Date: May 20, 2009

By Winstar Display

ISTN-LCD - A New Alternative Solution for

High Contrast/Wide View Angle Display

Nowadays, the demand of high contrast ratio for electronic devices is always be an

important issue. Relevant technology aims at the development to improved contrast

for monochrome LCD display is to offer DFSTN (Double-Film-Compensated STN)

or OLED display.

However, the cost for these two solutions is much higher compared to ISTN-LCD

technology. Due to the properties of the ISTN technology of high contrast and with

wide viewing angles and high brightness, it is very suitable for automotive instrument,

hand held applications, automotive instrument, test and measurement equipment and

other industrial products.

ISTN-LCD technology offers a real alternative to mono LCD for applications that

require exceptional contrast ratios and wider viewing angles.

ISTN-LCD Display with Red LED Backlight

What is ISTN-LCD Technology?

ISTN (Improved Super Twisted Nematic) incorporates a special dichroic dye into

normal STN liquid crystal. The ISTN technology adds a compound called the

dichroic dye into the liquid crystal and which has the feature of anti-isotropic to

absorb the visible light coefficient. Since the amount of the extra compound of

dichroic dye was very small, amounting under 1%, it has been called as Guest and the

original liquid crystal called as Host. Therefore, the ISTN technology also is known

as Guest-Host liquid crystal display (GH-LCD).

Technical theory of ISTN:

The ISTN technology is adding a rod-like dichroic dye into the normal STN liquid

crystal. Just like the drawings shown in the below picture I, the external electric

field changed, the dichroic dye direction will be changed as normal liquid crystal.

While without any voltage apply to the ISTN-LCD, the incident light direction

through the polarizer is parallel to the dichroic dye, therefore, the light would be

absorb by the dichroic dye molecules which is shown as the below drawing (a).

When voltage has been applied to the ISTN-LCD, the incident light direction through

the polarizer is vertical to the dichroic dye, therefore, the most portion of the light

would pass through the dichroic dye molecule which is shown as the below drawing

(b). The absorption difference by the incident light pass through the polarizer is

called as dichroic ratio. It’s obviously to see the difference of the wavelength v.s

absorption for the above mentioned (a) and (b) drawings of without and with voltage

apply to the ISTN-LCD. Through the above theory of the ISTN-LCD mode, we can

take the advantage of this feature to get a wide viewing angle and high penetration of

high contrast display.

Polarizer

(b)

(a)

Absorption

700

600

500

400

Wavelength(nm)

: Dye molecule

: LC molecule

ISTN-LCD

Polarizer

(b) Apply Voltage(V=Vop )

(a) Without Voltage(Vop= 0)

Incident Light(White)

Incident light(White)

Features of ISTN-LCD:

A very important characteristic of ISTN-LCD is the dichroic ratio of ISTN-LCD

varies from the proportion of doped dye molecule and doped concentration. Below

picture II is an example absorption spectrum for using different ratio of dye molecule

as reference.

Picture I

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

300

400

500

600

700

800

900

4wt%

VA

3wt%

8wt%

20wt%

Wavelength(nm)

Main Features:

1. Very dark background display

2. High contrast and brightness

3. Wide viewing angle

By using the advantages of different color and chroma of dichroic dye along with the

different LED backlights and special polymer film as a second cell to compensate

light dispersion resulting in a thinner display and improved viewing properties such as

wide viewing angles and high brightness. Below drawings are the spectrum

examples by using dichroic dye and LED backlight as reference.

Picture II

=

+

B /L e m is s io n

s p e c tr u m

B /L e m is s io n

s p e c tr u m

=

+

d is p la y s p e c tr u m

n o n - d is p la y

s p e c tr u m ( B a c k g r o u n d )

D y e a b s o r p tio n

s p e c tr u m

( w /o v o lta g e )

D y e a b s o rp tio n

s p e c tru m
( A p p ly v o lta g e )

The best performance of ISTN-LCD display is with RED, Amber, and Green LEDs.

ISTN-LCD Display with Amber LED Backlight

Hopefully with this article, it would be a great help for the readers to have basic

information about ISTN-LCD Technology. If you need further information, please

contact with us. Thank you.

Winstar Display Co. Ltd.

No. 163 Chung-Chung Road, Taichung City, Taiwan, R.O.C.

Tel: [phone]

Fax: [phone]

[e-mail]

www.winstar.com.tw

ISTN-LCD Display with Green LED Backlight