EP1783564A2

EP1783564A2 - Printing apparatus for transferring using heat

Info

Publication number: EP1783564A2
Application number: EP05292185A
Authority: EP
Inventors: Klaus Hense
Original assignee: Sagem SA
Current assignee: Sagemcom Documents SAS
Priority date: 2005-10-17
Filing date: 2005-10-17
Publication date: 2007-05-09
Anticipated expiration: 2025-10-17
Also published as: DE05292185T1; EP1783564A3; EP1783564B1

Abstract

In a printing apparatus, comprising a layer (3) which can be magnetized at least in sections, a first magnetizing device (1) with a first north-south polarization direction (4) for introducing a first magnetization direction (25) into the magnetizable layer (3), and a second magnetization device (2) with a second north-south polarization plane (17) for introducing a second magnetization direction (26) into the magnetizable layer (3), with the first magnetization device (1) and the second magnetization device (2) being provided for the predeterminable magnetization of a first position (22) of the magnetizable layer (3), with a displacement of the first position (22) to an effective region of the second magnetization device (2) being optionally provided, it is proposed for improving the print quality, especially the achievable resolution, that the first magnetization device (1) and the second magnetization device (2) are arranged in such a way that a first magnetization direction (25) can be produced at the first position (22) and/or a second magnetization direction (26) which is substantially normal to the first magnetization direction (25).

Description

The invention relates to a printing apparatus, comprising a layer which can be magnetized at least in sections, a first magnetizing device with a first north-south polarization direction for introducing a first magnetization direction into the magnetizable layer, and a second magnetization device with a second north-south polarization plane for introducing a second magnetization direction into the magnetizable layer, with the first magnetization device and the second magnetization device being provided for the predeterminable magnetization of a first position of the magnetizable layer, with a displacement of the first position to an effective region of the second magnetization device being optionally provided.
Printing apparatuses are known in which a magnetization apparatus magnetizes or writes a magnetizable area of a print drum, and thereafter magnetic toner is applied to said magnetized areas. Thereafter, the toner is then delivered to a part to be printed, such as a sheet of a paper. Prior to the renewed magnetizing, the magnetizable print drum is magnetized with a further magnetization device in the best homogeneous manner, with the previously magnetized areas being overwritten, which is why this process is also known as erasure. It is provided for in these known printing apparatuses that the north-south polarization plane of the magnetization apparatuses for writing and the magnetization apparatus for erasing are identical. It is provided for in conventional solutions that the north-south polarization plane is arranged substantially parallel to the surface of the print drum. As a result, the so-called Weiss domains of the magnetizable drum are arranged parallel to its surface. The written and erased areas differ substantially by the frequency with which they follow each other. It can be provided that the erased areas have a substantially higher frequency of the sequence of successive north-south transitions, as a result of which this area does not have any resulting magnetic field for coarse-grained toner.
The disadvantage in this known printing apparatus is that the same have a limited resolution as a result of the parallel alignment of the north-south transitions. Although an increase in the resolution is possible within a certain range by a reduction of the thickness of the magnetizable layer, this will lead to a decrease in the magnetic effect and thus the ability to bind the toner. By forming the erasure areas as areas with north-south transitions alternating at high frequency, it is only possible to use toner in such printing apparatuses which is coarse enough so as not to respond to said north-south transitions.
It is the object of the present invention to provide a printing apparatus of the kind mentioned above with which the mentioned disadvantages can be avoided and which allows an improvement in the printing quality, especially the achievable resolution, while offering an unchanging thickness of the magnetic layer.
This is achieved in accordance with the invention in such a way that the first magnetization device and the second magnetization device are arranged in such a way that a first magnetization direction and/or a second magnetization direction can be produced at the first position, and that the second magnetization direction is substantially right-angled to the first magnetization direction.
The achievable resolution can thus be increased considerably in a magnetizable printing apparatus without reducing the thickness of the magnetic layer. This allows using more fine-grained toner than in printing apparatuses with magnetization apparatuses arranged in one plane. The more fine-grained toner offers a higher sharpness, especially a higher contour sharpness and a further improved resolution. By changing the plane of the magnetization device during the writing process it is possible to use a substantially simpler structured writing unit because the unwritten areas remain unused during a writing or magnetization process.
