Active energy ray curable inkjet ink, method for producing the same, inkjet recording method, and inkjet recording system

Abstract

To provide an active energy ray curable inkjet ink in which glossiness is improved in an image to be formed, a method for producing the same, an inkjet recording method, and an inkjet recording system.SOLUTION: An active energy ray curable inkjet ink according to the present invention includes a pigment, a dispersant, a gelling agent, and an additive. A compound having a structure derived from a hydroxy fatty acid and a basic functional group is contained as the dispersant. A compound having a pyridine structure is contained as the additive.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an actinic energy ray-curable inkjet ink, a method for producing the same, an inkjet recording method, and an inkjet recording system, and more particularly to an actinic energy ray-curable inkjet ink which forms an image with improved gloss. [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 active energy ray curable ink. In the case of active energy ray curable ink, droplets of the ink are landed on a recording medium, and then the ink is cured by irradiating the ink with active energy rays to form an image. In the inkjet recording method using active energy ray curable ink, images can be formed even on recording media that do not absorb ink. Furthermore, the images formed have high abrasion resistance and adhesion, and have been attracting attention in recent years.

[0003] In the inkjet recording method, since it is necessary to eject ink droplets from the nozzles of an inkjet head, the ink is required to have ejection stability. In addition, when ink droplets that land on a recording medium mix with adjacent droplets, the formed dots merge and white spots occur. In addition, when color inks are used, problems such as color mixing occur. For this reason, the ink must be fixed after the ink droplets land on the recording medium. In particular, when recording at high speed, the ink must be fixed immediately after the ink droplets land on the recording medium.

[0004] However, in inks that are quickly fixed on a recording medium, the pigment is likely to aggregate during the fixing process, and therefore further improvement in the gloss of the formed images is required.

[0005] Patent Document 1 discloses a technology relating to a radiation-curable inkjet ink set containing a specific pigment in the range of 1.5 to 2.5% by mass. The ink set may further contain a polymer dispersant, and technology relating to applicable polymer dispersants is disclosed. However, even when this technology is used, the gloss obtained in the formed image is not sufficient.

[0006] Sol-gel phase transition ink is known as an ink that quickly fixes on a recording medium. Sol-gel phase transition ink is transformed into a sol or gel depending on the temperature, and the viscosity changes. For example, when the ink is ejected, the ink is transformed into a sol by being placed in a relatively high temperature environment. This reduces the viscosity of the ink, and good ink ejection stability is obtained. When the ink lands, the ink is transformed into a gel by being placed in a relatively low temperature environment. This increases the viscosity of the ink, and the ink is easily fixed. However, since the viscosity of the sol-gel phase transition ink increases rapidly when the ink lands, the pigment is more likely to aggregate.

[0007] Patent Document 2 discloses a technology for an actinic radiation curable inkjet ink containing a photopolymerizable compound, a photopolymerization initiator, a gelling agent, a colorant, and a polymer dispersant. It also discloses a technology for a polymer dispersant having an amine group. The amine group functions as an adsorptive functional group for a water-insoluble organic pigment. Although the technology can be used to form an image having a certain degree of glossiness, further improvement in glossiness is required. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2013-213196 A [Patent Document 2] JP 2015-52082 A Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above problems and circumstances, and an object of the present invention is to provide an actinic energy ray-curable inkjet ink which improves the gloss of formed images, a manufacturing method thereof, an inkjet recording method, and an inkjet recording system. [Means for solving the problem]

[0010] Means for Solving the Problems The present inventors have investigated the causes of the above problems in order to solve the above problems, and as a result, have found that in an active energy ray-curable inkjet ink containing a pigment, a dispersant, a gelling agent, and an additive, the ink contains a compound having a hydroxy fatty acid-derived structure and a basic functional group as the dispersant, and contains a compound having a pyridine structure as the additive, thereby improving the gloss of an image formed using the ink, and have arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0011] 1. An active energy ray curable inkjet ink containing a pigment, a dispersant, a gelling agent and an additive, The dispersant contains a compound having a structure derived from a hydroxy fatty acid and a basic functional group, The additive contains a compound having a pyridine structure. 1. An actinic ray-curable ink-jet ink comprising:

[0012] 2. The compound having a pyridine structure is an acrylic polymer compound. 2. The actinic ray-curable ink-jet ink according to claim 1,

[0013] 3. The compound having a structure derived from a hydroxy fatty acid and a basic functional group has a structure derived from hydroxystearic acid and an amine value in the range of 10 to 20 mgKOH / g. 2. The actinic ray-curable ink-jet ink according to claim 1,

[0014] 4. The content of the compound having a pyridine structure is within the range of 0.1 to 0.6% by mass based on the total mass of the active energy ray-curable inkjet ink. 2. The actinic ray-curable ink-jet ink according to claim 1,

[0015] 5. The mass ratio of the compound having a structure derived from a hydroxy fatty acid and a basic functional group to the compound having a pyridine structure is within the range of 2.73:1 to 16.4:1. 2. The actinic ray-curable ink-jet ink according to claim 1,

[0016] 6. 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 ray-curable ink-jet ink according to claim 1,

[0017] 7. Manufacturing an active energy ray-curable inkjet ink A method for manufacturing an active energy ray-curable inkjet ink, comprising the steps of: The actinic energy beam-curable inkjet ink is the actinic energy beam-curable inkjet ink according to any one of items 1 to 6, preparing a pigment dispersion containing the pigment and the dispersant; and preparing the active energy ray-curable inkjet ink containing the pigment dispersion, the gelling agent, and the additives. 13. A method for producing an active energy ray-curable inkjet ink, comprising:

[0018] 8. An ink jet recording method for recording by ejecting ink onto a recording medium, comprising the steps of: The ink is an actinic ray-curable ink-jet ink according to any one of items 1 to 6, The ink ejection temperature is within a range of 40 to 120°C; The temperature of the recording medium is 60° C. or less. 1. An ink-jet recording method comprising:

[0019] 9. An inkjet recording system that records by ejecting ink onto a recording medium, The ink is an active energy ray-curable ink-jet ink according to any one of items 1 to 6. 1. An inkjet recording system comprising: Effect of the Invention

[0020] According to the above-mentioned means of the present invention, it is possible to provide an actinic ray-curable ink-jet ink which forms an image with improved glossiness, a method for producing the same, an ink-jet recording method, and an ink-jet recording system.

[0021] The mechanism by which the effects of the present invention are exerted or the mechanism of action is not clear, but is presumed to be as follows: In this specification, the "active energy ray-curable ink-jet ink" is also simply referred to as "ink".

[0022] In the present invention, the term "dispersant" refers to a component that is contained for the purpose of dispersing a pigment. As will be described in detail later, in the preparation of the ink, first, a pigment dispersion liquid containing a pigment and a dispersant is prepared. Then, the pigment dispersion liquid and other components of the ink are mixed to prepare the ink. The term "additives" refers to components that are contained in the 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 in the preparation of the ink.

[0023] When an ink containing a gelling agent is dropped onto a recording medium, the ink viscosity increases rapidly and is quickly fixed. Therefore, the pigment in an ink containing a gelling agent is more likely to aggregate than in an ink not containing a gelling agent. As a result, although there is no practical problem with the glossiness of an image formed by an ink containing a gelling agent, there is room for improvement, and further improvement in glossiness is required.

[0024] In the present invention, a compound having a structure derived from a hydroxy fatty acid and a basic functional group is contained as a dispersant. Also, a compound having a pyridine structure is contained as an additive. Some compounds having a pyridine structure also have a function of dispersing pigments.

[0025] That is, when preparing a pigment dispersion, the pigment first interacts with a compound having a hydroxy fatty acid-derived structure and a basic functional group as a dispersant. Then, when mixing with the ink components, the pigment is thought to interact with a compound having a pyridine structure as an additive. The compound having a hydroxy fatty acid-derived structure and a basic functional group, and the compound having a pyridine structure are thought to interact with different sites on the pigment. It is thought that high dispersion stability is obtained by the pigment interacting with these two types of compounds.

[0026] According to the inventor's investigation, even if these two compounds are contained as dispersants, the effect of the present invention is small. More specifically, even if a pigment dispersion containing a pigment and these two compounds is prepared and then the pigment dispersion is mixed with other ink components, the effect of the present invention is not as good as that of the present invention.

[0027] In addition, even if a compound having a pyridine structure is added as a dispersant and a compound having a structure derived from a hydroxy fatty acid and a basic functional group is added as an additive, the effect of the present invention is small. More specifically, a pigment dispersion liquid containing a pigment and a compound having a pyridine structure is first prepared. Then, even if the pigment dispersion liquid, the compound having a structure derived from a hydroxy fatty acid and a basic functional group, and other ink components are mixed, the effect of the present invention is not obtained.

