JP5030562B2 - Ink jet ink composition and ink jet recording method - Google Patents

Description

  The present invention relates to an ink composition used for inkjet recording, and an inkjet recording method using the inkjet ink. More specifically, the present invention relates to an ink composition for ink jet recording that is cured with high sensitivity to irradiation with actinic radiation, and an image portion after ink curing has sufficient flexibility, and an ink jet recording method using the ink composition.

As an image recording method for forming an image on a recording medium such as paper based on an image data signal, there are an electrophotographic method, a sublimation type and a melt type thermal transfer method, an ink jet method and the like. The electrophotographic system requires a process of forming an electrostatic latent image on a photosensitive drum by charging and exposure, and there is a problem that the system becomes complicated and consequently the manufacturing cost becomes high. In addition, although the thermal transfer system is inexpensive, there are problems such as high running costs and waste materials due to the use of ink ribbons.
On the other hand, the ink jet system is an inexpensive apparatus and ejects ink 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. Further, the ink jet method has less noise and is excellent as an image recording method.

As an ink composition (radiation curable ink composition) that can be used for ink jet recording ink compositions and can be cured by irradiation with actinic radiation such as ultraviolet rays, it can be cured with high sensitivity to form a high-quality image. Is required. By achieving high sensitivity of the radiation curable ink composition, high curability is imparted by irradiation with actinic radiation, reducing power consumption and extending the life of equipment by reducing the load on the actinic radiation generator In addition to the above advantages, there are various advantages such as suppression of volatilization of uncured low-molecular substances and reduction in the strength of the formed image. Further, the improvement of the cured film strength by increasing the sensitivity of the radiation curable ink composition brings high strength and durability to the image area formed by this ink composition.
Although such an ink composition is excellent in the strength of the formed image portion, it is poor in flexibility, and when applied to a recording medium such as a resin film having excellent flexibility and flexibility, the deformation of the recording medium However, the image portion formed on the surface does not follow, and depending on the use mode, there is a problem that the image portion is damaged such as a crack.

As an ultraviolet curable ink composition, for example, an ink composition that uses a combination of monomers having different functional groups among monofunctional monomers or polyfunctional monomers has been proposed (see Patent Document 1). Moreover, the composition containing polyfunctional acrylate is proposed as a radiation-curable composition (refer patent document 2). Although these ink compositions all have excellent curability, the flexibility of the film formed by these is insufficient.
A technique of adding an amine compound having a specific structure to an ink composition for the purpose of forming a high-definition image by an inkjet recording method is disclosed (for example, see Patent Document 3). Amine compounds are used in various ink compositions in an amount of 0.1 to several percent for the purpose of improving weather resistance (see, for example, Patent Document 4), but certain amine compounds start polymerization. Since there is a property of trapping radicals generated from the agent, there is a concern that the curing sensitivity may be lowered, and there is also a concern that the formed film may be sticky, and there is a problem that the amount used and the compound that can be used are limited. there were.
As described above, there is a demand for an ink composition having excellent adhesion to a recording medium, excellent curing sensitivity and image strength, and excellent flexibility in the formed image area. is there.
Japanese Patent Laid-Open No. 5-214280 JP-A-8-41133 JP 2004-238456 A Japanese Patent Laid-Open No. 3-122172

  An object of the present invention is an ink jet which can be cured with high sensitivity to irradiation with actinic radiation and can form a high quality image, and the image after ink curing has flexibility and high adhesion to a recording medium. It is an object to provide a recording ink composition and an ink jet recording method using the ink composition.

  As a result of intensive studies, the present inventors have improved the flexibility of the image after ink curing while maintaining high sensitivity by using a specific polymerizable amine compound in the ink composition. It has been found that an ink composition suitable for ink jet recording can be obtained with improved adhesion to a recording medium, and the present invention has been completed.

  That is, the ink composition of the present invention comprises (A) 12 to 50% by mass of a compound having a polymerizable unsaturated bond and a partial structure represented by the following general formula (1) in the molecule, and (B) radical polymerization. An ink composition for ink-jet recording, comprising an initiator and (C) a pigment as a colorant.

In the general formula (1), R ¹ represents an alkyl group or a substituted alkyl group, and R ^{2 to} R ⁵ each independently represent a methyl group or an ethyl group.

  The inkjet recording method of the present invention includes (i-1) a step of ejecting the ink composition of the present invention onto a recording medium, and (i-2) irradiating the ejected ink composition with actinic radiation. And a step of curing the ink composition.

  According to the present invention, an inkjet that can be cured with high sensitivity to irradiation with actinic radiation and can form a high-quality image, and the image after ink curing has flexibility and high adhesion to a recording medium. A recording ink composition and an ink jet recording method using the ink composition can be provided.

[Ink composition for inkjet recording]
The ink composition for ink-jet recording of the present invention comprises (A) 12 to 50% by mass of a compound having a polymerizable unsaturated bond and a partial structure represented by the following general formula (1) in the molecule, and (B) a radical. It contains a polymerization initiator and a pigment (C) as a colorant.

In the general formula (1), R ¹ represents an alkyl group or a substituted alkyl group, and R ^{2 to} R ⁵ each independently represent a methyl group or an ethyl group.
Hereinafter, components essential to the ink composition for ink jet recording of the present invention will be described.

<(A) Compound having a polymerizable unsaturated bond and a partial structure represented by formula (1) in the molecule>
The ink composition for ink jet recording of the present invention comprises (A) a compound having a polymerizable unsaturated bond and a partial structure represented by the following general formula (1) in the molecule [hereinafter referred to as (A) a specific polymerizable compound as appropriate. It is characterized by containing 12-50 mass% in the total solid content of the composition.

In the general formula (1), R ¹ represents an alkyl group or a substituted alkyl group, and R ^{2 to} R ⁵ each independently represent a methyl group or an ethyl group.
Hereinafter, (A) “compound having a polymerizable unsaturated bond and a partial structure represented by the general formula (1) in the molecule (specific polymerizable compound)” which is a characteristic component in the present invention will be described in detail. .
As the specific polymerizable compound (A) that can be used in the present invention, any compound having a partial structure represented by the following general formula (1) and a polymerizable double bond in the molecule can be used.

In general formula (1), R ¹ represents an alkyl group or a substituted alkyl group.
R ¹ is an alkyl group having 1 or more carbon atoms, preferably an alkyl group having 1 to 20 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms. More preferred examples of the alkyl group include a methyl group, an ethyl group, an n-butyl group, an n-hexyl group, an n-nonyl group, and the like, and has a hydrogen atom on a carbon atom adjacent to a nitrogen atom. It is preferable that the number of hydrogen atoms is 2 or more.
When R ¹ is a substituted alkyl group, examples of the substituent that can be introduced include an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an acyl group, an amino group, a hydroxyl group, a cyano group, a nitro group, and a halogen atom. It is done.

R ^{2 to} R ⁵ each independently represent a methyl group or an ethyl group, preferably a methyl group, and more preferably all of R ^{2 to} R ⁵ are methyl groups.
In the specific polymerizable compound (A) of the present invention, the partial structure represented by the general formula (1) is linked to a polymerizable double bond via a linking group. Except for the site where R ^{2 to} R ⁵ are present in the member ring, any site may be linked to the polymerizable double bond. Among them, on the alkyl group or substituted alkyl group represented by R ¹ or is preferably connected in position (*) shown below, and more to be connected in listed below position (*) preferable.

