EP2090429B1 - Imaging of an offset printing plate - Google Patents

Abstract

The method involves applying a printing form (2) of a pourable, hardenable coating material e.g. lacquer (3), on a hydrophobic surface in a printing machine by application devices (8, 9, 10). The coating material is hardened by ultraviolet or infrared irradiation or drying by irradiation devices (11, 12), where the hardened material exhibits a hydrophilic surface. The hardened material is removed by laser irradiation so that the hydrophobic surface of the printing form is laid open, where the printing forms with a carrier structure of steel or aluminum and a surface layer of nickel and copper. The coating material consists of amino group, carboxyl group and silane. Independent claims are also included for the following: (1) a device for imaging a printing form (2) an offset-printing form comprising a carrier structure and a surface layer.

Description

The invention relates to the imaging of a printing form in an offset printing machine, preferably wet offset, and for this purpose has a method and a device for the subject. Furthermore, it relates to an imaged offset printing form and an offset printing form in a not yet illustrated raw state. The printing press may in particular be a rotary printing press, preferably for web-fed printing. A preferred application is newspaper printing. The machine preferably operates in the coldset, i. the paint is dried by air drying without heating.

From the DE 198 26 377 A1 and the DE 10 2005 021 346 A1 For example, methods of imaging are known that rely on the use of printing forms that are reversibly switchable between a hydrophobic and a hydrophilic state. The surface of the printing plates is formed by metal oxides. After DE 198 26 377 A1 Color is applied and in wet offset also moisture is applied directly to the metal oxide surface. After DE 10 2005 021 346 A1 An organic compound is adsorbed on the metal oxide surface and the surface of the printing form is thereby rendered hydrophobic. The hydrophobing is supported by UV and IR radiation. For imaging, the hydrophobized surface is image-wise exposed to IR laser pulses at an intensity below the ablation threshold to produce the hydrophilic sites of the surface. The printing form can be erased by means of IR irradiation, with the temperature in the near-surface region of the printing form briefly reaching approximately 500 ° C. The problem with the reversibly switchable printing forms are their still short life, so that larger runs can not be printed with the printing plates.

The US 6,908,544 describes an offset printing plate for smaller runs with a surface which may include as an ingredient metals, such as aluminum, chromium, nickel or mixture thereof. The ablation of the printing plates, or the hydrophilic surfaces of the printing plates by means of Lifrarotstrahlen. From the DE 27 34 508 A1 In general, a method for producing a planographic printing plate or a planographic printing plate is known in which a substrate made of an oleophilic plastic is coated with a polymerizable hydrophilic radical. This surface is then exposed to actinic radiation to form a hydrophilic film chemically bonded to the substrate. The US 6,477,955 B1 describes a laser erasable waterless printing plate that can be exposed in the printing press. The printing plates are particularly thin and therefore well suited for use on PBI (plate blanket image) cylinders.

It is an object of the invention to image a printing plate in an offset printing machine in a simple manner and to increase the service life of the imaged printing plate, wherein the image information of the printing plate is preferably erasable.

According to the invention, a flowable, preferably liquid, coating material is applied to a printing form having a hydrophobic surface in such a way that it wets the printing surface of the printing plate everywhere. The coating material is hardened on the entire surface and forms a hydrophilic surface of the printing plate in the hardened state. The hardened coating material is removed according to the image by means of irradiation, so that the hydrophobic surface of the printing form which lies beneath the coating material is exposed in accordance with the image. As a result, a printing plate is obtained which has a color-transferring surface in printing operation, which is composed of a printed image to be transferred from the hydrophilic surface sites formed by the coating material and the exposed hydrophobic surface areas. According to the invention thus results in the printing operation, the material of the printing plate, which is generally more resistant to abrasion than the coating material, the color, while the hardened coating material remains free or as preferred the dampening solution leads. The coating material contains hydrophilic groups, preferably amino groups, carboxyl groups, silane groups or other group IV compounds, or a combination of several or all of these groups or compounds.

The coating material may in particular be a lacquer.

The coating material can be completely removed by means of a radiation corresponding to the imaging and the printing form can be reimaged in the same way. The method therefore includes, in an advantageous further development, erasing the printed image and re-imaging the printing form.

Preferably, an aqueous coating material is used, ie a coating material with water as solvent.

