JP2020097671A - Inkjet ink, determination method and printed matter - Google Patents

Abstract

To provide an inkjet ink which has more complicated operation for visualizing hidden printing than a conventional ink using an ultraviolet light emitting dye, and has a simpler authenticity determination method than an ink using a DNA taggant, a determination method, and a printed matter.SOLUTION: An inkjet ink contains a resin, a solvent and a lanthanoid compound, in which the lanthanoid compound is a precursor of a light emitting lanthanoid complex, and has no light emitting property under irradiation with ultraviolet light. A determination method includes applying a solution containing a ligand capable of forming a lanthanoid element and a light emitting lanthanoid complex on an object to be determined, and irradiating the object with ultraviolet light. Another method includes bringing determination equipment impregnated with the solution containing the ligand into contact with an object to be determined, and irradiating the determination equipment with ultraviolet light. A printed matter is subjected to printing using the inkjet ink.SELECTED DRAWING: None

Description

The present invention relates to an inkjet ink, a determination method and a printed matter, and more specifically, an inkjet ink that can be made to emit light by ultraviolet irradiation and can be used for traceability of industrial products and prevention of counterfeit products, and the presence or absence of printing by the ink is determined. And a printed matter printed with the ink.

Conventionally, there has been known a method of concealing printing with an ink using a europium complex that emits ultraviolet light or a fluorescent whitening agent as a coloring material, and visualizing it by irradiating ultraviolet light (see, for example, Patent Documents 1 and 2). Actually widely used.
However, since it can be easily visualized with an ultraviolet light or the like, it is difficult to say that the security is optimum, especially from the viewpoint of preventing counterfeit products. That is, since the visualization means is simple, it is easy to distinguish the hidden print, and it is relatively disadvantageous that the marking is forged.
In addition, anti-counterfeit inks and the like using DNA taggants have also been proposed (see, for example, Patent Documents 3 to 5), and by using such inks, the security property is significantly improved in terms of anti-counterfeiting.
However, the product could not be specified unless the printed surface was scraped off, DNA was extracted, and the base sequence was specified. That is, the authenticity specifying operation is complicated, and the ink and the appraisal cost are expensive.

JP, 2004-203924, A JP, 2013-203801, A Japanese Patent Publication No. 2016-500518 Japanese Patent Publication No. 2016-521129 Japanese Patent Publication No. 2017-532015

In view of the above-mentioned prior art, the present invention has a more complicated operation for visualizing a hidden print than a conventional ink using an ultraviolet-emitting dye, while the authenticity determination method is far more than an ink using a DNA taggant. An object is to provide a simple inkjet ink, a determination method, and a printed matter.

The present invention has the following configuration in order to solve the above problems.
That is, the inkjet ink of the present invention contains a resin, a solvent, and a lanthanoid compound, and the lanthanoid compound is a precursor of a luminescent lanthanoid complex and does not have a luminescent property under UV irradiation.

The determination method of the present invention uses a ligand capable of forming a lanthanoid element and a luminescent lanthanoid complex on the determination target in order to determine whether or not the printing with the inkjet ink is formed on the determination target. A solution containing the same is applied and ultraviolet rays are irradiated.

The determination method of the present invention also comprises a solution containing a lanthanoid element and a ligand capable of forming a luminescent lanthanoid complex in order to determine whether or not the printing with the inkjet ink is formed on the determination target. After the impregnated judging device is brought into contact with the object to be judged, the judging device is irradiated with ultraviolet rays.

The printed matter of the present invention is printed using the inkjet ink.

In the following, the “ink jet ink” of the present invention may be simply referred to as “ink”.

Printing with the ink of the present invention does not have a light emitting property under irradiation of ultraviolet rays. When a solution containing a ligand capable of forming a complex with a lanthanoid element to form a luminescent lanthanoid complex is applied to the printed portion, light can be emitted under ultraviolet irradiation.
In this way, the printed part does not emit light even if it is irradiated with ultraviolet light, so it has higher security than the ink using conventional UV-emitting dyes, while applying a solution containing a ligand to the printed surface. It is superior to the ink using DNA taggant in that it can emit ultraviolet light by a simple method.

