GB2589481A

GB2589481A - Evaporator body

Info

Publication number: GB2589481A
Application number: GB2019836.2A
Authority: GB
Inventors: Goetz Philipp
Original assignee: Cvt & Co KG GmbH
Current assignee: Cvt & Co KG GmbH
Priority date: 2018-06-06
Filing date: 2019-05-23
Publication date: 2021-06-02
Anticipated expiration: 2039-05-23
Also published as: GB2589481B; GB202019836D0; CN112218974B; DE102018113528B4; WO2019233775A1; DE102018113528A1; CN112218974A

Abstract

An evaporator body (1) for evaporating metal in a PVD metallization system, comprising: - a top side (3) which has a first and a second longitudinal edge (5-1, 5-2) and a first and a second transverse edge (7-1, 7-2) which extend transversely to the longitudinal edges; and - a first and a second longitudinal groove (11-1, 11-2) which are formed in the top side (3), wherein: - the first longitudinal groove (11-1) extends adjacent to and along the first longitudinal edge (5-1) and the second longitudinal groove (11-2) extends adjacent to and along the second longitudinal edge (5-2); - ends of the longitudinal grooves (11-2, 11-2) have a distance from the transverse edges (7-1, 7-2); and - an inner evaporation surface (13) formed by the top side (3) of the evaporator body (1) is directly delimited on the longitudinal sides by the longitudinal grooves (11-1, 11-2).

Description

EVAPORATOR BODY

The invention relates to an evaporator body for evaporating metal in a PVD (physical vapour deposition) metallisation system.

A common method for coating flexible substrates with metals is the so-called vacuum strip metallisation in accordance with the PVD technique. Paper, plastic films and textiles are for example considered as the flexible substrates and aluminium is largely used as the metal. Substrates coated in this manner have for example a wide application for packaging and decoration purposes, in condenser manufacture and in environmental technology (insulation).

The coating of the flexible substrates takes place in so-called metallisation systems. In the metallisation system, the substrate to be coated is guided over a cooled roller and in doing so is exposed to metal vapour, which is precipitated on the substrate surface as a thin metal layer. In order to generate the required metal vapour flow, resistance-heatable evaporator bodies, e.g. in the form of so-called evaporator boats are used, which are heated in the direct flow passage to e.g. 1450-1600°C. Metal wire or aluminium wire is supplied to an evaporation side (generally this is the surface of the evaporator body), liquefied on the evaporation side and evaporated in a vacuum at approx. 10-4 mbar.

Non-flexible substrates are coated according to the PVD technique e.g. in batches in a discontinuous process, e.g. 30 by means of flash evaporation. Non-flexible substrates are -2 -e.g. television screens and plastic parts such as e.g. headlamp reflectors.

