JP6293808B2 - Photocurable inkjet ink composition - Google Patents

Description

  The present invention relates to a photocurable inkjet ink composition, and more particularly, to a photocurable inkjet ink composition having excellent curability by ultraviolet LED light and excellent adhesion to plastic films such as polyethylene terephthalate, polypropylene, and polyethylene.

As ink-jet inks, water-based and solvent-based inks are often used, and their applications are properly used according to their characteristics.
However, water-based inks have problems such as restrictions on the printing substrate, relatively poor water resistance, and high ink drying energy.
Solvent-based inks can improve the above-mentioned problems with water-based inks, but have problems such as adhesion of ink components to the head due to drying, generation of odor due to solvent volatilization, and the need for equipment such as a ventilator. . Therefore, in recent years, replacement with a photocurable ink having relatively low volatility is expected.
In this way, the use of photocurable ink has been increasing in recent years due to cost reductions by simplifying the drying process and the replacement of solvent-based inks due to the benefits of reducing solvent volatilization as an environmental measure. It is supplied and used for offsets, silk screens, top coats, etc.

However, plastic films, particularly films such as polyethylene terephthalate, polypropylene, and polyethylene, have a feature that their surface polarity is small, they are chemically stable, and are hardly attacked by organic solvents.
Therefore, when no surface treatment is performed on these films, there are disadvantages such as poor surface wettability and insufficient ink adhesion and bending resistance.
As a means for improving the adhesion and the bending resistance, it is conceivable to lower the crosslinking density of the monomer. However, in this case, the curing rate is lowered, so that the productivity is lowered.
In addition, as a means for improving adhesion and bending resistance, it is effective to perform a corona discharge process or a frame process on the recording medium in advance, but the apparatus is large and expensive, and after the process, There were drawbacks such as a decrease in adhesion with time.
Therefore, in actual use, it was impossible to improve productivity and reduce the cost of equipment while obtaining sufficient adhesion and bending resistance.

By the way, as a photocurable inkjet ink, in an inkjet ink comprising at least (A) dipropylene glycol diacrylate, (B) N-vinylcaprolactam, and (C) a monofunctional acrylic monomer having a Tg of less than 20 ° C., (A) , (B), (C) is a total of 60 to 90% by weight of all ink components, and the amount of monofunctional acrylic monomer having a Tg of 20 ° C. or higher is less than 10% by weight. A curable inkjet ink is known (see Patent Document 1). According to this technique, it is said that an ultraviolet curable ink-jet ink excellent in ejectability, curability and flexibility can be provided.
An energy ray curable inkjet ink composition containing a colorant and a polymerizable monomer, wherein the polymerizable monomer has a monofunctional monomer having an aromatic hydrocarbon ring structure in the molecule and a fat in the molecule. There is also known an energy ray curable inkjet ink composition containing a monofunctional monomer having an aromatic hydrocarbon-based cyclic structure and 90% by mass or more of the polymerizable monomer being a monofunctional monomer (see Patent Document 2). . According to this technique, an energy beam curable inkjet ink composition having high adhesion to the surface of a recording medium made of various materials and having excellent stretchability after curing can be provided. The

JP 2011-122063 A JP 2013-142104 A

The ink compositions described in Patent Document 1 and Patent Document 2 have not been sufficiently studied for their suitability for plastic films such as polyethylene terephthalate, polypropylene, and polyethylene, and there is still room for improvement in practice.
For this reason, the main object of the present invention is to make the adhesiveness and bending resistance particularly superior to those of conventional plastic films. However, as long as it is used as an inkjet ink, other ink characteristics cannot be sacrificed.
Accordingly, the present invention provides a photocurable inkjet ink composition having good adhesion and bending properties to plastic films such as polyethylene terephthalate, polypropylene, and polyethylene without impairing photocurability, storage stability, and ejection properties. It is intended to provide.

In order to solve the above problems, the present invention has the following configuration.
That is, the photocurable inkjet ink composition according to the present invention includes at least (A) a monofunctional monomer, (B) a photopolymerization initiator, and (C) a surface conditioning agent. (A) As monofunctional monomer, (A-1) monofunctional (meth) acrylate monomer having an alicyclic hydrocarbon group of 60 to 85% by mass with respect to the total amount of (A) monofunctional monomer, (A-2) It contains 15 to 30% by mass of a monofunctional (meth) acrylate monomer having an aromatic hydrocarbon group, and 0.5 to 10% by mass of a monofunctional (meth) acrylate monomer having a saturated chain hydrocarbon group (A-3). .
In the following, regarding the present invention, when simply referred to as “ink composition”, it refers to “photocurable inkjet ink composition”.

According to the present invention, it is possible to provide an ink composition that has good adhesion and bending resistance to plastic films such as polyethylene terephthalate, polypropylene, and polyethylene, and is excellent in photocurability, dischargeability, and storage stability. Can do.
As a result, the printed material has good adhesion and bending resistance without surface treatment such as corona discharge treatment or frame treatment on the recording medium in advance, and provides printed matter with excellent surface curability and internal curability even in single-pass inkjet. It is also possible to do.

