JP5900517B2 - Image forming method using actinic ray curable inkjet ink - Google Patents

Description

  The present invention relates to an image forming method using an actinic ray curable inkjet ink.

  The ink jet recording system is used in various printing fields because it can form an image easily and inexpensively. As one of the ink jet recording methods, there is an ultraviolet curable ink jet method in which droplets of ultraviolet curable ink are landed on a recording medium and then cured by irradiation with ultraviolet rays to form an image. The ultraviolet curable ink jet method has been attracting attention in recent years because it can form an image having high scratch resistance and adhesion even on a recording medium having no ink absorbability.

  When ink is recorded on a recording medium having no ink absorbability, ink droplets ejected by the recording head are mixed on the recording medium, and image quality such as sharpness and graininess is deteriorated. In order to prevent this and obtain a high-quality image, it is necessary to quickly fix (pinning) the droplet after landing on the recording medium.

  As an example of a method for improving the pinning property of an ultraviolet curable inkjet ink, it has been studied to add a gelling agent to the ink and cause a sol-gel phase transition by temperature. In other words, it has been studied to suppress dot coalescence by discharging ink droplets in a liquid state at a high temperature and landing them on a recording medium, and at the same time cooling the ink droplets to gel. As the gelling agent added to the ink, stearone and the like are disclosed (see Patent Documents 1 and 2).

  However, the surface of the image formed on the recording medium by the ultraviolet curable ink jet method may not be smooth. There has been a problem that an image cured with a non-smooth image surface becomes a low gloss image or an image with a relief (relief).

  As a method of smoothing the image surface, there is a method of fixing an image by applying a heating unit and a pressurizing unit to a recording medium. A method for improving the gloss by smoothing the image surface has been studied (see Patent Document 3).

US Patent Application Publication No. 2007/0058020 International Publication No. 2007/025893 JP 2006-301656 A

  However, ultraviolet curable ink-jet ink has low pinning properties of ink droplets that have landed on a recording medium, and image quality may deteriorate due to mixing of adjacent ink droplets. Applying heating means and pressure means to such an image does not improve the image quality. Also, even if heating means and pressurizing means are applied to an image formed with hot melt ink, the hardness of the ink is too high and the image cannot be smoothed and an image with low gloss tends to be formed.

  On the other hand, an actinic ray curable inkjet ink containing a gelling agent has a strong pinning property of ink droplets landed on a recording medium and can form a high-quality image. However, since the pinning property is strong, the image surface is not smooth and it may be difficult to form a high gloss image.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming method capable of forming a high quality image, in particular, a high gloss image.

  The present inventors have found that high-quality image formation, particularly high gloss image formation, can be achieved by applying heating means and pressure means to actinic ray curable inkjet ink containing a gelling agent.

The above object of the present invention is achieved by the following configurations.
[1] A step of landing droplets of an actinic ray curable inkjet ink containing a coloring material, an actinic ray curable monomer, a photopolymerization initiator, and a gelling agent on a recording medium, and a liquid that has landed on the recording medium Applying a heating and pressing member to the image surface formed by the droplets to smooth the image surface, and irradiating the image surface with an actinic ray to cure the image surface,
The viscosity of the inkjet ink is 1.0 × 10 ^{3 to} 5.0 × 10 ⁴ mPa · s at 25 ° C.,
Wherein the temperature T _B of the heating member is the difference between the gelling temperature T _A of the ink contained in the ink-jet ink (T _A -T _B) is 5 ° C. or more and 15 ℃ or less, and wherein the T _B Is an image forming method having a temperature of less than 80 ° C.
[2] The image forming method according to [1], wherein the gelling agent is in the range of 1 to 10% by mass with respect to the total mass of the ink.
[3] The image forming method according to [1] or [2], wherein a nip pressure in the heating and pressing member is 0.1 MPa or more and less than 0.5 MPa.
[4] The image forming method according to any one of [1] to [3], wherein a surface material of a heating roller or a heating belt of the heating and pressing member is silicon resin or fluorine resin.

  According to the image forming method of the present invention, high-quality image formation, particularly high gloss image formation can be performed.

FIG. 1A is a diagram illustrating an example of a configuration of a main part of an ink jet recording apparatus having a heating belt as a heating and pressing member. FIG. 1B is a diagram illustrating an example of the configuration of the head carriage. It is a figure which shows an example of a structure of the principal part of the inkjet recording device which does not have a heating belt in a heating-pressing member.

Hereinafter, the present invention will be described with reference to embodiments, but the present invention is not limited to the following embodiments.
1. About actinic-light curable inkjet ink The actinic-light curable inkjet ink used for this embodiment contains a coloring material, an actinic-light curable monomer, a photoinitiator, and a gelatinizer.

<About gelling agent>
The gel is a lamellar structure, a polymer network formed by non-covalent bonds or hydrogen bonds, a polymer network formed by a physical aggregation state, an agglomerated structure of fine particles, and an interaction of precipitated microcrystals. This refers to the structure in which substances have lost their independent movements and assembled. Gelling means solidifying, semi-solidifying, or thickening with a sudden increase in viscosity or elasticity. The gelation temperature refers to a temperature at which the viscosity suddenly changes from a fluid solution state to a gel state. It is synonymous with terms called gel transition temperature, gel dissolution temperature, phase transition temperature, sol-gel phase transition temperature, and gel point. Further, the solification means a state in which the interaction formed by the gelation is eliminated and the liquid state is changed to a fluid state. The solubilization temperature is a temperature at which fluidity develops due to the sol formation when the gelled ink is heated.

  In general, a gel becomes a fluid solution (sometimes called a sol) by heating, and a thermoreversible gel that returns to the original gel when cooled. There is a heat irreversible gel that does not return. The gel formed by the gelling agent used in the present embodiment is preferably a thermoreversible gel from the viewpoint of preventing clogging in the head.

  In the present embodiment, the gelation temperature (phase transition temperature) of the actinic ray curable inkjet ink is preferably 40 ° C. or higher and lower than 90 ° C., more preferably 45 ° C. or higher and 70 ° C. or lower. Considering the temperature in the summer environment, if the phase transition temperature of the ink is 40 ° C. or higher, stable ejection characteristics can be obtained without being affected by the printing environment temperature when ejecting ink droplets from the inkjet recording head. be able to. Moreover, if it is less than 90 degreeC, it is not necessary to heat an inkjet recording device to excessively high temperature, and the load to the inkjet recording head of an inkjet recording device or the member of an ink supply system can be reduced.

  The gelation temperature of the ink is measured using, for example, various rheometers (for example, a stress control type rheometer using a cone plate, Physica MCR series, manufactured by Anton Paar). A temperature change curve of the viscosity is obtained while changing the temperature of the high-temperature ink in the sol state at a low shear rate. And gelation temperature can be calculated | required from the temperature change curve of the obtained viscosity. In addition, a method in which a small iron piece sealed in a glass tube is placed in a dilatometer and a phase transition point is defined as a point at which the ink liquid does not naturally fall in response to a temperature change (J. Polym. Sci., 21, 57). (1956)). In addition, when an aluminum cylinder is placed on the ink and the gel temperature is changed, the temperature at which the aluminum cylinder naturally falls is measured as the gelation temperature (Journal of Japanese Society of Rheology, Vol. 17, 86 (1989)). ) An example of a simple method is to place a gel-like test piece on a heat plate, heat the heat plate, measure the temperature at which the shape of the test piece collapses, and obtain this as the gelation temperature. it can. The gelation temperature of the ink can be appropriately adjusted by changing the type of gelling agent used, the amount of gelling agent added, and the type of actinic ray curable monomer.

