Sheet-fed rotary offset printing press with equipment for drying radiation-curing special inks

Abstract

Sheet-fed printing press for single- or multi-color printing of printing inks onto printed sheets, comprising a feeder (1), one or more printing units (2, 3, 4, 5, 11) for applying special printing inks to a substrate, incorporating an inking / moistening unit, a plate cylinder (P), a rubber cylinder (G) and an impression cylinder (D) in each printing unit (2, 3, 4, 5, 11), wherein the special printing inks are mixed with photoinitiators and are suitable for curing by means of UV radiation, with a delivery conveyor (8) and a delivery unit (10) receiving a stack of sheets, characterized in that that in the area directly after a last printing unit (5, 11) suitable for printing a special printing ink, at least one first emitter device (13, 14) is provided on the printed side of the printed sheets for introducing heat energy into the printing ink layer on the printed sheets. and that on the conveying path of the boom conveyor (8) to the boom (10) at a distance in the sheet travel direction of at least the length of a printed sheet from the position of the first radiation device (13, 14) a second radiation device (12) for applying radiation that triggers the hardening of the printing ink layer on the printed sheet is arranged, wherein the first emitter device (13, 14) on the conveying path of the boom conveyor (8) or the counter-pressure cylinder (D) of the last printing unit (5, 11) is designed as a thermal air blowing device (14) for applying a heated air stream to the ink layer on the freshly printed sheet.

Description

[0001] The invention relates to a sheet-fed rotary offset printing machine with facilities for drying uncoated multicolor prints.

[0002] It is known to apply a fast-drying coating, such as a varnish, to printed sheets after printing a multi-colored image in order to protect the ink surface which has not yet hardened.

[0003] UV-reactive inks are also used to produce fast-drying ink layers. These inks cross-link after exposure to UV light, instantly creating a dry surface. However, because these inks do not continue to dry on the substrate like conventional offset inks, complete cross-linking of the ink layers is essential. Otherwise, the resulting printed product would be entirely unusable.

[0004] US Patent 2002 / 0178944 A1 discloses a rotary printing press with an integrated coating unit. Integrating coating units into rotary printing presses makes it possible, in a manner known per se, to achieve special printing effects, particularly gloss effects, on a substrate. When processing substrates with integrated coating units, specific adjustments to the printing speed are necessary to ensure sufficient drying of the coating before the substrate, especially a sheet, enters a subsequent printing unit or a sheet delivery system.

[0005] From DE 10 2008 014 269 A1, a method and a device for radiation curing of a substrate coating are known. The coating is irradiated with UV light by at least one UV lamp at an irradiation location for an irradiation duration that may be defined by a relative movement of the substrate. An inert gas is supplied from a gas supply device to reduce the negative effects of oxygen on the coating. The inert gas is supplied only during part of the irradiation duration, and the supply is interrupted during the remaining part of the irradiation duration.

[0006] From DE 10 2006 032 831 A1, a drying device for treating a substrate surface in a processing machine is known. The drying device is improved in such a way that the proportion of infrared (IR) radiation emitted by a radiation unit can be reduced from the total radiation energy directed at the substrate using simple means. For this purpose, the reflector of the drying device has a dichroic layer on its front surface facing the radiation unit and a first IR absorber layer on its back surface.

[0007] From EP 1671788 B1, a rotary printing press with an integrated coating unit is known. In the rotary printing press, a radiation device is provided in a sheet exit section downstream of the printing nip in the sheet travel direction. This device serves to irradiate the coating applied to the substrate with coating-curing and / or coating-drying radiation immediately after exiting the printing nip. In a section of the printing cylinder assembly downstream of the radiation device in the sheet travel direction, a blowing device for blowing conditioned air onto the irradiated coating is arranged parallel to the printing cylinder assembly.

[0008] This makes it possible to initiate and pre-cure the drying or curing process of the varnish transferred to the substrate immediately after the substrate exits the printing nip. Further drying or curing can then take place within the same cylinder quadrant by applying conditioned air. The wavelength of this radiation is preferably in the range of 350 nm to 4000 nm, particularly in the range of 700 nm to 4000 nm. The air is preferably conditioned to a specified humidity / temperature condition.

[0009] The emitter can be an IR cold radiator or combined with a UV radiator. The intensity of the radiation applied to the substrate by the IR cold radiator can be adjustable. Preferably, the temperature of the air supplied by the air-jet nozzle assembly is also adjustable. This makes it possible to control the amount of heat introduced or, if necessary, dissipated by the air supply to the varnish or the substrate.

