Water-based inkjet ink, water-based inkjet ink set, and inkjet recording method

Abstract

To provide an active energy ray-curable water-based inkjet ink that has excellent dischargeability and can be, therefore, discharged with high efficiency and left to stand with high stability, and that can form a cured film having excellent properties such as scratch resistance and water resistance, and an inkjet recording method using the same.SOLUTION: The water-based inkjet ink is an active energy ray-curable water-based inkjet ink including a water-soluble monomer having a polymerizable group. The water-based inkjet ink further includes a hydrazide compound. The water-soluble monomer is a curable substance having a ketone structure. The ink jet recording method includes the steps of: discharging the water-based inkjet ink from an inkjet recording head to a recording medium, to form a first uncured image; and curing the first uncured image by an active energy ray curing reaction and a chemical crosslinking reaction to form an image.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an active energy ray-curable aqueous inkjet ink, an aqueous inkjet ink set, and an inkjet recording method using them.

Background Art

[0002] Conventionally, a method of irradiating a liquid composition applied on a recording medium with active energy rays to cure a curable substance in the liquid composition to form a cured film and record an image is known. This method is classified, for example, into a technique of applying a liquid composition (curable emulsion paint) obtained by adding a coloring material to an aqueous vehicle in which a non-aqueous active energy ray-curable substance is emulsified and dispersed to a medium and then irradiating with ultraviolet rays to record an image.

[0003] Active energy ray-curable liquid compositions and various paints have been widely applied in recent years in fields such as graphic art, sign art, display panel manufacturing, label recording, package recording, and manufacturing of electronic circuit boards. Among them, a technique applied to an inkjet recording method using a liquid composition containing an active energy ray-curable substance as an ink is known.

[0004] For active energy ray-curable inks applied to the inkjet recording method, non-aqueous or aqueous compounds are used as curable substances. Active energy ray-curable inks using non-aqueous curable substances are classified into two major types. One is a so-called oil-based ink in which a pigment is dispersed in an organic solvent such as toluene or methyl ethyl ketone. The other is a so-called 100% curable ink (non-solvent ink) that does not use an organic solvent and contains liquid monomers, oligomers, and a pigment dispersion.

[0005] When using oil-based ink, since organic solvents are likely to volatilize into the atmosphere, sufficient consideration for the environment is required. Also, when using 100% curable ink, since all the components applied on the recording medium are made into a cured film, steps (unevenness) are likely to occur between the recorded part and the non-recorded part, and it is difficult to improve the glossiness of the image. For this reason, it is difficult to expand the application of active energy ray-curable ink using a non-aqueous curable substance to applications that require high image quality.

[0006] On the other hand, in the case of ink using an aqueous curable substance, since an aqueous solvent mainly composed of water is used, the addition to the environment due to the volatilization of the solvent is extremely small. Also, since unevenness is less likely to occur in the image, the glossiness of the image can be improved. For the above reasons, it can be said that applying an active energy ray-curable aqueous ink liquid composition using an aqueous curable substance to an inkjet recording method is extremely useful. And, various water-soluble curable substances used for such active energy ray-curable aqueous ink have been studied.

[0007] In addition, for such a water-soluble curable substance, for example, it is required to have characteristics such as high water solubility in the state before curing, not reducing the performance of the ink even when coexisting with colorants, being stable even under normal temperature conditions, and not reducing the ejection property of the ink. Furthermore, for the water-soluble curable substance, it is also required to have characteristics such as showing high sensitivity to light of a predetermined wavelength, being able to form a cured film with excellent abrasion resistance, showing high resistance to various organic solvents and water, and being less likely to turn yellow or the like under various environments.

[0008] Various curable substances used in active energy ray-curable aqueous inks have been proposed so far. For example, an ink using a polyfunctional acrylamide compound having both water solubility and photocurability as a curable substance has been proposed (Patent Document 1). Also, a monofunctional acrylamide proposed to be used in combination with the curable substance proposed in Patent Document 1 has been proposed (Patent Document 2). On the other hand, various types of inks that cure without using active energy rays have also been studied. For example, an ink containing a polymer compound having an acrylamide structure and a crosslinkable functional group and capable of curing by a crosslinking reaction has been proposed (Patent Document 3).

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, since the curable substance proposed in Patent Document 1 is a polyfunctional compound, there is a problem that the crosslinking density of the formed cured film becomes too high and the cured film tends to be brittle. Also, by using the acrylamide compound proposed in Patent Document 2, the properties of the cured film are improved, but there is a problem that the crosslinking density is low and the water resistance decreases.

[0011] Furthermore, even in the case of the polymer compound proposed in Patent Document 3, since the absolute amount of the crosslinking component is small, problems such as a decrease in water resistance still existed. In addition, in order to stably eject an ink containing a polymer compound by an inkjet method, it is necessary to contain a solvent component. However, since the solvent component easily affects the water resistance of the formed cured film, it has been difficult to achieve both the ejection property of the ink and the properties such as the water resistance of the formed cured film.

[0012] Therefore, an object of the present invention is to provide an active energy ray-curable aqueous inkjet ink that is excellent in ejection performance such as ejection property and storage stability, and can form a cured film excellent in properties such as scratch resistance and water resistance. Another object of the present invention is to provide an active energy ray-curable aqueous inkjet ink set that is excellent in ejection performance such as ejection property and storage stability, and can form a cured film excellent in properties such as scratch resistance and water resistance. Furthermore, an object of the present invention is to provide an inkjet recording method using the above aqueous inkjet ink and aqueous inkjet ink set, respectively.

