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This paper presents a study on the influence of the polarization of the pump beam on the emission properties of dye-doped polymer optical fibers. The fiber samples, which are pumped transversely with linearly polarized light, are graded-index polymer optical fibers doped with rhodamine 6G. The variation of the intensity and angular distribution of the output emission are theoretically and experimentally analyzed as the polarization direction of the pump is changed. The analysis is carried out both in the regime of fluorescence and in the regime of amplified spontaneous emission. It is shown that a pump polarization perpendicular to the fiber symmetry axis yields not only higher emission efficiency but also narrower axial angular width. The effect of the polarization of the pump beam on the properties of the amplified spontaneous emission is also measured, including its threshold-like energy, relative efficiency, and optical gain. The results indicate that the pump polarization determines the light-emitting performance of dye-doped polymer optical fibers.

The properties of the amplified spontaneous emission in rhodamine-6G doped graded-index polymer optical fibres of two different dopant concentrations have been analyzed by using the Variable Stripe Length method, both theoretically and experimentally. A theoretical model based on the laser rate equations describes the dependence of the emitted spectrum on the pumped length successfully. The fibre gains and their dependence on the dopant concentration have been analyzed.

Several kinds of optical polymer films in liquid crystal displays (LCDs) greatly contribute to image quality. However, contrast ratio of LCDs degrades with an increase in birefringence of polymer films used in the LCDs. The major types of birefringence are orientational birefringence and photoelastic birefringence. Furthermore, it was recently found that the birefringence caused by specified conformation and degree of orientation of polymer chains strongly depends on the temperature. We designed and synthesized a temperature-independent zero-birefringence polymer (TIZBP): poly(methyl methacrylate/benzyl methacrylate/phenyl methacrylate = 45/22/33(wt.%)) that has zero intrinsic birefringence over a wide temperature range in the random copolymerization method. However, the glass transition temperature Tg of this TIZBP is 95°C, and heat-drawn films of this TIZBP shrank at lower temperature than Tg, for example, at about 60°C. Upper limit of operating temperature of LCDs in automobile is higher than 60°C. Therefore, this TIZBP is not proper for practical use in automobile. In this research, after analysis of heat shrinkage of heat-drawn films, heat-resistant TIZBP (HRTIZBP) that exhibits sufficiently low heat shrinkage at 60°C, zero intrinsic birefringence and zero temperature coefficient of intrinsic birefringence was designed and synthesized. First of all, heat shrinkage ratio of heat-drawn films of poly(methyl methacrylate)，poly(methyl methacrylate/benzyl methacrylate) and TIZBP was investigated. The heat shrinkage of polymer films began at Tg-55°C. Based on the results, because targeting Tg for HRTIZBP was determined to 125°C, higher than 115°C with a sufficient margin, poly(methyl methacrylate/phenyl methacrylate/N-ethyl maleimide = 39/45/16 (wt.%)) was synthesized. This polymer exhibits lower heat shrinkage than the existing polymers, especially the heat shrinkage at 60°C is 0.0%. Therefore, this polymer was confirmed to be HRTIZBP.

We have proposed a light-emitting diode (LED) downlight lens that is made of a highly scattered optical transmission (HSOT) polymer. The HSOT polymer contains optimized heterogeneous structures that produce homogeneously scattered light with forward directivity. The full width at half maximum of the illuminance distribution angle can be increased from 16.7° to 37.9° as the concentration of the scattering particles in the HSOT polymer LED downlight lenses of identical shape is increased from 0.015 to 0.100 wt%. The colors in an illuminated area are highly uniform, which is not discernible by the human eye, with a high output efficiency greater than 85 %.