[0010] It is possible to combine the blowing device and the IR cold radiator into a drying module or assembly.

[0011] The blowing device and the IR cold radiator are preferably arranged so compactly that irradiation and air exposure occur at an angle of less than 45° on the printing cylinder. Such a compact arrangement of a paint drying unit can advantageously be positioned in the circumferential area of ​​the printing cylinder located between the printing gap and the transfer area to the transfer cylinder.

[0012] It is still known that special UV-reactive inks can be used to produce fast-drying printed products. However, in addition to the very high energy consumption and environmental concerns regarding their use, such as ozone production, the question of further processing such products is not sufficiently resolved. In most cases, treating the printed images with UV lamps is insufficient to achieve a durable and therefore abrasion-resistant ink surface, and thus a suitable ink application for further processing in a reliably controllable process.

[0013] Furthermore, the use of special UV lamps to improve the curing of the ink layers only achieves an unsatisfactory gloss result that is inferior to printing with conventional offset inks.

[0014] The invention is therefore based on the objective of enabling the application of radiation-curing special inks to a substrate in a sheet-fed offset printing machine with the fastest and most complete drying possible, whereby the equipment should offer advantages.

[0015] According to the invention, a sheet-fed printing press for single- or multi-color printing of printing inks onto printed sheets is used, comprising a feeder, one or more printing units for applying special printing inks to a substrate, and inking / moistening units, plate cylinders, rubber cylinders, and impression cylinders. The special printing inks are mixed with photoinitiators for curing by UV radiation. The printed sheets are fed to a sheet stack of a delivery unit by a delivery conveyor.

[0016] In the area immediately following the last printing unit suitable for printing a special ink, at least one first heat emitter is provided on the printed side of the sheet's conveying path for introducing heat energy into the ink layer. Along the conveying path of the boom conveyor to the boom, a second heat emitter is arranged in the sheet-travel direction at a distance of at least the length of a sheet from the first heat emitter for applying radiation that triggers the curing of the ink layer on the sheet.

[0017] Preferably, the first emitter device in the area of ​​the last printing unit is associated with a sheet-guiding counter-pressure cylinder after its printing gap with a rubber cylinder.

[0018] In further training, the first radiation device is located in or near the infeed area of ​​the printed sheets to the boom conveyor that directly follows the last printing unit and in the area of ​​the boom conveyor.

[0019] Preferably, the first emitter device is configured as an IR emitter device for irradiating the freshly printed sheets with IR (infrared) radiation, which heats the ink layer on the printed sheet. According to the invention, the first emitter device is configured as a thermal air blower device for irradiating the ink layer on the freshly printed sheets with a heated airflow.

[0020] Preferably, the first emitter assembly consists of one or more modules, wherein the multiple modules are arranged to be operated individually or together as variably switchable groups. In a further development, the IR emitter assemblies can be operated separately or together with thermal air blowing units, or vice versa. Preferably, the second emitter assembly is arranged on the conveying path of the boom conveyor in the area in front of or near the boom and is arranged as a UV emitter assembly consisting of one or more UV emitters.

[0021] In further training, a maximum dry section is formed between the first module of the first radiant unit and the last module of the second radiant unit on the conveying path of the boom conveyor.

[0022] In further training, the modules of the first emitter unit and the UV emitters of the second emitter unit are arranged in such a coordinated and switchable manner that a drying path adapted to the substrate, ink and drying requirements results between the last IR emitter or the last thermal air blowing unit in the direction of the sheet travel and the first UV emitter in the direction of the sheet travel towards the delivery arm.

[0023] Claim 7 describes a method for operating a sheet-fed printing press for single- or multi-color printing of special printing inks on printed sheets, in which a single- or multi-color printed image is applied to a printed sheet by means of the printing units, the print is dried without further coating, the special printing inks of the color image are heated by means of a first radiation device, the heated printed sheets are transported over at least one sheet length without further radiation treatment, the special printing inks of the printed image are subjected to a radiation treatment by means of a second radiation device to cure the special printing inks, and the printed sheets with cured special printing inks are laid down in the delivery on a sheet stack.

[0024] Preferably, each printed sheet is subjected to radiation treatment after the last printing unit by means of at least one IR emitter device and / or a thermal air blowing device (14) and, after a waiting period during further transport by means of the boom conveyor, is treated by means of a UV emitter device to completely cure the special printing inks in the color image on the printed sheet.

