Ink set for permeable substrate and image recording method

Abstract

Provided is an ink set for permeable substrates, said ink set including an inkjet ink and a treatment solution, wherein the inkjet ink contains water, a water-soluble organic solvent, a pigment, a pigment-dispersing resin, and a resin component (X) that is a water-soluble resin and / or resin particles, and the treatment solution contains water, a water-soluble organic solvent, and an organic acid salt that has a molecular weight of 130 or less. Also provided is an image recording method.

Description

[Technical Field]

[0001] The present disclosure relates to ink sets for permeable substrates and image recording methods. [Background technology]

[0002] In recent years, a set including a combination of an ink containing a coloring material and a liquid other than the ink has become known. Liquids other than ink are called reaction liquids, processing liquids, etc. For example, Patent Document 1 discloses a set of ink and reaction liquid that can obtain an image with high image density and can form an image in which transfer to another recording medium is suppressed even shortly after image formation, the set comprising an ink containing a pigment and a water-soluble resin and a reaction liquid that has buffering ability in the acidic range, wherein the pigment is a self-dispersing pigment having a surface charge amount determined by colloid titration of 0.20 mmol / g or more, and the water-soluble resin is a copolymer having a unit derived from (meth)acrylic acid.

[0003] Patent Document 1: See Japanese Patent Application Laid-Open No. 2012-223975 Summary of the Invention [Problem to be solved by the invention]

[0004] Treatment liquids containing acid (for example, the reaction liquid described in Patent Document 1) have the property of aggregating components in ink (hereinafter also referred to as "aggregation force"). By applying such treatment liquid and ink to a recording medium, it is expected that the aggregating force of the treatment liquid will lead to improved image quality. However, the inventors' investigations have revealed that when an image is recorded on a permeable substrate (such as coated paper), if the cohesive force of the treatment liquid is too high, streak-like defects (hereinafter simply referred to as "streaks") may occur in the image. This tendency is particularly pronounced when the recording medium on which the image is recorded is a permeable substrate such as coated paper. Furthermore, the inventors have found through their investigations that if the cohesive force of the processing liquid is weakened too much in an attempt to suppress the occurrence of streaks, bleeding of the image may occur.

[0005] The present disclosure has been made in light of the above circumstances. An object of one aspect of the present disclosure is to provide an ink set for permeable substrates and an image recording method that can record images on permeable substrates with reduced streaks and bleeding. [Means for solving the problem]

[0006] Specific means for solving the problems include the following aspects. <1> Contains an inkjet ink and a treatment liquid, The inkjet ink contains water, a water-soluble organic solvent, a pigment, a pigment dispersion resin, and a resin component (X) which is at least one of a water-soluble resin and resin particles, The treatment liquid contains water, a water-soluble organic solvent, and an organic acid salt having a molecular weight of 130 or less. Ink set for permeable substrates. <2> The resin component (X) contains a water-soluble resin. <1> 1. An ink set for a permeable substrate according to claim 1. <3> The water-soluble resin includes a water-soluble resin X1 having an alkyl group having 1 to 3 carbon atoms, an anionic group, and a cyclic structure. <2> 1. An ink set for a permeable substrate according to claim 1. <4> The cyclic structure includes an aromatic ring. <3> 1. An ink set for a permeable substrate according to claim 1. <5> The water-soluble resin X1 contains a structural unit derived from a (meth)acrylic acid alkyl ester in which the alkyl group in the alkyl ester structure has 1 to 3 carbon atoms, a structural unit derived from (meth)acrylic acid, and a structural unit derived from a polymerizable monomer having a cyclic structure. <3> or <4> 1. An ink set for a permeable substrate according to claim 1. <6> the acid value of the resin component (X) divided by the pKa of an organic acid corresponding to an organic acid salt having a molecular weight of 130 or less is 35 to 65; <1> ~ <5> 1. An ink set for a permeable substrate according to any one of the above. <7> The organic acid salt having a molecular weight of 130 or less is at least one selected from the group consisting of formate, acetate, and lactate. <1> ~ <6> 1. An ink set for a permeable substrate according to any one of the above. <8> The water-soluble organic solvent in the treatment liquid is diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, dipropylene glycol, tripropylene glycol, and Tripropylene glycol monoalkyl ether The organic solvent S1 is at least one selected from the group consisting of: <1> ~ <7> 1. An ink set for a permeable substrate according to any one of the above. <9> <1> ~ <8> The ink set for a permeable substrate according to any one of the above items is used, applying a treatment liquid onto the permeable substrate; a step of applying an inkjet ink by an inkjet method to the area of ​​the permeable substrate to which the treatment liquid has been applied, thereby recording an image; An image recording method comprising: <10> the permeable substrate comprises paper; <9> The image recording method according to claim 1. <11> The water droplet contact angle on the image-recording surface of the permeable substrate is 70° or more 3 seconds after the water droplet is applied. <9> or <10> The image recording method according to claim 1. <12> In the area where an image is to be recorded, the ratio of the applied mass of the treatment liquid to the applied mass of the inkjet ink is 0.05 to 0.50; <9> ~ <11> 10. The image recording method according to claim 9, wherein the image is recorded in a recording medium. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, there are provided an ink set for permeable substrates and an image recording method that can record images on permeable substrates with reduced streaks and bleeding. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 10 is a diagram conceptually illustrating a character image used in the evaluation of image bleeding in the examples. [Figure 2] FIG. 10 is a diagram for explaining details of evaluation criteria for image bleeding in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the present disclosure, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced by the upper or lower limit value of another numerical range described in stages, or may be replaced by a value shown in an example. In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0010] The term "solid content" in the present disclosure means components excluding solvents, and liquid components such as low-molecular-weight components other than solvents are also included in the term "solid content" in this specification. In the present disclosure, the term "solvent" is used to encompass water, organic solvents, and mixed solvents of water and organic solvents.

[0011] In the present disclosure, both or either of acrylic and methacrylic may be expressed as "(meth)acrylic." For example, "(meth)acrylic acid" includes both acrylic acid and methacrylic acid. In the present disclosure, both or either of acrylate and methacrylate may be referred to as "(meth)acrylate."

[0012] The weight average molecular weight (Mw) in this disclosure is measured by gel permeation chromatography (GPC). GPC was performed using an HLC-8220GPC (Tosoh Corporation) with three columns connected in series: TSKgel Super HZ2000, TSKgel Super HZ4000, and TSKgel Super HZ-H (all 4.6 mm x 15 cm, Tosoh Corporation). NMP (N-methylpyrrolidone) was used as the eluent. The sample concentration was 0.3% by mass, the flow rate was 0.35 mL / min, the sample injection volume was 10 μL, the measurement temperature was 40°C, and an RI (Refractive Index) detector was used. A calibration curve was also prepared using six samples from Tosoh Corporation's "TSK Standard, Polystyrene": "F-80," "F-20," "F-4," "F-2," "A-5000," and "A-1000."

[0013] In the present disclosure, the term "ink set for permeable substrates" refers to an ink set for recording images on permeable substrates as recording media.

[0014] [Ink set for penetrable substrates] The ink set for a permeable substrate according to the present disclosure comprises: Contains an inkjet ink and a treatment liquid, The inkjet ink contains water, a water-soluble organic solvent, a pigment, a pigment dispersion resin, and a resin component X which is at least one of a water-soluble resin and resin particles, The treatment liquid contains water, a water-soluble organic solvent, and an organic acid salt having a molecular weight of 130 or less.

[0015] Hereinafter, the ink set for permeable substrates and the inkjet inks may be simply referred to as the "ink set" and "inks," respectively.

[0016] The ink set of the present disclosure makes it possible to record images on permeable substrates with reduced streaking and bleeding. The reason why such an effect is achieved is presumed to be as follows.

[0017] As mentioned above, the inventors' investigations have revealed that when an image is recorded on a permeable substrate (e.g., coated paper), if the cohesive force of the treatment liquid is too high, streaks may appear in the image, and if the cohesive force of the treatment liquid is too weak, bleeding of the image may occur. In the ink set of the present disclosure, it is believed that the organic acid salt with a molecular weight of 130 or less in the treatment liquid functions as an aggregating agent that aggregates the components in the ink (for example, pigment, resin component X, etc.). In the ink set of the present disclosure, by using an organic acid salt as an aggregating agent in the treatment liquid, it is thought that the aggregating force is prevented from becoming too high compared to when an organic acid is used without an organic acid salt, and as a result, streaks in the image are suppressed. Furthermore, in the ink set of the present disclosure, by using an organic acid salt with a molecular weight of 130 or less as the aggregating agent in the treatment liquid, it is thought that the aggregating force is prevented from becoming too weak, compared to when an organic acid salt with a molecular weight of more than 130 is used instead of an organic acid salt with a molecular weight of 130 or less, and as a result, bleeding of the image is suppressed.

[0018] The ink set of the present disclosure may contain only one type of the above ink, or may contain two or more types. The ink set of the present disclosure may contain only one type of the treatment liquid, or may contain two or more types. The ink set of the present disclosure may include a liquid other than the above inks and the above treatment liquid (for example, an ink other than the above inks, or a treatment liquid other than the above treatment liquid).

[0019] As described above, the ink set of the present disclosure is an ink set for recording an image on a permeable substrate as a recording medium. The permeable substrate, which is the recording medium in the present disclosure, will be described below.

[0020] <Permeable base material> The ink set of the present disclosure is used for recording images on porous substrates. In the present disclosure, a permeable substrate refers to a substrate having a water absorption rate (unit: mass %, measurement time: 24 hours) of 0.2 or more according to ASTM test method ASTM D570.

[0021] The permeable substrate has a water absorption coefficient Ka of 0.05 mL / m from the viewpoint of further improving the image quality. 2 ·ms 1 / 2 It is preferable that this is equal to or greater than this. The water absorption coefficient Ka of the permeable substrate is 0.05 mL / m 2 ·ms 1 / 2 ~0.5mL / m 2 ·ms 1 / 2 More preferably, 0.1 mL / m 2 ·ms 1 / 2 ~0.4 mL / m 2 ·ms 1 / 2 More preferably, 0.2 mL / m 2 ·ms 1 / 2 ~0.3 mL / m 2 ·ms 1 / 2 is more preferred.

[0022] The water absorption coefficient Ka is the same as that described in JAPAN TAPPI Paper and Pulp Testing Method No. 51:2000 (published by the Paper and Pulp Technology Association). The absorption coefficient Ka is a value calculated from the difference in the amount of water transferred between a contact time of 100 ms and a contact time of 900 ms using an automatic scanning liquid absorption meter KM500Win (manufactured by Kumagai Riki Co., Ltd.).

