WO2005040937A1

WO2005040937A1 - Method and device for correction for paper shrinkage

Info

Publication number: WO2005040937A1
Application number: PCT/EP2004/009660
Authority: WO
Inventors: Peter Thiemann; Herbert Gibisch; Dieter JÖRGENS
Original assignee: Oce Printing Systems Gmbh
Priority date: 2003-09-24
Filing date: 2004-08-30
Publication date: 2005-05-06
Also published as: DE10344237A1

Abstract

The invention relates to a method and a device for the printing of a medium (94), whereby a medium is printed, in a first printing process, with a first toner image. The first toner image is fixed on the medium in a first fixing device, whereby the medium shrinks along at least one main axis (L2). The same medium is then printed, in a second print process, with a second toner image, whereby the second toner image is applied to the medium in a form compressed along the direction of the main axis relative to the first printing process by means of a compensation lens (96).

Description

Method and device for correcting paper shrinkage

The invention relates to a method and a device for printing on a recording medium, in which a recording medium is printed with a first toner image by a printing device in a first printing process, the first toner image is fixed on the recording medium in a fixing device, the recording medium at least lengthways a main axis shrinks, and in which the same recording medium is then printed with a second toner image in a second printing process.

There are numerous printing modes in which a recording medium undergoes a fixing process after being printed with a first toner image. During this fixing process, which generally takes place under pressure and at a relatively high temperature, the moisture in the recording medium, generally paper, is reduced, as a result of which shrinkage takes place in the longitudinal direction and / or width direction. In these two directions, the shrinkage effect can be different, depending on the direction of the fibers in the paper. The degree of shrinkage also depends on the parameters of the fixing process. If a further toner image is subsequently applied to the same recording medium, the two printed images are no longer a perfect fit for one another with the same printing process, which leads to a loss in quality. Typically, shrinkage in the direction of a major axis can be up to 1%, i.e. in the case of a sheet of size DIN A4, the shrinkage in the longitudinal direction can be more than 2 mm. The effect becomes even clearer with larger formats.

A method for operating a printer with two printing units is known from WO 98/18054 by the same applicant, in which different operating modes can be implemented. In a duplex printing operation, single sheets are printed on both sides, with a fixation taking place between the respective printing process. Another mode of operation is two-color simplex printing, in which two image patterns of different colors are printed on the front of a single sheet. This operating mode is also known as highlight color printing. Another mode of operation is two-color duplex printing, in which the front and the back of an egg leaf are printed with image patterns of different colors. In connection with the description of an embodiment, reference is again made to the cited document below. This document is hereby incorporated by reference into the disclosure content of the present patent application.

Furthermore, EP 0 699 315 AI discloses an electrographic printing device for printing on tape-shaped recording media with different bandwidths. A paper tape is transported and printed on a single printing unit with a usable width of at least twice the width of the paper tape in side by side -: - position. In the various printing modes, the first toner image is temporarily fixed, one

Shrinkage of the paper web takes place. The content of this document is discussed in more detail in connection with the description of exemplary embodiments. This document is hereby incorporated by reference into the disclosure content of the present patent application.

It is possible to reduce the scuffing effect by drying the carrier material to a low relative humidity before printing. The shrinkage effect is then reduced in the subsequent first fixation. However, such a measure involves a great deal of effort. Another It is possible to treat the substrate material climatically after the first fixing process and to restore the original relative humidity prevailing during the first printing process. The shrinking process that occurred during fixation is thus reversed. This measure is also associated with a very high technical outlay.

It is an object of the invention to provide a method and a device which make it possible to produce a high print quality on the carrier material with relatively little technical effort. _ -

This object is solved by the features of the independent claims. Advantageous further developments are specified in the dependent claims.

According to the invention relating to a method, the second toner image is applied to the recording medium in a compressed form in the direction of the main axis in a second printing process. The compression corresponds approximately to the degree of shrinkage in the direction of this main axis. If the recording medium, generally paper, then expands again under normal climatic conditions, the second toner image in the direction of this main axis has the same extent as the first toner image, whereby the shrinkage effect is compensated for.

According to a further aspect of the invention, a device for printing on a recording medium is specified. This device enables compensation of the shrinkage effect.

