FR3041649B1 - METHOD FOR MANUFACTURING CONDUCTIVE INK COMPRISING COPPER NANOPARTICLES, AND CORRESPONDING INK - Google Patents

Abstract

A process for producing a conductive ink comprising adding to a liquid carrier copper nanoparticles in an amount of between 12% and 25% mass fraction of nanoparticles, and adding to said carrier liquid a dispersing additive in a quantity between 100 ppm and 100% mass fraction of the amount of nanoparticles.

Description

BACKGROUND OF THE INVENTION The invention relates to the general field of coaxial inks, and more particularly to conductive inks comprising copper.

Conductive inks are used for so-called printed electronic applications, in which they are printed on possibly flexible substrates to form conductive layers.

From the prior art, there are known inkscomportant silver particles dispersed in a liquid vector. These inks have the advantage of being chemically stable during the preparation steps, and of being hardly oxidized, which enables them to exhibit good behavior over time. These inks also make it possible to obtain metal films with low electrical resistivity after coalescence obtained during a low temperature annealing step.

Inks with silver particles have the disadvantage of being costly (for example 100 milliliters from 600 euros or 5,000 to 10,000 euros per liter), which prevents their use for large-scale industrial applications.

It has therefore been proposed conductive inks comprising copper particles and which are less expensive. However, these ink coatings oxidize easily, reducing their electrical conductivity, copper oxide being less conductive than copper. This oxidation occurs both during the synthesis of the copper particles and during the annealing step carried out after printing with the encrudator.

To solve this problem of oxidation of copper particles, it has been proposed to modify the annealing step which is carried out after printing.

In particular, it has been proposed to use UV or laser light sources, and it has also been proposed to implement photonic annealing.

A photonic annealing, also called flash annealing, is a annealing using light pulses. These intense pulses of light have a duration of the order of a few microseconds, and they use wavelengths ranging from ultraviolet to infrared. The light pulses are absorbed by the oxidized copper particles which increase their temperature in situ, which allows the appearance of a reduction reaction of the copper oxide present on the surface of the particles. This increase in temperature takes place over a very short lapse of time, so that the oxygen molecules do not have time to diffuse into the copper particles to oxidize them again.

A photonic annealing thus makes it possible to obtain coalescence and thus avoids the oxidation of the particles. In addition, the use of short pulses makes it possible not to damage the support on which printing is performed using the ink.

The American company Novacentrix has developed such anneals, and it has also developed inks based on copper oxide nanoparticles that can be used with these photonic anneals. However, these inks have disadvantages, since they make it possible to form conductive films that have poor adhesion with the substrates on which an impression is made. The invention aims in particular to overcome these disadvantages, and to obtain a conductive ink having better characteristics during printing.

Object and summary of the invention

The present invention responds to this need by proposing a method of manufacturing a conductive ink comprising an addition in a liquid carrier of copper nanoparticles in an amount comprised between 12% and 25% mass fraction of nanoparticles, and an addition in said liquid vector of a dispersing additive in an amount of between 100 ppm and 100% mass fraction of the amount of anoparticles.

The mass fraction of the nanoparticles is defined, as we can see, with respect to the set formed by the nanoparticles encapsulated, the dispersant, and the vector liquid. The dispersant additive can adjust the rheology of the ink, and adjust the behavior of the ink relative to the medium on which it is printed (spreading and wettability). By using a dispersant additive, the surface tension at the interface between (inorganic) particles and their surrounding environment (which may be an organic medium) can be reduced.

It may be noted that the nanoparticles may be encapsulated in a protective material. The mass fractions indicated above apply to encapsulated nanoparticles and non-encapsulated nanoparticles.

In a particular mode of implementation, the nanoparticles have a diameter of between 5 and 100 nanometers, or between 5 and 20 nanometers, or between 5 and 8 nanometers.

The inventors have observed that by using nanoparticles having a diameter of between 5 and 100 nanometers, or between 5 and 20 nanometers, or between 5 and 8 nanometers, the annealing step is facilitated since the optical density of the particles increases, which allows nanoparticles of copper to better absorb light, especially if a photonic product is implemented next.

