• Title/Summary/Keyword: Thermal diffusing

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Preparation and Characteristics of PC and PMMA-Based Diffusers for LED Backlight Unit (PC 및 PMMA 수지를 이용한 LED 백라이트용 확산판의 제조 및 특성 연구)

  • Kim, Nam Yi;Kim, Hyo Jin;Kim, Dong Won;Jo, Jae Hyun;Kim, Seong Woo
    • Journal of the Semiconductor & Display Technology
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    • v.11 no.1
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    • pp.21-27
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    • 2012
  • The optical diffuser for direct-lit LED backlight unit was prepared by using extrusion compounding followed by thermoforming process. Poly(methyl methacrylate) (PMMA) with superior optical characteristics and polycarbonate (PC) with good thermal property were used as base resins, and crosslinked polystyrene (PS) and PMMA beads as diffusing agents were incorporated into resin matrix to derive light scattering and diffusing action. In the compounded plate, the diffusing beads were observed to be dispersed uniformly and distinctly in the continuous phase. The inclusion of polymeric beads up to 3 wt% substantially enhanced the optical characteristics such as luminance, luminance uniformity, haze for the diffuser. Two different diffusers of PC and PMMA-based compound with various compositions were compared in terms of measured optical, thermal, and mechanical properties, which would be expected to be utilized for the industrial application of LED backlight unit.

Microstructure and Dielectric Properties of (Sr.Ca)$TiO_3$-based Ceramics on the thermal diffusing time (열확산 시간에 따른 (Sr.Ca)$TiO_3$계 세라믹의 미세구조 및 유전특성)

  • Kang, Jae-Hun;Kim, Chung-Hyeok;Song, Min-Jong;Choi, Woon-Shik
    • Proceedings of the KIEE Conference
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    • 2001.07c
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    • pp.1387-1389
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    • 2001
  • In this paper, the microstructure and the dielectric properties of the $Sr_{1-x}Ca_xTiO_3$($0{\leq}x{\leq}0.2$)-based grain boundary layer ceramics were investigated. The 2nd phase formed by thermal diffusing from the surface lead to a very high apparent dielectric constant, ${\varepsilon}_r$ > 50000, and tan$\delta$ < 0.05, $\Delta$C < ${\pm}$ 10%.

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A study on the dielectric and electrical conduction properties of$(Sr_{1-x}.Ca_x)TiO_3$ grain boundary layer ceramics ($(Sr_{1-x}.Ca_x)TiO_3$입계층 세라믹의 유전 및 전기전도특성에 관한 연구)

  • 최운식;김충혁;이준웅
    • Electrical & Electronic Materials
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    • v.8 no.5
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    • pp.611-618
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    • 1995
  • The (Sr$_{1-x}$ .Ca$_{x}$)TiO$_{3}$+0.6[mol%]Nb$_{2}$O$_{5}$ (0.05.leq.x.leq.0.2) ceramics were fabricated to form semiconducting ceramics by sintering at about 1350[.deg. C] in a reducing atmosphere(N$_{2}$ gas). Metal oxides, CuO, was painted on the both surface of the specimens to diffuse to the grain boundary. They were annealed at 1100 [.deg. C] for 2 hours. The 2nd phase formed by thermal diffusing from the surface lead to a very high apparent dielectric constant. According to increase of the frequency as a functional of temperature, all specimens used in this study showed the dielectric relaxation, and the relaxation frequency was above 106 [Hz], it move to low frequency with increasing resistivity of grain. The specimens showed three kinds of conduction mechanisms in the temperature range 25-125 [.deg. C] as the current increased: the region I below 200 [V/cm] shows the ohmic conduction. The region rt between 200 [V/cm] and 2000 [V/cm] can be explained by the Poole-Frenkel emission theory, and the region III above 2000 [V/cm] is dominated by the tunneling effect.fect.

