EP1478512B1 - Method and device for printing wherein a hydrophilic layer is produced and structured - Google Patents

Abstract

In a method and device to generate a print image on a carrier material, a separate hydrophilic layer is applied onto a surface of a print carrier. By a structuring of the hydrophilic layer, hydrophilic regions and hydrophobic regions are created corresponding to a structure of a print image to be printed. At the surface of the print carrier, a fountain solution is applied whereby the fountain solution layer forms on the hydrophilic regions such that ink-attracting regions and ink-repelling regions are created corresponding to the print image structure. Ink that adheres to the ink-attracting regions and that is not substantially absorbed by the ink-repelling regions is applied on the surface. The applied ink is transferred onto the carrier material. Before a new structuring process, the surface of the print carrier is cleaned.

Description

The invention relates to a method and a device for producing a printed image on a carrier material, wherein on the surface of the print carrier ink-attracting and ink-repellent regions are generated according to the structure of the printed image to be printed, wherein the ink-repellent regions are provided with a layer of a ink-repellent medium in that ink is applied to the surface of the print substrate, which adheres to the ink-attracting areas and which is not accepted by the ink-repellent areas, and in which the color distributed on the surface is printed on the substrate.

In the prior art, waterless offset printing methods are known whose non-printing areas are fat-repellent and therefore do not accept printing ink. The printed areas, on the other hand, are fat-absorbing and pick up the greasy ink. According to the structure of the print image to be printed, ink-attracting and ink-repellent areas are distributed on the printing plate. The printing plate can be used for a variety of transfer printing operations. For each print image, a new plate must be created with ink-attracting and ink-repellent areas.

From the US-A-5,379,698 For example, a method is known which is called a direct imaging method in which a printing original is created in the printing device on a multilayer, silicone-coated film by selective burning away of the silicone top layer. The silicone-free areas are the ink-attracting areas that accept printing ink during the printing process. Every new print requires a new foil.

In the standard water-based offset process, hydrophobic and hydrophilic areas corresponding to the structure of the print image to be printed are formed on the surface of the print substrate. Before application of the paint, a thin film of moisture is first applied to the print substrate using applicator rollers or spraying devices, which wets the hydrophilic area of the print substrate. Subsequently, the inking roller transfers ink to the surface of the print substrate, which wets only those areas not covered by the moisture film. After dyeing, the color is finally transferred to the carrier material.

In the known offset printing process can be used as a print carrier multi-layer processless thermal printing plates, see. eg WO00 / 16988 , According to the structures of the print image to be printed on the surface of the print carrier, a hydrophobic layer is removed by partial burning away and exposing a hydrophilic layer. The hydrophilic layer can be wetted with an ink-repellent fountain solution. The hydrophobic areas are ink accepting and can absorb ink during the printing process. To create a new print image, a new printing plate must be used.

Furthermore, a method of the US-A-6,016,750 in which an ink-attracting substance is deposited from a film by means of a thermal transfer process, transferred to the hydrophilic surface of the print substrate and solidified in a fixing process. In the printing process, the remaining hydrophilic areas are wetted with ink-repellent dampening solution. Subsequently, the ink is applied to the surface of the print carrier, which, however, adheres only to the provided with the ink-attracting substance areas. The inked print image is then transferred to the substrate. For the creation of a new print image, a new film with the color attracting substance is necessary.

In the standard offset process or planographic printing process, the wetting of the printing plate with the ink-repelling dampening solution is achieved by targeted roughening and structuring of the plate surface. The resulting increase in surface area and porosity produces microcapillaries and leads to an increase in the effective surface energy and thus to a good wetting or spreading of the dampening solution. As further measures, wetting-promoting substances are added to the wetting agent during offset printing. These reduce the surface tension of the fountain solution, which also leads to improved wetting of the surface of the print carrier. In this context, the literature Teschner, H .: Offsettechnik, 5th edition, Fellbach, Fachschriften-Verlag 1983, pp. 193 - 202 and p. 350 , referenced.

