EP2527148B1 - Printing method and offset printer - Google Patents

Description

The present invention relates to a printing method and suitable for performing the printing process offset printing units.

Coloring units for the planographic offset printing are designed either as zone-free short inking units or as inking units with zonal inking. The zoneless short inking units have an anilox roller. The inking units with zonal ink dosing have a paint box, which has a metering device with ink zones. The color zones arranged side by side over the printing width enable a different ink dosage from ink zone to ink zone. The ink zones can be formed by zone screws.

In web presses, the inking units with the zonal metering are designed as film inking units, in which a ink fountain roller together with a film roller has a film gap of, for example, 10 cm. B. forms 0.05 mm. Due to the film gap, the film roller does not touch the ink fountain roller. The film roll rotates at a faster rate than the ink fountain roller and mills the top layer of a paint film on the ink fountain roller to pick up ink from the ink fountain roller.

In sheetfed presses, the inking units with the zonal metering are designed as lifting inking units. In the case of the squeegee inking units, a squeegee roller takes over the ink from the ink fountain roller. The squeegee roll is not permanently, but discontinuously on the ink fountain roller. The squeegee roller periodically contacts the ink fountain roller to take over the ink from it.

There have also been developed zonenlose short inking units (inking units without dispensers with ink zones), which have no Aniloxwalze. In DE 102006061393 A1 is described a zonenloses short inking unit, in which a roller together with a metering roller forms a metering gap, which is about 20 microns. The said roller rotates at the same peripheral speed as the printing form cylinder. For the said roller and the printing form cylinder are Cooling provided. The described short inking unit is intended for the use of high-viscosity inks.

Previously known offset printing units basically have a certain property, regardless of whether the offset printing unit is part of a web-fed printing press or a sheet-fed press, whether the offset printing unit has an inking unit with ink zones or an inking unit without ink zones and whether the offset printing unit a Film inking unit or a lift inking unit has. The specific feature is that the ink at their z. B. with the Aniloxwalze or with the zonal metering dosage taking place has a higher viscosity than in the applied to the printing form cylinder state of the ink. Offset printing inks are thixotropic and therefore the viscosity of the offset printing inks is reduced by their rheological stress in the nip of the inking unit on the way to metering the printing forme cylinder.

Furthermore, from the DE10119735 a printing method is known in which a printing ink is zonally metered in a printing machine at a first viscosity by means of a metering device and at a second viscosity, which is greater than the first viscosity, is transmitted by means of a printing forme cylinder.

The invention has for its object to provide a further printing method and to provide suitable offset printing works to its implementation.

This object is achieved by a printing method having the features of claim 1, by an offset printing unit having the features of claim 6, by an offset printing unit having the features of claim 7 and by an offset printing unit having the features of claim 8.

In the printing method according to the invention, a printing ink is zonal in a printing machine at a first viscosity by means of a metering device and the ink is transferred at a second viscosity, which is at least 10 times greater than the first viscosity, by means of a printing forme cylinder, wherein the first viscosity less than 1 pascal second and the second viscosity is greater than 10 pascal seconds.

The printing method according to the invention differs fundamentally from the printing methods of the prior art, in which the second viscosity is less than the first viscosity. In the printing method according to the invention, the ink has a lower viscosity at its zonal dosage than in its state on the Printing form cylinder as defined in claim 1. Due to the low, first viscosity, the hydrodynamic loading of the dosing device is reduced by the color and consequently the precision of the zonal dosing is improved. The larger second viscosity achieves a particularly sharp separation of printing areas and non-printing areas on the printing form cylinder and prevents the non-printing areas from accepting color (toning).

The printing method according to the invention can be a direct printing method according to a first variant and an indirect printing method according to a second variant. In the direct printing process, the ink is transferred from the plate cylinder directly to the substrate. In the indirect printing method, the ink is transferred from the printing form cylinder to a transfer cylinder (blanket cylinder), from which the ink is applied to the substrate, for. B. a printing substrate or preferably a printing material, is transmitted.