  Hereinafter, preferred embodiments of the ink composition according to the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention is not impaired. And can be changed as appropriate.

[A: Monofunctional monomer]
The ink composition of the present invention includes at least (A) a monofunctional monomer, and (A) a monofunctional (meth) acrylate monomer having an alicyclic hydrocarbon group as the (A) monofunctional monomer; A-2) a monofunctional (meth) acrylate monomer having an aromatic hydrocarbon group and (A-3) a monofunctional (meth) acrylate monomer having a saturated chain hydrocarbon group.

<A-1: Monofunctional (meth) acrylate monomer having an alicyclic hydrocarbon group>
In the present invention, (A-1) a monofunctional (meth) acrylate monomer having an alicyclic hydrocarbon group (hereinafter sometimes referred to as “alicyclic monofunctional (meth) acrylate”) A polymerizable (meth) acrylate monomer having one or more alicyclic hydrocarbon groups.
Examples of the alicyclic hydrocarbon group include aliphatic cyclic structures such as a cycloalkane skeleton, a norbornane skeleton, and an adamantane skeleton.

Such alicyclic monofunctional (meth) acrylates include isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalate, 2 -(Meth) acryloyloxypropylhexahydrohydrogenphthalate, 4-n-butylcyclohexyl (meth) acrylate, 4-t-butylcyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) Examples thereof include (meth) acrylate compounds having an alicyclic hydrocarbon group in the molecule, such as acrylate, dicyclopentenyloxyethyl (meth) acrylate, and 3,5,5-trimethylcyclohexyl (meth) acrylate. These can be used alone or in combination of two or more.
Among these, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, 1-adamantyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) One or more acrylates are preferred, and isobornyl (meth) acrylate and / or dicyclopentenyl (meth) acrylate is particularly preferred. By containing isobornyl (meth) acrylate and / or dicyclopentenyl (meth) acrylate, it is excellent in solubility of a photopolymerization initiator, a pigment dispersant and the like, and good storage stability can be obtained.
In particular, two or more types are preferably used in combination, and excellent wettability and adhesion can be obtained for recording media of various materials, particularly plastic films such as polyethylene terephthalate, polypropylene, and polyethylene.
In the present invention, “(meth) acrylate” represents acrylate or methacrylate, and the notation such as “(meth) acryloyloxy” has the same meaning.

<A-2: Monofunctional (meth) acrylate monomer having an aromatic hydrocarbon group>
In the present invention, (A-2) a monofunctional (meth) acrylate monomer having an aromatic hydrocarbon group (hereinafter sometimes referred to as “aromatic monofunctional (meth) acrylate”) is one in the molecule. The polymerizable (meth) acrylate monomer which has the above aromatic hydrocarbon group is said.
Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups such as monocyclic aromatic groups such as benzene and polycyclic aromatic groups such as naphthalene and anthracene.

Examples of such aromatic monofunctional (meth) acrylates include phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxymethyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxyethylene glycol (meth) acrylate, Phenoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol polypropylene glycol (meth) acrylate, monohydroxyethyl (meth) acrylate phthalate, monohydroxypropyl (meth) acrylate phthalate, 2-hydroxy-3-phenoxypropyl (meth) acrylate O-Phenylphenol EO modified (meth) acrylate, paracumylphenol EO modified (meth) acrylate, nonylphenol EO modified One or more aromatic hydrocarbon ring structures in the molecule such as (meth) acrylate, nonylphenol PO-modified (meth) acrylate, nonylphenoxypoly (ethylene glycol propylene glycol) (meth) acrylate, EO-modified cresol (meth) acrylate (Meth) acrylate compounds having These can be used alone or in combination of two or more.
Among these, one or more of phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxymethyl (meth) acrylate, and phenoxyethyl (meth) acrylate are preferable, and benzyl (meth) acrylate is particularly preferable. By containing benzyl (meth) acrylate, it is possible to obtain excellent curability for recording media of various materials, especially plastic films such as polyethylene terephthalate, polypropylene, polyethylene, etc., and a low viscosity ink composition Since a product can be obtained, the discharge property is excellent.

<A-3: Monofunctional (meth) acrylate monomer having a saturated chain hydrocarbon group>
In the present invention, (A-3) a monofunctional (meth) acrylate monomer having a saturated chain hydrocarbon group (hereinafter sometimes referred to as “saturated chain monofunctional (meth) acrylate”) A polymerizable (meth) acrylate monomer having one or more saturated chain hydrocarbon groups.
Examples of the saturated chain hydrocarbon group include a linear or branched structure that does not have a cyclic structure such as an alicyclic group or an aromatic ring group.

