Flat screens increasingly suffer from quality losses in terms of sharpness, color intensity and contrast at larger viewing angles. The color distortions can vary in intensity in both viewing axes, but they are particularly pronounced in the diagonal viewing direction. All these effects are causally related to the arrangement of the liquid crystals.
These color distortions, which mainly occur in TN technology, are reduced by design measures and a different alignment of the liquid crystals. One technology developed for this is In-Plane Switching (IPS), which achieves viewing angles of 160 ° in all viewing directions without significant deterioration of contrast and sharpness. Furthermore, the displayed color quality is consistent even when viewing the image from extreme viewing angles.
With IPS technology, the electrodes are located next to each other in one plane, parallel to the screen surface. When a voltage is applied to the electrodes, the liquid molecules in the screen plane align themselves parallel to the field lines and the substrate surfaces - hence the name In-Plane - whereas with Twisted Nematic (TN) they rotate helically through 90 degrees. This technique reduces contrast reduction at larger viewing angles.
In-plane switching and its variants
IPS technology is available in many manufacturer-specific variants. Thus Super-IPS, S-IPS, developed by Hitachi in 1998, which is characterized by a shorter refresh rate and has no color distortion; Advanced Super IPS, AS-IPS, introduced by Hitachi in 2002, which has an improved contrast ratio and high transmittance; Advanced High Performance IPS,( AH-IPS), from LG Display for smaller displays for smartphones and tablets; IPS-Provectus (IPS-Pro) from IPS Alpha Technology, which features improved contrast and, more importantly, a wider color gamut; Horizontal IPS (H-IPS), which uses twisted electrodes for improved contrast ratio and an optional white polarizing film for more natural white reproduction; and Enhanced IPS (E-IPS), developed in 2009, which has a wider aperture for more efficient light emission. This allows E-IPS to operate with lower power and simpler backlighting.