The radiation energy of the image-wise radiation preferably originates from a different wavelength range of the electromagnetic spectrum than the radiation energy serving for hardening. Furthermore, it is advantageous if the irradiation for curing over the surface is uniform, while the imagewise irradiation of the fineness of the print is correspondingly focused, so that each individual pixel of the print image to be generated can be selectively irradiated individually. Alternatively, the radiation energy used for hardening can also be selected from the same wavelength range as the radiation energy of the image-wise irradiation. The radiation may in both cases even have the same wavelength. In such embodiments, the same irradiation device can serve for both curing and image-wise irradiation, with at least one radiation parameter of the irradiation device being variable in order to fulfill the dual function. Thus, the irradiation device can be used by focusing for the image-wise irradiation and by defocusing for hardening. Alternatively or additionally, the power of the irradiation device can also be adjusted to the respective purpose. Another possibility is the variation of the speed with which the printing form moves once upon curing and the other time as the image is irradiated relative to the irradiation device.

To quickly and evenly cure the paint over the entire surface, the printing plate can be thermally irradiated. More preferably, however, it is irradiated with UV or IR light. Accordingly, in preferred embodiments, a lacquer hardening under UV or IR irradiation is used. Since the light in the vicinity of the printing plate, as far as light is present, is not sufficient for the desirable rapid hardening, although in principle a hardening under ambient light is conceivable and also advantageously used, the irradiation is expediently carried out with artificial UV or IR light. which is generated by a UV or IR irradiation device and directed to the printing plate. For the UV radiation, the entire UV wavelength range of 250 to 400 nm comes into question. Preferably, UV radiation from the wavelength range of 350 to 380 nm is used.

The coating material is preferably applied in a thickness which is smaller than a maximum length or largest width of an image pixel of the imaged printing plate executed printing process. The thickness of the application layer is preferably at most 10 μm. Preferably, the thickness is preferably at least 1 μm.

The coating material may alternatively or in addition to an active irradiation also by simple air drying, i. Heat exchange with the environment, to be dried at room temperature, in particular by convection. The simple air drying can already be sufficient, especially for the above-described small layer thickness of the coating material alone for curing.

At the surfaces of the surface to be hydrophobically formed, the hardened application material is preferably removed by means of laser irradiation, for example IR laser radiation. The paint is thermally decomposed by this irradiation imagewise (thermal decomposition).

The imagewise removal of the coating material immediately produces the print form which can be used for printing. Immediately after the imagewise removal of the coating material, paint can be applied to the printing plate. If the printing form is preferably a printing form for the wet offset printing, moisture is applied beforehand in order to wet the hydrophilic areas formed by the coating material with the dampening solution, preferably water, before applying the paint. When using an aqueous coating material is obtained as a further advantage for a preferred wet offset printing that not or not fully hardened residues of the coating material transported away by a dampening agent used in printing from the printing plate and transferred to the first copy copies and thus the printing form of such residues right at the beginning the pressure is cleaned.

In order to keep the time required for the imaging as short as possible, the coating material in fine distribution may contain particles that absorb the radiation energy of the imagewise radiation in a special way and thus ensure a more rapid thermal decomposition at the irradiated points. The particles may be dark, preferably black, pigments or consist of one or more other materials which are tuned to the wavelength of the radiation in order to maximize absorption.

Instead of using a coating material with absorbent particles or advantageously in addition to such a measure, it is advantageous if the printing form, at least in a depth region comprising the hydrophobic surface, consists of a material which absorbs a high proportion of the radiation energy of the second irradiation.

Apart from the hardened coating material, the printing form may consist in particular of aluminum or preferably of stainless steel. The printing form without the coating material layer according to the invention is also referred to below as a printing plate carrier. The printing plate support made of steel or aluminum or in principle also of another material has a thin, color-friendly, d. H. hydrophobic surface layer forming the hydrophobic surface of the printing form. This surface layer consists of copper or an alloy of copper, which contains copper at least as an essential component. The surface layer may preferably be 1 to 100 .mu.m, preferably 1 to 10 .mu.m thick and be applied, for example, by electroplating.

The coating material can be applied directly to the printing form, to be more precise the printing form carrier, for example by spraying. More preferably, the coating material is applied by means of a roller. The coating material can be sprayed onto this paint applicator roll or otherwise applied directly. Advantageously, it is applied by means of a further roller to the application roller forming a transfer nip with the printing forme. It is also advantageous if the coating material is conveyed to the printing form via an axially reciprocating distributor roller.

