Two products can both be sold as “switchable film” and behave in opposite ways: one turns opaque when you cut the power (normal mode), the other turns clear (reverse mode). The catalogue photos look alike — but what your glass does in a power failure, and how many hours a day it draws current, are reversed.
Published 21 August 2026 · Miraigen Inc.
The short answer
| Unpowered (switched off, or a power cut) | Powered | |
|---|---|---|
| Normal mode almost everything sold as “PDLC” | Opaque | Clear |
| Reverse mode usually sold under the name “PNLC” | Clear | Opaque |
The common one is normal mode. If a product is described only as “switchable film” or “PDLC”, it is almost certainly this, and designing on that assumption rarely causes trouble. But both types are on the market, so this is not something to settle without checking.
PDLC (polymer-dispersed liquid crystal) is droplets of liquid crystal dispersed through a resin. With no voltage applied, the droplets point in random directions, light scatters, and the film looks milky white. Apply a voltage and the droplets line up, light passes straight through, and the film goes clear. In other words, it is drawing current the entire time it is clear.
Reverse mode does the opposite: clear unpowered, opaque powered. What makes it opposite is not a different class of material but the alignment, designed so that the liquid crystal is already ordered when no voltage is applied.
⚠ “PNLC” is not really the name of a mode. PNLC (polymer-network liquid crystal) describes a structure with less resin, and there are normal-mode PNLC materials. In practice, though, in the switchable film trade reverse-mode products are commonly sold as “PNLC” or “reverse PDLC”. Do not infer the behaviour from the letters PDLC / PNLC in the product name — check what the datasheet says the unpowered state is.
1. Which state you want during a power failure
This is the big one. When the power stops, the film falls back to whichever state you bought. Somewhere privacy comes first — a meeting room, a consulting room — normal mode makes sense, because a power cut leaves the glass opaque. Somewhere you want to be able to see through precisely when the lights are out — an escape route, the entrance area of a shop — reverse mode is the safer default. Changing your mind later means replacing the film itself, so decide this at the start.
2. Which state it sits in longer — that is the time it draws current
Normal mode draws current while it is clear; reverse mode draws current while it is opaque. Pick the type so that whichever state the glass sits in for most of the day is the unpowered one, and the film spends less time drawing current. Glass that is normally clear and only hides things now and then favours reverse mode; a partition you mostly want opaque favours normal mode.
3. Availability
As far as our own sourcing and enquiries go, normal-mode (PDLC) film is the one in volume. Sizes, thicknesses, tints, and the number of converters willing to process it all tend to be wider on that side.
Our controller is designed so the output can be matched to a given film. It works with ordinary AC-driven PDLC / PNLC switchable film (products that need unusual drive conditions may not be a fit). Dividing one sheet of glass into several zones and setting each zone independently — our multi-zone switchable glass system — works with either type.
What limits the area you can drive is not the type of film but its power draw in W/m². Figures are tabulated under the evaluation kit outline specification. Note that a W/m² figure only means something alongside the frequency it was measured at — see why the power draw of switchable film depends on drive frequency.
We offer an evaluation kit so you can check multi-zone control on the switchable film you already work with.
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