formed, for example, by crosslinking an uncrosslinked polymer dispersant with a crosslinking agent. The uncrosslinked polymer dispersant is preferably a water-soluble polymer dispersant.

[0121] In this disclosure, "water-soluble" in "water-soluble polymer dispersant" means the property of dissolving 1 g or more in 100 g of water at 25°C. Preferably, "water-soluble" means dissolving 3 g or more (more preferably 10 g or more) in 100 g of water at 25°C.

[0122] Furthermore, even if an uncrosslinked polymer dispersant is water-soluble, a polymer dispersant with a crosslinked structure is not necessarily water-soluble.

[0123] Examples of uncrosslinked polymer dispersants include vinyl resins, acrylic resins, urethane resins, and polyester resins. The uncrosslinked polymer dispersant is preferably an acrylic resin. In this disclosure, resin and polymer are synonymous.

[0124] The uncrosslinked polymer dispersant is preferably a polymer dispersant having a functional group that can be crosslinked by a crosslinking agent. Examples of crosslinkable functional groups include carboxyl groups or their salts, isocyanate groups, and epoxy groups. Among these, from the viewpoint of improving the dispersibility of pigments, the crosslinkable functional group is preferably a carboxyl group or its salt, and a carboxyl group is particularly preferred. In other words, the uncrosslinked polymer dispersant is preferably a resin containing carboxyl groups.

[0125] The uncrosslinked polymeric dispersant is preferably a copolymer containing structural units derived from monomers containing carboxyl groups (hereinafter referred to as "carboxyl group-containing monomers"). The copolymer may contain only one type of structural unit derived from carboxyl group-containing monomers, or two or more types. The copolymer may be a random copolymer or a block copolymer, but a random copolymer is preferred.

[0126] Examples of monomers containing a carboxyl group include (meth)acrylic acid, β-carboxyethyl acrylate, fumaric acid, itaconic acid, maleic acid, and crotonic acid.

[0127] The carboxyl group-containing monomer is preferably (meth)acrylic acid or β-carboxyethyl acrylate, and more preferably (meth)acrylic acid, from the viewpoint of crosslinkability and dispersibility.

[0128] The content of structural units derived from carboxyl group-containing monomers is preferably 5% to 40% by mass, more preferably 10% to 35% by mass, and even more preferably 10% to 30% by mass, based on the total amount of the uncrosslinked polymer dispersant.

[0129] The uncrosslinked polymer dispersant preferably contains structural units derived from hydrophobic monomers in addition to structural units derived from carboxyl group-containing monomers. The structural units derived from hydrophobic monomers contained in the uncrosslinked polymer dispersant may be one type or two or more types.

[0130] Examples of hydrophobic monomers include (meth)acrylates having an alkyl group with 1 to 20 carbon atoms, (meth)acrylates having an aromatic ring (e.g., benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc.), styrene, and styrene derivatives.

[0131] The content of structural units derived from hydrophobic monomers is preferably 60% to 95% by mass, more preferably 65% ​​to 90% by mass, and even more preferably 70% to 90% by mass, based on the total amount of the uncrosslinked polymer dispersant.

[0132] The uncrosslinked polymeric dispersant is preferably a random copolymer comprising structural units derived from a carboxyl group-containing monomer and at least one of structural units derived from a (meth)acrylate having an alkyl group having 1 to 20 carbon atoms and structural units derived from a (meth)acrylate having an aromatic ring; more preferably a random copolymer comprising structural units derived from (meth)acrylic acid and structural units derived from a (meth)acrylate having an aromatic ring; and even more preferably a copolymer comprising structural units derived from (meth)acrylic acid and structural units derived from benzyl (meth)acrylate.

[0133] The weight-average molecular weight (Mw) of the uncrosslinked polymer dispersant is not particularly limited, but from the viewpoint of pigment dispersibility, it is preferably 3,000 to 300,000, more preferably 5,000 to 200,000, and even more preferably 7,000 to 100,000.

[0134] The preferred range for the weight-average molecular weight of a polymer dispersant having a crosslinked structure is the same as the preferred range for the weight-average molecular weight of an uncrosslinked polymer dispersant.

[0135] Furthermore, if the polymer dispersant in the ink does not have a crosslinked structure, the preferred range for the weight-average molecular weight of the polymer dispersant in the form without a crosslinked structure is the same as the preferred range for the weight-average molecular weight of the uncrosslinked polymer dispersant described above.

[0136] The crosslinking agent used when crosslinking an uncrosslinked polymer dispersant is preferably a compound having two or more reaction sites with the uncrosslinked polymer dispersant (for example, a resin having a carboxyl group). One type of crosslinking agent may be used, or two or more types may be used.

[0137] A preferred combination of a crosslinking agent and an uncrosslinked polymer dispersant is a compound having two or more epoxy groups (i.e., a bifunctional or more epoxy compound) and a resin having a carboxyl group. In this combination, a crosslinked structure is formed by the reaction between the epoxy groups and the carboxyl groups. It is preferable that the formation of the crosslinked structure by the crosslinking agent is carried out after the pigment has been dispersed by the uncrosslinked polymer dispersant.

[0138] Examples of bifunctional or more epoxy compounds include 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.

[0139] Among these, the preferred epoxy compounds with two or more functions are polyethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, or trimethylolpropane triglycidyl ether.

[0140] The crosslinking agent may be a commercially available product. Examples of commercially available products include Denacol EX-321, EX-821, EX-830, EX-850, and EX-851 (manufactured by Nagase ChemteX Corporation).

[0141] The molar ratio of the reaction site in the crosslinking agent (e.g., epoxy group) to the reaction site in the uncrosslinked polymer dispersant (e.g., carboxyl group) 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, from the viewpoint of crosslinking reaction rate and dispersion stability after crosslinking.

[0142] In the inks of this disclosure, the ratio of pigment content to polymer dispersant content is preferably 1:0.02 to 1:2 by mass, more preferably 1:0.03 to 1:1.5, and even more preferably 1:0.04 to 1:1.

[0143] <Surfactants> The inks of this disclosure preferably contain at least one surfactant.

