Treinamento tv lcd sanyo

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 -------------------------------------------------------------------- 12- 13 4-2 Super TN (STN) Type---------------------------------------------------------------------------- 12- 13 4-3 Triple STN (TSTN) Type / Film STN (FSTN) Type --------------------------------------- 12- 13 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 Glass Plate

Pixel (Picture Element) Transparent 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 by switching the drive transistor (TFT) on and off.

Note: Alignment film is not shown in this figure.

Fig. 1 Construction

of LCD Display

(Transparent Type TFT LCD) -3-

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) LCD Shutter

Alignment Film Liquid Crystal Alignment Film Transparent Electrode (Common) Color Filter Glass Plate Polarized Board

LCD Layer Module (Front)

Fig. 2 Construction

of LCD Display

(Cross Section)

Backlight

LCD Panel (LCD Shutter)

LCD Display

LCD Module TFT Display Drive Circuit (with IC) -5-

Fig. 3 Assembly of LCD Display

â– 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 Electrode

Electric Field

Liquid Crystal

Electric Field

Liquid Crystal Molecule

Electric Dipole

Fig. 6 Operation of Liquid Crystal

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â– 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 90Âş(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 direction of a polarized board differs from the oscillating direction of light

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

Passage Light The two boards are the same directions.

White

Fig. 7 Operation of Polarized Board

Interception Light The two boards are shifted right-angled.

Black

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Fig. 8 Operation of Polarized Board

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 90ยบ 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 90ยบ 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 Plate

Alignment Film

Direction of Groove

Liquid Crystal Molecule

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

Alignment Film

Direction 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 90ยบ 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 90ยบ 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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Principle of Liquid Crystal

Training Manual Principle of LCD

On the contrary, in the condition (Switch-On) that voltage is supplied, the liquid crystal molecules are arranged in a line at right angles to a glass plate. Since vertical liquid crystal molecules do not affect the oscillating direction of light, the light that passed the upper polarized board passes as it is without changing the oscillating direction. Since the oscillating direction of this light differs from direction of the lower polarized board which is shifted 90º and arranged, the light collides with this polarized board and cannot pass. This is the liquid crystal shutter-off condition and the LCD panel (LCD shutter) blocks the light.

This is the basic structure (On—Off of the light by the LCD shutter) of an LCD panel. It is a sandwich structure of the upper and lower sides of transparent electrodes, alignment films, and polarized boards, with an enclosed liquid crystal material between them.

The LCD panel shown in Fig. 10 is a type of panel that changes the light into a passage condition when voltage is not supplied between the upper-and-lower polarized boards that are arranged at 90º. This type of panel has the advantage that black contrast is improved, and it usually works well. This mode is called “Normally White Mode.”

An LCD panel that passes light when voltage is not supplied is referred to as “Normally Black Mode.” In practice, with this type (when the upper-and-lower polarized boards are arranged in the same direction), displaying perfect black becomes difficult due to the leakage of light caused by variations in the arrangement of the liquid crystal molecules.

Lig

Lig

ht

ht Polarized Board Transparent Electrode (Upper)

Polarized Board Transparent Electrode (Upper)

Alignment Film

Alignment Film Liquid Crystal

Liquid Crystal

Alignment Film Transparent Electrode (Lower) Polarized Board

Alignment Film Transparent Electrode (Lower) Polarized Board

Fig. 10 Operation of Passage

Interception

LCD Panel

3-4 Transparent Electrode In order to generate an electric field in liquid crystal, voltage is supplied to the upper-and-lower electrodes. If metal is used for these electrodes, the light is interrupted by this metal and cannot pass into the liquid crystal. Therefore, a transparent electrode that passes light is used for the electrode of the LCD shutter.

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■ Type of LCD Display Construction

Training Manual Principle of LCD

4 Type of LCD Display Construction 4-1 Twisted Nematic (TN) Type A Nematic type of LCD Display where the liquid crystal molecules are twisted 90º between upper and lower boards is called a Twisted Nematic type (TN type) liquid crystal.

