Cyclo-olefin Polymer Film Research Articles

Low Pressure Sensing Characteristics of Mechanoluminescence Film with 3D Microstructure

Mechanoluminescence (ML), which is light emitting repeatedly induced by external mechanical stimuli, has received widespread attention worldwide because it has been applied to various applications [1-3]. Among different applications, pressure sensors using a composite of ML material and organic resin have superior advantages in wireless detection using light-emitting and multi-scalable applications compared with electric devices. For this interest worldwide, we have applied an ML phenomenon into the pressure sensing technique using an ML composite sheet composed of europium doped strontium aluminate (SrAl2O4:Eu) ML material and epoxy resin. As a result of evaluating the load response of the flat ML composite sheets formed on rigid acrylic plates, it was found that the load distribution on the sole due to human weight bearing can be visualized two-dimensionally with relatively high spatial resolution. However, we also found that such a simple configuration, like a flat composite film on a rigid substance, limits detection sensitivity to several hundred newtons. Here, we conceived the improvement technique in the low-pressure response of the ML composite film. It is well-known that the ML intensity is proportional to the equivalent strain and its rate. When the same load is applied to different structures, the ML intensity of a configuration with the augmentation of stress or with the stress concentration region will be higher. Thus, it could be expected that we can control the pressure sensitivity of the ML sensor by designing a surface structure of the ML composite sheet. In this study, therefore, we challenged improving low-pressure sensing characteristics with a focus on the surface geometry of the ML composite film.In our pursuit of enhancing low-pressure sensing characteristics, we embarked on an innovative approach the use of micro-sized pillar array films. These films were prepared using a thermal imprinting method with cyclo olefin polymer (COP) or laminated poly methyl methacrylate/polycarbonate (PMMA/PC) films. The micro-pillar array pattern was transferred onto these polymer films, and an ML ink consisting of a mixture of SrAl2O4:Eu ML material and epoxy resin was directly sprayed on the surface of those polymer films with micro-pillar array patterns. Before forming the ML layer on the COP film, we introduced a SiO2 interlayer using a photo-assisted chemical solution deposition (PCSD) process [4] to enhance the adhesive strength between the ML layer and COP film. The SrAl2O4:Eu ML material was synthesized by a high-temperature solid-state reaction method [5]. We then evaluated the pressure-sensing characteristics under compression testing in the load range of 0 – 90 N using the prepared ML films with different configurations.Considering the amplified mechanism of the ML intensity for the micro-pillar array film, we can predict that the ML intensity is primarily affected by the configuration of the micro-pillar arrays, such as height, width (diameter), and pillar density, as well as the elastic modulus of the base polymer. Thus, we investigated the effect of such a configuration and mechanical factors of the micro-pillar array on the pressure-sensing characteristics. As a result, we found that high height and low elastic modulus micro-pillar array exhibited the highest ML intensity and responded even to small loads of 1 N or less. This finding suggests the potential of micro-array films for high-sensitivity pressure sensing applications. To verify the amplified mechanism of the ML intensity for the micro-pillar array film, we observed cross-sectional ML images under dynamic compression tests. The cross-sectional ML distribution image showed that the micro-pillars made of soft resin (COP) were more easily deformed and exhibited higher ML intensity than micro-pillars made of hard resin (PMMA/PC). Furthermore, since bending deformation is observed as the height of the micro-pillar increases, it is concluded that soft and tall micro-pillars produce high ML intensity by more considerable deformation and bending mode.

Comparison of vacuum ultraviolet irradiation and oxygen plasma treatment as pretreatment for copper seed layer on cycloolefin polymer

This study explores the factors governing the peel strength characteristics between a cycloolefin polymer (COP) film and a copper plating layer with a copper seed layer, for applying to antenna circuits in 6 G communications. The peel strength depended on the surface modification methods as pretreatment for copper seed layer formation: vacuum ultraviolet (VUV) irradiation and oxygen plasma treatment. VUV irradiation induced a modified layer with brittleness on the COP surface, leading to substrate failure. Conversely, oxygen plasma treatment formed a quite thin modified layer and facilitated Cu2O formation by bonding functional groups on the topmost COP surface with copper in the seed layer at the interface between the COP film and the copper plating layer, resulting in interface failure rather than substrate failure. Therefore, enhancing peel strength involves preventing the formation of a modified layer on the surface and generating a significant quantity of functional groups on the topmost surface.

