Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/14—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by electrical means
  • B05D3/141—Plasma treatment
  • B05D3/142—Pretreatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
  • B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/06—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to radiation
  • B05D3/061—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to radiation using U.V.
  • B05D3/062—Pretreatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2252/00—Sheets
  • B05D2252/02—Sheets of indefinite length

Definitions

• the invention relates to the deposition of thin layers on a substrate for the "functionalization" of the surface of the substrate by conferring physicochemical properties appropriate for a given use.
• the invention relates more particularly to obtaining thin polymeric layers from polymerizable precursor droplets whose size and electrical charge are controlled so as to achieve a homogeneous electrostatic deposition and having a high retention rate of the functionality and / or of the structure brought by the precursor.
• the plasma processes are for their part in so-called “dry” way using no solvents and whose activation steps are fast compared to conventional processes in "wet” way.
• the plasma processes have the disadvantage of a low specificity of functional grafting, especially when the deposits are made at atmospheric pressure.
• the grafting is effectively limited by a limited choice of gases (air, N 2 , He for example) which makes selective grafting of functions impossible.
• the atmospheric pressure deposition techniques also have inhomogeneity problems, related to the presence of filamentary discharges (streamers according to the English terminology) in the electric discharge that is operated to generate the plasma. Research is currently focused on the establishment of atmospheric pressure luminescent discharges, but many technical problems persist. In particular, problems of relatively slow inhomogeneity and deposition rate (of the order of a few tens of nm / min) can be mentioned.
• the plasmas processes generate a fairly strong decomposition of the precursor, which has the consequence of limiting the retention rate of the reactive function and of causing poor surface homofunctionality of the substrate.
• it is thus possible to observe, in addition to desired COOH functions, the presence of OH, C O, C-O-R type functions.
• one of the solutions envisaged consists of sweeping the deposition reactor with an inert gas which limits the oxygen partial pressure and consequently the formation of ionization fronts.
• the flow of inert gas is relatively important and contributes to increasing the cost of such a solution.
• the distances between electrodes of the order of a few millimeters, prevent 3D object processing.
• the object of the invention is to meet this need, and proposes for this purpose, and according to a first aspect, a method of depositing a thin polymeric layer on a substrate for the functionalization of the surface of the substrate, comprising a step of electrohydrodynamically spraying a polymerizable precursor towards the substrate so as to electrostatically deposit electrically charged droplets of said precursor and form the thin layer on the surface of the substrate by polymerization of the droplets, the method being characterized in that it further comprises a step for causing excited species to interact with the droplets of the pulverized precursor, thus favoring the polymerization reactions of said precursor.
• the spraying step is carried out in air, at atmospheric pressure;
• the plasma is generated in the air, at atmospheric pressure;
• the electric discharge can be a continuous or alternative discharge; the process can be adapted to the deposition of a thin polymer layer on a moving film substrate;
• the spraying and activation zones may be located sufficiently close to the species excited by the sputtering zone; electric discharge may interact with the droplets of the powdered precursor;
• the excited species can also be driven from the activation zone to the spray zone, so that at least a portion of excited species can interact with the droplets of the sprayed precursor; the entrainment of the excited species towards the spray zone can be carried out by subjecting said species to a gas flow;
• the activation zone may be located upstream, in the direction of travel of the film substrate, of the spray zone, so that the spray is carried out on a portion of the film substrate whose surface has been previously activated;
• the method may further comprise a finishing step of cross-linking the thin polymeric layer deposited on the substrate.
• the invention also relates, according to a second aspect, to a device for the deposition of a thin polymeric layer on a substrate for the functionalization of the surface of the substrate comprising means adapted to perform an electrohydrodynamic spraying of a polymerizable precursor towards the substrate. substrate, so as to electrostatically deposit electrically charged droplets of said precursor and form the polymer thin film on the surface of the substrate, characterized in that it further comprises means for forming excited species and in that said means Spraying and forming co-operate in such a way that at least a portion of the excited species interacts with the droplets of the pulverized precursor, thereby promoting the polymerization reactions of said precursor.