[0023] Preferably, the permeable substrate comprises paper. In this case, the permeable substrate may be a permeable substrate consisting of paper only (e.g., high-quality paper, neutral paper, etc.), or a permeable substrate containing paper and a coating layer (e.g., art paper, coated paper, lightweight coated paper, lightly coated paper, etc.). The coating layer preferably contains an inorganic pigment. The inorganic pigment is not particularly limited, but is preferably at least one selected from silica, kaolin, clay, calcined clay, zinc oxide, tin oxide, magnesium sulfate, aluminum oxide, aluminum hydroxide, pseudoboehmite, calcium carbonate, calcium bicarbonate, satin white, aluminum silicate, smectite, zeolite, magnesium silicate, magnesium carbonate, magnesium oxide, and diatomaceous earth, and more preferably calcium carbonate, calcium bicarbonate, silica, and kaolin.

[0024] Commercially available products may be used as the permeable substrate including paper. Commercially available products include: High-quality paper (A) such as "OK Prince High-Quality" manufactured by Oji Paper Co., Ltd., "Shiraoi" manufactured by Nippon Paper Industries Co., Ltd., and "New NPI High-Quality" manufactured by Nippon Paper Industries Co., Ltd.; High-quality coated paper such as "Silver Diamond" manufactured by Nippon Paper Industries Co., Ltd.; Lightly coated papers such as "OK Everlight Coat" manufactured by Oji Paper Co., Ltd. and "Aurora S" manufactured by Nippon Paper Industries Co., Ltd.; Lightweight coated paper (A3) such as "OK Coat L" manufactured by Oji Paper Co., Ltd. and "Aurora L" manufactured by Nippon Paper Industries Co., Ltd.; Coated paper (A2, B2) such as "OK Top Coat+" manufactured by Oji Paper Co., Ltd. and "Aurora Coat" manufactured by Nippon Paper Industries Co., Ltd.; Art paper (A1) such as "OK Kinto+" manufactured by Oji Paper Co., Ltd. and "Tokubishi Art" manufactured by Mitsubishi Paper Mills; Various photo papers for inkjet recording; "Bon Ivory" by Oji Paper; "CalolinaC2S" manufactured by Intemational; "CartaIntegra" manufactured by Metsaboard; "VJFP Series" manufactured by YUPO; MAGNO® Gross, a coated paper manufactured by Sappi; Examples include:

[0025] The permeable substrate may be a permeable substrate having a water droplet contact angle of 70° or more on the surface on which an image is to be recorded, 3 seconds after the application of a water droplet. Generally, such permeable substrates are capable of suppressing bleeding and recording images with excellent definition, but may be prone to streaks in the images. However, with the ink set of the present disclosure, it is possible to record images with reduced streaks even on permeable substrates with a water droplet contact angle of 70° or greater.

[0026] The water droplet contact angle can be measured using a contact angle meter in accordance with the method described in JIS R3257:1999. As a contact angle meter, for example, Dropmaster DM700 (manufactured by Kyowa Interface Science Co., Ltd.) can be used.

[0027] The ink set of the present disclosure may contain only one type of the above ink, or may contain two or more types. The ink set of the present disclosure may contain only one type of the treatment liquid, or may contain two or more types. The ink set of the present disclosure may include a liquid other than the above inks and the above treatment liquid (for example, an ink other than the above inks, or a treatment liquid other than the above treatment liquid). The inks and treatment liquid in the ink set of the present disclosure will be described below.

[0028] <Ink> The ink in the ink set of the present disclosure (i.e., inkjet ink) contains water, a water-soluble organic solvent, a pigment, a pigment dispersion resin, and a resin component X which is at least one of a water-soluble resin and resin particles.

[0029] (water) The inks in the present disclosure contain water. The water content is not particularly limited, but is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more, based on the total amount of the ink. The upper limit of the water content varies depending on the contents of other components, but is, for example, 99 mass %, 90 mass %, 80 mass %, etc.

[0030] (Water-soluble organic solvent) The ink of the present disclosure contains at least one water-soluble organic solvent. This ensures proper ejection from the inkjet head (hereinafter simply referred to as "ink ejection property").

[0031] In the present disclosure, "water-soluble" in the context of a water-soluble organic solvent refers to the property of dissolving 5 g or more in 100 g of water at 20°C.

[0032] Examples of the water-soluble organic solvent include alkanediols (polyhydric alcohols) such as glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, and propylene glycol; sugar alcohols; alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, and isopropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, and ethylene glycol mono-t-butyl ether. Examples of the glycol ether include diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, and tripropylene glycol monomethyl ether; and amide compounds such as formamide, N,N-dimethylformamide, N,N-dimethylacetamide, 2-pyrrolidone, and N-methylpyrrolidone. The water-soluble organic solvents can be used alone or in combination of two or more.

[0033] The water-soluble organic solvent preferably contains a first organic solvent having a boiling point of 110° C. to 240° C. By containing the first organic solvent in the water-soluble organic solvent, the content of a high-boiling-point solvent (for example, a second organic solvent having a boiling point of 245° C. to 300° C.) can be relatively reduced. This improves drying properties and reduces stickiness of the image.

[0034] Examples of the first organic solvent having a boiling point of 110°C to 240°C include ethylene glycol (198°C), propylene glycol (188°C), dipropylene glycol (230°C), ethylene glycol monomethyl ether (124°C), ethylene glycol diethyl ether (162°C), propylene glycol monoethyl ether (120°C), dipropylene glycol dimethyl ether (171°C), diethylene glycol monomethyl ether (194°C), diethylene glycol diethyl ether (188°C), and N-methylpyrrolidone (202°C).

[0035] Examples of the second organic solvent having a boiling point of 245°C to 300°C include diethylene glycol (245°C), glycerin (290°C), 2-pyrrolidone (245°C), and triethylene glycol monomethyl ether (248°C).

[0036] From the viewpoint of head maintenance, the first organic solvent and the second organic solvent are preferably alcohol-based organic solvents and ether-based organic solvents, which are less likely to adhere to the inside of an inkjet head than amide-based organic solvents (e.g., 2-pyrrolidone), which tend to interact with polymer components, and therefore improve the maintainability of the inkjet head.

[0037] Specific examples of the alcohol-based organic solvent include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and glycerin.

[0038] Examples of the ether-based organic solvent include the alkyl ethers of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and glycerin. Specific examples of the ether-based organic solvent include alkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol diethyl ether, propylene glycol monoethyl ether, dipropylene glycol dimethyl ether, diethylene glycol monomethyl ether, and diethylene glycol diethyl ether.

[0039] In the present disclosure, the first organic solvent and the second organic solvent are preferably each at least one alcohol-based organic solvent selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, dipropylene glycol, and glycerin, and alkyl ethers thereof.

[0040] When the water-soluble organic solvent contains a first organic solvent, the content of the first organic solvent (S 1 ) to the content of the second organic solvent (S 2 ) mass ratio (S 2 / S 1 ) is preferably in the range of 0 to 0.3. 2 / S 1 When the amount of the organic solvent having a high boiling point is within the above range, the amount of the organic solvent having a high boiling point is kept low, and therefore stickiness of the image after drying is suppressed. S 2 / S 1 For the same reasons as above, the range of 0 to 0.2 is more preferable.

[0041] The ink of the present disclosure may contain organic solvents other than the above-mentioned water-soluble organic solvents, as long as the effects of the present disclosure are not significantly impaired.

[0042] The total amount of the first organic solvent and the second organic solvent in the ink is preferably 5% by mass to 30% by mass relative to the total amount of the ink. When the total amount of the first organic solvent and the second organic solvent is within the above range, the amount of organic solvent is kept low, thereby suppressing stickiness of the image after drying. Furthermore, when the total amount of the first organic solvent and the second organic solvent is 5% by mass or more, clogging of the ejection holes due to solidified ink generated at the air interface in the inkjet head is suppressed, resulting in good ejection properties. For the same reasons as above, the total amount of the first organic solvent and the second organic solvent is more preferably 7.5% by mass to 40% by mass, and even more preferably 10% by mass to 30% by mass.

[0043] (pigment) The ink of the present disclosure contains at least one pigment. The pigment functions as a coloring material for coloring the ink. Pigments include organic pigments and inorganic pigments.

[0044] Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Of these, azo pigments and polycyclic pigments are preferred. Examples of azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments. Examples of polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples of dye chelates include basic dye chelates and acid dye chelates.

[0045] Examples of inorganic pigments include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black.

[0046] Specific examples of the pigment include the pigments described in paragraphs 0142 to 0145 of JP-A No. 2007-100071.

[0047] The volume average particle diameter of the pigment is preferably 10 nm to 200 nm, more preferably 10 nm to 150 nm, and even more preferably 10 nm to 100 nm. When the volume average particle diameter is 200 nm or less, color reproducibility is improved, and when recording images by an inkjet method, droplet ejection characteristics are improved. Furthermore, when the volume average particle diameter is 10 nm or more, light resistance is improved. The particle size distribution of the pigment in the ink is not particularly limited and may be either a broad particle size distribution or a monodisperse particle size distribution. Two or more pigments having a monodisperse particle size distribution may be mixed together.

[0048] The volume average particle size and particle size distribution of the pigment in the ink are values ​​measured using a particle size distribution measuring device that uses light scattering (for example, Microtrac UPA (registered trademark) EX150 manufactured by Nikkiso Co., Ltd.).

[0049] The content of the pigment in the ink is not particularly limited and may be appropriately selected depending on the purpose and application, etc. From the viewpoints of coloring properties and storage stability, the content of the pigment in the ink is preferably 1% by mass to 20% by mass, and more preferably 1% by mass to 10% by mass, relative to the total amount of the ink.

[0050] (pigment dispersion resin) The ink of the present disclosure contains at least one pigment dispersing resin. The pigment dispersing resin coats a part or the whole of the surface of the pigment and functions as a dispersant for dispersing the pigment.

[0051] The pigment dispersing resin preferably contains at least one anionic group, which can further enhance the dispersibility of the hydrophobic pigment in an ink containing water and a water-soluble organic solvent. Examples of anionic groups that can be contained in the pigment dispersing resin include acid groups (e.g., carboxy groups, sulfo groups, phosphate groups, etc.) and salts of acid groups (e.g., salts of carboxy groups, salts of sulfo groups, salts of phosphate groups). The pigment dispersing resin may contain only one type of anionic group, or two or more types of anionic groups. Preferred embodiments of the anionic group that can be contained in the pigment dispersing resin are the same as the preferred embodiments of the anionic group that can be contained in the water-soluble resin X1 described below.