Most LCD displays are of this type and feature high contrast (ratio) under low voltage and power.

4-2 Super TN (STN) Type Super TN type (STN type) LCD Displays are used for LCD televisions, personal computer monitors, cellular phones, etc. A liquid crystal material developed to improve visual characteristics, such as contrast ratio is used.

In this STN type liquid crystal molecules are twisted 180º to 270º and arranged between upper and lower electrodes. By supplying voltage to this liquid crystal, the transparent ratio of light changes more steeply.

Therefore, with the STN type as compared to the TN type, contrast and rise characteristic of the voltage (response of switch On and Off) are improved, and a clearer picture on larger screens becomes possible.

4-3 Triple STN (TSTN) Type / Film STN (FSTN) Type A fault of the STN type is that the display colors during On and Off of the LCD shutter become yellowish green and navy blue. (In TN type, they are white and black.) This is because light of a specific wavelength is reflected and scattered by the thickness of the LCD panel. Therefore, even if a color filter of RGB is attached to an STN type liquid crystal, bluish green is mixed with the colors from black, gray to white, and a natural color picture cannot be displayed. The triple STN type (TSTN type) and the film STN type (FSTN type) have been developed as an advanced type of STN. In the TSTN type, optically compensated films (high polymer films) which sandwich the upper and lower LCD panels are used. They compensate for the twist of the light crystal cell, and the display colors of yellowish green and navy blue are changed to the correct white and black. The “FSTN” type uses a single optically compensated film

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Type of LCD Display Construction

TN Type

Training Manual Principle of LCD

Module

LCD Layer

Module Twist of molecule (90ยบ)

STN Type Module

LCD Layer

Module Twist of molecule (180ยบ - 270ยบ)

TSTN Type Optically Compensated Film Module

LCD Layer

Module Optically Compensated Film Fig. 11 Type of LCD Display Construction -13-

■ System of LCD Display

Training Manual Principle of LCD

5 System of LCD Display 5-1 Dot-Matrix System LCD displays have two drive systems, Segment and Dot-Matrix. The Dot-Matrix system is used for LCD television displays.

The picture elements (pixels) of the display unit are arranged horizontally (X line) and vertically (Y row) by this Dot-Matrix system, and various characteristics and figures can be displayed.

Fig. 12 shows a matrix of “X x Y = 10 (pixels)” with the character “Y” displayed. In this Dot-Matrix system, by making the size of a pixel smaller and increasing the whole number of pixels, the big screen with fine character or picture becomes possible.

With the present liquid crystal manufacture technology, the number of pixels per inch has reached 200ppi*, and very high definition screen display is possible. Moreover, the number of pixels of an LCD display panel corresponding to bigger screen sizes can be specified and manufactured. For example, the number of pixels of the SXGA* panel is about 1,300,000 (1,280 x 1,024 = 1,310,720 pixels).

✐ ppi: pixel per inch ✐ SXGA: Super eXtended Graphics Array

R G B

In colorization of LCD panel, one pixel consists of 3 RGB dots (sub-pixels).

X

A character or a figure is displayed by making the pixel of each X and Y intersection turn on (or off).

Y Fig. 12 Dot-Matrix System

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System of LCD Display

Training Manual Principle of LCD

5-2 Colorization Since an LCD shutter only passes or blocks light, in itself it cannot display a color picture. The color picture is made by mixing the three colors of RGB (three primary colors of light) respectively, like the CRT color television. The color LCD panel has a color filter of RGB attached to the monochrome panel. See Fig. 13. In this color LCD panel, by controlling the voltages and the waveforms that are supplied at each RGB pixel, the transparent ratio is controlled and hue and brightness are adjusted. Therefore, smaller pixels and more numbers of pixels are required for the color LCD Display. For example, although the SXGA panel described before has about 1,300,000 pixels, in colorization, there are about 4 million dots (sub-pixels).