In order to apply the coating material to the printing form, the printing press can have an application device which only serves to apply the coating material. If it is preferably a wet offset printing machine, the coating material is preferably applied by means of a damp coater, which in printing operation promotes the fountain solution required for printing on the printing form. The dampening applicator thus also forms a part of the Auftragseimichtung for the coating material in a dual function. If the dampening unit has one or more dampening rollers, the one or more or a part of the plurality of dampening rollers can optionally serve either to apply the coating material or to apply the dampening solution by applying the coating material to the dampening roller or one of several dampening rollers and from this is transferred directly or first via one or more dampening rollers on the printing form. Thus, the coating material can be advantageously applied directly to a distributor roller of the dampening application device, for example sprayed on.

The irradiation for curing can advantageously be a UV or IR irradiation, as already mentioned. The UV or IR radiation may, for example, be generated by one or more UV or IR emitters which extend or extend over the entire width of the surface of the printing form to be irradiated or are axially reciprocable, to be able to irradiate the entire surface. In a preferred modification, the UV or IR light is guided by means of optical waveguides from a UV or IR light source to the surface of the printing plate. The UV or IR source can supply multiple printing forms simultaneously or sequentially with UV or IR light. In embodiments with such a UV or IR source whose light is coupled centrally into the system of the optical waveguide and brought by them to the surface of the printing plates and emitted to the respective surface.

In order to improve the adhesion of the coating material to the hydrophobic surface of the printing plate, the surface can be pretreated, for example by means of uniform UV irradiation, which can be stirred by means of a further irradiation device or advantageously by means of the irradiation device for curing. Alternatively, or in addition to such pretreatment, a primer may be applied to the hydrophobic surface onto which the coating material is then applied.

In an advantageous development, the imaged printing form is erased by completely removing the imagewise remaining coating material in the printing press by thermal decomposition from the hydrophobic surface. In particular, the same irradiation device that previously performs the imaging can be used for the erasure. Upon erasing, this irradiation device can uniformly irradiate the printing plate. Alternatively, a radiation corresponding to the negative print image is conceivable, in which case only the hydrophilic spots of the printing form formed by the paint are selectively irradiated, preferably with an enlarged edge area.

If the printing form is also erased as preferred in the printing press, in order subsequently to be able to image it again, it is advantageous if the printing press is equipped with a cleaning device with which the printing form can be cleaned after erasing. As a cleaning device, for example, a washing device in question, by means of which paint residues can be washed off

For irradiation for curing and for imagewise irradiation, different irradiation devices can be provided, ie an irradiation device for curing and a further irradiation device for imagewise irradiation. In an alternative embodiment, the same irradiation device, ie the same emitters, can be used both for curing and for imagewise irradiation. The irradiation device can be adjusted for the fulfillment of such a dual function. For example, the radiation power or the focusing of the irradiation device can be adjustable in order to apply the radiation uniformly to the surface of the printing plate with strong focusing and preferably high power in accordance with the image and with defocused irradiation device and preferably lower power , Furthermore, a control of the printing press can be set up, preferably programmed, such that the printing form is moved faster during curing than in the case of imagewise irradiation relative to the irradiation device. The ability to speed variation in imaging may be provided alternatively or in combination with the aforementioned variation possibilities.

The printing machine is preferably a rotary printing press with color transfer printing cylinders. Such a printing cylinder can form the printing form immediately. More preferably, however, the printing form is mounted on a printing cylinder, preferably detachable. The printing form can be a sleeve pushed onto the printing cylinder. However, the invention is particularly suitable for printing forms which are formed as flexible printing plates, as is common nowadays. Such printing plates are easily replaceable if necessary, for example in the case of mechanical damage or wear.

The invention also provides the imaged printing form as such and also a printing form blank with the hardened coating material, preferably paint, which covers the surface serving for printing everywhere. Such Druckfornroing simplifies the printing form logistics, since the unimaged blanks do not have to be assigned in each case exactly one place in the printing press, but the blanks can still be randomly distributed to the printing stations of the printing press. An application device for the coating material is not required when using such blanks. Furthermore, the invention also relates to a device for imaging a printing form, in an offset printing machine to the subject, which is suitable for carrying out the method and accordingly has an application device for the coating material. In the case of a wet offset printing press, it is particularly preferable to use a dampening unit in a double function once for applying the coating material and the other time for applying dampening solution.

The above statements apply equally to the method, the device and the printing plate.

The subclaims and their combination further features of the invention are disclosed.

