HK1083223B - A method for the production of conductive and transparent nano-coatings and nano-inks and nano-powder coatings and inks produced thereby - Google Patents

Description

Method for manufacturing conductive transparent nano coating and nano ink, and nano powder coating and nano ink prepared by method

Technical Field

The present invention relates generally to a method of making transparent conductive coatings and inks and to nanopowder coatings and inks obtained with the method.

Background

Nanoparticles, in particular metal nanoparticles, have very specific properties, directly related to which are their size, and the fact that a large proportion of the atoms in the particles are located on the particle surface or on grain and grain boundaries. These properties include optical properties, sintering and diffusion properties, electrical properties such as capacitance, impedance and resistance, catalytic activity and many others.

These enhanced properties have a wide range of uses and applications; such as catalysts for chemical reactions, electrodes, fuel cells, medical devices, water purification techniques, electronics, coatings, and more.

Applicant's us patent 5476535 proposes a method of making nanopowders, particularly silver. The method comprises the following steps: (a) forming an aluminum-silver alloy having a specific mixed composition; (b) the aluminium component is leached in a series of subsequent leaching steps, with fresh lixiviant reacting with the treated solid material to form a silver alloy which becomes progressively porous and homogeneous. In step (c) ultrasonic vibration is applied to disintegrate the agglomerates and facilitate penetration of the lixiviant into the growing pores of the alloy due to the large application of ultrasonic vibration. The lixiviant leaves silver agglomerates in step (d) which are then washed and dried in a final step.

In applicant et al, U.S. patent 6012658, this very similar process is used to form the foil. Therefore, the following two main steps are taken: the alloy obtained in the above-mentioned us patent 5476535 is pulverized into prescribed particles, and then the obtained particles are shaken into a ribbon-shaped high porosity alloy having predetermined characteristics.

Summary of The Invention

The core of the present invention is to provide a useful and novel method for coating a substrate with conductive and/or transparent nanopowders in a regular or irregular pattern, which is naturally formed or printed. The scope of the present invention includes the use of nanometal additives to form transparent-conductive coatings, such as nano-titania additives that prove useful in making coatings that are transparent to visible light but opaque to ultraviolet light; for nano silica additives, it was found that they can be used to make transparent coatings with special electrical resistance properties; in the case of nanopigments, it has proven useful for the production of transparent, coloured coatings.

It is also an object of the present invention to provide a useful and novel method of making conductive and transparent coatings containing metal nanopowders. The method comprises the following steps: (i) mixing metal nanopowder with at least one of the following ingredients: binders, surfactants, additives, polymers, buffers, dispersants and/or coupling agents to form a homogenized solution; (ii) different methods are adopted: screen printing, spreading, spin coating, dip coating and the like, and the homogenized mixture prepared in the steps is applied to the surface to be coated; (iii) evaporating solvent from the homogenized mixture; and (iv) sintering the coating layer to obtain an electrically conductive and transparent coating on said surface.

It is within the scope of the invention that the metal nanopowder is used alone or in combination with an additive capable of increasing the electrical conductivity selected from at least one of the following: metal colloids and/or metal reducible salts and/or organometallic complexes and/or organometallic compounds which decompose to form conductive species. Preferably, the concentration of the metal nano-powder in the mixed solution is between 1 wt% and 50 wt%, more preferably in the range of 2 wt% to 10 wt%.

It is also within the scope of the invention for the mixed solution to contain an organic solvent or a mixture of organic solvents. The organic solvent is characterized by an evaporation rate at room temperature that is greater than the evaporation rate of water. The concentration of the organic solvent or the mixture of organic solvents in the mixed solution is between 20% by weight and 85% by weight. More preferably, the concentration is within a narrow range of 40 wt.% to 80 wt.%. It follows that the solvent may be selected from at least one of the following: petroleum ether, hexane, heptane, toluene, benzene, dichloroethane, trichloroethylene, chloroform, dichloromethane, nitromethane, dibromomethane, cyclopentanone, cyclohexanone or any mixture thereof.

