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日本語

Diamond-like carbon (DLC) is a hard carbon film material with various functions such as high biocompatibility and oxygen impermeability. It is widely used in sliding parts of tools and automobiles, especially as a functional protective coating material that protects the surface of the base material while at the same time imparting sliding properties (slipperiness) to the base material due to its low friction coefficient. This hard carbon film can only be synthesized by vacuum plasma technology. Since the deposition rate for existing technologies is a few 100 nm/min, there are few advantages in terms of cost effectiveness to apply to mass-produced products, and they have mainly been applied to high added-value products. Additionally, since there is essentially a trade-off between the hardness of the film and the deposition rate, the development of technologies that improve deposition rate while maintaining the hardness (quality) of films is desirable from an applied engineering standpoint.

The research team proposed a unique gas injection method in which two kinds of gas were ejected in a jet shape and mixed in a vacuum, and achieved ultra-high-rate film formation for hard carbon films exceeding the deposition rate for existing techniques by more than one order of magnitude, with a plasma deposition device utilizing this gas injection method. By achieving ultra-high-rate film formation through this gas injection method, the team has removed the need to form a complex discharge electrode in or around the object being coated, so it can be expected to be used as a highly versatile process that can be applied to a diverse range of materials and shapes.

In the initial stages of the research, problems such as carbon film adhesion in unintended places and clogging of the gas exhaust system due to large amounts of dust occurred due to the generation position and expansion of the plasma, and the desired results of hard film formation and improved deposition speed were not obtained. By making multiple improvements to the equipment based on the knowledge obtained through a process of trial and error, ultra-high-rate film formation exceeding a rate of 2µm/min was eventually achieved through plasma generation utilizing the team's unique gas injection method. This technology is based on the combination of gases and well-known existing techniques for the formation of plasma, which forms the basis for film formation. In combining these techniques, the team was able to create an environment that is very different locally from the existing methods. As a result, they could obtain new results that surpassed the need for the trade-off between film hardness and deposition speed which had previously been considered unavoidable.

The research team plans to expand the size of the high-speed deposition area to improve the practical applications of equipment utilizing this technology. They believe that coating of cylindrical inner walls and complex structures will eventually become possible through further research and development. In the future, they hope to achieve the widespread adoption of this new coating technology. In doing so, they hope to contribute to the creation of a society capable of sustainable development, by improving energy consumption through the application of the superior sliding properties of hard carbon films.

This research was conducted with the support of the Osawa Scientific Studies Grants Foundation.