In the printing method of the present invention, the second viscosity is at least 10 times greater than the first viscosity, and the first viscosity is less than 1 pascal second and the second viscosity is greater than 10 pascal seconds.

According to further developments, the first viscosity can be adjusted by reducing the viscosity of the printing ink in the printing machine and / or the second viscosity of the printing ink can be adjusted by increasing the viscosity of the printing ink in the printing press.

The reduction of the viscosity can be effected, for example, by a heating of the printing ink and the increase in the viscosity can be effected, for example, by a cooling of the printing ink.

The offset printing unit according to the invention comprises an ink fountain with a metering device with ink zones, an ink fountain roller, an inking roller, which is permanently applied to the ink fountain roller, and a printing form cylinder, wherein the Ink fountain roller and the printing form cylinder are driven such that both have the same peripheral speed. In the case of the offset printing unit according to the invention, according to various variants, the ink fountain roller can be equipped with a heating device and / or the printing plate cylinder can be equipped with a cooling device. By means of the ink fountain roller heating device, the printing ink can be heated to reduce the viscosity of the printing ink, so that the ink has a reduced viscosity in its zonal color metering by means of the metering device. By means of the cooling device of the printing form cylinder, the printing ink can be cooled in order to increase the viscosity of the printing ink, so that the printing ink on the printing form cylinder has an increased viscosity.

By the invention and its developments, it is possible to control the viscosity of the color specifically. The control takes place so that in the area of the color metering the color viscosity is smaller than one pascal second. The control of the ink viscosity continues to be such that in the field of image formation, on the printing form cylinder, the ink viscosity is greater than 10 pascal seconds. The difference in viscosity between the range of color metering and the area of image formation and, more specifically, the increase in viscosity from the range of color metering to the area of image forming can be achieved in various ways. For example, the low viscosity in the range of color metering can be given by a low viscosity of the printing ink at room temperature without its temperature control. Alternatively, the low viscosity in the area of the ink metering can be achieved by a targeted reduction of the ink viscosity. The reduction can be done by heating the ink. The reduction can also be achieved by increasing the inking speed and / or generating a relative movement resulting in heat and smoothing. In addition, for the purpose of reducing the ink viscosity, it is possible to add water in droplet form or to add fountain solution in droplet form. In addition, the action of ultrasound on the ink is possible to reduce the viscosity. Due to the reduced viscosity of the paint, the ink metering can be done at machine speed and is the use of a squeegee roller and the Use of a film roller is not required. In addition, the inking unit can be built as short as an anilox inking unit. In contrast to such an anilox inking unit, in the inking unit according to the invention, however, the color dosage can be changed zonally over the entire printing width. For color metering, a knife ink fountain is preferably used because of the high circumferential speed of the ink fountain roller. The inking zones of the knife paint box can be formed by zone screws, which bend through a metering knife of the knife paint box in the individual ink zones to different degrees. The zone screws can be driven manually or by motor.

In order that the ink viscosity is greater than 10 pascal seconds in the area of image formation (on the printing form cylinder), the ink viscosity can be increased in various ways. For example, to increase the ink viscosity, the ink can be cooled. To increase the viscosity, a carrier liquid of the printing ink can be evaporated therefrom. In addition, the ink may be or contain an electrorheological fluid and the viscosity may be increased by an electric field. In addition, vaporizing of components of the ink can be effected selectively to increase the ink viscosity.

In order to increase the viscosity of the ink from the ink fountain to the printing forme cylinder, it is also possible to use a paint which has a low-viscosity carrier liquid which evaporates on the printing-plate cylinder. In addition, paint components on the printing plate cylinder can be melted and crosslinked, resulting in an additional increase in viscosity. Similarly, the ink may contain an IR (infrared) absorber or NIR (near-infrared) absorber or contain UV (ultraviolet) photoinitiators, e.g. B. IR laser radiation or NIR laser radiation or UV radiation (generated by means of a UV lamp, UV LED or UV laser) absorb. As a result, a controlled increase in viscosity can be achieved. The increase in viscosity may be due to physical effects (especially evaporation or accelerated evaporation) or to chemical crosslinking. It may be necessary to evaporate or evaporate Aspirate paint components and provide a corresponding suction in the printing unit. In the case of chemical crosslinking, which can be effected by the UV radiation, the use of inertization may be expedient.