It is also within the scope of the invention that the concentration of the above-described binder in the mixed solution is between 0 wt.% and 3 wt.%. The binder is preferably, but not limited to, ethyl cellulose and/or modified urea.

It is another object of the present invention to provide a useful and novel method of making an ink or solution containing metal nanopowders for making transparent and conductive coatings. The method is similar in principle to the one described above, comprising the steps of: (i) mixing the nanopowder with at least one of the following ingredients: binders, surfactants, additives, polymers, buffers, dispersants and/or coupling agents to form a homogenized solution; (ii) mixing the homogenized mixture with water or a water-miscible solvent mixture to form a W/O type emulsion; (iii) applying the emulsion prepared in the step on the surface to be coated, wherein the application method comprises spreading, spin coating, dipping and the like; (iv) evaporating solvent from the homogenized mixture to form a self-assembled network pattern in situ; finally, (v) sintering the network pattern to form the conductive and transparent coating.

It is within the scope of the invention for the concentration of the above-mentioned surfactant or surfactant mixture to be between 0% and 4% by weight and/or for the concentration of the surfactant or surfactant mixture in the dispersion emulsion to be between 0% and 4% by weight. The W/O type emulsion is preferably prepared by the method.

It is further within the scope of the invention that the concentration of the water-miscible solvent or water-miscible solvent mixture in the dispersed emulsion is between 5% and 70% by weight. The surfactant or surfactant mixture preferably, but not exclusively, includes at least one of a nonionic and an ionic compound selected from SPAN-20, SPAN-80, glyceryl monooleate, sodium lauryl sulfate, or any combination thereof. Furthermore, it is within the scope of the invention that the concentration of the water-miscible solvent or water-miscible solvent mixture in the dispersed emulsion is between 15% and 55% by weight.

It is further within the scope of the present invention that the above water-miscible solvent or solvent mixture is selected from (but not limited to) at least one of the following: water, methanol, ethanol, ethylene glycol, glycerol, dimethylformamide, dimethylacetamide, acetonitrile, dimethylsulfoxide, N-methylpyrrolidone or any mixture thereof.

The present invention relates to a method according to any of the above, wherein the surface to be coated is selected from glass, soft or less soft polymeric films or sheets or any combination thereof. More particularly, the present invention relates to the above process wherein the polymeric film comprises at least one of the following: polyesters, polyamides, polyimides, polycarbonates, polyethylenes, polyethylene products, polypropylenes, acrylate-containing products, Polymethylmethacrylate (PMMA), copolymers or any combination thereof, and any other transparent substrate. In addition or alternatively, the above process comprises a further step of treating the surface to be coated with a corona treatment and/or a method of coating a primer.

It is further within the scope of the present invention that the primer is selected from (but not limited to) at least one of the following: 3-aminopropyltriethoxysilane, phenyltrimethoxysilane, glycidyltrimethoxysilane, commercially available Tween products, Tween-80, neoalkoxy tris (dioctylpropylphosphato) titanate or any combination thereof.

It is further within the scope of the present invention that the nanopowder described above comprises a metal or mixture of metals selected from (but not limited to) silver, gold, platinum, palladium, nickel, cobalt, copper or any combination thereof.

Further included within the scope of the present invention is the use of a coating composition selected from the group consisting of simple coatings; soaking; spin coating; dipping or any other suitable technique, the homogenized mixture is applied to the surface to be coated. Furthermore, according to one embodiment of the present invention, the step of applying the homogenized mixture to a surface to be coated to form one or more coatings has a wet thickness of 5 to 200 μm.

It is further within the scope of the invention to subject the evaporated homogenized solution to a sintering treatment at a temperature in the range of 50 c to 300 c for a period of 0.5 to 2 hours. Alternatively, the mesh pattern is subjected to a sintering process at a temperature ranging from 50 ℃ to 150 ℃ for 2 to 30 minutes.

It is another object of the present invention to provide a cost-effective and novel metal nanopowder-containing electrically conductive and transparent coating made by the method of claim 1 or any of the preceding claims thereof. In addition, or alternatively, the present invention provides an electrically conductive and transparent ink or coating characterized by having a self-assembled network pattern, which is obtainable by the process of claim 11 or any one of the preceding claims thereof.

