EP4182490A1

EP4182490A1 - Method and device for the outer-wall and/or inner-wall coating of hollow bodies

Info

Publication number: EP4182490A1
Application number: EP21749105.9A
Authority: EP
Inventors: Montgomery Jaritz
Original assignee: Rheinisch Westlische Technische Hochschuke RWTH
Current assignee: Rheinisch Westlische Technische Hochschuke RWTH
Priority date: 2020-07-15
Filing date: 2021-07-09
Publication date: 2023-05-24
Also published as: CN115605631A; JP2023533569A; WO2022013087A1; DE102020118718A1; US20230323529A1

Abstract

The invention relates to a device and a method for the outer-wall and/or inner-wall coating of hollow bodies (4) made of an electrically nonconductive material, in particular plastic bottles or canisters, in which the hollow body (4) is placed into a process chamber (12), which is divided by the hollow body (4) into an inner and an outer reaction space (4a, 4b), wherein at least one process gas is introduced into one of the two reaction spaces (4a, 4b) under a process pressure, in particular while the other of the two reaction spaces (4b, 4a) is kept at a pressure less than or greater than the process pressure, wherein a plasma is generated in the reaction space (4a, 4b) that is kept under process pressure, and reaction products and/or fragments formed in the plasma are precipitated out of the at least one process gas to form a layer on that side of the wall of the hollow body (4) which is facing the plasma, characterized in that the plasma is influenced with respect to at least one operating parameter by means of a magnetic field permeating the two reaction spaces (4a, 4b).

Description

Process and device for coating the outer and/or inner walls of hollow bodies

The invention relates to a method for coating the outer and/or inner walls of hollow bodies made of an electrically non-conductive material, in particular plastic bottles or canisters, preferably made of PE (HD-PE, LD-PE), PET, PP, PC or PLA , in which the hollow body is inserted into a process chamber which is divided by the hollow body into an inner and an outer reaction chamber, with at least one process gas being introduced into one of the two reaction chambers at a process pressure, while the other of the two reaction chambers is pressurized to a pressure which is less than or equal to is kept greater than the process pressure and wherein a plasma is generated in the reaction space kept under process pressure and fragments and/or reaction products formed in the plasma are separated from the at least one process gas to form a layer on the side of the wall of the hollow body that faces the plasma.

The invention also relates to a device for coating the outer and/or inner walls of hollow bodies made of an electrically non-conductive material, in particular plastic bottles or canisters, comprising a process chamber into which the hollow body can be inserted and which from the hollow body inserted into an inner and an outer reaction chamber, at least one vacuum pump with which the reaction chambers can be evacuated, in particular optionally, at least one process gas feed line, by means of which at least one process gas can be introduced, in particular optionally, into one of the reaction chambers, in particular by means of the in connection with the at least one vacuum pump a process pressure with the at least one process gas in one of at least one energy generating unit, in particular at least one microwave generator, with which energy can be radiated, in particular selectively, into one of the two reaction chambers to generate a plasma. The energy for igniting the plasma is preferably radiated from a reaction space in which no plasma ignites, through the hollow body into the reaction space in which the plasma is to be ignited. For this purpose, the irradiated reaction space is kept at a pressure that is lower than the process pressure.

Such a device can be used to alternatively provide the inner wall or the outer wall or both sequentially with a layer, in particular to use the layer to deposit a diffusion barrier or other functional layer on the respective wall from at least one process gas comprising precursors on a respective wall.

For example, a gas containing gaseous monomers can be used as a process gas. For example, it is known to deposit SiOx as a diffusion barrier on a hollow body, e.g. bottles, from a process gas mixture containing hexamethyldisiloxane (HMDSO) and oxygen as precursors. The invention preferably makes use of this application as well, but is not limited to it. Other process gases are e.g. hexamethyldisilazane (HMDSN), silane (S1H4), ethyne (C2H2), methane (CH4), difluoroethylene (C2H2F2) or similar.

For this purpose, a process pressure that is lower than the surrounding atmospheric pressure is generated in the reaction space, which contains the process gas or into which the process gas is supplied, in order to create conditions for a plasma. In particular, this process pressure is in the range from 10 Pa to 30 Pa. In the reaction chamber containing the process gas under the process pressure, a plasma is generated by irradiating energy, for example microwave radiation, which is generated by the energy generating unit. The plasma fragments the at least one process gas. The fragments and/or reaction products formed from the fragments are deposited as a layer on the wall of the hollow body that faces the plasma. In order to avoid plasma ignition in the other reaction space, this is evacuated, for example, to a pressure that is lower than the process pressure. For example, this pressure is less than 10 Pa, preferably less than or equal to 5 Pa. Alternatively, the reaction space in which no plasma should ignite, on a Maintained pressure that is greater than the process pressure, eg at the ambient atmospheric pressure.

