JP2004042464A - Printing method to three-dimensional object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inkjet ink by a pigment having a full light fastness. <P>SOLUTION: In a printing method to three-dimensional objects, a plurality of three-dimensional objects are continuously transferred, and printing is carried out by the inkjet ink of 5-100 mPas at 25°C which contains 10-90 weight % of a monomer that can be polymerized with solid objects being transferred. Then, electron beams are applied to harden the ink. The method has good adhesiveness to media with non porous surfaces. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a printing method for printing on a three-dimensional object.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, printing on a three-dimensional molded product such as plastic, glass, metal, or the like has been performed by a printing method such as screen printing, dry offset printing, or transfer printing. Above all, there are few restrictions on the shape of the printing medium, thick printing is possible, various types of recording liquids can be used because resins with different drying and curing conditions can be used as a binder, and printing pressure is low. Screen printing is widely used because of its features such as printing on a printing medium such as fragile glass.
[0003]
However, in general, molded products are mainly produced in a large variety and small quantities, so screen plate making is expensive, and as the thickness of the container becomes thinner, the molded product is deformed due to printing pressure and cannot be handled by screen printing. There is a problem. Therefore, there is a demand for a plateless and on-demand pressureless printing system. In response to this demand, printing by an ink jet method has been proposed.
[0004]
In general, ink-jet inks have a configuration in which drying of the ink is suppressed and drying of the ink at the nozzles is prevented, so that printing on non-permeable printing materials is slow and causes a problem. In order to improve the drying speed of the ink, a method of increasing the drying property by applying heat to the ink and a method of curing the ink by irradiation with ultraviolet rays have been considered. However, in these methods, the recording medium is heated, and there is a limitation on the use of a material that is easily deformed by heat. Further, when the ink is cured by ultraviolet rays, the curing speed varies depending on the transmittance of the ultraviolet rays of the ink. Therefore, in the case of black ink, it is necessary to add an excessive amount of a photoinitiator or a sensitizer. Furthermore, an ink containing an excessive amount of a photoinitiator or a sensitizer is disadvantageous in terms of price because it uses a lot of expensive materials, and there is a problem in that migration of the photoinitiator and the sensitizer from the ink tends to occur. Is also worried.
[0005]
On the other hand, the curing or cross-linking technology by electron beam irradiation has attracted attention as an energy-saving and environmentally friendly process that does not release solvents, from the viewpoint of environmental problems, which are global issues like ultraviolet curing. Considerations are being made. This method is a method in which electrons are accelerated by a voltage in a vacuum, the accelerated electrons are taken out into a normal-pressure atmosphere such as air, and an object is irradiated with an electron beam.
[0006]
The advantages of curing and crosslinking by electron beam irradiation include the following.
(1) Since it is not necessary to include an organic solvent as a diluent, it is environmentally friendly.
(2) The curing speed is high, the productivity is high, and post-processing can be performed immediately because cooling and aging are not required.
(3) The work area for curing is smaller than that of thermal drying, and the work management is easier than the temperature control at the time of thermal drying.
(4) There is no thermal damage to the substrate due to room temperature curing.
(5) Since no initiator and sensitizer are required, the cured product has improved weather resistance and stability, and has low odor.
(6) High density printing is possible because it can be cured regardless of the density.
However, the conventional electron beam irradiation apparatus has a high acceleration voltage of usually 300 kV to 1 MV, and the shielding and inerting of the secondary X-ray are also large. Therefore, the apparatus becomes very large, and what is called a scanning type is also required. The scanning coil is used in the electron beam generating section to scan the direction of the electron beam, and there is no way to easily move and use the irradiation device itself.
[0007]
[Problems to be solved by the invention]
The present invention is directed to printing on a three-dimensional object. The present invention relates to a printing method using an active energy ray-curable inkjet ink having good adhesion even to a medium having a non-porous surface. It is another object of the present invention to provide a pigment ink jet ink having a sufficient improvement in light resistance.
[0008]
[Means for Solving the Problems]
That is, the present invention conveys a plurality of three-dimensional objects continuously, and at 25 ° C containing 10 to 90% by weight of a polymerizable monomer in the conveyed three-dimensional objects, has a viscosity of 5 to 100 mPa. The present invention relates to a method for printing on a three-dimensional object, wherein printing or printing is performed with an inkjet ink of s, and then the ink is cured by irradiation with an electron beam. The present invention also relates to the above printing method, wherein the polymerizable monomer is one or a combination of two or more selected from the group consisting of a monofunctional monomer, a difunctional monomer, and a trifunctional monomer. The present invention also relates to the printing method, wherein the irradiation of the electron beam is performed by a vacuum tube type electron beam irradiation device. The present invention also relates to a printing method wherein the electron beam has an acceleration voltage of 10 kV to 150 kV. The present invention also relates to the printing method, wherein the three-dimensional object is a beverage can. The present invention also relates to the printing method, wherein the three-dimensional object is a resin laminate can. In addition, the present invention relates to the above printing method using an inkjet ink containing a pigment, a dispersant, and a polymerizable monomer and not containing a photopolymerization initiator. Further, the present invention relates to a printed matter printed by the above printing method.