For zonal control of the viscosity, a zonally controllable light source or laser source can be used, which can preferably be controlled in wide zones, but optionally also in a print-image-accurate manner. In this case, the control can take place both in the direction of rotation of the printing form cylinder and transversely thereto.

The offset printing unit according to the invention can be a printing unit for wet offset printing. In wet offset printing, a certain amount of dampening solution must emulsify into the printing ink. As a result, a point closure is avoided, which would otherwise be very dense printing screens or dot screens, z. B. at 80% -grastern, would occur. In order to avoid this point closure despite the comparatively high viscosity of the printing ink on the printing forme cylinder in the present invention, the printing ink can have an increased water content or the printing ink can contain an additive which promotes emulsification with the dampening solution. Remedy could also be a more than three rollers existing inking, z. B. bring a maximum of four to six rollers existing inking unit, which conveys the emulsion formation in a sufficient manner. The inking can z. B. have only two inking rollers, which roll on the printing form cylinder in the printing operation. Such an inking unit would be more effective in terms of Emulisionsbildung compared with a conventional anilox inking unit and would be cheaper to produce compared with conventional squeegee and conventional film inking units due to the reduced number of rolls.

Another way the ink on the plate cylinder to impart a higher viscosity than in the ink fountain is the networking of color components, eg. B. by the fusion of latex particles, by the curing by means of UV radiation or by the precipitation of color components. For latex or synthetic resin dispersions on z. As styrene-butadiene or styrene-methacrylate base or dispersions based on other polymers which dispersions form the ink, the increase the viscosity can be achieved by various measures. So z. As the printing form cylinder are heated, resulting in aqueous dispersions on the one hand to an increase in the concentration of the particles and thus to a combination of the individual polymer particles and on the other when exceeding the minimum film formation temperature leads to the formation of a continuous color film, which is highly viscous. In other cases, the viscosity of the color dispersion can be greatly increased by contact with polyvalent or polyvalent cations. Here you would z. B. the surface of the plate cylinder, so the printing plate with multi-valent cations such. B. divalent calcium cations or divalent magnesium cations or trivalent aluminum cations z. B. in the form of aqueous solutions whose fluorides or sulfates or nitrates act. Upon contact with the ink, ionic clusters are formed, which significantly increase the viscosity of the ink. A viscosity increase by adding acids would also be conceivable. In the case of acrylate-based UV printing inks, the viscosity increase can also be achieved by curing the printing ink with UV radiation. Here, the intensity and the wavelength range of the UV radiation is chosen so that it comes only to a very weak cross-linking by formation of a few bonds on the surface of the paint. As a result, an increase in viscosity is achieved without there being any adhesion of the ink to the printing form cylinder.

Another way to control the viscosity of the ink so that the ink at its zonal dosing by means of the metering device has a lower viscosity than in the transfer of the ink by means of the printing forme cylinder, consists in the use of a printing ink which latent heat storage particles (Phase Change Material PCM ), z. As paraffin contains. PCM are based on the principle that the material can absorb a lot of thermal energy during the phase transition from solid to liquid, which it gives off later. For example, paraffin is liquid at temperatures above 26 ° C and can then absorb no further energy. A capsule effect guarantees the reversibility and prevents the paraffin from escaping. When using the PCM as a component of the printing ink, a specific "comfort range" of the temperature tailored to the printing press would have to be defined. By adding the latent heat storage particles to Printing ink can store the latter latent heat. The stored thermal energy can also be dissipated with the ink on the substrate, whereby a further increase in temperature or a reduction of the ink viscosity can be counteracted in the inking unit. The influence of the ink viscosity by the use of latent heat storage particles contained in the printing ink can also with other methods for changing the ink viscosity, z. B: be combined by means of ultrasound. As a result, the viscosity of the ink can be adjusted independently of temperature effects.

