WO2005098077A2

WO2005098077A2 - Metalization method and plant

Info

Publication number: WO2005098077A2
Application number: PCT/IB2005/000926
Authority: WO
Inventors: Paolo Tortolone; Carlo Orsi
Original assignee: Metalnova S.R.L.
Priority date: 2004-04-08
Filing date: 2005-04-08
Publication date: 2005-10-20
Also published as: WO2005098077A3; EP1733068A2; CN1997767A; ITTO20040221A1

Abstract

Described herein is a method for metalization in high-vacuum conditions for bestowing particular colourings or chromatic effects on the article to be metalized, said method comprising two steps of metalization: sublimation in the vacuum bell in high-vacuum conditions of a first metal; and sublimation in the vacuum bell in high-vacuum conditions of a second metal in the presence of a gas basically constituted by oxygen or ozone. The second metalization bestows upon the article thus treated a particular colouring and/or particular chromatic effects.

Description

Metalization method and plant"

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Field of the invention The present invention relates to a new method of metalization and a plant for implementation of said method. In particular, the present invention relates to a method and corresponding plant for metalization in high-vacuum conditions capable of bestowing particular colourings or chromatic effects upon the article to be metalized. State of the prior art The method of metalization in vacuum conditions is known in the art and substantially envisages the introduction of the article to be metalized into a vacuum bell and the sublimation of the metal to be deposited on the surface of the article via heating of the substrate on which the metal is to be deposited. Once the temperature of sublimation of the metal has been reached, this passes to the gaseous state and is deposited on the article present inside the bell, giving rise to a generally reflecting and non-coloured metallic layer. The colouring is subsequently bestowed upon the article thus metalized via a further step of painting with metalized or pigmented paints, which generally envisages the application of a number of layers of paint to obtain the desired colouring. Summary of the invention The purpose of the present invention is to develop a method of metalization that will enable a colouring or a particular chromatic effect to be bestowed upon the article in question in a single process carried out inside the vacuum bell. According to the invention, said purpose is achieved thanks to the solution referred to specifically in the ensuing claims. The method of metalization of an article according to the present invention initially involves the preparation of the article set inside a vacuum bell, on a satellite rotary support, via application of an ionic discharge and subsequent degassing followed by metalization of the article, which is conducted in two steps : i) sublimation of a first metal in a bell in high- vacuum conditions, through application of a voltage to the electrically conductive support for the first metal ; and ii) sublimation of a second metal in a bell in high-vacuum conditions in the presence of a gas basically constituted by oxygen or ozone, through application of a voltage to a second electrically conductive support for the second metal. The step of preparation of the article to be metalized is indispensable for the metalization method, in so far as it enables the necessary adhesion of the metallic layer on the surface of the article to be obtained; said surface must then be cleaned from any contaminants that may be present thereon. The application of at least one ionic discharge for a duration of approximately 4-6 minutes inside the bell in pre-vacuum conditions - at a pressure for example comprised between lxlO^"1 and 6xl0^~2 mbar enables the surface to be cleaned. The ionic discharge occurs by applying a current intensity (for example, in the region of 250-350 mA) to a cathode present in the bell where the article - appropriately mounted on a satellite rotary support - constitutes the anode. At the end of the ionic discharges a further degassing is carried out for approximately 35 minutes so as to achieve an optimal cleaning of the surface of the article to be metalized. Next, the first metalization step is carried out in high-vacuum conditions, i.e., at a pressure typically comprised between 8xl0^~4 and 6xl0^"5 mbar, having a duration, for example, of approximately 1 -

1.5 minutes . The first metalization step takes place by sublimating the first metal to be applied on the surface of the article in question - generally chosen from aluminium, chromium, nickel, copper, or alloys thereof . The sublimation of this first metal is performed by applying a voltage to its support, so that the temperature of sublimation in vacuum conditions of the metal used is reached, which by passing to the gaseous state deposits on the surface of the article present in the bell. The support for said first metal is conveniently constituted by a tungsten filament generally having a helical conformation. The first metal to be sublimated - in a bar conformation - is introduced within the tungsten filament, so that it can reach its temperature of sublimation faster. It is possible or even preferable to use more than one bar of the first metal to be sublimated, preferably three or five bars interlaced in order to have the necessary amount of metal for a complete metalization of the articles present in the bell and at the same time an almost immediate sublimation of all the metal bars so as to obtain a metallic layer that is as homogeneous as possible on the surface of the article.

