Effect of roll patterns on the Ink transfer in R2R printing process

Abstract

Ink transfer process from the printing roller to the web was investigated using a CFD technique for the roll-to-roll printing applications. A parametric study was conducted to identify the effects of roll pattern geometry on the ink transfer process. In order to make the present analysis more relevant to the real printing system, 3-D computational configuration was set up using the information obtained from the typical roll-to-roll system. Simplified one-dimensional semi-analytic analysis based on Reynolds equation was also conducted in order to assess the validity of the 3-D CFD results. Pressure information suggests that even a simplified 1-D analysis is reasonably good in capturing the relevant flow physics. 3-D simulation shows that the quality of the ink transfer process is very sensitive to the width of the roll patterns. This sensitivity is believed to be due to the relative importance of surface tension over any other force modes under the 100 micrometer range.

Study on the web deformation in ink transfer process for R2R printing application

“…Since the present configuration involves a continuous distortion of free surface formed by the ink, the popular VOF method 15 incorporated in the Fluent Package which uses CSF (continuum surface force) model was invoked to track the interface between the ink and the environmental air and subsequently to obtain a volume fraction C as was done in Lee & Na. 14 The density and the viscosity of the working fluid are matched to those of the silver ink (Parelec Inc.) being used in the printed electronics industry as described in Table 2. Values for surface tension and contact angle were measured at the given viscosity of 0.3 Pa-s.…”

A numerical study of the ink transfer process for roll-to-roll printing applications

“…However, a recent study 20 reported that the time for the combined drying and curing processes could be successfully reduced by a factor of as large as 5. Therefore, higher web, handling speeds of up to 30 mpm (¼0.5 m/s) compared to the speeds chosen in previous studies, [17][18][19] was considered in this study. Obviously, a relatively higher speed shortens the convection time-scale, thus increasing the importance of the inertial effect relative to that of viscous action.…”

“…For the purpose of development and proper validation of the numerical methodology at the first stage, this study aims to establish the effects of the various roll patterns shown in Figure 2 in terms of the shape of the transferred ink, which is a very important task for improving the printing quality. 17 Considering recent progress in reducing the time required for curing and drying processes, 20 the web handling speed used in earlier studies [17][18][19] was raised by a factor of up to 5 in this study. This significant increase in the web moving speed is expected to deteriorate the printing quality due to the enhanced effect of convection.…”

“…They successfully illustrated the role of surface wettability and cavity size of their model. In more recent studies by Lee and Na 17,18 and Kim and Na, 19 the geometry of gravure printing, which is one of the most popular R2R printing methods, was considered for direct relevance to real applications. Kim and Na 19 showed that the characteristics of the transferred ink strongly depend on the magnitude of the viscosity under the assumption of Newtonian fluid.…”

A Study of the Bubbles in UV Micro Roll-to-Roll Imprinting

“…Lee and Na (2009) and Kim et al (2012) studied the ef-fects of roll pattern geometry on ink transfer process in R2R. Lee and Na (2009) and Kim et al (2012) studied the ef-fects of roll pattern geometry on ink transfer process in R2R.…”