Polyethylene Naphthalate Film Research Articles

Modification of PEN and PET film surfaces by plasma treatment and layer-by-layer assembly of polyelectrolyte multilayer thin films

The surfaces of polyethylene naphthalate and polyethylene terephthalate films were modified by plasma treatment, layer-by-layer (LbL) assembly of polyelectrolyte multilayer thin films and subsequent deposition of SiO2 particles. Plasma treatment rendered the film surfaces hydrophilic and led to the formation of fibrillar patterns. The plasma-treated film surfaces were compatible with multilayers acquired via LbL assembly, and the outer adsorbed polyelectrolyte layer determined the charge of the multilayer surfaces. Negatively charged SiO2 particles were adsorbed to the positively charged surface of the multilayers. This process is potentially applicable to surface modifications of polymer materials by charged compounds.

Gradient Functional Characteristic of Polymer/Nanoparticle Stacks on a Polyethylene Naphthalate Film

Gradient refractive index layered antireflection (GRIL-AR) films were fabricated using a layer-by-layer (LbL) self-assembly method. As a substrate, we chose indium tin oxide–polyethylene naphthalate (ITO–PEN; the refractive index of PEN is 1.77). We deposited the GRIL-AR films on the PEN side of ITO–PEN, and the refractive index was gradually decreased from 1.59 to 1.35 by alternating deposition cycles of SiO2 as a low-refractive-index material and TiO2 as a high-refractive-index material. In the LbL process, each material was movable because it was coated in wet conditions; this may have led to fabrication of the gradient refractive index. When poly(ethylene imine) (PEI) was compared with poly(diallyldimethylammonium chloride), antireflection (AR) using PEI showed high abrasion durability because of the loopy structure of the polymer and a high polymer ratio in the film. With the drying process, the prepared film showed enhanced abrasion durability. GRIL-AR on ITO–PEN showed broad-band AR properties.

Surface hydrophilization of two polyester films by atmospheric-pressure plasma and ultraviolet excimer light exposures

Polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) films were treated with an atmospheric-pressure plasma (APP) jet and a 172-nm ultraviolet (UV) excimer light in air. The advancing and receding water contact angles on both films decreased after the treatments, especially after APP treatment. After the treatments, the hydrophobic recovery was observed and almost diminished within a week. The dispersive component of the surface free energy of the two polyester films did not change due to the APP and UV exposure, whereas the acid–base component drastically increased after the treatments. The X-ray photoelectron spectroscopy results showed that the polyester film surfaces were oxidized by the treatments. From the AFM images, the topographical change on the film surfaces due to the treatments was clearly observed. It was found that the APP treatment of the PET film prevented the deposition of particulate soils in air due to the decrease in the contact area between the film and the soil particle. Furthermore, the soil release in the aqueous solutions was promoted as a result of the hydrophilization of the polyester films due to the APP treatment.

The Development of Polyethylene Naphthalate Films by Low-pressure High-frequency Plasma Chemical Vapor Deposition System with Advance Oxidations Process

AbstractThe low-pressure high-frequency plasma chemical vapor deposition (CVD) system was developed with non-thermal plasma process to study the Polyethylene naphthalate (PEN) surface characteristics. Plasma surface treatment by oxygen can improve the adhesive properties. A mixture of Ar and O

Direct Gold Plating Selectively on UV Modified Polymer Film Using Tiopronin-Gold

An economic and low toxicity gold plating process for bio-compatible device fabrication was investigated. A tiopronin-gold complex altered by mercaptothiodiazole or mercaptotriazole derivatives gave a form of the complex that could be reduced autocatalytically to enable electroless gold plating. Catalytic ca. 5 nm gold particles were selectively grafted into cycloolefin polymer and polyethylenenaphthalate film surfaces by adsorption of tiopronin-gold complex from solution into 20–30 nm deep ultra-violet light modified surface layers followed by reduction with sodium borohydride. Exposure of the catalyst adsorbed surfaces to baths composed of tiopronin-gold complex, mercaptothiodiazole and ascorbic acid resulted in selective electroless plating on the modified surfaces. Observation of the interface cross-section by transmission electron microscopy revealed that the gold deposits were physically anchored to the substrate by nanometer scale octopus trap like structures.