For a better understanding of the present invention, reference is made below to the preferred exemplary embodiments illustrated in the drawings, which are described using specific terminology. It is however, it is pointed out that the scope of the invention is not intended to be limited thereby, since such changes and further modifications to the devices and / or the methods shown, as well as such further applications of the invention, as indicated therein, are considered to be customary (current or future specialist knowledge) The figures show exemplary embodiments of the invention, namely:

FIG. 1 shows a single-sheet printing system with two printing units and two fixing stations,

FIG. 2 shows the printing system according to FIG. 1 in the duplex printing mode,

FIG. 3 shows a printing system for tape-like paper that is printed twice,

FIG. 4 shows an arrangement with an LED character generator,

FIG. 5 shows an arrangement with compensation optics to compensate for paper shrinkage.

Figure 6 shows an arrangement with an optical pre-distortion and an optical post-distortion to compensate for the paper shrinkage.

1 shows a high-performance printer 10 in which the invention can be used. The high-performance printer 10 is used for the rapid printing of single sheets of paper and contains a first printing unit D1 and a second printing unit D2. Both printing units D1, D2 work according to the known electrographic process. The printing units D1, D2 are each followed by fixing stations 12, 14, which are indicated schematically by two pairs of rollers. To the high-performance printer 10 is one Paper input 16 connected, which contains a plurality of storage containers 18 to 24 with single sheets and an external paper input channel 26. Single sheets are fed to an input section 28 via a transport channel 27. Output side, a paper output 30 is connected to the high-performance printer 10, ^• a plurality of output receptacles contains 32 to 36. Furthermore, two output channels 38, 40 are provided, via which single sheets can be output at further processing stations. The high-performance printer 10 delivers the printed single sheets via the output section 42.

Transport paths for the transport of the single sheets are arranged in the interior of the high-performance printer 10, through which different operating modes of the high-performance printer are realized. The printing units D1, D2 are each assigned transfer printing transport paths 44, 46, which are each set by drives in such a way that the individual sheets fed to the printing units D1, D2 have their transfer printing speed. Both transfer printing transport paths 44, 46 are connected to one another via a connecting channel 48. The transport path around the first printing unit D1 is supplemented to form a ring by a feed channel 50, via which individual sheets can also be fed from the input section 28 to the second transfer printing transport path 46. The transport path for the second printing unit D2 is similarly supplemented to form a ring by a discharge channel 52, via which individual sheets printed by the printing unit D1 can be fed to the output section 42.

A first switch W1 is arranged between the input section 28, the first transfer printing path 44 and the feed channel 50, which enables individual sheets from the input section 28 to be optionally fed to the first transfer printing path 44 or the feed channel 50. A further variant consists in that W1 was transported on the feed channel 50 in the direction of the first switch Single sheets can be fed to the first transfer printing transport path 44.

Furthermore, a second switch W2 and a third switch W3 are arranged at the ends of the connecting channel 48 and connect the adjacent transport paths 44, 48, 52 and 46, 48, 50, respectively. A fourth switch W4 is located in the vicinity of the delivery section 42 and connects the adjacent transport routes. The paper output 30 contains a fifth switch W5, which works as a turning device. Furthermore, it should also be pointed out to a control device 54, to which reject single sheets are fed via a switch W6.

The described arrangement in Figure 1 various ^"operating modes of the high-performance printer 10 can be realized. In simplex printing, the single sheets of a printing unit Dl or D2 only printed on one side and from the Fixierstati.on 12 -or 14 is fixed. That- Shrinkage problem described above does not occur in this mode.

Figure 2 shows schematically the duplex printing operation in which the single sheets are printed on both sides. The single sheets fed to the input section 28 are fed to the first transfer printing path 44 through the first switch W1 (arrow P13). After printing by the printing unit D1 and the subsequent fixing in the station 12, the respective single sheet is conveyed a turning distance according to the arrow P14 beyond the switch W2. This turning path is part of the discharge channel 52. The conveying device is then reversed according to arrow Pl5, and the switch W2 then guides the single sheet according to the arrow P16 into the connecting channel 48. The single sheet is then from the switch W3 in the direction of the arrow P17 to the second Transfer printing path 46 deflected. The printing unit D2 is therefore the not yet printed back of the single sheet fed for printing. This single sheet has shrunk due to the fixation process. After the second printing, a new fixing process follows in the fixing station 14 with the application of heat and pressure. The successive single sheets are then fed to the switch W4 according to the arrow P18 - and transported into the paper output 30 along the arrow P19. As the single sheet is transported with its back upwards in this state, it must still be turned over in compartments 32 to 36. The W5 switch serves this purpose. The single sheet is first guided through the switch W5 in the direction of arrow P20 for a predetermined turning distance. Then, the transport Richting according to arrow P21 is reversed and the shunt W5 conveys the sheet in the direction of arrow -P22, whereupon it is placed true to side in the stackers 32 to. ^"36

