Active energy ray curable aqueous inkjet ink and printhead

Abstract

The present application relates to a method for producing a photosensitive polymerizable composition comprising water, a radically curable di(meth)acrylate monomer, a radically curable (meth)acrylate compound of formula (I): JPEG2024525334000022.jpg52149 (In the formula, X + Na + Or Li + , preferably Na + and one or more co-initiators. The present application also relates to a printed feature comprising a cured ink layer, a document comprising said printed feature, a thermal inkjet printhead comprising said ink, and a method of printing a feature made with said ink onto a substrate.

Description

Detailed description of the invention

[0001] [Field of Invention] This application relates to inkjet inks and printheads. More specifically, it relates to active energy ray-curable aqueous inkjet printing inks. The application also relates to thermal inkjet printheads containing the said inks.

[0002] [Background of the Invention] Active energy ray radical-curable inks are cured by a free radical mechanism consisting of the activation of one or more photoinitiators that can release free radicals by the action of active energy rays, particularly UV light, and then polymerization begins to form a cured layer.

[0003] UV energy is typically supplied by mercury lamps, especially medium-pressure mercury lamps. Mercury lamps require a large amount of energy, necessitate an efficient and expensive heat dissipation system, readily form ozone, and have a limited lifespan.

[0004] Recently, UV-LED-based lamps and systems have been developed for curing inks and coatings. In contrast to medium-pressure mercury lamps, which have emission bands in the UV-A, UV-B, and UV-C regions of the electromagnetic spectrum, UV-LED lamps emit radiation in the UV-A region. Furthermore, current UV-LED lamps emit quasi-monochromatic radiation, that is, they emit at only one wavelength, such as 365 nm, 385 nm, 395 nm, or 405 nm.

[0005] Conventionally, active energy ray inks are solvent-based inks; this means that all raw materials are solvent-soluble, and all technical results well known in the art relate to the use of solvent systems.

[0006] Solvent-based inks in the inkjet field are typically plagued by several significant problems: relatively low reliability of inkjet printheads, flammability and health risks, chemical compatibility with printhead materials, and unpleasant odors.

[0007] When using solvent-based inks, there is a possibility of chemical species migrating through packaging. This could lead to the ink's chemical components contaminating food and potentially exposing consumers to harmful substances. These issues must be considered for the sake of human health and the environment.

[0008] Therefore, there is a demand in this technology for alternatives to solvent-based inks. To solve the problems caused by solvent-based inks, aqueous active energy ray curable inks have been developed.

[0009] Water-based inks, such as those described in U.S. Patent Application Publication No. 2009136680, have been developed.

[0010] While solving the aforementioned problems is important, the water-based ink must exhibit at least the same chemical, mechanical, and technical properties as the solvent-based active energy ray ink when printed and crosslinked. More precisely, the developed ink must, Good ejectability of single-color or multi-ink printheads using thermal inkjet printheads. High reliability of ink loaded in our proprietary thermal inkjet printheads, High compatibility between various types of materials commonly used in printhead assembly (hydraulic adhesives, sponges, fibers, plastic reservoirs, photopolymers, etc.) and inks. Good ink decapping time, Short drying time for ink on printed media, High optical density, Good adhesion when cured on various substrates (plastic, metal, paper, etc.), High crosslinking density and degree of transformation after radiation irradiation, (In porous and / or non-porous media) advantageous durability or chemical resistance, To support good human health and environmental sustainability, there should be no or limited migration of chemicals (e.g., to food packaging or pharmaceutical packaging). Curing time / temperature conditions compatible with other parts of the printing tool This must be guaranteed.

[0011] The inventors have succeeded in formulating an aqueous ink that meets all the criteria outlined above. In order to use these formulations in all application areas, raw materials meeting specific requirements are necessary.

[0012] The first object of the present invention is an aqueous active energy ray radical-curable inkjet printing ink.

[0013] The described inks and printheads containing them are the result of fine-tuning their components to meet all the requirements of the final intended use.

[0014] This invention involves introducing an aqueous ink that ensures good adhesion to a substrate after irradiation with an active energy ray lamp, such as an LED lamp. The precise emission of energy from the lamp enables efficient reticulation of the reactive portions included in the ink formulation. As a result, a highly durable printed ink is obtained regardless of the substrate.

[0015] An innovative aspect of the present invention is that the developed formulation can achieve water resistance and solvent resistance when crosslinked. Furthermore, by using an appropriate pigment dispersion system in the colored ink formulation, discoloration due to contact with solvents such as water and ethanol can be avoided.

[0016] A second object of the present invention is a printed feature comprising a cured ink layer made from an active energy ray radical-curable inkjet printing ink.

[0017] Furthermore, the present invention relates to an article or document comprising a print head substrate and one or more print features according to a second object of the present invention.

[0018] Another object of the present invention is a thermal inkjet print head containing an ink for active energy ray radical curable inkjet printing according to the present invention.

[0019] Finally, the present invention also relates to a method of printing features on a substrate by thermal inkjet printing, including the step of applying the ink for active energy ray radical curable inkjet printing of the present invention.

[0020] [Summary of the Invention] Therefore, it is an object of the present invention to overcome the drawbacks of the prior art. This is i) at least 55 wt% water, ii) a radically curable di(meth)acrylate monomer which is polyethylene glycol di(meth)acrylate having 5 or more ethylene oxide groups per molecule, in an amount of about 2 wt% to about [20 wt%]; iii) a radically curable (meth)acrylate compound which is a hydroxyalkyl (meth)acrylate in which the alkyl group is methyl, ethyl, propyl, butyl or isobutyl, preferably a hydroxyalkyl (meth)acrylate in which the alkyl group is methyl, ethyl, propyl, butyl or isobutyl, in an amount of about 1 wt% to about 15 wt%; iv) about 1 wt% to about 5 wt% of formula (I): [Chemical formula] (wherein X + is Na + or Li + , preferably Na + ) photoinitiator v) one or more coinitiators selected from the group consisting of N-[3-(dimethylamino)propyl]methacrylamide and / or poly(methylhydroxysiloxane), in an amount of about 0.1 wt% to about 2 wt%; This is achieved by providing an active energy ray radical-curable inkjet printing ink, which includes and is a weight percentage relative to the total weight of the active energy ray radical-curable inkjet printing ink.

