DE102017108831A1 - Electrically conductive adhesive film - Google Patents

Abstract

The present invention relates to an electroconductive adhesive film comprising at least one adhesive layer comprising or consisting of an amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms; and at least one conductive layer comprising or consisting of conductive non-metallic nanoparticles. In addition, the present invention relates to the use of such an adhesive film for coating or bonding substrates, as well as a corresponding composite and method for producing such a composite.

Description

The present invention relates to an electroconductive adhesive film comprising at least one adhesive layer comprising or consisting of an amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms; and at least one conductive layer comprising or consisting of conductive non-metallic nanoparticles. In particular, the present invention also relates to an electrically conductive adhesive film which responds to a stimulus. Moreover, the present invention relates to the use of an adhesive film according to the invention for coating or bonding substrates, as well as a composite of an adhesive film according to the invention and one or more substrate (s) and methods for producing a composite according to the invention.

Submicroscopic conductive layers are used in sensor electronics for the detection of current signals and capacitance measurements. As electrode material, they can be used for photovoltaic applications or (organic) light-emitting diodes. The use of ITO (indium tin oxide) layers as electrode material for photovoltaic cells, which are vapor-deposited in a vacuum process, is widespread. Even electrochromic glasses whose transparency changes when an electrical voltage is applied and which can thus become "smart windows" require a conductive glass substrate and, for example, FTO glasses are used which are equipped with fluorine-doped tin oxide. Graphene or (partially) reduced graphene oxide is gaining in importance.

Graphene monolayers are usually applied to substrates in gas phase processes (eg PVD or CVD, see WO 2012174040 A1 ). Graphene composites (eg graphene / polystyrene composites) have also been described, which show percolation threshold concentrations of between 0.1 and 1% by weight, which should allow the production of conductive layers as soon as the composite layer thicknesses are at least 100 nm ( Stankovich et al., Nature, 442, 2006, 282-286 ). If transparent matrices are used, such composites are highly transparent.

According to Zhu et al. (Advanced Materials, 22, 2010, 3906-3924) be transparent (at least 70% transmission) graphene-based layers by spin coating, dip or spray coating with graphene oxide formulations (and subsequent reduction, Li et al., Nature Nanotechnology, 3, 2008, 101-105), by vacuum filtration of graphene oxide suspensions ( and subsequent reduction), by Langmuir-Blodgett method, or by transfer of graphene material grown in CVD processes. The optical transmission as a function of the number of graphene layers (in pure graphene films) is described in Zhu et al. (Europhysics Letters, 108, 17007, 2014) and is about 75% at 10 plies.

Low electrical layer resistances with high transmission at the same time allow graphene layers produced by CVD ( Loh et al., Nature Chemistry, 2, 2010, 1015-1024 ). Only in this manufacturing method, which requires a vacuum system during manufacture, are nanometer thin, transparent and highly conductive layers obtained. The adhesion of such layers to substrates as well as to lying layer systems is determined by comparatively weak van der Waals forces.

US2011 / 012164 A1 discloses sandwich composite structures within which two graphene layers are connected via a one-dimensional nanostructure. Transparent and conductive films of single-walled carbon nanotubes (SW-CNT) and fullerenes are off US09315679 B2 known.

Layer-by-layer self-organization-based graphene oxide (GO) / polyelectrolytes nanocomposite films and their use as moisture sensors are out Zhang et al. (Sensors and Actuators B: Chemical, 203, 2014, 263-270 ) known.

Poly (diallyl dimethyl ammonium chloride) (PDDA) serves as a positively charged poly (sodium 4-styrenesulfonate) (PSS) as a negatively charged polyelectrolyte sublayer system. The adhesion to substrates is determined here by the adhesion of PDDA or PSS to the substrate. The nano-layer sequence is disclosed as PDDA-PSS-PDDA-GO-PDDA-GO. The layer spacing between graphene oxide layers is 0.776 nm. The sensors are after the immersion of the substrate in successive steps (and intermediate rinsing steps) dried for two hours at 50 ° C and finally read capacitive.

Su et al. (Sensors and Actuators B: Chemical, 200, 2014, 9-18) describe resistively read moisture sensors, which are applied in layer-by-layer processes using graphene oxide on aminoalkylthiol-functionalized gold electrodes and partially reduced by means of NaBH ₄ .

The covalent attachment of reduced graphene oxide (rGO) to aminopropyltriethoxysilane (APTES) -modified SiO ₂ / Si layers is described in Ou et al. (Langmuir, 26 (20), 2010, 15830-15836). APTES can be attached via condensation reactions to hydroxide groups on substrate surfaces. The terminal, primary amino group of modified surface covalently binds to the GO layer.

The transparent and conductive ultrathin, continuous and homogeneous graphene films of exfoliated graphene oxide (or graphite oxide) by dip-loading of hydrophilic substrates (such as pretreated quartz) at 70 ° C and subsequent thermal reduction (for example at 550 ° C to 1100 ° C) can be produced in Wang et al. (Nano Letters, 8 (1), 2008, 323-327) described.

Also known is the formation of two-layer systems based on GO, on which a polypeptide (eg polylysine) is adsorbed ( Zhang et al., Biosensors & Bioelectronics, 42, 2013, 112-118) ,

Vacuum or gas phase processes for coating substrates are usually complex and expensive. Multi-stage methods such as layer-by-layer processes e.g. using differently charged polyelectrolytes usually require a whole series of intermediate rinsing and / or drying steps and are therefore also not efficient. A solid, in particular covalent, binding of the conductive layers is generally possible only on specially modified substrates.

It was therefore an object of the present invention to provide materials and methods with which submicroscopic conductive layers can be applied to the widest possible spectrum of substrates with as little effort as possible and a stable adhesion is achieved.

In addition, it was also an object of the present invention to provide conductive layers which have such good adhesive properties that they are also suitable for bonding two or more substrates.

Another object of the present invention was to provide conductive layers that are sensitive to stimulus, particularly through measurable conductivity / capacitance changes.

Finally, it was also an object of the present invention to provide possibilities to selectively control the stacking of conductive layers as well as to facilitate the release of substances from the layers.

1. (i) mindestens eine Haftschicht, welche ein amphiphiles Polymer, das funktionelle Gruppen mit basischen und bevorzugt nukleophilen Stickstoffatomen enthält, umfasst oder daraus besteht; und
2. (ii) mindestens eine Leitschicht, welche leitfähige, nichtmetallische Nanopartikel umfasst oder daraus besteht.

These objects are achieved according to the invention by an electrically conductive adhesive film comprising

1. (i) at least one adhesive layer comprising or consisting of an amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms; and
2. (ii) at least one conductive layer comprising or consisting of conductive non-metallic nanoparticles.

• - ein Stromsignal ausgelesen (z.B. Leitfähigkeitsmessung)
• - eine Kapazitätsmessung durchgeführt (z.B. Feuchtesensorik, chemische Sensorik)
• - um als Sensor zur Ermittlung des Zustands oder von Änderungen des Zustands an Grenzflächen von Polymerschichten enthaltenden Verbunden verwendet zu werden
• - um als Elektrodenmaterial für photovoltaische Anwendungen verwendet zu werden
• - um als Elektrodenmaterial für (flexible), (organische) Leuchtdioden (OLEDs) verwendet zu werden.

oder aktiv:

• - ein resistives Erhitzen durchgeführt,
• - eine elektrische Polarisation durchgeführt,
• - um eine Anti-Eis-Wirkung oder anti-Fouling zu erzielen.

