詳細

中山　敬三 （ナカヤマ　ケイゾウ）

  • 理工学部 電気電子通信工学科　准教授
Last Updated :2024/04/25

コミュニケーション情報 byコメンテータガイド

  • コメント

    液晶のセキュリティ素子への応用を研究しています。液晶をIDカード等に埋め込み、その液晶が示すランダムなパターンを識別情報として利用することにより、カード等の偽造防止効果を狙います。

研究者情報

学位

  • 博士（工学）（2000年03月 大阪大学）

ホームページURL

J-Global ID

研究キーワード

  • 光セキュリティ   液晶眼鏡   液晶   色弁別補助装置   electrooptic effect ferroelectric liquid crystal optical security system encrypted hologram   

現在の研究分野（キーワード）

    液晶のセキュリティ素子への応用を研究しています。液晶をIDカード等に埋め込み、その液晶が示すランダムなパターンを識別情報として利用することにより、カード等の偽造防止効果を狙います。

研究分野

  • ライフサイエンス / リハビリテーション科学
  • ナノテク・材料 / 光工学、光量子科学

経歴

  • 2021年04月 - 現在  近畿大学理工学部 電気電子工学科准教授
  • 2005年04月 - 2021年03月  近畿大学理工学部 電気電子工学科講師
  • 2000年04月 - 2005年03月  静岡大学工学部助手
  • 1997年04月 - 2000年03月  日本学術振興会特別研究員DC1

学歴

  • 1997年04月 - 2000年03月   大阪大学   大学院工学研究科 博士後期課程   電子工学専攻
  • 1995年04月 - 1997年03月   大阪大学   大学院工学研究科 博士前期課程   電子工学専攻
  • 1993年04月 - 1995年03月   奈良工業高等専門学校   専攻科   電子情報工学専攻
  • 1988年04月 - 1993年03月   奈良工業高等専門学校   Advanced Engineering Faculty   情報工学科

所属学協会

  • 電子情報通信学会   電気学会   レーザー学会   日本光学会   応用物理学会   日本液晶学会   照明学会   

研究活動情報

論文

  • 中山 敬三; 中山 満子
    照明学会誌 104 2 76 - 81 2020年02月 [査読有り]
  • 中山 敬三
    Electronics and Communications in Japan 102 8 17 - 24 2019年07月 [査読有り]
     
    Translated from Volume 139 Number 5, pages
    246–252, DOI: 10.1541/ieejfms.139.246
    of IEEJ Transactions on Fundamentals and
    Materials (Denki GakkaiRonbunshi A)
  • Shuhei Yoshida; Keizo Nakayama
    OSA Continuum 2 6 1908 - 1916 2019年06月 [査読有り]
  • 中山 敬三
    電気学会論文誌Ａ（基礎・材料・共通部門誌） 139 5 246 - 252 2019年05月 [査読有り]
  • 紫外線硬化型液晶素子の不均一性を特徴として利用する液晶光IDタグ
    中山 敬三; 大坪 順次
    電気材料技術雑誌 25 1 6 - 11 2016年12月 [査読有り]
  • Keizo Nakayama; Junji Ohtsubo
    APPLIED OPTICS 55 5 1012 - 1016 2016年02月 [査読有り]
     
    We proposed and quantitatively evaluated an optical security device that provides nonuniform or random patterns of schlieren texture in nematic liquid crystal as unique identification information with a design by employing computer image processing and normalized cross correlation. Using the same photomask as the first author's university logo, the written patterns, which were composed of polymerized isotropic areas and polymerized nematic areas, were stable among different cells. Judging from the maximum correlation coefficient of 0.09, the patterns of the schlieren texture were unique in different cells. These results indicate that photocurable nematic liquid crystal materials have the potential to be applied to security devices for anticounterfeiting measures. (C) 2016 Optical Society of America
  • 平井 亮圭; 中山 敬三
    電気学会論文誌Ａ（基礎・材料・共通部門誌） 136 8 549 - 550 2016年 [査読有り]
     
