DE102016206009A1 - Process for coating a substrate - Google Patents

Abstract

The invention relates to a method for coating a substrate, wherein a plasma jet (PS) is generated from a working gas (AG), at least one first precursor (P1) being supplied to the working gas (AG) and / or the plasma jet (PS) and in the plasma jet (PS) is reacted, wherein formed in this reaction oxide reaction products are deposited on a surface of the substrate to form an oxide layer matrix, wherein at least a second, amino-functionalized precursor (P2) to the plasma jet (PS) supplied and in the plasma jet (PS) is reacted, wherein resulting in this reaction amino group-containing reaction products are deposited as plasma polymers with the oxidic layer matrix to form a mixed layer.

Description

The invention relates to a method for coating a substrate.

Layers and surfaces suitable for use in a biological environment can be fabricated using plasma-based surface engineering techniques. In recent publications, a major focus of investigations has been in the production of functionalized surfaces with the aid of plasma polymer coatings, which enable the immobilization or absorption of biologically active molecules on the layer.

For this the following publications are known:
KS Siow, L. Britcher, S. Kumar, and HJ Griesser, "Plasma Methods for the Generation of Chemically Reactive Surfaces for Biomolecule Immobilization and Cell Colonization-A Review," Plasma Processes and Polymers, Vol. 3, No. 6-7, pp. 392-418, 2006 ,
D. Merche, N. Vandencasteele and F. Reniers, "Atmospheric plasmas for thin film deposition: A critical review," Thin Solid Films, Vol. 520, Item 13, pp. 4219-4236, 2012 ,
Finke, K. Schröder and A. Ohl, "Plasma Retention and Water Stability of Microwave Plasma Polymerized Films from Allylamines and Acrylic Acids," Plasma Processes and Polymers, Vol. 6, No. S1, pp. S70-S74, 2009 ,
F. Reno, D. D'Angelo, G. Gottardi, M. Rizzi, D. Aragno, G. Piacenza, F. Cartasegna, M. Biasizzo, F. Trotta, and M. Cannas, "Atmospheric Pressure Plasma Surface Modification of Poly (D, L-lactic acid) Increases Fibroblast, Osteoblast and Keratinocyte Adhesion and Proliferation, "Plasma Processes and Polymers, Vol. 9, No. 5, pp. 491-502, 2012 ,
K. Lachmann, MC Rehbein, M. Jänsch, M. Thomas and C.-P. Klages, "Deposition of Thermoresponsive Plasma Polymer Films from N-Isopropylacrylamide Using Dielectric Barrier Discharge at Atmospheric Pressure," Plasma Medicine, Vol. 2, No. 1-3, 2012 ,
H. Aizawa, Y. Gokita, Y. Yoshimi, T. Hatta, SM Reddy, and S. Kurosawa, "Synthesis and characterization of organic thin film using atmospheric-pressure plasma polymerization," Sensors and Materials, Vol. 22, No. 7 , pp. 337-345, 2010 ,
A. Vogelsang, A. Ohl, R. Foest, K. Schröder and K.-D. Weltmann, "Deposition of thin films of amino group containing precursors with an atmospheric pressure microplasma jet," Plasma Processes and Polymers, Vol. 8, No. 1, pp. 77-84, 2011 ,
J.-C. Ruiz, A. St-Georges-Robillard, C. Thérésy, S. Lerouge, and MR Wertheimer, "Fabrication and Characterization of Amine-Rich Organic Thin Films: Focus on Stability," Plasma Processes and Polymers, Vol. 7, No. 9 -10, pp. 737-753, 2010 ,
M. Schnabelrauch, R. Wyrwa, H. Rebl, C. Bergemann, B. Finke, M. Schlosser, U. Walschus, S. Lucke, K.-D. Weltmann and JB Nebe, "Surface-coated polylactide fiber meshes as tissue engineering matrices with enhanced cell integration properties," International Journal of Polymer Science, Vol. 2014, 2014. http://dx.doi.org/10.1155/2014/439784

The invention is based on the object to provide an improved method for coating a substrate.

