EP4058618A1

EP4058618A1 - Machine for the surface processing of products through plasma deposition of thin layers of coating materials, and method for processing products through plasma

Info

Publication number: EP4058618A1
Application number: EP20817491.2A
Authority: EP
Inventors: Alessio NOE'; Stefano Ferrari
Original assignee: Astro SRL
Current assignee: Astro SRL
Priority date: 2019-11-12
Filing date: 2020-11-10
Publication date: 2022-09-21
Also published as: WO2021094919A1

Abstract

Machine for the surface processing of products through plasma deposition of thin layers of coating materials, comprising an inductive high radio frequency plasma source, a dome, at least one inlet for a reactive gas entering said dome, at least one inlet for a mixture of precursor gas and carrier gas, a supply device for supplying said plasma source with said mixture of precursor gas and carrier gas, the machine comprising : - at least one first tank adapted to contain liquid for at least one precursor liquid, - a mass flow meter for measuring the mass flow rate of the precursor liquid exiting from said at least one first tank, - at least one second tank for a carrier gas, - a device for mixing and expanding the precursor liquid coming from said mass flow meter and said carrier gas coming from said at least one second tank, - a supply duct for supplying said expanded mixture from said mixing and expansion device to said at least one inlet for a mixture of precursor gas and carrier gas into said dome.

Description

MACHINE FOR THE SURFACE PROCESSING OF PRODUCTS THROUGH PLASMA DEPOSITION OF THIN LAYERS OF COATING MATERIALS, AND METHOD FOR PROCESSING PRODUCTS THROUGH PLASMA.

Description Technical Field

[001] The invention relates to the surface processing of products through plasma, in particular, although not exclusively, of slab-shaped products, such as resin-based processing, painting, protective coating etc. More in particular, the object of the invention is a machine for the surface processing of products through plasma deposition of coating materials, and a method for processing products through plasma.

State of the Art

[002] In the last years, the problems linked to the corrosion and wear of materials used in products for industrial, decorative and home living, have driven the development of new materials and process technologies for producing protective coatings, in order to improve performance and useful life of, for example, mechanical tools, to decrease the production costs and to improve environmental impact.

[003] The protective coating, where the thickness is comprised between few nanometers and some microns, fall into the category of so-called thin films; where the thickness is greater than dozens microns, they fall into the category of thick films. [004] Due to the their particular structure, thin films have been studied mainly for use in electronics and optics industry, but the use thereof is increasingly increasing in different sectors, for example mechanical processing, decorative applications, eyewear.

[005] Ceramic-based thin films have been particularly studied for hardness and relative inertia with the aim to using them as protective materials against corrosion, oxidation and wear.

[006] Plasma deposition is one of the known processes for depositing materials on products.

[007] In general, for plasma deposition it is necessary to mix a gaseous substance having the desired technical features with a carrier gas, and to combine this mixture with a reactive gas in a plasma source. [008] Plasma high temperature stresses these substances, significantly increasing the reactivity thereof. Thus, the product resulting from the reactivity is perfectly deposited on the material and strongly adheres to the surface thereof. A layer is formed, whose functional surface properties can be defined in advance based on the type of used substances.

[009] Not all materials can be conveniently used in plasma deposition. Some precursor materials are difficult to be managed in gaseous form, and should be used starting from a liquid form, then gasified. This can be difficult to manage in terms of control of the exact amount to be used for plasma reaction, practically resulting in a material devoid of the desired features.

[010] Moreover, plasma deposition technologies is no perfectly adapted for producing large materials, for the difficult adequately to control thicknesses, and to make the process sufficiently fast for treating many products.

Summary [Oil] The general object of the invention is to overcome the problems of plasma deposition of thin layers of materials on large products.

[012] Adequately, an important object of the invention is to provide a machine for the surface processing of products through deposition of thin layers of coating materials, as well as a processing method, allowing to process large products. [013] A further important object of the invention is to provide a machine for the surface processing of products through deposition of thin layers of coating materials (as well as a processing method), allowing to have particularly hard thin layers.

[014] A further object of the invention is to provide a machine for the surface processing of products through deposition of thin layers of coating materials (as well as a processing method), allowing high production rates.

[015] These and other objects, that will be better described below, are achieved through a machine for the surface processing of products through plasma deposition of thin layers of coating materials, comprising: a closed gastight space, provided with at least one opening, that can be closed, for inserting and removing the products to be processed, a device for reducing the pressure inside the closed space up to a value lower than the ambient pressure, a surface processing device comprising an inductive high radio frequency plasma source, operatively connected to a high radio frequency generator and provided in the closed space, the source comprising o an open dome facing the at least one closed space, o a vacuum closed electrode adapted to surround the center of the dome and to start the plasma generation discharge, and operatively connected to the inductive coil, o at least one inlet for a reactive gas entering the dome, o at least one inlet for a mixture of precursor gas and carrier gas, - a supply device for supplying said plasma source with said mixture of precursor gas and carrier gas, comprising o at least one first tank adapted to contain liquid for at least one precursor liquid, o a flow-meter for measuring the mass flow rate of the precursor liquid exiting from the at least one first tank, o at least one second tank for a carrier gas, o a device for mixing and expanding the precursor liquid coming from the mass flow meter and the carrier gas coming from the at least one second tank, o a supply duct for supplying the expanded mixture from the mixing and expansion device to the at least one inlet for a mixture of precursor gas and carrier gas into the dome.

[016] Adequately, the plasma source comprises a primary circuit provided with inductive means, such as one or more inductive coils, operatively connected with the frequency generator, and a secondary circuit provided with induced means, such as one or more induced coils, operatively connected to the electrode for starting plasma discharged.

