• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11a
• /
• pp.324-327
• /
• 2001

Liquid crystal alignments on a rubbed polyimide layer were investigated by using optical transmission method. Using this technique, we also studied the pretilt angle of the polymer molecules near the surface of a side-chain polymer layer as a function of the rubbing strength. In particular, we obtained the optical characteristics of liquid crystal orientations and pretilt angles for LC cell photo-aligned by UV as well after rubbing alignment. High pretilt angle of 3.84 degree was obtained on the weekly rubbed polymide layer during UV irradation time of 60min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.398-398
• /
• 2007

The Liquid Crystal (LC) alignment uniformity is very important in LC devices. The alignment mechanism of LC molecules on a rubbed polyimide (PI) surface is very important for both LC fundamental research and application. So, Generally a rubbing method to align LC has been widely used to mass-produce LCD panels. But because rubbing method is contact method between rubbing fabric and indium-tin-oxide glass or flexible substrate, rubbing method has some defects, such as the electrode charges and the creation of contaminating particles. Thus we strongly recommend a non-contact alignment technique for getting rid of some defects of rubbing method. Most recently, the LC aligning capabilities achieved by ion-beam exposure on the organic and nonorganic thin film surface have been reported successfully. In this research, we studied the tilt angle generation and electro-optical performances for a NLC on homeotropic polyimide surfaces with ion-beam exposure. The LC aligning capabilities of a nematic liquid crystal (NLC) on a homeotropic PI surface using a new ion-beam method were studied. On the homeotropic PI surface, the tilt angle of the NLC by exposure ion-beam had a tendency to decrease as increased ion-beam energy density. And, on the homeotropic PI surface, the alignment character of the NLC with respect to ion-beam energy was good. And we achieved satisfactory result for EO character.

• Transactions on Electrical and Electronic Materials
• /
• v.9 no.6
• /
• pp.243-246
• /
• 2008

We have studied the liquid crystal (LC) alignment, the pretilt angle generation, and the annealing behavior for a nematic liquid crystal (NLC) on the homogeneous polyimide (PI) surfaces by using the rubbing method and the ion beam (IB) method. An excellent LC alignment of the NLC on the PI surface with rubbing and IB irradiation were observed. The pretilt angle of NLC on the homogeneous PI surface for the rubbing method is decreased from $4.5^{\circ}$ to $3.5^{\circ}$ as rubbing time is increased, that of the for the IB irradiation method is decreased from $0.5^{\circ}$ to $0.1^{\circ}$ as the time of IB irradiation is increased. After the annealing, the pretilt angles of the rubbed PI surfaces increased up to $4^{\circ}$, these of the IB irradiated PI surfaces little increased. It is considered the side chain of the rubbed PI show the its abilities of the original capacities, while the side chain of the IB irradiated PI cannot show the its abilities of the original capacities due to the IB has already destroyed the side chain of the PI.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.949-952
• /
• 2002

The mechanisms of pretilt angle generation for a nematic liquid crystal (NLC) with negative dielectric anisotropy on the blended polyimide (PI) surface containing trifluoromethyl moiety was studied. High LC pretilt angle on the blended polymer surface with F3 was measured and the pretilt angle increased with rubbing strength. However, the low LC pretilt angle on the blended polymer surface with F1 and F2 was measured. The high LC pretilt angle generated is attributable to trifluoromethyl moiety in backbone structure on the blended PI surface. Therefore, the high pretilt angle of NLC can be achieved by using the blended polymer surface.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.11
• /
• pp.981-984
• /
• 2002

The mechanisms of pretilt angle generation for a nematic liquid crystal (NLC) with negative dielectric anisotropy on the blended polyimide (PI) surface containing trifluoromethyl moiety were studied. High LC pretilt angle on the blended polymer surface with F3 was measured and the pretilt angle increased with rubbing strength. However, the low LC pretilt angle on the blended polymer surface with F1 and F2 was measured. The high LC pretilt angle generated is attributable to trifluoromethyl moiety in backbone structure on the blended PI surface. Therefore, the high pretilt angle of NLC can be achieved by using the blended polymer surface.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.12
• /
• pp.1110-1114
• /
• 2003

