JP2010235640A - Ink composition and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition having high sensitivity and favorable curability to irradiation with active energy rays and excellent solvent resistance, wherein a cured product formed by curing the composition does not peel from a recording medium, and to provide an inkjet recording method for forming a favorable image on a recording medium by using the ink composition. <P>SOLUTION: The ink composition contains (A) an oxetane compound expressed by general formula (1), (B) a polymerization initiator, and (C) at least one kind of compound in vinyl ether compounds or epoxy compounds. In general formula (1), R<SP>1</SP>and R<SP>2</SP>each independently represent a group having an oxetane skeleton; m represents an integer of 1 to 3; n represents an integer of 0 to 2, with (m+n) equal to 2 or 3; A represents a group having a valence of (m+n) and including an aliphatic bicyclo-ring or tricyclo-ring in which the elements constituting the rings are carbon atoms only. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink composition that is cured by irradiation with active energy rays using a cationic polymerizable compound, and an ink jet recording method using the same, and more specifically, is cured with high sensitivity to irradiation with active energy rays. In addition, the present invention relates to an ink composition and an inkjet recording method in which the formed cured product has sufficient flexibility.

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 method 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. Furthermore, there is little noise and it is excellent as an image recording method.

  UV inks that are cured by ultraviolet (UV) irradiation are known as inkjet inks that are suitable for printing on non-water-absorbing recording media such as plastics (see, for example, Patent Documents 1 to 3). Compared to the above, there is an advantage that time and equipment for volatilizing the organic solvent are unnecessary. For curing using such an ink, a system using radical polymerization of monomer components is widely used. In recent years, an ultraviolet curable ink jet ink using a cationically polymerizable compound has also been proposed. However, it is not easy to design a low-viscosity ink that has particularly high sensitivity, good curability, and can be stably ejected. In order to solve such problems, ink jet inks containing an oxetane compound having a cationic polymerizable group having an aliphatic condensed ring structure such as a bicyclo ring or a tricyclo ring structure have been proposed (for example, Patent Documents 4 to 4). 7) is still not sufficient as an ink composition excellent in curing sensitivity and solvent resistance, and there is still room for improvement in terms of ejection stability when used as an inkjet ink.

Japanese Patent Laid-Open No. 9-183927 JP 2003-246818 A JP 2003-292855 A JP 2004-250434 A JP 2007-137926 A JP 2007-211099 A JP 2008-13646 A

An object of the present invention is to provide an ink composition that is highly sensitive to irradiation with active energy rays and the like , has good curability, has excellent solvent resistance, and does not peel off a cured product formed by curing from a recording medium. Is to provide. Furthermore, it is providing the inkjet recording method which forms a favorable image on a recording medium using this ink composition.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by using an ink composition containing an oxetane compound having a specific structure, a photopolymerization initiator, and a vinyl ether compound or an epoxy compound. The present invention has been completed. That is, the means for solving the problems are as follows.

<1> An ink composition comprising (A) an oxetane compound represented by the following general formula (1), (B) a polymerization initiator, and (C) a vinyl ether compound or an epoxy compound.

In the general formula (1), R ¹ and R ² each independently represent a group having an oxetane skeleton. m represents an integer of 1 to 3, n represents an integer of 0 to 2, and (m + n) is 2 or 3. A represents a (m + n) -valent group containing an aliphatic bicyclo ring or tricyclo ring in which the elements forming the ring are composed of only carbon atoms.

<2> The ink composition according to <1>, wherein A in the general formula (1) is an (m + n) -valent group including a skeleton represented by the following (2).

<3> The ink according to <1> or <2>, wherein the oxetane compound represented by the general formula (1) (A) is a compound represented by the following general formula (3) or the general formula (4). Composition.

In General Formula (3) and General Formula (4), R ³ to R ⁶ each independently represent a group having an oxetane skeleton.

<4> (A) Any of <1> to <3>, wherein the content of the oxetane compound represented by the general formula (1) is 10% by mass or more and less than 50% by mass with respect to the total mass of the polymerizable compound. 2. The ink composition according to item 1.
<5> The ink composition according to any one of <1> to <4>, which is an inkjet recording ink.
<6> The ink composition according to any one of <1> to <5>, which is cured by irradiation with an active energy ray.

<7> (a) a step of discharging the ink composition according to any one of <1> to <6> on a recording medium; and (b) an active energy ray applied to the discharged ink composition. An ink jet recording method comprising a step of irradiating and curing the ink composition.

  The oxetane compound used in the present invention is represented by the general formula (1), and an oxygen atom that connects an alicyclic bicyclo ring or a tricyclo ring to an oxetane skeleton is directly bonded to a carbon atom constituting the alicyclic ring. Therefore, since the curability is improved, the solvent resistance is excellent, and the alicyclic structure is present, it is presumed that the ink cured by irradiation with active energy rays is rich in flexibility.

According to the present invention, an ink composition having high sensitivity to irradiation with active energy rays, etc. , good curability, excellent solvent resistance, and a cured product formed by curing is not peeled off from a recording medium. Things can be provided. Furthermore, it is possible to provide an ink jet recording method for forming a good image on a recording medium using the ink composition.

Hereinafter, the present invention will be described in detail.
The ink composition of the present invention comprises (A) an oxetane compound represented by the following general formula (1) (hereinafter referred to as “specific polymerizable compound A” as appropriate), (B) a polymerization initiator, and (C). It contains at least one compound of a vinyl ether compound or an epoxy compound (hereinafter referred to as “specific polymerizable compound C” as appropriate).
First, the individual compounds that constitute the ink composition of the present invention will be described in detail.

<(A) Oxetane compound represented by general formula (1) = specific polymerizable compound A>
The ink composition of the present invention includes (A) an oxetane compound (specific polymerizable compound A) represented by the following general formula (1).

In the general formula (1), R ¹ and R ² each independently represent a group having an oxetane skeleton. m represents an integer of 1 to 3, n represents an integer of 0 to 2, and (m + n) is 2 or 3. A is a (m + n) -valent group containing an aliphatic bicyclo ring or tricyclo ring in which the elements forming the ring consist of only carbon atoms.

In the general formula (1), A is an (m + n) -valent group, and the ring included in the linking group represented by A is an aliphatic bicyclo ring in which an element forming the ring consists of only carbon atoms, or an aliphatic group Tricyclo ring.
In the present invention, the “bicyclo ring” and “tricyclo ring” are aliphatic cyclic structures having a condensed ring portion, and the interatomic bond in the cyclic structure necessary for opening the cyclic structure to a chain structure is broken. A case where the number is 3 is “tricyclo ring”, and a case where the number is 2 is “bicyclo ring”. In the present invention, molecular skeletons composed of such a ring structure are referred to as “tricyclo ring skeleton” and “bicyclo ring skeleton”. A condensed ring is a ring structure in which a plurality of rings share at least one bond, and does not include, for example, a bicyclohexyl skeleton (the following structure) in which two rings do not share a bond.

  The bicyclo ring or tricyclo ring in A of the general formula (1) may have an arbitrary substituent, for example, an alkyl group having 1 to 12 carbon atoms, or an allyl having 1 to 12 carbon atoms. Group, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkoxycarbonyl group having 1 to 12 carbon atoms, a hydroxyl group, a halogen atom, and the like. Among these, a C1-C6 alkyl group and a C1-C6 alkoxy group are preferable.

