IPS (In-Plane Switching technology) panel is a technology used for liquid crystal displays (LCDs). It was invented to solve the main limitations of TN-matrices at the time: relatively slow response times, small viewing angles and low-quality color reproduction. In-Plane Switching involves arranging and switching the molecules of the liquid crystal (LC) layer between the glass substrates essentially in a plane parallel to these glass plates.
One approach was to use interdigital electrodes on one glass substrate only to produce an electric field essentially parallel to the glass substrates (Abstract). To take full advantage of the properties of this In Plane Switching (IPS) technology further work was needed. After thorough analysis, details of advantageous embodiments were filed in Germany by Guenter Baur et al. and patented in various countries (Abstract). The Fraunhofer Society in Freiburg, where the inventors worked, assigned these patents to Merck KGaA, Darmstadt, Germany.
Shortly thereafter, Hitachi of Japan filed patents to further improve this IPS technology.
The diagram shows a simplified model of a particular implementation of the IPS technology. In this case, both linear polarizing filters P and A have the same orientation of their axes of transmission. To obtain the 90-degrees twisted nematic structure of the LC layer between the two glass plates shown on the left without an applied electric field, the inner surfaces of the glass plates are treated to align the bordering LC molecules at an angle of approx. 90 degrees. This molecular structure is practically the same as in TN LCDs. However, the arrangement of the electrodes e1 and e2 is different, as they are in the same plane on one glass plate only to generate an electric field essentially parallel to the glass plate. The LC molecules have a positive dielectric anisotropy, i.e. they align themselves with their long axis parallel to an applied electric field. In the OFF state on the left of the diagram entering light L1 becomes linearly polarized by polarizer P. The twisted nematic LC layer rotates the polarization axis of the passing light by 90 degrees, so that ideally no light passes through the analyzer A. When a sufficient voltage is applied between electrodes e1 and e2, the corresponding electric field E will realign the LC molecules as shown on the right of the diagram so that light L2 can pass the display device in the ON state.
The diagram can be misleading as the dimensions are not realistic: the LC layer is only a few micrometers thick and small compared with the distance between the electrodes e1 and e2. In practice, other schemes of implementation exist which have a different structure of the LC molecules, for example without twist in the OFF state.
To achieve a wider viewing angle and faster response speed required using a compensatory film and complicated multi-domain technology to divide pixels into parts. As both electrodes are on the same substrate, they take more space than electrodes of TN matrices. This reduces contrast and brightness.
Super-IPS was later introduced with even better response times and color reproduction.
History
The first twisted nematic (TN) LCD was invented in Switzerland in 1970 and became the basis for LCD monitors. The TN method was applied in active matrix TFT LCDs in the late 1980s and early 1990s. The early panels showed gray inversion from up and down, and had slow response speed. In the mid 1990s, some technologies—typically IPS and VA (Vertical Alignment)—that could resolve these weaknesses were applied to large monitor panels.One approach was to use interdigital electrodes on one glass substrate only to produce an electric field essentially parallel to the glass substrates (Abstract). To take full advantage of the properties of this In Plane Switching (IPS) technology further work was needed. After thorough analysis, details of advantageous embodiments were filed in Germany by Guenter Baur et al. and patented in various countries (Abstract). The Fraunhofer Society in Freiburg, where the inventors worked, assigned these patents to Merck KGaA, Darmstadt, Germany.
Shortly thereafter, Hitachi of Japan filed patents to further improve this IPS technology.
Technology
The diagram shows a simplified model of a particular implementation of the IPS technology. In this case, both linear polarizing filters P and A have the same orientation of their axes of transmission. To obtain the 90-degrees twisted nematic structure of the LC layer between the two glass plates shown on the left without an applied electric field, the inner surfaces of the glass plates are treated to align the bordering LC molecules at an angle of approx. 90 degrees. This molecular structure is practically the same as in TN LCDs. However, the arrangement of the electrodes e1 and e2 is different, as they are in the same plane on one glass plate only to generate an electric field essentially parallel to the glass plate. The LC molecules have a positive dielectric anisotropy, i.e. they align themselves with their long axis parallel to an applied electric field. In the OFF state on the left of the diagram entering light L1 becomes linearly polarized by polarizer P. The twisted nematic LC layer rotates the polarization axis of the passing light by 90 degrees, so that ideally no light passes through the analyzer A. When a sufficient voltage is applied between electrodes e1 and e2, the corresponding electric field E will realign the LC molecules as shown on the right of the diagram so that light L2 can pass the display device in the ON state.The diagram can be misleading as the dimensions are not realistic: the LC layer is only a few micrometers thick and small compared with the distance between the electrodes e1 and e2. In practice, other schemes of implementation exist which have a different structure of the LC molecules, for example without twist in the OFF state.
To achieve a wider viewing angle and faster response speed required using a compensatory film and complicated multi-domain technology to divide pixels into parts. As both electrodes are on the same substrate, they take more space than electrodes of TN matrices. This reduces contrast and brightness.
Super-IPS was later introduced with even better response times and color reproduction.
Super PLS
Samsung Electronics introduced technology named Super PLS (Plane-to-Line Switching) with the intent of superseding conventional IPS. It seems that Samsung adopted PLS panels instead of AMOLED panels because AMOLED panels still have difficulties in realizing full HD resolution on mobile devices. PLS technology is Samsung’s new wide-viewing angle LCD technology, and it is known as a similar technology to LG’s IPS technology.
Samsung claims the following benefits of Super PLS (commonly referred to as just "PLS") over IPS:
Further improvement in viewing angle
10 percent increase in brightness
Up to 15 percent decrease in production costs
Increased image quality
Samsung claims the following benefits of Super PLS (commonly referred to as just "PLS") over IPS:
Further improvement in viewing angle
10 percent increase in brightness
Up to 15 percent decrease in production costs
Increased image quality
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