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 Copper nano-particles, method of preparing the same, and method of forming copper coating film using the sameUSPTO Application #: 20070180954Title: Copper nano-particles, method of preparing the same, and method of forming copper coating film using the same Abstract: The present invention relates to copper nano-particles having controlled particle size, high monodispersity, and oxidation stability, a method of preparing the copper nano-particles, and a method of forming a copper coating film using the copper nano-particles. The present invention provides a method of preparing copper nano-particles, comprising mixing a copper salt solution with a mixture of a reducing agent and a solvent; where the copper salt solution is added to the mixture at a temperature of 300° C. or less so that the copper salt solution can react with the mixture. It is thus possible to obtain copper nano-particles with controlled particle size and monodispersity by inducing uniform nucleation and nucleus growth through control of the reaction rate and/or the amount of copper ions during synthesis of the copper nano-particles. Moreover, the copper nano-particles of the present invention employ capping organic molecules, which provide oxidation stability by forming a protective dispersant shell around the copper nano-particles. (end of abstract)
Agent: Cantor Colburn, LLP - Bloomfield, CT, US Inventors: Jang Sub KIM, Joo Ho MOON, Sun Ho JEONG, Dong Jo KIM, Bong Kyun PARK USPTO Applicaton #: 20070180954 - Class: 75373 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070180954. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001]This application claims priority to Korean Patent Application No. 10-2006-0011805, filed on Feb. 7, 2006, and all the benefits accruing therefrom under 35 U.S.C. .sctn.119, and the contents of which are incorporated herein by reference in their entirety. BACKGROUND OF THE INVENTION [0002]1. Field of the Invention [0003]The present invention relates to metal nano-particles, and more particularly, to copper nano-particles, a method of preparing the same, and a method of forming a copper coating film using the same. [0004]2. Description of the Related Art [0005]Generally, nano-particles of a material exhibit characteristics that are different from the characteristics of the bulk material. When the particle size is decreased to nanometer (nm) levels, the nanometer-sized particles have physical, chemical, electromagnetic and optical characteristics which are quite different from those of particles of a micrometer level, due to changes in the electronic and crystalline structures of the material itself or due to an increase in surface energy related to increases in the surface areas of the particles. These nano-particles have a wide range of applications, and therefore nano-particles are actively being studied. [0006]Generally, the melting point of nano-particles is reduced as the size of the crystalline nano-particles is decreased. For instance, the melting point of copper (Cu) is 1,083.degree. C.; however, when the diameter of copper particles becomes 50 nm or less, the surface energy of the particles is rapidly increased as the surface area per unit volume of the particles is increased, and the copper particles begin to fuse with one another even below the melting point. In a liquid phase, in contrast to a solid phase with strong bonding, it is possible to reduce the surface energy by minimizing the surface area of the particles through rearrangement of surface atoms, thus reducing the surface atoms with high energy. That is, the surface atoms intend to reach a stable state by means of reduction of the surface area of the particles. Therefore, the nano-particles can be melted even at a temperature lower than the melting point of an ordinary material. [0007]The characteristics of the nano-particles can be very useful in the case of metals. Recently, there has been activity in developing a flexible device for information display that is light and thin and has high impact resistance by using a substrate based on a flexible plastic film rather than on a conventional hard silicon or glass substrate. With such a display, electric and electronic devices can be fabricated on a plastic substrate. This inevitably requires an electrode formed at low temperature so as to secure thermal stability of a plastic substrate with a relatively low melting point. That is, all processes should be performed at a low temperature that is less than the melting point of the plastic substrate. Since the melting point of a metal can be considerably reduced upon formation of a metal material from nano-particles as mentioned above, such a metal can be applied to a low-temperature process. BRIEF SUMMARY OF THE INVENTION [0008]An exemplary embodiment of the present invention is to provide metal nano-particles that can be applied using a low-temperature process, and a method of preparing the same. [0009]Another exemplary embodiment of the present invention is to provide a method of forming a metal coating film exhibiting high conductivity using the metal nano-particles by means of heat treatment at a low temperature. [0010]To achieve the above embodiments, the present invention provides a method of preparing copper nano-particles, comprising the steps of preparing a copper salt solution, a reducing agent, and a solvent; mixing the reducing agent with the solvent; and adding the copper salt solution to the mixture at a temperature of 300.degree. C. or less so that the copper salt solution can react with the mixture. [0011]The copper salt solution may comprise copper acetate, copper chloride, copper carbonate, copper nitrate, copper sulfate, or a combination comprising at least one of the foregoing copper salts. [0012]The reducing agent may comprise sodium phosphinate monohydrate, sodium azide, hydrazine hydrate, sodium borohydride, lithium aluminum hydride, or a combination comprising at least one of the foregoing reducing agents. [0013]The solvent may comprise ethylene glycol, diethylene glycol (DEG), triethylene glycol, or a combination comprising at least one of the foregoing solvents. [0014]Mixing of the reducing agent with the solvent may further comprise mixing a dispersant with the mixture of copper salt, reducing agent, and solvent. The dispersant may be capping organic molecule (i.e., an organic molecule having polar and a non-polar end groups) and may comprise polyvinylpyrrolidone (PVP), thioglycolic acid, trioctylphosphine, trioctylphosphine oxide, cetyltrimethylammonium bromide, or a combination comprising at least one of the foregoing dispersants. [0015]The addition of the copper salt solution to the mixture may be performed by injecting the copper salt solution into the mixture using a syringe pump. [0016]The present invention provides copper nano-particles having a particle size of 20 to 300 nm and comprising capping organic molecules adsorbed onto surfaces of the copper nano-particles. The capping organic molecules may comprise polyvinylpyrrolidone (PVP), thioglycolic acid, trioctylphosphine, trioctylphosphine oxide, cetyltrimethylammonium bromide, or a combination comprising at least one of the foregoing capping organic molecules. The copper nano-particles may be prepared by a polyol method. [0017]The present invention provides a method of forming a copper coating film, comprising preparing a coating solution in which copper nano-particles prepared by a polyol method are dispersed; coating the coating solution on a substrate; and heat-treating the coating solution coated on the substrate. [0018]The coating solution may further comprise capping organic molecules adsorbed onto surfaces of the copper nano-particles. [0019]The solvent may comprise a primary solvent including ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, glycerol, or a combination comprising at least one of the foregoing primary solvents. The solvent may further comprise a cosolvent including ethyl alcohol, methyl alcohol, acetone, isopropanol, toluene, hexane, heptane, methyl ethyl ketone, ethyl lactate, or a combination comprising at least one of the foregoing cosolvents. [0020]The coating of the coating solution may be performed by means of spin coating, dip coating, droplet casting, inkjet printing or screen printing. [0021]The heat treatment may be performed at a temperature of 200 to 350.degree. C., or may be performed in a vacuum atmosphere, a reduction atmosphere using hydrogen gas, or an inert atmosphere. Continue reading... Full patent description for Copper nano-particles, method of preparing the same, and method of forming copper coating film using the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Copper nano-particles, method of preparing the same, and method of forming copper coating film using the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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