The polymerizable double bond bonded via the linking group is preferably a radical polymerizable double bond. (A) The number of polymerizable double bonds present in the specific polymerizable compound, that is, linked to the partial structure is set to a low-viscosity composition suitable as an ink for ink jet recording, and flexible curing From the viewpoint that a film can be obtained, it is preferably 1 to 3, more preferably 1 to 2, and particularly preferably 1.
Preferred functional groups containing a polymerizable double bond include a (meth) acryloyl group, an allyl group, a styryl group, and a vinyloxy group, and a (meth) acryloyl group is preferable from the viewpoint of the curing sensitivity of the ink composition. More specifically, a compound having a polymerizable double bond as represented by the general formula (2) is preferable.

In said general formula (2), R < ¹ > -R < ⁵ > is synonymous with general formula (1) respectively, R < ⁶ > represents a methyl group or a hydrogen atom, and it is preferable that it is a hydrogen atom.
Z represents a divalent linking group, preferably an oxygen group or an alkylene group obtained by removing a hydrogen atom from the alkyl group represented by R ¹ described above, and preferably an alkylene group having 1 to 20 carbon atoms. The alkylene group may have a divalent group selected from —CO—, —O—, —S— or —NR ⁷ — in the methylene chain consisting of a methylene group (—CH ₂ —). A case where an alkylene chain having a methylene group has an ether bond (—O—) is mentioned as a preferable embodiment, and an aspect having an ether bond (—O—) at both ends of the alkylene group is particularly preferable. Here, R ⁷ has the same meaning as when R ¹ is an alkyl group.

Here, as the alkylene group, specifically, an alkylene group having about 3 to 12 carbon atoms is preferable, and examples thereof include a propylene group, a butylene group, an octylene group, and a nonylene group, and the methylene group in these alkylene groups. The chain structure may have a divalent group selected from the above-described —CO—, —O—, —S—, or —NR ⁷ —. Further, these divalent linking groups may be divalent linking groups configured by combining two or more kinds.
Specific examples of the specific polymerizable compound (A) [Exemplary compounds (A-1) to (A-19)] that can be suitably used in the present invention are shown below, but the present invention is limited to these. It is not a thing. Moreover, when a stereoisomer exists in each exemplary compound, any of them may be used, and a mixture of stereoisomers may be used.

Among these, (A-1), (A-2), (A-3), (A-12) and the like having a (meth) acryloyl group in the molecule are preferable, and (A-1) and (A -2) is more preferable.
(A) The specific polymerizable compound is, for example, Makromolekulare Chemie. 181 3 595-634 (1980), Journal of Applied Polymer Science 69 13 13 2649-2656 (1998), Journal of Applied Polymer Science 75 9 9 1103-1114 (2000) ), Polymers for Advanced Technologies, Vol. 13, pp. 247-253 (2002), Japanese Patent Application Laid-Open No. 3-25169, and can be produced by a known synthesis method such as Fancryl FA-711MM (Hitachi). It is also available as a commercial product such as Kasei Kogyo.

(A) Only 1 type may be used for the specific polymeric compound in the ink composition of this invention, and 2 or more types may be used for it.
The content of the specific polymerizable compound (A) in the ink composition of the present invention is selected from the viewpoints of the balance between the curing speed and the adhesion to the substrate, the flexibility after curing, and the ink-jet suitability of the ink composition. It is necessary to be in the range of 12 to 50% by mass relative to the total mass of the composition, more preferably in the range of 15 to 40% by mass, and still more preferably in the range of 15 to 35% by mass. When the addition amount is less than 12% by mass, a sufficient curing speed improvement, that is, a sensitivity improvement effect cannot be obtained, and when the content exceeds 50% by mass, the improvement of the effect is not recognized. And the content of the colorant is limited, and desirable film properties cannot be obtained after curing.

<(B) Radical polymerization initiator>
The ink composition for inkjet recording of the present invention is required to contain a radical polymerization initiator.
As the radical polymerization initiator, a known polymerization initiator can be appropriately selected and used according to the kind of the polymerizable compound used in combination and the purpose of use of the ink composition.
The radical polymerization initiator used in the ink composition of the present invention is a compound that absorbs external energy and generates a polymerization initiating species. External energy used for initiating polymerization is roughly divided into heat and radiation, and a thermal polymerization initiator and a photopolymerization initiator are used, respectively. Examples of radiation include γ rays, β rays, electron beams, ultraviolet rays, visible rays, and infrared rays.
Known compounds can be used as the thermal polymerization initiator and the photopolymerization initiator.

Preferred radical polymerization initiators that can be used in the present invention include (a) aromatic ketones, (b) acylphosphine oxide compounds, (c) aromatic onium salt compounds, (d) organic peroxides, (e) thios. Compound, (f) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, (l) carbon halogen bond And (m) an alkylamine compound.
In the present invention, the radical polymerization initiator may be used alone or in combination. From the viewpoint of the effect, it is preferable to use two or more kinds of radical polymerization initiators in combination.

  The radical polymerization initiator (B) in the present invention is based on the total amount of the (A) specific polymerizable compound and the pigment as the colorant (C) described later, or (A) the specific polymerizable compound and (C ) When the colorant and (D) another polymerizable compound as an optional component to be described later are used in combination, the range of 0.01 to 35% by mass is preferable with respect to the total amount of the polymerizable compound. The range of 0.1-30 mass% is more preferable, and the range of 0.5-30 mass% is still more preferable.

  Moreover, (B) radical polymerization initiator is a mass ratio of polymerization initiator: sensitizing dye with respect to (E) sensitizing dye that can be used as necessary, and is 200: 1 to 1: 200. Preferably, it is contained in the range of 50: 1 to 1:50, more preferably 20: 1 to 1: 5.

<(C) Pigment as colorant>
The ink composition for inkjet recording of the present invention contains (C) a colorant. The pigment that can be used as a colorant in the present invention is excellent in weather resistance and rich in color reproducibility. The colorant that can be suitably used in the ink composition of the present invention is a compound that does not function as a polymerization inhibitor in a polymerization reaction that is a curing reaction, from the viewpoint of not reducing the sensitivity of the curing reaction by actinic radiation. preferable.

Although it does not necessarily limit as a pigment which can be used as a coloring agent in this invention, For example, the organic or inorganic pigment of the following number described in a color index can be used.
Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, and 53: 1. 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144, 146 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13 16, 20, 36,
As the blue or cyan pigment, Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17-1, 22, 27, 28, 29, 36, 60 Pigment Green 7, 26, 36, 50,
As the yellow pigment, Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193,
As the black pigment, Pigment Black 7, 28, 26,
As a white pigment, Pigment White 6, 18, 21
Etc. can be used according to the purpose.

  It is preferable that the pigment used in the present invention is appropriately dispersed in the ink after being added to the ink composition for ink jet recording of the present invention. For the dispersion of the pigment, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, or a paint shaker can be used.

Further, when dispersing the pigment as the colorant, it is possible to add a dispersant. The type of the dispersant is not particularly limited, but a polymer dispersant is preferably used. Examples of the polymer dispersant include a commercially available Solsperse series manufactured by Noveon. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. In the present invention, these dispersant and dispersion aid are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the colorant.
In addition, when a certain kind of amine compound is used, the dispersion stability of the pigment in the ink composition may be significantly reduced due to the interaction with the pigment used as the colorant of the ink composition. Although it was unsuitable for ink-jet ink compositions having a low product viscosity, in the present invention, since the (A) specific polymerizable compound is used as an amine compound, there is no such concern. It also has advantages.

