JP2006274078A - Ink composition and image-forming method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance light resistance of a photocurable dye ink composition. <P>SOLUTION: The ink composition comprises a dye and a vinyl ether group-containing compound and an oxetane group-containing compound as polymerizable compounds. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink composition and an image forming method using the same, and more particularly to an ink composition that can be polymerized and cured after recording and suitable for recording a robust image and an image forming method using the same.

  As an ink having fading resistance and the like, a UV ink that is cured by irradiation with ultraviolet rays (UV) and has a UV light shielding property is known (for example, see Patent Document 1). Curing using such an ink is widely used in systems utilizing a radical polymerization system of monomer components, and acrylate monomers are generally used as monomer components (see, for example, Patent Documents 2 to 4). ).

  As described above, in the case of curing using a radical polymerization reaction, in the ink field, radical polymerization is generally susceptible to polymerization inhibition by oxygen, and the side of the recording material to which ink is applied when performing image recording. In general, a layer having an oxygen blocking function or the like is not provided, and since the ink viscosity is low, the polymerization is greatly inhibited by the presence of oxygen.

Therefore, in general, in the ink field where recording is performed in the presence of oxygen, the curing speed tends to be greatly reduced, or the ink physical properties after curing, specifically, the light resistance of the image tends to be greatly impaired.
Of the coloring materials, it is widely known that dyes tend to fade when exposed to light. However, as described above, if the light resistance of the image after curing is insufficient, the image is stable for a long period of time. Can not hold on. Therefore, the commercial value of such an ink as a recording material is remarkably lowered, and it is substantially unsuitable for image recording applications. Therefore, in reality, inks using pigments rather than dyes are widely provided as coloring materials for inks.

  On the other hand, curing using a cationic polymerization reaction is less susceptible to polymerization inhibition by oxygen as in a radical polymerization reaction, but generally has a problem that the polymerization rate is slower than that in the case of radical polymerization. Therefore, it is not necessarily suitable as a photo-curing type polymerization form, and is not widely used for applications requiring rapid curing. For example, in the ink field, the quick drying of the ink after recording is obtained, the improvement of the recording speed is required as one of the technical problems in image recording, and the recorded image is clear and stable. In general, a radical polymerization system is used rather than a cationic polymerization system.

That is, when using a dye that easily fades when exposed to light, if the curing speed is slow as described above, the dye will fade before light is cured by light irradiation, and the desired hue, An image with a clear density cannot be obtained.
However, a cured product cured by cationic polymerization has a characteristic that it is superior in light resistance to a cured product by radical polymerization.

In relation to the above, an active energy ray-curable composition having a fast curing using a compound having an oxetane ring is disclosed (for example, see Patent Documents 5 to 6). There is also an example of a composition using a pigment together with the compound having an oxetane ring (see, for example, Patent Document 7). However, these all relate to applications that require rapid curing, such as paper and plastic coatings, and ink applications that use pigments as coloring materials. It is only what was constituted as an issue to improve.
Therefore, when dyes are still used as coloring materials, the formation of clear images with excellent hue (hue) and color density, and the technology for improving the light resistance of the formed images have not yet been established. is there.

  In addition, vinyl ether group-containing compounds are also known as polymerizable compounds, and the reaction of polymerizing and curing them generally proceeds rapidly. However, the cationic polymerization initiator used for cationic polymerization is ionic and polar, but the vinyl ether group-containing compound is nonpolar, so the solubility of the cationic polymerization initiator in the presence of the vinyl ether group-containing compound is small, The reaction tends to be difficult to proceed. Therefore, sufficient curing may not always be possible depending on the system.

JP 2003-221528 A JP 2003-246818 A JP 2003-292855 A Japanese Patent Laid-Open No. 9-183927 JP-A-7-53711 JP 7-62082 A JP 2004-143135 A

  As described above, radical polymerization can be rapidly cured, but light resistance is insufficient. On the other hand, cationic polymerization is more advantageous in terms of improving light resistance than radical polymerization. However, the curing speed until curing is slow, and simply selecting a vinyl ether compound does not provide an effect of improving curability. As a result, according to the conventional technology, in a system using a dye, there is a technology that can record a clear image with a good hue and color density and has a high light resistance. It has not yet been proposed.

  The present invention has been made in view of the above, and in a photocurable ink composition using a dye as a coloring material, it is excellent in curability by cationic polymerization (including the degree of curing and the curing rate) and is comparable to a pigment. To provide an ink composition having a high degree of light resistance and an image forming method using the ink composition and capable of forming an image having excellent hue and color density and having excellent light resistance. The purpose is to achieve the purpose.

In the present invention, the image after polymerization and curing is superior in fastness to light when it is based on cationic polymerization rather than radical polymerization, and is improved in light resistance and curability including fading at the time of cationic polymerization upon exposure (curing degree). For example, a combination of a vinyl ether group-containing polymerizable compound and an oxetane group-containing polymerizable compound is effective. In particular, a magenta dye that easily fades with light is used. It was obtained based on the knowledge that the system was particularly effective.
Specific means for achieving the above object are as follows.

<1> An ink composition comprising a dye, a vinyl ether group-containing compound, an oxetane group-containing compound, and a cationic polymerization initiator.
<2> The ink composition according to <1>, wherein the dye is an oil-soluble dye.
<3> The ink composition according to <2>, wherein the oil-soluble dye has an oxidation potential nobler than 1.0 V (vs SCE).

<4> The ink composition according to <2> or <3>, wherein the oil-soluble dye is the following magenta dye and / or a substitute thereof.

<5> The ink composition according to any one of <1> to <4>, which is used for inkjet recording.
<6> An image recording step of recording an image on a recording material using the ink composition according to any one of <1> to <5>, and irradiating the recorded image with active energy rays And an image curing process for curing.
<7> The image forming method according to <6>, wherein the image recording step includes inkjet recording of the image by discharging the ink composition.

  According to the present invention, in a photocurable ink composition using a dye as a coloring material, the ink is excellent in curability by cationic polymerization (including the degree of cure and the cure speed) and has a high light resistance comparable to that of a pigment. The composition and the ink composition can be used to provide an image forming method capable of forming an image having excellent hue and color density and excellent in light resistance.

  Hereinafter, the ink composition of the present invention and the image forming method using the same will be described in detail.

