Reaction liquid and inkjet recording method

Abstract

To provide a reaction liquid for inkjet recording that is used with aqueous ink, allows recording of high-quality images, and offers superior intermittent discharge stability.SOLUTION: The present invention provides a reaction liquid for inkjet recording, applicable to an inkjet recording method that records an image on a recording medium using an aqueous reaction liquid that contains aqueous ink and a reaction agent reactable with the aqueous ink. The reaction liquid contains a polyvalent metal salt and a surfactant. The surfactant is a compound with a hydrophilic site including an anionic group and a hydrophobic site being an aliphatic hydrocarbon group. In the reaction liquid, the content of the polyvalent metal salt (mass%) is 10.0 times or more and 35.0 times or less of the content of the surfactant (mass%).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a reaction liquid and an ink-jet recording method. [Background technology]

[0002] Conventionally, as a method for recording an image by an inkjet system, a two-liquid reaction system has been proposed that uses an ink and a reaction liquid containing a reaction agent that thickens the ink by contacting with the ink (Patent Documents 1 and 2). Polyvalent metal salts, organic acids, and cationic resins are commonly used as reaction agents. Among the reaction agents, polyvalent metal salts are preferably used because they can efficiently reduce the migration of coloring materials and can record high-quality images. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2004-512987 [Patent Document 2] JP 2005-205611 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have investigated the use of the reaction liquids proposed in these patent documents to record images by an inkjet method, and as a result, have found that when the ejection of the reaction liquid is temporarily stopped and then ejected again, the ejection properties are degraded, that is, the intermittent ejection stability is degraded.

[0005] Therefore, an object of the present invention is to provide an inkjet reaction liquid that can be used with an aqueous ink, can record high-quality images, and has excellent intermittent ejection stability. Another object of the present invention is to provide an inkjet recording method using the reaction liquid. [Means for solving the problem]

[0006] That is, according to the present invention, there is provided an inkjet reaction liquid used in an inkjet recording method in which an image is recorded on a recording medium using an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink, the reaction liquid comprising a polyvalent metal salt and a surfactant, the surfactant being a compound having a hydrophilic moiety containing an anionic group and a hydrophobic moiety that is an aliphatic hydrocarbon group, and the content (mass %) of the polyvalent metal salt in the reaction liquid is 10.0 to 35.0 times, in mass ratio, relative to the content (mass %) of the surfactant. Effect of the Invention

[0007] According to the present invention, it is possible to provide an inkjet reaction liquid that is used together with an aqueous ink, is capable of recording high-quality images, and has excellent intermittent ejection stability. Also, according to the present invention, it is possible to provide an inkjet recording method that uses this reaction liquid. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of an inkjet recording apparatus. [Diagram 2] FIG. 2 is a perspective view showing an example of a liquid application device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the ink in the form of dissociation into ions, but for convenience, it is expressed as "containing a salt." In addition, the aqueous ink and reaction liquid for inkjet printing may be simply referred to as "ink" and "reaction liquid." Physical property values ​​are values ​​at room temperature (25°C) unless otherwise specified. When "(meth)acrylic acid" and "(meth)acrylate" are written, they mean "acrylic acid, methacrylic acid" and "acrylate, methacrylate," respectively.

[0010] In the inkjet recording method, liquid such as ink or a reaction liquid is discharged from an inkjet recording head and deposited on a recording medium to record an image, and further improvement in image quality is required. Under such circumstances, improvement of intermittent discharge stability is considered to be a particularly important issue. When attempting to discharge liquid from the discharge port of the recording head again after temporarily pausing the discharge of the liquid from the discharge port, the discharge of the first drop of liquid may become unstable or ink may not be discharged, resulting in a faint or distorted image.

[0011] The present inventors have investigated the quality of images recorded by an inkjet recording method using an ink and a reaction liquid containing a polyvalent metal salt. As a result, it has been found that when the ejection of the reaction liquid is temporarily stopped and then ejected again, the intermittent ejection stability of the reaction liquid decreases, and the recorded image is likely to become blurred. Furthermore, it has been found that such a phenomenon is a peculiar phenomenon that occurs when the reaction agent is a polyvalent metal salt.

[0012] A surfactant is usually added to the reaction liquid in order to improve the quality of the recorded image by making the reaction liquid quickly wet and spread when it comes into contact with the recording medium. When the inside of the ink flow path connected to the ejection port of the recording head filled with the reaction liquid was observed with a microscope, it was found that after the ejection of the reaction liquid was stopped, oil droplets-like objects were generated in the ink flow path over time. When the ejection of the reaction liquid was stopped, liquid components such as water in the reaction liquid evaporated, and the components of the reaction liquid became locally highly concentrated at the gas-liquid interface in the ink flow path. In the reaction liquid in which polyvalent metal salts are dissolved and there are many ionic components, the dissolved state of the surfactant tends to become unstable. Therefore, it is considered that the surfactant with a locally high concentration could not be completely dissolved in the liquid medium in the reaction liquid, and precipitated out and became oil droplet-like, which is the cause of the decrease in the intermittent ejection stability.

[0013] In consideration of the cause of the decrease in intermittent ejection stability, the present inventors have investigated the composition of the reaction liquid. As a result, they have found that a compound having a hydrophilic portion including an anionic group and a hydrophobic portion that is an aliphatic hydrocarbon group can be used as a surfactant to be coexisted with a polyvalent metal salt. This makes it difficult for the surfactant to precipitate at the gas-liquid interface near the ejection port, and makes it easier to improve the intermittent ejection stability of the reaction liquid.

[0014] When a surfactant is added to water, the surfactant orients itself at the gas-liquid interface, and when the surfactant reaches a certain concentration, it forms spherical micelles with the hydrophobic portion facing inward and the hydrophilic portion facing outward (toward the water). The ease of forming micelles is considered to be determined by the compatibility of the hydrophilic portion of the surfactant with the components in the reaction solution, including water; the compatibility of the hydrophobic portions of the surfactant with each other; and the balance between the hydrophilic and hydrophobic portions.

[0015] When a surfactant having a hydrophilic portion containing an anionic group and a hydrophobic portion which is an aliphatic hydrocarbon group is used, the anionic group electrostatically interacts with a polyvalent metal salt having a high charge. Therefore, it is considered that the compatibility between the hydrophilic portion of the surfactant and the polyvalent metal salt is improved. In addition, the aliphatic hydrocarbon group which is the hydrophobic portion of the surfactant has a strong intermolecular force. Therefore, it is considered that the hydrophobic portions of the surfactant exist stably and have good compatibility with each other. In addition to using a specific surfactant, it is necessary to set the content (mass%) of the polyvalent metal salt in the reaction solution to 10.0 times or more and 35.0 times or less in mass ratio to the content (mass%) of the surfactant. This adjusts the balance between the hydrophilic portion and the hydrophobic portion, forms stable micelles, and suppresses the precipitation of the surfactant, which is considered to improve the intermittent ejection stability.

[0016] <Reaction solution> The reaction liquid of the present invention is an inkjet reaction liquid used in an inkjet recording method in which an image is recorded on a recording medium using an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink. The reaction liquid of the present invention contains a polyvalent metal salt and a surfactant, and the surfactant is a compound having a hydrophilic portion containing an anionic group and a hydrophobic portion that is an aliphatic hydrocarbon group. In the reaction liquid, the content (mass%) of the polyvalent metal salt is 10.0 times or more and 35.0 times or less in mass ratio to the content (mass%) of the surfactant. Each component used in the reaction liquid will be described in detail below.

[0017] [Reactants] The reaction liquid reacts with the ink when it comes into contact with the ink, and aggregates the components in the ink (components having anionic groups such as resins, surfactants, and self-dispersing pigments), and contains a reaction agent. When the reaction agent is present, the state of existence of the components having anionic groups in the ink can be destabilized when the ink and the reaction agent come into contact with each other on the recording medium, and the aggregation of the ink can be promoted. In addition to polyvalent metal ions, examples of the reaction agent include cationic components such as cationic resins and organic acids. The reaction agent may be used alone or in combination of two or more.

