JP2017047387A - Manufacturing method of cured film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a cured film very excellent in internal curability, concerning a method for manufacturing the cured film by applying light from an LED light source to an ink composition containing bisacylphosphine oxide as a photoinitiator.SOLUTION: A long wavelength light irradiation process is performed, in which a coating film of an ink composition containing a polymerizable monomer and bisacylphosphine oxide is irradiated with light having the maximum peak wavelength of 390 nm or more and 440 nm or less from an LED light source.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a cured film obtained by curing an ink composition.

  Conventionally, surface treatment for forming a resin coating film on the surface of a metal plate, a plated steel plate or the like using various paints, inks, or the like has been performed. The main purpose of the surface treatment is to provide electrical insulation and corrosion resistance, and to improve molding processability and designability (for example, Patent Document 1). In addition, it is common practice to form a resin coating film by printing various paints and inks on a synthetic resin substrate such as a bottle.

  Examples of a method for forming a resin coating film on a metal plate, a plated steel plate, a synthetic resin base material, etc. include a screen printing method, a flat plate printing method, a flexographic printing method, and a UV curable ink jet printing method. Above all, the UV curable ink jet printing method does not require a plate and can be applied to small-lot production. Furthermore, it is highly useful in terms of cost. In addition, the UV curable ink composition does not need to contain an organic solvent, and is excellent from the viewpoint of reducing VOC (volatile organic compound) emissions.

  In the UV curable ink jet printing method, UV irradiation is performed immediately after an ink composition is discharged from a printing apparatus, and ink droplets are cured. When the ink composition is repeatedly applied, a thick cured film in which ink droplets overlap is formed on the substrate. In order to sufficiently increase the strength of such a cured film (thick film), it is necessary to increase both the surface curability and the internal curability of the cured film (thick film). Moreover, when using a cured film as a protective film of an electronic circuit board, etc., it is necessary to improve the adhesiveness of a base material and a cured film to such an extent that it does not peel even if bent. Furthermore, in such applications, scratch resistance and abrasion resistance may be required, and in order to improve these, it is necessary to further increase the surface curability of the cured film.

  Here, for the purpose of enhancing the curability of the UV curable ink composition, it has been studied to combine two or more kinds of photopolymerization initiators or to add a photoinitiator aid. For example, Patent Documents 1 to 3 disclose that 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (α-aminoketone-based initiator, trade name) as a photopolymerization initiator. An ink composition using “Irgacure 907” (manufactured by BASF) and isobutylthioxanthone has been proposed. In addition, an ink composition to which an amine is added as a photoinitiator is also proposed (Patent Documents 4 and 5). Moreover, the ink composition (patent document 6) which used together the alpha-hydroxyketone type | system | group initiator and the acylphosphine oxide type initiator, and the ink which used the alpha-aminoketone type | system | group initiator and the acylphosphine oxide type initiator together. Compositions (Patent Documents 7 and 8) have also been proposed. Furthermore, the use of a photopolymerization initiator having a good surface curability and a photopolymerization initiator having a good internal curability has also been studied. For example, two types of α-hydroxyketone initiators, acyls An ink composition (Patent Document 9) using a phosphine oxide-based initiator in combination has also been proposed.

  In recent years, it has been studied to apply an ultraviolet light emitting diode (hereinafter also referred to as “ultraviolet LED”) as a light source for curing the UV curable ink composition as described above, and an inkjet equipped with an ultraviolet LED. A printer has also been developed (for example, Patent Document 10). The ultraviolet LED has the advantages that it consumes less power than a conventional light source and can increase the output.

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 2004-188920 A

  Conventionally, high-pressure mercury lamps, metal halide lamps, and the like that have been used to cure UV-curable ink compositions can irradiate light having a wavelength of 250 nm to 600 nm, and have a wide emission wavelength range. . Therefore, it was possible to activate various photopolymerization initiators by light from these light sources.

  On the other hand, the LED light source has a single emission peak wavelength and has an extremely narrow emission wavelength range (± 5 to 10 nm in half width). In addition, it is difficult to irradiate short wavelength ultraviolet light having a wavelength of 350 nm or less with an LED light source. Therefore, it is necessary to sufficiently match the emission peak wavelength of the LED light source and the absorption wavelength of the photopolymerization initiator. That is, depending on these combinations, the photopolymerization initiator cannot be activated sufficiently, and it is difficult to improve the curability of the ink composition.

  Here, it is known that bisacylphosphine oxide has a large absorption of light in the vicinity of a wavelength of 356 nm and is activated by light irradiation to contribute to the internal curability of the ink composition. However, there is a problem that even when an ink composition containing bisacylphosphine oxide is irradiated with light having a wavelength of about 356 nm from an LED light source, the internal curability of the ink composition is difficult to increase.

  In view of such circumstances, the present invention relates to a method for producing a cured film by irradiating light from an LED light source to an ink composition containing bisacylphosphine oxide as a photopolymerization initiator, and the internal curability is very excellent. A method for producing a cured film is provided.

According to this invention, the manufacturing method of the following cured films is provided.
[1] A long wavelength light irradiation step of irradiating light having a maximum peak wavelength of 390 nm or more and 440 nm or less from a first LED light source onto a coating film of an ink composition containing a polymerizable monomer and bisacylphosphine oxide. The manufacturing method of a cured film.

[2] The method for producing a cured film according to [1], wherein the maximum illuminance of the first LED light source is 500 to 4000 mW / cm ² .
[3] The method for producing a cured film according to [1] or [2], further including a step of applying the ink composition with an inkjet apparatus.

