WO2017014014A1 - 色インクを用いたインクジェット記録方法 - Google Patents
色インクを用いたインクジェット記録方法 Download PDFInfo
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- WO2017014014A1 WO2017014014A1 PCT/JP2016/069206 JP2016069206W WO2017014014A1 WO 2017014014 A1 WO2017014014 A1 WO 2017014014A1 JP 2016069206 W JP2016069206 W JP 2016069206W WO 2017014014 A1 WO2017014014 A1 WO 2017014014A1
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
- C09D11/30—Inkjet printing inks
- C09D11/40—Ink-sets specially adapted for multi-colour inkjet printing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/21—Ink jet for multi-colour printing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/485—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by the process of building-up characters or image elements applicable to two or more kinds of printing or marking processes
- B41J2/505—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by the process of building-up characters or image elements applicable to two or more kinds of printing or marking processes from an assembly of identical printing elements
- B41J2/515—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by the process of building-up characters or image elements applicable to two or more kinds of printing or marking processes from an assembly of identical printing elements line printer type
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M5/00—Duplicating or marking methods; Sheet materials for use therein
- B41M5/0023—Digital printing methods characterised by the inks used
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M7/00—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock
- B41M7/0081—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock using electromagnetic radiation or waves, e.g. ultraviolet radiation, electron beams
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
- C09D11/02—Printing inks
- C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
- C09D11/037—Printing inks characterised by features other than the chemical nature of the binder characterised by the pigment
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
- C09D11/02—Printing inks
- C09D11/10—Printing inks based on artificial resins
- C09D11/101—Inks specially adapted for printing processes involving curing by wave energy or particle radiation, e.g. with UV-curing following the printing
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
- C09D11/02—Printing inks
- C09D11/10—Printing inks based on artificial resins
- C09D11/106—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- C09D11/107—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from unsaturated acids or derivatives thereof
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
- C09D11/30—Inkjet printing inks
- C09D11/32—Inkjet printing inks characterised by colouring agents
- C09D11/322—Pigment inks
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
- C09D11/30—Inkjet printing inks
- C09D11/38—Inkjet printing inks characterised by non-macromolecular additives other than solvents, pigments or dyes
Definitions
- the present invention relates to an ink jet recording method using color ink.
- the image forming method by the ink jet recording method is a method of forming an image by ejecting ink supplied from an ink tank through a flow path from a recording head for ejection.
- the ink jet recording method is used for forming various images because an image can be formed easily and inexpensively.
- One of the inks used in the ink jet recording system is actinic ray curable ink jet ink. Since the actinic radiation curable inkjet ink contains a photopolymerizable compound, the ink component can be cured by irradiating actinic rays such as ultraviolet rays to polymerize the photopolymerizable compound.
- actinic ray curable inkjet ink contains a photopolymerizable compound
- the ink component can be cured by irradiating actinic rays such as ultraviolet rays to polymerize the photopolymerizable compound.
- a gel ink containing a gelling agent such as wax has been developed.
- an image is formed by dissolving a gel in a high temperature state and landing on a recording medium and gelling (solidifying) the landed ink droplets.
- the dots are isolated and irregularities occur in the image area, or a glossy inhomogeneity may occur.
- the temperature of the recording medium plain paper or the like
- the gelation temperature of the ink ejected on the downstream side is lowered accordingly.
- the ink on the downstream side is prevented from solidifying rapidly and the gloss is stabilized.
- Patent Document 2 discloses an ink set in which the gelation temperature of the clear ink is higher than the gelation temperature of the color ink as an ink set for forming a printed image having both high image quality and a uniform matte feeling. Has been. Although this document does not describe the relationship between the gelation temperatures of a plurality of color inks used, in the color ink set used in the examples, the gelation temperature of the color inks printed in the order of YMCK is The last printing K is set lower than the first printing Y.
- Patent Documents 1 and 2 described above there is no specific description of image formation using a cardboard or cardboard as a recording medium.
- Patent Document 3 discloses a method and apparatus for forming an image on corrugated paper using ultraviolet curable gel ink.
- JP 2012-121288 A Japanese Patent Laying-Open No. 2015-40281 US Patent Application Publication No. 2008/0204538
- the above-mentioned document does not describe a method for forming a high-quality image on corrugated paper or the like that easily stores heat by using a plurality of actinic ray curable color inks.
- Papers with low thermal conductivity, thin corrugated cardboards made of medium lining and liners, etc. receive a large amount of heat from the ink to the recording medium when the gel ink lands, or when the radiant heat of the head is applied to the substrate during transportation
- the heat is stored and the temperature of the base material rises without being dissipated like ordinary paper.
- the temperature of the surface of the recording medium rises as it goes downstream. Since the gel ink controls pinning and leveling according to the phase transition temperature (gelation temperature) of the ink, it is difficult to maintain a constant image quality when the temperature of the recording medium surface changes.
- the present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inkjet image forming method that can form a high-quality color image on a thick recording medium with low thermal conductivity. To do.
- the present invention is the following inkjet recording method.
- an ink set including at least two actinic ray curable color inks including a photopolymerizable compound, a gelling agent, and a color material
- a plurality of color ink droplets are ejected to land on a recording medium.
- Irradiating actinic rays to the color ink landed on the recording medium to cure the ink, and a single-pass recording inkjet recording method The following conditions (a) and (b): (A) The gel temperature of the most downstream color ink is 3.0 ° C. to 15.0 ° C.
- the gel set temperature of the color ink positioned thereafter is the same as the gel temperature of the adjacent upstream color ink or higher than the gel temperature of the adjacent upstream color ink.
- the recording medium is a paper having a basis weight of 200 g / m 2 or more, or a thin corrugated cardboard made of a medium lining and a liner.
- the gelation temperature of the second and subsequent color inks is higher than the gelation temperature of the adjacent upstream color ink, [1] or [2 ]
- the ink set is an ink set including four color inks of yellow (Y), magenta (M), cyan (C), and black (K) and other color inks.
- the recording method according to any one of [1] to [3].
- General formula (G2): R3-COO-R4 In the general formula (G1) and general formula (G2), R1 to R4 each independently represents a hydrocarbon group containing a straight chain part having 12 or more carbon atoms and further containing a branched part.
- the gelation temperature of the color ink is adjusted in consideration of the base material heat storage generated when printing on a recording medium having a low thermal conductivity and a thickness. A decrease in ink curability caused by an increase in temperature can be suppressed. Therefore, by using the method of the present invention, it is possible to form a high-quality color image free from gloss difference, color unevenness and white spot.
- FIG. 3A Schematic diagram showing the position at which the surface temperature of the recording medium is measured when printing with a single-pass recording type inkjet recording apparatus using four color ink sets, and shows the change in the surface temperature of the recording medium with respect to the measurement position It is a graph.
- 2A and 2B are diagrams illustrating an example of a configuration of a main part of a single-pass recording type inkjet recording apparatus, in which FIG. 3A is a side view and FIG.
- the present invention uses a first step in which a plurality of color ink droplets are ejected and landed on a recording medium using an ink set including at least two colors of color ink, and actinic rays are applied to the color ink landed on the recording medium. And a second step of irradiating and curing the ink.
- the color ink used in the present invention is an actinic ray curable color ink containing a photopolymerizable compound, a gelling agent, and a coloring material.
- the photopolymerizable compound is a compound that is crosslinked or polymerized by actinic rays.
- the actinic rays are, for example, electron beams, ultraviolet rays, ⁇ rays, ⁇ rays, and X rays, and preferably ultraviolet rays and electron beams.
- the photopolymerizable compound is a radically polymerizable compound or a cationically polymerizable compound, preferably a radically polymerizable compound.
- the radical polymerizable compound is a compound (monomer, oligomer, polymer or mixture thereof) having an ethylenically unsaturated bond capable of radical polymerization.
- a radically polymerizable compound may be used independently and may be used in combination of 2 or more type.
- 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.
- the radically polymerizable compound is preferably an unsaturated carboxylic acid ester compound, and more preferably (meth) acrylate.
- the (meth) acrylate 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) acrylates 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 (meta Acrylate, t
- (meth) acrylate is 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.
- (Meth) acrylate may be a modified product.
- modified products include ethylene oxide-modified (meth) acrylates such as ethylene oxide-modified trimethylolpropane tri (meth) acrylate and ethylene oxide-modified pentaerythritol tetraacrylate; caprolactone modifications such as caprolactone-modified trimethylolpropane tri (meth) acrylate (Meth) acrylates; and caprolactam-modified (meth) acrylates such as caprolactam-modified dipentaerythritol hexa (meth) acrylate.
