JP2013177525A - Ink storage body, ultraviolet-curable ink composition for inkjet recording stored in the storage body, and inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink storage body storing an ultraviolet-curable ink composition for inkjet recording excellent in curability, preservation stability and jet stability.SOLUTION: An ink storage body stores an ultraviolet-curable ink composition for inkjet recording containing at least vinyl ether group-containing (meth)acrylic acid esters represented by general formula (I) and a hindered amine compound, and an amount of dissolved oxygen is 20 ppm or less.

Description

  The present invention relates to an ink container, an ultraviolet curable ink composition for ink jet recording, and an ink jet recording apparatus accommodated in the container.

  Conventionally, various methods have been used as a recording method for forming an image on a recording medium such as paper 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. Furthermore, the inkjet method is excellent as a recording method because of its low noise.

  In recent years, an ultraviolet curable ink composition for ink jet recording that cures when irradiated with ultraviolet rays in an ink jet recording method in order to form an image having high water resistance, solvent resistance, scratch resistance, etc. on the surface of a recording medium. Things are being used.

  For example, Patent Document 1 discloses an inkjet ink containing a coloring material, water, and an active energy ray crosslinkable polymer compound, wherein the active energy ray crosslinkable compound has a plurality of side chains in the hydrophilic main chain, Disclosed is an inkjet ink that is a polymer compound that can be cross-linked between side chains by irradiating active energy rays, and the dissolved oxygen concentration in the ink at 25 ° C. is 0.05 ppm or more and 1.8 ppm or less, It is also disclosed that the ink has excellent light-emitting properties, excellent image-rendering gloss, bleed resistance, and scratch resistance (paragraph 0023 of Document 1).

  For example, Patent Document 2 is an ultraviolet curable inkjet ink containing at least a coloring material, an ultraviolet polymerizable compound, and a photopolymerization initiator in an aqueous medium, and the dissolved oxygen concentration in the ink at 25 ° C. An ink-jet ink of 0.1 to 2 ppm is disclosed, and it is also disclosed that stable ejection performance can be obtained even when recording is performed for a long period of time (paragraphs 0017 and 0019 of Document 2).

JP 2007-138070 A JP 2004-196936 A

  However, both the inks disclosed in Patent Documents 1 and 2 have a problem that they are inferior to at least one of curability, storage stability, and ejection stability.

  Accordingly, an object of the present invention is to provide an ink container containing an ultraviolet curable ink composition for ink jet recording excellent in curability, storage stability, and ejection stability.

  Another object of the present invention is to provide an ultraviolet curable ink jet recording ink composition accommodated in the ink container, and an ink jet recording apparatus using the ultraviolet curable ink jet recording ink composition. To do.

The present inventors have intensively studied to solve the above problems. First, in order to be suitably used in an ink jet recording apparatus (hereinafter, also simply referred to as “recording apparatus”), an ultraviolet curable ink composition for ink jet recording (hereinafter simply referred to as “the recording apparatus”) having excellent ejection stability and curability. Also referred to as “ink composition”. As a result, the ink composition contains the predetermined vinyl ether group-containing (meth) acrylic acid esters and has a dissolved oxygen amount (dissolved air amount) reduced to a predetermined value or less by performing a deaeration process. I found that it was better to be accommodated in the body.
Here, it has been found that an ink composition containing a predetermined vinyl ether group-containing (meth) acrylic acid ester is very excellent in curability and inferior in storage stability. Therefore, as a result of further studies, the present inventors have excellent storage stability even when the amount of dissolved oxygen is small due to the ink container containing an ink composition further containing a hindered amine compound as a polymerization inhibitor. As a result, the present invention has been completed.

That is, the present invention is as follows.
[1]
The following general formula (I):
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
Wherein 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.)
An ink container containing an ultraviolet curable ink composition for ink jet recording containing at least a vinyl ether group-containing (meth) acrylic acid ester represented by the formula (1) and a hindered amine compound and having a dissolved oxygen content of 20 ppm or less. .
[2]
The ink container according to [1], wherein the ultraviolet curable ink composition for inkjet recording further includes a thioxanthone compound.
[3]
[1] or less than 5.0 cc · 20 μm / (m ² · day · atm) at 23 ° C. and 65% humidity when the constituent material contacting the ultraviolet curable ink composition for inkjet recording is 23 ° C. and 65% humidity. The ink container according to [2].
[4]
The ink container according to [1] or [2], wherein the ultraviolet curable ink composition for inkjet recording can be accommodated in a volume of 100 to 1,000 mL.
[5]
The ink container according to any one of [1] to [4], wherein the vinyl ether group-containing (meth) acrylic acid ester is 2- (vinyloxyethoxy) ethyl acrylate.
[6]
The ink container according to any one of [1] to [5], wherein the hindered amine compound is a compound having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton.
[7]
Any one of [1] to [6], wherein the content of the vinyl ether group-containing (meth) acrylic acid ester is 10 to 70% by mass with respect to the total mass of the ultraviolet curable ink composition for inkjet recording. The ink container according to 1.
[8]
The ink container according to any one of [2] to [7], wherein a content of the thioxanthone compound is 0.5 to 4% by mass with respect to a total mass of the ultraviolet curable ink composition for inkjet recording. .
[9]
[1] An ultraviolet curable ink composition for inkjet recording, which is accommodated in the ink container according to any one of [8].
[10]
[1] to [8] An ink jet recording apparatus comprising at least a discharge means for discharging the ultraviolet curable ink composition for ink jet recording contained in the ink container according to any one of [1] to [8] from a head.
[11]
The ink jet recording apparatus according to [10], wherein the ultraviolet curable ink composition for ink jet recording discharged from the head has a dissolved oxygen content of 20 ppm or less.
[12]
The ink jet recording apparatus according to [11], wherein the dissolved oxygen amount of the ink increases in the process of supplying ink from the ink container to the head.
[13]
[1] to [8] An inkjet recording method comprising at least an ejection step of ejecting the ultraviolet curable inkjet recording ink composition accommodated in the ink container according to any one of [1] to [8] from a head.

It is a perspective view showing an ink pack which is an example of the ink container of the present invention. It is a figure which shows an example around the head of the inkjet recording device of this invention.

  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 this specification, “curability” refers to a property of curing in response to light. “Storage stability” refers to the property that the viscosity of an ink composition is difficult to change before and after storage. “Ejection stability” refers to the property of ejecting droplets of a stable ink composition from a nozzle without clogging the nozzle.
In the present specification, “(meth) acrylate” means at least one of acrylate and its corresponding methacrylate, “(meth) acryl” means at least one of acrylic and its corresponding methacryl, “(Meth) acryloyl” means at least one of acrylic and methacryl corresponding thereto.

