JP2019188771A - Image formation method, active ray curable ink jet ink and image formation apparatus - Google Patents

Abstract

To provide an image formation method, active ray curable ink jet ink and image formation apparatus which facilitate control of the dot diameter of ink discharged to an intermediate transfer medium, and can form a smooth and high-quality image with small thickness irregularity by enhancing the transfer property of the ink to a recording medium.SOLUTION: An image formation method comprises an ink adhesion process of making ink adhere to an intermediate transfer body 11 by discharging droplets of ink jet ink from a nozzle of an ink jet recording head 14, and a transfer process of transferring the ink droplets adhering to the intermediate transfer body to a recording medium 12, the ink jet ink containing a magnetic material and the transfer process being executed in the magnetic field. Also provided are active ray curable ink jet ink and image formation apparatus.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming method, an actinic ray curable inkjet ink, and an image forming apparatus.

  The inkjet method is used in various printing fields because it can form an image easily and inexpensively. As one of the ink jet methods, there is an image forming method using an ink that is liquid at high temperature but becomes solid at room temperature, so-called “hot melt ink”. In this method, hot-melt ink is heated to 130 to 140 ° C., and liquid ink is ejected from the nozzles of the ink jet recording head to cause ink droplets to adhere to the surface of the intermediate transfer medium. The ink droplets are partially cooled by the intermediate transfer medium and then transferred to a recording medium to form an image.

  Conventional “hot melt inks” are mainly composed of crystalline wax. In order to eject such ink from the nozzles of the ink jet recording head, it was necessary to heat the ink to a high temperature to make it liquid. Further, an image made of a conventional hot melt ink has a problem of low abrasion resistance. As means for overcoming such a problem, a phase change type ink-jet ink containing a photopolymerizable compound and a gelling agent such as wax has been proposed. For example, Patent Document 1 discloses an ink containing at least one curable component, and if necessary, an initiator, a colorant, a non-curable component, and other additives. Patent Document 2 discloses an ink containing one or more radiation-curable oil-soluble components and one or more thermal solvents. Such a phase change type ink-jet ink can eject ink at a relatively low temperature. Moreover, since the ink droplets can be cured by irradiation with actinic rays after the ink droplets are transferred to the recording medium, it is considered that the scratch resistance of the printed image is increased.

JP 2007-297625 A JP 2006-176882 A

  When the present inventor examined the phase change type ink-jet ink described in Patent Documents 1 and 2 (hereinafter, “ink-jet ink” is often abbreviated as “ink”), the storage elastic modulus of the ink droplet is high, and the intermediate transfer When transferring the ink from the medium to the recording medium, there is a problem that the ink hardly adheres to the recording medium and the transferability of the ink is low. Furthermore, there is a problem that the ink droplets are hard and difficult to smooth. For this reason, uneven thickness and steps are likely to occur in the printed image, and uneven gloss is likely to occur.

  The present invention makes it easy to control the dot diameter of ink ejected to an intermediate transfer medium and enhances the transferability of ink to a recording medium, thereby forming a smooth, low-thickness, high-quality image. It is an object of the present invention to provide an image forming method, an actinic ray curable inkjet ink, and an image forming apparatus that can perform the above.

  According to the present invention, as a first means for solving the above-described problems, an ink-jet ink droplet is ejected from a nozzle of an ink-jet recording head and adhered to an intermediate transfer member, and the ink is attached to the intermediate transfer member. And a transfer step of transferring the ink droplets to a recording medium, wherein the inkjet ink contains a magnetic material, and the transfer step is performed in a magnetic field.

  Furthermore, the present invention provides an actinic ray curable inkjet ink containing a photopolymerizable compound, a gelling agent, and an organic magnetic substance as a second means for solving the above problems.

  The present invention also provides, as a third means for solving the above-described problems, an intermediate transfer member, an ink attachment portion for attaching the inkjet ink to the intermediate transfer member, and a recording medium on which the inkjet ink is transferred from the intermediate transfer member. Provided is an image forming apparatus having a recording medium transport unit for transporting and a magnetic field generator.

  According to the present invention, it is possible to easily control the dot diameter of ink ejected to an intermediate transfer medium, and to improve the transferability of ink to a recording medium, thereby forming a smooth, low-thickness, high-quality image. Image forming method, actinic ray curable inkjet ink, and image forming apparatus can be provided.

FIG. 1 is a schematic diagram showing the relationship between the intermediate transfer member, ink, and recording medium in the transfer step of the image forming method of the present invention. FIG. 2 is a schematic diagram showing an outline of an image forming apparatus according to an embodiment of the present invention.

  In the method of forming an image by directly ejecting ink onto the surface of the recording medium, the dot diameter of the ink droplets that have landed on the recording medium is uniquely determined by the physical properties of the ink and the physical properties of the recording medium. Therefore, the dot diameter can change due to the difference in the recording medium (for example, the difference in paper hygroscopicity). On the other hand, in the method in which ink droplets are landed on the intermediate transfer member and then transferred to the recording medium, the dot diameter of the ink droplets is controlled on the intermediate transfer member, so that the difference in the recording medium is achieved. Regardless, it is possible to form an image with the same dot diameter. However, in order to secure a certain dot diameter on the transfer medium, it is necessary that the affinity between the ink and the transfer medium is high, the affinity between the ink and the recording medium is relatively low, and the transferability is lowered. Tend to.

  For example, as shown in FIG. 1, when the ink 3 landed on the surface of the transfer body 4 is transferred to the recording medium 2, the relationship between the ink 3 and the recording medium 2 (closeness of structure, interaction, surface energy). ) And an affinity F1 caused by capillary action, and an affinity F2 caused by the relationship between the ink 3 and the intermediate transfer body 4 (closeness of structure, interaction, surface energy). At this time, if F1 is larger than F2, the ink transferability is good. However, if F2 is small, there is a concern that the ink droplets do not spread on the surface of the intermediate transfer member and cannot be controlled to the target dot diameter.

  Therefore, earnest research was conducted on a method for obtaining F1 necessary to achieve good transferability to a recording medium while maintaining F2 large enough to control the dot diameter. As a result, an image forming method was found in which a magnetic material was added to the ink 3 and a magnetic field 1 was applied in the direction from the intermediate transfer body 4 to the recording medium 2 during transfer. In this way, even when using an ink having a high affinity F2 with the intermediate transfer member and easy dot diameter control, a magnetic force is applied to the magnetic material in the ink, and F1 is forced by an external force (magnetic field 1). By making it larger than F2, it becomes possible to improve the transferability of the ink. Therefore, by controlling the dot diameter of the ink discharged to the intermediate transfer medium easily and improving the transferability of the ink to the recording medium, it is possible to form a high-quality image that is smooth and has little thickness unevenness. An image forming method, an actinic ray curable inkjet ink, and an image forming apparatus can be provided.

  Embodiments of the present invention will be described below.

1. Image Forming Method The image forming method of the present invention includes at least the following two steps.
(1) an ink adhesion step in which ink droplets are ejected from the nozzles of an ink jet recording head and adhered to an intermediate transfer member; and (2) the ink droplets adhered to the intermediate transfer member are applied to a recording medium. Transfer process to transfer.

(1) Ink attachment process Ink droplets are ejected from the nozzles of an ink jet recording head and attached to an intermediate transfer member. The ink used here is not particularly limited as long as ink-jet printing is possible and the ink contains a magnetic material. Therefore, the composition of the ink used in the image forming method of the present invention is not particularly limited as long as it is based on the composition of a known aqueous ink or radical polymerization type ink and contains a magnetic substance. However, since an image with high character quality and high gloss uniformity can be easily obtained, actinic ray curable ink is preferable, and actinic ray curable ink containing a gelling agent is more preferable. The actinic ray curable ink containing the gelling agent gels quickly by the sol-gel phase transition when landing on the intermediate transfer medium, and the coalescence of the ink droplets is suppressed, so that the image quality can be improved. Become. Further, since the ink droplets are gelled, it is difficult for oxygen to enter the ink droplets, and the curing of the photopolymerizable compound is difficult to be inhibited by oxygen when curing is performed by irradiation with actinic rays.

  The magnetic substance contained in the ink is not particularly limited as long as it is a substance capable of being magnetized, and includes a diamagnetic substance, a paramagnetic substance, and a ferromagnetic substance, and a ferromagnetic substance is preferable. In addition, the magnetic material includes an inorganic magnetic material and an organic magnetic material, both of which can be used. The type of magnetic substance contained in the ink may be one type or two or more types. Details of the magnetic material are as described later in connection with the actinic ray curable inkjet ink of the present invention.

  Further, when the ink is an actinic ray curable ink, in addition to the magnetic substance, a photopolymerizable monomer having a CLogP value of 1 or more and 12 or less is contained in an amount of 5 to 40% by mass with respect to the total mass of the ink. It is preferable to contain 7% by mass or more and 38% by mass or less. Details of the photopolymerizable monomer are as described later in connection with the actinic ray curable inkjet ink of the present invention.

  The ink preferably further contains a gelling agent. Details of the gelling agent are as described later in connection with the actinic ray curable inkjet ink of the present invention.

  In order to improve the discharge property of the ink droplets, it is preferable to heat the ink-jet ink in the ink-jet recording head, and it is usually preferable to set the temperature within the range of 20 ° C. or higher and 90 ° C. or lower. From the viewpoint of ejection stability, the viscosity of the ink is preferably 3 mPa · s or more and less than 20 mPa · s at the temperature in the inkjet recording head.

  In particular, when the ink contains a gelling agent, the temperature of the inkjet ink in the inkjet recording head is preferably set to a temperature that is 10 ° C. or more and less than 40 ° C. higher than the gelation temperature of the ink. By setting the gelation temperature of the ink in the ink jet recording head to 10 ° C. or higher, the ink does not gel in the ink jet recording head or on the nozzle surface, and the ink can be ejected satisfactorily. Moreover, the thermal load of an inkjet recording head can be made small by making the temperature of the ink in an inkjet recording head into less than the gelation temperature of ink +40 degreeC. Particularly, in an ink jet recording head using a piezo element, the performance is likely to deteriorate due to a thermal load. Therefore, the ink temperature is particularly preferably within the above range.

  The ink is preferably heated in an ink jet recording head of an ink jet recording apparatus, an ink flow path connected to the ink jet recording head, an ink tank connected to the ink flow path, or the like. The amount of droplets ejected from each nozzle of the inkjet recording head is preferably 1 to 10 pl, although it depends on the resolution of the image.