The intrinsic birefringence Δn0 and photoelastic coefficient C of poly(methyl methacrylate), poly(2,2,2-trifluroethyl methacrylate), poly(phenyl methacrylate), and poly(2,2,3,3,3-pentafluorophenyl methacrylate) were determined. We categorized these methacrylate polymers into four birefringence-types, even though their molecular structures differed only by the substituents on the side chains. Based on the results of Δn0 and C, novel polymers that exhibit neither orientational nor photoelastic birefringence, i.e., zero–zero-birefringence polymers, were designed and synthesized by quaternary copolymerization system. Furthermore, we confirmed that the mechanisms of orientational birefringence and photoelastic birefringence generation were different in these methacrylate polymers. The conformation of the repeat unit of the polymers was nearly constant during the generation of orientational birefringence. In contrast, the conformation of the repeat unit of the polymers changed during the generation of photoelastic birefringence in the glassy state. These findings demonstrated the reasonability of evaluating orientational and photoelastic birefringence separately, as well as the adequacy of the classification of polymers into four birefringence-types. Given these results and the fact that zero–zero-birefringence polymers could be prepared successfully by four-birefringence type monomers, we demonstrated the reasonability of the method for designing the zero–zero-birefringence polymers. POLYM. ENG. SCI., 55:1330–1338, 2015. © 2015 Society of Plastics Engineers

Mirrorless graded-index polymer optical fibers doped with the organic dye rhodamine 6G result in very compact broadband fiber lasers in the visible region when pumped from the side. The emission spectrum, threshold, and efficiency obtained on both fiber ends depend on the lengths of the directly illuminated region and of the non-excited ones. The paper analyzes such parameters both experimentally and theoretically for the first time.

Liquid crystal displays (LCDs) are composed of two glass substrates, two polarizers and some optical films. These components are laminated by pressure sensitive adhesives (PSAs). When a polarizer shrinks by humidity or the heat from a backlight of LCDs, stress appears and deforms PSAs. PSAs tend to exhibit birefringence due to applied stress and temperature change, which causes light leakage degrading image quality of LCDs. PSAs are consisted of main chain polymers and cross-linkers. To evaluate birefringence of PSAs at room temperature is difficult because PSAs easily plastically deform at the temperature. The purpose of this article is to design temperature-independent zero-birefringence PSAs (TIZBPSAs) exhibiting almost no birefringence even during stress-induced deformation over a wide temperature range. Butyl acrylate (BA) and phenoxyethyl acrylate (PHEA) were selected as the monomers of main chain polymers and an isocyanate-type cross-linker was added. Trilaminar films were prepared in which PSAs were sandwiched between two supporting films. We successfully evaluated birefringence and temperature dependence of birefringence of PSAs for the first time by using temperature-independent zero-birefringence polymers (TIZBPs) as the supporting films. TIZBPs, designed in our group, show almost no orientational birefringence even when the polymer main chain is in an oriented state and almost no temperature dependence of orientational birefringence over a wide temperature range. We have proposed a novel method to design PSAs having desirable the birefringence properties by determining the contributions of BA, PHEA and the cross-linker to birefringence and temperature dependence of PSAs quantitatively. Furthermore, we have designed TIZBPSAs by the proposed method.

The emission properties of a graded-index thermoplastic polymer optical fiber and a step-index thermosetting one, both doped with rhodamine 6G, have been studied. The work includes a detailed analysis of the amplified spontaneous emission together with a study of the optical gains and losses of the fibers. The photostability of the emission of both types of fibers has also been investigated. Comparisons between the results of both doped polymer optical fibers are presented and discussed. This work has been funded in part by the Fondo Europeo de Desarrollo Regional (FEDER); by the Ministerio de Economia y Competitividad under project TEC2015-638263-C03-1-R; by the Gobierno Vasco/Eusko Jaurlaritza under projects IT933-16 and ELKARTEK (KK-2016/0030 and KK-2016/0059); by the University of the Basque Country UPV/EHU under program UFI11/16; and by the Japan Society for the Promotion of Science through the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program), initiated by the Council for Science and Technology. The work carried out by I. Parola has been funded by a research grant given by the Departamento de Educacion, Politica Linguistica y Cultura del Gobierno Vasco/Eusko Jaurlaritza for her PhD thesis. We also thank Stela Diamant and Oleg Palchik, from the company Intellisiv Ltd, for providing the thermosetting samples.