[0052] The anionic group in the pigment dispersing resin may be introduced into the structure of the pigment dispersing resin by polymerizing a polymerizable monomer containing an anionic group. That is, the pigment dispersing resin may contain a structural unit derived from a polymerizable monomer containing an anionic group.

[0053] Specific examples of constitutional units derived from polymerizable monomers containing an anionic group are shown below. However, the constituent units derived from polymerizable monomers containing an anionic group are not limited to these. For example, examples of structural units derived from polymerizable monomers containing an anionic group include structural units in which the acid group (e.g., —COOH) in the structural units of the specific examples below is neutralized to form a salt of the acid group (e.g., —COONa).

[0054] [ka]

[0055] Furthermore, in the pigment dispersing resin that coats a part or all of the surface of the pigment, a plurality of "structural units derived from a polymerizable monomer containing an anionic group" may be crosslinked with a crosslinking agent. The pigment dispersing resin of this embodiment can be formed, for example, by dispersing a pigment using an uncrosslinked pigment dispersing resin containing a constituent unit derived from a polymerizable monomer containing an anionic group, and then crosslinking the uncrosslinked pigment dispersing resin that coats at least a portion of the pigment with a crosslinking agent (see, for example, Japanese Patent No. 4964165).

[0056] When the pigment dispersing resin contains a structural unit derived from a polymerizable monomer containing an anionic group, from the viewpoint of pigment dispersibility, the content of the structural unit derived from a polymerizable monomer containing an anionic group is preferably 5% by mass to 40% by mass, and more preferably 8% by mass to 20% by mass, relative to the total amount of the pigment dispersing resin.

[0057] The pigment dispersing resin preferably contains an aromatic ring. When the pigment dispersing resin contains an aromatic ring, the pigment dispersing resin tends to be more hydrophobic, which makes it easier for the pigment dispersing resin to cover part or all of the surface of the pigment, thereby improving the stability of the pigment in water.

[0058] In the present disclosure, an aromatic ring means a cyclic unsaturated ring having aromatic properties. Examples of aromatic rings that can be contained in the pigment dispersing resin include: aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, an anthracene ring, and a pyrene ring; heteroaromatic rings such as a pyridine ring, a pyrrole ring, a furan ring, a thiophene ring, an imidazolyl ring, and an acridone ring; Examples include: Of these, aromatic hydrocarbon rings are preferred.

[0059] The aromatic ring in the pigment dispersing resin may be introduced into the structure of the pigment dispersing resin by polymerization of a polymerizable monomer containing an aromatic ring. In other words, the pigment dispersing resin may contain structural units derived from a polymerizable monomer containing an aromatic ring.

[0060] As the polymerizable monomer containing an aromatic ring, a polymerizable monomer containing an aromatic ring and an ethylenically unsaturated double bond is preferred, and a vinyl polymerizable monomer containing an aromatic ring is more preferred. Examples of polymerizable monomers containing an aromatic ring include styrene, methylstyrene, divinylbenzene, vinylpyridine, diallyl phthalate, and aromatic ring-containing (meth)acrylates (for example, benzyl acrylate, phenoxyethyl acrylate).

[0061] The polymerizable monomer containing an aromatic ring may be unsubstituted or may be substituted with a substituent, such as a halogen atom, an alkyl group, a carboxylic acid group, or a hydroxyl group. Examples of the halogen atom include a chlorine atom, a bromine atom, and an iodine atom. The alkyl group is preferably an alkyl group having 1 to 12 carbon atoms (preferably 1 to 8 carbon atoms), and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, etc. The alkyl group may be unsubstituted or may have the same substituents as those described above.

[0062] Specific examples of structural units derived from polymerizable monomers containing an aromatic ring are shown below. The present disclosure is not limited to the following specific examples. Note that "*" in each structure indicates a bond. Furthermore, "iBu" represents isobutyl, "nBu" represents normal butyl, and "tBu" represents tertiary butyl.

[0063] [ka]

[0064] The content of the structural unit derived from a polymerizable monomer containing an aromatic ring is preferably 50% by mass to 85% by mass, and more preferably 60% by mass to 80% by mass, based on the total amount of the pigment dispersing resin.

[0065] The pigment dispersing resin may contain, in addition to a constituent unit derived from a polymerizable monomer containing an aromatic ring, a constituent unit derived from a polymerizable monomer containing no aromatic ring. Suitable examples of structural units derived from polymerizable monomers that do not contain an aromatic ring include alkyl(meth)acrylates.

[0066] The alkyl(meth)acrylate is preferably an alkyl(meth)acrylate in which the number of carbon atoms in the alkyl moiety is 1 to 20. Examples of the alkyl(meth)acrylate include methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, and stearyl(meth)acrylate.

[0067] Specific examples of pigment-dispersing resins include the following copolymers. The mass ratio of the monomers in the copolymer can be appropriately selected within the range of the weight-average molecular weight. Note that the present disclosure is not limited to the following specific examples. Benzyl methacrylate / acrylic acid copolymer Benzyl methacrylate / methacrylic acid copolymer Styrene / acrylic acid / stearyl acrylate copolymer Styrene / acrylic acid / stearyl methacrylate copolymer Benzyl methacrylate / methacrylic acid / stearyl methacrylate copolymer Phenoxyethyl methacrylate / methacrylic acid / stearyl methacrylate copolymer Phenoxyethyl methacrylate / methacrylic acid / stearyl methacrylate / hydroxyethyl methacrylate copolymer

[0068] From the viewpoint of pigment dispersibility and dispersion stability, the acid value of the pigment dispersing resin is preferably 50 mgKOH / g to 180 mgKOH / g, more preferably 50 mgKOH / g to 150 mgKOH / g, and even more preferably 50 mgKOH / g to 120 mgKOH / g. The acid value can be measured by titration with an indicator, and is a value measured by the method described in Japanese Industrial Standards (JIS) K0070:1992.

[0069] The weight average molecular weight (Mw) of the pigment dispersing resin is preferably from 1,000 to 100,000, and more preferably from 10,000 to 50,000.

[0070] The content of the pigment dispersing resin in the ink is preferably 10% to 80% by mass, and more preferably 25% to 70% by mass, relative to the amount of the pigment, from the viewpoint of improving the dispersibility of the pigment.

[0071] (Resin component (X)) The ink of the present disclosure contains a resin component (X) which is at least one of a water-soluble resin and resin particles. The resin component (X) may be at least one type of resin particle, at least one type of water-soluble resin, or a combination of at least one type of resin particle and at least one type of water-soluble resin. In image recording using the ink set of the present disclosure, when the ink is applied to an area of ​​a permeable substrate to which a treatment liquid has been applied, the resin component (X) in the ink aggregates, causing the ink to thicken. This thickening of the ink inhibits the movement of ink droplets on the permeable substrate, ensuring the image quality. For example, the image definition is improved, and image bleeding is further inhibited.

[0072] In the present disclosure, "water-soluble" in a water-soluble resin means that the amount of the resin that dissolves in 100 g of water at 25° C. is 1 g or more. Preferably, "water-soluble" means that the amount of the resin that dissolves in 100 g of water at 25° C. is 3 g or more (more preferably 10 g or more).

[0073] The resin particles are preferably particles made of a water-insoluble resin. The term "water-insoluble" in the context of a water-insoluble resin means that the amount of the resin that dissolves in 100 g of water at 25°C is less than 1 g.

[0074] The content of the resin component (X) in the ink is preferably 1% by mass to 10% by mass relative to the total amount of the ink. When the content of Resin B is 1% by mass or more, the effect of thickening the ink is easily obtained. When the content of Resin B is 10% by mass or less, the ejection properties of the ink are further improved.

[0075] -Water-soluble resin- From the viewpoint of more effectively suppressing streaks in an image, the resin component (X) preferably contains a water-soluble resin. From the viewpoint of more effectively suppressing streaks in an image, the proportion of the water-soluble resin in the total amount of the resin component (X) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

[0076] -Water-soluble resin X1- When the resin component (X) contains a water-soluble resin, the water-soluble resin preferably contains a water-soluble resin X1 containing an alkyl group having 1 to 3 carbon atoms, an anionic group, and a cyclic structure, which further improves the adhesion between the image and the laminate substrate when the laminate substrate is heat-sealed onto the image (hereinafter also referred to as "image lamination suitability").

[0077] When the water-soluble resin contains the water-soluble resin X1, the proportion of the water-soluble resin X1 in the total amount of the water-soluble resin is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass. When the water-soluble resin contains the water-soluble resin X1, the proportion of the water-soluble resin X1 in the total amount of the resin component (X) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

[0078] -Alkyl group having 1 to 3 carbon atoms- The alkyl group having 1 to 3 carbon atoms in the water-soluble resin X1 is a methyl group, an ethyl group, or a propyl group (that is, an n-propyl group, an i-propyl group), preferably a methyl group or an ethyl group, more preferably a methyl group. The water-soluble resin X1 may contain only one type of alkyl group having 1 to 3 carbon atoms, or may contain two or more types.

[0079] The alkyl group having 1 to 3 carbon atoms in the water-soluble resin X1 may be introduced into the structure of the water-soluble resin X1 by polymerizing a polymerizable monomer containing an alkyl group having 1 to 3 carbon atoms. That is, the water-soluble resin X1 may contain a structural unit derived from a polymerizable monomer containing an alkyl group having 1 to 3 carbon atoms.

[0080] From the viewpoint of further improving the lamination suitability of an image, the polymerizable monomer containing an alkyl group having 1 to 3 carbon atoms is preferably a (meth)acrylic acid alkyl ester in which the alkyl group in the alkyl ester structure has 1 to 3 carbon atoms (hereinafter also referred to as "(meth)acrylic acid C1-3 alkyl ester").

[0081] The (meth)acrylic acid C1-3 alkyl ester is specifically methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, or i-propyl (meth)acrylate. The (meth)acrylic acid C1-3 alkyl ester is preferably methyl (meth)acrylate or ethyl (meth)acrylate, more preferably methyl (meth)acrylate. Moreover, as the (meth)acrylic acid C1-3 alkyl ester, methacrylic acid C1-3 alkyl ester is preferred.