Another mode is the two-color simplex printing, often referred to as highlight color printing, in which the front side of a single sheet with two image patterns of different color is printed. ^"The two printing units Dl, D2 then print image patterns of different colors. In this mode, the single sheet is fed to the printing unit D1 via the switch W1, printed, and fixed for the first time, with shrinkage occurring in the fixing station 12. Then the single sheet is connected to the connecting channel 48 without turning and then via the switch W3 to the printing unit The printing unit D2 prints the shrinked front side with a color different from the color of the printing unit D. Then the single sheet is fixed a second time in the fixing station 14 and output to the paper output 30 via the switch W4 , in which the printing unit D2 prints first and after fixing the printing unit Dl d Print the second toner image:. Another operating mode with intermediate fixation is two-color duplex printing, in which the front and the back of a single sheet are printed with image samples of different colors. The prerequisite for this is that the printing units D1 and D2 print differently colored print images. The two-color printing on the front is carried out in the same way as in the two-color simplex printing mode described above. First, the single sheet is printed in two colors on one side with the printing units Dl and D2. Then the single sheet is again fed to the printing unit Dl via the channel 48 and the switch Wl and W6 for printing on the back. So that this back side is fed to the printing unit Dl, the single sheet must be turned on the transport path between the printing unit D2 and the printing unit Dl. This turning can take place, for example, on the switch W4, the switch W2 or the switch W3. The second color is then printed on the printing unit D2 on the back of the single sheet. The individual sheet may experience different shrinkages during the various fixing processes.

The various operating modes are described in more detail in the aforementioned WO 98/18054. Reference is hereby made to the statements made there.

FIG. 3 shows a further example of a high-performance printing system 58 which works with a band-shaped carrier material 60. Sections of the carrier material 60 are guided twice past a photoconductor drum 68 with at least twice the width of the tape material and printed, with an intermediate fixation taking place with the inevitable shrinking process.

The various units for the electrophotographic process are grouped around the photoconductor drum 61.

A charging device 62 in the form of a charging corotron for

Charging the intermediate carrier 61, which acts as a photoconductor drum is trained; an LED character generator 63 with a light-emitting diode comb for character-dependent exposure of the intermediate carrier 61, which extends over the entire usable width of the intermediate carrier 61; a developer station 64 for coloring the character-dependent charge image on the intermediate carrier 61 using a one- or two-component developer mixture; a transfer printing station 65, which extends over the width of the intermediate carrier 61 and with which the toner images are transferred to the recording medium 61. To remove the residual toner after the development and transfer printing, a cleaning station 66 is provided, with an integrated cleaning brush with associated suction device and a discharge device 67 .. The intermediate carrier 61 is driven by an electric motor and moved in the direction of the arrow in the printing mode.

Furthermore - 'includes the printing device - 58 a of the transfer station 65 in the transport direction of Aufzeichnungsträ- gers downstream of fuser 68, as a thermal printing fusing ^station' is formed is arranged downstream with a heated fuser roll 69 to 'associated pressure roller 70, and the fixing guide rollers 71, the among other things ₌ as output elements for. a stacking device 72 serve for the recording medium 60. Instead of the fusing station shown, other fusing stations are also possible, for example with a heated or unheated inlet saddle. The tape-shaped recording medium 60 is made up, for example, as prefolded continuous paper provided with edge perforations and is fed from a storage area 73 via feed rollers 74 to the transfer station. It is also possible to feed a recording medium without edge perforations in this way or via a roll feed.

The recording medium 60 is preferably transported via a transport device 75 assigned to the transfer printing station 65 in the form of pins Conveyor belts which, guided via drive shafts 77, engage in the perforations on the edge of the recording medium 60. In the event that a transport-hole-free recording medium is used, an adapted transport device familiar to the person skilled in the art is to be provided, which transports the recording medium, for example by friction, controlled by a control arrangement scanning synchronization marks. Furthermore, a deflection device 78 is arranged in the housing area of the printing device between the storage area 73 and the fixing station 68, via which the recording medium 60 is returned from the fixing station 68 to the transfer printing station 65. .-

The electrographic printing device is suitable for printing on ^• recording media of different bandwidths. For this purpose, has der-- intermediate carrier 61 - (photoconductor drum) ^• a usable width that corresponds to the maximum width of recording medium (such as an A3 across) -. This width corresponds to the double A4 width. This makes it possible, ^'in the area of the transfer station 65, two recording media widths A4 along next to one another. The fuser 68 and. the other electrophotographic units, such as developer station 64, character generator 63, cleaning station 66, are designed in accordance with this usable width.