Polymers that exhibit neither orientational nor photoelastic birefringence, called zero–zero-birefringence polymers, are candidate materials for preparing optical components of liquid crystal displays (LCDs). Analyzing the birefringences for various methacrylate polymers is an issue of current importance in developing zero–zero-birefringence polymers with appropriate characteristics for LCDs. The researchers have investigated different types of birefringence for poly(2,2,2-trichloroethyl methacrylate) (PTCEMA) and have shown that PTCEMA exhibits negative orientational and photoelastic birefringences. By using TCEMA as a comonomer, a zero–zero-birefringence polymer having much higher glass transition temperature (Tg) compared with previous researches has been prepared by ternary copolymerization. Moreover, the researchers have fabricated zero–zero-birefringence polymers in a quaternary system containing TCEMA. The property analyses indicate that Tg can be controlled while maintaining the zero–zero-birefringence property, which shows that designing a quaternary zero–zero-birefringence polymer permits selective synthesis with the most appropriate characteristics. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

We proposed a polarized laser backlight to improve light use efficiency of liquid crystal displays, and evaluated its basic polarization properties. In order not to degrade the polarization state, light guide plates were fabricated of polymer free of orientational and photoelastic birefringence, which is called zero-zero-birefringence polymer.

We designed and synthesized quaternary copolymers of methyl methacrylate (MMA), 2,2,2-trifluoroethyl methacrylate (TFEMA), benzyl methacrylate (BzMA), and 3,3,5-trimethylcyclohexyl methacrylate (TMCHMA) and we investigated their birefringence, thermal properties, and other optical properties. When the copolymer composition was MMA/TFEMA/BzMA/TMCHMA = 50:38:8:4, 40:30:7:23, or 30:21:7:42 (wt%), a zero–zero-birefringence polymer that exhibited neither orientational nor photoelastic birefringence was obtained. We demonstrated that such zero–zero-birefringence polymers with a variety of compositions could be successfully prepared in the quaternary system by using the same compensation method as applied in ternary random copolymerization. We also demonstrated that the glass-transition temperature (Tg) and refractive index (nD) of these copolymers could be controlled with high accuracy while retaining their zero–zero-birefringence property. We can therefore predict the type of birefringence, the Tg, and the nD of a particular copolymer before polymerization. Zero–zero-birefringence polymers with the most appropriate characteristics can then be synthesized selectively by quaternary copolymerization.

To reduce the light leakage of LCDs for a PC monitor, we fabricated the hard type zero-birefringence pressure sensitive adhesives (HZB-PSA) for the first time. HZB-PSA reduced the light leakage by eliminating birefringence of PSA and prohibiting the change in the angle of the absorption axis of a polarizer (CAAP).

Transparent polymers free of birefringence and scattering polymers free of wavelength dependency are demonstrated. They enable us to improve performance of optical films, pressure sensitive adhesives and backlights. Based on these polymers, we propose a novel LCD structure using a directional backlight and a scattering film.

Copolymers of methyl methacrylate (MMA) with 2,3,4- and 2,4,6-trifluorophenyl maleimides (TFPMIs) were synthesized by a free radical initiator, azobisisobutyronitrile, in 1,4-dioxane and also in bulk. The refractive indexes of the copolymers were in the range of 1.49–1.52 at 532 nm. The Tgs were 133–195 °C depending on copolymer compositions. In addition, the copolymers were thermally stable, Td > 350 °C. The orientational and photoelastic birefringence of the copolymers were also investigated. As both of the orientational and photoelastic birefringences of PMMA are negative, whereas those of poly(TFPMI)s are positive, we could obtain nearly zero orientational and photoelastic birefringence polymers when the ratios of 2,3,4-TFPMI/MMA were 15/85 and 5/95 mol %, respectively. For 2,4,6-TFPMI, zero orientational and photoelastic birefringences could be obtained when the ratios of 2,4,6-TFPMI/MMA were 12/88 and 3/97 mol %, respectively. The Tgs of those copolymers with zero birefringences were in the range of 135–140 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Copolymers of N-pentafluorophenyl maleimide (PFPMI) with methyl methacrylate (MMA) were synthesized by a free radical initiator, such as AIBN. The refractive indexes of the copolymers remained nearly constant (1.4970 at 532 nm) regardless of the polymer composition. These copolymers also showed high thermal stability. The orientational and photoelastic birefringence of the copolymers obtained were measured. Since both of the orientational and photoelastic birefringences of PMMA are negative whereas poly(PFPMI) exhibits positive, thus we have obtained nearly zero orientational and photoelastic birefringence polymers when the ratios of MMA/PFPMI were 91.8/8.2 and 97.0/3.0 mol%, respectively. Based on the experimental data, the ratios of MMA/PFPMI for zero birefringence were determined to be 88.9/11.1 and 93.8/6.2 mol% for orientational and photoelastic birefringence, respectively. The T gs of corresponding copolymers were estimated to be 128 and 122 °C.

