Processing solution, ink set, and recording method

Abstract

The present invention provides a processing solution that can suppress curling of recorded material on absorbent recording media, even when used with ink. [Solution] A processing liquid used for recording on an absorbent recording medium together with an inkjet ink composition containing a colorant, comprising a flocculant and a sugar alcohol that is solid at room temperature, wherein a 50% by mass aqueous solution of the sugar alcohol that is solid at room temperature contained in the processing liquid has a mass change rate (after / before) of 120% or less when left at 25°C and 95% RH for 7 days.

Description

[Technical Field]

[0001] The present invention relates to a processing solution, an ink set, and a recording method. [Background technology]

[0002] Inkjet recording methods enable the recording of high-resolution images and are undergoing rapid development in various fields. To date, a wide range of studies have been conducted, not only on the development of inks used in inkjet technology, but also on recording devices and recording methods. For example, Patent Document 1 describes the use of a processing solution with the intention of improving the color development of an inkjet ink composition. The same document states that the suppression of the penetration of the inkjet ink composition into the recording medium by the processing solution is one of the reasons for the improved color development. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-068306 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, when a processing solution is used, the water contained in the solution adheres to the recording medium. This can cause the recording medium to curl due to the water in the processing solution. Furthermore, when the processing solution is used together with the ink, the amount of water adhering to the recording medium increases, which can lead to increased curling of the recorded material, especially in the case of absorbent recording media. [Means for solving the problem]

[0005] One embodiment of the processing solution according to the present invention is: A water-based processing solution used for recording onto an absorbent recording medium, together with an inkjet ink composition containing a colorant, It contains a flocculant and a sugar alcohol that is solid at room temperature. The 50% by mass aqueous solution of the sugar alcohol, which is solid at room temperature, contained in the processing solution, exhibits a mass change rate (after / before standing) of 120% or less when left standing at 25°C and 95% RH for 7 days.

[0006] One embodiment of the ink set according to the present invention is: The present invention comprises the processing solution and inkjet ink composition described above.

[0007] One aspect of the recording method according to the present invention is: This is carried out using the processing solution and inkjet ink composition described above. A processing liquid application step in which the processing liquid is applied to a recording medium which is an absorbent recording medium, The process includes an ink application step of ejecting the inkjet ink composition from an inkjet head and adhering it to the recording medium. [Brief explanation of the drawing]

[0008] [Figure 1] A conceptual diagram explaining primary curl. [Figure 2] A conceptual diagram explaining secondary curl. [Figure 3] A schematic cross-sectional view of a recording device that can be used in the recording method according to this embodiment. [Figure 4] Table 1 shows the composition of the treatment solution and the evaluation results of the examples. [Figure 5] Table 2 shows the treatment solution composition and evaluation results for the examples and comparative examples. [Modes for carrying out the invention]

[0009] Embodiments of the present invention are described below. The embodiments described below illustrate examples of the present invention. The present invention is not limited in any way to the embodiments described below and includes various modifications that are implemented without changing the gist of the present invention. Not all of the configurations described below are necessarily essential to the present invention.

[0010] 1. Processing liquid The treatment liquid according to this embodiment is an aqueous treatment liquid used for recording on a recording medium, which is an absorbent recording medium, together with an inkjet ink composition containing a coloring material. Further, the treatment liquid according to this embodiment contains a flocculant and a sugar alcohol that is solid in its single form at normal temperature. And, when a 50% by mass aqueous solution of the sugar alcohol that is solid in its single form at normal temperature contained in the treatment liquid is left standing at 25°C and 95% RH for 7 days, the mass change rate (after standing / before standing) is 120% or less. The inkjet ink composition containing a coloring material will be described later.

[0011] 1.1. Flocculant The treatment liquid contains a flocculant that aggregates the components of an inkjet ink composition (ink). The flocculant has the effect of aggregating coloring materials and resin particles by reacting with components such as the coloring materials contained in the ink and the resin particles that may be contained in the ink. Note that the degree of aggregation of the coloring materials and resin particles by the flocculant varies depending on the types of the flocculant, coloring material, and resin particles, and can be adjusted. Further, the flocculant can aggregate the coloring materials and resin particles by reacting with the coloring materials and resin particles contained in the ink. By such aggregation, for example, the color development of the coloring material can be enhanced, the fixing property of the resin particles can be enhanced, and / or the viscosity of the ink can be enhanced.

[0012] The flocculant is not particularly limited, and examples thereof include metal salts, inorganic acids, organic acids, cationic compounds, etc. As the cationic compound, a cationic resin (cationic polymer), a cationic surfactant, etc. can be used. Among these, polyvalent metal salts are preferred as the metal salts.

[0013] A polyvalent metal salt is a compound composed of a metal ion with two or more valencies and an anion. Examples of metal ions with two or more valencies include calcium, magnesium, copper, nickel, zinc, barium, aluminum, titanium, strontium, chromium, cobalt, and iron. Among the metal ions that make up these polyvalent metal salts, it is preferable that at least one of calcium ions and magnesium ions is present, given its excellent ability to aggregate the ink components. In other words, it is preferable that the polyvalent metal salt is at least one of a calcium salt and a magnesium salt, and more preferably a calcium salt.

[0014] The anions constituting the polyvalent metal salt are inorganic ions or organic ions. That is, the polyvalent metal salt in this invention consists of an inorganic ion or organic ion and a polyvalent metal. Examples of such inorganic ions include chloride ions, bromide ions, iodide ions, nitrate ions, sulfate ions, hydroxide ions, etc. Examples of organic ions include organic acid ions, such as carboxylate ions. The polyvalent metal salt is more preferably an inorganic salt, for example, calcium nitrate, magnesium sulfate, etc., and even more preferably calcium nitrate. Using a polyvalent metal salt can further improve the color development of the inkjet ink composition used together.

[0015] Furthermore, the polyvalent metal compound is preferably an ionic polyvalent metal salt, and in particular, when the polyvalent metal salt is a magnesium salt or a calcium salt, the stability of the treatment solution is better, which is preferable. Calcium salts are especially preferred. In addition, either an inorganic acid ion or an organic acid ion may be used as the counterion for the polyvalent metal.

[0016] Specific examples of the polyvalent metal salts mentioned above include calcium carbonate (heavy calcium carbonate and light calcium carbonate), calcium nitrate, calcium chloride, calcium sulfate, magnesium sulfate, calcium hydroxide, magnesium chloride, magnesium carbonate, barium sulfate, barium chloride, zinc carbonate, zinc sulfide, aluminum silicate, calcium silicate, magnesium silicate, copper nitrate, calcium formate, calcium acetate, magnesium acetate, and aluminum acetate. These polyvalent metal salts may be used individually or in combination of two or more.

[0017] Among these, at least one of calcium formate, magnesium sulfate, calcium nitrate, and calcium chloride is preferred because it ensures sufficient solubility in water and reduces residue left by the treatment solution (making the residue less noticeable), with calcium formate and calcium nitrate being more preferred. These metal salts may also contain water of hydration in their raw material form.

[0018] Examples of metal salts other than polyvalent metal salts include monovalent metal salts such as sodium salts and potassium salts, such as sodium sulfate and potassium sulfate.

[0019] Suitable organic acids include, for example, poly(meth)acrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphate, pyrrolidone carboxylic acid, pyrrone carboxylic acid, pyrrole carboxylic acid, furanic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, or derivatives of these compounds, or salts thereof. Organic acids may be used individually or in combination of two or more. Salts of organic acids that are metal salts are included in the above-mentioned metal salts.

[0020] Examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. Inorganic acids may be used individually or in combination of two or more.

[0021] Examples of cationic resins (cationic polymers) include cationic urethane resins, cationic olefin resins, and cationic amine resins. Cationic polymers are preferably water-soluble.

[0022] As cationic urethane resins, commercially available products can be used, such as Hydran CP-7010, CP-7020, CP-7030, CP-7040, CP-7050, CP-7060, CP-7610 (product names, manufactured by Dainippon Ink and Chemicals, Inc.), Superflex 600, 610, 620, 630, 640, 650 (product names, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and Urethane Emulsion WBR-2120C, WBR-2122C (product names, manufactured by Taisei Fine Chemical Co., Ltd.).

