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A SEMINAR REPORT ON LCD DISPLAY

     Guided by Er Sachin Yele  

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SUBMITTED BY:-

Content…….. 1.Introduction 2.Development of LCD 3.Implementation of LCD 4.specications 5.Application of LCD 6.Drawbacks 7.Conclusion

WHAT IS LIQUID CRYSTAL DISPLAY

?

* A liquid crystal display (LCD) is a thin,non emissive flat panel used for electronically displaying information such as text, images, and moving pictures. Its uses include monitors for computers, televisions, instrument panels, and other devices such as video players, gaming devices, clocks, watches, calculators, and telephones.

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* Among its major features are its lightweight construction, its

*It is an electronicallymodulated optical device made up of any number of pixels

*Each pixel of an LCD

typically consists of a layer of molecules aligned between two transparent electrodes, and two polarizing filters,

Some LCD Equipments

Development display

of

LCD

1.1888: Friedrich Reinter (1858-1927) discovers the liquid crystalline nature of cholesterol extracted from carrots 2.1911: Charles Mauguin first experiments of liquids crystals confined between plates in thin layers.

•1922: Georges Friedel describes the structure and properties of liquid crystals and classified them in 3 types (nematics, smectics and cholesterics). •1936: The Marconi Wireless Telegraph Company patents the first practical application of the technology, "The Liquid Crystal Light Valve". •1962: The first major English language publication on the subject "Molecular Structure and Properties of Liquid Crystals", by Dr. George W. Gray •1962: Richard Williams of found that liquid crystals had some interesting electro-optic characteristics •

•1964 George H. Heilmeie was inducted in the National Inventors Hall of Fame and credited with the invention of LCD. •1970: On December 4, 1970, the twisted nematic field effect in liquid crystals was filed for patent by Hoffmann-LaRoche in Switzerland Hoffmann-La Roche then licensed the invention to the Swiss manufacturer Brown, Boveri & Cie who produced displays for wrist watches during the 1970s and also to Japanese electronics industry which soon produced the first digital quartz wrist watches with TN-LCDs and numerous other products. •1972: The first active-matrix liquid crystal display panel was produced in the United States by T. Peter Brody. •2008: LCD TVs become the majority with a 50% market share of the 200 million TVs •

HOW LIQUID CRYSTAL TECHNOLOGY IS IMPLEMENTED IN LIQUID CRYSTAL DISPLAY UNITS

The term liquid crystal refers to the fact that these compound has a crystalline arrangement of molecules ,yet they flow like liquid .as shown in figure two glass plate ,each containing a light polarizer at right angle to each other sandwich the liquid crystal material . The intersection of two conductor defines a pixel position . when the molecule are on state the polarized light passing through the material is twisted so that it will pass through opposite polarizer .

LIQUID CRYSTAL DISPLAY

T h e lig h t is th a n re fle ct b a ck to th e vie w e r . to tu rn o f th e p ixe lw e a p p ly vo lta g e to th e in te rse ctin g co n d u cto rs to a lig n th e m o le cu le so th a t th e lig h t is n o t tw iste d . th is typ e o f fla t p a n e ld isp la y re fe rre d to a s a p a ssive m a trix LC D . A n o th e r m e th o d fo r co n stru ctin g LC D is to p la ce a tra n sisto r. T h e tra n sisto r a re u se to co n tro lth e vo lta g e a t p ixe l lo ca tio n to p re ve n t th e ch a rg e th a t g ra d u a lly le a kin g o u t fro m th e liq u id crysta lce lls. T h is d e vice a re ca lle d a ctive m a trix d isp la y

Specifications

Important factors to consider when evaluating an LCD monitor: •Resolution: The horizontal and vertical screen size expressed in pixels (e.g., 1024x768). Unlike CRT monitors •Dot pitch: The distance between the centers of two adjacent pixels. The smaller the dot pitches size, the fewer granularities is present, resulting in a sharper image. •Viewable size: The size of an LCD panel measured on the diagonal (more specifically known as active display area). •Response time: The minimum time necessary to change a pixel's color or brightness. Response time is also divided into rise and fall time. For LCD monitors, this is measured in bib (black to black) or gag (gray to gray). •Refresh rate: The number of times per second in which the monitor draws the data it is being given. The picture definition is stored in refresh buffer and the screen is refreshed at a rate of 60 frames per second. •Matrix type: Active TFT or Passive. •Color support: How many types of colors are supported (coll., more specifically known as color gamut). •Brightness: The amount of light emitted from the display (coll., more specifically known as luminance). •Contrast ratio: The ratio of the intensity of the brightest bright to the darkest dark.

APPLICATION OF DISPLAY

LIQUID CRYSTAL

1. Digital television 2. Liquid crystal display television (LCD TV) 3. Computer monitor 4. LCD projector 5. Aircraft Instrumentation displays 6. Mobile technology

DRAWBACK

OF LCD

LCD technology still has a few drawbacks in comparison to some other display technologies:

1. Many LCDs are incapable of displaying very low resolution screen modes. 2. Some types of LCDs have a more limited color resolution. 3. Although LCDs typically have more vibrant images than CRTs, they do have lower contrast ratios than CRTs in terms of how deep their blacks are. A contrast ratio is the difference between a completely on (white) and off (black) pixel, and LCDs can have "backlight bleed" where light (usually seen around corners of the screen) leaks out.

4. LCDs typically have longer response times 5. LCD panels using TN tend to have a limited viewing angle relative to CRT and plasma displays. This reduces the number of people able to conveniently view the same image – laptop screens are a prime example 6. cheap LCD monitors unsuitable for work where color is important, such as in graphic design work, as the colors change when the eyes are moved slightly up or down, 7. Consumer LCD monitors tend to be more fragile than their CRT counterparts

conclusion

Though LCD brought revolution to the display unit but the major drawback is the inability view clearly at wider angle because it is totally based on reflection .So in accordance to the principle it should not based only reflection but also scattering of light so that we can increase the viewing angle.