INKJET RECORDING METHOD, PRINT MATERIAL, METHOD FOR PRODUCING MOLD PRINT MATERIAL, AND MOLD PRINT MATERIAL

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an inkjet recording method, a print material, a method for producing a mold print material, and a mold print material. [0003] 2.

Description of the Related Art

[0004] As an image recording method for forming an image on a recording medium based on an image data signal, there are an electrophotographic system, sublimation-type and melt-type thermal transfer systems, an inkjet system, and the like. Since the inkjet system uses . inexpensive equipment and forms an image directly on a recording medium by discharging ink only on a required image area, the ink composition can be used efficiently and thereby the running cost is low. In addition, the noise of the inkjet system is small and thereby the system is excellent as an image recording system.

[0005] Examples of an ink composition containing metal pigments are described in JP2009-091550Aand JP2008-088228A.

SUMMARY OF THE INVENTION

[0006] An object of the present invention is to provide an inkjet recording method, a print material, a method for producing a mold print material, and a mold print material, from which a metallic glossy image having excellent discharging stability and excellent pencil hardnesscan be obtained.

[0007] The above-described objects are realized as follows.

[0008] According to a first aspect of the present invention, there is provided an inkjet recording method including the steps of:

image forming step A in which an ink composition A containing aluminum metal pigments is discharged through nozzles having a nozzle diameter of 30 μm or more and 100 μm or less to form an image on a recording medium;

curing step A in which the discharged ink composition A is irradiated with active radiation to carry out curing;

image forming step B in which an ink composition B containing pigments other than aluminum metal pigments is discharged through nozzles having a nozzle diameter of 10 μm or more and less than 30 μm to form an image on a recording medium; and

curing step B in which the discharged ink composition B is irradiated with active radiation to carry out curing.

[0009] In the inkjet recording method, the volume average particle diameter of the aluminum metal pigments is preferably in the range of 0.2 μm or more to 2.0 μm or less.

[0010] In the inkjet recording method, the ink composition A and the ink composition B preferably contain a polymerizable compound and a photopolymerization initiator. [0011]

In the inkjet recording method, the ink composition A and the ink composition B each preferably contain a dispersant

[0012] In the inkjet recording method, the ink composition A and the ink composition B are preferably a radically polymerizable ink composition or a cationically polymerizable ink composition.

[0013] According to a second aspect of the present invention, there is provided a print material obtained by the inkjet recording method.

[0014] According to a third aspect of the present invention, there is provided a method for producing a mold print material, including the steps of:

image forming step A in which an ink composition A containing aluminum metal pigments is discharged through nozzles having a nozzle diameter of 30 μm or more and 100 urn or less to form an image on a recording medium;

curing step A in which the discharged ink composition A is irradiated with active radiation to carry out curing,

image forming step B in which an ink composition B containing pigments other than aluminum metal pigments is discharged through nozzles having a nozzle diameter of 10 urn or more and less than 30 μm to form an image on a recording medium;

curing step B in which the discharged ink composition B is irradiated with active radiation to carry out curing, and

molding processing in which the recording medium having the cured image is subjected to molding processing.

[0015] In the method for producing a mold print material, the volume average particle diameter of the aluminum metal pigments is preferably in the range of 0.2 μm or more to 2.0 um or less.

[0016] In the method for producing a mold print material, the ink composition A and the ink composition B preferably contain a polymerizable compound and a photopolymerization initiator.

[0017] In the method for producing a mold print material, the ink composition A and the ink composition B preferably contain a dispersant.

[0018] In the method for producing a mold print material, the ink composition A and the ink composition B are preferably a radically polymerizable ink composition or a cationically polymerizable ink composition.

[0019] According to a fourth aspect of the present invention, there is provided a mold print material obtained by the method for producing a mold print material.

[0020] According to the present invention, an inkjet recording method, a print material, a method for producing a mold print material, and a mold print material, from which a metallic glossy image having excellent discharging stability and excellent hardness, can be provided can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Fig. 1 is a schematic view showing an example of a configuration used in a molding processing test.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The inkjet recording method of an aspect of the present invention may include:

[0023] image forming step A in which an ink composition A containing aluminum metal pigments (which may also be hereinafter simply referred to as "ink composition A") is discharged through nozzles having a nozzle diameter in the range of 30 urn or more to 100 µm or less to form an image on a recording medium; curing step A in which the discharged ink composition A is irradiated with active radiation to carry out curing; image forming step B in which an ink composition B containing pigments other than aluminum metal pigments which may also be hereinafter simply referred to as "ink composition B") is discharged through nozzles having a nozzle diameter in the range of 10 μm or more to less than 30μm to form an image on a recording medium; and curing step B in which the discharged ink composition B is irradiated with active radiation to carry out curing.

[0024] Moreover, in the specification, the descriptions of "X to Y" showing the numerical value ranges are the same as "X or more to Y or less" unless otherwise specified. Further, the descriptions of "(meth)acrylate" and the like are the same as "methacrylate and/or acrylate" and the like. Still further, a simple descripti on of the "ink composition" means both of the ink composition A and the ink composition B.

First, the ink composition used in the present invention will be described. In addition, the "recording medium" treated in each step using the ink composition A and the ink composition B means the same medium unless otherwise specified.

[0025] I. Ink Composition

[0026] The ink composition used in the present invention is an oily ink composition that is curable by active radiation. The "active radiation" is radiation that can provide energy w generates an initiating species in the ink composition when irradiated, and examples thereof include a rays, y rays, X rays, ultraviolet rays, visible light, an electron beam, and the like.

Among those, ultraviolet rays and an electron beam are preferable from the viewpoints of curing sensitivity and the availability of equipment, and ultraviolet rays are particularly
preferable.

[0027] The ink composition may be any one as long as it is an ink composition that is cured by active radiation, and is preferably radically polymerizable or cationically polymerizable.

First, the radically polymerizable ink composition will be described, and then the cationically polymerizable ink composition will be described.

[0028] II. Radically Polymerizable Ink Composition

[0029] The radically polymerizable ink composition contains aluminum metal pigments or colorants other than the aluminum metal pigments, a radically polymerizable compound, and a radical polymerization initiator. Hereinafter, each of the components will be described.

[0030] (Aluminum Metal Pigments)

[0031] The ink composition A contains aluminum metal pigments.

[0032] As the aluminum metal pigments, any known aluminum powder may be appropriately selected and used. The aluminum powder may be prepared by any preparation method.

Examples of the preparation method for the aluminum powder include a method involving grinding while rolling an aluminum ingot, a method involving vapor-depositing aluminum on a thin film and powdering it, a method involving very finely powdering a foil having good brightness, and the like, but the present invention is not limited thereto.

Further, the aluminum powder to be added may be in either a paste form or a powder form. As an aluminum powder in the paste form, a paste form in which an aluminum powder is dispersed in a hydrocarbon-based solvent (for example, ethyl acetate) may be exemplified.

[0033] The aluminum powder used in the present invention may be subjected to a surface treatment or the like. For example, an aluminum powder having stearic acid or the like adsorbed on the surface of the powder may be exemplified, and when an aluminum powder treated by this method is used, the aluminum powders tend to align in parallel to each other on the surface of the discharged ink, thus giving a recorded material having a surface close to a mirror-finished surface. In addition, an aluminum powder coated with a resin may be exemplified, and this is preferable since it enables the adhesion, chemical resistance, weather resistance, and the like to be improved. On the other hand, the glossiness or the hiding property tends to be poor.

[0034] Aluminum powders are commercially available, and examples of the aluminum powder in the paste form, that is dispersed in a hydrocarbon-based solvent, include ROTOVARIO 500 series (manufactured by Eckart) and ASTROSHINE T-8990 and ASTROSHINE T-8765 (both manufactured by Nihonboshitsu Co., Ltd.).

[0035] In the present invention, the aluminum metal pigments are preferably dispersed in the polymerizable compound. That is, the aluminum metal pigments are preferably not dispersed in water or a solvent.

[0036] From the viewpoint of the metallic glossiness, the volume average particle diameter of the aluminum metal pigments is preferably in the range of 0.2 urn or more to 2.0 μm or less, more preferably 0.25 to 1.8 μm, and still more preferably 0.3 to 1.5 μm.

The volume average particle size is measured using a laser diffraction/scattering particle size distribution analyzer (product name: Microtrac MT3300EX, manufactured by Nikkiso Co., Ltd.), or the like by diluting with the same liquid as a dispersion medium.

[0037] In the present invention, the content of the aluminum metal pigments is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, and still more preferably 5 to 18% by mass, relative to the total amount (total mass) of the ink composition. Within these ranges, a good impression of luminosity can be obtained and the stability of the ink composition is good.

[0038] The ink composition A is a preferably a dispersion including a polymerizable compound, a photopolymerization initiator, and aluminum metal pigments, dispersed in a non-aqueous system. The ink composition A is prepared (made into an ink) by, for example, adding the polymerizable compound, the photopolymerization initiator, the aluminum metal pigments, and if necessary, various types of additive.

[0039] Moreover, in the present invention, it is preferable to use a dispersant in the preparation 6 of the ink composition, and it is more preferable to use an acidic dispersant as the dispersant. It is also possible to prepare the ink composition A by first preparing a dispersion having a high aluminum metal pigment concentration, and diluting this by adding the polymerizable compound or various types of additive.

[0040] For dispersion of the aluminum metal pigments, dispersion equipment such as, for example, a ball mill, a sand mill, an attritor, a roll mill, a jet mill, a homogenizer, a paint shaker, a kneader, an agitator, a HenscheJ mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet type jet mill, and the like may be used.

[0041] In the present invention, when carrying out dispersion, it is preferable to finely disperse at least the aluminum metal pigments, the polymerizable compound, and the dispersant using beads (dispersion media). As dispersion equipment, a ball mill, an agitator mill, a paint shaker, or the like may be used.

[0042] Examples of the beads (dispersion media) include glass beads, stainless steel beads, alumina beads, zirconia beads, and the like, and among these, it is preferable to use zirconia beads as the beads (dispersion media). The zirconia beads are preferable since they have excellent strength and hardness and there is little powder generated as a result of the cutting of the beads (dispersion media).

[0043] Furthermore, when dispersion of the aluminum metal pigments is carried out as described above, it is preferable to add a dispersant. In the present invention, it is preferable to use an acidic dispersant as the dispersant, and the acidic dispersant as mentioned herein means a polymer compound having an acidic pigment-hydrophilic group at one terminus of the main chain by means of a block or graft structure. It is preferable to use an acidic dispersant since dispersion of the aluminum metal pigments proceeds quickly and a stable dispersion can be obtained.

[0044] Examples of the acidic pigment-hydrophilic group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group.

[0045] Examples of the polymer include a polyacrylate, a polyurethane, a polyester, and modified products thereof.

[0046] These dispersants are commercially available, and examples thereof include DISPERBYK-102, DISPER8YK-110, DISPERBYK-111, DISPERBYK-112, and DISPERBYK-180 (all manufactured by BYK-Chemie) and SOLSPERSE (registered trademark) 26000, SOLSPERSE 36000, and SOLSPERSE 41000 (all manufactured by Lubrizol Corporation). Further, the dispersant may be used singly or in combination of two or more kinds thereof.

[0047] In the ink composition A, a solvent may be added as a dispersion medium for various components such as the aluminum metal pigments, and alternatively, the polymerizable compound, which is a low molecular weight component, may be used as a dispersion medium without using a solvent. In the present invention, since the ink composition is a radiation-curing ink and is cured after the ink is applied to a recording material, it is preferable for the ink composition to be solventless or to be a low solvent ink.

[0048] As the structure of the polymerizable compound used in the dispersion medium, an ethylene oxide (EO) chain, those including a propylene oxide (PO) chain, or a benzene ring are preferable, particularly since disperseability is improved. Further, those having a polymerizable group are preferable from the viewpoint of curability.

[0049] As a particularly preferable example, examples of the dispersion medium including an EO chain include triethylene glycol divinyl ether (RAPI-CURE DVE-3, manufactured by ISP Japan, Ltd.), polyethylene glycol di(meth)acrylate, 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA), and ethoxylated trimethylolpropane triacrylate (EOTMPTA), and the like.

[0050] Examples of the dispersion medium including a PO chain include tripropylene glycol methyl ether, polypropylene glycol diacrylate, propoxylated neopentyl glycol diacrylate (NPGPODA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), alkoxylated tetrahydrofurfuryl acrylate (CD611, manufactured by Sartomer Inc.), and the like.

[0051] Examples of the dispersion medium including a benzene ring include phenoxyethyl acrylate (PEA), phenoxyethyloxyethyl acrylate (EBECRYL 110, manufactured by Daicel Cytec Co., Ltd.), and OXT-211 (manufactured by Toagosei Co., Ltd.), and the like.

[0052] (Colorant Other Than Aluminum Metal Pigments)

[0053] The ink composition B contains a colorant in addition to the aluminum metal pigments (which may also be simply hereinafter referred to as a "colorant"). In the present invention, a combined use of the ink composition A and the ink composition B can allow a metallic glossy image with various types of color variation to be obtained.

[0054] The colorant is not particularly limited, but is preferably a pigment and an oil-soluble dye having excellent weather resistance and sufficient color reproductivity. Further, any colorant may be arbitrarily selected from known colorants such as soluble dyes and the like, and used.

[0055] The pigment that can be used in the present invention is not particularly limited, but for example, organic and inorganic pigments having the numbers below described in the Color Index may be used. That is, as a red or magenta pigment, Pigment Red 3, 5, 19, 22, 31, 38, 42, 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, or 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, or 88, and Pigment Orange 13, 16, 20, or 36; as a blue or cyan pigment, Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17-1, 22, 27, 28, 29, 36, or 60; as a green pigment, Pigment Green 7, 26, 36, or 50; as a yellow pigment, Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 120, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, or 193; as a black pigment, Pigment Black 7, 28, or 26; or the like may be used according to the purpose. [0056] As a white pigment, titanium oxide is preferable.