Normal evaporator bodies consist e.g. of ceramic material, 5 which contains as the main components e.g. titanium diboride and boron nitride and/or aluminium nitride. Titanium diboride is in this case, the electrically-conductive component and boron nitride and/or aluminium nitride are the electrically-insulating component(s) which, 10 when mixed together, lead to specific electric heat resistances of 80-6000 pOhm*cm, with a mixing ratio of conductive to non-conductive components of e.g. in each case 50% by weight being present. ;A problem that often occurs in practice is the wetting of the evaporation side of the evaporator body with the metal to be evaporated. In the case of uneven and incomplete wetting of the evaporation side, for example at the start of an evaporation, there is a problem in that the evaporation side is cooled unevenly by the metal to be evaporated and this can appear in temperatures that are excessively high in non-wetted regions of the evaporation side which damage (decompose) the evaporator body. This effect is further increased in that the electric total resistance in relation to the already wetted region is greater in the non-wetted region of the evaporator body since the metal to be evaporated forms a parallel resistance to the evaporator body in the wetted regions and therefore reduces the electric total resistance of the evaporator body in the wetted region. Wearing of the evaporator body by high temperature corrosion due to the aggressive metal melt also takes place in the wetted regions of the evaporation side such that the evaporator -3 -body must be provided with a sufficient material strength to achieve sufficient useful lives. This leads to high material costs for the evaporator body. ;Therefore, the evaporation side is often provided with a plurality of cavities in the prior art which should enable improved wetting of the evaporation side. For example, DE 10 2013 211 034 Al shows an evaporator body with an inner and a circumferential outer cavity which are separated from one another by a web. However, this leads to a locally reduced thickness of the evaporator body in the region of the inner cavity (molten bath) particularly affected by the high temperature corrosion whereby the useful life of an evaporator body of this type can be reduced and the influence of the parallel resistance of the metal melt on the total resistance of the evaporator body can be great. ;It is an object of the present invention to provide a hard-wearing and durable evaporator body. Additionally, the evaporator body should be easy and cost-effective to manufacture and be easily operable in a PVD metallisation system. ;To this end, the invention provides an evaporator body according to claim 1 and a PVD metallisation system in combination with an evaporator body according to claim 15. Further embodiments of the evaporator body are described in the dependent claims. ;The evaporator body according to the invention for evaporating metal in a PVD metallisation system has an upper side (for example evaporation side), from which supplied metal can be evaporated. For example, metal such -4 -as e.g. aluminium or an aluminium alloy in the form of a metal wire can be supplied to the upper side. Alternatively/additionally, it is possible to supply already melted metal to the upper side. In the case of the metal wire, the metal supplied to the upper side is firstly liquefied/melted on the hot upper side and then evaporated. The evaporator body can for example have a longitudinally-stretched shape, with optionally a rectangular upper side. ;The upper side can e.g. have a first and a second longitudinal edge and a first and a second transverse edge (for example short in relation to the longitudinal edge), which extend transversally (e.g. orthogonally) to the longitudinal edges. The edges can for example be connected to one another at their ends in order to form a circumferential edge of the upper side. ;The upper side can also have e.g. a first and a second longitudinal channel, which are formed in the upper side, and the first longitudinal channel can extend adjacent and (for example parallel) along the first longitudinal edge and the second longitudinal channel can extend adjacent and (e.g. parallel) along the second longitudinal edge. For example, ends of the longitudinal channels can have a distance to the transverse edges. The longitudinal channels can directly delimit on the longitudinal side e.g. an inner (e.g. between the longitudinal channels) evaporation surface formed by the upper side of the evaporator body. Furthermore, the bottoms of the longitudinal channels can form an additional evaporation surface (e.g. auxiliary or secondary evaporation surface). -5 - ;The evaporator body can also have for example a first and a second transverse channel, and the first transverse channel can extend adjacent and (e.g. parallel) along the first transverse edge and the second transverse channel can extend adjacent and (e.g. parallel) along the second transverse edge. For example, ends of the transverse channels can be connected to the ends of the longitudinal channels in order to form a (e.g. at least substantially completely) circumferential channel in the upper side from which the inner evaporation surface formed by the upper side of the evaporator body is delimited directly (e.g. completely) along the circumference. Alternatively, the evaporator body can have an individual transverse channel which is connected to the ends of the longitudinal channels, which are facing one of the transverse edges, in order to form a U-shaped channel in a top view of the upper side, and the limbs of the U shape can correspond to the longitudinal edges. ;The evaporation surface can have e.g. a surface area which can be in a range of e.g. 25% to 85%, preferably in a range of e.g. 40% to 65% and further preferably in a range of e.g. SO% to 60% of a surface area of the upper side of the evaporator body. ;A ratio of the surface area of the evaporation surface to a surface area, which takes in the longitudinal and/or transverse channels in the upper side (for example a surface area of a bottom surface of the channels), can be in a range of e.g. 10:1 to 3:1 and preferably in a range of e.g. 8:1 to 5:1. -6 - ;The longitudinal channels can have e.g. a length which is in a range of 50% to 