Adapting the width of the character generator 63 to different recording medium widths does not require any mechanical change to the character generator if, as in this case, an LED character generator is used with a large number of LEDs arranged in rows. An adaptation to the recording medium width used is done electronically by control. The deflection device 78 arranged in a return channel for narrow recording media from the fixing station to the transfer printing station has two functions: running operation for laterally displacing the recording medium web and in turning operation for rotating the back of the recording medium 60 from the rear. It is designed to be switchable depending on the operating mode.

For double-sided, single-color printing of a narrow recording medium (single-color duplex operation), as shown in FIG. 3, the narrow, for example DIN A4-wide, recording medium 60 is fed from the supply area 73 via the feed rollers 74 to the transfer station 65 and on its upper side printed with a front toner image. The front side of the recording medium 60 is identified by solid transport arrows, the underside by dashed transport arrows. Thereafter, the recording medium 60 with the front toner image is fed to the fixing station 68 - and. the front-side toner image is fixed, whereby the recording medium 60 shrinks. Over the guide rollers 71 is carried out, a "further transport ..des Aufzeichnungsträ- ^gers' 60 -to --Umlenkeinrichtung 78. From the deflection means 78" of the recording carrier ^"is turned with respect to its front and back again via the feed rollers 74 of the .Umdruckeinrichtung 65 so After that, the recording medium 60 is again fed to the fixing station 68 and the backside toner image is fixed, and then the recording medium printed on both sides is stored in the stacking device 72. The printing device is also in the operating mode "two-color duplex mode" suitable for multi-color printing. For this purpose, the developer station 64 is designed in such a way that it generates developer zones E1 and E2 which can be colored separately on the intermediate carrier 61. Each position area of the narrow recording medium 60 is a corresponding developer zone E1 or E2 on the intermediate carrier 61 as it passes through the transfer printing station 65 assigned. In order to produce these separately colorable developer zones E1 and E2, two developer stations 64/1 and 64/2 arranged one behind the other can be assigned to the developer zones. The developer station 64/1 contains a toner mixture of a first color, for example red and the developer station 64/2 contains an developer in a second color, for example black. The developer stations 64/1 and 64/2 are designed so that they can be activated separately with respect to the developer zones El and E2.

In order to be able to print a narrow recording medium 60 on both sides with different colors, as shown in FIG. 3, the recording medium 60 is guided through the printing device in the manner already described. In a first pass through the transfer printing station .65, a front side image is applied in a first color, for example red via the developer station 64/1 in the developer zone E2. This is followed by - fixing in the fixing station 68. In a second ^; Passing through the transfer printing station 65, after the turning process via the deflection device 78, a rear toner image in a second color, for example black, is applied via the developer station 64/2 in the developer zone El.

Another operating mode is the "two-color simplex mode", in which a narrow recording medium 60, for example A4 in width, is printed on one side with two colors. Each recording medium position on the transfer printing station 65 is assigned a separately colorable developer zone E1, E2 A first pass through the transfer printing station 65 involves the printing of a toner image over the developer zone E2 in a first color, for example red. The toner image of this first color is then fixed in the fixing station 68, shrinking of the recording medium taking place and the recording medium 60 becoming without turning the transfer station 65 fed again with the associated developer zone El. The deflection device 28 is in the continuous position and the recording medium is only displaced in width while maintaining the front-back assignment. On the second pass through the transfer station 65 ^■ the first -fixed toner image with the first color is superimposed (red) a second toner image with the second color (e.g., black), thus producing a two-color picture. The superimposed toner image is then fixed again in the fixing station 68 and the recording medium printed on one side is deposited in the stacking device 72.

Further details on the printing system according to FIG. 3 can be found in the already mentioned EP 0 699 315 AI, which is hereby incorporated into the disclosure content of the present patent application. ,

"Another application for the present invention for shrinkage compensation is given in the arrangement of printers as a twin system. Here two printers are coupled to one another in such a way that two printers carry out two printing processes in succession with an intermediate fixation and the second printer is the back of the paper. After the first printing, the fixing takes place, with the shrinkage effect occurring. Between the first printer and the second printer, a reversing device or a continuous device can be arranged. In this way, the previously described two-color simplex printing or duplex printing can be achieved with a twin printing system.

