EP1177914B1 - Method to reclaim a reusable printing plate - Google Patents

Abstract

The assembly to erase a cleaned printing plate (36), to be used again for printing with a new illustration/text image, applies a cleaning solution (42) as a liquid or gas from a controlled jet unit (44). During the erasure action, the plate is subjected to ultrasonic waves (50) from an ultrasonic transmitter (48). The cleaning solution is water, an acid or a lye. The printing plate processing can be at the printing press, or at a remote station.

Description

The invention relates to a method for deleting a wiederbebilderbaren printing form, which in particular is cleaned of printing ink.

The most important printing process today, the offset printing process, is based on the Immiscibility of water and greasy ink. Non-printing jobs one Offset printing form are processed in such a way that they are in a hydrophilic state This means that they accept water or a dampening solution while the printing locations of an offset printing plate are in the hydrophobic state, the means they do not accept water or dampening solution. When moistening the z. B. on one Plate cylinder applied printing form thus become only the hydrophilic sites wetted, so that in the subsequent inking of the printing form, the greasy ink only on the hydrophobic and at the same lipophilic, ie fat-accepting sites the printing form is applied. The printed image thus generated is then from Plate cylinder on a blanket cylinder and from there under pressure on a Print carrier, z. As paper, cardboard or foil transferred. The offset method is thus an indirect printing process.

Conventional printing plates used in offset printing usually consist of pre-coated aluminum plates whose pressure surface by mechanical and / or electrolytic processes were roughened at the non-printing sites, so that These sites create fine pores or capillaries that absorb the dampening solution film and hold. At the printing areas, on the other hand, the printing forms have a fine, closed surface on which dampening solution does not accept, but the ink one offers good adhesion to the substrate. However, these printing forms can only be imaged once then clearing the print image and repainting with a new print image is not possible.

There are also known printing forms, which can be imaged multiple times. These Printing forms have a surface, the z. B. from the hydrophobic state reversible in the hydrophilic state can be transferred.

EP 0 911 154 A1 describes such a printing form whose surface is in contact with Titanium oxide or zinc oxide is coated. The surface property of this printing form changes under the influence of UV radiation of preferably less than 400 nm wavelength, from the hydrophobic to the hydrophilic state. Furthermore, the printing form under Heat effect, z. B. mediated by an infrared laser or a heating elements arrangement, be put back into the hydrophobic state, which at the same time represents the lipophilic state. The print image is now generated in such a way that the coated printing form, which originally in the hydrophobic or lipophilic Condition is fully irradiated with ultraviolet radiation and thus is completely hydrophilic. At the places to be printed then becomes local for example Heat is supplied by means of the heating elements arrangement, whereby the printing form is local imaged, that is locally lipophilic. Thereafter, printing ink and dampening solution on the Surface of the printing form applied, the ink and dampening only on adheres to the respective, these accepting bodies and thus the printing for Printing is prepared. After printing, the printing plate is in a washing facility initially cleaned of printing ink and re-exposure to UV radiation again set back in the full-surface hydrophilic state. The print is thus deleted from the printing form and this can be another imaging process be subjected.

From EP 0 911 155 A1 there is furthermore a likewise with titanium oxide or zinc oxide coated printing form, which is as described in EP 0 911 154 A1 Printing form by use of UV radiation in the hydrophilic and by use of Heat can be added to the lipophilic state. The described printing form is initially in the lipophilic state and is only local to the non-printing Make exposure to UV radiation to these sites in the hydrophilic state convict. The printing form is therefore negatively imaged. After printing, the First printing form of the remaining ink cleaned and then by Heat treatment fully restored back to the lipophilic state, thereby deleted and prepared for another imaging process.

The described deletion of the printing form, however, takes a duration of several Minutes, for example about 10 minutes at a temperature of about 150 ° C. These Duration can only be reduced by increasing the temperature. For example, a To reach extinguishing duration of 10 seconds, the temperature must be during the Heat treatment already increased to 250 ° C. A gradual reduction of Erase duration is on the one hand the temperature compatibility, in particular the Destruction of the oxide layer by the heat, on the other hand Temperature sensitivity of the extinguishing device, which, for example, in the Printing machines can be located, as well as the printing press itself. Especially in the case from computer-to-press applications, that is in applications where the image data be directed by a computer directly into the press, but the imaging and the deletion of the printing plates in the printing machine and at the same time the Duration of both operations, in particular the duration of the deletion, are minimized to to be able to make a quick print job change. One according to the state of However, technology deleted printing form would have to be greatly heated and consequently undergo a cooling phase before the subsequent imaging process, whereby the total duration of Wiederbebilderung increases unfavorably again.

