The booming smart phone market is always dominated by external touch panels, but this situation is about to be changed. Apple and Samsung have placed embedded touch panels in their own mobile phones, and shipments reached nearly 40% of the market share last year, which undoubtedly indirectly brought pressure on other panel manufacturers and had to compete to enter the battle of embedded touch panels.
IHS Research Director Xie Zhongli
The Embedded Type touch panel led by the panel manufacturer has been developed for many years, but except for the import and use of Apple and Samsung's smartphones or tablets, it has not really opened up the market. At that time, in addition to the technology and yields were not yet mature, even though the panel manufacturers were good at panel-related processes, the touch performance needed the assistance of touch chip manufacturers.
Even so, except for the high-end models of Apple and Samsung that have the strength to require customization in the panel supply chain, other brands will naturally prefer the touch structure of the plug-in (Add-on Type) after considering the customized cost and procurement supply sources.
Apple owns In-cell touch technology patent (USPTO 8,234,027), and almost a single model can influence market development. Samsung uses On-cell, which has a relatively simple process, but the main advantage is that it has the support of the Samsung Display (SDC) panel factory within the group, and Samsung Display also needs brands to digest the huge AMOLED production capacity of A2 (G5.5).
After 2013, touch chip manufacturers successfully developed single-layer multi-point patterns and used them on On-cell TFT LCDs, giving other brands and panel manufacturers new opportunities; after two consecutive years of development, all embedded touch panels have reached nearly 40% of the shipment of mobile phone applications in 2014. Therefore, embedded touch panels have become a force that cannot be ignored.
Embedded touch panel definition
is generally determined by the position of the induction electrode in the panel structure when defining In-cell and On-cell. As for the LCD panel, it mainly consists of two glasses above and below, which are the substrates of the TFT circuit and the color filter. The liquid crystal layer is in the middle, and the two glasses will be attached to the polarizing plate on the outside. For RGB-coated AMOLED, since there is no filter, the upper glass substrate is quite clean and is for packaging purposes only. That's why Samsung Display chose On-cell to develop AMOLED panels with embedded touch. The induction circuit of
On-cell is located in a simple position, both of which are located on the top surface of the upper glass (filter glass or packaging glass) (the side facing the user) and are located under the polarizer.
From the perspective of structure and principle, On-cell is actually very similar to an external touch panel. The main difference is that filter glass or encapsulated glass is used as a touch sensing circuit substrate, rather than extra glass or film substrate. In-cell induction lines are usually in the Open Cell area (especially the TFT backplane), and to avoid patent conflicts, there are often different lines or location combinations.
For example, the mutual capacitance In-cell panel used by Apple iPhone uses Tx (drive electrode) and Rx (sensing electrode) on the Vcom layer of the FFS panel and the TFT substrate; the AIT of the Legion Display (LGD) also places the electrodes on the Vcom layer, but adopts the principle of self-capacitance.
As for the mutual capacitance Pixel Eyes from Japan Display Company (JDI), when applied to the IPS panel, Tx is positioned on the TFT backplane glass with Vcom, but Rx is like an On-cell, on the top surface of the filter glass, so it is called "hybrid type".
In addition, some variations are also adopted by panel manufacturers or touch chip manufacturers, such as placing Tx and Rx on the filter glass respectively, or Tx on the TFT backplane glass, but Rx is embedded in the black matrix area of the color filter.
Therefore, the possible combinations and positions of In-cell are indeed much more complex than On-cell. For the scope and convenience of definition, we define In-cell as long as one of the electrodes in the induction line is in the Open Cell area, it can be called In-cell. This can include the structural form of Apple and Japan Display Company; the former is called "Full Type" to distinguish it from the latter's hybrid.
In-cell Embedded Touch Panel
Since Apple iPhone brought the trend of touch screen as a new generation of human-computer interfaces in 2007, panel manufacturers have also proposed embedded touch technologies with different technical principles, such as capacitors (Charging Sensing), resistors (Voltage Sensing) and optics (Photo Sensing); but in fact, there are almost no ones that can eventually go to stable mass production.