In a further development of the invention it can be provided that the magnetizable layer is arranged in the region of a first surface of a preferably rotationally-symmetrical basic body, preferably that the first surface is formed by the at least one magnetizable layer. As a result, a magnetic image of an original can be transferred to a surface, from which this can then be transferred to a further medium. The use of a rotationally-symmetrical basic body (especially a drum or roller) allows realizing a simple revolving process.
In this connection it can be provided for in a further development of the invention that the first magnetization direction is arranged substantially normal to the first surface. A strong, but finely resolved stray field can thus be achieved, as a result of which toner can easily be absorbed at such places.
According to another embodiment of the invention it can be provided that a writing unit is provided, comprising at least one heat source acting upon the magnetizable layer for heating a writing area on the magnetizable layer to a temperature in the region of the curie temperature of the magnetizable layer. A predeterminable area for magnetization can thus be triggered in a purposeful manner.
One variant of the invention can be that the writing unit comprises at least a first cooling unit for cooling the writing area, which unit is provided downstream of the first heat source, and that the first magnetization device is associated with the first cooling unit and, especially after a heating of the writing area, acts upon the writing area to be cooled. A predeterminable magnetization can thus be applied upon the area heated by the first heat source.
It can be provided for in a further embodiment of the invention that an erasure unit is provided, comprising at least one second heat source acting upon the magnetizable layer for heating an erasure area on the magnetizable layer to a temperature in the region of the curie temperature of the magnetizable layer. A predeterminable area for magnetizing or erasing can thus be triggered.
It can be provided in a further development of the invention that the erasure unit comprises at least one second cooling unit for cooling the erasure unit downstream of the second heat source, and that the second magnetization device is associated with the second cooling unit, and, especially after a heating of the erasure area, acts upon the erasure area to be cooled. A predeterminable magnetization can thus be applied upon the area heated by the second heat source.
Another possible embodiment can be that the erasure unit is provided upstream of the writing unit. This ensures that the magnetizable layer has a defined magnetic state during the writing process, as a result of which it is possible to omit the magnetization of the areas not be printed, which allows providing the printing head with a substantially simpler configuration.
According to a further embodiment of the invention it can be provided that the first and/or second heat source comprise(s) at least one laser and/or at least one thermal resistance element. This allows a precisely defined heating of individual areas of the magnetizable layer and thus also a high resolution.
In this connection it can be provided for in a further development of the invention that the writing unit comprises in outgoing circuit at least one toner delivery element for delivering magnetic toner to the magnetizable layer. This allows the application of toner onto the magnetizable layer.
It can be provided for in a further development of the invention that toner transfer means for transferring magnetic toner to a medium to be printed are provided downstream of the toner delivery element, as a result of which a medium can be printed with toner.
It can be provided for in accordance with a further embodiment of the invention that the toner transfer means comprise at least one magnetic unit. This ensures a complete transfer of the toner to the medium to be printed. The printing density is thus increased, the consumption of toner is reduced and an additional cleaning of the magnetizable layer prior to the next writing process can be omitted.
The invention further relates to a printer with a printing apparatus in accordance with the invention, as a result of which all advantages of a printing apparatus in accordance with the invention can be used in a printer.
The invention further relates to a method for magnetizing a magnetizable layer, especially a magnetizable layer for a printing apparatus, preferably for a printing apparatus in accordance with the invention.
It is therefore the object of the present invention to provide a method of the kind mentioned above with which the initially mentioned disadvantages can be avoided and which allows an improvement of the print quality, especially the achievable resolution, whilst maintaining an even thickness of the magnetic layer.
This is achieved in accordance with the invention in such a way that the magnetizable layer is magnetized in a second magnetizing device and thereafter magnetized in sections in a first magnetizing direction which is substantially normal to the second magnetizing direction.
The achievable resolution can thus clearly be increased in a magnetic printing apparatus without reducing the thickness of the magnetic layer. It is thus possible to use a more fine-grained toner than in printing apparatuses with magnetizing devices arranged in one plane. As a result of the more fine-grained toner, it is possible to achieve a higher sharpness, especially a higher contour sharpness and a further improved resolution. As a result of the change of the plane of the magnetizing direction during the writing process it is possible to use a writing unit of simpler configuration because the areas not be written remain unaffected during a writing or magnetizing process.
