EP4371778A1 - Method for hardening a uv-curable medium in a printing machine - Google Patents
Method for hardening a uv-curable medium in a printing machine Download PDFInfo
- Publication number
- EP4371778A1 EP4371778A1 EP22208481.6A EP22208481A EP4371778A1 EP 4371778 A1 EP4371778 A1 EP 4371778A1 EP 22208481 A EP22208481 A EP 22208481A EP 4371778 A1 EP4371778 A1 EP 4371778A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- light source
- curable medium
- radiation
- light
- curable
- 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.)
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- 238000000034 method Methods 0.000 title claims abstract description 34
- 238000007639 printing Methods 0.000 title claims abstract description 32
- 230000005855 radiation Effects 0.000 claims abstract description 29
- 239000000976 ink Substances 0.000 claims description 11
- 239000000463 material Substances 0.000 claims description 9
- 230000003287 optical effect Effects 0.000 claims description 9
- 238000007641 inkjet printing Methods 0.000 claims description 8
- 239000002966 varnish Substances 0.000 claims description 7
- 239000000123 paper Substances 0.000 claims description 6
- 239000000758 substrate Substances 0.000 claims description 6
- 229910052724 xenon Inorganic materials 0.000 claims description 6
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 claims description 6
- 238000010276 construction Methods 0.000 claims description 2
- 238000001723 curing Methods 0.000 description 48
- 239000007789 gas Substances 0.000 description 10
- 239000011261 inert gas Substances 0.000 description 3
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910052756 noble gas Inorganic materials 0.000 description 1
- 238000007348 radical reaction Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
Images
Classifications
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- 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
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- 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
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- 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
- B41J2/435—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material
- B41J2/447—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material using arrays of radiation sources
- B41J2/45—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material using arrays of radiation sources using light-emitting diode [LED] or laser arrays
- B41J2/451—Special optical means therefor, e.g. lenses, mirrors, focusing means
Definitions
- the invention relates to a method for curing UV-curable media such as UV inkjet inks or UV varnishes in a printing machine.
- UV-curable printing media such as UV inkjet inks and UV varnishes.
- UV-curable media that are to be cured by UV radiation usually contain one or more photoinitiators. After printing on the substrate such as paper, cardboard or film, the UV-curable media must be cured, which is sometimes also referred to as drying. This then produces the finished printed product, which no longer rubs off and meets the requirements for commercial use.
- Two-stage curing processes for UV-curable media are known in principle from the state of the art.
- Mercury vapor lamps are usually used, but their use is increasingly undesirable from an environmental point of view.
- two-stage curing processes are carried out in such a way that the UV-curable medium is only partially cured in the first curing step, i.e. only partially cured and thus not fully cured.
- Pre-curing is also known as pinning. Only at the end of the printing process in the printing machine is the partially cured printed product then finally cured, usually by irradiation with high-intensity UV radiation.
- UV light-emitting diodes UV LEDs
- gas discharge lamps as radiation sources for curing UV-curable media in printing machines is also described in principle in the state of the art.
- EP 3 718 777 A1 describes a device for curing UV ink on a printing substrate, whereby UV LED radiation sources are used for curing, the beam angle of which is limited in order to reduce or prevent undesirable matting effects on the printing substrate.
- UV light-emitting diodes are used for both initial curing and final curing, whereby the radiation emitted by the UV light-emitting diodes is more strongly focused during initial curing than during final curing and the irradiation time is shorter during initial curing than during final curing. Accordingly, a higher irradiance and a shorter irradiation time are used during initial curing, and a lower irradiance and a longer irradiation time are used during final curing.
- the method according to the invention enables rapid and complete curing of the UV-curable medium on the substrate in the printing press.
- Conventional UV light-emitting diodes or flash lamps such as gas discharge lamps can be used as radiation sources, which do not require a large amount of space in the machine.
- UV light-emitting diodes and gas discharge lamps are comparatively inexpensive and generate little waste heat, which does not have to be dissipated by expensive cooling.
- the use of mercury vapor lamps in the printing press which are increasingly undesirable from an environmental point of view, can be avoided.
- the process according to the invention results in hardened printed products of high quality.
- the present invention relates to a method for curing a UV-curable medium in a printing machine, in which, in a first step, the UV-curable medium is irradiated with UV radiation from a first light source and thereby partially cured, and in a second step the partially cured UV-curable medium is irradiated with UV radiation from a second light source and thereby finally cured, wherein the UV-curable medium is irradiated in the first step with UV radiation of an irradiation intensity S 1 and an irradiation duration t 1 and the partially cured UV-curable medium is irradiated in the second step with UV radiation of an irradiation intensity S 2 and an irradiation duration t 2 , wherein the irradiation intensity S 1 is greater than the irradiation intensity S 2 and the irradiation duration t 1 is shorter than the irradiation duration t 2 .
