Polyethylene Naphthalate Film Research Articles

Cellular polyethylene-naphthalate films for ferroelectret applications: foaming, inflation and stretching, assessment of electromechanically relevant structural features

AbstractCellular polymer films are frequently employed for packaging, insulation, and printing. They can also be used as ferroelectrets in transducer applications. Here, we propose a preparation process for cellular polyethylene-naphthalate (PEN) films with the following steps: (1) foaming by means of supercritical carbon dioxide (CO2), (2) controlled inflation through gas diffusion and expansion, and (3) biaxial stretching. We describe and assess the cellular structure that is formed under suitable processing conditions. For foaming, the PEN films are saturated with supercritical CO2 at room temperature for a few hours, at a pressure as high as 100 bar. The subsequent temperature treatment is very critical for controlling the sample density. Additional inflation can improve the cellular geometry and higher stabilization temperatures during the inflation process cause stronger inflation and thus lower densities. Stretching may be employed in order to achieve a regular cellular structure with lens-like voids. High electromechanical responses, i.e. large piezoelectric thickness coefficients are found only on samples within the proper density range and with optimal cellular structures

Improvement in durability of flexible plastic dye-sensitized solar cell modules

Large-area integrated modules of flexible plastic type dye-sensitized solar cell (DSC) have been fabricated based on polyethylene naphthalate (PEN) film for practical applications such as ubiquitous power sources. From the view point of improving durability, composition of organic solvent-based electrolytes has been investigated. As a result, a plastic DSC module using LiI-free electrolyte maintained its energy conversion efficiency of 2% over 220 h under the accelerated condition of 55 °C and 95% relative humidity.

Temperature behavior of atmospheric-pressure non-equilibrium microwave discharge plasma jets for poly(ethylene naptharate)-surface processing

To understand the mechanism of surface processing using an atmospheric-pressure non-equilibrium microwave discharge plasma jet, we used optical emission spectroscopy to measure the vibrational and rotational temperatures of plasma. A microwave (2.45 GHz) power supply was used to excite the plasma. The vibrational and rotational temperatures in the plasma were measured at approximately 0.18 eV and 0.22 eV. We also conducted plasma surface processing of polyethylene naphthalate (PEN) film to measure changes in the water contact angle before and after the PEN film was processed, as well as while the rotational temperature of the plasma increased. The hydrophilicity of the PEN film surface was found to improve as the rotational temperature of the plasma increased.

Ultrasmooth Ni thin films evaporated on polyethylene naphthalate films for spin quantum cross devices

Surface morphology of Ni thin films vacuum-deposited on polyethylene naphtalate (PEN) organic films has been investigated as a function of Ni film thickness for spin quantum cross devices. The surface roughness of the Ni films decreases from 1.3nm, being the roughness of PEN films, down to 0.69nm as the thickness of Ni films increases up to 41nm. As a result of the scaling investigation of the surface roughness, the surface roughness for Ni films of sub-10-nm thickness, in the scanning scale of the film thickness, is less than 0.23nm, corresponding to one atomic layer thickness. These experimental results indicate that Ni thin films on PEN films are suitable as a candidate of metal/insulator hybrid materials used for spin quantum cross devices and may open up a novel research field on the electric characteristics of a few atoms or molecules, which leads to high-density memories.

Basic Characteristics for PEN Film Surface Modification using Atmospheric-Pressure Non-equilibrium Microwave Plasma Jet

To understand the mechanism of surface processing using an atmospheric-pressure non-equilibrium microwave discharge plasma jet, we used optical emission spectroscopy to measure the vibrational and rotational temperatures of plasma. A microwave (2.45GHz) power supply was used to excite the plasma. The vibrational and rotational temperatures in the plasma were measured at approximately 0.18 eV and 0.22 eV. We also conducted plasma surface processing of polyethylene naphthalate (PEN) film to measure changes in the water contact angle before and after the PEN film was processed and as the rotational temperature of the plasma increased. Analysis of all the results from XPS, and surface free energy as calculated from the contact angle confirms that the improvement in hydrophilic properties of the PEN film surface using the microwave discharge plasma jet were effective, after comparing improvements in the hydrophilic properties of PEN film surface by plasma exposure. We conclude that the hydrophilicity of the polyethylene naphthalate film surface improves as the rotational temperature of the plasma increases.