[0028] In other words, by incorporating these two types of compounds into the ink in two stages, these two types of compounds act effectively on the pigment. Although the details are not clear, it is believed that the two types of compounds are probably attached to the pigment in an optimal ratio. As a result, it is believed that even if the viscosity of the ink increases suddenly on the recording medium, the pigment can be prevented from flocculating too much. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic diagram showing an exemplary configuration of an image forming apparatus 100. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The active energy ray-curable inkjet ink of the present invention is an active energy ray-curable inkjet ink containing a pigment, a dispersant, a gelling agent and an additive, and is characterized in that the dispersant contains a compound having a structure derived from a hydroxy fatty acid and a basic functional group, and the additive contains a compound having a pyridine structure. This feature is a technical feature common to or corresponding to the following embodiments.

[0031] In an embodiment of the present invention, from the viewpoint of storage stability of the ink, the compound having a pyridine structure is preferably an acrylic polymer compound.

[0032] In an embodiment of the present invention, from the viewpoint of injection stability, it is preferred that the compound having a structure derived from a hydroxy fatty acid and a basic functional group has a structure derived from hydroxystearic acid and has an amine value within the range of 10 to 20 mgKOH / g.

[0033] In an embodiment of the present invention, from the viewpoint of pigment dispersion stability and ink ejection stability, the content of the compound having a pyridine structure is preferably within the range of 0.1 to 0.6% by mass with respect to the total mass of the active energy ray-curable inkjet ink.

[0034] In an embodiment of the present invention, from the viewpoint of pigment dispersibility and image gloss, it is preferable that the mass ratio of the compound having a hydroxy fatty acid-derived structure and a basic functional group to the compound having a pyridine structure is within the range of 2.73:1 to 16.4:1.

[0035] In an embodiment of the present invention, from the viewpoint of image density, it is preferable that the pigment is carbon black or a magenta pigment, and the magenta pigment contains any one of CI Pigment Violet 19, CI Pigment Red 122, and CI Pigment Red 202.

[0036]

[0033] The method for producing an active energy ray-curable inkjet ink of the present invention is a method for producing the ink, and preferably includes a step of preparing a pigment dispersion containing the pigment and the dispersant, and a step of preparing the active energy ray-curable inkjet ink containing the pigment dispersion, the gelling agent, and the additives.

[0037] In the inkjet recording method of the present invention, it is preferable that 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 lower.

[0038] The inkjet recording system of the present invention preferably uses the above ink.

[0039] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after the symbol "to" are included as the lower limit and upper limit.

[0040] 1. Overview of active energy beam-curable inkjet inks The active energy ray-curable inkjet ink of the present invention is an active energy ray-curable ink containing a pigment, a dispersant, a gelling agent and an additive, and is characterized in that the dispersant contains a compound having a structure derived from a hydroxy fatty acid and a basic functional group, and the additive contains a compound having a pyridine structure.

[0041] 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".

[0042] 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, the term "sol-gel phase transition" refers to the following series of phenomena. At high temperatures, the ink is in a solution state with fluidity, but when cooled below the gelling temperature, the entire liquid gels and changes to a state in which it has lost fluidity. Conversely, at low temperatures, the ink is in a state in which it has lost fluidity, but when heated to a temperature above the sol-formation temperature, it returns to a liquid state with fluidity.

[0043] "Gel" refers to a state in which substances lose fluidity and aggregate due to interactions between substances, resulting in a solidified, semi-solidified, or thickened state accompanied by a sudden increase in viscosity and elasticity. Interactions occur in substances, such as 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.

[0044] The term "sol" refers to a liquefied state in which the interactions occurring in the gel state are eliminated and the substance has fluidity.

[0045] 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 it is heated. The "gelation temperature" refers to the temperature at which ink in a gelled state becomes less fluid due to the gelation when it is cooled.

[0046] The term "active energy rays" refers 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.

[0047] 2. Components of active energy beam-curable inkjet ink The ink of the present invention contains a pigment, a dispersant, a gelling agent and additives, and may also contain a polymerizable compound, etc., if necessary. The dispersant, additives, pigment, gelling agent, and other components will be described in this order below.

[0048] (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. In addition, the ink may contain other dispersants as necessary to the extent that the effects of the present invention are not impaired.

[0049] 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 having a basic functional group.

[0050] Details will be described later, but for example, the compound described below is a reaction product between a polyester or polyesteramide having a structure derived from a hydroxy fatty acid and a polyallylamine. The polyallylamine has an amino group that exhibits basicity. A part of the amino group of the polyallylamine reacts 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 having a function of adsorbing a pigment to be introduced into the structure derived from a hydroxy fatty acid having a function of solvation. As a result, it functions well as a pigment dispersant.

[0051] The dispersant preferably has a function of suppressing aggregation of pigments by steric hindrance in addition to a function of adsorbing to the pigment and a function of solvating the pigment, and therefore the pigment dispersant is preferably a polymer compound.

[0052] 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.

[0053] (1.1) Constituents of polyester derivatives having an amine value Specifically, the dispersant according to the present invention is preferably a compound having a structure derived from a hydroxy fatty acid and modified 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 in which a polyester or polyesteramide having a structure derived from a hydroxy fatty acid is modified with polyallylamine" will also be simply referred to as a "polyester derivative having an amine value."

[0054] "Amine value" refers to the number of milligrams of acid and potassium hydroxide equivalent 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 derivative having an amine value" refers to a polyester derivative having an amine component.

[0055] The polyester derivative having an amine value has a structure represented by the following general formula (I).

[0056] [ka]

[0057] In the 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. 1 At least one of the above has a group represented by general formula (III).

[0058] [ka]

[0059] [ka]

[0060] 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. 1 represents the position of the carbon bonded to In addition, general formula (II) indicates that the carboxy group is modified with an amino group through an ionic bond.

[0061] 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 a polyallylamine. Each component will be described below.

[0062] (1.1.1) Compounds having a structure derived from hydroxy fatty acids Examples of compounds having a structure derived from a hydroxy fatty acid include polyesters made from hydroxy fatty acids, and polyesteramides which are co-condensation products of these polyesters and polyamides. Hereinafter, polyesters and polyesteramides having a structure derived from a hydroxy fatty acid are also simply referred to as "polyesters" and "polyesteramides".

[0063] 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 have repeating structures represented by the following general formulas (IV) and (V) polymerized randomly.

[0064] [ka]

[0065] In general formula (IV), R 3 represents a linear or branched alkylene group having a carbon atom number in the range of 2 to 20. a represents an integer of 2 to 100.

[0066] [ka]

[0067] In general formula (V), R 4 is an alkylene group having 2 to 20 carbon atoms; -C 6 H 4 R represents - or -CH=CH-. 5R 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 above formula, the alkylene group may be linear or branched, and b represents an integer of 2 to 100. In addition, the alkylene group may have an ether bond in the chain.

[0068] The polyester in the polyesteramide essentially has a structure represented by the above general formula (IV), which is a structure derived from a hydroxy fatty acid. In addition to the structure represented by the above general formula (IV), the polyester may have a structure represented by the above general formula (V). Furthermore, the polyester may have repeating structures represented by the above general formulas (IV) and (V) randomly polymerized.

[0069] The polyamide in the polyesteramide has, for example, a structure represented by the following general formula (VI) or (VII): In addition, the polyamide may have repeating structures represented by the following general formulas (VI) and (VII) polymerized randomly.

[0070] [ka]

[0071] In general formula (VI), R 6 represents a linear or branched alkylene group having a carbon atom number in the range of 2 to 20. c represents an integer of 2 to 100.

[0072] [ka]

[0073] In general formula (VII), R 4 is an alkylene group having 2 to 20 carbon atoms; -C 6 H 4 R represents - or -CH=CH-. 7 R represents an alkylene group having 2 to 20 carbon atoms. 4 and R7 In the above formula, the alkylene group may be linear or branched. d represents an integer of 2 to 100.

[0074] (1.1.1.1) Polyester The synthesis of polyesters having structures represented by the above general formulas (IV) and (V) will be described below.

[0075] (1.1.1.1.1) Synthesis of polyester having a structure represented by general formula (IV) The polyester having the structure represented by the above general formula (IV) can be synthesized from 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 a hydroxy group and a carboxy group in a molecule of a hydroxy fatty acid.

[0076] 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.

[0077] The reaction time is preferably within a range of 0.5 to 72 hours. By carrying out the reaction under a nitrogen gas flow, the degree of polymerization can be increased. 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 mol or less per mol of lactone.

[0078] [ka]

[0079] [ka]

[0080] In general formula (VIII), R 3 represents a linear or branched alkylene group having 2 to 20 carbon atoms.

[0081] 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.

[0082] Examples of lactones include ε-caprolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, 4-methylcaprolactone, and 2-methylcaprolactone.

[0083] 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 iodine; 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.

[0084] 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.

[0085] 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.

