To improve optical lens transmission characteristics, anti-reflection film is applied to a lens surface. The substrate temperature strongly affects optical thin film durability and determines the thin film structure. Therefore, substrate temperature fluctuation from 25 ℃ to 400 ℃ during deposition was verified to improve mechanical properties while maintaining optical properties. As anti-reflection films, SiO₂ and Nb₂O₅ were used. Each single-layer thin film was prepared using high-density plasma assisted vapor deposition at different substrate temperatures. Then, each single-layer film was evaluated using a falling sand test. The amount of transmittance change during testing after production at high temperatures was small for each film. Behaviors of refractive index and film stress demonstrated that these films were dense and stable after production at high temperatures. Furthermore, their surface roughness revealed that SiO₂ films had small values and that Nb₂O₅ films had large values under high substrate temperatures. For these analyses, cross-sections of the tested films were observed using SEM（Scanning Electron Microscope）. Both thin films' hardness was measured by nanoindentation. These tests revealed high brittleness of the SiO₂ thin film. Actually, Nb₂O₅ thin film tends to be plastically deformed: different heights of damage during extrusion affect the surface roughness. XPS（X-ray Photoelectron Spectroscopy）results showed differences in films from the bonding state according to the substrate temperature. Various measurement results obtained at various temperatures and fluctuation patterns revealed that the most durable films of each thin film type are produced at high temperatures.

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An autocatalytic electroless tin plating process is necessary for the formation of a tin deposit layer on small connecting terminals of miniature electronic devices. Formulae using titanium（III）chloride as a reducing agent have been reported to date. However, the practical use of such a process has not been achieved because the poor catalytic activity of tin makes it difficult to form dense tin deposits at a satisfactory deposition rate.
Our newly developed formula for electroless tin deposition contains a germanium compound as a deposition accelerator. By adding the germanium compound to the plating bath, dense tin deposits comprising large crystal grains were obtained with increasing deposit thickness proportional to the plating time. The deposits have a double-layered structure comprising a tin-germanium underlayer and a tin upper layer. Presumably, the presence of tin and germanium mutually accelerates their deposition. The tin-germanium layer is formed initially, followed by the primary deposition of tin on the tin-germanium layer.

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Wastewater containing tetrafluoroboric acid-hexavalent chromium was decomposed to fluorine （HF） and boron （H₃BO₃） in acidic conditions using excess aluminum sulfate at normal temperature. In subsequent processing, boron was separated by coagulation-sedimentation using ettringite and calcium hydroxide in highly alkaline conditions. This processing reduced the boron concentration to 10 mg dm^－3 or less in the effluent standard. The ettringite used in this experiment was prepared using aluminum sulfate and calcium hydroxide. Alkaline filtered water containing aluminum ion and calcium ion was pH-adjusted to 6.5－7.0 for fluoride removal. This continuous process produced fluorine concentrations of 8 mg dm^－3 or less in the effluent standard. Based on these experiments, we devised a practical advanced wastewater treatment system including processing of tetrafluoroboric acid using ettringite. The contents of this paper will contribute to solving treatment problems for metal surface treatment wastewater containing fluorine and boron, also help in the treatment of other industrial wastewater.

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