[0018] As the reactant, a polyvalent metal ion is used. Examples of the polyvalent metal ion constituting the polyvalent metal salt include Ca. 2+ , Cu 2+ , Ni 2+ , Mg 2+ , Sr 2+ , B.A. 2+ , and Zn 2+ Divalent metal ions such as Fe 3+ , Cr 3+ , Y 3+ , and Al 3+Examples of trivalent metal ions include trivalent metal ions such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 112, 123, 131, 142, 143, 154, 165, 170, 186, 197, 198, 199, 102, 199, 103, 199, 104, 199, 105, 199

[0019] As the polyvalent metal ion, it is preferable to use a polyvalent metal ion having a strong coagulating property that strongly reacts with anionic groups of the pigment, resin particles, etc. in the ink. Among them, the polyvalent metal ion is preferably Mg 2+ , Ca 2+ , and Al 3+ It is preferable that the metal oxide is at least one selected from the group consisting of Mg 2+ More preferably, the polyvalent metal salt is a magnesium salt. 2+ Among divalent metal ions, Mg has a small ionic radius and a strong polarizability. 2+ When the surfactant is used, the power to polarize the anionic group of the surfactant is strong, so that a more stable micelle structure is formed, and the intermittent ejection stability can be further improved.

[0020] Examples of anions constituting polyvalent metal salts include Cl. - , Br - , I - , ClO - , ClO2 - , ClO3 - , ClO4 - , NO2 - , NO3 - , SO4 2- , CO3 2- , HCO3 - , PO4 3- , HPO4 2- , and H2PO4 - Inorganic anions such as HCOO - , (COO- )2, COOH(COO - ), CH3COO - , CH3CH(OH)COO - , C2H4(COO - )2, C6H5COO - , C6H4(COO - )2, and CH3SO3 - From the viewpoint of solubility, NO3 - , SO4 2- , Cl - It is preferable to use SO4 from the viewpoint of corrosion resistance. 2- It is particularly preferable to use the following. That is, the polyvalent metal salt is preferably a sulfate of a polyvalent metal. By using a sulfate of a polyvalent metal, it is possible to further improve the ejection stability when ejecting the reaction liquid for a long period of time.

[0021] The content (mass%) of the polyvalent metal salt in the reaction solution is preferably 1.00 mass% or more and 20.00 mass% or less based on the total mass of the reaction solution. In this specification, when the polyvalent metal salt is a hydrate, the "content (mass%) of the polyvalent metal salt in the reaction solution means the "content (mass%) of the anhydrous polyvalent metal salt" excluding water as the hydrate.

[0022] The content (mass%) of the polyvalent metal salt in the reaction liquid is 10.0 times or more and 35.0 times or less in mass ratio to the content (mass%) of the specific surfactant. If the mass ratio is less than 10.0 times, the amount of the surfactant that does not interact with the polyvalent metal becomes relatively large, and micelles are difficult to form. As a result, the surfactant is easily precipitated, and the intermittent ejection stability of the reaction liquid decreases. On the other hand, if the mass ratio is more than 35.0 times, the amount of the surfactant is relatively small, and micelles are difficult to form. As a result, the surfactant is easily precipitated, and the intermittent ejection stability of the reaction liquid decreases. In addition, in this case, the surface tension of the reaction liquid is difficult to decrease sufficiently, so that the reaction liquid is difficult to blend with the recording medium, and the quality of the recorded image may decrease.

[0023] In the reaction solution, the content (mass%) of the polyvalent metal salt is preferably 10.0 times or more and 20.0 times or less in terms of the mass ratio to the content (mass%) of the specific surfactant. By setting the mass ratio within the above range, more stable micelles are formed, so that precipitation of the surfactant is further suppressed. In particular, the mass ratio is more preferably 13.0 times or more and 20.0 times or less. By setting the mass ratio within the above range, the balance between the content of the polyvalent metal and the specific surfactant that interacts therewith is good, and micelles are efficiently formed, so that intermittent ejection stability is particularly easily improved.

[0024] (Surfactant) The surfactant used is a compound (anionic surfactant) having a hydrophilic portion containing an anionic group and a hydrophobic portion which is an aliphatic hydrocarbon group. The content (mass%) of the surfactant in the reaction liquid is preferably 0.20% by mass or more and 3.00% by mass or less based on the total mass of the reaction liquid, and from the viewpoint of further improving the image quality and suppressing precipitation, it is more preferably 0.30% by mass or more and 1.50% by mass or less. Among them, the content (mass%) of the surfactant in the reaction liquid is particularly preferably 0.50% by mass or more and 1.50% by mass or less.

[0025] The anionic group may be at least one selected from the group consisting of a carboxylic acid group, a carboxylic acid ester group, a sulfonic acid group, a sulfate ester group, a phosphoric acid group, a phosphoric acid ester group, a phosphonic acid group, and a phosphonic acid ester group. These anionic groups may form salts with an alkali metal ion, an ammonium ion, or an organic ammonium ion. The hydrophilic site may be an alkylene group, an amide group, a sulfonyl group, an imino group, a carbonyl group, an ester group, an ether group, an alkylene oxide group, or a combination thereof, which has these anionic groups.

[0026] The anionic group in the surfactant is preferably a sulfonic acid group or a sulfate ester group. The anionic surfactant strongly interacts electrostatically with polyvalent metal ions and easily forms micelles with the anionic group facing outward (toward the water side). In addition, the sulfonic acid group and the sulfate ester group are more likely to undergo ionic dissociation than other anionic groups and have a large ionic radius. For this reason, the electron cloud is more likely to become biased, the polarizability is increased, and the anionic surfactant is more likely to interact strongly with polyvalent metal ions, which makes it easier to form a more stable micelle structure, and therefore makes it easier to further improve the intermittent ejection stability.

[0027] The anionic group in the surfactant is more preferably a sulfate group. Since a surfactant having a sulfate group has high water solubility, it is less likely to precipitate, and it is particularly easy to improve the intermittent ejection stability. Examples of surfactants having a sulfate group as acid type (H type) include polyoxyethylene alkyl ether sulfate and alkyl sulfate.

[0028] The aliphatic hydrocarbon group may be a linear, branched, or cyclic aliphatic hydrocarbon group. However, the aliphatic hydrocarbon group does not have an aromatic ring. Specific examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, and a cycloalkenyl group.

[0029] The aliphatic hydrocarbon group in the surfactant is preferably an alkyl group having a carbon number of 6 to 16. A surfactant having an alkyl group having a carbon number of 6 to 16 has a good balance of hydrophilicity and hydrophobicity, and can more stably form a micelle structure oriented inwardly toward the hydrophobic site.

[0030] The aliphatic hydrocarbon group in the surfactant is preferably an alkyl group having a branched structure. Even if the number of carbon atoms is the same, the alkyl group having a branched structure has a substantially shorter carbon chain length than a linear alkyl group, and therefore can form a more compact and stable micelle structure. Examples of anionic surfactants having an alkyl group having a branched structure include sulfonates, sulfate ester salts, and dialkylsulfosuccinate sodium salts of branched alcohols, such as sodium 7-ethyl-2-methyl-4-undecyl sulfate and sodium 2-ethylhexyl sulfate.

[0031] Specific examples of acid type (H type) surfactants include alkylsulfonic acids, polyoxyethylene alkyl ether sulfates, polyoxyethylene lauryl ether sulfates, alkyl sulfate esters, alkyl taurines, alkylsulfoacetic acids, carboxylated polyoxyethylene alkyl ethers, alkyl phosphoric acids, polyoxyethylene alkyl ether phosphoric acids, alkyl phosphoric acid esters, aliphatic carboxylic acids, polyoxyethylene alkyl ether carboxylic acids, N-acyl sarcosines, and N-acyl glutamic acids.