  The gelling agent contained in the inkjet ink may be a high molecular compound or a low molecular compound, but a low molecular compound is preferable from the viewpoint of inkjet ejection properties.

  Although the example of the gelatinizer which can be used for this embodiment below is shown, it is not limited to these compounds.

Examples of the polymer compound preferably used in the present embodiment include fatty acid inulins such as inulin stearate, fatty acid dextrins such as dextrin palmitate and dextrin myristate (available from Chiba Flour as the Leopard series),
Examples include glyceryl behenate, glyceryl behenate, and polyglyceryl behenate (available from Nisshin Oilio as the Nomcoat series).

Examples of low molecular weight compounds preferably used in the present embodiment include, for example, low molecular weight oil gelling agents described in JP 2005-126507 A, JP 2005-255821 A, and JP 2010-1111790 A,
Amide compounds such as N-lauroyl-L-glutamic acid dibutylamide and N-2 ethylhexanoyl-L-glutamic acid dibutylamide (available from Ajinomoto Fine Techno),
Dibenzylidene sorbitols such as 1,3: 2,4-bis-O-benzylidene-D-glucitol (available from Gelol D Shin Nippon Rika),
Paraffin wax, microcrystalline wax, petrolactam, candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax, jojoba ester, beeswax, lanolin, whale wax, montan wax, hydrogenated wax, hardened castor Various waxes such as oil or hardened castor oil derivative, montan wax derivative, paraffin wax derivative, microcrystalline wax derivative or polyethylene wax (derivative), α-olefin maleic anhydride copolymer wax (UNILIN series manufactured by Baker-Petrolite, LUNAC BA Kao Corporation, Kao Wax T1 Kao Corporation),
Higher fatty acids such as behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, erucic acid,
Higher alcohols such as stearyl alcohol and behenyl alcohol,
Hydroxystearic acid such as 12-hydroxystearic acid, 12-hydroxystearic acid derivatives,
Fatty acid amides such as lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, 12-hydroxystearic acid amide (for example, Nikka Amide series Nippon Kasei Co., Ltd., ITOWAX series Ito Oil N-substituted fatty acid amides such as N-stearyl stearamide, N-oleyl palmitate, N, N'-ethylenebisstearylamide, N, N'-ethylenebis-12 -Special fatty acid amides such as -hydroxystearylamide, N, N'-xylylenebisstearylamide,
Higher amines such as dodecylamine, tetradecylamine or octadecylamine,
Stearyl stearic acid, oleyl palmitic acid, glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid ester, polyoxyethylene fatty acid ester, etc. And Poem series manufactured by RIKEN VITAMINS)
Sucrose fatty acid esters such as sucrose stearic acid and sucrose palmitic acid (for example, Ryoto Sugar Ester series manufactured by Mitsubishi Chemical Foods),
Dimer acid, dimer diol (PRIPOR series manufactured by CRODA) and the like are included. A gelling agent may be used independently and may be used in mixture of 2 or more types.

  The ink-jet ink used in the present embodiment contains a gelling agent, and when discharged on a recording medium having a temperature lower than the gelation temperature after being ejected from the ink-jet recording head, the ink temperature decreases. It immediately enters a gel state. By being in a gel state, dot mixing and dot coalescence are suppressed, and high image quality can be formed during high-speed printing. Thereafter, it is cured by irradiation with actinic rays to form a firm image film fixed on the recording medium.

  1-10 mass% is preferable and, as for content of the gelatinizer contained in an inkjet ink, 2-7 mass% is more preferable. By setting the amount to 1% by mass or more, gel formation is sufficient, deterioration of image quality due to dot coalescence can be suppressed, and oxygen inhibition is achieved when a radical curing system is used by thickening ink droplets due to gel formation. The curability can be reduced. Moreover, by setting it as less than 10 mass%, degradation of the cured film by the uncured component after actinic ray irradiation can be reduced.

  The inkjet ink used in the present embodiment contains the gelling agent, and the following effects are obtained. Since the ink droplets after landing on the recording medium have high pinning properties, a high-quality image can be formed. Further, since the ink droplet is pinned, it is not necessary to immediately irradiate the active light beam. Since the ink droplet before irradiation with actinic light is in a gel form, the surface can be smoothed even at a low nip pressure. Therefore, an image without blur and a glossy image can be formed.

<About polymerization method>
The actinic ray curable inkjet ink used in the present embodiment may use any polymerization method, but is preferably a cationic polymerization method or a radical polymerization method.

<About actinic ray curable monomer>
Examples of actinic rays in the present embodiment include electron beams, ultraviolet rays, α rays, γ rays, X-rays, etc., but they are dangerous to human bodies and easy to handle, and their use is widespread industrially. UV light or electron beam is preferred. In the present embodiment, ultraviolet rays are particularly preferable.

  An actinic ray curable monomer is a compound that crosslinks or polymerizes upon irradiation with actinic rays. In addition, the actinic ray curable monomer used in the present embodiment may be an oligomer or polymer having a monomer polymer as a main chain. Examples of the cationic polymerizable compound and radical polymerizable compound used in the cationic polymerization method and radical polymerization method are shown below.

(Cationically polymerizable compound)
Examples of the cationic polymerizable compound include JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937. And epoxy compounds, vinyl ether compounds, oxetane compounds and the like exemplified in JP-A-2001-220526.

  In order to suppress the shrinkage of the recording medium during ink curing, it is preferable to contain at least one oxetane compound as an actinic ray curable monomer and at least one compound selected from an epoxy compound and a vinyl ether compound.

  Examples of aromatic epoxides include di- or polyglycidyl ethers produced by the reaction of polyphenols having at least one aromatic nucleus or their alkylene oxide adducts with epichlorohydrin. For example, di- or polyglycidyl ether of bisphenol A or its alkylene oxide adduct, di- or polyglycidyl ether of hydrogenated bisphenol A or its alkylene oxide adduct, and novolak type epoxy resin are included. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Examples of alicyclic epoxides include cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Cyclopentene oxide-containing compounds are included.

  Examples of the aliphatic epoxide include aliphatic polyhydric alcohol or di- or polyglycidyl ether of an alkylene oxide adduct thereof. Typical examples include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or diglycidyl ether of 1,6-hexanediol, diglycidyl ether of alkylene glycol, glycerin or its alkylene oxide adduct di- or tri- Polyglycidyl ether of polyhydric alcohol such as glycidyl ether, diglycidyl ether of polyethylene glycol or its alkylene oxide adduct, diglycidyl ether of polyalkylene glycol such as polypropylene glycol or diglycidyl ether of its alkylene oxide adduct, etc. . Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in consideration of curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable. In this embodiment, one of the above epoxides may be used alone, but two or more may be used in appropriate combination.

  Examples of vinyl ether compounds include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, triethylene glycol Di- or trivinyl ether compounds such as methylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n-propyl vinyl Ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monomethyl ether, include monovinyl ether compounds such as octadecyl vinyl ether.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In this embodiment, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in appropriate combination.

  The oxetane compound that can be used in the present embodiment is a compound having an oxetane ring. Any known oxetane compound as described in JP-A Nos. 2001-220526 and 2001-310937 can be used.

  When a compound having 5 or more oxetane rings is used, the viscosity of the ink-jet ink is increased, which makes it difficult to handle, and the glass transition temperature of the ink-jet ink is increased. It may disappear. The compound having an oxetane ring used in the present embodiment is preferably a compound having 1 to 4 oxetane rings.

  Examples of the compound having an oxetane ring that can be preferably used in this embodiment include compounds represented by general formula (1) described in paragraph (0089) of JP-A-2005-255521, The general formula (2), the general formula (7) of the paragraph number (0107), the general formula (8) of the paragraph number (0109), the paragraph number (0166) described in the paragraph number (0092) of the same publication The compound represented by the general formula (9) and the like is included.

