Method and system for digital printing with controlled matte

Abstract

A method and system for digital printing with controlled matte. The method comprises: inkjet-printing a digital image, by depositing curable coloured ink on a substrate (2); and, by means of curing radiation, partially solidifying the deposited coloured ink, microfolding the surface of the deposited coloured ink, and completely solidifying the deposited coloured ink after its surface has been microfolded. To obtain printouts or printout areas with different degrees of matte, the curing radiation for partial solidification and / or the curing radiation for microfolding are applied with a level of radiation intensity that is different for each printout or printout area of the digital image.

Description

[0001] DIGITAL PRINTING PROCEDURE AND SYSTEM WITH MATTE CONTROL

[0002] DESCRIPTION

[0003] OBJECT OF THE INVENTION

[0004] The present invention relates to a method and system for obtaining decorative prints with a controlled degree of matte or gloss, by means of inkjet printing.

[0005] The invention is applicable, for example, to the production of cardboard packaging, for which there is a market demand to easily provide matte designs.

[0006] BACKGROUND OF THE INVENTION

[0007] To obtain decorative inkjet prints with a controlled degree of matte or gloss, two distinct groups of solutions are known in the state of the art.

[0008] A first group of known solutions is based on the application of a curable varnish that is spread over the inkjet-printed decoration. The varnish undergoes a microfolding process, which creates micro-folds on its surface. These micro-folds, through the optical effect of light scattering across the varnish's microstructure, produce the required matte appearance.

[0009] To perform the microfolding, the partially cured varnish is subjected to a special curing radiation called excimer radiation. A higher degree of matte finish is achieved by partially curing the varnish to a lesser extent before applying the excimer radiation. For example, patent document DE 102006042063 A1 describes such a solution.

[0010] As an alternative to excimer radiation curing for microfolding, it is also known that the varnish used incorporates curing-promoting agents or photoinitiators located primarily in a surface area of ​​the varnish. For example, patent document DE 102016120878 A1 describes such a solution.

[0011] A second group of known solutions involves adjusting the size of the ink droplets deposited in the inkjet-printed decoration by adjusting the curing intensity of the print. By modifying the curing intensity level, greater or lesser contraction or expansion of the droplets can be achieved.

[0012] The matte finish is achieved in this case by the optical effect of the varying reflection of light as it strikes the print, depending on the size or spread of the deposited droplets. Greater droplet spread or greater coverage of the printed surface produces more gloss, due to the coalescence of the droplets and the elimination of gaps between them. For example, patent document WO 2013078297 A1 describes a solution of this type.

[0013] These known solutions from the second group have the disadvantage, compared to the known solutions from the first group, of affecting the range of colors and tones of the print, since it is determined by the separation and distribution of the drops in the different print layers.

[0014] On the other hand, the use of colorant inks with matting agents is well known, allowing for decorative prints with the required degree of matte. However, these solutions do not allow for automated and easy control of the matte level, as it is necessary to select the matting agents for each different print.

[0015] Inkjet inks typically have a glossy appearance once cured, making it necessary to apply a matte control procedure to increase or decrease the degree of matte finish. This is the case, for example, with cardboard packaging.

[0016] The present invention aims to provide a digital printing process and system with matte control as an alternative to existing processes and systems in the prior art. In particular, the present invention seeks to overcome the limitations of known solutions by providing a digital printing process and system with matte control that makes it possible to obtain matte-finished prints in an automated and easy manner.

[0017] EXPLANATION OF THE INVENTION

[0018] To achieve the aforementioned objective, as well as additional technical advantages that may be derived from the present descriptive report, the invention provides a digital printing process with matte control, comprising the following steps: a) inkjet printing a digitized image, depositing curable dye ink onto a substrate; b) partially solidifying the deposited dye ink; c) microfolding the surface of the deposited dye ink; and d) completely solidifying the deposited dye ink after microfolding its surface.

[0019] Stages b), c) and d), i.e., partial solidification, surface microfolding and complete solidification, are performed by curing radiation.

[0020] According to the invention, to obtain prints or print areas with different degrees of matte, the curing radiation for partial solidification and / or the curing radiation for microfolding are applied with a different radiation intensity level for each print or print area of ​​the digitized image.

[0021] Applying curing radiation to partially solidify the print at varying radiation intensity levels allows for controlled matte finishes. This is because the application of curing radiation for micro-folding produces a more pronounced surface micro-folding the less curing or solidification of the ink deposited during printing occurs.

[0022] Similarly, the curing radiation for microfolding can be applied at a different intensity level for each print or print area of ​​the digitized image, either as an alternative or in addition to the different intensity levels of curing radiation used for partial solidification. This allows the same effect of varying matte finishes to be achieved in a controlled manner across different print areas or prints.