We have investigated the generation of pretilt angle for a nematic liquid crystal (NLC) alignment with rubbing alignment method on polyimide surfaces using thin plastic substrates. It was found that monodomain alignment of NLC is obtained with rubbing alignment method on polyimide surfaces using thin plastic substrates. The NLC pretilt angles generated are about 3$^{\circ}$ by the rubbing alignment method on thin plastic substrates, However, the pretilt angle are at about 1.7$^{\circ}$ lower on the glass substrate than on thin plastic substrate. We obtain that AFM (atomic force microscope) image of rubbed PI surface with polymer film has formed the micro-groove structure at the low curring temperature (120$^{\circ}C$). However, no grooves are obtained on the glass substrate at the same temperature. It is considered that this alignment may be attributed to roughness of micro-groove substrate. The tilt angle increases with increasing baking temperature for making polyimide layer using glass substrate. It was concluded that the pretilt angle in the polyimide surface is attributable to the increasing of imidization rato.

• Transactions on Electrical and Electronic Materials
• /
• v.7 no.2
• /
• pp.81-86
• /
• 2006

In this paper, the response surface modeling of the control of the pretilt angle in the nematic liquid crystal on the homogeneous polyimide surface with different surface treatment is investigated. The pretilt angle is one of the main factors to determine the alignment of the liquid crystal display. The pretilt angle is measured to analyze the variation of the characteristics on the various process conditions. The rubbing strength and the hard baking temperature are considered as input factors. After the design of experiments is performed, the process model is then explored using the response surface methodology. The analysis of variance is used to analyze the statistical significance and the effect plots are also investigated to examine the relationship between the process parameters and the response.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.330-330
• /
• 2008

It is widely investigated to liquid crystal (LC) alignment using non-contact alignment method such as ion-beam (IB) irradiation, UV alignment, and oblique deposition. Because conventional rubbing method has some drawbacks. These include defects from dust and electrostatic charges and rubbing scratch during rubbing process. In addition, rubbing method needs additional process to remove these defects. Therefore rubbing-free methods like ion-beam irradiation are strongly required. We studied LC alignment effect on poly imide surface by IB irradiation and electro-optical (EO) characteristics of twisted nematic liquid crystal display (TN-LCD). In this experiment, a good uniform alignment of the nematic liquid crystal (NLC) with the ion-beam exposure on the polyimide (PI) (SE-150 from Nissan Chemical) surface was observed. We also achieved low pretilt angle as a function of ion-beam irradiation intensity. In addition, it can be obtained the good EO properties of the IB-aligned TN-LCD on PI surface. Some other experiments results and discussion will be included in the poster.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.2
• /
• pp.130-132
• /
• 2001

The mechanisms of pretilt angle generation in nematic liquid crystal (NLC) with negative dielectric anisotropy on a rubbed polyimide (PI) surface for homeotropic alignment were studied. The pretilt angle of negative type NLC was smaller than that of the positive type NLC for all rubbing strength regions on the rubbed PI surface. The pretilt angle generated in NLC does not attributable to steric interaction between the fluorine moiety of NLC and the polymer surface on the rubbed PI surface. Consequently, the mechanism of the pretilt angle generation for homeotropic alignment is different from the one for homogeneous alignment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11b
• /
• pp.337-340
• /
• 2001

The control of high pretilt angle far nematic liquid crystal (NLC) with negative dielectric anisotropy on the rubbed blending polyimide (homeotropic and homogeneous alignment) surface were studied. High NLC pretilt angle generated on the blending polyimide (homeotropic polyimide and SE-7492 surface was measured and the NLC pretilt angle increases with blending ratio and rubbing strength. However, the NLC pretilt angle generated on the blending polyimide (homeotropic polyimide and SE-150 surface was not varied. The high pretilt angle the NLC using blending polyimide surface can be acheived.