Published papers

現在のIT社会における光学ポリマーデバイスの重要性、光学ポリマーにおける複屈折の発現機構について述べ、さらにゼロ複屈折性光学ポリマーとその実用化への可能性および波及効果について解説する。

We report on a method to compensate the photoelastic birefringence of a polymer. In this method, a rod-like molecule that has a polarizability anisotropy was chosen and doped in a polymer. We demonstrated this method by compensating the negative photoelastic birefringence of poly(methylmethacrylate) at a wavelength of 633 nm. Homogeneous doping with 2.2 wt. % of trans-stilbene almost eliminated the photoelastic birefringence of the polymer. The photoelastic coefficient of the synthesized zero-photoelastic birefringence polymer was 0.057×10-12 Pa-1. We found that the photoelastic birefringence of poly(methylmethacrylate) was compensated by the motion of trans-stilbene in the polymer by the analysis of the infrared absorption spectrum.

We proposed low-loss perdeuterated PMMA (PMMA-d8) based GI-POFs enabling a gigabit data transmission over 300-m prepared by a modified interfacial-gel polymerization process. With using this process, the PMMA-d8 material could be used only in its core region and the index exponent g value of the GI-POF was closed to optimized value (g=2.3). It was verified that the hydrogen bonding in the PMMA that composed the cladding had a small effect on the total attenuation. Furthermore, the -3 dB bandwidth of the GI-POF when all the modes were uniformly launched was 1.02 GHz through 300-m.

これまで当研究室にて研究開発してきたフォトニクスポリマーについて解説し、これらの現状と今後の展開について述べた。

Bending effects on bandwidth and loss of a graded index polymer optical fiber (GI POF) were investigated, and those influences on the optical link performance were discussed simultaneously for the first time.

We report the anisotropic molecular dopant method for compensating the photoelastic birefringence of polymers. In this method, a rodlike molecule that has a polarizability anisotropy was chosen and doped in a polymer. We demonstrate this method by compensating the negative photoelastic birefringence of PMMA and poly (2,2,2-trifluoroethyl methacrylate) at a wavelength of 633nm. Trans-Stilbene and fluorine were selected as the anisotropic molecules. Homogeneous doping with the molecule almost eliminated the photoelastic birefringence of the polymers. We found that the photoelastic birefringence of PMMA was compensated by the elastic motion of trans-stilbene in the polymer as determined by the analysis of the infrared absorption spectrum. Furthermore, the orientation distribution function of trans-stilbene in a uniaxcially strained PMMA film in a solid glass state was estimated by the investigation of the infrared dichotic ratios.

A perfluorinated monomer, perfluoro-2-methylene-4-methyl-1,3-dioxolane (PFMMD), was synthesized by various methods. The monomer was polymerized in bulk and/or in the solution by a free radical mechanism using perfluorodibenzoyl peroxide and/or perfluorodi-tert-butyl peroxide as an initiators. The polymers obtained (poly(PFMMD)) were colorless and transparent. However, a polymer rod exposed to the atmosphere turned hazy. When the polymers were purified by precipitating the polymer solution into chloroform, they did not turn hazy when exposed to air for a long period of time and remained clear with a high UV-vis light transmittance. The glass transition temperature of the purified polymer was 130-134 °C. NMR measurements indicate that the purified polymers have mostly vinyl addition polymer structure. Nevertheless, we suppose that the pristine polymers contain structural units formed by ringopening polymerization. The molecular weight of poly(PFMMD) samples can be regulated using carbon tetrachloride, carbon tetrabromide, and sulfuryl chloride as chain transfer agents. Polymerization in the presence of these regulators is characterized by nondegradative chain transfer. The intrinsic viscosity of poly(PFMMD) samples was determined in hexafluorobenzene. Hexafluorobenzene is a thermodynamically good solvent for poly(PFMMD). The molecular weights of poly(PFMMD)s were characterized by the intrinsic viscosity and dynamic light scattering (DLS). The refractive index of poly(PFMMD) between 400 and 1550 nm was between 1.3360 and 1.3270. The material dispersion of poly(PFMMD) is superior to that of a commercial poly(1,1,2,4,4,5,5,6,7,7-decafluoro-3-oxa-1,6-heptadiene) (Cytop).

