# High-Resolution Printing of Various Electronic Materials by Electrophotography
## 1 Introduction  
The global environment must be considered for any mass-production process, including electronics, with the increasing demand for information technology. Microfabrication processes in modern semiconductor industries require large amounts of materials and energy for high-temperature, high-vacuum, and high-resolution fabrication. These conventional microfabrication processes continue to be essential for high-end semiconductor products such as processors and memory. However, nanoscale fabrication is not required for most electronics, except for state-of-the-art semiconductor chips. Photolithography and etching-based fabrication may not be necessary for macro-scale circuits and devices or even small-scale integrated circuits (ICs) because small-scale integrated circuits, such as logic ICs or analog-digital converter ICs, are fabricated using several standard micrometer processes, not with several nanometer-scale processes. Early commercial processors such as Intel 4004 and 8008 were fabricated using a 10 \(\upmu\)m process rule. Therefore, regarding printing resolution, except for the interior of a high-performance processor, simple processors and peripheral circuits can be fabricated using printed electronics technologies [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15]. Printed electronics are an additive manufacturing process for next-generation flexible electronics; specifically, they are clean and produce less chemical waste than conventional photolithography and etching processes. Although conventional photolithography and etching processes are mature and have high resolution, they produce various chemical wastes, including resists, development, and etching chemicals, as well as waste liquids, including heavy metals, because they are subtractive. This waste was not produced during additive processing. Another advantage is that electronic products can be made much smaller using high-resolution printed electronics. The ability to reduce the size of electronic products is restricted by the standard size of general-purpose ICs. The size, arrangement, and pitch of the IC pins were fixed according to standard specifications such as the Dual Inline Package (DIP). For example, one DIP IC has the pin pitch of 2.54 mm and package width of 15.2,10.16, or 7.62 mm. However, the area of the Si chip is smaller than the package size. The occupation area of the internal IC circuit was much smaller than that of the Si chip. More specifically, the occupied area of a commercial IC is much larger than the area necessary to perform the expected function. Therefore, the internal circuit patterns of ICs have to be extended to match the 2.54 mm pin pitch. The occupation size of the ICs can be reduced by printing the entire product from individual transistors and diodes on a um scale to macrowires, including antennas, on a millimeter scale. Printed electronics are accomplished using various printing methods, such as gravure printing [16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27], screen printing [28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42], inkjet printing [43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78; 79; 80; 81; 82; 83], and electrophotography. Gravure and screen printing are advantageous for high-throughput mass production; however, the preparation of printing plates is necessary before performing these processes. Conversely, inkjet and electrophotography are on-demand and direct digital printing techniques; i.e., they do not need a printing plate but only require digital data. Therefore, they are advantageous in prototyping and manufacturing a wide variety of products in small quantities. In addition, electrophotography is advantageous for multilayer and page printing because it does not require solvents or chemical agents. The absence of solvent completely suppressed the exhaustion of volatile organic compounds (VOCs).