[Ink container]
One embodiment of the present invention relates to an ink container containing a predetermined ultraviolet curable ink composition for inkjet recording. The ink composition includes a vinyl ether group-containing (meth) acrylic acid ester (hereinafter also referred to simply as “vinyl ether group-containing (meth) acrylic acid ester”) represented by the following general formula (I), and a hindered amine. And at least a compound. In addition, the dissolved oxygen content of the ink composition accommodated in the ink container is 20 ppm or less.
Hereinafter, additives (components) that are or can be included in the ink composition of the present embodiment will be described.

(Polymerizable compound)
The polymerizable compound contained in the ink composition can be polymerized at the time of light irradiation alone or by the action of a photopolymerization initiator described later to cure the printed ink.

(Vinyl ether group-containing (meth) acrylic acid esters)
The ink composition contains a vinyl ether group-containing (meth) acrylic acid ester represented by the following general formula (I) as a polymerizable compound.
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
Wherein 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 vinyl ether group-containing (meth) acrylic acid esters, the ink curability can be improved, and the viscosity of the ink can be lowered. In addition, it is better to use a compound having both a vinyl ether group and a (meth) acryl group in one molecule than to use a compound having a vinyl ether group and a compound having a (meth) acryl group separately. It is preferable for improving curability.

In the above general formula (I), the divalent organic residue having 2 to 20 carbon atoms represented by R ² is a linear, branched or cyclic substituted having 2 to 20 carbon atoms. May be an alkylene group, an optionally substituted alkylene group having an oxygen atom by an ether bond and / or an ester bond in the structure, and an optionally substituted divalent alkylene group having 6 to 11 carbon atoms. Aromatic groups are preferred. 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 the general formula (I), the monovalent organic residue having 1 to 11 carbon atoms represented by R ³ is a linear, branched or cyclic substituted group having 1 to 10 carbon atoms. Suitable alkyl groups and optionally substituted aromatic groups having 6 to 11 carbon atoms are 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 each of the organic residues 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.

  Examples of the vinyl ether group-containing (meth) acrylic acid esters include, but are not limited to, for example, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxypropyl (meth) acrylate, and 1-methyl (meth) acrylate. 2-vinyloxyethyl, 2-vinyloxypropyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 1-methyl-3-vinyloxypropyl (meth) acrylate, 1-vinyloxymethyl (meth) acrylate Propyl, 2-methyl-3-vinyloxypropyl (meth) acrylate, 1,1-dimethyl-2-vinyloxyethyl (meth) acrylate, 3-vinyloxybutyl (meth) acrylate, 1-methyl- (meth) acrylate 2-vinyloxypropyl, 2-vinyloxybutyl (meth) acrylate, (meth) a 4-vinyloxycyclohexyl silylate, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, 3-vinyloxymethylcyclohexylmethyl (meth) acrylate, (meth) acrylic acid 2-vinyloxymethylcyclohexylmethyl, p-vinyloxymethylphenylmethyl (meth) acrylate, m-vinyloxymethylphenylmethyl (meth) acrylate, o-vinyloxymethylphenylmethyl (meth) acrylate, (meth) 2- (vinyloxyethoxy) ethyl acrylate, 2- (vinyloxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxy) propyl (meth) acrylate, 2- (vinyloxy) (meth) acrylate Ethoxy) isopropyl, (meth) acrylic acid 2- Vinyloxyisopropoxy) propyl, 2- (vinyloxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyisopropoxy) (meth) acrylate ) Ethyl, 2- (vinyloxyisopropoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) propyl (meth) acrylate 2- (vinyloxyethoxyisopropoxy) propyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) propyl (meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) propyl (meth) acrylate, (Meth) acrylic acid 2- (vinylo) Xylethoxyethoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyethoxyisopropoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyisopropoxyethoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyisopropoxy) Isopropoxy) isopropyl, (meth) acrylic acid 2- (vinyloxyethoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (vinyloxyethoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxy) ) Ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxyethoxy) ethyl, (meth) acrylic acid 2- (isopropenoxyethoxyethoxyethoxy) D ) Ethyl, and (meth) Polyethylene glycol monovinyl ether acrylate, and (meth) acrylic acid polypropylene glycol monovinyl ether.

  Among these, since the viscosity of the ink can be further lowered, the flash point is high, and the curability of the ink is excellent, 2- (vinyloxyethoxy) ethyl (meth) acrylate, that is, 2- (vinyloxy) acrylate At least one of ethoxy) ethyl and 2- (vinyloxyethoxy) ethyl methacrylate is preferable, and 2- (vinyloxyethoxy) ethyl acrylate is more preferable. In particular, since 2- (vinyloxyethoxy) ethyl acrylate and 2- (vinyloxyethoxy) ethyl methacrylate have a simple structure and a small molecular weight, the viscosity of the ink can be significantly reduced. 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. Incidentally, 2- (vinyloxyethoxy) ethyl acrylate is superior in terms of curability compared to 2- (vinyloxyethoxy) ethyl methacrylate.

  A vinyl ether group containing (meth) acrylic acid ester may be used individually by 1 type, and may be used in combination of 2 or more type.

The vinyl ether group-containing (meth) acrylic acid esters, particularly the content of 2- (vinyloxyethoxy) ethyl (meth) acrylate, is 10 to 70 mass with respect to the total mass (100 mass%) of the ink composition. % Is preferable, and 30 to 50% by mass is more preferable. When the content is 10% by mass or more, the viscosity of the ink can be reduced and the curability of the ink can be further improved. On the other hand, when the content is 70% by mass or less, the storage stability of the ink can be maintained in an excellent state.
In addition, when content of the said vinyl ether group containing (meth) acrylic acid ester is near the upper limit of said preferable range, the storage stability of an ink composition may deteriorate. However, when the hindered amine compound described later is included in the ink composition together with the vinyl ether group-containing (meth) acrylic acid esters, excellent storage stability can be maintained even in the above case.