The high optical density thus favors warming of the particles which can coalesce more rapidly and form a single compound comprising copper after the annealing.

Moreover, by using particles having a diameter of between 5 and 100 nanometers, or between 5 and 20 nanometers, or between 5 and 8 nanometers, printing is facilitated since the size of the particles reduces the risk of clogging of the printing system used. It is thus more simple to project the particles.

It may be noted that the diameter of the nanoparticles may be the diameter of the encapsulated nanoparticles. Protective layers can result in nanoparticle diameter changes in the order of 2.8%, which is negligible.

According to a particular mode of implementation, the method comprisesa preliminary step of grinding intermediate nanoparticles of the average cuivreau of a planetary mill, to obtain said nanoparticles nanoparticles having a diameter of between 5 and 100 nanometers, or between 5and 20 nanometers, or between 5 and 8 nanometers. As an indication, the nanoparticles may be obtained ina synthesis solution which comprises: a quantity of between 0.1% and 55% or 0.3% and 15% of a mass fraction of a protective material intended to encapsulate the copper nanoparticles, and an amount of between 0.05% and 13% of a mass fraction of a reducer.

The inventors have observed that by using the above mentioned amounts of protective and reducing material, a good prevention of the oxidation of the copper nanoparticles is obtained, since the copper is protected from the air, and this in particular if a photonic annealing is implemented later. This makes it possible to obtain good electrical conduction since the copper oxide layer present on the surface of the copper nanoparticles is minimized.

It has also been observed that this protective material can be chosen to facilitate the adhesion of copper (for example by choosing a polymeric protection material), and in particular on flexible or flexible substrates. By using a polymeric protective material, the annealing step allows the protective material to flow at the interface between the substrate and the formed copper film. The formation of this layer at the interface makes it possible to increase the adhesion between the substrate and the copper film.

It may also be noted that it is possible for a residual oxidation to be present (for example, if the encapsulation is not complete, in the present application the term encapsulate is used, including for partial encapsulation), this being the case. The use of a protective material makes it possible to minimize the amount of layer-shaped copper oxide present on the surface of the nanoparticles.

It may be noted that it is possible that a residual oxidation is present (for example, if the encapsulation is not complete, in the present application the term encapsulate is used, including for partial encapsulation), that being the case, the use of a protective material enables the amount of layer-shaped copper oxide present on the surface of the nanoparticles to be minimized.

In a particular embodiment, the liquid carriercomporte at least a first sub-liquid vector having a boiling temperature of between 100 ° C and 400 ° C (or preferably between 100 ° C and 200 ° C), a voltage of a surface area of between 35 and 73 mN / m (milliNewton per meter) (or preferably between 35 and 50 mN / m), and a viscosity of between 5 and 22 centipoise, and preferably a second sub-liquid carrier having a boiling point below 115 ° C, a surface tension of between 20 and 45 mN / m (milliNewton per meter) (or preferably between 20 and 30 mN / m), and a viscosity of between 0.3 and 16 centipoise, the liquid vector comprising between 1 % and 50% or between 40% and 50% of said second sub-liquid vector.

It can be noted that the viscosity and surface tension values provided herein are measured at ambient temperature. The viscosity can be measured with a viscometer and surface tension with a goniometer.

The characteristics of the first sub-liquid vector make it possible to facilitate printing by inkjet technology (typically called jettability).

As can be seen, these characteristics depend on the printing system used. The inventors have observed that the characteristics mentioned above are particularly well suited for the Dimatix machine of the American company Fujifilm referenced DMP-2831.

The characteristics of the second sub-liquid vector make it possible to reduce the boiling temperature of the carrier liquid and to reduce viscosity.

Moreover, after the implementation of a printing step and during the annealing step, the solvent evaporates more rapidly on the edges of the printed pattern since it is present in smaller amounts than in the center of the pattern. This causes the nanoparticles to migrate from the center to the edges of the pattern to fill this gap. This creates an inhomogeneity on the surface of the films that the person skilled in the art designates by the Anglo-Saxon expression "coffee ring". However, this inhomogeneity of the films is compensated for by a phenomenon called "Marangoni flux" which occurs from places with a low surface tension (especially the edges) to places with a high surface tension (especially the center). It has been observed that the intensity of this phenomenon is greater by using sub-liquid vectors having different boiling temperatures and substantially different surface stresses as proposed above. The surface tension gradient within the liquid vector being a determining factor for the optimization of the Marangoni flow.

