Microsharp on a roll

Printing-style technology means precision micro-structured optical film can for the first time be developed in the UK. Siobhan Wagner reports.

A UK company has recently installed a machine that is able to manufacture precision micro-structured optical film in a continuous roll-to-roll ‘printing’ process.

Microsharp claims that its optical film unit in Oxfordshire has capabilities that are unique in Europe.

The company’s marketing business development director David Brogden said Microsharp is now working on developing, among other products, films for light-emitting polymers, lightweight Fresnel lens structures for solar concentrators and nanostructured self-cleaning films.

‘Previously, if companies had required circuit-structured films to be developed, they would have had difficulty doing that in Europe because most of it is mass produced in Asia,’ he said.

Brogden said that unlike the large machines in Asia, Microsharp’s is relatively small and flexible, which means it can work with specialist companies in industries such as aerospace on developing specific structures required for a variety of applications.

‘It can produce structures with depths of between two and 75 microns on substrates with a thickness of between 25 and 250 microns at a speed of 15m/min,’ he said.

He said as soon as a polymer film enters the machine it is coated with one of Microsharp’s special UV curable lacquers. The base film and lacquer are compressed against a precision-structured moulding drum and a high-intensity UV light cures the material while still in contact with the roller mould. The film, with the now structured polymer on its surface, then peels off the drum and is collected, or laminated with a protective film.

‘It’s like conventional printing — but it lays a 3D structure on the film,’ said Brogden.

Microsharp is working with partners to improve its technology. One collaboration with David Robertson, a researcher at Durham University, has resulted in a patented mould cutting technology that leads to more precise reproduction of opital facets. Called INADIT (Include Angle Diamond Turning) this process will be used initially in the development of thin-film Fresnel lenses for solar concentrators, devices used to optimise the efficiency of solar power. The concentrators use Fresnel lenses to take a large area of sunlight and direct it towards a solar cell by bending the rays of light and focusing them.

Brogden said his company received funding from the Carbon Trust. ‘The Carbon Trust agreed with us that there is a market for a much cheaper and much lighter concentrator device in the fast-growing solar business,’ he said.

The next big step for Microsharp’s manufacturing technology will be adding the capability to produce its own metal drums for moulding the polymer films. The production of these is now outsourced to another company.

Brogden said Microsharp is working with the Integrated Knowledge Centre in Ultra Precision and Structured Surfaces, at the Optic Technium in North Wales, to commission a new drum cutting machine.

This machine will use a diamond cutting tool to etch grooves on the drums in a highly controlled manner. These grooves act as a template.

Brogden said Microsharp has been working on the drum-cutting machine for two years and it will be ready for use within a few months.