Reverse-offset roll-to-plate printing has become increasingly popular in the printing industry because of the ease with which the printing process can be manipulated to achieve a high-resolution pattern with line widths as narrow as 5 lm with precision and accuracy。 The printing procedure involves three stages, and a roller is required to transfer ink from each stage。 The substrates used throughout this experiment were chosen by measuring their contact angles (h) and using them in accordance with the sequence: h (Stage 1) >h (roller) >h (Stage 2) and h (Stage 3)。 An ultraviolet (UV) light-emitting diode (LED)-curable ink was used during the printing process; however, the pristine solution of this ink was unsuitable for printing a final pattern on the substrate because of its viscosity。 Diluting the solution of the UV LED-curable ink with 40% CH3OH resulted in reduced viscosity。 The original solution had a vis- cosity of approximately 40。7 cP whereas that of the diluted solution was approximately 25 cP。 The two solutions behaved as non-Newtonian, dilatant, shear-thickening fluids。 The UV LED-curable ink solutions, both dilute and non-dilute, were successfully printed by use of an inkjet printer and three- dimensional printing methods。76179

Key words: Reverse-offset printing, roll to plate, RO-R2P, contact angle, viscosity, UV LED

INTRODUCTION

Electronic printing technology has become highly important because if its variety  of applications    in

high-quality images on to flexible substrates, reverse-offset can result in the highest-resolution printing of patterns with line widths as narrow as

solar  cells,  and  for  radio-frequency identification

5 lm, with small thickness  deviations。

However,tags and display technology。1 The most common non-contact printing methods include gravure offset printing, flexographic printing, screen printing, and reverse-offset printing,2–6 The precision and accu- racy of each of these techniques, in terms of line

these  specifications  are  only  possible  when ideal

printing conditions are met。

The main factors affecting the quality of the reverse-offset printing are the rheological properties of the ink and its interfacial relationship with the

width, line edge straightness, thickness, and thick-

substrates involved in the process。

In reverse-ness deviation, varies。 Although many non-contact printing   processes   are   capable   of    transferring

offset  printing, the ink is coated on  to an   initial

substrate and the roller must transfer the ink between several stages before the process is com- plete。 When the roller has a continuous layer of ink it has to roll over a cliche´ containing the negative of the desired pattern。 The interfacial energy between the  cliche´   and  the  ink  must  be  higher  than that

between the roller and the ink for the pattern to be formed。 Therefore, the wetting properties of the ink

on the substrate determine whether the ink is suc- cessfully transferred。

The smaller the contact angle between the droplet and the substrate, the more well spread the droplet; the larger the contact angle the more spherical- shaped the droplet, which does not allow the liquid to be uniformly spread。11,12 A liquid vapor interfa- cial energy that has a smaller contact angle shows that the adhesive forces are stronger than the cohesive forces between the molecules, which allows the molecules to spread on the  substrate  rather than sticking to each other。 In the reverse-offset printing process, the contact angle between stages and  the  roller  must  be  optimized  to  aid  the ink-