Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
  • B41J11/0015—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form for treating before, during or after printing or for uniform coating or laminating the copy material before or after printing
  • B41J11/002—Curing or drying the ink on the copy materials, e.g. by heating or irradiating
  • B41J11/0021—Curing or drying the ink on the copy materials, e.g. by heating or irradiating using irradiation
  • B41J11/00214—Curing or drying the ink on the copy materials, e.g. by heating or irradiating using irradiation using UV radiation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
  • B41J11/0015—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form for treating before, during or after printing or for uniform coating or laminating the copy material before or after printing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
  • B41J11/0015—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form for treating before, during or after printing or for uniform coating or laminating the copy material before or after printing
  • B41J11/002—Curing or drying the ink on the copy materials, e.g. by heating or irradiating
  • B41J11/0021—Curing or drying the ink on the copy materials, e.g. by heating or irradiating using irradiation
  • B41J11/00212—Controlling the irradiation means, e.g. image-based controlling of the irradiation zone or control of the duration or intensity of the irradiation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/21—Ink jet for multi-colour printing
  • B41J2/2107—Ink jet for multi-colour printing characterised by the ink properties
  • B41J2/2114—Ejecting specialized liquids, e.g. transparent or processing liquids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/21—Ink jet for multi-colour printing
  • B41J2/2107—Ink jet for multi-colour printing characterised by the ink properties
  • B41J2/2114—Ejecting specialized liquids, e.g. transparent or processing liquids
  • B41J2/2117—Ejecting white liquids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M7/00—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock
  • B41M7/0081—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock using electromagnetic radiation or waves, e.g. ultraviolet radiation, electron beams
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/0011—Pre-treatment or treatment during printing of the recording material, e.g. heating, irradiating
  • B41M5/0017—Application of ink-fixing material, e.g. mordant, precipitating agent, on the substrate prior to printing, e.g. by ink-jet printing, coating or spraying

Definitions

• the present invention relates to a method and a system for obtaining decorative printouts with a controlled degree of matt or gloss, by means of inkjet printing.
• the invention is applicable, for example, to the production of cardboard packaging, regarding which there is commercial demand for matt designs that are easy to achieve.
• a first set of known solutions is based on the application of a curable varnish which is spread, covering the decoration which has been printed by inkjet.
• the varnish is subjected to a process of microfolding, by means of which microfolds are created at the surface of the varnish which, through the optical effect of dispersion of light through their microstructure, give rise to the desired matt appearance.
• the partially cured varnish is subjected to special curing radiation, referred to as excimer radiation.
• excimer radiation special curing radiation
• a greater degree of matt is achieved by partially curing the varnish to a low degree before applying the excimer radiation.
• patent document DE 102006042063 A1 describes a solution of this type.
• a second set of known solutions is based on adjusting the size of the droplets of ink deposited for the decoration which is printed by inkjet, by adjusting the intensity of curing of the printout. By playing with the level of intensity of curing, greater or lesser contraction or expansion of the droplets is obtained.
• the matt finish is achieved in this case by the optical effect of the different reflection of the light striking the printout, depending on the size or expansion of the droplets deposited. Greater expansion of the droplets or greater coverage of the surface printed results in a higher gloss, owing to the coalescence between the droplets and the elimination of hollows between droplets.
• patent document WO 2013078297 A1 describes a solution of this type.
• this second set of known solutions has the drawback of affecting the range of colours and tones of the printout, since this is determined by the separation and distribution of the droplets in the various pixels of the printout.
• inkjet inks once cured, have a gloss appearance, such that it is necessary to implement a method for control of matt which makes it possible to increase the degree of matt, or reduce the degree of gloss. This is the case, for example, with cardboard packaging.
• the present invention aims to provide a method and a system for digital printing with control of matt offering an alternative to the methods and systems existing in the prior art.
• the present invention aims to overcome the limitations of the known solutions by providing a method and system for digital printing with control of matt which makes it possible to obtain printouts with matt finishes automatically and easily.
