JP5773671B2 - Active energy ray-curable inkjet ink composition and resin-coated metal plate - Google Patents

Description

  The present invention relates to an active energy ray-curable inkjet ink composition and a metal plate coated with the inkjet ink composition.

  In order to process the surface of a metal plate, a plated steel plate, or the like, a surface treatment is performed to form a resin coating film on a part of the metal surface using various paints or inks. The main purpose of the surface treatment is to improve electrical insulation, corrosion resistance, molding processability, designability, and the like. Examples of the partial coating method include screen printing, flat printing, flexographic printing, UV curable ink jet printing, and the like. Among these, UV curable ink jet printing does not require a plate, and thus is highly useful in terms of cost in small lot production. Moreover, since the amount of the organic solvent added in the ink can be reduced by adopting the UV curable type, it is excellent in terms of environment in that VOC emission can be reduced.

  In the UV curable ink jet printing, unlike other printing methods, UV irradiation is performed for each ejection of ink droplets, and the ink droplets are superimposed to form a film. For this reason, in order to obtain sufficient film strength, it is necessary to satisfy both the surface curability of each ink droplet and the internal curability of a thick film formed by overlapping these ink droplets. Further, when the resin-coated metal plate is used as a component for the electric and electronic field, it is necessary to ensure the adhesion of the film to such an extent that it does not peel off even when bent. In addition, it is necessary to increase the degree of UV curing in order to improve scratch resistance, wear resistance, and the like.

  As a photopolymerization initiator excellent in surface curability, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (α-aminoketone initiator, trade name “Irgacure 907”) , Manufactured by BASF) and an isobutylthioxanthone added together (Patent Documents 1 to 3) have been proposed. Further, inks (Patent Documents 4 and 5) in which an amine is added as a photoinitiator aid have been proposed. Also, an ink using an α-hydroxyketone initiator and an acyl phosphine oxide initiator (Patent Document 6), an ink using an α-aminoketone photopolymerization initiator and an acyl phosphine oxide initiator together (Patent Document) 7 and 8) have been proposed. Furthermore, as an example in which a photopolymerization initiator with good surface curability and a photopolymerization initiator with good internal curability are used in combination, two types of α-hydroxyketone initiators and an acylphosphine oxide initiator An ink (Patent Document 9) in which an agent is used in combination has been proposed.

  The metal plate for resin coating is washed and dried after degreasing treatment such as alkali degreasing, solvent degreasing or electrolytic degreasing. Further, the metal plate may be further pickled after the degreasing treatment, and then washed and dried. However, since there is usually a thick oxide film on the surface of the metal plate, adhesion to the resin film is often insufficient even when sufficient degreasing treatment is performed. If the adhesion between the metal plate and the resin film is insufficient, it becomes difficult to precisely process the resin-coated metal plate into a desired shape. Accordingly, the coating resin is required to have sufficient adhesion with the metal plate.

  In order to improve the adhesion to the printing plate, inks (Patent Documents 10 and 11) to which a phosphate ester polymerizable compound is added have been proposed. In order to improve adhesion to a metal plate, a paint (Patent Document 12) to which a phosphate ester polymerizable compound, a polyurethane resin, an amine and an α-hydroxyketone initiator are added has also been proposed.

JP 2001-207098 A JP 2002-187343 A JP 2004-18656 A JP 2001-288387 A JP 2003-25707 A JP 2001-525479 A JP 2002-241647 A JP 2006-137183 A JP 2006-282756 A JP 2006-328227 A JP 2009-235272 A JP 2008-30474 A

  However, the above-described ink and the like cannot achieve both sufficient adhesion to the metal plate and sufficient UV curability. The present invention has been made in view of such problems of the prior art, and the object is to provide a resin-coated metal plate having a resin film with sufficient adhesion to metal and excellent strength. It is in providing the ink composition for inkjets which can obtain. Moreover, the place made into the subject of this invention is providing the resin coating metal plate which has sufficient adhesiveness with respect to a metal and has a resin film excellent in intensity | strength.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have determined (i) a phosphoric acid ester-based polymerizable compound in order to achieve both film adhesion to metal and UV curability of the formed resin film. (Ii) an α-hydroxyketone-based initiator having 1 or less phenyl groups in the skeleton, and acylphosphine, in order to achieve an appropriate amount of addition, and (ii) both surface curability and internal curability of the resin film It has been found that the above-mentioned problems can be achieved by using an oxide-based initiator in combination, and the present invention has been completed.

  That is, according to the present invention, the following inkjet ink composition, resin-coated metal plate, and method for producing a resin-coated metal plate are provided.

  [1] A polymerizable monomer that can be polymerized by active energy rays, and a photopolymerization initiator, and the polymerizable monomer has a phosphate ester group and an ethylenic double bond group in the molecule. 0.5 to 13% by mass of a polymerizable phosphate ester compound, and 10 to 75% by mass of a monofunctional monomer having one ethylenic double bond group in the molecule and no phosphate ester group And the photopolymerization initiator comprises an acyl phosphine oxide initiator and an α-hydroxyketone initiator having a phenyl group contained in the skeleton of 1 or less, and has a viscosity at 25 ° C. of 3 to 50 mPa An ink-jet ink composition that is s.

  [2] The inkjet ink composition according to [1], wherein the polymerizable phosphate ester compound is a compound represented by any one of the following general formulas (A1) to (A4).

