[Agile Electronics Story] The New Battlefield of Smartphones... Foldable Display

[Asia Economy Reporter Ki-min Lee] ‘Agile Electronics Stories’ is a column that keenly examines small details about electronic and mechanical products and devices. We kindly cover hot new products frequently appearing in advertisements and news, nostalgic items, puzzling products and industry terms, all from a beginner’s perspective.

Following Samsung Electronics’ first foldable phone, the Galaxy Fold, the second model released this year, the ‘Galaxy Z Flip,’ has been selling out immediately upon release, gaining great popularity.

Not only Samsung Electronics but also Motorola has already launched the foldable phone ‘Razr,’ and Huawei is preparing to release a new foldable phone, the ‘Mate Xs,’ next week. Additionally, LG Electronics, which adopted a ‘dual screen’ composed of two different displays rather than foldable screens, announced at the year-end earnings conference call last month that foldable phone technology verification has been completed. Because of this, there are forecasts that the foldable phone sector will become a new battleground in the smartphone market.

◆ Foldable Displays... Did They Suddenly Appear One Day?

A foldable display, as the name suggests, is a display that can be folded. To realize a foldable display, technologies such as flexible OLED, a cover window that protects and maintains performance better than glass when bent, hard coating materials to increase hardness, and foldable touch integrated circuits (ICs) are required.

▲Samsung Electronics Galaxy Round equipped with Samsung Display's flexible display panel

In fact, foldable display technology did not suddenly fall from the sky one day. It is the result of new attempts to create technology that surpasses existing flat displays. Samsung Electronics, a pioneer in foldable phones, released the ‘Galaxy Round’ equipped with flexible OLED in 2013 before launching foldable phones.

In 2015, Samsung Electronics released the ‘Galaxy S6 Edge,’ which adopted curved displays on both the left and right sides of the screen. Flexible display technology was also applied to wearable devices such as smartwatches. Simply put, bending technology came before folding technology.

There is also an assessment that the display war was already predicted. Smartphone companies like Samsung Electronics and Apple have been engaged in a specs war for over a decade to attract consumers. As a result, most smartphone specifications have been standardized at a high level. As the smartphone war continued, display sizes increased, and smartphones became so large that they were inconvenient to hold with one hand or carry in pockets or bags.

Because of this, foldable displays, which have been steadily developed as a strategy to maintain existing smartphone hardware performance while providing users with differentiated experiences, have been chosen as an option.

To Commercialize Foldables, Durability Must Be Increased and Thickness Reduced... Development of a New Dimension of Displays

According to market research firm Strategy Analytics, the foldable phone market is expected to expand from 1 million units last year to 8 million units this year, and to 100 million units by 2025.

However, customers have consistently raised complaints about the weak durability of foldable displays. A foreign media outlet reported issues such as bubbles forming on the plastic OLED screen of Motorola’s foldable phone Razr kept in a pants pocket and the cover window peeling off. Also, polyimide (PI) films develop many wrinkles at the folding parts.

To overcome these problems, Samsung Electronics introduced ultra-thin tempered glass (UTG) made by Samsung Display in the Galaxy Z Flip. UTG is a product developed by Samsung Display in collaboration with domestic material companies since 2013. It is glass processed to a thickness of about 30 micrometers (μm, one-millionth of a meter) with special materials added to enhance flexibility and durability. However, UTG is more vulnerable to impact than tempered glass used in regular smartphones and has higher repair costs. To improve this, domestic electronic component companies are developing hard coating liquids for cover windows that further strengthen UTG or UTG that does not require a screen protector.

Samsung Display is also developing a touch-integrated flexible touch screen panel (TSP) to reduce the thickness of foldables. Samsung Display’s method is based on using double layers of substrates or thin transparent substrates for flexible displays and creating pixels and touch sensing with transparent electrode materials between the substrates.

In addition, display companies worldwide are researching and developing new dimension display products to commercialize not only foldable displays that fold both front and back or fold twice but also rollable displays that can be rolled up and stretchable displays that can elastically expand the screen.