  The method for producing the vinyl ether group-containing (meth) acrylic acid esters 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 halide. And esterification of (meth) acrylic anhydride and hydroxyl group-containing vinyl ether (production method D), esterification of (meth) acrylic acid ester and hydroxyl group-containing vinyl ether Method of exchange (Production method E), Method of esterifying (meth) acrylic acid and halogen-containing vinyl ether (Method of production F), Method of esterifying alkali (earth) metal salt of (meth) acrylic acid and halogen-containing vinyl ether (Production G), hydroxyl group-containing (meth) acrylic acid ester and carboxylic acid vinyl ester How to vinyl exchange and Le (Procedure H), hydroxyl group-containing (meth) How to ether exchange and acrylic acid ester and an alkyl vinyl ether (Process 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 the N-vinyl compound include N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, and derivatives thereof.

  Among other polymerizable compounds, an ester of (meth) acrylic acid, that is, (meth) acrylate is preferable.

  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, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol ( (Meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate , Tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, lactone-modifiable Examples include flexible (meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate. Among these, phenoxyethyl (meth) acrylate is preferable.

  Among the (meth) acrylates, examples of the bifunctional (meth) acrylate include triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and dipropylene glycol di ( (Meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonane Di (meth) acrylate, neopentyl glycol di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, EO (ethylene oxide) adduct di (meth) acrylate of bisphenol A DOO, PO bisphenol A (propylene oxide) adduct di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, and polytetramethylene glycol di (meth) acrylate. Among these, dipropylene glycol di (meth) acrylate is preferable.

  Among the above (meth) acrylates, trifunctional or more polyfunctional (meth) acrylates include, for example, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, and pentaerythritol tri (meth) acrylate. , Pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, glycerin propoxytri (meth) acrylate, cowprolactone modified trimethylolpropane tri (meth) acrylate, pentaerythritol Examples include ethoxytetra (meth) acrylate and caprolactam-modified dipentaerythritol hexa (meth) acrylate.

  Among these, other polymerizable compounds preferably include monofunctional (meth) acrylates. In this case, the ink composition has a low viscosity, is excellent in solubility of the photopolymerization initiator and other additives, and is easy to obtain ejection stability during ink jet recording. Furthermore, since the toughness, heat resistance, and chemical resistance of the coating film are increased, it is more preferable to use a monofunctional (meth) acrylate and a bifunctional (meth) acrylate, and among them, phenoxyethyl (meth) acrylate and dipropylene glycol. It is more preferable to use di (meth) acrylate in combination.

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

  The content of the other polymerizable compound is preferably 5 to 85% by mass and more preferably 15 to 80% by mass with respect to the total mass (100% by mass) of the ink composition. When the content is within the above range, the viscosity and odor can be reduced, and the solubility and reactivity of the photopolymerization initiator can be improved.

(Polymerization inhibitor)
The ink composition contains at least a hindered amine compound as a polymerization inhibitor.

(Hindered amine compounds)
When the ink composition contains a hindered amine compound as a polymerization inhibitor, the storage stability of the ink can be improved.

  Examples of the hindered amine compound include, but are not limited to, a compound having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton, a compound having a 2,2,6,6-tetramethylpiperidine skeleton, Examples thereof include compounds having a 2,2,6,6-tetramethylpiperidine-N-alkyl skeleton and compounds having a 2,2,6,6-tetramethylpiperidine-N-acyl skeleton.

As a commercial product of a hindered amine compound, ADK STAB LA-7RD (2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl) (trade name, manufactured by ADEKA), IRGASTAB UV 10 (4,4 ′-[ 1,10-dioxo-1,10-decandiyl) bis (oxy)] bis [2,2,6,6-tetramethyl] -1-piperidinyloxy) (CAS. 2516-92-9), TINUVIN 123 (4-hydroxy-2,2,6,6, -tetramethylpiperidine-N-oxyl) (above, trade name manufactured by BASF), FA-711HM, FA-712HM (2,2,6,6-tetramethyl) Piperidinyl methacrylate, trade name of Hitachi Chemical Company, Ltd.), TINUVIN 111FDL, TINUVIN 14 4, TINUVIN 152, TINUVIN 292, TINUVIN 765, TINUVIN 770DF, TINUVIN 5100, SANOL LS-2626, CHIMASSORB 119FL, CHIMASSORB 2020 FDL, CHIMASSORB 944 FDL, TINLDIN 622 FBA, TINLDIN 622 LA-57, LA-62, LA-63P, LA-68LD, LA-77Y, LA-77G, LA-81, LA-82 (1,2,2,6,6-pentamethyl-4-piperidyl methacrylate), LA-87 (trade name, manufactured by ADEKA) is mentioned.
Of the above-mentioned commercial products, LA-82 is a compound having a 2,2,6,6-tetramethylpiperidine-N-methyl skeleton, and Adeka Stab LA-7RD is 2,2,6,6-tetramethyl. It is a compound having a piperidine-N-oxyl skeleton.

  Among these, a compound having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton is preferable because the storage stability of the ink can be further improved while maintaining excellent curability. .

Specific examples of the compound having the above 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton include, but are not limited to, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1- Oxyl, 4,4 ′-[1,10-dioxo-1,10-decandiyl) bis (oxy)] bis [2,2,6,6-tetramethyl] -1-piperidinyloxy, 4-hydroxy- 2,2,6,6, -tetramethylpiperidine-N-oxyl, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate, bis (2,2) decanedioate , 6,6-tetramethyl-1- (octyloxy) -4-piperidinyl) ester.
As said commercial item, ADK STAB LA-7RD, IRGASTAB UV10 is mentioned, for example.

  A hindered amine compound may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the hindered amine compound is preferably 0.05 to 0.5% by mass and more preferably 0.1 to 0.5% by mass with respect to the total mass (100% by mass) of the ink composition. When the content is 0.05% by mass or more, the storage stability of the ink can be further improved, and when the content is 0.1% by mass or more, the storage stability of the ink is further improved. It can be excellent. Moreover, the outstanding sclerosis | hardenability can be effectively maintained as content is 0.5 mass% or less.

(Other polymerization inhibitors)
The ink composition may further contain a substance other than the hindered amine compound as a polymerization inhibitor. Other polymerization inhibitors include, but are not limited to, for example, p-methoxyphenol, hydroquinone monomethyl ether (MEHQ), hydroquinone, cresol, t-butylcatechol, 3,5-di-t-butyl-4-hydroxytoluene 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-butylphenol), and 4,4′-thiobis (3-methyl-6-t) -Butylphenol).

  Another polymerization inhibitor may be used individually by 1 type, and may be used in combination of 2 or more type. The content of other polymerization inhibitors is not particularly limited because it depends on the relationship with the content of other components.