[0057] The titanium oxide is not particularly limited and may be selected appropriately from known titanium oxides used as white pigments. Either rutile-type titanium dioxide or anatase-type titanium dioxide may be used, but the rutile type titanium dioxide is preferably used from the viewpoints of low catalytic activity and excellent stability overtime. [0058] Titanium oxide is commercially available, and examples thereof include Tipaque CR60-2 and Tipaque A-220 (both manufactured by Ishihara Sangyo Kaisha Ltd.); KRONOS 1001, 1014, 1071, 1074, 1075, 1077, 1078, 1080, 1171, 2044, 2047, 2056, 2063, 2080, 2081, 2084, 2087, 2160, 2190, 2211, 2220, 2222, 2225, 2230, 2233, 2257, 2300, 2310, 2450, 2500, 3000, and 3025 (all manufactured by KRONOS); and the like.

[0059] Further, the titanium oxide may be subjected to a surface treatment, as necessary. Specifically, it may be treated with silica, alumina, zinc, zirconia, or an organic substance, and weather resistance and oleophilicity are varied according to the treatment method. In the present invention, one treated with alumina, zinc, zirconia, or a basic organic substance is preferable.

[0060] In the present invention, a disperse dye in such an amount that the disperse dye can be dissolved in a water-immiscible organic solvent may also be used. Examples of the disperse dye generally include water-soluble dyes. However, the disperse dye is preferably used in such an amount that it can be dissolved in the water-immiscible organic solvent in the present invention.

[0061] Preferable specific examples of the disperse dye include C. L Disperse Yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184:1, 186, 198, 199, 201, 204, 224, and 237; C. I. Disperse Orange 13, 29, 31:1, 33, 49, 54, 55, 66, 73, 118, 119, and 163; C. I.

Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167:1, 177, 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356, and 362; C. I. Disperse Violet 33; C. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165:1, 165:2, 176, 183, 185, 197, 198, 201, 214, 224, 225, 257, 266, 267, 287, 354, 358, 365, and 368; C. I. Disperse Green 6:1 and 9; and the like.

[0062] Any of various dispersing machines, such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a HENSCHEL mixer, a colloid mill, an ultrasonic wave homogenizer, a pearl mill, a wet-type jet mill, a paint shaker, and the like may be used to disperse the colorant.

[0063] In the preparation of the ink composition B, the colorant may be directly added together with the respective components. Alternatively, to improve the disperseability, the colorant may be added to a solvent or a dispersion medium such as the specific sulfide compound used in the present invention or an additional polymerizable compound, which may be added as needed, and uniformly dispersed or dissolved therein, and the resultant may be then added to the other components.

[0064] In the present invention, the colorant is preferably added to and mixed with one of at least one sulfide compound or a mixture of sulfide compounds to avoid use of a solvent, which may remain in a cured image and degrade the solvent resistance of the image, and problems regarding VOC (Volatile Organic Compounds). When only disperseability is considered, the polymerizable compound added to the colorant is preferably a monomer having a low viscosity. One or more of those colorants may be selected and used according to the intended purpose of the ink composition B.

[0065] Further, when using a colorant such as a pigment and the like, that remains as a solid in the ink composition B, it is preferable that the types of the colorant, a dispersant, and a dispersion medium, and dispersion and filtration conditions are properly selected in order to control the average diameter of the colorant particles to be within the range of 0.005 to 0.5 μm. The average diameter is more preferably 0.01 to 0.45 μm, and still more preferably 0.015 to 0.4 Jim. Controlling the average diameter of the colorant particles can suppress clogging in a nozzle head and maintains the storage stability, transparency, and curing sensitivity of the ink composition B, which is thus preferable.

[0066] The content of the colorant in the ink composition B may be appropriately selected according to the color and the intended purpose, but is preferably 0.01 to 30% by mass relative to the total mass of the ink composition B. [0067] (Dispersant)

[0068] The ink composition of an aspect of the present invention may contain a dispersant.

In the case where a pigment is particularly used as a colorant, a dispersant is preferably contained so as to stably disperse the pigment in the ink composition. As the dispersant, a polymer dispersant is preferable.

[0069] The content of the dispersant in the ink composition B is appropriately selected according to the intended purpose, but is preferably 0.05 to 15% by mass relative to the total mass of the ink composition.

[0070] (Radically Polymerizable Compound)

[0071] The radically polymerizable compound is a compound having an ethylenically unsaturated bond, which can undergo radical polymerization, and is any one that has at least one ethylenically unsaturated bond which can undergo radical polymerization in the molecule.

Examples thereof include those having chemical configurations such as a monomer, an
oligomer, a polymer, and the like. The radically polymerizable compound may be used
singly or in combination of two or more kinds thereof at any ratio so as to improve the desired characteristics. In addition, it is more preferable to use a monofunctional compound and a polyfunctional compound.

[0072]

[0073] As the monofunctional monomer, a compound having one ethylenically unsaturated group that is radically polymerizable in the molecule is preferable, and a monofunctional monomer having one ethylenically unsaturated group which is selected from a (meth)acrylate group, a (meth)acrylamide group, a vinyloxy group, and an N-vinyl group is more preferable.

By incorporating the monofunctional monomer, an image having excellent curability and flexibility can be obtained. Preferable examples of the monofunctional monomer include a compound represented by Formula (b-1), a compound represented by Formula (b-2), an aromatic monofunctional monomer, and the like.

[0074]

[0075] The ink composition of an aspect of the present invention preferably contains a compound represented by Formula (b-1). By incorporating the compound represented by Formula (b-1), an ink composition which can provide an image having high curability and film hardness can be obtained.

[0076]


[0077] In Formula (b-1), R1 represents a hydrogen atom or a methyl group, X represents a single bond, an alkylene group, an oxyalkylene group, or a group formed by combination of two or more oxyalkylene groups above, an ester bond, or a group formed by combination thereof, R2 and R3 each independently represent a hydrogen atom or an alkyl group, R to R each independently represent a hydrogen atom, an alkyl group, an alkoxyl group, an amino group, or an aminoalkyl group, at least one of R to R represents a hydrogen atom, and any two or more of R2 to R8 may be combined with one another to form a cyclic structure.

[0078] In Formula (b-1), R represents a hydrogen atom or a methyl group, and preferably a hydrogen atom.

[0079] X represents a single bond, an alkylene group, an oxyalkylene group, or a group
formed by combination of two or more oxyalkylene groups above, an ester bond, or a group formed by combination thereof.

[0080] The alkylene group is preferably an alkylene group having 1 to 10 carbon atoms, and more preferably an alkylene group having 1 to 8 carbon atoms.

[0081] The oxyalkylene group or a group formed by combination of two or more oxyalkylene groups above is a group in which an alkylene group is bonded to an oxygen atom of the (meth)acryloyloxy group in Formula (b-1). As the alkylene group included in the oxyalkylene group, an alkylene group having 1 to 5 carbon atoms, which is linear or branched, is preferable, an alkylene group having 2 or 3 carbon atoms, which is linear or branched, is more preferable, and an isopropylene group is still more preferable. In the case of a combination of two or more oxyalkylene groups, the number of the oxyalkylene groups is preferably 10 or less, and more preferably 5 or less.

[0082] In the case where X contains an ester bond (-COO- or -OCO-), X is preferably a group formed by combination of the alkylene group with the ester bond. That is, X is an
oxycarbonylalkylene group in which an oxygen atom is bonded to a carbon atom bonded to R and R is preferable.

[0083] R2 and R3 each independently represent a hydrogen atom or an alkyl group, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom or a methyl group.

[0084] R4 to R8 each independently represent a hydrogen atom, an alkyl group, an alkoxyl group, an amino group, or an aminoalkyl group.

[0085] As the alkyl group, an alkyl group having 1 to 10 carbon atoms, which is linear or branched, is preferable. As the alkoxyl group, an alkoxyl group having 1 to 5 carbon atoms, which is linear or branched, is preferable, and a methoxy group is more preferable. Examples of the amino group include an amino group, a monoalkylamino group, and a dialkylamino group, and as the alkyl group, an alkyl group having 1 to 3 carbon atoms, which is linear or branched, is preferable. As the amino group, a dimethylamino group* a diethylamino group, or a diisopropylamino group is preferable. The amino group included in the aminoalkyl group is the same^as the above-described ammo group. That is, examples of the aminoalkyl group include a monoalkylaminoalkyl group and a dialkylaminoalkyl group. The moiety of the alkyl group of the aminoalkyl group having an amino group removed therefrom is preferably alkyl having 1 to 3 carbon atoms. As the aminoalkyl group, a dimethylaminomethyl group, a diethylaminomethyl group, or a diisopropylaminomethyl group is preferable.

[0086] At least one of R4 to R8 is a hydrogen atom. When at least one of R4 to R8 is a hydrogen atom, ah ink composition having excellent curability can be obtained. [0087] Any two or more of R? to R8 may be combined with one other to form a cyclic structure. A ring formed by R4 or R5 with any one of R6 to R8 being combined with each other is preferable, a cyclic ether group having a reduction number of 4 to 6 is more preferably formed, a cyclic ether group having a reduction number 5, that is, a tetrahydrofurfuryl group is still more preferably formed.

[0088] Since the compound represented by Formula (b-1) has excellent curability, it is preferably one having a tetrahydrofurfuryl group, and more preferably a compound represented by Formula (b-1-1).

[0089]

[0090] In Formula (b-1-1), R1 represents a hydrogen atom or a methyl group, X represents a single bond, an alkylene group, an oxyalkylene group, or a group formed by combination of two or more oxyalkylene groups above, an ester bond, or a group formed by combination thereof.

[0091] X and a preferable range thereof are the same as for X in Formula (b-1).

[0092] Hereinafter, specific examples of the compound represented by Formula (b-1) are shown, but the present invention is not limited to these specific examples. Further, among the exemplified compounds R represents a hydrogen atom or a methyl group.

[0093]

[0095]

[0096] The ink composition of an aspect of the present invention preferably contains a compound represented, by Formula (b-2).

[0097]

[0098] In Formula (b-2), n represents an integer of 1 to 5.

[0099] In Formula (b-2), n represents an integer of 1 to 5, from the viewpoints of flexibility after curing the ink composition, adhesiveness with a recording medium, and availability of raw materials, n is preferably an integer of 2 to 4, n is more preferably 2 or 4, and n is particularly preferably 4, that is N-vinyl caprolactam is particularly preferable. The N-vinyl eaprolactam is preferable since it has excellent safety, is available at relatively low cost, and can provide particularly good ink curability and adhesiveness of a cured film to a recording medium.

[0100] The total content of the compound represented by Formula (b-1) and the compound represented by Formula (b-2) in the radically polymerizable compound is preferably 5 to 99.9% by mass, more preferably 10 to 90% by mass, and still more preferably 15 to 80% by mass. Within the above-described ranges of numerical values, the adhesiveness to a recording medium and the storage stability are excellent.

[0101]

[0102] The ink composition of an aspect of the present invention preferably contains an aromatic monofunctional monomer as a monofunctional monomer. As the aromatic monofunctional monomer, a monomer having one radically polymerizable ethylenically unsaturated group and at least one aromatic group in the molecule is preferable, and a monomer having one (meth)acryloyloxy group or (meth)a(lamide group, and at least one aromatic hydrocarbon group in the molecule is more preferable. Preferable specific examples of the aromatic monofunctional monomer include aromatic monofunctional radically polymerizable monomers described in Paragraph Nos. 0048 to 0063 of JP2009-096985A. Among these, as the aromatic monofunctional radically polymerizable monomer, a compound represented by Formula (b-3) is preferable.

[0103]

[0104] In Formula (b-3), R1 represents a hydrogen atom or a methyl group, X1 represents a divalent linking group, Ar represents an aromatic hydrocarbon group, R5 represents a substituent, u represents an integer of 0 to 5, and R5's with a number present of u may be the same as or different from each other.

[0105] In Formula (b-3), R1 is preferably a hydrogen atom.

[0106] X1 represents a divalent linking group, and preferably an ether group (-O-), an ester group (-O(O)O- or -OC(0», an amide group (-C(0)NR'-), a carbonyl group (-C(0», an imino group (-NR'-), an optionally substituted alkylene group having 1 to 15 carbons, or a divalent group in which two or more thereof are combined. R1 represents a hydrogen atom, a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

[0107] In Formula (b-3), the end of X1 that is bonded to the vinyl group is preferably an ester group or an amide group via which a carbonyl carbon of X1 is bonded to the vinyl group, more preferably an ester bond, and particularly preferably one having the structure HzOR-CCOp-. In this case, another moiety of X1 that is bonded to the norbornane skeleton may be a single bond or one freely selected from the groups above.

[0108] The vinyl moiety containing R1 and X1 (HiOCCR^X1-) may be bonded to any position on the aromatic hydrocarbon group Ar.

[0109] Furthermore, from the viewpoint of increasing the affinity with the aluminum metal pigments or the colorant, the end of X1 that is bonded to the aromatic hydrocarbon group Ar is preferably an oxygen atom, and more preferably an ethereal oxygen atom, and X1 is preferably *-C(0)0(LO)q- or *-C(0)NH(LO)q-. Herein, * represents the position at which X1 and the vinyl group in Formula (b-3) are bonded, q is an integer of 0 to 10, and L represents an alkylene group having 2 to 4 carbon atoms. Among them, X1 is preferably *-C(0)0(LO)q-, and q is preferably an integer of 0 to 4, more preferably an integer of 0 to 2, and still more preferably 1 or 2. (LO)q is preferably an ethylene oxide chain or a propylene oxide chain.

