• Title/Summary/Keyword: Cylindrical microlens

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Fabrication of Cylindrical Microlens Using Slot-die Coating and Thermal Reflow Method (슬롯 다이 코팅과 Thermal Reflow방법을 이용한 Cylindrical 마이크로렌즈 제조)

  • Lee, Jinyoung;Park, Jongwoon
    • Journal of the Semiconductor & Display Technology
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    • v.19 no.3
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    • pp.30-35
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    • 2020
  • A microlens has been fabricated by various methods such as a thermal reflow, hot embossing, diamond milling, etc. However, these methods require a relatively complex process to control the microlens shape. In this work, we report on a simple and cost-effective method to fabricate a cylindrical microlens (CML), which can diffuse light widely. We have employed a slot-die head with the dual plate (a meniscus guide with a protruded μ-tip and a shim with a slit channel) for coating of a narrow stripe using poly(methyl methacrylate) (PMMA). We have shown that the higher the coating gap, the lower the maximum coating speed, which causes an increase in the stripe width and thickness. The coated PMMA stripe has the concave shape. To make it in the shape of a convex microlens, we have applied the thermal reflow method. When the stripe thickness is small, however, its effect is negligible. To increase the stripe thickness, we have increased the number of repeated coating. With this scheme, we have fabricated the CML with the width of 223 ㎛ and the thickness of 7.3 ㎛. Finally, we have demonstrated experimentally that the CML can diffuse light widely, a feature demanded for light extraction efficiency of organic light-emitting diodes (OLEDs) and suppression of moiré patterns in displays.

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Fabrication of Solution-Based Cylindrical Microlens with High Aspect Ratio (고종횡비를 갖는 용액기반 원통형 마이크로렌즈 제조)

  • Jeon, Kyungjun;Lee, Jinyoung;Park, Jongwoon
    • Journal of the Semiconductor & Display Technology
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    • v.20 no.1
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    • pp.70-76
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    • 2021
  • A cylindrical microlens (CML) has been widely used as an optical element for organic light-emitting diodes (OLEDs), light diffusers, image sensors, 3D imaging, etc. To fabricate high-performance optoelectronic devices, the CML with high aspect ratio is demanded. In this work, we report on facile solution-based processes (i.e., slot-die and needle coatings) to fabricate the CML using poly(methyl methacrylate) (PMMA). It is found that compared with needle coating, slot-die coating provides the CML with lower aspect ratio due to the wide spread of solution along the hydrophilic head lip. Although needle coating provides the CML with high aspect ratio, it requires a high precision needle array module. To demonstrate that the aspect ratio of CML can be enhanced using slot-die coating, we have varied the molecular weight of PMMA. We can achieve the CML with higher aspect ratio using PMMA with lower molecular weight at a fixed viscosity because of the higher concentration of PMMA solute in the solution. We have also shown that the aspect ratio of CML can be further boosted by coating it repeatedly. With this scheme, we have fabricated the CML with the width of 252 ㎛ and the thickness of 5.95 ㎛ (aspect ratio=0.024). To visualize its light diffusion property, we have irradiated a laser beam to the CML and observed that the laser beam spreads widely in the vertical direction of the CML.

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Fabrication of Anti-Moiré Filter Using Multi-Array Needle Coating for LED Screens (다중 배열 니들 코팅을 이용한 LED 스크린용 Anti-Moiré 필터 제작)

  • Jeon, Kyungjun;Lee, Jinyoung;Park, Jongwoon
    • Journal of the Semiconductor & Display Technology
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    • v.20 no.1
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    • pp.77-82
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    • 2021
  • Using a multi-array needle module developed for coating of high-density cylindrical microlens array (C-MLA), we have fabricated an anti-Moiré filter for LED screens. The Moiré phenomenon appears due to the interference between the array pattern of image sensors in a camera and the non-emission area (grid pattern) of a LED screen. To suppress it, we have employed poly(methyl methacrylate) (PMMA) and coated it on a glass substrate in the form of a grid and non-grid (parallel lines). We have rotated the needle module in order to increase the number of C-MLAs. With this scheme, we have fabricated the 150 mm × 150 mm anti-Moiré filters where 836 microlens lines are formed. They show the average width of 255.4 ㎛, the average distance between CMLs of 94.6 ㎛, and C-MLA width non-uniformity of 4.7%. We have shown that the Moiré patterns still appear in the presence of the parallel (non-grid)-type filter, whereas they disappeared completely by the grid-type filter. It is due to the fact that the Moiré patterns are diffused more effectively by the grid-type C-MLA.

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Measurement of the Refractive Index of a Mixed Polymer by a Prism Spectrometer and its Application (프리즘 분광계를 이용한 혼합 폴리머의 굴절률 측정과 응용)

  • Kim, Ji-Young;Ju, Young-Gu
    • Korean Journal of Optics and Photonics
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    • v.28 no.5
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    • pp.221-228
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    • 2017
  • We measured the refractive index of a mixed polymer (NOA61, NOA84) in the liquid and solid states. First we made a hollow prism and filled it with UV (ultraviolet) epoxy. Measurement of the apex angle and the minimum-deviation angle gave the refractive index of the liquid polymer. To measure the refractive index of the solid polymer, an additional structure was included in the hollow prism, and the UV epoxy filling in the hollow prism was hardened. In both cases of liquid and solid polymers, the refractive index of the mixed polymer turned out to be proportional to the mix ratio. These results provide a method to vary the focal length of a double stacked cylindrical microlens array using UV epoxy.