The object is achieved by a method having the features of claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

In a method according to the invention for coating a substrate, a plasma jet is generated from a working gas, wherein at least one first precursor is supplied to the working gas and / or the plasma jet and reacted in the plasma jet, resulting in this reaction oxide reaction products on a surface of the substrate Formation of an oxide layer matrix are deposited, wherein at least a second, amino-functionalized precursor is supplied to the working gas and / or the plasma jet and reacted in the plasma jet, resulting in this reaction amino-containing reaction products are deposited as plasma polymers with the oxidic layer matrix to form a mixed layer. Thus, interwoven mixed layer system is produced.

The thus deposited layer serves as a chemically reactive base for the immobilization of biologically active molecules, is thus suitable as a biocompatible surface. Optionally, improved cell adhesion can be achieved. The deposition of the amino group-containing plasma polymers in conjunction with an oxidic layer matrix, for example silicon dioxide, surprisingly leads to a separation of pure amino group-containing plasma polymer layers which is significantly more abrasion-resistant and more adhesive than that described in the prior art. The embedding of the amino group-containing plasma polymers in the oxidic layer matrix prevents or reduces the washing out of the amines from the layer in contact with aqueous solutions.

In one embodiment, the first precursor and / or the second precursor to the plasma process via a Y-nozzle or a remote nozzle or a combination nozzle or by means of a Accumulation of the working gas supplied before generating the plasma.

In one embodiment, the first precursor used is hexamethyldisiloxane and / or tetraethoxysilane and / or tetramethylsilane. In this way, silicon oxide results as an oxide layer component. Likewise, a titanium-containing first precursor such as titanium (IV) tetraisopropoxide can be used. In this way, an oxide layer component of titanium oxide results.

In one embodiment, the second precursor used is ethylenediamine and / or allylamine. Allylamine and ethylenediamine as precursors have a sufficiently high vapor pressure to be introduced into the plasma by means of a bubbler. In addition, both substances are cheap and readily available. For allylamine also speaks the double bond in the structure, which theoretically allows a free radical polymerization. Ethylenediamine has a high ratio of primary amines to carbon.

Likewise, other amino compounds such as cyclopropylamine or propargylamine can be used as the second precursor.

In one embodiment, the first precursor and / or the second precursor is / are supplied to the working gas and / or the plasma in dissolved form, as an aerosol, in vapor form or in dispersed form. The precursor is preferably introduced in the gaseous state into the working gas or the plasma stream. Liquid or solid, in particular pulverulent, precursors can also be used, but are preferably converted into the gaseous state or an aerosol-like state before introduction, for example by evaporation and / or atomization. Likewise, the precursor can first be introduced into a carrier gas, entrained therefrom, and introduced together with it into the working gas or the plasma stream.

In one embodiment, the plasma is generated in a free-jet plasma source. In this method, a high-frequency discharge between two concentric electrodes is ignited, which is led out by an applied gas flow, the forming hollow cathode plasma as Plasmajet from the electrode assembly usually several centimeters in the free space and the surface to be coated. The precursor can be introduced both before the excitation in the working gas (direct plasma processing) and then in the already formed plasma or in the vicinity (remote plasma processing). Another possibility of plasma generation is the exploitation of a dielectrically impeded discharge. In this case, serving as a dielectric working gas, in particular air, passed between two electrodes. The plasma discharge takes place between the electrodes, which are supplied with high-frequency high voltage.

In one embodiment, the deposition is performed at atmospheric pressure. Normal pressure plasma processes require considerably less technical effort than low-pressure or vacuum processes, since there is no need to evacuate a reaction chamber. In the plasma flow due to the enrichment of the working gas with the precursor and through plasma-initiated chemical conversion processes, the plasma pressure-chemical vapor deposition (APCVD) initially forms crystallization nuclei and solid nanoparticles, which grow to a thin layer on the substrate surface. The size of the agglomerates forming from such particles and thus essential properties of the coating can be adjusted inter alia by the distance of the plasma source from the surface, by the metering rates of the precursors, by the plasma power introduced and the process gases / gas mixtures used.