Backlight

Backlight

ite

ite

Wh

Wh r

lo Co

e

R G B

m hro c o

n

Mo

Color Filter LCD Shutter

LCD Shutter

Color Panel

Monochrome Panel Fig. 13 Colorization of LCD Display

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System of LCD Display

Training Manual Principle of LCD

5-3 Drive System The drive systems for LCD display are divided into the following classifications: The Static Drive System, which is seldom used; The Passive Matrix System, which is used for still pictures, such as calculators and notebook PCs; The Active Matrix System, which is suitable for high definition and the high-speed response needed for big screen LCD television.

Drive System

Static Drive System Dynamic Drive System

Passive Matrix System

Classification of LCD Drive System

Active Matrix System

5-4 Passive Matrix System In the structure of a passive matrix system, Y electrodes of the vertical direction (Y-direction) are formed in upper glass plate, and X electrodes of the horizontal direction (X direction) are formed in lower glass plate as a matrix. The liquid crystal molecules are sandwiched between these electrodes. By supplying voltage between the Y electrode and the X electrode in sequence, at a certain time, an electric field is generated in the liquid crystal where the selected Y electrode and X electrode cross. Therefore, the liquid crystal molecules of this pixel address (X, Y electrode intersection) change arrangement and an LCD shutter is turned On or Off.

Y Electrode Y0

Y1

Y2

Y3

Y4

Glass Plate X0 X1 X2 X3

Liquid Crystal Layer

X4 Glass Plate

X Electrode

These electrodes are transparent electrodes.

Fig. 14 Passive Matrix System

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System of LCD Display

Training Manual Principle of LCD

Y1 Y0

Y1

Y2

LCD shutter is turned on or turned off in this address (X2, Y1).

X0 X1 X2

Liquid Crystal

X3 X2 Fig. 15 Passive Matrix System

In the dynamic drive system, since the electric signal (voltage) is supplied to the Y electrode and the X electrode in sequence, the number of pixels which makes all pixels (the total number of pixels are “X x Y”) turn on or off becomes “X+Y”. Therefore, compared with the static drive system that has an independent electrode for each pixel, the number of electrodes of the dynamic drive system is very few.

However, with this dynamic drive system, since the electrode itself is the wiring, it has resistance that cannot be disregarded in the big screens. This resistance causes the speed of the shutter to become slower. Therefore, when displaying moving pictures etc., an afterimage is generated.

This passive matrix system is not suitable for LCD televisions with big screens that require moving pictures and high resolution.

The active matrix system was developed in order to overcome these faults.

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System of LCD Display

Training Manual Principle of LCD

5-5 Active Matrix System In the active matrix system, a switch element is attached for every pixel at the intersection of the X and Yelectrodes of a passive matrix system. Each pixel is now controlled by the switch element (active element). Since the switch for each pixel is turned On and Off independently, the response speed is increased. Thin Film Transistor (TFT) is used for the switch element and is attached on the glass board.

The LCD display using this TFT is called “TFT LCD display”.

The upper electrode for the whole pattern is formed on the upper glass plate and is called the “Common Electrode”. A pixel electrode (pixel pattern), TFT (switch element) which drives a pixel electrode, and X electrode for gate input and Y electrode for source input of TFT are formed on the lower glass plate. In this structure, the electric field is generated in the area between the pixel electrode and the common electrode, and the LCD shutter for 1 pixel is operated.

When an electric signal (voltage) is supplied to the Y and X electrode of TFT, TFT is turned On, and the liquid crystal molecules are operated as a light switch. Refer to Fig. 17 (Address X1 and Y0).

