EP1440178A1

EP1440178A1 - Apparatus for vacuum deposition, specifically for metallizing plastic film

Info

Publication number: EP1440178A1
Application number: EP02788542A
Authority: EP
Inventors: Andrea Fusi; Mario Ceni
Original assignee: Galileo Vacuum Systems Srl
Current assignee: Galileo Vacuum Systems Srl
Priority date: 2001-11-02
Filing date: 2002-10-29
Publication date: 2004-07-28
Also published as: WO2003038142A1; ITFI20010205A1

Abstract

The apparatus comprise a vacuum chamber (3) inside which a feeding device of the substrate (F) and a bank (25) of vaporization sources are arranged. The substrate feeding device can be extracted from the vacuum chamber. Conversely, the vaporization source bank can be raised from a lower vaporization position to a higher maintenance position without needing to be extracted from said vacuum chamber.

Description

APPARATUS FOR VACUUM DEPOSITION, SPECIFICALLY FOR METALLIZING PLASTIC FILM

Description Technical field The invention relates to an apparatus for vacuum metallizing of plastic film, and more generally to an apparatus for vacuum vaporizing material intended to form a coating on a laminar substrate, such as a film or the like. State of the Art

Systems equipped with a vacuum chamber where a first reel of film to be metallized is arranged are frequently used for metallizing plastic film. The film is gradually fed to a process area around a process roller where it receives the coating metal which deposits and condenses on the film surface. The metallized film is then rewound on a second metallized film reel. A bank of vaporization sources, i.e. of sources which provide the metal in vapor form, is arranged in front of the process roller. The metal is vaporized by means of heat, usually by the Joule effect. A source of electrically conducting material is heated by being crossed by a high-intensity, low-voltage current. The source resistor, e.g. made of sintered material with suitable electrical resistance and heat resistance properties, is heated by dissipation of electrical power. The generated heat gradually melts a metallic wire fed from a reel, e.g. aluminum wire. The molten aluminum forms a pool in a specific depression in the source where it vaporizes.

These apparatuses normally present a prismatic or cylindrical shaped, horizontal axis vacuum chamber. The supports of the two reels, the process roller and the other idle rollers of the film or other laminar material to be metallized can be extracted from the side of one of the vacuum chamber bases with a movement which is parallel to the axis of the chamber itself. The members are carried for this purpose by a so-called "winding carriage". Thanks to this configuration, a reel of material to be metallized can be arranged on the respective support and the winding carriage can be introduced in the vacuum chamber to start the metallizing process after extracting the air from the chamber using suitable vacuum pumps. The vaporization sources are carried by a support, which is integral with a carriage movable parallel with the axis of the vacuum chamber, to extract and insert the support from the vacuum chamber sources and in the vacuum chamber, respectively. The carriage carrying the source bank is commonly called "source carriage". A flange arranged between the carriage and the source support closes the vacuum chamber on source extraction side. The transformers which are used to power each source with a low voltage current are fitted on the carriage. Stiff cylindrical conductors lead from each transformer to the respective source. Examples of arrangements of this type are described in G. Tonini et al., "A new Generation of Film Metallizing", in Paper, Film & Foil Converter, February 1980.

The sources need to be extracted for maintenance and for replacing the reels or rolls of metallic wire arranged on both sides of the vaporization source bank. Sources especially need to be extractabie in apparatuses whose structure is particularly compact in which the supports of the reels of material to be metallized and of the reels of metallized material are arranged on one side with respect to the axis of the vacuum chamber and in which the process roller and the sources are arranged on the opposite side.

An arrangement of this type, in which the source carriage and the winding carriage are extracted from opposites sides of the vacuum chamber, presents a number of advantages and considerable shortcomings. Firstly, since the supports of the reels are extracted from one end of the vacuum chamber and the sources are extracted from the other end, a plenty of room is required on both sides of the apparatus, with considerable occupation of otherwise useful space. This situation which is costly per se becomes even more so as the width of the substrates to be metallized, i.e. the axial length of the vacuum chamber, increases. This because the useful length of both the reel supports and the vaporization source bank supports is at least equal to the width of the substrate to be metallized. Secondly, the electrical connection between the transformers on the carriage and the sources which are overhangingly supported by the carriage is complex and costly and generates very strong electromagnetic interference due to the length of the conductors and the fact that each conductor connecting the transformer to the respective source carries a single phase while there is one single earth conductor in common for all vaporization sources. This generates strong electromagnetic fields and consequently high electromagnetic pollution.