It is also known that the hydrophilic effect of the printing plate when stored in the Darken within hours or within weeks, depending on the titanium dioxide modification, loses again. At the molecular level, OH groups which are the Hydrophilicity cause, and instead deposits oxygen, which is responsible for the Hydrophobicity of the surface is responsible.

As wiederbebilderbare printing plates printing forms are still used, which after the cleaning process in a coating process with an imageable Surface to be recoated. It is not the relevant printing technology Surface layer in the molecular range changed and deleted, but one already imaged layer coated with a not yet imaged layer.

The invention is accordingly based on the object, a method to create, with which wiederbebilderbare printing forms in a short time Time can be deleted.

This object is achieved by the features according to claim 1 solved. Further features of the invention are contained in the subclaims.

The method according to the invention for deleting a re-imageable printing form, which is in particular cleaned of printing ink, is characterized in that the Printing form is treated with a liquid or gaseous extinguishing agent.

By the inventive treatment of the printing form with a liquid or gaseous extinguishing agent, the extinguishing process can advantageously in a very short time be performed. The action of the extinguishing agent on the surface of the printing form, which may be, for example, a titanium dioxide layer, this leads, for example, from hydrophilic in the hydrophobic state or from hydrophobic to hydrophilic Condition over. The user of the method according to the invention thus becomes allows the erasure of re-imageable printing forms in such a short time to perform that, for example, printing forms in computer-to-press applications can be deleted by the method according to the invention. However, it is more advantageous Way also possible, printing forms, which from a printing cylinder in one Printing presses were removed outside the press in a very short time to clear the Wiederbebildern and then back to the press use.

In a further embodiment of the method according to the invention, the Printing form during the treatment with the liquid extinguishing agent with ultrasound be treated. By the simultaneous treatment of the printing form with the liquid Extinguishing agent and with ultrasound, the duration of the deletion process in an advantageous manner further shortened. The deletion process can be both in the printing press as well as in a Ultrasonic bath be performed outside the printing machine, the liquid Extinguishing agent can form at least a portion of the dip liquid. After completion Extinguishing process is the printing plate surface in a hydrophobic state.

It may in a further embodiment of the method according to the invention be provided, the printing plate during the treatment with the liquid extinguishing agent to be exposed to the action of a heat source. By the action of the heat source on the printing form during treatment with the liquid extinguishing agent is the time which is required to erase the printing form, in an advantageous manner further shortened. In this case, the printing form of the action of the heat source within the printing press get abandoned. However, it may also be provided, the action of the heat source to perform on the printing form outside the printing press. In both cases, as Heat source at least one infrared laser, at least one heat radiator and / or at least one hot air blower can be used. It may also be provided that the Power of the heat source is changeable, with manual adjustment as well can be done automatically. When using water as an extinguishing agent and at the same time Heat is the printing technology relevant outer layer of the printing plate in one holistically hydrophobic state switched back.

It is also possible, in carrying out the method according to the invention the printing form during the treatment with the liquid extinguishing agent over the Normal pressure to expose elevated ambient pressure. By increasing the Ambient pressure, the boiling point of the liquid extinguishing agent is also increased and it is thus possible to carry out the erasing process at a temperature which is higher than the boiling point of the liquid extinguishing agent at atmospheric pressure. That's the way it works For example, in a further advantageous embodiment of the invention Be provided method that water is used as a liquid extinguishing agent. The use of water as an extinguishing agent for wiederbebilderbare printing forms leads for the Operator for a significant cost savings, since water is very low, and on the other hand to a substantial work easier a water connection in the rule near each printing press, especially near a lithographic Offset printing machine, is available. When using water as an extinguishing agent, if As mentioned above, the ambient pressure was increased from the normal pressure, the Temperature of the extinguishing agent during the action of the heat source above 100 ° C increase.