- the reactive UV-curable medium is not yet fully converted. However, further processing in the printing machine is possible in this state without any disadvantages, particularly for the printed image.
- the final “final curing” process the already partially cured, still reactive UV-curable medium is then essentially completely cured and thus reacted, so that after it is discharged from the printing machine and later used commercially, no disadvantages such as smearing or discoloration occur.
- the irradiance S 1 that is applied to the UV-curable medium in the first step of curing is lower than the irradiance S 2 that is applied to the cured UV-curable medium in the second step of final curing.
- the irradiance describes the incident radiation power per area and is measured in watts per square centimeter.
- the first light source and the second light source are each independently selected from at least one light-emitting diode and at least one flash lamp, preferably from UV light-emitting diodes and gas discharge lamps, especially xenon gas discharge lamps.
- UV light-emitting diodes or UV LEDs are known in principle to those skilled in the art. Such light-emitting diodes emit a particularly high proportion of UV radiation and are commercially available, for example from Seoul Semiconductor Co., Ltd., Ansan, South Korea.
- Flash lamps are also known in principle to those skilled in the art. According to the invention, these are preferably gas discharge lamps, particularly preferably xenon gas discharge lamps.
- Flash lamps such as xenon gas discharge lamps have the advantage over UV light-emitting diodes that the parameters of the different irradiation intensities and irradiation durations according to the invention can be set particularly easily by selecting the appropriate electrode voltage, current intensity and duration of the discharge.
- the first light source is selected from at least one light-emitting diode, the UV radiation of which is focused by means of an optical device.
- the optical device comprises at least one optical lens. This allows the UV radiation emitted by the light-emitting diode to be applied to the printing material in a bundled manner. "Focusing" means bundling the light rays so that the power incident on the printing material per unit area, in other words the irradiance, is increased in contrast to unfocused light rays.
- no focusing of the UV radiation is carried out in the second step. Accordingly, only in the first step of initial curing is the UV radiation of the first light source focused and the UV radiation of the second light source, preferably at least one UV light-emitting diode or at least one flash lamp, is not focused in the second step of final curing.
- the UV radiation of the light source preferably at least one light-emitting diode
- the UV radiation of the light source is then focused more weakly in the second step than in the first step.
- the irradiance of the UV radiation in the second step i.e. the final curing
- the UV radiation of the light source is focused in the second step by means of an optical device, very particularly preferably by means of an optical device which comprises at least one optical lens.
- the wavelength spectrum of the at least one light-emitting diode in the first step is substantially identical to the wavelength spectrum of the at least one light-emitting diode in the second step.
- identically constructed light-emitting diodes are used in the first step and in the second step.
- the first light source and the second light source are each selected from at least one flash lamp, in particular from at least one xenon gas discharge lamp.
- the at least one flash lamp selected as the first light source and the at least one flash lamp selected as the second light source are of identical construction and the at least one flash lamp selected as the first light source and the at least one flash lamp selected as the second light source are electrically controlled differently.
- at least one xenon gas discharge lamp is used as the first and second light source.
- the first light source is located at a different location than the second light source.
- two separate light sources are used.
- the UV-curable medium is selected from UV-curable inkjet inks and UV-curable varnishes.
- Such UV-curable media are known in principle to the person skilled in the art and generally comprise one or more photoinitiators which are converted into a reactive state by irradiation with UV light, which initiates the curing reaction, usually via a radical reaction mechanism.
- the UV-curable medium comprises one or more photoinitiators.
- UV inkjet inks that can be printed in inkjet printing machines can be used as UV-curable inkjet inks.
- the selection of UV-curable varnishes is also not limited and in principle includes all UV varnishes that can be printed in inkjet printing machines.
- the printing machine in which the method according to the invention is carried out is an inkjet printing machine, which usually comprises at least one inkjet print head and one or more curing devices.
- the UV-curable medium is located on a printing material selected from paper, cardboard and film.
- the UV-curable medium is usually printed onto one of the printing materials mentioned, for example using one or more inkjet print heads.
- the UV-curable medium it is also possible for the UV-curable medium to be applied to the printing material by other methods, for example by spraying using a nozzle, which is particularly preferred for UV varnishes.
- the process according to the invention does not generally need to be carried out in the presence of an inert gas such as nitrogen or noble gas, although this is possible. If curing is carried out in the presence of an inert gas, preferably only the second step of the final curing is carried out in the presence of the inert gas.
- an inert gas such as nitrogen or noble gas
- Figure 1 shows schematically the method according to the invention using a preferred example.
- the UV inkjet ink printed on a printing material (2) for example paper
- a printing material (2) for example paper
- the printed paper is then coated with the hardened UV inkjet ink further conveyed through the inkjet printing machine (1), printed with other colors if necessary, and finally conveyed to the UV light emitting diode (4) for final curing.