In preferred applications of coatings according to the invention, an electrical voltage is applied to them and passively:

• - read out a current signal (eg conductivity measurement)
• - a capacitance measurement carried out (eg humidity sensor, chemical sensors)
• to be used as a sensor for determining the state or changes in state at interfaces of polymer layer-containing composites
• - to be used as electrode material for photovoltaic applications
• - to be used as electrode material for (flexible), (organic) light-emitting diodes (OLEDs).

or active:

• - performed a resistive heating,
• - performed an electrical polarization,
• - to achieve an anti-ice effect or anti-fouling.

An adhesive film, in the context of the present invention, also serves to determine the adhesion in an adhesive zone, i. the adhesive film causes at least partially either one or both sides of an adhesion.

Sensor electronics can be operated with voltages up to 10 V at currents in the microampere range and with layer resistances of a few megohms. Adhesive films according to the invention not only have a broad adhesion spectrum (to substrates and overlying layers), but they are preferably also only a few nanometers thick, but sufficiently conductive.

The amphiphilic polymer, which contains functional groups with basic and preferably nucleophilic nitrogen atoms (N-based functional groups), is a surface-active polymer, hereinafter also referred to as "interface active agent". As a polymeric Interfactant is meant a polymeric wettable, molecular wetting agent which wets substrates in such a way that in Direction perpendicular to the substrate surface one or two Interfactant molecule layers. After adsorption on a wide range of different substrate surfaces such Interfactants are within a time that is above a typical layer formation process time (about one hour), no longer washable with water from the substrate. N-based functional groups with basic and preferably nucleophilic nitrogen atoms have a free electron pair on the nitrogen, which is protonated as a base and may optionally also act as a nucleophile. Such groups may be, for example, amine and amide groups. Further possibilities are described below. Preferred polymers are, for example, in DE 10 2014 221 181 A1 called, for example, laccase or bovine albumin (BSA) or polymer mixtures containing these polypeptides. In addition, polysaccharides such as maltodextrin, metallic or complexed metal ions or salts containing materials may be included in these layers.

(Complexed) metal ions and polysaccharides essentially control the behavior of the adhesive layers in themselves (cohesively) and in interaction with surrounding conductive layers (adhesively). Thus, during the wet-chemical layer production, they have an effect on the formation, structure and composition of the adhesive films. During cure / conditioning of the films in the conversion of GO into (partially) (thermally) reduced GO, (complexed) metal ions and polysaccharides affect the internal film structure and the structure of the film interfaces, such as the formation of wrinkles in the conductive layers during conditioning. (Complexed) metal ions can in particular catalyze crosslinking reactions between interferants and GO and thus allow at lower temperatures than in the non-catalyzed case. In cured / conditioned adhesive films, (complexed) metal ions and polysaccharides as an additional layer component affect the response of the adhesive layers (and thus also the adhesive films) to stimuli, i. they change them (ie increase or decrease or allow or make specific) by influencing the conductivity and / or the water absorbency and / or the swelling behavior when absorbing water. In particular, they can interact laterally with the other adhesive layer constituents in the presence or absence of the external stimuli (ie in the direction parallel to the layer plane) and change the adhesive layer structure and the adhesive layer structure, complexed metal ions e.g. by coordinative crosslinking and polysaccharides act as hydrophilic spacers. Finally, vertically (ie in the direction perpendicular to the layer plane), they can also influence the (adhesive) interaction between the adhesive layer and one (or both) of the surrounding conductive layers.

The adhesion of laccase to silica, carbon or magnesium surfaces has already been described ( Corrales Ureña et al., Applied Adhesion Science, 2016, 4: 2; Corrales Ureña et al., Applied Surface Science, 385, 2016, 216-224 ; Stamboroski et al., Applied Adhesion Science, 2016, 4: 6 ), such as the adhesion of bovine albumin to silica surfaces ( Jachimska et al., Colloids and Surfaces A: Physicochemical and Engineering Aspects, 489, 2016, 163-172 ).

Such polymers allow the conductive material to be materially joined and bonded to substrates. The electrically conductive material thus has, on the one hand, over its underside a full-surface adhesion to different substrates, such as e.g. Carbon, polymers, metals and ceramics and on the other hand, the adhesion behavior of the top is also fully adjustable, e.g. by applying a further adhesive layer. The film thickness can also be adjusted by stacking alternating adhesive and conductive layers. The adhesive film of the invention, the adhesion to different, even in turn layer-forming materials, for. As well as adhesives, mediate and thus used for the variable structure of different layer structures.

As a conductive layer former, e.g. Nanoparticles of (partially) reduced graphene oxide, carbon nanotubes, carbon black or a mixture of the aforementioned materials in question. Preferred nanoparticles are described below.

According to one embodiment of the present invention, the adhesive film has a thickness of less than 100 nm, preferably less than 20 nm, particularly preferably less than 10 nm. The light transmissivity of the adhesive film according to the invention may be at least 1%, at least 10%, at least 30%, preferred at least 80%, or more preferably at least 90%.

The adhesive film according to the invention may thus have submicroscopic thicknesses and even be transparent, which may be advantageous for certain optical applications.

Similar to a parallel connection of ohmic resistors, the conductivity is higher for thicker layers. Thus, the conductivities are often given in relation to the layer thickness of the adhesive film, which can be quantified indirectly via the light transmissivity. The numerical values listed below are numerical values for the "combined" measured variable "Conductivity of transparency" with the unit S / m (Siemens per meter).

In the case of the above-described light transmissivities of the adhesive films according to the invention, they are Values for the electrical conductivity (measured between two electrical contact points several millimeters apart with the adhesive film) between 0.1 S / m and 5000 S / m. Preferred values in the case of adhesive films with a light transmissivity greater than 90% (measured at a light wavelength of 550 nm) are between 1 and 500 S / m.

According to a preferred embodiment, the at least one adhesive layer and / or the at least one conductive layer is in each case a monolayer.

In the context of the present invention, a monolayer or a single layer means an arrangement in which each molecule of the adhesion layer is ideally in contact with the substrate and the nanoparticles of the conductive layer simultaneously or, in the case of alternating adhesion and conductive layers, simultaneously Contact with the nanoparticles of the underlying and overlying conductive layer is. Particularly suitable for the formation of such monolayer as an adhesive layer are polypeptides, in particular globular proteins, such as laccases and albumins. According to one embodiment of the present invention, the individual polymer molecules of the adhesion layer are not crosslinked with one another.

Similarly, a monolayer or a single layer of the conductive layer means that each nanoparticle is in contact with the underlying adhesive layer and optionally simultaneously with the overlying adhesive layer. In this case, according to one embodiment of the present invention, only van der Waals interactions can occur between the interacting agent and the nanoparticles of the conductive layer, while in another embodiment covalent bonds between the interacting agent and the conducting layer formers may occur, as well as a chemically covalent bridging between two adjacent conductive layers ,

According to the invention, a conductive adhesive film is particularly preferred, wherein the conductive, non-metallic nanoparticles of the at least one conductive layer are nanoflakes which are arranged such that they partially overlap.