[0144] Examples of surfactants include polyoxyalkylene alkyl ether compounds (i.e., polyoxyalkylene alkyl ether surfactants), acetylene compounds (i.e., acetylene surfactants), and silicone compounds (i.e., silicone surfactants).

[0145] For surfactants, refer to paragraphs 0112-0130 of International Publication No. 2024 / 241860 as appropriate.

[0146] As the silicone compound, polyether-modified silicone compounds are preferred, and compounds represented by the following formula (D1) are more preferred.

[0147]

[0148] In formula (D1), 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. PO represents a propylene oxy group, and EO represents an ethylene oxy group. a, b, m, and n represent the average number of moles added for each unit, where a is 0 to 10, b is 1 to 50, m is 1 to 500, and n is 1 to 50.

[0149] In formula (D1), the arrangement of PO and EO may be a block copolymer arrangement or a random copolymer arrangement. In formula (D1), the arrangement of the structural unit denoted by the subscript m and the structural unit denoted by the subscript n may be a block copolymer arrangement or a random copolymer arrangement.

[0150] R １R 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.

[0151] It is more preferable that a is 0, b is 1 to 15, m is 1 to 10, and n is 1 to 5. Furthermore, it is even more preferable that a is 0, b is 3 to 10, m is 1 to 3, and n is 1 to 3.

[0152] The silicone compound may be a commercially available product. Examples of commercially available silicone compounds 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, and KF-64 3. Examples include KF-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.), TEGOWet KL245, TEGOWet 240, TEGOWet 250, TEGOWet 260, TEGOWet 270, TEGOWet 280 (all manufactured by Evonik), etc.

[0153] (Acetylene-based surfactants) As acetylene-based surfactants, compounds represented by the following formula (A1) are preferred.

[0154]

[0155] In formula (A1), R １ and R ４ Each of these independently represents an alkyl group having 3 to 10 carbon atoms, R ２ and R３ Each of these independently represents either a methyl group or an ethyl group. a, b, c, and d represent the average number of moles added for each unit, ranging from 0 to 50.

[0156] Suitable examples of acetylene-based surfactants include, for example: acetylene glycol selected from the group consisting of 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-hexyne-2,5-diol, and 2,5,8,11-tetramethyl-6-dodecine-5,8-diol; and ethylene oxide adducts of the above acetylene glycols. Acetylene-based surfactants can be synthesized, for example, by reacting acetylene with a ketone or aldehyde corresponding to the desired acetylene glycol. Acetylene-based surfactants can be obtained, for example, by the methods described on pages 94-107 of "New Introduction to Surfactants" (Revised Edition) by Takehiko Fujimoto (published by Sanyo Chemical Industries, Ltd., 1992).

[0157] The acetylene-based surfactant preferably includes an acetylene-based surfactant having an HLB value of 3.0 to 9.0 (preferably 3.5 to 9.0). When the acetylene-based surfactant includes an acetylene-based surfactant with an HLB value of 3.0 or higher, the image resolution is further improved. When the acetylene-based surfactant includes an acetylene-based surfactant with an HLB value of 9.0 or lower, the image granularity is further improved.

[0158] Commercially available acetylene-based surfactants may be used. Examples of commercially available acetylene-based surfactants include those manufactured by Nisshin Chemical Co., Ltd. Examples of acetylene-based surfactants manufactured by Nisshin Chemical include Surfinol 104 (HLB value 4.0), Surfinol 420 (HLB value 4.0), Surfinol 440 (HLB value 8.0), Surfinol SE (HLB value 6.0), Surfinol SE-F (HLB value 6.0), Surfinol 61 (HLB value 6.0), Surfinol 82 (HLB value 4.0), Surfinol DF110D (HLB value 3.0), Dynol 604 (HLB value 8.0), Dynol 607 (HLB value 8.0), Surfinol 2502 (HLB value 8.0), Surfinol TG (HLB value 9.0), Orphin E1004 (HLB value: 7.0-9.0), Orphin E1010 (HLB value: 13.5), and others.

[0159] From the viewpoint of further improving the image blocking resistance, it is preferable that the acetylene-based surfactant includes an acetylene-based surfactant having an HLB value of 6 or less (more preferably 3 to 6).

[0160] The content of acetylene-based surfactant (for example, acetylene-based surfactant with an HLB value of 6 or less) relative to the total amount of ink is preferably 0.05% to 2.5% by mass, more preferably 0.1% to 2.0% by mass, and even more preferably 0.2% to 1.5% by mass, from the viewpoint of improving the blocking resistance of the image.

[0161] The surfactant content is preferably 0.01% to 5.0% by mass, more preferably 0.02% to 4.0% by mass, and even more preferably 0.1% to 3.0% by mass, based on the total amount of ink.

[0162] (Other Components) The inks in this disclosure may contain other components besides those described above, as necessary. Examples of other components include resin particles, colloidal silica, inorganic salts, solid wetting agents (such as urea), fade inhibitors, emulsifying stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, fungicides, pH adjusters, defoamers, viscosity modifiers, dispersion stabilizers, rust inhibitors, chelating agents, water-soluble polymer compounds, and the like.

[0163] (Physical properties of the ink) - Viscosity - The viscosity of the ink is preferably 1.2 mPa·s to 15.0 mPa·s, more preferably 2.0 mPa·s to 13.0 mPa·s, and even more preferably 2.5 mPa·s to 10.0 mPa·s. The viscosity of the ink is measured at a temperature of 30°C using a rotational viscometer, for example, a product named "VISCOMETER TV-22" manufactured by Toki Sangyo Co., Ltd.

[0164] -pH- The pH of the ink is preferably 6.0 to 11.0, more preferably 7.0 to 10.0, and even more preferably 7.0 to 9.5, from the viewpoint of the storage stability of the ink. The pH of the ink is measured at a temperature of 25°C using a pH meter, for example, a product named "WM-50EG" manufactured by Toa DKK Co., Ltd.

[0165] [Inkjet Recording Method] The inkjet recording method of this disclosure includes recording an image by applying the ink described above to a substrate being transported at a transport speed of 200 m / min or more using an inkjet method.