In vivo transmission electron microscopy of the alternating structure of the protrusions between adjacent macrophage-like cells on micropatterns

ObjectivesWe investigated the behavior of macrophages in the defined microtopography of materials. MethodsPatterned cyclo-olefin polymer films were implanted into the femurs of seven-week-old rats. After 1 and 4 weeks, the rats were fixed with glutaraldehyde and OsO4, and their bones were observed with transmission electron microscopy (TEM). ResultsTEM and segmentation revealed an alternating structure in which multiple protrusions of adjacent macrophage-like cells overlapped. They were approximately 2 μm long and almost uniform in width, and were induced by the limited topography. ConclusionNew structures appeared between the macrophage-like cells as a result of microtopography.

High-performance ITO thin films for on-cell touch sensor of foldable OLED displays

ITO thin films must have good electro-optical and mechanical characteristics to use them as integrated touch sensors for flexible OLED displays. We fabricated ITO thin films on a separation-layer-coated glass substrate under various deposition or annealing conditions, and then transferred them to cyclo-olefin polymer films to evaluate their electro-optical and mechanical characteristics. ITO films with a thickness of approximately 136 nm deposited at 250°C showed a sheet resistance of 36 Ω/□, light transmittance of 88%, and 2.4% of elongation at break. The 136 nm thick ITO films deposited at 150 °C and transferred on 50 μm thick COP film survived 500 h of 85 °C, 85% relative humidity under 180-degree bending preservation test, endured at 200,000-time repetitive bending test with a curvature radius of 1.5 mm. These high-performance ITO thin films can be applied to fabricate on-cell touch sensors for foldable OLED displays.

Au-Capped Nanopillar Immobilized with a Length-Controlled Glycopolymer for Immune-Related Protein Detection.

A Au-capped nanopillar chip was prepared using nanoimprint lithography (NIL) and Au sputtering onto a cyclo-olefin polymer film. The Au surface of the chip exerting localized surface plasmon resonance (LSPR) phenomena was immobilized with a glycopolymer for the detection of cytokines. The glycopolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization for controlled polymer chain length, and thiol-terminated glycopolymers with chain lengths of 20-, 100-, and 200-mers were designed. The thickness of the biomolecular layer on the Au surface was controlled by changing the polymer chain length of the immobilized glycopolymer, and the absorption of proteins onto the Au surface was detected by the shift of absorbance peak wavelength. The value of absorbance peak wavelength shift by protein adsorption increased as the glycopolymer layer thickness became thinner. This difference in LSPR signal response was remarkable for cytokine recognition compared to larger proteins. It was shown that controlling the biomolecular layer thickness was effective for the detection of small proteins, and our research suggested the usefulness of the controlled glycopolymer surface as a molecular recognition material for cytokine detection.

A Planar Millimeter-Wave Resonator-Array to Sense the Permittivity of COP Film with the 5G Handset Back-Cover.

In this paper, a new sensor is developed to estimate the dielectric constant of Cyclo Olefin Polymer (COP) film utilizable for 5G mobile phones’ multi-layered back-cover. It is featured by the electrical characterization of the thin layer of the COP film at 28 GHz as the material under test (MUT) directly contacting the planar probe (which is an array of resonating patches) and a new meta-surface as metal patterned on the COP film inserted between the planar probe and the 5G multi-layered back-cover for enhanced physical interpretation of the data by way of impedance matching. In this approach to delving into the material, a thin and small meta-surface film with an area of 25.65 × 21.06 mm2 and a thickness of 55 μm is examined for applications to 5G mobile 28 GHz-frequency communication on the basis of the below −10 dB-impedance matching for the 1-by-4 array sensor. Along with this, the real and commercial handset back-cover is brought to the test. The proposed method presents the advantages of geometrical adequacy to the realistic 5G handset antenna configuration, the idea of impedance-matching via meta-materials, and the suitability of characterizing the film-type structure as compared to the open-ended coaxial waveguide, waveguide-to-waveguide and TX horn-to-RX horn free-space test methods.

Fabrication and spectroscopic characterization of graphene transparent electrodes on flexible cyclo-olefin substrates for terahertz electro-optic applications

We demonstrate graphene on flexible, low-loss, cyclo-olefin polymer films as transparent electrodes for terahertz electro-optic devices and applications. Graphene was grown by chemical vapor deposition and transferred to cyclo-olefin polymer substrates by the thermal release tape method as layers on an approximate area of 4 cm2. The structural and electromagnetic properties of the graphene samples as well as their spatial variation were systematically mapped by means of µRaman, terahertz time-domain and mid-infrared spectroscopy. Thanks to the small thickness and very low intrinsic absorption of the employed substrates, both high transmittance and conductivity were recorded, demonstrating the suitability of the technique for the fabrication of a new class of transparent and flexible electrodes working in the terahertz spectrum.