［式中、Ｒは水素原子又はメチル基を表し、Ｒ_１は炭素数が１〜４のアルキレン基を表す］

[Wherein, R represents a hydrogen atom or a methyl group, and R ₁ represents an alkylene group having 1 to 4 carbon atoms]

［式中、ＲとＲ_１はそれぞれ前記一般式（Ａ１）と同様に定義される］

[Wherein, R and R ₁ are defined as in the general formula (A1), respectively]

［式中、ＲとＲ_１はそれぞれ前記一般式（Ａ１）と同様に定義され、Ｒ_２は炭素数が１〜１０のアルキレン基を表す］

[Wherein, R and R ₁ are each defined in the same manner as in the general formula (A1), and R ₂ represents an alkylene group having 1 to 10 carbon atoms]

［式中、Ｒ、Ｒ_１およびＲ_２はそれぞれ前記一般式（Ａ３）と同様に定義される］

[Wherein, R, R ₁ and R ₂ are defined in the same manner as in the general formula (A3)]

  [3] The polymerizable monomer further contains 10 to 75% by mass of a polyfunctional monomer having two or more ethylenic double bond groups in the molecule and no phosphate ester group in all monomers. The inkjet ink composition according to [1] or [2].

  [4] having a metal plate and a resin film made of a cured product of the ink-jet ink composition according to any one of [1] to [3], which covers at least a part of the surface of the metal plate. Resin coated metal plate.

  [5] A step of discharging the inkjet ink composition according to any one of [1] to [3] on a metal plate; a step of irradiating an active energy ray to cure the inkjet ink composition; A method for producing a resin-coated metal plate comprising:

  The ink-jet ink composition of the present invention is capable of obtaining a resin-coated metal plate having a resin film excellent in strength while having sufficient adhesion to metal. In addition, since the ink-jet ink composition of the present invention can be stably ejected using an ink-jet recording apparatus, a printing plate is not necessary, and it is useful in terms of cost. The resin-coated metal plate using the ink-jet ink composition of the present invention has a sufficient adhesion to metal and has a resin film excellent in strength.

Inkjet ink composition The inkjet ink composition of the present invention (hereinafter also simply referred to as “ink composition”) includes a polymerizable monomer polymerizable by active energy rays and a photopolymerization initiator, and has a viscosity at 25 ° C. Is 3 to 50 mPa · s. The polymerizable monomer is 0.5 to 13% by mass of a polymerizable phosphate ester compound having a phosphate ester group and an ethylenic double bond group in the molecule, and one ethylene in the molecule. 10 to 75% by mass of a monofunctional monomer having a functional double bond group and no phosphate ester group. The photopolymerization initiator is composed of an acyl phosphine oxide initiator and an α-hydroxyketone initiator having one or less phenyl groups in the skeleton. Hereinafter, the details of the ink composition of the present invention will be described.

(1) Polymerizable phosphate ester compound The polymerizable phosphate ester compound is a compound having a phosphate ester group and an ethylenic double bond group in the molecule. The phosphate ester compound has a great effect in improving metal adhesion as compared with a compound containing a carboxyl group. Therefore, since the effect can be obtained with a small amount, the ink composition containing the same can reduce the viscosity. Therefore, the ink composition of the present invention containing a polymerizable phosphate ester compound has an advantage that it has a low viscosity and can be stably ejected by inkjet.

  The phosphate ester group refers to a group represented by any of the following formulas (a1) to (a3). As the phosphate group, a group represented by the formula (a2) or (a3), a so-called acidic phosphate group is preferable. This is because these groups have a phosphoric acid group and thus improve the adhesion to the metal by causing a condensation reaction with a hydroxyl group present on the metal surface. The composition containing a compound having a group represented by the formula (a3) gives a cured product particularly excellent in adhesion to a metal. Moreover, the composition containing the phosphate ester group represented by the formula (a2) has an advantage that the viscosity is extremely low. Therefore, the structure of the phosphate ester group may be appropriately selected according to the intended physical properties.

  The ethylenic double bond group means a group obtained by extracting one hydrogen atom from ethylene. In this case, ethylene may have a substituent. Examples of the ethylenic double bond group include a (meth) acryloyl group, a vinyl group, and a vinylidene group. Especially, since it is easy to acquire, it is preferable that an ethylenic double bond group is a (meth) acryloyl group. The (meth) acryloyl group means a methacryloyl group or an acryloyl group. Therefore, the polymerizable phosphoric acid ester compound is preferably a compound obtained by esterifying a compound having a (meth) acryloyl group and a hydroxyl group in the molecule with phosphoric acid.

Examples of compounds having a (meth) acryloyl group and a hydroxyl group in the molecule include the following.
Such as 2-hydroxymethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, etc. Hydroxyalkyl (meth) acrylate.

  (Poly) ethylene glycol (meth) acrylates such as ethylene glycol (meth) acrylate, diethylene glycol (meth) acrylate, triethylene glycol (meth) acrylate, and tetraethylene glycol (meth) acrylate.

  Among these, as the polymerizable phosphate compound, compounds represented by the following general formulas (A1) to (A4) are preferable. It is because it is excellent in adhesiveness with a metal and is easily available.

In the formula (A1), R represents a hydrogen atom or a methyl group, and R ₁ represents an alkylene group having 1 to 4 carbon atoms. R is preferably a methyl group in order to reduce the viscosity of the compound. R ₁ is preferably an ethylene group in order to improve the balance between adhesion to metal and alkali peelability. The compound in which R ₁ is an ethylene group is also referred to as 2- (meth) acryloyloxyethyl acid phosphate or 2- (meth) acryloyloxyethyl phosphate.