85%, preferably in a range of 60 to 80% of a length of the corresponding longitudinal edge. ;The ends of the longitudinal channels can have a distance e.g. to the transverse edges (e.g. in a longitudinal direction of the evaporator body at one or at both sides) which is in a range of 8% to 30%, preferably in a range of 10% to 25% of the length of the corresponding longitudinal edge. ;A width-to-depth ratio of the channels can be in a range of e.g. 1:0.5 to 3:1 and preferably at e.g. 1:1 (e.g. the channels can have the same width-to-depth ratio over their entire length, and the depth and therefore the width can be different at least in sections). ;A width of the channels can e.g. be in a range of e.g. 0.5 mm to 2.5 mm and preferably in a range of e.g. 1 mm to 2 20 mm. ;For example, the transverse channels can have a greater distance to the transverse edges than the longitudinal channels to the longitudinal edges, and e.g. a distance of the longitudinal channels to the longitudinal edges can be in a range of 1 mm to 5 mm, preferably in a range of 1.5 mm to 2.5 mm and a distance of the transverse channels to the transverse edges can be in a range of 5 mm to 15 mm, preferably in a range of 10 mm to 12 mm. ;The evaporation surface and a region of the upper side between the channels and the edges (for example a web) can be or end (e.g. at least substantially) at the same height (for example the evaporator body can have the same thickness in these regions). ;The evaporator body can also have e.g. a first and a second 5 side surface (for example rectangular side surfaces), and the first side surface can adjoin the first longitudinal edge (e.g. directly) and can extend along it and the second side surface can adjoin the second longitudinal edge (e.g. directly) and can extend along it. A groove (e.g. two, 10 three or more) can e.g. he formed in the side surfaces which can extend adjacent and (e.g. parallel) along the corresponding longitudinal edge. ;The groove can have e.g. a width in a range of 0.5 mm to 15 2.0 mm, preferably of 1 mm and a depth in a range of 1 mm to 2.5 mm, preferably of 2 mm. ;A length of the groove can be e.g. in a range of 100% to 50%, preferably in a range of 100% to 80% of the length of the corresponding longitudinal edge (i.e. the length of the groove can extend over the entire length of the side surface). The lengths and ends of the grooves can simultaneously or alternately e.g. correspond to the lengths and the ends of the first and the second longitudinal channels (for example the ends of the grooves can have the same distance to the transverse edges as the ends of the longitudinal grooves). ;The PVD metallisation system according to the invention in combination with the above-described evaporator body can have e.g. a first and a second (for example cooled) electrode, with the evaporator body being contactable (electrically conductively) e.g. in the region of the -8 -transverse edges (for example at transverse sides corresponding thereto) by the electrodes (e.g. the transverse sides with the respective electrode are located in a surface contact in order to allow an electric current to flow through the electrodes by way of the evaporator body to heat the evaporator body). ;The invention is explained below on the basis of exemplary embodiments with reference to the drawing. In the drawing 10 are shown: Figure 1 a perspective view of an evaporator body according to an exemplary embodiment with two longitudinal channels, Figure 2 a sectioned view of the evaporator body along the line I-I in Figure 1, Figure 3 a sectioned view of the evaporator body along the line II-II in Figure 1, Figure 4 a perspective view of an evaporator body according to a further exemplary embodiment with a circumferential channel, Figure 5 a channel cross-section according to an exemplary embodiment, Figure 6 a perspective view of an evaporator body according to a further exemplary embodiment with side grooves, -9 -Figure 7 a sectioned view of the evaporator body along the line in Figure 6, and Figure 8 a perspective view of an evaporator body in a PVD metallisation system. ;Reference is made in the following detailed description to the enclosed figures which form part of said description and in which are shown specific embodiments for illustration purposes and the invention can be implemented in said embodiments. It goes without saying that other embodiments can be used and structural or logical changes can be made without deviating from the present invention. It also goes without saying that the features of the different exemplary embodiments described herein can be combined with one another, unless otherwise specified (for example embodiments which combine different longitudinal and transverse channels with lateral grooves in the evaporator body). The following detailed description is therefore not to be understood in a limiting sense, and the scope of protection of the present invention is defined by the enclosed claims. ;The numbers or range values used herein have normal 25 tolerances of ± 5% even without explicit mentioning. ;In the figures, sizes, thicknesses, distances, ratios etc. of illustrated elements (for example the channels and/or grooves) may be exaggerated for illustration purposes. ;Figures 1 to 4 and 6 and 7 show an evaporator body 1 for evaporating metal, moreover for example aluminium or an aluminium alloy, in a PVD metallisation system. The -10 - evaporator body 1 is formed in the shape of a so-called evaporator boat and consists of ceramic material, which contains as the main components titanium diboride and boron nitride, with titanium diboride being the electrically-conductive component and boron nitride being the electrically-insulating component. A mixing ratio of conductive to non-conductive component is e.g. in each case 50', resulting in a specific resistance of approx. 80-6000 pOhm*cm. The evaporator body 1 is formed as a plate body or square body with a length L of e.g. 130 mm, a width W of e.g. 35 mm and a thickness D of e.g. 10 mm. Through electrically-conductive contacting of the short sides (transverse sides) of the evaporator body 1 by means of electrodes and applying an electric voltage, a flc02, of current can be generated through the evaporator body 1 which heats it (= electrically-conductive resistance-heatable evaporator body).