Nonwoven electrowetting textiles

Electrowetting of two nonwoven textile platforms is reported. Demonstrated nonwoven textiles include a polyethylene naphthalate film that was laser milled with ∼125μm pores, and pressed paper that was made using wood microfibers of 35–50μm diameter. Vacuum deposition provided an Al electrode on the polymer textile whereas layer-by-layer nanoassembly provided an organic PEI-PEDOT:PSS electrode on the wood microfibers. Both textiles were electrically insulated with parylene C and fluoropolymer. Irreversible electrowetting of water was achieved over contact angles of ∼120° to ∼70° by applying 0–100V. Completely reversible electrowetting of water/oil was also demonstrated.

Cellular polyethylene-naphthalate ferroelectrets: Foaming in supercritical carbon dioxide, structural and electrical preparation, and resulting piezoelectricity

Polymer foams with electrically charged cellular voids, the so-called ferroelectrets, are soft piezoelectric transducer materials. Several polymers such as polyethylene terephthalate or cyclo-olefin copolymers are under investigation with respect to their suitability as ferroelectrets. Here, the authors report an additional ferroelectret polymer, cellular polyethylene-naphthalate (PEN), which was prepared from commercial uniform polymer films by means of foaming in supercritical carbon dioxide, inflation, biaxial stretching, electrical charging, and metallization. Piezoelectric d33 coefficients of up to 140pC∕N demonstrate the suitability of such cellular PEN films for transducer applications. Their piezoelectricity is partially stable at elevated temperatures as high as 100°C.

High performance flexible pentacene thin-film transistors fabricated on titanium silicon oxide gate dielectrics

Pentacene thin-film transistors (TFTs) with a high dielectric constant gate insulator, titanium silicon oxide (TiSiO2), were fabricated on flexible polyethylene naphthalate films coated with indium tin oxide layers. In order to define the device characteristics, the thickness dependence of the gate dielectric properties was studied. The pentacene TFT with a 132-nm-thick TiSiO2 film showed high performance with a threshold voltage of −0.88V, an inverse subthreshold slope of 317mV/decade. From the current-voltage characteristics, the field-effect mobility was obtained, resulting in an impressive mobility of 0.67cm2∕Vs at an operating voltage as low as −5V.

Study of Gold Thin Films Evaporated on Polyethylene Naphthalate Films toward the Fabrication of Quantum Cross Devices

AbstractMolecular electronics devices continue to be pursued as a technology that offers the prospect of scaling device dimensions down to a few nanometers and also promote a practical introduction for high-density memory applications. One of several molecular devices is a cross-bar memory device fabricated by nanoimprint lithography process, which has achieved the production of 30-nm half-pitch patterning. However, today's production procedures such as nanoimprint lithography, optical lithography, and electron-beam lithography, do not allow for the resolution to achieve sub-10-nm line-width structures. Recently we have proposed a double nano-“baumkuchen” (DNB) structure, composed of two thin slices of alternating metal/insulator nano-“baumkuchen” as a lithography-free nano-structure fabrication technology. The DNB has potential application in a high-density memory device, the cross point of which can scale down to ultimately a few nanometers feature sizes because the pattering resolution is determined by the metal-deposition rate, ranging from 0.01 nm/s to the order of 0.1 nm/s. One element of the DNB structure is called a quantum cross (QC) device that consists of two metal nano-ribbons having edge-to-edge configuration. In the area of edge-to-edge QC devices there has been no experimental reports, meanwhile face-to-face devices such as cross-bar devices and spin tunneling devices, have been widely studied both theoretically and experimentally. In our present work, as the first experimental attempt toward the fabrication of QC devices, we have studied gold thin films evaporated on polyethylene naphtalate (PEN) organic films, which can be a candidate of metal/insulator part used for QC devices, by using the atomic force microscope (AFM). Au thin films were thermally evaporated on PEN films in the high vacuum chamber including the film-rolled-up system. The Au thickness was measured by a mechanical method using the stylus surface profiler and an optical method using the diode pumped solid state (DPSS) green laser. Surface morphologies of Au thin films on PEN films were analyzed by the AFM at room temperature. As the thickness of Au films evaporated on PEN films decreases from 20 nm to 5 nm, the AFM surface roughness is reduced from 4.8 nm down to 1.5 nm in the scanning area of 500~500 nm2. The Au grain size is 28.0-4.6 nm for 5-nm-thick Au films and 45.8-5.8 nm for 10-nm-thick Au films, respectively. As a result of the scaling investigation of the surface roughness, the surface roughness of 5-nm-thick Au films is 0.22 nm, corresponding to one atomic size, in the scanning scale of 5 nm. These experimental results indicate that Au thin films on PEN films are suitable as a candidate of metal/insulator(organic films) hybrid materials used for QC devices, and may open up a noble research field to clarify the electric characterization of QC devices using a few atoms or molecules leading to high-density memories.

