Multiple-layer Coating

Abstract

A method and apparatus for coating at least part of a surface of an article in vacuo, in a deposition chamber in which the vacuum is maintained during and between coating operations, the surface to be coated being maintained in a coating position during each coating operation and different coating materials being provided by different sources disposed on a carrier in the chamber, the carrier being displaceable for moving each source in succession into an operative position where emission of material from the source will produce a coating layer on the surface at the coating position.

Description

BACKGROUND OF THE INVENTION

The invention relates to a method and apparatus for surface coating articles, and particularly glass sheets, by deposition of coating materials in vacuo.

It is known to surface-coat articles by placing them in an evacuated enclosure opposite a source from which atoms or molecules of the substance to be deposited are emitted, either by thermal evaporation or by cathode sputtering.

The present invention is primarily concerned with the deposition in vacuo of successive coating layers, either on top of one another or adjacent one another.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to simplify such coating operations.

Another object of the present invention is to permit multiple-layer operations to be carried out automatically, and with a high degree of accuracy.

Still another object of the present invention is to apply successive layers of different coating materials without interrupting the vacuum in the chamber in which such coating operations are carried out.

These and other objects according to the present invention are achieved by a method of forming at least two different coating layers on at least part of a surface of an article, by deposition of different coating materials in vacuo in a single chamber, each different layer being formed by the emission of atoms or molecules from a respective one of a plurality of different sources, emission from each source occurring when that source is at at least one given operative position having a predetermined oppositional relationship to the surface to be coated. The method according to the present invention includes the steps of displacing the emission sources periodically for bringing each source in succession to a given operative position and maintaining it at such position for the time required to effect the desired deposition, emitting material from each source in succession during the period when it is at the operative position for coating such article surface with successively applied layers, and maintaining an uninterrupted vacuum in each chamber during and between the successive coating operations. According to a preferred employment of the present invention, the article is constituted by a glass sheet.

The present invention also involves apparatus for forming at least two different coating layers on at least part of the surface of the article by deposition of different coating materials in vacuo. This apparatus essentially includes means defining a deposition chamber in which the partial vacuum can be maintained, means associated with the chamber for supporting therein an article whose surface is to be coated so that the surface part to be coated is in coating position, and at least one carrier means disposed in the chamber and carrying a plurality of emission sources, each for emitting atoms or molecules of a different coating substance when suitably activated. The carrier is displaceable relative to such article for bringing each source in succession to at least one operative position where an emission of its respective substance will produce a coating layer of the article surface in the coating position, the carrier means being displaceable without interrupting the vacuum in the chamber.

The expression "oppositional relationship" refers to a spatial relationship which is independent of the distance of the emission source from the space area on which the coating substance is to be deposited. A change in oppositional relationship constitutes a movement of the point on this deposition area where this area is intersected by the axis of an imaginary "beam" of atoms or molecules from the emission source. For example, if the centers of the emission source and a fixed surface part being coated are on a common axis normal to such surface, then a change in the spacing of the emission source and surface, along that axis, does not involve a change in the oppositional relationship.

Apparatus according to the invention can be designed so that it is suitable for carrying out the coating method hereinfore defined and for performing other coating techniques. For example, the apparatus can be designed so that a continuous ribbon of material to be coated can be conveyed through the vacuum chamber while the partial vacuum is maintained, and in that case successive portions of the ribbon can be surface-coated with materials emitted from different sources, these being brought successively into a standard operating position in the chamber.

The advantages afforded by the invention can be appreciated by considering a specific example of its use, namely, in the formation of a plural layer coating on a sheet of glass to form an interference filter. If such filters are formed by deposition of the coating layers in vacuo in existing vacuum-coating apparatus, time is lost in replacing one source of coating substance by another and the delay is appreciable because this exchange of sources necessitates interrupting the partial vacuum and reestablishing it before coating can recommence. Proposals hitherto made to prelocate different sources of coating substance at different operative positions in the chamber have not proved to be satisfactory in practice because the thin layers of the interference filter did not have the necessary high-degree of uniformity. By depositing the different coatings from sources occupying the same oppositional relationship to the surface to be coated, this problem is solved, and apparatus according to the invention permits this solution to be adopted without interruption of the partial vacuum and the consequential delays.