[0023] Cationic olefin resins have olefins such as ethylene and propylene as their structural framework, and known ones can be appropriately selected and used. Cationic olefin resins may also be in an emulsion state dispersed in a solvent such as water or an organic solvent. Commercially available cationic olefin resins can be used, such as Arrowbase CB-1200 and CD-1200 (trade names, manufactured by Unitika Ltd.).

[0024] As cationic amine resins (cationic polymers), any resin having an amino group in its structure is acceptable, and known resins can be appropriately selected and used. Examples include polyamine resins, polyamide resins, and polyallylamine resins. Polyamine resins are resins This is a resin that has amino groups in the main structure of the lipid. Polyamide resins are resins that have amide groups in the main structure of the resin. Polyallylamine resins are resins that have a structure derived from allyl groups in the main structure of the resin.

[0025] Furthermore, examples of cationic polyamine resins include Unisense KHE103L (hexamethylenediamine / epichlorohydrin resin, 1% aqueous solution with a pH of approximately 5.0, viscosity of 20-50 (mPa·s), and solid content of 50% by mass) and Unisense KHE104L (dimethylamine / epichlorohydrin resin, 1% aqueous solution with a pH of approximately 7.0, viscosity of 1-10 (mPa·s), and solid content of 20% by mass) manufactured by Senka Co., Ltd. Furthermore, specific examples of commercially available cationic polyamine resins include FL-14 (manufactured by SNF), Arafix 100, 251S, 255, 255LOX (manufactured by Arakawa Chemical Co., Ltd.), DK-6810, 6853, 6885; WS-4010, 4011, 4020, 4024, 4027, 4030 (manufactured by Seikou PMC Co., Ltd.), and Papiogen P-105 (manufactured by Senka Co., Ltd.). Examples include Sumirez Resin 650(30), 675A, 6615, SLX-1 (manufactured by Taoka Chemical Industry Co., Ltd.), Kachiomaster (registered trademark) PD-1, 7, 30, A, PDT-2, PE-10, PE-30, DT-EH, EPA-SK01, TMHMDA-E (manufactured by Yokkaichi Gosei Co., Ltd.), and Jetfix 36N, 38A, 5052 (manufactured by Satoda Chemical Co., Ltd.).

[0026] Polyamine resins can also be cited as examples of polyamine-based resins. Examples of polyamine resins include polyallylamine hydrochloride, polyallylamineamide sulfate, allylamine hydrochloride / diallylamine hydrochloride copolymer, allylamine acetate / diallylamine acetate copolymer, allylamine acetate / diallylamine acetate copolymer, allylamine hydrochloride / dimethylallylamine hydrochloride copolymer, allylamine / dimethylallylamine copolymer, polydiallylamine hydrochloride, polymethyldiallylamine hydrochloride, polymethyldiallylamineamide sulfate, polymethyldiallylamine acetate, polydiallyldimethylammonium chloride, diallylamine acetate / sulfur dioxide copolymer, diallylmethylethylammonium ethyl sulfate / sulfur dioxide copolymer, methyldiallylamine hydrochloride / sulfur dioxide copolymer, diallyldimethylammonium chloride / sulfur dioxide copolymer, and diallyldimethylammonium chloride / acrylamide copolymer.

[0027] Multiple types of flocculants may be used. Furthermore, selecting at least one of these flocculants—a polyvalent metal salt, an organic acid, or a cationic resin—results in better flocculation, thus enabling the formation of higher-quality images (particularly those with good color development). It is more preferable to use a polyvalent metal salt as the flocculant, and even more preferable to use a calcium salt. This further improves the image quality of the resulting images.

[0028] The total content of the flocculant in the treatment solution is, for example, 0.1% by mass or more and 25% by mass or less, preferably 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less, based on the total mass of the treatment solution. Alternatively, 2 to 20% by mass is preferred, 5 to 20% by mass is more preferred, and 8 to 20% by mass is even more preferred.

[0029] Furthermore, even when the coagulant is shared in a solution or dispersion, it is preferable that the solid content is within the above range. If the coagulant content is above the above range, the coagulant will have sufficient ability to coagulate the components contained in the ink. Also, if the coagulant content is below the above range, the solubility and dispersibility of the coagulant in the treatment solution will be better, and the storage stability of the treatment solution can be improved.

[0030] 1.2. Sugar alcohols The processing solution of this embodiment contains a sugar alcohol that is solid at room temperature. Here, "room temperature" means This refers to a temperature of 25°C. Furthermore, "elementary form" refers to the sugar alcohol existing alone, rather than in a solution such as an aqueous solution. Sugar alcohols are sugars produced by the reduction of the carbonyl group of aldoses and ketoses.

[0031] The sugar alcohol may be a chain-like sugar alcohol or a cyclic sugar alcohol. Examples of sugar alcohols include erythulitol, inositol, mannitol, xylitol, sorbitol, lactitol, and glycerin. However, the sugar alcohol contained in the processing solution of this embodiment is a sugar alcohol that is solid at room temperature. Therefore, for example, glycerin is a type of sugar alcohol, but it does not belong to the category of sugar alcohols that are solid at room temperature.

[0032] Furthermore, the sugar alcohols that are solid at room temperature and contained in the processing solution of this embodiment are selected from among these to have the following properties. That is, the sugar alcohols that are solid at room temperature and contained in the processing solution of this embodiment are characterized by the hygroscopicity or moisture retention of their 50% by mass aqueous solution.

[0033] The 50% by mass aqueous solution of a sugar alcohol, which is solid at room temperature and contained in the processing solution of this embodiment, exhibits a mass change rate (after / before) of 120% or less when left at 25°C and 95% RH for 7 days. The mass change rate (%) = mass after / before × 100. The mass change rate is also called the moisture retention coefficient.

[0034] The processing solution of this embodiment may contain multiple types of sugar alcohols that are solid at room temperature. If it contains multiple types of sugar alcohols that are solid at room temperature, all of the sugar alcohols contained in the processing solution are considered as a mixture in the mass ratio contained in the processing solution, and a 50% by mass aqueous solution of this mixture satisfies the above-mentioned rate of mass change.

[0035] The container used for the standing experiment should be one in which the surface area of ​​a 50% by mass aqueous solution of sugar alcohol, which is solid at room temperature, is in a predetermined state. For example, a Neo Mini Cup No. 5 manufactured by Maruemu Co., Ltd. (capacity 5 ml, inner diameter of the mouth without a flange 25.2 mm) should be used. In addition, 1 ml of the 50% by mass aqueous solution of sugar alcohol should be placed in the container before standing. The mass after standing for 7 days at 25°C and 95% RH (mass of the aqueous solution) should be divided by the mass before standing (mass of the aqueous solution) to determine the mass change rate (%). Note that even if the sugar alcohol is a mixture of multiple types of sugar alcohol, the mass change rate should be measured in the same manner as above.

[0036] Figure 1 is a conceptual diagram illustrating primary curl. Figure 2 is a conceptual diagram illustrating secondary curl.

[0037] As shown on the left of Figure 1, when a processing solution or inkjet ink composition adheres to the fibers of a recording medium, the hydrogen bonds between the cellulose molecules that make up the fibers are broken by water or solvent molecules. In the areas where the hydrogen bonds are broken, the fibers swell, generating stress that deforms the fibers. It is thought that primary curl occurs through this mechanism. Then, as shown on the right of Figure 1, when the breaking of hydrogen bonds between fibers becomes saturated, the generation of stress subsides, the primary curl converges, and it is thought that the fibers remain swollen because drying has not progressed at this point and water or solvent remains inhibiting the hydrogen bonds between the cellulose molecules.

[0038] On the other hand, as shown on the left of Figure 2, as the processing solution and inkjet ink composition dry and water and solvent evaporate from the swollen fibers, it is thought that hydrogen bonds begin to form again between the fibers (cellulose). Then, as the solvent evaporates further and hydrogen bonds between the fibers begin to form again, as shown on the left of Figure 2, it is thought that the reformed hydrogen bonds occur in a disordered manner. These reformed hydrogen bonds adhere to the processing solution and inkjet ink composition. It is thought that the curl forms in a position different from the original state before attachment. This is thought to create a state where stress is applied to the recording medium in a partial manner, resulting in secondary curling.