  Specifically, the exemplified compounds 1 to 6 described in paragraph numbers (0104) to (0119) of the same publication and the compounds described in paragraph number (0121) are included.

(Radically polymerizable compound)
Examples of radically polymerizable compounds include those radically polymerizable compounds described in JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, and JP-A-10-863. It is.

  The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization. The compound is not limited as long as it has at least one ethylenically unsaturated bond capable of radical polymerization in the molecule, and includes compounds having chemical forms such as monomers, oligomers, and polymers. Only one kind of radically polymerizable compound may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve desired properties.

  Examples of compounds having an ethylenically unsaturated bond capable of radical polymerization include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and their salts, esters, urethanes, amides. And radically polymerizable compounds such as various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides and unsaturated urethanes.

  Any known (meth) acrylate monomer and / or oligomer can be used as the actinic ray curable monomer used in the present embodiment. The term “and / or” as used in the present embodiment means that it may be a monomer, an oligomer, or both. The same applies to the items described below.

  Examples of monofunctional monomers include isoamyl acrylate, stearyl acrylate, lauryl acrylate, octyl acrylate, decyl acrylate, isomyristyl acrylate, isostearyl acrylate, 2-ethylhexyl-diglycol acrylate, 2-hydroxybutyl acrylate, 2-acryloyl acrylate Roxyethyl hexahydrophthalic acid, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxypropylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2 -Hydroxypropyl Chryrate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid, lactone modified flexibility Acrylate, t-butylcyclohexyl acrylate, and the like are included.

  Examples of bifunctional monomers include triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexane Diol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, dimethylol-tricyclodecane diacrylate, PO adduct diacrylate of bisphenol A, hydroxypivalate neopentyl glycol diacrylate, polytetramethylene glycol diacrylate Acrylate and the like are included.

  Examples of trifunctional or higher polyfunctional monomers include trimethylolpropane triacrylate, pentaerythritol triacrylate, EO-modified trimethylolpropane triacrylate, pentaerythritol tetraacrylate, EO-modified pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, ditritriol. Examples include methylolpropane tetraacrylate, glycerin propoxytriacrylate, caprolactone-modified trimethylolpropane triacrylate, pentaerythritol ethoxytetraacrylate, caprolactam-modified dipentaerythritol hexaacrylate.

  In addition, polymerizable oligomers can be blended in the same manner as the monomer. Examples of the polymerizable oligomer include epoxy acrylate, aliphatic urethane acrylate, aromatic urethane acrylate, polyester acrylate, linear acrylic oligomer, and the like. More specifically, Yamashita Shinzo, “Crosslinker Handbook” (1981, Taiseisha); Kato Kiyomi, “UV / EB Curing Handbook (Raw Materials)” (1985, Polymer Publications); Radtech Study Group, “Application and Market of UV / EB Curing Technology”, page 79 (1989, CMC); written by Eiichiro Takiyama, “Polyester Resin Handbook” (1988, Nikkan Kogyo Shimbun) Commercially available products or radically polymerizable or crosslinkable monomer oligomers and polymers known in the industry can be used.

  Among these, polyethylene glycol diacrylate, EO-modified trimethylolpropane triacrylate, EO-modified pentaerythritol tetraacrylate, and the like are preferable.

  As the radical polymerizable compound used in the present embodiment, a vinyl ether monomer and / or oligomer and a (meth) acrylate monomer and / or oligomer may be used in combination. Examples of vinyl ether monomers include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, triethylene glycol Di- or trivinyl ether compounds such as methylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl Vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monomethyl ether, include monovinyl ether compounds such as octadecyl vinyl ether. When a vinyl ether oligomer is used, a bifunctional vinyl ether compound having a molecular weight of 300 to 1000 and having 2 to 3 ester groups in the molecule is preferable. For example, compounds available as a VEctomer series of ALDRICH, VEctomer 4010, VEctomer 4020, VEctomer 4040 , Vectomer 4060, Vectomer 5015, and the like, but are not limited thereto.

  Moreover, various vinyl ether compounds and maleimide compounds can be used in combination as the radical polymerizable compound used in the present embodiment. Examples of maleimide compounds include N-methylmaleimide, N-propylmaleimide, N-hexylmaleimide, N-laurylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N, N'-methylenebismaleimide, polypropylene glycol-bis (3-maleimidopropyl) ether, tetraethylene glycol-bis (3-maleimidopropyl) ether, bis (2-maleimidoethyl) carbonate, N, N ′-(4,4′-diphenylmethane) bismaleimide, N, N ′ -2,4-tolylene bismaleimide or polyfunctional maleimide compounds which are ester compounds of maleimide carboxylic acid and various polyols disclosed in JP-A-11-124403 are included, but are not limited thereto. Not.

  The content of the actinic ray curable monomer contained in the inkjet ink is preferably 1 to 97% by mass, and more preferably 30 to 95% by mass.

<About color materials>
A dye or a pigment can be used as the color material constituting the inkjet ink used in the present embodiment without limitation. Among these, it is preferable to use a pigment having good dispersion stability with respect to the ink component and excellent weather resistance. Although it does not necessarily limit, the organic or inorganic pigment of the following number described in a color index can be used for the example of a pigment.
Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53. : 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, 36,
Examples of blue or cyan pigments include Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17-1, 22, 27, 28, 29, 36. , 60,
Examples of green pigments include Pigment Green 7, 26, 36, 50,
Examples of yellow pigments include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137. 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193,
Examples of black pigments include Pigment Black 7, 28, 26, and the like depending on the purpose.

  Specific examples of product names include chromo fine yellow 2080, 5900, 5930, AF-1300, 2700L, chromo fine orange 3700L, 6730, chromo fine scarlet 6750, chromo fine magenta 6880, 6886, 6891N, 6790, 6877, Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4993 5205, 5208, 5214, 5221, 5000P, chromofine green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, chromophy Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400 (B), 2500, 2600, ZAY-260, 2700 (B), 2770, Seica Fast Red 8040, C405 (F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seikalite Rose R40, Seikalite Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C718, A 12, cyanine blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichi Seika Kogyo), KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (Dai Nippon Ink (Chemical), Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigmen Yellow 1705, Colortex Orange 202, Colortex Red 101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN , Colortex Maron 601, Colortex Brown B610N, Colortex violet 600, Pigment Red 122, Colortex Blue 516, 517, 518, 519, A818, P-908, 510, Color5 Green402, 403, Col70 Lionol Blue G7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink), Toner Magenta E02, Permanent RubinF6B, Toner Yellow HG, Permanent Yellow GG-02, Hostape Blue G Hostaperm Pink E, Hostaperm Blue B2G (manufactured by Clariant), carbon black # 2600, # 2400, # 2350, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 850, MCF88, # 750, # 650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77, # 52, # 50, # 47, # 45, # 45L, # 40, # 33, # 32, # 30, # 25, # 20, # 10, # 5, # 44, CF9 (Mitsubishi Chemical) and the like are included.

  For the dispersion of the pigment, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like can be used.

  Moreover, a dispersing agent can also be added when dispersing a pigment. A polymer dispersant is preferably used as an example of the dispersant, and examples of the polymer dispersant include Avecia's Solsperse series and Ajinomoto Fine-Techno's PB series. Furthermore, the following are included.

  Pigment dispersants include hydroxyl group-containing carboxylic acid esters, salts of long chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, high Molecular copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene nonylphenyl Includes ether, stearylamine acetate, pigment derivatives and the like.

