Display Technology Comparison: IPS/LTPS/CGS/IGZO/AMOLED
Aug 16, 2021
What screens are IPS, LTPS, CGS, IGZO, and AMOLED, and what is the difference?
The current mobile phone screen technology is too much, this article aims to introduce various panels and screen technology so that everyone can better distinguish.
In recent years, mobile phone screen technologies have emerged endlessly.
As early as a few years ago, AMOLED and IPS screens were used on mobile phones, and later there were screens such as CGS. Do you know what screen the iPhone 5 uses? The iPhone uses another new mobile phone screen technology, namely the LTPS low-temperature polysilicon screen. What are the connections and differences between these various mobile phone screen technologies?
The current mobile phone screen technology and panel types are too much, not to mention ordinary consumers, even players who often play mobile phones may be easily confused. It is necessary to interpret them.
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First of all, we want to emphasize that there are only two types of screens for mobile phones, namely TFT-LCD and OLED. Most of the OLEDs on the market are AMOLED, and they represent passive and active display screens respectively.
Manufacturers now like to use panel types to label TFT-LCD panels. Common panels mainly include TN, VA, IPS, CPA (AVS), etc., while a-Si, IGZO, LTPS, and CGS are material technologies. At present, the common OLED screens on mobile phones are mainly Samsung's SuperAMOLED screens.
The SuperAMOLED panel is called the Super Active Matrix Organic Light Emitting Diode (SuperActiveMatrixOrganicLightEmittingDiode).
Since LCD technology is inherently supported (supported by backlight), there is always a loss of brightness no matter what, and the light has to pass through two layers of glass and various films to produce polarized light, which will bring color loss and pixels It is also more difficult to increase the density, and the cost will be higher. Therefore, people need a screen that can be close to lossless, so the offensive display technology that can emit light has been developed. This is what we call AMOLED.
Since it does not require thick glass and a backlight, the light emitted by this screen can be directly received by the human eye, so this screen is ideal regardless of color loss or viewing angle. But God is often fair, OLED also has its insurmountable shortcomings, that is, the three-color luminescence loss is inconsistent.
We know that the current white light is composed of three primary colors, namely red, green, and blue. If we want to emit these three kinds of light, the energy we have to give is not consistent, which reflects that the applied current is not consistent (E =hv, the energy required for different frequencies is also different), which is like you hit something, the greater the force you use, the easier the tool is to damage, so the red-emitting electrode in AMOLED is damaged than blue-green The electrode should be slow, which means that the more the screen is used, the more red it will be. Therefore, to slow down this effect, some manufacturers will adjust the screen to be blue when it leaves the factory so that the color of the screen will be normal after a period of use.
Passive panels need backlight support, and there are mainly the following types.
The TN panel is called TwistedNematic, and its low cost is destined to be the most widely used one. TN is sometimes called TFT (well, this is a popular and unscientific term for folks). The disadvantages of TN panels are the small viewing angle and limited color reproduction capabilities.
The full name of the VA panel is vertical alignment panel (VerticalAlignment), and there are two types: Fujitsu's MVA and Samsung's PVA. Compared with TN panels, VA panels can provide wider viewing angles and better color reproduction capabilities. Samsung's PVA (Patterned Vertical Alignment) panel technology is developed and inherited from Fujitsu's MVA. The disadvantages of VA panels are higher power consumption and higher prices.
The full name of the IPS panel is In-Plane Switching. It is a panel technology developed by Hitachi in 1996. It is improved from the TFT panel, so it is also called the "Super-TFT" panel. IPS panels are divided into S-IPS, AS-IPS, H-IPS, S-IPS, and E-IPS. They also have the advantages of large viewing angles and strong color reproduction capabilities, but their power consumption is higher than SuperAMOLED screens.
CPA is a wide viewing angle panel (ContinuousPinwheelAlignment) with a continuous firework-like arrangement mode. This kind of panel also belongs to Sharp. Sharp CPA panel has excellent color reproduction and viewing angles, but it is expensive. It should be noted that Sharp collectively refers to the wide-view technology products such as TN+Film, VA, and CPA that it has used as ASV.
Many high-end mobile phones use IPS panels as a selling point
Introduction of several display material technologies
a-Si is an amorphous silicon technology that is currently the most widely used. It has simple technology and low cost. However, the area of the pixel itself occupied by the switch is so large that the brightness cannot be made very high (that is, the aperture ratio is low). In addition, PPI can only achieve a level of about 200 PPI.
IGZO is the abbreviation of Indium Gallium Zinc Oxide (IndiumGalliumZincOxide), which is a thin film transistor technology, which achieves better electronic performance by adding an IGZO metal oxide layer on the active layer of TFT-LCD. Compared with a-Si, its switching transistor is smaller in size and can achieve a higher pixel aperture ratio, and its PPI is generally below 300. The advantages of IGZO are high precision, low power consumption, and high touch performance. Apple's iPad uses this technology panel.
LTPS (Low-Temperature Polysilicon) low-temperature polysilicon technology was developed to solve the shortcomings of monocrystalline silicon. Compared with a-Si, LTPS integrates peripheral circuits into the panel substrate, which is more operable, and the carrier movement speed is faster. The design is simpler, the PPI can achieve up to 500+, and generally above 300PPI are using this technology. Representative products are HTCOneX and iPhone4/4S/5.
CGS (CG-silicon) continuous granular crystalline silicon screen technology is a variant of LTPS (Sharp's official original "CG-siliconised variant of the LTPS process using laser annealing to get large domains"), and its carrier movement speed is 3 times that of LTPS (Low-Temperature Poly-silicon, low-temperature polysilicon) technology, Which is 600 times that of ordinary A-si (amorphous silicon) technology. A higher aperture ratio can be achieved. Under the same backlight brightness condition, the screen brightness is higher, and under the same condition of the screen brightness, a lower brightness backlight can be used to save power. In addition, it is lighter and thinner, resistant to impact and distortion.
CGS screen technology
About glass bonding and touch screen integration process
We have talked about single-glass bonding technology in our previous reviews of many mobile phones. These technologies all integrate the touch control part into the inner glass or the display screen to reduce the thickness, simplify the process, increase the screen's transparency, reduce reflection, and prevent dust. At present, this type of technology mainly includes OneGlass/TouchonLens solutions led by touch screen manufacturers, and On-Cell and In-Cell solutions led by panel manufacturers.
OneGlass/TouchonLens integrates the touch screen with the protective glass by coating an ITO conductive layer on the inside of the protective glass. The representative products are Meizu MX2 and Xiaomi mobile phone 2. Subsequently invalidated
On-Cell is to embed the touch screen between the color filter substrate and the polarizer of the display, which represents Samsung's Galaxy S3;
Samsung's SuperAMOLED screen uses On-Cell technology
In-Cell embeds the touch sensor into the liquid crystal pixel, which represents Apple's iPhone.
Comparison of 4 touch solutions
About screen glass
The glass lamination process was mentioned above, and the way also mentioned the glass aspect. The smartphone glasses currently on the market are mainly Corning's "Gorilla" glass and AGC's "Dragontrail" glass. The representative products of the two are the iPhone and Sony XperiaZ. Gorilla Glass belongs to soda-lime glass, while Dragontrail glass belongs to aluminum silicate chemically strengthened glass.
Summarize
Having said so much, I don't know if you understand it. For example, the iPhone 5 is a product that uses the second-generation IPS (in-panel switching) + low-temperature polysilicon (LTPS) + In-Cell touch panel + Gorilla Gorilla Glass.
