WO2011157425A1

WO2011157425A1 - Apparatus for the continuous plasma treatment and/or plasma coating of a piece of material

Info

Publication number: WO2011157425A1
Application number: PCT/EP2011/002972
Authority: WO
Inventors: Peter Palm
Original assignee: WPNLB UG (haftungsbeschränkt) & Co. KG
Priority date: 2010-06-17
Filing date: 2011-06-16
Publication date: 2011-12-22
Also published as: DE102010024135A1

Abstract

An apparatus (10) for the continuous plasma treatment and/or plasma coating of an, in particular, web- or plate-like piece (12) of material comprises at least one barrier electrode (13) which is arranged on one side (14) of the piece (12) of material and has an electrically conductive electrode core (17) and a dielectric casing (18), and a counterelectrode (16) which is arranged on the other side (15) of the piece (12) of material, so that a plasma discharge can be generated by means of a high voltage which is applied between the barrier electrode (13) and the counterelectrode (16). At least one electrically conductive probe (21) is arranged on the same side (14) of the piece (12) of material as the barrier electrode (13), at a relatively short distance from the barrier electrode (13).

Description

Apparatus for continuous plasma treatment and / or plasma coating of a piece of material

The invention relates to a device for continuous plasma treatment and / or plasma coating of a particular sheet- or plate-shaped piece of material, comprising at least one arranged on one side of the piece of material barrier electrode with an electrically conductive electrode core and a dielectric sheath, and arranged on the other side of the piece of material counter electrode in that a plasma discharge can be generated by means of a high voltage applied between the barrier electrode and the counterelectrode.

Such devices for corona treatment of a piece of material are widely known. Due to the dielectric covering of the barrier electrode, a dielectrically impeded discharge (barrier discharge or silent discharge) occurs between the barrier electrode and the counterelectrode, producing a plasma to which a surface of the material piece to be treated is exposed. If, during the operation of such a device, a breakage of the dielectric covering of the barrier electrode occurs, a short circuit may occur in the case of a metallic counterelectrode, which in any case can damage the piece of material to be treated, but in the worst case also the counterelectrode. In the case of a counter-electrode provided with a dielectric barrier, or if the material piece to be treated itself acts as a dielectric, however, there is no short circuit, so that it may take a long time until the

CONFIRMATION COPY Fracture of the dielectric cladding is discovered. Since a fraction of the dielectric envelope usually leads to a highly inhomogeneous discharge, the quality of the material piece thus treated is usually insufficient, which can result in significant downtime as a result.

The object of the invention is to provide a device in which the described negative effects due to the breakage of the dielectric coating of the barrier electrode can be prevented.

The invention achieves this object by the means of independent claim 1. The distance between the barrier electrode and the electrically conductive probe is relatively small, i. sufficiently small to cause a short-circuit discharge between the barrier electrode and the electrically conductive probe according to the invention in the event of breakage of the dielectric sheath. The corresponding short-circuit current, or a corresponding voltage dip, can easily be detected by suitable means, in particular can lead to an immediate shutdown of the device. The probe according to the invention is a particularly simple means for detecting a rupture of the dielectric covering of the barrier electrode, since the already existing high voltage is used to trigger the short-circuit current and electrical means for detecting a short circuit are usually also present. Since the probe is arranged on the same side of the material piece as the barrier electrode, the material piece and the counter electrode are advantageously not affected by the short-circuit current.

The distance between the probe and the barrier electrode is preferably in the range of the distance between the barrier electrode and the barrier electrode. Rode and the counter electrode and is preferably at most twice, more preferably at most 1.5 times this distance. Preferably, the distance of the probe to the barrier electrode is less than the distance between the barrier electrode and the counter electrode, more preferably at most half as large. In the case of a metallic counterelectrode, this can ensure that no short-circuit discharge takes place to the counterelectrode or to the piece of material to be treated.

In order to generate the short-circuit current in the case of the barrier electrode occupied by the high voltage, it is expediently easy to earth the probe.

If a plurality of barrier electrodes is provided in a preferred embodiment, it is advantageous if they are at the same potential, so that only a high-voltage potential has to be generated. In this case, an electrically conductive probe is preferably arranged at a sufficiently small distance for each barrier electrode so that a possible break in the dielectric envelope of each barrier electrode can be detected by means of a corresponding short-circuit current.

If, in a preferred embodiment, a plurality of electrically conductive probes is provided, it is advantageous if, for the sake of simplicity, they are at the same potential, in particular ground potential.

Preferably, the plasma discharge is a corona discharge. A corona discharge is a plasma discharge that is generated at atmospheric pressure, preferably without protective gas. It differs from a simple field strength in that ne (partial) ionization of the fluid (usually air) takes place and a small current flows.

The invention will be explained below with reference to advantageous embodiments with reference to the accompanying figures.

