Abstract:
A system for vacuum deposition of a coating on a web material (N), includes: a feed path of the web material in a vacuum environment; along the feed path, a process roller ( 19 ) around which the web material is guided; associated with the process roller, at least one vaporization source ( 31 ) of a material to form the coating; upstream of this source, along the feed path of the web material, an applicator unit ( 51 ) to apply a masking agent to the web material according to a pre-established pattern. The applicator unit in turn comprises a printing cylinder ( 53 ), cooperating with a distributor cylinder ( 55 ) of the masking agent, and a source ( 57 ) of masking agent. The applicator unit ( 51 ) includes at the ends thereof, an adjustment device ( 73 ) separate from each other to adjust the position of the applicator unit ( 51 ) with respect to the process roller ( 19 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation under 37 CFR 1.53(b) of pending prior application Ser. No. 11/550,226 filed Oct. 17, 2006 and claims the benefit of priority under 35 U.S.C. §119 of European Patent Application EP 05425831.4 filed Nov. 23, 2005. The entire contents of each of the applications is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a system or device for metallization of a continuous substrate, such as paper, a polymer film or another material. 
         [0003]    More specifically, the present invention relates to a device of the aforesaid type which has means to create metal-free areas of various shapes, for example to obtain a particular pattern or also technical-functional characteristics of the finished product, such as strips of non-conductive material, to produce capacitors. 
       BACKGROUND OF THE INVENTION 
       [0004]    To perform vacuum deposition of layers of metal materials on substrates, such as polymer films, paper or the like, vacuum metallization systems are commonly employed, in which a reel of substrate to be coated is inserted in a chamber and in which the substrate is subsequently unwound and fed around a process roller to be rewound in a reel of treated product. Positioned under the process roller are vaporization sources, which generate vapors of metal (or another material) which then condenses in the form of a thin coating layer on the corresponding face of the film or other substrate. 
         [0005]    The vaporization sources are, for example, composed of boats made of highly conductive sintered material resistant to temperature, which are heated by Joule effect through the passage of an electric current. The metal to be vaporized is fed to these boats. In continuous feed systems this metal is fed in the form of wires of aluminum or another suitable material, unwound from respective reels with a feed speed corresponding to the hourly quantity of metal to be vaporized. 
         [0006]    Systems of this type are described in WO-A-03/038142; EP-A-0082001; U.S. Pat. No. 4,962,725; U.S. Pat. No. 5,350,598. Particular embodiments of boats or vaporization sources heated by Joule effect suitable for use in these systems are described in EP-A-1408135. 
         [0007]    For some specific applications, for example to produce a metallized film for the production of capacitors, or a metallized film for packaging, it is necessary to create metal-free areas according to a pattern. For this purpose, U.S. Pat. No. 5,223,038, by way of example, describes a system of nozzles that spray an oil onto the substrate to be metallized to prevent the metal from adhering in areas that must remain metal-free. Consequently, when the film is fed around the process roller in front of the vaporization source, the areas wet with oil remain metal-free. The quantity of oil applied is extremely small and normally evaporates from the film without the need to provide specific removal means. 
         [0008]    A system for the same purpose, in which the oil is applied to a longitudinal covering strip, to produce longitudinal metal-free bands, is described in U.S. Pat. No. 4,478,878. U.S. Pat. No. 5,652,022 describes a vacuum metallization device in which metal-free strips are obtained by masking formed with a continuous flexible member which covers the portion of film to remain metal-free. Both these systems are only suitable to produce metal-free bands or strips extending longitudinally. 
         [0009]    U.S. Pat. No. 4,832,983 and U.S. Pat. No. 5,136,462 describe a system in which oil is transferred to the film to be coated in metal by a pair of rotating rollers, one to distribute the oil on the film and the other to collect the oil from a source. The latter can be composed in turn of a take-up roller and of a storage tank, or by a series of nozzles or orifices through which the oil flows to be distributed on the surface of the roller. 
         [0010]    U.S. Pat. No. 6,048,402 describes a device for distributing oil on a film to be metallized, composed of a transverse conduit provided with a plurality of nozzles, from which oil evaporates to condense on the film which is fed in front of the nozzles. A similar system is described in U.S. Pat. No. 5,942,283. 
         [0011]    EP-A-0.447.550 describes a roller system to apply oil to a film to be metallized. The applicator roller can have a raised pattern of varied configuration according to the conformation of the metal-free areas to be obtained. 