Substituents of the bicyclo ring or tricyclo ring may be linked to each other to form a further condensed ring structure (for example, a tetracyclo ring), but are preferably a bicyclo ring or a tricyclo ring from the viewpoint of molecular weight and brittleness. Bicyclo ring and tricyclo ring are preferable because curing sensitivity is improved and solvent resistance is good.
Specific examples of the structure containing a ring selected from a bicyclo ring and a tricyclo ring included in the specific polymerizable compound A include, but are not limited to, the following.

In the general formula (I) representing the specific polymerizable compound A, the bicyclo ring and tricyclo ring contained in the linking group A are the ring structures represented by the following (2), or the partial structures represented by the following (2) It is preferable that it is a structure containing. The structure may have an arbitrary substituent that does not interfere with performance. Specific examples of the substituent that can be introduced include an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, and an aryloxy group having 6 to 12 carbon atoms. Can be mentioned. These substituents may be bonded to each other to form a further ring structure.
Since the condensed ring structure represented by the following (2) can be formed from an inexpensive compound by, for example, Diels-Alder reaction, it is advantageous from the viewpoint of simplicity of synthesis and cost.

In the general formula (1), R ¹ represents a group having oxetane as a partial structure. Specific examples of R ¹ include an alkyl group having 1 to 12 carbon atoms including an oxetane ring structure, an aryl group having 9 to 15 carbon atoms, and an acyl group having 1 to 12 carbon atoms. Furthermore, R ¹ may have an arbitrary substituent. Examples of the substituent include an alkyl group having 1 to 12 carbon atoms, an allyl group having 1 to 12 carbon atoms, and an aryl group having 6 to 12 carbon atoms, A C1-C12 alkoxy group, a hydroxyl group, etc. are mentioned, Among these, a C1-C6 alkyl group and a C1-C6 alkoxy group are preferable. The group having an oxetane ring represented by (R ¹ -O) is directly bonded to the bicyclo ring skeleton or the tricyclo ring skeleton, and is an essential site in the specific polymerizable compound of the present invention. The presence of this group makes it possible to achieve both desired curability and flexibility.
In general formula (1), m represents the number of groups having an oxetane skeleton represented by (R ¹ —O), and m is an integer of 1 to 3.

Specific examples of R ¹ include, but are not limited to, the following groups.

In the general formula (1), R ² represents a group having oxetane as a partial structure. Specific examples of R ² include an alkyl group having 1 to 12 carbon atoms including an oxetane ring structure, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, and carbon. Examples thereof include an alkoxycarbonyl group having 1 to 12 carbon atoms and an acyl group having 1 to 12 carbon atoms.
R ² may have an arbitrary substituent. Examples of the substituent include an alkyl group having 1 to 12 carbon atoms, an allyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, and carbon. A C1-C12 alkoxy group, a hydroxyl group, etc. are mentioned, Among these, a C1-C6 alkyl group and a C1-C6 alkoxy group are preferable. In general formula (1), n represents the number of groups having an oxetane skeleton represented by R ² , and n is an integer of 0 or more and 2 or less. (M + n) is 2 or 3. That is, the specific polymerizable compound A of the present invention has 2 or 3 oxetane rings in the molecule. Particularly preferred combinations of m and n are when m = n = 1 and when m = 2 and n = 0.

Specific examples of R ² include the following groups, but are not limited thereto.

  Furthermore, the specific polymerizable compound A of the present invention is preferably a compound represented by the following general formula (3) or general formula (4). By setting it as the compound represented by General formula (3) or General formula (4), it becomes favorable from a viewpoint of coexistence of sclerosis | hardenability and brittleness. In addition, since the skeleton part can be easily synthesized by Diels-Alder reaction or the like, it is suitable for mass production and is particularly advantageous in terms of cost.

In general formula (3) and general formula (4), R ^{3 to} R ⁶ each independently represent a group having an oxetane skeleton. In the general formula (3) and the general formula (4), a straight line extending between the bonds may be bonded to any atom sandwiching the straight line. The specific polymerizable compound A represented by the general formula (3) or the general formula (4) may be a regioisomer mixture. Preferred examples of R ^{3 to} R ^{6 are the same} as the specific examples and preferred examples given for R ¹ in the general formula (I).

  The molecular weight of the specific polymerizable compound A of the present invention is preferably 100 to 800, more preferably 150 to 650, and particularly preferably 200 to 500. The specific polymerizable compound of the present invention is preferably a liquid at normal temperature (25 ° C.), but may be a solid because it may be used by dissolving in another polymerizable compound.

Although the specific example of the specific polymeric compound A of this invention is given to the following, it is not limited to these.
A straight line extending from between the bonds indicates that the atom may be bonded to any atom sandwiching the straight line. The specific polymerizable compound A may be a regioisomer mixture.

  The content of the specific polymerizable compound A in the ink composition is preferably 10% by mass to 50% by mass, and more preferably 15% by mass to 35% by mass with respect to the total solid content of the ink composition. By setting it within this range, the curability is improved, the solvent resistance is improved, and a film having no problem with brittleness can be formed.

<(B) Polymerization initiator>
The ink composition of the present invention contains (B) a polymerization initiator that generates an acid upon irradiation with active energy rays (radiation). Examples of the polymerization initiator that can be used in the present invention include photocationic polymerization initiators, photodecoloring agents for dyes, photochromic agents, and light used in microresists (400 to 200 nm ultraviolet rays, far ultraviolet rays, particularly Preferably, a compound that generates an acid by irradiation with g-line, h-line, i-line, KrF excimer laser light), ArF excimer laser light, electron beam, X-ray, molecular beam, ion beam, or the like is appropriately selected and used. be able to.
In the ink composition of the present invention, as described above, it is preferable to select a polymerization initiator having sensitivity to ultraviolet rays because ultraviolet irradiation is suitable.

  Such polymerization initiators include onium salt compounds such as diazonium salts, phosphonium salts, sulfonium salts, iodonium salts, imide sulfonates, oxime sulfonates, diazodisulfones, disulfones, o which generate acids upon decomposition upon irradiation with radiation. -Sulfonate compounds, such as nitrobenzyl sulfonate, etc. can be mentioned. Examples of the polymerization initiator that can be used in the ink composition of the present invention, specific compounds, and preferable examples include compounds described in paragraphs [0066] to [0122] of JP-A-2008-13646. Which can be applied to the present invention.

  Preferred examples of the photocationic polymerization initiator that can be used in the present invention include compounds represented by the following formulas (b1), (b2), and (b3).

In the formula (b1), R ²⁰¹ , R ²⁰² , and R ²⁰³ each independently represents an organic group. X ⁻ represents a non-nucleophilic anion, preferably a sulfonate anion, a carboxylate anion, a bis (alkylsulfonyl) amide anion, a tris (alkylsulfonyl) methide anion, BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ or the following It includes such groups shown, preferably _{^{BF 4 -, PF 6 -,}} SbF 6 - is.

  Although the preferable compound example of the photocationic polymerization initiator which can be used for this invention is given below, this invention is not limited to these.

(B) A polymerization initiator can be used individually by 1 type or in combination of 2 or more types.
The content of the polymerization initiator (B) in the ink composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and still more preferably based on the total solid content of the ink composition. Is 1-7 mass%. By making it within this range, curability is improved, and peeling on the recording medium can be prevented when cured.

(Sensitizer)
A sensitizer that accelerates polymerization and curing may be further added to the ink composition of the present invention, and an anthracene compound is preferably used as the sensitizer. The anthracene compound may have a substituent.

