Micro-lenses demand substantial development effort, and the global market can be measured in hundreds of tonnes. Auto glazing demands more volume, but from few suppliers.

Plastics have largely replaced glass in the packaging field, but it could be some time before they repeat the act in two other key glass markets, precision optics and glazing. However, some applications in these areas do provide potential for keeping some high-technology processors busy in the West, even as many mainstream applications are sourced in Asia.

Micro-optical parts with nano-structured surfaces, and large-area automobile windows with perfect clarity and long-term resistance to attrition, are at the cutting edge of plastics processing technology. That much was made clear at the German Plastics Engineers'' (VDI-K) annual injection molding conference in Baden-Baden in February.

Several speakers discussed technologies for applying micro-optical moldings directly onto electronic circuitry—applications where the precision required stretches injection molding to its limits. In fact, as noted by Wolfgang Karthe of the Fraunhofer Institute for Applied Optics and Precision Engineering (Jena, Germany), in optical communication systems where part dimensions are under 1 mm and tolerances are under 1 µm, it may be necessary to use such alternative techniques as UV reaction molding, in which polymer is cast onto a semiconductor wafer, and then cured with ultraviolet radiation.

Karthe cites numerous applications in coupling elements and arrays for opto-electronic systems. But he also notes that the potential world market for plastics in such applications is just 200 tonnes/yr.

Unlike steel and plastics, where the two industries have, by and large, remained separate, traditional optical glass companies are buying into plastics technology. Late last year, Jenoptik (Jena) boosted the optics line of its Photonics business division with the acquistion of one of the leading European producers of injection molded optical components, Wahl Optoparts GmbH, in Triptis, Germany.

One of the largest potential applications for optical plastics is automotive glazing, and one of the leading developers is Freeglass GmbH in Schwaikheim, Germany, a joint venture between glassmaker Saint Gobain and plastics processor Schefenacker, which specializes in exterior mirrors and lighting. Freeglass already makes the rear sidelites for the DaimlerChrysler smart fortwo coupe (previously called the city coupe) and smart roadster.

But indications are that its biggest breakthrough so far will come at the end of this month with the launch of smart''s forfour. The company won''t comment, but is understood to be producing no fewer than four polycarbonate glazing components for the four-door sedan, including a sunroof of 1 sq m.

One problem common to plastics in optical applications is scratch resistance. Even the hardest plastics have surface properties significantly inferior to those of glass. But developments in plasma technology allow the application of coatings that yield surfaces on plastics with comparable long-term scratch resistance.

Schott HiCotec, in Mainz, Germany, originally developed its Plasma Impulsed Chemical Vapor Deposition (PICVD) technology for glass, but it is now being transferred to plastics. Helge Vogt says the challenge has been to develop a process to apply several different functional coatings that reduce reflections and dust pickup, as well as increase scratch resistance, in one operation. Over six different layers, based on silicon dioxide and titanium dioxide, may ultimately be involved.

Peter Mapleston [email protected]

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