A membrane touch switch is a momentary electrical on/off switch for activating and de-activating a circuit. The appearance of these graphic overlays is integral to the operator's view of the equipment. Embossing can be used with either tactile or non-tactile switches but pillow embossing alone does not give a tactile response. A membrane switch is a touch sensitive device created by the printing, cutting and laminating of precision thin film plastic materials. A variety of overlay materials are used in membrane switch applications. Polycarbonate is a commonly used material because it is easy to print on, die cut and emboss – making it a very cost effective alternative. The disadvantage of polycarbonate is that it begins to show signs of wear sooner than some of the alternate materials. In most applications polycarbonate overlays will last a minimum of 100,000 cycles during life cycle testing. Uncoated polycarbonate is also susceptible to damage from a variety of chemicals. If a polycarbonate overlay is going to be in an environment that will subject it to chemicals, a hardcoat should be used to protect the overlay. Polyester is a more robust material that has superior life cycle and chemical resistance properties. In life cycle testing, polyester shows no signs of wear at 1,000,000 cycles. However, polyester, due to its memory properties, frequently requires hydroforming rather than embossing. Hydroforming is more expensive for both tooling and unit cost. Polyester is also more difficult to die cut resulting in more frequent reblading of steel rule dies. Both polyester and polycarbonate are available with a variety of textures and hardcoats. In their uncoated glossy form both materials are very susceptible to scratching. For this reason we recommend that gloss materials receive a hardcoat.
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