JP5807606B2 - Actinic ray curable inkjet ink and inkjet recording method - Google Patents

Description

  The present invention relates to an actinic ray curable inkjet ink and an inkjet recording method.

  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 jet 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.

  Further, in the ultraviolet curable ink jet method, high-speed recording; for example, high-speed recording by a single-pass recording method or a high-speed serial method with a few passes has been studied. However, when high-speed recording is performed, there is a problem in that since the interval between adjacent ink droplets (dots) is small, adjacent dots are likely to be united and image quality is likely to be degraded. In order to suppress such unification of adjacent dots, it has been studied to improve the pinning property of the ultraviolet curable inkjet ink.

  As a method for improving the pinning property of the ultraviolet curable ink-jet ink, for example, it has been studied to add a gelling agent to the ink and cause a sol-gel phase transition by temperature. That is, it has been studied to suppress dot coalescence by ejecting ink droplets in a liquid state at high temperature and landing them on a recording medium, and at the same time cooling the ink droplets to gel. As gelling agents added to the ink, waxes such as stearons are disclosed (for example, Patent Documents 1 and 2).

US Patent Application Publication No. 2007/0058020 JP 2007-63553 A

  However, when wax is included in the ink, the wax is deposited on the surface of the printed material after the ink is cured. There is a problem that the appearance deteriorates due to the crystallization of the wax.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an actinic ray curable inkjet ink that has high pinning properties and little appearance deterioration after curing.

The first of the present invention relates to the actinic ray curable inkjet ink shown below.
[1] An actinic ray curable compound comprising an actinic ray curable compound, 1 to 10% by mass of wax, and 0.01 to 3% by mass of a non-polymerizable liquid component, and reversibly undergoes sol-gel phase transition depending on temperature. An actinic ray, which is an inkjet ink, wherein the liquid component has a boiling point of 150 ° C. or higher, the liquid component has a melting point of 25 ° C. or lower, and the solubility of the wax in the liquid component is 1% by mass or higher at 40 ° C. A curable inkjet ink.
[2] The actinic ray curable inkjet ink according to [1], wherein the liquid component is a fatty acid ester.
[3] The actinic ray curable inkjet ink according to [1] or [2], wherein the actinic ray curable compound is a radical polymerizable compound.
[4] The actinic ray curable inkjet ink according to any one of [1] to [3], wherein the addition amount of the wax is 1% by mass or more and less than 7% by mass.

The second aspect of the present invention relates to the following inkjet recording method.
[5] A step of injecting the actinic radiation curable inkjet ink according to any one of [1] to [4] onto a recording medium, irradiating the ink ejected on the recording medium with an actinic ray, and curing the ink jet recording how.

  The actinic ray curable inkjet ink of the present invention suppresses the phenomenon of “blooming” caused by the precipitation and crystallization of the wax on the image surface, even though the wax is blended. Therefore, according to the actinic ray curable inkjet ink of the present invention, a high quality image can be formed.

It is a figure which shows an example of a structure of the principal part of the inkjet recording apparatus of a line recording system. It is a figure which shows an example of a structure of the principal part of the inkjet recording device of a serial recording system.

  The actinic ray curable inkjet ink of the present invention contains an actinic ray curable compound, a wax, and a non-polymerizable liquid component.

[Actinic ray curable compound]
The actinic ray curable compound is a photopolymerizable compound that is crosslinked or polymerized by actinic rays. The actinic rays are, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, and preferably ultraviolet rays and electron beams. The actinic ray curable compound is a radical polymerizable compound or a cationic polymerizable compound, and is preferably a radical polymerizable compound.

  The radically polymerizable compound is a compound (monomer, oligomer, polymer or mixture thereof) having a radically polymerizable ethylenically unsaturated bond. Only one kind of radically polymerizable compound may be contained in the actinic ray curable inkjet ink, or two or more kinds thereof may be contained.

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

  Especially, it is preferable that a radically polymerizable compound is an unsaturated carboxylic acid ester compound, and it is more preferable that it is a (meth) acrylate compound. The (meth) acrylate compound may be not only a monomer described later, but also an oligomer, a mixture of a monomer and an oligomer, a modified product, an oligomer having a polymerizable functional group, and the like.

Examples of (meth) acrylate compounds include isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, isomyristyl (meth) acrylate, isostearyl (meth) ) Acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate , Methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (meth) ) Acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- (Meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl-2-hydroxyethyl-phthalic acid, t-butylcyclohexyl (meth) acrylate, etc. Monofunctional monomer;
Triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,4-butanediol di (Meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, bisphenol A bifunctional monomer such as PO adduct di (meth) acrylate of A, neopentyl glycol di (meth) acrylate hydroxypivalate, poly (tetramethylene glycol di (meth) acrylate);
Trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, glycerin propoxytri (meth) acrylate And trifunctional or higher polyfunctional monomers such as pentaerythritol ethoxytetra (meth) acrylate.

  From the viewpoint of photosensitivity, (meth) acrylate compounds are stearyl (meth) acrylate, lauryl (meth) acrylate, isostearyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, isobornyl (meth) acrylate, tetraethylene glycol di (Meth) acrylate, glycerin propoxytri (meth) acrylate and the like are preferable.

  The (meth) acrylate compound may be a modified product. Examples of modified products include ethylene oxide-modified (meth) acrylate compounds such as ethylene oxide-modified trimethylolpropane tri (meth) acrylate and ethylene oxide-modified pentaerythritol tetraacrylate; caprolactone such as caprolactone-modified trimethylolpropane tri (meth) acrylate Modified (meth) acrylate compounds; and caprolactam-modified (meth) acrylate compounds such as caprolactam-modified dipentaerythritol hexa (meth) acrylate.

