Jun Masuda

Microstructural and topographical changes of Ni-P plated moulds in glass lens pressing

The changes in microstructure and topography of nickel-phosphorus (Ni-P) plated steel moulds in a glass lens moulding process were investigated by heating tests. The results show that, at a high temperature, Ni atoms diffuse from the inner Ni-P plating layer into the outer release agent coating consisting of precious metals. The atomic diffusion leads to partial surface swelling, which makes the mould surface rough and cloudy. The diffusion is influenced by the temperature, interface structure and stress state of the moulds. These findings provide references for developing new mould materials and for improving the service life of the moulds.

Thermally induced atomic diffusion at the interface between release agent coating and mould substrate in a glass moulding press

In a glass moulding press (GMP) for refractive/diffractive hybrid lenses, to improve the service life of nickel–phosphorus (Ni–P) plated moulds, it is necessary to control the diffusion of constituent elements from the mould into the release agent coating. In this study, diffusion phenomena of constituents of Ni–P plating are investigated for two types of release agent coatings, iridium–platinum (Ir–Pt) and iridium–rhenium (Ir–Re), by cross-sectional observation, compositional analysis and stress measurements. The results show that Ni atoms in the plating layer flow from regions of compressive stress to regions of tensile stress. In the case of the Ir–Pt coated mould, the diffusion of Ni is promoted from the grain boundaries between the Ni and Ni3P phases in the plating towards the surface of the Ir–Pt coating. However, in the Ir–Re coated mould, the diffusion of Ni is suppressed because the diffusion coefficient of Ni in the Ir–Re alloy is smaller than that in the Ir–Pt alloy, although the stress state is similar in both cases. By controlling the diffusion of Ni atoms, the use of Ir–Re alloy as a release agent coating for Ni–P plated moulds is expected to lead to a high degree of durability.

Ultraprecision mass fabrication of aspherical Fresnel lens by glass molding press

Glass molding press (GMP) was applied to the fabrication of glass aspherical Fresnel lens for high-efficiency mass production. A pair of molds for the Fresnel lens was precisely fabricated on the Nickel Phosphorous (Ni-P) plating layer by the single diamond cutting with multi-axis machining center. A kind of low transition temperature (Tg) glass was heated to several tens degree centigrade above its Tg and compressed between the two molds. In this way, the shape of the mold was replicated to the glass lens surface. The molding process was simulated by finite element method (FEM), and the molding condition was optimized to minimize the residual stress.