When the anthracene has a substituent, examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, etc. Among them, an alkoxy group having 1 to 4 carbon atoms is particularly preferable. The number of anthracene substituents is preferably 1 to 4, more preferably 1 to 2. In particular, the position of the substituent in the case of 1 substitution is preferably 9-position, and the position of the substituent in the case of 2 substitution is preferably 9-position.
Among these, a 9,10-substituted anthracene compound which is the 9th and 10th positions in the case of 2 substitution is particularly preferable.

  In the present invention, a compound other than anthracene may be added with a sensitizing dye, and it can be used in combination with anthracene or independently. Examples of sensitizers other than anthracene according to the present invention include those belonging to the compounds listed below and having an absorption wavelength in a wavelength region of 350 nm to 450 nm.

  For example, polynuclear aromatics (eg, pyrene, perylene, triphenylene, 2-ethyl-9,10-dimethoxyanthracene, etc.), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal, etc.) , Cyanines (eg, thiacarbocyanine, oxacarbocyanine, etc.), merocyanines (eg, merocyanine, carbomerocyanine, etc.), thiazines (eg, thionine, methylene blue, toluidine blue, etc.), acridines (eg, Acridine orange, chloroflavin, acriflavine, etc.), anthraquinones (eg, anthraquinone, etc.), squaliums (eg, squalium, etc.), coumarins (eg, 7-diethylamino-4-methylcoumarin, etc.), etc. Mentioned That.

  The ink composition of the present invention may further contain a known compound having a function of further improving sensitivity or suppressing inhibition of polymerization by oxygen as a cosensitizer.

  Examples of 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 such as thiol compounds described in JP-A-53-702, JP-B-55-500806, and JP-A-5-142277, No. 56-75643, such as 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercapto. And naphthalene.

Other examples of the co-sensitizer include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in JP-B-48-42965 (eg, tributyltin acetate), JP-B 55- No. 34414, a hydrogen donor described in JP-A-6-308727 (eg, trithiane), a phosphorus compound described in JP-A-6-250387 (eg diethylphosphite), Examples include Si-H and Ge-H compounds described in 191605.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total amount (total mass) of the ink composition.

<(C) Vinyl ether compound or at least one compound of epoxy compound = specific polymerizable compound C>
The ink composition of the present invention includes (C) at least one compound of a vinyl ether compound or an epoxy compound (specific polymerizable compound C). Examples of the vinyl ether compound and the epoxy compound that are the specific polymerizable compound C include, for example, JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, and JP-A-2001. Monofunctional and polyfunctional vinyl ether compounds and epoxy compounds described in JP-A-310938, 2001-310937, and 2001-220526.

As the vinyl ether compound, any of monofunctional and polyfunctional compounds can be used. Specific examples and preferred examples are described in paragraphs [0042] to [0044] of JP-A-2008-13646. A compound etc. can be mentioned and these are applicable also to this invention.
Of these, di- or trivinyl ether compounds are preferable from the viewpoints of curability, adhesion to a recording medium, surface hardness of the formed image, and the like, and divinyl ether compounds are particularly preferable.

  Examples of the monofunctional vinyl ether compound include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, 4- Methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl Ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloro Examples thereof include ethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxy polyethylene glycol vinyl ether and the like.

Examples of the polyfunctional vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide. Divinyl ethers such as divinyl ether and bisphenol F alkylene oxide divinyl ether; trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol Vinyl ether, dipentaerythritol hexavinyl ether, ethylene oxide-added trimethylolpropane trivinyl ether, propylene oxide-added trimethylolpropane trivinyl ether, ethylene oxide-added ditrimethylolpropane tetravinyl ether, propylene oxide-added ditrimethylolpropane tetravinyl ether, ethylene oxide-added pentaerythritol And polyfunctional vinyl ethers such as tetravinyl ether, propylene oxide-added pentaerythritol tetravinyl ether, ethylene oxide-added dipentaerythritol hexavinyl ether, and propylene oxide-added dipentaerythritol hexavinyl ether.
Of the polyfunctional vinyl ether compounds described above, di- or trivinyl ether compounds are preferable from the viewpoints of curability, adhesion to a recording medium, surface hardness of the formed image, and the like, and particularly divinyl ether compounds are more preferable.

Examples of the epoxy compound that can be used in the polymerizable composition C of the present invention include aromatic epoxides, alicyclic epoxides, and aliphatic epoxides. Among these, alicyclic epoxides are preferable from the viewpoint of curability. .
As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is mentioned preferably.
Kinds of epoxides that can be used in the polymerizable composition C of the present invention, specific compounds, and preferable examples include compounds described in paragraph numbers [0037] to [0040] of JP-A-2008-13646. These can also be applied to the present invention.

  Examples of the monofunctional epoxy compound include phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, 1,2-butylene oxide, and 1,3-butadiene monooxide. 1,2-epoxydodecane, epichlorohydrin, 1,2-epoxydecane, styrene oxide, cyclohexene oxide, 3-methacryloyloxymethylcyclohexene oxide, 3-acryloyloxymethylcyclohexene oxide, 3-vinylcyclohexene oxide, etc. It is done.

Examples of the polyfunctional epoxy compound include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S di Glycidyl ether, epoxy novolac resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane, bis (3,4-epoxycyclohexyl) Rumethyl) adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3 ′, 4′-epoxy-6 '-Methylcyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane), dicyclopentadiene diepoxide, di (3,4-epoxycyclohexylmethyl) ether of ethylene glycol, ethylenebis (3,4-epoxycyclohexanecarboxylate) , Epoxyhexahydrophthalate dioctyl, epoxyhexahydrophthalate di-2-ethylhexyl, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, Resin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers, 1,1,3-tetradecadiene dioxide, limonene dioxide, 1,2,7,8-di Examples thereof include epoxy octane, 1,2,5,6-diepoxycyclooctane and the like.
Among these epoxy compounds, aromatic epoxides and alicyclic epoxides are preferable from the viewpoint of excellent curing speed, and alicyclic epoxides are more preferable.

In the ink composition of the present invention, as the specific polymerizable compound C, one kind of vinyl ether compound or epoxy compound may be used, or two or more kinds may be used in combination. Moreover, you may use together a vinyl ether compound and an epoxy compound.
The content of the specific polymerizable compound C in the ink composition is preferably 10 to 80% by mass, more preferably 15 to 70% by mass, and further preferably 25 to 55% by mass with respect to the total solid content of the ink composition. %. By being in this range, it becomes favorable in terms of both curability and brittleness.

(Other polymerizable compounds)
In the ink composition of the present invention, other polymerizable compounds other than the specific polymerizable compound A and the specific polymerizable compound C can be used as necessary. The polymerizable compound other than the above is not particularly limited as long as it is a compound that initiates a polymerization reaction upon irradiation with active energy rays and cures, and various known cationic polymerizable monomers known as photocationic polymerizable monomers are used. can do. 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. Other oxetane compounds not included in the specific polymerizable compound A described in each publication such as 220526 are listed.

  As other oxetane compounds not included in the specific polymerizable compound A, either monofunctional or polyfunctional can be used, and JP-A Nos. 2001-220526, 2001-310937, and 2003-341217. Any known oxetane compound can be arbitrarily selected and used. As the compound having an oxetane ring that can be used in combination with the specific polymerizable compound in the present invention, a compound having 1 to 4 oxetane rings in its structure is preferable. By using such a compound, it becomes easy to maintain the viscosity of the composition in a favorable range of handling properties, and when applied to an ink composition or the like, the cured composition and the recording medium High adhesion can be obtained. Specific types of oxetane compounds that can be used in the polymerizable composition of the present invention, specific compounds, and preferable examples thereof include specific polymerizable properties described in paragraphs [0045] to [0062] of JP-A-2008-13646. The compound etc. which are not contained in the compound A can be mentioned.