  The surface temperature of the intermediate transfer medium at the time of ink landing is not particularly limited as long as it is lower than the ink temperature. When the ink contains a gelling agent, the temperature is preferably 5 ° C. or more lower than the gelation temperature of the ink in consideration of the sharpness of the image. In particular, the temperature of the intermediate transfer medium is preferably 30 ° C. or higher and lower than 55 ° C., more preferably 40 to 50 ° C.

  There is no particular limitation on the temperature control method of the intermediate transfer medium. For example, a cooling device and a heating device can be provided inside the intermediate transfer medium, and the temperature can be adjusted from the inside of the intermediate transfer medium. Further, a refrigerant, a heater, or the like can be provided on the outer periphery of the intermediate transfer medium, and the temperature can be controlled from the outside.

(2) Transfer process The ink droplets formed on the intermediate transfer medium are transferred to the recording medium. In the present invention, the transfer process is performed in a magnetic field. As described above, since the ink contains a magnetic material, a magnetic field is applied in the direction of the recording medium from the intermediate transfer material at the time of transfer, thereby applying a magnetic force to the magnetic material in the ink and forcing the ink by an external force. The transferability of the ink is improved by increasing the affinity between the recording medium and the recording medium.

  The magnetic field can be generated by a magnetic field generator. The magnitude of the magnetic field is usually set to a magnetic flux of 5000 to 15000 gauss, and preferably 7000 to 13000 gauss. Within the above range, the affinity between the ink containing the magnetic material and the recording medium can be increased.

  Further, during ink transfer, it is preferable to apply a pressure (nip pressure) between the intermediate transfer medium and the recording medium. The nip pressure is preferably 0.1 MPa or more and less than 0.5 MPa, and more preferably 0.1 MPa or more and less than 0.3 MPa. If the nip pressure is less than 0.1 MPa, the ink may not be sufficiently transferred from the intermediate transfer medium to the recording medium side. On the other hand, when the nip pressure is low, the image surface transferred to the recording medium cannot be sufficiently smoothed and gloss uniformity may be lowered. On the other hand, if the nip pressure is 0.5 MPa or more, the ink droplets are crushed and the image is blurred, and the image quality sharpness may be reduced.

  The temperature of the recording medium when transferring an image from the intermediate transfer medium to the recording medium is preferably lower than the temperature of the intermediate transfer medium. Specifically, it is preferably 5 ° C. or more and less than 15 ° C., more preferably 5 ° C. or more and less than 10 ° C. lower than the temperature of the intermediate transfer medium. When the temperature of the recording medium is lower than the temperature of the intermediate transfer medium, the ink is easily transferred to the recording medium side, and the transfer residue is reduced.

  The temperature control method for the recording medium is not particularly limited, and for example, a cooling device or a heating device may be provided on the recording medium conveying member to control the temperature from the back surface (ink non-transfer surface) side of the recording medium. Further, it is possible to adjust the temperature from the ink transfer surface side of the recording medium by providing a refrigerant, a heater, an IR laser, or the like in the conveyance path of the recording medium. Furthermore, the temperature of the recording medium before being installed in the ink jet recording apparatus can be adjusted to a predetermined temperature. From the viewpoint that the temperature of the recording medium can be adjusted even during ink transfer, temperature control from the back side of the recording medium is preferable.

  There is no particular limitation on the type of recording medium. Examples of recording media include: base materials made of paper such as plain paper, fine paper, coated paper, art paper; resin-coated paper in which both sides of the base paper are coated with resin; various laminating papers; synthetic papers; various plastics Film; Metal substrate; Glass substrate and the like are included. Examples of plastic films include polyethylene terephthalate (PET) film, biaxially oriented polystyrene (OPS) film, biaxially oriented polypropylene (OPP) film, biaxially oriented nylon (ONY) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, triacetyl cellulose (TAC) film and the like are included.

  The conveyance speed of the recording medium when transferring ink from the intermediate transfer medium to the recording medium is preferably 500 to 3000 mm / s. The higher the conveyance speed, the higher the image forming speed, which is preferable. However, if the conveyance speed is too high, the image quality may deteriorate or the ink may be insufficiently cured.

(3) Curing Step The image forming method of the present invention preferably further includes the following third step when the ink is an actinic ray curable ink.
(3) A curing step of irradiating the ink droplets transferred to the recording medium with actinic rays to cure each ink droplet.

  The actinic ray curable ink transferred from the intermediate transfer medium to the recording medium can be irradiated with actinic rays to cure the ink, that is, to crosslink or polymerize the photopolymerizable compound contained in the ink droplets. By curing the ink, a printed image having high hardness and excellent abrasion resistance can be obtained.

There is no particular limitation on the actinic light applied to the ink, and for example, an electron beam or ultraviolet light is preferable.
There is no particular limitation on the electron beam irradiation method, and for example, a scanning method, a curtain beam method, and a broad beam method may be used, but the curtain beam method is preferable from the viewpoint of processing capability. Moreover, it is preferable to set the acceleration voltage at the time of electron beam irradiation to the range of 30-250 kV, More preferably, it is 30-100 kV. Moreover, when performing normal electron beam irradiation whose acceleration voltage is 100-250 kV, it is preferable that electron beam irradiation amount is 30-100 kGy, and it is more preferable that it is 30-60 kGy.

  Examples of the electron beam irradiation means include “Curetron EBC-200-20-30” manufactured by Nissin High Voltage Co., Ltd., “Min-EB” manufactured by AIT Co., Ltd., and the like.

There is no particular limitation on the light source for ultraviolet irradiation. Examples of light sources include fluorescent tubes (low pressure mercury lamps, germicidal lamps), cold cathode tubes, ultraviolet lasers, low pressure, medium pressure, high pressure mercury lamps, metal halide lamps, LEDs, etc. with operating pressures from several hundred Pa to 1 MPa. It is. From the viewpoint of curing the actinic ray curable ink satisfactorily, a light source having an illuminance of 100 mW / cm ² or more is preferable, and a high pressure mercury lamp, a metal halide lamp, and an LED are preferable. Among them, an LED with low power consumption is preferable.

  The total film thickness of the image after curing is preferably 2 to 25 μm. The “total film thickness of the image” is the maximum film thickness of the cured film formed on the recording medium. Whether the image is a single color image or an image in which a plurality of colors are superimposed, the total film thickness is preferably in the above range.

2. Actinic ray curable inkjet ink An actinic ray curable inkjet ink contains a photopolymerizable compound, a gelling agent, and a magnetic substance. The actinic ray curable inkjet ink contains a colorant, a photopolymerization initiator, and other additives as necessary.

(1) Magnetic material The magnetic material contained in the ink may be an inorganic magnetic material or an organic magnetic material, and the type of magnetic material contained in the ink may be one or two or more.

As the inorganic magnetic material, it is preferable to use a ferromagnetic material exhibiting ferromagnetism or ferrimagnetism. Specific examples of the ferromagnetic material include Fe, Ni, Co and alloys thereof, and oxides such as CrO ₂ . Specific examples of ferrimagnetic materials include spinel ferrite (MnFe ₂ O ₄ , Fe ₃ O ₄ , γ-Fe ₂ O ₃ , NiZnFe ₂ O _4, etc.), garnet (Y ₃ Fe ₆ O ₁₂ ), and the like. Spinel type ferrite is more preferable.

  The particle size of the inorganic magnetic particles is preferably 1 μm or less, and more preferably 500 nm or less. The smaller the particle size of the inorganic magnetic particles, the better from the viewpoint of preventing nozzle clogging of the inkjet head.

  The organic magnetic material used as a magnetic material in the present invention is an organic compound that exhibits magnetism and is magnetized with a specific chemical structure at a strength corresponding to an external magnetic field. Examples of such organic compounds include organic complexes, charge transfer complexes and charge transfer molecules containing iron, cobalt and / or nickel ions.

  Specific examples of the organic complex include iron phthalocyanine and its derivatives, cobalt phthalocyanine, nickel phthalocyanine, ferrocene, cobaltocene, nickelocene, metallo-porphyrin complexed with iron, cobalt or nickel, hemoglobin, ferrocene polymer, C0PNA (condensed polycyclic ring) (Polynuclear aromatic) type ferromagnetic resin, polytetraazaporphyrin iron complex, poly-bis-2 ° 6-bilicincyylmethylidenenitrohexamethylenenitromethylidene / iron sulfate (PPH-iron sulfate).

  Specific examples of the charge transfer complex include TCNQ / TTL (7,7,8,8-tetracyanoquinodimethane / tetrathiafulvalene).

  Specific examples of charge transfer molecules include quinacridone derivatives.

  The magnetic substance contained in the ink is preferably an organic magnetic substance, and more preferably an organic charge transfer complex having magnetic properties. Organic magnetic materials are easier to interact with other components in the ink (for example, photopolymerizable compounds and gelling agents) than inorganic magnetic materials. It becomes easy to transfer the components in the ink to the recording medium together with the magnetic material. In particular, when an organic charge transfer complex is present in an ink together with a photopolymerizable monomer having a CLogP value of 1 or more and 12 or less, the transfer rate of the ink can be increased by strong interaction.

  The content of the organic magnetic material with respect to the total mass of the ink is not particularly limited, but is preferably 1% by mass or more and 50% by mass or less, and more preferably 2% by mass or more and 30% by mass or less. When the content of the magnetic material is within the above range, it is possible to ensure image stability without inhibiting the color gamut of the image.

(2) Photopolymerizable compound The photopolymerizable compound is a compound that crosslinks or polymerizes when irradiated with actinic rays. The actinic rays are, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, preferably ultraviolet rays or electron rays, and particularly preferably ultraviolet rays. The photopolymerizable compound can be a radical polymerizable compound or a cationic polymerizable compound. A radical polymerizable compound is preferred.

(2-1) Cationic polymerizable compound The cationic polymerizable compound may be an epoxy compound, a vinyl ether compound, an oxetane compound, or the like. These are disclosed in JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937. And compounds exemplified in JP-A-2001-220526. Only one kind of the cationic polymerizable compound may be contained in the actinic ray curable inkjet ink, or two or more kinds thereof may be contained.