, especially the first two, may require deformation of the panel glass, which is even more unrealistic when cover glass is generally designed for mobile phones and tablets. Although Apple is not a panel factory, its engineering team has recruited many technical talents from panel factories, so Apple was able to develop its own In-cell technology and set a benchmark for the touch and panel industry.
At present, almost all mass-produced In-cell touch technology is related to Apple's patents, especially the Vcom layer is patterned (Segmented Vcom) and the display and touch functions are driven simultaneously with time-sharing. The
Vcom layer is a unique structure in the liquid crystal panel. The main purpose is to act as a reference electrode and cooperate with the pixel electrode (Vpixel) to form a voltage value that drives the liquid crystal molecules to different deflection angles.
When the deflection angle of the liquid crystal molecules varies, different light transmission amounts can be transmitted through color filters to achieve the required gray scale. Early panel manufacturers used additional touch sensors when designing embedded touch control, but now most of the technology uses the Vcom layer that already exists in the LCD panel to double as the touch electrode.
As for the concept of "time-sharing homework", it is mainly because the same Vcom layer can only do one thing and one function at a time, and cannot drive display and touch at the same time, so it must be carried out crosswise with the time difference. The In-cell panels that have been mass-produced, such as the Japanese display company Pixel Eyes or the Advanced In-cell Touch, although the structure is different from Apple's technology, they are the same in patterned Vcom and time-sharing operations; therefore, it can be seen that Apple has a profound impact on the current In-cell technology development.
After nearly three years of import and maturity, some people have further developed In-cell in integrating panel driver chips and touch control chips, which is the so-called "TDDI" (Touch and Display Driver Integration).
However, whether TDDI will be a general trend still needs to be observed based on individual technologies, and it may not necessarily be an absolute trend. As for Apple's two generations of In-cell panel development, the panel driver chip comes from RSP (Renesas SP Drivers), while the touch chip is an ASIC (BCM5976) commissioned by Broadcom. Although RSP was acquired by Synaptics in June 2014, this does not mean that Synaptics' touch chips can replace Apple's solution, or may allow Synaptics to integrate the two. In Apple's case, even if it doesn't integrate, it doesn't affect its functionality, and the integration requirement is not so immediately and significant.
On-cell embedded touch panel
Compared with In-cell, On-cell touch technology is relatively simple; the so-called simplicity means that induction line design and preventing noise interference, On-cell can save time in panel factory development compared to In-cell.
On the surface, due to the saving of substrate costs, On-cell TFT LCD should have the opportunity to be cheaper than plug-in (for example, GF1, which also uses a single-layer multi-point GF1); however, in fact, due to factors such as process yield, touch lines combined with glass thinning process, On-cell TFT LCD may not be really competitive than plug-in during 2014.
Even so, in addition to reducing the advantages of mobile phone thickness, brands are still willing to focus on long-term potential to cultivate this supply chain; this is why after two years of introduction, On-cell TFT LCD can gradually gain a foothold in mid- and low-level smartphones.
On-cell TFT LCD touch line design benefits from the single-layer multi-point technology developed by chip manufacturers that can reduce costs and began to enter the low- and medium-level smartphone market in 2013.
Currently, the panel manufacturers most interested in developing On-cell TFT LCD touch technology are Taiwan and mainland China, such as Qunchuang, Huaying, Caijing, AUO, Tianma and BOE. The main shipment applications are almost all concentrated in smartphones. However, Samsung Display has different ideas.
Super AMOLED (On-cell AMOLED) displayed by Samsung was originally mainly supplied to Samsung and Nokia, especially the former advanced models. However, in 2014, Samsung's market share in smartphones was greatly challenged, which also affected the shipment of Super AMOLED. Therefore, in addition to hoping that Samsung can also apply Super AMOLED to mid-range models (for example, the new A and E series), it has also increased its marketing efforts to mainland second-tier brands (such as Vivo) since 2015.
