Active ray-curable inkjet ink, method for producing active ray-curable inkjet ink and inkjet recording method

Abstract

To provide an active ray-curable inkjet ink having excellent image uniformity and storage stability and capable of suppressing satellite formation during injection, a method for producing an active ray-curable inkjet ink and an inkjet recording method.SOLUTION: There is provided an active ray-curable inkjet ink containing a pigment, a dispersant, a gelling agent and an additive, which contains a basic compound having a structure derived from a hydroxy fatty acid as the dispersant and contains a polyether phosphate ester compound and a polyamine compound as the additive.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an actinic radiation-curable inkjet ink, a method for producing an actinic radiation-curable inkjet ink, and an inkjet recording method. In particular, the present invention relates to an actinic radiation-curable inkjet ink that is excellent in image uniformity and storage stability and can suppress the occurrence of satellites during ejection. [Background technology]

[0002] Inkjet recording methods are used in various printing fields because they can form images easily and inexpensively. One type of ink used in inkjet recording methods is actinic ray-curable ink. With actinic ray-curable ink, ink droplets are deposited on a recording medium, and then the ink is cured by irradiation with actinic ray to form an image. Inkjet recording methods using actinic ray-curable ink can form images even on recording media that do not absorb ink. Furthermore, the images formed have high abrasion resistance and adhesion, and have therefore attracted attention in recent years.

[0003] Inkjet recording requires ink droplets to be ejected from the nozzles of an inkjet head, so the ink must have ejection stability. Furthermore, when ink droplets that land on a recording medium mix with adjacent droplets, the resulting dots merge, resulting in blank areas. Furthermore, when color inks are used, problems such as color mixing can occur. Therefore, in Patent Document 1, a cationic UV ink containing a basic carbon black pigment and a dispersant having an acid value and an amine value is used to suppress the mixing of ejection properties and dots.

[0004] As another ink, Patent Document 2 discloses a radically polymerizable UV ink containing a specific azo pigment and a polymer dispersant, which improves long-term storage properties and high-temperature storage properties. In Patent Document 3, the storage stability and abrasion resistance are improved by preparing a UV ink containing a compound having a radically polymerizable ethylenically unsaturated group as a dispersion aid.

[0005] Incidentally, when recording on a recording medium at high speed, it is necessary to fix the ink immediately after the ink droplets land on the recording medium. For this reason, it is known that by including a gelling agent in actinic radiation-curable ink, the ink quickly thickens on the recording medium after landing, preventing the ink dots from coalescing. Preventing the ink dots from coalescing enables high-speed printing and printing on non-absorbent recording media, and improves image uniformity. However, inks containing gelling agents have the problem that the gelling agent's functionality deteriorates when stored for a long period of time. Furthermore, due to the components and physical properties of actinic radiation-curable inks, satellites can occur during ejection, which can degrade image quality, especially in high-speed printing. Here, satellite refers to a phenomenon in which a droplet (main droplet) ejected from a nozzle of an inkjet head separates before landing on a recording medium, and the main droplet and another droplet land on the recording medium. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2006 / 075468 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-202684 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-242684 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above problems and circumstances, and an object of the present invention is to provide an actinic radiation-curable inkjet ink that is excellent in image uniformity and storage stability and that can suppress the occurrence of satellites during ejection, a method for producing the actinic radiation-curable inkjet ink, and an inkjet recording method. [Means for solving the problem]

[0008] The present inventors have investigated the causes of the above problems in order to solve the above problems. The present inventors have incorporated a basic compound having a structure derived from a hydroxy fatty acid as a dispersant into an ink containing a gelling agent, and have incorporated a polyether phosphate ester compound and a polyamine compound as additives. They have found that this method provides excellent image uniformity and storage stability, and also suppresses the occurrence of satellites during ejection. That is, the above-mentioned problems of the present invention are solved by the following means.

[0009] 1. An actinic radiation curable inkjet ink containing a pigment, a dispersant, a gelling agent and additives, The dispersant contains a basic compound having a structure derived from a hydroxy fatty acid, The additives include a polyether phosphate ester compound and a polyamine compound. 1. An actinic radiation curable inkjet ink comprising:

[0010] 2. The content of the polyether phosphate ester compound and the polyamine compound is within the range of 0.1 to 0.6% by mass relative to the total mass of the actinic radiation-curable inkjet ink. 2. The actinic radiation-curable inkjet ink according to claim 1,

[0011] 3. The basic compound having a structure derived from a hydroxy fatty acid has a structure derived from hydroxystearic acid and has an amine value in the range of 10 to 20 mgKOH / g. 2. The actinic radiation-curable inkjet ink according to claim 1,

[0012] 4. The pigment is carbon black or a magenta pigment; The magenta pigment contains any one of CI Pigment Violet 19, CI Pigment Red 122, and CI Pigment Red 202. 2. The actinic radiation-curable inkjet ink according to claim 1,

[0013] 5. Manufacturing an actinic radiation-curable inkjet ink A method for manufacturing an actinic radiation-curable inkjet ink, comprising the steps of: the actinic radiation-curable inkjet ink is the actinic radiation-curable inkjet ink according to any one of items 1 to 4, preparing a pigment dispersion containing the pigment and the dispersant; preparing the actinic radiation-curable inkjet ink containing the pigment dispersion, the gelling agent, and the additives. 1. A method for producing an actinic radiation-curable inkjet ink, comprising:

[0014] 6. An inkjet recording method in which ink is ejected onto a recording medium to record, The ink is the actinic radiation-curable inkjet ink according to any one of items 1 to 4, The ink ejection temperature is within a range of 40 to 120°C, and The temperature of the recording medium is 60° C. or less. An inkjet recording method comprising: [Effects of the Invention]

[0015]

[0023] The above-described means of the present invention can provide an actinic radiation-curable inkjet ink that is excellent in image uniformity and storage stability and that can suppress the generation of satellites during ejection, a method for producing an actinic radiation-curable inkjet ink, and an inkjet recording method.

[0016] In this specification, the "active energy ray-curable inkjet ink" is also simply referred to as "ink." In the present invention, the term "dispersant" refers to a component contained for the purpose of dispersing a pigment. As will be described in detail later, in preparing an ink, first, a pigment dispersion containing a pigment and a dispersant is prepared. Then, the pigment dispersion and other components of the ink are mixed to prepare the ink. The term "additives" refers to components that are contained in ink for the purpose of adjusting the properties of the ink. As will be described in detail later, additives are added when the pigment dispersion liquid is mixed with other ink components during ink preparation.

[0017] The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows. In the present invention, the ink containing a gelling agent contains a basic compound having a structure derived from a hydroxy fatty acid as a dispersant, and a polyether phosphate ester compound and a polyamine compound as additives, thereby enabling the production of images with minimal dot mixing even after long-term storage of the ink. Furthermore, the occurrence of satellites during ejection can be suppressed, resulting in the production of high-quality images. Because the gelling agent in the ink is a hydrophobic component, prolonged storage of the ink can result in some of the gelling agent adsorbing to the pigment surface, causing dot mixing. Therefore, by using an additive containing a polyether phosphate ester compound and a polyamine compound, the additive coats part of the hydrophobic surface of the pigment. This prevents the gelling agent from adsorbing to the pigment surface. As a result, it is believed that ink performance can be maintained over the long term, dot mixing can be prevented, image uniformity can be improved, and satellites can be prevented from occurring during ejection. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram illustrating an exemplary configuration of an image forming apparatus; DETAILED DESCRIPTION OF THE INVENTION

[0019] The actinic radiation-curable inkjet ink of the present invention is an actinic radiation-curable inkjet ink containing a pigment, a dispersant, a gelling agent, and additives, and is characterized in that the dispersant contains a basic compound having a structure derived from a hydroxy fatty acid, and the additives contain a polyether phosphate ester compound and a polyamine compound. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0020] In an embodiment of the present invention, the content of the polyether phosphate ester compound and the polyamine compound is preferably within a range of 0.1 to 0.6% by mass relative to the total mass of the actinic radiation-curable inkjet ink, which can more reliably suppress the generation of satellites when the ink is ejected from the head.

[0021] In terms of ink ejection stability, it is preferable that the basic compound having a structure derived from a hydroxy fatty acid has a structure derived from hydroxystearic acid and has an amine value within the range of 10 to 20 mgKOH / g.

[0022] It is preferable in terms of image density that the pigment is carbon black or a magenta pigment, and that the magenta pigment contains any one of CI Pigment Violet 19, CI Pigment Red 122, and CI Pigment Red 202.

[0023] The method for producing an actinic radiation-curable inkjet ink of the present invention is a method for producing an actinic radiation-curable inkjet ink, the method comprising the steps of: preparing a pigment dispersion containing the pigment and the dispersant; and preparing the actinic radiation-curable inkjet ink containing the pigment dispersion, the gelling agent, and the additives. This allows for excellent image uniformity and storage stability, and suppresses the occurrence of satellites during ejection.

[0024] The inkjet recording method of the present invention is characterized in that the ink is used, the ink is ejected at a temperature within a range of 40 to 120° C., and the temperature of the recording medium is 60° C. or less. This allows recording under conditions suitable for ink containing a gelling agent.

[0025] The present invention, its components, and embodiments and modes for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0026] [Outline of the actinic radiation-curable inkjet ink of the present invention] The actinic radiation-curable inkjet ink of the present invention is an actinic radiation-curable inkjet ink containing a pigment, a dispersant, a gelling agent, and additives, wherein the dispersant contains a basic compound having a structure derived from a hydroxy fatty acid, and the additives contain a polyether phosphate ester compound and a polyamine compound.

[0027] In the present invention, the term "active energy ray-curable inkjet ink" refers to an inkjet ink that is cured by irradiation with active energy rays. In this specification, it is also simply referred to as "ink."

[0028] The ink of the present invention, containing a gelling agent, can undergo a reversible sol-gel phase transition depending on the temperature. In the present invention, "sol-gel phase transition" refers to the following series of phenomena: At high temperatures, the ink is in a fluid solution state, but when cooled below the gelation temperature, the entire liquid gels and loses its fluidity. Conversely, at low temperatures, the ink is in a fluid state, but when heated above the solization temperature, it returns to a fluid liquid state.

[0029] "Gel" refers to a solidified, semi-solidified, or thickened state in which substances lose their fluidity and aggregate due to interactions between them, accompanied by a sudden increase in viscosity and elasticity. Interactions occur in substances formed, for example, by lamellar structures, polymer networks formed by non-covalent bonds or hydrogen bonds, polymer networks formed by physical aggregation, and aggregated structures of fine particles. Interactions also occur in precipitated microcrystals.

[0030] "Sol" refers to a liquefied state in which the interactions that occur in the gel state are eliminated and the substance has fluidity.

[0031] There are various methods for causing a phase transition from sol to gel and vice versa. In the ink of the present invention, the phase transition can be reversible depending on the temperature. The "solation temperature" refers to the temperature at which ink in a gelled state becomes fluid due to the solation when heated. The "gelation temperature" refers to the temperature at which ink in a gelled state becomes fluid due to the gelation when cooled.

