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