However, it is also possible that in the process according to the invention an acid or an alkali is used as a liquid extinguishing agent. At this chemical extinction The printing plate is again in a uniform depending on the acid or alkali used connected hydrophobic or hydrophilic surface state.

A preferred embodiment of the method according to the invention can continue characterized in that the liquid extinguishing agent using at least one Spraying device is applied to the printing plate. This will be advantageous Make a uniform, areal order of the liquid extinguishing agent on the Printing form achieved, while still a very accurate dosage of extinguishing agent by adjusting the spray nozzles or by adjusting the pressure with which the Extinguishing agent is applied, is made possible.

Preferably, in a further embodiment of the method according to the invention Printing form during treatment with the gaseous extinguishing agent of the action be removed from light, as the gaseous extinguishing agent, for example, oxygen can be used. Treating the printing form with an oversupply Oxygen in a darkened environment leads the entire printing form back into one uniform hydrophobic state and thus deletes one on the printing plate itself located print image. The deletion process can, for example, within the printing press be performed, wherein the area around the printing form cylinder on which the Printing form is located, as far as possible darkened, for example by a Abschottvorrichtung effected, and whereby with the help of one or more Feeders, for example in the form of nozzles, the printing form surface pure Oxygen is offered.

In general, it is possible to use all the above-described embodiments of the inventive method both within a printing press and outside a printing press, wherein only the devices with which the Procedure can be performed, the appropriate conditions, in particular the Conditions within a printing press, need to be adjusted. So it can be for Example sprayers continue to be provided by an additional Abschotteinrichtung the environment around the spray device within a Protect printing press from the action of sprayed extinguishing agents. It can but also additional suction for sucking the excess sprayed Extinguishing agent be provided.

The above-described advantageous embodiments of the method according to the invention, in which the printing form increased compared to the normal pressure Ambient pressure is exposed, preferably outside of the printing press in separate extinguishing devices are performed. Such devices have to Example, a pressure-tight sealable space in which the printing plate during of erasing, and that by means of an overpressure unit, for example a compressor, is pressurized to a pressure higher than the normal pressure Air is.

An apparatus for erasing a re-imageable printing form, which is cleaned of ink, characterized by a means for applying of liquid or gaseous extinguishing agent on the printing form.

The means for applying extinguishing agent to the printing form may, for example a spraying device, in particular one or more spray nozzles, an applicator roll, a mist chamber or means for applying the extinguishing agent be electrostatic charge of the extinguishing agent and the printing form. The device Further, a unit for adjusting the dosage of the extinguishing agent in Apply to the printing form include. By the described facilities for Applying an extinguishing agent on the printing form, it is advantageously the Printer allows the extinguishing agent over the entire surface and in the desired dosage on the Apply printing form, creating optimal conditions for the deletion of wiederbebilderbaren printing form can be achieved, and thus the deletion process in time can be performed.

Further embodiments of the device can be a Ultrasonic source for irradiating the printing plate with ultrasound or a heat source provide for heating the printing form. As a heat source can at least one Infrared laser, at least one heat radiator and / or at least one hot air blower be used. The ultrasound source and the heat source can be used in the Be arranged near the printing forme cylinder such that they are the means for Applying the extinguishing agent on the printing plate in the direction of rotation of the printing forme cylinder are arranged downstream, which advantageously the ultrasound or heat directly acts on the previously treated with extinguishing printing form.

There are also conceivable printing processes, which are characterized by the fact that at each Rotation of the plate cylinder deleted the previous image and the printing plate new is pictured. This is a very fast and effective extinguishing process necessary, the method and apparatus described above, as far as they are can be used on-press.

The invention will be described below with reference to the drawings with reference to preferred Embodiments described, wherein matching parts in different Embodiments are provided with the same reference numerals.

