EP1581347A2

EP1581347A2 - Substrate comprising a polar plasma-polymerised coating

Info

Publication number: EP1581347A2
Application number: EP03813057A
Authority: EP
Inventors: Eva Maria Moser; Heidi Hopp
Original assignee: Wipf AG
Current assignee: Wipf AG
Priority date: 2002-12-17
Filing date: 2003-12-17
Publication date: 2005-10-05
Anticipated expiration: 2023-12-17
Also published as: AU2003303016A1; EP1581347B1; US20060165975A1; WO2004054728A2; WO2004054728A3; ATE423633T1; DE50311232D1

Abstract

Substrates which are coated with a polar plasma-polymerized coating of a thickness (d) in the nanometer range, the coating having multi-functional properties with long-term stability. The process gas contains at least one hydrocarbon that can be substituted and at least one inorganic gas. In a first zone or stage, the substrate is coated using process gases that contain at least one hydrocarbon compound, at least one hydrocarbon compound comprising functional groups containing nitrogen or nitrogen and oxygen and/or at least one inorganic gas containing nitrogen or nitrogen and oxygen. A second zone or stage uses process gases that are devoid of nitrogen and comprise at least one hydrocarbon compound, at least one hydrocarbon compound with functional groups that contain oxygen and/or at least one inorganic gas containing oxygen. The two stages permit a corresponding lower and upper coating to be applied to the substrate.

Description

Substrate with a polar plasma polymerized layer

The invention relates to a method for coating substrates with a polar plasma-polymerized layer with a thickness in the nanometer range, which has long-term stable, multifunctional properties, the process gas each containing at least one also substituted hydrocarbon compound and at least one inorganic gas. The invention further relates to a coated substrate produced by this method and its use.

It has been known for some time to coat all types of substrates with a thin plasma-polymerized layer. The originally poor adhesion of paints, varnish, etc. to the substrate and / or the poor wettability of the substrate could be improved with the introduction of low-pressure plasma processes, especially with regard to the long-term values. The coating of substrates, in particular also of flexible polymeric substrates, takes place, inter alia, with a view to the surface quality. It is often also necessary to protect the substrate chemically, physically and / or mechanically. If the plasma-polymerized layer has to perform several functions at the same time, one speaks of a multifunctional layer.

From US 4465738 A an organic substrate and a method with a coating is known which consists of a lower layer of a plasma-polymerized alkane, for example methane, and an upper layer of a plasma-polymerized polar organic component. The coating is characterized by improved wettability and hydrophilicity.

A breakthrough was achieved with WO 99/39842 A1. Anhydrous process gases are used to produce a polar coating by means of plasma polymerization, which means that with this use with at least one each substituted carbon water compound with up to 8 carbon atoms and an organic gas a long-term stability not previously achieved can be achieved. The plasma coating has an initial surface tension of at least 45 mN / m, which remains unchanged for at least one year. The layer thicknesses are usually less than 100 nm, i.e. in the nanometer range. According to the paragraph bridging pages 5 and 6 of WO 99/39842 A1, all low-pressure plasma processes are suitable for carrying out the process, for example at a pressure of 1.6 x 10 ^"2 mbar. A series of examples is shown in Table 1 of WO 99/39842 A1 In summary, the use of these polar, long-term stable layers is extraordinarily diverse as a result of the adhesion imparting, ie the improved adhesion to polar substances and materials, especially the printability, the scratch protection, an anti-fog effect and the weldability.

The object of the present patent application is to provide a method for coating a wide variety of substrates with a plasma-polymerized layer and a product of the type mentioned at the outset, which further improve the properties even with an expanded substrate base, in particular the adhesion to the plasma-polymerized layer and increase this layer on the substrate.

With regard to the method, the object is achieved according to the invention in that

in a first zone or stage with process gases which contain at least one hydrocarbon compound, at least one hydrocarbon compound with nitrogen-containing or nitrogen- and oxygen-containing functional groups and / or at least one nitrogen-containing or one nitrogen- and oxygen-containing inorganic gas,

in a second zone or stage with nitrogen-free process gases which contain at least one hydrocarbon compound, at least one hydrocarbon contain oxygen compound with oxygen-containing functional groups and / or at least one oxygen-containing inorganic gas,

is coated. Special and further developing embodiments of the method are the subject of dependent patent claims.