[0032] "Active energy rays" refer to radiation that acts physically and chemically on a polymerization initiator or a polymerizable compound to promote crosslinking and polymerization reactions. Specific examples of active energy rays include visible light, ultraviolet light, X-rays, electron beams, α-rays, β-rays, and γ-rays.

[0033] [Ink components] The ink of the present invention contains a pigment, a dispersant, a gelling agent, and additives, and may also contain a polymerizable compound, etc., as needed. The dispersant, additives, pigment, gelling agent, and other components will be described below in that order.

[0034] (1) Dispersant The ink of the present invention contains a compound having a structure derived from a hydroxy fatty acid and a basic functional group as a dispersant. If necessary, the ink may contain other dispersants to the extent that the effects of the present invention are not impaired.

[0035] In the present invention, the term "compound having a structure derived from a hydroxy fatty acid and a basic functional group" refers to a compound having a structure derived from a hydroxy fatty acid and a basic functional group.

[0036] Although details will be described later, for example, the compound described below is a reaction product of a polyester or polyesteramide having a structure derived from a hydroxy fatty acid and a polyallylamine. The polyallylamine has amino groups that exhibit basicity. Some of the amino groups in the polyallylamine react with the polyester or polyesteramide having a structure derived from a hydroxy fatty acid to form a salt or an acid amide. This allows a basic functional group capable of adsorbing a pigment to be introduced into the structure derived from a hydroxy fatty acid that has the ability to solvate. As a result, the compound functions well as a pigment dispersant.

[0037] The dispersant preferably has the function of suppressing aggregation of pigment particles by steric hindrance in addition to the function of adsorbing to and solvating the pigment, and therefore is preferably a polymer compound.

[0038] The content of the dispersant is preferably within a range of 10 to 60% by mass relative to the total mass of the pigment. When the content of the dispersant is 10% by mass or more, the dispersion stability of the pigment is improved. When the content of the dispersant is 60% by mass or less, the ejection stability of the ink from the inkjet head is improved.

[0039] (1.1) Constituent of polyester derivative having amine value Specifically, the dispersant according to the present invention is preferably a compound obtained by modifying a compound having a structure derived from a hydroxy fatty acid with polyallylamine. The compound having a structure derived from a hydroxy fatty acid is preferably a polyester having a structure derived from a hydroxy fatty acid, or a co-condensation product of a polyester and a polyamide (polyesteramide). Hereinafter, the "compound obtained by modifying a polyester or polyesteramide having a structure derived from a hydroxy fatty acid with polyallylamine" may also be simply referred to as a "polyester derivative having an amine value."

[0040] "Amine value" refers to the number of milligrams of potassium hydroxide equivalent to the acid required to neutralize the amine component contained in 1 g of sample. The amine value can be measured in accordance with ASTM D2074. "Having an amine value" means that the amine value defined above is greater than 0. In other words, "polyester derivatives having an amine value" refer to polyester derivatives that have an amine component. The polyester derivative having an amine value has a structure represented by the following general formula (I).

[0041] [ka]

[0042] In general formula (I), X and Y each independently represent a hydrogen atom, a polymerization initiator residue, or a chain transfer catalyst residue. 1 is a group represented by the following general formula (II) or (III), where n represents an integer in the range of 2 to 1000. However, when n R 1 At least one of the groups has a group represented by general formula (III).

[0043] [ka]

[0044] [ka]

[0045] In the general formulas (II) and (III), R 2 represents a residue obtained by removing a carboxy group from a polyester or polyesteramide having a structure derived from a hydroxy fatty acid. * represents a residue obtained by removing a carboxy group from a polyester or polyesteramide having a structure derived from a hydroxy fatty acid. 1 represents the position of the carbon bonded to The general formula (II) indicates that the carboxy group is modified with an amino group through an ionic bond.

[0046] The polyester derivative having an amine value can be obtained by reacting a polyester or polyesteramide having a structure derived from a hydroxy fatty acid with polyallylamine. Each component will be described below.

[0047] (1.1.1) Compounds having a structure derived from hydroxy fatty acids Examples of compounds having a structure derived from hydroxy fatty acids include polyesters made from hydroxy fatty acids, and polyesteramides, which are co-condensation products of such polyesters and polyamides. Hereinafter, polyesters and polyesteramides having a structure derived from a hydroxy fatty acid will also be simply referred to as "polyesters" and "polyesteramides."

[0048] The polyester essentially has a structure represented by the following general formula (IV), which is a structure derived from a hydroxy fatty acid. In addition to the structure represented by the following general formula (IV), the polyester may have a structure represented by the following general formula (V). Furthermore, the polyester may be formed by randomly polymerizing the repeating structures represented by the following general formulas (IV) and (V).

[0049] [ka]

[0050] In general formula (IV), R 3 represents a linear or branched alkylene group having 2 to 20 carbon atoms; a represents an integer of 2 to 100;

[0051] [ka]

[0052] In general formula (V), R 4represents an alkylene group having 2 to 20 carbon atoms, -C6H4-, or -CH=CH-. 5 R represents an alkylene group having 2 to 20 carbon atoms or a residue obtained by removing two hydroxy groups from a polyalkylene glycol. 4 and R 5 In the formula (I), the alkylene group may be linear or branched, and b represents an integer of 2 to 100. The chain may contain an ether bond.

[0053] The polyester in the polyesteramide essentially has a structure represented by the general formula (IV) above, which is a structure derived from a hydroxy fatty acid. In addition to the structure represented by the general formula (IV), the polyester may have a structure represented by the general formula (V) above. Furthermore, the polyester may be formed by randomly polymerizing the repeating structures represented by the general formulas (IV) and (V).

[0054] The polyamide in the polyesteramide has, for example, a structure represented by the following general formula (VI) or (VII): In addition, the polyamide may be formed by randomly polymerizing the repeating structures represented by the following general formulas (VI) and (VII).

[0055] [ka]

[0056] In general formula (VI), R 6 represents a linear or branched alkylene group having 2 to 20 carbon atoms. c represents an integer of 2 to 100.

[0057] [ka]

[0058] In general formula (VII), R 4 represents an alkylene group having 2 to 20 carbon atoms, -C6H4-, or -CH=CH-. 7represents an alkylene group having 2 to 20 carbon atoms. 4 and R 7 In the formula (I), the alkylene group may be linear or branched. d represents an integer of 2 to 100.

[0059] (1.1.1.1) Polyester The synthesis of polyesters having structures represented by the above general formulas (IV) and (V) will be described below.

[0060] (1.1.1.1.1) Synthesis of polyester having a structure represented by general formula (IV) The polyester having the structure represented by the general formula (IV) above can be synthesized using a hydroxy fatty acid having the structure represented by the following general formula (VIII) or a lactone represented by the following general formula (IX) as a raw material. The lactone represented by the following general formula (IX) can be synthesized by dehydration condensation of the hydroxy group and the carboxy group in the molecule of the hydroxy fatty acid.

[0061] Specifically, the polyester can be synthesized by adding a polymerization catalyst to a hydroxy fatty acid alone, a lactone alone, or a mixture of a hydroxy fatty acid and a lactone, and then heating the mixture. The reaction temperature is preferably within a range of 120 to 220°C, and more preferably within a range of 160 to 210°C.

[0062] The reaction time is preferably within the range of 0.5 to 72 hours. By carrying out the reaction under a nitrogen gas flow, the degree of polymerization can be increased. Furthermore, by using a polymerization initiator, the reaction can be easily controlled. When lactone is used as a raw material, the amount of monocarboxylic acid in the polymerization initiator is preferably 0.5 moles or less per mole of lactone.

[0063] [ka]

[0064] [ka]

[0065] In general formula (VIII), R 3 represents a linear or branched alkylene group having 2 to 20 carbon atoms.

[0066] Examples of hydroxy fatty acids include glycolic acid, 2-hydroxycaproic acid, ricinoleic acid, ricinolenic acid, a mixture of 9- and 10-hydroxystearic acid, 12-hydroxystearic acid, castor oil fatty acid, hydrogenated castor oil fatty acid, and lactic acid.

[0067] Examples of lactones include ε-caprolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, 4-methylcaprolactone, and 2-methylcaprolactone.

[0068] Examples of the polymerization catalyst include quaternary ammonium salts such as tetramethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium iodide, tetrabutylammonium iodide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, and benzyltrimethylammonium iodide; tetramethylphosphonium chloride, tetrabutylphosphonium chloride, tetramethylphosphonium bromide, tetrabutylphosphonium bromide, tetramethylphosphonium iodide, tetrabutylphosphonium iodide, and benzyltrimethylammonium iodide; quaternary phosphonium salts such as benzyltrimethylphosphonium chloride, benzyltrimethylphosphonium bromide, benzyltrimethylphosphonium iodide, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, and tetraphenylphosphonium iodide; phosphorus compounds such as triphenylphosphine; organic carboxylates such as potassium acetate, sodium acetate, potassium benzoate, and sodium benzoate; alkali metal alcoholates such as sodium alcoholate and potassium alcoholate; tertiary amines; organic tin compounds; organic aluminum compounds; organic titanate compounds; and zinc compounds such as zinc chloride.

[0069] Examples of the polymerization initiator include monocarboxylic acids, such as aliphatic monocarboxylic acids such as acetic acid, propionic acid, caprylic acid, nonanoic acid, capric acid, octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, isononanoic acid, and arachic acid; and aromatic monocarboxylic acids such as benzoic acid and p-butylbenzoic acid.

[0070] An example of the synthesis of a polyester having a structure represented by general formula (IV) is shown below: The following polyester can be synthesized from ε-caprolactone and 12-hydroxystearic acid.

[0071] [ka]

[0072] In the synthesized polyester, -CO-CH 10 The structure represented by -O- is a repeating structure derived from ε-caprolactone. 10 H 20 -CHC6H 13 The structure represented by -O- is a repeating unit derived from 12-hydroxystearic acid. These repeating units may be randomly polymerized. In the synthesized polyester, a1 and a2 represent an integer of 1 or more, and the sum of a1 and a2 is an integer of 2-100.

[0073] (1.1.1.1.2) Synthesis of polyester having a structure represented by general formula (V) The polyester having the structure represented by the general formula (V) above can be synthesized by reacting a dibasic acid having the structure represented by the following general formula (X) with a diol having the structure represented by the following general formula (XI).

[0074] Specifically, the synthesis can be carried out by adding a polymerization catalyst to a mixture of the dibasic acid and diol and heating the mixture. However, it is preferable to add a slight excess of the dibasic acid. The reaction temperature is preferably within the range of 120 to 220°C, more preferably within the range of 160 to 210°C. The reaction time is preferably within the range of 0.5 to 72 hours. The degree of polymerization can be increased by carrying out the reaction under a nitrogen stream. Furthermore, the use of a polymerization initiator makes it easy to control the reaction.

[0075] [ka]

[0076] [ka]

[0077] In general formula (X), R 4represents an alkylene group having 2 to 20 carbon atoms, -C6H4-, or -CH=CH-. In general formula (XI), R 5 R represents an alkylene group having 2 to 20 carbon atoms or a residue obtained by removing two hydroxy groups from a polyalkylene glycol. 4 and R 5 In the formula, the alkylene group may be linear or branched.

