Liquid crystal displays or LCDs introduced during the late 1980s suffered from several limitations. These include poor viewing angle and low-quality color reproduction, as well as poor off-axis image quality and moving picture quality. The development of in-plane switching technology and its subsequent commercialization marked another turning point to the overall history of LCD technology.
Issues About the Limitations of TN LCD
LCDs featuring the breakthrough twisted nematic effect or TN display technology were initially more suitable for use in alphanumeric readouts such as those found in some calculator displays, digital wristwatches, and earlier models of mobile phones. Earlier predictions assumed that the application of LCD would be limited to these small-display devices.
The TN screen technology was the only viable technology for the active matrix TFT LCD during the late 1980s and early 1990s. But the demand for LCD applications grew along with the developments in consumer electronic devices and digital technology. There was a need to address the limitation of TN technology and other LCD technologies.
Nevertheless, LCD technologies have evolved rapidly over the past two decades as manufacturers became heavily invested, and display and consumer electronic markets became highly competitive and innovative. The introduction of in-plane switching or IPS screen technology marked another breakthrough in LCD application—expanding rapidly from small-display devices to television and high-definition mobile devices.
The Birth of IPS LCD Technology
In-plane switching or IPS is a display technology that involves arranging and switching the orientation of the molecules of the liquid crystal layer between the glass substrates. As mentioned, it is simply a variant of a thin-film transistor or TFT LCD.
Take note that there are actually just two general or common variants of TFT LCDs. These are twisted nematic or TN TFT LCD and IPS TFT LCD.
In an IPS screen, the liquid crystals are aligned horizontally to the screen instead of vertically. Furthermore, IPS also uses a lateral electrical field in which the electrical field is applied between each end of the crystal molecules to keep the crystals parallel to the electrode pair and the glass substrate of the screen.
The liquid crystal molecules can also move freely to the desired arrangement because they are not anchored to the lower glass substrate. A similar concept was introduced in 1974, but the implemented output was unable to surpass TN displays.
Guenter Baur and colleagues in 1990 filed a patent in the United States and several countries for the details of advantageous molecular arrangements. They assigned the patent to Merck KGaA, a German multinational chemical and pharmaceutical company.
Mass Production of In-Plane Switching
Japanese multinational conglomerate Hitachi filed patents to improve the technology. They eventually introduced the implemented product in 1996. The initial reception was poor because of the high manufacturing cost. Hence, IPS was limited to high-end monitors. Over time and like any other technology, improvements and refinements had brought down the cost to levels that were acceptable for mass-production.
Korean multinational company LG also developed their version of IPS LCDs and subsequently introduced the resulting product in 2007. The company has since become the biggest manufacturer of LCDs based on in-plane switching.
It is worth mentioning that the technology further become popular when Apple introduced the first-generation iPad in January 2010. Steve Jobs explained that in-plane switching is one of the main selling points of this flagship product. Other devices from other manufacturers also positioned IPS as their selling point due to its advantages.
Further Developments in IPS LCD Technology
Researchers and manufacturers have pushed the limits of IPS LCDs to compete against other display technologies such as organic light-emitting diode or OLED displays, as well as the emerging quantum dot and microLED display technologies.
Apple introduced a specific trademark and brand of LCD called the Retina Display or, more specifically, the Liquid Retina Display in 2014 alongside the introduction of the iPhone 4. The underlying technology was similar to other IPS implementations.
However, a Liquid Retina Display is specifically an IPS LCD with resolution and pixel density high enough to make individual pixels invisible from a normal viewing distance, thus resulting in the reproduction of sharp graphical images with smooth curves.
A specific variant of in-plane switching called Mini-LED IPS LCD started emerging around 2019 and 2019. Note that it is not a specific display technology. Instead, it is a backlighting scheme used in panels based on LED-backlit LCD technology.
Mini-LED displays use small-sized light-emitting diodes to illuminate LCD panels, improve local dimming capabilities, and increase the contrast ratio. Hence, an IPS display with this backlighting scheme can arguably match the advantages of OLED displays.
To improve further the capabilities of IPS LCD technology, other manufacturers developed complementary technologies. Examples include the use of low-temperature polysilicon or LTPS and low-temperature polycrystalline oxide or LTPO backplane technologies.