Effect of taper tension profile on the telescoping in a winding process of high speed roll to roll printing systems

이창우,강현규,김호준,신기현 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.11

Winding is an integral operation in almost every roll to roll system. A center-wound roll is one of the suitable and general schemes in a winding mechanism. In general, the quality of wound roll is known to be related to the lateral displacement error and starring defect of a wound roll. Especially, a telescoping within a center-wound roll can cause damages such as misalignment between layers, folding, wrinkle, etc. Taper tension is known to be one of the major factors which affect the shape of a wound roll. It is therefore necessary to analyze the relationship between taper tension profile and telescoping within the center-wound roll to prevent winding failure and to sustain high quality of the printed materials. It is hard to compensate for undesirable winding roll shapes such as telescoping, because a winding is commonly a final process in roll to roll systems and has no feedback control mechanism to correct winding roll shape directly during winding operation. Therefore, an optimal taper tension profile and the accurate control of it in a winding section could be one way to shape the fail-safe of a wound roll. Through the correlation between taper tension profile and telescoping in a winding process, a mathematical model for the telescoping due to tension distribution in cross machine direction was developed, and verified by experimental study. A new logic to determine the proper taper tension profile was designed by combining and analyzing the winding mechanism which includes nip induced tension model, relationship between taper tension profile and telescoping, relationship between taper value and telescoping. Numerical simulations and experimental results show that the proposed method is very useful for determining the desirable taper tension profile during the winding process and preventing defects of winding roll shape such as telescoping.

Positional accuracy of micropatterns in the roll-to-roll imprinting process using a wrapped roll mold

황은수,권신,김동민,조영태,정윤교 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4

Various micropatterns in flexible devices can be fabricated using the roll-to-roll (R2R) imprinting process, wherein a raw flexible plasticfilm is released from a roller and subjected to several patterning processes such as imprint lithography. In case a thin-film-transistorliquid-crystal display (TFT-LCD) is formed on the flexible film, overlay accuracy becomes the most important factor in the patterningprocess. To achieve positional accuracy, the process parameters that affect dimensional changes should be analyzed. In our system, theroll mold was fabricated by wrapping a thin film sheet to the roller. During the process, the substrate was deformed by web tension andbent by overall system architecture. Thus, web tension, misalignment angle, mold thickness, and substrate bending effects were regardedas the main parameters, which were analyzed and modeled into mathematical formulas. Positional errors and their tolerances were estimatedusing the formulas, and process parameters were designed to compensate for each error. Finally, the color filters in the flexibleTFT-LCD display were manufactured using R2R imprinting and ink-jet printing. Dimensional error can be minimized to approximately±15 μm for the entire area of 200 mm × 150 mm.

Improvement of a Splicing Machine to Decrease Abrupt Tension Changes and Tail Defects during the Roll Exchange Process in a Roll-to-Roll Manufacturing System

이종수,이창우 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.8

The use of the splicing system is necessary to exchange a fully unwound roll to a new one without stopping the roll-to-roll manufacturing machine. However, abrupt tension changes and tail defects, which is an overlap of completely unwound films with films in the process of being unwound, could occur during the roll exchange phase causing film loss and deterioration of product quality. Herein, we improved the splicing machine in an industrial scale R2R manufacturing system to decrease abrupt tension errors and tail defects. First, the effects of the factors generating the tail defects in the splicing machine on the net tail lengths were analyzed using designed mathematical models. Furthermore, the reason for the abrupt tension disturbance in the roll exchange process was determined. Based on the analyses, a passive dancer system was applied to the unwinding section to attenuate the tension error, and the time interval between the pressing and cutting phases was decreased by changing the signal processing method of the previous version of the splicing machine. Experimental results showed that the abrupt tension change was decreased by an average of 46.5%, while tail lengths were decreased by more than 2.5 times, thereby verifying the superior performance of the upgraded splicing machine.