The inventors have observed that the surface tension and the proportion of the second sub-liquid vector is particularly decisive in order to maximize the flow of Marangoni, and that this proportion ispreferentially between 40% and 50% in the vector liquid.

In a particular mode of implementation, the method furthermore comprises an impression of a pattern on a support comprising said conductive ink, a drying of said pattern, and a photonic annealing of said pattern.

In a particular mode of implementation, the photonic annealing is implemented by a plurality of pulses of duration between 40 and 80ps (or preferably between 40 and 60ps), a pause time between pulses between 400 and 1200ps (or preferably between 400 and 600ps), a voltage of between 230 and 400V (or preferably between 360 and 400V), and a number of pulses less than or equal to 20 or less than or equal to 10.

It can be noted that the exposure time is preferably sufficiently short so as not to damage the printed pattern or to crack it. The pause time is preferably chosen to be long enough for the printed pattern to cool before receiving a new pulse. The number of pulses is also chosen (for example less than 10) to avoid damaging the printed pattern. Voltage attenuator of 400V is preferably a maximum for the values indicated above of durations.

In a particular mode of implementation, said supportcomporte glass, polyimide, or polyethylene terephthalate (PET).

A support comprising polyimide may for example be a Kapton HN (trademark) support sold by the company DuPont. The invention is particularly suitable for forming filmconductors on flexible supports on which film adhesion is favored. The invention also provides a conductive ink comprising copper nanoparticles and a carrier liquid.

According to a general characteristic, the ink comprises a quantity of between 12% and 25% mass fraction of nanoparticles, and a dispersant additive in an amount of between 100 ppm and 100% by mass fraction of the quantity of nanoparticles.

In a particular embodiment, the nanoparticles have a diameter of between 5 and 100 nanometers, or between 5 and 20 nanometers, or between 5 and 8 nanometers.

In a particular embodiment, the ink comprises after drying the carrier liquid between 0.5% and 1% of mass fraction of said dispersant additive.

In a particular embodiment, the liquid carriercomporte at least a first sub-liquid vector having a boiling temperature of between 100 ° C and 400 ° C (or preferably between 100 ° C and 200 ° C), a surface tension included between 35 and 73 mN / m (or preferably between 35 and 50 mN / m), and a viscosity between 5 and 22 centipoises, and a second sub-liquid carrier having a boiling point below 115 ° C, a surface tension of between 20 and 50 mN / m. and 45 mN / m (or preferably between 20 and 30 mN / m), and a viscosity of between 0.3 and 16 centipoises, the liquid vector comprising between 1% and 50% or between 40% and 50% of said second sub-liquid vector.

In a particular embodiment, the ink has a viscosity of between 8 and 25 centipoise, a surface tension of between 28 and 46 mN / m and a boiling point of between 40 ° C. and 200 ° C., or preferably between 50 ° C. and 200 ° C. ° C and 150 ° C. The ink as defined above can be obtained directly by all modes of implementation of the method as defined above. The invention also provides a support comprising a printed pattern comprising the printed ink as defined above.

According to a particular embodiment, the support (on which the emotive is printed) comprises glass, polyimide, or polyethylene terephthalate.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the present invention will be described from the following description with reference to the accompanying drawings which illustrate an example devoid of any limiting character.

In the figures: - Figure 1 schematically shows different stages according to a method of implementation of the invention, - Figure 2 is a thermogravimetric analysis curve of an ink according to an embodiment of the invention, - FIGS. 3a, 3b, 3c, 3d and 3e are images of the nanoparticles and printed patterns.

Detailed description of an embodiment

We will now describe a method of manufacturing a conductive ink comprising copper nanoparticles according to a particular embodiment of the invention.

In Figure 1, there is shown schematically the steps of a method of manufacturing an ink. The first steps of this process are aimed at the synthesis of copper nanoparticles. The synthesis is described here only as an example.