  The cured film obtained by the production method of the present invention has very good internal curability. Therefore, according to the manufacturing method of the present invention, for example, a metal decorative board having a resin coating film with high definition and excellent design, an electronic circuit board, various resin boards, and the like can be obtained. Moreover, the cured film manufactured with the manufacturing method of this invention can be used as the resist for various etching, and moldability, such as a metal plate, can be improved by using the said cured film.

  The method for producing a cured film of the present invention is a method for producing a cured film of an ink composition comprising a polymerizable monomer and bisacylphosphine oxide. As described above, bisacylphosphine oxide is known to absorb a large amount of light in the vicinity of a wavelength of 356 nm, and is activated by light irradiation to contribute to the internal curability of the ink composition. Therefore, conventionally, a UV-curable ink containing bisacylphosphine oxide is generally irradiated with a wavelength including light in the vicinity of a wavelength of 356 nm to form a resin coating film.

  However, as a result of intensive studies by the present inventors, an ink composition containing bisacylphosphine oxide is unlikely to have sufficiently high internal curability even when irradiated with light having a maximum peak wavelength in the vicinity of a wavelength of 356 nm from an LED light source. I found out. In addition, it was found that the internal curability of the ink composition is remarkably improved when light having a maximum peak wavelength at a wavelength of 390 nm to 440 nm is irradiated from an LED light source. The “maximum peak wavelength” refers to a wavelength at which the intensity is maximum when light is analyzed with a spectrophotometer.

  The reason why the internal curability of the ink composition is enhanced when irradiated with light having a maximum peak wavelength at a wavelength of 390 nm or more is presumed as follows. Bisacylphosphine oxide contains two CO—PO bonds, and this CO—PO bond is cleaved by photoreaction. There are a plurality of types of radicals generated by this cleavage, and the types of radicals that are easily generated differ depending on the wavelength of the irradiated light. And the reactivity of the radical produced when irradiating light with a wavelength of 390 nm or more is especially high, and it is guessed that it contributes greatly to the internal curability of a cured film. Further, when the bisacylphosphine oxide is irradiated with light, the P—O bond is cleaved and the conjugated system is broken, so that the light is easily transmitted to the inside of the coating film of the ink composition (photo bleaching effect). However, since radicals generated by irradiation with light having a wavelength of less than 390 nm are likely to recombine with each other, it is difficult to obtain a sufficient photobleaching effect. In contrast, radicals generated by irradiating light with a wavelength of 390 nm or more are unlikely to cause such recombination, so that a sufficient photobleaching effect is sufficiently obtained and the internal curability of the cured film is increased. Is done.

  In view of such knowledge, in the method for producing a cured film of the present invention, the coating film of the ink composition containing bisacylphosphine oxide is irradiated with light having a maximum peak wavelength of 390 nm to 440 nm from the LED light source. A light irradiation process is performed. As a result, a cured film having extremely excellent internal curability can be obtained. For example, a metal decorative board, an electronic circuit board, various resin boards, and the like having a resin coating film with high definition and excellent design are produced. It becomes possible. Moreover, the cured film manufactured with the manufacturing method of this invention can also be used as the resist for various etching, and moldability, such as a metal plate, can be improved by using the said cured film.

  Hereinafter, the ink composition used in the production method of the present invention will be described first, and then the method for curing the ink composition will be described.

1. Ink composition The ink composition used in the method for producing a cured film of the present invention contains at least bisacylphosphine oxide and a polymerizable monomer. The ink composition may appropriately include other components as necessary, and may include, for example, an α-hydroxyketone-based initiator and other components.

(1) Bisacylphosphine oxide Bisacylphosphine oxide is a compound having absorption on the long wavelength side compared to a general photopolymerization initiator and contributing to the internal curability of the coating film of the ink composition. It is. When the ink composition contains a bisacylphosphine oxide-based initiator, the internal curability of a cured film formed by overlapping ink droplets is improved.

  The ink composition preferably contains 2 to 10% by mass of bisacylphosphine oxide, more preferably 4 to 8% by mass. When the ink composition contains bisacylphosphine oxide in the above range, the internal curability of the cured film is likely to increase.

  The structure of the bisacylphosphine oxide is not particularly limited, and a known bisacylphosphine oxide can be applied. Specific examples of bisacylphosphine oxide include compounds having a structure represented by the following general formula (1). The ink composition may contain only one kind of bisacylphosphine oxide, or may contain two or more kinds.

一般式（１）において、Ｒ_５１〜Ｒ_５３は、それぞれ独立に、置換基を有してもよい脂肪族炭化水素基、または置換基を有してもよい芳香族炭化水素基を表す。

In the general formula (1), R _{51 to} R ₅₃ each independently represents an aliphatic hydrocarbon group that may have a substituent, or an aromatic hydrocarbon group that may have a substituent.

The aliphatic hydrocarbon group that may be R _{51 to} R ₅₃ may have any of a linear, branched, or cyclic structure, but it may be a linear or branched hydrocarbon group. preferable. Specific examples of the aliphatic hydrocarbon group include a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms; a linear, branched, or cyclic alkenyl group having 2 to 20 carbon atoms. A linear, branched or cyclic alkynyl group having 2 to 20 carbon atoms; Among these, a linear or branched alkyl group is preferable.

On the other hand, specific examples of the aromatic hydrocarbon group which may be R _{51 to} R ₅₃ include aryl groups having 6 to 18 carbon atoms such as phenyl group, tolyl group and xylyl group; condensed ring groups such as naphthyl group; included.

  Examples of the substituent of the hydrocarbon group or aromatic hydrocarbon group include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.) and the like.

  Specific examples of the bisacylphosphine oxide having the structure represented by the general formula (1) include bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2. , 4,4-trimethyl-pentylphosphine oxide, bis (2,6-dimethylbenzoyl) -ethylphosphine oxide, and the like. Among these, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide is particularly preferable from the viewpoints of availability and cost.

