Abstract:
A device used for plasma-enhanced coating of a container, e.g. a plastic bottle, and/or a container blank, e.g. a container preform, with at least one high-frequency source, at least one gas feed for feeding process gas, and at least one plasma source, e.g. a plasma nozzle. The plasma source has an inner electrode surrounded by a nozzle tube, the plasma source is adapted to be introduced in a container to be coated and configured such that it is able to generate a plasma under ambient pressure, e.g. in a pressure range of 800 to 1,200 hPA, and the plasma can be discharged from a nozzle tube end. The temperature of the generated plasma lies within the range of the ambient temperature, e.g. between 10 and 50 ° C. The nozzle tube of the plasma source includes a longitudinal nozzle tube element and a lateral nozzle tube element projecting laterally from the longitudinal nozzle tube element ( 201 ). Plasma is dischargeable through the lateral nozzle tube end.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is the US national phase of International Patent Application No. PCT/EP2013/050707, filed Jan. 16, 2013, which application claims priority of German Application No. 102012206081.2, filed Apr. 13, 2012. The priority application, DE 102012206081.2, is hereby incorporated by reference. 
     
    
     BACKGROUND  
       [0002]    For reducing the permeability of the walls of containers/hollow bodies, e.g. with respect to undesirable substances, it is advantageous to provided these walls with a barrier layer, e.g. through plasma-enhanced chemical vapor deposition (PECVD), as described e.g. in EP0881197A2. 
         [0003]    Such barrier layers are e.g. required for reducing the transmission rates of gases through the plastic wall of a container. CO 2  losses from the product filled into the container or an ingress of oxygen into the product can be minimized in this way. In addition, it is thus possible to protect the product against substances which originate from the container material and which may cause changes in the color or the taste of the product. 
         [0004]    For coating containers by means of a plasma treatment, e.g. for plasma coating the inner surfaces of plastic bottles by means of plasma, a so-called high-frequency plasma may, for example, be used in so-called low-pressure plants. 
         [0005]    To this end, the interior of the container is first evacuated to a pressure in the range of 1-10 Pa. The area of the surface to be coated, e.g. the interior of the container, has then introduced therein a process gas, which is used for forming the layer, the so-called “precursor”, whereby the pressure in the interior of the container may increase to 10-30 Pa. 
         [0006]    With the aid of electromagnetic radiation, e.g. microwave or high-frequency or other electric fields, this gas or mixture of gases can then be transferred, partly or fully, into a plasma state and, in so doing, be broken down into its components. Parts of the gas undergo a plasma-enhanced reaction in the gaseous phase or on the surface of the substrate to be coated, e.g. on the inner wall of a plastic bottle, and condense on this surface thus forming a closed layer. 
         [0007]    One of the drawbacks of this coating technique is e.g. the complex vacuum technology required for this purpose and also the sometimes substantial thermal loads acting on the substrate. This is critical in particular as regards plastic surfaces, since these surfaces may be damaged by this kind of treatment. 
         [0008]    In the meantime plasma sources have become known, which are able to generate plasma under ambient pressure, so-called plasma nozzles, described e.g. in EP1335641, US 2007116891, EP0761415 and US20020179575. 
       OBJECT 
       [0009]    It is therefore the object of the present disclosure to improve a device for coating containers and/or container shapes by means of a plasma treatment, e.g. the coating of plastic bottles and/or container blanks, in particular with regard to minimizing the complexity and increasing the efficiency of the coating device. 
       SUMMARY OF THE DISCLOSURE  
       [0010]    A device according to the present disclosure used for plasma-enhanced coating of a container, e.g. a plastic bottle, and/or a container blank, e.g. a container preform, may comprise at least one high-frequency source, at least one gas feed for feeding process gas, and at least one plasma source, e.g. a plasma nozzle. The plasma source may comprise an inner electrode and said inner electrode may be surrounded by a nozzle tube. The at least one plasma source can thus be introduced in a container to be coated and it can be configured such that it is able to convert the process gas, partly or fully, into a plasma under ambient pressure, e.g. in a pressure range of 800 to 1,200 hPA, and the plasma can be discharged from a nozzle tube end, the temperature of the generated plasma lying within the range of the ambient temperature, e.g. between 10 and 50° C. The nozzle tube of the plasma source may comprises a longitudinal nozzle tube element and a lateral nozzle tube element, and said lateral nozzle tube element may project laterally from the longitudinal nozzle tube element, and plasma may be dischargeable through the lateral nozzle tube end. 