Facile preparation of reduced graphene oxide-based gas barrier films for organic photovoltaic devices

Reduced graphene oxide-based films were prepared to assess their effects as gas barriers on the stability of organic photovoltaic (OPV) devices. The direct spin-casting of a graphene oxide suspension onto an aluminum electrode was performed to encapsulate the associated OPV device with a reduced graphene oxide film. The lifetime of the OPV device after the reduction process was found to be increased by a factor of 50. The gas barrier properties of a graphene oxide layer are closely related to its surface roughness and dispersibility. Furthermore, these gas barrier properties can be enhanced by controlling the thermal reduction conditions. The thermal reduction of a graphene oxide film at a low heating rate results in a low water vapor permeability, only 0.1% of that of an as-prepared polyethylene naphthalate film. These results indicate that the dispersibility, surface roughness, and reduction conditions of a graphene oxide film significantly influence its gas barrier performance. Further investigations of the reduction of graphene oxide films are expected to enable further improvements in performance.

1 μm-thickness ultra-flexible and high electrode-density surface electromyogram measurement sheet with 2 V organic transistors for prosthetic hand control.

A 64-channel surface electromyogram (EMG) measurement sheet (SEMS) with 2 V organic transistors on a 1 μm-thick ultra-flexible polyethylene naphthalate (PEN) film is developed for prosthetic hand control. The surface EMG electrodes must satisfy the following three requirements; high mechanical flexibility, high electrode density and high signal integrity. To achieve high electrode density and high signal integrity, a distributed and shared amplifier (DSA) architecture is proposed, which enables an in-situ amplification of the myoelectric signal with a fourfold increase in EMG electrode density. In addition, a post-fabrication select-and-connect (SAC) method is proposed to cope with the large mismatch of organic transistors. The proposed SAC method reduces the area and the power overhead by 96% and 98.2%, respectively, compared with the use of conventional parallel transistors to reduce the transistor mismatch by a factor of 10.

Effect of Reflective Platinum Film on the Performance of Flexible Dye Solar Cell (DSC)

Robust and flexible dye solar cell (DSC) made up of nanocrystalline TiO2 encapsulated in polyethylene naphthalate (PEN) substrate will be able to fulfill the demand for indoor power applications as it has lower energy and manufacturing cost, produces electricity in low light conditions even under artificial light. The fabrication using PEN substrate has the advantage of scalability and compatible with the roll to roll manufacturing method. This paper reports the study on the effect of platinum film reflectance on the counter electrode to the DSC performance and efficiency. The reflective counter electrode uses the commercially available Pt/Ti PEN film with 100% reflectance properties. The transparent counter electrode with 20.9% reflectance is prepared using pre-treated indium doped tin oxide (ITO). The platinum film is sintered at 170°C followed by direct heat of 150°C to achieve a good bonding between the ITO and the deposited platinum film. Both cells uses TiO2 coated ITO PEN as the working electrode. The DSC test cell with reflective counter electrode increases the cell efficiency compared to the non-reflective counter electrode as there is a higher light spectrum response on the reflective DSC cell.

Space charge, conduction and photoluminescence measurements in gamma irradiated poly (ethylene-2,6-naphthalate)

Polyethylene naphthalate (PEN) thin films were subjected to gamma rays at different doses and changes in both the dielectric and photophysical properties were investigated. Samples were irradiated in air at room temperature by means of a 60Co gamma source at a dose rate of approximately 31Gy/min. Total doses of 650kGy (344h) and 1023kGy (550h) were adopted in this work. The space charge profiles and residual electric field of virgin material and material exposed to these representative doses, obtained after 30min of depolarization following field application in the range 40–200kV/mm, have been examined by Focused Laser-Intensity Modulation Method (FLIMM). The dependence of space charge density with electric field values and irradiation dose is analyzed. Under high DC voltages and after irradiation, PEN tends to accumulate space charge. Space charge versus electric field and current-field characteristics issued from FLIMM method and conduction measurements exhibit good agreement. The high radiation resistance of PEN film is highlighted.

Contrast Enhanced Microscopy Digital Image Correlation: A General Method to Contact-Free Coefficient of Thermal Expansion Measurement of Polymer Films

Thermal expansion represents a vital indicator of the processing history and dimensional stability of materials. Solvent-sensitive, thin, and compliant samples are particularly challenging to test. Here we describe how textures highlighted by contrast enhanced optical microscopy modes (i.e., polarized light (PL), phase contrast (PC)) and bright field (BF) can be used to determine the thermal expansion of polymer films in a contact-free way using digital image correlation (DIC). Three different films were explored: polyetherimide (PEI), polyimide (PI), and polyethylene naphthalate (PEN). Image textural features (e.g., intensity, size, speckle pattern characteristics) obtained by BF, PC, and PL were analyzed by two-dimensional Fourier transform and autocorrelations. The measured in-plane CTEs of PEI, PI, and PEN films, 51.8, 20.5, and 10.2 ppm/K, respectively, closely approached those previously reported using DIC with artificially applied speckle patterns.