- Preferred examples of the (meth) acrylate compound include (1) a trifunctional or higher functional methacrylate having 3 to 14 structures represented by (—C (CH 3 ) H—CH 2 —O—) in the molecule, or Examples thereof include acrylate compounds, and (2) bifunctional or higher methacrylate or acrylate compounds having a cyclic structure in the molecule.
- These (meth) acrylate compounds have high photocurability and little shrinkage when cured. Furthermore, since these (meth) acrylate compounds have relatively high hydrophobicity and are excellent in solubility of the gelling agent, the reproducibility of the sol-gel phase transition is high.
- a trifunctional or higher functional methacrylate or acrylate compound having 3 to 14 structures represented by (—C (CH 3 ) H—CH 2 —O—) in the molecule includes, for example, 3 or more A hydroxyl group of a compound having a hydroxyl group is modified with propylene oxide, and the resulting modified product is esterified with (meth) acrylic acid.
- Specific examples of this compound include 3PO-modified trimethylolpropane triacrylate Photo 4072, 3PO-modified trimethylolpropane triacrylate Miramer M360 and the like are included.
- the bifunctional or higher functional methacrylate or acrylate compound having a cyclic structure in the molecule is obtained by esterifying the hydroxyl group of a compound having two or more hydroxyl groups and tricycloalkane with (meth) acrylic acid. is there.
- this compound include Tricyclodecane dimethanol diacrylate NK ester A-DCP, Tricyclodecane dimethanol dimethacrylate NK ester DCP and the like are included.
- (meth) acrylate compounds include 1,10-decanediol dimethacrylate, NK ester DOD-N, and the like.
- a preferable photopolymerizable compound may further contain a photopolymerizable compound other than the (meth) acrylate compound.
- 4EO modified hexanediol diacrylate CD561, manufactured by Sartomer
- 3EO modified trimethylolpropane triacrylate SR454, manufactured by Sartomer
- 4EO modified pentaerythritol tetraacrylate SR494, manufactured by Sartomer
- 6EO modified trimethylolpropane SR454, manufactured by Sartomer
- Triacrylate (SR499, manufactured by Sartomer); caprolactone acrylate (SR495B, manufactured by Sartomer); polyethylene glycol diacrylate (NK ester A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.), (NK ester A-600, manufactured by Shin-Nakamura Chemical Co., Ltd.) ); Polyethylene glycol dimethacrylate (NK ester 9G, manufactured by Shin-Nakamura Chemical Co., Ltd.), (NK ester 14G, manufactured by Shin-Nakamura Chemical Co., Ltd.); tetraethylene Recall diacrylate (V # 335HP, manufactured by Osaka Organic Chemical Co.); Stearyl acrylate (STA, manufactured by Osaka Organic Chemical Co.); Phenol EO modified acrylate (M144, manufactured by Miwon); Nonylphenol EO modified acrylate (M166, manufactured by Miwon) Etc. are included.
- the (meth) acrylate may be a polymerizable oligomer, and examples of such a polymerizable oligomer include an epoxy (meth) acrylate oligomer, an aliphatic urethane (meth) acrylate oligomer, and an aromatic urethane (meth) acrylate oligomer. , Polyester (meth) acrylate oligomers, linear (meth) acrylic oligomers, and the like.
- the cationically polymerizable compound can be an epoxy compound, a vinyl ether compound, an oxetane compound, or the like.
- a cationically polymerizable compound may be used independently and may be used in combination of 2 or more type.
- 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.
- the aliphatic polyhydric alcohol include ethylene glycol, propylene glycol, alkylene glycol such as 1,6-hexanediol, and the like.
- the alkylene oxide in the alkylene oxide adduct can be ethylene oxide, propylene oxide, and the like.
- 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.
- An 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.
- the compound represented by the general formula (1) described in paragraph No. 0089 of JP-A No. 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.
- the general formulas (1), (2), (7) to (9) described in JP-A-2005-255821 are shown below.
- the content of the photopolymerizable compound in the actinic ray curable inkjet ink is preferably 1 to 97% by mass, and more preferably 30 to 95% by mass.
- the actinic radiation curable inkjet ink may contain a photopolymerization initiator.
- the photopolymerization initiator contained in the actinic radiation curable inkjet ink includes a radical photopolymerization initiator and a cationic photopolymerization initiator, and the radical photopolymerization initiator includes an intramolecular bond cleavage type and There is an intramolecular hydrogen abstraction type.
- intramolecular bond cleavage type photopolymerization initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2 -Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4 Acetophenones such as -thiomethylphenyl) propan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone; benzoins such as benzoin, benzoin methyl ether and benzoin isopropyl ether; 2 , 4,6-Trimethylbenzoindiphenylphosphine oxy Acylphosphine oxide, such as de; as benzyl and methyl,
- intramolecular hydrogen abstraction type photopolymerization initiators examples 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's ketone, 4,4'-diethylaminobenzophenone; 10-butyl-2-chloroacridone
- cationic photopolymerization initiators examples include photoacid generators.
- a chemically amplified photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187-192. Page).
- the content of the photopolymerization initiator in the actinic ray curable ink-jet ink is preferably 0.01% by mass to 10% by mass, although it depends on the type of actinic ray or photopolymerizable compound.
- 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.
- 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.
- 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.
- polymerization inhibitors include (alkyl) phenol, hydroquinone, catechol, resorcin, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone , Nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupron, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N- (3-oxyanilino- 1,3-dimethylbutylidene) aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraloxime, methyl ethyl ketoxime, cyclohexanone oxime
- the actinic ray curable color ink used in the present invention is a sol-gel phase transition type ink containing a gelling agent.
- the gelling agent When the gelling agent is crystallized in the ink, it is preferable to form a space three-dimensionally surrounded by crystals which are the crystallized product of the gelling agent and encapsulate the photopolymerizable compound in the space.
- the structure in which the photopolymerizable compound is encapsulated in the space three-dimensionally surrounded by the gelling agent crystal is sometimes referred to as “card house structure”.
- the liquid photopolymerizable compound can be held and ink droplets can be pinned. Thereby, the color mixing of droplets can be suppressed.
- the photopolymerizable compound dissolved in the ink and the gelling agent are compatible.
- the compatibility between the photopolymerizable compound and the gelling agent must be good in a sol-like ink (at a high temperature, for example, about 80 ° C.). is necessary.
- gelling agents examples include Aliphatic ketone compounds; aliphatic ester compounds; petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam; candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax, jojoba ester, etc.
- Plant waxes animal waxes such as beeswax, lanolin and whale wax; mineral waxes such as montan wax and hydrogenated wax; hardened castor oil or hardened castor oil derivative; montan wax derivative, paraffin wax derivative, microcrystalline wax Modified waxes such as 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 alcohol and behenyl alcohol; hydroxystearic acid such as 12-hydroxystearic acid; 12-hydroxystearic acid derivatives; lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, Fatty acid amides such as 12-hydroxystearic acid amide (eg Nikka Amide series manufactured by Nippon Kasei Co., Ltd.
- N-stearyl stearic acid amide N-oleyl palmitic acid amide, etc. N-substituted fatty acid amides; special fatty acid amides such as N, N′-ethylenebisstearylamide, N, N′-ethylenebis-12-hydroxystearylamide, and N, N′-xylylenebisstearylamide; Fatty acid ester compounds such as 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 ( For example, EMALLEX series by Nihon Emulsion, Rikenmar series by Riken Vitamin, Poem series by Riken Vitamin, etc.); Esters of sucrose fatty acids such as sucrose stea
- the actinic ray curable inkjet ink of the present invention contains gelling agent A containing a linear alkyl group having 12 to 26 carbon atoms as a gelling agent.
- gelling agent A contains a linear alkyl group having 12 to 26 carbon atoms
- the aforementioned “card house structure” is easily formed.
- the structure of the gelling agent may have a branched chain.
- the gelling agent containing a linear alkyl group having 12 to 26 carbon atoms include aliphatic ketone compounds, aliphatic ester compounds, higher fatty acids, higher fatty acids having a linear alkyl group having 12 to 26 carbon atoms. Alcohols, fatty acid amides and the like are included.
- the gelling agent is preferably an aliphatic ketone compound or an aliphatic ester compound. That is, a compound represented by the following general formula (G1) or (G2) is preferable.
