engleski

Influence of Printing Process on Printing Plate’s Surface Characteristics

The difference between printing and non-printing areas in lithography is achieved through different physical-chemical properties. Non-printing areas must attract water based fountain solution which enables them to repel oil based printing ink. Printing plates are today made of aluminium sheet which must be mechanically, chemically and electrochemically processed to define specific micro rough surface with porous aluminium-oxide layer. The aim of this paper is to determine changes of the non-printing areas surface characteristics, roughness and wetting properties during exploitation of the printing plate. Surface topography is one of the critical factors which could cause the instability in the quality performance and the durability of the printing forms during printing process. Measurement of contact angle and surface roughness was made to determine roughness parameters and surface free energy. Measurements were made on thermal CtP plate before printing process and after 123 000, 177 000 and 300 000 prints. Results have shown that contact angle values, surface roughness and consequently surface free energie values of non-printing areas (polar characteristics) have been significantly changed depending on the print run. This research has proved that contact angle and roughness parameters has a specific and most important role in determination of wetting properties of the investigated surfaces.

non-printing elements; contact angle; surface free energy; surface roughness

nije evidentirano