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A clearer future for screen printers
The UK screen print sector has faced a number of tough challenges in the last few years. In particular, the movement of low value work (such as sign and textile printing) to low cost regions and the growth in high quality digital printing, especially for short run jobs.
This has led to a declining UK market with greater pressure as margins are squeezed and the hunt for traditional jobs becomes more competitive.
However, it’s not all bad news for screen printers, especially those handling work requiring higher technical precision or complexity. Typically, this type of work is unlikely to move to low cost areas because the logistics of producing and shipping smaller numbers of high value products are less compelling. Similarly, screen printing is widely acknowledged as a cost effective method of manufacturing technically demanding parts, with known production tolerances, accuracy and repeatability. As a result, there is currently no commercial or technical imperative to move this type of work to digital printing.
Also, unlike many traditional screen printing applications, demand for specialised technical components is actually growing. This is fuelled by: growth in consumer and industrial electronics products, which increasingly use touch screens, complex sensors and integrated keyboard/graphics displays; and rapid take up of new technologies such as solar panels, RFID tags and biosensors.
Mirroring the emergence of new computer and electronics technologies is the development of new screen materials and coated film substrates, which can play an important role in helping printers maximise the potential. By embracing new materials technology, printers can provide customers with a range of new features which help enhance the value of each order. For example, substrate properties such as antimicrobial, anti-glare and anti-reflection can transform a component’s performance, while processes such as film insert moulding can help drive down system assembly costs while enhancing overall system functionality.
Medical devices and industrial equipment
The latest generation of film substrates are already being used in applications where components such as control panels and touch screens are being incorporated into medical devices, industrial equipment and automotive panels.
Key throughout is the ability of each film to offer a complex combination of properties. Perhaps the most fundamental requirement is a film’s ability to be processed using standard screen printing equipment and either conventional or specialised inks. Also, film must be easy to handle (during printing and subsequent assembly operations) and must provide a resilient surface in use: resistant to scratches, chemicals and fingerprints.
Substrates should also offer characteristics appropriate to individual applications. For example, touch screens and displays are prone to reflection and glare, making them difficult to read under changing light conditions.
A solution to this problem can be found in films such as Autoflex MARAG, which incorporates surface nano-structures based on the compound eye structures of moths and which limit the effect ambient light has on displays. The film is designed to offer extremely low levels of reflectivity over the entire visible spectrum, reflecting less than one per cent of light across the visible wavelength range. Thus, the problems of iridescence and light glare often associated with conventional display materials are eliminated, enabling clear viewing from almost any angle, even in bright sunlight.
Similarly, films used in keyboards and electroluminescent lamps have to combine excellent light transmission (without introducing colour casts), yet remain stable under wide temperatures and operating conditions. An example is car dashboard displays and instruments, such as those manufactured by Pacel Electronics, where electroluminescent lamps using micro-encapsulated phosphor inks are produced with two outer protective layers manufactured using Autotex hard-coated polyester film. This was developed for use both with high performance screen inks and sputter deposition processes to provide a hard wearing material resistant to surface abrasion, solvents and chemicals, while providing excellent light transmission.
Precise thickness
Pacel Electronics’ Nick Bainton explained: “The material variations of the Autotex film that was used are almost non-existent, enabling us to achieve a precise thickness for each individually printed layer. This is crucial to the performance of each EL lamp, in terms of evenness of illumination.”
Another example where substrate technology is providing excellent results is an epilepsy alarm from Danish Care Technology. This uses a special film with an anti-microbial coating as part of the control panel. Key to the alarm’s development was the need to minimise the serious threat from bacteria. Also, the front moulded control panel needed to withstand daily use and regular cleaning.
The film features an even distribution of Microban antimicrobial agent throughout the surface that will not wash or wear away. Thus, the film offers antimicrobial protection for the alarm’s life and, after extensive testing, is proven to inhibit growth of bacteria, fungi and moulds including MRSA, salmonella enteritidis, escherichia coli and listeria monocytogenes.
The film’s outer hard-coat layer
is resistant to scratches and abrasions and is unaffected by common solvents and chemicals encountered during everyday use and rigorous cleaning. The film is designed to be reverse printed, allowing high definition graphics and legends. It is also designed to offer a long flex life and excellent ink adhesion, ideal for embossed keys.
New production processes, such as film insert moulding (aka in mould decoration), are also offering new screen print opportunities. FIM is a cost effective method of producing three dimensional components such as mobile phone covers and automotive fascias. A specially designed film substrate is screen printed before being formed into solid components using a combination of pressure and injection moulding.
The technique significantly reduces the process operations while improving component quality. Also, as the first stage is screen printing, small numbers of parts can be customised, while the economies of scale associated with injection moulding are retained.
The focus on efficiency is essential for screen printers to win high value work. In addition to using new materials and equipment to provide cost effective quotes and short turnaround times, focussing on the science of screen printing is crucial. This lets screen printers improve preparation and set up processes by understanding screen printing equipment requirements and following manufacturers’ recommendations closely.
Improving print quality
For example, each element in the screen printing process should be configured to do one job well, rather than compensating for weaknesses elsewhere: mesh should be used to control the ink deposit; the stencil to control the deposit’s shape; and inks chosen for their colour, not their ability to solve problems relating to poor mesh or stencil choice. This lets screen printers choose the best materials for each job, improving print quality and efficiency.
If the benefits presented by new materials and processes are embraced, there are many exciting new opportunities available to screen printers. Manufacturers are increasingly looking for cost effective ways of producing high quality printed components and products. Digital printing is proving to have benefits of its own but with the right approach screen printing still has a lot to offer.