Glass Plate (Upper)

COMMON Electrode

Pixel Electrode (Pixel Pattern)

Liquid Crystal Layer

X Electrode Glass Plate (Lower)

Y Electrode

Equivalent Circuit (TFT)

Liquid Crystal

Y0

Y Electrode Y1

COMMON Electrode

Matrix System

Equivalent Circuit (Switch) COMMON

COMMON COMMON Electrode

Fig. 16 Structure of Active

TFT (Switch Element)

Liquid Crystal

Pixel Electrode

Drain

Drain

X1 X Electrode X1 X2 TFT

Pixel Electrode

X1 Gate

Gate

Source

Source Y0

TFT

By TFT, the shutter of a pixel at the address (X1, Y0) is turned On or Off.

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Y0

Switch (On / Off)

Fig. 17 Equivalent Circuit of Active Matrix System

System of LCD Display

Y0

Y1

Training Manual Principle of LCD

Y2

Y3 X0

TFT (Switch) Liquid Crystal COMMON Electrode

X1 X2 X3

The LCD shutter is operated by TFT at the address (X1, Y0).

Fig. 18 Structure of TFT Matrix The amplification operation of a transistor is used for the TFT switch in the active matrix system. In this system, switching speed is unified over the whole display, increasing drive response speed as compared with the passive matrix system. Therefore, TFT LCD display (active matrix system) is adopted for the highly efficient display, which can provide the response speed required for big screens or quickly moving pictures. However, further response speed is needed for high definition LCD television. This will be described later.

5-6 Drive of Active Matrix System

Voltage to liquid crystal

The TFT LCD display consists of a matrix of n lines of X direction (X0 - Xn-1) and of n rows of Y direction (Y0 - Yn-1). The line of X direction is called the “gate line” and the line (row) of Y direction is called the “data line.”

First, the scan is started from the pixel address Since the time for the drive voltage to reach its required value is shorter in the active matrix system, (X0, Y0), and when the address (X0, Yn-1) is the response time of the display becomes quicker. selected the scan of X0 line is completed. Next, all the pixels from X1 line to Xn-1 line are scanned in Active Matrix System sequence, and the final address is (Xn-1, Yn-1).

The operation of selected pixel address (X1, Y2) is explained below.

First, (signal) voltage is supplied to X1 line (gate of TFT), next voltage is supplied to Y2 row (source of TFT), and the address of the intersection of X1 Passive Matrix System line and Y2 row is selected and its TFT is turned On or Off. However, just switching the TFT on and off will not change the brightness of the screen.

The brightness of a screen is changed by controlTime ling the voltage of a data line (Y row). Fig. 19 shows the voltage characteristic of the matrix sysFig. 19 Voltage Characteristic of Matrix System tem.

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System of LCD Display

Training Manual Principle of LCD

In Fig. 20, the voltage of the data line (Y2) is supplied in the positive direction to a common electrode (DC drive). In practice a uniform AC voltage is supplied to the common electrode (AC drive) to prolong the life of the liquid crystal.

Data Line Drive Circuit (Y row)

Y0 Y1 Y2 Y3 • • • Yn-1 X0 X1 X2 X3

Pixel Electrode Glass Plate (Common)

•••

Liquid Crystal

Xn-1

Glass Plate (TFT)

Gate Line Drive Circuit (X line)

TFT

COMMON X Direction

Variable Voltage

Video Data Processor Y Direction

Timming Controller (Scan Converter)

Power Circuit COMMON

X1 Y2 TFT: On (X1, Y2) Brightness of Screen

Y2

COMMON

TFT: On

Y2 In practice, driven by AC signal to COMMON. (AC Drive)

Y2 TFT: Off

Y2

Fig. 20 LCD Drive Circuit (Normally White Type)

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■ Improvement Technology of LCD Display

Training Manual Principle of LCD

6 Improvement Technology of LCD Display 6-1 Subject of LCD Display 6-1-1 Angle of View Angle of view means the normal visible range (angle) of a screen.

In an LCD display, the angle of view is narrow compared with a CRT or PDP (Plasma Display Panel). The viewing angle of the typical TN type LCD display is about 100º. However with the new improved technology that has been developed the angle of view for LCD display has increased to 160º or 170º. This improved system will be described later. (The angle of view for a CRT or PDP is 180º.)

