JP5441381B2 - Photocurable ink composition and ink jet recording method - Google Patents

Description

  The present invention relates to a photocurable composition that is cured by irradiation with actinic radiation, an ink composition useful for inkjet recording including the composition, and an inkjet recording method using the ink composition.

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

  As an ink composition (radiation curable ink composition) that can be used for an ink composition for ink jet recording and can be cured by irradiation with active radiation such as ultraviolet rays, it can be cured with high sensitivity to form a high-quality image. Things are sought.

  By achieving high sensitivity of the radiation curable ink composition, high curability can be obtained by irradiation with actinic radiation, which reduces power consumption and extends the life of equipment by reducing the load on the actinic radiation generator. In addition to the advantages, it also has various advantages such as suppression of volatilization of uncured low-molecular substances and suppression of a decrease in formed image strength. Further, the improvement of the cured film strength by increasing the sensitivity of the radiation curable ink composition brings high strength and durability to the image area formed by this ink composition.

  As an ultraviolet curable ink composition, for example, an ink composition that uses a combination of monomers having different functional groups among monofunctional monomers or polyfunctional monomers has been proposed (for example, see Patent Document 1). . A composition containing a polyfunctional acrylate has been proposed as a radiation curable composition that can be applied to an ink composition or the like (see, for example, Patent Document 2). Although these ink compositions are excellent in curing speed and can form images without bleeding, they have a problem that adhesiveness (adhesion) with a recording medium is reduced due to volume shrinkage during curing.

  In addition, regarding the adhesiveness to the recording medium in the ultraviolet curable ink composition, a radiation curable ink using N-vinylcaprolactam as a component for promoting the adhesiveness to the recording medium and the flexibility after curing. The composition is disclosed (for example, refer patent documents 3-5). However, N-vinylcaprolactam is not so-called stickiness of the surface of the ink image after curing or low molecular weight component exuding from the surface due to low copolymerization with a general-purpose radical polymerizable monomer such as acrylate. There is a concern that ejection may occur, and furthermore, the storage stability is insufficient, such as an increase in the viscosity of the ink due to the reactivity of N-vinylcaprolactam, or the ejection stability when drawing by the inkjet method There were various problems such as inferiority.

As described above, the ink composition has excellent adhesion to the recording medium and excellent storage stability (particularly, ejection stability when used in an ink jet apparatus) while maintaining excellent curing sensitivity and image strength. Although a (photo-curable composition) is desired, it is not yet provided.
Japanese Patent Laid-Open No. 5-214280 JP-A-8-41133 JP-A-4-323275 JP-A-5-202331 JP-T-2004-514014

This invention is made | formed in view of the said various circumstances in the prior art, and makes it a subject to achieve the following objectives.
It is an object of the present invention has high sensitivity to irradiation with active radiation, it is possible to form an image excellent in curability, image after curing has high adhesion to the recording medium, and stored An object of the present invention is to provide a photocurable ink composition suitable for ink jet recording having excellent stability and excellent ejection stability when used in an ink jet apparatus, and an ink jet recording method using the ink composition.

The present inventors have result of intensive studies, the use of certain compounds in the photocurable ink composition, found that can solve the above problems, the photocurable Lee ink composition of the present invention, and The ink jet recording method using the ink composition has been completed.

That is, the photocurable ink composition of the present invention contains the (A) N-vinyl piperidone, a polymerizable compound having a structure that is different from the (B) N-vinyl piperidone; and (C) a photopolymerization initiator (A) The N-vinylpiperidone content is 0.1% by mass or more and 50% by mass or less based on the total amount of the ink composition .

One of the preferred embodiments of the photocurable ink composition of the present invention is an embodiment further containing (D) a colorant. The total content of (A) N-vinylpiperidone and the polymerizable compound having a structure different from (B) N-vinylpiperidone is 60% by mass or more and 95% by mass or less based on the total amount of the ink composition. (B) It is a preferred embodiment that the polymerizable compound having a structure different from that of N-vinylpiperidone contains N-vinylcaprolactam.

The ink composition of the present invention is particularly useful as an ink composition for inkjet recording.

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

According to the present invention, an image having high sensitivity to irradiation with actinic radiation and excellent curability can be formed, the image after curing has high adhesiveness with a recording medium, and storage stability is high. It is possible to provide an ink composition for ink jet recording which is good and has excellent ejection stability when used in an ink jet apparatus, and an ink jet recording method using the ink composition.

[Photocurable composition]
The photocurable ink composition of the present invention (hereinafter also simply referred to as “ink composition”) comprises (A) N-vinylpiperidone, (B) a polymerizable compound different from N-vinylpiperidone, and (C) photopolymerization initiation. And (A) the content of N-vinylpiperidone is 0.1% by mass or more and 50% by mass or less based on the total amount of the ink composition . Hereinafter, components essential to the photocurable composition of the present invention will be sequentially described.

[(A) N-vinyl piperidone]
The photocurable ink composition of the present invention contains (A) N-vinylpiperidone. (A) N-vinyl piperidone (CAS No. 4370-23-4) used in the present invention is available from chemical product manufacturers such as 3B Scientific Corporation (USA) and Sino Chemexper Company (China). Moreover, it can synthesize | combine by the well-known synthesis | combining method described in Journal of the American Chemical Society 74 volume 2012-2015 (1952), Unexamined-Japanese-Patent No. 8-59584, Unexamined-Japanese-Patent No. 8-231383, etc. .