[0110] R5's with a number present of u each independently represent a hydroxyl group, a substituted or unsubstituted amino group, a thiol group, a siloxane group, or an optionally substituted hydrocarbon group or heterocyclic group, having a total carbon number of 30 or less.

[0111] u represents an integer of 0 to 5, and preferably 0.

[0112] Ar represents an aromatic hydrocarbon group. Examples of the aromatic hydrocarbon group include a monocyclic or polycyclic aromatic hydrocarbon group having 1 to 4 rings, and specifically, a group in which at least one hydrogen atom is removed from naphthalene, anthracene, lH-indene, 9H-fluorene, lH-phenalene, phenanthrene, triphenylene, pyrene, naphthacene, tetraphenylene, biphenylene, as-indacene, s-indacene, acenaphthylene, fluoranthene, acephenanthrylene, aceanthrylene, chrysene, pleiadene, or the like. Among these, in the present invention, a phenyl group and a naphthyl group are preferable, a monocyclic aromatic hydrocarbon group, that is, a phenyl group is more preferable. In addition, the aromatic hydrocarbon group Ar in Formula (b-3) may be an aromatic heterocycle containing a hetero atom such as O, N, S, and the like, but preferably does not contain a hetero atom.

[0113] In the present invention, preferable examples of the compound represented by Formula (b-3) include 2-phenoxyethyl acrylate. [0114]

[0115] The ink composition may contain other monofunctional monomers, in addition to the compound represented by Formula (b-1), the compound represented by Formula (b-2), and the aromatic monofunctional monomer. As the other monofunctional monomer, a (meth)acrylic ester compound is preferable. Examples of the (meth)acrylic ester compound include those having a chemical configuration such as a monomer, an oligomer, a polymer, and the like. The (meth)acrylic ester compound may be used singly or in combination of two or more kinds thereof at any ratio so as to improve the desired characteristics.

[0116] Specific examples thereof include monofunctional (meth)acrylic ester compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl
(meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, isooctyl (meth)acrylate,
n-lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-cetyl(meth)acrylate, n-stearyl
(meth)acryiate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobomyl (meth)acrylate, adamantyl(meth)acrylate, vinyl (meth)acrylate, aryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate,2-diethylamino ethyl (meth)acrylate, (poly)ethylene glycol mono(meth)acrylate, (polyethylene glycol (meth)acrylate methyl ester, (polyethylene glycol (meth)acrylate ethyl ester, (polypropylene glycol mono(meth)acrylate, (polypropylene glycol (meth)acrylate methyl ester, (polypropylene glycol (meth)acrylate ethyl ester, FANCRYL FA-513A (dicyclopentanyl acrylate), FANCRYL FA-513M (dicyclopentanyl methacrylate), FANCRYL FA-711MM (pentamethylpiperidinyl methacrylate), and FANCRYL FA-712HM (tetramethylpiperidinyl methacrylate) manufactured by Hitachi Chemical Co., Ltd., and the SR & CD series of functional monomers and sold as functional oligomers, the CN series, manufactured by Sartomer Japan Inc., and the like.

[0117] More specifically, radically polymerizable (meth)acrylic ester monomers that are
commercial products or are industrially known, such as those described in "Kakyozai
Handobukku (Crosslinking Agent Handbook)", Ed. S. Yamashita (1981, Taiseisha); "UV-EB Koka Handobukku (Genryohen)" (UV-EB Curing Handbook (Starting Materials)) Ed. K. Kato (1985, Kobunshi Kankoukai); "UV-EB Koka Gijutsu no Oyo to Shijyo (Application and Market of UV-EB Curing Technology)", p. 79, Ed. RadTech (1989, CMC); and E. Takiyama "Poriesuteru Jushi Handobukku (Polyester Resin Handbook)", (1988, The Nikkan Kogyo Shimbun Ltd.), and the like may be used.

[0118] Furthermore, as the radically polymerizable compound, for example, photocuring type polymerizable compounds used in photopolymerizable compositions described in publications such as JP1995-159983A(JP-H07-159983A), JP1995-031399B(JP-H07-031399B), JP1996-224982A(JP-H08-224982A), JP1998-000863A(JP-H10-000863A), JP1997-134011A(JP-H09-134011A), and JP2004-514014A are known, and (meth)acrylic esters described therein may also be applied to the ink composition of an aspect of the present invention.

[0119] The total content of the monofunctional monomers in the ink composition is preferably 5 to 85% by mass, more preferably 7.5 to 84.5% by mass, and still more preferably 10 to 84% by mass. Within the above-described ranges of the numerical values, an image having excellent flexibility can be obtained.

[0120]

[0121] As the polyfunctional monomer, a polyfunctional monomer having two or more
radically polymerizable ethylenically unsaturated groups is preferable, a polyfunctional
monomer having two or more ethylenically unsaturated groups selected from the group
consisting of a (meth)acrylate group, a (meth)acrylamide group, and a vinyloxy group and N-vinyl group is more preferable, and a polyfunctional monomer having at least two
(meth)acrylate groups are still more preferable.

[0122] The number of the functional groups included in the polyfunctional monomer is referably 2 to 6, more preferably 2 to 4, and still more preferably 2.

[0123] Examples of the polyfunctional monomer include 1,6-hexanediol di(meth)acrylate, ,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, is(4-acryloxypolyethoxyphenyl)propane, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, neopentyl glycol hydroxypivalate diacrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, ethylene oxide (EO)-modified pentaerythritol tri(meth)acrylate, propylene oxide (PO)-modified pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, EO-modified
pentaerythritol tetra(meth)acrylate, PO-modified pentaerythritol tetra(meth)acrylate,
pentaerythritol tri(meth)acrylate tolylene diisocyanate urethane prepolymer, pentaerythritol tri(meth)acrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol tri(meth)acrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol tetra(meth)acrylate, EO-modified dipentaerythritol tetra(meth)acrylate, PO-modified dipentaerythritol tetra(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropanetri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, PO-modified trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, EO-modified tetramethylolmethane tetra(meth)acrylate, PO-modified tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, modified glycerol tri(meth)acrylate, modified bisphenol A di(meth)acrylate, bisphenol A PO adduct di(meth)acrylate, bisphenol A EO adduct di(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane, diallyl phthalate, triallyl trimellitate, and the like.

[0124] Moreover, a vinyl ether compound may be used as a radically polymerizable compound.

[0125] Examples of the vinyl ether compound include di- or tri-vinyl ether compounds such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, trimethylolpropane trivinyl ether, and the like; and monovinyl ether compounds such as ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl vinyl ether, dodecyl vinyl ether, ethylene glycol monovinyl ether, diethylene glycol monovinyl ether, triethylene glycol monovinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, octadecyl vinyl ether, and the like.

[0126] The content of the polyfunctional monomer in the ink composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and still more preferably 1 to 5% by mass, from the viewpoint of satisfying both curability and flexibility.

[0127] The content of the radically polymerizable compound in the ink composition is preferably 60 to 99% by mass, more preferably 62.5 to 97.5% by mass, and still more preferably 65 to 95% by mass, from the viewpoint of prevention of bleeding of the curing/non-curing components.

[0128] (Radical Photopolymerization Initiator)

[0129] The ink composition of an aspect of the present invention preferably contains a radical photopolymerization initiator (which may also be hereinafter referred to as a "polymerization initiator"). The polymerization initiator is a compound that generates a radical polymerization initiating species upon absorption of external energy such as active radiation and the like. Examples of the polymerization initiator that can be used in the present invention include aromatic ketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, keto oxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, carbon-halogen bond-containing compounds, and the like. Specific examples of the polymerization initiator include the polymerization initiators described in JP2008-208190A and JP2009-096985A. The polymerization initiator may be used singly or in combination of two or more kinds thereof.

[0130] Among these, as the polymerization initiator, acylphosphine compounds and aromatic ketones are preferable. As the aromatic ketone, thioxanthone compounds are preferable. Combined use of an acylphosphine compound and a thioxanthone compound is particularly preferable.
[0131]
[0132] Preferred examples of the acylphosphine compound (b) include the acylphosphine oxide compounds described in Paragraph Nos. 0080 to 0098 of JP2009-096985A, and among these, a compound having in its structure a structure represented by Formula (c-1) or Formula (c-2) is preferable. [0133]

[0134] In particular, as the acylphosphine oxide compound, a compound Having a chemical structure of Formula (c-3) or Formula (c-4) is particularly preferable.

[0135]

[0136] In Formula (c-3), R6, R7, and R8 represent an aromatic hydrocarbon group, which may have a methyl group or an ethyl group as a substituent.

[0137] With regard to a monoaeylphosphine oxide compound represented by Formula (c-3), it is preferable that R6 to R8 be phenyl groups, which may have a methyl group as a substituent, and it is more preferable that R7 and R8 be phenyl groups and R6 be a phenyl group having 1 to 3 methyl groups. Among these, as the monoaeylphosphine oxide compound represented by Formula (c-3), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Darocur TPO: manufactured by Ciba Specialty Chemicals, Lucirin TPO: manufactured by BASF) is preferable.

[0138]

[0139] In Formula (c-4), R9, R10, and Ru represent an aromatic hydrocarbon group, which may have a methyl group or an ethyl group as a substituent

[0140] In the present invention, with regard to a bisacylphosphine oxide compound represented by Formula (c-4), it is preferable that R9to Ru be phenyl groups, which may have a methyl group as a substituent, and it is more preferable that R11 be a phenyl group and R9 and R10 be phenyl groups having 1 to 3 methyl groups. Among these, as the bisacylphosphine oxide compound represented by Formula (c-4), bfe(2,4,6-trimiethylhenzoyI)phenylphosphine oxide (IRGACURE 819, manufactured by Ciba Specialty Chemicals) is preferable.

[0141]

[0142] The thioxanthone compound is preferably a compound represented by Formula (c-5).

[0143]


[0144] In Formula (c-5), R1 to R8 each independently represent a hydrogen atom, an alkyl group, a halogen atom, a hydroxyl group, a eyano group, a nitro group, an amino group, an alkylthio group, an alkylarnino group (including ones mono-substituted or di-substituted), an alkoxyl group, an alkoxycarbonyl group, an acyloxy group, an aeyl group, a carboxyl group, or a sulfo group,

[0145] The alkyl moiety in the alkyl group, the alkylthio group, the alkylamino group, the alkoxyl group, the alkoxycarbonyl group, the acyloxy group, and the acyi group preferably has 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 4 carbon atoms.

[0146] Two of adjacent R1 to R8 may be linked to each other to form a ring. Examples of the ring structure in the case of forming a ring therefrom include 5- or 6-membered aliphatic rings, aromatic rings, and the like, and may be heterocycles containing elements other than a carbon atom, and rings formed may be further combined to form a binuclear ring, for example, a condensed ring. The ring structure may further contain a substituent. Examples of the substituent include a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, an alkylthio group, an alkylamino group, an alkoxyl group, an alkoxycarbonyl group, an acyloxy group, an acyl group, a carboxyl group, and a sulfo group. Examples of the hetero atom in the case where the formed ring structure is a heterocycle include N, O, and S.

[0147] Examples of the thioxanthone compound include thioxanthone, 2-isopropyIthioxanthone, 2-chlorothioxanthone, 2-dodecylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, 1-methoxyearbonylthioxanthone, 2-ethoxycarbonylthioxanthone, 3-(2-memoxyethoxycarbonyl)thioxanthone, 4-but6xycarbonyltiiioxanthone, 3-butoxycarbonyI-7-methylthioxanthone, l-cyano-3-chIorothioxanthone, l-ethoxycarbonyl-3-chlorothioxanthone, l-emoxycarbonyl-3-ethoxythioxanthone, l-emoxycarbonyl-3-(minothioxanthone, l-emoxycarbonyl-3-phenylsulfurylthidxanthone, 3,4-di-[2-(2-memox:yethoxy)ethoxycarbonyl]thioxanthone, l-emoxycarbonyl-3-(l-methyl-l-morpholinoethyl)thioxanthone, 2-methyl-6-dimethoxymethylthioxanthone, 2-methyl-6-(l, l-dimethoxybenzyl)thioxanthone,
2-morpholinomethylthioxanthone, 2-methyl-6-morpholinomethylthioxanthone,
n-allylthioxanthone-3,4-dicarboximide, n-octylthioxanthone-3,4-dicarboximide,
N-(l,l,3,3-tetramethylbutyl)thioxanthone-3,4-dicarboximide, 1-phenoxythioxanthone, 6-etb.oxycarbonyl-2-methoxythioxantb.one, 6-ethoxycarbonyl-2-methylthioxanthone, thioxanthone-2-polyethylene glycol ester, and
2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-tWoxanthon-2-yloxy)-N,N,N-trimethyl-l-propanaminiu m chloride. Among these, from the viewpoint of availability and curability, 2-isopropylthioxanthone and 4-isopropylthioxanthone are more preferable.

[0148] In the present invention, from the viewpoint of curability, an acylphosphine compound and a thioxanthone compound are preferably used in combination. In the case of using the acylphosphine compound and the thioxanthone compound in combination, the mass ratio of the acylphosphine compound:the thioxanthone compound is preferably in the range of 99:1 to 1:99, more preferably 90:10 to 50:50, and still more preferably 80:20 to 50:50.

[0149] In the present invention, the total amount of the radical photopolymerization initiator to be used is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and more preferably 5 to 10% by mass, relative to the total mass of the ink composition, from the viewpoint of curability. [0150] (Surfactant)

[0151] A surfactant may be added to the ink composition that can be used in the present invention in order to impart long-term discharge stability. Examples of the surfactant include those described in JP1987-173463A(JP-S62-173463A) and
JP1987-183457A(JP-S62-183457A), and for example, anionic surfactants such as dialkylsulfosuccinic acid salts, alkylnaphthalene sulfonic acid salts, fatty acid salts, and the like, nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene/polyoxypropylene block copolymers, and the like, and cationic surfactants such as alkylamine salts, quaternary ammonium salts, and the like.