[0025] According to the invention, when using several modules of the IR emitter devices (13) and / or thermal air blowing devices (14) and the UV emitter device, the modules emitter devices are switched depending on the print subject in such a way that sufficient curing of the special printing inks is achieved for the intended further processing of the printed sheets by ensuring sufficient heating of the ink image, sufficient waiting time until the curing treatment and sufficient exposure to the curing radiation.

[0026] The invention will be explained in more detail below with reference to graphic representations.

[0027] This shows Fig. 1 a schematic representation of a sheet-fed printing press with printing units and drying equipment and Fig. 2 an enlarged representation of an arrangement according to the invention in the area of ​​a boom conveyor of a boom.

[0028] In Fig. Figure 1 shows a sheet-fed rotary offset printing press of a known design. This press has a feeder 1 for the individual feeding of printed sheets to a first printing unit 2, with further printing units 3, 4, 5 following the first printing unit 2. The printing units 2 to 5 are all identical in construction and have a plate or form cylinder P, a rubber or blanket or transfer cylinder G, and an impression or impression cylinder D, with each plate cylinder P being assigned an inking unit and optionally a dampening unit.

[0029] The sheet-fed rotary offset printing press according to Fig. 1 also has a dryer module 6 after the last printing unit 5. From the dryer module 6, the printed sheets are fed to a coating module 7.

[0030] From the coating module 7, the printed sheets are fed to a cantilever conveyor 8 designed as an endless chain conveyor system. In the cantilever conveyor 8, the printed sheets are transported by means of rotating gripper systems 8A in a sheet transport direction R to a cantilever 10 and finally laid out on a sheet stack in the cantilever 10.

[0031] Within the boom conveyor 8, devices for non-contact surface treatment are provided in the form of irradiation devices 12, 13 and 14, which are arranged along the conveying path of the boom conveyor 8 so that they can irradiate the printed side of the printed sheets. For this purpose, UV irradiation devices 12, IR irradiation devices 13 and thermal air blowing devices 14 are provided parallel to the conveying path of the lower chain run of the boom conveyor 14.

[0032] The dryer module 6 can also be equipped with IR emitter devices 13 and thermal air blowing devices 14.

[0033] Within the defined extent of the conveying path for the printed sheets between the first and last ejector devices 12, 13 or 14 seen in the sheet transport direction R, a drying section 9 is defined, which is mainly arranged inside the boom conveyor 8.

[0034] When the dryer module 6 is included, the maximum drying distance 9 can also be significantly longer, as indicated by the marking for the drying distance 9' (dashed outline).

[0035] The drying section is divided into the exposure sections of the radiation emitters 12, 13, 14 and the free transport of the printed sheets between the first and second radiation emitters. Therefore, in Fig. 1, designated as a subsection of the drying section 9, is a waiting section 9A. There, the printed sheets are transported from the first radiation emitters 13, 14 to the second radiation emitters 12, whereby the effect of the first radiation emitters on the ink layers of the printed sheet can still have an effect.

[0036] The waiting section 9A can also be extended by section 9A' when the dryer module 7 is included.

[0037] In the case of producing printed sheets without an additional coating on the color print, the coating module 7 is deactivated. The printed sheets then pass through the coating module 7 without any processing step. Thus, the dryer module could be used, in accordance with the invention, for irradiating the uncoated printed sheets.

[0038] Preferably, however, a sheet-fed rotary offset printing press is used which does not have a dryer module 6 and a coating module 7 and is therefore simpler and more cost-effective in its structure and significantly smaller in its dimensions.

[0039] The aforementioned configuration is in Fig. Figure 2 shows a final printing unit 11 for printing a color image, which is directly assigned to the boom conveyor 8. The printed sheets B are thus transferred from the impression cylinder D of the printing unit 11 to the boom conveyor 8 in a fully inked state and then conveyed further along the lower run of the boom conveyor 8, which is designed as an endless chain conveyor.

[0040] In the ascending section of the boom conveyor 8, which is referred to here as the arc ascent 15, several radiation devices are arranged parallel to each other and aligned with the conveying path of the boom conveyor 8.

[0041] In Fig. 2 are shown in alternating arrangement IR emitter devices 13 and thermal air blowing devices 14.