<Ink composition>
The ink composition of the present invention contains a dye, a vinyl ether group-containing compound and an oxetane group-containing compound (hereinafter sometimes collectively referred to as “polymerizable compound according to the present invention”) and a cationic polymerization initiator. Thus, after recording an image on the recording material, the recorded image can be cured by irradiation with an active energy ray. Moreover, it can comprise using other components, such as other polymeric compounds other than the polymeric compound concerning this invention, and various additives other than the said component as needed.

-Vinyl ether group-containing / oxetane group-containing compound-
The ink composition of the present invention contains both at least one vinyl ether group-containing compound and at least one oxetane group-containing compound as the polymerizable compound. Moreover, it is good also as a structure which used together other polymerizable compounds other than these with an oxetane group containing compound and an oxirane group containing compound.

  All of these compounds are polymerized upon irradiation with active energy rays by the action of a cationic polymerization initiator described later, and cure themselves, and the curing reaction can be carried out in a short time. It is particularly effective in preventing fading in images during and after reaction, and can form an image having excellent hue (hue), color density and vividness, and light resistance comparable to pigments.

  The content ratio (x / y; mass ratio) between the vinyl ether group-containing compound (x) and the oxetane group-containing compound (y) is 5/5 in that the light resistance of the cured image can be more effectively improved. A range of 95 to 50/50 is preferable, and a range of 10/90 to 33/67 is particularly preferable.

<Vinyl ether group-containing compound>
The vinyl ether group-containing compound according to the present invention can be appropriately selected from known compounds containing at least one vinyl ether group in the molecule. This compound is rapidly photocured by cationic polymerization, is suitable as a polymerization curing component of a system using a dye, and can effectively improve the light resistance of an image after curing.

Preferable specific examples include the following compounds [Exemplary compounds (i) to (vi)]. However, the present invention is not limited to these.

  Of the above, exemplary compound (iii), exemplary compound (iv), exemplary compound (v), exemplary compound (vi) are more preferred.

<Oxetane group-containing compound>
The oxetane group-containing compound according to the present invention can be appropriately selected from compounds containing at least one oxetane group (oxetanyl group) in the molecule.

  This compound is used together with the vinyl ether group-containing compound, and when the vinyl ether group-containing compound is contained as a polymerizable compound, the solvent solubility of the cationic polymerization initiator described later that cannot be secured due to the influence of the vinyl ether group-containing compound. And can be cured by cationic polymerization in a short time. That is, in the present invention, the oxetane group-containing compound also functions as a solvent for dissolving the cationic polymerization initiator. This makes it possible to prevent fading in the image (curing reaction) during and after curing of light-fading dyes, and is excellent in hue (hue), color density and vividness, and has the same light resistance as a pigment. The image which has can be formed.

  For example, as a compound having one oxetane group in the molecule, a compound represented by the following general formula (1-a) is preferable, and as a compound having two or more oxetane groups in the molecule, the following general formula ( The compounds represented by 1-b) are preferred.

First, the oxetane group-containing compound represented by the general formula (1-a) will be described.
In the general formula (1-a), Z represents an oxygen atom or a sulfur atom, and an oxygen atom is preferable. R ^1a is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, or a butyl group), a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, or an aryl group. Represents a furyl group or a thienyl group, and an alkyl group having 1 to 6 carbon atoms (particularly a methyl group or an ethyl group) is preferred.

R ^2a is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, or a butyl group), an alkenyl group having 1 to 6 carbon atoms (for example, a 1-propenyl group, 2- Propenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, etc.), aryl group (for example, phenyl group, benzyl group, fluoro Benzyl group, methoxybenzyl group, phenoxyethyl group, etc.), alkylcarbonyl group having 1 to 6 carbon atoms (for example, propylcarbonyl group, butylcarbonyl group, pentylcarbonyl group, etc.), alkoxycarbonyl group having 1 to 6 carbon atoms (for example, Ethoxycarbonyl group, propoxycarbonyl group, butyroxycarbonyl group, etc.), C1-C6 alkoxycarbamoyl group (for example, , Ethoxy carbamoyl group, propoxy carbamoyl group, butyl pentyl b alkoxy carbamoyl group), representing the like.

Of the oxetane group-containing compounds represented by the general formula (1-a), R ^1a is a lower alkyl group (particularly an ethyl group), and R ^2a is a hydrogen atom, a butyl group, a phenyl group, or a benzyl group. An embodiment in which Z is an oxygen atom is particularly preferred. Here, the lower alkyl group refers to an alkyl group having 1 to 3 carbon atoms (the same applies hereinafter).
In addition, the oxetane group-containing compound represented by the general formula (1-a) may be used alone or in combination of two or more.

Next, the oxetane group-containing compound represented by the general formula (1-b) will be described.
In the general formula (1-b), m represents 2, 3 or 4, Z represents an oxygen atom or a sulfur atom, and Z is preferably an oxygen atom.

In the general formula (1-b), R ^1b is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 6 carbon atoms (eg, a methyl group, an ethyl group, a propyl group, a butyl group), a phenyl group, or a carbon number. 1 to 6 fluoroalkyl groups, allyl groups, aryl groups, or furyl groups are represented.

R ^2b is a divalent group selected from the group consisting of a linear or branched alkylene group having 1 to 12 carbon atoms, a linear or branched poly (alkyleneoxy) group, or the following general formulas (3), (4) and (5). Represents a group of

The linear or branched alkylene group having 1 to 12 carbon atoms is preferably a group represented by the following general formula (2). R ³ in the following general formula (2) represents a lower alkylene group such as a methylene group, an ethylene group, or a propylene group.

In the general formula (3), n represents 0 or an integer of 1 to 2000, and R ⁴ represents an alkyl group having 1 to 10 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, A hexyl group, a heptyl group, an octyl group, a nonyl group, or the like) or a group selected from groups represented by the following general formula (6). R ⁵ represents an alkyl group having 1 to 10 carbon atoms (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, etc.), preferably a methyl group It is.

In the general formula (6), j represents 0 or an integer of 1 to 100, and R ⁶ represents an alkyl group having 1 to 10 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, A hexyl group, a heptyl group, an octyl group, a nonyl group, etc.), preferably a methyl group.