In the formula (A2), R independently represents a hydrogen atom or a methyl group, and R ₁ independently represents an alkylene group having 1 to 4 carbon atoms. “Independently” means that one of two Rs may be a hydrogen atom and the other may be a methyl group. R is preferably a methyl group in order to reduce the viscosity of the compound. R ₁ is preferably an ethylene group in order to enhance the adhesion and solubility of the compound with the metal. A compound in which R ₁ is an ethylene group is also called di {2- (meth) acryloyloxyethyl} acid phosphate or di-2- (meth) acryloyloxyethyl phosphate.

In the formula (A3), R each independently represents a hydrogen atom or a methyl group, R ₁ represents an alkylene group having 1 to 4 carbon atoms, and R ₂ represents an alkylene group having 1 to 10 carbon atoms. R is preferably a methyl group in order to reduce the viscosity of the compound. R ₁ is preferably an ethylene group in order to enhance the adhesion between the compound and the metal, and R ₂ is preferably a pentene group.

In formula (A4), each R independently represents a hydrogen atom or a methyl group, each R ₁ independently represents an alkylene group having 1 to 4 carbon atoms, and each R ₂ independently represents 1 to 10 carbon atoms. Represents an alkylene group. R is preferably a methyl group in order to reduce the viscosity of the compound. R ₁ is preferably an ethylene group in order to increase the balance between the adhesion and solubility of the compound with the metal, and R ₂ is preferably a pentene group.

  The ink composition of the present invention contains a polymerizable phosphoric acid ester compound as a polymerizable monomer in an amount of 0.5 to 13% by mass in all monomers. When the content of the polymerizable phosphoric ester compound is less than 0.5% by mass, the adhesion of the cured product of the ink composition (hereinafter also referred to as “cured film”) to the metal is not sufficient. Moreover, when the content exceeds 13% by mass, not only the physical strength (scratch hardness (pencil method)) of the cured film is not sufficient, but also the viscosity limit of ink jet ink at 25 ° C. may exceed 50 mPa · s. Increases nature. Since the cured film has excellent adhesion and physical strength (scratch hardness (pencil method)) and can maintain an appropriate viscosity range of the ink, the content of the polymerizable phosphate ester compound is 4 to 13 masses. % Is more preferable. Moreover, since the ink composition of the present invention contains a polymerizable phosphoric ester compound and can be peeled off by immersing the UV cured film in an alkaline aqueous solution, it can also be used as an etching resist ink.

(2) Polyfunctional monomer The ink composition of the present invention preferably contains a polyfunctional monomer having two or more ethylenic double bond groups in the molecule and having no phosphate group. The content of this polyfunctional monomer is preferably 10 to 75% by mass, more preferably 55 to 65% by mass, based on all monomers. Examples of the polyfunctional monomer include compounds containing 2 to 6 ethylenic double bond groups in the molecule. Especially, as a polyfunctional monomer, the compound which contains two or more (meth) acryloyl groups in a molecule | numerator is preferable. This is because it is easily available and is easily polymerized by active energy rays. When the ink composition contains a polyfunctional monomer, the crosslinking density is further improved, and the strength of the cured film is further improved. However, if the polyfunctional monomer is added too much, the crosslink density becomes too high, and the adhesiveness may decrease due to curing shrinkage of the cured film. An appropriate amount of the polyfunctional monomer is preferably added in view of the balance between the physical strength of the cured film and the solubility of the photopolymerization initiator.

  A known polyfunctional monomer may be used. However, in the present invention, it is preferable to use a compound represented by the following general formula (B1) or (B2).

In general formula (B1), R represents a hydrogen atom or a methyl group each independently. R < ₁₀ > represents a C1-C5 alkyl group each independently. P represents the number of R ₁₀ substituted on the benzene ring and is an integer of 0 to 4. X represents a single bond, a methylene group, or an isopropylidene group, and n and m each represents a number of 0 to 6. Such a compound is available as (meth) acrylate of ethylene glycol-modified bisphenol. A compound obtained by reacting bisphenol with ethylene glycol and acrylic acid is preferable. In this case, n + m is preferably 3 to 5, and more preferably 4.

In the general formula (B2), R each independently represent a hydrogen atom or a methyl group, R ₂₀ represents an alkylene group having 3-9 carbon atoms. The alkylene group also includes its isomer. The alkylene group having 3 to 9 carbon atoms is preferably a hexyl group or a pentyl group.

(3) Monofunctional monomer The ink composition of the present invention comprises a monofunctional monomer having one ethylenic double bond group in the molecule and no phosphate ester group. Examples of the monofunctional monomer include the following compounds.

  2-phenoxyethyl acrylate, acryloylmorpholine, N-vinylcaprolactam, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, isobutyl acrylate, t-butyl acrylate, isooctyl acrylate, isobornyl acrylate, Cyclohexyl acrylate, 2-methoxyethyl acrylate, methoxytriethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, 3-methoxybutyl acrylate, benzyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydipropylene Glycol acrylate, methyl Roh carboxyethyl acrylate, dipropylene glycol acrylate.

  Among these, as the monofunctional monomer, a compound containing a (meth) acryloyl group in the molecule is preferable. This is because it is easily available and is easily polymerized by active energy rays.

  These compounds may be used alone or in combination. Ink compositions containing these monofunctional monomers exhibit low viscosity and can be stably ejected by inkjet. The ink composition of this invention contains 10-75 mass% of monofunctional monomers in all monomers as a polymerizable monomer. If the content of the monofunctional monomer is less than 10% by weight, the resulting ink composition has a high viscosity, which may make it difficult to eject by ink jet. When the content exceeds 75% by weight, the physical strength (scratch hardness (pencil method)) of the cured film may be lowered.