[0166] As mentioned above, in general, high-speed inkjet recording methods (for example, inkjet recording methods that apply inkjet ink to a substrate being transported at a transport speed of 200 m / min or more) tend to result in uneven image density and a decrease in image density due to the shorter drying time. However, since the inkjet recording method of this disclosure uses the ink described above, it is possible to effectively suppress the decrease in image density even when using a high-speed inkjet recording method (for example, inkjet recording methods that apply inkjet ink to a substrate being transported at a transport speed of 200 m / min or more). Furthermore, it is possible to suppress the decrease in image lightfastness, which is a problem that tends to occur with inks containing dyes.

[0167] The inkjet recording method described herein will be explained in detail below.

[0168] <Substrate> The substrate used in the inkjet 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 high-quality paper, neutral paper, etc., which is mainly composed of cellulose, to provide a coating layer.

[0169] 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.

[0170] <Substrate transport speed> In the inkjet recording method of this disclosure, the substrate transport speed is 200 m / min or more. This enables high-speed inkjet recording.

[0171] The conveying speed of the substrate should be 200 m / min or more, and may or may not be constant. The upper limit of the conveying speed of the substrate is, for example, 300 m / min.

[0172] <Ink Application by Inkjet Method> In the inkjet recording method of this disclosure, an image is recorded by applying the aforementioned ink of this disclosure to a transported substrate by an inkjet method. The ink application by the inkjet method is performed by ejecting ink from an inkjet head.

[0173] 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.

[0174] 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.

[0175] <Other Operations> The inkjet recording method of this disclosure may include other operations besides applying ink. Other operations include, for example, preheating the substrate and drying the ink-coated substrate.

[0176] Hereinafter, an example of an inkjet recording apparatus used in the inkjet recording method of this disclosure will be described with reference to the drawings.

[0177] In the drawings and descriptions herein, substantially identical elements (e.g., parts or components) may be denoted by the same reference numeral, and redundant descriptions may be omitted.

[0178] Figure 1 is a conceptual diagram showing an inkjet recording apparatus 100, which is an example of an inkjet recording apparatus used in the inkjet recording method of this disclosure.

[0179] As shown in Figure 1, the inkjet recording device 100 includes an ink application unit 101 that includes a first inkjet head 111A for ejecting a first ink, a second inkjet head 111B for ejecting a second ink, a third inkjet head 111C for ejecting a third ink, and a fourth inkjet head 111D for ejecting a fourth ink, applied to continuous paper 110 as a substrate. Here, at least one of the first to fourth inks is the ink of this disclosure.

[0180] The ink application unit 101 is configured, for example, with four full-line inkjet heads 111A, 111B, 111C, and 111D arranged in order from the upstream side in the transport direction of the continuous paper 110. Each of the inkjet heads 111A, 111B, 111C, and 111D applies, for example, black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink to the continuous paper 110. However, the types and number of colors are not limited to these.

[0181] A preferred full-line inkjet head used here is a non-recirculating head. This type of inkjet head is available from Kyocera. A second preferred full-line inkjet head has an ink circulation channel in the ink supply system. This channel allows fresh ink to be ejected and can be part of the ink supply system or part of a specially developed channel that runs behind the nozzle plate. The ink supply system preferably runs behind the nozzle plate to allow for the use of more ink without impairing the restart / standby behavior. This type of inkjet head is available from Fujifilm Dimatix and Kyocera.

[0182] The ink ejected from each inkjet head contains a pigment and an organic solvent. The details of the first and second inks are as described above.

[0183] The continuous sheet of paper 110 is fed out from the main winding roller 102 and sent by the transport roller 112 of the transport unit 103 onto the transport guide member 113 which is positioned opposite the ink application unit 101, and is transported (moved) guided by the transport guide member 113.

[0184] The continuous sheet of paper 110, to which ink has been applied by the ink application unit 101, is sent by the discharge roller 118 through a heating and drying device (not shown) and wound onto the winding roller 105.

[0185] Furthermore, the inkjet recording device may be equipped with a preheating and drying device for preheating the substrate, and a substrate inversion device for applying ink to both sides of the substrate. In addition, a heating device may be provided for applying radiant heating to the ink-coated substrate. "Radiant heating" means the propagation of thermal energy through space or a medium, and an example of this is the flow of electromagnetic waves (electromagnetic radiation).

[0186] 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. Hereinafter, the term "dispersant" simply means a polymeric dispersant, and the term "solvent" simply means an organic solvent.

[0187] [Example 1] <Preparation of Black Pigment Dispersion 1 Containing an Uncrosslinked Dispersant> The mixture of the following composition is pre-dispersed to a uniform state, and then dispersed using a bead mill (LMZ-015 (manufactured by Ashizawa Fine Tech)) and zirconia beads with a diameter of 0.3 mmφ until the target particle size is achieved. This yields Black Pigment Dispersion 1 containing an uncrosslinked dispersant ("Solsperse 43000").

[0188] -Composition- • "Nipex 170" (carbon black pigment, manufactured by Orion) ... 20 parts by mass • "Solsperse 43000" (manufactured by Lubrizol Japan) (polymer dispersant) ... 12 parts by mass (6 parts by mass of solids) • Water ... remaining amount totaling 100 parts by mass

[0189] <Ink Preparation> The aforementioned pigment dispersion and each component shown in Table 2 are mixed and stirred with a stirrer for 60 minutes. Then, the mixture is filtered using a membrane filter (hydrophilic PTFE type, pore size 1 μm, manufactured by Advantec) to obtain an ink having the composition shown in Table 2.

[0190] In the "Ink Composition" column of Table 2, the numerical values ​​corresponding to each component represent the content relative to the total ink volume, and a blank space means that the corresponding component is not present. For water, "residue" refers to the amount remaining when the total is 100% by mass.