All-plastic dye-sensitized solar cell using a polysaccharide film containing excess redox electrolyte solution

All-plastic dye-sensitized solar cells (DSSCs) using TiO2 paste (SP-210), indium tin oxide-coated polyethylene naphthalate (PEN/ITO) film and a Pt-coated PEN/ITO film counter electrode, were fabricated with 1.0 wt% κ-carrageenan solid electrolyte containing the redox electrolytes (I-/I3-) solution. The cell performance of the all-plastic cell using 1.0 wt% κ-carrageenan solid electrolyte was investigated in comparison with liquid type one, showing that the values of Voc (open circuit voltage) and ff (fill factor) were the same, but Jsc (short circuit current) and η (conversion efficiency) were slightly larger for the liquid type electrolyte cell than the solid type one. A higher conversion efficiency was exhibited by UV-irradiation before heat treatment of the PEN/ITO/TiO2(SP-210) film than that after heat treatment. The effect of heat treatment conditions was investigated according to a modified hydrothermal treatment of the PEN/ITO/TiO2(SP-210) film, showing that the ff values become high (>0.7) by hydrothermal treatment. The electrochemical impedance spectroscopy (EIS) has shown the important comparison of each charge transport processes between the all-plastic and the conventional cells.

A transparent sheet display by plastic MEMS

Abstract— A new type of color‐image display pixel based on MEMS (microelectromechanical systems) technology of plastic materials is presented. The mechanism for making color is optical interference using a Fabry‐Perot interferometer. A thin sheet of PEN (polyethylene naphthalate) with a metal half‐mirror was laminated over a glass or PEN substrate with an optical cavity inside. The electrostatically controlled deformation of the PEN film changes the color of the transmitting light by interference within the optical cavity. Color pixels of three primary colors (red, green, and blue) were successfully developed and demonstrated, with a driving voltage ranging from 80 to 120 Vdc. Thanks to the mechanical flexibility of the PEN films, the display could operate even when placed on a curved surface.

Transparent amorphous conductive Cd–In–Sb–O thin films for flexible devices

Transparent conductive amorphous Cd–In–Sb–O thin films were deposited on a flexible polyethylene naphthalate film by rf magnetron sputtering at room temperature. The large Hall mobility of ∼26 cm 2 V −1 s −1 was observed on the films with carrier density >10 20 cm −3. The carrier density varied from the order of 10 20 to 10 17 cm −3 with increasing the oxygen partial pressure. The Hall mobility reached up to ∼17 cm 2 V −1 s −1, even at carrier density of ∼10 17 cm −3. Flexible transparent filed-effect transistor was also fabricated using the Cd–In–Sb–O thin films as a channel layer and the device performance was investigated. The device exhibited a field-effect mobility of ∼0.45 cm 2 V −1 s −1 and an on–off ratio of ∼10 2 at room temperature.

Transparent color pixels using plastic MEMS technology for electronic papers

We present a new type of image display device that could be used as, for instance, over-sized rewritable color posters by using a simple MEMS fabrication technique. The mechanism of making colors is based upon the optical interference of the Fabry-Perot interferometer. A thin PEN (polyethylene naphthalate) film with metal half-mirror was laminated over a glass substrate with an optical cavity, and the electrostatic deformation of the film controlled the color of the transmitting light. Color pixels of three primary colors (red, green and blue) were successfully demonstrated with driving voltage ranging from 80 to 120Vdc.

P-56: The Impact of Environment on Dimensional Reproducibility of Polyester Film during Flexible Electronics Processing

DuPont Teijin Films(DTF) have developed engineered substrates specifically for the flexible electronics market. Teonex ®Q65 is a biaxially oriented crystalline polyester with a tailored surface and it is emerging as a competitive material for the base substrate in OLED displays and active matrix backplanes. Given the demanding dimensional reproducibility requirements in the more demanding display applications, uncontrolled moisture absorption during the processing cycle could potentially be far more significant than the inherent shrinkage of the base substrate. Understanding the impact of this effect and optimising the processing steps involved in device manufacture will be critical to achieving the ultimate performance that can be achieved with the base substrate. This contribution will discuss the impact of the processing environment on dimensional reproducibility of polyethylene naphthalate film (Teonex® Q65) and give examples of the film in use.