The energy is supplied by irradiating microwaves into the reaction space containing the process gas, preferably through the other reaction space. Preferably, the procedure of the invention is the same, but not limited to this. In general, any electromagnetic radiation can be generated by at least one signal generator of the energy generating unit, which generates radiation with a frequency that is suitable for igniting the plasma with the selected process gas. The radiation can preferably be matched to the absorption bands of the process gas used. More preferably, the radiation can be irradiated in a pulsed manner. A signal generator used, in particular one each for inner and outer coating, can be designed as a module in which the components for generating and irradiating the electromagnetic radiation are combined, with each module being arranged exclusively in the reaction space in which no plasma ignites. A respective signal generator can generate electromagnetic waves in the microwave band and/or the HF band.

Several problems can arise in connection with the mentioned method and the known device. With comparatively large flea bodies, e.g. with a volume greater than 5 liters, a large plasma extension is required. Especially when microwave excitation of the plasma is used, minima and maxima of the microwave intensity in the reaction space and local absorption of the microwave energy can occur, which can lead to an inhomogeneous plasma, from which non-uniform layers then arise.

Due to the large extent of the plasma, there is still a large energy requirement in order to generate a sufficient energy density throughout the plasma. This is relevant on the one hand for large hollow bodies and on the other hand for external coatings, since here the plasma is not limited by the inner volume of the hollow body, but rather by the process chamber surrounding the hollow body, which is always larger than the hollow body.

Furthermore, it is problematic with external coatings that in addition to the outer wall of the hollow body to be coated, the interior of the Process chamber is also coated. A continuous implementation of such a coating process has thus far not been possible without cleaning interruptions. In addition, the co-coating of the process chamber elements leads to a change in process parameters, eg with regard to the permeability for microwave radiation, so that these have to be adjusted during the course of the process in order to ensure consistent quality of the layers.

In Europe, it is mainly the interior coatings of hollow bodies, such as PET bottles, that have established themselves, but for certain applications, such as in the chemical industry, the achievable barriers are sometimes too low. In plasma polymer barrier layers, internal stresses develop during the layer growth process with increasing layer thickness, which lead to cracks in the layer above a certain layer thickness. It is therefore not possible to increase the barrier performance by increasing the layer thickness. Furthermore, depending on the deposition conditions, open pores are formed in the layers, which can have a negative effect on the barrier.

An improvement in the barrier is already possible through a correct process design in terms of plasma homogeneity and through the deposition of a multi-layer system consisting of, for example, alternating silicon-organic (SiOCH) and silicon oxide (SiOx) coatings. Since SiOCH layers form intrinsic tensile stresses and SiOx layers compressive stresses, the layer stress of the entire system can be reduced and the layer thickness and the permeation barrier can be increased. The permeation paths are lengthened, since pores in the individual layers of a multi-layer system are unlikely to lie directly on top of each other. However, it is also well known that increasing the number of layers does not result in a linear increase in the barrier. On the one hand, this is due to the fact that the layer stress development in the layer system can only be partially restricted. On the other hand, defects and pores in the layers propagate into the next layer despite the intermediate layer. The latter can only be overcome by applying the coating from both sides. With a coating on both sides, for example, it is possible to reduce the transmission of gases through the system to almost zero. This is mainly for chemical companies industry attractive. For example, in the field of agrochemicals, packaging is often used that consists of several different plastics, each of which has a function (e.g. barrier against water, barrier against gases, etc.). Such groups can no longer be economically separated from one another, so that the post-consumer waste produced can often only be incinerated. Plasma polymer high barrier coatings can solve this problem and enable recyclable containers with high barrier properties.

It is therefore an object of the invention to provide a method and a device of the type mentioned at the outset, with which homogeneous inner coatings and outer coatings can be achieved while avoiding or at least reducing the co-coating of the process chamber and preferably with which comparatively large ones can be achieved regardless of the coating side Hollow bodies, in particular with volumes greater than 5 liters, preferably greater than 50 liters, more preferably greater than 100 liters, even more preferably at least up to 200 liters, can be coated with high quality.

This object is also achieved in the above-mentioned method, inter alia, in that the plasma is influenced with regard to at least one operating parameter by means of a magnetic field penetrating the process chamber, in particular both reaction chambers.