- R1 to R4 each independently represents an alkyl group containing a straight chain portion having 12 to 26 carbon atoms.
- R1 to R4 may include a branched portion.
- the alkyl group represented by R1 and R2 is not particularly limited, but is preferably an alkyl group containing a linear portion having 12 to 26 carbon atoms.
- Examples of the aliphatic ketone compound represented by the above general formula (G1) include dilignoceryl ketone (C24-C24), dibehenyl ketone (C22-C22), distearyl ketone (C18-C18), dieicosyl.
- Examples of commercially available compounds represented by the general formula (G1) include 18-Pentriacontanon (manufactured by Alfa Aeser), Hentriacontan-16-on (manufactured by Alfa Aeser), Kao wax T1 (manufactured by Kao Corporation), and the like. included.
- the aliphatic ketone compound contained in the ink may be only one type or a mixture of two or more types.
- the alkyl group represented by R3 and R4 is not particularly limited, but is preferably an alkyl group containing a linear portion having 12 to 26 carbon atoms.
- Examples of the aliphatic ester compound represented by the general formula (G2) include behenyl behenate (C21-C22), icosyl icosanoate (C19-C20), stearyl stearate (C17-C18), palmityl stearate (C17).
- Examples of commercially available aliphatic ester compounds represented by the general formula (G2) include Unistar M-2222SL (manufactured by NOF Corporation), EXCEPARL SS (manufactured by Kao Corporation), EMALEXCC-18 (Nippon Emulsion Co., Ltd.) Product), Amreps PC (manufactured by Higher Alcohol Industry Co., Ltd.), EXCEPARL MY-M (manufactured by Kao Corporation), SPALM ACETI (manufactured by NOF Corporation), EMALEX® CC-10 (manufactured by Nippon Emulsion Co., Ltd.) and the like. Since these commercial products are often a mixture of two or more types, they may be separated and purified as necessary.
- fatty acid ester compounds such as glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid ester, polyoxyethylene fatty acid ester (for example, Japanese emulsion) EMALLEX series manufactured by company, Rikenmar series manufactured by Riken Vitamin Co., poem series manufactured by Riken Vitamin Co., etc.) may be used in combination.
- the actinic ray curable color ink used in the present invention is a sol-gel phase transition type ink containing a gelling agent.
- the gelling agent content in the gel ink is preferably 1% by mass or more and less than 15% by mass, more preferably 1% by mass or more and less than 7% by mass, and more preferably 1% by mass or more and 5% by mass or less. More preferably it is.
- the gelation temperature of the actinic radiation curable inkjet ink used in the present invention is 30 ° C. or higher and 100 ° C. or lower, and preferably 30 ° C. or higher and 80 ° C. or lower.
- a low-temperature gel-based ink having a gelling temperature of 30 ° C. or higher and 60 ° C. or lower is preferable from the viewpoint of reducing power consumption because the temperature of the recording medium during printing can be kept low.
- the gelling agent suitable for the preparation of the low-temperature gel-based ink include aliphatic ester compounds such as behenyl behenate, stearyl stearate, behenyl stearate, and ethylene glycol distearate.
- the color material contained in the actinic ray curable ink-jet ink may be a dye or a pigment, but a pigment is preferable 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.
- red or magenta pigments examples 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, and the like.
- Examples of blue or cyan pigments include PigmentBlue® 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17-1, 22, 27, 28, 29, 36, 60 etc. are included.
- 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 are included.
- Examples of black pigments include Pigment Black 7, 7, 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, 4773, 5205, 5208, 5214, 5221, 5000P, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromofine Rack A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400 (B), 2500, 2600, ZAY
- the pigment can be dispersed by, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like.
- the pigment is dispersed such that the volume average particle diameter of the pigment particles is preferably 0.08 to 0.5 ⁇ m, and the maximum particle diameter is preferably 0.3 to 10 ⁇ m, more preferably 0.3 to 3 ⁇ m. It is preferable.
- the dispersion of the pigment is adjusted according to the selection of the pigment, the dispersant, and the dispersion medium, the dispersion conditions, the filtration conditions, and the like.
- the actinic ray curable inkjet ink may further contain a dispersant in order to improve the dispersibility of the pigment.
- 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 Solspers
- 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 dispersing agent and the dispersing aid is preferably 1 to 50% by mass with respect to the pigment.
- the actinic ray curable inkjet ink may further include a dispersion medium for dispersing the pigment as necessary.
- a solvent may be included in the ink as a dispersion medium, in order to suppress the residual solvent in the formed image, a photopolymerizable compound as described above (particularly a monomer having a low viscosity) is used as the dispersion medium. Is preferred.
- the dye can be an oil-soluble dye or the like.
- oil-soluble dyes include the following various dyes.
- magenta dyes include MSMagenta VP, MS Magenta HM-1450, MS Magenta HSo-147 (above, manufactured by Mitsui Toatsu), AIZENSOT ⁇ Red-1, AIZEN SOT Red-2, AIZEN SOTRed-3, AIZENSOT Pink 1.
- cyan dyes examples include MS Cyan HM-1238, MS Cyan HSo-16, Cyan HSo-144, MS Cyan VPG (above, Mitsui Toatsu), AIZENSOT Blue-4 (Hodogaya Chemical Co., Ltd.), RESOLINBR .
- Blue FB-LL 330% manufactured by Bayer Japan
- KAYASETYBlue FR KAYASET Blue N
- Blue GL-5200 Light Blue BGL-5 200 (manufactured by Nippon Kayaku Co., Ltd.), DAIWA Blue 7000, Olesol Fast Blue GL (above, Daiwa Kasei), DIARESINBlue P (manufactured by Mitsubishi Kasei), SUDABlu NEOPEN Blue 808, ZAPON Blue806 (above, manufactured by BASF Japan Ltd.) and the like are included.
- yellow dyes examples include MS Yellow HSm-41, Yellow KX-7, Yellow EX-27 (manufactured by Mitsui Toatsu), AIZENSOT Yellow-1, AIZENSOT YellowW-3, AIZENSOT Yellow-6 (above, Hodogaya Chemical) Manufactured by the company), MACROLEX Yellow 6G, MACROLEX FLUOR.
- Yellow 10GN (above, Bayer Japan), KAYASETYello SF-G, KAYASETYello2G, KAYASET YellowA-G, KAYASET YellowE-G (above, made by Nippon Kayaku), DAIWADAYellow 330HB (Daiwa Kasei 330HB) (Manufactured by Mitsubishi Kasei Co., Ltd.), SUDANYello® 146, NEOPEN® Yellow® 075 (above, manufactured by BASF Japan Ltd.) and the like.
- black dyes examples include MS Black VPC (Mitsui Toatsu), AIZEN SOT Black-1, AIZEN SOT Black-5 (above, Hodogaya Chemical Co., Ltd.), RESORN Black GSN 200%, RESOLINBlackBS (above, Bayer) Japan)), KAYASET Black A-N (Nippon Kayaku), DAIWA Black MSC (Daiwa Kasei), HSB-202 (Mitsubishi Kasei), NEPTUNEBlack X60, NEOPEN Black X58 (above, BASF Japan) Manufactured) and the like.
- the content of the pigment or dye is preferably 0.1 to 20% by mass, 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.
- the actinic ray curable inkjet ink may further contain other components as necessary.
- Other components may be various additives, other resins, and the like.
- 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.
- basic compounds include basic alkali metal compounds, basic alkaline earth metal compounds, basic organic compounds such as amines, and the like.
- other resins include resins for adjusting the physical properties of the cured film, such as polyester resins, polyurethane resins, vinyl resins, acrylic resins, and rubber resins.
- the actinic ray curable inkjet ink can be obtained by mixing the above-described photopolymerizable compound, gelling agent, colorant, and other arbitrary components such as a photopolymerization initiator under heating. it can. It is preferable to filter the obtained liquid mixture with a predetermined filter.
- the ink set used in the present invention contains at least two colors of the actinic ray curable color ink described above, and the following conditions (a) and (b): (A) The gelation temperature of the most downstream color ink is 3.0 ° C. to 15 ° C. higher than the gel temperature of the most upstream color ink, and (b) the second and later from the upstream side in the transport direction. The gel temperature of the color ink located is the same as the gel temperature of the adjacent upstream color ink or higher than the gel temperature of the adjacent upstream color ink. When the color ink to be printed is two colors, only the condition (a) is satisfied, and when the color ink included in the ink set is three or more colors, the conditions (a) and (b) are all satisfied. .