[0042] Continuing in the direction of sheet transport R, the printed sheets B are conveyed by the gripper systems 8A parallel to the conveying path of the boom conveyor 8 in the area of ​​a drying section 9 until second emitter devices in the form of one or more UV emitters 12 are arranged parallel to the conveying path of the boom conveyor 8.

[0043] In the area between the last IR emitter 13 or the last thermal air blowing device 14 and the first UV emitter 12, a waiting section 9A is defined as part of the entire drying section 9, over which the printed sheets B are not treated during transport after heat treatment by the IR emitters 13 or the thermal air blowing devices 14, so that the heating of the printed sheet B with the applied ink layers can be evenly distributed over the printed sheet B.

[0044] Following the radiation treatment with UV radiation by the UV lamps 12, whereby the ink layers on the printed sheet B are cured, the printed sheet B is placed on the sheet stack in the delivery unit 10.

[0045] The principle of the invention is therefore that by using an IR emitter 13 and a UV emitter 13 in the arrangement described above, acting on a freshly printed sheet B with special printing inks and left without a varnish layer, the printed and dried special printing ink appears glossy, with 50 to 60 gloss points being achievable.

[0046] The process can be designed quite flexibly within the framework of the machine configuration shown.

[0047] After printing the special printing inks, for example the first IR emitter 13 arranged in the sheet transport direction R and the last UV emitter 12 arranged in the sheet transport direction can be used for irradiation and hardening treatment.

[0048] Furthermore, it was recognized that a distance is required between the first and second radiation devices (IR emitter 13, UV emitter 12), which is designated as waiting section 9A. The waiting section 9A evens out the effect of the heat on the ink layers in such a way that the effect of the UV radiation from the UV emitters 12, arranged at the distance of waiting section 9A, on the ink layers of the printed sheet is improved to such an extent that a good gloss is achieved on the printed image.

[0049] Furthermore, the illustrated device is also variable in that the gloss of the printed sheet after curing by means of the UV lamp(s) 12 can be influenced by the use of one or more IR emitters 13. The simple rule is that the more IR emitters 13 are used, the higher the measurable gloss on the printed image.

[0050] The type of UV emitters 12 used as a second radiation device with regard to their system-related design with the use of mercury or different doping with iron or other known materials, plays no role in the context of the effectiveness of the UV radiation for the gloss of the printed image or the hardening of the ink layers.

[0051] Along with the improved gloss of the printed image after curing using the UV lamps 12, a particular advantage of the system according to the invention is that a high abrasion resistance of the printed ink layers can be achieved after curing. This is achieved even though a significantly reduced lamp power is used for UV irradiation.

[0052] Alternatively, or in combination with the IR emitters 13, hot air can be used by activating the thermal air blowing devices 14 located in the area of ​​the sheet feeder 15 to heat the ink layers. This achieves the same gloss level of the printed image as using the IR emitters 13.

[0053] Advantageously, a combination of IR emitters 13 and thermal air blowing devices 14 can also be used.

[0054] The waiting period for equalizing the heat effect in the printing ink layers can also be controlled by the variable switching and arrangement of the IR emitters 13 and the thermal air blowing devices 14.

[0055] According to the invention, with a significantly reduced electrical power output for the UV radiation used (fewer lamps or less operating power), the drying result leads to good curing of the ink layers with a scrub-resistant surface and a glossy image on the printed sheet. Reference symbol list 1 investor 2 printed matter 3 Printed matter 4 Printing work 5 Printed matter 6 Dryer module 7 Paint module 8 cantilever system 9 Dry track 10 outriggers 11 Printed matter 12 Second radiation device, UV radiation device 13 First radiation device, IR radiation device 14 First radiation device, thermal air blowing device 15 Arched staircase 8A Gripper system 9A Waiting Area B Printed sheet P plate cylinder G Rubber cylinder D Counterpressure cylinder R Bow direction, transport direction