The content of N- vinylpiperidone in the photo-curable ink composition of the present invention, the mass of the entire curable compositions, Ri range der of 0.1 to 50 mass%, in the range of 1 to 40 wt% good preferred, have further preferred range of 2 to 35 wt%.
Photocurable Lee ink composition of the present invention, N- content piperidone is that in the above range, adhesion to the curing rate, the cured film and the recording medium after curing, and excellent by storage stability In addition, the ink jet aptitude is further improved.

[(B) Polymerizable compound having a structure different from that of N-vinylpiperidone]
In addition to (A) N-vinylpiperidone, the photocurable ink composition of the present invention (B) is a polymerizable compound having a structure different from that of N-vinylpiperidone (hereinafter referred to as “other polymerizable compound” as appropriate). .).

As the other polymerizable compound in the present invention, any of a radical polymerizable compound and a cationic polymerizable compound may be used. Various characteristics of the target photocurable ink composition, or a photopolymerization initiator described later In this connection, it may be appropriately selected and used.
Hereinafter, other polymerizable compounds applicable to the present invention will be further described.

<Radically polymerizable compound>
The radical polymerizable compound that can be used as the other polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization, and any compound having at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. Any type may be used, including those having chemical forms such as monomers, oligomers, and polymers. Only one kind of radically polymerizable compound may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve desired properties. It is preferable to use two or more kinds in combination for controlling performance such as reactivity and physical properties.

  Examples of the polymerizable compound having an ethylenically unsaturated bond capable of radical polymerization include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and esters or amides thereof, N -Radical polymerizable compounds such as N-vinyl compounds such as vinylamide and N-vinyllactam, styrene, and various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides and unsaturated urethanes.

  Specifically, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, tridecyl acrylate, 2-phenoxyethyl acrylate, bis (4-acryloxypolyethoxyphenyl) Propane, polyethylene glycol diacrylate, polypropylene glycol diacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, oligoester acrylate, N-methylolacrylamide, diacetone acrylamide, epoxy acrylate, isobornyl acrylate, dicyclopentenyl acrylate, Dicyclopentenyloxyethyl acrylate, Acrylic acid derivatives such as cyclopentanyl acrylate; n-butyl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2-bis (4-methacryloxypoly) Methacryl derivatives such as ethoxyphenyl) propane; N-vinyl compounds such as N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylacetamide, N-vinylimidazole; and allyl glycidyl ether, diallyl phthalate, triallyl trimellitate And derivatives of allyl compounds such as More specifically, commercially available products or industries described in Shinzo Yamashita, “Crosslinker Handbook” (1981, Taiseisha); Eiichiro Takiyama, “Polyester Resin Handbook” (1988, Nikkan Kogyo Shimbun) And known radically polymerizable or crosslinkable monomers, oligomers and polymers can be used.

  Among these polymerizable compounds having an ethylenically unsaturated bond capable of radical polymerization, acrylates or methacrylates are preferably used.

  Among the acrylates and methacrylates, alcohol acrylates having an ether oxygen atom such as tetrahydrofurfuryl acrylate and 2-phenoxyethyl acrylate are preferable from the viewpoints of curability and film properties after curing. For the same reason, an acrylate of an alcohol having an alicyclic structure is also preferable, and a bicyclo ring structure or a tricyclo ring structure such as isobornyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, dicyclopentanyl acrylate, etc. Specific examples of preferable acrylates include dicyclopentenyl acrylate and dicyclopentenyloxyethyl acrylate having a double bond in the alicyclic structure.

Furthermore, a vinyl ether compound can be used as the radical polymerizable compound. Suitable vinyl ether compounds include, for example, ethylene glycol divinyl ether, ethylene glycol monovinyl ether, diethylene glycol divinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol. Di- or trivinyl ether compounds such as divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, trimethylolpropane trivinyl ether; ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octade Monovinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-O-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether, etc. Examples include vinyl ether compounds.
Commercially available products such as Rapi-Cure DVE-3 and Rapi-Cure DVE-2 (both manufactured by ISP Europe) can be used as the vinyl ether compound.

  Other polymerizable compounds include (meth) acrylic monomers or prepolymers, epoxy monomers or prepolymers, (meth) acrylic acid esters such as urethane monomers or prepolymers (hereinafter referred to as “acrylate compounds” as appropriate). The following compounds may be used as compound examples.

  That is, EO adduct acrylate, modified glycerin triacrylate, bisphenol A diglycidyl ether acrylic acid adduct, modified bisphenol A diacrylate, phenoxy-polyethylene glycol acrylate, bisphenol A PO adduct diacrylate, bisphenol A EO adduct di Acrylate, dipentaerythritol hexaacrylate, pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer, lactone-modified flexible acrylate, propylene glycol diglycidyl ether acrylic acid adduct, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, Ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate DOO hexamethylene diisocyanate urethane prepolymer, lactone-modified acrylate, and the like.