(2) Polymerizable monomer A polymerizable monomer will not be restrict | limited especially if it is a compound containing the group which can superpose | polymerize, For example, it can be set as the compound etc. which have an ethylenic double bond group. The kind of the polymerizable monomer is not particularly limited, and may be a monofunctional monomer or a polyfunctional monomer included in a known ultraviolet curable ink composition. The ink composition may contain only one type of polymerizable monomer or two or more types.

  The ink composition preferably contains 60 to 90% by mass of the polymerizable monomer, more preferably 70 to 85% by mass. When the ink composition contains the polymerizable monomer in the above range, the adhesion between the cured film and the substrate is increased, and the strength of the cured film is increased.

  Here, when forming the cured film manufactured by this invention on the surface of the base material which consists of a metal plate, a plated steel plate, etc., it is calculated | required that a cured film has high adhesiveness with a metal. Therefore, in such a case, it is preferable to include a polymerizable phosphate compound, a polyfunctional monomer, a monofunctional monomer, and a polymerizable carboxylic acid compound as the polymerizable monomer. When the ink composition contains these polymerizable monomers, the adhesion between the cured film obtained from the ink composition and the metal tends to increase. Hereinafter, although these polymerizable monomers are demonstrated, the polymerizable monomer which an ink composition contains is not limited to these.

(2-1) 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. When the ink composition contains a polymerizable phosphate ester compound, the adhesion between the resulting cured film and the metal is greatly increased.

  The “phosphate ester group” contained in the polymerizable phosphate ester compound refers to a group represented by any of the following formulas (a1) to (a3). The phosphate ester group contained in the polymerizable phosphate ester compound is preferably a group represented by the formula (a2) or (a3), so-called acidic phosphate ester group. These groups have a hydroxyl group and undergo a condensation reaction with a hydroxyl group present on the metal surface. Therefore, when the polymerizable phosphate compound has these groups, the adhesion between the cured film and the metal is particularly likely to increase. Here, when it is desired to greatly improve the adhesion between the cured film and the metal, it is preferable to select a polymerizable phosphate compound having a group represented by the formula (a3). On the other hand, when it is desired to lower the viscosity of the ink composition, it is preferable to select a polymerizable phosphate ester compound having a group represented by the formula (a2). In addition, in the use which carries out alkali peeling of the cured film from a metal as needed after formation of a cured film, these phosphate ester groups also bear the function which improves the alkali peelability of a cured film.

  On the other hand, the “ethylenic double bond group” contained in the polymerizable phosphate compound refers to a group in which one hydrogen atom is extracted from ethylene. At this time, ethylene may have a substituent, and 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.

  A polymerizable phosphoric acid ester compound having a (meth) acryloyl group is obtained by esterifying a “compound having a (meth) acryloyl group and a hydroxyl group in the molecule” and “phosphoric acid”. Examples of “compounds having (meth) acryloyl groups and hydroxyl groups in the molecule” include 2-hydroxymethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxy Hydroxyalkyl (meth) acrylate such as butyl (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, ethylene glycol (meth) acrylate, diethylene glycol (meth) acrylate, triethylene glycol (meth) acrylate, tetraethylene (Poly) ethylene glycol (meth) acrylate such as glycol (meth) acrylate is included.

  Specific examples of the polymerizable phosphoric acid ester compound obtained by esterifying “a compound having a (meth) acryloyl group and a hydroxyl group in the molecule” and “phosphoric acid” include the following general formulas (A1) to (A4). ) Is included. All of these compounds are excellent in adhesion to metals and alkali peelability, and are easily available.

In General Formula (A1), R represents a hydrogen atom or a methyl group, and R ₁ represents an alkylene group having 1 to 4 carbon atoms. From the viewpoint of lowering the viscosity of the ink composition, R is particularly preferably a methyl group. R ₁ is particularly preferably an ethylene group from the viewpoint of improving the adhesion between the cured film and the metal and further improving the 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 General Formula (A2), each R independently represents a hydrogen atom or a methyl group, and each R ₁ independently represents an alkylene group having 1 to 4 carbon atoms. Two Rs and R ₁ contained in one molecule may be the same or different. In the compound represented by the formula (A2), R is particularly preferably a methyl group from the viewpoint that the viscosity of the ink composition becomes low. Moreover, it is especially preferable that R ₁ is an ethylene group from the viewpoint that the adhesion between the cured film and the metal is enhanced and the alkali peelability is also improved. 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 General Formula (A3), each R 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. In the compound represented by the formula (A3), R is particularly preferably a methyl group from the viewpoint of decreasing the viscosity of the ink composition. Further, from the viewpoint of improving the adhesion between the cured film and the metal and further improving the alkali peelability, R ₁ is preferably an ethylene group, and R ₂ is preferably a pentene group.

In General 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. A plurality of R, R ₁ , and R ₂ contained in one molecule may be the same or different. In the compound represented by the formula (A4), R is particularly preferably a methyl group from the viewpoint of decreasing the viscosity of the ink composition. Further, from the viewpoint of improving the adhesion between the cured film and the metal and further improving the alkali peelability, R ₁ is preferably an ethylene group, and R ₂ is preferably a pentene group.

  The ink composition preferably contains 0.5 to 13% by mass, and more preferably 1 to 13% by mass, of the polymerizable phosphate compound in the polymerizable monomer. If the content of the polymerizable phosphate compound is less than 0.5% by mass, the adhesion of the cured film of the ink composition to the metal may not be sufficiently increased. On the other hand, when the content exceeds 13% by mass, the etching solution resistance may not be sufficient when the cured film requires etching solution resistance.