Fig. 1

einen Ablaufplan des erfindungsgemäßen Verfahrens, wobei die Druckform mit Ultraschall behandelt wird,

Fig. 2

einen Ablaufplan des erfindungsgemäßen Verfahrens, wobei die Druckform mit Wasser unter Zufuhr von Wärme behandelt wird,

Fig. 3

einen Ablaufplan des erfindungsgemäßen Verfahrens, wobei die Druckform mit Sauerstoff unter Entzug von Lichteinwirkung behandelt wird,

Fig. 4

eine Seitenansicht einer Vorrichtung, die eine Sprüheinrichtung und eine Ultraschallquelle umfasst,

Fig. 5

eine Seitenansicht einer Vorrichtung, die eine Sprüheinrichtung und einen Infrarot-Laser umfasst,

Fig. 6

eine Seitenansicht einer Vorrichtung, die eine Sprüheinrichtung und einen Wärmestrahler umfasst,

Fig. 7

eine Seitenansicht einer Vorrichtung, die zwei Sprüheinrichtungen und ein Heißluftgebläse umfasst,

Fig. 8

eine Seitenansicht einer Vorrichtung, die eine Sprüheinrichtung und eine Abschotteinrichtung umfasst.

In the drawings show:

Fig. 1

a flow chart of the method according to the invention, wherein the printing plate is treated with ultrasound,

Fig. 2

a flow chart of the method according to the invention, wherein the printing form is treated with water with the supply of heat,

Fig. 3

a flow chart of the method according to the invention, wherein the printing form is treated with oxygen with the removal of light,

Fig. 4

a side view of a device comprising a spraying device and an ultrasonic source,

Fig. 5

a side view of an apparatus comprising a spraying device and an infrared laser,

Fig. 6

a side view of an apparatus comprising a spraying device and a heat radiator,

Fig. 7

a side view of a device comprising two sprayers and a hot air blower,

Fig. 8

a side view of an apparatus comprising a spraying device and a Abschotteinrichtung.

The flowchart of a method for deleting a re-imageable printing form shown in FIG. 1 shows a first method step 2, in which the printing form is first cleaned of the printing ink. This cleaning of the printing plate can be carried out by means of a known washing device. In a further method step 4, it is determined whether the deletion process is to be carried out subsequently in the printing press (on-press) or outside the printing press (off-press). If the deletion process is carried out off-press, in a further method step 6, the printing form is removed from the printing cylinder and used in the subsequent method step 8 in an extinguishing device located outside the printing press. The printing plate may be plate-shaped or cylindrical, wherein the plate-shaped printing plate is fixed by a known disk clamping device on the printing form cylinder, while a cylindrical printing form is pushed axially on the printing form cylinder and withdrawn from this. The printing forme, which has, for example, a titanium dioxide layer on its surface, is then treated, in method step 10, with a liquid extinguishing agent, wherein the liquid extinguishing agent can be applied to the printing form by means of an applicator, for example a spraying device, or the printing form in a dip, which consists at least partially of the liquid extinguishing agent is introduced. The deletion of the printing plate by means of a dip bath is preferably used in the off-press embodiment of the method according to the invention. By performing in step 10 treatment of the printing plate with a liquid extinguishing agent, the printing plate is set back over the entire surface in a hydrophilic or hydrophobic state depending on the extinguishing agent used, whereby all image information on the surface of the printing plate are irreversibly deleted. For switching back the surface layer 36 of the printing form in the hydrophobic starting state, for example, hydrogen peroxide H ₂ O ₂ can be used, while the surface layer 36 can be added, for example, with sodium hydroxide NaOH in the hydrophilic starting state. In this case, a 30% aqueous solution of H ₂ O ₂ and a 20% aqueous solution of NaOH can be used. In order to further support this deletion process, in step 12, the printing plate is additionally treated with ultrasound during the treatment with the liquid extinguishing agent. By means of the ultrasound-mediated energy supply, the extinguishing process is advantageously further supported and shortened. It is preferably possible to use ultrasound in the frequency range between 30 kHz and 50 kHz.

FIG. 2 shows a further embodiment of the method according to the invention, in which the printing form is treated with water as a liquid extinguishing agent and continues to be exposed to the action of a heat source. Process steps 2, 4, 6 and 8 are equal to the method steps described in FIG. 1. By doing Process step 14 is the printing plate first with water as a liquid extinguishing agent treated. This may be ordinary tap water, but also special treated extinguishing water, which, for example, subjected to a distillation process became, act. In the following method step 16, the printing for the Support of the extinguishing process additionally the action of a heat source exposed. The supply of heat energy, for example in the form of heat radiation, provides advantageous support for the deletion process and further reduction the duration of the deletion process. Another method step 18 includes the Increase of the ambient pressure of the printing plate compared to the normal pressure of the air during the treatment of the printing form with the liquid extinguishing agent water and the Supply of heat energy. By said increase in ambient pressure can at Use of water as a liquid extinguishing agent at temperatures higher than 100 ° C the deletion of the printing form are carried out, and thus the duration of the deletion of Printing form can be further shortened in an advantageous manner. A temperature of the Compressor 36, or the surface thereof, to about a temperature in the range of 50 ° C to 120 ° C proves to be favorable in support of the extinguishing agent-induced Deletion.