Examples of such saturated chain monofunctional (meth) acrylates include normal butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, normal octyl (meth) acrylate, and isooctyl (meth) acrylate. , Isononyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, tridecyl (meth) Acrylate, 2-decyltetradecanyl (meth) acrylate, behenyl (meth) acrylate, hexadecyl (meth) acrylate, isohexadecyl (meth) acrylate, heptadecyl (meth) a Relate, isoheptadecyl (meth) acrylate, undecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate. These (meth) acrylates can be used alone or in combination of two or more.
Among these, one or more of stearyl (meth) acrylate, isostearyl (meth) acrylate, lauryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and 2-decyltetradecanyl (meth) acrylate Are preferred, and lauryl (meth) acrylate and isostearyl (meth) acrylate are particularly preferred. By containing lauryl (meth) acrylate and / or isostearyl (meth) acrylate, it is possible to obtain excellent folding resistance to recording media of various materials, especially plastic films such as polyethylene terephthalate, polypropylene, and polyethylene. And good adhesiveness can be obtained.

<Content of (A) Monofunctional Monomer in Ink Composition>
The ink composition of the present invention contains 60 to 85% by mass of (A-1) a monofunctional (meth) acrylate monomer having an alicyclic hydrocarbon group based on the total amount of (A) monofunctional monomer, and (A- 2) A monofunctional (meth) acrylate monomer having an aromatic hydrocarbon group is contained in an amount of 15 to 30% by mass, and (A-3) a monofunctional (meth) acrylate monomer having a saturated chain hydrocarbon group is contained in an amount of 0.5 to 10%. Including mass%.
By containing these three types of monofunctional monomers in the above ranges, sufficient adhesion, bending resistance and wettability can be imparted to the resulting ink composition.
(A-1) Monofunctional (meth) acrylate monomer having an alicyclic hydrocarbon group is contained in an amount of 70 to 80% by mass, and (A-2) monofunctional (meth) acrylate monomer having an aromatic hydrocarbon group is 20 to 20%. It is preferable that 2 to 8% by mass of (A-3) a monofunctional (meth) acrylate monomer having a saturated chain hydrocarbon group is contained.

[B: Photopolymerization initiator]
The ink composition of the present invention contains a photopolymerization initiator for initiating polymerization by a low energy irradiation means. In particular, it is desirable to contain a radical polymerization type photopolymerization initiator.
As the photopolymerization initiator, those that exhibit an initiator function by light having a wavelength of 450 to 300 nm are preferable.
Specific examples of the photopolymerization initiator include (B-1) acylphosphine oxide compounds, (B-2) thioxanthone compounds, and (B-3) alkylphenone compounds, and it is particularly preferable to use these three types in combination.

<B-1: Acylphosphine oxide compound>
(B-1) Specific examples of the acylphosphine oxide compound include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, 2,4, Preferred examples include 6-trimethylbenzoylphenylethoxyphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis ( 2,4,6-trimethylbenzoyl) phenylphosphine oxide is particularly preferred. These can be used alone or in combination of two or more.

<B-2: Thioxanthone compound>
Specific examples of the (B-2) thioxanthone compound include thioxanthone, 4-isopropylthioxanthone, 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and the like. 4-Isopropylthioxanthone 2-isopropylthioxanthone and 2,4-diethylthioxanthone are particularly preferred. These can be used alone or in combination of two or more.

<B-3: Alkylphenone compound>
(B-3) Specific examples of the alkylphenone compound include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, and 2-hydroxy. 2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy- 1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, 2-methyl-1- (4-methylthiophenyl) -2- Morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2- (dimethylamino) -2-[(4-methylphenol Nyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one and the like are preferred. -Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2- (dimethylamino)- 2-[(4-Methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one Is particularly preferred. These can be used alone or in combination of two or more.

<Content of (B) Photopolymerization Initiator in Ink Composition>
The content of the (B) photopolymerization initiator in the ink composition is preferably 2 parts by mass or more, more preferably 100 parts by mass with respect to 100 parts by mass of the ink composition, although it depends on the content and type of the polymerizable compound. It is 5 parts by mass or more, preferably 30 parts by mass or less, more preferably 20 parts by mass or less. When the content of the photopolymerization initiator is in the above range, sufficient curability can be imparted to the ink composition, and the ink composition can be prevented from being precipitated at a low temperature.
In addition, (B-1) the acylphosphine oxide compound is included in an amount of 40 to 70% by mass, (B-2) the thioxanthone compound is included in an amount of 20 to 40% by mass with respect to the total amount of (B) the photopolymerization initiator, 3) It is preferable to contain 5-20 mass% of alkylphenone compounds.
By containing these three types of photopolymerization initiators within the above ranges, the resulting ink composition is sufficiently excellent in surface curability or internal curability, and therefore provides a sufficient effect speed even in single-pass inkjet. be able to.
More than (B-1) 50-60 mass% of acylphosphine oxide compounds, (B-2) 25-35 mass% of thioxanthone compounds, and (B-3) 10-15 mass% of alkylphenone compounds. preferable.

  When the ink composition of the present invention contains a photopolymerization initiator other than the acylphosphine oxide compound, the thioxanthone compound and the alkylphenone compound as the photopolymerization initiator (B), the content of the other photopolymerization initiator Is preferably 5 parts by mass or less based on 100 parts by mass of the ink composition. If the content of the other photopolymerization initiator is too large, the reactivity or storage stability may be lowered.