[0191] Details of each component in Table 2 are as follows: - Pigment Dispersions - ・Black pigment dispersion 1… As described above. ・Black pigment dispersion 2 containing crosslinked dispersant… To be described later. ・Black pigment dispersion 3 containing crosslinked dispersant… To be described later. - Dyes - ・C.I. Direct Black 168… Azo dye ・C.I. Direct Black 19… Azo dye ・C.I. Basic Black 2… Triarylmethane dye ・C.I. Direct Black 22… Azo dye ・Colored resin particles 1-6 containing dyes… To be described later. - Solvents - ・GL… Glycerin (SP value 37.4 MPa) １／２ ) ・TEGmBE … Triethylene glycol monobutyl ether (SP value 20.3 MPa) １／２ ) PG… Propylene glycol (SP value 31 MPa) １／２ ) ・DEGmEE … Diethylene glycol monoethyl ether (SP value 21.6 MPa) １／２ ) PGmBE … Propylene glycol monobutyl ether (SP value 20 MPa) １／２ ) EGmHE... Ethylene glycol monohexyl ether (SP value 20.7 MPa) １／２ ) EGiPE...Ethylene glycol isopropyl ether (SP value 21.1 MPa) １／２ ) ・Polypropylene glycol... (SP value 25.57 MPa) １／２ ) ・DEG...Diethylene glycol (SP value 29.2 MPa) １／２) ・1,2HDO...1,2-Hexanediol (SP value 26.7 MPa) １／２ ) ・DEGiPE...Diethylene glycol isopropyl ether (SP value 20.3 MPa) １／２ ) ・DEGiBE...Diethylene glycol isobutyl ether (SP value 19.8 MPa) １／２ ) PGmME...Propylene glycol monomethyl ether (SP value 22.6 MPa) １／２ ) PGmPE...Propylene glycol monopropyl ether (SP value 20.5 MPa) １／２ ) - Surfactants - ・Emulgen 120... Polyoxyethylene lauryl ether (manufactured by Kao Corporation) ・Surfinol 104PG50... Propylene glycol solution of 2,4,7,9-tetramethyl-5-decine-4,7-diol (50% by mass of effective content) (manufactured by Nisshin Chemical Industry Co., Ltd. and Air Products & Chemicals Inc.) ・SAG-005... Silicone-based surfactant ("Sylface SAG005" manufactured by Nisshin Chemical Industry Co., Ltd.) ・BYK-345... Silicone-based surfactant (manufactured by BYK Inc.) ・Dynol 604... "Dynol 604" manufactured by Nisshin Chemical Industry Co., Ltd. (50% by mass of solid content) (acetylene glycol-based surfactant; 2,5,8,11-tetramethyl-6-dodecine-5,8-diol ethoxylate)・Emulgen 103… "Emulgen 103" manufactured by Kao Corporation (polyoxyethylene alkyl ether surfactant, which is a lauryl ether with 3 repeating units of polyoxyethylene) - Other additives - ・Aqueous dispersion of resin particles… To be described later. ・Hi-Tec E-6314… "Hi-Tec E-6314" manufactured by Toho Chemical Industry Co., Ltd. (polyethylene wax emulsion) (solid content 35% by mass) ・AQUACER 531… "AQUACER 531" manufactured by BIC Chemie Japan Co., Ltd. (polyethylene wax emulsion) (solid content 45% by mass) ・Urea… Manufactured by Nissan Chemical Corporation

[0192] - Preparation of aqueous dispersion of resin particles - An aqueous dispersion of resin particles to be used as an additive is prepared as follows: In a 2-liter three-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, water (932 g), 12-methacrylamide dodecanoic acid (2.02 g), potassium bicarbonate (0.76 g), 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical (0.42 mg), and Orphine E1020 (surfactant, manufactured by Nisshin Chemical Industry Co., Ltd., 17 mg) are charged, and the mixture is heated to 80°C under a nitrogen stream and stirred until homogenized. A mixed solution consisting of potassium persulfate (0.27 g), potassium bicarbonate (0.22 g), and water (18.2 g) is added and stirred. Next, a monomer solution prepared by mixing methyl methacrylate (206.0 g), benzyl methacrylate (60.0 g), styrene (60.0 g), and n-butyl acrylate (14.0 g) is added dropwise to the three-necked flask, along with an aqueous monomer solution consisting of 12-methacrylamidodecanoic acid (23.2 g), potassium bicarbonate (8.62 g), 2-hydroxyethyl methacrylate (60 g), water (160 g), and p-methoxyphenol (15 mg). A mixed solution consisting of potassium persulfate (1.44 g), potassium bicarbonate (1.11 g), and water (127 g) is added dropwise simultaneously with the start of the addition of the monomer solution and the aqueous monomer solution. After the monomer solution and monomer aqueous solution have been added dropwise, the mixture is stirred further, and then water (58 g) and PROXCEL GXL(S) (benzoisothiazolin-3-one solution, manufactured by Arch Chemicals Japan, 0.4 g) are added. The resulting reaction mixture is filtered through a 50 μm mesh to obtain an aqueous dispersion of resin particles with a solid content of 25% by mass.

[0193] <Inkjet Recording> Prepare an inkjet head (Samba G3L) manufactured by FUJIFILM Dimatix, and load the above ink into the storage tank connected to the inkjet head. Set the inkjet head and storage tank in the inkjet recording device. Use gloss coated paper "OK ​​Topcoat+" (manufactured by Oji Paper Co., Ltd.) as the substrate, and while transporting the substrate, ink is applied from the inkjet head to the transported substrate to perform image recording (i.e., inkjet recording). The detailed conditions for inkjet recording are as follows.

[0194] <Inkjet Recording Conditions> ・Substrate: Glossy coated paper "OK ​​Topcoat+" (manufactured by Oji Paper Co., Ltd.) ・Substrate transport mechanism: Roll to roll ・Inkjet head temperature: 32℃ ・Inkjet head resolution: 1200 dpi x 600 dpi ・Ink droplet size: 3.5 pL ・Environment around inkjet head: Temperature 25℃ ± 1℃, relative humidity 25℃ ± 5% ・Substrate transport speed: 200 m / min ・Substrate tension during transport: 60 N

[0195] <Evaluation> The inkjet recording described above was performed, and the following evaluation was conducted. The results are shown in Table 2.