  Since the actinic ray curable inkjet ink of the present invention is a sol-gel phase transition type, it is preferable that at least a part of the actinic ray curable compound is an ethylene oxide-modified (meth) acrylate compound. This is because the ethylene oxide-modified (meth) acrylate compound has high photosensitivity and easily forms a card house structure (described later) when the ink gels at a low temperature. In addition, the ethylene oxide-modified (meth) acrylate compound is easily dissolved in other ink components at high temperatures and has little curing shrinkage, so that curling of the printed matter hardly occurs.

  Examples of ethylene oxide-modified (meth) acrylate compounds include 4EO-modified hexanediol diacrylate CD561 (molecular weight 358), 3EO-modified trimethylolpropane triacrylate SR454 (molecular weight 429), 6EO-modified trimethylolpropane triacrylate SR499 manufactured by Sartomer. (Molecular weight 560), 4EO-modified pentaerythritol tetraacrylate SR494 (molecular weight 528); polyethylene glycol diacrylate NK ester A-400 (molecular weight 508), polyethylene glycol diacrylate NK ester A-600 (molecular weight 742) manufactured by Shin-Nakamura Chemical Co., Ltd. , Polyethylene glycol dimethacrylate NK ester 9G (molecular weight 536), polyethylene glycol dimethacrylate NK ester 4G (molecular weight 770); Tetraethylene glycol diacrylate V # 335HP (molecular weight 302) manufactured by Osaka Organic Chemical Co .; 3PO-modified trimethylolpropane triacrylate Photomer 4072 (molecular weight 471, ClogP 4.90) manufactured by Cognis; Shin-Nakamura Chemical 1,10-decanediol dimethacrylate NK ester DOD-N (molecular weight 310, Clog P 5.75), tricyclodecane dimethanol diacrylate NK ester A-DCP (molecular weight 304, Clog P 4.69) and tricyclodecandi Methanol dimethacrylate NK ester DCP (molecular weight 332, Clog P 5.12) and the like are included.

  The (meth) acrylate compound may be a polymerizable oligomer. Examples of polymerizable oligomers include epoxy (meth) acrylate oligomers, aliphatic urethane (meth) acrylate oligomers, aromatic urethane (meth) acrylate oligomers, polyester (meth) acrylate oligomers, and linear (meth) acrylic oligomers. included.

  The cationically polymerizable compound can be an epoxy compound, a vinyl ether compound, an oxetane compound, or the like. Only one kind of cationic polymerizable compound may be contained in the actinic ray curable inkjet ink, or two or more kinds thereof may be contained.

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

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

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

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

Examples of vinyl ether compounds include 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. monovinyl ether compounds such as -o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether;
Diethylene 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, cyclohexane dimethanol divinyl ether, trimethylolpropane trivinyl ether, etc. Or a trivinyl ether compound etc. are contained. Of these vinyl ether compounds, di- or trivinyl ether compounds are preferred in view of curability and adhesion.

The oxetane compound is a compound having an oxetane ring, and examples thereof include oxetane compounds described in JP-A Nos. 2001-220526, 2001-310937, and JP-A-2005-255821. Among them, the compound represented by the general formula (1) described in paragraph No. 0089 of JP-A-2005-255821, the compound represented by the general formula (2) described in paragraph No. 0092 of the same publication, the paragraph Examples include a compound represented by general formula (7) of number 0107, a compound represented by general formula (8) of paragraph number 0109, a compound represented by general formula (9) of paragraph number 0116, and the like. General formulas (1), (2), and (7) to (9) described in JP-A-2005-255821 are shown below.

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

[wax]
In the present invention, the wax is generally defined as an organic substance that is solid at room temperature and becomes liquid when heated. The melting point of the wax is preferably 30 ° C. or higher and lower than 150 ° C. The wax contained in the actinic radiation curable inkjet ink of the present invention is at least 1) soluble in the actinic radiation curable compound at a temperature higher than the gelation temperature, and 2) in the ink at a temperature below the gelation temperature. It is necessary to crystallize.

  When the wax is crystallized in the ink, it is preferable to form a space three-dimensionally surrounded by plate crystals that are crystallized wax, and enclose the actinic ray curable compound in the space. Thus, the structure in which the actinic ray curable compound is encapsulated in the space three-dimensionally surrounded by the plate crystal is sometimes referred to as “card house structure”. Once the card house structure is formed, the liquid actinic radiation curable compound can be retained and the ink droplets can be pinned. Thereby, coalescence of droplets can be suppressed. In order to form the card house structure, it is preferable that the actinic ray curable compound dissolved in the ink and the wax are compatible. On the other hand, if the actinic ray curable compound dissolved in the ink and the wax are phase-separated, it may be difficult to form a card house structure.

The type of wax is not particularly limited. Preferred examples of wax include
Ketone waxes such as dilignoseryl ketone, dibehenyl ketone, distearyl ketone, diecosyl ketone, dipalmityl ketone, dimyristyl ketone, myristyl palmityl ketone, palmityl stearyl ketone, etc. (for example, 18-Pentatria contananon (Alfa Aeser) ), Hentriacantan-16-on (manufactured by Alfa Aeser), Kao wax T1 (manufactured by Kao Corporation), etc.);
Ester waxes such as behenyl behenate, icosyl icosanoate, stearyl stearate, palmityl stearate, cetyl palmitate, myristyl myristate, cetyl myristate, and myricyl serotate (eg Unistar M-2222SL (manufactured by NOF Corporation), Exepearl SS (manufactured by Kao Corporation, melting point 60 ° C.), EMALEX CC-18 (manufactured by Nippon Emulsion Co., Ltd.), Amreps PC (manufactured by Higher Alcohol Industry Co., Ltd.), EXCEPARL MY-M (manufactured by Kao Corporation), SPALM ACETI (NOF) Manufactured by Co., Ltd.), EMALEX CC-10 (manufactured by Nippon Emulsion Co., Ltd.), etc.);
Petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam;
Plant waxes such as candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax, and jojoba ester;
Animal waxes such as beeswax, lanolin and whale wax;
Mineral waxes such as montan wax and hydrogenated wax;
Hydrogenated castor oil or hydrogenated castor oil derivative;
Modified waxes such as montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives or polyethylene wax derivatives;
Higher fatty acids such as behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid;
Higher alcohols such as stearyl alcohol and behenyl alcohol;
Hydroxystearic acid such as 12-hydroxystearic acid;
12-hydroxystearic acid derivatives; fatty acid amides such as lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, 12-hydroxystearic acid amide (for example, Nikka Amide series manufactured by Nippon Kasei Co., Ltd.) ITOWAX series manufactured by Ito Oil Co., Ltd., FATTYAMID series manufactured by Kao Corporation, etc.);
N-substituted fatty acid amides such as N-stearyl stearamide and N-oleyl palmitate amide;
Special fatty acid amides such as N, N′-ethylenebisstearylamide, N, N′-ethylenebis-12-hydroxystearylamide, and 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. Marl series, RIKEN VITAMIN POM series, etc.);
Esters of sucrose fatty acids such as sucrose stearic acid and sucrose palmitic acid (eg Ryoto Sugar Ester series manufactured by Mitsubishi Chemical Foods);
Synthetic waxes such as polyethylene wax and α-olefin maleic anhydride copolymer wax (such as UNILIN series manufactured by Baker-Petrolite);
Dimer acid;
Dimer diol (such as PRIDA series manufactured by CRODA) is included.
Only one kind of these waxes may be contained in the actinic ray curable inkjet ink, or two or more kinds thereof may be contained.

  The wax is particularly preferably a ketone wax, an ester wax, a higher fatty acid, a higher alcohol, or a fatty acid amide, and more preferably a ketone wax or an ester wax.

  The content of the wax in the actinic ray curable inkjet ink of the present invention is 1 to 10% by mass, and more preferably 1 to 7% by mass. When two or more kinds of waxes are included, the total amount thereof is preferably in the above range. If the wax content is less than 1% by mass, the actinic radiation curable inkjet ink of the present invention may not sufficiently undergo sol-gel phase transition. On the other hand, when the wax content exceeds 10% by mass, the ink ejectability from the inkjet head may deteriorate.

[Gelling agent]
The actinic ray curable inkjet ink of the present invention may contain a gelling agent that assists the sol-gel phase transition by the wax. Examples of gelling agents include fatty acid inulins such as inulin stearate; fatty acid dextrins such as dextrin palmitate and dextrin myristate (such as Leopard Series manufactured by Chiba Flour Mills); glyceryl behenate; eicosane polyglyceryl behenate; Nisshin Oilio Co., Ltd. Nomucoat series, etc.); N-lauroyl-L-glutamic acid dibutylamide, amide compounds such as N- (2-ethylhexanoyl) -L-glutamic acid dibutylamide (available from Ajinomoto Finetechno); 1 , 3: 2,4-bis-O-benzylidene-D-glucitol (Gelol D, available from Shin Nippon Chemical Co., Ltd.) and the like; JP-A-2005-126507, JP-A-2005-255821 Low as described in Kai 2010-1111790 And the like; child oil gelling agent.

  1-10 mass% is preferable and, as for the quantity of the gelatinizer in the actinic-light curable inkjet ink of this invention, 1-7 mass% is more preferable. If the amount of the gelling agent is excessive, ink ejection properties from the inkjet head may be reduced.

[Liquid component]
The liquid component is a non-polymerizable compound that is not polymerized by actinic rays. Since the liquid component is a non-polymerizable component, the liquid component has low compatibility with the cured product of the actinic ray curable compound and exists at a high concentration near the surface of the ink cured product. When the wax in the cured product is dissolved in this liquid component, it becomes difficult for the wax to precipitate and “blooming” is suppressed.

  The liquid component has a boiling point of 150 ° C. or higher, preferably 200 ° C. or higher, more preferably 250 ° C. or higher. If the boiling point is 150 ° C. or higher, a decrease due to volatilization of the liquid component can be suppressed. The boiling point is a value measured according to JIS K2254.

  The melting point of the liquid component is 25 ° C. or less, preferably 5 ° C. or less. The melting point of the liquid component is 25 ° C. or lower; that is, if the liquid component is liquid at room temperature, “blooming” that occurs during normal use of the recording medium can be suppressed. The melting point is a value measured according to JIS K6004.

  The solubility of the wax in the liquid component at 40 ° C. is 1% by mass or more. When actinic ray-curable inkjet ink contains a plurality of types of wax, the solubility of all waxes in the liquid component is 1% by mass or more, respectively. Further, when a plurality of types of liquid components are contained in the actinic ray curable inkjet, the solubility of the wax with respect to any one liquid component is 1% by mass or more. If the solubility of the wax in the liquid component at 40 ° C. (near the storage temperature of the ink cured product) is less than 1% by mass, the wax deposited on the surface of the cured product cannot be sufficiently dissolved and “blooming” is suppressed. The effect is reduced.

  The solubility is the ratio of the maximum amount (mass) of wax to be dissolved to the liquid component amount (mass) at 40 ° C. The solubility can be specified by dissolving wax in a liquid component at 90 ° C., cooling it to 40 ° C., and confirming whether the wax is precipitated. The solubility of the wax in the liquid component is adjusted by selecting a liquid component that is highly compatible with the wax.

  The type of the liquid component is not particularly limited as long as it is a compound having compatibility with the gelling agent, but fatty acid esters are preferred from the viewpoint of wax solubility.

Specific examples of fatty acid esters include cetyl 2-ethylhexanoate, methyl coconut fatty acid, methyl laurate, isopropyl myristate, isopropyl palmitate, 2-ethylhexyl palmitate, octyldodecyl myristate, butyl stearate, 2-stearate Ethylhexyl, isotridecyl stearate, methyl oleate, isobutyl oleate, methyl erucate, butyl laurate, octyl palmitate, octyl stearate, octyl oleate, butyl stearate, ethyl oleate, hexyldecyl isostearate, isocetyl myristate , Isocetyl stearate, Isopropyl isostearate, Isostearyl palmitate, Ethyl linoleate, Isopropyl linoleate, Octyl neopentanoate Sill, esters derived from fatty acids, monohydric alcohols such as salicylate butyl octyl;
Dinormal alkyl phthalate (C8-C10), di-2-ethylhexyl phthalate, diisononyl phthalate (DINP), didecyl phthalate (n-DDP), dialkyl phthalate (C10-C12), ditridecyl phthalate (DTDP), Trinormal alkyl trimellitic acid (C8-C10), tri-2-ethylhexyl trimellitic acid, tri-2-ethylhexyl trimellitic acid, triisodecyl trimellitic acid, diisobutyl adipate (DIBA), diisodecyl adipate (DIDA), adipic acid ester Esters derived from polybasic acids and monohydric alcohols such as diethyl sebacate, diisopropyl adipate, diisopropyl sebacate, diethylhexyl naphthalene dicarboxylate, dibutyloctyl sebacate;
Sorbitan monolaurate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, sorbitan monooleate, sorbitan sesquioleate, sorbitan monolaurate, sorbitan monooleate, polyoxyethylene sorbitan monolaurate, polyethylene glycol mono Laurate, polyethylene glycol monooleate, pentaerythritol monooleate, polyglyceryl-2 triisostearate, propylene glycol dicaprate, propylene glycol caprylate, pentaerythrityl tetraethylhexanoate, propylene glycol dicaprylate, trimethylolpropane triethylhexanoate , Trimethylolpropane triisostearate, triethylhexanoin, trica Lil glyceryl esters or derivatives from fatty acid esters, polyhydric alcohols, such as ethylhexanoic acid butyl ethyl propane diol;
Fatty acid esters such as oleic acid monoglyceride, 2-ethylhexanoic acid triglyceride, caprylic acid mono-diglyceride, caprylic acid triglyceride;
Sucrose fatty acid esters such as sucrose oleate and sucrose erucate;
Hydroxyl group-containing esters such as diisostearyl malate, triethylhexyl citrate, polyglyceryl-2 triisostearate;
Polyglyceryl fatty acid esters such as polyglyceryl triisostearate-2, polyglyceryl-4 pentaoleate, polyglyceryl heptaoleate-10, polyglyceryl-10 decaisostearate, polyglyceryl-10 decaoleate, polyglyceryl-10 decamacademia nut fatty acid; It is. The ester contained in the actinic ray curable inkjet ink may be only one kind or a mixture of two or more kinds. The fatty acid ester is particularly preferably an ester derived from a fatty acid / monohydric alcohol.

  The amount of the liquid component in the actinic ray curable inkjet ink of the present invention is 0.01 to 3% by mass, preferably 0.1 to 1% by mass. When two or more liquid components are contained, the total of these contents is within the above range. If the amount of the liquid component is too small, the wax deposited on the surface of the ink cured product cannot be sufficiently dissolved, and the blooming suppressing effect cannot be obtained. On the other hand, if the amount of the liquid component is excessive, the liquid component inhibits the crystallization of the wax in the ink before curing. That is, the sol-gel phase transition effect by the wax cannot be obtained, and the pinning property of the ink is lowered. Further, when the amount of the liquid component is increased, stickiness or the like occurs in the ink cured product.

[Photopolymerization initiator]
The actinic ray curable inkjet ink may further contain a photopolymerization initiator. Specifically, when the actinic ray is an electron beam, a photopolymerization initiator may ordinarily not be included. However, when the actinic ray is an ultraviolet ray, a photopolymerization initiator is preferably contained.

  Photopolymerization initiators include an intramolecular bond cleavage type and an intramolecular hydrogen abstraction type. Examples of intramolecular bond cleavage type photopolymerization initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2. -Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4 Acetophenones such as -thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone; benzoins such as benzoin, benzoin methyl ether, benzoin isopropyl ether; 2 Acylphosphine oxide systems such as 1,4,6-trimethylbenzoindiphenylphosphine oxide; benzyl and And methylphenylglyoxyester.

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

  The content of the photopolymerization initiator in the actinic ray curable inkjet ink is preferably 0.01% by mass to 10% by mass, although it depends on the type of actinic ray or actinic ray curable compound.

  The actinic ray curable inkjet ink may contain a photoacid generator as a photopolymerization initiator. Examples of photoacid generators include chemically amplified photoresists and compounds used for photocationic polymerization (Organic Electronics Materials Study Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187. To page 192).