(Photopolymerization initiator)
The ink composition may further contain a photopolymerization initiator. The photopolymerization initiator is used to form a print by curing the ink present on the surface of the recording medium by photopolymerization by ultraviolet irradiation. By using ultraviolet rays (UV) among the radiation, the safety is excellent and the cost of the light source lamp can be suppressed. There is no limitation as long as it generates active species such as radicals and cations by the energy of light (ultraviolet rays) and initiates polymerization of the polymerizable compound, but photo radical polymerization initiators and photo cationic polymerization initiators are used. Among them, it is preferable to use a photo radical polymerization 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.), α-aminoalkyls, and the like. Examples include phenone compounds, hexaarylbiimidazole 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 ink curability can be further improved, a thioxanthone compound is preferable, and a combination of an acylphosphine oxide compound and a thioxanthone compound is 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, diethylthio Xanthone, 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.

  Among these, diethylthioxanthone is preferable because ultraviolet light (UV light) in a wide range can be efficiently converted into active species.

  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- (2-hydroxyethoxy) ethyl ester mixture) (above, manufactured by BASF), Speedcure TPO, Speedcure DETX (2,4-diethylthioxanthone), Speedcure ITX (2-isopropylthioxanthone) (above, manufactured by Lambson), KAYACURE DETX-S (2 , 4-diethylthioxanthone) (manufactured by Nippon Kayaku Co., Ltd.), Lucirin TPO, LR8883, LR8970 (above, manufactured by BASF), and Ubekrill P36 (manufactured by UCB).

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

  The content of the photopolymerization initiator is preferably 5 to 20% by mass with respect to the total mass (100% by mass) of the ink composition. When the content is within this range, the ultraviolet curing rate can be sufficiently exerted, and the undissolved portion of the photopolymerization initiator and coloring derived from the photopolymerization initiator can be avoided.

  In particular, when the photopolymerization initiator contained in the ink composition is a thioxanthone compound, the content of the thioxanthone compound is preferably 0.5 to 4% by mass with respect to the total mass (100% by mass) of the ink composition. 1 to 4% by mass is more preferable. When the content is 0.5% by mass or more, the curability of the ink can be further improved. Moreover, the outstanding discharge stability can be effectively maintained as content is 4 mass% or less. When the ink composition contains a thioxanthone compound, the curability of the ink composition is particularly excellent. On the other hand, when the amount of dissolved oxygen in the ink composition is relatively high, the ejection stability tends to decrease. The present embodiment is particularly useful. The cause is estimated that the thioxanthone compound remaining as fine particles in the ink induces bubbles as bubble nuclei, but the cause is not limited to this.

  In addition, it is possible to omit the addition of a photopolymerization initiator by using a photopolymerizable compound as the polymerizable compound described above, but it is easier to start polymerization by using a photopolymerization initiator. It can be adjusted and is preferred.

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

(Pigment)
By using a pigment as the color material, the light resistance of the ink composition can be improved. 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, chelate azo pigments, etc., 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), dyeing lakes (basic dye rakes, acid dye rakes), nitro pigments, nitroso pigments, aniline black, daylight A fluorescent pigment is mentioned.

  More specifically, as a carbon black used for 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 using said pigment, the average particle diameter has preferable 300 nm or less, and 50-200 nm is more preferable. 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)
A dye can be used as the coloring 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 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's Ajisper series, Solspers series (Solsperse 36000, etc.) available from Avecia and Noveon, and BYK Chemie's Dispersic series. , Disparon series manufactured by Enomoto Kasei.

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

[Physical properties of UV-curable ink composition for inkjet recording]
The ink composition in the present embodiment is characterized in that the dissolved oxygen amount is 20 ppm or less. By performing treatment such as deaeration so that the amount of dissolved oxygen is 20 ppm or less, an ink composition having excellent ejection stability and curability can be obtained. Thereby, the ink composition can be suitably used for an ink jet recording apparatus. In addition, when used in an ink jet recording apparatus, the amount of dissolved oxygen may increase because air dissolves in the ink as it passes through the ink flow path. However, if the dissolved oxygen content of the ink composition in the ink container is 20 ppm or less, when the ink is filled from the ink container into the ink jet recording apparatus and recording is performed, the ejection stability and curability are excellent. It can be set as an ink composition.

  Moreover, 1-20 ppm is preferable, as for the said dissolved oxygen amount, 3-20 ppm is more preferable, and 5-15 ppm is further more preferable. In particular, when the amount of dissolved oxygen is 1 ppm or more, the polymerization of the polymerizable compound can be appropriately inhibited, so that excellent storage stability can be effectively maintained. Therefore, when the ink composition contains the above-mentioned hindered amine compound as a polymerization inhibitor and has an amount of dissolved oxygen within a predetermined range, the storage stability is extremely excellent.

Here, the “dissolved oxygen amount” in the present specification may be at least within the above predetermined range when the ink composition is filled in the ink jet recording apparatus. More specifically, during a period in which the amount of dissolved oxygen needs to be within the predetermined range, after the ink container is shipped, the ink container or the ink composition in the container is attached to the recording apparatus, filled, or Until just before being used. Further, in the case of a recording apparatus provided with a deaeration mechanism, the amount of dissolved oxygen can be reduced in the recording apparatus. However, even in this case, there is a limit to the deaeration capability, so the amount of dissolved oxygen in the ink container is preferably within the above range. On the other hand, in the case of a recording apparatus in which the amount of dissolved oxygen does not change (almost) in the recording apparatus, even if the recording apparatus is not equipped with a deaeration mechanism, at least the amount of dissolved oxygen in the ink container is determined. It may be within the above range.
In addition, although the dissolved oxygen amount in this specification can be measured by a conventionally well-known method, the value obtained by the measuring method implemented in the below-mentioned Example shall be employ | adopted for convenience.

  Here, when treatment such as deaeration is not performed for the purpose of reducing the amount of dissolved oxygen, the amount of dissolved oxygen in the ink composition is usually about 50 to 60 ppm. Therefore, a treatment such as deaeration is required to make the dissolved oxygen amount 20 ppm or less. Examples of the treatment include, but are not limited to, a degassing mechanism and inert gas bubbling.

[Configuration of ink container]
The shape of the ink container of the present embodiment is not limited to the following, but examples include an ink cartridge, a pack, a bottle, a tank, a bottle, and a can. Among these, ink cartridges, packs, bottles and tanks are preferred, packs are more preferred, and film packs are particularly preferred because they are widely used and the oxygen permeability described below can be easily controlled to a desired value.

