GB2262067A

GB2262067A - Printing press using planographic process

Info

Publication number: GB2262067A
Application number: GB9223814A
Authority: GB
Inventors: Rainer Buschulte
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1991-11-15
Filing date: 1992-11-13
Publication date: 1993-06-09
Also published as: GB9223814D0; FR2683766A1; JPH05229090A

Abstract

A press using the planographic process comprises a printing forme with hydrophobic and hydrophilic regions according to an image to be printed, with means being provided by which the regions for the production of a lithograph are reversible electrochemically from the hydrophobic to the hydrophilic state by means of a current-flow apparatus. The apparatus preferably has a matrix-like action, and with a fluid-application apparatus, said fluid-application apparatus - in order to produce a lithograph - applying a hydrophobic fluid over the full surface area, particularly to the surface of the printing forme, said hydrophobic fluid then being removed again electrochemically by means of a control apparatus region by region according to the hydrophilic regions required for the image to be printed, through the formation of corresponding current paths. <IMAGE>

Description

PRINTING PRESS USING PLANOGRAPHIC PROCESS The invention relates to a printing press using the planographic process, said printing press comprising a printing forme with hydrophobic and hydrophilic regions according to an image to be printed, with means being provided by which the regions for the production of a lithograph are reversible electrochemically from the hydrophobic to the hydrophilic state by means of a current-flow apparatus, said current-flow apparatus having preferably a matrix-like action, and with a fluid-application apparatus, said fluid-application apparatus - in order to produce a lithograph - applying a hydrophobic fluid over the full surface area to the surface of the printing forme or similar, said hydrophobic fluid then being removed again electrochemically by means of a control apparatus region by region according to the hydrophilic regions required for the image to be printed, through the formation of corresponding current paths.

A printing press of the aforementioned kind is described in U.K. P tent Application No.9113833.9.

The possibility of making~hydrophilic (water-accepting) and/or hydrophobic (water-rejecting) regions on a printing forme reversible by means of an electrochemical process has the advantage over classical printing formes that a change of image can be performed in simple manner, preferably within the printing press.

There is no need, therefore, for the complicated photochemical production of the classical printing formes or for their installation and removal.

The object of the invention is to create a printing press in which the lithograph can be produced and/or modified or removed again in particularly simple manner.

The object of the invention is achieved in that the current-flow apparatus removes the regions of the fluid by dissolving in acid or alkali formed in the current paths owing to the current flow, with the solubility 6f the fluid in the acid or alkali being able to be influenced by exposure to energy by means of a treatment device in such a manner that the fluid is convertible into an insoluble state. In order to produce the lithograph, the fluid-application apparatus applies a hydrophobic fluid over the full surface area to the surface of the printing forme or to a separate apparatus, said hydrophobic fluid then being removed again electrochemically by means of the control apparatus region by region according to the hydrophilic regions required for the image to be printed, through the formation of corresponding current paths.The regions are removed by being dissolved in acid or alkali formed in the current paths owing to the current flow.

The current flow takes place between the means holding the lithograph, for example the control matrix, and a counter-electrode, which is electrically connected to the fluid preferably through the intermediary of an electrolyte bridge. The properties of the fluid can be influenced by means of exposure to energy in such a manner that the fluid is soluble or insoluble either in the acid or in the alkali. This has the advantage that, in the insoluble state, the lithograph is protected from environmental influences and also from destruction by maloperation (if, for example, acid gets onto the lithograph during the washing of the rubber blanket).

According to the invention, it is thus possible in simple manner to produce a durable lithograph. Once, therefore, the image to be printed has been produced by the appropriate formation of current paths, it is subjected to exposure to energy with the treatment device. This may be in the form of exposure to light and/or ultraviolet radiation (UV) and/or temperature.

