# Dry Printing of Ag-Ni Conductive Particles Using Toner-Type Printed Electronics
## 3 Results  
Figure 3 demonstrates an SEM image of the developer used for conductive toner printing. Toner printing uses a developer, which is a mixture of the toner and carrier particles. The small (\(<\)5 \(\upmu\)m) and bright gray particles are the Ag-Ni conductive toner particles, while the large (\(\sim\)40 \(\upmu\)m) and dark gray particles are the carrier particles. Toner particles were distributed on the surface of the carrier particles. The conductive Ag-Ni particles sufficiently adhere to the carrier particle surface, owing to an image force between a charged Ag-Ni particle and carrier particle [34]. The toner and carrier weight ratio in the developer was 1:40. The toner particles were transferred from the carrier particle surface onto the plastic film substrate by applying an external electrostatic force during the printing process. In contrast, carrier particles (P-02 standard carrier, distributed by the Imaging Society of Japan, Tokyo, Japan) consist of a magnetic material and help the toner particles disperse, remain stable in air, and form a magnetic brush structure (shown in Figure 5b later), which are necessary for toner printing. Therefore, the carrier particles remain on the developer and are not transferred to the plastic substrate film. Figure 4a presents a schematic illustration of the electrostatic potential distribution formed on the PET film surface. The PET film was back-coated with an Al thin film and placed on the charging equipment; the gradation pattern of the electrostatic potential on the PET surface was formed, as illustrated in Figure 4a. The arrangement of the electrical potential on the positively charged PET film was 0, +100, +80, +60, +40, and +20 V from left to right, and that on the negatively charged PET film was 0, \(-\)100, \(-\)80, \(-\)60, \(-\)40, and \(-\)20 V. We developed the Ag-Ni toner particle on the PET film using primitive electrophoretic printing equipment, which was the same as that depicted in Figure 5. The results of the development of the positively charged PET surface are shown in Figure 4b, which demonstrates that a thin Ag-Ni toner particle was distributed in the 0 V region. However, fewer Ag-Ni particles were distributed in the positively charged region. Moreover, the Ag-Ni particles were effectively repelled in the high-electrical-potential region. Conversely, as shown in Figure 4c, dense Ag-Ni particles were distributed in the  
Figure 2: (**a**) Scanning electron microscopy (SEM) image of a Ag–Ni composite toner particle. (**b**) Energy dispersive X-ray spectroscopy (EDX) image of the Ag K\(\alpha\) X-ray emission distribution, EDX image of the Ni K\(\alpha\) X-ray emission distribution (**c**), and superimposed EDX image of the Ag and Ni EDX K\(\alpha\) emission (**d**). negatively charged region compared to the 0 V region, and the gradation of the Ag-Ni particle density changed from the \(-20\) V to \(-100\) V region. Therefore, Ag-Ni particles were effectively attracted to the lower electric potential region. These results clearly demonstrate that Ag-Ni particles mixed and frictionally charged with the P-02 carrier particles have a net positive charge. Therefore, it is possible to attract and repel conductive Ag-Ni particles using the polarity of an applied external electric field. Figure 5a demonstrates the schematic of the primitive electrographic printing equipment. The developer, comprised of the toner and carrier particles, is loaded into the developer reservoir, which consists of a non-magnetic metal plate. The magnet row moving in a reciprocating motion below the developer reservoir forms the magnetic brush of the developer particle along the magnetic lines of the force, as shown in Figure 5b. An insulator plate with a target electrode and counter electrode was placed above the developer reservoir, and external development and counter electric fields were applied during development.