    We fabricated a visual observation system for a rotating object with an automatic synchronizing function using a ferroelectric liquid crystal (FLC) cell. Stroboscopic vision was achieved not using a flash light but using a FLC cell as a fast-response optical shutter. A reflective photosensor was used for sensing a rotating object. For the drive of the liquid crystal shutter synchronized with the rotating object, an electric circuit mainly composed of a microcontroller and a H bridge unit, which were made up of easily available electric parts, was designed. The automatic synchronizing function was evaluated from the visibility of a character on the center of the propeller. The results indicate the automatic synchronizing function can work over 6.2 × 103 rpm.
  • 中山 敬三; 大坪 順次
    日本液晶学会討論会講演予稿集 2015 _3C08 - 1_-_3C08-2 日本液晶学会 2015年 
    By using an ultraviolet-curable nematic liquid crystal material, some designed patterns can be stored in the liquid crystal cells with areas polymerized under isotropic and nematic phases. We have proposed a security device that uses the random pattern of optical texture in each cell. In other words, the random patterns of schlieren in each cell can be used as identifiers. For security system using these devices, it is necessary to develop the computer-based system capable of comparing optical texture patterns. In this research, methods of extraction of written patterns were studied for security system.
  • 中山 敬三; 大坪 順次
    日本液晶学会討論会講演予稿集 2014 PB35  日本液晶学会 2014年 

    We have proposed a security device that uses the random pattern of fingerprint texture in a UV-curable chiral nematic liquid crystal for unique identification information. For the security system using the patterns provided by the proposed security devices embedded in ID cards, it is important to evaluate the similarity between these patterns. Althoug the basic method is cross-correlation using the intensities of each pixel in the images, we studied the method in which the stripe directions extracted from fingerprint texture patterns were used.

  • 中山 敬三; 大坪 順次
    日本液晶学会討論会講演予稿集 2013 _PA28 - 1_-_PA28-2 日本液晶学会 2013年 
    We have proposed a security device that uses the random pattern of a chiral nematic liquid crystal for unique identification information. In this study, we studied the application of the random texture of a nematic liquid crystal. Random schlieren texture is observed in a planar cell of the nematic liquid crystal. Using an ultraviolet-curable liquid crystal, many films with an unique random pattern can be fabricated by photopolymerization without a process for making the unique information. These random patterns of shlieren in each cell can be used as identifiers.
  • Keizo Nakayama; Junji Ohtsubo
    OPTICAL ENGINEERING 51 4 040506-1 - 040506-3 2012年04月 [査読有り]
     
    An optical security device providing the function of a fingerprint for authentication along with a designed pattern storage function has been proposed. The proposed device uses the random fingerprint texture in the chiral nematic phase of an ultraviolet-curable liquid crystal. Using photopolymerization along with a mask of the designed pattern, a unique pattern can be fixed in the shape of the designed pattern. The random patterns can be used as a fingerprint for such devices. This proposed device has the potential to be an optical security device and an authenticity or information indicator for the user. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.OE.51.4.040506]
  • Keizo Nakayama; Junji Ohtsubo
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 516 253 - 259 2010年 [査読有り]
     
    We proposed the application of fingerprint textures in cholesteric liquid crystal for a security device that can be used as an index for distinguishing individual artificial materials, for example, ID cards. The randomness of such texture was checked quantitatively by normalized cross-correlation and found to be high. For the fixation of the fingerprint texture a photo-polymerization technique was used, and the fixed pattern was invariable even at high temperature. These results indicate that fingerprint texture in cholesteric liquid crystal realizes the unique and permanent properties of human fingerprints.
  • Keizo Nakayama; Junji Ohtsubo
    Optical Review 14 5 290 - 296 2007年09月 [査読有り]
     
    In practical optical security systems we must consider various circumstances for reading and decrypting encrypted holograms. Binarization of the hologram is best suited for such applications because of the ease of handling encrypted data. However, the decrypted image is greatly degraded by binarization. Therefore, optimization of a binary hologram is essential in using such a technique. In this paper, we propose a fast optimization method of a binary encrypted hologram to obtain a good reconstruction based on the error correction algorithm. In the proposed method, multiple pixels of the binary hologram are simultaneously flipped for the optimization according to the priority for the correction. The time for the optimization is only 3% of that of the simulated annealing method. © 2007 The Optical Society of Japan.
  • 中山 敬三; 坂井 雅彦; 北村 潤一郎; 大坪 順次
    日本液晶学会討論会講演予稿集 2006 206 - 206 THE JAPANESE LIQUID CRYSTAL SOCIETY 2006年 
    半導体レーザに戻り光が生じると発振が不安定化し、戻り光雑音と呼ばれるノイズが出力光に発生する。戻り光雑音はランダムな雑音ではなく、カオスによる不規則振動現象であることから、半導体レーザと外部共振器を組合せた戻り光半導体レーザを形成し、光学的なカオス信号発生源として用いる研究が盛んに行われている。本研究では、端面発光型半導体レーザへの戻り光の状態を液晶素子により変化させレーザ発振状態の制御を行った。
  • K Nakayama; J Ohtsubo; M Ozaki; K Yoshino
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 434 415 - 423 2005年 [査読有り]
     