[0196] (Image Density (OD (Optical Density))) Perform the inkjet recording described above, and record a solid image with an ink droplet size of 3.5 pL and a resolution of 1200 dpi x 600 dpi. Measure the OD of the solid image using a Konica Minolta FD-7 fluorescence spectrophotometer. Based on the measurement results, evaluate the image density (OD) for each color according to the following criteria.

[0197] - Image Density (OD) Evaluation Criteria (Black) - A: OD is 2.10 or higher B: OD is 2.00 or higher and less than 2.10 C: OD is 1.92 or higher and less than 2.00 D: OD is 1.85 or higher and less than 1.92 E: OD is less than 1.85

[0198] (Evaluation of lightfastness) The solid images whose image density (OD) has been evaluated as described above will be subjected to a 7-day exposure test using a Xe weather meter "XL75" (manufactured by Suga Test Instruments Co., Ltd.) and filters (Inner = 320, Outer = quartz) at a black panel temperature of 28°C and an illuminance of 99,000 (Lux). The OD of the solid images after the exposure test will be measured in the same manner as the evaluation of image density (OD) described above. Based on the OD before and after the exposure test, the change in OD due to the exposure test will be calculated, and the lightfastness of the images will be evaluated according to the evaluation criteria below based on the obtained results.

[0199] - Criteria for evaluating image lightfastness - A: Change in OD is less than 15% B: Change in OD is 15% or more but less than 30% C: Change in OD is 30% or more

[0200] [Examples 2-41, Comparative Examples 1-4] The same procedure as in Example 1 was followed, except that the ink composition was changed as shown in Tables 2-6. The results are shown in Tables 2-6.

[0201] <Preparation of Colored Resin Particles 1-5 (Examples 11-15 and 24-28)> As shown in Tables 3 and 5, in Examples 11-15 and 24-28, one of the colored resin particles 1-5, which contain dye, is used instead of C.I. Direct Black 168 in Example 1. In Tables 3 and 5, the numerical value (mass%) for "Dye" in the column for Colored Resin Particles 1-5 represents the amount of dye (mass%) relative to the total amount of ink. The numerical value (mass%) for Polymers P1-P4 in the column for Colored Resin Particles 1-5 represents the amount of Polymers P1-P4 (mass%) relative to the total amount of ink. The method for preparing Colored Resin Particles 1-5 is shown below.

[0202] (Synthesis of Polymer P1) In a three-necked flask, 73.4 g of isophorone diisocyanate (IPDI), a compound for forming unit (1), 13.4 g of 2,2-dimethylolpropanoic acid (DMPA), a compound for introducing hydrophilic groups, 225 g of other compounds (compound A below (polycarbonate diol (PCD))) (Duranol T5651, manufactured by Asahi Kasei Corporation), and 311.8 g of ethyl acetate so that the reaction solution concentration is 50% by mass are charged and heated to 70°C. 0.2 g of Neostan U-600 (inorganic bismuth catalyst, manufactured by Nitto Kasei Co., Ltd.; hereinafter also referred to as "U-600") is added and stirred at 70°C for 5 hours. Next, 218.0 g of isopropyl alcohol and 197.0 g of ethyl acetate are added and stirred at 70°C for 3 hours. After stirring, the reaction solution is allowed to cool to room temperature (23°C), and then the concentration is adjusted with ethyl acetate to obtain a 30% by mass solution of polymer P1 (solvent: a mixed solution of ethyl acetate and isopropyl alcohol). The weight-average molecular weight of polymer P1 is 10,000.

[0203]

[0204] (Synthesis of Polymers P2 to P4) 30% by mass solutions of polymers P2 to P4 are obtained in the same manner as in the synthesis of polymer P1, except that the type and amount of compounds used to form the polymer are changed as shown in Table 1. The stirring time before adding isopropyl alcohol is until the weight-average molecular weight reaches 10,000, and the reaction is carried out. In Table 1, "N1" represents "compound for introducing hydrophilic groups", "N2" represents "diisocyanate compound", and "N3" represents "diol compound, dithiol compound, or diamine compound". The PCD is the same compound used in the production of polymer P1 (compound A (PCD), Duranol T5651, manufactured by Asahi Kasei Corporation).

[0205]

[0206] (Preparation of dispersion of colored resin particles 1 containing dye) - Preparation of oil phase component - Ethyl acetate, a 30% by mass solution of polymer P1, and the dye C. I. Solvent Black 3 (SB-3, trade name: Oil Black 860, manufactured by Orient Chemical Industry Co., Ltd.) are mixed and stirred for 15 minutes to obtain 149.8 g of an oil phase component with a solid content of 30% by mass. In the preparation of the oil phase component, the amount of the 30% by mass solution of polymer P1 and SB-3 used is such that the content (by mass) of polymer P1 and SB-3 relative to the solid content of the colored resin particles produced is 60% by mass and 40% by mass, respectively.

[0207] - Preparation of the aqueous phase component - The aqueous phase component is prepared by mixing 135.3 g of distilled water with sodium hydroxide as a neutralizing agent and stirring for 15 minutes. The amount of sodium hydroxide used as a neutralizing agent is adjusted so that the degree of neutralization in the colored resin particles produced is 90%. The specific amount of sodium hydroxide is determined by the following formula: Amount of sodium hydroxide (g) = Total amount of oil phase component (g) × (Solid content concentration of oil phase component (mass%) / 100) × (Polymer P1 content relative to the solid content of oil phase component (mass%) / 100) × Acid value of polymer P1 (mol / g) × 0.9 × Molecular weight of sodium hydroxide (g / mol) / 1000

[0208] -Preparation of Dispersion of Colored Resin Particles 1- The oil phase component and the aqueous phase component are mixed, and the resulting mixture is emulsified at room temperature using a homogenizer at 18,000 rpm for 10 minutes to obtain an emulsion. The obtained emulsion is added to 48.0 g of distilled water, and the resulting liquid is heated to 50°C and stirred at 50°C for 5 hours to remove ethyl acetate and isopropyl alcohol from the liquid by distillation. The liquid from which ethyl acetate and isopropyl alcohol have been removed is diluted with distilled water to a solid content of 20% by mass to obtain a dispersion of colored resin particles 1. The average particle size of colored resin particles 1 is 150 nm.