[0021] Furthermore, this specification describes a print feature comprising a cured ink layer made from an active energy ray radical-curable inkjet printing ink described herein, as well as an article or document comprising a substrate and one or more print features described herein.

[0022] Further described herein are a printhead; a nozzle layer comprising a plurality of nozzles formed through a nozzle layer; a plurality of ink ejection chambers corresponding to the plurality of nozzles; a plurality of heater resistors formed on the printhead substrate and corresponding to the plurality of ink ejection chambers, wherein each heater resistor is located in a different ink ejection chamber such that the ejection of an ink droplet through each nozzle is caused by heating one of the heater resistors located in the corresponding ink ejection chamber; and a thermal inkjet printhead comprising an active energy ray radical-curable inkjet printing ink as described herein.

[0023] Furthermore, this specification describes a method for printing a feature on a substrate by a thermal inkjet printing process, and a feature obtained thereby. a) a step of applying an active energy ray radical-curable inkjet printing ink as described herein by thermal inkjet printing to form an ink layer, preferably step a) being performed using a thermal inkjet printhead as described herein, b) The ink layer should be at least 150 mJ / cm² 2 The steps include exposing the ink layer to an active energy ray at a dose and curing the ink layer with an active energy ray source, This includes methods and features. [Brief explanation of the drawing]

[0024] [Figure 1A] Figures 1A and 1B are schematic diagrams of a printhead cartridge compatible with the active energy ray radical-curable inkjet printing ink of the present invention. [Figure 1B] Figures 1A and 1B are schematic diagrams of a printhead cartridge compatible with the active energy ray radical-curable inkjet printing ink of the present invention. [Figure 2A] Figures 2A and 2B are schematic diagrams of a multi-ink printhead cartridge compatible with the active energy ray radical-curable inkjet printing ink of the present invention. [Figure 2B] Figures 2A and 2B are schematic diagrams of a multi-ink printhead cartridge compatible with the active energy ray radical-curable inkjet printing ink of the present invention.

[0025] [Detailed description] The following definitions should be used to interpret the meaning of terms discussed in the specification and enumerated in the claims.

[0026] As used herein, the term “approximately” means that the quantity or value in question may be a specific value or another value in its vicinity. Generally, the term “approximately” when referring to a particular value is intended to indicate a range of ±10% of the value. For example, the expression “approximately 100” indicates a range of 100 ± 10, i.e., 90 to 110. Generally, when the term “approximately” is used, it can be expected that similar results or effects according to the present invention will be obtained within a range of 105% of the indicated value.

[0027] As used herein, the term "and / or" means that all or just one of the elements of the aforementioned group may be present. For example, "A and / or B" means "simply A, or simply B, or both A and B." In the case of "simply A," the term also extends to the possibility that B is absent, i.e., "simply A and no B."

[0028] As used herein, the term “contains” is intended to be non-exclusive and unrestricted. Therefore, for example, a coating composition containing compound A may also contain other compounds in addition to A. However, in its particular embodiments, the term “contains” also has more restrictive meanings of “essentially consisting of” and “consisting of,” so for example, “a fountain solution containing A, B and optionally C” may further consist of A and B (essentially), or A, B and C (essentially).

[0029] The term "active energy rays" refers to energy rays such as electron beams, ultraviolet rays, and infrared rays that affect the electron orbitals of an irradiated object, thereby triggering radical, cation, anion, or similar polymerization reactions. "Active energy ray curable ink" describes an ink that forms a hardened film when irradiated with these types of active energy rays.

[0030] As used herein, the term "UV" (ultraviolet) is intended to mean irradiation having wavelength components in the UV portion of the electromagnetic spectrum; typically 200 nm to 420 nm.

[0031] In the context of this invention, the term "(meth)acrylate" refers to acrylate and the corresponding methacrylate. Similarly, "di(meth)acrylate" refers to diacrylate and the corresponding dimethacrylate.

[0032] Where this specification refers to “preferred” embodiments / features, combinations of these “preferred” embodiments / features should also be considered disclosed insofar as such combinations of “preferred embodiments / features” have technical significance.

[0033] The radical-curable inks described herein are cured by a free radical mechanism, which consists of activation by the energy of one or more photoinitiators, in which free radicals are released and then the free radicals initiate polymerization.

[0034] If there is a large amount of water in the ink, it will hinder the strong evaporation from the nozzle, which is typical in solvent-based systems, and will render the solvent-based ink unreliable.

[0035] In one embodiment of the present invention, the active energy ray radical-curable inkjet printing ink is a UV radical-curable inkjet printing ink.

[0036] In one embodiment of the present invention, the active energy ray radical-curable inkjet printing ink of the present invention is an LED radical-curable inkjet printing ink.

[0037] More preferably, the active energy ray radical-curable inkjet printing ink of the present invention is a UV-LED radical-curable inkjet printing ink, that is, an ink that forms a cured film by irradiation with an LED lamp that emits ultraviolet light, hereinafter referred to as a "UV-LED lamp".

[0038] It is known in the art that a large number of reactive functional groups per monomer are used to produce printing elements with good properties, but the diacrylate described is i) To maintain a viscosity below a certain critical value for good ejection, enabling the manufacture of high-quality printing elements; ii) The more evaporation there is, the higher the viscosity, which limits ink evaporation in the printhead chamber during its lifespan. This makes it possible.

[0039] The described di(meth)acrylate monomers, which have five or more ethylene oxide groups per molecule, can prevent the precipitation of ink components that would be unsuitable for the final application.

[0040] The radical-curable inks described herein further comprise a radical-curable di(meth)acrylate monomer, which is polyethylene glycol di(meth)acrylate having five or more ethylene oxide groups per molecule, in an amount of about 2 wt% to about 20 wt%, preferably about 4 wt% to about 15 wt%, and most preferably about 5 wt% to about 12 wt%.