         [0011]    This has the advantage that an otherwise commonly practised expensive and complicated vacuum generation in the plasma treatment area, e.g. within and/or without a container to be coated, can be avoided, and that thermal loads on the substrate to be coated, e.g. a plastic bottle, can be minimized so as to avoid damage to the substrate. 
         [0012]    The process gas that may here be used for depositing quartzous layers may e.g. be a mixture of oxygen and a gaseous organosilicon monomer, such as hexamethyldisiloxane (HMDSO), HMDSN, TEOS, TMOS, HMCTSO, APTMS, SiH4, TMS, OMCTS or similar compounds. 
         [0013]    Analogously, C 2 H 2 , C 2 H 4 , CH 4 , C 6 H 6  or other carbonic swelling substances may be used in the process gas for depositing carbonic layers (so-called diamond like carbon “DLC” layers). 
         [0014]    In addition, the plasma source may be movable linearly, e.g. parallel and/or transversely to the direction of gravity, and/or rotatively about the longitudinal axis and/or a parallel axis of the longitudinal nozzle tube element. 
         [0015]    Likewise, the container to be coated may be movable relative to the plasma source linearly, e.g. parallel and/or transversely to the direction of gravity, and/or rotatively about the longitudinal axis of the container and/or rotatively about an axis that is parallel to the longitudinal axis of the container. 
         [0016]    It is also imaginable that the container is rotatable about and/or translatively movable along some other axis, which is not parallel to the direction of gravity or to the longitudinal axis or the parallel axis of the longitudinal nozzle tube element. 
         [0017]    This allows e.g. that the discharge of plasma can advantageously follow the container contour at a constant distance from the container wall to be coated. 
         [0018]    The above described degrees of movement of the plasma source and/or of a container to be coated offer, among other advantages, the advantage that e.g. a plasma source having a lateral nozzle tube element/having lateral nozzle tube elements can more easily be introduced in a container and that the discharge of the plasma from a nozzle tube end can take place close to the substrate, e.g. preferably with a distance of 0.1-2 cm between the nozzle tube end and the substrate. 
         [0019]    Furthermore, it is imaginable that the nozzle tube ends are movable, e.g. provided with controllable elements such as controllable pivotable flaps, for controlling the propagation direction and the discharge angle of the plasma discharged, and for limiting e.g. the plasma discharge angle to a range of 30° to 170°. 
         [0020]    The term plasma discharge angle should here and in general be understood as the angle between the propagation direction of the plasma and the longitudinal axis of the longitudinal nozzle tube element. 
         [0021]    The plasma source may comprise a plurality of nozzle tubes and electrodes. 
         [0022]    The plasma source may, for example, comprise at least one longitudinal nozzle tube with an electrode, and the nozzle tube end of the longitudinal nozzle tube element may open at the end of the plasma source in the direction of gravity, and may further comprise a plurality of lateral nozzle tube elements with electrodes that may laterally project from the longitudinal nozzle tube element at regular or irregular intervals. The plasma may here be discharged through the lateral nozzle tube ends and through the longitudinal nozzle tube end. 
         [0023]    The longitudinal nozzle tube may, however, also be closed at its longitudinal end, so that plasma can only be discharged through the lateral nozzle tube ends. 
         [0024]    The electrodes suitable for insertion in the plasma source may e.g. be pin electrodes. The ends of the electrodes may e.g. taper or they may be rounded off. 
         [0025]    Furthermore, a device according to the present invention used for plasma-enhanced coating of substrates may be configured as a rotary machine comprising a plurality of treatment units for plasma-enhanced coating of containers and/or container blanks. 
         [0026]    In a method used for plasma-enhanced coating of substrates, such as a container, e.g. a plastic bottle, and/or of a container blank, e.g. a container preform, a plasma source may have supplied thereto a process gas and the process gas may be converted, partly or fully, into a plasma. The plasma can here be ignited at the end of at least one inner electrode, which may have applied thereto a high frequency, under ambient pressure, e.g. in a pressure range of 800 to 1,200 hPA, and at temperatures in a range of e.g. 10 to 50° C., and it can be discharged through a nozzle tube end of the nozzle tube element surrounding the inner electrode and coat a substrate, e.g. a container, such as a plastic bottle, and/or a container blank, e.g. a container preform. 
         [0027]    It is also possible to deposit layers, e.g. multi-layered systems comprising layers of different compositions and layer characteristics, in a plurality of coating steps. For example, an intermediate layer may be deposited as an adhesive agent, e.g. silicon oxide with methyl group residues, between the substrate, e.g. a plastic bottle, and the actual coating, e.g. a gas barrier layer. 