[0086] [ka]

[0087] In the polyester synthesized, -CO-C 5 H 10 The structure represented by -O- is a repeating structure derived from ε-caprolactone. 10 H 20 -CHC 6 H 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.

[0088] (1.1.1.1.2) Synthesis of polyester having a structure represented by general formula (V) The polyester having the structure represented by the above general formula (V) 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).

[0089] Specifically, the compound can be synthesized 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 little 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. The reaction can be easily controlled by using a polymerization initiator.

[0090] [ka]

[0091] [ka]

[0092] In general formula (X), R 4 is an alkylene group having 2 to 20 carbon atoms; -C 6 H 4 In the 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 above formula, the alkylene group may be linear or branched.

[0093] 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.

[0094] Examples of the diol 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.

[0095] The polymerization catalyst and polymerization initiator that can be used are the same as those used in the synthesis of the polyester having the structure represented by general formula (IV).

[0096] 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 an equimolar amount of the above diol and dibasic acid, and the mixture is heated. The reaction conditions are preferably the same as those for the synthesis of a polyester having a structure represented by general formula (IV).

[0097] The 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. Then, these are subjected to dehydration condensation to obtain the polyester.

[0098] The molecular weight of the polyester is preferably within the range of 300 to 20,000. From the viewpoint of dispersibility of the pigment, 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 to an appropriate length, resulting in excellent dispersibility. By adjusting the molar ratio of the polymerization initiator, the raw materials hydroxy fatty acid, lactone, diol and dibasic acid, a polyester having a desired molecular weight can be obtained. In addition, by observing the acid value of the reaction product during the synthesis reaction of the polyester and adjusting the reaction time, a polyester having a desired molecular weight can be obtained.

[0099] (1.1.1.2) Polyesteramide The polyesteramide is a co-condensation product of the above polyester and the below polyamide. It can be synthesized by polymerizing one or more polyester raw materials and one or more polyamide raw materials. Alternatively, the above polyester and the below polyamide can be pre-condensed and then co-condensed. The reaction conditions are preferably the same as those for the synthesis of the below polyamide. The molecular weight (degree of polymerization) of the polyesteramide can be measured by the acid value.

[0100] (1.1.1.2.1) Synthesis of polyamide having a structure represented by general formula (VI) The polyamide having the structure represented by the above general formula (VI) 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.

[0101] Specifically, the compound can be synthesized by heating 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 polycondensation reaction is preferably carried out under a nitrogen gas flow. The reaction temperature is preferably within a range of 110 to 250°C, and more preferably within a range of 150 to 210°C. By keeping the reaction temperature at 250°C or less, coloring of the reaction product can be suppressed, and by keeping the reaction temperature at 110°C or more, a sufficient reaction rate can be obtained.

[0102] 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 the acid value. When lactam is used as the raw material, the amount of monocarboxylic acid in the polymerization initiator is preferably 0.5 mol or less per mol of lactam.

[0103] [ka]

[0104] [ka]

[0105] 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.

[0106] Examples of lactams include ε-caprolactam, ω-laurolactam, etc. Examples of aminocarboxylic acids include aminocaproic acid, 11-aminoundecanoic acid, etc. 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).

[0107] (1.1.1.2.2) Synthesis of polyamide having a structure represented by general formula (VII) The polyamide having the structure represented by the above general formula (VII) can be synthesized using a dibasic acid having the structure represented by the above general formula (X) and a diamine represented by the following general formula (XIV) as raw materials.

[0108] [ka]

[0109] In general formula (XIV), R 7 represents a linear or branched alkylene group having 2 to 20 carbon atoms.

[0110] Examples of diamines include ethylenediamine, 1,4-diaminobutane, and hexamethylenediamine.

[0111] In the synthesis of the polyamide having the structure represented by the general formula (VII), the reaction conditions etc. can be the same as those in the synthesis of the polyamide having the structure represented by the above general formula (VI).

[0112] (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.

[0113] The polymerization initiator is not particularly limited, and examples thereof include ketone peroxides such as methyl ethyl ketone, diacyl peroxides such as benzoyl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane, hydroperoxides such as t-butyl hydroperoxide, peroxyesters such as t-butyl peroxypivalate, and others, azobisisoptylonitrile, hydrogen peroxide, ferrous salts, etc. Also, the polymerization initiators described in JP-B-2-14364 may be used.

[0114] 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.

[0115] The number average molecular weight of the 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.

[0116] By setting the number average molecular weight to 150 or more, sufficient adsorption to the pigment can be obtained, and by setting the number average molecular weight to 100,000 or less, aggregation between the pigments can be suppressed.

[0117] 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.).

[0118] Polyallylamine having any molecular weight may be synthesized by using the method described in JP-B-2-14364.

[0119] (1.1.3) Synthesis of polyester derivatives with amine values The terminal carboxy groups of polyester or polyesteramide are modified with polyallylamine to synthesize a polyester derivative having an amine value.

[0120] The polyester or polyesteramide having a free carboxy group is preferably 1 mole or more in total per mole of polyallylamine having n amino groups, where n is the same as n in the above general formula (I) and is an integer in the range of 2 to 1000. From the viewpoint of pigment dispersibility, the polyester or polyesteramide having a free carboxy group is more preferably in the range of 2 to 2n moles.

[0121] The polyester or polyesteramide may be used alone or in combination of two or more kinds. Different kinds of polyesters or polyesteramides may be reacted with polyallylamine at the same time. A polymerization catalyst may be used in the reaction, and the polymerization catalyst may be the same as that used in the synthesis of the polyester having the structure represented by general formula (IV). In addition, a solvent such as xylene or toluene may be used as a reaction solvent.

[0122] The reaction between polyester or polyesteramide and 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. In the reaction between polyester or polyesteramide and polyallylamine, whether a salt or an acid amide is formed depends on the reaction conditions.

[0123] 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. By keeping the reaction temperature at 250°C or less, coloration of the reaction product can be suppressed, and by keeping the reaction temperature at 90°C or more, a sufficient reaction rate can be obtained. In addition, by carrying out the reaction under a nitrogen stream, a reaction product with little coloring can be obtained.

[0124] On the other hand, the reaction temperature in the salt formation reaction is preferably within the range of 20 to 140°C.

[0125] The polyester derivative having an amine value preferably has an acid amide bond. From the viewpoint of pigment dispersibility, it is preferable that the terminal carboxyl group of the polyester or polyester amide reacts with 1 mole of the polyallylamine having n amino groups at a ratio of 2 moles or more. Here, n is the same as n in the above general formula (I) and is an integer in the range of 2 to 1000.

[0126] In the above general formula (I), n R 1 Among them, the residues in the form of bonded via an acid amide bond represented by the above general formula (III) are present in the range of preferably 60 to 95%, more preferably 65 to 90%.

[0127] That is, 60% or more of the amino groups in the polyallylamine are covalently bonded to the polyester or polyesteramide via an amide bond. This makes it possible to suppress the aggregation of pigments, and the polyallylamine functions as a pigment dispersant. Also, 95% or less of the amino groups in the polyallylamine are covalently bonded to the polyester or polyesteramide via an amide bond. In other words, by leaving more than 5% of the amino groups as amino groups, the polyallylamine can be sufficiently adsorbed to the pigment, and functions as a pigment dispersant.

[0128] (amine value) In the polyester derivative having an amine value, the amino group of the polyallylamine is bonded by a covalent bond within the above range. To this end, the amine value A immediately after mixing the polyester or polyesteramide having a carboxy group at one end with at least one of the polyallylamine and the amine value B after the reaction is completed are measured, and the change between these values ​​is calculated. (Formula) Percentage of covalent bonds of amino groups in polyester derivatives with amine values ​​[%] ={(AB) / A}×100

[0129] The amine value immediately after mixing may be measured. 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. 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 desired amine value.

[0130] In the synthesis of the 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.

[0131] 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 between the pigments can be suppressed.

[0132] 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.

[0133] In the present invention, the structure derived from hydroxy fatty acid is not necessarily polyester. The compound having a structure derived from hydroxy fatty acid and a basic functional group according to the present invention may have a carboxy group of hydroxy fatty acid modified with amine. If necessary, dibasic acid, diol, aminocarboxylic acid, lactam or diamine may be further used.

[0134] The polyester derivative having an amine value has a 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. 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.

[0135] In the present invention, since the pigment dispersion is contained in an active energy ray-curable inkjet ink, the dispersion medium is preferably a polymerizable compound, which will be described later.

[0136] (1.2) Other dispersants Examples of other dispersants that can be used in combination include polymer dispersants other than the above-mentioned dispersants, surfactants, etc. Among these, polymer dispersants are preferred.

[0137] 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.

[0138] (2) Additives The ink of the present invention contains a compound having a pyridine structure as an additive. In addition, other additives may be contained as necessary to the extent that the effect of the present invention is not impaired. The other additives will be described later.