[0032] [Aqueous medium] The reaction liquid is an aqueous reaction liquid containing at least water as an aqueous medium. Examples of the aqueous medium used in the reaction liquid include the same aqueous medium as that which can be contained in the ink, which will be described later. The content (mass%) of the water-soluble organic solvent in the reaction liquid is preferably 1.00% by mass or more and 50.00% by mass or less, based on the total mass of the reaction liquid. The content (mass%) of water in the reaction liquid is preferably 1.00% by mass or more and 95.00% by mass or less, based on the total mass of the reaction liquid.

[0033] [First water-soluble organic solvent having a relative dielectric constant of 35 or more and 110 or less] The water-soluble organic solvent in the reaction solution preferably contains a first water-soluble organic solvent having a dielectric constant of 35 or more and 110 or less. The magnitude of the dielectric constant is correlated with the magnitude of polarity. A water-soluble organic solvent having a low dielectric constant is also less polarized. For this reason, in a reaction solution in which a polyvalent metal salt is dissolved and there are many ionic components, a water-soluble organic solvent having a low dielectric constant is less likely to interact with water, and the dissolved state becomes unstable, so it is considered that it is more likely to separate from the aqueous medium. On the other hand, a water-soluble organic solvent having an excessively high dielectric constant is polarized, but in a reaction solution in which a polyvalent metal salt is dissolved and there are many ionic components, it is considered that it is more likely to interact with ionic components and to separate or to be in a non-uniform state. By making the reaction solution contain a first water-soluble organic solvent having a dielectric constant of 35 or more and 110 or less together with a polyvalent metal salt, precipitation of a surfactant at the gas-liquid interface near the discharge port is more unlikely to occur, and the intermittent discharge stability of the reaction solution can be further improved. Among them, the relative dielectric constant of the first water-soluble organic solvent is more preferably from 45 to 60, and particularly preferably from 45 to 59. The first water-soluble organic solvent having a relative dielectric constant within the above range interacts more strongly with polyvalent metal ions, and therefore can particularly improve the intermittent discharge stability of the reaction liquid.

[0034] The content (mass %) of the first water-soluble organic solvent having a relative dielectric constant of 35 to 110 in the reaction liquid is preferably 10.00 mass % to 30.00 mass % based on the total mass of the reaction liquid. When the content of the first water-soluble organic solvent is within the above range, the intermittent ejection stability can be further improved.

[0035] Examples of the first water-soluble organic solvent having a dielectric constant of 35 or more and 110 or less, with the dielectric constant shown in parentheses, include 1-(2-hydroxyethyl)-2-pyrrolidone (38), ethylene glycol (40), glycerin (42), γ-butyrolactone (42), trehalose (49), dimethyl sulfoxide (49), ethylene urea (50), sorbitol (59), ethyl isopropyl sulfone (59), xylitol (59), urea (110), etc. Among these, those having a lower vapor pressure than water at 25° C. or those which are solid at 25° C. are preferred.

[0036] The relative dielectric constant of a water-soluble organic solvent or water can be measured using a dielectric constant meter (for example, trade name "BI-870" (manufactured by BROOKHAVEN INSTRUMENTS CORPORATION)) at a frequency of 10 kHz. The relative dielectric constant of a water-soluble organic solvent that is solid at a temperature of 25°C is a value calculated from the relative dielectric constant of a 50% by mass aqueous solution by measuring the relative dielectric constant and using the following formula (A). Usually, "water-soluble organic solvent" means a liquid, but in the present invention, water-soluble organic solvents that are solid at 25°C (room temperature) are also included. ε sol =2ε 50% -ε water (A) ε sol : Dielectric constant of solid water-soluble organic solvent at 25℃ ε 50% : Relative dielectric constant of a 50% by mass aqueous solution of a solid water-soluble organic solvent at 25°C ε water : relative dielectric constant of water

[0037] Specific examples of water-soluble organic solvents that are solid at 25°C and are generally used in inks and reaction liquids include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, polyethylene glycol with a number average molecular weight of 1,000, sorbitol, xylitol, and trehalose. The reason for calculating the dielectric constant of a water-soluble organic solvent that is solid at 25°C from the dielectric constant of a 50% by mass aqueous solution is as follows. Among water-soluble organic solvents that are solid at 25°C and can be components of inks and reaction liquids, there are some that are difficult to prepare high-concentration aqueous solutions of more than 50% by mass. On the other hand, in low-concentration aqueous solutions of 10% by mass or less, the dielectric constant of water becomes dominant, and it is difficult to obtain a reliable (effective) value of the dielectric constant of the water-soluble organic solvent. Therefore, the present inventors conducted an investigation and found that most of the water-soluble organic solvents that are solid at 25°C used in inks and reaction liquids can be used to prepare aqueous solutions to be measured, and the calculated dielectric constant is consistent with the effects of the present invention. For the above reasons, in the present invention, the dielectric constant of a water-soluble organic solvent that is solid at 25°C is calculated from the dielectric constant of a 50% by mass aqueous solution and used. Even if the water-soluble organic solvent is solid at 25°C, if its solubility in water is low and a 50% by mass aqueous solution cannot be prepared, an aqueous solution of the saturated concentration is used, and the above ε sol For convenience, the value of the relative dielectric constant calculated in accordance with the calculation of

[0038] Specific examples of the water-soluble organic solvent (including specific examples of the first water-soluble organic solvent) include monohydric alcohols having 1 to 4 carbon atoms, such as methanol (33), ethanol (24), n-propanol (12), isopropanol (18), n-butanol, sec-butanol, and tert-butanol; 1,2-propanediol (29), 1,3-butanediol (30), 1,4-butanediol (31), 1,5-pentanediol (27), 1,2-hexanediol (15), 1,6-hexanediol (7), and 2-methyl-1,3-propanediol (28). , 3-methyl-1,3-butanediol (24), 3-methyl-1,5-pentanediol (24), 2-ethyl-1,3-hexanediol (19), and other dihydric alcohols; 1,2,6-hexanetriol (29), glycerin (42), trimethylolpropane (34), trimethylolethane, sorbitol (59), xylitol (59), trehalose (49), and other polyhydric alcohols; ethylene glycol (40), diethylene glycol (32), triethylene glycol (23), tetraethylene glycol (21), hexylene glycol, thiodiglycol, and other alkylene glycols; ethylene glycol monobutyl ether (9), diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (10), triethylene glycol monobutyl ether (10), tetraethylene glycol monobutyl ether (9), tripropylene glycol monomethyl ether (9), and other glycol ethers; polyethylene glycols having a number average molecular weight of 200 (19), polyethylene glycols having a number average molecular weight of 600 (11), and polyethylene glycols having a number average molecular weight of 1,000 (12); 5), polyalkylene glycols having a number average molecular weight of 200 to 1,000, such as polypropylene glycol; nitrogen-containing compounds, such as 2-pyrrolidone (28), N-methyl-2-pyrrolidone (32), 1-(2-hydroxyethyl)-2-pyrrolidone (38), 1,3-dimethyl-2-imidazolidinone, N-methylmorpholine, urea (110), ethyleneurea (50), triethanolamine (32), 1-hydroxymethyl-5,5-dimethylhydantoin (24), and 1,3-bis(2-hydroxyethyl)-5,5-dimethylhydantoin (16);Examples of the sulfur-containing compounds include dimethyl sulfoxide (49) and bis(2-hydroxyethylsulfone); and cyclic ethers such as γ-butyrolactone (42). (The value in parentheses is the relative dielectric constant at 25°C.) Some of the first water-soluble organic solvents having a relative dielectric constant of 35 or more and 110 or less may be specific water-soluble hydrocarbon compounds.