    Optical recording by smectic layer rotation is proposed and demonstrated. Smectic layer rotation is induced by the application of asymmetric voltage pulses, and the use of an amorphous silicon layer as a photoconductor allows the area for rotation to be selected by partial irradiation of the cell. The anisotropy of smectic layer rotation is clarified, and the recording resolution is found to differ between patterns oriented parallel and perpendicular to the smectic layer normal. This anisotropy is attributed to differences in the ease of boundary formation in the smectic layer.
  • J Ohtsubo; K Nakayama
    2004 IEEE LEOS ANNUAL MEETING CONFERENCE PROCEEDINGS, VOLS 1 AND 2 342 - 343 2004年 [査読有り]
     
    Fast optimization method of encrypted binary hologram in optical security systems is proposed based on the error information for the estimated decryption pattern. The time required to obtain an optimized image is only 3 % of the iterative error reduction method.
  • NAKAYAMA K; OHTSUBO J; OZAKI M; YOSHINO K
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 409 243 - 250 2004年 [査読有り]
  • K Nakayama; J Ohtsubo; M Ozaki; K Yoshino
    APPLIED PHYSICS LETTERS 80 14 2439 - 2441 2002年04月 [査読有り]
     
    Optical recording in a ferroelectric liquid crystal using smectic layer rotation induced by the application of asymmetric voltage pulses has been proposed. This recording method is based on the temperature dependence of the rotation rate and the fact that the rate in the smectic A (SmA) phase is considerably smaller than that in the chiral smectic C (SmC*) phase. The transition from the SmC* to the SmA phase can be induced by the photothermal effect. The application of asymmetric voltage pulses during partial laser irradiation results in the patterning of the layer alignment. This recording method can erase and invert the stored pattern and can handle gray-level patterns. (C) 2002 American Institute of Physics.
  • SB Lee; K Nakayama; T Matsui; M Ozaki; K Yoshino
    IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 9 1 31 - 38 2002年02月 [査読有り]
     
    Silica particles dispersed in liquid crystals exhibit a novel behavior such as a unique migrating behavior and alignment. These characteristics are found to depend on the size of the nanoparticles, the surface state of nanoparticles, the liquid crystal (LC) phases, the amplitude and the frequency of applied voltage. These are discussed in terms of anisotropic particle-particle and particle-LC molecules interactions in the anisotropic environment of liquid crystal matrix.
  • Tatsunosuke Matsui; Sergey B. Lee; Keizo Nakayama; Masanori Ozaki; Katsumi Yoshino
    Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals 367 37 - 43 2001年 [査読有り]
     
    The alignment characteristics and dynamics of SiO2 particles dispersed in a liquid crystal (LC) under an applied electric field have been studied. In the system composed of LC, surfactant and SiO2 particles, a well-ordered aggregation of particles has been observed under the applied electric field. For this aligned aggregation of particles, phase separation behavior between the LC and surfactant, and electrohydrodynamic flow at the LC/surfactant interface seem to play an important role. The possibility for the fabrication method of photonic crystal is also discussed. © 2001 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint, a member of the Taylor & Francis Group.
  • K Yoshino; Y Shimoda; K Nakayama; T Tamura; T Matsui; H Kajii; M Ozaki
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 364 501 - 509 2001年 [査読有り]
     
