Liquid Crystal Display

    LCD short for liquid crystal display, a type of display used in digital and mobile devices . LCD displays utilize two sheets of polarizing material with a liquid crystal solution between them. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal, therefore, is like a shutter, either allowing light to pass through or blocking the light.
For mobile phone screen, the screen material determines the phone display effect in a large part. If categories in screen materials, there are two mainstream smartphone screen currently: One is the Liquid Crystal Display (LCD), the other is Organic Light - Emitting Diode (OLED).
    LCD is a more traditional screen material and the technology is more mature. LCD display need the support of backlight when displaying, and the light needs to go through two layers of glass, substrate and various optical diaphragms, polyimide film, color filter to generate the polarized light, the brightness and color loss is inevitable. LCD can be divided into there main subclasses: TFT, IPS, SLCD. It should be noted that, TFT and LCD are conceptual overlapped. TFT is a general name for all LCD panels. But we classify the TFT as a subclass of LCD in this part.
    Different from LCD, OLED screen displays the image pixels through self-illumination, it does not need the backlight. AMOLED is a branch of OLED screen and this technology mainly belongs to SamSung. Currently, the AMOLED has been developed to third generation: AMOLED, Super AMOLED and Super AMOLED Plus.
Material  For Short Type (Full Name)  Advantages 
LCD        TFT    Thin Film Transistor  It gets high brightness, contrast, strong sense of hierarchy and bright colors, but it is more power consumption 
IPS  In-Plane Switching  IPS is a LCD technology which is developed by HITACHI based on TFT-LCD. IPS technology has changed the arrangement of TFT liquid crystal molecules to makes itself get larger viewing angle and more realistic color reproduction and press its surface without any apparent water ripples 
SLCD   splice liquid crystal display  SLCD is a LCD technology which is developed by SONY based on the LCD , which is highest technical level of the display screen. It can be used as a display as well 
OLED      AMOLED  Active-matrix Organic Light Emitting Diode  AMOLED is a LCD technology which is developed by SAMSUN Gbased on OLED, which is faster recreation, higher contrast, wide viewing angle and due to the characteristics of glow by itself, the power consumption is only 60% of the TFT, but it needs better technology level and higher costs, in addition, on account of the gorgeous color of AMOLED, it may bring about imagine distortion 
Super AMOLED   Super Active-matrix Organic Light Emitting Diode  Super AMOLED is the update edition from AMOLED that is thinner, brighter and more flexible.  
View Angle
    Viewing angles are a key feature for LCD screens. What is viewing angle? When the backlight passes polarizing film, liquid crystal and alignment layer, the output light will have a direction. That is to say, most light is perpendicular from the screen and you cannot see the original color but all-white or all-black when you watch the LCD screen from a certain large angle. Viewing angle is the maximum angle at which a display can be viewed with acceptable visual performance with original color (from left to right, up to down).

    Generally, screen manufacturers would like to develop wide viewing angles, and there are three mainstream technologies: TN+Film, IPS (In-Plane-Switching) and MVA (Multi-Domain Vertical).
  • TN + FILM technology adds a layer of wide viewing angle compensation film based on original TN technology. This compensation film layer can increase the viewing angle to 150 degrees. This way is simple and widely applied in LCD screens. However, this technique does not improve the performance of contrast and response time. For screen manufacturers, TN + FILM might not be the best solution, but it really is the cheapest one, so most Taiwanese manufacturers make 15-inch LCD screen in this method.
  • In-Plane Switching (IPS), commonly known as “Super TFT”, was developed by Hitachi Ltd. in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time. Its name comes from the main difference from TN panels, that the crystal molecules move parallel to the panel plane instead of perpendicular to it. This change reduces the amount of light scattering in the matrix, which gives IPS its characteristic wide viewing angles and good color reproduction.

    An IPS-LCD is a type of thin display that offers better viewing angles than TFT-LCDs. IPS-LCDs feature two transistors for each pixel, where TFT-LCDs use just one. This requires a more powerful backlight, which delivers more accurate colors, and allows the screen to be viewed from a wider angle. The downside is that an IPS-LCD may consume more power than a TFT-LCD. IPS-LCDs typically are found on high-end cell phones and portable devices.