It is also within the scope of the present invention that the above-described conductive and transparent coating be characterized by a light transmittance within the range of 30% to 90% at a wavelength of 400 nm to 700 nm; the resistance is in the range of 0.1 ohm/square to 10 kilo-ohm/square, and the haze value is in the range of 0.5% to 10%; and the electrically conductive and transparent ink layer is characterized by having a light transmittance in the range of 10% to 90% at a wavelength of 400 nm to 700 nm; the resistance is in the range of 0.1 ohm/square to 1000 ohm/square and the haze value is in the range of 0.1% to 5%.

It is further within the scope of the present invention that the above-described conductive and transparent coatings are characterized by having regular or irregular patterns produced by printing, ink-jet dispensing, self-assembly or self-organization or any other suitable technique. The conductive and transparent coating or multilayer arrangement is further characterized by providing a protective layer, a scratch resistant layer, a layer that enhances conductivity, a layer that enhances adhesion to the surface to be coated, or any combination thereof. Furthermore, the electrically conductive and transparent coating or the above-described multilayer arrangement produced is particularly suitable for at least one of the following applications: a screen, a display, an electrode, a PCB, an inkjet product, an inkjet configured product, a smart card, an RFID, an antenna, a thin film transistor, an LCD, or any combination thereof.

Brief description of the drawings

In order to understand the invention and to see how it may be carried out, preferred examples will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

FIG. 1 is an optical microscope photograph showing an ink pattern formed by self-assembly on a glass surface according to a method of an embodiment of the present invention;

FIG. 2 is an optical micrograph of an ink pattern formed on a glass surface by self-assembly according to another embodiment of the present invention;

FIG. 3 is an optical micrograph of an ink pattern formed on a glass surface by self-assembly according to another embodiment of the present invention;

FIG. 4 is an optical micrograph showing an ink pattern self-assembled on a glass surface according to a method of another embodiment of the present invention; and

FIG. 5 is an optical photomicrograph showing an ink pattern formed by self-assembly on the surface of a polymeric film according to another embodiment of the present invention; and the number of the first and second groups,

fig. 6 is a view showing an ink pattern printed on a glass surface according to another embodiment of the present invention.

Detailed description of the invention

The following description, as well as all chapters of the present invention, are provided to enable any person skilled in the art to make and use the present invention and to describe the best mode contemplated by the inventor of carrying out the present invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined specifically for the methods of making metallic nanopowder coatings and inks and all products made therefrom.

The present application presents a novel method of making conductive and transparent coatings and inks containing metal nanopowders. The comparatively described method exploits the fact that nanoparticles and grains have a much larger surface area than bulk material, have special optical properties and are operable to produce a conductive state. In the present invention, the coating of a substrate with a pre-dispersed "ink", solution or paste, can produce cost-effective nano-conductive materials and/or conductive transparent coatings. These coatings and inks are typically characterized by (1) a light transmission in the visible region of wavelengths of about 400 nm to 700 nm of between 40% and 90%; (2) resistance between 0.1 ohm/square and 9 kohm/square, and (3) lower haze values, typically in the range of 1% to 10%.

In the present invention, the term "coating" refers to any electrically and optically transparent layer obtained by mixing metal nanopowder with at least one of the following ingredients: binders, surfactants, additives, polymers, buffers, dispersants and/or coupling agents, formed into a homogenized solution; coating the homogenized mixture prepared in the above step on the surface to be coated; evaporating solvent from the homogenized mixture; the coated layer is then sintered to form a conductive and transparent coating on the surface.

In the present invention, the term "ink" refers to any ink containing one or more metal nanopowders, in particular an emulsion based composition for coloring materials, or to a legend ink (marking ink) suitable for printing on a Printed Circuit Board (PCB).

More specifically, in the present invention, the term "ink" refers to any conductive and transparent surface pattern, which is prepared by mixing metal nanopowder with at least one of the following ingredients in a solvent: binders, additives, polymers, buffers, dispersants and/or coupling agents to form a homogenized solution; mixing the homogenized mixture with water or a water-miscible solvent mixture to form a W/O emulsion; coating the homogenized mixture prepared in the above step on the surface to be coated; evaporating solvent from the homogenized mixture to form a self-assembled network pattern in situ; the mesh pattern is then sintered to produce a conductive and transparent ink.