[0082] When the water-soluble resin X1 contains a (meth)acrylic acid C1-3 alkyl ester unit, the (meth)acrylic acid C1-3 alkyl ester unit in the water-soluble resin X1 may be of one type or two or more types. The content of the (meth)acrylic acid C1-3 alkyl ester unit in the water-soluble resin X1 is preferably 3 mass % to 80 mass %, more preferably 3 mass % to 50 mass %, and even more preferably 5 mass % to 50 mass %, relative to the total amount of the water-soluble resin X1.

[0083] -Anionic group- Examples of the anionic group in the water-soluble resin X1 include an acid group (such as a carboxy group, a sulfo group, or a phosphate group) and a salt of an acid group (such as a salt of a carboxy group, a salt of a sulfo group, or a salt of a phosphate group). The anionic group contained in the water-soluble resin X1 may be of one type only, or may be of two or more types. The water-soluble resin X1 may contain both an acid group and a salt of an acid group as the anionic group.

[0084] Salts of acid groups (e.g., salts of carboxy groups, salts of sulfo groups, and salts of phosphate groups) can be formed by neutralizing acid groups (e.g., carboxy groups, sulfo groups, and phosphate groups) with a neutralizing agent. The neutralization of the acid group may be carried out before polymerizing the polymerizable monomer containing the acid group, or may be carried out after polymerizing the polymerizable monomer. Examples of the neutralizing agent for neutralizing the acid group include inorganic bases such as hydroxides of alkali metals and hydroxides of alkaline earth metals, and organic bases such as organic amines. Examples of alkali metals include potassium (K) and sodium (Na). Examples of alkaline earth metals include calcium (Ca) and magnesium (Mg). Examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide. Examples of the hydroxides of alkaline earth metals include calcium hydroxide and magnesium hydroxide. Examples of organic amines include ammonia, primary amines (e.g., ethylamine, monoethanolamine, etc.), secondary amines (e.g., diethylamine, ethylenediamine, etc.), tertiary amines (e.g., triethylamine, triethanolamine, isopropylethylamine, pyrrolidine, piperidine, etc.), and quaternary ammonium salts. Among these, from the viewpoint of storage stability, organic amines having a boiling point of 80°C or higher are preferred. From the viewpoint of storage stability, the neutralizing agent is preferably an alkali metal hydroxide or an organic amine, and more preferably an alkali metal hydroxide or an organic amine having a boiling point of 80° C. or higher. Examples of organic amines having a boiling point of 80°C or higher include ethylenediamine (117°C), triethylamine (90°C), monoethanolamine (170°C), triethanolamine (208°C), isopropylethylamine (127°C), pyrrolidine (87°C), and piperidine (106°C).

[0085] From the viewpoint of effectively exerting the ink thickening effect and further suppressing streaks in the image, the water-soluble resin X1 preferably contains at least one of a carboxy group and a salt of a carboxy group as an anionic group. In this case, the proportion (mol %; hereinafter also referred to as the degree of neutralization) of the salt of the carboxy group to the total of the carboxy group and the salt of the carboxy group is preferably 40 mol % or more, more preferably 50 mol % or more, more preferably 60 mol % or more, and even more preferably 80 mol % or more. The upper limit of the degree of neutralization can be set to 100 mol %.

[0086] The anionic group that can be contained in the water-soluble resin X1 may be introduced into the structure of the water-soluble resin X1 by polymerizing a polymerizable monomer containing an anionic group (and, if necessary, neutralizing it with a neutralizing agent). That is, the water-soluble resin X1 may contain a structural unit derived from a polymerizable monomer containing an anionic group. As the polymerizable monomer containing an anionic group, (meth)acrylic acid is particularly preferred.

[0087] When the water-soluble resin X1 contains a structural unit derived from a polymerizable monomer containing an anionic group (for example, (meth)acrylic acid), the content of the structural unit derived from a polymerizable monomer containing an anionic group is preferably 5% by mass to 40% by mass, and more preferably 8% by mass to 20% by mass, based on the total amount of the water-soluble resin X1.

[0088] From the viewpoint of further improving lamination suitability, the cyclic structure in the water-soluble resin X1 preferably contains at least one of an aromatic ring and an aliphatic ring, and more preferably contains an aromatic ring. The water-soluble resin X1 may contain only one type of cyclic structure, or may contain two or more types of cyclic structures.

[0089] In the present disclosure, an aromatic ring means a cyclic unsaturated ring having aromatic properties. Examples of aromatic rings include: aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, an anthracene ring, and a pyrene ring; heteroaromatic rings such as a pyridine ring, a pyrrole ring, a furan ring, a thiophene ring, an imidazolyl ring, and an acridone ring; Examples include: Of these, aromatic hydrocarbon rings are preferred.

[0090] When the cyclic structure in the water-soluble resin X1 contains an aromatic ring, the aromatic ring can be introduced into the structure of the water-soluble resin X1 by polymerization of a polymerizable monomer containing an aromatic ring. As the polymerizable monomer containing an aromatic ring, a polymerizable monomer containing an aromatic ring and an ethylenically unsaturated double bond is preferred, and a vinyl polymerizable monomer containing an aromatic ring is more preferred. Examples of polymerizable monomers containing an aromatic ring include styrene, methylstyrene, divinylbenzene, vinylpyridine, diallyl phthalate, and aromatic ring-containing (meth)acrylates (for example, benzyl acrylate, phenoxyethyl acrylate).

[0091] The polymerizable monomer containing an aromatic ring may be unsubstituted or may be substituted with a substituent, such as a halogen atom, an alkyl group, a carboxylic acid group, or a hydroxyl group. Examples of the halogen atom include a chlorine atom, a bromine atom, and an iodine atom. The alkyl group is preferably an alkyl group having 1 to 12 carbon atoms (preferably 1 to 8 carbon atoms), and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, etc. The alkyl group may be unsubstituted or may have the same substituents as those described above.

[0092] Specific examples of structural units derived from polymerizable monomers containing an aromatic ring that can be contained in the water-soluble resin X1 are the same as the specific examples of structural units derived from polymerizable monomers containing an aromatic ring that can be contained in the pigment dispersion resin described above.

[0093] The content of structural units derived from polymerizable monomers containing a cyclic structure (for example, an aromatic ring) in the water-soluble resin X1 is preferably 50 to 85% by mass, more preferably 60 to 80% by mass, based on the total amount of the water-soluble resin X1.

[0094] In order to further improve the lamination suitability of images, water-soluble resin X1 is a structural unit derived from a (meth)acrylic acid C1-3 alkyl ester (i.e., a (meth)acrylic acid alkyl ester in which the alkyl group in the alkyl ester structure has 1 to 3 carbon atoms); a structural unit derived from (meth)acrylic acid; a structural unit derived from a polymerizable monomer containing a cyclic structure; It is particularly preferred that the composition contains: In this embodiment, the preferred content of each structural unit is as described above. In the above embodiment, the concept of "structural units derived from (meth)acrylic acid" encompasses both structural units obtained by polymerization of (meth)acrylic acid (i.e., structural units containing a carboxy group) and structural units obtained by polymerization and neutralization of (meth)acrylic acid (i.e., structural units containing a salt of a carboxy group) (here, neutralization may be carried out before or after polymerization).

[0095] The weight-average molecular weight of the water-soluble resin X1 is preferably 5,000 to 100,000. When the weight-average molecular weight of the water-soluble resin X1 is in the above range, bleeding and blocking of the image are further suppressed, and the ink ejection properties are also more excellent. The weight average molecular weight of the water-soluble resin X1 is more preferably from 10,000 to 80,000, and even more preferably from 10,000 to 30,000, from the viewpoint of ink ejection properties.

[0096] The acid value of the water-soluble resin X1 is preferably 28 mgKOH / g to 230 mgKOH / g. When the acid value is 230 mgKOH / g or less, even a small amount of the water-soluble polymer can easily achieve the ink thickening effect, thereby improving bleeding in the image. Furthermore, from the viewpoint of the ink thickening effect, the acid value is more preferably 50 mgKOH / g or more, and may further be 100 mgKOH / g or more, or even 150 mgKOH / g or more. The acid value can be measured by titration of an indicator in the same manner as for the pigment dispersing resin, and is a value measured by the method described in Japanese Industrial Standards (JIS) K0070:1992.

[0097] In the present disclosure, when the resin component (X) (e.g., water-soluble resin X1) is a neutralized resin, the acid value of the resin component (X) (e.g., water-soluble resin X1) means the acid value of the resin component (X) (e.g., water-soluble resin X1) that is a neutralized resin.

[0098] The glass transition temperature (Tg) of the water-soluble resin X1 is preferably at least 80° C. When Tg is at least 80° C., image blocking is further suppressed. The Tg of Resin B is more preferably 95° C. or higher, and even more preferably 110° C. or higher. The upper limit of the Tg of Water-soluble Resin X1 is desirably 250° C. or lower from the viewpoint of synthesis suitability.

[0099] Tg is measured by preparing a sample by drying a solution of water-soluble resin X1 under reduced pressure at 150°C for 6 hours and using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min. As the DSC, for example, a DSC7000X differential scanning calorimeter (DSC) manufactured by Hitachi High-Tech Science Corporation can be used.

[0100] When the ink contains water-soluble resin X1, the pigment dispersion resin preferably has more hydrophobic properties than water-soluble resin X1, that is, the ClogP of the pigment dispersion resin is greater than the ClogP of water-soluble resin X1, from the viewpoint that the pigment dispersion resin can easily coat part or all of the surface of the pigment to enhance dispersibility. The ClogP of the pigment dispersion resin is preferably 1.75 or greater, more preferably 1.80 or greater, and even more preferably 1.85 or greater.

[0101] On the other hand, from the viewpoint of dissolving the water-soluble resin X1 in the ink and effectively exerting the effect of thickening the ink applied to the recording medium (i.e., the effect of improving image quality), it is preferable that the water-soluble resin X1 has hydrophilic properties compared to the pigment dispersion resin A, i.e., a resin whose ClogP is smaller than that of the pigment dispersion resin A. The ClogP of Resin B is preferably 1.80 or less, more preferably 1.74 or less, even more preferably 1.72 or less, and even more preferably 1.70 or less.

[0102] From the viewpoint of further improving the blocking resistance of the image and the ejection properties of the ink, the ClogP of the water-soluble resin X1 is more preferably 0.90 to 1.50, even more preferably 0.95 to 1.45, and even more preferably 0.97 to 1.43. When the ClogP of the water-soluble resin X1 is 0.90 or more, the blocking resistance of the image is further improved. When the ClogP of the water-soluble resin X1 is 1.50 or less, the ink ejection properties are further improved.