From the US Patent No. 5,067,404 a printing method is known in which a fountain solution is applied to the surface of the printing format. The dampening solution is vaporized by selective application of radiant energy in image areas. The anhydrous areas later form the ink-bearing areas, which are led past a development unit and colored by means of a paint vapor. To produce the structured dampening solution, energy-intensive partial evaporation processes are required.

Furthermore, the patent documents WO 97/36746 and WO 98/32608 directed. In the in the WO 97/36746 described method, the dampening agent is generated by evaporation of a discrete volume of water, which condenses on the surface of the print carrier. According to the WO 98/32608 and the resulting US-A-6,295,928 a continuous ice film is applied and patterned. In both cases, locally high thermal energy must be used for structuring.

From the DE-A-10132204 (not prepublished) the same applicant, a CTP (computer-to-press) method is described, wherein on the same surface of the print carrier multiple structuring processes can be performed. The surface of a print substrate is coated with an ink-repellent or ink-receptive layer. In a structuring process, ink-attracting regions and ink-repelling regions are produced according to the structure of the printed image to be printed. The ink-attracting areas are then colored with paint. Before a new patterning process, the surface of the print substrate is cleaned and coated again with an ink-repellent or ink-receptive layer. The layer used is a fountain solution layer or an ice layer.

From the EP-A-0 963 839 a method and apparatus according to the preamble of the independent claims is known. The document proposes to manufacture the surface of the printing form from such a material (eg TiO ₂ ) whose wetting properties are reversibly changeable between a state with a very small contact angle and a state with a relatively large contact angle. By the action of light of a certain wavelength, one of the two states can be adjusted, whereby a picture structuring takes place in which ink-attracting areas and ink-repelling areas arise in accordance with the structuring carried out. With the help of a cleaning device, the surface of the printing plate can be brought back into an initial state.

EP 0 769 372 A1 relates to a process for lithographic printing. To produce hydrophilic and oleophilic areas corresponding to a print image to be printed, a zirconium ceramic printing plate is exposed with the aid of light, whereby different ink-attracting and ink-repelling areas are formed. With the help of a thermally activated oxidation, the image areas can be deleted again. The characterizing features of the independent claims of the present invention are not addressed in this document.

EP 0 911 155 A1 relates to a printing process in which color-attracting and ink-repelling regions are produced by means of a photoparalytic reaction. By heating the surface of the printing plate, the image areas are deleted and the surface of the printing plate can be restructured with a new image. Again, this document does not disclose the characterizing features of the independent claims of the present invention.

It is an object of the invention to provide a printing method and a printing device, which is or simply constructed for digital printing with changing print images on the same print carrier and allows high print quality.

This object is achieved for a method by the features of claim 1.

According to the invention, a hydrophilic layer in a layer thickness of less than 0.1 μm is produced on the surface of a print carrier that can be used for printing. Before or after the application of a fountain solution layer, the hydrophilic layer is structured in a patterning process, so that hydrophilic and hydrophobic areas accordingly the structure of the printed image to be printed are generated. By applying the dampening solution layer, a dampening solution film adheres only to the hydrophilic areas and color-attracting and ink-repelling areas arise in accordance with the structuring carried out. After transfer printing and cleaning, the same surface of the print substrate can be restructured and optionally provided with a modified print image.

The invention reduces the complexity of structuring. The energy required to structure a hydrophilic layer is reduced compared to the structuring of a fountain solution layer. Accordingly, the hardware required is reduced.

According to a further aspect of the invention, a device is provided by means of which the said method can be realized. In the dependent claims for method and device advantageous embodiments are given.

It should be noted that in the further description often the term color repellent or ink-receptive layer occurs. This layer is adapted to the applied color. For example, in the case of a water-containing fountain solution layer and an oil-containing paint, the fountain solution layer is color-repellent. However, if the paint contains water, this fountain solution layer is color-attracting. In practice, mainly oily inks are used, so that a water-containing fountain solution layer is ink repellent.