(2-2) Polyfunctional monomer As a polyfunctional monomer, the compound which has two or more ethylenic double bond groups in a molecule | numerator, and does not have a phosphate ester group is mentioned. The structure of the polyfunctional monomer is not particularly limited, but the total amount of ethylenic double bond groups in the polyfunctional monomer is preferably 4 × 10 ⁻³ to 8 × 0 ⁻³ mol / g. When the amount of the ethylenic double bond group in the entire polyfunctional monomer is in the above range, the adhesiveness with a metal plate or the like is likely to be increased when a cured film is formed. In addition, when the cured film is required to have etching solution resistance and alkali peelability, these characteristics are likely to be improved. The “ethylenic double bond group amount” is defined as the ethylenic double bond group amount / molecular weight contained in one molecule, and the unit is mol / g.

In order to keep the amount of ethylenic double bond groups of the entire polyfunctional monomer within the above range, the ink composition has a number of ethylenic double bond groups of 4 × 10 ⁻³ to 8 × 0 ⁻³ mol / g. Only functional monomers (hereinafter also referred to as “specific polyfunctional monomers”) may be included. In addition, the ink composition may contain a polyfunctional monomer having an ethylenic double bond group amount not in the above range. By combining two or more types of polyfunctional monomers, the ethylenic double bond of the entire polyfunctional monomer may be used. The bonding group amount may fall within the above range.

When combining two or more types of polyfunctional monomers, the amount of ethylenic double bond groups in the entire polyfunctional monomer is determined as follows. For example, when the following monomers x, y, and z are used as the polyfunctional monomer, the amount of the ethylenic double bond group is obtained by the formula (1).
Monomer x: Number of ethylenic double bond groups Nx (pieces), molecular weight Mx (g / mol), blending ratio x (mass%)
Monomer y: Number of ethylenic double bond groups Ny (pieces), molecular weight My (g / mol), blending ratio y (mass%)
Monomer z: Ethylene double bond group number Nz (pieces), molecular weight Mz (g / mol), blending ratio z (mass%)
Ethylenic double bond group amount of curable resin = (Nx) / (Mx) × x / 100 + (Ny) / (My) × y / 100 + (Nz) / (Mz) × z / 100 (1) )

  The polyfunctional monomer may be a known compound or the like containing 2 to 6 ethylenic double bond groups in the molecule, but is particularly preferably a compound represented by the general formula (B1) or (B2). preferable.

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.

  The compound represented by the general formula (B1) is available as (meth) acrylate of ethylene glycol-modified bisphenol. It can also be obtained by reacting a compound obtained by modifying bisphenol with ethylene glycol and acrylic acid. N + m in the general formula (B1) 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 includes isomers thereof, and R ₂₀ is preferably a hexyl group or a pentyl group.

  The ink composition preferably contains 10 to 75% by mass of the polyfunctional monomer in the polymerizable monomer, and more preferably 55 to 65% by mass. When the polymerizable monomer is contained in an amount of 10% by mass or more, the crosslinking density of the obtained cured film is sufficiently increased, and the strength of the cured film is improved. On the other hand, when the amount of the polymerizable monomer is 75% by mass or less, these properties are likely to be favorable when the cured film is required to have etching resistance, alkali peelability, or the like.

(2-3) Monofunctional monomer The monofunctional monomer is not particularly limited as long as it is a monomer having one ethylenic double bond group in the molecule and no phosphate group. When the ink composition contains a monofunctional monomer, the viscosity of the ink composition tends to be low, and for example, it becomes easy to stably discharge from an ink jet apparatus or the like.

  Examples of monofunctional monomers include 2-phenoxyethyl acrylate, acryloyl morpholine, N-vinyl caprolactam, 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 Le acrylate, methyl phenoxyethyl acrylate, dipropylene glycol acrylate. Among these, a compound containing a (meth) acryloyl group in the molecule is preferable from the viewpoint of easy availability and easy polymerization. The ink composition may contain only one type of monofunctional monomer or two or more types.

  The ink composition preferably contains 10 to 75% by mass of the monofunctional monomer in the polymerizable monomer. When the amount of the monofunctional monomer is less than 10% by mass, the viscosity of the ink composition tends to increase. On the other hand, if the amount of the monofunctional monomer exceeds 75% by mass, the etching resistance of the resulting cured film may be lowered.

(2-4) Polymerizable carboxylic acid compound The polymerizable carboxylic acid compound is a compound having a carboxyl group and an ethylenic double bond group in the molecule. When the ink composition contains a polymerizable carboxylic acid compound, the carboxyl group of the polymerizable carboxylic acid compound reacts with the hydroxyl group present on the metal surface, and the adhesion between the cured film and the metal is very likely to increase. In addition, when the cured film of the ink composition is required to have an etchant resistance and an alkali peelability, these characteristics are likely to be enhanced.

一般式（Ｃ）において、Ｒは、水素原子またはメチル基を表し、Ｘは炭素数が１〜３のアルキレン基を表し、Ｙは炭素数が２または３のアルキレン基を表す。 Examples of the polymerizable carboxylic acid compound include a compound having a structure represented by the following general formula (C).

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

  In the general formula (C), examples of the alkylene group having 1 to 3 carbon atoms that may be X include a methylene group, an ethylene group, a propylene group, an isopropylene group, and an isopropylidene group. X is preferably a methylene group or an ethylene group, and particularly preferably an ethylene group.

  In the polymerizable carboxylic acid 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. .

  In the general formula (C), examples of the alkylene group having 2 or 3 carbon atoms that may be Y include an ethylene group, a propylene group, an isopropylene group, and an isopropylidene group. Y is preferably an ethylene group.