The object is achieved in the device in that it comprises at least one element with which a magnetic field penetrating the process chamber can be generated, in particular for influencing the plasma that can be generated with regard to at least one parameter of the plasma.

The at least one element with which a magnetic field penetrating the process chamber can be generated is preferably at least one element that is provided in addition to the power generation unit and/or in addition to devices that interact with the power generation unit during plasma generation and with which the plasma is generated . Thus, it can be provided, especially when microwaves are preferably used for plasma generation, that electromagnetic radiation is generated with the microwaves, with which a time-varying, in particular with the frequency of the microwaves, time-varying radiation magnetic field is generated. In such a case, the invention therefore provides that the magnetic field penetrating the process chamber for influencing the plasma is different, or is generated with different devices, than the possibly existing magnetic field with which the plasma is generated. The magnetic field, which influences the plasma in the process chamber, can thus be adjusted and/or changed separately from the plasma generation, in order in this way to enable the plasma generated to be influenced.

The magnetic field with which the plasma is influenced can preferably be static over time, preferably at least during the existence of a plasma or if it changes over time, have a lower frequency of change over time compared to the plasma-generating magnetic field.

The invention makes use here of the fact that the ions of the fragments and/or reactive products of the one or more process gases that are present in the plasma can be deflected by a magnetic field, and in particular can therefore be influenced. There is thus the possibility of exerting an influence on the plasma with regard to one or more parameters by means of a magnetic field which penetrates the process chamber during the implementation of the method and thus also penetrates the two reaction chambers, in particular the one in which the plasma is present.

The magnetic field causes the ions to accelerate along the magnetic field lines due to the Lorentz force. This leads to spatial flomogenization of the plasma, in particular by which is meant that greater homogeneity is achieved under the effect of the magnetic field compared to a plasma without an active magnetic field. For example, the homogeneity can be observed at a constant distance along the wall of the hollow body to be coated. This effect is particularly advantageous in the case of comparatively large hollow bodies.

Preferably, the magnetic field can be chosen such that in a given longitudinal direction of the hollow body, in which it has its greatest extent, the field lines run predominantly in this longitudinal direction. This can be achieved, for example, if the poles of the generated magnetic field are spaced apart in this longitudinal direction. Accordingly, the magnetic field generating elements can be positioned on the device to effect this. The invention can also provide for the energy density of the plasma to be increased by the magnetic field, in particular with a greater energy density being achieved under the effect of the magnetic field in comparison to a plasma without an active magnetic field. In this way, the energy requirement can be reduced, particularly in the case of comparatively large hollow bodies.

As a further parameter, the local position of the plasma can be influenced with the magnetic field. This is preferably done in such a way that the effect of the magnetic field keeps the plasma at a greater distance from the process chamber wall and/or elements in the process chamber compared to the distance that would exist without an active magnetic field. It is precisely this that leads to the plasma being restricted to an area directly around the hollow body to be coated. The plasma is therefore closer to the hollow body in comparison to the plasma without a magnetic field. Due to the effect of the magnetic field, a co-coating of the process chamber or of elements in the process chamber can be reduced or advantageously completely prevented, particularly in the case of layer deposits on the outer wall of the hollow body. As a result, the exterior wall coating can be carried out much more economically than was previously possible.

In particular in connection with the influencing of the local position of the plasma by the magnetic field, it can be provided that at least one sensor, preferably an optical sensor, in particular a camera, is used on the device or in the method, with which the local position of the plasma generated is detected in particular during the influence of the magnetic field, is preferably detected contactlessly and depending on the detected data of the at least one sensor, the at least one element generating the magnetic field is controlled, in particular in order to influence or change the magnetic field depending on this data. For example, a regulation can be implemented in this way that keeps the plasma at a predetermined minimum distance or within a predetermined distance range from the wall of the hollow body to be coated and/or from the process chamber wall.

A large number of containers with different volumes and sometimes complex geometries are used in the plastic packaging industry. The plasma process for coating the containers with a functional layer preferably adapted according to the invention to the respective container, in particular to be able to ensure a homogeneous coating with the desired functionality. At the same time, the invention can offer a high degree of flexibility for the coating system with regard to the container sizes and geometries to be coated.

By using magnetic fields designed according to the containers, the plasma can be flexibly adapted to the geometry of the container, both for the inner and outer coating.

A further possible embodiment of the invention can therefore provide that the expansion and intensity of the plasma influenced by the magnetic field lines is detected by the aforementioned at least one optical sensor, preferably an imaging sensor, such as a CCD or infrared camera system, and feedback of this Data is made with the coil system.

