DE102016117861A1 - Electrophotography station and method for generating a charge image without loading unit - Google Patents

Abstract

An electrophotography station (100) is described which, instead of a charging device (106) for charging the surface of an image carrier (101), comprises field generating means (401, 402) for generating an electric field (340) acting externally on the surface of the image carrier (101). having. By printing data-dependent exposure of pixels of the image carrier (101) under the action of the electric field (340) charge points (436) can then be generated on the surface of the image carrier (101) for an electric charge image. Thus, high-quality charge images can be efficiently produced on an image carrier (101).

Description

The invention relates to a digital printer for printing a recording medium. In particular, the invention relates to an apparatus and a method for generating a charge image on an image carrier.

In toner-based digital printers, particularly an electrographic printer, a latent image (particularly an electrical charge image) of an image carrier is colored with toner (e.g., liquid toner or dry toner). The resulting toner image is transferred directly from the image carrier or indirectly via a transfer station to a recording medium.

To generate a latent charge image, a typical image carrier with a charging device is charged to a loading potential. The latent image is then generated by pixel-wise unloading the image carrier. The charging of the image carrier by a charging device can lead to an inhomogeneous loading potential on the image carrier, whereby the quality of the printed image produced thereby can be impaired.

The present document addresses the technical problem of providing a method and an electrophotography station that can avoid print quality degradation due to image carrier loading.

The object is solved by the independent claims. Advantageous embodiments are described i.a. in the dependent claims.

In one aspect, an electrophotography station for a digital printer is described. The electrophotography station comprises an image carrier which is designed so that a latent charge image can be produced on a surface of the image carrier by exposure, which can be colored with toner in order to produce a printed image. The electrophotography station also includes field generating means arranged to generate an electric field applied externally to the surface of the image carrier. Furthermore, the electrophotography station comprises a character generator with N exposure units, which are set up to expose N pixels of a line of the latent charge image on the image carrier by generating N light beams under the action of the electric field to N charge points on the surface of the image carrier at the N pixels where N is a natural number with N> 0.

According to a further aspect, a method is described for generating a charge latent image on an image carrier, which is designed so that a latent charge image can be formed on a surface of the image carrier by exposure, which can be toned with toner to produce a printed image. The method comprises generating an external electric field acting on the surface of the image carrier. Furthermore, the method comprises exposing N pixels of a line of the latent charge image on the image carrier by N light beams under the action of the electric field, so that at the N pixels N charge points on the surface of the image carrier, where N is a natural number, with N> 0.

In the following, embodiments of the invention will be described in more detail with reference to schematic drawings. Show

1 a view of a digital printer in an exemplary configuration of the digital printer;

2 a schematic structure of a printing unit of the digital printer after 1 ;

3a exemplary potentials on an image carrier;

3b exemplary charge situations during the exposure of a charged image carrier;

4a exemplary charge situations during the exposure of a non-charged image carrier;

4b exemplary potentials on a non-charged image carrier; and

5 a flowchart of an exemplary method for generating a latent charge image on an image carrier.

According to 1 shows an exemplary digital printer 10 for printing a record carrier 20 one or more printing units 11a - 11d and 12a - 12d on, for example, each a toner image on the recording medium 20 print, and so a printed image 20 ' on the record carrier 20 produce. 1 shows a liquid toner based digital printer 10 , The aspects described in this document are analogously applicable to dry toner based printers or to ink jet based printers.

As a record carrier 20 can - as shown - a web-shaped record carrier 20 from a roll 21 with the help of a developer 22 unwound and the first printing unit 11a (continuously) are supplied. In a fuser unit 30 becomes the print image 20 ' on the record carrier 20 fixed. Subsequently, the record carrier 20 on a roll 28 with the help of a rewinder 27 be wound up. Such a configuration is also referred to as a roll-to-roll printer. Alternatively, sheet or sheet-shaped recording media 20 through the digital printer 10 be printed. Details of the in 1 illustrated exemplary digital printer 10 are in the patent DE 10 2013 201 549 B3 as well as in the corresponding patent applications JP 2014/149526 A and US 2014/0212632 A1 described. These documents are incorporated herein by reference.