  Specific examples of the polymerizable carboxylic acid compound represented by the general formula (C) include 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid, 2-acryloyloxypropyl succinic acid, 2- Acrylroyoxyethyl malonic acid and 2-acryloyloxyethyl glutaric acid are included.

  The polymerizable carboxylic acid compound may be a commercially available product, (i) a monoester is synthesized by reacting a dicarboxylic acid such as succinic acid and a diol such as ethylene glycol, and (ii) the monoester and Alternatively, it may be synthesized by reacting acrylic acid or methacrylic acid.

  The ink composition preferably contains 1 to 10% by mass of the polymerizable carboxylic acid compound in the polymerizable monomer. When the polymerizable carboxylic acid compound is contained in an amount of 1% by mass or more, the adhesion between the obtained cured film and the metal is likely to increase. In addition, when a large amount of the polymerizable carboxylic acid compound is contained, the viscosity of the ink composition may be excessively increased. However, if the amount of the polymerizable carboxylic acid compound is 10% by mass or less, the viscosity of the ink composition is desired. Easy to fit in the range.

(3) α-Hydroxyketone Initiator The ink composition preferably further contains an α-hydroxyketone initiator. The α-hydroxyketone-based initiator is a photopolymerization initiator that contributes to the surface curability of the photocurable ink composition.

  Generally, when the ink composition is cured, if the surface curability is low, the ink composition on the surface will drip and the printing accuracy will be low. In particular, when the ink composition is ejected by an ink jet apparatus, the ink droplets become minute. That is, the surface area per unit mass of the ink composition is increased as compared with other printing methods. Therefore, curing failure (oxygen inhibition) due to the influence of oxygen tends to occur during the curing of the ink composition, and the surface curability of the resulting cured film tends to decrease. On the other hand, when the ink composition contains an α-hydroxyketone-based initiator, the surface curability for each ink droplet is improved.

  The type of the α-hydroxyketone initiator contained in the ink composition is not particularly limited, but if the α-hydroxyketone initiator contains two or more phenyl groups in the molecule, it becomes difficult to be compatible with other components. There is a tendency, and the viscosity of the ink composition tends to increase. Therefore, the number of phenyl groups contained in the α-hydroxyketone initiator is preferably 1 or less.

  Examples of α-hydroxyketone initiators having 1 or less phenyl groups in the molecule include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4- (2-hydroxyethoxy) phenyl -(2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone and the like are included.

  The ink composition preferably contains 5 to 20% by mass, more preferably 8 to 16% by mass, of an α-hydroxyketone initiator. When the ink composition contains the α-hydroxyketone initiator in the above range, the surface curability of the resulting cured film is sufficiently increased.

  Further, the content ratio of the bisacylphosphine oxide and the α-hydroxyketone initiator is such that the content of bisacylphosphine oxide (A) / the amount of α-hydroxyketone initiator (B) is 2/1. It is preferable that it is ˜1 / 3, and it is more preferable that (A) / (B) = 1 / 1−1 / 2. When the content ratio of the components is within the above range, it becomes easy to achieve both surface curability and internal curability of the cured film.

(4) Other components The ink composition may contain components other than the above, if necessary. Examples of such components include resins, inorganic fillers, organic fillers, coupling agents, tackifiers, antifoaming agents, leveling agents, plasticizers, antioxidants, polymerization inhibitors, ultraviolet absorbers, Includes flame retardants, pigments, dyes and the like.

  Further, the ink composition can be appropriately colored depending on the application. For example, when the cured film is a metal protective film or the like, it is not particularly necessary to color the ink composition, but it may be colored for confirmation of print quality such as pinhole check. The colorant used in that case is not particularly limited, but is preferably a dye that is more easily dissolved in other components than a pigment that needs to be dispersed in other components.

  The ink composition substantially does not require a solvent, but may contain a solvent as necessary. Examples of solvents include ketones such as methyl ethyl ketone and methyl isobutyl ketone; acetates such as ethyl acetate and butyl acetate; aromatic hydrocarbons such as benzene, toluene and xylene; ethylene glycol monoacetate, propylene glycol monomethyl ether, butyl alcohol, etc. Alcohol, other known organic solvents may be included.

(5) Physical properties of ink composition Hereinafter, the physical properties of the ink composition will be described.

(5-1) Viscosity The viscosity of the ink composition is appropriately selected according to the method of applying the ink composition. When the ink composition is applied by an ink jet apparatus, the viscosity at 25 ° C. is 3 to 3. It is preferably 50 mPa ·. In addition, the viscosity is preferably 3 to 35 mPa · s and more preferably 7 to 20 mPa · s at the ink discharge temperature (usually 25 to 80 ° C.) of the ink jet apparatus. When the viscosity is in the above range, the ink composition can be stably discharged by the ink jet apparatus. In addition, when the viscosity at 25 ° C. is less than 3 mPa · s, in a piezo-type inkjet head having a high frequency of 10 to 50 kHz, a decrease in ejection followability may be observed. On the other hand, 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 is adjusted by the amount of the polymerizable monomer (particularly, the amount of the polymerizable phosphate compound or the polymerizable carboxylic acid compound). The viscosity of the ink composition is measured with a cone plate viscometer. The measurement conditions at this time are a shear rate of 230 (1 / s) and a rotational speed of 60 rpm.

(5-2) Surface tension Since the surface tension of the ink composition affects the ejection properties of the ink composition from various coating devices and the printing accuracy of the cured film obtained, the surface tension is 20 to 40 mN / m. Preferably there is. The surface tension of the ink composition is adjusted by the addition of various surfactants. The surface tension is measured by a known method, for example, a hanging drop method or a ring method, but is preferably measured by a plate method. The surface tension can be measured using, for example, CBVP-Z type manufactured by Kyowa Interface Science Co., Ltd.