Figur 1

eine Prinzipdarstellung einer Druck- einrichtung, bei der eine Ten- sidschicht aufgebracht wird,

Figur 2

schematisch einen Querschnitt durch den Druckträger vor und nach der Strukturierung durch einen Laser- strahl,

Figur 3

ein Ausführungsbeispiel, bei dem eine hydrophilisierte Schicht strukturiert wird,

Figur 4

ein Ausführungsbeispiel, bei dem eine aufgetragene hydrophile Schicht struk- turiert wird,

Figur 5

einen schematischen Querschnitt durch den Druckträger vor und nach der Strukturierung der hydrophilen Schicht, und

Figur 6

eine Druckeinrichtung mit einer Rege- lung der Feuchtmittel-Schichtstärke.

Embodiments of the invention are described below with reference to the FIGS. 4 and 5 explained. The further figures show components for the use of the invention. Show:

FIG. 1

a schematic representation of a printing device in which a Ten- sidschicht is applied,

FIG. 2

FIG. 2 schematically shows a cross section through the print carrier before and after structuring by means of a laser beam, FIG.

FIG. 3

an embodiment in which a hydrophilized layer is structured,

FIG. 4

an embodiment in which a coated hydrophilic layer is structured,

FIG. 5

a schematic cross section through the print carrier before and after structuring of the hydrophilic layer, and

FIG. 6

a printing device with a control of dampening solution layer thickness.

In FIG. 1 is a schematic representation of a printing device shown, which is constructed similar to that in the US Patent No. 5,067,404 the same applicant is described. A print carrier 10, in the present case an endless belt, is passed through a pretreatment device 12, which contains a scoop roller 14 and an applicator roller 16. The scoop roller 14 immersed in a liquid contained in a container 13, which contains a wetting-promoting substance. On the surface of the print carrier 10 is applied over the applicator roll 16, this substance containing surfactant, in a molecular layer thickness less than 0.1 microns. The surface of the print carrier 10 is then guided in the direction of arrow P1 to a dampening unit 18, which applies a ink-repelling or ink-attracting dampening solution, for example water, from a dampening solution reservoir 24 to the surface of the print substrate 10 via a scoop roller 20 and an applicator roller 22. In principle, dampening solutions other than water can also be used. The order of the fountain solution layer can also be done by other methods, for example by steaming or spraying. The pressure-active surface of the print carrier 10 is completely provided with this fountain solution layer. The fountain solution layer typically has a layer thickness of less than 1 μm.

The generally ink-repellent fountain solution layer is then patterned by an imaging device 26. In the present case, laser radiation 28 is used for this purpose. In this patterning process, ink-attracting regions and ink-repelling regions are formed according to the structure of the printed image to be printed. Subsequently, the structured fountain solution layer passes to an inking unit 30, which by means of the rollers 32, 34, 36 transfers color from a reservoir 38 to the surface of the print carrier 10. The oil-containing color deposits on areas without water-containing dampening solution. It should be noted that the ink can also be transferred to the surface of the print carrier 10 by spraying, knife coating or condensing.

Upon further transport of the print carrier 10, a transfer to a carrier material 40, generally a paper web. For transfer printing, the carrier material 40 is passed between two rollers 42, 44. During the transfer printing process, a blanket cylinder (not shown) and further intermediate cylinders can be connected between the roller 42 and the print carrier 10, which effects a color split, as is known per se from the field of offset printing methods.

During further transport of the print carrier 10, the surface of the print carrier 10 is cleaned in a cleaning station 46. In this case, the color residues and also the residues of the surfactant layer are removed. The cleaning station 46 includes a brush 48 and a wiper lip 50, which are brought into contact with the surface of the print carrier 10. Furthermore, the cleaning can be assisted by using ultrasound, high pressure liquid and / or steam. The cleaning can also be done using cleaning fluids and / or solvents.

Subsequently, a new application of the wetting-promoting substance, for example a surfactant application, and a fountain solution application as well as a renewed structuring can take place. In this way, with each revolution of the print carrier 10, a new print image can be printed. However, it is also possible to print the same image multiple times. The cleaning device 46, the device 12 and the device 26 are then switched inactive. The still present in color residues print image is then through the inking unit 30 dyed and reprinted. In this mode, therefore, a plurality of identical printed images can be printed.

FIG. 2 schematically shows a cross section through the print carrier 10 before and after structuring using the laser beam 28. According to the invention, the wetting is promoted by the application of a wetting-promoting substance on the print carrier surface 10. This happens within the printing cycle before the application of the ink-repellent dampening solution. Due to its physical and chemical properties, the wetting-promoting substance can be applied to the surface as an extremely thin layer of a few molecule layers, preferably smaller than 0.1 .mu.m. This layer is sufficient to favor on its free surface, the wetting with the ink-repellent fountain solution, so that this can also be applied as a very thin layer 54, preferably less than 1 micron. The continuing printing process is not affected by the small amount of wetting-promoting substance, in this case a surfactant layer 52. It can be easily removed by the cleaning process integrated in the printing cycle.

Advantages arise above all in the area of digital planographic printing or offset printing, ie a planographic printing method or offset printing method with changing printing information from printing cycle to printing cycle. By the wetting-promoting layer 52 can be dispensed with the otherwise roughened, porous printing plate surface. Instead, a smooth surface of the print carrier 10 is possible to clean with significantly less effort. A fast and stable cleaning process is indispensable for such a digital lithographic printing process or offset printing process and a decisive factor for its effectiveness. Accordingly, the surface of the printing medium 10 has a roughness which is smaller than that Roughness used in the standard offset printing process. Typically, the mean roughness R _{z is} less than 10 microns, preferably less than 5 microns. Expressed as the average roughness value R _a , the roughness value lies in the range of less than 2 μm, preferably less than 1 μm.

A change in the molecular or atomic structure of the material of the print carrier and a permanent and firmly anchored to the surface of the print carrier wetting-promoting layer is not necessary. The additionally applied wetting-promoting substance proposed here, for example the surfactant layer 52, develops its wetting-promoting action even at very low levels. Accordingly, its influence on the characteristics of the print substrate 10 is negligible in many respects. Another advantage arises from the now possible renouncement of the wetting-promoting additives usually present in offset printing in dampening solutions.

According to the FIG. 2 For example, the dampening agent layer 54 and the surfactant layer 52 are removed by the laser beam 28 in accordance with the required image structure. These areas are then colored by the inking unit 30 with color. Due to the very smooth surface of the print carrier 10, the cleaning is facilitated, the surfactant layer 52 is completely removed again. Furthermore, the wear of the surface of the print carrier 10 is reduced.

The FIGS. 3, 4 and 5 show a further embodiment of the invention. In FIG. 3 takes place in contrast to the embodiment according to FIG. 1 prior to the application of the ink-repellent or ink-receptive layer on the usable surface of the print substrate, a structuring of a hydrophilic layer with a layer thickness less than 0.1 microns. In the present example, a steam device 60 is used, which is the Surface of the print carrier 10 subjected to hot steam. The print carrier 10 is provided on its surface with a SiO 2 coating. After the steam treatment, the print carrier 10 is dried by a suction device 62. The hot water vapor generates a hydrophilic molecular structure on the outer surface, eg SiOH.

After the subsequent structuring by the structuring device 26 by means of laser radiation 28, hydrophilic regions and hydrophobic regions arise in accordance with the structure of the printed image to be printed. By the downstream dampening unit 18, the entire usable surface of the print carrier 10 is brought into contact with a dampening agent layer, wherein the fountain solution only attaches to the hydrophilic areas, so that ink-attracting areas and ink-repellent areas arise in accordance with the structuring. Subsequently, a paint is applied by the inking unit 30, wherein the oil-containing color attaches to areas without aqueous dampening solution. Subsequently, the transfer printing of the printed image onto the carrier material 40 takes place.

After the further transport of the print carrier 10, its surface is cleaned in a cleaning station 46. It will remove the paint residues as well as the remains of a possible wetting-promoting substance. Subsequently, a new structuring process can take place.

In the present example according to FIG. 3 the hydrophilic layer is patterned on the surface of the print carrier 10 according to the printed image. The hydrophilic layer is extremely thin and only a few nanometers, typically less than 4 nm. It can therefore be patterned with very little energy expenditure during a printing cycle, whereby the hydrophilic molecular layer disappears. Then the fountain solution is applied, which produces a moisture film only on the non-hydrophilic areas. Dyeing and transfer printing takes place according to the described known principles of planographic printing or offset printing. After cleaning, in which not only the color residues but also the hydrophilic layer can be removed, but not necessarily removed, the printing cycle can begin again. The hydrophilic layer is regenerated or reapplied, and then the hydrophilic layer is patterned according to the new image data.

For example FIG. 3 the hydrophilic layer is formed by activating the surface of the print substrate and by suitably changing the outer molecular surface structure. For example, this can be made possible by the use of chemical activators, reactive gases and / or a suitable energy supply. In addition to the use of water vapor as in the example below FIG. 3 can also be formed by the action of hot water and by leaching, such as NaOH, a hydrophilic SiOH structure on the surface. The print carrier is to be provided for this purpose with a SiO2 coating. It is also possible for the print carrier to pass through an activator bath to produce hydrophilization of the surface. It is also possible to order an activator via a nozzle system. Another possibility is to produce the hydrophilic layer by flaming the surface of the print carrier 10. In this case too, wetting-promoting surface structures are produced in a layer thickness of less than 0.1 μm.

An advantageous arrangement is the combination of hydrophilization with cleaning. Thus, for example, both the cleaning and the hydrophilizing effect of a hot water jet or a hot steam jet can be used. Purification and production of hydrophilic Layer are then performed in a single process step.

In FIG. 4 another variant is shown. In this case, a wetting-promoting substance is applied to the surface of the print carrier to produce the hydrophilic layer. For example, in the embodiment of FIG. 1 described pretreatment device 12 can be used. With the help of the scoop roller 14 and the applicator roller 16, a liquid can be applied from the container 13, which contains a wetting-promoting substance, for example a surfactant, in a layer thickness less than 0.1 microns are applied. As a further wetting-promoting substance are also alcohols into consideration. The job can alternatively be done by doctoring, spraying and vapor deposition.

Due to the very thin hydrophilic layer thinner than 0.1 microns, the partial removal of this hydrophilic layer can be done by local thermal energy supply. Due to the small layer thickness, the energy consumption can be low. In addition to the in the FIGS. 3 and 4 used laser radiation 28 and laser diodes, LEDs, LED combs or heating elements can be used.

Also in the example of the FIGS. 3 and 4 can be done per circulation of the print carrier 10, a re-structuring, whereby each circulation a new print image is printed. However, it is also possible, as in the example below FIG. 1 to print the same print image multiple times, wherein the existing print image is colored again by the inking unit 30 and reprinted. The devices for the restructuring are then switched inactive.

FIG. 5 shows a cross section through the print carrier 10 before and after patterning by the laser beam 28 for the example FIG. 4 , The surface of the print carrier 10 is very smooth, as is the case with the previous examples. The thin surfactant layer 52 is patterned by the laser beam 28, ie, hydrophilic regions 68 and hydrophobic regions 64 are produced. By the dampening unit 18, a thin water-containing wet film is applied only to the hydrophilic areas. The regions 64 are then colored by the inking unit 30 with an oily color which is repelled by the fountain solution 54 in the region of the hydrophilic regions 68. FIG. 6 shows a further embodiment. In offset printing and especially in the digital method, for example after the US Patent No. 5,067,404 and US-A-6,295,928 same applicant, the constant and well-defined thickness of the dampening solution layer on the surface of the print carrier plays a crucial role for the stability and efficiency of the printing process. According to the example FIG. 6 a printing device is described which allows and monitors a defined, controllable and controllable very thin application of dampening solution. The standardized offset printing process usually uses a dampening system consisting of a number of rotating rollers for the application of the dampening solution. Together with a roughened or porous well-water pressure plate results in a sufficiently stable for standard offset printing water film. The amount of dampening solution and the thickness of the fountain solution layer can be adjusted for example by the delivery of certain rollers to each other or the speed of the scoop roller. Here, the storage effect of the dampening unit and also the pressure plate leads to a strong delaying response to adjustment measures. For the production of a sufficiently stable water film, however, the roughened, strongly water-storing printing plates are essential. It is also known from the prior art, by cooling the printing plate and the consequent condensation the humidity on the printing plate to produce a very thin film of water. However, the thickness of the water film is highly dependent on the ambient conditions, such as humidity and temperature, and is to be kept constant over a long period of time.

According to the embodiment FIG. 6 a structure is used which is similar to that in the aforementioned DE-A-101 32 204 described structure which realizes a CTP (Computer-To-Press) method.

In the FIG. 6 shown printing device allows to produce 10 different printed images on the same surface of the cylindrical print carrier. The printing device includes the inking unit 30, with a plurality of rollers, is transferred by the oily ink from the reservoir 38 to the surface of the print carrier 10. The inked surface of the print carrier 10 transmits the ink to a blanket cylinder 90. From there, the ink reaches the paper web 40, which is pressed by the impression cylinder 42 against the blanket cylinder 90.

The dampening unit 18 transfers dampening solution, eg water, from the dampening solution reservoir 24 onto the surface of the print carrier 10 via three rollers. Before application of the dampening solution layer, the surface of the print carrier 10 can be coated using wetting agents and / or surfactants or by corona and / or Plasma treatment are brought into a more hydrophilic state, as has already been described above. In the course of the dampening solution layer is selectively removed by supplying energy by means of a laser beam 28 and there is the desired image structure. As mentioned, the inking by the inking unit 30 then takes place at the ink-attracting areas of the structuring. After patterning, the color may be solidified using a fuser 92.

Also in this example two modes are possible. In a first operating mode, a large number of printing processes take place before the surface is restructured. The print image located on the print carrier 10 is inked and reprinted once per print, ie there is a multiple inking of the printed image. In a second mode, a new print image is applied to the surface of the print carrier. Before that, the previous structured ink-repellent layer and the paint residues to be removed, for which the cleaning station 46 is provided. This cleaning station can be pivoted to the print carrier 10 according to the arrow P2 and swung away from it again. Further details of the structure of the printing device after FIG. 6 are in the mentioned DE-A-101 32 204 described.

As seen in the transport direction P1, after the dampening unit 18 there is arranged an energy source 94, which emits heat energy to the dampening solution film on the surface of the print carrier 10. This energy reduces the thickness of the fountain solution layer. As seen in the transport direction, the energy source is followed by a layer thickness measuring device 96. This layer thickness measuring device 96 determines the actual thickness of the dampening solution film and outputs an electrical signal corresponding to the thickness to a controller 98. The controller 98 compares the measured actual thickness with a predetermined target thickness. With a desired-actual value deviation, the energy source 94 is driven so that the thickness of the fountain solution layer is reduced to the desired target thickness.

The layer thickness measuring device 96 can operate without contact, for example, according to the triangulation method, the transmission method or the capacitive method. As energy source 94 comes one or more IR lamps, radiant heaters, Laser systems, laser diodes or heating elements into consideration.

The interaction of the energy source 94, the Schichtdikkenmeßgeräts 96 and the controller 98 may be such that only a monitoring function is performed. If the layer thickness exceeds or falls below a predetermined desired value, then a corresponding warning signal is emitted and then the energy supply for the energy source 94 is readjusted. However, the energy source 94, the Schichtdickenmeßgerät 96 and the controller 98 can also be combined to form a control loop in which the energy source 94 is driven so that at a control deviation between the actual value and target value of the layer thickness minimizes this deviation and preferably to zero is regulated.

The power source 94 may be driven by the controller using analog voltage regulation or digitally by pulse modulation, as indicated by the signal sequence 100.

According to the example FIG. 6 In a first process step over the usable width of the print carrier 10, a thick-constant dampening solution film is produced, which is reduced in its layer thickness defined in a subsequent second step. The result is a uniform fountain solution layer with a defined and very small thickness. The subsequent structuring can thus be carried out with minimal energy and with consistent results. Overall, the print quality is thus increased. The advantages of the printing device shown are that a direct reaction to a change in the layer thickness of the dampening solution layer can take place, that a known and defined thickness of the fountain solution layer can be adjusted and that extremely thin fountain solution layers can be produced. Furthermore, can the required structuring energy is minimized, in particular for digital printing processes.