As the colorant of the present invention, it is indispensable to use the pigment, but it is necessary for various purposes such as adjusting the hue of an image to be formed and controlling light transmittance, as long as the effects of the present invention are not impaired. Accordingly, oil-soluble dyes, water-soluble dyes, and disperse dyes can be used in combination as colorants.
The colorant that can be suitably used in the ink composition of the present invention is a compound that does not function as a polymerization inhibitor in a polymerization reaction that is a curing reaction, from the viewpoint of not reducing the sensitivity of the curing reaction by actinic radiation. preferable.

  In the preparation of the ink composition of the present invention, the colorant may be blended by direct addition with each component. However, in order to improve dispersibility, the solvent or the (A) specific polymerizable compound or the like used in the present invention is used in advance. If desired, (D) it may be added to a dispersion medium such as other polymerizable compound and uniformly dispersed or dissolved, and then blended.

In the present invention, in order to avoid the problem of deterioration of solvent resistance when the solvent remains in the cured image and the problem of VOC (Volatile Organic Compound) of the remaining solvent, the colorant is (A) specified. It is preferable to add and mix in advance with any one of the polymerizable compound or (D) other polymerizable compound used in combination or a mixture thereof. In consideration of only dispersibility, it is preferable to select a monomer having the lowest viscosity as the polymerizable compound used for the addition of the colorant.
These colorants may be used by appropriately selecting one type or two or more types according to the purpose of use of the ink composition.

  In the ink composition of the present invention, since a colorant such as a pigment that exists as a solid is used, the average particle diameter of the colorant particles is preferably 0.005 to 1.5 μm, more preferably 0. It is preferable to set the colorant, dispersant, dispersion medium selection, dispersion conditions, and filtration conditions so as to be 0.01 to 1.2 μm, and more preferably 0.015 to 1.0 μm. This particle size control is preferable because clogging of the head nozzle can be suppressed and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  The content of the pigment as the colorant (C) in the ink composition of the present invention is appropriately selected depending on the purpose of use, but generally considering the ink physical properties and colorability, It is preferable that it is 1-10 mass% with respect to mass, and it is more preferable to contain 2-8 mass%.

In the ink composition of the present invention, in addition to the essential components described above, other components can be used in combination for the purpose of improving physical properties as long as the effects of the present invention are not impaired.
Hereinafter, these optional components will be described below.

<(D) Other polymerizable compound>
The ink composition of the present invention preferably contains (D) another polymerizable compound in addition to (A) the specific polymerizable compound. Examples of other polymerizable compounds that can be used in combination with the present invention include radically polymerizable compounds and cationically polymerizable compounds. (D) Other polymerizable compounds may be appropriately selected and used in relation to the intended properties or the (B) radical polymerization initiator.

In the present invention, the total content of the polymerizable compound, that is, the total content of (A) the specific polymerizable compound and (D) the other polymerizable compound is based on the total mass of the ink composition of the present invention. It is 45-95 mass%, More preferably, it is 50-90 mass%.
In the ink composition of the present invention, (A) the specific polymerizable compound contains the total content of the polymerizable compound contained in the ink composition (that is, (A) the specific polymerizable compound and (D) other polymerizations. 10 to 60% by mass or more, more preferably 15 to 50% by mass or more, and further preferably 25 to 35% by mass or more with respect to the total content of the active compound component).
Hereinafter, other polymerizable compounds applicable to the present invention will be described.

  The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization, and may be any compound as long as it has at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. , Oligomers, polymers and the like having a chemical form. Only one kind of radically polymerizable compound may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve desired properties. It is preferable to use two or more kinds in combination for controlling performance such as reactivity and physical properties.

  Examples of the polymerizable compound having an ethylenically unsaturated bond capable of radical polymerization include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and salts thereof, Examples thereof include radically polymerizable compounds such as anhydrides having a saturated group, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.

  Specifically, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, bis (4-acryloxypolyethoxyphenyl) propane (weight average molecular weight exceeding 360) ), Polyethylene glycol diacrylate (weight average molecular weight exceeding 360), polypropylene glycol diacrylate (weight average molecular weight exceeding 360), dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, oligoester acrylate, N- Methylol acrylamide, diacetone acrylamide, epoxy acrylate, isobornyl acrylate, dicyclopentenyl amine Acrylic acid derivatives such as relate and dicyclopentenyloxyethyl acrylate; methyl methacrylate, n-butyl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, polyethylene glycol dimethacrylate (weight average molecular weight over 360) , Methacryl derivatives such as polypropylene glycol dimethacrylate (weight average molecular weight exceeding 360), 2,2-bis (4-methacryloxypolyethoxyphenyl) propane (weight average molecular weight exceeding 360), etc .; allyl glycidyl And derivatives of allyl compounds such as ether, diallyl phthalate and triallyl trimellitate. "Dobook", (1981 Taiseisha); Kato Kiyomi ed., "UV / EB Curing Handbook (raw material)" (1985, Polymer Publishing Society); Radtech Study Group, "Application of UV / EB Curing Technology" Market ", p. 79, (1989, CMC); Eiichiro Takiyama," Polyester Resin Handbook ", (1988, Nikkan Kogyo Shimbun), etc. or a radically polymerizable or cross-linkable known in the industry. Monomers, oligomers and polymers can be used.

  Examples of the radically polymerizable compound include JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, JP-A-10-863, JP-A-9-134011, and JP-T-2004. There are known photocurable polymerizable compound materials used in the photopolymerizable compositions described in each publication such as JP-A-514014, and these can also be applied to the ink composition of the present invention.

Furthermore, it is preferable to use a vinyl ether compound as the radical polymerizable compound. Suitable vinyl ether compounds include, for example, ethylene glycol divinyl ether, ethylene glycol monovinyl ether, diethylene glycol divinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol. Di- or trivinyl ether compounds such as divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, trimethylolpropane trivinyl ether; ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octade Monovinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-O-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether, etc. Examples include vinyl ether compounds.
Of these vinyl ether compounds, divinyl ether compounds and trivinyl ether compounds are preferable from the viewpoints of curability, adhesiveness, and surface hardness, and divinyl ether compounds are particularly preferable. A vinyl ether compound may be used individually by 1 type, and may be used in combination of 2 or more type as appropriate.

  Other polymerizable compounds include (meth) acrylic monomers or prepolymers, (meth) acrylic acid esters such as epoxy monomers or prepolymers, urethane monomers or prepolymers (hereinafter referred to as acrylate compounds as appropriate). .) May be used, and the following compounds are listed as compound examples.

  That is, 2-ethylhexyl-diglycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxybutyl acrylate, hydroxypivalate neopentyl glycol diacrylate, 2-acryloyloxyethyl phthalate, methoxy-polyethylene glycol acrylate, Tetramethylol methane triacrylate, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, dimethylol tricyclodecane diacrylate, ethoxylated phenyl acrylate, 2-acryloyloxyethyl succinic acid, nonylphenol EO adduct acrylate, modified glycerin Triacrylate, bisphenol A diglycidyl ether acrylic acid adduct, modified bisphenol A diacrylate, phenoxy-poly Tylene glycol acrylate, 2-acryloyloxyethylhexahydrophthalic acid, PO adduct diacrylate of bisphenol A, EO adduct diacrylate of bisphenol A, dipentaerythritol hexaacrylate, pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer Lactone-modified flexible acrylate, butoxyethyl acrylate, propylene glycol diglycidyl ether acrylic acid adduct, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, 2-hydroxyethyl acrylate, methoxydipropylene glycol acrylate, ditrimethylolpropane Tetraacrylate, pentaerythritol triacrylate hexamethyl Nji diisocyanate urethane prepolymer, stearyl acrylate, isoamyl acrylate, isomyristyl acrylate, isostearyl acrylate, lactone-modified acrylate, and the like.