[0009]
Specific examples of the three-dimensional object include a beverage can, a laminated can, a paper container, a bottle, a tube, and a molded product such as plastic, glass, and metal. The shape of the three-dimensional object may be a cylinder, a sphere, a box, an irregular shape, or the like. Among these, there are many uses for cans. Examples of the material of the can include an aluminum can, a steel can, a tin can, a resin film laminated can, and the like, but are not particularly limited. There are no particular limitations on types of cans, such as two-piece cans and three-piece cans. Particularly, in the case of two-piece cans, they are printed after being processed into a cylindrical shape, and immediately after the ink curing process, the production line. Since it flows above, the effects of the present invention can be exhibited to the maximum.
[0010]
In the manufacture of cans such as beer and other alcoholic beverages and soft drinks such as carbonated beverages, juices, tea and coffee cans, or monoblock aerosol cans, steel plates or aluminum plates are used. It is processed into a can body, and the surface of the can body is subjected to printing and painting, and the printing ink and paint on the surface are baked in an oven. Usually, such a series of processes is performed by a continuous line, and a mechanism for continuously transporting a plurality of three-dimensional objects is provided.
[0011]
Examples of the inkjet method include a drop-on-demand (piezo method, bubble jet (registered trademark) method, thermal jet method), and a continuous injection (Hertz method, mead method, sweet method). A three-dimensional object on which an image is recorded by an ink jet method is cured and fixed by an electron beam to create a printed matter.
[0012]
In the present invention, the ink-jet ink is an electron beam-curable ink that is cured by an electron beam, and appropriately mixes components such as an electron beam-curable compound, a thermal polymerization inhibitor, a colorant, and a solvent for adjusting viscosity, and a discharge method. Are adjusted in accordance with the characteristics of the above. The ink used in the present invention does not contain a photoinitiator or a sensitizer, unlike an ink that is cured by ultraviolet light. In the continuous injection type apparatus, an additive for adjusting conductivity is added as needed. As the colorant, any of a dye and a pigment can be used, but from the viewpoint of improving various resistances including light resistance, it is preferable to use a pigment.
[0013]
Specific examples of the colorant include a dye and a pigment. As the dye, an oil-soluble dye that is soluble in a polymerizable monomer and can exhibit water resistance and light resistance is preferable. Basic dyes, disperse dyes, acid dyes and the like can also be used because of their compatibility with the resin to be cured. Examples of pigments include inorganic pigments such as titanium oxide, titanium black, iron oxide, carbon black, and calcium carbonate, and quinacridone-based organic pigments, phthalocyanine-based organic pigments, benzimidazolone-based organic pigments, isoindolinone-based organic pigments, and azo-based pigments. Organic pigments such as organic pigments can be used. The average particle size of the pigment in the ink is preferably from 10 to 300 nm in order to obtain the stability of the ejection, the stability of the recording liquid, and the transparency and clarity of the color. The colorant is preferably contained in the ink in a solid content of 0.1 to 15% by weight, and the viscosity of the ink is 5 to 100 mPa.s. s (25 ° C.) is preferred.
[0014]
As the electron beam-curable compound, monomers, oligomers, prepolymers and the like having an ethylenically unsaturated double bond can be used. Specific examples of the electron beam curable compound include 2-phenoxyethyl acrylate, isobornyl acrylate, 2-hydroxyethyl (meth) acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, and 1,6-hexanediol di (meth). Acrylate, ethoxylated 1,6-hexanediol di (meth) acrylate, propoxylated 1,6-hexanediol di (meth) acrylate, hydroxypivalate neopentyl glycol diacrylate, ethoxylated neopentyl glycol diacrylate, propoxylated neo Pentyl glycol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacryle DOO, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, and the like. These electron beam-curable compounds may be used alone or, if necessary, in two or more kinds.
[0015]
For the ink, a thermosetting or thermoplastic resin having excellent compatibility with the electron beam curable compound can be used depending on the required physical properties. Examples of the thermosetting or thermoplastic resin include polyvinyl chloride, poly (meth) acrylate, epoxy resin, polyurethane resin, cellulose derivatives (eg, ethyl cellulose, cellulose acetate, nitrocellulose), and polyvinyl chloride-vinyl acetate. Coalesce, a polyamide resin, a polyvinyl acetal resin, a diallyl phthalate resin, and a synthetic rubber such as a butadiene-acrylonitrile copolymer. One or more of these resins can be used.
[0016]
Further, in order to obtain the stability of the ink over time and the stability in the recording apparatus, the ink may contain 0.01 to 5% by weight of a thermal polymerization inhibitor as needed. As the thermal polymerization inhibitor, aromatic derivatives such as hydroquinone, p-methoxyphenol, t-butylcatechol, and pyrogallol are used, but compounds other than aromatic compounds may be used in combination. The ink is prepared by pre-dispersing a concentrated dispersion containing an electron beam-curable compound, a thermal polymerization inhibitor, and a colorant, then diluting with an additive, and filtering with a filter having a pore size of 3 μm or less and 0.5 μm or less. It is preferable to produce by filtration.