[0041] Preferably, the radical-curable di(meth)acrylate monomer is a polyethylene glycol di(meth)acrylate having seven or more ethylene oxide groups per molecule.

[0042] More preferably, the radical-curable di(meth)acrylate monomer is a polyethylene glycol di(meth)acrylate having 10 or more ethylene oxide groups per molecule.

[0043] In a preferred embodiment, the radical-curable di(meth)acrylate monomer has a molecular weight contained in about 300 to about 600 g / mol.

[0044] In the context of the present invention, the best radical-curable di(meth)acrylate monomer is the exemplified diacrylate (PEG diacrylate having ethoxylation number 10). This radical-curable di(meth)acrylate monomer imparts the ability of the ink to viscosize upon evaporation of water without significantly increasing the base viscosity.

[0045] The radical curable ink described in this specification further comprises a radical curable (meth)acrylate compound of about 1 wt% to about 15 wt%, preferably about 2 wt% to about 12 wt%, most preferably about 3 wt% to about 9 wt% of a hydroxyalkyl (meth)acrylate wherein the alkyl group is methyl, ethyl, propyl, butyl or isobutyl, preferably a hydroxyalkyl (meth)acrylate wherein the alkyl group is methyl, ethyl, propyl, butyl or isobutyl.

[0046] The radical curable ink described in this specification further comprises about 1 wt% to about 5 wt%, preferably about 1.5 wt% to about 4.5 wt%, most preferably about 2.2 wt% to about 3.8 wt% of a photoinitiator of formula (I)

Chemical formula

[0047] The photoinitiator enables correct curing of the ink of the present invention without the need to use an excessive amount of active ray energy.

[0048] In a preferred embodiment, the photoinitiator of formula (I) is BAPO - ONa.

Chemical formula

[0049] The photoinitiator of formula (I) can be incorporated into the composition according to the present invention at a lower concentration than photoinitiators of the prior art, such that the risk associated with migration of unbound photoinitiator or photoinitiator decomposition products is reduced, even when a photoinitiator with a low migration potential is used.

[0050] This is particularly advantageous for UV inkjet compositions because relatively high concentrations of photoinitiators are usually required to help overcome the effects of oxygen inhibition, an inherent problem associated with UV curing of inkjet compositions in air. It is quite common for UV inkjet compositions to contain a photoinitiator blend of 8% w / w or higher to achieve the desired UV curing reaction.

[0051] In particular, any of the photoinitiators used in the compositions according to the present invention preferably exhibit a migration of less than 10 ppb.

[0052] The migration potential of a given photoinitiator is measured by the method described in the EFSA Guideline - Memo on Guidance for FCM Assessment, August 7, 2008.

[0053] The migration potential of a given photoinitiator is measured at 60°C.

[0054] The radical-curable inks described herein further comprise one or more co-initiators selected from the group consisting of N-[3-(dimethylamine)propyl]methacrylamide and / or poly(methylhydrosiloxane) in an amount of about 0.1 wt% to about 2 wt%, preferably about 0.2 wt% to about 1.5 wt%, and most preferably about 0.2 wt% to about 1.2 wt%.

[0055] A co-initiator selected from the group consisting of N-[3-(dimethylamine)propyl]methacrylamide and / or poly(methylhydrosiloxane) imparts a sufficient degree of crosslinking to the ink and then provides sufficient water resistance to the cured ink.

[0056] In one embodiment of the present invention, the active energy ray radical-curable inkjet printing ink further comprises about 1.0 wt% to about 15 wt%, preferably about 2 wt% to about 12 wt%, most preferably about 3 wt% to about 10 wt%, of a colorant, where the weight percentage is relative to the total weight of the active energy ray radical-curable inkjet printing ink. The colorants described herein include pigments and / or dyes.

[0057] The colored ink formulations described herein (i.e., including one or more colorants, i.e., one or more pigments and / or dyes) may be used to print images and / or colored text on various types of materials, ensuring excellent durability over time on the printed support.

[0058] Examples of dyes, though not limited to them, include azo dyes, anthraquinone dyes, xanthene dyes, azine dyes, and combinations thereof. Organic pigments may be a single pigment or a combination of pigments, such as pigment yellow numbers 12, 13, 14, 17, 74, 83, 114, 126, 127, 174, 188; pigment red numbers 2, 22, 23, 48:1, 48:2, 52, 52:1, 53, 57:1, 112, 122, 166, 170, 184, 202, 266, 269; pigment orange numbers 5, 16, 34, 36; pigment blue numbers 15, 15:3, 15:4; pigment violet numbers 3, 23, 27; and / or pigment green number 7. The inorganic pigment may be any of the following non-limiting pigments: iron oxide, titanium dioxide, chromium oxide, ferric ammonium ferrocyanide, iron oxide black, pigment black number 7, and / or pigment white numbers 6 and 7. Other organic and inorganic pigments and dyes, as well as combinations to achieve the desired color, may also be used.

[0059] The colorant is preferably dispersed in a mixture containing one or more mono(meth)acrylate monomers and / or one or more di(meth)acrylate monomers and / or one or more tri(meth)acrylate monomers before being incorporated into the ink.

[0060] Alternatively, colorant-free active energy ray radical-curable inkjet printing inks may be used to print images and / or text, and may optionally be used as a cover to protect images or text printed with colored or black inks.

[0061] In one embodiment, the active energy ray radical-curable inkjet printing ink further contains about 0.05 wt% to about 2 wt%, preferably about 0.1 wt% to about 1.8 wt%, most preferably about 0.15 wt% to about 1.5 wt%, of a nonionic fluorinated surfactant, where the weight percentage is relative to the total weight of the active energy ray radical-curable inkjet printing ink.

[0062] The addition of the nonionic fluorinated surfactant reduces the surface tension of the ink, thereby allowing the ink to spread properly on the substrate surface to be printed on.

[0063] Preferably, the nonionic fluorinated surfactant is a nonionic polymeric ethoxylate fluorinated surfactant and / or a nonionic polymeric acrylic fluorinated surfactant.

