The present invention relates to a method for obtaining and / or transferring a metal sheet, in particular of a substantially pure metal or in an alloy thereof, preferably of a noble metal such as gold or silver.

Generally, to obtain a gold sheet of particularly reduced thickness, for example about 140-150 nm for 24 carat gold or 100 nm for 18 or 21 carat gold alloys, a rolling operation is first carried out by means of the passage through a plurality of pairs of lamination rollers (i.e. pairs of parallel and opposed rollers rotating on themselves) arranged in sequence and which thin a starting plate, which passes between them, until it reaches a sheet to be subjected to a or more typing operations.

Another way of making a particularly thin metal sheet is to use the physical vapor deposition of metal particles on a support substrate.

In particular, the known technique provides that, after the vacuum deposition step through the physical vapor deposition technique, the obtained bi-layer (formed by the polymeric support substrate in PET and the metal sheet) is taken up again to be sprayed, on the metal side, with a solidifying chemical product / compound, which must solidify in order to create a further hardened layer that adheres perfectly to the metal surface. In particular, this operation serves to give the metal sheet a force that can counteract the "peeling" operation, i.e. the mechanical detachment of the sheet itself from the polymeric substrate on which it was deposited. Once the substrate has been removed, the assembly formed by the metal sheet with said further hardened chemical layer is immersed in a solvent (for example: toluene, acetone and the like), and this in order to dissolve said hardened chemical layer obtained and thus obtain the single sheet of metal. The final operation involves washing the metal sheet in order to clean it of any solvent molecules remaining on the surface, and subsequent drying.

The drawbacks of the known art are related to the need to use solvents and to the numerous steps that are necessary, after the metal deposition step with physical vapor deposition, to obtain the metal sheet alone. In particular, the method according to the known art provides six steps:

1. Spreading of the solidifying chemical compound on the bi-layer formed by the polymeric substrate and the metal sheet,

2. Waiting for the solidification of the solidifying chemical compound,

3. Manual detachment of the foil-solidifier assembly from the polymer substrate,

4. Immersion of the foil-solidifier assembly in a solvent, to remove the solidifying chemical compound from the foil,

5. Washing of the foil to eliminate possible solvent residues (in particular this operation is mandatory for foil of precious metals to be used for human consumption or for curative purposes),

6. Drying of the foil resulting from the previous steps. This known method requires the use of potentially toxic substances, such as solvents as well as the solidifying chemical compound. This involves quality problems when noble metal sheets are produced for human consumption (such as edible gold) or for use in cosmetics (such as gold flakes) or in the pharmaceutical field.

This known method provides for a recovery / processing of the foil in several phases / passages and is difficult to automate, and therefore exposes the foil itself to greater risks of breakage in each of the processing phases compared to a semi-automated process or with fewer work phases.

US2015 / 0090582 describes a method for making a water transfer printing film in which the previously created relief motifs are coated with a metallic layer and then the metallic layer is coated with a PVA solution.

The object of the invention is to propose a method which allows to overcome, at least in part, the drawbacks of the known solutions.

Another object of the invention is to propose a method which allows to reduce the number of steps envisaged in the known solutions.

Another object of the invention is to propose a method that can be automated or semi- automated.

Another object of the invention is to propose a method which allows to reduce the manual operations.

Another object of the invention is to propose a method which allows a standardization of the final result.

Another object of the invention is to propose a method which allows to avoid the use of substances that are dangerous and potentially toxic to humans (solvents).

Another object of the invention is to propose a method which allows to speed up the production times of the metal sheet.

Another object of the invention is to propose a method which allows to apply metal sheets of the desired size on different surfaces.

Another object of the invention is to propose a method which is alternative and / or improvement with respect to the known solutions.

Another object of the invention is to propose a method which has an alternative structural and / or functional configuration with respect to traditional solutions.

Another object of the invention is to propose a method which can be implemented in a simple, rapid and low-cost manner.

All these purposes, both individually and in any combination thereof, and others which will result from the following description, are achieved, according to the invention, with a method having the characteristics indicated in claim 1.

The present invention is further clarified hereinafter in a preferred embodiment thereof and in some executive variants, reported purely by way of non-limiting example. The method according to the invention, to obtain and / or transfer a metal sheet, comprises the following steps:

- a roll of a bi-layer is prepared consisting of a water-soluble polymeric substrate and a sheet of said metal,

- said bi-layer is unrolled and the water-soluble polymeric substrate of said bi-layer is removed by means of jets of steam and / or water, to thus obtain said foil by itself,

- said sheet is dried by means of jets of hot air.