[017] The plasma source preferably comprises an impedance matching network, preferably automatic. [018] Adequately, the machine comprises an operational area for arranging the product to be processed; the dome is arranged above, and directed towards, the operational area.

[019] According to preferred embodiments, the at least one inlet for a mixture of precursor gas and carrier gas into the dome comprises a tube, which extends with an approximately ring shape and along whose surface calibrated holes are provided, forming the nozzles for the exit of the precursor gas-carrier gas mixture; the tube preferably surrounding the center of the dome.

[020] According to preferred embodiments, the device for mixing and expanding the precursor liquid coming from the mass flow meter and the carrier gas coming from the at least one second tank comprises a mixing chamber, an inlet for atomizing the precursor liquid thus creating an aerosol, a second inlet for the carrier gas entering the mixing chamber, a valve for controlling the pressure inside the mixing chamber, an outlet for the mixture exiting from the said device, a heat exchanger provided between the mixing chamber and the outlet and adapted to increase the temperature of the mixture to make the liquid part completely evaporate.

[021] According to preferred embodiments, the machine comprises at least one tank for at least one reactive gas; the tank preferably comprises oxygen (O2).

[022] According to some embodiments, the at least one precursor liquid first tank is adapted to contain trimethylaluminum (TMA) or hexamethyldisiloxane (HDMSO), or titanium isopropoxide (TTIP), so that, in combination with the reactive gas oxygen (O2), preferably inside the dome, during plasma formation, a deposition material is produced comprised of aluminum oxide (AI2O3) or of silica oxide (SiOx), or of titanium dioxide (T1O2); two first tanks are preferably provided, one of them adapted to contained trimethylaluminum (TMA) and the other one adapted to contain hexamethyldisiloxane (HDMSO), or one of them adapted to contain trimethylaluminum (TMA) and the other one adapted to contain hexamethyldisiloxane (HDMSO) or titanium isopropoxide (TTIP), or one of them adapted to contain hexamethyldisiloxane (HDMSO) and the other one adapted to contain trimethylaluminum (TMA) or titanium isopropoxide (TTIP); or three tanks are provided, adapted to contain trimethylaluminum (TMA), titanium isopropoxide (TTIP), hexamethyldisiloxane (HDMSO) respectively.

[023] According to preferred embodiments, the at least one carrier gas second tank is adapted to contain inert gas, for example argon. [024] According to preferred embodiments, the closed space comprises at least one accumulation chamber, separate from the processing area, where products are accumulated; from an operational viewpoint, once all products to be processed have been inserted into the at least one chamber, the chamber is closed and the pressure inside is reduced up to an operational processing pressure, then the products are processed, and lastly the at least one chamber is opened and the products are taken therefrom.

[025] The machine preferably comprises in the at least one chamber, a moving device for moving the products from the bottom upwards and in reverse, so as to accumulate at least two products on levels put over one another, a plan moving device for moving the products from and towards the at least one opening when the products are arranged at the same level of the at least one opening, wherein, from an operational viewpoint, a plurality of products are inserted into the at least one chamber, and at least two products of the plurality of products are over one another for a span of processing, and wherein, once all the products to be processed have been inserted into the at least one chamber, the chamber is closed and the pressure inside is decreased up to an operational processing pressure, and then the at least one chamber is opened again and the products are removed therefrom.

[026] Preferably, the closed space comprises a processing room adjacent to the at least one accumulation chamber; the products are moved from the at least one accumulation chamber to the processing room in order to be processed.

[027] The closed space preferably comprises at least two accumulation chambers connected to each other, each chamber being adapted to receive a plurality of products put over one another.

[028] The surface processing device for processing a product is preferably arranged between the two accumulation chambers.

[029] Preferably, between the two chambers a processing room is provided, where the surface processing device is arranged, and where the operational area for arranging the product is provided, so that the products are adapted to move from a chamber to the following one passing through the room, where the processing is carried out.

[030] The processing room has preferably dimensions adapted to receive the whole product to be processed; the product is preferably adapted to be moved from a first chamber to the room, where it is arranged stationary so as to carry out the deposition processing. [031] According to preferred embodiments, the plan moving device is adapted to allow the products to pass from a chamber to the following one under the processing device.

[032] Preferably, the plan moving device is adapted to allow the products to pass from a chamber to the following one under the processing device during the processing step; the room has preferably smaller dimensions than the dimensions of the products so that the deposition processing is carried out on the portion of the product inside the room while the product is moving.

[033] According to preferred embodiments, the plan moving device is common to the chambers; preferably the plan moving device is a conveyor belt crossing the chambers from an entrance first opening of the machine up to an exit second opening of the machine, passing under the processing device.

[034] According to some preferred embodiments, the processing machine comprises a first opening for the products entering the closed space, defined in the first chamber, and a second opening for the products exiting the closed space, defined in the second chamber, respective sealing doors being provided associated with the openings.

[035] According to preferred embodiments, in each chamber a moving device is provided for moving the products from the bottom upwards so as to accumulate at least two products over one another.

[036] According to preferred embodiments, in the at least two chambers there is defined a moving plane for moving the products from the entrance to the exit of the closed space, crossing the chambers passing under the processing device, each bottom- upwards moving device defines N positions raised from the moving plane, and the maximal number of products that can be processed in the machine is N+l .