  In this invention, when using the said acrylate compound as another polymeric compound, it is preferable that the said acrylate compound is 30 mass% or more with respect to the total mass of another polymeric compound, and it is 40 mass% or more. It is preferable that it is 50 mass% or more. Moreover, all the other polymerizable compounds can also be made into the said acrylate compound.

Further, the other polymerizable compound preferably includes an N-vinyl compound different from N-vinyl piperidone from the viewpoint of curability of the photocurable ink composition, and the acrylate compound and N-vinyl piperidone are different from N. -It is preferable to use together with a vinyl compound. As the N-vinyl compound, N-vinyl lactam is more preferable, and N-vinylcaprolactam is particularly preferable from the viewpoint of availability and safety.

  When N-vinylcaprolactam is used as another polymerizable compound, the ratio of (A) N-vinylpiperidone is (N-vinylpiperidone) :( N-vinylcaprolactam) = 1: 99 to 80:20 in terms of mass ratio. 10:90 to 60:40 is more preferable, and 20:80 to 50:50 is particularly preferable.

In the photocurable ink composition of the present invention, the total content of the polymerizable compound, that is, the total content of (A) N-vinylpiperidone and (B) the other polymerizable compound described above is the total content of the ink composition. From the viewpoint of physical properties and curing sensitivity, it is 60% by mass or more and 95% by mass or less, and more preferably 70% by mass or more and 90% by mass or less with respect to the total mass of the photocurable ink composition of the present invention.
Moreover, photocurable Lee ink composition of the present invention, the total content of the above range of the polymerizable compound, a curable ink composition, jetting stability in the case of using the ink composition as an ink for inkjet recording And is good.

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

[(C) Photopolymerization initiator]
The photocurable ink composition of the present invention is required to contain (C) a photopolymerization initiator.

As the photopolymerization initiator, a known photopolymerization initiator can be appropriately selected and used according to the kind of the polymerizable compound used in combination and the purpose of use of the ink composition.
The photopolymerization initiator used in the photocurable ink composition of the present invention is a compound that absorbs external energy and generates a polymerization initiating species. Known compounds can be used as the photopolymerization initiator.

  Preferred photopolymerization initiators that can be used in the present invention include (a) aromatic ketones, (b) acylphosphine oxide compounds, (c) aromatic onium salt compounds, (d) organic peroxides, (e) Thio compound, (f) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, (l) carbon halogen Examples include a compound having a bond, and (m) an alkylamine compound.

In this invention, a photoinitiator may be used independently and may be used together. From the viewpoint of the effect, it is preferable to use two or more radical polymerization initiators in combination. From the viewpoint of curability of the photocurable ink composition, as the photopolymerization initiator, (a) aromatic ketones, (b) acylphosphine oxide compounds, and the like are preferable. Further, when two or more photopolymerization initiators are used in combination, for example, a combination of (a) an aromatic ketone and (b) an acylphosphine oxide compound is preferably exemplified.

  The photopolymerization initiator in the present invention is based on the total amount of (A) N-vinylpiperidone and (B) other polymerizable compounds. The range of 1-50 mass% is preferable with respect to the total amount of the specific polymerizable compound, (B) other polymerizable compound, and (D) colorant, more preferably 2-40 mass%, and 5-35. A range of mass% is more preferred.

Moreover, as preferable content of the photoinitiator in a photocurable ink composition, it is the range of 0.1-15 mass%, and it is more preferable that it is the range of 1-12 mass%.

  Moreover, when it contains the sensitizing dye which can be used as needed later, a photoinitiator is the mass ratio of a photoinitiator: sensitizing dye with respect to this sensitizing dye, Preferably it is 200. : 1-1: 200, more preferably 50: 1-1: 50, still more preferably 20: 1-1: 5.

[(D) Colorant]
The photocurable ink composition of the present invention may contain (D) a colorant. In particular, photocurable Lee ink composition of the present invention, various colorants are preferably used, it is possible thereby to form a colored image.

  There is no restriction | limiting in particular as a coloring agent which can be used for this invention, It can select and use from arbitrary well-known coloring agents, such as a pigment, an oil-soluble dye, a water-soluble dye, a disperse dye. Among these, as the colorant, pigments and oil-soluble dyes that are excellent in weather resistance and rich in color reproducibility are preferable, and pigments are more preferable.

  The colorant that can be suitably used in the ink composition of the present invention is a compound that does not function as a polymerization inhibitor in a polymerization reaction that is a curing reaction, from the viewpoint of not reducing the sensitivity of the curing reaction by actinic radiation. preferable.

<Pigment>
Although it does not necessarily limit as a pigment which can be used for this invention, For example, the organic or inorganic pigment of the following number described in a color index can be used.

Examples of the red or magenta pigment include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53. : 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144 , 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, 36, and the like.
Examples of the blue or cyan pigment include Pigment Blue 1,15,15: 1,15: 2,15: 3, 15: 4,15: 6,16,17-1,22,27,28,29,36. , 60, and the like.
Examples of the green pigment include Pigment Green 7, 26, 36, 50, and the like.
Examples of the yellow pigment include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 120. , 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193, and the like.
Examples of the black pigment include Pigment Black 7, 28, 26, and the like.
Examples of the white pigment include Pigment White 6, 18, 21, and the like.
These pigments can be appropriately selected and used according to the purpose.

<Oil-soluble dye>
Below, the oil-soluble dye which can be used by this invention is demonstrated.
The oil-soluble dye that can be used in the present invention means a dye that is substantially insoluble in water. Specifically, the solubility in water at 25 ° C. (the mass of the dye that can be dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0.1 g or less. Accordingly, the oil-soluble dye means a so-called water-insoluble pigment or oil-soluble dye, and among these, an oil-soluble dye is preferable.

  Among the oil-soluble dyes that can be used in the present invention, any yellow dye can be used. For example, phenols, naphthols, anilines, pyrazolones, pyridones, aryl or heteryl azo dyes having open-chain active methylene compounds as coupling components; for example, azomethine dyes having open-chain active methylene compounds as coupling components 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 dye species such as quinophthalone dyes, nitro Examples thereof include nitroso dyes, acridine dyes, acridinone dyes and the like.

  Among the oil-soluble dyes that can be used in the present invention, any magenta dye can be used. For example, aryl or heteryl azo dyes having phenols, naphthols, anilines as coupling components; for example, azomethine dyes having pyrazolones, pyrazolotriazoles as coupling components; for example, arylidene dyes, styryl dyes, merocyanine dyes, Methine dyes such as oxonol dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes and xanthene dyes; quinone dyes such as naphthoquinone, anthraquinone and anthrapyridone; A ring dye; and the like.

  Of the oil-soluble dyes applicable to the present invention, any cyan dye can be used. For example, indoaniline dyes, indophenol dyes or azomethine dyes having pyrrolotriazoles as coupling components; polymethine dyes such as cyanine dyes, oxonol dyes, merocyanine dyes; carboniums such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes Examples include dyes; phthalocyanine dyes; anthraquinone dyes; aryl or heteryl azo dyes having phenols, naphthols, and anilines as coupling components; indigo / thioindigo dyes;

  Each of the above dyes may exhibit yellow, magenta, and cyan colors only after a part of chromophore (chromogenic atomic group) is dissociated. In this case, the counter cation may be an alkali metal or ammonium. Such inorganic cations may be used, and organic cations such as pyridinium and quaternary ammonium salts may be used. Furthermore, polymer cations having such a structure may be used.

Although not limited to the following, preferred specific examples include C.I. I. Solvent Black 3, 7, 27, 29 and 34; C.I. I. Solvent Yellow 14, 16, 19, 29, 30, 56, 82, 93 and 162; C.I. I. Solvent Red 1, 3, 8, 18, 24, 27, 43, 49, 51, 72, 73, 109, 122, 132 and 218; I. Solvent Violet 3; C.I. I. Solvent Blue 2,11,25,35,38,67 and 70; I. Solvent Green 3 and 7; I. Solvent orange 2; and the like.
Among these, particularly preferred are the Black Black PC-0850, Oil Black HBB, Oil Yellow 129, Oil Yellow 105, Oil Pink 312, Oil Red 5B, Oil Scallet 308, Vali Fast Blue 2600e, Orient Chemical Co., Ltd.), Aizen Spillon Blue GNH (Hodogaya Chemical Co., Ltd.), Neopen Yellow 075, Neopen Mazena SE1378, Neopen Blue 808, Neopen FF4012, Neopen FF4012 .

<Disperse dye>
In the present invention, a disperse dye can be used as long as it is soluble in a water-immiscible organic solvent. The disperse dye generally includes a water-soluble dye, but in the present invention, the disperse dye is preferably used as long as it is soluble in a water-immiscible organic solvent.
Preferable specific examples of the disperse dye include C.I. I. Disperse Yellow 5,42,54,64,79,82,83,93,99,100,119,122,124,126,160,184: 1,186,198,199,201,204,224 and 237 C. I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1,177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse Violet 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225 , 257, 266, 267, 287, 354, 358, 365 and 368; I. Disperse Green 6: 1 and 9;

The colorant that can be used in the present invention is preferably added to the photocurable ink composition of the present invention and then subjected to a dispersion treatment so as to be appropriately dispersed in the ink. For dispersing the colorant, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, or a paint shaker can be used.

  It is also possible to add a dispersant when dispersing the colorant. The type of the dispersant is not particularly limited, but a polymer dispersant is preferably used, and examples of the polymer dispersant include Noveon's Solsperse series and Ajinomoto Fine Techno's Ajisper series. Is mentioned. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. In the present invention, these dispersant and dispersion aid are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the colorant.

In the preparation of the photocurable ink composition of the present invention, the colorant may be blended by direct addition with each component, but in order to improve dispersibility, a solvent or the specific heterocyclic compound in the present invention, If desired, it may be added to a dispersion medium such as another polymerizable compound used in combination, and uniformly dispersed or dissolved, and then blended.

One or more colorants may be appropriately selected and used depending on the purpose of use of the photocurable ink composition.

In the photocurable ink composition of the present invention, when using a colorant such as a pigment that remains in a solid state, the average particle diameter of the colorant particles is preferably 0.005 to 0.5 μm, It is preferable to set the colorant, the dispersant, the dispersion medium, the dispersion conditions, and the filtration conditions so as to be more preferably 0.01 to 0.45 μm, and still more preferably 0.015 to 0.4 μm.
By such control of particle size, Oite photocurable Lee ink composition, clogging of a head nozzle can be suppressed, and the storage stability of the ink, it is possible to maintain the ink transparency and curing sensitivity.

The content of the colorant in the photocurable ink composition of the present invention is appropriately selected depending on the purpose of use of the photocurable ink composition, but generally, considering the physical properties and colorability of the composition, It is preferable that it is 0.5-10 mass% with respect to the mass of the whole photocurable composition, and it is more preferable that it is 1-8 mass%.
In addition, if the photocurable ink composition of the present invention is applied to a white ink composition using a white pigment such as titanium oxide as a colorant, the content of the colorant is set to ensure concealment. The content of the ink composition is preferably 5 to 30% by mass, and more preferably 10 to 25% by mass with respect to the total mass of the ink composition.

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

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

  As the sensitizing dye, a compound corresponding to the wavelength of actinic radiation that generates an initiation species in the radical polymerization initiator used in the ink composition may be used. Considering that it is used for a curing reaction of a general ink composition, examples of preferable sensitizing dyes include those belonging to the following compounds and having an absorption wavelength in the 350 nm to 450 nm region. Can be mentioned.

  Polynuclear aromatics (eg, anthracene, pyrene, perylene, triphenylene), thioxanthones (eg, isopropylthioxanthone), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (eg, Thiacarbocyanine, oxacarbocyanine), merocyanines (eg, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones (For example, anthraquinone), squalium (for example, squalium), coumarins (for example, 7-diethylamino-4-methylcoumarin), and the like. Xanthones may be mentioned as preferred class.

[(F) Co-sensitizer]
The photocurable ink composition of the present invention can also contain a co-sensitizer. In the present invention, the co-sensitizer has functions such as further improving the sensitivity of the sensitizing dye to actinic radiation or suppressing polymerization inhibition of the polymerizable compound by oxygen.

  Examples of co-sensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Science”, Vol. 10, page 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 co-sensitizers include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (eg, tributyltin acetate), Japanese Patent Publication No. 55-34414. Hydrogen donors described in JP-A-6-308727, sulfur compounds (e.g., trithiane) described in JP-A-6-308727, phosphorus compounds (such as diethyl phosphite) described in JP-A-6-250387, JP-A-8-65779 Examples include Si—H and Ge—H compounds.

<(G) Other ingredients>
If necessary, other components can be added to the photocurable ink composition of the present invention. Examples of other components include a polymerization inhibitor and a solvent.

  A polymerization inhibitor may be added from the viewpoint of enhancing the storage stability. Further, when the photocurable composition of the present invention is applied to an ink composition for ink jet recording, the ink composition is preferably discharged in the range of 40 to 80 ° C. by heating and reducing the viscosity. In order to prevent head clogging due to thermal polymerization, it is preferable to add a polymerization inhibitor. The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the ink composition of the present invention. Examples of the polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.

It is preferable that the radiation curable ink composition of the present invention does not contain a solvent so that it can react quickly and cure immediately after landing of the ink composition. However, a predetermined solvent can be included as long as the curing rate of the ink composition is not affected. In the present invention, an organic solvent or water can be used as the solvent. In particular, an organic solvent can be added in order to improve adhesiveness with a recording medium (a support such as paper). Suitable solvents include propylene carbonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, and mixtures thereof.
The amount of the organic solvent is, for example, in the range of 0.1 to 5% by mass, preferably 0.1 to 3% by mass, with respect to the total mass of the photocurable ink composition of the present invention.

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

The photocurable ink composition of the present invention, other radiation curable ink composition, coating composition, photocurable materials for color filters, can be used photoresist, a paint or the like.

[Ink composition]
The ink composition of the present invention is suitable for ink jet recording because of its excellent storage stability.
Hereinafter, the ink composition of the present invention will be described.

[Properties of ink composition]
The preferred physical properties of the ink composition of the present invention will be described.
The ink composition of the present invention has a viscosity of preferably 7 to 30 mPa · s, more preferably at a temperature at the time of ejection (for example, 40 to 80 ° C., preferably 25 to 50 ° C.) in consideration of ejectability. Is 7 to 25 mPa · s. For example, the viscosity of the ink composition of the present invention at room temperature (25 to 30 ° C.) is preferably 10 to 50 mPa · s, more preferably 12 to 40 mPa · s.

  It is preferable that the composition ratio of the ink composition of the present invention is appropriately adjusted so that the viscosity is in the above range. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be avoided, and uncured monomers and odors can be reduced. Furthermore, ink bleeding at the time of ink droplet landing can be suppressed, and as a result, the image quality is improved.

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

[Inkjet recording method]
The ink jet recording method of the present invention and the ink jet recording apparatus applicable to the ink jet recording method will be described below.

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

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

-Inkjet recording device-
There is no restriction | limiting in particular as an inkjet recording device used for the inkjet recording method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and can be used. That is, any known inkjet recording apparatus including a commercially available product can eject ink onto the recording medium in step (1) of the inkjet recording method of the present invention.

Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and an actinic radiation source.
The ink supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head has a multi-size dot of 1 to 100 pl, preferably 8 to 30 pl, for example, 320 × 320 to 4000 × 4000 dpi, preferably 400 × 400 to 1600 × 1600 dpi, and more preferably 720 ×. It can drive so that it can discharge with a resolution of 720 dpi. In the present invention, dpi represents the number of dots per 2.54 cm.