In a further development of the invention it can be provided that the magnetizable layer is heated locally prior to magnetization to a temperature in the range of its curie temperature and is cooled during magnetization in a homogeneous magnetic field. A predeterminable area for magnetization can thus be triggered in a purposeful manner and a predeterminable magnetic field can be applied to said area.
The invention is explained in closer detail by reference to the enclosed drawings which show an especially preferable embodiment, wherein:

Fig. 1 shows a schematic representation of a preferred embodiment of a printing apparatus in accordance with the invention;
Fig. 2 shows an enlarged section of a basic body of a printing apparatus in accordance with Fig. 1, and
Fig. 3 shows a schematic representation of a further embodiment of a printing apparatus in accordance with the invention with special illustration of the magnetizable layer.

Figs. 1, 2 and 3 show especially preferred embodiments of a printing apparatus, comprising a layer 3 magnetizable at least in certain sections, a first magnetization device 1 with a first north-south polarization direction 4 for introducing a first magnetization direction 25 into the magnetizable layer 3, and a second magnetization device 2 with a second north-south polarization plane 17 for introducing a second magnetization direction 26 into the magnetizable layer 3, with the first magnetization device 1 and the second magnetization device 2 being provided for the predeterminable magnetization of a first point 22 of the magnetizable layer 3. Optionally, a displacement of the first point 22 to the effective region of the second magnetization device 2 is provided, with the first magnetization device 1 and the second magnetization device 2 being arranged in such a way that a first magnetization direction 25 and/or a second magnetization direction 26 can be produced at the first position 22, and that the second magnetization direction 26 is substantially right-angled to the first magnetization direction 25.
The achievable resolution can thus be clearly increased in a magnetic printing apparatus without reducing the thickness of the magnetic layer 3. It is thus possible to use more fine-grained toner than in printing apparatuses with magnetization directions 25, 26 arranged in one plane. The more fine-grained toner allows achieving a higher sharpness, especially a higher contour sharpness and a further improved resolution. By changing the plane of the magnetization direction 25, 26 during the writing process it is possible to use a writing unit 7 with a substantially simpler configuration because areas not to be written remain unaffected during a writing or magnetizing process.
This can be described in a further manner by a printing apparatus, comprising at least one layer 3 which is magnetizable at least in sections, a first magnetization device 1 with a first north-south polarization direction 4 for introducing a first magnetization direction 25 into the magnetizable layer 3, and a second magnetization device 2 with a second north-south polarization plane 17 for introducing a second magnetization direction 26 into the magnetizable layer 3, with the first magnetization device 1 and the second magnetization device 2 being provided for the predeterminable magnetization of at least one point 23 on a surface of the first point 22 of the magnetizable layer 3, with the first magnetization direction 25 enclosing at the first point 22 a first angle α relative to a first predeterminable tangent 24 through a first point 23, and that the second magnetization direction 26 which is caused by the second magnetization device 2 in the first point 23, optionally after a displacement of the first point 23 and the tangent 24 to an effective region of the second magnetization device 2, encloses in the first point 23 a second angle β relative to the tangent 24 which is optionally displaced together with the first point 23, and that the sum of the difference from the first angle α to the second angle β is substantially 90°.
Point 22 can be understood as being a region of the magnetizable layer 3 which comprises a spatial expansion which allows the occurrence of a first and/or a second magnetization direction 4, 17. A point 22 therefore preferably comprises the spatial expansion of two Weiss domains which are arranged relative to each other in close spatial proximity. This allows that both a first as well as a second magnetization direction 4, 17 occurs at the point 22. The first point 23 can concern a single molecular magnet, therefore the smallest spatial expansion in the magnetic sense.
The first angle α as well as the second angle β are determined in the mathematically positive sense, i.e. counter-clockwise, starting from the tangent 24 to the magnetizable layer in the first point 23.
The predeterminable tangent 24 can concern a straight line which can be predetermined freely in the space and which touches the magnetizable layer 3 in the first point 23. It is provided especially that the tangent 24 has an ascent in the first point 23 of the magnetizable layer. Especially in the case of a three-dimensionally changing magnetizable layer 3, this need not concern the largest ascent occurring locally at the first point 23. In the case of especially preferred embodiments of the present invention it can be provided that the tangent 24 has the highest possible ascent in the first point 23.
It can be provided in a printing apparatus in accordance with the invention that the first magnetization device 1 and the second magnetization device 2 are arranged at spatially different places which can be reached or triggered with the magnetizable layer 3. The invention relates to the arrangement of the magnetization direction 25 relative to the second magnetization direction 26 in the magnetizable layer 3. This can be independent of the spatial arrangement of the first magnetization device 1 relative to the second magnetization device 2. It may rather be provided that the first magnetization device 1 can assume any predeterminable position relative to the second magnetization device 2, such that by suitable displacement of the magnetizable layer 3 between the first magnetization device 1 and the second magnetization device 2 it can be achieved that the first magnetization direction 25 is or can be arranged substantially normal to the second magnetization direction 26.
Displacement can be understood as being a transport or a movement of the magnetizable layer 3, which is therefore a movement which brings the first point 22 from the first magnetization device 1 to the second magnetization device 2 or vice-versa. A movement of both the magnetizable layer 3 and/or the first and/or second magnetization device 1, 2 can be provided. There can also be a temporal sequence instead of a spatial change of location.
The printing apparatus in accordance with the invention can concern a printing apparatus for use in any kind of printer, such as printers for connection to computers, fax machines, calculating machines and/or cash registers, printers for measuring devices, printing machines for books and/or newspapers or the like. In accordance with the invention, the use can be provided with merely one colour such as black-and-white printers or with several colours. In this case, a printing apparatus in accordance with the invention must be provided in analogous multiple configuration of at least individual modules depending on the scope of colour.
It is provided for in a printing apparatus in accordance with the invention that a negative image of a copy to be printed is produced on a magnetizable layer 3, with the copy being formed by regions with different magnetic states, so-called written areas 19 and erased areas 20. At certain areas with a specific magnetic state it is possible that magnetic toner will adhere to the magnetizable layer 3 (written area 19), which can be passed on to a medium 15 to be printed, such as cellulose material like paper or cardboard, and/or textile fabric.
It can be provided for in preferred embodiments that the magnetizable layer 3 is arranged on a basic body 6. It is preferably provided that the magnetizable layer 3 is arranged in the region of a first surface 5 of the basic body 6, and/or that preferably the first surface 5 is formed by the magnetizable layer 3, of which there is at least one. The basic body 6 is preferably made of a material which is not magnetizable or only with difficulty such as plastic or a metal such as aluminium or non-magnetic special steel. The basic body 6 can have any shape. It can be provided especially that the basic body 6 has a shape diametrically opposed to the medium 15 to be printed, such as the shape of a plane plate. It can be provided for preferably that the basic body 6 is rotationally symmetrical. It can also be provided that the shape can be provided diametrically opposed to a medium to be printed, e.g. in form of a barrel, a cylinder or roller and/or a cone or truncated cone. The rotationally symmetrical configuration of the basic body 6 allows realizing an especially simple process sequence with a printing apparatus in accordance with the invention, with an image being applied to a position of a rotating basic body 6. At a further position, the toner can be applied to the respectively described areas 19 of the basic body 6. At another position the toner can be supplied to the medium 15 to be printed. Prior to the application or writing of a further image it is possible to erase the preceding image, e.g. by producing a defined magnetization state which is as even as possible over the entire width and/or surface of the basic body 6.
It is provided for in a printing apparatus in accordance with the invention that an image of a picture to be printed is applied onto the magnetizable layer 3. A homogeneous magnetization is preferably applied to the magnetizable layer 3. Since all images which may previously have been applied onto the magnetic layer 3 are erased, this process can also be designated as erasure. The respective areas of homogeneous magnetization are designated as erased areas 20. An image of a picture to be printed is formed in a printing apparatus in accordance with the invention by the written areas 19. The written areas 19 have magnetic states which differ from the magnetic states of the erased areas 20. Only areas are written on which are provided for in the printing process for blackening or colouring. The areas not to be printed which are not provided for blackening or colouring maintain their magnetic state. It can be provided for in particular that the written areas 19 which are part of an image comprise a first magnetization direction 25 which is arranged substantially normal to the first surface.