By energizing the coils for generating the magnetic field differently depending on the evaluation of the spatial extent of the plasma in and/or outside of a container by the at least one sensor, the magnetic field and thus the plasma can be flexibly adapted to any container geometry and size during the process and be calibrated.

A coil can preferably be used as an element generating a magnetic field. This has the advantage of being able to have a direct influence on the magnetic field strength through the current strength. Plasma parameters can thus be changed by changing the current supply. The current supply can preferably be selected depending on the shape and/or size of the flotation body to be coated. In this way, the device and the method can be individually adapted to the flea body.

In a preferred embodiment, the invention can provide that the effective magnetic field is generated by superimposing the magnetic fields of a plurality of magnetic field-generating elements, in particular a plurality of coils.

For example, the magnetic field lines of the effective magnetic field can thereby be controlled, in particular by controlling the magnetic field as a function of the shape of the flea body Generating elements, in particular by depending on the shape of the hollow body energization of the coils, are at least partially adapted in their course to the course of the wall of the hollow body to be coated.

In general, the invention can provide that it comprises a plurality of elements with which a magnetic field penetrating the process chamber can be brought about by superimposition of the magnetic fields generated by the respective elements. The at least one element can advantageously be designed as a coil that can be energized.

It can also be provided that several elements are formed by a first number of permanent magnets and a second number of coils whose magnetic fields are superimposed. A variation of the magnetic field, e.g. to change plasma parameters, can be generated by changing the coil energization, in particular with a base magnetic field strength being able to be generated by the permanent magnets, around which the variation is possible.

In one possible embodiment, it can be provided that several coils for generating a superimposed magnetic field are arranged one behind the other in an axial extension direction of the process chamber, in particular which corresponds to the longitudinal direction of a hollow body to be coated. As mentioned at the outset, the direction of spacing of the poles can thus be placed in the direction of longitudinal extent.

In a further development, the invention can provide that at least one of the coils is arranged on an axial end of the process chamber, in particular opposite an axial end face of a hollow body, and has a smaller winding diameter than the other coils, in particular which are arranged on the outside around the process chamber , or, in the case of an arrangement in the process chamber, surround at least one hollow body which can be inserted therein on the outside. The coils arranged at the axial end can produce the effect of a magnetic mirror, as a result of which the plasma can be limited to the axial length of the hollow body, and in particular can be kept at a distance from the axial process chamber walls.

At least one of a plurality of coils or the sole coil for radial confinement of the plasma is preferably external to the Process chamber wall arranged. In particular, this is possible and preferred when the process chamber wall is non-metallic, for example made of glass, preferably borosilicate glass or quartz glass. Coils at the axial end, opposite the axial end face of a hollow body, can be arranged in the process chamber or outside. In particular depending on the choice of material for the axial process chamber wall.

An embodiment of the invention can also provide that at least one energy transmission element, in particular at least one waveguide, through which energy can be radiated into the process chamber, is arranged in an axial spaced area between axially adjacent different coils or between axially adjacent winding sections of the same coil. In this way, the energy can be radiated through the coil arrangement.

In a preferred embodiment, the invention can also provide that several elements generating the influencing magnetic field are designed such that they comprise or form at least two groups of energizable coils, with which a magnetic field influencing the plasma can be generated or generated in the process becomes, in particular, independent for each group and/or also dependent on another group. Provision can be made for the at least two groups to generate the plasma-influencing magnetic field, in particular the same plasma-influencing magnetic field in each case in chronological succession, in particular for successive coating cycles of different hollow bodies or for a coating cycle of the same hollow body, in particular with a temporary overlap in the energization of two groups. For such a sequential energization of the groups, the device can comprise a control unit, which is set up for the corresponding energization.

Each group preferably has at least one coil that can be energized, preferably several coils that can be energized, in particular which can have one of the aforementioned arrangements, i.e. in particular can include coils which limit the magnetic field radially with respect to the longitudinal axis of the container and/or limit it axially, preferably in the manner of aforementioned magnetic mirror.

In particular, provision can be made for each group of coils to have at least essentially the same magnetic field configuration or magnetic field geometry generate, in particular form a respective so-called magnetic bottle. The magnetic bottles of all groups are preferably identical, in particular in a respective at least temporarily static case during plasma generation.

In particular, the same magnetic field configuration/geometry is understood to mean that the magnetic fields generated by the groups each have the same local field strength in the process chamber, in particular with at least substantially identical course of field lines.

Coils and permanent magnets can also be combined in one group in order to generate the magnetic field, in particular as described above. The invention preferably includes the coating of flea bodies on the inside and/or outside with a volume of 0.2-500 liters, preferably 1-100 liters and more preferably 5-30 liters.