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

  The ink composition for ink jet recording of the present invention using the above ink jet recording apparatus is ejected by heating the ink composition to 40 to 80 ° C., more preferably 25 to 50 ° C. The viscosity of is preferably 7-30 mPa · s, and more preferably 7-25 mPa · s. In particular, it is preferable to use an ink composition having an ink viscosity of 25 to 500 mPa · s at 25 ° C. as the ink composition for ink jet recording of the present invention, because a large effect can be obtained. By using this method, high ejection stability can be realized.

  A radiation curable ink composition such as the ink composition of the present invention generally has a higher viscosity than a water-based ink that is usually used in inks for inkjet recording. The ink viscosity fluctuation has a great influence on the change of the droplet size and the change of the droplet discharge speed, and causes the image quality deterioration. Therefore, it is necessary to keep the temperature of the ink at the time of ejection as constant as possible. Therefore, in the present invention, it is appropriate that the control range of the ink temperature is ± 5 ° C. of the set temperature, preferably ± 2 ° C. of the set temperature, more preferably ± 1 ° C. of the set temperature.

Next, (2) a step of irradiating the ejected ink composition with active radiation to cure the ink composition will be described.
The ink composition ejected on the recording medium is cured by irradiation with actinic radiation. This is because the photopolymerization initiator contained in the ink composition of the present invention is decomposed by irradiation with actinic radiation to generate a starting species such as a radical, and depending on the function of the starting species, a specific heterocyclic compound or, if desired, This is because the polymerization reaction of other polymerizable compounds used in combination occurs and is accelerated. At this time, if a sensitizing dye is present together with the photopolymerization initiator in the ink composition, the sensitizing dye in the system absorbs actinic radiation to be in an excited state and promotes its decomposition by contact with the photopolymerization initiator. A more sensitive curing reaction can be achieved.

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

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

  Mercury lamps and gas / solid lasers are mainly used as actinic radiation sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing ultraviolet light curable ink compositions. . However, from the viewpoint of environmental protection, mercury-free is strongly desired, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, LED (UV-LED) and LD (UV-LD) are small, have a long life, have high efficiency, and are low in cost, and are expected as light sources for photo-curable ink jets.

  Further, a light emitting diode (LED) and a laser diode (LD) can be used as the active radiation source. In particular, when an ultraviolet light source is required, an ultraviolet LED and an ultraviolet LD can be used. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. If even shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit actinic radiation centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. The actinic radiation source particularly preferred in the present invention is a UV-LED, particularly preferably a UV-LED having a peak wavelength at 350 to 420 nm.

Incidentally, it is preferable that maximum illumination intensity of the LED on a recording medium is ^{10mW / cm 2 ~2,000mW / cm 2} , more preferably ^{20mW / cm 2 ~1,000mW / cm 2} , particularly preferably is a ^{50mW / cm 2 ~800mW / cm 2} .

The ink composition of the present invention is suitably irradiated with such actinic radiation for, for example, 0.01 seconds to 120 seconds, preferably 0.1 seconds to 90 seconds.
Actinic radiation irradiation conditions and a basic irradiation method are disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit including the ink ejection device, and the head unit and the light source are scanned by a so-called shuttle method. Irradiation with actinic radiation is performed for a certain period of time after ink landing (for example, 0.01 seconds to 0.5 seconds, preferably 0.01 seconds to 0.3 seconds, more preferably 0.01 seconds to 0.15). Seconds). In this way, by controlling the time from ink landing to irradiation to an extremely short time, it is possible to prevent the ink that has landed on the recording medium from spreading before curing. Further, since the ink can be exposed to the porous recording medium before the ink penetrates to a deep part where the light source does not reach, the residual unreacted monomer can be suppressed, and as a result, the odor can be reduced. .

  Further, the curing may be completed by another light source that is not driven. International Publication No. 99/54415 pamphlet discloses a method using an optical fiber or 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 as an irradiation method. Such a curing method can also be applied to the ink jet recording method of the present invention.

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

Thus, the ink composition of the present invention can be cured with high sensitivity by irradiation with actinic radiation, whereby a high-definition and high-strength image can be formed on the surface of the recording medium. In addition, an image excellent in adhesiveness with a recording medium can be formed.
Furthermore, when the ink composition of the present invention is applied to an ink jet apparatus, it does not cause deposition of contained components around the ink jet head or the like, and is an ink composition having excellent ejection stability. Image formation can be performed.

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

[Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink composition.

