Ink composition for photo-curable inkjet recording and ink set

Abstract

To provide an ink composition for photo curing inkjet recording, which shows excellent curability and contains a yellow colorant.SOLUTION: An ink composition for photo-curing inkjet recording which contains a yellow colorant, a polymerizable compound, and a photopolymerization initiator, in which the yellow colorant is contained in the concentration of 4.6 wt.% or smaller in the ink composition, the ink composition has the viscosity at 25°C of 12 mPa s or smaller, has absorbance of light of a wave length 365 nm of the ink composition diluted to 1000 times in a cell having an optical path of 10 mm of 0.6 or smaller.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a photocurable ink composition for ink jet recording, and more particularly to a photocurable ink composition for ink jet recording that contains a yellow colorant. [Background technology]

[0002] Inkjet recording methods include, for example, a photocurable inkjet recording method in which a coating film is cured by irradiation with active energy rays such as ultraviolet rays, and an inkjet recording method in which an ink is allowed to penetrate into a recording medium and the solvent is removed by drying, etc. In general, the photocurable inkjet recording method has the advantages of forming images with superior coating film strength, superior printability for design images, and suitability for high-speed printing, as compared with solvent-based inkjet recording methods.

[0003] A typical example of high-speed printing using a photocurable inkjet recording method is a single-pass inkjet printing method in which ink is applied to a substrate by using multiple inkjet heads arranged in the transport direction of the substrate, and then the ink is cured. Photocurable inkjet recording ink compositions are cured using a single light source such as a mercury lamp, a metal halide lamp, or, in recent years, a UV-LED.

[0004] However, as printing speed increases, the amount of light irradiated onto the applied ink decreases, causing a problem of insufficient curing of the photocurable ink composition for ink jet recording.

[0005] When printing in full color with an inkjet printer, the basic colors are usually a combination of black, cyan, magenta, and yellow inks. Of these colors, black and yellow are known to absorb a large amount of energy in the UV radiation wavelength range due to the absorption characteristics of the coloring materials. Yellow in particular is used not only alone, but also in what are called secondary colors, green (cyan + yellow) and red (magenta + yellow).

[0006] Patent Document 1 describes an active energy ray-curable ink set for use in a one-pass inkjet system, in which the sum of the light absorption amounts of the initiators contained in the inks at 380 to 410 nm is 50 or more, and the ink set is designed so that the sum of the light absorption amounts of the inks becomes smaller according to the printing order. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2015-81311 A Summary of the Invention [Problem to be solved by the invention]

[0008] In photocurable inks containing yellow colorants, the yellow colorant absorbs a large amount of UV energy, which reduces the efficiency of radical generation by UV irradiation, so sufficient curing may not be achieved even if the amount of photopolymerization initiator is increased. If the curing property of yellow ink is poor, the aesthetics of the printed matter may be impaired.

[0009] The present invention has been made to solve the above-mentioned problems in the conventional art, and an object of the present invention is to provide a photocurable ink composition for inkjet recording, which contains a yellow colorant and shows good curability even when subjected to high-speed printing. [Means for solving the problem]

[0010] The present invention provides a photocurable ink composition for ink-jet recording, comprising a yellow colorant, a polymerizable compound, and a photopolymerization initiator, the yellow colorant is contained in the ink composition at a concentration of 4.6% by weight or less; the ink composition has a viscosity of 12 mPa s or less at 25°C; The present invention provides a photocurable ink composition for ink jet recording, which, when diluted 1000 times and placed in a cell having an optical path length of 10 mm, has an absorbance of 0.6 or less for light having a wavelength of 365 nm.

[0011] In one embodiment, the ink composition is diluted 1000 times and placed in a cell with an optical path length of 10 mm, and the total absorbance of light having a wavelength of 365 to 435 nm is 105 or less.

[0012] In one embodiment, any one of the ink compositions described above has a viscosity change rate of 20% or less after storage for 28 days in an environment of 60° C. compared to the ink composition before storage.

[0013] In one embodiment, any one of the ink compositions described above uses a UV lamp as a curing light source.

[0014] In one embodiment, any one of the ink compositions described above is used in a single-pass inkjet recording method.

[0015] In one embodiment, the yellow colorant comprises CI Pigment Yellow 150.

[0016] In one embodiment, the polymerizable compound is represented by the formula CH2=CR1-COOR2-O-CH=CH-R3...(I) (In the formula, R1 represents a hydrogen atom or a methyl group, R2 represents a divalent organic residue having 2 to 20 carbon atoms, and R3 represents a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.) The vinyl ether group-containing (meth)acrylic acid ester is represented by the following formula:

[0017] The present invention provides an ink set comprising any one of the photocurable ink compositions for ink jet recording described above. Effect of the Invention

[0018] According to the present invention, there is provided a photocurable ink jet recording ink composition containing a yellow colorant, which exhibits good curability even when subjected to high-speed printing. Also, according to the present invention, there is provided a photocurable ink jet recording ink set including the photocurable ink jet recording ink composition containing a yellow colorant. [Brief description of the drawings]

[0019] [Figure 1] 1 is a graph showing the ultraviolet-visible absorption spectra of ink compositions (Y-1) to (Y-4) of the present invention diluted 1000 times. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, the embodiments of the present invention will be described in detail. In this specification, acrylic and methacrylic may be referred to as "(meth)acrylic". In addition, the compound name may be followed by "based" to collectively refer to the compound and its derivatives. When the compound name is followed by "based" to represent the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative, or that the repeating unit derived from the compound or its derivative is chemically modified after polymerization.

[0021] <Photocurable ink composition for inkjet recording> The ink composition for inkjet recording according to the embodiment of the present invention (hereinafter, sometimes referred to as the ink composition) is preferably used in a single-pass type inkjet recording device. The ink composition contains a pigment, a polymerizable compound, and a photopolymerization initiator. The polymerizable compound includes a vinyl ether group-containing (meth)acrylic acid ester, a monofunctional monomer, and a polyfunctional monomer. The vinyl ether group-containing (meth)acrylic acid ester is represented by the general formula (I). The monofunctional monomer is at least one selected from the group consisting of an acrylamide monomer and a monofunctional (meth)acrylic monomer. The content of the monofunctional monomer is 1% by mass or more and 9% by mass or less. The content of the polyfunctional (meth)acrylic monomer is 5% by mass or more and 50% by mass or less. The glass transition temperature of the polymer of the monofunctional (meth)acrylic monomer is 30° C. or more, and the glass transition temperature of the polymer of the polyfunctional (meth)acrylic monomer is 30° C. or more.