Vertical

Angle of View

Horizontal Angle of View Fig. 21 Angle of View 6-1-2 Response Characteristic The response characteristic of the LCD display is the speed at which the display is refreshed by the input signal (video data signal).

If this response characteristic is slow, an afterimage will appear on the screen. Therefore, in large screen LCD television, improving this response characteristic becomes very important.

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Improvement Technology of LCD Display

Training Manual Principle of LCD

6-2 Angle of View (TN Type) The principle of optical penetration and the interception of the LCD shutter by the arranged direction of cylindrical liquid crystal molecules controls the direction of light. Therefore, brightness, hue, and contrast depend on the direction of view of the LCD display. The range (angle) where these look normal is called the “angle of view.� The fault of the TN LCD display is that this angle of view is narrow.

Fig. 22 shows that brightness changes depending on the angle the screen with a gray picture is viewed.

In this figure, the liquid crystal molecule leans diagonally. Therefore, the amount of optical penetration will change depending on the angle when watching the screen from the front or the side.

The brightness becomes different depending on the angle of view.

Polarized Board Transparent Electrode (Common) Alignment Film

Glass Plate

Liquid Crystal Molecule

Alignment Film Transparent Electrode (Pixel, TFT) Polarized Board

Glass Plate

Fig. 22 Angle of View (TN type)

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Improvement Technology of LCD Display

Training Manual Principle of LCD

6-3 Multi-Domain System The arrangement of the TN LCD display is one directional. In this Multi-Domain System, one pixel is divided into two or more different arranged domains.

Fig. 23 shows the example of Multi-Domain System with two domains. The quantity of the light per pixel from various angles is equalized by this system. Moreover, the angle of view becomes even wider by increasing the number of divisions. However, manufacturing is difficult in the rubbing process*.

� Refer to 2-2 Rubbing-process.

The brightness of a screen is equalized as macro view.

Polarized Board Transparent Electrode (Common) Alignment Film

Glass Plate

Liquid Crystal Molecule

Glass Plate Alignment Film Alignment Film (Left) (Right)

Transparent Electrode (Pixel, TFT) Polarized Board Fig. 23 Multi-Domain System

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Improvement Technology of LCD Display

Training Manual Principle of LCD

6-4 MVA (Multi-domain Vertical Alignment) System In the MVA system, the (alignment) film is arranged so that the liquid crystal molecules are stood vertically. The MVA system combines vertical alignment with the Multi-domain system. By vertically aligning the liquid crystal molecules, the influence of optical interception is lost, and the angle of view and contrast are improved.

A type of material is used that causes the liquid crystal molecules to become vertical to the glass plate without supplying voltage. (Nega-Nematic liquid crystal*) In the MVA system, attaching the boss by resin and making the liquid crystal molecules stand diagonally on the transparent electrode make multiple alignment domains. Therefore, since the rubbing process can be skipped at the alignment film production, manufacturing becomes easier compared with the multidomain system.

� Generally, a Posi-Nematic system is used that aligns the liquid crystal molecules by supplying voltage.

Polarized Board Transparent Electrode (Common) Alignment Film

Glass Plate

Liquid Crystal Molecule (Nega-Nematic) Alignment Film Boss (Left)

(Right)

Glass Plate

Transparent Electrode (Pixel, TFT) Polarized Board

Fig. 24 MVA (Multi-domain Vertical Alignment) System

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Improvement Technology of LCD Display

Training Manual Principle of LCD

6-5 IPS (In-Plain Switching) System The structure of an IPS system is shown in Fig. 25. The pixel and common electrodes are mounted to the transparent film (drive transistor) side and the electric field is generated horizontally to the glass plate. With this electric field, the alignment direction of liquid crystal molecules is rotated 90ยบ in parallel to the glass plate.

