Manufacturing Touch Screens


Membrane Switch News Editor: Alan Burk

ITO-coated polyester is extremely sensitive and requires care in etching and handling. A single scratch to the coating will cause screen failure, even if the scratch occurs outside of the viewing area. Keeping the insulators that separate the layers invisible is also challenging. They need to be small yet still maintain the actuation characteristics of the touch screen.

Though methods of producing resistive touch screens are very similar to those used for standard membrane switches, each step in the conventional production process must be modified to successfully produce touch screens. Design, ITO etching, ink selection, screen printing, laminating, and testing are just a few of the procedures that will change. Also, the cost of ITO-coated polyester is more then ten times higher than the cost of uncoated polyester used in non-transparent membrane switches. So be confident of your processes before sending a large order to the production floor.

Membrane-switch manufacturers have an advantage over companies that produce touch screens with one of the other technologies described previously. They can easily combine touch screens with other membrane technologies to create custom keyboard assemblies. For example, manufacturers can add custom graphic layers, as well as transparent colors to create filtered touch-screen displays. Adding other tactile or non-tactile switches near the touch screen is also possible, and graphic layers can be common to both transparent and non-transparent sections.

Jumping into this technology is not easy, but if you allow ample time to develop touch-screen production skills, they can be a very good complement to your membrane switch options. Once you’ve learned to etch and handle ITO properly, your half way there. And once you have these processes in place, you can also adapt them to other applications, such as producing electroluminescent lamps.

Another option for manufacturers is to source the transparent membrane from other sources for resale or as a value added component of a membrane switch assembly.

For Etching ITO see this product from Triangle Ink.

Membrane Switch & Touch Screen Design & Consulting
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