Means for Solving the Problems

[0013] That is, according to the present invention, there is provided an active energy ray-curable aqueous inkjet ink containing a water-soluble monomer having a polymerizable group, further containing a hydrazide compound, and the water-soluble monomer being a curable substance having a ketone structure.

Effects of the Invention

[0014] According to the present invention, it is possible to provide an active energy ray-curable aqueous inkjet ink that is excellent in ejection performance such as ejection property and storage stability, and that can form a cured film excellent in properties such as abrasion resistance and water resistance. Further, according to the present invention, it is possible to provide an active energy ray-curable aqueous inkjet ink set that is excellent in ejection performance such as ejection property and storage stability, and that can form a cured film excellent in properties such as abrasion resistance and water resistance. Furthermore, according to the present invention, it is possible to provide an inkjet recording method using the above aqueous inkjet ink and aqueous inkjet ink set, respectively.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in more detail by giving preferred embodiments. Further, the aqueous ink for inkjet may be simply referred to as "ink". Furthermore, the aqueous ink set for inkjet may be simply referred to as "ink set". Physical property values are values at room temperature (25°C) unless otherwise specified.

[0017] <Aqueous Inkjet Ink, Aqueous Inkjet Ink Set> The ink of the present invention is an active energy ray-curable aqueous inkjet ink containing a water-soluble monomer having a polymerizable group. And the ink of the present invention further contains a hydrazide compound, and the water-soluble monomer is a curable substance having a ketone structure. The water-soluble monomer is a curable substance that cures by an active energy ray curing reaction. Further, since the water-soluble monomer has a ketone structure in its molecular structure, it is also a curable substance that cures by a chemical crosslinking reaction with the hydrazide compound. Therefore, by using the ink of the present invention, while maintaining the ejection performance at a high level, both the active energy ray curing reaction and the chemical crosslinking reaction can proceed, and a cured film (image) excellent in properties such as scratch resistance and water resistance can be formed.

[0018] The ink set of the present invention includes a combination of an active energy ray-curable first aqueous inkjet ink (first ink) containing a water-soluble monomer having a polymerizable group and a second aqueous inkjet ink (second ink) containing a hydrazide compound. And the water-soluble monomer is a curable substance having a ketone structure. The water-soluble monomer in the first ink is a curable substance that cures by an active energy ray curing reaction. Further, since the water-soluble monomer has a ketone structure in its molecular structure, it is also a curable substance that cures by a chemical crosslinking reaction with the hydrazide compound in the second ink. Therefore, by using the ink set of the present invention, while maintaining the ejection performance at a high level, both the active energy ray curing reaction and the chemical crosslinking reaction can proceed, and a cured film (image) excellent in properties such as scratch resistance and water resistance can be formed. Hereinafter, the ink of the present invention, and the first ink and the second ink constituting the ink set of the present invention are also simply collectively referred to as "each ink".

[0019] (Water-soluble monomer) The water-soluble monomer is a curable substance having a polymerizable group and a ketone structure. The molecular weight of the water-soluble monomer is preferably 5,000 or less, more preferably 3,000 or less, and particularly preferably 1,000 or less. By using a water-soluble monomer having a molecular weight within the above range, it is possible to achieve both discharge performance and cured film properties at a higher level. The curable substance that is the water-soluble monomer is preferably an acrylamide-based compound. Further, the acrylamide-based compound is preferably at least one selected from the group consisting of diacetone acrylamide and diacetone methacrylamide. In addition, "water-soluble" as used in this specification means the property of dissolving 1 mass% or more in water at 25°C.

[0020] The second ink constituting the ink set may contain a curable substance having a ketone structure. The content of the curable substance having a ketone structure in each ink is preferably 5 mass% or more and 80 mass% or less, more preferably 10 mass% or more and 60 mass% or less, based on the total mass of each ink. By setting the content of the curable substance having a ketone structure in each ink within the above range, the discharge characteristics of the ink and the properties of the formed cured film can be further improved.

[0021] Together with the curable substance having the above-mentioned ketone structure, a curable substance other than the curable substance having a ketone structure (other curable substances) can also be used. Examples of other curable substances include functional compounds having reactivity such as surfactants, curing accelerators, water-soluble aids, and viscosity modifiers. Specific examples of other curable substances include acryloylmorpholine, N-vinylpyrrolidone, acrylamide, hydroxyethylacrylamide, methylenebisacrylamide, monoacrylate of oligoethylene oxide, and monoacrylate of dibasic acid. Furthermore, commercially available products of other curable substances include, under the following trade names, FOM-3008 (water-soluble bifunctional acrylamide), FOM-3007 (water-soluble trifunctional acrylamide), FOM-3006 (water-soluble tetrafunctional acrylamide), and FOM-3009 (water-soluble tetrafunctional acrylamide) (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), etc.

[0022] If the content of each other curable substance in each ink is too high, the intended effect may be somewhat insufficient. Therefore, the content of each other curable substance in each ink is preferably 0.01 part by mass or more and 100 parts by mass or less, more preferably 0.1 part by mass or more and 75 parts by mass or less, and particularly preferably 1 part by mass or more and 50 parts by mass or less, based on 100 parts by mass of the curable substance having a ketone structure.

[0023] (Polymerization initiator) Each ink can contain a polymerization initiator. As the polymerization initiator, for example, a compound that generates an active species capable of initiating the curing (polymerization) of the curable substance having a ketone structure by the transfer of light can be used. Among them, since the curable substance having a ketone structure undergoes a significant curing reaction by the generation of radicals, it is preferable to use a polymerization initiator that generates radicals by the transfer of light.

