What Is an IPS Display? IPS LCD Modules Explained for Engineers

IPS - in-plane switching - is a way of arranging the liquid crystal in a TFT LCD so the picture barely changes when you look at it from the side. It is why modern panels hold their colour and contrast across a wide viewing cone, and it is the default we recommend for any display the operator does not face straight on. It is not a different kind of display from TFT: an IPS panel is a TFT panel with IPS liquid crystal on top.

Written by the Junxian applications engineering team. Figures quoted for “our models” are calculated from the 103 models on this site that carry a full parameter set, so they change when the catalogue changes.

What IPS actually means

Each sub-pixel of an LCD is a small cell of liquid crystal between two polarisers. The voltage across the cell turns the crystal and changes how much backlight gets through. In a TN (twisted nematic) cell the crystal is twisted between the two glass plates and tilts up out of the plane of the glass when it is switched. In an IPS cell the electrodes sit side by side on one substrate and turn the crystal within the plane of the glass. Because the molecules stay parallel to the glass, the light path changes much less as your eye moves off-axis - so colour and contrast stay stable across a wide cone.

IPS vs TFT: why that comparison misleads

TFT - thin-film transistor - describes the backplane: one transistor per sub-pixel that holds its charge between refreshes. That is what makes an active-matrix colour LCD possible, and almost every colour LCD module is a TFT. IPS describes the liquid crystal mode on top of that backplane. So 'TFT vs IPS' compares a layer with the layer above it; the real choice is IPS against TN or VA. When a module listing says only 'TFT', it is often a TN panel - check the glass-mode line of the specification. On our product pages the display type is its own row for exactly this reason.

What IPS changes, in terms you can specify

Viewing angle. IPS panels are typically specified at or near 80 degrees in all four directions (at a contrast ratio of 10:1). TN panels are commonly specified narrower and unevenly, with one weak direction - usually from below. Colour and grey levels off-axis. IPS keeps them stable; TN shows grey levels inverting when viewed from its weak side, which is what makes a TN screen look 'negative' from the wrong angle. Contrast. IPS typically sits in the high hundreds to around 1,000:1 in a dark room; VA goes higher, TN lower. Normally black. An undriven IPS cell blocks light, so the screen is black at power-up with the backlight on; TN is usually normally white.

What IPS costs

IPS glass costs more than TN glass of the same size and resolution, and an IPS cell passes a little less of the backlight, so reaching a given brightness can take slightly more backlight power. Response is slower than TN but comfortably fast enough for an HMI, a gauge or a menu. None of this is a reason to avoid IPS where the viewing angle varies; it is a reason not to pay for it on a fixed console that the user always faces head-on.

When to specify IPS - and when TN is the honest choice

Specify IPS when the operator reads the display from different positions: a machine panel read while standing beside it, a handheld tilted in the hand, a wall unit seen from across a room, or a round or square display where there is no single 'correct' viewing direction. TN remains a sound engineering choice for a fixed console viewed head-on, for cost-driven products and where the fastest response matters. Our TN vs IPS vs VA guide goes through the trade-offs mode by mode.

IPS and TN across our own catalogue

Generic comparisons only go so far - here is the glass-mode mix of the models published on this site, by size.

Read from the display type field of each published model. Some models are listed as a combination (IPS/TN, STN/FSTN) because the same glass is offered both ways - those are counted under each mode they support.