Plastic Film Substrates Research Articles

Effect of Deposition and Storage Conditions on the Gas Permeability of SiOx Thin Films

SiOx films (80 nm thick) were vacuum deposited onto a 25-μm-thick polyethylene terephthalate (PET) substrate under various conditions. The effects of chamber pressure, evaporating temperature, and chamber gas composition on the time evolution of the oxygen transmission rate (OTR) were investigated together with changes in the films composition. It was found that the OTR decreases over time when the films are left in air, the rate of the decrease being greater at higher pressures during the formation of the films. However, if the pressure is too high, the OTR immediately reaches a high value after evaporation and does not decrease over time, not even if the films are left in air for a week. It is possible to obtain acceptable low OTR values by employing a moderate operating pressure, a suitable evaporating temperature, and an aging treatment after deposition without using a high-capacity vacuum system and without heat damage of the plastic film substrate.

Low-temperature Growth of Organic-inorganic Hybrid Materials by Organic Catalytic CVD

Organic catalytic CVD (O-Cat-CVD) is an extension of the conventional Cat-CVD technique to organic substances. O-Cat-CVD utilizes metal organic (MO) compounds as CVD sources and provides various types of organic-inorganic hybrid materials at low substrate temperature below 200oC. The growth instrument using high-melting-temperature metal filaments seems to be simple and easily scaled up. Chemical reactions at the hot filament, vapor phase reactions and substrate surface reaction must be taken into account. Although deep understanding is necessary to the mechanism of O-Cat-CVD growth, the method is quite promising as a key thin-film growth method in the industry like film-based electronics which provides various types of flexible devices such as flexible OLED and flexible solar cells using plastic film substrates.

Cleaning-Free Deposition of Highly Crystallized Si Films on Plastic Film Substrates Using Pulsed-Plasma CVD under Near-Atmospheric Pressure

By employing a pulsed-discharge, near-atmospheric-pressure plasma-enhanced chemical vapor deposition, equally qualified pair of poly-Si films are grown on polyethylene terephthalate (PET) substrates placed at both the grounded and the powered electrodes. This finding leads to a roll-to-roll-type deposition system of cleaning-free operation for film growth.

42.1: Invited Paper: Processing Flexible Displays

AbstractWe present the fabrication aspect of flexible displays. Fabrication of flexible displays requires proper material selection, handling of plastic film substrates, low temperature process for the fabrication of TFTs on plastic substrate. In addition, for the low cost fabrication approach, direct printing of TFT patterning without photolithography process is also required. We describe Samsung LCD's approach path to the fabrication of flexible displays and future plan to develop the practical method that leads to the production level of flexible displays.

Adhesion of functional layer on polymeric substrates for optoelectronic applications

The use of plastic film substrates for organic electronic devices promises to enable new applications, such as flexible displays. Plastic substrates have several distinct advantages, such as ruggedness, robustness, ultra lightness, conformability and impact resistance over glass substrates, which are primarily used in flat panel displays (FPDs) today. However, high transparency, proper surface roughness, low gas permeability and high transparent electrode conductivity of the plastic substrate are required for commercial applications. Polyesters, both amorphous and semicrystalline, are a promising class of commercial polymer for optoelectronic applications. Surface modification of polyester films was performed via chemical solution determining hydrolysis or oxidation. Hydrolysis was carried out by means of sodium hydroxide solution and oxidation by using standard clean 1 (SC-1) of RCA procedure [1]. For this work we have used commercial polymer films of 100µm in thickness: AryLite™ [2], supplied by Ferrania Imaging Technologies S.p.A. and characterised by very high glass transition temperature, Mylar™ (Polyethylene Terephthalate PET) and Teonex™ (Polyethylene Naphthalate PEN) both supplied by Dupont. More over, a bioriented and semicrystalline PET have been used. The aim of this study is modifying the polymer surface to improve the adhesion between organic-inorganic layer. It was found that the NaOH and SC-1 treatment cause a decrease of contact angles. In the present study we have deposited a thin films of amorphous hydrogenated silicon (a-Si:H) and its oxide (SiO2) on a new high temperature polymer substrate, AryLite™, by plasma enhanced chemical vapour deposition (PECVD) [3], with a radio frequency plasma system.