[0024] The polymerization initiator is preferably a compound having a water-soluble group. Examples of the water-soluble group include a hydroxyl group, a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a carboxylate group, a sulfonate group, a phosphate group, an ether group, an amide group, and the like. When the ink contains a coloring material having an anionic group, in order to suppress hydrolysis, it is preferable to use a polymerization initiator having no ester group. Specific examples of the polymerization initiator include compounds (polymerization initiators A to C) represented by the following structural formulas (A) to (C). Polymerization initiator A is an example of an acylphosphine-based active energy ray polymerization initiator. Polymerization initiator B is an example of an α-hydroxyketone-based active energy ray polymerization initiator. Further, polymerization initiator C is an example of a thioxanthone-based active energy ray polymerization initiator.

[0025] TIFF0007710947000001.tif90170

[0026] The content of the polymerization initiator in each ink is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.01% by mass or more and 10% by mass or less, and particularly preferably 0.01% by mass or more and 5% by mass or less, based on the total mass of each ink. If the amount of the polymerization initiator is too large, unreacted polymerization initiator tends to remain in the cured film, and the strength of the cured film may be slightly reduced.

[0027] It is also possible to use a polymerization initiator and a sensitizer in combination, or to use two or more polymerization initiators in combination. By using two or more polymerization initiators in combination, further generation of radicals is expected by using light of a wavelength that cannot be effectively utilized by only one type of polymerization initiator. Note that the polymerization initiator may not be contained when an electron beam curing method using an electron beam as an active energy ray is employed.

[0028] (Hydrazide compound) The hydrazide compound is a component that functions as a crosslinking agent for curing a curable substance having a ketone structure, which is a water-soluble monomer, by a chemical crosslinking reaction. As the hydrazide compound, a polyfunctional hydrazide compound is preferable. Specific examples of the hydrazide compound include carbohydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanediohydrazide, hexadecanediohydrazide, terephthalic acid dihydrazide, isophthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4'-bisbenzene dihydrazide, 1,4-cyclohexane dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, iminodiacetic acid dihydrazide, N,N'-hexamethylenebis semicarbazide, itaconic acid dihydrazide, ethylenediaminetetraacetic acid tetrahydrazide, citric acid trihydrazide, butanetrichydrazide, 1,2,3-benzenetrihydrazide, 1,4,5,8-naphthoic acid tetrahydrazide, nitrilotriacetic acid trihydrazide, cyclohexanetricarboxylic acid trihydrazide, pyromellitic acid tetrahydrazide, and polyacrylic acid hydrazide (i.e., N-aminopolyacrylamide), 1,3-bis(hydrazinocarboethyl)-5-isopropylhydantoin, and the like. Further, a polyfunctional hydrazide derivative obtained by reacting these polyfunctional hydrazide compounds with ketones such as acetone and methyl ethyl ketone can also be used. As the hydrazide compound, adipic acid dihydrazide is preferable in terms of handleability and reactivity with the ketone structure (carbonyl group).

[0029] The content of the hydrazide compound in the ink of the present invention and in the second ink constituting the ink set of the present invention is preferably 0.5% by mass or more and 50% by mass or less, more preferably 1% by mass or more and 30% by mass or less, based on the total mass of each ink.

[0030] (Solvent) Each ink is an aqueous ink containing water as the main solvent. The water content in each ink is preferably 30% by mass or more, more preferably 50% by mass or more, based on the total mass of each ink.

[0031] Also, for the purpose of improving various performances and within a range that does not impair the original characteristics, various organic solvents may be further contained. For example, certain organic solvents can impart non-volatility to the ink. Also, various organic solvents can be contained in each ink for purposes such as adjusting viscosity, adjusting surface tension, and imparting wettability to the recording medium.

[0032] Examples of the organic solvent include glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, and propylene glycol monomethyl ether; monohydric alcohols such as methanol, ethanol, propanol, butanol, and pentanol; and the like.

[0033] The curable substance having a ketone structure may be contained in each ink in the state of an emulsion emulsified and dispersed without being completely dissolved in a solvent such as water. Also, the encapsulation technique may be applied.

[0034] (Colorant) Each ink can contain a colorant. As the colorant, pigments and dyes can be used. Examples of the pigment include magnetic fine particles such as magnetite and ferrite, inorganic pigments such as titanium black and carbon black, and organic pigments. Examples of carbon black include furnace black, lamp black, acetylene black, channel black, and the like.

[0035] Examples of organic pigments include azo pigments such as toluidine red and Hansa yellow; phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; quinacridone pigments such as quinacridone red and quinacridone magenta; perylene pigments such as perylene red and perylene scarlet; isoindolinone pigments such as isoindolinone yellow and isoindolinone orange; imidazolone pigments such as benzimidazolone yellow and benzimidazolone orange; pyranthrone pigments such as pyranthrone red and pyranthrone orange; and the like.

[0036] When the organic pigments are indicated by Color Index (C.I.) numbers, examples include C.I. Pigment Yellow 12, 13, 14, 17, 20, 24, 55, 74, 83, 86, 93, 97, 98, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185; C.I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71; C.I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 202, 209, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272; C.I. Pigment Violet 19, 23, 29, 30, 37, 40, 50; C.I. Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 22, 60, 64; C.I. Pigment Green 7, 36; C.I. Pigment Brown 23, 25, 26; and the like.

[0037] When a pigment is contained in each ink, it is preferable to use a pigment dispersion in which the pigment is uniformly dispersed in an aqueous medium. As the pigment dispersion, conventionally known pigment dispersions used in aqueous gravure inks, pigment dispersions for aqueous writing utensils, and inks for inkjet printers can be preferably used. Among them, a pigment dispersion in which the pigment is stably dispersed in an aqueous medium by an anionic group is preferable. Examples of the pigment dispersion in which the pigment is stably dispersed in an aqueous medium by an anionic group are disclosed in JP-A-8-143802, JP-A-8-209048, JP-A-10-140065, US Patent No. 5,837,045, and US Patent No. 5,851,280.

[0038] When using a pigment, a dispersant may be used in combination. As the dispersant, block polymers, random polymers, graft polymers, etc. can be used. More specific examples of the dispersant include styrene-acrylic acid copolymers, styrene-maleic acid copolymers, vinyl naphthalene-acrylic acid copolymers, vinyl naphthalene-maleic acid copolymers, benzyl methacrylate-methacrylic acid copolymers, and salts thereof. Further, as the pigment, so-called self-dispersing pigments, which can be dispersed in a medium without using a dispersant by bonding an ionic group to the particle surface of the pigment, can also be used.

[0039] Examples of the dyes include C.I. Acid Yellow 11, 17, 23, 25, 29, 42, 49, 61, 71; C.I. Direct Yellow 12, 24, 26, 44, 86, 87, 98, 100, 130, 132, 142; C.I. Acid Red 1, 6, 8, 32, 35, 37, 51, 52, 80, 85, 87, 92, 94, 115, 180, 254, 256, 289, 315, 317; C.I. Direct Red 1, 4, 13, 17, 23, 28, 31, 62, 79, 81, 83, 89, 227, 240, 242, 243; C.I. Acid Blue 9, 22, 40, 59, 93, 102, 104, 113, 117, 120, 167, 229, 234, 254; C.I. Direct Blue 6, 22, 25, 71, 78, 86, 90, 106, 199; C.I. Direct Black 7, 19, 51, 154, 174, 195; etc., when indicated by the Color Index (C.I.) number.

[0040] Each ink can also be used as a so-called transparent ink that substantially does not contain a coloring material. By using the transparent ink, a substantially colorless and transparent cured film can be formed. Examples of the uses of such a transparent ink include, for example, an undercoat for imparting various aptitudes to a recording medium; surface protection of an image recorded with a normal ink; an overcoat for the purpose of decoration or gloss imparting; etc. Further, each ink can also contain, in a dispersed state, a colorless pigment or fine particles that are not for the purpose of coloring, according to applications such as antioxidant and anti-fading. By containing these pigments and fine particles, various properties such as image quality, fastness, and workability (handling property) can be improved.

[0041] (Others) Each ink can also be used as a so-called transparent ink that substantially does not contain a coloring material. By using a transparent ink, a substantially colorless and transparent cured film can be formed. Examples of the uses of such transparent inks include an undercoat for imparting various aptitudes to a recording medium; surface protection of an image recorded with a normal ink; an overcoat for the purpose of decoration or gloss imparting; and the like. Further, the ink can also contain, in a dispersed state, a colorless pigment or fine particles that are not for the purpose of coloring, depending on the uses such as antioxidant and anti-fading. By containing these pigments and fine particles, various properties such as image quality, fastness, and workability (handling property) can be improved.

[0042] (Others) Each ink is an aqueous ink for inkjet. Among them, it is suitable as an ink used in an inkjet recording apparatus equipped with a recording head that discharges the ink by the action of thermal energy. Further, each ink is also suitable as a liquid accommodated in a cartridge (liquid cartridge) having a liquid storage portion and as a filling liquid for the liquid cartridge.

[0043] <Inkjet Recording Method> The first inkjet recording method of the present invention has a step of discharging the aforementioned aqueous inkjet ink from an inkjet recording head and applying it to a recording medium to form a first uncured image. And the first inkjet recording method further has a step of curing the first uncured image by an active energy ray curing reaction and a chemical crosslinking reaction to form an image that is a cured film.

[0044] Furthermore, the second inkjet recording method of the present invention includes a step of forming a second uncured image. In this step, the first aqueous inkjet ink and the second aqueous inkjet ink that constitute the aforementioned aqueous inkjet ink set are ejected from an inkjet recording head respectively, and applied to a recording medium so that at least a part thereof overlaps. Thereby, a second uncured image is formed. And the second inkjet recording method further has a step of curing the second uncured image by an active energy ray curing reaction and a chemical crosslinking reaction to form an image that is a cured film.

[0045] As described above, the ink of the present invention and the first ink that constitutes the ink set of the present invention each contain a water-soluble monomer that is a curable substance cured by an active energy ray curing reaction by irradiation with active energy rays and a chemical crosslinking reaction by a hydrazide compound. Therefore, by irradiating the first uncured image formed using the ink of the present invention and the second uncured image formed using the ink set of the present invention with active energy rays, a chemical crosslinking reaction can be caused together with the active energy ray curing reaction. Thereby, the first uncured image and the second uncured image can be cured respectively to form an image that is a cured film excellent in cured film properties such as scratch resistance and water resistance.

[0046] The step of forming the first uncured image and the step of forming the second uncured image can both be carried out according to the procedure of the conventional inkjet recording method. When carrying out these steps, a conventional inkjet recording apparatus can be used.

[0047] Also, the step of curing the first uncured image to form an image and the step of curing the second uncured image to form an image can both be carried out using an inkjet recording apparatus equipped with means for irradiating active energy rays. Hereinafter, the inkjet recording apparatus that can be used for the first inkjet recording method and the second inkjet recording method will be described.

[0048] <Inkjet Recording Apparatus> The inkjet recording apparatus includes a recording head that discharges ink by an inkjet method. As the inkjet method, a method of applying thermal energy to discharge ink, which can easily achieve high-density multi-orifices of the recording head and can record high-resolution and high-quality images at high speed, is preferable.

[0049] As the recording head of the method of applying thermal energy to discharge ink, for example, those adopting the basic principles disclosed in U.S. Patent No. 4,723,129 and U.S. Patent No. 4,740,796 are preferable. Such a method is applicable to both so-called on-demand type and continuous type. In the case of the on-demand type, it is preferable to apply at least one drive signal corresponding to the recording information and causing a rapid temperature rise exceeding nucleate boiling to an electrothermal converter disposed corresponding to a sheet or a liquid path in which ink is held. Thereby, thermal energy is generated in the electrothermal converter, film boiling occurs on the heat acting surface of the recording head, and as a result, it corresponds one-to-one to this drive signal and bubbles can be formed in the ink, which is effective.

[0050] The ink is discharged from the discharge port by the growth and contraction of the bubbles to form at least one droplet. When this drive signal is in a pulse shape, the bubbles grow and contract immediately and appropriately, so it is preferable because the ink can be discharged particularly responsively. The drive signal in a pulse shape is suitable as described in U.S. Patent No. 4,463,359 and U.S. Patent No. 4,345,262. In addition, it is preferable to adopt the conditions regarding the rate of temperature rise of the heat acting surface described in U.S. Patent No. 4,313,124.

[0051] The configuration of the recording head is preferably a combination configuration (linear liquid flow path or right-angled liquid flow path) of a discharge port, a liquid path, and an electrothermal converter as disclosed in each of the above-mentioned specifications. In addition, the configuration disclosed in U.S. Patent No. 4,558,333 and U.S. Patent No. 4,459,600, in which the heat acting portion is disposed in a bent region, is also suitable. Furthermore, the discharge method of the air communication type described in Japanese Patent No. 2962880, Japanese Patent No. 3246949, and Japanese Patent Application Laid-Open No. 11-188870 is also effective. In addition, a configuration (such as Japanese Patent Application Laid-Open No. 59-123670) in which a common discharge hole serves as the discharge portion of the electrothermal converter for a plurality of electrothermal converters is also effective.

[0052] As the full-line type recording head having a length corresponding to the width of the maximum recording medium that the recording apparatus can record, the following can be used. For example, either a configuration that satisfies the length by a combination of a plurality of recording heads as disclosed in the above-mentioned specifications or a configuration as an integrally formed single recording head may be used. Furthermore, an exchangeable chip type recording head that enables electrical connection to the apparatus main body and ink supply from the apparatus main body by being mounted on the recording apparatus, and a cartridge type recording head provided integrally with the recording head are also effective.

[0053] It is also preferable to add a recovery means, a preliminary auxiliary means, etc. to the recording head. Specifically, the capping means, cleaning means, pressurizing or suction means, electrothermal converter, heating element, preliminary heating means, and preliminary discharge mode of the recording head can be mentioned.

[0054] FIG. 1 is a perspective view schematically showing an example of the configuration of an inkjet recording apparatus. The inkjet recording apparatus shown in FIG. 1 uses a short serial head and adopts a shuttle method in which the head is scanned in the width direction of the recording medium for recording. The carriage 100 is connected to an endless belt 101 and is movable along a guide shaft 102. The endless belt 101 is stretched between pulleys 103 and 104. A drive shaft of a motor 105 is connected to the pulley 103. Therefore, the carriage 100 reciprocates in the main scanning direction of arrow A along the guide shaft 102 by the rotational drive of the motor 105.

[0055] On the carriage 100, a recording head (not shown) in which a plurality of ink ejection nozzles are arranged in parallel and an ink tank IT as a container for storing ink are mounted. At least one end of the carriage 100 in the main scanning direction A is provided with an active energy ray irradiation unit 20. Therefore, it is possible to irradiate the recording surface with active energy rays from the active energy ray irradiation unit 20 immediately after ink is applied onto the recording medium. Examples of the active energy rays include electron beams, ultraviolet rays, α rays, β rays, γ rays, X rays, etc. Among them, ultraviolet rays are preferable.

[0056] The recording head has a plurality of ink ejection ports arranged in the conveyance direction (sub-scanning direction of arrow B) of the paper P on the ejection port surface facing the paper P as the recording medium. The recording head is provided with ink paths communicating with each of the plurality of ejection ports. Corresponding to each ink path, an electrothermal converter for generating thermal energy for ejecting ink is provided.

[0057] The electrothermal converter generates heat when an electric pulse corresponding to drive data is applied, causes film boiling in the ink by the heat, and ejects the ink from the ejection port as bubbles are generated. A common liquid chamber communicates with each of the ink paths in common, and the common liquid chamber is connected to the ink tank IT.

[0058] The inkjet recording apparatus shown in FIG. 1 is provided with a linear encoder 106 for detecting the moving position of the carriage 100. That is, on the linear scale 107 provided along the moving direction of the carriage 100, slits are formed at equal intervals, for example, 1,200 slits per inch. On the other hand, on the carriage 100 side, for example, a slit detection system 108 having a light emitting part and a light receiving sensor and a signal processing circuit are provided. Therefore, from the linear encoder 106, a discharge timing signal indicating the ink discharge timing and information on the moving position of the carriage 100 are output in accordance with the movement of the carriage 100. By discharging ink every time a slit on the linear scale 107 is detected, an image with a resolution of 1,200 dpi in the main scanning direction can be recorded.

[0059] The paper P as a recording medium is intermittently conveyed in the sub-scanning direction of the arrow B orthogonal to the operation direction of the carriage 100. The paper P is supported by a pair of roller units 109 and 110 on the upstream side in the conveyance direction and a pair of roller units 111 and 112 on the downstream side in the conveyance direction. And a constant tension is applied and it is conveyed in a state where flatness with respect to the recording head 10 is ensured. The driving force for the roller units 111 and 112 is supplied from a paper conveyance motor (not shown).

[0060] In the inkjet recording apparatus shown in FIG. 1, by alternately repeating recording with a width corresponding to the array width of the ejection ports of the recording head while moving the carriage 100 and feeding the paper P, an image can be recorded on the entire paper P. The carriage 100 stops at the home position as necessary at the start of recording or during recording. A cap member 113 for capping the ejection surface side of each recording head is provided at this home position. A suction recovery means (not shown) for forcibly absorbing ink from the ejection port and preventing clogging of the ejection port is connected to the cap member 113.

[0061] In addition to the above shuttle method, there is a line method that uses a line head in which recording elements are arranged corresponding to the entire area of one side of a recording medium. In the line method, by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, image recording can be performed on the entire surface of the recording medium. For this reason, a conveyance system such as a carriage for scanning a short head is not required. In addition, complicated scanning control between the movement of the carriage and the recording medium is not required, and only the recording medium moves, so the recording speed can be increased compared to the shuttle method.

Example

[0062] Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Unless otherwise specified, "parts" and "%" regarding component amounts are based on mass.

[0063] <Manufacture of Ink (1)> (Ink 1) A pigment (C.I. Pigment Red 122) and a dispersant (random copolymer of styrene / acrylic acid / ethyl acrylate, weight average molecular weight = 3,500, acid value = 150 mgKOH / g) were mixed and then subjected to dispersion treatment in a bead mill. As a result, a magenta pigment dispersion having a pigment solid content of 10% and a pigment:dispersant (mass ratio) of 3:1 was obtained. Next, each of the following components was mixed and sufficiently stirred, and then pressure-filtered through a filter with a pore size of 0.5 μm to obtain Ink 1. The pH of the obtained Ink 1 was 9. Among the following components, "Acetylenol E100" is the trade name of a nonionic surfactant (ethylene oxide adduct of acetylene glycol) manufactured by Kawaken Fine Chemicals. Also, "FOM-3006" is the trade name of a curable substance (water-soluble tetrafunctional acrylamide) manufactured by Fujifilm Wako Pure Chemical Industries.

[0064] [Composition of Ink 1] ·Magenta pigment dispersion 40% ·Diacetone acrylamide 10% ·FOM-3006 5% · 2% of polymerization initiator A · 1% of adipic acid dihydrazide · 1% of acetylenol E100 · 0.5% of triethanolamine · 40.5% of ion-exchanged water

[0065] (Ink 6) Ink 6 was prepared in the same manner as Ink 1 described above, except that the same amount of ion-exchanged water was used instead of adipic acid dihydrazide.

[0066] (Ink 10) Ink 10 was prepared in the same manner as Ink 1 described above, except that the same amount of carbodiimide compound (trade name "Carbodilite SV-02", manufactured by Nisshinbo Chemicals) was used instead of adipic acid dihydrazide.

[0067] (Inks 2, 3, 7, and 11) Inks 2, 3, 7, and 11 were prepared in the same manner as Ink 1 described above, except that the formulations shown below were used. Among the components shown below, "FOM-3008" is the trade name of a curable substance (water-soluble bifunctional acrylamide) manufactured by Fujifilm Wako Pure Chemical Corporation.

[0068] [Composition of Ink 2] · 40% of magenta pigment dispersion · 25% of diacetone acrylamide · 5% of FOM-3008 · 3% of polymerization initiator A · 1% of acetylenol E100 · 26% of ion-exchanged water

[0069] [Composition of Ink 3] · 20% of FOM-3008 · 2% of polymerization photoinitiator A · 6% of adipic acid dihydrazide · 14% of carbohydrazide · 1% of acetylenol E100 · 57% of ion-exchanged water

[0070] [Composition of Ink 7] · FOM-3008 20% · Polymerization initiator A 2% · Acetylenol E100 1% · Ion-exchanged water 77% [Composition of Ink 11] · FOM-3008 20% · Polymerization photoinitiator A 2% · Magnesium nitrate 15% · Acetylenol E100 1% · Ion-exchanged water 62%

[0071] [Recording of Image (Formation of Hardened Film) (1)] An on-demand type recording apparatus (trade name "Pro-10", manufactured by Canon) that discharges ink by applying thermal energy according to a recording signal was prepared. An inkjet recording apparatus equipped with a UV-LED irradiation device (trade name "M30", manufactured by Ushio Electric, 395 nm) adjacent to the recording head of this recording apparatus was used. Specifically, as shown in FIG. 2, a UV-LED irradiation device 30 was mounted at a position adjacent to the mounting position (10) (GY cartridge mounting position) at the ink cartridge mounting position 50 of the recording head 10. The integrated irradiation energy of the active energy ray (ultraviolet ray) under the drawing condition of one-way one-pass was 2,000 mJ / cm2. In this inkjet recording apparatus, the recording duty of an image recorded under the condition of applying 8 drops of 3.8 ng of ink to a unit area of 1 / 600 inch × 1 / 600 inch with a resolution of 600 dpi × 600 dpi is defined as 100%. Using this inkjet recording apparatus, an image was recorded on a PET film (trade name "Easy Adhesive White PET", manufactured by Teijin).

