• Title/Summary/Keyword: Liquid Crystal Polymers

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PDMS기판에 이온빔 처리에 따른 수평 액정의 배향 연구

  • Kim, Yeong-Hwan;O, Byeong-Yun;Kim, Byeong-Yong;Lee, Won-Gyu;Im, Ji-Hun;Na, Hyeon-Jae;Seo, Dae-Sik
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.11a
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    • pp.159-159
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    • 2009
  • We characterize a flexible self-assembled liquid crystal display (LCD) fabricated from a polyimide (PI) alignment layer with polydimethylsiloxane pixel walls. Ion beam (IB) irradiation aligned LC molecules in the PI layer and bonded two flexible plastic substrates in a one-step assembly of the pixel walls. X-ray photoelectron spectroscopic analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy provided chemical and physical evidence for the formation of stable chemical bonds between the PI layer and the PDMS pixel walls in addition to the important maintenance of a uniform 6 um gap between the two substrates without the use of any epoxy resins or other polymers.

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White Light-Emitting Diodes Using Conjugated Polymer Blends

  • Hwang, Do-Hoon;Park, Moo-Jin;Kim, Suk-Kyung;Lee, Chang-Hee;Kim, Yong-Bae
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.585-587
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    • 2004
  • We report the characterization of white light emitting devices fabricated using conjugated polymer blends. Blue emissive poly[9,9-bis(4'-n-octyloxyphenyl) fluorene-2,7-diyl-co-10-(2'-ethylhexyl)phenothiazine-3,7-diyl] [poly(BOPF-co-PTZ)] and red emissive poly(2-(2'-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene) (MEH-PPV) were employed in the blends. The inefficient energy transfer between these blue and red light emitting polymers (previously deduced from the PL spectra of the blend films) enables the production of white light emission through control of the blend ratio. The PL and EL emission spectra of the blend systems were found to vary with the blend ratio. The EL devices were fabricated in the ITO/PEDOT/blend/LiF/Al configuration and white light emission was obtained for one of the tested blend ratios.

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Digitally Printing Electronics with Piezo Ink Jet

  • Creagh, Linda T.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.188-190
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    • 2004
  • As an effort to reduce cost and lead-time and to increase flexibility and responsiveness, manufacturers are using digital printing in numerous process steps. Typically, these processes require the precise dispensing of various fluids. Piezo ink jet printheads are proving to be reliable tools for depositing active materials such as light emitting polymers (LEP) for mobile phone displays and color filter inks for liquid crystal displays. Ink jets are also being used to provide uniform coatings of polyimide alignment layers and spacers for LCDs. Success with legend printing on PCBs using ink jets has encouraged the design of equipment for directly printing both etch resist and solder mask for PCBs. Development of printers for passive components such as capacitors and resistors is underway. This paper will present the attributes of an ink jet printhead designed to a precision deposition tool and discuss how it is being used to digitally print electronic and flat panel display components. Status of commercialization of digital printing will be discussed along with issues to be resolved before wide adoption takes place.

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Dielectric Properties of Liquid Crystalline Polymers and $CaTiO_3-LaAlO_3$ Composites for Embedded Matching Capacitors (내장형 capacitor를 위한 LCP와 $CaTiO_3-LaAlO_3$ 복합재의 유전특성)

  • Kim, Jin-Cheol;Oh, Jun-Rok
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.232-233
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    • 2007
  • We manufactured Liquid Crystal Polymer (LCP) and (1-x)CaTiO3-xLaAlO3 (CT-LA) ceramic composites and investigated dielectric properties to use as embedded capacitor in printed circuit boards and replace LTCC substrate. The dielectric properties of these composites are varied with volume fraction of CT-LA and ratios of CT/LA. Dielectric constants are in the range of 3~15. In addition, we could get low TCC and High Q value that could not achieve in other ceramic-polymer composites. Especially, in composite with x=0.01 and 30 vol% CT-LA, the dieletric constant and Q-value are 10 and 200, respectively. And more TCC is $-28{\sim}300ppm/^{\circ}C$ in the temperature range of $-55{\sim}125^{\circ}C$. We think that this composites can be used high-Q substrate material like LTCC and embedded temperature compensation capacitor in printed circuit boards.

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Synthesis and Photopolymerization of Discotic Liquid Crystals Containing Hydrogen Bondings and Two Polymerizable Groups (두 종류의 중합기와 수소결합을 가지는 원반형 액정의 합성과 광중합)

  • Lee Jun-Hyup;Lee Seung-Jun;Jang Ji-Sun;Jho Jae-Young
    • Polymer(Korea)
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    • v.30 no.5
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    • pp.373-379
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    • 2006
  • Polymerizable discotic liquid crystals containing diacetylene and acryloyl groups were formed through hydrogen bonding between phloroglucinol core and polymerizable pyridine derivatives, and their photopolymerization behavior was investigated. The discotic complexes exhibited discotic columnar and rectangular columnar mesophases depending on the number of aromatic rings. Photopolymerization of the discotic complexes was carried out by UV irradiation in the liquid crystalline state. IR and UV-Vis spectroscopy affirmed that diacetylene and acryloyl groups were selectively Polymerized, and that crosslinked polymers containing short conjugated diacetylene oligomers were produced by 1,4-addition. X-ray diffraction experiment showed that the columnar order in the discotic complex containing phenyl-pyridine moiety was maintained after photopolymerization, and that the rectangular columnar order in he discotic Complex with biphenyl units was changed to the lamellar order.