From the DE 103 06 939 A1 an offset printing ink with PCM located therein is already known. The described PCM makes a phase transition from solid to liquid, can be encapsulated and z. B. are present as paraffin. The described offset printing ink comprises the PCM in order to equip the workpieces coated with the offset printing ink (eg tarpaulins) so that they can store heat on their surface. It is described that for this purpose an intimate connection between the PCM and the workpiece is required. A targeted removal of heat from an offset printing inking unit by means of PCM, however, is not described.

Further, the EP 2 087 998 A1 already a rubber jacket of a roll, which has PCM for heat regulation. Again, the removal of heat by means of the PCM is not described.

The storage and removal of heat from a printing unit using PCM can preferably be achieved by the following method: A method for removing heat energy from a printing unit, wherein a printing ink is processed, the ink comprises a substance (preferably PCM), the substance to a first time within the printing unit is in a first state of matter, the substance is in a second state of aggregation at a second time within the printing unit, between the first and the second time, a phase transition between the first and the second state of matter of the substance takes place while heat energy is absorbed by the substance, and the heat energy is removed with the substance from the printing unit.

For the process, PCMs having a phase transition temperature between about 20 and about 50 ° C and a particle size between about 0.1 and 50 microns are suitable. The addition to the offset printing ink is preferably carried out with a mass fraction of between about 5 and about 40% by weight.

The PCM (or the latent heat storage) is preferably selected as paraffin and also preferably introduced in encapsulated form in the printing ink. Such encapsulated paraffins can be obtained, for example, from BASF under the trademark Mikronal. They typically have a size between 2 and 20 microns and the maximum heat capacity is typically about 110 kJ / kg. Such PCM may be dispersed into known offset inks for use in the above process. In this case, a weight percentage of about 10% by weight is preferably selected. As offset ink z. For example, the following color can be selected: K + E Novastar F 912 MAGIC BIO. In this example, the storage capacity of the ink is about 11 kJ / kg. With a typical heat capacity of offset inks of about 1.5 to about 2.5 kJ / Kelvin x kg, the heat storage by the PCM capsules compensates for an otherwise-elevated temperature increase of the offset ink from about 4.4 to about 7.3 Kelvin. Preferred PCM particles are: Mikronal DS 5000 X with a capsule diameter of 5 μm and a phase transition temperature of about 26 ° Celsius.

The encapsulated PCM particles can also take on additional functions in the offset printing ink. For example, the capsules can act as so-called spacers and abrasion protection particles. As spacers, the particles preferably have a size between about 1 and about 50 microns. The addition to the offset printing ink is then preferably carried out with a weight percentage of about 0.5 to about 5% by weight.

In addition to the use in offset printing inks, the use in flexographic printing inks, UV inks, paints and also the use directly in the substrate is conceivable.

Further structurally and functionally advantageous developments of the printing method according to the invention and the offset printing units according to the invention are evident from the following examples of preferred embodiments and the accompanying drawings.

Figur 1

ein Offset-Druckwerk mit einer beheizten Farbkastenwalze,

Figur 2

ein Offset-Druckwerk mit einem gekühlten Druckformzylinder,

Figur 3

ein Offset-Druckwerk mit einer beheizten Farbkastenwalze und einem gekühlten Druckformzylinder und

Figur 4

ein Offset-Druckwerk mit einem auf die Druckfarbe auf dem Druckformzylinder gerichteten Strahler.

In this shows:

FIG. 1

an offset printing unit with a heated ink fountain roller,

FIG. 2

an offset printing unit with a cooled printing form cylinder,

FIG. 3

an offset printing unit with a heated ink fountain roller and a cooled plate cylinder and

FIG. 4

an offset printing unit with a directed onto the ink on the plate cylinder radiator.