• the invention provides a method for digital printing with control of matt, which comprises the following steps:
• Steps b), c) and d), in other words the partial solidification, the microfolding of the surface and the complete solidification, are carried out by means of curing radiation.
• 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 digitalized image.
• the application, in the partial solidification of the printout, of curing radiation with different levels of radiation intensity makes it possible to obtain different degrees of matt in a controlled manner. This is because the application of curing radiation for microfolding produces microfolding at the surface which is more accentuated the lower the degree of curing or solidification of the coloured ink deposited during printing is upon application of said curing radiation for microfolding.
• the curing radiation for microfolding itself may be applied with a level of radiation intensity that is different for each printout or printout area of the digitalized image, as an alternative or in addition to the different levels of intensity of curing radiation for partial solidification. It is thus possible to achieve the same effect of different degrees of matt in a controlled manner in different printout areas or different printouts.
• level of intensity of curing radiation means, in particular, the curing radiation energy irradiated per unit area for solidification, partial or complete, or for microfolding.
• the different level of radiation intensity may be applied to different printout areas of the same printed digitalized image, or to different printouts corresponding to different digitalized images.
• the invention makes it possible to obtain printouts with different degrees of matt or gloss automatically and easily, since each of the steps of the method may be carried out automatically and easily, and may be controlled individually or in a coordinated manner.
• the invention makes it possible to obtain printouts with improved resistance to wear, owing to the increase in local bending inertia of the microfolding of the coating of the printout itself.
• microfolding of the surface of a coating means the phenomenon whereby a liquid surface layer of the coating is hardened with respect to the core of the coating, such that said surface layer deforms, contracting, resulting in structuring or folding of the surface layer with a magnitude measured in microns, or even tenths of a micron (distance between peak and trough).
• this phenomenon of microfolding is generally known per se in the prior art.
• the invention therefore, it has been found that, surprisingly, it is possible to generate microfolding by making use of the actual coloured ink deposited by inkjet printing.
• the coloured ink deposited which forms the printout corresponding to the digitalized image as it is perceived visually on the substrate, may be microfolded directly, making it possible to control the degree of matt or gloss of the printout directly.
• the coloured ink of the printout may be spread across a coating having a thickness of the order of tens of microns, or even microns. This facilitates the microfolding of a layer of coloured ink duly spread, bearing in mind that, as stated, the structuring resulting from microfolding may be of the order of microns or tenths of a micron.
• the method for digital printing with control of matt described may further comprise the following steps:
• the curing radiation for partial solidification and/or the curing radiation for microfolding are applied - to the printout and to the agglutinant liquid in each corresponding step - with a level of radiation intensity that is different for each printout or printout area of the digitalized image.
• agglutinating means, in particular, joining up (the coloured ink) by connecting the droplets of coloured ink deposited, through the contact which occurs between the agglutinant liquid and the liquid of the droplets of coloured ink.
• an agglutinant liquid capable of agglutinating a given coloured ink and having other properties that may be envisaged by the invention, is known per se to those skilled in the art.
• an agglutinant liquid with a chemical composition identical or similar to the coloured ink facilitates the agglutination or coalescence between the agglutinant liquid and the coloured ink.
• specific chemical agents makes it possible, in particular, to ensure any viscosity and surface tension properties required.
• the curing radiation for solidification, partial or complete, or the curing radiation for microfolding may be applied both to the coloured ink deposited and to the agglutinant liquid supplied.
• the curing radiation for partial solidification of the coloured ink and the agglutinant liquid, and/or the curing radiation for microfolding the surface of the coloured ink and of the agglutinant liquid are applied with a level of radiation intensity that is different for each printout or printout area of the digitalized image.
• Each printout or each printout area may comprise, at least locally, coloured ink and/or agglutinant liquid.
• curing refers to the chemical process of reticulation which causes hardening of polymer materials by crosslinking of their polymer molecules, which occurs upon the application of curing radiation.
• curing radiation is any electromagnetic or subatomic particle radiation which initiates or accelerates a curing process.
• curing radiation use is usually made of ultraviolet (UV) radiation, although use may also be made, for example, of electron beam (EB) radiation.
• UV radiation ultraviolet
• EB radiation electron beam
• the curable materials are mixtures of polymers which include chemical agents such as photoinitiators or surfactants.
• the coloured ink and the agglutinant liquid must be curable by means of curing radiation, for solidification, partial or complete, and for microfolding, in particular, and the curing radiation may be the same both for solidification, partial or complete, and for microfolding.
• Acrylates or acrylate polymers are used extensively in inkjet printing and, in particular, may be used as curable material for the coloured ink and the agglutinant liquid in accordance with the invention.
• the selection of a curable material with specific properties for each application, for example in relation to its hardening and solidification, through the selection of an appropriate type of polymer and chemical agents, is known per se to those skilled in the art.
• solidification means, in particular, the hardening which occurs substantially throughout the thickness of the material deposited. Partial solidification means hardening substantially throughout the thickness of the material deposited, albeit incomplete.
• complete solidification means the final step of solidification by curing radiation, in addition to partial solidification, in accordance with the invention.
• complete solidification in particular, a degree of solidification that is effective and permanent for normal use of the printout to be obtained is achieved.
• the exposure time and the intensity of the curing radiation for solidification may be especially critical. Insufficient curing may result in the material not reaching its effective properties, whereas overexposure can damage the material.
• curing radiation for solidification partial or complete, use may preferably be made of UV radiation, in the UV-A, UV-B and/or UV-C range of wavelengths.
• this radiation may be excimer radiation.
• Excimer radiation is substantially monochromatic radiation, of short wavelength and with high radiation energy. This radiation does not penetrate deeply into the layer of liquid deposited, the radiated energy being concentrated in a surface area of the layer, such that, as the liquid is partially solidified, microfolding is generated.
• excimer radiation for example, of excimer radiation, substantially concentrated, in particular in the UV-C range of wavelengths, for example at 172 nm. Since at 172 nm photons have a high rate of absorption by oxygen in the air, irradiation is performed in an inert atmosphere, preferably in an inerted chamber under a supply of nitrogen.
• the application of curing radiation for partial solidification may begin, in particular may take place, prior to the application of the excimer radiation. This makes it possible to ensure solidification of the core of the coating, of coloured ink and/or agglutinant liquid deposited, which is sufficient to produce microfolding.
• the level of intensity of the curing radiation for partial solidification, applied to the coloured ink and/or to the agglutinant liquid, in particular prior to the application of the excimer radiation must preferably lie in a range, between a minimum and a maximum. In general, this range depends on the thickness of the material which receives the excimer radiation and on the final degree of matt finish which it is desired to obtain.
• the minimum level of intensity is necessary because, if the layer of material deposited which receives the excimer radiation is very fluid, hardening of the surface layer does not result in proper microfolding, but cracks occur as a consequence of the hardening gradients occurring at the surface.
• the maximum level of intensity is necessary because, if the layer of material deposited is highly solidified, this also prevents proper microfolding since the surface is not able to deform further to give rise to the microfolds.
• microfolding may also be carried out by means other than the application of excimer radiation.
• the coloured ink and/or the agglutinant liquid, on the surfaces of which the microfolding takes place may be configured to promote surface curing when a specific curing radiation, in particular other than excimer radiation, is applied.
• the same curing radiation may be used for partial solidification and for microfolding, especially in the case of microfolding by promotion of surface curing.
• the application of curing radiation for partial solidification may be carried out before and/or simultaneously with the application of curing radiation for microfolding, in particular by means of the same irradiation means.
• partial solidification may occur before and/or during microfolding.
• the application of curing radiation for partial solidification begins, in particular takes place, prior to the application of the radiation for microfolding, especially in the case of application with excimer radiation, regardless of whether they may be carried out with the same or different irradiation means.
• This allows greater control, as it is possible to disassociate the process of solidification from that of microfolding.
• the agglutinant liquid may be in the form of a liquid layer which is spread over the substrate, in particular in contact with the substrate. Coloured ink is printed directly on the layer of agglutinant liquid, the coloured ink being deposited directly on said layer.
• the agglutinant liquid supplied agglutinates the droplets of ink deposited, like a bed on which the droplets of ink of the printout are laid.
• the layer of agglutinant liquid may be transparent or pigmented with any colour.
• Layers of white agglutinant liquid have the advantage of acting as a background for printing to enhance the visual appearance of decorative printouts, especially if the surface of the substrate printed is not white.
• the layer of agglutinant liquid itself to act as a primer layer to facilitate the adhesion of the printout to the substrate.
• the layer of agglutinant liquid may be configured to have this adhesion function by selecting a suitable composition of chemical agents, such as surfactants.
• the layer of agglutinant liquid may be spread over the substrate, for example, by means of a roller or spraying. In particular, spraying may be carried out using nozzles.
• the liquid layer may also be spread by means of inkjet printing or any other known method.
• the agglutinant liquid may be supplied by being intermingled with droplets of coloured ink deposited, corresponding to the printout of the digitalized image.
• the agglutinant liquid may be spread, for example, by spraying through nozzles or, preferably, by means of inkjet printing, using agglutinant liquid ink.
• the agglutinant liquid or ink is, preferably, transparent. It is thus possible to preserve the colours and tones of the printed image formed by the droplets of coloured ink.
• the agglutinant liquid makes it possible to make the degree of matt finish uniform in the irradiated area, regardless of the amount of coloured ink deposited per area, which in principle depends on the corresponding colour and tone of the digitalized image printed. It is thus possible to neutralize the matt effect produced by the expansion and contraction of the droplets of coloured ink themselves.
• the agglutinant liquid in that it must be curable by means of curing radiation, for the purposes of partial and complete solidification, as well as curable by means of curing radiation for microfolding, in particular by means of excimer radiation and/or by means of radiation for the promotion of surface curing.
• the partial solidification of transparent agglutinant liquid and/or the complete solidification, of agglutinant liquid and/or of the printout of the digitalized image may be carried out by means of mercury UV lamps.
• the partial solidification of non-transparent agglutinant liquid and/or of the printout of the digitalized image may be carried out by means of gallium UV lamps. Efficient curing is thus achieved, taking advantage of the property of gallium UV lamps to penetrate into the thickness of the printout and/or of the agglutinant liquid deposited.
• the implementation of the method of the invention makes it possible to obtain matt finishes over a wide range, in particular in the range from 10 to 100 GU (gloss units), measured at 85o in accordance with the standard ISO 2813:2014 (or the equivalent standard UNE-EN ISO 2813:2015).
• the coloured ink and/or the agglutinant liquid are configured such that, if they undergo complete solidification separately, applying only the curing radiation and without microfolding the surface (without applying curing radiation for microfolding), they have a degree of gloss, measured at 85o in accordance with the standard ISO 2813:2014, of greater than or equal to 60 GU, preferably 75 GU, more preferably 90 GU.
• the coloured ink and the agglutinant liquid are configured such that, if they undergo complete solidification separately, applying only the curing radiation and without microfolding the surface, the difference in their degree of gloss, measured at 85o in accordance with the standard ISO 2813:2014, is less than or equal to 10 GU, preferably 5 GU, more preferably 1 GU. This minimizes any differences in gloss between different printout areas for the different formulations of coloured ink and/or agglutinant liquid that may be selected.
• the droplet size for printing may be used, the droplet size for printing, the thicknesses of the layers, etc. the invention may be applied, in particular, with droplet sizes corresponding to the usual printing resolutions, such as for example 360 dpi.
• the printout may have thicknesses of the order of microns or tens of microns.
• the layer of agglutinant liquid or agglutinant liquid also may have thicknesses of microns or tens of microns.
• the primer layers for the printout may be adapted as a function of the type of substrate to be printed. For example, for cardboard they may be approximately 5-10 microns, for wood or plastic, approximately 10-40 microns.
• the invention also relates to a system for digital printing with control of matt, for carrying out a method for digital printing as described above.
