New Hard-Coating Technology for Large, Curved Auto Glazing

New plasma CVD coating over a wet coating offers wider design freedom than previous hard coats.

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Teijin Ltd. of Japan recently announced that it had developed a new hard-coating technology that can be applied evenly on large or complex-shaped polycarbonate automotive windows. The new coating method reportedly achieves abrasion resistance comparable to glass, satisfying new Japanese standards and also those of the U.S. and EU.

A common method today of protecting PC glazing from abrasion and UV-induced yellowing is to apply a wet hard-coat layer over the plastic. According to Teijin, this method does not meet new Japanese auto safety standards that take effect this July. There is another technology that applies a second hard coating via plasma-enhanced chemical vapor deposition (CVD) over the wet hard-coat layer, but the size of the window is restricted to around 0.3 m2, and it is also hard to apply plasma CVD to complex curved surfaces. So this technology also does not offer a practical solution under the new Japanese standards, Teijin says.

Teijin collaborated with Tsukishima Kikai Co., Ltd. to develop a plasma CVD pilot plant that can treat large, 3D molded plastic windows with a uniform coating. Glazing exceeding 1 m2 in size, including ones with complex curves for rear windows, are being coated at a pilot plant in Japan. Teijin says the plasma CVD layer doubles the UV discoloration resistance obtained with the wet coat alone. Teijin continues to verify the new method’s potential for mass production of a wide range of car windows, aiming at early launch of full-scale commercial manufacturing. Teijin Kasei America, Peachtree Corners, Ga., is the U.S. branch for sale of PC resin, sheet, and film.

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