Figure 4 shows a printing unit with an LED character generator. A module plate 84 is arranged on a carrier 80 of the LED character generator 82 which is designed as a heat sink and which contains a large number of driver ICs (integrated integrated circuits) 86 and a line 88 with LEDs (light-emitting diodes) 90 carries. Each LED corresponds to a pressure point. The distance between the LEDs in line 90 corresponds to the desired resolution of the print image. The light emission surfaces of the LEDs are imaged on a photoconductor 94 using a glass fiber optic, a so-called Selfoc module 92 or a microlens array, on a scale of 1: 1. In this way, a latent electrostatic image is formed on the surface of the photoconductor 94 , which can be colored by a developer station with toner. Since there is a separate light source for each pixel of an exposure line 90, an entire pixel line on the photoconductor surface can be exposed at the same time without moving parts in the character generator by keeping all LEDs. _--

FIG. 5 shows an example of a shrinkage correction, with a compensation optics 96 being arranged between the Selfoc module 92 and the LED line .90 of the character generator 82 based on the example according to FIG. 4. that on the photoconductor surface 94 the line 90 depicted is reduced with LED luminous areas. Starting from a -: -. length L1 of the LED line 90, the image line depicted on the photoconductor surface 94 has a shortened length L2 due to the compensation optics 96 , For example, a cylindrical lens can be used as compensation optics 96. Alternatively, a plane-parallel optical plate can be used as the compensation optics, which is slightly curved in one axis by a tensioning device of the type of the compensation optics shown in FIG. The clamping device can clamp the optical plate at the edges. This curvature is then created by pressure on these edges. Alternatively, the optical disk can be displaced in the region of the central axis 98 by means of a clamping element in order to produce the curvature. The use of an optical plate has the advantage that the curvature to be set can take place depending on the degree of shrinkage of the recording medium in the line direction.

It can be seen in FIG. 5 that the optical imaging is slightly changed by inserting the compensation optics 96. Due to the imaging effect of the compensation optics 96, the light of each LED emanates from a virtual line 98, as can be seen for an LED in FIG. 5 using two beam paths 100, 102. Here, the beam path 100 is the one without compensation optics 96 and the beam path 102 is the one with compensation optics 96.

Figure 6 shows a further embodiment of the inventions ^■ fertil, wherein -for each printing operation is a change of the optical image. When the toner image is applied by means of a "first printing unit D1, the image dot lines are stretched with the aid of a first cylindrical lens 104 with a negative refractive power. In this case, the length. AI of an image dot line is increased to the length A2. Compression of the toner image, a cylindrical lens 106 with a positive refractive power shortening the length of a pixel line A3 to the length A4. Of course, plane-parallel plates can also be used in this example, the curvature of which is adjusted with the aid of a tensioning element as in the example according to FIG The total compensation for the shrinkage is therefore divided into two processes according to Figure 6. First, the toner image with the increased length A2 (greater than the length AI) is applied to the recording medium, and the shrinkage that occurs when this toner image is fixed leads to a reduction in the size When printing with the printing unit D2, a toner image with a further reduced length A4 is then applied. The advance caused by the cylindrical lens 104 distortion and the post-distortion caused by the cylindrical lens 106 overall compensates for the shrinkage effect.

As can be seen from FIG. 6, the shrinkage effect can also be compensated for by the fact that, during the printing process alone, a predistortion takes place in the printing unit D1, which corresponds to the degree of shrinkage that occurred during fixing. In the printing process on the printing unit D2, post-distortion is then not necessary. The overall effect is that the second toner image is applied to the recording medium in a form that is compressed compared to the first printing process.

Another way of compensating for the effect of the shrinkage is to act on the clock frequency with which an LED character generator according to the figure. 4 is controlled. After the first printing unit has applied a toner image to the recording medium and this "toner image together with the recording medium has passed through the fixing station, the shrinkage has to be taken into account when printing the second toner image. If this second toner image is applied to the through without If shrinkage is applied to shortened paper, and if this shrinkage later regresses, this second print image is extended in the respective main axes. Typical shrinkage values are 0.1 to 0.15% at 26% relative humidity of the carrier material Embodiment with otherwise the same transport speed of the carrier material as in the first printing process, the clock frequency is increased in the same ratio as the shrinkage that occurs compared to the first printing process. Conversely, the shrinkage that occurred during the subsequent fixing process can of course also occur in the first printing process Clock frequency are reduced in order to increase the line spacing between the lines at the same transport speed as in the second printing process.

In character generators with a single laser beam or with a laser beam fanned out into several partial beams, the photoconductor is exposed line by line using a polygon rotating mirror. The line frequency depends on the speed of the polygen rotating mirror. In order to cause compression of the toner image in the line feed direction, this speed can be increased while the transport speed of the carrier material is otherwise constant, as in the first printing process, in order to effect shrinkage compensation.

LED character generators and laser beam character generators are described in "The Printer Book" in Section 4 "Optical Character Generators", ISBN 3-00-001019-X, Edition 4a, May 1999, Oce Printing Systems GmbH. This document is hereby incorporated by reference into the disclosure content of the present patent application.

A dynamic shrinkage correction can advantageously be carried out. For this purpose, the degree of shrinkage is to be measured, for example by measuring the length and / or the width of a single sheet. In the case of tape material, this length can be determined, for example, using image masks. A light barrier can be used for length measurement, which is arranged in front of the second printing unit. For example, the time of the

Passed by a single sheet measured and deduced the length of this single sheet at a constant transport speed. Depending on the degree of shrinkage, the clock frequency when driving the character generator, the rotational speed of the rotating mirror or the deflection of a plane-parallel plate can then be set according to the examples in FIGS. 5 and 6. Preferably light barriers are arranged on each printing unit. The running time of the single sheet on the first printing unit Dl can be defined as the target running time. The deviation and thus the degree of shrinkage is then determined on the second printing unit D2 with respect to this target running time.

According to a further example of the invention, to compensate for the shrinkage, the transport speed of the recording medium in the second printing process can be reduced compared to the transport speed in the first printing process. It is also achieved in this way that the second toner image is applied to the recording medium in compressed form compared to the first printing process. For dynamic compensation of the shrinkage, the degree of shrinkage can - as mentioned before - be determined and, depending on this degree, the transport speed during the second printing process can be set. It is advantageous if the transport speed in the two printing devices is set by stepping motors. In this case, the signal frequency with which the stepper motors are driven can be changed depending on the degree of shrinkage in order to effect the shrinkage compensation.

The degree of shrinkage of the record carrier can advantageously also be determined empirically. In the second printing process, the compensation for the shrinkage is then set as a function of the empirically determined shrinkage, for example by adjusting the transport speed, the clock frequency of the

Character generator or the speed of the rotating mirror is changed or the deflection of the plane-parallel plates is set.

With reference to the examples according to FIGS. 1 to 3, the shrinkage compensation can advantageously be used. In the single sheet printing system according to FIGS. 1 and 2 Both the example according to FIGS. 5 and 6 relating to the compensation optics and the examples relating to the change in the clock frequency for the LED character generator, the change in the rotational speed of the rotating mirror in the case of a laser beam character generator or the change in the transport speed can be used. The same applies to the aforementioned twin system.

Numerous variants are possible for the examples described. Thus, the optical compensation along an axis, namely the line axis, can be combined with compensation in the axis perpendicular thereto, for example by changing the transport speed of the carrier material or the line frequency. Compensation measures acting in the same direction can also be combined, such as the line frequency change and the change in the transport speed. The .compensation measures can only be carried out on one printing device or can be distributed over both printing devices, if necessary also. with different compensation measures. - ';. ^~

Although preferred exemplary embodiments have been shown and described in detail in the drawings and in the preceding description, this should be regarded as purely exemplary and not as limiting the invention. It is pointed out that only the preferred exemplary embodiments are shown and described and all changes and modifications which are presently and in the future within the scope of protection of the invention are to be protected. LIST OF REFERENCE NUMBERS

10 high performance printers

Dl first printing unit

D2 second printing unit

12, 14 fuser stations

16 paper input

18 - 24 storage containers

26 paper input channel

27 transport channel

28 input section

30 paper outputs

32 - 36 output containers

38, 40 output channels - ^■ -

42 output section.

44, 46 transfer printing transport routes

48 connecting channel

50 - feed channel

52 discharge channel.

Wl - W6 switches:.