[0152] (Other Components)

[0153] The sensitizer, polymerization inhibitor, the ultraviolet ray absorber, the anitoxidant, the colorfading inhibitor, conductive salts, solvents, polymer compounds, alkaline compounds, and the like as described in JP2009-096985A may be added as other components, to the ink composition of an aspect of the present invention. [0154] HI. Cationic Polymerizable Ink Composition

[0155] In the present invention, the ink composition may be a cationically polymerizable ink composition. Hereinafter, the cationically polymerizable ink composition will be described.

[0156] (Aluminum Metal Pigments)

[0157] The aluminum metal pigments used in the radically polymerizable ink composition may also be preferably used in a cationically polymerizable ink composition, and its preferred range is also the same as in the case of the radically polymerizable ink composition.

[0158] (Cationic Polymerizable Compound)

[0159] The cationically polymerizable ink composition contains a cationically polymerizable compound. As the cationically polymerizable compound that can be used in the present invention, known cationic polymerization compounds such as a compound having an oxirane ring (also referred to as an "epoxy ring") (also referred to as an "oxirane compound" or "epoxy compound"), a compound having an oxetane ring (also referred to as an "oxetane compound"), a vinyl ether compound, and the like can be used without particular limitation.

[0160] The cationically polymerizable compound is not particularly limited as long as it is a compound that initiates a polymerization reaction by a cationic polymerization initiating species generated by the cationic photopolymerization initiator as described later, and is cured, and various cationic photopolymerizable monomers known as a cationic photopolymerizable monomer may be used. Examples of the cation polymerizable monomer include epoxy compounds, vinyl ether compounds, and oxetane compounds described in for example, JP1994-009714A (JP-H06-009714A), JP2001-031892A, JP2001-040068A, JP2001-055507A, JP2001-310938A, JP2001-310937A, JP2001-220526A, and the like. Further, as the cationically polymerizable compound, polymerizable compounds which are applied in cationically polymerizable photocurable resins are known. Recently, for example, polymerizable compounds which are applied in the cationic photopolymerizable photocurable resins sensitized in the visible light wavelength range of 400 nm or more have been disclosed in JP1994-043633A_(JP-H06-043633A) and JP1996-324137A(JP-H08-324137A).

[0161] A compound having a cyclic ether structure, such as an oxetane compound, an epoxy compound, and the like, is preferably contained as a cationically polymerizable compound. When the ink composition has a cyclic ether structure, an ink composition having improved dispersion stability of the aluminum metal pigments or the colorant, and excellent stability over time can be obtained.

[0162] An oxetane compound or an epoxy compound is preferably contained as a monofunctional monomer included in the cationically polymerizable compound, and only an oxetane compound is more preferably contained.

[0163] An oxetane compound or an epoxy compound is preferably contained as a polyfunctional monomer included in the cationically polymerizable compound, and only an oxetane compound is more preferably contained.

[0164] Preferred examples of the epoxy compound include aromatic epoxide, alicyclic epoxide, aliphatic epoxide, and the like. Examples of the aromatic epoxides include a di- or polyglycidyl ether produced via reaction of a polyvalent phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof with epichlorohydrin, and examples thereof include a di- or polyglycidyl ether of bisphenol A or an alkylene oxide adduct thereof, a di- or polyglycidyl ether of hydrogenated bisphenol A or an alkylene oxide adduct thereof, a novolac-based epoxy resin, and the like. Examples of the alkylene oxide mentioned herein include ethylene oxide, propylene oxide, and the like.

[0165] Preferable examples of the alicyclic epoxide include a compound including cyclohexene oxide or cyclopentene oxide that are obtained by epoxidating a compound having at least one cycloalkane ring such as a cyclohexene ring, a cyclopentene ring, and the like with an appropriate oxidizer such as hydrogen peroxide, a peracid, and the like.

[0166] Examples of the aliphatic epoxide include di- or poly-glycidyl ethers of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. Specific examples thereof include diglycidyl ethers of an alkylene glycol such as a diglycidyl ether of ethylene glycol, a diglycidyl ether of propylene glycol, and a diglycidyl ether of 1,6-hexanediol, a polyglycidyl ether of a polyhydric alcohol such as a di- or tri- glycidyl ether of glycerol or an alkylene oxide adduct thereof, a diglycidyl ether of a polyalkylene glycol such as a diglycidyl ether of polyethylene glycol or an alkylene oxide adduct thereof, a diglycidyl ether of polypropylene glycol or an alkylene oxide adduct thereof, and the like. Examples of the alkylene oxide mentioned herein include ethylene oxide, propylene oxide, and the like.

[0167] The monofunctional and polyfunctional epoxy compounds that can be used in the present invention will be exemplified in detail.

[0168] Examples of the monofunctional epoxy compound include phenyl glycidyl ether,
p-tert-butylphenyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl
glycidyl ether, 1,2-butylene oxide, 1,3-butadiene monooxide, 1,2-epoxydodecane,
epichlorohydrin, 1,2-epoxydecane, styrene oxide, cyclohexene oxide, 3-methacryloyloxymethylcyclohexene oxide, 3-acryloyloxymethylcyclohexene oxide, 3-vinylcyclohexene oxide, and 4-vinylcyclohexene oxide.

[0169] Furthermore, examples of the polyfunctional epoxy compounds include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether, epoxy novolac resins, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexenecarboxylate, 2-(3,4-epoxycyclohexyl)-5,5-spiro-3,4-epoxy)cyclohexane methadioxane, bis(3,4-epoxycyclohexylmethyl) adipate, bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate,
3,4-epoxy-6-methylcyclohexenyl-3',4'-epoxy-6'-methylcyclohexenecarboxylate,
methylenebis(3,4-epoxycyclohexane), dicyclopentadiene diepoxide,
di(3,4-epoxycyclohexylmethyl)ether of ethylene glycol, ethylene
bis(3,4-epoxycyclohexanecarboxylate), dioctyl epoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,13-tetradecadiene dioxide, limonene dioxide, 1,2,7,8-diepoxyoctane, 1,2,5,6-diepoxycyclooctane, and the like.

[0170] Among these epoxy compounds, the aromatic epoxides and the alicyclic epoxides are preferable from the viewpoint of an excellent curing speed, and the alicyclic epoxides are particularly preferable.

[0171] The oxetane compound refers to a compound having at least one oxetane ring and may be arbitrarily selected from known oxetane compounds such as those described in JP2001-220526A, JP2001-310937A, and JP2003-341217A, and used.

[0172] The oxetane compound that can be used in the present invention is preferably a compound having 1 to 4 oxetane rings in its structure. Use of such a compound enables the viscosity of the ink composition to be maintained in a range that gives ease of handling and enables high adhesion of the ink composition to a recording medium after curing to be obtained.

[0173] Examples of the compound having 1 to 2 oxetane rings in the molecule include the compounds represented by Formulae (1) to (3) below, and the like.

[0174]

[0175] Ral represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, an ally! group, ah aryl group, a furyl group, or a thienyl group. In the case where two R^'s are present in the molecule, they may be the same as or different from each other.

[0176] Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and the like, and preferable examples of the fluoroalkyl group include the alkyl group in which any one of the hydrogen atoms is substituted with a fluorine atom.

[0177] R*2 represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a group having ah aromatic ring, an alkylcarbonyl group having 2 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 6 carbon atoms, or an N-alkylcarbamoyl group having 2 to 6 carbon atoms. Examples of the alkenyl group include a 1-propenyl group, a 2-propenyl group, a 2-methyl-l-prppenyl group, a 2-methyl-2-propenyl group, a 1-butenyl grbup, a 2-butenyl group, a 3-butenyl group, and the like, and examples of the group having an aromatic ring include a phenyl group, a benzyl group, a fluorobenzyl group, a methoxybenzyl group, a phenoxyethyl group, and the like. Examples of the alkylcarbonyl group include an ethylcarbonyl group, a propylcarbonyl group, a butylcarbonyl group, and the like, examples of the alkoxycarbonyl group include an ethoxyearbonyl group, a propoxycarbonyl group, a butoxycarbonyl group, and the like, and examples of the N-alkylcarbamoyl group include an ethylcarbamoyl group, a propylcarbamoyl group, a butylcarbamoyl group, a pentylearbamoyl group, and the like. In addition, R*2 may have a substituent, and examples of the substituent include an alkyl group having 1 to 6 carbon atoms, and a fluorine atom.

[0178] R33 represents a linear or branched alkylene group, a linear or branched poly(alkyleneoxy) group, a linear or branched unsaturated hydrocarbon group, a carbonyl group, an alkylene group containing a carbonyl group, an alkylene group containing a carboxyl group, an alkylene group containing a carbamoyl group, or groups shown below. Examples of the alkylene group include an ethylene group, a propylene group, and a butylene group, and examples of the poly(alkyleneoxy) group include a poly(ethyleneoxy) group, a poly(propyleneoxy) group, and the like. Examples of the unsaturated hydrocarbon group include a propenylene group, a methylpropenylene group, a butenylene group, and the like.

[0179]

[0180] m the case where Ra3 is me polyvalent group above, Ra4 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, a halogen atom, a nitro group, a cyano group, a mercapto group, a lower alkpxycarbonyl group, a carboxyl group, or a carbonyl group.

[0181] Ra5 represents an oxygen atom, a methylene group, NH, SO, SQfc C(CF3)2, or C(CHj)2. [0182] Ra6 represents an alkyl group having 1 to 4 carbon atoms, or an aryl group, and n represents an integer of 0 to 2,000. Ra7 represents an alkyl group having 1 to 4 carbon atoms, an aryl group, or a monovalent group having the structure below. In the following formula, R48 represents an alkyl group having 1 to 4 carbon atoms, or an aryl group, and m represents an integer of 0 to 100.

[0183]

0[0184] Examples of the compound represented by Formula (1) include 3-ethyl-3-hydroxymethyloxetane (OXT-101: manufactured by Toagosei Cor, Ltd.), 3-emyl-3-(2-e%mexyloxymethyl)oxetane (QXT-212: manufactured by Toagosei Co., Ltd.), and 3-ethyl-3-phenoxymethyioxetane (OXT-211: manufactured by Toagosei Co., Ltd.). Examples of the compound represented by Formula (2) include
l,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene (OXT-121: manufactured by Toagosei Co., Ltd.). Further, examples of the compound represented by Formula (3) include bis(3-ethyl-3-oxetanyImethyl ether (OXT-221: manufactured by Toagosei Go., Ltd.), [0185] Examples of the compound having 3 to 4 oxetane rings in the molecule include a compound represented by Formula (4) as below.

[0186]

[0187] In Formula (4), R*1 is the same as that in Formula (1). Further, examples of R*9 which is a polyvalent linking group include a branched alkylene group having 1 to 12 carbon atoms, such as groups represented by A to C below, and the like, branched poly(alkyleneoxy) groups having 1 to 12 carbon atoms, such as a group represented by D, and the like, and a branched polysiloxy group, such as a group represented by E. j is 3 or 4.

[0188]

[0189] In the above A, Ral° represents a methyl group, an ethyl group, or a propyl group. Further, in D above, p is an integer of 1 to 10.

[0190] Furthermore, other embodiments of the oxetane compound that can be preferably used in the present invention include a group having an oxetane ring in the side chain, represented by the following formula (5).

[0191]

[0192] In Formula (5), Ral and R*8 are the same as in the Formulae above. Ral1 is an alkyl group having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a butyl groupr and the like, or a trialkylsilyl group, and r is 1 to 4.

[0193] Such compounds having oxetane rings are described in detail in Paragraph Nos. 0021 to 0084 of JP2Q03-341217A, and the compounds described therein can also be preferably used in the present invention.

[0194] The oxetane compound described in JP2004-091556A can also be used in the present invention, and described in detail in Paragraph Nos. 0022 to 0058 of JP2004-091556A.

[0195] Examples of the cationically polymerizable compound that is preferably used in the present invention are listed below.

[0196]

[0197]

[0198] The ink composition of an aspect of the present invention may contain a vinyl ether compound as a cationically polymerizable compound. Examples of the vinyl ether compound include di- or tri-vinyl ether compounds such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, trimethylolpropane trivinyl ether, and the like, and monovinyl ether compounds such as ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, eyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl vinyl ether, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl monovinyl ether, and the like.

[0199] Hereinafter, the monofunctional vinyl ether and the polyfunctional vinyl ether will be exemplified in detail.

[0200] Examples of the monofunctional vinyl ether include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, eyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, 4-methyl cyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethyl cyclohexylmethyl vinyl ether, diethylene glycol mono vinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenyl ethyl vinyl ether, phenoxy polyethylene glycol vinyl ether, and the like. [0201] Furthermore, examples of the polyfunctional vinyl ether include divinyl ethers such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide divinyl ether, and the like; and polyfunctional vinyl ethers such as trimethylol ethane trivinyl ether, trimethylblpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, an ethylene oxide adduct of trimethylolpropane trivinyl ether, a propylene oxide adduct of trimethylolpropane trivinyl ether, an ethylene oxide adduct of ditrimethylolpropane tetravinyl ether, a propylene oxide adduct of ditrimethylolpropane tetravinyl ether, an ethylene oxide adduct of pentaerythritol tetravinyl ether, a propylene oxide adduct of pentaerythritol tetravinyl ether, an ethylene oxide adduct of dipentaerythritol hexavinyl ether, a propylene oxide adduct of dipentaerythritol hexavinyl ether, and the like.