In the general formula (4), R ⁷ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, Nonyl groups, etc.), C1-C10 alkoxy groups (eg, methoxy, ethoxy, propoxy, butoxy, pentoxy, etc.), halogen atoms (eg, fluorine, chlorine, bromine, iodine, etc.) ), A nitro group, a cyano group, a mercapto group, an alkoxycarbonyl group (for example, a methyloxycarbonyl group, an ethyloxycarbonyl group, a butyloxycarbonyl group, etc.), or a carboxyl group.

In the general formula (5), R ⁸ represents an oxygen atom, a sulfur atom, NH, SO, SO ₂ , CH ₂ , C (CH ₃ ) ₂ , or C (CF ₃ ) ₂ .

Among the oxetane group-containing compounds represented by the general formula (1-b), in the general formula (1-b), R ^1b represents a lower alkyl group (for example, a methyl group, an ethyl group, a propyl group, etc.). And particularly preferably an ethyl group, and R ^2b is a group in which R ^{7 in the} general formula (4) is a hydrogen atom, a hexamethylene group, R ^{3 in the} general formula (2) is an ethylene group, or a general formula An embodiment in which R ^{5 in} (3) is a methyl group and R ⁴ is a group in which R ^{6 in} general formula (6) is a methyl group, Z is an oxygen atom, and m is 2 is preferable.

  Furthermore, examples of the compound having two or more oxetane groups in the molecule include compounds represented by the following general formula (7) or (8).

In the general formula (7), r represents an integer of 25 to 200, and R ⁹ represents an alkyl group having 1 to 4 carbon atoms or a trialkylsilyl group. Note that R ¹ in the general formulas (7) and (8) and R ⁶ in the general formula (7) are R ^1b in the general formula (1-b) and R ^{6 in the} general formula (6), respectively. It is synonymous with.

  Hereinafter, preferable specific examples [Exemplary compounds 1 to 37 and (a) to (f)] of the oxetane group-containing compound represented by the general formula (1-a) or (1-b) are listed. However, the present invention is not limited to these.

Synthesis of the above oxetane group-containing compound is as follows: (1) HAJ Curless, “Synthetic Organic Photochemistry”, Plenum, New York (1984), (2) M. Braun, Nachr. Chem. Tech. Lab., 33, 213 (1985), (3) SHSchroeter, J. Org. Chem., 34, 5, 1181 (1969), (4) DRArnold, Adv. Photochem., 6, 301 (1968), (5) “Heterocyclic Compounds with Three- and Four-membered Rings ”, Part Two, Chapter IX, Interscience Publishers, John Wiley & Sons, New York (1964), (6) Bull. Chem. Soc. Jpn., 61, 1653 (1988), (7) Pure Appl. Chem., A29 (10), 915 (1992), (8) Pure Appl. Chem., A30 (2 &amp; 3), 189 (1993), (9) JP-A-6-16804, (10) German Patent No. 1,021,858 , Etc. can be referred to.
In addition, the oxetane group-containing compound represented by the general formula (1-b) can also be used in combination of two or more, in addition to being used alone.

  Of the above oxetane group-containing compounds, the exemplified compound (a), the exemplified compound (b), the exemplified compound (d) and the exemplified compound (f) are preferable.

  In the present invention, as a combination aspect in which both the vinyl ether group-containing compound and the oxetane group-containing compound are combined, an aspect in which the exemplary compound (b) and the exemplary compound (iii) are combined, the exemplary compound (b) And the exemplary compound (vi) in combination are particularly preferred in that polymerization curing is good and light resistance can be improved more effectively.

It is also possible to use other known polymerizable compounds in combination with the above-mentioned vinyl ether group-containing compound and oxetane group-containing compound. Another polymerizable compound is a compound having at least one ethylenic double bond as a polymerizable functional group (polymerizable group), and the polymerizable group has one monofunctional monomer and two or more polymerizable groups. Bifunctional or higher functional monomers can be selected as appropriate.
Examples of the polymerizable group include an acryloyl group, a methacryloyl group, an allyl group, a vinyl group, an internal double bond group (such as maleic acid), and the like for the purpose of adjusting the degree of polymerization and the physical properties of the ink composition. Among them, an acryloyl group and a methacryloyl group are preferable, and an acryloyl group is particularly preferable from the viewpoint of polymerization rate and versatility. From the above, preferable examples of other polymerizable compounds include acrylates, methacrylates, acrylamides, methacrylamides, olefins, styrenes, and vinyl ethers, and acrylates and methacrylates are preferable.

  The total amount (mass) of the vinyl ether group-containing compound and the oxetane group-containing compound in the ink composition can be arbitrarily selected according to the desired physical properties of the ink composition, but is preferably in the range of 50 to 99 mass%. A range of 90 to 98% by mass is more preferable.

-Cationic polymerization initiator-
The ink composition of the present invention contains at least one cationic polymerization initiator that polymerizes and cures the polymerizable compound according to the present invention (and other polymerizable compound that is contained as necessary). The cationic polymerization initiator has absorption in the wavelength region of the active energy ray, and when the active energy ray is applied, it undergoes a chemical change through the action of the active energy ray or the interaction with the electronically excited state of the sensitizing dye, A cationic species is generated to initiate and accelerate the polymerization and curing of the polymerizable compound (that is, the ink composition).

  In the present invention, “active energy rays” are actinic rays that generate cations from a cationic polymerization initiator, and include ultraviolet rays (UV light), visible rays, γ rays, α rays, X rays, and other electron rays. As specific light sources, for example, LD, LED, fluorescent lamp, low-pressure mercury lamp, high-pressure mercury lamp, metal halide lamp, carbon arc lamp, xenon lamp, chemical lamp, and the like can be applied. Preferred light sources include LEDs, high pressure mercury lamps, and metal halide lamps.

