engleski

Screens of the Ofset Prints and Ink Content in Recycling Process

In the contemporary graphic production, in principle, only the digital screening techniques have been used nowadays. In spite of all changes, which were brought by the new technologies the basic principle stayed unchanged – to change the continuous- tone originals into the series of tiny elements, which are indistinguishable for human eye, in order to obtain the plastic image. By the development of science and digital technologies and their implementation into the contemporary processes of the graphic reproduction, only numerous ways of transformations of the continuous-tone originals into the series of screen elements have become possible. It is possible to realize the screen reproduction in two ways, either by the amplitude modulation of screen elements or by frequency modulation of screen elements. Generally, screen can be defined by the screen finesse, screening angle and the shape of the screen element. The main difference is that the impression of different tones by frequency modulated screen is achieved by changing the number of screen elements (frequency) as opposed to the amplitude modulated screen by which the impression of different tones is achieved by changing the size of the screen element (change of the amplitude). The measuring results of the ink content important for understanding the deinking performance in the case of offset prints recycling based on the amplitude modulated screens with ruling of 60 l/cm and 80 l/cm as well as frequency modulated screens with the finesse of 20µm and 40µm are presented in this work. An ink removal efficiency based on effective residual ink concentration measurement and dirt count across the different unit operations shows what has happened to the ink and quantifies if a process change has improved related to ink content. In this context the obtained results are discussed especially in relation to different substrates used in printing.

ofset prints ; ink ; recycling process

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