32 Industrial Laser Solutions JANUARY/FEBRUARY 2016 www.industrial-lasers.com
Fiber laser enables
marking of advanced
IN-LINE INKLESS LASER MARKING NOW REPLACES
TRADITIONAL ROTARY GRAVURE AND PAD PRINTING
SCOTT R. SABREEN
Breakthrough FDA-approved addi- tives blended into polymers during primary processing optimize laser marking of plastics. Fast speed, superior contrast, and cost sav- ings are among the significant ben- efits. Novel chemical additives can
produce jet-black, light-colored, and custom color contrast,
using both “on-the-fly” and secondary operations. Designed
for affordable ytterbium fiber lasers, in-line inkless laser marking now replaces traditional rotary gravure and pad printing.
Clear, semi-transparent, and opaque colored polymers, including nylons, polyethylene terephthalate (PE T), polycarbonates,
polyolefins, polyvinyl chloride (PVC), styrenics, and thermo-
plastic elastomers (TPUs) and thermoplastic polyurethanes
( TPEs), are uniquely formulated using non-heavy metal, FDA/
European Food Safety Authority (EFSA)-approved additives to
achieve high-contrast marking quality (FIGURE 1). Polymer clarity, spectral transmission, and base physical properties are not
affected. Non-contact digital laser marking replaces expensive
adhesive labels and ink-chemical printing processes. The result
is a cost-effective, environmentally friendly, superior aesthetic
appeal in the application.
Polymeric laser marking reaction mechanism
The advancements achieved in formulating laser chemical
additives for use with near-infrared (NIR) lasers (1060–1080nm
wavelength) are their compatibility with ytterbium fiber, vana-
date, and predecessor Nd:YAG lasers. Most polymers do not
possess NIR absorption properties without chemical additives
[ 1]. Polymers that can
be marked by lasers
are those that absorb
laser light and convert
it from light energy
to thermal energy.
Experts utilize addi-
tives, fillers, pigments,
and dyes to enhance
the absorption of laser
energy for localized
color changes. Vastly
different formulation chemistries and laser optics/setup parameters are used depending upon the desired marking contrast
The most common surface reaction mechanism is termed
thermal chemical “carbonization” or “charring,” where the energy
absorbed in the substrate raises the local temperature of the
material surrounding the absorption site high enough to cause
thermal degradation of the polymer. The darkness or lightness
of the mark is dependent on the energy absorbed as well as the
material’s unique thermal degradation pathway. By optimizing
the laser setup, there is minimal surface carbonization residue.
Near-infrared laser additives improve the degree of contrast, which can be further intensified by changing the laser
setup parameters. Polymers possess inherent characteristics
to yield “dark-colored” or “light-colored” marking contrast.
Some colorant compounds containing low amounts of titanium dioxide (TiO2) and carbon black may also absorb laser
light, and in some instances, improve the marking contrast.
FIGURE 1. White contrast on
dark-blue automotive exterior/
under-hood components using IPG
Photonics’ YLPN Laser. It has been
traditionally difficult to achieve
white contrast using long-pulse-width lasers.