WO2023237192A1

WO2023237192A1 - Electrically conductive elastomeric printing ink for contactless printing processes

Info

Publication number: WO2023237192A1
Application number: PCT/EP2022/065577
Authority: WO
Inventors: Sabin-Lucian Suraru; Dirk SCHLINKMANN
Original assignee: Wacker Chemie Ag
Priority date: 2022-06-08
Filing date: 2022-06-08
Publication date: 2023-12-14

Abstract

The invention relates to an electrically conductive, cross-linking silicone elastomer composition as an electrically conductive printing ink in contactless printing processes for producing electrodes for sensors, actuators or EAP layer systems.

Description

Electrically conductive elastomeric printing ink for contactless

Printing process

The invention relates to a method for producing an electrically conductive, crosslinking silicone elastomer composition as an electrically conductive printing ink in contactless printing processes for producing electrodes for sensors, actuators or EAP layer systems.

Electrically conductive printing inks are used for the production of printed electronics in order to apply large-area or structured electrodes to a substrate in electronic components using any printing process. The printing of electrically conductive elastomers onto an elastic carrier (such as silicone, TPU) enables the construction of completely or partially elastic electronic components that retain their electrical properties almost unchanged even when stretched or compressed. Additionally, electrically conductive elastomeric printing inks can be printed on flexible (but not stretchable) substrates, such as. B. on PET, PE, PTFE or paper, in order to keep the mechanical damage to the printed electrode to a minimum, even under long-term mechanical stress due to repeated bending, and thus to prevent a change in the electrical conductivity due, for example, to an increase in resistance. Conductive printing inks for printed electronics are known and some are also commercially available. They typically contain at least one polymeric binder, at least one conductive component such as. B. Metal or carbon particles and at least one solvent to adjust the viscosity. Basically, conductive carbon particles such as B. Carbon black and carbon nanotubes (CNT) as fillers have the disadvantage that they greatly increase the viscosity of the formulation, which affects the printability of the ink significantly more difficult, so that solvents are typically used for dilution in order to reduce the effective concentration of the particles in the printing ink and thus make the printing ink usable. US9253878 describes such a formulation based on a silicone elastomer, conductivity carbon black and CNT, the latter being characterized by being at least 30 nm thick. The latter property gives the solvent-based, conductive printing ink good printability in screen printing, which is not possible with thin CNTs (< 30 nm). However, the formulation does not work without solvents.

US2016351289 describes that a solvent content of at least 10% must be contained in a silicone-based conductive printing ink in order for it to be applicable. Typically, organic solvents are used in the area of silicone printing inks, which are then very difficult to completely remove and entail high costs for the user in terms of occupational safety and environmental protection.

CNT-containing silicone elastomers are known. Silicone elastomers containing both CNT and carbon black are described in CN103160128. The silicone elastomers described here are characterized by a high soot content. At least 3.7% by weight of carbon black is required, but the examples show that in order to obtain good electrical properties so that the specific resistance is <20 ohm*cm, a total filler content (CB + CNT) of at least 8.5% is necessary. No printing process using these compositions is disclosed.

Solvent-free silicone-based printing inks are little known: For example, US2014060903 describes a solvent-free, silicone-based, conductive printing ink, which, however, does not contain conductive particles with a high aspect ratio (such as carbon nanotubes = CNT) and is therefore not suitable for stretchable applications. For stretchable applications, which include the dielectric elastomer sensors, actuators and generators, stretchable binders (elastomers) are used in combination with conductive anisotropic particles that possess a high aspect ratio, typically CNT. The high aspect ratio of the conductive particles ensures that, in contrast to spherical particles, the conductive particles can form a conductive network through the entire system with smaller amounts of filler, which persists even when the elastomer is stretched. This ensures good electron conduction even when the elastomer is stretched.

The methods known in the prior art for applying silicone layers, in particular those that are suitable for producing electrode layers and/or dielectric layers in actuators, sensors and other electroactive polymer layer systems, are outstanding in their variability, application precision, throughput and in the component efficiency achieved later effectiveness and durability limited.

The so-called laser transfer printing process is known in the prior art for applying layers. However, this process has so far been limited in its application to low-viscosity inks and dispersions as well as metals.

WO 2009/153192 A2 (=corresponding to US2011151614A), for example, describes a method for producing conductive layers on semiconductor structures, wherein a metal powder dispersion is applied to a carrier and detached from the carrier onto a target by a laser beam. US2011298878A (= corresponding to WO 2010/069900 Al) describes, for example, laser transfer printing of color.