[0023] In the context of the present invention, the level of curing radiation intensity can be understood, in particular, as the curing radiation energy irradiated per unit area to solidify, partially or completely, or microfold.

[0024] The different level of radiation intensity can be applied to different printing areas of the same printed digitized image, or to different prints corresponding to different digitized images.

[0025] Thus, the invention makes it possible to obtain prints with different degrees of matte or gloss in an automated and easy way, since each of the stages of the procedure can be carried out in an automated and easy way, and can be controlled individually or in a coordinated manner.

[0026] Unlike prior art processes, this invention allows for decorative prints with controlled matte or gloss finishes without requiring a varnish layer to cover the printed decoration and without altering the display of colors and tones. This is possible because the curing radiation for microfolding is applied directly to the print, microfolding its surface.

[0027] Advantageously, it should also be noted that thanks to the microfolding transferred to the surface of the print, the invention achieves prints with improved wear resistance, due to the increased local bending inertia of the microfolding of the print coating itself.

[0028] In the context of the present invention, microfolding of a coating surface refers to the phenomenon whereby a liquid surface layer of the coating hardens relative to the coating core, such that the surface layer deforms by contracting, resulting in a structuring or folding of the surface on the order of micrometers or even tenths of a micrometer (peak-to-valley distance). As previously stated, this microfolding phenomenon is generally known in the prior art.

[0029] According to the invention, it has been surprisingly found that it is possible to generate a microfold using the dye ink deposited during inkjet printing. The deposited dye ink, which forms the print corresponding to the digitized image as visually perceived on the substrate, can be directly microfolded, allowing for direct control of the print's matte or glossy finish.

[0030] Indeed, it has been shown that, especially for the usual resolutions and speeds of digital inkjet printing, the dye ink can spread across a coating with a thickness on the order of tens of micrometers or even micrometers. This makes it possible to microfold a suitably spread layer of dye ink, considering that, as mentioned, the structure produced by microfolding can be on the order of micrometers or tenths of a micrometer.

[0031] Preferably, the invention contemplates that the described digital printing process with matte control may further comprise the following steps:

[0032] - supplying a binding liquid to bind the deposited colorant ink, the binding liquid being curable; and, by curing radiation,

[0033] - partially solidify the supplied binding liquid, together with the deposited coloring ink, in step b);

[0034] - microfolding the surface of the supplied binder liquid, together with the surface of the deposited colorant ink, in step c); and

[0035] - completely solidify the supplied binding liquid after microfolding its surface, along with the deposited coloring ink, in step d).

[0036] According to the invention, to obtain prints or print areas with varying degrees of matte, curing radiation for partial solidification and / or curing radiation for microfolding are applied—to the print and the binding fluid at each corresponding stage—with a different radiation intensity level for each print or print area of ​​the digitized image. In the context of this aspect of the invention where binding fluid is supplied, "binding" (the deposited colorant) means, in particular, joining (the colorant) by connecting the deposited colorant droplets through contact between the binding fluid and the fluid in the colorant droplets.

[0037] The selection of a binding liquid capable of binding a specific colorant ink and possessing other properties that may be provided for the invention is itself known to those skilled in the art. For example, a binding liquid with a chemical composition equal to or similar to that of the colorant ink facilitates the binding or coalescence between the binding liquid and the colorant ink. The use of specific chemical agents makes it possible, in particular, to provide the required viscosity and surface tension properties.

[0038] Thus, in the case of supplying binder liquid, the curing radiation to solidify, partially or completely, or the curing radiation to microfold, can be applied to both the deposited colorant ink and the supplied binder liquid.

[0039] In this regard, the curing radiation used to partially solidify the dye ink and binder, and / or the curing radiation used to microfold the surface of the dye ink and binder, is applied at a different radiation intensity level for each print or print area of ​​the digitized image. Each print or print area may comprise, at least locally, dye ink and / or binder.

[0040] Generally, and in the context of the present invention, curing refers to the chemical crosslinking process that causes the hardening of polymeric materials through crosslinking of their polymeric molecules, which takes place by applying a curing radiation.

[0041] Curing radiation is any electromagnetic or subatomic particle radiation that initiates or accelerates a curing process. Ultraviolet (UV) radiation is most commonly used for curing, although electron beam (EB) radiation can also be used. Curable materials are polymer mixtures that include chemical agents such as photoinitiators or surfactants.

[0042] The coloring ink and the binding liquid must be curable by curing radiation, to solidify, partially or completely, and to microfold, in particular, the same curing radiation being able to be used both to solidify, partially or completely, as well as to microfold.

[0043] Acrylates or acrylate polymers are widely used in inkjet printing and, in particular, can be used as a curable material for the dye ink and binder according to the invention. The selection of a curable material with properties specific to each application, for example, in relation to its hardening and solidification, through the choice of a suitable polymer type and chemical agents, is well known to those skilled in the art.