The invention is primarily intended for surface-coating flat surfaces, e.g., sheets of glass, each coating layer being formed by emission of atoms or molecules from a source located symmetrically with respect to a central axis intersecting the surface to be coated and normal to such surface.

The carrier or carriers for coating substances can be constructed to hold a quantity or quantities of metal or other material, e.g., a dielectric, for evaporation, and/or to hold a quantity or quantities of metal in the form of an electrode or as part of an electrode (e.g., as an electrode coating) for coating articles by cathode sputtering, and the carrier(s) can be associated with means for supplying electrical energy for the thermal evaporation or cathodic sputtering as the case may be. Superposed layers on one and the same surface can be applied in vacuo by different techniques; e.g., one layer may be applied by thermal evaporation and another by cathode sputtering, and a given apparatus may accordingly be provided with coating material sources of different types. The carrier or carriers can also carry "cleaning electrodes," i.e., electrodes for exerting a cleaning action on a surface to be coated, e.g., by glow discharge.

There is preferably a common carrier for the different emission sources, the carrier being displaceable to move the sources in unison. The carrier may be in the form of a carriage displaceable along a guideway or guideways which may be straight or curved. As an alternative, the carrier may be a rotary carrier. A particularly suitable form of rotary carrier is one constructed for holding separate quantities of coating substances at positions angularly spaced about its axis of rotation. The carrier may be driven by a stepping motor. The different operative positions of the carrier can be positively determined, e.g., by stop or locking means.

It is particularly convenient to provide a rotary carrier comprising spaced rotary end pieces between which one or more sputtering electrodes or one or more containers for coating substance to be thermally evaporated extend, parallel with the axis of rotation of the carrier. The types of emission sources at given positions on the carrier can be varied by making different types of emission sources interchangeable. The rotary carrier may be supported in bearings in opposed walls of the vacuum chamber. The carrier may have hollow stub shafts or trunnions and these may be connected into a cooling liquid circuit for supplying coolant through sputtering electrodes. Alternatively, hollow stub shafts or trunnions closed at their inner ends may serve to house electrical contacts and components of a coolant-circulating system so that these contacts and components are accessible from the outside of the vacuum chamber. If deposition by thermal evaporation of substance from a container is to take place, the substance to be thermally evaporated can also be fed into the container through hollow trunnions or stub shafts; quantities of the appropriate substance to be evaporated can then be fed into the container at any time without interruption of the vacuum.

The emission sources, i.e., the separate quantities of coating substance, are preferably held by the carrier in such a way that the position of each source can be independently adjusted according to the required spacing of the source from the article to be coated when the source is in operative position. This spacing influences the thickness of the deposit formed by the emission. Different emission sources may accordingly have to be set at different distances from the work when forming a coating comprising superposed coating layers of different thicknesses.

Electrical current can be supplied to the emission sources via fixed terminals by providing cooperating contacts on the carrier(s) for the emission sources or, in the case of an electrode emission source, on the electrode itself. If different sources require currents with different voltage or other characteristics, there may be different pairs of fixed terminals connectable to different current sources and at each emission source position on the carrier there may be a pair of cooperating contacts which are formed or located so that they will make contact only with the appropriate pair of fixed contacts.

A masking screen may be provided to prevent substance emitted at the coating station from depositing on the source, or sources, of coating material which are for the time being not in use. It is therefore not necessary for the emission sources to be carried at widely spaced positions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional elevational view of an arrangement according to the present invention composed of a vacuum chamber with an article support and three sources of coating substances.

