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LCD Glossary

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LCD Glossary


Active Area Physical glass area occupied by Liquid Crystal. AA= n x Dot Pitch + Dot Size. where n is the number of pixel on any axis.
AMEPD Active Matrix Electrophoretic Display. Better known as E-paper displays, AMEPD are based on titanium dioxide and hydrocarbon oil technology.
AMOLED Active-Matrix OLED. OLED with TFT layer.
Array BLU Matrix of LEDs located on the back of glasses, about 5 mm thick. Price and power consumption depend on the number of LEDs employed. Homogeneous luminosity.
Bias Lowest voltage level for multiplexed voltage methods. Indicates the number of driving voltage levels: with bias=1/x, there are x+1 driving voltage levels (1, 1/2, 1/3 ... 1/x times the max voltage level). Bias is correlated to Duty value.
BL/BLU BackLight Unit. Light source for TFT and LCDtrasmissive/trasflective. BLU definition includes BLU source (LEDs, EL or CCFL) and light guide.
Booster Electronic device that generates all voltage levels (Bias) for the multiplexed voltage methods. Sometimes it is integrated into IC controller, sometimes requires addition of external capacitors.
Brightness The amount of light emitted from the display.
CCFL Cold Cathode Fluorescent Lamp. Low power and bright white light source, with life-time up to 30,000 hours. Requires light-guide and DC/AC converter.
COB Chip On Board. The ICs are on PCB. It requires a mounting media to both electrically and physically connect the PCB to the glass.
COF Chip On Film. Technology on FPC for IC and other electronic components. Minimize display sizes. More robust than TAB but bigger pads/tracks pitch.
COG Chip On Glass. The glass of the display is the physical support for the IC, therefore the glass surface needs to be few millimeter bigger in one axis to accommodate IC.
Color LCD LCD with different color areas. Color filter, color screen print or color polarizer are used.
Connector Method/support part that connects display module to the application. From the module: pins, Heat-Seals, FFC, COF end, TAB end, exposed pads/tracks and through holes. From application: ZIF, LIF, through hole, pins and exposed pads/tracks.
Contrast Ratio The ratio between the luminosities of the brightest and the darkest point that the module is capable of producing.
Crosstalk Visible defect that occurs because of interference by adjacent pixels of segment/common.
CSTN Color STN. They employ RGB pixels. Different technology than (area) Color LCD.
DC/AC Converter Amplifier circuit that converts DC to AC voltage, used to power CCFL and EL back lights.
Die Unpackaged IC. Plural: dies or dice.
DIP Dual In Line.
Dot Pitch Corresponds to the dimensions of a pixel plus the gap between a pixel and the one.
Dot Size Dimesions of a single pixel.
Duty Multiplexing index for multiplexed voltage method: used to reduce the number of ITO tracks and inter-connector lines. Duty= 1/y, means 1 lines activates y segments. Higher duty comes with less contrast quality.
Edge BLU LEDs in-line, usually embedded in the light-guide. Homogeneity of light depend on light-guide quality, however inferior than Array BLU (more expensive though).
EL Electro-Luminescence. Thin BLU located on the back of glass, with homogeneous but no extremely bright emission; life time: 2~3,000 hours. Low power consumption but they require DC/AC converter. Good color variety.
E-paper displays Type of screens technically known as AMEPD.
ESD Electro-Static Discharge. ESD is a major cause of failure in electronic components. Human body and activity are common sources of ESD.
FFC Flat Flexible Cable.
FPC Flexible Printed Circuit. General definition for COF, FFC TAB and TCP.
FPD Flat Panel Displays.
FSTN Film Super Twisted Nematic. Compensation RCF (Retardation Control Film) is used to achieve black dot on white color. Usual color: (positive) dark-blue dot on light-grey or yellow/green; (negative) white dot on blue.
Ghosting A condition where "off" segments become slightly visible.
Glare filter Additional anti-reflective filter to improve viewability in harsh lighting conditions.