Numerous other variations of the above-described embodiments are possible. For example, both an endless belt and a cylinder can be used as the print carrier. The transfer to the substrate can be done directly or with the interposition of a blanket cylinder or other intermediate cylinders for a color separation. The layer thickness control according to the example according to FIG. 6 can also be used for the other examples. Similarly, for the examples according to the FIGS. 1 to 5 a fixation of the applied color by means of a fixing device. Furthermore, the cleaning station 46, the dampening unit 18 and the image forming device can be switched inactive and active, for example by pivoting.

LIST OF REFERENCE NUMBERS

10

print carrier

12

Vorbehandlungsvörrichtung

13

container

14

scoop roller

16

applicator roll

18

dampening

20

scoop roller

22

applicator roll

24

Dampening solution reservoir

26

An image forming apparatus

28

laser beam

30

inking

32, 34, 36

roll

38

reservoir

40

support material

42, 44

roll

46

cleaning station

48

brush

50

wiper lip

52

surfactant

54

Fountain solution layer

60

steam device

62

suction

64

hydrophobic areas

68

hydrophilic areas

90

Blanket cylinder

92

fixing

94

energy

96

Coating Thickness

98

control

100

signal sequence

P1

transport direction

P2

arrow

Claims (9)

1. A method for generating a print image on a carrier material (40), in which

   - a hydrophilic layer (52) with a layer thickness of less than 0.1 µm is applied on the surface of a print carrier (10) usable for printing,

   - on the surface of the print carrier (10) a fountain solution layer (54) is applied, wherein a fountain solution film (54) forms only on the hydrophilic regions (68),

   - in a structuring process, the hydrophilic layer (52) prior to the application of the fountain solution layer (54) or the hydrophilic layer (52) together with the fountain solution layer (54) after application of the fountain solution layer (54) are structured, as a result whereof hydrophilic regions (68) and hydrophobic regions (64) are generated corresponding to the structure of the print image to be printed so that ink-attracting regions and ink-repelling regions are created corresponding to the effected structuring,

   - ink that adheres to the ink-attracting regions (64) and that is not absorbed by the ink-repelling regions (68) is applied on the surface of the fountain solution layer,

   - the applied ink is transferred onto the carrier material (40) in the further course,

   - prior to a new structuring process, the surface of the print carrier (10) is cleaned and a hydrophilic layer (52) is again applied, a surfactant layer (52) being applied on the surface of the print carrier (10) as a hydrophilic layer (52).
2. The method according to claim 1, in which the application of the hydrophilic layer (52) takes place via rolling, scraping or spraying.
3. The method according to one of the preceding claims, in which the cleaning and the generation of the hydrophilic layer takes place in one single process step.
4. The method according to claim 3, in which hot water and/or water vapor is used for cleaning.
5. The method according to one of the preceding claims, in which radiation is used for structuring.
6. The method according to claim 5, in which the radiation of a laser system, a laser, laser diodes, LEDs or a laser diode array is used.
7. A device for generating a print image on a carrier material (40), in which means are provided by which

   - a hydrophilic layer (52) with a layer thickness of less than 0.1 µm is applied on the surface of the print carrier (10) usable for printing,

   - on the surface of the hydrophilic layer (52) a fountain solution layer (54) is applied,

   - in a structuring process, the hydrophilic layer (52) or the hydrophilic layer (52) and the fountain solution layer (54) are structured to generate hydrophilic regions (68) and hydrophobic regions (64) corresponding to the structure of the print image to be printed so that ink-attracting regions and ink-repelling regions are created corresponding to the effected structuring,

   - ink that adheres to the ink-attracting regions (64) and that is not absorbed by the ink-repelling regions (68) is applied on the surface of the fountain solution film (54),

   - the applied ink is transferred onto the carrier material (40) in the further course, and by which,

   - prior to a new structuring process, the surface of the print carrier (10) is cleaned and a hydrophilic layer (52) is again applied, the hydrophilic layer (52) being a surfactant layer (52).
8. The device according to claim 7, in which the surface of the print carrier (10) is a generated cylinder surface or a continuous band.
9. The device according to claim 7, in which the surfactant layer (52) has a thickness of less than 100 nm.

Images