1. Field of the Invention
The present invention relates to a flexible transparent electrode and a method for manufacturing the same, and, more particularly, to a flexible transparent electrode and a method for manufacturing the same using electrohydrodynamic jet printing.
2. Background Art
Conventional transparent electrodes mainly use indium tin oxide (ITO). Indium tin oxide is a mixture of In2O3 and SnO2, and generally has 90% of In2O3 and 10% of SnO2. In general, Indium tin oxide is called “ITO”. ITO has transparency when it is manufactured into a thin film. Moreover, ITO has high electrical conductivity and optical transparency. However, such characteristics are applied only when ITO is a thin film, and if ITO exceeds a predetermined thickness, electrical conductivity increases but optical transparency decreases. The thin film of ITO may be generally deposited onto the surface by electron beam deposition, vapor deposition, or sputtering.
As shown in
However, the transparent electrode using indium tin oxide according to the prior art has a problem in that manufacturing price is high because material prices of indium tin oxide are high due to limited resources of indium. Furthermore, indium tin oxide has another problem in that it is fragile because it is weak to an external force, such as flexure. Additionally, a general process to manufacture an indium tin oxide thin film is very complicated because it requires a high vacuum condition.
Due to the above-mentioned problems, studies on various materials to substitute for indium tin oxide are under way. For instance, as such materials, there are carbon nanotube (CNT), graphene, silver nanowire, and so on. However, it is hard for such materials to satisfy electrical conductivity as well as transparency.
In order to overcome the various problems, a method for manufacturing a metal mesh structure on a transparent film was proposed, and a representative example of the method is lithography which is used in the semiconductor process.
As another method, there is an inkjet method. The inkjet method is a direct writing method capable of patterning a mesh structure but is disadvantageous in manufacturing the transparent electrode due to a thick linewidth. In detail, in order to manufacture the transparent electrode, the pattern of the mesh structure must have a linewidth under 50 μm. However, the conventional inkjet method cannot be applied to the transparent electrode manufacturing method because it cannot embody the linewidth under 50 μm.
In other words, in the conventional inkjet method, because the size of a nozzle has an absolute influence on the size of droplets, the size of the nozzle must be reduced in proportion to the size of the size of droplets in order to spray fine droplets. However, when a nozzle of a fine size is used, there are several limitations in that nozzle clogging frequently occurs at a nozzle outlet and in that it is difficult to attach the sprayed droplets onto a designated position of the surface of the substrate owing to the Brownian movement in the air.
Nevertheless, because the inkjet printing technology has many advantages in that manufacturing costs are reduced and in that it is easy to realize a large area, technology development for solving the above-mentioned problems is on the way. In detail, in a thesis entitled ‘study on fabrication of high-resolution inkjet-printed conductive patterns assisted by soft lithography’ written by Seong Ji Soo at Hanyang University in 2013 as a dissertation, the method for producing high-solution conductive patterns using inkjet printing technology and soft lithography has been proposed.
The producing method proposed in the thesis is a method including the steps of treating SU-8 patterns made through nanoimprint with UV/O3, forming a wettability contrast formed through microcontact printing on the surface of a substrate and forming electrode patterns using inkjet printing.
The producing method proposed in the thesis can partially solve the problems of the prior arts because it can form high-solution patterns using inkjet technology, but has a new problem in that it requires complicated processes in production. In addition, the producing method proposed in the thesis has another problem in that time required for production is long and manufacturing costs are increased because the method needs pre-treatment processes of multiple stages for inkjet printing.
Therefore, people need technology for producing a transparent electrode to which materials to substitute for the expensive indium tin oxide can be applied and which can reduce manufacturing costs because it is easily produced through a simple manufacturing process. For this, technology for utilizing an electrohydrodynamic jet printing device has been developed.
The electrohydrodynamic jet printing technology is a printing technology carrying out printing through the steps of applying high voltage a solution to provide charges and ultra-atomizing the solution having charges.
Referring to
As shown in
As shown in
Therefore, also the transparent electrode manufacturing method using the electrohydrodynamic jet printing technology according to the prior art cannot obtain a stable pattern.
Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior arts, and it is an object of the present invention to provide a flexible transparent electrode and a method for manufacturing the same which can apply DC voltage without any influence of an electric field and form a pattern of a mesh structure because droplets charged equally are attached onto a substrate when voltage is applied to an object to be printed and an injection nozzle using an electrohydrodynamic jet printing device, thereby easily manufacturing a flexible transparent electrode.