• the system for printing with control of matt comprises:
• the printing system may comprise substrate conveyor means, for conveying the substrate through the printer and the radiation stations, so as to carry out the method of the invention.
• the conveyor means may also be controlled by the controller.
• UV curing radiation For the application of UV curing radiation, use may be made of the usual lamps which emit in the UV-A, UV-B and/or UV-C spectrum, for example, arc discharge lamps or LED lamps.
• Arc discharge lamps include mercury vapour lamps, usually referred to as “mercury lamps", which emit UV radiation substantially distributed around the wavelengths of 254 nm and 365 nm, with a greater concentration of energy in the short wavelengths.
• Mercury vapour lamps doped with heavy metal compounds such as gallium iodide or iron iodide are also used.
• Lamps doped with gallium iodide usually referred to as "gallium lamps”, make it possible to change the emission spectrum of mercury lamps, emitting UV radiation substantially distributed around wavelengths of 400 to 450 nm.
• gallium lamps are suitable for curing coloured ink or non-transparent agglutinant liquid since, owing to the pigmentation of these materials, they to some degree block UV radiation of shorter wavelength. With gallium lamps, as the wavelengths are longer, the radiation penetrates further into the material and the qualitative result is gradual curing at depth rather than at the surface, and therefore more effective solidification, right through the thickness to the surface.
• LED lamps for the emission of UV curing radiation, in particular for solidification, partial or complete, and/or for microfolding.
• LED lamps configured to emit UV radiation, in particular at 260 nm, 360 nm, 385 nm and/or 395 nm, may be suitable for the invention.
• the curing radiation for partial solidification of the printout may be applied with different levels of radiation intensity for the different areas of the printout by means of an array of LED lamps, of the same or different wavelength.
• the system for digital printing with control of matt in accordance with the invention further comprises a station for supplying the agglutinant liquid, wherein the system may be provided 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 agglutinant liquid.
• the same curing radiation station may be used (for microfolding, partial solidification and/or complete solidification) both for the coloured ink and for the agglutinant liquid.
• the station for supplying agglutinant liquid may be of various types, depending on the variant of the method for printing with control of matt of the invention for which the system may be configured.
• agglutinant is spread as a layer of liquid
• means for coating by roller, spray nozzles or an agglutinant liquid inkjet printer may be used, for example, for supplying agglutinant liquid.
• an agglutinant liquid inkjet printer may be used, for example.
• the coloured ink inkjet printer corresponding to the digital image may be the same as the agglutinant ink inkjet printer, in which case different heads or rows of heads of nozzles may be used for the different inks.
• the same curing radiation station may be used to carry out different steps of the method of the invention, in particular for microfolding, partial solidification and/or complete solidification.
• the curing radiation station for microfolding may be configured also for partial and/or complete solidification.
• a curing radiation station may be used to carry out only one step of the method of the invention.
• a curing radiation station for partial solidification of the agglutinant liquid prior to printing the digitalized image, especially in the case in which the agglutinant liquid is spread in the form of a layer on the substrate.
• the controller of the system is additionally configured to process and send control signals to the curing radiation station for partial solidification and/or to the curing radiation station for microfolding the agglutinant liquid (together with the coloured ink), so as to apply different levels of radiation intensity to each printout or printout area and thus obtain printouts or printout areas with different degrees of matt.
• the controller may additionally be configured to process and send control signals to other stations or units of the system for correct operation thereof, for example to the coloured ink inkjet printer, agglutinant liquid inkjet printer, curing radiation station for complete solidification and/or to the substrate conveyor means, etc.
• the present invention also relates to a substrate printed digitally with control of matt, which may be obtained by means of a method or with a system for digital printing as described above.
• the substrate may be a laminar material, especially for packaging or containers.
• the substrate may be cardboard, in particular comprising cardboard or being a cardboard box.
• the invention may be advantageously applicable to packaging or containers for food since, by virtue of the improvement of the method in terms of curing efficiency, migration of the printout and/or agglutinant liquid to the interior of the packaging is prevented.
• the system for digital printing with control of matt (1) shown corresponds to a first embodiment of the invention.
• the system (1) comprises an inkjet printer (10) for injecting coloured ink, a curing radiation station (20) for partial solidification of the printout, an excimer radiation station (30) for microfolding the surface of the printout and a curing radiation station (40) for complete solidification of the printout.
• the inkjet printer (10) is a single pass printer, the substrate (2) being printed as it moves, passing under the print heads (11, 12, 13, 14) of the printer (10).
• Each head (11, 12, 13, 14) is formed by rows of injection nozzles, through which the coloured ink is injected.
• the substrate (2) may be, for example, a laminar material for packaging, in particular a laminar material which comprises cardboard or a cardboard box.
• the printer (10) includes pinning lamps (15, 16, 17, 18), which are positioned after each print head (11, 12, 13, 14), and which serve to freeze the droplets of ink to a given degree when the substrate (2) is being printed.
• the system (1) includes a station for applying a layer of transparent agglutinant liquid (50), by means of a roller, and a partial curing radiation station (60), prior to inkjet printing, the printout being deposited directly on the layer of agglutinant liquid generated, like a bed.
• 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 chamber inerted with nitrogen (32).
• the curing radiation stations (20, 40) which come after printing are formed by gallium UV lamps and the curing radiation station (60) prior to printing is formed by mercury UV lamps, since the layer of agglutinant liquid generated is transparent.
• the system (1) includes a conveyor means (80) for conveying the substrates (2), with a conveyor belt (81) for conveying the substrates (2) through the system (1), from the point where they are supplied (on the left in the figure) to the point where they are collected (on the right in the figure), as the various corresponding steps of the method of the invention are carried out.
• the printer (10), the curing radiation stations (20, 40, 60), the excimer radiation station (30), the station for applying the layer of agglutinant liquid (50) and the conveyor means (80) are controlled by means of a controller (90).
• the controller (90) processes and sends control signals to the various subsystems so as to apply different levels of radiation intensity to each printout or printout area and thus obtain printouts or printout areas with different degrees of matt.
• the system for digital printing with control of matt (1) shown corresponds to a second embodiment of the invention.
• the system (1) comprises an inkjet printer (10) for injecting coloured ink, a curing radiation station (20) for partial solidification of the printout, an excimer radiation station (30) for microfolding the surface of the printout and a curing radiation station (40) for complete solidification of the printout.
• the system (1) of this second embodiment differs from the system (1) of the first embodiment in that, instead of including a station for applying a layer of agglutinant liquid (50) and a corresponding partial curing radiation station (60), the system (1) includes a station for applying the agglutinant liquid by inkjet (70).
• the partial curing radiation station (60) is located before the inkjet printer (10).
• the station for applying the agglutinant liquid by inkjet (70) is located after the inkjet printer (10).
• 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 station for applying the layer of agglutinant liquid (70) and the conveyor means (80) are controlled by means of the controller (90).
• the controller (90) processes and sends control signals to the various subsystems so as to apply different levels of radiation intensity to each printout or printout area and thus obtain printouts or printout areas with different degrees of matt.
• the agglutinant liquid is supplied by means of inkjet printing (70) using transparent ink, which is intermingled with deposited droplets of the printout of the digitalized image.
• the agglutinant liquid ink is injected through the nozzles arranged in the heads (71, 72) and, as in the printer (10), the station (70) is provided with pinning lamps (73, 74) for freezing the ink injected.
• the heads (71, 72) of the station for applying (70) the transparent liquid in general, may be arranged as in the printer (10) that prints the digitalized image, in other words in one or two rows (offset from one another) or aligned if redundancy is sought. It is thus possible to adjust the droplets of agglutinant ink to the resolution of printing of the digitalized images.
• agglutinant liquid by inkjet makes it possible to deposit the agglutinant liquid selectively in different printout areas, with, for example, a greater amount of liquid per unit area being deposited in some areas than in others. Moreover, in general, this may be carried out in correspondence with printout areas having a lesser amount of coloured ink deposited per area, obtaining a layer of more uniform thickness over the entire digital printout and, therefore, a resulting matt finish which is also more uniform.
• the partial curing radiation station (20) may be formed by an array of LED lamps, which makes it possible to apply a different level of curing intensity in different printout areas.
• a higher level of partial curing makes it possible to inhibit to a greater degree the effect of microfolding, such that by varying the intensity of the LED lamps by area it is possible to obtain a different matt finish in the different areas.
• the array of LED lamps may consist of a row or a matrix of LED lamps.
• Another general variant which is conceivable as regards the embodiments described is the provision of an additional coating layer on the printout obtained.
• These layers may be, for example, functional layers, structuring or texturing layers, protective layers, etc.
• a layer of varnish may be spread over the printout.
• microfolding per se provides greater resistance to wear than the resistance obtained by coating the printout without microfolding.
• additional layers may be applied on the microfolded printed layer before, during or after complete solidification.
• a given degree of partial curing of the printed layer, with or without agglutinant liquid, may promote the adhesion of a surface layer to its surface.
• the inherent characteristics of the microfolded printed layer, as regards its small thickness and surface distribution of the ink or agglutinant liquid, may themselves facilitate adhesion.
• Figures 3A and 3B show two photographs corresponding to the respective substrates printed.
• the printed substrate in Figure 3A (referred to in the table in Figure 4 as “S. Fig.3A ") was obtained with a low degree of matt (high gloss).
• the printed substrate in Figure 3B (referred to in the table in Figure 4 as “S. Fig.3B ”) was obtained with a high degree of matt (low gloss).
• coloured ink and the agglutinant liquid use was made of a mixture of acrylates curable with UV radiation, by means of mercury lamps and gallium lamps, and curable with excimer radiation at 172 nm in an inerted chamber under a supply of nitrogen.
• Digital printing by inkjet was carried out in the usual manner, with a single pass printer (10) with a resolution of 360 dpi and print heads (11, 12, 13, 14) with coloured inks C ( “cyan” ) , M ( “magenta” ) , Y (" yellow “), K (" black “).
• the substrates (2) were conveyed through the system (1) at a conveyor speed of 20 m/min.
• Partial solidification was carried out with a different level of radiation intensity for each one of the substrates (2).
• the printed substrate (2) in Figure 3A was irradiated with radiation energy of approximately 50 mJ/cm 2 .
• the printed substrate (2) in Figure 3B was irradiated with radiation energy of approximately 10 mJ/cm 2 .
• Partial solidification was followed by microfolding, applying excimer radiation (30) by means of an excimer radiation lamp (31) at 172 nm, placed in a chamber inerted with nitrogen (32).
• the radiation energy supplied by the excimer radiation to each substrate (2) was approximately 130 mJ/cm 2 .
• the substrates (2) were subjected to curing radiation for the complete solidification of the printout and the agglutinant liquid, by means of gallium lamps (40) at 80 W/cm.
• the radiation energy supplied by this curing radiation to each substrate was approximately 1060 mJ/cm 2 .
• the table in Figure 4 presents the gloss measurements, performed in accordance with standard ISO 2813:2014, for each of the printed substrates obtained. To be specific, the gloss measurements were performed in a black area of the printout.
• gloss values GU measured at 85o were obtained, namely 44.3 GU for the printed substrate in Figure 3A ("S. Fig.3A ”) and 9.2 GU for that in Figure 3B ("S. Fig.3B ").
• the gloss values GU measured at 60o were similar for the two printed substrates (2), namely 3.1-3.4 GU.
• the invention provides a method and system for digital printing with control of matt which makes it possible to obtain printed substrates with matt finishes automatically and easily, overcoming the limitations of the prior art and providing additional technical advantages.

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• 2024
  • 2024-07-01 EP EP24382710.2A patent/EP4674630A1/fr active Pending
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  • 2025-06-26 WO PCT/ES2025/070385 patent/WO2026008902A1/fr active Pending

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