The challenges of making a foldable display

By James Lu - on 28 Jan 2019, 7:56pm

In November last year, at its annual developer conference, Samsung unveiled a remarkable device: a smartphone with a foldable display that can be opened like a book. The device has a normal 4.5-inch display on the outside, but can be opened up to reveal the 7.3-inch Infinity Flex Display on the inside. The Flex Display is rumored to have a 4.2:3 aspect ratio and a 2,152 x 1,536 pixels resolution (420ppi). The benefits of a flexible display like this are obvious. Imagine being able to carry around a tablet in your pocket, or opening up your smartphone to watch large screen videos or for multitasking with up to three full apps running side-by-side simultaneously.

Samsung has been rumored to be developing its foldable display since at least 2013, but it’s taken this long for it to finally reach the stage where it’s ready for commercial production. The long wait is due to the many challenges Samsung has had to overcome to make its display. After all, consumers will want and expect foldable display smartphones to deliver all of the same benefits they've come to expect from current flagship smartphones. That includes superior clarity, brightness, viewing angles, durability, scratch-resistance, and long battery life.

Samsung’s first big challenge was finding a suitable replacement for glass. Glass displays are durable and provide great optical clarity but they’re inherently inflexible. To enable the screen to flex, Samsung had to create a new fortified plastic display that has almost the same weight, thickness, durability and transmissivity as glass. Folding and unfolding the display also carries its own unique durability issues. The completely folded over design of Samsung’s device should put a large amount of stress on the inside seam, but Samsung’s new display is apparently so durable it can be folded and unfolded thousands of times without any degradation.

The second problem faced by Samsung is that displays have always been static, which means that once the component layers were combined, they never had to move. But with a folding display, there’s a certain amount of flex whenever the screen is opened or closed. To achieve this, Samsung had to develop a new kind of malleable adhesive that lets the display layers be laminated together while enabling them to flex.

Finally, Samsung’s biggest challenge was how to keep the display thin. A display that can fold over on itself has the potential to be extremely thick, which wouldn't provide a good consumer experience. Samsung solved this problem by reducing the thickness of the polarizer, the layer in the display that filters external light and reduces glare so users can read the display. Samsung managed to create a new polarizer that is 45 percent thinner than those used previously.

Samsung is expected to fully unveil its foldable display device, rumored to be called either the Samsung Galaxy X or Galaxy F at its Unpacked event next month, with a release to follow in March. The phone is rumored to cost around S$2,400.

James Lu

James Lu / Former Associate Editor

Don't be fooled by specs, nobody needs an 18000 DPI gaming mouse.