  • MVA technology is to increase prominences to form several viewable areas. Liquid crystal molecules is not completely vertically aligned in a static status, but when the liquid crystal molecules is horizontally arranged under the applied voltage, then light can pass layers. MVA technology will improve the viewing angle to 160 degrees, and make response time shorter more than IPS and TN + FILM. This technology is developed by Fujitsu, now is authorized to Taiwan's Chi Mei (CMO of the mainland is a subsidiary of CMV) and Taiwan's AU Optronics to use this technique
  • The principle of On-cell technology is to insert the touch panel between the colored filter-sheet  of display panel (LCD) and polarizer, that means, laying touch sensor onto LCD panel.
  • The principle of In-cell technology is to insert the touch panel function into liquid crystal layer, that means, embedding touch sensor into LCD panel.
Resolution usually contains two types: display resolution and image resolution. Display resolution shows the precision of an image and it indicates how many pixel number can a screen show. Image resolution means the pixel number of each inch in an image, its definition makes it more colser to resolution definition.
The more pixel numbers a screen shows, the finer an image looks, and the more details can be seen in the same display area. That's why display resolution is one of the most important fator of mobile phone display. The most common display resolutions are:
    Color Gamut
Gamut is an encoding method for a color. It also refers to the entire range of colors available on a particular device. Gamuts are commonly represented as areas in the CIE 1931 chromaticity diagram as shown as below. There is a new CIE 1976 chromaticity diagram, which is not used as widely as CIE 1931.

    NTSC, sRGB and Adobe RGB standards are commonly used to measure gamut level for television and desktop monitor, they are seen as subsets of CIE 1931 chromaticity diagram with different range. For the mobile phone screen, sRGB and NTSC standard are more common. sRGB is a standard RGB color space created cooperatively by Microsoft, HP and Epson for use between monitors, printers, scanners and other computer peripherals and application program. NTSC is a colour gamut developed by the National Television Standards Committee of the United States. It has a wider range than sRGB, gengerally, the sRGB color gamut covers about 72% of the NTSC gamut. Therefore, some screens that cover over 80% of NTSC gamut are considered more than 100% sRGB color gamut, and many screen manufacturers are using these data as selling points.

    Pentile Matrix is a configuration of RGB subpixels that used in OLED mobile phones. Pentile differs from more traditional RGB pixels in appearance: the area of traditional tricolor, red, green and blue is equal, but the area of Pentile RGB is not equal, the area of red and green is always twice the area of green.

    Pentile RGB vs traditional RGB

    Pentitle appears following the birth of OLED display materials. Traditional RGB is always used in LCD, which needs a light source (backlight) to drive light, and the realization way of RGB in the display is optical filter that is simple to produce. And the cost is not very high to make high-density RGB color banding. However, it is totally different for OLED, of which corresponding RGB use organic materials. The display’s resolution used nowadays in our daily life is very high, and this requires that each optical material is small but integrated with high-density. So OLED needs a complex technology and the cost is much higher. With Pentile RGB, each display unit contains two materials of larger area, so it reduces the technology difficulty and the cost decreases.
    PPI (pixels per inch) in the context of a display, this is the number of pixels per inch, as measured along either the vertical or horizontal linear axis. (as pixels are almost always square, the number is generally the same both horizontally and vertically). this is also known as pixel density. more pixels per inch produces a sharper image with better detail and smoother lines and text. displays with less pixels per inch can show "jagged" edges on things displayed , especially angled or curved lines, and text, due to the pixels being visible.
    PPI refers only to the number of pixels per inch, not the display's total number of pixels, nor the total physical size of the display. but all three are related. consider two displays that are the same physical size, if one has more total pixels(resolution) then it will necessarily also have greater PPI.
  • Theoretically, PPI can be calculated from knowing the diagonal size of the screen in inches and the resolution in pixels (width and height). This can be done in two steps:
  • Calculate diagonal resolution in pixels using the Pythagorean theorem:
  • Calculate PPI:
  • is diagonal resolution in pixels
  • is width resolution in pixels
  • is height resolution in pixels
  •  is diagonal size in inches (this is the number advertised as the size of the display).
    For example, Mi 2 mobile phone is 4.3 inch with a resolution 1280x720, then the PPI is about 342
    When PPI reaches a specific number, the naked eyes is unable to distinguish grainy. According the retina technology introduction of the iPhone 4 conference by Apple’s Steve Jobs in 2010, “It turns out there’s a magic number right around 300 pixels per inch, that when you hold something around to 10 to 12 inches away from your eyes, is the limit of the human retina to differentiate the pixels.”

Comparison of Different Smartphones


Screen Display





























Galaxy Note 2






    LCD Suppliers
    There are many LCD suppliers in the mobile phone market, the most famous ones are: LG, SamSung, Sharp, Toshiba, NEC, Sony. Besides these well-know brands, there are many other LCD suppliers, click below link to read the full list.