Published papers

情報技術の骨格をなしている、情報ネットワーク技術、情報表示技術及び情報蓄積技術と関連させて本プロジェクトで研究を概略的に紹介している。

平成13年6月28日に行われた三田演説会での講演録。「高速光通信が今後どんな生活をもたらすか」ということに焦点を当て,光ファイバーで可能になる生活につき、わかり易く解説した。

近年、期待が高まっている情報家電機器間の高速ネットワーク、ならびに高速オフィス、キャンパスLANなどの通信メディアとして期待が寄せられているGI型POFの伝送損失特性、信頼性、伝送帯域特性および、応用展開に関する近年の動向について述べる。

Optical polymers which exhibit no birefringence with any orientation of polymer chains are desirable to realize high performance optical devices that handle light. We defined such polymers as "zero-birefringence polymer" and demonstrated two methods for synthesizing the polymers: the random copolymerization method and the anisotropic molecular dopant method. Orientational birefringence is compensated by random copolymerization using positive and negative birefringence monomers at special ratio in the random copolymerization method. Poly (MMA-co-BzMA) (82/18 (wt/wt)) synthesized by this method showed no orientational birefringence with any orientation degree. In the anisotropic molecular dopant method, orientational birefringence of polymers is compensated by doping anisotropic molecules having opposite anisotropy of polarization compared to host polymers. Orientational birefringence of PMMA was completely compensated by doping with 3% of trans-stilbene as the anisotropic molecule. Furthermore, we demonstrated the isotropic particle dopant method to reduce orientational birefringence of polymers. Orientational birefringence for PMMA film was decreased by approximately 20% by doping with 2% of silica particles with average diameter 7nm as the isotropic particle dopant.

ITにおけるこれらの骨格技術と相関する、フォトニクスポリマーとして、屈折率分布型ポリマー光ファイバ（GI型POF）、光散乱ポリマー導光体、それに０複屈折性ポリマー（偏波保存ポリマー）を提案し、それらの問題の解決法と今後の展開について述べる。

近年、従来の金属線と同様な取扱い性を有しながらギガビット以上の伝送を可能とする高速プラスチック光ファイバーに新たな注目が寄せられている。ビデオをレンタルしないで家庭にいながらのダウンロード、臨場感あるリアルタイム動画伝送など、ギガビット光ファイバー網が可能とする膨大な新しい光通信市場を展望する

We have demonstrated the anisotropic molecular dopant method for synthesizing a zero-birefringence polymer that showed no orientational birefringence at any orientation degree of polymer chains. In this method, rod-like molecules such as trans-stilbene having opposite Polarizability anisotropy to that of a host polymer were chosen to compensate orientational birefringence. Orientational birefringence of PMMA was completely compensated by doping with some type of anisotropic molecules. Compensation of orientational birefringence for drawn films of the zero-birefringence polymers was analyzed by the rotating parallel nicols method, and orientation functions for polymer main chains and anisotropic molecules were determined by IR Dichroism, which showed that both the polymer chains and the anisotropic molecules were oriented almost equivalently in the drawing process resulting in complete compensation at any draw ratio. Furthermore, the high transparency of the zero-birefringence polymer was confirmed by light scattering measurement.

GI-POFにつき、その開発史、構造、性能につき簡潔に解説した。

これまでディスプレイの主役であったCRTディスプレイは、急速にフラットパネルディスプレイに置き換わりつつある。本講演では、これからの液晶ディスプレイ支えていくと期待される「ゼロ複屈折性光学ポリマー」と「光散乱ポリマー導光体」について紹介する。

We proposed the “birefringent crystal dopant method” in order to compensate the birefringence of polymers. In this method, the birefringence was compensated by homogeneous doping with a needlelike crystal which has the opposite birefringence to that of the polymers. Strontium carbonate (SrCO3) was selected for this purpose because it has a large birefringence and a needlelike shape. SrCO3 was synthesized, with a length of about 200 nm and a width of about 20 nm, and doped into a poly-(MMA/BzMA)78/22(w/w)) film. The film was drawn at 130 °C and 4 mm/min. The orientational birefringence of the drawn polymer film at a wavelength of 633 nm was compensated by doping with 0.3 wt % SrCO3 without losing its transparency and thermostability. The analysis of infrared dichroism of the films showed that the birefringence of the films was compensated at a low concentration of SrCO3 because of its orientation-inhibition effect and its high orientation degree as compared with that of the polymer main chains.