  The epoxy compound is an aromatic epoxide, an alicyclic epoxide, an aliphatic epoxide, or the like, and an aromatic epoxide or an alicyclic epoxide is preferable in order to increase curability.

  The aromatic epoxide may be a di- or polyglycidyl ether obtained by reacting a polyhydric phenol or an alkylene oxide adduct thereof with epichlorohydrin. Examples of the polyhydric phenol to be reacted or an alkylene oxide adduct thereof include bisphenol A or an alkylene oxide adduct thereof, hydrogenated bisphenol A or an alkylene oxide adduct thereof, and a novolac type epoxy resin. The alkylene oxide in the alkylene oxide adduct can be ethylene oxide, propylene oxide, and the like.

  The alicyclic epoxide can be a cycloalkane oxide-containing compound obtained by epoxidizing a cycloalkane-containing compound with an oxidizing agent such as hydrogen peroxide or peracid. The cycloalkane in the cycloalkane oxide-containing compound can be cyclohexene or cyclopentene.

  The aliphatic epoxide can be a di- or polyglycidyl ether obtained by reacting an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof with epichlorohydrin. Examples of the aliphatic polyhydric alcohol include alkylene glycol such as ethylene glycol, propylene glycol, 1,6-hexanediol, polyethylene glycol, and polypropylene glycol, glycerin, and the like. Examples of the alkylene oxide in the alkylene oxide adduct include ethylene oxide and propylene oxide.

Examples of vinyl ether compounds include 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, triethylene glycol Di- or trivinyl ether compounds such as methylolpropane trivinyl ether;
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 Monovinyl ether compounds such as vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether; The vinyl ether compound is preferably a di- or trivinyl ether compound in consideration of curability and adhesion.

  An oxetane compound is a compound having an oxetane ring, and examples thereof include oxetane compounds described in JP-A Nos. 2001-220526 and 2001-310937. When an oxetane compound having 5 or more oxetane rings is included, the viscosity of the actinic radiation curable inkjet ink is increased, and the handling tends to be difficult. In addition, the glass transition temperature of the oxetane compound increases, and the tackiness of the cured product of the actinic ray curable inkjet ink may not be sufficient. Therefore, the oxetane compound is preferably a compound having 1 to 4 oxetane rings.

  The oxetane compound is a compound represented by general formula (1) described in paragraph No. 0089 of JP-A-2005-255821, and a compound represented by general formula (2) described in paragraph No. 0092 of the same publication. , A compound represented by general formula (7) in paragraph number 0107, a compound represented by general formula (8) in paragraph number 0109, a compound represented by general formula (9) in paragraph number 0116, and the like. Specifically, there are exemplified compounds 1 to 6 described in paragraph numbers 0104 to 0119 of the same publication and compounds described in paragraph number 0121 of the publication. General formulas (1), (2), and (7) to (9) described in JP-A-2005-255821 are shown below.

(2-2) Radical polymerizable compound The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization. The compound is not limited as long as it is a compound having at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. The radical polymerizable compound may be any of a monomer, an oligomer, a polymer and the like. Examples of the radical polymerizable compound include radical polymerizable compounds described in JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, and JP-A-10-863. sell. The actinic ray curable inkjet ink may contain only one type of radical polymerizable compound or two or more types thereof.

  Examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include an unsaturated carboxylic acid and a salt thereof, an unsaturated carboxylic acid ester compound, an unsaturated carboxylic acid urethane compound, an unsaturated carboxylic acid amide compound and an anhydride thereof, Acrylonitrile, styrene, unsaturated polyester, unsaturated polyether, unsaturated polyamide, unsaturated urethane and the like are included. Examples of the unsaturated carboxylic acid include (meth) acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and the like.

  Especially, it is preferable that a radically polymerizable compound is an unsaturated carboxylic acid ester compound, and it is more preferable that it is a (meth) acrylate compound. The (meth) acrylate compound may be not only a monomer but also an oligomer, a mixture of a monomer and an oligomer, a modified product, an oligomer having a polymerizable functional group, or the like. Here, “(meth) acrylate” refers to both and / or “acrylate” and “methacrylate”, and “(meth) acryl” refers to both and / or “acryl” and “methacryl”.

Examples of (meth) acrylate compounds include isoamyl acrylate, stearyl acrylate, lauryl acrylate, octyl acrylate, decyl acrylate, isomyristyl acrylate, isostearyl acrylate, 2-ethylhexyl-diglycol acrylate, 2-hydroxybutyl acrylate, 2- Acryloyloxyethyl hexahydrophthalic acid, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxypropylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate 2-hydro Cypropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid, lactone-modifiable Monofunctional monomers such as flexible acrylate, t-butylcyclohexyl acrylate;
Triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9- Bifunctional monomers such as nonanediol diacrylate, neopentyl glycol diacrylate, dimethylol-tricyclodecane diacrylate, PO adduct diacrylate of bisphenol A, neopentyl glycol diacrylate of hydroxypivalate, polytetramethylene glycol diacrylate;
Trimethylolpropane triacrylate, pentaerythritol triacrylate, EO modified trimethylolpropane triacrylate, pentaerythritol tetraacrylate, EO modified pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, glycerin propoxytriacrylate, caprolactone modified And a trifunctional or higher functional monomer such as trimethylolpropane triacrylate, pentaerythritol ethoxytetraacrylate, caprolactam-modified dipentaerythritol hexaacrylate, and the like.

  The (meth) acrylate compound may be a modified product. Examples thereof 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 and the like are included.

  The radical polymerizable compound may be a mixture of vinyl ether monomer and / or oligomer and (meth) acrylate monomer and / or oligomer. Examples of vinyl ether monomers include 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, triethylene glycol Di- or trivinyl ether compounds such as methylolpropane trivinyl ether; 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 Contains etc.; vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  The vinyl ether oligomer is preferably a bifunctional compound having a molecular weight of 300 to 1000 and having 2 to 3 ester groups in the molecule. Examples of vinyl ether oligomers include, but are not limited to, compounds available as a VEctomer series from ALDRICH (such as VEctomer 4010, VEctomer 4020, VEctomer 4040, VEctomer 4060, VEctomer 5015, etc.).

  The radical polymerizable compound may be a mixture of a vinyl ether monomer and / or oligomer and a maleimide compound. Examples of maleimide compounds include N-methylmaleimide, N-propylmaleimide, N-hexylmaleimide, N-laurylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N, N′-methylenebismaleimide, polypropylene glycol-bis (3-maleimidopropyl) ether, tetraethylene glycol-bis (3-maleimidopropyl) ether, bis (2-maleimidoethyl) carbonate, N, N ′-(4,4′-diphenylmethane) bismaleimide, N, N ′ Examples include -2,4-tolylene bismaleimide, and ester compounds of maleimide carboxylic acid and various polyols described in JP-A-11-124403, but are not limited thereto.

  The radical polymerizable compound may be a polymerizable oligomer. Examples of polymerizable oligomers include epoxy (meth) acrylate oligomers, aliphatic urethane (meth) acrylate oligomers, aromatic urethane (meth) acrylate oligomers, polyester (meth) acrylate oligomers, and linear (meth) acrylic oligomers. included. Specifically, Yamashita Shinzo, “Cross-linking agent handbook” (Taisei, 1981); Kato Kiyosumi, “UV / EB curing handbook (raw material)” (185, Polymer publication society); Commercial editions described in the conference edition, “Application and Market of UV / EB Curing Technology”, p. 79, (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun) Products, or known radically polymerizable or crosslinkable oligomers and polymers.

  Since radically polymerizable compounds are particularly high in photosensitivity and have little cure shrinkage, polyethylene glycol di (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, ethylene oxide-modified pentaerythritol tetra (meth) acrylate Etc.

(2-3) Photopolymerizable monomer The ink preferably contains a photopolymerizable monomer having a CLogP value of 1 or more and 12 or less as a photopolymerizable compound. Since the photopolymerizable monomer having a CLogP value of 1 or more is likely to interact with the organic magnetic substance, the transfer property of the ink is easily improved by including the monomer in the ink. Moreover, compatibility with a gel is suppressed as a CLogP value is 12 or less, and it can set to an appropriate gelation temperature. In addition, it is preferable that the ClogP value of the photopolymerizable monomer is 2 or more and 11 or less because the above-described effect is more easily exhibited.

  Examples of the photopolymerizable monomer having a CLogP value of 1 or more include STA (Osaka Organic Co., Ltd., CLogP value: 9.8), SR495B (Satomer Co., CLogP value: 2.1), A-DCP (Shin Nakamura). Chemical Co., CLogP value: 4.7), A-DOG (Shin Nakamura Chemical Co., CLogP value: 3.0), APG-100 (Shin Nakamura Chemical Co., CLogP value: 2.0), SR368 ( First Industrial Co., Ltd., CLogP value: 2.6), SR355 (Sartomer Co., CLogP value: 4.9), OTA 480 (Daicel Co., CLogP value: 2.7), SR494 (Sartomer Co., CLogP value) : 2.28), SR499 (Sartomer, CLogP value: 3.57), and the like, but not limited thereto. More preferably, SR494 and SR499 are mentioned.

  The “CLogP value” is a LogP value calculated by calculation. The CLogP value can be calculated by a fragment method, an atomic approach method, or the like. More specifically, ClogP values are calculated in the literature (C. Hansch and A. Leo, “Substituent Constants for Correlation Analysis in Chemistry and Biology” (John Wiley & Sons, New York, 69). Or the following commercially available software package 1 or 2 may be used.

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

  The numerical value of the ClogP value described in this specification and the like is a “ClogP value” calculated using the software package 2.

(2-4) Content of photopolymerizable compound The content of the photopolymerizable compound is preferably 1 to 97 mass%, more preferably 30 to the total mass of the actinic radiation curable inkjet ink. 95% by mass. When there is too little quantity of a photopolymerizable compound, the discharge property of the ink from an inkjet recording device will fall. On the other hand, when the amount of the photopolymerizable compound is excessive, the amount of the gelling agent and the photopolymerization initiator is relatively small, and the sol-gel phase transition may not be sufficiently performed or the curing is insufficient. there is a possibility.

  When the photopolymerizable compound contains a photopolymerizable monomer having a CLogP value of 1 or more and 12 or less, the content of the photopolymerizable monomer with respect to the total mass of the ink may be 5% by mass or more and 40% by mass or less. Preferably, it is 7 mass% or more and 38 mass% or less. It is preferable for the content of the photopolymerizable monomer to be in the above range since the compatibility with the gel is optimized.