[0039] The processing solution of this embodiment contains sugar alcohols that are solid at room temperature and have a mass change rate of 120% or less. Therefore, when the processing solution adheres to an absorbent recording medium, it is easier to evaporate moisture and suppress primary curling compared to cases where the mass change rate exceeds 120%. Furthermore, because the processing solution of this embodiment contains sugar alcohols that are solid at room temperature, when the processing solution adheres to an absorbent recording medium and dries, it is easier to inhibit the reformation of hydrogen bonds in the fibers and suppress secondary curling.

[0040] In this embodiment, a 50% by mass aqueous solution of a sugar alcohol that is solid at room temperature, contained in the processing liquid, is left at 25°C and 95% RH for 7 days. The mass change rate (after / before) is 120% or less. From the above viewpoint, a mass change rate of 110% or less is more preferable, 100% or less is even more preferable, and 90% or less is even more preferable. On the other hand, 80% or more is preferable, 90% or more is even more preferable, 100% or more is even more preferable, and 110% or more is even more preferable. Furthermore, if the value is below the above range, curl suppression is better and preferable. If the value is above the above range, discharge stability is better and preferable.

[0041] The total content of the above-mentioned sugar alcohols, which are solid at room temperature, in the processing solution is, for example, 0.5% by mass or more relative to the total volume of the processing solution. More preferably, it is 0.5% by mass or more and 10% by mass or less, 0.5% by mass or more and 7% by mass or less, 1% by mass or more and 5% by mass or less, and more preferably 2% by mass or more and 4% by mass or less.

[0042] 1.3.Water The processing solution according to this embodiment is an aqueous-based processing solution containing water. An aqueous-based solution is a composition that contains water as one of its main solvent components. In this way, it is possible to perform recording with reduced environmental impact and less odor.

[0043] Water may be included as the main solvent component of the treatment solution and is a component that evaporates and dissipates upon drying. Preferably, the water is pure water or ultrapure water from which ionic impurities have been removed as much as possible, such as ion-exchanged water, ultrafiltered water, reverse osmosis water, or distilled water. Furthermore, using water sterilized by ultraviolet irradiation or hydrogen peroxide addition is preferable because it can suppress the growth of mold and bacteria when the treatment solution is stored for a long period of time. The water content is preferably 45% by mass or more of the total amount of the treatment solution. The upper limit is, for example, 99% by mass or less. More preferably, it is 50% by mass or more and 98% by mass or less, and even more preferably 55% by mass or more and 95% by mass or less.

[0044] 1.4. Other ingredients (1) Surfactants The processing solution according to this embodiment may contain a surfactant. The surfactant is not particularly limited, but examples include acetylene glycol-based surfactants, fluorine-based surfactants, and silicone-based surfactants. The surfactant has the function of adjusting the surface tension of the processing solution and adjusting, for example, the wettability with the recording medium.

[0045] Acetylene glycol-based surfactants are not particularly limited, but examples include Surfinol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA, DF110D (all of the above are product names, manufactured by Air Products Japan Co., Ltd.), Olfin B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP.4001, EXP.4036, EXP.4 Examples include 051, AF-103, AF-104, AK-02, SK-14, AE-3 (all product names, manufactured by Nisshin Chemical Industry Co., Ltd.), and acetylenol E00, E00P, E40, E100 (all product names, manufactured by Kawaken Fine Chemical Co., Ltd.).

[0046] As the fluorine-based surfactant, it is preferable to use a fluorine-modified polymer, and a specific example is BYK-340 (trade name, manufactured by BYK-Chemie Japan Co., Ltd.).

[0047] While not particularly limited, polysiloxane compounds are preferred as silicone-based surfactants. Examples of such polysiloxane compounds include polyether-modified organosiloxanes. Examples of commercially available polyether-modified organosiloxanes include BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-348 (all product names, manufactured by Bic Chemie Japan Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (all product names, manufactured by Shin-Etsu Chemical Co., Ltd.), Silface SAG503A, Silface SAG014 (both product names, manufactured by Nisshin Chemical Industry Co., Ltd.).

[0048] The above-mentioned surfactants may be used individually or in combination of two or more. When surfactants are included, it is preferable that their total content be 0.1% by mass or more and 1.5% by mass or less, relative to the total mass of the inkjet ink composition.

[0049] (2) Resin particles The processing solution may contain resin particles. Resin particles can sometimes further improve the adhesion of images to the recording medium using ink. Examples of resin particles include urethane resins, acrylic resins (including styrene-acrylic resins), fluorene resins, polyolefin resins, rosin-modified resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymers, and ethylene vinyl acetate resins. Among these, urethane resins, acrylic resins, polyolefin resins, and polyester resins are preferred. These resin particles are often handled in emulsion form, but they may also be in powder form. Furthermore, the resin particles can be used individually or in combination of two or more types.

[0050] The glass transition temperature (Tg) of the resin particles is preferably between -50°C and 200°C, more preferably between 0°C and 150°C, and even more preferably between 50°C and 100°C. A temperature between 50°C and 80°C is particularly preferred. When the glass transition temperature (Tg) of the resin particles is within the above range, the durability and resistance to clogging tend to be superior. The glass transition temperature is measured, for example, using a differential scanning calorimeter "DSC7000" manufactured by Hitachi High-Tech Science Corporation, in accordance with JIS K7121 (Method for measuring the transition temperature of plastics).

[0051] The volume-average particle diameter of the resin particles is preferably 10 nm to 300 nm, more preferably 30 nm to 300 nm, even more preferably 30 nm to 250 nm, and particularly preferably 40 nm to 220 nm. The volume-average particle diameter can be measured by the method described above.

[0052] The resin of the resin particles preferably has an acid value of 50 mgKOH / g or less, more preferably 30 mgKOH / g or less, even more preferably 20 mgKOH / g or less, and particularly preferably 10 mgKOH / g or less. The lower limit of the acid value is 0 mgKOH / g or more, and 5 mgKOH / g The above is preferable, and 10 mg KOH / g or more is more preferable. Furthermore, 15 mg KOH / g or more is preferable. In this case, image quality and other properties are excellent and therefore preferable. Also, when the acid value of the resin particles contained in the ink is above the above range, it is easier to make the viscosity of the ink composition of the ink described later above, which is preferable. The acid value can be measured by the method described above.

[0053] The resin particle content of the processing liquid is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 1% by mass or less, and particularly desirable if 0.1% by mass or less, or it may not be included at all. On the other hand, if it is included, it is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more.

[0054] The resin particle content of the ink is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even better 3% by mass or more, as solid content relative to the total mass of the ink. Furthermore, it is preferably 20% by mass or less, more preferably 10% by mass or less, and even better 8% by mass or less.

[0055] (3) Organic solvents The processing solution according to this embodiment may contain an organic solvent. The organic solvent is preferably water-soluble. One function of the organic solvent is to improve the wettability of the processing solution to the recording medium and to enhance the moisture retention of the processing solution. Furthermore, the organic solvent can also function as a humectant and a penetrating agent.

[0056] Examples of organic solvents include esters, alkylene glycol ethers, cyclic esters, nitrogen-containing solvents, and polyhydric alcohols. Examples of nitrogen-containing solvents include cyclic amides and acyclic amides. Examples of acyclic amides include alkoxyalkylamides.

[0057] Examples of esters include glycol monoacetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, and ethylene glycol monobutyl ether acetate, as well as glycol diesters such as ethylene glycol diacetate, diethylene glycol diacetate, and propylene glycol diacetate.

[0058] The alkylene glycol ethers can be any monoether or diether of alkylene glycol, with alkyl ethers being preferred. Specific examples include alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, and diethylene glycol monomethyl ether, and alkylene glycol dialkyl ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether.

[0059] Examples of cyclic esters include cyclic esters (lactones) such as β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, and β-butyrolactone, as well as compounds in which the hydrogen atoms of the methylene group adjacent to the carbonyl group are substituted with alkyl groups having 1 to 4 carbon atoms.

[0060] Examples of alkoxyalkylamides include 3-methoxy-N,N-dimethylpropionamide, 3-methoxy-N,N-diethylpropionamide, 3-methoxy-N,N-methylethylpropionamide, and 3-ethoxy-N,N-dimethylpropionamide. Examples include 3-ethoxy-N,N-diethylpropionamide, 3-ethoxy-N,N-methylethylpropionamide, 3-n-butoxy-N,N-dimethylpropionamide, 3-n-butoxy-N,N-diethylpropionamide, and 3-n-butoxy-N,N-methylethylpropionamide.