In situ deposition of polythiophene nanoparticles on flexible transparent films: Effect of the process conditions

Polythiophene (PTh) was deposited as a thin film and nanoparticles on polyethylene naphthalate (PEN) films via ultrasonication or via magnetic stirring with or without a cationic (cetyltrimethylammonium bromide, CTAB) or non-ionic (Triton X-100) surfactant. The resulting conductive flexible films were characterized by UV-Vis spectroscopy, fluorescence spectrometry, field-emission scanning electron microscopy, contact angle measurements, the four-point-probe technique, X-ray diffraction, and cyclic voltammetry. The highest conductivity was obtained for PTh-CTAB nanoparticles, which had the most compact surface morphology among nanoparticles on PEN films. In general, the surface morphology, electrical conductivity, and whether PTh nanoparticles had been precipitated or deposited depended on the surfactant used, the surfactant/monomer ratio, the oxidant/monomer ratio, and the monomer concentration.

Deposition of electrically conductive ceria/polypyrrole nanocomposite particles on flexible polyethylene naphthalate film via in situ photo-induced polymerization

To achieve a flexible and transparent conductive film via a simple method, ceria/polypyrrole nanocomposite particles were coated on Piranha-treated polyethylene naphthalate (PEN) film as the flexible substrate. Photo-induced polymerization was carried out by cerium (III) nitrate hexahydrate dissolved in acetonitrile and irradiation by UV wavelengths for 2 h. The effect of Piranha treatment on deposition of the conductive nanocomposite particles was examined. Deposited PEN samples prepared at various conditions were characterized using FESEM, AFM and STM, UV–vis spectroscopy, four-probe conductivity and contact angle measurements. Adhesion quality of the deposited nanoparticles was investigated by Scotch-tape test.

Preparation of conductive flexible films by in situ deposition of polythiophene nanoparticles on polyethylene naphthalate

Deposition of Polythiophene (PTh) nanoparticles on the unmodified and modified polyethylene naphthalate (PEN) films via solution based in situ chemical polymerization was investigated as conducting transparent anode electrodes in order to produce transparent conducting films with applications in opto-electronic devices, such as flexible displays. The surface of PEN films were modified by different methods. Surface modification was carried out using Piranha and alkaline (KOH) solution and ultraviolet (UV) radiation as a physical method. Combination of chemical and physical treatments (Piranha and UV) was also examined. The effect of surface modification methods on the properties of the in situ deposited PTh nanoparticles was studied. It was found that electrical conductivity increases ~20 times in effect of modification of PEN by the examined methods. Highly ordered morphology of PTh nanoparticles were observed by field emission scanning electron microscope (FESEM) in the case of surface modification by UV radiation. Hydrophilicity, transparency and surface morphology of the PEN films were found to be influenced by surface modification techniques as well.

6Li Embedded Biaxially Stretched Scintillation Films for Thermal Neutron Detection and Neutron/Gamma Discrimination

Biaxially stretched composite polyethylene naphthalate (PEN) films (BSCPF) embedded with submicron lithium fluoride (6LiF) particles and luminescent molecules were fabricated to make large area scintillation films (≈1 m × 1 m) for thermal neutron detection. BSCPF had 20.2% higher neutron light yield as compared to unstretched composite film (UCPF), and were 2.46 ± 1.47 times more efficient for detecting thermal neutrons than lithiated glass GS20 above lower level discriminator corresponding to an intrinsic efficiency for gamma <10−6. MCNPX simulations for a layered BSCPF detector resulted 6.1 cps for 1 ng 252Cf, thus meeting the Pacific Northwest National Laboratory criteria for absolute neutron detection efficiency and intrinsic gamma‐neutron discrimination. BSCPF have alpha to beta ratio of 0.25, which is higher than that for UCPF (0.11), and also for GS20 (0.22), which offers the possibility of excellent neutron/gamma discrimination.

Flexible and lightweight thermoelectric generators composed of carbon nanotube–polystyrene composites printed on film substrate

A flexible thermoelectric generator (TEG) was fabricated on a polyethylene naphthalate film substrate using a printing process. The thermoelectric material used in this study, a composite material consisting of carbon nanotubes (CNTs) and polystyrene, contained approximately 35 vol. % of voids. Because of the reduction in the density of the CNT–polystyrene composite caused by the voids, the TEG was remarkably lightweight (weight per unit area: ≈15.1 mg/cm2). The TEG generated approximately 55 mW/m2 of power at a temperature difference of 70 °C.

Role of Nanoparticles and Relaxation on Strain-Induced Crystallization Behavior in Uniaxially Stretched Polyethylene Naphthalate Films: A Mechano-Optical Study

The effects of nanoparticle concentration and processing conditions on the relaxation behavior of PEN nanocomposites are investigated using mechano optical techniques where birefringence, true stress and true strain are measured while subjecting the polymer films to uniaxial deformation followed by relaxation. For this purpose, two different stretching temperatures were employed to stretch the films containing 0.5 and 2 wt % nanoparticles: one above and the other below the Tll (liquid–liquid transition). Increasing the temperature as well as the addition of nanoparticles suppresses the spontaneous deformation processes leading to sharp increase in true strain. An instantaneous stress drop is observed during relaxation below the Tll corresponding to the initial glassy component observed in the stress-optical behavior during stretching. This stress is attributed to the presence of segmental rigid correlations that were not broken during the stretching stage. This behavior was found to be absent above the li...

Solution-Processed Flexible Fluorine-doped Indium Zinc Oxide Thin-Film Transistors Fabricated on Plastic Film at Low Temperature

Transparent flexible fluorine-doped indium zinc oxide (IZO:F) thin-film transistors (TFTs) were demonstrated using the spin-coating method of the metal fluoride precursor aqueous solution with annealing at 200°C for 2 hrs on polyethylene naphthalate films. The proposed thermal evolution mechanism of metal fluoride aqueous precursor solution examined by thermogravimetric analysis and Raman spectroscopy can easily explain oxide formation. The chemical composition analysed by XPS confirms that the fluorine was doped in the thin films annealed below 250°C. In the IZO:F thin films, a doped fluorine atom substitutes for an oxygen atom generating a free electron or occupies an oxygen vacancy site eliminating an electron trap site. These dual roles of the doped fluorine can enhance the mobility and improve the gate bias stability of the TFTs. Therefore, the transparent flexible IZO:F TFT shows a high mobility of up to 4.1 cm2/V·s and stable characteristics under the various gate bias and temperature stresses.

Damage and recovery processes for the luminescence of irradiated PEN films

The degradation and recovery of the optical emission characteristics of polyethylene naphthalate (PEN) films were studied during irradiation with MeV protons and UV photons. The photo-stimulated luminescence (PL) consisting of two major peaks decreased with the incident energy fluence, particularly for ion irradiation. At the beginning of irradiation, the rate of reduction of the PL intensity in the UV-irradiated film was comparable to that for ion irradiation, but the residual PL intensity in the UV-irradiated film was considerably larger at higher fluences. In addition, no change in the PL characteristics of the UV-irradiated film was observed after stopping the UV irradiation, indicating that the damage caused by the UV photons was permanent. However, the PL intensity from the ion irradiated film increased immediately when the film was exposed to air. The recovery of the luminescence centers in the ion-irradiated PEN film is attributed to ion-induced surface modification, which plays a role in the enhancement of the dissociation of water molecules and the diffusion process for constituent atoms.

Effect of crystal texture on the anisotropy of thermal expansion in polyethylene naphthalate: measurements and modelling

This paper reports measurements of thermal expansion in polyethylene naphthalate films and relates them to the crystal texture. X-ray diffraction shows that the naphthalate ring planes are distributed with a strong maximum in the plane of the film. The crystal c axes are aligned in the machine direction for uniaxially drawn films but have a bimodal distribution for biaxially oriented samples. Parameters extracted from the distributions were combined with experimental and estimated values of the thermal expansion and stiffness constants for the isotropic amorphous and anisotropic crystalline phases to obtain predictions of thermal expansion coefficient using Ward’s aggregate model. The Voigt average (crystals and amorphous regions in parallel) is very close to the uniaxial experimental expansion coefficients. In the biaxial samples, the model predicts the widthwise variation of principal directions of the expansivity tensor well. A linear combination of the Voigt and Reuss (series arrangement) averages reproduces the measured values.

Conformal thin film silicon photovoltaic modules

A polymer composite material system and a process for encapsulation of thin film solar cells were developed for profiled roofing elements, in view of building-integrated photovoltaic (PV) applications. Amorphous silicon cells were deposited on a polyethylene naphthalate film and encapsulated with additional polymer layers in the form of a flat laminate using industrial processes. The process technology developed in this work included a pre-forming step of the PV laminate and a moulding step of a glass fibre-reinforced polyester composite. These two steps were optimised using thermo-elastic analyses, with attention paid to laminate designs and process windows compatible with the thermo-mechanical limits of the fragile active PV layers. A demonstrator with standard 1.0 m×1.8 m corrugated roofing profile, a weight of 6.3 kg and 60 W of output power was produced. The long-term endurance of the conformal modules was also validated using humidity-freeze, damp-heat and water immersion tests.