WO2010057853A1

WO2010057853A1 - Method for atmospheric coating of nanosurfaces

Info

Publication number: WO2010057853A1
Application number: PCT/EP2009/065234
Authority: WO
Inventors: Alexander Knospe; Thomas Beer; Michael KÜBLER; August Burr
Original assignee: Plasmatreat Gmbh
Priority date: 2008-11-24
Filing date: 2009-11-16
Publication date: 2010-05-27
Also published as: DE102008058783A1

Abstract

The invention relates to a method for applying a coating onto a nanosurface of a work piece, wherein an atmospheric plasma beam is generated by electric discharge in a working gas and a precursor material is fed in a spatially separate manner from the working gas, wherein the precursor material is fed directly to the plasma beam and the applied layer comprises a nanosurface which substantially corresponds to the nanosurface of the work piece. The invention relates in particular to a method for applying a separation layer in molding processes, wherein the work piece to be molded comprises a nanosurface.

Description

Process for the atmospheric coating of

Nano Surfaces

The invention relates to a method for applying a layer to a nano-surface of a workpiece, in which an atmospheric plasma jet is generated by electrical discharge in a working gas and a precursor material is supplied spatially separated from the working gas, wherein the precursor material is supplied directly to the plasma jet and the applied layer has a nano-surface corresponding to the nano-surface of the workpiece.

Workpieces with a nano-surface are often used for plastic molding, in particular as forms in compression or embossing processes in the processing of thermosets or multi-component injection molding, for example in

Two-component injection molding process, used for the mass production of nano-surface plastic components.

A nano-surface is understood to mean a surface whose typical structure sizes are at least partially in the range between 10 and 10,000 nm, preferably in the sub-micron range, in particular in the nanometer range, at least in one spatial dimension. Such structures are also referred to below as nanostructures.

A nano-surface also means a surface whose flatness is at least partially in the range between 10 and 10,000 nm in at least one spatial direction, preferably in submicrometer, in particular in the nanometer range.

Furthermore, a nano-surface also means a surface with larger structures, for example in the millimeter or micrometer range, whose structural accuracy, in particular in edge regions, is in the range between 10 and 10,000 nm, preferably in the submicrometer, in particular in the nanometer range.

Nano-surfaced workpieces, for example, play an important role in the production of micro-optics, diffractive optical elements, holographic surface structures, lab-on-a-chip (microfluidic) applications, and surfaces with surface effects for hydrophobization

(Lotus flower effect), hydrophilization or for antireflection (moth eye effect).

It is also conceivable to use these workpieces for producing nano-surfaces with bioactive properties for diagnostic applications. For example, such a nano-surface may have bioadhesive properties or influence the growth direction of cells applied thereto. For prostheses can by a

Nano-surface, the ingrowth with the tissue can be improved.

Furthermore, such nano-surfaces can improve the look or feel of materials. For example, a synthetic leather surface can be created by the overlapping of larger ones Narrow structures with micro and / or nanostructures can be improved.

Furthermore, such workpieces for forming in Ur- or forming processes, for example in

Reaction injection molding or laminating, used.

In the prior art, for example in thermoplastic injection molding or reaction injection molding, a plastic, for example, a low-viscosity two-component polyurethane plastic, an epoxy resin, silicone or other crosslinking polymers is placed in or on the mold. These methods have the disadvantage when applied to molds with a nano-surface, that due to the increased surface of the mold due to the nanostructures and the resulting increased adhesion forces between mold and plastic, great forces have to be expended in order to separate mold and plastic from each other. Especially with chemically crosslinked polymers are very high adhesion forces to overcome. Comparable disadvantages also occur

Reaction injection molding, the so-called Reaction Injection Molding on.