The Alignment of Liquid Crystals on the Film Surfaces of Soluble Aromatic Polyimides Bearing t-Butylphenyl and Trimethylsilylphenyl Side Groups

  • Hahm, Suk-Gyu;Jin, Kyeong-Sik;Park, Sam-Dae;Ree, Moon-Hor;Kim, Hyung-Sun;Kwon, Soon-Ki;Kim, Yun-Hi
    • Macromolecular Research
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    • v.17 no.12
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    • pp.976-986
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    • 2009
  • With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride(BTPD), and 2,2'-bis(4"-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyirnides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from $0.45{\times}10^{-4}\;-\;1.37{\times}10^{-4}\;J/m^2$ and from $0.86{\times}10^{-5}\;-\;4.26{\times}10^{-5}\;J/m^2$, respectively, depending on the polyimides. The pretilt angles of the LCs were in the range $0.10-0.62^{\circ}$. In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.

Polarization Converting Waveguide Devices Incorporating UV-curable Reactive Mesogen

  • Chu, Woo-Sung;Kim, Sung-Moon;Kim, Jun-Whee;Kim, Kyung-Jo;Oh, Min-Cheol
    • Journal of the Optical Society of Korea
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    • v.15 no.3
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    • pp.289-292
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    • 2011
  • Reactive mesogen (RM) is an organic liquid crystal molecule that can be self-aligned to have an optic axis of birefringence when coated over a polyimide alignment film. A free-standing optical wave-plate film consisting of RM and low-loss optical polymers was fabricated in this work, and the film was inserted across the polymer waveguide to form an integrated optical polarization converter. For convenient evaluation of the polarization converters, a waveguide polarizer and analyzer were fabricated in series. The polarization conversion efficiency was measured to be 25 dB for the wavelength range from 1520 to 1580 nm. The wave plate exhibited a temperature-dependent retardation of $4.5^{\circ}$ for a temperature change from 25 to $100^{\circ}C$.

Development of Process and Equipment for Roll-to-Roll convergence printing technology

  • Kim, Dong-Su;Bae, Seong-U;Kim, Chung-Hwan
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2010.05a
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    • pp.19.1-19.1
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    • 2010
  • The process of manufacturing printed electronics using printing technology is attracting attention because its process cost is lower than that of the conventional semiconductor process. This technology, which offers both a lower cost and higher productivity, can be applied in the production of organic TFT (thin film transistor), solar cell, RFID(radio frequency identification) tag, printed battery, E-paper, touch screen panel, black matrix for LCD(liquid crystal display), flexible display, and so forth. In general, in order to implement printed electronics, narrow width and gap printing, registration of multi-layer printing by several printing units, and printing accuracy of under $20\;{\mu}m$ are all required. These electronic products require high precision to the degree of tens of microns - in a large area with flexible material, and mass productivity at low cost. As such, the roll-to-roll printing process is attracting attention as a mass production system for these printed electronic devices. For the commercialization of this process, two basic electronic ink technologies, such as conductive ink and polymers, and printing equipment have to be developed. Therefore, this paper addressed basis design and test to develop fine patterning equipment employing the roll-to-roll printing equipment and electronic ink.

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High Performance Polyimides for Applications in Microelectronics and Flat Panel Displays

  • Ree Moonhor
    • Macromolecular Research
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    • v.14 no.1
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    • pp.1-33
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    • 2006
  • Polyimides (PIs) exhibit excellent thermal stability, mechanical, dielectric, and chemical resistance properties due to their heterocyclic imide rings and aromatic rings on the backbone. Due to these advantageous properties, PIs have found diverse applications in industry. Most PIs are insoluble because of the nature of the high chemical resistance. Thus, they are generally used as a soluble precursor polymer, which forms complexes with solvent molecules, and then finally converts to the corresponding polyimides via imidization reaction. This complexation with solvent has caused severe difficulty in the characterization of the precursor polymers. However, significant progress has recently been made on the detailed characterization of PI precursors and their imidization reaction. On the other hand, much research effort has been exerted to reduce the dielectric constant of PIs, as demanded in the microelectronics industry, through chemical modifications, as well as to develop high performance, light-emitting PIs and liquid crystal (LC) alignment layer PIs with both rubbing and rubbing-free processibility, which are desired in the flat-panel display industry. This article reviews this recent research progresses in characterizing PIs and their precursors and in developing low dielectric constant, light-emitting, and LC alignment layer PIs.

Thermotropic Liquid Crystalline Properties of α,ω-Bis(4-cyanoazobenzene-4'-oxy)alkanes (α,ω-비스(4-사이아노아조벤젠-4'-옥시)알케인들의 열방성 액정 특성)

  • Jeong, Seung Yong;Kim, Hyo Gap;Ma, Yung Dae
    • Applied Chemistry for Engineering
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    • v.22 no.4
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    • pp.358-366
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    • 2011
  • A homologous series of linear liquid crystal dimers, the ${\alpha},{\omega}$-bis(4-cyano-azobenzene-4'-oxy)alkanes (CATWETn, where n, the number of methylene units in the spacer, is 2~10) were synthesized, and their thermotropic liquid crystalline phase behavior were investigated. The CATWETn with n of 3 and 6 exhibited monotropic nematic phases, whereas other derivatives showed enantiotropic nematic phases. The nematic-isotropic transition temperatures of the dimers and their entropy variation at the phase transition showed a large odd-even effect as a function of n. This phase transition behavior was rationalized in terms of the change in the average shape of the spacer on varying the parity of the spacer. The thermal stability and degree of order in the nematic phase and the magnitude of the odd-even effect of CATWETn were similar to those for the methoxy-, nitro-, and pentyl-substituted dimers, while they were significantly different from those for the monomesogenic compounds, 1-{4-(4'-cyanophenylazo)phenoxy}alkylbromides and the side-chain liquid-crystalline polymers, the poly[1-{4-(4'-cyanophenylazo)phenoxyalkyloxy}ethylene]s. The results were discussed in terms of 'virtual trimer model' by Imrie.