[0139] (2.1) Compounds having a pyridine structure The compound having a pyridine structure is preferably a polymeric compound from the viewpoint of interacting with the pigment and contributing to pigment dispersibility. Specifically, the compound having a pyridine structure is preferably a compound having a monomer unit structure represented by the following general formula (1).

[0140] [ka]

[0141] From the viewpoint of storage stability of the ink, the compound having a pyridine structure is preferably an acrylic polymer compound further having a monomer unit structure represented by the following general formula (2) or (3). By using an acrylic polymer compound, solvation with the polymerizable compound contained in the ink is excellent, and therefore good storage stability of the ink can be obtained. In the present invention, the term "acrylic polymer compound" refers to a polymer obtained by copolymerizing a monomer component containing an acrylic acid ester.

[0142] [ka]

[0143] In general formula (2), R 11 R represents an alkyl group having 2 to 15 carbon atoms. 11 The alkyl group in R may be linear, branched, or have a ring structure. 11 is preferably an alkyl group having 2 to 8 carbon atoms, more preferably an alkyl group having 4 to 8 carbon atoms, and further preferably an n-butyl group.

[0144] [ka]

[0145] In general formula (3), R 12 R represents a polyalkylene oxide group having 10 to 50 carbon atoms and a terminal hydroxyl group or alkoxy group. 12 The polyalkylene oxide group in R is preferably a polyethylene oxide group or a polypropylene oxide group. 12 is preferably a polyalkylene oxide group having a carbon number in the range of 10 to 50 and terminated with an alkoxy group. Of these, the polyalkylene oxide group is more preferably a polyethylene oxide group.

[0146] The method for synthesizing the copolymer having the structure of the monomer unit represented by the general formula (1), the monomer unit represented by the general formula (2), and the monomer unit represented by the general formula (3) is not particularly limited. For example, the synthesis method includes living radical polymerization using a nitroxide initiator (NMP initiator).

[0147] The content of the monomer unit represented by general formula (1) is preferably within a range of 5 to 50 mol %, and more preferably within a range of 10 to 30 mol %, based on the total number of moles of all monomers constituting the compound having a pyridine structure. By being within the above range, the storage stability of the ink is excellent.

[0148] The molar ratio of the monomer unit represented by general formula (2) to the monomer unit represented by general formula (3) is preferably within the range of 2:1 to 1:2, and more preferably within the range of 1.5:1 to 1:1.5.

[0149] The compound having a pyridine structure is preferably a block copolymer. More preferably, the block copolymer is composed of a block in which the monomer units represented by general formula (1) are bonded and a block in which the monomer units represented by general formula (2) and the monomer units represented by general formula (3) are randomly bonded. This structure provides excellent storage stability of the ink.

[0150] The weight average molecular weight (Mw) of the compound having a pyridine structure is preferably within the range of 10,000 to 70,000. The weight average molecular weight (Mw) is more preferably within the range of 12,000 to 30,000, further preferably within the range of 13,000 to 25,000, and particularly preferably within the range of 15,000 to 20,000.

[0151] The weight average molecular weight can be measured by gel permeation chromatography (GPC). For example, "HLC-8020GPC" (manufactured by Tosoh Corporation) is used as the GPC. "TSKgel SuperHZM-H, TSKgel SuperHZ4000, TSKgel SuperHZ200" (manufactured by Tosoh Corporation, 4.6 mm ID x 15 cm) is used as the column. THF (tetrahydrofuran) is used as the eluent, and the column oven temperature is set to 40°C. Standard polystyrene is used as the standard for calculating the weight average molecular weight.

[0152] The compound having a pyridine structure may be a commercially available product. Examples of the commercially available compound having a pyridine structure include "DISPERBYK series, BYK series" (manufactured by BYK) and "EFKA series" (BASF).

[0153] The content of the compound having a pyridine structure is preferably within a range of 0.1 to 0.6% by mass relative to the total mass of the ink. When the content is 0.1% by mass or more, the storage stability of the ink is improved. When the content is 0.6% by mass or less, an increase in the viscosity of the ink can be suppressed, and the ink has excellent ejection stability.

[0154] The mass ratio of the compound having a hydroxy fatty acid-derived structure and a basic functional group as the dispersant to the compound having a pyridine structure as the additive is preferably within a range of 2.73: 1 to 16.4: 1. By being within the above range, the effects of the present invention can be significantly obtained.

[0155] (3) Pigments The ink of the present invention contains a pigment. The pigment is not particularly limited, and any known pigment can be used.

[0156] Examples of the pigment include inorganic pigments such as titanium dioxide, iron oxide, cadmium sulfide, calcium carbonate, barium carbonate, barium sulfate, clay, talc, yellow lead, carbon black, etc. Examples of the pigment include organic pigments such as azo-based, diazo-based, condensed azo-based, thioindigo-based, indanthrone-based, quinacridone-based, anthraquinone-based, benzimidazolone-based, perylene-based, perinone-based, phthalocyanine-based, halogenated phthalocyanine-based, anthrapyridine-based, and dioxazine-based.

[0157] Among these, the pigment is preferably carbon black or an organic pigment. By using carbon black or an organic pigment as the pigment, the storage stability of the ink is improved, and the effects of the present invention can be significantly achieved.

[0158] The organic pigment is preferably a magenta pigment. 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.

[0159] 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. 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, and dispersion medium, setting the dispersion conditions, and filtration conditions, etc. By controlling the particle size of the pigment, clogging of the head nozzle can be suppressed, and the storage stability, transparency, and curing sensitivity of the ink can be maintained.

[0160] The particle size of the pigment can be measured by a known measuring method, specifically, a centrifugal sedimentation light transmission method, an X-ray transmission method, a laser diffraction scattering method, or a dynamic light scattering method.

[0161] The pigment content is preferably within the range of 0.1 to 20% by mass, and more preferably within the range of 0.4 to 10% by mass, based on the total mass of the ink. When the pigment content is 0.1% by mass or more, good color development is obtained, and when it is 20% by mass or less, appropriate viscosity of the ink is obtained.

[0162] (4) Gelling agent In the present invention, the "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 is preferably soluble in a polymerizable compound described below at a temperature higher than the gelling temperature. In addition, the gelling agent is preferably crystallized in the ink at a temperature equal to or lower than the gelling temperature.

[0163] 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.

[0164] When the gelling agent crystallizes in the ink, it is preferable that the plate-like crystals, which are the crystallized product of the gelling agent, form a three-dimensionally enclosed space. It is preferable that the plate-like crystals encapsulate the polymerizable compound in the space thus formed. Such a 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."

[0165] The formation of the house-of-cards structure makes it possible to hold the liquid polymerizable compound and fix (pin) the ink droplets. Furthermore, it is possible to prevent the droplets from coalescing. In order to form the 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 the house-of-cards structure.

[0166] 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 amide, stearic amide, behenic amide, oleic amide, erucic amide, ricinoleic amide, and 12-hydroxystearic 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'-ethylene bisstearylamide, N,N'-ethylene bis-12-hydroxystearylamide, and N,N'-xylylene bisstearylamide; 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.

[0167] The gelling agent used may be a commercially available product. Commercially available ketone waxes include, for example, "18-Pentatriacontanone" (manufactured by Alfa Aeser), "Hentriacontan-16-on" (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), "Exepar (registered trademark) SS" (manufactured by Kao Corporation, melting point 60°C), "EMALEX (registered trademark) CC-18" (manufactured by Nippon Emulsion Co., Ltd.), "Amureps (registered trademark) PC" (manufactured by Kokyu Alcohol Kogyo Co., Ltd.), "Exepar (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 Industry 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).

[0168] Among them, 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.

[0169] 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 a straight chain portion having 12 or more carbon atoms and which may be branched.

[0170] The general formula (G1) is called ketone wax, and the general formula (G2) is called fatty acid ester. These gelling agents can gel ink droplets more stably and with high reproducibility. Therefore, they can suppress the coalescence of ink droplets (dots) that land on a recording medium.

[0171] The sol-gel transition temperature of the ink can be set arbitrarily. From the viewpoints of stable ejection of ink droplets and the adverse effects associated with high-temperature heating, the sol-gel transition temperature is preferably within the range of 30 to 100° C. In addition, the sol-gel transition temperature is preferably a temperature between the temperature of the ink in the inkjet head and the temperature of the recording medium.

[0172] 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, for example, the viscoelasticity measuring device "MCR300" (manufactured by Physica).

[0173] The sol-gel transition temperature can be adjusted by the type, content, etc. of the polymerizable compound described below.

[0174] When the temperature of the ink droplets ejected from the inkjet head and landed on the recording medium drops below the sol-gel phase transition temperature, the ink droplets quickly gel. This prevents the dots (ink droplets) from mixing with each other or merging, allowing high-quality images to be formed even at high-speed printing. The gelled ink droplets are then irradiated with active energy rays and hardened, thereby being fixed on the recording medium to form a strong image film.

