"Cold UV"

A typical UV lamp operates with a quartz tube surface temperature of 800 to 900 degrees Celsius (approximately 1600 degrees Fahrenheit). This elevated temperature generates IR energy which is directed away from the surface. Visible light is also generated by the lamp as a normal part of its output spectrum. In most cases, this visible and IR energy does not cause a problem for the substrate being processed. For some heat sensitive substrates, however, this extra energy can potentially cause heat effects. In these cases, heat management techniques are necessary to keep the temperature under control.

Cold Mirror Reflectors

Cold Mirror reflectors (also called dichroic reflectors) reflect UV, but allow visible and infra red energy to pass through to an absorbing layer. The chart above shows the UVDoctors cold mirror reflector. Note that there is a high reflectivity in the UV regions, but a very low reflectivity in the visible and IR. Compared to a standard aluminum reflector, the cold mirror reflector allows much less unusable energy to be reflected to the substrate.

When used in place of an aluminum reflector, the cold mirror reflector transmits much less energy to the substrate and results in a lower temperature rise at a given line speed.

Other Heat Reduction Techniques

Depending on the application, UVDoctors engineers may recommend additional techniques to reduce the temperature rise of the substrate. Among these are the following:

  • Infinitely variable power ramping
  • IR filters (hot mirrors)
  • Enhanced lightshield cooling