  Specific examples of pigment dispersant products are “Anti-Terra-U (polyaminoamide phosphate)”, “Anti-Terra-203 / 204 (high molecular weight polycarboxylate)” manufactured by BYK Chemie, “Disperbyk-101”. (Polyaminoamide phosphate and acid ester), 107 (hydroxyl group-containing carboxylic acid ester), 110 (copolymer containing an acid group), 130 (polyamide), 161, 162, 163, 164, 165, 166, 170 (high Molecular copolymer) ”,“ 400 ”,“ Bykumen (high molecular weight unsaturated acid ester) ”,“ BYK-P104, P105 (high molecular weight unsaturated acid polycarboxylic acid) ”,“ P104S, 240S (high molecular weight unsaturated) Acid polycarboxylic acid and silicon system "," Lactimon (long-chain amine and unsaturated acid polycal Including the phosphate and silicon) ".

  Also, “Efka CHEMICALS” “Efka 44, 46, 47, 48, 49, 54, 63, 64, 65, 66, 71, 701, 764, 766”, “Efka Polymer 100 (modified polyacrylate), 150 (aliphatic) System modified polymer), 400, 401, 402, 403, 450, 451, 452, 453 (modified polyacrylate), 745 (copper phthalocyanine system) "; Kyoei Chemical Co., Ltd." Floren TG-710 (urethane oligomer) "," “Flonon SH-290, SP-1000”, “Polyflow No. 50E, No. 300 (acrylic copolymer)”; “Disparon KS-860, 873SN, 874 (polymer dispersing agent), # 2150, manufactured by Enomoto Kasei Co., Ltd. (Aliphatic polycarboxylic acid), # 7004 (polyether ester type) "

  Furthermore, “Demol RN, N (Naphthalenesulfonic acid formalin condensate sodium salt), MS, C, SN-B (aromatic sulfonic acid formalin condensate sodium salt), EP”, “Homogenol L-18 (made by Kao Co., Ltd.) Polycarboxylic acid type polymer) "," Emulgen 920, 930, 931, 935, 950, 985 (polyoxyethylene nonylphenyl ether) "," acetamine 24 (coconut amine acetate), 86 (stearyl amine acetate) "; "Solspers 5000 (phthalocyanine ammonium salt type), 13240, 13940 (polyesteramine type), 17000 (fatty acid amine type), 24000, 32000" manufactured by Nikko Chemical Co., Ltd. "Nikkor T106 (polyoxyethylene sorbitan monooleate), MY" -IEX (polyoxyethylene monostearate), including Hexagline4-0 (hexaglyceryl ruthenate Huwei rate) "and the like.

  These pigment dispersants are preferably contained in the ink in the range of 0.1 to 20% by mass. Further, as the dispersion aid, pigment derivatives (synergists) corresponding to various pigments can be used. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is a solvent or a polymerizable compound.

  In this embodiment, since the ink droplets landed on the recording medium are irradiated with actinic rays to cure the image, it is preferable that the inkjet ink to be used is solvent-free. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The average particle diameter of the pigment is preferably 0.08 to 0.5 μm, and the maximum particle diameter of the pigment is 0.3 to 10 μm, preferably 0.3 to 3 μm. In order to adjust the average particle diameter of the pigment, the selection of the pigment, the dispersant and the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set. By controlling the particle size, clogging of the nozzles of the recording head can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  Moreover, conventionally known dyes, preferably oil-soluble dyes can be used as necessary for the ink-jet ink used in the present embodiment. Examples of oil-soluble dyes that can be used in this embodiment include, but are not limited to, the following.

(Magenta dye)
MS Magenta VP, MS Magenta HM-1450, MS Magenta HSo-147 (manufactured by Mitsui Toatsu Co., Ltd.), AIZENSOT Red-1, AIZEN SOT Red-2, AIZEN SOTRed-3, AIZEN SOT Pink-1, SPERON Red GE SPECIAL (above, manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN Red FB 200%, MACROLEX Red Violet R, MACROLEX ROT5B (above, manufactured by Bayer Japan), KAYASET Red B, KAYASET Red 130, KAYASET Red Japan 802 ), PHLOXIN, ROSE BENGAL, ACID Red (above, made by Daiwa Kasei), HSR-31, DIARESIN Red K (below) , Manufactured by Mitsubishi Kasei Co., Ltd.), Oil Red (manufactured by BASF Japan Co., Ltd.).

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

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

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

  The content of the pigment or oil-soluble dye is preferably from 0.1 to 20% by mass, more preferably from 0.4 to 10% by mass, based on the total mass of the ink. If it is 0.1% by mass or more, good image quality can be obtained, and if it is 20% by mass or less, an appropriate ink viscosity in ink ejection can be obtained. In addition, two or more kinds of colorants can be mixed as appropriate for color adjustment.

<Photopolymerization initiator>
The ink-jet ink used in the present embodiment preferably contains at least one photopolymerization initiator when ultraviolet rays or the like are used as actinic rays. However, in many cases where an electron beam is used as the actinic ray, no photopolymerization initiator is required.

  Photopolymerization initiators used in the radical polymerization method can be broadly classified into two types: intramolecular bond cleavage type and intramolecular hydrogen abstraction type.

  Examples of intramolecular bond cleavage type photopolymerization initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2. -Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4 Acetophenones such as -thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone; benzoins such as benzoin, benzoin methyl ether, benzoin isopropyl ether; 2 , 4,6-Trimethylbenzoindiphenylphosphi Such acylphosphine oxide of oxide; benzyl, include such as methyl phenylglyoxylate ester.

  On the other hand, examples of intramolecular hydrogen abstraction type photopolymerization initiators include benzophenone, methyl 4-phenylbenzophenone, o-benzoylbenzoate, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl. Benzophenones such as diphenyl sulfide, acrylated benzophenone, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, 3,3'-dimethyl-4-methoxybenzophenone; 2-isopropylthioxanthone, 2 1,4-dimethylthioxanthone, 2,4-diethylthioxanthone, thioxanthone series such as 2,4-dichlorothioxanthone; Michler-ketone, aminobenzophenone series such as 4,4'-diethylaminobenzophenone; 10-butyl-2-chloro Acridone, 2-ethyl anthraquinone, 9,10-phenanthrenequinone, include camphorquinone, and the like.

  Examples of the radical polymerization initiator include triazine derivatives described in JP-B-59-1281, JP-B-61-9621, JP-A-60-60104, and the like, JP-A-59-1504, and Organic peroxides described in JP-A Nos. 61-243807, JP-B 43-23684, JP-B 44-6413, JP-B 44-6413, JP-B 47-1604, etc. And diazonium compounds described in U.S. Pat. No. 3,567,453, U.S. Pat. Nos. 2,848,328, 2,852,379 and 2,940,853. Organic azide compounds, ortho-quinonediazides described in JP-B 36-22062, JP-B 37-13109, JP-B 38-18015, JP-B 45-9610 and the like, Various onium compounds described in JP-A-55-39162, JP-A-59-14023, and the like, and “Macromolecules, Vol. 10, page 1307 (1977)”; -142205, an azo compound described in JP-A-1-54440, European Patent No. 109,851, European Patent No. 126,712, etc., “Journal of Imaging Science (J. Imag. Sci.), 30, 174 (1986) ", (oxo) sulfonium organoboron complexes described in Japanese Patent Nos. 2711491 and 2803454, -Titanocenes described in JP-A-151197, “Coordination Chemistry Review” (Coordination Chemistry Review), Vol. 84, pages 85-277 (1988) ”and transition metal complexes containing transition metals such as ruthenium described in JP-A-2-182701, JP-A-3-209477 2,4,5-triarylimidazole dimer described in the publication, carbon tetrabromide, organic halogen compounds described in JP-A-59-107344, and the like.

  The content in the case of using a photopolymerization initiator is preferably in the range of 0.01 to 10% by mass with respect to the mass of the actinic ray curable monomer.

