• Composites Research
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• v.13 no.4
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• pp.11-18
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• 2000

This study is mainly concerned with friction and wear properties for the piston ring of non-lubricating air compressor which made of PTFE-polyimide composites. At the PTFE and polyimide alone mixture specimens, PTFE80%-polyimide20%, which shows the lowest mean friction coefficient and specific wear rate at 0.94m/s sliding speed. In case of the specific wear rate, copper30% specimen shows the lowest value of 2.537-5(mm3/Nm) in all specimens. It considered that the friction coefficient is affected by generating speed and quantity of wear film. In case specific wear rate, it is attributed to the fact that the surface hardness of wear film is proportioned to specific wear rate.

• 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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• 2001.11b
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• pp.209-212
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• 2001

Polyimide(PI) films have been considered as the interlayer dielectric materials due to low dielectric constant, low water absorption, high gap-fill and planarization capability. The PI mm Was etched with using inductively coupled plasma (ICP). The etching characteristics such as etch rate and selectivity were evaluated to gas mixing ratio. High etch rate was $8300{\AA}/min$ and vertical profile was approximately acquired $90^{\circ}$ at $CF_{4}/(CF_{4}+O_{2})$ of 0.2. The selectivies of polyimide to PR and $SiO_{2}$ were 1.2, 5.9, respectively. The etching profiles of PI films with an aluminum pattern were measured by a scanning electron microscope (SEM). The chemical states on the PI film surface were investigated by x-ray photoelectron spectroscopy (XPS). Radical densities of oxygen and fluorine in different gas mixing ratio of $O_{2}/CF_{4}$ were investigated by optical emission spectrometer (OES).

• Korean Membrane Journal
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• v.4 no.1
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• pp.25-35
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• 2002

The gas permeation properties have been studied on carbon molecular sieve (CMS) membranes prepared by pyrolysis of P84 polyimide under various conditions. P84 polyimide shows high permselectivities (O$_2$/N$_2$= 9.17 and CO$_2$/N$_2$= 35) for various gas pairs and has a good processibility because it is easily soluble in high polar solvents such as N-methylpyrrolidinone (NMP), dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc). After pyrolysis under Ar flow, the change in the heating rate was found to affect the gas permeation properties to some extent. The permeabilities of the selected gases were shown to be in the order He ＞ CO$_2$＞ O$_2$＞ N$_2$for all the CMS membranes, whose order was in accordance with the order of kinetic gas diameters. It also revealed that the pyrolysis temperature considerably influenced the gas permeation properties of the CMS membranes derived from P84 polyimide. The CMS membranes pyrolized at 700$\^{C}$ temperature exhibited the highest permeability with relatively targe loss in permselectivity. This means that the pyrolysis temperature should be varied in accordance with target gases to be separated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.11
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• pp.1998-2003
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• 2007

A flexible but implantable polyimide-based neural implant was fabricated for reliable and stable long-term monitoring of neural activities from brain. The developed neural implant provides 3-dimensional (3D) $3{\times}3$ structure, avoids any hand handling, and makes the insertion more efficient and reliable. Any film curvature caused by residual stress was not observed in the electrode. The 3D flexible polyimide electrode penetrated a dense gel whose stiffness is close to live brain tissue, because a ${\sim}1{\mu}m$ thick nickel was electroplated along the edge of the shank in order to improve the stiffness. The recording sites were positioned at both side of the shank to increase the probability of recording neural signals from a target volume of tissue. Impedance remained stable over 72 hours because of extremely low moisture uptake in the polyimide dielectric layers. At electrical recording test in vitro, the fabricated electrode showed excellent recording performance, suggesting that this electrode has the potential for great recording from neuron firing and long-term implant performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.105-108
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• 1993

Behavior of electron in polyimide LB films of Al/polyimide LB films/Au (MIM) structures is reported in the present paper. From experimental results, it is known that there is a process where electron moves from Au electrode to Al electrode through LB film. And the electrons are presumed to move by diffusion since the direction is opposite to electric field.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1715-1718
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• 2006

Evaluating method of the device parameters of liquid crystal display (LCD) by means of the renormalized transmission spectroscopic ellipsometry is demonstrated. Dielectric and elastic constant, threshold voltage, pretilt angle, cell gap and Anchoring strength coefficients can be evaluated from the measurement of ellipsometric parameters measured by the symmetrically oblique incidence transmission ellipsometry (SOITE). Furthermore, rapid evaluating method for rubbed polyimide film is also demonstrated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.517-518
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• 2006

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.661-664
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• 2004

In this paper, it was demonstrated that the organic thin film transistors with the organic gate insulators were fabricated by vapor deposition polymerization (VDP) processing. The configuration of OTFTs was a staggered-inverted top-contact structure and gate dielectric layer was deposited with 0.45 ${\mu}m$ thickness. In order to form polyimide as a gate insulator, VDP process was also introduced instead of spin-coating process. Polyimide film was respectively co-deposited with different materials. One was from a 4,4'-oxydiphthalic anhydride (ODPA) and 4, 4'-oxydianiline (ODA) and the other was from 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and ODA. And it was also cured at 150 $^{\circ}C$ for 1 hour followed by 200 $^{\circ}C$ for 1 hour. Electrical characteristics of the organic thin-film transistors were detailed comparisons between the ODPA-ODA and the 6FDA-ODA which were used as gate insulator.

• Transactions on Electrical and Electronic Materials
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• v.6 no.3
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• pp.106-109
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• 2005

We have investigated the generation of pretilt angle for a nematic liquid crystal (NLC) alignment with in-situ photoalignment method on polyimide (PI) surfaces using polymer films. Especially, we studied in-situ photoalignment changing heating temperature from $50^{\circ}C\;to\;120^{\circ}C$ on the polymer film. The LC aligning capabilities and pretilt angle on the polymer substrates were better than those on the glass substrate using in-situ photoalignment method. It is considered that this increase in pretilt angle may be attributed to the roughness of the micro-groove substrate induced by the in-situ photoalignment. As temperature of heated subtrate and UV exposure time increase, pretilt angle of the cell used polymer film increased. It is considered that the heating temperature of substrate is attributed to generate pretilt angle. Also, electro-optical performances of the in-situ photoaligned TN cell using the polymer substrate are almost the same as that of the TN cell using the glass substrate.