         [0028]    For example, an adhesive agent layer consisting of amorphous carbon may be applied first, this layer being then followed by a barrier layer of silicon oxide. DLC layers may be applied, depending on the layer thickness, as barrier layers, e.g. for layer thicknesses in the range of 50 to 200 nm, or as adhesive agents, e.g. for layer thicknesses in the range of 1 to 10 nm. 
         [0029]    A barrier layer may additionally be provided/coated with a protective layer so as to protect it e.g. against chemical attacks through the product. Alkaline products or products which are only slightly acidic may e.g. partially dissolve and damage a SiOx layer. 
         [0030]    Also additional functional layers may be applied for UV protection, abrasion protection, easier emptying of residues through surface modification, reduction of gushing (abrupt foaming after pressure relief during the bottling process or when the bottles are opened by the consumer), surface modifications allowing easier application of labels by means of an adhesive or easier direct printing. 
         [0031]    Likewise, coatings having a sterilizing effect, e.g. coatings with silver ions or with reactive layers, e.g. singlet-oxygen-containing or singlet-oxygen-creating layers, are imaginable. 
         [0032]    It is also imaginable to additionally apply merely decorative layers so as to accomplish color, frosted, gloss and reflection effects. 
         [0033]    In addition, e.g. also “sandwich” coatings can be provided in an advantageous manner. In such coatings, e.g. a barrier layer is provided between two adhesive agent layers, or between an adhesive agent layer and some other functional or decorative layer. 
         [0034]    In this way, multi-layer coatings can advantageously be produced, said coatings having characteristics which are otherwise difficult to combine. Good barrier layers are e.g. often brittle/friable and have poor adhesion properties, whereas layers having good adhesion properties often have hardly any barrier effect (e.g. “soft” silicon oxide layers) or they have an undesirably intensive brown hue (DLC layers). 
         [0035]    It is also possible to accomplish in one or in a plurality of coating steps a smooth/continuous transition in the layer material and/or the layer composition and/or the layer characteristics within one layer or between different layers. A silicon oxide layer that becomes harder as the thickness increases may e.g. be produced. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0036]    The figures enclosed show exemplarily: 
           [0037]      FIG. 1 : plasma source. 
           [0038]      FIG. 2 : alternative plasma source in a container. 
           [0039]      FIG. 3 : alternative plasma source in a container. 
           [0040]      FIG. 4 : alternative plasma source in a container. 
           [0041]      FIG. 5 : alternative plasma source in a container. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0042]      FIG. 1  shows exemplarily the diagram of a plasma source  100  as a plasma nozzle. The plasma source may here comprise a nozzle tube  101  with a nozzle tube end  102 . 
         [0043]    The nozzle tube  101  may comprise an inner electrode  103 , e.g. a pin electrode, which is adapted to have applied thereto a high frequency from the high-frequency source  107 . The nozzle tube  101  may here be connected to ground or earth potential  106 . A process gas  108  may be supplied to the cavity  110  between the inner electrode and the nozzle tube  101 . At the end  109  of the inner electrode, the process gas can be converted, partly or fully, into a plasma  105  through electric discharges, and the plasma  105  can be discharged from the nozzle tube end  102  and impinge on the substrate  104  to be coated, e.g. a container wall or a container blank surface, which may be spaced apart from the nozzle tube end  102  at a distance  111 , preferably a distance of 0.1-2 cm. The nozzle tube end  102  may be shaped such that it tapers conically to the plasma discharge opening  112 . 
         [0044]    In addition, it is imaginable that the nozzle tube end  102  may be provided with controllable pivotable flaps (not shown), which are capable of controlling the plasma propagation direction  112  and the plasma discharge angle  113  insofar as e.g. the discharge angle  113  of the plasma can be limited to a range of 30° to 170°. 
         [0045]      FIG. 2  shows exemplarily a plasma source  200  that is adapted to be inserted into a container  208 . The plasma source  200  may here consist of a longitudinal nozzle tube element  201  and of a lateral nozzle tube element  202  with a nozzle tube end  203 , said nozzle tube element  202  projecting laterally from said nozzle tube element  201 . The angle  209  between the lateral nozzle tube element  202  and the longitudinal nozzle tube element  201  may lie between 45° and 135°. The preferred angle  209  is an angle between 80° and 100° or, as shown in  FIG. 2 , an angle of 90°. 
         [0046]    It is here also imaginable that the lateral nozzle tube element  202  is pivotable, e.g. by means of a ball and socket joint connection between the lateral nozzle tube element  202  and the longitudinal nozzle tube element  201 . This is another possibility of controlling the propagation direction and the discharge angle of the plasma, and of limiting e.g. the plasma discharge angle to a range of 30° to 170°. 