[037] According to preferred embodiments, each product is borne by a respective support, so that the products enter and exit the closed space on these supports, and the bottom-upwards moving device and the plan moving device are adapted to move the products by directly moving the supports. [038] According to preferred embodiments, each product is in the form of a slab, preferably made of stone, glass, wood, ceramic or metal.

[039] According to a further aspect, the invention relates to a method for thin layer plasma deposition, providing for a product, with a surface to be coated with a thin layer, arranged inside a vacuum processing room, with pressure preferably comprised between 6 x 10³ mbar and 1.1 x 10² mbar, wherein in the processing room a surface processing device is provided, comprising a high radio frequency inductive plasma source arranged in the closed space, and wherein the source comprises

- an open dome facing the at least one closed space, with which a high frequency inductive coil is associated, operatively connected to a high radio frequency generator,

- a vacuum closed electrode adapted to surround the center of the dome and to start the plasma generation discharge, and operatively connected to the inductive coil,

- at least one inlet for a reactive gas entering the dome,

- at least one inlet for a mixture of precursor gas and carrier gas, the method providing the following steps for the product inside the vacuum processing room: a) supplying a mass flow meter with a precursor liquid, b) measuring the mass flow rate of the precursor liquid, c) supplying a mixing and expanding device with the desired mass flow rate of the precursor liquid, d) supplying the mixing and expanding device with a carrier gas, so that the precursor liquid and the carrier gas form a gaseous mixture, e) supplying the at least one inlet for a mixture of precursor gas and carrier gas with the gaseous mixture, f) supplying the at least one inlet for a reactive gas entering the dome with a reactive gas, g) generating, through the high frequency generator, an electromagnetic wave to obtain an inductive plasma of the mixture, h) waiting the time for the material formed from the inductive plasma to deposit.

[040] Preferably, in the mixing and expanding device, - the precursor liquid is atomized inside a pressure-controlled mixing chamber, to form an aerosol,

- the carrier gas is inserted into the mixing chamber,

- the precursor/carrier gas mixture exits from the mixing chamber, - the mixture is heated so that the liquid part thereof completely evaporates,

- the gaseous mixture of precursor gas/carrier gas exits from the said mixing and expanding device.

[041] The reactive gas preferably comprises oxygen (O2).

[042] Preferably, the precursor liquid is trimethylaluminum (TMA) or hexamethyldisiloxane (HDMSO), or titanium isopropoxide (TTIP), so that, in combination with the reactive gas oxygen (O2) inside the dome during plasma formation, a deposition material is produced comprised of aluminum oxide (AI2O3) or of silica oxide (SiOx), or of titanium dioxide (TiCh).

[043] The carrier gas preferably comprises inert gas, preferably argon. [044] According to preferred embodiments, the method comprises the step of arranging a plurality of products to be subjected to plasma surface processing inside a closed space, making the closed space vacuum and moving the products, one by one, towards the processing room provided in the closed space to carry out, for one product at a time, the steps a)-h); once these steps have been carried out, the product is exited from the processing room and a subsequent product is inserted thereinto.

[045] The products are preferably moved towards the processing room from a first chamber to make the plasma deposition; after the steps a)-h), each product being housed in a second chamber of the closed space, different than the first chamber.

Brief description of the drawing [046] The invention will be better understood by following the description below and the attached drawing, showing some non-limiting embodiments of the invention. More particularly, in the drawing:

- Fig. l is a schematic side view of a line of a surface processing plant using the processing machine of the invention; - Fig. 2 is a schematic side view, partially cut-away longitudinally, of a surface processing machine with a double sealed chamber; - Fig. 3 is a schematic front view, partially cut-away transversally, of the processing machine of Fig. 2; each of Figs. 4a to 4e is a schematic front view, partially cut-away transversally, of a portion of the processing machine of Fig. 2, relating to a specific step of loading the products in the sealed chambers of the machine;

- Fig. 5 is a schematic side view, partially cut-away longitudinally, of a machine similar to that of Fig. 2, wherein the processing room has larger dimensions than those of the slab;

- Fig. 6 is a schematic side view, partially cut-away longitudinally, of a machine with only one chamber where only one slab is introduced to carry out the plasma deposition processing thereon;

- Fig. 7 is a diagram of a plasma source arranged on the top of the processing room of a machine according to the previous figures, where some components are highlighted. Detailed description of embodiments

[047] With reference to the aforementioned figures, a machine for the surface processing of products through plasma deposition of thin layers of coating materials, according to the invention is indicated as a whole with the reference number 10. It is inserted in a processing line indicated with 100. More in particular, in this example the line is a line for the surface processing of slabs L made of stone, such as marble, granite and the like, or of glass, wood, ceramic, metal etc. The line is well known, with the exception of the part relating to the processing machine 10.

[048] The line 1 comprises, in succession, a rotating storage space 101 for slabs L, an automatic loader 102 taking the slabs L from the storage space 101 and putting them on a comb-shaped loading conveyor belt 103 transferring the slabs L onto a first pantograph lifting device 104.

[049] This latter allows arranging the slabs at the level where they can enter the processing machine 10 of the invention described below.

[050] At the exit from the processing machine 10 a second pantograph lifting device 105 is provided, bringing the slabs to the level of a comb-shaped unloading conveyor belt 106, after which an automatic unloader 107 and a further rotating storage space 108 for slabs L are provided. [051] Adequately, in correspondence of the first pantograph lifting device 104, a support LI for a slab L is provided, in the form of a mainly flat metal frame comprising poles and crossbars, onto which the slab is fastened in a flat fashion. For each slab arriving on the first pantograph lifting device 104 a corresponding support LI is provided for moving the slab inside the processing machine 10.