With the method according to the invention, long-term stable, plasma-polymerized polar protective layers are possible using efficient gas mixtures which can be used regardless of the pressure range and the type of discharge. A way for the combination of several layers for multifunctional properties is shown. In the case of more than two layers, it is essential to the invention that the layer deposited directly on the substrate contains nitrogen, and the uppermost layer is nitrogen-free but contains oxygen.

Polar plasma layers which contain functional groups containing oxygen and / or nitrogen can be produced even at pressures far higher than is customary in low-pressure processes. a. Because a certain proportion of air does not harm the processes, but can even be useful, a pressure range of up to 1000 mbar is possible. Under these conditions, practically all known plasma coating techniques can be used for planar or three-dimensional workpieces.

The plasma layer according to the invention can be connected upstream or downstream of a production step almost as desired, irrespective of whether the workpiece has already been introduced into a vacuum chamber and subsequently z. B. a metallization takes place or whether it is an adhesion-promoting coating taking place at atmospheric pressure before printing. The workpiece can also be used directly as an anti-fog functional layer.

The surface of the plasma-coated workpieces can be smoother than that untreated substrate. Softer surface contours favor surface wetting and thus the essential antifog effect. The nitrogen-containing process gases of the first zone or stage on the one hand ensure good anchoring of the plasma layer on the substrate and on the other hand, depending on the control of the process parameters (power, gas mixture), can smooth and / or structure or modulate the surface to a greater or lesser extent. The main reason for this effect is the caustic effect of aggressive gases, such as laughing gas, ammonia and oxygen, especially if these gases are added with an increased proportion.

XPS (X-ray photoelectron spectroscopy) measurements confirm or confirm the expected enrichment with oxygen and nitrogen and the incorporation of oxygen, in particular as hydroxyl, carbonyl or carboxyl (ester) groups.

The plasma-polymerized layers deposited according to the invention are distinguished by their controllable multifunctionality; the plasma layer can be adapted to the respective application by varying parameters. The long-term stability is common to all plasma-polymerized layers produced according to the invention. Another property that is usually required is a permanently high surface tension of the plasma-polymerized polar layers, which are therefore hydrophilic, which also means good adhesion to emulsion paints. Further examples of the multi-functionality of the polar layers are the mentioned anti-fog effect, the formation of a scratch protection layer, a barrier layer against additives, gases and liquids, which migrate from the substrate to the surface or from the environment. the surface can be deposited, or a flame retardant layer.

The plasma-polymerized layers are preferably deposited at a process pressure p between 10 ^-3 and 1000 mbar, in particular between 0.1 and 500 mbar. For the reasons mentioned, the process pressure is significantly higher than in comparable conventional methods, in particular also than according to WO 99/39842. The plasma reactor is expediently pumped down to a base pressure which is lower than the process pressure, preferably at least about ten times lower, and then filled with process gas. After a coating process below 1000 mbar, the plasma reactor is flooded with, for example, air, nitrogen or argon until normal pressure is reached and the reactor can be opened. Flooding with argon is too expensive for most processes; air is usually sufficient for this.

The organic compound in the process gas can be a pure hydrocarbon compound or a hydrocarbon compound with substituted functional groups, in particular oxygen and / or nitrogen-containing polar functional groups.

The hydrocarbon compounds themselves can be of various types:

- Alkanes, for example methane, ethane, propane

- Alkenes, for example ethylene, propylene

- alkynes, e.g. acetylene - polyenes, i.e. Hydrocarbons with multiple double bonds

each in aliphatic, alicyclic or aromatic form, without or with branching.

Acetylene (C ₂ H ₂ , ethyne) in particular is used as the layer-forming process gas, the other process gases contribute to the functional groups and can therefore also remove atomic layers from the surface.

As mentioned, the hydrocarbons can be substituted with halogens, such as chlorine and / or fluorine, or with functional polar groups. Examples of functional polar groups are hydroxyl, carbonyl, carboxylic acid, carboxyl ester, amine, imine, amide and / or conjugated nitrile groups. When process gases containing silicon are admixed, functional groups containing SiO _{x are} additionally generated in the upper and / or lower layers, thereby increasing the oxygen content. Partly carbon atoms can also be replaced by silicon atoms.

For both substituted and unsubstituted hydrocarbon compounds, it is advantageous if the molecules contain up to a maximum of eight carbon atoms.

The inorganic component of the process gases advantageously comprises oxygen, carbon dioxide, carbon monoxide, nitrogen, NOx, ammonia, hydrogen, at least one halogen and / or at least one noble gas, but is preferably anhydrous.