[0061] Examples of cyclic amides include lactams, such as pyrrolidones including 2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, 1-propyl-2-pyrrolidone, and 1-butyl-2-pyrrolidone. These are preferred in terms of their solubility for flocculants and their ability to promote the film formation of resin particles, as described later, with 2-pyrrolidone being particularly preferred.

[0062] Furthermore, it is also preferable to use compounds represented by the following general formula (1) as alkoxyalkylamides.

[0063] R 1 -O-CH2CH2-(C=O)-NR 2 R 3 ...(1)

[0064] In the above equation (1), R 1 R represents an alkyl group having 1 to 4 carbon atoms. 2 and R 3 Each independently represents either a methyl group or an ethyl group. The "alkyl group having 1 to 4 carbon atoms" can be a linear or branched alkyl group, for example, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, or a tert-butyl group. The compound represented by formula (1) above may be used alone or as a mixture of two or more.

[0065] One function of nitrogen-containing solvents is to improve the surface drying and fixing properties of the processing solution applied to a low-absorption recording medium. In particular, the compound represented by formula (1) has excellent properties for moderately softening and dissolving vinyl chloride resins. Therefore, the compound represented by formula (1) can soften and dissolve the recording surface containing vinyl chloride resin, allowing the processing solution to penetrate into the interior of the low-absorption recording medium. As the processing solution penetrates the low-absorption recording medium in this way, the processing solution becomes firmly fixed, and the surface of the processing solution dries easily. Consequently, the resulting image tends to have excellent surface drying properties and fixing properties.

[0066] When a nitrogen-containing solvent is used in the processing solution, its content is preferably not more than 15% by mass of the total mass of the processing solution, more preferably not more than 10% by mass, and even more preferably not more than 5% by mass. Furthermore, it is preferably not more than 2% by mass, and even more preferably not more than 1% by mass. In particular, it is preferable that the processing solution does not contain the amide solvent mentioned above. This further improves the granularity and abrasion resistance of the resulting image.

[0067] Examples of polyhydric alcohols include 1,2-alkanediols (e.g., ethylene glycol, propylene glycol (also known as propane-1,2-diol), 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, and other alkanediols), and polyhydric alcohols other than 1,2-alkanediols (polyols) (e.g., diethylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol (also known as 1,3-butylene)). Examples include glycols, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexanediol, 3-methyl-1,5-pentanediol, 2-methylpentane-2,4-diol, trimethylolpropane, glycerin, etc.

[0068] Examples of polyhydric alcohols include alkanediols and polyols. Among the alkanediols, those with 5 or more carbon atoms are preferred. The number of carbon atoms in the alkane is preferably 5 to 10, more preferably 5 to 8, and even more preferably 5 to 6. Preferably, it is a 1,2-alkanediol. Examples of preferred alkanediols include 1,2-hexanediol and 1,2-pentanediol.

[0069] Including a 1,2-alkanediol with 5 or more carbon atoms improves the spreadability of the processing solution on the recording medium, allows for more uniform adhesion of the flocculant, and further improves the color development of the inkjet ink composition. Furthermore, it also improves the discharge stability of the processing solution.

[0070] The alkanediols may also be alkanediols with four or fewer carbon atoms.

[0071] Examples of polyols include condensates formed by the condensation of intermolecular hydroxyl groups of alkanediols, and polyols having three or more hydroxyl groups. Among condensates formed by the condensation of intermolecular hydroxyl groups of alkanediols, those in which the hydroxyl groups of alkanediols having four or fewer carbon atoms are condensed are preferred.

[0072] Among polyhydric alcohols, alkanediols with 4 or fewer carbon atoms, condensates formed by the condensation of hydroxyl groups between alkanediol molecules, and polyols with 3 or more hydroxyl groups are preferable because they have excellent moisturizing properties among organic solvents and can be used as humectants (moisturizing solvents), and they have superior discharge stability.

[0073] Alkanediols and polyols can primarily function as penetrating solvents and / or moisturizing solvents. However, alkanediols tend to have stronger penetrating properties, while polyols tend to have stronger moisturizing properties.

[0074] The processing solution may contain an organic solvent that is a polyhydric alcohol with a standard boiling point of 170°C to 240°C, which is preferable as it can further improve the granularity and abrasion resistance of the image. It is even more preferable that the processing solution contains an organic solvent that is a polyol with a standard boiling point of 170°C to 240°C. This is even more preferable in the respects mentioned above.

[0075] If the treatment solution contains an organic solvent, one type of organic solvent may be used alone, or two or more types may be used in combination. Furthermore, the total content of the organic solvent relative to the total mass of the treatment solution should be, for example, 1% by mass or more and 50% by mass or less.

[0076] Furthermore, the content is preferably 5% by mass or more and 50% by mass or less, preferably 10% by mass or more and 45% by mass or less, more preferably 15% by mass or more and 40% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less. Moreover, 25 to 35% by mass is preferred. Having the organic solvent content within the above range provides an even better balance between wetting spreadability and drying properties, making it easier to form higher quality images.

[0077] The content of the organic solvent, which is a polyol with a standard boiling point of 170°C to 240°C, is also preferably within the above range.

[0078] The treatment solution preferably does not contain 1% by mass or more of polyhydric alcohols with a standard boiling point exceeding 280°C, and more preferably does not contain 0.5% by mass or more. Furthermore, it is also preferable that the content of organic solvents, not limited to polyhydric alcohols with a standard boiling point exceeding 280°C, be within the above range.

[0079] (4) Wax The processing solution may contain wax. Since wax has the function of providing a smooth surface to the ink-based image, it may reduce image peeling and other issues.

[0080] The components of the wax can be, for example, plant and animal waxes such as carnauba wax, candelilla wax, beeswax, rice wax, and lanolin; petroleum waxes such as paraffin wax, microcrystalline wax, polyethylene wax, oxidized polyethylene wax, and petrolatum; mineral waxes such as montan wax and ozokerite; synthetic waxes such as carbon wax, Hoechst wax, polyolefin wax, and stearic acid amide; and natural and synthetic wax emulsions and blended waxes such as α-olefin-maleic anhydride copolymers, which can be used individually or in combination of multiple types. Among these, polyolefin wax (especially polyethylene wax and polypropylene wax) and paraffin wax are preferred from the viewpoint of being superior in their ability to improve adhesion to flexible packaging films, as described later.

[0081] Commercially available waxes can be used as is, for example, Nopcoat PEM-17 (product name, manufactured by Sunnopco Co., Ltd.), Chemipearl W4005 (product name, manufactured by Mitsui Chemicals, Inc.), and AQUACER 515, 539, and 593 (all product names, manufactured by Big Chemie Japan Co., Ltd.).

[0082] Furthermore, it is preferable to use a wax with a melting point of 50°C to 200°C, more preferably 70°C to 180°C, and even more preferably 90°C to 150°C.

[0083] The wax may be supplied in the form of an emulsion or suspension. The wax content is 0.1% to 10% by mass, more preferably 0.5% to 5% by mass, and even more preferably 0.5% to 2% by mass, based on solid content relative to the total mass of the processing liquid. When the wax content is within the above range, the functions of the wax can be exhibited well. Furthermore, if the processing liquid and at least one of the clear ink composition, ink composition, and ink composition described later contain wax, the function of imparting smoothness to the image can be obtained more fully.

[0084] (5) Betaines The processing solution of this embodiment may contain betaines. Betaine refers to a compound that has positive and negative charges at non-adjacent positions within the same molecule, where the positively charged atom does not have any dissociable hydrogen atoms bonded to it, and which can form an intramolecular salt, and the molecule as a whole has no charge. In this embodiment, it is preferable that the betaine has a quaternary ammonium cation as the positively charged site.

[0085] When the processing solution contains betaine, it can suppress deviations in the flow of the processing solution and non-discharge caused by the drying of the processing solution at the nozzle of the inkjet head, resulting in improved clogging resistance. Furthermore, when the processing solution contains betaine, secondary curl can be further suppressed.

[0086] Betaines are not particularly limited, but examples include trialkylglycines such as trimethylglycine and triethylglycine, γ-butyrobetaine, homarin, trigonelline, carnitine, homoserine betaine, valine betaine, lysine betaine, ornithine betaine, alanine betaine, stachydrine, and glutamate betaine. Among these, trialkylglycine is used as the glycine contained in the inkjet ink composition. It is preferable to select from the following, and more preferably to include trimethylglycine. Trialkylglycine is a compound in which three alkyl groups are substituted on the nitrogen atom of glycine. This tends to further improve clogging properties. Betaine may be used alone or in combination of two or more types.