  As the cationic polymerization initiator, those known to those skilled in the art can be used without limitation, for example, Bruce M. Monroe et al., Chemical Revue, 93, 435 (1993), RSD Davidson, Journal of Photochemistry and biology A: Chemistry, 73.81 (1993), JP Faussier "Photoinitiated Polymerization-Theory and Applications": Rapra Review vol. 9, Report, Rapra Technology (1998)., M. Tsunooka et al., Prog. Polym. Sci. , 21, 1 (1996). Chemically amplified photoresists are described in “Organic Materials for Imaging” (edited by Organic Electronics Materials Research Group, Bunshin Publishing (1993), p. 187-192). And compounds described as compounds used for photocationic polymerization. Furthermore, FDSaeva, Topics in Current Chemistry, 156, 59 (1990)., GG Maslak, Topics in Current Chemistry, 168, 1 (1993)., HB Shuster et al, JACS, 112, 6329 (1990)., IDF A group of compounds described in Eaton et al, JACS, 102, 3298 (1980). Etc., which undergoes oxidative or reductive bond cleavage through interaction with the electronically excited state of the sensitizing dye can also be mentioned.

Preferred are (a) aromatic ketones, (b) aromatic onium salt compounds, (c) organic peroxides, (d) hexaarylbiimidazole compounds, (e) ketoxime ester compounds, (f) Examples thereof include a borate compound, (g) an azinium salt compound, (h) a metallocene compound, (i) an active ester compound, and (j) a compound having a carbon halogen bond.
Among these, (b) aromatic onium salt compounds and (i) active ester compounds are useful. Hereinafter, the above (b) and (i) useful for the present invention will be mainly described.

Examples of the (b) aromatic onium salt compound include elements belonging to Groups 15, 16, and 17 of the Long Periodic Table, specifically, N, P, As, Sb, Bi, O, S, Se. , Te, or I aromatic onium salts. For example, European Patent No. 104143, US Pat. No. 4,837,124, Japanese Patent Laid-Open No. 2-150848, Japanese Patent Laid-Open No. 2-96514, iodonium salts, European Patent Nos. 370693, 233567, 297443, The sulfonium salts and diazonium described in the specifications of U.S. Pat. Salts (such as benzenediazonium which may have a substituent), diazonium salt resins (formaldehyde resin of diazodiphenylamine), N-alkoxypyridinium salts and the like (for example, US Pat. No. 4,743,528, JP, Sho 63-13834 , JP-A-63-142345, JP-A-63-142346, and JP-B-46-42363, specifically 1-methoxy-4-phenylpyridinium tetrafluoroborate. Etc.), and compounds described in JP-B Nos. 52-147277, 52-14278, and 52-14279.
In particular, aromatic sulfonium salts such as triarylsulfonium salts, aromatic iodonium salts such as diaryliodonium salts, and the like are preferable, and aromatic sulfonium salts are preferable from the viewpoint of being relatively stable thermally.

When the aromatic sulfonium salt or aromatic iodonium salt is used as an onium salt photoinitiator, BF ₄ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , PF ₆ ⁻ , PF ₆ ⁻ , B ( C ₆ F _{5) 4} ^-, and the like preferably.

As the cationic polymerization initiator according to the present invention, an aromatic sulfonium PF ₆ salt or SbF ₆ salt is preferable in that it has solubility and moderate polymerization activity. Further, in terms of improving the solubility, the aromatic group (particularly phenyl group) of the aromatic group iodonium salt or aromatic sulfonium salt has at least 1 alkyl group having 1 to 10 carbon atoms or alkoxy group having 1 to 10 carbon atoms. One of the introduced structures is preferred. Commercially available PF ₆ salts or SbF ₆ salts of aromatic sulfonium salts include those manufactured by Union Carbide Japan, Adekaoptomer SP series (Aromatic sulfonium PF ₆ manufactured by Asahi Denka Kogyo Co., Ltd.). Salt).

  Since the aromatic sulfonium salt has an absorption up to about 360 nm and the aromatic iodonium salt has an absorption up to about 320 nm, an active energy ray including the spectral energy of each absorption region (for example, It is preferable to irradiate (ultraviolet rays).

Examples of the active ester compound (i) include, for example, the specifications of European Patent Nos. 0290750, 046083, 156153, 271851, and 0388343, U.S. Pat. Nos. 3,901,710, and 4,181,531. Nitrobenzester compounds described in JP-A-60-198538 and JP-A-53-133022, European Patent Nos. 099672, 84515, 199672, 0441115, and 0101122. No. 4,618,564, U.S. Pat. No. 4,371,605 and U.S. Pat. No. 4,431,774, and JP-A 64-18143, JP-A-2-245756, and JP-A-4-365048. An iminosulfonate compound described in JP-B-62-62 No. 3, JP-B-63-14340, and are exemplified compounds described in each publication of JP-59-174831.
In particular, nonionic initiators such as nitrobenzyl ester of sulfonic acid are suitable.

  In addition, the compounds described as “organic materials for imaging” (edited by Organic Electronics Materials Study Group, Bunshin Publishing (1993)) as chemically amplified photoresists and compounds used for photocationic polymerization are useful. .

  Examples other than the above include the photopolymerization initiators described in Kiyotsugu Kato's “UV Curing System” (published by General Technology Center Co., Ltd. (1989), pages 65-148).

  From the viewpoint of stability, it is desirable to select a compound that does not decompose up to 70 ° C.

Two or more kinds of cationic polymerization initiators may be used in combination in addition to one kind alone.
The content of the cationic polymerization initiator is 0.05 to the total amount of the above-described polymerizable compound according to the present invention (and other polymerizable compound contained as necessary) and the cationic polymerization initiator. The range of 10% by mass is preferable, and the range of 0.1 to 5% by mass is more preferable. When the content is particularly in the above range, the curing speed is high and good curability is obtained, which is effective for recording robust images, and the abrasion resistance when the images are rubbed may be deteriorated. Absent.

-Dye-
The ink composition of the present invention contains at least one dye and is configured to form a visible image. Dyes include water-soluble dyes and oil-soluble dyes, and oil-soluble dyes are preferred in the present invention.

  As the dye, conventionally known dyes can be appropriately selected and used. Specific examples include dyes described in paragraphs [0023] to [0089] of JP-A No. 2002-114930.

  Examples of yellow dyes include, for example, phenols, naphthols, anilines, pyrazolones, pyridones, aryl or heteryl azo dyes having open-chain active methylene compounds as coupling components, for example, open-chain active methylene compounds as coupling components Azomethine dyes having, for example, methine dyes such as benzylidene dyes and monomethine oxonol dyes, for example, quinone dyes such as naphthoquinone dyes and anthraquinone dyes, and other dyes include quinophthalone dyes, nitro, Nitroso dyes, acridine dyes, acridinone dyes and the like can be mentioned.