- the finished printed product is discharged from the inkjet printing machine (1).
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- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Ink Jet (AREA)
- Supply, Installation And Extraction Of Printed Sheets Or Plates (AREA)
Abstract
Die Erfindung betrifft ein Verfahren zum Härten eines UV-härtbaren Mediums wie UV-Inkjettinte in einer Druckmaschine, bei dem man in einem ersten Schritt das UV-härtbare Medium mit UV-Strahlung hoher Bestrahlungsstärke und kurzer Bestrahlungsdauer bestrahlt und dadurch anhärtet und in einem zweiten Schritt das angehärtete UV-härtbare Medium mit UV-Strahlung niedrigerer Bestrahlungsstärke und längerer Bestrahlungsdauer bestrahlt und dadurch endhärtet. Als Lichtquellen können UV-Leuchtdioden und Blitzlampen verwendet werden. Durch dieses Verfahren erhält man gehärtete Druckerzeugnisse hoher Qualität.The invention relates to a method for curing a UV-curable medium such as UV inkjet ink in a printing machine, in which, in a first step, the UV-curable medium is irradiated with UV radiation of high irradiance and short irradiation time and thereby partially cured, and in a second step, the partially cured UV-curable medium is irradiated with UV radiation of lower irradiance and longer irradiation time and thereby finally cured. UV light-emitting diodes and flash lamps can be used as light sources. This method produces high-quality cured printed products.
Description
Die Erfindung betrifft ein Verfahren zum Härten von UV-härtbaren Medien wie UV-Inkjettinten oder UV-Lacken in einer Druckmaschine.The invention relates to a method for curing UV-curable media such as UV inkjet inks or UV varnishes in a printing machine.
In der Druckindustrie sind zahlreiche Druckverfahren mit UV-härtbaren Druckmedien wie UV-Inkjettinten und UV-Lacken bekannt. UV-härtbaren Medien, die durch UV-Strahlung gehärtet werden sollen, umfassen in der Regel einen oder mehrere Photoinitiatoren. Nach dem Aufdrucken auf den Bedruckstoff wie Papier, Karton oder Folie müssen die UV-härtbaren Medien gehärtet werden, was manchmal auch als Trocknung bezeichnet wird. Anschließend erhält man das fertige Druckerzeugnis, das nicht mehr abfärbt und den Anforderungen an eine kommerzielle Verwendung gerecht wird.In the printing industry, numerous printing processes are known using UV-curable printing media such as UV inkjet inks and UV varnishes. UV-curable media that are to be cured by UV radiation usually contain one or more photoinitiators. After printing on the substrate such as paper, cardboard or film, the UV-curable media must be cured, which is sometimes also referred to as drying. This then produces the finished printed product, which no longer rubs off and meets the requirements for commercial use.
Aus dem Stand der Technik sind zweistufige Härtungsverfahren für UV-härtbare Medien prinzipiell bekannt. Dabei werden üblicherweise Quecksilberdampflampen eingesetzt, deren Verwendung jedoch aus Umweltgesichtspunkten zunehmend unerwünscht ist. In der Regel wird in zweistufigen Härtungsverfahren so vorgegangen, dass man das UV-härtbare Medium im ersten Härtungsschritt nur anhärtet, also nur teilweise härtet und somit noch nicht vollständig durchhärtet. Das Anhärten wird auch als Pinnen bezeichnet. Erst am Ende des Druckvorgangs in der Druckmaschine wird das angehärtete Druckerzeugnis dann endgehärtet, meist durch Bestrahlung mit UV-Strahlung von hoher Intensität. Prinzipiell im Stand der Technik beschrieben ist auch die Verwendung von UV-Leuchtdioden (UV-LEDs) oder Gasentladungslampen als Strahlungsquellen zum Härten von UV-härtbaren Medien in Druckmaschinen.Two-stage curing processes for UV-curable media are known in principle from the state of the art. Mercury vapor lamps are usually used, but their use is increasingly undesirable from an environmental point of view. As a rule, two-stage curing processes are carried out in such a way that the UV-curable medium is only partially cured in the first curing step, i.e. only partially cured and thus not fully cured. Pre-curing is also known as pinning. Only at the end of the printing process in the printing machine is the partially cured printed product then finally cured, usually by irradiation with high-intensity UV radiation. The use of UV light-emitting diodes (UV LEDs) or gas discharge lamps as radiation sources for curing UV-curable media in printing machines is also described in principle in the state of the art.