In the ink composition of the present invention, when other polymerizable compound is used in combination with the specific polymerizable compound A and the specific polymerizable compound C, the content ratio of the specific polymerizable compound A is based on the total amount of the polymerizable compound. It is preferably 10% by mass or more and 50% by mass or less, and more preferably 15% by mass or more and 35% by mass or less. That is, if the specific polymerizable compound A is within this range among all polymerizable compounds, the ink composition of the present invention can exhibit effects such as high sensitivity, excellent film properties, and solvent resistance.
The content ratio of the specific polymerizable compound C is preferably 10% by mass or more and 85% by mass or less, and more preferably 15% by mass or more and 75% by mass or less with respect to the total amount of the polymerizable compound.

  Further, in addition to the above, the ink composition of the present invention may include a colorant such as a pigment or a dye, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, a solvent, or a polymer compound surface active as necessary. An agent, a polymerization inhibitor, and the like can be added. I will state below.

(Coloring agent)
The ink composition of the present invention may contain a colorant depending on the purpose. Moreover, in the ink composition of this invention, it can be set as the ink composition which can form a visible image by adding a coloring agent.
The colorant that can be used in the ink composition of the present invention is not particularly limited, and various known color materials (pigments, dyes) can be appropriately selected and used depending on the application. For example, when forming an image excellent in weather resistance, a pigment is preferable. As the dye, both water-soluble dyes and oil-soluble dyes can be used, but oil-soluble dyes are preferred.

(Pigment)
First, a pigment that is preferably used as a colorant in the ink composition of the present invention will be described. When a pigment is used as the colorant, a colored image formed using the ink composition has excellent light resistance.
The pigment is not particularly limited, and all commercially available organic pigments and inorganic pigments or pigments dispersed in an insoluble resin or the like as a dispersion medium, or a resin is grafted on the pigment surface. Can be used. Moreover, what dye | stained the resin particle with dye can be used.
Examples of these pigments include, for example, “Pigment Dictionary” (2000), edited by Seijiro Ito. Herbst, K.M. Hunger “Industrial Organic Pigments”, JP 2002-12607 A, JP 2002-188025 A, JP 2003-26978 A, and JP 2003-342503 A3.
Specific examples of organic pigments and inorganic pigments that can be used in the present invention include compounds described in paragraph numbers [0126] to [0131] of JP-A-2008-13646, and these are also included in the present invention. Can be applied.

For dispersion of the pigment, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, a jet mill, a homogenizer, a paint shaker, a kneader, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, or a wet jet mill is used. Can do.
It is also possible to add a dispersant when dispersing the pigment. Examples of the dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a high molecular weight unsaturated acid ester, a high molecular weight copolymer, a modified polyacrylate, an aliphatic polyacrylate. Carboxylic acid, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester, pigment derivative and the like. It is also preferable to use a commercially available polymer dispersant such as Solsperse series manufactured by Lubrizol.
Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment.

  In the ink composition, as a dispersion medium for various components such as pigments, a solvent may be added, and the polymerizable compound which is a low molecular weight component without a solvent may be used as a dispersion medium. The ink composition of the invention is a radiation curable ink, and is preferably solvent-free in order to be cured after the ink is applied to a recording medium. This is because if the solvent remains in the cured ink image, the solvent resistance is deteriorated or a problem of VOC (Volatile Organic Compound) of the remaining solvent occurs. From such a viewpoint, a polymerizable compound is used as the dispersion medium, and among them, it is preferable to select a cationically polymerizable monomer having the lowest viscosity from the viewpoint of improving dispersibility and handling properties of the ink composition.

  The volume average particle diameter of the pigment particles in the ink composition is preferably 0.02 to 0.60 μm, more preferably 0.02 to 0.10 μm. Further, the maximum particle size is preferably 3 μm or less, more preferably 1 μm or less, and the selection of the pigment, dispersant, dispersion medium, dispersion conditions, and filtration conditions are set so as to be in such a range. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

(dye)
The dye can be appropriately selected from conventionally known compounds (dyes). Specific examples include compounds described in paragraph numbers [0023] to [0089] of JP-A No. 2002-114930 and paragraph numbers [0136] to [0140] of JP-A No. 2008-13646. These can also be applied to the present invention.

  The colorant is preferably added in an amount of 0.05 to 20% by mass, more preferably 0.2 to 10% by mass, based on the total mass of the ink composition. When an oil-soluble dye is used as the colorant, the content is particularly preferably 0.2 to 6% by mass with respect to the total mass (including the solvent) of the ink composition.

-UV absorber-
An ultraviolet absorber can be added to the ink composition of the present invention from the viewpoint of improving the weather resistance of the obtained cured product or image and preventing discoloration.
Examples of the ultraviolet absorber are described in JP-A Nos. 58-185677, 61-190537, JP-A-2-782, JP-A-5-97075, and JP-A-9-34057. Benzotriazole compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc., JP-B Nos. Cinnamic acid compounds described in JP-A-10-88106, JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, Special Tables The triazine compounds described in JP-A-8-501291, Research Disclosure No. Examples thereof include compounds described in US Pat. No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, and so-called fluorescent brighteners.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total amount (total mass) of the ink composition.

-Antioxidant-
An antioxidant may be added to the ink composition of the present invention to improve stability. Examples of the antioxidant include European published patents, 223739, 309401, 309402, 310551, 310552, 359416, and 3435443. JP, 54-85535, 62-262417, 63-113536, 63-163351, JP-A-2-262654, JP-A-2-71262, Examples thereof include those described in Kaihei 3-121449, JP-A-5-61166, JP-A-5-119449, US Pat. No. 4,814,262, US Pat. No. 4,980,275, and the like.
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total amount (total mass) of the ink composition.

-Anti-fading agent-
In the ink composition of the present invention, various organic and metal complex anti-fading agents can be used. Examples of the organic anti-fading agent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. Examples of the metal complex anti-fading agent include nickel complexes and zinc complexes. No. 17643, No. VII, I to J, i. 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in No. 15162 and the compounds included in the general formulas and compound examples of representative compounds described in JP-A-62-215272, pages 127 to 137 can be used. .
The addition amount is appropriately selected according to the purpose, but is generally about 0.01 to 10% by mass with respect to the total amount (total mass) of the ink composition.

-Conductive salts-
The ink composition of the present invention is added with conductive salts such as potassium thiocyanate, lithium nitrate, ammonium thiocyanate, and dimethylamine hydrochloride for the purpose of controlling ejection properties, particularly when used in an ink composition for inkjet recording. can do.

-Solvent-
It is also effective to add a very small amount of an organic solvent to the ink composition of the present invention in order to improve the adhesion between a solid surface such as a recording medium and a cured product or a formed image.
Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, and diethyl ketone, alcohol solvents such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, and tert-butanol, and chlorine such as chloroform and methylene chloride. Solvents, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, butyl acetate and isopropyl acetate, ether solvents such as diethyl ether, tetrahydrofuran and dioxane, glycols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether And ether solvents.
In this case, it is effective to add in a range where the solvent resistance does not deteriorate, and the amount is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass with respect to the entire ink composition. It is.