In contrast to this it can be provided that the erased areas 20 which are not part of the image or which are indirectly part of the image as erased areas 20 not to be printed but shall remain white in the finished picture comprise a second magnetization direction 26 which is arranged substantially normal to the first magnetization direction 25. It is provided for in particular that the second magnetization direction 26 is arranged substantially parallel to the first surface 5. It is preferably provided that prior to the application of the image onto the magnetizable layer 3, the magnetizable layer 3 is applied with a substantially homogeneous magnetic second magnetization direction 26 substantially parallel to the first surface 5. A continuous magnetic field is thus formed which hardly contains any stray fields and thus does not attract any magnetic toner.
In an especially preferable embodiment, a writing unit 7 for applying the image onto the magnetizable layer 3 and/or an erasing unit 10 for producing the best possible homogeneous magnetic polarization or magnetization direction 25, 26 are provided, with the erasing unit 10 preferably being upstream of the writing unit 7.
The writing unit, of which there is at least one, preferably comprises at least a first heat source 8 acting upon the basic body 6 for heating a writing area 9 on the first surface 5, to a temperature in the range of the curie temperature of the magnetizable layer 3. By heating the magnetizable layer 3 in a writing area 9 to a temperature in the range of the curie temperature, said heated area will become non-magnetic spontaneously. This allows providing the area during the cooling in a defined magnetic field with a magnetic north- south polarization plane 4, 17 or a first magnetization direction 25 and/or a second magnetization direction 26. It is therefore preferably provided that the writing unit 7 comprises at least a first cooling unit for cooling the writing area 9, which cooling unit is downstream of the first heat source 1, and that the first magnetization device 1 is associated with the first cooling unit and acts upon the writing area 9 to be cooled off. It has been noticed that for applying a predeterminable first or second magnetization direction 25, 26 with a predeterminable magnetic north- south polarization plane 4, 17 it is not necessary to heat the magnetizable layer 3 over its curie temperature. It can be sufficient on the other hand when the achieved temperature is approx. 85 to 90% of the curie temperature.
A writing area 9 is preferably an area which is intended for printing and which is therefore written with the data belonging to a picture or an image, or which should be capable of being written with such data. The writing area 9 can have a different spatial expansion depending on the type and the application.
The first magnetization device 1 can be formed by each arrangement emitting a magnetic field. It can be provided that the first magnetization device 1 comprises at least one permanent magnet and/or an arrangement of such a one. It can also be provided that the first magnetization device 1 comprises at least one electromagnet and/or an arrangement of such a one. A combination of permanent magnet and electromagnet can be provided. It is preferably provided that the magnetic effect is limited to the narrowest possible area, with the first magnetization device 1 being configured accordingly. One advantage of the invention is that a focussing of the magnetic effect to individual pixels can be omitted. One feature of the first magnetization device 1 is the first north-south polarization plane 4, which therefore leads to the alignment of the magnetic field generated by the first magnetization device 1.
The first heat source 8 is preferably configured in such a way that it allows a predeterminable heating of individual areas on the magnetizable layer 3. Since the first magnetization direction 25 is changed in the direction of the magnetic first north-south polarization plane 4 during the subsequent cooling in the magnetic field of the first magnetization device 1 in each area heated by the first heat source 8, every heated area will receive toner and cause a blackening on the medium 15 to be printed. The fineness with which individual areas can be heated on the magnetizable layer 2 is therefore directly proportional to the achievable printing resolution. As a result of the alignment of the first magnetization direction 25 normal to the first surface 5, the resolution is additionally increased relative to a printer with identical magnetization directions in the described areas 19 and the erased areas 20.
It can preferably be provided that the first heat source 8 comprises at least one laser and/or at least one thermal resistance element. Preferably, means are provided which allow a predeterminable heating of every possible pixel to be written. A predeterminable number of lasers with respective focussing apparatuses or at least one thermal resistance element per pixel to be printed can be provided for heating a pixel individually provided for printing.
It can be provided that upon operation of the printing apparatus, the basic body 6 performs a relative movement to the writing unit 7 or is provided for such a relative movement, such that the writing unit 7 is moved past the basic body 6 or the first surface 5, or vice-versa. This is provided especially in the case of specially preferred embodiments with a rotationally-symmetrical basic body 6. It can also be simply be implemented by rotating the basic body 6.