[0044] In the context of the present invention, solidification may be understood, in particular, as hardening that takes place throughout substantially the entire thickness of the deposited material. Partial solidification implies hardening throughout substantially the entire thickness of the deposited material—albeit incomplete.

[0045] Furthermore, complete or final solidification refers to the final stage of solidification by radiation curing, complementary to partial solidification, according to the invention. Complete solidification achieves, in particular, an effective and permanent degree of solidification for normal use of the resulting print.

[0046] Therefore, the exposure time and intensity of the curing radiation required for solidification can be especially critical. Insufficient curing can result in the material not reaching its effective properties, while overexposure can cause the material to degrade.

[0047] As curing radiation for partial or complete solidification, UV radiation in the UV-A, UV-B, and / or UV-C wavelength range may preferably be used. Regarding curing radiation for microfolding, according to a preferred embodiment of the invention, this radiation may be excimer radiation.

[0048] Excimer radiation is essentially monochromatic, short-wavelength, and high-energy radiation. This radiation does not penetrate deeply into the deposited liquid layer, concentrating the radiated energy in a surface area of ​​the layer. Because the liquid is partially solidified, this generates microfolding.

[0049] The use of excimer radiation to produce a microfold is itself known, for example, from patent document DE 102006042063 A1, the disclosure of which in this respect is incorporated by reference to the present descriptive memorandum.

[0050] For the invention, substantially concentrated excimer radiation, particularly in the UV-C wavelength range, for example at 172 nm, can be used. Because 172 nm photons are highly absorbed by atmospheric oxygen, the irradiation is carried out in an inert atmosphere, preferably in an inerted chamber with a nitrogen supply.

[0051] In the case of using excimer radiation for microfolding according to the invention, it is envisaged that the application of curing radiation for partial solidification begins, or in particular is carried out, prior to the application of the excimer radiation. This ensures adequate solidification of the core of the coating, the deposited colorant ink and / or binder liquid, suitable for producing the microfolding.

[0052] For the implementation of the invention, it should be noted that the intensity level of the curing radiation for partial solidification, applied to the colorant ink and / or the binding liquid, particularly prior to the application of excimer radiation, should preferably be within a range between a minimum and a maximum. Generally, this range depends on the thickness of the material receiving the excimer radiation and the desired final matte finish.

[0053] The minimum intensity level is due to the fact that, if the layer of deposited material that receives the excimer radiation is very fluid, the hardening of the surface layer does not produce adequate microfolding, but rather introduces cracks as a result of the hardening gradients that occur on the surface.

[0054] The maximum intensity level is due to the fact that, if the deposited material layer is very solidified, adequate microfolding cannot occur because the surface is unable to deform further to produce the microfolds.

[0055] According to the invention, microfolding can also be performed by means other than the application of excimer radiation. For example, the colorant ink and / or the binding liquid on whose surfaces the microfolding is performed can be configured to promote surface curing by applying a specific curing radiation, particularly one other than excimer radiation.

[0056] This process of promoting the surface curing of coatings to generate a microfolding in them is itself known, for example, from patent document DE 102016120878 A1, whose disclosure in this respect is incorporated by reference to the present descriptive memorandum.

[0057] The invention also contemplates the use of the same curing radiation for both partial solidification and microfolding, especially in the case of microfolding by surface curing promotion. Furthermore, it contemplates that the application of curing radiation for partial solidification can be carried out before and / or simultaneously with the application of curing radiation for microfolding, particularly using the same irradiation means. Moreover, partial solidification can occur before and / or during microfolding.

[0058] In any case, preferably, the curing radiation application for partial solidification begins, and in particular is carried out, prior to the application of radiation for microfolding, especially in the case of excimer radiation, regardless of whether it can be done with the same or different irradiation methods. This allows for greater control by enabling the decoupling of the solidification process from the microfolding process.

[0059] With regard to the use of a binding agent according to a general embodiment of the invention, the binding agent may be in the form of a liquid layer spread over the substrate, particularly in contact with it. The printing of the colorant ink is carried out directly onto the layer of binding agent, with the colorant ink being deposited directly onto said layer. In this way, the supplied binding agent binds the deposited ink droplets together, forming a bed on which the ink droplets rest during printing.

[0060] The binder layer can be transparent or pigmented with any color. White binder layers have the advantage of serving as a printing background to enhance the visibility of decorative prints, especially when the substrate being printed on is not white.

[0061] It is also envisioned that the binder layer itself can serve as a primer layer to facilitate the adhesion of the print to the substrate. Configuring the binder layer with this adhesion function can be achieved by selecting a suitable composition of chemical agents, such as surfactants.

[0062] These chemical agents make it possible, in particular, to provide viscosity and surface tension properties that may be required, in a manner that is already known to the expert in the field.

[0063] The liquid binder layer can be applied to the substrate, for example, by rolling or spraying. Spraying, in particular, can be done using nozzles. The liquid layer can also be applied by inkjet printing or any other known method.

[0064] According to another general embodiment of the invention, the binding liquid can be supplied interposed between deposited drops of colorant ink corresponding to the printing of the digitized image. The binding liquid can be applied, for example, by spraying through nozzles or, preferably, by inkjet printing using binding liquid ink.

[0065] If the binding agent spreads between drops of colored ink, it should preferably be transparent. This helps preserve the colors and tones of the printed image formed by the drops of colored ink.

[0066] The binding liquid ensures a uniform matte finish across the irradiated area, regardless of the amount of dye applied per unit area, which primarily depends on the color and tone of the printed digital image. This process neutralizes the matte effect caused by the expansion and contraction of the dye droplets themselves.

[0067] Everything indicated regarding the characteristics of the coloring ink applies to the binding liquid, in that it must be curable by curing radiation, to produce partial and complete solidification, as well as curable by curing radiation for microfolding, in particular, by excimer radiation and / or by radiation for the promotion of surface curing.

[0068] Specifically, it is envisaged that the partial solidification of the transparent binding liquid and / or the complete solidification of the binding liquid and / or the digitized image print will be carried out using mercury UV lamps. Likewise, it is envisaged that the partial solidification of the opaque binding liquid and / or the digitized image print will be carried out using gallium UV lamps. This approach achieves efficient curing by taking advantage of the ability of gallium UV lamps to penetrate the thickness of the deposited print and / or binding liquid.

[0069] By applying the procedure of the invention, matte finishes can be obtained in a wide range, in particular, in the range of 10 to 100 GU (gloss units), measured at 85 e according to ISO 2813:2014 (or its equivalent standard UNE-EN ISO 2813:2015).

[0070] Preferably, the colorant ink and / or the binder are configured so that, if they solidify completely separately, applying only the curing radiation and without microfolding the surface (without applying curing radiation for microfolding), they exhibit a degree of gloss, measured at 85 e according to ISO 2813:2014, greater than or equal to 60 GU, preferably 75 GU, more preferably 90 GU.

[0071] In particular, the colorant ink and the binding liquid are configured so that, if they solidify completely separately, applying only the curing radiation and without microfolding the surface, they exhibit a difference between them in degree of gloss, measured at 85 eAccording to ISO 2813:2014, less than or equal to 10 GU, preferably 5 GU, and more preferably 1 GU. This minimizes differences in brightness that may exist between different printing areas for the different formulations of dye ink and / or binder liquid available.

[0072] On the other hand, regarding the amount of usable colorant ink and / or binder liquid, printing drop size, layer thicknesses, etc., the invention can be applied, in particular, with drop sizes corresponding to usual printing resolutions, such as 360 dpi.

[0073] For example, printing thicknesses on the order of micrometers or tens of micrometers are considered. Similarly, thicknesses of the binding liquid layer, or the binding liquid itself, are also considered to be on the order of micrometers or tens of micrometers. In particular, the primer layers for printing can be adjusted depending on the type of substrate being printed. For example, for cardboard it might be approximately 5-10 micrometers, and for wood or plastic, approximately 10-40 micrometers.

[0074] According to another aspect of the present invention, the invention also relates to a matte-controlled digital printing system for performing a digital printing process as described above.

[0075] According to the invention, the matte-controlled printing system comprises:

[0076] - a dye-in-ink printer for printing a digitized image, in particular a single-pass inkjet printer; - a curing radiation station for microfolding the surface of the deposited dye ink;

[0077] - a curing radiation station to partially solidify the deposited colorant ink and / or the curing radiation station to microfold the surface, also configured to partially solidify;

[0078] - a curing radiation station to completely solidify the colorant ink deposited after microfolding; and

[0079] - a controller configured to process and send control signals to the curing radiation station for partial solidification and / or to the curing radiation station for microfolding, to apply different levels of radiation intensity to each print or print area and thus obtain prints or print areas with different degrees of matte.

[0080] The printing system may include substrate transport means for conveying the substrate through the printer and radiation stations to carry out the procedure of the invention. In such a case, the transport means may also be controlled by the controller.

[0081] For UV curing radiation, standard lamps emitting in the UV-A, UV-B, and / or UV-C spectrum can be used. For example, arc discharge lamps or light-emitting diode (LED) lamps.

[0082] Among the arc discharge lamps are mercury vapor lamps, usually called "mercury" lamps, which emit UV radiation substantially distributed around the wavelengths of 254 nm and 365 nm, with a higher concentration of energy at the shorter wavelengths.

[0083] Mercury vapor lamps doped with heavy metal compounds, such as gallium iodide or iron iodide, are also used. Gallium iodide-doped lamps, commonly called "gallium" lamps, allow the emission spectrum of mercury lamps to be altered, emitting UV radiation substantially distributed around wavelengths of 400 to 450 nm.

[0084] In their application to the invention, gallium lamps are suitable for curing the colorant ink or the non-transparent binding liquid because, due to the pigmentation of these materials, they partially block shorter-wavelength UV radiation. With gallium lamps, since the wavelengths are longer, the radiation penetrates the material more deeply, resulting in a progressive curing process that occurs more at depth than on the surface, and therefore more efficient solidification from the bottom of the layer to the surface.

[0085] According to the invention, LED lamps can also be used for UV curing radiation emission, in particular for producing partial or complete solidification and / or microfolding. For example, LED lamps configured to emit UV radiation at 260 nm, 360 nm, 385 nm, and / or 395 nm may be suitable for the invention.

[0086] To achieve different matte or glossy effects in different areas of a print corresponding to the same digitized image, according to the invention, the curing radiation to partially solidify the print can be applied with different levels of radiation intensity for the different areas of the print by means of an arrangement of LED lamps, of the same or different wavelength.

[0087] Preferably, the digital printing system with matte control according to the invention further comprises a binder supply station, and the system may be equipped with a curing radiation station for microfolding, a curing radiation station for partial solidification, and / or a curing radiation station for complete solidification of the binder. In particular, the same curing radiation station (for microfolding, partial solidification, and / or complete solidification) may be used for both the colorant ink and the binder.

[0088] In particular, the liquid binder supply station can be of different types, depending on the matte control printing procedure variant of the invention for which the system can be configured.

[0089] Thus, if the binder is applied as a liquid layer, roller coating equipment, spray nozzles, or a binder inkjet printer can be used for its application. Conversely, if the binder is applied between the drops of the colorant ink corresponding to the digital image, a binder inkjet printer can be used, for example.

[0090] For its part, the dye-based inkjet printer corresponding to the digital image can be the same inkjet printer as the binder-based ink, for which different printheads or rows of nozzle printheads can be used for the different inks.

[0091] In this regard, it is also envisioned that a single curing radiation station can be used to perform different stages of the invention's process, in particular, for microfolding, partial solidification, and / or complete solidification. For example, especially when microfolding is performed by promoting surface curing, the curing radiation station for microfolding can also be configured for partial and / or complete solidification.

[0092] In other cases, a curing radiation station can be used to carry out a single step of the invention's procedure. For example, the invention provides for the arrangement of a curing radiation station to partially solidify the binding liquid prior to printing the digitized image, especially when the binding liquid is spread as a layer on the substrate.

[0093] Of course, when the system incorporates the binder supply station, the system controller is additionally configured to process and send control signals to the curing radiation station to partially solidify and / or to the curing radiation station to microfold the binder liquid (along with the coloring ink), to apply different levels of radiation intensity to each print or print area and thus obtain prints or print areas with different degrees of matte.

[0094] Furthermore, the invention also contemplates that the controller is additionally configured to process and send control signals to other stations or units of the system for their proper operation. For example, to the dye-based inkjet printer, the liquid-binding inkjet printer, the curing radiation station for complete solidification, and / or the substrate transport system, etc.

[0095] According to another aspect, the present invention also relates to a digitally printed substrate with matte control, obtainable by a procedure or with a digital printing system as described above.

[0096] Preferably, the substrate can be made of a sheet material, especially for packaging. The substrate can be cardboard, in particular comprising cardboard or being cardboard itself. In this respect, the invention can be advantageously applied to food packaging because, as a result of the improved curing process, migration of the print and / or binding liquid into the packaging is prevented.

[0097] BRIEF DESCRIPTION OF THE DRAWINGS

[0098] The invention is described in greater detail below for illustrative and non-limiting purposes, as well as with respect to a preferred embodiment by way of example, with reference to the accompanying drawings. In the drawings:

[0099] Figure 1 schematically represents a system for carrying out a digital matte control printing procedure according to a first embodiment of the invention.

[0100] Figure 2 schematically represents a system for carrying out a digital matte control printing procedure according to a second embodiment of the invention.

[0101] Figures 3A and 3B show two photographs of two substrates printed with the same digitized image, but with different degrees of brightness, obtained following an example of a matte control digital printing procedure according to the first embodiment of the invention.

[0102] Figure 4 shows a table that collects the measured brightness values, according to the ISO 2813:2014 standard, for two printed substrates whose photographs are shown in Figures 3A and 3B.

