Tailoring the properties of deposited thin coating and print features in flexography by application of UV-ozone treatment

Abstract

Printed functional materials are a rapidly growing area of interest for low-cost high-speed device manufacture with flexographic printing seen as a route to achieving this. The relationship between surface tension of the ink and surface free energy (SFE) of the photopolymer plate is a key for optimum performance. However, traditional methods of surface tension modification of the ink/coating often cannot be employed for functional inks. In this research, rapid, permanent modification of flexographic printing plate's SFE is achieved through controlled UV-ozone treatment, and the effects of the treatment on the polar and dispersive component of SFE are analyzed by Fourier transform infrared attenuated total reflectance spectroscopy, swelling experiments, and roughness measurements. Printing trials using the modified printing plates reveal improved print uniformity and control of deposited ink layer thickness, as well as improved print features-particularly track and pad junctions which can be problematic for printed electronic applications. The ability to rapidly tailor printing plate SFE is of benefit to all volume printing applications. Furthermore, it is of critical importance for functional printing and printed electronics where surface tension of the ink is determined by the functional material and chemical modification is not possible or desirable.

Effect of the Common Solvents on UV-Modified Photopolymer and EPDM Flexographic Printing Plates and Printed Ink Films

“…Printing plate samples were treated with 10×, 20×, and 30× passes under the UV radiation source of 100% intensity and with 4 m/s speed. As was shown in previous research, the additional UV treatment of the printing plates leads to the continued crosslinking process in the core of analyzed polymeric materials, affecting the mechanical and surface properties of the material as well [32,33,43].…”

“…Hardness is the parameter influencing the deformation of the printing plate during the engagement in the printing process and is related to elastic deformation of the plate. In the production of the printing plates, the hardness of the printing plates may vary due to the crosslinking process in the printing plates [33]. In order to monitor the changes in the flexographic printing plate's quality, changes in hardness of flexographic printing plates produced under different UV treatment conditions before and after the immersing of the printing plates in solvents were examined.…”

“…If one of those parameters is changed due to the interaction of the printing plates with solvents, the adsorption of the inks will be changed, resulting in obtaining printed films of altered qualitative properties. On the other hand, previous research in the area of printing plates has proven that by additional surface treatment of the printing plate's surface, it is possible to adjust these properties of the plates, causing the optimal interfacial interaction between the plate and printing ink [31][32][33]. It was shown that additional UV treatment of the printing plate surface could be used as a method for obtaining a maximal possible quality in the reproduction process, and it can be used for adjustment of the printing plates' surface properties for deposition of different coatings.…”

Optimizing the Neural Network Architecture for Automation of the Tailored UV Post-Treatment of Photopolymer Printing Plates

“…The aim was to build an optimized ANN for the prediction of the SFE components of these printing plates when UV post treatments are varied, thereby enabling the tailoring of the photopolymer's surface properties before engaging in the printing plate production process. Since the primary prerequisite of this research was to retain the functional properties of printing plates in the reproduction process throughout all modifications, all procedures in the printing plate production work-flow prior to the UV post-treatment needed to be kept constant and standardized, in order to result in a functional printing plate [29].…”

Analysis of the Interactions in the “Varnish – Photopolymer” System

“…In this experiment, swelling of the photopolymer sample was carried out in four varnishes mentioned in 2.1. Swelling experiments were performed until the equilibrium (normalized degree of swelling) was reached (Tomašegović et al, 2016). Measurements were performed by gravimetric method using analytical scale Mettler Toledo XS205 (MT laboratories, n.d.) in a controlled environment with a constant temperature of 23°C and relative humidity of 55±2 %.…”