(3) Gelling agent The ink contains a gelling agent. The gelling agent has a function of causing the actinic ray curable inkjet ink to reversibly undergo a sol-gel phase transition depending on temperature. The actinic radiation curable ink-jet ink of the present invention is gelled (i.e., increases in viscosity) when it is landed on the intermediate transfer medium after being ejected from the ink-jet recording head. By increasing the viscosity of the droplet, mixing of dots (that is, dot coalescence) is suppressed. Further, since the viscosity of the droplet is increased, it is difficult for oxygen to enter the droplet, and the inhibition of the polymerization of the photopolymerizable compound by oxygen can be suppressed.

  The term “gel” as used in the present invention refers to an interaction such as a lamellar structure, a polymer network formed by non-covalent bonds or hydrogen bonds, a polymer network formed by a physical aggregation state, and an aggregate structure of fine particles. Or a structure in which substances lose their independent motion due to the interaction of precipitated microcrystals. Further, “gelation” means solidification, semi-solidification, or thickening with a sudden increase in viscosity or elasticity.

  The gelling agent contained in the actinic radiation curable inkjet ink may be a high molecular compound or a low molecular compound, but a low molecular compound is preferable from the viewpoint of ejection from an inkjet recording apparatus.

  Examples of gelling agents made of a polymer compound include fatty acid inulins such as inulin stearate; fatty acid dextrins such as dextrin palmitate and dextrin myristate (Reopearl series manufactured by Chiba Flour Mills); glyceryl behenate; glyceryl behenate; Acid eicosane diacid polyglyceryl (Nisshin Oilio Co., Ltd. Nomucoat series) and the like are included.

Examples of the gelling agent comprising a low molecular compound include, for example, low molecular oil gelling agents described in JP-A-2005-126507, JP-A-2005-255821, and JP-A-2010-1111790;
Amide compounds such as N-lauroyl-L-glutamic acid dibutylamide, N-2 ethylhexanoyl-L-glutamic acid dibutylamide;
Dibenzylidene sorbitols such as 1,3: 2,4-bis-O-benzylidene-D-glucitol (Gerol D manufactured by Shin Nippon Chemical Co., Ltd.);
Paraffin wax, microcrystalline wax, petrolactam, candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax, jojoba ester, beeswax, lanolin, whale wax, montan wax, hydrogenated wax, hardened castor Various waxes such as oil or hydrogenated castor oil derivative, montan wax derivative, paraffin wax derivative, microcrystalline wax derivative or polyethylene wax (derivative), α-olefin maleic anhydride copolymer wax (UNILIN series manufactured by Baker-Petrolite, Lunac BA and Kao wax T1 made by Kao Corporation;
Higher fatty acids such as behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, erucic acid;
Higher alcohols such as stearyl alcohol and behenyl alcohol;
Hydroxystearic acid, such as 12-hydroxystearic acid, 12-hydroxystearic acid derivatives;
Fatty acid amides such as lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, 12-hydroxystearic acid amide (for example, Nikka Amide series manufactured by Nippon Kasei Co., Ltd. ITOHWAX series manufactured by Kao Corporation, FATTYAMID series manufactured by Kao Corporation), N-substituted fatty acid amides such as N-stearyl stearamide, N-oleyl palmitic acid amide, N, N′-ethylenebisstearylamide, N, N′- Special fatty acid amides such as ethylenebis12-hydroxystearylamide, N, N'-xylylenebisstearylamide;
Higher amines such as dodecylamine, tetradecylamine or octadecylamine;
Stearyl stearic acid, oleyl palmitic acid, glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid ester, polyoxyethylene fatty acid ester Rikenmar series made by RIKEN and Poem series made by Riken Vitamin Co.);
Sucrose fatty acid esters such as sucrose stearic acid and sucrose palmitic acid (for example, Ryoto Sugar Ester series manufactured by Mitsubishi Chemical Foods);
Dimer acid, dimer diol (PRIDOR series manufactured by CRODA);
Etc. are included. The actinic ray curable inkjet ink may contain only one kind of gelling agent or two or more kinds.

  The content of the gelling agent is 0.5% by mass or more and less than 10% by mass with respect to the total mass of the ink, preferably 1% by mass or more and less than 10% by mass, and more preferably 2-7% by mass. By setting the content of the gelling agent to 0.5% by mass or more, the storage elastic modulus of the droplet after landing on the intermediate transfer medium is sufficiently increased. Moreover, by making the content of the gelling agent less than 10% by mass, the uncured component hardly remains after irradiation with actinic rays. Further, the flexibility of the ink droplet before curing is relatively high.

(4) Photopolymerization initiator The actinic ray curable inkjet ink may contain a photopolymerization initiator. By including a photopolymerization initiator, it is possible to form an image with higher strength and improved rub resistance.

  The photopolymerization initiator is appropriately selected depending on the type of the photopolymerizable compound and the type of actinic rays irradiated when the ink is cured.

  Photopolymerization initiators contained in radical polymerization type actinic ray curable inkjet inks include an intramolecular bond cleavage type and an intramolecular hydrogen abstraction type. Examples of intramolecular bond cleavage type photopolymerization initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2. -Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4 Acetophenones such as -thiomethylphenyl) propan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone; benzoins such as benzoin, benzoin methyl ether and benzoin isopropyl ether; 2 , 4,6-Trimethylbenzoindiphenylphosphine Acylphosphine oxide, such as Sid; as benzyl and methyl phenylglyoxylate esters include.

  Examples of intramolecular hydrogen abstraction type photopolymerization initiators include benzophenone, methyl 4-phenylbenzophenone o-benzoylbenzoate, 4,4′-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4′-methyl-diphenyl. Benzophenones such as sulfide, acrylated benzophenone, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 3,3′-dimethyl-4-methoxybenzophenone; 2-isopropylthioxanthone, 2,4 -Thioxanthone series such as dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone; Aminobenzophenone series such as Michler ketone, 4,4'-diethylaminobenzophenone; 10-butyl-2-chloroacridone, 2-ethyl Anthraquinone, 9,10-phenanthrene Non, include camphor quinone and the like.

  Examples of the photopolymerization initiator contained in the radical polymerization type actinic ray curable ink jet ink include Japanese Examined Patent Publication Nos. 59-1281, 61-9621, and 60-60104. Triazine derivatives described in JP-A-59-1504, and organic peroxides described in JP-A-61-243807; JP-B-43-23684, JP-B-44-6413, Diazonium compounds described in JP-A-44-6413, JP-B-47-1604, and US Pat. No. 3,567,453; US Pat. No. 2,848,328, US Pat. , 852, 379, and U.S. Pat. No. 2,940,853, etc .; Japanese Patent Publication No. 36-22062, Japanese Patent Publication Ortho-quinonediazides described in JP-A-37-13109, JP-B-38-18015, JP-B-45-9610, etc .; JP-B-55-39162, JP-A-59-14023, and “Macro” Various onium compounds described in “Moleculars”, Vol. 10, page 1307 (1977), etc .; azo compounds described in JP-A-59-142205; JP-A-1-54440, Europe Patent No. 109,851, European Patent No. 126,712, and “Journal of Imaging Science” (J. Imag. Sci.), Vol. 30, p. 174 (1986) Metal oxo complexes described in JP-A Nos. 2711491 and 2803454 (oxo) Ruphonium organoboron complexes; titanocenes described in JP-A-61-151197; “Coordination Chemistry Review”, Vol. 84, pages 85-277 (1988), and JP-A Transition metal complexes containing a transition metal such as ruthenium described in JP-A-2-182701; 2,4,5-triarylimidazole dimer described in JP-A-3-209477; carbon tetrabromide and JP And organic halogen compounds described in JP-A-59-107344.

  The amount of the photopolymerizable compound contained in the radical polymerization-type actinic ray curable inkjet ink depends on the type of actinic rays and the photopolymerizable compound, but is 0.01% by mass or more and 10% by mass with respect to the total mass of the ink. % Or less is preferable.

  The actinic ray curable inkjet ink of the cationic polymerization system contains an acid generation type photopolymerization initiator (photo acid generator). Examples of acid-generating photopolymerization initiators include chemically amplified photoresists and compounds used for photocationic polymerization (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993). Year), pages 187-192).

Examples of acid-generating photopolymerization initiators include aromatic onium compounds (cations) such as aromatic diazonium, aromatic ammonium, aromatic iodonium, aromatic sulfonium, aromatic phosphonium, and B ( C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , salts with anions such as CF ₃ SO ₃ ⁻ (onium salts) are included. The aromatic onium compound may be a compound described in paragraph number 0134 of JP-A No. 2005-255821.

  The acid-generating photopolymerization initiator may be a sulfonated product that generates sulfonic acid; a halide that generates hydrogen halide; an iron allene complex, or the like. Examples of the sulfonated product include compounds described in paragraph No. 0136 of JP-A No. 2005-255821. Examples of the halide include compounds described in paragraph No. 0138 of JP-A No. 2005-255821. Examples of the iron allene complex include compounds described in paragraph No. 0140 of JP-A No. 2005-255821.

  The amount of the acid-generating photopolymerization initiator contained in the actinic ray curable inkjet ink of the cationic polymerization method is 0.01 mass relative to the total mass of the ink, although it depends on the type of actinic rays and photopolymerizable compounds. It is preferable that it is% -10 mass%.

  The actinic ray curable inkjet ink may further contain a photopolymerization initiator auxiliary agent, a sensitizer, a polymerization inhibitor, and the like as necessary. The photopolymerization initiator assistant may be a tertiary amine compound, preferably an aromatic tertiary amine compound. 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, N, N-dimethylhexylamine and the like are included. Of these, N, N-dimethylamino-p-benzoic acid ethyl ester and N, N-dimethylamino-p-benzoic acid isoamyl ethyl ester are preferred. Only one kind of these compounds may be contained in the actinic ray curable inkjet ink, or two or more kinds thereof may be contained.

  The sensitizer is preferably a compound having ultraviolet spectrum absorption on the longer wavelength side than the wavelength of 300 nm. Examples of the sensitizer include a polycyclic aromatic compound having at least one hydroxyl group, an aralkyloxy group which may have a substituent, or an alkoxy group; a carbazole derivative; a thioxanthone derivative; an anthracene derivative.