The process gases for the deposition of the lower and upper layers differ fundamentally only with regard to the nitrogen and / or oxygen content.

The two-stage coating according to the invention is also indicated in particular for food packaging. It has been found that nitrogen-containing gases clean the substrate surface with the formation of a CN bond. This also leads to better anchoring of the functional polar groups, which in turn leads to a higher chemical resistance. On this underlayer, which can also be very thin, e.g. B. about 0.3 nm, a nitrogen-free, oxygen-containing top layer is deposited, so that the nitrogen-containing layer cannot come into contact with food or other nitrogen-sensitive objects.

Two plasma sources are advantageously used for the deposition of a lower and an upper layer. In the first zone / plasma source, for example, a gas mixture containing nitrogen, oxygen and hydrocarbon is supplied and an underlayer is deposited on the substrate. With the second zone / plasma source, a nitrogen-free, oxygen-hydrocarbon process gas mixture containing a top layer deposited on the bottom layer. Plasma chambers with two plasma sources as used here are known to the person skilled in the art.

According to a further variant, a single plasma source can be used and the nitrogen-hydrocarbon-containing or nitrogen-oxygen-hydrocarbon-containing gas mixture can be introduced first, and the oxygen-hydrocarbon-containing process gas mixture can be introduced in the second pass.

With regard to the product, the object is achieved according to the invention in that a plasma-polymerized polar layer in the nanometer range is applied as a nitrogen-containing lower layer applied to the substrate and a nitrogen-free, oxygen-containing polar top layer applied thereon. Special and further developing embodiments of the product result from the dependent patent claims.

The nitrogen-containing underlayer preferably has a proportion of 40 to 90% of the total layer thickness, the polar top layer a proportion of 60 to 10% of the total layer thickness, preferably about 50% each. The total layer thickness is preferably in the range from 1 to 100 nm. The coated substrates can be welded to one another.

In a layer with a top and bottom layer made of hydrocarbon compounds with oxygen-containing functional groups, the oxygen / carbon ratio is preferably in the range from 0.03 to 0.8, in the bottom layer the nitrogen / carbon ratio is in the same range , The polar top layer, averaged in the uppermost about 2 nm, ie on the surface, preferably has an oxygen / carbon ratio of 0.2 to 0.6, preferably 0.3 to 0.5 and a permanent surface tension of at least 50 mN / m. Carboxyl groups which increase the oxygen content can be formed on the surface of the top layer. With the high surface tension, a good anti-fog effect is guaranteed tet, especially with a suitable surface topography.

The layer according to the invention can be deposited on all types of substrates, for example on polymeric, glass-like, ceramic, metallic or natural surfaces, in particular on a polycarbonate, polyethylene terephthalate, polypropylene, polyethylene, polyamide, fluoropolymer, wool, cotton, silk, glass, Ceramics or composite materials or composite materials, all materials (including natural ones) in the form of foils, moldings, containers, textiles, nonwovens, membranes, granules, powders, fibers, grids and yarns, containers as well as in the form of coated, activated or treated surfaces of all kinds of materials.

A product according to the invention is explained in more detail with reference to a layer structure shown schematically in FIG. 1. This figure shows a coated substrate 10 with a substrate 12, an underlayer 14 and an upper layer 16. The two polar plasma-polymerized layers 14, 16 in the present case have a total thickness d of about 10 nm in the present case. The underlayer 14 contains nitrogen, it shows excellent adhesion to substrate 12. A possible amine formation due to the lower layer 14 could have a disadvantage. This disadvantage is prevented by the oxygen-containing, but low-nitrogen to nitrogen-free top layer 16.

Example: multi-layer deposition with a microwave discharge

A thin underlayer 14 is deposited on a substrate 12 with a microwave source at 2.45 GHz using a process gas mixture of ethylene, carbon dioxide, laughing gas and argon, which is introduced in the first zone at the plasma source or at the first plasma source. In the second zone or the second plasma source, the gas mixture of ethylene, carbon dioxide and argon is introduced in order to produce the upper layer. With a pressure range of 0.01 to 320 mbar and a power range of 60 to 2000 watts, polyester, polypropylene pylene and polyethylene surface tensions of 54 to 75 mN / m, which have a polar fraction of 23 to 51 mN / m and characterized with an oxygen to carbon ratio of 0.3 to 0.5 and a carboxyl to carbonyl group ratio of 0.2 to 1.2 are. The surface tension can also be controlled via the feed speed, among other things. The ratio of oxygen to carbon and the ratio of carboxyl to carbonyl groups in the uppermost atomic layers of the deposited layers was determined using surface-sensitive XPS (photoelectron spectroscopy).

The same layer properties can also be achieved with all other types of discharge, each with excitation frequencies from zero to 20 GHz and with or without magnetic field support. Examples include DBDs (Dielectric Barrier Discharges), low-pressure to atmospheric-pressure glow discharges, APNEDs (Atmospheric Pressure Non-Equilibrium Discharges), surface Discharges, plasma nozzles and plasma broad-beam burners.

Claims

claims

1. Method for coating substrates (12) with a polar plasma-polymerized layer with a thickness (d) in the nanometer range, which has long-term stable, multifunctional properties, the process gas each containing at least one also substituted hydrocarbon compound and at least one inorganic gas,

characterized in that

in a second zone or stage with nitrogen-free process gases which contain at least one hydrocarbon compound, at least one hydrocarbon compound with oxygen-containing functional groups and / or at least one oxygen-containing inorganic gas,

is coated.

2. The method according to claim 1, characterized in that with a process pressure (p) of 10 ^{~ 3} <p <1000 mbar, preferably 0.1 <p <500 mbar, is coated.

3. The method according to claim 1 or 2, characterized in that with process gases, the organic components hydrocarbon compounds with up to a maximum of eight carbon atoms, and as inorganic components oxygen, nitrogen, hydrogen, carbon dioxide, carbon monoxide, nitrogen oxides, ammonia, contain at least one halogen and / or at least one noble gas, is coated.

4. The method according to any one of claims 1 to 3, characterized in that the lower and / or upper layer (14, 16) is deposited with additional silicon-containing process gases.

5. The method according to any one of claims 1 to 4, characterized in that with a process gas, the aliphatic, alicyclic and / or aromatic hydrocarbon compounds, preferably with functional polar groups, such as hydroxyl, carbonyl, carboxylic acid, carboxyl ester, amine , Imine, amide and / or conjugated nitrile groups, contains, is coated.

6. The method according to any one of claims 1 to 5, characterized in that the nitrogen-containing or nitrogen- and oxygen-containing lower layer (14) with a first plasma source, the oxygen-containing upper layer (16) with a second plasma source, or the lower layer (14) and Top layer (16) from the same plasma source with applied or alternating process gases is applied to different zones.

7. Coated substrate (10) with at least two multifunctional layers (14, 16) deposited by means of plasma polymerization and made of hydrocarbon compounds,

characterized in that

a plasma-polymerized polar layer (14, 16) in the nanometer range is applied as a nitrogen-containing lower layer (14) applied to the substrate (12) and a nitrogen-free, oxygen-containing polar top layer (16) applied thereon.

8. Coated substrate (10) according to claim 7, characterized in that the nitrogen-containing or nitrogen- and oxygen-containing lower layer (14) accounts for 40 to 90%, in particular about 50%, of the total layer thickness (d) and the top layer (16) accounts for 60 to 10%, especially about 50%, of total layer thickness (d), the layer thickness preferably being 1 to 100 nm.

9. Coated substrate (10) according to claim 7 or 8, characterized in that the nitrogen / carbon and / or the oxygen / carbon ratio in the range of 0 in the plasma-polymerized polar layer (14, 16) of substituted hydrocarbon compounds , 03 is 0.8, in the lower layer (14) the nitrogen. Carbon ratio in the same range.

10. Coated substrate (10) according to one of claims 7 to 9, characterized in that the polar top layer (16), averaged in the uppermost approximately 2 nm, a carbon / oxygen ratio of 0.2 to 0.6, preferably of 0 , 3 to 0.5, and has a permanent surface tension of preferably at least 50 mN / m.

11. Coated substrate (10) according to one of claims 7 to 10, characterized in that it can also be welded with plasma-polymerized polar layer (14, 16).

12. Use of the coated substrate (10) according to one of claims 7 to 11 as an adhesion-promoting layer (14, 16) for any polar material or any substance, as food packaging or as an anti-fog layer.

13. Use of the coated substrate (10) according to claim 12 for an antifog layer, in particular in the food sector.

14. Use of the coated substrate (10) according to claim 12 as Protective layer against migration to the surface, as a bilateral barrier for gases, additives and liquids, as protection against degradation and / or scratch protection.