DE102016206009B4 - Process for coating a substrate - Google Patents

Abstract

A method for coating a substrate, a plasma jet (PS) being 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) for Reaction is brought, with oxidic reaction products arising during this reaction being deposited on a surface of the substrate to form an oxidic layer matrix, with at least one second, amino-functionalized precursor (P2) being supplied to the working gas (AG) and / or the plasma jet (PS) and in the Plasma jet (PS) is made to react, with reaction products containing amino groups being deposited as plasma polymers with the oxidic layer matrix to form a mixed layer, with the first precursor (P1) and / or the second precursor (P2) being added to the plasma process via a Y Nozzle (YD) or a remote nozzle (RD) or a combination nozzle (KD).

Description

The invention relates to a method for coating a substrate.

Layers and surfaces that are suitable for use in a biological environment can be produced using plasma-based surface technology processes. In more recent publications, the main focus of the investigations is the creation of functionalized surfaces with the help of plasma polymer coatings, which enable the immobilization or absorption of biologically active molecules on the layer.

• K. S. Siow, L. Britcher, S. Kumar und H. J. Griesser, „Plasma Methods for the Generation of Chemically Reactive Surfaces for Biomolecule Immobilization and Cell Colonization-A Review,“ Plasma processes and polymers, Bd. 3, Nr. 6-7, pp. 392-418, 2006 .
• D. Merche, N. Vandencasteele und F. Reniers, „Atmospheric plasmas for thin film deposition: A critical review,“ Thin Solid Films, Bd. 520, Nr. 13, pp. 4219-4236, 2012 .
• B. Finke, K. Schröder und A. Ohl, „Structure retention and water stability of microwave plasma polymerized films from allylamine and acrylic acid,“ Plasma Processes and Polymers, Bd. 6, Nr. S1, pp. S70-S74, 2009 .
• F. Reno, D. D'Angelo, G. Gottardi, M. Rizzi, D. Aragno, G. Piacenza, F. Cartasegna, M. Biasizzo, F. Trotta und 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, Bd. 9, Nr. 5, pp. 491-502, 2012 .
• K. Lachmann, M. C. Rehbein, M. Jänsch, M. Thomas und C.-P. Klages, „Deposition of Thermoresponsive Plasma Polymer Films from N-Isopropylacrylamide Using Dielectric Barrier Discharge at Atmospheric Pressure,“ Plasma Medicine, Bd. 2, Nr. 1-3, 2012 .
• H. Aizawa, Y. Gokita, Y. Yoshimi, T. Hatta, S. M. Reddy und S. Kurosawa, „Synthesis and characterization of organic thin film using atmosphericpressure plasma polymerization,“ Sensors and Materials, Bd. 22, Nr. 7, pp. 337-345, 2010 .
• A. Vogelsang, A. Ohl, R. Foest, K. Schröder und K.-D. Weltmann, „Deposition of thin films from amino group containing precursors with an atmospheric pressure microplasma jet,“ Plasma Processes and Polymers, Bd. 8, Nr. 1, pp. 77-84, 2011 .
• J.-C. Ruiz, A. St-Georges-Robillard, C. Theresy, S. Lerouge und M. R. Wertheimer, „Fabrication and Characterisation of Amine-Rich Organic Thin Films: Focus on Stability,“ Plasma Processes and Polymers, Bd. 7, Nr. 9-10, pp. 737-753, 2010 .
• M. Schnabelrauch, R. Wyrwa, H. Rebl, C. Bergemann, B. Finke, M. Schlosser, U. Walschus, S. Lücke, K.-D. Weltmann und J. B. Nebe, „Surface-coated polylactide fiber meshes as tissue engineering matrices with enhanced cell integration properties,“ International Journal of Polymer Science, Bd. 2014, 2014 . http://dx.doi.org/10.1155/2014/439784

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, No. 13, pp. 4219-4236, 2012 .
• B. Finke, K. Schröder and A. Ohl, "Structure retention and water stability of microwave plasma polymerized films from allylamine and acrylic acid," 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 from 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. Theresy, 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. Lücke, 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

From the US 2012/0190950 A1 the deposition of mixed layers of allylamine and HMDSO by means of pulsed plasma in the low pressure range is known.

From the DE 32 23 253 A1 a multi-stage process is known in which in a step (a) a surface of an object is exposed to a low-temperature plasma which is generated in a gas atmosphere containing an organic amine compound and in which in a step (b) the surface of the object before or after Step (a) the low-temperature plasma is exposed to a gas atmosphere containing an organic silicon compound.

From the DE 10 2010 044 114 A1 a method is known in which a plasma polymer layer is deposited in each case on a first and a second substrate by means of an atmospheric pressure plasma jet which is generated with a plasma nozzle.