- the recording method of the present invention is for forming a high-quality color image on a recording medium having a high thermal storage property having a thermal conductivity of less than 0.10 W / (m ⁇ K) and a thickness of 0.4 mm or more. Is the method. This method is based on the knowledge that a recording medium with low thermal conductivity stores heat during printing, and the temperature of the recording medium rises. For example, in the measurement shown in FIGS. 1 and 2 of the present application, a single-pass recording type inkjet recording apparatus in which the temperature of the recording medium is set to 45 ° C.
- the surface temperature of the thin coated paper changes very little (about 1 ° C.) between the upstream side (position 0) and the downstream side (position 3 in FIG. 1 or position 5 in FIG. 2) in the recording medium conveyance direction. )Met. This is considered to be because the heat brought into the recording medium diffuses to the transport table side.
- the surface temperature of the recording medium immediately before the start of printing is set immediately before the ink head to be printed last (position 3 in FIG. 1 or The surface temperature of the recording medium measured at position 5) in FIG. 2 was increased by 6 ° C. or more.
- Such a temperature rise is considered to be caused by the fact that a large amount of heat transferred from the ink to the recording medium when the gel ink is landed and the radiant heat of the head applied to the recording medium during conveyance are stored in the recording medium.
- the temperature of the recording medium when printing with the last ink positioned on the downstream side is the same as that when printing with the first ink positioned on the upstream side because of the heat storage of the recording medium. It becomes higher than the temperature of the recording medium. If the surface temperature of the recording medium is higher than the gelation temperature of the ink, the ink droplets that land on the surface of the recording medium are less likely to gel, so the pinning and leveling properties of the ink decrease, and the image has a gloss difference, Color unevenness and white spots are likely to occur.
- the gel temperature of the ink is increased in accordance with the increase in the surface temperature of the recording medium, that is, the printing is performed last more than the gel temperature of the color ink to be printed first.
- the gelation temperature of the color ink located at the most upstream side in the ink set used in the present invention is 30 ° C. or higher and 100 ° C. or lower, preferably 30 ° C. or higher and 80 ° C. Hereinafter, it is more preferably 30 ° C or higher and 60 ° C or lower.
- the gelation temperature of the color ink located at the most downstream side that is, the color ink that is ejected last must be higher than the gelation temperature of the color ink that is ejected first, It is preferable to determine the gelation temperature of the color ink to be recorded first in consideration of the gelation temperature of the color ink ejected on the ink.
- the gelation temperature of the color ink located on the most downstream side in the ink set that is, the color ink that is finally ejected satisfies the condition (a).
- the gelation temperature of the color ink located on the most downstream side is higher by 3.0 ° C. to 15.0 ° C., preferably 3.0 ° C. to 10 ° C. than the gelation temperature of the most upstream color ink. It is higher by 0.0 ° C, more preferably by 3.0 ° C to 8.0 ° C.
- the difference between the gelation temperature of the first color ink to be ejected and the gelation temperature of the last color ink to be ejected is less than 3.0 ° C, set the gelation temperature of the last color ink to be ejected high. The effect of doing so is insufficient, and a high-quality image cannot be printed on a recording medium with high heat storage properties.
- the gelation temperature of the color ink located second or later from the upstream side in the transport direction is the same as the gelation temperature of the adjacent upstream color ink, or the adjacent upstream color ink It is designed to be higher than the gelation temperature.
- the gelation temperature of the ink on the downstream side must correspond to the heat storage of the recording medium.
- the heat storage amount of the recording medium is the difference between the temperature of the recording medium immediately before printing and the temperature of the recording medium at the position where ink is ejected.
- the difference in gelation temperature between the inks is less than ⁇ 3 ° C., there is no variation in image quality and high quality. It has been known. In other words, with respect to the gelation temperature of the ink, there is a ⁇ 3 ° C. swing that is acceptable for achieving high image quality.
- the gelation temperature of the ink printed after the second is (gelation temperature of the first ink) + (heat storage of the recording medium) ) ⁇ (swing width less than 3 ° C.).
- the effect of the present invention can be achieved even if the gelling temperature of the ink printed after the second is the same as the gelling temperature of the ink printed immediately before.
- the gelation temperature of all the inks located in the middle may be the same as the gelation temperature of the ink initially ejected, or the gelation temperature of the ink located in the middle is stepwise. It may be higher.
- the gelation temperature of the ink disposed between the first ink and the last ink is also stepwise so as to correspond to the temperature increase of the recording medium. It is preferable to change to Specifically, when the gelation temperatures of two adjacent inks are different, the gelation temperature difference is preferably 1 ° C. to 5 ° C., more preferably in the range of 1 ° C. to 3 ° C.
- the gelation temperature of the color inks in the ink set are all different, and when using an ink set that gradually rises from the upstream side to the downstream side, the gelation temperature of the ink responds finely to the temperature rise of the recording medium. Therefore, it is possible to form a high-quality image regardless of the type of recording medium.
- the gelation temperature can be changed by changing the type of photopolymerizable compound, the type of gelling agent, and the amount added.
- an ink having different gelation temperatures is prepared by first preparing one ink, measuring its gelation temperature, and then changing its composition slightly. can do.
- the gelation temperature can be increased by increasing the amount of the gelling agent. Therefore, a plurality of inks may be prepared, the respective gelation temperatures may be measured, and inks having desired gelation temperatures may be combined to form an ink set.
- the gelation temperature of the ink can be obtained from the temperature change of the dynamic viscoelasticity of the ink measured with a rheometer. Specifically, the ink is heated to 100 ° C., 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 a temperature change curve of the viscosity is created. What is necessary is just to let the temperature used as 200 mPa * s be a gelling temperature.
- the number of colors included in the ink set used in the present invention is not particularly limited as long as it is 2 or more, but 4-color or 6-color ink sets are common.
- the colors included in the ink set are not particularly limited, but an ink set including four color inks of yellow (Y), magenta (M), cyan (C), and black (K) and other color inks. It is preferable that Examples of inks other than the four colors include orange (O), violet (V), green (G), and white (W), but are not limited thereto.
- the order of the colors to be recorded is not particularly limited, but the possibility of image quality decreasing as it goes downstream increases, so it is difficult to see even if there is image quality deterioration, and the ink with the highest brightness is recorded last. It is preferable to arrange it on the most downstream side. For example, they can be arranged so that the brightness increases from the upstream side toward the downstream side. When using four colors of YMCK, it is preferable to record K first and Y last, and more preferably KCMY.
- the recording medium used in the present invention is a recording medium having a thermal conductivity of less than 0.10 W / (m ⁇ K) and a thickness of 0.4 mm or more.
- the type of recording medium there are no particular limitations on the type of recording medium, and there are paper bases, coated paper with both sides of the base paper coated with resin, various types of laminated paper, synthetic paper, thin cardboard, various non-absorbing plastics and films thereof. Can be mentioned.
- the recording method of the present invention is used for printing on papers having a basis weight of 200 g / m 2 or more, or thin corrugated cardboards made of medium shin and a liner, a high-quality color image can be obtained.
- the actinic ray curable ink as described above is ejected from an ink jet recording head and landed on a recording medium.
- An ink jet recording head that discharges actinic ray curable ink is a single pass recording method (also called a line method).
- ink discharge nozzles for each color are provided in a line shape across the width direction of the printer (the direction orthogonal to the conveyance direction of the recording medium). For example, black (K), yellow (Y), magenta (M), discharge nozzles such as cyan (C) are provided in a line.
- the head equipped in the ink jet recording apparatus may be equipped with a heating device, and the ink may be heated to lower the ink viscosity.
- the heating temperature of the ink is preferably 25 to 150 ° C., more preferably 30 to 70 ° C. If it is lower than 25 ° C, the viscosity of the ink may not be lowered, and if it exceeds 150 ° C, the ink may be cured.
- the heating temperature of the ink is determined in consideration of the curability of the photopolymerizable compound or the photopolymerization initiator with respect to heat, and is set lower than the temperature at which curing starts with heat.
- Examples of the method of heating the inkjet ink to a predetermined temperature include at least one of an ink tank constituting a head carriage, an ink supply system such as a supply pipe and an anterior chamber ink tank immediately before the head, a pipe with a filter, and a piezo head Is heated to a predetermined temperature by any one of a panel heater, a ribbon heater, warm water and the like.