In the IPS system, liquid crystal molecules rotate all at once in the horizontal direction. Since these liquid crystal molecules do not lean like the TN type, there is little change in the picture characteristics (contrast, brightness, hue, etc.) and the angle of view becomes wider. However, there are a few problems.

The quantity of transparent light is reduced, slower response speed, and a white picture becomes a little bluish or yellowish depending on the viewing direction. The S-IPS (Super-IPS) type was developed to improve upon these problems. In the S-IPS type, the structure of the electrode for driving the liquid crystal molecules becomes a zigzag form, which reduces the change of color, increases the viewing angle to about 160ยบ and has high definition equivalent to a CRT.

Polarized Board

Basic Structure of IPS System

Glass Plate (Without Transparent Electrode) Alignment Film

Electric Field

Transparent Electrode (Pixel)

Alignment Film Transparent Electrode (Common)

Glass Plate Liquid Crystal Molecule (Vertical)

Polarized Board Polarized Board

Normally Black Mode

Alignment Film Liquid Crystal Molecule (Vertical)

Dark (Switch Off)

Bright (Switch On)

Fig. 25 IPS (In-Plain Switching) System -25-

Improvement Technology of LCD Display

Training Manual Principle of LCD

6-6 Optically Compensated Film By using the optically compensated film, the phase shift of the STN type of LCD display is corrected, and the angle of view and contrast are improved.

(Refer to 4-3 Triple STN Type.)

Three methods for attaching the optically compensated film are shown in Fig. 26.

1 sheet / 1 side

Polarized Board Compensated Film

Liquid Crystal

Polarized Board

2 sheets / 1 side

2 sheets / 2 sides

Polarized Board Compensated Film 1 Compensated Film 2

Polarized Board Compensated Film 1

Liquid Crystal

Polarized Board

Liquid Crystal

Polarized Board

Compensated Film 2

Fig. 26 Optically Compensated Film

6-7 OCB (Optically Compensated Birefringence) System The OCB system combines the bend-alignment system where the liquid crystal molecules are bent and aligned between the upper and lower boards and optically compensation film. This system has the features of increased angle of view and quicker response speeds. However, bend-alignment is difficult to make uniform and stable.

Polarized Board Optically Compensated Film Transparent Electrode (Common)

Glass Plate

Alignment Film Liquid Crystal Molecule

Alignment Film Transparent Electrode (Pixel, TFT) Polarized Board

Glass Plate

Fig. 27 OCB System -26-

Improvement Technology of LCD Display

Training Manual Principle of LCD

6-8 Improvement of Response Speed 6-8-1 Inpulse System In order to reduce afterimage and dim outline, there is the system that has the backlight blinked for every writing of one picture or an all black picture in inserted in the fixed cycle. It is called the “Inpulse System.”

For example, with the system called “Super Inpulse System,” the black data is written in every 1/60 second, and the afterimage and the ghosts are reduced.

With the usual LCD panel, since the picture is displayed continuously, the front picture becomes dim as the afterimage.

In the inpulse system, by inserting black data between the picture data, the afterimage is reduced and the high-speed response is improved.

Black Data

Fig. 28 Inpulse System

Picture Data

6-8-2 FFD (Feed Forward Driving) System

Over-Shoot

Waveform (Normal)

Voltage

Voltage

The response speed of LCD brightness can be improved by adding over-shoot characteristic to the data line voltage. Fig. 29 shows the actual overdrive circuit used in a digital drive system.

Waveform with Over-Shoot

Time

Time

Response Time Brightness

Brightness

Response Time

(By Overdrive Circuit)

Time Voltage

Voltage

Time

Time

Time

Overdrive Circuit

Drive Circuit (Normal)

Fig. 29 Overdrive Circuit

-27-

â– Appendix

Training Manual Principle of LCD

7 Appendix 7-1 Backlight An LCD panel does not emit light itself. For the display, a light source is required, and normally fluorescent lights are used for the backlight of the LCD television.