Fig. 1 shows a schematic view of a plasma treatment apparatus in a longitudinal section;

Fig. 2 shows a schematic, not to scale

Top view of the plasma treatment apparatus of Fig. 1;

FIGS. 3, 4 are schematic longitudinal sectional views of plasma processing apparatuses in further embodiments; and

FIGS. 5-10 show schematic longitudinal sectional views of various electrode arrangements for plasma treatment apparatuses in further embodiments.

The plasma treatment apparatus 10 for continuous plasma treatment, in particular corona treatment of a surface 11 of a flat, in particular web or plate-shaped piece of material 12, here a material web, for example a plastic film, comprises at least one on one side 14 of the piece of material 12 arranged, in particular rod-shaped barrier electrode 13 and a the other side 15 of the piece of material 12 arranged electrically conductive, in particular metallic counter electrode 16, which is in particular at ground potential. The distance d between the barrier electrode 13 and the piece of material 12 is greater than zero. Between the Barrier electrode 13 and the counter electrode thus a gas-filled free discharge space 20 is formed, in which the plasma or corona discharges are generated. The preferably gap-shaped discharge chamber 20 is in particular free of dielectric materials. The extent d of the discharge space 20 is preferably greater than 0.5 mm, more preferably greater than 1 mm. After the above, barrier electrode 13 and piece of material 12, and / or barrier electrode 13 and counter electrode 16 are arranged at a distance from one another. In another embodiment, not shown, the gas-filled free discharge space 20, or a part thereof, may also be arranged between the material web 12 and the counter electrode, ie on the side of the counter electrode 16.

The barrier electrode 13 has an electrically conductive, in particular metallic, electrode core 17 and an in particular all-round jacket 18 made of a dielectric material, for example a ceramic. The electrode core 17 forming the actual electrode is placed on a high-voltage potential generated by means of a high-voltage generating device 19. The high voltage may in particular be a high-frequency alternating voltage in the range of, for example, 10 to 50 kHz. The high voltage can also be pulsed.

By a suitable choice of the high-voltage parameters, a plasma discharge impeded by the dielectric sheath 18, in particular a corona discharge, is generated in the discharge space 20 between the barrier electrode 13 and the counter electrode 16, which is indicated by dashed lines in FIG. The plasma generated in the space 20, the surface 11 of the piece of material 12 is modified and / or coated in the desired manner. The plasma treatment and / or plasma coating can advantageously take place under atmospheric pressure, so that means for generating a Vacuums are dispensable.

As can be seen from FIG. 2, the barrier electrode 13 preferably extends over the entire width or transverse extent of the piece of material 12. The plasma treatment apparatus 10 has means, not shown, for moving the piece of material 12 in the longitudinal direction between the barrier electrode 13 and the counter-electrode 16 Passing plasma treatment device 10 through or past this, so that optionally a continuous and complete plasma treatment of the surface 11 of the piece of material 12 can be achieved. The continuous delivery of the piece of material 12 is indicated in the figures 1 to 4 by arrows. It may be a translatory conveying or linear conveying, as shown in Figures 1 and 3. Alternatively, the piece of material 12 can be conveyed rotationally past the barrier electrode 13, for example by means of a counter-electrode 16 designed as a roller, as shown in FIG. 4. Instead of conveying the material piece 12, it is also conceivable that the piece of material is fixed and instead the electrode arrangement is guided over the piece of material 12 in the longitudinal direction.

In the longitudinal direction offset to the barrier electrode 13 is on the same side 14 of the piece of material 12, a not (at least not completely) dielectrically shielded, electrically conductive, in particular metallic probe 21 is arranged. The probe 21 has, at least on the side facing the barrier electrode 13, a region extending expediently over its length, for example a slot-shaped region which is free of a dielectric coating. Preferably, the entire probe 21 is completely free of a dielectric sheath. The probe 21 preferably extends over the entire width or transverse extent of the material web 12 and is advantageously arranged parallel to the barrier electrode 13, as shown in FIG. 2 can be seen. In the figures, the probe 21 is plate-shaped, but the probe 21 may also have another suitable shape. If, for example, the sheath 18 of the barrier electrode 13 breaks due to fatigue, a short-circuit discharge to the electrically conductive probe 21 can take place through the breakage point. Suitable detection means 22 are provided in the high-voltage circuit in order to detect a short circuit current caused by a short circuit discharge or a voltage dip caused thereby and to cause a shutdown of the device 10. The electronic detection means 22 may be active or passive, it may be, for example, a simple backup or an electronic monitoring device.

Preferably, the distance of the probe 21 to the barrier electrode 13 is at most twice, more preferably at most 1.5 times the distance between the barrier electrode 13 and the counter electrode 16. As can be seen from Fig. 1, for example, the distance of the probe 21 from the barrier electrode preferably smaller, preferably at most half as large as the distance of the counter electrode 16 of the barrier electrode 13. This may optionally be achieved that advantageously no short-circuit discharge between the barrier electrode 13 and the counter electrode or to be treated piece of material 12 takes place.