US2017189995A (= corresponding to WO 2015/181810 Al) describes a laser transfer process for printing metallic bodies. A metal film is heated at specific points on a transparent support and positioned in the form of drops.

Creating smooth surfaces that are free of particles is particularly difficult with electrically conductive silicone compositions containing CNTs. The reason for this is the strong tendency of CNTs to form agglomerates, which cannot be completely broken down when incorporated into a matrix even when high shear forces are used, so that particulate agglomerates can be found in the silicone. The particulate agglomerates can have a size of 25, 50 or even over 100 pm and are noticeable as protruding spikes in thin raked or printed layers.

The object of the present invention was therefore to provide a method for producing electrically conductive, cross-linking silicone elastomer compositions which, despite the simultaneous use of conductivity carbon black and CNT, have a high aspect ratio but without the use of solvents, but at the same time have good application properties as printing inks in contactless printing processes such as for example, the laser transfer printing process, and after application it provides a smooth surface that is free of particles.

Surprisingly, it was found in the present invention that an electrically conductive silicone elastomer composition based on conductivity carbon black (0, 5 - 3 % by weight and MWCNT (0.1 - 3% by weight), without the addition of a solvent, can be used as a printing ink to print electrodes for dielectric elastomer sensors and actuators if all or parts of the composition are used in at least a two-stage Step are processed in which the components MWCNT and conductivity carbon black are incorporated together

1. is initially dispersed in a first step (dispersion) using a high-speed mixer so that the specific resistance is less than 50 Qcm, and

2. is then mechanically treated in a second step (post-treatment) using a three-roll mill in order to break down larger agglomerates. The final silicone composition of the 1K or 2K electrode material can, if necessary, be obtained by diluting it in a subsequent step. The resulting printed image has a smooth surface and is free of jagged edges.

In order not to make the number of pages in the description of the present invention too extensive, only the preferred embodiments of the individual features are listed below.

However, the expert reader should explicitly understand this type of disclosure to mean that every combination of different preference levels is explicitly disclosed and explicitly desired.

The invention therefore relates to a process for producing an electrically conductive, crosslinking silicone elastomer composition, containing:

0.5 to 3.0% by weight of conductivity carbon black, 0.1 to 3.0% by weight of multi-walled carbon nanotubes (MWCNT),

- NO solvent, with the proviso that a) in IK systems all components are mixed in one or more steps, or that b) in 2K systems only the components of the A or the B composition can be mixed in one or more steps, with the proviso that for mixing at least one step consists of a two-stage processing in which the components MWCNT and conductivity carbon black are incorporated together, for which the total amounts of both components or only partial amounts are used both components or a combination of the total amount of one with a subset of the other component can be used, whereby

MWCNT, conductivity carbon black and at least one other component are dispersed in a first step (= dispersion) using a high-speed mixer so that the specific resistance of the mixture is at most 50 Qcm, and then this mixture is mixed in a second step (= mechanical aftertreatment) with a Three-roller mill is post-treated.

The MWCNTs used according to the invention preferably have an aspect ratio of L/B>10, particularly preferably of L/B>100.

The measurement of the specific resistance of the above. g. Mixing is done using the following measuring method:

Against level measurement:

In a four-wire measurement, the contact resistance is not measured because the current is applied to two contacts, and The voltage U of the current I _v that has already flowed through the sample is measured at two further contacts.

U R = - [fi] lu

The resistance R of unvulcanized siloxanes is measured using the Multimeter Model 2110 5

digit from Keithley Instrument and a measuring apparatus made from natural PP and stainless steel (1.4571) electrodes. The measuring device is connected to the electrodes using brass contacts and laboratory cables. The measuring apparatus is a mold with defined dimensions for L x W x H of 16 cm x 3 cm x 0.975 cm, into which the siloxane is spread for measurement. The two outer flat electrodes are placed at a distance of 16 cm, so that the current flows through the entire sample. The two point electrodes with a diameter of 1 cm are located in the base plate at a distance of 12 cm ( 1 ) and measure the voltage. The following formula is used to calculate the specific resistance from the measured resistance R.

with sample height h [cm], sample width w [cm] and electrode distance 1 [cm]

(here: h = 0, 975 cm, w = 3 cm, 1 = 12 cm)

The methods for dispersing the conductive fillers, for mixing the components and the apparatus that can be used are well known to those skilled in the art from the prior art.