We demonstrated that a method based on the analysis of both orientational birefringence (intrinsic birefringence) and photoelastic birefringence (photoelastic coefficient) is effective for designing polymers that are processed in a molten state and used in a glassy state. The designed polymer exhibits no birefringence for any orientation of the polymer main chains or under elastic deformation. Birefringence is close to zero even in injection-molded plates of the polymer. We have also shown that it is possible to compensate and control birefringence of polymers using inorganic nanocrystals, and we have obtained valuable information on the optimal size of nanocrystals for compensation and control of birefringence. Nanocrystals measuring ∼200 nm in length and 20 nm in width are sufficiently small to compensate for birefringence, but sufficiently large to permit control of orientation by casting. Reverse birefringence wavelength dispersion of a polymer film containing nanocrystals was achieved by casting and heat drawing. We demonstrated that a method based on the analysis of both orientational birefringence and photoelastic birefringence is effective for designing polymers that are processed in a molten state and used in a glassy state. The designed polymer exhibits no birefringence for any orientation of the polymer main chains or under elastic deformation. Birefringence is close to zero even in injection-molded plates of the polymer. We have also shown that it is possible to compensate and control the birefringence of polymers using inorganic nanocrystals, and we have obtained valuable information on the optimal size of nanocrystals for compensation and control of birefringence.

The relationship between the intrinsic birefringence and the composition ratio and between the photoelastic coefficient and the composition ratio in poly(methyl methacrylate (MMA)/styrene (St)) was investigated. A linear relationship was observed between the orientational birefringence and the composition ratio but not between the photoelastic coefficient and the composition ratio. The influence of the compositional distribution on the birefringence was investigated, and the results suggested that the compositional distribution of poly(MMA/St) minimally affects birefringence. We also analyzed the mechanism by which birefringence is generated in poly(MMA/St) by focusing on changes in St conformation. The results of this analysis suggested that the conformational changes in St units are different for orientational and photoelastic birefringence generation. We analyzed the generation mechanism of birefringence in poly(methyl methacrylate (MMA)/styrene (St)) through measurement of infrared (IR) dichroism. Through IR measurement, the conformational changes in the St unit were suggested and found to differ between orientational and photoelastic birefringence generation. We thought that, during photoelastic birefringence generation, the α-CH3 group of the MMA unit hinders the rotation of the benzene ring of St units that are adjacent to MMA units. The influence of compositional distribution on birefringence was also investigated and the results suggested that the compositional distribution of poly(MMA/St) minimally affects the birefringence.

To reduce the light leakage of liquid crystal displays (LCDs), pressure sensitive adhesives (PSAs) that exhibit no birefringence at any orientation were fabricated by the novel evaluation method of the birefringence of PSAs. This PSA successfully prevented the light leakage through the crossed polarizers after the accelerated aging test.

We proposed a polarized laser backlight to improve light use efficiency of liquid crystal displays, and evaluated the basic polarization properties of prototype of the backlight. The prototype backlight consisted of a laser, a polarizer, a diffusion sheet and two light guide plates of zero zero-birefringence polymer, which is free of orientational and photoelastic birefringence. The front output light from the backlight was highly polarized and the backlight maintained high degree of polarization.

