At CES 2024, Lenovo showcased the ThinkBook X concept 13.5-inch laptop, which features E Ink Prism color-changing e-paper technology on the cover, capable of displaying eight colors to create any pattern desired by designers. Thanks to the bistable characteristics of e-paper, this color e-ink screen can operate at ultra-low power without affecting the laptop’s battery life【1】.
Figure 1 ThinkBook X concept cover
When it comes to e-paper, one cannot ignore the Kindle e-reader, which made e-paper products known to the public, marking the beginning of a new era of electronic reading. E-paper technology is a revolutionary display technology that can mimic the appearance and feel of paper while allowing for the flexible presentation of digital content, becoming a popular display technology for innovation and application.
The core technology of e-paper is electronic ink display technology, evolving from black-and-white e-paper to full-color e-paper, and from a single application in e-readers to applications in POP displays, electronic billboards, smart tags, electronic logistics boxes, and many other fields. Innovations in electronic ink displays have continuously driven the development of e-paper products, opening up broader market prospects for e-paper applications.
This article takes E Ink Holdings, a representative company in the e-paper industry, as an example, focusing on the iterative path of its e-paper products and revealing how high-tech companies protect their patents during the product iteration process, providing references for companies to develop patent strategies and conduct patent layouts.
2. Patent Technology Analysis of the Company
E Ink Holdings, founded in 1992, is a Taiwan-based company specializing in the production of electrophoretic e-paper displays and TFT LCDs. E Ink Holdings was an early investor in e-paper R&D and production, acquiring Philips’ e-paper division in 2005 and the American e-ink leader E Ink Corporation in 2009, completing the integration of the e-paper production chain, thereby becoming the world’s largest manufacturer of e-paper displays, holding an important position in the global e-paper industry.
As of December 10, 2023, E Ink Holdings has a total of 346 e-paper-related patents worldwide. Based on the content of the technical solutions of the patents, we can observe the distribution of E Ink Holdings’ patent technologies (as shown in Figure 2) and the distribution of patent application scenarios (as shown in Figure 3).
Figure 2 E Ink Holdings’ e-paper patent technology distribution (units: items)
Figure 3 E Ink Holdings’ e-paper patent application scenario distribution (units: items)
In terms of technological innovation, E Ink Holdings focuses on electrophoretic technology, as the fundamental principle of electronic ink display is based on the electrophoretic phenomenon. Therefore, E Ink Holdings continuously innovates and improves electrophoretic display technology, accumulating a total of 77 related patent applications. Additionally, E Ink Holdings also focuses on display driving technology, with related patents reaching 40. Moreover, as display technology continues to improve, E Ink Holdings has gradually begun to move towards color display and flexible display, proposing solutions and conducting patent layouts in these areas. To meet the needs of different application scenarios, such as video display and outdoor advertising, E Ink Holdings is also committed to improving refresh rates and temperature width technology, proposing multiple patents.
In terms of structural innovation, E Ink Holdings focuses on pixel electrodes and driving chips, with 67 patents related to pixel electrodes and 44 patents related to driving chips. Additionally, the number of patents in areas such as filter films, edge sealing, and transparent films is similar, each around 10. The number of patents for e-paper films is the least, totaling 3. From the layout of structural patents, it can be seen that E Ink Holdings focuses primarily on the basic structure of e-paper, namely the pixel electrode, followed by the structure of the driving chip.
In terms of application scenarios, most of E Ink Holdings’ patents are concentrated in the e-book sector, with a total of 19 patents. This is because e-books were the earliest applicable scenario for e-paper, and the products have continued to upgrade and evolve to this day. In addition to e-books, E Ink Holdings is also actively seeking other potential application scenarios for e-paper technology, such as electronic tags, electronic business cards, writable e-paper, smart wearable devices, and electronic billboards, and has laid out a certain number of patents in these scenarios as well.
3. E-Paper Products – Patent Perspective
To showcase the iterative process of e-paper products and the development path of technological innovation, this article presents a patent technology iteration map of E Ink Holdings’ e-paper products (as shown in Figure 4).