The dispersion takes place in a high-speed mixer (=dissolver), whereby a scraper can also preferably be used to ensure a uniform distribution of the to achieve conductive fillers. A planetary dissolver with a scraper is preferably used. A vacuum planetary dissolver with a scraper and a bar stirrer is particularly preferred. Dissolver disks with any arrangement and number of teeth can be used. In principle, all silicone elastomer compositions known in the prior art can be used as base materials for the silicone elastomer composition.

For example, addition-curing, peroxide-curing, condensation-curing or radiation-curing silicone elastomer compositions can be used. Peroxidic or addition-crosslinking compositions are preferred. Addition-crosslinking compositions are particularly preferred.

The silicone elastomer compositions can be formulated as one or two components. The silicone elastomer compositions are crosslinked by applying heat, UV light and/or moisture. The following silicone elastomer compositions are suitable, for example: HTV (addition-crosslinking), HTV (radiation-crosslinking), LSR, RTV 2 (addition-crosslinking), RTV 2 (condensation-crosslinking), RTV 1, TPSE (thermoplastic silicone elastomer), thiol-ene and cyanacetamide-crosslinking systems.

In the simplest case, the preferred addition-curing silicone elastomer compositions contain

(A) at least one linear compound that has residues with aliphatic carbon f-carbon f multiple bonds,

(B) at least one - preferably linear - organopolysiloxane compound with Si-bonded hydrogen atoms, or instead of (A) and (B) or in addition to (A) and (B) (C) at least one linear organopolysiloxane compound that has Si-C-bonded residues with aliphatic carbon f-carbon f multiple bonds and Si-bonded hydrogen atoms, and

(D) at least one hydrosilylation catalyst.

For the method according to the invention, it is very important that at least partial amounts of conductivity carbon black and MWCNT are dispersed together in the silicone in two successive steps, with the dispersion being carried out in a first step using a high-speed mixer in order to achieve a homogeneous distribution and comminution of the To obtain filler aggregates so that the specific resistance of the mixture is less than 50 Q*cm, and then in a second step the mixture is mechanically treated using a three-roller mill in order to crush larger agglomerates. The amount of siloxane, conductivity black and MWCNT can be such that it corresponds to the desired solids proportions of conductivity black and MWCNT in the finished mixture, or a so-called masterbatch batch can also be produced. Either the amount of siloxane and/or the amount of conductivity carbon black and MWCNT is measured in such a way that a higher proportion of solids results in the mixture than is later required. With the masterbatch approach, the concentrated solids dispersion can be diluted down to the target solids value with additional siloxane. The same siloxane or at least one different siloxane or mixtures of the same siloxane and at least one different siloxane can be used for dilution.

For dispersion, the components of the siloxane composition according to the invention can be added and dispersed in any order. For dispersion, both conductivity carbon black and MWCNT can be used as a solid or prepared in advance. provided mixtures can be used. Before the actual dispersion, it can be advantageous to stir or mix the solids into the siloxane at a lower rotational speed of the mixing tools. In this way, appropriate pre-wetting of the solids with siloxane can be achieved.

In a particularly preferred embodiment, a premixed soot premix can be used instead of the soot solid.

In a further embodiment of the process, one or both premixes can be produced using a roller mill.

It has proven to be advantageous to produce the soot premix using a roller mill.

In a preferred embodiment of the process, the carbon black premix, consisting of conductivity carbon black and siloxane, is first produced using a roller mill and then combined with MWCNT as a solid and additional siloxane to form a masterbatch. In the embodiment according to the invention, this combined masterbatch, in which MWCNTs and conductivity carbon black are present together, is dispersed in a first step using a high-speed mixer so that the specific resistance of the mixture is less than 50 Q * cm, and then in a second step Mixture mechanically treated using a three-roll mill.

In a further embodiment of the process, the conductivity carbon black and MWCNT are mixed independently of one another in parts of the siloxane and, if necessary. predispersed, i.e. H . mixed in different mixing containers and if necessary. pre-dispersed, and then the two mixtures (soot premix and MWCNT premix) are mixed with if necessary. other components combined. In the embodiment according to the invention In this form, this combined mixture, in which MWCNTs and conductivity carbon black are present together, is dispersed in a first step using a high-speed mixer so that the specific resistance of the mixture is less than 50 Q*cm, and then in a second step the mixture is mixed using Fe of a three-roll mill mechanically treated. The final silicone composition of the 1K or 2K electrode material can be used if necessary. can be obtained by dilution in a subsequent step.