[0022] [1. Single pass method] A single-pass type inkjet recording device is equipped with a line head that covers the entire area of ​​the recording medium in a direction perpendicular to the recording medium transport direction. This inkjet recording device moves the recording medium in the transport direction only once relative to the fixed line head, and forms an image on the recording medium by ejecting ink droplets from the nozzles of the line head in conjunction with this movement. Therefore, a single-pass type inkjet recording device is capable of high-speed printing and can improve productivity. The ejection method is preferably a piezo method.

[0023] As a light source for curing the ink, a UV lamp is preferably used. The wavelength of the light emitted by a UV-LED is limited, and the wavelength range is narrow, so the light may not reach the depth of the adhesive coating, which may cause poor curing. The output of a UV-LED is lower than that of a UV lamp, and this is also a cause of poor curing of the adhesive coating when a UV-LED is used as a light source for curing the ink.

[0024] As the UV lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a high power metal lamp, etc. can be used. The output of the UV lamp is generally 80 to 240 W / cm, preferably 160 to 240 W / cm. If the output of the UV lamp is less than 80 W / cm, there is a risk of insufficient irradiation and curing failure during high speed printing. If a UV lamp with an output exceeding 240 W / cm is used, there is a risk of deformation of the printing substrate due to heat generated during UV irradiation. Among these, the preferred UV lamps are high pressure mercury lamps and metal halide lamps.

[0025] [2. Photopolymerization initiator] In this specification, the photopolymerization initiator absorbs active energy rays and initiates a photopolymerization reaction (chain polymerization reaction). Examples of the photopolymerization initiator include acylphosphine oxide compounds, alkylphenone compounds, and thioxanthone compounds.

[0026] Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Examples of commercially available acylphosphine oxide compounds include "OmniradTPO" (trade name) and "Omnirad819" (trade name) manufactured by IGM.

[0027] Examples of alkylphenone compounds include 2,2-dimethoxy-1,2-diphenylethan-1-one and 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one. Commercially available alkylphenone compounds include "Omnirad651" (trade name) and "Omnirad907" (trade name) manufactured by BASF.

[0028] Examples of thioxanthone compounds include thioxanthone, 2,4-dimethylthioxanthone, 2-chlorothioxanthone, 2-ethylthioxanthone, and 1-chloro-4-propoxythioxanthone.

[0029] From the viewpoint of efficiently progressing the photopolymerization reaction, the content of the photopolymerization initiator is preferably 5 parts by mass or more and 25 parts by mass or less, and more preferably 10 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the ink composition.

[0030] [3. Polymerizable compound] In this specification, a polymerizable compound is a compound that can form a polymer by a polymerization reaction. The polymerizable compound includes a vinyl ether group-containing (meth)acrylic acid ester represented by general formula (I), at least one monofunctional monomer selected from the group consisting of an acrylamide monomer and a monofunctional (meth)acrylic monomer, and a polyfunctional (meth)acrylic monomer. The glass transition temperature of the polymer of the monofunctional (meth)acrylic monomer is 30°C or higher. The glass transition temperature of the polymer of the polyfunctional (meth)acrylic monomer is 30°C or higher.

[0031] (3-1. Vinyl ether group-containing (meth)acrylic acid esters) The vinyl ether group-containing (meth)acrylic acid esters are represented by the general formula (I): CH2=CR1-COOR2-O-CH=CH-R3...(I) [In the general formula (I), R1 represents a hydrogen atom or a methyl group, R2 represents a divalent organic residue having 2 to 20 carbon atoms, and R3 represents a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms] Hereinafter, the vinyl ether group-containing (meth)acrylic acid ester represented by general formula (I) may be referred to as (meth)acrylic acid ester (I). The vinyl ether group-containing (meth)acrylic acid ester (I) has a structure having both a radical polymerizable group and an ionically polymerizable group in the molecule, and can provide an ink composition with excellent reactivity and curability.

[0032] Examples of divalent organic residues having 2 to 20 carbon atoms include alkylene groups having 2 to 20 carbon atoms, cycloalkylene groups having 3 to 20 carbon atoms, and divalent aromatic groups having 6 to 10 carbon atoms. The divalent organic residues having 2 to 20 carbon atoms may be substituted.

[0033] The alkylene group having 2 to 20 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 2 to 20 carbon atoms include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, and a hexadecylene group. The alkylene group having 2 to 20 carbon atoms is preferably an alkylene group having 2 to 9 carbon atoms, more preferably an oxoalkylene group having 1 to 8 carbon atoms, an alkylene group having 9 to 15 carbon atoms and substituted with either 2 to 4 oxygen atoms, and an alkylene group having 2 to 6 carbon atoms.

[0034] The alkylene group having from 2 to 9 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having from 2 to 9 carbon atoms include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, and a nonylene group.

[0035] An oxoalkylene group having from 1 to 8 carbon atoms is linear or branched and unsubstituted. An oxoalkylene group having from 1 to 8 carbon atoms is a substituent in which one -CH2- in an alkylene group having from 2 to 9 carbon atoms is replaced with -O-.

[0036] The alkylene group having 9 to 15 carbon atoms is linear or branched and unsubstituted. Examples of the alkylene group having 9 to 15 carbon atoms include a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tridodecylene group, a tetradecylene group, a tetradecylene group, and a pentadecylene group.

[0037] The alkylene group having from 2 to 6 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having from 2 to 6 carbon atoms include an ethylene group, a propylene group, a butylene group, a pentylene group, and a hexylene group.