[0078] Examples of dibasic acids include dibasic acids having an unsaturated bond such as maleic anhydride and fumaric acid; aromatic dibasic acids such as phthalic anhydride and terephthalic acid; and saturated dibasic acids such as adipic acid and sebacic acid.

[0079] Examples of diols include alkylene glycols such as ethylene glycol, propylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,6-hexanediol; and ether bond-containing diols such as diethylene glycol, dipropylene glycol, and triethylene glycol.

[0080] The polymerization catalyst and polymerization initiator may be the same as those used in the synthesis of the polyester having the structure represented by general formula (IV).

[0081] A polyester in which the repeating units represented by general formula (IV) and general formula (V) are randomly polymerized can be synthesized by the following method. A polymerization catalyst is added to a mixture of a hydroxy fatty acid alone, a lactone alone, or a mixture of a hydroxy fatty acid and a lactone, and equimolar amounts of the above-mentioned diol and dibasic acid, and the mixture is heated. The reaction conditions are preferably the same as those used to synthesize a polyester having a structure represented by general formula (IV).

[0082] A polyester in which the repeating units represented by general formula (IV) and general formula (V) are polymerized in a block form can be synthesized by the following method: A polyester having a structure represented by general formula (IV) and a polyester having a structure represented by general formula (V) are synthesized in advance, and then these are subjected to dehydration condensation to obtain the polyester.

[0083] The molecular weight of the polyester is preferably within the range of 300 to 20,000. Furthermore, from the viewpoint of pigment dispersibility, the molecular weight is preferably within the range of 1,000 to 10,000. By having the molecular weight within the above range, the side chain of the dispersant can be made an appropriate length, resulting in excellent dispersibility. A polyester with a desired molecular weight can be obtained by adjusting the molar ratio of the polymerization initiator and the raw materials, hydroxy fatty acid, lactone, diol, and dibasic acid. Furthermore, a polyester with a desired molecular weight can be obtained by monitoring the acid value of the reaction product during the polyester synthesis reaction and adjusting the reaction time.

[0084] (1.1.1.2) Polyesteramide Polyesteramide is a co-condensation product of the above polyester and the following polyamide. It can be synthesized by polymerizing one or more polyester raw materials with one or more polyamide raw materials. Alternatively, it can be synthesized by pre-condensing the above polyester and the following polyamide, respectively, and then co-condensing them. The reaction conditions are preferably the same as those for synthesizing the following polyamide. The molecular weight (degree of polymerization) of polyesteramide can be measured by the acid value.

[0085] (1.1.1.2.1) Synthesis of polyamide having a structure represented by general formula (VI) The polyamide having the structure represented by the general formula (VI) above can be synthesized using a lactam having the structure represented by the following general formula (XII) or an aminocarboxylic acid having the structure represented by the following general formula (XIII) as a raw material.

[0086] Specifically, a lactam having a structure represented by the following general formula (XII), an aminocarboxylic acid having a structure represented by the following general formula (XIII), or a mixture of a lactam and an aminocarboxylic acid The mixture can be synthesized by heating. The polycondensation reaction is preferably carried out under a nitrogen stream. The reaction temperature is preferably within the range of 110 to 250°C, and more preferably within the range of 150 to 210°C. A reaction temperature of 250°C or less can suppress coloration of the reaction product, and a reaction temperature of 110°C or more can ensure a sufficient reaction rate.

[0087] The reaction time is preferably within the range of 0.5 to 72 hours. Furthermore, the use of a polymerization initiator makes it easy to control the reaction. Furthermore, the addition of a polymerization catalyst can shorten the reaction time. The molecular weight of the polyamide can be measured by its acid value. When lactam is used as a raw material, the amount of monocarboxylic acid in the polymerization initiator is preferably 0.5 moles or less per mole of lactam.

[0088] [ka]

[0089] [ka]

[0090] In the general formula (XII) and the general formula (XIII), R 6 represents a linear or branched alkylene group having 2 to 20 carbon atoms.

[0091] Examples of lactams include ε-caprolactam and ω-laurolactam. Examples of aminocarboxylic acids include aminocaproic acid and 11-aminoundecanoic acid. The polymerization catalyst and polymerization initiator can be the same as those used in the synthesis of polyesters having a structure represented by general formula (IV).

[0092] (1.1.1.2.2) Synthesis of polyamide having a structure represented by general formula (VII) The polyamide having the structure represented by the general formula (VII) above can be synthesized using a dibasic acid having the structure represented by the general formula (X) above and a diamine represented by the following general formula (XIV) as raw materials.

[0093] [ka]

[0094] In general formula (XIV), R 7 represents a linear or branched alkylene group having 2 to 20 carbon atoms.

[0095] Examples of diamines include ethylenediamine, 1,4-diaminobutane, and hexamethylenediamine.

[0096] In the synthesis of the polyamide having the structure represented by general formula (VII), the reaction conditions etc. can be the same as those in the synthesis of the polyamide having the structure represented by general formula (VI).

[0097] (1.1.2) Polyallylamine Polyallylamine can be obtained by polymerizing allylamine in the presence of a polymerization initiator and, optionally, in the presence of a chain transfer catalyst.

[0098] The polymerization initiator is not particularly limited, and examples thereof include ketone peroxides such as methyl ethyl ketone; diacyl peroxides such as benzoyl peroxide; diisopropyl Examples of the initiator include peroxydicarbonates such as peroxydicarbonate, peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane, hydroperoxides such as t-butyl hydroperoxide, peroxyesters such as t-butyl peroxypivalate, azobisisoptylonitrile, hydrogen peroxide, ferrous salts, etc. Furthermore, the polymerization initiators described in JP-B-2-14364 may also be used.

[0099] The chain transfer catalyst is not particularly limited, and examples thereof include alkyl mercaptans such as lauryl mercaptan; thiocarboxylic acids such as mercaptoacetic acid, 2-mercaptopropionic acid, and 3-mercaptopropionic acid; and thiocarboxylic acid esters such as butyl thioglycolate and 2-ethylhexyl thioglycolate.

[0100] The number average molecular weight of polyallylamine is not particularly limited as long as it is within the range of 150 to 100,000, but is preferably within the range of 600 to 20,000.

[0101] By having a number average molecular weight of 150 or more, sufficient adsorption to the pigment can be obtained, and by having a number average molecular weight of 100,000 or less, aggregation of the pigment particles can be suppressed.

[0102] Commercially available polyallylamine products may be used, such as "PAA-1LV," "PA-1," "PA-1L," "PA-1LV," "PAA-1.4L," "PAA-10C," "PAA-15," "PAA-15B," "PAA-L," "PAA-H," and "PAA-1L-15C" (all manufactured by Nitto Boseki Co., Ltd.).

[0103] Alternatively, polyallylamine of any molecular weight may be synthesized using the method described in Japanese Patent Publication No. 2-14364.

[0104] (1.1.3) Synthesis of polyester derivatives with amine values The terminal carboxyl groups of polyester or polyesteramide are modified with polyallylamine to synthesize a polyester derivative having an amine value.

[0105] The polyester or polyesteramide having free carboxy groups is preferably 1 mole or more in total per mole of polyallylamine having n amino groups, where n has the same meaning as n in the general formula (I) above and is an integer in the range of 2 to 1000. From the viewpoint of pigment dispersibility, the polyester or polyesteramide having free carboxy groups is more preferably in the range of 2 to 2n moles.

[0106] The polyester or polyesteramide may be used alone or in combination of two or more. Different types of polyester or polyesteramide may be simultaneously reacted with polyallylamine. A polymerization catalyst may be used in the reaction, and the same polymerization catalyst as that used in the synthesis of the polyester having the structure represented by general formula (IV) may be used. Furthermore, a solvent such as xylene or toluene may be used as the reaction solvent.

[0107] The reaction between a polyester or polyesteramide and a polyallylamine is a salt formation or acid amide bond formation reaction via the terminal free carboxy group of the former and the free amino group of the latter. Depending on the type of polyester or polyesteramide and the reaction conditions, an ester-amide exchange reaction also occurs simultaneously between the ester of the polyester or polyesteramide and the amino group in the side chain of the polyallylamine. Whether a salt or an acid amide is formed in the reaction between a polyester or polyesteramide and a polyallylamine depends on the reaction conditions.

[0108] The salt formation reaction and the acid amide bond formation reaction proceed simultaneously. The reaction temperature in the acid amide bond formation reaction is preferably within the range of 90 to 250°C, more preferably within the range of 90 to 210°C, and even more preferably within the range of 100 to 210°C. A reaction temperature of 250°C or less can suppress coloration of the reaction product, while a reaction temperature of 90°C or higher can ensure a sufficient reaction rate. Furthermore, by carrying out the reaction under a nitrogen stream, a reaction product with little coloration can be obtained.

[0109] On the other hand, the reaction temperature in the salt-forming reaction is preferably within the range of 20 to 140°C.

[0110] The polyester derivative having an amine value preferably has an acid amide bond. From the viewpoint of pigment dispersibility, it is preferable that 1 mole of polyallylamine having n amino groups reacts with 2 moles or more of the terminal carboxyl group of the polyester or polyesteramide. Here, n has the same meaning as n in the above general formula (I) and is an integer in the range of 2 to 1,000.

[0111] In the above general formula (I), n R 1 Among these, the residues in the form of bonded by an acid amide bond represented by the above general formula (III) are present preferably in the range of 60 to 95%, more preferably in the range of 65 to 90%.

[0112] In other words, 60% or more of the amino groups in the polyallylamine are covalently bonded to the polyester or polyesteramide via amide bonds. This prevents pigments from flocculating, allowing the polyallylamine to function as a pigment dispersant. Furthermore, 95% or less of the amino groups in the polyallylamine are covalently bonded to the polyester or polyesteramide via amide bonds. In other words, more than 5% of the amino groups remain as amino groups, allowing the polyallylamine to be sufficiently adsorbed to the pigment and function as a pigment dispersant.

[0113] (amine value) In a polyester derivative having an amine value, the amino group of the polyallylamine is covalently bonded within the above range. To achieve this, the amine value A can be calculated by measuring the amine value A immediately after mixing a polyester or polyesteramide having a carboxy group at one end with at least one polyallylamine, and the amine value B after the reaction is completed, and then calculating the change between these values. (Formula) Percentage of covalent bonds of amino groups in polyester derivatives with amine values ​​[%] ={(AB) / A}×100

[0114] The amine value may be measured immediately after mixing. However, since the reaction has not progressed immediately after mixing, the amine value of the polyallylamine used as a raw material can also be calculated from the masses of the polyester or polyesteramide and polyallylamine added to the reaction. Note that even if the carboxy group of the polyester or polyesteramide and the amino group of the polyallylamine form a salt, this does not affect the calculated amine value.

[0115] In the synthesis of a polyester derivative having an amine value, the mass ratio of polyallylamine to polyester or polyesteramide is preferably within the range of 1 / 5 to 1 / 30.

[0116] From the viewpoint of pigment dispersibility, the amine value (mgKOH / g) of the polyester derivative having an amine value is preferably within a range of 2.5 to 50, more preferably within a range of 5 to 30, and even more preferably within a range of 10 to 20. When the amine value is 2.5 or more, sufficient adsorption to the pigment can be achieved, and when the amine value is 50 or less, aggregation of the pigments can be suppressed.