In the APCVD, organosilicon compounds, for example hexamethyldisiloxane (HMD-SO) or tetraethoxysilane (TEOS) or tetramethylsilane (TMS), are used as silicon oxide layer-forming precursor substances. Usually air is used as working gas, but also the use of nitrogen or argon as Working gas is suitable for adjusting certain functionalities, for example a hydrophilic effect. When using a silicon oxide layer as a composite layer further, suitable for a particular application layer components are embedded in the matrix. For example, the embedding of functional nanoparticles in a layer matrix is known. As a result of the reaction of the amino-functionalized precursor in the plasma jet, plasma polymers are formed. The deposition of an amino group-containing plasma polymer with the layer matrix to form a mixed layer is carried out by adding appropriate liquid or dispersed and then atomized precursor substances (precursors) in the plasma jet. In addition to the usually preferred use of silicon oxide layer matrices, it is also possible to use titanium dioxide layer matrices. In the APCVD titanium dioxide layer-forming precursor substances titanium organic compounds, such as titanium (IV) tetraisopropoxide (TTIP) are used. In particular, air is used as the working gas, but also the use of nitrogen or argon as working gas is suitable for the adjustment of certain functionalities, for example a hydrophilic effect.

The methods described in the prior art allow the preparation of amino-containing plasma polymer coatings, which allow the immobilization or the absorption of biologically active molecules on the layer. In order to produce such layers, low-pressure plasma processes are preferably used in the prior art due to the exclusion of the surrounding atmosphere, the excitation of the working gas generally taking place with the aid of microwave or radio-frequency radiation. By using plasma sources operating under atmospheric pressure conditions, technological advances are expected, as in this case the use of expensive vacuum technology can be dispensed with. Atmospheric plasmas (or plasmas operating in the rough vacuum range) can be produced, for example, by means of dielectrically impeded discharges, wherein the surface electrodes used in the process can only handle limitedly complicated 3D geometries. From this point of view, free-jet plasma systems can be of advantage since, with their open plasma jets, they can process virtually any desired surface geometry and substrate materials (conductive, dielectric).

The throughput of the working gas and / or the precursor is preferably variable and controllable and / or controllable. In particular, the throughputs working gas and precursor are independently controllable and / or controllable. In addition to the distance of the coating device to the surface to be coated so is another means for influencing the layer properties, such as the layer thickness or the morphology available. Likewise, gradient layers can be realized in this way.

In one embodiment, an inert gas such as nitrogen or argon or a mixture of these gases with air is used as working gas in order to prevent or completely avoid a premature oxidative conversion of the amino-functionalized precursor expected in the plasma.

In one embodiment, parameters of the plasma enhanced chemical vapor deposition are performed so that a hydrophobic or hydrophilic behavior of the surface is achieved. The behavior can be varied by the choice of the first precursor, its concentration in the plasma and the working gas. For a hydrophobic behavior, hexamethyldisiloxane (HMDSO) is the first precursor with the working gas air. In order to produce as hydrophilic a behavior as possible of the resulting mixed layer, tetraethoxysilane (TEOS) with the working gas air or nitrogen and HMDSO with nitrogen can be used as the first precursor. The chemical composition of the mixed layer itself is not changed with the exception of the proportion of residual organic groups; in addition, changes in the surface morphology of the mixed layers can be specifically produced.

The invention further relates to a component comprising a substrate having at least one surface on which a mixed layer comprising amino group-containing reaction products, so-called plasma polymers embedded in an oxidic layer matrix by means of a method according to one of the preceding claims.

The deposited mixed layer can be used as a biocompatible layer, as a hydrophobic layer, as an organo-modified layer with incorporated functional groups, for the adhesion improvement, for example of paints and adhesives, or for the chemical bonding of further layers.

The component coated in this way can be used in particular in the biomedical sector, for example for the production of amino-functionalized support materials for cell growth studies or as an amino-functional coating in the area of implant materials. Further applications arise in the field of lightweight materials for the production of sandwich components, in particular of metal-polymer sandwich components. With regard to applications in the field of bonding, the functionalization according to the invention of a component surface using suitable adhesives, coating systems or other organic coatings enables improved adhesion.

Embodiments of the invention are explained in more detail below with reference to drawings.

Show:

1A to 1E schematic representations in a method according to the invention used nozzle shapes and variants of the precursor, and

2 a diagram for the detection of water resistance by means of the method according to the invention deposited mixed layers.

1A to 1E show schematic representations in a method according to the invention used nozzle shapes and variants of the precursor.

In various experiments, mixed layers were deposited on substrates, wherein a plasma jet PS was produced from a working gas AG, wherein at least a first precursor P1, in particular hexamethyldisiloxane, was supplied to the working gas AG and / or the plasma jet PS and reacted in the plasma jet PS, wherein reaction products formed in this reaction were deposited on a surface of the substrate to form an oxide layer matrix, wherein at least a second, amino-functionalized precursor P2, in particular ethylenediamine or allylamine, was supplied to the plasma jet PS and reacted in the plasma jet PS, resulting in this reaction amino-containing reaction products were deposited as plasma polymers to form a mixed layer with the oxide layer matrix. Deposition was at atmospheric pressure using various plasma jet designs.

In one embodiment, hexamethyldisiloxane is used as the first precursor P1 and ethylenediamine as the second precursor P2. This first precursor P1 and the second precursor P2 can be metered directly into the plasma in accordance with the process procedure, or can be supplied only in the vicinity of the plasma jet PS. For this purpose, as in 1A to 1E In this embodiment, different variants of plasma nozzles are used: a Y-nozzle YD (FIG. 1A and 1B ), a remote nozzle RD ( 1C and 1D ) and a combination of these two types, a variant KD (referred to as combi nozzle) ( 1E ). These nozzles are characterized in particular by the fact that the first precursor P1 and the second precursor P2 can be supplied in different positions relative to the plasma jet PS. With regard to the production of ethylenediamine / hexamethlydisiloxane composite coatings, all three nozzle shapes are suitable, but the choice of the plasma nozzle has some influence on the chemical composition of the coating produced. By means of the different plasma nozzles, the interaction time of the precursors P1, P2 in the plasma and thus the conversion can be influenced in a targeted manner.

In the case of the Y-nozzle YD, the second precursor P2 in a carrier gas TG is supplied to the plasma jet PS in a region which allows a longer interaction time for conversion into the plasma. The first precursor P1 can either be previously metered into the working gas AG ( 1A ) or also in a carrier gas TG are fed to the plasma jet PS via the Y-nozzle YD ( 1B ). In the remote nozzle RD, the second precursor P2 is supplied in a carrier gas TG to the plasma jet PS in a region outside the actual plasma nozzle, near the substrate surface, whereby a very short interaction time for the reaction in the plasma is present. This is advantageous in particular for thermally or hydrolytically sensitive precursors. The first precursor P1 can either be previously metered into the working gas AG ( 1C ) or also in a carrier gas TG are supplied to the plasma jet PS via the remote nozzle (RD) ( 1D ). With the combination nozzle KD in 1E For example, the second precursor P2 in a carrier gas TG is supplied to the plasma jet PS outside the actual plasma nozzle, near the substrate surface, as in the case of the remote nozzle RD. The first precursor P1 is in this case supplied in a carrier gas TG to the plasma jet PS in the upper region as in the Y-nozzle YD. This results in different lengths of interaction times for the conversion in the plasma for the first precursor P1 and the second precursor P2.

For the experiments, a free-jet plasma system with a plasma power of 75-100 W was used.

In a first experiment V1, the deposition was carried out by means of a remote nozzle RD at a plasma power of 75 W. In a second experiment V2 was the deposition by means of a remote nozzle RD at a plasma power of 100 W. In a third attempt V3 was the deposition by means of a Y-nozzle YD at a plasma power of 75 W. In a fourth experiment V4, the deposition was carried out using a combination nozzle KD with a plasma power of 75 W.

The feed of the first precursor P1 hexamethyldisiloxane was carried out by means of a mass flow control system, the flow rate was 2.5 ml / min for the Y-nozzle YD and the combined nozzle KD, in the case of the remote nozzle RD, this value was 10 ml / minute The feed of the second precursor P2 ethylenediamine was carried out with the aid of a bubbler system, the flow rate of the carrier gas TG was at 100 ml / min to 300 ml / min. The enriched with ethylene diamine gas mixture was added to an additional carrier gas flow of 4 l / min to further dilute the second precursor P2 and homogenize. Nitrogen was used as working gas AG, as carrier gas TG for the ethylenediamine and as carrier gas TG for the hexamethyldisiloxane.

The element distribution measured on the surface of the coated substrates by means of photoelectron spectroscopy (XPS) shows that for the mixed layers, independent of the nozzle shape, stable nitrogen contents of 9% and stable silicon contents of 17% were achieved. The samples prepared by Y and combination nozzle YD, KD show higher levels of oxygen and lower levels of carbon compared to the remote nozzle RD. This is due to the incomplete conversion of HMDSO into SiO _x at the remote nozzle RD. in the Comparison of the mixed layers deposited by remote nozzle RD at 75 W and 100 W reveals only slight differences.

To determine the water resistance of the mixed layers, the coated samples were aged in deionized water for five minutes.

The determination of the content of primary amines to carbon ([NH ₂ ] / [C]) was carried out in the deposited mixed layers by means of XPS measurements. Although nitrogen can be easily detected by XPS and it is also possible to make statements about the bonding conditions via the heights of the binding energies, a statement as to whether the detected nitrogen is in the form of primary amines is not possible. Thus, the corresponding samples were derivatized with pentafluorobenzaldehyde (PFBA) prior to XPS analysis to quantify the content of fluorine for the NH ₂ groups.

2 shows the ratio NH ₂ / C of amines NH ₂ to carbon C for the mixed layers deposited in the experiments V ₁ to V ₄ and the ratio NH ₂ / C after aging of the samples coated in the tests V ₁ to V ₄ in water V 1 'to V 4'.

The determined ratio NH ₂ / C of amines NH ₂ to carbon C for the mixed layers deposited in the experiments V ₁ to V 4 before the water storage of up to 2.5% corresponds to the currently achieved state of the art. It has also surprisingly been found that by means of combined parallel deposition of ethylenediamine and hexamethyldisiloxane it is possible to produce sufficiently water-resistant, amine-containing plasma polymer layers. Clearly visible in 2 the drop of the values to [NH ₂ ] / [C] ~ 0.3% after aging in water. Only the sample V3 'deposited by means of the Y-nozzle YD shows the highest value with an NH ₂ / C ratio of about 0.4%, as it did before the removal from water.

LIST OF REFERENCE NUMBERS

AG

working gas

KD

Combined nozzle

PS

plasma jet

P1

first precursor

P2

second precursor

RD

Remote nozzle

TG

carrier gas

V1 to V4

attempt

V1 'to V4'

attempt

YD

Y nozzle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• KS Siow, L. Britcher, S. Kumar, and HJ Griesser, "Plasma Methods for the Generation of Chemically Reactive Surfaces for Biomolecule Immobilization and Cell Colonization-A Review," Plasma Processes and Polymers, Vol. 3, No. 6-7, pp. 392-418, 2006 [0003]
• D. Merche, N. Vandencasteele and F. Reniers, "Atmospheric plasmas for thin film deposition: A critical review," Thin Solid Films, Vol. 520, Item 13, pp. 4219-4236, 2012 [0003]
• Finke, K. Schröder and A. Ohl, "Plasma Retention and Water Stability of Microwave Plasma Polymerized Films from Allylamines and Acrylic Acids," Plasma Processes and Polymers, Vol. 6, No. S1, pp. S70-S74, 2009 [0003]
• F. Reno, D. D'Angelo, G. Gottardi, M. Rizzi, D. Aragno, G. Piacenza, F. Cartasegna, M. Biasizzo, F. Trotta, and M. Cannas, "Atmospheric Pressure Plasma Surface Modification of Poly (D, L-lactic acid) Increases Fibroblast, Osteoblast and Keratinocyte Adhesion and Proliferation, "Plasma Processes and Polymers, Vol. 9, No. 5, pp. 491-502, 2012 [0003]
• K. Lachmann, MC Rehbein, M. Jänsch, M. Thomas and C.-P. Klages, "Deposition of Thermoresponsive Plasma Polymer Films from N-Isopropyl Acrylamide Using Dielectric Barrier Discharge at Atmospheric Pressure," Plasma Medicine, Vol. 2, No. 1-3, 2012 [0003]
• H. Aizawa, Y. Gokita, Y. Yoshimi, T. Hatta, SM Reddy, and S. Kurosawa, "Synthesis and characterization of organic thin film using atmospheric-pressure plasma polymerization," Sensors and Materials, Vol. 22, No. 7 , pp. 337-345, 2010 [0003]
• A. Vogelsang, A. Ohl, R. Foest, K. Schröder and K.-D. Weltmann, "Deposition of thin films of amino group containing precursors with an atmospheric pressure microplasma jet," Plasma Processes and Polymers, Vol. 8, No. 1, pp. 77-84, 2011 [0003]
• J.-C. Ruiz, A. St-Georges-Robillard, C. Thérésy, S. Lerouge, and MR Wertheimer, "Fabrication and Characterization of Amine-Rich Organic Thin Films: Focus on Stability," Plasma Processes and Polymers, Vol. 7, No. 9 -10, pp. 737-753, 2010 [0003]
• M. Schnabelrauch, R. Wyrwa, H. Rebl, C. Bergemann, B. Finke, M. Schlosser, U. Walschus, S. Lucke, K.-D. Weltmann and JB Nebe, "Surface-coated polylactide fiber meshes as tissue engineering matrices with enhanced cell integration properties," International Journal of Polymer Science, Vol. 2014, 2014. http://dx.doi.org/10.1155/2014/439784 [0003]

Claims (10)

 A process for coating a substrate, wherein from a working gas (AG) a plasma jet (PS) is generated, wherein at least a first precursor (P1) supplied to the working gas (AG) and / or the plasma jet (PS) and in the plasma jet (PS) for Reaction is brought, wherein in this reaction resulting oxide reaction products are deposited on a surface of the substrate to form an oxide layer matrix, wherein at least a second, amino-functionalized precursor (P2) to the working gas (AG) and / or the plasma jet (PS) fed and Plasma jet (PS) is reacted, which formed in this reaction amino-containing reaction products are deposited as plasma polymers with the oxidic layer matrix to form a mixed layer.  The method of claim 1, wherein the first precursor (P1) and / or the second precursor (P2) to the plasma process via a Y-nozzle (YD) or a remote nozzle (RD) or a combination nozzle (KD) or by means of a Enrichment of the working gas (AG) are supplied before generating the plasma.  A method according to claim 1 or 2, wherein hexamethyldisiloxane and / or tetraethoxysilane and / or or tetramethylsilane and / or titanium (IV) tetraisopropoxide is used as the first precursor (P1).  Method according to one of claims 1 to 3, wherein as the second precursor (P2) ethylenediamine and / or allylamine is used.  Method according to one of the preceding claims, wherein the first precursor (P1) and / or the second precursor (P2) to the working gas (AG) and / or the plasma jet (PS) in dissolved form, as an aerosol, vapor or in dispersed form supplied will be.  The method of any one of claims 1 to 5, wherein the plasma is generated in a free-jet plasma source. A method according to any one of the preceding claims, wherein the deposition is carried out at atmospheric pressure. Method according to one of the preceding claims, wherein the working gas (AG) air, nitrogen or a nitrogen / air mixture or argon or an argon / air mixture or an argon / nitrogen mixture is used. A component comprising a substrate having at least one surface on which a mixed layer comprising amino group-containing reaction products embedded in an oxidic layer matrix is deposited by a method according to any one of the preceding claims. Use of the component according to claim 9 as an amino-functionalized support material for cell growth studies, as an implant, as an amino-functionalized surface for improved adhesion of adhesives and / or paints and / or organic coatings or in the field of lightweight composite materials, in particular metal-polymer sandwich structures.

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