JP2012241097A - Radiation-curing ink composition, inkjet recording method, and inkjet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation-curing ink composition to which a nozzle face of a print head shows excellent ink repellent properties and which exhibits excellent ejection stability, and an inkjet recording method and an inkjet recording apparatus each using the radiation-curing ink composition.SOLUTION: The radiation-curing ink composition is used for the inkjet recording apparatus equipped with the print head including the nozzle face, wherein the nozzle face has a fluorine atom on at least a part of a section in contact with ink. The radiation-curing ink composition includes at least one or more of a compound with a dibenzylidene-sorbitol skeleton and a sugar, and a polymerizable compound, and a total content of at least one or more of the compound with a dibenzylidene-sorbitol skeleton and the sugar is 0.5-5.0 mass% with respect to the total mass of the radiation-curing ink composition.

Description

  The present invention relates to a radiation curable ink composition, and an ink jet recording method and an ink jet recording apparatus using the same.

  Conventionally, various methods have been used as a recording method for forming an image on a recording medium based on an image data signal. Among these, the ink jet system is an inexpensive apparatus, and ink is ejected only to a required image portion to form an image directly on a recording medium. Therefore, the ink can be used efficiently, and the running cost is low.

  In recent years, development of a solvent-free radiation-curable ink composition that can be cured by irradiation with ultraviolet rays, electron beams, or other radiation has been advanced, and attempts have been made to apply this radiation-curable ink composition to an inkjet recording system. (For example, refer to Patent Document 1). Ink jet recording systems to which a radiation curable ink composition is applied can be recorded on non-absorbing substrates such as glass, metal, plastic substrates, etc., so that the applicable range of substrates is wide. Therefore, the radiation curable ink composition is superior to conventional solvent-based inks such as water-based inks and solvent-based inks in terms of image abrasion resistance, curability, and productivity.

JP 2009-233976 A

  However, when the radiation curable ink composition is applied to an ink jet recording apparatus, the ink repellency of the print head nozzle surface with respect to the radiation curable ink composition is inferior. Arise.

  Accordingly, the present invention provides a radiation curable ink composition in which the nozzle surface of a print head exhibits excellent ink repellency and excellent ejection stability, and an ink jet recording method and an ink jet recording apparatus using the same. Is one of the purposes.

  The present inventors have intensively studied to solve the above problems. First, an attempt was made to improve the ink repellency of the radiation curable ink composition and to improve the ejection stability by improving the nozzle surface. However, it has been found that it is difficult to improve ink repellency and improve ejection stability only by improving the nozzle surface.

  Therefore, as a result of further studies by the present inventors, the radiation curable ink composition, and further improved the material of the nozzle surface, the ink repellency of the radiation curable ink composition with respect to the nozzle surface is excellent, and the ejection The present invention was completed by finding out that the stability could be improved.

That is, the present invention is as follows.
[1]
A radiation curable ink composition used in an ink jet recording apparatus provided with a print head including a nozzle surface, wherein the nozzle surface has fluorine atoms in at least a part of a portion in contact with the ink, and the radiation curable ink composition The ink composition includes at least one of a compound having a dibenzylidene sorbitol skeleton and a sugar and a polymerizable compound, and the total content of at least one of the compound having a dibenzylidene sorbitol skeleton and the sugar is the radiation. A radiation curable ink composition that is 0.5 to 5.0% by mass relative to the total mass of the curable ink composition.
[2]
The radiation curable ink composition according to [1], wherein at least one of the compound having a dibenzylidene sorbitol skeleton and a sugar is a compound having a dibenzylidene sorbitol skeleton.
[3]
At least one of the compound having a dibenzylidene sorbitol skeleton and the sugar is at least one of 1,3: 2,4-dibenzylidene sorbitol and 1,3: 2,4-di (p-methylbenzylidene) sorbitol. The radiation curable ink composition according to [1] or [2].
[4]
A print head including a nozzle surface having fluorine atoms in at least a part of a portion in contact with the ink is provided, and the print head ejects the radiation curable ink composition according to any one of [1] to [3]. An inkjet recording apparatus.
[5]
The inkjet recording apparatus according to [4], wherein the nozzle surface has a siloxane bond in a region less than 1 μm from a portion in contact with the ink.
[6]
An inkjet recording method comprising discharging the radiation curable ink composition according to any one of [1] to [3] from the print head.
[7]
A radiation curable ink composition comprising at least one of a compound having a dibenzylidene sorbitol skeleton and a sugar and a polymerizable compound, wherein the total content of at least one of the compound having the dibenzylidene sorbitol skeleton and the sugar Is a radiation curable ink composition, which is 0.5 to 5.0% by mass relative to the total mass of the ink composition.

1 is a perspective view of an ink jet recording apparatus that can be used in the present embodiment. FIG. 3 is a cross-sectional view schematically illustrating an example of a print head. It is a conceptual diagram of the coupling | bonding of the fluororesin film | membrane in a nozzle plate surface. It is a front view of the radiation irradiation apparatus shown in FIG. It is an AA arrow line view of FIG.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. In addition, this invention is not restrict | limited to the following embodiment, A various deformation | transformation can be implemented within the range of the summary.

  In the present specification, “ink repellency” means a property of repelling a radiation curable ink composition. “Discharge stability” refers to the property of ejecting stable ink droplets from the nozzles without clogging the nozzles. “Curable” refers to the property of curing in response to light.

  In this specification, “(meth) acrylate” means at least one of acrylate and its corresponding methacrylate, and “(meth) acryl” means at least one of acryl and its corresponding methacryl.

  In this specification, the “nozzle surface” refers to all portions (surfaces) of the nozzle that may come into contact with ink droplets. Physical or chemical in order to change the surface of the nozzle material itself or the properties of the nozzle surface. Or a surface of a film formed on the nozzle surface. The “nozzle surface” is not limited to a flat surface, and may be a surface other than a flat surface such as a curved surface, and specifically includes not only the outer surface of the nozzle plate but also the inner wall (inner surface) of the ink discharge port and the vicinity thereof.

[Radiation curable ink composition]
A radiation curable ink composition according to an embodiment of the present invention includes at least one of a compound having a dibenzylidene sorbitol skeleton and a sugar and a polymerizable compound, and the compound having the dibenzylidene sorbitol skeleton and the sugar. At least one or more is 0.5 to 5.0% by mass with respect to the total mass (100% by mass) of the radiation curable ink composition.

  Hereinafter, additives (components) contained in or capable of being contained in the radiation curable ink composition of the present embodiment (hereinafter also simply referred to as “ink composition”) will be described.

[Compounds and sugars having a dibenzylidene sorbitol skeleton]
The ink composition of the present embodiment includes at least one compound selected from a compound having a dibenzylidene sorbitol skeleton and a saccharide having a dibenzylidene sorbitol skeleton. These compounds are compounds containing two or more hydroxyl groups in the molecule.

  Among these, a compound having a dibenzylidene sorbitol skeleton is preferable because of excellent discharge stability of ink from the nozzle holes.

