Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/20—Conductive material dispersed in non-conductive organic material
  • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S977/00—Nanotechnology
  • Y10S977/70—Nanostructure
  • Y10S977/773—Nanoparticle, i.e. structure having three dimensions of 100 nm or less
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S977/00—Nanotechnology
  • Y10S977/84—Manufacture, treatment, or detection of nanostructure
  • Y10S977/89—Deposition of materials, e.g. coating, cvd, or ald
  • Y10S977/892—Liquid phase deposition

Definitions

• the present invention relates to a process for the preparation of conductive surface coatings with dispersion with electrostatically stabilized silver nanoparticles, dispersions particularly suitable for this process and a process for their preparation.
• EP 1 493 780 A1 describes the preparation of conductive surface coatings with a liquid conductive composition of a binder and silver particles, wherein said silver-containing silver particles may be silver oxide particles, silver carbonate particles or silver acetate particles, each of which may have a size of 10 nm to 10 microns.
• the binder is a polyvalent phenolic compound or one of various resins, ie, in each case a polymeric component. According to the EP 1 493 780 A1 is obtained from this composition after application to a surface with heating a conductive layer, wherein the heating is preferably carried out at temperatures of 140 ° C to 200 ° C.
• compositions described are dispersions in a dispersing agent selected from alcohols such as methanol, ethanol and propanol, isophorones, terpineols, triethylene glycol monobutyl ethers and ethylene glycol monobutyl ether acetate.
• a dispersing agent selected from alcohols such as methanol, ethanol and propanol, isophorones, terpineols, triethylene glycol monobutyl ethers and ethylene glycol monobutyl ether acetate.
• dispersion stabilizers such as hydroxypropyl cellulose, polyvinylpyrrolidone and polyvinyl alcohol from aggregation. These dispersion stabilizers are also polymeric components.
• the silver-containing particles are always sterically stabilized in the dispersion medium by the abovementioned dispersion stabilizers or the binder as dispersion stabilizer against aggregation.
• dispersion stabilizers or the binder as dispersion stabilizer against aggregation.
• polymeric steric dispersion stabilizers have - as already mentioned above - but the disadvantage that they are in the resulting conductive coatings by the surface coverage of the silver particles reduce the direct contact of the particles with each other and thus the conductivity of the coating.
• the organic solvents used as dispersants accelerate the drying time or reduce the drying temperatures of the coatings applied thereto, so that also temperature-sensitive plastic surfaces can be coated, however, dissolve such organic dispersants on the surface of plastic substrates or can diffuse into them, causing swelling or damage the substrate surface and any layers underneath.
• the object was to find such a method and dispersions suitable for this purpose.
• the aforementioned, disadvantageous combination of improved stabilization against aggregation with the reduction of the conductivity of the surface coatings produced from the dispersions should be avoided.
• the possibility of using this method for coating plastic surfaces with short drying and sintering times and / or low drying and sintering temperatures should not be accompanied by the risk of surface damage.
• a process for the preparation of conductive surface coatings comprising a dispersion comprising at least one liquid dispersant and electrostatically stabilized silver nanoparticles, wherein the silver nanoparticles have a zeta potential in the range of -20 to -55 mV in the above dispersant at a pH Value in the range of 2 to 10, is applied to a surface and the surface and / or the dispersion located thereon to at least a temperature in the range of 50 ° C below the boiling point of the dispersing agent to 150 ° C above the boiling point of the dispersing agent of Dispersion is brought, solves the above object.
• the process of the invention does not require steric, optionally polymeric dispersion stabilizers and it is possible, when using plastic substrates, to avoid high drying and sintering temperatures at which the substrate to be coated can be damaged.
• the liquid dispersant (s) is preferably water or mixtures containing water and organic, preferably water-soluble, organic solvents.