The basic structure of a printing unit 11 . 12 is in the 2 shown. This in 2 shown printing unit based on the electrophotographic principle, in which a photoelectric image carrier (in particular a photoconductor 101 ) is dyed with the aid of a liquid developer with charged toner particles and the resulting toner image on the recording medium 20 is transmitted. The printing unit 11 . 12 consists essentially of an electrophotography station 100 , a developer station 110 and a transfer station 120 ,

Core of the electrophotography station 100 is a photoelectric image carrier having on its surface a photoelectric layer (a so-called photoconductor). The photoconductor is here as a roller (photoconductor roller 101 ) and has a hard surface. The photoconductor roller 101 turns on the various elements to create a print image 20 ' over (turn in the direction of the arrow).

The electrophotography station 100 includes a character generator 109 , which, depending on print data, a latent image on the photoconductor 101 generated. The latent image is passed through the developer station 110 dyed with (charged) toner particles to produce a colored image. The developer station 110 for this purpose has a rotating developer roller 111 put on a layer of liquid developer to the photoconductor 101 approach leads. The liquid developer comprises electrically charged toner particles in a toner carrier liquid, wherein the toner carrier liquid may comprise a mineral oil.

The inked image rotates with the photoconductor roller 111 to a first transfer point, where the inked image on a transfer roller 121 is substantially completely transferred and a toner image on the transfer roller 121 generated. The record carrier 20 runs in the transport direction 20 " between the transfer roller 121 and a counter pressure roller 126 therethrough. The contact area (Nip) represents a second transfer point in which the toner image is applied to the recording medium 20 is transmitted. The record carrier 20 may be made of paper, cardboard, cardboard, metal, plastic and / or other suitable and printable materials. More details about that in 2 illustrated exemplary printing unit 11 . 12 are in the patent DE 10 2013 201 549 B3 as well as in the corresponding patent applications JP 2014/149526 A and US 2014/0212632 A1 described.

Electrophotography printer 10 thus work with electrostatic forces that act on charged toner particles. The electrostatic forces on the toner particles are caused by electric fields. For the development of a latent image with toner, image and non-image spots are formed on the surface of the image carrier 101 charged differently to define corresponding attractive or repulsive forces for the charged toner particles. For this purpose, in a first process step, the surface of the image carrier 101 Charged with a uniform amount of charge (by using the charging device 106 ), leaving the surface of the image carrier 101 is raised to a uniform loading potential. Based on the character generator 109 become in dependence of the pressure data regarding the print image to be printed 20` individual pixels of the surface of the image carrier 101 at least partially unloaded to surface on the image carrier 101 to generate a latent charge image, which, via the locally different potentials, the print image to be printed 20` reproduces.

3a shows the potential of different areas or at different places / locations of the surface of an image carrier 101 , In particular, illustrated 3a the potentials that a region (eg a pixel) of the surface of the image carrier 101 during a process run consisting of charging, exposure and erasure. After charging the picture carrier 101 (represented by the arrow 323 ) by a charging device 106 is the surface of the image carrier 101 on the loading potential 314 , By the character generator 109 become individual pixels on the surface of the image carrier 101 illuminated (represented by the arrow 321 ) and thereby discharge, so that an exposed pixel on a development potential 312 located. The amount of development potential 312 typically depends on a gray level of a corresponding pixel of the print image 20` from. The development potential 312 is below a bias potential 313 the developer roller 111 , As a result, (charged) toner particles become the surface of the image carrier 101 pulled when an area of the surface of the image carrier 101 at the development potential 312 located. On the other hand, toner particles are repelled as the area of the surface of the image carrier 101 on the loading potential 314 located. In a subsequent to the toner transfer deletion is (by a erasing light 102 or by a corona) causes the surface of the image carrier 101 to a saturation potential 311 typically still below development potential 312 is arranged (represented by the arrow 322 ). So can the picture carrier 101 be prepared for the exposure with a new latent charge image.

The loading of the surface of the image carrier 101 takes place in the charging device 106 typically with a charge roller or with a non-contact corotron. In this case, for example, a non-contact corona by the generation and deposition of reaction products from the corona plasma contaminants on the charging device 106 produce. The impurities may unevenly on screen and wire of the charging device 106 settle and so can the charge flow to charge the image carrier 101 influence. This can lead to a streakiness of the surface charge (in the transport direction 20`` ) on the picture carrier 101 to lead. charging devices 106 with a charge roller can be achieved by the direct contact of an elastomer cover layer of the charge roller with the image carrier 101 have a decreasing due to the preferred direction of the charging current with time decreasing effect on the charging ability. In addition, especially when using liquid toner, impurities of the cover layer may come from substances of the carrier liquid of the liquid toner. Consequently, uneven charging of the image carrier may occur even when using a charge roller 101 be effected.