In the embodiments according to FIGS. 3 and 4, the counterelectrode 16 has a dielectric barrier 23 on the side facing the barrier electrode 13. In the embodiment according to FIG. 4, the dielectric barrier 23 is added. For example, formed by a dielectric coating of the particular metallic roller 16. Here, the electrically conductive probe 21 provides a simple and secure automatic detection ^"of breakage of the dielectric coating 18 of the barrier electrode 13 because in such a case due to the dielectric barrier 23 can be no short circuit discharge to the counter electrode 16 under normal conditions. The same applies, for example in the case of a metallic counterelectrode (see FIG. 1), if the material piece 12 to be treated acts as a dielectric and prevents a short-circuit current to the counter electrode 16.

The embodiments according to FIGS. 5 to 10 make clear that the device 10 is not limited to a barrier electrode 13 and / or to an electrically conductive probe 21. In particular, a plurality of barrier electrodes 13 may be provided, whereby the process speed can be increased due to the increased treatment area. For example, FIG. 5 shows an embodiment with a central probe 21 and two barrier electrodes 13 symmetrically arranged relative to the probe 21. FIG. 8 shows a series connection of two electrode arrangements according to FIG. 5; Also, more than two such electrode arrangements are possible.

In FIGS. 1 to 4, the probe 21 is arranged behind the barrier electrode 13 in the conveying direction. Alternatively, the probe 21 may be arranged in the conveying direction in front of the barrier electrode 13. The embodiment according to FIG. 6 clarifies that in each case an electrically conductive probe 21 can also be arranged in front of and behind the barrier electrode 13; This may be advantageous to detect a break at various locations of the enclosure 18 of the barrier electrode 13 to be able to. In general, a plurality of probes 21 may be associated with a barrier electrode 13. 6 shows an electrode unit consisting of a central barrier electrode 13 and two probes 21 symmetrically arranged relative to the barrier electrode 13. FIG. 10 shows a series connection of two electrode arrangements according to FIG. 6; Also, more than two such electrode arrangements, and / or combinations with electrode arrangements according to Figures 5, 8 are possible. FIGS. 7 and 9 show series arrangements of alternating barrier electrodes 13 and probes 21.

As can be seen from the figures, irrespective of the number of barrier electrodes 13 and / or the probes 21, at least one electrically conductive probe 21 is arranged at a relatively small distance to each barrier electrode 13 in order to break in the dielectric sheath 18 of each barrier electrode 13 to be able to detect.

It is also possible that in regular operation with intact barrier electrode 13 in addition to the discharge between the barrier electrode 13 and the counter electrode 16, a plasma discharge between the barrier electrode 13 and the probe 12 takes place. In such an embodiment, the probe 12 additionally has the function of a further electrode. In a preferred embodiment, it is a particular rod-shaped metal electrode.

Claims

Claims :

1. Device (10) for continuous plasma treatment

and / or plasma coating of a particular sheet or plate-shaped piece of material (12) comprising at least one barrier electrode (13) arranged on one side (14) of the piece of material (12) with an electrically conductive electrode core (17) and a dielectric sheath (18), and a counterelectrode (16) arranged on the other side (15) of the piece of material (12), so that a plasma discharge can be generated by means of a high voltage applied between the barrier electrode (13) and the counterelectrode (16), characterized in that on the same Side (14) of the piece of material (12) as the barrier electrode (13) at least one electrically conductive probe (21) is arranged at a relatively small distance from the barrier electrode (13).

2. Device according to claim 1, wherein the distance of the probe (21) to the barrier electrode (13) is smaller than the distance between the barrier electrode (13) and the counter electrode (16).

A device according to any one of the preceding claims, wherein the probe (21) is grounded.

4. Device according to one of the preceding claims, wherein a plurality of barrier electrodes (13) is provided.

5. Apparatus according to claim 4, wherein all the barrier electrodes (13) are at the same potential.

6. Device according to claim 4 or 5, wherein at each barrier Ren electrode (13) at a relatively small distance an electrically conductive probe (21) is arranged.

7. Device according to one of the preceding claims, wherein a plurality of electrically conductive probes (21) is provided.

8. Apparatus according to claim 7, wherein all the probes (21) are at the same potential, in particular ground potential.

9. Device according to one of the preceding claims, comprising means (22) for detecting an electrical short circuit due to a short-circuit discharge between the probe (21) and the barrier electrode (13).

10. Apparatus according to claim 9, wherein the short circuit detecting means (22) is arranged to turn off the device (10) due to the detection of a short circuit.

11. Device according to one of the preceding claims, wherein the counter electrode (16) on the barrier electrode (13) side facing a dielectric barrier (23).

12. Device according to one of the preceding claims, wherein between the barrier electrode (13) and the probe (12) takes place a plasma discharge.

13. Device according to one of the preceding claims, characterized in that the plasma discharge is a corona discharge.