[0117] The molecular weight of the polyester derivative having an amine value is preferably within the range of 2,000 to 100,000 from the viewpoint of pigment dispersibility.

[0118] In the present invention, the structure derived from a hydroxy fatty acid does not necessarily have to be a polyester. In the compound according to the present invention having a structure derived from a hydroxy fatty acid and a basic functional group, the carboxy group of the hydroxy fatty acid may be modified with an amine. Furthermore, if necessary, a dibasic acid, a diol, an aminocarboxylic acid, a lactam, or a diamine may be further used.

[0119] A polyester derivative having an amine value has the property of dispersing a pigment well in a resin or an organic solvent, and can be used as a pigment dispersant. The pigment dispersion may contain the polyester derivative having an amine value and the organic solvent used in the synthesis of the polyester derivative having an amine value. Furthermore, the polyester derivative having an amine value may be prepared as a pigment dispersion by distilling off the organic solvent used in the synthesis and then adding another solvent.

[0120] In the present invention, since the pigment dispersion is contained in an actinic radiation-curable inkjet ink, the dispersion medium is preferably a polymerizable compound, which will be described later.

[0121] (1.2) Other dispersants Examples of other dispersants that can be used in combination include polymer dispersants other than the above dispersants, surfactants, etc. Among these, polymer dispersants are preferred.

[0122] Examples of polymer dispersants include (meth)acrylic resins, styrene-(meth)acrylic resins, hydroxy group-containing carboxylic acid esters, salts of long-chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, naphthalenesulfonic acid formalin condensate salts, aromatic sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, stearylamine acetate, and pigment derivatives. In order to improve dispersibility, a dispersing aid may be further contained, if necessary.

[0123] (2) Additives The ink of the present invention contains a polyether phosphate ester compound and a polyamine compound as additives. If necessary, the ink may contain other additives to the extent that the effects of the present invention are not impaired. The other additives will be described later.

[0124] (2.1) Polyether phosphate ester compounds and polyamine compounds The polyether phosphate ester compound and the polyamine compound may be added separately or as a mixture, but it is more preferable to use them as a mixture. Examples of polyether phosphate ester compounds include polyoxyethylene alkylene ether phosphates and polyoxyethylene alkylphenyl ether phosphates. Examples of commercially available polyether phosphate ester compounds include Disparlon DA-375 (Kusumoto Chemicals Co., Ltd.) and Plysurf A-208 (Dai-ichi Kogyo Seiyaku Co., Ltd.).

[0125] Examples of polyamine compounds include ethylenediamine and polyallylamine. Examples of commercially available polyamines include the PAA series and PAS series (Nittobo Medical Co., Ltd.).

[0126] It is particularly preferable that the polyether phosphate ester compound and the polyamine compound are a mixture in order to exert the effects of the present invention. An example of a commercially available mixture of a polyether phosphate ester compound and a polyamine compound is DA-325 (Kusumoto Chemicals Co., Ltd.).

[0127] The content of the polyether phosphate ester compound and the polyamine compound is preferably within a range of 0.1 to 0.6% by mass relative to the total mass of the ink, since this can suppress the generation of satellites when the ink is ejected from an inkjet head. When the content is 0.1% by mass or more, the effect of suppressing the generation of satellites is enhanced. When the content is 0.6% by mass or less, the viscosity of the ink when ejected from the head can be kept within an appropriate range.

[0128] The mass ratio of the compound having a structure derived from a hydroxy fatty acid and a basic functional group as a dispersant to the polyether phosphate ester compound and polyamine compound as additives is preferably within the range of 2.73: 1 to 16.4: 1. By keeping the mass ratio within this range, a particularly significant effect on the storage stability of the ink can be obtained.

[0129] (3) Pigments The ink of the present invention contains a pigment. There are no particular restrictions on the pigment, and any known pigment can be used.

[0130] Examples of pigments include inorganic pigments such as titanium dioxide, iron oxide, cadmium sulfide, calcium carbonate, barium carbonate, barium sulfate, clay, talc, yellow lead, and carbon black, as well as organic pigments such as azo pigments, diazo pigments, condensed azo pigments, thioindigo pigments, indanthrone pigments, quinacridone pigments, anthraquinone pigments, benzimidazolone pigments, perylene pigments, perinone pigments, phthalocyanine pigments, halogenated phthalocyanine pigments, anthrapyridine pigments, and dioxazine pigments.

[0131] Among these, the pigment is preferably carbon black or an organic pigment, since the storage stability of the ink is improved and the effects of the present invention can be more pronounced.

[0132] The organic pigment is preferably a magenta pigment, and the magenta pigment is preferably CI Pigment Violet 19, CI Pigment Red 122, or CI Pigment Red 202. These may be contained alone or in combination of two or more.

[0133] The average particle size of the pigment is not particularly limited. However, from the viewpoint that the finer the particle size, the better the color development, it is preferably within the range of 0.01 to 0.4 μm, and more preferably within the range of 0.02 to 0.2 μm. Furthermore, the maximum particle size of the pigment is preferably about 3 μm, and more preferably about 1 μm. The particle size of the pigment can be adjusted by selecting the type of pigment, dispersant, dispersion medium, dispersion conditions, filtration conditions, etc. Controlling the particle size of the pigment can prevent clogging of the head nozzle and maintain the storage stability, transparency, and curing sensitivity of the ink.

[0134] The particle size of the pigment can be measured by a known measurement method, specifically, a centrifugal sedimentation light transmission method, an X-ray transmission method, a laser diffraction scattering method, or a dynamic light scattering method.

[0135] The pigment content is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.4 to 10% by mass, relative to the total mass of the ink. A pigment content of 0.1% by mass or more provides good color development, while a pigment content of 20% by mass or less provides appropriate ink viscosity.

[0136] (4) Gelling agent In the present invention, the term "gelling agent" refers to an organic substance that is solid at room temperature and becomes liquid when heated. The melting point of the gelling agent is preferably within a range of 30 to 150°C. The gelling agent preferably dissolves in the polymerizable compound described below at a temperature higher than the gelling temperature. Furthermore, the gelling agent preferably crystallizes in the ink at a temperature equal to or lower than the gelling temperature.

[0137] The "sol-gel phase transition temperature" refers to the temperature at which a material changes (transitions) from a sol state to a gel state. The "sol-gel phase transition temperature" is synonymous with the terms gel transition temperature, gel melting temperature, gel softening temperature, sol-gel transition point, and gel point.

[0138] When the gelling agent crystallizes in the ink, plate-like crystals, which are crystallized products of the gelling agent, preferably form a three-dimensionally enclosed space. The plate-like crystals preferably encapsulate the polymerizable compound in the formed space. This structure, in which the polymerizable compound is encapsulated in the three-dimensionally enclosed space formed by the plate-like crystals, is called a "house of cards structure."

[0139] The formation of a house-of-cards structure makes it possible to hold the liquid polymerizable compound and fix (pin) the ink droplets. This also makes it possible to prevent the droplets from coalescing. To form a house-of-cards structure, it is preferable that the polymerizable compound and the gelling agent dissolved in the ink are compatible with each other. If the polymerizable compound and the gelling agent dissolved in the ink are phase-separated, it is difficult to form a house-of-cards structure.

[0140] The gelling agent is not particularly limited. Examples of gelling agents include ketone waxes such as dilignoceryl ketone, dibehenyl ketone, distearyl ketone, dieicosyl ketone, dipalmityl ketone, dilauryl ketone, dimyristyl ketone, myristyl palmityl ketone, and palmityl stearyl ketone; Ester waxes such as behenyl behenate, icosanoic acid icosyl, stearyl stearate, palmityl stearate, cetyl palmitate, myristyl myristate, cetyl myristate, and myricyl cerotenate; Petroleum-based waxes such as paraffin wax, microcrystalline wax, and petrolactam; Vegetable waxes such as candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax, and jojoba esters; Animal waxes such as beeswax, lanolin, and whale wax; Mineral waxes such as montan wax and hydrogenated wax; hydrogenated castor oil or hydrogenated castor oil derivatives; Modified waxes such as montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives, and polyethylene wax derivatives; higher alcohols such as stearyl alcohol and behenyl alcohol; hydroxystearic acids such as 12-hydroxystearic acid; 12-hydroxystearic acid derivatives; fatty acid amides such as lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, and 12-hydroxystearic acid amide; N-substituted fatty acid amides such as N-stearyl stearic acid amide and N-oleyl palmitic acid amide; Special fatty acid amides such as N,N'-ethylenebisstearylamide, N,N'-ethylenebis-12-hydroxystearylamide, and N,N'-xylylenebisstearylamide; higher amines such as dodecylamine, tetradecylamine, and octadecylamine; fatty acid ester compounds such as stearyl stearic acid, oleyl palmitic acid, glycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene glycol fatty acid esters, and polyoxyethylene fatty acid esters; esters of sucrose fatty acids such as sucrose stearate, sucrose palmitate, etc.; Synthetic waxes such as polyethylene wax and α-olefin maleic anhydride copolymer wax; Dimer acid; Dimer diol and the like. These may be contained alone or in combination of two or more.

[0141] The gelling agent may be a commercially available product. Commercially available ketone waxes include, for example, "18-Pentatriacontanone" (manufactured by Alfa Aeser), "Hentriacontan-16-one" (manufactured by Alfa Aeser), and "Kao (registered trademark) Wax T1" (manufactured by Kao Corporation). Examples of ester waxes include "Unistar (registered trademark) M-2222SL" (manufactured by NOF Corporation), "Excepar (registered trademark) SS" (manufactured by Kao Corporation, melting point 60°C), "EMALEX (registered trademark) CC-18" (manufactured by Nippon Emulsion Co., Ltd.), "Amleps (registered trademark) PC" (manufactured by Kokyu Alcohol Kogyo Co., Ltd.), "Excepar (registered trademark) MY-M" (manufactured by Kao Corporation), "Sperm Acetate" (manufactured by NOF Corporation), and "EMALEX (registered trademark) CC-10" (manufactured by Nippon Emulsion Co., Ltd.). Commercially available fatty acid amides include, for example, the "Nikkaamide (registered trademark) series" (manufactured by Nippon Kasei Chemical Co., Ltd.), the "ITOWAX series" (manufactured by Ito Oil Mills Co., Ltd.), and the "FATTYAMID series" (manufactured by Kao Corporation). Commercially available fatty acid ester compounds include, for example, the "EMALLEX (registered trademark) series" (manufactured by Nippon Emulsion Co., Ltd.), the "Rikemal (registered trademark) series" (manufactured by Riken Vitamin Co., Ltd.), and the "Poem (registered trademark) series, etc." (manufactured by Riken Vitamin Co., Ltd.). Commercially available sucrose fatty acid esters include, for example, the "Ryoto Sugar Ester (registered trademark) series" (manufactured by Mitsubishi Chemical Foods Corporation). Examples of commercially available synthetic waxes include the "UNILIN (registered trademark) series" (manufactured by Baker-Petrolite). Commercially available dimer diol products include, for example, the "PRIPOR series" (manufactured by CRODA).