(4) Carboxy group-containing polymerizable compound The ink composition of the invention preferably contains 1 to 30% by mass of the carboxyl group-containing polymerizable compound represented by the following general formula (I) in all monomers.

  In general formula (I), X represents an alkylene group having 1 to 3 carbon atoms, Y represents an alkylene group having 2 or 3 carbon atoms, and R represents a hydrogen atom or a methyl group.

  The carboxyl group-containing polymerizable compound represented by the general formula (I) gives a cured product having excellent adhesion to metal, etching resistance, and alkali peelability. The adhesion to the metal is considered to be improved because the carboxyl group of the carboxyl group-containing polymerizable compound can react with a hydroxyl group or the like present on the metal surface. It is considered that the etching solution resistance is improved when the carboxyl group-containing polymerizable compound has a stable chemical structure with respect to the etching solution and forms a crosslinked structure with other monomers to give a strong cured product. The alkali peelability is considered to be improved by the hydrolysis of the carboxyl group of the carboxyl group-containing polymerizable compound or the ester group derived therefrom with an alkali.

  Further, the carboxyl group-containing polymerizable compound is likely to associate in the molecule as shown by the following general formula (1). Therefore, it is difficult to form a dimer with other molecules like a compound having a general carboxyl group (see the following general formula (2)). Therefore, the carboxyl group-containing polymerizable compound has a viscosity even when a sufficient amount is added to the ink composition in order to improve the adhesion between the cured product and the metal, the etching solution resistance, and the alkali peelability. Hard to increase.

  In the formulas (1) and (2), Z represents an arbitrary organic group, and X represents an alkylene group having 1 to 3 carbon atoms.

  In the general formula (I), when X is a methylene group, the carbonyl group and the carboxyl group are likely to approach each other, so that intramolecular association shown in the general formula (1) is likely to occur. Further, when X is an ethylene group or a propylene group, although the distance between the carbonyl group and the carboxyl group is slightly separated, intramolecular association is likely to occur because the carbon-carbon bond in the alkylene group is rotatable. On the other hand, when X is an alkylene group having 4 or more carbon atoms, the distance between the carbonyl group and the carboxyl group becomes too long, so that intramolecular association hardly occurs. Further, when X is an aromatic hydrocarbon group such as a 1,2-phenylene group, the bond between two carbons on the aromatic ring to which the carbonyl group is bonded cannot be rotated, so that intramolecular association is less likely to occur. As described above, a compound that hardly causes intramolecular association is likely to be dimerized by association with other molecules as represented by the general formula (2).

  Examples of the alkylene group having 1 to 3 carbon atoms include a methylene group, an ethylene group, a propylene group, an isopropylene group, and an isopropylidene group. Among these, X is preferably a methylene group or an ethylene group, and particularly preferably an ethylene group, because intramolecular association is likely to occur. In the carboxyl group-containing polymerizable compound, a compound in which X is a methylene group is also called a malonic acid ester compound, a compound in which X is an ethylene group is also called a succinic acid ester compound, and a compound in which X is a propylene group is also called a glutaric acid ester compound.

  Examples of the alkylene group having 2 or 3 carbon atoms represented by the general formula (I) or Y include an ethylene group, a propylene group, an isopropylene group, and an isopropylidene group. As described above, the carboxyl group is bonded to the metal surface, and the polymerizable functional group is polymerized with other polymerizable functional groups. As the number of carbon atoms in Y increases, the molecular weight between the polymerizable functional group and the carboxyl group increases, so the distance between the bonding site with the metal and the polymerization site becomes longer, and moisture easily penetrates during this time. There is. As a result, when the carbon number of Y increases, the water resistance of the cured product may decrease. For this reason, Y is preferably an ethylene group. R is a hydrogen atom or a methyl group.

  Specific examples of the carboxyl group-containing polymerizable compound include 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid, 2-acryloyloxypropyl succinic acid, 2-acryloyloxyethyl malonic acid, and 2 -Acryloyloxyethyl glutaric acid is included.

  The viscosity of 2-acryloyloxyethyl succinic acid at 25 ° C. is 180 mPa · s. The viscosity of 2-methacryloyloxyethyl succinic acid at 25 ° C. is 160 mPa · s. On the other hand, the viscosity at 25 ° C. of 2-acryloyloxyethyl hexahydrophthalic acid, which is a polymerizable compound not included in the concept of the general formula (I), is about 4000 mPa · s, and contains a carboxyl group used in the present invention. It is higher than the viscosity of the polymerizable compound. The viscosity of these compounds is measured at 25 ° C. with a cone plate viscometer. A known cone plate viscometer may be used. The measurement conditions are preferably a shear rate of 230 (1 / s) and a rotational speed of 60 rpm.

The carboxyl group-containing polymerizable compound may be obtained by purchasing a commercially available product, or may be obtained by synthesis. The polymerizable ester compound can be synthesized, for example, through the following steps.
(1) A step of reacting a dicarboxylic acid such as succinic acid with a diol such as ethylene glycol to obtain a monoester,
(2) A step of reacting the monoester obtained in the previous step with acrylic acid or methacrylic acid.
In addition, you may perform each said process by a usual method.

  The content of the carboxyl group-containing polymerizable compound is preferably 1 to 30% by mass, and more preferably 1 to 10% by mass, based on all monomers constituting the ink composition.