         [0047]    The inner electrode  205 , which may be encompassed by the nozzle tube elements  201  and  202  and which may have applied thereto a high frequency from the high-frequency source  216 , can here follow the geometrical profile of the contour of the nozzle tube elements  201  and  202 . 
         [0048]    The plasma source can here be movable linearly, e.g. parallel  210  and/or transversely  211  to the direction of gravity, and/or rotatively about the longitudinal axis  215  and/or a parallel axis  214  of the longitudinal nozzle tube element. Likewise, the container  208  may be movable relative to the plasma source  200  linearly, e.g. parallel and/or transversely to the direction of gravity, and/or rotatively about the longitudinal axis of the container and/or rotatively about an axis  214  that is parallel to the longitudinal axis of the container. 
         [0049]    It is also imaginable that the container  208  is rotatable about and/or translatively movable along some other axis, which is not parallel to the direction of gravity or to the longitudinal axis  215  or the parallel axis  214  of the longitudinal nozzle tube element. 
         [0050]    This allows e.g. that the discharge of plasma can advantageously follow the container contour at a constant distance from the container wall to be coated. 
         [0051]    The process gas  216  can be supplied to the cavity between the inner electrode  205  and the nozzle tube elements  201  and  202  and, at the end  206  of the electrode  205 , it can be converted partly or fully into a plasma  204  that can be discharged through the plasma discharge opening  218  at the nozzle tube end  203  and can thus coat e.g. an inner wall  207  of the container  208 . 
         [0052]      FIG. 3  shows exemplarily a further plasma source  300  that can be introduced in a container  308 . The plasma source  300  may here be provided with a longitudinal nozzle tube element  301  from which a plurality of lateral nozzle tube elements  302  may laterally project. The lateral nozzle tube elements  302  may be provided on one side or also on a plurality of sides along the longitudinal axis of the longitudinal nozzle tube. The vertical distances  309  between neighboring lateral nozzle tube elements  302  may here be regular or irregular, and may e.g. be distances between 1 and 4 cm, preferably approx. 2 cm. 
         [0053]    The end  312  located in the direction of gravity of the longitudinal nozzle tube element  301  may also be configured as a nozzle tube end provided with a plasma discharge opening  313  so that the bottom  314  of the container  308  can be coated with the discharged plasma  315  in an advantageous manner. Said longitudinal nozzle tube end  312  may define e.g. an angle  311  between 45° and 135° with the directly adjacent lateral nozzle tube element  316 . 
         [0054]    As can be seen in the figure, the angles  310  between the lateral nozzle tube elements  302 ,  316  and the longitudinal nozzle tube element  301  may e.g. be 90° angles, but they may also be in the range of 45° to 135° or in the range of 80° to 100° (cf. in this respect also  FIG. 4 ). 
         [0055]    Just as in the case of the above described plasma source  200 , the plasma source  300  may be movable linearly, e.g. parallel  320  and/or transversely  321  to the direction of gravity, and/or rotatively  329  about the longitudinal axis and/or a parallel axis or at an angle relative to the axis of the longitudinal nozzle tube element  301  Likewise, the container  308  may be movable relative to the plasma source  300  linearly, e.g. parallel and/or transversely to the direction of gravity, and/or rotatively about the longitudinal axis of the container and/or rotatively about an axis parallel to the longitudinal axis of the container. 
         [0056]    It is also imaginable that the container  308  is rotatable about and/or translatively movable along some other axis, which is not parallel to the direction of gravity or to the longitudinal axis or the parallel axis of the longitudinal nozzle tube element  301 . 
         [0057]    The inner electrode element  322  may comprise a plurality of inner electrodes whose number may correspond to that of the nozzle tube elements, e.g. a longitudinal electrode  331  encompassed by the longitudinal nozzle tube element  301 , and lateral electrodes  324  encompassed by the lateral nozzle tube elements  302 ,  316 . 
         [0058]    The process gas  326  may be supplied to the cavity  330  between the inner electrode element  322  and the nozzle tube elements  301 ,  302  and  316 . At the ends  323 ,  325  of the inner electrodes, the process gas can be converted, partly or fully, into a plasma  328 , which can be discharged through the plasma discharge openings  313  of the nozzle tube ends  312 ,  317  and  319  and can thus coat e.g. an inner wall  318  and/or the bottom  314  of the container  308 . 