(6) Method for producing ink composition The ink composition can be produced by dispersing or dissolving each component using a mixer, a disperser, and a stirrer. Examples of mixers, dispersers, and stirrers include propeller type stirrers, dissolvers, homomixers, ball mills, sand mills, ultrasonic dispersers, kneaders, line mixers, propeller type stirrers, piston type high pressure emulsifiers, homogenizers. Examples include a mixer, an ultrasonic emulsifier / disperser, a pressure nozzle emulsifier, a high-speed rotation / high shear type agitator / disperser, a colloid mill, and a media type disperser. A media-type disperser is an apparatus that performs pulverization, dispersion, or the like using a medium such as glass beads or steel balls. Examples include a sand grinder, an agitator mill, a ball mill, an attritor and the like. You may use these apparatuses in combination of 2 or more types. Moreover, a mixer, a disperser, and a stirrer can also 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.

2. Method for Producing Cured Film The method for producing a cured film of the present invention is a method for producing a cured film by curing the coating film of the ink composition described above. Light having a maximum peak wavelength of 390 nm or more and 440 nm or less (hereinafter referred to as “light”) , Also referred to as “long wavelength light”) at least a long wavelength light irradiation step of irradiating from the first LED light source.

  The method for producing a cured film of the present invention may further include a step of forming a coating film of the ink composition and a step of irradiating light having a maximum peak wavelength different from the long wavelength light from another LED light source. In particular, when the ink composition contains an α-hydroxyketone-based initiator, it is preferable to perform a short wavelength light irradiation step of irradiating light having a maximum peak wavelength of 360 nm or more and 370 nm or less from the second LED light source. When the short wavelength light irradiation step is performed, the α-hydroxyketone initiator is sufficiently activated, and the surface curability of the coating film of the ink composition is increased.

  Here, when performing the long wavelength light irradiation step and the short wavelength light irradiation step, the order thereof is not particularly limited, but the long wavelength light irradiation step is performed simultaneously with the short wavelength light irradiation step or before the short wavelength light irradiation step. It is preferable to carry out. The inside of the coating film (ink droplet) of the ink composition is cured by the long wavelength light irradiation process, and then the surface of the ink composition is cured by the short wavelength light irradiation process, so that the ink composition on the surface of the ink droplet is liquid. It becomes difficult to drool, and the printing accuracy of the cured film is likely to increase.

  The interval from the long wavelength light irradiation step to the short wavelength light irradiation step is preferably within 0.2 seconds, more preferably within 0.1 seconds, and particularly preferably within 0.05 seconds. If the interval is within 0.2 seconds, dripping is further less likely to occur after the long wavelength light irradiation step. In the manufacturing method of the cured film of this invention, it is most preferable to perform a long wavelength light irradiation process and a short wavelength light irradiation process simultaneously. Here, the long wavelength light irradiation step and the short wavelength light irradiation step are usually performed by relatively moving the coating film of the ink composition, the first LED light source, and the second LED light source. And "irradiation of light to the coating film of the ink composition" is performed from the moment when one end of the coating film (ink droplet) of the ink composition reaches the end of the spot of the energy ray emitted from each LED light source for the first time. It can be said. Therefore, “the interval from the long wavelength light irradiation step to the short wavelength light irradiation step” means that “one end of the coating film (ink droplet) of the ink composition is first at one end of the energy ray spot emitted from the first LED light source. The length (time) from the point of arrival to the point of time when one end of the coating film (ink droplet) of the ink composition first reaches one end of the spot of the energy rays emitted from the second LED light source.

  In addition, it is preferable that the total film thickness of the cured film (resin coating film) manufactured with the manufacturing method of the cured film of this invention is 2-40 micrometers. If the film thickness is less than 2 μm, it is difficult to sufficiently enhance the wear resistance and scratch resistance of the cured film. In addition, when the cured film is an insulating film, sufficient insulation may not be ensured. Conversely, when the film thickness exceeds 40 μm, the printing accuracy of the cured film may be reduced.

  Hereinafter, a coating film forming step, a long wavelength light irradiation step, and a short wavelength light irradiation step included in the method for producing a cured film of the present invention will be described.

(1) Coating film forming step The ink composition is applied onto a substrate by various methods to form a coating film of the ink composition. The base material to which the ink composition is applied is not particularly limited, and may be a resin base material, a metal plate, a plated steel plate, or the like.

  The resin base material can be appropriately selected from known resin base materials according to the application. Examples of the resin constituting the substrate include polyester, polyvinyl chloride, polyethylene, polyurethane, polypropylene, acrylic resin, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate, polybutadiene terephthalate, and the like. Moreover, in order to improve the adhesiveness of the cured film of an ink composition, the surface of the resin-made base material may be corona-treated or plasma-treated.

  As the metal plate, a base material made of a known metal can be appropriately selected according to the application. Examples of the metal constituting the metal plate include austenitic stainless steels such as SUS304 and SUS316; and ferritic stainless steels such as SUS430 and SUS444. In applications where mechanical strength is required, the metal constituting the metal plate is a material obtained by work hardening of austenitic or ferritic stainless steel by cold rolling; martensitic stainless steel such as SUS410 and SUS420; SUS631 It is preferable to use precipitation strengthened stainless steel such as. Examples of the metal constituting the metal plate include copper, carbon steel, iron-nickel alloy, etc. other than the stainless steel plate.

