DISPERBYK® is a wetting and dispersing additive for solvent-borne systems . It is composed of a solution of a copolymer with acidic groups. This prod. Solution of a copolymer with acidic groups. Acts as a wetting and dispersing additive for aqueous and solvent-borne systems. Provides deflocculation through . Material Safety Data Sheet. DISPERBYK Version Revision Date 08/14/ Print Date 08/14/ 1 / SECTION 1. PRODUCT AND COMPANY.
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Year of fee payment: A conductive ink includes metallic nanoparticles, a polymeric dispersant, and a solvent. The polymeric dispersant may be ionic, non-ionic, or any combination of ionic and non-ionic dispebyk dispersants. The solvent may include water, an organic solvent, or any combination thereof. The conductive ink may include djsperbyk stabilizing agent, an adhesion promoter, a surface tension modifier, a defoaming agent, a leveling additive, a rheology modifier, a wetting agent, an ionic strength modifier, or any combination thereof.
The present invention is related to conductive inks.
Printed conductive films have the potential to lower manufacturing costs for microelectronics and large area electronics. Recently, metal 1110 having consistent size and shape have been developed. The inventors have discovered that these nanoparticles may be used to prepare well-dispersed inks. These metallic ink dispersions may be used for printing conductors, thereby making the direct writing of electronic circuits possible. Silver and gold nanoparticle-based inks are beginning to be used for printing electronics.
These metals may be used because of their relatively high stabilities toward oxidation by molecular oxygen. Copper, with a resistivity of 1. Moreover, copper is less costly than silver or gold, thereby making it a more attractive material for printed conductors. Oxidation of copper nanoparticles during printing and curing, however, has been difficult to avoid.
To achieve a stable dispersion of metal nanoparticles, dispersants are adsorbed onto the surface of the nanoparticles. The function of these dispersants is to keep the individual nanoparticles apart and prevent them from aggregating and agglomerating together. Dispersants may be organic polymers or long chain molecules.
Such compounds have high boiling points or decomposition temperatures, and are difficult to remove during a curing process. Any residues from these dispersants remaining in the cured metallic films will result in higher resistivities being obtained in the metal conductor that is formed because these dispersants and their decomposition products are non-conducting organic compounds, or insulators. In one aspect, a conductive ink includes metallic nanoparticles, a polymeric dispersant, and a solvent.
In some implementations, the polymeric dispersant may be ionic, non-ionic, or any combination of ionic and non-ionic polymeric dispersants. In some implementations, the solvent includes water, an organic solvent, or any combination thereof. In certain implementations, the conductive ink includes a stabilizing 1110, an adhesion promoter, a surface tension modifier, a defoaming agent, a leveling additive, a rheology modifier, a wetting agent, an ionic strength modifier, or any combination thereof.
In certain implementations, the polymeric dispersant comprises about 0. The alcohol may be isopropanol, isobutyl alcohol, ethanol, polyvinyl alcohol, ethylene glycol, or combinations thereof. In some cases, the dispersant may be polyvinylpyrrolidone, polyethylene glycol, isostearyl ethylimidazolinium ethosulfate, oleyl ethylimidazolinium ethosulfate, or combinations thereof. In some cases, the dispersant may be phosphoric acid modified phosphate polyester copolymers, sulfonated styrene maleic anhydride esters, or combinations thereof.
The film may be substantially free of imperfections, such as pin holes. Metallic inks suitable for forming conductors may be formulated with metal nanoparticles, conductive polymers, and a carrier system, such as water, organic solvents, or a combination thereof. The nanoparticles may be, for example, copper, silver, nickel, iron, cobalt, aluminum, palladium, gold, tin, zinc, cadmium, etc.
The nanoparticles may be about 0. Steps to form a stable dispersion from dispedbyk metallic nanopowder may include wetting the powder, breaking up agglomerates in the powder de-agglomeratingand stabilizing the dispersed particles to inhibit flocculation.