FIG. 1B is a view similar to that of FIG. 1A of another embodiment of the present invention.

FIG. 2 is a cross-sectional elevational view, along the line 2--2 of FIG. 3, a part of an apparatus according to the invention.

FIG. 3 is a plan view of the arrangement of FIG. 2.

FIG. 4 is a plan view of an assembly of holders for coating substances according to the present invention.

FIG. 5 is a layout of the relationship between FIGS. 5A and 5B.

FIG. 5A is a partly cross-sectional view of part of the left-hand side of an apparatus according to the invention.

FIG. 5B shows part of the right-hand side of this apparatus after modification, the upper portions of FIGS. 5A and 5B(above line A--a) being shown in cross section.

FIG. 6 is an elevational view of another apparatus according to the invention.

FIG. 7 is an elevational view of a further embodiment of the invention.

FIG. 8 is a layout showing the relationship between FIGS. 8A and 8B. FIG. 8A is a partly cross-sectional, elevation view of part of the left-hand side of another apparatus according to the invention.

FIG. 8B is a view similar to FIG. 8A of part of the left-hand side of the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus according to FIG. 1A comprises a chamber 1 in which thin layers of coating material are to be deposited on articles in vacuo. The chamber has an inlet air lock 2 and an outlet air lock 2' via which articles to be coated are introduced and removed, respectively. A batch of articles to be coated is suspended from, or fixed to, a frame 3 which travels along guide rails 4. A screen 5 is disposed in the chamber 1 and forms the top of a compartment 6 in which emission sources 7, 7' and 7" are accommodated.

The sources are mounted on a carriage 8 which is displaceable along the compartment 6 under control from outside the chamber by any well-known means (not shown). The screen 5 is formed with a central aperture 9. By movement of the carriage, the sources 7, 7' and 7" can be brought successively into working position, i.e., directly beneath the aperture 9.

In operation, the frame 3 carrying the articles to be coated is advanced into the chamber 1 through the air lock 2 and into a control position as illustrated. It will be assumed that a triple-layer coating is to be formed on each of the articles, the layers being composed of substances originating from the sources 7, 7' and 7", respectively. For depositing the first layer, the carriage 8 is brought into position with source 7 opposite the aperture 9 and emission of material from this source is effectuated in any well known manner.

When the first layer has attained the required thickness, the source 7 is rendered inoperative so as to terminate emission therefrom and the carriage 8 is moved to bring source 7' opposite the aperture 9 whereupon the second layer is deposited. Subsequently, the third layer is deposited from the source 7".

The vacuum in the chamber is maintained, without interruption, during the entire period of forming the three layers. When the three layers have been deposited, the frame 3 is removed from the chamber 1 through the outlet air lock 2', and another frame 3 can be introduced into the evacuated chamber 1 through the air lock 2. The vacuum in the chamber can also be maintained during these further operations so that the introduction of the batch of articles carried on the further frame can proceed immediately.

Apparatus as diagrammatically represented in FIG. 1A can also be arranged, as shown in FIG. 1B, for example, for depositing a thin layer on a continuous ribbon, or strip, or material advancing through the chamber 1, with the possibility of changing the nature of the layer at any time merely by moving the carriage 8 to bring different emission source into operative position.

The apparatus according to FIG. 1B comprises a vacuum chamber 1 in which thin layers can be deposited on a long glass ribbon, or strip, S. The glass ribbon enters and leaves the chamber via air locks 2 and 2', respectively, in which there are rollers 4' for supporting the glass.

Within the chamber there is a rotary carrier 8' comprising end pieces with four radial arms on which there are four sources of coating substances of different types, these sources being designated C.sup.1, C.sup.2, C.sup.3 and C.sup.4. The drawing is intended merely to illustrate a general form of apparatus exemplifying the principle of apparatus according to the invention. Therefore, the coating substance sources are shown merely by rectangles and each of these can be taken as representing an electrode or a group of electrodes, or a trough or group of troughs for containing substance for thermal evaporation, or a cleaning electrode. The source C.sup.1 is in the operative position and the substance emitted from this source forms a layer on the facing surface of the glass ribbon 5 while the latter is being displaced through the chamber, or, if so desired, while the ribbon is stationary. The other sources, C.sup.2, C.sup.3 and C.sup.4 are inoperative during this period.

