JP2012036245A - Photopolymerization initiator composition and active energy ray curable printing ink composition using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active energy ray curable ink composition which can be cured simply and in a low energy irradiation.SOLUTION: There is provided a method for producing a photopolymerization initiator composition including one or more photopolymerization initiators (A) having an absorption coefficient at a wavelength of 365 nm in a methanol solution of <4.5×10[ml/g-cm], and two or more photopolymerization initiators (B) having an absorption coefficient of ≥4.5×10[ml/g-cm], wherein the content of the photopolymerization initiators (A) is 5 to 40 mass%, and the content of the photopolymerization initiators (B) is 60 to 95 mass%.

Description

  The present invention is an ultraviolet curable type that can be easily obtained by adding a photopolymerization initiator that can easily obtain an ultraviolet curable ink that cures well under low irradiation energy conditions to a conventional ink. It relates to printed matter.

  In the production of ultraviolet curable prints, ultraviolet lamps (UV lamps) such as low pressure, high pressure mercury lamps, xenon lamps and metal halide lamps have been widely used as curing systems as light sources.

  On the other hand, in recent years, a new ultraviolet curable ink that can be cured satisfactorily under lower irradiation energy conditions has attracted attention from the viewpoint of environmental conservation.

  The above-mentioned low irradiation energy conditions refer to general conditions in which the amount of irradiated ultraviolet energy is clearly smaller than before, such as reducing the input power of an ultraviolet light emitting lamp or reducing the number of lamps used. In addition to methods using existing ultraviolet lamps, various ultraviolet irradiation light sources including ultraviolet light-emitting diode light sources (UV-LEDs), low-power ultraviolet fluorescent lamps, special ultraviolet lamps, etc., which have been attracting attention in recent years. It is assumed.

  For example, as an example of the aforementioned ultraviolet light-emitting diode light source (UV-LED), there is a printing method (see Patent Document 1) that improves the curability of the UV-LED light source in combination with a laminate film, and UV-LED (low irradiation energy). ) Examples of initiators that work effectively in curing are given.

  In order to obtain good drying properties even under low irradiation energy conditions, it is necessary to use an ultraviolet curable ink having a component composition different from that of conventional inks, but photopolymerization that works effectively under low irradiation energy conditions. Initiators are generally expensive, and in many cases it is necessary to increase the amount of initiator used, which tends to increase the cost of raw materials for ink compared to conventional inks, making it difficult to integrate with conventional inks. there were. Therefore, in the printing company, more types of ink must be managed in stock and used properly according to the situation, which has become a factor that increases the burden on work such as ink replacement and machine cleaning.

The above-mentioned conventional inks refer to all inks that are cured and dried well when irradiated with ultraviolet energy of about 40 mJ / cm ² or more by an existing ultraviolet lamp. For example, the Dicure Abilio series (DIC graphic) Etc.). Similarly, examples of inks that are cured and dried well under low irradiation energy conditions include, for example, the Dicure Abilio LED series (manufactured by DIC Graphics), which can be cured and dried satisfactorily with an ultraviolet light emitting diode light source. Examples of the ink that is cured and dried satisfactorily under the condition where the power and number of lamps are reduced include, for example, Dicure Abilio SE series (manufactured by DIC Graphics).

  Therefore, by adding an additive in which a photopolymerization initiator is liquefied to a conventional ink, it becomes possible to easily obtain an ultraviolet curable ink that can be cured well under low irradiation energy conditions.

  A liquid initiator composition is preferable because it is effective for ultraviolet curable inks and considering mixing after addition. However, existing liquid initiator products use only an initiator having a low extinction coefficient at a wavelength of 350 to 420 nm, or a ratio of an initiator having a high extinction coefficient is low, or an initiator reaction efficiency with respect to the added amount For example, when added to conventional inks, it has been difficult to obtain a sufficient curing reaction under low irradiation energy conditions.