[0064] More preferably, the nonionic fluorinated surfactant is selected from the group including Hexafor672(MAFLON) and Hexafor644-D(MAFLON).

[0065] In one embodiment, the active energy ray radical-curable inkjet printing ink further comprises about 1 wt% to about 5 wt%, preferably about 1.5 wt% to about 4.5 wt%, most preferably about 2.2 wt% to about 3.8 wt%, of one or more radical-curable oligomers having a molecular weight of at least 80 g / mol, where the weight percentage is relative to the total weight of the active energy ray radical-curable inkjet printing ink.

[0066] The radical-curable oligomer having a molecular weight of at least 80 g / mol enhances the curing and resistance of the ink.

[0067] Preferably, the radical-curable oligomer having a molecular weight of at least 80 g / mol is selected from the group consisting of tri(meth)acrylate oligomers, tetra(meth)acrylate oligomers, hexa(meth)acrylate oligomers, and mixtures thereof.

[0068] More preferably, the radical-curable oligomer having a molecular weight of at least 80 g / mol is one or more hexa(meth)acrylate oligomers having a molecular weight of at least 80 g / mol.

[0069] In a more preferred embodiment, the radical-curable oligomer having a molecular weight of at least 80 g / mol is Photomer Aqua 6903 (IGM).

[0070] In one embodiment, the hydroxyalkyl (meth)acrylate of iii) is a hydroxyalkyl mono(meth)acrylate monomer in which the alkyl group is methyl, ethyl, propyl, butyl, or isobutyl, preferably a 4-hydroxyalkyl mono(meth)acrylate monomer in which the alkyl group is methyl, ethyl, propyl, butyl, or isobutyl, more preferably a 4-hydroxybutyl mono(meth)acrylate monomer.

[0071] In one embodiment, the active energy ray radical-curable inkjet printing ink further comprises about 0.1 wt% to about 3 wt%, preferably about 0.15 wt% to about 2.25 wt%, most preferably about 0.2 wt% to about 1.5 wt%, of a second photoinitiator, where the weight percentage is relative to the total weight of the active energy ray radical-curable inkjet printing ink.

[0072] The presence of a second photoinitiator enhances the curing of the ink.

[0073] Preferably, the second photoinitiator comprises one or more thioxanthone compounds having a molecular weight of less than 400 g / mol, preferably 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chlorothioxanthone, 2-chloro-4-isopropoxythioxanthone, and mixtures thereof, the weight percentage being relative to the total weight of the active energy ray radical-curable inkjet printing ink.

[0074] More preferably, the second photoinitiator is 2-isopropylthioxanthone.

[0075] Preferably, the active energy ray radical-curable inkjet printing ink has a viscosity in the range of about 0.5 to about 10 c Poise at 25°C.

[0076] Those skilled in the art are familiar with methods for measuring the viscosity of fluids. For example, and without being bound by such examples, one may measure ink viscosity using RHEOLOGICA VISCOTECH-(RD312) according to the manufacturer's instructions.

[0077] Preferably, the active energy ray radical-curable inkjet printing ink has a viscosity in the range of about 1 to about 9 c-poise, more preferably about 2 to 8 c-poise, as measured at 25°C.

[0078] The viscosity of the ink and the amount of water give the ink the desired reliability of the print head during its lifespan, which is, Throughout the entire shelf life of the ink cartridges, the printhead will not exhibit significant nozzle failures. The printhead does not exhibit significant "decapping problems" even during print pauses exceeding 3 minutes. The print head operates properly at the frequencies typically required for applications such as card printing, coding, and marking. It means that.

[0079] For a formulation to be stable and printable by a thermal inkjet printhead, it must contain only water-soluble or dispersible raw materials (monomers, photoinitiators, surfactants, co-initiators, etc.).

[0080] The compositions according to the present invention may also contain other components that enable the performance of the intended purpose. These components include, but are not limited to, stabilizers, wetting aids, slip agents, acrylic polymers, defoamers, fillers, rheological aids, and inert resins such as amine synergies.

[0081] The radical-curable inks described herein may further contain one or more additional surfactants to ensure proper wetting of the substrate and to reduce the surface tension of the ink.

[0082] In preferred embodiments of the present invention, any component used in the composition according to the present invention preferably exhibits migration of less than 10 ppb.

[0083] The migration potential of a given component is measured by the method described in the EFSA Guideline - Memo on Guidance for FCM Assessment, August 7, 2008.

[0084] The migration potential of a given component is measured at 60°C.

[0085] Another aspect of the present invention is a printed feature comprising a cured ink layer made from the above-described active energy ray radical-curable inkjet printing ink.

[0086] The present invention also relates to an article or document comprising a substrate and one or more of the printing features listed above.

[0087] Typical examples of substrates include, but are not limited to, fibrous substrates, preferably cellulose fiber-based substrates such as paper and paper-containing materials, polymer materials, composite materials (e.g., substrates obtained by laminating a paper layer with a polymer film), metals or metallized materials (e.g., aluminum), silicon, ceramics, glass, ceramics, and combinations thereof. Typical examples of polymer substrates include ethylene or propylene homopolymers and copolymers such as polypropylene (PP) and polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polyamide (PA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET).

[0088] Preferably, the base material of the article or document is a paper-containing material, a polymer-based material, a composite material, a metal, glass, a ceramic, or any combination thereof.

[0089] Another aspect of the present invention is a thermal inkjet printhead comprising: a printhead substrate; a nozzle layer including a plurality of nozzles formed through a nozzle layer; a plurality of ink ejection chambers corresponding to the plurality of nozzles; a plurality of heater resistors formed on the printhead substrate and corresponding to the plurality of ink ejection chambers, each heater resistor located in a different ink ejection chamber such that the ejection of an ink droplet through each nozzle is caused by heating one of the heater resistors located in the corresponding ink ejection chamber; and an active energy ray radical curable inkjet printing ink according to the present invention.

[0090] Thanks to the aforementioned printhead and the chemical properties of the developed ink, it is possible to successfully meet market requirements in terms of the number of printable substrates, printing speed, flexibility of the printable area, and system reliability.