-Polymer compound-
Various polymer compounds can be added to the ink composition of the present invention in order to adjust film physical properties. High molecular compounds include acrylic polymers, polyvinyl butyral resins, polyurethane resins, polyamide resins, polyester resins, epoxy resins, phenol resins, polycarbonate resins, polyvinyl butyral resins, polyvinyl formal resins, shellacs, vinyl resins, acrylic resins. Rubber resins, waxes and other natural resins can be used. Two or more of these may be used in combination. Of these, vinyl copolymer obtained by copolymerization of acrylic monomers is preferred. Furthermore, a copolymer containing “carboxyl group-containing monomer”, “methacrylic acid alkyl ester”, or “acrylic acid alkyl ester” as a structural unit is also preferably used as the copolymer composition of the polymer binder.

-Surfactant-
The ink composition of the present invention preferably contains a known surfactant. Examples of known surfactants include those described in JP-A Nos. 62-173463 and 62-183457. Specifically, for example, anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene -Nonionic surfactants such as polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. An organic fluoro compound may be used instead of the known surfactant. The organic fluoro compound is preferably hydrophobic. Examples of the organic fluoro compounds include fluorine surfactants, oily fluorine compounds (eg, fluorine oil) and solid fluorine compound resins (eg, tetrafluoroethylene resin). No. (columns 8 to 17) and those described in JP-A Nos. 62-135826.

-Polymerization inhibitor-
Polymerization inhibitors include phenolic hydroxyl group-containing compounds, quinones, N-oxide compounds, piperidine-1-oxyl free radical compounds, pyrrolidine-1-oxyl free radical compounds, N-nitrosophenylhydroxylamines, And a compound selected from the group consisting of cationic dyes.

Specifically, hydroquinone monoalkyl ethers such as hydroquinone monomethyl ether and hydroquinone monobutyl ether, 4,4′-thiobis (3-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-methyl-6- A hindered phenol such as t-butylphenol is preferred.
The content of the polymerization inhibitor in the ink composition is preferably 50 to 30000 ppm, more preferably 100 to 10000 ppm, and more preferably 100 to 3000 ppm with respect to the total amount (total mass) of the ink composition.

In addition to the above, the ink composition of the present invention includes, for example, leveling additives, matting agents, waxes for adjusting film physical properties, and adhesion to recording media such as polyolefin and PET. In order to improve this, a tackifier or the like that does not inhibit the polymerization can be contained.
As the tackifier, specifically, a high-molecular-weight adhesive polymer described in JP-A-2001-49200, 5-6p (for example, (meth) acrylic acid and an alkyl group having 1 to 20 carbon atoms). Copolymers composed of esters with alcohols having an ester, esters of (meth) acrylic acid with alicyclic alcohols having 3 to 14 carbon atoms, and esters of (meth) acrylic acid with aromatic alcohols having 6 to 14 carbon atoms And low molecular weight tackifying resin having a polymerizable unsaturated bond.

<Preferred physical properties of ink composition>
When the ink composition of the present invention is applied to inkjet recording, the ink viscosity at the temperature at the time of ejection is preferably 5 to 30 mPa · s, and more preferably 7 to 20 mPa · s, in consideration of ejection properties. For this reason, it is preferable to adjust and determine a composition ratio suitably so that it may become the said range.
The viscosity of the ink composition at room temperature (25 to 30 ° C.) is preferably 7 to 120 mPa · s, and more preferably 10 to 80 mPa · s. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be prevented, uncured monomer can be reduced, and odor can be reduced. Dot bleeding at the time of landing can be suppressed, and as a result, image quality can be improved.

  The surface tension of the ink composition of the present invention is preferably 20 to 40 mN / m, and more preferably 20 to 30 mN / m. In addition, when recording the ink composition of the present invention on various recording media such as polyolefin, PET, coated paper, and uncoated paper, the surface tension is preferably 20 mN / m or more from the viewpoint of bleeding and penetration, and is wet. From the viewpoint of properties, it is preferably 30 mN / m or less.

The ink composition of the present invention can be suitably used as an ink for inkjet recording. There are no particular restrictions on the ink jet recording method, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezo element, and an electrical signal that is acoustic Either an acoustic ink jet system that irradiates ink by irradiating it with ink instead of using a beam, or a thermal ink jet system that uses ink to form bubbles by heating the ink and use the generated pressure. Also good. The inkjet recording method includes a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent. A method using ink is included.
Among the above, the ink composition of the present invention is suitable as a drop-on-demand ink jet recording ink using a piezoelectric element.

<Inkjet recording method>
Next, an ink jet recording method that can be suitably employed in the image recording method of the present invention will be described below.

  The image forming method in the present invention includes (a) a step of ejecting the ink composition of the present invention onto a recording medium, and (b) irradiating the ejected ink composition with active energy rays to form an ink composition. It is preferable that the inkjet recording method includes a step of curing the product.

System As an ink jet recording system for ejecting ink, a form as shown in Japanese Patent Application Laid-Open No. 2002-11860 is given as an example, but the invention is not limited to this, and other forms may be used.

Ink holding means As a means for holding ink, it is preferable to fill a known ink cartridge, and it can be stored in a deformable container and used as a tank as disclosed in JP-A-5-16377. It is. Further, as disclosed in Japanese Patent Laid-Open No. 5-16382, if a sub tank is provided, the supply of ink to the head is further stabilized. Further, as disclosed in JP-A-8-174860, it is also possible to use a cartridge that supplies ink by moving a valve when the pressure in the ink supply chamber decreases. As a negative pressure applying method for appropriately maintaining the meniscus in the head with these ink holding means, a method based on the height of the ink holding means, that is, water head pressure, a method based on the capillary force of the filter provided in the ink flow path, In addition, a method of controlling the pressure with a pump or the like, and a method of holding the ink on the ink absorber and applying a negative pressure by this capillary force as disclosed in Japanese Patent Application Laid-Open No. 50-74341 are suitable. is there.

Ink supply path As a method of supplying ink from these ink holding means to the head, a method of directly connecting the holding means to the head unit or a method of connecting by a flow path such as a tube may be used. The ink holding means and the flow path are preferably made of a material having good wettability with respect to the ink or subjected to a surface treatment.

-As a method of ejecting head ink, as disclosed in Japanese Patent Laid-Open No. 5-104725, ink droplets are continuously ejected, and the droplets are deflected according to the image to land on the recording material. Alternatively, a method of selectively controlling whether or not to perform the operation may be used, or a so-called on-demand method, in which ink droplets are ejected only to a portion necessary as an image, may be used. As disclosed in JP-A-5-16349, the on-demand system may be a system that generates and discharges ink pressure by deformation of a structure using a piezoelectric element or the like. As disclosed, it may be a method of discharging at a pressure generated by expansion accompanying vaporization by thermal energy. Further, as disclosed in Japanese Patent Application Laid-Open No. 2001-277466, a method of controlling ejection to a recording material by an electric field may be used.

  In the ink jet recording method, image recording is performed on a recording medium using the ink composition of the present invention, and there are no particular restrictions on the ink discharge nozzles used at that time, and it may be appropriately selected according to the purpose. it can. For example, a form described in JP-A-5-31908 can be applied to the nozzle. At this time, in order to eject ink of a plurality of colors, the nozzles are configured in a plurality of rows as described in JP-A-2002-316420, so that a color image can be formed at high speed. Furthermore, it is possible to further increase the speed by arranging a plurality of head units having a plurality of nozzle rows.

