Journal of Materials Processing Technology 225 (2015) 337–346 Contents lists available at ScienceDirect Journal of Materials Processing Technology journal homepage: www.elsevier.com/locate/jmatprotec Diamond micro engraving of gravure roller mould for roll-to-roll printing of fine line electronics XinQuan Zhang ∗ , Kui Liu, Vasudivan Sunappan, Xuechuan Shan Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075, Singapore article info Article history: Received 20 October 2014 Received in revised form 5 May 2015 Accepted 20 May 2015 Available online 24 June 2015 Keywords: Ultraprecision diamond machining Slow slide servo Roll-to-Roll gravure printing Metal mesh film abstract Printing electronics has attracted great attention in recent years due to its various superior performances compared with conventional silicon-based semiconductor industry. Roll-to-Roll gravure printing is able to transfer conductive nanoparticle ink onto the flexible film substrate to form continuous fine metal lines using a gravure roller mould with tens of thousands of tiny gravure cells on its surface. However, it is difficult to scale down the printed line width, which is crucial for the film’s circuit density, resolution and transparency, because the market-available rollers fabricated by conventional engraving techniques for graphic printing usually have gravure cells larger than 25 m. Hence, in this study, a novel method based on ultraprecision machining technology, Diamond Micro Engraving (DME), is introduced to miniaturize the gravure cells in order to reduce the ink volume transfer during the printing process. A V-shape sharp diamond tool is used to continuously generate concave inverted micro pyramidal structures on the gravure roller surface using the Slow Slide Servo technology. Geometrical modelling of the engraving process is conducted to help programming the tool path to realize accurate control of the instantaneous position of two linear axes and one rotatory axis. Through applying the DME process, generation of consistent cell structure is achieved. The engraved gravure cell width is successfully miniaturized to 7 m. With the optimized cell spacing value, the DME-machined roller moulds are used in gravure printing of metal mesh film, which works as a potential transparent conductive film to replace the expensive indium- tin-oxide (ITO). The printed line width is reduced from 47 m to 19 m, and the transmittance of the printed metal mesh film for visible light is increased from 65.2% to 80.4% accordingly, which is comparable to the transmittance of ITO film. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Recently, printing electronics has received significant atten- tion because of its low manufacturing cost per unit area, light weight, and high flexibility compared to conventional silicon-based semiconductor electronics. It provides a better alternative to real- ize low-cost and high-volume manufacturing of a wide range of flexible and costless electronic systems, such as radio-frequency identification tags (RFID), electronics labels, sensors, and transpar- ent conductive films. There are a number of attempts by researchers to realize printing electronics using various methods, such as inkjet printing, screen printing, flexographic printing, offset printing, pad printing, and Roll-to-Roll (R2R) gravure printing. Compared to the other printing methods, R2R gravure printing has the advantages of excellent pattern fidelity, homogeneous thickness of printed ∗ Corresponding author. E-mail address: zhangxq@simtech.a-star.edu.sg (X. Zhang). layer, high throughput due to high printing speed, high printing resolution. Pudas et al. (2005) firstly applied R2R gravure print- ing technique to transfer conductive inks onto flexible substrates to form conductive lines on paper and plastic films. Then, Sung et al. (2010) has used R2R gravure printing to realize the scaling of printed conductive line width down to 30 m. Hrehorova et al. (2011) also successfully applied gravure printing of electronics on glass, which is more common but rigid. Gravure printing was widely used in high-quality graphic print- ing (e.g. fine art, bank notes, magazines, postage stamps, and photography reproduction) due to its remarkable density range since the late of 19th century. Colour intensities of the printed fea- ture are directly determined by the amount of ink transferred onto the substrates. Typically, the size of printed features of gravure printing is larger than 50 m. Miniaturization of cell size is not necessary in paper printing industry because it will exceed the capability of human vision with naked eyes. However, for print- ing of high-performance electronics, Kang et al. (2012) has found that scaling down of the printed features is essential because http://dx.doi.org/10.1016/j.jmatprotec.2015.05.032 0924-0136/© 2015 Elsevier B.V. All rights reserved.