IPS panel

IPS panel

  

IPS (In-plane switching) is a screen technology used for liquid crystal displays (LCDs). It was designed to solve the main limitations of the twisted nematic field effect (TN) matrix LCDs in the late 1980s, such as relatively high response time, strong viewing angle dependence and low-quality color reproduction. In-plane switching involves arranging and switching the molecules of theliquid crystal (LC) layer between the glass substrates. This is done in a plane parallel to these glass plates.

Contents

·         1 History

·         2 Technology

o    2.1 Advantages

o    2.2 Disadvantages

·         3 Super PLS

·         4 Manufacturers

·         5 See also

·         6 References

·         7 External links

History

The TN method was the only viable technology for active matrix TFT LCDs in the late 1980s and early 1990s. Early panels showed gray inversion from up to down, and had a high response time (lower is better, for example 1ms grey-to-white-to-grey transition time (GTG) is visually better than 5ms GTG, but, it is well known that manufacturers fudge these numbers due to there not being any industry standard for arriving at their numbers^{[citation needed]}). In the mid-1990s new technologies were developed—typically IPS and VA (Vertical Alignment)—that could resolve these weaknesses and were applied to large monitor panels.

One approach patented in 1974 was to use interdigital electrodes on one glass substrate only to produce an electric field essentially parallel to the glass substrates.^[1][2] However, the inventor was not yet able to implement such IPS-LCDs superior to TN displays.

After thorough analysis, details of advantageous molecular arrangements were filed in Germany by Guenter Baur et al. and patented in various countries incl. USA on 9 January 1990.^[3][4] TheFraunhofer 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.

Today, IPS technology is widely used in panels for TVs, tablet computers and smartphones.

Technology

Schematic diagram IPS LC display

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° twisted nematic structure of the LC layer, between the two glass plates without an applied electric field (OFF state), the inner surfaces of the glass plates are treated to align the bordering LC molecules at a right angle. This molecular structure is practically the same as in TN LCDs. However, the arrangement of the electrodes e1 and e2 is different. Because they are in the same plane and on only one glass plate, they generate an electric field parallel to the glass plate. Note that the diagram is not to scale: the LC layer is only a few micrometers thick and so is very small compared with the distance between the electrodes e1 and e2.

The LC molecules have a positive dielectric anisotropy and align themselves with their long axis parallel to an applied electric field. In theOFF state (shown on the left), 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 polarizer A. In the ON state, a sufficient voltage is applied between electrodes e1 and e2, a corresponding electric field E is generated realigns the LC molecules as shown on the right of the diagram. Here, light L2 can pass through the polarizer A.

In practice, other schemes of implementation exist which have a different structure of the LC molecules - for example without any twist in the off state. To achieve a wider viewing angle and faster response speed requires using a compensatory film and complicated multi-domain technology to divide pixels into parts.^[5] As both electrodes are on the same substrate, they take more space than electrodes of TN matrices. This also reduces contrast and brightness.^[6]

Super-IPS was later introduced with even better response times and color reproduction.^[7]

This pixel layout is found in S-IPS LCDs. A chevron shape is used to widen the viewing cone.

Advantages[]

·         IPS panels display consistent, accurate color from all viewing angles^[8] and without having any blur.

·         Unlike TN LCDs, IPS panels do not lighten or show tailing when touched. This is important for touch-screen devices, such assmartphones and tablets.^[6]

·         IPS panels can process high speed signals without data loss by using copper wiring with low resistance values.

·         IPS Panels offer clear images and stable response time.^[6]

Disadvantages[]

·         IPS panels require up to 15% more power than TN displays.

·         IPS panels are more expensive to produce than TN displays.

Super PLS[]

In 2012, 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 in the past AMOLED panels had difficulties in realizing full HD resolution on mobile devices. PLS technology was Samsung’s wide-viewing angle LCD technology, and it is known as a similar technology to LG’s IPS technology.^[9]

Samsung claimed the following benefits of Super PLS (commonly referred to as just "PLS") over IPS:^[10]

·         Further improvement in viewing angle

·         10 percent increase in brightness

·         Up to 15 percent decrease in production costs

·         Increased image quality

·         Flexible panel