JPWO2006134766A1 - Active energy ray curable flexographic ink and active energy ray curable gravure ink - Google Patents

Abstract

The present invention provides an active energy ray curable gravure ink and an active energy ray curable flexo ink that have a low environmental burden, are safe, and have excellent storage stability over a long period of time. The active energy ray curable gravure ink and the active energy ray curable flexo ink have an active energy containing at least one photoacid generator selected from sulfonium salts represented by the following general formulas [1] to [4]. It comprises a wire curable composition. [Chemical 1]

Description

  The present invention relates to an active energy ray-curable flexographic ink and an active energy ray-curable gravure ink containing a photoacid generator.

  Aromatic solvents such as toluene in gravure ink (hereinafter represented by toluene) are excellent solvents as ink solvents, but they evaporate at the time of printing and drying after printing. On the other hand, it has been pointed out that there is a fear of having an adverse effect. Regarding such solvent evaporation, although a large-scale facility is provided in the printing factory to prevent solvent vapor from diffusing into the atmosphere, it is not possible to completely prevent vapor diffusion into the atmosphere. In addition, although countermeasures have been taken against worker hygiene in the printing factory, it cannot be said that the worker's hygiene problem has been sufficiently solved.

  In conventional gravure printing, solvent-based inks using a vehicle in which a resin is dissolved in an ester-based or ketone-based volatile organic solvent have been used. However, these printing inks have safety issues such as air pollution due to volatilization of organic solvents, deterioration of the working environment, or the risk of fires. And some have been put to practical use.

  In the field of gravure printing, as an example of an attempt to use an ultraviolet curable ink, a gravure printing method using an ordinary ultraviolet curable ink has been proposed. That is, normal UV curable ink stored in a tank provided on the printing press is heated using a heating device, and the viscosity is reduced to the same level as gravure inks such as solvent-type inks. The excess ink is scraped off and printed, and the ink transferred to the paper is cured using an ultraviolet irradiation device. (For example, refer to Patent Documents 1 to 5.)

  On the other hand, flexographic printing is easy to make using rubber or plastic as the plate material, and the cost required for printing is low. It has been applied to printing using a wide range of materials up to permeable raw materials. Conventionally, in flexographic printing, solvent-type flexographic inks using varnishes in which resins are dissolved in solvents have been mainly used. However, from the heightened awareness of the environment, active energy ray-curable resin compositions that do not contain solvents are used. The use of flexo ink is increasing. Conventionally, as an active energy ray-curable resin composition, a mixture composed of various acrylates and methacrylates and a prepolymer such as urethane acrylate or polyester acrylate has been used (see, for example, Patent Document 6).

  In these active energy ray-curable resin compositions described above, the ink using the radically polymerizable compound is subject to an oxygen inhibiting action, and thus tends to cause curing inhibition when the amount of ink droplets is small. In contrast, inks using cationically polymerizable compounds do not have an oxygen inhibition effect, and even when the amount of ink droplets is small, there is no curing inhibition, and it is possible to print a high-definition image. .

However, an initiator used in an ink using a cationic polymerizable compound has a problem that benzene is generated by ultraviolet irradiation. In addition, since the initiator is thermally unstable, there is a problem that the storage stability of the ink is poor, and the cured film formed by the ink is more easily yellowed when stored for a long period of time. Yes, improvements are desired.
JP-A-6-220385 JP-A-3-213340 JP-A-3-213341 JP-A-3-215039 JP-A-3-2104040 JP 2003-321636 A

  The present invention has been made in view of the above problems, and its purpose is to reduce the burden on the environment, to be safe, and to have a long-term storage stability. It is to provide a mold flexographic ink.

  The above object of the present invention can be achieved by the following constitution.

  1. An active energy ray-curable flexo comprising an active energy ray-curable composition containing at least one photoacid generator selected from sulfonium salts represented by the following general formulas [1] to [4] ink.

[Wherein R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, R _{4 to} R ₇ do not represent a hydrogen atom at the same time, R _{8 to} R ₁₁ do not represent hydrogen atoms at the same time, and R _{12 to} R ₁₇ do not represent hydrogen atoms at the same time. X represents a non-nucleophilic anionic residue. ]
2. 1. The sulfonium salt represented by the general formulas [1] to [4] is at least one selected from sulfonium salts represented by the following general formulas [5] to [13] The active energy ray-curable flexographic ink as described.

