Sanyo LCD Panel, LCD Shutter Schematic

Training Manual

Principle of LCD Display

FILE NO.

CONTENTS

	Pages
1. Construction of LCD Display -----------------------------------------------------------------------		2 - 5
1-1 Principle of LCD Display -------------------------------------------------------------------------------		2
1-2 Construction of LCD Display ---------------------------------------------------------------------		2 - 3
1-3 Main Component of LCD Display ---------------------------------------------------------------		4 - 5
2. Principle of Liquid Crystal ---------------------------------------------------------------------------		6 - 8
2-1 Liquid Crystal ---------------------------------------------------------------------------------------------		6
2-2 Rubbing-process-------------------------------------------------------------------------------------		6 - 7
2-3 Operation of Liquid Crystal ----------------------------------------------------------------------------		8
3. Principle of LCD ---------------------------------------------------------------------------------------	9	- 11
3-1 Operation of Polarized Board for LCD Panel (Shutter)-----------------------------------------		9
3-2 Operation of Alignment Film-------------------------------------------------------------------------		10
3-3 Operation of LCD Panel ------------------------------------------------------------------------	10	- 11
3-4 Transparent Electrode --------------------------------------------------------------------------------		11
4. Type of LCD Display Construction ------------------------------------------------------------	12	- 13
4-1 Twisted Nematic (TN) Type --------------------------------------------------------------------	1213
4-2 Super TN (STN) Type----------------------------------------------------------------------------	1213
4-3 Triple STN (TSTN) Type / Film STN (FSTN) Type ---------------------------------------	1213
5. System of LCD Display ----------------------------------------------------------------------------	14	- 20
5-1 Dot-Matrix System -------------------------------------------------------------------------------------		14
5-2 Colorization ----------------------------------------------------------------------------------------------		15
5-3 Drive System --------------------------------------------------------------------------------------------		16
5-4 Passive Matrix System--------------------------------------------------------------------------	16	- 17
5-5 Active Matrix System ----------------------------------------------------------------------------	18	- 19
5-6 Drive of Active Matrix System-----------------------------------------------------------------	19	- 20
6. Improvement Technology of LCD Display --------------------------------------------------	21	- 27
6-1 Subject of LCD Display -------------------------------------------------------------------------------		21
6-1-1 Angle of View -----------------------------------------------------------------------------------------		21
6-1-2 Response Characteristic---------------------------------------------------------------------------		21
6-2 Angle of View--------------------------------------------------------------------------------------------		22
6-3 Multi-Domain System ---------------------------------------------------------------------------------		23
6-4 MVA (Multi-domain Vertical Alignment) System -----------------------------------------------		24
6-5 IPS (In-Plain Switching) System -------------------------------------------------------------------		25
6-6 Optically Compensated Film ------------------------------------------------------------------------		26
6-7 OCB (Optically Compensated Birefringence) System ----------------------------------------		26
6-8 Improvement of Response Speed -----------------------------------------------------------------		27
6-8-1 Inpulse System---------------------------------------------------------------------------------------		27
6-8-2 FFD (Feed Forward Driving) System-----------------------------------------------------------		27
7. Appendix -----------------------------------------------------------------------------------------------	28	- 31
7-1 Backlight--------------------------------------------------------------------------------------------------		28
7-2 LVDS Circuit---------------------------------------------------------------------------------------------		29
7-3 Block Diagram Example------------------------------------------------------------------------	30	- 31

REFERENCE NO. TI5110LCD

■ Construction of LCD Display

Training Manual Principle of LCD

1. Construction of LCD Display

1-1 Principle of LCD Display

The LCD (Liquid Crystal Device) Display is used to display the electric signal, converted from picture data similar to a CRT display. The transistor (TFT) switched by the electric signal changes the transmission to light in small picture elements (pixels) of the LCD. The LCD display makes the picture by grouping these elements of each RGB color.

1-2 Construction of LCD Display

LCD Display

Liquid Crystal is packed between the board modules (TFT and Common) and the LCD panel (or LCD shutter) is constructed. A back light is attached to the LCD panel for LCD Display.

Board Module (Common Electrode)

The Common Electrode consists of a polarized board, a color filter, and a transparent electrode on a glass plate. An alignment film is formed on the transparent electrode.