[052] Analogously, the set comprised of support LI and slab L arriving from the machine 10 onto the second pantograph lifting device 105 is separated, and the slab L is taken from the comb-shaped unloading conveyor belt 106 while the support LI returns to the comb-shaped loading conveyor belt 103 through a pair of movable belts 107 provided below the machine 10.

[053] From a practical viewpoint, a number of supports L 1 is provided at least equal to the number of slabs to be processed in the processing machine 10, as it will be better explained below. For example, in the case illustrated in the figure the number of supports is equal to the number of slabs to be treated in the machine 10 plus four. The surface processing machine 10 comprises a casing 11, internally defining two consecutive sealed chambers, respectively a first sealed chamber 12 and a second sealed chamber 13, separated through an intermediate room 14. The two sealed chambers and the room define a gastight closed space.

[054] The first sealed chamber 12 comprises an entrance first opening 15 for a support LI (bearing a first slab L; here below this set will be referred to as “support- slab L”) entering the machine 10. The second sealed chamber 13 comprises an exit second opening 16 for a support-slab L. Respective sealing doors 17, that can be opened and closed, are associated with these openings 15, 16.

[055] The room 14, arranged between the two chambers 12 and 13, has two passages 18 for accessing the two chambers.

[056] The intermediate room 14 is a room where the surface processing is carried out through plasma deposition of adequate material, and where a surface processing device 26 (preferably arranged on the top of the room 14) carries out the processing through plasma deposition. [057] To allow processing through plasma deposition, the machine comprises a known apparatus 30 for reducing the pressure in the gastight closed space comprised of the two chambers 12 and 13 and the room 14 (for example up to a pressure comprised between 6 x 10³ mbar e 1.1 x 10² mbar), the apparatus being part of an air suction system and being omitted in the figures for the sake of simplicity of drawing. For example, the apparatus 30 comprises the following elements (not shown in the figures for the sake of simplicity): an oil-less rotary pump with pumping speed of 650 m³/h and flow rate, up to 10^-3 mbar with the aid of roots pump, of 2000 m³/h, and an air-cooled turbomolecular pump with pumping speed of 22001/s and flow rate up to 10⁸ mbar, with a gas pressurized dry air purge system, so ad to protect it against any corrosive gases resulting from the reaction.

[058] Therefore, the apparatus 30 is adapted to manage the development of corrosive gases. Automatic on/off valves may be provided on the pumping lines, allowing to evacuate the feeding chamber and the deposition chamber alternatively. [059] To a certain extent, the pumping system flow rate may be controlled by means of an electronic unit acting on the rotation speed of the turbomolecular pump (throttle). In this way it is possible to adjust the pressure in the chamber and the gaseous flows in a (partially) independent way.

[060] The surface processing device 26 comprises an inductive high radio frequency plasma source 200 provided in the top of the room 14, allowing processing through IPECVD-Inductive Plasma Enhanced Chemical Vapor Deposition. In Fig. 7 a diagram is shown of the plasma source 200.

[061] The inductive plasma source 200 is, for example, a marketed source, such as the models RS-DPR COPRA RING Source manufactured by the German firm CCR GmbH.

[062] The inductive plasma source is, for example, the same as that described in the patent application US20030091482 A1 of the inventors Manfred Weiler and Roland Dahl, to which reference should be made and which is intended as incorporated in the present description. [063] The source 200 provides, for example, for an induction primary circuit Cl, provided with an induction coil, operatively connected with a high radio frequency generator 203 (the generator being, for example, a 5000 W solid state generator, with radio frequency of 13.56 MHz, provided with an LCD indicating the supplied power and the transmitted and reflected power), and inductively coupled to an induced secondary circuit C2 provided with a respective induced coil 202. The secondary circuit C2 has the starting electrode 204 for starting the plasma generation discharge. [064] The plasma source 200 comprises an automatic impedance matching network 203 A. In combination with the circuits Cl and C2 it comprises, for example, two capacitors in series, so as to have variable electrical capacity. In this way, it is possible to control the generated input and output power, without the risk of damaging the radio-frequency generator due to reflected current surges. This automatic impedance matching network 203A is, for example, as one of those described in the patent application US 20050001490 A1 of the inventors Weiler Manfred and Roland Dahl, to which reference should be made and which is intended as incorporated in the present description. This automatic impedance matching network 203 A may operate manually or automatically.

[065] From a structural viewpoint, the source 200 provides for an open dome 201 facing the room 14, on the flanks of which the induced coil 202 is provided. [066] The vacuum closed electrode 204 is adapted to surround the center of the dome 201 (for example the central axis, or a central area thereof), and to start the plasma generation discharge, being operatively connected to the induced coil. The electrode 204 is, for example, the same as the electrode (or set of electrodes) disclosed in the above mentioned patent application US 20030091482 Al. The electrode is shaped, for example, like an open ring.

[067] For entering the dome 201 two inlets are provided, a first inlet 205 for a reactive gas and a second inlet 206 for a mixture of precursor gas and carrier gas. [068] The second inlet 206 for the mixture of precursor gas and carrier gas entering the dome comprises a tube 206A, which extends with an approximately ring shape and along whose surface calibrated holes 206B are provided, forming the nozzles for the exit of the precursor gas-carrier gas mixture; the tube 206A surrounds, for example, the center of the dome. The tube may be, for example, a closed ring, where the beginning and the end of the tube match, or an open ring, where an end of the tube is closed. [069] The machine 10 further comprises a supply device 207 for supplying the plasma source with the mixture of precursor gas and carrier gas.