[0103] From the viewpoint of more effectively achieving the dispersion stability of the pigment and the thickening effect of the ink applied to the recording medium (i.e., the effect of improving image quality), it is preferable that in the ink of the present disclosure, the ClogP of the pigment dispersing resin is 1.75 or more and the ClogP of the water-soluble resin X1 is 1.74 or less.

[0104] The ClogP of each resin is calculated by taking a weighted average of the ClogP of each polymerizable monomer used to form that resin. For example, the ClogP of polyacrylic acid is calculated as the ClogP of acrylic acid, and the ClogP of a polyacrylic acid-polymethacrylic acid copolymer (copolymerization ratio = 50:50 [mass ratio]) is calculated by multiplying the ClogP of acrylic acid and the ClogP of methacrylic acid by their respective mass ratios (0.5 in this case), and the sum of the resulting values ​​is taken as the ClogP value of the polyacrylic acid-polymethacrylic acid copolymer (copolymerization ratio = 50:50 [mass ratio]). As described above, the ClogP of each polymerizable monomer is calculated using ChemDraw (registered trademark) Professional (ver. 16.0.1.4) manufactured by PerkinElmer Informatics.

[0105] -Resin particles- The resin component (X) may contain resin particles. Here, the resin particles are distinguished from the pigment dispersion resin in that they are particles made of resin. As described above, the resin constituting the resin particles is preferably a water-insoluble resin.

[0106] The resin particles are preferably particles made of an acrylic resin (hereinafter also referred to as acrylic resin particles), particles made of a polyester resin (hereinafter also referred to as polyester resin particles), particles made of a polyurethane resin (hereinafter also referred to as polyurethane resin particles), or particles made of a polyolefin resin (hereinafter also referred to as polyolefin resin particles).

[0107] In the present disclosure, the polyester resin refers to a polymer compound containing an ester bond in the main chain. Examples of the polyester resin include a polycondensation product of a polycarboxylic acid (e.g., a dicarboxylic acid) and a polyalcohol (e.g., a diol). In the present disclosure, polyolefin resin refers to a polymer (homopolymer or copolymer) of raw material monomers containing olefin. Examples of polyolefin resins include polymers of one type of olefin, copolymers of two or more types of olefin, and copolymers of one or more types of olefin and one or more other monomers. Examples of olefins include α-olefins having 2 to 30 carbon atoms. In the present disclosure, polyurethane resin refers to a polymer compound containing a urethane bond.

[0108] The resin particles preferably include acrylic resin particles. The proportion of acrylic resin particles in the resin particles is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0109] As the resin particles, known resin particles described, for example, in paragraphs 0062 to 0076 of JP 2016-188345 A and paragraphs 0109 to 0140 of WO 2013 / 180074 can be used.

[0110] The preferred ranges of the weight average molecular weight, acid value, and glass transition temperature of the resin constituting the resin particles are the same as the preferred ranges of the weight average molecular weight, acid value, and glass transition temperature of the water-soluble resin X1, respectively.

[0111] (Other ingredients) In addition to the components described above, the ink of the present disclosure may further contain other components as necessary. Other ingredients include drying inhibitors (swelling agents), coloring inhibitors, penetration enhancers, UV absorbers, preservatives, rust inhibitors, antifoaming agents, viscosity adjusters, pH adjusters, chelating agents, and the like.

[0112] (Ink properties) The surface tension of the ink is not particularly limited and can be, for example, 20 mN / m or more. From the viewpoint of coatability onto a recording medium, it is preferably 25 mN / m to 40 mN / m, and more preferably 27 mN / m to 37 mN / m. The surface tension of the ink is a value measured at 25° C. by the plate method using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

[0113] The pH of the ink (25°C ± 1°C) is preferably 6 to 10, and more preferably 7 to 10. The pH is a value measured in a 25°C environment using a pH meter (for example, WM-50EG manufactured by Toa DDK Co., Ltd.) with the treatment liquid temperature adjusted to 25°C.

[0114] From the viewpoint of ink ejection properties, the viscosity of the ink is preferably in the range of 1 mPa·s to 30 mPa·s, more preferably in the range of 1 mPa·s to 20 mPa·s, even more preferably in the range of 2 mPa·s to 15 mPa·s, and particularly preferably in the range of 2 mPa·s to 10 mPa·s. The viscosity refers to a value measured under conditions of 25° C. The viscosity can be measured using, for example, a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO., LTD.).

[0115] <Processing liquid> The treatment liquid in the ink set of the present disclosure contains water, a water-soluble organic solvent, and an organic acid salt with a molecular weight of 130 or less.

[0116] (water) The treatment liquid in the present disclosure contains water. The water content is not particularly limited, but is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more, based on the total amount of the treatment liquid. The upper limit of the water content varies depending on the contents of other components, but is, for example, 99 mass %, 90 mass %, 80 mass %, etc.

[0117] (Water-soluble organic solvent) The treatment liquid in the present disclosure contains at least one water-soluble organic solvent. This reduces the surface tension of the treatment liquid, improving the suitability for applying (eg, coating) the treatment liquid.

[0118] The water-soluble organic solvent in the processing liquid is, from the viewpoint of further suppressing streaks and bleeding in the image, diethylene glycol monoalkyl ether (preferably a diethylene glycol monoalkyl ether in which the alkyl group in the alkyl ether structure has 1 to 6 carbon atoms (for example, diethylene glycol monobutyl ether)); triethylene glycol monoalkyl ether (preferably, a triethylene glycol monoalkyl ether in which the alkyl group in the alkyl ether structure has 1 to 6 carbon atoms (for example, triethylene glycol monomethyl ether)); propylene glycol monoalkyl ether (preferably, a propylene glycol monoalkyl ether in which the alkyl group in the alkyl ether structure has 1 to 6 carbon atoms (for example, propylene glycol monomethyl ether)); dipropylene glycol, tripropylene glycol, and Tripropylene glycol monoalkyl ether (preferably, triethylene glycol monoalkyl ether in which the alkyl group in the alkyl ether structure has 1 to 6 carbon atoms (for example, tripropylene glycol monomethyl ether)) It is more preferable that the ink contains at least one organic solvent S1 selected from the group consisting of: Organic solvent S1 is a water-soluble organic solvent that is hydrophobic (i.e., has a low SP (Solvent Parameter) value) compared to alkylene glycol (e.g., propylene glycol), which is another example of a water-soluble organic solvent. When the water-soluble organic solvent in the treatment liquid contains organic solvent S1, the quality of the film (i.e., the image) formed by the ink is improved compared to when the water-soluble organic solvent in the treatment liquid does not contain organic solvent S1 but contains alkylene glycol, and as a result, it is thought that streaks and bleeding in the image are further suppressed. The proportion of the organic solvent S1 in the water-soluble organic solvent in the treatment liquid is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass.

[0119] The content of the water-soluble organic solvent in the treatment liquid is not particularly limited, but from the viewpoint of suppressing curling, it is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 15% by mass, relative to the total amount of the treatment liquid.

[0120] (organic acid salts with molecular weight of 130 or less) The treatment liquid according to the present disclosure contains at least one organic acid salt having a molecular weight of 130 or less. As described above, the organic acid salt having a molecular weight of 130 or less functions as an aggregating agent that aggregates the components in the ink (for example, pigment, resin component (X), etc.). By including an organic acid salt in the treatment liquid, the coagulation force that causes the components in the ink to aggregate is prevented from becoming excessive, compared to when the treatment liquid includes an organic acid but not an organic acid salt, and as a result, streaks in the image are suppressed. When the molecular weight of the organic acid salt is 130 or less, the lack of cohesive force is suppressed compared to when the molecular weight of the organic acid salt exceeds 130, and as a result, bleeding of the image is suppressed. The organic acid salt preferably has a molecular weight of 80 or less.

[0121] As the organic acid salt having a molecular weight of 130 or less, an alkali metal salt is preferred, a sodium salt or potassium salt is more preferred, and a sodium salt is most preferred.

[0122] From the viewpoint of more effectively suppressing streaks and bleeding in an image, the organic acid salt having a molecular weight of 130 or less is preferably at least one selected from the group consisting of formate, acetate, and lactate, more preferably at least one selected from the group consisting of sodium formate, potassium formate, sodium acetate, potassium acetate, sodium lactate, and potassium lactate, and most preferably sodium formate.

[0123] From the viewpoint of more effectively suppressing streaks and bleeding in an image, the content of the organic acid salt having a molecular weight of 130 or less is preferably 1% by mass to 30% by mass, more preferably 2% by mass to 20% by mass, and even more preferably 3% by mass to 15% by mass, relative to the total amount of the treatment liquid.

[0124] From the viewpoint of more effectively suppressing streaks and bleeding in an image, it is also preferable to adjust the balance between the acid value (mgKOH / g) of the resin component (X) in the ink and the pKa of the organic acid corresponding to the organic acid salt having a molecular weight of 130 or less in the treatment liquid. Specifically, the acid value of the resin component (X) divided by the pKa of the organic acid corresponding to the organic acid salt having a molecular weight of 130 or less (hereinafter also referred to as the "ratio [acid value / pKa]") is preferably 35 to 65. When the ratio [acid value / pKa] is 35 or more, streaks in the image are further suppressed. When the ratio [acid value / pKa] is 65 or less, bleeding of the image is further suppressed.

[0125] Here, the organic acid corresponding to the organic acid salt of a molecular weight of 130 or less is a cation (e.g., Na) in the organic acid salt of a molecular weight of 130 or less. + , K. + ) to protons (H + ) is replaced by organic acid.

[0126] When two or more components corresponding to the resin component (X) are present in the ink, the acid value of the resin component (X) in the ratio [acid value / pKa] is the weighted average of the acid values ​​(mgKOH / g) based on the mass ratio of the individual components. When two or more organic acid salts having a molecular weight of 130 or less are present in the treatment solution, the pKa of the organic acid corresponding to the organic acid salt having a molecular weight of 130 or less in the ratio [acid value / pKa] is a weighted average value of the pKa of the organic acid corresponding to each organic acid salt, based on the mass ratio of the content of each organic acid salt.

[0127] (Other ingredients) The treatment liquid according to the present disclosure may contain components other than the above components. Examples of other components include a flocculant other than an organic acid salt having a molecular weight of 130 or less, an antifoaming agent, and a nitrogen-containing heterocyclic compound.