Object and summary of the invention

Object of the invention is to realize an apparatus for metallizing of plastic film, and more generally an apparatus for vacuum vaporizing and coating a laminar substrate by deposition, comprising a vacuum chamber and a bank of vaporization sources which overcomes the problems of existing systems and apparatuses.

More specifically, the object of the invention is to realize an apparatus in which the vaporization bank source is easily accessible to eliminate the problems of large dimension and electromagnetic pollution of the known systems.

These and other objects and advantages, which will be clear to experts of the field from the text that follows, are essentially obtained by an apparatus comprising a vacuum chamber in which a substrate feeding device and a bank of vaporization sources are arranged, the feeding device being carried by a winding carriage, which can be extracted from the vacuum chamber, characterized in that the vaporization source bank can be raised from a lower vaporization position to a higher maintenance position without needing to be extracted from said vacuum chamber.

In this way, the source bank can be taken to a suitable height to perform maintenance operations without needing to extract it from the vacuum chamber, consequently reducing the necessary space on the sides of the apparatus. This is particularly advantageous particularly when the substrate to be metallized is very wide and consequently the vacuum chamber and the source bank are particularly long. According to a particularly advantageous embodiment of the invention, the vaporization source bank is arranged against the lateral wall of the vacuum chamber in vaporization position and the source bank is arranged at a larger distance from the vacuum chamber wall in maintenance position. In this configuration, a passage for an operator is created between the wall and the source bank and the bank can be accessed from both the sides which are parallel to the direction of alignment of the sources. In working configuration, i.e. when the source bank is in low position, the sources are arranged against the lateral wall of the vacuum chamber and a large space is made available in the rest of the chamber for introducing the substrate reel supports and the various rollers around which the substrate is entrained. The vacuum chamber is consequently particularly compact. According to an advantageous embodiment of the invention, the metallic wire reels feed the vaporization sources; the metallic wire is melted and vaporized by said sources. In this case, the wire reels are arranged on both sides of the source bank and are accessible because the sources move. The bank is advantageously supported by an articulated parallelogram system to raise and distance the source bank from the lateral wall of the vacuum chamber. This mechanism is particularly simple and cost-effective requiring only a single actuator or one actuator on each side operated in parallel to obtain the required movement.

Typically, the sources are heated by the Joule effect and are equipped with flexible electrical cables connecting said sources to transformers to supply low voltage electrical current. Advantageously, each of said cables comprises a phase connector and an earth connector to reduce electromagnetic emissions. Furthermore, according to a particularly advantageous arrangement, the transformers are arranged under the source bank, specifically under the base of the vacuum chamber.

Additional advantageous characteristics and embodiments of the invention are indicated in the accompanying claims. Brief description of the drawings

The invention will be better understood with reference to the description and the attached drawing which shows a practical non-limiting embodiment of the invention. More particularly, in the drawing:

Fig. 1 is a cross-sectional view according to a plane which is orthogonal to the axis of the vacuum chamber of the entire apparatus;

Fig. 2 and Fig. 3 are two cross-sectional views, similar to the cross- section shown in Fig. 1 , of the vacuum chamber only showing two different positions of the source bank, without the film reel supports and the respective idle and process reels, with the source bank in working and maintenance or servicing position, respectively;

Fig. 4 and Fig. 5 show the vaporization source bank in working position and in maintenance or servicing position; and

Fig.6 is a schematic view of the sources and the electrical power circuit with an indication of the voltage found in the various parts. Detailed description of an embodiment of the invention

Reference numeral 1 in Fig. 1 indicates the apparatus as a whole. The view is orthogonal to axis A of the vacuum chamber, indicated by reference numeral 3. In the example shown, the vacuum chamber presents an essentially circular cross-section cylindrical shape, cut along the base 3A with which the vacuum chamber 3 rests on the floor P. It is understood that the vacuum chamber cross-section may have a different shape, e.g. polygonal.