Hereinafter, preferred embodiments of the inkjet ink, the determination method, and the printed matter 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, appropriate modifications may be made without departing from the spirit of the present invention.

[Inkjet ink]
The inkjet ink of the present invention contains a resin, a solvent, and a lanthanoid compound.

<Resin>
The resin used in the present invention is not particularly limited, and may be appropriately determined in consideration of the compatibility with the lanthanoid compound, the solubility in a solvent, the fixability on a print target, and the like.
Specifically, for example, polyester resin, acrylic resin, phenol resin, amine resin, butyral resin, epoxy resin, chlorinated polyolefin, vinyl chloride-vinyl acetate copolymer resin, urethane resin, rosin-modified maleic acid resin and the like are preferable. Can be mentioned. You may combine 2 or more types of resin.

<Solvent>
The solvent used in the present invention is not particularly limited and may be appropriately determined in consideration of the solubility of the resin and the lanthanoid compound, the drying property of the ink, and the like.
Specifically, for example, water, a ketone-based solvent, an alcohol-based solvent and the like are preferably mentioned. You may combine 2 or more types of solvents.
Preferred examples of the ketone solvent include acetone, methyl ethyl ketone, dipropyl ketone, methyl isobutyl ketone, and methyl isopropyl ketone. Among them, methyl ethyl ketone can be preferably used for inks for continuous ink jet printers because of its solubility of resins, dispersibility of pigments, conductivity, and drying property of inks.
Preferable examples of the alcohol solvent include methanol, ethanol, propanol, and isopropanol.

<Lanthanoid compound>
Lanthanoid is a general term for elements having atomic numbers 57 to 71. Specifically, lanthanoids include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.
In the lanthanoid, the 4f orbit becomes clogged with electrons as the atomic number increases. The elements of the lanthanoids have similar properties because the way of packing electrons in the outermost shell (5d orbit and 6s orbit) does not change much.

When a lanthanoid forms a complex with a specific ligand, it emits fluorescent light by excitation light such as ultraviolet light.
As such a luminescent lanthanoid complex, a complex of samarium, europium and dysprosium is particularly preferable from the viewpoint of exhibiting strong fluorescence.

The lanthanoid compound used in the ink of the present invention is a precursor of the luminescent lanthanoid complex as described above, and does not emit light when irradiated with ultraviolet rays.
Examples of such lanthanoid compounds include chloride salts, oxides, nitrates, β-diketone compound complexes, and the like. From the viewpoint of solubility in water, chloride salts and nitrates are preferable, and from the viewpoint of solubility in ketone solvents or alcohol solvents, β-diketone compound complexes are preferable. Among the β-diketone compound complexes, acetylacetonato complex and 2,2,6,6-tetramethyl-3,5-heptanedionato complex are particularly preferable. As described above, an appropriate lanthanoid compound can be selected depending on whether the ink is water-based or solvent-based. Whether to use an aqueous system or a solvent system may be appropriately determined in consideration of the material of the material to be printed.

<Other optional ingredients>
The ink according to the present invention can be suitably used for an inkjet printer, particularly a charge amount control type continuous inkjet printer. In this case, a conductive agent is usually used to adjust the deflection amount of the ink droplets ejected from the printer due to the electric field.
Preferable examples of such a conductive agent include ammonium thiocyanate, potassium thiocyanate, sodium thiocyanate, lithium nitrate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium bromide, and tetraphenylboron quaternary ammonium salt. ..

Further, the ink of the present invention may contain a coloring material such as a usual pigment or dye. Therefore, the ink of the present invention includes not only colorless ink but also colored ink.
In the colored ink, unlike the colorless ink, letters and figures made of normal coloring materials such as pigments and dyes are visually recognized under visible light.
Although colorless inks or colored inks do not have ultraviolet light emitting properties as they are, ultraviolet light emitting properties can be imparted by complex formation of a lanthanoid element and a ligand.