Regardless of the exact process, MWCNT, conductivity carbon black and components (A) to (D) can be added in portions or by adding the entire amount. Optionally, the mixing container and thus the mixed material contained can be tempered during dispersion, i.e. H . be kept at a target temperature by cooling or heating. The temperature is usually in a range of 0 - 200 ° C, preferably in a range of 20 - 100 ° C. Optionally, the process according to the invention can be carried out under vacuum. Dispersion is preferably carried out, i.e. H . Dispersion intervals including dispersion pauses, under vacuum. The vacuum is usually <1. 000 mbar, preferably <800 mbar and particularly preferably <500 mbar.

Furthermore, it can be advantageous to apply a vacuum following the dispersion. This can be done in the same device as the dispersion, or in a different device. The vacuum is usually applied while stirring. The vacuum is usually <1. 000 mbar, preferably <800 mbar and particularly preferably <500 mbar.

The dispersion takes place at a high rotational speed of the dispersing tools and in particular of the dissolver disk. The high power input achieved in this way leads to the desired finely dispersed distribution of the conductive fillers MWCNT and/or conductivity carbon black in the siloxane. Essential for the dispersion result and therefore for an optimally high one Electrical conductivity of the conductive, cross-linking silicone elastomer composition is a maximum power input from the mixing tools. The maximum power input depends on the selected mixing tools, their geometric arrangement, the rotational speed of the dissolver disk in particular, the temperature and the effective viscosity of the mix, i.e. H . the viscosity of the siloxane, which depends, among other things, on the degree of polymerization of the siloxane and the amount of filler added. The dispersion is followed by a mechanical post-treatment with the three-roll mill in order to crush particulate agglomerates.

The method according to the invention can be supplemented by a final aftertreatment using pressure filtration. However, this post-treatment using pressure filtration can also be dispensed with.

Should such an aftertreatment take place, it is characterized in that c) in IK systems the pressure filtration is carried out through a metal mesh with a mesh size of at least 100 pm, preferably at least 200 pm, or that d) in 2K systems each only for the A or the B composition is pressure filtered through a metal mesh with a mesh size of at least 100 pm, preferably at least 200 pm.

A further subject of the present invention are the electrically conductive, crosslinking silicone elastomer compositions, obtainable by the process according to the invention.

A further subject of the invention is the use of the conductive, crosslinking silicone elastomer composition according to the invention as an electrically conductive printing ink Contactless printing process for the production of electrically conductive elastomers on elastic supports.

If the electrically conductive, crosslinking silicone elastomer composition according to the invention produced in this way is used as a printing ink, for example in a contactless printing process, a printed image is created which has a smooth surface that is free of particles (jagged edges). This is a decisive advantage if multi-layer systems are to be produced in which the conductive material is to be introduced between further layers, e.g. B. by lamination or overlaying.

Contactless printing processes have the advantage that the printing material experiences as little mechanical stress as possible during the printing process. The electrically conductive, crosslinking silicone elastomer composition according to the invention can be used as a printing ink for other non-contact printing processes such as. B. Spray, drop-on-demand processes or laser transfer printing (LI FT process) can be used. It is preferably used in laser transfer printing (LI FT process).

The electrically conductive, crosslinking silicone elastomer composition according to the invention is particularly suitable as a printing ink for printing electrodes for dielectric elastomer sensors, actuators and generators and EAP layer systems.

Examples of embodiments

The following examples describe the basic feasibility of the present invention, without however limiting it to the contents disclosed therein.

The following examples were taken at a pressure of the surrounding atmosphere, i.e. at around 1013 hPa, and, if not otherwise stated, carried out at room temperature, i.e. about 23 ° C or a temperature that occurs when the reactants combine at room temperature without additional heating or cooling.

Chemicals:

MWCNTs LUCAN BT1001M, manufacturer LG Chem Ltd., average diameter according to manufacturer's information: 10 nm

To produce the carbon black premix, 5% by weight of the high-conductivity carbon black Ketjenblack EC-600JD (available from Nouryon) was incorporated into 95% by weight of ViPo 1,000 on a three-roll mill.