58 high-performance printing system

60 carrier material

61 intermediate supports

62 loading device

63 ^■ Character generator

64 developer station

65 transfer station

66 Cleaning station

67 unloading device

68 fuser

69 fuser roller

70 pressure roller

71 leadership roles

72 stacking device

73 storage area

74 feed rollers 75 Transport device

76 conveyor belt

77 drive shaft

78 deflection device

El, E2 developer zones

80 carriers

82 LED character generator

84 module plate

86 driver ICs

88 line

90 LEDs

92 Selfoc block

94 photoconductor

96 compensation optics

Ll, L2 length

98. central axis

100,, 102 beam paths -

104 cylindrical lens

AI, A2. length

106 cylinder lens

A3, A4 length

Claims

Expectations

1. A method for printing on a recording medium, in which a recording medium is printed with a first toner image in a first printing process, the first toner image is fixed on the recording medium in a fixing device (12, 14; 68), the recording medium being arranged along at least one main axis shrinks, and in which the same recording medium is subsequently printed with a second toner image in a second printing process, the second toner image being applied to the recording medium in a ^" compressed ^" form in relation to the first printing process in the direction of the main axis.

2. The method according to claim 1, characterized in that for applying the first toner image, a first printing device (Dl) and for applying the second toner image, a second printing device (D2) is provided that the second printing device (D2) after an elec- Trographic printing process works, in which a latent image is generated on an image carrier, which forms the second toner image after inking with toner, that the latent image is generated line by line in the transport direction of the image carrier, and that for generating the second toner image in a compressed form, the line spacing between the lines is reduced at the same transport speed as in the first printing process.

3. The method according to claim 2, characterized in that the latent image on the image carrier designed as a photoconductor is produced by exposure with a character generator (63, 82), that the character generator (63, 82) corresponds to the latent image line by line Line frequency generated, and that for generating the second toner image in compressed form, the line frequency is increased compared to the line frequency in the first printing process.

4. The method according to any one of the preceding claims 1 to 3, characterized in that in the second printing process for applying the second toner image in compressed form, the transport speed of the recording medium in the second printing device compared to the transport speed for the first printing. Operation is reduced.

5. The method according to claim 4, characterized in that the transport speed in the second printing device is set by stepper motors, and that the signal frequency with which the stepper motors are controlled is set depending on the degree of shrinkage.

6. The method according to any one of the preceding claims, characterized in that the degree of shrinkage of the record carrier is determined empirically, and that during the second printing process the reduced transport speed or the increased line frequency of the character generator (63, 82) in the second printing device is set depending on the empirically determined shrinkage.

7. The method according to any one of the preceding / claims, characterized in that the shrinkage is determined during the printing operation with the aid of detectors, and that in the second printing process the reduced transport speed or the line frequency of the character generator (63, 82) in the second printing device ( D2) is set depending on the determined shrinkage ".

8. The method according to claim 7, characterized in that in the case of a recording medium in the form of individual> older the length of the respective individual sheet is determined before being fed to the respective printing device, and that in the second printing process the reduction in the transport speed or the increase in Line frequency of the character generator (63, 82) in the second printing device (D2) is set depending on the length difference of the single sheet.

9. The method according to claim 7, characterized in that the length of the respective single sheet is determined using light barriers.

10.A method according to one of the preceding claims, characterized in that a second printing device (D2) for generating the second toner image works according to an electrographic printing method in which a latent image is generated on an image carrier, which, after inking with toner, forms the second toner image, that the latent image, as seen in the transport direction of the image carrier, is generated line by line by exposure with a character generator (63, 82), and that in at least one printing process for generating one of the toner images between the character generator ( 63, 82) and the image carrier a compensation optics (96) is arranged, which shortens the length of the line of the second toner image relative to the first toner image.

11. The method according to claim 10, characterized in that a cylindrical lens is used as the compensation optics (96), which is arranged between the character generator (82) and a Selfoc element (92).

12.The method according to claim 11, characterized in that the cylindrical lens is a plane-parallel optical plate which is arched in one axis by a clamping device. \

13. The method according to claim 12, characterized in that the clamping device clamps the optical plate at the edges.

14. The method according to claim 12, characterized in that the optical plate is displaced by a clamping element in the region of the central axis in order to produce the curvature.

15.The method according to any one of the preceding claims 10 to 14, characterized in that the curvature of the optical disc is adjusted in the line direction depending on the shrinkage of the record carrier.

16.The method according to any one of the preceding claims 10. to 15, characterized in that in the first printing device (DI) the first toner image is applied in a stretched shape in the direction of the main axis in the first printing process, in which shrinkage takes place in the fixing device. -

17. The method according to claim 16, characterized in that a cylindrical lens is used to apply the first toner image in stretched form, which causes the latent image on the image carrier to be stretched in the line direction.