For corona-based charging devices 106 For example, glass sheath wires can be used to reduce sensitivity to wire contamination. This can be achieved in particular in that the glass sheath wires no longer serve as the actual charge source, but are used to build up the necessary field strength for igniting a corona, from the charges for charging the surface of the image carrier 101 can be deducted. Furthermore, soiling can be achieved by a suitable air flow in ventilated chambers of the charging device 106 and be reduced by a corresponding extraction of the reaction products. Nevertheless, an uneven charging of a picture carrier 101 typically only by a relatively frequent maintenance and / or cleaning of the charging device 106 reliably avoided.

3b makes a picture carrier 101 in cross-section dar. The image carrier 101 includes two blocking layers 331 . 333 , an intermediate photoconductive layer 332 and a (typically grounded) body 337 , The blocking layers 331 . 333 are designed such that the layer junctions between the blocking layer 331 and the photoconductive layer 332 as well as between the blocking layer 333 and the photoconductive layer 332 (similar to a diode) allow current to flow in a forward direction but block in a direction opposite to the forward direction. In particular, the blocking layers 331 . 333 in interaction with the photoconductive layer 332 the charge balance between the loaded surface of the image carrier 101 and the grounded body 337 effectively prevent, while the corresponding charge transport from the photoconductive layer 332 remains possible to a substantial extent. For example, negative charged particles from the photoconductive layer 332 to the surface of the image carrier 101 (ie from bottom to top, in the representation of 3b ) and positive charged particles from the photoconductive layer 332 in the opposite direction (ie from top to bottom, in the illustration of 3b ) to the main body 337 flow. The blocking layers 331 . 333 may be formed in a corresponding manner for charged particles having opposite polarities.

When exposing a pixel of the image carrier 101 (represented by the arrow 321 ) arise in the photoconductive layer 332 one or more electron-hole pairs 335 , By charging the surface of the image carrier 101 caused charge layer 334 (with positive charged particles) effected with the grounded body 337 an electric field 340 through which the negative charged particles (especially electrons) from the one or more electron-hole pairs 335 through the blocking layer 331 through to the surface of the image carrier 101 be pulled and unite there with the positive charged particles (reference character 336 ) and thus the potential of the surface of the image carrier 101 reduce locally. The same electric field 340 leaves the positive charges of the electron-hole pairs 335 to the main body 337 flow away. It is through the charge layer 334 with the main body 337 an internally effective electric field 340 that generates as a driving force on the photogenerated electron-hole pairs 335 acts.

In order to generate the latent charge image is thus with the character generator 109 Light irradiated in the photoconductor layer 332 Electron-hole pairs 335 generated in the electric field 340 between the charge applied by the load 334 and the grounded body 337 of the picture carrier 101 separate according to their polarity. With positive loading (as in 3b the electrons rise to the surface in order to compensate the charge, so that at these points the ground potential of the the body 337 comes to effect, after accordingly the positive charges through the blocking layer 333 on the main body 337 of the picture carrier 101 have drained off.

A similar effect can also be achieved without charging the surface of the image carrier by means of a charging device 106 be reached when the electric field 340 for the separation of the electron-hole pairs generated during the exposure 335 otherwise (ie without a charge layer 334 on the surface of the image carrier 101 ) is produced. For example, as in 4 represented an electric field 340 through an electrode 402 be effected in front of the surface of the image carrier 101 (ie without contact to the surface of the image carrier 101 ) is arranged. By dispensing with charging the surface of the image carrier 101 can thus on a charging device 106 be dispensed with, so that with an uneven charge the surface of the image carrier 101 related disadvantages can be avoided.

4a represents a section of an electrophotography station 100 dar. The electrophotography station 100 includes an electrode 402 and a voltage source 401 , where the voltage source 401 is set up, a potential difference between the electrode 402 and the body 337 of the picture carrier 101 to cause so over the cross section of the image carrier 101 an electric field 340 acts. It is through the electrode 402 with the main body 337 an externally defined electric field 340 that generates as a driving force on photogenerated electron-hole pairs 335 acts. When exposing a pixel of the image carrier 101 become the negative charged particles of the electron-hole pairs formed during the exposure 335 through the electric field 340 through the blocking layer 331 to the surface of the image carrier 101 pulled and form a locally located cargo point 436 at the exposed pixel (see the lower part of 4a ). Due to the blocking effect of the blocking layer 331 this local charge point remains 436 even after elimination of the external electric field 340 consist.

