The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:
1 is a graph that shows the results of TGA (Thermogravimetric Analysis) of the ink for ink jet printing according to Comparative Example 1; and
Reference will now be made in detail to the preferred embodiments of the present invention. However, the following examples and comparative examples are illustrative only, and the scope of the present invention is not limited thereto.
A solution of AgNO3 in ethylene glycol and a solution of PVP (polyvinyl pyrrolidone), a surfactant, in ethylene glycol were provided, and both solutions were mixed and agitated under reflux for about 1 hour at 150° C. to allow them to react. After the reaction, a dispersion containing Ag nanoparticles with a size of 70˜150 nm dispersed therein was obtained.
To 10 ml of the solution of Ag nanoparticles obtained by the above-described polyol process, 20 ml of acetone and 10 ml of THF were added. The resultant mixture was subjected to centrifugal separation (5000 rpm, 20 minutes) and the supernatant was removed. Next, the precipitate was dispersed again into 5 ml of ethanol. Then, 10 ml of acetone and 10 ml of THF were added thereto, and the resultant mixture was subjected to centrifugal separation, followed by removing the supernatant. The above procedure was repeated twice, and then the resultant precipitate was dispersed into a solvent (such as ethanol) to provide ink.
The ink had a solid content of 52.58 wt % and a viscosity of 14.5 cps. After measuring by TGA, the amount of the remaining surfactant was 1.5 parts by weight based on 100 parts by weight of Ag solid particles (see
Ag nanoparticles were prepared in the same manner as described in Example 1. Next, ink was provided in the same manner as described in Example 1, except that the ink had a solid content of 70 wt %, and then the ink was subjected to an ink jet patterning test.
The ink had a viscosity of 30.5 cps. The ink was applied onto a substrate by subjecting it to ink jetting once and was sintered at 400° C. for 30 minutes. After the sintering, a pattern having a line width of 90 μm, a thickness of 0.68 μm and a line length of 2.1 cm was obtained, and the pattern showed a line resistance of 16.3Ω and a specific resistivity of 4.75 μΩ.cm. Further, the ink was applied onto a substrate by subjecting it to ink jetting once and was sintered at 580° C. for 30 minutes. After the sintering, a pattern having a line width of 44.7 μm, a thickness of 1.2 μm and a line length of 1.5 cm was obtained, and the pattern showed a line resistance of 12Ω and a specific resistivity of 4.29 μΩ.cm.
Nanoparticles, ink and an electrode pattern were obtained in the same manner as described in Example 1, except that surplus surfactant remaining in the solution of Ag nanoparticles was not sufficiently washed off.
Since the solution had a high viscosity due to the absence of a step of washing the surplus surfactant, the solid content was reduced to ensure an adequate viscosity. for ink jetting. Finally, the solution had a solid content of 21.85 wt % and a viscosity of 16.5 cps. After measuring by TGA, the amount of the surfactant remaining in the solution was 45.0 parts by weight based on 100 parts by weight of the Ag solid particles (see
After sintering, the resultant pattern had a line width of 134 μm, a thickness of 2.297 μm and a line length of 4.3 cm, and its resistance was not available.
Ink was provided in the same manner as described in Comparative Example 1, except that the ink had a solid content increased to 50 wt %. In this example, the ink had a viscosity of 100 cPs or higher, which could not be measured by using a viscosimeter provided by the inventors of the present invention. Due to such a high viscosity, ink jetting was not allowed either.
As can be seen from the foregoing, the method for preparing metal nanoparticles for use in ink for ink jet printing comprises a step of washing surplus surfactant with at least one solvent. By doing so, the surplus surfactant remaining on the surfaces of the metal nanoparticles can be minimized, resulting in a drop in viscosity of ink comprising the metal nanoparticles. Therefore, even if the ink has a metal nanoparticle content of 50 wt % or more, the ink can satisfy a viscosity condition required for ink jet printing, and thus can form an electrode pattern with high conductivity.
While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment and the drawings. On the contrary, it is intended to cover various modifications and variations within the spirit and scope of the appended claims.
Number | Date | Country | Kind |
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2006-96405 | Sep 2006 | KR | national |
2007-12942 | Feb 2007 | KR | national |