by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
FLEXO Magazine : September 2014
INK CURING SPEED & EFFECTIVENESS The IPA Swab Test, an industry accepted test- ing method, was used to determine ink curing effectiveness. The test requires a cotton swab, the substrate and isopropyl alcohol. The cotton swab is immersed in the alcohol and the swab is then moved with consistent pressure in one direction over the print sample. While consis- tency was strived for, some variability existed: • Pressure of cotton swab during appli- cation • Amount of alcohol on the cotton swab • Speed of swabbing • Durability of the substrate • Ink composition resistance to alcohol The average number of strokes required to remove the ink for conventional UV and LEDUVareshowninTable 3 andTable 4, respectively: Conventional UV test runs on paper seem to be highly durable, indicating better or faster curing. The most durable results came from run C (paper, conventional UV, low speed) and run D (paper, conventional UV, high speed). Following these, run E (paper, LED UV, low speed) performed relatively well compared to the other runs. For the cyan ink samples, run E averaged 4.9, while the other LED UV runs averaged 2.1 and 2.4 . For the magenta ink samples, run E averaged 4.4, while the other LED UV runs averaged 2.3 and 3.2. For the yellow ink sam- ples, run E averaged 5.4, while the other LED UV runs averaged 2.6, 3.1, and 3.7. For the black ink samples, run E performed similarly to the other runs. The number of strokes for the black ink samples is significantly less be- cause black is the most difficult to cure. This is because black ink absorbs, or blocks, UV light. Special photoinitiators or special black ink formulations can be used to help improve this issue (Vest). Paper printed with conventional UV seems to be the most durable. On paper, conventional UV curing outperformed LED UV curing, as well as all film samples. LED UV is negligibly better when printing on film. None of the LED UV samples exceeded an average of 3.5 SEPTEMBER 2014 | FLEXO 71 Table 3 Average Number of Strokes Required to Remove Ink for Conventional UV Print Samples Cyan Ink Samples Magenta Ink Samples Yellow Ink Samples Black Ink Samples (A) Film, Low Speed 1.9 2.3 2.8 1.2 (B) Film, High Speed 2.1 2.9 3.5 1.1 (C) Paper, Low Speed 28.1 26 26.1 1.0 (D) Paper, Low Speed 10.9 12.9 13.3 1.1 Table 4 Average Number of Strokes Required to Remove Ink for LED UV Print Samples Cyan Ink Samples Magenta Ink Samples Yellow Ink Samples Black Ink Samples (E) Paper, Low Speed 4.9 4.4 5.4 1.1 (F) Film, Low Speed 2.4 3.2 3.7 1.2 (G) Film, High Speed 2.1 2.3 2.6 1.2 (H) Paper, High Speed 2.4 2.3 3.1 1.0