The ink of the present invention may contain various components for various purposes, in addition to the above components, within a range that does not impair the effects of the present invention. For example, components conventionally used in inkjet inks such as a surface conditioner, a dispersant, a surfactant, a high boiling point solvent, and a stabilizer can be contained.

<Ink formulation>
The content ratio of the resin with respect to the total weight of the ink is not particularly limited, but is, for example, preferably 1 to 30% by weight, and more preferably 1 to 25% by weight. If this proportion exceeds 30% by weight, there is a risk of causing pipe clogging in the inkjet device. On the other hand, if it is less than 1% by weight, the fixing property to the printing object may be deteriorated.

The content ratio of the solvent with respect to the total weight of the ink is not particularly limited, but is, for example, preferably 50 to 95% by weight, and more preferably 60 to 90% by weight. If this ratio exceeds 90% by weight, other components may not be blended in an appropriate ratio. On the other hand, if it is less than 60% by weight, the viscosity becomes high, and there is a risk of causing pipe clogging in the inkjet device.

The content ratio of the lanthanoid compound with respect to the total weight of the ink is preferably 0.01 to 5% by weight, and more preferably 0.1 to 3% by weight. If this ratio exceeds 5% by weight, the lanthanoid compound may not be completely dissolved in the solvent and may precipitate. On the other hand, if it is less than 0.01% by weight, sufficient emission intensity cannot be obtained, and the visibility of printing may be deteriorated.

When the above-mentioned conductive agent is blended, the content ratio with respect to the total weight of the ink is preferably 0.3 to 2.5% by weight. If the content of the conductive agent is less than 0.3% by weight, sufficient conductivity may not be obtained, and it may not be possible to maintain stable deflection in the printer. On the other hand, if the content of the conductive agent exceeds 2.5% by weight, the compatibility with other components cannot be sufficiently maintained and the stability over time decreases, which may lead to an unstable printing state on the printer. There is.

[Use of ink]
INDUSTRIAL APPLICABILITY The ink of the present invention can be applied to printing on various kinds of printing materials as an inkjet ink.
The material to be printed is not particularly limited, and examples thereof include paper, metal, glass, plastics, and a coated material having a surface coated with these materials.
It is possible to obtain a printed matter on which various codes such as characters, barcodes, and data matrix codes are printed by ejecting ink droplets of an ink on the surface of such a printed matter with an inkjet printer. it can

The printing formed on the printing material as described above does not have ultraviolet light emission as it is.
However, by applying a solution containing a ligand capable of forming a complex with a lanthanoid element to form a luminescent lanthanoid complex to the printed portion, it is possible to impart luminescent property by ultraviolet irradiation.
If the print is not formed, the luminescent lanthanoid complex is not formed and the luminescence does not occur due to the irradiation of ultraviolet rays.Therefore, a ligand that can form a luminescent lanthanoid complex by forming a complex with the lanthanoid element on the determination target is selected. It is possible to determine whether or not a print with the ink of the present invention is formed on the determination target by applying the solution containing the solution and irradiating the solution with ultraviolet rays.
The method of applying the solution containing the ligand is not particularly limited, and examples thereof include brush coating, dipping, spraying, rollers, and an inkjet method.

As another method for determining whether or not the printing is formed on the determination target, a determination tool impregnated with a solution containing a lanthanoid element and a ligand capable of forming a luminescent lanthanoid complex is used as the determination target. A method of irradiating the determination device with ultraviolet rays after the contact is made can also be adopted.
The determination device is not particularly limited as long as it can be impregnated with a solution containing a ligand and can transfer the lanthanoid compound from the printed portion, and examples thereof include gauze, absorbent cotton, cotton swabs, and swabs. , Brushes and the like.
After impregnating such a judging device with a solution containing a ligand capable of forming a lanthanoid complex with a lanthanoid element, the judging device is pressed against the judging object, or the judging object is rubbed with the judging object. Then, when the lanthanoid compound in the printed portion is transferred to the determination device by bringing the determination device into contact with the determination target, a luminescent lanthanoid complex is formed in the determination device.
Then, when the judging device is irradiated with ultraviolet rays, the luminescent lanthanoid complex in the judging device emits light, and the presence of the printed portion can be confirmed.