The backlight consists of fluorescent lights, a reflective plate, and a diffusion sheet (or board). Fig. 30 shows the structure and photograph of 30V and 15V LCD televisions backlights.

30V Type LCD Panel

Fluorescent Lights (30V: 16pcs)

Diffusion Sheet (Board)

Reflective Plate

15V Type LCD Panel

Fluorescent Lights (15V: 2pcs, 20V:3pcs)

Diffusion Sheet

Reflective Plate

Fig. 30 Backlight

-28-

Appendix

Training Manual Principle of LCD

7-2 LVDS Circuit (1) LVDS Interface For transmitting the video signal information, an interface circuit with an LVDS (Low Noise Differential Signaling) standard is used, which has the merit of low noise, high speed operation by a small amplitude, and low power consumption.

The LVDS cable connects the transmitter in the driving circuit and the receiver in the module.

Fig. 31 LVDS Interface

Transmitter (Driving Circuit)

100â„Ś Terminated

3.5mA

Receiver (LCD Panel)

LVDS Cable

1.2V

345/200mV

(2) Driving Circuit Fig. 32 shows the block diagrams of a panel driving circuit. The final video information (signal) from the video processor (for example pixelworks) is transmitted to the LCD panel module through an LVDS cable.

Fig. 32 Block Diagrams of Panel Driving Circuit

Video Processor (pixelworks)

LVDS Transmitter TxOUT TxIN

Part of Panel Display (in the module) DATA (LVDS)

LVDS Receiver RxIN

RxOUT

R

8

R

8

G

8

G

8

B

8

B

8

Vsync

Vsync

Hsync

Hsync

BLANK

BLANK

PARITY

PARITY PDWN

DCLK

TxCLKIN

DCLK

CLOCK (LVDS)

-29-

LVDS

RxCLKOUT

LCD Module

Part of (Panel) Driving Circuit

Appendix

Training Manual Principle of LCD

7-3 Block Diagram Example (1) CLT-1583 R

Speaker (R)

U45 R

Audio AMP

3

LA4263

1

10

Tuner Board

1 30

S_CLK / SIN_OUT/ ENABLE_IN / ENABLE_OUT V33D

DRO [0-7]

Video Decoder

VY [0-7]

V L R

L_PC 11

L2

GBE [0-7]

VCPU 33 37

Flash ROM

U30

8Mbits

V33D

AVDD PVDD

R

V L R Y Cb Cr

G H

Component AV2 Input

B_PC

Red_PC

9

AV1 Input

THC63LVDM83A

54 30 48 31 43

R2

8

CVBS2

4 R1

2

V L R

S

Monitor Output

1

CVBS1

SY1

5

DBO [0-7]

MENORY DATA

Graphic A/D AD9883

R_PC

16

L1

3

SC1

7 S1

R_OUT

L_OUT

CVBS_OUT

AV Switch U46 CXA2089Q 33 30 32

LVDS Interface

DGO [0-7]

U6 18

34

V33

5 4 6

GGE [0-7]

74 71

Main Scaler / (Main)CPU PW113-10Q PIXELWORKS

VUV [0-7]

VPC3230D

40 43 45

41 39

IC1

U36

INPUT_Y INPUT_Cb/Pb INPUT_Cr/Pr

CVBS

47 48 46

VCPU 33/18

U19

SELECTED_C

72

AUDIO_L

AUDIO_R

L_TV

R_TV

3 2 1

SELECTED_Y

CC_R CC_G CC_B

7 6

V_TV

Main Board

NJW1138M

Tuner / IF TMQJ8

+9V

LCD Panel

Audio Processor

IIC +CONTROL

17

Speaker (L)

GRE [0-7]

Sub CPU M37272M6

16

HS_PC G_PC VS_PC

+9V

U101 TU201

L

U44

8 23

RX CLK+/-

R

8

Headphone (J26)

L

RX IN+/-[0-3]

4

L

+12V

B V

D-SUB

Fig. 33 Block Diagram: CLT-1583

PC Input

(2) CLT-2053 R

Speaker (R)