[0039] [Water-soluble hydrocarbon compounds] The water-soluble organic solvent in the reaction liquid preferably contains a specific water-soluble hydrocarbon compound, which will be described later as a compound that can be contained in the ink. By containing a specific water-soluble hydrocarbon compound in the reaction liquid, cockling and curling of the recording medium on which an image is recorded can be effectively suppressed. The content (mass %) of the water-soluble hydrocarbon compound in the reaction liquid is preferably 1.00 mass % or more and 20.00 mass % or less based on the total mass of the ink.

[0040] [Other ingredients] The reaction liquid may contain various other components as necessary, including the same components as those that can be contained in the ink, which will be described later.

[0041] [Physical properties of reaction solution] The reaction liquid is an aqueous reaction liquid applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the reaction liquid at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the reaction liquid at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the reaction liquid at 25°C is preferably 5.0 or more and 9.5 or less, and more preferably 6.0 or more and 9.0 or less.

[0042] <Ink> The reaction liquid of the present invention is a liquid used in an ink-jet recording method together with an aqueous ink. The ink is preferably an aqueous ink for ink-jet recording containing a coloring material. Each component used in the ink will be described in detail below.

[0043] [Colorant] The ink preferably contains a coloring material. Pigments or dyes can be used as the coloring material. The content (mass %) of the coloring material in the ink is preferably 0.50 mass % or more and 15.00 mass % or less, and more preferably 1.00 mass % or more and 10.00 mass % or less, based on the total mass of the ink.

[0044] Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide, and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, dioxazine, etc. The pigments may be used alone or in combination of two or more.

[0045] As the dispersion method of the pigment, a resin-dispersed pigment using a resin as a dispersant, a self-dispersed pigment in which a hydrophilic group is bonded to the pigment particle surface, etc. can be used. In addition, a resin-bonded pigment in which an organic group containing a resin is chemically bonded to the pigment particle surface, and a microcapsule pigment in which the surface of the pigment particle is coated with a resin, etc. can be used. It is also possible to use a combination of pigments with different dispersion methods among these. In the present invention, it is preferable to use a resin-dispersed pigment in which a resin as a dispersant is physically adsorbed on the pigment particle surface, rather than a resin-bonded pigment or a microcapsule pigment.

[0046] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin having an anionic group can be used, and it is preferable to use a resin as described below, especially a water-soluble resin. The content (mass%) of the pigment in the ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the content (mass%) of the resin dispersant.

[0047] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the anionic group is a salt type, examples of the cation that serves as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Specific examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. In addition, it may be a group that is a combination of these groups.

[0048] The dye preferably has an anionic group. Specific examples of the dye include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone dyes. The dye may be used alone or in combination of two or more. The coloring material is preferably a pigment, and more preferably a resin-dispersed pigment or a self-dispersed pigment.

[0049] [resin] The ink can contain a resin. By using an ink containing a resin, an image with improved abrasion resistance can be recorded. The content (mass%) of the resin in the ink is preferably 0.10% by mass or more and 20.00% by mass or less, and more preferably 0.50% by mass or more and 15.00% by mass or less, based on the total mass of the ink. The resin can be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary. Also, (ii) to improve various properties of the recorded image. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. Also, the resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be resin particles that are dispersed in an aqueous medium. The resin may be used alone or in combination of two or more types.

[0050] [Resin Composition] Examples of the resin include acrylic resins, urethane resins, olefin resins, etc. Among them, acrylic resins and urethane resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylate are more preferred.

[0051] The acrylic resin preferably has a hydrophilic unit and a hydrophobic unit as constituent units. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer is preferred. In particular, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of styrene and α-methylstyrene is preferred. These resins are likely to interact with pigments, and therefore can be suitably used as a resin dispersant for dispersing pigments.

[0052] The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of the hydrophilic monomer having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Examples of cations constituting the salts of acidic monomers include ions of lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit not having a hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer not having a hydrophilic group such as an anionic group. Specific examples of the hydrophobic monomer include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0053] The urethane resin can be obtained by reacting, for example, polyisocyanate with a polyol. In addition, a chain extender may be further reacted with the urethane resin. Examples of the olefin resin include polyethylene and polypropylene.

[0054] [Resin properties] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, the resin is present in an aqueous medium in a state in which it does not form particles whose particle size can be measured by a dynamic light scattering method. Whether or not a resin is water-soluble can be determined according to the following method. First, a liquid (resin solid content: 10 mass%) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by a dynamic light scattering method, if no particles having a particle size are measured, the resin can be determined to be water-soluble. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3 times, and measurement time: 180 seconds. In addition, a particle size analyzer using a dynamic light scattering method (for example, the product name "UPA-EX150", manufactured by Nikkiso) can be used as a particle size distribution measuring device. Of course, the particle size distribution measuring device and the measurement conditions are not limited to those described above.

[0055] The acid value of the water-soluble resin is preferably 100 mgKOH / g or more and 250 mgKOH / g or less, and the weight average molecular weight of the water-soluble resin is preferably 3,000 or more and 15,000 or less.

[0056] The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 3,000,000 or less, and more preferably 100,000 or more and 3,000,000 or less. The volume-based cumulative 50% particle diameter (D 50) is preferably 50 nm or more and 500 nm or less. The volume-based cumulative 50% particle diameter of the resin particles is the diameter of the particles that is 50% of the total volume of the measured particles when integrated from the small particle diameter side in a particle diameter integration curve. The volume-based cumulative 50% particle diameter of the resin particles can be measured using the dynamic light scattering particle size analyzer and measurement conditions described above. The glass transition temperature of the resin particles is preferably 40° C. or more and 120° C. or less, and more preferably 50° C. or more and 100° C. or less. The glass transition temperature (° C.) of the resin particles can be measured using a differential scanning calorimeter (DSC). The resin particles do not need to contain a coloring material.

[0057] [Wax particles] The ink may contain particles formed of wax (wax particles). By using an ink containing wax particles, an image with improved abrasion resistance can be recorded. In this specification, the wax may be a composition containing components other than wax, or the wax itself. The wax particles may be dispersed by a dispersant such as a surfactant or a resin. The wax may be used alone or in combination of two or more kinds. The content (mass %) of the wax particles in the ink is preferably 0.10 mass % or more and 10.00 mass % or less, and more preferably 1.00 mass % or more and 5.00 mass % or less, based on the total mass of the ink.

[0058] In the narrow sense, wax is an ester of a water-insoluble higher monohydric or dihydric alcohol and a fatty acid, and includes animal waxes and vegetable waxes, but does not include oils and fats. In the broad sense, wax includes high melting point fats, mineral waxes, petroleum waxes, and blends and modified products of various waxes. In the present invention, any wax in the broad sense can be used without particular restrictions. Wax in the broad sense can be classified into natural waxes, synthetic waxes, blends thereof (blended waxes), and modified products thereof (modified waxes).

[0059] Examples of natural waxes include animal waxes such as beeswax, spermaceti, and wool wax (lanolin); vegetable waxes such as wood wax, carnauba wax, sugarcane wax, palm wax, candelilla wax, and rice wax; mineral waxes such as montan wax; and petroleum waxes such as paraffin wax, microcrystalline wax, and petrolatum. Examples of synthetic waxes include hydrocarbon waxes such as Fischer-Tropsch wax and polyolefin wax (e.g., polyethylene wax and polypropylene wax). The blended wax is a mixture of the above-mentioned various waxes. The modified wax is a wax obtained by subjecting the above-mentioned various waxes to a modification treatment such as oxidation, hydrogenation, alcohol modification, acrylic modification, and urethane modification. One of the above waxes may be used alone, or two or more may be used in combination. The wax is preferably at least one selected from the group consisting of microcrystalline wax, Fischer-Tropsch wax, polyolefin wax, paraffin wax, and modified or blended products thereof. Among them, a blend of multiple types of wax is more preferable, and a blend of a petroleum wax and a synthetic wax is particularly preferable.

