Is your display up to scratch?
It’s important to take a step back and consider just what your application really needs when it comes to wear and tear. Because while the ultimate in toughness might be your immediate choice, it could be like using a sledgehammer to crack a nut – it’ll do the job, but did you really need all that power?
And display protection doesn’t always mean scratch resistance. While a thick coverglass may well protect a device from the impact of an accidently dropped screwdriver during servicing, it could still leave a nasty scratch. This is a problem across a number of devices which are designed for heavy use and exposure, such as public transport payment terminals (scratched by credit or debit cards, jewellery rings or coins), industrial terminals (gloves, dirty with sand or metal parts, inflicting scratching) or medical devices (operation with steel tools). So, to counteract scratching, impact resistance alone is not enough. A hard surface is obviously more scratch resistant than a soft material and the industry measures this hardness by scratching the surface with graphite pens.
If your application provides visual data, in most cases a Liquid Crystal Modul (LCM) is implemented for its brightness, clarity of the image, high resolution and contrast. This will often sit with a TFT module, which provides excellent optical performance and can be selected from a vast number of variations to fit the requirements. Regular unenhanced LCMs provide a Mohs hardness of 3H of the top most layer of the image area, which is made of plastic. Consider that both gold and copper also have about 3H hardness in their purest state and can be easily scratched by a sharp knife.
Adding a glass surface to the LCM is a common practice, as it increases impact resistance, but also allows for the device to be operated with a single finger. Soda lime glass gives a hardness of around 6.5-7H, which is durable enough to prevent scratching from softer plastic materials, like credit cards or fingernails.
However, something as innocuous as a little grain of sand can have an even higher hardness. So, as we mentioned earlier, using touchscreens in an industrial setting, with dirty hands or gloves, can easily leave scratches. This might not seem like too troublesome on the face of it, but remember, enough scratches in a high-use area can cause the screen to lose its transparency – and that can be a safety issue.
Glass can be chemically or thermally strengthened to increase the impact resistance, but this doesn’t usually improve the scratch situation much. Better scratch protection almost always comes at an additional cost, usually in the shape of specific types of glass, such as quartz glass or sapphire-coated varieties. There are also other, pricier industrial coatings available which increase the surface hardness.
You might be wondering what the higher values of hardness look like, particularly if you’ve seen your mobile phone screen protectors that claim to offer 9H superior hardness. I think we can safely say that these claims of 9H are not what we would consider to be 9H when working with our customers. And these plastics certainly won’t have undergone the same levels of testing. After all, most people wouldn’t be willing to pay such a high price for a screen protector that has genuine 9H Mohs scratch resistance. Moissanite, a naturally occurring silicon carbide often used in jewelry has 9H hardness. Diamonds are 10H. Hardly the kinds of material you’d be looking for in a disposable sheet!
Making the right choice isn’t always a matter of material, however. When we work with our customers, we look at every aspect of the product – not just how it is built, but how it is used. So, while we certainly explore industrial coatings and understand precisely what kind of day-to-day wear and tear is expected, we also think about prevention. After all, a pressing motion can produce a very different result to a swiping motion on a screen and can keep those pesky scratches to a minimum without any costly coatings.
Our Avnet Displays come in a range of form-factors and our display-experts are on hand to guide you in the creation of display or touch solutions that meet your requirements. Find out how Avnet Displays can propel your product innovation and get in touch today.
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Avnet’s Displays team solves product design challenges for OEMs looking to build the perfect display technology into their products. Our in-house team works directly with businesses to solve all the challenges of integrating a display into a product design, from tiny wearables to massive outdoor screens. We design, build and deliver display solutions all over the world for established household brand names and industry disruptors alike. If you need a display designed and integrated into your product, our team is here to help. Get in touch today to tell us about your challenge.