The inks (e.g., ink pastes, inks, solutions, coatings) of the present invention are particularly suitable for use in or on transparent substrates. The above inks are suitable for coating, covering, dipping, impregnating, and/or embedding on or in a solid or semi-solid substrate, or applied to glass or any polymer substrate, including flexible, semi-flexible or rigid materials, using any other suitable technique. Due to their great transparency in the visible wavelength region of about 400 nm to 700 nm, the above conductive inks are particularly suitable for screens, displays, liquid crystal displays, smart cards and/or any technology using ink jet printers or any other technology of printing electronic devices.

The coating techniques used are screen printing, hand coater and hand coating. Other suitable techniques such as spin coating, spray coating, ink jet printing, offset printing and any suitable technique may also be used. Any type of transparent as well as opaque substrate may be coated, such as glass, polycarbonate, polymeric films, and the like.

Various ink/paste and coating systems have been found to be suitable for making transparent-conductive coatings, and these ink/paste and coating systems differ in their formulation concepts and the major ingredients that result in conductivity and transparency. The main ingredients are selected from metal nano powder; metal nanopowders and metal colloids; metal nanopowders and metal reducible salts; and/or an organometallic complex and/or an organo-metallic compound capable of decomposing to form a conductive species, all of which are present in the self-organizing system.

These nanometal based coating systems can achieve light transmission up to 95% (measured between 400 nm and 700 nm), low haze values, and resistances as low as 1 ohm/square.

The ink or paste was prepared according to the following general procedure. Care should be taken to obtain good dispersion of the conductive additives (metal nanopowders, salts, colloids and other additives).

The substrate is coated with an ink or paste. The coating can be carried out using the different techniques described above. The appropriate technique is chosen to control some physical parameters such as thickness and print geometry (to achieve the desired light transmittance and resistance). The sample may be heated to achieve the desired resistance, between 50 c and 300 c for 0.5 to 2 hours.

In the present invention, the term "sintering" refers to any process of forming an object from a metal powder by heating the powder at a temperature below the melting point of the metal powder. Casting is often impractical when manufacturing small metal objects. By chemical or mechanical methods, very fine metal powders can be produced. When the powder is pressed into the desired shape and heated, i.e. sintered, for up to 3 hours, the particles constituting the powder will be bonded together to form a single solid body.

Examples

Examples of formulations for each method are described below. These are merely representative examples to demonstrate the various possibilities covered by the present invention, in which the particular properties of the nanometal powder are applied. It is further understood that the formulations in these examples may also be made from various binders, solvents, metal powders, additives, polymers, buffers, surfactants, dispersants and/or coupling agents. However, in the present invention, it is particularly preferable that the particle size is small (D)₉₀< 0.1 micron) is electrically conductive. The concentration can be adjusted to control the viscosity and resistance and transparency of the coated substrate.

Example 1

The binder is mixed in a solvent, for example, 13 wt% ethyl cellulose, and the solvent is aromatic ester and aldehyde, preferably terpineol. The 25 parts by weight of the resulting binder solution were further homogenized using a high-speed homogenizer with: 50% (w/w) silver nanopowder (D)₉₀< 0.1 micron), a solvent such as 20% (w/w) terpineol and a coupling agent such as 1% (w/w) isopropyl dioleate (dioctylphosphate) titanate, i.e. commercially available NDZ-101 KRTTS.

Example 2

A metal nanopowder, a binder as a tackifier and water were mixed, for example, the metal nanopowder was 12% (w/w) colloidal silver, the binder was 2.5% (w/w) polyvinylpyrrolidone (PVP), and the water content was 32% (w/w). All components are thoroughly mixed using ultrasonic energy and/or high rotational speed dispersing equipment. In addition, the metal nanopowder and the solvent are mixed by a high-speed homogenizer, for example, the metal nanopowder is 14% (w/w) silver nanopowder (D)₉₀< 0.1 micron), the solvent was 39.5% (w/w) ethanol. Finally, the solution obtained in the first step is mixed with the solution obtained in the second step to obtain a homogenized solution.

Example 3

The metal nanopowder is 1 part by weight of silver formate and the dispersant is 2% (w/w) trioctylphosphine oxide (TOPO) in a solvent, such as 80% (w/w) ethyl acetate as solvent. The solution was heated to about 60 ℃ until all components were dissolved. Mixing metal nanopowder, such as 17% (w/w) silver powder (D)₉₀< 0.1 μm) was mixed into the brown solution obtained in the first step and the mixture obtained was homogenized using a high-speed homogenizer.

Example 4

The metal nanopowder is mixed into a buffer, for example, 4% (w/w) soluble silver nitrate and 9.5% (w/w) 25% ammonia solution. Further mixed with 47% (w/w) of water and a dispersant, a solvent and metal nano-powder, for example, the dispersant is 3.5% (w/w) of polycarboxylic acid ammonium salt (such as commercially available T1124 product), the solvent is 24% (w/w) of ethanol, and the metal nano-powder is 12% (w/w)% weight/weight of silver powder (D)₉₀< 0.1 μm) and then homogenizing the resulting mixture using a high speed homogenizer.

The optical and electrical resistance data for the metallic nanopowder coatings and inks prepared in the above examples are as follows:

table 1: optical and resistance data for nano-metal powder coatings and inks

Example No. 2	Printing geometry	Light transmittance%	Resistance ohm/square	Haze%)	Remarks for note
						Blank space		92		8	Glass slide
1	Screen	60-90	4-100	0.5-2	Ultraviolet opaque
						2	In succession	20-85	2-4000	1-10	Ultraviolet opaque
3	In succession	30-90	10-1200	1-10	Ultraviolet opaque
						4	In succession	55-90	150-8000	1-6	Ultraviolet opaque

The light transmission was measured between 400 nm and 700 nm. Heat treatment is carried out at 280 ℃ for about 1 hour.

In another embodiment of the present invention, a novel and simple method of making transparent and conductive coatings and inks on or in glass and/or polymeric surfaces is presented. This novel method is based on the application of the above-mentioned predetermined mixture on the surface to be coated. Upon evaporation of the organic solvent from the coating mixture, a self-assembled network pattern is formed in situ, i.e., on the surface. After drying is complete, the formed pattern is sintered at a lower temperature, such as a temperature in the range of 50 ℃ to 150 ℃ for about 2 to 30 minutes. The conductive layer has a final resistance in the range of about 1 to 1000 ohms/square, a light transmission in the range of about 50 to 95%, and a haze value in the range of about 0.5 to 5%.

The specific mixture is a W/O type emulsion of a suspension of water or a water-miscible solvent (or a mixture of these solvents) in a suspension of fine metal particles in an organic solvent or a mixture of two or more solvents that are not miscible with water.

In this embodiment of the invention, the mixture further comprises at least one emulsifier, binder or any mixture thereof. Thus in another embodiment of the invention the dispersed phase is selected from, but not limited to, water, methanol, ethanol, ethylene glycol, glycerol, dimethylformamide, dimethylacetamide, acetonitrile, dimethylsulfoxide, N-methylpyrrolidone and/or other water miscible solvents.

In another embodiment of the present invention, the continuous phase is selected from, but not limited to, petroleum ether, hexane, heptane, toluene, benzene, dichloroethane, trichloroethylene, chloroform, dichloromethane, nitromethane, dibromomethane, cyclopentanone, cyclohexanone, or any mixture thereof. The solvent or solvents preferably used in the continuous phase are characterized by a volatility that is greater than the volatility of the dispersed phase.

Similarly, the emulsifier is selected from, but not limited to, non-ionic and ionic compounds such as commercially available SPAN-20, SPAN-80, glyceryl monooleate, sodium lauryl sulfate, or any combination thereof. Furthermore, the binder is selected from, but not limited to, modified celluloses such as ethyl cellulose MW (100000-.