The evaporator body 1 of an exemplary embodiment shown in Figures 1 to 3 has an upper side 3 with a first and a second longitudinal edge 5-1, 5-2 and a first and a second transverse edge 7-1, 7-2, which extend transversally (e.g. orthogonally) to the longitudinal edges 5-1, 5-2. The edges 5-1, 5-2, 7-1, 7-2 form a circumferential edge 9, which (e.g. at least substantially) completely surrounds the upper side 3.

The evaporator body 1 also has a first and a second longitudinal channel 11-1, 11-2 which are formed in the upper side 3. The first longitudinal channel 11-1 is formed extending adjacent and parallel along the first longitudinal edge 5-1 and the second longitudinal channel 11-2 is formed extending adjacent and parallel along the second longitudinal edge 5-2. An inner evaporation surface 13 formed (e.g. at least substantially flat) by the upper surface 3 of the evaporator body 1 is delimited directly on the longitudinal side by the two longitudinal channels 11- 1, 11-2. The longitudinal channels 11-1, 11-2 can receive molten aluminium on the evaporation surface 13 which can flow into the longitudinal channels 11-1, 11-2 and is therefore prevented from leaving the upper side 3 of the evaporator body 1 (except for due to evaporation) (for example the longitudinal channels 11-1, 11-2 form an auxiliary or secondary evaporation surface for the received aluminium). A respective (first and second) web 15-1, 15-2 is formed between the circumferential edge 9 and the longitudinal channels 11-1, 11-2 in the upper side 3 of the evaporator body 1, which do not (e.g. at least substantially) receive aluminium during melting/evaporation of the aluminium wire (for example splashes of molten aluminium can reach the upper side of the webs 15-1, 15-2). The webs 15-1, 15-2 prevent aluminium melt flowing out of the longitudinal channels 11-1, 11-2.

The evaporation surface 13 has a surface area which is in a range of e.g. 502) to 60' of a surface area of the upper side 3 of the evaporator body 1. A ratio of the surface area of the evaporation surface 13 to a surface area, which takes in the longitudinal channels 11-1, 11-2 in the upper side 3, is in a range of e.g. 5:1 to 6:1. In this way, a sufficiently large surface is provided for evaporating (e.g. as the main evaporation surface the evaporation surface 13 and as the auxiliary or secondary evaporation surface the bottoms of the longitudinal channels 11-1, 112) on the upper side 3 of the evaporator body 1, which, however, is arranged remote from the longitudinal edges 5- -12 - 1, 5-2 of the upper side 3 in order to prevent molten aluminium flowing away from the evaporator body 1. The evaporation surface 13 is preferably arranged in the middle of the upper side 3.

The longitudinal channels 11-1, 11-2 each have a length L', which is in a range of 80% of the length L of corresponding longitudinal edge 5-1, 5-2. In addition, the longitudinal channels 11-1, 11-2 have a distance Al of e.g. 1.5 mm to 2.5 mm to the corresponding longitudinal edges 5-1, 5-2; the distance Al corresponds to the width of the webs 15-1, 15-2. Moreover, the ends of the longitudinal channels 11-1, 11-2 have a distance A2 of e.g. 5 mm to 15 mm to the corresponding transverse edges 7-1, 7-2.

The longitudinal channels 11-1, 11-2 have a width B' transverse to their extension direction (along the circumferential edge 9), which is in a range of e.g. 1 mm to 2 mm. Additionally, the longitudinal channels 11-1, 11-2 have a width-to-depth ratio (W-D ratio) of e.g. 1:1. The indicated widths or ratios are not limited to constant values, but can vary e.g. in sections along the extension direction of the longitudinal channels 11-1, 11-2. For example, shorter channel sections can have a smaller depth and/or smaller width in comparison to longer channel sections.