In the FIGS. 1 to 4 are mutually corresponding elements and components designated by the same reference numerals.

First, the common features of the various embodiments will be described. In the FIGS. 1 to 4 In each case a printing press 1 is shown in fragmentary form. The printing machine 1 is a sheet-fed printing machine. The offset printing unit 2 comprises an inking unit 3 and a dampening unit 4. The inking unit 3 comprises an ink fountain 5 with a ink fountain metering device 6 for the printing width (perpendicular to the image plane of FIGS. 1 to 4 ) different zonal dosing of a printing ink 7, which is stored in the ink fountain 5.

The ink fountain metering device 6 comprises ink zones which are arranged side by side in a row which runs parallel to a rotation axis of a ink fountain roller 8. The ink zones can be formed by zone screws, metering slides, metering levers or metering tongues arranged in said row. The ink fountain metering device 6 may comprise a metering knife, which is divided into said metering tongues. The ink zone metering device 6 limited together with the ink fountain roller 8 a metering, in which the ink 7 is metered. The dosing gap can be adjusted by varying the dosing elements (dosing slide, dosing lever, dosing tongues) or by adjusting the color screws from the color zone to the ink zone differently wide opened. This zonal adjustment takes place as a function of the printed image to be printed and causes a corresponding color profile in the ink film, which is formed by the zonal ink metering on the ink fountain roller 8.

The ink fountain roller 8 cooperates with an ink fountain roller 9, which is permanently applied to the ink fountain roller 8 in a roller contact point 10 in the printing operation. The inking roller 9 is an inking roller, which rolls on a printing form cylinder 11 in the printing operation to colorize an offset printing plate 12 mounted thereon. The outer circumference of the inking unit roller 9 is substantially the same length as the outer circumference of the printing plate cylinder 11. The printing form cylinder 11 and its offset printing plate 12 transmits the ink located thereon on a transfer or blanket cylinder 13, which the drawing ink not a drawing transmits illustrated sheet-shaped substrate, whereby on this a printed image is generated.

The dampening unit 4 comprises a fountain roller 14 and a metering roller 15 adjacent thereto against which a dampening roller 16 rests. An axially iridescent distributor roller 17 rests only on the dampening roller 16. A bridge roller 18 is at the same time at the dampening roller 16 and the inking roller 9 at. The illustrated roller contact positions refer to the state of the printing operation.

The ink fountain roller 8, the ink fountain roller 9 and the printing form cylinder 11 are rotatably driven such that these three rotation body 8, 9, 11 rotate in the printing operation at the same peripheral speed 22. In this case, the ink fountain roller 8 and the ink fountain roller 9 rotate in synchronism, ie, in opposite directions of rotation. Regarding the FIGS. 1 to 4 The inking roller 9 rotates clockwise and rotates the ink fountain roller 8 in the counterclockwise direction. The roller contact point 10 is a so-called squeezing gap, in which the inking roller 9 is pressed against the ink fountain roller 8 or the ink fountain roller 8 to the inking unit roller 9.

Hereinafter, the specifics of the embodiments will be described separately from each other.

At the in FIG. 1 illustrated embodiment, a heater 19 for heating the ink 7 in the ink fountain 5 is present. The heating device 19 is integrated in the ink fountain roller 8 and can for example by a Temperiermittelkanal for a heating fluid, for. As hot water, are formed. By the heater 19, the peripheral surface of the ink fountain roller 8 is heated, which is in contact with the ink 7 in the ink fountain 5 and thereby the ink 7 is heated. By heating the ink 7 whose viscosity is reduced, so that the ink 7 has a low viscosity as defined in claim 1, when the ink 7 is metered by the ink fountain metering device 6.

