EP0756544B1 - Thermoelectric printing unit for transferring ink to a print carrier - Google Patents

Description

The invention relates to a thermoelectric printing unit for Transfer of an ink to a recording medium. It Various thermoelectric printing units are known:

Thermal printing uses thermosensitive paper with a heatable print head by heating selected areas of the Printed on paper by discoloring the warmed areas.

In the thermal transfer printing process, one is on a carrier film existing, color-containing wax layer with the help of heatable printing elements partially melted and on paper transfer.

In a thermal ink printing unit, ink is applied from a nozzle injected a record carrier. The nozzles have one Heating device that can be activated individually for each nozzle is. The ink contained in the nozzle is removed by the heater warmed, creating a gas bubble that the Ejects ink from the nozzle.

A liquid, the color pigments, serves as the ink contains. It is also heat-resistant up to approx. 350 ° C non-toxic - e.g. water-based - and does not cause any deposits in the nozzles.

The nozzles are usually located in a print head. Of the Printhead has an ink supply from which the nozzles are supplied with ink by capillary forces. The maximal Spray frequency of such ink printing units with thermoelectric Converter (bubble-jet) is limited to approx. 4 kHz. Depending on Drop size requires the ink 250µs and more, until the through Capillary suction of ink for the next spraying process is available. The activation time for the heating element in the nozzle of approx. 5 to 10µs and the time until In contrast, droplet formation of approx. 50µs is relatively short. The In principle, the spray frequency cannot be increased significantly.

From US 4,785,311 a cylindrical pressure roller is known the jacket of which a plurality of arranged in a matrix Has openings for a highly viscous ink. The Ink is stored inside the platen. Every passage opening is a selectively controllable heating element assigned, with the help of a flow of ink through the passage opening can be released. The released ink flows directly to you due to gravity Record carrier that is in contact with the corresponding, in the area of the approved passage opening surface of the platen roller.

With the known printing roller, the printing speed can increase. Due to the principle-related immediate There is contact of the printing roller with the recording medium the risk that the through-openings become dirty and as a result the quality of the printed image is reduced. In addition, it is through the direct contact between Print roller and recording medium absolutely necessary the passage openings according to the print image resolution to be arranged on the printing roller as an endless matrix. Thereby the fineness of the print image resolution is limited because a large number of through openings electrically a control unit must be coupled and the coupling paths cannot be reduced to any size. Through stockpiling the ink in the platen is a change of ink extremely difficult using the same platen roller noticeable.

The present invention is based on the object thermoelectric printing unit for transferring an ink to show a record carrier that allows the Print speed without loss of print resolution, the print image quality and the maintainability of the thermoelectric Conditional printing unit.

This object is achieved by the specified in claim 1 Features resolved. Developments and refinements of Invention are specified in the subclaims.

By arranging more than one matrix line of printing elements on a printing drum and filling it with Ink from the surface of the print drum is largely at any print image resolution a high print image quality while increasing the printing speed reachable. By exchanging the circumference of the printing drum arranged inking station can change the color of the printed image can be changed easily. The increased printing speed is due to the multiple arrangement of the printing elements reachable. This can take the time to refill the Ink in the printing elements, as well as thermal stabilization take a relatively long time. They are spray frequencies reachable from 20kHz. Through a so-called overlapping The control of two matrix lines is the spray frequency Can be increased to over 40 kHz. With overlapping control a subsequent spraying process is already initiated, while a current spraying process is taking place. The matrix rows of printing elements arranged on the printing drum with the heating elements inside and for the Power supply lines required are with the help of Manufacturing techniques known from semiconductor technology are producible.

According to an embodiment of the invention the inking station on a distributor roller, the surface rolls tangentially on the surface of the printing drum. The The distributor roller is partially immersed in one along the distributor roller extending tub filled with ink a. The ink can thereby over the entire longitudinal extent the print drum evenly dosed to the print drum brought up and filled into the pressure elements.