FIG. 3 shows a further flowchart for a method according to the invention, which is described in FIG the process steps 2, 4, 6 and 8 with the method shown in FIGS. 1 and 2 matches. In the following process step 20, the printing plate with oxygen treated as a gaseous extinguishing agent, whereby the printing plate in a full-surface hydrophobic state and any image information on the surface the printing form is lost. It can in a further method step 22 for Support the extinguishing process to continue to be provided, the printing plate during the Treatment with oxygen to remove the action of light. So can for example the printing forme by a Abschotteinrichtung in substantially complete Darkness while being exposed to an oxygen bath. By preventing the action of light on the surface of the printing plate is the transfer into the hydrophobic state of the surface favors and temporally shortened.

The illustrated in Fig. 4 embodiment of the device comprises a printing form cylinder 30, a blanket cylinder 32 and a Impression cylinder 34. A printed image, which is on the surface of a reusable printing plate 36 is placed on a blanket 38 of the Transfer blanket cylinder 32 and from there to an image carrier 40, for example a Paper sheet or a paper web, which through the nip between the Rubber cylinder 32 and the impression cylinder 34 is running, transfer. To delete the wiederbebilderbaren printing plate 36 on the plate cylinder 30 in an on-press Embodiment of the device is the printing plate 36, after it was cleaned by an unillustrated washing device of ink, with a liquid extinguishing agent 42, which by means of a spray 44 on the Surface of the wiederbebilderbaren printing plate 36 is sprayed treated. The Liquid extinguishing agent forms a thin film 46 on the surface of the wiederbebilderbaren printing form 36, which, starting from the point at which the liquid extinguishing agent 42 is sprayed onto the printing plate in the direction of rotation of the Printing form cylinder 30 extends. By one of the sprayer 44 in the direction of rotation of the Compression plate cylinder 30 downstream ultrasonic source 48, the printing plate 36 with Ultrasound 50 treated. A motor 52 rotates the printing forme cylinder with it arranged wiederbebilderbaren printing plate 36 during the deletion in the by The arrow 54 shown direction of rotation. By a control unit 56, the dosage the extinguishing agent 42 and the intensity of the ultrasonic radiation 50 controlled. That's it For example, possible by a sensor unit, not shown, the printed image or remains of the print image on the surface of the reimageable printing plate 36 to detect and depending on the amount of liquid extinguishing agent 42, the point of application of the liquid extinguishing agent 42 or the local intensity of the ultrasonic radiation 50 for a more efficient erase process to the detected image or to the not yet to adjust deleted remnants of the printed image. The control unit 56 further controls the Motor 52 for rotating the plate cylinder 30, so that a targeted, for example gradual, slow or fast rotation of the plate cylinder in forward or Reverse direction is enabled.

In the embodiment shown in Fig. 5 apparatus for Erasing a re-imageable printing form, the spraying device 44 is an infrared laser 58 downstream in the direction of rotation of the plate cylinder 30. The with the liquid Extinguishing agent 42 treated surface of the reimageable printing plate 36 is further treated with infrared radiation 60. The infrared laser unit 58 can in this case consist of a single infrared laser 58, the laser beam 60 by a not shown Abscanneinrichtung over the surface of wiederbebilderbaren Printing form 36 is reciprocated in the axial direction. It can, however be provided, an infrared laser unit in the form of a linear, axial Laser arrangement of several infrared laser use, which is near the surface the wiederbebilderbaren printing form 36 parallel to the axis 31 of the plate cylinder 30th is arranged. By the control unit 56, the power of the infrared laser 58th controlled and continuously, for example, during the progress of the deletion process be reduced.

