Published papers

Inherent light scattering losses by several methacrylic ester polymers were investigated. The intensities of polymerization scattering Vv from PMMA reported so far were in the order of 10-5 cm-1 even in a sample polymerized with rigorous purification, and had angular dependence in its Vv intensity, which implied the existence of large size heterogeneities of several hundred Å. In this paper, alkyl (ethyl and isobutyl) and fluoroalkyl (trifluoroethyl and trihydroperfluoropropyl) methacrylate glasses as well as PMMA, in which the Vv intensities were in the order of 10-6 cm-1 and no large size of heterogeneities were recognized, were prepared for the first time. Considering that our data are quite near the value predicted by the thermally induced fluctuation theory, and on the basis of our previous study, it is suggested that the thermally induced fluctuation theory, and on the basis of our previous study, it is suggested that the scattering data presented in this paper show an inherent limited loss for these methacrylic ester polymer glass in the atmosphere.

近視用コンタクトレンズへの屈折率分布材料の応用を提案、実証した。

A PMMA glass with the lowest light scattering loss among data reported so far and with no angular dependence in its scattering intensity was prepared by radical polymerization above Tg (Sample A). The temperature dependence of the light scattering intensity for this PMMA glass was investigated, in comparison with the PMMA glass polymerized below Tg and having excess scattering loss due to large-size heterogeneous structures (Sample B). In the sample A, the polarized scattering intensity (Vv) slightly changed below Tg and increased smoothly with increasing temperature above Tg in accordance with the fluctuation theory for structureless liquids. On the other hand, in the sample B, an abrupt decrease in Vv scattering around Tg was observed with increasing temperature. On the basis also of our previous study, it is suggested that the different trend of temperature dependence of light scattering and of excess scattering even in highly purified PMMA glasses depends on whether the strain inhomogeneities generated during the polymerization process are already relaxed above Tg or retained below Tg, and that the scattering behavior is not directly affected by first order structures such as molecular weight, tacticity, and remaining monomers.

オプトエレクトロニクスの中で、光の伝達部分を担当するプラスチック光ファイバー、光導波路について、最近の研究成果と今後の可能性について概説する。

光学特性の測定法の中で、測定精度が高く実際的である方法に絞って解説する。

全フッ素化ポリマーを母材として作製したGI型POFの伝送帯域が石英系の伝送帯域を凌駕することが明らかになった結果を示した招待講演。

In this paper we report that plastic with GRIN was applied to material of contact lens. The plastic GRIN was successfully prepared by a special 2 step co-polymerization technique. The index profile of the plastic GRIN was measured by shearing interferometry. It was confirmed that the index profile was almost quadratic and the index difference between at the center and at the periphery was 0.03. We confirmed that the plastic GRIN corrects a spherical aberration of contact lens.

We have proposed four techniques to prepare axial-, radial-, spherical-, and other novelGRIN materials. The technologies of obtaining GRIN polymer and the resulting products, proposed in our laboratory until now are summerized. Since the two-step copolymerization and photocoplymerization techniques have been frequently reported so far, we focus, in this paper, on the GRIN optical fiber and optical waveguide by the interfacial-gel copolymerization technique, and the spherical GRIN spher lens with a low spherical aberration by the suspension polymerization technique.

A new interfacial-gel copolymerization technique is proposed to prepare steric GRIN optical waveguides and lens arrays. Since the GRIN profile is obtained from the thin-gel phase formed on the wall of a polymer substrate, many geometrical GRIN materials, such as axial-, radical-GRIN, can be monolithically fabricated. In this paper, the principle of GRIN formation is clarified, and a few steric radial-GRIN circuit components are demonstrated.

有機ポリマーは、無機ガラスに比べ、いろいろな分布屈折率パターンを形成しうることから、今まで得られなかった新しいGRIN光デバイスが試作されはじめており、興味深い。軸ずれ収差が原理的に存在しない低収差GRIN球レンズ、立体GRIN光導波路素子、レンズアレーなどである。これらの光デバイスならびに、広伝送帯域GRIN光ファイバーの開発について述べる。（解説）

国際会議GRIN’87への参加報告。

従来の球に比べ、内部に球対称に屈折率分布を付与とすると集光スポットが小さくなることを立証.。

The sphere lens with a spherical GRIN was prepared for the first time by two modified suspension polymerization techniques. The index change of the 0.05-3.0 mm diam GRIN sphere was 0.02-0.04, and the index profile was almost quadratic. The optimum condition minimizing the spherical aberration of the GRIN sphere embedded in a certain substrate was confirmed. Furthermore, 1-D GRIN sphere lens arrays were fabricated.

本題について、現状と展望を中心に解説。

プラスチック工学材料について解説。

An axial GRIN lens, where the refractive index varies along the optical axis of a convex lens, can reduce the spherical aberration compared with the conventional homogeneous lens. The transparent plastic axial GRIN material was successfully fabricated by chemical copolymerization and diffusion technique. The depth of the gradient index was 〜20 mm with the refractive-index change Δn=0.07. By carrying out the ray tracing of the axial gradient index, the optimum refractive-index distribution reducing the spherical aberration was determined. If we assume that the axial GRIN lens was constructed from the sample experimentally obtained, it was theoretically confirmed that the spherical aberration of this lens would be remarkably improved.

The refractive-index distribution patterns obtainable by the photocopolymerization of ternary monomer systems were predicted with the help of the mechanism for forming a radial gradient index reported by Ohtsuka and Koike. On the basis of this prediction, we successfully fabricated a convex lens, a concave lens, and a fiber with the W-shaped index distribution expected of an optical fiber with low modal dispersion. It was theoretically and experimentally confirmed that the index distribution of the rod by the photocopolymerization of a ternary monomer system could be widely controlled.

The attenuation of light transmittance through a POF in the range of visible light is governed by light scattering loss. In this paper, the possibility of decreasing scattering loss in PMMA, which is one of the core materials of POF, is discussed. The light scattering loss of the PMMA glass prepared from a contaminant-free monomer depended on the conditions of polymerization and heat-treatment. We succeeded in preparing the PMMA glass with a light scattering loss lower than the value, 14 dB/km, which was reported as the theoretical limitation at 633 (nm)-wavelength in the fluctuation theory for structureless liquids. The angular dependence of light-scattering intensity suggested the existence of heterogeneous regions (several hundreds Å) with the order of 10-5 of refractive-index differences. This fluctuation would be caused by the stress-strain due to volume-contraction during tacticity nor by the small amount of remaining monomer.

Plastic GRIN rod lenses have been fabricated by photocopolymerization of ternary monomer system. To select the monomer appropriate to photocopolymerization, we developed a computer program to predict the physical constants of homopolymer from the chemical structure. Furthermore, according to the model of the gradient-index formation, MMA-VB monomer system and MMA-benzyl acrylate-VB monomer system were chosen as suitable systems. In both monomer system, plastic GRIN rods with good lens functions up to the periphery were successfully obtained.

In this paper, we propose a general mechanism for forming a radial GRIN rod by photocopolymerization in multiple monomer systems and a method of selecting new monomer systems applicable to GRIN. By using the simulation with various monomer systems, it is shown that the index distribution of a plastic GRIN rod can be tightly controlled by the selection of ternary monomer system and the photocopolymerization condition.