Since entering the e-paper field in 2005 with the acquisition of Philips’ e-paper division, E Ink Holdings has focused on R&D of e-paper products. Patent CN1975547A proposes an electronic ink display method that simplifies the manufacturing process by reducing the steps required for the thin-film transistor array substrate, achieving simplified processes and reduced production costs; meanwhile, the design of each pixel area of the thin-film transistor array substrate is a dual-gate structure, which prevents leakage and improves the display quality of the electronic ink display device.
In 2007, e-paper products were applied to the first generation of Amazon’s Kindle e-reader. This product integrated E Ink Holdings’ R&D achievements over the past two years. Among them, TW200736786A (2006, thin-film transistor array substrate and electronic ink display device) proposed a dual-gate structure for the thin-film transistors, reducing leakage current and improving the aperture ratio and display area of each pixel. TWI320602B (2006, display device and its repair method) proposed a method for repairing defective pixel units with bright or dark spots, improving yield. JP2008026851A involves a driving method for a bistable display, eliminating complex driving structures and improving the performance of bistable displays. TW200732807A proposed an electronic ink display device that creates holes in the metal pattern layer, allowing UV light to penetrate the metal pattern layer and adequately cure the adhesive, improving the sealing degree between substrates and protecting internal components from moisture.
In 2009, E Ink Holdings acquired E Ink Corporation, becoming the world’s largest supplier of electronic ink. In the same year, they collaborated with Amazon to launch e-paper products for the second generation of Kindle. Compared to the first generation, the second generation Kindle utilized E Ink technology, achieving more energy-efficient and lighter products. CN101546525B (2009, voltage selection circuit, electrophoretic display device, and electronic device) involves a voltage selection circuit that provides power voltage to the latch circuit, reducing circuit area and conserving energy. CN101630101B (2008, electrophoretic display device and its packaging structure) proposed a COF bonded to the back surface of the panel without an additional frame, thus reducing the weight and thickness of the display device. TWI380254B (2008, flexible display panel) designed a flexible display panel with electrophoretic and electrowetting pixel units, where static images can be displayed by a bistable electrophoretic layer and dynamic images can be displayed by a rapidly switching electrowetting layer, achieving both energy efficiency and improved refresh rates.
In 2013, E Ink Holdings launched the second generation color e-paper Triton 2, used in some e-book readers from Ectaco and Pocketbook. This product introduced features including enhanced filter performance, compatibility with both black-and-white and color displays, fade resistance, and black-and-white color mode switching. Among them, CN102736346B (2011, color e-paper structure and its manufacturing method) added a protective color layer between the color resist layer and transparent adhesive layer to prevent the adhesive layer from eroding the color resist layer, thereby solving the problem of color fading. CN103365021B (2012, electrophoretic display device that can switch between color and black-and-white modes) designed an optical path that allows the electrophoretic display device to switch to color mode when the light source is on, while the reflected light from the ambient light does not follow the designed optical path, thus presenting the original black-and-white display mode.
In 2016, E Ink Holdings released the first generation ACeP color e-paper, designed for displaying color images while maintaining low power consumption, mainly applied in electronic billboards. The technical improvements of this product mainly include improving color deviation, enhancing display brightness, and increasing color saturation. Among them, CN104678472B (2014, color filter substrate and display device) used a color filter substrate to mitigate color deviation in the display device. CN105022200A (2015, display device) replaced the transparent conductive film with a nano-metal mesh layer, improving light extraction efficiency and enhancing display brightness. CN105319795B (2015, electrophoretic display) increased the area ratio of the color resist patterns R, G, and B filled in the pixels or sub-pixels by forming an outer shape with the first and second wires, thereby increasing the color saturation of the electrophoretic display.
In 2019, E Ink Holdings developed the world’s first full-color electronic paper advertising board, becoming an alternative to traditional paper advertisements. The technical improvements of this product mainly include enhancing optical properties, backlight capabilities, color performance, and resistance to electromagnetic interference. Among them, TW201831973A (2017, electrophoretic display device) addressed the issue of poor color mixing effects in existing technologies by proposing that the color filter layer includes multiple color filter patterns, with the electrophoretic display film configured between the driving array substrate and the color filter layer, using the color filter layer and charged particles to display preset colors in the pixel units, thereby enhancing the optical properties of the electrophoretic display. TW201947308A (2018, electrophoretic display device) utilized a polymer light-emitting diode module for backlighting in dark environments to clearly display images. CN110082980B (2018, reflective color electrophoretic display device) controlled the display area size through mechanical and electrode driving, maintaining the resolution of the display device while improving color performance. TWI688938B (2018, display device and display driving circuit that suppresses electromagnetic interference) effectively reduced electromagnetic interference in the display device by appropriately attenuating the timing signals provided to the display driver.
In 2021, E Ink Holdings launched the second generation ACeP “color e-paper” E Ink Gallery 4100. To address the issue of grid-like textures when displaying white patterns in existing reflective color electrophoretic display devices, TWI779520B (2021, color filter module) proposed that multiple color resist units are arranged in a non-continuous pattern, reducing the appearance of grid-like textures when adjacent pixel areas wish to display white. CN114167659A (2021, color electrophoretic display) shortened the distance between the color filter layer and the display medium layer, reducing total internal reflection and scattering of light between the two layers, thereby improving color saturation and increasing the viewing angle of the color electrophoretic display.
In 2022, E Ink Holdings launched E Ink Prism™ variable color e-paper for BMW vehicle exteriors, allowing the car’s surface to transition between two colors. The patent WO2023126477A1, jointly applied with BMW, proposed that the decorative film has two electrode layers and a decorative layer set between the two electrode layers, whose optical reflection or transmission properties can change by applying voltage, allowing the decorative film to switch between two color states. DE102022000003A1 proposed a vehicle with an electrically pressurized window display film that uses an e-paper film that can switch between transparent and opaque, allowing the window to switch between the first and second colors.
In 2023, E Ink Holdings launched E Ink Spectra 6 full-color e-paper and E Ink foldable Gallery™3 full-color e-paper, with technical improvements mainly including reducing delamination, enhancing display effects, increasing bend resistance, and preventing interface delamination. Among them, CN109031841B involves a patterned structure with a flexible stacked structure, where each patterned structure’s width adjacent to the first protective layer is smaller than that away from it, thereby increasing the adhesion between the second protective layer and the first protective layer to reduce delamination. Additionally, as the display device includes the aforementioned flexible stacked structure, it has better structural reliability. TWI723483B (2019, display device) simultaneously drives the electronic ink layers on both sides of the array substrate, stitching together the display area in the expanded state. Therefore, the display device does not need to use two array substrates, saving manufacturing costs. Since the electronic ink layers on both sides do not overlap with the folding area, the electronic ink layers will not be bent in the expanded state, avoiding material creep and arc deformation after long-term bending, thus improving display quality. CN114724455A (2021, flexible display panel) utilized a housing structure to enhance the bearing strength of the flexible display panel, increasing the number of bending cycles. TW202326266A (2021, flexible display device) proposed strengthening edge sealing to avoid wrinkles and buckling, preventing interface delamination.
From the iterative path of E Ink Holdings’ products, it can be seen that the company is developing e-paper displays along the path of black-and-white to color to full-color, continuously improving product performance in terms of brightness, color saturation, bistability, energy consumption, and yield. At the same time, E Ink Holdings has anticipated that flexible screens are the future development direction of e-paper products, initiating research on flexible e-paper early on and continuously overcoming challenges such as edge blurriness, delamination, deformation, and bend resistance, until the launch of mature flexible foldable full-color e-paper products in 2023.
4. Conclusion
Currently, the growth and success of high-tech companies not only require continuous technological breakthroughs and innovative products but also necessitate a comprehensive patent layout to maintain technological and market monopolies, thereby allowing them to stay at the forefront of market competition.
【1】: “Global E-Paper Industry Weekly Report｜Lenovo Think Book X Featuring Color Changing E-Paper Prism at CES 2024″,https://it.sohu.com/a/751514682_121793872, accessed on 2024-1-12