Die im Stand der Technik beschriebenen Verfahren zur Härtung von UV-härtbaren Medien in Druckmaschinen sind jedoch für manche Anwendungsfälle nicht zufriedenstellend. So ist bei hohen Druckgeschwindigkeiten und somit einem hohen Durchsatz an Bedruckstoffen eine besonders kurze Härtungszeit erforderlich, welche mit herkömmlichen Härtungsmethoden nicht oder nur technisch aufwendig erreichbar ist. Insbesondere bei Low-Migration-Inkjettinten, die hochreaktiv sind und sehr schnell aushärten, sind die Härtungsverfahren des Standes der Technik bisher apparativ sehr aufwendig. Eine zufriedenstellende Härtung von Low-Migration-Inkjettinten mittels UV-Leuchtdioden ist bisher nicht beschrieben worden.However, the methods described in the prior art for curing UV-curable media in printing machines are not satisfactory for some applications. At high printing speeds and thus a high throughput of printing materials, a particularly short curing time is required, which cannot be achieved with conventional curing methods or can only be achieved with great technical effort. In particular with low-migration inkjet inks, which are highly reactive and cure very quickly, the state-of-the-art curing processes have so far been very complex in terms of equipment. Satisfactory curing of low-migration inkjet inks using UV light-emitting diodes has not yet been described.
Überraschenderweise wurde nun gefunden, dass eine besonders effektive Härtung von UV-härtbaren Medien in zweistufigen Härtungsverfahren mit Anhärten und Endhärten möglich ist, wenn man sowohl zum Anhärten als auch zum Endhärten UV-Leuchtdioden verwendet, wobei man die von den UV-Leuchtdioden abgegebene Strahlung beim Anhärten stärker fokussiert als beim Endhärten und die Bestrahlungsdauer beim Anhärten kürzer wählt als beim Endhärten. Dementsprechend wird beim Anhärten eine größere Bestrahlungsstärke und eine kürzere Bestrahlungsdauer angewendet, beim Endhärten eine geringere Bestrahlungsstärke und eine längere Bestrahlungsdauer. Diese Ergebnisse sind überraschend, weil man ausgehend von den Erfahrungen mit Quecksilberdampflampen eigentlich davon ausgehen sollte, dass die stärkere Fokussierung der UV-Strahlung und die damit verbundene höhere Bestrahlungsstärke der UV-Strahlung beim Endhärten im Gegensatz zum Anhärten angewendet werden sollte. Es wurde jedoch festgestellt, dass die Anwendung der im ersten Schritt des Anhärtens verwendeten hohen Bestrahlungsstärke bei einer längeren Einwirkzeit wie im zweiten Schritt des Endhärtens in der Regel zu einer Beschädigung des UV-härtbaren Mediums und des Bedruckstoffes führt.Surprisingly, it has now been found that particularly effective curing of UV-curable media is possible in two-stage curing processes with initial curing and final curing if UV light-emitting diodes are used for both initial curing and final curing, whereby the radiation emitted by the UV light-emitting diodes is more strongly focused during initial curing than during final curing and the irradiation time is shorter during initial curing than during final curing. Accordingly, a higher irradiance and a shorter irradiation time are used during initial curing, and a lower irradiance and a longer irradiation time are used during final curing. These results are surprising because, based on experience with mercury vapor lamps, one would actually assume that the stronger focusing of the UV radiation and the associated higher irradiance of the UV radiation should be used during final curing as opposed to initial curing. However, it has been found that the application of the high irradiance used in the first step of pre-curing with a longer exposure time as in the second step of final curing usually leads to damage of the UV-curable medium and the substrate.
Mit dem erfindungsgemäßen Verfahren ist eine rasche und vollständige Härtung des UV-härtbaren Mediums auf dem Bedruckstoff in der Druckmaschine möglich. Es können herkömmliche UV-Leuchtdioden oder Blitzlampen wie Gasentladungslampen als Strahlungsquellen verwendet werden, für die kein großer Platzbedarf in der Maschine erforderlich ist. UV-Leuchtdioden und Gasentladungslampen sind vergleichsweise kostengünstig und erzeugen wenig Abwärme, welche nicht aufwendig durch Kühlung abgeführt werden muss. Außerdem kann man den Einsatz von aus Umweltgesichtspunkten zunehmend unerwünschten Quecksilberdampflampen in der Druckmaschine vermeiden. Als Ergebnis des erfindungsgemäßen Verfahrens erhält man gehärtete Druckerzeugnisse von hoher Qualität.The method according to the invention enables rapid and complete curing of the UV-curable medium on the substrate in the printing press. Conventional UV light-emitting diodes or flash lamps such as gas discharge lamps can be used as radiation sources, which do not require a large amount of space in the machine. UV light-emitting diodes and gas discharge lamps are comparatively inexpensive and generate little waste heat, which does not have to be dissipated by expensive cooling. In addition, the use of mercury vapor lamps in the printing press, which are increasingly undesirable from an environmental point of view, can be avoided. The process according to the invention results in hardened printed products of high quality.