         [0059]      FIG. 4  shows exemplarily a further plasma source  400  which is configured analogously to the above described plasma source  300 , but which exhibits an exemplary arrangement of the lateral nozzle tube elements  402 ,  403  and  404  whose orientation relative to the longitudinal nozzle tube element  401 , characterized by the angles  406 ,  407 ,  408  between the longitudinal nozzle tube element  401  and the lateral nozzle tube elements  404 ,  403 ,  402 , may be different from 90°. 
         [0060]    For example, the angle  406  between the longitudinal nozzle tube end  405  and the neighboring nozzle tube end  404  may be smaller than 90°, e.g. between 10° and 85°, and the angle  408  between the lateral nozzle tube  402  and the longitudinal nozzle tube element  401  may be larger than 90° and lie e.g. in the range of 95° to 170°. 
         [0061]    According to an advantageous embodiment, one or a plurality of lateral nozzle tube elements  402 ,  403 ,  404 , which are arranged closer to the process gas inlet  418  leading into the longitudinal nozzle tube element, may be tilted towards said process gas inlet  418  (in  FIG. 4  e.g. upwards), i.e. the angle  419  between the lateral nozzle tube element  402  and the process gas inlet  418  of the longitudinal nozzle tube element  401  may be less than 90° and may preferably lie between 10° and 85°. One or a plurality of lateral nozzle tube elements that are more remote from the process gas inlet  418  may be tilted away from the process gas inlet  418  (in  FIG. 4  e.g. downwards). 
         [0062]    One of the advantages of this arrangement is that e.g. corners, such as the corner  417  between the container bottom  413  and the container wall  414 , or oblique container walls, e.g. the container wall slope  415 , can be coated more easily. 
         [0063]    Apart from the above described angles, the plasma source  400  may have the same features as the plasma source  300 . The plasma source  400  may, for example, be movable linearly, e.g. parallel  409  and/or transversely  410  to the direction of gravity, and/or rotatively  411  about the longitudinal axis and/or a parallel axis of the longitudinal nozzle tube element Likewise, the container  420  may be movable relative to the plasma source  400  linearly, e.g. parallel and/or transversely to the direction of gravity, and/or rotatively about the longitudinal axis of the container and/or rotatively about an axis parallel to the longitudinal axis of the container. 
         [0064]    It is also imaginable that the container  420  is rotatable about and/or translatively movable along some other axis, which is not parallel to the direction of gravity or to the longitudinal axis or the parallel axis of the longitudinal nozzle tube element  401 . 
         [0065]      FIG. 5  shows exemplarily a further plasma source  500 , which may comprise a longitudinal nozzle tube element  501  from which lateral nozzle tube elements  502 ,  503  project in pairs from opposed sides of the longitudinal nozzle tube element  501 . 
         [0066]    The angles  515 ,  514  between the lateral nozzle tube elements  502 ,  503  and the longitudinal nozzle tube element  501  may lie in the range between 45° and 135°. Preferably, these angles are, however, pairwise identical. The angle  515  between the longitudinal nozzle tube end  504  and the nearest lateral nozzle tube elements  503  may preferably be smaller than 90° and may, for example, lie between 10° and 85°. 
         [0067]    Just as in the case of the above described plasma sources  200 ,  300  and  400 , the plasma source  500  may be movable linearly, e.g. parallel  506  and/or transversely  507  to the direction of gravity, and/or rotatively  508  about the longitudinal axis and/or a parallel axis of the longitudinal nozzle tube element Likewise, the container  500  may be movable relative to the plasma source  500  linearly, e.g. parallel and/or transversely to the direction of gravity, and/or rotatively about the longitudinal axis of the container and/or rotatively about an axis parallel to the longitudinal axis of the container. 
         [0068]    It is also imaginable that the container  500  is rotatable about and/or translatively movable along some other axis, which is not parallel to the direction of gravity or to the longitudinal axis or the parallel axis of the longitudinal nozzle tube element  501 . 
         [0069]    Neighboring nozzle tube elements may also be vertically displaced relative to one another and they may e.g. be able to rotate e.g. about the longitudinal nozzle tube element. 
         [0070]    By means of the increased number of lateral nozzle tube elements in comparison with an embodiment having its lateral nozzle tube elements not arranged in pairs, the surface area that can be coated per unit time can be increased and the amount of time required for coating can thus be reduced. It would be imaginable to optimize the coating time still further by another increase in the number of lateral nozzle tube elements, e.g. by means of a collar of lateral nozzle tube elements comprising more than two lateral nozzle tube elements per collar. 
         [0071]    In addition, it is imaginable that a plasma source comprises lateral nozzle tube elements which are adapted to be extended from a longitudinal nozzle tube telescopically and/or in an umbrella-like manner and/or which are adapted to be folded out from said longitudinal nozzle tube.