Further, as described in Japanese Patent Laid-Open No. 63-160849, the nozzles are arranged by a width equal to or larger than the width of the image to form a so-called line head, and the recording material is moved simultaneously with the droplet ejection from these nozzles. As a result, an image can be formed at high speed.
Further, the surface of the nozzle is subjected to a surface treatment as disclosed in Japanese Patent Laid-Open No. 5-116327, whereby it is possible to prevent ink droplets from adhering to the nozzle surface and ink droplets from adhering.

Even if such treatment is performed, dirt may still adhere, and therefore it is preferable to perform cleaning with a blade as disclosed in JP-A-6-71904.
In addition, the inks of the respective colors are not necessarily ejected from the nozzles uniformly, and specific inks may not be ejected for a long time. In such a case, in order to keep the meniscus stable, as disclosed in Japanese Patent Application Laid-Open No. 11-157102, ink is appropriately ejected outside the image area, and new ink is supplied to the head, thereby providing ink physical properties. Is preferably maintained at a suitable value.

Further, even if such treatment is performed, bubbles may enter the head or be generated in the head. In such a case, as described in JP-A-11-334092, by forcibly sucking ink from outside the head, the ink whose physical properties have changed is discarded, and bubbles are also discharged outside the head. be able to. In the case where the droplets are not ejected for a long time, the nozzle surface can be protected by covering the nozzle surface with a cap as disclosed in JP-A-11-138830. Even if these measures are taken, there is a case where the liquid is still not discharged.
If an image is printed in a state where some of the nozzles do not discharge, problems such as unevenness in the image occur. In order to avoid such a situation, it is effective to take a measure by detecting that no discharge has occurred, as disclosed in Japanese Unexamined Patent Publication No. 2000-343686.

  When the head unit is mechanically moved as described in Japanese Patent Laid-Open No. 6-115099 and the recording material is intermittently moved in the orthogonal direction in synchronization with the head unit, This has the effect of making it difficult to see the unevenness caused by the inaccuracy of the intermittent movement of the material, and can achieve high image quality. At this time, the relationship between the image quality and the recording speed can be set to a preferable relationship by appropriately setting the relationship between the moving speed of the head, the moving amount of the recording material, and the number of nozzles.

  On the other hand, the same effect can be obtained by fixing the head and mechanically reciprocating the recording material in a predetermined direction and intermittently moving the recording material in a direction orthogonal thereto.

-Temperature control The ink jet recording apparatus is preferably provided with a means for stabilizing the ink composition temperature, and the part to be kept at a constant temperature is a piping system from the ink tank (intermediate tank if there is an intermediate tank) to the nozzle ejection surface, All of the members are targeted.

  In the inkjet recording method, the ink composition is heated to 40 to 80 ° C., and the viscosity of the ink composition is reduced to 30 mPa · s or less, preferably 20 mPa · s or less, and then ejected. By using this, high injection stability can be realized. In general, radiation curable ink compositions generally have a higher viscosity than aqueous inks, so that the viscosity fluctuation range due to temperature fluctuations during printing is large. This viscosity variation of the ink composition directly affects the droplet size and droplet ejection speed as it is, which causes image quality deterioration. Therefore, it is necessary to keep the ink composition temperature as constant as possible during printing. is there. For this purpose, it is preferable to have an ink temperature detecting means, an ink heating means, and a control means for controlling heating according to the detected ink temperature.

The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the ink composition flow rate and the environmental temperature. 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 thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.
Alternatively, it is also preferable to have means for controlling energy applied to the means for ejecting ink according to the ink temperature.

  The control range of the ink composition temperature is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and further preferably set temperature ± 1 ° C.

-Exposure As the light source, a commonly used mercury lamp, metal halide lamp, or the like may be used, or a light emitting diode, a semiconductor laser, a fluorescent lamp, or the like may be used. Further, a hot cathode tube, a cold cathode tube, an electron beam, an X-ray or the like, a light source in which a polymerization reaction of the ink proceeds, an electromagnetic wave, or the like can be used, and these become an active energy ray source.

When using a metal halide lamp, the lamp should be designed 10~1000W / cm ^2, it is preferable that the illuminance of ^1mW / cm ^{2 ~100W} / cm 2 at the recording material surface.
Further, since high pressure mercury lamps, metal halide lamps and the like generate ozone with discharge, it is preferable to have an exhaust means. The exhaust means is preferably arranged so as to also collect ink mist generated during ink ejection.

  Next, preferable irradiation conditions of active energy rays will be described. A basic irradiation method is disclosed in JP-A-60-132767. Specifically, light sources are provided on both sides of the head unit, and the head and the light sources are scanned by a shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. International Publication No. 99/54415 pamphlet discloses a method using an optical fiber and a method of irradiating a recording unit with UV light by applying a collimated light source to a mirror surface provided on the side of the head unit. In the present invention, these irradiation methods can be used.

  When active energy rays for curing are applied to the ink discharge nozzles, ink mist attached to the surface of the nozzle surface may solidify and hinder ink discharge. In order to keep it, it is preferable to take measures such as shading. Specifically, it is preferable to provide a partition wall that prevents the nozzle plate from being irradiated, or to provide means for limiting the incident angle to the recording material so as to reduce stray light.

  In the present invention, the time from landing to irradiation is desirably 0.01 to 0.5 seconds, preferably 0.01 to 0.3 seconds, and more preferably 0.01 to 0.15 seconds later. Is to irradiate. Thus, by controlling the time from landing to irradiation to an extremely short time, it is possible to prevent the landing ink from bleeding before being cured. Also, since the ink composition can be exposed to a porous recording medium before it penetrates deeper than the light source reaches, unreacted monomer remains, and as a result, odor can be reduced. Can do. By using the inkjet recording method described above and the ink composition of the present invention in combination, a great synergistic effect is brought about. By adopting such a recording method, 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.

System parameters In forming an image, the ink landing diameter on the recording material is preferably between 10 and 500 μm, and for this purpose, the diameter of the ink droplets during ejection is from 5 to 250 μm. In this case, the nozzle diameter is preferably 15 to 100 μm.
In order to form an image, the number of pixels per inch is preferably 50 to 2400 dpi, and for that purpose, the nozzle density of the head is preferably 10 to 2400 dpi. Here, even if the nozzle density of the head is low, high-density landing can be achieved with a head with a large nozzle interval by tilting with respect to the recording material conveyance direction or by displacing multiple head units relative to each other. Is possible. In addition, by reciprocating the head or the recording material as described above, each time the head moves at a low nozzle pitch, the recording material is conveyed by a predetermined amount, and ink droplets are landed at different positions, thereby recording high-density images. Can be realized.

The amount of ink droplets to be recorded on the recording material is preferably controlled to an arbitrary amount between 0.05 and 25 g / m ² in order to express a good gradation. It is preferable to control the size and / or quantity of the ejected ink droplets from.

  If the distance between the head and the recording material is too wide, the flying of the ink droplets is disturbed by the air flow accompanying the movement of the head or the recording material, and the landing position accuracy decreases. On the contrary, if the interval is narrow, there is a risk that the head and the recording material come into contact with each other due to unevenness of the recording material, vibration due to the transport mechanism, and the like, and it is preferable to maintain the recording material at about 0.5 to 2 mm.

-Ink set The ink may be a single color, cyan, magenta, yellow, or four colors including black, or a specific color other than these called special color. Also good. The coloring material may be a dye or a pigment. These inks may be ejected in order of landing in order of increasing lightness, may be landed in order of increasing lightness, or are preferably ejected in an order suitable for image recording quality.