Prior to the implementation of the process, it is possible to prepare a reaction solvent in which the nanoparticles of the compound will be formed.

This reaction solvent may comprise one or more solvents selected from the following solvents: benzyl ether, water, alcohols (methanol, ethanol, isopropanol, 1-methoxy propanol, butanol, ethyl alcohol alcohol and terpineol), glycols (glycerin ethyl acetate ether diethylene glycol, butyl acetate ether, ethylene glycol, diethylene glycolmonoethyl ether, ethylene glycol monoethyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, dibutyl phthalate, diocyl phthalate, diocyl phthalate, tributyl phosphate, 1,3 butylene glycol, propylene glycol), acetates (ethyl acetate, butyl acetate, methoxy propyl acetate, carbitol acetate, and ethyl carbitol acetate), ethers (methylcellosolve, butyl cellosolve, benzyl ether, diethyl ether, tetrahydrofuran, dioxane), ketones (methyl ethyl ketone, acetone, dimethylformamide, 2-methyl-2-pyrrolidone), hydrocarbons (hexane, heptane, dodecane), paraffin oil, naphtha ord ("spirit ore" enanglais), aromatic (benzene, toluene, xylene), halogenated solvents (chloroform, methylene chloride, carbon tetrachloride), acetonitrile, dimethylsulfoxide, pyridine, or methylene chloride. To this solvent is added a protective material intended to encapsulate the copper nanoparticles that will be formed (step E1). Preferably, this protective material is a polymer.

This polymer will form a protective sheath around the copper nanoparticles, which prevents their oxidation, and it will also act as a dispersing agent used to prevent aggregation of nanoparticles with each other.

With respect to the total synthesis solution in which the nanoparticles are formed, an amount of protective material of between 0.1% and 55% of mass fraction is added. Preferably, 0.3% to 15% of mass fraction is added. .

The protective material may comprise one or more protective materials chosen from the following molecules or polymer: oleic acid, oleylamine, gelatin, hyaluronic acid, gumglane, xanthan gum, polyethylene glycol (PEG), polypropylene glycolpolyvinyl alcohol, polyvinylpyrrolidone, poly (2- ethyl-2-oxazoline), acrylic (acrylic acid, acrylamide, polyurethane), polyesters, maleic anhydride polymers and polymers, polymers with at least one functionamine (allylamines, ethyleneimine, oxazoline), and other polymers containing amino groups on their main chains or lateral (eg ramifications).

In a second step E2, the temperature is raised to a temperature between 40 ° C and 200 ° C, or preferably between 60 ° C and 160 ° C.

While maintaining this temperature, (mixture E3) is added to the mixture formed by the protective material and the reaction solvent, a reducing agent and then a copper precursor. The reducer makes it possible to form metallic copper seeds from the precursor. As an indication, one or more reducing agents may be chosen from the group consisting of: tri-sodium citrate, sodium phosphate monobasicmonohydrate, dopamine hydrochlorate, ascorbic acid, di-sodium tartrate, hydrazine, glucose, hydroquinone, acethydrazide, sodium borohydride or potassium, dimethylamine borane , butylamineborane, sodium hypophosphite, 1,2 hexadecanediol.

The amount of reducing agent added is between 0.05% and 13% of the mass fraction of the synthesis solution which will be obtained. As an indication, one can choose a copper precursor such as a copper precursor II (copper phosphate, anhydrous copper sulfate, copper sulfate pentahydrate, copper acetate monohydrate, copper chloride dihydrate (CuCl2), sodium hydroxide phosphate). copper, copper acetylacetonate) and / or copper I (copper thiocyanate, copper chloride (CuCl), copper naphthenate, acetylacatonate copper).

The amount of copper precursor added is between 0.05% and 10% of the mass fraction of the synthesis solution which is obtained at this stage (after the addition of the copper precursor).

The reduction used makes it possible to obtain intermediate nanoparticles (step E4) having dimensions of the order of 50 nanometers and which are encapsulated by said protective material. In particular, it is possible to recover the intermediate nanoparticles parcentrifugation.