According to a development and embodiment of the invention the rolling area of the distributor roller on the printing drum in Downstream of the direction of movement of the printing drum is a squeegee, which extend along the surface of the printing drum stretches and wipes excess ink off the surface. This causes excess ink to enter the inking station returned. The surface of the printing drum is from any ink residue is cleaned. The cleaning effect is by the design of the invention, after which the lateral surface the printing drum by a hydrophobic and / or oliophobic Protective layer is formed, supported. Whether the hydrophobic and / or the oliophobic protective layer is selected from depending on the ink used.

By developing the invention, according to which the scope of the Printing drum a cleaning station that can be used with the Surface of the printing drum can be contacted is, the printing drum can be in larger printing pauses or in any necessary cleaning intervals of adherent Ink or dirt.

According to a further development and configuration of the Invention is the record carrier as an intermediate carrier formed on the area of a counter pressure device a printing material rolls off, whereby the printed image on the Substrate is transferable. Through the intermediate carrier direct influence of the printing material, for example Paper on which the print drum can be prevented. The reliability of the printing unit and the quality of the printed image can thereby further increased. The life of the print drum can also be increased. Preferably the Intermediate carrier made of an elastic material, for example Made of rubber or silicone. That way he can become one rough surface or irregular shapes, e.g. at the Adjust label printing, of a substrate. During the transfer printing process from the printing drum to the intermediate carrier is nevertheless given an even distance between their surfaces, thereby avoiding blurring of the printed image.

According to a further development and configuration of the Invention are a plurality of printing drums the intermediate carrier assigned. The printing elements of various printing drums can be filled with differently colored inks will. This enables multi-color printing. There the transfer printing on the individual printing drums contactless to If there is an intermediate carrier, color spreading is excluded.

Figur 1

ein thermoelektrisches Druckwerk zur Übertragung einer Tinte auf einen Aufzeichnungsträger mit einer Drucktrommel und einer Einfärbestation für die Drucktrommel,

Figur 2

eine Drucktrommel mit einer Anordnung von Druckelementen als Endlosmatrix,

Figur 3

ein Ausschnitt aus der Oberfläche der Drucktrommel gemäß Figur 2,

Figur 4

eine stirnseitige Ansicht der Drucktrommel gemäß Figur 2 mit einer Ansteuereinheit für die Druckelemente,

Figur 5

eine Schnittdarstellung eines Druckelements,

Figur 6

eine Drucktrommel mit einer Anordnung von vier axial auf der Drucktrommel verlaufenden Matrixzeilen,

Figur 7

ein Prinzipschaltbild für die Ansteuerung der Heizeinrichtungen einer Spalte in den unterschiedlichen Matrixzeilen gemäß Figur 6,

Figur 8

eine Anordnung einzelner Druckelemente einer Matrixzeile gemäß Figur 6,

Figur 9

eine Schnittdarstellung eines Druckelements gemäß Figur 6,

Figur 10

eine Drucktrommel mit einer diagonal zwischen den Stirnseiten verlaufenden Matrixzeile,

Figur 11

einen Ausschnitt aus der Oberfläche der Drucktrommel gemäß Figur 10 mit einzelnen Druckelementen,

Figur 12

eine Schnittdarstellung eines Druckelements gemäß Figur 10,

Figur 13

ein thermoelektrisches Druckwerk mit einem Zwischenträger zwischen Drucktrommel und Aufzeichnungsträger und

Figur 14

ein thermoelektrisches Druckwerk mit einer Mehrzahl von dem Zwischenträger zugeordneten Drucktrommeln.

