Liquid crystal displays introduced during the late 1980s suffered from several limitations, particularly poor viewing angle and low-quality colour reproduction, as well as poor off-axis image quality and moving picture quality. In addition, these displays that featured 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. It is in this regard that 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 application grew along with the evolution in consumer electronic devices and digital technology. There was a need to address the limitation of TN-effect technology and other LCD technologies. Interestingly, 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.
What is in-plane switching or IPS screen technology?
In-plane switching is a screen technology that involves arranging and switching the orientation of the molecules of the liquid crystal layer between the glass substrates. As mentioned, it is actually just a variant of thin film transistor or TFT LCD. 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 are also able to move freely to the desired arrangement because they are not anchored to the lower glass substrate.
Similar concept was introduced in 1974 but the implemented product was unable to surpass TN display.
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, German multinational chemical and pharmaceutical company.
Japanese multinational conglomerate Hitachi filed patents to improve the technology. They eventually introduced the implemented product in 1996. Initial reception was poor because of high manufacturing cost. As such, IPS was merely featured in-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 screen technology and subsequently introduced the product in 2007. The company has since become the biggest manufacturer of LCDs that feature IPS screen technology.
It is worth mentioning that IPS further catapulted into popular consciousness when Apple introduced the first generation iPad in January 2010. The late Steve Jobs highlighted the IPS technology as one of the main selling points of the much awaited device. Several mobile and tablet devices have also highlighted IPS as one of their selling points.
Advantages of IPS screen technology over TN and AMOLED
Displays featuring TN screen technology suffered from poor viewing angle and poor colour reproduction. These limitations result in poor off-axis image quality and moving picture quality.
Of course, there are high-quality TN LCDs but the limitations of this screen technology are naturally evident in average products. In laptops and computer screens, most TN LCDs can only represent 70 percent of the 24-bit colour available from graphic cards because they can only display 6-bits per RGB colour.
The introduction of IPS resolves the shortcomings of TN LCDs. One key advantage of IPS screen technology is the wide viewing angle. This is achievable because the technology is able to change the physical behaviour of the liquid crystal layer by making the crystal molecules respond to the electric field in parallel to the TFT. This also results in better colour reproduction.
Because of the qualities of IPS screen technology, it becomes very popular in displays for television, computers, and laptops. Furthermore, it has become popular in consumer electronic devices, particularly smartphones and tablets. Ensuring that devices can be held in a variety of ways without distracting or uncomfortable viewing angle issues has been a major consideration for both device manufacturers and consumers.
It is without a doubt that IPS outperforms TN displays. However, the main competitor of this screen technology is OLED or more importantly, the active matrix organic light emitting diode or AMOLED screen technology.
Between the two, the advantages of IPS over AMOLED include better colour reproduction and representation, intense white colours, and better response times. There are other IPS displays that have sharper and clearer images and better viewing angle than AMOLED. Of course, these advantages are depended on the manufacturer and display quality as determined by a particular IPS or AMOLED technology iteration.
Under bright outdoor lights or direct sunlight, an IPS screen is more viewable or readable than an AMOLED screen because of a built-in backlight. An AMOLED does not have an accompanying backlight because light directly comes from each diode.
Another worthy advantage of IPS over AMOLED is the considerably lengthier lifespan. AMOLED display has short lifespans because the organic constituents tend to degrade faster. Hence, between an IPS and AMOLED screen displays, the former would last for several years while it is possible for the latter to feature burn-ins or death pixels.
Disadvantages of IPS as compared to TN and AMOLED
One of the disadvantages of IPS screen technology as compared to TN and AMOLED is power consumption. A typical IPS screen requires 15 percent more power than TN. It also needs a strong backlight unlike an AMOLED display to improve screen clarity. This requirements results in higher power consumption and faster battery drainage.
Producing IPS screen displays is more expensive than producing a TN LCD because of the involved engineering complexity. Thus, this screen technology is commonly featured in high-end devices. Casual consumer electronics such as netbooks or entry-level smartphones and affordable tablets usually feature TN LCDs.
Some IPS screens have poor blacks and contrast ratios unlike AMOLED screens. Take note that AMOLED produces the deepest blacks in all display technologies available.
The refresh rate of IPS is also slower than both TN or AMOLED. This disadvantage makes a conventional IPS screen unsuitable for watching high definition movies or playing fast-paced video games due to ghosting effects. Furthermore, images can be less fluid and more straining to the eyes than an AMOLED.
However, it is important to note that IPS screen technology has improved over time. Some IPS displays have better contrast ratios and black levels—depending on the manufacturer. An example of this is the Retina display from Apple. But better IPS screen screens are more expensive because of the higher manufacturing cost. As such, they are featured mostly on high-end devices.
EDITOR’S NOTE: Several information from the article are culled from the review study “Technical evolution of liquid crystal displays” by Kyeong-Hyeon Kim and Jang-Kun Song and published in 2009 in the journal NPG Asia Materials; from the study “IPS vs. AMOLED: Effects of panel type on smartphone users’ viewing experience” by Ki Joon Kim, Eunil Park, and S. Shyam Sundar, and published in 2012 in the book Human Technology and Service in Smart Space; and in the study “Advanced IPS technology for mobile applications” by N. Aoki et al and published in 2012 in the Journal of the Society for Information Display.