  In addition, as a usage mode of the ink container of the present embodiment, (A) a separate body from the recording apparatus, a form such as an ink cartridge that is attached to the recording apparatus and sequentially supplies ink to the recording apparatus, and (B ) Separate from the recording apparatus, and when ink is used, only the ink is transferred from the ink container such as a bottle to the recording apparatus; and (C) a tank or the like that is provided in advance in the recording apparatus and stores the ink; At least.

The above (A) and (B) can be said to be ink containers from when the ink containers are shipped to just before the ink is supplied (transferred) to the recording apparatus. The above (C) can be said to be an ink container from when the recording apparatus is shipped to before the first use of ink in the recording apparatus is started.
Note that the above (A) and (C) can be referred to as an ink container that performs printing on the recording apparatus in a state where ink is supplied from the ink container to the recording apparatus via a connecting portion such as an ink tube. it can.

  The above (B) can be said to be an ink container that performs printing with the recording apparatus after ink is transferred from the ink container to the recording apparatus. In addition, as the target to which the ink is transferred in (B), a tank or the like provided in the recording apparatus can be cited.

  In addition, the constituent material of the ink container is not limited to the following. For example, plastics such as polyethylene terephthalate (PET) and polypropylene (PP), various metals (including alloys), polyethylene, and ethylene vinyl acetate are used. Examples include polymers and polyolefins such as polypropylene. However, the present invention is not limited thereto, and may be a polymer obtained by blending or laminating each of the above polymers in an appropriate ratio, a film thereof, or the like.

Among the constituent materials of the ink container, the oxygen permeability (hereinafter simply referred to as “oxygen permeability”) of the constituent material that comes into contact with the ink composition, that is, the member that comes into contact with the ink and contains the ink is 5. 0 cc · 20 μm / (m ² · day · atm) or less is preferable, and 2.0 cc · 20 μm / (m ² · day · atm) or less is more preferable. When the oxygen permeability is within the above range, the dissolved oxygen amount of the ink composition being stored is hardly changed. The constituent material or member is not particularly limited. In the case of an ink pack, the film can be heat-sealed (heat sealed) and processed into a bag shape. Examples of the film used for the ink pack include high-density, low-density, or linear low-density polyethylene, polypropylene, an ethylene-vinyl alcohol copolymer, and stretched plastic films such as polystyrene. It is good also as a laminated film which bonded together the film of two or more layers. When the oxygen permeability can be obtained with the above film, the film may be composed only of the film, or the oxygen permeability may be ensured by laminating a gas barrier layer on the film. As the gas barrier layer, a metal layer such as an aluminum layer, an inorganic oxide layer such as a silicon oxide or an aluminum oxide layer may be used, and among the above films, an ethylene-vinyl alcohol copolymer having a low oxygen permeability, polyvinyl Alcohol or the like may be laminated. The total film thickness of the film is preferably 50 μm or more, preferably 70 μm or more, and more preferably 70 to 200 μm. When the film thickness is above, the dissolved oxygen content of the ink composition being stored is unlikely to change, and the strength and flexibility of the pack can be obtained. Among these, a film made of an ethylene-vinyl alcohol copolymer is preferable in terms of low oxygen permeability and excellent strength. In addition, in the case of a container other than a pack, in addition to the above, other synthetic resins, glass, metal and the like can be mentioned.

In this specification, the unit of oxygen permeability is cc · 20 μm / (m ² · day · atm), and “atm” is a pressure (atm) under the conditions of 23 ° C. and humidity 65%. In addition, the oxygen permeability was determined by the method defined in ISO 14663-2: 1999 (Annex C), that is, the oxygen permeation rate permeating the film using a coulometric sensor (relative humidity reached an equilibrium state). Sometimes it can be calculated by measuring.

Although the capacity | capacitance of the ink composition which an ink container can accommodate is not restrict | limited below, 100-2,000 mL is preferable, 100-1,000 mL is more preferable, 200-800 mL is further more preferable. When the capacity is within the above range, all of the curability, storage stability, and ejection stability can be further improved.
If the volume is within the above range, the ink composition can be used up or stored while the amount of dissolved oxygen in the ink container is almost unchanged after the start of use of the ink container. There are advantageous effects such as the amount of dissolved oxygen of the ink composition hardly changing. Further, it is particularly preferable that the ink container has the oxygen permeability of the member of the ink container and the capacity of the ink composition that can be stored is in the above range. Further, “capacity” in this specification means volume.

  Here, an ink pack which is an example of the ink container of the present embodiment will be described. FIG. 1 is a perspective view showing the ink pack 1. The ink pack 1 includes an ink outlet 2 and a film 10. The material of the film 10 can use the above-mentioned thing. The ink pack 1 may be stored in a box-shaped container (not shown) for protection during transportation. The ink pack 1 can be used as an ink cartridge as in the above-described usage mode (A), but the usage mode of the ink pack 1 is not limited thereto.

  As described above, according to the present embodiment, it is possible to provide an ink container containing an ultraviolet curable ink composition for ink jet recording excellent in all of storage stability, curability, and ejection stability.

[UV-curable ink composition for inkjet recording]
One embodiment of the present invention relates to an ultraviolet curable ink composition for inkjet recording, which is accommodated in the ink container of the above embodiment. As described above, the ultraviolet curable ink composition for inkjet recording is excellent in all of storage stability, curability, and ejection stability.

[Inkjet recording method]
One embodiment of the present invention relates to an ink jet recording method using the ultraviolet curable ink composition for ink jet recording accommodated in the ink container of the above embodiment.

  The inkjet recording method includes a discharge step of discharging the ink composition onto a recording medium, and a curing step of curing the ink composition by irradiating the ink composition discharged in the discharge step with ultraviolet rays. ,including. In this way, a coating film (cured film) is formed by the ink composition cured on the recording medium.

[Inkjet recording apparatus]
In addition, an embodiment of the present invention relates to an ink jet recording apparatus that performs recording by the above ink jet recording method. FIG. 2 is a schematic view showing an example of the periphery of the head of the ink jet recording apparatus of the present embodiment.

  The sub tank 200 is supplied with ink from an ink cartridge (not shown), and passes through a deaeration module 204, which is an example of a deaeration mechanism, and a heater 220 in order by a pressure pump 202. 100.