[0209] (Preparation of dispersion of colored resin particles 2) The same procedure as for colored resin particles 1 was performed, except that polymer P1 was changed to polymer P2, to obtain a dispersion of colored resin particles 2. The average particle size of colored resin particles 2 is 150 nm.

[0210] (Preparation of dispersion of colored resin particles 3) The same procedure as for colored resin particles 1 is performed, except that polymer P1 is changed to polymer P3 and its content is changed to 40% by mass (60% by mass of dye) to obtain a dispersion of colored resin particles 3. The average particle size of colored resin particles 3 is 150 nm.

[0211] (Preparation of dispersion of colored resin particles 4) The same procedure as for colored resin particles 1 is performed, except that polymer P1 is changed to polymer P4 and its content is changed to 25% by mass (dye is 75% by mass), to obtain a dispersion of colored resin particles 4. The average particle size of colored resin particles 4 is 150 nm.

[0212] (Preparation of dispersion of colored resin particles 5) The same procedure as for colored resin particles 4 was performed, except that the dye for colored resin particles 4 was changed to solvent black 28, to obtain colored resin particles 5. The average particle size of colored resin particles 5 is 150 nm.

[0213] <Preparation of Black Pigment Dispersion 2 Containing a Crosslinked Dispersant (Examples 16-19, 24-31, 32-41)> As shown in Tables 4-6, in Examples 16-19, 24-31, and 32-41, instead of Black Pigment Dispersion 1 containing an uncrosslinked dispersant ("Solsperse 43000") as in Example 1, Black Pigment Dispersion 2 containing a crosslinked dispersant (i.e., a dispersant having a crosslinked structure) is used.

[0214] (Synthesis of Dispersant A) Add 6.1 g of Perbutyl O (manufactured by NOF Corporation) to 186.0 g of DPG (dipropylene glycol) and stir to prepare an initiator solution. Separately, add 282.6 g of benzyl methacrylate, 77.5 g of methacrylic acid, and 6 g of butyl 3-mercaptopropionate as a chain transfer agent to 139.5 g of DPG and stir to prepare a monomer solution. Place 241.5 g of DPG in a 2 L three-necked flask, raise the internal temperature to 85°C under a nitrogen stream, and begin adding the initiator solution and monomer solution simultaneously, over 5 hours and 4 hours, respectively. After adding the initiator solution, the mixture was stirred at 85°C for 2 hours, then cooled to 70°C. 64.5 g of 50% potassium hydroxide aqueous solution, 43.8 g of water, and 27.4 g of DPG were added, and the mixture was stirred at 70°C for 2 hours to obtain a DPG solution of polymer dispersant (A). Water was then added to this solution in an amount that brought the solid content concentration of the dispersant to 30% by mass, and the mixture was stirred for another 2 hours to obtain a DPG-water mixed solution of polymer dispersant (A) (dispersant solution 1). The weight-average molecular weight (Mw) of polymer dispersant (A) is 18000.

[0215] (Neutralization of Dispersant A (Preparation of Uncrosslinked Dispersant A Solution)) After cooling the solution containing dispersant A obtained above to room temperature, an aqueous solution of NaOH as an aqueous solution of the neutralizing base is added to neutralize 80 mol% of the carboxyl groups in dispersant A. This yields a solution containing a dispersant with a degree of neutralization of 80% (i.e., the dispersant obtained by neutralizing dispersant A; hereinafter also referred to as "uncrosslinked dispersant A"). The solid content concentration in the obtained solution is adjusted to 21% by mass to obtain an uncrosslinked dispersant A solution (21% by mass solid content concentration).

[0216] (Preparation of Uncrosslinked Dispersion) Using uncrosslinked dispersant A solution, the mixture of the following composition is pre-dispersed to a uniform state, and then dispersed using a bead mill (LMZ-015 (manufactured by Ashizawa Fine Tech)) with zirconia beads with a bead diameter of 0.3 mmφ until the target particle size is achieved. This yields an uncrosslinked dispersion containing uncrosslinked dispersant A. -Composition- ・Printex F80 (manufactured by Orion, carbon black pigment, primary particle size 16 nm) ... 20 parts by mass ・Uncrosslinked dispersant A solution ... 39 parts by mass (solid content 8.2 parts by mass) ・Dipropylene glycol ... 6 parts by mass ・Water ... remaining amount totaling 100 parts by mass

[0217] (Preparation of Pigment Dispersion 2 Containing Crosslinked Dispersant) Next, the uncrosslinked dispersion obtained above is diluted with water to a pigment concentration of 11.5 parts by mass to obtain a diluted solution of the uncrosslinked dispersion (100 parts by mass). Next, the diluted solution of the uncrosslinked dispersion (100 parts by mass) is mixed with 0.33 parts by mass of Denacol EX-321 (manufactured by Nagase ChemteX, trimethylolpropane polyglycidyl ether: crosslinking agent) and 3.64 parts by mass of a 4% boric acid solution. The resulting liquid is reacted at 70°C for 5 hours and then cooled to 25°C to crosslink the uncrosslinked dispersant A in the uncrosslinked dispersion with the crosslinking agent, thereby obtaining a crosslinked dispersion containing a crosslinked dispersant. The crosslinked dispersion obtained above (i.e., pigment dispersion) is centrifuged at 7000 G for 20 minutes in a centrifuge to remove coarse particles. Next, the centrifugated crosslinked dispersion is filtered through a LABO-PURE filter (0.5 μm) manufactured by Rokitechno to further remove coarse particles. Then, the filtered crosslinked dispersion is ultrafiltered through an ultrafiltration apparatus (cross-flow type ultrafilter (UF), manufactured by Sartorius) equipped with a polyethersulfone (PESU) membrane (micropore size: 0.1 μm) at a flow rate of 600 mL per minute. At this time, the liquid temperature is adjusted to 25°C, and ultrafiltration is performed 10 times, with each ultrafiltration being one times the volume ratio of the charged liquid. After that, ion-exchanged water is added to bring the pigment concentration to 15% by mass, and pigment dispersion 2 containing the crosslinked dispersant is obtained. The acid value of the crosslinked dispersant in pigment dispersion 2 is 2 mmol / g. The acid value is determined by neutralization titration. In crosslinking, a crosslinked structure is formed in the polymer dispersant by a reaction between at least one of the unneutralized acid groups (-COOH groups) and neutralized acid groups (-COO- groups) in the polymer dispersant and the epoxy groups of the crosslinking agent (specifically, the epoxy groups in the structure of the glycidyl group). In this way, at least one of the unneutralized acid groups and neutralized acid groups is consumed to form the crosslinked structure, so the acid value of the polymer dispersant decreases due to crosslinking. Therefore, the acid value of the dispersant contained in the crosslinked dispersion can be adjusted by the degree of neutralization of the acid groups before crosslinking and the amount of boric acid aqueous solution and crosslinking agent added thereafter.