These acrylate compounds are polymerizable compounds that have been used in UV curable inks, have low skin irritation and sensitization (ease of rashes), and have relatively low viscosity and stable ink ejection properties. It is preferable because the sensitivity and adhesiveness with the recording medium are good.
Here, (D) monomers listed as other polymerizable compounds are low in sensitization even with a low molecular weight, have high reactivity, low viscosity, and adhesion to a recording medium. Excellent.

In order to further improve the sensitivity, bleeding, and adhesion to the recording medium, (D) as other polymerizable compound component, monoacrylate, polyfunctional acrylate monomer having a molecular weight of 400 or more, preferably 500 or more, or polyfunctional It is a preferred embodiment to use an acrylate oligomer in combination.
In particular, in an ink composition used for recording on a flexible recording medium such as a PET film or a PP film, a monoacrylate selected from the above compound group and the above-mentioned (A) specific polymerizable compound are selected. The combined use of the seed and the polyfunctional acrylate monomer or polyfunctional acrylate oligomer selected from the component (D) is preferable because the film strength can be increased while the film is made flexible to enhance the adhesion.
In addition, the embodiment in which at least three kinds of polymerizable compounds of monofunctional, bifunctional, and trifunctional or higher polyfunctional monomers are used in combination improves sensitivity, bleeding, and adhesiveness to the recording medium while maintaining safety. From the viewpoint that it can be further improved, it is mentioned as a preferred embodiment.

As monoacrylates, stearyl acrylate, isoamyl acrylate, isomystil acrylate, and isostearyl acrylate have high sensitivity and low shrinkage to prevent curling, and are preferable in terms of prevention of bleeding, odor of printed matter, and cost reduction of irradiation apparatus. .
As the oligomer that can be used in combination with the monoacrylate, an epoxy acrylate oligomer and a urethane acrylate oligomer are particularly preferable.
In addition, methacrylate has better skin irritation than acrylate.
Among the above compounds, when alkoxy acrylate is used in an amount of 70% by mass or less and the balance is acrylate, it is preferable because it has good sensitivity, bleeding characteristics, and odor characteristics.

  In the present invention, when the acrylate compound is used as the other polymerizable compound (D), the acrylate compound is 30% by mass with respect to the total mass of the other polymerizable compound (that is, the total amount of the component (D)). Preferably, it is 40% by mass or more, and more preferably 50% by mass or more. Moreover, (D) all the other polymerizable compounds used together can also be made into the said acrylate compound.

  In the present invention, regarding the selection of the polymerization initiator and the polymerizable compound, radical polymerization may be performed according to various purposes (for example, as a means for preventing a decrease in sensitivity due to the light-shielding effect of the colorant used in the ink composition). In addition to the combination of the polymerizable compound and the radical polymerization initiator, a radical-cation hybrid curable ink may be used in combination with the cationic polymerizable compound and the cationic polymerization initiator.

  The cationically polymerizable compound that can be used in the present invention is not particularly limited as long as it is a compound that initiates a polymerization reaction with an acid generated from a photoacid generator and cures, and various known cationic polymerizations known as photocationically polymerizable monomers. Sex monomers can be used. Examples of the cationic polymerizable monomer include JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and 2001-2001. Examples thereof include epoxy compounds, vinyl ether compounds, oxetane compounds and the like described in each publication such as No. 220526.

  In addition, as the cationic polymerizable compound, for example, a polymerizable compound applied to a cationic polymerization type photocurable resin is known, and recently, a photo cationic polymerization type sensitized in a visible light wavelength region of 400 nm or more. Examples of the polymerizable compound applied to the photo-curable resin are disclosed in JP-A-6-43633 and JP-A-8-324137. These can also be applied to the ink composition of the present invention.

Examples of the cationic polymerization initiator (photoacid generator) that can be used in combination with the cationically polymerizable compound in the present invention include chemically amplified photoresists and compounds used for photocationic polymerization (organic). (See "Organic Materials for Imaging" edited by Electronics Materials Research Group, Bunshin Publishing (1993), pages 187-192). Examples of the cationic polymerization initiator suitable for the present invention are listed below.
First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, phosphonium, etc. be able to. Secondly, sulfonated products that generate sulfonic acid can be mentioned. Thirdly, a halide that generates hydrogen halide can also be used. Fourthly, an iron allene complex can be mentioned.
The above cationic polymerization initiators may be used alone or in combination.

[(E) Sensitizing dye]
A sensitizing dye (E) can be added to the ink composition of the present invention in order to accelerate the decomposition of the radical polymerization initiator (B) by irradiation with actinic rays. A sensitizing dye absorbs specific actinic radiation and enters an electronically excited state. The sensitizing dye in an electronically excited state is brought into contact with the polymerization initiator to cause actions such as electron transfer, energy transfer, and heat generation, thereby causing a chemical change of the polymerization initiator, that is, decomposition, radical, acid or base. It promotes the generation of.

As the sensitizing dye, a compound corresponding to the wavelength of the active radiation that generates the starting species in the radical polymerization initiator (B) used in the ink composition may be used, but for a general ink composition curing reaction. Considering that it is used, examples of preferable sensitizing dyes include those belonging to the following compounds and having an absorption wavelength in the 350 nm to 450 nm region.
Polynuclear aromatics (for example, anthracene, pyrene, perylene, triphenylene), thioxanthones (for example, isopropylthioxanthone), xanthenes (for example, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (for example, thiaxene) Carbocyanine, oxacarbocyanine), merocyanines (eg, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones ( For example, anthraquinone), squalium (for example, squalium), coumarins (for example, 7-diethylamino-4-methylcoumarin), and the like can be mentioned. Xanthones may be mentioned as preferred class.

  More preferable examples of the sensitizing dye include compounds represented by the following formulas (IV) to (VIII).

In the general formula (IV), A ¹ represents a sulfur atom or NR ⁵⁰ , R ⁵⁰ represents an alkyl group or an aryl group, and L ² represents a basic nucleus of the dye in combination with the adjacent A ¹ and the adjacent carbon atom. Represents a nonmetallic atomic group to be formed, R ⁵¹ and R ⁵² each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁵¹ and R ⁵² are bonded to each other to form an acidic nucleus of the dye. Also good. W represents an oxygen atom or a sulfur atom.

In general formula (V), Ar < ¹ > and Ar < ² > represent an aryl group each independently, and are connected through the bond by -L < ³ >-. Here, L ³ represents —O— or —S—. W is synonymous with that shown in Formula (IV).

In the general formula (VI), A ² represents a sulfur atom or NR ⁵⁹ , L ⁴ represents a nonmetallic atomic group that forms a basic nucleus of the dye together with adjacent A ² and a carbon atom, R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represent a monovalent nonmetallic atomic group, and R ⁵⁹ represents an alkyl group or an aryl group.

In general formula (VII), A ³ and A ⁴ each independently represent —S— or —NR ⁶² — or —NR ⁶³ —, wherein R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted alkyl group, substituted Or an unsubstituted aryl group, L ⁵ and L ⁶ each independently represent a nonmetallic atomic group that forms a basic nucleus of a dye in cooperation with adjacent A ³ , A ^4, and adjacent carbon atoms; ⁶⁰ and R ⁶¹ are each independently a hydrogen atom or a monovalent nonmetallic atomic group, or can be bonded to each other to form an aliphatic or aromatic ring.