It can therefore be provided in embodiments in which the basic body 6 carries out a relative movement towards the writing unit 7, especially when the writing unit 7 is guided over the first surface 5 such as in the longitudinal direction of a printing area, that lasers or thermal resistance elements are arranged merely for heating at least one row of pixels along the maximally provided printing width.
As a result, the entire provided printing width can be printed with the maximum possible resolution in a preferred embodiment. It can also be provided (e.g. in the case of special applications where no constant resolution is required over the printing width) that the type, configuration and density of the employed thermal resistance elements is not constant over the width of the printing area or is provided with a different configuration in sections.
The erasure unit 10, of which there is at least one, can be preferably configured substantially equivalent to the at least one writing unit. The erasure unit 10 therefore preferably comprises at least one second heat source 11 acting upon the basic body 6 for heating an erasure area 12 on the first surface 5, to a temperature in the range of the curie temperature of the magnetizable layer 3, and a second cooling unit for cooling the erasure area 12, which cooling unit is provided downstream of the heat source 11, with the second magnetization device 2 being associated with the second cooling unit and acting upon the erasure area 12 to be cooled.
Erasure shall be understood as producing the best possible homogeneous second magnetization direction 26 or a homogeneous north-south polarization of the magnetizable layer 3, substantially over the entire printing area. Erasure area 12 shall be understood as the area which is respectively erased. This can concern the entire surface to be printed, or it can also preferably be provided (especially in embodiments in which the erasure unit 10 is or should be moved relative to the basic body 6 like a writing unit 7) that the erasure area 12 merely assumes a partial area of the surface to be printed, especially a partial area extending over the width of a basic body 6 movable in the longitudinal direction relative to the erasure unit 10.
With respect to type and configuration, the second heat source 11 can have any type and configuration as described above in connection with the explanation of the first heat source 8. However, the second heat source 11 can be provided with a configuration which is less focussing, because a precise heating of individual defined pixels need not be necessary during erasure.
The second magnetization device 2 can be configured with respect to its type and configuration in an equivalent manner to the first magnetization device 1. It can be provided with a configuration which is less focussing.
Fig. 1 shows a highly schematic view of an especially preferred embodiment of a printing apparatus in accordance with the invention, with the basic body 6 being rotationally symmetrical. The printing apparatus is shown in a projecting manner towards the longitudinal extension of the basic body 6. The individually shown modules are merely shown schematically in an exemplary manner. The dimensions, proportions and the precise position at which the individual components are arranged are merely exemplary and can depart from the illustrated dimensions, proportions and the precise position.
It is provided for in the illustrated embodiment that the basic body 6 moves clockwise in operation, i.e. it moves according to the illustrated arrow 18. At one point of the basic body 6, which is the top position in Fig. 1, the writing unit 7, of which there is at least one, is arranged.
This is symbolized by a cuboid shown with the broken line. The writing unit 7 comprises the first heat source 8 which acts upon the writing area 9 shown with the dotted line. The writing unit 7 further comprises the first cooling unit. It can simply concern an area which is not heated. It is also possible that a ducted cooling is provided for the writing area 9 which is heated above by the first heat source 8. In the region of the cooling unit (therefore in a simple embodiment in a writing area 9 for cooling the same as heated by the first heat source 8), a first magnetization device 1 is arranged which acts upon the magnetizable layer 3 with a magnetic field with the first north-south polarization plane 4. As a result, the writing area 9 which is heated above to a temperature in the range or over the curie temperature cools off in a homogeneous magnetic field, as a result of which the first north-south polarization plane is applied to the writing area 9 and has the first magnetization direction 25. Fig. 1 clearly shows how the first magnetization device 1, which is shown symbolically by a bar magnet, is arranged with a first north-south polarization plane 4 normal to the first surface.
In especially preferred embodiments like the embodiment shown in Fig. 1, the writing unit 7 is provided downstream with at least one toner delivery element 13, for supplying magnetic toner to the magnetizable layer 3. It can be provided in this respect that the toner delivery element 13 comprises means for the purposeful delivery of magnetic toner to the written areas. It should thus prevent that toner is delivered to erased areas 20, which should hardly be given anyway as a result of the substantially lower stray field in the erased areas 20.