- the droplet amount of the inkjet ink when ejected is 2 pL or more and 20 pL or less.
- the recording medium may be heated depending on the gelation temperature of the actinic radiation curable ink used.
- the temperature of the recording medium (base material temperature) is in the range of 35 ° C. to 80 ° C., preferably 35 ° C. to 60 ° C.
- various heaters and heating rollers for heating the recording medium in a contact type may be used, or a lamp or the like for heating the front or back surface of the recording medium in a non-contact type.
- the heating means for heating the recording medium in a contact type is usually disposed on the back surface of the recording medium.
- a second actinic ray curable ink droplet landed on the recording medium is irradiated with actinic rays to cure the ink droplets. Perform the process.
- Examples of actinic rays used in the second step of the present invention include ultraviolet rays, near ultraviolet rays, natural light (including filter cut products), and ultraviolet rays are preferred.
- Examples of the ultraviolet irradiation light source include a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a cold cathode tube, a hot cathode tube, a black light, an LED (light emitting light diode), and the like.
- a cathode tube, a hot cathode tube, a mercury lamp or a black light is preferable, and an LED is particularly preferable because of its long life and low cost.
- an LED is a single wavelength light source, and its illuminance tends to be lower than a light source having a plurality of emission line spectra such as a high-pressure mercury lamp.
- a light source having a plurality of emission line spectra such as a high-pressure mercury lamp.
- the proportion of radicals bonded to oxygen and deactivated increases. Therefore, even if the irradiation time is extended and the integrated light quantity is the same, it becomes difficult to cure. Therefore, it is required that the ink jet ink can be cured with low illuminance and low integrated light quantity.
- the wavelength of the irradiation light source is preferably 280 to 420 nm, and more preferably 350 to 410 nm.
- the wavelength is a long wavelength in the optical ultraviolet region and is highly safe.
- the integrated light amount applied to the ink-jet ink droplets landed on the recording medium is in the range of 10 to 500 mJ / cm 2 . Within this range, it is advantageous from the viewpoint of energy saving, space saving and cost.
- the recording medium is preferably to 8W / cm 2 or less illuminance, and more preferably set to 2W / cm 2 or less.
- Light with an illuminance higher than 8 W / cm 2 generates a large amount of heat, so that a recording medium with low heat resistance is easily deformed. Further, there may be a problem that the amount of leakage light increases and the ink is cured on the head nozzle surface. Furthermore, light with high illuminance consumes high energy, has a large light source space, and increases costs.
- the actinic ray irradiation method is not particularly limited, and can be performed by, for example, the following method.
- a light source is provided on both sides of the head unit, the head and the light source are scanned by a shuttle method, and irradiation is performed after a certain time from ink landing. Further, the curing is completed by irradiating light from another light source that is not driven (see Japanese Patent Application Laid-Open No. 60-132767).
- light may be irradiated using an optical fiber, or ultraviolet light from a collimated light source may be reflected by a mirror surface provided on the side surface of the head unit and irradiated to the recording unit (US Pat. No. 6,145). , 979).
- irradiation with actinic rays may be divided into two stages.
- the first irradiation is preferably performed within 0.001 to 1.0 seconds after the ink droplet has landed on the recording medium.
- the second irradiation may be performed after the first irradiation. That is, the second irradiation may be performed downstream of the first irradiation in the conveyance direction of the recording medium.
- the integrated light quantity (D1) per recording medium unit area by the first irradiation is preferably smaller than the integrated light quantity (D2) per recording medium unit area by the second irradiation. That is, it is preferable that D1 ⁇ D2.
- the total ink film thickness after the ink has landed on the recording medium and cured by irradiation with actinic rays is preferably 2 to 25 ⁇ m.
- Total ink film thickness means the maximum value of the film thickness of ink drawn on a recording medium. Whether it is a single color or a two-color overlap (secondary color), a three-color overlap, or a four-color overlap (white ink base), the total ink film thickness is preferably 0.1 to 5 ⁇ m.
- the recording method of the present invention is performed using a single pass recording type (line type) ink jet recording apparatus.
- the single-pass recording type inkjet recording apparatus is preferable to the serial type inkjet recording apparatus from the viewpoint of high-speed recording.
- FIG. 3 is a diagram illustrating an example of a configuration of a main part of a line recording type inkjet recording apparatus. Among these, (A) is a side view and (B) is a top view.
- the inkjet recording apparatus 10 stores a head carriage 16 that houses a plurality of inkjet recording heads 14, an ink flow path 30 connected to the head carriage 16, and ink supplied through the ink flow path 30.
- An ink tank 31 that covers the entire width of the recording medium 12, a light irradiation unit 18 that is disposed downstream of the head carriage 16 (in the conveyance direction of the recording medium), and a temperature control unit that is disposed on the lower surface of the recording medium 12. 19 and.
- the head carriage 16 is fixedly arranged so as to cover the entire width of the recording medium 12, and accommodates a plurality of inkjet recording heads 14 provided for each color.
- Ink is supplied to the ink jet recording head 14.
- the ink may be supplied directly or by an ink supply unit (not shown) from an ink cartridge (not shown) that is detachably attached to the inkjet recording apparatus 10.
- a plurality of inkjet recording heads 14 are arranged in the transport direction of the recording medium 12 for each color.
- the number of inkjet recording heads 14 arranged in the conveyance direction of the recording medium 12 is set according to the nozzle density of the inkjet recording head 14 and the resolution of the print image. For example, when an image having a resolution of 1440 dpi is formed using the inkjet recording head 14 having a droplet amount of 2 pl and a nozzle density of 360 dpi, the four inkjet recording heads 14 may be arranged so as to be shifted with respect to the conveyance direction of the recording medium 12. That's fine.
- the two ink jet recording heads 14 may be arranged in a shifted manner.
- dpi represents the number of ink droplets (dots) per 2.54 cm.
- the ink tank 31 is connected to the head carriage 16 via the ink flow path 30.
- the ink flow path 30 is a path for supplying the ink in the ink tank 31 to the head carriage 16.
- the ink in the ink tank 31, the ink flow path 30, the head carriage 16, and the ink jet recording head 14 is heated to a predetermined temperature to maintain the gel state.
- the light 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 conveyance direction of the recording medium.
- the light irradiation unit 18 irradiates the droplets ejected by the inkjet recording head 14 and landed on the recording medium with an actinic ray to cure the droplets.
- 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.
- Yellow pigment Pigment Yellow 180 (manufactured by Dainichi Seika Co., Ltd., Chromofine Yellow 6280JC)
- M pigment dispersion An M pigment dispersion was prepared in the same manner as the Y pigment dispersion except that the Y pigment was changed to the following magenta (M) pigment.
- Magenta pigment Pigment Red 122 (manufactured by Dainichi Seika Co., Ltd., Chromo Fine Red 6112JC)
- C pigment dispersion A C pigment dispersion was prepared in the same manner as the Y pigment dispersion, except that the Y pigment was changed to the following cyan (C) pigment.
- Cyan pigment Pigment Blue 15: 4 (manufactured by Dainichi Seika Co., Ltd., Chromofine Blue 6332JC)
- K pigment dispersion A K pigment dispersion was prepared in the same manner as the Y pigment dispersion, except that the Y pigment was changed to the following black (K) pigment.
- Black pigment Pigment Black 7 (Mitsubishi Chemical Corporation, # 52)
- V pigment dispersion A V pigment dispersion was prepared in the same manner as the Y pigment dispersion except that the Y pigment was changed to the following violet (V) pigment.
- Violet pigment Pigment Violet 23 (manufactured by DIC, P-RL)
- O pigment dispersion An O pigment dispersion was prepared in the same manner as the Y pigment dispersion except that the Y pigment was changed to the following orange (O) pigment.
- Orange pigment Pigment Orange 64 (manufactured by BASF, K2960)
- W pigment dispersion A W pigment dispersion was prepared in the same manner as the Y pigment dispersion, except that the Y pigment was changed to the following white (W) pigment.
- White pigment Titanium oxide (manufactured by Sakai Chemical Industry Co., Ltd., TCR-52)
- the gelation temperature (Tgel) (° C.) of each prepared ink was measured by the following method. First, the temperature change of the dynamic viscoelasticity of the ink was measured with a rheometer. Specifically, the ink was heated to 100 ° C., 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 a temperature change curve of viscosity was obtained. The gelation temperature was determined as the temperature at which the viscosity was 200 mPa ⁇ s in the temperature change curve of the viscosity.