Further developments and refinements of the invention are specified in further subclaims. Exemplary embodiments of the invention are explained in more detail below with reference to the drawing. Show

Figure 1

a thermoelectric printing unit for transferring an ink onto a recording medium with a printing drum and a coloring station for the printing drum,

Figure 2

a printing drum with an arrangement of printing elements as an endless matrix,

Figure 3

2 shows a section of the surface of the printing drum according to FIG. 2,

Figure 4

3 shows an end view of the printing drum according to FIG. 2 with a control unit for the printing elements,

Figure 5

2 shows a sectional illustration of a pressure element,

Figure 6

a printing drum with an arrangement of four matrix lines running axially on the printing drum,

Figure 7

5 shows a basic circuit diagram for the control of the heating devices of a column in the different matrix rows according to FIG. 6,

Figure 8

an arrangement of individual printing elements of a matrix line according to FIG. 6,

Figure 9

6 shows a sectional illustration of a pressure element according to FIG. 6,

Figure 10

a printing drum with a matrix line running diagonally between the end faces,

Figure 11

10 shows a section of the surface of the printing drum according to FIG. 10 with individual printing elements,

Figure 12

10 shows a sectional illustration of a pressure element according to FIG. 10,

Figure 13

a thermoelectric printing unit with an intermediate carrier between the printing drum and recording medium and

Figure 14

a thermoelectric printing unit with a plurality of printing drums assigned to the intermediate carrier.

A thermoelectric printing unit for transferring an ink 13 on a record carrier 14 contains a circular cylindrical Printing drum 10, which rotates in the direction of rotation 15. Of the Record carrier 14 is at a transfer printing point 18 in Recording medium transport direction 16 at a distance 17 on the Printing drum passed. At the transfer location 18 are Recording medium transport direction 16 and direction of rotation 15 the printing drum 10 rectified. At the transfer location 18 a transfer roller 19 is arranged. The axis of symmetry of the Transfer roller 19 runs parallel to the axis of rotation of the printing drum 10 and perpendicular to the recording medium transport direction 16. Between the transfer roller 19 and the printing drum 10, the record carrier 14 is transported through. The record carrier 14 rolls tangentially over his entire width on the transfer roller 19. Through the transfer roller 19 is thus the uniform distance 17 between the Record carrier and the printing drum 10 guaranteed.

The thermoelectric printing unit also contains a coloring station 11 arranged on the circumference of the printing drum 10 is. The coloring station 11 contains a circular cylindrical one Distribution roller 12, the surface of which is tangential to the surface the printing drum 10 rolls. The distribution roller 12 is stored in a tub 20 which extends along the distribution roller 12 extends. The tub 20 is filled with ink 13 so that the distribution roller 12 partially, for example with the Half of its circumference in which ink 13 is dipped. When immersing the distribution roller 12 picks up the ink 13 and transfers it the ink 13 adhering to it to the printing drum 10. Um to be able to transport sufficient quantities of ink 13, the distribution roller contains 12 porous material.

The rolling area between the printing drum 10 and the distributor roller 12, a wiper strip 21 is arranged in the direction of rotation 15, which extend along the surface of the printing drum 10 extends and excess ink 13 from the surface thereof strips off. The excess ink 13 becomes through the tub 20 caught and by means not shown again in the ink supply 13 located in the tub 20.

The thermoelectric printing unit also contains an as Cleaning roller 22 trained cleaning station. The cleaning roller 22 can be pivoted onto the printing drum 10 in such a way that they tangentially over the entire width of the printing drum 10 this rolls off. The surface of the cleaning roller 22 is formed by absorbent material, for example a flow. In the case of pivoting the cleaning roller 22 to the Printing drum 10 becomes the inking station 11 or its distribution roller 12 pivoted away from the printing drum 10.

On the printing drum 10 are from one end of the Printing drum 10 matrix lines extending to the other end face 33 arranged. A matrix line 33 exposes itself a plurality of individual printing elements 30 together. The Pressure elements 30 are as depressions in the surface of the Printing drum 10 formed, being in the recess a selectively activatable heater 31 is located.