The intermediate nanoparticles are then dried (step E5) to separate them from the reaction solvent. This drying step is carried out by means of an oven at a temperature of between 50 ° C. and 70 ° C.

Subsequent to drying, the intermediate nanoparticles encapsulated in the protective material are ground to obtain particles having a desired diameter, for example between 5 and 8 nanometers, or between 5 and 20 nanometers, or between 5 and 100 nanometers. As a guide, a planetary mill from the German company Fritsch can be used for a period of time between 3 hours and 10 hours, and with a milling speed of between 600 and 1100 revolutions per minute. The parameters that can be adapted by those skilled in the art depending on the desired diameter for the nanoparticles.

After grinding, the nanoparticles are recovered in a liquid vector.

The vector liquid comprises a first sub-liquid carrier having a boiling point of between 100 ° C. and 400 ° C. (or preferably between 100 ° C. and 200 ° C. for some of the sub-liquid vectors described below), a tension of surface area of between 35 and 73 mN / m (or preferably between 35 and 50 mN / m), and a viscosity of between 5 and 22 centipoise. This first sub-liquid vector can be a glycol ether or a combination of ether glycols selected from: glycerin ethyl acetate ether, diethylene glycol butyl ether acetate; ethylene glycol butyl ether acetate; diethylene glycol monoethyl ether; ethylene glycol monoethyl ether; dipropylene glycol methyl ether; ethylene glycol, tripropylene glycol methyl ether; tetraethylene glycol; tributyl phosphate, 1,3 butylene glycol, propylene glycol.

The carrier liquid also comprises a second sub-liquid reactor having a boiling point of less than 115 ° C., a surface tension of between 20 and 45 mN / m (or preferably between 20 and 30 mN / m), and a viscosity of between 0.3 and 16 centipoises. The second sub-liquid vector comprises one or more of: methanol, ethanol, isopropanol, hexane, 1-methoxy propanol, butanol, ethyl alcohol alcohol, terpineol, 2-methoxyethanol, iso-propoxy ethanol. The vector liquid comprises a proportion of between 1% and 50% of the second sub-liquid vector.

The carrier liquid may also simply be a single solvent among the families of solvents mentioned above. In a last step E7, the crushed nanoparticles are recovered in the carrier liquid, with a quantity of encapsulated and ground copper nanoparticles comprised between 12% and 25% of mass fraction to said vector liquid.

A conductive ink is thus obtained comprising copper nanoparticles having dimensions of between 5 and 8 nanometers, or between 5 and 20 nanometers, or between 5 and 100 nanometers, and which have been encapsulated.

A dispersant additive in an amount of between 100 ppm and 100% mass fraction of the quantity of nanoparticles is also added during step E7. Other additives may be added to adjust, in particular, the rheological parameters of the ink (viscosity, surface tension), so that it is adapted to the machine and to the print head used later. It may be noted that these parameters also have an influence on the spreading of the ink on its support, and as a result, a person skilled in the art can take into account the type of support to obtain a desired wettability for the ink on the support.

As regards the dispersant additives, it will be possible to choose a polymer intended to be grafted onto the encapsulated nanoparticles in order to minimize the interface voltage between these nanoparticles and their surrounding organic medium. The dispersant additive is a surfactant that reduces the surface tension between the particles and the carrier liquid. The dispersing additive may be a polymer chosen from: polyalkylpolybutadiene and / or polyaryl, methacrylic acid esters, poly (meth) acrylamides and poly (meth) acrylonitrile, polybutyl acrylates, alkoxylated polymers, polysiloxanes or methacrylate-butadiene-styrene (MBS ) copolymers and copolymers of methacrylate-acrylonitrile-butadiene-styrene, ethylacetates, polymers with oxirane, -methyl (2-aminopropyl methyl ether, mono [(diethylamino) alkyl] ether), 2- [2- (2-methoxyethoxy) ethoxy] acetic acid, oxyalkylated aminoalcohols, polyphosphoric acids, polymers with dihydro-3- (octadecen-1-yl) -2,5-furandione, ethylene, 2,5-furandione, dihydro-3- (octadecen-1) yl) - polymers with 1,2-ethanediol, 3- (hexadecen-1-yl) dihydro-2,5-furandionet oxirane.

In particular, and preferably the dispersant additive may have the following form:

R - (O-CnH2n) - R2

With R 1 and R 2, groups or a succession of groups chosen from: hydrogen, alkyl, amine, hydroxylamine, oxyalkyl silane (triethoxysilane, for example), ketone, alcohol, ether, sulphonic acid, acrylic acid.

It may be noted that it is possible to use several dispersing additives chosen from the group defined above.

Also, a quantity of dispersant additive of between 100 ppm and 100% of mass fraction of the quantity of nanoparticles is added.

Finally, it is possible to implement an impression on a support, for example by using a Dimatix machine from Fujifilm. Beforehand, for example, for pattern printing, these patterns can be dried in an oven (70 ° C. for 10 minutes). , and this before implementing a photonic annealing.

To implement photonic annealing, it is possible to use the machine marketed by Novacentrix under the name Pulseforge.

In such annealing, pulses of light are emitted to heat the nanoparticles to a temperature close to 400 ° C to obtain their coalescence. This also causes deoxidation of nanoparticles, which may have a residual copper oxide layer.

This deoxidation is achieved by means of the protective material (which has carbon in a hydrocarbon chain) used as a dispersant which reduces the copper oxide. During annealing, the protective material flows between the interstices between the copper nanoparticles. It is the carbon that oxidizes by reducing copper oxide to Cu2O and Cu2O to copper when the temperature becomes high.

The parameters of the photonic annealing step may be the following for printing on kapton: the voltage is fixed at 400V, the duration of the pulses is between 40 and 80 microseconds, the pulse frequency is between 900 Hz and 4.2 kHz. The number of pulses can be between 10 and 20 pulses.

These parameters make it possible to form a continuous pattern of copper in the form of a film, and to promote the adhesion of this pattern on its support.

In FIG. 2, there is shown a graph of the gravimetric analysis of an ink obtained by the method described in reference in FIG.

In this figure, the curve in continuous line corresponds to the measured mass fraction, and the curve in dashed line corresponds to the variation of this mass fraction.

In the example of Figure 2, an additive protective material was added as described above.

It can be noted that 1.610% of the mass fraction is first lost by the evaporation of the residual liquid vector.

Then, the first peak of the fractional fraction variation curve (dashed line) corresponds to a loss of mass from about 100 ° C due to the departure of oxygen molecules according to the reduction reaction under nitrogen of copper oxide II (CuO) with copper oxide I (Cu2O):

CuO -> Cu2O + 1/2 02

The second peak of this curve corresponds to a loss of mass starting around 180 to 200 ° C of nanoparticles envelope comprising the protective material and the dispersant additive. From this figure it can be deduced that the nanoparticles of the copper are surrounded, after drying, by 7% to 9% of organic material, of between 0.5 to 1% of dispersant additive and between 6.5% and 8% of material protection.

The last peak corresponds to the loss of mass due to the departure of the oxygen molecules according to the reduction reaction under nitrogen of copper oxide I (Cu 2 O) to metallic Cu:

Cu2O -> Cu + 1 / z 02

FIG. 3a is an image obtained by Transmission Electron Microscopy (TEM) of the intermediate nanoparticles obtained after the implementation of the step E5 described with reference to FIG. 1. As can be seen in this figure, the nanoparticles have a diameter of order of about fifty nanometers.

FIG. 3b is an image obtained by TEM of the nanoparticles obtained at the end of the process of FIG. 1. As can be seen in this figure, the dimensions of the nanoparticles are much smaller than those of the nanoparticles of FIG. 3a.

FIG. 3c is an image obtained by Scanning Electron Microscopy (SEM) of a film obtained after printing and photonic annealing.

FIGS. 3d and 3e are photographs of conductive tracks obtained on a Kapton HN support and with an ink according to the invention. As can be seen in these figures, continuous lines having a width of the order of 200 micrometers are obtained.

The inventors observed that the printed patterns exhibited a resistivity of the order of 8 micro ohms per centimeter, and that the printed patterns resisted tearing according to the standardized tape-adhesive test.