  Examples of the magenta dye include phenols, naphthols, anilines, pyrazolones, pyridones, pyrazolotriazoles, and ring-closing active methylene compounds (for example, dimedone, barbituric acid, 4-hydroxycoumarin) as coupling components. Derivatives), electron-rich heterocycles (eg, pyrrole, imidazole, thiophene, thiazole derivatives), or aryl or heteryl azo dyes, eg, azomethine dyes having pyrazolones, pyrazolotriazoles as coupling components, eg, arylidene dyes, styryl Dyes, merocyanine dyes, methine dyes such as oxonol dyes, carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, such as naphthoquinone, anthraquinone, anthrone Quinone dyes such Rapiridon, it can be mentioned condensed polycyclic dyes such as, for example, dioxazine dye.

  Examples of cyan dyes include azomethine dyes such as indoaniline dyes and indophenol dyes, cyanine dyes, oxonol dyes, polymethine dyes such as merocyanine dyes, diphenylmethane dyes, triphenylmethane dyes, carbonium dyes such as xanthene dyes, Examples of phthalocyanine dyes and anthraquinone dyes include phenols, naphthols, anilines, pyrrolopyrimidin-one, aryl or heteryl azo dyes having pyrrolotriazin-one derivatives, and indigo / thioindigo dyes as coupling components.

  Each of the above dyes may exhibit yellow, magenta, and cyan colors only after a part of the chromophore is dissociated. In this case, the counter cation is an inorganic cation such as an alkali metal or ammonium. Alternatively, it may be an organic cation such as pyridinium, quaternary ammonium salt, or a cationic polymer having a partial structure thereof.

  The dye that can be used in the present invention is preferably oil-soluble. “Oil-soluble” specifically means that the solubility in water at 25 ° C. (the mass of the dye dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0. .1 g or less. Therefore, so-called water-insoluble oil-soluble dyes are preferably used.

The dye used in the present invention preferably has an oil-solubilizing group introduced into the above-described dye matrix in order to dissolve the necessary amount in the ink composition.
Examples of the oil-solubilizing groups include long-chain or branched alkyl groups, long-chain or branched alkoxy groups, long-chain or branched alkylthio groups, long-chain or branched alkylsulfonyl groups, long-chain or branched acyloxy groups, long-chain or branched alkoxycarbonyl groups. A long chain or branched acyl group, a long chain or branched acylamino group, a long chain or branched alkylsulfonylamino group, a long chain or branched alkylaminosulfonyl group, and an aryl group containing these long chain or branched groups, an aryloxy group, An aryloxycarbonyl group, an arylcarbonyloxy group, an arylaminocarbonyl group, an arylaminosulfonyl group, an arylsulfonylamino group, etc. are mentioned.

  In addition, a water-soluble dye having a carboxylic acid group or a sulfonic acid group is converted into an oil-solubilizing alkoxycarbonyl group, aryloxycarbonyl group, alkylaminosulfonyl group using a long-chain or branched alcohol, amine, phenol, or aniline derivative. The dye may be obtained by conversion to an arylaminosulfonyl group.

  The oil-soluble dye preferably has a melting point of 200 ° C. or lower, more preferably has a melting point of 150 ° C. or lower, and still more preferably has a melting point of 100 ° C. or lower. By selecting a low melting point dye as the oil-soluble dye, the crystal precipitation of the dye in the ink composition is suppressed, and the storage stability of the ink composition can be improved.

  In addition, it is desirable that the oxidation potential is noble (high) in order to improve the resistance to the discoloration, in particular, the oxidizing substance such as ozone and the curing characteristics. For this reason, as the oil-soluble dye, those having an oxidation potential nobler than 1.0 V (vs SCE) are preferable. A higher oxidation potential is preferable, an oxidation potential of 1.1 V (vs SCE) or higher is more preferable, and a voltage of 1.15 V (vs SCE) or higher is particularly preferable.

As the yellow dye, a compound having a structure represented by the general formula (Y-I) described in JP-A No. 2004-250483 is preferable.
Particularly preferred dyes are dyes represented by the general formulas (Y-II) to (Y-IV) described in paragraph [0034] of JP-A No. 2004-250483. And the compounds described in paragraph numbers [0060] to [0071] of JP-A-250483. The oil-soluble dye of the general formula (Y-I) described in the publication may be used not only for yellow but also for inks of any color such as black ink and red ink.

The magenta dye is preferably a compound having a structure represented by the general formulas (3) and (4) described in JP-A No. 2002-114930. Specific examples include paragraphs of JP-A No. 2002-114930. Examples include the compounds described in [0054] to [0073].
Particularly preferred dyes are azo dyes represented by general formulas (M-1) to (M-2) described in paragraph numbers [0084] to [0122] of JP-A No. 2002-121414. Examples thereof include compounds described in JP-A No. 2002-121414, paragraph numbers [0123] to [0132]. The oil-soluble dyes represented by the general formulas (3), (4) and (M-1) to (M-2) described in the publication are used not only for magenta but also for any color ink such as black ink and red ink. May be.

Examples of cyan dyes include dyes represented by formulas (I) to (IV) described in JP-A No. 2001-181547, and paragraphs [0063] to [0078] of JP-A No. 2002-121414. The dyes represented by the general formulas (IV-1) to (IV-4) are preferable, and specific examples thereof include paragraphs [0052] to [0066] of JP-A No. 2001-181547 and JP-A No. 2002. And the compounds described in paragraph Nos. [0079] to [0081] of JP-A-1221414.
Particularly preferred dyes are phthalocyanine dyes represented by general formulas (CI) and (C-II) described in paragraph numbers [0133] to [0196] of JP-A No. 2002-121414, A phthalocyanine dye represented by (C-II) is preferred. Specific examples thereof include the compounds described in JP-A No. 2002-121414, paragraph numbers [0198] to [0201]. The oil-soluble dyes of the formulas (I) to (IV), (IV-1) to (IV-4), (CI), and (C-II) are not only cyan but also black ink or green ink. The ink may be used for any color ink.

-Oxidation potential-
The oxidation potential value (Eox) of the dye in the present invention can be easily measured by those skilled in the art. As for this method, for example, “New Instrumental Methods in Electrochemistry” by P. Delahay (1954, published by Interscience Publishers), AJBard et al. “Electrochemical Methods” (1980, published by John Wiley & Sons), Akira Fujishima et al. It is described in the book "Electrochemical measurement method" (1984, published by Gihodo Publisher).