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Effect of BLU Ingredient on Electrical and Optical Properties of Light Diffusing Film used for TFT-LCD TV (백라이트 유니트 구성요소가 TFT-LCD TV용 광확산필름의 전기, 광학적 특성에 미치는 영향)

  • Ahn, Cheol-Heung;Kim, Geon-Joong
    • Applied Chemistry for Engineering
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    • v.17 no.4
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    • pp.397-402
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    • 2006
  • We have investigated the effect of each ingredient in the light diffusing film (LDF) which was used as backlight unit (BLU) of TFT-LCD TV on physical, electrical, thermal and optical properties of LDF. In anti-blocking layer, the excellent anti-blocking ability was obtained when 0.5~1.5 wt% of acrylic bead was added, and good decay-time and water-stability were shown when 0.8 wt% of tertiary ammonium salt was added. Optimal results for adhesion strength, curing rates and flexibility on the surface of PET film have been obtained in the light diffusing layer by using acrylic polyol as a binder resin, and by addition of 30~35 wt% non-yellowing type HDI crosslinker. In addition, the highest normal luminance value was obtained by addition of 250 wt% poly-dispersive polystyrene ($20{\mu}m$ PS) and polymethylmethacrylate ($20{\mu}m$ PMMA) beads into the binder resin (100 wt%). The higher normal luminance could be got for PMMA beads than PS beads because of the transmittance difference.

Numerical Study of Three-Dimensional Compressible Flow Structure Within an S-Duct for Aircraft Engine Inlet

  • Cho, Soo-Yong;Park, Byung-Kyu
    • International Journal of Aeronautical and Space Sciences
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    • v.1 no.1
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    • pp.36-47
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    • 2000
  • Three-dimensional compressible turbulent flow fields within the passage of a diffusing S-duct have been simulated by solving the Navier-Stokes equations with SIMPLE scheme. The average inlet Mach number is 0.6 and the Reynolds number based on the inlet diameter is $1.76{\times}10^6$ The extended $k-{\varepsilon}$ turbulence model is applied to modeling the Reynolds stresses. Computed results of the flow in a circular diffusing S-duct provide an understanding of the flow structure within a typical engine inlet system. These are compared with experimental wall static-pressure, total-pressure fields, and secondary velocity profiles. Additionally, boundary layer thickness, skin friction values, and streamlines in the symmetric plane are presented. The computed results depict the interaction between the low energy flow by the flow separation and the high energy flow by the reversed duct curvature. The computed results obtained using the extended $k-{\varepsilon}$ turbulence model.

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Influence of Heat Diffusing Temperature for a (Sr.Ca)$TiO_3$-based Ceramics on Voltage-Current Properties ((Sr.Ca)$TiO_3$계 세라믹의 전압-전류 특성에 미치는 열확산 온도의 영향)

  • 강재훈;박용필;장경욱;오재한;최운식
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.07a
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    • pp.697-700
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    • 2001
  • In this paper, the structural and electrical properties of the Sr$_{1-x}$ Ca$_{x}$TiO$_3$ (0$\leq$x$\leq$0.2) (0$\leq$r$\leq$0.2)-based grain boundary layer ceramics were investigated by X-ray, SEM and V-I system. Increasing the Ca content, the average grain size and the lattice constant were decreased. The relative density of all specimens was >96%. The 2nd phase formed by thermal diffusing from the surface lead to a very excellent electrical properties, that is, $\varepsilon$$_{r}$>50000, tan$\delta$<0.05, $\Delta$C< $\pm$ 10%.\pm$ 10%.%.

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Application of rapid thermal annealing process to the aluminum induced crystallization of amorphous silicon thin film (비정질 실리콘의 부분적 알루미늄 유도 결정화 공정에서의 급속 열처리 적용 가능성)

  • Hwang, Ji-Hyun;Yang, Su-Won;Kim, Young-Kwan
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.29 no.2
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    • pp.50-53
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    • 2019
  • In this study, polycrystalline silicon thin film useful for the solar cells was fabricated by AIC(Aluminum Induced Crystallization) process. A diffusing barrier for this process is prepared with $Al_2O_3$. For the maximization of the grain size of the polycrystalline silicon, a selective blasting of the $Al_2O_3$ diffusing barrier was conducted before annealing treatment. The heat treatment for the activation of the amorphous-Si (a-Si) layer was carried out with Rapid Thermal Annealing (RTA) process. Crystallization of the a-Si layer was analyzed with XRD. It was confirmed that a-Si was crystallized at $500^{\circ}C$ and the silicon crystal is observed to be formed and the grain size of the polycrystalline silicon was observed to be $15.9{\mu}m$.