In addition to the smart phone market, panel manufacturers are gradually applying On-cell TFT LCD technology to large-size applications, such as tablets or laptops. As for tablets, the Samsung Tab S series (8.4-inch and 10.5-inch) released in 2014 uses On-cell AMOLED. In the second half of 2014, Qunchuang's On-cell TFT LCD, which uses a single-layer multi-point, was also shipped to domestic brands and channel tablet computer markets.
is limited by the sensitivity and performance of the touch circuit. If the single-layer multi-point On-cell touch panel is to develop to a larger 10-inch or more, it seems to be unsatisfactory. However, if the panel manufacturer uses SITO touch circuits, its cost may not be advantageous compared to the general plug-in conductive film (GFF) or single-piece glass solution (OGS). In addition, the profits and shipment growth of tablets are questioned, and relatively speaking, laptop applications are currently receiving more attention from panel manufacturers.
The four major panel manufacturers have listed embedded touch panels for laptop applications in the product development blueprint. Except for Lejin Display, which is still obsessed with In-cell (self-capacitance principle), the other three are currently mainly on On-cell touch technology.
Interestingly, they proposed two On-cell solutions to the brand. The first solution is the general On-cell technology, which AUO calls OTP (On-cell Touch Panel), while the second is the "simple version", which AUO calls OTP-lite. It is not much different from the former in terms of structure and principle, but it can mainly save the cost of Cover Glass, which may be beneficial to the touch panel in the low-level laptop computer market. The "simple version" saving method mainly applies a hardened layer (Hard Coating) to the polarizing plate, so that the protection of the cover glass is not required.
Embedded touch panel development
From the perspective of induction lines, principles and structure, the embedded touch panel is currently roughly mature. The subsequent development should mainly be the improvement of the panel process, the improvement of touch efficiency and cost-effectiveness.
: On-cell is used in smart phones, On-cell AMOLED will continue to be dominated by Samsung Display and have a slightly higher product positioning; while On-cell TFT LCD is actively invested by panel manufacturers in Taiwan and mainland China, and its product positioning is on the medium and low level.
On-cell is relatively simple than In-cell, and has nothing to do with panel resolution, time-sharing operations and Vcom patterning. What the panel factory needs to invest more is process optimization and production costs. At the same time, in order to achieve touch performance and product positioning, in addition to single-layer multi-point lines, SITO lines with higher sensitivity will be the choice of medium and large sizes; however, SITO requires at least four optical masks, and the optical mask and yield cost control will be the key to determining whether On-cell can compete with external plug-ins in the future.
As for In-cell, which is more difficult to develop, Apple's own technology and Japanese display company Pixel Eyes are currently the two mainstream trends; in 2015, the self-capacitor In-cell, led by Lejin Display, will soon join the battle.
All three In-cell technologies use the Vcom layer to make touch-controlled induction electrodes, so they all require time-sharing operations, that is, there is a problem of time resource competition between the driver display and the driver touch-controlled induction electrode, especially when the panel resolution is higher, this problem will be more prominent.
In addition, the internal wiring and noise interference of the panel are also serious problems with touch sensitivity. At present, Apple's In-cell and Japanese display company's Pixel Eyes have been successfully used in advanced models; especially Huawei and Xiaomi, which have been shipping more and more in recent years, have adopted Japanese display Pixel Eyes in 2015. Even the 2015 advanced model (G4) may also use the Pixel Eyes. Although Lejin also has self-capacitor In-cell, the LG brand only uses the mid-to-low-end models in 2015; it is obvious that it may take some time for AIT to become more mature.
With the continuous development and expansion of embedded touch panels, TDDI has also become the focus of attention.
From the perspective of supply chain, touch chip manufacturers should be happy to see it; because after integration, the original customers can be further brought to the panel factory from the brand and touch module factory, and the turnover will be expanded to the range of display driver chips. This is why in 2014, Xinsi International and Duntai wanted to merge RSP and Xuyao respectively.
The same thinking also occurs when existing display driver chip manufacturers, such as Qijing and Lianyong have been deploying touch chips for a while. From the perspective of component simplification, integration can reduce the number of chips, and it can also combine signal lines for display and touch, which is indeed helpful for the limited institutional space in smart phones. Moreover, the brand also hopes that the chip procurement cost can be saved after integration; however, based on the development cost in a short period of time, chip manufacturers may not agree that the integrated chip quotation is lower than the sum of the two chips. From a technical point of view, TDDI may have different situations.
In terms of On-cell, the touch line itself has no direct relationship with the panel display driver. Even if there is signal interference, it is not as serious as the In-cell situation. Therefore, the touch and display driver chips are supplied by different chip manufacturers, which is advantageous in terms of the diversity of supply chain supplies. This kind of procurement consideration is actually similar to the plug-in touch panel, and the procurement incentive for integrated chips is mainly price.
From the perspective of In-cell, the TDDI import situation between Apple and Japanese display companies should be possible, but there is no urgent need to do it. The benefit of TDDI integrated suppliers to these two In-cell technologies is that when the signal interference between the touch and the panel display driver or there are some connection problems, if they are two different chip manufacturers, the responsibility and problem solving methods are not easy to deal with, and the same chip manufacturer will have no choice.
However, in terms of Apple's situation, when the brand's technical capabilities and strength are strong, it should not be too difficult to let different chip manufacturers handle and solve problems together. Conversely, Japanese display companies must also play such a role when developing the Pixel Eyes.
. The most important thing to do TDDI should actually be the self-capacitor In-cell. The mutual capacitance acts on the induction electrodes like pulling apart the X-axis and the Y-axis. The interlaced two axes will generate a touch sensing point.
These induction points are connected to the front end (ADC) of the touch chip through leads; if there are ten lines on the X axis and fifteen lines on the Y axis (250 coordinates are generated), then there are twenty-five lines to be sorted out. However, the same method of changing the coordinate number to self-capacitor In-cell requires 250 patterned Vcom blocks, and each block requires a lead, and all of them have 250 lines to be sorted out. The larger the touch area, the more leads, so it is inevitable that all leads will be converged to a single touch wafer like mutual capacitors. This is not a technical problem, but a problem of wiring in a limited area.
Therefore, the self-capacitance method will make the wiring of the leads similar to the panel (source): when the area is larger, the partition converges through several front-end chips, instead of one front-end chip to converge all the leads; such partition convergence will not cause too many leads to cause too large panel border problems when wiring.
Further, when the source chip displayed on several panels is parallel to the touch front-end chip, TDDI can further reduce the number of wafers on the panel frame, and after the two are integrated, the number of signal lines required for the connection signal can also be reduced, and the T-CON and the touch wafer back-end (MCU) can be connected separately for processing.
Future touch panel market competition
Since 2015, embedded architecture touch panels have become more important in smart phone applications. The contestants that have already come to the table include: Apple's In-cell (manufactured by LGD, SHARP and JDI), Samsung's On-cell AMOLED (Super AMOLED), LeGin Display AIT (Advanced In-cell, Self-sensing In-cell), and On-cell thin-film transistor LCD displays that Taiwan and mainland China are actively investing in.
is still limited to the size of mobile phones, but the panel manufacturer has applied On-cell AMOLED and On-cell TFT LCD to tablet and laptop computer sizes between 2014 and 2015. Although the plug-in touch panel still has a sufficient supply chain, the pressure from the panel manufacturers to integrate the touch sensor terminal (Touch Sensor) will only increase day by day.
Therefore, in addition to developing emerging applications, how to strengthen its key modular assembly capabilities, and even cooperate with panel manufacturers to reshape the supply chain process will be the key to competitiveness and survival.
For more information, please follow Jiwei.com WeChat public account: jiweinet or Lao Yao’s personal WeChat public account: laoyaoshow
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-