To accomplish the above object, according to the present invention, there is provided a flexible transparent electrode including: a substrate made of a flexible and transparent material; and a metal pattern which is formed on the substrate in a mesh form and has an electroconductive metal material, wherein the metal pattern is formed by being patterned on an upper side of the substrate using an electrohydrodynamic jet printing method and being sintered, and the electrohydrodynamic jet printing method is a method of forming a metal pattern on the upper side of the substrate after applying AC voltage of a predetermined power to the substrate and an injection nozzle of an electrohydrodynamic jet printing device.
In this instance, the material of the substrate is at least one selected from groups comprised of polyethylene naphthalate (EN), polycarbonate (PC), polyethersulfone (PES), polyarylate (PAR), polysulfone (PSF), cyclic-olefin copolymer (COC), polyimide (PI), PI-fluoro-based high molecular compound, polyetherimide (PEI) and epoxy resin.
In an embodiment, the electroconductive metal material of the metal pattern is at least one selected from groups comprised of silver (Ag), gold (Au), copper (Cu), aluminum (Al) and iron (Fe).
Moreover, the metal pattern has a structure that at least two squares are arranged to adjoin each other.
Furthermore, the metal pattern has a structure that a structure that at least two polygons are arranged to adjoin each other.
In an embodiment, the linewidth (w) of the metal pattern is within a range of 1 μm to 30 μm.
Additionally, a distance (p) between lines of the metal pattern is in a range of 200 μm to 1,000 μm.
In an embodiment, an injection cycle of the injection nozzle of the electrohydrodynamic jet printing device and an AC cycle are in integer multiple relationship with each other, and the injection nozzle carries out injection at the highest voltage or the lowest voltage of AC voltage.
In another aspect of the present invention, there is provided a transparent electrode manufacturing method including: a) a preparation step of preparing a substrate made of a flexible and transparent material, a metal nanocolloidal solution and an electrohydrodynamic jet printing device; b) a substrate fixing step of fixing the substrate at a position spaced apart from an injection nozzle of the electrohydrodynamic jet printing device at a predetermined interval in order to print a metal pattern on the substrate using the electrohydrodynamic jet printing device; c) an AC voltage applying step of applying AC voltage of a predetermined power to the substrate and the injection nozzle of the electrohydrodynamic jet printing device; d) a pattern forming step of printing the metal pattern on an upper side of the substrate by the metal nanocolloidal solution using the electrohydrodynamic jet printing device in a state where the AC voltage of the predetermined power is applied to the substrate and the injection nozzle; and e) a pattern sintering step of sintering the metal pattern formed on the substrate.
In this instance, the material for the metal nanoparticles forming the metal nanocolloidal solution is at least one selected from groups comprised of silver (Ag), gold (Au), copper (Cu), aluminum (Al) and iron (Fe).
In an embodiment, the pattern forming step includes the steps of: d-1) controlling the power of AC voltage; d-2) controlling injection pressure of the injection nozzle; d-3) controlling a distance between the injection nozzle and the substrate; and d-4) moving a flat position of the substrate according to the preset form of the metal pattern.
Moreover, in the pattern forming step, an injection cycle of the injection nozzle of the electrohydrodynamic jet printing device and an AC cycle are in integer multiple relationship with each other, and the injection nozzle carries out injection at the highest voltage or the lowest voltage of AC voltage.
In an embodiment, in the pattern sintering step, sintering temperature is 170° C. to 190° C. and a sintering period is 15 minutes to 25 minutes.
In a further aspect of the present invention, there is provided a transparent electrode manufacturing apparatus including: an electrohydrodynamic jet printing device having a fixing unit for fixing a substrate and an injection nozzle for printing a pattern on the substrate fixed on the fixing unit; an AC voltage supplier for applying AC voltage of a predetermined power to the fixing unit and the injection nozzle; a driving unit for changing a flat position of the fixing unit according to a preset form of a metal pattern; and a control unit for controlling the electrohydrodynamic jet printing device, the AC voltage supplier and the driving unit.
In an embodiment, the transparent electrode manufacturing apparatus further includes a camera which monitors the state of the metal pattern printed on the substrate by the electrohydrodynamic jet printing device.
In addition, the present invention provides an electronic apparatus of a flexible structure including the transparent electrode.
As described above, the transparent electrode according to the present invention can reduce manufacturing costs because it can be manufactured utilizing a high molecular compound or resin which is more inexpensive than the prior arts.
Moreover, the transparent electrode according to the present invention provides a pattern with a linewidth thinner than that of the prior arts, thereby enhancing transparency.
Furthermore, the transparent electrode manufacturing method according to the present invention can manufacture a transparent electrode through the more simplified process than the prior arts because using the electrohydrodynamic jet printing method by applying AC voltage to a flexible and high dielectric material like a PET film.
Additionally, the transparent electrode manufacturing method according to the embodiment of the present invention can manufacture a transparent electrode having a pattern with a thinner linewidth than that of the prior art because using the electrohydrodynamic jet printing method.
Furthermore, the transparent electrode manufacturing method according to the embodiment of the present invention can manufacture a transparent electrode utilizing a high molecular compound or resin which is more inexpensive compared with the prior arts and manufacture a transparent electrode by more simplified processes compared with the prior arts, thereby reducing manufacturing costs.
In addition, the transparent electrode manufacturing method according to the embodiment of the present invention is safe and does not cause environmental pollution because not using special chemical substances which are dangerous.
The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which:
Hereinafter, reference will be now made in detail to the preferred embodiments of the present invention with reference to the attached drawings, but the scope of the present invention is not limited by the attached drawings and embodiments. In addition, in the description of the present invention, when it is judged that detailed descriptions of known functions or structures related with the present invention may make the essential points vague, the detailed descriptions of the known functions or structures will be omitted.
Referring to
In this instance, the metal pattern 120 formed on the upper side of the substrate 110 may be manufactured by being sintered after being patterned on the upper side of the substrate 110 using the electrohydrodynamic jet printing method. Here, the electrohydrodynamic jet printing method will be described in detail later.
The material which is applicable to the substrate 110 according to the present invention is not limited if it is a transparent and flexible material. For instance, the material may be polyethylene terephthalate (PET). Additionally, the material which is applicable to the substrate 110 may be at least one selected from groups comprised of polyethylene naphthalate (EN), polycarbonate (PC), polyethersulfone (PES), polyarylate (PAR), polysulfone (PSF), cyclic-olefin copolymer (COC), polyimide (PI), PI-fluoro-based high molecular compound, polyetherimide (PEI) and epoxy resin.
In addition, the electroconductive metal material which forms the metal pattern 120 formed on the upper side of the substrate 110 may be silver (Ag). The electroconductive metal material is prepared in a colloidal solution state, and then, is formed on the upper side of the substrate 110 by the electrohydrodynamic jet printing method. Preferably, the electroconductive metal material is silver (Ag), but may be formed on the upper side of the substrate 110 by the electrohydrodynamic jet printing method and may be substituted with any electroconductive material. For instance, the electroconductive metal material may be at least one selected from groups comprised of silver (Ag), gold (Au), copper (Cu), aluminum (Al) and iron (Fe). Here, the electrohydrodynamic jet printing method will be described in detail later.
Referring to the drawings, the metal pattern 120 formed on the upper side of the substrate 110 may have a mesh structure. As shown in
In the meantime, referring to
In order to quantifiably indicate an area ratio of the metal pattern 120 formed on the upper side of the substrate 110, the filling factor (FF) may be defined as follows:
In the equation 1, the filling factor (FF) is a value showing the area ratio to form the metal pattern 120 contrast to the area of the substrate 110, p is a linewidth of the metal pattern 120, and w is a distance between the lines of the metal pattern 120.
As shown in the equation 1, the area of the metal pattern 120 formed on the upper side of the substrate 110 is increased as the FF value increases. Of course, the FF value is not limited if it does not considerably reduce transmittance and electroconductivity of the transparent electrode, but, preferably, is less than 0.3, and more preferably, less than 0.07.
Referring to
In detail, the electrohydrodynamic jet printing device 210 is a device applying an electrohydrodynamic spray technology to ultra-atomize a solution having charges after providing charges by applying high voltage. The electrohydrodynamic jet printing can electrically carry out the preconditioning process before printing after conveying lots of ink toward an object to be sprayed, remarkably enhance resolution of nano-scale compared with the conventional inkjet printing method because it is capable of applying a flow of an electrically induced fluid to a nano-scale nozzle, and control a printed state in a new way to control electrically.
In general, as shown in
Furthermore, the AC voltage supplier 220 can apply AC voltage of a predetermined size to the fixing part 211 and the injection nozzle 212, and the control unit 240 controls the electrohydrodynamic jet printing device 210, the AC voltage supplier 220 and the driving unit 230.
