• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.130-131
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• 2005

• Polymer(Korea)
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• v.27 no.5
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• pp.484-492
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• 2003

How the characteristics and stability of the rubbing-induced alignment of nematic liquid crystals (LCs) relate to the interfacial characteristics of LC-polyimide has been studied. The characteristics of the LC alignment (such as the LC texture, the pretilt angle, and the anchoring energy) and their thermal stability have been investigated for 5 polyimides synthesized for this work. The work showed that the rubbed polyimide alignment layer induces the strong LC anchoring and that the characteristics and stability of LC alignment are determined by the short-ranged interactions between LC and polyimide molecules at the alignment layer surface. The increased flexibility of the polyimide accelerates thermal imidization, increases the pretilt angle, and improves the alignment stability. It also turned out that fluorination of the polyimide tends to deteriorate the alignment uniformity and stability. No distinct differences in the alignment characteristics were shown for the aromatic- and alicyclic-dianhydride polyimides.

• Polymer(Korea)
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• v.35 no.4
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• pp.350-355
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• 2011

A soluble polyamide containing photosensitive l,4-phenylenediacrylic acid (PDA) in main chain with biphenyl moiety was synthesized. The chemical structure of synthesized polyamide was investigated by means of $^1H$ NMR spectroscopy. The polymer was stable up to $280^{\circ}C$ and soluble in organic solvents, giving a good quality of thin films. The photoreaction of unpolarized LTV irradiated films was investigated by means of UV-vis absorption spectroscopy and FTlR spectroscopy, and liquid crystals (LCs) alignment property was examined by exposing to linearly polarized UV light (LPUVL) of 260~380 nm. The polyamide in film has excellent photoreactivity to unpolarized UV light. Direction selective photoreaction of PDA moiety in Lhe film was found to further induce nematic liquid -crystals to align along a perpendicular direction with respect to the electric vector of LPUVL, regardless of exposure energy of LPUVL. In addition, pretilt angle was measured by means of crystal rotation method. LPUVL-exposed polymer film induced the alignment of liquid-crystals (LC) with a pretilt angle of 0.2~$0.5^{\circ}$.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.89-90
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• 2006

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.293-294
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• 2009

We proposed a novel single gap transflective liquid crystal display (LCD) using liquid crystal with negative dielectric anisotropy. We designed cell structure driven by fringe electric field in the transmissive (T) part and vertical electric field in the reflective (R) part. In the device, high surface pretilt angle of the LC in the R-part is achieved through polymerization of an UV curable reactive mesogen (RM) monomer at surfaces. By optimizing the parameters, a newly developed transflective display has characteristics such as single gap and single gamma curve.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.51-52
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• 2008

A single gap transflective liquid crystal display(LCD) driven by fringe electric field in the transmissive(T) region and vertical electric field in the reflective(R) region was designed. Because the pretilt angle is formed in $53^{\circ}$ through polymerization of an UV curable reactive mesogen(RM) monomer at the surface, the effective cell retardation $(d{\Delta}n_{eff})$ value of the R region becomes half of that in the T region where the LCs are homogenously aligned. Consequently, a transflective display driven by a vertical and fringe electric field with a single cell gap and single gamma curves is realized.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.280-281
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• 2006

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a Titanium dioxide ($TiO_2$) thin film by rf magnetron sputtering system for 15min under various rf power. A very low pretilt angle by ion beam exposure on the $TiO_2$ thin film was measured. A good LC alignment by the ion beam alignment method on the $TiO_2$ thin film surface was observed at annealing temperature of $200^{\circ}C$, and the alignment defect of the NLC was observed above annealing temperature of $250^{\circ}C$. Consequently, the low NLC pretilt angle and the good thermal stability of LC alignment by the ion beam alignment method on the $TiO_2$ thin film by sputter method as various rf power condition can be achieved.

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

• Transactions on Electrical and Electronic Materials
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• v.6 no.1
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• pp.22-24
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• 2005

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of the SiC (Silicon Carbide) thin film. The SiC thin film exhibits good chemical and thermal stability. The good thermal and chemical stability makes SiC an attractive candidate for electronic applications. A vertical alignment of nematic liquid crystal by ion beam exposure on the SiC thin film surface was achieved. The about $87{\circ}$ of stable pretilt angle was achieved at the range from $30{\circ}$ to $45{\circ}$ of incident angle. The good LC alignment is maintained by the ion beam alignment method on the SiC thin film surface at high annealing temperatures up to $300{\circ}C$.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.409-412
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• 2002

We found that polyimide surfaces bombarded by a low energy argon ion beam align liquid crystals. The pretilt angle of the liquid crystals is controlled by ion beam parameters, such as the energy of the incident ions, the angle of incidence, exposure time and current density. The alignment direction of liquid crystal on substrates corresponded to ion beam direction. By argon ion beam the pretilt angle of the liquid crystals was controlled between $0.5^{\circ}$ and $4^{\circ}$for SE-3140 under the proper conditons. By the atomic force microscope (AFM), polyimide surfaces before and after bombarded by ion beam are compared.