A screen 5' helps to prevent the sources C.sup.2, C.sup.3 and C.sup.4 from being coated with the substance being emitted from source C.sup.1. When it is desired to apply a different substance, either on top of the coating formed by means of source C.sup.1, or on a succeeding part of the glass ribbon, the carrier 8' is indexed to bring the selected one of the other three sources into the operative position, but the vacuum in the chamber is maintained without interruption. As source C.sup.1 moves out of the operative position, the emission of atoms or molecules therefrom ceases. The manner in which the carrier can be supported for rotation and the manner in which the coating substance can be fed with current from outside the chamber will be understood from the more detailed description of the embodiments of the invention shown in the subsequent figures of the drawings. Such apparatus can be used for coating successive lengths of the ribbon with different coating substances while the ribbon is in continuous movement. Only a narrow uncoated zone will be present between the successive coatings, corresponding with the time interval required to move the carrier stepwise. By way of example, a ribbon of glass coming from a flat-glass-manufacturing plant can be passed through the chamber for deposition of different coating substances, e.g., gold and titanium dioxide, to successive portions of the ribbon length. Alternatively, such apparatus can be used for depositing single or plural-layer coatings on any given area of a strip or ribbon, or on each of successive areas thereof, while the strip or ribbon is stationary.

The apparatus may alternatively or in addition be constructed to support an article, e.g., a sheet of glass, wholly within the chamber, for deposition of two or more superposed coating layers of different composition on a surface thereof.

It is to be understood that it is not essential for there to be a common working position for all of the coating substance sources. For example, two different coating substance sources may at any given time be within a given operative range of and opposite to the surface to be coated, and in that case different coatings may be applied from these particular sources without any rotary motion of the carrier.

A particular construction of a carriage 8 for the apparatus of FIG. 1A, with three emission sources, is shown in detail in FIGS. 2 and 3. The carriage comprises a rectangular frame 10 formed by welding together four angle irons 10a, 10b, 10c and 10d. Attached to, and supporting, the frame 10 are freely rotatable rollers 11a and 11b enabling the frame 10 to move over a guide path formed by further angle irons 12 and 12' which extend parallel to one another along the bottom 12a of the vacuum chamber 1. The carriage can be located in any selected one of its three operative positions by a ball-and-socket-indexing arrangement or any other type of catch or lock. The carriage is moved into each of its working positions by any known type of linear motor (not shown).

At positions 14 and 15 on the frame 10 there are arranged electrodes constituting cathode-sputtering sources. At another position along the frame there is a container 16 for a substance to be emitted by thermal evaporation. These specific units being mentioned only for exemplary purposes. By way of example, the emission sources may be selected for forming an interference filter or semireflecting coating comprising successively deposited layers of copper, gold and silicon monoxide, such as may be required on various optical components. By maintaining the article surface stationary and moving each source into an accurately determined operative position, the present invention permits the attainment of the high degree of uniformity in the deposition, from one coating layer to the next, required for such optical components.

At the position 14, there are two electrodes 17, 18 of solid copper which when in the operative position below aperture 9 are connected to an alternating high-voltage source producing 3,000 volts. Each electrode has a longitudinal bore 19 (as shown in the case of electrode 18 in FIG. 2) through which a cooling liquid, for example, transformer oil, is circulated. The coolant is supplied to the electrodes through a conduit 20 and returns through a conduit 21. These conduits are made of an electrical insulating material to prevent short circuits from appearing between the various electrodes. The conduits 20 and 21 are common to the several sets of electrodes mounted on the frame 10 and at locations 22 removable plugs are fitted to provide for the connection of further branch conduits at these places if at any time it should be required to fit further electrodes in place of the container 16.