Three novel partially fluorinated monomers, bis(2,2-difluorovinyl)formal (I), bis(2,2-difluorovinyl)difluoroformal (II), and bis(1-deutrio-2,2-difluorovinyl)difluoroformal (III) , were prepared. These monomers were polymerized in bulk via free radical mechanism. Monomer I produced a cross-linked polymer, but monomers II and III yielded amorphous polymers (II-P and III-P) having five – and six- membered rings along the backbone. Polymers II-P and III-P were soluble not only in fluorinated solvents but also in nonfluorinated solvents such as THF, 1, 4-dioxane, DMF, and DMSO. They have good thermal stability, high glass transmission temperature, and low dielectric constant. Furthermore, these polymers are completely amorphous and possess outstanding optical clarity extending from visible to near-IR region. The refractive indices of both polymers were measured at various wavelengths to evaluate material dispersion. The material dispersion of II-P and III-P were similar and had low values, which are comparable to perfluorinated polymers and much lower than perdeuterioPMMA. The unique optical properties of these polymers make them attractive for use optical materials.

これまで行ってきた研究成果を光の偏波（またはフォトン）と高分子物質との係わりという視点で原子系のディメンジョンからマクロな不均質構造にわたって順に述べた。

A plastic optical fiber having a W-shaped refractive index profile [W-shaped plastic optical fiber (POF)] was prepared for the first time to realize a higher bit rate transmission than those of the conventional silica-based multimode fiber and graded-index (GI) POF links. Since the W-shaped POF has a valley of the refractive index at the boundary of the core and cladding of the conventional GI POF, the group delay of higher order modes is strongly influenced, thus compensating the modal dispersion that exists in the GI POF. The modal dispersion compensation effect by the W-shaped index profile was theoretically and experimentally confirmed.

Partially fluorinated and perfluorinated dioxolane and dioxane derivatives have been prepared to investigate the effect of fluorine substituents on their free-radical polymerization products. The partially fluorinated monomer 2-difluoromethylene-1,3-dioxolane (I) was readily polymerized with free-radical initiators azobisisobutyronitrile or tri (n-butyl) borane-air and yielded a vinyl addition product. However, the hydrocarbon analogue, 2-methylene-1,3-dioxolane (II), produced as much as 50% ring opening product at 60 °C by free-radical polymerization. 2-Difluoromethylene-4-methyl-1,3-dioxolane (III) was synthesized and its free-radical polymerization yielded ring opening products: 28% at 60 °C, decreasing to 7 and 4% at 0 °C and -78 °C, respectively. All the fluorine-substituted, perfluoro-2-methylene-4-methyl-1,3-dioxolane (IV) produced only a vinyl addition product with perfluorobenzoylperoxide as an initiator. The six-membered ring monomer, 2-methylene-1,3-dioxane (V), caused more than 50% ring opening during free-radical polymerization. However, the partially fluorinated analogue, 2-difluoromethylene-1,3-dioxane (VI), produced only 22% ring opening product with free-radical polymerization and the perfluorinated compound, perfluoro-2-methylene-1,3-dioxane (VII), yielded only the vinyl addition polymer. The ring opening reaction and the vinyl addition steps during the free-radical polymerization of these monomers are competitive reactions. We discuss the reaction mechanism of the ring opening and vinyl addition polymerizations of these partially fluorinated and perfluorinated dioxolane and dioxane derivatives.

通信媒体となりうるプラスチック光ファイバーのうち、高速通信が可能な屈折率分布型プラスチックファイバー(GI型POF)について解説する。