[0218] <Preparation of Black Pigment Dispersion 3 Containing a Crosslinked Dispersant (Examples 20-23)> As shown in Table 4, in Examples 20-23, instead of Black Pigment Dispersion 1 containing an uncrosslinked dispersant ("Solsperse 43000") as in Example 1, Black Pigment Dispersion 3 containing a crosslinked dispersant (i.e., a dispersant having a crosslinked structure) is used. Black Pigment Dispersion 3 containing a crosslinked dispersant is prepared as follows.

[0219] (Preparation of Uncrosslinked Dispersion) Using a Joncryl JDX-6180 (BASF), the mixture of the following composition is pre-dispersed to a uniform state. Then, using a bead mill (LMZ-015 (Ashizawa Finetech)), zirconia beads with a diameter of 0.3 mm are used to disperse the mixture until the target particle size is achieved. This yields an uncrosslinked dispersion containing an uncrosslinked dispersant. -Composition- ・Nipex170IQ (carbon black, Orion) ... 20 parts by mass ・Joncryl JDX-6180 (BASF) ... 22.2 parts by mass (equivalent to 6 parts by mass in solids) ・Water ... Remaining amount totaling 100 parts by mass

[0220] (Preparation of Black Pigment Dispersion 3 Containing Crosslinked Dispersant) Next, the uncrosslinked dispersion obtained above is diluted with water to a pigment concentration of 11.5 parts by mass to obtain a diluted solution of the uncrosslinked dispersion (100 parts by mass). Next, the diluted solution of the uncrosslinked dispersion (100 parts by mass) is mixed with 1.25 parts by mass of Denacol EX-321 (manufactured by Nagase ChemteX, trimethylolpropane polyglycidyl ether: crosslinking agent) and 14 parts by mass of a 4% boric acid solution. The resulting liquid is reacted at 70°C for 5 hours and then cooled to 25°C to crosslink the uncrosslinked polymer dispersant A in the uncrosslinked dispersion with the crosslinking agent and obtain a crosslinked dispersion. Finally, the crosslinked dispersion is ultrafiltered through a polyethersulfone membrane to obtain a black pigment dispersion 3 containing the crosslinked dispersant.

[0221]

[0222]

[0223]

[0224]

[0225]

[0226] As shown in Tables 2 to 6, the ink-jet ink contains water, an organic solvent, a dye, a pigment, and a polymer dispersant, wherein the content of the dye relative to the total content of the pigment and the dye is 5% by mass to 25% by mass, and the average SP value of the organic solvent is 26.0 MPa １／２ to 31.0 MPa １／２ In each example where an image is recorded on a substrate conveyed at a conveyance speed of 200 m / min or more using the above-described ink-jet ink, an image excellent in density and light resistance can be obtained. In contrast, in Comparative Example 1 in which the content of the dye relative to the total content of the pigment and the dye exceeds 25% by mass, the light resistance of the image decreases. Further, in Comparative Example 2 in which the content of the dye relative to the total content of the pigment and the dye is less than 5% by mass, the density of the image decreases. Further, when the average SP value of the organic solvent is 31.0 MPa １／２ In Comparative Example 3, which exceeds the above range, the density of the image decreases. It is considered that the decrease in image density in Comparative Example 3 results from ink landing interference caused by an excessively high average solubility parameter of the organic solvent, and image density unevenness caused by the landing interference. Further, when the average SP value of the organic solvent is 26.0 MPa １／２ In Comparative Example 4, which is below the above range, the density of the image also decreases. It is considered that the decrease in image density in Comparative Example 4 results from excessive penetration of the ink into the substrate caused by an excessively low average solubility parameter of the organic solvent.

[0227] From the results of Examples 1 to 5 and 6 to 11, it can be seen that when the total content of the pigment and the dye is 6% by mass or more relative to the total amount of the ink-jet ink (Examples 6 to 11), the image density is further improved.

[0228] From the results of Examples 7 and 11, it can be seen that when the ink-jet ink contains colored resin particles including a dye and a resin (Example 11), the image density is further improved.

[0229] The results from Examples 11 and 24 show that when the polymer dispersant has a cross-linked structure (Example 24), the image density is further improved.

[0230] The above describes examples and comparative examples using black ink. Next, we will describe examples and comparative examples using magenta ink.

[0231] [Examples 101-105, Comparative Examples 101-102] The same procedure as in Example 1 was followed, except that the ink composition was changed to the magenta ink composition shown in Table 7, and the criteria for evaluating image density were changed as follows. The results are shown in Table 7.

[0232] - Criteria for evaluating image density (OD) (magenta) - A: OD is 1.00 or higher B: OD is 0.90 or higher and less than 1.00 C: OD is less than 0.90

[0233] In the preparation of magenta inks in Examples 101-105 and Comparative Examples 101-102, a dispersion of colored resin particles 6-8 and a magenta pigment dispersion containing a crosslinked dispersant were used. The details of these manufacturing methods are described below.

[0234] <Preparation of Dispersions of Colored Resin Particles 6-8> The same procedure as for preparing the dispersion of colored resin particle 4 was followed, except that the dye (C.I. Solvent Black 3) in colored resin particle 4 was changed to C.I. Solvent Red 24 (colored resin particle 6), C.I. Disperse Red 60 (colored resin particle 7), and C.I. Vat Red 41 (colored resin particle 8), respectively, to obtain the dispersions of colored resin particles 6-8. The average particle size of colored resin particles 6-8 is 150 nm.