Claims

Sheet-fed printing press for single- or multi-color printing of printing inks onto printing sheets, comprising a feeder (1), one or more printing units (2, 3, 4, 5, 11) for applying special printing inks to a substrate, incorporating an inking / moistening unit, a plate cylinder (P), a rubber cylinder (G), and an impression cylinder (D) in each printing unit (2, 3, 4, 5, 11), wherein the special printing inks are mixed with photoinitiators and are suitable for curing by means of UV radiation, with a delivery conveyor (8) and a delivery unit (10) receiving a stack of sheets, characterized in that, in the area directly after a last printing unit (5, 11) suitable for printing a special printing ink, at least one first emitter device (13) is assigned to the conveying path of the printed sheets on the printed side of the printed sheets.14) is provided for introducing heat energy into the printing ink layer on the printed sheet, and that on the conveying path of the boom conveyor (8) to the boom (10) at a distance in the sheet-travel direction of at least the length of a printed sheet from the position of the first radiant device (13, 14) a second radiant device (12) for applying radiation that triggers the curing of the printing ink layer on the printed sheet is arranged, wherein the first radiant device (13, 14) on the conveying path of the boom conveyor (8) or the impression cylinder (D) of the last printing unit (5, 11) is designed as a thermal air blowing device (14) for applying a heated air stream to the ink layer on the freshly printed printed sheet. Sheet-fed printing press according to claim 1, characterized in that the first emitter device in the area of ​​the last printing unit (5, 11) is assigned to a sheet-guiding counter-pressure cylinder (D) after its printing gap with a rubber cylinder (G), or that the first emitter device is assigned in or near the infeed area of ​​the printed sheets to the boom conveyor (8) directly following the last printing unit (5, 11) and in the area of ​​the boom conveyor (8), and that the first emitter device on the conveying path is assigned to the printed printed sheets on their printed side. Sheet-fed printing press according to claim 1 or 2, characterized in that the first emitter device consists of one or more modules, wherein the multiple modules are arranged to be operated individually or as variably switchable groups, wherein IR emitter devices (13) can be operated separately or together with thermal air blowing devices (14) or thermal air blowing devices (14) can be operated separately or together with IR emitter devices (13). Sheet-fed printing press according to one or more of claims 1 to 3, characterized in that the second emitter device is arranged on the conveying path of the boom conveyor (8) in an area in front of or near the boom (10) and is designed as a UV emitter device (12) which is arranged to consist of one or more UV emitters. Sheet-fed printing press according to claim 4, characterized in that a maximum drying section (9) is formed between the first module of the first emitter device and the last module of the second emitter device on the conveying path of the boom conveyor (8). Sheet-fed printing press according to one or more of claims 1 to 5, characterized in that the modules (13, 14) of the first emitter device and the UV emitters (12) of the second emitter device are arranged in such a coordinated and switchable manner that a drying path (9A) adapted to the substrate, ink and drying requirements is provided between the last IR emitter (13) or the last thermal air blowing device (14) in the sheet-fed direction and the first UV emitter (12) of the second emitter device in the sheet-fed direction to the delivery (10). Method for operating a sheet-fed printing press for single- or multi-color printing of printing inks onto printing sheets with a feeder (1), with one or more printing units (2, 3, 4, 5, 11) when applying special printing inks to a substrate, incorporating an inking / moistening unit, a plate cylinder (P), a rubber cylinder (G), and an impression cylinder (D) in each printing unit (2, 3, 4, 5, 11), wherein the special printing inks are mixed with photoinitiators and are suitable for curing by means of UV radiation, with a delivery conveyor (8) and a delivery unit (10) for receiving a stack of sheets, and with radiant devices in the area of ​​the delivery conveyor (8) for drying a color image, comprising the following steps: - a single- or multi-color printed image is applied to a printing sheet by means of the printing units (2, 3, 4, 5, 11), - no further coating is applied before the color image on the printing sheet dries of the pressure,- one or all of the special printing inks of the color image on the printed sheet are heated by means of a first radiation device, - the printed sheet is transported in the heated state over at least one sheet length without further radiation treatment, - one or all of the special printing inks of the printed image are subjected to a radiation treatment by means of a second radiation device to cure the special printing inks, and - the printed sheet with fully cured special printing inks is laid out on a sheet stack in the delivery (10), wherein, when using several modules of the first radiation device as IR radiation devices (13) and / or thermal air blowing devices (14) and the second radiation device as a UV radiation device (12), the modules of the first and second radiation devices are switched depending on the print subject,that sufficient curing of the special printing inks for intended further processing of the printed sheets results from sufficient heating of the ink image, sufficient waiting time before the curing treatment and sufficient exposure to the curing radiation. Method according to claim 7, characterized in that the printed sheet with a printed image made of special printing inks is treated after the last printing unit (5, 11) by means of a radiation treatment using at least one IR emitter device (13) and / or a thermal air blowing device (14) and that after a waiting period during the further transport of the printed sheet by means of the boom conveyor (8) the printed sheet is treated by means of a UV emitter device (12) to completely cure the special printing inks in the color image on the printed sheet.

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