[0128] Examples of flocculants other than organic acid salts having a molecular weight of 130 or less include organic acids, polyvalent metal salts, metal complexes, and cationic polymers. Examples of flocculants other than organic acid salts having a molecular weight of 130 or less include known flocculants described in WO 2019 / 004485, WO 2019 / 150878, WO 2019 / 163581, etc. However, from the viewpoint of more effectively obtaining the effects of the ink set of the present disclosure, the proportion of organic acid salts having a molecular weight of 130 or less in all flocculants in the treatment liquid is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass. Similarly, from the viewpoint of more effectively obtaining the effects of the ink set of the present disclosure, the total content of aggregating agents other than organic acid salts having a molecular weight of 130 or less (for example, at least one selected from the group consisting of organic acids, polyvalent metal salts, metal complexes, and cationic polymers) in the treatment liquid is preferably less than 5% by mass, more preferably less than 2% by mass, and particularly preferably 0% by mass (i.e., the treatment liquid does not contain aggregating agents other than organic acid salts having a molecular weight of 130 or less).

[0129] Examples of the antifoaming agent include silicone compounds (silicone antifoaming agents) and pluronic compounds (pluronic antifoaming agents). Among these, silicone antifoaming agents are preferred. As the silicone antifoaming agent, silicone antifoaming agents containing a polysiloxane structure are preferred.

[0130] The defoaming agent may be a commercially available product, such as BYK-012, 017, 021, 022, 024, 025, 038, or 094 (manufactured by BYK Japan), KS-537, KS-604, or KM-72F (manufactured by Shin-Etsu Chemical Co., Ltd.), TSA-739 (manufactured by Momentive Performance Materials Japan LLC), or Olfine AF104 (manufactured by Nissin Chemical Industry Co., Ltd.). Of these, silicone-based defoaming agents such as BYK-017, 021, 022, 024, 025, 094, KS-537, KS-604, KM-72F, or TSA-739 are preferred, and from the viewpoint of ink ejection stability, BYK-024 is particularly preferred.

[0131] When the treatment liquid contains an antifoaming agent, the content of the antifoaming agent is preferably 0.0001 to 1% by mass, and more preferably 0.001 to 0.1% by mass, relative to the total mass of the treatment liquid. Furthermore, when the treatment liquid contains a silicone-based antifoaming agent as the antifoaming agent, the treatment liquid preferably contains the silicone-based antifoaming agent in an amount equivalent to 50 ppm to 200 ppm of silicone oil.

[0132] (Properties of processing solution) The surface tension of the treatment liquid is not particularly limited and can be, for example, 20 mN / m or more. From the viewpoint of coatability to the recording material, it is more preferably 20 mN / m to 60 mN / m, and even more preferably 25 mN / m to 45 mN / m. The surface tension of the treatment liquid is a value measured by the plate method under conditions of 25° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

[0133] From the viewpoint of the ink aggregation rate, the pH (25° C.±1° C.) of the treatment liquid is preferably in the range of 7.0 or less, more preferably 1.0 to 7.0, even more preferably 2.0 to 6.5, and still more preferably 3.0 to 6.0. The pH is a value measured in a 25°C environment using a pH meter (for example, WM-50EG manufactured by Toa DDK Co., Ltd.) with the temperature of the treatment liquid adjusted to 25°C.

[0134] From the viewpoint of the ink aggregation speed, the viscosity of the treatment liquid is preferably in the range of 1 mPa·s to 30 mPa·s, more preferably in the range of 1 mPa·s to 20 mPa·s, even more preferably in the range of 2 mPa·s to 15 mPa·s, and particularly preferably in the range of 2 mPa·s to 10 mPa·s. The viscosity refers to a value measured under conditions of 25° C. The viscosity can be measured using, for example, a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO., LTD.).

[0135] [Image Recording Method] The image recording method of the present disclosure includes: The ink set of the present disclosure described above is used, a step of applying the treatment liquid onto the permeable substrate (hereinafter also referred to as a "treatment liquid application step"); a step of applying the ink by an inkjet method to the area on the permeable substrate to which the treatment liquid has been applied, thereby recording an image (hereinafter also referred to as the "ink application step"); Includes: The image recording method of the present disclosure may include other steps as necessary.

[0136] In the image recording method of the present disclosure, the ink set of the present disclosure described above is used, and therefore the same effect as that of the ink set of the present disclosure described above (i.e., the effect of being able to base-lock an image in which streaks and bleeding are suppressed) can be achieved. Each step in the image recording method of the present disclosure will be described below.

[0137] <Processing liquid application step> The treatment liquid application step is a step of applying the treatment liquid described above onto the permeable substrate. The preferred embodiments of the permeable substrate and the treatment liquid are as explained in the section "Ink Set."

[0138] The treatment liquid can be applied to the permeable substrate by a known liquid application method. Known liquid application methods include, for example, a coating method, an inkjet method, and a dipping method.

[0139] Examples of coating methods include spray coating, size press methods such as horizontal size press and calendar size press; knife coating methods such as air knife coating; roll coating methods such as gate roll coating, direct roll coating, reverse roll coating and squeeze roll coating; blade coating methods such as bill blade coating; bar coating methods such as rod bar coating; cast coating; gravure coating; curtain coating; die coating; brush coating; and the like. Alternatively, a coating method may be applied in which the coating amount is controlled using a coating device equipped with a liquid amount limiting member, as in the coating device described in JP-A-10-230201. Details of the inkjet method are the same as those of the inkjet method that can be applied to the ink application step described below.

[0140] Mass of processing liquid applied per unit area (g / m 2 ) is, for example, 0.1 g / m 2 ~10g / m 2 , preferably 0.5 g / m 2 ~6.0g / m 2 , more preferably 1.0 g / m 2 ~4.0g / m 2 is.

[0141] In the treatment liquid application step, the treatment liquid applied to the permeable substrate may be dried by heating. Examples of means for heating and drying the pretreatment liquid include known heating means such as a heater, known air blowing means such as a dryer, and a combination of these. Examples of methods for heating and drying the pretreatment liquid include: A method of applying heat using a heater or the like from the side opposite to the surface of the permeable substrate to which the treatment liquid has been applied. a method of applying warm or hot air to the surface of the permeable substrate to which the treatment liquid has been applied; a method of applying heat by an infrared heater to the surface of the permeable substrate to which the treatment liquid has been applied or to the side opposite to the surface to which the treatment liquid has been applied; A combination of these methods, etc.

[0142] The heating temperature during heating and drying of the treatment liquid is preferably 35°C or higher, and more preferably 40°C or higher. There is no particular upper limit to the heating temperature, but the upper limit may be, for example, 100°C, preferably 70°C, and more preferably 60°C. The heat drying time is not particularly limited, but is preferably 0.5 seconds to 60 seconds, more preferably 0.5 seconds to 20 seconds, and particularly preferably 0.5 seconds to 10 seconds.

[0143] <Ink application process> The ink application step is a step in which the ink described above is applied by an ink jet method to the area on the permeable substrate to which the treatment liquid has been applied, thereby recording an image.

[0144] The ink ejection method in the inkjet method is not particularly limited, and may be any of known methods, such as a charge control method that uses electrostatic attraction to eject ink, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electric signal into an acoustic beam and irradiates the ink with it, thereby ejecting the ink using radiation pressure, and a thermal inkjet (Bubble Jet (registered trademark)) method that heats the ink to form bubbles and uses the resulting pressure. As an ink jet method, in particular, the method described in Japanese Patent Laid-Open No. 54-59936 can be effectively used, in which ink subjected to the action of thermal energy undergoes a sudden change in volume, and the force caused by this change in state causes the ink to be ejected from a nozzle. As the inkjet method, the method described in paragraphs 0093 to 0105 of JP-A No. 2003-306623 can also be applied.

[0145] Inkjet head methods include a shuttle method in which a short serial head is scanned across the width of a permeable substrate to perform printing, and a line method in which a line head is used in which printing elements are arranged to cover the entire area of ​​one side of the permeable substrate. In the line method, an image can be recorded on the entire surface of the permeable substrate by scanning the permeable substrate in a direction intersecting the arrangement direction of the recording elements. The line method does not require a transport system such as a carriage that scans the short head in the shuttle method. Furthermore, compared to the shuttle method, the line method does not require complex scanning control of the carriage movement and the permeable substrate, and only the permeable substrate moves. Therefore, the line method achieves faster image recording than the shuttle method.

[0146] The ink is preferably applied using an inkjet head having a resolution of 300 dpi or more (more preferably 600 dpi or more, and even more preferably 800 dpi or more), where dpi stands for dots per inch, and 1 inch is 2.54 cm.

[0147] The amount of ink droplets ejected from the nozzles of the inkjet head is preferably 1 pL (picoliter) to 10 pL, and more preferably 1.5 pL to 6 pL, from the viewpoint of obtaining a high-definition image. Furthermore, from the viewpoint of improving image unevenness and continuous gradation, it is also effective to eject droplets of different amounts in combination.

[0148] In the ink application step, the ink applied to the permeable substrate may be dried by heating. Examples of means for heating and drying ink include known heating means such as a heater, known air blowing means such as a dryer, and a combination of these. Examples of methods for heating and drying ink include: A method of applying heat using a heater or the like from the side opposite to the ink-applied surface of the permeable substrate. a method of applying warm or hot air to the ink-applied surface of the permeable substrate; a method of applying heat by an infrared heater from the ink-applied surface of the permeable substrate or the side opposite to the ink-applied surface; A combination of these methods, etc.

[0149] The heating temperature during heat drying of the ink is preferably 35°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher. There is no particular upper limit to the heating temperature, but the upper limit is, for example, 150°C, preferably 140°C, and more preferably 130°C. There is no particular limitation on the heat drying time, but it is preferably 0.5 seconds to 60 seconds, and more preferably 0.5 seconds to 20 seconds.

[0150] <Applied mass ratio [treatment liquid / ink]> In the image recording method of the present disclosure, the applied mass ratio [treatment liquid / ink] (i.e., the ratio of the applied mass of the treatment liquid to the applied mass of the ink in the area where the image is recorded) is preferably 0.01 to 0.80, more preferably 0.05 to 0.50, and even more preferably 0.08 to 0.50. When the applied mass ratio [treatment liquid / ink] is 0.01 or more, bleeding of the image is further suppressed. When the applied mass ratio [treatment liquid / ink] is 0.80 or less, streaks in the image are further suppressed. [Example]

[0151] Examples of the present disclosure will be described below, but the present disclosure is not limited to the following examples. In the following, unless otherwise specified, "parts" and "%" are by mass. In the following, "water" means ion-exchanged water unless otherwise specified.

[0152] [Preparation of resin component (X)] As the resin component (X) in the ink, the following water-soluble resin and resin particles were prepared.