[070] The supply device 207 includes an advantageous first tank 208 adapted to contain the precursor liquid, for example trimethylaluminum (TMA), and a second tank 209 adapted to contain the carrier gas, for example an inert gas such as argon. [071] In this example, a further first tank 208A is provided, adapted t contain a second precursor liquid used in the machine, for example hexamethyldisiloxane (HDMSO). [072] In a further embodiment, a further first tank is provided (not shown in the figures), adapted to contain a third precursor liquid, for example titanium isopropoxide (TTIP).

[073] In other embodiments only one tank is provided, or two first tanks, or three first tanks, with the desired combinations of the precursor liquids cited above.

[074] Adequately, the supply device 207 comprises a mass flow meter 210 for measuring the mass flow rate of the precursor liquid exiting from the first tank 208 (or 208A).

[075] The supply device 207 further comprises a device 211 for mixing and expanding the precursor liquid, coming from the mass flow meter 210, and the carrier gas, coming from the second tank 209.

[076] More in particular, the mixing and expanding device 211 comprises a mixing chamber 211 A, an inlet 21 IB for atomizing the liquid in the mixing chamber, thus creating an aerosol, a second inlet 211 C for the carrier gas entering the mixing chamber 211 A, a valve 21 ID for controlling the pressure inside the mixing chamber, an outlet 21 IE for the mixture exiting the mixing and expanding device 211.

[077] In the mixing and expanding device 211 a heat exchanger 21 IF is also provided, arranged between the mixing chamber 211 A and the outlet 21 IE of the device 211, allowing to increase the temperature of the mixture to make the liquid part thereof completely evaporate.

[078] A supply duct 212 supplies the expanded mixture from the mixing and expanding device 211 to the second inlet 206 into the dome 201.

[079] A third tank 213 is obviously provided, adapted to contain the reactive gas. The third tank is adapted, for instance, to contain oxygen (O2), so that inside the dome, during plasma formation, in combination with the precursor trimethylaluminum (TMA) deposition material is produced formed by aluminum oxide (AI2O3), whilst in combination with the precursor hexamethyldisiloxane (HDMSO), deposition material is produced formed by silica oxide (SiOx), and, in combination with the precursor titanium isopropoxide (TTIP), deposition material is produced formed by titanium dioxide (TiCk).

[080] A duct 214 connects the third tank 213 to the first inlet 205 into the dome 201

[081] The dome 201 is provided on the top 14A of the intermediate room 14. Under the dome, on the bottom of the room 14, an operational area 220 is provided for arranging the support-slab L. The dome is directed towards the operational area, so that the plasma processing is directed towards the slab. When the support-slab L passes through the room 14, at least during processing, it is preferably grounded.

[082] A plan moving device 19, i.e. a device for moving longitudinally, i.e. from the right to the left and in reverse, for example for moving horizontally (where movements according to a more or less inclined direction are even possible), is realized for example through a chain conveyor (defined by two lateral chains spaced from each other) arranged in the machine 10 and extends according to a rectilinear direction from the first opening 15 to the second opening 16 and vice versa, passing through the passages 18 of the intermediate room 14, i.e. crossing this room. It should be noted that the plan moving device 19 practically defines a moving plane 19A for the support- slab L, aligned with, i.e. crossing, the openings 15 and 16 and the passages 18.

[083] In each chamber 12, 13 a respective moving device 20 is provided for moving, from the bottom upwards and in reverse, i.e. in this example in substantially vertical direction, the supports-slabs L entering the respective chamber, in order to accumulate the supports-slabs L on levels arranged over one another.

[084] For example, each vertical moving device 20 comprises a rack defining a plurality of resting levels arranged over one another, where the supports-slabs L can rest. Through one or more translation actuators 22 the rack translates vertically, lifting in succession the supports-slabs L following one another in the respective chamber, resting on the conveyor belt 19.

[085] In particular, the rack comprises two side support flanks, each of which defines rests 23 for the supports-slabs L, that are vertically spaced. More in particular, each flank is formed by two horizontally spaced uprights 24, along which the rests 23 project.

[086] In plan view, the uprights 24 are outside the conveyor belt 19, so that the rests 23 do not interfere with the conveyor belt 19 (see Figs. 3 and 4). Furthermore, the supports-slabs L are wider than the conveyor belt 19, thus allowing the rests 23 abutting below the side edges of the same supports-slabs L. [087] The translation actuators 22 can be for example four worm actuators, the movable sliders of which are integral with the respective uprights 24.

[088] The worms of the actuators are connected to a gear motor actuation system 25 provided with pinions and wheels with threaded bar. [089] From an operational viewpoint, the slabs L, borne by the support LI, enter one by one the first sealed chamber 12 through the first opening 15, with the aid of the conveyor belt 19. When the first slab L’ enters the first chamber 12, it stops in correspondence of the rack of the vertical moving device 20. The moving device 20 has the uprights 24 completely lowered, so that the first rests 23’ of the uprights 24, i.e. the ones arranged at the top, are at the same level as the support-slab moving plane 19A, i.e. below the supports-slabs L (Fig. 4a).

[090] The vertical moving device 20 is actuated and the uprights 24 are lifted, to bring the second subsequent rests 23 ”, that are at a lower level relative to the first rests 23’, up to the support-slab moving plane 19A. Obviously, the first slab L’ is lifted with respect to this moving plane by a distance greater than the thickness of the set support- slab L (Fig. 4b).