Thus, the electric field used to generate a latent image becomes 340 not by a surface load 334 but through an external field. The electrons of the electron-hole pairs 335 then neutralize no charge on the surface, but themselves form a charge point 436 (the one opposite the loading layer 334 out 3b having opposite polarity).

4b shows the potentials at different areas of the surface of the image carrier 101 , The surface of the image carrier 311 can default to a basic potential 411 (eg at the potential of the main body 337 or at the saturation potential 311 ) of the image carrier 101 are located. By exposure of a portion of the surface of the image carrier 101 (represented by the arrow 321 ) can be a charge point 436 on the surface of the image carrier 101 are generated, so that the potential at the exposed pixel is locally changed (eg reduced). In particular, the surface of the image carrier may be 101 at the point of loading 436 at a loading potential 412 with a value of the loading potential 412 typically depends on the print data. In particular, the charge amount of a charge point typically depends 436 and thus the loading potential 412 from the print data. The bias potential 413 a developer station 110 lies between the base potential 411 and the pixel-dependent loading potential 412 so that a reliable development of a latent charge image is made possible.

The polarity of the loading point 436 can by the layer structure and in particular the doping of the photoconductive layer 332 be adjusted. Thus, depending on requirements, the exposure of a pixel can be a positively charged charge point 436 or a negatively charged charge point 436 (as well as corresponding pixel-dependent loading potentials 412 ) are effected. The change of the polarity of the charge point 436 conditioned thereby also the change of the polarity of the external electric field 340 ,

The external field 340 for charge separation during the exposure of a pixel can thus assume both polarities and thus allows depending on the polarity of the toner particles, the realization of black or white writers. For this purpose, the photoconductive layer 332 adapted to the changed polarity (eg by doping).

The photoconductive layer 332 may include amorphous silicon (a-Si). The blocking layers 331 . 333 have together with the photoconductive layer 332 depending on a diode-like characteristic, which is caused by a charge point 436 by the flow of charged particles to the surface of the image carrier 101 can arise, the charged particles of the charge point 436 but can not drain again as soon as the outer field 340 disappears.

a-Si as a photoconductive material in the photoconductive layer 332 has the property that higher wavelength light relatively little in the photoconductive layer 332 penetrates. Consequently, the case is that the relatively slow positive charges to the surface of the image carrier 101 rise and accordingly the relatively fast electrons the longer way to the main body 337 Cover for the benefit Generation of a (positively charged) charge point 436 ,

To delete a latent image with charge points 436 An extinguishing corona (possibly in combination with an extinguishing light) can be used. So can the charged particles of the charge points 436 reliable and non-contact from the surface of the image carrier 101 be removed.

By eliminating a charging device 106 may be the number of components of an electrophotography station 100 be reduced, so that the number of possible sources of error in terms of print quality disturbances can be reduced. Furthermore, by eliminating the charging device 106 the cost (including operating costs) of a digital printer 10 be reduced.

Thus, this document becomes an electrophotography station 100 for a digital printer 10 described. The electrophotography station 100 includes a picture carrier 101 which is designed such that on a surface of the image carrier 101 can be generated by exposure a latent charge image that can be colored with toner to a printed image 20` to create. In particular, the image carrier 101 a photoconductive layer 332 with a photoconductive material (eg, amorphous silicon). By exposure of pixels of the image carrier 101 can then pixel-wise, isolated charge points 436 on the surface of the image carrier 101 are generated, which together represent an electric charge image. The electric charge image can be in a developer station 110 be developed with (charged) toner. Furthermore, the resulting developed toner image can directly or indirectly via a transfer station 120 as a print image 20` on a record carrier 20 to be printed.

The picture carrier 101 can be designed in particular as a roller whose lateral surface can be described at each revolution with a new latent charge image. Alternatively, the image carrier 101 be executed as (endlessly circulating) band. Thus, in a continuous manner, charge images and corresponding print images 20` be generated.

The electrophotography station 100 further comprises field generating means 401 . 402 that are set up from the outside to the surface of the picture carrier 101 acting electric field 340 to create. In particular, an electric field 340 be generated, already above the surface of the image carrier 101 acts. The electric field 340 can be caused by electrical charge that is not on the surface of the image carrier 101 itself, but above the surface of the image carrier 101 is arranged. Thus, in a robust manner, an electric field 340 be generated (even for long periods of operation of the electrophotography station 100 ). In particular, such an electric field 340 be generated, regardless of operational impairments of the image carrier 101 is.