The oxidation potential is determined by dissolving 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / liter of the test sample in a solvent such as dimethylformamide or acetonitrile containing a supporting electrolyte such as sodium perchlorate or tetrapropylammonium perchlorate. The voltammetry apparatus approximates the oxidation wave when carbon (GC) is swept to the oxidation side (noble side) using carbon (GC) as the working electrode and the rotating platinum electrode as the counter electrode. The intermediate potential value of the line segment formed by the intersection of the straight line and the intersection of the straight line and the saturation current line (or the intersection of the straight line parallel to the vertical axis passing through the peak potential value) is a value for the SCE (saturated calomel electrode). Measure as Although this value may be deviated by several tens of mil volts due to the influence of the liquid potential difference or the liquid resistance of the sample solution, the reproducibility of the potential can be guaranteed by inserting a standard sample (for example, hydroquinone). The supporting electrolyte and solvent to be used can be selected appropriately depending on the oxidation potential and solubility of the test sample. The supporting electrolyte and the solvent that can be used are described in pages 101 to 118 of Akira Fujishima et al., “Electrochemical measurement method” (published by Gihodo Publishing Co., 1984). In the concentration range of the measurement solvent and the phthalocyanine compound sample, the oxidation potential in a non-association state is measured.
The value of Eox represents the ease of transfer of electrons from the sample to the electrode. The greater the value of Eox, that is, the higher the oxidation potential, the less transfer of electrons from the sample to the electrode, in other words, oxidation. Indicates difficult.

  Specific examples of suitable dyes in the present invention are shown below. However, the present invention is not limited to these specific examples.

  Among the above, the following magenta dyes and substitution products thereof are most preferable in that they are particularly excellent in the effect of improving light resistance and curability when combined with the aforementioned vinyl ether group-containing compound and oxetane group-containing compound.

  Examples of the substituent forming the substituent include a substituted or unsubstituted alkyl group having 1 to 16 carbon atoms (more preferably 1 to 8 carbon atoms), and 0 to 16 carbon atoms (more preferably 0 carbon atoms). A substituted or unsubstituted amide group of ˜8), a substituted or unsubstituted sulfonamide group having 0 to 16 carbon atoms (more preferably 0 to 8 carbon atoms), and the like are preferable. Next, specific examples of preferred substituents are shown below. However, the present invention is not limited to these.

  The amount of the dye (particularly oil-soluble dye) in the ink composition is preferably 0.05 to 15% by mass, and 0.1 to 10% by mass with respect to the total mass (including the organic solvent) of the ink composition. More preferably, 0.2-6 mass% is especially preferable.

-Additives-
In the ink composition of the present invention, in addition to the above-described components, a sensitizing dye, a co-sensitizer, an ultraviolet absorber, etc. may be used in combination as additives and other components as required for the purpose and application. Can do. Hereinafter, the additive and other components will be described.

-Sensitizing dye-
In the present invention, a sensitizing dye can be added for the purpose of improving the sensitivity of the cationic polymerization initiator. Hereinafter, the sensitizing dye will be described.

  Examples of the sensitizing dye 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, carbomerocyani, 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.

  Preferred examples of the sensitizing dye in the present invention include compounds represented by the following general formulas (vi) to (x).

In the general formula (vi), A ¹ represents a sulfur atom or NR ⁵⁰ , and R ⁵⁰ represents an alkyl group or an aryl group. L ¹ represents a nonmetallic atomic group that forms a basic nucleus of a dye together with adjacent A ¹ and adjacent carbon atoms. R ⁵¹ and R ⁵² each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁵¹ and R ⁵² may be bonded to each other to form an acidic nucleus of the dye. W represents an oxygen atom or a sulfur atom.

In the general formula (vii), Ar ¹ and Ar ² each independently represent an aryl group and are linked via a bond with L ² . L ² represents —O— or —S—. W is synonymous with W in the general formula (vi).

In the general formula (viii), A ² represents a sulfur atom or NR ⁵⁹ , and R ⁵⁹ represents an alkyl group or an aryl group. L ³ represents a nonmetallic atomic group that forms a basic nucleus of a dye in cooperation 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.

In the general formula (ix), A ³ and A ⁴ each independently represent —S—, —NR ⁶² —, or —NR ⁶³ —, and R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted group. A substituted alkyl group or a substituted or unsubstituted aryl group is represented. L ⁴ and L ⁵ each independently represent a nonmetallic atomic group that forms a basic nucleus of a dye together with A ³ or A ⁴ and an adjacent carbon atom. R ⁶⁰ and R ⁶¹ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁶⁰ and R ⁶¹ may be bonded to each other to form an aliphatic or aromatic ring. .

In the general formula (x), R ⁶⁶ represents an aromatic ring or a hetero ring which may have a substituent. A ⁵ represents an oxygen atom, a sulfur atom, or NR ⁶⁷ —. R ⁶⁴ , R ⁶⁵ and R ⁶⁷ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group. R ⁶⁷ and R ⁶⁴ , and R ⁶⁵ and R ⁶⁷ may be bonded to each other to form an aliphatic or aromatic ring.

  Hereinafter, preferable specific examples of the compounds represented by the general formulas (vi) to (x) will be given. However, the present invention is not limited to these.

The said sensitizing dye may be used individually by 1 type, and may use 2 or more types together.
The content of the sensitizing dye in the ink composition is preferably 0.01 to 20% by mass and preferably 0.1 to 15% by mass with respect to the total mass of the ink composition from the viewpoint of the colorability of the ink composition. % Is more preferable, and still more preferably in the range of 0.5 to 10% by mass. Further, the content ratio (a / c) in the ink composition of the sensitizing dye (a) and the cationic polymerization initiator (c) is an improvement in the decomposition rate of the cationic polymerization initiator and the transparency of irradiated light. From the viewpoint, the mass ratio is preferably a / c = 200 to 0.5, more preferably a / c = 50 to 1, and further preferably a / c = 10 to 1.5.

-Co-sensitizer-
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, JP-A-5-142772, 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 depending on the purpose, but is generally about 0.01 to 10% by mass with respect to the total mass of the ink composition.