  Examples of the compound having a dibenzylidene sorbitol skeleton include, but are not limited to, for example, 1,3: 2,4-dibenzylidene sorbitol, 1,3: 2,4-di (p-methylbenzylidene) sorbitol, 3: 2,4-di (p-ethylbenzylidene) sorbitol, 1,3: 2,4-di (pn-propylbenzylidene) sorbitol, 1,3: 2,4-di (pi-propylbenzylidene) ) Sorbitol, 1,3: 2,4-di (pn-butylbenzylidene) sorbitol, 1,3: 2,4-di (ps-butylbenzylidene) sorbitol, 1,3: 2,4-di (Pt-butylbenzylidene) sorbitol, 1,3: 2,4-di (p-methoxybenzylidene) sorbitol, 1,3: 2,4-di (p-ethoxybenzylidene) Sorbitol, 1,3: 2,4-di (p-chlorobenzylidene) sorbitol, 1,3: 2,4-di (p-chlorobenzylidene) sorbitol, and 1,3: 2,4-bis (dimethylbenzylidene) Compounds having the same kind of benzylidene group in the molecule such as sorbitol, 1,3-benzylidene-2,4-p-ethylbenzylidene sorbitol, 1,3-benzylidene-2,4-p-chlorobenzylidene sorbitol, 1,3- p-methylbenzylidene-2,4-benzylidene sorbitol, 1,3-p-methylbenzylidene-2,4-p-chlorobenzylidene sorbitol, 1,3-p-methylbenzylidene-2,4-p-ethylbenzylidene sorbitol, 1,3-p-ethylbenzylidene-2,4-benzylidenesorbitol, 1,3- -Ethylbenzylidene-2,4-p-methylbenzylidene sorbitol, 1,3-p-ethylbenzylidene-2,4-p-chlorobenzylidene sorbitol, 1,3-p-chlorobenzylidene-2,4-benzylidene sorbitol, , 3-p-chlorobenzylidene-2,4-p-methylbenzylidenesorbitol, 1,3-p-chlorobenzylidene-2,4-p-ethylbenzylidenesorbitol, and the like. Can be mentioned.

  Examples of commercially available compounds having a dibenzylidene sorbitol skeleton include IRGACLEAR D, IRGACLEAR DM (trade name, manufactured by BASF), Gelall MD, Gelall D, Gelall MD-R, Gelall DH, Gelall T (all, Shin Nippon Rika) (Trade names manufactured by New Japan Chemical Co., Ltd.), EC1, EC1-55, EC-4 (trade names manufactured by EC Chemical Productions Ltd.).

  Examples of the sugar include, but are not limited to, monosaccharides such as glucose, fructose, and galactose, disaccharides such as saccharose, maltose, and lactose, and polysaccharides such as starch and glycogen.

  In addition, the ink composition of the present embodiment may further include a compound having a dibenzylidene sorbitol skeleton and a compound containing two or more hydroxyl groups in a molecule other than sugar. Examples of such compounds include, but are not limited to, sugar alcohols and polyhydric alcohols.

  Examples of the sugar alcohol include, but are not limited to, glycerin, diglycerin, polyglycerin, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-butylene glycol, and erythritol.

  Examples of the polyhydric alcohol include, but are not limited to, sorbitol, maltose, xylitol, and maltitol.

  Among these, at least one or more of 1,3: 2,4-dibenzylidene sorbitol and 1,3: 2,4-di (p-methylbenzylidene) sorbitol is excellent in terms of excellent ink ejection stability from the nozzle holes. Is preferred.

  When the ink composition of this embodiment contains the compound having the dibenzylidene sorbitol skeleton, the compound may be used alone or in combination of two or more. Moreover, when the ink composition of this embodiment contains the saccharide | sugar which has the said dibenzylidene sorbitol skeleton, the said saccharide | sugar may be used individually by 1 type, and may be used in combination of 2 or more type. And when the ink composition of this embodiment contains both the compound and sugar which have the said dibenzylidene sorbitol skeleton, the said compound and the said sugar may be used individually by 1 type, respectively, and at least one is combined 2 or more types. It may be used.

  At least one or more of the compound having a dibenzylidene sorbitol skeleton and the sugar is 0.5 to 5.0 mass as a total content in the ink composition with respect to the total mass (100 mass%) of the ink composition. %, Preferably 1.0 to 2.0 mass%. When the content is within the above range, precipitation of these compounds on the coating film surface can be suppressed.

(Polymerizable compound)
The ink composition of this embodiment contains a polymerizable compound. This polymerizable compound is polymerized at the time of light irradiation by the action of a photopolymerization initiator described later, and the printed ink can be cured.

(Vinyl ether group-containing (meth) acrylic acid esters)
The polymerizable compound preferably contains a predetermined vinyl ether group-containing (meth) acrylic acid ester (hereinafter referred to as “monomer A”). This monomer A is a compound having both a vinyl group and a (meth) acryl group in the molecule, and is represented by the following general formula (I).
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
(In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms. Group.)

  When the ink composition contains the monomer A, the ink curability and the like can be improved.

In the general formula (I), the divalent organic residue represented by R ² includes a linear, branched or cyclic alkylene group having 2 to 20 carbon atoms, an ether bond and an ester in the structure. An alkylene group having 2 to 20 carbon atoms having an oxygen atom due to at least one of the bonds, and an optionally substituted divalent aromatic group having 6 to 11 carbon atoms are preferable. Among these, C2-C6 alkylene groups such as ethylene group, n-propylene group, isopropylene group, and butylene group, oxyethylene group, oxy n-propylene group, oxyisopropylene group, and oxybutylene group An alkylene group having 2 to 9 carbon atoms having an oxygen atom due to an ether bond in the structure is preferably used.

In said general formula (I), as a C1-C11 monovalent organic residue represented by R < ³ >, a C1-C10 linear, branched or cyclic alkyl group, carbon An optionally substituted aromatic group of formula 6 to 11 is preferred. Among these, C6-C2 aromatic groups, such as a C1-C2 alkyl group which is a methyl group or an ethyl group, a phenyl group, and a benzyl group, are used suitably.

  When the above organic residue is an optionally substituted group, the substituent is divided into a group containing a carbon atom and a group not containing a carbon atom. First, when the substituent is a group containing a carbon atom, the carbon atom is counted in the carbon number of the organic residue. Examples of the group containing a carbon atom include, but are not limited to, a carboxyl group and an alkoxy group. Next, examples of the group not containing a carbon atom include, but are not limited to, a hydroxyl group and a halo group.