After this dosage, the ink gives off heat to the environment, eg. B. to the inking roller 9, so that the viscosity of the ink increases again. The ink 7, when it is on the printing form cylinder 11 or its offset printing plate 12, due to the cooling, a viscosity as defined in claim 1, which is at least by a factor of 10 greater than the viscosity of the ink 7 in the ink fountain 5 , This larger viscosity has the ink preferably already in the moment of transfer of the ink from the ink fountain roller 9 on the plate cylinder 11 and its offset printing plate 12 and at the latest in the transfer of the ink from the printing plate cylinder 11 and its offset printing plate 12 on the blanket cylinder 13th

In the embodiment according to FIG. 2 is a cooling device for cooling the ink 7 on the plate cylinder 11 and its offset printing plate 12 is present. The cooling device 2 is integrated in the printing form cylinder 11 and can by a Temperiermittelkanal for a cooling fluid, for. As cooling water, be formed. The cooling device 20 cools the printing form cylinder 11 and thus the offset printing plate 12 and ultimately the printing ink 7 located thereon by cooling the printing ink 7 the printing form cylinder 11 and its offset printing plate 12, the viscosity of this ink is increased such that it is at least by a factor of 10 greater than the viscosity of the same ink in the ink fountain 7 or when dosing with the ink fountain metering device 6.

The embodiment according to FIG. 3 is a combination of the embodiments according to the Figures 1 and 2 , wherein both the heating device 19 of the ink fountain roller 8 and the cooling device 20 of the plate cylinder 11 is present. Here, the temperature difference between the ink 7 in the ink fountain 5 and the same ink on the plate cylinder 11 and its offset printing plate 12 and the difference in viscosity resulting from the difference in viscosity by the heating of the ink 7 in the ink fountain 5 by means of the heater 19 and by the simultaneous Cooling of the ink on the printing plate cylinder 11 effected by means of the cooling device 12.

In the embodiment according to the FIG. 4 a radiator 21 is directed to a peripheral region of the printing form cylinder 11, which is seen in the direction of rotation of the printing forme cylinder 11, after the inking roller 9 and before the blanket cylinder 13 is located. The emitter 21 emits radiation onto the printing ink applied by the inking unit roller 9 to the printing form cylinder 11 or its offset printing plate 12, thereby increasing its viscosity. The viscosity of the ink located on the printing form cylinder is increased by the irradiation thereof so that this viscosity is at least a factor of 10 greater than the viscosity of the same ink in the ink fountain 5 or during dosing with the ink fountain metering device 6.

When the printing ink 7 processed in the offset printing unit 2 is a UV color and contains UV photoinitiators, the radiator 21 can receive a UV emitter, e.g. B. be a UV laser. Due to the UV radiation emitted by the radiator 21, superficial or partial crosslinking of the printing ink takes place on the printing form cylinder 1 l, as a result of which the viscosity thereof increases.

However, the printing ink 7 processed in the offset printing unit 2 can also contain IR absorbers or NIR absorbers, the emitter 21 being an IR emitter or NIR emitter. By taking place by the radiator 21 irradiation of the ink 7 on the printing form cylinder 11, this is heated so that certain components of this ink evaporate or accelerate evaporation, whereby the viscosity of the ink increases on the printing form cylinder 11.

LIST OF REFERENCE NUMBERS

1

press

2

Offset printing unit

3

inking

4

dampening

5

paintbox

6

Ink zone metering

7

printing ink

8th

Ink fountain roller

9

Inking roller

10

Roller contact point

11

Plate cylinder

12

Offset printing forme

13

Blanket cylinder

14

dipping roller

15

metering

16

Dampener roller

17

distributor roller

18

bridge roller

19

heater

20

cooler

21

spotlight

22

circumferential speed

Claims (8)

1. Printing method wherein in a printing press (1), a printing ink (7)

   - is zonally metered by means of a metering device (6) when the ink (7) has a first viscosity,