[0017]
As the electron beam irradiation in the present invention, it is necessary to reduce damage to the substrate, and as the acceleration voltage, a device having a different energy level from that of a normal large electron beam irradiation device is preferable. Preferably, it is 10 to 150 kV, more preferably 30 to 130 kV. By setting the acceleration voltage, the adhesion can be improved without damaging the base material.
[0018]
The vacuum tube type electron beam irradiator according to the present invention is different from a conventional drum type electron beam irradiator, which irradiates an electron beam while constantly evacuating the inside of a drum which is an electron beam generating unit. Since the generator does not need to be evacuated, it is small and can be moved. In addition, as a vacuum tube type electron beam irradiation apparatus, an irradiation tube having a columnar shape is generally used, and one or a plurality of irradiation tubes are used. An apparatus having an irradiation tube having such a configuration is disclosed in U.S. Pat. No. 5,414,267, and is known as a Min-EB apparatus by Ushio International Technologies (UIT). In this device, even at a low accelerating voltage, the reduction in the penetrating power of the electron beam is small, and the electron beam can be extracted effectively. As a result, the electron beam can be applied at a low depth, and the recording medium and the recording liquid on the recording medium can be efficiently processed or cured without adversely affecting the base material. Further, the generation amount of the secondary electron beam can be reduced by the low acceleration voltage and the low energy, so that a large-scale shield structure is not required.
[0019]
【Example】
Hereinafter, the present invention will be described based on examples.
(Preparation of electron beam curable ink)
Using a device equipped with an electron beam irradiation device at the back of the inkjet head, printing was performed on a continuously transported three-dimensional object to create a recorded material. An electron beam-curable ink having the following composition was prepared. In the examples, "part" represents% by weight.
Pigment: carbon black (“Printex 150T” manufactured by Degussa) 2 parts Trimethylolpropane triacrylate (“KS-TMPTA” manufactured by Nippon Kayaku) 55 parts N-vinylformamide (beam set 770) manufactured by Arakawa Chemical Co., Ltd. 40 parts 0.5 parts of an aliphatic modified dispersant (“Solspers 24000” manufactured by Abisia) 0.5 parts of a pigment dispersant (“Solspers 5000” manufactured by Abisia) 0.05 parts of the above components were mixed and dispersed by a sand mill for 4 hours. After that, the solution was subjected to pressure filtration with a 3 μm membrane filter to give a viscosity of 20 mPa. s (25 ° C.) electron beam curable ink was prepared.
[Example 1] Using a prototype ink-jet ink on the surface of a molded beverage can, printing was performed by an ink-jet printer having a piezo-type head and a nozzle having a diameter of 40 µm, and the ink was cured by an electron beam irradiation device with an acceleration voltage of 70 KV. , Adhered. The obtained recorded image sufficiently reproduced the desired image quality.
[Example 2] A design formed on a computer screen was recorded on a molded polyethylene terephthalate resin laminate can using a prototype ink jet ink using an ink jet printer having a piezo type head and a nozzle having a diameter of 40 µm. The recorded image sufficiently reproduced the desired image quality.
Example 3 A design formed on a computer screen was recorded in a molded glass container by an inkjet printer having a piezo-type head and a nozzle having a diameter of 40 μm using a prototype inkjet ink. The recorded image sufficiently reproduced the desired image quality.
[0020]
According to the present invention, an image can be formed on a three-dimensional molded product by ink jet. Furthermore, a variable image designed on a computer screen can be formed into a three-dimensional object using an inkjet recording system using an electron beam curable ink, so that it is easy to satisfy a product image according to personal tastes. Can be.

Claims (8)

A plurality of three-dimensional objects are continuously conveyed. A method for printing on a three-dimensional object, wherein printing or printing is performed with the inkjet ink of s, and then the ink is cured by irradiating with an electron beam. The printing method according to claim 1, wherein the polymerizable monomer is one kind or a combination of two or more kinds selected from the group consisting of a monofunctional monomer, a difunctional monomer, and a trifunctional monomer. 3. The printing method according to claim 1, wherein the irradiation of the electron beam is performed by a vacuum tube type electron beam irradiation device. The printing method according to claim 3, wherein an acceleration voltage of the electron beam is 10 kV to 150 kV. The printing method according to any one of claims 1 to 4, wherein the three-dimensional object is a beverage can. The printing method according to any one of claims 1 to 4, wherein the three-dimensional object is a resin laminate can. The printing method according to claim 1, wherein an ink-jet ink comprising a colorant, a dispersant, and a polymerizable monomer and containing no photopolymerization initiator is used. A printed matter printed by the printing method according to claim 1.