[0038] The cycloalkylene group having 3 to 20 carbon atoms is cyclic and unsubstituted. Examples of the cycloalkylene group having 3 to 20 carbon atoms include cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene, cyclooctylene, cyclononylene, cyclodecylene, cycloundecylene, and cyclohexadecylene. The cycloalkylene group having 3 to 20 carbon atoms may be a cycloalkylene group having 3 to 20 carbon atoms that may be substituted with a plurality of alkyl groups having 1 to 3 carbon atoms. The alkyl group having 1 to 3 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, a propyl group, and an isopropyl group.

[0039] The divalent aromatic group having 6 to 10 carbon atoms is cyclic and unsubstituted. Examples of the divalent aromatic group having 6 to 10 carbon atoms include a phenylene group and a naphthylylene group. The divalent aromatic group having 6 to 10 carbon atoms may be a divalent aromatic group having 6 to 10 carbon atoms that may be substituted with a plurality of alkyl groups having 1 to 3 carbon atoms.

[0040] Examples of monovalent organic residues having 1 to 11 carbon atoms include alkyl groups having 1 to 10 carbon atoms, cycloalkyl groups having 3 to 10 carbon atoms, and monovalent aromatic groups having 6 to 10 carbon atoms.

[0041] The alkyl group having 1 to 10 carbon atoms is linear or branched and unsubstituted. Examples of the alkyl group having 1 to 10 carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, nonyl, and decyl. The alkyl group having 1 to 10 carbon atoms is preferably an alkyl group having 1 to 3 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms which may be substituted with a phenyl group, and further preferably a methyl group, an ethyl group, and a benzyl group. The monovalent aromatic group having 6 to 10 carbon atoms which may be substituted is preferably a phenyl group. The alkyl group having 1 to 3 carbon atoms is synonymous with an alkyl group having 1 to 3 carbon atoms in a cycloalkylene group having 3 to 20 carbon atoms.

[0042] Cycloalkyl groups having from 3 to 10 carbon atoms are cyclic and unsubstituted. Examples of cycloalkyl groups having from 3 to 10 carbon atoms include cyclopentane, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups.

[0043] The monovalent aromatic group having 6 to 10 carbon atoms is cyclic and unsubstituted. Examples of the monovalent aromatic group having 6 to 10 carbon atoms include a phenyl group and a naphthyl group.

[0044] Examples of the (meth)acrylic acid esters (I) include vinyloxyalkyl (meth)acrylates, vinyloxycycloalkyl (meth)acrylates, alkylvinyloxyalkyl (meth)acrylates, vinyloxyalkylcycloalkylalkyl (meth)acrylates, vinyloxyalkylarylalkyl (meth)acrylates, vinyloxyalkoxyalkyl (meth)acrylates, vinyloxyalkoxyalkoxyalkyl (meth)acrylates, and vinyloxyalkoxyalkoxyalkoxyalkyl (meth)acrylates. These (meth)acrylic acid esters (I) may be used alone or in combination of two or more.

[0045] Examples of the vinyloxyalkyl (meth)acrylate include 2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, and 2-vinyloxybutyl (meth)acrylate.

[0046] Examples of the vinyloxycycloalkyl (meth)acrylate include vinyloxycyclohexyl (meth)acrylate.

[0047] Examples of the alkyl vinyloxyalkyl (meth)acrylate include 2-methyl-3-vinyloxypropyl (meth)acrylate and 1-methyl-2-vinyloxypropyl (meth)acrylate.

[0048] Examples of the vinyloxyalkylcycloalkylalkyl (meth)acrylate include 3-vinyloxymethylcyclohexylmethyl (meth)acrylate.

[0049] An example of the vinyloxyalkylarylalkyl (meth)acrylate is p-vinyloxymethylphenylmethyl (meth)acrylate.

[0050] Examples of vinyloxyalkoxyalkyl (meth)acrylates include 2-(2-vinyloxyethoxy)ethyl acrylate (VEEA), 2-(2-vinyloxyethoxy)ethyl methacrylate (VEEM), 2-(vinyloxyisopropoxy)propyl (meth)acrylate, and 2-(vinyloxyisopropoxy)isopropyl (meth)acrylate.

[0051] Examples of the vinyloxyalkoxyalkoxyalkyl (meth)acrylate include vinyloxyethoxyethoxyethyl (meth)acrylate.

[0052] Examples of the vinyloxyalkoxyalkoxyalkoxyalkyl (meth)acrylate include vinyloxyethoxyethoxyethoxyethyl (meth)acrylate.

[0053] Among these (meth)acrylic acid esters (I), 2-(2-vinyloxyethoxy)ethyl (meth)acrylate is preferred because it has a low viscosity, a low odor, can suppress irritation to the skin, a high flash point, and excellent reactivity and curing properties, and the coating film formed by curing has excellent adhesion.

[0054] From the viewpoint of being able to reduce the viscosity of the ink and improve the reactivity and adhesion, the content of the (meth)acrylic acid esters (I) in the ink composition is preferably from 30% by mass to 50% by mass, more preferably from 35% by mass to 50% by mass, and more preferably from 35% by mass to 45% by mass.

[0055] (3-2. Monofunctional Monomers) In this specification, a monofunctional monomer has one polymerizable portion (for example, an ethylenic double bond) in one molecule. The monofunctional monomer is at least one selected from the group consisting of an acrylamide monomer and a monofunctional (meth)acrylic monomer. The content of the monofunctional monomer is 1% by mass or more and 9% by mass or less in the ink composition. The glass transition temperature Tg of the polymer of the monofunctional (meth)acrylic monomer is 30° C. or more. The monofunctional monomer has a relatively low viscosity, and the glass transition temperature Tg of the polymer of the monofunctional (meth)acrylic monomer is relatively high. Therefore, when the ink composition contains a monofunctional monomer at a content of 1% by mass or more and 9% by mass or less, it can function as a diluent for the (meth)acrylic acid esters (I) and the polyfunctional (meth)acrylic monomer, and can form a coating film that is excellent in ejection stability and safety and has excellent strength, that is, an ink composition that has a good balance of the three properties can be provided. From the viewpoint of further improving the above three properties, the content of the monofunctional monomer in the ink composition is preferably 7% by mass or more and 9% by mass or less, and more preferably 5% by mass or more and 9% by mass or less.