[0153] <Preparation of water-soluble resin [MMA / MAA / IBOMA] solution> A 500 mL three-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube was charged with propylene glycol (35 g) and heated to 90 °C under a nitrogen stream. A mixed solution containing 5.55 g of V-601 (radical polymerization initiator; Fujifilm Wako Pure Chemical Industries, Ltd.), 10.7 g of methacrylic acid (MAA), 69.3 g of methyl methacrylate (MMA), 20.0 g of isobornyl methacrylate (IBOMA, ClogP = 4.97), 1.63 g of dodecyl mercaptan, and 65.00 g of propylene glycol was added dropwise at a constant rate under conditions that would complete the addition within 2 hours. After the addition of the mixed solution was complete, the mixture was stirred for 1 hour. Next, a mixed solution of 1.85 g of V-601 and 24.62 g of propylene glycol was added to the resulting reaction mixture, and the mixture was stirred for an additional 1.5 hours. After adding 120.21 g of propylene glycol to the resulting reaction mixture, 8.56 g of a 50% by mass aqueous solution of sodium hydroxide (alkali metal hydroxide) was added dropwise using a dropping funnel to obtain a solution of a water-soluble resin [MMA / MAA / IBOMA] (solid concentration 30% by mass).

[0154] The water-soluble resin [MMA / MAA / IBOMA] had an acid value of 60 mgKOH / g, a ClogP of 1.40, a weight-average molecular weight (Mw) of 15,000, and a glass transition temperature (Tg) of 127°C.

[0155] <Preparation of water-soluble resin [MMA / MAA / St] solution> A solution of water-soluble resin [MMA / MAA / IBOMA] (solid concentration 30 mass%) was obtained in the same manner as in the preparation of the solution of water-soluble resin [MMA / MAA / IBOMA], except that the MMA, MAA, and IBOMA used in the preparation of the solution of water-soluble resin [MMA / MAA / IBOMA] were changed to 70.0 g of methyl methacrylate (MMA), 10.7 g of methacrylic acid (MAA), and 19.7 g of styrene (St).

[0156] The water-soluble resin [MMA / MAA / St] had an acid value of 150 mgKOH / g, a ClogP of 0.97, a weight-average molecular weight (Mw) of 18,000, and a glass transition temperature (Tg) of 109°C.

[0157] <Preparation of water-soluble resin [C18MA / MAA / St] solution> A solution of water-soluble resin [C18MA / MAA / St] (solids concentration 30% by mass) was obtained in the same manner as in the preparation of the water-soluble resin [MMA / MAA / IBOMA] solution, except that the MMA, MAA, and IBOMA used in the preparation of the water-soluble resin [MMA / MAA / IBOMA] solution were changed to 20.0 g of stearyl methacrylate (C18MA), 45.0 g of methacrylic acid (MAA), and 35.0 g of styrene (St).

[0158] The water-soluble resin [C18MA / MAA / St] had an acid value of 120 mgKOH / g, a ClogP of 1.48, a weight-average molecular weight (Mw) of 21,000, and a glass transition temperature (Tg) of 97°C.

[0159] <Preparation of water-soluble resin [C18MA / MAA] solution> A solution of water-soluble resin [C18MA / MAA] (solid concentration 30% by mass) was obtained in the same manner as in the preparation of the solution of water-soluble resin [MMA / MAA / IBOMA], except that the MMA, MAA, and IBOMA used in the preparation of the solution of water-soluble resin [MMA / MAA / IBOMA] were changed to 36.0 g of stearyl methacrylate (C18MA) and 64.0 g of methacrylic acid (MAA).

[0160] The water-soluble resin [C18MA / MAA] had an acid value of 100 mgKOH / g, a ClogP of 1.43, a weight-average molecular weight (Mw) of 17,000, and a glass transition temperature (Tg) of 93°C.

[0161] <Preparation of resin particles [DCPMA / MMA / MAA]> A 2-liter three-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube was charged with 360.0 g of methyl ethyl ketone and heated to 75°C. While maintaining the temperature inside the reaction vessel at 75°C, a mixed solution consisting of 36.0 g of dicyclopentanyl methacrylate (DCPMA), 306.0 g of methyl methacrylate (MMA), 18.0 g of methacrylic acid (MAA), 72 g of methyl ethyl ketone, and 1.44 g of "V-601" (radical polymerization initiator; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise at a constant rate so that the addition was completed within 2 hours. After the dropwise addition was completed, a solution consisting of 0.72 g of "V-601" and 36.0 g of methyl ethyl ketone was added and stirred at 75 ° C for 2 hours. A further solution consisting of 0.72 g of "V-601" and 36.0 g of methyl ethyl ketone was added and stirred at 75 ° C for 2 hours. The temperature was then raised to 85 ° C and stirring was continued for another 2 hours. Next, 668.3 g of the polymerization solution was weighed, 388.3 g of isopropanol, and 122.1 ml of a 1 mol / L aqueous NaOH solution were added, and the temperature inside the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was added dropwise at a rate of 20 ml / min to disperse the mixture in water. The temperature inside the reaction vessel was then maintained at 80 ° C for 2 hours, 85 ° C for 2 hours, and 90 ° C for 2 hours under atmospheric pressure, and the solvent was distilled off. Thereafter, the pressure inside the reaction vessel was further reduced, and a total of 913.7 g of isopropanol, methyl ethyl ketone, and distilled water was distilled off, yielding an aqueous dispersion (emulsion) of resin particles [DCPMA / MMA / MAA] with a solid content concentration of 28.0 mass %.

[0162] The resulting aqueous dispersion of resin particles [DCPMA / MMA / MAA] had a pH of 8.4, a volume average particle size of 80 nm, a weight average molecular weight (Mw) of 50,000, and a Tg of 116°C.

[0163] The pH of the aqueous dispersion of resin particles [DCPMA / MMA / MAA] was measured at 25°C using a pH meter WM-50EG (manufactured by Toa DDK Co., Ltd.) after adjusting the temperature to 25°C. The volume average particle size of the resin particles [DCPMA / MMA / MAA] was measured using a Microtrac UPA EX-150 (manufactured by Nikkiso Co., Ltd.).

[0164] Example 1 <Preparation of Cyan Pigment Dispersion Liquid 1> -Preparation of pigment dispersing resin A-1- A 500 ml three-neck flask equipped with a stirrer and condenser was charged with 44 g of methyl ethyl ketone and heated to 72°C under a nitrogen atmosphere. A solution of 0.43 g of dimethyl 2,2'-azobisisobutyrate, 35 g of benzyl methacrylate (BzMA), 5 g of methacrylic acid (MAA), and 10 g of methyl methacrylate (MMA) dissolved in 25 g of methyl ethyl ketone was added dropwise over 3 hours. After the addition was completed and the mixture was allowed to react for another hour, a solution of 0.21 g of dimethyl 2,2'-azobisisobutyrate dissolved in 1 g of methyl ethyl ketone was added, and the mixture was heated to 78°C and heated for 4 hours. The resulting reaction solution was reprecipitated twice in a large excess of hexane, and the precipitated resin was dried to obtain 43 g of pigment dispersion resin A-1.

[0165] The pigment dispersing resin A-1 had an acid value of 65.4 mgKOH / g, a ClogP of 1.89, and a weight average molecular weight (Mw) of 42,000.

[0166] -Preparation of Cyan Pigment Dispersion 1- A mixture of 10 parts of Cyan Pigment Blue 15:3 (Phthalocyanine Blue A220, manufactured by Dainichiseika Color & Chemicals Co., Ltd.), 5 parts of the pigment dispersion resin A-1, 42 parts of methyl ethyl ketone, 5.5 parts of a 1 mol / L aqueous solution of sodium hydroxide (NaOH), and 87.2 parts of ion-exchanged water was used. The mixture was dispersed in a bead mill using 0.1 mm diameter zirconia beads for 2 to 6 hours. Methyl ethyl ketone was removed from the resulting dispersion at 55°C under reduced pressure, and some of the water was then removed to obtain Cyan Pigment Dispersion 1, which had a pigment concentration of 10.2% by mass.

[0167] <Ink Preparation> The above-mentioned cyan pigment dispersion 1 and a solution of water-soluble resin [MMA / MAA / St] were mixed to prepare a mixed solution with the following composition: After preparation, coarse particles were removed from the mixed solution using a 5 μm filter, and cyan ink C-1 was prepared as the ink. Cyan ink C-1 had a viscosity of 4.1 mPa·s (25°C), a surface tension of 38.4 mN / m (25°C), and a pH of 8.9 (25°C).

[0168] -Composition of Cyan Ink C-1- Cyan pigment (Pigment Blue 15:3, manufactured by Dainichi Seika Chemicals Co., Ltd.) …3% by mass Pigment Dispersion Resin A-1 …2% by mass ·Water-soluble resin [MMA / MAA / St] (resin component (X)) …5% by mass (solid content equivalent) Propylene glycol (PG; Fujifilm Wako Pure Chemical Industries, Ltd.) …20% by mass Olfin E1010 (Nissin Chemical Industry Co., Ltd., nonionic surfactant) … 1% by mass ·water …Amounts that total 100% by mass

[0169] <Preparation of processing solution> The components in the following composition were mixed to obtain a treatment liquid. The resulting treatment liquid had a viscosity of 4.5 mPa·s (25°C), a surface tension of 41.0 mN / m (25°C), and a pH of 5.0 (25°C). The viscosity, surface tension, and pH were measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO., LTD.), an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.), and a pH meter WM-50EG (manufactured by Toa DDK Co., Ltd.), respectively.

[0170] -Composition of processing solution- ·DEGmBE (Diethylene glycol monobutyl ether) …2% by mass Sodium formate (flocculant; organic acid salt with a molecular weight of less than 130) …5% by mass ·water …Amounts that total 100% by mass

[0171] <Ink set> An ink set was prepared as a combination of the above ink and the above treatment liquid for use in the following image recording.