In each of the above methods, the ligand capable of forming a luminescent lanthanoid complex with the lanthanoid element is, for example, 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl. Acetylacetone having a fluoroalkyl group such as -4,6-octadione, trifluoroacetylacetone, hexafluoroacetylacetone, 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, and benzoyltrifluoroacetone. Derivatives are preferred.
In addition, as a solvent that can be used for the solution containing such a ligand, for example, water, a ketone solvent, an alcohol solvent and the like are preferably mentioned. You may combine 2 or more types of solvents.

Hereinafter, the inkjet ink, the determination method, and the printed material according to the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples. In the following, when simply referred to as “part”, it means “part by weight”.

[Example 1]
As shown in Table 1, 2 parts of europium(III) acetylacetonate dihydrate, 10 parts of acrylic resin "Dianal RB50" (trade name, manufactured by Mitsubishi Chemical Co.) were replaced with methyl ethyl ketone (hereinafter abbreviated as "MEK"). It was dissolved in 87.6 parts, and 0.4 parts of tetraphenylboron quaternary ammonium was further added and dissolved.
The obtained solution was filtered with a filter having an opening of 1 μm to prepare an inkjet ink according to Example 1.
Inkjet printing was performed on the retort pouch bag for food packaging using the obtained ink. A continuous inkjet printer (model CCS3000) manufactured by Kishu Giken Kogyo Co., Ltd. was used for inkjet printing. In this state, the printed portion was invisible under both visible light and ultraviolet irradiation.
Next, a brush containing a solution of 3 parts of 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octadione, which is an acetylacetone derivative, and 97 parts of ethanol is applied to the above-mentioned printing spot. It was applied by coating. Although the applied portion was invisible under visible light, it was illuminated by ultraviolet light (wavelength: 365 nm) to emit red light and was visually readable.
At this time, when the brush used for applying the ligand solution was irradiated with ultraviolet rays, it emitted red light, and the presence of the ink used for printing could be visually confirmed.

[Example 2]
As shown in Table 1, Example 1 was repeated except that 2 parts of tris(2,2,6,6-tetramethyl-3,5-heptanedionato) europium(III) was used as the lanthanoid compound instead of europium acetylacetonate. An ink was prepared in the same manner as in.
Inkjet printing was performed on the retort pouch bag for food packaging using the obtained ink. A continuous inkjet printer (model CCS3000) manufactured by Kishu Giken Kogyo Co., Ltd. was used for inkjet printing. In this state, the printed portion was invisible under both visible light and ultraviolet irradiation.
Next, a solution consisting of 3 parts of trifluoroacetylacetone and 97 parts of ethanol as a ligand was applied to the above-mentioned printed portion by brush coating, and the same result as in Example 1 was obtained.

[Example 3]
As shown in Table 1, 2 parts of europium (III) chloride hexahydrate, 30 parts of styrene-acrylic resin "Johncryl 57J" (trade name, 37% aqueous solution, manufactured by BASF) and 68 parts of water were mixed and dissolved. ..
The obtained solution was filtered with a filter having an opening of 1 μm to prepare an inkjet ink according to Example 3.
Inkjet printing was performed on the retort pouch bag for food packaging using the obtained ink. A continuous inkjet printer (model CCS3000) manufactured by Kishu Giken Kogyo Co., Ltd. was used for inkjet printing. In this state, the printed portion was invisible under both visible light and ultraviolet irradiation.
Next, when a solution containing 3 parts of hexafluoroacetylacetone and 97 parts of ethanol as a ligand was applied to the above-mentioned printed portion by brush coating, the same result as in Example 1 was obtained.