비선형 접촉을 고려한 대면적 롤투롤 가압 공정의 접촉 압력 분포 해석

강유성,전용호,이문구 한국생산제조학회 2022 한국생산제조학회지 Vol.31 No.6

With the emergence of the climate crisis in modern society, international environmental regulations on the automobile market are becoming strict. Accordingly, the market's core is rapidly changing to electric vehicles, and the demand for rechargeable battery technology is also increasing. A lithium-ion battery cell is manufactured by the roll-to-roll pressing process. However, the contact area has a nonuniform stress distribution due to the roll's bending. In this study, the nonuniform stress distribution of a 1,400 mm roll pressing process was analyzed by finite element analysis. A finite element model of the roll pressing process was established. In the model, the two rollers—support and rubber—were brought close to each other by 1 mm after their contact. The maximum and minimum stress distributions generated at the contact surface were 11.7 MPa and 0.71 MPa, respectively. A stress deviation of approximately 11 MPa was confirmed.

Full Roll-to-Roll Fabrication Process of Large-Area Flexible OLED with Silver-nanowire Transparent Electrode

김찬호,정상규,김상우,박윤택,조성민 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Large-area flexible OLED panels were fabricated by a roll-to-roll thermal evaporator. The panels were fabricated on the silver-nanowire embedded flexible transparent electrode with barrier layer inserted between electrode and PET substrate. The barrier layer was composed of the organic polymer layer and the inorganic Al2O3 layer. Organic polymer layer was deposited by plasma-enhanced chemical vapor deposition (PECVD) and the inorganic Al2O3 layer was deposited with atomic layer deposition (ALD). Both depositions were carried out in a vacuum single roll-to-roll equipment. With those full roll-to-roll fabrication processes (from the electrode to OLED deposition), we could effectively reduce the process time and cost.

롤투롤 인쇄 전자 시스템에서 건조 온도와 유연기판의 열변형간 상관관계에 대한 연구

이종수(Jongsu Lee),이창우(Changwoo Lee) Korean Society for Precision Engineering 2014 한국정밀공학회지 Vol.31 No.8

Roll-to-Roll printing process has become a great issue as a breakthrough for low cost and mass production of electronic devices such as organic thin film transistor, and etc. To print the electronic devices, multi-layer printing is essential, and high precision register control is required for this process. Unlike stop-and-repeat printing process, it is impossible to control the register in a static state since the roll-to-roll process is a continuous system. Therefore, the behavior of web such as polyethylene terephthalate (PET) and polyimide (PI) by the tensile and thermal stress generated in the roll-to-roll process as well as motor control of driven rolls has to be considered for a high precision register control. In this study, the correlation between curing temperature and thermal deformation of PET web is analyzed. Finally, it is verified experimentally that the temperature disturbance generates the more serious register error under the higher curing temperature.

롤투롤 공정에서 측정지연을 보상하는 압력제어

김지현,김영진,김태형,이병철,오동호 대한기계학회 2019 大韓機械學會論文集A Vol.43 No.2

The roll-to-roll printed electronics process is a next generation process that can replace various photolithography techniques applied to semiconductors, display panels, and electronic components. In the roll-to-roll process, printing pressure affects the uniformity of the line width and the thickness of the printed pattern and is an important factor determining the print quality. The printing pressure control system predominantly used today employs an indirect measurement system for printig pressure. When printing pressure is measured indirectly, a measurement delay inevitably occurs. To calculate the measurement delay, we performed an impact test on the impression roll near the nip where the impression roll meets the plate roll. The measurement delay is compensated for by a time delay predictor, and the printing pressure can then be uniformized. 롤투롤 인쇄전자 공정은 다양한 인쇄공정의 융합이 가능한 공정으로 현재 반도체, 디스플레이 패널, 전자부품 등의 공정에 적용되는 포토리소그래피 기법을 대체할 수 있는 차세대 공정 중 하나이다. 롤투롤 공정에서 인쇄압력은 인쇄 패턴의 선폭 및 두께의 균일도에 영향을 주어 인쇄 품질을 결정하는 중요한 요인이다. 현재 주로 사용하는 인쇄압력 계측 및 제어 장치는 로드셀을 이용하여 인쇄압력을 간접적으로 측정하는 시스템으로 간접적인 측정으로 인해 측정지연이 불가피하게 발생하게 된다. 롤과 롤이 접촉하는 닙 근처의 임프레션 롤에서의 충격시험을 통해 로드셀 신호와의 관계를 확인하여 측정지연을 계산한다. 그리고 시간지연 예측기를 이용하여 측정지연을 보상하고 인쇄압력 균일화를 수행한다.

