E-paper’s bistability, reflective properties, and flexibility make it low-power and eco-friendly, and it’s finding applications in e-books, smartwatches, electronic price tags, and more. By combining the advantages of traditional paper with display technology, e-paper is increasingly becoming a new alternative to protect the environment and reduce costs, and it has the potential to play a key role in future societies, especially those that seek sustainability.
As the joke goes, “You can live a day without food, but you can’t live a day without electronics.” As such, electronics are deeply embedded in modern life. In particular, the media we watch and read, such as TVs, smartphones, and PMPs, are all made possible by technology. Today’s lives are tightly interconnected with real-time information, video content, and the digitization of work, which is driving the demand for display devices and increasing interest in new display technologies. The only media that have not yet been digitized and remain analog are the newspaper delivered in the morning and the books on our bookshelves. But even these paper media are undergoing a wave of electronification. At the center of this change is e-paper, which is being touted as the next generation of display technology that can effectively replace paper.
The basic principle of e-paper is simple. It consists of a series of tiny capsules called microcapsules arranged between metal plates on top and bottom, with a tiny electrical circuit running underneath. The microcapsules are filled with a colloidal liquid and contain charged ink microparticles. The black ink particles are positively charged and the white ink particles are negatively charged. These charges attract opposite poles and repel the same poles, making it easy to display information on e-paper.
When you look deeper into how e-paper works, its innovation becomes clear. When a positive voltage is applied to the electrical circuit underneath the paper, the negatively charged white capsules are attracted to the direction of the voltage, while the positively charged black capsules move to the other side, revealing black ink. Conversely, if you apply a negative voltage, white ink will appear. In this way, e-paper presents text or images just like paper. Unlike conventional displays, which use light to make information visible, e-paper uses color differences in the ink to display information, making it easier on the eyes for long periods of reading and significantly lowering power consumption.
E-paper has three distinct advantages: bistability, reflexive, and flexibility. First, bistability means having two stable states: the liquid in the microcapsules is highly tacky, so once the ink is moved, it doesn’t move easily until voltage is applied again. This means that even when each capsule appears black or white, it remains stable when powered off, retaining information for a long time. This makes traditional e-books and e-paper exceptionally well-suited to low-power displays like billboards.
E-paper is also a reflective display, which means it doesn’t light up itself, but rather reflects ambient light to display information. This makes it easy to read at a natural light level that matches the ambient brightness, and it’s especially visible in sunlight, making it low-power and environmentally friendly. Finally, the flexibility of e-paper allows the display to be thin and bendable, allowing it to be used in a variety of forms, including smartphones, e-books, and fashion wearables.
E-books are not the only revolutionary change that e-paper technology will bring. Recently, smart watches, smart cards, and traffic information displays have been developed using the bistable and reflective properties of e-paper. For example, e-paper watches can display the time for days on a single charge, and personalized information can be displayed on the watch face as needed. E-paper is also being explored for industrial applications, such as RFID tags in logistics or libraries. E-paper tags are efficient because they display product information or inventory status and only use power when they need to be updated.
Other examples include electronic price tags and smart name tags that utilize the bistability of e-paper. In large supermarkets and retail stores, e-paper displays can be used as price tags for products, which can be easily updated and retain the existing information even when the power is cut, saving power. This makes e-paper an eco-friendly and economical choice that can reduce operating costs while protecting the environment.
E-paper is not yet a perfect replacement for traditional paper in all aspects. E-paper is a bit slower to respond, which limits its ability to work with fast-moving videos and graphics, and it can be harder to read in low-light conditions. In the early days, information could only be presented in black and white, but with the advent of color e-paper technology, it is expected to be used in a variety of areas, including advertising, education, and publishing.
E-paper, which combines the advantages of paper with the advantages of display, is likely to be applied in many more fields in the future. With the enormous amount of paper used globally every year and its impact on the natural environment, the widespread use of e-paper can be an option to practice sustainability. This makes e-paper an important alternative for the new era of harmonizing IT technology and environmental protection.