[Example 4]
As shown in Table 1, 2 parts of europium(III) chloride hexahydrate, 10 parts of butyral resin (molecular weight 19000, hydroxyl group about 36%, acetyl group 3%, butyralization degree 74%) were dissolved in 87 parts of ethanol. Further, 1 part of ammonium thiocyanate was added and dissolved.
The obtained solution was filtered with a filter having an opening of 1 μm to prepare an inkjet ink according to Example 4.
Inkjet printing was performed on the retort pouch bag for food packaging using the obtained ink. A continuous inkjet printer (model CCS3000) manufactured by Kishu Giken Kogyo Co., Ltd. was used for inkjet printing. In this state, the printed portion was invisible under both visible light and ultraviolet irradiation.
Next, when a solution containing 3,4 parts of 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione as a ligand and 97 parts of ethanol was applied to the above-mentioned printed portion by brush coating, The same result as in Example 1 was obtained.

[Example 5]
As shown in Table 1, 2 parts of terbium(III) chloride hexahydrate, 32 parts of styrene-acrylic resin "Johncryl 57J" (trade name, 37% aqueous solution, manufactured by BASF) and 66 parts of water were mixed and dissolved. ..
The obtained solution was filtered with a filter having an opening of 1 μm to prepare an inkjet ink according to Example 5.
Inkjet printing was performed on the retort pouch bag for food packaging using the obtained ink. A continuous inkjet printer (model CCS3000) manufactured by Kishu Giken Kogyo Co., Ltd. was used for inkjet printing. In this state, the printed portion was invisible under both visible light and ultraviolet irradiation.
Next, a solution containing 2 parts of benzoyltrifluoroacetone and 98 parts of ethanol as a ligand was applied to the above-mentioned printed portion by brush coating. Although the applied portion was invisible under visible light, it emitted green light when irradiated with ultraviolet light (wavelength: 365 nm), and became visually readable.
Further, at this time, when the brush used for applying the ligand solution was irradiated with ultraviolet rays, it emitted green light, and the presence of the ink used for printing could be visually confirmed.

[Example 6]
As shown in Table 1, 2 parts of tris(acetylacetonato)terbium (III) (trihydrate) and 20 parts of polyester resin (average molecular weight 8000, thermoplastic saturated copolymerized polyester resin) were dissolved in 77 parts of MEK, Further, 1 part of tetrabutylammonium hexafluorophosphate was added and dissolved.
The obtained solution was filtered with a filter having an opening of 1 μm to prepare an inkjet ink according to Example 6.
Inkjet printing was performed on the retort pouch bag for food packaging using the obtained ink. A continuous inkjet printer (model CCS3000) manufactured by Kishu Giken Kogyo Co., Ltd. was used for inkjet printing. In this state, the printed portion was invisible under both visible light and ultraviolet irradiation.
Next, a solution consisting of 2 parts of 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octadione and MEK of 98 parts as a ligand was applied to the above-mentioned printed portion by brush coating. Applied. Although the applied portion was invisible under visible light, it emitted green light when irradiated with ultraviolet light (wavelength: 365 nm), and became visually readable.
Further, at this time, when the brush used for applying the ligand solution was irradiated with ultraviolet rays, it emitted green light, and the presence of the ink used for printing could be visually confirmed.