Also, by implementing an X-ray diffraction ("X-ray diffraction: XRD in English") analysis, it can be determined that a quantity of copper oxide CuO remains present in the vicinity of the surface of the printed film, and that the amount of copper oxide CuO is less than 10% of the volume fraction of the film. By way of example, nanoparticles can be formed according to the following method.

In benzyl ether (reaction solvent), amounts of between 8.5% and 8% respectively of oleylamine oleic acid fraction (protective material) may be added.

1,2-hexadecanediol (reductant) is then added to give a final mass fraction of 12.9%. 1,2-Hexadecanediol is added to the benzyl ether.

This solution is heated to a temperature of 105 ° C stirring, and then this temperature is maintained for 10 minutes.

Then, a copper precursor (acetylacetonate decuivre (II)) with a mass fraction of 1.3% is added. The copper precursor is added already dissolved in benzyl ether. The mass fractions mentioned above are defined with respect to the solution obtained at cestade.

The temperature is then raised to 190 ° C and is stirred for 30 minutes.

Centrifugation is then carried out and the separated particles are washed and dried in an oven under argon.

The particles are then recovered in hexane (liquidvector) and then ground in a ball mill for a period of 3 hours at 900 revolutions per minute.

The crushed particles are recovered and then filtered through a filter having a porosity of 5 microns to separate the nanoparticles beads. The filtrate is recovered and diluted in hexane until obtaining an ink based on nanoparticles with a mass fraction of 25%.

A dispersant such as a fatty acid ethoxylate (C13EO6 (CH3- (CH2) 12- (O-CH2-CH2) 6- · OH)) is then used with a 1% mass fraction based on the mass of the nanoparticles. introduced.

A printing of the ink by a Dimatix printer allows the printing of tracks which are oven dried at 40 ° C and then undergo photonic annealing. This annealing is done with the following parameters:

Duration of insolation: 60 microseconds

Break time: 400 microseconds

Voltage: 400V

Number of taps: 10

This makes it possible to obtain robust films which have a resistance of the order of 350 Ohm per square.

Claims (3)

1. A method for printing a conductive ink, the manufacture of the conductive ink comprising an addition in a liquid vector of nanoparticles of copper in an amount of between 12% and 25% mass fraction of nanoparticles, and an addition in said liquidvector a dispersant additive in an amount of 100 to 100% by mass fraction of the amount of nanoparticles, the printing method comprising printing a pattern on a substrate comprising said conductive ink, drying said pattern, and photonic annealing; of said pattern, characterized in that the photonic annealing is carried out by a plurality of pulses of duration between 40 and 80ps or between 40 and 60ps, a duration of pause between pulses between 400 and 1200ps or between 400 and 600ps, a voltage between 230 and 400V or between 360 and 400V, and a number of pulses less than or equal to 20 or less than or equal to 10. 2. The method of claim 1, wherein the nanoparticles have a diameter between 5 and 100 nanometers, or between 5 and 20 nanometers, or between 5 and 8 nanometers. The method according to claim 2, wherein the manufacture of the conductive ink comprises a prior step of grinding an intermediate copper nanoparticles by means of a planetary mill, to obtain said copper nanoparticles having a diameter of between 5 and 100 nanometers, or between 5 and 20 nanometers, or between 5 and 8 nanometers. 4. Process according to any one of claims 1 to 3, in which the carrier liquid comprises at least a first sub-liquid driver having a boiling point of between 100 ° C. and 400 ° C. between 100 ° C. and 200 ° C., a surface tension of between 35 and 73 mN / m or between 35 and 50 mN / m, and a viscosity of between 5 and 22 centipoises, and a second sub-liquid vector having a boiling point of less than 115 ° C., a tension of with a surface area of between 20 and 45 mN / m, or between 20 and 30 mN / m and a viscosity of between 0.3 and 16 centipoises, the carrier liquid comprising between 1% and 50% of mass fraction or between 40% and 50% of fraction. mass of said second sub-liquidvector. 5. The process according to claim 1, wherein said carrier comprises glass, polyimide, or polyethylene terephthalate.