In the context of the present invention, nanoflakes are to be understood as meaning uneven particles in which one dimension is significantly smaller than the other two and at least one dimension is in the nanometer range. Typical nanoflakes are a maximum of 10 μm wide. A flake is not necessarily completely flat, but overall has a rather flat shape. In the partially overlapping arrangement described above, such nanoflakes are ideally disposed on the adhesive layer such that each flake is in contact with the adhesive layer, but the edge regions of adjacent flakes overlap to form a continuous layer completely covering the adhesive layer. The interaction with the adhesive layer is crucial for the morphology. The effect of the interactant is that if a layer of single-, two- or multi-layered nanoflakes, eg (partially) reduced graphene oxide flakes, or graphene stacks is formed on the substrate, the resulting layer has a maximum of two graphene stack layers. Thick high. This means that as soon as a first adsorbate is bound, a second always binds to a gap (see 2 and 5 ). In 2 For example, a geometric arrangement of conductive layer-forming flakes is obtained, for example, obtained from a graphene oxide dispersion which is option 1 in FIG 3 equivalent. In 5 For example, a geometric arrangement of conductive layer-forming flakes is obtained, for example, obtained from a graphene oxide dispersion which is option 2a in FIG 3 equivalent. The interactant choice thus controls the formation of nanoparticle monolayers as well as the lateral overlap of the conducting layer-forming nanoparticles.

According to the invention, in particular an electrically conductive adhesive film as described above, wherein the polymer in the adhesive layer one or more basic and preferably nucleophilic, N-based functional groups selected from the group consisting of amino groups, amide groups, peptide groups, imide groups, in particular amide groups and imide groups of Carboxylic acids, dicarboxylic acids and polycarboxylic acids, as well as ester amide groups and diamide groups, in particular urethane groups and urea groups.

Polymers bearing the abovementioned functional groups have proven to be particularly suitable for the formation of adhesive films according to the invention. They are soluble in water or (colloidally) dispersible. In a preferred embodiment of the present invention, they are present as single molecules, which are not crosslinked with one another, and they have a molecular weight of 200 to 200,000 g / mol, preferably from 2000 to 100,000 g / mol. In a further preferred embodiment, the amine groups form no covalent bonds with the conductive layer, at least at room temperature. They are characterized by amphiphilic properties and their protonability or deprotonability. At the isoelectric point they are uncharged and have a particularly good adhesion to different substrates. By choosing the pH, they are also reloadable, for example, from positive to negative, which is not readily possible with polyelectrolytes. When using alternating positively and negatively charged polyelectrolyte layers, it is therefore necessary to select materials which are differently charged at the same pH. The polymers of the invention are on the other hand, it is able to connect the conductive layer as a monolayer to various substrates.

• a = 0-3,
• b = 1-5,
• A eine Brückenstruktureinheit ist,
• R¹ unabhängig voneinander H oder ein aliphatischer, aromatischer, olefinischer, cyclischer, heterocyclischer, polycyclischer oder polyheterocyclischer Rest ist,
• R² unabhängig voneinander ein polymeres Grundgerüst ist,
• X unabhängig voneinander eine funktionelle Gruppe ist ausgewählt aus der Gruppe bestehend aus Amiden oder Imiden von Carbonsäuren, Dicarbonsäuren und Polycarbonsäuren,
• und wobei die Molmasse des Polymers vorzugsweise zwischen 200 und 10.000, besonders bevorzugt zwischen 400 und 6.000 g/mol liegt,

enthält oder daraus besteht.Particularly preferred according to the invention is an electrically conductive adhesive film, wherein the at least one adhesive layer is a polymer having the formula (R ¹ ) _a A (R ² X) _b in which

• a = 0-3,
• b = 1-5,
• A is a bridge structure unit,
• R ^{1 is} independently H or an aliphatic, aromatic, olefinic, cyclic, heterocyclic, polycyclic or polyheterocyclic radical,
• R ^{2 is} independently a polymeric backbone,
• X is independently a functional group selected from the group consisting of amides or imides of carboxylic acids, dicarboxylic acids and polycarboxylic acids,
• and wherein the molecular weight of the polymer is preferably between 200 and 10,000, more preferably between 400 and 6,000 g / mol,

contains or consists of.

The molar mass of the polymers can be determined here in each case by matrix assisted laser desorption ionization - time of flight mass spectrometry (MALDI-TOF-MS).

Such polymers are made DE 10 2012 217693 A1 which discloses its role as a corrosion inhibitor for the surface of metals. The term "bridge structural unit" means a non-polymeric organic structural element as in DE 10 2012 217693 A1 described. Surprisingly, these polymers have also proved to be particularly suitable adhesion-promoting agents.

Particularly preferred according to the invention is an electrically conductive adhesive film as described above, wherein the at least one adhesive layer comprises or consists of a polypeptide or protein having a molecular weight between 200 and 200,000, preferably between 2,000 and 100,000 g / mol, in particular laccase or an albumin.

Polypeptides or proteins are particularly suitable for forming the molecular monolayers according to the invention. In particular, laccases and albumins can form globular structures, which can mediate as a single molecule directly the contact between the substrate and the conductive layer or between two layers.

Further according to the invention is an electrically conductive adhesive film as described above, wherein the at least one adhesive layer comprises a mixture of at least one polymer having the formula (R ¹ ) _a A (R ² X) _b as defined above and at least one polypeptide or protein having a molecular weight between 200 and 200,000, preferably between 2000 and 100,000 g / mol, in particular laccase or an albumin, comprises or consists thereof.

According to one embodiment of the present invention, the adhesive film is at least partially responsive to a stimulus.

If the adhesive film according to the invention is stimulus-responsive, it can act like a sensor element. A stimulus is to be understood as meaning any external influence which can cause one of the reactions described below. As a response to a stimulus, for example, there is a geometric deformation of the adhesive film, which can be detected microscopically, ie by electron microscopy or scanning probe microscopy. The adhesive layer can deform in the first line and the conductive layer in contact with the adhesive layer. However, if the deformation of the adhesive layer is, for example, in a swelling, primarily only the distance between two adjacent conductive layers or between the conductive layer and the substrate changes (see 2 ).

• - mechanische Verformung (Dehnung, Scherung), also vor allem eine elastische (komplett reversible) Verformung,
• - Kratzer oder Risse in oder durch den Haftfilm, also (nicht völlig reversible) Verformung; z.B. durch Ritzen mit einer Skalpellklinge,
• - Temperatur (Geometrieänderung durch Wärmedehnung, Leitfähigkeitsänderung),
• - Eindringen von Medien, z.B. Wasser, Ionen, Gase, Dielektrika wie Lösungsmittel; auch Lösungsmittel in Klebstoffen/Lacken oder Bestandteile aus Mischungen reaktiver Monomere und Präpolymere in Klebstoffen/Lacken),
• - in Nachbarschaft härtende (typischerweise schrumpfende) Mischungen reaktiver Monomere und Präpolymere (in Klebstoffen, Lacken, Beschichtungen),
• - bei transparenten Schichten: Licht (über thermische Wirkung, Änderung der Leitfähigkeit).

Possible stimuli or reactions which ultimately lead to deformations of the adhesive film are, for example:

• mechanical deformation (elongation, shear), ie above all an elastic (completely reversible) deformation,
• - Scratches or cracks in or through the adhesive film, ie (not completely reversible) deformation; eg by scoring with a scalpel blade,
• Temperature (change in geometry due to thermal expansion, change in conductivity),
• - Ingress of media, eg water, ions, gases, dielectrics such as solvents; also solvents in adhesives / lacquers or components of mixtures of reactive monomers and prepolymers in adhesives / lacquers),
• - curing in the neighborhood (typically shrinking) mixtures of reactive monomers and prepolymers (in adhesives, paints, coatings),
• - for transparent layers: light (via thermal effect, change in conductivity).

As a possible (measurable) response (response) comes z. B. an impedance change (electrical conductivity / electrical resistance, capacity) in question.

Such a reaction is particularly advantageous in connection with the "health monitoring" in the case of bonds or composites, especially in the case of fiber / matrix composites, where the adhesive film would be located on the surface of a flat fiber layer (in the case of tissue / scrim / fiber mats) , This reaction is also advantageous in the case of (optical) single-fibers, which are introduced into polymers for "health monitoring", so-called fiber Bragg gratings (FBG sensors). To prove such sensors with the adhesive films according to the invention in addition to the introduction between an adhesive system and a joining part is an essential application of the adhesive film according to the invention.