  In the cationic polymerization method, a photoacid generator is used.

  As the photoacid generator, for example, a chemically amplified photoresist or a compound used for cationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187-192. Page). Examples of compounds suitable for this embodiment include, but are not limited to:

  B (C6F5) 4-, PF6-, AsF6-, SbF6-, CF3SO3- salts of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, phosphonium and the like are included. Examples of the onium compound include the compounds described in paragraph No. (0132) of JP-A No. 2005-255821.

  Specific examples of the sulfonated compound that generates sulfonic acid include the compounds described in paragraph No. (0136) of JP-A-2005-255821.

  Specific examples of halides that generate hydrogen halide include compounds described in paragraph No. (0138) of JP-A No. 2005-255821.

  The iron allene complex described in paragraph number (0140) of JP-A-2005-255821 is included.

  The ink-jet ink used in the present embodiment may further contain a photopolymerization initiator auxiliary agent, a sensitizer, a polymerization inhibitor and the like as necessary.

  The photopolymerization initiator assistant may be a tertiary amine compound, preferably an aromatic tertiary amine compound. Examples of aromatic tertiary amine compounds include N, N-dimethylaniline, N, N-diethylaniline, N, N-dimethyl-p-toluidine, N, N-dimethylamino-p-benzoic acid ethyl ester, N, N-dimethylamino-p-benzoic acid isoamyl ethyl ester, N, N-dihydroxyethylaniline, triethylamine, N, N-dimethylhexylamine and the like are included. Of these, N, N-dimethylamino-p-benzoic acid ethyl ester and N, N-dimethylamino-p-benzoic acid isoamyl ethyl ester are preferred. These compounds may be used alone or in combination of two or more.

  The sensitizer is preferably one having ultraviolet spectrum absorption at a wavelength longer than 300 nm, and a polycyclic aromatic compound having at least one hydroxyl group, optionally substituted aralkyloxy group or alkoxy group as a substituent. Carbazole derivatives, thioxanthone derivatives, anthracene derivatives and the like.

  Examples of polymerization inhibitors include (alkyl) phenol, hydroquinone, catechol, resorcin, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone , Nitrosobenzene, 2,5-di-tert-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cuperone, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N- (3-oxyanilino- 1,3-dimethylbutylidene) aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraloxime, methyl ethyl ketoxime, cyclohexanone oxime and the like.

<About other additives>
The ink-jet ink used in the present embodiment can use various additives other than those described above. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added. In addition, any known basic compound can be used for the purpose of improving storage stability. Typical examples include basic organic compounds such as basic alkali metal compounds, basic alkaline earth metal compounds, and amines. Etc. are included.

<About Sol-Gel Phase Transition Inkjet Ink>
Since the actinic radiation curable inkjet ink contains a gelling agent as described above, it undergoes a sol-gel phase transition reversibly depending on the temperature. Actinic ray curable inkjet ink that undergoes a sol-gel phase transition is a liquid (sol) at a high temperature (for example, about 80 ° C.), and thus can be ejected in a sol state from an inkjet recording head. When actinic ray curable inkjet ink is ejected at a high temperature, ink droplets (dots) land on the recording medium and then naturally cool to gel. Thereby, coalescence of adjacent dots can be suppressed and image quality can be improved.

The viscosity at 25 ° C. of the inkjet ink used in the present embodiment is preferably 1.0 × 10 ^{3 to} 5.0 × 10 ⁴ mPa · s, and 3.0 × 10 ^{3 to} 2.0 × 10 ^4. More preferably, it is mPa · s. Ink with an ink viscosity at 25 ° C. of less than 1.0 × 10 ³ mPa · s is insufficient to prevent dot coalescence on various recording media, and the image quality deteriorates in the above temperature range. Resulting in. Further, the ink viscosity at 25 ° C. exceeds 5.0 × 10 ⁴ , the viscosity after gelation is high, and the effect of smoothing the image surface is sufficiently obtained in the step of applying a heating and pressing member to the image surface. I can't.

  The viscosity of the ink can be appropriately adjusted by changing the type of gelling agent used, the amount of gelling agent added, and the type of actinic ray curable monomer. The viscosity as used in the present invention is measured at a shear rate of 11.7 s-1 using a stress-controlled rheometer using a cone plate (Physica MCR series, manufactured by Anton Paar).

2. Inkjet recording apparatus and image recording method using the same An image recording method according to the present embodiment includes at least the following three steps.
(1) A step of ejecting droplets of an actinic ray curable inkjet ink from an inkjet recording head and adhering them onto a recording medium (2) A heating and pressing member is formed on the image surface formed by the droplets landed on the recording medium Step of smoothing the image surface by applying (3) Step of irradiating the image surface with an actinic ray to cure

<About (1) process>
In the inkjet image forming method according to the present embodiment, ink droplets are ejected by an inkjet recording head unit. In order to improve the ejection property of the ink droplets, it is preferable to heat the temperature of the inkjet ink in the inkjet recording head in a temperature range of 10 ° C. or more and less than 40 ° C. of the gelation temperature. By setting the temperature of the ink in the ink jet recording head to 10 ° C. or more, good ejection properties can be obtained without the ink gelling in the ink jet recording head or on the nozzle surface. In addition, by setting the temperature of the ink in the ink jet recording head to less than 40 ° C., the thermal load on the ink jet recording head can be reduced, and in particular, the performance of the recording head using a piezoelectric element is hardly deteriorated. In addition, at the temperature in the ink jet recording head, the viscosity of the ink is preferably 3 mPa · s or more and less than 20 mPa · s from the viewpoint of ejection stability.

  Therefore, it is only necessary to heat the ink jet ink in the ink jet recording head, the ink flow path connected to the ink jet recording head, or the ink tank connected to the ink flow path, and discharge the ink jet ink droplets at the above temperature.

  The amount of droplets ejected from each nozzle of the inkjet recording head is preferably 1 to 10 pl, although it depends on the resolution of the image.

  The ink droplets that have landed on the recording medium are cooled and rapidly gelled by the sol-gel phase transition. As a result, the ink droplets can be pinned without diffusing. Furthermore, as described above, oxygen inhibition of the actinic ray curable monomer can be reduced.

  The recording medium is not particularly limited. Plain paper used for copying, etc., paper substrate used for offset printing, fine paper, coated paper, art paper, etc., both sides of the base paper are resin, etc. In addition to coated paper coated with, various pasting papers, synthetic papers, etc., various non-absorbable plastics used for so-called soft packaging and films thereof can be used. Examples of various plastic films include PET film, OPS film, OPP film, ONY film, PVC film, PE film, and TAC film. It can also be applied to metals and glasses.

  The surface temperature of the recording medium is preferably 5 to 15 ° C lower than the gelation temperature of the ink, and more preferably 5 to 10 ° C lower. Examples of the temperature control means for the recording medium include a method of adjusting the temperature of the recording medium from the back side by attaching a cooling device and a heating device to a conveyance base for fixing the recording medium or a fixing drum in advance, a cool air or a hot air The method of adjusting the temperature by spraying the recording medium, the method of attaching a refrigerant or heater on the upper surface of the recording medium fixing position on the apparatus and adjusting the temperature without contact, the method of adjusting the temperature by irradiating an IR laser, etc. In addition, a method of previously adjusting the temperature of the recording medium before ink jet recording is included. Among them, a method of adjusting the temperature of the recording medium from the back surface is preferable in order to make the temperature of the recording medium uniform.

  The image forming method according to the present embodiment is effective in both the so-called shuttle recording method and the single pass recording method. In particular, in a single-pass recording method that is high-speed recording, a remarkable effect can be obtained compared to a conventional image forming method using an actinic ray curable inkjet ink.