[0103] DETAILED DESCRIPTION OF THE INVENTION

[0104] Referring to Figure 1, the digital printing system with matte control (1) shown corresponds to a first embodiment of the invention. The system (1) comprises a dye-injected inkjet printer (10), a curing radiation station (20) for partial solidification of the print, an excimer radiation station (30) for microfolding the print surface, and a curing radiation station (40) for complete solidification of the print.

[0105] The inkjet printer (10) is a single-pass printer, with the substrate (2) being printed as it moves under the printheads (11, 12, 13, 14) of the printer (10). Each printhead (11, 12, 13, 14) consists of rows of nozzles through which the dye ink is injected.

[0106] The substrate (2) can be, for example, a sheet material for packaging, in particular a sheet material comprising cardboard or a carton.

[0107] The printer (10) incorporates fixing lamps (usually called "pinning") (15, 16, 17, 18), which are arranged behind each print head (11, 12, 13, 14), serving to fix the ink drops to some extent when the substrate (2) is being printed.

[0108] According to this first embodiment, the system (1) includes a station for applying a transparent binder liquid layer (50) by means of a roller, and a partial curing radiation station (60), prior to inkjet printing, with the print being deposited directly onto the generated binder liquid layer, as a bed.

[0109] By way of example, in this embodiment the excimer radiation station (30) is configured to emit substantially monochromatic radiation at 172 nm and comprises an excimer radiation lamp (31) arranged in a nitrogen-inertized chamber (32). Furthermore, the post-printing curing radiation stations (20, 40) consist of gallium UV lamps, and the pre-printing curing radiation station (60) consists of mercury UV lamps, since the resulting binder layer is transparent.

[0110] The system (1) incorporates a means of transport (80) of the substrates (2) with a transport belt (81) to transport the substrates (2) through the system (1), from when they are fed (on the left of the figure) until they are collected (on the right of the figure), as the various corresponding stages of the procedure of the invention are carried out.

[0111] The printer (10), the curing radiation stations (20, 40, 60), the excimer radiation station (30), the binder liquid layer application station (50) and the transport means (80) are controlled by a controller (90).

[0112] The controller (90) processes and sends control signals to the various subsystems to apply different levels of radiation intensity to each print or print area and thus obtain prints or print areas with different degrees of matte.

[0113] Referring to Figure 2, the digital printing system with matte control (1) shown corresponds to a second embodiment of the invention. As in the first embodiment described, the system (1) comprises a dye-injection inkjet printer (10), a curing radiation station (20) for partial solidification of the print, an excimer radiation station (30) for microfolding the print surface, and a curing radiation station (40) for complete solidification of the print.

[0114] The system (1) of this second embodiment differs from the system (1) of the first embodiment in that, instead of including a binder layer application station (50) and a corresponding partial curing radiation station (60), the system (1) includes an inkjet application station (70) for the binder. By way of example, the partial curing radiation station (60) is located upstream of the inkjet printer (10). Likewise, in particular, the inkjet application station (70) for the binder is located downstream of the inkjet printer (10).

[0115] Otherwise, the general operation of the system (1) is as in the first embodiment. The printer (10), the curing radiation stations (20, 40), the excimer radiation station (30), the binder layer application station (70), and the transport means (80) are controlled by means of the controller (90).

[0116] The controller (90) processes and sends control signals to the various subsystems to apply different levels of radiation intensity to each print or print area and thus obtain prints or print areas with different degrees of matte.

[0117] According to this embodiment, the supply of the binding liquid is carried out by inkjet printing (70) with transparent ink, which is interposed between deposited droplets of the digitized image print. The injection of the binding liquid ink is carried out through nozzles arranged in the printheads (71, 72) and, as in the printer (10), the station (70) is equipped with fixation lamps (73, 74) to fix the injected ink.

[0118] The printheads (71, 72) of the transparent liquid application station (70) can generally be arranged as in the printer (10) of the digitized image, i.e., in one or two rows (offset from each other) or aligned if redundancy is desired. This allows the binder ink droplets to be adjusted to the printing resolution of the digitized images.

[0119] The application of binder by inkjet allows for the selective deposition of the binder in different printing areas, so that, for example, some areas receive more binder per unit area than others. Furthermore, this can generally be done in areas with less colorant deposited per unit area, resulting in a more uniform layer thickness across the entire digital print and, consequently, a more uniform matte finish. As a general variation of the described embodiments, the partial curing radiation station (20) is comprised of an array of LED lamps, allowing for the application of different curing intensity levels to different printing areas. A higher level of partial curing further inhibits the micro-folding effect, so varying the intensity of the LED lamps in different areas can achieve different matte finishes.The LED lamp arrangement can consist of a row or an array of LED lamps.

[0120] Another general advantage considered regarding the described applications is the application of an additional coating layer over the resulting print. These layers can be, for example, functional layers, structuring or relief layers, protective layers, etc.

[0121] Specifically, as a protective layer to provide greater wear resistance to the matte print, a layer of varnish is being applied over the print. However, the micro-folding itself provides greater wear resistance than simply coating the print without micro-folding.

[0122] According to the invention, additional layers can be applied to the microfolded printing layer before, during, or after complete solidification. A certain degree of partial curing of the printing layer, with or without a binding agent, can promote the adhesion of a surface layer to its surface. However, the inherent characteristics of the microfolded printing layer, such as its thinness and the surface distribution of the ink or binding agent, can also facilitate adhesion.

[0123] The following, with reference to Figures 3 and 4, provides a practical example of matte-controlled printed substrates obtained according to the first embodiment of the invention. The prints were made on two separate wooden substrates, using the same digitized image.

[0124] Figures 3A and 3B show the two photographs corresponding to the respective printed substrates. The printed substrate in Figure 3A (referenced in the table in Figure 4 as “S.Fig.3A”) was obtained with a low matte finish (high gloss). The printed substrate in Figure 3B (referenced in the table in Figure 4 as “S.Fig.3B”) was obtained with a high matte finish (low gloss).

[0125] For the coloring ink and the binding liquid, a mixture of acrylates curable with UV radiation was used, using mercury lamps and gallium lamps, and curable with excimer radiation at 172 nm in an inert chamber under nitrogen supply.

[0126] Digital inkjet printing was performed in the usual way, with a single-pass printer (10) with a resolution of 360 dpi and printheads (11, 12, 13, 14) with dye inks C (“cyan”), M (“magenta”), Y (“yellow”), K (“black”). The substrates (2) were transported through the system (1) at a transport speed of 20 m / min.

[0127] After applying a first layer of transparent binding liquid approximately 20 microns thick, using a roller (50), a partial solidification prior to printing was carried out with mercury lamps (60) of 120 W / cm, supplying a radiation energy to each substrate of approximately 130 mJ / cm 2 .

[0128] Next, digital printing (10) was carried out with the colorant ink, followed by fixing (“pinning”) with LED lamps (15, 16, 17, 18) at 395 nm.

[0129] After printing the digitized image, partial solidification of the print was carried out along with the lower layer of binding liquid. This was done using gallium lamps (20) of 80 W / cm².

[0130] Partial solidification was performed with different levels of radiation intensity for each of the substrates (2). For the printed substrate (2) in Figure 3A, a radiation energy of approximately 50 mJ / cm² was irradiated. 2 For the printed substrate (2) in Figure 3B, a radiation energy of approximately 10 mJ / cm² was irradiated. 2 .

[0131] After partial solidification, microfolding was carried out by applying excimer radiation (30) using a 172 nm excimer radiation lamp (31) located in a nitrogen-inert chamber (32). The radiation energy delivered by the excimer radiation to each substrate (2) was approximately 130 mJ / cm². 2 .

[0132] Finally, the substrates (2) were subjected to curing radiation for complete solidification of the impression and the binding liquid, using gallium lamps (40) of 80 W / cm². The radiation energy supplied by this curing radiation to each substrate was approximately 1060 mJ / cm². 2 .

[0133] The table in Figure 4 shows the gloss measurements, taken according to ISO 2813:2014, for each of the printed substrates obtained. Specifically, the gloss measurements were taken in a black area of ​​the print.

[0134] As can be seen in the table, GU brightness values ​​were obtained measured at 85 e of 44.3 GU for the printed substrate in Figure 3A (“S.Fig.3A”) and of 9.2 GU for that in Figure 3B (“S.Fig.3A”). The GU brightness values ​​measured at 60 e They were similar for both printed substrates (2), of 3.1-3.4 GU.

[0135] Gloss measurement was also performed on a sample of printed substrate to which only curing radiation was applied without microfolding the surface. This substrate had been printed with the same ink as the substrates in Figures 3A and 3B and without a binder. The GU gloss value measured at 85 e According to ISO 2813:2014, for the black area of ​​the print and once fully solidified, it was 91.2 GU.

[0136] In short, as shown in this document, the invention provides a digital printing procedure and system with matte control that makes it possible to obtain printed substrates with matte finishes in an automated and easy way, overcoming the limitations of the state of the art and providing additional technical advantages.

[0137] To that end, the invention is not limited to the embodiments presented, but includes all variations, modifications, and combinations within the scope of the appended claims. List of reference signs

[0138] 1 Printing system

[0139] 2 Impression substrate

[0140] 10 Digital Imaging Inkjet Printer

[0141] 11, 12, 13, 14 Print nozzle heads

[0142] 15, 16, 17, 18 Print Fixing Lamps

[0143] 20 Partial curing radiation station

[0144] 30 Excimer Radiation Station

[0145] 31 Excimer radiation lamp

[0146] 32 Nitrogen-inerted chamber

[0147] 40 Complete curing radiation station

[0148] 50 Binder Layer Application Station

[0149] 60 Partial curing radiation station

[0150] 70 Binder Liquid Inkjet Application Station

[0151] 71, 72 Print nozzle heads

[0152] 73, 74 Print Fixing Lamps

[0153] 80 Substrate transport medium

[0154] 81 Conveyor belt

[0155] 90 Printing system controller

Claims

CLAIMS 1. A digital printing process with matte control, comprising: a) inkjet printing a digitized image, depositing curable dye ink onto a substrate (2); and, by means of curing radiation, b) partially solidifying the deposited dye ink; c) microfolding the surface of the deposited dye ink; and d) completely solidifying the deposited dye ink after microfolding its surface; such that, in order to obtain prints or print areas with different degrees of matte, the curing radiation for partial solidification and / or the curing radiation for microfolding are applied with a different radiation intensity level for each print or print area of ​​the digitized image.

2. A digital printing process with matte control according to claim 1, characterized in that it comprises: - supplying a binding liquid to bind the deposited colorant ink, the binding liquid being curable; and, by curing radiation, - partially solidify the supplied binding liquid, together with the deposited coloring ink, in step b); - microfolding the surface of the supplied binder liquid, together with the surface of the deposited colorant ink, in step c); and - completely solidify the supplied binding liquid after microfolding its surface, along with the deposited coloring ink, in step d).

3. Digital printing process with matte control according to claim 2, characterized in that the supply of the binding liquid is carried out by spreading a liquid layer, in particular transparent, on the substrate (2), on which the coloring ink is deposited directly.

4. Digital printing process according to claim 3, characterized in that the liquid layer is spread by means of a roller (5), spraying or inkjet printing.

5. Digital printing process according to one of claims 3 or 4, characterized in that the liquid layer is partially solidified by radiation curing, prior to depositing the coloring ink.

6. Digital printing process according to claim 2, characterized in that the binding liquid is supplied by interposing between drops of deposited colorant ink, in particular, by inkjet printing (70) with transparent ink.

7. A digital printing process with matte control according to any one of claims 2 to 6, characterized in that the colorant ink and the binder liquid are configured such that, if they solidify completely separately, applying only the curing radiation without microfolding the surface, they exhibit a difference between them in degree of gloss, measured at 85 e according to ISO 2813:2014, less than or equal to 10 GU, preferably 5 GU, more preferably 1 GU.

8. A digital printing process according to any of the preceding claims, characterized in that the colorant ink and / or the binder liquid are configured so that, if they solidify completely separately, applying only the curing radiation without microfolding the surface, they exhibit a degree of gloss, measured at 85 e according to ISO 2813:2014, greater than or equal to 60 GU, preferably 75 GU, more preferably 90 GU.

9. Digital printing process with matte control according to one of the preceding claims, characterized in that the curing radiation for microfolding is excimer radiation.

10. A digital printing process with matte control according to one of the preceding claims, characterized in that the coloring ink and / or the binding liquid, on whose surface the microfolding is carried out, are configured to promote surface curing when the microfolding curing radiation is applied to them.

11. Digital printing process according to one of the preceding claims, characterized in that the curing radiation for partial solidification and / or the curing radiation for microfolding are applied with different levels of radiation intensity for different printing areas by means of an arrangement of LED lamps.

12. A digital printing system with matte control (1), for performing a digital printing process according to one of the preceding claims, comprising: - a dye-in-inkjet printer (10) for printing a digitized image, in particular a single-pass inkjet printer (10); - a curing radiation station for microfolding the surface (30) of the deposited colorant ink; - a curing radiation station for partially solidifying (20) the deposited colorant ink and / or the curing radiation station for microfolding the surface (30) also being configured to partially solidify; - a curing radiation station to completely solidify (40) the deposited colorant ink; and - a controller (90) configured to process and send control signals to the curing radiation station for partially solidifying (20) and / or to the curing radiation station for microfolding (30), to apply different levels of radiation intensity to each print or print area and thus obtain prints or print areas with different degrees of matte.

13. Digital printing system with matte control according to claim 12, characterized in that it comprises a supply station for the binding liquid (50, 70), in particular, the curing radiation station for microfolding the surface (30), the curing radiation station for partially solidifying (20) and / or the curing radiation station for completely solidifying (40), both of the colorant ink and the binding liquid.

14. Digital printing system with matte control according to one of claims 12 or 13, characterized in that the curing radiation station for microfolding the surface is an excimer radiation station (30).

15. Digitally printed substrate (2) with matte control, characterized in that it is obtainable by a digital printing process according to one of claims 1 to 11, in particular, the substrate (2) being made of cardboard, more particularly, being a packaging or container.

Images