Millisecond time-range analysis of space-charge distribution and electroluminescence in insulating polymers under transient electric stress

The combined analysis of the space charge and electroluminescence (EL) in insulating polymers provides useful information on charge transport and energy dissipation. We are particularly interested in defining critical transport regimes leading to energy releases potentially harmful for the material. These critical regimes can be characterized by investigating the internal charge distribution when electroluminescence is detected. The dc case has been adequately covered: however, very few results are reported involving transient electric stress because its investigation needs a very fast space-charge detection setup. We have carried out such an analysis in the case of low-density polyethylene and polyethylene naphthalate (PEN) films by using fast acquisition techniques for both, the space-charge profile (resolution of 40μs in time and 15μm in depth) and the electroluminescence acquisition (250μs time resolution). The films were subjected to a voltage ramp up to a targeted level followed by a stabilization and a short circuit, the whole wave form lasting for 50 ms. Voltage rise rates from 300 to 3000kV∕s and fields up to 200kV∕mm were used as well as ac stress in a frequency range from 0.2 to 50 Hz. Mobile charges following the voltage application were in evidence in PEN. Two contributions have been distinguished in the EL excitation mechanisms: one is due to hot carrier impact processes driven by dV∕dt, and the other is linked with recombination and controlled by the dc transport properties of the material.

A technique to measure Poisson’s ratio of ultrathin polymeric films using atomic force microscopy

Atomic force microscopy (AFM) has been used to measure Poisson’s ratio of ultrathin polymeric films used as substrates in magnetic tapes. A technique has been developed to measure the longitudinal and lateral displacements under uniaxial loading of the films on a microscale. Uniaxial tension is applied by means of a tensile stage. Surface height profiles obtained from the AFM images of unstretched and stretched samples are used to monitor the changes in displacements of the polymer samples in the longitudinal and lateral directions simultaneously. Standard polyethylene terephthalate, tensilized polyethylene terephthalate, and tensilized polyethylene naphthalate films are used to demonstrate the technique.

Mechanical property and dimensional stability of substrates for magnetic tapes

We have performed a comparative study on mechanical property and dimensional stability of substrates for magnetic tapes. The substrates include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and aromatic polyamide (ARAMID), which could be used for linear-type magnetic tapes for computer data storage. We have demonstrated that ARAMID is the most attractive substrate and that PET has the advantage of considerably smaller irreversible creep deformation and lateral contraction caused by tension as compared to PEN film. In this paper, we also introduce recently developed PET (Advanced PET) with higher glass transition temperature compared to conventional PET; moreover, we discuss the relationship between film properties and polymeric structures of these substrates.

Anisotropic absorption spectra of polyester films in the ultraviolet and vacuum ultraviolet regions

Reflection spectra of polyethylene terephthalate (PET) and polyethylene naphthalate films were measured for 50 to 600 nm, using a Seya–Namioka type monochromator at UVSOR, and were converted into absorption spectra by Kramers–Kronig formula. Dichroic nature of drawn films was clearly displayed in the whole region. Previous analysis was confirmed to be true that the third absorption peak of PET, which appeared in the limit of atmospheric measurement, consisted of two peaks of different polarization. Their VI and VII absorption bands at 13.3–15.5 eV originated in transitions associated with σ electrons, and had absorption coefficients of 1.1–1.3×10 6 cm −1.

Organic thin-film transistor-driven polymer-dispersed liquid crystal displays on flexible polymeric substrates

We have fabricated organic thin-film transistor (OTFT)-driven active matrix liquid crystal displays on flexible polymeric substrates. These small displays have 16×16 pixel polymer-dispersed liquid crystal arrays addressed by pentacene active layer OTFTs. The displays were fabricated using a low-temperature process (<110 °C) on flexible polyethylene naphthalate film and are operated as reflective active matrix displays.

INFLUENCE OF TEMPERATURE ON WORK OF FRACTURE PARAMETERS IN SEMI-CRYSTALLINE POLYESTER FILMS

Plane-stress ductile fracture of semi-crystalline polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT) films of thickness 0.125 mm was studied as a function of temperature using essential work of fracture (EWF) methodology. The results indicated that the specific EWF, w e, for all three materials is independent of temperature between 23 and 80°C but shows temperature dependence outside this range. The w e values for PET and PEN materials were remarkably similar and were considerably greater than the PBT values. The effect of temperature on w e was reasonably explained using COD, where σ y is the tensile yield stress of the material, COD is the crack opening displacement of the advancing crack front, and λ is a constant. The results for specific non-EWF, βw p, indicated that PEN has the highest value and PBT the lowest value at any given temperature.