[In each formula, X represents a non-nucleophilic anionic residue. ]
3. 3. The active energy ray-curable flexographic ink as described in 1 or 2 above, further comprising an oxetane compound or a vinyl ether compound.

  4). 4. The active energy ray-curable flexographic ink according to any one of 1 to 3, further comprising an epoxy compound.

  5). An active energy ray-curable gravure comprising an active energy ray-curable composition containing at least one photoacid generator selected from sulfonium salts represented by the following general formulas [1] to [4] ink.

[Wherein R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, R _{4 to} R ₇ do not represent a hydrogen atom at the same time, R _{8 to} R ₁₁ do not represent hydrogen atoms at the same time, and R _{12 to} R ₁₇ do not represent hydrogen atoms at the same time. X represents a non-nucleophilic anionic residue. ]
6). 5. The sulfonium salt represented by the general formulas [1] to [4] is at least one selected from sulfonium salts represented by the following general formulas [5] to [13] The active energy ray-curable gravure ink as described.

[In each formula, X represents a non-nucleophilic anionic residue. ]
7). The active energy ray-curable gravure ink as described in 5 or 6, further comprising an oxetane compound or a vinyl ether compound.

  8). The active energy ray-curable gravure ink according to any one of 5 to 7, further comprising an epoxy compound.

  According to the present invention, an active energy ray curable gravure ink (hereinafter also simply referred to as gravure ink) and an active energy ray curable flexo ink (hereinafter referred to as “gravure ink”), which have a low environmental impact, are safe and have excellent storage stability over a long period of time. Simply called flexo ink).

  As a result of intensive studies in view of the above problems, the inventors of the present invention have an active energy ray containing at least one photoacid generator selected from sulfonium salts represented by the general formulas [1] to [4]. Active energy ray curable flexographic ink or active energy ray curable gravure ink characterized by containing a curable composition, air pollution due to volatilization of the organic solvent that each ink had, deterioration of work environment, or fire Issues related to safety such as the risk of occurrence, oxygen inhibition in inks using radically polymerizable compounds as active energy ray-curable resin compositions, and benzene generation by UV irradiation by initiators when using cationically polymerizable compounds Or the thermal instability of this initiator and the change of the formed cured film when stored over a long period of time. The active energy ray curable gravure ink (and the active energy ray curable flexo ink, which has a low environmental impact, is safe, and has excellent storage stability over a long period of time, has been found to be realized. .

  Details of the present invention will be described below.

The active energy ray-curable composition according to the present invention is characterized by containing a sulfonium salt represented by the above general formulas [1] to [4] as a photoacid generator. It is a compound that does not generate benzene by energy beam irradiation, and does not substantially generate benzene. Specifically, an image having a thickness of 15 μm and about 100 m ² is printed using gravure ink or flexographic ink containing 5% by mass of a sulfonium salt (photoacid generator) in the composition of gravure ink or flexographic ink, When the gravure ink or flexo ink film surface is kept at 30 ° C., the amount of benzene generated when irradiated with an active energy ray in such an amount that the photoacid generator can be sufficiently decomposed is extremely small or less than 5 μg. Point to.

In the general formulas [1] to [4], R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, and R _{4 to} R ₇ represent simultaneously. It does not represent a hydrogen atom, R _{8 to} R ₁₁ do not represent a hydrogen atom at the same time, and R _{12 to} R ₁₇ do not represent a hydrogen atom at the same time.

The substituent represented by R _{1 to} R ₁₇ is preferably an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, or a hexyl group, Alkoxy groups such as methoxy group, ethoxy group, propyl group, butoxy group, hexyloxy group, decyloxy group, dodecyloxy group, acetoxy group, propionyloxy group, decylcarbonyloxy group, dodecylcarbonyloxy group, methoxycarbonyl group, ethoxycarbonyl Group, carbonyl group such as benzoyloxy group, phenylthio group, halogen atom such as fluorine, chlorine, bromine and iodine, cyano group, nitro group and hydroxy group.

X represents a non-nucleophilic anion residue, for example, a halogen atom such as F, Cl, Br, or I, B (C ₆ F ₅ ) ₄ , R ₁₈ COO, R ₁₉ SO ₃ , SbF ₆ , AsF ₆ , PF ₆ , BF _{4 and the} like. However, R ₁₈ and R ₁₉ are each an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a halogen atom such as fluorine, chlorine, bromine or iodine, a nitro group, a cyano group, a methoxy group or an ethoxy group. Represents an alkyl group or a phenyl group which may be substituted with an alkoxy group or the like. Among these, B (C ₆ F ₅ ) ₄ and PF ₆ are preferable from the viewpoint of safety.

  The above compounds can be obtained from THE CHEMICAL SOCIETY OF JAPAN Voi. 71 no. 11, 1998, similar to the photoacid generator described in “Organic Materials for Imaging”, edited by Organic Electronics Materials Study Group, Bunshin Publishing (1993), can be easily synthesized by a known method.

  In the present invention, the sulfonium salt represented by the general formulas [1] to [4] is particularly preferably at least one of the sulfonium salts selected from the general formulas [5] to [13].

  X represents a non-nucleophilic anion residue and is the same as described above.

Specific examples of the sulfonium salt according to the present invention include the following compounds in addition to X = PF _{6 in} the formulas (5) to (13).

Further, in the active energy ray-curable flexographic ink or the active energy ray-curable gravure ink of the present invention, the general formulas [1] to [4] according to the present invention are represented within a range that does not impair the object effects of the present invention. In combination with the sulfonium salt, an iodonium salt having a substituent on the benzene ring bonded to I ⁺ is preferably used in combination. Specific compounds of iodonium salts are shown below.

  In the active energy ray-curable composition according to the present invention, it is preferable to use an oxetane compound, a vinyl ether compound or an epoxy compound as a photopolymerizable compound.

  The oxetane compound used in the present invention is a compound having one or more oxetane rings in the molecule. Specifically, 3-ethyl-3-hydroxymethyloxetane (manufactured by Toa Gosei Co., Ltd .; trade name OXT101 etc.), 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene (OXT121) Etc.), 3-ethyl-3- (phenoxymethyl) oxetane (OXT211 etc.), di (1-ethyl-3-oxetanyl) methyl ether (OXT221 etc.), 3-ethyl-3- (2-ethylhexyloxy) Methyl) oxetane (OXT212, etc.) can be preferably used, and in particular, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (phenoxymethyl) oxetane, di (1-ethyl-3-oxetanyl) Methyl ether can be preferably used. These can be used alone or in combination of two or more.

  The oxetane compound applicable to the present invention is blended in the active energy ray curable composition in an amount of 30 to 95% by mass, preferably 50 to 80% by mass.

  The vinyl ether compound contained in the active energy ray-curable composition according to the present invention includes, 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, Di- or trivinyl ether compounds such as dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexane dimethanol divinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, trimethylolpropane trivinyl ether, ethyl vinyl ether, n- Butyl vinyl ether, isobut Vinyl ether, octadecyl vinyl 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 And monovinyl ether compounds.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in appropriate combination.

  A vinyl ether compound is an arbitrary blending component, and can be adjusted to a viscosity required for the active energy ray-curable composition by blending. Also, the curing rate can be improved. The vinyl ether compound is blended in an amount of 0 to 40% by mass, preferably 0 to 20% by mass, in a liquid component composed of an oxirane group-containing compound and an oxetane ring-containing compound.

  The epoxy compound that can be preferably used in the present invention is an epoxy compound in which each carbon of the oxirane ring has at least one substituent, and the substituents may be bonded to each other to form a ring. When the carbon substituents of the oxirane ring are bonded to each other to form a ring, a 5- to 7-membered ring is preferable, and a 6-membered ring is more preferable. The most preferred epoxy compound is a compound represented by the following general formula (21), (22) or (23).

In the formula, R ₁₀₀ , R ₁₀₁ and R ₁₀₂ each represent a substituent. Examples of the substituent include, for example, a halogen atom (for example, chlorine atom, bromine atom, fluorine atom, etc.), an alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group). Group), an alkoxy group having 1 to 6 carbon atoms (for example, methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, tert-butoxy group, etc.), acyl group (for example, acetyl group) Group, propionyl group, trifluoroacetyl group, etc.), acyloxy group (eg, acetoxy group, propionyloxy group, trifluoroacetoxy group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, tert-butoxycarbonyl group) Etc.). As the substituent, an alkyl group, an alkoxy group, and an alkoxycarbonyl group are preferable.

  m0, m1, and m2 each represents 0 to 2, and 0 or 1 is preferable.

L ₀ represents an r0 + 1 valent linking group or single bond having 1 to 15 carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain, and L ₁ represents 1 to carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain. 15 represents an r1 + 1 valent linking group or a single bond, and L ₂ represents an R2 + 1 valent linking group or a single bond having 1 to 15 carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain.