(In the formula (VIII), R ⁶⁶ represents an aromatic ring or a hetero ring which may have a substituent, and A ⁵ represents an oxygen atom, a sulfur atom or ═NR ^67. R ⁶⁴ , R ⁶⁵ and R ⁶⁷ Each independently represents a hydrogen atom or a monovalent non-metallic atomic group, and R ⁶⁷ and R ⁶⁴ , and R ⁶⁵ and R ⁶⁷ can be bonded to each other to form an aliphatic or aromatic ring. .)

  Preferable specific examples of the compounds represented by formulas (IV) to (VIII) include those shown below.

<(F) Co-sensitizer>
The ink composition of the present invention can also contain a co-sensitizer. In the present invention, the co-sensitizer has functions such as further improving the sensitivity of the sensitizing dye to actinic radiation or suppressing polymerization inhibition of the polymerizable compound by oxygen.
Examples of such co-sensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Society”, Vol. 10, 3173 (1972), Japanese Patent Publication No. 44-20189, Japanese Patent Publication No. 51-82102, Japanese Patent Publication No. 52-134692, Japanese Patent Publication No. 59-138205. No. 60-84305, JP-A 62-18537, JP-A 64-33104, Research Disclosure 33825, and the like. Specific examples include triethanolamine. P-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline and the like.

  Other examples of co-sensitizers include thiols and sulfides, for example, thiol compounds described in JP-A-53-702, JP-B-55-500806, JP-A-5-142773, and JP-A-56. And the like. Specific examples include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzoimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercaptonaphthalene. Etc.

  Other examples include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (eg, tributyltin acetate), and hydrogen described in Japanese Patent Publication No. 55-34414. Donors, sulfur compounds described in JP-A-6-308727 (eg, trithiane), phosphorus compounds described in JP-A-6-250387 (diethylphosphite, etc.), Si-H described in JP-A-8-65779 , Ge—H compounds and the like.

<(G) Other ingredients>
If necessary, other components can be added to the ink composition of the present invention. Examples of other components include a polymerization inhibitor and a solvent.
A polymerization inhibitor may be added from the viewpoint of enhancing the storage stability. Further, when the ink composition of the present invention is used as an ink composition for ink jet recording, it is preferably discharged at a temperature in the range of 40 to 80 ° C. with a reduced viscosity, and also for preventing head clogging due to thermal polymerization. It is preferable to add a polymerization inhibitor. The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the ink composition of the present invention. Examples of the polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.

In view of the fact that the ink composition of the present invention is a radiation curable ink composition, it is preferable that no solvent is contained so that the ink composition can react quickly and cure immediately after landing of the ink composition. However, a predetermined solvent can be included as long as the curing rate of the ink composition is not affected. In the present invention, an organic solvent or water can be used as the solvent. In particular, an organic solvent can be added in order to improve adhesiveness with a recording medium (a support such as paper). The addition of an organic solvent is effective because the VOC problem can be avoided.
The amount of the organic solvent is, for example, 0.1 to 5% by mass, preferably 0.1 to 3% by mass with respect to the mass of the entire ink composition of the present invention.

  In addition to this, a known compound can be added to the ink composition of the present invention as necessary. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, waxes and the like are appropriately selected and added. be able to. In order to improve the adhesion to a recording medium such as polyolefin or PET, it is also preferable to include a tackifier that does not inhibit the polymerization. Specifically, a high molecular weight adhesive polymer described in JP-A-2001-49200, pages 5 to 6 (for example, (meth) acrylic acid and an alcohol having an alkyl group having 1 to 20 carbon atoms). An ester, a copolymer of (meth) acrylic acid and an alicyclic alcohol having 3 to 14 carbon atoms, a copolymer of an ester of (meth) acrylic acid and an aromatic alcohol having 6 to 14 carbon atoms), and polymerizability. Examples thereof include a low molecular weight tackifying resin having an unsaturated bond.

[Properties of ink composition for inkjet recording]
Since the ink composition of the present invention is used as an ink for ink jet recording, preferred physical properties in such a use mode will be described.
The ink composition for ink jet recording of the present invention has a viscosity of preferably 7 to 30 mPa · s at a temperature at the time of ejection (for example, 40 to 80 ° C., preferably 25 to 50 ° C.) in consideration of ejectability. More preferably, it is 7 to 25 mPa · s. For example, the viscosity of the ink composition of the present invention at room temperature (25 to 30 ° C.) is preferably 10 to 50 mPa · s, more preferably 12 to 40 mPa · s.
It is preferable that the composition ratio of the ink composition of the present invention is appropriately adjusted so that the viscosity is in the above range. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be avoided, and uncured monomers and odors can be reduced. Furthermore, ink bleeding at the time of ink droplet landing can be suppressed, and as a result, the image quality is improved.

  The surface tension of the ink composition of the present invention is preferably 20 to 30 mN / m, more preferably 23 to 28 mN / m. When recording on various recording media such as polyolefin, PET, coated paper, and non-coated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and the wettability is preferably 30 mN / m or less.

[Inkjet recording method]
The ink jet recording method of the present invention and the ink jet recording apparatus applicable to the ink jet recording method will be described below.
In the inkjet recording method of the present invention, the ink composition of the present invention is ejected onto a recording medium (support, recording material, etc.) for ink jet recording, and active radiation is applied to the ink composition ejected onto the recording medium. , And the ink is cured to form an image.

That is, the inkjet recording method of the present invention comprises (i-1) a step of ejecting the ink composition of the present invention onto a recording medium, and (i-2) irradiating the ejected ink composition with actinic radiation. And a step of curing the ink composition.
By including the steps (i-1) and (i-2), the ink jet recording method of the present invention forms an image with the ink composition cured on the recording medium.

  In the step (i-1) of the ink jet recording method of the present invention, an ink jet recording apparatus described in detail below can be used.

-Inkjet recording device-
There is no restriction | limiting in particular as an inkjet recording device used for the inkjet recording method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and can be used. That is, any known inkjet recording apparatus including a commercially available product can eject ink onto a recording medium in step (i-1) of the inkjet recording method of the present invention.
Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and an actinic radiation source.
The ink supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head has a multi-size dot of 1 to 100 pl, preferably 8 to 30 pl, for example, 320 × 320 to 4000 × 4000 dpi, preferably 400 × 400 to 1600 × 1600 dpi, and more preferably 720 × 720 dpi. It can drive so that it can discharge with the resolution of. In the present invention, dpi represents the number of dots per 2.54 cm.

  As described above, since it is desirable that the radiation-curable ink, like the ink composition of the present invention, has a constant temperature for the ink to be ejected, heat insulation and heating are performed from the ink supply tank to the inkjet head portion. It can be carried out. The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors at each piping site and perform heating control according to the ink flow rate and the environmental temperature. The temperature sensor can be provided near the ink supply tank and the nozzle of the inkjet head. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

Using the above inkjet recording apparatus, the ink composition of the present invention is ejected by heating the ink composition to 40 to 80 ° C., more preferably 25 to 50 ° C. Preferably it is performed after lowering to 7-30 mPa · s, more preferably 7-25 mPa · s. In particular, it is preferable to use an ink composition having an ink viscosity at 25 ° C. of 35 to 500 mPa · s as the ink composition of the present invention because a large effect can be obtained. By using this method, high ejection stability can be realized.
A radiation curable ink composition such as the ink composition of the present invention generally has a higher viscosity than a water-based ink usually used in ink jet recording inks, and therefore has a large viscosity fluctuation due to temperature fluctuations during ejection. The ink viscosity fluctuation has a great influence on the change of the droplet size and the change of the droplet discharge speed, and causes the image quality deterioration. Therefore, it is necessary to keep the temperature of the ink at the time of ejection as constant as possible. Therefore, in the present invention, it is appropriate that the control range of the ink temperature is ± 5 ° C. of the set temperature, preferably ± 2 ° C. of the set temperature, more preferably ± 1 ° C. of the set temperature.