  Examples of polymerization inhibitors include (alkyl) phenol, 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, cupron, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N- (3-oxyanilino- 1,3-dimethylbutylidene) aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraloxime, methyl ethyl ketoxime, cyclohexanone oxime, etc. It is included.

(5) Coloring material The actinic ray curable inkjet ink may further contain a coloring material. The colorant can be a dye or a pigment. A pigment is more preferable because it has good dispersibility with respect to the components of the ink and is excellent in weather resistance.

  The dye can be an oil-soluble dye or the like. Examples of oil-soluble dyes include the following various dyes. Examples of magenta dyes include MS Magenta VP, MS Magenta HM-1450, MS Magenta HSo-147 (manufactured by Mitsui Toatsu), AIZENSOT Red-1, AIZEN SOT Red-2, AIZEN SOTRed-3, and AIZEN SOT. Pink-1, SPIRON Red GEH SPECIAL (above, manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN Red FB 200%, MACROLEX Red Violet R, MACROLEX ROT5B (above, manufactured by Bayer Japan), KAYASET Red B, KAYASET RED130 802 (above, Nippon Kayaku Co., Ltd.), PHLOXIN, ROSE Bengal, ACID Red (above, Daiwa Kasei Co., Ltd.), H R-31, DIARESIN Red K (manufactured by Mitsubishi Kasei Corp.), include Oil Red (manufactured by BASF Japan Ltd.).

  Examples of cyan dyes include MS Cyan HM-1238, MS Cyan HSo-16, Cyan HSo-144, MS Cyan VPG (manufactured by Mitsui Toatsu), AIZEN SOT Blue-4 (manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN BR. Blue BGLN 200%, MACROLEX Blue RR, CERES Blue GN, SIRIUS SUPRATURQ. Blue Z-BGL, SIRIUS SUTRA TURQ. Blue FB-LL 330% (above, Bayer Japan), KAYASET Blue FR, KAYASET Blue N, KAYASET Blue 814, Turq. Blue GL-5 200, Light Blue BGL-5 200 (above, Nippon Kayaku Co., Ltd.), DAIWA Blue 7000, Oleosol Fast Blue GL (above, Daiwa Kasei), DIARESIN Blue P (Mitsubishi Kasei), SUDAN Blue 670, NEOPEN Blue 808, ZAPON Blue 806 (above, manufactured by BASF Japan Ltd.) and the like are included.

  Examples of yellow dyes include MS Yellow HSm-41, Yellow KX-7, Yellow EX-27 (Mitsui Toatsu), AIZEN SOT Yellow-1, AIZEN SOT Yellow W-3, AIZEN SOT Yellow-6 (above, Hodogaya) Chemical Co., Ltd.), MACROLEX Yellow 6G, MACROLEX FLUOR. Yellow 10GN (above, manufactured by Bayer Japan), KAYASET Yellow SF-G, KAYASET Yellow 2G, KAYASET Yellow AG, KAYASET Yellow EG (above, manufactured by Nippon Kayaku Co., Ltd.), Daiwa Yellow 330H HSY-68 (manufactured by Mitsubishi Kasei Co., Ltd.), SUDAN Yellow 146, NEOPEN Yellow 075 (above, manufactured by BASF Japan Ltd.) and the like.

  Examples of black dyes include MS Black VPC (Mitsui Toatsu Co., Ltd.), AIZEN SOT Black-1, AIZEN SOT Black-5 (above, manufactured by Hodogaya Chemical Co., Ltd.), RESORIN Black GSN 200%, RESOLIN BlackBS (above, Bayer Japan), KAYASET Black A-N (Nippon Kayaku), DAIWA Black MSC (Daiwa Kasei), HSB-202 (Mitsubishi Kasei), NEPTUNE Black X60, NEOPEN Black X58 (above, BASF Japan product).

  The pigment is not particularly limited, and may be, for example, an organic pigment or an inorganic pigment having the following numbers described in the color index.

  Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53. : 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, 36, etc. are included. Examples of blue or cyan pigments include Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17-1, 22, 27, 28, 29, 36. , 60 and the like. Examples of green pigments include Pigment Green 7, 26, 36, 50. Examples of yellow pigments include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137. 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193 and the like. Examples of the black pigment include Pigment Black 7, 28, 26, and the like.

Examples of commercially available pigments include chromofine yellow 2080, 5900, 5930, AF-1300, 2700L, chromofine orange 3700L, 6730, chromofine scarlet 6750, chromofine magenta 6880, 6886, 6891N, 6790, 6887, chromo Fine Violet RE, Chromo Fine Red 6820, 6830, Chromo Fine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4972, 5205, 5208, 5214, 5221, 5000P, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400 (B), 2500, 2600, ZAY-260, 2700 (B), 2770, Seica Fast Red 8040, C405 (F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seikalite Rose R40, Seikalite Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C718, A6 2, Cyanine Blue 4933M, 4933GN-EP, 4940,4973 (manufactured by Dainichiseika Color & Chemicals Mfg.);
KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (Dainippon Ink Chemical Co., Ltd.);
Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigment Yellow 1705, Colortex Orange 202, Color103 Red, 101 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex Brownex600 Red 122, Colortex Blue 516, 517, 518, 519, A8 8, P-908,510, Colortex Green402,403, Colortex Black 702, U905 (manufactured by Sanyo Color Works);
Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink),
Toner Magenta E02, Permanent RubinF6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapeam Blue B2G (manufactured by Hoechst Industry);
Novoperm P-HG, Hostaperm Pink E, Hostaperm Blue B2G (manufactured by Clariant);
Carbon black # 2600, # 2400, # 2350, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 850, MCF88, # 750, # 650, MA600, MA7, MA8, MA11 , MA100, MA100R, MA77, # 52, # 50, # 47, # 45, # 45L, # 40, # 33, # 32, # 30, # 25, # 20, # 10, # 5, # 44, CF9 (Mitsubishi Chemical).

  The average particle size of the pigment is preferably 0.08 to 0.5 μm, and the maximum particle size of the pigment is preferably 0.3 to 10 μm, more preferably 0.3 to 3 μm. By adjusting the particle size of the pigment, clogging of the nozzles of the ink jet recording head can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  The content of the pigment or dye is preferably 0.1 to 20% by mass, and more preferably 0.4 to 10% by mass with respect to the total mass of the ink. This is because when the content of the pigment or dye is too small, the resulting image is not sufficiently colored, and when it is too large, the viscosity of the ink is increased and the dischargeability is lowered.

  The pigment can be dispersed by, 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, and a paint shaker. The pigment is dispersed so that the average particle size of the pigment particles is preferably 0.08 to 0.5 μm, and the maximum particle size is preferably 0.3 to 10 μm, more preferably 0.3 to 3 μm. Is preferred. The dispersion of the pigment is adjusted by the selection of the pigment, the dispersant, and the dispersion medium, the dispersion conditions, the filtration conditions, and the like.

  In order to improve the dispersibility of the pigment, the actinic ray curable inkjet ink may further contain a dispersant. Examples of the dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, a high molecular weight unsaturated acid ester , Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene Nonylphenyl ether, stearylamine acetate, pigment derivatives and the like are included.

  Examples of commercially available dispersants include “Anti-Terra-U (polyaminoamide phosphate)”, “Anti-Terra-203 / 204 (high molecular weight polycarboxylate)” manufactured by BYK Chemie, “Disperbyk-101”. (Polyaminoamide phosphate and acid ester), 107 (hydroxyl group-containing carboxylic acid ester), 110 (copolymer containing an acid group), 130 (polyamide), 161, 162, 163, 164, 165, 166, 170 (high Molecular copolymer) ”,“ 400 ”,“ Bykumen ”(high molecular weight unsaturated acid ester),“ BYK-P104, P105 (high molecular weight unsaturated acid polycarboxylic acid) ”,“ P104S, 240S (high molecular weight unsaturated) Acid polycarboxylic acid and silicon) "," Lactimon (long-chain amine and unsaturated acid polycarboxylic acid) Include silicon), "it said.

  Examples of commercially available dispersants include “Efka CHEMICALS” “Efka 44, 46, 47, 48, 49, 54, 63, 64, 65, 66, 71, 701, 764, 766”, “Efka Polymer 100 (modified) Polyacrylate), 150 (aliphatic modified polymer), 400, 401, 402, 403, 450, 451, 452, 453 (modified polyacrylate), 745 (copper phthalocyanine)); "710 (urethane oligomer)", "Furonon SH-290, SP-1000", "Polyflow No. 50E, No. 300 (acrylic copolymer)"; "Disparon KS-860, 873SN, 874" manufactured by Enomoto Kasei Co., Ltd. Polymer dispersant), # 2150 (aliphatic polyvalent carboxylic acid), # 7004 (polyether S) Le type) "and the like are also included.

  Furthermore, examples of commercially available dispersants include “Demol RN, N (Naphthalenesulfonic acid formalin condensate sodium salt), MS, C, SN-B (aromatic sulfonic acid formalin condensate sodium salt), manufactured by Kao Corporation, "EP", "Homogenol L-18 (polycarboxylic acid type polymer)", "Emulgen 920, 930, 931, 935, 950, 985 (polyoxyethylene nonylphenyl ether)", "Acetamine 24 (coconut amine acetate), 86 (stearylamine acetate) ”;“ Solspers 5000 (phthalocyanine ammonium salt type), 13240, 13940 (polyesteramine type), 17000 (fatty acid amine type), 24000, 32000 ”manufactured by Zeneca;“ Nikkor T106 (Nikko Chemical Co., Ltd.) ” Polyoxyethylene sorbi Nmonooreto), MYS-IEX (polyoxyethylene monostearate), also includes Hexagline4-0 (hexaglyceryl ruthenate Huwei rate) "and the like.

  The actinic ray curable inkjet ink may contain a dispersion aid. Examples of the dispersion aid include Avecia's Solsperse series and Ajinomoto Fine Techno's PB series.

  The total amount of the dispersant and the dispersion aid is preferably 1 to 50% by mass with respect to the pigment.

  The actinic radiation curable inkjet ink may further include a dispersion medium for dispersing the pigment as necessary. The dispersion medium may be a solvent, but in order to suppress the residual solvent in the formed image, the above-described photopolymerizable compound (particularly a monomer having a low viscosity) is preferably the dispersion medium.