• the liquid dispersing agent (s) are particularly preferably water or mixtures of water with alcohols, aldehydes and / or ketones, more preferably water or mixtures of water with mono- or polyhydric alcohols having up to four carbon atoms, such as eg Methanol, ethanol, n-propanol, iso-propanol or ethylene glycol, aldehydes of up to four carbon atoms, e.g. Formaldehyde, and / or ketones of up to four carbon atoms, e.g. Acetone or methyl ethyl ketone.
• Very particularly preferred dispersant is water.
• Silver nanoparticles in the context of the invention are to be understood as those having a d 50 value of less than 100 nm, preferably less than 80 nm, particularly preferably less than 60 nm, measured by means of dynamic light scattering.
• a ZetaPlus Zeta Potential Analyzer from Brookhaven Instrument Corporation is suitable for the measurement by means of dynamic light scattering.
• a dispersion in the sense of the present invention denotes a liquid comprising these silver nanoparticles.
• the silver nanoparticles are in the dispersion in an amount of 0.1 to 65 wt .-%, particularly preferably from 1 to 60 wt .-%, most preferably from 5 to 50 wt .-%, based on the total weight of the dispersion.
• At least one electrostatic dispersion stabilizer is added during the preparation of the dispersions.
• An electrostatic dispersion stabilizer in the context of the invention is to be understood as one by whose presence the silver nanoparticles are provided with repulsive forces and no longer tend to aggregate on the basis of these repulsive forces. Consequently, the presence and action of the electrostatic dispersion stabilizer between the silver nanoparticles causes repulsive electrostatic forces which counteract the van der Waals forces acting on the aggregation of the silver nanoparticles.
• the electrostatic dispersion stabilizer (s) are preferably carboxylic acids having up to five carbon atoms, salts of such carboxylic acids or sulfates or phosphates.
• Preferred electrostatic dispersion stabilizers are di- or tri-carboxylic acids having up to five carbon atoms or their salts. When using the di- or tri-carboxylic acids they can be used to adjust the pH together with amines. Suitable amines include monoalkyl, dialkyl or dialkanolamines, e.g. Diethanolamine, in question.
• the salts may preferably be the alkali or ammonium salts, preferably the lithium, sodium, potassium or ammonium salts, e.g.
• Electrostatic dispersion stabilizers are citric acid or citrates, e.g. Lithium, sodium, potassium or tetramethylammonium citrate. Most preferably, citrate, e.g. Lithium, sodium, potassium or tetramethylammonium citrate, used as an electrostatic dispersion stabilizer.
• citrate e.g. Lithium, sodium, potassium or tetramethylammonium citrate
• Any excess of the electrostatic dispersion stabilizer (s) is preferably removed prior to application of the dispersion to the surface.
• known purification methods such as diafiltration, reverse osmosis and membrane filtration are suitable.
• electrostatic dispersion stabilizers are advantageous over polymeric dispersion stabilizers which are sterically stabilizing by surface occupation, such as, PVP, because they promote the formation of said zeta potential of the silver nanoparticles in the dispersion, but at the same time have no or only a negligible steric hindrance of the silver nanoparticles in the later obtained from the dispersion conductive surface coating result.
• the stabilization of the silver nanoparticles in the dispersion against aggregation does not become sterically hindered for the first time but the silver nanoparticles no longer tend to aggregate based on repulsive forces. Consequently, there are repulsive electrostatic forces between the silver nanoparticles which counteract the van der Waals forces acting on the aggregation of the silver nanoparticles.
• the silver nanoparticles of the dispersion have a zeta potential in the range of -25 to -50 mV in the above dispersant with electrostatic dispersion stabilizer at a pH in the range of 4 to 10, most preferably a zeta potential in the range of -28 to -45 mV in the above dispersion medium with electrostatic dispersion stabilizer at a pH in the range of 4.5 to 10.0.
• the determination of the pH is carried out by means of a pH electrode, preferably in the form of a glass electrode in the design as Einstabmesskette, at 20 ° C.
• the measurement of the zeta potential is carried out by means of electrophoresis.
• electrophoresis different devices known in the art, such. those of the ZetaPlus or ZetaPALS series from Brookhaven Instruments Corporation.
• ELS electrophoretic light scattering
• the light scattered by the particles moving in the electric field undergoes a change in frequency due to the Doppler effect, which is used to determine the migration speed.
• phase analysis light scattering (PALS)” technique for example with ZetaPALS devices
• PALS phase analysis light scattering
• the stabilization by means of electrostatic repulsion ensures that conductive surface coatings can be produced from the dispersion in a simplified manner.
• the surface and / or the dispersion located thereon is at least at a temperature in the range of 20 ° C below the boiling point of the dispersing agent to 100 ° C above the boiling point of the dispersing agent, more preferably at least one temperature in the range of 10 ° C below the boiling point of the dispersing agent is brought to 60 ° C above the boiling point of the dispersing agent at the prevailing pressure.
• the heating serves both the drying of the applied coating and the sintering of the silver nanoparticles.
• the period of heating is preferably 10 seconds to 2 hours, more preferably 30 seconds to 60 minutes.
• the period of heating required to achieve the desired specific conductivity is shorter the higher the temperature (s) at which the surface and / or the dispersion located thereon are heated.
• the surface and / or the dispersion located thereon is heated to at least a temperature below the Vicat softening temperature of this plastic substrate.
• temperatures which are at least 5 ° C, more preferably at least 10 ° C, most preferably at least 15 ° C below the Vicat softening temperature of this plastic substrate.
• the Vicat softening temperature B / 50 of a plastic is the Vicat softening temperature B / 50 according to ISO 306 (50 N, 50 ° C / h).
• citrate as electrostatic dispersion stabilizer is particularly advantageous because it already melts at temperatures of 153 ° C, or decomposes at temperatures above 175 ° C.
• the conductive surface coatings obtained from the dispersions it may be desirable to remove not only the dispersing agent but also the electrostatic dispersion stabilizer as much as possible from the coatings because it has reduced conductivity over the silver nanoparticles and thus the specific conductivity of the resulting coating slight can affect. Due to the aforementioned properties of citrate, this can be achieved in a simple manner by heating.
• dispersions of the invention can be dispensed with the use of polymeric substances as stabilizers which slow down the drying and / or sintering of the surface coating obtained from the dispersion, or even require an elevated temperature until drying and / or sintering and thus a conductivity of the Surface coating occurs by sintering of the silver particles.
• the surface to be coated is preferably the surface of a substrate. These may be substrates of any uniform or different materials and of any shape.
• the substrates may e.g. Glass, metal, ceramic or plastic substrates or substrates in which such components were processed together.
• Particular advantages of the inventive method in the coating of plastic-containing substrate surfaces since they are exposed only moderate thermal stress due to the possible low drying and sintering temperatures and short drying and sintering times and so unwanted deformation and / or other damage can be avoided.
• the surface to be coated is particularly preferably the surface of a plastic substrate, preferably a plastic film or sheet or a multilayer composite sheet or sheet.
• the conductive surface coating produced according to the method of the invention preferably has a specific conductivity of 10 2 to 3 ⁇ 10 7 S / m.
• the specific conductivity is determined as the reciprocal value of the specific resistance.
• the resistivity is calculated by determining the ohmic resistance and the geometry of tracks.
• High specific conductivities of more than 10 5 S / m, preferably of more than 10 6 S / m, can be achieved with the process according to the invention. However, depending on the application, it may well be sufficient to produce surface coatings with lower specific conductivities, and thereby lower temperatures and shorter times for drying and / or sintering than would be required to achieve a higher specific conductivity.
• the conductive surface coating produced according to the method of the invention preferably has a dry film thickness of 50 nm to 5 ⁇ m, more preferably of 100 nm to 2 ⁇ m.
• the dry film thickness is determined, for example, by means of profilometry. For this purpose, for example, a MicroProf ® the company Fries Research & Technology (FRT) GmbH.
• the dispersion is an ink, preferably a printing ink.