Lifetime Improvement of Organic Light-Emitting Diodes Using Cyclo-Olefin Polymer Film as Passivation for Flexible Display

Lifetime Improvement of Organic Light-Emitting Diodes Using Cyclo-Olefin Polymer Film as Passivation for Flexible Display

Lifetime Improvement of Organic Light-Emitting Diodes Using Cyclo-Olefin Polymer Film as Passivation for Flexible Display

Lifetime Improvement of Organic Light-Emitting Diodes Using Cyclo-Olefin Polymer Film as Passivation for Flexible Display

Characterisation of buried glass/cyclo-olefin polymer film interfaces by sum-frequency generation vibrational spectroscopy

ABSTRACTPlasma gas-modified cyclo-olefin polymer (COP) surfaces and the interfaces between borosilicate glass and COP films were investigated by sum-frequency generation (SFG) vibrational spectroscopy. Upon exposure to oxygen gas plasma, the SFG signal intensities increased, indicating an improvement in the orientational order at the surface functional groups. In addition, thermal annealing following lamination improved the COP interphase molecular ordering and increased the number density of functional molecules at the interfaces.

Fabrication of Metallic Nanodot Arrays Using Nano-Chemical Stamping Technique with a Polymer Stamp

The aim of this study is to develop metallic nanodot arrays with controlled morphology and alignment. To produce gold nanodot arrays with high throughput, the authors propose a new efficient fabrication process based on the templated thermal dewetting method, using a nano-chemical stamping technique with a polymer mold. This process comprises four steps: sputter etching on a quartz glass substrate, patterning of micrometer size by printing with acetone on the substrate by stamping with a polymer film stamp, deposition of a thin Au film on the substrate, and self-organization of the metal nanodot arrays by thermal dewetting. A new method, using a cyclo-olefin polymer film mold for chemical patterning by nano-chemical stamping, was examined. Since the acetone stamped on the substrate reduces the surface energy and affects the contact angle of the gold nanodots, the gold nanodots are distributed along the stamped pattern. It is found that the pattern stamped with acetone on the substrate works as a template for the thermal dewetting process. The nano-chemical stamping technique is useful in controlling the size and distribution of the nanodots.

Effects of Polymeric Dielectric Morphology on Pentacene Morphology and Organic TFT Characteristics

In this paper, we report on the effects of the polymeric dielectric morphology on pentacene morphology and organic thin film transistor (TFT) characteristics. The morphology and thickness of cyclo-olefin polymer (COP) dielectric could be controlled by selecting a solvent. Higher the solvent’s boiling point is, thinner and smother COP films could be obtained. Using the solvent of trimethylcyclohexane, the spin-coated COP films of ca. 330 nm with the peak-to-valley of 7.35 nm and the roughness of root mean square of 0.58 nm were obtained, and pentacene TFT showed high mobility of 2.0 cm 2 V -1 s -1 , which originated from highly ordering of pentacene thin films deposited on the smoother and thinner COP films.

Efficient Fabrication Process of Metal Nanodot Arrays Using Direct Nanoimprinting Method with a Polymer Mold

A new fabrication process of metal nanodot arrays using the thermal dewetting method was developed in this study. This process was comprised of three steps: thin Au film deposition on a quartz glass substrate, groove patterning by direct nanoimprinting, and self-organization of metal nanodot arrays by thermal dewetting. A new idea to utilize a polymer film mold for groove patterning by direct nanoimprinting was examined. The polymer film mold was prepared by hot-embossing groove patterns of a mother mold on a cyclo olefin polymer (COP) film. The mother mold was prepared from a silicon wafer. The polymer film mold was used for direct nanoimprinting on a metal film deposited on a quartz substrate. The experimental results revealed that the COP film mold can effectively form a micro groove pattern on the Au film despite the COP film mold being softer than the Au film. The micro groove on the Au film was also found to be effective in aligning the nanodots in lines. The micro groove patterning using the COP film mold was also confirmed to be useful in controlling the dot size and alignment during the thermal dewetting process.

Terahertz laminated-structure polarizer with high extinction ratio and transmission power

A terahertz polarizer consisting of a laminated metal-slit array on a polymer film is presented. Here, the iterative design is efficiently performed with a mode-matching method; the proposed polarizer’s characteristics are shown to be superior to those of conventional polarizers. To verify the proposed design, a copper metal-slit array was fabricated on a cyclo-olefin polymer film by sputtering and punching. Measurements confirm a high extinction ratio, below −50 dB from 0.28 to 1.09 THz and below −40 dB from 0.2 to 1.98 THz, with a TM-mode transmission power that averages 76% from 0.2 to 1.95 THz.