According to FIGS. 2 and 3, a plurality of matrix lines run 33 axially evenly spaced on the printing drum 10. The row spacings 34 correspond to the column spacings 35 the resolution of the printed image. The arrangement of the Printing elements 30 thus corresponds to an endless matrix. At a resolution of 240 dpi (dots per inch) corresponds to the Row spacing 34 and column spacing 35 1/240 inches. Of the Diameter of the depression of a pressure element 30 is about 50µm. The in the depressions of the pressure elements 30th contained heating elements 31 are through a network of columns and Row lines 42, 43 can be selectively activated. The column and Row lines 42, 43 are for this purpose with a control unit 40 coupled.

According to FIG. 4, the control unit 40 is on the front side of the Printing drum 10 arranged. The control unit 40 is through a module that has a plurality of integrated circuits has, formed and on the front side of the printing drum 10th assembled. By bonding or laser beam welding, the Connections to column and row lines 42, 43 produced. The arrangement of the control unit 40 on the Printing drum 10 ensures that always that matrix line 33 with print information supplied by the printer or copier is applied, which is located at the transfer location 18th located.

The pressure element 30 is constructed in accordance with FIG. 5. On one Carrier 23, which forms the core of the printing drum 10, is one first layer 24 applied. In this first layer 24 are Column lines 42 embedded. In a second, look over the layer 25 located in the first layer 24 are row lines 43 embedded. At their crossing points are between column lines 42 and row lines 43 Heating elements 31 introduced. The second layer 25 instructs Intersections on circular cylindrical penetrations, which the depressions reaching up to the heating elements 31 form. In the area of the depression is on the heating element 31 a protective layer 26 is provided, which is an immediate Contact between heating element 31 and ink 13 prevented. A third layer 27, which encloses the second layer 25, forms the outer surface of the printing drum 10. The third Layer 27 points with the depressions of the pressure elements 30 aligned funnel-shaped penetrations 36. The third Layer consists of hydrophobic material. A cluster of Ink 13 on the drum surface is thereby avoided. The funnel-like penetration 36 favors the filling of the Pressure element 30 by avoiding air pockets the distributor roller 12.

The distribution roller 12 is during the printing operation with the Printing drum 10 always in contact. The distributor roller 12 feeds ink 13 into the printing elements 30. The ink 13 remains in the printing element 30 and up to the transfer location 18 will depend on the respective print information expelled the pressure element 30. This will be done at the crossing point the row and column lines 43, 42 arranged Heating resistors 31 supplied with current and thus heated. This heat is transferred to the ink 13, causing forms a vapor bubble. The vapor bubble drives the ink 13 out of the pressure element 30. The teardrop-shaped ink 13 strikes the record carrier 14. Melt there the ink drops, which despite the non-overlapping geometric arrangement of the pressure elements 30 a closed Lettering received. The pressure elements 30 from which on this way the ink 13 has been removed in the inking station 11 subsequently filled again with ink 13.

According to FIGS. 6 to 9, there are four matrix lines 33 axially on the printing drum 10 between its end faces run, arranged on the printing drum 10. The scope of the Printing drum 10 is the printing drum in this embodiment 10 divided into four sectors isolated from each other. Each sector is based on that, the core of the Carrier 23 forming printing drum 10 constructed in the following manner: An electrically conductive layer 39 is over a Insulation 29 applied to the carrier 23. Layer 39 serves as a row line 43. On the layer 39 is a film 38 arranged that a matrix line with printing elements 30 and contains the associated column lines 42. The single ones Sectors are separated by an insulation 28 which is between the Sectors is introduced, electrically isolated from each other. A control unit is located on one end of the printing drum 10 40 arranged according to Figure 4, with the as foil conductor tracks trained column lines 42 and the row line 43 is coupled.

The control unit 40 has column switches 41 according to FIG. 7 and a line switch 44. The line switch 44 connects that matrix row 33 with a voltage source 45, which is located in the area of the transfer location 18. With the column switches 41 according to the present Pressure information of the heating element 31 of a pressure element 30 connected to the voltage source 45. The heating element 31 has an electrical resistance of 30 to 100 ohms and is supplied by the voltage source 45 with a voltage between 5 and 40 volts applied.