(Cyan ink composition)
N-vinyl piperidone 10.5 parts Monofunctional acrylate (Sartomer SR339) 36.5 parts Monofunctional acrylate (Sartomer SR506) 23.7 parts Bifunctional acrylate (Sartomer SR508) 4.0 parts・ N-Vinylcaprolactam 14.0 parts (V-CAP manufactured by ASP Japan)
・ Solsperse 32000 (Noveon dispersant) 1.2 parts ・ Irgalite Blue GLVO 3.0 parts (Ciba Japan Co., Ltd. pigment)
-First cure ST-1 (polymerization inhibitor manufactured by Chem First) 0.05 parts-Lucirin TPO (photoinitiator manufactured by BASF) 5.0 parts-Irgacure 369 0.5 parts (photoinitiator manufactured by Ciba Japan)
・ 4-phenylbenzophenone (Tokyo Kasei Kogyo Co., Ltd. photoinitiator) 1.0 part ・ Darocur ITX 0.5 part (Ciba Japan Co., Ltd. photoinitiator)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

(Evaluation of ink composition)
Recording was performed on a sheet made of polyvinyl chloride using an ink jet recording apparatus having the obtained cyan ink composition and a piezo type ink jet head (CA3 head manufactured by Toshiba Tec). The ink supply system is composed of an original tank, supply piping, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head, and temperature control is performed so that the nozzle portion is always 45 ° C. ± 3 ° C. (100% Print coated image). After discharging the ink composition, irradiation was performed by passing it through a light beam of an iron-doped ultraviolet lamp (power 120 W / cm ² ) at a speed of 40 m / min to cure the ink and obtain a printed matter.
At this time, the following evaluation was performed. The obtained evaluation results are shown together in Table 1 together with the evaluation results of other examples and comparative examples.

<Curing sensitivity>
The exposure energy in curing was measured with a light quantity integrator (UV PowerMAP manufactured by EIT). It is evaluated that the smaller this value is, the higher the sensitivity is. As a result, it was confirmed that the ink composition of Example 1 was cured with high sensitivity because the cumulative exposure amount of ultraviolet rays on the sheet was about 400 mJ / cm ² .

<Curing property>
The curability was evaluated by curing a printed matter of this ink composition with an ultraviolet ray cumulative exposure amount of about 600 mJ / cm ² on the sheet, and palpating the cured image portion. Curability is evaluated by the presence or absence of tackiness on the surface of the cured film.
As a result, it was confirmed that the ink composition of Example 1 had completely lost the tackiness after curing and was excellent in curability.

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

<Discharge stability>
The obtained ink composition was stored at 60 ° C. for 2 weeks and at −15 ° C. for 2 weeks, and then recorded on a recording medium using the above-described inkjet recording apparatus having a piezoelectric inkjet nozzle. When continuous printing was performed for time, the presence or absence of dot omission and ink splattering was visually observed, and the average value of the results of performing this three times was evaluated according to the following criteria. The results are shown in Table 1 below. “B” or higher is a level where there is no practical problem, and “C” and “D” are levels where there is a practical problem.
A: Dot missing or ink splatter does not occur or occurs less than 1 point B: Dot missing or ink splatter occurs at 1 or more and less than 2 places C: Dot missing or ink splatter occurs at 2 or more and 6 places Occurrence of less than D: Occurrence of dot missing or ink scattering at 6 or more locations

[Example 2]
The following components were stirred with a high-speed water-cooled stirrer to obtain a magenta UV inkjet ink composition.

(Magenta ink composition)
・ 13.0 parts of N-vinylpiperidone ・ 15.0 parts of N-vinylcaprolactam (V-CAP manufactured by ASP Japan)
・ Bifunctional acrylate (Sartomer SR9045) 20.7 parts ・ Monofunctional acrylate (Sartomer SR339) 59.0 parts ・ Multifunctional acrylate (Sartomer SR399) 1.0 part ・ Rapi-Cure DVE-3 4 .0 part (vinyl ether compound manufactured by ISP Europe)
Solsperse 32000 (Noveon dispersant) 1.2 parts Cinquasia Magenta RT-355D [component (C)] 3.6 parts (Ciba Japan Co., Ltd. pigment)
-Firstcure ST-1 (polymerization inhibitor manufactured by Chem First) 0.05 parts-Lucirin TPO (photoinitiator manufactured by BASF) 5.0 parts-Irgacure 369 0.4 parts (photoinitiator manufactured by Ciba Japan)
・ 4-phenylbenzophenone (Tokyo Kasei Kogyo Co., Ltd. photoinitiator) 1.0 part ・ Darocur ITX 1.0 part (Ciba Japan Co., Ltd. photoinitiator)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

The obtained magenta ink composition was discharged on a polyvinyl chloride sheet in the same manner as in Example 1 and cured.
The magenta ink composition and the printed material obtained using the ink composition were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3
The following components were stirred with a high-speed water-cooled stirrer to obtain a black UV inkjet ink composition.

(Black ink composition)
-N-vinyl piperidone 22.0 parts-Monofunctional acrylate (SR339 manufactured by Sartomer) 41.0 parts-Monofunctional acrylate (SR489 manufactured by Sartomer) 21.2 parts-Multifunctional acrylate (SR399 manufactured by Sartomer) 1.0 part -Rapi-Cure DVE-3 4.0 parts (vinyl ether compound made by ISP Europe)
・ Solsperse 32000 (Noveon dispersant) 1.2 parts ・ Microlith Black CK [component (C)] 2.6 parts (Ciba Japan Co., Ltd. pigment)
First ST-1 (Chem First manufactured polymerization inhibitor) 0.05 parts Lucirin TPO (BASF photoinitiator) 4.4 parts Irgacure 369 0.5 part (Ciba Japan photoinitiator)
・ 4-phenylbenzophenone (Tokyo Kasei Kogyo Co., Ltd. photoinitiator) 1.0 part ・ Darocur ITX 1.0 part (Ciba Japan Co., Ltd. photoinitiator)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

The obtained black ink composition was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured.
The black ink composition and the printed material using the ink composition were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.