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

  Examples of polymerization inhibitors include (alkyl) phenol, hydroquinone, catechol, resorcin, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone , Nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, 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.

[Color material]
The actinic ray curable inkjet ink may further contain a coloring material as necessary. The coloring material can be a dye or a pigment, but is preferably a pigment because it has good dispersibility with respect to the components of the ink and is excellent in weather resistance. The pigment is not particularly limited, and may be, for example, an organic pigment or an inorganic pigment having the following numbers described in the color index.

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

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

  The pigment can be dispersed by, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker. The pigment is dispersed so that the average particle size of the pigment particles is preferably 0.08 to 0.5 μm, and the maximum particle size is preferably 0.3 to 10 μm, more preferably 0.3 to 3 μm. Is preferred. The dispersion of the pigment is adjusted by the selection of the pigment, the dispersant, and the dispersion medium, the dispersion conditions, the filtration conditions, and the like.

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

  The actinic ray curable inkjet ink may further contain a dispersion aid as necessary. The dispersion aid may be selected according to the pigment.

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

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

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

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

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

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

  The content of the pigment or dye is preferably 0.1 to 20% by mass, and more preferably 0.4 to 10% by mass with respect to the actinic ray curable inkjet ink. This is because if the content of the pigment or dye is too small, the color of the resulting image is not sufficient, and if it is too large, the viscosity of the ink increases and the jetting property decreases.

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

  The actinic ray curable inkjet ink can be obtained by mixing the actinic ray curable compound, the wax, the liquid component, and any of the components under heating. It is preferable to filter the obtained liquid mixture with a predetermined filter.

[Actinic ray curable inkjet ink]
As described above, the actinic ray curable inkjet ink of the present invention is an ink that undergoes a sol-gel phase transition reversibly with temperature. Since the sol-gel phase transition type actinic ray curable ink is a sol at a high temperature (for example, about 80 ° C.), it can be ejected 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.

  In order to improve the ejection property of the sol-gel phase transition type ink, it is preferable that the viscosity of the ink at a high temperature is not more than a certain level. Specifically, the actinic ray curable inkjet ink preferably has a viscosity at 80 ° C. of 3 to 20 mPa · s. On the other hand, in order to suppress coalescence of adjacent dots, it is preferable that the viscosity of the ink at normal temperature after landing is a certain level or more. Specifically, the viscosity at 25 ° C. of the actinic ray curable inkjet ink is preferably 1000 mPa · s or more.

  The gelation temperature of the sol-gel phase transition ink is preferably 40 ° C. or higher and 70 ° C. or lower, and more preferably 50 ° C. or higher and 65 ° C. or lower. If the gelation temperature of the ink exceeds 70 ° C. when the ejection temperature is in the vicinity of 80 ° C., gelation tends to occur at the time of ejection, resulting in poor ejection properties. On the other hand, if the gelation temperature is less than 40 ° C., the gelation does not occur immediately after landing on the recording medium. The gelation temperature is a temperature at which the fluidity decreases due to gelation in the process of cooling the ink in the sol state.

  The viscosity at 80 ° C., the viscosity at 25 ° C. and the gelation temperature of the sol-gel phase transition type ink can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink with a rheometer. Specifically, a temperature change curve of viscosity is obtained when the ink is heated to 100 ° C. and cooled to 20 ° C. under conditions of a shear rate of 11.7 (/ s) and a temperature decrease rate of 0.1 ° C./s. And the viscosity in 80 degreeC and the viscosity in 25 degreeC can be calculated | required by reading the viscosity in 80 degreeC and 25 degreeC in the temperature change curve of a viscosity, respectively. The gelation temperature can be determined as the temperature at which the viscosity becomes 200 mPa · s in the temperature change curve of the viscosity.

  As the rheometer, a stress control type rheometer Physica MCR series manufactured by Anton Paar can be used. The cone plate can have a diameter of 75 mm and a cone angle of 1.0 °.

  In order to improve the ejection property of the ink from the ejection recording head, the sol-gel phase transition type ink has an ink temperature of (gelation temperature + 10) ° C. to ( The gelling temperature is preferably set to +30) ° C. When the temperature of the ink in the ejection recording head is less than (gelation temperature + 10) ° C., the ink is gelled in the ejection recording head or on the nozzle surface, and the ink ejection property is likely to deteriorate. On the other hand, when the temperature of the ink in the ejection recording head exceeds (gelation temperature + 30) ° C., the ink becomes too high, and the ink component may deteriorate.

[Inkjet recording method]
The inkjet recording method of the present invention includes 1) a step of ejecting the actinic ray curable inkjet ink of the present invention onto a recording medium, and 2) a step of irradiating the ink landed on the recording medium with an actinic ray to cure the ink. And including.

  1) In the ejection step, the inkjet ink stored in the ejection recording head may be ejected as droplets toward the recording medium through the nozzles. At this time, the temperature of the inkjet ink stored in the ejection recording head is set to a temperature at which the content of the wax contained in the ink is equal to or lower than the saturated dissolution amount of the wax in the ink. That is, the wax is dissolved as much as possible in the inkjet ink stored in the ejection recording head.

  2) In the curing step, the ink that has landed on the recording medium is irradiated with light. What is necessary is just to select suitably the light irradiated according to the kind of actinic-light curable compound, and may be an ultraviolet-ray, an electron beam, etc.

  The actinic ray curable ink jet recording apparatus of the present invention will be described. Actinic ray curable ink jet recording apparatuses include a line recording method (single pass recording method) and a serial recording method. The line recording method (single-pass recording method) is preferable from the viewpoint of high-speed recording, although it may be selected according to the required image resolution and recording speed.