[(C) Surface conditioner]
By combining the above-described (A) monofunctional monomer and (B) photopolymerization initiator, an ink composition having appropriate curability and adhesion can be produced. However, plastic films such as polyethylene terephthalate, polypropylene, and polyethylene tend to get wet easily because the ink composition is difficult to wet, and therefore the present invention is sufficiently contacted by using (C) a surface conditioner. I'm trying to lower the corner.

(C) As the surface conditioner, it is preferable to use a silicon-based surface conditioner from the viewpoints of surface tension reducing ability and compatibility with the polymerizable monomer.
Specific examples of the silicon-based surface conditioner preferably include a modified product of a dimethylsiloxane skeleton.

Preferably, a silicon-based surface conditioner containing a (meth) acryl group is contained as the silicon-based surface conditioner. Not only good wettability can be obtained for the film, but also the (meth) acrylic group in the structure has a (meth) acrylic group-containing silicon-based surface conditioner accompanying radical polymerization of the monofunctional monomer (A). Because of the curing reaction with each other and (A) the monofunctional monomer, the surface curability of the printed dots is increased, and the scratch resistance and curability are improved.
Specific examples of the (meth) acryl group-containing silicon-based surface conditioner include, for example, TEGO Rad 2010, 2011, 2100, 2200N, 2250, 2300, 2500, 2600, 2700 (manufactured by Evonik Industries AG), BYK- UV3570, 3575, 3576 (manufactured by Big Chemie) and the like.
In particular, it is preferable to use a polyether-modified silicon (meth) acrylate monomer as the (meth) acryl group-containing silicon-based surface conditioner.

Particularly preferably, the polyether-modified silicon (meth) acrylate monomer and the polyether-modified siloxane are used in combination. Thereby, sufficient wettability can be obtained with respect to the film.
Specific examples of the polyether-modified siloxane include BYK-345, BYK-347, BYK-348, BYK-349, BYK-3455 (manufactured by BYK Chemie), Silface SAG001, Silface SAG003, and Silface SAG005. (Manufactured by Nissin Chemical Industry Co., Ltd.), L-7001, L-7002, 57 ADDITIVE, FZ-2105 (manufactured by Toray Dow Corning), AFCONA-3231, 3236, 3238, 3250, 3280 (manufactured by AFCONA) and the like. It is done. Among these, BYK-345, BYK-347, BYK-348, BYK-349, Sylface SAG003, Sylface SAG005, 57 ADDITIVE are particularly preferable, and good wettability can be obtained with respect to the above film, and adhesiveness Will improve.

The content of the (C) surface conditioner in the ink composition is preferably 2.5% by mass or less, and more preferably 0.02 to 2.5% by mass with respect to the entire ink composition. (C) When there is more content of a surface conditioning agent than 2.5 mass%, there exists a possibility that an undissolved substance may arise or foaming may be caused.
(C) As the surface conditioner, it is preferable to include a polyether-modified silicon (meth) acrylate monomer and a polyether-modified siloxane in a ratio of 1:10 to 10: 1 on a mass basis.

[Other ingredients]
The ink composition of the present invention may contain other general components as described below in detail as the ink composition.

<Coloring material>
Since the ink composition of the present invention is an ink composition, it usually contains a coloring material.
Conventionally known various dyes can be used as the colorant, but it is preferable to use either or both of an inorganic pigment and an organic pigment from the viewpoint of weather resistance.
Basically, a pigment having a cyan color, a pigment having a magenta color, a pigment having a yellow color, a black pigment, a white pigment, and the like can be used. In some cases, an image having excellent color reproducibility can be formed by using special color pigments such as violet, blue, green, orange and red. In addition to general black pigments and white pigments, and three primary color pigments of cyan, magenta and yellow, depending on the purpose, for example, metallic luster pigments such as gold and silver, colorless or light color extender pigments, etc. May be.
In addition, a fine particle diameter of the pigment is preferable in view of suitability for inkjet ink. For this miniaturization, various known techniques can be used. The particle diameter may be about 0.01 to 1 μm as the average particle diameter, but is preferably 0.3 μm or less in order to avoid sedimentation.

  Specific examples of the inorganic pigment include zinc white, titanium oxide, zinc oxide, lithopone, iron oxide, aluminum oxide, silicon dioxide, kaolinite, montmorillonite, talc, barium sulfate, calcium carbonate, silica, alumina, and cadmium. Red, brown, molybdenum red, chrome vermilion, molybdate orange, yellow lead, chrome yellow, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, pyridian, cobalt green, titanium cobalt green, cobalt chrome green, ultramarine blue, ultra Examples include marine blue, bitumen, cobalt blue, cerulean blue, manganese violet, cobalt violet, and mica.

  Specific examples of organic pigments include azo, azomethine, polyazo, phthalocyanine, quinacridone, anthraquinone, indigo, thioindigo, quinophthalone, benzimidazolone, and isoindoline organic pigments. Etc. Carbon black made of acidic, neutral or basic carbon may be used.

  Specific examples of the pigment having a cyan color include C.I. I. Pigment blue 1, 15, 15: 1, 15: 3, 15: 4, 15: 6, 16, 22, 60, 64, and the like. Among these, from the viewpoint of weather resistance and coloring power, C.I. I. Either or both of CI Pigment Blue 15: 3 and 15: 4 are preferable.

  Specific examples of pigments having a magenta color include C.I. I. Pigment red 48, 57, 57: 1, 122, 123, 168, 185, 202, 221, 254, C.I. I. Pigment violet 19 and the like. Among these, from the viewpoint of weather resistance and coloring power, C.I. I. Pigment Red 57: 1, 122, 185, 202, C.I. I. Pigment Violet 19 and the like are preferable.

  Specific examples of the pigment having a yellow color include C.I. I. Pigment yellow 3, 74, 83, 93, 95, 109, 110, 120, 128, 129, 138, 139, 150, 151, 153, 154, 155, 168, 180, 185, 215 and the like. Among these, from the viewpoint of weather resistance, C.I. I. Pigment Yellow 74, 83, 109, 110, 120, 128, 139, 150, 151, 154, 155 and the like are preferable.

  Specific examples of the black pigment include, for example, # 2650, # 2600, # 2350, # 2300, # 1000, # 980, # 970, # 960, # 950, # 900, # 850, # 52, # 47. # 45, # 45L, # 44, # 40, # 33, # 32, # 30, # 25, MA77, MA7, MA8, MA11, MA100, MA100R, MA100S, MA230 (Mitsubishi Chemical Corporation), SPECIAL BLACK 100 , SPECIAL BLACK 250, SPECIAL BLACK 350, SPECIAL BLACK 550, NIPex 35, NIPex 60, NIPex 70, NIPex 90 (manufactured by Orion Engineered Carbons), REGAL 250R, REGAL 300R, REGAL 330, REGAL 3 0R, REGAL 350R, REGAL 400, REGAL 400R, REGAL 660, REGAL 660R (manufactured by Cabot Corporation) and the like are preferable.

As the white pigment, titanium oxide is preferably used in terms of hiding power and coloring power. More preferably, it is preferable to use titanium oxide having a rutile type crystal structure produced by a sulfuric acid method. Specifically, for example, Taipei R-820N, Taipei R-830, Taipei R-930, Taipei R-980, Taipei R-550, Taipei R-630, Taipei R-680 (Ishihara Sangyo Co., Ltd.), R- 25, R-21, R-32, R-5N, R-62N, R-42, R-45M, D-918 (manufactured by Sakai Chemical Industry Co., Ltd.) and the like.
In addition to titanium oxide, extender pigments such as calcium carbonate, barium sulfate, and aluminum hydroxide may be used as necessary.

  The content of the colorant in the ink composition may be appropriately selected depending on the color and the purpose of use. Furthermore, it is more preferable to contain 0.3-15 mass%. When the content of the colorant is within the above range, the fluidity is maintained without increasing the viscosity of the ink composition, and the ink composition of the present invention having excellent image coloring power can be obtained.

When a pigment is used as the coloring material, a pigment derivative or a pigment dispersant may be further used to improve the dispersibility of the pigment. Specific examples of the pigment derivative include Solsperse 5000S (manufactured by Lubrizol). Specific examples of the pigment dispersant include, for example, a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, High molecular weight unsaturated acid ester, high molecular weight copolymer, modified polyurethane, modified poly (meth) acrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, poly Oxyethylene alkyl phosphate ester, polyoxyethylene nonyl phenyl ether, polyester polyamine, stearylamine acetate and the like can be used.
In the present invention, it is preferable to use a dispersant having an ester structure or a modified poly (meth) acrylate structure from the viewpoint of storage stability and ejection properties over time.

  Specific examples of the dispersant for the pigment having an ester structure or a modified poly (meth) acrylate structure include Solsperse 9000, 13940, 17000, 18000, 28000, 32000, J-180, J-200 (manufactured by Lubrizol), DA -703-50, DA-7300, DA234 (manufactured by Enomoto Kasei Co., Ltd.), DISPERBYK-2022, 2025, 2050, 2096, BYKJET-9150, 9051, 9052 (manufactured by BykCemie) and the like. The content of the pigment derivative and the pigment dispersant is sufficient if the pigment can be sufficiently dispersed in the ink composition, and can be set to an appropriate amount.

<Other arbitrary polymerizable compounds>
The ink composition of the present invention may contain not only a monofunctional monomer (A) but also a polyfunctional monomer and / or a polymerizable oligomer as a polymerizable compound.
Specifically, EO-modified 1,6-hexanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, EO-modified bisphenol A di (meth) ) Acrylate, PO modified bisphenol A di (meth) acrylate, EO modified bisphenol F di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, caprolactan modified hydroxypivalic acid ester neopentyl glycol di (meth) acrylate, Polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, neopentyl glycol modified trimethylolpropane di (meth) a Relate, tripropylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, EO modified trimethylolpropane tri (meth) acrylate, PO modified Trimethylolpropane tri (meth) acrylate, trimethylolpropanebenzoate (meth) acrylate, tris (acryloxyethyl) isocyanurate, dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, alkyl-modified di Pentaerythritol tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol ester Kishitetora (meth) acrylate, pentaerythritol tetra (meth) acrylate and the like, but not limited thereto. These can be used alone or in combination of two or more.