[0091] Furthermore, as mentioned above, the presence of a large amount of water in the ink used in the writing system prevents the rapid evaporation typical of nozzles in solvent-based systems, thus the system is inherently highly reliable.

[0092] The system's responsiveness, along with the aforementioned chemical and physical properties of the ink and the unique features of its printhead, provides a complete system that meets the extremely demanding printing requirements of the market.

[0093] The present invention relates to a method for printing features onto a substrate by a thermal inkjet printing process, a) The step of applying the active energy ray radical-curable inkjet printing ink according to the present invention by thermal inkjet printing to form an ink layer, b) The ink layer should be at least 150 mJ / cm² 2 The steps include exposing the ink layer to an active energy ray at a dose and curing the ink layer with an active energy ray source. This includes methods.

[0094] Preferably, step a) of the process is performed using a thermal inkjet printhead as listed above.

[0095] Preferably, the active energy source in step b) is a UV-LED source.

[0096] Preferably, step b) of the process consists of exposing the ink layer to one or more wavelengths between approximately 380 nm and approximately 420 nm. Typically, commercially available UV-LED sources use one or more wavelengths such as 365 nm, 385 nm, 395 nm, and 405 nm.

[0097] Preferably, the process speed range is within approximately 0 to approximately 60 m / min.

[0098] The velocity range is measured at room temperature.

[0099] Preferably, the drying time range of the process is within about 0.02 seconds to about 1 second, more preferably within about 0.07 seconds to about 0.44 seconds.

[0100] In one embodiment of the present invention, the printing frequency is higher than approximately 7 kHz. In a preferred embodiment, the printing frequency is higher than approximately 8 kHz. More preferably, the printing frequency is higher than approximately 9 kHz.

[0101] In one embodiment of the process, an ink layer made of an active energy ray radical-curable inkjet printing ink is transparent, and the ink is applied at least partially in the form of one or more indicia on a print feature.

[0102] The processes described herein are particularly suitable for generating one or more printed features on a substrate, the one or more printed features may be continuous or discontinuous.

[0103] These and other purposes, advantages, and features of the present invention will become apparent to those skilled in the art upon reading the details of the methods and formulations described more fully below. [Examples]

[0104] The present invention will be described in more detail below with reference to non-limiting embodiments.

[0105] A. Ink according to the present invention Several inks were formulated according to the instructions of the present invention: Compositions E1 to E5 of these inks are disclosed below. [Table 1]

[0106] (Ink preparation) All the compounds used in this process were commercially available and were used as received without any further purification.

[0107] The raw materials were introduced into a glass container containing a magnetic stirring rod in the following order: monomer, water; surfactant, co-initiator, photoinitiator, dye / pigment, at room temperature. The resulting mixture was then stirred at room temperature for 45–60 minutes. The solution was then filtered, and the filtrate was introduced into the printhead under vacuum conditions. Filtration was performed using a Versapore filter with a pore size of 0.3–3.0 μm. The resulting ink was introduced into the printhead by an ink unit (Xynertech semi-automatic filling system).

[0108] The colored inks were prepared similarly using the same process, with the following composition: [Table 2]

[0109] B. Comparative Ink To evaluate whether the ink of the present invention achieved at least the same chemical, mechanical, and technical performance as solvent-based UV inks when printed and UV crosslinked, the ink of the present invention was compared with the following inks prepared by prior art. [Table 3]

[0110] C. Comparison The ink was tested against several criteria that indicate the requirements expected to meet market needs. Among them: The degree of reticularization achieved after the hardening process must be high. The viscosity must be sufficiently low to ensure proper ink ejection. UV water-based ink formulations contain components that have been researched to provide polymers with high adhesion to a vast number of printable materials. The mechanical durability of UV water-based inks is also essential; tests were conducted to evaluate their adhesion performance on printed surfaces. [Table 4]

[0111] (Printing test) The printhead types used during the printing tests were single-ink and multi-ink printheads. The printing tests were performed using the FARGO INK1000 card printer and the Neopost printer system. Curing was performed using a commercially available Phosen FJ100 (16W) UV lamp (for "dynamic" printing tests, colored inks) at a distance of 4 mm, emission wavelength of 395 nm, window size of 2 × 7.5 cm, and belt speed of 60 m / min, and using an internally developed UV lamp (for "static" printing tests, transparent inks). The energy values ​​imparted by irradiation were measured using a UV-Design radiometer UV-MC Microprocessor Integrator. The degree of crosslinking of the formulation after printing and irradiation was determined by FTIR measurement using a Nicolet FT-IR Nexus spectrometer.

[0112] General experimental procedure ("dynamic" printing test): A single-ink printhead containing the desired formulation is introduced into the Neopost printer system. The substrate is placed at the top of a conveyor belt with adjustable speed. The substrate then reaches the printhead station (where printing takes place) and a UV lamp (where it is irradiated). Finally, the printed media is collected.

[0113] General experimental procedure ("static" printing test): A printhead containing multiple inks with the desired formulation is introduced into the FARGO INK1000 card printer. A card is loaded into the machine and heated to the desired temperature. Then, printing is done on the card, and it is "statically" irradiated with a UV lamp. After the irradiation process, the card is ejected from the printer.

[0114] (Crosslinking measurement process) Evaluation of the degree of material transformation, measured by FTIR spectroscopy.

[0115] Typical monomer signals are measured using an FTIR instrument. Monomer reactions are monitored by observing infrared vibrational peaks associated with acrylate functional groups that disappear as a function of UV energy dose.

[0116] (Chemical resistance testing process) Chemical resistance evaluation is performed by immersing the sample in water for 24 hours. If the printing ink remains unchanged, the test is OK. If the cured ink is removed after immersion, the water resistance is OK. If the cured ink is not removed by water but is altered anyway, the ink is considered to have imperfect water resistance.

[0117] (Viscosity method process) Ink viscosity is measured using the RHEOLOGICA VISCOTECH-(RD312) tool, which is equipped with a constant temperature bath to maintain the precise temperature (25°C) of the ink during measurement.