(5) Photopolymerization initiator The photopolymerization initiator contained in the ink composition of the present invention includes an acylphosphine oxide initiator and an α-hydroxyketone initiator having one or less phenyl groups in the skeleton. It consists of an agent.

  The α-hydroxyketone-based initiator is a photopolymerization initiator that contributes to improving the surface curability of the photocurable ink composition. For this reason, when this (alpha) -hydroxyketone type | system | group initiator is used as a photoinitiator, the surface curability for every ink drop will become favorable. On the other hand, the acylphosphine oxide initiator is a compound having an absorption region on the long wavelength side as compared with the α-hydroxyketone initiator, and contributes to the improvement of the internal curability of the photocurable ink composition. It is a photopolymerization initiator. For this reason, when this acylphosphine oxide-based initiator is used as a photopolymerization initiator, the internal curability of the thick film formed by overlapping ink droplets is improved. In addition, as a result of intensive studies, the present inventors have obtained the following findings (i) and (ii).

  (I) An amine photoinitiator added as a conventional means for improving oxygen polymerization inhibition and obtaining sufficient UV curability reacts with a polymerizable phosphate ester compound to form a salt. Precipitate. For this reason, the amine photoinitiator aid cannot be used in combination with the polymerizable phosphate compound. For the same reason, α-aminoketone initiators cannot be used to react with the polymerizable phosphate compound. Since these basic polymerization initiators and photoinitiator aids cannot be used, the types of polymerization initiators that can be used are greatly limited. Therefore, even if sufficient adhesion to the metal plate can be ensured, it is difficult to obtain sufficient UV curability.

  (Ii) A combined system of an acyl phosphine oxide-based initiator and an α-hydroxyketone-based initiator can be used because it does not form a salt with the polymerizable phosphate compound. However, since the α-hydroxyketone initiator having two or more phenyl groups contained in the skeleton is hardly compatible with other ink components, the viscosity of the obtained ink composition excessively increases. For this reason, a sufficient amount of the polymerizable phosphate ester compound used for improving the adhesion to the metal plate is required to obtain a dischargeable viscosity (50 mPa · s or less) required for the ink composition for inkjet. There is a problem that it cannot be added.

  In view of the above findings (i) and (ii), in the present invention, as a component constituting the photopolymerization initiator together with the acylphosphine oxide-based initiator, the number of phenyl groups contained in the skeleton is 1 or less. -A hydroxyketone initiator is used. That is, the photopolymerization initiator contained in the ink composition of the present invention is substantially free of an α-hydroxyketone initiator having 2 or more phenyl groups contained in the skeleton. In this way, by using an α-hydroxyketone initiator having 1 or less phenyl groups in the skeleton, instead of an α-hydroxyketone initiator having 2 or more phenyl groups in the skeleton. Even when a sufficient amount of the polymerizable phosphoric acid ester compound is added, an ink composition having an appropriate viscosity capable of being ejected for inkjet use can be obtained without excessively increasing the viscosity.

  Furthermore, the α-hydroxyketone-based initiator having one or less phenyl groups contained in the skeleton is an ink composition as compared with the α-hydroxyketone-based initiator having two or more phenyl groups contained in the skeleton. Is highly soluble. For this reason, the α-hydroxyketone-based initiator having one or less phenyl groups contained in the skeleton can be easily dissolved even if a necessary amount for curing the ink composition is added.

Examples of the acylphosphine oxide initiator include the following compounds.
Bis (2,4,6 trimethylbenzyl) -phenylphosphine oxide (BASF, trade name “Irgacure 819”), 2,4,6 trimethylbenzoyl-diphenylphosphine oxide (BASF, trade name “Darocur TPO” ").

Examples of the α-hydroxyketone photopolymerization initiator in which the number of phenyl groups contained in the skeleton is 1 or less include the following compounds.
2-Hydroxy-2-methyl-1-phenylpropan-1-one (manufactured by BASF, trade name “Darocur 1173”), 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone ( BASF, trade name “Irgacure 2959”), 1-hydroxycyclohexyl-phenyl ketone (BASF, trade name “Irgacure 184”).

  The addition amount of the photopolymerization initiator is preferably 1.0 to 20.0% by mass, and more preferably 10.0 to 17.0% by mass with respect to the ink composition. When the addition amount of the photopolymerization initiator is less than 1.0% by mass, the ink composition tends not to be sufficiently cured. On the other hand, when the addition amount of the photopolymerization initiator exceeds 20.0% by mass, the viscosity of the ink composition tends to increase excessively, and it may be difficult to discharge from the inkjet head.

  The content ratio of the acylphosphine oxide-based initiator (A) and the α-hydroxyketone-based photopolymerization initiator (B) in which the number of phenyl groups contained in the skeleton is 1 or less is (A) / (B ) = 2/1 to 1/3, and (A) / (B) = 1/1 to 1/2 is more preferable. By setting the content ratio of these components within the above range, both the surface curability and the internal curability of the ink composition can be achieved.

(6) Other additives Furthermore, the ink composition of the present invention is a compound other than those described above and does not react with other components, a resin, an inorganic filler, an organic filler, and a coupling agent, if necessary. , Tackifiers, antifoaming agents, leveling agents, plasticizers, antioxidants, polymerization inhibitors, ultraviolet absorbers, flame retardants, pigments, dyes, and the like may be used in combination as appropriate.

  The ink composition of the present invention does not need to be colored, but may be colored for confirmation of printing quality such as pinhole check and design impartment. The color pigment that can be used in that case is not particularly limited.