Next, (i-2) a step of irradiating the discharged ink composition with actinic radiation to cure the ink composition will be described.
The ink composition ejected on the recording medium is cured by irradiation with actinic radiation. This is because the radical polymerization initiator (B) contained in the ink composition of the present invention is decomposed by irradiation with actinic radiation to generate radicals and other starting species, and (A) specific polymerizability is determined by the function of the starting species. This is because the polymerization reaction of the compound and the other polymerizable compound (D) used together as desired occurs and is accelerated. At this time, if (E) a sensitizing dye is present together with (B) the radical polymerization initiator in the ink composition, (E) the sensitizing dye in the system absorbs actinic radiation and becomes excited, and (B) radical polymerization. By contacting with the initiator, (A) decomposition of the polymerization initiator can be promoted, and a more sensitive curing reaction can be achieved.

  Here, α rays, γ rays, electron beams, X rays, ultraviolet rays, visible light, infrared rays, or the like can be used as the active radiation used. In particular, any one of electron beam, ultraviolet light, and visible light is preferable. Although the peak wavelength of actinic radiation is based also on the absorption characteristic of a sensitizing dye, it is preferable that it is 200-600 nm, for example, it is more preferable that it is 300-450 nm, and it is still more preferable that it is 350-420 nm.

In addition, the polymerization initiation system in the ink composition of the present invention has sufficient sensitivity even with a low output actinic radiation. Thus, the output of the active radiation is preferably 2,000 mJ / cm ² or less, more preferably from 10 to 2,000 mJ / cm ^2, more preferably be 20 to 1,000 mJ / cm ² Particularly preferably, it is 50 to 800 mJ / cm ² .
Furthermore, the actinic radiation is, the exposure surface illuminance of, for example, 10 to 2,000 mW / cm ^2, preferably, suitably be irradiated at 20 to 1,000 mW / cm ^2.

Mercury lamps and gas / solid lasers are mainly used as actinic radiation sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing UV photocurable ink jet recording inks. Yes. However, from the viewpoint of environmental protection, mercury-free is strongly desired, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, LED (UV-LED) and LD (UV-LD) are small, have a long life, have high efficiency, and are low in cost, and are expected as light sources for photo-curable ink jets.
Further, a light emitting diode (LED) and a laser diode (LD) can be used as the active radiation source. In particular, when an ultraviolet light source is required, an ultraviolet LED and an ultraviolet LD can be used. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. When even shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit actinic radiation centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. The actinic radiation source particularly preferred in the present invention is a UV-LED, particularly preferably a UV-LED having a peak wavelength at 350 to 420 nm.
Incidentally, it is preferable that maximum illumination intensity of the LED on a recording medium is 10 to 2,000 mW / cm ^2, more preferably 20 to 1,000 mW / cm ^2, particularly preferably 50 to 800 mW / cm ² .

The ink composition of the present invention is suitably irradiated with such actinic radiation for, for example, 0.01 to 120 seconds, preferably 0.1 to 90 seconds.
Actinic radiation irradiation conditions and a basic irradiation method are disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit including the ink ejection device, and the head unit and the light source are scanned by a so-called shuttle method. Irradiation with actinic radiation takes a certain time (for example, 0.01 to 0.5 seconds, preferably 0.01 to 0.3 seconds, more preferably 0.01 to 0.15 seconds) after ink landing. Will be done. In this way, by controlling the time from ink landing to irradiation to an extremely short time, it is possible to prevent the ink that has landed on the recording medium from spreading before curing. Further, since the ink can be exposed to the porous recording medium before the ink penetrates to a deep part where the light source does not reach, the residual unreacted monomer can be suppressed, and as a result, the odor can be reduced. .
Further, the curing may be completed by another light source that is not driven. WO99 / 54415 pamphlet discloses a method using an optical fiber and a method of applying a collimated light source to a mirror surface provided on the side surface of the head unit and irradiating the recording unit with UV light as an irradiation method. The curing method can also be applied to the ink jet recording method of the present invention.

By adopting the ink jet recording method as described above, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In addition, in order to obtain a color image, it is preferable to superimpose in order from the color with the lowest brightness. By superimposing the inks in the order of low lightness, it becomes easy for the irradiation line to reach the lower ink, and good curing sensitivity, reduction of residual monomers, reduction of odor, and improvement of adhesiveness can be expected. In addition, irradiation can be performed by discharging all colors and collectively exposing, but exposure for each color is preferable from the viewpoint of promoting curing.
In this way, the ink composition of the present invention can form a high-definition and high-strength image on the surface of the recording medium by curing with high sensitivity by irradiation with actinic radiation.

  In addition, as described above, an image formed by the ink composition of the present invention is generally used for production of printed matter because it is excellent in strength, adhesion to a recording medium and flexibility. In addition, for example, when an image is formed on a flexible resin film and the film is attached to a curved surface, the image portion is not damaged. It can be applied to any use.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the embodiments in these examples. The following examples relate to UV ink jet recording ink of each color. Further, in the following description, unless otherwise specified, “parts” means “parts by mass”.

[Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink.
(Cyan ink composition)
Specific polymerizable compound [Exemplary compound (A-1): Component (A)] 12.0 parts Tridecyl acrylate 11.0 parts (Sartomer SR498E)
-23.4 parts of 2-phenoxyethyl acrylate (SR339 manufactured by Sartomer)
N-vinylcaprolactam 13.0 parts Trimethylolpropane triacrylate [(D) component] 8.0 parts (Sartomer SR351)
-Solsperse 32000 (Noveon dispersant) 0.4 part-Irgalite Blue GLVO (component (C)) 3.6 parts (Ciba Specialty Chemicals pigment)
・ Genorad 16 (Rahn, polymerization inhibitor) 0.05 part ・ Rapi-Cure DVE-3 4.0 part (vinyl ether compound made by ISP Europe)
・ Lucirin TPO (Photoinitiator manufactured by BASF: Component (B)) 8.5 parts ・ Benzophenone (Photoinitiator: Component (B)) 4.0 parts ・ Irgacure 184 4.0 parts (Ciba Specialty Chemicals Co., Ltd.) Initiator: component (B)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

Recording was performed on a sheet made of polyvinyl chloride using an ink jet recording apparatus having the obtained cyan ink composition and a piezo type ink jet head (CA3 head manufactured by Toshiba Tec). The ink supply system is composed of an original tank, supply piping, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head, and temperature control is performed so that the nozzle portion is always 45 ° C. ± 3 ° C. (100% Print coated image). After discharging the ink composition, irradiation was performed by passing it through a light beam of an iron-doped ultraviolet lamp (power 120 W / cm ² ) at a speed of 40 m / min to cure the ink and obtain a printed matter.
At this time, the following evaluation was performed.

<Curing sensitivity>
The exposure energy in curing was measured with a light quantity integrator (UV PowerMAP manufactured by EIT). It is evaluated that the smaller this value is, the higher the sensitivity is. As a result, it was confirmed that the ink composition of Example 1 was cured with high sensitivity because the cumulative exposure amount of ultraviolet rays on the sheet was about 330 mJ / cm ² .

<Curing property>
The curability was evaluated by curing the printed matter with this ink at a cumulative exposure amount of about 330 mJ / cm ² of ultraviolet rays on the sheet and palpating the cured image portion. Curability is evaluated by the presence or absence of tackiness on the surface of the cured film.
As a result, it was confirmed that the tackiness after curing was completely lost and the curability was excellent.

<Adhesion with recording medium>
Adhesiveness with a recording medium is evaluated by a cross hatch test (EN ISO 2409), and expressed by the notations 5B to 1B by the ASTM method. It is evaluated that 5B has the most excellent adhesiveness, and 3B or more is a level having no practical problem.
As a result, the ink composition of Example 1 had high adhesiveness, and the value thereof was 4B as expressed by the ASTM method.

<Flexibility>
The evaluation of the flexibility was evaluated by the degree of cracks generated in the cured film after bending the sheet image-formed with ink 10 times. This bending test is performed in a five-step evaluation with 5 points indicating a state in which no crack is generated, and 3 points or more are evaluated as having no problem in practice.
As a result, in Example 1, only slight cracks that did not affect the printed image were observed, and the evaluation was 4 points.

[Example 2]
Specific polymerizable compound [Exemplary Compound (A-1): Component (A)] 20.0 parts N-Vinylcaprolactam [Component (D)] 15.0 parts 2-Phenoxyethyl acrylate 26.4 parts (Sartomer SR339)
Trimethylolpropane triacrylate [(D) component] 5.0 parts (Sartomer, SR351)
Solsperse 32000 (manufactured by Noveon, dispersant) 0.4 part Cinquasia Magenta RT-355D [component (C)] 3.6 parts (produced by Ciba Specialty Chemicals, pigment)
-Genorad 16 (Rahn, polymerization inhibitor) 0.05 parts-Rapi-Cure DVE-3 4.0 parts (ISP Europe, vinyl ether compound)
・ Lucirin TPO (manufactured by BASF, photoinitiator: component (B)) 8.5 parts ・ benzophenone (photoinitiator: component (B)) 4.0 parts ・ Irgacure 184 4.0 parts (manufactured by Ciba Specialty Chemicals) , Photoinitiator: (B) component)
・ Isopropylthioxanthone (ITX) 1.0 part ・ Byk 307 (manufactured by BYK Chemie, defoaming agent) 0.05 part

  The obtained magenta color ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

Example 3
The following components were stirred with a high-speed water-cooled stirrer to obtain a yellow UV inkjet ink.
(Yellow color ink composition)
Specific polymerizable compound [Exemplary compound (A-1): Component (A)] 18.0 parts Specific polymerizable compound [Exemplary compound (A-14): Component (A)] 4.0 parts N-vinyl Caprolactam [component (D)] 16.0 parts 2-phenoxyethyl acrylate 21.4 parts (Sartomer SR339)
Trimethylolpropane triacrylate [(D) component] 3.0 parts (SR351, manufactured by Sartomer)
Dipropylene glycol diacrylate [(D) component] 1.0 part (SR508 manufactured by Sartomer)
-Solsperse 32000 (Noveon dispersant) 0.4 part-Chromophthalal Yellow LA (C) component 3.6 parts (Ciba Specialty Chemicals pigment)
・ Genorad 16 (polymerization inhibitor manufactured by Rahn) 0.05 part ・ Rapi-Cure DVE-3 2.0 parts (vinyl ether compound manufactured by ISP Europe)
・ Lucirin TPO (Photoinitiator manufactured by BASF: Component (B)) 8.5 parts ・ Benzophenone (Photoinitiator: Component (B)) 4.0 parts ・ Irgacure 184 4.0 parts (Ciba Specialty Chemicals Co., Ltd.) Initiator: component (B)
・ Isopropylthioxanthone (ITX) 1.0 part ・ Byk 307 (BYK Chemie antifoam) 0.05 part

  The obtained yellow ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

Example 4
The following components were stirred with a high-speed water-cooled stirrer to obtain a black UV inkjet ink.
(Black ink composition)
Specific polymerizable compound [Exemplary compound (A-2): Component (A)] 20.0 parts Isobornyl acrylate [Component (D)] 17.0 parts (SR506D manufactured by Sartomer)
2-phenoxyethyl acrylate [(D) component] 28.4 parts (SR339, manufactured by Sartomer)
Trimethylolpropane triacrylate (component (D)) 6.0 parts (Sartomer SR351)
・ Solsperse 32000 (Noveon's dispersant) 0.4 part ・ Microlith Black CK [component (C)] 2.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (Rahn polymerization inhibitor) 0.05 part-Lucirin TPO (BASF photoinitiator: (B) component) 8.5 parts-Benzophenone (photoinitiator: (B) component) 4.0 Part Irgacure 184 4.0 parts (Ciba Specialty Chemicals photoinitiator: component (B))
・ Isopropylthioxanthone (ITX) 1.0 part ・ Byk 307 (BYK Chemie antifoam) 0.05 part

  The obtained black ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

Example 5
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink.
(Cyan ink composition)
Specific polymerizable compound [Exemplary compound (A-12): Component (A)] 26.0 parts 2phenoxyethyl acrylate 38.4 parts (Sartomer SR339)
Trimethylol propane triacrylate [component (D)] 2.0 parts (Sartomer SR351)
Dipropylene glycol diacrylate (component (D)) 2.0 parts (Sartomer SR508)
-Solsperse 32000 (Noveon dispersant) 0.4 part-Irgalite Blue GLVO (component (C)) 3.6 parts (Ciba Specialty Chemicals pigment)
・ Genorad 16 (polymerization inhibitor manufactured by Rahn) 0.05 part ・ Rapi-Cure DVE-3 2.0 parts (vinyl ether compound manufactured by ISP Europe)
・ Lucirin TPO (BASF Photoinitiator: Component (A)) 8.5 parts ・ Benzophenone (Photoinitiator: Component (A)) 4.0 parts ・ Irgacure 184 4.0 parts (Ciba Specialty Chemicals Initiator: (A) component)
・ Isopropylthioxanthone (ITX) 1.0 part ・ Byk 307 (BYK Chemie antifoam) 0.05 part

  The obtained cyan ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[Comparative Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink.
(Cyan ink composition)
Specific polymerizable compound [Exemplary compound (A-1): Component (A)] 9.0 parts Tridecyl acrylate 14.0 parts (SR498E manufactured by Sartomer)
-23.4 parts of 2-phenoxyethyl acrylate (SR339 manufactured by Sartomer)
N-vinylcaprolactam 13.0 parts Trimethylolpropane triacrylate (component (D)) 8.0 parts (Sartomer SR351)
-Solsperse 32000 (Noveon dispersant) 0.4 part-Irgalite Blue GLVO (component (C)) 3.6 parts (Ciba Specialty Chemicals pigment)
・ Genorad 16 (polymerization inhibitor manufactured by Rahn) 0.05 part ・ Rapi-Cure DVE-3 4.0 parts (vinyl ether compound manufactured by ISP Europe)
・ Lucirin TPO (Photoinitiator manufactured by BASF: Component (B)) 8.5 parts ・ Benzophenone (Photoinitiator: Component (B)) 4.0 parts ・ Irgacure 184 4.0 parts (Ciba Specialty Chemicals Co., Ltd.) Initiator: component (B)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