  Specific examples of the monomer A represented by the above general formula (I) include, but are not limited to, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxypropyl (meth) acrylate, (meth) acrylic acid 1-methyl-2-vinyloxyethyl, 2-vinyloxypropyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 1-methyl-3-vinyloxypropyl (meth) acrylate, (meth) acrylic acid 1- Vinyloxymethylpropyl, 2-methyl-3-vinyloxypropyl (meth) acrylate, 1,1-dimethyl-2-vinyloxyethyl (meth) acrylate, 3-vinyloxybutyl (meth) acrylate, (meth) acrylic acid 1 -Methyl-2-vinyloxypropyl, 2-vinyloxybutyl (meth) acrylate, 4-bi (meth) acrylate Roxycyclohexyl, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, 3-vinyloxymethylcyclohexylmethyl (meth) acrylate, 2-vinyloxymethyl (meth) acrylate Cyclohexylmethyl, (meth) acrylic acid p-vinyloxymethylphenylmethyl, (meth) acrylic acid m-vinyloxymethylphenylmethyl, (meth) acrylic acid o-vinyloxymethylphenylmethyl, (meth) acrylic acid 2- ( Vinyloxyethoxy) ethyl, 2- (vinyloxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxy) propyl (meth) acrylate, 2- (vinyloxyethoxy) isopropyl (meth) acrylate, ( 2-methacrylic acid (vinyloxy) Propoxy) propyl, 2- (vinyloxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) propyl (meth) acrylate, (meth ) 2- (vinyloxyethoxyisopropoxy) propyl acrylate, 2- (vinyloxyisopropoxyethoxy) propyl (meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) propyl (meth) acrylate, (meth) Acrylic acid 2- (vinyloxyethoxy ester) Toxi) isopropyl, (meth) acrylic acid 2- (vinyloxyethoxyisopropoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyisopropoxyethoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyisopropoxyisopropoxy) ) Isopropyl, 2- (vinyloxyethoxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxyethoxyethoxy) ethyl (meth) acrylate, 2- (isopropenoxyethoxy) ethyl (meth) acrylate , 2- (Isopropenoxyethoxyethoxy) ethyl (meth) acrylate, 2- (Isopropenoxyethoxyethoxyethoxy) ethyl (meth) acrylate, 2- (Isopropenoxyethoxyethoxyethoxyethoxy) acrylate (meth) acrylate ethyl (Meth) Polyethylene glycol monovinyl ether acrylate, and (meth) acrylic acid polypropylene glycol monovinyl ether.

  Among those described above, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxypropyl (meth) acrylate, 1-methyl-2-vinyloxyethyl (meth) acrylate, 2-vinyloxypropyl (meth) acrylate, ( 4-vinyloxybutyl (meth) acrylate, 4-vinyloxycyclohexyl (meth) acrylate, 5-vinyloxypentyl (meth) acrylate, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxy (meth) acrylate Methylcyclohexylmethyl, p-vinyloxymethylphenylmethyl (meth) acrylate, 2- (vinyloxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, (meth) acrylic The acid 2- (vinyloxyethoxyethoxyethoxy) ethyl is preferred Arbitrariness.

  Of these, 2- (vinyloxyethoxy) ethyl (meth) acrylate is preferred because of its low viscosity, high flash point, and excellent curability, and it also has low odor and suppresses irritation to the skin. In addition, 2- (vinyloxyethoxy) ethyl acrylate is more preferable because it is excellent in reactivity and adhesion.

  Examples of 2- (vinyloxyethoxy) ethyl (meth) acrylate include 2- (2-vinyloxyethoxy) ethyl (meth) acrylate and 2- (1-vinyloxyethoxy) ethyl (meth) acrylate. Examples of 2- (vinyloxyethoxy) ethyl acrylate include 2- (2-vinyloxyethoxy) ethyl acrylate and 2- (1-vinyloxyethoxy) ethyl acrylate.

  The monomer A is contained in an amount of 20 to 50% by mass, preferably 22 to 40% by mass, based on the total mass (100% by mass) of the ink composition. When the content is within the above range, the ink adhesion, rubbing resistance, and alcohol resistance can be improved.

  The production method of the monomer A represented by the general formula (I) is not limited to the following, but is a method of esterifying (meth) acrylic acid and a hydroxyl group-containing vinyl ether (production method B), (meth) acrylic acid. Method of esterifying halide and hydroxyl group-containing vinyl ether (Production method C), Method of esterifying (meth) acrylic anhydride and hydroxyl group-containing vinyl ether (Production method D), (Meth) acrylic acid ester and hydroxyl group Method of Transesterifying Containing Vinyl Ethers (Production Method E), Method of Esterifying (Meth) acrylic Acid and Halogen-Containing Vinyl Ethers (Production Method F), Alkali (Meth) Acrylic Acid (Earth) Metal Salt and Halogen Containing Method of esterifying vinyl ethers (Production G), hydroxyl group-containing (meth) acrylic acid esters and carboxylic acid vinyl ester How to vinyl exchange and Le (Procedure H), hydroxyl group-containing (meth) How to ether exchange and acrylic acid esters and alkyl vinyl ethers (formula I).

  Among these, since the desired effect can be further exhibited in this embodiment, the production method E is preferable.

(Polymerizable compounds other than the above)
As the polymerizable compound other than the above (hereinafter, referred to as “other polymerizable compound”), conventionally known various monomers and oligomers such as monofunctional, bifunctional, and trifunctional or more polyfunctional can be used. . Examples of the monomer include unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, crotonic acid, isocrotonic acid and maleic acid, salts or esters thereof, urethane, amide and anhydride thereof, acrylonitrile, styrene, various types Unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes. Examples of the oligomer include oligomers formed from the above monomers such as linear acrylic oligomers, epoxy (meth) acrylate, oxetane (meth) acrylate, aliphatic urethane (meth) acrylate, and aromatic urethane (meth). Acrylate and polyester (meth) acrylate are mentioned.

  Moreover, an N-vinyl compound may be included as another monofunctional monomer or polyfunctional monomer. Examples of such N-vinyl compounds include N-vinylcaprolactam, N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, N-vinylpyrrolidone, and acryloylmorpholine, and derivatives thereof.

  Among other polymerizable compounds, an ester of (meth) acrylic acid, that is, (meth) acrylate is preferable, polyfunctional (meth) acrylate having 2 or more functions is more preferable, and polyfunctional acrylate is more preferable. In particular, the ink composition of the present embodiment includes a polyfunctional acrylate as a polymerizable compound in addition to the predetermined amount of the monomer A, so that the ink composition has excellent ink adhesion, abrasion resistance, and alcohol resistance. It becomes.

  Among the above (meth) acrylates, monofunctional (meth) acrylates include, for example, isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, iso Myristyl (meth) acrylate, isostearyl (meth) acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxy Diethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate Rate, phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl ( Examples include meth) acrylate, lactone-modified flexible (meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate.