  The conveyance speed of the recording medium in the single pass recording method is preferably 500 to 3000 mm / s. The higher the conveyance speed, the higher the image forming speed, which is preferable. However, when the conveyance speed is too high, the image quality is deteriorated or the ink is not sufficiently cured.

<(2) Process>
The image forming method according to the present embodiment forms a high gloss image by heating and pressurizing ink droplets landed on a recording medium to smooth the image. Either the heating roller or the heating belt may be used for the heating and pressing treatment by the heating and pressing member. The heating roller is paired with a pressure roller, and heat and pressure processing is performed when the recording medium is conveyed between both rollers. The heating belt is a belt that conveys the recording medium, and passes the recording medium between the heating roller and the pressure roller. A heating and pressing process is performed when the heating belt conveys the recording medium. Since the recording medium is heated by the heating belt, it is preferable that the heating belt has good thermal conductivity.

The heating temperature (T _B ) of the heating and pressing member is a value at which the difference (T _A −T _B ) from the gelation temperature (T _A ) of the ink is 5 ° C. or more and 15 ° C. or less, and T _B Is preferably less than 80 ° C. If T _A -T _B is greater than 15 ° C., the ink droplets cannot be sufficiently smoothed, resulting in a low gloss image. On the other hand, when T _A -T _B is less than 5 ° C. or T _B exceeds 80 ° C., the ink droplet gelled on the recording medium is likely to be sol. For this reason, ink droplets spread and it becomes impossible to suppress the coalescence of the droplets, resulting in a low-quality image.

  The nip pressure in the heating and pressing member is preferably 0.1 MPa or more and less than 0.5 MPa, and more preferably 0.1 MPa or more and less than 0.3 MPa. If the nip pressure is lower than the above range, the image surface cannot be smoothed, resulting in a low gloss image. On the other hand, when the nip pressure is higher than the above range, the image is blurred and the image quality is deteriorated. The ink hardness at the time of heating and pressurizing the inkjet ink used in the present embodiment is smaller than that of hot melt ink or the like. Therefore, the present invention can smooth the image surface even at a low nip pressure.

  The surface material of the heating roller and the heating belt, which are fixing members at the time of heating and pressing, is preferably a silicon resin or fluororesin having releasability.

  Examples of the silicon resin include a silicon resin produced using a curable silicon such as a solvent addition type silicon or a condensation curable type silicon. Among these, a silicon resin produced using solvent addition type silicon is preferable.

  The solvent-added silicon is obtained by reacting linear methyl vinyl polysiloxane having vinyl groups at both ends, or both ends and chains with methyl hydrogen polysiloxane in the presence of a platinum-based catalyst. .

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

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

  The thickness of the release layer made of silicon resin is preferably 1 to 50 μm, and more preferably 10 to 30 μm.

  Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), alone or mixed And preferably used.

  The thickness of the releasable layer made of a fluororesin is preferably 5 to 30 μm, and more preferably 10 to 20 μm.

  The surface contact angle of the releasable layer with respect to pure water is preferably 100 to 120 degrees, and more preferably 105 to 115 degrees. The surface contact angle is, for example, an automatic contact angle meter DAC-VZ (manufactured by Kyowa Interface Science Co., Ltd.), and a droplet method (approximately 15 μl of pure water is gently dropped on the measurement surface and 0.5 seconds after contact. Measure the contact angle).

  By using silicon resin or fluororesin as the surface material of the heating roller or heating belt, the fixing member does not peel off and the occurrence of offset during image fixing can be reduced.

<(3) Process>
By irradiating the smoothed image surface with actinic rays, the actinic ray curable monomer contained in the ink droplets is crosslinked or polymerized to cure the ink droplets, resulting in a high hardness image.

  The actinic ray irradiation is preferably performed after all images are drawn. That is, in the case of a line recording type ink jet recording apparatus, it is preferable to attach an actinic ray irradiation device behind all the recording heads and heating and pressing members and irradiate the active ray after the image is completed. In the case of a serial recording type inkjet recording apparatus, it is preferable to irradiate actinic rays after an image is completed in each pass. When actinic rays are irradiated before the image is completed (for example, when a line recording method is used, a light source is placed between colors, or when a serial recording method is used, thin dots are drawn and actinic rays are emitted for each pass) ) May cause the ink droplets to be repelled on the cured film to disturb the image quality or to reduce the gloss uniformity. The gloss uniformity in the present invention is not an absolute gloss value, for example, a 60-degree regular reflection gloss value. The image does not appear to have a non-uniform gloss, such as unnatural glitter caused by microscopic gloss differences on the image, unnecessary gloss reduction, or streaky uneven glossiness. This means that the gloss of the entire surface, especially the solid print area, is uniform.

  The total ink droplet thickness after curing is preferably 2 to 25 μm. “Total ink droplet thickness” is the maximum value of the ink droplet thickness drawn on the recording medium, and even for a single color, other two-color layers (secondary colors), three-color layers, four-color layers Even when (white ink base) image formation is performed, the meaning of the total ink film thickness is the same.

(Electron beam irradiation)
Examples of the irradiation method when an electron beam is used as the actinic ray include a scanning method, a curtain beam method, a broad beam method, and the like. The curtain beam method is preferable from the viewpoint of processing capability.

  The acceleration voltage of electron beam irradiation can be set to a range of 30 to 250 kV to form a cured film. It is preferable to set to 30 to 100 kV at which equivalent curability can be obtained with a lower irradiation dose. In addition, when the acceleration voltage of electron beam irradiation is set in the range of 30 to 100 kV, the irradiation dose of the electron beam is set to a value lower than normal, energy saving by high energy efficiency, and production efficiency by increasing printing speed. You can also plan for the top and bottom. In normal electron beam irradiation with an acceleration voltage of 100 to 250 kV, the electron beam irradiation amount is preferably 30 to 100 kGy, and more preferably 30 to 60 kGy.

  Examples of electron beam irradiation means that can be used in the present invention include “Curetron EBC-200-20-30” manufactured by Nissin High Voltage Co., Ltd., “Min-EB” manufactured by AIT Co., Ltd., and the like. included.

(UV irradiation)
When ultraviolet rays are used as the actinic rays, examples of the ultraviolet irradiation light source include fluorescent tubes (low pressure mercury lamps, germicidal lamps), cold cathode tubes, ultraviolet lasers, low pressures having medium operating pressures from several hundred Pa to 1 MPa, medium pressures, High pressure mercury lamps, metal halide lamps, LEDs and the like are included. From the viewpoint of curability, a light source capable of emitting high-intensity ultraviolet rays having an illuminance of 100 mW / cm ² or more, such as a high-pressure mercury lamp, a metal halide lamp, and an LED is preferable. Among them, an LED with low power consumption is preferable, but not limited thereto.

<Inkjet recording device>
An ink jet recording apparatus that can be used in the image forming method according to the present embodiment will be described as an example of an ultraviolet irradiation method having a heating and pressing member.

  Hereinafter, a recording apparatus that can be used in the present invention will be described with reference to the drawings as appropriate. Note that the recording apparatus shown in the drawings is merely an embodiment of the recording apparatus that can be preferably used in the present invention, and the present invention is not limited to this drawing.

  FIG. 1A shows an example of a configuration of a main part of an ink jet recording apparatus having a heating belt as a heating and pressing member.

  The recording medium conveying means 2 in FIG. 1A sends the recording medium 1 from the conveying roller pair 21. The sent recording medium 1 is subjected to image formability by an ink jet recording head provided in the head carriage 3.