Individual drive cross-coupled control system to compensate for measurement time-delay for roll-to-roll contact pressure uniformization

김대현,김영진,김형래,김주연,Jongmo Kang,최유창,오동호 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.11

As the market demand for products such as flexible displays, IoT devices, and healthcare devices increases, attention has been drawn to printed electronics by a roll-to-roll process that can continuously produce electronic products on flexible substrates using functional inks. In particular, printed patterns need to be uniform in terms of the line width and thickness, which requires uniform control of the contact pressure during the roll-to-roll process, in processes that require ultra-fine pattern printing such as thin-film transistors for flexible displays. Because the contact pressure is indirectly measured using load cells, the performance of the conventional contact pressure control method tends to deteriorate due to the occurrence of time-delay and magnitude errors. Using the transfer function between the actual contact pressure and load cell, the time-delay is measured and compensated. To achieve contact pressure uniformization, the individual drive cross-coupled control system with the time-delay compensation is proposed.

Deformation Analysis of Roll Mold for Nano-flexible Devices

Amin Khaliq(Amin Khaliq ),Usama Tahir(Usama Tahir ),Jeong Myung Yung (Jeong Jeong) 한국마이크로전자및패키징학회 2021 마이크로전자 및 패키징학회지 Vol.28 No.4

Nanoimprint lithography (NIL) has revolutionized the fabrications of electronics, photonics, optical and biological devices. Among all the NIL processes, roll-to-roll nanoimprinting is regarded best for having the attributes of low cost, continuous, simple, and energy-efficient process for nanoscale device fabrication. However, large-area printing is limited by the master mold deformation. In this study, a finite element model (FEM) has been constructed to assess the deformation of the roll mold adhesively wrapped on the carbon fiber reinforced material (CFRP) base roll. This study also optimizes the deformations in the metallic roll mold with respect to nip-forces applied in the printing process of nano-fabrication on large scale. The numerical simulations were also conducted to evaluate the deflection in roll mold assembly due to gravity. The results have shown decreasing trend of the deformation with decreasing nip-force. Also, pressure uniformity of about 40% has been optimized by using the current numerical model along with an acceptable deflection value in the vertical axis due to gravity.

Polymer Masking Method for a High Speed Roll-to-Roll Process

송준호,임수정,임세진,유재웅 한국고분자학회 2018 Macromolecular Research Vol.26 No.9

A new polymer masking system with photo-degradable material applicable to high-speed roll-to-roll vacuum deposition processing was studied. Specifically, a process using intense pulsed light to quickly and cleanly remove polymer masks was developed. Poly(methyl methacrylate) (PMMA) and TiO2 were blended together with the positive photoresist to prepare a photo-degradable polymer masking. Infrared spectroscopy confirmed that the positive photoresist moiety, diazonaphtoquinone, was photo-decomposed by white intense pulsed light. The process time required to remove the polymer mask was short enough that this method could be used even in high-speed roll-to-roll processes. It was confirmed that the polymer mask film could be easily removed even at a high process speed by using pressurized gas and adhesive roller tape. The transparent electrode was patterned using a polymer mask and an etching paste, and full solution processed inverted type OPV devices were fabricated. The fabricated OPV by direct etching showed a 94% efficiency compared with that of the reference device.