• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.397.1-397.1
• /
• 2014

최근 방사선 진단 영역에 이용되고 있는 증감지는 입사된 방사선의 감도를 증가시키기 위해 형광체를 사용하고 있으며, 외부의 에너지를 흡수하여 빛으로 방출하는 역할을 한다. 이는 방사선 검출기, 디스플레이, 의료기기 등 다양한 분야에 활용되고 있다. 필름에 X선을 노출 할 경우 형광체의 사용 유무에 따라 방사선 흡수 효율에 영향을 미치며, 이는 발광 효율 및 감도에 주요한 인자로 작용한다. 현재 상용화되어 있는 형광체는 낮은 발광 효율로 인한 한계를 가지므로, 발광 효율 향상을 위하여 제작 구조에 대한 연구가 진행되고 있다. 이 중 반사막을 활용하는 연구가 활발히 진행되고 있다. 일반적으로 형광체의 제조를 위하여 보편적으로 이용하고 있는 스크린프린팅 방법에서 건조 공정을 수행 시 균일도가 감소하는 현상이 발생한다. 이러한 현상은 반사막의 증착을 불균일하게 만드는 원인으로 작용하고 빛의 산란을 초래하는 현상을 초래한다. 이에 본 연구에서는 증착 시 투명도 저하에 따라 반사율이 증가되는 반사막 성질을 가지며, 방수성 및 절연성과 같은 보호층 특성을 지닌 유기성 투명 박막 페를린에 대하여 연구하고자 한다. 본 연구에서는 화학적 증기 증착법(Chemical Vapor Deposition, CVD)을 이용하여 투명 필름의 상단에 페를린을 코팅한 시편과 코팅하지 않은 시편으로 구분하여 제작하였고, 상단에 스크핀프린팅 방법을 활용하여 형광체를 도포 하였다. 시편 제작 후 실험은 시편을 필름 상단에 위치시키고, 일반진단에너지 대역(Model-SF 80)의 X선을 조사하였다. 이 후 현상기(model-pro14)를 통해 현상된 필름에 나타난 광학적 농도(Optical Density, O.D)를 농도계(Fluke Biomedical Nuclear Associates Densitometer)로 측정하였는데, 불확실성을 줄이기 위하여 총 5회를 측정하여 그 중 2번째로 높은 값을 도출하였다. 측정 결과, 페를린을 코팅한 형광체에서는 1.71의 O.D 값이 측정되었고, 페를린을 코팅하지 않은 형광체에서는 1.43의 O.D 값이 측정되었다. 이를 이용하여 투명도를 산출한 결과 상대적으로 약 1.76% 차이가 나타났다. 이러한 결과는 페를린 활용 시 환자의 피폭 선량 저감화 및 해상력 개선을 도모할 수 있을 것으로 사료된다.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.6
• /
• pp.21-27
• /
• 1998

Electrical and optical characteristics of ZnS:Mn/ZnS:Tb multilayer TFEL devices were investigated for multi-color electroluminescent display applications. Emission spectra of M $n^{2+}$ and T $b^{3+}$ ions were observed from ZnS:Mn/ZnS:Tb multi-layer TFEL devices, and were very broad from 540 nm to 640 nm. Saturation luminance measured at 155 V was 1025 Cd/$m^2$. C-V, $Q_{t}$ - $V_{p}$ curves showed that the phosphor capacitance ( $C_{p}$ ) and the insulator capacitance ( $C_{i}$ ) were 13.5nF/$\textrm{cm}^2$ and 60 nF/$\textrm{cm}^2$, respectively. Threshold voltage( $V_{thl}$) was shown to decrease from 126 V to 93 V due to the increase of the applied voltage from 155 V to 185 V, which was attributed to the increase of the polarization charge. The equation for the calculation of the threshold voltage as a function of the applied voltage was proposed for the first time. The calculated threshold voltage agreed well with the data obtained from the measurement.t.t.t.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.311-311
• /
• 2009