In order to build up the required magnetic flux density for influencing the plasma, large-volume hollow bodies, in particular the aforementioned volumes, require correspondingly large coils through which a few amperes of current must flow, depending on the number of turns.

The electrical power introduced into the coils can be higher than the thermal energy loss via convection and radiation, so that the coils can heat up considerably during continuous operation. In this case, the invention can provide for the coils to be assigned at least one cooling system.

In a preferred embodiment, the invention can also provide, in particular to avoid a cooling system, to reduce the heating of coils by sequential switching and energizing of groups of the aforementioned type or by an energizing strategy, in particular which makes it possible to dispense with additional cooling of the coils . One aim of the invention is preferably to keep an average temperature of the coils in the fatigue strength range of the coil material by assigning sufficiently long cooling times to these coils or groups. This can be done by allowing at least one other group to cool down when current is supplied to one group to generate the influencing magnetic field. In order to be able to ensure the fatigue strength of the coils, they should preferably not get hotter than 90° C. or the current through them ^{should not exceed a value of approx. 2.5 A/mm 2} , in particular not on average over time.

Possibilities for implementing a sequential switching of groups and/or an energization strategy are discussed below in the exemplary embodiment.

An embodiment of the invention is explained with reference to the following figures.

The device according to the invention shown in FIG. 1 makes it possible to apply a sequential and respectively exclusive inner and/or outer coating to a flotation device 4 made of plastic, e.g. to large-volume containers 4 made of plastic. To produce a layer, at least one process gas is introduced into the respective reaction space 4a or 4b via one of the respective flea antennas 3 and excited to form a plasma, as a result of which plasma polymerisation is produced. The reaction space 4a is given here by the interior of the float body 4 . The reaction space 4b through the space between the outer wall of the float body 4 and the process chamber 12.

The coating process takes place overall under low pressure, i.e. a pressure lower than the surrounding atmospheric pressure. The necessary pressure can be generated for each of the two reaction chambers 4a/4b by means of a vacuum pump 15. The plasma is ignited with pulsed microwave excitation, which is generated by the signal generators 1 and emitted by flea antennas 3 and/or waveguides 5 . According to the invention, the plasma is influenced here by a magnetic field that is generated by energized coils 13, 16 and 17.

In the process, the flea body 4 is fixed gas-tight in the process chamber 12 . After the process chamber 12 is closed, process gases are first introduced into the outer reaction space 4b through a gas lance 3 in the reactor cover 2, which is also a microwave antenna for the inner coating, for example for the outer coating, and a process pressure of 10 to 30 Pa, for example, is regulated.

The inner reaction space 4a of the container 4 preferably remains under atmospheric pressure or close to atmospheric pressure. Microwave radiation is transmitted via an antenna 3, which is adapted in particular to the container geometry, in particular, which in turn is also a gas lance for the internal coating, is introduced into the process chamber 12 . The radiation traverses the inner reaction space 4a of the hollow body 4 with almost no loss. The significantly higher pressure in the inner reaction space 4a prevents the ignition of a plasma here. The microwave radiation reaches the outer reaction space 4b of the hollow body 4 and meets suitable conditions there for a plasma state, as a result of which the deposition process on the outer wall of the hollow body 4 is initiated.

At the same time, a magnetic field is generated via a coil arrangement of coils 16 and 17, which homogenizes the plasma along the field lines by the generated acceleration of the charged particles and at the same time keeps it away from the chamber walls of the process chamber 12 by magnetic confinement. In Figure 1, in relation to the longitudinal axis A of the hollow body 4, a coil 17 is provided at the axial end and opposite the upper axial end wall of the hollow body 4 and has a smaller diameter than the coil 16, which constricts the field lines at the axial end and thus has the effect of a magnetic Mirror generated for the plasma. Here such a coil 17 is only arranged at one axial end, here the upper end of the hollow body 4 . The invention can also provide for such a coil 17 to be provided at the other end, here the lower end of the hollow body, in particular as shown in FIG.

Figure 2 visualizes the course of the field lines for a schematically illustrated embodiment with coils 17 arranged at both axial ends. The course of the field lines of the effectively acting magnetic field is shown and illustrates the magnetic pole spacing in the axial direction A. The constriction of the field lines can be clearly seen at the axial end, the is effected by the coils 17 with a smaller winding diameter than the coils 16, which are arranged radially with respect to the axis A around the hollow body 4. Here, the field lines of the magnetic field are forced into a bottleneck-shaped course, in particular so that the field lines are largely bent back into themselves inside the confinement volume. With this device, the plasma can be limited to the immediate vicinity of the surface of the hollow body to be coated and kept away from the process chamber walls. Furthermore, the plasma homogenized and preferably compressed, which increases the energy density and thus the layer deposition rate.