  FIG. 1 is a diagram illustrating an example of a configuration of a main part of a line recording type ink jet recording apparatus. Among these, Fig.1 (a) is a side view, FIG.1 (b) is a top view. As shown in FIG. 1, the ink jet recording apparatus 10 includes a head carriage 16 that accommodates a plurality of ink ejection recording heads 14, covers the entire width of the recording medium 12, and the head carriage 16 (recording medium conveyance direction). An actinic ray irradiation unit 18 disposed on the downstream side and a temperature control unit 19 disposed on the lower surface of the recording medium 12 are included.

  The head carriage 16 is fixedly arranged so as to cover the entire width of the recording medium 12 and accommodates a plurality of ink ejection recording heads 14 provided for each color. Ink is supplied to the ink ejection recording head 14. For example, the ink may be supplied directly or by an ink supply unit (not shown) from an ink cartridge (not shown) that is detachably attached to the inkjet recording apparatus 10.

  A plurality of ink discharge recording heads 14 are arranged in the transport direction of the recording medium 12 for each color. The number of ink ejection recording heads 14 arranged in the conveyance direction of the recording medium 12 is set according to the nozzle density of the ink ejection recording head 14 and the resolution of the print image. For example, when an image having a resolution of 1440 dpi is formed using the ink ejection recording head 14 having a droplet amount of 2 pl and a nozzle density of 360 dpi, four ink ejection recording heads 14 are provided in the transport direction of the recording medium 12. What is necessary is just to shift and arrange. Further, when an image having a resolution of 720 × 720 dpi is formed using the ink discharge recording head 14 having a droplet amount of 6 pl and a nozzle density of 360 dpi, the two ink discharge recording heads 14 may be arranged in a shifted manner. dpi represents the number of ink droplets (dots) per 2.54 cm.

  The actinic ray irradiation unit 18 covers the entire width of the recording medium 12 and is disposed on the downstream side of the head carriage 16 in the recording medium conveyance direction. The actinic ray irradiation unit 18 irradiates the droplets ejected by the ink ejection recording head 14 and landed on the recording medium with actinic rays to cure the droplets.

When the actinic ray is ultraviolet ray, examples of the actinic ray irradiating unit 18 (ultraviolet ray irradiating means) include a fluorescent tube (low pressure mercury lamp, germicidal lamp), a cold cathode tube, an ultraviolet laser, and an operating pressure of several hundred Pa to 1 MPa. These include low pressure, medium pressure, high pressure mercury lamps, metal halide lamps and LEDs. From the viewpoint of curability, ultraviolet irradiation means for irradiating ultraviolet rays having an illuminance of 100 mW / cm ² or more; specifically, high-pressure mercury lamps, metal halide lamps, and LEDs are preferable, and LEDs are more preferable from the viewpoint of low power consumption. Specifically, a 395 nm, water-cooled LED manufactured by Phoseon Technology can be used.

  When the actinic ray is an electron beam, examples of the actinic ray irradiating unit 18 (electron beam irradiating unit) include electron beam irradiating means such as a scanning method, a curtain beam method, and a broad beam method. Therefore, a curtain beam type electron beam irradiation means is preferable. Examples of the electron beam irradiation means include “Curetron EBC-200-20-30” manufactured by Nissin High Voltage Co., Ltd., “Min-EB” manufactured by AIT Co., Ltd., and the like.

  The temperature control unit 19 is disposed on the lower surface of the recording medium 12 and maintains the recording medium 12 at a predetermined temperature. The temperature control unit 19 can be, for example, various heaters.

  Hereinafter, an image recording method using the line recording type inkjet recording apparatus 10 will be described. The recording medium 12 is conveyed between the head carriage 16 and the temperature control unit 19 of the inkjet recording apparatus 10. On the other hand, the recording medium 12 is adjusted to a predetermined temperature by the temperature control unit 19. Next, high-temperature ink is ejected from the ink ejection recording head 14 of the head carriage 16 and adhered (landed) on the recording medium 12. Then, the actinic ray irradiating unit 18 irradiates the ink droplets attached on the recording medium 12 with an actinic ray to cure.

  When the ink is ejected from the ink ejection recording head 14, the temperature of the ink in the ink ejection recording head 14 is 10 to 30 ° C. higher than the gelation temperature of the ink in order to improve the ink ejection property. It is preferable to set the temperature. When the ink temperature in the ink discharge recording head 14 is less than (gelation temperature + 10) ° C., the ink is gelled in the ink discharge recording head 14 or on the nozzle surface, and the ink ejection property is likely to be lowered. On the other hand, when the temperature of the ink in the ink ejection recording head 14 exceeds (gelling temperature + 30) ° C., the ink becomes too high, and the ink component may deteriorate.

  The amount of droplets ejected from each nozzle of the ink ejection recording head 14 is preferably 1 pl to 10 pl in order to form a high resolution image, although it depends on the resolution of the image. More preferably, it is 0.5-4.0pl.

  Irradiation with actinic rays is performed within 10 seconds, preferably within 0.001 seconds to 5 seconds, more preferably after ink droplets are deposited on the recording medium, in order to prevent adjacent ink droplets from coalescing. It is preferable to carry out within 0.01 second to 2 seconds. Irradiation with actinic rays is preferably performed after ink is ejected from all the ink ejection recording heads 14 accommodated in the head carriage 16.

  When the actinic ray is an electron beam, the acceleration voltage for electron beam irradiation is preferably 30 to 250 kV and more preferably 30 to 100 kV in order to perform sufficient curing. When the acceleration voltage is 100 to 250 kV, the electron beam irradiation amount is preferably 30 to 100 kGy, and more preferably 30 to 60 kGy.