[091] Analogously to what above, a second slab L” enters the first chamber 12 and stops in correspondence of the rack of the vertical moving device 20 (i.e. below the first slab L’, which is above the second slab). The moving device 20 is actuated and the second slab L’ ’ (i.e. the set support-slab), supported by the subsequent second rests 23”, is translated upwards. Analogously, also the first slab L’ is translated upwards. Subsequent third rests 23” of the uprights 24 are at the same level as the support-slab moving plane, so as to receive a new support-slab (Fig. 4d). [092] This procedure goes on based on how many levels or overlapping positions

N have been provided for the machine. In the case illustrated in the figures, three levels are provided, arranged over one another, defined by three sets of rests 23.

[093] The last slab L^IV inserted into the first chamber 12 remains on the conveyor belt 19 (Fig. 3). The sealing doors 17 are closed and the pressure inside the machine (i.e. the pressure in the common ambient formed by the first chamber 12, the second chamber 13 and the room 14, all directly connected together through the passages 18) is reduced, through the pressure reducing device 30, up to the desired depressurization value.

[094] The last slab L^IV passes through the room 14. It should be noted that the length of the processing room 14, i.e. the dimension corresponding to the moving direction of the slabs in the machine, is lower than the dimensions of the single sealed chambers. [095] When the slab L^IV passes in the room 14, the surface processing device 26 is actuated and the surface finishing material is thus deposited on the slab through plasma deposition. [096] The plasma deposition processing can provide for more coats, i.e. when the slab L^IV arrives in the second chamber 13 the movement of the conveyor belt 19 is reversed and the slab is brought again in the first chamber for a further finishing. When the slab L^IV has been processed again, the movement of the conveyor belt 19 is reversed again and the slab returns in the second chamber 13 (if necessary, a third finishing can be also applied). This forwards/backwards movement is performed based on the specific needs.

[097] Once the slabs have returned in the first chamber, the closed spaced formed by the two chambers and the processing room is depressurized up to a pressure of preferably 6 x 10³ mbar and 1.1 x 10²mbar.

[098] If the processing provides for the deposition of a thin layer of aluminum oxide (AI2O3) on a slab L, this latter is made pass through the processing room 14. A gaseous mixture of precursor material and carrier gas, of the desired stoichiometric composition, in this case trimethylaluminum (TMA) and argon, is supplied to the dome. The dome is contemporaneously supplied with a reactive gas, for example oxygen (O2). The high frequency generator generates an electromagnetic wave to realize an inductive plasma of the mixture, thus producing vapors of the deposition material, in this case aluminum oxide (AI2O3). This operation continues until the slab has completely passed through the processing room. [099] More in particular, the plasma deposition process provides for supplying the mass flow meter with the precursor liquid, accurately measuring the mass flow rate of the precursor liquid, and supplying the mixing and expanding device with the desired measured mass flow rate of precursor liquid.

[100] At the same time, the mixing and expanding device is supplied with the carrier gas, so that the precursor liquid and the carrier gas form a gaseous mixture that, thanks to the mass flow meter, has the right amount of precursor (starting from a liquid) necessary for the reaction in the dome for forming the deposition material.

[101] More in particular, in the mixing and expanding device the precursor liquid is atomized inside a pressure-controlled mixing chamber, to form an aerosol: in the same chamber the carrier gas is inserted. The precursor/carrier gas mixture exits from the mixing chamber and is heated through a heat exchanger, so that the liquid part thereof evaporates substantially completely. Then, the completely gaseous mixture is supplied to the inlet into the dome. [102] Almost at the same time the reactive gas is supplied to the inlet into the dome, so that in the dome there are the reactive gas and the mixture with the precursor.

[103] Then, through the high frequency generator, the induced coil, the impedance matching network, and the open-ring electrode, an electromagnetic wave is generated to realize the discharge generating the inductive plasma of the mixture.

[104] The plasma allows the mixture components to react so as to have vapors of the coating material that are deposited downwards, towards the operational area, where the slab is arranged.

[105] It is now necessary to wait the time necessary for the deposition of the material formed by the inductive plasma, this time depending on the deposition material, the thickness of the material to be deposited on the slab, the type of slab, etc.

[106] When the plasma deposition processing of the slab L^IV is finished, the slab is stopped in the second chamber 13 (the slab L^IV is indicated by a broken line in Fig. 2), where the respective vertical moving device 20 lifts the slab L^IV up to the next level. [107] In the first chamber 12, the slab L’ ” is lowered by one level up to the moving plane. From here, the slab L’” moves and is processed in the same manner as the slab L^IV up to the second chamber 13, where it is lifted by one level through the respective moving device.

[108] It is therefore clearly apparent that the maximum number of slabs that can be processed in the machine is equal to N+l for each closing of the doors.

[109] Once all the slabs have been processed and brought to the second chamber 13, the doors are opened and the slabs exit one by one from the second opening, with reversed sequence with respect to the sequence of insertion into the first chamber; it is therefore clearly apparent that the machine operates according to a FIFO (first in - first out) logic.

[110] It should be noted that, as shown in Fig. 5, the invention also provides for a machine where the length, i.e. the dimension corresponding to the moving direction of the slabs in the machine, of the processing room, indicated with the reference number 314 in the figure in question, is similar to that of the sealed chambers; anyway, it is equal to, or greater than, the dimensions of the single slabs under processing, i.e. of the single sets support-slab. Differently than in the previous case, in this embodiment the supports-slabs enter the processing room 314 from the first chamber 12, remain in the processing room for the time necessary for the plasma deposition processing, and move to the second chamber only when the plasma deposition processing has been carried out. In practice, differently than in the previous case, the slab is processed while remaining still in the processing room, instead of moving through the processing room.