(6) Other components The actinic ray curable inkjet ink may further contain other components as necessary. Other components may be various additives, other resins, and the like. Examples of the additive include a surfactant, a leveling additive, a matting agent, an ultraviolet absorber, an infrared absorber, an antibacterial agent, and a basic compound for enhancing the storage stability of the ink. Examples of basic compounds include basic alkali metal compounds, basic alkaline earth metal compounds, basic organic compounds such as amines, and the like. Examples of other resins include resins for adjusting the physical properties of the cured film, such as polyester resins, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes. It is.

(7) Physical properties of actinic ray curable inkjet ink Since the actinic ray curable inkjet ink of the present invention contains a gelling agent as described above, it undergoes a sol-gel phase transition reversibly depending on the temperature. Actinic ray curable ink that undergoes a sol-gel phase transition is a liquid (sol) at a high temperature (for example, about 80 ° C.), and is thus ejected from an inkjet recording head in a sol state. On the other hand, ink droplets (dots) land on the intermediate transfer medium, and are then naturally cooled to gel. Therefore, the ink droplets do not coalesce, and an image with high sharpness is formed on the intermediate transfer medium. Further, since the ink is gelled, the ink droplets do not coalesce until the ink is transferred from the intermediate transfer medium to the recording medium without being cured. Accordingly, a sharp image is transferred to the recording medium.

  In the present invention, “high gloss uniformity” does not indicate that the absolute gloss value, for example, the 60 ° specular gloss value is high. “High gloss homogeneity” means that the gloss is not uniform in some parts of the image, such as unnatural glitter caused by microscopic gloss differences on the image, unnecessary reduction in gloss, and streaky gloss unevenness. This means that the gloss of the entire image, particularly the solid print portion, is uniform.

In the present invention, the viscosity of the ink at the temperature of the intermediate transfer medium upon landing of the ink is 1 × 10 ³ mPa · s or more and less than 5 × 10 ⁴ mPa · s, preferably 3 × 10 ³ mPa · s. As described above, it is less than 1 × 10 ⁴ mPa · s. When the viscosity of the intermediate transfer medium at the time of ink landing is 1 × 10 ³ mPa · s or more, the droplets that have landed on the intermediate transfer medium are difficult to spread and the droplets are difficult to coalesce. On the other hand, when it is less than 5 × 10 ⁴ mPa · s, the ejection property from the ink jet recording head is improved.

  In addition, in order to improve the discharge property of the ink droplets, it is preferable that the viscosity of the ink at a high temperature is not more than a certain value. Specifically, the actinic ray curable inkjet ink preferably has a viscosity at 80 ° C. of 3 to 20 mPa · s. The viscosity of the actinic ray curable inkjet ink can be adjusted by the type of gelling agent, the content of the gelling agent, the type of the photopolymerizable compound, and the like.

The viscosity can be measured by a stress control type rheometer using a cone plate, Physica MCR series, manufactured by Anton Paar). The viscosity is measured at a shear rate of 11.7 s ⁻¹ while changing the temperature from 90 ° C. at a temperature drop rate of 0.1 ° C. in the rotation mode. The storage elastic modulus is measured at a strain of 5% and an angular frequency of 10 radian / s while changing the temperature from 90 ° C. at a temperature drop rate of 0.1 ° C. / in the oscillation mode.

  The gelling temperature of the actinic ray curable inkjet ink is preferably 40 ° C. or higher and lower than 90 ° C., and more preferably 45 ° C. or higher and 70 ° C. or lower. Considering the summer temperature, if the phase transition temperature of the ink is 40 ° C. or higher, the ink can be stably ejected without being influenced by the environmental temperature. If the phase transition temperature of the ink is less than 90 ° C., the ink can be stably ejected without heating the ink to an excessively high temperature. Therefore, it is possible to reduce the thermal load on the ink jet recording head of the ink jet recording apparatus and the members of the ink supply system. The gelation temperature of the ink can be appropriately adjusted depending on the type of gelling agent used, the amount of gelling agent added, and the type of photopolymerizable compound.

  The gelation temperature of ink refers to a temperature at which the viscosity of the ink suddenly changes from a fluid solution state to a gel state. It is synonymous with terms called gel transition temperature, gel dissolution temperature, phase transition temperature, sol-gel phase transition temperature, and gel point. Further, “solation” means that the interaction formed by the gelation is eliminated and the liquid state changes to a fluid state. The solubilization temperature is a temperature at which fluidity develops due to the sol formation when the gelled ink is heated.

  The gelation temperature of the ink can be measured with a rheometer similar to the viscosity and storage modulus measurement (for example, a stress-controlled rheometer using a cone plate, Physica MCR series, manufactured by Anton Paar). While gradually lowering the temperature of the ink, the viscosity is measured at a low shear rate to create a temperature change curve of the viscosity. Then, from the temperature change curve of the viscosity, a temperature at which the viscosity rapidly increases is obtained and used as the gelation temperature.

  In addition, a method in which a small iron piece sealed in a glass tube is placed in an dilatometer together with ink to lower the ink temperature, and a point at which the small iron piece does not naturally drop in the ink liquid is used as a gelation temperature (J. Polym. Sci., 21, 57 (1956)). In addition, a method of setting the temperature at which an aluminum cylinder naturally falls when an aluminum cylinder is placed on the ink and heating the ink to the gelation temperature (Journal of Japanese Society of Rheology, Vol. 17, 86 (1989)) is also obtained. It is done. As an example of a simpler method, there is a method in which a gel ink test piece is placed on a heat plate, the heat plate is heated, and the temperature at which the shape of the test piece collapses is set as the gelation temperature.

(8) Method for Preparing Inkjet Ink The actinic ray curable inkjet ink is obtained by mixing the above-mentioned photopolymerizable compound, magnetic material, gelling agent, colorant and the like under heating. Preferably, a pigment dispersant in which a color material (particularly a pigment) is dispersed in a part of the photopolymerizable compound is prepared and mixed with the pigment dispersant and other ink components. The obtained ink is preferably filtered through a predetermined filter.

3. Inkjet recording apparatus The image forming method of the present invention can be performed using an inkjet recording apparatus. The apparatus includes an intermediate transfer member, an ink attachment unit that attaches inkjet ink to the intermediate transfer member, a recording medium conveyance unit that conveys a recording medium onto which the inkjet ink is transferred from the intermediate transfer member, and a magnetic field generator. An image forming apparatus.

  In particular, when the ink is an actinic ray curable ink, the image forming apparatus preferably further includes a light irradiation unit for performing the curing step.

  FIG. 2 is a diagram illustrating an example of the configuration of the ink jet recording apparatus. As shown in FIG. 2, the inkjet recording apparatus 10 stores a head carriage 16 that houses a plurality of inkjet recording heads 14, an ink flow path 30 connected to the head carriage 16, and ink supplied through the ink flow path 30. An ink tank 31, an intermediate transfer medium 11 that receives ink discharged from the inkjet recording head 14 and transfers the ink to the recording medium 12, a pressure roller 20 that pressurizes the intermediate transfer medium 11, and a magnetic field generator 21. The recording medium 12 includes a conveying member 15 and a temperature control unit 19 disposed on the lower surface of the recording medium 12. Furthermore, a light irradiation unit 18 and / or a cleaning member 13 may be disposed on the downstream side of the intermediate transfer medium 11 (in the conveyance direction of the recording medium).

  The head carriage 16 is fixedly arranged so as to cover the entire width of the intermediate transfer medium 11 and accommodates a plurality of ink jet recording heads 14. Ink is supplied to the ink jet recording head 14. For example, the ink may be supplied directly or by an ink supply unit (not shown) from an ink cartridge (not shown) that is detachably attached to the inkjet recording apparatus 10.

  A plurality of inkjet recording heads 14 are arranged in the conveyance direction of the recording medium 12 for each color. The number of inkjet recording heads 14 arranged in the conveyance direction of the recording medium 12 is set according to the nozzle density of the inkjet recording head 14 and the resolution of the print image. For example, when an image having a resolution of 1440 dpi is formed using the inkjet recording head 14 having a droplet amount of 2 pl and a nozzle density of 360 dpi, the four inkjet recording heads 14 may be arranged so as to be shifted with respect to the conveyance direction of the recording medium 12. That's fine. Further, when an image having a resolution of 720 × 720 dpi is formed using the ink jet recording head 14 having a droplet amount of 6 pl and a nozzle density of 360 dpi, the two ink jet recording heads 14 may be arranged in a shifted manner. dpi represents the number of ink droplets (dots) per 2.54 cm.

  The ink tank 31 is connected to the head carriage 16 via the ink flow path 30. The ink flow path 30 is a path for supplying the ink in the ink tank 31 to the head carriage 16. In order to stably discharge ink droplets, the ink in the ink tank 31, the ink flow path 30, the head carriage 16, and the ink jet recording head 14 is heated to a predetermined temperature to maintain a sol state.

  The intermediate transfer medium 11 is disposed between the head carriage 16 and the recording medium 12. The intermediate transfer medium 11 has an ink landing surface on which ink ejected from the inkjet recording head 14 lands. The shape of the intermediate transfer medium is not particularly limited as long as the ink landing surface is smooth. Examples thereof include an endless belt shape and a drum shape.

The intermediate transfer medium usually has a substrate and a release layer formed on the surface thereof.
The material of the base material of the intermediate transfer medium is appropriately selected in consideration of the shape and strength of the intermediate transfer medium. Examples of base materials include metals such as iron, stainless steel, and aluminum; polyimide (PI), polyphenylene sulfide (PPS), polyethersulfone (PES), polyamide (PA), polyethylene terephthalate (PET), polyimide amide Resins such as (PIA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP); ethylene propylene rubber (EPDM) In addition, elastomers such as silicone rubber and fluororubber are included.

  The release layer formed on the surface of the substrate is preferably a layer having release properties with respect to ink. The release layer can be a silicone resin layer or a fluororesin layer.

  The silicone resin layer is preferably a layer obtained by curing a solvent addition type silicone or a condensation curable type silicone, and particularly preferably a layer obtained by curing a solvent addition type silicone.