In addition, the electrophotography station includes 100 a character generator 109 with N exposure units arranged by generating N light beams under the action of the electric field 340 N pixels of a line of the latent charge image on the image carrier 101 to expose. N is a natural number with N> 0 (eg N = 1, 2 or more, in particular N> 100, 1000, 10000). By the exposure of the N pixels are (in particular due to the photoconductive properties of the image carrier 101 ) at the N pixels N charge points 436 on the surface of the picture carrier 101 generated. The N exposure units typically become N pixels of a print image to be printed, depending on print data for N pixels 20` driven. In this case, the print data can in particular indicate the exposure times and / or the light intensities for the exposure of the N pixels (for example by specifying the gray levels of the pixels of the print image 20` ).

The exposure of N pixels allows charged particles of a first polarity in a photoconductive material of the image carrier 101 generated on the surface of the image carrier 101 N charge points 436 form with the first polarity. It is thus possible to generate a latent charge image that has charge points at exposed pixels 436 having charged particles of the first polarity and having no charged particles at unexposed pixels.

It thus becomes an electrophotography station 100 described that instead of a charging device 106 for charging the surface of an image carrier 101 (and for generating an electric field 340 ) Field generating means 401 . 402 for generating an externally on the surface of the image carrier 101 acting electric field 340 having. By printing data-dependent exposure of pixels of the image carrier 101 under the action of the electric field 340 can then charge points 436 on the surface of the image carrier 101 are generated for an electric charge image. So can efficiently create high quality charge images on an image carrier 101 be generated.

The outside of the surface of the image carrier 101 acting field 340 is generated simultaneously and spatially with the exposure of the N pixels. In other words, the field-generating means 401 . 402 are set up, the electric field 340 at a certain time in the field the surface of the image carrier 101 to generate in which the character generator 109 at the given time, the N pixels of a line of the latent charge image on the image carrier 101 exposed. The area where the electric field 340 is generated at the certain point in time, thus comprises the area of the N pixels on the surface of the image carrier 101 which are exposed at the given time. Thus, the exposure of the N pixels may be effected by the action of the field generating means 401 . 402 generated electric field 340 respectively.

The picture carrier 101 typically includes a photoconductive layer 332 and one between the surface and the photoconductive layer 332 arranged blocking layer 331 , The blocking layer 331 indicates a flow of charged particles of a first polarity from the photoconductive layer 332 to the surface has a lower resistance than for a flow of charged particles of the first polarity from the surface to the photoconductive layer 332 , For example, the resistance in the direction of flow to the surface may be greater by a factor of 10, 100 or more than the resistance in the reverse flow direction. In particular, the blocking layer 331 have a diode function, which is a flow of charged particles of the first polarity to the surface of the image carrier 101 and prevents a flow of charged particles of the first polarity in the opposite direction (substantially). Thus, reliably charged particles of the first polarity on the surface of the image carrier 101 held to the life of the charge image on the surface of the image carrier 101 to extend.

The photoconductive layer 332 is typically designed such that upon exposure of a pixel moving charge particles of the first polarity in the photoconductive layer 332 arise. In particular, pairs of (mobile) charged particles of the first polarity and of an opposite second polarity can be generated. In this case, the number of charged particles (or pairs of charged particles) generated typically depends on the number of photons with which a pixel is exposed (ie on the light intensity and / or the exposure time of a light beam).

The electric field 340 can be arranged, a force on the charged particles of the first polarity to the surface of the image carrier 101 to effect. In particular, the electric field 340 have a polarity that causes the charged particles of the first polarity to become the surface of the image carrier 101 down (and through the blocking layer 331 through), and so a charge point 436 of charged particles of the first polarity on the surface of the image carrier 101 is formed.

The first polarity can be a positive polarity and the N charge points 436 One line of the latent charge image may accordingly have a positive polarity. By using positively charged charged particles (which typically have a lower mobility than negatively charged charged particles (in particular electrons)), particularly (time-) stable charge images can be generated.

The picture carrier 101 may be one from the surface of the image carrier 101 remote (electrically conductive, especially metallic, and possibly grounded) basic body 337 exhibit. The field generating means 401 . 402 can be an over and / or on the surface of the image carrier 101 arranged electrode 402 include. Here is the electrode 402 typically arranged such that between the electrode 402 and the surface of the image carrier 101 an air gap is located. Furthermore, the field generating means 401 . 402 be set up, one between the electrode 402 and the body 337 running electric field 340 to create. For this purpose, the field generating means 401 . 402 a voltage source 401 which is arranged, a potential difference between the electrode 402 and the body 337 to create. So can reliably a homogeneous electric field 340 for generating a row of charge points 436 are generated for the latent charge image.

The field generating means 401 . 402 are thus preferably designed such that over a certain area of the surface of the image carrier 101 a substantially homogeneous electric field 340 is produced. The area can be the pixels of an entire line of a print image 20` comprise (transverse to the transport direction 20`` ). Furthermore, the area can be the pixels of several directly consecutive lines of the print image 20` include. To generate a homogeneous electric field 340 (ie an electric field 340 with a constant field strength over a certain area of the surface of the image carrier 101 ) can be an electrode 402 the field generating agent 401 . 402 one of the surface of the image carrier 101 have corresponding shape or contour to a consistently large gap between the electrode 402 and the surface of the image carrier 101 to effect. In particular, the electrode 402 when using a roller as image carrier 101 have a curved shape so that the electrode 402 the surface of the roller follows at a constant distance. This allows precise latent charge images to be generated.

The electrode 402 can thus generate a homogeneous electric field 340 a contour of the surface of the image carrier 101 consequences. With In other words, the electrode 402 can according to the contour of the surface of the image carrier 101 be shaped. The electrode 402 may then have a (transparent) area corresponding to that of the character generator 109 produced N light beams for exposing the N pixels of a line of the latent charge image on the image carrier 101 at least partially permeable. The transparent area may, for example, through an opening (eg a slot) in the electrode 402 or by the use of a transparent electrically conductive material (eg a tranparent conductive oxide, TCO) in the electrode 402 be formed. In this case, the transparent region is preferably bar-shaped transversely to the transport direction 20`` (ie along a line of the latent charge image). So can the character generator 109 starting from the surface of the image carrier 101 behind the electrode 402 be arranged to compactly the exposure by the character generator 109 and the generation of the electric field 340 through the electrode 402 in a common area on the surface of the image carrier 101 to overlay.

Preferably located between the electrode 402 and the surface of the image carrier 101 a gap, as such a wear of the surface of the image carrier 101 can be reduced. In principle, however, this can be done externally on the surface of the image carrier 101 acting electric field 340 also by one on the surface of the image carrier 101 grinding or rolling electrode 402 (ie through one, the surface of the image carrier 101 contacting electrode 402 ) be generated.

The picture carrier 101 may be one between the photoconductive layer 332 and the body 337 arranged second blocking layer 333 include. The second blocking layer 333 can for a flow of charged particles of the second polarity of the photoconductive layer 332 to the main body 337 have a lower resistance than for a flow of charged particles of the second polarity of the main body 337 to the photoconductive layer 332 , For example, the resistance in the direction of flow to the main body 337 by a factor of 10, 100 or more greater than the resistance in the reverse flow direction. In particular, the second blocking layer 333 have a diode function, which is a flow of charged particles of the second polarity to the main body 337 of the picture carrier 101 and prevents a flow of charged particles of the second polarity in the opposite direction (substantially). So can the life of the charge image on the surface of the image carrier 101 be extended.

The electrophotography station 100 typically includes an erase light 102 , which is set up (in particular by means of a corona and / or by means of a deletion light) the N charge points 436 from the surface of the image carrier 101 to remove the latent charge image. So can the picture carrier 101 be prepared reliably and gently for writing a subsequent charge image.

The electrophotography station 100 may further comprise moving means, which are arranged, the image carrier 101 on the one hand and the character generator on the other 109 and the erasing unit or erasing light 102 on the other hand relative to each other in a transport direction 20`` to move the line of the latent charge image from the character generator 109 to the extinguishing unit 102 to move. In this case, a line of the latent image is transverse to the transport direction 20`` and a column of the latent image in the transport direction 20`` , The character generator 109 is typically set up, sequentially different lines of N pixels on the surface of the image carrier 101 to expose, wherein a line of pixels is typically exposed at the same time. In this case, the total energy of the light beams for the exposure of the pixels for the different lines can be adjusted as a function of the print data. Thus, by the relative movement sequentially, line by line, latent charge images with N columns (in the transport direction 20`` ) and a large number of lines are generated. In this case, the pixels of a column are typically printed by an exposure unit (in a one-to-one relationship).