ViPo 1,000: Vinyldimethylsiloxy-terminated polydimethylsiloxane with a viscosity of 1,000 mPa*s, available from Gelest Inc. under the product name DMS-V31 (Gelest catalog).

HPo 1,000: Hydridodimethylsiloxy-terminated polydimethylsiloxane with a viscosity of 1,000 mPa*s, available from Gelest Inc. under the product name DMS-H31 (Gelest catalog).

An a, w-dimethylhydrogensiloxy-poly (dimethylmethylhydrogen) siloxane (viscosity 130 - 200 mm ² /s; 0.145 - 0.165% by weight of H) was used as the crosslinker.

A platinum complex with phosphite ligands was chosen as the hydrosilylation catalyst for one-component systems, as described in EP2050768B1 (catalyst 6). WACKER® KATALYSATOR OL (available from Wacker Chemie AG) was used for two-component systems. 1-Ethynyl-l-cyclohexanol is available from Sigma Aldrich (CAS number: 78-27-3).

Viscosity measurement:

The viscosity measurements were carried out on an air-bearing MCR 302 rheometer from Anton Paar at 25 °C. A cone-plate system (25 mm, 2°) with a gap size of 105 pm was used. The excess material was removed (trimmed) with a spatula at a gap distance of 115 pm. The cone then moved to a gap distance of 105 pm so that the entire gap was filled. Before each measurement, a "pre-shear" is performed, where the shear history is cleared through sample preparation, application and trimming. Pre-shearing takes place for 60 seconds at a shear rate of 10 s ^-1 , followed by a rest period of 300 seconds. The shear viscosity is determined using a step profile in which the sample is sheared at constant shear rates of 1 s ^-1 , 10 s ^-1 and 100 s ^-1 for 100 seconds each. A measured value is recorded every 10 seconds, resulting in 10 measuring points per shear rate. The average of these 10 measuring points gives the shear viscosity at the respective shear rate.

The storage modulus G' was determined using an amplitude test. In this oscillation experiment, the amplitude y is varied from 0.01 to 1000% (at an angular frequency w of 10 s ^-1 , logarithmic ramp, 30 measuring points). Typically, at low amplitude values, the linear viscoelastic (LVE) region is found, in which G', when plotted double-logarithmically over y, has a plateau value. The plateau value is the storage modulus G' to be determined.

Resistance measurement (as already described above in the text): In a four-wire measurement, the contact resistance is not measured because the current is applied to two contacts and the voltage U of the current I _v that has already flowed through the sample is measured at two further contacts.

U R = - [fi] lu

digit from Keithley Instrument and a measuring apparatus made from natural PP and stainless steel (1.4571) electrodes. The measuring device is connected to the electrodes using brass contacts and laboratory cables. The measuring apparatus is a mold with defined dimensions for L x W x H of 16 cm x 3 cm x 0.975 cm, into which the siloxane is spread for measurement. The two outer flat electrodes are placed at a distance of 16 cm, so that the current flows through the entire sample. The two point electrodes with a diameter of 1 cm are located in the base plate at a distance of 12 cm ( 1 ) and measure the voltage. The following formula is used to calculate the specific resistance p from the measured resistance R.

with sample height h [cm], sample width w [cm] and electrode distance 1 [cm]

(here: h = 0, 975 cm, w = 3 cm, 1 = 12 cm)

Change in resistance under stretch

According to ISO 37, the printing inks were vulcanized in the form of a 2 mm plate and the Type 1 shoulder bar was punched. The test specimen is subjected to a four-wire measurement. This is clamped in the middle between two electrically conductive clamping jaws so that the distance between them is 84.0 mm. The Clamping jaws, which represent the two outer electrical contacts, are structured, which means that the structure achieves a penetration effect into the material (grooving).

The two internal contacts are made by positioning two tendon 11 clamps at a distance of 29.5 mm from the nearest clamping jaw and at a distance of 25 cm from one another. The two inner measuring terminals are pre-treated with silver conductive paste. The resistance measured in this way without stretching (L=Lo) is Ro. The two outer clamping jaws also enable the uniaxial stretching of the test specimen and thus the measurement of the resistance R of the printed electrode at the stretching (L-Lo) /Lo = 50%.