In another embodiment of the invention, the metal fine particles and nanopowders are selected from, but not limited to, silver, gold, platinum, palladium, nickel, cobalt, copper or any combination thereof, said metal or mixture of metals being characterized by an average particle size of less than 1 micron, more preferably less than 0.5 micron, most preferably less than 0.1 micron. The small particle size enhances the optical properties of the coatings produced by the process of the invention. In a particularly preferred embodiment of the invention, the above-mentioned metal or metal mixture is selected from noble metals, since they enhance chemical stability and increase electrical conductivity.

Table 2. basic mixture formulation of nano-inks and nano-powders obtained by the method described in the above examples.

Components	The lowest content%	The highest content%
			Organic solvents or mixtures	40	80
Adhesive agent	0	3
			Emulsifier	0	4
Metal powder	2	10
			Water-miscible solvents or mixtures	15	55

The mixture can be prepared as follows: the emulsifier and/or binder is dissolved in an organic solvent or mixture and the metal powder is added. The metal powder is dispersed in the organic phase using sonication, high shear mixing, high speed mixing or any other method used to prepare suspensions and emulsions. After the addition of the water miscible solvent or mixture, the W/O emulsion is prepared by sonication, high shear mixing, high speed mixing or any other method for preparing an emulsion.

The self-assembled network pattern described above may be formed on different surfaces: glass, polymeric films and sheets (polyesters, polyamides, polycarbonates, polyethylenes, polypropylenes, etc.). The surface to be coated may be untreated or treated to change the surface properties (corona treatment or primer coating). As the primer, a 1-2% acetone or hexane solution of 3-aminopropyltriethoxysilane, phenyltrimethoxysilane, glycidyltrimethoxysilane, Tween-80, neoalkoxytris (dioctylpropylphosphato) titanate, or the like can be used. The coating technology can be simple coating, spin coating and oil immersion. The wet thickness of the coating is 5 to 200 microns.

Another technique for coating polymeric films is to form a self-assembled network on glass and print the pattern on the polymer.

Example 5

A surfactant, such as 0.1 grams SDS, is mixed into 40 grams of water. Then, a binder and a nano-powder metal are mixed in a solvent, for example, the solvent is 60 g of toluene, the binder is 1 g of ethyl cellulose, and the nano-powder metal is 8 g of silver nano-powder (D)₉₀< 0.1 μm). The resulting solution is then homogenized using ultrasonic energy and/or high speed dispersion equipment. Finally, 31 g of the solution obtained in the first step are mixedMixing with the solution prepared in the second step.

Example 6

Mixing metal nanopowder, solvent and binder, for example, 4 grams of silver powder (maximum particle size less than 0.12 microns), 30 grams of 1, 2-dichloroethane as solvent and 0.2 grams of BYK-410 as binder; ultrasonic treatment with 180 watt power is adopted for 1.5 minutes to homogenize the solution; 15 g of distilled water was mixed in, and the resulting emulsion was homogenized by ultrasonic treatment at a power of 180 watts for 30 seconds. The formulation was printed on glass surfaces to form a good network with large cells (greater than 40 to 70 microns, line width 2-6 microns). The resistance is in the range of 7 to 40 ohms/square, the transparency is 72 to 81%, and the haze value is between 0.8 to 1.8%. Referring to fig. 1, there is shown an optical microscope photograph of a pattern formed on a glass surface according to the method of example 6.

Example 7

Mixing metal nanopowder, solvent and binder, for example, 4 grams of silver powder (maximum particle size less than 0.12 microns), 30 grams of toluene as solvent and 0.2 grams of BYK-410 as binder; ultrasonic treatment with 180 watt power is adopted for 1.5 minutes to homogenize the solution; 15 g of distilled water was mixed in, and the resulting emulsion was homogenized by ultrasonic treatment at a power of 180 watts for 30 seconds. The formulation was printed on a glass surface to form a fine network with smaller cells (about 10 microns, line width about 1-4 microns). After sintering at 150 ℃ for 5 minutes, the resistance was in the range of 7 to 40 ohm/square, the transparency was between 45 and 65% and the haze value was between 1.5 and 3.0%. Referring to fig. 2, there is shown an optical microscope photograph of a pattern formed on a glass surface according to the method of example 7.

