# Determining the Print Quality Due to Deformation of the Halftone Dots in Flexography
## 1 Introduction  
The development and progress of flexography is constantly increasing, and it can be said that the developments and trends in food packaging are responsible for such great expansion of this printing technique. Flexography is based on a simple concept of ink transfer, but a closer look at the process can reveal many variables that affect the transfer of ink and, of course, the final quality of the reproduction [1]. The quality of the reproduction is conditioned by a combination of various parameters concerning the properties of the plates [2] and the processing of photopolymer printing plates [3], anilox rollers, printing pressure and the properties of the printing substrates [4]. Therefore, in flexography, it is necessary to define the entire process or at least a larger part of the process as precisely as possible [5]. The most common, and at the same time most efficient mode, of achieving the best print quality is coordination with the goal values in the ISO 12647-6 standard [6].  
Due to the elastic printing plates, this printing technique makes it possible to print on a variety of absorbent and non-absorbent printing media, such as thin films, flexible and rigid foils, almost all papers, cardboards of various thicknesses and weights and rough surface packaging materials [7]. PLA films, as non-absorbent materials, require modification of the surface before the printing process in order to improve the wettability of the substrate and to obtain proper ink adhesion to the substrate [8]. Dot deformation is a term that refers to the quality of halftone dots, such as dot sharpness, edge smoothness and the uniformity of the density across dots, as influenced by different characteristics of the printing process [9].  
Digital technologies for the production of polymer plates pay great attention to the dot geometry, although recently, the emphasis has been on the shape of the top of the dot. The shoulders of the dot serve as a support for the printing surface, and the shoulder angle itself plays a significant role during printing [10]. One of the most widespread printing plate manufacturing processes is based on the Laser Ablative Mask System (LAMS) technology, and its characteristic is the rounded top of the dot [11]. Printing plates come into contact and interact with various liquid media during their processing and operation, resulting in plate swelling [12]. Swelling alters the plate deformation properties and thus has an effect on increasing the tonal values in the print.  
The development of flexographic printing machines and the application of advanced technologies for making polymer plates has enabled a considerable increase in print quality. The print consists of finer dots which ultimately create the image on the print. Various anomalies in dots result in reduced print quality (e.g., more or less visible errors like excessive dot gain, halo effect, the doughnuts or hollow dots effect, dot bridging, filling-in effect and dirty print). This paper is a continuation of previous research aimed at defining the optimal qualitative parameters in the flexographic printing process with the aim of increasing the print quality primarily for the highlight tones.