[0087] The number of carbon atoms in the betaine is preferably between 4 and 12, more preferably between 4 and 7, and even more preferably between 4 and 6. Having the number of carbon atoms in the betaine within this range tends to more significantly suppress pigment sedimentation.

[0088] When betaines are included in the treatment solution, the content is preferably 1.0% by mass or more relative to the total mass of the treatment solution. Furthermore, it is preferable that the content be 2.0% by mass or more and 10.0% by mass or less, more preferably 3.0% by mass or more and 9.0% by mass or less, and even more preferably 4.0% by mass or more and 8.0% by mass or less.

[0089] (6) Additives The treatment solution may contain additives such as ureas, amines, and sugars. Examples of ureas include urea, ethylene urea, tetramethylurea, thiourea, and 1,3-dimethyl-2-imidazolidinone.

[0090] Examples of amines include diethanolamine, triethanolamine, and triisopropanolamine. Ureas and amines may also be used as pH adjusters. Examples of sugars include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose.

[0091] (7) Others The treatment solution according to this embodiment may further contain, if necessary, components such as preservatives, fungicides, rust inhibitors, chelating agents, viscosity modifiers, antioxidants, and mold inhibitors.

[0092] 1.5. Recording media The processing solution in this embodiment is used for recording onto an absorbent recording medium. The absorbent recording medium is used in the Bristow method, from the start of contact for 30 msec. 1 / 2 Up to 10 mL / m² of water absorption capacity 2 This refers to a "super recording medium." The Bristow method is the most widely used method for measuring liquid absorption in a short time, and is used by the Japan Paper & Pulp Technology Association (JAPAN). It is also used by TAPPI. Details of the test method are described in standard No. 51 "Paper and cardboard - Liquid absorbency test method - Bristow method" of the "JAPAN TAPPI Paper and Pulp Test Methods 2000 Edition".

[0093] Examples of liquid-absorbent recording media include those in which the substrate itself is liquid-absorbent. Such recording media include fabrics made of fibers and paper made from pulp. Examples of paper include plain paper, cardboard, and liner paper. Liner paper is made from kraft pulp, recycled paper, etc. Examples of plain paper include what is generally called fine paper, neutral paper, and copy paper.

[0094] Examples of liquid-absorbing recording media include those that have a liquid-absorbing receiving layer on their surface. For example, inkjet paper (paper specifically for inkjet printers) is one such example. The liquid-absorbing receiving layer may be composed of a liquid-absorbing resin, a liquid-absorbing inorganic fine particle, or the like.

[0095] The processing solution according to this embodiment can be used and implemented without being restricted by the recording medium, but a more significant effect can be obtained by using an absorbent recording medium. Furthermore, this effect is even more pronounced if the recording medium itself is a liquid absorbent recording medium.

[0096] 1.6. Physical properties and manufacturing of the processing solution In this embodiment, from the viewpoint of ensuring appropriate wetting spread onto the recording medium, the surface tension of the processing solution at 25°C is preferably 40 mN / m or less, more preferably 38 mN / m or less, more preferably 35 mN / m or less, and even more preferably 30 mN / m or less. The surface tension can be measured by using an automatic surface tensimeter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) to check the surface tension when a platinum plate is wetted with the composition in an environment of 25°C.

[0097] It is more preferable that the processing solution is applied to the recording medium by an inkjet method. In this case, the viscosity at 20°C is preferably 1.5 mPa·s to 15 mPa·s, more preferably 1.5 mPa·s to 7 mPa·s, and more preferably 1.5 mPa·s to 5.5 mPa·s. When the processing solution is applied to the recording medium by an inkjet method, it is easy to efficiently form a predetermined processing solution application area on the recording medium.

[0098] The processing solution of this embodiment can be obtained by mixing the above-mentioned components in any order and removing impurities by filtration or other means as necessary. A preferred mixing method involves sequentially adding the materials to a container equipped with a stirring device such as a mechanical stirrer or magnetic stirrer and then stirring and mixing them. For filtration, centrifugal filtration or filter filtration can be performed as needed.

[0099] 2. Ink Set The processing solution described above is used for recording together with an inkjet ink composition containing a colorant. The ink set according to this embodiment has the above-described processing solution and inkjet ink composition. The inkjet ink composition containing a colorant is described below.

[0100] 2.1. Inkjet Ink Compositions Inkjet ink compositions are water-based ink compositions containing colorants.

[0101] 2.1.(1) Colorants An inkjet ink composition is an ink containing a colorant. Examples of colorants include dyes and pigments. The colorant can be, for example, a colorant such as cyan, yellow, magenta, or black, or a white colorant. Other options include spot inks such as red, orange, blue, and green, or light inks such as light magenta, light cyan, and gray.

[0102] The colorant may be either a dye or a pigment, or a mixture thereof. However, it is more preferable to include a pigment among the dye and pigment. The pigment should have excellent storage stability, such as lightfastness, weather resistance, and gas resistance, and from this viewpoint, it is even more preferable to use an organic pigment.

[0103] Specifically, pigments used include azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelated azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; dye chelates; dye lakes; nitro pigments; nitroso pigments; aniline black; daylight fluorescent pigments; and carbon black. These pigments can be used individually or in combination of two or more. Furthermore, luminous pigments are used as colorants. You may also use [this].

[0104] Examples of pigments, though not limited to them, include the following:

[0105] Examples of black pigments include No.2300, No.900, MCF88, No.33, No.40, No.45, No.52, MA7, MA8, MA100, No.2200B, etc. (all manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (all manufactured by Carbon Columbia), Rega1 400R, Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (manufactured by CABOT JAPAN) KK)), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color B1ack S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex Examples include the V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, and Special Black 4 (all manufactured by Degussa).

[0106] Examples of yellow pigments include CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 167, 172, and 180.

[0107] Examples of magenta pigments include CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48(Ca), 48(Mn), 57(Ca), 57:1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or CI Pigment Violet. Numbers 19, 23, 32, 33, 36, 38, 43, and 50 can be cited.

[0108] Examples of cyan pigments include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:34, 15:4, 16, 18, 22, 25, 60, 65, 66, and CI Bat Blue 4, 60.

[0109] In addition, pigments other than magenta, cyan, and yellow are not particularly limited, but include, for example, CI Pigment Green 7, 10, CI Pigment Brown 3, 5, 25, 26, and CI Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63.

[0110] Pearl pigments are not particularly limited, but examples include titanium dioxide-coated mica, fish scale foil, and bismuth acid chloride, which are pigments that have a pearly or interference luster.

[0111] The metallic pigments are not particularly limited, but examples include particles made from elements or alloys of aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, copper, etc.

[0112] Examples of white colorants include metal compounds such as metal oxides, barium sulfate, and calcium carbonate. Examples of metal oxides include titanium dioxide, zinc oxide, silica, alumina, and magnesium oxide. In addition, particles with a hollow structure may be used as the white colorant, and known particles with a hollow structure can be used. Among the examples given, titanium dioxide is preferred as the white colorant from the viewpoint of good whiteness and abrasion resistance.

[0113] Furthermore, various dyes commonly used for inkjet recording can be used as dyes, such as direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, and reactive disperse dyes.

[0114] The colorant is preferably able to be stably dispersed or dissolved in the dispersion medium, and may be dispersed using a dispersant if necessary.

[0115] The colorant is preferably able to be stably dispersed in a dispersion medium, and for this purpose, a dispersant may be used for dispersion. Examples of dispersants include resin dispersants, and they should be selected from those that can provide good dispersion stability of the colorant in the inkjet ink composition. Alternatively, the colorant may be used as a self-dispersing pigment by modifying the surface of the pigment particles by oxidizing or sulfonating the pigment surface with, for example, ozone, hypochlorous acid, or fuming sulfuric acid.