[0142] Among these, the gelling agent is preferably a ketone wax, an ester wax, a higher fatty acid, a higher alcohol, or a fatty acid amide, and more preferably a ketone wax or an ester wax.

[0143] Particularly preferred gelling agents include compounds represented by the following general formula (G1) or (G2). General formula (G1):R 21 -CO-R 22 General formula (G2):R 23-COO-R 24 In the formula, R 21 ~R 24 each independently represents an alkyl chain having 12 or more carbon atoms, a straight chain portion, and which may be branched.

[0144] General formula (G1) is called a ketone wax, and general formula (G2) is called a fatty acid ester. These gelling agents can gel ink droplets more stably and with high reproducibility. This can prevent ink droplets (dots) from coalescing when they land on a recording medium.

[0145] The sol-gel transition temperature of the ink can be set as desired. From the viewpoints of stable ejection of ink droplets and preventing adverse effects associated with high-temperature heating, the sol-gel transition temperature is preferably within the range of 30 to 100°C. Furthermore, the sol-gel transition temperature is preferably between the temperature of the ink in the inkjet head and the temperature of the recording medium.

[0146] The sol-gel transition temperature can be measured, for example, by placing a gel-like test piece on a heat plate. The heat plate is then heated to measure the temperature at which the test piece loses its shape, and this temperature can be determined as the sol-gel phase transition temperature. Alternatively, the temperature can be measured using a commercially available viscoelasticity measuring device, such as the viscoelasticity measuring device "MCR300" (manufactured by Physica).

[0147] The sol-gel transition temperature can be adjusted by the type, content, etc. of the polymerizable compound described below.

[0148] When the temperature of ink droplets ejected from an inkjet head and deposited on a recording medium drops below the sol-gel phase transition temperature, the ink droplets quickly gel. This prevents ink droplets (ink droplets) from mixing or merging, enabling high-quality images to be produced even at high speeds. The gelled ink droplets are then cured by exposure to active energy rays, forming a solid image film on the recording medium.

[0149] The ink droplets that land on the recording medium quickly gel, making them less likely to spread on the recording medium and preventing oxygen from entering the ink droplets. As a result, the ink is less susceptible to oxygen inhibition during curing.

[0150] The content of the gelling agent is preferably within the range of 1 to 10% by mass, more preferably within the range of 1 to 7% by mass, relative to the total mass of the ink. When two or more types of gelling agents are contained, it is preferable that the total mass of these is within the above range. When the content of the gelling agent is 1% by mass or more, the ink undergoes a sufficient sol-gel phase transition. When the content of the gelling agent is 10% by mass or less, ink ejection stability from an inkjet head is obtained.

[0151] (5) Polymerizable compound The ink of the present invention preferably contains a polymerizable compound that is cured by irradiation with actinic energy rays. By using an ink containing a polymerizable compound, it is possible to form an image even on a recording medium that does not absorb ink.

[0152] Examples of the polymerizable compound include a radically polymerizable compound, a cationically polymerizable compound, and a mixture thereof. The compound includes a monomer, a polymer (oligomer or polymer), and a mixture thereof. The polymerizable compound may be contained alone or in combination of two or more.

[0153] The content of the polymerizable compound is preferably within a range from 1 to 97% by mass, and more preferably within a range from 30 to 95% by mass, relative to the total mass of the ink.

[0154] (5.1) Radical polymerizable compound The term "radically polymerizable compound" refers to a compound having an ethylenically unsaturated bond capable of radical polymerization. Examples of radically polymerizable compounds include unsaturated carboxylic acids and their salts; unsaturated carboxylic acid ester compounds; unsaturated carboxylic acid urethane compounds; unsaturated carboxylic acid amide compounds and their anhydrides; acrylonitrile; styrene; unsaturated polyesters; unsaturated polyethers; unsaturated polyamides; and unsaturated urethanes. Examples of unsaturated carboxylic acids include (meth)acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid.

[0155] In this specification, (meth)acrylic acid is a general term for acrylic acid and methacrylic acid, and means either or both of these. "(Meth)acrylate" is a general term for acrylate and methacrylate, and means either or both of them. "Acrylate" is a general term for acrylate monomers and acrylate oligomers, and means either or both of them. Similarly, "methacrylate" is a general term for methacrylate monomers and methacrylate oligomers, and means either or both of them.

[0156] Among them, the polymerizable compound is preferably an unsaturated carboxylic acid ester compound, more preferably a (meth)acrylate compound. The (meth)acrylate compound may be not only a monomer described below, but also an oligomer, a mixture of a monomer and an oligomer, a modified product, or the like.

[0157] (5.1.1) (Meth)acrylate compounds Examples of the (meth)acrylate compound include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomylstyryl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, and methoxypolyethylene. Examples of monofunctional monomers include glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, and t-butylcyclohexyl (meth)acrylate.

[0158] Examples of the (meth)acrylate compound include bifunctional monomers such as triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A PO adduct di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate.

[0159] Examples of the (meth)acrylate compound include trifunctional or higher polyfunctional monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate.

[0160] Among these, from the viewpoint of photosensitivity and the like, the (meth)acrylate compound is preferably stearyl (meth)acrylate, lauryl (meth)acrylate, isostearyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, isobornyl (meth)acrylate, tetraethylene glycol di(meth)acrylate, or glycerin propoxy tri(meth)acrylate.

[0161] The (meth)acrylate compound may be a modified product. Examples of the modified product include ethylene oxide-modified (meth)acrylate compounds such as ethylene oxide-modified trimethylolpropane tri(meth)acrylate and ethylene oxide-modified pentaerythritol tetraacrylate; caprolactone-modified (meth)acrylate compounds such as caprolactone-modified trimethylolpropane tri(meth)acrylate; and caprolactam-modified (meth)acrylate compounds such as caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0162] Since the ink of the present invention is a sol-gel phase transition type, it is preferable that at least a portion of the polymerizable compound is an ethylene oxide-modified (meth)acrylate compound. Ethylene oxide-modified (meth)acrylate compounds are highly photosensitive and tend to form a house-of-cards structure when the ink gels at low temperatures. Furthermore, ethylene oxide-modified (meth)acrylate compounds tend to dissolve in other ink components at high temperatures. Ethylene oxide-modified (meth)acrylate compounds have little cure shrinkage, which can prevent curling of printed matter.

[0163] Examples of the ethylene oxide-modified (meth)acrylate compound include: 4EO-modified hexanediol diacrylate "CD561" (molecular weight: 358), 3EO-modified trimethylolpropane triacrylate "SR454" (molecular weight: 429), 6EO-modified trimethylolpropane triacrylate "SR499" (molecular weight: 560), 4EO-modified pentaerythritol tetraacrylate "SR494" (molecular weight: 528) (all manufactured by Sartomer); Polyethylene glycol diacrylate "NK Ester A-400" (molecular weight: 508), polyethylene glycol diacrylate "NK Ester A-600" (molecular weight: 742), polyethylene glycol dimethacrylate "NK Ester 9G" (molecular weight: 536), polyethylene glycol dimethacrylate "NK Ester 14G" (molecular weight: 770) (all manufactured by Shin-Nakamura Chemical Co., Ltd.); Tetraethylene glycol diacrylate "V#335HP" (Osaka Organic Chemical Industry Co., Ltd., molecular weight: 302); 3PO-modified trimethylolpropane triacrylate "Photomer (registered trademark) 4072" (manufactured by Cognis, molecular weight: 471, ClogP: 4.90); Examples include 1,10-decanediol dimethacrylate "NK Ester DOD-N" (molecular weight: 310, ClogP: 5.75), tricyclodecane dimethanol diacrylate "NK Ester A-DCP" (molecular weight: 304, ClogP: 4.69), and tricyclodecane dimethanol dimethacrylate "NK Ester DCP" (molecular weight: 332, ClogP: 5.12) (all manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0164] Here, the "logP value" is a coefficient that indicates the affinity of an organic compound for water and 1-octanol. "P" is the 1-octanol / water partition coefficient, which is the ratio of the equilibrium concentrations of a compound in each solvent at equilibrium when a trace amount of compound is dissolved as a solute in a two-phase solvent consisting of 1-octanol and water. The logarithm of the 1-octanol / water partition coefficient to the base 10 is expressed as logP. In other words, the "logP value" is the logarithm of the 1-octanol / water partition coefficient and is known as an important parameter that indicates the hydrophilicity or hydrophobicity of a molecule.

[0165] The "ClogP value" refers to a logP value calculated by calculation. The ClogP value can be calculated by the fragment method, the atomic approach method, or the like. Specific methods for calculating the ClogP value include the fragment method described in the literature (C. Hansch and A. Leo, "Substituent Constants for Correlation Analysis in Chemistry and Biology": John Wiley & Sons, New York, 1969). Other methods include a method using the commercially available software package 1 or 2 listed below.

[0166] Software Package 1: MedChem Software (Release 3.54, August 1991, Medicinal Chemistry Project, Pomona College, Claremont, CA) Software package 2: ChemDraw Ultra ver. 8.0 (April 2003, CambridgeSoft Corporation, USA)

[0167] The numerical values ​​of the ClogP values ​​described in this specification are "ClogP values" calculated using software package 2.

[0168] The (meth)acrylate compound may be a polymerizable oligomer, such as an epoxy (meth)acrylate oligomer, an aliphatic urethane (meth)acrylate oligomer, an aromatic urethane (meth)acrylate oligomer, a polyester (meth)acrylate oligomer, or a linear (meth)acrylic oligomer.

[0169] (5.2) Cationic polymerizable compounds The term "cationically polymerizable compound" refers to a compound having a cationically polymerizable group in the molecule. Examples of the cationically polymerizable compound include epoxy compounds, vinyl ether compounds, and oxetane compounds. These compounds may be contained alone or in combination of two or more.

[0170] (5.2.1) Epoxy compounds Examples of epoxy compounds include aromatic epoxides, alicyclic epoxides, aliphatic epoxides, etc. Among these, aromatic epoxides or alicyclic epoxides are preferred from the viewpoint of enhancing curability.

[0171] Examples of aromatic epoxides include diglycidyl ethers or polyglycidyl ethers obtained by reacting a polyhydric phenol or its alkylene oxide adduct with epichlorohydrin. Examples of polyhydric phenols or their alkylene oxide adducts to be reacted include bisphenol A or its alkylene oxide adducts. Examples of alkylene oxides in the alkylene oxide adducts include ethylene oxide and propylene oxide.

[0172] Examples of alicyclic epoxides include cycloalkane oxide-containing compounds obtained by epoxidizing a cycloalkane-containing compound with an oxidizing agent such as hydrogen peroxide, peracid, etc. Examples of cycloalkanes in the cycloalkane oxide-containing compounds include cyclohexene and cyclopentene.

[0173] Examples of aliphatic epoxides include diglycidyl ethers or polyglycidyl ethers obtained by reacting an aliphatic polyhydric alcohol or its alkylene oxide adduct with epichlorohydrin. Examples of aliphatic polyhydric alcohols include alkylene glycols such as ethylene glycol, propylene glycol, and 1,6-hexanediol. Examples of the alkylene oxide in the alkylene oxide adduct include ethylene oxide and propylene oxide.