Heat-Seals Mounting method and connector type. Flexible support with interface tabs made of a conductive hot melt adhesive. Connection requires pressing hot bar.
Hot-Spot Undesired bright spots that cause inhomogeneous luminosity, usually due to not perfectly designed light-guide.
HTN Higher Twisted Nematic. Their crystal molecules have a higher twisted angle than TN, thus provide clearer visibility and wider viewing angle.
I/O Input/Output.
Inter-connector Mounting method/support that connects glass to the rest of display module. Zebra, pins, heat-seals.
ITO Indium Tin Oxide. It is transparent and colorless in thin conductor layers, used as signal carrier on glass for pixels activation.
LCD Liquid Crystal Display: liquid crystal sits within a pair of transparent electrodes.
LCM LCD Module. LCD glass with controllers or/and drivers circuit, inter-connector, possibly with BLU and connector.
LED Light Emitting Diode. Source unit for BLU with minimum 50,000 life time. Broad color variety.
LIF Low Insertion Force.
Light-Guide Light diffuser located between BLU source and glass, it scatters light homogeneously over the View Area. Usually included into BLU definition.
NRE Non-Recurring Engineering refers to the one-time cost to research, develop, design and test a new product.
OEL Organic ElectroLuminescence. OLEDsynonymous.
OLED Organic LED. Emissive display technology (do not require BLU) that comprises a film of organic compounds. Wide 160' Viewing Angle and stunning definition for both monochromatic and color display. High brightness and low power consumption.
PCB Printed Circuit Board.
PDP Plasma Display Panels.
Pin Inter-connector for COB or connector for low I/O display; it can be straight or banded. In COB pins connect glass to PCB; in glass or COG, pins connect LCM to the application board. Pins pinch the glass upon ITO tracks and can be soldered at the other end. Robust but pin pitch can't be as little as other mounting methods.
PLED Polymer LED. OLED synonymous.
Polarizer A stretched polymer which transmits light in only one axis. A typical display has polarizer on the front and back.
PPI Pixels Per Inch. Measurement of pixel density of a display.
Reflective A viewing mode which uses ambient front lighting to provide the illumination for the display. Reflective displays do not support backlight and can be only positive mode.
SMD Surface Mount Device.
SMT Surface Mount Technology.
SOIC Small Outline IC.
STN Super Twisted Nematic. Their crystal molecules have a higher twisted angle than HTN. For high-duty drive LCD.
TAB Tape Automated Bonding. Technology on FPC for IC only. Smaller pads/tracks pitch than COF, but less robust though. Minimize display sizes. Smaller pads/tracks pitch than COF, less robust though. External connectors: FPC or Heat-Seals.
TCP Tape Carrier Package, technology FPC .
Temperature Operating temperatures: Standard about 0 C to +50 C; wide about -20 C to +70 C; very wide about -40 C to +90 C for TN or -40 C to +80 C for other technologies. Storage temperature: ranges about -10 C and + 10 C wider than working temperatures.
TFT Thin Film Transistor. Active-Matrix (but not active display) variant of color LCDtechnology. Negative displays with high brightness and wide viewing angle. Broadly used as mobile phone displays.
TN Twisted Nematic. The simplest and cheapest crystal technology for low duty displays. Limited viewing angle.
Transflective A viewing mode which uses both back-lit and ambient light reflection. Tansflective displays can be either negative or positive mode.
Trasmissive The only emission light is back-lit. Trasmissive displays can be either negative or positive mode.
TSSOP Thin Shrink Small Outline Package.
View Area Glass area which is visible through a bezel or cut-out in an application device. This area is made up of the Active Area and a boarder around the Active Area.
Viewing Angle Viewing angle is the maximum angle at which a display can be viewed with acceptable definition.
Y-G Yellow-Green color.
Zebra Elastomeric (rubber) conductive strip used on COB module to electrically connect board exposure contacts to ITO tracks. Mechanically robust but adds extra thickness to LCM. It requires bezel for physical anchoring to PCB.
ZIF Zero Insertion Force.


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