Low-cost replication of self-organized sub-micron structures into polymer films

In this paper, the results of exploiting self-organized sub-micron polystyrene (PS) wrinkle patterns possessing random orientation, in preparation of a nickel stamp for hot embossing purposes, are presented. Self-organized patterns were prepared employing a method in which a stiff cross-linked capping layer on the topmost part of the soft polystyrene layer was created by using reactive ion etching (RIE) device with mild conditions and argon as a process gas, and the wrin- kle formation was initiated thermally. Different surface patternings were obtained using silicon and stainless steel (SST) wafers as substrates. Prepared Ni-stamps were employed in hot embossing of polycarbonate (PC) and cyclo-olefin polymer (COP) films, using a nano-imprinting process. The replication quality of the self-organized wrinkle structures in PC and COP films was monitored by comparing the shape and dimensions of the original and final surface structures. The hot embossed sub-micron scale features, originally formed on stainless steel substrate, were found to have influence on the optical properties of the PC and COP films by lowering their reflectances.

フレキシブル薄フィルム上2層構造カットワイヤーによるテラヘルツ波用大口径1/4波長板の設計と評価

The polarization control of a terahertz wave can provide fruitful technology for communication, imaging, and exploration of novel phenomena in terahertz frequencies. However, it is not so easy to realize a high-performance wave plate with a large aperture, flexibility, and thinness at low cost and by easy fabrication. We design and fabricate a terahertz quarter-wave plate on a cyclo-olefin polymer film with a copper layer by etching. Measurements by terahertz time-domain spectroscopy confirm a transmission power with 82% and an ellipticity with -1.0 at 0.43 THz. The quarter-wave plate would lead to compact transmission devices and many progressive applications.

Fabrication of flexible metallic wire grid polarizer using thermal NIL and lift-off processes

► Double layer metallic/dielectric gratings were fabricated for WGP components. ► Thermal NIL, aluminum lift-off, and dielectric etching were adopted in experiments. ► 192:1 Extinction ratio and 1.2× brightness gain were obtained with 240 nm pitch WGP. ► Designed optical performance and better process tolerance could be achieved. ► Low retardation COP films provide adequate optical performance. This work is dedicated to the fabrication of metallic/dielectric double layer gratings on polymeric films for wire grid polarizer (WGP) to obtain designed optical performance as well as better process tolerance. The fabrication process was based on thermal nanoimprint and aluminum lift-off techniques. Polymeric substrates PET (Polyethylene terephthalate) and COP (Cyclo-olefin polymer) were brought into comparison for the birefringence property. At the same time, by applying RCWA (Rigorous coupled-wave analysis) simulated optical designs, it would be also capable of minimizing difficulties of ultra-precision manufacturing. Experimental results revealed that using the 240 nm pitch stacked metallic/dielectric gratings performed 192:1 extinction ratio and 1.2× brightness enhancement, which allowed larger pitch replacing the smaller pitch of WGP gratings, but still possessed similar optical performance. Hence, these designs and process configuration not only make the continuous roll-to-roll process more feasible, but also relieve the difficulties of fabricating the imprint roller stamp.

Formation of Fine Circuit Patterns on Cyclo Olefin Polymer Film

In recent years, with the miniaturization of electric devices, the demand for flexible printed circuits (FPCs) using polyimide has increased, because of its excellent heat resistance and size stability. Polyimide also has good flexibility and surface smoothness. However, polyimide absorbs moisture readily and is highly permeable to gas. In contrast, Cyclo Olefin Polymer (COP) has low moisture absorption, excellent size stability and excellent high frequency electrical properties. Therefore, COP is attractive as a substrate for FPCs. However, it is difficult to form a metal film using electroless plating on the COP with conventional processes. We could form a copper film with high adhesion strength while maintaining a smooth resin surface by modifying the surface using UV irradiation. Surface modification by UV irradiation was effective to achieve good adhesion (about 1.0 kN/m) between the COP resin and the deposited metal without roughening the COP surface. The interface electric conductivity of the printed circuit on COP produced by this method indicated a value of approximately 80% up to around 30 GHz.

ＵＶ改質を用いたシクロオレフィンポリマーフィルム上へのメタライジング

ＵＶ改質を用いたシクロオレフィンポリマーフィルム上へのメタライジング

Fabrication of On-Chip Fuel Cells on Polymer Substrates

Here we report fabrication of tiny on-chip fuel cells on polymer films. Since on-chip cells which we have so far fabricated on silicon substrates through a series of microfabrication procedures are of a simple microchannel-based design, their fabrication on a polymer substrate by molding is attractive in terms of the rapid fabrication and of the inexpensive fabrication procedures and materials. To do so, a nickel mold was first prepared by electroplating from the conventional silicon-based cell, i.e., a master, and then the cell was replicated on cycloolefin polymer films by hot embossing. The microchannel thus replicated on the polymer film was confirmed to be almost identical to the silicon master by observation with a confocal microscope. Finally, Au current collectors sufficiently adhesive to the polymer were successfully deposited after the surface modification by an oxygen plasma treatment.