The electrodes 17 and 18 are fixed to the frame 10 by nuts and capscrews countersunk in the ends of the electrodes and shown at 25, 25'. Insulating plates 26, 27, 26'and 27'are provided to electrically insulate the electrodes from the frame 10. By varying the thickness of the insulating plates, the vertical position of the electrodes can be regulated to some extent.

The electrodes at the position 15 are connected to the frame 10 and cooled in the same way. These further electrodes, however, are formed of tungsten which has been covered with gold, e.g., by electrolysis.

The container 16 is made of any suitable metal and comprises a trough portion 28 which can hold a substance to be thermally evaporated, e.g., silicon monoxide. The ends of the container, when the latter is in its operative position, are connected to a source of e.m.f. of about 100 volts which heats the container by Joule effect.

In the drawing, the carriage 8 is located so that the electrodes 17 and 18 are in the working position opposite aperture 9 (shown in broken line in FIG. 3). At this position, and adjacent the frame 10, there are mounted stationary contacts 29, 30 and 29', 30'. These are high-voltage contacts and they are spaced about the two longitudinal sides of the frame 10 by a distance which is substantially greater than the thickness of the ends of the container 16. For cooperating with the container 16, low-voltage fixed contacts 31, 31' are disposed at the working position, laterally abreast of the frame 10, at positions such that they can not be contacted by the ends of the cathode-sputtering electrodes. The different emission sources become automatically connected to the appropriate voltage sources as the former move into working position.

Beneath the emission sources is provided a screen 32, which is fixed to the frame 10, to avoid contamination of underlying parts.

FIG. 4 shows a modified form of container for coating substances to be thermally evaporated. In this case the container, which can be connected to the frame 10 (FIG. 3) in the same way as container 16, comprises parallel strips, 40, 41 of electrically conductive material, between which there is a series of metal wells 42 for containing the material to be evaporated. This provides a more powerful evaporation source than that shown in FIG. 3. When using the evaporation source shown in FIG. 4, the contacts 31 and 31' shown in FIGS. 2 and 3 must be slightly offset in relation to one another in the direction of movement of the support 8, so that each can contact a different one of the strips 40 and 41 when the container is in the operative position.

The apparatus shown in FIGS. 5A and 5B comprises a drum-type carrier for the emission sources of the coating substances. The drum is composed of two hollow stub shafts 50 and 50' extending through the walls 51a and 51b, respectively, of a vacuum chamber. Between each stub shaft and its associated chamber wall there is a bearing 51c of a suitable construction known per se, for maintaining an airtight seal. Discs 52 and 52', with respective peripheral flanges 53 and 53' are each welded to a respective shaft. These discs can support electrodes 54, 55, 56 and 57 or, as shown at 58 in FIG. 5B, a container for coating substances to be thermally evaporated. The emission sources are connected to the disc flanges by capscrews and nuts 59 and 59', electrical insulating plates 60, 61 and 60' being interposed between the disc flanges and the emission sources. The electrodes and container (when used) form bracing struts between the two flanged discs.

The supply of high and low-voltages is performed in a manner similar to that shown in FIG. 3, by means of fixed contacts 62 and 62' (high voltage) and 63 and 63' (low voltage). The ends of the electrodes 54 to 57 and of the container 58 are so shaped and dimensioned, and the fixed contacts 62, 62', 63 and 63' are so disposed that the connection of the different coating substances sources to their suitable voltage sources is performed automatically on movement of the sources into working position by rotation of the drum. The fixed contacts 62,62', 63 and 63' are adjacent an aperture 64 in a generally cylindrical screen which encloses the drum, this screen being shown by broken lines 65a and 65b.

The cathode-sputtering electrodes are cooled by the circulation of oil through a longitudinal bore, such as 66, provided in each electrode. The cooling liquid is fed through the hollow stub shaft 50, and is distributed to the various electrodes via conduits 67 which are made of electrical insulating material and which are connected to apertures, such as 68, in the electrodes, the liquid being discharged via similar conduits 67' and through the opposite stub shaft 50'.

It is advantageous to have the coolant circulate through all the electrodes mounted on the drum, with a view to extracting the maximum amount of heat from the vacuum chamber.

When a thermal evaporation source, such as that shown at 58 in FIG. 5B is used, the outer ends of the corresponding conduits 67 and 67' are closed by plugs.

In the apparatus shown in FIGS. 5A and 5B each electrode on the drum is a cathode and the electrodes cooperate with a common anode (not shown) suitably disposed elsewhere in the vacuum chamber. The electrodes on the drum are fed with direct current. A container, such as container 58, for a substance to be evaporated can be heated by either direct or alternating current. As the container is only heated when it is in the working position, the contents of the container will be in a solidified condition when the container is at other positions, thus there is no danger of the substance spilling out as the drum is rotated.

The drum can be turned by an electric stepping motor 50a, which may be of any known type. A pin 71 on the inside of the chamber wall 51a pivotally supports a roller 70 through the intermediary of an arm which is biassed so that during rotation of the drum the roller sequentially engages in locating notches in a disc 69 secured to stub shaft 50, thereby to accurately locate the drum in each of its successive working positions.

A second screen 72 is provided which is disposed radially inwardly of the path of the cathodes to prevent contamination of one emission source by material falling towards the interior of the drum from another source.

FIG. 6 shows a drum-type carrier with polygonal-shaped ends supporting the emission sources. Each drum end is formed by a plurality of bars 80 welded together to form a hexagon. The hexagon can be regular, as shown in FIG. 6, or irregular. If drums ends of irregular hexagonal shape are used, the distances of different emission sources from the axis of rotation will be different and these distances can be individually selected according to the nature of the sources of emission and the thicknesses of the coating layers to be formed. The hexagonal ends of the drum shown in FIG. 6 are secured to hollow shafts or trunnions, such as 81, by spokes 82.

Sputtering electrodes 83 are held in position by fasteners 85 which extend through open-ended slots in the bars 80. The positions of the fasteners along these slots determine to some extent the spacing of the appertaining electrodes from the drum axis. The bars 60 can be made of electrical insulating material, or other means can be employed for insulating the electrodes 83.

The drum is surrounded by a screen 84, 84' formed with two apertures corresponding to two working positions so that two articles can be coated simultaneously if they are appropriately held opposite the respective screen apertures.

FIG. 7 shows one end of a simple rotary carrier comprising rotary end pieces with four radical arms mounted directly on stub shafts, the shaft at the end shown being denoted 91. The outer ends of the radial arms are bent inwards, as indicated by 90a, 90b, 90c and 90d, to form flanges to which electrodes 92, 93, 94 and 95, respectively, are secured by bolts (not shown) passing through the electrodes and through the said flanges. The electrodes are in the form of bars extending normally to the plane of the drawing. The side edge faces of the bars are chamfered as shown at 92a and 93a and the aforesaid bolts clamp these chamfered side edge faces of the bars against insulating members 96, 97, 98 and 99. The outwardly projecting margins of these insulating members serve as partitioning walls to prevent the contamination of the nonoperative electrodes by substances emitted from the electrode or electrodes which are in operation. Containers for substances to be thermally evaporated could equally well be connected to a simple rotary carrier of this type.

FIG. 8 shows an apparatus in which all of the electrical connections, and the connections and conduits for cooling fluid, are disposed outside the vacuum chamber, the sidewalls of which are shown at 101a and 101b.