  Among the (meth) acrylates, examples of the polyfunctional (meth) acrylate include triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and 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, di (meth) acrylate of bisphenol A, neopentyl glycol di (meth) acrylate of hydroxypivalate, and poly Bifunctional (meth) acrylates such as tetramethylene glycol di (meth) acrylate, as well as trimethylolpropane tri (meth) acrylate, glycerin propoxytri (meth) acrylate, cowprolactone modified trimethylolpropane tri (meth) acrylate, ditri (Meth) having a pentaerythritol skeleton such as methylolpropane tetra (meth) acrylate, sorbitol penta (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and pentaerythritol ethoxytetra (meth) acrylate Acrylate, dipentaerythritol hexa (meth) acrylate, caprolactam-modified dipentaerythritol hexa (meth) acrylate , (Pentaerythritol penta (meth) acrylate), (meth) acrylate having a dipentaerythritol skeleton such as caprolactone-modified dipentaerythritol hexa (meth) acrylate, propionic acid-modified tripentaerythritol penta (meth) acrylate, tripentaerythritol hexa (Meth) acrylate, tripentaerythritol hepta (meth) acrylate, (meth) acrylate having a tripentaerythritol skeleton such as tripentaerythritol octa (meth) acrylate, tetrapentaerythritol penta (meth) acrylate, tetrapentaerythritol hexa ( (Meth) acrylate, tetrapentaerythritol hepta (meth) acrylate, tetrapentaerythritol octa ( (Meth) acrylate, tetrapentaerythritol nona (meth) acrylate, tetrapentaerythritol nona (meth) acrylate, tetrapentaerythritol deca (meth) acrylate and other (meth) acrylates having pentapentaerythritol skeleton, pentapentaerythritol undeca ( (Meth) acrylate and (meth) acrylate having a pentapentaerythritol skeleton such as pentapentaerythritol dodeca (meth) acrylate, and at least one of these ethylene oxide (EO) adduct and propylene oxide (PO) adduct, etc. Trifunctional or higher functional (meth) acrylates may be mentioned.

  Among these, since excellent flexibility of the coating film, at least one of phenoxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate is preferable, and at least one of phenoxyethyl acrylate and 4-hydroxybutyl acrylate Is more preferable.

The said other polymeric compound may be used individually by 1 type, and may use 2 or more types together.
The other polymerizable compound may be contained in an amount of 5 to 50% by mass with respect to the total mass (100% by mass) of the ink composition.

(Polymerization inhibitor)
The ink composition of this embodiment may contain a polymerization inhibitor. Examples of polymerization inhibitors include, but are not limited to, p-methoxyphenol, cresol, t-butylcatechol, di-t-butylparacresol, hydroquinone monomethyl ether, α-naphthol, 3,5-di-t-butyl. -4-hydroxytoluene, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-butylphenol), and 4,4'-thiobis (3- Phenol compounds such as methyl-6-tert-butylphenol), p-benzoquinone, anthraquinone, naphthoquinone, phenanthraquinone, p-xyloquinone, p-toluquinone, 2,6-dichloroquinone, 2,5-diphenyl-p-benzoquinone 2,5-diacetoxy-p-benzoquinone, 2,5-dicaproxy-p- Quinone compounds such as nzoquinone, 2,5-diacyloxy-p-benzoquinone, hydroquinone, 2,5-dibutylhydroquinone, mono-t-butylhydroquinone, monomethylhydroquinone, and 2,5-di-t-amylhydroquinone, phenyl- β-naphthylamine, p-benzylaminophenol, di-β-naphthylparaphenylenediamine, amine compounds such as dibenzylhydroxylamine, phenylhydroxylamine, and diethylhydroxylamine, nitro compounds such as dinitrobenzene, trinitrotoluene, and picric acid , Oxime compounds such as quinonedioxime and cyclohexanone oxime, and sulfur compounds such as phenothiazine.

(Photopolymerization initiator)
The ink composition of this embodiment preferably contains a photopolymerization initiator. By using a photopolymerizable compound as the above-described polymerizable compound, it is possible to omit the addition of a photopolymerization initiator. However, it is preferable to use a photopolymerization initiator because the start of polymerization can be easily adjusted.

  The photopolymerization initiator is used to form an image by curing ink present on the surface of a recording medium by photopolymerization by irradiation with radiation. Here, examples of the radiation include γ rays, β rays, electron beams, ultraviolet rays (UV), visible rays, and infrared rays. Among these, ultraviolet rays are preferable because they are excellent in safety and can reduce the cost of the light source. The photopolymerization initiator is not limited as long as it generates active species such as radicals and cations by the energy of light and initiates the polymerization of the polymerizable compound. A polymerization initiator can be used, and among these, it is preferable to use a radical photopolymerization initiator.

  Examples of the photo radical polymerization initiator include aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thio compounds (thioxanthone compounds, thiophenyl group-containing compounds, etc.), hexaarylbiimidazoles, and the like. Examples include compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon halogen bond, and alkylamine compounds.

  Among these, since the curability of the ink can be particularly improved, at least one of an acylphosphine oxide compound and a thioxanthone compound is preferable, and an acylphosphine oxide compound and a thioxanthone compound are more preferable.

  Specific examples of the photo radical polymerization initiator include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine. , Carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4′-dimethoxybenzophenone, 4,4′-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyldimethyl ketal, 1- (4-isopropylphenyl) ) -2-Hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethyl Oxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, bis (2,4,6-trimethylbenzoyl) -phenyl Phosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2,4-diethylthioxanthone, and bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide Can be mentioned.

  Examples of commercially available photo radical polymerization initiators include IRGACURE 651 (2,2-dimethoxy-1,2-diphenylethane-1-one), IRGACURE 184 (1-hydroxy-cyclohexyl-phenyl-ketone), DAROCUR 1173. (2-hydroxy-2-methyl-1-phenyl-propan-1-one), IRGACURE 2959 (1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane- 1-one), IRGACURE 127 (2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one}, IRGACURE 907 (2-Methyl-1- (4-methylthiophenyl) -2-morphol Linopropan-1-one), IRGACURE 369 (2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1), IRGACURE 379 (2- (dimethylamino) -2-[(4- Methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone), DAROCUR TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide), IRGACURE 819 (bis (2, 4,6-trimethylbenzoyl) -phenylphosphine oxide), IRGACURE 784 (bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1-) Yl) -phenyl) titanium), IRGACURE OXE 01 (1.2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)]), IRGACURE OXE 02 (ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime)), IRGACURE 754 (oxyphenylacetic acid, 2- [2-oxo-2-phenylacetoxyethoxy] ethyl ester and oxyphenylacetic acid, 2- (Mixture of (2-hydroxyethoxy) ethyl ester) (above, manufactured by BASF), Speedcure TPO (manufactured by Lambson), KAYACURE DETX-S (2,4-diethylthioxanthone) (Nippon Kayaku Co., Ltd. )), Lucirin TPO, LR8883, LR8970 (above, manufactured by BASF), and Ubecryl P36 (manufactured by UCB), and the like.

  The said photoinitiator may be used individually by 1 type, and may be used in combination of 2 or more type.

  The photopolymerization initiator exhibits a sufficient radiation curing rate, and avoids undissolved photopolymerization initiator and coloring derived from the photopolymerization initiator, so that the total mass (100% by mass) of the ink composition is used. 5 to 20% by mass is preferable.

[Color material]
The ink composition of the present embodiment preferably further includes a color material. As the color material, at least one of a pigment and a dye can be used.

(Pigment)
In this embodiment, the light resistance of the ink composition can be improved by using a pigment as the coloring material. As the pigment, both inorganic pigments and organic pigments can be used.

  As the inorganic pigment, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black, iron oxide, and titanium oxide can be used.

  Organic pigments include insoluble azo pigments, condensed azo pigments, azo lakes and chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Polycyclic pigments, dye chelates (eg basic dye chelates, acid dye chelates, etc.), dye rakes (basic dye rakes, acid dye rakes), nitro pigments, nitroso pigments, aniline black, daylight A fluorescent pigment is mentioned.

  More specifically, as carbon black used as black ink, No. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B and the like (manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (and above, manufactured by Columbia Columbia), Regal 400R, Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (from CABOT JAPAN K. F. C. , Color Black FW2, Color Black FW2V, Color Black FW 18, Color Black FW200, Color B1ack S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Sep, Special Black S6, Color Black S160, Color Black S160, Color Black S170, Color Black S170, Color Black S170, Color Black S170, Color Black S170, Color Black S170, Color Black S170 Degussa)).

  Examples of pigments used in white ink include C.I. I. Pigment white 6, 18, and 21.

  Examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 167, 172, 180.

  Examples of pigments used in magenta ink include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or C.I. I. Pigment violet 19, 23, 32, 33, 36, 38, 43, 50.

  Examples of pigments used for cyan ink include C.I. I. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15:34, 15: 4, 16, 18, 22, 25, 60, 65, 66, C.I. I. Bat Blue 4, 60.

  Examples of pigments other than magenta, cyan, and yellow include C.I. I. Pigment green 7,10, C.I. I. Pigment brown 3, 5, 25, 26, C.I. I. Pigment orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63.

  The said pigment may be used individually by 1 type, and may use 2 or more types together.

  When the above pigment is used, the average particle size is preferably 10 to 300 nm, and more preferably 50 to 250 nm. When the average particle diameter is in the above range, the ink composition is more excellent in reliability such as ejection stability and dispersion stability, and an image with excellent image quality can be formed. Here, the average particle diameter in the present specification is measured by a dynamic light scattering method.

(dye)
In the present embodiment, a dye can be used as the color material. The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. Examples of the dye include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 52, 80, 82, 249, 254, 289, C.I. I. Acid Blue 9, 45, 249, C.I. I. Acid Black 1, 2, 24, 94, C.I. I. Food Black 1, 2, C.I. I. Direct Yellow 1,12,24,33,50,55,58,86,132,142,144,173, C.I. I. Direct Red 1,4,9,80,81,225,227, C.I. I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. I. Directed Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. Reactive black 3, 4, and 35 are mentioned.

  The said dye may be used individually by 1 type, and may use 2 or more types together.

  The content of the color material is preferably 1 to 20% by mass with respect to the total mass (100% by mass) of the ink composition because excellent concealability and color reproducibility are obtained.

[Dispersant]
When the ink composition of this embodiment contains a pigment, it may further contain a dispersant in order to improve pigment dispersibility. Although it does not specifically limit as a dispersing agent, For example, the dispersing agent currently used for preparing pigment dispersion liquids, such as a polymer dispersing agent, is mentioned. Specific examples include polyoxyalkylene polyalkylene polyamines, vinyl polymers and copolymers, acrylic polymers and copolymers, polyesters, polyamides, polyimides, polyurethanes, amino polymers, silicon-containing polymers, sulfur-containing polymers, fluorine-containing polymers, and epoxies. The thing which has 1 or more types of resin as a main component is mentioned. Commercially available polymer dispersants include Ajinomoto Fine Techno Co., Ajisper series, Solsperz series available from Avecia Co. (Solsperse 36000, etc.), BYK Dispersic series (DISPERBYK-168). Etc.), and Dispalon series manufactured by Enomoto Kasei.

[Slip agent]
The ink composition of the present embodiment may further contain a slip agent (surfactant) because excellent abrasion resistance is obtained. The slip agent is not particularly limited. For example, as the silicone surfactant, polyester-modified silicone or polyether-modified silicone can be used, and polyether-modified polydimethylsiloxane or polyester-modified polydimethylsiloxane is particularly used. preferable. Specific examples include BYK-377, BYK-UV3500 (above, manufactured by BYK), and KF-615A (manufactured by Shin-Etsu Chemical).

[Other additives]
The ink composition of the present embodiment may include additives (components) other than the additives listed above. Such components are not particularly limited, and may include, for example, conventionally known polymerization accelerators, penetration enhancers, wetting agents (humectants), and other additives. Examples of the other additives include conventionally known fixing agents, antifungal agents, preservatives, antioxidants, radiation absorbers, chelating agents, pH adjusting agents, and thickeners.

[Recording medium]
The radiation curable ink composition of the present embodiment can be recorded by being ejected onto a recording medium by an inkjet recording method described later. Examples of the recording medium include an absorptive or non-absorbable recording medium. The above ink jet recording method is widely applied to recording media having various absorption performances, from non-absorbing recording media in which the ink composition is difficult to penetrate to absorbent recording media in which the ink composition is easily penetrated. it can. However, when the ink composition is applied to a non-absorbable recording medium, it may be necessary to provide a drying step after being cured by irradiation with radiation.

  The absorbent recording medium is not particularly limited. For example, plain paper such as electrophotographic paper excellent in ink permeability, inkjet paper (an ink absorbing layer composed of silica particles or alumina particles, or polyvinyl alcohol). Art paper or coated paper used for general offset printing with relatively low ink permeability from (PVA) and inkjet pyrrolidone (PVP) and other hydrophilic polymers such as polyvinylpyrrolidone (PVP). And cast paper.

  The non-absorbable recording medium is not particularly limited. For example, films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, and polyethylene terephthalate (PET), and metals such as iron, silver, copper, and aluminum are used. Examples thereof include a plate, a metal plate produced by vapor deposition of these various metals, a plastic film, a plate made of an alloy such as stainless steel or brass.

  As described above, according to the present embodiment, when the radiation curable ink composition is applied to an ink jet recording apparatus, the radiation curable ink has excellent ink repellency on the nozzle surface of the print head and excellent ejection stability. A composition can be provided.

[Inkjet recording apparatus]
An ink jet recording apparatus according to an embodiment of the present invention relates to an ink jet recording apparatus including a print head having fluorine on at least a part of a nozzle surface.

  The radiation curable ink composition of the above embodiment is used in the ink jet recording apparatus, and the nozzle surface exhibits excellent ink repellency. Hereinafter, the ink jet recording apparatus will be described in detail.

  FIG. 1 is a perspective view of an ink jet recording apparatus that can be used in this embodiment. The ink jet recording apparatus 20 shown in FIG. 1 has a motor 30 for feeding a recording medium P in the sub-scanning direction SS, a platen 40, and a radiation curable ink composition having a fine particle size and ejected from a head nozzle to be recorded. A print head 52 as a recording head for discharging onto the medium P, a carriage 50 on which the print head 52 is mounted, a carriage motor 60 for moving the carriage 50 in the main scanning direction MS, and a radiation curable ink composition by the print head 52. Are provided with a pair of radiation irradiating devices 90A and 90B that irradiate the ink adhering surface on the recording medium P on which the ink is discharged.

  The carriage 50 is pulled by a pulling belt 62 driven by a carriage motor 60 and moves along a guide rail 64.

  A capping device 80 for sealing the nozzle surface of the print head 52 when stopped is provided at the home position of the carriage 50 (the position on the right side in FIG. 1). When the recording job is completed and the carriage 50 reaches the top of the capping device 80, the capping device 80 is automatically raised by a mechanism (not shown) to seal the nozzle surface of the print head 52. This capping prevents the ink in the nozzles from drying out. The positioning control of the carriage 50 is performed to accurately position the carriage 50 at the position of the capping device 80, for example.

  The print head 52 shown in FIG. 1 is a full color recording serial type head that ejects ink of three or more colors, and is provided with a large number of head nozzles for each color. In addition to the print head 52, the carriage 50 on which the print head 52 is mounted is supplied to the print head 52 and a black cartridge 54 serving as a black ink container containing black ink supplied to the print head 52. A color ink cartridge 56 is mounted as color ink containing color ink. The ink stored in each cartridge 54, 56 is the radiation curable ink composition of the above embodiment.

  FIG. 2 is a cross-sectional view schematically showing an example of a print head. The print head 152 shown in FIG. 2 includes main members such as a nozzle plate 110, a pressure chamber substrate 112, a vibration plate 114, and a piezoelectric element 116. A pressure chamber substrate 112 is provided on the nozzle plate 110, and the pressure chamber 118 is formed by being partitioned by the pressure chamber substrate 112. A flexible vibration plate 114 is provided on the pressure chamber substrate 112, and the internal pressure of the pressure chamber 118 can be instantaneously increased by bending the vibration plate 114. A piezoelectric element 116 is provided on the vibration plate 114 at a position corresponding to the pressure chamber 118. The piezoelectric element 116 to which the pressure PS is applied is entirely covered with a cover 120.

  The pressure chamber substrate 112 is provided with an ink introduction port (not shown) for introducing ink into the head. The ink introduction port is connected to an ink reservoir (not shown), and is formed so that ink can be accumulated in the ink reservoir. Further, the ink reservoir communicates with the pressure chamber 118 through the flow path 122, and the ink ejection side of the pressure chamber 118 is connected to the ink ejection port 124 provided in the nozzle plate 110.

The nozzle plate 110 is supplied to the pressure chamber 118 and is provided with a plurality of ink ejection openings 124 for ejecting pressurized ink. In particular, the present embodiment is characterized in that the nozzle plate 110 has fluorine atoms in at least a part of the nozzle plate surface 110a.
The material of the nozzle plate 110 is not particularly limited, and stainless steel (for example, SUS), polyimide, or the like can be used. When the material of the nozzle plate 110 is stainless steel, the plasma polymerization film 126 is formed by plasma polymerizing a silicone material on the nozzle plate surface 110a. Examples of the raw material of the plasma polymerized film 126, that is, the silicone material, include alkoxysilanes such as silicone oil and dimethylpolysiloxane. Specific products include TSF451 (manufactured by GE Toshiba Silicones Co., Ltd.) and SH200 (manufactured by Dow Corning Toray Co., Ltd.). It is done.

An ink-repellent fluororesin film 128 is formed on the surface of the plasma polymerization film 126. The fluororesin film 128 is preferably an alkoxysilane monomolecular film having a long-chain polymer chain containing fluorine atoms. Examples of the long-chain polymer chain containing a fluorine atom include a perfluoroalkyl chain and a perfluoropolyether chain having a molecular weight of 1000 or more. Examples of the alkoxysilane having a long chain polymer chain include the silane coupling agents having the long chain polymer chain exemplified above. Examples of the silane coupling agent include heptatriacontafluoroicosyltrimethoxysilane and the like, and commercially available products include OPTOOL DSX (trade name, manufactured by Daikin Industries, Ltd.), KY-130 ( Trade name, manufactured by Shin-Etsu Chemical Co., Ltd., etc.
When the material of the nozzle plate 110 is polyimide, the fluororesin film 128 may be formed directly on the nozzle plate 110 without forming the plasma polymerization film 126.

  FIG. 3 is a conceptual diagram of the fluororesin film 128 formed on the surface of the plasma polymerization film 126. When the nozzle plate 110 is immersed in an alkoxysilane solution having a long polymer chain containing fluorine atoms, the surface of the plasma polymerization film 126 on the nozzle plate 110 is made of an alkoxysilane having a long chain polymer chain containing fluorine atoms. A polymerized fluororesin film 128 is formed. The silicon atoms of the fluororesin film 128 are bonded to the plasma polymerization film 126 (so-called siloxane bond) through oxygen atoms. Therefore, the long polymer chain 128a containing a fluorine atom is located on the surface side. At this time, the state of the fluororesin film 128 is such that silicon atoms are three-dimensionally bonded and long-chain polymer chains containing fluorine atoms are intertwined in a complicated manner. For this reason, the fluororesin film 128 is in a high-density state, and it is difficult for ink to penetrate into the fluororesin film 128. Since such a print head 152 has a monomolecular fluororesin film 128, siloxane is not present in a region less than 1 μm from the nozzle plate surface 110 a (the surface of the fluororesin film 128) that forms the ink discharge ports 124. You will have a bond.

  Further, by forming a eutectoid plating film of Ni ions and fluororesin on the nozzle plate surface 110a, at least a part of the nozzle plate surface 110a on which the ink discharge ports 124 are formed may have fluorine atoms.

  According to the print head 152 having fluorine atoms on at least a part of the nozzle plate surface 110a forming the ink discharge port 124, the ink repellency of the radiation curable ink composition on the nozzle plate surface 110a is improved, thereby The ejection stability from the print head during recording can be improved.

  By using the inkjet recording apparatus 20 as described above, the radiation curable ink composition of the above embodiment can be stably discharged from the print head 152 to a recording medium.

  By irradiating the radiation curable ink composition discharged onto the recording medium with radiation, the radiation curable ink composition is cured and an image can be recorded on the recording medium. 4 is a front view of the radiation irradiation apparatus 90A (corresponding to 190A in FIG. 4) and 90B (corresponding to 190B in FIG. 4) shown in FIG. FIG. 5 is an AA arrow view of FIG.

  As shown in FIGS. 1, 4, and 5, the radiation irradiating apparatuses 190 </ b> A and 190 </ b> B are respectively attached to both side ends along the moving direction of the carriage 50.

  As shown in FIG. 4, the radiation irradiating device 190A attached to the left side of the print head 52 is placed on the recording medium P when the carriage 50 moves rightward (in the direction of arrow B in FIG. 4). The ejected ink layer 196 is irradiated with radiation. On the other hand, the radiation irradiator 190B attached to the right side of the print head 52 has an ink layer ejected onto the recording medium P during left scanning when the carriage 50 moves leftward (direction of arrow C in FIG. 4). Radiation is applied to 196.

  Each of the radiation irradiation devices 190A and 190B is attached to the carriage 50, and controls a light source control circuit (not shown) that controls the light emission and extinction of the radiation light source 192, and a housing 194 that aligns and supports the radiation light sources 192 one by one. And. As shown in FIGS. 4 and 5, the radiation irradiation apparatuses 190A and 190B are each provided with one radiation light source 192, but two or more radiation light sources 192 may be provided. As the radiation light source 192, either a light emitting diode (LED) or a laser diode (LD) is preferably used. Thereby, compared with the case where a mercury lamp lamp, a metal halide lamp, and other lamps are used as a radiation light source, it is possible to avoid an increase in the size of the radiation light source due to the provision of a filter or the like. In addition, the radiation intensity emitted by absorption by the filter does not decrease, and the radiation curable ink composition can be efficiently cured.

  In addition, each radiation light source 192 may have the same wavelength or different wavelengths. When an LED or LD is used as the radiation light source 192, the emission peak wavelength of the emitted radiation may be in the range of about 350 to 430 nm.

  According to the radiation irradiation apparatuses 190A and 190B described above, as shown in FIG. 4, the ink layer 196 deposited on the recording medium P by the ejection from the print head 52 is covered with the covering near the print head 52. The radiation light source 192 that irradiates the recording medium P is irradiated with radiation 192a, and the surface and the inside of the ink layer 196 can be cured.

Since the illuminance of radiation varies depending on the thickness of the ink layer 196 deposited on the recording medium P, it cannot be specified strictly, and preferable conditions are selected as appropriate, but the radiation curable ink composition of the above embodiment is used. Since the product is used, it can be sufficiently cured with an illuminance of about 10 to 2,000 mW / cm ² .

According to the inkjet recording apparatus 20, a plurality of radiation curable ink compositions ejected onto the recording medium P even during full color recording in which the radiation curable ink composition has a low viscosity and the ink layer thickness is relatively thin. Goods can be cured well without causing problems such as bleeding or color mixing.
The configuration of the inkjet recording apparatus 20 is not limited to the configuration of the recording head, carriage, light source, and the like described above, and various forms can be adopted based on the purpose of the inkjet recording apparatus of the present embodiment. it can.

  Thus, according to the present embodiment, an ink jet recording apparatus using a radiation curable ink composition having excellent ink repellency on the nozzle surface of the print head and excellent discharge stability can be provided.

[Inkjet recording method]
An ink jet recording method according to an embodiment of the present invention is a method using the ink jet recording apparatus 20 including the print head 152 having fluorine on at least a part of the nozzle plate surface 110a, and the radiation curable ink of the above embodiment. It includes discharging the composition from the print head 152.

  Hereinafter, the embodiments of the present invention will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to only these examples.

[Materials used]
The materials used in the following examples and comparative examples are as follows.
(Polymerizable compound)
4-Hydroxybutyl acrylate (manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD., Trade name “4-HBA”, abbreviated as 4-HBA in Tables 2 and 3)
・ 2- (2-vinyloxyethoxy) ethyl acrylate (Nippon Shokubai Co., Ltd., trade name “VEEA”, abbreviated as VEEA in Tables 2 and 3)
Phenoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name “Biscoat # 192”, abbreviated as PEA in Tables 1 to 3)
[Compounds and sugars having a dibenzylidene sorbitol skeleton]
Compound A (manufactured by Tokyo Chemical Industry Co., Ltd., D-(+)-saccharose)
Compound B (BASF, 1,3: 2,4-dibenzylidene sorbitol)
Compound C (BASF, 1,3: 2,4-di (p-methylbenzylidene) sorbitol)
In the following table, “a compound and a sugar having a dibenzylidene sorbitol skeleton” are simply abbreviated as “dibenzylidene sorbitol skeleton”.
(Photopolymerization initiator)
IRGACURE 819 (trade name, manufactured by BASF, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, abbreviated as 819 in Tables 2 and 3)
DAROCUR TPO (BASF product name, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, abbreviated as TPO in Tables 2 and 3)
[Slip agent]
BYK-UV3500 (trade name manufactured by BYK, polydimethylsiloxane having a polyether-modified acrylic group, abbreviated as UV3500 in Tables 2 and 3)
(Polymerization inhibitor)
P-methoxyphenol (trade name, manufactured by Kanto Chemical Co., Ltd., abbreviated as MEHQ in Tables 2 and 3)
[Pigment]
・ White pigment (Ishihara Sangyo Kaisha, Ltd., titanium oxide)
[Dispersant]
Dispersant B (trade name “Solsperse 36000” manufactured by LUBRIZOL)

[Examples 1 to 16, Comparative Examples 1 to 25]
(Preparation of pigment dispersion)
The materials described in Table 1 below were added so as to have the composition (unit: part by mass) described in Table 1, and stirred with a stirrer for 1 hour. The mixture after stirring was dispersed by bead mill dispersion to obtain a pigment dispersion. Dispersion conditions were such that zirconia beads having a diameter of 0.65 mm were filled at a filling rate of 70%, the peripheral speed was 9 m / s, and the dispersion time was 2 to 4 hours. In this way, white pigment dispersions were respectively prepared.

[Preparation of radiation curable ink composition]
The materials listed in Tables 2 and 3 below were added so as to have the compositions (units: parts by mass) described in Tables 2 and 3, and mixed and dissolved by stirring. An ink composition was obtained.

〔Evaluation item〕
The ink repellency and ejection stability of the radiation curable inkjet ink composition prepared above were evaluated by the following methods.

(1. Ink repellency)
First, five types of print heads having different nozzle plates (hereinafter also referred to as “NP”) were prepared. The characteristics of the used NP are as follows.
NP1: SUS is used as the NP substrate, and the surface treatment is not performed.
-NP2: Polyimide is used as the NP substrate, and the surface treatment is not performed.
NP3: SUS is used as the NP substrate, and a eutectoid plating film of Ni ions and fluororesin (localized on the NP surface) is formed on the NP surface including the portion where the ink contacts. The surface treatment of NP3 was performed based on the examples of JP-A-3-274163 and JP-A-6-246921.
NP4: SUS is used as the NP substrate, and after forming a plasma polymerized film by plasma polymerizing dimethylpolysiloxane, which is a silicone material, on the NP surface including the part where the ink contacts, a long chain polymer containing fluorine A fluororesin film is formed of alkoxysilane having a chain. The surface treatment of NP4 was performed based on the description from paragraph 0034 to paragraph 0038 of JP-A No. 2004-351923.
NP5: Polyimide is used as the NP substrate, and a fluororesin film is formed of alkoxysilane having a long-chain polymer chain containing fluorine on the NP surface including a portion where the ink contacts. The surface treatment of NP5 was performed based on the description from paragraph 0045 to paragraph 0049 of JP-A-2006-334903.

Next, wiping was performed 30,000 times at 40 ° C. with a butyl rubber wipe while continuously dropping the obtained radiation curable ink composition onto the nozzle plate surface of the prepared nozzle.
The evaluation criteria are as follows. ○ is a practically acceptable evaluation standard. Specifically, when the evaluation is “◯”, it can be determined that the ink repellency is excellent in the portion where the ink comes into contact. The evaluation results are shown in Tables 4-7.
◯: There was no ink on the nozzle plate after 30,000 times of wiping.
X: Ink remained on the nozzle plate after 30,000 times of wiping.

(2. Discharge stability)
First, a total of five inkjet printers PX-5000 (trade names, manufactured by Seiko Epson Corporation) provided with any one of the above-described NP1 to NP5 were prepared. Using each ink jet printer, the radiation curable ink compositions (ink production examples 1 to 21) obtained above were solid on a PET film under the conditions of a resolution of 720 dpi × 720 dpi, a droplet weight of 10 ng, and an environmental temperature of 40 ° C. Recording as a pattern image was performed continuously for 48 hours. At this time, the missing dots, the flying curve, and the occurrence of ink scattering were visually observed. Note that this solid pattern image is an image in which dots are recorded for all of the pixels that are the minimum recording unit area defined by the recording resolution.
The evaluation criteria are as follows. ◎ and ○ are practically acceptable evaluation criteria. The evaluation results are shown in Tables 4-7.
A: Occurrence of missing dots, flying bends, and ink scattering was less than 50 times.
○: Occurrence of missing dots, flying bends, and ink scattering were 50 times or more and less than 100 times.
X: Occurrence of dot omission, flight bending, and ink scattering occurred 100 times or more.

NP3, NP4, and NP5 having fluorine on the NP surface correspond to examples, and NP1 and NP2 having no fluorine on the NP surface correspond to comparative examples.
Further, ink production examples 1, 2, 7, wherein the content of compounds A, B, and C, which are at least one of a compound having a dibenzylidene sorbitol skeleton and a sugar, is less than 0.5% by mass in the ink composition. And 14 correspond to comparative examples. In addition, when the ink in which the content of the compounds A, B, and C exceeded 5% by mass in the ink composition was prepared, there was a problem that these compounds were deposited on the surface of the coated film after curing.

(3. Curability)
The radiation curable ink composition (ink production examples 1 to 21) obtained above was applied onto a PET film with a bar coater (as the thickness of the cured film) to a film thickness of 10 μm. Irradiation was performed with a UV-LED (peak wavelength: 395 nm, irradiation intensity: 60 mW / cm ² ), and irradiation energy irradiated until a tack-free state was obtained was determined. The irradiation energy [mJ / cm ² ] was determined from the product of the irradiation intensity [mW / cm ² ] on the irradiated surface irradiated from the light source and the irradiation duration [s]. The irradiation intensity was measured using an ultraviolet intensity meter UM-10 and a light receiving unit UM-400 (both manufactured by KONICA MINOLTA SENSING, INC.). Moreover, the state which becomes tack free was judged on the following conditions. That is, the determination was made based on whether the ink sticks to the cotton swab or whether the cured ink on the recording medium is scratched. The cotton swab used here was a Johnson swab manufactured by Johnson & Johnson. The number of rubbing was 10 reciprocations and the rubbing strength was 100 g load.
The evaluation criteria are as follows. The evaluation results are shown in Table 8 below.
A: Irradiation energy at tack free 200 mJ / cm ² or less,
○: Irradiation energy at tack free 200 mJ / cm ^{2 to} 300 mJ / cm ² or less,
△: irradiation energy 300mJ / cm ² than at the time of tack-free.

From Table 4 to Table 7, using a nozzle surface having fluorine on the surface, and containing at least one of a compound having a dibenzylidene sorbitol skeleton and a sugar and a polymerizable compound, among the compound having a dibenzylidene sorbitol skeleton and the sugar It was found that the radiation curable ink composition containing at least one of 0.5 to 5.0% by mass was excellent in ink repellency and also in discharge stability.
From Table 8 above, a radiation curable ink containing at least one of a compound having a dibenzylidene sorbitol skeleton and a saccharide and a polymerizable compound, and at least one of the compound having a dibenzylidene sorbitol skeleton and a saccharide containing 7% by mass. The composition was found to be inferior in curability.

  DESCRIPTION OF SYMBOLS 20 ... Inkjet recording device 30 ... Motor, 40 ... Platen, 50 ... Carriage, 52 (152) ... Print head (recording head), 54 ... Black ink cartridge, 56 ... Color ink cartridge, 60 ... Carriage motor, 62 ... Towing Belt, 64 ... guide rail, 80 ... capping device, 90A (190A) ... radiation irradiation device, 90B (190B) ... radiation irradiation device, 110 ... nozzle plate, 110a ... nozzle plate surface, 112 ... pressure chamber substrate, 114 ... vibration Plate 116: Piezoelectric element 118 ... Pressure chamber 120 ... Cover 122 ... Flow path 124 ... Ink discharge port 126 ... Plasma polymerized film 128 ... Fluorine resin film 128a ... Long chain polymer chain containing fluorine, 152 ... print head, 192 ... radiation source, 192a ... radiation , 194 ... housing, 196 ... ink layer, P ... recording medium, PS ... pressure, MS ... main scanning direction, SS ... sub scanning direction.

Claims (7)

A radiation curable ink composition used in an ink jet recording apparatus having a print head including a nozzle surface,
The nozzle surface has a fluorine atom in at least a part of a portion in contact with ink,
The radiation curable ink composition includes at least one of a compound having a dibenzylidene sorbitol skeleton and a sugar and a polymerizable compound,
Radiation curable ink wherein the total content of at least one or more of the compound having a dibenzylidene sorbitol skeleton and sugar is 0.5 to 5.0% by mass with respect to the total mass of the radiation curable ink composition. Composition.   The radiation curable ink composition according to claim 1, wherein at least one of the compound having a dibenzylidene sorbitol skeleton and the sugar is a compound having a dibenzylidene sorbitol skeleton.   At least one of the compound having a dibenzylidene sorbitol skeleton and the sugar is at least one of 1,3: 2,4-dibenzylidene sorbitol and 1,3: 2,4-di (p-methylbenzylidene) sorbitol. The radiation curable ink composition according to claim 1, comprising:   A print head including a nozzle surface having fluorine atoms in at least a part of a portion in contact with the ink, the print head ejecting the radiation curable ink composition according to claim 1. An inkjet recording apparatus.   The ink jet recording apparatus according to claim 4, wherein the nozzle surface has a siloxane bond in a region less than 1 μm from a portion in contact with the ink.   An inkjet recording method comprising discharging the radiation curable ink composition according to claim 1 from the print head. A radiation curable ink composition comprising a compound having at least one of a compound having a dibenzylidene sorbitol skeleton and a sugar and a polymerizable compound,
A radiation curable ink composition, wherein a total content of at least one or more of the compound having a dibenzylidene sorbitol skeleton and a sugar is 0.5 to 5.0% by mass with respect to the total mass of the ink composition.