Mixing methods:

The mixtures were stored in a Labotop ILA from PC Laborsystem GmbH with a capacity of 1 liter

300 mbar vacuum and room temperature. The tools used were a dissolver disk (14 teeth, teeth 90° to the disk, diameter 52 cm), a bar stirrer (standard tool) and a scraper with temperature measurement. For larger batches, a laboratory mixer (Mischtechnik Hoffmann & Partner GmbH Andrä - Wördern, Austria) with a capacity of 10 liters with a toothed dissolver disk (four teeth, diameter 98 mm), bar stirrer and scraper was used. The double-walled stirred tank was set to a jacket temperature of 19 °C using a thermostat.

A laboratory stirrer was used to mix the A and B components

(IKA RW20) with 3-bladed propeller stirrer (R 1381) from IKA® -Werke GmbH & Co. KG, Staufen, Germany.

A three-roll mill from EXAKT (model 80E) was used. The roll gap was set to 15 pm between rolls 1 and 2 and to a minimum distance (<5 pm) between rolls 2 and 3. Example 1 Production of the masterbatch Ml

In a laboratory mixer with a capacity of 10 L with a toothed dissolver disk (diameter 98 mm with four teeth), bar stirrer and scraper, MWCNT (36 g) and 1783 g of the carbon black premix in ViPo 1,000 (581 g) were mixed for 60 min at 1800 rpm ( Dissolver) and 50 rpm (beam stirrer) mixed in. The double-walled stirred tank was set to a jacket temperature of 19 °C using a thermostat. A homogeneous, black paste with a specific resistance of 5.4 Q*cm was obtained. The viscosity is 296 Pa*s at a shear rate of 10 s ^-1 and the storage modulus G' in the LVE range is 51200 Pa.

Example 2 Production of the masterbatch M2

Masterbatch Ml was processed using a three-roll mill. A homogeneous, black paste with a specific resistance of 5.4 Q*cm was obtained. The viscosity is 274 Pa*s at a shear rate of 10 s ^-1 and the storage modulus G' in the LVE range is 50500 Pa.

Assessment of the masterbatch Ml and M2

To assess the masses, a 100 pm layer was applied to a silicone film (ELASTOSIL<®> film with a thickness of 100 pm, available from WACKER Chemie AG) using a ZAA2300 automatic film applicator with a ZUA 2000 universal applicator from Zehntner GmbH, Switzerland. lolled. The layer raked with M2 was smooth, shiny and free of jagged edges. The Ml-based layer has a rough surface with spikes emerging from the layer.

Example 3 Production of the printing ink la

In a laboratory mixer with a capacity of 1 L, 134 g of the masterbatch M2 were mixed into a mixture of ViPo 1,000 (21 g), HPo 1,000 (77 g), crosslinker (10 g), Pt catalyst (0.2 g) and 1-ethynyl -l-cyclohexanol (15°mg) with a bar stirrer (100 rpm, laboratory mixer without dissolver disk) mixed for 30 min. A homogeneous, black paste was obtained.

Example 4 Production of the printing ink lb (not according to the invention)

Printing ink lb was produced analogously to printing ink la, with the difference that masterbatch Ml was used instead of M2. A homogeneous, black paste was obtained.

Example 5 Production of printing ink 2a

The masterbatch M2 from Example 2 was diluted to a platinum-containing component A and a platinum-free component B: To produce the A component, 2500 g of the masterbatch M2 with Vipo 1000 (2138 g) and WACKER® CATALYST OL (9.25 g) mixed with a bar stirrer (100 rpm, laboratory mixer without dissolver disk) for 30 min.

Component B was produced analogously to component A with the difference that 2500 g of the masterbatch M2 with HPo 1000

(1163 g), crosslinker (650 g), Vipo 1000 (335 g) and 1-ethynyl-1-cyclohexanol (6.5 g) was mixed.

To produce the printing ink 2a, components A and B were mixed in a ratio of 1:1 for 1 min with a propeller stirrer (800 rpm). A homogeneous, black paste was obtained.

Example 6 Production of printing ink 2b (not according to the invention)

Printing ink 2b was produced analogously to printing ink 2a, with the difference that masterbatch Ml was used instead of M2. A homogeneous, black paste was obtained.

Pressure tests

The LIFT process was carried out as described in US2021367140A (= corresponding to WO2020156632). The printing was carried out using a common, commercial laser engraving system from TROTEC Laser Deutschland GmbH. A system from the Speedy l OO flexx 60/20 series with dual is used

Laser source (60 W 10.6 pm CO2 laser; 20 W 1064 nm fiber laser). Common quartz glass plates (300x300x3 mm) from GVB GmbH Solution in Glas, Germany, are used as carriers and printing mass carriers. A ZAA2300 automatic film applicator with a ZUA 2000 universal applicator from Zehntner GmbH, Switzerland, is used to apply the printing material film.