Dementsprechend betrifft die vorliegende Erfindung ein Verfahren zum Härten eines UV-härtbaren Mediums in einer Druckmaschine, bei dem man in einem ersten Schritt das UV-härtbare Medium mit UV-Strahlung einer ersten Lichtquelle bestrahlt und dadurch anhärtet und in einem zweiten Schritt das angehärtete UV-härtbare Medium mit UV-Strahlung einer zweiten Lichtquelle bestrahlt und dadurch endhärtet, wobei man das UV-härtbare Medium im ersten Schritt mit UV-Strahlung einer Bestrahlungsstärke S1 und einer Bestrahlungsdauer t1 bestrahlt und das angehärtete UV-härtbare Medium im zweiten Schritt mit UV-Strahlung einer Bestrahlungsstärke S2 und einer Bestrahlungsdauer t2 bestrahlt, wobei die Bestrahlungsstärke S1 größer ist als die Bestrahlungsstärke S2 und die Bestrahlungsdauer t1 kürzer ist als die Bestrahlungsdauer t2.Accordingly, the present invention relates to a method for curing a UV-curable medium in a printing machine, in which, in a first step, the UV-curable medium is irradiated with UV radiation from a first light source and thereby partially cured, and in a second step the partially cured UV-curable medium is irradiated with UV radiation from a second light source and thereby finally cured, wherein the UV-curable medium is irradiated in the first step with UV radiation of an irradiation intensity S 1 and an irradiation duration t 1 and the partially cured UV-curable medium is irradiated in the second step with UV radiation of an irradiation intensity S 2 and an irradiation duration t 2 , wherein the irradiation intensity S 1 is greater than the irradiation intensity S 2 and the irradiation duration t 1 is shorter than the irradiation duration t 2 .
Beim "Anhärten" wird dabei das reaktive UV-härtbare Medium noch nicht vollständig umgesetzt. Eine Weiterverarbeitung in der Druckmaschine ist jedoch in diesem Zustand bereits ohne Nachteile insbesondere für das Druckbild möglich. Beim abschließenden "Endhärten" wird das bereits angehärtete, immer noch reaktive UV-härtbare Medium dann im Wesentlichen vollständig durchgehärtet und damit abreagiert, so dass nach dem Ausschleusen aus der Druckmaschine und der späteren kommerziellen Verwendung keine Nachteile wie Verschmieren oder Abfärben auftreten.During the "partial curing" process, the reactive UV-curable medium is not yet fully converted. However, further processing in the printing machine is possible in this state without any disadvantages, particularly for the printed image. During the final "final curing" process, the already partially cured, still reactive UV-curable medium is then essentially completely cured and thus reacted, so that after it is discharged from the printing machine and later used commercially, no disadvantages such as smearing or discoloration occur.
Erfindungsgemäß ist die Bestrahlungsstärke S1, die im ersten Schritt des Anhärtens auf das UV-härtbare Medium angewendet wird, geringer als die Bestrahlungsstärke S2, die im zweiten Schritt des Endhärtens auf das angehärtete UV-härtbare Medium angewendet wird. Die Bestrahlungsstärke beschreibt die auftreffende Strahlungsleistung pro Fläche und wird in Watt pro Quadratzentimeter gemessen.According to the invention, the irradiance S 1 that is applied to the UV-curable medium in the first step of curing is lower than the irradiance S 2 that is applied to the cured UV-curable medium in the second step of final curing. The irradiance describes the incident radiation power per area and is measured in watts per square centimeter.
In einer bevorzugten Ausführungsform sind die erste Lichtquelle und die zweite Lichtquelle jeweils unabhängig voneinander ausgewählt unter wenigstens einer Leuchtdiode und wenigstens einer Blitzlampe, bevorzugt unter UV-Leuchtdioden und Gasentladungslampen, speziell Xenon-Gasentladungslampen. UV-Leuchtdioden oder UV-LEDs sind den Fachmann prinzipiell bekannt. Solche Leuchtdioden emittieren einen besonders hohen Anteil an UV-Strahlung und sind kommerziell erhältlich, beispielsweise von der Fa. Seoul Semiconductor Co., Ltd., Ansan, Südkorea. Blitzlampen sind dem Fachmann ebenfalls prinzipiell bekannt. Hierbei handelt es sich erfindungsgemäß bevorzugt um Gasentladungslampen, besonders bevorzugt um Xenon-Gasentladungslampen. Blitzlampen wie Xenon-Gasentladungslampen haben gegenüber UV-Leuchtdioden den Vorteil, dass über die geeignete Wahl der Elektrodenspannung, der Stromstärke und der Dauer der Entladung die erfindungsgemäßen Parameter der unterschiedlichen Bestrahlungsstärken und Bestrahlungsdauern besonders einfach eingestellt werden können.In a preferred embodiment, the first light source and the second light source are each independently selected from at least one light-emitting diode and at least one flash lamp, preferably from UV light-emitting diodes and gas discharge lamps, especially xenon gas discharge lamps. UV light-emitting diodes or UV LEDs are known in principle to those skilled in the art. Such light-emitting diodes emit a particularly high proportion of UV radiation and are commercially available, for example from Seoul Semiconductor Co., Ltd., Ansan, South Korea. Flash lamps are also known in principle to those skilled in the art. According to the invention, these are preferably gas discharge lamps, particularly preferably xenon gas discharge lamps. Flash lamps such as xenon gas discharge lamps have the advantage over UV light-emitting diodes that the parameters of the different irradiation intensities and irradiation durations according to the invention can be set particularly easily by selecting the appropriate electrode voltage, current intensity and duration of the discharge.