  The total ink film thickness after curing is preferably 2 to 25 μm. The “total ink film thickness” is the maximum value of the ink film thickness drawn on the recording medium.

  FIG. 2 is a diagram illustrating an example of a configuration of a main part of the serial recording type inkjet recording apparatus 20. As shown in FIG. 2, the inkjet recording apparatus 20 has a width narrower than the entire width of the recording medium, instead of the head carriage 16 fixedly arranged so as to cover the entire width of the recording medium, and a plurality of ink ejection devices. Except for having a head carriage 26 that accommodates the recording head 24 and a guide portion 27 for moving the head carriage 26 in the width direction of the recording medium 12, the configuration can be the same as in FIG.

  In the serial recording type inkjet recording apparatus 20, the head carriage 26 ejects ink from the ink ejection recording head 24 accommodated in the head carriage 26 while moving in the width direction of the recording medium 12 along the guide portion 27. After the head carriage 26 has completely moved in the width direction of the recording medium 12 (for each pass), the recording medium 12 is sent in the transport direction, and the actinic light irradiation unit 28 irradiates the active light. Except for these operations, an image is recorded in substantially the same manner as the line recording type inkjet recording apparatus 10 described above.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not construed as being limited by these descriptions.

[Production of actinic ray curable inkjet ink]
An actinic ray curable inkjet ink was prepared using the following components (wax, liquid component, polymerizable compound, polymerization inhibitor, polymerization initiator, pigment dispersion).

[wax]
Aliphatic ketone (Kao wax T1, Kao)
Behenyl behenate (Unistar M-2222SL, NOF)
Behenic acid (Lunac BA, Kao)
Erucamide (Neutron S, Nippon Seika)
Behenyl alcohol (behenyl alcohol 80R, higher alcohol industry)

[Liquid component]
2-ethylhexyl palmitate (Exepal EH-P, Kao, boiling point 407 ° C, melting point -2 ° C)
Cetyl 2-ethylhexanoate (Exepal HO, Kao, boiling point 228 ° C, melting point 4 ° C or less)
Isopropyl palmitate (Exepal IPP, Kao, boiling point 332 ° C, melting point 8-15 ° C)
Isotridecyl stearate (Exepal TD-S, Kao, boiling point 490 ° C, melting point 4 ° C or less)
Isopropyl myristate (Exepal IPM, Kao, boiling point 193 ° C, melting point -5 ° C)
Sucrose erucic acid ester (ER-190, Mitsubishi Chemical Foods, boiling point 150 ° C or higher, melting point 4 ° C or lower)
Polyoxyethylene alkyl ether (Emulgen 707, boiling point 250 ° C or higher, melting point -3 ° C)

[Polymerizable compound]
Polyethylene glycol # 400 diacrylate (A-400, Shin-Nakamura Chemical)
4EO modified pentaerythritol tetraacrylate (SR494, SARTOMER)
6EO modified trimethylolpropane triacrylate (SR499, SARTOMER)

[Polymerization inhibitor]
Irgastab UV10 (Ciba Specialty Chemical)
[Polymerization initiator]
DAROCURE TPO (Ciba Specialty Chemical)

[Pigment dispersion]
Preparation of Pigment Dispersion Liquid 1 (M: Magenta) The following dispersant, actinic ray curable compound and polymerization inhibitor were placed in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a 65 ° C hot plate. It was. After cooling the resulting solution to room temperature, 21 parts by mass of the following magenta pigment 1 was added, sealed in a glass bottle together with 200 g of zirconia beads having a diameter of 0.5 mm, and dispersed for 8 hours with a paint shaker. Thereafter, the zirconia beads were removed to prepare a pigment dispersion 1 having the following composition.
[Composition of Pigment Dispersion Liquid 1]
Dispersant: Ajisper PB824 (manufactured by Ajinomoto Fine Techno Co., Ltd.) 9 parts by mass Actinic ray curable compound: APG-200 (tripropylene glycol diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.) 70 parts by mass Polymerization inhibitor: Irgastab UV10 (Ciba Japan) 0.02 part by mass Magenta pigment 1: Pigment Red 122 (manufactured by Dainichi Seika, Chromo Fine Red 6112JC)

[Preparation of ink]
According to the composition shown in Table 1, the mixture obtained by mixing each component was heated to 80 ° C. and stirred. The obtained solution was filtered through a # 3000 metal mesh filter under heating, and then cooled to prepare an ink. In Table 1, the unit of the amount of each component is part by mass.

[Wax solubility in liquid components]
10 g of the liquid component added in each Example and Comparative Example was put in a stainless beaker, 0.1 g of the wax added in the same Example and Comparative Example was added and heated to 90 ° C. to completely dissolve. Then, it moved to the 40 degreeC hotplate and confirmed whether there was any precipitation. Evaluation was performed as follows.
○: 0.1 g of wax was completely dissolved in a liquid component at 40 ° C.
X: 0.1 g of wax was not dissolved in the liquid component at 40 ° C., and precipitation was observed.

[Image Forming Method]
With the actinic ray curable inkjet ink obtained in each example and comparative example, a monochromatic image was formed using a line inkjet recording apparatus. The temperature of the inkjet head of the inkjet recording apparatus was set to 80 ° C. A blank character, a solid image of 5 cm × 5 cm, or a density gradation patch was printed on the recording medium. After the image was formed, the ink was cured by irradiating the image with ultraviolet light using an LED lamp (395 nm manufactured by Phoseon Technology, water-cooled LED) disposed in the downstream portion of the recording apparatus.