• - Einsatz Stimulus-responsiver Interfactants. Beispiel: Wasseraufnahme-bedingtes Quellen von Laccase bei Exposition in feuchten oder nassen Medien;
• - Einsatz Stimulus-responsiver Komposite, deren Stimulus-Responsivität nicht auf ein an sich schon für einen betrachteten Stimulus responsives Interfactant resultiert sondern auf eine Stimulus-responsive Substanz zurückgeht, die in die Interfactant-Schicht eingebracht wird und die Responsivität bewirkt (ein Metall, Metallkomplex, Metallsalz).
• - Insbesondere sind schließlich synergistisch Stimulus-responsive Hybride zu nennen (z.B. Laccase ist im Gemenge mit Metallpartikeln anders responsiv als reine Laccase).

The response to an external excitation (stimulus) can be achieved in the Interfactant layer by the following composition of this layer:

• - Use of stimulus-responsive interferants. Example: Water uptake of laccase on exposure in moist or wet media;
• - The use of stimulus-responsive composites whose stimulus-responsiveness does not result in a responsive intrinsic stimulus, but is due to a stimulus-responsive substance that is incorporated into the interacting layer and causes responsiveness (a metal, metal complex , Metal salt).
• Finally, synergistic stimulus-responsive hybrids should be mentioned (eg laccase reacts differently with metal particles than pure laccase).

Another reaction may be the release of the polymer (interferent) from the adhesive layer.

According to a preferred embodiment, the adhesive layer consists of individual interacting molecules which are not crosslinked with one another. As a result of a scribe perpendicular through the adhesive film so Interfactant molecules that are installed between adjacent conductive layers, accessible from the outside and are released on contact with, for example, (rain) water from the Leitschicht space. Now, for example, the corrosion-inhibiting polymers DE 10 2012 217693 A1 - As described above - used, then provide such adhesive films active corrosion protection. This corresponds to an encapsulation of the drug molecules (here the interferants) which is close to the upper / border area. Accordingly, the interactant is encapsulated in a quasi -2D adsorbate phase between the substrate and the conductive layer or between two conductive layers.

According to the invention, the multifunctionality of the interactants is used, which on the one hand function as an adhesive layer during film formation and on the other hand as a release substance when the adhesive film is damaged, deformation of the adhesive film (or of the conductive layer) leading to a change in the impedance, which in turn the "Health Monitoring" can be exploited. The film itself is thus multifunctional, since it also serves as a depot for an active ingredient (the Interfactant).

Particularly preferred according to the invention is an electrically conductive adhesive film as described above, wherein the conductive layer comprises or consists of at least partially reduced graphene oxide.

Graphene oxide, in particular graphene oxide flakes, is preferably used as the conductive layer former. These can be used in an (aqueous) dispersion for layer formation. Graphene oxide flakes have acidic carboxylic acid groups on the edge and above and above the flake plane next to hydroxy, especially epoxy groups. Up to about every fifth carbon atom of the flakes is part of an epoxy / oxirane triplet. In contrast, partially reduced graphene oxide has fewer epoxy groups.

The (partial) reduction of graphene oxide takes place - for example in a conditioning step after formation of the inventive adhesive film or before - by thermal (for example in the convection oven or by resistive heating pre-reduced layers) energy supply, or by photonic or chemical processes. In this case, according to an embodiment of the present invention, covalent bonds are formed between the adhesion layer and the graphene oxide. For example, in-situ wet-in-wet processing occurs in successive dipping or spraying processes, i. with reactive graphene oxide (not with conductive graphene) in the adhesive / lacquer application followed by in situ reduction during curing of the adhesive / lacquer (eg thermal - if isothermal at least 150 ° C, or eg supported by the catalytic effect of the Interfactant layer incorporated transition metal cations).

Also, according to the present invention, an electroconductive adhesive film as described above comprising three, four or more layers (i) and (ii) is in an alternating sequence.

By stacking alternating adhesive layers and conductive layers, variable thickness structures can be produced and the Light transmissivity in the visible and near ultraviolet spectral range are controlled.

According to another embodiment of the present invention, the above-described electrically conductive adhesive film has wrinkles.

The folding can be controlled so that unfolded to highly folded structures can be formed on a scale of 0 to 10. Being folded up means that, starting from a 10 nanometer thin film, wrinkle heights greater than 30 nanometers can be achieved. In this case, the measurement of the pleat height takes place relative to the film level.

• - der Haftfilm einseitig haftet, also als Beschichtung eingesetzt ist. Dann entsteht eine nanostrukturierte Schichtoberfläche. Liegt diese nanostrukturierte Schicht auf einem mikrorauen Substrat (liegen also zwei Rauheits-„Niveaus“ vor, „Lotuseffekt“), so können superhydrophobe (oder auch superhydrophile) Oberflächen hergestellt werden. Diese können Wassertropfen abperlen lassen oder auch eine Anti-Fouling-Wirkung (Bewuchshemmung) hervorrufen.
• - der Haftfilm beidseitig haftet, weil die Wechselwirkung mit die Haftschicht umgebenden Medien (oder Monomeren, Polymeren), die Verformungsneigung (z.B. horizontallaterale Dehnbarkeit) der Leitschicht sowie die Impedanz der Leitschicht (Kapazität oder Leitfähigkeit) und deren Stimulus-Reaktion von den Falten beeinflusst werden.

The wrinkling in the conductive layer leads to a (re) structuring of the adhesive film. This is relevant if:

• - The adhesive film is liable on one side, that is used as a coating. Then a nanostructured layer surface is created. If this nanostructured layer lies on a microrough substrate (ie two roughness "levels", "lotus effect"), then superhydrophobic (or even superhydrophilic) surfaces can be produced. These can cause drops of water to bead off or even cause an anti-fouling effect (inhibition of growth).
• - The adhesive film adheres to both sides, because the interaction with the adhesive layer surrounding media (or monomers, polymers), the tendency to deformation (eg horizontal lateral extensibility) of the conductive layer and the impedance of the conductive layer (capacitance or conductivity) and their stimulus reaction are influenced by the wrinkles ,

So far, for example, wrinkling could be targeted by mechanical deformations of "flat" layers ( Chen et al., Advanced Materials, 28, 2016, 3564-3571 ) can be achieved; According to the invention, wrinkling is achieved by interactions between interferants and graphene oxide (during thermal reduction) and is influenced / controlled by polysaccharides or metal ions in the subbing layers.

Thus, according to the invention, particularly easily folded folded conductive layers can be produced. While the primary goal to date has been to produce as flat, highly conductive graphene layers as possible, folded structures are particularly suitable for use in sensors because their conductivity (impedance) is particularly sensitive to stimuli, i. that small changes can be recorded, but no particularly high conductivity is necessary.

Another aspect of the present invention relates to the use of an electrically conductive adhesive film as described above for coating one or joining two or more substrates.

According to the present invention, not only the (entire) adhesive film adheres to the substrate or adherend, but also the surface of the adhesive film is liable to promote adhesion to other layers (e.g., primer or adhesive). If the adhesive film is e.g. placed in the substrate-near zone of a bond, it determines the adhesion. The total adhesive film thus serves the adhesion control in the bond. It is assumed that unlike the LbL (layer-by-layer) deposition based on alternating electrostatic charges (pos., Neg., Pos., Neg.), Van der Waals forces occur in the adhesive film of the invention and optionally after reaction between on the one hand primary and secondary amino groups (as nucleophile) and on the other hand epoxy groups of graphene oxide also covalent bonds.