[0202] As the vinyl ether compound, a di- or tri-vinyl ether compound is preferable from the viewpoints of curability, adhesion with a recording medium, the surface hardness of the formed image, and the like, and a divinyl ether compound is particularly preferable

[0203] From the viewpoint of curability, the proportion of the polyfunctional monomer in the cationically polymerizable compound is preferably 15 to 99.9% by mass, more preferably 17 to 95% by mass, and still more preferably 20 to 90% by mass.

[0204] Furthermore, from the viewpoints of flexibility and metallic glossiness, the proportion of the monofunctional monomer in the cationically polymerizable compound is preferably 0.1 to 85% by mass, more preferably 5 to 83% by mass, and still more preferably 10 to 80% by mass.

[0205] The content of the cationically polymerizable compound in the ink composition is preferably 10 to 95% by mass, more preferably 30 to 90% by mass, and still more preferably 50 to 85% by mass, based on the total solid content of the ink composition.

[0206] (Cationic Photopolymerization Initiator)

[0207] The cationically polymerizable ink composition preferably contains a cationic photopolymerization initiator. The cationic photopolymerization initiator in the present invention is preferably a photoacid generator. Examples of the photoacid generator include the compounds used in chemically amplified photoresists or cationic photopolymerization (see pages 187 to 192 of "Organic Materials for Imaging" edited by The Japanese Research Association for Organic Electronics Materials and published by Bun-Shin Shuppan in 1993). Examples of the cationic polymerization initiator that is preferable in the present invention are as follows.

[0208] The photoacid generator used in the present invention is a compound that generates an acid by irradiation with active radiation. As the photoacid generator, any one may be appropriately selected and used from a photoinitiator of cationic photopolymerization, a photoinitiator of radical photopolymerization, a photo-achromatic agent, a photo-discoloring agent, and a compound that generates an acid by irradiation with light used for micro-resistors and the like (ultraviolet rays of 400 to 200 nm, far ultraviolet rays, g-line, h-line, i-line, and KrF excimer laser light), an ArF excimer laser light, an electron beam, X-rays, a molecular beam, an ion beam, or the like.

[0209] Examples of the photoacid generator include onium salt compounds such as a diazonium salt a phosphonium salt, a sutfonium salt, an iodonium salt, and the like, and sulfonate compounds such as imide sulfonate, oxime sulfonate, diazodisulfone, disulfone, o-nitrobenzylsulfonate, and the like, which generate an acid by irradiation with active radiation. Among these, onium salts are preferably used as the photoacid generator.

[0210] Preferable examples of the - photoacid generator that can be used in the present invention include compounds represented by the following formula (b1), (b2), or (b3).

[0211]

[0212] In Formula (b1), R201, R202, and R203 each independently represent an organic group. [0213] X" represents a non-nucleophilic anion, and preferable examples include a sulfuric acid anion, acarboxylie acid anion, a bis(alkylsulfonyl) amide anion, a tris(alkylsulfonyl)methide anion, BF4", PFe\ SbF, and the like. Rd1 represents a hydrogen atom or an alkyl group.

[0218] Re , Re4, and Re5 each independently represent an organic group. Preferable examples of the organic groups of Re3, Re4, and Re5 include the same ones as the organic group of Re , and most preferably, the organic group is a perfluoroalkyl group having 1 to 4 carbon atoms. Re3 and Re4 may be combined with each other to form a ring. Examples of the group formed by Re3 and Re4 combined with each other include an alkylene group and an allylene group, and preferably a perfluoroalkylene group having 2 to 4 carbon atoms.

[0219] The organic groups of Rcl, and Re3 to Re5 are most preferably an alkyl group having the first position substituted with a fluorine atom or a fluoroalkyl group, or a phenyl group substituted a fluorine atom or a fluoroalkyl group. By including a fluorine atom or a fluoroalkyl group, the acidity of the acid generated by light irradiation increases and the sensitivity is improved.

[0220] The organic groups of R201, R202, and R203 preferably have 1 to 30 carbon atoms, and more preferably 1 to 20 carbon atoms.

[0221] Furthermore, two of R201 to R203 may be combined with each other to form a ring structure, and R to R203 may contain an oxygen atom, a sulfur atom, an ester bond, an amide bond, or a carbonyl group. Examples of the group formed by combination of two of R201 to R203 with each other include an alkylene group (for example, a butylene group and a pentylene group).

[0222] Specific examples of the organic group as R201, R202, and R203 include the corresponding groups in the compounds (bl-1), (bl-2), and (bl-3) as described later.

[0223] Further, the photoacid generator may be a compound having a plurality of the structures represented by Formula (b1). For example, the photoacid generator may be a compound having a structure in which at least one of R201 to R203 in the compound represented by Formula (b1) is bonded directly or via a linking group to at least one of R'U1 to R™ in another compound represented by Formula (b1).

[0224] Further preferable examples of the (b1) component include the compounds (bl-1), (bl-2), and (bl-3) as described later.

[0225] The compound (bl-1) is an arylsulfonium compound in which at least one of R'U1 to R203 in the compound represented by Formula (b1) is an aryl group, that is, a compound having arylsulfonium as a cationic ion.

[0226] 1] In the arylsulfonium compound, all of R201 to R203 may be aryl groups, or a 0part of R to R may be an aryl group and the rest may be an alkyl group or a cycloalkyl group.

[0227] Examples of the arylsulfonium compound include a triarylsulfonium compound, a diarylalkylsulfonium compound, an aryldialkylsulfonium compound, a diarylcycloalkylsulfonium compound, an aryldicycloalkylsulfonium compound, and the like.

[0228] As the aryl group of the arylsulfonium compound, aryl groups such as a phenyl group, a naphthyl group, and the like, and heteroaryl groups such as an indole residue, a pyrrole residue, and the like are preferable, and a phenyl group and an indole residue are more preferable. In the case where the arylsulfonium compound has two or more aryl groups, two or more aryl groups may be the same as or different from each other.

[0229] As the alkyl group that the arylsulfonium compound may contain as necessary, a linear or branched alkyl group having 1 to 15 carbon atoms is preferable, and examples thereof include a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, a t-butyl group, and the like.

[0230] As examples of the cycloalkyl group which the arylsulfonium compound may contain as necessary, a cycloalkyl group having 3 to 15 carbon atoms is preferable, and examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclohexyl group, and the like.

[0231] The aryl group, the alkyl group, and the cycloalkyl group of R201 to R203 may contain an alkyl group (for example, having 1 to 15 carbon atoms), a cycloalkyl group (for example, having 3 to 15 carbon atoms), an aryl group (for example, having 6 to 14 carbon atoms), an alkoxyl group (for example, having 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, or a phenylthio group as a substituent The substituent is preferably a linear or branched alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a linear, branched, or cyclic alkoxyl group having 1 to 12 carbon atoms, and most preferably an alkyl group having 1 to 4 carbon atoms, or an alkoxyl group having 1 to 4 carbon atoms. The substituent may be substituted on any one of three of R201 to R203, or on all of them. Further, in the case where R201 to R203 are aryl groups, the substituent is preferably substituted on the p-position of the aryl group.

[0232] Next, the compound (bl-2) will be described.

[0233] The compound (bl-2) is a compound in which R201 to R203 in Formula (b1) each independently represent an organic group containing no aromatic ring. Here, the aromatic ring also includes an aromatic ring containing a hetero atom.

[0234] The organic group containing no aromatic ring as R201 to R203 generally contains 1 to 30 carbon atoms, and preferably 1 to 20 carbon atoms.

[0235] R201 to R203 each independently preferably represent an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group, more preferably, a linear, branched, or cyclic 2-oxoalkyl group, or an alkoxycarbonylmethyl group, and particularly preferably, a linear or branched 2-oxoalkyl group.

[0236] The alkyl group as R201 to R203 may be either linear or branched, and examples thereof preferably include a linear or branched alkyl group having 1 to 10 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group), and more preferably a linear or branched 2-oxoalkyl group, and an alkoxycarbonylmethyl group.

[0237] Examples of the cycloalkyl group as R201 to R203 preferably include a cycloalkyl group having 3 to 10 carbon atoms (a cyclopentyl group, a cyclohexyl group, and a norbornyl group), and more preferably a cyclic 2-oxoalkyl group.

[0238] Examples of the linear, branched, cyclic 2-oxoalkyl group of R201 to R203 preferably include groups having >C=0 on the 2-position of the alkyl group and the cycloalkyl group.

[0239] Examples of the alkoxy group in the alkoxycarbonylmethyl group as R to R preferably include an alkoxyl group having 1 to 5 carbon atoms (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a pentoxy group).

[0240] R201 to R203 may be further substituted with a halogen atom, an alkoxyl group (for example, having 1 to 5 carbon atoms), a hydroxyl group, a cyano group, or a nitro group.

[0241] The compound (bl-3) is a compound represented by Formula (b 1-3) below, and is also a compound having a phenacylsulfonium salt structure.

[0242]

[0243] In Formula (bl-3), Rlc to R5c each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxyl group, or a halogen atom.

[0244] R6c and R7c each independently represent a hydrogen atom, an alkyl group, or a cycloalkyl group.

[0245] Rx and Ry each independently represent an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group.

[0246] Any two or more of Rlc to R5c, R6c and R7c, and Rx and Ry may be each combined with one another to form a ring structure.

[0247] Zc" represents a non-nucleophilic anion, and examples thereof include the same one as the non-nucleophilic anion of X" in Formula (b1).

[0248] The alkyl group as Rlc to R7c may be either linear or branched, and preferable examples thereof include linear and branched alkyl groups (for example, a methyl group, an ethyl group, a linear or branched propyl group, a linear or branched butyl group, and a linear or branched pentyl group) having 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms.

[0249] Preferable examples of the cycloalkyl group as Rlc to R7c include cycloalkyl groups having 3 to 8 carbon atoms (for example, a cyclopentyl group and a cyclohexyl group).

[0250] The alkoxyl group as Rlc to R5c may be any type of linear, branched, and cyclic types, and examples thereof include alkoxyl groups having 1 to 10 carbon atoms, preferably linear and branched alkoxyl groups having 1 to 5 carbon atoms (for example, a methoxy group, an ethoxy group, a linear or branched propoxy group, a linear or branched butoxy group, and a linear or branched pentoxy group), and cyclic alkoxyl groups having 3 to 8 carbon atoms (for example, a cyclopentyloxy group and a eyclohexyloxy group).

[0251] Examples of the group formed by combination of any two or more of Rlc to R5c, R6c and R7c, and Rx and Ry include a butylene group, a pentylene group, and the like.

This ring structure may contain an oxygen atom, a sulfur atom, an ester bond, or an amide bond.

[0252] Any of Rlc to R5c is preferably a linear or branched alkyl group, a cycloalkyl group, or a linear, branched, or cyclic alkoxyl group, and still more preferably the sum of the carbon atoms of Rlc through R5c is 2 to 15. By this, the solvent solubility is further improved and generation of particles during storage is inhibited, which is thus preferable.

[0253] Examples of the alkyl group and the cycloalkyl group as Rx and Ry include the same ones as the alkyl group and the cycloalkyl group for Rlc to R7c. [0254] Rx and Ry are preferably a 2-oxoalkyl group or an alkoxycarbonylmethyl group. [0255] Examples of the 2-oxoalkyl group include groups having >C=0 on the 2-position of the alkyl group and the cycloalkyl group as Rlc to R5c.

[0256] Examples of the alkoxy group in the alkoxycarbonylmethyl group include the same ones as the alkoxyl group for Rlc to R5c.

[0257] Rx and Ry are preferably an alkyl group and a cycloalkyl group, having 4 or more carbon atoms, more preferably having 6 or more carbon atoms, and still more preferably an alkyl group and a cycloalkyl group, having 8 or more carbon atoms.

[0258] In Formulae (b2) and (b3), R204 to R207 each independently represent an aryl group, an alkyl group, or a cycloalkyl group. X' represents a non-nucleophilic anion, and examples thereof include the same ones as the non-nucleophilic anion of X' in Formula (b1).

[0259] The aryl group of R204 to R207 is preferably a phenyl group and a naphthyl group, and more preferably a phenyl group.

[0260] The alkyl group as R204 to R207 may be either linear or branched, and preferable examples thereof include linear or branched alkyl groups having 1 to 10 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group). Preferable examples of the cycloalkyl group as R204 to R207 include cycloalkyl groups having 3 to 10 carbon atoms (a cyclopentyl group, a cyclohexyl group, and a norbornyl group).

[0261] Examples of the substituent that R204 to R207 may contain include an alkyl group (for example, having 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), an aryl group (for example, having 6 to 15 carbon atoms), an alkoxyl group (for example, having 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, a phenylthio group, and the like.

[0262] Furthermore, R204 and R205, or R206 and R207 may be combined to form a ring structure, and they may contain an oxygen atom, a sulfur atom, an ester bond, an amide bond, or a carbonyl group. Examples of the group formed by combination of R204 and R205, and R206 and R207 include alkylene groups (for example, a butylene group and a pentylene group).

[0263] Further, the photoacid generator may be a compound having a plurality of the structures represented by Formula (b2) or (b3). For example, they may be a compound having a structure in which at least one of R204 or R205 in the compound represented by Formula (b2) is bonded directly or via a linking group to at least one of R204 or R205 in another compound represented by Formula (b2).

[0264] Examples of the photoacid generator include compounds represented by the following formulae (b4)s (b5), and (b6).

[0265]

[0266] In Formulae (b4) to (b6), Ar3 and Ar4 each independently represent an aryl group.
[0267] R206, R207, and R208 each independently represent an alkyl group, a cycloalkyl group, an aryl group, or a cyano group.