The fluid is thus converted from its soluble state to the insoluble state. The printing process can now take place. If the printer wishes to remove the image, then it is possible, according to a further development of the invention, to re-expose the image to energy by means of the treatment device, with different parameters (different wavelength, different treatment time) preferably being used as compared with the aforementioned exposure to energy, depending on the type of fluid, in order again to convert it from the insoluble state to the soluble state.

It emerges from the above that the fluid consists of an energy-reactive material, being reactive in particular to light exposure, radiation and/or temperature, said material being irradiated by means of the treatment device following the inscription process for production of the lithograph and/or in order to remove the image from the lithograph.

The fluid has either a liquid, particularly a viscous, or solid initial state. Preferably, it is provided that, when in its solid initial state, the fluid is in the form of a foil.

Said foil is associated, particularly by means of the customary paper-transport apparatus of the printing press or by means of a separate feed apparatus, with the printing-forme cylinder or with a separate apparatus serving the purpose of inscription.

According to a preferred embodiment, the fluid consists of a plastics material. Preferably, it contains diazonium compounds or consists of the latter.

Alternatively, it is also possible for the fluid to consist of azides or to contain them. Futhermore, the possibility exists for the fluid to consist of diazo quinones or for it to contain them.

The aforementioned current-flow apparatus comprises the control apparatus, an electrode arrangement, an electrolyte and at least one voltage source. The electrolyte is preferably in the form of an aqueous solution of salts, particularly in the form of potassium chloride (KCl) or sodium chloride (NaCl).

It is possible to produce the image on the printingforme cylinder, i.e. the printing-forme cylinder is provided with the fluid; this may be done by application in the form of a liquid or by clamping the foil on the cylinder. Subsequently, the lithograph is produced on the printing-forme cylinder by means of the current-flow apparatus, which is suitably activated by the control apparatus. Alternatively, however, it is also possible to provide a separate image-producing device with which the lithograph is produced according to the preceding embodiments, with the lithograph, after completion, being transferred from the image-producing device to the printing-forme cylinder. Such transfer takes place by transfer-printing in the case of a liquid or viscous fluid and by foil transfer in the case of a solid fluid (foil).The image-producing apparatus has a cylinder, on the outer cylindrical surface of which the lithograph is produced. Said lithograph is in its soluble state and is transferred by contact with the printing-forme cylinder to the outer cylindrical surface of the printing-forme cylinder by means of the aforementioned transfer-Printing process. If a foil is being used, it is clamped onto the cylinder of the image-producing apparatus and is then provided with the image.

subsequently, the foil is transferred to the printingforme cylinder, where it is clamped, with the result that - after the lithograph has been exposed to energy in order to convert it to its insoluble state - printing may then commence. The foil may be irradiated either on the cylinder of the image-producing apparatus or on the printing-forme cylinder or, alternatively, during transfer from the image-producing apparatus to the printing-forme cylinder.

In order to apply the fluid to the cylinder of the image-producing apparatus, it is associated with the aforementioned fluid-application apparatus. If a liquid fluid is being used, then the fluid may be applied, for example, by means of an immersion bath or by means of a spraying apparatus. The fluid may also be applied via a roller arrangement to the outer cylindrical surface of the cylinder of the image-producing apparatus. If the fluid is being used in the form of a foil, the fluidapplication apparatus feeds the foil to the cylinder, i.e. the foil is clamped on the outer cylindrical surface of the cylinder.

The invention is illustrated in the drawings, in which: Fig. 1 shows a cross section through a printing-forme cylinder of a printing press; Fig. 2 shows a printing forme, provided with an electrode arrangement, in a developed representation on line A-B in Fig. 1; Fig. 3 shows a schematic detail view of the surface of the printing forme; Fig. 4 shows the representation according to Fig. 3, but with activated electrode as well as counter electrode; Fig. 5 shows a representation according to Fig. 4 after completion of an electrochemical process; Fig. 6 shows a flowchart and Fig. 7 shows a schematic cross-sectional view of the printing press, said printing press comprising a separate image-producing apparatus.