Two supports for an equal number of film reels to be metallized are arranged in the vacuum chamber 3. A first reel B1 of film to be metallized is carried by the first support 7 and a second reel B2 of metallized film is carried by the second support. The film being processed, indicated by reference F, follows a path defined by a plurality of idle rollers 12-21 , along which a process roller 23 is arranged.

The supports 7, 9, the idle rollers 12-21 and the process roller 23 are carried by an equipment (winding carriage) which can be extracted from the vacuum chamber 3 in a direction which is parallel to the axis A of the chamber. Fig. 2 shows the chamber from where the winding carriage has been extracted.

A bank of vaporization sources, generally indicated by reference numeral 25, is arranged under the process roller 23. The vaporization source bank consists of two reciprocally displaced sets of sources, indicated by reference numerals 27 and 29, respectively (see detail in Fig. 4 and Fig. 5). The displaced arrangement of the sources 27, 29 is a non-limiting example. In practice, the sources may be aligned instead of displaced. Furthermore, when they are displaced, they may present a reciprocal overlapped area or not. In all cases, also when the sources are aligned, the sources may be fed from both sides of the bank of sources, possibly also using two metallic wires for each source.

The sources 27, 29 are carried by a unit 31 which develops essentially along the entire axial length of the vacuum chamber 3, orthogonally with respect to the plane of the figure. It is supported by two pairs of pivoting arms arranged on the ends of the unit and indicated by reference numerals 33 and 35. Only one pair of arms is visible in the drawing, the other being parallel to the first. The arms 33, 35 are pivotally mounted at 33A and 35A to the unit 31 and at 33B, 35B to the base 3A of the vacuum chamber 3. The elbow arm 33 is fastened at 33C to the rod 37 of a cylinder-piston actuator 39, e.g. of the hydraulic type, whose piston is fastened at 39A to the base 3A of the vacuum chamber 3. Other types of actuators can be used, e.g. a mechanical jack, an electrical motor with suitable transmission or the like.

As appears from comparing Fig. 2-3 and Fig. 4-5, the actuator 39 takes the unit 35 with the bank 25 of vaporization sources 27, 29 from a working position (Fig. 1 , 2 and 4) to a maintenance and service position (Fig. 3, 5). In the first position, the unit 31 is close to the base of the vacuum chamber and arranged next to the lateral wall of the chamber on the opposite side to the supports 7, 9 of the reels B1 , B2 with respect to axis A. In this position, there is sufficient space in the vacuum chamber to introduce the process roller 23, the idle rollers 12-21 of the film F and the supports 7, 9 for the reels B1 , B2.

In the raised position, the unit 31 is distanced from the lateral wall of vacuum chamber 3 and creates a gap 41 which can be accessed by a person from each sides of the unit 31 , as clearly shown in Fig. 3. An operator can consequently access the sources 27, 29 from both sides of the unit 31. Furthermore, the unit 31 is raised with respect to the working height and the operator will not need to bend over to reach the members carried by the unit 31. ln addition to the sources 27, 29, the unit 31 carries the reels or rolls of metallic wire to be vaporized, indicated by reference R. The reels are arranged on both sides of the unit 31 to feed metallic wire FM to the sources 27 and 29 from the sides towards which the sources are displaced with respect to the middle line. A number of reels R of metallic wire FM which is equal to the number of sources to be fed are found on the two sides of the unit 31 supported by corresponding supporting arms 45.

Each vaporization source 27, 29 is withheld between a central terminal 47 and lateral terminal 49, which is elastically held against the central terminal 47. The terminals 47, 49 ensure the electrical contact of each vaporization source with the electrical power line. This comprises, for each source 27, 29, a flexible member 51 developing from a connection 53 through the base 3A of the vacuum chamber 3 to the unit 31. Connection 53 crosses the wall of the vacuum chamber and connects the respective flexible cable 51 to a transformer 55 located in a pit 57 under the vacuum chamber 3 (Fig. 1). A bank formed by a suitable number of transformers for powering all the sources 27, 29 is arranged in the pit 57.

Each flexible member 51 comprises a first conductor connected to the phase and a second conductor connected to earth. The conductor 51 F (Fig. 6) connected to the phase of each flexible member 51 is fastened to the unit 31 via a terminal 59 for electrically powering the sources via bus bars 61 for sources 29 and 63 and for sources 27. The conductor 51 T connected to the earth of each flexible member 51 is electrically connected to the central terminal 47 to which all sources are electrically connected and to which the entire unit 31 is electrical connected.

Fig. 6 shows the voltage of the various parts in the system with different types of lines. The unit 31 and the wall of the vacuum chamber 3 are connected to earth via a flexible earth connector 65 and via the earth connectors of each transformer 55. Since the general power system is a three-phase system and each transformer is a single-phase device, one phase conductor 51 F and one earth conductor connected to a specific source lead from each transformer. The sequence of transformers on the phases RST is arranged to optimize the phases of the vaporization sources. In essence, phase distribution is achieved to obtain a balanced system. In Fig. 6, the two sources 27, 29 are connected to two bus bars 61 , 63 indicated with two different types of lines, representing two different phases of the three-phase power system. The two phases come from two different single-phase transformers. The wall of the vacuum chamber 3, the central terminal 47, the conductors 51 T, the conductor 65 and the central terminal 47 are drawn with the same line, indicating that the voltage in all these parts is equal to zero. The combination of a phase conductor and an earth conductor in each flexible member 51 drastically reduces the electromagnetic emissions of the system. Furthermore, the length of the conductors is contained also when the apparatus has a considerable axial length for processing very wide film.

The electrical system is cooled by water circulation in a way known per se. The cooling water circulation ducts, indicated by reference numeral 70, are shown in part in Fig. 4 and Fig. 6. Cooling water also circulates inside each flexible member 51 carrying the conductors 51 F, 51 T.

It is understood that the drawing shows only one practical embodiment of the invention, the forms and arrangements of which may vary without thereby departing from the scope of the idea forming the basis of the invention. The presence of any reference numbers in the accompanying claims has solely the purpose of facilitating the reading thereof in the light of the above description and the accompanying drawings and does not limit in any way the scope of protection.

Claims

1. An apparatus for vacuum deposition of a coating on a substrate, comprising a vacuum chamber in which a substrate feeding device and a bank of vaporization sources are arranged, the feeding device being carried by a winding chamber which can be extracted from the vacuum chamber, characterized in that said vaporization source bank can be raised from a lower vaporization position to a higher maintenance position without needing to be extracted from said vacuum chamber.

2. Apparatus according to claim 1 , characterized in that the vaporization source bank is arranged against the lateral wall of the vacuum chamber in vaporization position and the source bank is arranged at a larger distance from the vacuum chamber wall in maintenance position, there being a passage for an operator between said wall and said bank which can be accessed from both the sides which are parallel to the direction of alignment of the sources.

3. Apparatus according to claim 2, characterized in that said sources are fed by reels of metallic wire which is melted and vaporized by said sources, the reels being arranged on both sides of the source bank.

4. Apparatus according to claim 2 or 3, characterized in that said source bank is supported by an articulated parallelogram system.

5. Apparatus according to one or more of the preceding claims, characterized in that said sources are heated by the Joule effect and that flexible electrical cables connect said sources to transformers for supplying low voltage electrical current.

6. Apparatus according to claim 5, characterized in that each of said cables comprises a phase connector and an earth connector.

7. Apparatus according to claim 5 or 6, characterized in that said transformers are arranged under the source bank.

8. Apparatus according to claim 7, characterized in that said transformers are arranged under the vacuum chamber, passing electrical connections being provided through the base of said vacuum chamber.

9. Apparatus according to one or more of the claims from 6 to 8, characterized in that each source is connected to a first individual clamp to which a phase connector of the respective flexible cable is connected and a common conductor to which all the sources and all the earth connectors of said flexible cables are connected.

10. Apparatus according to one or more of the preceding claims, characterized in that: said vacuum chamber presents a longitudinal axis; that the feeding device of the substrate comprises a first support for a reel of substrate to be fed, and a second support for a winding reel of the processed substrate on which the coating was deposited and a process roller around which the substrate is driven, the process roller being arranged approximately over the vaporization source bank, said first and second support being arranged on a side of the vacuum chamber and said process roller being arranged on the opposite side of the vacuum chamber with respect to the middle line which is parallel to the longitudinal axis of the vacuum chamber; said feeding device being extractable from the vacuum chamber with a movement that is parallel to the longitudinal axis of the chamber.