[Example 7]
As shown in Table 1, europium (III) acetylacetonate dihydrate 2 parts, carbon black (REGAL330R, Cabot) 2 parts, DYSPERBYK-111 (Big Chemie) 1 part, butyral resin (molecular weight 19000, hydroxyl group about 36%) , Acetyl group 3%, butyralization degree 74%) 4.2 parts, rosin-modified maleic acid resin 10 parts, tetrabutylammonium hexafluorophosphate 0.7 parts were dissolved and mixed in MEK 80.1 parts, and then the bead mill ( The dispersion treatment was carried out using Nanomill NM-L, Asada Tekko.
The obtained solution was filtered with a filter having an opening of 1 μm to prepare an inkjet ink according to Example 7.
Inkjet printing was performed using the obtained ink on a retort pouch bag for food packaging. For inkjet printing, a continuous inkjet printer (model CCS3000) manufactured by Kishu Giken Co., Ltd. was used. In this state, black printing with a coloring material (carbon black) was readable under visible light, but no luminescence under UV irradiation was observed.
Next, a solution consisting of 2 parts of trifluoroacetylacetone and 98 parts of MEK as a ligand was applied to the above-mentioned printed portion by brush coating. Although the applied portion was black under visible light, it was confirmed that printing was performed using the ink according to Example 7 because it emitted red light when irradiated with ultraviolet rays (wavelength: 365 nm). That is, the authenticity could be judged.

[Example 8]
As shown in Table 1, 2 parts of tris(acetylacetonato)terbium(III) (trihydrate), 4 parts of Solvent Black 27 (Varifast Black 3820, Orient Chemical Co., Ltd.), polyester resin (average molecular weight 8000, heat) 20 parts of plastic saturated copolyester resin) was dissolved in 73 parts of MEK, and further 1 part of tetrabutylammonium hexafluorophosphate was added and dissolved.
The obtained solution was filtered with a filter having an opening of 1 μm to prepare an inkjet ink according to Example 8.
Then, inkjet printing was performed on the retort pouch bag for food packaging using the obtained ink. A continuous inkjet printer (model CCS3000) manufactured by Kishu Giken Kogyo Co., Ltd. was used for inkjet printing. In this state, black printing with a coloring material (solvent black 27) was readable under visible light, but no luminescent property under ultraviolet irradiation was observed.
Next, a solution consisting of 2 parts of benzoyltrifluoroacetone and 98 parts of MEK as a ligand was applied to the above-mentioned printing spot by brush coating. Although the applied portion was black under visible light, it was confirmed that printing was performed using the ink according to Example 8 because it emitted green light when irradiated with ultraviolet light (wavelength: 365 nm). That is, the authenticity could be judged.

Claims (9)

An inkjet ink comprising a resin, a solvent and a lanthanoid compound, wherein the lanthanoid compound is a precursor of a luminescent lanthanoid complex and has no luminescent property under UV irradiation. The inkjet ink according to claim 1, wherein the lanthanoid compound as a precursor of the luminescent lanthanoid complex is one or more selected from the group consisting of lanthanoid salts and complexes in which organic ligands are coordinated. The resin is selected from the group consisting of polyester resin, acrylic resin, phenol resin, amine resin, butyral resin, epoxy resin, chlorinated polyolefin, vinyl chloride-vinyl acetate copolymer resin, urethane resin and rosin-modified maleic acid resin. The inkjet ink according to claim 1, which is one kind or two or more kinds. The inkjet ink according to any one of claims 1 to 3, wherein the solvent is one or more selected from the group consisting of water, a ketone solvent, and an alcohol solvent. The inkjet ink according to claim 1, further comprising a conductive agent. A lanthanoid element and a luminescent lanthanoid complex can be formed on the object to be judged in order to judge whether or not the printing by the inkjet ink according to any one of claims 1 to 5 is formed on the object to be judged. A determination method of applying a solution containing a ligand and irradiating with ultraviolet rays. A lanthanoid element and a ligand capable of forming a luminescent lanthanoid complex are included in order to determine whether or not the printing by the inkjet ink according to any one of claims 1 to 5 is formed on the determination target. A method for making a judgment, in which a judging device impregnated with a solution is brought into contact with an object to be judged and then the judging device is irradiated with ultraviolet rays. The determination method according to claim 6, wherein the ligand is an acetylacetone derivative. A printed matter printed with the inkjet ink according to any one of claims 1 to 5.