[0060] The wax is preferably solid at room temperature (25°C). The melting point (°C) of the wax is preferably 40°C or higher and 120°C or lower, and more preferably 50°C or higher and 100°C or lower. The melting point of the wax can be measured in accordance with the test method described in 5.3.1 (melting point test method) of JIS K2235:1991 (petroleum wax). In the case of microcrystalline wax, petrolatum, and a mixture of multiple types of wax, the test method described in 5.3.2 can be used to measure more accurately. The melting point of the wax is easily affected by characteristics such as molecular weight (the higher the molecular weight, the higher the melting point), molecular structure (the higher the melting point if the chain is straight, and the lower the melting point if there is branching), crystallinity (the higher the crystallinity, the higher the melting point), and density (the higher the crystallinity, the higher the melting point). Therefore, by controlling these characteristics, it is possible to obtain a wax having a desired melting point. The melting point of the wax in the ink can be measured in accordance with the above test method, for example, after the ink is subjected to ultracentrifugation, the wax separated is washed and dried.

[0061] [Aqueous medium] The ink is an aqueous ink containing at least water as an aqueous medium. The ink may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As the water, deionized water or ion-exchanged water is preferably used. The content (mass%) of water in the aqueous ink is preferably 50.00 mass% or more and 95.00 mass% or less based on the total mass of the ink. In addition, the content (mass%) of the water-soluble organic solvent in the aqueous ink is preferably 2.00 mass% or more and 40.00 mass% or less based on the total mass of the ink. As the water-soluble organic solvent, any of those usable for inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing solvents, and sulfur-containing solvents, can be used. The water-soluble organic solvent may be used alone or in combination of two or more.

[0062] [Water-soluble hydrocarbon compounds] The water-soluble organic solvent contained in the ink preferably contains a specific water-soluble hydrocarbon compound. This water-soluble hydrocarbon compound is a compound having a hydrocarbon chain having three or more carbon atoms substituted with two or more hydrophilic groups selected from the group consisting of hydroxyl groups, amino groups, and anionic groups. However, the hydrocarbon chain may be interrupted by a sulfonyl group or an ether group. When the hydrocarbon chain has three or four carbon atoms, the hydrophilic group contains an anionic group, or the hydrocarbon chain is interrupted by a sulfonyl group.

[0063] In the present invention, a hydrocarbon compound that is dissolved in water at 25°C at the content of the compound in the ink is considered to be "water-soluble". In other words, the solubility in water at 25°C is greater than the content in the ink. The fact that the hydrocarbon chain is interrupted by a sulfonyl group or an ether group means that a sulfonyl group (-S(=O)2-) or an ether group (-O-) is present in the middle of the hydrocarbon chain. Water-soluble hydrocarbon compounds have hydrogen-bonding groups such as hydroxyl groups, amino groups, anionic groups, sulfonyl groups, and ether groups. Therefore, by using an ink containing this hydrocarbon compound, cockling and curling of a recording medium on which an image is recorded can be suppressed. General hydrocarbon compounds having a hydrocarbon chain with a relatively small number of carbon atoms (3 or 4) tend to have a small molecular weight and a low vapor pressure. However, since the above water-soluble hydrocarbon compounds have anionic groups of hydrogen bonds or the hydrocarbon chain is interrupted by a sulfonyl group, they are difficult to evaporate due to inter- or intra-molecular interactions, and remain between fibers to suppress cockling and curling. The content (mass %) of the water-soluble hydrocarbon compound in the ink is preferably from 1.00 mass % to 20.00 mass % based on the total mass of the ink.

[0064] The number of carbon atoms in the hydrocarbon chain constituting the water-soluble hydrocarbon compound is preferably from 3 to 50, and more preferably from 3 to 10. Examples of the anionic group include a sulfonic acid group and a carboxylic acid group. Specific examples of water-soluble hydrocarbon compounds include alkanediols such as 1,5-pentanediol and 1,6-hexanediol; amino acids such as alanine, β-alanine, trimethylglycine, amidosulfuric acid (also known as sulfamic acid), aminomethanesulfonic acid, taurine (also known as 2-aminoethanesulfonic acid), carbamic acid, glycine, aspartic acid, glutamic acid, sulfanilic acid, or salts of the above-mentioned acids, phenylalanine, leucine, isoleucine, threonine, tryptophan, valine, methionine, lysine, and arginine; sulfonyl compounds such as bis(2-hydroxyethyl)sulfone; alkylene glycols such as triethylene glycol, tetraethylene glycol, tripropylene glycol, and polyethylene glycols having a number average molecular weight of about 200 to 1,000; and sugars such as sorbitol, D-sorbitol, xylitol, trehalose, fructose, and D(+)-xylose. The water-soluble hydrocarbon compound may be used alone or in combination of two or more. Among the specific water-soluble hydrocarbon compounds, there are some that can be the first water-soluble organic solvent having a relative dielectric constant of 35 or more and 110 or less.

[0065] [Other ingredients] In addition to the above components, the ink may contain various additives, such as antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, reduction inhibitors, etc. However, it is preferable that the ink does not contain the reactants used in the reaction liquid as described above.

[0066] [Ink properties] The ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less.

[0067] <Inkjet recording method and inkjet recording apparatus> The inkjet recording method of the present invention (hereinafter also simply referred to as "recording method") is a method for recording an image on a recording medium using an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink. The recording method of the present invention has a reaction liquid applying step of applying a reaction liquid to the recording medium, and an ink applying step of applying an aqueous ink to the recording medium so as to overlap at least a part of the area of ​​the recording medium to which the reaction liquid has been applied. The reaction liquid is the reaction liquid described above. Hereinafter, an inkjet recording method according to one embodiment of the present invention and an inkjet recording apparatus that can be suitably used for the inkjet recording method will be described with reference to the drawings.

[0068] 1 is a schematic diagram showing an example of a schematic configuration of an inkjet recording apparatus 100 according to the present embodiment. The inkjet recording apparatus 100 is an inkjet recording apparatus that records an image on a recording medium using ink and a reaction liquid containing a reactant that reacts with the ink. The X direction, Y direction, and Z direction respectively indicate the width direction (total length direction), depth direction, and height direction of the inkjet recording apparatus. The recording medium is transported in the X direction.

[0069] The inkjet recording apparatus 100 of the embodiment shown in FIG. 1 is configured to include a recording unit 1000, a heating unit 2000, a fixing unit 3000, and a paper discharge unit 4000. In the recording unit 1000, various liquids are applied by a liquid application unit 1200 to a recording medium 1100 conveyed from a paper feeder 1400 by a conveying member 1300. In the heating unit 2000, the liquid components of an image formed by the liquid applied to the recording medium 1100 are heated by a heating unit 2100 to evaporate and dry the image. In the fixing unit 3000, a fixing member 3100 is brought into contact with an area of ​​the recording medium 1100 including the image, thereby heating the image and promoting the fixing of the image to the recording medium 1100. Thereafter, the recording medium 1100 is conveyed by a conveying member 4100 of the paper discharge unit 4000, and is stacked and accommodated in a recording medium accommodation unit 4200. Here, an example having a heating unit 2000 and a fixing unit 3000 will be described, but the heating unit and the fixing unit may be omitted depending on the recording conditions (type of ink and recording medium, recording speed, etc.). In the examples described later, recording was performed without using the heating unit 2000 and the fixing unit 3000.