  Examples of the solvent addition type silicone include KS-887, KS-779H, KS-778, KS-835, X-62-2456, X-62-2494, X-62-2461, KS- manufactured by Shin-Etsu Silicone. 3650, KS-3655, KS-3600, KS-847, KS-770, KS-770L, KS-776A, KS-856, KS-775, KS-830, KS-830E, KS-839, X-62- 2404, X-62-2405, KS-3702, X-62-2232, KS-3503, KS-3502, KS-3703, KS-5508, and the like.

  Examples of the condensation curable silicone include silicones such as KS-881, KS-882, KS-883, X-62-9490, and X-62-9028 manufactured by Shin-Etsu Silicone.

  The thickness of the silicone resin layer (release layer) is preferably 1 to 50 μm, and more preferably 10 to 30 μm.

  Examples of the fluororesin contained in the fluororesin layer (release layer) include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer Combined (FEP) is included. In the fluororesin layer, only one type of fluororesin may be included, or two or more types may be included.

  The thickness of the fluororesin layer (release layer) is preferably 5 to 30 μm, and more preferably 10 to 20 μm.

  The surface contact angle of the release layer with respect to pure water is preferably 100 to 120 °, and more preferably 105 to 115 °. The surface contact angle is a contact angle between the measurement surface and pure water 0.5 seconds after about 15 μl of pure water is gently dropped on the measurement surface. Automatic contact angle meter DAC-VZ (manufactured by Kyowa Interface Science Co., Ltd.) ).

  The ink landing surface of the intermediate transfer medium 11 is transported in a certain direction (the direction indicated by the arrow in FIG. 1) after ink landing and is pressure-bonded to the recording medium 12. At this time, a predetermined pressure (nip pressure) is applied between the recording medium 12 and the ink landing surface by the pressure roller 20. The nip pressure is adjusted by adjusting the distance between the recording medium 12 and the intermediate transfer medium 11 or the like. An intermediate transfer medium temperature control unit (not shown) for adjusting the temperature of the intermediate transfer medium 11 at the time of ink landing is provided inside or outside the intermediate transfer medium 11. The intermediate transfer medium temperature control unit may be various heaters, for example.

  The magnetic field generator 21 is disposed so as to generate a magnetic field from the recording medium 12 side toward the intermediate transfer medium 11 when the recording medium 12 and the intermediate transfer medium 11 are pressure-bonded. Specifically, it can be provided on the lower surface side of the conveying member 15 that conveys the recording medium 12 and in the vicinity of the intermediate transfer medium 11. The magnetic field generator 21 is not particularly limited, but an apparatus capable of generating a magnetic field of about 5,000 to 15,000 gauss is preferable. For example, a neodymium magnet layer is provided as a magnetism generating means on a drum made of a metal ring, and a thin film layer of polyethylene terephthalate (PET) is provided thereon as a protective layer. An apparatus composed of magnetic domains repeated as 8 μm is conceivable. An apparatus using a neodymium bonded magnet instead of the neodymium magnet can also be used.

  In such a device, the leakage flux directly above the neodymium magnet layer can be about 5000-15000 gauss. Further, when a neodymium bonded magnet is used, the magnetic flux can be about 2000 to 8000 gauss.

  The conveying member 15 is arranged to convey the recording medium 12 to the intermediate transfer medium 11 and the light irradiation unit 18 side at a constant speed. A temperature control unit 19 is disposed on the lower surface of the conveying member 15. The temperature control unit 19 maintains the temperature of the recording medium 12 at a predetermined temperature. The temperature control unit 19 can be, for example, various heaters.

  The light irradiation unit 18 covers the entire width of the recording medium 12 and is disposed on the downstream side of the intermediate transfer medium 11 in the conveyance direction of the recording medium 12. The light irradiation unit 18 irradiates the ink droplet transferred to the recording medium 12 with light, and cures the droplet.

  The cleaning member 13 is disposed downstream of the intermediate transfer medium 11 (in the recording medium conveyance direction) and wipes and removes transfer residue (active light curable inkjet ink, etc.) adhering to the surface of the intermediate transfer medium 11 with a blade or the like. To do. The cleaning member 13 is usually provided with a collection unit (not shown) for collecting the transfer residue. The member for wiping and removing the transfer residue is not limited to the blade, and may be, for example, a brush roll, an air knife, an adhesive roll, or the like.

  Hereinafter, an image forming method using the inkjet recording apparatus 10 will be described. The recording medium 12 is conveyed between the conveying member 15 of the inkjet recording apparatus 10 and the intermediate transfer medium 11. At this time, the temperature of the recording medium 12 is adjusted by the temperature control unit 19. On the other hand, high-temperature ink droplets are ejected from the inkjet recording head 14 of the head carriage 16 and adhered (landed) on the intermediate transfer medium 11. After the ink droplet discharge is completed, the ink landing surface of the intermediate transfer medium 11 is rotated in a certain direction (the direction indicated by the arrow in FIG. 2).

  Then, the recording medium 12 and the intermediate transfer medium 11 are pressure-bonded in a magnetic field generated by the magnetic field generator 21, and the ink droplets on the intermediate transfer medium 11 are transferred to the recording medium 12. The recording medium 12 and the intermediate transfer medium 11 may be pressure-bonded in the magnetic field after the magnetic field is generated, or the magnetic field may be generated after the recording medium 12 and the intermediate transfer medium 11 are pressure-bonded. Thereafter, the recording medium 12 to which the ink droplets are transferred is moved.

  The recording medium 12 is moved to the light irradiation unit 18 side, and the ink droplets attached on the recording medium 12 are irradiated with light to be cured. The transfer residue adhering to the intermediate transfer medium 11 is wiped away by the cleaning member 13.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely using an Example and a comparative example, this invention is not limited to a following example.

The following components were used for the preparation of the actinic ray curable inkjet ink.
(Magnetic material)
Ferrocene polymer [prepared by the method described in Mitsubishi Electric Industrial Times, 77.49 (1989, 4)]
Iron phthalocyanine [manufactured by Aldrich Chemical Co.]
Maghematite (particle size: 150nm)

(Gelling agent)
LUNAC BA (Kao Corporation): behenic acid Kao wax T1 (Kao Corporation): distearyl ketone stearamide

(Photopolymerizable monomer)
NK ester A-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.): polyethylene glycol diacrylate (Clog P value: 0.47)
SR494 (manufactured by Sartomer): 4EO-modified pentaerythritol tetraacrylate (Clog P value: 2.28)
SR499 (manufactured by Sartomer): 6EO-modified trimethylolpropane triacrylate (Clog P value: 3.57)

(Photopolymerizable oligomer)
Urethane acrylate oligomer

(Photopolymerization initiator)
TPO: DAROCUR TPO (BASF)
ITX (manufactured by DKSH Japan)
EDB: DAROCUR EDB (BASF)

(Photopolymerization inhibitor)
Irgastab UV10 (manufactured by Ciba Japan)

(Surfactant)
KF-352 (manufactured by Shin-Etsu Chemical Co., Ltd.)

(Preparation of pigment dispersion)
The following pigment dispersant, photopolymerizable compound, and polymerization inhibitor were placed in a stainless beaker and stirred for 1 hour while heating on a 65 ° C. hot plate.
Pigment dispersant: Azisper PB824 (manufactured by Ajinomoto Fine Techno Co., Ltd.) 9 parts Photopolymerizable compound: APG-200 (Tripropylene glycol diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., CLogP value: 2.21) 70 parts Polymerization inhibitor: Irgastab UV10 (Ciba Japan Co., Ltd.) 0.02 part

  After cooling the mixed solution to room temperature, 21 parts by mass of Pigment Red 122 (manufactured by Dainichi Seika, Chromofine Red 6112JC) was added thereto. The mixed solution was put in a glass bottle together with 200 g of zirconia beads having a diameter of 0.5 mm and sealed, and dispersed with a paint shaker for 8 hours. Thereafter, the zirconia beads were removed to obtain a pigment dispersion.

[Inks 1 to 13 and 15 to 17: Preparation of radical polymerization type inkjet ink]
Each compound was mixed with the composition ratio described in Table 1 below, and the mixture was heated to 100 ° C. and stirred. Thereafter, the obtained liquid was filtered through a # 3000 metal mesh filter under heating. This was cooled to prepare a radical curable inkjet ink. The obtained inks were used as inks 1 to 13 and 15 to 17 in the following examples and comparative examples.

[Ink 14: Adjustment of water-based ink]
13.5 g of polyvinyl butyral BL-S (manufactured by Sekisui Chemical Co., Ltd.), 13.5 g of dye (Neozapon Blue 807), 17.7 g of iron phthalocyanine and 107.3 g of ethyl acetate were placed in a separable flask and stirred. The polymer and dye were completely dissolved. To this was added dropwise an aqueous solution in which 16 g of sodium lauryl sulfate and 10 g of Joncryl-61J were dissolved in 200 g of ion-exchanged water, followed by emulsification for 10 minutes using an ultrasonic disperser (UH-150 type: manufactured by SMT). . Thereafter, ethyl acetate was removed under reduced pressure to obtain a colored fine particle dispersion impregnated with the dye. Next, 100 g of this dispersion, 40 g of diluting liquid for ink formation (ethylene glycol / glycerin / Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.) = 15/15 / 0.1% ion exchange water) are mixed and stirred did. The obtained mixture was filtered through a 1 μm filter to obtain an ink containing cyan dye-colored resin fine particles. The content of the magnetic substance in the obtained ink was 4.9 g.
The obtained ink was used as the ink 14 in the following examples.

  The types and amounts of the magnetic substances contained in each of the obtained inks 1 to 17 are shown in Table 2 below.

[Example 1]
Using the ink 1 produced above, an image was formed according to the following method.
Ink 1 was loaded on a magenta head carriage of a line head type ink jet recording apparatus equipped with a piezo ink jet recording head to form a monochromatic image. The ink supply system is composed of an ink tank, a supply pipe, a front chamber ink tank immediately before the print head, a pipe with a filter, and a piezo head, and is insulated from the front chamber ink tank of the ink supply system to the print head portion. Warmed to ° C. Also, a heater was incorporated in the piezo head, and the ink in the recording head was also heated.

  In addition, the recording head has a nozzle diameter of 24 μm and a resolution of 512 dpi arranged in a staggered manner to achieve a recording resolution of 1200 dpi × 1200 dpi. The amount of magenta ink droplets ejected from the head was 3.5 pl per droplet, and the droplet ejection speed was 6 m / sec. The intermediate transfer medium was a belt having a polyimide film coated with a silicone resin.