[0116] Examples of resin dispersants (dispersant resins) include (meth)acrylic resins and their salts such as poly(meth)acrylic acid, (meth)acrylic acid-acrylonitrile copolymer, (meth)acrylic acid-(meth)acrylic acid ester copolymer, vinyl acetate-(meth)acrylic acid ester copolymer, vinyl acetate-(meth)acrylic acid copolymer, vinylnaphthalene-(meth)acrylic acid copolymer; styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, styrene-α-methylstyrene-(meth)acrylic acid copolymer, styrene-α-methylstyrene-(meth)acrylic acid copolymer Examples of styrene-based resins and their salts include acrylic acid-(meth)acrylic acid ester copolymers, styrene-maleic acid copolymers, and styrene-maleic anhydride copolymers; urethane-based resins and their salts that contain urethane bonds formed by the reaction of isocyanate groups and hydroxyl groups, which may be linear and / or branched, and may or may not have a crosslinked structure; polyvinyl alcohols; vinylnaphthalene-maleic acid copolymers and their salts; vinyl acetate-maleic acid ester copolymers and their salts; and water-soluble resins such as vinyl acetate-crotonic acid copolymers and their salts. Among these, copolymers of monomers having hydrophobic functional groups and monomers having hydrophilic functional groups, and polymers consisting of monomers having both hydrophobic and hydrophilic functional groups are preferred. The copolymer can be used in any form, such as a random copolymer, a block copolymer, an alternating copolymer, or a graft copolymer. Among the styrene-based resins, copolymers with (meth)acrylic monomers are also (meth)acrylic resins.

[0117] Examples of commercially available styrene resin dispersants include X-200, X-1, X-205, X-220, X-228 (manufactured by Seikoh PMC), Nopcospers® 6100, 6110 (manufactured by Sunnopco Corporation), Joncryl 67, 586, 611, 678, 680, 682, 819 (manufactured by BASF), DISPERBYK-190 (manufactured by Bic Chemie Japan Co., Ltd.), N-EA137, N-EA157, N-EA167, N-EA177, N-EA197D, N-EA207D, and E-EN10 (manufactured by Daiichi Kogyo Seiyaku).

[0118] Furthermore, commercially available acrylic resin dispersants include BYK-187, BYK-190, BYK-191, BYK-194N, BYK-199 (manufactured by Big Chemie Co., Ltd.), Aron A-210, A6114, AS-1100, AS-1800, A-30SL, A-7250, and CL-2 (manufactured by Toagosei Co., Ltd.).

[0119] Furthermore, commercially available urethane resin dispersants include BYK-182, BYK-183, BYK-184, BYK-185 (manufactured by Bic Chemi Co., Ltd.), TEGO Disperse710 (manufactured by Evonic Tego Chemi), and Borchi® Gen1350 (manufactured by OMG Borschers).

[0120] The dispersant may be used alone or in combination of two or more types. The total content of the dispersant is preferably 0.1 parts by mass or more and 30 parts by mass or less per 50 parts by mass of the white colorant, more preferably 0.5 parts by mass or more and 25 parts by mass or less, even more preferably 1 part by mass or more and 20 parts by mass or less, and even more preferably 1.5 parts by mass or more and 15 parts by mass or less. By having a dispersant content of 0.1 parts by mass or more per 50 parts by mass of the colorant, the dispersion stability of the colorant can be further enhanced. Also, if the dispersant content is 30 parts by mass or less per 50 parts by mass of the colorant, the viscosity of the resulting dispersion can be kept low.

[0121] Among the dispersants exemplified above, it is even more preferable that at least one is selected from anionic dispersant resins. In this case, it is even more preferable that the weight-average molecular weight of the dispersant be 500 or more. Furthermore, it is preferable that it be between 5000 and 100000, and more preferably between 10000 and 50000.

[0122] By using such a resin dispersant as a dispersant, the dispersion and aggregation of pigments are improved, resulting in better dispersion stability and even better image quality. Furthermore, it is preferable that the viscosity of the inkjet ink composition, as described later, can be increased by five times or more.

[0123] Anionic dispersant resins are resins that exhibit anionic properties because they possess anionic functional groups. Examples of anionic functional groups include carboxyl groups, sulfo groups, and phosphate groups. Among these groups, carboxyl groups are more preferred.

[0124] The dispersant resin preferably has an acid value, preferably 5 mg KOH / g or more, more preferably 10 to 200 mg KOH / g, and even more preferably 15 to 150 mg KOH / g. Further preferably 20 to 100 mg KOH / g, and even more preferably 30 to 80 mg KOH / g. Furthermore, the lower limit is preferably 40 mg KOH / g or more, even more preferably 50 mg KOH / g or more, particularly preferably 60 mg KOH / g or more, and especially more preferably 70 mg KOH / g or more. In this case, it is preferable as it is easier to increase the viscosity of the inkjet ink composition, as described later, by 5 times or more.

[0125] The acid value can be measured by neutralization potentiometric titration in accordance with JIS K0070. For example, the "AT610" manufactured by Kyoto Electronics Manufacturing Co., Ltd. can be used as the titrator.

[0126] The colorant content is preferably 0.3% to 20% by mass, more preferably 0.5% to 15% by mass, relative to the total mass of the inkjet ink composition. Furthermore, 1% to 10% by mass is preferred, and 2% to 7% by mass is more preferred.

[0127] When using pigments as colorants, the volume average particle size of the pigment particles is preferably 10 nm to 300 nm, more preferably 30 nm to 250 nm, and 50 nm to 250 nm. The lower range is even more preferable, and 70 nm to 200 nm is particularly preferable. Furthermore, 80 nm to 150 nm is preferable. The volume average particle diameter of the colorant is measured as an initial state using the volume average particle diameter confirmation method described above. When the volume average particle diameter is within the above range, it is preferable because the desired colorant is easier to obtain and the properties of the colorant are easier to improve.

[0128] 2.1.(2) Water The inkjet ink composition according to this embodiment is a water-based ink containing water. A water-based ink is a composition that contains water as one of its main solvent components. This allows for recording with reduced environmental impact and less odor. The water used can be the same as that used in the processing solution described above, and therefore no further explanation is provided.

[0129] 2.1.(3) Other ingredients In addition to colorants and water, inkjet ink compositions may also contain components such as resin particles, organic solvents, surfactants, waxes, additives, preservatives / fungal agents, rust inhibitors, chelating agents, viscosity modifiers, antioxidants, and fungicides.

[0130] The components of the inkjet ink composition other than the colorants may be the same as those used in the components of the processing solution other than the coagulant, and may be selected independently of the processing solution. These components may all be the same as those in the processing solution described above, and by replacing "processing solution" with "inkjet ink composition," a detailed explanation can be omitted.

[0131] 2.2. Physical properties and manufacturing of inkjet ink compositions The inkjet ink composition used in the recording method of this embodiment preferably has a surface tension of 40 mN / m or less, preferably 38 mN / m or less, more preferably 35 mN / m or less, and even more preferably 30 mN / m or less at 25°C, from the viewpoint of ensuring appropriate wetting and spreading properties on the recording medium. The surface tension can be measured by using an automatic surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) to check the surface tension when a platinum plate is wetted with the composition in an environment of 25°C.

[0132] The inkjet ink composition is deposited onto the recording medium by the inkjet method. Therefore, the viscosity at 20°C is preferably 1.5 mPa·s to 15 mPa·s, more preferably 1.5 mPa·s to 7 mPa·s, and even more preferably 1.5 mPa·s to 5.5 mPa·s.

[0133] The inkjet ink composition of this embodiment can be obtained by mixing the above-mentioned components in any order and removing impurities by filtration or other means as necessary. A preferred mixing method involves sequentially adding the materials to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer and then stirring and mixing them. For filtration, centrifugal filtration or filter filtration can be performed as needed.

[0134] According to the ink set of this embodiment, since it contains the processing liquid described above, even when used for recording together with an inkjet ink composition, it is possible to form a recorded material in which curling of the recording medium is suppressed.

[0135] 3. Recording Method The recording method according to this embodiment is performed using the above-described processing liquid and the above-described inkjet ink composition, and comprises a processing liquid application step of applying the processing liquid to a recording medium which is an absorbent recording medium, and an ink application step of ejecting the inkjet ink composition from an inkjet head and applying it to the recording medium.

[0136] 3.1. Processing liquid application process The treatment liquid adhesion step may be performed by various methods such as the roller method, spray method, dip method, inkjet method, etc. In particular, the inkjet method, that is, it may be discharged from an inkjet head and adhered to a recording medium. According to the inkjet method, it is preferable because it is easy to control the adhesion amount and adhesion position.