  The obtained cyan ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[Comparative Example 2]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink.
(Cyan ink composition)
Specific polymerizable compound [Exemplary compound (A-1): Component (A)] 3.0 parts Tridecyl acrylate 20.0 parts (SR498E manufactured by Sartomer)
-23.4 parts of 2-phenoxyethyl acrylate (SR339 manufactured by Sartomer)
N-vinylcaprolactam 13.0 parts Trimethylolpropane triacrylate (component (D)) 8.0 parts (Sartomer SR351)
-Solsperse 32000 (Noveon dispersant) 0.4 part-Irgalite Blue GLVO (component (C)) 3.6 parts (Ciba Specialty Chemicals pigment)
・ Genorad 16 (polymerization inhibitor manufactured by Rahn) 0.05 part ・ Rapi-Cure DVE-3 4.0 parts (vinyl ether compound manufactured by ISP Europe)
・ Lucirin TPO (Photoinitiator manufactured by BASF: Component (B)) 8.5 parts ・ Benzophenone (Photoinitiator: Component (B)) 4.0 parts ・ Irgacure 184 4.0 parts (Ciba Specialty Chemicals Co., Ltd.) Initiator: component (B)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

  The obtained cyan ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[Comparative Example 3]
The following components were stirred with a high-speed water-cooled stirrer to obtain a black UV inkjet ink.
(Black ink composition)
Specific polymerizable compound [Exemplary compound (A-2): Component (A)] 55.0 parts Isobornyl acrylate [Component (D)] 7.0 parts (SR506D manufactured by Sartomer)
2-phenoxyethyl acrylate [component (D)] 3.4 parts (Sartomer SR339)
Trimethylolpropane triacrylate (component (D)) 6.0 parts (Sartomer SR351)
・ Solsperse 32000 (Noveon's dispersant) 0.4 part ・ Microlith Black CK [component (C)] 2.6 parts (Ciba Specialty Chemicals pigment)
-Genorad 16 (Rahn polymerization inhibitor) 0.05 part-Lucirin TPO (BASF photoinitiator: (B) component) 8.5 parts-Benzophenone (photoinitiator: (B) component) 4.0 Part Irgacure 184 4.0 parts (Ciba Specialty Chemicals photoinitiator: component (B))
・ Isopropylthioxanthone (ITX) 1.0 part ・ Byk 307 (BYK Chemie antifoam) 0.05 part

  The obtained black ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[Comparative Example 4]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink.
(Cyan ink composition)
・ Comparative compound A 26.0 parts (Hankuri FA-712HM manufactured by Hitachi Chemical Co., Ltd.)
・ 38.4 parts of 2-phenoxyethyl acrylate (SR339 manufactured by Sartomer)
Trimethylol propane triacrylate [component (D)] 2.0 parts (Sartomer SR351)
Dipropylene glycol diacrylate (component (D)) 2.0 parts (Sartomer SR508)
-Solsperse 32000 (Noveon dispersant) 0.4 part-Irgalite Blue GLVO (component (C)) 3.6 parts (Ciba Specialty Chemicals pigment)
・ Genorad 16 (polymerization inhibitor manufactured by Rahn) 0.05 part ・ Rapi-Cure DVE-3 2.0 parts (vinyl ether compound manufactured by ISP Europe)
・ Lucirin TPO (BASF Photoinitiator: Component (A)) 8.5 parts ・ Benzophenone (Photoinitiator: Component (A)) 4.0 parts ・ Irgacure 184 4.0 parts (Ciba Specialty Chemicals Initiator: (A) component)
・ Isopropylthioxanthone (ITX) 1.0 part ・ Byk 307 (BYK Chemie antifoam) 0.05 part

  The obtained cyan ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

[Comparative Example 5]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink.
(Cyan ink composition)
-26.0 parts of the following comparative compound B (TINUVIN 292 manufactured by Ciba Specialty Chemicals)
・ 38.4 parts of 2-phenoxyethyl acrylate (SR339 manufactured by Sartomer)
Trimethylol propane triacrylate [component (D)] 2.0 parts (Sartomer SR351)
Dipropylene glycol diacrylate (component (D)) 2.0 parts (Sartomer SR508)
-Solsperse 32000 (Noveon dispersant) 0.4 part-Irgalite Blue GLVO (component (C)) 3.6 parts (Ciba Specialty Chemicals pigment)
・ Genorad 16 (polymerization inhibitor manufactured by Rahn) 0.05 part ・ Rapi-Cure DVE-3 2.0 parts (vinyl ether compound manufactured by ISP Europe)
・ Lucirin TPO (BASF Photoinitiator: Component (A)) 8.5 parts ・ Benzophenone (Photoinitiator: Component (A)) 4.0 parts ・ Irgacure 184 4.0 parts (Ciba Specialty Chemicals Initiator: (A) component)
・ Isopropylthioxanthone (ITX) 1.0 part ・ Byk 307 (BYK Chemie antifoam) 0.05 part

  The obtained cyan ink was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured. The printed matter with this ink was evaluated in the same manner as in Example 1. The results are shown in Table 1 below.

As is apparent from Table 1, the ink compositions of Examples 1 to 5 were all cured with high sensitivity, and all of the curability of the image area, the adhesion to the recording medium, and the flexibility of the formed image. The evaluation items were excellent and practically no problem.
Among them, as the specific polymerizable compound (A), a compound in which the partial structure represented by the general formula (1) and the polymerizable double bond are bonded by a linking group having an ether bond (—O—) is used. It is found that both the adhesiveness and the flexibility are excellent. Further, from the comparison between Example 1 and Example 2, it can be seen that, in the compound represented by the general formula (2), the compound having R ⁶ of hydrogen atom shows a more excellent effect.
On the other hand, even if the (A) specific polymerizable compound (Exemplary Compound A-1) in the ink composition of Example 1 was used, the ink composition of Comparative Example 1 whose content was outside the scope of the present invention. In the ink composition of Comparative Example 2, in which the coating surface was found to be sticky and inferior in curability, and the content of the component (A) was further less, the ink composition of Comparative Example 2 was not cured by exposure under the same conditions. Evaluation was not possible. In Comparative Example 3 in which the content of the component (A) is too large, the curability was excellent, but the adhesiveness was inferior.
Moreover, in Comparative Example 4 in which a compound in which R ¹ is a hydrogen atom in the partial structure represented by the following general formula (1) was added as an amine compound, the formed coating film was insufficient in its curability and the surface was sticky. The adhesion was inferior. Further, in Comparative Example 5 using a compound having two partial structures similar to those in Comparative Example 4 in the molecule, the cured film could not be evaluated because it was not cured by exposure under the same conditions.

Claims (2)

(A) 12 to 50% by mass of a compound having a polymerizable unsaturated bond and a partial structure represented by the following general formula (1) in the molecule;
(B) a radical polymerization initiator;
(C) A pigment as a colorant, and an ink composition for inkjet recording, characterized by comprising:

In the general formula (1), R ¹ represents an alkyl group or a substituted alkyl group, and R ^{2 to} R ⁵ each independently represent a methyl group or an ethyl group. (I-1) a step of discharging the ink composition for ink jet recording according to claim 1 onto a recording medium; and
(I-2) a step of irradiating the discharged ink composition for inkjet recording with active radiation to cure the ink composition;
An ink jet recording method comprising: