EP3795934A1 - Method for hardening ink on a printed matter - Google Patents

Method for hardening ink on a printed matter Download PDF

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Publication number
EP3795934A1
EP3795934A1 EP19197749.5A EP19197749A EP3795934A1 EP 3795934 A1 EP3795934 A1 EP 3795934A1 EP 19197749 A EP19197749 A EP 19197749A EP 3795934 A1 EP3795934 A1 EP 3795934A1
Authority
EP
European Patent Office
Prior art keywords
ink
inert gas
radiator
radiation
curing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP19197749.5A
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German (de)
French (fr)
Inventor
Dr. Jorge Manuel Caramelo Soares
Dr. Peter Hachmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Heidelberger Druckmaschinen AG
Original Assignee
Heidelberger Druckmaschinen AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Heidelberger Druckmaschinen AG filed Critical Heidelberger Druckmaschinen AG
Priority to EP19197749.5A priority Critical patent/EP3795934A1/en
Priority to CN202010547669.8A priority patent/CN112519408A/en
Publication of EP3795934A1 publication Critical patent/EP3795934A1/en
Pending legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B13/00—Machines and apparatus for drying fabrics, fibres, yarns, or other materials in long lengths, with progressive movement
    • F26B13/10—Arrangements for feeding, heating or supporting materials; Controlling movement, tension or position of materials
    • F26B13/14—Rollers, drums, cylinders; Arrangement of drives, supports, bearings, cleaning
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41F—PRINTING MACHINES OR PRESSES
    • B41F23/00—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing
    • B41F23/04—Devices for treating the surfaces of sheets, webs, or other articles in connection with printing by heat drying, by cooling, by applying powders
    • 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
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
    • F26B21/14—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects using gases or vapours other than air or steam, e.g. inert gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/28—Drying solid materials or objects by processes involving the application of heat by radiation, e.g. from the sun
    • F26B3/283—Drying solid materials or objects by processes involving the application of heat by radiation, e.g. from the sun in combination with convection

Definitions

  • the present invention relates to a method for curing ink on a printing substrate according to the preamble of claim 1.
  • the invention is in the technical field of the graphics industry and there in particular in the field of curing, in particular curing with UV radiation, of liquid ink on sheet or web-shaped printing materials, preferably made of paper, cardboard, cardboard, plastic or composite material.
  • the drying and / or hardening (or more generally: the treatment) of preferably liquid or pasty printing media / fluids (such as printing ink, varnish or ink) on a printing material can be done in various ways, which can also be combined: by applying hot air, with electromagnetic radiation (e.g. UV or IR) or particle radiation (e.g. electrons) or by contacting the printing material with heated surfaces (e.g. cylinders, rollers or belts).
  • Water-based printing media are usually dried thermally, preferably with IR, while polymerizable printing media are usually dried with UV.
  • Mercury vapor lamps and increasingly LED lamps are used as UV radiation sources. It is known that UV-curable inks can be hardened under an inert gas.
  • UV-curable inks can take place in several steps, for example so-called pinning (pre-curing) and then final curing can take place first
  • WO2019007979A1 discloses UV curing and subsequent UV curing under Inert gas.
  • the EP3045477A1 reveals something similar.
  • the EP2767407B1 also discloses something similar, the initial hardening being a so-called pinning. According to these documents, the last curing step in each case takes place under inert gas.
  • the EP1473341B1 discloses two UV curing steps; both under inert gas.
  • the EP2596874A1 discloses drying (not UV curing) under inert gas and subsequent UV curing.
  • the problem can arise that the result of UV curing of the ink is not sufficient (insufficient crosslinking / polymerization of the UV-curable ink) and that consequently problematic migration of low-molecular and potentially health-endangering ink components into packaging products, e.g. food, is to be expected.
  • a (re) formulation of the ink with higher molecular weight and therefore less migrating components is possible, but this reduces the viscosity of the ink, which can lead to problems when printing the ink.
  • inert gas can prevent undesired migration, since fewer (potentially migrating) inhibitors can be used in the ink in a curing environment that is poor in oxygen.
  • curing under inert gas is costly, among other things. because a lot of space is required for the corresponding components and inert gas is required.
  • a method for curing ink on a printing material wherein at least one UV-curable ink is applied in the form of drops to a printing material and exposed to UV radiation by means of at least one first UV radiator and thereby pre-cured, is characterized in that the ink is exposed to UV radiation by means of at least one second UV radiator of a UV dryer under inert gas, under inert gas-enriched air or under oxygen-reduced air and is thereby further hardened, and that the ink is then further hardened by means of at least one third UV radiator of a further UV The dryer is exposed to UV radiation and thereby post-cured.
  • the invention advantageously enables UV-curable inks to be cured sufficiently so that undesired migration of low-molecular ink constituents is reduced or avoided.
  • hardening takes place in three successive steps: pre-hardening or so-called pinning, further hardening and post-hardening.
  • the pre-hardening serves to increase the viscosity of the ink on the printing material and thereby prevent the ink from running too heavily on the printing material, in particular the printing dots generated by ink droplets on the printing material.
  • the viscosity is only slightly increased; in particular, the ink has not yet hardened through. This can improve the print quality, in particular by preventing inks of different colors from running into one another (so-called "inter color bleeding").
  • the further hardening serves to further increase the viscosity of the ink (in relation to the pre-hardening).
  • the ink then adheres well to the substrate and has adequate abrasion resistance.
  • the further hardening is preferably carried out in such a way that more than 90% of the double bonds are converted in the ink.
  • Post-curing ultimately serves to combine monomers still present in the ink and thereby reduce or prevent potential migration.
  • the second hardening step (referred to as "further hardening” or alternatively: intermediate hardening) - and preferably only this step - takes place under inert gas, inert gas-enriched air or under oxygen-reduced air, i.e. not under ambient air like the other two steps.
  • the post-curing (alternatively referred to as: final curing) ensures that the ink is largely and preferably essentially completely cured when it leaves the printing press.
  • inert gas alternatively referred to as protective gas
  • inert gas-enriched air or under oxygen-reduced air whereas all other curing steps are preferably carried out under untreated air, for example ambient air.
  • inert gas means that essentially pure inert gas, for example nitrogen or helium, is preferably used.
  • air enriched with inert gas means that the proportion of inert gas, for example nitrogen or helium, in the air used or another gas mixture used is preferably significantly higher than in the ambient air.
  • Under oxygen-reduced air means that the proportion of oxygen in the air used or another gas mixture used is preferably significantly reduced compared to the ambient air.
  • the increase or decrease is "essential" if this measure preferably achieves that i) an inhibition of the radicals generated by UV photons and photoinitiators, which is problematic with regard to migration, is avoided, and / or that ii) one with regard to migration insufficient and therefore problematic crosslinking is avoided or sufficient crosslinking is achieved and / or that iii) the amount of (potentially migrating and therefore health-endangering) Photoinitiators in the ink can be reduced to a level that is problem-free with regard to migration.
  • a device for hardening under inert gas or the like e.g. an inert gas housing including inert gas supply and discharge, can advantageously be limited to the second hardening step or its location or station. As a result, installation space, components and the associated costs can be saved. In addition, the amount of inert gas required can be reduced.
  • a preferred development of the invention can be characterized in that the ink is exposed to UV radiation by means of the first UV radiator under air.
  • An inert gas device is not required here. Installation space and costs can be saved.
  • a preferred development of the invention can be characterized in that the ink is exposed to UV radiation by means of the third UV radiator under air.
  • An inert gas device is also not required here. Installation space and costs can be saved.
  • a preferred development of the invention can be characterized in that nitrogen, alternatively helium, is used as the inert gas or protective gas.
  • a preferred development of the invention can be characterized in that the UV dryer comprises several second UV emitters, e.g. two, three or four.
  • a preferred development of the invention can be characterized in that the second UV radiators are arranged in a common inert gas housing.
  • the housing can be formed from sheet metal, with a shape adaptation, for example a curvature, preferably being made to the transport path.
  • a preferred development of the invention can be characterized in that the further UV dryer comprises several third UV radiators, e.g. two, three or four.
  • the further UV dryer comprises at least two stations spaced apart from one another with a plurality of third or a plurality of fourth UV emitters.
  • the substrate can be guided by means of several deflection rollers, e.g. in a meander shape.
  • a preferred development of the invention can be characterized in that at least one second UV radiator and / or at least one third UV radiator and / or at least one fourth UV radiator hardens the ink through the printing material.
  • This development is particularly advantageous for (UV) transparent substrates.
  • the ink is preferably applied to a front side of the printing material and at least one radiator is arranged in the space on the rear side of the printing material, or vice versa.
  • a preferred development of the invention can be characterized in that the printing material is moved along the at least one second UV radiator by means of a preferably heated temperature control roller that supports the curing treatment.
  • Figure 1 shows a schematic representation of an inkjet printing machine 1 (in short: machine) when carrying out a preferred embodiment of the method according to the invention.
  • the machine processes printing material 2 in web form, preferably paper, cardboard or plastic film.
  • the printing material is fed, for example, from a roll feeder and then printed with ink.
  • Printing takes place in a first station 3 of the machine, namely in an ink printing unit 3 with several, preferably eight rows of print heads 4 each with several ink heads for generating ink droplets (preferably corresponding to a print image to be printed).
  • a respective first UV radiator 5 is preferably arranged directly downstream of each print head row.
  • These emitters are used to pre-harden, i.e. only partially polymerize, the ink (so-called pinning).
  • the exposure to UV radiation takes place here preferably under air, for example ambient air unchanged in its composition, and not under an inert gas other than air.
  • the Pinning is preferably done with UV radiation of 385 nm or (for white ink) of 395 nm wavelength.
  • the printing material 2 leaves the first station at B and is passed on to C, where it is fed to a second station 10.
  • the second station forms a UV dryer 10 with at least one, but preferably several second UV radiators 11, for. B. two UV emitters 11a and 11b. These emitters are used for further hardening, preferably for extensive (but still not complete) hardening or polymerizing of the ink.
  • the further hardening of the ink does not take place under (ambient) air, but under an inert gas, under inert gas-enriched air or under oxygen-reduced air or similar functions.
  • the inert gas used is preferably nitrogen; alternatively, helium or another noble gas can be used.
  • the UV emitters 11 can be designed, for example, as UV lamps, preferably mercury vapor lamps or alternatively UV LED emitters and each have between 200 and 300 W / cm (assuming a web transport speed of about 50 m / min).
  • an inert gas housing 12 which preferably houses the second UV radiators 11 together. This can be formed from sheet metal. It has an inert gas feed line 13 and an inert gas discharge line 14.
  • the temperature control in particular heating, can support the hardening process.
  • the temperature of the surface can preferably be between 40 and 50 ° C. and can preferably be regulated as a function of the speed.
  • the printing material web 2 can then be passed through an optional flexographic printing unit 15 in which UV-curable lacquer can preferably be applied.
  • the web 2 leaves the second station 10 and at E becomes a third station 20, ie a further UV dryer 20 and at F 'optionally a fourth station 30, ie one again another UV dryer 30 is supplied.
  • the third and fourth stations can be arranged at a distance from one another, in particular the path 2 between E 'and F' can have a meandering path.
  • the third station 20 comprises at least one, but preferably several third UV radiators 21, e.g. B. two UV emitters 21a and 21b. These emitters are used to post-harden the ink, preferably to substantially completely harden or polymerize the already pre-hardened and further hardened (and thereby preferably largely hardened) ink.
  • the optional fourth station 30 comprises at least one, but preferably several further third UV emitters 31, e.g. B. two UV emitters 31a and 31b. These emitters are also used for post-curing.
  • the third radiators 21 and the further third radiators 31 can be referred to collectively as “third radiators”.
  • the third UV radiator 21 and the optional further third UV radiator 31 can preferably be designed as mercury vapor lamps or alternatively UV-LED radiators and each have between 100 and 200 W / cm (assuming a web transport speed of about 50 m / min).
  • the post-curing in the third and the optional fourth station is preferably carried out under air, e.g. ambient air unchanged in its composition, and not under an inert gas other than air.
  • the post-curing of the ink, i.e. exposure to UV radiation, in the third and / or fourth station can be carried out from the printed side 40 of the printing material (cf. Figure 2 ) or it can be done through the printing substrate 2 (from the unprinted rear side of the printing substrate).
  • a combination (of the printed and the unprinted side of the substrate) is also possible: B. irradiation in the third station 20 from the printed side and in the fourth station 30 from the unprinted side.
  • the second station 10 can also Irradiation take place from the unprinted side (through the printing material 2) and therefore different from what is shown in the figures.
  • the method according to the invention thus comprises i) UV pre-curing under air, then ii) further UV curing under inert gas, under inert gas-enriched air or under oxygen-reduced air or the similar and finally iii) the UV post-curing in air. Further upstream, intermediate or downstream UV curing steps or temperature control steps are also possible.
  • Figure 2 shows (also schematically) a side view of the machine 1 from FIG Figure 1 when carrying out the preferred embodiment of the method according to the invention.
  • the web path 41 of the printing material 2 preferably runs in a meander shape and can include several deflecting rollers 6.
  • the inert gas housing 12 can, as shown, be arranged in the area of the web guide by means of the temperature control roller 7. It can comprise (inlet and outlet) diaphragms 9 which have the effect that inert gas fed to the housing 12 at 13 is essentially discharged again at 14 and does not escape in an uncontrolled manner at other points.

Abstract

Ein erfindungsgemäßes Verfahren zum Härten von Tinte auf einem Bedruckstoff, wobei wenigstens eine UV-härtbare Tinte in Form von Tropfen auf einen Bedruckstoff (2) aufgebracht und mittels wenigstens eines ersten UV-Strahlers (5) mit UV-Strahlung beaufschlagt und dadurch vorgehärtet wird, zeichnet sich dadurch aus, dass die Tinte mittels wenigstens eines zweiten UV-Strahlers (11, 11a, 11b) eines UV-Trockners (10) unter Inertgas, unter inertgasangereicherter Luft oder unter sauerstoffreduzierter Luft mit UV-Strahlung beaufschlagt und dadurch weiter gehärtet wird, und dass die Tinte anschließend mittels wenigstens eines dritten UV-Strahlers (21, 21a, 21b, 31, 31a, 31b) eines weiteren UV-Trockners (20, 30) mit UV-Strahlung beaufschlagt und dadurch nachgehärtet wird. Die Erfindung ermöglicht es, UV-härtbare Tinten ausreichend zu härten, so dass eine unerwünschte Migration von niedermolekularen Tintenbestandteilen reduziert oder vermieden wird.

Figure imgaf001
A method according to the invention for curing ink on a printing material, wherein at least one UV-curable ink is applied in the form of drops to a printing material (2) and exposed to UV radiation by means of at least one first UV radiator (5) and thereby pre-cured, is characterized in that the ink is exposed to UV radiation by means of at least one second UV radiator (11, 11a, 11b) of a UV dryer (10) under inert gas, under inert gas-enriched air or under oxygen-reduced air and is thereby further hardened, and that the ink is then exposed to UV radiation by means of at least one third UV radiator (21, 21a, 21b, 31, 31a, 31b) of a further UV dryer (20, 30) and is thereby post-cured. The invention makes it possible to cure UV-curable inks sufficiently so that undesired migration of low molecular weight ink constituents is reduced or avoided.
Figure imgaf001

Description

Erfindunginvention

Die vorliegende Erfindung betrifft ein Verfahren zum Härten von Tinte auf einem Bedruckstoff gemäß dem Oberbegriff von Anspruch 1.The present invention relates to a method for curing ink on a printing substrate according to the preamble of claim 1.

Technisches Gebiet der ErfindungTechnical field of the invention

Die Erfindung liegt auf dem technischen Gebiet der grafischen Industrie und dort insbesondere im Bereich des Härtens, insbesondere des Härtens mit UV-Strahlung, von flüssiger Tinte auf bogen- oder bahnförmigen Bedruckstoffen, bevorzugt aus Papier, Karton, Pappe, Kunststoff oder Verbundmaterial.The invention is in the technical field of the graphics industry and there in particular in the field of curing, in particular curing with UV radiation, of liquid ink on sheet or web-shaped printing materials, preferably made of paper, cardboard, cardboard, plastic or composite material.

Stand der TechnikState of the art

Das Trocknen und/oder Härten (oder allgemeiner: das Behandeln) von bevorzugt flüssigen oder pastösen Druckmedien/Fluiden (wie z.B. Druckfarbe, -lack oder -tinte) auf einem Bedruckstoff kann auf verschiedene, auch kombinierbare Weisen erfolgen: durch Beaufschlagen mit Heißluft, mit elektromagnetischer Strahlung (z.B. UV oder IR) oder Teilchenstrahlung (z.B. Elektronen) oder durch Kontaktieren des Bedruckstoffs mit erwärmten Flächen (z.B. Zylindern, Walzen oder Bändern). Wasserbasierte Druckmedien werden meist thermisch, bevorzugt mit IR getrocknet, polymerisierbare Druckmedien meist mit UV. Als Strahlungsquellen UV kommen Quecksilberdampflampen und zunehmend LED-Strahler zum Einsatz. Das Härten von UV-härtbaren Tinten kann bekanntermaßen unter Inertgas erfolgen.The drying and / or hardening (or more generally: the treatment) of preferably liquid or pasty printing media / fluids (such as printing ink, varnish or ink) on a printing material can be done in various ways, which can also be combined: by applying hot air, with electromagnetic radiation (e.g. UV or IR) or particle radiation (e.g. electrons) or by contacting the printing material with heated surfaces (e.g. cylinders, rollers or belts). Water-based printing media are usually dried thermally, preferably with IR, while polymerizable printing media are usually dried with UV. Mercury vapor lamps and increasingly LED lamps are used as UV radiation sources. It is known that UV-curable inks can be hardened under an inert gas.

Das Härten von UV-härtbaren Tinten kann in mehreren Schritten erfolgen, z.B. kann zuerst ein so genanntes Pinnen (Vorhärten) und dann ein Endhärten erfolgen: Die WO2019007979A1 offenbart das UV-Härten und das anschließende UV-Härten unter Inertgas. Die EP3045477A1 offenbart Ähnliches. Die EP2767407B1 offenbart ebenfalls Ähnliches, wobei das initiale Härten ein so genanntes Pinnen darstellt. Der jeweils letzte Härtungsschritt erfolgt diesen Dokumenten zufolge unter Inertgas. Die EP1473341B1 offenbart zwei UV-Härtungsschritte; beide unter Inertgas. Die EP2596874A1 offenbart das Trocknen (nicht UV-Härten) unter Inertgas und das anschließende UV-Härten.The curing of UV-curable inks can take place in several steps, for example so-called pinning (pre-curing) and then final curing can take place first WO2019007979A1 discloses UV curing and subsequent UV curing under Inert gas. The EP3045477A1 reveals something similar. The EP2767407B1 also discloses something similar, the initial hardening being a so-called pinning. According to these documents, the last curing step in each case takes place under inert gas. The EP1473341B1 discloses two UV curing steps; both under inert gas. The EP2596874A1 discloses drying (not UV curing) under inert gas and subsequent UV curing.

Im Stand der Technik kann das Problem auftreten, dass das Ergebnis einer UV-Härtung von Tinte nicht ausreichend ist (unzureichende Vernetzung/Polymerisation der UV-härtbaren Tinte) und dass folglich mit problematischer Migration von niedermolekularen und potentiell gesundheitsgefährdenden Tintenbestandteilen in Verpackungsprodukte, z.B. Lebensmittel, zu rechnen ist.In the prior art, the problem can arise that the result of UV curing of the ink is not sufficient (insufficient crosslinking / polymerization of the UV-curable ink) and that consequently problematic migration of low-molecular and potentially health-endangering ink components into packaging products, e.g. food, is to be expected.

Eine (Um-) Formulierung der Tinte mit höhermolekularen und daher weniger migrierenden Bestandteilen ist zwar möglich, dabei wird allerdings die Viskosität der Tinte verringert, was zu Problemen beim Verdrucken der Tinte führen kann.A (re) formulation of the ink with higher molecular weight and therefore less migrating components is possible, but this reduces the viscosity of the ink, which can lead to problems when printing the ink.

Der Einsatz von Inertgas kann unerwünschte Migration verhindern, da in sauerstoffarmer Härtungs-Umgebung weniger (potentiell migrierende) Inhibitoren in der Tinte eingesetzt werden können. Das Härten unter Inertgas ist allerdings kostenintensiv, u. a. da viel Bauraum für entsprechende Komponenten beansprucht und Inertgas benötigt wird.The use of inert gas can prevent undesired migration, since fewer (potentially migrating) inhibitors can be used in the ink in a curing environment that is poor in oxygen. However, curing under inert gas is costly, among other things. because a lot of space is required for the corresponding components and inert gas is required.

Aufgabetask

Es ist daher eine Aufgabe der Erfindung, eine Verbesserung gegenüber dem Stand der Technik zu schaffen, welche es insbesondere ermöglicht, UV-härtbaren Tinten ausreichend zu härten, so dass eine unerwünschte Migration von niedermolekularen Tintenbestandteilen reduziert oder vermieden wird.It is therefore an object of the invention to create an improvement over the prior art which in particular makes it possible to cure UV-curable inks sufficiently so that undesired migration of low-molecular ink constituents is reduced or avoided.

Erfindungsgemäße LösungSolution according to the invention

Diese Aufgabe wird erfindungsgemäß durch ein Verfahren nach Anspruch 1 gelöst.This object is achieved according to the invention by a method according to claim 1.

Vorteilhafte und daher bevorzugte Weiterbildungen der Erfindung ergeben sich aus den Unteransprüchen sowie aus der Beschreibung und den Zeichnungen.Advantageous and therefore preferred developments of the invention emerge from the subclaims as well as from the description and the drawings.

Ein erfindungsgemäßes Verfahren zum Härten von Tinte auf einem Bedruckstoff, wobei wenigstens eine UV-härtbare Tinte in Form von Tropfen auf einen Bedruckstoff aufgebracht und mittels wenigstens eines ersten UV-Strahlers mit UV-Strahlung beaufschlagt und dadurch vorgehärtet wird, zeichnet sich dadurch aus, dass die Tinte mittels wenigstens eines zweiten UV-Strahlers eines UV-Trockners unter Inertgas, unter inertgasangereicherter Luft oder unter sauerstoffreduzierter Luft mit UV-Strahlung beaufschlagt und dadurch weiter gehärtet wird, und dass die Tinte anschließend mittels wenigstens eines dritten UV-Strahlers eines weiteren UV-Trockners mit UV-Strahlung beaufschlagt und dadurch nachgehärtet wird.A method according to the invention for curing ink on a printing material, wherein at least one UV-curable ink is applied in the form of drops to a printing material and exposed to UV radiation by means of at least one first UV radiator and thereby pre-cured, is characterized in that the ink is exposed to UV radiation by means of at least one second UV radiator of a UV dryer under inert gas, under inert gas-enriched air or under oxygen-reduced air and is thereby further hardened, and that the ink is then further hardened by means of at least one third UV radiator of a further UV The dryer is exposed to UV radiation and thereby post-cured.

Die Erfindung ermöglicht in vorteilhafter Weise, UV-härtbaren Tinten ausreichend zu härten, so dass eine unerwünschte Migration von niedermolekularen Tintenbestandteilen reduziert oder vermieden wird.The invention advantageously enables UV-curable inks to be cured sufficiently so that undesired migration of low-molecular ink constituents is reduced or avoided.

Erfindungsgemäß erfolgt das Härten in drei aufeinander folgenden Schritten: dem Vorhärten bzw. so genannten Pinnen, dem weiteren Härten und dem Nachhärten.According to the invention, hardening takes place in three successive steps: pre-hardening or so-called pinning, further hardening and post-hardening.

Das Vorhärten (Pinnen) dient dazu, die Viskosität der Tinte auf dem Bedruckstoff zu erhöhen und dadurch zu verhindern, dass die Tinte auf dem Bedruckstoff, insbesondere die von Tintentropfen erzeugten Druckpunkte auf dem Bedruckstoff, zu stark verlaufen. Die Viskosität wird nur wenig erhöht; die Tinte ist insbesondere noch nicht durchgehärtet. Hierdurch kann die Druckqualität verbessert werden, insbesondere durch das Vermeiden des Ineinanderlaufens von Tinten verschiedener Farben (so genanntes "inter colour bleeding".The pre-hardening (pinning) serves to increase the viscosity of the ink on the printing material and thereby prevent the ink from running too heavily on the printing material, in particular the printing dots generated by ink droplets on the printing material. The viscosity is only slightly increased; in particular, the ink has not yet hardened through. This can improve the print quality, in particular by preventing inks of different colors from running into one another (so-called "inter color bleeding").

Das weitere Härten dient der weiteren Erhöhung der Viskosität der Tinte (in Bezug auf das Vorhärten). Die Tinte haftet dann gut am Bedruckstoff an und weist eine ausreichende Abrasionsbeständigkeit auf. Das weitere Härten erfolgt bevorzugt derart, dass in der Tinte mehr als 90% der Doppelbindungen umgesetzt sind.The further hardening serves to further increase the viscosity of the ink (in relation to the pre-hardening). The ink then adheres well to the substrate and has adequate abrasion resistance. The further hardening is preferably carried out in such a way that more than 90% of the double bonds are converted in the ink.

Das Nachhärten dient schließlich dazu, noch in der Tinte vorhandene Monomere zu verbinden und dadurch eine potentielle Migration zu reduzieren oder zu verhindern.Post-curing ultimately serves to combine monomers still present in the ink and thereby reduce or prevent potential migration.

Eine 100%ige Durchhärtung ist auch mit drei oder mehr Härtungsschritten nicht zu erreichen. Allerdings sind ausreichend gute Härtungsergebnisse mit dem erfindungsgemäßen Härten erzielbar.100% curing cannot be achieved even with three or more curing steps. However, sufficiently good hardening results can be achieved with the hardening according to the invention.

Der zweite Härtungsschritt (das "weitere Härten" oder alternativ bezeichnet: das Zwischenhärten) - und bevorzugt nur dieser Schritt - erfolgt dabei unter Inertgas, inertgasangereicherter Luft oder unter sauerstoffreduzierter Luft, also nicht unter Umgebungsluft wie die beiden anderen Schritte. Das Nachhärten (alternativ bezeichnet: Endhärten) stellt sicher, dass die Tinte beim Verlassen der Druckmaschine weitgehend und bevorzugt im Wesentlichen vollständig ausgehärtet ist.The second hardening step (referred to as "further hardening" or alternatively: intermediate hardening) - and preferably only this step - takes place under inert gas, inert gas-enriched air or under oxygen-reduced air, i.e. not under ambient air like the other two steps. The post-curing (alternatively referred to as: final curing) ensures that the ink is largely and preferably essentially completely cured when it leaves the printing press.

Bevorzugt erfolgt also nur der zweite Härtungsschritt unter Inertgas (alternativ bezeichnet: Schutzgas), inertgasangereicherter Luft oder unter sauerstoffreduzierter Luft, alle anderen Härtungsschritte dagegen erfolgen bevorzugt unter unbehandelter Luft, z.B. Umgebungsluft. "Unter Inertgas" meint dabei, dass bevorzugt Wesentlichen reines Inertgas, z.B. Stickstoff oder Helium, verwendet wird. "Unter inertgasangereicherter Luft" meint dabei, dass bevorzugt der Anteil an Inertgas, z.B. Stickstoff oder Helium, in der verwendeten Luft oder einem sonstigen verwendeten Gasgemisch gegenüber der Umgebungsluft wesentlich erhöht ist. "Unter sauerstoffreduzierter Luft" meint dabei, dass bevorzugt der Anteil an Sauerstoff in der verwendeten Luft oder einem sonstigen verwendeten Gasgemisch gegenüber der Umgebungsluft wesentlich verringert ist. Die Erhöhung oder die Verringerung ist dabei "wesentlich", wenn durch diese Maßnahme bevorzugt erreicht wird, dass i) eine hinsichtlich der Migration problematische Inhibierung der durch UV-Photonen und Photoinitiatoren erzeugten Radikale vermieden wird, und/oder dass ii) eine hinsichtlich der Migration unzureichende und daher problematische Vernetzung vermieden wird bzw. eine ausreichende Vernetzung erreicht wird und/oder dass iii) die Menge an (potentiell migrierenden und daher gesundheitsgefährdenden) Photoinitiatoren in der Tinte auf ein hinsichtlich der Migration problemloses Maß reduziert werden kann.Preferably, only the second curing step is carried out under inert gas (alternatively referred to as protective gas), inert gas-enriched air or under oxygen-reduced air, whereas all other curing steps are preferably carried out under untreated air, for example ambient air. In this context, “inert gas” means that essentially pure inert gas, for example nitrogen or helium, is preferably used. In this context, “air enriched with inert gas” means that the proportion of inert gas, for example nitrogen or helium, in the air used or another gas mixture used is preferably significantly higher than in the ambient air. “Under oxygen-reduced air” means that the proportion of oxygen in the air used or another gas mixture used is preferably significantly reduced compared to the ambient air. The increase or decrease is "essential" if this measure preferably achieves that i) an inhibition of the radicals generated by UV photons and photoinitiators, which is problematic with regard to migration, is avoided, and / or that ii) one with regard to migration insufficient and therefore problematic crosslinking is avoided or sufficient crosslinking is achieved and / or that iii) the amount of (potentially migrating and therefore health-endangering) Photoinitiators in the ink can be reduced to a level that is problem-free with regard to migration.

Eine Vorrichtung für das Härten unter Inertgas o.ä., z.B. ein Inertgas-Gehäuse samt Inertgas-Zufuhr und -abfuhr, kann in vorteilhafter Weise auf den zweiten Härtungsschritt bzw. dessen Ort bzw. Station beschränkt werden. Hierdurch können Bauraum, Bauteile und damit verbundene Kosten eingespart werden. Zudem kann die Menge an benötigtem Inertgas reduziert werden.A device for hardening under inert gas or the like, e.g. an inert gas housing including inert gas supply and discharge, can advantageously be limited to the second hardening step or its location or station. As a result, installation space, components and the associated costs can be saved. In addition, the amount of inert gas required can be reduced.

Auf diese Weise kann mit Vorteil ein (für industriell hergestellte Druckprodukte hoher bis sehr hoher Qualität) ausreichendes Härten erreicht werden, insbesondere für den Fall, dass die Druckprodukte industriell weiterverarbeitet werden, z.B. zur Herstellung von Verpackungen.In this way, sufficient hardening (for industrially produced printed products of high to very high quality) can advantageously be achieved, especially in the event that the printed products are further processed industrially, e.g. for the production of packaging.

Auf diese Weise kann bei der Herstellung von Verpackungen ebenfalls mit Vorteil erreicht werden, dass eine unerwünschte (weil potentiell gesundheitsgefährdende) Migration von niedermolekularen Bestandteilen der Tinte in die Verpackung und in das verpackte Produkt, z.B. ein Lebensmittel, ausreichend reduziert oder vermieden wird.In this way, in the production of packaging, it can also be advantageously achieved that an undesired (because potentially health-endangering) migration of low-molecular-weight components of the ink into the packaging and into the packaged product, e.g. a food, is sufficiently reduced or avoided.

Weiterbildungen der ErfindungDevelopments of the invention

Eine bevorzugte Weiterbildung der Erfindung kann sich dadurch auszeichnen, dass die Tinte mittels des ersten UV-Strahlers unter Luft mit UV-Strahlung beaufschlagt wird. Eine Inertgas-Vorrichtung wird hier nicht benötigt. Bauraum und Kosten können eingespart werden.A preferred development of the invention can be characterized in that the ink is exposed to UV radiation by means of the first UV radiator under air. An inert gas device is not required here. Installation space and costs can be saved.

Eine bevorzugte Weiterbildung der Erfindung kann sich dadurch auszeichnen, dass die Tinte mittels des dritten UV-Strahlers unter Luft mit UV-Strahlung beaufschlagt wird. Eine Inertgas-Vorrichtung wird hier ebenfalls nicht benötigt. Bauraum und Kosten können eingespart werden.A preferred development of the invention can be characterized in that the ink is exposed to UV radiation by means of the third UV radiator under air. An inert gas device is also not required here. Installation space and costs can be saved.

Eine bevorzugte Weiterbildung der Erfindung kann sich dadurch auszeichnen, dass Stickstoff, alternativ Helium, als das Inertgas oder Schutzgas verwendet wird.A preferred development of the invention can be characterized in that nitrogen, alternatively helium, is used as the inert gas or protective gas.

Eine bevorzugte Weiterbildung der Erfindung kann sich dadurch auszeichnen, dass der UV-Trockner mehrere zweite UV-Strahler, z.B. zwei, drei oder vier umfasst.A preferred development of the invention can be characterized in that the UV dryer comprises several second UV emitters, e.g. two, three or four.

Eine bevorzugte Weiterbildung der Erfindung kann sich dadurch auszeichnen, dass die zweiten UV-Strahler in einem gemeinsamen Inertgas-Gehäuse angeordnet sind. Das Gehäuse kann aus Blech geformt sein, wobei bevorzugt eine Formanpassung, z.B. eine Krümmung, an den Transportpfad erfolgt.A preferred development of the invention can be characterized in that the second UV radiators are arranged in a common inert gas housing. The housing can be formed from sheet metal, with a shape adaptation, for example a curvature, preferably being made to the transport path.

Eine bevorzugte Weiterbildung der Erfindung kann sich dadurch auszeichnen, dass der weitere UV-Trockner mehrere dritte UV-Strahler, z.B. zwei, drei oder vier umfasst.A preferred development of the invention can be characterized in that the further UV dryer comprises several third UV radiators, e.g. two, three or four.

Eine bevorzugte Weiterbildung der Erfindung kann sich dadurch auszeichnen, dass der weitere UV-Trockner wenigstens zwei voneinander beabstandete Stationen mit mehreren dritten bzw. mehreren vierten UV-Strahlern umfasst. Im Zwischenraum entlang des Abstands zwischen den Stationen kann der Bedruckstoff mittels mehrerer Umlenkwalzen geführt werden, z.B. mäanderförmig.A preferred development of the invention can be characterized in that the further UV dryer comprises at least two stations spaced apart from one another with a plurality of third or a plurality of fourth UV emitters. In the space between the stations, the substrate can be guided by means of several deflection rollers, e.g. in a meander shape.

Eine bevorzugte Weiterbildung der Erfindung kann sich dadurch auszeichnen, dass wenigstens ein zweiter UV-Strahler und/oder wenigstens ein dritter UV-Strahler und/oder wenigstens ein vierter UV-Strahler die Tinte durch den Bedruckstoff hindurch härtet. Diese Weiterbildung ist insbesondere bei (UV-) transparenten Bedruckstoffen von Vorteil. Dabei ist die Tinte bevorzugt auf einer Vorderseite des Bedruckstoffs aufgetragen und wenigstens ein Strahler im Raum auf der Rückseite des Bedruckstoffs angeordnet, oder umgekehrt.A preferred development of the invention can be characterized in that at least one second UV radiator and / or at least one third UV radiator and / or at least one fourth UV radiator hardens the ink through the printing material. This development is particularly advantageous for (UV) transparent substrates. The ink is preferably applied to a front side of the printing material and at least one radiator is arranged in the space on the rear side of the printing material, or vice versa.

Eine bevorzugte Weiterbildung der Erfindung kann sich dadurch auszeichnen, dass der Bedruckstoff mittels einer die Härtungsbehandlung unterstützenden bevorzugt erwärmten Temperierwalze entlang des wenigstens einen zweiten UV-Strahlers bewegt wird.A preferred development of the invention can be characterized in that the printing material is moved along the at least one second UV radiator by means of a preferably heated temperature control roller that supports the curing treatment.

Die Merkmale der Erfindung, der Weiterbildungen der Erfindung und der Ausführungsbeispiele zur Erfindung stellen auch in beliebiger Kombination miteinander vorteilhafte Weiterbildungen der Erfindung dar. Weiterbildungen der Erfindung können zudem die - im obigen Abschnitt "Technisches Gebiet der Erfindung" offenbarten - Einzelmerkmale oder Merkmalskombinationen aufweisen.The features of the invention, the developments of the invention and the exemplary embodiments of the invention also represent advantageous developments of the invention in any combination with one another. Further developments of the invention can also have the individual features or combinations of features disclosed in the above section "Technical Field of the Invention".

Ausführungsbeispiele zur ErfindungEmbodiments of the invention

Die Erfindung und deren bevorzugte Weiterbildungen werden nachfolgend unter Bezug auf die Zeichnungen anhand bevorzugter Ausführungsbeispiele näher beschrieben. Einander entsprechende Merkmale sind in den Figuren mit denselben Bezugszeichen versehen.The invention and its preferred developments are described in more detail below with reference to the drawings using preferred exemplary embodiments. Features that correspond to one another are provided with the same reference symbols in the figures.

Die Zeichnungen zeigen:

Figur 1
Schemadarstellung einer verfahrensdurchführenden Druckmaschine; und
Figur 2
Seitenansicht der Tintendruckmaschine.
The drawings show:
Figure 1
Schematic representation of a printing machine carrying out the process; and
Figure 2
Side view of the inkjet printing machine.

Figur 1 zeigt eine schematische Darstellung einer Tintendruckmaschine 1 (kurz: Maschine) bei der Durchführung einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens. Die Maschine verarbeitet bahnförmigen Bedruckstoff 2, bevorzugt Papier, Karton oder Kunststofffolie. Der Bedruckstoff wird bei A z.B. von einem Rollenanleger zugeführt und dann mit Tinte bedruckt. Figure 1 shows a schematic representation of an inkjet printing machine 1 (in short: machine) when carrying out a preferred embodiment of the method according to the invention. The machine processes printing material 2 in web form, preferably paper, cardboard or plastic film. At A, the printing material is fed, for example, from a roll feeder and then printed with ink.

Das Bedrucken erfolgt in einer ersten Station 3 der Maschine und zwar in einem Tintendruckwerk 3 mit mehreren, bevorzugt acht Druckkopfreihen 4 mit jeweils mehreren Tintendruckköpfen zum Erzeugen von Tintentropfen (bevorzugt entsprechend einem zu druckendem Druckbild). Jeder Druckkopfreihe ist ein jeweiliger erster UV-Strahler 5 bevorzugt direkt nachgeordnet. Diese Strahler dienen dem Vorhärten, das heißt dem nur teilweise Polymerisieren, der Tinte (dem sogenannten Pinnen). Die Beaufschlagung mit UV-Strahlung erfolgt hier bevorzugt unter Luft, z.B. in ihrer Zusammensetzung unveränderter Umgebungsluft, und nicht unter von Luft verschiedenem Inertgas. Das Pinnen erfolgt bevorzugt mit UV-Strahlung von 385 nm oder (für weiße Tinte) von 395 nm Wellenlänge. Der Bedruckstoff 2 verlässt bei B die erste Station und wird weiter zu C geführt, wo er einer zweiten Station 10 zugeführt wird.Printing takes place in a first station 3 of the machine, namely in an ink printing unit 3 with several, preferably eight rows of print heads 4 each with several ink heads for generating ink droplets (preferably corresponding to a print image to be printed). A respective first UV radiator 5 is preferably arranged directly downstream of each print head row. These emitters are used to pre-harden, i.e. only partially polymerize, the ink (so-called pinning). The exposure to UV radiation takes place here preferably under air, for example ambient air unchanged in its composition, and not under an inert gas other than air. The Pinning is preferably done with UV radiation of 385 nm or (for white ink) of 395 nm wavelength. The printing material 2 leaves the first station at B and is passed on to C, where it is fed to a second station 10.

Die zweite Station bildet einen UV-Trockner 10 mit wenigstem einem, bevorzugt jedoch mehreren zweiten UV-Strahlern 11, z. B. zwei UV-Strahler 11a und 11b. Diese Strahler dienen dem weiteren Härten, bevorzugt dem weitgehenden (aber immer noch nicht vollständigen) Aushärten beziehungsweise Polymerisieren der Tinte. Das weitere Härten der Tinte erfolgt hier nicht unter (Umgebungs-) Luft, sondern unter einem Inertgas, unter Inertgas angereicherter Luft oder unter sauerstoffreduzierter Luft oder funktional Ähnlichem. Als Inertgas wird bevorzugt Stickstoff verwendet; alternativ kann Helium oder ein sonstiges Edelgas verwendet werden.The second station forms a UV dryer 10 with at least one, but preferably several second UV radiators 11, for. B. two UV emitters 11a and 11b. These emitters are used for further hardening, preferably for extensive (but still not complete) hardening or polymerizing of the ink. The further hardening of the ink does not take place under (ambient) air, but under an inert gas, under inert gas-enriched air or under oxygen-reduced air or similar functions. The inert gas used is preferably nitrogen; alternatively, helium or another noble gas can be used.

Die UV-Strahler 11 können z.B. als UV-Lampen, bevorzugt Quecksilberdampflampen oder alternativ UV-LED-Strahler ausgebildet sein und jeweils zwischen 200 und 300 W/cm aufweisen (bei angenommener Bahntransportgeschwindigkeit von etwa 50 m/min).The UV emitters 11 can be designed, for example, as UV lamps, preferably mercury vapor lamps or alternatively UV LED emitters and each have between 200 and 300 W / cm (assuming a web transport speed of about 50 m / min).

Zur Bestrahlung unter Inertgas ist ein Inertgas-Gehäuse 12 vorgesehen, welches die zweiten UV-Strahler 11 bevorzugt gemeinsam einhaust. Dieses kann aus Blech geformt sein. Es weist eine Inertgas-Zuleitung 13 und eine Inertgas-Ableitung 14 auf.For irradiation under inert gas, an inert gas housing 12 is provided, which preferably houses the second UV radiators 11 together. This can be formed from sheet metal. It has an inert gas feed line 13 and an inert gas discharge line 14.

Es kann vorgesehen sein, den Bedruckstoff 2 mittels einer Temperierwalze 7 beziehungsweise deren temperierter Oberfläche 8 oder einer sonstigen temperierten Oberfläche 8 entlang der zweiten UV-Strahler 11 zu führen. Die Temperierung, insbesondere eine Erwärmung, kann den Härtungsprozess unterstützen. Die Temperatur der Oberfläche kann bevorzugt zwischen 40 und 50 °C betragen und kann bevorzugt geschwindigkeitsabhängig geregelt werden.Provision can be made for the printing substrate 2 to be guided along the second UV radiator 11 by means of a temperature control roller 7 or its temperature-controlled surface 8 or another temperature-controlled surface 8. The temperature control, in particular heating, can support the hardening process. The temperature of the surface can preferably be between 40 and 50 ° C. and can preferably be regulated as a function of the speed.

Die Bedruckstoffbahn 2 kann anschließend durch ein optionales Flexo-Druckwerk 15 geführt werden, in welchem bevorzugt UV-härtbarer Lack aufgetragen werden kann. Bei D verlässt die Bahn 2 die zweite Station 10 und wird bei E einer dritten Station 20, d.h. einem weiteren UV-Trockner 20 und bei F' optional einer vierten Station 30, d.h. einem nochmals weiteren UV-Trockner 30 zugeführt. Die dritte und die vierte Station können zu einander beabstandet angeordnet sein, insbesondere kann die Bahn 2 zwischen E' und F' einen mäanderförmigen Bahnverlauf aufweisen.The printing material web 2 can then be passed through an optional flexographic printing unit 15 in which UV-curable lacquer can preferably be applied. At D, the web 2 leaves the second station 10 and at E becomes a third station 20, ie a further UV dryer 20 and at F 'optionally a fourth station 30, ie one again another UV dryer 30 is supplied. The third and fourth stations can be arranged at a distance from one another, in particular the path 2 between E 'and F' can have a meandering path.

Die dritte Station 20 umfasst wenigsten einen, bevorzugt jedoch mehrere dritte UV-Strahler 21, z. B. zwei UV-Strahler 21a und 21b. Diese Strahler dienen dem Nachhärten der Tinte, bevorzugt dem im Wesentlichen vollständigen Aushärten beziehungsweise Polymerisieren der bereits vorgehärteten und weiter gehärteten (und hierdurch bevorzugt weitgehend gehärteten) Tinte.The third station 20 comprises at least one, but preferably several third UV radiators 21, e.g. B. two UV emitters 21a and 21b. These emitters are used to post-harden the ink, preferably to substantially completely harden or polymerize the already pre-hardened and further hardened (and thereby preferably largely hardened) ink.

Die optionale vierte Station 30 umfasst wenigstens eine, bevorzugt jedoch mehrere weitere dritte UV-Strahler 31, z. B. zwei UV-Strahler 31a und 31b. Auch diese Strahler dienen dem Nachhärten. Die dritten Strahler 21 und die weiteren dritten Strahler 31 können gemeinsam als "dritte Strahler" bezeichnet werden.The optional fourth station 30 comprises at least one, but preferably several further third UV emitters 31, e.g. B. two UV emitters 31a and 31b. These emitters are also used for post-curing. The third radiators 21 and the further third radiators 31 can be referred to collectively as “third radiators”.

Die dritte UV-Strahler 21 und die optionalen weiteren dritte UV-Strahler 31können bevorzugt als Quecksilberdampflampen oder alternativ UV-LED-Strahler ausgebildet sein und jeweils zwischen 100 und 200 W/cm aufweisen (bei angenommener Bahntransportgeschwindigkeit von etwa 50 m/min).The third UV radiator 21 and the optional further third UV radiator 31 can preferably be designed as mercury vapor lamps or alternatively UV-LED radiators and each have between 100 and 200 W / cm (assuming a web transport speed of about 50 m / min).

Das Nachhärten in der dritten und der optionalen vierten Station erfolgt bevorzugt unter Luft, z.B. in ihrer Zusammensetzung unveränderter Umgebungsluft, und nicht unter von Luft verschiedenem Inertgas.The post-curing in the third and the optional fourth station is preferably carried out under air, e.g. ambient air unchanged in its composition, and not under an inert gas other than air.

Das Nachhärten der Tinte, das heißt das Bestrahlen mit UV-Strahlung, in der dritten und/oder der vierten Station kann von der bedruckten Seite 40 des Bedruckstoffs (vergleiche Figur 2) her erfolgen oder es kann durch den Bedruckstoff 2 hindurch (von der ungedruckten Rückseite des Bedruckstoffs her) erfolgen. Auch eine Kombination (von der bedruckten und von der ungedruckten Seite des Bedruckstoffs her) ist möglich: z. B. eine Bestrahlung in der dritten Station 20 von der bedruckten Seite her und in der vierten Station 30 von der ungedruckten Seite her. Zudem kann auch in der zweiten Station 10 das Bestrahlen von der ungedruckten Seite her erfolgen (durch den Bedruckstoff 2 hindurch) und demnach anders als in den Figuren dargestellt.The post-curing of the ink, i.e. exposure to UV radiation, in the third and / or fourth station can be carried out from the printed side 40 of the printing material (cf. Figure 2 ) or it can be done through the printing substrate 2 (from the unprinted rear side of the printing substrate). A combination (of the printed and the unprinted side of the substrate) is also possible: B. irradiation in the third station 20 from the printed side and in the fourth station 30 from the unprinted side. In addition, the second station 10 can also Irradiation take place from the unprinted side (through the printing material 2) and therefore different from what is shown in the figures.

Das erfindungsgemäße Verfahren, beispielhaft mit der gezeigten Maschine 1 durchgeführt, umfasst somit i) das UV-Vorhärten unter Luft, anschließend ii) das weitere UV-Härten unter Inertgas, unter Inertgas angereicherter Luft oder unter sauerstoffreduzierter Luft oder funktional Ähnlichem und abschließend iii) das UV-Nachhärten unter Luft. Auch weitere vor-, zwischen- oder nachgeschaltete UV-Härtungsschritte oder Temperierschritte sind möglich.The method according to the invention, carried out by way of example with the machine 1 shown, thus comprises i) UV pre-curing under air, then ii) further UV curing under inert gas, under inert gas-enriched air or under oxygen-reduced air or the similar and finally iii) the UV post-curing in air. Further upstream, intermediate or downstream UV curing steps or temperature control steps are also possible.

Figur 2 zeigt (ebenfalls schematisch) eine Seitenansicht der Maschine 1 aus Figur 1 bei der Durchführung der bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens. Figure 2 shows (also schematically) a side view of the machine 1 from FIG Figure 1 when carrying out the preferred embodiment of the method according to the invention.

Gegenüber Figur 1 ist erkennbar, dass der Bahnpfad 41 des Bedruckstoffs 2 bevorzugt mäanderförmig verläuft und mehrere Umlenkwalzen 6 umfassen kann.Across from Figure 1 it can be seen that the web path 41 of the printing material 2 preferably runs in a meander shape and can include several deflecting rollers 6.

Das Inertgas-Gehäuse 12 kann, wie dargestellt, im Bereich der Bahnführung mittels der Temperierwalze 7 angeordnet sein. Es kann (Einlauf- und Auslauf-) Blenden 9 umfassen, die bewirken, dass bei 13 dem Gehäuse 12 zugeleitetes Inertgas im Wesentlichen bei 14 wieder abgeleitet wird und nicht an anderen Stellen unkontrolliert entweicht.The inert gas housing 12 can, as shown, be arranged in the area of the web guide by means of the temperature control roller 7. It can comprise (inlet and outlet) diaphragms 9 which have the effect that inert gas fed to the housing 12 at 13 is essentially discharged again at 14 and does not escape in an uncontrolled manner at other points.

Figur 2 lässt auch erkennen, dass die Strahler 21a und 21b der dritten Station 20 von der bedruckten Seite des Bedruckstoffs her UV-Strahlung beaufschlagen und dass die Strahler 31a und 31b der vierten Station 30 von der ungedruckten Seite des Bedruckstoffs 2 her (also durch den Bedruckstoff 2 hindurch) UV-Strahlung beaufschlagen. Dies ist eine bevorzugte, allerdings nur beispielhafte Konfiguration. Figure 2 It can also be seen that the emitters 21a and 21b of the third station 20 act on UV radiation from the printed side of the printing substrate and that the emitters 31a and 31b of the fourth station 30 apply from the unprinted side of the printing substrate 2 (i.e. through the printing substrate 2 through) apply UV radiation. This is a preferred, but only exemplary, configuration.

Der Bahnverlauf beziehungsweise der Bahntransport zwischen den Stationen 3, 10 und 20, d.h. zwischen B und C sowie zwischen D und E kann mittels mehreren Umlenkwalzen 6 erfolgen, ebenso zwischen E' und F', d.h. zwischen den Stationen 20 und 30.The course of the web or the transport of the web between stations 3, 10 and 20, ie between B and C and between D and E, can take place by means of several deflecting rollers 6, as well as between E 'and F', ie between stations 20 and 30.

BezugszeichenlisteList of reference symbols

11
TintendruckmaschineInk printing machine
22
Bedruckstoff / BahnSubstrate / web
33
Tintendruckwerk / erste StationInk printer / first station
44th
Druckkopfreihen / TintendruckköpfePrinthead rows / inkjet printheads
55
erste UV-Strahler (für das Vorhärten)first UV lamp (for pre-curing)
66th
UmlenkwalzenGuide rollers
77th
TemperierwalzeTempering roller
88th
temperierte Oberflächetempered surface
99
BlendenBezels
1010
UV-Trockner / zweite StationUV dryer / second station
11, 11a, 11b11, 11a, 11b
zweite UV-Strahler (für das weitere Härten)second UV lamp (for further hardening)
1212th
Inertgas-GehäuseInert gas housing
1313th
Inertgas-ZuleitungInert gas feed line
1414th
Inertgas-AbleitungInert gas discharge
1515th
FlexodruckwerkFlexographic printing unit
2020th
weiterer UV-Trockner / dritte Stationfurther UV dryer / third station
21, 21a, 21,b21, 21a, 21, b
dritte UV-Strahler (für das Nachhärten)third UV emitter (for post-curing)
3030th
weiterer UV-Trockner / vierte Stationfurther UV dryer / fourth station
31, 31a , 31b31, 31a, 31b
weitere dritte UV-Strahler (für das Nachhärten)further third UV lamps (for post-curing)
4040
Tintenauftrag / Bedruckte Seite des BedruckstoffsInk application / printed side of the substrate
4141
Pfad des BedruckstoffsPath of the substrate
A bis FA to F
Transportpfad des Bedruckstoffs durch die MaschineTransport path of the printing material through the machine

Claims (10)

Verfahren zum Härten von Tinte auf einem Bedruckstoff, wobei wenigstens eine UV-härtbare Tinte in Form von Tropfen auf einen Bedruckstoff (2) aufgebracht und mittels wenigstens eines ersten UV-Strahlers (5) mit UV-Strahlung beaufschlagt und dadurch vorgehärtet wird,
dadurch gekennzeichnet,
dass die Tinte mittels wenigstens eines zweiten UV-Strahlers (11, 11a, 11b) eines UV-Trockners (10) unter Inertgas, unter inertgasangereicherter Luft oder unter sauerstoffreduzierter Luft mit UV-Strahlung beaufschlagt und dadurch weiter gehärtet wird, und
dass die Tinte anschließend mittels wenigstens eines dritten UV-Strahlers (21, 21a, 21b, 31, 31a, 31b) eines weiteren UV-Trockners (20, 30) mit UV-Strahlung beaufschlagt und dadurch nachgehärtet wird.Method for curing ink on a printing material, wherein at least one UV-curable ink is applied in the form of drops to a printing material (2) and exposed to UV radiation by means of at least one first UV radiator (5) and thereby pre-cured,
characterized,
that the ink is exposed to UV radiation by means of at least one second UV radiator (11, 11a, 11b) of a UV dryer (10) under inert gas, under inert gas-enriched air or under oxygen-reduced air and is thereby further hardened, and
that the ink is then exposed to UV radiation by means of at least one third UV radiator (21, 21a, 21b, 31, 31a, 31b) of a further UV dryer (20, 30) and thereby post-cured. Verfahren nach Anspruch 1,
dadurch gekennzeichnet,
dass die Tinte mittels des ersten UV-Strahlers (5) unter Luft mit UV-Strahlung beaufschlagt wird.Method according to claim 1,
characterized,
that the ink is exposed to UV radiation by means of the first UV radiator (5) under air. Verfahren nach Anspruch 1 oder 2,
dadurch gekennzeichnet,
dass die Tinte mittels des dritten UV-Strahlers (21, 21a, 21b, 31, 31a, 31b) unter Luft mit UV-Strahlung beaufschlagt wird.Method according to claim 1 or 2,
characterized,
that the ink is exposed to UV radiation by means of the third UV radiator (21, 21a, 21b, 31, 31a, 31b) under air. Verfahren nach einem der Ansprüche 1 bis 3,
dadurch gekennzeichnet,
dass Stickstoff als das Inertgas verwendet wird.Method according to one of Claims 1 to 3,
characterized,
that nitrogen is used as the inert gas. Verfahren nach einem der Ansprüche 1 bis 4,
dadurch gekennzeichnet,
dass der UV-Trockner (10) mehrere zweite UV-Strahler (11, 11a, 11b) umfasst.Method according to one of Claims 1 to 4,
characterized,
that the UV dryer (10) comprises several second UV radiators (11, 11a, 11b). Verfahren nach Anspruch 5,
dadurch gekennzeichnet,
dass die zweiten UV-Strahler (11, 11a, 11b) in einem gemeinsamen Inertgas-Gehäuse (12) angeordnet sind.Method according to claim 5,
characterized,
that the second UV radiators (11, 11a, 11b) are arranged in a common inert gas housing (12). Verfahren nach einem der Ansprüche 1 bis 6,
dadurch gekennzeichnet,
dass der weitere UV-Trockner (20, 30) mehrere dritte UV-Strahler (21, 21a, 21b, 31, 31a, 31b) umfasst.Method according to one of Claims 1 to 6,
characterized,
that the further UV dryer (20, 30) comprises several third UV radiators (21, 21a, 21b, 31, 31a, 31b). Verfahren nach Anspruch 7,
dadurch gekennzeichnet,
dass der weitere UV-Trockner (20, 30) eine dritte Station (20) mit mehreren dritten UV-Strahlern (21, 21a, 21b) und eine vierte Station (30) mit mehreren weiteren dritten UV-Strahlern (31, 31a, 31b) umfasst.Method according to claim 7,
characterized,
that the further UV dryer (20, 30) has a third station (20) with several third UV emitters (21, 21a, 21b) and a fourth station (30) with several further third UV emitters (31, 31a, 31b ) includes. Verfahren nach einem der Ansprüche 1 bis 8,
dadurch gekennzeichnet,
dass wenigstens ein zweiter UV-Strahler (11, 11a, 11b) und/oder wenigstens ein dritter UV-Strahler (21, 21a, 21b) und/oder wenigstens ein weiterer dritter UV-Strahler (31, 31a, 31b) die Tinte durch den Bedruckstoff (2) hindurch härtet.Method according to one of Claims 1 to 8,
characterized,
that at least one second UV radiator (11, 11a, 11b) and / or at least one third UV radiator (21, 21a, 21b) and / or at least one further third UV radiator (31, 31a, 31b) the ink through the substrate (2) hardens through it. Verfahren nach einem der Ansprüche 1 bis 9,
dadurch gekennzeichnet,
dass der Bedruckstoff (2) mittels einer Temperierwalze (7) entlang des wenigstens einen zweiten UV-Strahlers (11, 11a, 11b) bewegt wird.Method according to one of Claims 1 to 9,
characterized,
that the printing material (2) is moved by means of a temperature control roller (7) along the at least one second UV radiator (11, 11a, 11b).
EP19197749.5A 2019-09-17 2019-09-17 Method for hardening ink on a printed matter Pending EP3795934A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP19197749.5A EP3795934A1 (en) 2019-09-17 2019-09-17 Method for hardening ink on a printed matter
CN202010547669.8A CN112519408A (en) 2019-09-17 2020-06-16 Method for hardening ink on printing material

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19197749.5A EP3795934A1 (en) 2019-09-17 2019-09-17 Method for hardening ink on a printed matter

Publications (1)

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