(White ink composition)
・ N-Vinyl Piperidone 15.0 parts ・ N-Vinyl Caprolactam 15.0 parts (V-CAP manufactured by ASP Japan)
-Bifunctional acrylate (Sartomer SR9045) 4.0 parts-Monofunctional acrylate (Sartomer SR339) 39.0 parts-Multifunctional acrylate (Sartomer SR399) 3.0 parts-Solperse 36000 (Noveon dispersion) Agent) 2.4 parts · MICROLITH WHITE RA 16.0 parts (pigment manufactured by Ciba Japan)
・ FirstST ST (polymerization inhibitor manufactured by Chem First) 0.05 part ・ Lucirin TPO (photoinitiator manufactured by BASF) 4.0 part ・ Irgacure 369 0.2 part (photoinitiator manufactured by Ciba Japan)
・ 4-phenylbenzophenone (Tokyo Kasei Kogyo Co., Ltd. photoinitiator) 1.1 parts ・ Darocur ITX 0.2 part (Ciba Japan Co., Ltd. photoinitiator)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

The obtained white ink composition was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured.
The white ink composition and the printed material using the ink composition were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.

(White ink composition)
・ N-Vinylcaprolactam 30.0 parts (V-CAP manufactured by ISP Japan)
-Bifunctional acrylate (Sartomer SR9045) 4.0 parts-Monofunctional acrylate (Sartomer SR339) 39.0 parts-Multifunctional acrylate (Sartomer SR399) 3.0 parts-Solperse 36000 (Noveon dispersion) Agent) 2.4 parts · MICROLITH WHITE RA 16.0 parts (pigment manufactured by Ciba Japan)
・ FirstST ST (polymerization inhibitor manufactured by Chem First) 0.05 part ・ Lucirin TPO (photoinitiator manufactured by BASF) 4.0 part ・ Irgacure 369 0.2 part (photoinitiator manufactured by Ciba Japan)
・ 4-phenylbenzophenone (Tokyo Kasei Kogyo Co., Ltd. photoinitiator) 1.1 parts ・ Darocur ITX 0.2 part (Ciba Japan Co., Ltd. photoinitiator)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

The obtained white ink composition of Comparative Example 1 was discharged on a polyvinyl chloride sheet in the same manner as in Example 1 and cured.
The white ink composition and the printed material using the ink composition were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink composition.

(White ink composition)
-Bifunctional acrylate (Sartomer SR9045) 4.0 parts-Monofunctional acrylate (Sartomer SR339) 69.0 parts-Multifunctional acrylate (Sartomer SR399) 3.0 parts-Solperse 36000 (Noveon dispersion) Agent) 2.4 parts · MICROLITH WHITE RA 16.0 parts (pigment manufactured by Ciba Japan)
・ FirstST ST (polymerization inhibitor manufactured by Chem First) 0.05 part ・ Lucirin TPO (photoinitiator manufactured by BASF) 4.0 part ・ Irgacure 369 0.2 part (photoinitiator manufactured by Ciba Japan)
・ 4-phenylbenzophenone (Tokyo Kasei Kogyo Co., Ltd. photoinitiator) 1.1 parts ・ Darocur ITX 0.2 part (Ciba Japan Co., Ltd. photoinitiator)
・ Byk 307 (defoamer manufactured by BYK Chemie) 0.05 parts

The obtained white ink composition was discharged onto a polyvinyl chloride sheet in the same manner as in Example 1 and cured.
The white ink composition and the printed material using the ink composition were evaluated in the same manner as in Example 1. The results are shown in Table 1.

  As is clear from Table 1, each ink composition of the examples is excellent in curability and adhesion of images obtained after curing in comparison with the ink compositions in the comparative examples. I understand. Furthermore, it can be seen that the ink compositions of the examples are excellent in stability over time (storage stability) because of high ejection stability even when applied to inkjet recording.

Claims (6)

(A) N-vinyl piperidone;
(B) a polymerizable compound having a structure different from that of N-vinylpiperidone;
(C) a photopolymerization initiator;
And (A) the content of N-vinylpiperidone is 0.1% by mass or more and 50% by mass or less based on the total amount of the ink composition. (D) a colorant further photocurable ink composition according to claim 1 containing. The total content of the (A) N-vinyl piperidone and the polymerizable compound having a structure different from the (B) N-vinyl piperidone is 60% by mass or more and 95% by mass or less based on the total amount of the ink composition. The photocurable ink composition according to claim 1 or 2.   The photocurable ink composition according to any one of claims 1 to 3, wherein the polymerizable compound (B) having a structure different from that of N-vinylpiperidone contains N-vinylcaprolactam. The photocurable ink composition according to any one of claims 1 to 4, which is for inkjet recording. (1) a step of discharging the photocurable ink composition according to claim 5 onto a recording medium; and
(2) discharged with actinic radiation by irradiating the photocurable ink composition, a step of curing the photocurable ink composition,
An ink jet recording method comprising: