JP6672432B1 - Ink composition and method for predicting metallic tone of printed matter with ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a versatile and printable active energy ray-curable ink composition having an excellent metallic tone. An active energy ray-curable ink composition comprising at least (A) a flaky metallic pigment, (B) a polymerizable compound, and (C) a photopolymerization initiator, the active energy ray-curable ink composition. An active energy ray-curable ink composition having an L * value of 30 or more at the liquid interface of the product. [Selection diagram] Fig. 1

Description

  The present invention relates to an active energy ray-curable ink composition, in particular, an ink composition capable of printing printed matter having an excellent metal tone even when using ink after long-term storage, and having excellent storage stability and The present invention relates to a method for predicting the metallic tone of the printed matter.

  Conventionally, a method of blending a metal pigment into an ink composition to express an image having an excellent metallic tone has been known, and various inks such as an aqueous ink, an organic solvent-based ink, and an active energy ray-curable ink are known. It has been studied to mix a metal pigment with the form (1).

  In particular, in order to achieve a metallic design, a flaky metal pigment is suitably used as the metallic pigment, but in order to realize an image having an excellent metallic tone using such a flaky metallic pigment, It is necessary to orient the flaky metal pigment uniformly in the coating film. Various techniques for improving the orientation of the flaky metal pigment are known.

  For example, Patent Documents 1 and 2 disclose a non-aqueous active energy ray-curable inkjet ink composition containing a polymerizable compound, a vapor-deposited metal pigment, and a phosphate group-containing polymer as a dispersant.

JP 2012-46561 A Japanese Patent No. 5855782

  However, in these inkjet ink compositions, when printed matter is printed using the ink, sufficient metallic luster cannot be obtained, and when printed matter is printed using the ink that has been stored for a long period of time, the ink before storage is not used. In some cases, the printed matter was inferior in metallic luster as compared with the case of using.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an active energy ray-curable type which is capable of printing a printed matter excellent in metal tone, and is capable of printing a printed matter having an excellent metal tone even when an ink after long-term storage is used. An object of the present invention is to provide a method for predicting a metallic tone of an ink composition and a printed matter.

The present inventors have achieved the object of the present invention by the following.
1. An active energy ray-curable ink composition containing at least (A) a flaky metal pigment, (B) a polymerizable compound, and (C) a photopolymerization initiator,
An active energy ray-curable ink composition, wherein the L * value at the liquid interface of the active energy ray-curable ink composition is 30 or more.
2. 2. The active energy ray-curable ink composition according to the above item 1, wherein the polymerizable compound (B) has a specific gravity of 0.98 to 1.15 and a surface tension of 33.0 to 45.0 mN / m.
3. (A) The flaky metal pigment has a 50% volume average diameter of 0.05 to less than 0.5 μm, an average thickness of 5.0 to less than 50.0 nm, and an aspect ratio (50% volume average). 3. The active energy ray-curable ink composition according to the above 1 or 2, wherein the diameter / average thickness is 4 or more and 50 or less.
4. A method for predicting a metal tone of a printed matter by an active energy ray-curable ink composition containing at least (A) a flaky metal pigment, (B) a polymerizable compound, and (C) a photopolymerization initiator,
A method for predicting a metallic tone of a printed matter by an active energy ray-curable ink composition, which is predicted by measuring a color difference L * value at a liquid interface of the ink composition.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to perform versatile printing by the ink composition which has an excellent metal tone and also excellent storage stability.

It is a conceptual diagram which shows the mode of the storage stability test by a color difference meter.

Hereinafter, the active energy ray-curable ink composition of the present invention (hereinafter, also simply referred to as an ink composition) will be described in detail.
<Active energy ray-curable ink composition>
The active energy ray-curable ink composition of the present invention is an active energy ray-curable ink composition containing at least (A) a flaky metal pigment, (B) a polymerizable compound, and (C) a photopolymerization initiator. Wherein the L * value at the liquid interface of the active energy ray-curable ink composition is 30 or more, and at least (A) a flaky metal pigment, (B) a polymerizable compound and (C) An active energy ray-curable ink composition containing a photopolymerization initiator, wherein the polymerizable compound (B) has a specific gravity of 0.98 to 1.15 and a surface tension of 33 to 45 mN / m. .

When the L * value at the liquid interface of the active energy ray-curable ink composition of the present invention is 30 or more, the flaky metal pigment is excellent in dispersibility in the ink, and thus the ink itself is excellent in long-term storage stability. Thus, it was found that the dispersibility of the flaky metal pigment can be determined by observing the specularity of the ink surface. That is, an ink having an excellent mirror surface of the ink liquid surface can obtain a metal-like printed matter which is also excellent as a printed matter.
The L * value at the liquid interface of the active energy ray-curable ink composition of the present invention is 30 or more, preferably 50 or more.

<(A) Scaly metal pigment>
The flaky metal pigment used in the active energy ray-curable ink composition of the present invention is a thin and flat metal pigment such as a foil, and is obtained, for example, by a production method utilizing vapor deposition. Examples of the scaly metal pigment include metal pigments such as aluminum, nickel, chromium, tin, copper, silver, platinum, and gold, with aluminum being preferred. The average particle diameter and the aspect ratio can be appropriately selected and used, and may be used alone or in combination of two or more.

  The flaky metal pigment of the present invention has a 50% volume average diameter of 0.05 to less than 0.5 μm and an average thickness of 5.0 to less than 50.0 nm.

In the present invention, the 50% volume average diameter refers to the 50% particle diameter (D ₅₀ ) of the volume-based particle size distribution, and can be determined from the particle size distribution measured using a flow type particle image analyzer.
As a flow type particle image analyzer, a product name “FPIA-3000S” manufactured by Sysmex Corporation can be exemplified. The measurement conditions in the flow type particle image analyzer are as follows.

Imaging unit: high magnification imaging unit magnification: 40x (eyepiece 20x x objective 2x)
Measurement mode: HPF measurement mode Measurement time: about 2 minutes Measurement solvent: ethanol binarization threshold setting coefficient: 85%
Dilution ratio by solvent during measurement: 2000 times
Sheath liquid: ethanol.

The flaky metal pigment preferably has a 50% volume average diameter of 0.05 to less than 0.5 μm. When the 50% volume average diameter is less than 0.05 or 0.5 μm or more, a metal tone cannot be obtained, and a printed material having no metallic luster is obtained.
The average thickness is preferably 5.0 or more and less than 50.0 nm. When the average thickness is 50 nm or more, a metal tone cannot be obtained, and a printed material having no metallic luster is obtained. On the other hand, when the average thickness is 5 nm or less, the metallic pigment cannot be obtained because the flaky metallic pigment is too thin.
The average thickness is preferably from 5.0 to 20.0 nm, more preferably from 10.0 to 18.0 nm.

The average thickness was determined as follows.
Several drops of flaky metal pigment diluted with acetone are dropped on a glass substrate and allowed to dry naturally. Next, using an atomic force microscope (trade name: "Nanopics 1000", manufactured by Seiko Instruments Inc.), 20 points of flake-like metal pigments forcibly oriented on the glass substrate were extracted, and the thicknesses of the respective pigments were determined by tapping mode. Is measured. Then, out of the 20 measured thicknesses, the average value of the thicknesses of the remaining 14 points excluding the three values of the upper and lower values was determined, and the average value was defined as the average thickness.
The aspect ratio (50% volume average diameter / average thickness) of the flaky metal pigment of the present invention is preferably 4 or more and 50 or less.

  The flaky metal pigment of the present invention can be produced by a known method, for example, a method described in Patent Document 2. For example, an undercoat layer compatible with a metal pigment is provided on a film support, and then a metal layer is provided on the undercoat layer by a vacuum deposition method or the like. The thickness of the metal layer substantially corresponds to the thickness of the flaky metal pigment. Next, the film support provided with the metal layer is placed in an ultrasonic dispersion device filled with a solvent that dissolves the undercoat layer, and ultrasonic dispersion treatment is performed. By this ultrasonic dispersion treatment, the metal layer is separated from the film support, and the average diameter can be adjusted by appropriately selecting the dispersion time.

Further, a method of cutting into a predetermined particle size before ultrasonic dispersion and then peeling off with an ultrasonic dispersion device filled with a solvent as described above can also be applied. To further reduce the size, high-pressure injection is also effective.
The thus obtained scaly metal pigment dispersion can be used in the ink composition by, for example, drying the dispersion or replacing a part of the solvent with a polymerizable compound after preparing the dispersion.

  In the ink composition of the present invention, the content of the flaky metal pigment is preferably 0.3 to 5.0% by mass.

≪Active energy ray curing≫
As the active energy ray in the present invention, ordinary active energy rays such as visible light, ultraviolet light, and electron beam can be used, and ultraviolet light is particularly preferable. As the active energy ray source, an ultraviolet ray source such as a mercury lamp, a metal halide lamp, a xenon lamp, an excimer laser, a dye laser, an LED lamp, and an electron beam accelerator can be used. The irradiation energy amount (integrated light amount) of the active energy ray is preferably from 200 to 2,000 mJ / cm ² .

<(B) Polymerizable compound>
The polymerizable compound used in the ink composition of the present invention is a monomer that undergoes radical polymerization and cationic polymerization by irradiation with active energy rays such as ultraviolet rays, visible rays, and electron beams, and has a specific gravity of 0.98 to 1.15 and a surface having a specific gravity of 0.98 to 1.15. If the tension is 33.0 to 45.0 mN / m (20 ° C.), it can be used without particular limitation.
As these polymerizable compounds, monofunctional monomers, polyfunctional monomers, cyclic ether compounds, oxetane compounds and the like can be used, and they may be used alone or in combination of two or more.

  In the ink composition of the present invention, the content of the polymerizable compound is preferably from 70 to 90% by mass.

  When the polymerizable compound of the present invention is a radical polymerizable compound, it is preferably an acrylate-based monomer including methacrylate, and more preferably a polyfunctional monomer. As the polyfunctional monomer, a 2- to 6-functional monomer can be used. The polyfunctional monomer preferably contains 50 to 95% by mass of the polymerizable compound, more preferably 60 to 85% by mass.

  The presence of the polyfunctional monomer promotes the orientation of the flaky metal pigment on the printing surface, and when printing by a printing method such as the one-pass method, when the printing is performed by a mirror-like tone or a printing method such as the multi-pass method. Can express the metallic tone more strongly. Here, “mirror tone” refers to a dense metallic luster without graininess, and “metallic tone” refers to a metallic glossiness with graininess.

The monomers that can be preferably used in the present invention are shown below (specific gravity, surface tension mN / m).
Monofunctional monomers: phenoxydiethylene glycol acrylate (1.11, 40.0), caprolactone-modified hydroxyethyl acrylate (1.10, 43.0), tetrahydrofurfuryl acrylate (1.06, 36.0), phenoxyethyl acrylate ( 1.11, 39.7), 4-hydroxybutyl acrylate (1.04, 38.8)

Bifunctional monomers: triethylene glycol diacrylate (1.11, 39.1), 1,4-butanediol diacrylate (1.06, 34.6), dimethylol tricyclodecane diacrylate (1.11, 40) .0), 1,9-nonanediol diacrylate (0.99, 34.8), 1,6-hexanediol diacrylate (1.02, 35.0)
Trifunctional monomers: trimethylolpropane triacrylate (1.11, 36.5) and the like.
When several kinds of monomers are used as a mixture, the specific gravity and the surface tension of the present invention use values based on the contained mass ratio.
<Other active energy ray-curable compounds>

In order to increase the strength of the print layer of the present invention, an acrylate oligomer or an acrylate polymer may be used as the active energy ray-curable compound. As the urethane oligomer, commercially available CN963J75, CN964, CN965, CN966J75 (all available from SARTOMER) and the like can be used. As the epoxy acrylate oligomer, commercially available CN120, CN131B (all available from SARTOMER) and the like can be used.
These active energy ray-curable compounds may be used alone or in a combination of two or more.

<(C) Photopolymerization initiator>
The photopolymerization initiator used in the ink composition of the present invention starts the polymerization of the polymerizable compound and other active energy ray-curable compounds by irradiating with an active energy ray. In the ink composition of the present invention, the content of the photopolymerization initiator is 1 to 25% by mass, preferably 3 to 20% by mass, and more preferably 3 to 15% by mass.

  As the photopolymerization initiator, a commercially available photopolymerization initiator can be appropriately selected and used, and examples thereof include a benzophenone-based compound, an acetophenone-based compound, a thioxanthone-based compound, and a phosphine oxide-based compound. In view of this, it is preferable that the wavelength of the active energy ray to be irradiated and the absorption wavelength of the photopolymerization initiator overlap as much as possible.

  From the viewpoint of the curability of the ink, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, 6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and 2,4-diethylthioxanthone are preferred, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine is preferred. Oxides are particularly preferred. These photopolymerization initiators may be used alone or in a combination of two or more.

≪Non-reactive solvent≫
The ink composition of the present invention may not contain water not involved in polymerization and a non-reactive solvent, but may have a content of 0.01% by mass to 5.00% by mass, The content is preferably 0.01% by mass or more and 2.00% by mass or less. Within this range, the occurrence of bleeding due to poor curing can be greatly suppressed, and is superior to that of a metal not included at all.

  In the present invention, when the amount of the non-reactive solvent is 0.10 to 1.50% by mass, it is possible to obtain a printed layer having particularly excellent metallic tone. Here, the amount of the non-reactive solvent contained in the ink composition can be measured by GC. In the present invention, the amount of the non-reactive solvent was determined by FID method using GC-14A manufactured by Shimadzu Corporation.

Examples of the non-reactive solvent of the present invention include organic solvents commonly used for aqueous inks and organic solvent-based inks, and have a boiling point of 60 to 190 ° C, preferably 70 to 150 ° C. Examples include ethyl acetate, methyl acetate, methyl ethyl ketone, cyclohexanone, 1-butanol, 2-butanol, and diethylene glycol diethyl ether. The non-reactive solvents may be used alone or in a combination of two or more.
After dispersing in the non-reactive solvent, the scaly metal pigment of the present invention may be replaced with a polymerizable compound using a rotary evaporator or the like. At that time, it is preferable that the content is 0.01 to less than 5.00% by mass in the ink composition.
<(D) Nonionic dispersant>

  In the active energy ray-curable ink composition of the present invention, a nonionic dispersant may be used. The nonionic dispersant is a nonionic dispersant having substantially no acid value or amine value. As the nonionic dispersant, commercially available SOLSPERSE 27000, SOLSPERSE 54000 (manufactured by Lubrizol), DISPERBYK-192 (manufactured by Big Chemie), and the like can be used.

  The mass ratio (D / A) of the (D) nonionic dispersant to the (A) flaky metal pigment is preferably 0.1 to 2.0. When it is 0.1 or more, the storage stability becomes better, and when it is 2.0 or less, the curability of the ink becomes better.

  The mass ratio (D / B) of the nonionic dispersant (D) to the polymerizable compound (B) is preferably 0.001 to 0.02. If it is 0.001 or more, the storage stability becomes better, and if it is 0.02 or less, the curability of the ink becomes better.

  The weight average molecular weight of the nonionic dispersant (D) is preferably from 500 to 5,000, more preferably from 800 to 3,500, and even more preferably from 1,000 to 2,000. The weight average molecular weight in the present invention is a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

<Other pigments and dyes>
The ink composition of the present invention may contain a coloring material such as a pigment or a dye in addition to the flaky metal pigment. As the coloring material, various pigments and dyes that impart a glossy color such as black, white, magenta, cyan, yellow, green, orange, and gold and silver, depending on the purpose and required characteristics of the composition of the present invention, are used. Can be used. The content of the coloring material may be appropriately determined in consideration of a desired color density, dispersibility in the composition, and the like, and is not particularly limited. It is preferably from 0.1 to 20% by mass.

  As the pigment, an inorganic pigment or an organic pigment can be used, and one kind may be used alone, or two or more kinds may be used in combination. The dye is not particularly limited, and for example, an acid dye, a direct dye, a reactive dye, and a basic dye can be used. One type may be used alone, or two or more types may be used in combination. Good.

<Other additives contained in the ink composition>
The ink composition of the present invention may contain a light stabilizer. As the light stabilizer, commercially available light stabilizers can be used, and cyanoacrylate compounds, benzophenone compounds, benzoate compounds, benzotriazole compounds, hydroxyphenyltriazine compounds, benzylidene camphor compounds, inorganic fine particles, and the like can be used. Of these, a hydroxyphenyltriazine-based compound having a shorter wavelength of ultraviolet absorption is preferable from the viewpoint of curability of the ink.

  From the viewpoint of curability, it is preferable that the wavelength of the active energy ray to be irradiated and the absorption wavelength of the light stabilizer do not overlap as much as possible. The content of the light stabilizer is preferably from 0.1 to 15% by mass, more preferably from 0.2 to 5% by mass, based on the total mass of the ink composition. These light stabilizers may be used alone or in a combination of two or more.

  The ink composition of the present invention may further contain a polymerization inhibitor. The content is preferably from 0.0001 to 5% by mass, more preferably from 0.05 to 1% by mass, based on the total mass of the ink composition.

  As the polymerization inhibitor, a commercially available polymerization inhibitor such as a hydroquinone compound, a phenol compound, a phenothiazine compound, a nitroso compound, and an N-oxyl compound can be used. These polymerization inhibitors may be used alone or in combination of two or more.

  The ink composition of the present invention may contain a resin in order to suppress gelation in the ink caused by the flaky metal pigment.

  The ink composition of the present invention includes additives commonly used in the ink industry, such as antioxidants, silane coupling agents, plasticizers, rust inhibitors, non-reactive polymers, pH adjusters, defoamers, A charge control agent, a stress relaxing agent, a penetrant, a surface conditioner, resin particles described in JP-A-2017-52870, and the like may be appropriately selected and blended within a range that does not impair the purpose of the present invention.

{Resin (P) having a weight average molecular weight of 12,000 or less and an acid value of 5 to 100}
The ink composition of the present invention is preferably characterized by containing a resin (P) having a weight average molecular weight of 12,000 or less and an acid value of 5 to 100.
The resin (P) has an acid group such as a carboxyl group having an acid value in the range of 5 to 100, and the acid group reacts with the surface of the flaky metal pigment, and the surface of the flaky metal pigment is coated with the resin (P). Can be covered with. Therefore, when the acid value of the resin (P) is 5 to 100, gelation in the ink can be effectively suppressed.

  The resin (P) needs to have a weight average molecular weight of 12,000 or less, and preferably has a weight average molecular weight of 6,000 or less. When the weight average molecular weight of the resin (P) is 12,000 or less, aggregation of the flaky metal pigment in the ink composition of the present invention can be more reliably prevented, and nozzle clogging during inkjet printing can be prevented. Can be prevented.

  In addition, when aggregation of the flaky metal pigment occurs, the metallic luster derived from the flaky metal pigment decreases. The resin (P) preferably has a weight average molecular weight of 3,000 or more. In the present invention, the weight average molecular weight is a value measured by gel permeation chromatography, and polystyrene is used as a standard substance.

  Since the resin (P) of the present invention has an acid value of 5 to 100 and a weight average molecular weight of 12,000 or less, the active energy ray-curable compound usually used in the active energy ray-curable ink composition ( For example, the resin (P) can be dissolved in a monofunctional compound and a polyfunctional compound described below, and the resin (P) can be directly compounded without the need to dissolve in a strong solvent in advance when preparing the ink.

  The resin (P) of the present invention is not particularly limited as long as it has the above-mentioned specific acid value and weight-average molecular weight. From the viewpoint of improving the scratch resistance of printed matter, acrylic resin, epoxy resin, polyester resin, Phenolic resins, phthalic acid resins, alkyd resins, fluororesins, urea (urea) resins, polyurethane resins, melamine resins, polyolefin resins, vinyl chloride resins, as well as modified resins of these resins, are polyester resins. Is preferred. The resin (P) may be used alone or in a combination of two or more.

  The resin (P) is obtained according to a usual synthesis method. As an example, a synthesis method of a polyester resin will be described. Polyester resin is a copolymer obtained by dehydration polycondensation of polyhydric carboxylic acid and polyalcohol which are monomers by a usual method, the type and amount of the monomer, the degree of progress of the reaction By adjusting, the desired weight average molecular weight and acid value are obtained.

  The polycarboxylic acid is a carboxylic acid having two or more carboxyl groups, and specific examples thereof include fumaric acid, maleic acid, itaconic acid, orthophthalic acid, isophthalic acid, terephthalic acid, oxalic acid, malonic acid, succinic acid, and glutaric acid. Acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, Examples thereof include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. These polyvalent carboxylic acids may be used alone or in a combination of two or more.

  The polyalcohol is an alcohol having two or more hydroxyl groups (—OH groups), and specific examples include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, and dipropylene glycol. , Tripropylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentyl glycol, butylethylpropanediol, , 6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexane Nji methanol, 1,4-cyclohexane diethanol, 1,10-decamethylene glycol, 1,12-dodecanediol, polyethylene glycol, polytrimethylene glycol, polytetramethylene glycol, and the like. These polyalcohols may be used alone or in combination of two or more.

  In the ink composition of the present invention, even if the resin (P) is blended in a high content of, for example, 3.0% by mass or more, the flaky metal pigment may aggregate in the ink composition of the present invention. The content of the resin (P) in the ink composition of the present invention is 15.0% by mass or less from the viewpoint of exhibiting excellent metallic luster, although it can prevent the clogging of the nozzle during inkjet printing. , And more preferably 10.0% by mass or less. On the other hand, in the ink composition of the present invention, the content of the resin (P) is preferably 3.0% by mass or more, more preferably 5.0% by mass or more, from the viewpoint of improving the scratch resistance of the printed matter.

  In the ink composition of the present invention, from the viewpoint of efficiently covering the surface of the flaky metal pigment, the mass ratio of the resin (P) to the flaky metallic pigment (resin P / the flaky metallic pigment) is 0.05 to 50. Is preferably, and more preferably 0.6 to 20.

<Preparation of ink composition>
The ink composition of the present invention is usually used by mixing at least (A) the flaky metal pigment, (B) the polymerizable compound, and (C) the initiation of photopolymerization with various components appropriately selected as necessary. It is prepared by filtering using a filter having a pore size of about 1/10 or less of the nozzle diameter of the ink jet print head to be used.

<Physical properties of ink composition>
The ink composition of the present invention preferably has a viscosity at 40 ° C. of 5.0 to 30.0 mPa · s. If the viscosity of the ink at 40 ° C. is within the above-specified range, good ejection stability can be obtained. The viscosity of the ink can be measured at 40 ° C. and a shear rate of 100 s ⁻¹ using a rheometer (MCR301 manufactured by Antonpaar).
The surface tension of the present invention was measured at 20 ° C. by a platinum plate method (automatic surface tensiometer CBVP-Z manufactured by Kyowa Interface Science). The specific gravity was measured at 20 ° C. according to JISZ8804: 2012.

<Metallic tone prediction method>
The metallic tone of the printed matter according to the present invention can be predicted from the L * value obtained by measuring the liquid level of the ink composition. For example, as shown in FIG. 1, the ink composition is placed in a petri dish and allowed to stand, and the liquid level is measured from a height of 1 cm with a color difference meter.

<Use fields>
The active energy ray-curable ink composition of the present invention is not particularly limited as long as it is a field in which an active energy ray-curable material is generally used, and can be appropriately selected depending on the purpose. It can be applied to paints, adhesives, insulating materials, release agents, coating materials, sealing materials, various resists, various optical materials, and the like, and is particularly useful when used as an inkjet ink composition.

  The ink composition of the present invention can be used in various ink jet printers. Examples of the inkjet printer include an inkjet printer that discharges an ink composition by a charge control method or a piezo method. In addition, a large-sized inkjet printer, specifically, an inkjet printer for printing on articles produced on an industrial line can also be suitably used.

