Masao Fukuyama

An aluminum solid electrolytic capacitor with an electroconducting-polymer electrolyte

Abstract A new type of aluminum solid electrolytic capacitor in which electroconducting polymer is applied as an electrolyte was developed. It was found that polypyrrole doped with alkylnaphthalenesulfonate (PPy/ANS) offers excellent thermal and moisture stabilities. By providing an etched and anodized aluminum foil electrode with a thin layer of pyrolytic manganese dioxide, higher coverage with electrochemically synthesized polypyrrole was accomplished. The newly developed capacitor not only has good frequency and temperature characteristics but also has good thermal and moisture stabilities.

Phenyl-capped oligothiophenes : novel light-emitting materials with different molecular alignments in thin films

We have developed novel light-emitting materials consisting of phenyl-capped oligothiophenes and studied their spectroscopic and structural characteristics in the thin film form. These oligothiophenes have one to four thiophene unit(s) in the molecule. Emission maxima for these materials cover the spectral range 470 to 620 nm and blue to orange emissions are clearly visible. On the basis of the X-ray diffraction studies, we show that the thin films exhibit different molecular alignment (either vertical or parallel) depending on the compounds, even though those films were prepared under the same condition. This is consistent with the results of the absorption spectroscopy.

Stability study of polypyrrole and application to highly thermostable aluminum solid electrolytic capacitor

Abstract This paper describes the stability of electropolymerized polypyrrole and a highly thermostable aluminum solid electrolytic capacitor in which polypyrrole is applied as an electrolyte. We found that polypyrrole doped with tri-i-propylnaphthalenesulfonate (PPy/TIPNS) shows excellent thermostability and its conductivity decay stems from the addition reaction of oxygen followed by thermal decomposition in which oxygen participates. On the basis of these results, we developed a highly thermostable aluminum solid electrolytic capacitor which is composed of an etched and anodized aluminum foil anode covered with electropolymerized PPy/TIPNS and is hermetically sealed. The capacitor continuously functioned for more than 3600 h at 150 °C without any deterioration. Moreover, the capacitor also showed ideal impedance-frequency characteristics comparable to those of the multilayer ceramic capacitor and flat temperature characteristics in the wide range of −50 to 150 °C.

Electroluminescent features of oligothiophenes dispersed as a dopant in host matrices

The electroluminescent (EL) features of oligothiophenes dispersed as a dopant in the host matrices comprising tris(8-hydroxyquinoline)aluminum have been investigated. We chose the oligothiophenes that are substituted with phenyl or methyl groups at both the molecular terminals and possess various degrees of polymerization. Regarding both the phenyl- and methyl-substituted materials, the EL spectra are progressively red-shifted with the increasing number of thiophenes. Comparing these spectra with the photoluminescent spectra, we have found out that the EL arises mostly from the dopant molecules of the oligothiophenes. The emission is dominated by energy transfer from host matrices to the dopant molecules, leading to the enhanced device efficiencies. The specific effects of the phenyl- or methyl-substitution and the extension of the π-delocalization in the molecules are also discussed.

Covering anodized aluminum with electropolymerized polypyrrole via manganese oxide layer and application to solid electrolytic capacitor

A new technology for covering an etched and anodized aluminum (Al) foil with polypyrrole (PPy) was developed. PPy was electropolymerized from an external electrode via an extremely thin semiconducting manganese oxide layer prepared on the etched and anodized Al foil in advance. Pyrolytic and reduced manganese oxide could be used with little difference in the performance of the PPy layer growth. To obtain a high coverage ratio, the optimal starting materials were manganese nitrate for the pyrolysis process and sodium permanganate for the reduction process. On the basis of the technology, two kinds of Al solid electrolytic capacitors, in which the PPy layers are used as electrolytes, were produced and characterized. These capacitors showed almost equal ideal impedance-frequency characteristics, excellent temperature characteristics and environmental stability, and independence of the manganese oxide synthesis route.

Effects of mono-substituted phenol additives on the electrical and mechanical properties of electrochemically synthesized polypyrrole

Abstract Polypyrrole (PPy) which is electrochemically synthesized with a mono-substituted phenol additive has enhanced conductivity, thermal stability and tensile strength. From elemental analysis data, mass spectra and FT-IR spectra, there is no obvious evidence that the additive is incorporated in PPy. Electronic absorption spectra and laser Raman spectra show that the additive reduces the polaron peak and enhances the bipolaron peak. The increased structural regularity is considered to be the reason for the improvement of the electrical and mechanical properties.

Materials Science of Conducting Polymers: An Approach to Solid Electrolytic Capacitors with a Highly-Stable Polypyrrole Thin Film

Abstract This paper summarizes the present status of materials science of conducting polymers relevant to the their technological applications. This paper also describes the development of solid electrolytic capacitors utilizing conducting-polymer thin films as a solid electrolyte. The capacitors are characterized by excellent frequency, temperature and life stabilities and have been put into commercial use in large quantity.