In especially preferred embodiments like the embodiment shown in Fig. 1 it can be provided that the toner delivery element 13 is provided downstream with toner transfer means 14 for transferring magnetic toner to a medium 15 to be printed. Such toner transfer means 14 can be formed in a simple embodiment by a roller or the like, which press the medium 15 to be printed (which in a simple embodiment can be a sheet of paper) against the basic body 6 and thus against the toner-adhering magnetizable layer 3. In order to achieve an especially residue-free removal of the magnetic toner from the magnetizable layer it can be provided for in especially preferred embodiments that the toner transfer means 14 comprise at least one magnetic unit 16. The magnetic unit 16 supports the transfer of the toner from the magnetizable layer 3 to the medium 15 to be printed. As a result, it is possible in preferred embodiments of the invention to substantially omit further means such as brushes, wipers or the like for removing excessive toner, which thus simplifies an especially preferred embodiment even further.
The erasure unit 10, of which there is at least one, is arranged before the writing unit 7 as seen in the process direction. The erasure unit 10 is arranged at the lowermost position in Fig. 1. The erasure unit 10 is symbolized by a cuboid shown with the broken line. The erasure unit 10 comprises the second heat source 11 which acts upon the erasure area 12 illustrated with the dotted line. The problems to be solved by the erasure unit 10 and the embodiments thereof have already been explained above.
It has proved to be especially advantageous when the distance of the erasure unit 10 from the writing unit 7 is as large as possible. As a result, the area 20 which is polarized and/or erased uniformly parallel to the first surface 5 will become especially large on the basic body 6. A uniform magnetic field is formed in the erased area 20 which hardly has a stray field.
Fig. 2 shows a strongly enlarged schematic representation of a preferred embodiment of a basic body 6 with a magnetizable layer 3 which forms a first surface 5. The thin magnetizable layer 3 can clearly be seen, which layer is between 100 nm and 200 µm, especially between 1 µm and 20 µm, and preferably between 5 µm and 15 µm. The respective prevailing first or second magnetization direction 25, 26 is illustrated by small arrows. The erased area 20 with its uniform second magnetization direction 26 parallel to the first surface 5 can clearly be seen. Further to be seen is the demagnetization area 21 which at the respective point in time is heated over the curie temperature, as well as the adjacent written areas 19 with the first magnetization direction 25 which is arranged normal to the first surface 5.
Fig. 3 shows a further strongly schematic illustration of the magnetizable layer 3 of a printing apparatus in accordance with the invention, comprising a first magnetization device 1 and a second magnetization device 2 which are arranged parallel with respect to each other. With respect to the surface of the magnetizable layer 3, the first magnetization device 1 and the second magnetization device 2 are arranged in such a way that the first magnetization direction 25 which is caused by the first magnetization device 1 in the magnetizable layer 3 is arranged normal relative to the second magnetization direction 26 which is caused by the second magnetization direction 2.
The magnetizable layer 3 is magnetized in a second magnetization direction 26 by the second magnetization device 2 at a first point 22 which is illustrated by an area marked with a broken line. The magnetizable layer 3 continues to move according to the direction of the arrow 18, as a result of which the first point 22 is moved or displaced to the effective environment of the first magnetization device 1. The first magnetization device 1 magnetizes the magnetizable layer 3 at the first point in a magnetization direction 25. In the region of the first magnetization device 1, an arrow indicating the first magnetization direction 25 and an arrow indicating the second magnetization direction 26 are shown extended to such an extent that they intersect. It can clearly be seen that they enclose an angle substantially of approx. 90°. The respective arrow illustrating the first magnetization direction 25 is further extended to such an extent that the first angle a can be recognized which encloses the first magnetization direction 25 relative to tangent 24 in the first point 23. Since the second north-south polarization plane 17 of the second magnetization device 2 is arranged parallel to the tangent 24 in the first point 23 closest to the second magnetization device 2, and therefore the second magnetization direction 26 is arranged parallel to tangent 24, the second angle b which the second magnetization direction 26 encloses to tangent 24 is zero in this illustrated embodiment. The amount of the difference of the first angle α and the second angle β is therefore substantially 90° or π/2. It is also possible to provide other arrangements of the first magnetization device 1 and the second magnetization device 2.