Advantageously, the adhesive film of the invention can be used on a wide variety of substrates, wherein the substrate surfaces need not be flat but may also be curved or irregular. In this case, the electrical conductivity of the adhesive film according to the invention also remains when bending flexible substrates.

The invention therefore provides a use as described above, wherein the substrate (s) are each independently rigid or flexible, transparent or non-transparent, preferably selected from the group consisting of polymers, ceramics, oxides, metals and composite materials. In particular, primers and / or adhesives can also be applied to the adhesive film according to the invention for further applications.

The present invention also relates to a composite comprising at least one substrate and an electrically conductive adhesive film as described above, wherein the at least one adhesive layer covers at least a part of at least one surface of the substrate.

Also preferred is a composite, wherein the electrically conductive adhesive film interconnects at least one surface of a substrate and at least one surface of a second substrate.

Particularly preferred is an embodiment in which, after completion of the layer formation process, the layer sequence present on the substrate is terminated in such a way that the surface present at the end of the layer formation process is substoichiometrically covered with interactant, so that when applying further layers (eg, in the adhesion process, the application of a primer or adhesive layer) may occur that components of these further layers covalently with (exposed) functional groups of the (flake-shaped) Leitschichtbildner nanoparticle (meaning especially epoxy Groups in the graphene oxide flakes) can form covalent bonds. In this case, a stimulus-resposive adhesive layer between two (partially) reduced graphene oxide flake conductive layers, terminated by a sub-stoichiometric interfactant layer (cf. 1 ).

1. (a) das Inkubieren mindestens eines Teils einer Oberfläche eines Substrats mit einer Lösung bzw. Dispersion enthaltend ein amphiphiles Polymer, das funktionelle Gruppen mit basischen und bevorzugt nukleophilen Stickstoffatomen enthält, und
2. (b) das Inkubieren mindestens eines Teils derselben Oberfläche mit einer Dispersion von nichtmetallischen Nanopartikeln.

According to a further aspect, the present invention also relates to a method for producing a composite comprising at least one substrate and an electrically conductive adhesive film as described above

1. (a) incubating at least a portion of a surface of a substrate with a solution or dispersion containing an amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms, and
2. (b) incubating at least a portion of the same surface with a dispersion of non-metallic nanoparticles.

According to the invention, a composite of liquid (preferably aqueous) phase is applied to the substrate. The adhesive layer-forming amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms (Interfactant), and the conductive layer-forming nanoparticles are respectively dissolved or dispersed.

Preferred is a method wherein the at least a portion of a surface of the substrate is incubated with a dispersion containing an amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms, and non-metallic nanoparticles.

The process of the present invention can be carried out in a single dip / incubation step when both adhesive layer and conductive layer formers are present in the dispersion simultaneously. The inventive method is more efficient and much less expensive than known from the prior art layer-by-layer processes. A corresponding dispersion containing both an amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms and non-metallic nanoparticles is also in accordance with the invention.

In the method according to the invention, the dispersed, non-metallic nanoparticles may also have, at least on parts of their surface, an adhesive layer of the amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms. Particularly preferably, the interactant is present in the dispersion essentially adsorbed and at best dissolved or dispersed to a slight extent in the dispersion medium. A corresponding dispersion is also according to the invention (see 3 ).

In the dispersion nanoparticles already provided with an adhesive layer can be present, which preferably also react to a stimulus. Such a dispersion containing nanoparticles provided with an adhesive layer, which preferably also react to a stimulus, is likewise in accordance with the invention (see 3 ).

A stimulus-responsive adhesive film may therefore already be present in the dispersed phase during the application, preferably between (at least) two nanoflakes, whose surface facing the dispersion medium need not be stimulus-responsive (see 3 ).

Alternatively, the stimulus-responsive adhesive film may be present in the phase adsorbed on the substrate during application. Preferably, after completion of the adsorption (ie, film formation) process on the substrate (the execution of this film formation process is the "application"), the (at least one) stimulus-responsive layer is sandwiched between (at least) two nanoflakes, and the one turned to the dispersant Adsorbate surface does not have to be stimulus-responsive. The layer sequence present on the substrate after completion of the layer formation process is preferably terminated in such a way that the surface facing the dispersion medium at the end of the layer formation process is under stoichiometrically covered with an interactant, so that when further layers are applied (eg in the adhesion process, the application of a primer or primer) Adhesive layer) may occur that components of these further layers covalently with (exposed) functional groups of the (flake-shaped) Leitschichtbildner- nanoparticle (meaning especially epoxy groups in the graphene oxide flakes) can form covalent bonds.

The dispersed, non-metallic nanoparticles are particularly preferably at least partially reduced graphene oxide flakes.

Advantageously, the graphene oxide flakes present in the dispersion during application may already be at least partially reduced, so that no reduction is necessary after the coating process. Such a dispersion is also according to the invention.

The surface of the layer or of the adhesive film according to the invention can be adjusted chemically and morphologically by suitable choice of the process parameters.

chemical:

• • The top (terminating) layer can be GO, that is epoxy groups.
• • The top (terminating) layer can be interactant, ie have adhesion / adhesion-conferring properties (as in DE 10 2014 221 181 A1 considered).

morphologically:

• • The layer surface can be flat parallel to the substrate.
• • The layer surface can be wrinkled-rough.

6 Figure 4 shows how the adhesive film of the present invention can respond to a stimulus by deformation (stimulus-response) and thus produce a wrinkled-rough morphology of the film surface from a substrate-parallel flat morphology.

The adhesive film according to the invention can ultimately be used as a coating, wherein the uppermost (terminating) layer such as (a lacquer) e.g. exposed to weathering.

According to the invention, in addition to the van der Waals interactions between substrate and graphene oxide nanoflakes emanating from adsorbed interactant molecules, covalent bonds may be formed before the (covalently reactive) epoxy groups in the graphene oxide are decomposed during conditioning, so that the electrical conductivity of the flakes noticeably (to a technically required level) increases.

Due to the process, it is advantageous that further layers can be applied to the uppermost (terminating) layer and firmly adhered, e.g. in the bonding process, the adhesive or a primer (a solution of chemically reactive monomers and prepolymers that "wets" surfaces well with solvent to be evaporated). This terminating layer must therefore be readily wettable and must have no loosely lying (or weakly bonded, physisorbed) molecule layers, but the strongly connected monolayer.

The subject matter of the present invention is also a composite, preferably a composite as described above, which can be produced or produced by a method as described above.

Description of the figures:

1 shows the process result, ie an adhesive film according to the invention, which is formed during the removal of the dispersion. On the substrate (at the bottom) a continuous (stoichiometric) adhesive layer (of interacting molecules) has formed on which overlapping nanoflakes of the conductive layer (shown in black) form a likewise continuous conductive layer as a monolayer. Above this is again a continuous adhesive layer, followed by another conductive layer. Finally, the adhesive film terminates a sub-stoichiometric adhesive layer, meaning that it does not completely cover the underlying conductive layer. This terminating adhesive layer is not necessarily stimulus responsive, while at least one of the lower adhesive layers in one embodiment of the present invention is stimulus responsive.

2 a ) shows the direction of current flow in the conductive layers of an adhesive film according to the invention. 2 b) shows the distance between two conductive layers of an adhesive film according to the invention. The capacitance C is dependent on the swelling state of the intermediate adhesive layer, which optionally deforms the conductive layer. This can be controlled according to the invention. 2 c) shows the distance between a conductive layer of an adhesive film according to the invention with insulating interacting layers and a conductive substrate. The capacitance C is dependent on the swelling state of the intermediate adhesive layer, which optionally deforms the conductive layer. This can be controlled according to the invention.