Fig. 6 shows a further embodiment of the device, in which instead of an infrared laser as shown in Fig. 5, a heat radiator 62 for Sprayer 44 adjacent near the surface of the re-imageable Printing form 36 is arranged. Also in this embodiment of the device for Erasing a reproducible printing form, it is possible by means of a Control unit 56, the output of the heat source in the form of a heat radiator 62nd to regulate.

Fig. 7 shows a device in which for heating the Surface of the reimageable printing plate 36 a hot air blower 64 adjacent to two sprayers 44 are disposed near the surface of the printing plate. The Use of two sprayers 44 allows for an extinguishing agent mixture to apply the surface of the printing plate 36, wherein the proportion of a first and a second extinguishing agent in the extinguishing agent mixture by a controlled adjustment of Metering can be effected at the spray 44.

The embodiment of the device for erasing shown in FIG a wiederbebilderbaren printing form shows a nozzle 66, which oxygen 68 against the Surface of wiederbebilderbaren printing form 36 blows. To an increased concentration of oxygen in the ambient air of the printing forme 36 is the Printing form cylinder 30 by a Abschotteinrichtung 70, which the printing form cylinder encloses as gas-tight as possible, surrounded. The amount of oxygen 68 supplied may be set by the control unit 56, wherein, for example, by a not shown sensor unit, the oxygen concentration within the Abschotteinrichtung 70 is determined and compared with a predetermined setpoint becomes.

LIST OF REFERENCE NUMBERS

2

Process step (cleaning the printing form)

4

Process step (on-press / off-press decision)

6

Process step (removal of the printing form)

8th

Process step (insertion in an extinguishing device)

10

Process step (treatment with liquid extinguishing agent)

12

Process step (treatment with ultrasound)

14

Process step (treatment with water)

16

Process step (treatment with heat)

18

Process step (increase of the ambient pressure)

20

Process step (treatment with oxygen)

22

Process step (removal of light exposure)

30

Plate cylinder

31

Axis of the plate cylinder

32

rubber cylinder

34

Impression cylinder

36

reproductible printing form

38

blanket

40

image carrier

42

liquid extinguishing agent

44

spraying

46

Extinguishing Media Movie

48

ultrasound source

50

Ultrasonic

52

engine

54

direction of rotation

56

control unit

58

Infrared Laser unit

60

Infrared radiation

62

Radiant heaters

64

Heat Guns

66

jet

68

oxygen

70

Abschotteinrichtung

Claims (12)

1. Method of clearing a re-imageable printing form having a surface, particularly a printing form from which the ink (2) has been washed,
   characterized in that the surface of the printing form is treated with a liquid or gaseous clearing medium (10, 14, 20) in such a way that the surface of the printing form is caused to be converted from the hydrophilic to the hydrophobic state or from the hydrophobic to the hydrophilic state.
2. Method according to claim 1,
   characterized in that the printing form is exposed to the radiation of an ultrasound source or treated with ultrasound (12) during treatment with the liquid clearing medium (10, 14).
3. Method according to claim 1,
   characterized in that the printing form is exposed to the effects of a heat source (16) during treatment with the liquid clearing medium (10, 14).
4. Method according to claim 3,
   characterized in that at least one infrared laser, at least one radiant heater and/or at least one hot-air blower are used as the heat source.
5. Method according to claim 3 or 4,
   characterized in that the printing form is exposed to higher ambient pressure than normal atmospheric pressure (18) during the treatment with the liquid clearing medium (10, 14).
6. Method according to one of the claims 2 to 5,
   characterized in that the liquid clearing medium is water (14).
7. Method according to claim 1,
   characterized in that the liquid clearing medium is an acid.
8. Method according to claim 1,
   characterized in that the liquid clearing medium is a base.
9. Method according to one of the preceding claims,
   characterized in that the liquid clearing medium is applied to the printing form using at least one sprayer.
10. Method according to claim 1,
    characterized in that the printing form is removed from the effect of light (22) during treatment with the gaseous clearing medium (20).
11. Method according to claim 10,
    characterized in that the gaseous clearing medium is oxygen (20).
12. Method according to one of the preceding claims,
    characterized in that the method is carried out in a printing press or in a clearing device outside a printing press.

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