In some cases, disperby dispersant or surfactant may be added to facilitate de-agglomeration of the powder. In some cases, the dispersant that provides the best performance at one step of the process may not provide the best performance at dispebryk step.
Thus, it may be beneficial to incorporate more than one dispersant or surfactant. Unlike the insulating residues of common dispersants, conductive organic compounds such as conductive polymers may not act as an insulating defect in the metallic conductors, but instead may act as a parallel-serial resistor R 2 with a metallic conductor R 1. The total resistance R may be described as:. Thus, residual conductive polymer may not increase the resistivity as much as insulating residues from non-conducting dispersants.
If the conductive polymer is also the dispersant for metallic nanoparticles, the resistivity of the resulting metallic films may be significantly reduced, due at least in part to limited or no additional contamination from residual non-conducting dispersants.
In some cases, metal inks may be cured to obtain conductive metal films with resistivities close to those of the bulk metal conductor itself. Steric stabilization, electrostatic stabilization, or a combination thereof may be used to prepare dispersions that remain stable during storage and deposition, thus yielding uniform and consistent coatings. Steric stabilization of metal nanoparticles may be achieved with a non-ionic dispersant or polymer.
Steric contributions include interactions between the surface of the metal nanoparticles and functional groups of polymers or long chain disperyk molecules, thereby making direct contact between the metal particles e. Strong interaction between the polymers or the long chain molecules and the solvent or water may inhibit the polymers from coming too closely into contact with one another.
Electrostatic stabilization occurs when charged dispergyk.
Electrostatic stabilization of a charged metal nanoparticle may be achieved with an ionic dispersant or polymer. Dispersants with a high hydrophile-lipophile balance HLB may be used with aqueous dispersions, and dispersants with a low HLB may be used with dispersions in non-polar organic liquids.
Nanoparticle dispersion may also be enhanced by charging a surface of a metal nanoparticle. Metallic nanoparticles may have an oxide layer on their surface. The oxide layer may have a thickness of, for example, about 1 nm to about 20 nm. In the presence of water, an acid-base reaction may occur, forming a hydroxide layer on the surface. The hydroxide layer may adsorb or lose protons to produce a positively or negatively charged surface. Thus, charging through proton gain or loss, or charging by adsorbed charges, may be involved in achieving a good dispersion.
At low pH, the hydroxide surface may react with protons to produce a positively charged surface. In contrast; at high pH, protons may be removed to produce a negatively charged surface.
Thus anionic and cationic dispersants may be adsorbed onto the surface of metal nanoparticles under conditions that depend on the pH of the solution or dispersion.
Therefore, charged conductive polymers having oppositely charged polyacid functionalities for charge compensation may be used to advantageously disperse metal nanoparticles in aqueous inks. Anionic polymeric dispersants, cationic polymeric dispersants, or a combination thereof may be used to form electrostatic dispersions with charged metallic surfaces in aqueous media.
Positively charged nanoparticles may form an electrostatic dispersion with a dispersant containing both anionic and cationic polymer chains. In some cases, the metallic surface may be heterogeneous, having both negatively and positively charged sites. With both anionic and cationic groups present in the dispersant, the dispersant is compatible with the different charge regions on the metal nanoparticles, and a stable dispersion may be achieved.
Conductive polymers including, but not limited to, conductive polythiophenes, conductive polyanilines, metallophthalocyanines, and metalloporphyrins may be used to prepare aqueous metallic inks. In an implementation in which ionic polythiophene conducting polymers are used to prepare aqueous metallic inks, the positive charge may be located within a polythiophene network. In another implementation, the positive charge may be appended as a cation such as, for example, sodium.
In each case, the multifunctional structure allows for low concentrations to be used to achieve stable nanoparticle dispersions. Conducting polymers with multiple binding sites may partially surround a metal nanoparticle, thereby keeping it from aggregating or agglomerating.
The nanoparticle may be, for example, copper. This multi-site attachment of a polymer to a nanoparticle leads to a thermodynamic advantage over a dispersant that only attaches via a single site.