What's new in digital displays?

Flexible displays using plastic film substrates are key devices for ubiquitous and universal services of digital broadcasting because of their mobile characteristics, low-cost productivity, and flexibility of viewing style. Polymer organic light-emitting devices (POLEDs) and ferroelectric liquid crystal (FLC) films composed of FLCs and polymer networks are promising display devices and materials for the reproduction of TV images in which gray-scale and high-speed response characteristics are required. Both prototype flexible displays of POLED and A4-sized FLC have been fabricated using phosphorescence materials. Performances of these displays showed substantial potential for ubiquitous and universal digital broadcasting services.

A Memorable and Flexible Dot Matrix Type Display Using Ferroelectric Liquid Crystals

The cause for the deterioration of the alignment and the electro-optical property in the SSFLC panels fabricated with the adhesive patterned spacer technology is investigated, and several results indicating the link between the deterioration and the insufficient baking temperature during the fabrication process are obtained. SSFLC panels with improved elector-optical property are fabricated using plastic film substrates with high heat resistance. Multiplex driving of a passive matrix type SSFLC panel with film substrates is achieved, and a memorable and flexible dot matrix type display using ferroelectric liquid crystals is realized.

Low-Temperature Growth of InAs on Glass and Plastic Film Substrates by Molecular-Beam Deposition

InAs layers were deposited on glass substrates by molecular-beam deposition at substrate temperatures of 180–240 °C at As/In beam equivalent pressure (BEP) ratios of 3–30. X-ray diffraction (XRD) patterns indicated that the InAs layers are polycrystalline and are more preferentially textured in the (111) plane when deposited at higher temperatures and lower As/In BEP ratios. Room-temperature Hall effect measurement showed that the films deposited at an As/In BEP ratio of 30 exhibit n-type conduction with electron concentrations of approximately 3 ×1018 cm-3, being almost independent of substrate temperature. With decreasing As/In BEP ratio from 30 to 3 at a fixed substrate temperature of 240 °C, the electron concentration decreased to 1.5 ×1018 cm-3 and the electron mobility increased to 610 cm2/(V·s). Preliminary results of the deposition on plastic substrates showed an electron mobility of 460 cm2/(V·s) when the layer was deposited at 280 °C at an As/In BEP ratio of 30.

An organic catalytic CVD: Principle, apparatus and applications

Organic catalytic CVD (O-Cat-CVD) is an extension of the conventional Cat-CVD technique to organic substances. O-Cat-CVD utilizes metal-organic (MO) compounds as CVD sources and provides various types of organic–inorganic hybrid materials at low substrate temperature below 200 °C. This paper introduces the research and development (R/D) to industrialize the O-Cat-CVD and related technologies in Material Design Factory (MDF) Co., Ltd. which is the first university-based venture business company of Osaka City University. Especially, this paper describes the development of a plasma-assisted catalytic CVD apparatus and the application to the growth of various types of organic–inorganic hybrid materials on plastic film substrates at low temperature.

Bistable FLC Panels with Film Substrates using a Novel Adhesive Patterned Spacer Technology

A novel adhesive patterned spacer technology has been developed to improve the strength against external forces and the cell gap uniformity of a liquid crystal panel. The feature of this technology is that the patterned spacers formed in the active (displaying) area of the panel are adhered to the both substrates by adding a small amount of a resin on the top surfaces of the spacers. Using this technology, bistable ferroelectric liquid crystal (FLC) panels with plastic film substrates have been fabricated.

Microcell Liquid Crystal Film for High-Contrast Flexible Display Applications

We have successfully fabricated high-contrast microcell liquid crystal displays (LCDs) using microstructure replication technology in thin plastic film substrates. These novel flexible LCDs comprise microcell replication, alignment treatments, and cell assembly. The cell gap of such flexible LCDs was maintained well by cross-type spacers formed by photolithography, despite bending: moreover, the deviation in cell gap under various bending states was less than 0.1 µm. The structure, fabrication technique, and basic display characteristics of the flexible LCD are also described. Finally, this device shows high mechanical stability against external bending, a high contrast ratio of 500:1, and an acceptable response time. Compared with photopolymerisation-induced phase separation, the micro-cell LCD has a higher contrast ratio, a more reliable fabrication process, and a strong potential as a high-performance flexible LCD.