We clarified the birefringence properties of poly(methyl methacrylate), poly(ethyl methacrylate), poly(isobutyl methacrylate), poly(cyclohexyl methacrylate), poly(isopropyl methacrylate), and poly(tert-butyl methacrylate). We demonstrated that the conformational change in polymer molecules that causes orientational birefringence differs from that causing photoelastic birefringence. Orientational birefringence depends mainly on the orientation of the main chains of the methacrylate polymers above Tg. On the other hand, photoelastic birefringence in elastic deformation below Tg depends mainly on the orientation of the side chains while the main chains are scarcely oriented. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2029–2037, 2010

In this research, we propose to reduce astigmatism and distortion in a progressive addition lens (PAL) by employing a polymer-based graded-index (GRIN) material. We adopted the diffusion copolymerization method for the GRIN-PAL fabrication. The GRIN material was prepared by partial diffusion of methyl methacrylate (MMA) and 2,2,2-trifluoroethyl methacrylate (3FMA) monomers into the cross-linked benzyl methacrylate polymer gel. GRIN-PAL was prepared by polymerization of the GRIN material in a mold of commercially available PAL. As a result, methods to control Deltan, the diffusion length, and the order of the GRIN profile in polymeric GRIN materials were demonstrated. In a combination of the PBzMA gel and the MMA/3FMA diffusion monomer, 50/50 in volume provides the highest Deltan. The diffusion period mainly affects the diffusion length. These two parameters consequently determine the order of the GRIN profile and the focusing power that the GRIN provides. The difference in the ease of diffusion caused by the difference in the cross-linking density provides a method for positional control of the GRIN profile. Furthermore, GRIN-PAL using a polymeric material was successfully fabricated. Improvement in astigmatism and distortion was demonstrated using GRIN. Therefore, the GRIN material is suggested to be applicable for the further modification of the PAL with low astigmatism and distortion.

This paper demonstrates a polarimetric pressure measurement using a multimode phase retarder plastic optical fiber fabricated from a birefringence-controllable copolymer. An optimal composition that gives the most pronounced response to pressure was studied by comparing the extinction ratio of fibers fabricated with different copolymer compositions. A simple sensor design with a single-fiber structure was proposed that has detection capabilities similar to those of the conventional dual-path structure of a Mach-Zehnder interferometer. A linear relationship between the fiber birefringence and the applied pressure was observed in a range from 0 to 0.06 MPa. A polarimetric sensitivity of 1.56 x 10(-5) MPa(-1) was obtained experimentally from the relationship between the birefringence and pressure.

In order to propose a multimode polarization-maintaining fiber in a large core diameter, polarization-maintaining graded-index plastic optical fiber (PMGIPOF) was fabricated using a birefringence-reduced copolymer of poly(methyl methacrylate/benzyl methacrylate). Successful reduction of orientational birefringence in the PMGIPOF was verified using polarized optical microscopy. The extinction ratio measured from the PMGIPOF was significantly higher than the value obtained for the step-index (SI) POF (14.3 and 0.5 dB for 1 m, respectively). Photoelastic birefringence in the PMGIPOF was studied using fiber macrobending. Retardation induced by the macrobending was observed in a manner of high regularity in the PMGIPOF, where as the other types of POFs did not show such regularity. Furthermore, the polarization-maintaining property of the PMGIPOF was effective at maximum 10 m propagation.

Copolymers of methyl methacrylate (MMA) and pentafluorophenyl methacrylate (PFPMA) of various compositions were prepared with a free-radical initiator. When PFPMA was included in the copolymers, the glass-transition temperatures increased and showed a positive deviation from the Gordon–Taylor equation. A copolymer containing 20 wt % PFPMA exhibited almost zero orientational birefringence, and the photoelastic birefringence became zero when the copolymer contained 13 wt % PFPMA. When 20 wt % PFPMA was incorporated into the MMA copolymer, its water absorption decreased to 0.4 wt % versus 1.8 wt % for poly(methyl methacrylate) (PMMA) under the same condition. The flammability of the PFPMA/MMA copolymer was reduced in comparison with that of the MMA homopolymer. The refractive indices of the PFPMA/MMA copolymers were very close to that of PMMA, and the transmittances of the copolymers were slightly better than that of PMMA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Surface-modified ZnTe nanoparticles were mixed in a zero-birefringence polymer matrix. Transmission electron microscopy images revealed that aggregates of ZnTe nanoparticles with a diameter of ∼20 nm were uniformly dispersed in the polymer. The transmittance of ZnTe nanocomposites rapidly decreased at wavelengths shorter than the critical wavelength corresponding to the band gap of ZnTe nanoparticles, an effect which became significant as the volume fraction of particles increased. In this way, the optical characteristic of ZnTe nanoparticles was added to the polymer. The intrinsic zero-birefringence was confirmed in the heat-drawn ZnTe nanocomposites. As the ZnTe nanocomposites were left in air, a lowering of transmittance was observed. This was due to the oxidation of Zn and the resultant deposition of Te in the ZnTe nanocomposite, as the light absorption of Te is significant. The formation of oxygen non-permeable SiO2 films onto the ZnTe nanocomposite by the sol-gel method was useful in preventing oxidation so that the decrement of transmittance decreased from 47.2% to 14.9% at 530 nm near the ZnTe band gap.