DISPERBYK® by Byk – Paint & Coatings
The head group may include, for example, amines, cationic alkylammonium groups, carboxylic acids, sulfonic acids, and phosphoric acid groups, along with their salts that have carboxylate, sulfonate and phosphate or phosphonate groups. In addition to the thermodynamic advantage that is gained by having multiple attachment points between the nanoparticle and the head group of a conductive polymer, there is also an advantage in the conducting polymer having a tail group to it.
For example, long chain alkyl or alkoxy functionalities have a high degree of conformational flexibility, which allows them to create a high exclusion volume. Another advantage of a high exclusion volume is that it allows for a low concentration of dispersant to be used, and therefore, only a small quantity of dispersant to be removed during the curing process.
A dispersant may be selected such that the head group is chemically compatible with or preferentially associates with the nanoparticleand the tail group is chemically compatible with or preferentially associates with the vehicle solvent. In a dispersion, the dispersant may act as a molecular bridge between the nanoparticle and the vehicle, thereby keeping the nanoparticles separated by one or more molecular layers.
The solubility of the tail group of the dispersant in the vehicle is also a factor in the selection of a dispersant for a given ink formulation. The head group of a dispersant may be selected such that the functionality of the group is compatible with the metal nanoparticle in an ink formulation. That is, the attraction between the head group and the nanoparticle is advantageously stronger than the attraction between the head group and the vehicle in the system.
The attraction may include charge attraction, specific donor-acceptor bands between unshared electron pairs and empty molecular orbitals, hydrogen bonding, electrostatic field trapping of polarizable molecules, or any combination thereof. For metal nanoparticles with positively or negatively charged surfaces, conductive metallic inks have been prepared using anionic components such as halide or carboxylate ions, or cationic components such as hydrogen ions or group I cations, respectively.
When the head group is a polymer, the polymer may provide multiple anchoring sites and thus multiple site coverage of the nanoparticle In some embodiments, a dispersion of metal nanoparticles is formed by adding the nanoparticles to a dispersion of a conductive polymer. A dispersion of the conductive polymer may be formed by adding the polymer to a carrier. The carrier may be, for example, water, an organic solvent, or any combination thereof. The pH of the dispersion may be from about 1 to about Metal nanoparticles may be added to the conductive polymer dispersion to form a metal nanoparticle dispersion.
An effective amount of dispersant may be used to achieve monolayer coverage of the nanoparticles with the head groups of the dispersant such that the surface of nanoparticle is substantially inaccessible to other nanoparticles for aggregation or agglomeration.
In some ink formulations, for example, an effective weight percentage of dispersant may be in a range from about 0. Coverage of less than a monolayer leaves open sites on the nanoparticle that may cause agglomeration. If a second monolayer of dispersant is present on the nanoparticle, the second layer may be oriented in the opposite direction from the first layer, thereby reducing the compatibility of the nanoparticle with the solvent.
Polymeric dispersants may have higher viscosities than liquids used as vehicles in conductive inks. A higher viscosity promotes forming of a dispersion suitable for ink-jet printing methods.
Also, the presence of multiple nanoparticle binding sites allows polymeric dispersants to be used at lower concentration than monomeric dispersants with single binding sites, aid still confer monolayer coverage of the metal nanoparticle. Lower concentrations of the dispersant are favorable because less organic material remains after the curing process. In some implementations, polyacids, such as polystyrenesulfonic acid, may be used for charge compensation in an ink formulation.
When agglomerates are present in a nanopowder, de-agglomeration facilitates formation of a stable dispersion. In some cases, nanoparticles in a metallic nanopowder may be agglomerated through a salt bridge, including a soluble salt precipitated in the formation of the nanopowder. These salt bridges may be dissolved by a dispersant to break up the agglomerates.
Dispersants that infiltrate crevices between nanoparticles in a nanopowder may also reduce the energy required to propagate cracks through the solid, and may thereby function as grinding aids.