• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.79-84
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• 2022

As various flexible display products are released, the demand for high-performance colorless and transparent polyimide (CPI) film is continuously increasing. The primary purpose of this study is to establish a systematic procedure for optimizing the optical performance of CPI films by applying the response surface method. After selecting three key factors (monomer type, stirring time for varnish synthesis, and maximum temperature of vacuum furnace for film production) affecting optical performance based on experiences and references, CPI films were manufactured according to the experimental sequence designed by the central composite design, and then the yellowness index (YI) and optical transmittance (Tr) of the films were measured. When producing a CPI film by pouring varnish into a petri dish, the change in optical properties according to thickness should be considered, and there was a meaningful linear relationship between YI and Tr. The species of monomer and the maximum temperature were the critical factors that had an influence on YI and Tr, respectively. It is expected that the procedure proposed in this study can serve as a starting point for CPI film optimization studies considering the other factors that were not considered and responses such as thermal properties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.1904-1911
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• 1999

The most effective material in the shape memory alloy(SMA) is the TiNi alloy, because its shape recovery characteristics are very excellent. We molded the composite material with shape memory function. The fiber of it is $Ti_{50}-Ni_{50}$ shape memory alloy and matrix of it is epoxy resin(Araldite B41, Hardner HT903. Ciba Geigy), its adhesive and optical sensitivity are very excellent. It was assured that the composite material could be used as model material of photoelastic experiment for intelligent materials or structures. In this research, the composite material with shape memory function is used as model material of photoelastic experiment. Photoelastic experimental hybrid method is developed in this research, it is assured that it is useful on the obtaining stress intensity factor and the separation of stress components from only isochromatic data. The measuring method of stress intensity factor of intelligent material by photoelastic experiment is introduced. In the mode I state, we can know that stress intensity factors are decreased more than 50% of stress intensity factor of room temperature when temperature of fiber is greater than 4$0^{\circ}C$, prestrain greater than 5% and fiber volume ratio greater than 0.42% and that stress intensity factors are decreased by 100% when fiber volume ratio is greater than 0.84%, prestrain greater than 5% and temperature greater than 60 $^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.262-268
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• 2009

We investigated the properties of inorganic diatomic films like silicon oxide ($SiO_2$) and zinc oxide (ZnO) and their composite films are packed as a passivation layer around Ca cells on glass substrates by using an electron-beam evaporation technique and rf-magnetron sputtering method. When these Ca cells are exposed to an ambient atmosphere, the water vapor penetrating through the passivation layers is adsorbed in the Ca cells, resulting in a gradual progress of transparency in the Ca cells, which can be represented by changes of the optical transmittance in the visible range. Compared with the saturation times for the Ca cells to become completely transparent in the atmosphere, the protection effects against permeation of water vapor are estimated for various passivation films. The thin composite films consist of$SiO_2$ and ZnO are found to show a superior protection effect from water vapor permeation compared with diatomic inorganic films like $SiO_2$ and ZnO. Also, this inorganic thin composite films are also found that their protection effect against permeation of water vapor can be significantly enhanced by choosing their suitable composition ratio and deposition method, in addition, the main factors affecting the permeation of water vapor through the oxide films are found to be the polarizability and the packing density.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.50-57
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• 2022

Ti-In-Zn-O (TIZO)/Ag/TIZO multilayer transparent electrodes were prepared on glass substrates at room temperature using RF/DC magnetron sputtering. Obtained multilayer structure comprising TIZO/Ag/TIZO (10 nm/10 nm/40 nm) with the total thickness of 60 nm showed a transmittance of 86.5% at 650 nm and a sheet resistance of 8.1 Ω/□. The multilayer films were expected to be applicable for use in energy-saving smart window based on polymer-dispersed liquid crystal (PDLC) because of their transmittance properties to effectively block infrared rays (heat rays). We investigated the effects of the content ratio of prepolymer, the thickness of the PDLC coating layer, and the ultraviolet (UV) light intensity on electro-optical properties, and the surface morphology of polyester acrylate-based PDLC systems using new TIZO/Ag/TIZO transparent conducting electrodes. A PDLC cell with a thickness of 15 ㎛ PDLC layer photocured at an UV intensity of 1.5 mW/cm² exhibited good driving voltage, favorable on-state transmittance, and excellent off-haze. The LC droplets formed on the surface of the polymer matrix of the PDLC composite had a size range of 1 to 3 ㎛ capable of efficiently scattering incident light. Also, the PDLC-based smart window manufactured using TIZO/Ag/TIZO multi-layered transparent electrodes in this study exhibited a light brown, which will have an advantage in terms of aesthetics.