Figur 1

einen mit Druckformen belegten Druckformzylinder während einer Bebilderung,

Figur 2

einen Abschnitt einer der Druckformen in einem Querschnitt,

Figur 3

eine modifizierte Druckform während eines Auftrags von Lack und

Figur 4

die modifizierte Druckform während eines Härtens des Lacks.

Hereinafter, embodiments of the invention will be explained with reference to figures. Characteristics disclosed in the embodiments form each individually and in each Combining the subjects of the claims and also the embodiments described above advantageous. Show it:

FIG. 1

a printing form cylinder covered with printing plates during an imaging,

FIG. 2

a section of one of the printing plates in a cross section,

FIG. 3

a modified printing form during a contract of lacquer and

FIG. 4

the modified printing form during curing of the paint.

FIG. 1 shows a printing form cylinder 1, on the cylinder circumference one or more printing plates 2 are arranged. Thus, as is generally known, one or more printing plates 2 can be arranged one after the other and one or more printing plates 2 next to one another in the circumferential direction over the circumference of the printing form cylinder 1 in the circumferential direction. For fixing the printing form or printing plates 2, the printing form cylinder 1, as also known, on the periphery have a single or more channels into which the printing plate or printing plates each with a Abbug at the leading and trailing end protrude and are secured by clamping. FIG. 1 shows a schematic representation of only a printing plate 2, which is shaped as a sleeve and surrounding the printing form cylinder 1 around the axis of rotation. However, the illustration is only schematic in this regard. Although a compression molding sleeve is a Ausfühningsvariante a printing form according to the invention, preferably the printing plate or the plurality of printing plates 2, however, each as a flexible pressure plate (s) formed, which is arranged as described on the printing form cylinder 1 and fixed or are.

The printing form cylinder 1 is associated with a transfer cylinder, preferably a blanket cylinder, to which it transfers imagewise during the printing operation. The transfer cylinder forms with a counter-pressure cylinder, preferably a further transfer cylinder with an associated further such printing form cylinder 1, a printing nip for a web to be printed. However, the impression cylinder may also be a non-printing cylinder, for example a steel cylinder of a satellite printing unit, for example a 9 or 10 printing unit.

The printing cylinder 1 is associated with an inking unit 5 and a dampening unit 6, which transfer dampening solution and ink to the printing form 2 and preferably further printing plates 2 during printing operation. In that regard, the printing form cylinder 2 with the associated transfer cylinder and the inking unit 5 and the dampening unit 6 form a conventional wet offset printing unit.

The printing unit further comprises an imaging device for imaging the printing form 2 and preferably further printing plates 2 in the printing press. In the following, reference will be made only to a single printing plate 2 as a representative of the preferred further printing plates 2 of the plate cylinder 1 reference. The imaging device comprises distributed over the circumference of the printing forme cylinder 1 an applicator by means of a liquid coating material, in the embodiment, a paint 3, on the printing form 2 can be applied, a first Irradiation Einriehtung 11 for curing the applied paint 3 and a second irradiation device 12 for imagewise irradiation of the hardened paint 3. The paint application device comprises a spraying device 10 and components of the dampening unit 6.

The dampening unit 6 comprises a plurality of rollers, by means of which fountain solution can be conveyed to the printing form 2. In the case of a Moisture Nuchtfeörderung, especially during printing, the dampening solution passes from a dampening roller 7 arranged in Druclcformzylinder 1 via a closer to the printing form cylinder 1 arranged Reiberwalze 8 on a Feuzyztmittelauftragswalze 9, with the Druckfolinzylinder 1, more precisely with the Druckfonn 2, a gap For spraying the spraying device 10 sprays the lacquer 3 onto the distributor roller 8, from which part of the lacquer 3 is conveyed to the printing form 2 via the dampening form roller 9 and another part is conveyed back via the dampening roller 7. Alternatively, during the application of the varnish 3, the roller sprayed with the varnish 3, in the exemplary embodiment the rubbing roller 8, can be separated from the dampening solution upstream components of the dampening unit, in the embodiment of the dampening roller 7, for example, from the upstream part. For the transfer of dampening solution in such embodiments, the compound is produced after completion of the paint job. With This paint application device 8, 9, 10, the paint 3 is applied uniformly distributed over the entire surface of the printing form 2, so that it forms a thin film there.