  Examples of existing liquid initiator products include IRGACURE500 (manufactured by BASF), IRGACURE1800 (manufactured by BASF), IRGACURE1870 (manufactured by BASF), IRGACURE754 (manufactured by BASF), DAROCUR4265 (manufactured by BASF), DAROCUR1173 (manufactured by BASF) ), DAROCUR EHA (manufactured by BASF), DAROCUR MBF (manufactured by BASF), ESACURE KIP100F (manufactured by Lamberti), ESACURE TZM (manufactured by Lamberti), GENOPOL AB-1 (manufactured by RAHN), GENOPOL (X) All of these can be easily dispersed by adding to ink products, but can effectively accelerate curing under low irradiation energy conditions. Not come.

JP2010-742

  An object of the present invention is to provide an active energy ray-curable ink composition that can be easily cured with low irradiation energy.

  The present inventors have found that the above problem can be achieved by employing an initiator mixture in which an initiator having a high extinction coefficient is effectively liquefied, and have reached the present invention.

That is, the present invention has at least one photopolymerization initiator (A) having an extinction coefficient in a methanol solution at a wavelength of 365 nm of less than 4.5 × 10 ² [ml / g cm], and an extinction coefficient of 4.5 × 10. ² [ml / g cm] or more of the photopolymerization initiator (B) of 2 or more types, the content of the photopolymerization initiator (A) described above is 5 to 40% by mass, and the photopolymerization initiator described above A photopolymerization initiator composition characterized in that the content of (B) is 60 to 95% by mass.

  Secondly, the present invention provides an active energy ray-curable printing ink composition characterized by having a step of adding the above-described photopolymerization initiator composition in a liquid state.

  Thirdly, the present invention provides a method for producing an active energy ray-curable printing ink composition comprising the step of adding the above-described photopolymerization initiator composition in a liquid state.

  According to the photopolymerization initiator composition of the present invention, it has been conventionally necessary to use a special high-sensitivity UV ink under a low irradiation energy condition, but an energy-saving curable ink can be obtained simply by adding to a general ink. It becomes possible. In addition, both conventional ink and high-sensitivity ink are inventoried to reduce the complexity and replacement / cleaning work depending on the situation.

  The present invention provides a method for producing an initiator mixture in which an initiator having a high extinction coefficient is effectively liquefied.

The initiator having a low extinction coefficient described herein means a photopolymerization initiator (A) having an extinction coefficient in a methanol solution at a wavelength of 365 nm of less than 4.5 × 10 ² [ml / g cm]. A high initiator indicates a photopolymerization initiator (B) having an extinction coefficient in a methanol solution at a wavelength of 365 nm of 4.5 × 10 ² [ml / g cm] or more.

Initiators with a high extinction coefficient at a wavelength of 365 nm generally have a large molecular weight compared to other initiators with low wavelength absorption, with some exceptions, and tend to have a long conjugation and lower solubility, This is a major factor that liquefaction is difficult and liquid initiators that can provide good drying properties under low irradiation energy conditions did not exist as existing products.
In the photopolymerization initiator composition of the present invention, in addition to the freezing point depressing action by mixing a plurality of polymerization initiators, liquefaction is promoted by mixing an appropriate amount of a low wavelength absorption initiator and mixed with conventional ink. It is characterized by providing a liquid polymerization initiator mixture that can be sufficiently cured under low irradiation energy conditions.

Examples of the photopolymerization initiator (A) having an extinction coefficient of less than 4.5 × 10 ² [ml / g cm] include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy- Cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-ketone, 4-methylbenzophenone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2- Methyl-1-propan-1-one, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one, Oxy-phenyl-acetic acid 2- [2 [oxo-2-phenyl-acetoxy-ethoxy-]-ethyl ester and oxy-phenyl-acetic acid 2- [2-hydroxy- Toxi] -ethyl ester mixture, phenylglyoxylic acid methyl ester, benzophenone, 4-methylbenzophenone, 2-benzoylmethyl benzoate, p-dimethylaminobenzoic acid ethyl ester, p-dimethylaminobenzoic acid butoxyethyl ester, p -Dimethylaminobenzoic acid 2-ethylhexyl ester, 2-dimethylaminoethylbenzoic acid, etc. are mentioned.
Among them, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, an initiator that is highly versatile and favorably liquefies the photopolymerization initiator composition, 2-Hydroxy-2-methyl-1-phenyl-propane-1-ketone, 4-methylbenzophenone, benzophenone, and p-dimethylaminobenzoic acid ethyl ester are preferred, with 1-hydroxy-cyclohexyl-phenyl-ketone being most preferred.