[111] In Fig. 6 the case is shown where only one chamber is provided, matching with the processing room. In this case, the only chamber 412 comprises an entrance first opening 415 for a support-slab L, and an exit second opening 416 for a support- slab L. Analogously to what described above, the machine comprises a plan moving device 419, analogous to the moving device 19. Obviously, also a pressure adjusting device 430 and the processing device 426 for surface processing through plasma deposition are also provided, as well as, in general, all the components necessary for plasma deposition, as described above for the processing room 14. In this configuration, the supports-slabs enter the chamber 412 one by one, and therefore the cycle of door closing-opening, during which depressurization and processing are performed, is carried out for one slab at a time.

[112] It is understood that what is illustrated purely represents possible non-limiting embodiments of the invention, which may vary in forms and arrangements without departing from the scope of the concept on which the invention is based. Any reference numerals in the appended claims are provided for the sole purpose of facilitating the reading thereof in the light of the description above and the accompanying drawings and do not in any way limit the scope of protection.

Claims

1. A machine for the surface processing of products through deposition of thin layers of coating materials, comprising a closed gastight space, provided with at least one opening, that can be closed, for inserting and removing the products to be processed, a device for reducing the pressure inside said closed space up to a value lower than the ambient pressure, a surface processing device comprising an inductive high radio frequency plasma source provided in said closed space and operatively connected to a high radio frequency generator, said source comprising o an open dome facing said at least one closed space, o a vacuum confined electrode adapted to surround the center of said dome and to start the plasma generation discharge, and operatively connected to said radio frequency generator, o at least one inlet for a reactive gas entering said dome, o at least one inlet for a mixture of precursor gas and carrier gas, a supply device for supplying said plasma source with said mixture of precursor gas and carrier gas, comprising o at least one first tank adapted to contain liquid for at least one precursor liquid, o a mass flow-meter for measuring the mass flow rate of the precursor liquid exiting from said at least one first tank, o at least one second tank for a carrier gas, o a device for mixing and expanding the precursor liquid coming from said mass flow meter and said carrier gas coming from said at least one second tank, o a supply duct for supplying said expanded mixture from said mixing and expansion device to said at least one inlet for a mixture of precursor gas and carrier gas into said dome.

2. The machine of claim 1, comprising an operational area for arranging the product to be processed, said dome being arranged above, and directed towards, said operational area.

3. The machine of claim 1 or 2, wherein said plasma source comprises an impedance matching network, preferably of the automatic type.

4. The machine of one or more of the previous claims, wherein said at least one inlet for a mixture of precursor gas and carrier gas into said dome comprises a tube, which extends with an approximately ring shape and along whose surface calibrated holes are provided, forming the nozzles for the exit of the precursor gas-carrier gas mixture; said tube preferably surrounding the center of said dome.

5. The machine of one or more of the previous claims, wherein said device for mixing and expanding the precursor liquid coming from said mass flow meter and said carrier gas coming from said at least one second tank comprises a mixing chamber, an inlet for atomizing the liquid thus creating an aerosol, a second inlet for the carrier gas entering said mixing chamber, a valve for controlling the pressure inside said mixing chamber, an outlet for the mixture exiting from said device, a heat exchanger provided between said mixing chamber and said outlet and adapted to increase the temperature of said mixture to make the liquid part completely evaporate.

6. The machine of one or more of the previous claims, comprising at least one tank for a reactive gas; said tank preferably comprising oxygen (O2).

7. The machine of one or more of the previous claims, wherein said at least one precursor liquid first tank is adapted to contain trimethylaluminum (TMA) or hexamethyldisiloxane (HDMSO), or titanium isopropoxide (TTIP), so that, in combination with the reactive gas oxygen (O2) inside said dome during plasma formation, a deposition material is produced comprised of aluminum oxide (AI2O3) or of silica oxide (SiOx), or of titanium dioxide (T1O2); two first tanks being preferably provided, one of them adapted to contained trimethylaluminum (TMA) and the other one adapted to contain hexamethyldisiloxane (HDMSO), or one of them adapted to contain trimethylaluminum (TMA) and the other one adapted to contain hexamethyldisiloxane (HDMSO) or titanium isopropoxide (TTIP), or one of them adapted to contain hexamethyldisiloxane (HDMSO) and the other one adapted to contain trimethylaluminum (TMA) or titanium isopropoxide (TTIP); or three tanks are provided, adapted to contain trimethylaluminum (TMA), titanium isopropoxide (TTIP), hexamethyldisiloxane (HDMSO) respectively.

8. The machine of one or more of the previous claims, wherein said at least one carrier gas second tank is adapted to contain inert gas, for example argon.

9. The machine of one or more of the previous claims, wherein said closed space comprises at least one accumulation chamber, separate from the processing area, where products are accumulated; from an operational viewpoint, once all products to be processed have been inserted into said at least one chamber, said chamber is closed and the pressure inside is reduced up to an operational processing pressure, then said products are processed, and lastly said at least one chamber is opened and the products are taken therefrom.

10. The machine of claim 9 comprising in said at least one chamber, a moving device for moving said products from the bottom upwards and in reverse, so as to accumulate at least two said products on levels put over one another, a plan moving device for moving said products from and towards said at least one opening when the products are arranged at the same level of said at least one opening, wherein, from an operational viewpoint, a plurality of said products are inserted into said at least one chamber, and at least two products of said plurality of products are over one another for a span of processing, and wherein, once all the products to be processed have been inserted into said at least one chamber, said chamber is closed and the pressure inside is decreased up to an operational processing pressure, and then said at least one chamber is opened again and the products are removed therefrom.

11. The processing machine of claim 10, wherein said closed space comprises a processing room adjacent to said at least one accumulation chamber; said products being moved from said at least one accumulation chamber to said processing room in order to be processed.

12. The processing machine of claim 9 or 10, wherein said closed space comprises at least two said accumulation chambers connected to each other, each chamber being adapted to receive a plurality of said products put over one another.

13. The processing machine of claim 11, wherein said surface processing device for processing a product is arranged between said two chambers.

14. The processing machine of claim 12, wherein between said two chambers a processing room is provided, where said surface processing device is arranged, and where said operational area for arranging the product is provided, so that the products are adapted to move from a chamber to the following one passing through said room, where the processing is carried out.

15. The machine of claim 11 or 14, wherein said room has dimensions adapted to receive the whole product to be processed; said product being preferably adapted to be moved from a said first chamber to said room, where it is arranged stationary so as to carry out the deposition processing.

16. The processing machine of claim 14 or 15, wherein said plan moving device is adapted to allow the products to pass from a chamber to the following one under the processing device.

17. The processing machine of claim 16, wherein said plan moving device is adapted to allow the products to pass from a chamber to the following one under the processing device during the processing step; said room having preferably smaller dimensions than the dimensions of the products so that the deposition processing is carried out on the portion of the product inside said room while the product is moving.

18. The processing machine of one or more of claims 10 to 17, wherein said plan moving device is common to said chambers; preferably said plan moving device is a conveyor belt crossing said chambers from an entrance first opening of the machine up to an exit second opening of the machine, passing under the processing device.

19. The processing machine of one or more of claims 12 to 18, comprising a first opening for the products entering the closed space, defined in a first said chamber, and a second opening for the products exiting the closed space, defined in a second said chamber, respective sealing doors being provided associated with said openings.

20. The processing machine of one or more of claims 10 to 19, wherein in each chamber a said moving device is provided for moving said products from the bottom upwards so as to accumulate at least two said products over one another.

21. The processing machine of one or more of claims 10 to 20, wherein in said at least two chambers there is defined a moving plane for moving said products from the entrance to the exit of said closed space, crossing said chambers passing under said processing device, wherein each bottom-upwards moving device defines N positions raised from said moving plane, and wherein the maximal number of products that can be processed in the machine is N+l .

22. The processing machine of one or more of claims 10 to 21, wherein each product is borne by a respective support, so that said products enter and exit said closed space on said supports, and wherein said bottom-upwards moving device and said plan moving device are adapted to move said products by directly moving said supports.

23. The processing machine of one or more of the previous claims, wherein each product is a form of slab, preferably made of stone, glass, wood, ceramic or metal.

24. A method for thin layer plasma deposition, comprising the following steps:

- arranged a product, with a surface to be coated with a thin layer, inside a vacuum processing room, with pressure preferably comprised between 6 x 10³ mbar and 1.1 x 10² mbar, wherein in said processing room a surface processing device is provided, comprising a high radio frequency inductive plasma source arranged in said closed space, and wherein said source comprises an open dome facing said at least one closed space, with which a high frequency inductive coil is associated, operatively connected to a high radio frequency generator, a vacuum confined electrode adapted to surround the center of said dome and to start the plasma generation discharge, and operatively connected to said inductive coil, at least one inlet for a reactive gas entering said dome, at least one inlet for a mixture of precursor gas and carrier gas, supplying a mass flow meter with a precursor liquid, measuring the mass flow rate of the precursor liquid, supplying a mixing and expanding device with the desired mass flow rate of the precursor liquid supplying said mixing and expanding device with a carrier gas, so that said precursor liquid and said carrier gas form a gaseous mixture, supplying said at least one inlet for a mixture of precursor gas and carrier gas with said gaseous mixture, supplying said at least one inlet for a reactive gas entering said dome with a reactive gas, generating, through said high frequency generator, an electromagnetic wave to obtain an inductive plasma of said mixture, waiting the time for the material formed from the inductive plasma to deposit.

25. The method of claim 24, wherein in said mixing and expanding device, said precursor liquid is atomized inside a pressure-controlled mixing chamber, to form an aerosol, said carrier gas is inserted into said mixing chamber, exiting the precursor/carrier gas mixture from said mixing chamber, heating said mixture so that the liquid part thereof completely evaporates, exiting the gaseous mixture of precursor gas/carrier gas from said mixing and expanding device.

26. The method of claim 24 or 25, wherein said reactive gas comprises oxygen (02).

27. The method of claim 24, 25 or 26, wherein said precursor liquid is trimethylaluminum (TMA) or hexamethyldisiloxane (HDMSO), so that, in combination with the reactive gas oxygen (O2) inside said dome during plasma formation, a deposition material is produced comprised of aluminum oxide (AI2O3) or of silica oxide (SiOx).

28. The method of claim 24, 25, 26 or 27, wherein said carrier gas comprises inert gas, preferably argon.

29. The method of one or more of the previous claims, comprising the step of arranging a plurality of products to be subjected to plasma surface processing inside a closed space, make said closed space vacuum and move said products, one by one, towards said processing room provided in said closed space to carry out, for one product at a time, the steps a)-h); once these steps have been carried out, the product is exited from the processing room and a subsequent product is inserted thereinto.

30. The method of claim 29, wherein said products are moved towards said processing room from a first chamber to make the plasma deposition; after the steps a)-h), each product being housed in a second chamber of said closed space, different than said first chamber.