Board Module (TFT Electrode)

The TFT Electrode consists of a polarized board and a transparent electrode (pixel electrode and drive transistor) on a glass plate. An alignment film is formed on the transparent electrode.

Backlight

A fluorescent light is used for the Backlight.

TFT: Thin Film Transistor

LCD Panel and LCD Shutter: They are the same things, but in the explanation LCD panel is used

for structure and LCD shutter is used for function.

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Construction of LCD Display	Training Manual Principle of LCD

	Backlight
	Polarized
	Board	Pixel
	Glass	(Picture Element)
			Transparent
	Plate	TFT
			Electrode
			(Pixel,TFT)
			Transparent
			Electrode
			(Common)
			Color Filter
			Glass
			Plate
			Polarized
	Board		Board
	Module
	(TFT side)
	LCD Layer

Board Module (Common side)

The light of each picture element is transmitted Note: Alignment film is not

by switching the drive transistor (TFT) on and off.	shown in this figure.

Fig. 1 Construction of LCD Display

(Transparent Type TFT LCD)

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Construction of LCD Display

Training Manual Principle of LCD

1-3 Main component of LCD Display

LCD Shutter

Supplying voltage to the transparent electrodes between the pixel and common sides changes the arrangement of liquid crystal. By assembling two polarized boards, the transfer of light from the backlight can be controlled by the transparent ratio of the LCD Shutter.

Liquid Crystal

Liquid Crystal is a material whose state is between a solid and a liquid. It has both characteristics of solids and liquids, and generally it is a white turbid liquid. Its molecules are normally arranged comparatively opaque and change to transparent with the application of voltage or heat.

Transparent Electrode (Film)

An LCD shutter is operated by supplying voltage derived from the video signal. Transparent film is used for its electrode.

Alignment Film

This is a film for arranging liquid crystal molecules and is made of Polymid resin.

Polarized Board

The light with a specified direction passes through a polarized board.

Drive Transistor

The thin film transistor (TFT) is used to drive the LCD shutter of each pixel.

Color Filter

It is a filter with three colors (R, G, B) arranged for each pixel.

Backlight

Liquid crystal does not emit light. A light source is needed for display. The light source placed on the reverse side of the LCD panel is called “Backlight.”

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Construction of LCD Display

Training Manual Principle of LCD

Backlight

		Polarized	Glass
		Board
			Plate
			Transparent Electrode
			(Pixel,TFT)
		Module
		(Back)	Alignment Film
	LCD	LCD Layer	Liquid Crystal
	Shutter		Alignment Film
		Module	Transparent Electrode
			(Common)
		(Front)	Color Filter
			Glass Plate
			Polarized
			Board

Fig. 2 Construction of LCD Display

(Cross Section)

Backlight

LCD Panel

(LCD Shutter)

LCD

Display

LCD

Module

TFT Display

Drive Circuit

(with IC) Fig. 3 Assembly of LCD Display

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■ Principle of Liquid Crystal

Training Manual Principle of LCD

2. Principle of Liquid Crystal

2-1 Liquid Crystal

What is Liquid Crystal?

Liquid Crystal is a material whose state is between a solid and liquid. It has characteristics of both solids and liquids, and generally is a white turbid liquid. Its molecules are normally arranged comparatively opaque and change to transparent with the application of voltage or heat.

Almost all the materials consist of an organic compound taking the form of a slender stick or a flat plate. There are three types of liquid crystal as shown in Fig. 4, and they depend on the construction and arrangement of molecules.

Generally Nematic liquid crystal is used for the display apparatus.

(a) Smectic

Molecules are in layers and arranged parallel to each other. The center of gravity is arranged at random in the layer.

(b) Nematic

Molecules are not in layers. They are arranged parallel. The center of gravity is able to move freely to the major axis.

(c) Cholesteric

Molecules are in layers and arranged parallel. The arranging direction of the major axis for the neighboring layers is shifted gradually.

In order to use liquid crystal for display, it is necessary to regularly arrange the molecules of Nematic (Rubbing-process).

2-2 Rubbing-process

After chemicals for arranging are put on the glass plate, they are hardened, and then the surface on the plate is rubbed with a cloth to fix the direction of the gaps that are made. The arranging direction of molecules is settled in the gaps.

This process is used to change the characteristics so the molecules that touch the rubbed surface are arranged to the major axis of the rubbed direction.

This thin film on the glass plate is called “Alignment film.”