  Moreover, a plated steel plate means the base material which coat | covered at least one part of the surface of various base materials with plating. The type of plating in the plated steel sheet is not particularly limited, and plating made of one kind of metal element selected from zinc, aluminum, cobalt, tin and nickel, or plating made of two or more kinds of these metal elements, etc. Can do. The plating may be alloy plating in which the metal element is combined with a different metal element or a nonmetal element. Examples of the dissimilar metal element include cobalt, molybdenum, tungsten, nickel, titanium, chromium, aluminum, manganese, iron, magnesium, lead, antimony, tin, copper, cadmium, arsenic, and the like. Examples of nonmetallic elements include inorganic substances such as silica, alumina, and titania. Furthermore, the plating may be single-layer plating or multi-layer plating.

  In addition, the ink composition coating method, that is, the coating film forming method is not particularly limited as long as the ink composition can be applied in a desired pattern, and is not limited to a screen printing method, a lithographic printing method, a flexographic printing method, A known method such as an inkjet printing method can be applied. Among these, the inkjet printing method is preferable from the viewpoint of being applicable to small-lot production and having high cost effectiveness. Hereinafter, although the inkjet apparatus which discharges an ink composition, the printing conditions at that time, etc. are demonstrated, the formation method of the coating film of an ink composition is not restrict | limited to the said method.

  The ink jet apparatus that discharges the ink composition preferably includes an ink composition supply unit and a temperature sensor. 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 ink composition is preferably discharged by heating the ink jet head and the ink composition to 35 to 100 ° C. A change in viscosity due to a change in temperature of the ink composition affects the printing accuracy. 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.

(2) Long wavelength light irradiation step In the long wavelength light irradiation step, the coating film formed on the substrate is irradiated with light (long wavelength light) having a maximum peak wavelength of 390 nm or more and 440 nm or less from the first LED light source. . A 1st LED light source will not be restrict | limited especially if it is a light source which can irradiate long wavelength light, A well-known light source can be used. In addition, when forming a coating film using an inkjet apparatus, it is preferable to irradiate the light of the said wavelength immediately after discharge of an ink drop, and to harden an ink drop (ink composition).

  Irradiation with long-wavelength light is preferably performed within 0.01 to 2.0 seconds after the formation of the coating film, that is, the ink composition adheres to the substrate. More preferably, it is performed in between. When the irradiation timing is made as early as possible, it is difficult for dripping to occur, and the printing accuracy of the coating film is increased.

At this time, the maximum illumination intensity of the first LED light source is preferably 500~4000mW / cm ^2, more preferably 800~3500mW / cm ^2, particularly preferably 1500~3000mW / cm ^2. If the maximum illuminance of the first LED light source is less than 500 mW / cm ² , long wavelength light may not be transmitted to the inside of the cured film due to insufficient illuminance, and the internal curability may not be sufficiently improved.

In general, the higher the illuminance for curing the ink droplet, the better the curability of the ink droplet. However, in this invention, when the maximum illumination intensity of a 1st LED light source exceeds 4000 mW / cm < ² >, it exists in the tendency for internal curability to become low. As described above, when bisacylphosphine oxide is irradiated with light, the P—O bond is cleaved to break the conjugated system, and the light is easily transmitted to the inside of the coating film of the ink composition (photo bleaching effect). However, when the maximum illuminance of the first LED light source exceeds 4000 mW / cm ² , radicals that have been cleaved in large quantities are easily recombined. And at the same time as the radicals are deactivated, the compound produced by the recombination of the radicals reduces the photobleaching effect (decreases the transmittance of long-wavelength light), and it is assumed that sufficient internal curability cannot be obtained. The

  In the present invention, the “maximum illuminance” of the first LED light source is a value of a UVV sensor measured by a product name UV Power Puck II manufactured by Electronic Instrument & Technology, USA. At this time, the distance between the measurement sensor portion of the ultraviolet light quantity meter and the bottom surface of the LED light source is 1 mm. The relative speed between the LED light source and the measurement sensor unit is 50 mm / sec.

(3) Short-wavelength light irradiation step In the short-wavelength light irradiation step, light having a maximum peak wavelength of 360 nm or more and 370 nm or less is applied to the coating film formed on the substrate in the coating film forming step (hereinafter referred to as “short wavelength”). (Also referred to as “light”) from the second LED light source. A 2nd LED light source will not be restrict | limited especially if it is a light source which can irradiate short wavelength light, A well-known light source can be used. As described above, the irradiation with the short wavelength light is preferably performed after the irradiation with the long wavelength light or at the same time, and is preferably performed within 0.2 seconds after the irradiation with the long wavelength light.

The maximum illumination intensity of the second LED light source is preferably at 2500 MW / cm ² or more, more preferably 3500mW / cm ² or more. As the maximum illuminance of the second LED light source is higher, the surface curability of the obtained cured film is improved, and dripping due to oxygen inhibition is less likely to occur.

  In the present invention, the “maximum illuminance” of the second LED light source is a value of a UVA sensor measured by a product name UV Power Puck II manufactured by Electronic Instrumentation & Technology, USA. At this time, the distance between the measurement sensor portion of the ultraviolet light quantity meter and the bottom surface of the LED light source is 1 mm. The relative speed between the LED light source and the measurement sensor unit is 50 mm / sec.

(4) Other process In the manufacturing method of the cured film of this invention, you may heat-process a cured film as needed after a long wavelength light irradiation and a short wavelength light irradiation process. When heat treatment is performed, adhesion may be improved due to effects such as internal stress relaxation of the cured film.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited by these Examples.

1. Preparation of Ink Composition Components other than the photopolymerization initiator shown in Table 1 were placed in a homomixer and stirred for 1 hour at 35 ° C. in a dry air atmosphere under light shielding. Thereafter, a photopolymerization initiator was further added to the homomixer and gently stirred until the photopolymerization initiator was dissolved.
The obtained mixture was filtered under pressure through a membrane filter having a pore size of 2 μm to obtain an ink composition. The viscosity at 25 ° C. of the obtained ink composition was measured with a cone plate viscometer (TVE-22L) manufactured by Toki Sangyo Co., Ltd. The measurement conditions were a shear rate of 230 (1 / s) and a rotational speed of 60 rpm. The viscosity is shown in Table 1.