<Other additives>
As other additives, for example, a polymerization initiation assistant may be used in combination with the (B) photopolymerization initiator.
Examples of the polymerization initiation aid include amine compounds such as N-methyldiethanolamine, ethyl 4- (dimethylamino) benzoate, 2-ethylhexyl dimethylaminobenzoate, 4,4′bis (diethylamino) benzophenone, and triethanolamine. Can be used alone or in combination of two or more.
By using the polymerization initiation assistant together with the photopolymerization initiator, the surface oxygen inhibition during the photoreaction in the air is reduced, thereby further improving the curability and adhesiveness.

  Furthermore, the ink composition of the present invention may contain additives such as ultraviolet absorbers, antioxidants and storage stabilizers as necessary in order to enhance printability and printed matter resistance.

[Use of ink composition]
The ink composition of the present invention can be used for recording media of various materials regardless of whether it is a permeable material or a non-permeable material.
The permeable material is not particularly limited, and examples thereof include paper such as art paper and coated paper.
Examples of non-permeable materials include plastic films and plates, metals, and glass.
The ink composition of the present invention is particularly excellent in adhesion and curability to plastic films and plates. For example, polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, polystyrene, polyamide and the like are used as materials. It is suitable for use on a recording medium.
In particular, it has excellent adhesion and curability to difficult-to-adhere materials such as polyethylene terephthalate, polypropylene, and polyethylene, where the printed dots are difficult to spread, and has excellent resistance to cracks in the cured film even when the recording medium is bent. Bendability can be obtained.

  In order to use the ink composition of the present invention, the ink composition is ejected from a printer for an ink jet recording system onto a recording medium and then irradiated with ultraviolet LED light. As a result, the ink composition on the recording medium is quickly cured.

  The irradiation time of the ultraviolet LED light is preferably 0.01 to 5 seconds, and more preferably 0.02 to 3 seconds. If the irradiation time of the ultraviolet LED light is longer than 5 seconds, the thermoplastic base material such as plastic tends to melt or deform, and if it is shorter than 0.01 seconds, the ink composition tends not to be cured sufficiently due to insufficient accumulated light amount. is there.

  The ink composition of the present invention can be used in combination of a plurality of colors as necessary when mounted on an ink jet printer. The combination is not limited, but can be used in combinations of cyan, magenta, yellow, black and white.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to an Example. “Part” in the examples represents “part by mass”.
In the following examples and comparative examples, a pigment dispersion was first prepared, and an ink composition was prepared using the pigment dispersion.
Therefore, in the following, first, the raw materials are described, and then the preparation of the pigment dispersion is described. Then, the preparation of ink compositions according to Examples and Comparative Examples using these, and the evaluation and consideration thereof are sequentially described.

〔material〕
<A: Monofunctional monomer>
(A-1: Alicyclic monofunctional (meth) acrylate)
・ Isobornyl acrylate ・ Dicyclopentenyl acrylate ・ Cyclohexyl acrylate ・ Dicyclopentanyl acrylate ・ 1-Adamantyl acrylate ・ Dicyclopentenyloxyethyl acrylate

(A-2: Aromatic monofunctional (meth) acrylate)
・ Benzyl acrylate ・ Phenyl acrylate ・ Phenoxymethyl acrylate ・ Phenoxyethyl acrylate ・ 2-Hydroxy-3-phenoxypropyl acrylate

(A-3: saturated chain monofunctional (meth) acrylate)
・ Isostearyl acrylate ・ Lauryl acrylate ・ Isooctyl acrylate

<Other polymerizable compounds>
(Monofunctional (meth) acrylate)
・ Methoxypolyethylene glycol acrylate (polyfunctional (meth) acrylate)
・ Trimethylolpropane EO (3.5) adduct triacrylate

<B: Photopolymerization initiator>
(B-1: Acylphosphine oxide compound)
BAPO (bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide)

(B-2: Thioxanthone compound)
2,4-diethylthioxanthone

(B-3: alkylphenone compound)
MABB (2- (dimethylamino) -2- (4-methylbenzyl) -1- (4-morpholinophenyl) butan-1-one)

<C: Surface conditioning agent>
・ Polyether-modified siloxane (Silface SAG005: manufactured by Nissin Chemical Industry Co., Ltd.)
Polyether-modified silicon acrylate (siloxane and silicon, 3- [3- (acetyloxy) -2-hydroxy] propoxypropyl methyl, di-methyl, 3- [2-hydroxy-3-[(1-oxo-2-pro Penyl) oxy] propoxypropyl methyl acrylate)
・ MegaFuck F-556 (fluoric group / hydrophilic group / new oil group-containing oligomer produced by DIC)
・ LF-1980 (Takamoto Kasei Co., Ltd. special acrylic polymer)

<Coloring material>
・ C. I pigment black 7 (black pigment)
・ C. I pigment yellow 155 (yellow pigment)
・ C. I pigment violet 19 (magenta pigment)
・ C. I pigment blue 15: 3 (cyan pigment)
・ C. I pigment white 6 (white pigment)

<Other additives>
(Pigment dispersant)
・ Solsperth J180 (manufactured by Lubrizol)
(Polymerization initiation aid)
・ Ethyl 4- (dimethylamino) benzoate (manufactured by Tokyo Chemical Industry Co., Ltd.)