  The ink composition of the present invention does not substantially require a solvent. For example, ketones such as methyl ethyl ketone and methyl isobutyl ketone, acetates such as ethyl acetate and butyl acetate, and aromatics such as benzene, toluene and xylene Hydrocarbons, alcohols such as ethylene glycol monoacetate, propylene glycol monomethyl ether, and butyl alcohol, and other commonly used organic solvents may be included.

(7) Viscosity The ink composition of the present invention has a viscosity at 25 ° C. of 3 to 50 mPa · s. Furthermore, the ink composition of the present invention preferably has a viscosity of 3 to 35 mPa · s, more preferably 7 to 20 mPa · s, at 25 to 80 ° C., which is generally regarded as a discharge temperature in inkjet. An ink composition having a viscosity within the above temperature range is excellent in ejection stability. When the viscosity at 25 ° C. is less than 3 mPa · s, in a high-frequency piezo-type ink jet head of 10 to 50 kHz, a decrease in ejection followability may be observed. If the viscosity at 25 ° C. exceeds 50 mPa · s, ejection may become unstable even if the heating device is arranged in an inkjet head. The viscosity of the ink composition can be adjusted by the content of the polymerizable phosphate ester composition. The viscosity is preferably measured with a cone plate viscometer.

(8) Surface tension The ink composition of the present invention preferably has a surface tension of 20 to 40 mN / m. The surface tension affects the ejection properties from the inkjet head and the resolution when drawing a pattern on a metal plate. An ink composition having a surface tension in the above range is excellent in dischargeability and the resolution. The surface tension is adjusted by a known method such as adding various surfactants. The surface tension may be measured by a known method, for example, a hanging drop method or a ring method, but is preferably measured by a plate method. For example, the surface tension can be measured using a trade name “CBVP-Z type” manufactured by Kyowa Interface Science Co., Ltd.

(9) Manufacturing method of ink composition The ink composition of the present invention is manufactured by dispersing or dissolving each component using a mixer, a disperser, and a stirrer. As a stirring mixer, a propeller type stirrer, a dissolver, a homomixer, a ball mill, a sand mill, an ultrasonic disperser, a kneader, a line mixer, and the like can be used. Dispersers include propeller-type stirrers, piston-type high-pressure emulsifiers, homomixers, ultrasonic emulsifier-dispersers, pressure-nozzle emulsifiers, high-speed rotary high-shear stirrers, colloid mills, and media-type dispersers. Can be used. The media type disperser is an apparatus that performs pulverization and dispersion using a medium such as glass beads and steel balls. Examples include sand grinders, agitator mills, ball mills, and attritors. These dispersers may be used in combination of two or more. Also, a stirring mixer can be used in combination. The ink composition is preferably filtered through a filter having a pore size of 3 μm or less, more preferably 1 μm or less.

(10) Method for producing resin-coated metal plate A resin-coated metal plate can be produced by using the ink composition of the present invention. The resin-coated metal plate may be arbitrarily produced as long as the effects of the present invention are not impaired, but a preferable method will be described below. The resin-coated metal plate is a method comprising: (a) a step of discharging the ink composition of the present invention onto a metal plate; and (b) a curing step of irradiating an active energy ray to cure the ink composition. Preferably it is manufactured.

  In the step (a), the ink composition of the present invention is discharged onto a metal plate using a normal ink jet recording apparatus. The ink jet recording apparatus preferably includes an ink composition supply unit, a temperature sensor, and an active energy ray irradiation unit. The ink composition supply means preferably includes an original tank for filling the ink composition, a supply pipe, an ink supply tank disposed in front of the inkjet head, a filter, and a piezo-type inkjet head. The piezo ink jet head is preferably 1-100 pl multi-dot. The resolution is preferably 320 × 320 to 4000 × 4000 dpi. The dpi is the number of dots per 2.54 cm.

  The discharge of the ink composition is preferably performed by heating the ink jet head and the ink composition to 35 to 100 ° C. A change in viscosity due to a temperature change of the ink composition affects the image quality. Therefore, it is preferable to keep the temperature constant while raising the temperature of the ink composition. The control range of the temperature of the ink composition is preferably ± 5 ° C. with respect to the set temperature, more preferably ± 2 ° C., and still more preferably ± 1 ° C.

  When an ink jet recording apparatus is used, ink droplets are normally ejected from the ink jet head in a superimposed manner at the same location. In this case, it is preferable to irradiate an active energy ray every time an ink droplet is discharged and to cure (pre-bake) the surface of each ink droplet (each ink composition). Thereby, the ink composition in which the surface was hardened can be piled up, and the cured film formed can be thickened.

The active energy ray is preferably irradiated for 0.01 to 2.0 seconds after the ink composition (ink droplet) adheres to the metal plate, and for 0.01 to 1.0 second. More preferably. When the irradiation timing is made as early as possible, a high-definition image can be formed. Moreover, it is preferable to use an active energy ray having a maximum illuminance of 500 to 3000 mW / cm ² in a wavelength range effective for curing.

  As the metal plate, austenitic stainless steel such as SUS304 or SUS316 or ferritic stainless steel such as SUS410 or SUS430 can be used. In applications where mechanical strength is required, materials obtained by cold hardening austenitic and ferritic stainless steel, martensitic stainless steel plates such as SUS420, and precipitation strengthened stainless steel plates such as SUS631 are used. It is preferable. In addition to the stainless steel plate, copper, carbon steel, or iron-nickel alloy may be used.

  In the step (b), the ink composition is cured by irradiating an active energy ray (mainly baked). Thereby, it hardens even the inside of the film | membrane which consists of ink compositions. Active energy rays refer to infrared rays, visible rays, ultraviolet rays, X-rays, electron beams, alpha rays, beta rays, gamma rays, and the like. Preferred examples of the active energy ray source used at this time include mercury lamps, low-pressure mercury lamps, various metals are ride lamps, low-pressure / solid-state lasers, xenon flash lamps, black lights, germicidal lamps, cold cathode tubes, light-emitting diodes ( LED), and laser diode (LD).

  In the present invention, it is preferable to use a lead-based metal halide lamp, an iron-based metal halide lamp, or a gallium-based metal halide lamp that emits intense light at 380 to 450 nm as the active energy ray source. A gallium metal halide lamp having strong emission at 400 to 430 nm is particularly preferable because the internal curability of the cured film (resin film) becomes good. In addition, GaN-based ultraviolet LEDs and ultraviolet LDs are preferable from the viewpoint of environmental protection because they do not use mercury. The ultraviolet LED is small, has a long life, is highly efficient, and is low in cost, and is expected as a light source for photo-curable ink jet.

In the step (b), in order to cure to the inside of the coating film made of the ink composition formed in the step (a), for example, while transporting the metal plate at a speed of 20 to 40 m / min, It is preferable to irradiate active energy rays. In addition, it is preferable to use an active energy ray having a maximum illuminance of 500 to 3000 mW / cm ² in a wavelength range effective for curing. In the present invention, two types of photopolymerization of an α-hydroxyketone initiator that contributes to improving the surface curability of each ink droplet and an acyl phosphine oxide initiator that contributes to improving the internal curability of the coating film. An ink composition containing an initiator is used. Therefore, it is possible to form a thick coating film while curing the surface of the ink droplets ejected in the step (a), and to sufficiently cure the inside of the coating film formed in the step (b).

  The total film thickness of the cured film (resin film) is preferably 2 to 40 μm. If the film thickness is less than 2 μm, it is difficult to ensure sufficient wear resistance and scratch resistance. Further, there may be a case where sufficient insulation as an electrical component cannot be ensured. Conversely, when the film thickness exceeds 40 μm, it may be difficult to obtain sufficient resolution. In the present invention, the cured film (resin film) may be heat-treated as necessary after irradiation with active energy rays. Adhesion may be improved by effects such as internal stress relaxation of the cured film (resin film).

The following polymerizable monomer and photopolymerization initiator were prepared.
[Compound of Formula (A1)]
2-Methacryloyloxyethyl acid phosphate (manufactured by Kyoeisha Chemical Co., Ltd., trade name “Light Ester P-1M”)
2-acryloyloxyethyl acid phosphate (manufactured by Kyoeisha Chemical Co., Ltd., trade name “Light Ester P-1A”)
[Compound of Formula (A2)]
Di {2-methacryloyloxyethyl} acid phosphate (manufactured by Kyoeisha Chemical Co., Ltd., trade name “Light Ester P-2M”)
[Mixture of Compound of Formula (A3) and Compound of Formula (A4)]
In formula (A3), R is a methyl group, R ₁ is an ethylene group, R ₂ is a pentylene group, and in formula (A4), R is a methyl group, R ₁ is an ethylene group, and R ₂ is a pentylene group. Mixture with a certain compound (trade name “Kayarad PM-21”, manufactured by Nippon Kayaku Co., Ltd.)

[Multifunctional monomer]
Tripropylene glycol diacrylate (trade name “anilox M-220” manufactured by Toagosei Co., Ltd.)
EO modified bisphenol A diacrylate n + m≈4 (manufactured by Kyoeisha Chemical Co., Ltd., trade name “Light acrylate BP-4EA”, diacrylate having ethylene oxide unit repetition number n + m of about 4)
[Monofunctional monomer]
Dodecyl Acrylate (Kyoeisha Chemical Co., Ltd., trade name “Light Acrylate LA”)
Methoxydipropylene glycol acrylate (Kyoeisha Chemical Co., Ltd., trade name “Light Acrylate DPM-A”)

[Α-hydroxyketone initiator]
1-hydroxycyclohexyl-phenyl ketone (trade name “Irgacure 184” manufactured by BASF)
2-Hydroxy-2-methyl-1-phenylpropan-1-one (trade name “Darocur 1173” manufactured by BASF)
4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (manufactured by BASF, trade name “Irgacure 2959”)
2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one (trade name “Irgacure 127” manufactured by BASF Corporation) )

[Acylphosphine oxide photopolymerization initiator]
Bis (2,4,6 trimethylbenzyl) -phenylphosphine oxide (manufactured by BASF, trade name “Irgacure 819”)
2,4,6 Trimethylbenzoyl-diphenylphosphine oxide (BASF, trade name “Darocur TPO”)

[Example 1]
7.0 parts by weight of di {2-methacryloyloxyethyl} acid phosphate, 28.0 parts by weight of EO modified bisphenol A diacrylate n + m≈4, 32.0 parts by weight of tripropylene glycol diacrylate, 24.0 parts by mass of dodecyl acrylate was placed in a homomixer, heated to 35 ° C. in a dry air atmosphere under light shielding, and stirred for 1 hour to obtain a dispersion. Next, 4.5 parts by weight of “Irgacure 184” and 4.5 parts by weight of “Irgacure 819”, which are photopolymerization initiators, are added to the dispersion, and gently stirred until the photopolymerization initiator is dissolved. To obtain a mixture. The obtained mixture was pressure filtered through a membrane filter having a pore size of 2 μm to obtain an ink composition. The viscosity of the obtained ink composition at 25 ° C. was measured using a cone plate viscometer (trade name “TVE-22L”) manufactured by Toki Sangyo Co., Ltd.

  Using an inkjet printer equipped with four piezo-type inkjet heads (trade name “KM1024SH” manufactured by Konica Minolta IJ Co., Ltd.), this ink composition was discharged onto the surface of SUS304 BA having a thickness of 0.5 mm. I drew an image. About 0.4 seconds after drawing, the metal plate was irradiated with UV by a UV irradiation apparatus (trade name “CoorArc”, gallium metal halide lamp, 240 W / cm) manufactured by Nordson, and the ink composition was cured to form a cured film. (Resin film) was formed to obtain a resin-coated metal plate. At this time, the conveyance speed of the metal plate was 10 m / min, and UV irradiation was performed four times. Further, heat treatment was performed in an oven at 150 ° C. for 3 minutes. The film thickness of the formed cured film was 19 μm and was uniform. The obtained resin-coated metal plate was evaluated as follows.

(1) Cross-cut adhesion Adhesive cuts were made in accordance with JIS G3320 into the cured film on the metal plate. Next, the adhesive tape was stuck on the cured film and peeled off to observe the peeled state of the cured film. The adhesion of the cured film was evaluated based on the number of grids without peeling per 100 grids. It is practical at 50/100 or more.

(2) Scratch hardness (pencil method)
In accordance with JIS K5600-5-4, the scratch hardness was evaluated by the pencil hardness at which the cured film on the metal plate was coherently broken (scratched or broken when the cured film was removed) using a pencil. It can be evaluated that the scratch hardness of 3H or more is practical.

(3) Stability over time The ink composition was heated to 60 ° C. to completely dissolve the photopolymerization initiator, and then stored at 5 ° C. for 1 month. After storage, the presence or absence of precipitation of the photopolymerization initiator was visually observed, and the temporal stability of the ink composition was evaluated according to the following criteria.
○: No precipitate is generated.
(Triangle | delta): Generation | occurrence | production of the trace amount deposit was recognized.
X: Generation | occurrence | production of a large amount of deposit was recognized.
Even when a small amount of precipitate is generated (Δ), it is practical if the particle size of the precipitate is 3 μm or less.

[Examples 2 to 14]
An ink composition was obtained in the same manner as in Example 1 using the monomers and photopolymerization initiator as shown in Table 1. Using the obtained ink composition, a resin-coated metal plate was prepared and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[Comparative Examples 1-6]
An ink composition was obtained in the same manner as in Example 1 using monomers and photopolymerization initiators as shown in Table 3. Using the obtained ink composition, a resin-coated metal plate was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 3.

  From the results shown in Tables 1 and 2, it is clear that the ink compositions of Examples 1 to 14 have viscosities suitable for ejection from an inkjet head and are excellent in stability over time. Moreover, it is clear that the hardened | cured material obtained from the ink composition of Examples 1-14 was excellent in the cross-cut adhesion with a metal plate, and scratch hardness (pencil method).

  On the other hand, in Comparative Example 2, since the viscosity of the obtained ink composition was too high, inkjet discharge could not be performed, and a cured film could not be produced. For this reason, physical property evaluation could not be performed. Moreover, about Comparative Examples 3-5, since a part of photoinitiator was insoluble, physical property evaluation was not able to be performed. These points are indicated as “−” in Table 3.

The ink composition of the present invention is useful as an ink composition for ink jet because it gives a cured product excellent in adhesion to a metal plate and scratch hardness (pencil method) and has a viscosity capable of being stably ejected by ink jet. It is.

Claims (5)

A polymerizable monomer polymerizable by active energy rays, and a photopolymerization initiator,
The polymerizable monomer is in all monomers,
0.5 to 13% by mass of a polymerizable phosphate ester compound having a phosphate ester group and an ethylenic double bond group in the molecule;
10 to 75% by mass of a monofunctional monomer having one ethylenic double bond group in the molecule and having no phosphate ester group,
The photopolymerization initiator comprises an acyl phosphine oxide-based initiator and an α-hydroxyketone-based initiator having one or less phenyl groups in the skeleton,
The ratio of the acylphosphine oxide initiator (A) to the α-hydroxyketone initiator (B) is in the range of (A) / (B) = 2/1 to 1/3,
The viscosity at 25 ° C. is 3 to 50 mPa · s.
Inkjet ink composition. The inkjet ink composition according to claim 1, wherein the polymerizable phosphate compound is a compound represented by any one of the following general formulas (A1) to (A4).

[Wherein, R represents a hydrogen atom or a methyl group, and R ₁ represents an alkylene group having 1 to 4 carbon atoms]

[Wherein, R and R ₁ are defined as in the general formula (A1), respectively]

[Wherein, R and R ₁ are each defined in the same manner as in the general formula (A1), and R ₂ represents an alkylene group having 1 to 10 carbon atoms]

[Wherein, R, R ₁ and R ₂ are defined in the same manner as in the general formula (A3)] The polymerizable monomer is in all monomers,
The inkjet ink composition according to claim 1 or 2, further comprising 10 to 75% by mass of a polyfunctional monomer having two or more ethylenic double bond groups in the molecule and having no phosphate ester group. .   A resin-coated metal plate comprising: a metal plate; and a resin film comprising a cured product of the ink-jet ink composition according to any one of claims 1 to 3, which covers at least a part of a surface of the metal plate. . Discharging the inkjet ink composition according to any one of claims 1 to 3 on a metal plate;
Irradiating an active energy ray to cure the inkjet ink composition;
A method for producing a resin-coated metal plate, comprising: