USA • MacDermid Graphics Solutions announced the commercial introduction of three new liquid photopolymer resins specifically designed for corrugated printing applications – MRC, LTS and M Cap 45. These new products are part of the M System platform of liquid photopolymer technology and service architecture. In no particular order, this series of articles introduces these products in detail.
LTS liquid photopolymer
The MacDermid LTS liquid photopolymer is a 25 durometer (Shore A) resin designed specifically to provide thick photopolymer printing plates for the corrugated environment. LTS resin has tack-free properties for excellent solids coverage, high resilience for lint-free printing and easy clean-up on press. LTS is dyed red to improve the contrast of the plate surface for assistance in mounting.
Key features include very low tack to provide clean performance on press; high durability with UV, heat, and humidity stability and high resilience with exceptional ink transfer. The wide imaging latitude images a variety of copy, including fine detail and there is an option to cap for reduced fluting. The LTS liquid photopolymer is well suited for in-position platemaking and offers the ability to reclaim resin and use soap and water washout, resulting in a high quality, sustainable plate. In addition, it also offers an optimized durometer for use for printing on recycled board, or board with thinner liner
LTS plates are processed the same as other MacDermid liquid photopolymer printing plates, but require an additional light-finishing step in order to ensure tack-free properties. After the plate has finished a ten minute post exposure step, it is placed into a dryer for 20-25 minutes at a temperature of 100-110° F (38-42° C). The plate must be completely dry and warm when placed into the light-finishing unit, and must remain warm during the entire light-finishing step. The plate is exposed in the light-finishing unit (MacDermid Germicidal Unit) for 18-22 minutes at 100° F-110° F (38° C-42° C).
The MacDermid light-finishing unit is pre-heated to ensure that plates remain warm and proper detacking occurs during exposure. When using other plate finishers, exhaust from the unit should be minimized to maintain the plate temperature, and longer processing times may be needed. For customers using a MacDermid sheet photopolymer detack unit, the warm plate should be detacked for 35-45 minutes (bulb intensity should be > 600mj). This will aid in providing the best tack-free plate surface.
Light-finishing units should be turned on 20 minutes prior to use each day to ensure the unit is warmed up. If the plate surface clouds or crazes after light-finishing, it may indicate that the plate has been exposed for too long. In that case, the amount of time in the light- finishing step must be reduced. After completion of light-finishing, LTS plates are ready for the press. As far as the washout chemistry is concerned, M Clean detergent can be used.
The range of plate thickness is 0.125” – 0.280”, the range of background thickness comprises 0.080” – 0.160” and the relief height spectrum is 0.040” – 0.125”. Tone range reproduction spans 2 – 95% at a maximum line screen of 100 lpi when used as a capped plate. LTS is packaged in 5-gallon (40 lbs, 18 kg) containers and totes are also available.
To be continued …