[0056] The Primary Irritation Index (PII value) is a physical property value that indicates skin irritation. The higher the PII value, the stronger the skin irritation and the more careful the compound should be when handled.

[0057] (3-2-1. Acrylamide monomers) Examples of the acrylamide monomer include dimethylacrylamide, diethylacrylamide, 2-hydroxyethylacrylamide, dimethylaminopropylacrylamide, and acryloylmorpholine (ACMO). Among these acrylamide monomers, acrylamide monomers having a cyclic structure (more specifically, an alicyclic structure or a heterocyclic structure, etc.) are preferred, and acryloylmorpholine is more preferred.

[0058] (3-2-2. Monofunctional (meth)acrylic monomers) The monofunctional (meth)acrylic monomer may, for example, be a monofunctional (meth)acrylic monomer having a chain structure or a cyclic structure. Here, the monofunctional (meth)acrylic monomer having a chain structure does not have a cyclic structure in its molecular structure, but has a straight chain structure or a branched structure. The monofunctional (meth)acrylic monomer having a cyclic structure has a cyclic structure in its molecular structure, and may further have a chain structure.

[0059] The monofunctional (meth)acrylic monomer preferably has a cyclic structure, from the viewpoint that the polymer of the monofunctional (meth)acrylic monomer has a glass transition temperature of 30° C. or more. Examples of the monofunctional (meth)acrylic monomer having a cyclic structure include monocyclic alicyclic (meth)acrylates, polycyclic alicyclic (meth)acrylates, and heterocyclic (meth)acrylates. Examples of the monocyclic alicyclic (meth)acrylates include cycloalkyl (meth)acrylates (more specifically, 3,3,5-trimethylcyclohexyl acrylate (TMCHA) and the like). Examples of the polycyclic alicyclic (meth)acrylates include isobornyl acrylate (IBOA), isobornyl methacrylate, norbornyl (meth)acrylate, amadantyl (meth)acrylate, and dicyclopentanyl (meth)acrylate. Examples of the heterocyclic (meth)acrylates include cyclic trimethylolpropane formal acrylate (CTFA). These monofunctional (meth)acrylic monomers may be used alone or in combination of two or more.

[0060] Among these monofunctional (meth)acrylic monomers, at least one selected from the group consisting of isobornyl acrylate (IBOA), 3,3,5-trimethylcyclohexyl acrylate (TMCHA), cyclic trimethylolpropane formal acrylate (CTFA), and isobornyl methacrylate is preferred, and at least one selected from the group consisting of isobornyl acrylate (IBOA), 3,3,5-trimethylcyclohexyl acrylate (TMCHA), and cyclic trimethylolpropane formal acrylate (CTFA) is more preferred.

[0061] The glass transition temperature Tg of the polymer of the monofunctional (meth)acrylic monomer is 30° C. or more from the viewpoint of improving the coating strength. The glass transition temperature of the monofunctional (meth)acrylic monomer is preferably 30° C. or more and 90° C. or less, more preferably 40° C. or more and 90° C. or less, from the viewpoint of improving the discharge stability and safety while maintaining an excellent coating strength. In this specification, the polymer of the monofunctional (meth)acrylic monomer is a polymer in which the monofunctional (meth)acrylic monomer is polymerized alone. That is, it means that the polymer is substantially composed of repeating units derived from one type of monofunctional (meth)acrylic monomer. The polymer is substantially composed of repeating units derived from one type of monofunctional (meth)acrylic monomer means that the repeating units derived from one type of monofunctional (meth)acrylic monomer are 99 mol % or more of the total repeating units constituting the polymer.

[0062] (3-3. Polyfunctional (meth)acrylic monomer) In this specification, a polyfunctional (meth)acrylic monomer has two or more polymerizable portions (e.g., ethylenic double bonds) in one molecule. Examples of polyfunctional (meth)acrylic monomers include difunctional (meth)acrylic monomers, trifunctional (meth)acrylic monomers, tetrafunctional (meth)acrylic monomers, and pentafunctional (meth)acrylic monomers. The polyfunctional (meth)acrylic monomer may have a chain structure or an alicyclic structure. Here, the polyfunctional (meth)acrylic monomer having a chain structure does not have a cyclic structure in its molecular structure, but has a linear structure or a branched structure. The polyfunctional (meth)acrylic monomer having an alicyclic structure has an alicyclic structure in its molecular structure, and may further have a chain structure.

[0063] From the viewpoints of providing a polymer of the polyfunctional (meth)acrylic monomer with a glass transition temperature of 30° C. or higher and improving the safety of the ink composition, the polyfunctional (meth)acrylic monomer is preferably a bifunctional (meth)acrylic monomer, more preferably contains a bifunctional (meth)acrylic monomer having a chain structure and a bifunctional (meth)acrylic monomer having an alicyclic structure, and even more preferably contains only a bifunctional (meth)acrylic monomer having a chain structure.

[0064] Examples of difunctional (meth)acrylic monomers having a chain structure include alkanediol diacrylates (more specifically, methyl-1,5-pentanediol diacrylate (MPDDA), 1,9-nonanediol diacrylate (1,9ND-A), and 1,10-decanediol diacrylate (DDDA), etc.), polyalkylene glycol diacrylates (more specifically, dipropylene glycol diacrylate (DPGDA), and tripropylene glycol diacrylate (TPGDA), etc.), and other diacrylates (more specifically, neopentyl glycol hydroxypivalic acid ester diacrylate (HPNDA), and neopentyl glycol propylene oxide diacrylate (NPGPODA), etc.). These polyfunctional (meth)acrylic monomers having a chain structure may be used alone or in combination of two or more.

[0065] An example of a difunctional (meth)acrylic monomer having a cyclic structure is dicyclopentanyl diacrylate (DCPDA).

[0066] Examples of polyfunctional (meth)acrylic monomers other than difunctional include trifunctional (meth)acrylic monomers such as propoxylated trimethylolpropane tri(meth)acrylate, glycerin propoxy tri(meth)acrylate, or pentaerythritol tri(meth)acrylate, tetrafunctional (meth)acrylic monomers such as pentaerythritol tetra(meth)acrylate, and pentafunctional (meth)acrylic monomers such as dipentaerythriyl hydroxypenta(meth)acrylate.