The film 38 is made with the help of printed circuit board technology known methods built. The pressure elements 30 are through Penetrations formed with funnel-shaped openings, the penetrations closed by the heating elements 31 are. The heating element 31 extends to the bottom the film 38 and can thereby directly with the layer 39th be contacted. The conductor tracks 42 are in the film 38 embedded.

Due to the expected thermal load on the film 38 and the current load of the voltage source 45 are the immediately adjacent printing elements 30 along the matrix line offset and arranged on both sides of a line of symmetry. Since the rotation speed of the printing drum 10 is greater than the transport speed of the recording medium 14, can nevertheless by appropriate control of the pressure elements 30, which are either on one or are on the other side of the line of symmetry 46, one positionally accurate transfer of the ink 13 to the recording medium 14 are guaranteed. The delayed control leads to an even current load of the Power source 45.

Another variant of the arrangement of a matrix row 33 the printing drum 10 is shown in FIGS. 10 and 11. Two matrix rows 33 run diagonally on the printing drum 10 between the faces of the printing drum 10. The speed of rotation the printing drum 10 is larger than that Media speed, and the individual printing elements 30 of the matrix rows are controlled accordingly, that the ink 13 is positioned precisely on the recording medium 14 is transmitted. As in the previous embodiments are the pressure elements 30 via column lines 42 is connected to a control unit 40. On the carrier 23 are, according to FIG. 12, the heating elements 31 and Layer 47 containing column lines 42 is applied. A layer 48 of oliophobic material is arranged above it, the penetrations in the area of the heating elements 31 49 has.

According to FIG. 13, the thermoelectric printing unit is in accordance with Figure 1 expanded by an intermediate support 51. On this Intermediate carrier 51 is the printed image with the help of a configured printing drum 10 transferred. The printing drum 10 acts with a coloring station 11, a squeegee 21 and a cleaning station 22 together. The transferred to the intermediate carrier 51 Print image is at a transfer printing point 56 on the recording medium 14 transferred.

The intermediate carrier 51 is a circular cylindrical roller elastic jacket surface. At the transfer location 56, the recording medium 14 between a counter pressure roller 55 and the intermediate carrier roller 51, the tangential roll on each other, transported through. The print image is caused by direct contact of the intermediate carrier roller 51 transferred to the record carrier 14 thereon. The elastic surface of the intermediate support roller 51 causes even with rough surfaces of the recording medium 14 or if the surface of the recording medium is uneven, as with label printing, a high quality of transfer printing is achievable. In addition, the use of the intermediate carrier roller 51 protect the printing drum 10 from any pollution caused by the transportation of the Record carrier 14 in the immediate vicinity of the printing drum 10 occurs. Through special spatial separation measures (not shown), e.g. the installation of the printing drum 10 in an almost completely closed housing, the spatial separation can be achieved.

A thermoelectric printing unit for multi-color printing is shown in Figure 14. An intermediate carrier 50 transports an applied to the intermediate carrier 50 multicolored printed image to a transfer location 56, where that 13 by the interaction of the intermediate carrier 50 and a counter-pressure roller 55 on the recording medium 14 is transferable. The intermediate carrier 50 is designed as an intermediate carrier belt between two Deflection rollers 53, 54 is transported. Along the intermediate carrier belt 50 are four transfer rolls 10.1, 10.2, 10.3, 10.4 arranged. With the help of these transfer rollers 10 becomes ink 13 transferred to the intermediate carrier 50. Each transfer roll 10 is assigned a coloring station 11.1, 11.2, 11.3, 11.4. Each inking station 11 is of different color with ink 13 filled. With the help of a squeegee 21.1, 21.2, 21.3, 21.4 this ink is removed from the surface of the printing drum 10 stripped. The transfer printing process between the printing drums 10 and the intermediate carrier 50 is controlled so that a complete, colored printed image on the intermediate carrier 50 is present and transported by this to the transfer location 56 where it is transferred to the record carrier 14. After transfer printing to the record carrier 14 on the intermediate carrier 50 remaining ink residues are removed by a cleaning station 52, which is arranged in front of the first printing drum 10.1 is removed. Because the transfer printing on the individual printing drums 10 is made contactless to the intermediate carrier tape 50 no fear of color spreading. A synchronization the drives of the printing drums 10 is by known mechanical or electronic means easily possible.