  An example of the configuration of the head carriage 3 in FIG. 1A is shown in FIG. 1B. As shown in FIG. 1B, a head carriage 3 for each color is arranged. Each color head carriage 3 includes a plurality of ink jet recording heads 5, and the plurality of ink jet recording heads 5 are arranged along the conveyance direction of the recording medium 1 indicated by an arrow A. The number of inkjet recording heads 5 in the head carriage 3 is set according to the nozzle density and the resolution of the print image. For example, when an image having a resolution of 1440 dpi is formed using the inkjet recording head 5 having a droplet amount of 2 pl and a nozzle density of 360 dpi, four inkjet recording heads 5 may be arranged along the conveyance direction of the recording medium 1. . When forming an image with a resolution of 720 × 720 dpi using the inkjet recording head 5 having a droplet amount of 6 pl and a nozzle density of 360 dpi, the two inkjet recording heads 5 are arranged along the conveyance direction of the recording medium 1. That's fine. dpi represents the number of ink droplets (dots) per 2.54 cm.

  A recording medium holding unit 34 that is disposed to face the head carriage 3 via the recording medium 1 is attached, and various heaters and the like built in the recording medium holding unit 34 appropriately adjust the temperature of the recording medium. To do.

  Next, the recording medium 1 is sent to the heating and pressing member 4 and passes between a heating roller 41 having a heating element 43 inside and a pressing roller 42 together with a heating belt 44 and a lower belt 45 driven by a driven roller 46. As a result, a heat and pressure treatment is performed.

  An actinic ray irradiating device 8 such as an electron beam or an ultraviolet ray is disposed on the downstream side of the heating and pressing member 4 so as to cover the entire width of the recording medium 1, and is activated by the lamp immediately after the image is heated and pressurized. Light is irradiated and the image is completely fixed. In FIG. 1A, for example, an LED lamp (385 nm manufactured by Hamamatsu Photonics) is used.

  Next, FIG. 2 shows an example of the configuration of the main part of an ink jet recording apparatus that does not have a heating belt as a heating and pressing member.

  The recording medium conveying unit 2 in FIG. 2 sends the recording medium 1 from the conveying roller pair 21. An image is formed on the fed recording medium 1 by an ink jet recording head provided in the head carriage 3.

  The head carriage 3 shown in FIG. 2 may be configured as shown in FIG. 1B, for example.

  A recording medium holding unit 34 that is disposed to face the head carriage 3 via the recording medium 1 is attached, and various heaters and the like built in the recording medium holding unit 34 appropriately adjust the temperature of the recording medium. To do.

  Next, the recording medium 1 is sent to the heating and pressing member 4 and passed between a heating roller 41 having a heating element 43 inside and the pressing roller 42 to perform a heating and pressing process.

  An actinic ray irradiating device 8 such as an electron beam or an ultraviolet ray is disposed on the downstream side of the heating and pressing member 4 so as to cover the entire width of the recording medium 1, and is activated by the lamp immediately after the image is heated and pressurized. Light is irradiated and the image is completely fixed. In FIG. 2, for example, an LED lamp (385 nm manufactured by Hamamatsu Photonics) is used.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

<Preparation of radical polymerization type ink>
(Preparation of pigment dispersion 1)
Pigment dispersion 1 was prepared by the following procedure. The following two compounds were placed in a stainless beaker and dissolved by stirring with heating for 1 hour while heating on a hot plate at 65 ° C.
Pigment dispersant: Azisper PB824 (manufactured by Ajinomoto Fine Techno Co., Ltd.) 9 parts by mass Actinic ray curable monomer: APG-200 (tripropylene glycol diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.) 70 parts by mass Polymerization inhibitor: Irgastab UV10 (Ciba (Made by Japan) 0.02 parts by mass

  After cooling to room temperature, 21 parts by mass of Pigment Red 122 (manufactured by Dainichi Seika, Chromofine Red 6112JC) was added as a pigment. Then, 200 g of zirconia beads having a diameter of 0.5 mm were placed in a glass bottle and sealed, and after a dispersion treatment with a paint shaker for 8 hours, the zirconia beads were removed to prepare pigment dispersion 1.

(Preparation of ink)
An ink was prepared using the prepared pigment dispersion 1 and the following components.

[Gelling agent]
LUNAC BA (manufactured by Kao)
FATTY AMID T (manufactured by Kao Corporation)

[Actinic ray curable monomer]
NK ester A-400 (polyethylene glycol diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.)
SR494 (4EO-modified pentaerythritol tetraacrylate, manufactured by SARTOMER)
SR499 (6EO-modified trimethylolpropane triacrylate, manufactured by SARTOMER)

[Photopolymerization initiator]
TPO (phosphine oxide, DAROCURE TPO, manufactured by Ciba Japan)

[Initiator aid]
ITX (Isopropylthioxanthone, Speedcure ITX, manufactured by Lambson)
EDB (Amine auxiliary, Speedcure EDB, manufactured by Lambson)

[Polymerization inhibitor]
Irgastab UV10 (manufactured by Ciba Japan)

[Surfactant]
KF-352 (polyether-modified silicon, manufactured by Shin-Etsu Chemical Co., Ltd.)

  According to the composition of the ink described in Table 1, each component and each part of the pigment dispersion 1 were mixed and heated to 100 ° C. and stirred. The resulting solution was filtered and cooled with a # 3000 metal mesh filter under heating.

<Preparation of cationic polymerization type ink>
(Preparation of pigment dispersion 2)
Pigment dispersion 2 was prepared by the following procedure. The following two compounds were placed in a stainless beaker and dissolved by stirring with heating for 1 hour while heating on a hot plate at 65 ° C.
Pigment dispersant: Ajisper PB824 (Ajinomoto Fine Techno Co., Ltd.) 9 parts by mass Actinic ray curable monomer: OXT221 (Oxetane compound, manufactured by Toagosei Co., Ltd.) 70 parts by mass

  Subsequent procedures were performed in the same manner as in the preparation of the pigment dispersion 1, and a pigment dispersion 2 was prepared.

(Preparation of ink)
An ink was prepared using the prepared pigment dispersion 2 and the following components.

[Gelling agent]
Kao Wax T1 (Kao Corporation)
ITOWAX J-700 (Ito Oil Co., Ltd.)

[Actinic ray curable monomer]
OXT221 (Oxetane compound, manufactured by Toagosei Co., Ltd.)
Celoxide 2021P (alicyclic epoxy, manufactured by Daicel Chemical Industries)

[Photopolymerization initiator]
CPI-100P (Prolyl carbonate 50% solution of triallylsulfonium salt, manufactured by San Apro)

[Sensitizer]
DEA (diethoxyanthracene, manufactured by Kawasaki Chemical Industries)

[Surfactant]
X22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.)

  In accordance with the composition of the ink described in Table 2, each component and each part of the pigment dispersion 2 were mixed and heated to 100 ° C. and stirred. The resulting solution was filtered and cooled with a # 3000 metal mesh filter under heating.

<Measurement of ink properties>
About the ink prepared by the said method, the gelation temperature and the ink viscosity were measured with the following method.

Ink prepared in a temperature-controllable stress-controlled rheometer (Physica MCR300, manufactured by Anton Paar) was set and heated to 100 ° C., cooled to 25 ° C. at a temperature decrease rate of 0.1 ° C./s, and a share rate of 11. Viscosity measurement at 7 s ⁻¹ was performed. The measurement was performed using a cone plate (CP75-1, manufactured by Anton Paar) having a diameter of 75 mm and a cone angle of 1 °. The temperature was controlled by a Peltier element type temperature controller (TEK150P / MC1) attached to the Physica MCR300. The temperature at which the viscosity rapidly increased was read from the viscosity curve obtained by the measurement, and the temperature at which the viscosity showed 500 mPa · s was defined as the gelation temperature.