Reactive vacuum vapor deposition of aluminum oxide thin films by an air-to-air metallizer

Reactive vacuum vapor deposition of aluminum oxide thin films by an air-to-air metallizer was examined via the direct simulation Monte Carlo method and experiments. Comparison of the calculated results with the measurements of the Al oxide thin film’s thickness showed (a) that the empirical flux of Al atoms arriving at the substrate is lower than the calculated result, probably due to the formation of Al oxide on the evaporation surface and (b) that the amount of oxygen calculated from the thickness of the film is twice the amount corresponding to the calculated flux, probably due to the effects of the decreased sticking coefficient of oxygen on the evaporating surface and sidewall, underestimated gas phase reaction, large mesh size overestimated film density, and formation of substoichiometric oxide. Aluminum oxide thin films deposited on plastic film substrates by this metallizer under strictly controlled O2 supply conditions have good transparency, an oxygen transmission rate of 2.7cc∕m2day, and an electrical resistivity of 4.4×106Ω2m. Furthermore it was found that the oxygen transmission rate was reduced greatly to 1.0cc∕m2day or less when the Al oxide coating film was laminated with another plastic film using an adhesive.

Room‐Temperature Synthesis of Porous Nanoparticulate TiO2 Films for Flexible Dye‐Sensitized Solar Cells

AbstractA novel room‐temperature method for the preparation of porous TiO2 films with high performance in dye‐sensitized solar cells (DSSCs) has been developed. In this method a small amount of TiIV tetraisopropoxide (TTIP) is added to an ethanolic paste of TiO2 nanoparticles, where it hydrolyzes in situ and connects the TiO2 particles to form a homogenous and mechanically stable film of up to 10 μm thickness without crack formation. Residual organics originating from the TTIP were removed by UV–ozone treatment of the films, leading to a remarkable improvement of the cell efficiency. Intensity‐modulated photocurrent/voltage spectroscopy (IMPS/IMVS) showed that the main effect of the UV–ozone treatment is to suppress the recombination of photogenerated electrons, thereby extending their lifetime. The efficiency was further increased by preheating the TiO2 nanoparticles before the paste preparation to remove contaminants originating from the preparation process of the particles. Solar‐to‐electric energy conversion efficiencies of 4.00 and 3.27 % have been achieved for cells with conductive glass and plastic film substrates, respectively, under illumination with AM 1.5 (100 mW cm–2) simulated sunlight.

56.2: Invited Paper: Pixel-Isolated Liquid Crystal Mode for Plastic Liquid Crystal Displays

Abstract We proposed a pixel-isolated liquid crystal (PILC) mode for enhancing mechanical stability of flexible display applications. Since the LC molecules in this mode are isolated in pixels by patterned or phase-separated microstructures, the LC alignment is stable against external pressure. Moreover, the cell gap of our structure is uniformly preserved against bending deformation of the plastic substrates since two substrates are tightly attached each other by the solidified polymer layer produced by photo-induced anisotropic phase separation. For flexible display applications, we have tested the mechanical stability of electro-optic properties in PILC structures with plastic substrates. 1. Introduction In recent years, roll-up displays have drawn considerable attention for next-generation information displays because of their excellent portability such as light weight, thin packaging, and flexibility. Among several available technologies, it is expected that a liquid crystal display (LCD) using plastic film substrates is the most promising device because of its superior visibility with low power consumption over other displays such as organic light-emitting device or electrophoretic displays. However, there are still critical problems regarding the fabrication of commercially available plastic LCDs with current technologies based on the glass substrates. One of those problems is the instability of LC structures due to hydrodynamic properties of LCs at bending and another is the separation of two plastic substrates due to the flexibility of film substrates. Such problems do not exist in conventional glass-substrate-based LCDs since glass substrates can sustain a stable LC alignment condition against external bending or pressure. To solve these problems, several types of polymer wall and/or network as supporting structures have been proposed and demonstrated [1]-[7]. These structures were fabricated using an anisotropic phase separation method from polymer and LC composite systems by applying a patterned electric field or spatially modulated UV intensity. However, these methods require high electric field to initiate the anisotropic phase separation or remain residual polymers in unexposed regions that reduce optical properties and increase the operating voltage of the devices.

