| Liquid
Crystal Alignment Agents
------ZKPI series of polyimide alignment
agents are high purity organo-soluble polyimide solutions which
can be transformed thermally to polyimide films with outstanding
thermal, mechanical, electrical characteristics and excellent
adhesion to ITO glass or the other substrates. They are excellent
alignment layers for liquid crystal in liquid crystal devices
(LCD), exhibiting stable and high pretilt angles as well as and
high voltage-holding ratio. The resins could be widely used as
alignment agents for many LCD mode, such as Twisted Nematic Liquid
Crystal Display Device (TN-LCD), Super-Twisted Nematic Liquid
Crystal Display Device (STN-LCD) with 240o
; Twisted angle and Thin Film Transistor driven active matrix
Liquid Crystal Display Device (TFT-AM-LCD). Another advantageous
feature is the low curing temperature with the maximum curing
temperature of 140-200 ℃.
Advantageous Features
1. Easy processing characteristics;
2. Wide alignment adaptability to different types of liquid
crystal molecules;
3. High purity. Na+ <1 ppm; K+ < 1 ppm
4. Excellent adhesion to ITO glass and substrates;
5. Low curing temperature;
6. Excellent thermal stability and thermo-oxidative stability
7. High electric insulating, low dielectric constant and low
dissipation factor.
8. Low thermal expansion coefficient and low stress;
9. High dimension-stability
Typical Applications
1. Alignment agent for Twisted Nematic Liquid Crystal Display
Device
(TN- LCD)
2. Alignment agent for Super-Twisted Nematic Liquid Crystal
Display
Device (STN-LCD) with 240o.of Twisted
angle
3. Alignment agent for Thin Film Transistor driven active matrix
Liquid
Crystal Display Device (TFT-AM-LCD)
Typical processing
The general processing procedure of ZKPI polyimide alignment agent
consists of the following 4 steps:
1. Coating the alignment agent on ITO glass surface;
2. Thermally curing in oven from 80 ℃ to 200 ℃ to produce
PI coating film;
3. Rubbing PI coating film with mechanical method;
4. Fabricating LC cell.
Note: Application of the coatings on ITO glass can be accomplished
in many methods such as dipping, dispersing and so on. The thermally
curing could be performed using a programmed procedure , which
may be modified depending on the end uses of the requirements.
Table 1 ZKPI LCD Alignment Layer Resins
| Feature\Products |
ZKPI-410 |
ZKPI-420 |
ZKPI-430 |
| Appearance |
Pale-yellow Liquid |
Pale-yellow Liquid |
Pale-yellow Liquid |
| Solid content, wt % |
4* |
4* |
4* |
| InherentViscosity, 25 ℃, |
0.8-1.1 |
0.9-1.2 |
1.0-1.2 |
| Solvents |
Organic Mixture |
Organic Mixture |
Organic Mixture |
| Density, 25 ℃ |
1.02-1.04 |
1.03-1.06 |
1.05-1.06 |
| Pretilt angle |
4-5 |
5-10 |
15-20 |
Impurity:
Na+
K+
Cl- |
< 1 ppm
< 1 ppm
< 2 ppm |
< 1 ppm
< 1 ppm
< 2 ppm |
< 1 ppm
< 1 ppm
< 2 ppm |
l Solid content and viscosity of the coatings could be depended
on custom requirements
Table 2 Properties of the Fully Cured ZKPI-300 PI films
| Features\Products |
ZKPI-410 |
ZKPI-420 |
ZKPI-430 |
| Mechanical Property |
|
|
|
Tensile strength, MPa
Elongation, %
Density, g/cm3
Moisture uptake, %
Hardness
Adhesion |
90-110
8-20
1.45
0.3~0.5
H
1 |
100-120
8-20
1.45
0.3~0.5
H
1 |
90-110
8-15
1.45
0.3~0.5
H
1 |
| Thermal Property |
|
|
|
Tg , ℃
Tin, ℃
T5, ℃
T10, ℃
CTE, ×10 -6/ ℃ |
265
>500
>520
>550
25-35 |
282
>500
>520
>550
25-35 |
275
>500
>520
>550
25-35 |
| Electric Property |
|
|
|
Dielectric Constant1 MHz; 0-50% RH
Dissipation factor1 MHz; 0-50% RH
Dielectric strength, V/µmR.T.; 0-50% RH
Volume resistivity, W×cm
Surface resistivity, W |
3.0-3.3
2-8 x 10-3
180-250
>1016
>1015 |
3.0-3.3
2-8 x 10-3
180-250
>1016
>1015 |
3.0-3.3
2-8 x 10-3
180-250
>1016
>1015 |
| Electric-optical Property |
|
|
|
Vsat,v
Vth,v
Contract |
2.49
1.73
1.44 |
2.49
1.73
1.44 |
2.49
1.73
1.44 |
|
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