The invention relates to a printing press of the kind described in U.K. Patent Application No.9113833.9 with the result that the entire contents (claims, specification, drawings) of the aforementioned patent application are incorporated herein by cross-reference.

The printing vest (not shown in greater detail) comprises an inking unit and a damping unit, with ink and damping solution being supplied via a roller arrangement to a printing-forme cylinder.

Fig. 1 shows - in cross section - an embodiment of a printing-forme cylinder 33, which carries a printing forme 32 on its outer cylindrical surface. Fig. 2 shows the printing forme 32 in a developed representation on line A-B in Fig. 1. The printing forme 32 may be in the form of a sleeve which is placed on the printing-forme cylinder 33 or in the form of a plate which is clamped in position. Alternatively, however, it is also possible for the printing forme 32 to be a constituent part of the printing-forme cylinder 33, i.e said parts form a homogeneous structural unit.

Common to all variants is that the surface of the printing forme 32 is provided with an electrode arrangement 38, which comprises a multiplicity of electrodes 39 disposed in the manner of a matrix. The individual electrodes 39 are electrically isolated from one another by means of insulating bars 40. Their cross-sectional dimensions are extremely small. For example, they may be in the form of squares with an edge length of 4.5 pm, with the insulating bar having a thickness of 0.5 pm. In the specimen embodiment, the matrix forms 3.3 x 101 elements (electrodes 39). It is possible, for example, to produce said matrix by means of micro-mechanics.

The individual electrodes 39 can be activated by means of a control apparatus 41 (not shown in any greater detail), i.e. they can be energized by a voltage, with one pole of the voltage source being connected to the respectively activated electrodes 39 and with the other pole of the voltage source being connected to a counterelectrode (to be described in greater detail below).

For activation, the control apparatus 41 comprises addressing modules 42.

Fig. 3 shows the electrode arrangement 38 in greater detail. Each electrode 39 projects beyond the surface 45 of the printing forme 32 by a section 44, as a result of which recesses 46 are formed between the individual electrodes 39, said recesses 46, in their entirety, forming a capillary structure 47. It is also possible for the electrode arrangement to be flat.

St is assumed that the design of a specific image to be printed has been prepared in the form of data information, with the data now being available to the control apparatus 41. Let it further be assumed that the surface 45 of the printing forme 32 is clean; it has, for example, been cleaned by means of a washing apparatus.

In order to produce a lithograph, a fluid 48 is first of all applied over the full surface area to the surface 45 of the printing forme 32 (Fig. 3, 4, 5). The fluid 48 may be a colorant (printing ink) or a substance independent of the colorant. After the fluid 48 has been applied over the full surface area, the lithograph is produced. For this purpose, the electrolyte 36 is applied, by means of an electrolyte-feeding apparatus, to the layer of fluid on the printing forme 32.

Subsequently, a current-flow apparatus-57 is activated according to the design to be produced, i.e. the appropriate electrodes 39 are activated by means of the control apparatus 41. They assume the potential of one pole of the voltage source. The electrolyte 36 is in contact - as can be seen from Fig. 4 - with a counterelectrode 49 connected to the other pole of the voltage source. This exposure to voltage leads, at the boundary layer 50 between the fluid 48 and the electrolyte 36, to an electrochemical reaction. The fluid 48 is removed along the current path 51 formed between electrode 39 and counter-electrode 49. This is achieved by dissolving in acid or alkali formed in the current path 51 owing to the current flow. The fluid 48, therefore, is soluble in acid or alkali.In the region of the nonactivated electrodes 39, the fluid 48 remains, this making it possible to produce the lithograph. In order to "preserve" the lithograph, i.e. to make it stable against external influences, after the lithograph has been produced, it is exposed to energy from a treatment device 60, which converts the fluid 48 from its soluble state into an insoluble state. The treatment device 60 emits light radiation, ultraviolet (W) radiation and/or heat radiation. The actual printing process may then commence. For this purpose, damping solution and ink are supplied to the printing forme 32 in conventional manner.The previously described electrochemical process has resulted in the formation of hydrophobic and hydrophilic regions, with the regions associated with the activated electrodes 39 having hydrophilic properties and with the regions associated with the nonactivated electrodes 39 having hydrophobic properties.

