Future of Mobile Phone Displays: What’s Coming Our Way?

Article By : Janice Mori

A look at the future of mobile phone displays, including foldables, OLED, and better user experience...

Someone once said, “You can never be too rich or too thin.” You can debate whether this is a healthy sentiment for people, but it certainly rings true for smartphones. The richness of the mobile displays, and the thinness of the devices are key differentiators in modern smartphones, along with the cameras, battery life, storage, and processor speed. A touchable display has always been central to the smartphone experience, and screen time has become a more important user measurement than call time or data consumption. Since the smartphone display is for many the primary window to the digital world, it makes perfect sense that the quality of that display — both the visual quality and the touch experience — is central to the value of a smartphone. The display also drives the physical form of the phone, from the size of the viewing area, to the cutouts for cameras and sensors, to the overall thickness of the device itself. As the displays have stretched to cover the entire front of the phone in recent years — even wrapping around the edges or starting to become foldable — changes in display technology will continue to be a driving force in the evolution of the smartphone. Synaptics has been at the forefront of the smartphone display evolution, creating and driving many of the key technologies needed to enable new display technologies. Synaptics’ touch and display technologies are found broadly throughout the world’s leading premium mobile devices — we have a unique perspective on where the future of smartphone displays is going. Here’s what we see coming. Flexible OLED is In Today’s flagship products are rapidly moving to flexible OLED displays. Broadly speaking, LCD displays, while still having a large market footprint, have become a low-cost solution, with rigid OLED seen in higher-end phones and flexible OLED increasingly dominating the premium and flagship segments. “Rigid” OLED uses a glass cover lens and generally has a thicker overall display “stack-up” (the sublayers that make up a display), while “flexible” OLED uses a plastic cover lens and is thinner overall. Flexible OLED takes the advantages of OLED technology including better contrast, higher brightness, fuller viewing angles, true blacks with a wider color range, and a faster refresh rate. Flexible OLED is brighter, as the plastic cover lens is generally thinner than Rigid OLED or LCD, and there are fewer sublayers of the display in-between the cover lens and the light-emitting pixels. The market for displays has evolved into two camps: LCD and OLED. LCD is an older technology, and while it continues to maintain a leading market share (we’ve seen the successful launch of new smaller form factor, lower cost LCD devices from Apple recently), OLED is now the standard for high-end phones. Rigid OLED may be thicker than flexible OLED, but both are thinner than LCD panels, as a consequence of using self-emitting light diodes rather than a passive display with a light source behind it as LCD does. Flexible OLED displays are typically used in flagship phones to enable more advanced designs like edgeless displays or displays that bend over the side, and as of 2019 even displays that can fold in half. By 2023, market forecasters predict one in four phones will use flexible or foldable OLED. Both rigid and flexible OLED offer a number of advantages including improved image quality (better contrast, higher brightness, fuller viewing angle, blacker blacks, a wider color range, and much faster refresh rates), lower power consumption, and better durability. In general, flexible OLED also allows the phone manufacturers to offer form factors with more innovative “wow” design characteristics, as well as deliver better performance and brighter displays for the consumer. All the advantages of flexible OLED come at a cost: a challenging touch performance environment. That’s because of electrical noise inherent in the architecture of OLED and made more prominent as the display gets thinner. This background display noise makes it difficult to detect the signal that indicates a finger has touched a panel. In a typical LCD display the touch and display circuitry occupies about 2.0mm of space. With the cover glass, the touch sensor is quite far from the noisy pixels and in the LCD world the pixels turn on and off allowing it to do touch sensing in the off or quiet cycle. Both factors make responsive and accurate touch performance relatively easier to achieve. On the other hand, with flexible OLED, the pixels never turn off — they’re always on. This requires greater synchronization between touch and display technologies. By using a technique called On-Cell, the touch technology is integrated into a thin film layer and is only 80µ away from the noisy display pixels (that’s a little more than a human hair). While it allows for much thinner devices, it makes it very hard to bring good touch performance due to that close proximity. It’s the difference between finding a flower in a mown sports field versus finding it in a forest. Synaptics has developed a novel display noise removal circuitry to resolve noise issues and deliver the necessary performance in a power-efficient manner. Essentially, it’s like having a camera that ignores all of the tree colors and only focuses on the flowers’ colors. Providing a great touch experience is central to unlocking the benefits of flexible OLED and making it more widely available. Foldable displays hold potential Over the last year we have seen the first foldable phones come to production and we already see strong interest in this area with foldable designs selling out as soon as they are offered. However, the market is still in an early adopter phase, and we think that the foldable market will take a few years to develop. Consistent with the introduction of other display technologies in the past, we see significant technical challenges that will need to be overcome before foldable phones become mainstream. While a lot of news headlines on foldable displays focus around today’s high cost, hinges, and durability of the cover glass in these first devices, a less highlighted but still significant area to enable widespread adoption of foldable displays is the touch performance. Foldable is even thinner than flexible OLED and introduces novel conditions that have to be overcome such as having two parts of the same panel right next to each other when folded. The larger form factor of many of these foldables is its own challenge. Finally, some use cases that are somewhat niche on today’s smartphone, like pen support, make a lot more sense on a screen that is essentially a small tablet. In our view, great touch performance is vital to the widespread adoption of any smartphone technology, including foldables. The 5G Impact We have all heard that 5G is coming and that it brings dramatic increases in the data bandwidth on our phones, but what does that mean for an everyday users’ life? Quite a lot actually. 5G will transform the smartphone we carry today from a supercomputer in our pocket to an immersive portal through which we connect with a cloud-computing powered virtual world. Processing for many tasks will be able to be moved from the smartphone to the cloud thus enabling more immersive games and video streaming, seamless augmented reality, and crystal-clear telepresence calls. Beautiful displays that are faster, brighter, and provide more depth and more responsiveness with ultra-low latency will be key to allowing consumers to interact seamlessly with this more immersive world. These displays will be power hungry, so developing low-power and power-saving solutions will also be important. Synaptics’ OLED touch controller for smartphones already supports the industry’s highest touch report rate at 270Hz. Synaptics’ OLED display driver IC’s (DDICs) are the first to support 90Hz and 120Hz refresh rates for smoother gaming and video experiences. These display and touch performance advancements will allow users to experience the benefits of 5G in a more meaningful way. Design and user experience features With the shift to flexible OLED and the underlying enabling technology, we can expect to see a range of new features in phones that improve the user experience and allow device makers to create even more innovative designs. In the future you can expect to see a continuing evolution of borderless or infinity displays, which extend not only across the entire front surface of the phone, but around the sides and even onto the back of the phone. With that, as well as the further integration of new touch and display technologies, phones may no longer have any physical buttons or controls — including the volume and power button now found on the side or tops of devices — which will be enabled instead by capacitive touch technology. In addition, we look forward to truly bezel-less designs, with an uninterrupted display surface on the phone. This could include a camera or other sensors completely integrated into the display itself, eliminating the need for the distractive notches and holes on the front surface of the phone. One of the key technologies to enable this is to integrate the Face Detect functionality directly into the display. This uses touch sensor technology to recognize when the phone is raised to the users’ ear, and at the same time, power down the display on the device to save battery. Today, Face Detect is typically done with an IR-sensor that adds another black hole and cost to the front of the display. With integrated Face Detect, this functionality can be done by the same touch controller that detects fingers on the display and the IR sensor can be removed, helping achieve the true bezel-less look. The touch experience will continue to evolve, including refinement of the stylus as an input method. We are working with partners to enhance Active Pen technology, which will allow pen-based input without any additional technology required from the manufacturer and allow the more precise pointing of a stylus versus a finger. Phones will continue to evolve The mobile phone and other mobile devices continue to take on an increasingly important role across all aspects of our lives that could have hardly been imagined back in 2007 when the first iPhone was introduced. While there has been a lot of hand wringing of late regarding the slowdown in the overall smartphone market, we see continual innovation in display technologies and we believe there is strong growth inside the market towards these innovative and advanced display technologies. Particularly as we move to the 5G era, the ability to more seamlessly interact with our devices via their screens will bring more productivity, enjoyment, and convenience to users. From the beginning, the display has always been what made the smartphone different. Moving from buttons to a touchscreen allowed the display to take over the front of the phone. The large, beautiful, touchable display is what has driven the smartphone to be the most popular consumer electronic device in history, with approximately 1.5 billion smartphones sold annually. Through the display, users consume and create content, stay informed, stay entertained, and stay connected. The display in our pocket has become a window to the world and has brought the world closer to us. — Janice Mori is a senior vice president and general manager of the mobile division at Synaptics

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