[0118] Viscosity measurements were performed as reported below: A volume of 0.925 ml of ink is deposited onto a temperature-controlled plate using a graduated pipette, taking care to avoid creating air bubbles. The measurement is initiated via the software: As the viscometer head lowers and the rotating plate reaches its connection with the thermostat-controlled base, the plate begins to rotate for a few seconds. The creep resistance or viscosity of the ink is measured and expressed in mPa*s (same as C Poise).

[0119] (Surface tension method process) The surface tension of the ink is measured using a KRUSS K12-(RD337) TENSIOMETER tool equipped with a constant temperature chamber to maintain the desired temperature of the ink during measurement.

[0120] Surface tension measurements should be performed as reported below: The platinum plate is washed with 37% hydrochloric acid followed by deionized water. Use a Bunsen flame to heat the platinum plate. Fill the glass cup with ink up to two-thirds full. Insert the glass cup into the appropriate slot to enable automatic ink thermosetting. (Using the appropriate knob) bring the glass cup close enough to the platinum plate so that the ink surface just barely touches the bottom edge of the plate. The instrument starts the measurement. Surface tension measurements are displayed on the tool display and expressed in dynes / cm.

[0121] (Taber test) The Taber test result refers to the number of wear cycles required for each ink tested to reach its stopping point. The stopping point is reached with a 50% reduction from the initial optical density measurement (ANSI INCITS 322-2008, Card Durability Test Method).

[0122] Sample preparation: The sample is prepared by printing a PVC card at a temperature of 70°C in 16-layer printing mode (smart single-ring printing mode) and irradiating it with UV light during printing.

[0123] Friction and abrasion resistance tests are performed using colored and clear inks, respectively. A clock meter tool is used to evaluate abrasion resistance: a piece of cotton cloth is rubbed 100 times on an aluminum sheet with a hardened ink (without applying weight to the arm). The evaluation is performed by measuring the change in colorimetric coordinates and expressed as a ΔE value.

[0124] The thickness of the deposit on the surface can be 1 to 50 μm depending on the desired wear resistance, and can be measured with a mechanical profiler (TENCOR) or an optical microscope.

[0125] D. Colored ink The colored inks (E6-E8) of the present invention were prepared, and tests were conducted to evaluate their curing ability.

[0126] The minimum energy dose required to achieve a conversion rate of 70% or more in the three colored inks is at least 50 mJ / cm². 2 That is the case.

[0127] The additional properties are reported in the table below: [Table 5]

[0128] (Smudge test) The smudge test results refer to the color change of the sample after rubbing it 100 times with a weight of 500g on the arm of a clock meter tool, and are expressed by the ΔE value.

[0129] Sample preparation: Samples are prepared by printing in 4-layer printing mode at 70°C, using a larger amount of ink (18% more by weight than in smart singling mode), and then passing them through a UV lamp four times after printing.

[0130] E. Additional Exams Additional tests were conducted to complete the comparison between the ink according to the present invention and that of the prior art.

[0131] (Other phosphine oxides) C5-C6 are based on E3, but as an exception, IRGACURE® 819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) was used instead of LFC3587. The exact composition is shown below. [Table 6]

[0132] Next, E3 was tested against these C5 and C6 inks by its crosslinking ability under UV light.

[0133] The resulting comparative ink exhibited extremely insufficient curing performance. [Table 7]

[0134] The test was repeated using lithium phenyl-2,4,6-trimethylbenzoylphosphinate instead of LFC3587.

[0135] Lithium phenyl-2,4,6-trimethylbenzoylphosphinate ("LAP") has the following formula: [ka]

[0136] [Table 8]

[0137] The degree of crosslinking of the comparative ink after UV irradiation is far from satisfactory. The amount of UV energy used to photocrosslink the ink is high (1000 mJ / cm²). 2 Despite this, the degree of conversion of the acrylate functional group is less than 50%.

[0138] (Triethanolamine instead of the claimed co-initiator) To evaluate the performance of triethanolamine in the aqueous formulation of the present invention, a new ink (C8) was prepared. This ink is similar to E5, but contains triethanolamine instead of polymethylhydrosiloxane (used in the same proportion as in E5). [Table 9]

[0139] (Other thioxanthones) Inks similar to those used in E6-E8 were employed, except that 0.5 wt% Omnipol TX (polymeric thioxanthone photoinitiator) was used instead of 1.0 wt% Omnirad ITX. The resulting comparative inks exhibited very poor curing performance.

[0140] (Acrylates with fewer than 5 ethylene oxide groups) To evaluate the feasibility of using diacrylates with n values ​​less than 5, three colored inks were prepared containing diacrylates with MW = 258 g / mol (n=3). [Table 10]

[0141] The inks were placed in glass jars and stored at room temperature for two days, after which they were checked for sedimentation. Sedimentation was particularly visible in C9 (cyan), fairly visible in C10 (magenta), and slightly visible in C11 (yellow). Sedimentation also occurred in the transparent formulation C12.

[0142] (Transition test experiment) The purpose of the migration experiment is to evaluate whether molecular ITX (which is low molecular weight in terms of molecular weight) does not migrate through the printing substrate, in accordance with European standards.

[0143] Due to their typical chemical behavior as type II photoinitiators, ITX molecules maintain their molecular structure after UV irradiation without photocleavage or chemical bonding to polymeric macromolecules, making them more likely to migrate outside the cured layer.

[0144] For this reason, the composition has been extensively studied in order to evaluate the transition values ​​of ITX.

[0145] The migration of these substrates was evaluated under set-off conditions after cured samples were stored at 60°C for 10 days in contact with 95% ethanol and 10% ethanol as simulated fluids.

[0146] The experiment will be conducted in accordance with the EFSA guidelines (EFSA Guidelines - Memo on Guidance for FCM Assessment 2008.08.07).

[0147] (Analysis method) This analytical method utilizes U-HPLC technology to enable confirmation and quantification using simulated fluids.

[0148] The detection limit is the total amount of photoinitiator detected in the simulated fluid and is expressed in ppb. The detection limit for Omnirad ITX is 10 ppb.