[0070] Any material may be used as the recording medium 1100, but it is preferable to use a recording medium made of paper or a resin material rather than fabric. For example, recording media having ink absorbency (permeability) such as recording media without a coating layer, such as plain paper, uncoated paper, and synthetic paper, and recording media with a coating layer, such as glossy paper and art paper, may be used. In addition, recording media having no permeability, such as films or sheets made of resin materials such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET), may be used. The basis weight (g / m2) of the recording medium 1100 may be determined by the following formula: 2 ) is 30g / m 2 More than 500g / m 2 It is preferable that the thickness is less than 50 g / m 2 More than 450g / m 2 It is even more preferable that:

[0071] [Recording Section] The recording unit 1000 includes a liquid applying device 1200. The liquid applying device 1200 includes a reaction liquid applying device 1201 and an ink applying device 1202. The reaction liquid applying device 1201 shown in FIG. 1 is an example of a unit using an inkjet type ejection head. In addition, the reaction liquid applying device may be configured using a gravure coater, an offset coater, a die coater, a blade coater, or the like. The reaction liquid may be applied by the reaction liquid applying device 1201 either before or after the ink application as long as it can come into contact with the ink on the recording medium 1100. However, in order to record high-quality images on various recording media having different liquid absorption characteristics, it is preferable to apply the reaction liquid before the ink is applied. An inkjet type ejection head (recording head) is used as the ink applying device 1202. The ejection method of the ejection head as the liquid applying device 1200 includes a method of ejecting liquid by generating film boiling in the liquid by an electrothermal converter to form bubbles, and a method of ejecting liquid by an electromechanical converter.

[0072] The liquid deposition device 1200 is a line head extending in the Y direction, and has ejection ports arranged in a range that covers an image recording area of ​​the widest possible recording medium. The ejection head has an ejection port surface (not shown) on its lower side (the recording medium 1100 side) where the ejection ports are formed, and the ejection port surface faces the recording medium 1100 at a very small distance of about several millimeters.

[0073] A plurality of ink applicators 1202 may be provided to apply ink of each color to the recording medium 1100. For example, when recording images of each color using yellow ink, magenta ink, cyan ink, and black ink, four ink applicators 1202 for ejecting the above four types of ink are arranged side by side in the X direction. Hereinafter, the ink and the reaction liquid may be collectively referred to as "liquid".

[0074] Fig. 2 is a perspective view showing an example of a liquid application device. The liquid application device 1200 shown in Fig. 2 is a line head, and a plurality of ejection element substrates 1203 each having an ejection port array are arranged in a straight line. The ejection element substrate 1203 has a plurality of ejection port arrays arranged thereon.

[0075] [Transport system] As shown in FIG. 1, the recording unit 1000 is configured to include a liquid applying device 1200 and a conveying member 1300 that conveys the recording medium 1100. The liquid applying device 1200 applies a reaction liquid and ink to a desired position of the recording medium 1100 conveyed by the conveying member 1300. Each liquid applying device 1200 receives an image signal of drawing data and applies the necessary reaction liquid and ink to each position. FIG. 1 shows the conveying member 1300 in the form of a conveying belt, but a spur, a conveying drum, or the like may be used as long as it has the function of conveying the recording medium 1100. In order to improve the conveying accuracy, a member that can fix the recording medium 1100 can be used as the conveying member 1300. Specifically, a method of providing a hole in the conveying member 1300 and fixing the recording medium 1100 by sucking from the back side, a method of forming the conveying member 1300 from an appropriate material and fixing the recording medium 1100 by electrostatic adsorption, etc. can be mentioned.

[0076] [Heating section] As shown in Fig. 1, the heating section 2000 is configured to include a heating device 2100 and a transport member 2200. The recording medium 1100, to which the reaction liquid and ink have been applied and an image has been recorded, is heated by the heating device 2100 while being transported by the transport member 2200, thereby evaporating and drying the liquid components of the image. It is preferable to further include a drying step between the ink application step and the fixing step, in which the recording medium to which the ink has been applied is heated in a non-contact manner to dry the ink. By including such a drying step, deformation (cockling and curling) of the recording medium 1100 can be effectively suppressed.

[0077] The heating device 2100 may have any configuration as long as it can heat the recording medium 1100, and various conventionally known devices such as a hot air dryer and a heater can be used. Among them, the use of a non-contact heater such as an electric heating wire or infrared heater is preferable from the standpoint of safety and energy efficiency. In addition, if a mechanism for blowing hot air with a built-in fan for spraying heated gas onto the recording medium 1100 is used, the drying efficiency can be easily improved.

[0078] Regarding the method of heating, the recording medium 1100 may be heated from the side to which the reaction liquid and the ink are applied, or from the back side, or from both sides. The transport member 2200 may be provided with a heating function. Although the transport member 2200 in the form of a transport belt is shown in FIG. 1, a spur, a transport drum, or the like may be used as long as it has the function of transporting the recording medium 1100.

[0079] [Fixing section] As shown in FIG. 1, the fixing unit 3000 conveys the recording medium 1100 by the conveying member 3200, and also brings the fixing member 3100 into contact with the recording medium 1100 under pressure, thereby heating the liquid such as the reaction liquid or ink applied to the recording medium 1100. This allows an image to be fixed on the recording medium 1100. From the recording medium 1100 on which the image has been recorded, the liquid components of the reaction liquid or ink permeate the recording medium 1100 or evaporate by passing through the heating unit 2000, and then the image is fixed in the fixing unit 3000, completing the image. By applying heat and pressure to the recording medium 1100 sandwiched between the fixing member 3100 and the conveying member 3200, the image of the recording medium 1100 and the fixing member 3100 come into close contact with each other, and the image is fixed on the recording medium. When a liquid such as ink containing resin particles and coloring material is used, the resin particles are softened and formed into a film mainly by heating by the fixing unit 3000, and the coloring material can be bound onto the recording medium 1100.

[0080] The fixing member 3100 can be heated by providing a heat source such as a halogen heater inside a roller that drives the fixing member 3100 as a fixing belt. Alternatively, a heat source such as an infrared heater can be provided at a location separate from the fixing member 3100. Furthermore, these methods may be combined.

[0081] [Paper output section] After the image is recorded, the recording medium 1100 is stored in a paper discharge unit 4000 (FIG. 1). Specifically, the recording medium 1100 on which the image has been recorded is transported by a transport member 4100, and is finally stored in a stacked state in a recording medium storage unit 4200. Two or more recording medium storage units 4200 may be provided in order to store different recorded materials, respectively. EXAMPLES

[0082] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples without departing from the gist of the invention. "Parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0083] <Preparation of surfactant> A 10% aqueous solution of the surfactant shown in Table 1 was prepared. The surfactants indicated as "synthesized" were synthesized as follows. 5.5 moles of chlorosulfonic acid were added to a reaction vessel containing 5.0 moles of raw material alcohol having a structure corresponding to the hydrophobic portion. The mixture was stirred at 40°C for 40 minutes to react, synthesizing a sulfate ester compound. An aqueous solution of sodium hydroxide was added to neutralize the sulfate ester, and water was added to adjust the concentration, to obtain an aqueous solution of the anionic surfactant with an anionic surfactant content of 10%. Commercially available surfactants were also diluted with water to prepare 10% aqueous solutions.

[0084] TIFF2024076970000001.tif232170

[0085] <Preparation of reaction solution> The components (unit: %) shown in the upper rows of Tables 2-1 to 2-6 were mixed and thoroughly stirred, and then pressure filtered using a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare each reaction solution. In Tables 2-1 to 2-6, "Rupasol FG" is the trade name of branched polyethyleneimine manufactured by BASF. The numbers attached to polyethylene glycol are number average molecular weights. The numbers in parentheses for water-soluble organic solvents and water-soluble organic compounds are relative dielectric constants. The properties of the reaction solutions are shown in the lower rows of Tables 2-1 to 2-6.