       SUMMARY OF THE INVENTION 
       [0012]    The object of the present invention is to produce a metallization device or system with which areas according to a pattern or in any case metal-free areas can be produced on a continuous substrate, with simple, reliable means which are nonetheless suitable to provide high quality in defining the metal-free areas. 
         [0013]    In substance, the invention provides for a system for vacuum deposition of a coating on a web material, comprising: a feed path of the web material in a vacuum environment; along the feed path, a process roller around which the web material is guided; associated with the process roller, at least one vaporization source of at least a first material to form the coating; upstream of the at least one source, along the feed path of the web material, an applicator unit to apply a masking agent to the web material according to a preestablished pattern, the applicator unit comprising a printing cylinder, cooperating with a distributor cylinder of the masking agent, and a source of the masking agent. Characteristically, the applicator unit comprises at the ends thereof, i.e. at the side, adjustment means separate from each other to adjust the position of the applicator unit with respect to the process roller and/or the contact force between the applicator unit and the process roller. 
         [0014]    Preferably, the vaporization source is a vaporization source of a metal, such as, although not exclusively, aluminum. However, the present invention could also be applied to vacuum coating systems, which form depositions of non-metallic materials, such as oxides. 
         [0015]    In a practical embodiment of the invention, the adjustment means comprises, for each side of the applicator unit, an actuator which stresses the printing cylinder towards the process roller. 
         [0016]    For example, a respective adjustable stop, defining the position of the printing cylinder with respect to the process roller, can be associated with each end of the applicator unit. 
         [0017]    According to an advantageous embodiment, the printing cylinder is supported in a removable way for rapid replacement. For example, on two side panels movable for movement towards the process roller, openable supports can be provided to allow removal and replacement of the printing cylinder, for example by engagement of the ends of the cylinder with gripping members operated by suitable equipment, such as a traveling crane or a hoist. 
         [0018]    The source of masking agent can advantageously comprise a reservoir containing the masking agent in liquid form, in which the distributor cylinder is partly immersed. 
         [0019]    The source of masking agent can comprise a reservoir and means for evaporation of the masking agent from the reservoir, the distributor cylinder being arranged in this case to obtain on the cylindrical surface thereof condensation of the masking agent evaporated from the source. 
         [0020]    Alternatively, the distributor cylinder can be arranged partly below the level of the masking agent to have a function of suction and transfer of the product to the printing cylinder. 
         [0021]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    In the drawings: 
           [0023]      FIG. 1  is a schematic cross section of the metallization system or device in which the invention is incorporated; 
           [0024]      FIG. 2  is an enlarged detail view of the system to apply oil to the substrate to be metallized; and 
           [0025]      FIG. 3  is a plan view of the unit or system to apply oil to the substrate to be metallized. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Referring to the drawings in particular,  FIG. 1  schematically shows, in a section along a vertical plane, the inside of a vacuum metallization system. 
         [0027]    It comprises a container or main evacuable chamber  3 , housing two supports  5  and  7  for the reels of the web substrate N to be metallized, for example a polymer film, a strip of paper or the like. Arranged on the support  5  is a reel B 1  of substrate still to be treated which is fed along a feed path defined by drive rollers  9 ,  11 ,  13   15 ,  17 . Positioned on the support  7  is a second reel being formed, on which the substrate is wound after metallization. 
         [0028]    Positioned between roller  11  and roller  13  is a process roller  19  with a larger diameter which projects partly inside a chamber  21  separated, by a wall  23 , from the chamber above  25  in which the supports  5  and  7  for the reels of substrate are arranged. The chamber  21  is kept under a higher degree of vacuum than the chamber  25 . Systems also exist in which there is no separating wall  23  and no division into chambers  21  and  25 . In this case the reel being unwound, the rewinding reel, the path of the substrate N, the process roller  19  and the vaporization sources are all in the same chamber. Systems also exist in which a third chamber, known as a guard chamber, is provided adjacent to the process roller. 
         [0029]    The web substrate N unwound from the reel B 1  and fed around the process roller  19  is gradually rewound to form a reel of metallized substrate on the support  7 . During unwinding, while the web substrate N is being fed around the process roller  19 , a metal which has been vaporized by a series of sources  31  located in the chamber  21 , under the process roller  19 , is deposited on the surface thereof which is not in contact with the process roller  19 . The vaporized material, schematically indicated with V, is emitted from the sources  31 , which are adjacent to each other according to an alignment orthogonal to the direction FN of feed of the substrate, i.e. orthogonal to the plane of the figure. Therefore, only one source is visible in  FIG. 1 . 
         [0030]    The structure of the metallization system can vary and the embodiment represented in  FIG. 1  is only a schematic example of a possible system in which the invention can be implemented. 
         [0031]    An applicator unit  51  is positioned on the process roller  19 , on the feed side of the substrate N fed from the reel B 1  and on which vacuum deposition must be performed, to apply, according to a suitable pattern, a thin film of oil on the surface of the substrate N before it passes in front of the metallization sources  31 . The configuration of the applicator unit  51  is described in greater detail hereunder with specific reference to the diagram in  FIG. 2 . 
         [0032]    The unit  51  comprises a first printing cylinder  53 , which has on its surface a raised pattern composed of projections with a conformation and distribution corresponding to the pattern to be produced on the substrate N by metal-free areas. The printing cylinder  53  rotates according to the arrow f 53  to have a zero relative velocity with respect to the substrate N fed around the process roller  19 . The cylindrical surface of the printing cylinder  53  can be produced at least in part in an elastically yielding material. 
         [0033]    The printing cylinder  53  is tangent to an anilox cylinder  55  rotating according to arrow f 55 , preferably at a peripheral speed equal to the speed of the printing cylinder  53 . This cylinder  55  forms a distributor cylinder of the oil on the raised pattern of the printing cylinder  53 . The surface of the anilox cylinder is engraved, for example with laser engraving, to create thereon a plurality of small cells (screen), inside which an oil distributed by a distributor unit  57  described in detail hereunder and forming the oil source, is retained. The oil that is retained in the cells of the anilox cylinder  55  is then transferred to the front surfaces of the projections or protuberances of the printing cylinder  53 . 
         [0034]    The distribution unit  57  in substance has a reservoir or container  59  containing oil O optionally heated by a system of resistors  61 . Two doctor blades, indicated generically with  63  and  65 , close the space between the aperture of the reservoir  59  and the cylindrical surface of the anilox cylinder  55 . Each of the two doctor blades  63 ,  65  comprises, in the example shown, a substantially rigid profile  63 A,  65 A oscillating about an axis of oscillation A or B and extending substantially for the entire longitudinal extension of the anilox cylinder  55  and of the reservoir or container  59 . Each of these profiles  63 A,  63 B is provided with a flexible sheet  63 B,  65 B which, during operation of the device, is in contact with the cylindrical side surface of the anilox cylinder  55 . 
         [0035]    The profiles  63 A,  65 A are stressed by compression springs  63 C,  65 C so as to press the sheets  63 B,  65 B against the cylindrical surface of the cylinder  55 . The compression springs  63 C,  65 C can be adjustable to adjust the pressure of the doctor blades on the anilox cylinder. 
         [0036]    The members described hereinbefore, namely the distribution unit or source  57 , the anilox or distributor cylinder  55  and the printing cylinder  53 , are supported by side panels  71 . These side panels can be adjusted to be closer to or farther from the cylindrical surface of the process roller  19  and consequently the substrate N fed around the roller, or can be thrust with a controlled force against the roller. Advantageously, adjustment of thrust and/or of the position can take place separately for the two side panels, i.e. for the two ends of the printing cylinder  53  and of the anilox or distributor cylinder  55 . 
         [0037]    The movement to adjust or to move the side panels  71  towards or away from the process roller  19  is indicated with f 71 . The printing cylinder  53  is supported on the side panels on an axis  53 A fixed with respect to the side panels  71 , so that a movement according to f 71  to adjust or move the side panels  71  towards the process roller means that the printing cylinder  53  is moved closer to the process roller  19  to a greater or lesser extent. Alternatively, the reciprocal position between the process roller  19  and the printing cylinder  53  can remain the same and equal to the thickness of the web material or substrate N to be treated, but the thrust exerted by the cylinder  53  on the process roller  19 , and consequently the contact force with the substrate N, can be suitably adjusted or controlled. 
         [0038]    According to an advantageous embodiment, a respective actuator  73  is associated with each of the two side panels  71 , in this example represented by a hydraulic or pneumatic piston-cylinder actuator. Alternatively, a mechanical or electrical actuator can be used, such as an electronically controlled electric motor with a mechanical transmission such as a worm screw. Further, in another embodiment a simple elastic thrust member can be provided. 
         [0039]    The arrangement of two actuators associated with the respective two side panels allows separate adjustment of the force with which each of the two side panels  71  is thrust towards the process roller  19 . This makes it possible to obtain uniform contact pressure between the printing cylinder  53  and the web material or substrate N across the entire width of the latter. Alternatively, or in combination, the actuators  73  can be produced to control the position of the printing cylinder with respect to the process roller, adjusting the two ends of the cylinder separately. 
         [0040]    A possible and advantageous solution can comprise an electric actuator with electronic control of the position and optionally control of the thrust for each side panel. 
         [0041]    In an advantageous embodiment of the invention, an adjustable stop  72  is associated with each side panel  71 , so that the position of each side panel can be adjusted separately from the other to allow optimal positioning of the printing cylinder with respect to the process roller  19 , the operating position being maintained through the thrust of the actuators  73  against the adjustable stops  72 . 
         [0042]    When the two adjustable stops  72  are provided, the actuators  73  can operate by taking the respective side panels in stable contact against these stops, which will define the reciprocal adjustable position of the printing cylinder with respect to the process roller  19 . Alternatively, or in combination, the stops can be elastic. In this case the actuators can thrust the side panels  71  against the stops  72 , which give sufficient elasticity to allow the system to adapt to any variations in the operating conditions, without undesirable stresses arising. 
         [0043]    In practice, various solutions can be used which comprise, individually or in combination: 
         [0044]    position-controlled actuators, for example with position encoders, 
         [0045]    thrust-controlled actuators, for example with load cells or other thrust sensors, 
         [0046]    rigid adjustable stops, in which case the actuators preferably have an elasticity of their own, they are for example pneumatic actuators, 
         [0047]    elastic or at least moderately elastic adjustable stops. 
         [0048]    It would also be possible to use only the actuators  73  with thrust and/or position control systems, without the stops, for example through suitable selection of the type of actuator and of the optional adjustment ring. 
         [0049]    The anilox cylinder  55  is supported in turn at the ends thereof by supporting blocks  75  mounted on guides (not shown) integral with the side panels  71 . A thrust member  77  on each of the two side panels  71  separately pushes the corresponding end of the anilox cylinder  55  towards the printing cylinder  53 , obtaining in this case as well a substantially uniform distribution of pressure (along the axial extension of the cylinders  55 ,  53 ) between the cylinders. Alternatively, according to a preferred embodiment, an adjustable stop  76  for the respective supporting block  75  is arranged on each side panel  71 , so that the position of the anilox cylinder  55  with respect to the printing cylinder  53  can be adjusted optimally. 
         [0050]    The thrust member  77  can be—as indicated by way of example and preferably—an elastic member, but can also be an actuator, for example of the hydraulic, pneumatic, electric or mechanical type. 
         [0051]    Also in the case of the thrust members  77  and the adjustable stops  76  (just as in the case of the actuators  73  and the stops  72 ) it would be possible to use actuators of various types or simple elastic thrust members, in combination with adjustable rigid or elastic stops, to adjust the position and/or thrust of the anilox cylinder  55  with respect to the printing cylinder  53 , with separate adjustment at the two ends of the cylinder  55 . 
         [0052]    The distributor  57  is preferably integral with the supporting blocks  75  so as to move with them together with the anilox distributor cylinder  55 . Alternatively to the representation in the drawing, in which the anilox cylinder  55  is immersed in the oil O contained in the reservoir  59 , the anilox cylinder  55  could be positioned above the free surface of the oil O and the latter could be made to evaporate from the reservoir and condense on the surface of the anilox cylinder  55 . 
         [0053]    With the expedients described above optimal adjustment and extremely regular operation of the applicator device  51  are obtained, allowing metal-free areas with high definition, precision and repeatability of the pattern to be produced. 
         [0054]    In at least some of the possible configurations of the applicator unit, the force with which one or other of the cylinders is thrust and/or the reciprocal position can be adjusted with the metallization chamber closed using an external control and also, if necessary, during the deposition process. In this way further advantages are obtained with regard to function and quality of the final product. 
         [0055]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.