The invention is based on the object of specifying an improved method for coating a substrate.

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

Advantageous refinements of the invention are the subject matter of the subclaims.

In a method according to the invention for coating a substrate, a plasma jet is generated from a working gas, at least one first precursor being supplied to the working gas and / or the plasma jet and being reacted in the plasma jet, with oxidic reaction products arising during this reaction on a surface of the substrate for the Training a oxidic layer matrix are deposited, at least one second, amino-functionalized precursor being fed to the working gas and / or the plasma jet and reacted in the plasma jet, with reaction products containing amino groups being deposited as plasma polymers with the oxidic layer matrix to form a mixed layer. This creates an interwoven mixed layer system.

The layer deposited in this way serves as a chemically reactive base for the immobilization of biologically active molecules and is therefore suitable as a biocompatible surface. If necessary, 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 layer that is significantly more abrasion-resistant and more adhesive than the deposition of pure amino-group-containing plasma polymer layers 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.

According to the invention, the first precursor and / or the second precursor are fed to the plasma process via a Y nozzle or a remote nozzle or a combination nozzle.

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

In one embodiment, ethylene diamine and / or allylamine is used as the second precursor. 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 inexpensive and readily available. The double bond in the structure also speaks in favor of allylamine, which theoretically enables free radical polymerization. Ethylenediamine has a high primary amine to carbon ratio.

Other amino compounds such as, for example, cyclopropylamine or propargylamine can also 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 into the working gas or the plasma stream in the gaseous state. Liquid or solid, in particular powdery, 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, carried away by it and introduced together with this into the working gas or the plasma flow.

In one embodiment, the plasma is generated in a free-jet plasma source. In this process, a high-frequency discharge is ignited between two concentric electrodes, and the hollow cathode plasma that forms is guided as a plasma jet from the electrode arrangement, usually several centimeters, into the free space and to the surface to be coated by an applied gas stream. The precursor can be introduced both before the excitation into the working gas (direct plasma processing) and afterwards into the plasma that has already formed or in its vicinity (remote plasma processing). Another possibility of generating plasma is to use a dielectrically impeded discharge. The working gas used as a dielectric, in particular air, is passed between two electrodes. The plasma discharge takes place between the electrodes, which are fed with high-frequency high voltage.

In one embodiment, the deposition is carried out at atmospheric pressure. Normal pressure plasma processes require significantly less technical effort than low pressure or vacuum processes, since there is no need for a reaction chamber to be evacuated. In the normal pressure plasma process (APCVD - Atmospheric Pressure Plasma Chemical Vapor Deposition - plasma-assisted chemical vapor deposition under atmospheric pressure conditions), crystallization nuclei and solid nanoparticles grow on the substrate surface to a thin layer due to the enrichment of the working gas with the precursor and plasma-initiated chemical conversion processes. The size of the agglomerates formed from such particles and thus essential properties of the coating can be adjusted, among other things, by the distance between the plasma source and the surface, by the dosing rates of the precursors, by the plasma power introduced and the process gases / gas mixtures used.

In APCVD, organic silicon compounds, for example hexamethyldisiloxane (HMDSO) or tetraethoxysilane (TEOS) or tetramethylsilane (TMS), are used as precursor substances that form silicon oxide layers. Usually, air is used as the working gas, but the use of nitrogen or argon as the working gas is also suitable for setting certain functionalities, for example a hydrophilic effect. When using a silicon oxide layer as a composite layer, further layer components suitable for a specific application are embedded in the matrix. For example, it is known to embed functional nanoparticles in a layer matrix. As a result of the conversion of the amino-functionalized precursor in the plasma jet, plasma polymers are formed. A plasma polymer containing amino groups is deposited with the layer matrix to form a mixed layer by metering appropriate liquid or dispersed and then nebulized precursors into the plasma jet. In addition to the usually preferred use of silicon oxide layer matrices, titanium dioxide layer matrices can also be used. In APCVD, organic titanium compounds, for example titanium (IV) tetraisopropoxide (TTIP), are used as precursor substances which form the titanium dioxide layer. In particular, air is used as the working gas, but the use of nitrogen or argon as the working gas is also suitable for setting certain functionalities, for example a hydrophilic effect.