With the squeegee system, a homogeneous layer with a thickness of 60 pm and dimensions 200x 200mm is applied to the center of a quartz glass pane on one side. The edge areas of the pane remain free of printing mass. A silicone film (ELASTOS IL<®> film with a thickness of 100 pm, available from WACKER Chemie AG) fixed by a film of water is placed in the cutting chamber of the laser on an uncoated glass pane as the surface to be printed. The coated pane is placed on the first pane at a distance of 200 pm with the coating side facing the uncoated pane. The distance is adjusted using spacers, such as 100 pm microscope plates. An area-filled geometry without gray areas and shading should be selected as the print template in the laser system's control software. Furthermore, the laser power in the fiber laser cutting mode between 40-60% with a 20 W laser is sufficient. The laser speed can be selected between 50 and 70%. The focus point should be approx. 4 to 4.5 mm above the interface of the coating or the quartz glass plate. The selected geometries could then be transferred to the silicone film using the laser. Assessment of the prints

The surface of the printed electrode was assessed visually. The layers printed with printing inks la and 2a are smooth, shiny and free of jagged edges. These printing inks are therefore suitable as electrode material for multi-layer systems, such as. B. in dielectric elastomer sensors, actuators and generators, particularly well suited.

Layers printed with the printing inks 1b and 2b (not according to the invention) have rough surfaces with points emerging from the layer and are therefore unsuitable for multi-layer systems.

Table 1 shows impressively that the other values of the printing inks are very comparable, but that the manufacturing process according to the invention is decisive for the suitability of a printing ink as an electrode material in multi-layer systems.

Table 1

Soot = conductivity soot

Claims

Expectations

1. Process for producing an electrically conductive, crosslinking silicone elastomer composition, containing:

0.5 to 3.0% by weight of conductivity carbon black,

0.1 to 3.0% by weight of multi-walled carbon nanotubes (MWCNT),

- NO solvent, with the proviso that a) in IK systems all components are mixed in one or more steps, or that b) in 2K systems only the components of the A or B composition are mixed in one or more steps are mixed in several steps, with the proviso that for mixing at least one step consists of a two-stage processing in which the components MWCNT and conductivity carbon black are incorporated together, for which the total amounts of both components or only partial amounts of both components or a combination of the total amount one can be used with a subset of the other component, where

MWCNT, conductivity carbon black and at least one other component are dispersed in a first step (= dispersion) using a high-speed mixer so that the specific resistance of the mixture is at most 50 Qcm, and then this mixture in a second step (= mechanical aftertreatment) with a three-roll mill is treated afterwards.

2. The method according to claim 1, characterized in that it is an electrically conductive, addition-curing silicone elastomer composition and contains the following components:

(A) at least one linear compound that has residues with aliphatic carbon-carbon multiple bonds,

(B) at least one - preferably linear - organopolysiloxane compound with Si-bonded hydrogen atoms, or instead of (A) and (B) or in addition to (A) and (B)

(C) at least one linear organopolysiloxane compound which has Si-C-bonded residues with aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms, and

(D) at least one hydrosilylation catalyst.

3. Electrically conductive, crosslinking silicone elastomer composition, obtainable by one of the processes according to claims 1 to 2.

4. Use of the conductive, crosslinking silicone elastomer composition according to claim 3 as an electrically conductive printing ink in contactless printing processes for producing electrically conductive elastomers on elastic supports.

5. Use according to claim 4, characterized in that the contactless printing process is laser transfer printing.

6. Use according to claim 4 and 5, characterized in that the electrically conductive elastomers produced on elastic supports are electrodes for dielectric elastomer sensors, actuators and generators and EAP layer systems.

7. The method according to claim 1, characterized in that the following aftertreatment takes place: c) for 1K systems, pressure filtration through a metal mesh with a mesh size of at least 100 gm, or d) for 2K systems only for the A or B composition, pressure filtration through a metal mesh with a mesh size of at least 100 gm.

8. The method according to claim 7, characterized in that a metal mesh with a mesh size of at least 200 gm is used.

9. The method according to claim 1, characterized in that there is no aftertreatment by means of pressure filtration through a metal mesh.