Example 8

Mixing binder, surfactant, solvent and nano-powder metal, for example, binder is 0.06 grams BYK-410, surfactant is 0.03 grams SPAN-80, solvent is 0.8 grams cyclopentanone and 16 grams toluene, nano-powder metal is 0.8 grams silver powder (maximum particle size less than 0.12 micron); ultrasonic treatment is carried out for 30 seconds by adopting 180 watt power, and the prepared solution is homogenized; 9 ml of distilled water was mixed and the resulting emulsion was homogenized by sonication at 180 watts for 20 seconds. The formulation was printed on glass pretreated with 3-aminopropyltriethoxysilane in a 1% acetone solution to form a good network of cells having 40 to 70 microns and line widths of 2-6 microns. After sintering in formic acid vapor at 50 ℃ for 30 minutes, the resistance was between 2 and 16 ohm/square, the transparency was between 72 and 81%, and the haze value was between 0.8 and 1.8%. The patterns printed on glass to different polymeric films hardly change the electrical and optical properties.

Example 9

Mixing metal nanopowder, solvent and binder, for example, 4 grams of silver powder (maximum particle size less than 0.12 microns), 30 grams of trichloroethylene, 0.2 grams of BYK-410; ultrasonic treatment with 180 watt power is adopted for 1.5 minutes, and the prepared solution is homogenized; the resulting emulsion was homogenized by mixing with 15 ml of distilled water and treating with ultrasonic waves at a power of 180 watts for 30 seconds. The formulation was printed on a glass surface to form a fine network with smaller cells (about 10 to 40 microns, line width about 2-4 microns). After sintering at 150 c for 5 minutes, the resistance was between 7 and 40 ohm/square and the transparency was 45 to 65%. The formulation can also be prepared using a high speed mixer (Premier type) instead of sonication. The formed reticular structure unit is larger, and the transparency is improved. This formulation has better performance when printed on trichloroethylene insoluble polymeric films such as PET, PEN, polyethylene. Referring to fig. 3, there is shown an optical microscope photograph of a pattern formed on a glass surface according to the method of example 9.

Example 10

Mixing a binder, a surfactant, a solvent mixture and metal nanopowder, for example, the binder is 0.06 grams BYK-410, the surfactant is 0.03 grams SPAN-20, the solvent mixture is 0.8 grams cyclohexanone and 24 grams trichloroethylene, the metal nanopowder is 1 gram silver powder (maximum particle size less than 0.12 micron); ultrasonic treatment is carried out for 30 seconds by adopting 180 watt power, and the prepared solution is homogenized; 9 ml of distilled water was mixed and the resulting emulsion was homogenized by sonication at 180 watts for 20 seconds. The formulation was printed on glass pretreated with 3-aminopropyltriethoxysilane in a 1% acetone solution to form a good network of cells having 50 to 100 microns and line widths of about 2-8 microns. After sintering in formic acid vapor at 50 ℃ for 30 minutes, the resistance was 1.8 to 10 ohm/square, the transparency was 79 to 86%, and the haze value was 1.8 to 2.8%. Referring to fig. 4, there is shown an optical microscope photograph of a pattern formed on a glass surface according to the method of example 10. The patterns printed on the various polymeric films did not significantly change the electrical and optical properties. Referring to fig. 5, there is shown an optical microscope photograph of a pattern formed on a polymer film according to the method of example 10.

Example 11

Mixing a binder, a surfactant, a solvent mixture and metal nanopowder, for example, the binder is 0.06 grams BYK-411, the surfactant is 0.2 grams SPAN-80, the solvent mixture is 1 gram cyclohexanone and 10 grams petroleum ether, the metal nanopowder is 1 gram silver powder (maximum particle size less than 0.12 micron); ultrasonic treatment is carried out for 30 seconds by adopting 180 watt power, and the prepared solution is homogenized; 7 ml of distilled water was mixed and the resulting emulsion was homogenized by sonication at 180 watts for 20 seconds. The formulation was printed on polyimide pretreated with phenyltrimethoxysilane in 1% acetone to form a good network of cells with more than 20 microns to 60 microns and line widths of about 2-6 microns. After sintering at 150 ℃ for 5 minutes, the resistance was between 20 and 30 ohm/sq, the transparency was 68 to 78% and the haze value was between 8 and 10%.