-Surfactant-
A surfactant can be added to the ink composition of the present invention. Examples of the surfactant 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-
A polymerization inhibitor can be added to the ink composition of the present invention. 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, haloquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, resorcinol, catechol, t-butylcatechol, hydroquinone monoalkyl ether (for example, hydroquinone monomethyl ether, hydroquinone monobutyl ether), Benzoquinone, 4,4-thiobis (3-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2,6,6-tetramethylpiperidine and its Derivatives, di-t-butyl nitroxide, 2,2,6,6-tetramethylpiperidine-N-oxide and derivatives thereof, piperidine 1-oxyl free radical, 2,2,6,6-tetramethylpiperidine 1-oxyl Free radicals, 4- Oxo-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-acetamido-2,2,6 6-tetramethylpiperidine 1-oxyl free radical, 4-maleimido-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-phosphonoxy-2,2,6,6-tetramethylpiperidine 1-oxyl Free radical, 3-carboxy-2,2,5,5-tetramethylpyrrolidine 1-oxyl free radical, N-nitrosophenylhydroxylamine cerium salt, N-nitrosophenylhydroxylamine aluminum salt, crystal violet, methyl violet, Ethyl violet , And Victoria Pure Blue BOH, and the like.

  Of the above, hydroquinone monoalkyl ethers such as hydroquinone monomethyl ether and hydroquinone monobutyl ether, 4,4′-thiobis (3-methyl-6-t-butylphenol), 2,2′-methylenebis (4-methyl-6-t) Hindered phenols such as -butylphenol) are preferred.

  The content of the polymerization inhibitor in the ink composition is preferably 10,000 to 30,000 ppm, more preferably 10,000 to 20,000 ppm, and even more preferably 10,000 to 15,000 ppm with respect to the total mass 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 resulting image and preventing discoloration.
Examples of the ultraviolet absorber are described in JP-A-58-185679, JP-A-61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. 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. 48-30492 and 56-21141 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, JP 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 depending on the purpose, but is generally about 0.01 to 10% by mass with respect to the 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 Patent No. 223739, No. 309401, No. 309402, No. 310551, No. 310552, No. 4594416, German Published Patent No. 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 depending on the purpose, but is generally about 0.01 to 10% by mass with respect to the total mass of the ink composition.

-Anti-fading agent-
Various organic and metal complex anti-fading agents can be added to the ink composition of the present invention. Examples of the organic anti-fading agent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. Examples of the anti-fading agent based on the metal complex include nickel complexes, zinc complexes, and the like. No. 17643, Nos. VII to I, J. 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 depending on the purpose, but is generally about 0.01 to 10% by mass with respect to the total mass of the ink composition.

-Conductive salts-
Conductive salts such as potassium thiocyanate, lithium nitrate, ammonium thiocyanate, and dimethylamine hydrochloride can be added to the ink composition of the present invention for the purpose of controlling ejection properties.

-Solvent-
In order to improve the adhesion to the recording material, it is also effective to add a very small amount of an organic solvent to the ink composition of the present invention.
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 the solvent within a range that does not cause the problem of solvent resistance and VOC, and the amount is preferably 0.1 to 5% by mass, more preferably 0.1 to the total mass of the ink composition. It is the range of -3 mass%.

-Polymer compound-
Various polymer compounds (polymers) can be added to the ink composition of the present invention in order to adjust film physical properties.
Examples of polymer 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. 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 suitable as the copolymer composition of the polymer binder.

In addition to the above, the ink composition of the present invention has, for example, leveling additives, matting agents, waxes for adjusting film properties, polyolefins, and adhesion to recording materials such as PET. For the purpose of improving, a tackifier or the like that does not inhibit 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 desirable 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) is preferably 7 to 120 mPa · s, more preferably 10 to 80 mPa · s. By setting the viscosity at room temperature high, even when a porous recording material is used, ink penetration into the recording material 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.
Further, when recording the ink composition of the present invention on various recording materials 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, In terms of wettability, 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.
Among these, the ink is suitable as a drop-on-demand type (pressure pulse type) ink jet recording ink using a piezo element.

<Image forming method>
The image forming method of the present invention includes an image recording step of recording an image on a recording material using the ink composition of the present invention described above, and curing by irradiating the recorded image with active energy rays (active rays). And an image curing step to be provided. In the present invention, a polymerizable compound that contributes to imaging by using an active energy ray in an image curing step and recording an image on a recording material in an image recording step and then irradiating the recorded image with the active energy ray. As the polymerization and curing proceed, the image is cured well and an image having high fastness can be formed.

  In the image recording step, it is preferable to apply an ink jet recording method using an ink jet printer. Specifically, in the image recording step, an aspect in which an ink image is inkjet-recorded by discharging the ink composition from, for example, an ejection nozzle of an inkjet printer is preferable. In the ink jet recording method, image recording is performed on a recording material using the ink composition of the present invention, but there are no particular restrictions on the ink discharge nozzles (for example, for an ink jet printer) used at that time, and the purpose and application It can be appropriately selected according to the like. There is no restriction | limiting in particular in an inkjet recording system, and it is as above-mentioned specifically.

  In the image curing step, an exposure process for accelerating polymerization and curing can be performed using a light source that emits active energy rays in a wavelength region corresponding to the sensitive wavelength of the ink composition. Specifically, a light source that emits active rays belonging to a wavelength region of 250 to 450 nm, for example, LD, LED, fluorescent lamp, low-pressure mercury lamp, high-pressure mercury lamp, metal halide lamp, carbon arc lamp, xenon lamp, chemical lamp, etc. It can be suitably performed. Preferred light sources include LEDs, high pressure mercury lamps, and metal halide lamps. What is necessary is just to select an exposure time and light quantity suitably according to the grade of the polymerization hardening of the polymeric compound which concerns on this invention.

-Recording material-
As the recording material, either an ink-permeable recording material or an ink-impermeable recording material can be used.

  Examples of the ink-permeable recording material 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.

  From the viewpoint of effectively expressing the effects of the present invention, it is preferable to use a non-ink-permeable (non-absorbing) recording material. Examples of the ink-impermeable recording material include art paper, synthetic resin, rubber, resin-coated paper, glass, metal, earthenware, and wood. In addition, in terms of adding each function, a base material obtained by combining a plurality of these materials can also be used.