[0072] [Example 1] An ink cartridge filled with Ink 1 was mounted at the mounting position (3) (Y cartridge mounting position) shown in FIG. 2. After recording a solid image with 1,200 dpi and 100% duty in one pass (drawing condition 1), UV irradiation was continuously performed to record an image (hardened film).

[0073] (Comparative Example 1) An image (cured film) was recorded in the same manner as in Example 1 described above, except that Ink 6 was used instead of Ink 1.

[0074] (Comparative Example 2) An image (cured film) was recorded in the same manner as in Example 1 described above, except that Ink 10 was used instead of Ink 1.

[0075] (Example 2) An ink cartridge filled with Ink 2 was mounted at the mounting position (3) (Y cartridge mounting position) shown in FIG. 2. Also, an ink cartridge filled with Ink 3 was mounted at the mounting position (6) (PBK cartridge mounting position) shown in FIG. 2. Ink 2 was ejected from the cartridge at the mounting position (3) at a discharge rate of 90% duty (1 pass), and continuously, Ink 3 was ejected from the cartridge at the mounting position (6) at a discharge rate of 10% duty (1 pass). Thereby, a solid image of 1,200 dpi and 100% duty was recorded (drawing condition 2). Next, UV irradiation was continuously performed to record an image (cured film). The ratio (mass ratio) of the curable substance having a ketone structure to the hydrazide compound was curable substance:hydrazide compound = 22.5:2.

[0076] (Example 3) An image (cured film) was recorded in the same manner as in Example 2 described above, except that the discharge rate from the cartridge at the mounting position (3) was changed to 80% duty and the discharge rate from the cartridge at the mounting position (6) was changed to 20% duty. The ratio (mass ratio) of the curable substance having a ketone structure to the hydrazide compound was curable substance:hydrazide compound = 5:1.

[0077] (Comparative Example 3) An image (cured film) was recorded in the same manner as in Example 2 described above, except that Ink 7 was used instead of Ink 3. (Comparative Example 4) An image (cured film) was recorded in the same manner as in Example 2 described above, except that Ink 11 was used instead of Ink 3.

[0078] (Example 4) An ink cartridge filled with Ink 3 was mounted at the mounting position (3) (Y cartridge mounting position) shown in FIG. 2. Also, an ink cartridge filled with Ink 2 was mounted at the mounting position (6) (PBK cartridge mounting position) shown in FIG. 2. Ink 3 was ejected from the cartridge at the mounting position (3) at a duty of 20% (1 pass), and continuously, Ink 2 was ejected from the cartridge at the mounting position (6) at a duty of 80% (1 pass). Thereby, a solid image of 1,200 dpi and 100% duty was recorded (drawing condition 3). Next, UV irradiation was continuously performed to record an image (cured film).

[0079] <Manufacture of Ink (2)> (Inks 8 and 9) Inks 8 and 9 were prepared according to the following procedure with reference to the method described in “Example 1” of Patent Document 3 (Japanese Patent No. 6015913).

[0080] [Synthesis of Comparative Compound 1] 30 parts of diacetone acrylamide, 70 parts of methacrylic acid, and 50 parts of ethanol were placed in a flask equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser. After purging the system with nitrogen, the temperature inside the system was raised to 80° C. 0.5 part of 2,2'-azoisobutyronitrile was added through the dropping funnel to initiate polymerization, and polymerization was carried out for 6 hours. After polymerization, ethanol vapor was blown in to obtain a 50% ethanol solution of a diacetone acrylamide-methacrylic acid copolymer. After washing with ethanol, it was dried to obtain a diacetone acrylamide-methacrylic acid copolymer (Comparative Compound 1, diacetone acrylamide:methacrylic acid = 30:70). Distilled water was added and sodium hydroxide was added to obtain a 20% aqueous solution (pH 7) of Comparative Compound 1.

[0081] [Manufacture of Pigment Dispersion] A magenta pigment dispersion with a pigment solid content of 10% and a pigment:dispersant (mass ratio) of 3:1 was obtained in the same manner as in the case of Ink 1 described above, except that Comparative Compound 1 was used as the dispersion resin. Then, Inks 8 and 9 were prepared in the same manner as Ink 1 described above, except that the obtained magenta pigment dispersion was used and the following formulations were used.

[0082] [Composition of Ink 8] · Magenta pigment dispersion 40% · Glycerin 20% · Acetylenol E-100 1% · Ion-exchanged water 39%

[0083] [Composition of Ink 9] · Magenta pigment dispersion 40% · Glycerin 5.5% · Acetylenol E-100 1% · Ion-exchanged water 53.5%

[0084] <Image recording (formation of cured film) (2)> (Comparative Example 5) An image (cured film) was recorded in the same manner as in Example 1 described above, except that Ink 8 was used instead of Ink 1 and UV irradiation was not performed.

[0085] (Comparative Example 6) An image (cured film) was recorded in the same manner as in Example 1 described above, except that Ink 9 was used instead of Ink 1 and UV irradiation was not performed.

[0086] <Manufacture of ink (3)> (Inks 4 and 5) A black pigment dispersion with a pigment solid content of 10% was obtained in the same manner as in the case of Ink 1 described above, except that carbon black was used as the pigment instead of C.I. Pigment Red 122. Then, Inks 4 and 5 were prepared in the same manner as Ink 1 described above, except that the obtained black pigment dispersion was used and the following formulations were used.