The "immediate" sublimation of all the bars present is obtained by exploiting the greater conduction of the heat emitted by the supporting filament by the bars when these are interlaced. At the end of this first step, the second metalization starts, which is designed to bestow upon the articles the colouring and/or chromatic effects of interest . The second metalization step is once again performed in the bell in high-vacuum conditions generally at a pressure conveniently of between 8xl0^"4 and 6xl0^~5 mbar - and has a duration, for example, of approximately 2 to 3.5 minutes according to the metal that is used in this second step. The second metal is generally selected from magnesium, manganese, cobalt, copper, or their alloys, so as to bestow upon the article a colouring that ranges from gold to blue or green according to the metal used. The second metal, which preferably presents a tablet conformation, is positioned on a second crucible-shaped support made preferably of a mixture of tungsten and molybdenum. The temperature of sublimation of the second metal is reached by applying a voltage to the crucible, which brings about a heating thereof and consequently heating up to sublimation of the second metal contained therein. According to a peculiar and fundamental characteristic of the invention, during the second metalization step oxygen or ozone is introduced in a dosed way into the bell so as to enable the tones or shades of colouring with the desired chromatic effects to be obtained. The greater the amount of gas introduced into the bell, the greater the burnishing of the article, irrespective of the colour bestowed by the second metal used. At the end of the second metalization step, a further degassing process is performed for the purpose of completing fixing of the metallic layers on the surface of the article treated. Said final degassing can last some minutes .

Detailed description of the invention Described hereinafter is an example of plant that enables implementation of the method of metalization according to the present invention, with reference to the annexed drawing, which represents, purely by way of non-limiting example, the diagram of such a plant. In the drawing, the reference number 1 designates the vacuum bell provided with a door 2, which can be opened and closed in a sealed way. The reference numbers 3 and 4 designate, respectively, the support consisting of tungsten filament for the first metalization step, and the support shaped like a crucible for the second metalization step. The reference 5 designates as a whole the cathode, generally shaped like a bar, for the production of the ionic discharge in co-operation with the anode constituted by the satellite rotary support, designated as a whole by 6, for the pieces to be metalized. Said support is in effect constituted by a multiplicity of supporting members for the pieces to be metalized, having a motion of rotation and a motion of revolution, said members being carried by a carriage (not illustrated) , which can be inserted into and extracted from the bell 1. For application of the high-vacuum conditions inside the bell 1 there are provided, in a generally conventional way, a generally mechanical primary pump 7, connected in series to a lobed pump of the Roots type 8 set in a suction line 9, connected with the bell 1 through a pre-vacuum solenoid valve 10. The line 9, operatively associated to which is a solenoid valve 11 for stabilization of the vacuum with corresponding micrometric regulator 12, is moreover connected to a suction line in parallel 13, in which a diffusion pump 14 is inserted with associated discharge solenoid valve 15. The line 13 is connected to the vacuum bell 1 through a high-vacuum solenoid valve 16. The solenoid valve 11 for stabilizing the vacuum is designed for injecting air into the bell 1 in a finely dosed way via the micrometric regulator 12 in such a way as to maintain therein the value of vacuum set constant, without having to reduce the flow rate during suction of the pumps 7 and 8. Designated by 17 and 18 are two solenoid valves, the former for cleaning a head for detecting high- vacuum conditions 19 and the latter for inlet of air into the bell 1 at end of cycle, and designated by 20 and 21 are heads for detecting the vacuum. The reference number 22 designates a solenoid valve connected to the bell 1 for introduction of air therein in the step of ionic discharge, associated to which is a micrometric regulator 23. Finally, designated by 24 is a tank of oxygen or ozone under pressure, connected, via an inlet solenoid valve 25 and a micrometric-regulating assembly 26, to the base of the vacuum bell 1. All of the components described above are operatively connected to a programmable electronic processor for implementation of the method described above, according to the cycle summarized hereinafter. Initially, after introducing the carriage with the support for the pieces into the vacuum bell 1, first the primary pump 7 and then the Roots pump 8 are activated: the solenoid valve 10 is opened, whilst the solenoid valves 15 and 16 are closed. Once the degree of vacuum set is reached, the next step is to proceed with ionic discharge up to completion of the step of preparation of the pieces, maintaining the solenoid valve 22 open and controlling via the micrometric regulator 23 introduction of air into the bell 1. The solenoid valve 11 with the micrometric regulator 12 associated thereto intervenes, if necessary, to maintain the level of vacuum inside the bell 1 constant . This is followed by the first metalization step in high-vacuum conditions as a result of closing of the solenoid valve 10 and of opening of the solenoid valves 15 and 16 so as to connect the diffusion pump 14, in series to the pumps 7 and 8, to the vacuum bell 1. The solenoid valve 22 is then closed, after a further period of degassing of the pieces, the tungsten filament or filaments 3 are electrically supplied to achieve the sublimation of the first metal to be applied on the surface of the pieces. At the end of the first metalization step, the duration of which, as has been said, may be comprised between 1 and 1.5 minutes, the second metalization step is carried out by electrically supplying the crucibles 4. In this step, via the solenoid valve 25 and the micrometric-regulating assembly 26, oxygen or ozone is introduced into the vacuum bell 1 so as to obtain the desired chromatic variants on the pieces. The duration of this step is generally longer than that of the first metalization step, and may, for example, be comprised between 2 and 3.5 minutes. Finally, the solenoid valves 25 and 16 are closed, and, after a further period of degassing and stabilization, the solenoid valve 18 is opened to enable opening of the bell 1 and extraction of the supports with the pieces. Of course, the details of construction and the embodiments of the plant may vary widely with respect to what is described and illustrated herein, without thereby departing from the scope of the present invention as defined in the ensuing claims.

Claims

1. A method for metalization of at least one article comprising the operations of preparation of said article in a vacuum bell and metalization of said article, said metalization being conducted in two steps : i) sublimation in said vacuum bell of a first metal in high-vacuum conditions, said first metal being sublimated via application of a voltage to a first electrically conductive support for said first metal; and ii) sublimation in said vacuum bell of a second metal in high-vacuum conditions, in the presence of a gas introduced in a dosed way within said bell and basically constituted by oxygen or ozone, said second metal being sublimated via application of a voltage to a second electrically conductive support for said second metal . 2. The method according to Claim 1, in which said preparation consists in the application of at least one ionic discharge to said at least one article set within said vacuum bell. 3. The method according to Claim 2, in which said at least one ionic discharge has a duration comprised between 4 and 6 minutes. 4. The method according to Claim 2, in which said ionic discharge is followed by a process of degassing of said article conducted in said vacuum bell at a pressure comprised between lxlO^"1 and 6xl0^"2 mbar. 5. The method according to Claim 1, in which said first metalization step is conducted at a constant pressure of between 8xl0^"4 and 6xl0^"5 mbar. 6. The method according to Claim 1, in which said first metalization step has a duration of between 1 and

1 . 5 minutes . 7. The method according to Claim 1, in which said first support of said first metal includes a tungsten filament having a helical conformation. 8. The method according to Claim 1, in which said first metal is selected from: aluminium, chromium, nickel, copper, or their alloys. 9. The method according to Claim 7, in which said first metal has a bar conformation and is positioned in the internal space defined by said helical conformation of said filament. 10. The method according to Claim 9, in which said first metal is present in at least three bars, preferably interlaced. 11. The method according to Claim 1, in which said second metalization step is conducted at a constant pressure of between 8xl0^"4 and 6xl0^"5 mbar. 12. The method according to Claim 1, in which said second metalization step has a duration of between 2 and 3.5 minutes. 13. The method according to Claim 1, in which said second support of said second metal is constituted by a crucible made of tungsten and molybdenum. 14. The method according to Claim 1, in which said second metal is selected from: magnesium, manganese, cobalt, copper, or their alloys. 15. The method according to Claim 1, in which said second metal has a tablet conformation. 16. The method according to Claim 1, in which said article to be metalized is mounted within said vacuum bell on a satellite rotary support. 17. The method according to Claim 1, in which said metalization is followed by a further degassing process . 18. A plant for the implementation of the metalization method according to one or more of the preceding claims, characterized in that it comprises means (24, 25, 26) for the dosed introduction of oxygen or ozone within said vacuum bell (1) . 19. The plant according to Claim 18, characterized in that said first electrically conductive support for said first metal within said vacuum bell (1) includes tungsten-filament means (3) with a helical conformation . 20. The plant according to Claim 18, characterized in that said second electrically conductive support for said second metal within said vacuum bell (1) includes crucible means made of tungsten and molybdenum (4) . 21. The plant according to Claim 18, characterized in that said vacuum bell (1) is equipped with vacuum- stabilizer means (11) with associated regulating means (12) for injecting air in a dosed way into said bell (1) in such a way as to maintain constant therein the value of vacuum set .