[0174] (5.2.2) Vinyl ether compounds Examples of vinyl ether compounds include monovinyl ether compounds such as ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

[0175] Examples of the vinyl ether compound include divinyl ether compounds and trivinyl ether compounds such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylolpropane trivinyl ether. From the viewpoint of curability, adhesion, etc., a divinyl ether compound or a trivinyl ether compound is preferred.

[0176] (5.2.3) Oxetane compounds The oxetane compound is a compound having an oxetane ring. Examples of the oxetane compound include the oxetane compounds described in JP-A-2001-220526, JP-A-2001-310937, and JP-A-2005-255821. More specifically, examples include the compound represented by general formula (1) described in paragraph 0089 of JP-A-2005-255821, the compound represented by general formula (2) described in paragraph 0092 of the same publication, the compound represented by general formula (7) described in paragraph 0107, the compound represented by general formula (8) described in paragraph 0109, and the compound represented by general formula (9) described in paragraph 0116.

[0177] (6) Fatty acids The ink of the present invention may further contain a fatty acid. By containing a fatty acid, the storage stability and ejection stability of the ink are improved. Furthermore, by containing a fatty acid, the ink surface slippage when ejected onto a recording medium is improved.

[0178] The fatty acid is preferably a compound having 12 or more carbon atoms. Examples of fatty acids include behenic acid (C 22 H 44 O2), arachidic acid (C 20 H 40 O2), stearic acid (C 18 H 36O2), palmitic acid (C 16 H 32 O2), myristic acid (C 14 H 28 O2), lauric acid (C 12 H 24 O2), oleic acid (C 18 H 34 O2), erucic acid (C 22 H 42 O2) etc.

[0179] Commercially available fatty acids may be used. Examples of commercially available products include "Lunac (registered trademark) BA," "Lunac (registered trademark) S-90V," "Lunac (registered trademark) S-98," "Lunac (registered trademark) P-70," "Lunac (registered trademark) P-95," "Lunac (registered trademark) MY-98," "Lunac (registered trademark) L-70," and "Lunac (registered trademark) L-98" (all manufactured by Kao Corporation), "NAA (registered trademark)-222S Beads," "NAA (registered trademark)-222 Powder," "Sakura Stearic Acid Beads," "Camellia Stearic Acid Beads," "Sakura Stearic Acid Powder," "Camellia Stearic Acid Powder," "NAA (registered trademark)-160," "NAA (registered trademark)-142," "NAA (registered trademark)-122," "NAA (registered trademark)-34," "NAA (registered trademark)-35," and erucic acid (all manufactured by NOF Corporation).

[0180] The content of the fatty acid is preferably in the range of 0.01 to 10 ppm by mass, more preferably in the range of 0.01 to 0.18 ppm by mass, relative to the total mass of the ink. A content of 0.01 ppm by mass or more provides good ink storage stability and ejection stability. Furthermore, when the ink is ejected onto a recording medium, the ink surface has good slip properties, preventing so-called paper jams. A content of 10 ppm by mass or less provides good ink storage stability.

[0181] (7) Polymerization initiator The ink of the present invention may further contain a polymerization initiator. Specifically, when the active energy rays are electron beams, the ink does not need to contain a polymerization initiator, but when the active energy rays are ultraviolet rays, the ink preferably contains a polymerization initiator.

[0182] Polymerization initiators are classified into intramolecular bond cleavage type and intramolecular hydrogen abstraction type.

[0183] Examples of the intramolecular bond cleavage type polymerization initiator include acetophenone-based initiators such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone; benzoins such as benzoin methyl ether and benzoin isopropyl ether; acylphosphine oxide-based initiators such as 2,4,6-trimethylbenzoin diphenylphosphine oxide; benzyl glyoxyesters; and methylphenyl glyoxyesters.

[0184] Examples of the intramolecular hydrogen abstraction polymerization initiator include benzophenone-based initiators such as benzophenone, o-benzoylmethylbenzoate-4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone-based initiators such as 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone; aminobenzophenone-based initiators such as Michler's ketone and 4,4'-diethylaminobenzophenone; 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0185] Although it depends on the constituent components of the ink, the content of the polymerization initiator is preferably within the range of 0.01 to 10% by mass relative to the total mass of the ink.

[0186] The ink of the present invention may contain a photoacid generator as a polymerization initiator. Examples of photoacid generators include compounds used in chemically amplified photoresists or photocationic polymerization. Details are described in "Organic Materials for Imaging," edited by the Organic Electronics Materials Research Group, Bunshin Publishing (1993), pp. 187-192.

[0187] (8) Polymerization initiator aid The ink of the present invention may further contain a polymerization initiator aid. Examples of the polymerization initiator aid include tertiary amine compounds, and among these, aromatic tertiary amine compounds are preferred.

[0188] Examples of aromatic tertiary amine compounds include N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-toluidine, N,N-dimethylamino-p-benzoic acid ethyl ester, N,N-dimethylamino-p-benzoic acid isoamyl ethyl ester, N,N-dihydroxyethylaniline, triethylamine, and N,N-dimethylhexylamine.

[0189] Among these, the aromatic tertiary amine compound is preferably N,N-dimethylamino-p-benzoic acid ethyl ester or N,N-dimethylamino-p-benzoic acid isoamyl ethyl ester, which may be contained alone or in combination of two or more.

[0190] (9) Polymerization inhibitor The ink of the present invention may further contain a polymerization inhibitor. Examples of polymerization inhibitors include (alkyl)phenols, hydroquinone, catechol, resorcinol, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupferron, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N-(3-oxyanilino-1,3-dimethyl)- butylidene)aniline oxide, dibutyl cresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, cyclohexanone oxime, etc.

[0191] (10) Other The ink of the present invention may further contain other components as necessary. Examples of other components include various additives other than the additives described above, other resins, etc. Examples of various additives other than the additives described above include surfactants, leveling additives, matting agents, ultraviolet absorbers, infrared absorbers, antibacterial agents, and basic compounds for improving the storage stability of the ink.

[0192] Examples of basic compounds include basic alkali metal compounds, basic alkaline earth metal compounds, and basic organic compounds such as amines. Examples of other resins include resins for adjusting the physical properties of the cured film. Examples of other resins include polyester, polyurethane, vinyl resin, acrylic resin, rubber-based resin, and wax.

[0193] [Ink properties] The ink of the present invention preferably has a viscosity at 80°C in the range of 3 to 20 mPa·s. This range ensures stable ejection of the ink from an inkjet head. Furthermore, the viscosity at 25°C is preferably 1000 mPa·s or greater. By having this range, the ink can be sufficiently gelled when cooled to room temperature after landing on a recording medium.

[0194] The ink preferably has a sol-gel phase transition temperature within the range of 40 to 70°C. When the ink has a phase transition temperature of 40°C or higher, the ink quickly thickens after landing on a recording medium, making it easy to fix. Furthermore, when the ink has a phase transition temperature of 70°C or lower, ink ejection stability is achieved even when the ink ejection temperature is set to the commonly used temperature of about 80°C.

[0195] The viscosity of the ink at 25°C, the viscosity at 80°C, and the phase transition temperature can be determined by measuring the temperature change of the ink's dynamic viscoelasticity using a rheometer. For example, the ink is heated to 100°C, and while measuring the viscosity using a stress-controlled rheometer, the ink is cooled to 20°C under conditions of a shear rate of 11.7 (1 / s) and a cooling rate of 0.1°C / s, to obtain a temperature change curve of viscosity. Note that, as the stress-controlled rheometer, for example, a "Physica MCR301" (cone plate diameter: 75 mm, cone angle: 1.0°, manufactured by Anton Paar) can be used.

[0196] The viscosity at 25°C and the viscosity at 80°C are determined by reading the viscosity at 25°C and 80°C, respectively, on the viscosity temperature curve. The phase transition temperature is determined as the temperature at which the viscosity reaches 200 mPa s on the viscosity temperature curve.

[0197] [Ink manufacturing method] The method for producing an actinic radiation-curable inkjet ink of the present invention includes the steps of preparing a pigment dispersion containing the pigment and the dispersant, and preparing the ink containing the pigment dispersion, the gelling agent, and the additives. That is, the pigment dispersion is first prepared, and then mixed with other components to prepare the ink.

[0198] (1) A step of preparing a pigment dispersion containing a pigment and a dispersant In this step, a pigment dispersion containing a pigment and a dispersant is prepared. The method for preparing the pigment dispersion is not particularly limited, and the pigment dispersion can be prepared by a known method. As the dispersion medium for the pigment dispersion, a polymerizable compound having a relatively low viscosity and a low molecular weight is preferred from the viewpoints of dispersibility and ease of handling with the polymerizable compound.

[0199] The pigment dispersion can be prepared by dispersing the pigment in the polymerizable compound using the dispersant. The pigment can be dispersed using, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like.

[0200] (2) A step of preparing an actinic ray-curable inkjet ink containing a pigment dispersion, a gelling agent, and additives. In this step, an ink containing a pigment dispersion, a gelling agent, and additives is prepared. The method for mixing the ink components is not particularly limited, and they can be mixed by any known method. For example, other ink components may be added to the prepared pigment dispersion and mixed while heating. The resulting mixture is preferably filtered through a predetermined filter.

[0201] [Inkjet recording method] The inkjet recording method of the present invention is an inkjet recording method in which the ink is ejected and impacted onto a recording medium, wherein the ink is ejected at a temperature within a range of 40 to 120°C, and the recording medium has a temperature of 60°C or less.

[0202] In the inkjet recording method of the present invention, the above-described ink is used. Specifically, when a multicolor image is formed using a plurality of inks with different compositions, at least one of the plurality of inks may be the ink of the present invention.

[0203] In the inkjet recording method of the present invention, an inkjet printer is used. Inkjet printers are generally classified into an on-demand type and a continuous type depending on the ink ejection method. The inkjet printer used in the present invention may be of either type. Examples of on-demand inkjet printers include electro-mechanical conversion types, including single-cavity, double-cavity, bender, piston, shear-mode, and shared-wall types; and electro-thermal conversion types, including thermal inkjet and bubble-jet (Bubble Jet is a registered trademark of Canon Inc.) types.

[0204] Inkjet printers are further classified into scan type and line type printers depending on the scanning method of the head. The inkjet printer used in the present invention may be of either type. Either type may be selected depending on the resolution and recording speed of the recorded matter (image). The ink of the present invention can be quickly fixed, so that high-quality recorded matter can be obtained even in high-speed recording using the line type.

[0205] The recording medium may be any recording medium on which an image can be formed using the ink of the present invention. Examples of recording media include non-absorbent recording media made of plastics including polyester, polyvinyl chloride, polyethylene, polyurethane, polypropylene, acrylic resin, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate, and polybutadiene terephthalate; non-absorbent inorganic recording media such as metals and glass; and papers such as coated printing paper and coated printing paper B.

[0206] Examples of plastic films include PP film, PET film, OPS film, OPP film, ONy film, PVC film, PE film, and TAC film.

[0207] (1) The process of ejecting ink from the head In the step of ejecting ink from the head, ink droplets are ejected from the nozzles of the head. The injection method is not particularly limited.

[0208] The temperature of the ink inside the head is preferably within the range of 40 to 120°C, and more preferably within the range of 50 to 85°C. When the temperature of the ink inside the head is 40°C or higher, ejection stability of the ink from the head is ensured. Furthermore, when the temperature is 120°C or lower, volatilization of the ink components is suppressed, and the thermal load on the head can be reduced.

[0209] When the temperature of the ink is within the range of 40 to 120°C, the viscosity of the ink is preferably within the range of 3 to 20 mPa·s.

[0210] It is also preferable to set the temperature of the ink inside the head to be 10 to 40°C higher than the gelling temperature of the ink. By setting the temperature of the ink inside the head to a temperature 10°C higher than the gelling temperature, the ink will not gel inside the head or on the nozzle surface, and the ink can be ejected well. Furthermore, by setting the temperature of the ink inside the head to a temperature 40°C higher than the gelling temperature, the thermal load on the head can be reduced. In particular, with heads that use piezoelectric elements, performance degradation due to thermal load is likely to occur, so it is preferable to set the temperature of the ink inside the head within the above range.

[0211] The method for heating the ink is not particularly limited. For example, the ink can be heated by heating at least one of the ink supply system, the piping with a filter, the piezo head, etc., using a panel heater, a ribbon heater, warm water, etc. The ink supply system includes an ink tank constituting the head carriage, a supply pipe, and a front chamber ink tank immediately before the head, etc.

[0212] From the viewpoint of recording speed and image quality, the amount of ink droplets ejected is preferably within the range of 2 to 20 pL.

[0213] (2) The process of impacting ink onto a recording medium In the process of directly impacting ink onto a recording medium, ink ejected in a previous process is impacted onto the recording medium.

[0214] From the viewpoint of fixing the ink, it is preferable that the temperature of the recording medium is lower than the temperature at which the ink is ejected, and is 60° C. or less. By keeping the temperature of the recording medium at 60° C. or less, the ink that has landed on the recording medium quickly thickens and can be fixed.

[0215] (3) A process of curing the ink by irradiating it with active energy rays. In the step of curing the ink by irradiating it with active energy rays, the surface of the recording medium on which the ink has landed is irradiated with active energy rays.

[0216] As described above, examples of active energy rays include visible light, ultraviolet light, X-rays, electron beams, α-rays, β-rays, and γ-rays. Of these, ultraviolet light is preferred from the viewpoint of ease of handling and minimal impact on the human body. Electron beams are preferred from the viewpoint of facilitating ink curing.

[0217] The ultraviolet light source is preferably a light-emitting diode (LED). By using an LED, it is possible to prevent the ink from melting due to the radiant heat of the light source, which can prevent poor curing of the ink. Examples of LED light sources include water-cooled LEDs with a wavelength of 395 nm, such as those manufactured by Phoseon Technology, Heraeus, Kyocera Corporation, HOYA Corporation, and Integration Technology.

[0218] The amount of energy emitted by the active energy rays is 200 to 1000 mJ / cm 2 The amount of energy is preferably in the range of 200 mJ / cm 2 By setting the energy amount to 1000 mJ / cm or more, the polymerizable compound can be sufficiently polymerized and crosslinked. 2 By setting the energy amount of the active energy rays to 300 to 800 mJ / cm or less, it is possible to suppress a decrease in the viscosity of the ink due to the heat of the active energy rays, and to suppress a decrease in the pinning property. 2 More preferably, it is in the range of 350 to 500 mJ / cm 2 It is more preferable that the range is within the range of

[0219] (4) Drying the ink In the step of drying the ink, the ink is irradiated with active energy rays and then dried as necessary. The drying method may be air drying or drying by applying heat, but drying by applying heat is preferred.

[0220] [Inkjet recording system] The inkjet recording system according to the present invention is preferably an inkjet recording system that performs recording by ejecting the ink onto a recording medium.

[0221] An image forming apparatus that forms an image using the ink of the present invention will be described. Note that, although an apparatus that forms an image by a single pass method will be described below, the ink of the present invention can also be used in an apparatus that forms an image by a scan method.

[0222] 1 is a schematic diagram showing an exemplary configuration of an image forming apparatus 100 used in the present invention. As shown in FIG. 1, the image forming apparatus 100 includes an inkjet head 110, a transport path 120, an active energy ray irradiation unit 130, and a temperature control unit 140. 1, arrow A indicates the transport direction of recording medium 150. Inkjet head 110 and active energy ray irradiation unit 130 are arranged in this order from the upstream side to the downstream side in the transport direction of the recording medium, in contact with transport path 120. Note that image forming apparatus 100 may also have an oxygen concentration adjustment unit (not shown) for adjusting the oxygen concentration when ink is irradiated with active energy rays.

[0223] 1, the image forming apparatus 100 has an ink flow path 170 and an ink tank 180 that stores ink to be supplied through the ink flow path 170. The ink flow path 170 is connected to a head carriage 160 that houses an inkjet head 110 for ink.

[0224] The head carriages 160 each house an inkjet head 110. The head carriages 160 include inkjet heads for each of the colors yellow (Y), magenta (M), cyan (C), and black (K). The head carriages 160 are fixedly disposed so as to cover the entire width of the recording medium 150, for example.

[0225] The ink tanks 180 contain inks of various colors. Ink is supplied to the inkjet head 110 from the ink tanks 180. The ink of the present invention may be used for all of the yellow (Y), magenta (M), cyan (C), and black (K) inks, or may be used for only some of the inks. In particular, it is preferable to use the ink of the present invention for the magenta ink or the black ink.

[0226] The inkjet head 110 ejects ink supplied from the ink tank 180 to the head carriage 160 via the ink flow path 170. At this time, it is preferable to heat the ink via the ink tank 180, the ink flow path 170, the head carriage 160, the inkjet head 110, etc. As mentioned above, the temperature of the ejected ink is preferably in the range of 40 to 120°C, and more preferably in the range of 50 to 85°C.

[0227] The active energy ray irradiation unit 130 covers the entire width of the recording medium 150 and is disposed downstream of the head carriage 160 in the transport direction A of the recording medium 150. The active energy ray irradiation unit 130 irradiates the ink droplets that are ejected by the inkjet heads 110 and land on the recording medium 150 with active energy rays, thereby curing the droplets.

[0228] The temperature control unit 140 is disposed on the lower surface of the recording medium 150. The temperature control unit 140 adjusts the surface temperature of the recording medium 150 to 60°C or less, lower than the temperature at which the ink is ejected. Examples of the temperature control unit 140 include various heaters. This allows the ink of the present invention to be quickly fixed after landing on the recording medium 150. Therefore, the ink of the present invention has high pinning properties and can suppress the seepage of the polymerizable compound from the formed dots.

[0229] Furthermore, an oxygen concentration adjusting unit (not shown) adjusts the oxygen concentration of the atmosphere surrounding the surface of the ink that has landed on the recording medium 150 when irradiated with active energy rays. [Example]

[0230] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0231] [Synthesis of various compounds] (1) Synthesis of dispersant Compounds 1 to 3 were synthesized as compounds having a structure derived from a hydroxy fatty acid and a basic functional group.

[0232] (1.1) Synthesis of Compound 1 The following components were placed in a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, and a reflux tube, and heated to 170°C under a nitrogen stream. Heating was continued until the remaining amount of ε-caprolactone was 1% or less. The reaction time was approximately 3.5 hours. The reaction mixture was then cooled to room temperature, yielding Polyester 1.

[0233] 2-Hydroxycaproic acid (Junsei Chemical Co., Ltd.) 10.00 parts by mass ε-caprolactone (manufactured by Junsei Chemical Co., Ltd.) 506.00 parts by mass Tetrabutyl titanate (manufactured by Junsei Chemical Co., Ltd.) 0.03 parts by mass

[0234] Polyester 1 had a number average molecular weight of 5630 and an acid value of 9.6 mgKOH / g.

[0235] The following components were charged into the reaction flask used to obtain Polyester 1. Toluene 194.25 parts by mass 10% aqueous solution of polyallylamine ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3000) 70.00 parts by mass

[0236] While stirring this mixture at 120°C, water was distilled off using a separator and toluene was returned to the reaction solution. After confirming that 50% by mass of water had been distilled off, the following components, heated to 120°C, were added while returning toluene to the reaction solution, and the reaction was carried out at 120°C for 5 hours. Compound 1 was then obtained. Polyester 1 122.50 parts by mass

[0237] Compound 1 had a solid content of 40.2%, an amine value of 5.0 mg KOH / g, and an acid value of 8.2 mg KOH / g.

[0238] (1.2) Synthesis of Compound 2 The following components were placed in a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux tube and heated under a nitrogen stream. The temperature was raised to 160°C over 4 hours, and after heating at 160°C for 2 hours, heating was continued until the remaining amount of ε-caprolactone was 1% or less. The reaction time was approximately 3.5 hours. The reaction mixture was then cooled to room temperature, yielding Polyester 2.

[0239] 12-hydroxystearic acid (manufactured by Junsei Chemical Co., Ltd.) 10.00 parts by mass ε-caprolactone (manufactured by Junsei Chemical Co., Ltd.) 60.00 parts by mass Tetrabutyl titanate (manufactured by Junsei Chemical Co., Ltd.) 0.01 parts by mass

[0240] Polyester 2 had a number average molecular weight of 2050 and an acid value of 26.3 mgKOH / g.

[0241] The following components were charged into the reaction flask used to obtain Polyester 2. Toluene 194.30 parts by mass 10% aqueous solution of polyallylamine ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3000) 70.00 parts by mass

[0242] While stirring this mixture at 120°C, water was distilled off using a separator and toluene was returned to the reaction solution. After confirming that 50% by mass of water had been distilled off, the following components, heated to 120°C, were added while returning toluene to the reaction solution, and the reaction was carried out at 120°C for 5 hours. Compound 3 was then obtained. Polyester 2 122.50 parts by mass

[0243] Compound 2 had a solid content of 40.2%, an amine value of 10.0 mg KOH / g, and an acid value of 23.2 mg KOH / g.

[0244] (1.3) Synthesis of Compound 3 The following components were placed in a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux tube and heated under a nitrogen stream. The temperature was raised to 160°C over 4 hours, and after heating at 160°C for 2 hours, heating was continued until the remaining amount of ε-caprolactone was 1% or less. The reaction time was approximately 3.5 hours. The reaction mixture was then cooled to room temperature, yielding Polyester 3.

[0245] 12-hydroxystearic acid (manufactured by Junsei Chemical Co., Ltd.) 10.00 parts by mass ε-caprolactone (manufactured by Junsei Chemical Co., Ltd.) 80.00 parts by mass Tetrabutyl titanate (manufactured by Junsei Chemical Co., Ltd.) 0.01 parts by mass

[0246] Polyester 3 had a number average molecular weight of 2920 and an acid value of 18.5 mgKOH / g.

[0247] The following components were charged into the reaction flask used to obtain Polyester 3. Toluene 194.30 parts by mass 10% aqueous solution of polyallylamine ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3000) 70.00 parts by mass

[0248] While stirring this mixture at 120°C, water was distilled off using a separator and toluene was returned to the reaction solution. After confirming that 50% by mass of water had been distilled off, the following components, heated to 120°C, were added while returning toluene to the reaction solution, and the reaction was carried out at 120°C for 5 hours. Compound 3 was then obtained. Polyester 3 122.50 parts by mass

[0249] Compound 3 had a solid content of 40.2%, an amine value of 20.0 mg KOH / g, and an acid value of 15.0 mg KOH / g.

[0250] Compounds 1 to 3 having a structure derived from a hydroxy fatty acid and a basic functional group as dispersants were synthesized as described above. The combinations of modifying resins and polyallylamine components in Compounds 1 to 3 are shown in Table I below. For Compounds 1 to 3, polyester was used as the modifying resin. The amine values ​​of compounds 1 to 3 are shown in Table I.

[0251] [Table 1]

[0252] (2) Preparation of additives Compounds 4 to 9 were prepared as additives. (2.1) Compound 4 Compound 4 was prepared by mixing the following components. Polyether phosphate ester compound: Plysurf A208F (Dai-ichi Kogyo Seiyaku Co., Ltd.) 0.5 parts by mass Polyamine compound: PAA-01 (manufactured by Nittobo Medical Co., Ltd.) 0.2 parts by mass

[0253] (2.2) Compound 5 Compound 5 was prepared by mixing the following components. Polyether phosphate ester compound: DA-375 (Kusumoto Chemicals Co., Ltd.) 0.5 parts by mass Polyamine compound: PAA-01 (manufactured by Nittobo Medical Co., Ltd.) 0.2 parts by mass

[0254] (2.3) Compound 6 DA-325 (manufactured by Kusumoto Chemicals Co., Ltd.), which is a mixture of a polyether phosphate ester compound and a polyamine compound, was used as Compound 6.

[0255] (2.4) Compound 7 Plysurf A208F (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), a polyether phosphate ester compound, was used as Compound 7.

[0256] (2.5) Compound 8 A polyamine compound, PAA-01 (manufactured by Nittobo Medical Co., Ltd.), was used as Compound 8.

[0257] (2.6) Compound 9 TEGO655 (manufactured by Evonik Japan), a polyether phosphate ester compound, was used as Compound 9.

[0258] The structures of compounds 4 to 9 are shown in Table II below.

[0259] [Table 2]

[0260] [Ink preparation] (1) Preparation of Ink 1 (1.1) Preparation of pigment dispersion 1 The following components were placed in a 200cc polyethylene container with a lid in a thermo bath at 55°C. The mixture was then heated and stirred for 30 minutes using a magnetic stirrer to dissolve the components. The resulting solution was then cooled to room temperature.

[0261] Polymerizable compound 1: dipropylene glycol diacrylate (DPGDA) "Laromer (registered trademark) DPGDA" (manufactured by BASF) 73.50 parts by mass Polymerization inhibitor: "Irgastab UV10" (manufactured by Ciba Japan) 0.50 parts by mass Dispersant: 6.00 parts by mass of the above compound 1

[0262] The following components were added to the solution and stirred thoroughly. This mixture was placed in a glass bottle together with 100 g of 0.5 mm diameter zirconia beads, sealed, and subjected to vibration dispersion for 2 hours in a vibration mill (Red Devil 5400HC). The zirconia beads were then removed to obtain Pigment Dispersion 1. The dispersant content was 30% by mass relative to the total mass of the pigment. Pigment: Pigment Blue 15:4 20.00 parts by mass

[0263] (2.2) Mixing of ink components The following ingredients were placed in a dissolving beaker and stirred for 30 minutes. Polymerizable compound 1: dipropylene glycol diacrylate (DPGDA) "Laromer (registered trademark) DPGDA" (manufactured by BASF) 84.13 parts by mass Polymerizable compound 2: Triethylene glycol dimethyl acrylate (TEGMA) 1.00 parts by mass Polymerization initiator: "DAROCURE TPO" (manufactured by Ciba Specialty Chemicals) 0.50 parts by mass

[0264] To this solution, the following ingredients were added and stirred for an additional 30 minutes. Pigment dispersion 1 (dispersant concentration: 6% by mass) 11.67 parts by mass

[0265] The mixture was heated to 80°C, and the following gelling agent was added and stirred for an additional 30 minutes. Compound 4 was then added and stirred for an additional 30 minutes. The mixture was then filtered through a membrane filter (nominal filtration accuracy 3 μm, SLS030 manufactured by Roki Techno Co., Ltd.) and cooled to prepare Ink 1. Gelling agent: "Kao (registered trademark) Wax T1" 2.00 parts by mass Additive: Compound 4 0.70 parts by mass

[0266] (2) Preparation of Inks 2 to 12 and 16 to 20 Inks 2 to 12 and 16 to 20 were prepared in the same manner as in preparing Ink 1, except that the types and amounts of dispersants and additives were changed as shown in Table III. In addition, in preparing Inks 9, 10, and 12, the amount of pigment dispersion added was changed according to the amount of dispersant in Table III, and the total amount was adjusted with dipropylene glycol diacrylate (DPGDA).

[0267] (3) Preparation of Inks 13 to 15 Ink 13 was prepared in the same manner as ink 12, except that a pigment dispersion prepared by changing the pigment types to PR122 and PV19 was used. The mass ratio of PR122 to PV19 was 1:1. Ink 14 was prepared in the same manner as ink 12, except that a pigment dispersion prepared by changing the pigment types to PR202 and PV19 was used. The mass ratio of PR202 to PV19 was 1:1. Ink 15 was prepared in the same manner as ink 12, except that a pigment dispersion prepared by changing the type of pigment to CB was used. In addition, in preparing inks 13 to 15, the amount of pigment dispersion added was changed according to the amount of dispersant in Table III, and the total amount was adjusted with dipropylene glycol diacrylate (DPGDA). The pigments listed in Table III below are as follows: PB15:4 (Pigment Blue 15:4) PR122 (Pigment Red 122) PV19 (Pigment Violet 19) CB (Carbon Black "MA7" (Mitsubishi Chemical Corporation))

[0268] The compositions of inks 1 to 20 are shown in Table III below. "-" in the table indicates that the corresponding ingredient was not added. The content in the table represents the content relative to the total mass of the ink. "Mass ratio A:B" represents the mass ratio of the content of dispersant A to additive B. In addition, the content of dispersant A and additive B (polyether phosphate ester compound and polyamine compound) in the table each represents mass % in the ink.

[0269] [Table 3]

[0270] [Image formation] Each ink was loaded into a single-pass inkjet image-forming device equipped with an inkjet head equipped with a piezoelectric inkjet nozzle. The ink supply system included an ink tank, an ink flow path, a sub-ink tank immediately before the inkjet head, piping with a filter, and the inkjet head. The temperature of the inkjet head was set to 80°C. The inkjet heads used were Konica Minolta inkjet (piezo type) with a resolution of 600 dpi, and head modules with two heads in one set (1200 dpi). Ink is ejected from the nozzle of the inkjet head and printed on coated paper (OK top coat + 104.7g / m 2 , manufactured by Oji Paper Co., Ltd.) at 10 g / m 2 Within 1 second after the droplets landed, the LED lamp (395 nm, 8 W / cm 2 The ink was cured by irradiating it with a UV lamp (manufactured by Phoseon Technology) (resolution: 1200 x 1200 dpi). The substrate temperature was set to 40°C during ink curing.

[0271] [evaluation] <Image uniformity> After storing each ink at 90°C for one week, they were ejected from the nozzles of an inkjet head according to the image formation method described above to obtain a 100% solid image. The solid image was visually observed and evaluated for image uniformity due to dot coalescence according to the following criteria. In the following criteria, A and B were considered to be acceptable for practical use. (standard) A: The solid image is uniform B: When you look closely, you can see that there are some uneven areas in the solid image. C: The solid image is uneven

[0272] <Injection properties> Using each ink, a solid image was formed continuously for 10 minutes according to the image forming method described above. The presence or absence of satellites, which are formed when droplets are ejected onto areas other than the characters, was then checked and evaluated according to the following criteria. In the following criteria, A, B, and C were deemed acceptable for practical use. (standard) A: No satellites were detected, or only very few were detected. B: Satellites were detected, but the visibility of the letters was not affected. C: The satellite was confirmed, and the letters looked a little unclear. D: The satellite was confirmed and the letters looked unclear.

[0273] <Storage stability> Each ink was sealed in a heat-resistant glass bottle and stored for two weeks at 90°C for forced aging. The viscosity (mPa·s) of each ink at 80°C was then measured using a rheometer (Paar Physica MCR300) before and after the forced aging treatment. The viscosity change rate before and after the forced aging treatment was calculated using the following formula, and the storage stability was evaluated according to the following criteria: A, B, and C were determined to be acceptable for practical use. Viscosity fluctuation rate = {(Ink viscosity after forced aging process - Ink viscosity before forced aging process) / Ink viscosity before forced aging process} x 100 (%) (standard) A: Viscosity fluctuation rate is less than 5.0% B: Viscosity fluctuation rate is 5.0% or more and less than 10.0% C: Viscosity fluctuation rate is 10.0% or more and less than 15.0% D: Viscosity fluctuation rate is 15.0% or more

[0274] [Table 4]

[0275] As shown by the above results, it is clear that the ink of the present invention is superior to the ink of the comparative example in terms of image uniformity, ejection performance and storage stability. [Explanation of symbols]

[0276] 100 Image forming device 110 Inkjet head 120 Transport path 130 Active energy ray irradiation unit 140 Temperature control unit 150 Recording Media 160 head carriage 170 Ink flow path 180 ink tanks

Claims

1. An actinic radiation curable inkjet ink containing a pigment, a dispersant, a gelling agent and additives, The dispersant contains a basic compound having a structure derived from a hydroxy fatty acid, The additives include a polyether phosphate ester compound and a polyamine compound.

1. An actinic radiation curable inkjet ink comprising:

2. the content of the polyether phosphate ester compound and the content of the polyamine compound are within a range of 0.1 to 0.6% by mass relative to the total mass of the actinic radiation-curable inkjet ink; 2. The actinic radiation curable inkjet ink according to claim 1.

3. The basic compound having a structure derived from a hydroxy fatty acid has a structure derived from hydroxystearic acid and has an amine value in the range of 10 to 20 mgKOH / g.

2. The actinic radiation curable inkjet ink according to claim 1.

4. the pigment is carbon black or a magenta pigment, The magenta pigment contains any one of C.I. Pigment Violet 19, C.I. Pigment Red 122, and C.I. Pigment Red 202.

2. The actinic radiation curable inkjet ink according to claim 1.

5. A method for producing an actinic radiation-curable inkjet ink, comprising: The actinic radiation-curable inkjet ink is the actinic radiation-curable inkjet ink according to any one of claims 1 to 4, preparing a pigment dispersion containing the pigment and the dispersant; preparing the actinic radiation-curable inkjet ink containing the pigment dispersion, the gelling agent, and the additives.

1. A method for producing an actinic radiation-curable inkjet ink, comprising:

6. An inkjet recording method for recording by ejecting ink onto a recording medium, comprising: The ink is an actinic radiation-curable inkjet ink according to any one of claims 1 to 4, The ink ejection temperature is within a range of 40 to 120°C, and The temperature of the recording medium is 60° C. or less. An inkjet recording method comprising:

Images