[0268] A represents an alkylene group, alkenylene group, or an allylene group.

[0269] Ar3 and Ar4, R206 to R208, and A may contain a substituent, and examples thereof include alkyl groups (for example, having 1 to 15 carbon atoms), cycloalkyl groups (for example, having 3 to 15 carbon atoms), aryl groups (for example, having 6 to 15 carbon atoms), alkoxyl groups (for example, having 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, a phenylthio group, and the like.

[0270] Further, the photoacid generator may be a compound having a plurality of the structures represented by Formulae (b4) to (b6). For example, they may be a compound having a structure in which at least one of R206 to R208 in the compound represented by
Formula (b6) is bonded directly or via a linking group to at least one ofR206 to R208 in another compound represented by Formula (b6).

[0271] Among the above-described photoacid generators, preferable examples thereof include compounds represented by Formulae (b1)to (b3).

[0272] Preferable examples of the photoacid generator that can be used in the present invention include those described in JP2010-1QQ833A [(b-1) to (b-96)], but the present invention is not limited thereto.

[0273] Further, the oxazole derivatives, the s-triazine derivatives, and the like described in Paragraph Nos. 0029 to 0030 of JP2002-122994A may also be preferably used.

[0274] In ddition, the onium salt compounds and the sulfonate-based compounds exemplified in Paragraph Nos. 0037 to 0063 of JP2002-122994A may also be preferably used in the present invention.

[0275] In the present invention, as the photoacid generator, a sulfonium salt is preferable, a compound represented by Formula (b1) is more preferable, and an arylsulfonium compound corresponding to the compound (bl-1) is still more preferable.

[0276] The photoacid generator may be used singly or in combination of two or more kinds thereof.

[0277] The content of the photoacid generator in the ink composition is preferably 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass, relative to the ink composition. Within the above-described range, the ink composition can be sufficiently cured and the uniformity in curability is excellent

[0278] Furthermore, in the present invention, in the case where a sensitizer as described later is used in the ink composition, the total amount of the polymerization initiator to be used relative to the sensitizer is one such that the mass ratio of the polymerization initiator:sensitizer is preferably 200:1 to 1:200, more preferably 50:1 to 1:50, and still more preferably 20:1 to 1:5.

[0279] In the present invention, a sensitizer may be added to the ink composition for the purpose of absorbing a specific actinic energy ray to promote the decomposition of the photoacid generator.

[0280] The sensitizer absorbs the specific actinic energy ray and attains an electronically excited state. The sensitizer in the electronically excited state contacts with a photoacid generator to cause the actions of electron transfer, energy shift, heat generation, and the like. By this, the photoacid generator attains chemical modification and decomposition to generate acids or cations.

[0281] Preferred examples of the sensitizer include those that belong to compounds below and have an adsorption wavelength in the region of 350 nm to 450 nm.

[0282] Polynuclear aromatic compounds (for example, anthracene, 9,10-dialkoxyanthracene, pyrene, perylene, triphenylene), xanthenes (for example, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (for example, thiacarbocyanine, oxacarbocyanine), merocyanines (for example, merocyanine, carbomerocyanine), thiazines (for example, thionine, methylene blue, toluidine blue), acridines (for example, acridine orange, chloroflavin, acriflavine), anthraquinones (for example, anthraquinone), squaryliums (for example, squarylium), and coumarins (for example, 7-ctiethylamino-4-methylcoumarin).

[0283] Further, more preferable examples of the sensitizer include the compounds represented by the following formulae (DC) to (XIII),

[0284]

[0285] In Formula (IX), A1 represents a sulfur atom or NR50, R50 represents an alkyl group or an aryl group, L2 represents a non-metallic atomic group that forms a basic nucleus of a dye in cooperation with a neighboring A1 and the neighboring carbon atom R51 and R52 each independently represent a hydrogen atom or a monovalent non-metallic atomic group, and R51 and R52 may be combined with each other to form an acidic nucleus of a dye. W represents an oxygen atom or a sulfur atom.

[0286]

[0287] In Formula (X), Ar1 and Ar2 each independently represent an aryl group and are connected to each other via a bond of -L3-. Here, L3 represents -O- or -S-. Further, W has the same meaning as that shown in Formula (EX).

[0288]

[0289] In Formula (XI), A2 represents a sulfur atom or NR59, L4 represents a non-metallic atomic group that forms a basic nucleus of a dye in cooperation with the neighboring A2 and carbon atom, R53, R54, R55, R56, R57, and R58 each independently represent a monovalent non-metallic atomic group, and R59 represents an alkyl group or an aryl group.

[0290]

[0291] In Formula (XII), A3 and A4 each independently represent -S-, -NR62-, or -NR63-, R62 and R63 each independently represent a substituted or unsubstituted alkyl group, of a substituted or unsubstituted aryl group, L5 and L6 each independently represent a non-metallic atomic group that forms a basic nucleus of a dye in cooperation with the neighboring A3 and A and neighboring carbon atom, and R60 and R61 each independently represent a hydrogen atom or a monovalent non-metallic atomic group, or are combined with each other to form an aliphatic or aromatic ring. [0292]

[0293] In Formula (XIH), R66 represents an aromatic ring or a hetero ring, which may have a substituent, and A5 represents an oxygen atom, a sulfur atom, or -NR-7-. R64, R65, and R67 each independently represent a hydrogen atom or a monovalent non-metallic atomic group, and R67 and R64, and R65 and R^ may be combined with each other to form an aliphatic or aromatic ring.

[0294] Specific preferable examples of the compounds represented by Formulae (IX) to (XIII) include (E-l) to (E-20) described in JP2010-100833 A.

[0295] In the present invention, the content of the sensitizer in the ink composition is appropriately selected according to the intended purpose, and is generally preferably 0.05 to 4% by mass, relative to the total mass of the ink composition.

[0296]

[0297] In the present invention, the ink composition preferably contains a cosensitizer (which may also be sometimes referred to as a "co-sensilizer" or a "supersensitizer"). In the present invention, the supersensitizer has a function of further improving the sensitivity of the sensitizing dye to active radiation and a function of suppressing inhibition by oxygen of polymerization of the polymerizable compound, and the like.

[0298] Examples of such a supersensitizer include amines such as compounds described in M. R. Sander et aL, Journal of Polymer Society, Vol. 10, p. 3173 (1972), JP1969-020189B (JP-S44-020189B),JP1976-082102A(JP-S51-082102A),JP1977-134692A(JP-S52-134692A), JP1984-138205A (JP-S59-138205A), JP1985-084305A (JP-S60-084305A), JP1987-018537A (JP-S62-018537A), JP1989-033104A(JP-S64-033104A), and Research Disclosure No. 33825, and the like.

[0299] Specific examples thereof include triethanolamine, ethyl p-dimethylaminobenzoate, p-formyldimethylaniline, p-methylthiodimethylaniline, and the like.

[0300] Other examples of the supersensitizer include thiols and sulfides, for example, thiol compounds described in JP 1978-000702 A (JP-S53-000702A), JP 1980-500806 A (JP-S55-500806A), and JP1993-142772A (JP-H05-142772A), disulfide compounds of JP1981-075643A(JP-S56-075643A), and the like.

[0301] Specific examples thereof include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4(3H)-quinazoline, P-mercaptonaphthalene, and the like.

[0302] Yet other examples of the supersensitizer include amino acid compounds (for example, N-phenylglycine and the like), organometallic compounds described in JP1973-042965B (JP-S48-042965B) (for example, tributyltin acetate and the like), hydrogen-donating compounds described in JP1980-034414B (JP-S55-034414B), sulfur compounds described in JP1994-308727A (JP-H06-308727A) (for example, trithiane and the like), phosphorus compounds described in JP 1994-2503 87A(JP-H06-2503 87A) (diethylphosphite and the like), Si-H and Ge-H compounds described in JP1996-054735A(JP-H08-054735A), and the like.

[0303] The content of the supersensitizer in the ink composition is appropriately selected according to the intended purpose, and is preferably 0.05 to 4% by mass relative to the total mass of the ink composition.

[0304] In the cationically polymerizable ink composition, a colorant, a dispersant, a surfactant, or other components may be preferably used, in addition to the aluminum metal pigments used in the radically polymerizable ink composition.

[0305] Properties of Ink

[0306] In the present invention, the ink composition has a viscosity at 25 °C of preferably not more than 40 mPa-s, more preferably 5 to 40 mPa-s, and still more preferably 7 to 30 mPa-s. Furthermore, the viscosity of the ink composition at the discharge temperature (preferably 25 to 80°C, and more preferably 25 to 50°C) is preferably 3 to 15 mPas, and more preferably 3 to 13 mPa-s. With regard to the ink composition, it is preferable that its component ratio be appropriately adjusted so that the viscosity is in the above-mentioned range. When the viscosity at room temperature is set to be high, even when a porous recording medium is used, penetration of the ink composition into the recording medium can be prevented, and uncured monomer can be reduced. In addition, ink spreading when ink droplets of the ink composition have landed can be suppressed, and as a result there is the advantage that the image quality is improved.

[0307] The surface tension of the ink composition at 25°C is preferably 20 to 35 mN/m, and more preferably 23 to 33 mN/m. When recording is carried out on various types of recording medium such as polyolefin, PET, coated paper, and uncoated paper, from the viewpoint of spread and penetration, it is preferably 20 mN/m or more, and from the viewpoint of wettability, it is preferably 35 mN/m or less.

[0308] IV. Ink Set

[0309] The ink set preferably contains at least one ink composition A containing an aluminum metal pigments and at least one ink composition B containing a colorant other than the aluminum metal pigments.

[0310] In the present invention, it is preferable that the ink set contain at least one ink composition B having colors selected from cyan, magenta, yellow, black, white, light magenta, and light cyan, in addition to the ink composition A, and the ink set more preferably has at least cyan, magenta, or yellow, and still more preferably, cyan, magenta, yellow, black, or white. Further, the ink set can be preferably used in the inkjet recording method of an aspect of the present invention.

[0311] V. Inkjet Recording Method and Printed Material

[0312] The inkjet recording method of an aspect of the present invention may include the steps of:

image forming step A in which an ink composition A containing aluminum metal pigments is discharged through nozzles having a nozzle diameter of 30 m or more and 100 urn or less to form an image on a recording medium;

curing step A in which the discharged ink composition A is irradiated with active radiation to carry out curing;
image forming step B in which an ink composition B containing pigments other than aluminum metal pigments is discharged through nozzles having a nozzle diameter of 10 urn or

more and less than 30 um to form an image on a recording medium; and
curing step B in which the discharged ink composition B is irradiated with active radiation to carry out curing.

[0313] In the present invention, the image forming step A, the curing step A, the image forming step B, and the curing step B may be provided in this order, or alternatively, curing step A and curing step B may be carried in one step after the image forming step A and the image forming step B.

[0314] Furthermore, the print material of an aspect of the present invention may be obtained by the inkjet recording method of an aspect of the present invention, and each of the steps will be described.

[0315] (Image forming step A)

[0316] The inkjet recording method of an aspect of the present invention includes image forming step A in which an ink composition A containing aluminum metal pigments is discharged through nozzles having a nozzle diameter of 30 fim or more and 100 um or less to form an image on a recording medium.

[0317] In the present invention, the recording medium is not particularly limited, and a recording medium known as a support or a recording material may be used. Examples thereof include paper, paper laminated with a plastic (for example, polyethylene, polypropylene, polystyrene, and the like), a metal plate (for example, aluminum, zinc, copper, and the like), a plastic film (for example, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinylacetal, and the like), paper or plastic film laminated or vapor-deposited with the above metal, and the like.

[0318] The inkjet recording device used in the image forming step A is not particularly limited, and any known inkjet recording device that can achieve an intended resolution may be used.

[0319] Examples of the inkjet recording device that can be used in the present invention include devices equipped with, for example, an ink supply system, a temperature sensor, and an active radiation source.

[0320] The ink supply system includes, for example, a main tank containing the ink composition A, a supply pipe, an ink supply tank for the ink composition A immediately before an inkjet head, a filter, and a piezo system inkjet head. The piezo system inkjet head may be driven so as to discharge a multisize dot of preferably 1 to 100 pL, more preferably 3 to 42 pL, and still more preferably 8 to 30 pL, at a resolution of preferably 320X320 to 4,000X4,000 dpi, and more preferably 400X400 to 1,600X1,600 dpi. Here, dpi as mentioned in the present invention refers to the number of dots per 2.54 cm.

[0321] It is preferable to blend aluminum metal pigments having a large size with the ink composition A in order to obtain an image having excellent metallic gloss.

[0322] Furthermore, in the image forming step A, the opening (discharge opening) of the nozzle for discharging the ink composition A of an aspect of the present invention has a diameter of 30 to 100 um. If the diameter of the opening of the nozzle is less than 30 urn, the metallic glossiness decreases. Further, if the diameter of the opening of the nozzle is more than 100 urn, the discharging stability decreases. The diameter of the opening of the nozzle is preferably 31 to 95 um, and more preferably 32 to 90 um. Within the range of the numerical values above, an image having an excellent dischargeability and metallic gloss can be obtained.

[0323] The shape of the opening of the nozzle is not limited to a circular shape, and for example, circular, elliptical, and polygonal shapes may also be included, hi the case of the opening that is not circular, the diameter of the opening of the nozzle means a diameter of a circle corresponding to the area of the opening of the nozzle.

