Breaking the glass ceiling for LCDs
February 26, 2019
We are all used to handling devices with glass displays and have accepted the limitations that are associated with their weight, breakability, rectangular shape and bulkiness. While some end-user applications may not be affected too much by these limitations, there are a lot of products for which a glass display creates design constraints and compromises the user experience. Luckily, new technologies are being developed which can eliminate those constraints and unlock design freedom, while also opening up new use cases – one such technology is plastic OLCD.
What is plastic OLCD?
Flat panel liquid crystal displays (LCDs) are made using conventional silicon thin-film transistor (TFT) technology on glass substrates. In a plastic Organic LCD (OLCD) the silicon TFTs are replaced with flexible, high-performance organic TFTs (OTFT), while the glass is replaced with light-weight, low-cost plastic substrates (like triacetyl cellulose - TAC) that can be as thin as 40 microns. The result is conformable, shapeable, thin and lightweight OLCDs that have no compromise in optical performance and are as scalable as glass LCDs.
Advantages of plastic OLCD over glass LCD
In addition to being a complementary technology to flexible OLED by addressing applications for which today’s flex OLED displays are not suitable, OLCDs have several advantages over glass LCDs. Product engineers and designers should consider using OLCD instead of glass LCD if any of the features below are important for their application.
Thin and lightweight
The ability to make OLCDs on thin sheets of TAC makes them thinner and lighter than their glass counterparts. This is enabled by low temperature processing (below 100°C) of the active materials. Unlike conventional silicon technology that uses high vacuum deposition systems to coat the active materials, OLCD processes require solution coating of liquid polymers such as the semiconductor and the dielectrics which can be carried out using solution coating at low temperatures.
The liquid crystal (LC) cell assembly process on glass helps to maintain a constant cell gap during the display operation and lifetime. Plastic LCDs on the other hand use polymer walls to maintain the cell gap on the flexible substrates. This results in high yield of the plastic LC assembly process and allows the displays to be bent down to 10mm bend radius. Additionally, the use of inherently flexible organic materials for the OTFT backplane facilitates the conformability of the OLCD.
Plastic OLCDs do not have to be rectangular. While glass LCDs can also be made into different shapes, this adds significant costs to their manufacture and hence the majority of glass LCDs are rectangular. Plastic OLCDs on the other hand can be easily profiled into any shape as well as have holes through. The ability to design displays (electrically) with unusual shapes is partly determined by the performance of the TFT technology that drives them. From a manufacturing and cost perspective, it is the ability to cut plastic LCD displays that makes them suitable for shaped displays. Plastic OLCD can be easily cut to unusual shapes using laser or a blade, both of which are much more difficult to do on glass LCD.
No loss of performance
OLCD uses high-performance OTFTs compared with amorphous silicon on glass, meaning there’s no tradeoff in optical performance of OLCD compared to its glass predecessor. Indeed, the ultra-thin plastic substrates used in OLCDs mean the image quality is enhanced. OLCD also opens the door to new exciting structures that will drastically enhance the contrast of LCD to OLED-like levels.
Applications that can benefit from plastic OLCD
There are several applications that can benefit from plastic OLCD. Below are a few key ones.
Smart home appliances
We may be used to the rectangular shape of a fridge, but many home appliances have curved and non-rectangular designs. Next generation smart home appliances like coffee machines, digital assistants and white goods can benefit from the bendability and shapeability of OLCDs, allowing displays to be added without compromising the familiar curved shapes of the existing products.
With vehicles becoming smarter, the ability of the vehicle to interact with the passengers will require the use of several displays in the interior as new use cases and designs are developed. OLCD adds freedom to car design and can give vehicles a state-of-the-art interior – these displays can be seamlessly integrated into the curved surfaces of the car.
Laptops and tablets
Laptops can be made lighter with OLCDs compared with their glass counterparts. With new generation laptops featuring dual displays, using plastic-thin and lightweight displays can bring a significant advantage to both designers and end users. Additionally, the ability to fold the edge of OLCD can enable borderless screens for notebooks and tablets.
Wrapping an OLCD around the face or body of a robot can make them look more human. With the rise of artificial intelligence (AI) and robotics, we are likely to see more robots in the home and office in the future– equipping a robot with a curved OLCD can help enhance the human-machine interaction.
Remote controls are widely used in the drones industry and they often feature glass displays that are used to monitor the drone location as well as a touch interface to its controls. However these displays are heavy, bulky and fragile. OLCD offers a lighter and more robust alternative to displays for remote controls and it can be also equipped with a touch function. Additionally, with the ability to make holes through plastic OLCDs, knobs can be incorporated into the design without having to extend outside the display area as in the case of a glass LCD.
Large screen applications
Digital signage has become a powerful tool in the retail sector where digital information displays are used in store for branding, promotion and entertainment. In the transportation sector, hubs, links and on-vehicle displays are also becoming advertising platforms as well as sources for up-to-date information. TVs are becoming a decorative feature in the smart home. OLCD can help make displays blend in the environment by enabling shapeable and conformable displays.
New use cases
New use-cases will emerge where the use of displays has been unthinkable due to the limitations of glass-based LCDs or the cost and reliability barriers of flexible OLED. Now with the advantages of industrially scalable OLCDs, displays manufacturers can breathe new life in their existing LCD factories in order to differentiate their products and capture new market opportunities.
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