[0137] In this case, for example, a mode of adhering the treatment liquid while performing scanning, which is the movement of the relative position between the inkjet head and the recording medium, using a recording device described later may be mentioned, and it may be performed by any method. Examples of the inkjet method include the serial method, line method, etc. By doing so, printing of a small amount of various types can be efficiently performed with a small-sized device.

[0138] The adhesion amount of the treatment liquid in the treatment liquid adhesion step is preferably 0.4 mg / inch 2 or more. Furthermore, 0.5 mg / inch 2 or more is preferable, 1.0 mg / inch 2 or more is preferably, 1.5 mg / inch 2 or more is more preferable, 2.0 mg / inch 2 or more is even more preferable. By doing so, an image having better filling properties can be obtained. Also, it is preferably that the maximum adhesion amount of the treatment liquid in the treatment liquid adhesion step is within the above range or more.

[0139] Also, the upper limit of the adhesion amount of the treatment liquid in the treatment liquid adhesion step is preferably 5.0 mg / inch 2 [[ID=好ましくは]] or less. Furthermore, 3.0 mg / inch 2 or less, even more preferably 2.5 mg / inch 2 or less, and even more preferably 2.0 mg / inch 2 or less. In particular, it is preferably that the maximum adhesion amount of the treatment liquid in the treatment liquid adhesion step is within the above range or less.

[0140] Furthermore, when the processing liquid deposition process is carried out by the inkjet method, the mass (ng) of the processing liquid droplets is preferably 0.5 ng or more and 10 ng or less, more preferably 1 ng or more and 7 ng or less, even more preferably 1 ng or more and 5 ng or less, and even more preferably 2 ng or more and 4 ng or less. In terms of dot size (ng / dot), the mass (ng) of the processing liquid droplets in the processing liquid deposition process is preferably 0.5 ng / dot or more and 10 ng / dot or less, more preferably 1 ng / dot or more and 7 ng / dot or less, even more preferably 1 ng / dot or more and 5 ng / dot or less, and even more preferably 2 ng / dot or more and 4 ng / dot or less.

[0141] The process may be configured such that the processing liquid is applied to the recording medium in the processing liquid application step, followed by the application of ink to the recording medium in the ink application step. Alternatively, the processing liquid application step may involve applying the processing liquid to the same scanning area as the scanning (pass) used to apply the ink composition to the recording medium.

[0142] The processing liquid application step is performed so that the ink composition applied to the recording medium by the ink application step and the processing liquid applied to the recording medium by the processing liquid application step can come into contact and react on the recording medium.

[0143] The processing liquid application step may be performed by ejecting the processing liquid from an inkjet head, which is a line-type inkjet head, and applying it to the recording medium in a single scan. When such a recording device is used, the inkjet ink composition adheres quickly after the processing liquid has adhered, which can lead to curling. However, it is possible to obtain a recording with suppressed curling, and for example, the recording can be stacked well after recording.

[0144] 3.2. Ink application process In the ink application process, the ink composition is ejected from the inkjet head and applied to the recording medium. The process of applying the inkjet ink composition to the recording medium can be carried out, for example, using a recording device described later. That is, the inkjet ink composition is ejected from a predetermined nozzle. The inkjet ink composition is loaded into the inkjet head so that it can be ejected from the head, and then ejected onto the recording medium at a predetermined timing, thereby adhering the inkjet ink composition to the recording medium.

[0145] 3.3. Other processes Furthermore, the recording method of this embodiment may optionally include a step of heating the recording medium. The step of heating the recording medium can be carried out, for example, by using an appropriate drying means when using an inkjet recording device. It can also be carried out by an appropriate drying means regardless of whether or not it is provided in the inkjet recording device. This dries the resulting image, which can suppress image blurring and allow for more efficient fixing. The method may also optionally include a step of replenishing ink in the ink container. Furthermore, the recording method of this embodiment may optionally include other steps, for example, a step of adding other compositions.

[0146] 3.4. Recording device Figure 1 shows a schematic cross-sectional view of a recording device that can be used in the recording method of the present invention. As shown in Figure 1, the line head 10 has a length greater than or equal to the recording width of the recording medium and is a means for ejecting an inkjet ink composition and adhering it to the recording medium M. The inkjet head 10 has a plurality of unit heads 12 arranged in the direction of the recording width of the recording medium on a nozzle surface 11 facing the recording medium M. The unit heads 12 have nozzles for ejecting processing liquid or inkjet ink composition, and the nozzles may be arranged in a row. A group of nozzles arranged in a row is also called a "nozzle row". The recording medium M is supported by a belt B and transported in the transport direction. The belt B is moved in the transport direction D1 by a belt roller 20. The recording device may include a paper feed tray, a paper output tray, etc., which are not shown.

[0147] The unit head 12 only needs to have such a nozzle row, and its structure is not limited to anything other than having a nozzle row. The part of the line head 10 that has one nozzle row is one unit head 12. It can also be said that the nozzle row is the unit head 12.

[0148] In a line-type system using a line head, for example, an inkjet head with a width greater than the recording width of the recording medium is fixed to the recording device. The recording medium is then moved along the scanning direction (the vertical direction of the recording medium, the transport direction), and an image is recorded on the recording medium by scanning in conjunction with this movement, in which ink droplets are ejected from the nozzles of the inkjet head.

[0149] Alternatively, the recording medium is fixed to the recording device. Then, an inkjet head having a width greater than or equal to the recording width of the recording medium is moved along the scanning direction, and an image is recorded on the recording medium by performing a scan in which ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement. The scanning direction is the direction of scanning.

[0150] In this type of line-based printing system using a line head, recording can be performed with a single scan of the line head and recording medium, thus improving printing speed.

[0151] In recording devices equipped with line-type inkjet heads, the printed surface expands during printing, which can cause curling (primary curling) immediately after printing. Furthermore, as drying progresses, the recombination of hydrogen bonds in the recording medium can cause curling (secondary curling) within tens of seconds to several minutes.

[0152] However, by using the aforementioned processing solution, it is possible to suppress or slow down the recombination of hydrogen bonds as drying progresses after printing, thereby reducing primary and / or secondary curl. The mechanism of curl will be explained further later.

[0153] Although the above describes an example using a line-type inkjet head, the recording method according to this embodiment may also be performed using a printer with a serial-type inkjet head (serial printer). In a serial printer, printing is performed by moving the inkjet head in a direction intersecting the transport direction while transporting the recording medium in the transport direction. Even with a serial printer, primary curl and / or secondary curl can be suppressed by using the processing solution described above.

[0154] 4. Examples and Comparative Examples The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Hereinafter, "parts" and "%" refer to mass unless otherwise specified. Evaluations are performed under conditions of 25°C and 40.0% relative humidity unless otherwise specified.

[0155] 4.1. Preparation of the treatment solution Each component is placed in a mixing tank to obtain the composition shown in Tables 1 and 2, mixed and stirred, and then filtered through a membrane filter to obtain the treatment solution for each example. Unless otherwise specified, the numerical values ​​of each component shown in the examples in the tables represent mass percentages.

[0156] The abbreviations and product ingredient details used in Tables 1 and 2 are as follows. • Sugar alcohol 1:PO-500, from Mitsubishi Corporation Life Sciences Co., Ltd. (a mixture of various sugar alcohols that are solid at room temperature) • Sugar alcohol 2:PO-20, from Mitsubishi Corporation Life Sciences Co., Ltd. (a mixture of various sugar alcohols that are solid at room temperature) • Sugar alcohol 3: xylitol • Sugar alcohol 4: sorbitol • Orphine E1010: Acetylene-based surfactant (manufactured by Nisshin Chemical Industry Co., Ltd.) • Orphine E1004: Acetylene-based surfactant (manufactured by Nisshin Chemical Industry Co., Ltd.)

[0157] Tables 1 and 2 show the moisture retention coefficients (percentage change in mass after leaving a 50% by mass aqueous solution at 25°C and 95% RH for 7 days) for several components. The moisture retention coefficient is calculated as follows: 1 ml of a 50% by mass aqueous solution of each component is placed in a Neo Mini Cup No. 5 (capacity 5 ml, inner diameter of the mouth without a flange 25.2 mm) manufactured by Maruemu Co., Ltd. Then, the mass after leaving it at 25°C and 95% RH for 7 days (mass of the aqueous solution) is divided by the mass before leaving it (mass of the aqueous solution) to obtain the moisture retention coefficient (percentage change in mass (%)). The moisture retention coefficients are listed in the table.

