Development of the New MACH (MACH with MLChips)

We have successfully developed the new MACH (Multilayer ACtuator Head). This is composed of MLChips (Multi-Layer Ceramic with Hyper-Integrated Piezo Segments) instead of MLP (Multi-Layer Piezo). MLChips is a ceramic MLA (Multi-Layer Actuator), in addition it has the ink chambers to reduce the production process. The features of MACH with MLChips through the comparison with MLP type MACH are described in this paper. Introduction Seiko Epson has successfully developed a new type of MACH (Multi-Layer Actuator Head) composed of MLChips (Multi-Layer Ceramic with Hyper-Integrated Piezo Segments) instead of MLP (Multi-Layer Piezo). MLChips is also a ceramic MLA (Multi-Layer Actuator) and in addition contains ink chambers to streamline the production process. In this paper I will describe the features of the MACH with MLChips through a comparison with the MLP type MACH. We have been pursuing higher image quality by developing ink jet heads with Piezo devices that excel in ink droplet control and offer high ink selectivity. However, since Piezo devices are ceramic, they are fragile and extremely difficult to process. For some reason their thickness is limited to 0.1 mm and this is a direct factor contributing to the high cost of printer heads. To solve this problem, we devised a Piezo device that is heat-treated simultaneously as an integrated ceramic multi-layer structure. That is, the Piezo device is made from a completely ceramic MLA (Multi-Layer Actuator). This allows the Piezo device to be made extremely thin while fully realizing its advantages in an ink jet head. MACH with MLChips We have already commercialized an ink jet head called MACH (multi-layer actuator head) using MLA, and its high image quality has been widely recognized. The first MACH used an MLP (multi-layer Piezo) for the MLA. In subsequent improvements, this MLP type achieved a nozzle density of 180 DPI and response of 14.4 kHz, making it twice as compact as the original version and higher in performance. We have also developed a MACH using another type of MLA called MLChips (multi-layer ceramic with hyperintegrated Piezo segments). In this paper, we discuss the Recent Progress in Ink Jet Technologies II 19 MLChips type while drawing comparisons with the MLP type. Structure of MACH with MLChips The structures of MLChips and MLP are compared in Figures 1 and 2. The MLP is a ceramic MLA with a multi-layer structure consisting of Piezo green sheets of approximately 20 microns alternately placed with electrodes. The actuator unit is machine processed at a 140-micron pitch to achieve a head nozzle density of 180 DPI. On the other hand, the MLChips structure integrates in its multi-layer structure several ink chambers, vibration plates, and Piezo devices. Unlike the MLP, it requires no further machine processing whatsoever. The ink chamber is formed using only a multi-layer structure of zirconium ceramic, which is chemically stable and highly tenacious. On top of this are stacked the electrodes and Piezo device, and this ceramic MLA is heat treated as a unit. The ink chamber requires no adhesives and is formed using only chemically stable ceramic. In addition the Piezo device is stable due to the unitized heat treatment of mechanical and electrical junctions. The reliability of the ink jet head can thus be assured extremely easily (electrical reliability including open shorts, mechanical reliability such as peeling and cracking, and chemical reliability such as ink resistance). However, the multi-layer structure allows less freedom in terms of shape, making it difficult to design a smooth flow channel. In initial designs, a whirlpool developed near the supply hole, where the flow speed sharply slowed down, and the flow necessary for air bubble ejection could not be obtained. Thus the supply hole side of the Figure 1. Structure of MLP type Vibration plate A A A A A A AA AA A A A