2. Formation of coating film and curing of coating film [Examples 1 to 18 and Comparative Examples 1 to 6]
The ink composition described above was used in an ink jet printer equipped with a piezo type ink jet head (Konica Minolta, KM1024SHB, ink droplet amount 6 pl) under the conditions of a head temperature of 50 ° C., a resolution of 1,440 dpi, and 8-pass printing. It applied on material (stainless steel plate or polyester film). Specifically, the ink composition is discharged onto a corona-treated surface of a stainless steel plate (SUS304 BA) having a thickness of 0.5 mm that has been alkali degreased in advance, or a polyester film (variety FE2001, No. 22) manufactured by Futamura Chemical Co., Ltd. A coating film consisting of a solid image of 5 cm × 5 cm was formed. Each of the formed coating films had a uniform thickness of 16 μm.

  Thereafter, the coating film was irradiated with light from an LED unit attached to the ink jet printer to cure the coating film. The LED unit was manufactured by UK Integration Technology (Solidcure 2 (UV irradiation width 120 mm)), and the LED irradiation units were arranged side by side in a direction perpendicular to the reciprocating direction of the inkjet head. Moreover, the wavelength of the light to irradiate was adjusted by replacing five types of modules whose maximum peak wavelengths are 365 nm, 375 nm, 385 nm, 395 nm, or 405 nm. Furthermore, the maximum illuminance of the LED irradiation unit was measured with an ultraviolet light meter (product name: UV Power Puck II) manufactured by Electronic Instrumentation & Technology, USA, and adjusted so as to have the values shown in Table 2 or Table 3. At this time, the distance between the measurement sensor unit of the ultraviolet light quantity meter and the bottom surface of the LED irradiation unit was 1 mm. The relative speed between the LED irradiation unit and the measurement sensor unit was 50 mm / sec. When a module having a maximum peak wavelength of 365 nm, 375 nm, or 385 nm was used for the LED unit, the value of the UVA sensor of the ultraviolet light quantity meter was set as the maximum illuminance. On the other hand, when a module having a maximum peak wavelength of 395 nm or 405 nm was used as the LED unit, the value of the UVV sensor of the ultraviolet light quantity meter was set as the maximum illuminance. Tables 2 and 3 show the wavelength and maximum illuminance of the irradiated light in each example and comparative example.

3. Evaluation [Evaluation of internal curability of cured film]
The internal curability of the cured films prepared in each Example and Comparative Example was evaluated from the composite elastic modulus Er (GPa) obtained by the nanoindentation measurement method. Specifically, using a Nano Indenter XP manufactured by MTS Systems, continuous stiffness measurement with a Berkovich (triangular pyramid) indenter (patent technology of MTS Systems, Inc. (method described in US Pat. No. 4,848,141)) Measured in accordance with And the average value (composite elastic modulus) of the value of 5 times in each measurement position was calculated | required, and the composite elastic modulus was evaluated on the following references | standards. Above Δ is a level where there is no practical problem.
A: Composite elastic modulus is 3.0 GPa or more O: Composite elastic modulus is 2.7 GPa or more and less than 3.0 GPa Δ: Composite elastic modulus is 2.0 GPa or more and less than 2.7 GPa X: Composite elastic modulus is less than 2.0 GPa

  As shown in Table 2 and Table 3 above, when the maximum peak wavelength of light emitted from the light source is less than 390 nm (Comparative Examples 1 to 6), the composite elastic modulus is low and the internal curability is insufficient. It was easy to be. On the other hand, when the maximum peak wavelength of the light irradiated from the light source was 390 nm or more (Examples 1 to 18), the composite elastic modulus was high and the internal curability of the cured film was good. The internal curing of the ink composition was sufficiently promoted by the fact that the bisacylphosphine oxide was sufficiently cleaved by light having a wavelength of 390 nm or more and contributed to the reaction, and further the photobleaching effect was sufficiently generated. Inferred.

At this time, when the maximum illuminance was 500 to 4000 mW / cm ² (Examples 1 to 12), the internal curability was particularly likely to increase. On the other hand, when the maximum illuminance was 300 W / cm ² (Examples 13 and 14), the internal curability tended to decrease. It is presumed that it was difficult to activate a sufficient amount of bisacylphosphine oxide, and the internal curability was not sufficiently increased. Moreover, also when the maximum illumination intensity exceeded 4000 mW / cm < ² > (Examples 15-18), there existed a tendency for internal curability to fall. When the maximum illuminance is excessively high, it is presumed that radicals generated by cleavage of bisacylphosphine oxide are recombined to make it difficult to obtain a photobleaching effect.

  The cured film obtained by the method for producing a cured film of the present invention has very good internal curability. Therefore, according to the manufacturing method of the present invention, for example, a metal decorative board having a resin coating film with high definition and excellent design, an electronic circuit board, various resin boards, and the like can be obtained. Moreover, the cured film manufactured with the manufacturing method of this invention can be used as the resist for various etchings, and can improve the moldability of a metal plate etc.

Claims (3)

Including a long wavelength light irradiation step of irradiating light having a maximum peak wavelength of 390 nm or more and 440 nm or less from a first LED light source to a coating film of an ink composition containing a polymerizable monomer and bisacylphosphine oxide;
A method for producing a cured film. The maximum illuminance of the first LED light source is 500 to 4000 mW / cm ² .
The manufacturing method of the cured film of Claim 1. Further comprising the step of applying the ink composition with an inkjet device,
The manufacturing method of the cured film of Claim 1 or 2.