N-(alkyl-substituted) maleimides (RMIs) were proposed as materials useful for the development of a zero–zero-birefringence polymer that exhibits no birefringence. We analyzed the optical and thermal properties of poly(RMI)s, such as the refractive index, birefringence, and glass transition temperature. The characteristics of the obtained polymers varied significantly because the shift of the density and polarizability derived from the change of the substituent structure influenced the optical properties, and the bulkiness of the substituents influenced the thermal properties. We also designed a zero–zero-birefringence polymer using N-ethyl maleimide (EMI) as a comonomer, and the obtained copolymer had no birefringence, relatively high heat resistance, and high transparency.

We report a method for compensating the birefringence of optical polymers by doping them with nanometer-size inorganic birefringent crystals. In this method, an inorganic birefringent crystal is chosen that has the opposite birefringence to the polymer and a rod like shape which is oriented when the polymer chains are oriented. As a result, the birefringence of the polymer is compensated by the opposing birefringence of the crystal. Positive orientational birefringence of poly(methylmethacrylate (MMA)-co-benzylmethacrylate (BzMA)) = 78/22 (wt/wt) was compensated by doping with 0.3 wt.% of the smaller strontium carbonate (SrCO3) crystals with a length of about 200 nm and a width of about 20 nm. The birefringence of the copolymer containing SrCO3 was almost zero with any draw ratio between 1.0 and 2.2. The polarization state was almost maintained when it passed through the film. On the other hand, we concluded that the size of the larger crystals (about 3.0 μm × about 300 nm) is too large to form an optically isotropic medium with the polymer. In spite of doping with 0.3 wt.% of the smaller SrCO3 crystal, the transmittance of the doped film with a thickness of 30 μm was almost the same as the undoped one in the visible region. The increase in haze by doping with 0.3 wt.% of the smaller SrCO3 crystal was 0.1%. Furthermore, the negative birefringence of PMMA was enhanced by the SrCO3 crystal.

We reported a method for compensating the birefringence of optical polymers by doping them with inorganic birefringent crystals. In this method, an inorganic birefringent material is chosen that has the opposite birefringence to the polymer and needle-like shape crystals which are oriented when the polymer chains are oriented. The birefringence of the polymer is thus compensated by the opposing birefringence of the crystal. Orientation behavior of the needle-like crystals and polymers was investigated. The orientation function of the needle-like crystal was increased with an increase in the aspect ratio of the needle-like crystal.

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 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.

We have proposed a low-loss, high-bandwidth and large-core graded-index plastic optical fiber (GI POF) in data-com. area. The GI POF enables us to eliminate the modal noise problem which is observed in medium-core silica fibers. Therefore, stable high-speed data transmission can be realized by the GI POF rather than medium-core silica fibers. Furthermore, advent of perfluorinated (PF) polymer based GI POF network can support higher transmission than silica fibers network because of the small material dispersion of PF polymer compared with silica. In addition, we proposed a highly scattering optical transmission (HSOT) polymer and applied it to a light guide plate of a liquid crystal display backlight. The HSOT polymer backlight that was designed using the HSOT designing simulator demonstrated twice the brightness of the conventional taransparent backlight with sufficient color uniformity. Furthermore, we proposed the two types of zero-birefringence polymers synthesized by the random copolymerization method and the anisotropic molecule dopant method. Both of the polymers exhibited no orientational birefringence for any orientation of polymer chains.