First, ink droplets were ejected from the recording head onto an intermediate transfer medium to form a predetermined image. Thereafter, the ink droplets were transferred from the intermediate transfer medium to the recording medium. At this time, a magnetic field generator was provided on the recording medium side, and a magnetic field was generated with a magnetic flux of 12,000 gauss. The recording media are coated paper A for printing (OK top coat (US basis weight 84.9 g / m ² ) manufactured by Oji Paper Co., Ltd.), and coated paper B (New Age (US basis weight manufactured by Oji Paper Co., Ltd.)). 104.7 g / m ² )) and art paper (SA Kinfuji (US basis weight 104.7 g / m ² ) manufactured by Oji Paper Co., Ltd.) were used.

After transferring the ink droplets to the recording medium, an LED lamp (385 nm, manufactured by Hamamatsu Photonics, a distance of 2 mm between the recording medium and the lamp, a maximum output of 3800 mW / cm ² (UV integrated photometer manufactured by Hamamatsu Photonics) : Measured by C9536-02)), and the ink droplets were cured by irradiation with ultraviolet rays. The conveyance speed of the recording medium was 500 mm / s. The image formation was performed in an environment of 23 ° C. and 55% RH.

[Examples 2 to 13, 17, 18 and Comparative Example 1]
Images were formed in the same manner as in Example 1 except that the inks 2 to 13 and 15 to 17 prepared above were used instead of the ink 1, respectively.

[Example 14]
An image was formed in the same manner as in Example 1 except that the ink 10 produced above was used and the magnetic field generated when transferring ink droplets from the intermediate transfer medium to the recording medium was changed to a magnetic flux of 5000 gauss.

[Example 15]
An image was formed in the same manner as in Example 1 except that the ink 10 produced above was used and the magnetic field generated when transferring ink droplets from the intermediate transfer medium to the recording medium was changed to a magnetic flux of 15000 gauss.

[Example 16]
An image was formed in the same manner as in Example 1 except that the ink 14 prepared above was used and no actinic ray irradiation was performed.

[Comparative Example 2]
An image was formed in the same manner as in Example 1 except that the ink 6 prepared above was used in place of the ink 1 and no magnetic field was generated when the ink droplets were transferred from the intermediate transfer medium to the recording medium.

  The images produced in Examples 1 to 18 and Comparative Examples 1 and 2 were evaluated for character quality, gloss uniformity, and relief according to the following criteria.

(Evaluation of character quality)
Coated paper A, coated paper B, and art paper were used as recording media, and the characters “excellent” of 3 points and 5 points of MS Mincho were printed. The obtained characters were visually observed and evaluated based on the following criteria.
○: Even if it is a 3-point character, the details can be reproduced without being crushed. △: The details are crushed if the 3-point characters are crushed.

(Evaluation of gloss uniformity)
Coated paper A, coated paper B, and art paper are used as recording media, and the dot rate (that is, the pixel density of output data) is 0%, 10%, 20%, 30%, 50% in an area of 2 cm × 2 cm, Density gradation patches with different values of 70% and 100% were prepared. The glossiness of the produced image was measured 20 times for one dot rate using a gloss meter “IG-330” manufactured by Horiba, Ltd. Based on the variation in glossiness, gloss uniformity was evaluated according to the following criteria.
○: Gloss variation is Δ7 or less for all dot ratios Δ: Gloss variation is Δ7 or more and less than 15 ×: Gloss variation is Δ15 or more

(Evaluation of relief feeling)
Using coated paper A, coated paper B, and art paper as recording media, images of natural images (high-definition color digital standard image data “cafeteria” published by the Japanese Standards Association) are displayed at Adobe Photoshop (registered trademark). An image converted to grayscale at 7.0 was prepared. The produced image was observed visually and the relief feeling was evaluated based on the following criteria.
◯: Smooth image quality without a feeling of relief Δ: Slightly uneven part ×: The whole surface has large unevenness, the relief feeling is remarkable, and the quality is not practical.

(Evaluation of color gamut)
Coated paper A was used as the recording medium, and a solid image was formed with an adhesion amount of 1.0 mg / cm ² . With respect to the formed solid image, L ^* a ^* b ^* of the 2002 color patch was measured using a spectrophotometer “Gretag Macbeth Spectrolino” manufactured by Gretag Macbeth. The color gamut volume ratio of the solid image was calculated by setting the color gamut volume ratio of Japan Color as 100%, and the color gamut was evaluated based on the following criteria.
○: Color gamut volume is 110% or more Δ: Color gamut volume is 105% or more and less than 110% ×: Color gamut volume is less than 105%

  The results of the above evaluation are shown in Table 2 below together with the number of the ink used, the type and amount of the magnetic substance contained therein, and the magnetic field used for the transfer bond.

  As is apparent from the results shown in Table 2 above, an ink attachment process in which droplets of inkjet ink containing a magnetic material are ejected from the nozzles of an inkjet recording head and adhered to the intermediate transfer member, and attached to the intermediate transfer member In Examples 1 to 16 in which image formation was performed by a method including a transfer step in which the ink droplets transferred were transferred to a recording medium in a magnetic field, all of character quality, gloss homogeneity, relief, and color gamut An image with good evaluation was obtained. In particular, Examples 5 and 6 in which the magnetic substance content of the ink is 1% by mass or more and 50% by mass or less record the coated papers A and B as compared with Example 4 in which the magnetic substance content is less than 1% by mass. The image used as the medium was excellent in character quality and gloss uniformity. Further, compared with Example 8 in which the magnetic substance content exceeds 50 mass%, all evaluations of character quality, gloss uniformity, relief, and color gamut were good regardless of the type of recording medium.

  Further, Examples 9 and 10 in which the magnetic substance contained in the ink was an organic magnetic substance had higher color gamut evaluation results than Examples 12 and 13 in which the magnetic substance contained in the ink was an inorganic magnetic substance. . Further, Example 10 using the actinic ray curable ink containing the gelling agent used the coated paper B and the art paper as the recording medium as compared with Example 16 using the water-based ink not containing the gelling agent. In the image, the character quality and gloss uniformity were excellent.

  As for the strength of the magnetic field used in the transfer process, the tenth embodiment, which is within the range of 7000 gauss to 13,000 gauss, is compared to the 14th embodiment having less than 7000 gauss and the 15th embodiment having more than 13,000 gauss. In an image using A and B as recording media, the character quality, gloss uniformity and relief were excellent.

  Further, in Example 1 in which the content of the photopolymerizable monomer having a CLogP value of 1 to 12 in the ink is 5% by mass to 40% by mass, the content of the photopolymerizable monomer is 40% by mass. Compared with Example 17 exceeding 18 or less than 5% by mass, particularly in an image using coated paper A as a recording medium, the character quality, gloss uniformity and relief were excellent.

  On the other hand, Comparative Example 1 in which image formation was performed using ink that did not contain a magnetic material, compared with Examples 5 and 10 that used ink of the same composition except that it contained a magnetic material, character quality and glossy uniformity. All the evaluations of relief and color gamut were bad. In addition, the image forming product of Comparative Example 2 that uses the ink 6 containing a magnetic substance but does not perform the transfer process in a magnetic field is the same as that of Example 6 in which the transfer process is performed in a magnetic field. The evaluation of character quality and color gamut was poor, and when coated paper A was used as the recording medium, the evaluation of gloss uniformity and relief was also poor.

  According to the present invention, it is easy to control the dot diameter of the ink ejected to the intermediate transfer medium, and improves the transferability of the ink to the recording medium, thereby forming a high-quality image that is smooth and has little thickness unevenness. Image forming method, actinic ray curable inkjet ink, and image forming apparatus can be provided.

DESCRIPTION OF SYMBOLS 1 Magnetic field 2 Recording medium 3 Ink 4 Intermediate transfer body F1, F2 Affinity 10 Inkjet recording device 11 Intermediate transfer medium 12 Recording medium 13 Cleaning member 14 Inkjet recording head 15 Conveyance member 16 Head carriage 18 Light irradiation part 19 Temperature control part 20 Addition Pressure roller 21 Magnetic field generator 30 Ink flow path 31 Ink tank

Claims (13)

An ink adhering step in which ink jet ink droplets are ejected from nozzles of an ink jet recording head and adhered to an intermediate transfer member;
A transfer step of transferring the ink droplets attached to the intermediate transfer member to a recording medium,
The inkjet ink contains a magnetic material,
An image forming method, wherein the transfer step is performed in a magnetic field.   The image forming method according to claim 1, wherein the inkjet ink is an actinic ray curable ink.   The image forming method according to claim 1, wherein the magnetic body is an organic magnetic body.   The image forming method according to claim 3, wherein the organic magnetic material is an organic charge transfer complex having magnetic properties.   5. The image forming method according to claim 1, wherein the content of the magnetic substance with respect to the total mass of the inkjet ink is 1% by mass or more and 50% by mass or less. The inkjet ink includes a photopolymerizable monomer having a CLogP value of 1 or more and 12 or less,
6. The image forming method according to claim 2, wherein the content of the photopolymerizable monomer with respect to the total mass of the inkjet ink is 5% by mass or more and 40% by mass or less.   The image forming method according to claim 1, wherein the inkjet ink further includes a gelling agent.   The image forming method according to claim 1, further comprising a curing step of irradiating the ink droplets transferred to the recording medium with actinic rays to cure each ink droplet.   An actinic ray curable inkjet ink containing a photopolymerizable compound, a gelling agent, and an organic magnetic substance.   The actinic ray curable inkjet ink according to claim 9, wherein the organic magnetic material is an organic charge transfer complex having magnetic properties.   The actinic ray curable inkjet ink according to claim 9 or 10, wherein the content of the organic magnetic substance with respect to the total mass of the inkjet ink is 1% by mass or more and 50% by mass or less. The photopolymerizable compound includes a photopolymerizable monomer having a CLogP value of 1 or more and 12 or less,
The actinic ray curable inkjet ink according to claim 9, wherein the content of the photopolymerizable monomer with respect to the total mass of the inkjet ink is 5% by mass or more and 40% by mass or less. An intermediate transfer member;
An ink adhering portion for adhering inkjet ink to the intermediate transfer member;
A recording medium transport unit that transports a recording medium onto which the inkjet ink is transferred from the intermediate transfer member;
A magnetic field generator;
An image forming apparatus.

Images