- the rheometer was a stress control type rheometer Physica MCR series manufactured by Anton Paar.
- the cone plate had a diameter of 75 mm and a cone angle of 1.0 °.
- Each prepared ink composition was loaded into a single-pass inkjet recording apparatus having an inkjet recording head equipped with a piezo-type inkjet nozzle.
- the ink supply system was composed of an ink tank, an ink flow path, a sub ink tank immediately before the ink jet recording head, a pipe with a filter, and a piezo head.
- the piezo head applies a voltage so that a 6 pl droplet is ejected, ejects it using four 360 dpi resolution heads, and produces a 1440 ⁇ 1440 dpi portrait image (high-definition color digital standard image, JIS X 9201). : 1995, N1) was formed on the recording medium described in Table 3. In the image formation, the temperature of the recording medium was set to the temperature shown in Table 4.
- the ink was cured by irradiating light (395 nm, 8 W / cm 2 , water cooled unit) from an LED lamp manufactured by Phoseon Technology.
- the distance from the lamp to the surface of the recording medium was 20 mm, the conveyance speed of the recording medium was 40 m / s, and the amount of light was 300 mJ / cm 2 .
- the amount of light was measured using an ultraviolet integrated light meter (C9536, H9958, manufactured by Hamamatsu Photonics).
- the recording medium is only a PS sheet (NOABELLE), and a 100% solid image is obtained using K ink on the recording medium. Then, a 100% solid image was formed with W ink so as to overlap with K ink. The ink was cured by exposure under the above conditions within 5 seconds after image formation.
- ⁇ Image evaluation method> (Curable) Immediately after outputting the image sample, the coated paper was placed on the image surface and rubbed 30 times with a weight of 500 g. The subsequent image surface was visually evaluated based on the following criteria. ⁇ : Density decrease after rubbing is not visually recognized ⁇ : Density decrease after rubbing is slightly visually recognized, but it is a level that is not a problem in practical use ⁇ : Density decrease after rubbing is remarkably visually recognized
- Color unevenness For the output image sample, the color unevenness of the high density portion was visually evaluated based on the following criteria. ⁇ : Color unevenness is not visually recognized ⁇ : Color unevenness is slightly visually recognized, but is at a level that does not cause any practical problem.
- Table 4 shows the evaluation results of images formed using each ink set.
- an ink set having an evaluation result of ⁇ or ⁇ is a practical ink set.
- Such a high-quality image was obtained even with a low-temperature gel-based ink set in which the gelation temperature was set low (40 ° C. to 48 ° C.) as in ink set 6.
- the use of a low-temperature gel-based ink set is preferable from the viewpoint of power consumption because the temperature of the recording medium during printing can be kept low.
- an ink set in which the gelation temperature does not change at all as in the ink set 1 or an ink set in which the gelation temperature of the ink to be recorded last is lower than the gelation temperature of the ink to be recorded first is in the ink set 7.
- the curability of the ink was lowered and the image quality was also lowered due to the influence of the temperature rise of the recording medium.
- the ink jet recording method of the present invention has low thermal conductivity, and even when printed on a recording medium such as a thick corrugated cardboard, the decrease in ink curability is suppressed. It is possible to form a high quality color image.
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Abstract
Description
[1] 光重合性化合物、ゲル化剤、および色材を含む活性光線硬化型の色インクを少なくとも2色含むインクセットを用い、複数の色インクの液滴を射出して記録媒体に着弾させる工程と、
前記記録媒体に着弾した色インクに活性光線を照射して、インクを硬化させる工程とを含む、シングルパス記録方式のインクジェット記録方法であって、
以下の条件(a)と(b):
(a)最も下流側の色インクのゲル化温度は、最も上流側の色インクのゲル化温度よりも3.0℃~15.0℃高い、および
(b)搬送方向の上流側から2番目以降に位置する色インクのゲル化温度は、隣接する上流側の色インクのゲル化温度と同じであるか、あるいは隣接する上流側の色インクのゲル化温度よりも高い
のうち、前記インクセットに含まれる色インクが2色の場合には、条件(a)のみを満たし、前記インクセットに含まれる色インクが3色以上の場合には、条件(a)および(b)を全て満たすものであり、
前記記録媒体が、熱伝導率が0.10W/(m・K)未満であり、且つ厚みが0.4mm以上の基材であることを特徴とする記録方法。
[2] 前記記録媒体が、坪量200g/m2以上の紙類、または中しんとライナーからなる薄段ボール類であることを特徴とする、[1]に記載の記録方法。
[3] 前記条件(a)において、2番目以降に位置する色インクのゲル化温度が、隣接する上流側の色インクのゲル化温度よりも高いことを特徴とする、[1]または[2]に記載の記録方法。