[0067] Among these polyfunctional (meth)acrylic monomers, dicyclopentanyl diacrylate (DCPDA), methyl-1,5-pentanediol diacrylate (MPDDA), dipropylene glycol diacrylate (DPGDA), neopentyl glycol hydroxypivalic acid ester diacrylate (HPNDA), 1,10-decanediol diacrylate (DDDA), tripropylene glycol diacrylate (TPGDA), neopentyl glycol propylene oxide diacrylate (NPGPODA) and 1,9-nonanediol diacrylate (1,9ND-A) are preferred, and at least one selected from the group consisting of dipropylene glycol diacrylate (DPGDA), neopentyl glycol hydroxypivalic acid ester diacrylate (HPNDA), 1,9-nonanediol diacrylate (1,9ND-A), tripropylene glycol diacrylate (TPGDA), and neopentyl glycol propylene oxide diacrylate (NPGPODA) is more preferred.

[0068] The glass transition temperature Tg of the polymer of the polyfunctional (meth)acrylic monomer is 30° C. or more from the viewpoint of improving the coating strength. The glass transition temperature Tg of the polyfunctional (meth)acrylic monomer is preferably 30° C. or more and 200° C. or less, more preferably 30° C. or more and 150° C. or less, from the viewpoint of improving the discharge stability and safety while maintaining excellent coating strength. In this specification, the polymer of the polyfunctional (meth)acrylic monomer is a polymer in which the polyfunctional (meth)acrylic monomer is polymerized alone. That is, it means that the polymer is substantially composed of repeating units derived from one type of polyfunctional (meth)acrylic monomer. The polymer is substantially composed of repeating units derived from one type of polyfunctional (meth)acrylic monomer means that the repeating units derived from one type of polyfunctional (meth)acrylic monomer are 99 mol % or more of the total repeating units constituting the polymer.

[0069] The content of the polyfunctional (meth)acrylic monomer is 5% by mass or more and 50% by mass or less in the ink composition from the viewpoint of improving the ejection stability and safety of the ink composition and improving the coating strength. When the ink composition contains a white colorant as a colorant, the content of the polyfunctional (meth)acrylic monomer is preferably 5% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less. When the ink composition contains a colorant other than white (more specifically, a cyan, magenta, yellow, or black colorant, etc.) as a colorant, the content of the polyfunctional (meth)acrylic monomer is preferably 25% by mass or more and 50% by mass or less, and more preferably 30% by mass or more and 45% by mass or less.

[0070] [4. Other Ingredients] The ink composition may further contain optional components as necessary, in addition to the polymerizable compound and the photopolymerization initiator. The optional components include, for example, surfactants (surface tension adjusters), colorants, polymerization inhibitors, dispersants, organic solvents, fixing resins, leveling agents, defoamers, antioxidants, pH adjusters, charge-imparting agents, bactericides, preservatives, deodorants, charge adjusters, wetting agents, and ultraviolet absorbing agents. These optional components may be used alone or in combination of two or more.

[0071] (4-1. Surfactants) The ink composition may contain a surfactant for the purpose of adjusting the wettability of the ink to the recording medium and / or the nozzle substrate of the inkjet head. Examples of the surfactant include silicone-based compounds. Examples of the silicone-based compounds are preferably silicone-based compounds having a dimethylsiloxane structure, and more preferably polyether-modified polydimethylsiloxane. Commercially available surfactants include, for example, BYK-350, 352, 354, 355, 358N, 361N, 381N, 381, 392, BYK-300, 302, 306, 307, 310, 315, 320, 322, 323, 325, 330, 331, 333, 337, 340, 344, 348, 370, 375, 377, 378, 355, 356, 357, 390, UV3500, UV3510, and UV3570 manufactured by BYK-Chemie, Tegorad-2100, 2200, 2250, 2500, and 2700 manufactured by Tego Chemical, and TEGO (registered trademark) Glide® manufactured by Evonik Degussa. 100, 110, 130, 403, 406, 410, 411, 415, 432, 435, 440, 450, and 482, but are not limited thereto. These surfactants may be used alone or in combination of two or more. From the viewpoint of maintaining good compatibility, it is preferable to use two or more surfactants. By using two or more surfactants in combination, the ink composition maintains good compatibility even when stored for a long period of time, so that the ink composition can be sufficiently wetted and spread on the recording medium, and the wide color reproducibility that is a characteristic of pigments can be maintained.

[0072] From the viewpoint of improving the wettability of the ink composition of the present invention to a recording medium, the content of the surfactant is preferably from 0.01 to 5 parts by mass, more preferably from 0.05 to 3 parts by mass, and even more preferably from 0.5 to 2 parts by mass, relative to 100 parts by mass of the ink composition.

[0073] (4-2. Polymerization inhibitors) The ink composition may contain a polymerization inhibitor for the purpose of controlling the progress of the photopolymerization reaction. Examples of the polymerization inhibitor include hydroquinone-based compounds, catechol-based compounds, and phenol-based compounds. Examples of the hydroquinone-based compounds include hydroquinone, methylhydroquinone, hydroquinone monomethyl ether, tert-butylhydroquinone, and ditert-butylhydroquinone. Examples of the catechol-based compounds include catechol, methylcatechol, and tert-butylcatechol. Examples of the phenol-based compounds include phenol, 3,5-ditert-butyl-4-hydroxytoluene (butylhydroxytoluene (BHT)), cresol, and methoquinone.

[0074] From the viewpoint of achieving both the storage stability of the ink composition of the present invention and the curability in a single pass system, the content of the polymerization inhibitor is preferably from 0.05 parts by mass to 5 parts by mass, more preferably from 0.20 parts by mass to 2 parts by mass, and more preferably from 0.1 parts by mass to 1 part by mass, relative to 100 parts by mass of the ink composition.

[0075] (4-3. Coloring material) Examples of coloring materials include pigments and dyes. From the viewpoint of improving the weather resistance of the formed image, pigments (more specifically, organic pigments and inorganic pigments, etc.) are preferred. A pigment generally refers to a coloring material that is poorly soluble in water.

[0076] Examples of black colorants include carbon black. Examples of commercially available black colorants include Toka Black manufactured by Tokai Carbon Co., Ltd.; HCF, MCF, RCF, LFF, and SCF manufactured by Mitsubishi Chemical Corporation; Color Black, Special Black, and Printex manufactured by Degussa-Huls Co., Ltd.; Raven manufactured by Columbia Corporation; and Monarch and Regal manufactured by Cabot Corporation.

[0077] Cyan colorants include, for example, copper phthalocyanine compounds, anthraquinone compounds, and basic dye lake compounds. Cyan colorants include, for example, CI Pigment Blue (1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, or 66).

[0078] Examples of yellow colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and arylamide compounds. Examples of yellow colorants include CI Pigment Yellow (1, 3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 138, 147, 150, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185, 191, 194, and 214). CI Pigment Yellow 150 is particularly preferred because it has relatively little absorption in the range of 365 to 435 nm.

[0079] The yellow colorant is contained in the ink composition of the present invention at a concentration of 4.6% by weight or less. If the content of the yellow colorant exceeds 4.6% by weight, the absorbance in the UV irradiated region increases, and the curing property of the deposited coating film may decrease. The lower limit of the content of the yellow colorant is not particularly limited, and is appropriately adjusted according to the desired coloring property. The content of the yellow colorant is preferably 2.5 to 4.5% by weight, more preferably 3.4 to 4.3% by weight.

[0080] Examples of magenta colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Examples of magenta colorants include CI Pigment Red (2, 3, 5, 6, 7, 19, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 150, 166, 168, 177, 184, 185, 202, 206, 220, 221, or 254).

[0081] Examples of white colorants include white organic pigments (more specifically, Pigment White 6, 18, 21, etc.) and white inorganic pigments (more specifically, basic lead carbonate, zinc oxide, titanium oxide, strontium titanate, etc.).

[0082] From the viewpoint of improving the dispersibility of the pigment in the ink composition, the dispersed average particle size of the pigment is preferably from 20 to 250 nm, and more preferably from 50 to 230 nm.

[0083] The content of the colorant is preferably 0.5 parts by mass or more and 25 parts by mass or less, more preferably 1.0 parts by mass or more and 20 parts by mass or less, and even more preferably 2.0 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the ink composition.

[0084] (4-4. Dispersants) For the purpose of dispersing the colorant in the ink composition, the ink composition may contain a dispersant (more specifically, a pigment dispersion or the like). Examples of the dispersant include polyvinyl alcohol, acrylic acid resins, styrene-acrylic acid resins, and vinyl acetate resins. Examples of the acrylic acid resins include polyacrylic acid, acrylic acid-acrylonitrile copolymers, and acrylic acid-alkyl acrylate copolymers. Examples of the styrene-acrylic acid resins include styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, and styrene-acrylic acid-alkyl acrylate copolymers. Examples of the vinyl acetate resins include vinyl acetate-ethylene copolymers, and vinyl acetate-maleic acid ester copolymers.

[0085] From the viewpoint of improving the dispersion stability of the ink composition and maintaining the same quality as at the beginning even after a long period of time, the content of the dispersant is preferably 0.1 parts by mass or more and 3 parts by mass or less, and more preferably 0.5 parts by mass or more and 1.5 parts by mass or less, relative to 100 parts by mass of the ink composition.

[0086] (4-5. Organic solvents) The ink composition may contain an organic solvent for the purpose of adjusting the viscosity of the ink composition. From the viewpoint of improving the drying property of the ink composition and the transferability of the formed image, it is preferable that the ink composition does not substantially contain an organic solvent. Since the ink composition does not need to contain an organic solvent for the purpose of dilution, it is not necessary to heat the ink composition excessively for the purpose of adjusting the viscosity when ejecting the ink composition. In addition, since the ink composition does not need to contain an organic solvent for the purpose of dilution, the ink composition is less likely to have an increase in viscosity due to the volatilization of the organic solvent in the ink composition during storage or use of the ink composition. Furthermore, even if the ink composition contains a pigment, the sedimentation of the pigment accompanying the increase in viscosity is suppressed, and the ink composition tends to have good dispersion stability. Thus, it is preferable that the ink composition does not substantially contain an organic solvent from the viewpoint of further improving the ejection stability. The content of the organic solvent is preferably 3 parts by mass or less, more preferably 1 part by mass or less, and even more preferably 0 parts by mass, relative to 100 parts by mass of the ink composition. Examples of the organic solvent include aromatic hydrocarbons, aliphatic hydrocarbons, ethers, and ketones.

[0087] [5. Primary Skin Irritation Index (PII value)] From the viewpoint of improving the safety of the ink composition, the PII value of the ink composition is preferably less than 2, more preferably less than 2.00, and even more preferably less than 1.70.

[0088] From the viewpoint of improving the safety of the ink composition, the content of the polymerizable compound having a primary skin irritation index of less than 2 is preferably 3 parts by mass or more and 35 parts by mass or less, and more preferably 5 parts by mass or more and 32 parts by mass or less, per 100 parts by mass of the polymerizable compound (total mass of the polymerizable compound: 100 parts by mass).

[0089] [6.Applications] The ink composition is suitable for use in image-formed products that come into contact with human hands, particularly when the primary skin irritation index PII value is less than 2. The ink composition can be used as an ink composition for recording food packaging on the surface of food packaging as a label. Examples of the label include the product name, product ingredients, manufacturer name, production date, lot number, and cautions.

[0090] [7. Method for preparing photocurable ink composition for ink jet recording] A conventionally known preparation method can be used for the preparation of the ink composition. A suitable preparation method when the ink composition contains a pigment as a colorant will be described below. A dispersing machine is used to premix the colorant, a part of the polymerizable compound, and any optional components (more specifically, a pigment dispersant, etc.) as necessary, and each component is dissolved or dispersed to prepare a primary dispersion. Examples of dispersing machines include a disperser, a container-driven media mill (more specifically, a ball mill, a centrifugal mill, and a planetary ball mill, etc.), a high-speed rotary mill (more specifically, a sand mill, etc.), and a media stirring mill (more specifically, a stirring tank type mill, etc.).

[0091] Next, the remaining polymerizable compound, photopolymerization initiator, surfactant (surface tension adjuster), and additives (more specifically, gelling inhibitor, etc.) are added to the obtained primary dispersion, and mixed uniformly using a stirrer. Examples of the stirrer include a disperser, a three-one motor, a homogenizer, and a magnetic stirrer. In this way, an ink composition can be obtained. The ink composition may also be mixed using a mixer such as a line mixer. Furthermore, the ink composition may also be mixed using a disperser such as a bead mill and a high-pressure jet mill for the purpose of further finely dispersing the particles in the ink composition.

[0092] The ink composition of the present invention has a viscosity of 12 mPa·s or less at 25°C. If the viscosity of the ink composition exceeds 12 mPa·s, the ink droplets ejected from the nozzles will become large, and the aesthetic appearance of the printed matter may deteriorate. The viscosity of the ink composition is preferably 5 to 11 mPa·s.

[0093] The ink composition of the present invention has an absorbance of 0.6 or less at a wavelength of 365 nm when the ink composition is diluted 1000 times and placed in a cell with an optical path length of 10 mm. If the absorbance of the ink composition exceeds 0.6, the curability of the discharged coating film may decrease. The absorbance of the ink composition is preferably 0.55 or less, more preferably 0.3 to 0.53.

[0094] The ink composition of the present invention has a total absorbance of 105 or less at wavelengths of 365 to 435 nm when the ink composition is diluted 1000 times and placed in a cell with an optical path length of 10 mm. If the total absorbance of the ink composition exceeds 100, the curability of the discharged coating film may decrease. The total absorbance of the ink composition is preferably 90 or less, more preferably 40 to 80.

[0095] The solvent used for dilution when measuring absorbance is not particularly limited, but a polymerizable compound used in an ink composition is preferred, and a polymerizable compound used when dispersing a pigment is particularly preferred from the viewpoint of stability when diluted.

[0096] The ink composition of the present invention preferably does not change in viscosity by more than 20% when stored for 28 days in an environment at 60° C. If the viscosity change rate of the ink composition exceeds 20%, the ejection properties of the ink composition may deteriorate over time. The viscosity change of the ink composition is preferably 15% or less, more preferably 5 to 11%.

[0097] The above characteristic values ​​of the ink composition of the present invention can be adjusted by appropriately changing the type and content of the colorant. The colorant referred to here is preferably a yellow pigment.

[0098] <Ink set> An ink set refers to a set of photocurable ink compositions for inkjet recording of multiple colors (for example, cyan, magenta, yellow, black, and white) that are used simultaneously when performing an inkjet recording method. The ink compositions for inkjet recording that constitute the ink set are combined in an unmixed state.

[0099] The ink set of the present invention includes at least one photocurable ink composition for ink jet recording of the present invention. The ink set of the present invention is, for example, a combination of cyan, magenta, yellow, and black. In a preferred embodiment, the yellow ink composition constituting the ink set is the photocurable ink composition for ink jet recording of the present invention. EXAMPLES

[0100] The present invention will be further described below using examples. Note that the present invention is not limited to the scope of the examples. Unless otherwise specified, "%" indicates "% by mass" and "parts" indicates "parts by mass".

[0101] [1. Preparation of ink composition] (1-1. Preparation of Pigment Dispersion) <Yellow pigment dispersion (Ya)>

[0102] [Table 1]

[0103] The above materials (pigment, pigment dispersant, and bifunctional acrylic monomer) were charged into a plastic bottle. The contents of the plastic bottle were stirred until homogeneous using a high-speed mixer to obtain a mill base. The mill base was then dispersed for 2 hours using a paint conditioner (manufactured by Toyo Seiki Co., Ltd.) to obtain a yellow pigment dispersion (Ya).

[0104] <Yellow pigment dispersion (Yb)> A yellow pigment dispersion (Yb) was prepared in the same manner as in the preparation of the yellow pigment dispersion (Ya), except that a disazo pigment (Pigment Yellow 155) (Clariant's Ink Jet Yellow 4GC) was used instead of the metal complex pigment "Levascreen Yellow G01" as the pigment.

[0105] <Yellow pigment dispersion (Yc)> A yellow pigment dispersion (Yc) was prepared in the same manner as in the preparation of the yellow pigment dispersion (Ya), except that an isoindoline pigment (Pigment Yellow 185) (BASF's "Paliotol Yellow D1150") was used instead of the metal complex pigment "Levascreen Yellow G01" as the pigment.

[0106] <Black pigment dispersion, cyan pigment dispersion, magenta pigment dispersion> A black pigment dispersion (Ka), a cyan pigment dispersion (Ca), and a magenta pigment dispersion (Ma) were prepared in the same manner as for the yellow pigment dispersion, except that a carbon black pigment (ORION's Special Black 250) was used as the black pigment, a copper phthalocyanine pigment (Clariant's Hosterperm Blue P-BFS) was used as the cyan pigment, and a quinacridone pigment (DIC's Fastogen Super Magenta RGT) was used as the magenta pigment, instead of the metal complex pigment "Levascreen Yellow G01."

[0107] (1-2. Preparation of Ink Composition) Into a plastic bottle containing a pigment dispersion, 2-(2-vinyloxyethoxy)ethyl acrylate (VEEA) as a (meth)acrylic acid ester, 3,3,5-trimethylcyclohexanol acrylate (TMCHA) as a monofunctional monomer, tripropylene glycol diacrylate (TPGDA) as a bifunctional monomer, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO") as a photopolymerization initiator, polyether-modified polydimethylsiloxane (UV3510") as a surfactant, and dibutylhydroxytoluene (BHT) as a polymerization inhibitor were added. The pigment dispersion and the additionally added components were stirred for 30 minutes using a magnetic stirrer to obtain a mixture. After stirring, the mixture was suction-filtered using a glass filter (manufactured by Kiriyama Seisakusho) to prepare an ink composition. Table 2 shows the composition of the prepared ink composition. Table 3 shows the names of the components of the ink composition.

[0108] [Table 2]

[0109] [Table 3]

[0110] 2. Evaluation method (2-1. Evaluation of absorbance of ink composition) The ink composition was diluted to a concentration of 1000 times by adding DPGDA monomer. The diluted ink composition was placed in a quartz cell with an optical path length of 10 mm, and the cell was set in a spectrophotometer ("V-570" manufactured by JASCO Corporation) to measure the absorbance using the Abs measurement mode. The baseline measurement was performed by filling the quartz cells on the reference side and the measurement side with DPGDA monomer.

[0111] 1 is a graph showing the ultraviolet-visible absorption spectra of ink compositions (Y-1) to (Y-4) diluted 1000 times. From these absorption spectra, the absorbance at a wavelength of 365 nm and the integrated absorbance value at every 1 nm between 365 nm and 435 nm were determined.

[0112] (2-2. Evaluation of the gloss of the coating film) The prepared ink composition was set in an inkjet discharge device equipped with an inkjet head (KJ4A-TA, manufactured by Kyocera Corporation). Next, this ink composition was used to print a 100% solid image on art paper (Art E PW, manufactured by Lintec Corporation) under printing conditions of a frequency of 20 kHz, a head temperature of 38°C, and an ink droplet volume of 14 pl. The printing speed was 50 m / min. A metal halide lamp with an output of 240 W / cm was used as a light source for curing the ink.

[0113] When printing secondary colors, two of the above heads were arranged in series and printing was performed in the order shown below.

[0114] R (Red): Magenta, Yellow G (green): Cyan, Yellow B (blue): Cyan, Magenta

[0115] The 60° gloss of the printed coating was measured using a gloss meter (BYK Gardner, "micro-TRI-gloss").

[0116] (2-3. Evaluation of ejection stability of ink composition: Viscosity measurement of ink composition) The viscosity of the ink composition was measured at 25°C and a cone rotation speed of 20 rpm using an R100 type viscometer (manufactured by Toki Sangyo Co., Ltd.) according to the method of JIS Z8803. The obtained viscosities (unit: mPa s) are shown in Table 5.

[0117] (2-4. Evaluation of viscosity change rate) The prepared ink composition was stored in a sealed glass bottle at 60° C. for 28 days, and the rate of change in viscosity before and after storage was determined. The rate of change in viscosity was calculated using the following formula.

[0118] Viscosity change rate (%) = {(viscosity after storage - initial viscosity) / (initial viscosity)} x 100

[0119] The obtained viscosity change rate was evaluated according to the following criteria.

[0120] --Evaluation criteria-- ○: Viscosity change rate is 10% or less △: Viscosity change rate is 10-20% ×: Viscosity change rate is 20% or more

[0121] [3. Experimental Results] Table 4 shows the types of inks constituting the ink sets used in the experiment, and the gloss levels of the resulting prints. Table 5 shows the property values ​​of the inks prepared.

[0122] [Table 4]

[0123] [Table 5]

[0124] With reference to Tables 4 and 5, the ink set 1 using ink Y-1 had suppressed absorbance in the UV irradiated region, good curing properties, and high gloss of the printed matter. The ink set 2 using ink Y-2 had a large absorbance value, and the pigment absorbed the light energy from UV irradiation, resulting in a decrease in curing properties and glossiness. In particular, the decrease in glossiness was significant in secondary colors such as green and red. The ink set 3 using ink Y-3 had a large absorption at 365 nm, which is the peak wavelength of the UV lamp, and the glossiness of the secondary colors was decreased compared to ink set 1. In addition, the viscosity of ink Y-3 changed significantly before and after storage, and it is considered that the ejection properties will deteriorate over time. The ink set 4 using ink Y-4 had a higher pigment concentration than ink set 1 using the same pigment, had a large absorbance in the UV irradiated region, and had a decrease in curing properties and glossiness. [Industrial Applicability]

[0125] The photocurable ink jet recording ink composition of the present invention can be suitably used in combination with other photocurable ink jet recording ink compositions to form an ink jet recording ink set.

Claims

1. A photocurable ink composition for ink-jet recording, comprising a yellow colorant, a polymerizable compound, and a photopolymerization initiator, the yellow colorant is contained in the ink composition at a concentration of 4.6% by weight or less; the ink composition has a viscosity of 12 mPa·s or less at 25° C., A photocurable ink composition for ink jet recording, wherein the ink composition, when diluted 1000 times and placed in a cell having an optical path length of 10 mm, has an absorbance of 0.6 or less for light having a wavelength of 365 nm.

2. 2. The photocurable ink composition for ink jet recording according to claim 1, wherein the ink composition is diluted 1000 times and placed in a cell having an optical path length of 10 mm, and the total absorbance of the ink composition is 105 or less for light having a wavelength of 365 to 435 nm.

3. 3. The photocurable ink composition for ink jet recording according to claim 1, wherein a viscosity change rate of the ink composition stored for 28 days in an environment at 60°C is within 20% compared to that of the ink composition before storage.

4. The photocurable ink composition for ink jet recording according to any one of claims 1 to 3, wherein a UV lamp is used as a light source for curing.

5. The photocurable ink jet recording ink composition according to any one of claims 1 to 4, which is used in a single-pass ink jet recording method.

6. The photocurable ink composition for ink jet recording according to any one of claims 1 to 5, wherein the yellow colorant contains C. I. Pigment Yellow 150.

7. The polymerizable compound is represented by the formula CH ２ =CR １ -COOR ２ -O-CH=CH-R ３ ・・・(I) [In the formula, R １ represents a hydrogen atom or a methyl group, R ２ represents a divalent organic residue having 2 to 20 carbon atoms; R ３ represents a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.

7. The photocurable ink composition for ink jet recording according to claim 1, further comprising a vinyl ether group-containing (meth)acrylic acid ester represented by the formula:

8. An ink set comprising the photocurable ink composition for ink jet recording according to any one of claims 1 to 7.

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