[0175] 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, so that the ink curing is less susceptible to oxygen inhibition.

[0176] 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, based on 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.

[0177] (5) Polymerizable compound The ink of the present invention preferably contains a polymerizable compound that is cured by irradiation with active energy rays. By using an ink containing a polymerizable compound, an image can be formed even on a recording medium that does not absorb ink.

[0178] Examples of the polymerizable compound include a radically polymerizable compound, a cationic polymerizable compound, or a mixture thereof. The compound includes a monomer, a polymer (oligomer or polymer), or a mixture thereof. The polymerizable compound may be contained alone or in combination of two or more kinds.

[0179] 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, based on the total mass of the ink.

[0180] (5.1) Radical polymerizable compound The term "radical polymerizable compound" refers to a compound having an ethylenically unsaturated bond capable of radical polymerization. Examples of the radical polymerizable compound 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 the unsaturated carboxylic acids include (meth)acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid.

[0181] In this specification, (meth)acrylic acid is a general term for acrylic acid and methacrylic acid, and means one or both of them. "(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.

[0182] 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.

[0183] (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)acryloyloxyethylhexahydrophthalic 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] Since the ink of the present invention is of the sol-gel phase transition type, it is preferable that at least a part 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 card house structure when the ink gels at low temperatures. In addition, 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 and can suppress curling of printed matter.

[0189] 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 of the copolymer 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.).

[0190] Here, the "logP value" is a coefficient indicating the affinity of an organic compound to 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 in a partition equilibrium state when a trace amount of a compound is dissolved as a solute in a two-phase solvent of 1-octanol and water. The logarithm of the 1-octanol / water partition coefficient to the base 10 is indicated by 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.

[0191] The "ClogP value" is 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)). In addition, a method using the commercially available software package 1 or 2 below can be mentioned.

[0192] Software Package 1: MedChem Software (Release 3.54, August 1991, Medicinal Chemistry Project, Pomona College, Claremont, CA) Software package 2: Chem Draw Ultra ver.8.0. (April 2003, CambridgeSoft Corporation, USA)

[0193] The numerical values ​​of ClogP values ​​described in this specification are "ClogP values" calculated using software package 2.

[0194] The (meth)acrylate compound may be a polymerizable oligomer. Examples of the polymerizable oligomer include an epoxy (meth)acrylate oligomer, an aliphatic urethane (meth)acrylate oligomer, an aromatic urethane (meth)acrylate oligomer, a polyester (meth)acrylate oligomer, and a linear (meth)acrylic oligomer.

[0195] (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.

[0196] (5.2.1) Epoxy compounds Examples of the epoxy compound include aromatic epoxides, alicyclic epoxides, aliphatic epoxides, etc. Among them, aromatic epoxides or alicyclic epoxides are preferred from the viewpoint of enhancing curability.

[0197] Examples of aromatic epoxides include diglycidyl ethers or polyglycidyl ethers obtained by reacting polyhydric phenols or their alkylene oxide adducts with epichlorohydrin. Examples of polyhydric phenols or their alkylene oxide adducts to be reacted include bisphenol A or its alkylene oxide adducts. Examples of the alkylene oxide in the alkylene oxide adduct include ethylene oxide and propylene oxide.

[0198] Examples of the alicyclic epoxide include a cycloalkane oxide-containing compound obtained by epoxidizing a cycloalkane-containing compound with an oxidizing agent such as hydrogen peroxide, peracid, etc. Examples of the cycloalkane in the cycloalkane oxide-containing compound include cyclohexene, cyclopentene, etc.

[0199] Examples of the aliphatic epoxide include diglycidyl ethers or polyglycidyl ethers obtained by reacting an aliphatic polyhydric alcohol or its alkylene oxide adduct with epichlorohydrin. Examples of the aliphatic polyhydric alcohol 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.

[0200] (5.2.2) Vinyl ether compounds Examples of the vinyl ether compound 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.

[0201] 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 viewpoints of curability, adhesion, etc., a divinyl ether compound or a trivinyl ether compound is preferred.

[0202] (5.2.3) Oxetane compounds The oxetane compound is a compound having an oxetane ring. Examples of the oxetane compound include oxetane compounds described in JP-A-2001-220526, JP-A-2001-310937, and JP-A-2005-255821. More specifically, 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) in paragraph 0107, the compound represented by general formula (8) in paragraph 0109, and the compound represented by general formula (9) in paragraph 0116 are included.

[0203] (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 surface slippage of the ink when ejected onto a recording medium is good.

[0204] The fatty acid is preferably a compound having 12 or more carbon atoms. Examples of fatty acids include behenic acid (C 22 H 44 O 2 ), arachidic acid (C 20 H 40 O 2 ), stearic acid (C18 H 36 O 2 ), palmitic acid (C 16 H 32 O 2 ), myristic acid (C 14 H 28 O 2 ), lauric acid (C 12 H 24 O 2 ), oleic acid (C 18 H 34 O 2 ), erucic acid (C 22 H 42 O 2 ) etc.

[0205] The fatty acids used may be commercially available products. 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", "Lunac (registered trademark) L-98" (all manufactured by Kao Corporation), "NAA (registered trademark)-222S beads", "NAA (registered trademark)-222 powder", "Beads Sakura Stearate", "Beads Camellia Stearate", "Powdered Sakura Stearate", "Powdered Camellia Stearate", "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).

[0206] The content of the fatty acid is preferably within a range of 0.01 to 10 ppm by mass, more preferably within a range of 0.01 to 0.18 ppm by mass, based on the total mass of the ink. When the content is 0.01 ppm by mass or more, the storage stability and ejection stability of the ink are good. In addition, when the ink is ejected onto a recording medium, the surface slipperiness of the ink is good, and so-called paper jams can be suppressed. When the content is 10 ppm by mass or less, the storage stability of the ink is good.

[0207] (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 may not contain a polymerization initiator, but when the active energy rays are ultraviolet rays, the ink preferably contains a polymerization initiator.

[0208] Polymerization initiators are classified into intramolecular bond cleavage type and intramolecular hydrogen abstraction type.

[0209] 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, benzoin methyl ether, and benzoin isopropyl ether; acylphosphine oxide-based initiators such as 2,4,6-trimethylbenzoin diphenylphosphine oxide; benzyl glyoxy esters; and methylphenyl glyoxy esters.

[0210] Examples of the intramolecular hydrogen abstraction type 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.

[0211] 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 with respect to the total mass of the ink.

[0212] 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. For details, see Organic Electronics Materials Research Group (ed.), "Organic Materials for Imaging," Bunshin Shuppan (1993), pp. 187-192.

[0213] (8) Polymerization initiator aid The ink of the present invention may further contain a polymerization initiator aid. The polymerization initiator aid may, for example, be a tertiary amine compound, and among these, an aromatic tertiary amine compound is preferred.

[0214] 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.

[0215] Among them, 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. These may be contained alone or in combination of two or more.

[0216] (9) Polymerization inhibitors The ink of the present invention may further contain a polymerization inhibitor. Examples of the polymerization inhibitor include (alkyl)phenols, hydroquinone, catechol, resorcin, 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-dimethylbutylidene)aniline oxide, dibutyl cresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, and cyclohexanone oxime.

[0217] (10)Other The ink of the present invention may further contain other components as necessary. The other components include various additives other than the additives described above, other resins, etc. The various additives other than the additives described above include, for example, surfactants, leveling additives, matting agents, ultraviolet absorbers, infrared absorbers, antibacterial agents, basic compounds for improving the storage stability of the ink, etc.

[0218] Examples of the basic compound include basic alkali metal compounds, basic alkaline earth metal compounds, and basic organic compounds such as amines. Examples of the other resin include resins for adjusting the physical properties of the cured film. Examples of the other resin include polyester, polyurethane, vinyl resin, acrylic resin, rubber-based resin, wax, and the like.

[0219] 3. Physical properties of active energy beam-curable inkjet ink 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 more. This range allows the ink to gel sufficiently when cooled to room temperature after landing on a recording medium.

[0220] 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 is easily fixed since it thickens quickly after landing on a recording medium. Furthermore, when the ink has a phase transition temperature of 70° C. or lower, the ink can be ejected stably when the temperature at the time of ejection is set to about 80° C., which is a commonly used temperature.

[0221] 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 dynamic viscoelasticity of the ink 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 temperature drop rate of 0.1°C / s to obtain a temperature change curve of the viscosity. Note that, for example, a "Physica MCR301" (cone plate diameter: 75 mm, cone angle: 1.0°, manufactured by Anton Paar) can be used as the stress-controlled rheometer.

[0222] The viscosities at 25°C and 80°C are determined by reading the viscosities 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 becomes 200 mPa s on the viscosity temperature curve.

[0223] 4. Method for producing active energy ray-curable inkjet ink The method for producing an active energy ray-curable inkjet ink of the present invention is characterized by comprising a step of preparing a pigment dispersion liquid containing the pigment and the dispersant, and a step of preparing the active energy ray-curable inkjet ink containing the pigment dispersion liquid, the gelling agent and the additives. In other words, first, the pigment dispersion liquid is prepared, and then the pigment dispersion liquid is mixed with other components to prepare the ink.

[0224] (1) A step of preparing a pigment dispersion containing a pigment and a dispersant In this step, a pigment dispersion liquid containing a pigment and a dispersant is prepared. Note that the compound having a pyridine structure also has a function of dispersing the pigment, but in the present invention, the compound having a pyridine structure is added as an additive in the next step.

[0225] 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 preferable from the viewpoints of dispersibility and handleability with the polymerizable compound.

[0226] 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.

[0227] (2) A step of preparing an active energy ray curable inkjet ink containing a pigment dispersion, a gelling agent, and additives. In this process, an ink containing a pigment dispersion, a gelling agent, and additives is prepared. The method for mixing the components of the ink is not particularly limited, and they can be mixed by a known method. For example, other components of the ink may be added to the prepared pigment dispersion liquid and mixed while heating. The obtained mixture is preferably filtered through a predetermined filter.

[0228] 5. Inkjet recording method The inkjet recording method of the present invention is an inkjet recording method in which the above-mentioned ink is ejected and landed on a recording medium to perform recording, and is characterized in that the ejection temperature of the ink is within a range of 40 to 120°C, and the temperature of the recording medium is 60°C or less.

[0229] In the inkjet recording method of the present invention, the above-mentioned ink is used. More specifically, when a multicolor image is formed using a plurality of inks having different compositions, at least one of the plurality of inks may be the ink of the present invention.

[0230] In the inkjet recording method of the present invention, an inkjet printer is used. In general, inkjet printers are divided into on-demand type and 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 type inkjet printers include electro-mechanical conversion type printers including single cavity type, double cavity type, bender type, piston type, share mode type, and shared wall type printers; and electro-thermal conversion type printers including thermal inkjet type and bubble jet (Bubble Jet is a registered trademark of Canon Inc.) type printers.

[0231] Inkjet printers are divided into scan type and line type 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). Since the ink of the present invention can be quickly fixed, a high-quality recorded matter can be obtained even in high-speed recording using the line type.

[0232] The recording medium may be any recording medium on which an image can be formed using the ink of the present invention. Examples of the recording medium 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 printing coated paper and printing coated paper B.

[0233] Examples of the plastic film include a PP film, a PET film, an OPS film, an OPP film, an ONy film, a PVC film, a PE film, and a TAC film.

[0234] (1) The process of ejecting ink from the head In the step of ejecting the ink from the head, droplets of the ink are ejected from the nozzles of the head. The ejection method is not particularly limited.

[0235] The temperature of the ink inside the head is preferably within a range of 40 to 120° C., and more preferably within a range of 50 to 85° C. When the temperature of the ink inside the head is 40° C. or higher, the ejection stability of the ink from the head can be obtained. Also, when the temperature is 120° C. or lower, the volatilization of the ink components can be suppressed, and the thermal load on the head can be reduced.

[0236] 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.

[0237] It is also preferable to set the temperature of the ink in the head to be 10 to 40°C higher than the gelling temperature of the ink. By setting the temperature of the ink in the head to a gelling temperature + 10°C or higher, the ink does 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 in the head to a gelling temperature + 40°C or lower, the thermal load on the head can be reduced. In particular, in a head using a piezoelectric element, performance degradation due to thermal load is likely to occur, so it is preferable to set the temperature of the ink in the head within the above range.

[0238] The method of 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., with a panel heater, a ribbon heater, warm water, etc. Examples of the ink supply system include an ink tank constituting the head carriage, a supply pipe, and a front chamber ink tank immediately before the head, etc.

[0239] 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.

[0240] (2) The process of depositing ink onto a recording medium In the process of directly impacting ink on a recording medium, the ink ejected in the previous process is impacted on the recording medium.

[0241] 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.

[0242] (3) A process of exposing the ink to active energy rays to harden the ink. In the process of irradiating the ink with active energy rays to cure the ink, the surface of the recording medium on which the ink has landed is irradiated with active energy rays.

[0243] As described above, examples of active energy rays include visible light, ultraviolet light, X-rays, electron beams, α rays, β rays, and γ rays. Among 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 curing of the ink.

[0244] 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 cause 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.

[0245] The amount of energy emitted by the active energy rays is 200 to 1000 mJ / cm 2 It is preferable that the amount of energy is within 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 it is possible to suppress a decrease in the pinning property. 2 More preferably, it is within the range of 350 to 500 mJ / cm 2 It is more preferable that the ratio is within the range of 1.

[0246] (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.

[0247] 6. Inkjet recording system The inkjet recording system of the present invention is characterized in that it is an inkjet recording system which records by ejecting the ink described above onto a recording medium, that is, it is characterized in that it uses the ink described above.

[0248] 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.

[0249] FIG. 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 has an inkjet head 110, a conveying path 120, an active energy ray irradiation unit 130, and a temperature control unit 140. In FIG. 1, an arrow A indicates the conveying direction of a recording medium 150. The inkjet head 110 and the active energy ray irradiation unit 130 are arranged in this order in contact with the conveying path 120 from the upstream side to the downstream side in the conveying direction of the recording medium. The image forming apparatus 100 may have an oxygen concentration adjustment unit (not shown) for adjusting the oxygen concentration when the ink is irradiated with active energy rays.

[0250] 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.

[0251] 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 carriage 160 is fixedly disposed so as to cover the entire width of the recording medium 150, for example.

[0252] 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 inks of yellow (Y), magenta (M), cyan (C) and black (K), or may be used for only some of the inks. Of these, it is preferable to use the ink of the present invention for the magenta ink or black ink.

[0253] 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 described above, the temperature of the ejected ink is preferably within a range of 40 to 120°C, and more preferably within a range of 50 to 85°C.

[0254] 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 ejected by the inkjet heads 110 and landing on the recording medium 150 with active energy rays, thereby curing the droplets.

[0255] 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.

[0256] 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. EXAMPLES

[0257] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the examples, the terms "parts" and "%" are used, but they represent "parts by mass" or "% by mass" unless otherwise specified. In the following examples, operations were carried out at room temperature (25° C.) unless otherwise specified.

[0258] 1. Synthesis of various compounds (1) Synthesis of dispersant Compounds 1 to 4 were synthesized as compounds having a structure derived from a hydroxy fatty acid and a basic functional group. Compound 5 was also synthesized as a comparative compound. Compound 5 did not fall under the category of compounds having a structure derived from a hydroxy fatty acid and a basic functional group.

[0259] (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 about 4 hours. The reaction mixture was then cooled to room temperature to obtain Polyester 1.

[0260] Glycolic acid (manufactured by Junsei Chemical Co., Ltd.) 10.00 parts by mass ε-caprolactone (manufactured by Junsei Chemical Co., Ltd.) 1306.00 parts by mass Tetrabutyl titanate (manufactured by Junsei Chemical Co., Ltd.) 0.07 parts by mass

[0261] Polyester 1 had a number average molecular weight of 8,570 and an acid value of 6.3 mg KOH / g.

[0262] The following components were charged into the reaction flask used for obtaining Polyester 1. Toluene 115.50 parts by mass 10% polyallylamine aqueous solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3000) 70.00 parts by mass

[0263] 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, which had been 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 70.00 parts by weight

[0264] Compound 1 had a solid content of 40.2%, an amine value of 5.0 mg KOH / g, and an acid value of 4.9 mg KOH / g.

[0265] (1.2) Synthesis of Compound 2 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 about 3.5 hours. The reaction mixture was then cooled to room temperature to obtain polyester 2.

[0266] 2-Hydroxycaproic acid (manufactured by 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

[0267] Polyester 2 had a number average molecular weight of 5630 and an acid value of 9.6 mg KOH / g.

[0268] The following components were charged into the reaction flask used for obtaining Polyester 2. Toluene 194.25 parts by mass 10% polyallylamine aqueous solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3000) 70.00 parts by mass

[0269] 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, which had been 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 2 was then obtained. Polyester 2 122.50 parts by weight

[0270] Compound 2 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.

[0271] (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, and polyester 3 was obtained.

[0272] 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

[0273] Polyester 3 had a number average molecular weight of 2050 and an acid value of 26.3 mg KOH / g.

[0274] The following components were charged into the reaction flask used for obtaining Polyester 3. Toluene 194.30 parts by mass 10% polyallylamine aqueous solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3000) 70.00 parts by mass

[0275] 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, which had been 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 weight

[0276] Compound 3 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.

[0277] (1.4) Synthesis of compound 4 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 about 3.5 hours. The reaction mixture was then cooled to room temperature, and polyester 4 was obtained.

[0278] 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

[0279] Polyester 4 had a number average molecular weight of 2920 and an acid value of 18.5 mg KOH / g.

[0280] The following components were charged into the reaction flask used for obtaining Polyester 4. Toluene 194.30 parts by mass 10% polyallylamine aqueous solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3000) 70.00 parts by mass

[0281] 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, which had been 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 4 was then obtained. Polyester 4 122.50 parts by weight

[0282] Compound 4 had a solids content of 40.2%, an amine value of 20.0 mg KOH / g, and an acid value of 15.0 mg KOH / g.

[0283] (1.5) Synthesis of compound 5 The following components were placed in a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, a reflux condenser, and a dropping funnel, and the temperature was raised to 85°C. Xylene 348.0 parts by mass

[0284] Then, a mixed solution of the following components was continuously dropped into the reaction flask over a period of 2 hours, and polymerization was then carried out at 85° C. for 1 hour. Methyl methacrylate 190.0 parts by mass Butyl methacrylate 158.0 parts by mass 2-Ethylhexyl methacrylate 75.0 parts by mass Styrene 60.0 parts by mass Acrylic acid 7.0 parts by mass 2-Hydroxyethyl methacrylate 110.0 parts by mass Azobisisobutyronitrile 11.0 parts by mass Dimethylacetamide 30.0 parts by mass

[0285] Thereafter, a solution in which the following components were mixed and dissolved was added to the reaction flask, and the polymerization reaction was further carried out at 85° C. for 5 hours, after which the reaction was terminated. Thus, acrylic resin 1 was obtained. Azobisisobutyronitrile 1.0 parts by mass Dimethylacetamide 10.0 parts by mass

[0286] Separately, the following components were charged into a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet and a reflux tube. Toluene 194.30 parts by mass 10% polyallylamine aqueous solution ("PA-1" manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3000) 70.00 parts by mass

[0287] 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 acrylic resin 1 heated to 120° C. was added while returning the toluene to the reaction solution, and the reaction was carried out at 120° C. for 5 hours. Compound 5 was then obtained. Acrylic resin 1 122.50 parts by mass

[0288] Compounds 1 to 4 having a structure derived from a hydroxy fatty acid and a basic functional group as a dispersant, and compound 5 as a comparison were synthesized as described above. The combinations of modifying resins and polyallylamine components in compounds 1 to 5 are shown in Table I below. For compounds 1 to 4, polyester was used as the modifying resin. For compound 5, acrylic resin was used instead of polyester as the modifying resin. Furthermore, the amine values ​​of compounds 1 to 5 are shown in Table I.

[0289] [Table 1]

[0290] (2) Synthesis of additives Compounds 7 and 8 were synthesized as compounds having a pyridine structure. As compound 6, poly(4-vinylpyridine) was used. As compound 9, "Efka (registered trademark) PX4701" (acrylic block copolymer, manufactured by BASF) was used. "TEGO (registered trademark) Dispers 655" (phosphate ester of special modified polyether polymer, manufactured by Evonik Corporation) was used as compound 10. Note that compound 10 was a comparative compound and did not correspond to a compound having a pyridine structure. Among the compounds 6 to 9, the compounds 7 to 9 were acrylic polymers.

[0291] (2.1) Synthesis of compound 7 (Step 1: Synthesis of polyacrylate) The following components were mixed uniformly in a reaction flask under a nitrogen atmosphere at 15 to 30°C. During mixing, degassing and N 2 A substitution treatment was then carried out. The mixture was then heated in an oil bath heated to a temperature within the range of 100 to 130°C, and a polymerization reaction was carried out within a range of 5 to 15 hours. When the solid content reached 50% by volume, the reaction product was cooled with liquid nitrogen to terminate the reaction. Then, the unreacted monomer was removed by vacuum distillation to obtain polyacrylate.

[0292] NMP initiator 1 12.00 parts by weight NMP initiator 2 4.00 parts by weight n-Butyl acrylate (manufactured by Mitsubishi Chemical Corporation) 84.00 parts by mass Details of the NMP initiator are shown below. NMP initiator 1: N-tert-Butyl-N-(2-Methyl-1-phenylpropyl)-O-(1-phenylethyl)hydroxylamine (Aldrich, product number 700703) NMP initiator 2: 2,2,5-Trimethyl-4-phenyl-3-azahexane-3-nitroxide (Aldrich, product number 710733)

[0293] (Step 2: Synthesis of polyacrylate-poly(vinylpyridine)) The following components were mixed uniformly in a reaction flask under a nitrogen atmosphere at 15 to 30°C. During mixing, degassing and N 2A substitution treatment was then carried out. The mixture was then heated in an oil bath heated to a temperature within the range of 100 to 140°C, and a polymerization reaction was carried out within the range of 2 to 5 hours. When the solid content reached 90% by volume, the reaction product was cooled with liquid nitrogen to terminate the reaction. Then, unreacted monomers were removed by vacuum distillation to obtain polyacrylate-poly(vinylpyridine).

[0294] NMP initiator 2 2.00 parts by weight Polyacrylate obtained in the first step: 66.00 parts by mass 4-Vinylpyridine "V0025" (Tokyo Chemical Industry Co., Ltd.) 32.00 parts by mass

[0295] (Step 3: Synthesis of a polymer having a pyridine skeleton) The following components were mixed uniformly in a reaction flask under a nitrogen atmosphere at 15 to 30°C. During mixing, degassing and N 2 A substitution treatment was performed. After that, the mixture was heated in an oil bath heated within the range of 100 to 140°C. Then, 0.2 parts by mass of a catalyst solution, lithium methanolate 10% methanol solution (manufactured by Aldrich, product code 62562), was added, and distilled under reduced pressure. This was repeated five times at 1-hour intervals. Then, the reactant was cooled with liquid nitrogen to stop the reaction, and compound 7 was obtained.

[0296] Polyacrylate-poly(vinylpyridine) obtained in the second step 33.00 parts by mass Poly(ethylene glycol) methyl ether (Mw=550g / mol, Wako Pure Chemical Industries, Ltd., product code 041561) 66.00 parts by mass

[0297] (2.2) Synthesis of compound 8 (a: Synthesis of macromonomer) The following ingredients were added to a reaction vessel: One-terminated aminated polypropylene glycol polyethylene glycol monomethyl ether copolymer "Genamine M41 / 2000" (Clariant) 100.00 parts by mass

[0298] The following components were then added dropwise to the reaction vessel over a period of 30 minutes while cooling with water. 2-isocyanatoethyl methacrylate 7.82 parts by mass

[0299] After the addition, a portion of the reaction solution was sampled, and infrared spectroscopy (IR) confirmed that the isocyanate groups derived from the MOI had almost completely disappeared and urea bonds had been formed, confirming that a macromonomer had been produced.

[0300] The number average molecular weight of the obtained macromonomer was measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a developing solvent. The number average molecular weight (Mn) of the macromonomer in terms of polystyrene was 3,300, and the polydispersity (PDI = Mw (weight average molecular weight) / Mn (number average molecular weight)) was 1.16.

[0301] (b: Polymer synthesis) The following ingredients were added to the reaction vessel: Polypropylene glycol "Uniol D-1200" (NOF Corporation) 137.60 parts by mass 2-Ethylhexyl methacrylate 16.00 parts by mass α-Methylstyrene 1.50 parts by mass 4-Vinylpyridine 12.00 parts by mass

[0302] The mixture was heated to 70° C. while bubbling nitrogen, and then the following components were added and polymerized for 4 hours. 2,2'-Azobis(dimethyl isobutyrate) "V-601" (FUJIFILM Wako Pure Chemical Industries, Ltd.) 0.20 parts by mass

[0303] Further, the following components were added, and polymerization was carried out at 70° C. for 4 hours to obtain Compound 8, which was a polymer. 2,2'-Azobis(dimethyl isobutyrate) "V-601" (FUJIFILM Wako Pure Chemical Industries, Ltd.) 0.10 parts by mass

[0304] The number average molecular weight (Mn) of compound 8 was 13,500, the polydispersity index (PDI) was 2.10, and the amine value of compound 8 was 57.6 mg KOH / g.

[0305] 2. 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.

[0306] 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

[0307] The following components were added to the solution and thoroughly stirred. This mixture was placed in a glass bottle together with 100 g of zirconia beads with a diameter of 0.5 mm, sealed, and subjected to vibration dispersion for 2 hours using a vibration mill (Red devil 5400HC). The zirconia beads were then removed to obtain pigment dispersion 1. The content of the dispersant was 30% by mass relative to the total mass of the pigment. Pigment: Pigment Blue 15:4 20.00 parts by mass

[0308] (2.2) Mixing of ink components The following ingredients were placed in a dissolution 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

[0309] To this solution were added the following ingredients and stirred for an additional 30 minutes. Pigment dispersion 1 (dispersant concentration: 6% by mass) 11.67 parts by mass

[0310] The mixture was heated to 80°C, and the following gelling agent was added and stirred for another 30 minutes. Compound 6 was added thereto and stirred for another 30 minutes. After that, it was filtered through a methoprene filter (nominal filtration accuracy 3μm, 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 6 0.70 parts by mass

[0311] (2) Preparation of Inks 2 to 23 Inks 2 to 23 were prepared in the same manner as in the preparation of Ink 1, except that the types and contents of the pigment, dispersant, and additives were changed as shown in Table II.

[0312] The compositions of Inks 1 to 23 are shown in Table II. A "-" in the table indicates that the corresponding ingredient was not added. Details of the pigments in the table are given below. PB15:4: Pigment Blue 15:4 PR122: Pigment Red 122 PR202: Pigment Red 202 PV19: Pigment Violet 19 CB: Carbon black "MA7" (manufactured by Mitsubishi Chemical Corporation)

[0313] In Example 15, the pigment used was "Fastogen Super Magenta JM02" (manufactured by DIC Corporation). This pigment contains both PR122 and PV19. In Example 16, the pigment used was "Ink Jet Magenta E7B" (manufactured by Clariant Corporation). This pigment contains both PR202 and PV19. The content in the table indicates the content relative to the total mass of the ink. "Mass ratio A:B" indicates the mass ratio of the content of the dispersant (A) to the content of the additive (B).

[0314] [Table 2]

[0315] 3. Evaluation (1) Gloss Each of the inks obtained above was ejected from the nozzle of an inkjet head. The temperature of the ink when ejected was 80°C. Then, the ink was deposited on aluminum-deposited PET paper "SPECIALITIES-352" (manufactured by Gojo Paper Co., Ltd.) and transparent PET film "AGT-ES100" (thickness: 100 μm, manufactured by Dynic Co., Ltd.). The ink was then cured to a thickness of 10 g / m 2 A solid image was created. The substrate temperature was 40°C during curing. Within 1 second after the ink was deposited, an LED lamp (wavelength: 395 nm, illuminance on substrate: 3 W / cm 2 (manufactured by Kyocera) with a light intensity of 500 mJ / cm 2 The ink was irradiated with ultraviolet light so that the ink The produced images were visually inspected and evaluated according to the following criteria. Grades B and above (A and B) were deemed to pass. Grade C is generally not problematic in practical use, but the present invention is extremely excellent in gloss, so grades B and above were deemed to pass.

[0316] (standard) A: Uniform gloss and low graininess on all substrates. B: Aluminum-deposited PET paper has a uniform gloss and low graininess. On the other hand, transparent PET film has a slightly non-uniform gloss but low graininess. C: For all substrates, gloss is non-uniform but graininess is low. D: For all substrates, the gloss is uneven and roughness is noticeable.

[0317] (2) Storage stability Each ink obtained above was placed in a heat-resistant glass bottle, sealed, and stored at 90°C for two weeks for forced aging. The viscosity (mPa s) of each ink at 80°C before and after the forced aging treatment was then measured using a rheometer "MCR300" (manufactured by Paar Physica). 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. Note that if the ink is rated B or above (AA to B), there is no problem in practical use.

[0318] (Formula) Viscosity fluctuation rate = {(Ink viscosity after forced deterioration process - Ink viscosity before forced deterioration process) / Ink viscosity before forced deterioration process} x 100 (%) (standard) AA: The viscosity fluctuation rate is less than 5.0%. A: The viscosity fluctuation rate is 5.0% or more and less than 10.0%. B: The viscosity fluctuation rate is 10.0% or more and less than 15.0%. C: The viscosity fluctuation rate is 15.0% or more.

[0319] (3) Injection properties Each ink obtained above was introduced into an inkjet head "HA1024 type" (manufactured by Konica Minolta, Inc.) and ejected. A nozzle check pattern was printed, and the printout was visually inspected for the presence or absence of nozzle missing or ejection deflection, and evaluated according to the following criteria. Note that if it was rated B or higher (A and B), there was no problem in practical use. "Nozzle failure" refers to the phenomenon in which ink is not ejected from the nozzle. "Deviated ejection" refers to the phenomenon in which ink is ejected from the nozzle in a curved direction. (standard) A: No nozzle defects or deflection of the injection nozzle were observed. B: Of the total 1,024 nozzles, nozzle chipping or deflection of the nozzles was observed in 1 to 9 nozzles. C: Of the total 1,024 nozzles, 10 or more nozzles were found to have missing nozzles or bent ejection.

[0320] (4) Image Density Each of the inks obtained above was introduced into an inkjet head "HA1024 type" (manufactured by Konica Minolta, Inc.). The ink was ejected and landed on a recording medium under the conditions of a print width of 100 mm x 100 mm, a resolution of 720 x 720 dpi, a voltage of 16 V, an ambient temperature of 25°C, and an ambient humidity of 55%. After that, the ink droplets that had landed were illuminated with 250 mJ / cm by an LED lamp. 2 The ink droplets were cured by irradiating them with ultraviolet light with an energy of 100. A solid image with a printing rate of 100% was then produced. As a recording medium, printing paper "OK ​​Topcoat (registered trademark)" (manufactured by Oji Paper Co., Ltd.) was used. The produced images were visually observed and evaluated according to the following criteria: If the image was rated B or higher (A or B), there was no problem in practical use. Note that "density unevenness" here refers to unintentional color shading that occurs in an image, such as localized shading spots in a solid image that is originally uniform in density.

[0321] A: There is almost no unevenness in density on the image surface, and the density is high. B: There are some unevenness in density on the surface of the image, and the density appears to be somewhat low. C: The image surface has uneven density and low density.

[0322] The evaluation results are shown in Table III.

[0323] [Table 3]

[0324] From the examples and comparative examples, it is clear that the glossiness of the images formed using the ink of the present invention is improved.

[0325] From Examples 2 to 4, 13 and 14, it is clear that the storage stability of the ink is improved when the compound having a pyridine structure is an acrylic polymer compound.

[0326] From Examples 1, 2, 5 and 6, it can be seen that the storage stability of the ink is improved when the compound having a structure derived from a hydroxy fatty acid and a basic functional group has a structure derived from hydroxystearic acid and an amine value within the range of 10 to 20 mgKOH / g.

[0327] From Examples 6, 7, 9 and 12, it can be seen that gloss and ejection performance are improved by adjusting the content of the compound having a pyridine structure within the range of 0.1 to 0.6 mass % relative to the total mass of the active energy ray-curable inkjet ink.

[0328] From Examples 6, 10 and 11, it can be seen that gloss and ejection properties are improved when the mass ratio of the compound having a structure derived from a hydroxy fatty acid and a basic functional group to the compound having a pyridine structure is within the range of 2.73:1 to 16.4:1.

[0329] From Examples 13 and 15 to 17, it can be seen that the pigment is carbon black or a magenta pigment, and the magenta pigment contains any one of CI Pigment Violet 19, CI Pigment Red 122, and CI Pigment Red 202, thereby improving the image density. [Explanation of symbols]

[0330] 100 Image forming device 110 Inkjet head 120 Transport Path 130 Active energy ray irradiation section 140 Temperature control unit 150 Recording media 160 Head Carriage 170 Ink flow path 180 Ink Tank

Claims

1. An actinic ray curable inkjet ink containing a pigment, a dispersant, a gelling agent and an additive, The dispersant contains a compound having a structure derived from a hydroxy fatty acid and a basic functional group, The additive contains a compound having a pyridine structure.

1. An actinic ray-curable ink-jet ink comprising:

2. The compound having a pyridine structure is an acrylic polymer compound.

2. The actinic ray curable ink-jet ink according to claim 1,

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

2. The actinic ray curable ink-jet ink according to claim 1,

4. The content of the compound having a pyridine structure is within a range of 0.1 to 0.6% by mass with respect to the total mass of the active energy ray-curable inkjet ink.

2. The actinic ray curable ink-jet ink according to claim 1,

5. The mass ratio of the compound having a structure derived from a hydroxy fatty acid and a basic functional group to the compound having a pyridine structure is within the range of 2.73:1 to 16.4:

1.

2. The actinic ray curable ink-jet ink according to claim 1,

6. 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 ray curable ink-jet ink according to claim 1,

7. A method for producing an active energy ray-curable inkjet ink, comprising the steps of: The actinic ray curable inkjet ink according to any one of claims 1 to 6, preparing a pigment dispersion containing the pigment and the dispersant; and preparing the active energy ray-curable inkjet ink containing the pigment dispersion, the gelling agent, and the additives.

13. A method for producing an active energy ray-curable inkjet ink, comprising:

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

1. An ink-jet recording method comprising:

9. An inkjet recording system that records by ejecting ink onto a recording medium, The ink is an active energy ray-curable ink-jet ink according to any one of claims 1 to 6.

1. An inkjet recording system comprising:

Images