• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.1
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• pp.72-77
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• 2019

The display that provides information to us through the visual sense is a very important information transmission means by intuitively transmitting information, and the liquid crystal display (LCD) is the most widely used information transmission display. In this paper, we studied solvent assisted micromolding as an alternative for the rubbing that is essential to align the liquid crystals in LCD and successfully aligned the liquid crystal molecules by constructing the nanostructures on conventional polyimide alignment layer. When generating the nanostructures on the polyimide film, there was a competitive correlation between the dissolution effect of the polymer by the solvent and the capillary effect of the polyimide molecules into the nanostructures of the mold depending on the process temperature. It was possible to form nanostructures with high step by deriving the optimum temperature. These nanostructures were able to align the liquid crystal molecules uniformly and demonstrated that they could form a desirable pretilt angle.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.199-202
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• 2003

We have investigated the generation of pretilt angle for a nematic liquid crystal (NLC) alignment with rubbing alignment method on two kinds of polyimide (PI) surfaces using thin plastic substrates. The generated NLC pretilt angles on the pre-imidized type PI are about $3.8^{\circ}$ by the rubbing alignment method with thin plastic substrates, However, the pretilt angle measured at about $2.8^{\circ}$ lower on the polyamic acid type PI than by pre-imidized type PI surface with thin polymer film. The tilt angle increases as increasing curring temperature for making polyimide layer using polyamic acid type PI. It was concluded that pretilt angle in the polyimide surface is attributable to the increasing of imide rato.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.81-83
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• 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 LNC is obtained with rubbing alignment method on polyimide surfaces using thin plastic substrates. The generated NLC pretilt angles are about $3^{\circ}$ by the rubbing alignment method on thin plastic substrates, However, the pretilt angle measured at about $1.7^{\circ}$ lower on the glass substrate than by thin plastic substrate. 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 pretilt angle in the polyimide surface is attributable to the increasing of imide rato.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.293-297
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• 1998

The influence of ion implantation on surface properties of polymers was studied. We investigated microhardness, friction, wear and wettablility of polyimide. Energies of 50, 200keV were used with doses range from $1{\times}10^{13} to 1{\times}10^{16} [ions/cm^2]$. The implanted ion species were B, N and Ar. The microhardness of polyimide was increased after implantation for doses of $1{\times}10^{15}\; [ions/cm^2]$. A reduction of the friction coefficient was in most case correlated with a reduction of wear. The contact angles of water for $B^+,N^+$ implanted polyimide decreased from $76^{\circ}C$ to zero, as the fluencies increased at energies of 50 and 200 KeV. However, the contact angle of Ar ion implanted polyimide did not change under ambient room conditions even if the time elapsed. SEM measurement was performed to characterize the modified surface layer.

• Korean Journal of Optics and Photonics
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• v.26 no.4
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• pp.195-202
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• 2015

We developed a reflection ellipsometer so that one can measure the extremely small optical anisotropy of a rubbed polyimide alignment layer, without being disturbed by the residual anisotropy of the substrate. The optical anisotropy of the alignment layer was measured as rubbing strength was increased, and the measured anisotropy was compared to the retardation obtained by using a transmission-type ellipsometer, to confirm the reliability of our reflection ellipsometer. With this measured anisotropy we could verify the formation of an alignment layer by rubbing, and could quantitatively evaluate the formation of the alignment layer.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.472-475
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• 2005

The electrical performances of liquid crystal (LC) cells with chloromethylated polyimide (CMPI) alignment layers were investigated. The CMPI layer was previously reported as a multifunctional layer that does role of LC alignment and planarization layer as well as photo-alignment material with high photosensitivity and excellent thermal stability. The capacitance-voltage (C-V) characteristics of LC cells with CMPI alignment layers were measured. Mechanical rubbing of the CMPI layer did not generate much difference in residual DC when compared to commercial PI. However, the LC cell with photo-oxidation CMPI layer shows a high residual DC value and a corresponding low voltage holding ratio (VHR) due to the photo-induced ionic charges on the alignment layer.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2004.05a
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• pp.101-107
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• 2004

각종 전자기기의 소형화, 고성능화 요구에 따라 회로 또는 기판의 고집적화에 따른 대안으로 도입된 COF(Chip On Film)공정에서 PI(polyimide)/buffer layer/Cu의 접착력 개선을 목적으로 본 연구가 진행 되었다. 그리고 buffer layer로써 Cr을 증착 할 때 부착력의 개선을 목적으로 개질처리를 할 때는 RF plasma장비를 사용하였다. 실험 변수로는 peel strength에 대한 buffer layer의 종류와 증착시간, 표면 개질처리시 $O_2$/Ar비이다. Buffer layer의 종류에 따른 접착력은 Cr보다 Ni이 우수하였고 peel strength와 Cu THK는 같은 buffer layer의 증착 structure에서 비례 관계를 나타냈으며, Cr의 증착 시간과 Cu의 증착 시간을 변수로 peel strength test한 값은 Cr증착시간이 30초, Cu증착시간이 20분일때 40g/mm로 최적의 접착력이 나타났다. 증착전 PI의 개질 처리시 $O_2$/Ar 유량비에 따른 peel strength값은 $O_2$/Ar유량비가 증가 할수록 향상되었으며, 2/5에서 최고값인 58g/mm가 나타났다. 그 이상에서는 오히려 감소하였다.

• 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.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.668-671
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• 2009

Photosensitive polyimide containing methoxy cinnamate derivatives as a photo-alignment layer is investigated. The anisotropy of alignment layer was induced by irradiation linearly polarized UV (LPUV). We studied the effect of the methoxy cinnamate groups on alignment LCs.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.90-93
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• 2004

In this study, we have reported an organic-inorganic hybrid membrane, which exhibits an asymmetric structure consisted of a carbonized skin layer and a polyimide porous substructure, to synthesize a novel gas separation membrane combining high gas permeability and selectivity. Both the gas permeability and selectivity of the carbonized layer significantly enhanced when compared with those determined in the control polyimide.