The emission source carrier is in the form of a drum which comprises two cylindrical end pieces 102 and 102' rotatably mounted in bearings 103 and 103', respectively, in the walls 101a and 101b, respectively. The inner ends of the cylindrical pieces are closed by round plates 104 and 104', respectively. To these plates cooling fluid-distributing boxes 105 and 105', respectively, are secured. These boxes are made of an insulating material. A supply conduit 106 leads into box 105 and an evacuation conduit 106' leads away from box 105'.

Sputtering electrodes and/or containers for substances to be thermally evaporated can be connected, as shown, to the end pieces 102 and 102'.

The drawings show a troughlike container 107, which is made of refractory material and is capable of holding the material for evaporation, in place on the rotary carrier. Inside the container is an electrical resistance heating element in the form of a ribbon 108 immersed in the material to be evaporated. One of the ends of the trough is secured to the end piece 102 by a connector 109 which is screwed through the end piece 102 into a nut 110 embedded in the refractory material of the trough. An electrically conductive rod 111 extends through this connection and one end of the rod is connected to the electrical resistance 108 while its other end carries an electrical contact 112. Insulating plates 113, 114 serve both as insulators and to form airtight seals. The portion of end piece 102 surrounding connector 109 is also of insulating material.

The other end of the troughlike container 107 is held to the end piece 102' by a component 115 which is screwed into a nut 110' embedded in the refractory material of the trough. This component 115 comprises connected tubes 116 and 120 through which material for evaporation can be supplied to the trough without having to interrupt the vacuum. The tube 116 has a stop collar 117, and insulating plates 113' and 114' are interposed at the joint. The lower end of the tube 116 opens into a supply conduit 118 through which the material to be evaporated is supplied so that it feeds into the trough along path 119.

The lower parts of FIGS. 8A and 8B show a cathode bar 121 connected by its ends to the end pieces 102 and 102' by straight tubes 122 and 122', respectively, which are screwed into sockets in the ends of the electrode. These tubes are made of electrically conductive material and are fitted with stop collars 123 and 123', respectively. The tubes 122 and 122' are connected to the coolant-distributing boxes 105 and 105', respectively, by releasable connections 125 and 125', respectively, and conduct the coolant to and from, respectively, a longitudinal bore 124 in the electrode. Insulating plates 113", 114", 113'" and 114'" are interposed at the joints between the tubes 122 and 122' and the electrodes. The tube 122 carries an electrical contact 126.

The contacts 112 and 126 cooperate with fixed contacts 127 and 128, respectively, disposed adjacent the working position of the metallization sources.

The contact 112 can touch only the fixed contact 127, whereas the contact 126 can touch only the contact 128. The material in container 107 is heated by a low-voltage current and the cathode-sputtering electrode 121 is fed with high voltage, when in the working position. This working position is opposite an aperture 129 in a screen 130, 131 enclosing the rotary carrier.

The carrier can be formed to take several electrodes or containers for material to be thermally evaporated.

If it is not desired to employ a tubular component such as 115 for feeding material into the troughlike container, then the corresponding end of the container can be secured to the appertaining end piece of the carrier by a simple connecting pin.

In any embodiment of the invention, one or more of the illustrated electrodes can constitute a cleaning electrode. For example, a cleaning electrode or electrodes may be substituted for one or more of the emission sources in any of the apparatus described with reference to the accompanying drawings.

In the drawings, the actual position of an article in relation to an emission source during deposition of a coating layer has not been shown but it will be understood that it is intended that the article will be placed so that the surface being coated faces the emission source in use. The invention is primarily intended to be employed in the coating of sheet material, e.g., sheets of glass. In such cases the sheet to be coated can be supported horizontally in the vacuum chamber, with the surface to be coated facing downwardly and the emission sources may operate from a position below the sheet. Also in such cases, the area of the surface to be coated will generally be substantially larger than the area from which atoms or molecules are emitted from the emission source.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

Claims

I claim:

1. Apparatus for forming at least two different coating layers on at least part of the surface of an article by deposition of different coating substances in vacuo, comprising, in combination:

means defining a deposition chamber in which a partial vacuum can be maintained and one area of which constitutes a coating position which is fixed relative to said chamber;

means associated with said chamber for supporting therein an article whose surface is to be coated so that at least one surface part to be coated is in such coating position;

a rotary carrier disposed in said chamber and supporting a plurality of emission sources, each for emitting atoms or molecules of a different coating substance when suitably activated, said sources being elongate in the direction of the axis of rotation of said carrier and having in that direction a dimension comparable to that of the surface to be coated, said carrier being rotatable relative to such coating position about an axis substantially parallel to the surface part in the coating position for bringing in each source in succession to at least one operative position and for holding it at that position for an interval wherein emission of its respective substance will produce a coating layer on at least one respective part of an article surface in a coating position, said carrier being displaceable without interrupting the vacuum in said chamber; and

means operatively connected for activating the emission sources.

2. An arrangement as defined in claim 1 wherein there is provided a single carrier which carries separate emission sources and which is displaceable by means located outside the vacuum chamber.

3. An arrangement as defined in claim 2 further comprising stationary electrical power supply contacts positioned for delivering electrical emission-activating energy to at least one of said sources only when it is at one said operative position.

4. An arrangement as defined in claim 3 wherein there are provided a plurality of sets of stationary contacts, each said set supplying a different type of electrical energy and being positioned for contacting each emission source of one type when that emission source is at said one operative position.

5. An arrangement as defined in claim 1 wherein said carrier carries said plurality of emission sources for different coating substances at positions which are angularly spaced about the axis of rotation of said carrier, said carrier being rotatable for bringing each said emission source in succession to the at least one operative position.

6. An arrangement as defined in claim 5 wherein said carrier is driven by a stepping motor.

7. An arrangement as defined in claim 5 wherein said carrier comprises spaced end pieces to which the ends of said emission source are connected.

8. An arrangement as defined in claim 5 further comprising bearings disposed in opposed walls of said vacuum chamber and rotatably supporting said carrier.

9. An arrangement as defined in claim 5 wherein said carrier comprises hollow shafts rotatably mounted in stationary bearings, and conduit means communicating with the interiors of said shafts and connected to said emission sources for supplying liquid coolant via said shafts to the interiors of said emission sources.

10. An arrangement as defined in claim 5 wherein said carrier means comprise hollow shafts which open to the outside of said vacuum chamber, and electrical power supply contacts extending into the interior of at least one said shaft and arranged for supplying activating power to said emission sources.

11. An arrangement as defined in claim 5 wherein at least one of said emission sources is constituted by a container for a coating substance to be evaporated, and wherein said carrier comprises hollow shafts rotatably mounted on stationary supports and supporting said emission sources, and delivery means communicating with the interior of at least one said shaft and with said container for supplying the coating substance to said container.

12. An arrangement as defined in claim 1 wherein said carrier supports at least one emission source for emitting a coating substance by thermal evaporation and said means for activating the emission sources for emitting a coating substance by thermal evaporation comprise electrical heating means associated with at least one emission source for heating the substances to its evaporation temperature.

13. An arrangement as defined in claim 1 for forming at least three different coating layers, wherein said carrier supports at least three emission sources.

14. An arrangement as defined in claim 1 wherein at least one of said emission sources is constituted by a container for a coating substance to be evaporated, and wherein said means for activating comprise electrical heating means associated with said container.

15. An arrangement as defined in claim 1 wherein at least one of said emission sources is constituted by a cathode for forming a coating by cathodic sputtering.

16. An arrangement as defined in claim 1 wherein said carrier also carries at least one cleaning electrode.

17. An arrangement as defined in claim 1 wherein said carrier is arranged for permitting the distance between any one emission source and the surface part to be coated when it is in a coating position to be varied.

18. An arrangement as defined in claim 1 further comprising partition means associated with said carrier for preventing a substance emitted from one said emission source from contaminating any other emission source.