In general, LCD is made of three main substances, including glasses, organic fluids and polarizers.  The display mechanism of LCD is utilizing the light bending phenomena occurring between two pieces of parallel glasses, usually thickness 0.55mm, 0.7mm, 1.1mm, etc.  Between these two glass plates, a coating of nematic liquid crystal was filled.  Nematic liquid crystal is thermo-tropic substance which posses definite pattern in arrangement.  In other words, the microscopic crystal molecules of nematic liquid crystal perform alignment in parallel array.

Between these two pieces of glasses, transparent electrodes printed on the internal surfaces.  The molecules of liquid crystal subject to an electromagnetic field between electrodes and hence electric charge can control the orientation of molecules.

Insulating polymers are sealed on one layer of electrodes acting as electrical barrier.  Another layer applied is alignment film causing molecules of nematic liquid crystal align in direction.  Outside layers of two glass plates are finally covered with polarizers.  Small rod-shaped glass called spacers are applied to produce a fixed gap space between two glass plates in order to provide even display appearance.  By filling liquid crystal inside the display, inletting opening was sealed with adhesive sealer.

Two halves of displays were placed at 90° degree to one another to form a helical structure between two electrodes.  When electric charge applied to liquid crystal molecules, the light strikes from one polarized glass to the other polarized glass will depend on the change of vibration of molecules matching angle correctly.  If the light passes through one glass layer that matches with the angle of another layer, no light can pass through and thus appearance of LCD will be darken.  Using this phenomenon, we can control the passing through of light rays.

There are many types of LCD, each with their definite properties and applications.  Referring to applications, we can use characteristic of display mode to develop Positive Type display and Negative Type display.

 Black display color with White background color           White display color with Black background color

According to LCD property, they can be classified into TN, HTN, STN, FSTN, etc.  Depending on many years of experiences and efficient technologies, Po Sing can provide high grade of TN, HTN, STN & FSTN types of LCD, both standard and custom-made products.  We introduce various variations of liquid crystal cell technology to produce different types of LCD.  Generally, structures of all above types of LCD are similar.  They all formed in nematic liquid crystal sandwiched between two plates of glasses, covering with two layers of polarizers.  But, for the FSTN LCD, an additional compensation film is involved that leads to different characteristics.

TN (Twisted Nematic) Type LCD  液晶分子扭曲導向列液晶顯示屏

TN is a common type of display mode in LCD technology.  This mode called twisted nematic because the movements of liquid crystal molecules have a twist angle of 90° affected by electric current.  The unit cost of this mode is economic and tooling cost is lower than other types of display modes.  It can be used for multiplex level up to 1/16 duty.  Common LCD applications like calculators, timepieces and games are using these types of mode.  However, as the limitation of its properties, TN LCD panel has only positive and negative features in gray mode.  But, it stills a good choice for large volume production and low cost products.

HTN (High Performance Twisted Nematic) Type LCD 液晶分子高度扭曲導向列液晶顯示屏

The performance of HTN is between the TN type LCD and STN type LCD.  HTN mode posses a twist angle of about 110°.  When comparing with TN mode, HTN has wider viewing angle than TN type.  But it is not suitable for very low temperature application.  It can be applied for multiplex level up to 1/32 duty.  Popular applications of this mode can be found in most instruments and meters.

STN (Super Twisted Nematic) Type LCD  液晶分子超級扭曲導向列液晶顯示屏

High contrast and excellent viewability of STN type LCD is due to the highly twisted structure of the liquid crystal molecules between electrodes.  The twist angle of STN mode ranges from 180° to 240°.  The technology is tried to broaden the electro-optic transition region for gray level while allowing for conventional addressing.  As the result of highly twisted angle, STN LCD suffered from background coloration causing to color background display appearance.  Therefore, STN cannot provide real black and white color mode as TN posses.  It can be used for multiplex level more than 1/32 duty cycles.

FSTN (Formulated Super Twisted Nematic) Type LCD 液晶分子格式化超級扭曲導向列液晶顯示屏

Under rapid development of LCD technology, FSTN type LCD is established.  Basically, FSTN is a modified mode of STN.  It utilizes an optical retarder as compensation film to eliminate the interfering color phenomena of STN display appearance.  Therefore, real black & white color mode can be achieved in FSTN.  FSTN has excellent contrast and broad viewing angle that especially suitable for high graphic types applications.

LCD Type Reference Table

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