As already explained above, the N exposure units typically become dependent on print data for the print image 20` the print data indicating exposure durations and / or intensities of the N light beams for exposure of the N pixels. The picture carrier 101 may be formed such that with increasing exposure time and / or intensity of an exposure unit, an amount of charge of the charge points generated by the exposure unit 426 rises (and vice versa). Thus, charge images can be generated by the different shades of gray of a printed image 20` be represented.

5 shows a flowchart of an exemplary method 500 for generating a latent charge image on an image carrier 101 which is designed such that on a surface of the image carrier 101 can be generated by exposure a latent charge image that can be colored with toner to a printed image 20` to create.

The procedure 500 includes generating 501 one, from the outside to the surface of the image carrier 101 acting electric field 340 , In particular, an electric field 340 generated from above the surface of the image carrier 101 on the surface of the image carrier 101 acts. In this case, the electric field 340 be generated without the surface of the image carrier 101 to touch (in particular by a spaced electrode 402 ). In addition, the process includes 500 the exposure 502 of N pixels of a line of the latent charge image on the image carrier 101 by N light rays under the action of the electric field 340 , so that at the N pixels N charge points 436 on the surface of the picture carrier 101 arise, where N is a natural number, with N> 0. In other words, the N light rays for exposure of N pixels of the surface of the image carrier 101 hit the surface of the picture carrier 101 on while the electric field 340 acts on the N pixels of the surface. Thus, at the same place and at the same time on the surface of the image carrier, an exposure and an action of an external electric field occur 340 , Thus, a latent charge image can be reliably generated without prior loading.

LIST OF REFERENCE NUMBERS

10

Digital printer

11, 11a-11d

Printing unit (front side)

12, 12a-12d

Printing unit (back)

20

record carrier

20 '

Print image (toner)

20 "

Transport direction of the recording medium

21

Role (input)

22

liquidator

23

Konditionierwerk

24

turning unit

25

register unit

26

tensioning mechanism

27

rewinder

28

Role (Edition)

30

fuser

40

Cooling module

50

power supply

60

controller

70

fluid management

71

Fluid control unit

72

reservoir

100

Electrophotography station

101

Image carrier (photoconductor, photoconductor roller)

102

erasing light

103

Cleaning device (photoconductor)

104

Doctor (photoconductor)

105

Collecting container (photoconductor)

106

Charger (Korotron)

106 '

wire

106 '

umbrella

107

Supply air duct (ventilation)

108

Exhaust duct (ventilation)

109

character generator

110

developer station

111

developer roller

112

storeroom

112 '

hydration

113

antechamber

114

electrode segment

115

Dosing roller (developer roller)

116

Doctor blade (metering roller)

117

Cleaning roller (developer roller)

118

Squeegee (cleaning roller of the developer roller)

119

Collecting container (liquid developer)

119 '

liquid output

120

transfer station

121

transfer roller

122

Cleaning unit (wet chamber)

123

Cleaning brush (wet chamber)

123 '

Cleaning fluid intake

124

Cleaning roller (wet chamber)

124 '

Cleaning fluid discharge

125

doctor

126

Backing roll

127

Cleaning unit (counter pressure roller)

128

Collecting container (counter pressure roller)

128 '

liquid output

129

Loading unit (corotron on transfer roller)

311

saturation potential

312

discharge potential

313

Bias potential

314

loading potential

321

exposure

322

deletion

323

charging

331, 333

Blocking layer

332

photoconductive layer

334

stratified

335

Electron-hole pair

336

unloaded place

337

body

340

electric field

401

voltage source

402

electrode

411

ground potential

412

Pixel-dependent loading potential

413

Bias potential

436

Locally located cargo point

500

Method for producing a latent image

501, 502

steps

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102013201549 B3 [0017, 0021]
• JP 2014/149526 A [0017, 0021]
• US 2014/0212632 A1 [0017, 0021]

Claims (12)