In einer besonders bevorzugten Ausführungsform ist die erste Lichtquelle ausgewählt unter wenigstens einer Leuchtdiode, deren UV-Strahlung man mittels einer optischen Einrichtung fokussiert. In einer ganz besonders bevorzugten Ausführungsform umfasst die optische Einrichtung wenigstens eine optische Linse. Damit lässt sich die emittierte UV-Strahlung der Leuchtdiode gebündelt auf den Bedruckstoff anwenden. Unter "fokussieren" wird eine Bündelung der Lichtstrahlen verstanden, so dass die pro Flächeneinheit auf dem Bedruckstoff auftreffende Leistung, mit anderen Worten die Bestrahlungsstärke, im Gegensatz zu nicht fokussierten Lichtstrahlen erhöht wird.In a particularly preferred embodiment, the first light source is selected from at least one light-emitting diode, the UV radiation of which is focused by means of an optical device. In a very particularly preferred embodiment, the optical device comprises at least one optical lens. This allows the UV radiation emitted by the light-emitting diode to be applied to the printing material in a bundled manner. "Focusing" means bundling the light rays so that the power incident on the printing material per unit area, in other words the irradiance, is increased in contrast to unfocused light rays.
In einer weiteren bevorzugten Ausführungsform führt man keine Fokussierung der UV-Strahlung im zweiten Schritt durch. Dementsprechend führt man nur im ersten Schritt der Anhärtung eine Fokussierung der UV-Strahlung der ersten Lichtquelle durch und die UV-Strahlung der zweiten Lichtquelle, bevorzugt wenigstens eine UV-Leuchtdiode oder wenigstens eine Blitzlampe, im zweiten Schritt der Endhärtung wird nicht fokussiert.In a further preferred embodiment, no focusing of the UV radiation is carried out in the second step. Accordingly, only in the first step of initial curing is the UV radiation of the first light source focused and the UV radiation of the second light source, preferably at least one UV light-emitting diode or at least one flash lamp, is not focused in the second step of final curing.
Es ist jedoch auch möglich, das UV-Licht auch im zweiten Schritt, also der Endhärtung, zu fokussieren. In dieser weiteren bevorzugten Ausführungsform fokussiert man dann die UV-Strahlung der Lichtquelle, bevorzugt wenigstens eine Leuchtdiode, im zweiten Schritt schwächer als im ersten Schritt. In dieser bevorzugten Ausführungsform ist die Bestrahlungsstärke der UV-Strahlung dann im zweiten Schritt, also der Endhärtung, trotz der Fokussierung geringer als im ersten Schritt, also der Anhärtung. In einer besonders bevorzugten Ausführungsform fokussiert man die UV-Strahlung der Lichtquelle, bevorzugt wenigstens eine Leuchtdiode, im zweiten Schritt mittels einer optischen Einrichtung, ganz besonders bevorzugt mittels einer optischen Einrichtung, die wenigstens eine optische Linse umfasst.However, it is also possible to focus the UV light in the second step, i.e. the final curing. In this further preferred embodiment, the UV radiation of the light source, preferably at least one light-emitting diode, is then focused more weakly in the second step than in the first step. In this preferred embodiment, the irradiance of the UV radiation in the second step, i.e. the final curing, is then lower than in the first step, i.e. the initial curing, despite the focusing. In a particularly In a preferred embodiment, the UV radiation of the light source, preferably at least one light-emitting diode, is focused in the second step by means of an optical device, very particularly preferably by means of an optical device which comprises at least one optical lens.
In einer weiteren bevorzugten Ausführungsform ist das Wellenlängenspektrum der wenigstens einen Leuchtdiode im ersten Schritt im Wesentlichen identisch mit dem Wellenlängenspektrum der wenigstens einen Leuchtdiode im zweiten Schritt. In einer besonders bevorzugten Ausführungsform der Erfindung nutzt man im ersten Schritt und im zweiten Schritt jeweils die baugleichen Leuchtdioden.In a further preferred embodiment, the wavelength spectrum of the at least one light-emitting diode in the first step is substantially identical to the wavelength spectrum of the at least one light-emitting diode in the second step. In a particularly preferred embodiment of the invention, identically constructed light-emitting diodes are used in the first step and in the second step.