[0324] In the present invention, since it is preferable to keep the ink composition A discharged at a certain temperature, the supply tank for the ink composition A through the inkjet head can be insulated or heated. The method for controlling the temperature is not particularly limited, but it is preferable to a provide plural temperature sensors at each piping portion, and control the heating in accordance with the flow rate of the ink composition A or the environmental temperature. The temperature sensor may be equipped around the supply tank for the ink composition A and the nozzle of the inkjet head. Further, the head unit heated is preferably thermally blocked or insulated so that the inkjet recording apparatus itself may not be affected by the external temperature. In order to shorten the time for a printer to start up that is necessary for heating, or to reduce the amount of loss of thermal energy, it is preferred to reduce the heat capacity of the whole heating unit, as well as insulating the same from other members.

[0325] Typically, the ink composition A used in the present invention exhibits a higher viscosity as compared with an ordinary aqueous ink composition that is a usually used as an inkjet recording ink composition, and thus, exhibits a greater range of change in viscosity caused by the change in temperature during discharging. Since the change in viscosity of the ink composition directly exerts a great influence on the size and the discharge speed of the droplets, it may become a cause of degradation in image quality. Accordingly, it is necessary to keep the temperature of the ink composition A as constant as possible during image recording (printing). The range in which the temperature of the ink composition A is to be controlled is preferably ±5°C from the set temperature, more preferably ±2°C from the set temperature, and still more preferably ±1°C from the set temperature. [0326] (Curing step A)

[0327] Next, the curing step A will be described.

[0328] The inkjet recording method of an aspect of the present invention includes curing step A in which the discharged ink composition A is cured by irradiation with active radiation.

[0329] The ink composition A discharged onto the recording medium is cured by irradiation with active radiation. This is due to a polymerization initiating species such as acids, cations, and the like being generated by decomposition of the polymerization initiator contained in the ink composition A of the present invention by irradiation with active radiation, in which the initiating species functions so as to make a polymerization reaction of a polymerizable compound take place and to promote it. At this time, if a sensitizing colorant is present together with the polymerization initiator in the ink composition A, the sensitizing colorant in the system absorbs active radiation, becomes excited, and promotes decomposition of the polymerization initiator by contact with the polymerization initiator, thus enabling a curing reaction with higher sensitivity to be achieved.

[0330] As the active radiation used herein, a rays, y rays, an electron beam, X rays, UV rays, visible light, IR rays, or the like may be used. Although it depends on the absorption characteristics of the sensitizing dye, the peak wavelength of the active radiation is, for example, preferably 200 to 600 nm, more preferably 300 to 450 nm, and still more preferably 350 to 420 nm.

[0331] Furthermore, in the present invention, the polymerization initiation system of the ink composition A of an aspect of the present invention has sufficient sensitivity for low output active radiation. Curing is preferably carried out at an illumination intensity on the exposed surface of preferably 500 to 3,000 mW/cm2, and more preferably 1,000 to 2,500 mW/cm2.

[0332] As an active radiation source, a mercury lamp, a gas/solid laser, or the like is mainly used, and as a light source used for an ultraviolet ray photocuring inkjet ink composition, a mercury lamp and a metal halide lamp are widely known. However, from the viewpoint of protection of the environment, there has recently been a strong desire for mercury not to be used, and replacement by a GaN-based semiconductor ultraviolet ray-emitting device is very useful from industrial and environmental viewpoints. Furthermore, LEDs (UV-LED) and LDs (UV-LD) have small dimensions, long life, high efficiency, and low cost, and their use as a photocuring inkjet light source can be expected.

[0333] Furthermore, light-emitting diodes (LED) and laser diodes (LD) may be used as an active radiation source. In particular, when an ultraviolet ray source is needed, an ultraviolet ray LED or an ultraviolet LD may be used. For example, Nichia Corporation has marketed a violet LED having a wavelength of the main emission spectrum of between 365 ran and 420 nm. Furthermore, when a shorter wavelength is needed, US6084250A discloses an LED that can emit active radiation whose wavelength is centered between 300 nm and 370 nm. Furthermore, other violet LEDs are available, and irradiation can be carried out with radiation of a different UV bandwidth. The active radiation source that is preferable in the present invention is a UV-LED, and a UV-LED having a peak wavelength at 350 to 420 nm is particularly preferable.

[0334] The ink composition A is desirably irradiated with such active radiation for preferably 0.01 to 120 seconds, more preferably 0.1 to 90 seconds, and still more preferably 0.01 to 10 seconds.

[0335] Furthermore, in the inkjet recording method of an aspect of the present invention, after the ink composition A is discharged, the ink composition A is preferably cured by irradiation with active radiation at an illumination intensity on the exposed surface of 2,000 mW/cm2 or less for 0.001 to 10 seconds

[0336] The irradiation conditions and the basic method for irradiation with active radiation are disclosed in JP1985-132767A(JP-S60-132767A). Specifically, a light source is provided on either side of a head unit that includes an ink discharge device of the ink composition A, and the head unit and the light source are made to scan by a so-called shuttle system. Irradiation with active radiation is carried out after a certain time (preferably 0.01 to 0.5 seconds, more preferably 0.01 to 0.3 seconds, and still more preferably 0.01 to 0.15 seconds) has elapsed from when the ink composition A has landed. By controlling the time from the ink composition A landing to irradiation so as to be a minimum in this way, it becomes possible to prevent the ink composition A that has landed on a recording medium from spreading before being cured. Furthermore, since the ink composition A can be exposed before it reaches a deep area of a porous recording medium that the light source cannot reach, it is possible to prevent the unreacted monomers from remaining, which is thus preferable.

[0337] In addition, curing may be completed using another light source that is not driven.

The pamphlet of WO99/054415A discloses, as an irradiation method, a method employing an optical fiber and a method in which a collimated light source is incident on a mirror surface provided on a head unit side face, and a recorded area is irradiated with UV light. Such a curing method can also be employed in the inkjet recording method of an aspect of the present invention.

[0338] By employing the above-mentioned inkjet recording method, it is possible to keep the diameter of landed ink composition A dots constant even for various recording media having different surface wettability, thus improving the image quality.

[0339] (Image forming step B)

[0340] The inkjet recording method of an aspect of the present invention includes image forming step B in which an ink composition B containing a colorant other than the aluminum metal pigments is discharged through nozzles having a nozzle diameter of 10 Jim or more and less than 30 fim to form an image on a recording medium. Hereinafter, only the differences thereof from the image forming step A will be described, and the remainder is the same as the image forming step A.

[0341] A piezo system inkjet head for discharging the ink composition B may be driven so as to discharge a muhisize dot of preferably 1 to 100 pL, more preferably 3 to 42 pL> and still more preferably 8 to 30 pL, at a resolution of preferably 320X320 to 4,000X4,000 dpi, and more preferably 400 X 400 to 1,600 X 1,600 dpi.

[0342] In the image forming step B, the diameter of the opening of the nozzle (discharging opening) for discharging the ink composition B is 10 Jim or more and less than 30 jam. If the diameter of the opening of the nozzle (discharging opening) is less than 10 Jim, the discharging stability decreases. Further, if the diameter of the opening of the nozzle (discharging opening) is more than 30 Jim, control of the amount of the liquid droplets and the image quality decrease. The diameter of the opening of the nozzle (discharging opening) is preferably 12.5 to 29 Jim, and more preferably 15 to 28 Jim. Within the above-described ranges of the numerical values, there is no case where the nozzle of the inkjet head is clogged, and therefore, a high-precision image having an excellent dischargeability can be obtained.

[0343] The shape of the opening of the nozzle is not limited to a circular shape, and for example, circular, elliptical, and polygonal shapes may also be included. In the case of the opening that is not circular, the diameter of the opening of the nozzle means a diameter of a circle corresponding to the area of the opening of the nozzle. [0344] (Curing step B)

[0345] The inkjet recording method of an aspect of the present invention includes curing step B in which the discharged ink composition B is irradiated with active radiation to carry out curing. The condition for the curing step B is the same as for the curing step A.

[0346] (Sequence of Respective Steps)

[0347] In order to obtain a color image, the colors are repeated in order from one having low brightness. By repeating the ink composition having low brightness in order, radiation easily reaches the lower part of the ink composition, and it is expected to attain good curing sensitivity, reduction in residual monomers, and improvement of adhesion. Further, irradiation can be carried about with exposure focused on one portion while discharging all of the colors. However, it is preferable to expose each one of the colors from the viewpoint of promotion of curing.

[0348] In the inkjet recording method of an aspect of the present invention, an ink set can be preferably used. The sequence of the respective coloring ink compositions discharged is not particularly limited, but it is preferable to impart them, starting from an ink composition having low brightness on a recording medium. In the case of using the ink composition A, and the yellow, cyan, magenta, and black ink compositions B, the ink composition A—^yellow—»cyan—>magenta—>black are preferably imparted on the recording medium. Further, in the case of additionally using white, white—»the ink composition A—^yellow—»cyan—»magenta-»black are preferably imparted on the recording medium. Further, the present invention is not limited to these, an ink set including the ink compositions B of at least light cyan and light magenta and the dark color ink compositions B of cyan, magenta, black, white, and yellow may also be used, and in this case, white-*the ink composition A-»light cyan—flight magenta-»yellow-»cyan—»magenta-»black are preferably imparted on the recording medium.

[0349] VI. METHOD FOR PRODUCING MOLD PRINT MATERIAL [0350] The method for producing the mold print material of an aspect of the present invention may include the steps of:

image forming step A in which an ink composition A containing aluminum metal pigments is discharged through nozzles having a nozzle diameter of 30 Jim or more and
100 m or less to form an image on a recording medium;

curing step A in which the discharged ink composition A is irradiated with active radiation to carry out curing;

image forming step B in which an ink composition B containing pigments other than aluminum metal pigments is discharged through nozzles having a nozzle diameter of 10 urn or more and less than 30 urn to form an image on a recording medium;

curing step B in which the discharged ink composition B is irradiated with active radiation to carry out curing, and

molding processing in which the recording medium having the cured image is molded on the recording medium.

[0351] Furthermore, the mold print material of an aspect of the present invention may be obtained by the method for producing the mold print material.

[0352] (Image forming step A, Curing step A, Image forming step B, and Curing step B)

[0353] In the method for producing the mold print material of an aspect of the present invention, the image forming step A, the curing step A, the image forming step B, and the curing step B are the same as the image forming step A, the curing step A, the image forming step B, and the curing step B of the inkjet recording method of an aspect of the present invention, but a recording medium that is preferably used in the method for producing the mold print material of an aspect of the present invention will be described.

[0354] The recording medium that can be used in the method for producing the mold print material of an aspect of the present invention is not particularly limited, but a known recording medium which is suitable for the molding processing can be used. Specific examples thereof include polyolefin-based resins such as polyethylene, polypropylene, polymethylpentene, polybutene, an olefin-based thermoplastic elastomer, and the like, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, a terephthalic acid-isophthalic acid-ethylene glycol copolymer, a terephthalic acid-ethylene glycol- 1,4-cyclohexanedimethanol copolymer, a polyester-based thermoplastic elastomer, and the like, polyamide resins such as nylon 6, nylon 9, nylon 6,6, and the like, fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene trifluoride, an ethylene-ethylene tetrafluoride copolymer, polyethylene tetrafluoride, and the like, acrylic-based resins, polyvinyl chloride, polystyrene, polycarbonate resins, and the like.

[0355] With regard to the acrylic-based resin, for example, a resin such as polymethyl (meth)acrylate, polyethyl (meth)acrylate, polybutyl (meth)acrylate, a methyl (meth)acrylate-butyl (meth)acrylate copolymer, an ethyl (meth)acrylate-butyl (meth)acrylate copolymer, a methyl (meth)acrylate-styrene copolymer, and the like may be used singly or in combination of two or more kinds thereof.

[0356] Among these, from the viewpoint of decorative printing being easy and various resistance properties of a finished mold print material being excellent, it is preferable to us sheets of polyethylene terephthalaie, a polycarbonate resin, or a resin formed by blending a polycarbonate resin with another resin, and further, the sheets of a polycarbonate resin and a resin formed by blending a polycarbonate resin with another resin are preferable. In addition, the recording medium may be singular or a laminate formed by lamination of two or more resin sheets.

[0357] The thickness of the recording medium in the present invention (the total thickness in the case of a laminate) is not particularly limited as long as it is a resin sheet having a thickness in a range that allows vacuum and pressure molding that employs the principles of embossing processing, vacuum molding, pressure molding, and vacuum/pressure molding to be carried out, and it is preferably 50 to 2,000 (im, more preferably 100 to 1,500 m, and still more preferably 150 to 1,000 xa.

[0358] It is possible to add an appropriate additive to the thermoplastic resin sheets, as necessary. As the additive, various types of additive may be added in an appropriate amount such that they do not impair the surface gloss or thermal behavior such as a melting point and the like. Examples thereof include ultraviolet ray absorbers such as a benzotriazole-based ultraviolet ray absorber, a benzophenone-based ultraviolet ray absorber, and the like, light stabilizers such as a hindered amine-based radical scavenger and the like, lubricants such as a silicone resin, a wax, and the like, a colorant, a plasticizer, a heat stabilizer, an antimicrobial agent, an anti-mold agent, an antistatic agent, and the like.

[0359] The mold print material of an aspect of the present invention may be produced by subjecting the thermoplastic resin sheet to vacuum molding, and the like, and an image is formed on the recording medium by the inkjet method prior to molding.

[0360] An image is generally formed on the reverse side of a transparent sheet (side facing the mold in vacuum molding), but an image may also be formed on the opposite side. It is also possible to form an image only on the opposite side depending on the circumstances, and in this case the thermoplastic resin sheet used as a substrate is not necessarily transparent.

[0361] (Molding Processing Process)

[0362] The method for producing the mold print material of an aspect of the present invention includes molding processing in which the recording medium having the cured image is subjected to molding processing.

[0363] For the molding processing, embossing processing, vacuum molding, pressure molding, or vacuum/pressure molding can be used. As a device for molding processing of the print material, a known device may be used, and it may be a device integrated with the inkjet recording device or a device different therefrom.