Carbon nanotubes (CNTs) belong to an ideal material for field emitters because of their superior electrical, mechanical, and chemical properties together with unique geometric features. Several applications of CNTs to field emitters have been demonstrated in electron emission devices such as field emission display (FED), backlight unit (BLU), X-ray source, etc. In this study, we fabricated a CNT cathode by using filtration processes. First, an aqueous CNT solution was prepared by ultrasonically dispersing purified single-walled CNTs (SWCNTs) in deionized water with sodium dodecyl sulfate (SDS). The aqueous CNT solution in a milliliter or even several tens of micro-litters was filtered by an alumina membrane through the vacuum filtration, and an ultra-thin CNT film was formed onto the alumina membrane. Thereafter, the alumina membrane was solvated by acetone, and the floating CNT film was easily transferred to indium-tin-oxide (ITO) glass substrate in an area defined as 1 cm with a film mask. The CNT film was subjected to an activation process with an adhesive roller, erecting the CNTs up to serve as electron emitters. In order to measure their luminance characteristics, an ITO-coated glass substrate having phosphor was employed as an anode plate. Our field emitter array (FEA) was fairly transparent unlike conventional FEAs, which enabled light to emit not only through the anode frontside but also through the cathode backside, where luminace on the cathode backside was higher than that on the anode frontside. Futhermore, we added a reflecting metal layer to cathode or anode side to enhance the luminance of light passing through the other side. In one case, the metal layer was formed onto the bottom face of the cathode substrate and reflected the light back so that light passed only through the anode substrate. In the other case, the reflecting layer coated on the anode substrate made all light go only through the cathode substrate. Among the two cases, the latter showed higher luminance than the former. This study will discuss the morphologies and field emission characteristics of CNT emitters according to the experimental parameters in fabricating the lamps emitting light on the both sides or only on the either side.

• Journal of the Korean Society of Radiology
• /
• v.3 no.1
• /
• pp.17-21
• /
• 2009

The Recently, large area matrix-addressed image detectors are investigated for X-ray imaging with medical diagnostic and other applications. In this paper, a new flat panel gas detector for diagnostic X-ray imaging is proposed, and its characteristics are investigated. The research of flat panel gas detector is not exist at all. Because of difficulty to inject gas against to atmospheric pressure. So almost gas detector made by chamber shape. We made flat panel sample by display technique. (ex: PDP, Fed, etc.) The experimental measurements, the transparent electrodes, dielectric layer, and the MgO protection layer were formed in front glass. And, the X-ray phosphor layer and address electrodes are formed in the rare glass. The dark current, the x-ray sensitivity and linearity as a function of electric field were measured to investigate the electrical properties. From the results, the stabilized dark current density and the significant x-ray sensitivity were obtained. And the good linearity as a function of exposure dose was showed in wide diagnostic energy range. These results means that the passive matrix-addressed flat panel gas detector can be used for digital x-ray imaging.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.9
• /
• pp.2609-2615
• /
• 2013

A series of fluorene-carbazole copolymers containing the pendant phosphor chromophore $Ir(absn)_2(acac)$ (absn: 2-(1-naphthyl)benzothiazole; acac: acetylacetone) were designed and synthesized via Yamamoto coupling. In the film state, these copolymers exhibited absorption and emission peaks at approximately 389 and 426 nm, respectively, which originated from the fluorene backbone. However, in electroluminescent (EL) devices, a significantly red-shifted emission at approximately 611 nm was observed, which was attributed to the pendant iridium(III) complex. Using these copolymers as a single emission layer, polymer light-emitting devices with ITO/PEDOT:PSS/polymer:DNTPD/TmPyPb/LiF/Al configurations exhibited a saturated red emission at 611 nm. The attached iridium(III) complex had a significant effect on the EL performance. A maximum luminous efficiency of 0.85 cd/A, maximum external quantum efficiency of 0.77, maximum power efficiency of 0.48 lm/W, and maximum luminance of 883 $cd/m^2$ were achieved from a device fabricated with the copolymer containing the iridium(III) complex in a 2% molar ratio.

• Current Optics and Photonics
• /
• v.3 no.6
• /
• pp.590-596
• /
• 2019

To improve the color gamut of a liquid-crystal display (LCD), we propose a bandpass filter that is added to the backlight unit to optimize the backlight spectrum. The bandpass filter can only transmit red, green and blue light in the visible range, while reflecting the unwanted light. We study the optical properties of the bandpass filter using the transfer-matrix method, and the effect of the bandpass filter on the color gamuts of LCDs is also investigated. When a bandpass filter based on a 5-layer configuration comprising low and high refractive indices ((HL)²H) is used in phosphor-converted white-light-emitting diode (pc-WLED), K₂SiF₆:Mn⁴⁺ (KSF-LED), and quantum-dot (QD) backlights, the color gamuts of the LCDs improve from 72% to 95.3% of NTSC, from 92% to 106.7% of NTSC, and from 104.3% to 112.2% of NTSC respectively. When the incident angle of light increases to 30°, the color gamuts of LCDs with pc-WLED and KSF-LED backlights decrease by 2.9% and 1% respectively. For the QD backlight, the color gamut almost does not change. When the (HL)²H structure is coated on the diffusion film, the color gamut can be improved to 92.6% of NTSC (pc-WLED), 105.6% of NTSC (KSF-LED), and 111.9% of NTSC (QD). The diffusion film has no obvious effect on the color gamut. The results have an important potential application in wide-color-gamut LCDs.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.263-265
• /
• 2005