[0086] TIFF2024076970000002.tif222170

[0087] TIFF2024076970000003.tif221170

[0088] TIFF2024076970000004.tif222170

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[0091] TIFF2024076970000007.tif255167

[0092] <Preparation of pigment dispersion> (Pigment dispersion 1) A styrene-ethyl acrylate-acrylic acid copolymer (resin 1) with an acid value of 150 mgKOH / g and a weight average molecular weight of 8,000 was prepared. 20.0 parts of resin 1 were neutralized with potassium hydroxide in an amount equimolar to the acid value, and an appropriate amount of pure water was added to prepare an aqueous solution of resin 1 with a resin (solid content) content of 20.00%. 20.0 parts of pigment (carbon black), 50.0 parts of the aqueous solution of resin 1, and 30.0 parts of ion-exchanged water were mixed to obtain a mixture. The obtained mixture was subjected to 50 passes of dispersion treatment at a pressure of 150 MPa using a Nanomizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.). After that, the mixture was centrifuged at a rotation speed of 5,000 rpm for 30 minutes to remove coarse particles. The mixture was filtered under pressure using a cellulose acetate filter (manufactured by Advantec) having a pore size of 3.0 μm to prepare Pigment Dispersion Liquid 1 having a pigment content of 20.00% and a resin dispersant (Resin 1) content of 10.00%.

[0093] (Pigment dispersion 2) The pigment was changed to CI Pigment Blue 15:3. Apart from this, Pigment Dispersion 2 was prepared in the same manner as Pigment Dispersion 1 described above, with a pigment (CI Pigment Blue 15:3) content of 10.00% and a resin dispersant (Resin 1) content of 3.00%.

[0094] (Pigment dispersion 3) The pigment was changed to a solid solution containing CI Pigment Violet 19 and CI Pigment Red 122. Other than this, Pigment Dispersion 3 was prepared in the same manner as Pigment Dispersion 1 described above, with a pigment (solid solution) content of 10.00% and a resin dispersant (Resin 1) content of 3.00%.

[0095] (Pigment Dispersion 4) The pigment was changed to CI Pigment Red 150. Other than this, Pigment Dispersion 4 was prepared in the same manner as Pigment Dispersion 1 described above, with a pigment (CI Pigment Red 150) content of 10.00% and a resin dispersant (Resin 1) content of 3.00%.

[0096] (Pigment Dispersion 5) The pigment was changed to CI Pigment Yellow 74. Other than this, Pigment Dispersion 5 was prepared in the same manner as Pigment Dispersion 1 described above, with a pigment (CI Pigment Yellow 74) content of 10.00% and a resin dispersant (Resin 1) content of 3.00%.

[0097] (Pigment Dispersion 6) A solution of 5.0 g of concentrated hydrochloric acid in 5.5 g of water was cooled to 5°C, and 1.5 g of 4-aminophthalic acid was added. The container containing this solution was placed in an ice bath, and while stirring to keep the temperature of the solution below 10°C, a solution obtained by dissolving 0.9 g of sodium nitrite in 9.0 g of ion-exchanged water at 5°C was added. After stirring for 15 minutes, 6.0 g of carbon black was added under stirring, and the mixture was stirred for another 15 minutes to obtain a slurry. The obtained slurry was filtered with filter paper (product name "Standard Filter Paper No. 2", Advantec), the particles were thoroughly washed with water, and dried in an oven at 110°C. Thereafter, sodium ions were replaced with potassium ions by ion exchange to obtain a self-dispersing pigment in which -C6H3-(COOK)2 groups were bonded to the pigment particle surface. An appropriate amount of pure water was added to adjust the pigment content, and a pigment dispersion liquid 6 with a pigment content of 20.00% was obtained.

[0098] <Preparation of resin particles> (Resin particles) In a four-neck flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 74.0 parts of ion-exchanged water and 0.2 parts of potassium persulfate were mixed. In addition, 24.0 parts of ethyl methacrylate, 1.5 parts of methacrylic acid, and 0.3 parts of a reactive surfactant (trade name "ADEKA REASOAP ER-20", manufactured by ADEKA) were mixed to prepare an emulsion. Under a nitrogen atmosphere, the prepared emulsion was dropped into the four-neck flask over 1 hour, and a polymerization reaction was carried out for 2 hours while stirring at 80°C. After cooling to 25°C, ion-exchanged water and an aqueous solution containing potassium hydroxide in an amount equimolar to the acid value of the resin particles were added to prepare an aqueous dispersion of resin particles with a resin particle (solid content) content of 25.00%.

[0099] <Ink Preparation> The components (unit: %) shown in Table 3 were mixed and thoroughly stirred, and then pressure filtered through a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare each ink. In Table 3, "Surfynol 465" is the trade name of a surfactant (ethylene oxide adduct of acetylene glycol) manufactured by Nissin Chemical Industry Co., Ltd. Also, "NIKKOL BL-4.2" is the trade name of a surfactant (polyoxyethylene lauryl ether, 4.2 moles of ethylene oxide group added) manufactured by Nikko Chemicals.

[0100] TIFF2024076970000008.tif117170

[0101] <Evaluation> The reaction liquid and ink combinations shown in Table 4 were filled into the reaction liquid deposition device 1201 and the ink deposition device 1202 of the inkjet recording device 100 having the configuration shown in FIG. 1. In this inkjet recording device 100, an image recorded under the condition that one ink droplet of 3.0 ng is deposited in a unit area of ​​1 / 1,200 inch x 1 / 1,200 inch is defined as having a recording duty of 100%. Coated paper (product name "OK Topcoat+, manufactured by Oji Paper Co., Ltd.") was used as the recording medium. In the present invention, the evaluation criteria for each item below were "AAA", "AA", "A", and "B" as acceptable levels, and "C" as unacceptable level. The evaluation results are shown in Table 4.

[0102] (Image quality) Using the inkjet recording device 100 having the above configuration, 10 solid images of 20 cm x 20 cm were recorded on a recording medium, with the reaction liquid recording duty being 15% and the ink recording duty being 100%. The recorded solid images were visually observed, and the image quality was evaluated according to the following evaluation criteria. A: Of 10 solid images, shading was observed in part of the image on one sheet. B: Of the 10 solid images, shading was observed in parts of the image on 2 sheets. C: Of 10 solid images, shading was observed in parts of the image on 3 or more images.

[0103] (Intermittent discharge stability) Using the inkjet recording device 100 having the above configuration, a 5 cm x 20 cm solid image was recorded on a recording medium (reference image) with a reaction liquid recording duty of 15% and an ink recording duty of 100%. After a predetermined rest period, a solid image was recorded on the recording medium under the same conditions as the reference image (evaluation image).

[0104] The two types of images recorded were scanned with a scanner (product name "DR-C225II", manufactured by Canon) in a 3 cm wide area from the recording start position, and the solid image was binarized to calculate the area ratio (%) of the part recorded according to the input data (dark part of the image). The reading conditions were color and 600 dpi. The binarization process was performed by converting the image to 8-bit using the image processing software "ImageJ", and then setting the value of [(255+Gtop) / 2] as the threshold value for the gradation value (Gtop) at the peak of the brightness histogram at white 255 / black 0. From the area above the threshold thus obtained, the ratio (area ratio) was calculated, and an area ratio of 99.0% or more was judged to be "no image unevenness due to a decrease in intermittent ejection stability". The intermittent ejection stability of the reaction liquid was evaluated according to the following evaluation criteria from the ejection pause time at which image unevenness occurred in the evaluation image.

[0105] AAA: Even after a 240-second pause, the area ratio was 99.5% or more, and no image unevenness occurred. AA: Even after a 240-second pause, the area ratio was 99.0% or more and less than 99.5%, and no image unevenness occurred. A: The ejection pause time during which image unevenness occurred was 120 seconds or more and less than 240 seconds. B: The ejection pause time during which image unevenness occurred was 60 seconds or more and less than 120 seconds. C: The ejection pause time during which image unevenness occurred was less than 60 seconds.