The varnish 3 is an aqueous UV varnish, i. H. a UV-curable lacquer with water as solvent. In the hardened state, the surface of the lacquer 3 is therefore hydrophilic. The Druckfonn 2 is a flexible metal plate, preferably made of steel, which has a hydrophobic surface on which by means of the paint applicator 8 to 10 of the paint 3 is applied in the form of a thin film. Optionally, an adhesion promoter can be applied to the hydrophobic surface of the printing form 2 before the application of the lacquer 3 in order to increase the adhesion of the lacquer 3 to the printing form 2. In yet another variant, the surface of the printing form 2 can be irradiated before the application of the lacquer 3, for example with UV light, in order to improve the adhesion of the lacquer 3.

The first irradiation device 11 is the paint application device 8 to 10 in the direction of rotation of the Druclcformzylinders 1, which is indicated by a direction of rotation downstream with the irradiation device 11, the entire surface of the printing plate 2 are uniformly irradiated while rotating Drtrckformzylinder 1 to the paint 3 cure. The irradiation device 11 is a UV irradiation device according to the choice of the varnish 3. Under under the irradiation device 11 continuous printing form 2 of the entire coating film 3 is cured by crosslinking the polymer chains of the paint 3 under the action of UV radiation, so that in the direction of rotation of the Druclcformzylinders 1 behind the irradiation device 11, a thin, hardened paint film 3, the hydrophobic surface of the Printing form 2 covered.

The second irradiation device 12 is arranged downstream of the first irradiation device 11 in the direction of rotation of the plate cylinder 1. By means of the irradiation device 12, the hard paint 3 is irradiated imagewise and removed at the irradiated points by thermal decomposition, so that the hydrophobic surface of the printing plate 2 is exposed at the irradiated points. The irradiation device 12 is a laser irradiation device. It may in particular be an irradiation irradiation for irradiation with IR laser light. The EP 1 036 655 A1 discloses exemplary embodiments of the irradiation device 12.

FIG. 2 shows a portion of the imaged printing form, 2. The hydrophobic surface of the printing plate 2 is denoted by 2a. The hydrophilic surface of the hardened lacquer 3 is designated by 3a. The lacquer 3, which is first applied as a uniformly thin film, wetting the surface 2a everywhere, and cured, is removed at the points irradiated by the irradiation device 12, except for the hydrophobic surface 2a. In FIG. 2 the remaining paint spots and the places exposed between them are recognizable. The paint 3 is shown only disproportionately thick for purposes of illustration compared to the printing form 2. In any case, the hydrophobic printing form points 2a and the hydrophilic lacquer points 3a together form the printing surface, ie the printed image, of the imaged printing plate 2, 3.

After the imaging, which, as far as the paint application, hardening and imagewise irradiation, after preferably a single revolution of the plate cylinder 1, but possibly also after several revolutions, is completed, the paint supply is stopped, and the dampening solution begins. After the hydrophilic lacquer areas 3a of the surface 2a and 3a of the printing plate 2, 3 are moistened with dampening solution, the inking unit 5 parked during the imaging of the printing form cylinder 1 is set against the printing form cylinder 1 and ink is transferred to the hydrophobic areas 2a. The printing form cylinder 1 performs under dampening solution preferably still a few turns with the inking unit off 5 to remove paint residues, for example, not hardened paint 3, from the surface of the imaged printing plate 2, 3. After hiring the inking unit 5, the print production can be started in a known manner.

After completion of the print production, the inking unit 5 is turned off and the image information of the printing form 2, 3 deleted. For deleting the image information, ie the printed image composed of the hydrophobic sites 2a and hydrophilic sites 3a, the paint spots 3a are removed. The removal can be done again by thermal decomposition. Advantageously, the irradiation device 12 can also be used as a quenching device by the surface of the printing plate 2, 3 is uniformly irradiated or according to the pattern of the paint spots 3a. The or preferably a plurality of lasers of the irradiation device 12 are thus in a double function in such embodiments used both for imagewise irradiation and for erasing, For the next print production, the same printing form 2 can be imaged again in the manner described. Before reprinting the printing form 2 is expediently freed with a cleaning device of the printing of any paint residues.