A plastic optical fiber (POF) having a W-shaped refractive index profile (W-shaped POF) was prepared for the first time that had a possibility 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 graded-index (GI) POF, the group delay of higher order modes is strongly influenced, and the modal dispersion in the GI POF is compensated. By comparing the propagating mode properties of the W-shaped POF with those of the GI POF, we clarified theoretically and experimentally that the index valley has a remarkable modal dispersion compensation effect.

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、特にゼロ複屈折光学フィルムと高輝度光散乱ポリマー導光体の最新の研究動向について詳しく報告した。

これまでに実証したゼロ複屈折性光学ポリマーを紹介した。特に最も新しいナノ粒子を添加したゼロ複屈折性光学ポリマーについて、詳細なデータとともにその可能性を詳しく解説した。複屈折制御という観点から、LCDへの応用が期待できる。

ゼロ複屈折性光学ポリマーの液晶ディスプレイへの応用とその波及効果について解説する。LCDのコストの内、ポリマー関連部材のコストは約６割を占めるといわれ、それらの高性能化とコスト低減ができれば、LCDにさらなる普及に貢献できる可能性が高い。

We investigated the way to reduce the mode-coupling in a GI POF, and it was found that the mode-coupling strength in the GI POF depended on the numerical aperture of the fiber. Moreover, we proposed a new optimum waveguiding design of GI POFs under the UFL condition and demonstrated its superiority.

We proposed low-loss perdeuterated PMMA (PMMA-d8) based GI-POFs enabling a gigabit data transmission over 200-m prepared by a modified interfacial-gel polymerization process. With using this process, the PMMA-d8 material could be used only in its core region and the index exponent g value of the GI-POF was closed to optimized value (g=2.3). It was verified that the hydrogen bonding in the PMMA that composed the cladding had a small effect on the total attenuation. Furthermore, the -3 dB bandwidth of the GI-POF when all the modes were uniformly launched was 1.42 GHz through 200-m.

ポリマー中に分極率異方性を持つ低分子を添加することにより、ポリマーの光弾性複屈折を消去する方法を提案した。実際にtrans-stilbene添加によりPMMAの光弾性複屈折消去にはじめて成功した。

Novel photonics polymers for the real time face to face communication in broadband society are proposed. The Graded-Index Optical Fiber (GI-POF) has been proposed for the first time from the Keio University. Very recentry, the data transmission of 10GHz bandwidth for 500m was achieved by the Perfluorinated GI-POF, which was higher than that of silica based multimode fiber. The highly scattering optical transmission (HSOT) polymer backlight of LCD has been proposed, where the brightness is two times of that of conventional transparent backlight. And also, the zero-birefringence polymers, which are doped with needle-like crystals, for novel LCD films have been proposed.

A PMMA glass was prepared for the first time, in which the light-scattering loss was much smaller than any reported data and no large size of heterogeneities existed. The total scattering loss was much 13dB/km which represents an intrinsic limiting loss of the PMMA glasses attainable in the atmosphere. The isotropic scattering loss widely varied between ca. 9 and 400 dB/km according to the conditions of polymerization or heat treatment, while the anisotropic scattering loss was almost unchanged in the range 4-6 db/km. The origins of the large heterogeneities with the diameter of ca. 1000Å, which have been invariably observed in PMMA glasses reported so far, were investigated by the angular dependence of the light scattering. The large excess scattering is caused mainly by the isotropic strain inhomogeneities caused during polymerization and not by a small amount of remaining monomers or additives, the molecular weight of polymers, the stereoregularity due to the specific tacticity of PMMA, or cross-linking as a result of the gel effect.

We reported the application of a GRIN plastic rod, a type of light focusing rod (LFR), a material of comparatively high central refractive index, the index gradually decreasing from principal optic axis (POA) to periphery. The LFR-GRIN possesses excellent properties for use as material for positive power contact leness (CL). This paper concerns negative power CL material application of GRIN type of light diffusing rod (LDR), whose POA index is lowest, the index gradually increasing from POA to periphery. As well LFR-GRIN and GRIN complexed LFR-LDR were used in negative power CLs. The result was that the center thickness of a CL made from LDR-GRIN is thinner than PMMA. From a theoretical focusing viewpoint, because the power differential between the center part of the CL and the periphery ranges from 1.00D to 3.00D.