   - is transferred by means of a printing forme cylinder (11) when the ink (7) has a second viscosity that is greater than the first viscosity at least by the factor 10, the first viscosity smaller than 1 pascal second and the second viscosity greater than 10 pascal seconds.
2. Printing method set forth in Claim 1,
   wherein the first viscosity is set by reducing the viscosity of the printing ink (7) in the printing press (1).
3. Printing method according to Claim 2,
   wherein the reduction of the viscosity of the printing ink (7) is caused by at least one of steps a)-g) from the group of steps comprising

   a) heating the printing ink (7) by means of a heating device (19),

   b) heating the printing ink by means of a heating device (19) of a fountain roller (8),

   c) subjecting the printing ink (7) to ultrasound treatment,

   d) adding water or dampening fluid to the printing ink (7),

   e) adding droplets of water or dampening fluid to the printing ink (7),

   f) subjecting the printing ink (7) to mechanical stress,

   g) subjecting the printing ink (7) to mechanical stress by kneading or shearing.
4. Printing method according to Claim 1,
   wherein the second viscosity of the printing ink (7) is set by increasing the viscosity of the printing ink (7) in the printing press (1).
5. Printing method according to Claim 6,
   wherein the increase in the viscosity of the printing ink (7) is caused by at least one of the steps h)-t) from the group of steps comprising

   h) cooling the printing ink (7) by means of a cooling device (20),

   i) cooling the printing ink by means of a cooling device (20) of the printing forme cylinder (11),

   j) subjecting the printing ink (7) to an electrorheological treatment,

   k) evaporating a low-viscosity component of the printing ink (7),

   l) evaporating a low-viscosity carrier liquid of the printing ink (7),

   m) precipitating a component of the printing ink (7),

   n) cross-linking a component of the printing ink (7),

   o) subjecting the printing ink (7) to UV radiation,

   p) subjecting the printing ink (7) to UV radiation from a laser,

   q) subjecting the printing ink (7) to IR radiation,

   r) subjecting the printing ink (7) to IR radiation from a laser,

   s) subjecting the printing ink (7) to NIR radiation, and

   t) subjecting the printing ink (7) to NIR radiation from a laser.
6. Offset printing unit (2) for implementing the printing method according to Claim 1, comprising

   - an ink fountain (5) with a printing ink (7) whose viscosity can be controlled as defined in Claim 1, and with a metering device (6) with ink zones,

   - an ink fountain roller (8) with a heating device (19),

   - an inking unit roller (9) in continuous engagement with the ink fountain roller (8),

   - a printing forme cylinder (11),

   wherein the ink fountain roller (8) and the printing forme cylinder (11) are driven in such a way that they have the same circumferential speed (22), and wherein the heating device heats the printing ink (7) in such a way that its viscosity is reduced so that the printing ink (1) has the viscosity defined in Claim 1.
7. Offset printing unit (2) for implementing the printing method according to Claim 1, comprising

   - an ink fountain (5) with a printing ink (7) whose viscosity can be controlled as defined in Claim 1, and with a metering device (6) with ink zones,

   - an ink fountain roller (8),

   - an inking unit roller (9) in continuous engagement with the ink fountain roller (8),

   - a printing forme cylinder (11) having a cooling device (20),

   wherein the ink fountain roller (8) and the printing forme cylinder (11) are driven in such a way that they have the same circumferential speed (22), and wherein the cooling device (20) cools the printing ink (7) in such a way that its viscosity is increased so that the printing ink (7) has the viscosity defined in Claim 1..
8. Offset printing unit (2) for implementing the printing method according to Claim 1, comprising

   - an ink fountain (5) with a printing ink (7) whose viscosity can be controlled as defined in Claim 1, and with a metering device (6) with ink zones,

   - an ink fountain roller (8) with a heating device (19),

   - an inking unit roller (9) in continuous engagement with the ink fountain roller (8),

   - a printing forme cylinder (11) with a cooling device (20),

   wherein the ink fountain roller (8) and the printing forme cylinder (11) are driven in such a way that they have the same circumferential speed (22), and wherein the heating device (19) heats the printing ink (7) in such a way that its viscosity is reduced and the cooling device (20) cools the printing ink (7) in such a way that its viscosity is increased so that the printing ink (7) has the viscosities defined in Claim 1.

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