The head 100 ejects ink onto a recording medium (not shown). The pressure adjusting valve 108 is opened by a valve opening actuator 320 to adjust the pressure of ink when supplying ink from the sub tank 200 to the head 100.
The ink that has passed through the deaeration module 204 flows into the branch joint 106 when the pressure adjustment valve 108 is opened. Inside the branch joint 106, the forward path 214 is branched into a plurality of passages and connected to the plurality of heads 100.
The ink that has not been ejected from the head 100 is circulated to the sub tank 200 via the integrated joint 210 and the return path 216 in a state where the opening / closing valve 212 is open. By circulating the ink between the sub tank 200 and the head 100, when the ink stays for a long time and the ink components are separated and settled, it can be recovered or the temperature of the circulating ink can be made constant. . When the ink is heated by the heaters 218, 220, and 222, the viscosity decreases, the viscosity becomes suitable for ejection from the head 100, and the ink is ejected from the head 100.

  These devices are provided in the main scanning movement table 64, and main scanning is performed to eject ink from the head 100 to the recording medium while moving relative to the recording medium together with the main scanning movement table.

  In the deaeration module 204, a deaeration chamber (not shown) into which ink flows and a decompression chamber (not shown) in contact with the deaeration chamber through a separation membrane that does not allow a liquid such as ink to pass through a gas such as air. ) And are provided. When the decompression chamber is depressurized by a decompression pump (not shown), bubbles such as oxygen and oxygen dissolved in the ink in the deaeration chamber are released, so there is no contamination of the bubbles. Ink having a dissolved oxygen concentration lower than that of the ink sent to the module 204 can be supplied to the head 100 and discharged from the head 100. The deaeration module 204 of the recording apparatus can continuously deaerate ink while supplying ink from the sub tank 200 to the head 100.

  The above recording apparatus can be configured as shown in FIG. 4 of Japanese Patent Application Laid-Open No. 2011-240565, for example. Note that a configuration such as a line printer in which ink is ejected from the head toward the recording medium while the recording medium moves relative to the head without moving the above-described apparatus may be employed. Further, instead of the degassing module continuously degassing the ink as described above, the pressure adjusting valve is closed without providing the separation membrane, and the pressure reducing chamber is depressurized to reduce the ink. And when the deaeration is completed, the decompression chamber is returned to the normal pressure and the pressure adjusting valve 108 is opened to supply the ink to the head alternately. Also good. The former is preferable in that the ink can be continuously deaerated, and the latter is preferable in that the deaeration ability is high.

  Here, when the dissolved oxygen amount of the ink accommodated in the ink cartridge is 20 ppm or less, if the recording device does not increase the dissolved oxygen amount in the ink supply process, the ejection stability is preferable. It can be discharged as a thing. On the other hand, even if the recording device increases the amount of dissolved oxygen in the process of supplying ink, the amount of dissolved oxygen can be reduced by providing a degassing module. If the amount of dissolved oxygen in the stored ink is 20 ppm or less, the dissolved oxygen amount of the ink can be kept at 20 ppm or less and ejected from the head 100 even when the deaeration capability of the deaeration module is limited. The increase in the amount of dissolved oxygen occurs due to the length and material of the supply pipe that supplies the ink in the recording apparatus to the head, the time during which the ink is in the process of supplying ink, the pressurization conditions required for supplying the ink, and the like. Therefore, the ink container of the present embodiment is preferable in terms of the degree of freedom in designing the recording apparatus.

[Recording medium]
A recorded matter is obtained by ejecting the ink composition onto a recording medium using the inkjet recording method of the present embodiment. Examples of the recording medium include an absorptive or non-absorbable recording medium. The ink jet recording method of this embodiment is a recording medium having various absorption performances, from a non-absorbing recording medium in which the water-soluble ink composition is difficult to penetrate to an absorbent recording medium in which the ink composition is easy to penetrate. Widely applicable to media. 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 ultraviolet rays.

  The absorbent recording medium is not particularly limited. For example, plain paper such as electrophotographic paper having high ink permeability, ink jet paper (an ink absorbing layer composed of silica particles or alumina particles, or polyvinyl alcohol ( Art paper, coated paper, etc. used for general offset printing with relatively low ink permeability, such as PVA) and polyvinyl pyrrolidone (PVP). Examples include 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.

[Discharge process]
In the ejection step, an ink jet recording apparatus described later can be used. When discharging the ink composition, the viscosity of the ink composition is preferably 25 mPa · s or less, more preferably 5 to 20 mPa · s. If the viscosity of the ink composition is as described above with the temperature of the ink composition set to room temperature or without heating the ink composition, the temperature of the ink composition is set to room temperature or the ink composition is not heated. Can be discharged. On the other hand, the ink composition may be discharged to a preferable viscosity by heating to a predetermined temperature. In this way, good discharge stability is realized.

  Since the ultraviolet curable ink composition has a higher viscosity than the water-based ink composition used in a normal inkjet ink, the viscosity fluctuation due to temperature fluctuation at the time of ejection is large. Such fluctuations in the viscosity of the ink have a great influence on the change in the droplet size and the change in the droplet discharge speed, which can cause image quality deterioration. Therefore, it is preferable to keep the temperature of the ink during ejection as constant as possible.

[Curing process]
Next, in the curing step, the ink composition ejected on the recording medium is cured by irradiation with ultraviolet rays (light). In other words, the ink coating film formed on the recording medium becomes a cured film when irradiated with ultraviolet rays. This is because the photopolymerization initiator that can be contained in the ink composition is decomposed by irradiation with ultraviolet rays to generate radicals, acids, bases, and other starting species, and the polymerization reaction of the photopolymerizable compound is the starting species. This is because it is promoted by function. Or it is because the photopolymerization reaction of a polymeric compound starts by irradiation of an ultraviolet-ray. At this time, if a sensitizing dye is present together with the photopolymerization initiator in the ink composition, the sensitizing dye in the system absorbs actinic radiation to be in an excited state and comes into contact with the photopolymerization initiator. Degradation can be accelerated and a more sensitive curing reaction can be achieved.

  Mercury lamps and gas / solid lasers are mainly used as ultraviolet sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing ink compositions for ultraviolet curable ink jet recording. Yes. On the other hand, there is a strong demand for mercury-free from the viewpoint of environmental protection, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, an ultraviolet light emitting diode (UV-LED) and an ultraviolet laser diode (UV-LD) are small, have a long lifetime, high efficiency, and low cost, and are expected as light sources for ultraviolet curable ink jets. Among these, UV-LED is preferable.

