Glassy carbon as a novel mould material for replicative forming of precision glass optics.

Abstract

Replicative forming of precision glass optics has been fast emerging as a rapid, net shape process chain for mobile camera lenses, CD/DVD pickup lenses, microscope objectives, night vision lenses, Fresnel lenses and so on. The process involves moulding a glass gob at high temperatures exceeding the glass transition temperature using a predefined loading and thermal cycle. Typically, the mould material is required to have high strength, low thermal expansion, chemical inertness and anti-adhesion properties, especially at high temperatures. Traditional mould materials, such as, invar or tungsten carbide are difficult to machine which adversely affects the cost of the entire process. In the present work, glassy carbon mould has been developed using p-tolune sulfonic acid (PTSA) cured phenolic resin by a process of carbonization where the composition ratio of phenolic resin and PTSA solution was standardised accompanied by the pyrolysing conditions. Detailed characterisation of the phase evolution, surface compositions, morphology and mechanical parameters of the glassy carbon has been conducted by X-Ray diffraction (XRD) technique, Raman Spectral (RS) analysis, X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron microscope (FESEM), Energy Dispersive Spectroscopy (EDX) and Nanomechanical testing which reveal an optimal combination of properties of the glassy carbon that makes it an attractive low cost mould material for replicative forming process chain of glass optics fabrication.

Keywords

• Phenolic resin
• glassy carbon
• mould
• XRD
• FESEM
• RS
• XPS