  Examples of the divalent linking group having 1 to 15 carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain include the following groups, and these groups and —O— group, —S— group, —CO— group. , A group formed by combining a plurality of —CS— groups.

Methylene group [—CH ₂ —]
An ethylidene group [> CHCH ₃ ],
Isopropylidene [> C (CH ₃ ) ₂ ]
1,2-ethylene group [—CH ₂ CH ₂ —],
1,2-propylene group [—CH (CH ₃ ) CH ₂ —],
1,3-propanediyl group [—CH ₂ CH ₂ CH ₂ —],
2,2-dimethyl-1,3-propanediyl group [—CH ₂ C (CH ₃ ) ₂ CH ₂ —],
2,2-dimethoxy-1,3-propanediyl group [—CH ₂ C (OCH ₃ ) ₂ CH ₂ —],
2,2-dimethoxymethyl-1,3-propanediyl group [—CH ₂ C (CH ₂ OCH ₃ ) ₂ CH ₂ —],
1-methyl-1,3-propanediyl group [—CH (CH ₃ ) CH ₂ CH ₂ —],
1,4-butanediyl group [—CH ₂ CH ₂ CH ₂ CH ₂ —],
1,5-pentanediyl group [—CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ —],
An oxydiethylene group [—CH ₂ CH ₂ OCH ₂ CH ₂ —],
A thiodiethylene group [—CH ₂ CH ₂ SCH ₂ CH ₂ —],
3-oxothiodiethylene group [—CH ₂ CH ₂ SOCH ₂ CH ₂ —],
3,3-dioxothiodiethylene group [—CH ₂ CH ₂ SO ₂ CH ₂ CH ₂ —],
1,4-dimethyl-3-oxa-1,5-pentanediyl group [—CH (CH ₃ ) CH ₂ OCH (CH ₃ ) CH ₂ —],
3-oxopentanediyl group [—CH ₂ CH ₂ COCH ₂ CH ₂ —],
1,5-dioxo-3-oxapentanediyl group [—COCH ₂ OCH ₂ CO—],
4-oxa-1,7-heptanediyl group [—CH ₂ CH ₂ CH ₂ OCH ₂ CH ₂ CH ₂ —],
3,6-dioxa-1,8-octanediyl group [—CH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ —],
1,4,7-trimethyl-3,6-dioxa-1,8-octanediyl group [—CH (CH ₃ ) CH ₂ O CH (CH ₃ ) CH ₂ OCH (CH ₃ ) CH ₂ —],
5,5-dimethyl-3,7-dioxa-1,9-nonanediyl group [—CH ₂ CH ₂ OCH ₂ C (CH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ —],
5,5-dimethoxy-3,7-dioxa-1,9-nonanediyl group [—CH ₂ CH ₂ OCH ₂ C (OCH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ —],
5,5-dimethoxymethyl-3,7-dioxa-1,9-nonanediyl group [—CH ₂ CH ₂ OCH ₂ C (CH ₂ OCH ₃ ) ₂ CH ₂ OCH ₂ CH ₂ —],
4,7-dioxo-3,8-dioxa-1,10-decandiyl group [—CH ₂ CH ₂ O—COCH ₂ CH ₂ CO—OCH ₂ CH ₂ —],
3,8-dioxo-4,7-dioxa-1,10-decandiyl group [—CH ₂ CH ₂ CO—OCH ₂ CH ₂ O—COCH ₂ CH ₂ —],
1,3-cyclopentanediyl group [-1,3-C ₅ H ₈ —],
1,2-cyclohexanediyl group [-1,2-C ₆ H _10- ],
1,3-cyclohexanediyl group [-1,3-C ₆ H _10- ],
1,4-cyclohexanediyl group [-1,4-C ₆ H _10- ],
2,5-tetrahydrofurandiyl group [2,5-C ₄ H ₆ O—]
p- phenylene _{[-p-C 6 H 4 -} ],
m- phenylene group _{[-m-C 6 H 4 -} ],
α, α′-o-xylylene group [—o—CH ₂ —C ₆ H ₄ —CH ₂ —],
α, α'-m- xylylene group _{[-m-CH 2 -C 6 H} 4 -CH 2 -],
α, α'-p- xylylene group _{[-p-CH 2 -C 6 H} 4 -CH 2 -],
Furan-2,5-diyl - bismethylene group _{[2,5-CH 2 -C 4 H} 2 O-CH 2 -]
Thiophene-2,5-diyl-bismethylene group [2,5-CH ₂ —C ₄ H ₂ S—CH ₂ —]
Isopropylidenebis -p- phenylene group _{[-p-C 6 H 4 -C} (CH 3) 2 -p-C 6 H 4 -]
Examples of the trivalent or higher linking group include groups formed by removing as many hydrogen atoms as necessary from the divalent linking groups listed above, and those with —O— group, —S— group, and —CO— group. , A group formed by combining a plurality of —CS— groups.

L ₀ , L ₁ and L ₂ may each have a substituent. Examples of the substituent include, for example, a halogen atom (eg, a chlorine atom, a bromine atom, a fluorine atom, etc.), an alkyl group having 1 to 6 carbon atoms (eg, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group). Etc.), an alkoxy group having 1 to 6 carbon atoms (for example, methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, tert-butoxy group, etc.), acyl group (for example, acetyl group) , Propionyl group, trifluoroacetyl group, etc.), acyloxy group (eg, acetoxy group, propionyloxy group, trifluoroacetoxy group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, tert-butoxycarbonyl group, etc.) ) And the like. As the substituent, an alkyl group, an alkoxy group, and an alkoxycarbonyl group are preferable.

L ₀ , L ₁ and L ₂ are preferably divalent linking groups having 1 to 8 carbon atoms which may contain an oxygen atom or a sulfur atom in the main chain, and the main chain having 2 to 1 carbon atoms having only carbon. A valent linking group is more preferred.

  p1 and q1 each represents 0 or 1, and p1 + q1 is preferably 1 or more.

  p2 and q2 each represents 0 or 1, and 1 is preferable for each.

  Specific examples of the compound represented by the general formula (21), (22) or (23) include, for example, EP-1 to EP described in paragraph numbers 0034 to 0040 of JP-A-2004-315778. -51.

  The addition amount of these compounds is preferably less than 80% by mass with respect to the active energy ray-curable composition. When it is 80% by mass or more, flexibility tends to deteriorate. More preferably, it is less than 50% by mass.

Examples of the active energy ray applied to cure the active energy ray-curable composition according to the present invention include visible light, ultraviolet rays, and electron beams. Preferred light irradiation methods include visible light irradiation and ultraviolet irradiation, and ultraviolet irradiation is particularly preferable. When performing ultraviolet irradiation, ultraviolet ray irradiation quantity is 100 mJ / cm ² or more, preferably 500 mJ / cm ² or more and 10,000 / cm ² or less, preferably performed at 5,000 mJ / cm ² or less. An ultraviolet irradiation amount within such a range is advantageous because a sufficient curing reaction can be carried out and the colorant can be prevented from fading due to ultraviolet irradiation. Examples of the ultraviolet light source include lamps such as metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, low pressure mercury lamps, and high pressure mercury lamps. For example, a commercially available product such as an H lamp, a D lamp, or a V lamp manufactured by Fusion System can be used.

  The metal halide lamp has a continuous spectrum as compared with a high-pressure mercury lamp (main wavelength is 365 nm), has high luminous efficiency in the range of 200 to 450 nm, and has a long wavelength range. Therefore, when a pigment is used as in the active energy ray-curable composition of the present invention, a metal halide lamp is suitable.

  The active energy ray-curable flexographic ink or gravure ink of the present invention contains a pigment as a coloring material. The pigments that can be preferably used in the present invention are listed below.

C. I Pigment Yellow-1, 3, 12, 13, 14, 17, 42, 74, 81, 83, 87, 93, 95, 109, 120, 128, 138, 139, 151, 166, 180, 185,
C. I Pigment Orange-16, 36, 38,
C. I Pigment Red-5, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 122, 144, 146, 177, 185,
C. I Pigment Violet-19, 23,
C. I Pigment Blue-15: 1, 15: 3, 15: 4, 18, 60, 27, 29,
C. I Pigment Green-7, 36,
C. I Pigment White-6, 18, 21,
C. I Pigment Black-7,
For the dispersion of the pigment, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used. As the dispersion medium, it is preferable in view of dispersion suitability to select a photoacid generator, and among them, a monomer having the lowest viscosity.

  The pigment is preferably dispersed so that the average particle size of the pigment particles is 0.08 to 0.5 μm, and the maximum particle size is 0.3 to 10 μm, preferably 0.3 to 3 μm. Select the dispersion medium, dispersion conditions, and filtration conditions as appropriate. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  In the active energy ray-curable flexographic ink or gravure ink of the present invention, the colorant concentration is preferably 1% by mass to 10% by mass of the total ink.

  As the pigment dispersant, one having a basic anchor portion is preferably used, and a polymer dispersant having a comb structure is more preferably used.

  Specific examples of the pigment dispersant that can be used in the present invention include Solsperse 9000, 17000, 18000, 19000, 20000, 24000SC, 24000GR, 28000GR, 28000, 32000, Ajinomoto Fine Techno, manufactured by Avecia. Ajisper PB821 and PB822 manufactured by the company, PLAAD ED214 manufactured by Enomoto Kasei Co., Ltd., ED251, DISPARLON DA-325, DA-234, EFKA-5207 manufactured by EFKA, 5244, 6220, and 6225. . In addition, pigment derivatives (synergists) that can be used in combination with the pigment dispersant include specific examples of pigment derivatives such as Solsperse 5000, 12000, and 22000 manufactured by Avecia, and EFKA-6746 and 6750 manufactured by EFKA. Etc.

  The active energy ray-curable composition according to the present invention contains a 4- to 10-membered aliphatic cyclic ester compound or a 5- or more-membered cyclic ether compound, so that the curability and adhesion to various substrates are improved. It is preferable because it improves.

  The cyclic ester compound is a 4- to 10-membered aliphatic cyclic ester compound. Specifically, ε-caprolactone-6-hydroxyhexanoic acid-1,6 lactone, β-propiolactone, β-butyrolactone, α-methyl-β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valero Lactone, ε-caprolactone, γ-caprolactone, γ-heptanolactone, coumarin, tetronic acid, pyrone, phthalide, 3-methyl-1,4-dioxa-2,5-dione, p-dioxanone, morpholinedione, morpholine Etc. In addition, a mixture thereof may be used.

  The cyclic ether compound is a cyclic ether compound having 5 or more members. More preferred is a cyclic ether compound having no carbonate ester structure. Specifically, 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, 1,3,5-trioxane, crown ether (12-crown-4 etc.), 1,2-dimethyltetrahydrofuran, 2-methyltetrahydrofuran, 2-methyldioxolane, 4-methyldioxolane and the like.

  The content of the 4- to 10-membered aliphatic cyclic ester compound and the 5- or more-membered cyclic ether compound is preferably 1 to 10% by mass.

  Various additives other than those described above can be used in the active energy ray-curable composition according to the present invention. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added. In addition, for the purpose of improving storage stability, any known basic compound can be used, but representative examples include basic alkali metal compounds, basic alkaline earth metal compounds, amines and other basic organic compounds. Etc. It is also possible to use a radical / cation hybrid curable ink.

  Basic compounds can also be added. By containing the basic compound, not only the ejection stability becomes good, but also the generation of wrinkles due to curing shrinkage is suppressed even under low humidity. As the basic compound, any known compounds can be used, and representative examples include basic alkali metal compounds, basic alkaline earth metal compounds, and basic organic compounds such as amines.

  Examples of the basic alkali metal compound include alkali metal hydroxides (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.), alkali metal carbonates (for example, lithium carbonate, sodium carbonate, potassium carbonate, etc.). ), Alkali metal alcoholates (for example, sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, etc.). Examples of the basic alkaline earth metal compound include alkaline earth metal hydroxides (eg, magnesium hydroxide, calcium hydroxide, etc.) and alkali metal carbonates (eg, magnesium carbonate, calcium carbonate, etc.). And alkali metal alcoholates (eg, magnesium methoxide).

  Examples of the basic organic compound include amines and nitrogen-containing heterocyclic compounds such as quinoline and quinolidine. Among these, amines are preferable from the viewpoint of compatibility with the photopolymerizable monomer, for example, octylamine, naphthylamine, Xylenediamine, dibenzylamine, diphenylamine, dibutylamine, dioctylamine, dimethylaniline, quinuclidine, tributylamine, trioctylamine, tetramethylethylenediamine, tetramethyl-1,6-hexamethylenediamine, hexamethylenetetramine and triethanolamine, etc. Is mentioned.

  The concentration when the basic compound is present is preferably in the range of 10 to 1000 ppm by mass, particularly 20 to 500 ppm by mass relative to the total amount of the photopolymerizable monomer. In addition, a basic compound may be used individually or may be used in combination of multiple.

  In the active energy ray-curable flexographic ink or gravure ink of the present invention, the viscosity of the active energy ray-curable composition at 25 ° C. is 7 to 40 mPa · s regardless of the curing environment (temperature and humidity). Is preferable for obtaining a stable and good curability.

  As a recording material that can be used in the present invention, in addition to ordinary uncoated paper, coated paper, etc., various non-absorbable plastics and films used for so-called soft packaging can be used. For example, polyethylene terephthalate (PET) film, stretched polystyrene (OPS) film, stretched polypropylene (OPP) film, stretched nylon (ONy) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, triacetyl cellulose (TAC) ) A film can be mentioned. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, PVA, rubbers and the like can be used. Moreover, it is applicable also to metals and glass.

  Examples of the present invention will be specifically described below, but the embodiments of the present invention are not limited to these examples.

Example 1
[Preparation of flexographic ink composition set]
5 parts by weight of a dispersant (PB822 Ajinomoto Fine Techno Co., Ltd.) and each photoacid generator listed in Table 1 (flexo ink) are placed in a stainless beaker and heated on a hot plate at 65 ° C. for 1 hour. Stir and mix to dissolve. Next, after adding various pigments to this solution, it was sealed in a plastic bottle together with 200 g of zirconia beads having a diameter of 1 mm, and dispersed for 2 hours in a paint shaker. Next, the zirconia beads were removed, and various additives such as each photopolymerizable compound, acid proliferating agent, basic compound, and surfactant were added in combinations shown in Table 1 to prepare a flexographic ink composition set. The ink viscosity was adjusted by the addition amount of the compound having an oxetane ring and the epoxy compound.

  Details of the abbreviations described in Table 1 are as follows. Moreover, all the numerical values described in Table 1 represent parts by mass.

(Photopolymerization initiator)
<* 1: Compound having an oxetane ring>
OXT-221: Oxetane ring-containing compound (manufactured by Toagosei Co., Ltd.)
OXT-101: Oxetane ring-containing compound (manufactured by Toagosei Co., Ltd.)
OXT-212: Oxetane ring-containing compound (manufactured by Toagosei Co., Ltd.)
<* 2: Vinyl ether compound>
* 3: Triethylene glycol divinyl ether <* 4: Oxirane compound>
* 5: Celoxide 3000 (molecular weight 168, manufactured by Daicel Chemical)
<Others>
* 6: I-3 / S-2 combination (1: 1)
(Photoacid generator)
UVI: UVI6992, Propion carbonate 50% solution manufactured by Dow Chemical Co., Ltd. * 7: Compound represented by general formula [10] (X = PF ₆ salt)
* 8: Compound represented by the general formula [13] (X = PF ₆ salt)
(* 9: Basic compound)
* 10: Tributylamine (fragrance)
* 11: Linalool (* 12: Silicone surfactant)
KF-351: Silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd.)
(Dispersant)
PB822: Ajinomoto Fine Techno Co., Ltd. Pigment 1: Pigment Black 7 (Mitsubishi Chemical Corporation, # 52)
Pigment 2: Pigment Blue 15: 4 (Sanyo Color Co., Ltd., cyanine blue 4044)
Pigment 3: Pigment Yellow 150 (manufactured by LANXESS, E4GN-GT CH20015)
Pigment 4: Pigment Red 122 (manufactured by Dainichi Seika Co., Ltd., special order)
(Other)
* 13: Sumilizer MDP-S: 2,2′-methylenebis (4-methyl-6-tert-butylphenol) manufactured by Sumitomo Chemical Co., Ltd.
* 14: Poly bd 605 Resin: epoxidized hydroxytelechelic polybutadiene manufactured by Elfatochem

[Image formation by flexo method]
Synthetic paper (synthetic paper YUPO FG manufactured by YUPO Corporation) is used as a recording material, and after applying to each ink composition set with a thickness of 3 μm, it is cured by irradiating 300 mJ / cm ² of ultraviolet rays with a metal halide lamp. It was. In addition, the illumination intensity of each irradiation light source measured the integrated illumination intensity of 254 nm using UVPF-A1 by Iwasaki Electric Co., Ltd.

[Evaluation of ink and printed image]
Each of the prepared active energy ray-curable flexographic inks and printed images was evaluated according to the following methods, and the results obtained are shown in Table 2.

(Evaluation of curability)
The cured film was rubbed with a nail, and whether or not the film was peeled off was visually observed and evaluated according to the following criteria.

○: It does not peel off even if it is rubbed strongly with a nail. △: It peels off when it is rubbed strongly with a nail, but it is practically usable level. X: It is easily peeled off when rubbed with a nail.

(Evaluation of safety of photoacid generator)
Regarding the photoacid generator used in the preparation of each active energy ray-curable flexo ink, the presence or absence of benzene was confirmed during curing, and the case where no benzene was generated was judged as ◯, and the case where benzene was observed was judged as ×. .

(Evaluation of yellowing resistance of cured film)
Each ink film cured on the substrate was treated for 96 hours with a sunshine carbonark type weather resistance tester, and then the change in color gamut of the cornea was visually observed, and the variable resistance was evaluated according to the following criteria. .

○: Almost no change in color gamut Δ: Slight change in color gamut, but usable level ×: Large change in color gamut, unusable level.

(Evaluation of storage stability)
Each ink was put into a polypropylene bottle and the change in viscosity after storage at 70 ° C. for 7 days was measured. The smaller the change in viscosity, the better the stability, and the storage stability was evaluated according to the following criteria. The viscosity of the ink was measured at 30 ° C. using a vibration viscometer (SV-100 manufactured by A & D Co., Ltd.).

○: Viscosity fluctuation is small and there is no problem in use. Δ: Although there is an increase in viscosity, the use lower limit level.

  As is clear from the results shown in Table 2, the active energy ray-curable ink of the present invention has less impact on the environment, is superior in safety and storage, and is formed by the flexographic printing method compared to the comparative example. It can be seen that the image is excellent in curability and yellowing resistance. The same effect was obtained even when YUPO FG was changed to another recording material as the recording material.

Example 2
[Image formation by gravure method]
Using flexographic ink composition sets 1 to 12 prepared in Example 1 as a gravure ink composition set, 250 lines / 2.54 cm (1 inch) on a coated paper for printing (Artpost Yasutsubo: 256 g, manufactured by Hokuetsu Paper) On the other hand, high-speed printing was performed at 600 to 800 rpm with a gravure printing machine. Subsequently, it was cured by irradiating 300 mJ / cm ² of ultraviolet rays with a metal halide lamp. In addition, the illumination intensity of each irradiation light source measured the integrated illumination intensity of 254 nm using UVPF-A1 by Iwasaki Electric Co., Ltd.

[Evaluation of printed image]
The image printed according to the above method was evaluated for curability and yellowing resistance in the same manner as in Example 1, and the results obtained are shown in Table 3.

  As is clear from the results shown in Table 3, the active energy ray-curable gravure ink of the present invention is superior to the comparative example in that the image formed by the gravure printing method is excellent in curability and yellowing resistance. I understand.

Claims (8)

An active energy ray-curable flexo comprising an active energy ray-curable composition containing at least one photoacid generator selected from sulfonium salts represented by the following general formulas [1] to [4] ink.

[Wherein R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, R _{4 to} R ₇ do not represent a hydrogen atom at the same time, R _{8 to} R ₁₁ do not represent hydrogen atoms at the same time, and R _{12 to} R ₁₇ do not represent hydrogen atoms at the same time. X represents a non-nucleophilic anionic residue. ] The sulfonium salt represented by the general formulas [1] to [4] is at least one selected from sulfonium salts represented by the following general formulas [5] to [13]. 2. The active energy ray-curable flexographic ink according to item 1.

[In each formula, X represents a non-nucleophilic anionic residue. ]   The active energy ray-curable flexographic ink according to claim 1 or 2, further comprising an oxetane compound or a vinyl ether compound.   The active energy ray-curable flexographic ink according to any one of claims 1 to 3, further comprising an epoxy compound. An active energy ray-curable gravure comprising an active energy ray-curable composition containing at least one photoacid generator selected from sulfonium salts represented by the following general formulas [1] to [4] ink.

[Wherein R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, R _{4 to} R ₇ do not represent a hydrogen atom at the same time, R _{8 to} R ₁₁ do not represent hydrogen atoms at the same time, and R _{12 to} R ₁₇ do not represent hydrogen atoms at the same time. X represents a non-nucleophilic anionic residue. ] The sulfonium salt represented by the general formulas [1] to [4] is at least one selected from sulfonium salts represented by the following general formulas [5] to [13]. The active energy ray-curable gravure ink according to item 5.

[In each formula, X represents a non-nucleophilic anionic residue. ]   The active energy ray-curable gravure ink according to claim 5 or 6, further comprising an oxetane compound or a vinyl ether compound.   The active energy ray-curable gravure ink according to any one of claims 5 to 7, further comprising an epoxy compound.