Conveniently, to prepare said roll of a bi-layer consisting of a water-soluble polymeric substrate and a sheet of said metal, a water-soluble polymeric substrate is preliminarily made available. Preferably, for example, the water-soluble polymeric substrate can be in poly (2-Ethyl- 2-Oxazoline) aliphatic tertiary amide, also called PEOX, or in polyvinyl alcohol (also called PVA or PVOH).

Conveniently, said water-soluble polymeric substrate can be made in the form of a roll of a water-soluble polymeric film.

The water-soluble polymeric substrate - and in particular the water-soluble polymeric film roll - is inserted into a vacuum chamber which is brought under vacuum, and preferably is brought to a vacuum between about 10 ^_1 and about 10 ⁷ Pascal, preferably between about 10 ² and approximately 10 ⁴ Pascal.

Subsequently, the metal deposition is carried out on the water-soluble polymeric substrate, to thus obtain a bi-layer which is formed by the substrate and the deposited metal sheet.

Conveniently, the metal deposition is carried out under vacuum with the technique of physical vapor deposition (PVD) or with the technique of chemical vapor deposition assisted by inductive plasma called ICP-CVD (in English " Inductively Coupled Plasma - Chemical Vapor Deposition").

The metal deposited, and which thus defines the foil, is a pure metal (ie it is not defined by a compound of a metal with other elements) or an alloy of a pure metal. Preferably, the deposited metal comprises a noble metal, in particular gold or silver, or copper or other metals such as for example aluminum, platinum, palladium or titanium. In particular, the deposited metal is not a semi-metal.

Suitably, the deposited metal is a grade 6N pure metal, ie it can be 99.9999% pure.

Suitably, the deposited metal can be a metal alloy. Advantageously, each of the precursors of said alloy can be pure at the 6N grade, ie it can be 99.9999% pure.

Conveniently, the metal sheet is deposited in such a way as to have a thickness comprised between 50 and 300 nm, preferably a thickness comprised between 80 and 150 nm. Conveniently, the deposited foil has a thickness of at least 50 nm. Conveniently, for the deposition step, the polymeric substrate is positioned in front of the evaporation cathode (which preferably comprises a " magnetron sputtering " source or plasma source), advantageously at a distance of about 5-30 cm, preferably about 10 -20 cm.

Advantageously, the roll of water-soluble polymeric film is unwound / unrolled at a suitable / adequate speed so that a metal deposit of the desired thickness is formed.

Advantageously, the roll of polymeric film with the deposited metal is rewound, preferably it is rewound immediately / promptly after the metal is deposited. Conveniently, the rewinding speed of the roll of polymeric film with the deposited metal substantially corresponds to the previous unrolling speed of the roll (before depositing the metal) so as to obtain a substantially constant speed and a substantially constant thickness of deposited metal.

Conveniently, the bi-layer is rewound with the metal sheet facing outwards, thus obtaining a rolled bi-layer.

Conveniently, the bi-layer thus obtained and rewound is brought back to atmospheric pressure. In particular, at the end of the foil deposition operation, the vacuum chamber is brought back to atmospheric pressure and the bi-layer is removed.

Conveniently, the rolled bi-layer is inserted in a rotating roller, preferably motorized in rotation, which is advantageously arranged substantially horizontally. In particular, the roller is rotatably rotating around a horizontal axis X corresponding to the longitudinal development axis of the rotating roller.

Conveniently, the rolled bi-layer is mounted on a motorized roller so that by unrolling said bi-layer the metal sheet faces downwards, while the polymeric substrate faces upwards.

Advantageously, a portion (preferably a small initial external portion) of the rolled bi-layer is unwound so as to be able to be hooked to a preferably motorized towing member, which is movable in translation in a substantially horizontal Y direction and perpendicular to the axis of rotation X of the motorized roller.

Preferably, said towing member comprises a motorized slide.

Conveniently, said towing member is movable in translation along a substantially horizontal direction Y corresponding to a horizontal development direction (preferably corresponding to the longitudinal development direction) of a perforated plane.

Preferably, said perforated surface is made of silicone. Preferably, said surface is microperforated. Preferably, the microholes are spaced about 8 mm apart to allow a constant air flow or suction on the surface of the foil.

Conveniently, a circuit fluidically connected to a pump is provided below the perforated surface to send an air flow out of said holes and, at a distinct moment, to suck into / aspire the air above the perforated top. Conveniently, in this way, during the subsequent operations, the foil can be selectively spaced from the perforated surface or kept adherent to the perforated surface. Conveniently, an air flow is first commanded to escape from the holes of the perforated surface in order to keep the metal sheet at a distance from the underlying perforated surface. In particular, the air flow exiting the perforated surface keeps the metal sheet at a distance, and therefore avoids the contact of the metal sheet, with the perforated surface, thus facilitating the spreading and unrolling of the bi-layer and also reducing the risk of breakage of the metal foil.