Reference list

10th

= Printing drum

11

= Coloring station

12th

= Distribution roller

13

= Ink

14

= Record carrier

15

= Direction of rotation

16

= Record carrier transport direction

17th

= Distance

18th

= Transfer point

19th

= Transfer roller

20th

= Tub

21

= Squeegee

22

= Cleaning station / cleaning roller

23

= Carrier

24th

= first layer

25th

= second layer

26

= Protective layer

27

= third layer

28

= Isolation

29

= Isolation

30th

= Pressure element

31

= Heating element / heating device

32

= Column

33

= Line / matrix line

34

= Line spacing

35

= Column spacing

36

= funnel-shaped penetration

38

= Slide

39

= Shift

40

= Control unit

41

= Column switch

42

= Column line

43

= Row line

44

= Line switch

45

= Voltage source

46

= Line of symmetry

47

= Shift

48

= Shift

50

= Intermediate carrier / intermediate carrier belt

51

= Intermediate carrier / intermediate carrier roller

52

= Cleaning station

53

= Pulley

54

= Pulley

55

= Counter pressure roller

56

= Transfer point

Claims (12)

1. A thermoelectric printing unit for transferring an ink onto a recording medium, with

   a printing drum,

   more than one matrix row of printing elements which are arranged on the printing drum and which are each designed as a depression in the surface of the printing drum, a selectively activatable heating device being provided in the depression,

   an inking station which is arranged on the circumference of the printing drum and by means of which ink can be introduced from the surface of the printing drum into the printing elements, and

   a transfer printing point, at which the heating elements can be activated according to printing information, as a result of which the ink can be expelled out of the corresponding printing elements towards the recording medium.
2. The thermoelectric printing unit as claimed in claim 1, with an inking station which contains:

   a distributor roller, the surface of which rolls tangentially on the surface of the printing drum,

   a trough which extends along the distributor roller and is filled with ink and into which the distributor roller partially dips.
3. The thermoelectric printing unit as claimed in claim 2, with a stripping batten which follows the rolling region in the direction of movement of the printing drum and which extends along the surface of the printing drum and strips excess ink from the surface.
4. The thermoelectric printing unit as claimed in one of the preceding claims, with a cleaning station which is arranged on the circumference of the printing drum and which can, if required, be brought into contact with the surface of the printing drum.
5. The thermoelectric printing unit as claimed in one of the preceding claims, with a hydrophobic and/or oliophobic protective layer forming the outer surface of the printing drum.
6. The thermoelectric printing unit as claimed in one of the preceding claims, with an arrangement of the printing elements as an endless matrix, said arrangement corresponding to the resolution of the printing image.
7. The thermoelectric printing unit as claimed in one of claims 1 to 5, with an arrangement of at least two matrix rows which extend axially on the printing drum and the heating elements of which can be activated alternately.
8. The thermoelectric printing unit as claimed in claim 7, in which the directly adjacent printing elements are arranged to be offset along the matrix row on both sides of a bisecting line.
9. The thermoelectric printing unit as claimed in one of claims 1 to 5, with matrix rows extending diagonally between the end faces of the printing drum.
10. The thermoelectric printing unit as claimed in one of the preceding claims, with a recording medium which is designed as an intermediate carrier and which rolls on a printing material in the region of a backing device, as a result of which the printing image can be transferred onto the printing material.
11. The thermoelectric printing unit as claimed in claim 10, with a plurality of printing drums assigned to the intermediate carrier.
12. The thermoelectric printing unit as claimed in one of the preceding claims, with an activation unit for the selectively activatable heating devices, which activation unit can be coupled to the printing drum.

Images