Recent years have seen an exponential rise in the popularity of automotive entertainment and information systems. Whereas devices such as satellite navigation units were seen as a luxury just a few years ago, now 4percent of new cars in the UK, and as many as 24percent in Germany, are being sold with integrated satellite navigation technology as standard.
These devices increasingly feature large high definition screen areas, enabling them to display visuals and information in great detail. These larger displays, however, are inherently prone to reflection and glare, both of which are particularly common inside vehicles, where light conditions are constantly changing and often extreme.
These problems can be especially problematic with satellite navigation systems mounted in central dashboard consoles at an angle to the driver, making displays difficult to read in both harsh sunlight and artificial light.
In an attempt to reduce the problems of reflection and glare, instrument manufacturers currently use specially developed optical films as part of the outer layer of display screens. Typically these are manufactured either using complex multi-layer coatings or dip coating processes; both of these can add significantly to component cost and, from a production point of view, are difficult to control.
Multi-layer coatings often require vacuum chamber environments, which can be expensive to build, maintain and operate.

Sputtering process

Each coating is applied using a sputtering process that makes achieving a uniform finish difficult due to inconsistencies in the application and, furthermore, three layers are typically required, lowering light transmission levels, and negatively affecting the readability of a display.
Likewise the dipped coating process also requires multiple applications; again, this makes it difficult to control and also increases production costs.
To address this problem a new generation of optical films has been developed that offer dramatically decreased levels of reflection and glare, helping to increase brightness and contrast, and enhance readability, while being resistant to scratches and marks. These films also offer excellent formability and can easily and cost effectively be incorporated in components using proven Film Insert Moulding, or In Mould Decoration, techniques.
Anti-reflection films effectively improve transmission and contrast by limiting the effect that ambient light has on a display, helping to reduce the power requirements of a unit as a result.
By means of a specially designed hard-coated surface, the films are able to offer extremely low levels of reflectivity over the entire visible spectrum, while enabling the display to be viewed clearly from any angle, even in bright sunlight.
As well as reflection, the human eye is also sensitive to glare, or specular reflection. Where this is a problem, new high quality hard-coated films are now on sale that offer low-haze, uniform texture, reduced specular reflection and extremely high levels of clarity, typically greater than 91percent.
Films which combine these properties offering anti-reflection and anti-glare, result in noticeably more readable displays.
Autoflex MARAG, the first film of its kind to combine both anti-reflective and anti-glare properties, offers an exceptional level of optical clarity, with a hardcoat finish that is resistant to scratches, chemicals and fingerprints.
The result is a tough, dimensionally stable and formable film, using PMMA, PC, PET or TAC substrates, which reflects less than 1percent of visible light, throughout the wavelength range, and eliminates the problems of iridescence and light glare that are often associated with conventional display materials.

Film insert moulding

Aside from offering greater performance than conventional material, the new generation of MacDermid Autotype films can also be moulded using proven film insert moulding (FIM) techniques – sometimes known as in mould decoration (IMD).
In this process, exceptionally tough, high quality three-dimensional automotive components can be produced using a combination of screen printing, pressure or vacuum forming, and injection moulding.
The use of FIM techniques can enable manufacturers to reduce component costs by up to 75 per cent, as the efficient process enables manufacturers to vary designs for use with different models quickly and simply by changing films.
This method is able to provide displays and surrounds with the exceptionally high quality finish demanded of today’s automotive manufacturers.
The FIM process involves reverse printing specialised optical films with the required graphics or legends, using high definition screen printing techniques.
Once printed, the film is then pressed to shape using a conventional vacuum press, with the specially developed mechanical properties of the films enabling deep drawn component parts to be formed, without the risk of stress fractures.
The formed components are then cut and trimmed before being placed into an injection mould cavity where molten resin is injected onto the underside of the shaped and printed film, producing a 3D item with an integrated printed design.
With the popularity of automotive entertainment and information systems showing no signs of slowing down, and with devices becoming more complex and incorporating larger displays, design engineers are looking for ways to meet these requirements while minimising costs.
By using the latest generation of optical films in conjunction with proven film insert moulding techniques, high quality and cost effective displays that minimise the effects of reflection and glare are now achievable.
MacDermid Autotype is a innovator, designer, developer and manufacturer of specialised coating technology for films used in a wide range of applications. These include touch and vision systems, membrane switches, film insert moulding (FIM) products for the automotive, telecommunications and domestic appliances sector and screen printing.
With specialist expertise in precision coating technology, MacDermid Autotype, transforms and enhances the performance of films for many high technology and demanding applications.
In recent years MacDermid Autotype has brought screen printing to new levels of control and repeatability, reinforcing the benefits of the process for new applications such as flexible circuit printing, DVD and industrial glass printing. MacDermid Autotype’s most recent launches have been of antimicrobial hard coated films for hygiene critical surface applications and of diffuser and anti-reflection films for use in flat panel displays.

Dr Keith Parsons is Technology Manager Light Management Films, MacDermid Autotype, Wantage, Oxon, UK. www.macdermidautotype.com