According to method in accordance with the invention for magnetizing a magnetizable layer 2, especially a magnetizable layer for a printing apparatus, it is provided that the magnetizable layer 3 is magnetized in a second magnetization direction 26, and is magnetized thereafter in sections in a first magnetization direction 25 which is substantially normal to the second magnetization direction 26. It can be provided in particular that the magnetizable layer 3 is heated prior to magnetization locally in the range of its curie temperature and is cooled during magnetization in a homogeneous magnetic field.
Further embodiments can be obtained by a combination of individual or all features of the described embodiments.

Claims

A printing apparatus, comprising a layer (3) which can be magnetized at least in sections, a first magnetization device (1) with a first north-south polarization direction (4) for introducing a first magnetization direction (25) into the magnetizable layer (3), and a second magnetization device (2) with a second north-south polarization plane (17) for introducing a second magnetization direction (26) into the magnetizable layer (3), with the first magnetization device (1) and the second magnetization device (2) being provided for the predeterminable magnetization of a first position (22) of the magnetizable layer (3), with a displacement of the first position (22) to an effective region of the second magnetization device (2) being optionally provided, characterized in that the first magnetization device (1) and the second magnetization device (2) are arranged in such a way that a first magnetization direction (25) and/or a second magnetization direction (26) can be produced at the first position (22), and that the second magnetization direction (26) is substantially right-angled to the first magnetization direction (25).
A printing apparatus according to claim 1, characterized in that the magnetizable layer (3) is arranged in the region of a first surface (5) of a preferably rotationally-symmetrical basic body (6), preferably that the first surface (5) is formed by the magnetizable layer (3), of which there is at least one.
A printing apparatus according to claim 1 or 2, characterized in that the first magnetization direction (25) is arranged substantially normal to the first surface (5).
A printing apparatus according to one of the claims 1 to 3, characterized in that a writing unit (7) is provided, comprising at least one heat source (8) acting upon the magnetizable layer (3) for heating a writing area (9) on the magnetizable layer (3) to a temperature in the region of the curie temperature of the magnetizable layer (3).
A printing apparatus according to claim 4, characterized in that the writing unit (7) comprises at least one cooling unit for cooling the writing area (9), which unit is provided downstream of the first heat source (1), and that the first magnetization device (1) is associated with the first cooling unit and, especially after a heating of the writing area (9), acts upon the writing area (9) to be cooled.
A printing apparatus according to one of the claims 1 to 5, characterized in that an erasure unit (10) is provided, comprising at least one second heat source (11) acting upon the magnetizable layer (3) for heating an erasure area (12) on the magnetizable layer (3) to a temperature in the region of the curie temperature of the magnetizable layer (3).
A printing apparatus according to claim 6, characterized in that the erasure unit (10) comprises at least one second cooling unit for cooling the erasure area (12) downstream of the second heat source (11), and that the second magnetization device (2) is associated with the second cooling unit, and, especially after a heating of the erasure area (12), acts upon the erasure area (12) to be cooled.
A printing apparatus according to claim 6 or 7, characterized in that the erasure unit (10) is provided upstream of the writing unit (7).
A printing apparatus according to claim 6, 7 or 8, characterized in that the first and/or second heat source (8, 11) comprise(s) at least one laser and/or at least one thermal resistance element.
A printing apparatus according to one of the claims 4 to 9, characterized in that the writing unit (7) comprises in outgoing circuit at least one toner delivery element (13) for delivering magnetic toner to the magnetizable layer (3).
A printing apparatus according to claim 10, characterized in that toner transfer means (14) for transferring magnetic toner to a medium (15) to be printed are provided downstream of the toner delivery element (13).
A printing apparatus according to claim 11, characterized in that the toner transfer means (14) comprise at least one magnetic unit (16).
A printer with a printing apparatus according to one of the claims 1 to 12.
A method for magnetizing a magnetizable layer (3), especially a magnetizable layer for a printing apparatus, preferably according to one of the claims 1 or 12, and/or a printer according to claim 13, characterized in that the magnetizable layer (3) is magnetized in a second magnetizing device (26), and thereafter magnetized in sections in a first magnetizing direction (25) which is substantially normal to the second magnetizing direction (26).
A method according to claim 14, characterized in that the magnetizable layer (3) is heated locally prior to magnetization to a temperature in the range of its curie temperature and is cooled during magnetization in a homogeneous magnetic field.