Web Coating

The Micro Gravure™ coater is a relatively new specialized coating technique that has found extensive use in the manufacturing of low coating weights on light gage films. It is used to coat a variety of products, for imaging, electronics, packaging, coated thin film batteries, and other specialty applications. This method can achieve a coating weight uniformity, of +/-2% at the low coating weights and the high quality levels required for these products. The majority of the standard coating methods cannot achieve the uniformity and quality required for these products.

The method is a reverse kiss gravure coater. The gravure rotates in the opposite direction to the substrate and, as it is a kiss coater, there is no backup roll.  The unique features of this method are it uses small diameter rolls, 20–50 mm (1–2 in.) versus 150–300 mm (6–12 in.) for conventional gravure. This requires low loading on the roll to prevent deflection and thus this technology is practiced in a kiss coating configuration with minimal deflection of the web as it passes above the roll. This results in a small stable bead that, combined with the reverse application, gives a very good quality and a low coating weight. AS with all coating applicators, there are several configurations that can be used.

The process for manufacturing these small rolls is significantly different than the traditional engraving process and produces gravure rolls with extremely tight tolerances.  Both Trihelical and quadrangular patterns have been sold; however, Trihelical patterns seem to be the more widely used for micro gravure.

Micro Gravure is a low-viscosity and low line-speed process. The operating parameters are:

This is a relatively small operating range and as such is not suitable for all applications. However, it is ideal to meet the uniformity and quality requirements for very uniform low coating weight products.  The low line speed is not a problem because these are typically small volume products and the volumes that can be produced are adequate.