In the case of molds which have no nanostructures on their surface, conventional release agents, in particular oily, waxy or powdered release agents, are used in the prior art in order to be able to separate the mold and the plastic from each other with less effort. These are sprayed onto the mold before the plastic is placed in or on the mold for molding. The use of conventional release agents, as are conventional in the art in non-nanostructured forms on the surface, is disadvantageous in nano-surfaced molds since the conventional release agents are known to have been used

Do not wet the surface of the nano-surface. Contouring here means the formation of a layer of substantially uniform thickness, so that the layer has a nano-surface that substantially corresponds to the nano-surface to which the layer is applied. Therefore, with a conventional release layer, no precise impression of the surface of the mold is possible. Furthermore, during demolding, i. when removing the Kunsstoffes from the mold, and a part of the release agent removed from the mold, so that it is necessary after only a few molding operations to apply new release agent on the mold. With repeated spraying of conventional release agents, there is also the formation of a deposit on the mold, so that the mold must be cleaned regularly.

Furthermore, the molded surface is contaminated by the release agent which has been removed, which is particularly disadvantageous in surfaces for diagnostic or medical applications. In these applications, silicones are often used, which are also problematic because of their adhesion during the impression. Even in the production of flat nano-surfaces, for example in the production of varnished wood veneers, conventional release agents or even a molding without release agent are disadvantageous because the surfaces after molding have a lower flatness and must be polished in a further step. Another prior art is EP 1301286 Bl. It discloses a method in which a gradient layer structure having a release layer in a plasma under low pressure conditions on a

Workpiece surface is applied. However, a release agent application under low-pressure conditions has the disadvantage that high investment costs arise due to the necessary vacuum chamber, the coating can only take place in batch operation and can only be laboriously incorporated into a process chain.

A method and apparatus for generating an atmospheric plasma jet, i. A plasma jet with an ambient pressure which is of the order of magnitude of the atmospheric pressure is known from EP 1 335 641 A1. For this purpose, a working gas, especially air, nitrogen, forming gas (mixture of nitrogen and hydrogen) or a noble gas, in particular argon or helium, passed through a channel in which by high voltage a plasma jet via an electrical discharge, i. a corona discharge and / or an arc discharge is generated.

In the case of coating processes using an atmospheric plasma jet, the effect of plasma polymerization, as disclosed in EP 1 230 414 Bl, is preferably used. In this method, a precursor material is introduced in liquid form directly into the plasma jet, there excited chemically and / or electronically, so that before, during or after the deposition of the excited precursor to a surface polymerization of the precursor begins. DE 10 2005 059 706 A1 discloses a method in which a separating layer with an atmospheric plasma jet is applied to a surface. However, the layer thicknesses of the layers applied with this method are too large in order to be able to wet nanostructures in a contour-following manner.

The invention is therefore based on the technical problem of improving the method for applying a thin contour-following layer, in particular a release layer to improve demolding in impression processes, on a nano-surface.

This technical problem is solved by a method with the features of claim 1. Further advantageous embodiments are specified in the subclaims.

The application of a contour-following layer to a workpiece can be improved by generating an atmospheric plasma jet by electrical discharge in a working gas and a precursor material for the layer separated from the working gas is introduced directly into the plasma jet and excited in the plasma jet precursor material by plasma deposition under atmospheric pressure is applied to the nano-surface of a workpiece in a thin layer. The term "electrical discharge" here, as stated above, corona discharges and / or arc discharges understood.

The described method has the advantage that under atmospheric pressure a thin layer, preferably with a Layer thickness in the submicrometer range, so can be applied to a nano-surface, that the applied layer has one of the nano-surface of the workpiece substantially corresponding nano-surface. The method therefore makes it possible to modify the properties, in particular physical, chemical and biological properties, of the workpiece surface while maintaining the structure as a nano-surface by applying a layer under atmospheric pressure. This method thus overcomes the technical prejudice that the great kinetic

Energy, with which a precursor material hits the surface to be coated by the plasma jet, prevents the formation of a nanostructure-sized layer.

The above-explained method for applying a layer to a nano-surface of a workpiece is particularly suitable for applying an anti-adhesive layer, in particular a release layer in an injection molding or pressing process. An anti-adhesive layer in this context means a layer which is distinguished in that the force holding it together with a layer applied thereto is less than the force which would hold together the layer and the workpiece applied directly to the workpiece.

The described method therefore has the advantage that the separation of, for example, a molded part from a mold is facilitated by the applied anti-adhesive layer, since less effort is required. The method is therefore particularly suitable for

Workpieces with a large surface, in which the detachment of a layer without an anti-adhesive layer a tremendous Force required. In addition, the method is particularly suitable for materials which have very high adhesive forces due to the material, for example polyurethanes, epoxies, silicones, unsaturated polyesters, acrylates, melams or phenoplasts.

Furthermore, the method has the advantage that the facilitated detachment, for example of the molding of the mold, also causes a cleaner detachment, that is, that the molding and the mold is not damaged in the Abloseprozess. This is particularly advantageous in the production of highly glossy or high gloss surfaces, since the erfmdungsgemaß molded surface has hardly any surface flaws and not further treated, for example, polished, must be to obtain the highly glossy or high gloss property.

A further advantage of this method is that the formation of a coating on the mold surface is reduced by the very small layer thickness of the release agent layer applied in this method, so that the mold workpiece must be cleaned less frequently.

The method is particularly suitable for applying a layer using a fluoro-organic precursor, in particular decafluoropentane and hexafluoropropene oxide. A layer deposited from a fluorine-organic precursor is suitable for contouring a nano-surface. In addition, such a layer shows particularly good anti-adhesive properties. These properties are particularly advantageous in nanostructured workpieces, since these have a particularly large surface area due to the nanostructures.

A further advantageous embodiment of the method is achieved in that a further layer, a secondary layer, is applied to the applied layer. Since the layer applied according to the invention has nanostructures on its surface corresponding to the nanostructures of the workpiece surface, these structures are also formed as an impression on the surface of the secondary layer which contacts the layer. Impression here means the formation of structures as a negative. Thus, with this method thin hidden layers can be produced which have a nanostructured shape corresponding to the workpiece surface. In addition, two complementary layers in their nanostructures can be produced with a separating layer between them.

Another particularly advantageous embodiment of the method is achieved by the use of plastics for the secondary layer, which are particularly suitable for the molding of nanostructures. The use of such a plastic leads to a particularly precise impression of the nanostructures of the layer in the secondary layer.

An advantageous embodiment of the method is achieved by removing the secondary layer after its application and, if necessary, curing. The nanostructure introduced as an impression in the secondary layer is essentially retained in this method, so that the method is particularly suitable for the molding of nanostructured workpieces, for example, by injection molding, is suitable. Another advantage of this method is that the deposited thin contour-following layer used as the release layer substantially remains on the workpiece in the peeling process of the secondary layer, so that the same release layer can be used for many molding processes without the need for re-deposition of a release layer. Due to the thinness of the separating layer, the formation of deposits on the workpiece is also limited even with multiple application of such a layer, so that the cleaning of the workpiece must also occur less frequently. Further, molded parts are not contaminated by adhering release agent residues after being released from the mold and therefore do not need to be cleaned separately.

Further features and advantages of the present invention will be explained in more detail in the description of an embodiment, reference being made to the accompanying drawings. In the drawing show

Fig. 1 shows an embodiment of an inventive

Process for the atmospheric plasma coating of a nano-surface, in which the layer is applied to the surface following the contour,

2 shows a molding process of a nano-surface,

FIG. 2 a shows a greatly enlarged section of the nanosurface from FIG. 2 with a layer applied thereto by the method according to the invention, FIG. FIG. 2b shows the section as in FIG. 2a with a secondary layer applied to the layer applied by the method according to the invention; and FIG

Fig. 2c shows the section as in Fig. 2b after detachment of the secondary layer.

The method shown in Fig. 1 for plasma coating 1 has a plasma jet 2 generating plasma source 3, with the after introduction of a precursor in the

Plasma jet a nano-surface 4, for example, a nanostructured nano-surface is coated.

The plasma source 3 has a nozzle tube 5 made of metal, which tapers conically to a nozzle tube outlet 6. At the

Nozzle tube outlet 6 opposite end, the nozzle tube 5, a swirl device 8 with an inlet 10 for a working gas, for example for nitrogen. An intermediate wall 12 of the twisting device 8 has a ring of inclined in the circumferential direction employed holes 14, through which the working gas is twisted. The downstream, conically tapered part of the nozzle tube is therefore traversed by the working gas in the form of a vortex 16, whose core extends on the longitudinal axis of the nozzle tube.

On the underside of the intermediate wall 12, an electrode 18 is arranged centrally, which protrudes coaxially in the direction of the tapered portion in the nozzle tube. The electrode 18 is electrically connected to the intermediate wall 12 and the remaining parts of the twisting device 8. The

Swirl device 8 is electrically insulated from the nozzle tube 5 by a ceramic tube 20. About the twisting device 8 is applied to the electrode 18 is a high-frequency high voltage, which is generated by a transformer 22. The inlet 10 is connected via a hose, not shown, to a variable flow rate pressurized working gas source. The nozzle tube 5 is grounded.

The applied voltage generates a high frequency charge in the form of an arc 24 between the electrode 18 and the nozzle tube 5. The term "arc" is used here as a phenomenological description of the discharge, since the discharge occurs in the form of an arc. However, the term "arc" is understood in DC discharge with substantially constant voltage values.

Due to the swirling flow of the working gas, however, this arc is channeled in the vortex core on the axis of the nozzle tube 5, so that it branches only in the region of the nozzle tube outlet 6 to the wall of the nozzle tube 5. The working gas in the area of the vortex core and thus in the immediate vicinity of the arc 24 with high

Flow rate rotates, comes into intimate contact with the arc and is thereby partially transferred to the plasma state, so that an atmospheric plasma jet 2 emerges through the nozzle tube outlet 6 from the plasma source 3. Downstream of the

Nozzle tube outlet 6 is a lance 26 is provided, to which a precursor source is connected via a hose, not shown. Precursor material is introduced directly into the plasma jet 2 through the lance 26. The precursor material is partially ionized in the plasma jet and transported by the plasma jet through the outlet opening 28. The partially ionized precursor material arrives with the plasma jet on the nano-surface 4 and forms there under plasma polymerization from a layer.

FIG. 2 shows a molding process on a nanostructured nano-surface of a workpiece using a release layer applied by a method according to the invention.

FIG. 2 a shows a section of the nano-surface 4 from FIG. 2 in a high magnification. The structures and recesses 30, 30 ', 30' 'formed on the nano-surface 4,

30 '' 'have a typical size in the order of 10 to 10,000 nm, preferably from 10 to 1,000 nm and more preferably from 10 to 400 nm. On the surface 4, a contour-following thin layer 32 was applied by a method according to the invention.

FIG. 2b shows a section as shown in FIG. 2a, wherein a secondary layer 34 has been applied to the contour-following layer 32.

Fig. 2c shows a section as shown in Fig. 2b, wherein the secondary layer 34 has been separated from the contour-following layer 32. The contour-following layer is essentially left on the nano-surface 4. The detached secondary layer has nanostructures 30 to 30 '' 'of the nano-surface 4 as impressing structures 36 to 36' '' on.

Claims

claims

A method for applying a layer (32) to a nano-surface (4) of a workpiece, wherein an atmospheric plasma jet (2) is generated by electrical discharge in a working gas in which a precursor material is supplied spatially separated from the working gas, wherein the Precursor material directly to the plasma jet (2) is supplied, LO characterized in that the applied layer (32) has one of the nano-surface (4) of the workpiece substantially corresponding nano-surface.

L5 2. The method of claim 1, characterized in that the applied layer (32) has anti-adhesive properties.

ZO 3. Process according to claims 1 or 2, characterized in that a fluorine-organic compound is used as precursor.

25 4. Process according to claims 1 to 3, characterized in that on the layer (32) a secondary layer (34) is applied.

5. Process according to claims 1 to 4, characterized in that a plastic suitable for the molding of nanostructures is used for the secondary layer (34).

6. Process according to claims 1 to 5, characterized in that the secondary layer (34) is removed again.