Evaluation of Indoor Thermal Comfort for Ceiling Type System Air-Conditioner with Various Discharge Angles (천장형 시스템 에어컨의 토출방향 변화에 따른 실내 열쾌적성 평가)

  • Lee, Jin-Hyung;Kim, You-Jae;Choi, Weon-Seok;Park, Sung-Kwan;Youn, Baek;Kim, Youn-Jea
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.1180-1185
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    • 2006
  • Modern people spend most of time at indoor space, such as office or classroom. Especially, occupants are exposed to the airtight indoor air quality (IAQ) for a long time, At present, many studies on the air-conditioning systems are more focused on the individual thermal comfort than the thermal efficiency due to increase of the concern of health. There are several factors which are influenced thermal comfort, such as temperature, humidity, convection and air movement, etc. Also, the individual factor, such as age, gender, Physical constitution and habit, should be considered. The 4-way cassette type air conditioner is known to bring out better performance about thermal comfort than the traditional one. This study is performed on the higher ceiling environment than the common buildings or classrooms. Also, this study analyzed on the Indoor thermal comfort by diffusing direction of 4-way cassette air conditioner with various discharge angles, $45^{\circ},\;50^{\circ},\;55^{\circ}$ and $60^{\circ}$. Using a commercial code, FLUENT, three-dimensional transient air thermal flow fields are calculated with appropriate wall boundary conditions and standard $k-{\epsilon}$ turbulence model. Results of velocity and temperature distributions are graphically depicted with various discharge angles.

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Improvement of Optical and Thermo-mechanical Properties of Polycarbonate-based Diffusers for LED Backlight Unit by Incorporation of Porous Silica Particles (실리카 다공체에 의한 발광다이오드 백라이트 유닛용 폴리카보네이트계 확산판의 광학 및 열-기계적 물성의 향상 연구)

  • Kim, Hyo Jin;Kim, Dong Won;Kim, Seong Woo
    • Polymer(Korea)
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    • v.36 no.6
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    • pp.761-767
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    • 2012
  • The polycarbonate (PC)-based optical diffusers for direct-lit LED backlight unit were prepared by using extrusion compounding followed by compression molding process. The application of inorganic porous silica particles as a diffusing agent in addition to conventional poly(methyl methacrylate) (PMMA) beads was attempted, and the optical, thermal, and mechanical properties of the prepared diffusers were investigated. The morphological observations revealed that the diffusing agents could be uniformly dispersed in the PC matrix without agglomeration by high shear stress generated during extrusion process. The incorporation of the porous silica particles mixed with PMMA beads remarkably enhanced the luminance uniformity with respect to both location and view angle for the diffuser, while minimizing the reduction in the absolute luminance, as compared with the diffuser containing only PMMA beads. In addition, thermal and mechanical properties of the diffusers were shown to be improved upon addition of the porous silica particles.

On the Effect and Design of Diffusing Aerator for Thermal De-stratification (산기장치를 이응한 호수의 성층파괴효과와 설계)

  • Song Museok;Seo Dongil
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.5 no.3
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    • pp.16-22
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    • 2002
  • The effect and the overall optimal operation of artificial aeration devices for mixing of thermally stratified water reservoir are under study, and its brief introduction is made. The study site is Yeoncho Lake in Geojae island, which is well known for its eutrophication problems in the summer. A few samplings have been made before and after the operation of two types of artificial aerators, and the effect is believed to be positive. Also, design methodology for such artificial aerators is reviewed and a few are applied to the case of Yeoncho Lake. Schladow's[1993] proposal is believed most proper based on the information we have gathered by now. In addition, a simple numerical experiment is also peformed to see the overall effect of the device on the flow and temperature profile.

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