[0158] 4.2. Evaluation Method 4.2.1. Primary curl A modified Seiko Epson LX-10050 (line inkjet printer) was filled with the processing fluids and inks used in each example, and the recording media (A4 size Xerox P paper, Fuji Xerox copy paper, basis weight 64 g / m²) was used. 2 For paper with a thickness of 88 μm, a solid pattern of 100 ppm is printed face-up at a temperature of 25°C and humidity of 50% with a print duty cycle of 100% for each processing liquid ink. Immediately after printing, the angle between the point where the paper is in contact with the floor and the edge of the paper is measured and evaluated as an indicator of primary curl.

[0159] The ink used is Bk ink for the LX-10050 (manufactured by Seiko Epson Corporation), and the line head is positioned so that the processing solution and then the ink adhere to the recording medium in that order. Furthermore, the Duty 100% is 4.5 mg / inch. 2 Let's assume that.

[0160] The following criteria will be used for evaluation, and the results will be recorded in the table. A: Less than 45° B: 45° or more and less than 90° C: 90° or more

[0161] 4.2.2. Secondary curl Similarly, a modified Seiko Epson LX-10050 (line inkjet printer) was prepared and filled with the processing fluids and inks from each example, and the recording media (A4 size Xerox P paper, Fuji Xerox copy paper, basis weight 64 g / m²) was used. 2 For paper with a thickness of 88 μm, a solid pattern of 100 ppm is printed face up at a temperature of 25°C and humidity of 50% with a print duty cycle of 100% for each processing liquid ink. After printing, the amount of lift of the paper edge from the floor is measured after leaving it face up for one week. The results are evaluated according to the following criteria and recorded in the table. A: Less than 10cm B: 10cm or more, less than 20cm C: 20cm or more

[0162] 4.2.3. Color Development (OD) Similarly, a modified Seiko Epson LX-10050 (line inkjet printer) was prepared and filled with the processing solutions and inks for each example. A solid pattern was printed at 100 ppm with a print duty cycle of 100% on a recording medium (A4 size business plain inkjet paper, Seiko Epson copy paper) for each processing solution and ink. The resulting color (OD) was measured. The results were evaluated according to the following criteria and recorded in the table. A: OD is 1.53 or higher B: OD is less than 1.53 but 1.46 or greater C:OD is less than 1.46

[0163] 4.2.4.Discharge stability Similarly, the cartridges of a modified Seiko Epson LX-10050 (line inkjet printer) were filled with the processing solution for each example. After confirming that the processing solution was ejected from multiple nozzles for a single ink cartridge, a test pattern was printed on 30 sheets of A4 paper in succession. After printing 30 sheets, a nozzle check was performed to evaluate the ejection characteristics. The evaluation was conducted according to the following criteria and recorded in the table. A: No nozzle is unstable and does not dispense. B: Nozzle disconnection, no more than 5 lines of distortion, can be fixed with one cleaning. C: Nozzle disconnection, no more than 10 streaks, can be fixed with 2 or more cleanings.

[0164] 4.3. Evaluation Results Tables 1 and 2 show that the treatment solutions in each example, which contain a flocculant and a sugar alcohol that is solid at room temperature, exhibit excellent suppression of curl in recorded materials. Furthermore, when a 50% by mass aqueous solution of the sugar alcohol, which is solid at room temperature, is left at 25°C and 95% RH for 7 days, the mass change rate (after / before) is 120% or less. In each example, the treatment solutions exhibit excellent suppression of curl in recorded materials. In addition, color development and discharge stability are also good. In contrast, the comparative examples that do not exhibit these characteristics all show poor suppression of curl in recorded materials.

[0165] The present invention includes configurations substantially identical to those described in the embodiments, for example, configurations with the same function, method, and results, or configurations with the same purpose and effect. Furthermore, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as those described in the embodiments. Finally, the present invention includes configurations that add known technology to the configurations described in the embodiments.

[0166] The following can be derived from the embodiments and modifications described above.

[0167] The processing solution is A water-based processing solution used for recording onto an absorbent recording medium, together with an inkjet ink composition containing a colorant, It contains a flocculant and a sugar alcohol that is solid at room temperature. The 50% by mass aqueous solution of the sugar alcohol, which is solid at room temperature, contained in the processing solution, exhibits a mass change rate (after / before standing) of 120% or less when left standing at 25°C and 95% RH for 7 days.

[0168] This processing solution can suppress curling of the recording medium.

[0169] In the above processing solution, The content of the sugar alcohol, which is solid at room temperature, may be 1% by mass or more and 5% by mass or less, relative to the total volume of the processing solution.

[0170] This processing solution can further suppress curling of the recording medium.

[0171] In the above processing solution, The aforementioned flocculant may be a polyvalent metal salt.

[0172] This processing solution can improve the color development of inkjet ink compositions.

[0173] In the above processing solution, The aforementioned flocculant may be a calcium salt.

[0174] This processing solution can further improve the color development of inkjet ink compositions.

[0175] In the above processing solution, It may also contain betaine.

[0176] This treatment solution can further suppress secondary curling.

[0177] In the above processing solution, The material may further contain 1,2-alkanediols having 5 or more carbon atoms.

[0178] This processing solution allows for better spread of the processing solution onto the recording medium, more uniform adhesion of the flocculant, and further improvement of the color development of the inkjet ink composition. Furthermore, it also improves the discharge stability of the processing solution.

[0179] In the above processing solution, It may be ejected from the inkjet head, adhered to the recording medium, and used for recording.

[0180] This processing solution allows for a reduction in the amount of processing solution used during recording.

[0181] The ink set is The system comprises one of the above-mentioned processing solutions and an inkjet ink composition.

[0182] This ink set allows for the formation of recordings with suppressed curling of the recording medium.

[0183] The recording method is: This is carried out using any of the above processing solutions and inkjet ink compositions. A processing liquid application step in which the processing liquid is applied to a recording medium which is an absorbent recording medium, The process includes an ink application step of ejecting the inkjet ink composition from an inkjet head and adhering it to the recording medium.

[0184] This recording method allows for obtaining recordings with minimal curling.

[0185] In the above recording method, The processing liquid application step may be performed by ejecting the processing liquid from an inkjet head, which is a line-type inkjet head, and applying it to the recording medium in a single scan.

[0186] This recording method allows for the acquisition of recordings with suppressed curling, even in situations where curling is likely to occur, and enables, for example, good stacking of the recorded materials after recording. [Explanation of Symbols]

[0187] 10...Line head, 11...Nozzle surface, 100...Recording device, B...Belt, D1...Scanning direction, D2...Width direction, M...Recording medium

Claims

1. A processing solution used for recording on an absorbent recording medium, together with an inkjet ink composition containing a colorant, It contains a flocculant and a sugar alcohol that is solid at room temperature. The 50% by mass aqueous solution of the sugar alcohol, which is solid at room temperature, contained in the processing liquid, when left at 25°C and 95% RH for 7 days, has a mass change rate (after / before) of 120% or less. Aqueous treatment solution.

2. In claim 1, The content of the sugar alcohol, which is solid at room temperature, is 1% by mass or more and 5% by mass or less of the total volume of the treatment solution.

3. In claim 1, The aforementioned flocculant is a polyvalent metal salt, and the treatment solution is also a flocculant.

4. In claim 3, The aforementioned flocculant is a calcium salt, and the treatment solution is a treatment solution.

5. In claim 1, A treatment solution that further contains betaine.

6. In claim 1, A treatment solution further containing a 1,2-alkanediol having 5 or more carbon atoms.

7. In claim 1, A processing liquid that is ejected from an inkjet head, adheres to the recording medium, and is used for recording.

8. An ink set comprising the processing liquid and inkjet ink composition according to any one of claims 1 to 7.

9. The process is carried out using the processing solution and inkjet ink composition described in any one of claims 1 to 7. A processing liquid application step in which the processing liquid is applied to a recording medium which is an absorbent recording medium, A recording method comprising an ink application step of ejecting the inkjet ink composition from an inkjet head and adhering it to the recording medium.

10. In claim 9, The aforementioned processing liquid application step is a recording method in which the processing liquid is ejected from an inkjet head, which is a line-type inkjet head, and applied to the recording medium in a single scan.

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