[4] 前記インクセットが、イエロー(Y)、マゼンタ(M)、シアン(C)、ブラック(K)の4色の色インクと、他の色インクとを含むインクセットであることを特徴とする、[1]~[3]のいずれかに記載の記録方法。
[5] 最も下流側に位置する色インクが、インクセット内で最も明度の高い色インクであることを特徴とする、[1]~[4]のいずれかに記載の記録方法。
[6] 前記インクセットに含まれる色インクのゲル化温度が、30℃~60℃の範囲以内であることを特徴とする、[1]~[5]のいずれかに記載の記録方法。
[7] 前記ゲル化剤が、下記の一般式(G1)で表される化合物、及び一般式(G2)で表される化合物のうちの少なくとも1種を含むことを特徴とする、[1]~[6]のいずれか1項に記載のインクジェット記録方法。
一般式(G1):R1-CO-R2
一般式(G2):R3-COO-R4
(該一般式(G1)及び一般式(G2)中、R1~R4は、それぞれ独立に、炭素数12以上の直鎖部分を含み、さらに分岐部分を含んでもよい炭化水素基を表す。)
本発明に用いる色インクは、光重合性化合物、ゲル化剤、および色材を含む活性光線硬化型の色インクである。
光重合性化合物は、活性光線により架橋または重合する化合物である。活性光線は、例えば電子線、紫外線、α線、γ線、およびX線等であり、好ましくは紫外線および電子線である。光重合性化合物は、ラジカル重合性化合物またはカチオン重合性化合物であり、好ましくはラジカル重合性化合物である。
トリエチレングリコールジ(メタ)アクリレート、テトラエチレングリコールジ(メタ)アクリレート、ポリエチレングリコールジ(メタ)アクリレート、トリプロピレングリコールジ(メタ)アクリレート、ポリプロピレングリコールジ(メタ)アクリレート、1,4-ブタンジオールジ(メタ)アクリレート、1,6-ヘキサンジオールジ(メタ)アクリレート、1,9-ノナンジオールジ(メタ)アクリレート、ネオペンチルグリコールジ(メタ)アクリレート、ジメチロール-トリシクロデカンジ(メタ)アクリレート、ビスフェノールAのPO付加物ジ(メタ)アクリレート、ヒドロキシピバリン酸ネオペンチルグリコールジ(メタ)アクリレート、ポリテトラメチレングリコールジ(メタ)アクリレート等の二官能モノマー;
トリメチロールプロパントリ(メタ)アクリレート、ペンタエリスリトールトリ(メタ)アクリレート、ペンタエリスリトールテトラ(メタ)アクリレート、ジペンタエリスリトールヘキサ(メタ)アクリレート、ジトリメチロールプロパンテトラ(メタ)アクリレート、グリセリンプロポキシトリ(メタ)アクリレート、ペンタエリスリトールエトキシテトラ(メタ)アクリレート等の三官能以上の多官能モノマー等が含まれる。
3PO変性トリメチロールプロパントリアクリレート Photomer 4072、
3PO変性トリメチロールプロパントリアクリレート Miramer M360等が含まれる。
トリシクロデカンジメタノールジアクリレート NKエステルA-DCP、
トリシクロデカンジメタノールジメタクリレート NKエステルDCP等が含まれる。
エチレングリコールジビニルエーテル、ジエチレングリコールジビニルエーテル、トリエチレングリコールジビニルエーテル、プロピレングリコールジビニルエーテル、ジプロピレングリコールジビニルエーテル、ブタンジオールジビニルエーテル、ヘキサンジオールジビニルエーテル、シクロヘキサンジメタノールジビニルエーテル、トリメチロールプロパントリビニルエーテル等のジまたはトリビニルエーテル化合物等が含まれる。これらのビニルエーテル化合物のうち、硬化性や密着性などを考慮すると、ジまたはトリビニルエーテル化合物が好ましい。
活性光線硬化型インクジェットインクは光重合開始剤を含んでもよい。活性光線硬化型インクジェットインクに含まれる光重合開始剤には、ラジカル系の光重合開始剤とカチオン系の光重合開始剤があり、ラジカル系の光重合開始剤には、分子内結合開裂型と分子内水素引き抜き型とがある。分子内結合開裂型の光重合開始剤の例には、ジエトキシアセトフェノン、2-ヒドロキシ-2-メチル-1-フェニルプロパン-1-オン、ベンジルジメチルケタール、1-(4-イソプロピルフェニル)-2-ヒドロキシ-2-メチルプロパン-1-オン、4-(2-ヒドロキシエトキシ)フェニル-(2-ヒドロキシ-2-プロピル)ケトン、1-ヒドロキシシクロヘキシル-フェニルケトン、2-メチル-2-モルホリノ(4-チオメチルフェニル)プロパン-1-オン、2-ベンジル-2-ジメチルアミノ-1-(4-モルホリノフェニル)-ブタノン等のアセトフェノン系;ベンゾイン、ベンゾインメチルエーテル、ベンゾインイソプロピルエーテル等のベンゾイン類;2,4,6-トリメチルベンゾインジフェニルホスフィンオキシド等のアシルホスフィンオキシド系;ベンジルおよびメチルフェニルグリオキシエステル等が含まれる。
本発明に用いる活性光線硬化型の色インクは、ゲル化剤を含むゾルゲル相転移型のインクである。
脂肪族ケトン化合物;脂肪族エステル化合物;パラフィンワックス、マイクロクリスタリンワックス、ペトロラクタム等の石油系ワックス;キャンデリラワックス、カルナウバワックス、ライスワックス、木ロウ、ホホバ油、ホホバ固体ロウ、およびホホバエステル等の植物系ワックス;ミツロウ、ラノリンおよび鯨ロウ等の動物系ワックス;モンタンワックス、および水素化ワックス等の鉱物系ワックス;硬化ヒマシ油または硬化ヒマシ油誘導体;モンタンワックス誘導体、パラフィンワックス誘導体、マイクロクリスタリンワックス誘導体またはポリエチレンワックス誘導体等の変性ワックス;ベヘン酸、アラキジン酸、ステアリン酸、パルミチン酸、ミリスチン酸、ラウリン酸、オレイン酸、およびエルカ酸等の高級脂肪酸;ステアリルアルコール、ベヘニルアルコール等の高級アルコール;12-ヒドロキシステアリン酸等のヒドロキシステアリン酸;12-ヒドロキシステアリン酸誘導体;ラウリン酸アミド、ステアリン酸アミド、ベヘン酸アミド、オレイン酸アミド、エルカ酸アミド、リシノール酸アミド、12-ヒドロキシステアリン酸アミド等の脂肪酸アミド(例えば日本化成社製 ニッカアマイドシリーズ、伊藤製油社製 ITOWAXシリーズ、花王社製 FATTYAMIDシリーズ等);N-ステアリルステアリン酸アミド、N-オレイルパルミチン酸アミド等のN-置換脂肪酸アミド;N,N'-エチレンビスステアリルアミド、N,N'-エチレンビス-12-ヒドロキシステアリルアミド、およびN,N'-キシリレンビスステアリルアミド等の特殊脂肪酸アミド;ドデシルアミン、テトラデシルアミンまたはオクタデシルアミンなどの高級アミン;ステアリルステアリン酸、オレイルパルミチン酸、グリセリン脂肪酸エステル、ソルビタン脂肪酸エステル、プロピレングリコール脂肪酸エステル、エチレングリコール脂肪酸エステル、ポリオキシエチレン脂肪酸エステル等の脂肪酸エステル化合物(例えば日本エマルジョン社製 EMALLEXシリーズ、理研ビタミン社製 リケマールシリーズ、理研ビタミン社製 ポエムシリーズ等);ショ糖ステアリン酸、ショ糖パルミチン酸等のショ糖脂肪酸のエステル(例えばリョートーシュガーエステルシリーズ 三菱化学フーズ社製);ポリエチレンワックス、α-オレフィン無水マレイン酸共重合体ワックス等の合成ワックス(Baker-Petrolite社製 UNILINシリーズ等);ダイマー酸;ダイマージオール(CRODA社製 PRIPORシリーズ等);ステアリン酸イヌリン等の脂肪酸イヌリン;パルミチン酸デキストリン、ミリスチン酸デキストリン等の脂肪酸デキストリン(千葉製粉社製 レオパールシリーズ等);ベヘン酸エイコサン二酸グリセリル;ベヘン酸エイコサンポリグリセリル(日清オイリオ社製 ノムコートシリーズ等);N-ラウロイル-L-グルタミン酸ジブチルアミド、N-(2-エチルヘキサノイル)-L-グルタミン酸ジブチルアミド等のアミド化合物(味の素ファインテクノ社より入手可能);1,3:2,4-ビス-O-ベンジリデン-D-グルシトール(ゲルオールD 新日本理化社より入手可能)等のジベンジリデンソルビトール類;特開2005-126507号公報、特開2005-255821号公報および特開2010-111790号公報に記載の低分子オイルゲル化剤;等が含まれる。
一般式(G1): R1-CO-R2
一般式(G2): R3-COO-R4
活性光線硬化型インクジェットインクに含まれる色材は、染料または顔料でありうるが、インクの構成成分に対して良好な分散性を有し、かつ耐候性に優れることから、顔料が好ましい。顔料は、特に限定されないが、例えばカラーインデックスに記載される下記番号の有機顔料または無機顔料でありうる。
KET Yellow401、402、403、404、405、406、416、424、KET Orange 501、KET Red301、302、303、304、305、306、307、308、309、310、336、337、338、346、KETBlue 101、102、103、104、105、106、111、118、124、KETGreen 201(大日本インキ化学社製);
Colortex Yellow301、314、315、316、P-624、314、U10GN、U3GN、UNN、UA-414、U263、FinecolYellow T-13、T-05、PigmentYellow1705、Colortex Orange 202、Colortex Red101、103、115、116、D3B、P-625、102、H-1024、105C、UFN、UCN、UBN、U3BN、URN、UGN、UG276、U456、U457、105C、USN、ColortexMaroon601、Colortex BrownB610N、Colortex Violet600、PigmentRed 122、ColortexBlue516、517、518、519、A818、P-908、510、ColortexGreen402、403、Colortex Black 702、U905(山陽色素社製);