Claims (20)

1. A method of preparing a transparent conductive coating containing metal nanopowders, the method comprising:

a. mixing in an organic solvent a metal nanopowder and at least one ingredient selected from the group consisting of: binders, surfactants, additives, polymers, buffers, dispersants and/or coupling agents to form a homogenized mixture;

b. applying the homogenized mixture to a surface to be coated;

c. evaporating solvent from the homogenized mixture; and

d. sintering the coated surface to form an electrically conductive and transparent coating on the surface.

2. The method of claim 1, wherein the sintering process is performed at a temperature ranging from 50 ℃ to 150 ℃ for 2 to 30 minutes.

3. The method of claim 1, wherein the concentration of the metal nanopowder in the homogenized mixture is between 1% and 50% by weight.

4. The method of claim 1, wherein the concentration of the metal nanopowder in the homogenized mixture is between 2% and 10% by weight.

5. The method of claim 1, wherein homogenizing the mixture comprises evaporating the organic solvent or mixture of organic solvents faster than water.

6. The method of claim 5, wherein the concentration of the organic solvent or mixture of organic solvents is between 20 wt.% and 85 wt.%.

7. The method of claim 5, wherein the concentration of the organic solvent or mixture of organic solvents is between 40 wt.% and 80 wt.%.

8. The method of claim 1, wherein the method further comprises:

i. mixing the homogenized mixture in water, a water-miscible solvent or a water-miscible solvent mixture to form a water/oil emulsion;

applying the emulsion to a surface to be coated;

evaporating solvent from the emulsion to form a self-assembled network pattern in situ;

sintering the mesh pattern to form a transparent conductive coating.

9. The method of claim 8, wherein the concentration of water, water miscible solvent or water miscible solvent mixture in the emulsion is between 5 wt.% and 70 wt.%.

10. The method of claim 8, wherein the concentration of water, water miscible solvent or water miscible solvent mixture in the emulsion is between 15 wt.% and 55 wt.%.

11. The method of claim 1, wherein the surface to be coated is selected from the group consisting of glass, flexible or less flexible polymeric films or sheets, polyethylene products, polypropylene products, acrylate-containing products, Polymethylmethacrylate (PMMA), copolymers thereof, or any combination thereof.

12. The method of claim 1, wherein the surface to be coated is a polymeric film selected from the group consisting of polyesters, polyamides, polycarbonates, polyethylenes, polypropylenes, copolymers thereof, or any combination thereof.

13. The method of claim 1, wherein the metal nanopowder is selected from silver, gold, platinum, palladium, nickel, cobalt, copper or any combination thereof.

14. The method of claim 1, wherein the metal nanoparticles have a D of less than 0.1 micron₉₀The value is obtained.

15. The method of claim 1, wherein the homogenized mixture comprises metal colloids, reducible metal salts, organometallic compounds capable of decomposing to form conductive species, organometallic complexes, and combinations thereof.

16. The method of claim 1, wherein the homogenized mixture is applied to the surface in a regular or irregular pattern.

17. The method of claim 1, wherein the homogenized mixture is applied to the surface by ink jet printing.

18. The method of claim 1, wherein the transparent conductive coating is characterized by a light transmission in the visible light range of wavelengths from 400 nm to 700 nm of between 40% and 90%; the resistance is between 0.1 ohm/square and 9 kilo-ohm/square; and has a haze value of 1% to 10%.

19. A transparent conductive coating made by the method of any one of claims 1-18.

20. The transparent conductive coating of claim 19, wherein the coating is incorporated into a screen, a display, an electrode, a Printed Circuit Board (PCB), an ink jet product, an ink jet configured product, a smart card, an RFID article, an antenna, a thin film transistor, an LCD, or any combination thereof.