In this way, a temperature of the evaporator body 1 in the region of (close to) the or in the longitudinal channels 11-1, 11-2 is increased by the two longitudinal channels 11-1, 11-2 such that a temperature profile can be set on the upper side 3 over the width B of the evaporator body 1. This is the case since, due to the local cross-sectional -13 -tapering of the evaporator body 1 through the longitudinal channels 11-1, 11-2, a local increase in heat output of the evaporator body 1 takes place. Additionally, a heat radiation emission/immission of the evaporator body 1 can be set by forming the longitudinal channels 11-1, 11-2. Therefore, a temperature of the evaporation surface 13 can be set at its longitudinal edges (transitions to the longitudinal channels) by forming the longitudinal channels 11-1, 11-2 e.g. such that a temperature profile is e.g. at least substantially constant at/on the evaporation surface 13 over the width B of the evaporator body 1 or increases towards the longitudinal edges of the evaporation surface 13.

Furthermore, the evaporation surface 13 and a region of the upper surface 3 between the longitudinal channels 11-1, 112 and the circumferential edge 9, i.e. an upper side of the webs 15-1, 15-2 and a region between the ends of the longitudinal channels 11-1, 11-2 and the transverse edges 7-1, 7-2 are (e.g. at least substantially) at the same height, i.e. the evaporator body 1 has in these regions the same thickness B such that the evaporator body 1 in the region of the evaporation surface 13, which is particularly strongly affected by the high temperature corrosion, has a maximum thickness and therefore a long useful life. This means that during operation of the evaporator body 1 the aluminium melt spreads (e.g. at least substantially) in the region between the longitudinal channels 11-1, 11-2 (evaporation surface 13) and excess aluminium melt flows into the longitudinal channels 11-1, 11-2 and is evaporated there. The evaporation in the longitudinal channels 11-1, 11-2 takes place, in relation to the evaporation surface 13, to a greater extent since the temperature in the -14 -longitudinal channels 11-1, 11-2 is higher due to a lower heat loss (mutual heating of the channel walls and of the channel bottom by heat radiation) than that of the evaporation surface 13.

In this way, an evaporation surface 13 is provided which is delimited on the longitudinal side by the longitudinal channels 11-1, 11-2 and which has on the transverse side a sufficiently large distance to the transverse edges 7-1, 7- 2. Since, as described above, the evaporator body 1 is electrically contacted on the transverse edges 7-1, 7-2 during operation in a metallisation system, for example by cooled electrodes of the metallisation system, there is the risk that an electrical flashover takes place from one electrode to the molten bath when the molten bath gets too near the electrode (transverse edge of the evaporator body). Through the selected distances, an electrical flashover to the molten aluminium is suppressed, while at the same time an evaporator body 1 is provided which has a large (thermal) inertia or mass due to the solely two longitudinal channels 11-1, 11-2.

Figure 4 shows an evaporator body 1 for evaporating metal according to a further exemplary embodiment, with a first and a second transverse channel 17-1, 17-2 also being formed in the upper side 3 of the evaporator body 1 in addition to the two longitudinal channels 11-1, 11-2. The first transverse channel 17-1 extends adjacent and parallel along the first transverse edge 7-1 and the second transverse channel 17-2 extends adjacent and parallel along the second transverse edge 7-2, with ends of the transverse channels 17-1, 17-2 being connected to the ends of the longitudinal channels 11-1, 11-2 to form a completely -15 -circumferential channel 19 in the upper side. The inner evaporation surface 13 formed by the upper side 3 of the evaporator body 1 is delimited directly and completely along the circumference by the circumferential channel 19.

That is to say that the transverse channels 17-1, 17-2 have the same distances A2 to the transverse edges 7-1, 7-2 as the ends of the longitudinal channels 11-1, 11-2. The transverse channels 17-1, 17-2 also fulfil the same function as the longitudinal channels 11-1, 11-2; the configurations indicated above for the longitudinal channels 11-1, 11-2 can apply analogously here to the transverse channels 17-1, 17-2.

In this way, the aluminium melt is held (e.g. at least substantially) in the inner region (evaporation surface 13) of the upper side 3 of the evaporator body 1 by the circumferential channel 19 without excessively reducing the (thermal) inertia or mass of the evaporator body 1.