When the colors are stacked in order from the lightest color, the active energy ray easily reaches the lower ink, and it is difficult for inhibition of curing sensitivity, increase of residual monomers, generation of odor, and deterioration of adhesion. Irradiation can be performed by injecting all colors and exposing them together, but exposure for each color is preferable from the viewpoint of curing acceleration.
The image signal to be recorded is preferably subjected to signal processing to obtain good color reproduction, as described in, for example, Japanese Patent Laid-Open No. 6-210905.

  The ink composition of the present invention can be used not only for inkjet recording but also for three-dimensional modeling, and can also be used for can printing and food. For these uses, it is possible to form an image using a known method. For example, the description in Japanese Patent No. 2679586 can be referred to.

-Recording medium-
As a recording medium to be recorded using the ink composition of the present invention, both an ink-permeable recording medium and an ink-impermeable recording medium can be used. Examples of the ink-permeable recording medium include plain paper, inkjet exclusive paper, coated paper, electrophotographic co-paper, cloth, non-woven fabric, porous film, and polymer absorber. These are described as “recording materials” in Japanese Patent Application Laid-Open No. 2001-181549.

  Examples of the ink-impermeable recording medium include art paper, synthetic resin, rubber, resin-coated paper, glass, metal, earthenware, and wood. In addition, in order to add each function, a base material obtained by combining a plurality of these materials can be used.

  As the synthetic resin, any synthetic resin can be used. For example, polyethylene terephthalate and polyester such as polybutadiene terephthalate; polyolefin such as polyvinyl chloride, polystyrene, polyethylene, polyurethane, and polypropylene; and acrylic resin, Examples include polycarbonate, acrylonitrile-butadiene-styrene copolymer, cellulose diacetate, cellulose triacetate, polyimide, cellophane, and celluloid.

  The shape (thickness) of the base material using the synthetic resin may be a film shape, a card shape or a block shape, and can be appropriately selected according to a desired purpose without particular limitation. These synthetic resins may be transparent or opaque. As the usage form of the synthetic resin, it is one of the preferred forms used in the form of a film used for so-called soft packaging, and various non-absorbable plastics and films thereof can be used. Examples of plastic films include polyethylene terephthalate (PET) film, biaxially oriented polystyrene (OPS) film, biaxially oriented polypropylene (OPP) film, biaxially oriented nylon (ONy) film, and polyvinyl chloride (PVC). A film, a polyethylene (PE) film, and a triacetyl cellulose (TAC) film can be mentioned.

  Examples of the resin-coated paper include a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both sides of the paper are laminated with a polyolefin resin, and both sides of the paper are laminated with a polyolefin resin. A paper support is particularly preferred.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

(Synthesis example)
A synthesis scheme of the specific polymerizable compound (1-1) is shown below.
i) Synthesis of Oxetane Compound (1-1b) Having Mesyl Group 3-ethyl-3-oxetanemethanol (1-1a below, manufactured by Tokyo Chemical Industry Co., Ltd.) 87.1 g (0.75 mol) in 250 mL of ethyl acetate After cooling to 0 ° C., 90.2 g (0.79 mol) of methanesulfonyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was added with stirring, and then 89.0 g (11.3 mol) of pyridine (manufactured by Wako Pure Chemical Industries, Ltd.) was added. The solution was added dropwise while maintaining the internal temperature in the range of 0 ° C to 15 ° C. After completion of the dropwise addition, the mixture was stirred at 25 ° C. for 4 hours, then cooled to 0 ° C., 350 mL of distilled water was added, the temperature was raised again to 25 ° C., and the mixture was stirred for 10 minutes. The reaction solution was transferred to a separatory funnel to remove the aqueous layer, and the organic layer was washed twice with 200 mL of 0.5 mol / L hydrochloric acid and then with 200 mL of saturated brine, dried over anhydrous sodium sulfate, and the solvent was distilled off under reduced pressure. This gave 122 g (yield 83%) of a crude product (yellow liquid) of compound (1-1b). The obtained compound (1-1b) was directly used for the synthesis of the specific polymerizable compound A (1-1) without purification.

ii) Synthesis of specific polymerizable compound A (1-1)
A diol sulfoxide (non-optically active substance) 1-1c 10.5 g (0.074 mol) of dimethyl sulfoxide synthesized by the method described in J. Org. Chem. 41; 1976; After adding 18.2 g (0.162 mol) of t-butoxide (manufactured by Wako Pure Chemical Industries, Ltd.) in 5/5 portions, the mixture was stirred at room temperature (about 25 ° C.) for 20 minutes. This solution was heated to 35 ° C., and 31.6 g (0.163 mol) of (1-1b) obtained in the above synthesis example was added dropwise while maintaining the internal temperature in the range of 35 ° C. to 55 ° C., and the addition was completed. Thereafter, the mixture was stirred at 60 ° C. for 30 minutes. The reaction solution is poured into 200 mL of distilled water, extracted with 150 mL of ethyl acetate, washed with 100 mL of water and 100 mL of saturated brine, dried over anhydrous sodium sulfate, and the solvent is distilled off under reduced pressure to contain the compound (1-1). A crude product was obtained. The obtained crude product was purified by silica gel chromatography to obtain 11.5 g (yield 46%) of compound (1-1) as a colorless transparent liquid.
It was confirmed by ¹ H-NMR (CDCl ₃ , 300 MHz) that the obtained compound corresponds to the specific polymerizable compound A and was a compound 1-1 (position and stereoisomer mixture) having the following structure. ¹ H-NMR δ: 0.91 (t, 6H), 1.2-1.8 (m, 10H), 2.4-2.7 (m, 2H), 3.5-4.2 ( m, 14H)

(Preparation of pigment dispersion)
C. I. Pigment Red 122 (Chromoval Jet Magenta DMQ, manufactured by Ciba Specialty Chemicals) 20% by mass, 3-ethyl-3-phenoxymethyloxetane (a polymerizable compound other than the specific polymerizable compound A and the specific polymerizable compound C) OXT-211) 72% by mass, and 8% by mass of a dispersant (SOLSPERSE 32000 manufactured by Lubrizol) were placed in a ball mill at this composition ratio, and dispersed for 16 hours using zirconia beads having a diameter of 0.6 mm. Thus, a pigment dispersion was obtained.

[Example 1]
The prepared pigment dispersion, specific polymerizable compound A, specific polymerizable compound C, polymerization initiator, sensitizing dye, and the like are mixed so as to have the following composition, stirred with a high-speed water-cooled stirrer, and used for UV inkjet A magenta ink composition was obtained.
Colorant: C.I. I. Pigment Red 122 (Chromoval Jet Magenta DMQ manufactured by Ciba Specialty Chemicals) 5.0 parts Dispersant: (Solsperse 32000 manufactured by Lubrizol Corporation) 2.0 parts Compound (1-1) which is the specific polymerizable compound A 25.0 parts · Photocationic polymerization initiator (structure B-1 below): (Tris (4-chlorophenyl) sulfonium hexafluorophosphate) 5.0 parts · Sensitizing dye: 9,10-butoxyanthracene (Kawasaki Chemical Industries) 3.0 parts / epoxy compound as specific polymerizable compound C: limonene dioxide (Delcel Chemical Industries, Celoxide 3000) 35.0 parts / other polymerizable compounds (OXT-211, Toagosei Co., Ltd.) 40 .0 part

[Examples 2-6, Comparative Examples 1-3]
In the formulation of Example 1, the ink composition of Example 1 was changed except that the types and amounts of the specific polymerizable compound A, the specific polymerizable compound C, and other polymerizable compounds were changed to the compositions shown in Table 1. In the same manner as the adjustment, the ink compositions of Examples 2 to 6 and Comparative Examples 1 to 3 were prepared.