• Polymer(Korea)
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• v.33 no.4
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• pp.347-352
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• 2009

Charged organic-inorganic composite particles were prepared for the application to electrophoretic display technology such as electronic paper. $TiO_2$ and $Co_3O_4$ particles were used for core particles and were coated with poly(methyl methacrylate) by dispersion polymerization. Composite particles were endowed with charge moiety for electrophoresis; positive charge for $TiO_2$ and negative charge for $Co_3O_4$ composite particles. Scanning electron microscopic results revealed that the charged composite particles have spherical shape. Densities of the composite particles were controlled to be that of medium of electrophoresis. Density of $TiO_2$ particle changed from 4.02 to 1.44 g/$cm^3$ after the polymer coating, and that of $Co_3O_4$ particles changed from 6.11 to 1.49 g/$cm^3$. Urea, melamine, and formaldehyde were used as wall materials for capsule, and microcapsule containing black or white particles inside were prepared by in-situ polymerization. Microcapsule showed the inspection by a video microscope demonstrated the formation of uniform transparent capsules.

• The Journal of the Acoustical Society of Korea
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• v.38 no.4
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• pp.459-466
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• 2019

When a laser pulse is irradiated on a CNT (Carbon Nanotube) and PDMS (Poly dimethylsiloxane) composite coated on a transparent PMMA (Poly methyl methacrylate) substrate, a strong ultrasonic wave is generated due to the thermoelastic effect. In this paper, the thermoacoustic theory related to the wave generation by the CNT/PDMS composite was established. The waveforms of ultrasonic waves when a laser pulse having a Gaussian waveform is irradiated on the composite with a thickness of $20{\mu}m$ were numerically simulated. From the results, it was confirmed that ultrasonic shock waves can be generated from the CNT/PDMS composite and the waveforms are changed little even if the physical properties of the composite are changed by ${\pm}20%$. It was found that the peak positive and negative pressures increase as the thermal expansion coefficient increases, or as density, heat capacity and sound speed decreased. However, those changes were not so sensitive with thermal conductivity. In addition, the physical properties of the CNT/PDMS composite fabricated in this study were estimated from the comparison of the measurement and simulation results.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.978-980
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• 2004

We report the preparation and properties of polymer paste solutions with CNTs using conventional paste forming process. Electrospinning has been used for the fabrication of nano-fiber composite. In this process, dispersion of CNTs is very important matter. So, we emphasize the necessity of dispersion of CNTs in the solution and investigate effects of process parameters of electrospinning. The advantage of simple electrospinning process will be discussed..

• Journal of the Korean Graphic Arts Communication Society
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• v.13 no.1
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• pp.93-104
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• 1995

Liquid crystal-polymer composite(LCPC) films promising new materials for both projection displays and vision product. LCPC films consist of a continous liquid crystal phase embedded in a three- dimensional network of polymer matrix. The liquid crystal in these LC phases can be elecrtrically switched giving rise to an opaque scattering off-stats and a transparent, non-scatting on- stats. In this work. a premixture is composed of LC, UV-curable monomer and photonitiator. LCPC films are formed by photopolymerization induced phase separation from this premixture. In conclusion, structure and electro-optical properties of LCPC films strongly depends on the selection of monomer, LC content and curing rate.

• Journal of the Korean Graphic Arts Communication Society
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• v.14 no.1
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• pp.89-114
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• 1996

Liquid crystal-polymer composite(LCPC) films consisting of a continuous LC phase embedded in a three-dimensional network of polymer matrix are formed by photopolymerization-induced phase separ on. The LCPC films are switched from a light-scattering stats to a highly transparent stats on the application of electric fields. Since the alignment of LC molecular determines the electro-optical properties of films, the requirement for good contrast is to generate the nematic phase at high concentration. On the other hand, the concentration of UV-curable monomer must be increased above some critical value to from the flexible matrix of unbounded polymer. The mixing ratio of LC and UV-curable monomer affects the electro-optical and viscoelastic properties of LCPD films in two opposing ways. By controlling the phase separation process, at an LC fraction of 0.7, the maximum performance of LCPC films has been achieved, the response time of which is 2ms on the application of electric fields.

• Journal of the Korean Ceramic Society
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• v.29 no.9
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• pp.739-749
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• 1992

The sols prepared by dialyzing solutions, in which the hydrolyzed precipitates of TEOT or directly Ti(OC3H7)4 were resolved, were the nanoparticulate sol with the average particle size less than 7 nm and the anatase crystal phase. In the pH range of 1.5 to 2.9, the particle size of the nanoparticulate TiO2 sols (0.09 mol/ι) increased gradually upto 15 nm~26nm with the increase of pH in the initial aging state but the sols were transparent all the time, and stable without growin any more after 30 days. When the slipcasted porous alumina tubes were coated by the sol-gel dipping method, the minimum particle size and the aging time for forming the coated gel layer at the given pH were optimized. For obtaining the very thin crack-free and reproducible membrane coating, the use of a nanoparticulate TiO2 sol (0.09 mol/ι) aged for about 30 dyas at pH=2.0 was found to be the best.