Figure 5 shows one of the longitudinal and transverse channels, moreover exemplarily the first longitudinal channel 11-1 of an evaporator body 1 according to the invention in detail (cross-section). The side walls (longitudinal walls) of the first longitudinal channel 11-1 have at a transition to the bottom of the first longitudinal channel 11-1 a curvature 21. As a result, during the operation of the evaporator body 1, the occurrence of hot spots in the region of the first longitudinal channel 11-1 (in the transition region of the channel bottom to the channel wall) and a notch effect can be avoided/reduced. For example, only one of the side walls of the first longitudinal channel 11-1 can also be designed as described above. Furthermore, the side wall of the first -16 -longitudinal channel 11-1 forms an angle of e.g. 900 with the section of the evaporation surface 13 adjoining the first longitudinal channel 11-1, whereby an accumulation of the aluminium melt on an upper border (edge) 23 of the first longitudinal channel 11-1 at the start of the operation of the evaporator body 1 is favoured before it flows into the first longitudinal channel 11-1 in order to achieve even wetting of the evaporation surface 13.

This means that the first longitudinal channel 11-1 has a wetting-promoting effect through the upper border (edge) 23 with the evaporation surface 13. The liquid aluminium accumulates at this upper border 23 and flows along the upper border 23 (along the first longitudinal channel 11-1) such that the aluminium melt firstly wets the evaporation surface 13 (e.g. at least substantially) primarily along the upper border 23. The wetting of the first longitudinal channel 11-1 by accumulated aluminium melt takes place suddenly and substantially locally over the upper corder 23. At the same time, aluminium melt is prevented from accumulating excessively on the evaporation surface 13, i.e. an excessive accumulation of the aluminium melt is prevented such that only evaporation of the molten aluminium on the evaporation surface 13 takes place, but no "boiling" with undesired spraying of aluminium melt.

Furthermore, an even and full-surface wetting of the evaporation surface 13 can be achieved, even when the supply of the aluminium wire takes place decentralised (e.g. in a region 1/3 the length L of the evaporator body 1). This means that the molten aluminium also wets substantially over the entire evaporation surface 13 when the aluminium wire meeting point on the evaporation surface -17 - 13 is not in the middle of the evaporation surface 13. The evaporator body 1 is user-friendly and hard-wearing in practical use as a result. For example in the case often encountered in practice, in which the aluminium wire meets the evaporation surface 13 at roughly 1/3 the length L of the evaporator body 1, only a transverse channel can be formed on the transverse edge which is located nearer to the meeting point of the aluminium wire on the evaporation surface 13.

The shape of the longitudinal and transverse channels 11-1, 11-2, 17-1, 17-2 is not limited to the above-described shapes; alternatively, they can have a rectangular cross-section without rounded portions or for example a triangular cross-section, a polygonal cross-section, etc. The channels 11-1, 11-2, 17-1, 17-2 can for example be produced by milling. If the evaporator body 1 is produced by sintering a green body, then the channels 11-1, 11-2, 17-1, 17-2 can also be formed during shaping of the green body, e.g. by correspondingly pressing in the green body mass.

The evaporator body is formed in one piece here as an electrically-conductive resistance-heatable evaporator body, for example in a square shape (e.g. alternatively as a column-shaped or longitudinally-stretched body with polygonal cross-section). Alternatively, the evaporator body can for example be formed as an electrically- insulating evaporator body outer part which has an inner hollow space for receiving an electrically-conductive resistance-heatable evaporator body core part. The outer part can in this case be heated using the pushed- -18 -in/inserted core part. In both cases, the evaporation surface of the evaporator body can also be provided with a wetting-promoting layer/coating. Such a coating can also serve to protect against wear and corrosion.

Figures 6 and 7 show an evaporator body according to a further exemplary embodiment with side grooves, with the evaporator body 1 being represented here with the circumferential channel 19 in the upper side 3 as an example (but the other above-described configurations of the evaporator body with longitudinal and transverse channels are also possible). The evaporator body 1 has a first and a second side surface 31-1, 31-2, with the first side surface 31-1 adjoining the first longitudinal edge 5-1 and extending completely along said first longitudinal edge (hidden in Figure 6) and the second side surface 31-2 adjoining the second longitudinal edge 5-2 and extending completely along said second longitudinal edge. The side surfaces 31-1, 31-2 are formed in a rectangular design and are oriented (e.g. at least substantially) orthogonally to the upper side 3 such that the plate-shaped evaporator body 1 is formed together with transverse sides, not described further, (to contact with the electrodes of the metallisation system) and a bottom side.

A groove 33-1 or 33-2 is formed in the side surfaces 31-1, 31-2 which extends adjacent and parallel along the corresponding longitudinal edge 5-1 or 5-2. A width B" (in the thickness direction D of the evaporator body 1) of the grooves 33-1, 33-2 is 1 mm and a depth T' thereof is 1.5 mm. The two grooves 33-1, 33-2 extend along the entire length L of the evaporator body 1. For example, ends of the grooves 33-1, 33-2 can alternatively correspond to the ends -19 -of the longitudinal channels 11-1, 11-2. In the thickness direction D of the evaporator body 1, the grooves 33-1, 332 are arranged roughly in the middle of the respective side surface 31-1, 31-2. Analogously and with reference to the above-described longitudinal and transverse channels 11-1, 11-2, 17-1, 17-2, the channels 33-1, 33-2 act in order to set a temperature profile on the surface of the evaporator body 1. In particular in cooperation with the corresponding longitudinal channels 11-1, 11-2, it is possible to set the temperature profile of the upper side 3 (evaporation surface 13).

Figure 8 schematically shows the evaporator body 1 with circumferential channel 19 in operation in a PVD metallisation system (strip metallisation system), with a starting status being represented, in which the process of evaporating the aluminium is just beginning. The evaporation process is carried out in a vacuum at approx. 10-4 mbar. To this end, the evaporator body 1 is arranged between a first and a second cooled electrode 51 of the metallisation system such that the transverse sides (corresponding to the transverse edges 7-1, 7-2) contact the electrodes 51 e.g. over the full surface and current flows through them in order to heat the evaporator body 1 (its upper side) to e.g. 1450-1600°C. An aluminium wire 53 is continuously applied in the middle of the evaporation surface 13 such that the aluminium wire 53 contacts the evaporation surface 13, is melted, the aluminium melt 55 spreads evenly on the evaporation surface 13 and begins to evaporate. By matching the supply rate of the aluminium wire 53 (for example by means of a wire feeding device) and of the electric current flowing through the evaporator body 1 (for example a power source), the evaporation rate of the -20 -aluminium is set. In a stationary state, the aluminium melt 55 wets the evaporation surface 13 e.g. completely, and any aluminium melt 55 flowing out via the evaporation surface 13, which enters the circumferential channel 19, is evaporated there at a higher evaporation rate/cm2 due to the higher temperature in the circumferential channel 19 such that excess aluminium melt 55 does not collect in the circumferential channel 19.

A removal of the material of the evaporator body 1 in the region of the evaporation surface 13 and the circumferential channel 19 due to the high temperature corrosion is therefore low or the material thickness sufficiently great such that the evaporator body 1 has a sufficient useful life. Similarly, the (thermal) inertia or mass of the evaporator body 1 is sufficient to bring about only small changes in the total resistance of the evaporator body 1 in the case of a varying molten bath (varying parallel resistance). In addition, the aluminium melt 55 is sufficiently remote from the electrodes 51 that electrical flashovers can be prevented.

A strip 57 to be coated (e.g. a plastic film; represented by a dashed line in Figure 8) is continually guided above 25 the evaporator body 1, on which strip the aluminium evaporated from the evaporator body 1 precipitates. Then, the strip 57, which has the aluminium coating on the side facing the evaporator body 1, is wound on a cooled roller 59.