• the means for forming excited species are means for activating the substrate surface adapted to subject said substrate to a plasma generated under the action of an electric discharge, a portion at least of the gaseous species excited by the discharge electric interacting with the droplets of the precursor;
• the means for forming excited species comprise a UV lamp emitting photons, said photons then interacting with the droplets of the precursor;
• the spraying means and the forming means are adapted to operate in air and at atmospheric pressure;
• the device can be adapted to the deposition of a thin film on a moving film substrate on a transport mechanism, the droplets being sprayed in a spray zone, and the activation means are arranged to activate the surface of the film.
• substrate at an activation zone located sufficiently close to the sputtering zone for the species excited by the electric discharge to interact with the droplets of the pulverized precursor;
• the device may also comprise means, for example means for generating and directing a gaseous flow, making it possible to drive at least a portion of the species excited by the plasma from the activation zone towards the spray zone;
• the activation means may be arranged upstream in the direction of travel relative to the spraying means;
• the spraying means may comprise means making it possible to collect a discharge current in the gas surrounding the polarized liquid.
• the invention proposes to perform the deposition of a thin polymer layer on a substrate for the functionalization of the surface of the substrate, the thin layer being obtained by polymerization on said surface of a polymerizable precursor.
• the invention In order to deposit a thin layer on a substrate, the invention generally proposes to spray a polymerizable precursor on the substrate.
• the precursor may be organic, for example an unsaturated organic precursor.
• the invention also advantageously makes it possible to pulverize an organic precursor that is generally difficult to polymerize by the known methods of the saturated organic precursor type (such as an organo-silica for example).
• the precursor may also be inorganic. Electrically charged droplets of the precursor are more precisely pulverized to effect electrostatic deposition and polymerize a polymeric thin layer on the substrate.
• the invention is more specifically based on the spraying, in the form of charged droplets, of a polymerizable precursor by electrohydrodynamic spraying (HDPE) type spraying means.
• HDPE electrohydrodynamic spraying
• HDPE spraying makes it possible to produce a nebulizer of electrically charged liquid droplets.
• HDPE essentially consists of applying an electric field to a liquid so as to induce on the surface of this liquid electric charges of the same polarity as the voltage applied thereto. These charges, accelerated by the electric field, cause a transformation of the liquid drop into a cone. At the apex of this cone, a jet of liquid is produced which breaks up into droplets (nebulisate or spray).
• electrohydrodynamic spraying device here means a device known per se for generating a nebulized liquid polarized, that is to say a nebulized liquid sprayed into electrically charged droplets.
• a device comprises liquid supply and distribution means, and means for electrically biasing the surface of this liquid.
• the liquid distribution means are provided by a conduit to an outlet (essentially consisting of a spray nozzle) from which the polarized liquid forms a conical meniscus, at the apex of which a jet then a dispersion of electrically charged liquid droplets .
• An HDPE device can be found for example in WO 99/49981.
• the device for for determining the device for determining the device for
• HDPE may further comprise means allowing, during the spraying of the liquid, to collect a discharge current in the gas surrounding the polarized liquid, such as in particular a conductive material having an opening of shape and dimensions allowing the passage of the liquid sprayed (no droplet collection) while ensuring the required electric field conditions on the surface of the liquid to allow spraying.
• Such means are for example constituted by a counter-electrode, or conductive material connected to ground or polarized, placed at a distance d
• Such means may in particular have an annular shape, as represented under reference 6 in FIG.
• Such means are particularly suitable to ensure that the field on the surface of the liquid in the spray zone remains independent of the charge densities under the ring.
• the droplet production conditions can thus be kept constant in the spray zone. It is then possible to obtain a better spread of the sprayed droplets, and therefore a more homogeneous deposition, and this whatever the surface potential of the substrate.
• such means can be constituted by a plate connected to ground and having a plurality of holes, each hole acting as a ring associated with a particular nozzle.
• the liquid may be a conventional solvent such as water, ethanol or acetone in which a polymerizable precursor is dissolved, in particular a polymerizable organic precursor.
• the flow rate of the liquid and its conductivity, the voltage applied to the liquid, as well as the geometry of the spray nozzle, constitute the parameters regulating device for controlling the size (from 0.5 to 200 ⁇ m) and the charge (of 10 "3 at 1 C / kg, positive or negative) of the droplets, as well as their mode of spraying (in particular mono-cone mode). jet "or multi" jet cone ").
• HDPE high density polyethylene
• This flexibility also makes it possible (in particular by regulating the size of the droplets) to control the conditions of evaporation of the droplets and consequently their kinetics of polymerization, as well as the thickness
• HDPE high density polyethylene
• HDPE makes it possible to avoid the processes of fragmentation of the precursor generally observed when the plasma processes are used (for which the precursor is degraded by the electrons and the short-lived species excited by the plasma, which leads to a low retention rate of the active function).
• electrohydrodynamic spray precursor droplets thus brings about an improvement in the polymerization performance, by associating a high retention rate with a very large deposition / substrate adhesion, which makes it possible to envisage a large number of applications, for example in the biotechnology sector.
• HDPE requires only limited consumption of solvent (and therefore non-polluting), and can be implemented at low energy costs (typically less than 1 Watt / cm 2 ) and maintenance compared to installations. plasma.
• the invention thus makes it possible to deposit reactive functions, such as the carboxylic, alcohol or primary amine functional groups, in order to perform a selective functional grafting on the substrate.
• the invention also makes it possible, for example, to produce ammonium deposits (in particular for bactericidal applications), fluorinated deposits (especially for membrane filtration applications), or even TiO 2 or SiO 2 type deposits from compounds. organo-silicas.
• the substrate is a film 1 traveling in the direction indicated by the arrow S 0 on a transport mechanism (not shown).
• the device for depositing a functionalized thin film on the moving film substrate comprises an HDPE device comprising one or more spray nozzles 2 positioned in such a way that the droplets are deposited on the moving film substrate 1.
• HDPE effectively makes it possible to carry out deposits at a high speed so that the functionalization can be carried out on a film moving at a high rate, for example at a speed of the order of a few hundred m / min, especially when several spray nozzles are simultaneously used.
• HDPE makes it possible to produce thin film deposition not only on 2D substrates, but also on 3D objects, while having a high retention rate, without any homogeneity in thickness.
• the method according to the invention further comprises a step for causing excited species to interact with the droplets of the pulverized precursor, so as to promote the sputtering reactions of said precursor.
• the method comprises a step of activating the surface of the substrate made by subjecting the substrate to a plasma generated under the action of an electric discharge, said steps of activation and spraying being carried out simultaneously so that at least a portion of the gaseous species excited by the electric discharge come into interaction with the precursor droplets.
• the excited species is just formed using a UV lamp, the photons emitted by the lamp thus playing the role of excited species interacting with one another. with the droplets of the precursor.
• the activation step can be carried out using means for activating the surface of the substrate generating a cold plasma under the action of an electric discharge.
• the electric shock can be a continuous (DC), alternative (AC) or pulsed discharge.
• the discharge preferably used is a discharge that can be carried out in ambient air, at atmospheric pressure, such as, for example, the alternating discharge known under the name of Dielectric Barrier Discharge (DBD).
• DBD Dielectric Barrier Discharge
• the DBD is obtained, for example, by applying a high voltage pulse across two electrodes, one of which is covered with a dielectric material that prevents the passage of the arc.
• Multiple plasma filaments can thus be obtained in air, at atmospheric pressure, for a series of discharges created between the two electrodes.
• the electric discharge makes it possible to generate excited species
• This activation makes it possible to create radical sites, capable of allowing the formation of covalent bonds at the deposition / substrate interface and the spreading of the deposit on the surface of the substrate. This activation also makes it possible to carry out prior cleaning of the generally contaminated substrates and to guarantee a good deposition / substrate adhesion.
• the activation in the air of the surface of the substrate makes it possible to graft polar functions onto the substrate, thus improving the wettability properties of the latter.
• the flux of the excited species also makes it possible to contribute to the crosslinking of the thin film deposited, and thus to its washing stability (which makes it possible in particular to produce insoluble deposits in water).
• the activation step is generally performed in such a way that the area of the substrate on which the droplets are sprayed has been previously activated. Note, however, that it is also possible to activate an area of the substrate after it has "undergone” spraying.
• FIG. 1 One can thus consider the case, represented in FIG. 1, where the activation step and the sputtering step are carried out simultaneously, for example when it is a question of making the deposition of a thin layer on a moving film substrate 1.
• the activation means 3 are then arranged upstream of the HDPE device 2 in the direction of travel indicated by the arrow SD, so that the portion of the film on which the sprayed droplets are deposited has already been activated beforehand.
• the activation means 3 and the HDPE device 2 are preferably separated from each other by a minimum distance of the order of the inter-electrode distance (typically about 10 cm) for protecting the HDPE device from the electrical influences of the activation means by electric discharge.
• the device according to the invention when the activation and sputtering steps are carried out simultaneously as mentioned above, also comprises means 4 enabling the excited species to interact with each other.
• Activation zone Z A is understood to mean the interelectrode zone of the activation means 3 in which the electric discharge takes place with a view to plasma activation.
• Spray zone Z P is understood to mean the zone in which the sprayed droplets are in suspension but also deposited on the substrate.
• a device may for this purpose include means 4 for generating and directing a gas flow 5 (for example a flow of N 2 , Ar or He) so as to cause at least one portion of excited species from the Z A plasma activation zone to the Z P spray zone in which the droplets are sprayed.
• a gas flow 5 for example a flow of N 2 , Ar or He
• a device can also be configured in such a way that the activation means are arranged sufficiently close to the spraying means for at least a portion of the excited species to be able to interact with the sprayed droplets in the sputtering zone, and this without any particular means (such as flow-type drive means gaseous) is necessary for this interaction to take place.
• the device according to the invention is not limited to a series arrangement of the activation means and the spraying device.
• the skilled person will bring to the embodiments described and represented many variants or modifications.
• the device described can be easily modified by those skilled in the art so that the activation means and the spraying device are arranged in parallel, so that the deposition of a thin polymer layer is operated according to a transverse or longitudinal scanning of the substrate, etc.
• the invention is not limited to excited species of gaseous species type excited by electric discharge but also extends to excited species of the photon type generated by a UV lamp.
• the UV lamp will preferably be arranged in such a way that the photon beam interacts directly with the droplets generated by the HDPE device in the spray zone Z A.
• the UV lamp can for this purpose be placed near the spray nozzle (s) of the PHED device.
• the UV lamp must not modify the electric field lines at the origin of the sputtering, and is therefore typically placed at a distance from the nozzle greater than the nozzle-substrate distance.
• the lamp can be oriented perpendicular to the height of the spray cone for the photons to interact with all the sprayed droplets of precursor.
• a UV lamp can be installed upstream and / or downstream of the spray nozzle.
• the thin layer may be subjected to one or more finishing steps intended for example to crosslink the deposited polymer layer by volume and / or to modify the surface of the thin layer deposited, in particular with a view to of his conditioning
• finishing steps can be carried out by subjecting the substrate to drying, for example under a UV lamp, or to an electric discharge.
• the main advantages of the invention are recalled below.
• the invention makes it possible in the first place to deposit thin functionalized layers on a substrate in air and at atmospheric pressure. In particular, it is therefore not necessary to use a pumping system to achieve the low pressures required for low pressure plasma deposition.
• the reactive function also has a high retention rate, ensuring a high density of grafted functions, essential for certain applications, particularly in the biotechnology sector.
• the invention can be implemented with a large choice of organic precursors, which makes it possible to envisage an extension of the application field of functionalized thin layers.
• the interaction of excited species and sprayed droplets makes it possible to envisage the polymerization of saturated precursors of the organosilicone type (for example with a view to applications in the field of packaging by deposition of SiO 2 layer acting as a barrier layer to water and oxygen).
• the deposition rates are further high and compatible with a substrate-film scroll of the order of a few hundred m / min.
• the invention can also be used to make deposits on 3D objects.
• the energy cost is low (less than 1 Watt / cm 2 ) and installation costs (unnecessary pumping system, limited consumption of organic precursor) and maintenance costs (compared to existing storage facilities). plasma for which corrosion is observed due to the oxidizing properties of discharges at atmospheric pressure in the air) are reduced.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Physical Vapour Deposition (AREA)

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• 2004
  • 2004-06-28 FR FR0407084A patent/FR2872068B1/fr not_active Expired - Fee Related
• 2005
  • 2005-06-28 US US11/631,102 patent/US7799389B2/en not_active Expired - Fee Related
  • 2005-06-28 WO PCT/FR2005/001627 patent/WO2006010845A1/fr active Application Filing
  • 2005-06-28 JP JP2007518640A patent/JP2008504442A/ja active Pending
  • 2005-06-28 EP EP05779692A patent/EP1771256A1/de not_active Withdrawn

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