Here, an ink composition that has a peak emission wavelength of preferably 365 to 405 nm, more preferably curable by irradiation with ultraviolet rays having a single wavelength in the range of 380 to 400 nm is used. It is preferable. The irradiation energy is preferably from 300 mJ / cm ² or less, 100~250mJ / cm ² is more preferable.

  In the above case, curing at low energy and high speed is possible due to the composition of the ink composition. The irradiation energy is calculated by multiplying the irradiation time by the irradiation intensity. The irradiation time can be shortened by the composition of the ink composition, and in this case, the printing speed is increased. On the other hand, the irradiation intensity can be reduced by the composition of the ink composition in the present embodiment, and in that case, the apparatus can be downsized and the cost can be reduced. In this case, UV-LED is preferably used for ultraviolet irradiation. Such an ink composition can be obtained by including a photopolymerization initiator that is decomposed by irradiation with ultraviolet rays in the above wavelength range and a polymerizable compound that initiates polymerization by irradiation with ultraviolet rays in the above wavelength range. The emission peak wavelength may be one or plural within the above wavelength range. Even in the case where there are a plurality, the total irradiation energy of the ultraviolet rays having the emission peak wavelength is set as the irradiation energy.

[Inkjet recording apparatus]
One embodiment of the present invention relates to an ink jet recording apparatus including at least an ejection unit that ejects the ultraviolet curable ink composition for ink jet recording contained in the ink container of the above embodiment from a head.

  The ink jet recording apparatus is not particularly limited as long as the apparatus can realize the ink jet recording method of the above embodiment. Preferably, the ink jet recording apparatus includes a curing unit that cures the ink composition ejected onto the recording medium by irradiation with ultraviolet rays, in addition to the ejection unit that ejects the ink composition from the head.

  Hereinafter, the embodiments of the present invention will be described more specifically by way of examples. However, the embodiments are not limited to these examples.

[Raw materials]
The raw materials used in the following examples and comparative examples are as follows.
[Color material]
・ C. I. Pigment Black 7 (Microlith Black CK [trade name], manufactured by BASF, abbreviated as “black pigment” in the following table)
[Dispersant]
Solsperse 36000 (trade name, manufactured by Noveon, abbreviated as “Sol 36000” in the table below)
[Vinyl ether group-containing (meth) acrylic acid esters]
VEEA (2- (2-vinyloxyethoxy) ethyl acrylate, trade name of Nippon Shokubai Co., Ltd., abbreviated as “VEEA” in the table below)
[Polymerizable compounds other than the above]
・ Biscoat # 192 (phenoxyethyl acrylate, trade name of OSAKA ORGANIC CHEMICAL INDUSTRY LTD., Abbreviated as “PEA” in the table below)
SR508 (dipropylene glycol diacrylate, trade name of Sartomer, abbreviated as “DPGDA” in the table below)
[Hindered amine compound (polymerization inhibitor)]
LA-82 (1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, trade name of ADEKA, abbreviated as “LA-82” in the table below)
Adekastab LA-7RD (2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, trade name of ADEKA, abbreviated as “LA-7RD” in the table below)
(Photopolymerization initiator)
IRGACURE 369 (trade name, manufactured by BASF, solid content: 100%, abbreviated as “369” in the table below)
DAROCURE TPO (trade name, manufactured by BASF, solid content: 100%, abbreviated as “TPO” in the table below)
Speedcure DETX (trade name, manufactured by Lambson, solid content: 100%, abbreviated as “DETX” in the table below)
Speedcure ITX (trade name, manufactured by Lambson, solid content: 100%, abbreviated as “ITX” in the table below)

[Examples 1 to 25, Comparative Examples 1 to 7]
(Preparation of pigment dispersion)
Prior to preparation of the ink composition, a pigment dispersion was prepared. The black pigment was mixed at a ratio of 18% by mass and the dispersant was 9% by mass, respectively, and stirred with a stirrer for 1 hour. The mixed liquid after stirring was dispersed with a bead mill to obtain a pigment dispersion. The 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.

[Preparation of ink composition for ultraviolet curable ink jet recording]
The components described in the following table were added so as to have the composition (unit: mass%) described in the following table, and this was stirred with a high-speed water-cooled stirrer, whereby a black UV-curable inkjet recording ink A composition was prepared.

[Measurement of dissolved oxygen content]
The dissolved oxygen content was measured by measuring the dissolved oxygen content of the ink composition using Gas Chromatography Agilent 6890 (manufactured by Agilent Technologies). Helium (He) gas was used as the carrier gas.

  Here, the positioning of each example and each comparative example will be described. First, in Examples 1 to 5, the ink compositions are the same, and the difference in each evaluation result when the dissolved oxygen amount is changed is examined. On the other hand, Comparative Examples 1 and 2 have the same ink composition as Examples 1 to 5 above, but each has a very high (30 ppm) and very low (1 ppm) dissolved oxygen content. It is a comparative control for 1-5.

  Moreover, Examples 6-12 and 25 mainly investigated the difference of each evaluation result when changing content of the thioxanthone compound as a photoinitiator. On the other hand, Comparative Example 3 is almost the same as the ink composition of Example 6 except that it does not contain a thioxanthone compound and the amount of dissolved oxygen is very high, and is a comparative control with respect to Example 6. Here, Example 24 differs from Example 6 in that it contains a thioxanthone compound, and Example 25 differs from Example 1 in that it does not contain a thioxanthone compound.

  Moreover, Examples 13-18 mainly differed in each evaluation result when content of the vinyl ether group containing (meth) acrylic acid ester (here VEEA) represented by general formula (I) was changed. Was investigated. On the other hand, Comparative Examples 4 and 5 are comparative examples for Examples 13 to 18 in that none of the vinyl ether group-containing (meth) acrylic acid esters (Comparative Example 5 further includes a hindered amine compound). It has become.

  Moreover, Examples 19-23 mainly investigated the difference of each evaluation result when the kind and content of a hindered amine compound were changed. On the other hand, Comparative Examples 6 and 7 are comparative controls with respect to Examples 19 to 23 in that both do not contain the hindered amine compound.

[Evaluation item]
For the ink composition for ultraviolet curable ink jet recording prepared in each example and each comparative example and adjusting the amount of dissolved oxygen by changing the deaeration time, the curability, storage stability, and ejection stability were as follows. Evaluated. For evaluation of curability and ejection stability, and measurement of dissolved oxygen amount in the table, the ink composition after storage under the conditions of storage stability evaluation was used.