Lionol Yellow1405G、LionolBlue FG7330、FG7350、FG7400G、FG7405G、ES、ESP-S(東洋インキ社製)、TonerMagenta E02、PermanentRubinF6B、Toner YellowHG、Permanent YellowGG-02、Hostapeam BlueB2G(ヘキストインダストリ社製);
Novoperm P-HG、HostapermPink E、HostapermBlue B2G(クラリアント社製);
カーボンブラック#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(三菱化学社製)などが挙げられる。
活性光線硬化型インクジェットインクは、必要に応じて他の成分をさらに含んでもよい。他の成分は、各種添加剤や他の樹脂等であってよい。添加剤の例には、界面活性剤、レベリング添加剤、マット剤、紫外線吸収剤、赤外線吸収剤、抗菌剤、インクの保存安定性を高めるための塩基性化合物等も含まれる。塩基性化合物の例には、塩基性アルカリ金属化合物、塩基性アルカリ土類金属化合物、アミンなどの塩基性有機化合物などが含まれる。他の樹脂の例には、硬化膜の物性を調整するための樹脂などが含まれ、例えばポリエステル系樹脂、ポリウレタン系樹脂、ビニル系樹脂、アクリル系樹脂、およびゴム系樹脂等が含まれる。
本発明で使用するインクセットは、上述した活性光線硬化型の色インクを少なくとも2色含むものであって、以下の条件(a)と(b):
(a)最も下流側の色インクのゲル化温度は、最も上流側の色インクのゲル化温度よりも3.0℃~15℃高い、および
(b)搬送方向の上流側から2番目以降に位置する色インクのゲル化温度は、隣接する上流側の色インクのゲル化温度と同じであるか、あるいは隣接する上流側の色インクのゲル化温度よりも高いのうち、前記インクセットに含まれる色インクが2色の場合には、条件(a)のみを満たし、前記インクセットに含まれる色インクが3色以上の場合には、条件(a)および(b)を全て満たすものである。
本発明で用いる記録媒体は、熱伝導率が0.10W/(m・K)未満であり、且つ厚みが0.4mm以上の記録媒体である。記録媒体の種類に特に限定はなく、紙製の基材、基紙の両面を樹脂等で被覆したコート紙、各種貼合紙、合成紙、薄段ボール、各種非吸収性のプラスチックおよびそのフィルムが挙げられる。特に坪量200g/m2以上の紙類、または中しんとライナーからなる薄段ボール類の印刷に本発明の記録方法を使用すると、高品質のカラー画像を得ることができる。
本発明の記録方法の第1の工程においては、上述したような活性光線硬化型インクをインクジェット記録ヘッドから吐出させて記録媒体上に着弾させる。活性光線硬化型インクを吐出するインクジェット記録ヘッドは、シングルパス記録方式(ライン方式ともいう)である。
本発明の記録方法は、シングルパス記録方式(ライン方式)のインクジェット記録装置を用いて行う。シングルパス記録方式のインクジェット記録装置は、高速記録の観点からシリアル方式のインクジェット記録装置よりも好ましい。
以下の手順でイエロー(Y)、マゼンタ(M)、シアン(C)、ブラック(K)、バイオレット(V)、オレンジ(O)、ホワイト(W)の顔料分散液を調整した。
以下2種の化合物をステンレスビーカーに入れ、65℃のホットプレート上で加熱しながら1時間かけて加熱攪拌して溶解した。
顔料分散剤:PB824(味の素ファインテクノ社製) 9質量部
光重合性化合物:トリプロピレングリコールジアクリレート 71質量部
イエロー顔料:Pigment Yellow 180(大日精化社製、クロモファインイエロー6280JC)
Y顔料を下記マゼンタ(M)顔料に変更したこと以外は、Y顔料分散液と同様にしてM顔料分散液を調製した。
マゼンタ顔料:Pigment Red 122(大日精化社製、クロモファインレッド6112JC)
Y顔料を下記シアン(C)顔料に変更したこと以外は、Y顔料分散液と同様にしてC顔料分散液を調製した。
シアン顔料:Pigment Blue 15:4(大日精化社製、クロモファインブルー6332JC)
Y顔料を下記ブラック(K)顔料に変更したこと以外は、Y顔料分散液と同様にしてK顔料分散液を調製した。
ブラック顔料:Pigment Black 7(三菱化学社製、#52)
Y顔料を下記バイオレット(V)顔料に変更したこと以外は、Y顔料分散液と同様にしてV顔料分散液を調製した。
バイオレット顔料:Pigment Violet 23(DIC社製、P-RL)
Y顔料を下記オレンジ(O)顔料に変更したこと以外は、Y顔料分散液と同様にしてO顔料分散液を調製した。
オレンジ顔料:Pigment Orange 64(BASF社製、K2960)
Y顔料を下記ホワイト(W)顔料に変更したこと以外は、Y顔料分散液と同様にしてW顔料分散液を調製した。
ホワイト顔料:酸化チタン(堺化学工業社製、TCR-52)
下記表1A~表1Dに記載したインクの組成にしたがって、各成分と上記顔料分散液とを混合し、80℃に加熱して攪拌した。加熱下において、得られた溶液をADVANTEC社製のテフロン(登録商標)メンブランフィルター(3μm)で濾過し、冷却して各色インクを得た。得られたインク(Y1~Y8インク、M1~M8インク、C1~C8インク、K1~K10インク、V8インク、O8インク、W9~W10インク)を用いてインクセット1~10を得た。
調製した各インクのゲル化温度(Tgel)(℃)は、以下の方法によって測定した。
初めに、インクの動的粘弾性の温度変化をレオメータで測定した。具体的には、インクを100℃に加熱し、剪断速度11.7/s、降温速度0.1℃/sの条件で20℃まで冷却し、粘度の温度変化曲線を得た。ゲル化温度は、粘度の温度変化曲線において、粘度が200mPa・sとなる温度として求めた。
調製した各インク組成物を、ピエゾ型インクジェットノズルを備えたインクジェット記録ヘッドを有するシングルパスのインクジェット記録装置に装填した。インク供給系は、インクタンク、インク流路、インクジェット記録ヘッド直前のサブインクタンク、フィルター付き配管、ピエゾヘッドからなり、インクタンクからヘッド部分までは100℃になるように加温した。
なお、画像形成の際には、記録媒体の温度を表4に示した温度に設定した。
(硬化性)
画像サンプルを出力した直後に、コート紙を画像面にのせ、500gの加重をかけて30回擦った。その後の画像表面を下記の基準に基づいて目視評価した。
○:擦り後の濃度低下が視認されない
△:擦り後の濃度低下がわずかに視認されるが、実用上問題ないレベルである
×:擦り後の濃度低下が顕著に視認される
出力した画像サンプルについて、濃淡部分における光沢違和感を下記の基準に基づいて目視評価した。
○:光沢違和感は視認されない
△:光沢違和感がわずかに視認されるが、実用上問題ないレベルである
×:光沢違和感が顕著に視認される
出力した画像サンプルについて、高濃度部分の色むらを下記の基準に基づいて目視評価した。
○:色むらは視認されない
△:色むらがわずかに視認されるが、実用上問題ないレベルである
×:色むらが顕著に視認される
出力した画像サンプルについて、白スジや白抜けについて、下記の基準に基づいて目視評価した。
○:白スジや白抜けなし
△:1、2箇所の白スジや白ヌケがあるが、実用上問題ないレベルである
×:白スジや白抜けが多数発生している
尚、上記評価の全てにおいて、評価結果が○または△となるインクセットが実用可能なインクセットである。
12 記録媒体
14 インクジェット記録ヘッド
16 ヘッドキャリッジ
18 光照射部
19 温度制御部
30 インク流路
31 インクタンク
Claims (7)
- 光重合性化合物、ゲル化剤、および色材を含む活性光線硬化型の色インクを少なくとも2色含むインクセットを用い、複数の色インクの液滴を射出して記録媒体に着弾させる工程と、
前記記録媒体に着弾した色インクに活性光線を照射して、インクを硬化させる工程とを含む、シングルパス記録方式のインクジェット記録方法であって、
以下の条件(a)と(b):
(a)最も下流側の色インクのゲル化温度は、最も上流側の色インクのゲル化温度よりも3.0℃~15.0℃高い、および
(b)搬送方向の上流側から2番目以降に位置する色インクのゲル化温度は、隣接する上流側の色インクのゲル化温度と同じであるか、あるいは隣接する上流側の色インクのゲル化温度よりも高い
のうち、前記インクセットに含まれる色インクが2色の場合には、条件(a)のみを満たし、前記インクセットに含まれる色インクが3色以上の場合には、条件(a)および(b)を全て満たすものであり、
前記記録媒体が、熱伝導率が0.10W/(m・K)未満であり、且つ厚みが0.4mm以上の記録媒体であることを特徴とする記録方法。 - 前記記録媒体が、坪量200g/m2以上の紙類、または中しんとライナーからなる薄段ボール類であることを特徴とする、請求項1に記載の記録方法。
- 前記条件(a)において、2番目以降に位置する色インクのゲル化温度が、隣接する上流側の色インクのゲル化温度よりも高いことを特徴とする、請求項1に記載の記録方法。
- 前記インクセットが、イエロー(Y)、マゼンタ(M)、シアン(C)、ブラック(K)の4色の色インクと、他の色インクとを含むインクセットであることを特徴とする、請求項1に記載の記録方法。
- 最も下流側に位置する色インクが、インクセット内で最も明度の高い色インクであることを特徴とする、請求項1に記載の記録方法。
- 前記インクセットに含まれる色インクのゲル化温度が、30℃~60℃の範囲以内であることを特徴とする、請求項1に記載の記録方法。
- 前記ゲル化剤が、下記の一般式(G1)で表される化合物、及び一般式(G2)で表される化合物のうちの少なくとも1種を含むことを特徴とする、請求項1に記載の記録方法。
一般式(G1):R1-CO-R2
一般式(G2):R3-COO-R4
(該一般式(G1)及び一般式(G2)中、R1~R4は、それぞれ独立に、炭素数12以上の直鎖部分を含み、さらに分岐部分を含んでもよい炭化水素基を表す。)
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