To this extent, the printing process can be carried out according to the classic offset technique.

In order, after a printing job has been terminated, again to remove the lithograph for a change of lithograph, the lithograph is once again exposed to energy by means of the treatment device 60, with, preferably, different parameters (radiation wavelength, treatment time) being used as compared with the first exposure to energy, as a result of which the fluid 48 is returned to its initial state, namely to a soluble state. The printing forme 32 can then be cleaned by means of a washing apparatus or similar.

Fig. 6 illustrates the previously described process.

The lithograph is produced at process step 61. It is then exposed to energy by means of the treatment device 60.

At step 62, the lithograph is then in the insoluble state. The printing process takes place in this state.

After the termination of the printing process, the treatment device 60 (or a different one) is used again to bring about the soluble state of the lithograph (of the fluid). At step 63, the soluble state of the fluid has been re-established, with the result that a new image can be produced on the lithograph.

The fluid 48 may be a liquid, in particular a pasty mass. Alternatively, however, it is also possible for the fluid to have a solid initial state, namely for it to be in the form of a foil. In order to produce the image, said foil is applied to the printing-forme cylinder 33 by means of the aforementioned fluidapplication apparatus. If a thin, current-conducting and hydrophobic foil, formed by the fluid 48, is applied, the technical, previously described process of image production remains unchanged. The foil can be brought into association with the printing-forme cylinder 33 of the printing press by way of known papertransport apparatuses of the press or by way of specially developed feeding apparatuses.

The fluid 48 consists of a plastics material. In particular, it contains or consists of diazonium compounds. Alternatively, it is also possible for the fluid to consist of or to contain azides. Furthermore, it is advantageous if the fluid consists of or contains diazo quinones.

The electrolyte 36 used is preferably an aqueous solution of salts, particularly potassium chloride (KCl) or sodium chloride (NaCl).

According to the specimen embodiment in Fig. 7, instead of the image being produced on the printing-forme cylinder 33 of the printing press, it may also be provided that a lithograph is produced by means of a separate image-producing device 64 and, after completion, is transferred to the printing-forme cylinder 33. More specifically, Fig. 7 shows a printing unit 65 of the printing press with inking and damping unit 66, a rubber-blanket cylinder 67, a backpressure cylinder 68 as well as transfer cylinders 69.

With the image-producing device 64, the fluid 48 is applied, via a roller arrangement 70, to a cylinder 71, one sector of which dips into an electrolyte bath 72 in which the counter-electrode 49 is also accommodated.

The cylinder 71 comprises the previously described electrode arrangement 38. After the fluid 48 has been applied to the cylinder 71, the image is produced there by suitable activation of the electrodes 39 and is then transferred, by means of a transfer-printing operation, to the outer cylindrical surface of the printing-forme cylinder 33, where the transferred image is then exposed to energy radiation from the treatment device 60, as a result of which the fluid 48 is converted from its soluble to its insoluble state. The printing process may then take place.

If the fluid 48 is in the form of a foil, there is no need for the roller arrangement 70 for the transfer of a liquid fluid 48. By means of a suitable fluidapplication apparatus, the foil is then clamped onto the cylinder 71 and - according to the previously described process - is provided with the image. The foil is then transferred from the cylinder 71 to the printing-forme cylinder 33.

The foil may be exposed to energy from the treatment device 60 either on the cylinder 71 or, alternatively, on the printing-forme cylinder 33 or in transit.

Daring running-on, the cylinder 71 is brought out of Kgagement with the printing-forme cylinder 33, with the result that it-is already possible, during the printing process, to produce a new printing forme on the cylinder 71.

