Divyesh Patel
B.E E&TC
What are liquid crystals ?
Liquid crystals form from organic compounds and is thought of as the phase of matter between the solid and liquid state of a
crystal.
What are liquid crystals ?
Liquid crystals form from organic compounds and is thought of as the phase of matter between the solid and liquid state of a
crystal.
• 1888:Friedrich Reinitzer discovers the liquid crystalline nature of cholesterol extracted from carrots.
• 1922:Georges Friedel describe the structure and properties of liquid crystals.
HISTORY OF LCD
• 1964:George H.Heilmer was credited with the invention of LCD.
• 1972:The first active matrix liquid crystal display panel was produced in the United states.
• 2008:LCD TVs get popularity in the market according to Display Bank.
HISTORY OF LCD
What IS LCD?
• LCD is a thin,flat panel used for elctronically displaying information.
• Made up of many number of pixels filled with crystals.
• Its major features are its lightweight construction, its portability.
LCD CONSTRUCTION
Active Matrix: (AMLCD)A switching device and a storage capacitor are integrated at the each cross point of the electrodes
Passive Matrix: (PMLCD)
Simple matrix type was used in the first stage of LCDs. In this
method, the transparent electrodes are set on X and Y axis.
There is not switching device.
• Display Size is limited because the more rows, the shorter time the on-voltage can be applied, resulting in poor contrast ratio, narrow viewing angle, and fewer gray levels.
• Crosstalk occurs when neighboring pixel voltages affect each other, reducing the gray scale, contrast, and viewing angle.
• Submarining occurs when slow-to-respond LC materials cannot respond quickly enough and the picture can disappear temporarily.
• One Solution: placing a switch at each pixel, such as a transistor or diode --> pixel matrix becomes “active.”
• Switching element at each pixel. Individual pixels isolated from each other. Thin Film Transistors most commonly used.
• Many passive display problems eliminated:
• pixel isolation eliminates crosstalk • Larger displays
can be realized.
TFT LCD (Thin Flat Transistor Liquid Crystal Display)has a sandwitch-like
structure with liquid crystal filled between two glass plates.
Conventional colour displays use a pixel arrangement called RGB. In this arrangement, red, green and blue pixels are arranged in equal proportion.
– at high pixel densities, RGB arrangement is adequate,
– when the number of pixels is limited, the image may appear fuzzy. To compensate for this, a GRGB arrangement can be used
TYPES OF LCD
• TRANSMISSIVE LCDS
• TRANSFLECTIVE LCDS
• REFLECTIVES LCDS
Specification Of LCD Monitor
• RESOLUTION
• COLOR SUPPORT BRIGHTNESS
• VIEWABLE SIZE
• DOT PITCH
• CONTRST RATIO
Estimated Annual Energy Use for CRTs and LCDs
Advantages• Slim profile
• Lighter and less bulky
• Does not suffer from glare in bright rooms
• Much lower power consumption than plasma or projection systems
• Limited colour resolution• Lower contrast ratio• Lower response time• More expensive• Narrower viewing angle
• Television and digital television
• Computer monitor
• LCD projector
• Aircraft Instrumentation display
• Digital clock
• Digital watches
• Digital signage
• Digital calculator
• LCDs provide size, weight, comfort, clarity, and energy advantages to users. Even better technologies (OLEDs, others) coming soon