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Principle of Liquid Crystal

Training Manual Principle of LCD

(a) Smectic

(b) Nematic

(c) Cholesteric

Fig. 4 Liquid Crystal

Liquid Crystal Molecule

Natural Condition

Arranging

Rubbing

Direction

Alignment Film

Fig. 5 Rubbing-Process

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Principle of Liquid Crystal

Training Manual Principle of LCD

2-3 Operation of Liquid Crystal

The chemistry substance required for liquid crystal material is one that reacts so that the arrangement direction is changed according to an applied electric field.

In the LCD display, a liquid crystal is placed between two electrodes. When the voltage is supplied between them, an electric field is generated in the liquid crystal, and liquid crystal molecules are moved and arranged. The Backlight applied to the liquid crystal is either passed or blocked according to the arrangement of the molecules.

If an electric field from an external source is applied to liquid crystal, electric dipoles will be generated that will react to the intensity and direction of the electric field. Through the operation of these electric dipoles and the electric field, the power changing direction of liquid crystal molecules is generated. Therefore, according to an external electric field, liquid crystal molecules move and change direction from horizontal to vertical.

Transparent

Liquid Crystal

Electrode

Electric

Field Electric

Field

Liquid Crystal

Molecule Electric

Dipole

Fig. 6 Operation of Liquid Crystal

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■ Principle of LCD

Training Manual Principle of LCD

3. Principle of LCD

3-1 Operation of Polarized Board for LCD Panel (Shutter)

Light is an electromagnetic wave that is oscillating at right angles to the direction of advance. In fact, the oscillating directions of all light is mixed. A polarized board can let only the light in the specific direction pass from the light with which these various oscillating directions were mixed. Therefore, only the light of the same direction as the polarization direction of a polarized board can be taken out by letting the light pass through this polarized board. That is, if the oscillating direction of light and the direction of a polarized board are in agreement, the light will pass through a polarized board. Moreover, if the direction of a polarized board differs from the oscillating direction of light, the light cannot pass through a polarized board. When the oscillating direction of a polarized board and light are shifted 90º(right-angled), the light is blocked completely. The light passes and looks bright if the two boards are in the same direction when looking at two polarized boards in piles, however, if shifted at right-angles, the light is blocked and looks dark.

Oscillating direction of light

Oscillating direction of light

Polarized

Board

The oscillating direction of light and the direction of a polarized board are in agreement.

The direction of a polarized board differs from the oscillating direction of light

Fig. 7 Operation of

Polarized Board

Passage

Interception

Fig. 8 Operation of

Light

The two boards are

Light

The two boards are

Polarized Board

the same directions.

shifted right-angled.

White

Black

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Principle of Liquid Crystal

Training Manual Principle of LCD

3-2 Operation of Alignment Film

Liquid crystal is inserted into alignment films of an upper and lower plate that have the direction of grooves shifted by 90º on the LCD display. The liquid crystal molecules of upper alignment plate are arranged along with the upper alignment film. The liquid crystal molecules of lower alignment plate are arranged along with the lower alignment film. The liquid crystal layer between these alignment films is twisted little by little and is arranged so that a spiral is formed. Light entering through the first alignment plate will have its oscillating direction twisted 90º by the liquid crystal layer between the alignment films. Now the direction of oscillation is aligned with the second alignment plate and the light will pass through.

Alignment

Film

Liquid

Crystal

Molecule

Alignment

Plate

Direction

of Groove

By the upper-and-lower alignment films, spirally, a liquid crystal molecules are twisted 90º and arranged.

	Alignment	Direction
	Film
		of Groove	Fig. 9 Operation of
			Alignment Film

3-3 Operation of LCD Panel

In the LCD panel, a liquid crystal is inserted and enclosed between two glass plates. The polarized board, transparent electrode, and the alignment film are formed on these glass plates. The light can be passed or blocked by supplying voltage or not to this LCD panel.

In the condition (Switch-Off) that the voltage is not supplied, the liquid crystal molecules are twisted 90º sideways and arranged spirally. The oscillating direction of the light that passed the upper polarized board is changed by the twisted liquid crystal molecule arrangement. Therefore, the direction of a polarized board and the oscillating direction of the light which is shifted 90º and arranged become the same, and this light can now pass through a polarized board. This is the liquid crystal shutter-on condition and an LCD panel (LCD shutter) passes the light.

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