[0106] (Discharge stability) Using the inkjet recording device 100 having the above configuration, 1,000 solid images of 5 cm x 20 cm were recorded on a recording medium, with the reaction liquid recording duty being 15% and the ink recording duty being 100%. For the first and 1,000th recorded images, the center of the solid image was read with a scanner (product name "DR-C225II", manufactured by Canon), the solid image was binarized, and the area ratio (%) of the part recorded according to the input data (dark part of the image) was calculated. The reading conditions were color and 600 dpi. The binarization process was performed by converting the image to 8-bit using the image processing software "ImageJ", and then setting the value of [(255 + Gtop) / 2] as the threshold value for the gradation value (Gtop) at the peak of the brightness histogram at white 255 / black 0. From the area above the threshold value thus obtained, the proportion (area rate) was calculated, and the ratio of the area rates in the first and 1,000th printed sheets (1,000th sheet / 1st sheet) was calculated, and the ejection stability of the reaction liquid was evaluated according to the evaluation criteria shown below. A: The "area ratio" was 0.990 or more. B: The "area ratio" was less than 0.990.

[0107] TIFF2024076970000009.tif227170

[0108] Comparing the intermittent ejection stability of Examples 1 and 10, Example 1 was relatively superior. In addition, the following evaluation was performed using the reaction liquids of Examples 38, 42, and 43 and the ink 1. Using the inkjet recording device 100 having the above configuration, a solid image was recorded on the entire surface of an A4-sized recording medium, with the reaction liquid having a recording duty of 15% and the ink having a recording duty of 100%. The obtained recorded matter was placed in an environment of a temperature of 25° C. and a relative humidity of 50% for 24 hours, and then the deformation (curl state) of the end of the recording medium was visually confirmed. As a result, the curl of the recording medium was relatively suppressed in the recorded matter obtained using the reaction liquids of Examples 42 and 43 containing the “water-soluble hydrocarbon compound” compared to the recorded matter obtained using the reaction liquid of Example 38 not containing the “water-soluble hydrocarbon compound”.

[0109] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) An inkjet reaction liquid used in an inkjet recording method for recording an image on a recording medium using an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink, comprising: The reaction liquid contains a polyvalent metal salt and a surfactant, the surfactant is a compound having a hydrophilic moiety containing an anionic group and a hydrophobic moiety which is an aliphatic hydrocarbon group, The reaction liquid, wherein the content (mass %) of the polyvalent metal salt in the reaction liquid is 10.0 to 35.0 times the content (mass %) of the surfactant in terms of mass ratio. (Configuration 2) The reaction liquid according to Configuration 1, wherein the content (mass %) of the polyvalent metal salt in the reaction liquid is 10.0 to 20.0 times the content (mass %) of the surfactant in the reaction liquid. (Configuration 3) The reaction solution according to configuration 1 or 2, wherein the polyvalent metal salt is a sulfate of a polyvalent metal. (Configuration 4) The reaction solution according to any one of Configurations 1 to 3, wherein the polyvalent metal salt is a magnesium salt. (Configuration 5) The reaction liquid according to any one of claims 1 to 4, wherein the anionic group is a sulfonic acid group or a sulfate ester group. (Configuration 6) The reaction solution according to any one of Configurations 1 to 4, wherein the anionic group is a sulfate ester group. (Configuration 7) The reaction solution according to any one of Configurations 1 to 6, wherein the aliphatic hydrocarbon group is an alkyl group having 6 to 16 carbon atoms. (Configuration 8) The reaction solution according to any one of Configurations 1 to 7, wherein the aliphatic hydrocarbon group is an alkyl group having a branched structure. (Configuration 9) The reaction liquid according to any one of Configurations 1 to 8, further comprising a first water-soluble organic solvent having a relative dielectric constant of 35 or more and 110 or less. (Configuration 10) The reaction liquid according to Configuration 9, wherein the content (mass %) of the first water-soluble organic solvent in the reaction liquid is 10.00 mass % or more and 30.00 mass % or less based on the total mass of the reaction liquid. (Method 1) An inkjet recording method for recording an image on a recording medium using an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink, comprising the steps of: a reaction liquid applying step of applying the reaction liquid to the recording medium; an ink applying step of applying the water-based ink to the recording medium so as to overlap at least a portion of an area of ​​the recording medium to which the reaction liquid has been applied, 11. An ink-jet recording method, wherein the reaction liquid is the reaction liquid described in any one of Configurations 1 to 10.

Claims

1. An inkjet reaction solution used in an inkjet recording method, which involves ejecting an aqueous ink and an aqueous reaction solution containing a reactant that reacts with the aqueous ink from an inkjet recording head and applying them to a recording medium to record an image, The reaction solution contains a polyvalent metal salt and a surfactant, The surfactant is a compound having a hydrophilic moiety containing an anionic group and a hydrophobic moiety that is an aliphatic hydrocarbon group. The reaction solution is characterized in that the content (mass%) of the polyvalent metal salt in the reaction solution is 10.0 times or more and 35.0 times or less in mass ratio to the content (mass%) of the surfactant.

2. The reaction solution according to claim 1, wherein the content (mass%) of the polyvalent metal salt in the reaction solution is 10.0 times or more and 20.0 times or less in mass ratio to the content (mass%) of the surfactant.

3. The reaction solution according to claim 1, wherein the polyvalent metal salt is a sulfate of a polyvalent metal.

4. The reaction solution according to claim 1, wherein the polyvalent metal salt is a magnesium salt.

5. The reaction solution according to claim 1, wherein the polyvalent metal salt is at least one selected from the group consisting of magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium chloride, aluminum sulfate, calcium nitrate, and calcium chloride.

6. The reaction solution according to claim 1, wherein the polyvalent metal salt is magnesium sulfate.

7. The reaction solution according to claim 1, wherein the anionic group is a sulfonic acid group or a sulfate ester group.

8. The reaction solution according to claim 1, wherein the anionic group is a sulfate ester group.

9. The reaction solution according to claim 1, wherein the aliphatic hydrocarbon group is an alkyl group having 6 to 16 carbon atoms.

10. The reaction solution according to claim 1, wherein the aliphatic hydrocarbon group is an alkyl group having a branched structure.

11. The reaction solution according to claim 1, wherein the surfactant is an alkyl sulfate ester.

12. The reaction solution according to claim 1, further comprising a first water-soluble organic solvent having a relative dielectric constant of 35 to 110.

13. The reaction solution according to claim 12, wherein the content (by mass) of the first water-soluble organic solvent in the reaction solution is 10.00% by mass or more and 30.00% by mass or less, based on the total mass of the reaction solution.

14. The reaction solution according to claim 12, wherein the first water-soluble organic solvent is at least one selected from the group consisting of 1-(2-hydroxyethyl)-2-pyrrolidone, glycerin, trehalose, xylitol, sorbitol, and urea.

15. The reaction solution according to claim 1, wherein the content (mass%) of the polyvalent metal salt in the reaction solution is 1.00% by mass or more and 20.00% by mass or less, based on the total mass of the reaction solution.

16. The reaction solution according to claim 1, wherein the content (mass%) of the surfactant in the reaction solution is 0.20% by mass or more and 3.00% by mass or less, based on the total mass of the reaction solution.

17. An inkjet recording method for recording an image on a recording medium using an aqueous reaction solution containing an aqueous ink and a reactant that reacts with the aqueous ink, A reaction solution application step in which the reaction solution is dispensed onto the recording medium from an inkjet recording head, The process includes an ink application step of applying the aqueous ink to the recording medium by ejecting it from an inkjet recording head so as to overlap with at least a portion of the area of ​​the recording medium to which the reaction solution has been applied, An inkjet recording method characterized in that the reaction solution is the reaction solution described in any one of claims 1 to 16.

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