Greater Efficiency in UV Curing Through the Use of High Peak Energy Light Sources

In previous papers we have examined the rate of cure and depth of cure of primarily free radical initiated chemistries as a function of lamp power and wavelength selection without a concerted effort to control the peak irradiance of the light source or the type and level of the Phi employed. In the past, all of the formulations that we evaluated were standard commercially available and proprietary mixtures over which we had no raw material or formulation control.

Insert numbers 1 and 2 list the types of chemistries tested along with the materials response as a function of bulb type and lamp operating power. Insert #1 deals w!th pigmented screen and offset inks while insert #2 shows the cure results for clear 2-piece can coatings.

For the pigmented screen ink systems we can increase the rate of cure at 300 w/in simply by changing from the short wavelength emitting "H" or mercury bulb to the longer wavelength producing "D" bulb. In some cases we are able to double the rate of cure.

While the effects of bulb changes are not as dramatic with offset inks, doubling the operating power of the light source increases the effective rate of cure by 2.6 to 3.6 times.