The FIGS. 3 and 4 show the application and curing of the varnish 3 in a modification of the application method and on the basis of a modified printing form. As in FIG. 3 illustrated, the paint 3 is sprayed by means of a spray 10 'directly on the hydrophobic surface of the printing plate. The in FIG. 4 shown hardening Cluitt corresponds to the curing of the described embodiment. The FIGS. 3 and 4 show isolated only a short section of the printing form, which is however arranged on the printing form cylinder 1 as described above in the paint application and all other steps of the imaging. The direction of rotation of the plate cylinder 1 is indicated by a direction of rotation arrow. In FIG. 4 the paint film 3 passing under the irradiation device 11 is subdivided into a leading region shown hatched and a non-hatched trailing region, the subdivision extending below the irradiation device 11. The shaded area is already hardened, while the unshaded area represents the still uncured paint 3. The curing and imagewise irradiation of the paint 3 correspond to the first embodiment.

The modified printing form consists of a flexible support plate 2 made of steel or optionally of aluminum, on which a thin, color-friendly surface layer 4 is applied, for example galvanically. The surface layer 4 forms the hydrophobic surface 4 a of the modified printing plate 2, 4. The surface layer 4 may consist, for example, of nickel, copper or an alloy of these metals. On this printing form 2, 4 is as in FIG. 3 shown directly sprayed the paint 3. Alternatively, for the paint job but also the paint applicator 8 to 10 may be provided, which is also given preference over the direct spraying.

Reference numerals:

1

Plate cylinder

2

Printing form, carrier, carrier base structure, carrier plate

2a

Hydrophobic sites

3

Coating material, paint

3a

Hydrophilic sites

4

surface layer

4a

Hydrophobic sites

5

inking

6

dampening

7

Pan roll

8th

Dampening roller, distributor roller

9

Dampening roller, dampener roller

10

spraying

10 '

spraying

11

first irradiation device

12

second irradiation device

Claims (28)

1. A method for forming an image on a printing form in an offset printing machine, in particular a newspaper printing machine, wherein:

   a) free-flowing, curable coating material (3) is applied to a hydrophobic surface (2a; 4a) of the printing form (2; 2, 4) in the printing machine;

   b) the coating material (3) is hardened by means of a first irradiation or drying, wherein the hardened coating material (3) exhibits a hydrophilic surface (3a);

   c) and the hardened coating material (3) is removed in accordance with the image by means of a second irradiation, whereby the hydrophobic surface (2a; 4a) of the printing form (2; 2, 4) is exposed in accordance with the image.
2. The method according to the preceding claim, characterised in that the coating material (3) is a varnish.
3. The method according to any one of the preceding claims, characterised in that an aqueous coating material is used as the coating material (3).
4. The method according to any one of the preceding claims, characterised in that a coating material which can be cured by means of UV irradiation or IR irradiation or drying is used as the coating material (3).
5. The method according to any one of the preceding claims, characterised in that a coating material (3) is used which contains amino groups, carboxyl groups, silanes or other Group IV compounds or combinations of two or more of said compounds.
6. The method according to any one of the preceding claims, characterised in that the first irradiation is a UV or IR irradiation.
7. The method according to any one of the preceding claims, characterised in that the coating material (3) is thermally decomposed by means of the second irradiation.
8. The method according to any one of the preceding claims, characterised in that the second irradiation is a laser irradiation.
9. The method according to any one of the preceding three claims, characterised in that both the first irradiation and the second irradiation are performed by the same irradiating means, and the irradiating means is defocused or reduced in terms of its power rating or exposure time for the first irradiation or the printing form is moved relative to the irradiating means at a greater speed during the first irradiation as compared to the second irradiation.
10. The method according to any one of the preceding claims, characterised in that the coating material is applied with a layer thickness which is smaller than a maximum length or maximum width of a printable image pixel which is printed in a printing operation using the printing form (2; 2, 4), wherein the layer thickness is preferably 10 µm at most.
11. The method according to any one of the preceding claims, characterised in that the coating material (3) is hardened on the printing form (2; 2, 4) by air drying.
12. The method according to any one of the preceding claims, characterised in that the coating material (3) contains particles in a fine distribution which absorb a substantial portion of the radiation energy of the second irradiation.
13. The method according to any one of the preceding claims, characterised in that the coating material (3) is applied to, preferably sprayed onto, a roller (8) and is applied to the printing form (2; 2, 4) by the same roller or preferably by another roller (9).
14. The method according to the preceding claim, characterised in that the coating material (3) is conveyed onto the printing form (2; 2, 4) via a distributor roller (8) which can be moved axially back and forth, and is preferably applied to the distributor roller (8).
15. The method according to any one of the preceding claims, characterised in that the coating material (3) is applied to the printing form (2; 2, 4) by at least one component (8, 9) of an applying means (6), preferably at least one roller (8, 9) of the applying means (6), which also applies moisture to the printing form (2; 2, 4) in a printing operation.
16. The method according to any one of the preceding claims, characterised in that an irradiating means (12) which performs the second irradiation when forming an image is also used to remove the coating material (3) which covers the printing form (2; 2, 4) in accordance with the image, when the printing form (2; 2, 4) is cleaned.
17. The method according to the preceding claim, characterised in that during cleaning, the irradiating means (12) irradiates the printing form (2; 2, 4) over its entire surface or irradiates it with inverse image information and an enlarged peripheral region as compared to the second irradiation.
18. The method according to any one of the preceding claims, characterised in that before the coating material (3) is applied, the printing form (2; 2, 4) is pre-treated, wherein it is preferably irradiated with UV light or an adhesion promoter is applied, in order to increase the adhesion of the coating material (3).
19. A device for forming an image on a printing form in an offset printing machine, said device comprising:

    a) an applying means (8, 9, 10; 10') for applying a free-flowing coating material (3) to the printing form (2; 2, 4);

    b) a first irradiating means (11) for curing the applied coating material (3);

    c) wherein at least one radiation parameter of the first irradiating means is adjustable, preferably its focusing or radiation conduction, in order to be able to use the first irradiating means to remove the hardened coating material (3) in accordance with the image, once the radiation parameter or parameters has/have been adjusted;

    d) or wherein the device comprises another, second irradiating means (12) for removing the hardened coating material (3) in accordance with the image.
20. The device according to the preceding claim, characterised in that the device also comprises dampening rollers (7, 8, 9) for applying moisture to the printing form (2; 2, 4), and the applying means (8, 9, 10) applies the coating material (3) to one of the dampening rollers (7, 8, 9) and preferably sprays the coating material (3) onto one of the dampening rollers (7, 8, 9) when forming an image.
21. The device according to any one of the preceding claims 19 and 20, characterised in that the second irradiating means (12) comprises emitters for generating radiation which thermally decomposes the hardened coating material (3), and the emitters can preferably also be used to delete the print image (2a, 3a; 3a, 4a) generated by forming an image on the printing form (2; 2, 4).
22. The device according to any one of the preceding claims 19 and 21, characterised in that the printing machine comprises a plurality of printing form cylinders (1), each comprising at least one printing form (2; 2, 4), and comprises an assigned device according to any one of the preceding claims for each printing form cylinder (1), and in that the plurality of first irradiating means (11) are provided with a common radiation source and with waveguides proceeding from it to the first irradiating means (11), via which radiation energy can be guided from the common radiation source to the first irradiating means (11).
23. An offset printing form, comprising:

    a) a carrier (2; 2, 4) which exhibits a hydrophobic surface (2a; 4a);

    b) and a hardened coating material (3), preferably a varnish, which covers the hydrophobic surface (2a; 4a) evenly or in accordance with an image and forms a hydrophilic free surface (3a) of the printing form (2, 3; 2, 3, 4), characterised in that the carrier (2, 4) comprises a carrier structure (2) which is coated on one surface with a surface layer (4) which forms the hydrophobic areas (4a), wherein the surface layer (4) contains copper or a copper-based alloy at least as a main constituent.
24. The offset printing form according to the preceding claim, characterised in that the printing form (2; 2, 4) exhibits a free surface comprising hydrophilic and hydrophobic areas (2a, 3a; 3a, 4a) in accordance with a print image to be transferred, and in that the carrier (2; 2, 4) forms the hydrophobic areas (2a; 4a) and the coating material (3a) forms the hydrophilic areas (3a).
25. The offset printing form according to any one of the preceding claims 23 and 24, characterised in that the coating material (3) contains radiation-absorbing particles, preferably dark-coloured pigments, in a fine distribution.
26. The offset printing form according to any one of the preceding claims 23 to 25, characterised in that at least a predominant portion of the mass and volume of the carrier (2; 2, 4) consists of steel or aluminium.
27. The offset printing form according to any one of the preceding claims 23 to 26, characterised in that a surface of the carrier (2; 2, 4) which forms the hydrophobic areas (2a; 4a) is dark, preferably black.
28. The offset printing form according to any one of the preceding claims 23 to 27, characterised in that the printing form (2; 2, 4) is a printing plate which is or can be fastened on a printing form cylinder (1).

Images