The magnetic influence on the plasma is based on the Lorentz force, which keeps the charged plasma particles, electrons and ions, in the magnetic field on helical paths, in particular thereby limiting the possible local areas, homogenizing the plasma and preferably also increasing the local energy density.

This magnetic confinement can preferably be achieved here in this example, but also with general validity for the invention, with cylindrical coils, since the magnetic field of such a coil is directed parallel to the coil axis, which prevents the loss of the particles in the radial direction.

If an inner coating sequentially following the outer coating is desired, the gas supply to the outer reaction chamber 4b can be terminated after the outer coating process for the following inner coating and this can be evacuated to a pressure level below the process pressure, preferably to about 5 Pa.

Process gas is introduced into the inner reaction space 4a of the hollow body 4 via the gas lance 3 and regulated to a process pressure, e.g. a pressure of approximately 10 to 30 Pa. Microwave radiation, which is now introduced into the process chamber 12 through the antenna 3 lying opposite and the laterally slotted waveguide 5, traverses the exterior space without losses due to the significantly lower pressure, which corresponds to an increased free path length.

The radiation now meets suitable conditions for a plasma state in the interior 4a of the hollow body 4, as a result of which the layer deposition process on the inner wall of the hollow body 4 is initiated. The magnetic field is switched on again, this time preferably solely for the purpose of homogenizing the plasma, which is particularly advantageous for the internal coating of large hollow bodies.

Depending on the volume of the hollow body, the total cycle time for the inner and outer coating is, for example, 10 to 120 seconds, in particular 1-30 seconds are required for the coating in each case. The remaining seconds are needed for evacuation and changing samples.

FIG. 3 shows a further exemplary embodiment of the invention. In this example, the cylindrical coils 13 and 22 can be designed with a smaller diameter than the coils 16 to 21 and preferably with a core made of a ferromagnetic material, so that high magnetic flux densities are possible with low current intensities. These coils 13 and 22 are therefore less critical with regard to the temperature load.

The cylindrical coils 16 to 21, on the other hand, have a larger inner radius (in particular corresponding to or larger than the outer radius of the process chamber 12) due to the process and system and preferably in this embodiment no core.

In an alternative embodiment, the antenna/gas lance 3 can preferably be made of a ferromagnetic material in order to achieve an increase in the magnetic flux density of the outer coils 16 to 21. This embodiment is particularly interesting for the magnetic confinement of the plasma igniting around the outside of the container wall, ie in the reaction space 4b, since the field lines will then run through and to the antenna 3.

The kinetic energy of the ions Ekin in a microwave plasma can typically reach values of up to 30 eV or 4.8E-18 J and depends on the coating process and the type of system. In order to deflect these charged particles with a magnetic field, a magnetic flux density of up to 0.01 T to 1 T is required, depending on Ekin. The inside diameter of the process chamber 12 must be approximately 350 mm for a 10 L container, for example. A magnetic flux density of approximately 0.05 T can be achieved, for example, with a cylinder coil with this inner diameter, preferably without a core, with, for example, 5000 turns and an energization of 3 A. The strength of this magnetic field can be further increased by the coils 13 and 22 depending on the power required. In this example, the coil reaches a critical fatigue strength temperature of e.g. B. 90 C°. After the coil has been switched off, it may take a few minutes for it to reset itself has cooled sufficiently. There are various possibilities to consider the cooling times of the coils in the process. Possible application examples are:

1. Different groups of coils are used in each coating cycle

Loading and unloading processes, vacuum generation and gas introduction are preferably included in the overall cycle time, so that this is determined depending on the container size and can be 10 s to 120 s, for example. During each coating process, only the coils of a specific group of coils are switched on in order to generate the plasma-influencing magnetic field, so that the coils of at least one other group of coils, in particular the coils used previously, can cool down. For example, the coils 16, 18 and 20 of a first group could be used in the first coating process and then the coils 17, 19 and 21 of another group could be used in the subsequent process. In this way, a uniform magnetic field can be generated in each case, in particular an at least essentially identical magnetic field in each case, and the coils of the groups experience sufficient cooling for renewed use in the following process.