The compounds used in Examples 2 to 6 and Comparative Examples 1 to 3 in Table 1 are as follows.
1-6: 1-6 exemplified for specific polymerizable compound A
1-8: 1-8 exemplified for specific polymerizable compound A
C-1: an oxetane compound having a condensed ring structure described in JP-A-2004-250434, and does not correspond to the specific polymerizable compound A of the present invention. The structure is shown below.
OXT-221: Bis (3-ethyl-3-oxetanylmethyl) ether (manufactured by Toagosei Co., Ltd.) Not applicable to the specific polymerizable compound A of the present invention.
DVE-3: Triethylene glycol divinyl ether (ISP Europe)
Celoxide 3000 and DVE-3 correspond to the specific polymerizable compound C of the present invention.

  The following printing and exposure were performed using the ink compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 3, and the sensitivity, ejection stability, and brittleness were evaluated by the following methods. The evaluation results are shown in Table 2.

(Printing, exposure)
Each ink composition was ejected using a piezo ink jet head. The head has a nozzle density of 150 per 25.4 mm and has 318 nozzles. By fixing these two nozzles in the nozzle row direction with a shift of 1/2 of the nozzle interval, the nozzle arrangement direction is placed on the recording medium. 300 drops per 25.4 mm.

The head and ink are controlled so that the vicinity of the ejection portion is 50 ± 0.5 ° C. by circulating hot water in the head. Ink ejection from the head is controlled by a piezo drive signal applied to the head, and can eject 6 to 42 pl per drop. In this embodiment, the medium is a recording medium at a position 1 mm below the head. Are ejected from the head while being conveyed. The conveyance speed can be set in the range of 50 to 200 mm / s. The piezo drive frequency can be up to 4.6 kHz, and the droplet ejection amount can be controlled by these settings.
By setting the conveyance speed to 90 mm / s and the drive frequency to 1.9 kHz, the ink ejection amount was controlled to 24 pl, and 10 g / m ² was ejected to obtain a solid print image.

After the droplets were ejected, the media were transported to an exposure section and exposed by an ultraviolet light emitting diode (UV-LED). As the UV-LED, NCCU033 (trade name) manufactured by Nichia Corporation was used. This LED outputs ultraviolet light having a wavelength of 365 nm from one chip. When a current of about 500 mA is applied, light of about 100 mW is emitted from the chip. A plurality of these are arranged at intervals of 7 mm, and a power of 0.3 W / cm ² is obtained on the surface of the medium that is the recording medium. The exposure time after the droplet ejection and the exposure time can be changed according to the transport speed of the medium and the distance between the head and the LED in the transport direction. In this embodiment, the exposure is performed about 0.5 seconds after landing. Depending on the setting of the distance to the medium and the conveyance speed, the exposure energy on the medium can be adjusted between 0.01 and 15 J / cm ² . In this embodiment, the exposure energy is adjusted according to the conveyance speed. For the measurement of exposure power and exposure energy, a spectroradiometer URS-40D (trade name) manufactured by USHIO ELECTRIC CO., LTD. Was used, and a value obtained by integrating between wavelengths 220 to 400 nm was used. In this evaluation, a PET film or a sheet made of polyvinyl chloride is used as a recording medium. H. Conducted in a 60% environment. The thickness of the cured image was 19 μm.

(1. Evaluation of sensitivity)
Each ink composition was printed on a sheet made of polyvinyl chloride using the above-mentioned apparatus, the integrated exposure was adjusted by changing the conveyance speed, and the ink was cured to obtain a printed matter. The exposure energy in curing was measured with a light quantity accumulator (UV Power MAP manufactured by EIT). Curability was determined by finger pitting for surface stickiness of the printed matter, and the minimum integrated exposure amount at which stickiness disappeared was evaluated according to the following criteria.
A: 100mJ / cm ² less B: 100mJ / cm ² or more 250 mJ / cm ² less than C: 250mJ / cm ² or more 400 mJ / cm ² less than D: 400mJ / cm ² or more 700 mJ / cm ² less than E: 700mJ / cm ² or more Practically, the sensitivity needs to be B or higher, and A is particularly preferable.

(2. Evaluation of brittleness)
A sample obtained by printing each ink composition on 175 μm PET was punched with a two-hole punch (Type C, trade name, manufactured by MAX), the state of the punched circular surface was observed, and evaluated according to the following criteria.
Rank 5: No peeling is observed.
Rank 4: A portion of the periphery is missing.
Rank 3: A part of the periphery is peeled off.
Rank 2: The periphery is peeled off.
Rank 1: The surface peels off.
Practically, the brittleness evaluation is required to be 3 or more, preferably 4 or more, and more preferably 5.

(3. Evaluation of solvent resistance of cured film)
According to the inkjet recording method, an A6 size solid image having an average film thickness of 12 μm was drawn. The cured film was rubbed five times with a cotton swab sufficiently containing isopropyl alcohol, and the degree of peeling of the cured film was evaluated. The evaluation criteria are as follows.
A: The cured film is not peeled off at all.
B: The cotton swab is lightly colored.
C: The upper surface of the cured film is peeled off and the color of the ink surface becomes light.
D: The cured film is peeled down to the bottom, and the support is exposed.

From the results shown in Table 2, the ink compositions of Examples 1 to 6 which are ink compositions containing the specific polymerizable compound of the present invention are all good in sensitivity, brittleness and solvent resistance. I understand. On the other hand, it can be seen that Comparative Examples 1 to 3 which do not use the present invention are particularly inferior in solvent resistance as compared with Examples, and Comparative Examples 2 and 3 have lower sensitivity.
Further, when Example 1 is compared with Example 3, Example 1 has higher sensitivity, and it is more preferable to use a compound having a structure represented by the general formula (3) among the specific polymerizable compounds of the present invention. It turns out that a result is obtained.
Furthermore, when the content of the specific polymerizable compound is within a preferable range from the comparison between Example 1, Example 4, and Example 5, good results can be obtained in any of sensitivity, brittleness, and solvent resistance. I understand.

Claims (7)

(A) An ink composition comprising an oxetane compound represented by the following general formula (1), (B) a polymerization initiator, and (C) a vinyl ether compound or an epoxy compound.

In the general formula (1), R ¹ and R ² each independently represent a group having an oxetane skeleton. m represents an integer of 1 to 3, n represents an integer of 0 to 2, and (m + n) is 2 or 3. A represents a (m + n) -valent group containing an aliphatic bicyclo ring or tricyclo ring in which the elements forming the ring are composed of only carbon atoms. The ink composition according to claim 1, wherein A in the general formula (1) is an (m + n) -valent group including a skeleton represented by the following (2).
The ink composition according to claim 1, wherein the oxetane compound represented by (A) the general formula (1) is a compound represented by the following general formula (3) or the general formula (4).

In General Formula (3) and General Formula (4), R ³ to R ⁶ each independently represent a group having an oxetane skeleton.   (A) The content of the oxetane compound represented by the general formula (1) is 10% by mass or more and less than 50% by mass with respect to the total mass of the polymerizable compound. The ink composition described in 1.   The ink composition according to any one of claims 1 to 4, which is an ink for inkjet recording.   The ink composition according to any one of claims 1 to 5, which is cured by irradiation with an active energy ray.   (A) a step of ejecting the ink composition according to any one of claims 1 to 6 onto a recording medium; and (b) irradiating the ejected ink composition with active energy rays. And a step of curing the ink composition.