For the capacitive properties of the adhesive film according to the invention, the following dependencies of the capacitance C apply in general, as for all electrical capacitances $$C={\epsilon }_0{\epsilon }_{r}A\text{/}d$$

Here, ε ₀ denotes the generally known electric field constant, ε _r the relative permittivity of the dielectric used, in this case the material of the adhesive film, A the area of the electrodes which in the present case is essentially determined by the surface of the layers, and the distance d between the individual layers of the adhesive film according to the invention. Apart from the invariable electrical field constant, all parameters can be changed within a wide range by changes in the chemical properties of the layers of the adhesive film according to the invention or by changes in the production process. As a result, therefore, the electrical properties of the adhesive film of the invention can be selectively changed in a wide range.

3 shows which ingredients in the dispersion may be present when applied to the substrate. At the far left, the dispersion contains only the nanoflakes of the conductive layer (Option 1). In the middle left, the nanoflakes are already covered by two adhesive layers (of interacting molecules) (option 2a). Interfactant-covered double flakes are present in the dispersion in the middle right (Option 2b). On the far right, parts of a nanoflake trapped adhesive layer are stimulus-responsive (option 3). The gray bar represents the substrate.

4 shows the advantages of the adhesive film or method according to the invention. At the very top, the interferent concentration was adjusted to substoichiometric, ie below the concentration leading to a saturation occupancy. The nanoflakes (in black) in the dispersion are therefore not completely covered with interactant (4a). In the sketch below, the Interfactant concentration is fully stoichiometric, ie set at saturation. The nanoflakes (in black) are therefore completely covered with interactant (4b).

5 shows that there is no bonding of the adhesive layer to the adhesive layer (Interfactant on Interfactant) (5a), but the already covered with an adhesive layer nanoflakes on gap on the surface of the substrate arrange (ie next to the Erst adsorbate, 5b).

6 shows how the adhesive film according to the invention to a stimulus by deformation responsive (stimulus response) and thus the structure of the flexible flakes of (partially) reduced graphene oxide (as present after reduction) can control. In particular, for example, the internal stresses of the adhesive film which occur during a thermal reduction can lead to plastic deformation.

7 shows one of the obtained scanning force micrographs. This comprises a 4 μm × 4 μm section of the surface of the occupied substrate AO1 (see Example 1). The representation is chosen so that heights and thus height differences between image areas are reflected by different shades of gray, as it is reproduced accompanying the scale shown. In the left image area of this figure is a flat-lying, in contrast to the environment 2 nm higher and about 4 microns large (graphene oxide) flake.

Example 1: Preparation of a Bonding Film According to the Invention on Crystalline Alumina

The preparation of an adhesive film according to the invention which has parallel to the substrate surface oriented 1 to 2 nm thin and laterally a few micrometers expanded Graphenoxidschichten - so-called flakes - on a crystalline alumina substrate is described below.

To incubate this substrate by incubation, two aqueous formulations are used. In the preparation of the first formulation at room temperature, use is made of a polymer of the formula (R ¹ ) _a A (R ² X) _b , where a = 0-3, b = 1-5, A is a bridging moiety, R ¹ independently H or an aliphatic, aromatic, olefinic, cyclic, heterocyclic, polycyclic or polyheterocyclic radical, R ^{2 is} independently a polymeric backbone, X is independently a functional group selected from the group consisting of amides or imides of carboxylic acids, dicarboxylic acids and polycarboxylic acids , and whose molecular weight is between 200 and 10,000. Suitable here is additive G50, which is available from Straetmans HighTAC GmbH, Hamburg, Germany. For the preparation of the formulation, a water-based formulation of additives G50 wb containing 4% by weight of organic components - namely in multiple mass excess of the amphiphilic polymer and to triethanolamine - by adding demineralized water with stirring to a concentration of 2% by weight diluted. The second formulation is a graphene oxide suspension containing 0.5 g / L graphene oxide in predominantly discrete graphene oxide layers (so-called flakes), about 1 nm thick and laterally a few micrometers thick, whose pH is adjusted with a 0.15 molar acetate buffer , Such a highly dispersed distribution of the nanoparticles is assisted by treating the suspension for 1 min in an ultrasonic bath. Such a treatment takes place in particular immediately before the application of the substrate. To prepare this suspension, a 4 g / L graphene oxide-containing suspension is available which is available from Graphenea, San Sebastian, Spain, and which is diluted with acetate buffer.

The allocation process of the described alumina substrate is carried out by a sequence of incubation and rinsing steps. Incubation in the described aqueous polymer formulation is for 17 hours, incubation in the graphene oxide formulation is for one hour, and each incubation step is followed by a one minute rinse. The rinsing step may be by incubation in demineralized water or by spraying the substrate with demineralized water, followed by draining the water film, which may be assisted by blowing off with a stream of air.

On a first alumina substrate AO1, an adhesive film was applied by means of a coating process comprising two incubation steps, wherein in the first incubation step an incubation in the described polymer formulation takes place and in the second incubation step an incubation in the described graphene oxide formulation. After the final rinsing step and drying of the coated substrate in air, graphene oxide layers oriented in 1 to 2 nm thin and laterally a few micrometers oriented in a plurality of independent regions aligned parallel to the substrate surface were detected by scanning force microscopy. 7 shows one of the obtained scanning force micrographs. This comprises a 4 μm × 4 μm section of the surface of the occupied substrate AO1. The representation is chosen so that heights and thus height differences between image areas are reflected by different shades of gray, as it is reproduced accompanying the scale shown. In the left image area of this figure is a flat-lying, in contrast to the environment 2 nm higher and about 4 microns large (graphene oxide) flake.

After an additional one-hour incubation in demineralized water at room temperature, graphene oxide layers oriented in 1 to 2 nm thin and laterally only a few micrometres oriented in several independent regions parallel to the substrate surface were again detected by scanning force microscopy.

A second alumina substrate AO2 was subjected to an occupancy process involving only one incubation step for comparison. In contrast to AO1, no adhesion layer according to the invention was applied during the coating of AO2, especially as the incubation step in the described polymer formulation was not carried out. Rather, only an incubation in the described Graphenoxidformulierung. After the rinsing step and a drying of the coated substrate in air, in contrast to the observations described for AO1 in AO2 in recorded by atomic force microscopy shots aligned parallel to the substrate surface aligned flakes predominantly in lateral sizes below one micrometer. Another difference to the observations described for AO1, characteristic of the invention after one hour incubation of the occupied AO2 in demineralized water significantly decreased the occupancy of the alumina substrate with these particles.

Example 2 Production of a Stimulus-Responsive Adhesive Film According to the Invention on a Quartz Glass Substrate

The preparation of a stimulus-responsive adhesive film according to the invention on a quartz glass substrate, its (partial) reduction in a conditioning step by thermal energy supply in the convection oven and the application of the coating thus obtained as a humidity sensor whose electrical resistance changes depending on moisture, will be described below.

On a 1 cm x 1 cm quartz glass substrate two 1 mm wide and 1 cm long electrical contacts are applied in a sputtering process near the edges on opposite sides of a base surface by first a few nanometers thin chromium layer and then a few nanometers thin gold layer is applied. A DC resistance measurement by contacting the two gold contacts, each with a probe tip results in an electrical resistance of more than 10 megohms.

To incubate this substrate by incubation, two aqueous formulations are used, each of which is adjusted to a pH of 4.75 with an acetate buffer. In the preparation of the first formulation is added at 25 ° C with stirring a 0.2 molar acetate buffer to reach a concentration of 0.1 mg / mL bovine serum albumin (BSA). Suitable here is a corresponding product available from Sigma-Aldrich as "Bovine Serum Albumin, lyophilized powder". The second formulation is a graphene oxide suspension which contains 0.5 g / L graphene oxide in predominantly discrete graphene oxide layers (so-called flakes) about 1 nm thick and laterally a few micrometers thick and whose pH is adjusted with a 2 mM acetate buffer. Such a highly dispersed distribution of the nanoparticles is assisted by treating the suspension for 1 min in an ultrasonic bath. Such a treatment takes place in particular immediately before the application of the substrate. To prepare this suspension, a 4 g / L graphene oxide-containing suspension is available which is available from the company Graphenea San Sebastian, Spain, and which is diluted with acetate buffer.

The assignment process of the described substrate is carried out by a sequence of incubation and rinsing steps. The incubation in the described aqueous formulations is carried out for one hour each, and each incubation step is followed by a one-minute rinse step. The rinsing step may be by incubation in demineralized water or by spraying the substrate with demineralized water, followed by draining the water film, which may be assisted by blowing off with a stream of air. On the 1 cm × 1 cm underside of the substrate and at the four edges, the applied layer is removed by rubbing with a cellulose cloth again, which ensures that the finally to be measured electrical resistance only by the on the Top of the substrate formed film is determined.

On an appropriately selected substrate, an adhesive film was applied by means of a coating process comprising four incubation steps, incubation in the described BSA formulation being carried out in the first incubation step, incubation in the described graphene oxide formulation in the second incubation step, incubation again in the third incubation step the BSA formulation described, and finally, in the fourth incubation step, another incubation in the described graphene oxide formulation. After the final rinse step and drying of the occupied substrate in air, a DC resistance measurement by contacting the two gold contacts, each with a measuring tip resulted in an electrical resistance of more than 10 megohms.

The thus-dried coated substrate was finally annealed in a convection oven in air at 227 ° C for one hour. After cooling to room temperature and rinsing with demineralized water, an electrical resistance of 625 kiloohms was measured. The adhesive film occupies next to the surface of the quartz glass and the surface of the gold contacts. If a drop of demineralized water not reaching the gold contacts is applied between these, the measured electrical resistance changes. After 45 minutes or after 105 minutes, an electrical resistance of 680 or 675 kilohms is measured. If the water droplet is allowed to dry in the air stream, the electrical resistance drops again to reach 629 kiloohms after drying for five hours, which is practically the same as the starting value before the water droplet is applied. If a drop of water is applied again, the electrical resistance increases again by 10%.

Example 3 Preparation of an Adhesive Film According to the Invention on a Silicate Glass Substrate

The preparation of an adhesive film according to the invention on a silicate glass substrate and its (partial) reduction in a conditioning step by thermal energy supply in the convection oven to achieve a technically relevant electrical conductivity of the transparent adhesive layer will be described below.

To cover this substrate by incubation at room temperature, two aqueous formulations are used. In the preparation of the first formulation adjusted to a pH of 4.75 with an acetate buffer, laccase is used at a concentration of 0.2 g / L and the dispersion is homogenized by shaking. A suitable laccase grade is available from Sigma-Aldrich as "Laccase from Trametes versicolor, powder". The second formulation is prepared from a suspension containing 4 g / L graphene oxide predominantly in the form of isolated graphene oxide layers (so-called flakes) about 1 nm thinner and laterally a few micrometers wide. A suitable 4 g / L graphene oxide-containing suspension is available from Graphenea, San Sebastian, Spain. It is diluted with demineralised water to which a corresponding aliquot of the suspension is added.

The assignment process of the described substrate is carried out by a sequence of incubation and rinsing steps. The incubation in the aqueous laccase formulation described is carried out for one hour, and the incubation in the described aqueous graphene oxide formulation is carried out for 15 minutes. Each incubation step is followed by ten rinsing steps lasting in each case for 5 seconds, which are reacted by incubation in demineralized water. After the last rinse step, the water film is allowed to drain, which can be assisted by blowing off with a stream of air.

On three appropriately selected substrates SG1, SG2 and SG4 were applied by means of three coating processes, each comprising several incubation steps and the subsequent rinsing steps, adhesive films with different film thickness. For this purpose, a basic incubation process comprising two incubation steps and subsequent rinsing steps was carried out with different frequency. The basic incubation process consists of a first incubation step, during which an incubation takes place in the aqueous laccase formulation described, and a second incubation step, during which an incubation takes place in the described graphene oxide formulation.

This basic incubation process was carried out once to occupy the substrate SG1, to deposit the substrate SG2 twice and to deposit the substrate SG4 four times. On the underside of the substrate and on the four edges, rubbing with a cellulose cloth removes the layer which has been applied, which ensures that the electrical resistance to be finally measured is determined exclusively by the film formed on the upper side of the substrate.

After the final rinse step and drying of the coated substrates in air, a DC resistance measurement by contacting the occupied sample top resulted in an electrical resistance of more than 10 megohms.

The thus-dried coated substrates were finally heated in a convection oven in a nitrogen stream under inert gas at a heating rate of 10 K / min to 250 ° C. At 250 ° C, the occupied substrate SG2 showed an electrical resistance of 250 kilohms.

In comparison with an unoccupied silicate glass substrate, the coated substrates SG1, SG2 and SG4 were characterized by surface X-ray photoelectron spectroscopy (XPS, ESCA) on at least two measuring positions. For the unoccupied substrate, an average Si2p signal intensity of 594500 (± 20000) cps × eV derived from the silicate glass substrate was obtained. In the case of the occupied substrates, a substrate signal which was weakened depending on the applied coverage was obtained. For SG1, an Si2p signal intensity of 131,000 (± 20,000) cps x eV was obtained, for SG2 a Si2p signal intensity of 57,000 (± 16,000) cps x eV and for SG4 a Si2p signal intensity of 11700 (± 2000) cps x eV. Assuming a mean free path of 3.2 nm for Si2p photoelectrons in the applied organic layers, it follows that each time the basic incubation process a comparable thick layer is applied, whose thickness after the described thermolysis of the coating. 3 to 5 nm.

At room temperature, the occupied and thermally treated substrate SG2 has a transparency of 83 (± 1)% compared to the unoccupied silicate glass substrate at a light wavelength of 550 nm.

Example 4 Production of an Adhesive Film According to the Invention on a Polvimid Plastic Film

The preparation of an adhesive film according to the invention on a polyimide plastic film as a substrate and its (partial) reduction in a conditioning step by thermal energy supply in the convection oven to achieve a technically relevant electrical conductivity will be described below.

A 5.5 cm x 1.5 cm polyimide substrate is contacted near the edge on opposite short sides with terminals and a DC resistance measurement results in an electrical resistance of more than 20 megohms.

To cover this substrate by incubation at room temperature, two aqueous formulations are used. In the preparation of the first formulation, adjusted to a pH of 4.75 with an acetate buffer, polylysine is used at a concentration of 0.2 g / L and the solution is homogenized by shaking. The second formulation is prepared from a suspension containing 4 g / L graphene oxide predominantly in the form of isolated graphene oxide layers (so-called flakes) about 1 nm thinner and laterally a few micrometers wide. A suitable 4 g / L graphene oxide-containing suspension is available from Graphenea San Sebastian, Spain. It is diluted with demineralised water to a concentration of 1 g / L, to which a corresponding aliquot of the suspension is added.

The assignment process of the described substrate is carried out by a sequence of incubation and rinsing steps. The incubation in the described aqueous polylysine formulation is carried out for one hour, and the incubation in the described aqueous graphene oxide formulation is carried out for 15 minutes. Each incubation step is followed by ten rinses of 5 seconds each, which are reacted by incubation in demineralized water. After the last rinse step, the water film is allowed to drain, which can be assisted by blowing off with a stream of air.

On an appropriately selected substrate, an adhesive film was applied by means of a coating process comprising four incubation steps, incubation in the aqueous polylysine formulation described in the first incubation step, incubation in the described graphene oxide formulation in the second incubation step, incubation in the third incubation step Finally, in the fourth incubation step incubation in the described Graphenoxidformulierung. After the final rinse step and drying of the coated substrate in air, a DC resistance measurement by contacting the plastic foil ends produced an electrical resistance of greater than 10 megohms.

The thus-dried coated substrate was finally heated in a convection oven in a nitrogen stream under inert gas at a heating rate of 10 K / min to 250 ° C and annealed at 250 ° C for one hour. At room temperature, a DC resistance measurement by contacting the plastic film ends gave an electrical resistance of 9 megohms. During stretching of the covered plastic film and also bending until the foil ends almost touched, an electrical resistance of 5 megohms was measured.

Example 5: Preparation of an Adhesive Film According to the Invention on a Gold Layer

The preparation of an adhesive film according to the invention on a gold layer as a substrate is described below.

To cover this substrate by incubation at room temperature, two aqueous formulations are used. In the preparation of the first formulation adjusted to a pH of 4.75 with an acetate buffer, laccase is used at a concentration of 0.2 g / L and the dispersion is homogenized by shaking. A suitable laccase grade is available from Sigma-Aldrich as "Laccase from Trametes versicolor, powder". The second formulation is prepared from an aqueous suspension containing 4 g / L graphene oxide predominantly in the form of isolated graphene oxide layers (so-called flakes) about 1 nm thick and laterally a few micrometers in size. A suitable 4 g / L graphene oxide-containing suspension is available from Graphenea, San Sebastian, Spain. The dispersion containing the 4 g / L graphene oxide is cleaned with the aim of separating flakes of lesser than 1 μm wide flakes several micrometers wide and possible water-soluble additives. For this purpose, an aliquot of the 4 g / L graphene oxide-containing suspension is diluted with demineralized water to seven times the volume V _{7 of} the aliquot taken and then centrifuged in a first centrifugation step at a speed of 10,000 revolutions per minute for 5 min. The supernatant is separated by a first decantation. The precipitate is filled with demineralized water to the volume V ₇ and redispersed for the first time by means of a one-minute ultrasound treatment. This is followed by a second centrifugation step carried out in accordance with the first centrifugation step. These are followed by a second decantation step as described and a second ultrasonic assisted redispersion step as described. This sequence of process steps is repeated eight more times. The final tenth redispersion step to seven times the volume of V _{7 of} the original aliquot taken, however, takes place in a 0.15 molar acetate buffer.

The occupation process of the described substrate is followed by a quartz crystal microbalance. Upon contacting the substrate with the Laccas formulation described, the formation of the laccase-containing adhesive layer is completed after 30 minutes. The adhesive layer is rinsed with demineralized water for one minute, with no significant mass loss observed. Upon subsequent contacting of the adhesive layer with the described buffered graphene oxide formulation, the formation of the graphene oxide-containing layer is completed after 30 minutes. The adhesive film is rinsed with demineralized water for one minute, with no significant mass loss observed. The frequency change of the quartz crystal microbalance quartz crystal crystal during adsorption of the graphene oxide-containing layer is about one third of the frequency change during adsorption of the laccase-containing adhesive layer. The resulting adhesive film is 5 (± 1) nm thin.

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 patent literature

• WO 2012174040 A1 [0003]
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Claims (14)

Comprising electrically conductive adhesive film (i) at least one adhesive layer comprising or consisting of an amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms; and (ii) at least one conductive layer comprising or consisting of conductive non-metallic nanoparticles. Electrically conductive adhesive film after Claim 1 wherein the at least one adhesive layer and / or the at least one conductive layer is or are each monolayer. An electrically conductive adhesive film according to any preceding claim, wherein the conductive non-metallic nanoparticles of the at least one conductive layer are nanoflakes arranged to partially overlap. Electrically conductive adhesive film according to one of the preceding claims, wherein the polymer in the at least one adhesive layer one or more basic and preferably nucleophilic, N-based functional groups selected from the group consisting of amino groups, amide groups, peptide groups, imide groups, in particular amide groups and imide groups of Carboxylic acids, dicarboxylic acids and polycarboxylic acids, as well as ester amide groups and diamide groups, in particular and contains urethane groups and urea groups. An electrically conductive adhesive film according to any one of the preceding claims, wherein the at least one adhesive layer is a polymer having the formula (R ¹ ) _a A (R ² X) _b wherein a = 0-3, b = 1-5, A is a bridging moiety, R ^{1 is} independently H or an aliphatic, aromatic, olefinic, cyclic, heterocyclic, polycyclic or polyheterocyclic radical, R ^{2 is} independently a polymeric backbone, X is independently a functional group selected from the group consisting of amides or imides of carboxylic acids, dicarboxylic acids and polycarboxylic acids, and wherein the molecular weight of the polymer is preferably between 200 and 10,000, more preferably between 400 and 6,000 g / mol, contains or consists thereof , Electrically conductive adhesive film according to one of Claims 1 to 4 wherein the at least one adhesive layer comprises or consists of a polypeptide or protein having a molecular weight between 200 and 200,000, preferably between 2,000 and 100,000 g / mol, in particular laccase or an albumin. The electrically conductive adhesive film of any of the preceding claims, wherein the adhesive film is at least partially responsive to a stimulus, and / or wherein the conductive layer comprises or consists of at least partially reduced graphene oxide and / or wherein the adhesive film has wrinkles. An electrically conductive adhesive film according to any one of the preceding claims comprising three, four or more layers (i) and (ii) in alternating sequence. Use of an electrically conductive adhesive film according to one of the preceding claims for coating one or two or more substrates, preferably wherein the substrate (s) are each independently rigid or flexible, transparent or non-transparent, preferably selected from the group consisting of Polymers, ceramics, oxides, metals and composite materials. Composite comprising at least one substrate and an electrically conductive adhesive film according to one of Claims 1 to 8th wherein the at least one adhesive layer covers at least a portion of at least one surface of the substrate or wherein the electrically conductive adhesive film interconnects at least one surface of a substrate and at least one surface of a second substrate. A method for producing a composite comprising at least one substrate and an electrically conductive adhesive film Claim 10 comprising (a) incubating at least a portion of a surface of a substrate with a solution containing an amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms, and (b) incubating at least a portion of the same surface with a dispersion of non-metallic nanoparticles. Method according to Claim 11 wherein the at least part of a surface of the substrate is coated with a dispersion containing an amphiphilic polymer having functional groups contains basic and preferably nucleophilic nitrogen atoms, and non-metallic nanoparticles are incubated. Method according to Claim 12 wherein the dispersed, non-metallic nanoparticles have at least parts of their surface an adhesive layer of the amphiphilic polymer containing functional groups with basic and preferably nucleophilic nitrogen atoms, and / or wherein the adhesive layer on the dispersed, non-metallic nanoparticles at least partially responds to a stimulus and or wherein the dispersed, non-metallic nanoparticles are at least partially reduced graphene oxide flakes. Composite, preferably composite according to Claim 10 manufactured or producible by a method according to one of Claims 11 to 13 ,

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