2. The groups of coils are alternately switched on and off within a coating cycle

Above all, the charging and discharging processes of the coils must be observed. A current that is accentuated by induction always counteracts the cause of its creation (change in the magnetic field). During the charging process, the flow of current is inhibited by the self-induced voltage of the coil. Depending on their configuration and size, the discharging and charging processes of the coils can last from a few milliseconds to a few tens of seconds. Taking these charging and discharging processes into account, groups of coils are alternately energized during the coating process, in particular so that a sufficiently high mean magnetic flux density is achieved at a sufficiently low maximum operating temperature. The inductances can be taken into account by means of a current increase in one group that is adapted to one another over time, while the current in another group is reduced until the Generation of the magnetic field which one group has replaced the other group. In this case, it is preferably ensured that the superimposed magnetic fields of both groups at the times when two groups are energized at the same time correspond to the magnetic field that each group also generates alone after the other group has been switched off.

Thus, the same magnetic field is generated both during the sole operation of a group and during the time interval of the operational changeover from one group to another.

FIG. 3 additionally shows reference number 23 for an optical sensor for detecting the plasma during operation in order to regulate it using the sensor measured values, in particular with regard to the plasma position or the distance between plasma and process chamber wall or plasma and hollow body wall.

Reference character list

1.) Signal generator

2.) Cover of the process chamber, in particular movable with

Guide rod (e.g. pneumatically operated)

3.) Gas lance / antenna (optionally made of ferromagnetic material)

4.) hollow body

5.) Waveguide arc

6.) Power distribution

7.) Waveguide

8.) Guide rod e.g. made of PEEK or similar materials that have a high permeability to microwaves and magnetic fields

9.) valve

10.) Gas flow regulator

11.) Gas reservoir

12.) Process chamber, e.g. with radial walls made of borosilicate glass or similar materials that are highly permeable to microwaves and magnetic fields

13.) Base of the process chamber with sealing surface to accommodate the

Hollow body and, if necessary, coil with core made of ferromagnetic material for magnetic mirror effect at the axial end

14.) Pressure measurement

15.) Pumping station with at least one vacuum pump Coil for generating a magnetic field Coil for generating a magnetic field Coil for generating a magnetic field Coil for generating a magnetic field Coil for generating a magnetic field Coil for generating a magnetic field Coil for generating a magnetic field, in particular with a core made of ferromagnetic material, for magnetic mirror effect at the axial end of the hollow body Sensor for detecting the spatial propagation of the plasma

Claims

patent claims

1. A method for coating the outer wall and/or inner wall of hollow bodies (4) made of an electrically non-conductive material, in particular plastic bottles or canisters, in which the hollow body (4) is inserted into a process chamber (12) which is separated from the hollow body (4) is divided into an inner and an outer reaction chamber (4a, 4b), at least one process gas being introduced into one of the two reaction chambers (4a, 4b) at a process pressure, in particular while the other of the two reaction chambers (4b, 4a) is kept at a pressure less than or greater than the process pressure, a plasma being generated in the reaction chamber (4a, 4b) kept under process pressure and fragments and/or reaction products formed from the at least one process gas in the plasma to form a layer on the surface to the plasma facing side of the wall of the hollow body (4) are deposited, characterized in that by means of both reaction spaces (4a, 4b) passing through Magnetic field, the plasma is influenced in terms of at least one operating parameter.

2. The method according to claim 1, characterized in that a parameter influenced by the magnetic field is at least one of the following: a. the homogeneity of the plasma, in particular viewed at a constant distance along the wall of the hollow body (4) to be coated, preferably with greater homogeneity being achieved under the effect of the magnetic field compared to a plasma without an active magnetic field, b. the energy density of the plasma, in particular with a greater energy density being achieved under the effect of the magnetic field compared to a plasma without an effective magnetic field, c. the local position of the plasma, in particular the effect of the magnetic field keeping the plasma at a greater distance from the wall of the process chamber (12) and/or elements in the process chamber (12) compared to the distance without an active magnetic field.

3. The method according to any one of the preceding claims, characterized in that the acting magnetic field is generated by superimposing the magnetic fields of a plurality of magnetic field-generating elements (13, 16, 17, 18, 19, 20, 21, 22), in particular a plurality of coils (13, 16, 17, 18, 19, 20, 21, 22) or permanent magnets.

4. The method according to claim 3, characterized in that the magnetic field lines of the acting magnetic field, in particular by activation of the magnetic field-generating elements (13, 16, 17, 18, 19, 20, 21, 22) dependent on the hollow body shape, in particular by the Current supply to the coils (13, 16, 17, 18, 19, 20, 21, 22) dependent on the shape of the hollow body can be adapted at least in some areas to the course of the wall of the hollow body (4) to be coated.

5. The method according to any one of the preceding claims, characterized in that the plasma-influencing magnetic field, in particular the same plasma-influencing magnetic field, is generated with at least two groups of coils (16, 18, 20/17, 19, 21) in chronological succession, in particular with a temporary overlap energizing two groups.

6. The method according to any one of the preceding claims, characterized in that with at least one sensor (23) the local position of the generated plasma, in particular during the influence of the magnetic field is detected, preferably contactless and depending on the detected data of the at least one Sensor (23), the at least one element (13, 16, 17, 18, 19, 20, 21, 22) generating the magnetic field is controlled, in particular in order to influence the magnetic field as a function of this data.

7. Device for coating the outer wall and/or inner wall of hollow bodies (4) made of an electrically non-conductive material, in particular plastic bottles or canisters, comprising a. a process chamber (12) into which the hollow body (4) can be inserted and which is divided by the inserted hollow body (4) into an inner and an outer reaction chamber (4a, 4b), b. at least one vacuum pump (15) with which the reaction chambers (4a, 4b) can be evacuated, in particular optionally, c. at least one process gas feed line (3), by means of which at least one process gas can be introduced, in particular optionally, into one of the reaction chambers (4a, 4b), in particular by means of which, in connection with the at least one vacuum pump (12), a process pressure with the at least one process gas in one of the two reaction spaces (4a, 4b) can be adjusted, d. at least one energy generating unit (1), in particular at least one microwave generator (1), with which energy can be radiated, in particular optionally, into one of the two reaction chambers (4a, 4b) to generate a plasma, preferably through the other reaction chamber (4b, 4a). , characterized in that it comprises at least one element (16, 17) with which a magnetic field penetrating the process chamber (12) can be generated, in particular for influencing the plasma that can be generated with regard to at least one parameter of the plasma.

8. The device according to claim 7, characterized in that it comprises a plurality of elements (13, 16, 17, 18, 19, 20, 21, 22) with which a process chamber (12) penetrating magnetic field by superimposing the of the respective elements (13, 16, 17, 18, 19, 20, 21, 22) generated magnetic fields can be effected.

9. Device according to one of the preceding claims 7 or 8, characterized in that the at least one element (13, 16, 17, 18, 19, 20, 21, 22) as an energizable coil (13, 16, 17, 18, 19, 20, 21, 22) or as a permanent magnet.

10. Device according to one of the preceding claims 7 to 9, characterized in that several elements (13, 16, 17, 18, 19, 20, 21, 22), in particular coils (13, 16, 17, 18, 19, 20 , 21, 22) are arranged one behind the other in an axial extension direction (A) of the process chamber (12), in particular which corresponds to the longitudinal direction of a hollow body (4) to be coated.

11. The device according to claim 10, characterized in that at least one of the elements, in particular at least one of the coils (13, 17, 22) at one end, in particular an axial end of the process chamber (12), in particular opposite an axial end face of a hollow body (4), is arranged, in particular such a coil having a smaller winding diameter than the other coils (16-21), in particular which are arranged outside around the process chamber (12), or in the case of an arrangement in the process chamber (12) at least one therein insertable hollow body (4) surrounded on the outside.

12. Device according to one of the preceding claims 7 to 11, characterized in that in an axial distance range between axially adjacent magnetic field generating elements (13, 16, 17, 18, 19, 20, 21, 22), in particular different coils (13, 16, 17, 18, 19, 20, 21, 22) or between axially adjacent winding sections of the same coil (13, 16, 17, 18, 19, 20, 21, 22) at least one energy transmission element (7), in particular at least one waveguide ( 7) is arranged, through which energy can be radiated into the process chamber (12).

13. Device according to one of the preceding claims 7 to 12, characterized in that it comprises at least one sensor (23) with which the local position of the generated plasma can be detected, in particular during the influence of the magnetic field, preferably can be detected without contact and depending on its measured values, the at least one element generating the magnetic field can be controlled.

14. Device according to one of the preceding claims 7 to 13, characterized in that several elements generating the influencing magnetic field are designed in such a way that they form at least two groups of energizable coils (17, 19, 21/16, 16, 20), with each of which a magnetic field influencing the plasma can be generated, in particular in each case at least essentially the same magnetic field can be generated.

15. Device according to one of the preceding claims 7 to 14, characterized in that it comprises a control unit which is set up to energize the groups of coils (17, 19, 21/16, 16, 20) in groups one after the other, in particular with a temporary Overlapping of the energization of two groups, in particular with a simultaneous partial energization of two groups in the temporary overlap.