According to circumstances, as shown in
Additionally, it is preferable that the transparent electrode manufacturing apparatus 200 according to the embodiment of the present invention be installed and managed inside a class-100 clean room 201.
Referring the drawings together with
In this instance, the substrate 110 made of the flexible and transparent material may be at least one selected from groups comprised of polyethylene naphthalate (EN), polycarbonate (PC), polyethersulfone (PES), polyarylate (PAR), polysulfone (PSF), cyclic-olefin copolymer (COC), polyimide (PI), PI-fluoro-based high molecular compound, polyetherimide (PEI) and epoxy resin. In addition, the material for the metal nanoparticles forming the metal nanocolloidal solution may be at least one selected from groups comprised of silver (Ag), gold (Au), copper (Cu), aluminum (Al) and iron (Fe).
Moreover, as shown in
The transparent electrode manufacturing method (S100) according to the embodiment of the present invention includes a substrate fixing step (S120) of fixing the substrate 211 at a position spaced apart from the injection nozzle 212 of the electrohydrodynamic jet printing device 210 at a predetermined interval in order to print the metal pattern 120 on the substrate 110 using the electrohydrodynamic jet printing device 210.
Furthermore, the transparent electrode manufacturing method (S100) according to the embodiment of the present invention includes an AC voltage applying step (S130) of applying AC voltage of a predetermined power to the substrate 211 and the injection nozzle 212 of the electrohydrodynamic jet printing device 210; and a pattern forming step (S140) of printing the metal pattern 120 on the upper side of the substrate 110 by the metal nanocolloidal solution using the electrohydrodynamic jet printing device 210 in a state where the AC voltage of the predetermined power is applied to the substrate 110 and the injection nozzle 212.
In detail, the injection nozzle 212 to which AC voltage is applied induces a sprayed flow of the metal nanocolloidal solution electrically so as to stably print the pattern on the upper side of the substrate 110.
Additionally, as shown in
Referring to the drawings, the transparent electrode manufacturing method (S100) will be described continuously.
The transparent electrode manufacturing method (S100) according to the embodiment of the present invention applies AC voltage of a predetermined power to the substrate 211 and the injection nozzle 212 of the electrohydrodynamic jet printing device 210.
In case that AC voltage of the predetermined power is applied to the substrate 211 and the injection nozzle 212 of the electrohydrodynamic jet printing device 210 in order to print a pattern, as shown in
Furthermore, in order to print the pattern more stably, as shown in
Through a series of the steps described above, the metal pattern 120 is printed on the upper side of the substrate 110, and then, manufacturing of the transparent electrode 110 is finally completed through a pattern sintering step (S150) of sintering the metal pattern 120 formed on the substrate 110. In this instance, in the pattern sintering step (S150), sintering temperature is 170° C. to 190° C. and a sintering period is 15 minutes to 25 minutes. Of course, the sintering temperature and the sintering period can be properly changed according to the design of the transparent electrode and the user's management.
Here, the sintering process is a method that metal powder particles become lumpy into one through a thermal activation process in the metallurgy. Because sintering is a well-known method in the metallurgy, its detailed description will be omitted.
As described above, the transparent electrode manufacturing method according to the embodiment of the present invention can manufacture a transparent electrode having a pattern with a thinner linewidth than that of the prior art because using the electrohydrodynamic jet printing method. Furthermore, the transparent electrode manufacturing method according to the embodiment of the present invention can manufacture a transparent electrode utilizing a high molecular compound or resin which is more inexpensive compared with the prior arts and manufacture a transparent electrode by more simplified processes compared with the prior arts, thereby reducing manufacturing costs. Additionally, the transparent electrode manufacturing method according to the embodiment of the present invention is safe and does not cause environmental pollution because not using special chemical substances which are dangerous.
As shown in
Referring to
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Referring to
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As shown in
As described above, while the present invention has been particularly shown and described with reference to the preferable embodiment thereof, it will be understood by those of ordinary skill in the art that the present invention is not limited to the above embodiment and that various changes, modifications and equivalences may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
This application is a division of U.S. patent application Ser. No. 14/804,906, filed Jul. 21, 2015, which claimed priority to Korean Patent Application No. 10-2014-0092813, filed Jul. 22, 2014, the disclosures of which are incorporated in their entireties herein by reference.
Number | Date | Country | |
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Parent | 14804906 | Jul 2015 | US |
Child | 15581367 | US |