18.The method according to any one of claims 16 or 17, characterized in that the cylindrical lens of the first printing device and no. Cylinder lens, the second printing device are constructed identically, and that the cylinder lenses of the two printing devices (Dl, D2) have opposite curvatures.

19.Device for printing on a recording medium, in which a recording medium is printed with a first toner image by a first printing device (DI) in a first printing process, the first toner image is fixed in a fixing device (12, 14; 68) on the recording medium, wherein the record carrier shrinks along at least one main axis, and in which the same record carrier is subsequently printed with a second toner image in a second printing process by a second printing device (D2), means are provided by which the second toner image is applied to the recording medium in the direction of the main axis in a form that is compressed compared to the first printing operation.

20. Device according to claim 19, characterized in that the second printing device (D2) works according to an electrographic printing method, - in which a latent image is generated on an image carrier, which forms the second toner image after coloring with toner, that the latent image is seen line by line in the transport direction of the image carrier, and that in order to produce the second toner image in compressed form, the line spacings between the lines are reduced at the same transport speed as in the first printing process.

21. Device according to claim 20, characterized in that the latent image on the image carrier designed as a photoconductor is generated by exposure with a character generator (63, 82), that the character generator (63, 82) corresponds to the latent image line by line Line frequency generated, and that for generating the second toner image in compressed form, the line frequency is increased compared to the line frequency in the first printing process.

22. Device according to one of the preceding claims 19 to 21, characterized in that during the second printing process for applying the second toner image in compressed form, the transport speed of the recording medium in the second printing device is is reduced compared to the transport speed during the first printing process.

23. Device according to claim 22, characterized in that the transport speed in the second printing device is set by stepper motors, and that the signal frequency with which the stepper motors are controlled is set depending on the degree of shrinkage.

24. Device according to one of the preceding claims, characterized in that the degree of shrinkage of the recording medium is determined empirically, and that in the second printing process. the reduced transport speed or the increased line frequency of the character generator (63, 82) in the second printing device is set depending on the empirically determined shrinkage.

25. Device according to one of the preceding claims, characterized in that the shrinkage during the printing operation is determined with the aid of detectors, and that the reduced transport speed or the line frequency of the character generator (63, 82) in the second printing device (D2) is dependent on the second printing process is set from the determined shrinkage.

26.The device according to claim 25, characterized in that in the case of a recording medium in the form of single sheets, the length of the respective single sheet is determined before being fed to the respective printing device, and that in the second printing process the reduction in the transport speed or the increase in the line frequency of the character generator (63, 82) in the second printing device (D2) is set as a function of the length difference of the single sheet.

27.The device according to claim 25, characterized in that the length of the respective single sheet is determined using light barriers.

28. Device according to one of the preceding claims, characterized in that the second printing device (D2) for generating the second toner image works according to an electrographic printing method, in which a latent image is formed on an image carrier, which forms the second toner image after inking with toner that the latent image seen in the transport direction of the image carrier - line by line. Expose with one. Character generator (63, 82) is generated, and that in at least one printing process for generating one of the toner images between the character generator (63, 82) and the image carrier, a compensation optics (96) is arranged, the length of the line of the second toner image relative to shortened first toner image.

29. Device according to claim 28, characterized in that a cylindrical lens is used as compensation optics (96), which is arranged between the character generator (82) and a Selfoc element (92).

30. Device according to claim 29, characterized in that the cylindrical lens is a plane-parallel optical plate which is arched in one axis by a clamping device.

3I. Claim 30, characterized in that the clamping device clamps the optical plate at the edges.

32. Establishment after. Claim 30, characterized in that the optical plate is displaced in the region of the central axis by a tensioning element in order to produce the curvature.

33. Device according to one of the preceding claims 28 to 32, characterized in that the curvature of the optical. Plate is set depending on the shrinkage of the recording medium in the line direction.

34. Device according to one of the preceding claims 24 to 33, characterized in that in the first printing device (Dl) - during the first printing process, the first toner image in a stretched form in the direction of the main axis, in which shrinkage takes place in the fixing device is applied.

35.The device according to claim 34, characterized in that a cylindrical lens is used to apply the first toner image in an elongated form, which causes the latent image on the image carrier to be stretched in the line direction.

36. Device according to one of claims 34 or 35, characterized in that the cylindrical lens of the first printing device and the cylindrical lens of the second printing device are constructed in the same way and that the cylindrical lenses of the two printing devices (D1, D2) have opposing curvatures.