Compared with the traditional resistive touch technology with the highest market share, capacitive touch technology offers users a number of advantages, including: 97% penetration and more realistic color rendering. The visual function is realized; the touch function can be realized by tapping or even not actually touching the screen, which brings more convenient and flexible manipulation to the user; for a longer service life, the touch life of the capacitive screen is about 200 million times. Four-wire resistive screen (one million times) two hundred times, five-wire resistive screen (40 million times) five times.
The signals detected by capacitive touch technology come from small changes caused by touch. According to different working principles, it can be roughly divided into surface capacitive touch technology (SCT, SurfaceCapaciTIveTouch) and projected capacitive touch technology (PCT, ProjectedCapaciTIveTouch). The former is common in large-scale outdoor applications, such as public information platforms (POI) and public service (sales) platforms (POS), while the latter is spurred by Apple's multi-touch mobile phone iPhone.
From the perspective of the development of touch technology, the earliest market for introducing touch technology is the field of industrial control. The purpose is to integrate the complicated and large-scale mechanical device control panel into a single window and multi-page screen. Large size resistive screen. However, the shortevity and tolerability of the resistive screen are not enough to meet the needs of the industrial control field. Therefore, the large-size SCT has been introduced, and the high-end equipment machine immediately switched to the SCT program. Until around 2003, due to the reduced manufacturing cost of the resistive screen, small sizes were used in portable products such as PDAs and GPS, and touch technology officially entered the consumer market. In 2006, the iPhone adopted a small-sized PCT, and its excellent optical characteristics and multi-touch function set off a wave of trends, becoming the most eye-catching touch technology in recent years.
From the above, it is not difficult to find that the consumer market with small size as the mainstream has only resistive and projected capacitive types in the choice of touch technology. Although the former is low in cost, poor optical performance and tolerance have long been affected. The market is criticized; although the latter has many advantages, there are only a handful of suppliers of real energy products, and the price is naturally quite expensive, so that it is only found on a few high-priced products.
At present, the small size market rarely uses SCT, which is mainly a cost issue. SCT panel manufacturers have long lacked key optical coating technology and must be outsourced, while SCT touch ICs are controlled by a small number of technology manufacturers, and the price is high. In addition, unlike the resistive screen, it can be used with a resistive IC. The SCT screen and IC must have excellent compatibility to work stably. All of the above factors make SCT's selling price in small-sized consumer applications not far from the PCT, and it is naturally difficult to be adopted by the customer base.
However, compared to resistive technology, SCT can greatly improve its defects; compared with PCT, SCT technology is more mature and stable, and can be mass-produced. Therefore, we can reasonably conclude that when the overall cost of SCT is greatly reduced due to the integration of strategic alliances and technical resources of industry members, SCT will have the opportunity to become the best solution for small-sized consumer applications.
The basic principles of PCT and SCT will be briefly introduced below, and a comparison will be made between the advantages and disadvantages of the two technologies.
Projected capacitive touch technology
PCT is built on the concept of a matrix. In the touch screen production part, the ITO of the PCT panel is etched to produce a specific pattern, in order to increase the SNR value of each touch point and enhance the accuracy of the recognition. By copying the aforementioned pattern several times in the X-axis and Y-axis directions (depending on the screen size), a keyboard-like PCT matrix is ​​formed. Figure 1 is the most common diamond pattern at present.
Figure 1: Diamond pattern layout of a projected capacitive screen.
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