Production Technologies of Film Solar Cell

AbstractLight-weight, large-area and flexible solar cells and modules were developed. Roll-to-roll processes including an improved film deposition process named “Stepping-roll process” are used to fabricate large-area hydrogenated amorphous silicon-based solar cells in succession on plastic film substrates. A unique device having through-hole contacts was developed and applied to simplify the production processes and to generate high voltage using connection in series. Production technologies, such as (1) light-weight and large area module fabrication, (2) plasma condition controlled chemical vapor deposition, (3) low substrate temperature selective reactive sputtering, and (4) large-area uniform transparent conductive oxide film deposition are reviewed.

A Transparent, High Barrier, and High Heat Substrate for Organic Electronics

The use of plastic film substrates for organic electronic devices promises to enable new applications, such as flexible displays and conformal lighting, and a new low-cost paradigm through high-volume roll-to-roll fabrication. Unfortunately, presently available substrates cannot yet deliver this promise because of the challenge in achieving the required combination of optical transparency, impermeability to water and oxygen, mechanical flexibility, high-temperature capability, and chemical resistance. Here, we describe the development and performance of a plastic substrate comprising a high heat polycarbonate film combined with a unique transparent coating package that is aimed at meeting this challenge.

Transparent hybrid inorganic/organic barrier coatings for plastic organic light-emitting diode substrates

We have developed a coating technology to reduce the moisture permeation rate through a polycarbonate plastic film substrate to below 1×10−5g∕m2∕day using plasma-enhanced chemical vapor deposition. Unlike other ultrahigh barrier (UHB) coatings comprised of inorganic and organic multilayers, our UHB coating comprises a graded single hybrid layer of inorganic and organic materials. Hardness and modulus of the inorganic and the organic materials are tailored such that they are similar to those of typical glass-like materials and thermoplastics, respectively. In this barrier structure, the composition is periodically modulated between the inorganic and the organic materials, but instead of having distinctive interfaces between two materials, there are “transitional” zones where the coating composition changes continuously from one material to another. Our UHB coating also has superior visible light transmittance and color neutrality suitable for the use of display and lighting device substrates.

Fabrication of Electrical Circuit Using Palladium Colloid

A precise electrically conductive circuit was fabricated on a plastic film substrate with an electroless Cu-plating layer that was formed on a metal colloid printed pattern. The printed pattern was formed with the inks that contain the mixture of silver colloid and palladium colloid. The degree of catalytic activity of the printed pattern upon the electroless Cu-plating was enhanced by the addition of an extremely small amount of palladium colloid into the metal colloid ink; plating speed was increased by the three times on the metal colloid pattern that was formed with the inks containing only 1 wt% of mixed metal colloids. The Electronic circuit formation and its practical performance were confirmed for the circuit fabricated by both PIJ (Cu-plating on ink jet pattern) and PFS (Cu-plating on filled and squeezed pattern) processes.

A4-sized flexible ferroelectric liquid-crystal displays with micro color filters

— We demonstrated an A4-paper-sized flexible ferroelectric liquid-crystal (FLC) color displays fabricated by using a new plastic-substrate-based process which was developed for large-sized devices. Finely patterned color filters and ITO electrodes were formed on a plastic substrate by a transfer method to avoid surface roughness and thermal distortion of the substrate, which induce disordering of the FLC molecular alignment. The thickness of an FLC/monomer solution sandwiched by two plastic-film substrates was well controlled over a large area by using flexographic printing and lamination techniques. Molecular-aligned polymer walls and fibers were formed in the FLC by a two-step photopolymerization-induced phase-separation method using UV-light irradiation. A fabricated A4-sized flexible-sheet display for color-segment driving was able to exhibit color images even when it was bent.

A light and flexible plasma tube array with a film substrate

— The plasma tube array is expected to lead to the realization of wall-sized displays. This method will realize an emissive-type display with a flexible screen and an expandable screen size. We have investigated a plastic film substrate with display electrodes for use as a flexible screen and successfully developed the world's largest bendable emissive display (1000 × 128 mm). The operating voltage distribution was improved compared to that with a plate substrate, and a sufficient voltage margin was maintained.