Every membrane switch starts with the graphic overlay — the visible face users touch. Choosing the right overlay substrate is the single most important material decision in the project, because it drives chemical resistance, durability, printing quality and cost. This guide explains how we select between polyester and polycarbonate on the factory floor.
The two materials in one sentence each
- Polyester (PET) is tough, chemically resistant and dimensionally stable, and it is the workhorse material for most custom graphic overlays.
- Polycarbonate (PC) is softer and more formable, with excellent clarity and impact resistance, which suits 3D-formed overlays and designs that need deep embossing.
Head-to-head comparison
| Property | Polyester (PET) | Polycarbonate (PC) |
|---|---|---|
| Chemical resistance | Excellent | Good, weaker against some solvents |
| Abrasion resistance | Excellent, especially with hard coat | Good |
| Dimensional stability | Very stable | Good |
| 3D forming | Limited | Excellent |
| Embossing depth | Shallow to medium | Deep, crisp |
| Clarity | Good | Excellent |
| UV stability | Good with UV-resistant inks | Fair, can yellow over time |
| Typical thickness | 0.125 – 0.25 mm | 0.25 – 0.75 mm |
| Relative cost | Lower | Higher |
When we recommend polyester
Most medical, industrial and laboratory interfaces use polyester because it shrugs off the aggressive cleaners those environments demand — isopropyl alcohol, bleach wipes and hospital disinfectants. Polyester also holds tight dimensional tolerances, which matters when the overlay must register precisely to cutouts, dome arrays or backlight windows over thousands of pieces.
When we recommend polycarbonate
Polycarbonate earns its place when the overlay needs deep tactile embossing, a formed 3D shape, or a rich visual depth. Think consumer appliances, automotive interior controls and premium HMI panels where the overlay wraps around a raised surface. We also use polycarbonate for large overlays that need extra stiffness to prevent flexing during installation.
The hybrid option: two-layer overlays
For demanding applications we often combine materials — for example a polycarbonate top layer with a polyester circuit-facing layer, or a polyester overlay with a polycarbonate window insert. This keeps chemical resistance where it matters while adding formability where it is needed. Hybrid constructions are standard work for us, not a special project.
Print, texture and hard coat
Whichever substrate you choose, the finish is decided by three add-ons: UV or screen printing for colors and icons, texturing (matte, gloss, anti-glare or soft-touch) and a hard coat for abrasion resistance. A matte texture with hard coat is the default for panels that get touched constantly; it hides fingerprints and resists scratching.
Unsure which material fits your environment? Send us your application details and cleaning protocols, and our engineers will specify the overlay stack — including material, texture and adhesive — within one business day, free of charge. You can also review the full graphic overlay product page for available options.