As the synthetic resin, any synthetic resin can be used. For example, polyester resins such as polyethylene terephthalate and polybutadiene terephthalate; polyolefin resins such as polyvinyl chloride, polystyrene, polyethylene, polyurethane, and polypropylene; and acrylic resins, Examples include polycarbonate, acrylonitrile-butadiene-styrene copolymer, diacetate, triacetate, polyimide, cellophane, and celluloid.
There is no restriction | limiting in particular about the shape of the base material using a synthetic resin, and its thickness, Any of a film form, a card | curd shape, or a block shape may be sufficient, and it can select suitably according to the desired objective. The synthetic resin may be either 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 various plastics films include PET films, OPS films, OPP films, ONy films, PVC films, PE films, and TAC films.

  Examples of the resin-coated paper include a paper support in which one side or both sides of the paper is coated with a polyolefin resin and the like, and a paper support in which both sides of the paper are laminated with a polyolefin resin is particularly preferable.

  As described above, according to the image recording using the ink composition of the present invention (the image forming method of the present invention), it is possible to obtain a high-quality, high-strength and robust image, The light resistance of the image is particularly excellent.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1
Each component having the following composition was stirred and mixed to prepare magenta ink (1) of the present invention.
・ OTX-211 (refer to the structure below) ... 14.0g
(Toa Gosei Co., Ltd .; Oxetane group-containing compound)
・ The following vinyl ether (1): 6.0 g
(RAPI-CURE DVB1D, manufactured by BASF Japan Ltd .; vinyl ether group-containing compound)
・ CYRAURE UVI-6992… 0.6g
(Union Carbide, Cationic photopolymerization initiator)
・ The following magenta dye M-1 (oil-soluble dye): 0.2 g

(Example 2)
In Example 1, except that the vinyl ether (1) was replaced with the following vinyl ether (2) [RAPI-CURE HDDVE, manufactured by BASF Japan Ltd .; vinyl ether group-containing compound], in the same manner as in Example 1, Magenta ink (2) was prepared.

(Example 3)
In Example 1, except that the vinyl ether (1) was replaced with the following vinyl ether (3) [RAPI-CURE CHVE, manufactured by BASF Japan Ltd .; vinyl ether group-containing compound], the same procedure as in Example 1 was followed. Magenta ink (3) was prepared.

(Comparative Examples 1-3)
In each of Examples 1 to 3, the same procedure as in Example 1 was conducted except that OTX-211 was not contained and the amount of each of vinyl ethers (1) to (3) was changed from 6.0 g to 20.0 g. Thus, a comparative magenta ink was prepared [Comparative Example 1: Magenta ink (4)].
However, in Comparative Examples 2-3, the curing was poor and the light resistance could not be evaluated.

(Comparative Example 4)
A magenta ink was prepared in the same manner as in Example 1 except that it did not contain vinyl ether (1) and the amount of OTX-211 was changed from 14.0 g to 20.0 g. However, the curing was poor and the light resistance could not be evaluated.

(Image recording)
Each of the present invention and comparative magenta inks (1) to (4) obtained as described above are sequentially loaded into an ink jet printer (printing density 300 dpi, droplet ejection frequency 1 kHz, nozzle number 64), and a PET film ( The color image is recorded by discharging the ink onto the film (50 μm thickness), and after recording, irradiation is performed using a UV lamp (manufactured by Fusion) under the conditions of UV-A (320 to 390 nm) energy of 500 mJ / cm ^2, and the density is about A color image sample of 1.0 was created. Subsequently, the following evaluation was performed for each of the obtained color images. The evaluation results are shown in Table 1 below.

1. Light resistance The Xenon Weather-ometer Ci65A (manufactured by ATLAS) is used on the PET film on which the color image is recorded as described above, and the lamp is turned on for 3.8 hours under an environmental condition of a temperature of 25 ° C. and a relative humidity of 32%. Thereafter, a cycle in which the lamp was turned off and left for 1 hour under an environmental condition of a temperature of 20 ° C. and a relative humidity of 91% was performed over 168 hours. The color density of each color before and after this cycle was measured with a reflection density meter (Xrite 938, manufactured by Xrite), and the residual ratio (%) of each color density was calculated.

2. Curability The surface of the color image was evaluated by the following tack-free test. That is, the surface of the color image, which is a cured film immediately after irradiation after recording, was touched with a finger and evaluated according to the following criteria from the degree of surface stickiness. The smaller the stickiness is, the better the curing speed is, and only ○ is a practically acceptable evaluation.
<Evaluation criteria>
○: There was no stickiness and the curing was good.
(Triangle | delta): Stickiness was recognized and it existed in the tendency which is hard to be hardened.
X: Stickiness was remarkable and curing was insufficient.

  As shown in Table 1, in the magenta inks (1) to (3) of the present invention constituted by using a vinyl ether group-containing compound and an oxetane group-containing compound as a polymerizable compound together with a magenta dye, these are each independently used. Compared to the comparative magenta ink used in 1), the dissolution of the polymerization initiator was good and excellent in curability, and the light resistance could be drastically improved. None of the comparative magenta inks were satisfactory in curability even though they had a certain effect of improving light resistance.

  In addition to the monomers (1) and (2) used in the above examples and combinations thereof, any combination of the exemplified compounds of the vinyl ether group-containing compound and the exemplified compounds of the oxetane group-containing compound described above is used. As described above, it is possible to form a color image having good curability and excellent light resistance.

Claims (7)

  An ink composition comprising a dye, a vinyl ether group-containing compound, an oxetane group-containing compound, and a cationic polymerization initiator.   The ink composition according to claim 1, wherein the dye is an oil-soluble dye.   The ink composition according to claim 2, wherein the oil-soluble dye has an oxidation potential nobler than 1.0 V (vs SCE). The ink composition according to claim 2 or 3, wherein the oil-soluble dye is the following magenta dye and / or a substituted product thereof.

  The ink composition according to any one of claims 1 to 4, which is used for inkjet recording.   An image recording step of recording an image on a recording material using the ink composition according to any one of claims 1 to 5, and an image curing step of irradiating and curing the recorded image with an active energy ray An image forming method comprising:   The image forming method according to claim 6, wherein in the image recording step, the image is inkjet-recorded by discharging the ink composition.