Metal Mesh Competitive as Transparent Conductor for Large Panels
Published: April 02, 2014 Category: Advanced Materials

Metal meshes – previously not under serious consideration as transparent conductors (TCs) because of their lack of transparency – have now overcome their performance limitations and are seen as serious competition for ITO in several applications, especially those that require large panels for displays, lighting, or solar energy. Bringing metal meshes into larger displays can be a way for metal mesh manufacturers to increase their revenue streams, which now are constrained because the markets that they are chasing, such as touch screen sensors, are not very large.

Metal Mesh TCs in Large Displays

The reasons to use metal mesh in large OLED displays are the same as for smaller displays – lower sheet resistance and potentially lower cost compared to ITO – and these factors become more of a concern the larger the display.

One big advantage for metal meshes in large OLED displays is the ability to spread out voltage uniformly over a large area. Metal meshes also eliminate the tradeoff between electrical conductivity and transmittance that is a problem when using ITO in these applications. Metal meshes can therefore provide a performance advantage, creating panels with more uniform and greater brightness.

TVs are probably the most obvious application requiring large screens, but there are others that may be compelling for metal mesh manufacturers. Niche applications that may increasingly use large touch screen panels include digital signage, advertising, gaming tables, and vending machines. Many of these, such as kiosks and slot machines, require curved screens. This is a place where the option of roll-to-roll processing could give metal mesh an advantage over other materials.

Advertising displays that incorporate touch have historically used IR technology, which does not require any TC. Recently, however, some large-format, interactive display screens have begun to use projective capacitive (pro-cap) technology. The electrodes are grids of fine metal wires behind a glass substrate – metal meshes. Unlike most metal meshes, these are not produced on plastic substrates such as PET, but flexible displays of this sort could certainly use PET films. This opens up opportunities for several alternative TCs fabricated on PET, including metal meshes.

Advertising displays are currently a very low volume market for TCs in terms of numbers of units, but each display uses a lot of area – up to several square meters. So even though this is not an area that the mainstream metal mesh companies are chasing in the short term, it could eventually be a reasonable source of revenue.

The transparency requirements for applications such as advertising are not as demanding as in handheld touch screen products. This could help metal mesh materials gain market share. Although it is true that interest in metal meshes is growing because the technology has improved to the point where companies can produce very fine pitches with invisible mesh, there is still a perception among some in the display industry that other TCs outperform meshes in transparency.

Companies Producing Industrial Displays

In the OLED TV space, the companies to watch are Samsung and LG. For industrial displays the players are not household names, but they have some products that may be able to expand the possibilities for metal meshes as TCs. These include:

Visual Planet: This company produces a pro-cap touch screen film called a touchfoil that appears to be based on metal mesh and is intended for large industrial displays. The company says it can manufacture the foils in sizes ranging from 30 to 167 inches diagonal. Visual Planet added multi-touch capability in 2011.

The touchfoil is usually applied to a glass substrate and can work with glass up to 25 mm thick, though it could work through any other nonmetallic surface as well. This opens up the opportunity for metal meshes on PET for curved displays, although the advantage of glass is protection from environmental damage and vandalism, as these displays are designed for outdoor and public usage.

Visual Planet envisions expanding possible applications of its technology to use in interactive museum displays, movie theaters, and more. The touchfoil product is interesting, but we do not see evidence that the market is yet ready for it. As touch continues to become more prevalent everywhere and consumers start to expect that every screen will be interactive, however, there could be a chance for companies like Visual Planet to engage a new generation of customers and grow as well.

Zytronic: Zytronic also manufactures pro-cap touch screens for industrial markets. The company has been producing pro-cap screens for ATMs for over a decade. It has also produced touch panels for interactive signs and maps, advertising kiosks, outdoor bulletin boards, vending machines, human/machine interfaces in factories, gas pumps, and more. The company is emphasizing its ability to create very large displays, up to 1 meter wide and 2 meters long – advertising applications can require screens this large.

All of Zytronic’s sensors are embedded behind glass. Its technology is based on printed metal meshes, 10 μm wide. Zytronic recently added mulit-touch capability so that up to ten users can access the screen at once. The sensors can operate behind fairly thick glass, up to 20 mm. The company says it can support curved screens, where the substrate might be an ultra thin glass or a thicker glass formed into a curved shape.

Challenges for Metal Mesh

Adding potential applications is a route toward increased revenue for metal mesh suppliers, but there are still hurdles to be overcome in perception, performance, and cost. Customers are reluctant to switch from the incumbent ITO and may feel that alternative TCs such as metal meshes are risky. Demonstration of successful products should help suppliers make headway.

Performance of metal meshes has improved a lot in the past year or so, but the challenge is to demonstrate performance in high volume production of large panels. The difficulties certain manufacturers have faced in scaling their processes have made customers a little wary. The fine metal meshes required for display applications are more difficult to produce than coarser meshes, which contributes to yield concerns and higher prices.

This is where industrial display applications have an advantage over consumer display applications– the optical requirements are not as stringent, allowing coarser grids to be perfectly acceptable. We do warn, however, that the market for TCs in large industrial displays is very small at present, so metal mesh suppliers are much more likely to see revenue from other applications in the next couple of years. Applications like advertising are, however, a reasonable longer-term goal.

Metal meshes will need to be cost-competitive in order to succeed. Profit margins in small displays are small or nonexistent, so metal mesh manufacturers that can break into markets for larger displays may have a better chance for survival in the long run. Even relatively small displays, such as those for all-in-one computers, are more lucrative than the smart phone market. But for all applications, cost will need to come down. Manufacturers say they are cost-competitive with ITO, but they will need to be priced lower than ITO to really be competitive. 

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