We have developed a highly scattering optical transmission (HSOT) polymer, and have succeeded in applying it to a highly efficient backlight light guide in liquid crystal displays (LCDs). In the present work, a multiple scattering modelling simulation has been developed. Also the effects of adjacent particles inside the HSOT polymer are demonstrated. The numerical calculation, improved by taking account of the adjacent particles, has precisely reproduced the multiple scattering phenomena inside the HSOT polymer. Based upon the results of the multiple scattering analysis, an optimal design has been developed and applied to an LCD backlighting system. By altering the internal particle conditions, uniformity of colour and brightness on the top face of the backlight has been achieved.

A novel coloration phenomenon in a colloidal dispersion with an amphiphilic polymer was found. The dispersion consists of tetrahydrofuran (THF), an aqueous solution of sodium thiosulfate (Na(2)S(2)O(3).5H(2)O), and hydroxypropylcellulose (HPC). The dispersion was emulsified by HPC as an amphiphilic polymer, so that the aqueous phase was confined in droplets in the THF matrix. It typically appeared bluish violet at room temperature and turned into blue with increasing temperature. In this system, the refractive indices of the inside and outside of the droplet coincided at a certain wavelength at which the light passes through without scattering, which is called the Christiansen effect. The color observed was successfully simulated by Mie's scattering theory in combination with the Christiansen effect.

大口径の屈折率分布型ポリマー光ファイバーのコア部に有機色素を添加することにより,ポリマー光ファイバー増幅器およびレーザーを作製した。中心ほど高屈折率・高色素濃度になるような屈折率分布と色素濃度分布によって,高効率の光増幅とレーザー発振,および高い耐光性を実現した。本稿では,これらの研究の現状と今後の展望について概説する。

We have demonstrated the advanced highly scattering optical transmission (HSOT) polymer backlight that was designed by the HSOT designing simulation program. This backlight exhibited approximately three times higher luminance and 20% higher efficiency than the conventional flat-type HSOT backlight of 14.1-inch diagonal because of the microscopic prism structures at the bottom of the advanced HSOT light guide plate. The HSOT polymer containing the optimized heterogeneous structures produced homogeneous scattered light with forward directivity and sufficient color uniformity. Optimization of the heterogeneous structure is important in order to utilize the taper effect and the microscopic prism structures.

In this work we perform a detailed experimental and theoretical analysis of the properties of amplified spontaneous emission (ASE) in a rhodamine-6G-doped graded-index polymer optical fiber when the fiber is pumped either longitudinally or transversally with respect to the fiber axis. The dependence of the ASE threshold and efficiency on fiber length has been compared for both schemes of excitation. A theoretical model for longitudinal excitation has been carried out by means of the laser rate equations as functions of time, distance traveled by light and wavelength. The analysis takes into account that the fiber is a typical graded-index POF in which the radial distributions of light power density and dye concentration are not uniform. The theoretical calculations agree satisfactorily with the experimental results. The photodegradation of the ASE intensity has also been measured for both pumping schemes.

Zero–zero-birefringence polymers which exhibit no orientational birefringence and no photoelastic birefringence may be suitable candidates for the components of optical devices. To develop zero–zero-birefringence polymers, a novel copolymerization system is required. We investigated two types of birefringence of poly(N-methylmaleimide) (PMeMI) and showed that PMeMI exhibits positive orientational and photoelastic birefringence. On the basis of the results, we calculated the optimal composition for compensating both types of birefringence by solving three equations which describe the relationship between birefringence properties and weight fraction of monomers. When the copolymer compositions were MMA/BzMA/MeMI = 86/8/6 and 88/8/4 (wt %), zero–zero-birefringence polymers were obtained. By using MeMI as a comonomer, these zero–zero-birefringence polymers have a much higher glass transition temperature (Tg) than those of previous researches. Also, this polymer film has high transparency comparable with that of PMMA film. Therefore, we conclude that we successfully prepared zero–zero-birefringence polymers using N-substituted maleimide and that N-substituted maleimide is a promising material for zero–zero-birefringence polymers for optical devices. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40423.

We proposed a highly scattering optical transmission (HSOT) polymer and applied it to a light pipe of a backlighting system for liquid crystal displays. Although the HSOT polymer backlighting system was composed of fewer parts than those of the conventional transparent one, the HSOT polymer backlighting system showed not only twice the brightness but also twice the efficiency of the conventional one. In addition, the HSOT polymer backlighting system had no degradation of color uniformity due to scattering in the HSOT polymer.