[0235] <Preparation of Magenta Pigment Dispersion Containing Crosslinked Dispersant> As shown in Table 7, in Examples 101 to 105 and Comparative Examples 101 to 102, a magenta pigment dispersion containing a crosslinked dispersant (i.e., a dispersant having a crosslinked structure) is used instead of the black pigment dispersion 1 containing an uncrosslinked dispersant ("Solsperse 43000") used in Example 1. The method for preparing the magenta pigment dispersion containing the crosslinked dispersant is shown below.

[0236] (Synthesis of Dispersant A) Dispersant A is synthesized by the same procedure as in the synthesis of dispersant A in Example 16 and others.

[0237] (Neutralization of dispersant A (preparation of uncrosslinked dispersant A solution)) Prepare the uncrosslinked dispersant A solution by the same procedure as in the neutralization of dispersant A (preparation of uncrosslinked dispersant A solution) in Example 16 and others.

[0238] (Preparation of uncrosslinked dispersion) Using uncrosslinked dispersant A solution, the mixture of the following composition is pre-dispersed to a homogeneous state. Then, dispersion is performed using a bead mill (LMZ-015 (manufactured by Ashizawa Finetech)) with zirconia beads with a diameter of 0.3 mmφ until the target particle size is achieved. This yields an uncrosslinked dispersion containing uncrosslinked dispersant A.

[0239] -Composition- ・P.R. 122 (Pigment Red 122) ... 20 parts by mass ・Uncrosslinked dispersant A solution ... 39 parts by mass (solid content 8.2 parts by mass) ・Dipropylene glycol ... 6 parts by mass ・Water ... remaining amount totaling 100 parts by mass

[0240] (Preparation of magenta pigment dispersion containing crosslinked dispersant) Next, the uncrosslinked dispersion obtained above is diluted with water to a pigment concentration of 11.5 parts by mass to obtain a diluted solution of the uncrosslinked dispersion (100 parts by mass). Next, the diluted solution of the uncrosslinked dispersion (100 parts by mass) is mixed with 0.66 parts by mass of Denacol EX-321 (manufactured by Nagase ChemteX, trimethylolpropane polyglycidyl ether: crosslinking agent) and 7.3 parts by mass of a 4% boric acid solution. The resulting liquid is reacted at 70°C for 5 hours and then cooled to 25°C to crosslink the uncrosslinked dispersant A in the uncrosslinked dispersion with the crosslinking agent, thereby obtaining a crosslinked dispersion containing a crosslinked dispersant. The crosslinked dispersion obtained above (i.e., pigment dispersion) is centrifuged at 7000 G for 20 minutes in a centrifuge to remove coarse particles. Next, the centrifugated crosslinked dispersion is filtered through a LABO-PURE filter (0.5 μm) manufactured by Rokitechno to further remove coarse particles. Then, the filtered crosslinked dispersion is ultrafiltered through an ultrafiltration apparatus (cross-flow type ultrafilter (UF), manufactured by Sartorius) equipped with a polyethersulfone (PESU) membrane (pore size: 0.1 μm) at a flow rate of 600 mL per minute. At this time, the liquid temperature is adjusted to 25°C, and ultrafiltration is performed 10 times, with each ultrafiltration cycle being 1x the volume of the charged liquid. After that, ion-exchanged water is added to bring the pigment concentration to 15% by mass, and a magenta pigment dispersion containing the crosslinked dispersant is obtained. The acid value of the crosslinked dispersant in the obtained magenta pigment dispersion is 1.5 mmol / g. The acid value is determined by neutralization titration. In crosslinking, a crosslinked structure is formed in the polymer dispersant by a reaction between at least one of the unneutralized acid groups (-COOH groups) and neutralized acid groups (-COO- groups) in the polymer dispersant and the epoxy groups of the crosslinking agent (specifically, the epoxy groups in the structure of the glycidyl group). In this way, at least one of the unneutralized acid groups and neutralized acid groups is consumed to form the crosslinked structure, so the acid value of the polymer dispersant decreases due to crosslinking. Therefore, the acid value of the dispersant contained in the crosslinked dispersion can be adjusted by the degree of neutralization of the acid groups before crosslinking and the amount of boric acid aqueous solution and crosslinking agent added thereafter.

[0241]

[0242] As shown in Table 7, the same effects as those observed in Examples 1 to 41 using black ink were confirmed in Examples 101 to 105, which used magenta ink.

[0243] The disclosure of Japanese Patent Application No. 2025-054588, filed on 27 March 2025, is incorporated herein by reference in its entirety. 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 noted to be incorporated by reference.

Claims

It contains water, organic solvents, dyes, pigments, and polymer dispersants. The content of the dye is 5% by mass to 25% by mass relative to the total content of the pigment and the dye. The weighted average value of the solubility parameters of the aforementioned organic solvent is 26.0 MPa. １／２ ~31.0 MPa １／２ That is, Inkjet ink. 　 The inkjet ink according to claim 1, wherein the total content of the pigment and the dye is 6% by mass or more of the total amount of the inkjet ink. 　 It contains colored resin particles comprising the aforementioned dye and resin, The dye comprises at least one selected from the group consisting of oil-soluble dyes, disperse dyes, and vat dyes. The resin contains a chain-like polymer, The inkjet ink according to claim 1, wherein the chain-like polymer comprises a structure represented by the following formula (G), a cyclic structure, and a hydrophilic group. In formula (G), Rg represents a hydrogen atom or substituent, and Lg represents -O-, -S-, or -NRz-. Rz represents a hydrogen atom or substituent. * indicates a bond position. 　 The inkjet ink according to claim 1, wherein the polymer dispersant has a crosslinked structure. 　 The inkjet ink according to claim 1, used as the ink in an inkjet recording method that includes applying ink to a substrate being transported at a transport speed of 200 m / min or more by an inkjet method to record an image. 　 An inkjet recording method comprising applying the inkjet ink described in claim 1 to a substrate being transported at a transport speed of 200 m / min or more by an inkjet method to record an image.

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