Focus on transparent multifunctional glass surfaces

DORTMUND, GERMANY: They protect drivers from bright sunlight, let water and dirt pearl off the windscreen and protect safety glass and the displays of mobile phones and tablets: we are talking about functional surfaces that turn glass into flexible masters of almost everything.

At glasstec 2014, LIMO Lissotschenko Mikrooptik GmbH, the laser and beam shaping specialist from Dortmund, is showing a new short-time tempering technology to heat and thereby functionalize these wafer-thin coating layers - very gently, extremely fast and with the highest level of precision.

The task sounds impossible: within fractions of a second, thin layers need to be heated to over 1000 degrees Celsius in order to activate their functions (such as sun protection or thin film electronics).

These surfaces are often thinner than human hair (in numbers: from 0.1 to more than 100 micrometres) and contain miniscule particles and molecules that need to have cooled off again only tenths of a second after they have reached their refinement temperature so that they keep their desired properties and structural sizes.

In addition, there is the problem that glass is a carrier material that can be weakened or destroyed through improper warming and cooling (what experts refer to as tempering).

"Glass is a fragile material. Processing the surface is a great challenge that can only be solved through very selective and extremely fast heating and cooling," says engineer and LIMO's director of Thin-Film Activation, Dirk Hauschild.

The solution is the so-called in-line high-temperature process that can heat large areas of extremely thin functional layers in milliseconds with greatest precision. This is done by the Activation Line 300, the most powerful L³ LIMO Line Laser source (the numbers for the experts: more than 13 kW CW output power with a homogeneous line focus 300 mm long; an intensity of up to 40 kW/cm²; unique beam quality M² < 3 in the processing direction; high electro-optic energy efficiency of over 40%).

LIMO developed this system to serve as an innovative system supplement to conventional oven and lamp tempering. Developed especially for continuous operation, this laser has an intensive and homogeneous output that is ideally suited for reliable 24/7 industrial surface tempering.

In addition: due to the low heat capacity, the layers cool off quickly. Patented LIMO beam shaping automatically desensitizes and stabilizes the parameters of the process, guaranteeing homogeneous, large-area processing.