As already mentioned, the fluid 48 may be the printing ink or a separate substance. Furthermore, it is particularly advantageous if the fluid is dried with IR radiation by means of the treatment device, thereby being converted to the insoluble state after inscription. After termination of the printing process, the thus stabilized fluid can be removed by suitable washing means. According to the aforementioned further development of the invention, however, it is also possible for. the stabilized fluid to be exposed once again to energy from the treatment device, as a result of which it again assumes its soluble state (destabilized state), thereby permitting particularly simple removal.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

CLAIMS:

1. Printing press using the planographic process, and comprising a printing forme with hydrophobic and hydrophilic regions according to an image to be printed, with means being provided by which the regions for the production of a lithograph are reversible electrochemically from the hydrophobic to the hydrophilic state by means of a currentflow apparatus and with a fluid-application apparatus, in order to produce a lithograph, applying a hydrophobic fluid over the full surface area, particularly to the surface of the printing forme, said hydrophobic fluid then being removed again electrochemically by means of a control apparatus region by region according to the hydrophilic regions required for the image to be printed, through the formation of corresponding current paths, wherein the current-flow apparatus removes the regions of the fluid by dissolving in acid or alkali formed in the current paths owing to the current flow, with the solubility of the fluid in the acid or alkali being able to be influenced by exposure to energy by means of a treatment device in such a manner that the fluid is convertible into an insoluble state.

2. A printing press according to claim 1 wherein the current flow apparatus has a matrix-like action.

3. A printing press according to claim 1 or 2 wherein the fluid can be returned from the insoluble state to the soluble state by re-exposure to energy by means of the treatment device.

4. A printing press according to any one of the preceding claims wherein the treatment device emits light radiation, ultraviolet (W) radiation and/or heat radiation.

5. A printing press according to any one of the preceding claims wherein the fluid is an energy-reactive material, being reactive in particular to light exposure, W radiation and/or temperature, said material being irradiated by means of the treatment device following the inscription process for production of the lithograph and/or in order to remove the image from the lithograph.

6. A printing press according to any one of the preceding claims wherein the fluid has a viscous or solid initial state.

7. A printing press according to any one of the preceding claims wherein the fluid forms a foil in its solid initial state.

8. A printing press according to claim 7 wherein the foil is associated, by means of the customary paper-transport apparatus of the printing press or by means of a separate feeding apparatus, with the printing-forme cylinder or with a cylinder of an image-producing device of the printing press.

9. A printing press according to any one of the preceding claims wherein the fluid is a plastics material.

10. A printing press according to any one of the preceding claims wherein the fluid consists of diazonium compounds or contains such compounds.

11. A printing press according to any one of the preceding claims wherein the fluid consists of azides or contains azides.

12. A printing press according to any one of the preceding claims wherein the fluid consists of diazo quinones or contains diazo quinones.

13. A printing press according to any one of the preceding claims wherein the current-flow apparatus comprises the control apparatus, an electrode arrangement, an electrolyte and at least one voltage source.

14. A printing press according to any one of the preceding claims wherein the electrolyte is in the form of an aqueous solution of salts, particularly in the form of potassium chloride (KC1) or sodium chloride (NaCl).

15. A printing press according to any one of the preceding claims characterised by an image-producing device with which the lithograph is produced, said lithograph, after completion, being transferred to the printing-forme cylinder.

16. A printing press according to any one of the preceding claims wherein the transfer to the printing-forme cylinder is by transfer-printing in the case of a viscous fluid or by foil transfer in the case of a solid fluid (foil).

17. A printing press according to any one of the preceding claims wherein the image-producing device comprises a cylinder on the outer cylindrical surface of which the lithograph is produced.

18. A printing press according to any one of the preceding claims wherein the image-producing device is associated with the fluid-application apparatus.

19. A printing press using the planographic process substantially as hereinbefore described with reference to the accompanying drawings.