(Preparation of pigment dispersion)
<Pigment dispersion 1>
Pigment dispersion 1 was prepared with the following composition.
Specifically, a pigment and a dispersant were added to the monomer, stirred until uniform, and the resulting mill base was dispersed by a horizontal bead mill.
・ C. I Pigment Black 7 15 parts, Solsperse J180 10 parts, Isobornyl acrylate 75 parts

<Pigment dispersion 2>
Pigment dispersion 2 was prepared by the same production method as pigment dispersion 1 with the following composition.
・ C. I Pigment Yellow 155 15 parts, Solsperse J180 15 parts, Isobornyl acrylate 70 parts

<Pigment dispersion 3>
Pigment dispersion 3 was prepared by the same production method as that of pigment dispersion 1 with the following composition.
・ C. I Pigment Violet 19 15 parts, Solsperse J180 10 parts, Isobornyl acrylate 75 parts

<Pigment dispersion 4>
Pigment dispersion 4 was prepared by the same production method as pigment dispersion 1 with the following composition.
・ C. I Pigment Blue 15: 3 15 parts, Solsperse J180 10 parts, Isobornyl acrylate 75 parts

<Pigment dispersion 5>
A pigment dispersion 5 was produced by the same production method as that of the pigment dispersion 1 with the following composition.
・ C. I Pigment White 6 30 parts, Solsperse J180 10 parts, Isobornyl acrylate 60 parts

[Example 1]
According to the description in Table 1 described later, each raw material was added while stirring sequentially from the top of the table. After stirring for 1 hour, it was confirmed that there was no undissolved residue, and the mixture was filtered through a 1.0 μ filter to prepare an ink composition.

[Examples 2 to 24]
In the same manner as in Example 1, an ink composition was prepared as described in Table 1 or 2 described later.

[Comparative Examples 1 to 12]
In the same manner as in Example 1, an ink composition was prepared as described in Table 3 described later.

[Evaluation]
The ink compositions according to the above Examples and Comparative Examples were evaluated as follows.

<Storage stability>
Storage stability was evaluated by measuring the viscosity of an ink composition that was allowed to stand for 3 months in an environment of 60 ° C., and the rate of change relative to the initial viscosity. The rate of change was calculated by the following formula.
Viscosity change rate (%) = {(viscosity value after storage at 60 ° C. for 30 days) − (initial viscosity value)} / (initial viscosity value) × 100
A: Viscosity change rate less than 5% B: Viscosity change rate 5% or more, less than 10% X: Viscosity change rate 10% or more

<Dischargeability>
The ink composition was ejected with HQ8000 manufactured by Kishu Giken Kogyo Co., Ltd., and continuous printing was performed 10,000 times at a dot occupancy of 37.1% in the print image, and evaluation was performed according to the following criteria.
◎: less than 1% of missing dots with respect to the total number of dots ○: less than 1% and less than 10% of missing dots with respect to the total number of dots ×: missing more than 10% with respect to the total number of dots

<Curing property>
The ink composition is discharged from a 100% solid image onto a polypropylene sheet by an ink jet discharge device, and immediately after that, the curability is determined from the conveyor speed when cured by irradiating ultraviolet rays with a UV-LED light 6 W / cm ² manufactured by Kyocera Corporation. evaluated. The evaluation criteria are as follows.
◎: 30 m / min or more ○: 25 m / min or more and less than 30 m / min Δ: 20 m / min or more and less than 25 m / min x: Less than 20 m / min

<Adhesion>
The evaluation was performed according to “Plain Test Cellotape (registered trademark) peeling” defined in JIS K5600-5-6. The evaluation criteria are as follows.
(Double-circle): Peeling is not recognized by 90 or more out of 100 pieces.
○: No peeling is observed at 80 to 89 of 100.
(Triangle | delta): Peeling is not recognized by 50 to 79 out of 100 pieces.
X: Peeling is not recognized in 49 or less out of 100 pieces.

<Bending resistance>
A 100% solid image was ejected from the HQ8000 manufactured by Kishu Giken Kogyo Co., Ltd., and immediately after curing with a UV-LED light manufactured by Kyocera Corporation, a printed matter was obtained. The printed surface of this printed matter was folded outward and evaluated according to the following criteria.
(Double-circle): A crack is not produced in a bending hardening film at 180 degrees.
○: Cracks do not occur in the cured film bent at 90 °, and cracks occur when bent at 180 °.
X: A crack occurs in the cured film bent at 90 °.