As an example of the photopolymerization initiator (B) which is not liquid at room temperature having an extinction coefficient of 4.5 × 10 ² [ml / g cm] or more, 2-benzyl-2-dimethylamino-1- (4-morpholino Phenyl) -butanone-1,2-dimethylamino-2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butan-1-one, 2-methyl-1 [4- (Methylthio) phenyl] -2-morpholinopropan-1-one, 4,4′-diethylaminobenzophenone, thioxanthone, 2,4-diethylthioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-diisopropylthioxanthone, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxone Tonnes, bis- (2,6-dichlorobenzoyl) phenylphosphine oxide, bis- (2,6-dichlorobenzoyl) -2,5-dimethylphenylphosphine oxide, bis- (2,6-dichlorobenzoyl) -4 -Propylphenylphosphine oxide, bis- (2,6-dichlorobenzoyl) -1-naphthylphosphine oxide, bis- (2,6-dimethoxybenzoyl) phenylphosphine oxide, bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis- (2,6-dimethoxybenzoyl) -2,5-dimethylphenylphosphine oxide, bis- (2,4,6-trimethylbenzoyl) phenylphosphine oxide 2,4,6-trimethyl Benzoyl-diphenylphosphine oxide, 2,6-dimethoxybenzoyl-diphenylphosphine oxide, 2,6-dichlorobenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoyl-phenylphosphinic acid methyl ester, 2-methyl Benzoyl-diphenylphosphine oxide, 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) ) -9H-carbazol-3-yl]-, 1- (O-acetyloxime), and the like.
Among them, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2-dimethylamino is an initiator that is highly versatile and exhibits good drying properties under low irradiation energy conditions. -2- (4-Methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butan-1-one, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropane -1-one, 4,4′-diethylaminobenzophenone, 2,4-diethylthioxanthone, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide are preferred.

  The photoinitiator composition of this invention is comprised from 1 or more types of photoinitiators (A) and 2 or more types of photoinitiators (B). It is preferable to use one or more photopolymerization initiators (A) in terms of easily liquefying the photopolymerization initiator composition and suppressing component precipitation and crystallization during storage. Also in the agent (B), it is preferable to use two or more types in terms of easily liquefying and suppressing the precipitation of components during storage. Moreover, also in the point which provides the outstanding ink drying property on low irradiation energy conditions, two or more types of photoinitiators (B) are used, "alpha-aminoalkyl phenone type compound", "dialkylamino benzophenone type compound". Rather than selecting two or more compounds of a single system from a group of compounds such as “thioxanthone compounds”, “acylphosphine oxide compounds”, etc., two or more different initiators are selected and combined. Are preferably used.

  It is preferable that the content rate in the ink composition of the photoinitiator composition added to the conventional ink of this invention exists in the range of 4-15 mass%. If the addition amount is less than 4% by mass, it is difficult to obtain good drying properties under low irradiation energy conditions. If the addition amount exceeds 15% by mass, the initiator amount becomes excessive, and the drying property is further improved. This is not preferable because it cannot be expected and the coloring power (pigment concentration) of the ink is reduced.

  Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Method for producing photopolymerization initiator composition (Example 1: Preparation of photopolymerization initiator composition (mixture 1))
Photopolymerization initiator composition (mixture 1) containing IRGACURE 369 (12.0 parts), DAROCUR TPO (55.0 parts), EAB-SS (18.0 parts), IRGACURE 184 (15.0 parts) shown in Table 1 ) Is added to Dicure Abilio Process Indigo (N type, manufactured by DIC Graphics), which is a conventional UV curable ink, and 0.150 ml is added as a simple color developer (RI tester, manufactured by Toyoe Seiko). Is printed on a PET film (DIC Corporation, Daitac UVPET Transparent 25FL) in an area range of about 220 cm ² , and a printed matter is produced under the UV lamp irradiation conditions and UV-LED irradiation conditions shown in Table 1. did.
A metal halide lamp (manufactured by Eye Graphics Co., Ltd.) is used as the UV lamp, and an ultraviolet light emitting diode irradiation device (Panasonic Electric Works, ANUD8002T01) having an emission wavelength peak of 385 nm is used as the UV-LED. UIT-150-A (USHIO Inc.) was used.
Standard irradiation conditions using a UV lamp include an irradiation distance of 11 cm, an output of 120 W / cm, three lamps, and a line speed of 120 m / min. And the integrated light quantity value was 69 mJ / cm ² .
Energy-saving irradiation conditions [1] (low irradiation energy conditions) using a UV lamp include an irradiation distance of 11 centimeters, an output of 120 W / cm, one lamp, and a line speed of 120 m / min. And the integrated light amount value was 23 mJ / cm ² .
The energy irradiation condition [2] (low irradiation energy condition) using the UV-LED includes an irradiation distance of 1 cm, an output of 100%, a single lamp, and a line speed of 120 m / min. And the integrated light amount value was 22 mJ / cm ² .

(Example 2: Preparation of photopolymerization initiator composition (mixture 2))
IRGACURE 369 (10.0 parts), DAROCUR TPO (40.0 parts), EAB-SS (20.0 parts), SPEEDCURE DETX (20.0 parts) and IRGACURE 184 (10.0 parts) shown in Table 1 were blended. 8% by mass of the photopolymerization initiator composition (mixture 2) is added to Dicure Abilio Process Ai (N type, manufactured by DIC Graphics), which is a conventional UV curable ink, and 0.150 ml is added to a simple color developing machine. (RI tester, manufactured by Toyoe Seiko Co., Ltd.), after printing in an area range of about 220 cm ² on a PET film (manufactured by DIC, Daitac UVPET transparent 25FL), both UV lamp irradiation conditions and UV-LED irradiation conditions A printed matter was produced under the same irradiation conditions as in Example 1.

[Comparative Example 1]
In Table 1, 0.150 ml of Dicure Abilio process indigo (N type, manufactured by DIC Graphics), which is a conventional UV curable ink, is used in a PET film using a simple color developing machine (RI tester, manufactured by Toyosei Seiko Co., Ltd.). After printing in an area range of about 220 cm ² on DIC Corporation, Daitac UVPET Transparent 25FL, a printed matter was produced under the same irradiation conditions as in Example 1 under both UV lamp irradiation conditions and UV-LED irradiation conditions.

[Comparative Example 2]
A photopolymerization initiator composition (mixture 3) containing IRGACURE369 (6.0 parts), DAROCUR TPO (25.0 parts), EAB-SS (9.0 parts), and IRGACURE184 (60.0 parts) shown in Table 1. ) Is added to Dicure Abilio Process Indigo (N type, manufactured by DIC Graphics), which is a conventional UV curable ink, and 0.150 ml is added as a simple color developer (RI tester, manufactured by Toyoe Seiko). After printing in an area range of about 220 cm ² on a PET film (Dicac UVPET transparent 25FL, manufactured by DIC Corporation), both the UV lamp irradiation conditions and the UV-LED irradiation conditions were the same as in Example 1. The printed matter was manufactured.

[Comparative Example 3]
A photo-polymerization initiator composition (mixture 4) containing IRGACURE 369 (15.0 parts), DAROCUR TPO (60.0 parts), and EAB-SS (25.0 parts) shown in Table 1 was used as a UV curable conventional ink. 8% by mass is added to Dicure Abilio process indigo (N type, manufactured by DIC Graphics), and 0.150 ml is added to a PET film (RI tester, manufactured by Toyosei Seiko Co., Ltd.) using a PET film ( After printing in an area range of about 220 cm ² on DIC Corporation, Daitac UVPET Transparent 25FL), a printed matter was produced under the same irradiation conditions as in Example 1 under both UV lamp irradiation conditions and UV-LED irradiation conditions.

[Comparative Example 4]
A photopolymerization initiator composition (mixture 5) containing IRGACURE 184 (50.0 parts) and BENZOPHENONE (50.0 parts) shown in Table 1 was added to a UV curing type conventional ink, Dycure Abilio Process Indigo (N type, 8% by mass to DIC Graphics) and 0.150 ml on a PET film (DIC, Daitac UV PET Transparent 25FL) using a simple color developer (RI tester, Toyoe Seiko Co., Ltd.) After printing in an area range of about 220 cm ^2, a printed matter was produced under the same irradiation conditions as in Example 1 under both UV lamp irradiation conditions and UV-LED irradiation conditions. The mixture 5 has the same composition as the liquid initiator mixture sold by BASF under the product name IRGACURE500.

[Comparative Example 5]
A photopolymerization initiator composition (mixture 6) blended with DAROCUR 1173 (50.0 parts) and DAROCUR TPO (50.0 parts) shown in Table 1 was used as a UV curable conventional ink, Dycure Abilio Process Indigo (N type). 8% by mass to DIC Graphics) and 0.150 ml on a PET film (DIC, Daitac UV PET Transparent 25FL) using a simple color developer (RI tester, Toyoe Seiko Co., Ltd.) After printing in an area range of about 220 cm ^2, a printed material was manufactured under the same irradiation conditions as in Example 1 under both the UV lamp irradiation conditions and the UV-LED irradiation conditions. As a photopolymerization initiator of Dicure Abilio process indigo, IRGACURU907: 2-methyl-1 [4- (methylthio) phenyl] -2-morphosonopropan-1-one 3% (manufactured by BASF), EAB-SS: Contains 4,4′-diethylaminobenzophenone 2.5% (manufactured by Daido Kasei Kogyo Co., Ltd.).
Mixture 6 has the same composition as the liquid initiator mixture sold by BASF under the product name DAROCUR4265.

[Evaluation method of photopolymerization initiator composition: liquid stability]
The photopolymerization initiator mixture was stored at room temperature (25 ° C.) for 1 week, the state of precipitation accompanying the decrease in solubility of the polymerization initiator was visually confirmed, and evaluated in the following three stages.
3. The polymerization initiator does not precipitate, and the appearance is transparent. 2. The cloudiness is generated, but it is not precipitated. 1. The polymerization initiator is precipitated.

[Evaluation method of ink added with photopolymerization initiator composition: ink viscosity]
Conventional ink: 8% by mass of the photopolymerization initiator composition of the present invention is added to DIC Graphics Dicure Abilio Process Indigo N type, and the state of viscosity reduction is evaluated by ○ × by incometer TV (tack value) measurement. did.
○: Decrease in ink viscosity after addition is small and has little effect on printability of ink ×: Decrease in ink viscosity after addition is large and has a large effect on printability of ink

[Evaluation method for printed matter: drying]
As a method for evaluating the drying property (curability) of the printed matter after irradiation with ultraviolet rays, the dried state of the ink was confirmed by a nail scratch test and evaluated in the following five stages.
5 ... Completely dry, no scratches on the film even when rubbed with strong force 4 ... Almost dry, slightly rubbed on the film when rubbed with strong force 3 ... The film is almost dry, and the film is clearly scratched when rubbed with a strong force. 2 ... It is slightly dry, and the film is clearly scratched even with a weak force.

The numerical values in Table 1 are mass%.
The chemical structure and manufacturer name of the photopolymerization initiator in Table 1 are shown below.
IRGACURE 184: 1-hydroxy-cyclohexyl-phenyl-ketone, BASF BENZOPHENONE: benzophenone, Lambson DAROCUR 1173: 2-hydroxy-2-methyl-1-phenyl-propane-1-ketone IRGACURE 369: 2-benzyl-2-dimethyl Amino-1- (4-morpholinophenyl) -butanone-1, DAROCUR TPO manufactured by BASF: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, EAB-SS manufactured by BASF: 4,4′-diethylamino Benzophenone, manufactured by Daido Kasei Kogyo Co., Ltd. SPEEDCURE DETX: 2,4-diethylthioxanthone, manufactured by Lambson

  In the results of Examples 1 and 2, the liquid stability of the photopolymerization initiator composition containing one or more photopolymerization initiators (A) and two or more (B) was not problematic, and when added to conventional inks It was confirmed that there was no practical problem with the drying property of (Evaluation: 5) in both standard irradiation conditions and energy-saving irradiation conditions (low irradiation energy conditions).

When no photopolymerization initiator composition is added (Comparative Example 1), when the composition ratio of the photopolymerization initiator (B) is low (Comparative Example 2), the ink drying property becomes poor under energy-saving irradiation conditions. It was confirmed. In Comparative Example 2, it was confirmed that the ink viscosity was greatly reduced.
Regarding the photopolymerization initiator composition (Comparative Example 3) in which no photopolymerization initiator (A) was present, it was confirmed that the liquid stability was poor.
Regarding the photopolymerization initiator compositions of Comparative Example 4 and Comparative Example 5 sold as existing liquid initiator mixtures, the ink viscosity is greatly reduced in addition to poor ink drying properties under energy-saving irradiation conditions. I confirmed that

  The method for producing the photopolymerization initiator composition and the ultraviolet curable composition of the present invention and the ultraviolet curable printed material using the composition include printed graphics, coatings, paints, in addition to graphic image printing that requires printing by UV curing. It can be suitably used in fields such as plastics and electronic materials.

Claims (5)

One or more photopolymerization initiators (A) having an extinction coefficient in a methanol solution at a wavelength of 365 nm of less than 4.5 × 10 ² [ml / g cm] and an extinction coefficient of 4.5 × 10 ² [ml / g cm ] Two or more kinds of photopolymerization initiators (B) that are not liquid at room temperature, and the content of the photopolymerization initiator (A) is 5 to 40% by mass. B) Content of 60-95 mass%, The photoinitiator composition characterized by the above-mentioned. The photopolymerization initiator (A) described above is 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl- One or more kinds selected from propane-1-ketone, 4-methylbenzophenone, and p-dimethylaminobenzoic acid ethyl ester, and the photopolymerization initiator (B) described above is “α-aminoalkylphenone compound”, “ 2. The photopolymerization initiator composition according to claim 1, wherein the composition is at least two kinds selected from “dialkylaminobenzophenone compounds”, “thioxanthone compounds”, and “acylphosphine oxide compounds”. The photopolymerization initiator (A) is 1-hydroxy-cyclohexyl-phenyl-ketone, and the photopolymerization initiator (B) is 2-benzyl-2-dimethylamino-1- (4-morpholino). Phenyl) -butanone-1 and 2-dimethylamino-2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butan-1-one and 2-methyl-1 [4- One or more selected from (methylthio) phenyl] -2-morpholinopropan-1-one, one or more selected from 4,4′-diethylaminobenzophenone and 2,4-diethylthioxanthone, and 2,4,6 The photoinitiator composition of Claim 1 comprised from -trimethylbenzoyl-diphenyl-phosphine oxide. An active energy ray-curable ink composition comprising 4 to 15% by mass of the photopolymerization initiator composition according to any one of claims 1 to 3. The step of adding the photopolymerization initiator composition described in any one of claims 1 to 3 in a liquid state to an ultraviolet ray active energy ray curable composition containing an active energy ray curable monomer and / or oligomer. A method for producing an active energy ray-curable printing ink composition, comprising: