[Agile Electronics Story] TV and Smartphone Market's Promising Candidate 'Rollable Display'

‘Agile Electronics Story’ is a corner that keenly examines small pieces of information about electronic and mechanical products and devices. From hot new products frequently appearing in advertisements and news, to nostalgic items, and puzzling products and industry terms and news, we will kindly cover them with the heart of a beginner.

Teaser video of the 'Rollable TV' unveiled by LG Electronics [Image source=Yonhap News]

LG Electronics has finally announced that it will unveil its Rollable TV. It has been about 1 year and 10 months since LG Electronics first showcased the world’s first Rollable TV at CES 2019. Before the launch event, LG Electronics has been attracting attention by posting teaser videos on YouTube and other platforms.

In this ‘Agile Electronics Story,’ following foldable displays and transparent displays, we have prepared the third story on next-generation displays: rollable displays.

◆The key to rolling up starts with flexible materials

LG Display's Rollable OLED Display Panel

What is the key to implementing rollable displays? The core of rollable displays that can be rolled up is ‘flexibility.’ In academia and industry, companies mainly adopt OLED to make rollable displays. The biggest distinction between OLED and LCD is self-emission. OLED elements can emit light by themselves, but LCDs require a backlight, making them thick and heavy, which is disadvantageous for rolling or changing shape.

The key components for implementing rollable displays mainly include transparent polyimide (PI) substrates on which OLEDs are mounted, thin-film transistors (TFT), and encapsulation layers that protect the elements from moisture and oxygen. Previously, glass substrates were used to make flat organic light-emitting diode (OLED) displays. To facilitate shape changes such as rolling in flexible displays, polyimide substrates, which are hard yet flexible and resistant to high temperatures, have mainly been used.

Thin-film transistors are transistors made using thin films. Transistors are semiconductor electronic circuit components that control the flow of current. In displays, transistors control the brightness of each pixel that makes up the screen. Research and development (R&D) on transistors is actively underway to improve their flexibility and performance. For example, a joint international research team including Senior Researcher Kyung-Geun Lim from the Korea Research Institute of Standards and Science, Dresden University of Technology in Germany, and the Chinese University of Hong Kong developed a vertical organic transistor this year that lowers voltage and improves performance by stacking transistors vertically.

For encapsulation of existing OLEDs, glass that perfectly blocks moisture and oxygen is mainly used. However, since glass can easily break in rollable displays, thin-film encapsulation is becoming an alternative material. Thin-film encapsulation is a technology that alternately stacks inorganic and organic layers. The inorganic layer blocks contaminants, and the organic layer compensates for pinholes (tiny holes) and rough surfaces in the inorganic layer.

Won’t thin and flexible rollable displays wrinkle or become floppy when unfolded? Of course, the display panel alone can become floppy or wrinkled. Companies have developed technology to roll and unroll the screen to prevent this. In LG Electronics’ case, a bar is attached behind the part of the TV panel that rolls. The bar looks like a sushi rolling mat and helps maintain the shape of the display while allowing it to be rolled up.

From TVs to smartphones? Convenience and space creation at the same time

Vehicle Roll-Down Display by LG Display

[Photo by LG Display Blog]

Rollable displays are expected to be used in various fields in the future as a weapon for convenience and space creation. As mentioned earlier, the beginning of rollable display products is TVs. LG Electronics will hold a launch event for the ‘LG Signature OLED R’ from the 14th to the 19th of this month at Banyan Tree Club & Spa Seoul. The current price is in the 100 million KRW range, but it is expected to decrease once mass production begins.

There is a high possibility that rollable displays will also be used in smartphones, vehicle displays, and more. First, LG Electronics hinted at the release of a rollable phone next year during the online unpacking event for the LG Wing smartphone held last month. Samsung Electronics is also registering technology patents related to rollable phones. Because of this, although the rollable display market is still in its early stages, related industries forecast that the shipment volume of rollable OLED TV panels will grow to about 1.6 million units by 2025.