Panel makers are extending in-cell touch sensors to larger-sized applications to increase revenue.
- In-cell touch by Vcom blocks has been a dominant touch technology for thin-film-transistor liquid-crystal display (TFT-LCD) displays in mobile phone application. However, the growth has slowed down after its high penetration rate. Panel makers will extend the technology to larger-sized tablet and notebook PC applications.
- Panel makers will prioritize the in-cell touch development for tablet PC application because of its bigger market size. The in-cell touch technology for notebook PC application will grow remarkably from 2021 onwards.
Although in-cell touch by Vcom blocks already accounts for more than 93% shipment shares of the total in-cell TFT-LCD shipments in mobile phone application, it seems that its remarkable growth in recent years will end soon (78% YoY in 2018 and 56% YoY in 2019). The reason is that AMOLED display demands, including on-cell and GF2 touch sensors, are surging and they are replacing in-cell TFT-LCD, especially in the midrange and high-end segments. Furthermore, two in-cell touch technologies—Apple’s Vcom pattern type and Japan Display’s (JDI) hybrid type—are declining because major smartphone brands are shifting to on-cell AMOLED.
The in-cell touch technology is currently not feasible on AMOLED because of technical difficulties of the TFT circuitry and touch sensor electrode. AUO and Raydium tried to implement self-sensing in-cell touch sensor on the rigid AMOLED for smartwatch application; however, they were not successful in applying the in-cell touch sensor on smartphone displays and flexible AMOLED. Despite that, in-cell touch by Vcom blocks is still a cost-effective and mature technology for TFT-LCD displays. In-cell touch by Vcom blocks is the only self-sensing touch technology that can be applied on display sizes larger than smartphone display sizes. Panel makers are also approaching tablet and notebook PC applications.
In-cell technology for tablet PC application
Panel makers, such as Innolux and BOE, started their embedded touch technology by applying the on-cell touch sensor on TFT-LCD displays for tablet PC application. The shipments of on-cell TFT-LCD reached 12.3 million in 2017, 11.6 million in 2018, and 10.5 million in 2019. On the other hand, the rising of in-cell TFT-LCD (Vcom blocks type) reached 6.7 million units in 2019. In-cell TFT-LCD shipments were only 255,000 in 2017 and 1.1 million in 2018. The year 2019 was the milestone for in-cell TFT-LCD’s growth in tablet PC application. Compared with on-cell TFT-LCD, in-cell TFT-LCD is more difficult, with technical thresholds on the TFT circuitry, and customized, with non-recurring engineering (NRE) and development costs at the beginning. Thus, panel makers opted for the on-cell touch technology first.
Recently, tablet PC brands, such as Huawei and Lenovo, welcomed in-cell TFT-LCD’s advantages, such as narrower borders and fewer flexible printed circuit board (FPCB) cables, and increased adoptions. This encourages panel makers to increase their effort in the in-cell touch development. Touch controller integrated circuit (IC) makers, such as FocalTech, Novatek, SiliconWorks, Parade, ELAN, and Himax, also proposed their touch and display driver integration (TTDI) solutions to panel makers. Based on the design-in projects to panel makers, Omdia estimates that in-cell TFT-LCD shipments in tablet PC application can easily reach more than 12–14 million units in 2020. Although the in-cell touch technology is growing, panel makers will not immediately abandon the on-cell touch sensor because of its maturity, in which it has a good touch sensitivity, and affordability, as photomasks depreciate. The transition from on-cell touch sensor to in-cell touch sensor will likely take three years, based on the timeline for smartphone displays.
However, in-cell and on-cell touch technologies have different adoption approaches. The in-cell touch sensor has a faster growth in the 10.x-ich tablet PC segment while the growth for on-cell touch sensor is stagnant in the smaller 7- or 8-inch tablet PC segment. For example, in-cell TFT-LCD shipments for 10.1-inch panels were 4.2 million, but on-cell TFT-LCD recorded 378,000 units only in 2019. Most on-cell TFT-LCD shipments concentrated on the 8-inch tablet PC (7.3 million units) and 7-inch tablet PC (2.8 million units) segments in 2019. The shipment results indicate the positioning strategies of these two embedded touch technologies have been different. On-cell TFT-LCD will mostly focus on the lower-level consumer segment, which consists of less than 10-inch tablet PCs; demand for on-cell TFT-LCD will also decline when the in-cell touch technology replaces on-cell TFT-LCD.
On the other hand, in-cell TFT-LCD will focus on the productive segment, which consists of larger than 10-inch tablet PCs; it will eventually grow to replace glass-film-film (GFF) sensor, One Glass Solution (OGS), or even metal mesh, which is mostly for the high-end segment, while its performance and active pen support receive further optimization. In addition, tablet PCs of more than 10 inches for productive computing will cannibalize some notebook PC demand, especially ultrabooks. It means these tablet PCs, with the productivity feature, offer a new form factor option other than clamshell design to end users who are purchasing the products for productive uses.
Compared with tablet PC application, the adoption of the in-cell touch technology is slower for notebook PC application. LG Display is the major supplier since 2015. Sharp started to ship 13.3-inch (FHD) in-cell TFT-LCD displays since April 2020 but only recorded 12,000 units in the second quarter of 2020. Its 14-inch FHD in-cell TFT-LCD option is also scheduled for the fourth quarter of 2020 (4Q20). It could be reasonable for other panel makers, especially AUO, BOE, and Innolux, to prioritize the in-cell touch sensor for tablet PC application; tablet PC shipments are more than 120 million units every year, but touch-enabled notebook PC shipments are only 30 million units. AUO will not start its in-cell touch products until 2021, and BOE might start in 4Q20. These two panel makers—accounting for 72.5% shipment shares out of total embedded touch display shipments for notebook PC application in 2019—are still focused on on-cell TFT-LCD. When AUO and BOE shift their focus to the in-cell touch technology, their development schedules for in-cell TFT-LCD will influence the in-cell TFT-LCD penetration rate.
Compared with on-cell TFT-LCD, which is less related to the display design consisting of silicon chips and TFT circuitry, panel makers are more concerned about in-cell TFT-LCD. The technical approaches and developments are not just replacing the on-cell touch sensor, which is moving from the color filter to the Vcom layer of TFT backplane; it also integrates silicon chips. T-CON can be embedded into display driver integrated circuit (DDI), and DDI will be integrated with the touch controller as TDDI. The chips used could be more than one to support resolutions higher than FHD, as well as increasing the silicon cost. In addition, FPCB and IC bonding—chip-on-glass (COG) or chip-on-film (COF)—are also considered to make the bottom border narrower.
It seems inevitable for panel makers to use the in-cell touch technology for notebook PC application owing to the TDDI trend and advantages, such as four-side narrow borders and the simplification of silicon chips. However, the transition from on-cell to in-cell touch technology will take some years as mentioned in tablet PC and mobile phone applications. Omdia estimates in-cell TFT-LCD shipments will increase notably from 2021 onwards because there will be more supplier sources. However, in-cell TFT-LCD, with weaker active pen performance, will not secure shares from the metal mesh sensor market anytime soon. Instead, it will have an impact on OGS and on-cell TFT-LCD, wherein both are positioned for the entry or midrange segment.