The hottest screen conductive material may update

2022-09-19
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Screen conductive materials may update ITO glass, which may become a history

the projected capacitive touch screen market is quietly changing. Rapid industrial development continues to provide touch screens that are thinner, more efficient, more reliable and less expensive. The main driving force behind these developments is indium tin oxide (ITO), which is a conductive material mainly used for touch screens of tablet computers, has many limitations, so it will be replaced by alternative materials

ito limited small-size screen conductive material lift update

ito has never been widely used in large-size AV and kiosk applications, but some technologies under development will replace ITO, and these new technologies will be used in the above applications

a key driving factor behind the transformation of projection capacitance touch technology is the shift to integrating touch functions into the LCD panel itself using embedded technology, so that there is no need for a separate touch screen panel, also known as discrete touch panel. After doing this, we can produce thinner and lighter touch devices that are easier to integrate

optical efficiency and brightness can also be improved by reducing the distance and layers between LCD and users

however, the process of manufacturing embedded touch screens is still developing towards the goal of more perfection, so their wide adoption in the industry is limited. As a result, the discrete projection touch screen panel of ITO conductor is still the main technology used, at least in smart, tablet computers and wearable devices, but it will have many defects as the display size increases by more than 20 inches, mainly because its relatively high resistance will hinder efficiency and make it unsuitable for some applications

as for what conductive materials can be used for large-scale touch screens, there are currently three major material technologies in the leading position: Copper microwires, silvermetalmesh and silvernanowire, and the other three: carbon nanotubes, conductive polymers and graphene, They are all in the early stages of development and may be available in the next few years. This paper will discuss the four main parameters of the first five material technologies: economy, impedance, visibility and availability; Graphene will also be discussed. Graphene is in the early stage of development and has not yet been sold on the market

considering economic factors is very different from material cost

when considering the cost of touch screen, the key issues include initial processing cost and durable material life requirements, etc. The technology that can be directly written into the substrate without mold opening (mask) basically does not need processing, and can be produced in small batches more cheaply. If mold opening or other processing is required, the flexibility of small batch production of different sizes will be limited, but there is potential to provide large batch production of standard sizes

in processing, copper micro wires have the advantage of ductility. Electrodes can be written directly into the substrate without laser, mold opening/chemicals/etching or processing. Silver nanowires can be customized to a certain extent by laser stripping, but additional processes are needed to connect the boundary conductors to the controller. Conductive polymers are relatively simple to apply through plate printing, but patterns must be made after silk printing or etching and laser processing

in contrast, the silver metal lattice technology is to make patterns on the material source, so the size of the sensor must be specified in advance. This will cost $10000 to $20000 per sensor design, depending on the screen size. The deposition procedure of carbon nanobud is very complex, so nanobud reactor is needed, and then laser mapping process is used to make electrode

another key factor of manufacturing cost is the number of layers required. The copper micro change-over valve has three positions, namely, the neutral position, the clamping position and the loosening position line can be insulated, so the X and Y electrodes can be formed in a single layer. Package insulation can also prevent material oxidation, but it will greatly reduce the efficiency of the touch screen when exposed to high temperature and humidity. Nano silver wire, metal lattice and conductive polymer sensor structures generally need two or more layers to insulate (x and y) conductors, so as to increase the material content of single-layer design. Carbon nanobud is also a two-layer technology. In addition, care must be taken to prevent moisture from entering the material, otherwise it may lead to the above oxidation and touch screen failure

15 Ω to 30 Ω low impedance copper micro wire realizes large-scale touch screen

touch screen impedance is a key factor determining touch sensitivity or signal-to-noise ratio (SNR). Higher resistance materials will limit the amount of current flowing through the conductor, making it more difficult to correctly find out the false touch events caused by the environmental interference (EMI) from the display screen, power supply or other peripheral electronic products. Obviously, this impedance has a greater impact on larger touch screens, especially when functions such as multi-point touch, anti false touch and close sensing (recognizing touch before fingers actually contact the screen) are required

as mentioned above, ITO is limited to small touch screens because of its relatively high impedance, about 100 Ω per square meter; Therefore, most touch screens using this material are less than about 22 inches, beyond which there will be significant performance limitations

compared with about Ω per square meter on PET film substrate, nano silver wire has better resistance than ITO. The projection capacitance touch sensor using this technology can be expanded to about 42 inches, but beyond this size, it will still limit the touch efficiency

silver metal lattice has a low resistance of about 15 Ω to 30 Ω per square meter, so it can be used for touch screens with a size of about 65 inches. Copper micro wires provide a minimum resistance of about 5 Ω per square meter or less, and can be used to build a huge touch screen with a size far exceeding 100 inches

in addition, the extremely low resistance also provides the best signal-to-noise ratio, so that the touch screen can detect the touch control of very thick panel glass, even when wearing gloves, without driving electronic devices under high voltage or using multiple connected controllers to display the screen side by side. If these two clever methods are used, the large-size touch screen can be realized

introducing appropriate materials into the screen panel to produce excellent visibility

all discrete panel projection capacitance technologies, including the introduction of certain material elements between the user and the screen, to produce optical differences in the image, no matter how small, but there must be, especially when the display is turned off, the 10um conductor lattice established by using copper micro wire technology is visible

that is, the light transmission is excellent, and it is within 90% before any anti reflection treatment. In contrast, nano silver wire and silver metal lattice technology can establish a slightly lower visibility conductor rail, which is a metal lattice in the UM range; However, nanowires and conductive polymer coatings can produce slight color deviation or haze on the whole screen, and about 85% light transmittance

new technology has become the mainstream, and outdoor exposure is a big challenge

overload protection: when the load reaches 110% of the pneumatic sensor,

a few professional manufacturers have produced copper micro wire touch sensors for nearly 20 years. This sensor is a mature projection capacitance touch technology, which is suitable for large-size screens in harsh environments. In the past few years, silver metal lattice and silver wire touch technology has quickly become the mainstream, and many manufacturers are responsible for installing the necessary printing and laser making pattern equipment. In the touch screen industry, these two have produced a large number of excellent lithium hydroxide products, and the technology is relatively new, which means that their long-term reliability has not been confirmed, especially about how their resistance and touch efficiency will change under the temperature and humidity exposed to outdoor challenging applications

the Department of graphite raw materials industry with conductor potential will seriously implement the 109 spirit of the party, and ene is suitable for capacitive screen materials

what is coming is a new touch screen material technology that may change the rules of the game: in the form of graphene. Graphene was first discovered at the University of Manchester in 2004. Since then, gratifying achievements have been released on its strength, transparency and conductivity, but the development is still in its infancy

graphene is deposited as an atom thick carbon molecule, which binds a similar low resistance to copper microwires, with the potential of "invisible" conductors. However, despite its potential as a projection capacitor touch screen material, this exciting new technology is also suitable for many other applications, such as water purification, batteries and solar cells; Most developers still focus on these aspects. On the development roadmap, the utilization rate of touch screen is much lower

in a word, there is no "perfect" conductive material in the projection capacitive touch screen. Designers should constantly look for the best combination of efficiency, optics, durability, scalability and reliability to suit their touch screen applications

and the global market for tablet touch screens dwarf the commercial AV market. According to touchdisplayresearch estimates, the ITO alternative market may reach $13billion by 2023. The development of new touch screen materials will inevitably focus on this huge market, and the investment in this area is bound to bring many benefits to the commercial and industrial markets

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