[1. Storage stability)
As an ink container, an ink pack as shown in FIG. 1 was prepared. The ink compositions of Examples and Comparative Examples were sealed in the ink pack and stored in an oven at 60 ° C. for 20 days. And the thickening rate before and behind storage was calculated | required. The capacity of the ink pack is 700 mL, the film is an ethylene-vinyl alcohol copolymer film (the oxygen permeability of the film is 2.0 cc · 20 μm / (m ² · day · atm), and the film thickness is 100 μm. ).
The evaluation criteria are as follows. The evaluation results are shown in the above table.
A: 3% or less B: Over 3% to 6% or less C: Over 6% to 9% or less D: Over 9% to 12% or less E: Over 12%

[2. Curability)
Using a bar coater, the ink composition of each example and each comparative example was applied on a PET film (PET50A PL Thin [trade name], manufactured by Lintec Corporation) to prepare an ink coating having a thickness of 10 μm. Thereafter, the coating film was cured by irradiating with ultraviolet rays having an irradiation intensity of 1,100 mW / cm ² and a wavelength of 395 nm. The cured coating film (cured film) was rubbed 10 times with a cotton swab at a load of 100 g, and the curing energy (irradiation energy) at the time when the scratch was not found 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.).
The evaluation criteria are as follows. The evaluation results are shown in the above table.
A: 150mJ / cm ² or less B: 150mJ / cm ² Beyond 200 mJ / cm ² or less C: 200mJ / cm ² Beyond 250 mJ / cm ² or less D: 250mJ / cm ² to greater than 300 mJ / cm ² or less E : Over 300mJ / cm ²

[3. (Discharge stability)
An ink jet evaluation machine (prototype) having 180 nozzles with a discharge nozzle diameter of 20 μm, a drive frequency of 24 kHz, and an ink discharge amount per time adjusted to 5 ng was prepared. Then, using the evaluation machine, the number of nozzles in which nozzle omission occurred when ink was ejected continuously for 60 minutes was determined.
The evaluation criteria are as follows. The evaluation results are shown in the above table.
A: None (0)
B: 1 to 5 C: 6 to 10 D: 11 to 15 E: 15 or more

  From the above results, an ink composition containing at least a vinyl ether group-containing (meth) acrylic acid ester represented by the general formula (I) and a hindered amine compound and having a dissolved oxygen content of 20 ppm or less was accommodated. It was found that the ink container (each example) was excellent in all of curability, storage stability, and ejection stability as compared with the ink container (each comparative example) containing an ink composition that was not. .

  Furthermore, the same ink composition as the ink composition of Example 2 was used, and the above-mentioned condition was used after storing in an oven at 60 ° C. for 20 days under the same conditions as in Example 2 except that the ink pack had a capacity of 50 mL. Each evaluation was performed. As a result, it was found that the dissolved oxygen amount was 18 ppm, the storage stability A, the curability A, and the discharge stability B.

An ink pack using the same ink composition as the ink composition of Example 2 and having a polyacrylonitrile film (oxygen permeability 10.0 cc · 20 μm / (m ² · day · atm), film thickness 70 μm) Except for the points described above, each of the above evaluations was performed after storage in an oven at 60 ° C. for 20 days under the same conditions as in Example 2. As a result, it was found that the dissolved oxygen amount was 20 ppm, the storage stability A, the curability A, and the discharge stability C.

  Further, using the recording apparatus of FIG. 2 and mounting the ink pack containing ink therein as an ink cartridge, supplying the ink to the head 100, collecting the ink in the sub tank 200 and the ink in the head 100, The amount of dissolved oxygen was measured. As a result, when the ink pack of Example 1 was installed as an ink cartridge, the ink in the sub tank 200 was 27 ppm and the ink in the head 100 was 20 ppm, whereas the ink pack of Comparative Example 1 was used as the ink. In the cartridge mounted, the ink in the sub tank 200 was 36 ppm, and the ink in the head 100 was 31 ppm.

  DESCRIPTION OF SYMBOLS 1 ... Ink pack, 2 ... Ink take-out port, 10 ... Film, 64 ... Main scanning movement table, 100 ... Head, 106 ... Branch joint, 108 ... Pressure adjustment valve, 200 ... Sub tank, 202 ... Pressure pump, 204 ... Desorption 210, integrated joint, 212, open / close valve, 214, forward path, 216, return path, 218, 220, 222, heater, 320, valve opening actuator.

Claims (13)

The following general formula (I):
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
Wherein 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.)
A vinyl ether group-containing (meth) acrylic acid ester represented by: and a hindered amine compound, and
An ink container containing an ultraviolet curable ink jet recording ink composition having a dissolved oxygen content of 20 ppm or less.   The ink container according to claim 1, wherein the ultraviolet curable ink composition for inkjet recording further comprises a thioxanthone compound. 2. The oxygen permeability of the constituent material that comes into contact with the ultraviolet ray curable ink composition for ink jet recording is 5.0 cc · 20 μm / (m ² · day · atm) or less at 23 ° C. and 65% humidity. Or the ink container as described in 2.   The ink container according to claim 1, wherein the ultraviolet curable ink composition for ink jet recording can be accommodated in a volume of 100 to 1,000 mL.   The ink container according to any one of claims 1 to 4, wherein the vinyl ether group-containing (meth) acrylic acid ester is 2- (vinyloxyethoxy) ethyl acrylate.   The ink container according to any one of claims 1 to 5, wherein the hindered amine compound is a compound having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton.   The content of the vinyl ether group-containing (meth) acrylic acid ester is 10 to 70% by mass with respect to the total mass of the ultraviolet curable ink jet recording ink composition. The ink container according to 1.   The ink container according to any one of claims 2 to 7, wherein a content of the thioxanthone compound is 0.5 to 4% by mass with respect to a total mass of the ultraviolet curable ink composition for inkjet recording. .   An ink composition for ultraviolet curable ink jet recording, which is accommodated in the ink container according to claim 1.   An ink jet recording apparatus comprising at least a discharge unit that discharges the ultraviolet curable ink composition for ink jet recording stored in the ink container according to claim 1 from a head.   The ink jet recording apparatus according to claim 10, wherein the dissolved oxygen content of the ultraviolet curable ink composition for ink jet recording discharged from the head is 20 ppm or less.   The inkjet recording apparatus according to claim 11, wherein the dissolved oxygen amount of the ink increases in the process of supplying ink from the ink container to the head.   An ink jet recording method comprising at least a discharge step of discharging the ultraviolet curable ink composition for ink jet recording contained in the ink container according to any one of claims 1 to 8 from a head.