• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.7
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• pp.625-629
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• 2000

We synthesized a new copoly (PM4Ch-ChMA) copoly(poly(4-methacryloyloxy) chalcone-cholesteryl methacrylate) having chalconyl and cholesteryl moiety for homeotropic liquid crystal(LC) alignment. Pretilt angles of nematic(N) LC generated by linearly polarized UV exposure on the copolymer surfaces were investigated. Good thermal stabilities of the synthesized copolymer were obtained by TGA (Thermogravimetric Analysis) measurement. Pretilt angles of the NLC decreased with increasing UV exposure time on the copolymer surfaces. We consider that the pretilt angle of the NLC is attributed to increased chalcone by increased UV exposure time. High pretilt angle of the NLC is attributed to increased chalcone by increased UV exposure time. High pretilt angle of 81$^{\circ}$was observed after the UV exposure for 3 min.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.950-953
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• 2000

Aligning capabilities of nematic liquid crystal(NLC) using an in-situ photo-alignment method with obliquely polarized UV exposure on a polyimide (PI) surface for homeotropic alignment were studied. The high angle for NLC can be measured by obliquely UV exposure of 30°on the PI surface for 10∼20 min. The pretilt angle of NLC generated using the in-situ photo-alignment was higher than that of a conventional photo-alignment method. Finally, we suggest that the control of pretilt angle in NLC with obliquely polarized UV exposure during imidization of the polymer for homeotropic alignment is promising method to generate high pretilt angle.

• Transactions on Electrical and Electronic Materials
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• v.9 no.3
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• pp.120-122
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• 2008

We have studied the tilt angle generation on the homeotropic polyimide (PI) surface using a low intensity ion beam source as a function of incident angle. An excellent LC alignment of nematic liquid crystal (NLC) on the PI surface with ion beam exposure for all incident angles was observed. The tilt angle of NLC on the homeotropic PI surface for all incident angles was from 90 to 88 degree was observed. Also the tilt angle of NLC on the homeotropic PI surface with ion beam exposure of 400 eV had a tendency to increase as ion beam energy incident angle become more instance from 45 degree. Finally, a good LC alignment thermal stability on the homeotropic PI surface with ion beam exposure can be achieved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.595-599
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• 2001

The mechanisms of pretilt angle generation for a nematic liquid cystal (NLC) using a photodimerization method with obliquely polarized UV exposure on the various new photo-crosslinkable polymer were studied. A good thermal stability of all the photo-crosslinkable polymers was obtained by thermogravimetric analysis (TGA) measurement until 450$\^{C}$. High pretilt angle of the NLC was observed by polarized UV exposure on the three kinds of the photo-crosslinkable polymers containing biphenyl(BP), decyl(de), and cholesteryl(chol) group, respectively. However, the low pretilt angle of the NLC was measured by obliquely polarized UV exposure on the two kinds of the photo-crosslinkable polymers containing fluorine and chalcone group. Consequently, the high NLC angle generated is attributable to the biphenyl and alkyl moieties, and photo-dimerized chalcone group of the photopolymer.

• Transactions on Electrical and Electronic Materials
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• v.7 no.3
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• pp.145-148
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• 2006

In this study, the response surface modeling of the pretilt angle control using in-situ photoalignment method with oblique UV exposure .on plastic substrate is investigated. The pretilt angle is the main factor to determine the alignment of the liquid crystal display. The response surface model is used to analyze the variation of the pretilt angle on the various process conditions. Heating temperature and UV exposure time are considered as input factors. The liquid crystal (LC) pretilt angle increased with increasing heating temperature and UV exposure time. 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.

• The Journal of the Korea Contents Association
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• v.11 no.9
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• pp.453-458
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• 2011

This study aimed to figure out the change of exposure dose to the radiologist according to the C-arm angle change. For the exam it was fixed with 101 kvp and 4.9mA for the exposure time with 3 seconds and 5 seconds respectively. C-arm Tube was located both under and over, then the average was taken after performing for 5 times with the change of angle from -30 degree to 0, 30, 60 and 90 degree. The detector measured in 160cm high from the position of the radiologist who operates the C-arm. The measurement was shown its highest result at -30 degree followed by 0, 30, 60, 90 from the highest order. Over tube method is higher than under tube method. Therefore, to reduce the exposure dose of the radiologist, it is required for using under tube method instead of over tube method. When the angle change is made, it is recommended to use the angle that tube is growing further apart from the radiologist. And it is also necessary to shorten exposed time as much as possible to create the same quality image and also to reduce the exposure dose.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.4
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• pp.341-344
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• 2001

We synthesized a photo-crosslinkable polymide (polymide (PI)-chalcone-biphenyl (BP)) based polymer and control of pretilt angle for a nematic liquid crystal (NLC) using two kinds of the photodimerization methods by polarized UV exposure the photopolymer surfaces was studied. Pretilt angle of the NLCs using a conventional photodimerization method could be varied between 0$^{\circ}$ and 3$^{\circ}$, by controlling the condition of UV exposure. Pretilt angle of the NLCs using the conventional photodimerization method was higher than a in-situ photodimerization method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.336-339
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• 2000

Effects of liquid crystal (LC) alignment using an in-situ photo-alignment method by linearly polarized UV exposure during imidization of polyirnide (PI) on the two kinds of PI surfaces with side chain were investigated. The generated pretilt angle in nematic (N) LC using an in-situ photo-alignment method was smaller than that of a conventional photo-alignment method for short UV exposure time. Also, the pretilt angle of the NLC using an in-situ photo-alignment method increases with increasing UV exposure time on the two kinds of the PI surfaces. Finally, the pretilt angle of NLC can be improved by annealing treatment.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.139-144
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• 2005

Because of the photorefractive recording dynamics, each newly recorded hologram partially erases all previously stored image. Thus achieving the desired diffraction efficiency profile for the entire sequence after all images have been recorded requires exposure time schedule. The often cited classical exposure-schedule model predicts a rising-exponential build-up and an exponential decay in An with an exposure time. However because we cannot directly measure the An, it's difficult to establish the relation of both. In this paper, we deduce the relation of diffraction efficiency and exposure time from experiment data and suggest an algorithm to make time schedule profile in angle/fractal multiplexing of holographic data storage. After that, we present simulated result with equal hologram diffraction efficiency for a sequence of 250 holograms recorded by angle/fractal multiplexing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.10
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• pp.871-875
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• 2000

Effects of liquid crystal (LC) alignment using a in-situ photoalignment method by polarized UV exposure on a polyimide (PI) surface with medium side chain were studied. The generated pretilt angle in nematic(N) LC using a in-situ photoalignment method was smaller than that of a conventional photoalignment method for short UV exposure time. Also, the pretilt angle of NLC using a in-situ photoalignment method increases with increasing UV exposure time on the PI surfaces. Finally, the pretilt angle of NLC can be improved by annealing treatment.