U45 R 4

Audio AMP

3

LA4263

1

10

R

8

+9V

Sub CPU M37272M6

16

Audio Processor

1 30

Tuner / IF TMQJ8

47 48 46 41 39

74 71

5

Main Scaler / (Main)CPU PW113-10Q PIXELWORKS

VUV [0-7]

VPC3230D

DGO [0-7] DBO [0-7]

LCD Panel

4 6

U36

MENORY DATA

U30

VCPU 33 37

Flash ROM 8Mbits

40 43 45

V L R Monitor Output

S

V L R

AV1 Input

9

11

V L R AV2 Input

R3

8

R2

4

L2

2

CVBS2

1

16

R1

CVBS1

5

L1

3

SC1

7

SY1

R_OUT

33 30 32

S1

AV Switch U46 CXA2089Q

L3

34

CVBS_OUT

VY [0-7]

18

L_OUT

+9V

DRO [0-7]

Video Decoder

INPUT_Y INPUT_Cb/Pb INPUT_Cr/Pr

CVBS

72

VCPU 33/18

U19

SELECTED_C

AUDIO_R

3 2 1

SELECTED_Y

CC_R CC_G CC_B

L_TV

R_TV

S_CLK / SIN_OUT/ ENABLE_IN / ENABLE_OUT V33D

7 6

V_TV

17

Speaker (L)

Main Board

NJW1138M

IIC +CONTROL

AUDIO_L

U101 TU201

L

U44

8 23

Tuner Board

Headphone (J26)

L

L

+14V

L R

Y Cb Cr

Audio Board

Component

Fig. 34 Block Diagram: CLT-2053 AV3 Input

-30-

Appendix

Training Manual Principle of LCD

(3) CLT1554 / CLT2054 AV1 AV1_Y 3

S Video Composite Video Audio

AV1_CV 1

IC1001

IC801

TV_CV 5

Video SW

CPU

7 AV1/TV_Y/CV 5

AV2

AV2_V 1 AV3_Y 3

Composite Video Audio

IC1002

36 37 22 23 OSD_HD VD (For Caption) 12 10 5V

13 11 OSD_HD VD 154 153

85

IC2001

AD_Y 48

Audio

AD_Cr 54

IC301

IC4101

AD_HS

IP Converter Screen Controller

(Y/UV)

38

AD_VS

IIC Bus

IC361 SDRAM

Sync Separation 15

R: 1

Tuner IF Sound Multiplex

AV3_L/R L: 28

R: 3

R: 4 TV_L/R L: 27

IIC Bus

LCD PANEL (15V)

AD_CLAMP

28

AV1_L/R L: 30 R: 2 AV2_L/R L: 29

IC781 LVDS Transmitter

IC1701

TV (A201)

R/G/B (0-7)

31

16 AD_Y 26

LCD PANEL (20V) (For 15V)

IIC Bus

AD_Cb 43 A/D Converter 30

(For 20V) R/G/B (0-7)

IIC Bus AD_R/G (0-7)

(480p)

152 151 150 148 149 R G B Y I

DEC_Y/C (0-7)

with AV3_Cb 94 Y/C Separation (480i)

Component Video

OSD_CC

DD Converter 3.3V

AV3_Cr 92 Digital Decoder

AV3

18 19 20 21 16 R G B Y I

IC871

7 SEL_Y/CV

Video SW

AV1_C 90

IIC Bus

IC001

10 SEL_R

16 R-OUT (+)

13

Audio SW Audio Control 21 SEL_L Surround

IC101

15 R-OUT (-)

SPEAKER (Right)

Audio AMP 9

24 L-OUT (+) 25 L-OUT (-)

IIC Bus

SPEAKER (Left)

Fig. 35 Block Diagram: CLT1554 / CLT2054

-31-

SEP / 2004

Printed in Japan

SANYO Electric Co., Ltd.