  The printing substrate of the present invention is not particularly limited, but a substrate used in an industrial line is preferably exemplified. Examples of the shape of the printing material include a plate shape and a film shape. Further, examples of the material of the substrate include plastics such as ABS resin, polycarbonate, polyvinyl chloride, polystyrene, polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polypropylene (PP); and metals such as stainless steel and aluminum. , Wood and glass.

  In the printing step of the present invention, a printing method such as a one-pass method is used to completely cover the base material in a specific area, and when the print layer after printing becomes smooth, a printed image having a mirror finish is obtained. Can be When a printing method such as a multi-pass method is used and the surface of the print layer is not smooth but has a dot shape, a printed image having a metallic tone with a granular feeling can be obtained.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

<Ink composition>
≫Preparation of flaky metal pigment dispersion 液
On a PET film having a thickness of 100 μm, a 3.0% by mass undercoat solution in which cellulose acetate butyrate (butylation degree: 37%) was dissolved in ethyl acetate was uniformly applied to form an undercoat layer on the PET film. .
Next, an aluminum deposited layer having an average thickness of 21 nm was formed on the undercoat layer by vacuum deposition to obtain a laminate.
The laminate was simultaneously subjected to peeling, miniaturization, and dispersion treatment in an ethyl acetate using an ultrasonic disperser to prepare a flaky metal pigment dispersion.

The obtained scaly metal pigment dispersion is filtered with a SUS mesh filter having an opening of 5 μm to remove coarse particles, and a scaly metal pigment dispersion 1 having a D ₅₀ = 0.6 μm and an average thickness of 21 nm ( Hereinafter, it may be referred to as dispersion liquid 1).
In the preparation of the ink composition, the scaly metal pigment dispersion 1 was used, and the concentration of the non-reactive solvent was adjusted to a predetermined non-reactive solvent concentration by distilling off the solvent or adding the solvent during the evaporator.
In the same manner as in this method, a flaky metal pigment dispersion 2 shown in Table 1 was prepared. The unit is mass%.

<< Synthesis of resin (P) >>
In a flask equipped with a thermometer, a stirrer, a nitrogen introducing tube and an outlet tube with a partial condenser, 320 parts by mass of isophthalic acid, 5 parts by mass of maleic anhydride, and 200 parts by mass of neopentyl glycol are added until a predetermined acid value is reached. A dehydration condensation reaction was performed at 240 ° C. Thereafter, the partial condenser was replaced with a reflux condenser with a water separator, xylene was added, and a dehydration condensation reaction was further performed. After confirming that the desired acid value and weight average molecular weight were obtained, xylene was removed with an evaporator to obtain a polyester resin (P).

<< Preparation of ink composition >>
The scaly metal pigment dispersion, the polymerizable compound, and the photopolymerization initiator were prepared as follows, and were adjusted to 100% by mass as the ink composition 1.
1) (A) Flake-shaped metal pigment dispersion: 1% by mass as aluminum solid content
2) (B) polymerizable compound:
a. Ethoxy-diethylene glycol acrylate b. Isobornyl acrylate c. Tetrahydrofurfuryl acrylate d. Phenoxyethyl acrylate e. Triethylene glycol diacrylate f. Neopentyl glycol diacrylate g. 1,9-nonanediol diacrylate h. 1,6-hexanediol diacrylate i. Caprolactone-modified hydroxyethyl acrylate j. Trimethylolpropane triacrylate

3) (C) Photopolymerization initiator:
2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by Lambson) 8.0% by mass
4) (D) Nonionic dispersant:
DISPERBYK-192 (manufactured by Big Chemie, nonionic, weight average molecular weight = 1,487)
5) Dispersant having acid value or amine value:
DISPERBYK-2013 (manufactured by Big Chemie, acid value = 8, amine value = 18, weight average molecular weight = 3,448)
6) Resin (P): acid value 11 weight average molecular weight 6,000
7) Polymerization inhibitor: hydroquinone monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.2% by mass
8) Non-reactive solvent: 1.0% by mass of ethyl acetate
In the same manner as in this method, ink compositions 2 to 8 shown in Table 2 were prepared. The unit is mass%. In the examples, a group having a common composition other than the flaky metal pigment dispersion was designated as the same ink composition No.