Claims

-21 -CLAIMS1. Evaporator body (1) for evaporating metal in a PVD metallisation system, with an upper side (3), which has: a first and a second longitudinal edge (5-1, 5-2) and a first and a second transverse edge (7-1, 7-2) which extend transversally to the longitudinal edges (5-1, 5-2) and a first and a second longitudinal channel (11-1, 11-2) which are formed in the upper side (3), wherein the first longitudinal channel (11-1) extends adjacent and along the first longitudinal edge (5-1) and the second longitudinal channel (11-2) extends adjacent and along the second longitudinal edge (5-2), wherein ends of the longitudinal channels (11-2, 11-2) have a distance to the transverse edges (7-1, 7-2) and wherein an inner evaporation surface (13) formed by the upper side (3) of the evaporator body (1) is delimited directly on the longitudinal side by the longitudinal channels (11-1, 11-2).
2. Evaporator body (1) according to claim 1, further comprising a first and a second transverse channel (17-1, 17-2), wherein the first transverse channel (17-1) extends adjacent and along the first transverse edge (7-1) and the second transverse channel (17-2) extends adjacent and along the second transverse edge (7-2), wherein ends of the transverse channels (17-1, 17-2) are connected to the ends of the longitudinal channels (11-1, 11-2) in order to form a circumferential channel (19) in the upper side, from which the inner evaporation surface (13) formed by the upper side (3) of the evaporator body (1) is delimited directly along the circumference.
-22 - 3. Evaporator body (1) according to claim 1 or 2, wherein the evaporation surface (13) has a surface area which is in a range of 25% to 85%, preferably in a range of 40% to 65% and further preferably in a range of 50% to 60% of a surface area of the upper side (3).
4. Evaporator body (1) according to any one of the preceding claims, wherein a ratio of the surface area of the evaporation surface (13) to a surface area, which takes in the channels (11-1, 11-2, 17-1, 17-2) in the upper side (3), is in a range of 10:1 to 3:1 and preferably in a range of 8:1 to 5:1.
5. Evaporator body (1) according to any one of the preceding claims, wherein the longitudinal channels (11-1, 11-2) have a length, which is in a range of 50-% to 85%, preferably in a range of 60% to 80% of a length of the corresponding longitudinal edge (5-1, 5-2).
6. Evaporator body (1) according to any one of the preceding claims, wherein the ends of the longitudinal channels (11-1, 11-2) have a distance to the transverse edges (5-1, 5-2), which is in a range of 8% to 30%, preferably in a range of 10% to 25% of the length of the corresponding longitudinal edge (5-1, 5-2).
7. Evaporator body (1) according to any one of the preceding claims, wherein a width-to-depth ratio of the channels (11-1, 11-2, 17-1, 17-2) is in a range of 1:0.5 to 3:1 and preferably 1:1.
-23 - 8. Evaporator body (1) according to any one of the preceding claims, wherein a width (B) of the channels (il1, 11-2, 17-1, 17-2) is in a range of 0.5 mm to 2.5 mm and preferably in a range of 1 mm to 2 mm.
9. Evaporator body (1) according to any one of claims 2 to 8, wherein the transverse channels (17-1, 17-2) have a greater distance (A2) to the transverse edges (7-1, 7-2) than the longitudinal channels (11-1, 11-2) to the longitudinal edges (5-1, 5-2).
10. Evaporator body (1) according to claim 9, wherein the distance (Al) of the longitudinal channels (11-1, 11-2) to the longitudinal edges (5-1, 5-2) is in a range of 1 mm to 5 mm, preferably in a range of 1.5 mm to 2.5 mm, and wherein the distance (A2) of the transverse channels (17-1, 17-2) to the transverse edges (7-1, 7-2) is in a range of 5 mm to 15 mm, preferably in a range of 10 mm to 12 mm.
11. Evaporator body (1) according to any one of the preceding claims, wherein the evaporation surface (13) and a region of the upper side (3) between the channels (11-1, 11-2, 17-1, 17-2) and the edges (5-1, 5-2, 7-1, 7-2) are at the same height.
12. Evaporator body (1) according to any one of the preceding claims, also comprising a first and a second side surface (31-1, 31-2), wherein the first side surface (31-1) adjoins the first longitudinal edge (5-1) and extends along it and the second side surface (31-2) adjoins the second longitudinal edge (5-2) and extends along it and wherein a groove (33-1, 33-2) is formed in the side surfaces (31-1, -24 - 31-2) which extends adjacent and along the corresponding longitudinal edge (5-1, 5-2).
13. Evaporator body (1) according to claim 12, wherein a 5 width (B") of the groove (33-1, 33-2) is in a range of 0.5 mm to 2.0 mm, preferably 1 mm and a depth (T') of the grooves is in a range of 1 mm to 2.5 mm, preferably 2 mm.
14. Evaporator body (1) according to claim 12 or 13, 10 wherein a length of the groove (33-1, 33-2) is in a range of 100% to 50%, preferably in a range of 100% to 80% of the length of the corresponding longitudinal edge (5-1, 5-2).
15. PVD metallisation system in combination with an evaporator body (1) according to any one of the preceding claims, wherein the PVD metallisation system has a first and a second electrode (51) and the evaporator body (1) is contactable in the region of the transverse edges (7-1, 72) by the electrodes (51).