Gadgets

Smartphone screen, scritch-scratch no more

Here’s a mystery that almost every smartphone owner is eventually confronted with — despite taking good care of the phone and diligently keeping it away from coins, keys and all things pointy, the screen still manages to acquire scratches.

The case is perplexing, since those annoying blemishes seem to appear despite putting sharp objects in another pocket altogether. Also, marketing spiel tells us modern smartphone displays are encased in special glass that can easily handle the daily grind. Hop onto YouTube, and you will come across ‘knife screen test’ videos of phone screens getting stabbed, poked and scratched, all in the name of science. Fortunately, most screens not only survive such torture tests, they do so without any major blemishes to their character.

Smartphone screen, scritch-scratch no more

These super-strong screens are from brands like Dragontrail, Xensation, Dinorex, Panda King Glass, and the most famous of the lot, Corning’s Gorilla Glass, which is used by over 30 phone manufacturers, and has apparently graced 4.5 billion devices so far. It is made from alkali-aluminosilicate panels that have been thermally and chemically hardened to be four to five times stronger than untreated glass. For example, Samsung’s latest flagship, the S9/S9+, uses Gorilla Glass 5, which has been designed to survive 1.6-metre, shoulder-height drops onto hard, rough surfaces “up to 80% of the time”, while also exhibiting a high resistance to “sharp contact damage”.

A line in the sand

So why do these high-tech screens scratch, even in the absence of any sharp contact? Well, after extensive testing, the mobile tech site XDA Developers concluded that it is not knives and keys you should be worried about. Instead be afraid, be very afraid, of sand. Not just the type you find on beaches, but also the gritty dirt and dust that swirl around you and get into your pockets — these particles can be harder than toughened glass, and every time you slide the phone in and out of your pocket, the screen has an intimate tête-à-tête with the abrasive specks. Similarly, if you wear faded jeans, check the pockets carefully — the sandblasting process tends to leave behind fine sand that can scuff up a phone.

Screen protectors, a necessary evil

Phone manufacturers, including Apple, have been toying with the use of sapphire glass, which is almost as hard as diamond and impervious to scratches. GT Advanced, a sapphire glass producer, tested it against available glass brands and found that, on the commonly-used Vickers hardness scale, Gorilla Glass came in at 600-700 kg/mm², while sapphire blew it away with a score of 2,200 kg/mm². However, the material is heavier, denser and more expensive to make — so it will be a few years before sapphire glass makes it to a phone near you.

If you plan to sell your phone for the highest possible price — the difference between a phone in ‘flawless condition’ and one with ‘minor scratches’ can easily be a few thousand rupees.

The many types of screen protectors

First, a disclaimer: Screen protectors can turn smooth glass into a ‘rubbery’ mess that feels cheap. They also reduce transparency, could be an eye-sore if the fit and finish is not perfect, and putting one on without any residue air bubbles is an art in itself.

The pecking order among screen protectors starts with PET (polyethylene terephthalate) film. It is usually just 0.1 mm thick, almost invisible, cheap and easy to find.

If you wear faded jeans, check the pockets carefully — the sandblasting process tends to leave behind fine sand that can scuff up a phone

On the downside, PET scratches easily, discolours over time, and feels sticky to touch. But move up a rung, and you will meet TPU (thermoplastic polyurethane) screen protectors that have been chemically treated for enhanced oil, grease and scratch resistance. They also have a softer surface that can better handle impact and recover from minor scratches — some brands hype this as a ‘self-healing’ screen protector. You will also come across the term ‘military-grade protection’, though we doubt the military cares much about such screen protectors. As expected, the TPU variants are expensive, and applying them can be tedious — some use the ‘wet method’ where you need to spray the phone screen and the protector with a soapy liquid, align it carefully, squeeze out excess water, and then wait a day or two for the remaining air bubbles to disappear.

The king of the hill, however, is tempered glass (TG) screen protector.

TG is multi-layered and safer to use — a sticky adhesive layer ensures that even if the screen protector shatters, the resulting shards stay put. TG protectors also come with an oleophobic coating that hides fingerprints and increases scratch resistance. Though watch out for claims about ‘9H Hardness’ — it simply means the screen protector can survive an assault by a 9H pencil!

Light matters

Apart from the type of materials used, screen protectors are classified by how they deal with light — the most common are the glossy ones that reflect ambient light. But you could also try matte, anti-glare screen protectors that enhance screen visibility outdoors — in theory, this lets you reduce the screen brightness and prolong battery life. Another niche option is a privacy screen guard that drastically cuts down on viewing angles, so that the screen content is visible only when you look at it straight on.

Curved screens: a new headache

Phones with curved screens might look sexy, but finding the best tempered glass screen protector for them usually becomes an expensive trial-and-error routine. Some brands tackle the curves by not tackling them — the screen protector covers only the flat part, leaving the curved edges exposed. Others bravely try to cover the curves, but with mixed results — the glue is typically only around the edges and dust tends to get under these protectors. Worse, they reduce touch sensitivity since the protector mostly ‘floats’ over the display. A better alternative involves coating the entire tempered glass surface with LOCA (liquid optically clear adhesive) and then curing it with UV light. These protectors are expensive — costing over $50 — and currently need to be imported.

China-made ‘full glue’ options have also started popping up on eBay and Amazon, with prices as low as ₹600.


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Printable version | Jul 29, 2021 4:41:57 PM | https://www.thehindu.com/sci-tech/technology/gadgets/smartphone-screen-scritch-scratch-no-more/article23728466.ece

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