[0172] <Image recording> As the permeable substrate, "MAGNO (registered trademark) Gross", a coated paper manufactured by Sappi, was prepared. The water droplet contact angle of this permeable substrate on the surface on which the image was to be recorded was 84° 3 seconds after the water droplet was applied. The permeable substrate was fixed on a stage moving at 500 mm / sec, and the treatment liquid was applied to the fixed permeable substrate at a rate of 1.7 g / m using a wire bar coater. 2 The coating was applied so that the coating amount was 100% and then immediately dried at 50°C for 2 seconds. Next, using a line head (Ricoh Co., Ltd. GELJET GX5000 printer head) arranged at an angle with respect to the movement direction of the permeable substrate, cyan ink C-1 was ejected and applied in the form of a solid image onto the treatment liquid application surface of the permeable substrate under ejection conditions of a resolution of 1200 × 1200 dpi (dots per inch), a droplet volume of 2.4 pL (picoliters), and a stage speed of 635 mm / sec, thereby obtaining a cyan undried solid image of 20 mm × 100 mm in size. Immediately thereafter, the permeable substrate was placed on a 60 ° C. hot plate with the side opposite to the image recording surface of the permeable substrate in contact, and 120 ° C. hot air was applied to the image recording surface using a dryer for 10 seconds to dry the undried solid image, obtaining a solid image. In the area where a solid image was recorded, the applied mass ratio [treatment liquid / ink] was 0.08 (see Table 1).

[0173] <Evaluation> The ink set and the solid image were evaluated as follows. The results are shown in Table 1.

[0174] (Image streaks) The solid image was observed visually and under an optical microscope (magnification: 50x), and streaks in the image were evaluated based on the following evaluation criteria.

[0175] -Evaluation criteria for streaks in images- 5: Visual observation confirmed no streaks in the solid image, and observation under an optical microscope (50x magnification) confirmed that there were no gaps between ink dots. 4: No streaks were observed in the solid image by visual observation, and observation under an optical microscope (50x magnification) confirmed that there were gaps between the ink dots, and these gaps were less than 1 / 10 of the ink dot diameter. 3: Visual observation revealed no streaks in the solid image, and observation under an optical microscope (50x magnification) revealed gaps between ink dots, with these gaps being more than 1 / 10 and less than 1 / 3 of the ink dot diameter. 2: By visual observation, streaks were partially confirmed in the solid image. 1: Upon visual observation, streaks were observed throughout the solid image.

[0176] (Image blur) The character images shown in Figure 1 (unicode: U+9DF9; 2pt, 3pt, 4pt, and 5pt) were recorded in the same manner as in the "image recording" described above, except that instead of applying ink in the form of a solid image, the ink was applied in the form of a character image. The recorded character image was observed and the bleeding of the image was evaluated according to the following evaluation criteria. The results are shown in Table 1. In the following evaluation criteria, the rank "5" indicates that image bleeding is most suppressed.

[0177] -Evaluation criteria for image bleeding- 5: 2pt characters were reproducible. 4: 3pt characters were reproducible, but 2pt characters were not reproducible. 3: 4pt characters could be reproduced, but characters smaller than 3pt could not be reproduced. 2: 5pt characters could be reproduced, but characters of 4pt or less could not be reproduced. 1: 5pt characters could not be reproduced. Note that the above-mentioned "reproducible" means that when viewed from a distance of 0.5 m, the horizontal line represented by 11 in Figure 2 and the horizontal line represented by 12 in Figure 2 in the character image shown in Figure 1 are separated.

[0178] (suitability for lamination) The same operations as those in the "Image Recording" section above were carried out except that the droplet volume of cyan ink C-1 was changed to 6.0 pL, thereby obtaining an image recording material including a permeable substrate and a solid image. A 12 μm thick laminate layer made of low density polyethylene (LDPE) was formed on the solid image of the obtained image recording material by melt lamination to obtain a laminate sample. The laminate sample was fixed to a tensile tester, and a portion of the laminate layer above the solid image on the laminate sample was peeled off and attached to the grip of the tensile tester. The laminate layer was pulled at a speed of 50 mm / min in a 180° peel direction from the solid image. The peel strength was determined from the maximum load during this process. If the laminate layer did not peel off from the solid image and broke, this was recorded. Based on the results of the above operations, the lamination suitability of the image was evaluated according to the following evaluation criteria. In the following evaluation criteria, the most excellent rank for lamination suitability is "5".

[0179] -Evaluation criteria for image lamination suitability- 5: The laminate layer did not peel off from the solid image and was broken. 4: The laminate layer peeled off from the solid image, and the peel strength was in the range of 60 N / m or more. 3: The laminate layer peeled from the solid image, and the peel strength was in the range of 40 N / m or more and less than 60 N / m. 2: The laminate layer peeled from the solid image, and the peel strength was in the range of 20 N / m or more and less than 40 N / m. 1: The laminate layer peeled off from the solid image, and the peel strength was in the range of less than 20 N / m.

[0180] Examples 2 to 4 The same operations as in Example 1 were carried out, except that the applied mass ratio [treatment liquid / ink] was changed as shown in Table 1 by changing the applied mass of the treatment liquid. The results are shown in Table 1.

[0181] Examples 5 to 10 The same procedure as in Example 1 was carried out, except that the type and / or amount of the flocculant (that is, organic acid salt with a molecular weight of 130 or less) in the treatment liquid was changed as shown in Table 1. The results are shown in Table 1.

[0182] Example 11 The same procedure as in Example 1 was carried out, except that the type of water-soluble organic solvent in the treatment liquid was changed as shown in Table 2. The results are shown in Table 2.

[0183] Examples 12 to 15 The same procedure as in Example 1 was carried out, except that the type of resin component (X) in the ink was changed as shown in Table 2. The results are shown in Table 2.

[0184] Comparative Examples 1 to 4 The same operations as in Example 1 were performed, except that the flocculant in the treatment liquid (i.e., organic acid salt with a molecular weight of 130 or less) was changed to the comparative flocculant shown in Table 2, and the evaluation of lamination suitability was omitted. The results are shown in Table 2. In Table 2, the notation "-" in the lamination suitability column for Comparative Examples 1 to 4 means that evaluation of lamination suitability was omitted.

[0185] [Table 1]

[0186] [Table 2]

[0187] As shown in Table 1, in each example using an ink set containing an ink and a treatment liquid, where the ink contains water, a water-soluble organic solvent, a pigment, a pigment dispersion resin, and a resin component (X) which is at least one of a water-soluble resin and resin particles, and the treatment liquid contains water, a water-soluble organic solvent, and an organic acid salt having a molecular weight of 130 or less, streaks and bleeding in the image were suppressed. In contrast to this, in Comparative Examples 1 to 3 in which a comparative flocculant with a molecular weight of more than 130 was used as the flocculant in the treatment liquid, the flocculating force was insufficient, and bleeding of the image occurred. Furthermore, in Comparative Example 4, in which a comparative flocculant that was an organic acid rather than an organic acid salt was used as the flocculant in the processing liquid, the coagulation force was too strong, and streaks occurred in the image.

[0188] Among Examples 1, 5 to 11, and 13 to 15, in Examples 1, 5 to 11, 13, and 14 in which the resin component (X) in the ink contained a water-soluble resin, streaks in the image were more effectively suppressed.

[0189] Of Examples 13 and 14, Example 13, in which the water-soluble resin in the ink contained a water-soluble resin X1 (specifically, C18MA / MAA / St) containing an alkyl group having 1 to 3 carbon atoms, an anionic group, and a cyclic structure, had better suitability for laminating images.

[0190] Of Examples 1 and 12, Example 1 in which the cyclic structure in the water-soluble resin X1 contained an aromatic ring further suppressed streaks in the image and had superior lamination suitability.

[0191] Of Examples 11 and 13, Example 11, in which the water-soluble resin X1 in the ink was "MMA / MAA / St" containing a structural unit derived from a (meth)acrylic acid alkyl ester in which the alkyl group in the alkyl ester structure has 1 to 3 carbon atoms, had better suitability for lamination of the image.

[0192] Of Examples 1 and 11, Example 1, in which the water-soluble organic solvent in the treatment liquid contained organic solvent S1 (specifically, DEGmBE, which is included in diethylene glycol monoalkyl ether), suppressed streaks and bleeding in the image and also had excellent suitability for lamination of the image.

[0193] Of Examples 1 and 2, in Example 1 where the applied mass ratio [treatment liquid / ink] was 0.05 or more, bleeding of the image was more effectively suppressed. Of Examples 3 and 4, in Example 4, where the applied mass ratio [treatment liquid / ink] was 0.50 or less, streaks in the image were more effectively suppressed.

[0194] The disclosure of Japanese Patent Application No. 2020-186069, filed on November 6, 2020, is incorporated herein by reference in its entirety. All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. Contains an inkjet ink and a treatment liquid, the inkjet ink contains water, a water-soluble organic solvent, a pigment, a pigment dispersion resin, and a resin component (X) which is at least one of a water-soluble resin and resin particles; The ink set for a permeable substrate, wherein the treatment liquid contains water, a water-soluble organic solvent, and an alkali metal salt of formic acid having a molecular weight of 130 or less.

2. The ink set for permeable substrates according to claim 1 , wherein the resin component (X) comprises the water-soluble resin.

3. 3. The ink set for permeable substrates according to claim 2, wherein the water-soluble resin comprises a water-soluble resin X1 that includes an alkyl group having 1 to 3 carbon atoms, an anionic group, and a cyclic structure.

4. The ink set for a permeable substrate according to claim 3 , wherein the cyclic structure comprises an aromatic ring.

5. 5. The ink set for penetrable substrates according to claim 3, wherein the water-soluble resin X1 comprises a structural unit derived from a (meth)acrylic acid alkyl ester in which the alkyl group in the alkyl ester structure has 1 to 3 carbon atoms, a structural unit derived from (meth)acrylic acid, and a structural unit derived from the polymerizable monomer containing a cyclic structure.

6. The ink set for penetrable substrates according to any one of claims 1 to 5, wherein a value obtained by dividing the acid value of the resin component (X) by the pKa of the organic acid corresponding to the alkali metal salt of formic acid having a molecular weight of 130 or less is 35 to 65.

7. The water-soluble organic solvent in the treatment liquid is diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, dipropylene glycol, tripropylene glycol, and Tripropylene glycol monoalkyl ether The organic solvent S1 is at least one selected from the group consisting of: The ink set for a permeable substrate according to any one of claims 1 to 6.

8. The ink set for a permeable substrate according to any one of claims 1 to 7 is used, applying the treatment liquid onto a permeable substrate; a step of applying the inkjet ink by an inkjet method to the area of ​​the permeable substrate to which the treatment liquid has been applied, thereby recording an image; An image recording method comprising:

9. The image recording method of claim 8 , wherein the permeable substrate comprises paper.

10. 10. The image recording method according to claim 8, wherein a water droplet contact angle of the surface of the permeable substrate on which the image is to be recorded is 70[deg.] or more 3 seconds after the application of the water droplet.

11. 11. The image recording method according to claim 8, wherein in the region where the image is recorded, a ratio of the applied mass of the treatment liquid to the applied mass of the inkjet ink is 0.05 to 0.50.

Images