〔result〕
The composition of each Example and Comparative Example and the results of the above evaluation are shown in Tables 1 to 3 below.
The “details of blending of A and B” in the middle row of both tables are (A) the content ratio of (A-1) to (A-3) in the monofunctional monomer, and (B) in the photopolymerization initiator (B- It summarizes the content ratios of 1) to (B-3). About (A-1), content and content rate are calculated including what is contained in the pigment dispersion.

[Discussion]
As shown in the results of Tables 1 and 2, each of the ink compositions of Examples satisfying all the conditions of the ink composition of the present invention sufficiently satisfied all the physical properties.

On the other hand, as shown in the results of Table 3, each ink composition of the comparative example does not satisfy the conditions of the ink composition of the present invention, so that sufficient results were obtained in any of the evaluations. In addition, high viscosity or precipitation does not provide ejection properties and storage stability, lack of wettability and adhesion to polypropylene, or bending resistance cannot be obtained, compatibility of monofunctional monomer and photopolymerization initiator Or the surface curability is poor and the curability cannot be obtained.
When it sees concretely, the result of Comparative Examples 1-4 has shown the necessity to use this invention predetermined (A-1)-(A-3) together.
Moreover, the result of the comparative example 5 has shown the necessity of containing the (C) surface conditioning agent.
Furthermore, the results of Comparative Examples 6 to 12 are not only used in combination with the present invention predetermined (A-1) to (A-3), but also (A-1) 60 to 85 mass%, (A-2) 15 The necessity of having to be in the range of ˜30 mass% and (A-3) 0.5 to 10 mass% is shown.

Moreover, from the results of Example 1 and Example 2, it was found that the adhesiveness was further improved by using two types as (A-1).
From the results of Example 1 and Example 4, it was found that the combination of isobornyl acrylate and dicyclopentenyl acrylate is particularly suitable as (A-1) from the viewpoint of storage stability.
From the results of Example 1 and Example 5, it was found that the content of (A-2) is particularly preferably 20 to 25% by mass from the viewpoint of curability.
From the results of Example 1 and Example 6, it was found that the content of (A-3) was 2 to 8% by mass, particularly from the viewpoint of bending resistance.
From the results of Example 1, Example 9 and Example 10, as (B) photopolymerization initiator, (B-1) 50-60 mass%, (B-2) 25-35 mass%, (B- 3) It was found that the range of 10 to 15% by mass is particularly preferable from the viewpoint of curability.
From the results of Example 1 and Examples 13 to 15, it is possible to use two types of (C) polyether-modified silicon (meth) acrylate monomer and polyether-modified siloxane as a surface conditioner in combination with curability and adhesion. From the viewpoint of the above, it was found to be particularly preferable.
From the results of Example 1 and Examples 16 to 18, it is possible to use the three types (B-1) to (B-3) defined in the present invention in combination as the photopolymerization initiator (B) from the viewpoint of curability. It was found to be particularly preferable.

Claims (7)

In a photocurable inkjet ink composition comprising at least (A) a monofunctional monomer, (B) a photopolymerization initiator, and (C) a surface conditioning agent,
(A) As monofunctional monomer, (A-1) monofunctional (meth) acrylate monomer having an alicyclic hydrocarbon group of 60 to 85% by mass with respect to the total amount of (A) monofunctional monomer, (A-2) 15-30% by mass of a monofunctional (meth) acrylate monomer having an aromatic hydrocarbon group, (A-3) 0.5-10% by mass of a monofunctional (meth) acrylate monomer having a saturated chain hydrocarbon group Characterized by
Photocurable inkjet ink composition.   (A-3) The photocurable inkjet ink composition according to claim 1, comprising at least isostearyl (meth) acrylate as a monofunctional (meth) acrylate monomer having a saturated chain hydrocarbon group.   (A-1) Monofunctional (meth) acrylate monomer having an alicyclic hydrocarbon group, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate The photocurable inkjet ink composition according to claim 1, comprising at least one selected from 1-adamantyl (meth) acrylate and dicyclopentenyloxyethyl (meth) acrylate.   (A-2) Monofunctional (meth) acrylate monomer having an aromatic hydrocarbon group is selected from benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxymethyl (meth) acrylate and phenoxyethyl (meth) acrylate The photocurable inkjet ink composition according to any one of claims 1 to 3, comprising at least one kind.   (B) The photopolymerization initiator according to any one of claims 1 to 4, comprising (B-1) an acylphosphine oxide compound, (B-2) a thioxanthone compound, and (B-3) an alkylphenone compound. Photocurable inkjet ink composition.   (B) 40 to 70% by mass of (B-1) acylphosphine oxide compound, (B-2) 20 to 40% by mass of thioxanthone compound, and (B-3) alkyl based on the total amount of the photopolymerization initiator. The photocurable inkjet ink composition of Claim 5 containing 5-20 mass% of phenone compounds.   (C) As a surface conditioner, it contains at least a polyether-modified silicon (meth) acrylate monomer and a polyether-modified siloxane in a mass ratio of 1:10 to 10: 1, and is applied to the polyolefin surface. The photocurable inkjet ink composition according to any one of claims 1 to 6.