• printing inks are preferably those which are suitable for printing by means of inkjet printing, gravure printing, flexographic printing, rotary printing, aerosol jetting, spin coating, doctor blading or roller application.
• the dispersion may be admixed with the corresponding additives, e.g. Binders, thickeners, flow control agents, color pigments, film formers, adhesion promoters and / or defoamers are added.
• the dispersion according to the invention may contain up to 2% by weight, preferably up to 1% by weight, of such additives, based on the total weight of the dispersion.
• co-solvents can also be added to the dispersion.
• the inventive dispersion can contain up to 20% by weight, preferably up to 15% by weight, of such cosolvents, based on the total weight of the dispersion.
• the inks in a preferred embodiment of the invention for inkjet printing have a viscosity of 5 to 25 mPas (measured at a shear rate of 1 / s), for flexographic printing a viscosity of 50 to 150 mPas (measured at a shear rate of 10 / s).
• the viscosities can be determined with a Physica Rheometer at the appropriate shear rate. on. This viscosity is preferably achieved by the addition of the aforementioned additives.
• additives are to be understood as meaning only those additional components which are used above for the preparation of a printing ink, but do not comprise polymeric, steric dispersion stabilizers.
• the dispersions according to the invention can be prepared by reducing a silver salt in a dispersion medium in the presence of an electrostatic dispersion stabilizer.
• the present invention accordingly further provides a process, characterized in that a silver salt in at least one dispersant is reduced to silver in the presence of at least one electrostatic dispersion stabilizer with a reducing agent.
• Suitable reducing agents for use in the abovementioned process according to the invention are preferably thioureas, hydroxyacetone, borohydrides, iron ammonium citrate, hydroquinone, ascorbic acid, dithionites, hydroxymethanesulfinic acid, disulfites, formamidine sulfinic acid, sulfurous acid, hydrazine, hydroxylamine, ethylenediamine, tetramethylethylenediamine and / or hydroxylamine sulfates.
• Particularly preferred reducing agents are borohydrides.
• Very particularly preferred reducing agent is sodium borohydride.
• Suitable silver salts are, for example, and preferably silver nitrate, silver acetate, silver citrate. Particularly preferred is silver nitrate.
• the electrostatic dispersion stabilizer (s) are preferably used in a molar excess to the silver salt and corresponding excesses are removed before the use of the dispersions for coating surfaces.
• known purification methods such as diafiltration, reverse osmosis and membrane filtration are suitable.
• the resulting reduction product is subjected to purification.
• Purification methods which may be used for this purpose are, for example, the methods generally known to the person skilled in the art, e.g. Diafiltration, reverse osmosis and membrane filtration.
• the ohmic resistance was determined by means of a multimeter (Benning MM6). The measurement was made at the outer points of the respective lines, i. at the two ends of the line, which corresponded to a distance of 9 cm.
• the values obtained are data in S / m ⁇ 10 6 .
• Example 1 Preparation of a Dispersion According to the Invention
• the resulting dispersion was then diluted 1/200 with distilled water to a solids content of 0.05% by weight based on the total weight of the sample, and it was diluted
• the pH of the resulting diluted dispersion was adjusted to various values by adding concentrated sodium hydroxide solution or concentrated hydrochloric acid according to the following table.
• Example 2 Measurement of the Zeta Potential of the Dispersions According to Example 1
• zeta potentials of the dispersions of Example 1 were measured according to the table below. All measurements of the samples were carried out three times and a resulting standard deviation of ⁇ 0.5 was determined. The measurement of the zeta potential is carried out with a Brookhaven Instruments Corporation 90 Plus, ZetaPlus Particle Sizing Software Version 3.59 measured in a dispersion having a solids content of 0.05% by weight, based on the total weight of the sample to be measured. ⁇ B> Table.
• the electrostatically stabilized silver nanoparticles of the dispersions according to the invention have a zeta potential in the range from -23 mV to -44 mV.
• Example 3 Production of a Conductive Surface Coating Using the Dispersion According to Example 1
• Example 3 Of the dispersion according to Example 1 (Sample 3) A 2 mm wide line was applied to a polycarbonate film (Bayer Material Science AG, Makrolon ® DE1-1) and eluted (for ten minutes in an oven at 140 ° C and ambient pressure 1013 hPa ) dried and sintered. The surface coating was thereafter already dry, so that wiping led to no visible removal of surface coating.
• the specific conductivity was determined directly by four-point resistance determination, wherein the distance between the contact point was 1 cm in each case.
• the calculated specific conductivity was 1.25 ⁇ 10 6 S / m.
• a dispersion with sterically stabilized silver nanoparticles was prepared.
• a 0.054 molar solution of silver nitrate were mixed with a mixture of a 0.054 molar sodium hydroxide solution and the dispersing aid Disperbyk ® 190 (manufactured by BYK Chemie) (1 g / l) in a volume ratio of 1: 1 was added and stirred for 10 min.
• An aqueous 4.6 molar aqueous formaldehyde solution was added to this reaction mixture while stirring so that the ratio of Ag + to reducing agent is 1:10. This mixture was heated to 60 ° C, held for 30 min at this temperature and then cooled.
• the particles were separated from the unreacted starting materials by diafiltration in a first step, and then the sol was upconcentrated using a 30,000 dalton membrane.
• the result was a colloid-stable sol with a solids content of up to 10 wt .-% (silver particles and dispersants).
• the proportion of Disperbyk ® 190 was, according to elemental analysis, after the membrane filtration 6 wt .-% based on the silver content.
• An investigation by means of laser correlation spectroscopy revealed an effective particle diameter of 78 nm.
• the silver particles are stabilized by polymeric steric stabilizers PVP K 15 and Disperbyk ® 190th
• Example 3 From this dispersion is applied in the same manner as described in Example 3, a surface coating on a polycarbonate film.
• the analogous to Example 3 certain specific conductivity could only be determined after one hour of drying and sintering at 140 ° C and ambient pressure (1013 hPa),
• the specific conductivity after this hour drying and sintering time was about 1 S / m. Only after a total drying and sintering time of four hours, a higher specific conductivity of 10 6 S / m could be determined.
• the surface coating produced with the dispersions according to the invention has a significantly higher conductivity even after a significantly shorter drying and sintering time at low drying and sintering temperatures.
• the surface coating produced with the dispersion with sterically stabilized silver nanoparticles requires substantially longer drying and sintering time to achieve a comparable specific conductivity.

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Conductive Materials (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Paints Or Removers (AREA)
• Powder Metallurgy (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)

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• 2010
  • 2010-03-12 PL PL10002605T patent/PL2369597T3/pl unknown
  • 2010-03-12 DK DK10002605.3T patent/DK2369597T3/da active
  • 2010-03-12 ES ES10002605.3T patent/ES2495390T3/es active Active
  • 2010-03-12 PT PT100026053T patent/PT2369597E/pt unknown
  • 2010-03-12 EP EP10002605.3A patent/EP2369597B1/fr not_active Not-in-force
• 2011
  • 2011-03-08 EP EP11157252A patent/EP2369598A1/fr not_active Withdrawn
  • 2011-03-09 US US13/044,129 patent/US8834960B2/en not_active Expired - Fee Related
  • 2011-03-09 CA CA2733600A patent/CA2733600A1/fr not_active Abandoned
  • 2011-03-11 KR KR1020110021860A patent/KR20110103351A/ko not_active Application Discontinuation
  • 2011-03-11 JP JP2011054046A patent/JP2011190535A/ja active Pending
  • 2011-03-11 CN CN201110058677.7A patent/CN102189072B/zh not_active Expired - Fee Related
  • 2011-03-11 TW TW100108208A patent/TWI592221B/zh not_active IP Right Cessation
• 2012
  • 2012-03-15 HK HK12102639.9A patent/HK1162395A1/zh not_active IP Right Cessation

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