The methods presented in the prior art allow the production of amino group-containing plasma polymer coatings which enable the immobilization or absorption of biologically active molecules on the layer. In the prior art, due to the exclusion of the surrounding atmosphere, low-pressure plasma processes are preferably used to produce such layers, with the excitation of the working gas mostly taking place with the aid of microwave or radio frequency radiation. Technological advances are expected through the use of plasma sources that work under atmospheric pressure conditions, since in this case the use of expensive vacuum technology can be dispensed with. Atmospheric plasmas (or plasmas operating in the low vacuum range) can be generated, for example, by means of dielectrically impeded discharges, with the surface electrodes used only being able to deal with more complex 3D geometries. From this point of view, free-jet plasma systems can be advantageous, as they can process practically any surface geometries and substrate materials (conductive, dielectric) with their open plasma jets.

The throughput of the working gas and / or the precursor is preferably variable and controllable and / or regulatable. In particular, the throughputs of working gas and precursor can be controlled and / or regulated independently of one another. In addition to the distance between the coating device and the surface to be coated, another means of influencing the layer properties, such as the layer thickness or the morphology, is available. Gradient layers can also be implemented 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 the working gas in order to prevent or completely avoid a premature oxidative conversion of the amino-functionalized precursor to be expected in the plasma.

In one embodiment, parameters of the plasma-assisted chemical vapor deposition are controlled in such a way that a hydrophobic or hydrophilic behavior of the surface is achieved. The behavior can be varied through the choice of the first precursor, its concentration in the plasma and the working gas. For a hydrophobic behavior, hexamethyldisiloxane (HMDSO) is suitable as the first precursor with the working gas air. In order to make the resulting mixed layer as hydrophilic as possible, 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 significantly changed, apart from the proportion of residual organic groups; changes in the surface morphology of the mixed layers can also be produced in a targeted manner.

A component can comprise a substrate with at least one surface on which a mixed layer, comprising reaction products containing amino groups, so-called plasma polymers, embedded in an oxidic layer matrix, is deposited by means of the method according to the invention.

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

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

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

• 1A bis 1E schematische Darstellungen in einem erfindungsgemäßen Verfahren verwendeter Düsenformen und Varianten der Precursorzufuhr, und
• 2 ein Diagramm zum Nachweis der Wasserfestigkeit mittels des erfindungsgemäßen Verfahrens abgeschiedener Mischschichten.

Show in it:

• 1A until 1E schematic representations of nozzle shapes and variants of the precursor supply used in a method according to the invention, and
• 2 a diagram for demonstrating the water resistance by means of the method according to the invention of deposited mixed layers.

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

Mixed layers were deposited on substrates in various experiments, using a working gas AG a plasma jet PS was generated, with at least a first precursor P1 , especially hexamethyldisiloxane, the working gas AG and / or the plasma jet PS fed and in the plasma jet PS was brought to reaction, with reaction products occurring during this reaction being deposited on a surface of the substrate to form an oxidic layer matrix, with at least one second, amino-functionalized precursor P2 , especially ethylenediamine or allylamine, the plasma jet PS fed and in the plasma jet PS was brought to reaction, with amino group-containing reaction products resulting from this reaction being deposited as plasma polymers to form a mixed layer with the oxidic layer matrix. The deposition took place at atmospheric pressure using various plasma nozzle designs.

In one embodiment, the first precursor P1 Hexamethyldisiloxane and as a second precursor P2 Ethylenediamine used. This first precursor P1 and the second precursor P2 can be metered directly into the plasma, depending on the procedure, or only in the vicinity of the plasma jet PS are fed. For this purpose, as in 1A until 1E shown, in this embodiment different variants of plasma nozzles are used: a Y-nozzle YD ( 1A and 1B) , a remote nozzle RD ( 1C and 1D ) and a combination of these two designs, a variant known as a combination nozzle KD ( 1E) . These nozzles are distinguished in particular by the fact that the first precursor P1 and the second precursor P2 in different positions relative to the plasma jet PS can be fed. With a view to the production of ethylenediamine / hexamethyldisiloxane composite coatings, all three nozzle shapes are suitable, but the choice of plasma nozzle has a certain influence on the chemical composition of the coating produced. The interaction time of the precursors P1 , P2 in the plasma and thus the implementation can be specifically influenced.

With the Y-nozzle YD becomes the second precursor P2 in a carrier gas TG the plasma jet PS fed in an area that allows a longer interaction time for conversion in the plasma. The first precursor P1 can either be in the working gas beforehand AG dosed ( 1A) or also in a carrier gas TG the plasma jet PS via the Y-nozzle YD are supplied ( 1B) . With the remote nozzle RD becomes the second precursor P2 in a carrier gas TG the plasma jet PS in an area outside the actual plasma nozzle, near the substrate surface, which means that there is a very short interaction time for conversion in the plasma. This is advantageous in particular for thermally or hydrolytically sensitive precursors. The first precursor P1 can either be in the working gas beforehand AG dosed ( 1C ) or also in a carrier gas TG the plasma jet PS via the remote nozzle ( RD ) are supplied ( 1D ). With the combi nozzle KD in 1E becomes the second precursor P2 in a carrier gas TG the plasma jet PS outside of the actual plasma nozzle, near the substrate surface, as with the remote nozzle RD . The first precursor P1 is here in a carrier gas TG the plasma jet PS fed in the upper area as with the Y-nozzle YD . This results in interaction times of different lengths for implementation in the plasma for the first precursor P1 and the second precursor P2 .

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

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

The feeding of the first precursor P1 Hexamethyldisiloxane took place with the help of a mass flow control system, the flow rate was 2.5 ml / min for the Y-nozzle YD and the combination nozzle KD , in the case of the remote nozzle RD this value was 10 ml / min. The feeding of the second precursor P2 Ethylenediamine was carried out with the help of a bubbler system, the flow rate of the carrier gas TG ranged from 100 ml / min to 300 ml / min. The gas mixture enriched with ethylenediamine was metered into an additional carrier gas flow of 4 l / min in order to create the second precursor P2 further dilute and homogenize. As working gas AG , as a carrier gas TG for the ethylenediamine and as a carrier gas TG nitrogen was used for the hexamethyldisiloxane.

The element distribution measured on the surface of the coated substrates by means of photoelectron spectroscopy (XPS) shows that stable nitrogen contents of 9% and stable silicon contents of 17% were achieved for the mixed layers, regardless of the nozzle shape. The Y-nozzle and the combination nozzle YD , KD The samples produced 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 traced back. In comparison with the remote nozzle RD only slight differences can be seen with mixed layers deposited at 75 W and 100 W.

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

The determination of the content of primary amines in relation to carbon ([NH ₂ ] / [C]) was carried out in the deposited mixed layers by means of XPS measurements. Nitrogen can be detected with XPS without any problems and it is also possible to make statements about the binding conditions via the levels of the binding energies, but it is not possible to make a statement as to whether the detected nitrogen is in the form of primary amines. Thus, the corresponding samples were derivatized with pentafluorobenzaldehyde (PFBA) before the XPS analysis in order to arrive _{at a quantitative statement regarding the NH 2 groups on the fluorine content.}

2 shows the ratio NH ₂ / C of amines NH ₂ to carbon C for those in the experiments V1 to V4 deposited mixed layers and the NH ₂ / C ratio after aging in the experiments V1 to V4 coated samples in water V1 'to V4' .

The determined ratio NH ₂ / C of amines NH ₂ to carbon C for the in the experiments V1 to V4 mixed layers deposited before water storage of up to 2.5% corresponds to the current state of the art. It was also surprisingly found that it is possible, by means of the combined parallel deposition of ethylenediamine and hexamethyldisiloxane, to produce sufficiently waterproof, amine-containing plasma polymer layers. It can be clearly seen in 2 the drop in values to [NH ₂ ] / [C] ~ 0.3% after exposure to water. Only with the Y-nozzle YD deposited sample V3 ' shows the highest value with an NH ₂ / C ratio of approx. 0.4%, as it did before the aging in water.

List of reference symbols

AG

Working gas

KD

Combination 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

Claims (7)

A method for coating a substrate, a plasma jet (PS) being 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) for Reaction is brought, with oxidic reaction products arising during this reaction being deposited on a surface of the substrate to form an oxidic layer matrix, with at least one second, amino-functionalized precursor (P2) being supplied to the working gas (AG) and / or the plasma jet (PS) and in the Plasma jet (PS) is made to react, with reaction products containing amino groups being deposited as plasma polymers with the oxidic layer matrix to form a mixed layer, with the first precursor (P1) and / or the second precursor (P2) being added to the plasma process via a Y Nozzle (YD) or a remote nozzle (RD) or a combination nozzle (KD). Procedure according to Claim 1 , hexamethyldisiloxane and / or tetraethoxysilane and / or or tetramethylsilane and / or titanium (IV) tetraisopropoxide being used as the first precursor (P1). Method according to one of the Claims 1 or 2 , Ethylenediamine and / or allylamine being used as the second precursor (P2). Method according to one of the preceding claims, wherein the first precursor (P1) and / or the second precursor (P2) are supplied to the working gas (AG) and / or the plasma jet (PS) in dissolved form, as an aerosol, in vapor form or in dispersed form will be. Method according to one of the Claims 1 until 4th , wherein the plasma is generated in a free-jet plasma source. Method according to one of the preceding claims, wherein the deposition is carried out at atmospheric pressure. Method according to one of the preceding claims, wherein air, nitrogen or a nitrogen / air mixture or argon or an argon / air mixture or an argon / nitrogen mixture is used as the working gas (AG).

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