<Printing method>
Using an inkjet printer (print head nozzle diameter 30 μm, filter # 2300 mesh in the head) and UV-LED (irradiation intensity 500 mW / cm ² , integrated light amount 500 mJ / cm ² ), heat the print head to 40 ° C. Printing was performed at a substrate temperature of 23 ° C. at room temperature. The substrate used was a commercially available polycarbonate plate.

<Evaluation>
The following evaluation was performed and the results are shown in Tables 3 and 4. The measurement was performed in an atmosphere of 23 ° C. and 55% RH unless otherwise specified.
≪Storage stability≫
The ink composition was stored at 50 ° C. for 28 days, and the viscosity of the ink composition before and after storage was measured to determine the rate of change in viscosity, and the storage stability was evaluated according to the following criteria. The viscosity of the ink composition was measured using a rheometer (MCR301 manufactured by Antonpaar) at 40 ° C. and a shear rate of 100 s−1.
A: Viscosity change rate is 0 to 4.9%
Good: The viscosity change rate is 5.0% to 9.9%.
Δ: The viscosity change rate is 10.0% to 19.9%.
×: The viscosity change rate is 20.0% or more {metal-like}
The printed matter obtained by printing using the ink composition before the storage stability test and the ink composition after the storage stability test, respectively, was measured using BYK-mac, a multi-angle colorimeter manufactured by BYK Gardner. The lightness index (L value) of 15 ° to 110 ° was measured, and the metal tone was evaluated from the FI value calculated by the following equation according to the following evaluation criteria.

(formula)
FI = 2.69 × (L ^* 15 ° −L ^* 110 °) ^1.11 / (L ^* 45 °) ^0.86
L ^* 45 °: Lightness index L ^* 15 obtained by irradiating light C from a first direction inclined at 45 ° to the vertical direction perpendicular to the surface of the metallic coating film and receiving light in the vertical direction (normal direction). °: Lightness index L ^* 110 ° obtained by receiving light in a second direction (−30 ° relative to the normal direction) raised 15 ° in the direction perpendicular to the first direction: 110 ° relative to the first direction Lightness index obtained by receiving light in the tilted third direction (65 ° with respect to the normal direction) ◎: FI value is 12.0 or more ：: FI value is 10.0% to 11.9%
Δ: FI value is 8.0% to 9.9%
×: FI value is less than 8.0% {metallic tone prediction method}

The prepared ink before or after storage was put into a petri dish, and a color difference meter CR-400 (manufactured by Konica Minolta) was fixed so that the measurement portion was at a position of 1 cm from the liquid level, and the L * value was measured.
：: L * value is 50 or more Δ: L * value is 30 or more and less than 50 X: L * value is less than 30

As described above, in the ink composition of the present invention, the metal tone of the printed matter using the ink before the storage stability test is not limited, but the metal tone of the printed matter using the ink after the storage stability test that reproduces long-term storage. It turns out that it is excellent also in the expression of the key.
Also, the expectation of the metallic tone according to the present invention is well matched with the metallic tone of the actual printed matter.

Claims (3)

An active energy ray-curable ink composition containing at least (A) a flaky metal pigment, (B) a polymerizable compound, and (C) a photopolymerization initiator,
Ri der L * value of 30 or more liquid interface of the active energy ray-curable ink composition,
(A) The flaky metal pigment has a 50% volume average diameter of 0.05 to less than 0.5 μm, an average thickness of 5.0 to less than 50.0 nm, and an aspect ratio (50% volume average). (Diameter / average thickness) is 4 or more and 50 or less.
Active energy ray-curable ink composition.   The active energy ray-curable ink composition according to claim 1, wherein the polymerizable compound (B) has a specific gravity of 0.98 to 1.15 and a surface tension of 33.0 to 45.0 mN / m. A method for predicting a metal tone of a printed matter by an active energy ray-curable ink composition containing at least (A) a flaky metal pigment, (B) a polymerizable compound, and (C) a photopolymerization initiator,
A method for predicting a metal tone of a printed matter by an active energy ray-curable ink composition, the method being performed by measuring an L * value of a liquid interface of the ink composition.

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