[0364] Embossing processing is a process in which a three-dimensional feel is given by indenting a print material and the like in a desired shape such as a pattern, a letter, and the like, and may be carried out using a roller, a press, or the like. Examples of the embossing processing include a hot/cold pressing method, and a method described in JP1998-199360A(JP-H10-199360A), and the like may be referred to. One example of an embossing molding device employing the hot/cold pressing method is shown below. In the embossing molding device, a lower platen and an upper platen are disposed so that they can move toward and away from each other. A plate-shaped heater is fixed on top of the lower platen, and a plate-shaped heater is also fixed to a lower face of the upper platen. This enables a recording medium to be hot pressed while it is heated. In this hot pressing machine, the plate-shaped heater on the lower platen is equipped with a mold having a projection following a predetermined embossing shape, and a mold having a recess that conforms to the shape of the projection is mounted so as to be in contact with the heater fixed to the lower face of the upper platen. A recording medium having an image formed thereon is positioned, a cushion sheet is placed between the recording medium and the mold with the recess, and the recording medium and the cushion sheet are pressed between the upper platen and the lower platen by lowering the upper platen, and the like. A pressure applied in this hot pressing step is, for example, 30 tons, and the heating temperature from the plate-shaped heater is, for example, 170°C. The upper platen is pressed against the lower platen, the recording medium and the cushion sheet are sandwiched between the molds, and this hot pressing is maintained for about 3 minutes. The recording medium is heated by the heaters via the molds, and a plurality of projections are formed due to thermal deformation. Subsequently, the recording medium and the cushion sheet sandwiched between the molds are subjected to cold pressing by placing them between internally water-cooled platens without heaters and applying a pressure of, for example, 30 tonnes by pressing the platens for about 3 minutes. This enables an embossed mold print material to be obtained in which the recording medium has a projecting shape due to thermal deformation by the hot pressing. The pressure applied and the heating temperature may be adjusted appropriately according to the material of the print material and conditions such as the shape that is to be formed, and the like.

[0365] Vacuum molding is a method in which a recording medium having an image formed thereon is preheated to a temperature at which it can be thermally deformed, and molding is carried out by pressing it against a mold and cooling while sucking it toward the mold by means of vacuum and stretching it; pressure molding is a method in which a recording medium having an image formed thereon is preheated to a temperature at which it can be thermally deformed, and molding is carried out by pressing it against a mold by applying pressure from the side opposite to the mold and cooling. Vacuum/pressure molding is a method in which molding is carried out by applying a vacuum and pressure at the same time. In detail, the "Thermal Molding" section described on p. 766 to 768 of Kobunshi Daijiten (Polymer Dictionary) (Maruzen) and publications cited in the section may be referred to. Examples

[0366] Examples and Comparative Examples are presented below, and the present invention will be described in more detail with reference thereto. However, the present invention is not limited to these Examples. Further, in the following description, "partes)" and "%" represent "part(s) by weight" and "% by weight", respectively, unless otherwise specified.

[0367] (Preparation of Aluminum Metal Pigment Mill Base All) Aluminum metal pigment (ROTOVARJO 500 022, aluminum flake pigment paste, manufactured by Eckart) 50 parts (solid content) NPGPODA (propoxylated neopentyl glycol diacrylate) 40 parts SOLSPERSE 36000 (manufactured by Lubrizol Corporation) 10 parts The above components were stirred to give a metal pigment mill base All. Further, preparation of the pigment mill base was carried out by putting it into a dispenser motor mill M50 (manufactured by Eiger) and dispersing using zirconia beads having a diameter of 0.65 mm at a peripheral speed of 9 m/s for 9 hours.

[0368] (Preparation of Aluminum Metal Pigment Mill Base A12) Aluminum metal pigment (ROTOVARJO 500 022, aluminum flake pigment paste, manufactured by Eckart) 50 parts (solid content) NPGPODA (propoxylated neopentyl glycol diacrylate) 40 parts SOLSPERSE 36000 (manufactured by Lubrizol Corporation) 10 parts The above components were stirred to give a metal pigment mill base A12. Further, preparation of the pigment mill base was carried out by putting it into a dispenser motor mill M50 (manufactured by Eiger) and dispersing using zirconia beads having a diameter of 0.65 mm at a peripheral speed of 9 m/s for 48 hours.

[0369] (Preparation of Cyan Mill Base)
Cyan pigment: IRGALITTE BLUE GLVO 30 parts PEA (phenoxyethyl acrylate) 50 parts SOLSPERSE 5000 (manufactured by Lubrizol Corporation) 10 parts SOLSPERSE 32000 (manufactured by Lubrizol Corporation) 10 parts The above components were stirred to give a cyan mill base. Further, preparation of the pigment mill base was carried out by putting it into a disperser motor mill M50 (manufactured by Eiger) and dispersing using zirconia beads having a diameter of 0.65 mm at a peripheral speed of 9 mJs for 8 hours.

[0370] The magenta mill base, the yellow mill base, the black mill base, and the white mill base described in Table 1 were prepared in the same manner as for the cyan mill base.

[0371]

[Table 1]

[0372] (Pigments)

• Cyan pigment; IRGALTTE BLUE GLVO (manufactured by Ciba Specialty Chemicals)

• Magenta pigment; CINQUASIA MAGENTA RT-355 D (manufactured by Ciba Specialty Chemicals)

• Yellow pigment; NOVOPERM YELLOW H2G (manufactured by Clariant)

• Black pigment; SPECIAL BLACK 250 (manufactured by Ciba Specialty
Chemicals)

• White pigment; alumina-treated titanium oxide (dispersion medium)

• PEA; phenoxyethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) (dispersant)

• SOLSPERSE 2000 (manufactured by Lubrizol Corporation)

• SOLSPERSE 32000 (manufactured by Lubrizol Corporation)

• SOLSPERSE 5000 (manufactured by Lubrizol Corporation)
■ SOLSPERSE 36000 (manufactured by Lubrizol Corporation)

[0373] Preparation of Ink Composition>

[0374] The materials described in Table 2 were mixed and stirred to obtain ink compositions of Nos. 1 to 7. Further, the numerical values in the Table denote the blending amounts of the respective components.

[0375]

[Table 2]

[0376] (Monofunctional Monomer)

• PEA; phenoxyethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

• NVC; N-vinyl caprolactam (manufactured by Tokyo Chemical Industry Co., Ltd.) (polyfunctional monomer)

• NPGPODA; propoxylated neopentyl glycol diacrylate (manufactured by Aldrich) (initiator)

• Irg 819; bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (IRGACURE 819,
manufactured by Ciba Specialty Chemicals) ITX; mixture of 2-isopropylthioxanthone and 4-isopropylthioxanthone (FIRSTCURE ITX, manufactured by ALBEMARLE)

[0377] (Example 1)

[0378]

[0379] Next, recording was carried out on a recording medium using a commercially available Inkjet recording device having a piezo system inkjet nozzle. The ink supply system included a main tank, a supply pipe, an ink supply tank immediately before an inkjet head, a filter, and a piezo system inkjet head, and a section from the ink composition supply tank to the inkjet head was thermally insulated and heated. A temperature sensor was provided on the ink supply tank and in the vicinity of the nozzle of the inkjet head, and the temperature was controlled so that the nozzle section was always at 40°C±2°C.

[0380] As the piezo system inkjet nozzle, the following two kinds of heads were used.

[0381] For the ink composition No. 1 including aluminum metal pigments, a head 1-1 having a nozzle size of 30 join was used so that the multi-size dots of 10 to 30 pL were discharged at a resolution of 1,200 X 1,200 dpi.

[0382] For the ink compositions No. 3 to 7 including other color pigments, a head 2-2 having a nozzle size of 25 μm was used so that multi-size dots of 1 to 10 pL were discharged at a resolution of 4,800 X 4,800 dpi.

[0383] The exposure system, the main scanning speed, and the discharge frequency were adjusted so that, after landing, UV light was focused to give an illumination intensity on the exposed surface of 700 mW/cm2, and irradiation started 0.1 seconds after the ink composition landed on the recording medium. Further, exposure energy was irradiated with an exposure time variable. As an ultraviolet ray lamp, a HAN250NL high-cure mercury lamp (manufactured by GS Yuasa Corporation) was used. Here, dpi as mentioned in the present invention denotes the number of dots per 2.54 cm. As he recording medium, an ester film E5000 (film thickness of 125 urn, manufactured by Toyobo Co., Ltd.) was used.

[0384] (Evaluation of Ink Film)

[0385]

[0386] The ink composition containing aluminum metal pigments (No. 1) was subjected to drawing of a solid image on a transparent substrate (polycarbonate) with an average film thickness of 12 urn at an excessive light exposure amount (30,000 mJ/cm2) in accordance with the above-described inkjet recording method, and the image was measured for its pencil hardness in accordance with JIS K5600-5-4 at 25°C. The results are shown in Table 3.
A: H or more
B:F
C: HB or less
A or B indicates that there is no problem in the practical use.

[0387]

[0388] Each ink composition was subjected to drawing of a solid image on a transparent substrate (polycarbonate) with an average film thickness of 12 μm at an excessive light exposure amount (15,000 mJ/cm2) in accordance with the above-described inkjet recording method, and the obtained image was measured with the naked eye. The evaluation criteria are as follows. The results are shown in Table 3.

A: The image was observed from immediately above the vertical direction, and can be assessed to be metallic.

B: The image was observed from immediately above the vertical direction, and can be assessed to be metallic at a point with inclination at 30 degrees from the horizon.

C: Close to gray.
A or B indicates that there is no problem in the practical use.

[0389]

[0390] ach ink composition described in Table 3 was continuously discharged using the inkjet head described in Table 3 at 45 °C for 60 minutes, and evaluated by the following criteria. The results are shown in Table 3.

A: Normally made into droplets. The inkjet dischargeability was extremely good.

B: Slight generation of mist being observed.

The inkjet dischargeability was at such a level that there is no problem in the practical use.

C: Not discharged at all. The inkjet dischargeability was poor.

A or B indicates that there is no problem in the practical use.

[0391] (Examples 2 to 7 and Comparative Example 1 and Comparative Example 2)

[0392] An image was produced and evaluated in the same manner as in Example 1 except that the ink composition and the head were changed to those described in Table 3. The evaluation results are shown in Table 3.

[0393]
[Table 3]

[0395] Vacuum molding was carried out using a Vacuum Molding Device 300X (manufactured by Seiko Sangyo Co., Ltd.). In the above-described inkjet recording method, the print material was produced under the same condition as in Example 1 except that Panlite PC-1151 (manufactured by Teijin Chemicals Ltd.) was used as a recording medium.

[0396] The temperature of a heater was set such that the temperature of the recording medium reached 90°C, and a wooden mold shown in Fig. 1 was placed at the center of a vacuum table to carry out vacuum molding. The mold print material was observed with the naked eye for occurrence of cracking. In addition, presence or absence of pinholes on the surface after the processing was observed with the naked eye. No cracking was observed.

WHAT IS CLAIMED IS:

1. An inkjet recording method comprising the steps of:

image forming step A in which an ink composition A containing aluminum metal pigments is discharged through nozzles having a nozzle diameter in the range of 30 μm or more to 100 μm or less to form an image on a recording medium;

curing step A in which the discharged ink composition A is irradiated with active radiation to carry out curing of the ink composition A;

image forming step B in which an ink composition B containing pigments other than aluminum metal pigments is discharged through nozzles having a nozzle diameter in the range of 10 μm or more to less than 30 μm to form an image on a recording medium; and
curing step B in which the discharged ink composition B is irradiated with active radiation to carry out curing of the ink composition A.

2. The inkjet recording method according to Claim 1, wherein the volume average particle diameter of the aluminum metal pigments is in the range of 0.2 to 2.0 urn.

3. The inkjet recording method according to Claim 1 or 2, wherein the ink composition A and the ink composition B contain a polymerizable compound and a photopolymerization initiator.

4. The inkjet recording method according to any one of Claims 1 to 3, wherein the ink composition A and the ink composition B contain a dispersant.

5. The inkjet recording method according to any one of Claims 1 to 4, wherein the ink composition A and the ink composition B are a radically polymerizable ink composition or a cationically polymerizable ink composition.

6. A print material obtained by the inkjet recording method according to any one of Claims 1 to 5.

7. A method for producing a mold print material, comprising the steps of:
image forming step A in which an ink composition A containing aluminum metal pigments is discharged through nozzles having a nozzle diameter in the range of 30 μm or more to 100 pm or less to form an image on a recording medium;

curing step A in which the discharged ink composition A is irradiated with active radiation to carry out curing;

image forming step B in which an ink composition B containing pigments other than aluminum metal pigments is discharged through nozzles having a nozzle diameter in the range of 10 μm or more to less than 30 μm to form an image on a recording medium;

curing step B in which the discharged ink composition B is irradiated with active radiation to carry out curing, and

molding processing in which the recording medium having the cured image is subjected to molding processing.

8. The method for producing a mold print material according to Claim 7, wherein the volume average particle diameter of the aluminum metal pigments is in the range of 0.2 to 2.0 pm.

9. The method for producing a mold print material according to Claim 7 or 8, wherein the ink composition A and the ink composition B contain a polymerizable compound and a photopolymerization initiator.

10. The method for producing a mold print material according to any one of Claims 7 to 9, wherein the ink composition A and the ink composition B contain a dispersant

11. The method for producing a mold print material according to any one of Claims 7 to 10, wherein the ink composition A and the ink composition B are a radically polymerizable ink composition or a cationically polymerizable ink composition.

12. A mold print material obtained by the method for producing a mold print material according to any one of Claims 7 to 11.