In the alternative current plasma display panel(AC-PDP) technology, it is very important to remove the image sticking for improving an image quality. In this paper, we have investigated the driving method of alternative current plasma display panel(AC-PDP) for preventing image sticking. We have investigated the driving method of alternative current plasma display panel(AC-PDP) for preventing image sticking. The preventing method of image sticking was proposed by adopting the Sticking Remove Pulse(SRP). The variation of brightness is most affected by the MgO to be formed at the surface of the phosphor layer. As a result, the image sticking is reduced when the driving method adopted an SRP.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.39 no.8
• /
• pp.17-23
• /
• 2002

The SrS:CuCl TFEL devices were fabricated by electron-beam deposition and the luminescent characteristics of the fabricated SrS:CuCl TFEL devices were studied. The SrS powder was used as the host materials and 0.05 ~ 0.6 at% of CuCl powder was added as the luminescent center. The deposition conditions of substrate temperature, electron beam current, and deposition rate were 500 $^{\circ}C$ , 20 ~ 40 mA, and 5 ~ 10 /sec, respectively The total thickness of the phosphor layer deposited was 6000 . The blue emission at low CuCl concentrations was observed from the luminescent centers of monomer, dimer, trimer, and tetramer, The bright greenish blue emission at high CuCl concentrations was observed from the dimer and trimer luminescent centers. The maxium luminance was observed from the SrS:CuCl TFEL devices doped with 0.2 at% of CuCl concentration and the threshold voltage, luminance(L$_{40}$ ), efficiency(η$_{20}$) and CIE coordinate obtained were 55 V, 728 cd/$m^2$, 0.49 lm/w, and (0.21, 0.33), respectively..

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.11a
• /
• pp.432-435
• /
• 2002

The ultimate study of this research is to improve the properties of digital X-ray receptor based on amorphous selenium. There are being two prominent studying for Digital Radiography. Direct and Indirect method of Digital Radiography are announced for producing high quality digital image. But each two systems have strength and weakness. This is a basic research for developing of Hybrid digital radiography which is a new type X-ray detector. ln this study, we investigated the electrical characteristic of multi-layer$(CaWO_4+a-Se)$ as a photoconductor according to the changing iodine composition ratio. The iodine composition ratio of a-Se compound is classified into 5 different kinds which have 30ppm, 100ppm, 300ppm, 500ppm, 700ppm and were made test sample throught thermo-evaporation. The phosphor layer of $CaWO_4$ was overlapped on a-Se using EFIRON optical adhesives. We measured the dark and photo current about the test sample and compared the electrical characteristic of the net charge and signal-to-noise ratio. Among other things, test sample of compound material of 700ppm iodine showed good characteristic of $2.53nA/cm^2$ dark current and $479nC/cm^2{\cdot}mR$ net charge at $3V/{\mu}m$.

• Journal of the Korean Society of Radiology
• /
• v.11 no.7
• /
• pp.611-617
• /
• 2017

In this study, it was expected that long-term stability against external mechanical external force could be secured if the phosphor layer had ductility. In this study, a bendable $Gd_2O_2S:Tb$ sensitized paper was fabricated by screen printing method and the image uniformity was evaluated through RMS analysis and histogram analysis to investigate the effect of fatigue accumulation due to long-term external force and repetitive external force. As a result, the dominant pixel area is maintained constant and the relative standard deviation is less than 10% for the long-term external force. However, for the repetitive external force, the dominant pixel area is divided into three areas and the image uniformity is adversely affected. Based on these results, it is suggested that the curved surface detector can be applied by securing the mechanical stability against the existing radiation sensitized paper. However, further studies are needed to apply it to the flexible detector. As a result, flexible radiation sensitizers can be applied to various curved surfaces, and it is expected to be applicable to various fields such as nuclear medicine, medical treatment, and industrial fields in the future.