In einer weiteren besonders bevorzugten Ausführungsform sind die erste Lichtquelle und die zweite Lichtquelle jeweils ausgewählt unter wenigstens einer Blitzlampe, insbesondere unter jeweils wenigstens einer Xenon-Gasentladungslampe.In a further particularly preferred embodiment, the first light source and the second light source are each selected from at least one flash lamp, in particular from at least one xenon gas discharge lamp.
In einer speziellen Ausführungsform sind die als erste Lichtquelle ausgewählte wenigstens eine Blitzlampe und die als zweite Lichtquelle ausgewählte wenigstens eine Blitzlampe baugleich und man steuert die als erste Lichtquelle ausgewählte wenigstens eine Blitzlampe und die als zweite Lichtquelle ausgewählte wenigstens eine Blitzlampe unterschiedlich elektrisch an. Bevorzugt werden in dieser speziellen Ausführungsform als erste und zweite Lichtquelle jeweils wenigstens eine Xenon-Gasentladungslampe verwendet.In a special embodiment, the at least one flash lamp selected as the first light source and the at least one flash lamp selected as the second light source are of identical construction and the at least one flash lamp selected as the first light source and the at least one flash lamp selected as the second light source are electrically controlled differently. Preferably, in this special embodiment, at least one xenon gas discharge lamp is used as the first and second light source.
In einer weiteren bevorzugten Ausführungsform ist die erste Lichtquelle an einem anderen Ort lokalisiert als die zweite Lichtquelle. In dieser Ausführungsform werden also zwei separate Lichtquellen verwendet. Prinzipiell möglich ist auch, dass nur eine Lichtquelle verwendet wird und durch Umlenkungen oder Weiterleitungen durch Spiegel oder Lichtleiter sowie lichtabschirmende Maßnahmen die Bestrahlung an den gewünschten Orten auf dem Bedruckstoff verwirklicht wird.In a further preferred embodiment, the first light source is located at a different location than the second light source. In this embodiment, two separate light sources are used. In principle, it is also possible to use only one light source and to achieve irradiation at the desired locations on the printing material by deflecting or forwarding the light using mirrors or light guides as well as light-shielding measures.
In einer weiteren bevorzugten Ausführungsform ist das UV-härtbare Medium ausgewählt unter UV-härtbaren Inkjettinten und UV-härtbaren Lacken. Solche UV-härtbare Medien sind dem Fachmann prinzipiell bekannt und umfassen in der Regel einen oder mehrere Photoinitiatoren, welche durch Bestrahlung mit UV-Licht in einen reaktiven Zustand überführt werden, welcher die Härtungsreaktion, meist über einen radikalischen Reaktionsmechanismus, einleitet. Dementsprechend umfasst das UV-härtbare Medium in einer weiteren bevorzugten Ausführungsform einen oder mehrere Photoinitiatoren.In a further preferred embodiment, the UV-curable medium is selected from UV-curable inkjet inks and UV-curable varnishes. Such UV-curable media are known in principle to the person skilled in the art and generally comprise one or more photoinitiators which are converted into a reactive state by irradiation with UV light, which initiates the curing reaction, usually via a radical reaction mechanism. Accordingly, in a further preferred embodiment, the UV-curable medium comprises one or more photoinitiators.
Als UV-härtbare Inkjettinten können prinzipiell alle in Inkjetdruckmaschinen verdruckbaren UV-Inkjettinten zum Einsatz kommen, auch die Auswahl an UV-härtbaren Lacken ist grundsätzlich nicht eingeschränkt und umfasst prinzipiell alle in Inkjetdruckmaschinen verdruckbaren UV-Lacke.In principle, all UV inkjet inks that can be printed in inkjet printing machines can be used as UV-curable inkjet inks. The selection of UV-curable varnishes is also not limited and in principle includes all UV varnishes that can be printed in inkjet printing machines.
In einer weiteren bevorzugten Ausführungsform ist die Druckmaschine, in der das erfindungsgemäße Verfahren ausgeführt wird, eine Inkjetdruckmaschine, welche in der Regel wenigstens einen Inkjetdruckkopf und eine oder mehrere Härtungsvorrichtungen umfasst.In a further preferred embodiment, the printing machine in which the method according to the invention is carried out is an inkjet printing machine, which usually comprises at least one inkjet print head and one or more curing devices.