Electrophotography station for a digital printer ( 10 ), wherein the electrophotography station ( 100 ), an image carrier ( 101 ) which is designed such that on a surface of the image carrier ( 101 ) can be generated by exposure a latent charge image that can be colored with toner to a printed image ( 20` ) to create; - field-generating means ( 401 . 402 ), which are arranged, from the outside to the surface of the image carrier ( 101 ) acting electric field ( 340 ) to create; and a character generator ( 109 ) with N exposure units which are set up by generating N light beams under the action of the electric field ( 340 ) N pixels of a line of the latent charge image on the image carrier ( 101 ) in order to obtain N charge points at the N pixels ( 436 ) on the surface of the image carrier ( 101 ) to create; where N is a natural number, where N> 0. An electrophotography station according to claim 1, wherein - the image carrier ( 101 ) a photoconductive layer ( 332 ) and between the surface and the photoconductive layer ( 332 ) blocking layer ( 331 ) having; The blocking layer ( 331 ) for a flow of charged particles of a first polarity from the photoconductive layer ( 332 ) has a lower resistance to the surface than for a flow of charged particles of the first polarity from the surface to the photoconductive layer ( 332 ); The photoconductive layer ( 332 ) is designed in such a way that upon the exposure of a pixel movable charge particles of the first polarity in the photoconductive layer ( 332 ) arise; and - the electric field ( 340 ) is applied, a force on the charged particles of the first polarity to the surface of the image carrier ( 101 ). An electrophotography station according to one of the preceding claims, wherein - the image carrier ( 101 ) one from the surface of the image carrier ( 101 ) remote body ( 337 ) having; - the field-generating means ( 401 . 402 ) one above or on the surface of the image carrier ( 101 ) arranged electrode ( 402 ); and - the field generating means ( 401 . 402 ), between the electrode ( 402 ) and the basic body ( 337 ) electric field ( 340 ) to create. An electrophotography station according to claim 3, wherein said field generating means ( 401 . 402 ) a voltage source ( 401 ), which is set up, a potential difference between the electrode ( 402 ) and the basic body ( 337 ) to create. An electrophotography station according to one of claims 3 to 4 with reference to claim 2, wherein - the image carrier ( 101 ) one between the photoconductive layer ( 332 ) and the basic body ( 337 ) arranged second blocking layer ( 333 ); The second blocking layer ( 333 ) for a flow of charged particles of a second polarity from the photoconductive layer ( 332 ) to the basic body ( 337 ) has a lower resistance than for a flow of charged particles of the second polarity of the main body ( 337 ) to the photoconductive layer ( 332 ); and - the second polarity and the first polarity are opposite to each other. An electrophotography station according to any one of claims 2 to 5, wherein - the first polarity is a positive polarity; and - the N charge points ( 436 ) have a positive polarity. An electrophotography station according to one of the preceding claims, wherein the electrophotography station ( 100 ), a deletion unit ( 102 ), which is set up, by means of a corona and / or by means of a deletion light the N charge points ( 436 ) from the surface of the image carrier ( 101 ) to clear the latent charge image; Movement means which are set up the image carrier ( 101 ) on the one hand and the character generator ( 109 ) and the deletion unit ( 102 ) on the other hand relative to each other in a transport direction ( 20`` ) to move the line of the latent charge image from the character generator ( 109 ) to the erasing unit ( 102 ) to move. An electrophotography station according to one of the preceding claims, wherein - the N exposure units depend on print data for the printed image ( 20` ) are controlled; The print data indicate exposure durations and / or intensities of the N light beams for exposure of the N pixels; and - the image carrier ( 101 ) such that, as the exposure time and / or intensity of an exposure unit increases, an amount of charge of the charge point generated by the exposure unit (FIG. 426 ) increases. An electrophotography station according to one of the preceding claims, wherein the image carrier ( 101 ) comprises amorphous silicon as the photoconductive material. An electrophotography station according to any one of the preceding claims, wherein the Field generating means ( 401 . 402 ), the electric field ( 340 ) at a certain time in the area of the surface of the image carrier ( 101 ) in which the character generator ( 109 ) at the certain point in time, the N pixels of a line of the latent charge image on the image carrier ( 101 ). An electrophotography station according to claim 10 with reference to claim 3, wherein - the electrode ( 402 ) a contour of the surface of the image carrier ( 101 ) follows; and the electrode ( 402 ) has a range that is appropriate for the character generator ( 109 ) generated N light beams for exposing the N pixels of a line of the latent charge image on the image carrier ( 101 ) is at least partially permeable. Method for generating a latent charge image on an image carrier ( 101 ) which is designed such that on a surface of the image carrier ( 101 ) can be generated by exposure a latent charge image that can be colored with toner to a printed image ( 20` ) to create; the method ( 500 ), - generating ( 501 ) one, from the outside to the surface of the image carrier ( 101 ) acting electric field ( 340 ); and - exposure ( 502 ) of N pixels of a line of the latent charge image on the image carrier ( 101 ) by N light rays under the action of the electric field ( 340 ), so that at the N pixels N charge points ( 436 ) on the surface of the image carrier ( 101 ) arise; where N is a natural number, where N> 0.

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