<Formation of inkjet image>
Using an M head carriage of the ink jet recording apparatus having the ink jet recording head shown in FIGS. 1A and 1B, a magenta monochrome image evaluation was performed. The ink jet recording head, the ink thus prepared was charged, coated printing paper A (manufactured by OK TOPCOAT rice basis weight 84.9 g / ^{m 2} Oji Paper Co., Ltd.), coated printing paper B (New Age rice basis weight 104.7g / M ² manufactured by Oji Paper Co., Ltd.) and art paper (SA Kanito, US basis weight 104.7 g / m ² manufactured by Oji Paper Co., Ltd.).

  The ink supply system consists of an ink tank, a supply pipe, a front chamber ink tank immediately before the print head, a pipe with a filter, and a piezo head. Warm up. The piezo head also had a built-in heater, and the ink in the recording head was also heated. The piezo head has a nozzle diameter of 24 μm and a nozzle number of 512 nozzles. Each of the droplets is ejected at a droplet velocity of about 6 m / sec under the condition that the droplet amount is 3.5 pl and printed at a recording resolution of 1200 dpi × 1200 dpi. .

After printing on the paper, the surface temperature of the heating roller or heating belt whose surface material is silicon resin was controlled to the temperatures shown in Tables 3 to 5. The image surface was smoothed by heating and pressing (0.2 MPa) with a heating roller or a heating belt. After this, an LED lamp disposed at the downstream portion of the recording apparatus (385 nm, manufactured by Hamamatsu Photonics, a distance of 2 mm between the recording medium and the lamp, and a maximum output of 3800 mW / cm ² (measured with a UV integrating photometer: C9536-02 manufactured by Hamamatsu Photonics)) ) Was irradiated with ultraviolet rays to cure the ink. The recording medium was recorded at a conveyance speed of 500 mm / s. The image formation was performed in an environment of 23 ° C. and 55% RH.

<Evaluation of formed image>
The formed image was evaluated for character quality, gloss uniformity, and relief according to the following methods.

(Evaluation of character quality)
On each of the coated paper A, coated paper B, and art paper for printing, the characters “excellent” of 3 points and 5 points of MS Mincho were printed with each colored ink. The obtained characters were visually observed and evaluated according to the following criteria.
○: Even if it is a 3-point character, it can be reproduced without being crushed. △: The detail is crushed if it is a 3-point character, but it can be reproduced without being crushed by a 5-point character.

(Evaluation of gloss uniformity)
Density gradation in which the dot rate is changed to 0%, 10%, 20%, 30%, 50%, 70%, 100% in the area of 2cm x 2cm on the coated paper A, coated paper B, and art paper for printing A patch was created, and the created image was visually evaluated and evaluated according to the following criteria. The dot rate means the pixel density of output data.
○: Uniform gloss is obtained at all dot ratios, and the gloss is uniform. Δ: Some parts are worried about glitter and matte. ×: Glitter and matte are noticeable and glossy. Heterogeneous and unacceptable quality

(Evaluation of relief feeling)
Convert natural images (high-definition color digital standard image data “Cafeteria” published by the Japanese Standards Association) to gray scale in Adobe Photoshop 7.0 on coated paper A, coated paper B, and art paper for printing The printed images were printed and evaluated according to the following criteria.
○: Smooth image quality without a relief △: There is a part that feels unevenness ×: The whole surface has large unevenness and a noticeable relief, making it unusable for practical use

Table 3 shows the ink physical properties and the image formation evaluation results of the ink compositions 1-1 and 1-2.

Table 4 shows the ink physical properties and image formation evaluation results of the ink compositions 2-1 to 2-3.

Table 5 shows the ink physical properties and image formation evaluation results of the ink compositions 1-3 to 1-8.

From the results of Tables 3 and 4, the character quality decreases when the difference (T _A -T _B ) between the roller temperature (T _B ) and the gel temperature (T _A ) is less than 5 ° C., regardless of the type of ink. doing. These are shown, for example, by comparing image numbers A1 to A5 and A6 to A7. This is because the ink droplets that have gelled during the heating and pressurizing process are solated, and adjacent ink droplets are mixed.

From the results shown in Tables 3 and 4, the gloss homogeneity feeling and the relief feeling have a difference (T _A -T _B ) between the roller temperature (T _B ) and the ink gelation temperature (T _A ) of 15 regardless of the type of ink. When the temperature is higher than 5 ° C. or lower than 5 ° C., the temperature decreases. In particular, when the temperature is higher than 15 ° C., it is significantly reduced. These are shown, for example, by comparing image numbers A1-A2 and A3-A7. When the ink viscosity is too high (ink number 2-3), the difference between the roller temperature (T _B ) and the gelation temperature (T _A ) of the ink (T _A -T _B ) is set between 5 and 15 ° C. Even so, the gloss homogeneity and relief are reduced. This is because the image surface could not be smoothed because the ink droplets became a strong gel.

  From the results of Table 5, when the ink is not gelled, all evaluations of character quality, glossy homogeneity and relief are lowered. In particular, the deterioration of character quality is remarkable. This is because the ink droplets landed on the recording medium cannot be pinned and the adjacent ink droplets are mixed. These are shown, for example, by comparing the ink composition 1-3 and the ink compositions 1-5 to 1-7. For the same reason, even when the ink is gelled, if the ink viscosity is too low, the image quality deteriorates. These are shown, for example, by comparing ink compositions 1-4 and ink compositions 1-5 to 1-7. On the other hand, when the ink viscosity is too high, as described above, it is difficult to appropriately smooth, and the gloss homogeneity feeling and the relief feeling are lowered. These are shown, for example, by comparing ink compositions 1-8 and ink compositions 1-5 to 1-7.

As is apparent from the above results, the image forming method of the present invention is carried out using the actinic ray curable inkjet ink containing the gelling agent used in the present invention, thereby improving character quality, gloss uniformity, and relief. An excellent image can be obtained.
This application is accompanied by a priority claim based on a Japanese patent application previously filed by the same applicant, ie, Japanese Patent Application No. 2012-022972 (filing date: February 6, 2012). The contents of which are incorporated herein as part of the present invention.

  According to the image forming method of the present invention, high-quality image formation, particularly high gloss image formation can be performed.

DESCRIPTION OF SYMBOLS 1 Recording medium 2 Recording medium conveyance means 21 Conveying roller pair 3 Head carriage 34 Recording medium holding part 4 Heating pressure member 41 Heating roller 42 Pressure roller 43 Heat generating body 44 Heating belt 45 Lower belt 46 Driven roller 5 Inkjet recording head

Claims (4)

A step of landing droplets of an actinic ray curable inkjet ink containing a coloring material, an actinic ray curable monomer, a photopolymerization initiator, and a gelling agent on a recording medium;
Wherein the surface of the image droplets landed on the recording medium can be formed by applying a heating member flat smoothed by said image surface, comprising: a step of curing by irradiation with actinic rays, a,
The viscosity of the inkjet ink is 1.0 × 10 ^{3 to} 5.0 × 10 ⁴ mPa · s at 25 ° C.,
Wherein the temperature T _B of the heating member is the difference between the gelling temperature T _A of the ink contained in the ink-jet ink (T _A -T _B) is 5 ° C. or more and 15 ℃ or less, and wherein the T _B Is an image forming method having a temperature of less than 80 ° C.   The image forming method according to claim 1, wherein the gelling agent is in the range of 1 to 10% by mass with respect to the total mass of the ink.   The image forming method according to claim 1, wherein a nip pressure in the heating and pressing member is 0.1 MPa or more and less than 0.5 MPa. 2. The image forming method according to claim 1, wherein a surface material of a heating roller or a heating belt of the heating and pressing member is silicon resin or fluorine resin.

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