  As the ink ejection recording head, a piezo head having a nozzle diameter of 20 μm and a nozzle number of 512 nozzles (256 nozzles × 2 rows, staggered arrangement, 1 row nozzle pitch 360 dpi) was used. The ejection conditions were such that the amount of one droplet was 2.5 pl, and ejection was performed at a droplet velocity of about 6 m / s, and recording was performed at a resolution of 1440 dpi × 1440 dpi. The recording speed was 500 mm / s. Image formation was performed in an environment of 23 ° C. and 55% RH. dpi represents the number of dots per 2.54 cm.

[Image Evaluation]
(Evaluation of blooming)
A solid image of 5 cm × 5 cm formed on the coated paper A for printing, which is a recording medium (OK top coat, US basis weight 128 g / m, manufactured by ² Oji Paper Co., Ltd.) by the above-described method, in an environment of 25 ° C. and 5 ° C., respectively. Stored for 1 month. The image after storage at each temperature was visually observed, and blooming was evaluated according to the following criteria.
○: No precipitate is observed on the image surface.
Δ: A thin precipitate is present on the image surface and can be visually confirmed.
X: The image surface is covered with the substance on the powder, and can be clearly confirmed visually.

(Evaluation of surface stickiness)
By the above method, a recording medium for printing coated paper A (manufactured by OK TOPCOAT rice basis weight 128 g / ^{m 2} Oji Paper Co., Ltd.) to form a solid image of 5 cm × 5 cm. On this solid image, superimposed printing coated paper A (manufactured by OK TOPCOAT rice basis weight 128 g / ^{m 2} Oji Paper Co., Ltd.), weight of 2kg from the top (bottom 100 cm × 100 cm) put a 1 day static I put it. Thereafter, the weight and the coated paper A for printing were removed, and whether or not the ink component adhered to the coated paper A for printing overlapped with the solid image was evaluated according to the following criteria.
◯: There is no adhesion of ink components to the overlying coated coated paper A.
Δ: Slight adhesion of ink component is observed on the stacked paper.
X: Adhesion of the ink component is clearly observed on the stacked paper.

(Evaluation of density unevenness)
By the above method, a solid image of 5 cm × 5 cm was printed on a recording medium for printing coated paper A (manufactured by OK TOPCOAT rice basis weight 128 g / m ² Oji Paper Co., Ltd.) was visually evaluated, density unevenness in accordance with the following evaluation criteria Was evaluated.
○: Observed from a position 15 cm away, no density unevenness is observed in the image Δ: Observed from a position 15 cm away, density unevenness is observed in a part of the image, but from the position 30 cm away, the density unevenness is observed X: Observed from a position 30 cm away, density unevenness is observed in the image

[Evaluation of injection stability]
Ink jet recording apparatus equipped with each of the inks prepared above ejected ink from the ink jet head, visually observed for the absence of nozzles and ejection bends, and evaluated the ejection stability according to the following criteria.
○: No nozzle missing was observed Δ: Nozzle missing was observed in 1 to 4 nozzles in all nozzles 512 ×: Nozzle missing was observed in 5 or more nozzles in all nozzles 512 The

It can be seen that blooming is suppressed in the inks of Examples 1 to 9 including the wax and the liquid component.
On the other hand, in the ink of Comparative Example 1 that does not contain a wax and a liquid component, the ink of Comparative Example 3 that does not contain wax and contains only the liquid component, and the ink of Comparative Example 4 that contains only a very small amount of wax. , Density unevenness was observed. This is because the pinning property of the ink was low.

  In addition, blooming occurred in the ink of Comparative Example 2 that did not contain a liquid component, Comparative Example 5 that contained a large amount of wax, and Comparative Example 6 that contained a small amount of liquid component. Moreover, in the comparative example 7 which contains a liquid component excessively, stickiness produced on the surface of hardened | cured material. This is because the liquid component leached excessively on the surface of the cured film. Further, in Comparative Example 8, since the solubility of the liquid component in the wax is low, the effect of preventing blooming is not obtained even though an appropriate amount is contained.

  The actinic ray curable ink-jet ink of the present invention hardly causes blooming in an image formed with it, and a high quality image can be obtained. Therefore, the present invention is suitable for producing various printed materials.

DESCRIPTION OF SYMBOLS 10, 20 Inkjet recording device 12 Recording medium 14, 24 Ink discharge recording head 16, 26 Head carriage 18, 28 Actinic ray irradiation unit 19 Temperature control unit 27 Guide unit

Claims (5)

An actinic ray curable inkjet ink comprising an actinic ray curable compound, 1 to 10% by mass of wax, and 0.01 to 3% by mass of a non-polymerizable liquid component, and reversibly sol-gel phase transition depending on temperature. There,
The boiling point of the liquid component is 150 ° C. or higher, the melting point of the liquid component is 25 ° C. or lower,
The actinic ray curable inkjet ink, wherein the solubility of the wax in the liquid component is 1% by mass or more at 40 ° C.   The actinic ray curable inkjet ink according to claim 1, wherein the liquid component is a fatty acid ester.   The actinic ray curable inkjet ink according to claim 1, wherein the actinic ray curable compound is a radical polymerizable compound.   The actinic-light curable inkjet ink as described in any one of Claims 1-3 whose addition amount of the said wax is 1 mass% or more and less than 7 mass%. A step of injecting the actinic radiation curable inkjet ink according to any one of claims 1 to 4 onto a recording medium;
Wherein by irradiating actinic rays to the ejected the ink to the recording medium, and curing the ink jet recording how.

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