[0087] [Composition of Ink 4] ·Black pigment dispersion: 30% ·Diacetone acrylamide: 25% ·FOM-3008: 5% ·Polymerization initiator A: 5% ·Acetylenol E100: 1% ·Ion-exchanged water: 34%

[0088] [Composition of Ink 5] ·Hydroxyethyl acrylamide: 15% ·Diacetone acrylamide: 10% ·Methylenebisacrylamide: 5% ·Polymerization photoinitiator A: 3% ·Adipic acid dihydrazide: 2% ·Acetylenol E100: 1% ·Ion-exchanged water: 64%

[0089] <Recording of Image (Formation of Cured Film) (3)> (Example 5) The ink cartridge filled with Ink 4 was installed at the installation position (3) (Y cartridge installation position) shown in Figure 2. Also, the ink cartridge filled with Ink 5 was installed at the installation position (6) (PBK cartridge installation position) shown in Figure 2. After discharging Ink 4 from the cartridge at the installation position (3) with a discharge duty of 100% (1 pass) to record a solid image, UV irradiation was continuously performed. Next, after discharging Ink 5 from the cartridge at the installation position (6) with a discharge duty of 100% (1 pass), UV irradiation was continuously performed to record an image (cured film). The ratio (mass ratio) of the curable substance having a ketone structure to the hydrazide compound was curable substance: hydrazide compound = 35:2.

[0090] <Evaluation> (1) Discharge performance (Basic discharge property) An ink cartridge filled with each ink was mounted on an inkjet recording apparatus. A suction recovery operation was performed, and after leaving it for 1 minute, a solid image with a resolution of 1,200 dpi and a 100% duty was recorded in one pass. The state of the recorded solid image was visually confirmed, and the basic ejection property was evaluated according to the evaluation criteria shown below. The results are shown in Table 1. A: It was a uniform solid image. B: Less than 10% of the writing part was blurred. C: The blurring of the writing part was 10% or more and less than 20%. D: The blurring of the writing part was 20% or more.

[0091] (Storage stability) An ink cartridge filled with each ink was mounted on an inkjet recording apparatus. A suction recovery operation was performed, and after leaving it for 3 days, a solid image with a resolution of 1,200 dpi and a 100% duty was recorded in one pass. The state of the recorded solid image was visually confirmed, and the basic ejection property was evaluated according to the evaluation criteria shown below. The results are shown in Table 1. A: It was a uniform solid image. B: Less than 10% of the writing part was blurred. C: The blurring of the writing part was 10% or more and less than 20%. D: The blurring of the writing part was 20% or more.

[0092] (2) Hard film properties (Scratch resistance) One day after forming the image (hard film), a pencil hardness test conforming to JIS K 5600-5-4:1999 was carried out, and the scratch resistance of the hard film was evaluated according to the evaluation criteria shown below. The results are shown in Table 1. A: No scratches or abrasions were observed at a pencil hardness of 2H. B: No scratches or peeling were observed at a pencil hardness of H or less. C: No scratches or peeling were observed at a pencil hardness of HB or less and B or more. D: Scratches and peeling were observed even at a pencil hardness of 2B or less.

[0093] (Water resistance) One day after forming the image (hardened film), 0.2 mL of ion-exchanged water was dropped onto the hardened film, and a silver paper was placed thereon 1 minute later. After pulling the silver paper while applying a load of 40 g / cm 2 the non-recording part (blank part) and the silver paper were visually observed, and the water resistance of the hardened film was evaluated according to the evaluation criteria shown below. The results are shown in Table 1. A: The area of the region where no stain was visible was 90% or more of the area of the silver paper. B: The area of the region where no stain was visible was 70% or more of the area of the silver paper. C: The area of the region where no stain was visible was 50% or more of the area of the silver paper. D: The area of the region where no stain was visible was less than 20% of the area of the silver paper.

[0094] TIFF0007710947000002.tif147170

Claims

1. An active energy ray-curable aqueous inkjet ink containing a water-soluble monomer having a polymerizable group, further containing a hydrazide compound, wherein the water-soluble monomer is a curable substance having a ketone structure, characterized aqueous inkjet ink.

2. The aqueous inkjet ink according to claim 1, wherein the curable substance is an acrylamide-based compound.

3. The aqueous inkjet ink according to claim 2, wherein the acrylamide-based compound is at least one selected from the group consisting of diacetone acrylamide and diacetone methacrylamide.

4. A combination of a first active energy ray-curable aqueous inkjet ink containing a water-soluble monomer having a polymerizable group and a second aqueous inkjet ink containing a hydrazide compound, wherein the water-soluble monomer is a curable substance having a ketone structure, characterized aqueous inkjet ink set.

5. The aqueous inkjet ink set according to claim 4, wherein the curable substance is an acrylamide-based compound.

6. The aqueous inkjet ink set according to claim 5, wherein the acrylamide-based compound is at least one selected from the group consisting of diacetone acrylamide and diacetone methacrylamide.

7. A step of discharging the aqueous inkjet ink according to any one of claims 1 to 3 from an inkjet recording head and applying it to a recording medium to form a first uncured image; A step of curing the first uncured image by an active energy ray curing reaction and a chemical crosslinking reaction to form an image; An inkjet recording method characterized by comprising.

8. A step of discharging the first aqueous inkjet ink and the second aqueous inkjet ink constituting the aqueous inkjet ink set according to any one of claims 4 to 6 from an inkjet recording head and applying them to a recording medium so that at least a part thereof overlaps to form a second uncured image; A step of curing the second uncured image by an active energy ray curing reaction and a chemical crosslinking reaction to form an image; An inkjet recording method characterized by comprising. ​

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