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LCDFAQs |  |
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Q. What are the types of driving modes used in LCDs? A.There are two types of driving modes. One is "Static" and the other is Multiplexed". "Static" is a method of activating an LCD where each segment has an independent connection, whereas the "Multiplexed" method is a method where the LCD is driven by different channels. This method requires additional information such as "Duty" and "Bias". For example, 1/2 duty, 1/4 Bias defines an 8 x 1 LCD display. Q. How do we define the viewing direction? A.We use four different viewing directions for LCDs: 3 o'clock, 6 o'clock, 9 o'clock and 12 o'clock viewing means you look at the LCD from its left side, 6 o'clock means you look at the LCD from the bottom...and so on. 6'clock is the most common viewing direction. Examples of 6 o'clock viewing are calculators and notebooks. Q.How do I know what type of LCD to use for our product? A.That will really depends on a number of
factors including multiplex driving scheme, temperature, voltage/power, artwork
design, contrast requirements and cost budget. Q.How does LCD gets driven? A.LCD is driven by AC (alternating current), it is best to use standard LCD driver IC to generate as this will simplified your development time. Alternatively, for simple TN segment drive, most MCU may emulate the AC current but would need a lot of background know how. For example, simple TN segment drive would require as low as 40Hz to as high as 120 Hz. Depending on the operating environment such as temperature and would affect the contrast of the display. Some experiment may be need to find the optimum operating condition. Q.What is ESD and does that affect LCDs? A.ESD stands for electro-static discharge, it is arc or discharge of electrons between two surface when potential difference is great enough for discharge to take place. Because LCD is made mainly by non-conductive material such as glass and plastic, ESD can happens in LCD. In most cases, this can be easily overcome by design of peripheral connection and mounting. Q.What is ITO? A.ITO stands for Indium Tin Oxide, more
precisely, it is a mixture of indium oxide and tin oxide. Two important
characteristic about this materials are: Q.What ITO resistance is available? A.For ITO, the term of resistance is based on ohms per square. Commonly, ITO resistance which we used are 200, 120, 100, 80 and 25 depending on the requirements. The choice could be based on artwork design (such as trace width and area), current requirements, etc.
Q.What interconnection technology is available to connect LCD to peripherals? A.Commonly available through us
are
Q.What test is done to LCD? A.Standard tests and control includes
Q.What is viewing angle? A.LCD utilize physical phenomena of liquid
crystal know as birefrigerance (which describe its properties of having two
different refractive index depending on orientation) to create the light
blocking and passing effect. Because of this, normally, the best viewing cone
is best at a certain direction which is know as viewing angle. Q.How does CCFL and EL get driven? A. Inverter is used to generate the AC current needs for both device. However, due to the high voltage requirements by CCFL, a transformer is often need to increase the supply voltage. Q.Does UV light affect LCDs? A.The answer really depends on material selection and configuration. Because liquid crystal is primarily organic compounds, most liquid crystal material are susceptible to UV disintegration. There are some liquid crystal which are specially design for outdoor application that is more UV resistance. When use with UV blocking polarizer, the LCD can be resistance to ultra violet damage.
Q.What other factors may affect life of LCD? A.Two factors:
Q.What is alignment layer and what is TOP coating? A. As previously explained, liquid crystal has two distinctive refractive index known as birefrigerance, in classical view and text book, liquid crystal used in common display application are in what we call nematic phase which is more like a glass rod which will turn when influence by electromagnetic force. Alignment layer is used to anchor the liquid crystal molecule at the glass surface forming the boundary condition for the display to work. coating is simply a material put under the alignment material which act as a barrier layer. The main purpose is to reduce chance of ionic contamination which will deteriorate the display performance and shorten its life time. Very often, silicon dioxide is used for this purpose. Q.Why does my LCD turns dark when left under the sun and is there any problems with the display? A. For most cases, both TN, HTN and STN utilize
the phase known as nematic for display purpose. Within this phase, the liquid
crystal has a "rod shape" exists within the solution which has fast response
and has excellent electro-optic properties. This phase, however, only exists
within a limited temperature range. The higher end of this temperature range is
known as clearing point, above which, the liquid crystal lost its
birefrigerance properties and cannot bend the light path anymore. Thus the
polarizer will then be the only factor which affect incoming and out coming
light. When the LCD is cooled down to below its clearing point, the display
should be working again. The temperature for the clearing point varies greatly
from material to material and you should contact our engineers regarding what
you have. Normally a safe margin should be used to avoid clearing point when
designing the display.
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