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Apr 13, 2018

ITO, that is, tin indium oxide (Indium Tin Oxide). It is the most commonly used thin film material for transparent electrodes for liquid crystal displays (LCDs), plasma displays (PDPs), electroluminescent displays (EL/OLEDs), touch panels (Touch panels), solar cells, and other electronic meters.

Future mobile terminals, wearable devices, and smart home appliances have strong demand for touch panels. Along with the large size and low price of touch panels, traditional ITO films cannot be used for flexible applications. Factors such as the optical rate and other intrinsic problems are not easily overcome, and panel manufacturers have begun to study alternatives to ITO, including nanosilver, metal grids, carbon nanotubes, and graphene.

The new material technology application can extend from the common panel size of smart phones all the way to 20-inch or more devices, and its resistance, extensibility, and bendability are better than ITO film. Although new material technologies cannot fully replace ITO films in a short period of time, new material technologies have great advantages. From the perspective of market reaction, the proportion of film products produced using new material technologies is increasing year by year. At present, graphene is being thrown into the R&D stage and there is still a long way from mass production. The industrialized mass production technology of carbon nanotubes has not been perfected, and the conductivity of the manufactured thin film products cannot reach the level of ordinary ITO films. Therefore, from the comprehensive evaluation of technology development and market application, metal grid and nano silver wire technology will be the two major protagonists of the recent emerging touch technology.

The Metal Mesh technology utilizes readily available and inexpensive raw materials such as silver, copper or other metal materials or oxides to press a formed conductive metal grid pattern on a plastic film such as PET. The theoretical minimum resistance value can reach 0.1 ohms/square inch, and there is a good electromagnetic interference shielding effect. However, due to the process level of printing production, the width of the metal lines of the touch sensor patterns obtained is relatively large, which is usually greater than 5 μm. This may result in very sharp Moiré interference ripples at high pixels (usually greater than 200 ppi). . Murray interference index code product display pixels, optical film and touch conductive metal patterns, in the horizontal and vertical direction, the regular alignment of the pixel and the object of the fine regular pattern overlap slightly offset, there will be interference Ripple pattern. Due to the presence of Murray intervention, thin-film products made from metal mesh technology are not suitable for high-resolution smartphones, tablet computers and other high-resolution products. They are only suitable for viewing screens with distant viewing distances, such as desktop integrated machines. , laptops, smart TVs, etc.

If the line width of the metal grid pattern in the thin film can be greatly reduced, the problem of Murray interference in the metal grid technology can be effectively reduced, especially if the line width of the metal grid pattern is reduced to about 1 um. The resulting film can also be mounted on high-resolution smart devices. At present, South Korea's Samsung Company uses micro-line width and patterning technology to reduce the line width of the metal grid pattern from the original 5um~6um to about 3um. However, it is not easy to reduce the line width drastically. The conventional press printing process cannot meet the requirements. The yellow light process is needed, the production cost will be greatly increased, and raw materials will be wasted; the fine metal wire width will be easily squeezed by the external force. Fracture; the resistance of the grid is increased, and higher sensitivity requirements are imposed on the downstream control IC chip. Therefore, how to reduce the cost of metal grid technology at the same time, to meet the downstream applications of multiple scenarios is a difficult point, but also need to further develop and improve the entire industry chain Caixing.

SNW (silvernano wire) technology applies nano-silver ink materials on plastic or glass substrates, and then uses laser lithography to characterize transparent conductive films with nano-level silver wire conductive network patterns. Due to its special physical mechanism, the diameter of the nano silver wire is very small, about 50 nm, and much smaller than 1 um. Therefore, there is no problem of Murray interference, and it can be applied to various sizes of display screens. In addition, due to the smaller line width, conductive films made of silver wire technology can achieve higher light transmittance than films made of metal mesh technology. For example, 3M's thin-film products made by micro-imprinting can achieve high light transmittance. 89% transmittance. Once again, the nanosilver film has a smaller bending radius than the metal mesh film, and has a smaller resistance change rate when it is bent. When it is applied to a device with a curved display, such as a smart watch, a wristband, etc. Advantages.

On the film, the total area of metal lines in the metal grid that can reflect visible light is not large; whereas, the silver nanowires are not grid-like but have an irregular distribution that covers the entire surface of the glass substrate. In contrast, nanosilver films have more severe diffuse reflections, both haze problems. The problem of haze on the screen will cause the screen to reflect light in the light of outdoor scenes. In severe cases, it will make the user unable to see the screen. However, some technical means can be used to reduce the light diffusion and solve the haze problem. For example, Nissan Chemical Co., Ltd. has developed a high-refractive-index material that can reduce haze by coating on a nanosilver film, effectively reducing the haze value. In addition, blackening the surface of the nanosilver wire, reducing the reflective intensity, and roughening the surface of the nanosilver wire can also effectively improve the haze problem.

Metal mesh technology uses ordinary silver, copper or other metal materials or oxides as raw materials to produce thin film panels using traditional press-pressing methods. The raw materials and production costs are very low, but such products have insurmountable The Swiss interference problem has limited application. If you want to reduce the metal line width in the metal mesh, you need to change the manufacturing process, the cost will increase, and there will be problems such as easy disconnection. Compared with the metal mesh technology, the nanosilver wire technology adopts the shape of the nanosilver ink materials. These nanosilver wire supply materials are in the hands of a few companies such as Cambrios Technologies. The cost of raw materials is higher, but the manufacturing process is simple. The rapid production of large-area touch panels using a printing process has a low overall cost. With large-scale production, the cost will be further reduced.

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