Method of forming a 3D conformal conductive pattern
The present disclosure relates to a method of forming a conductive pattern by printing a conductive ink on a substrate having a three-dimensional surface. The method includes a substrate providing step of mounting the substrate; an ink injection step of printing a conformal conductive pattern on the three-dimensional surface of the substrate by injecting a conductive ink using a nozzle while applying an electric field; and a curing step of forming the injected conductive pattern into a cured conductive pattern by curing.
1 . A method of printing a conductive element comprising a conductive ink on a substrate having a three-dimensional surface, the method comprising:
positioning the substrate;
spraying, during an ink spraying step, the conductive ink through a nozzle by electrohydrodynamic (EHD) printing while applying an electric field to print a conformal conductive pattern on the three-dimensional surface of the substrate, wherein the conformal conductive pattern has a width to height aspect ratio in a range of 0.05:1 to 0.3:1; and
curing, during a curing step, the sprayed conductive pattern to form a cured conductive pattern, wherein the conductive ink comprises:
an electric field reaction element that is a water-soluble polymer including a heterogeneous element that can react to assist the movement of charges in the electric field; and
a charge transfer element that provides a charge that moves in the electric field in the conductive ink,
wherein the charge transfer element is split into ions in an aqueous solution state and moves as a charge, affecting the electric field reaction element to control the fluidity of the conductive ink,
wherein the electric field reaction element and the charge transfer element are included in a weight ratio of 10:1 to 3:1,
wherein the electric field reaction element and the charge transfer element interact with each other and determine ejection performance of the conductive ink in the electric field during the ink spraying step to conformally print the conductive pattern on the three-dimensional surface.
2 . The method of claim 1 , wherein the conductive pattern is thermally or optically cured after the spraying.
3 . The method of claim 2 , wherein the substrate having the three-dimensional structure has a three-dimensional structure on the surface or is curved or bent into a three-dimensional shape.
4 . The method of claim 3 , wherein in the spraying of the conductive ink, the three-dimensional surface comprises top, bottom, and side surfaces of a bent edge of the substrate, and the conductive ink forms an electrical pattern continuously connecting the top surface and the side surface or the bottom surface and the side surface.
5 . The method of claim 1 , wherein the conductive pattern having a line width W 1 is formed in the spraying of the conductive ink, and
the conductive pattern has a line width W 2 after being cured by laser having power of 6000 mA to 8000 mA in the curing,
where W 2 /W 1 is 0.9 to 1.1.
6 . The method of claim 5 , wherein in the spraying of the conductive ink, a portion of side and top surfaces is printed to form a portion of the pattern, and a portion of side and bottom surfaces is printed by inverting the substrate.
7 . The method of claim 6 , wherein in the spraying of the conductive ink, as the nozzle approaches one surface of the substrate, the conductive ink moves toward the substrate and a line of the conductive ink ejected from the nozzle is printed on the one surface of the substrate facing the nozzle.
8 . The method of claim 7 , wherein in the spraying of the conductive ink, the printing is performed by passing the nozzle from one side to the other of the substrate and then moving the nozzle in the opposite direction.
9 . The method of claim 1 , wherein the nozzle used in the spraying of the conductive ink comprises a plurality of nozzles.
10 . The method of claim 9 , wherein in the spraying of the conductive ink, the spraying forms the conductive pattern due to a linear jet flow portion (J 1 ) or a spinning jet flow portion (J 2 ).
11 . The method of claim 1 , wherein in the printing, the electric field has a voltage of 1 kV to 2 kV.