Conveniently, the method involves unrolling and spreading the bi-layer. In particular, the unrolling action of the bi-layer by means of the motorized rotating roller and the pulling action of the moving moving drive member hooked to the bilayer, stretches and unrolls said bi-layer until the desired unrolling portion is defined or until said bi-layer is completely unrolled.

Subsequently, the unrolled and spread bi-layer is made to come into contact and adhere with the perforated surface. In particular, for this purpose, the flow of air leaving the holes in the perforated surface is interrupted or preferably reversed. Conveniently, the metal sheet of the bi layer is sucked in and made to adhere to the perforated surface, also creating a surface tension on the sheet.

Conveniently, as said, the method provides for removing the water-soluble polymeric substrate of the unrolled and spread bi-layer by means of jets of steam and / or water, preferably at a pressure of about 50-100 atm, more preferably of 70-90 atm. Preferably, for this purpose, water and / or steam nebulizers are provided positioned above the unrolled and spread bi-layer, so as to face the water-soluble polymeric substrate of said bi-layer. In particular, said nebulizers are oriented downwards so that the jets of steam and / or water act on the water-soluble polymeric substrate of said bi-layer.

Advantageously, the steam and / or water jets are applied on said water-soluble polymeric substrate intermittently, and this to avoid that the polymer (of the substrate) in the hydrolysis phase shrinks too fast and can create cracks in the underlying metal sheet due to the tension forces. Preferably, for this purpose, said nebulizers are configured to emit an intermittent jet lasting less than one second, preferably with a pause of about 3 - 20 seconds between one jet and the next, more preferably of about 5 -10 seconds. Conveniently, during this phase of dissolution of the polymeric substrate by means of jets of steam and / or water, the foil is kept adherent to the underlying perforated surface and, in particular, for this purpose, the pump continues to suck air above the perforated surface through the holes in the top itself.

Conveniently, the water jets are nebulized and are at room temperature.

Preferably, each jet of water and / or steam acts on an area of the substrate with a length of about 10-20 cm.

Conveniently, the jets of steam and / or nebulized water are applied on the polymeric substrate until the complete dissolution of said substrate.

Conveniently, the jets of water and / or steam act in such a way as to dissolve, and therefore remove, the water-soluble polymeric substrate of the bi-layer, and therefore only the metal sheet of said bi-layer remains. Preferably, the jets of water and / or steam act in such a way as to dissolve, and therefore remove, the water-soluble polymeric substrate for the entire length of the unwound portion which is in contact and / or adheres to the underlying perforated surface.

Conveniently, as said, the method provides for then drying the metal sheet, thus obtained, by means of jets of hot air, preferably at a temperature of about 30 - 80° C, more preferably of about 50 - 70° C. Preferably, the hot air jets are sent at a speed of about 10 - 40 m/s, and more preferably about 20 - 30 m/s. Preferably, for this purpose, means (for example nozzles) are provided for emitting said jets of hot air onto the underlying foil, in particular on the side of the latter which was previously in contact with the removed substrate. In particular, said means for emitting jets of hot air are positioned above the foil and are oriented downwards so that the jets of hot air act on the underlying foil. Advantageously, during this drying phase, the foil is kept in contact and / or adhering to the underlying perforated surface and, in particular, for this purpose, the pump continues to suck air above the perforated surface through the holes in the same surface.

Advantageously, the sheet thus obtained and dried can then be sheared to a desired length. Conveniently, for this purpose, the foil hooked to the movable drawing member is made to slide, preferably also by means of the unwinding operated by the motorized roller and / or the escape of air from the perforated surface, towards a blanking station. Conveniently, the blanking station comprises a support base, made of metal (for example made of steel or the like), and traditional blanking means.

Advantageously, the steps - and the corresponding operations - of the method according to the invention can be carried out continuously and in a highly automated way. Conveniently, the method can be fully automated or it can be semi-automated (ie all phases and operations can be automated with the exception of the assembly of the double-layer roll on the unwinding roller and the coupling to the movable towing member).

Conveniently, the method described above can also be configured so that the bi-layer is unrolled on a surface to be covered (for example in leather, or in any other material) so that the sheet faces said surface, and in so as to then dissolve the polymeric substrate by means of said jets of steam and / or nebulized water, preferably intermittent, and finally drying the resulting sheet by means of jets of hot air. Conveniently, the jets of steam and / or nebulized water are applied on the polymeric substrate until the complete dissolution of said substrate and perfect attachment of the foil to the surface to be covered.

Conveniently, the surface to be covered can be in any material, such as ferrous and non- ferrous metals (steel, stainless steel, titanium, brass, aluminum, alloys of all kinds), glass and crystals, ceramics, wood, polymers or plastics materials.

Conveniently, therefore, in the method according to the invention the polymeric substrate is removed by hydrolysis by means of jets of water and / or steam. Conveniently, the foil can comprise a layer or more superimposed layers of the same metal or of different metals.

Conveniently, the gold or silver sheet obtained with the method according to the invention can be used as a gold or silver leaf for the coating of various surfaces. In particular, gold or silver (or other noble or precious metal) foil can be used as a substitute for gold or silver leaf in the gilding or silvering process of the traditional technique.

Advantageously, by means of the method according to the invention a metal sheet is obtained without the use of solvents, glues and solidifying materials. In particular, the removal of the polymeric substrate is carried out by making it dissolve through jets of steam and / or water, and not by immersion in water, thus avoiding that the tensile force of the polymeric material of the substrate when it is dissolved tears the foil, in particular when this is not thick enough to oppose a force at least equal and opposite. Advantageously, in this way, the polymeric substrate is completely dissolved, leaving the underlying sheet intact, which is then suitably dried immediately with a flow of hot air.

Advantageously, the method according to the invention allows to continuously and / or transfer a metal sheet, in particular a noble metal such as gold, silver or other precious metal, without using layers of tissue paper in between.

Advantageously, the method according to the invention allows the sheet obtained to be sheared directly in line, allowing to obtain sheets of the desired dimensions.

Advantageously, the method according to the invention allows to and / or transfer a high quality foil with the desired dimensions and thickness, without contamination by added chemical agents, with minimal human intervention and with a higher speed than known production techniques foils of precious metals.

Advantageously, the method according to the invention also allows to create a bi-layer comprising a foil, in which said bi-layer is suitable for being rolled up on a pin and for being used, for example, to gild or silver surfaces through the classic technique of gilding with gold leaf, but with the advantage of being able to cut the size of the sheets to be used to carry out these operations in the desired length.

Advantageously, the method according to the invention allows to overcome the current dimensional constraint of the gold, silver, platinum leaves obtained by means of a classic beating system, allowing larger surfaces to be covered in less time.

Advantageously, the bi-layer consisting of substrate and foil can be applied, according to the method according to the invention, on various surfaces, including delicate ones (for example leather), to cover / coat said surfaces with said foil. In particular, in this way, the use of the hot stamping technique is avoided, reducing the risk of excessive burning of the leather surface and without the need for dedicated systems for this operation. Conveniently, unlike current techniques such as hot stamping from foil or manual application of the foil only on the surface to be covered, the method according to the invention allows the foil to be transferred without the need to use pressure and high temperatures, but simply by gluing and dissolving the polymeric layer with steam and / or nebulized water and subsequent drying with a flow of hot air.

In particular, the bi-layer consisting of substrate and foil can be glued, for example, to the surface to be gilded, previously wet with a suitable glue for the operation (as envisaged in the classic gilding technique), with the part of the metal sheet facing towards the surface to be covered and spread manually or with other known tools or techniques. Subsequently, according to the method of the present invention, the substrate is removed by steam nebulization, and subsequently dried with a jet of hot air.

The present invention also relates to a roll of said double layer formed by:

- a water-soluble polymeric substrate or removable by jets of water and / or steam,

- a metal sheet associated with said substrate and obtained by physical vapor deposition or chemical vapor deposition assisted by inductive plasma called ICP-CVD (in English " Inductively Coupled Plasma - Chemical Vapor Deposition") of particles of said metal on the substrate.

Advantageously, the roll can be inserted into a suitable containment package and, once extracted from the latter, the end user can unroll, tear or cut only the desired part of said double layer roll.

The present invention also relates to a process for transferring a metal sheet onto a surface, in particular to coat said surface with said metal sheet thus transferred, said process being characterized in that a method is used according to one or more of the characteristics described above. In particular, said process provides for transferring, and thus obtaining, a metal sheet on said surface, by means of the aforementioned method in which:

- a roll of a bi-layer is prepared consisting of a water-soluble polymeric substrate and a sheet of said metal,

- said bi-layer is unrolled and the water-soluble polymeric substrate of said bi-layer is removed by means of jets of steam and / or water, to thus obtain said foil by itself,

- said sheet is dried by means of jets of hot air.

Conveniently, the transfer process can also comprise one or more of the other characteristics of the aforesaid method, as referred to above.

The present invention has been illustrated and described in some of its preferred embodiments, but it is understood that executive variations may apply thereto in practice, without however departing from the scope of protection of the present patent for industrial invention.