[0149] The following are printing substrates prepared using a Phoseon FJ-100 UV lamp: [Table 11]

[0150] (Transition test conditions) The specific migration of the photoinitiator is measured by indirect contact (set-off). For the indirect contact test, the surface of each cured sample is pressed onto an unprinted substrate at 20 kg (196 N) at room temperature for 10 days.

[0151] After the set-off, the base material was cut to the following dimensions. Total surface = 2.54cm x 2.54cm = 6.45cm 2

[0152] Each sample is cut from a different coated foil using a cutter.

[0153] Surface / volume ratio: 0.6 cm 2 / ml (according to EFSA guidelines requiring a surface / volume ratio of 0.5-2).

[0154] Each sample is placed in a 20ml vial in contact with 10ml of accurately measured simulated fluids: 95% ethanol and 10% ethanol.

[0155] The sample was completely covered and stored in a water bath at 60°C for 10 days under dark conditions.

[0156] Each vial is tightly sealed and properly labeled to prevent evaporation of the simulated fluid.

[0157] After storage, each vial is cooled to room temperature, and the filtered simulated fluid is transferred to a clean vial (20 ml).

[0158] Furthermore, a standard substrate (unprinted) is left in contact with the simulated fluid under the same conditions to obtain a blank solution.

[0159] All transition tests will be repeated twice.

[0160] Each sample of the simulated fluid is analyzed by UHPLC equipped with a UV diode array and an MS single-quad detector.

[0161] The results are expressed as ppb of the simulated fluid.

[0162] The analysis of each sample will be repeated three times.

[0163] (Results from blank samples) Along with the identification of the samples, a summary of the analytical results (average values ​​of the three samples) is reported in Table 12 below. The results are expressed in ppb content for both simulated fluids. [Table 12] [Table 13] [Table 14]

[0164] In conclusion, it was found that ITX has transition values ​​below the acceptable limit of 10 ppb.

[0165] Furthermore, LFC3587 was not detected at levels higher than the detection limit of the analytical instrument used. This is more predictable due to the chemical behavior of this type I photoinitiator, which undergoes photocleavage when irradiated with UV light, and the initiator chemical by-product remains chemically bound to the polymer.

[0166] The exemplary black ink formulations (E3 and E5) have passed migration tests according to European standards and are therefore suitable for pharmaceutical and coding / marking applications, as well as the food and beverage sector.

[0167] The curing ink also exhibits moisture resistance, and the printed image remains legible even after storage at -15°C and 4°C, as well as after thermal cycling between these two temperatures and room temperature.

[0168] The curing ink also demonstrated high lightfastness equivalent to three years of exposure to direct sunlight (outdoor tests conducted using an XXL+ sunlight testing apparatus equipped with a xenon lamp).

[0169] Sunlight testing method: The optical density of the sample is measured using a reflectance densitometer (ANSI STATUS I): GretagMacbeth DensyEye700. The sample is exposed to a xenon lamp for 12 days without a window filter (illumination intensity: 0.35 watts / m² on a card surface at 340 nm). 2 (Test room temperature: 50℃±5℃). Final optical density measurement: The final evaluation is performed by measuring the percentage loss of optical density. The final evaluation of outdoor exposure is performed considering the percentage loss of optical density within the following ranges. [Table 15]

[0170] All sunlight test results for the colored inks were good, with OD loss percentages of 15% or less.

[0171] The sunlight test results for the black ink were also good, with OD loss of 0% to 10%.

[0172] Considering the tests shown previously, the lamp-cured development formulation meets the following requirements: High crosslinking density, High conversion rate (percentage of covalent bond formation), High adhesion to printed surfaces (paper, plastic, metal), High chemical resistance to water and ethanol. High friction resistance and wear resistance, High sunlight resistance It will be readily apparent to those skilled in the art that this can be guaranteed.

[0173] Therefore, the developed formulation achieves the performance of a solvent-based UV ink.

[0174] Exemplary formulations (black and colored) meet the above requirements, and the black ink formulation in particular is suitable for both food and beverage applications.

[0175] F. Print head according to the present invention The present invention also relates to a printhead cartridge configured for use with the ink described above. Such a printhead cartridge, shown in Figure 1A, consists of a printhead ejection assembly 1 comprising a printhead chip 2 coupled to a flexible print circuit 3. This chip houses electrical and hydraulic components for directing ink to various ejection points, providing energy as needed, and generating ink droplets for printing. A nozzle plate is attached to the top surface of the chip, providing nozzles for ink ejection. The entire ejection assembly is then coupled to a cartridge 4, which includes an ink reservoir closed by a lid 5. Suitable ink slots 6 are provided in the cartridge body 7, shown in Figure 1B, so that ink can reach the printhead chip and, depending on the printhead layout, reach the microfluidic circuit through machined slots 8 in the chip or from the edges of the chip.

[0176] The multi-ink printhead cartridge shown in Figure 2A naturally has multiple ink reservoirs and multiple ink paths leading to the printhead. To prevent the inks from mixing, they are hydraulically isolated from each other. Since the cartridge is made up of various parts and materials, the joints between the parts must ensure not only good bonding but also a complete and permanent ink seal in the areas in contact with the ink. There are many ways to bond various materials: the use of a suitable adhesive has many advantages if it can be accurately distributed to the bonding area. For example, a suitable adhesive can be distributed on the plane around the flow path 6 of the main body to ensure a secure bond with the tip and to further seal the underside of the tip's slot 8 well. In this way, the ink can flow from the reservoir to the tip without mixing or leaking.

[0177] Furthermore, the cartridge bodies of multi-ink printheads require special manufacturing processes: for example, in the case of three ink cartridges with parallel nozzle arrangements, the parts cannot be obtained at once in a single molding process by casting technology: more specifically, as shown in Figure 2B, the cartridge body 7 has three ink reservoirs 9 and is divided by a wall 10. Due to the small lateral distance between the different color nozzle arrangements, it is impossible to manufacture three separate linear ink paths while maintaining the required hydraulic characteristics and suitable structural robustness. A possible solution is to use two additional parallel slide inserts (as described in European Patent No. 189622) to create the desired fluid structure inside the cartridge body. Once the casting process is complete, two windows 11 remain on the side 12 of the cartridge by removing the two slide inserts: these windows must be closed by suitable plugs 13 that are conveniently coupled to the cartridge. The downward vertical axis y in the figure coincides with the ink ejection direction of the printhead. A possible method for coupling the plugs is to use an adhesive distributed along the flat, recessed surfaces 14 of the window boundaries. This ensures a tight seal at the opening, preventing ink leakage from the reservoir. Due to the front flange of the plug and the corresponding recess in the cartridge body, UV-curing adhesives are not suitable for sealing purposes. The adhesive is not efficiently illuminated by ultraviolet light, resulting in insufficient polymerization and poor bonding and sealing performance.

[0178] Regarding electrical control, the printhead is controlled by C-MOS technology. This technology is more expensive than conventionally used technologies, but it is more powerful. Certain tools improve the logic control of the printhead, allowing it to be operated while significantly saving energy. C-MOS technology allows for greater design flexibility, enables more complex electronic integration on the chip, and reduces space and energy consumption.

[0179] In modern times, thanks to the system's responsiveness, the aforementioned chemical and physical properties of the inks, and the unique features of the printheads, complete systems can meet even the most demanding printing requirements.

[0180] In any case, since other embodiments may exist, the present invention cannot and should not be limited to the embodiments specifically described in this document. The present invention extends to any equivalent means and combinations of technically operating means.

Claims

1. i) at least 55 wt% water ii) A radical-curable di(meth)acrylate monomer, which is polyethylene glycol di(meth)acrylate having five or more ethylene oxide groups per molecule, in an amount of 2 wt% to 20 wt%; iii) A radical-curable (meth)acrylate compound comprising 1 wt% to 15 wt% of a hydroxyalkyl (meth)acrylate in which the alkyl group is methyl, ethyl, propyl, butyl, or isobutyl, preferably a hydroxyalkyl (meth)acrylate in which the alkyl group is methyl, ethyl, propyl, butyl, or isobutyl; iv) Formula (I) for 1 wt% to 5 wt%: 【Chemistry 1】 (In the formula, X ＋ is Na ＋ or Li ＋ Preferably Na ＋ (is) photoinitiator v) 0.1 wt% to 2 wt% of one or more co-initiators selected from the group consisting of N-[3-(dimethylamine)propyl]methacrylamide and / or poly(methylhydrosiloxane); Active energy ray radical-curable inkjet ink, including, and the weight percentage is relative to the total weight of the active energy ray radical-curable inkjet ink.

2. The active energy ray radical-curable inkjet printing ink according to claim 1, wherein the radical-curable di(meth)acrylate monomer, which is a polyethylene glycol di(meth)acrylate having five or more ethylene oxide groups per molecule, has a molecular weight contained in 300 to 600 g / mol.

3. The active energy ray radical-curable inkjet printing ink according to claim 1 or 2, further comprising 1.0 wt% to 15 wt% of a colorant, wherein the weight percentage is relative to the total weight of the active energy ray radical-curable inkjet printing ink.

4. The active energy ray radical-curable inkjet

5. The active energy ray radical-curable inkjet printing ink according to claim 1 or 2, wherein the hydroxyalkyl (meth)acrylate of iii) is a hydroxyalkyl mono(meth)acrylate monomer in which the alkyl group is methyl, ethyl, propyl, butyl, or isobutyl, preferably a 4-hydroxyalkyl mono(meth)acrylate monomer in which the alkyl group is methyl, ethyl, propyl, butyl, or isobutyl, more preferably a 4-hydroxybutyl mono(meth)acrylate monomer.

6. The active energy ray radical-curable inkjet ink according to claim 1 or 2, further comprising 0.1 wt% to 3 wt% of a second photoinitiator, the weight percentage being relative to the total weight of the active energy ray radical-curable inkjet ink, wherein the second photoinitiator comprises one or more thioxanthone compounds having a molecular weight of less than 400 g / mol, preferably 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chlorothioxanthone, 2-chloro-4-isopropoxythioxanthone, and mixtures thereof.

7. An active energy ray radical-curable inkjet printing ink according to claim 1 or 2, having a viscosity in the range of 0.5 to 10 c Poise at 25°C.

8. A printable feature comprising a cured ink layer made from an active energy ray radical-curable inkjet printing ink according to claim 1 or 2.

9. An article or document comprising a substrate and one or more print features as described in claim 8.

10. The article or document according to claim 9, wherein the substrate is a paper-containing material, a polymer-based material, a composite material, a metal, glass, a ceramic, or any combination thereof.

11. A thermal inkjet printhead comprising: a printhead substrate; a nozzle layer including a plurality of nozzles formed through a nozzle layer; a plurality of ink ejection chambers corresponding to the plurality of nozzles; a plurality of heater resistors formed on the printhead substrate and corresponding to the plurality of ink ejection chambers, wherein each heater resistor is located in a different ink ejection chamber such that the ejection of an ink droplet through each nozzle is caused by heating one of the heater resistors located in the corresponding ink ejection chamber; and the active energy ray radical curable inkjet printing ink according to claim 1 or 2.

12. A method for printing features onto a substrate using a thermal inkjet printing process, a) The step of applying the active energy ray radical-curable inkjet printing ink according to claim 1 or 2 by thermal inkjet printing to form an ink layer, b) The ink layer is at least 150 mJ / cm² ２ The steps include exposing the ink layer to an active energy ray at a dose and curing the ink layer with an active energy ray source. A method that includes this.

13. The method according to claim 12, wherein step a) is performed using the thermal inkjet print head described in claim 11.

14. The method according to claim 12, wherein step b) is to expose the ink layer to one or more wavelengths between 380 nm and 420 nm.

15. The method according to claim 12, wherein the ink layer made of an active energy ray radical-curable inkjet printing ink is transparent, and the ink is applied at least partially in the form of one or more marks on a printed feature.

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