In einer weiteren bevorzugten Ausführungsform befindet sich das UV-härtbare Medium auf einem Bedruckstoff, der ausgewählt ist unter Papier, Karton und Folie. Üblicherweise wurde das UV-härtbare Medium auf einen der genannten Bedruckstoffe aufgedruckt, beispielsweise mittels eines oder mehrerer Inkjetdruckköpfe. Es ist jedoch auch möglich, dass das UV-härtbare Medium durch andere Verfahren auf den Bedruckstoff aufgebracht wurde, beispielsweise durch Sprühen mittels einer Düse, was besonders bei UV-Lacken bevorzugt ist.In a further preferred embodiment, the UV-curable medium is located on a printing material selected from paper, cardboard and film. The UV-curable medium is usually printed onto one of the printing materials mentioned, for example using one or more inkjet print heads. However, it is also possible for the UV-curable medium to be applied to the printing material by other methods, for example by spraying using a nozzle, which is particularly preferred for UV varnishes.
Das erfindungsgemäße Verfahren braucht in der Regel nicht in der Gegenwart eines Inertgases wie Stickstoff oder Edelgas durchgeführt zu werden, wenngleich dieses möglich ist. Wird in Gegenwart eines Inertgases gehärtet, so wird bevorzugt nur der zweite Schritt der Endhärtung in Gegenwart des Inertgases durchgeführt.The process according to the invention does not generally need to be carried out in the presence of an inert gas such as nitrogen or noble gas, although this is possible. If curing is carried out in the presence of an inert gas, preferably only the second step of the final curing is carried out in the presence of the inert gas.
- 11
- Inkj etdruckmaschineInkjet printing machine
- 22
- PapierPaper
- 33
- UV-Leuchtdiode zum AnhärtenUV LED for curing
- 44
- UV-Leuchtdiode zum EndhärtenUV LED for final curing
Claims (14)
dadurch gekennzeichnet,
dass die Bestrahlungsstärke S1 größer ist als die Bestrahlungsstärke S2 und die Bestrahlungsdauer t1 kürzer ist als die Bestrahlungsdauer t2.Method for curing a UV-curable medium in a printing machine, in which in a first step the UV-curable medium is irradiated with UV radiation from a first light source and thereby hardened and in a second step the hardened UV-curable medium is irradiated with UV radiation from a second light source and thereby finally hardened, wherein the UV-curable medium is irradiated in the first step with UV radiation of an irradiation intensity S 1 and an irradiation duration t 1 and the hardened UV-curable medium is irradiated in the second step with UV radiation of an irradiation intensity S 2 and an irradiation duration t 2 ,
characterized,
that the irradiance S 1 is greater than the irradiance S 2 and the irradiation time t 1 is shorter than the irradiation time t 2 .
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP22208481.6A EP4371778A1 (en) | 2022-11-21 | 2022-11-21 | Method for hardening a uv-curable medium in a printing machine |
| EP23206605.0A EP4371779A1 (en) | 2022-11-21 | 2023-10-30 | Method for curing uv-curable inkjet ink in a printing machine |
| CN202311552578.3A CN118056683A (en) | 2022-11-21 | 2023-11-21 | Method for curing ultraviolet curable inkjet inks in a printing press |
| US18/515,579 US20240165967A1 (en) | 2022-11-21 | 2023-11-21 | Method of curing uv-curable inkjet ink in a printing machine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP22208481.6A EP4371778A1 (en) | 2022-11-21 | 2022-11-21 | Method for hardening a uv-curable medium in a printing machine |
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| EP4371778A1 true EP4371778A1 (en) | 2024-05-22 |
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| EP22208481.6A Pending EP4371778A1 (en) | 2022-11-21 | 2022-11-21 | Method for hardening a uv-curable medium in a printing machine |
| EP23206605.0A Pending EP4371779A1 (en) | 2022-11-21 | 2023-10-30 | Method for curing uv-curable inkjet ink in a printing machine |
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| EP23206605.0A Pending EP4371779A1 (en) | 2022-11-21 | 2023-10-30 | Method for curing uv-curable inkjet ink in a printing machine |
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| JP2010274584A (en) * | 2009-05-29 | 2010-12-09 | Afit Corp | Image forming method by inkjet |
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2022
- 2022-11-21 EP EP22208481.6A patent/EP4371778A1/en active Pending
-
2023
- 2023-10-30 EP EP23206605.0A patent/EP4371779A1/en active Pending
- 2023-11-21 US US18/515,579 patent/US20240165967A1/en active Pending
- 2023-11-21 CN CN202311552578.3A patent/CN118056683A/en active Pending
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| JP2010274584A (en) * | 2009-05-29 | 2010-12-09 | Afit Corp | Image forming method by inkjet |
| US20130286095A1 (en) * | 2012-04-27 | 2013-10-31 | Seiko Epson Corporation | Print apparatus and print method |
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| Publication number | Publication date |
|---|---|
| US20240165967A1 (en) | 2024-05-23 |
| EP4371779A1 (en) | 2024-05-22 |
| CN118056683A (en) | 2024-05-21 |
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