    Various liquid crystals can be infiltrated into interconnected nanosize voids in a three-dimensional periodic array of SiO2 spheres, synthetic opals, as photonic crystals. As an example of tunable photonic crystals, it has been demonstrated that the optical stop band in transmission spectrum of the liquid crystal infiltrated opal shifts with changing temperature, which can be interpreted in terms of temperature dependence of the refractive index and confirmed by the theoretical calculation of the band structure. This phenomenon can be utilized as a method to evaluate the refractive index. Tunability of optical properties of photonic crystal is also demonstrated in infiltrated replicas of opals. Effects of electric field application on properties of the infiltrated opals are also clarified.
  • Y Shimoda; K Nakayama; M Ozaki; K Yoshino
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 368 4119 - 4126 2001年 [査読有り]
     
    The infiltration of a nematic liquid crystal into opal with a three-dimensional periodic structure has been studied. In the infiltrated opals, the stop band has been confirmed to be controlled by adjusting various conditions such as temperature. Opal replica has been prepared and it has been found that optical stop band of the opal replica also shifts upon infiltration with organic materials.
  • T Matsui; K Nakayama; M Ozaki; K Yoshino
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 368 4199 - 4211 2001年 [査読有り]
     
    We proposed an optical fabrication method of designed multidomain structure in an azo-dye-doped ferroelectric liquid crystal with chiral nematic (N*) - chiral smectic C (SmC*) phase sequence (NC-FLC). This layer alignment control is based on the N*-SmC* phase transition induced by the photoisomerization of doped azo-dye. This photo-assisted layer switching can be applied to the fabrication of the designed multidomain structure in the electrooptic elements such as display, optical memory and optical grating. Anomalous layer switching upon the electric field has also been observed.
  • K Yoshino; SB Lee; T Sonoda; H Kawagishi; R Hidayat; K Nakayama; M Ozaki; K Ban; K Nishizawa; K Ohta; H Shirai
    JOURNAL OF APPLIED PHYSICS 88 12 7137 - 7143 2000年12月 [査読有り]
     
    Comparative study of optical properties of alkylthio-group-substituted phthalocyanine rare-earth metal sandwich complexes ([(CnS)(8)Pc](2)M,M=Eu,Lu,Tb) is presented. Photoluminescence and photoconductivity of [(CnS)(8)Pc](2)M complex is very weak. Two photoluminescence bands were observed at around 400-650 and 720-800 nm in chloroform solution corresponding to the Soret and Q bands in the absorption spectra, respectively. However, the emission from Eu3+ ion (as well as Tb3+) was not found compared with other Eu complexes because the 5d levels of the Eu3+ ion lie higher than the triplet level of the ligand. The significant enhancement of the photoconductivity of [(C16S)(8)Pc](2)M after C-60 doping is reported. The photoconductivity is positive at the low electric field in the ohmic regime while it becomes negative at the high electric field upon photoexcitation with strongly absorbed light. The negative photoconductivity is attributed to space-charge effects. The mechanism of photoluminescence and photoconductivity are discussed by taking the electronic energy schemes of phthalocyanine ligands and lanthanide ion and C-60 into consideration. (C) 2000 American Institute of Physics. [S0021-8979(00)05522-5].
  • T Matsui; K Nakayama; M Ozaki; K Yoshino
    APPLIED PHYSICS LETTERS 76 10 1228 - 1230 2000年03月 [査読有り]
     
    Photoinduced layer alignment control has been proposed in an azo-dye-doped ferroelectric liquid crystal with a chiral nematic (N*)-chiral smectic C (SmC*) phase sequence. This layer alignment control is based on the N*-SmC* phase transition induced by the photoisomerization of the azo-dye. Trans-cis photoisomerization of the azo-dye upon UV irradiation in the SmC* phase induces the N* phase, and an opposite isomerization process upon sequentially stopping the UV irradiation induces the SmC* phase again. The photoinduced SmC*-N*-SmC* phase transition under an appropriate electric field allows us to control the smectic layer alignment. This photoassisted layer switching can be applied to the fabrication of the designed multidomain structure in electro-optic elements such as display, optical memory, and optical grating. (C) 2000 American Institute of Physics. [S0003-6951(00)02010-6].
  • 下田 雄紀; 中山 敬三; 尾崎 雅則; 吉野 勝美
    日本液晶学会討論会講演予稿集 2000 529 - 530 日本液晶学会 2000年 
    The infiltration of a nematic liquid crystal into synthetic opal with a three-dimensional periodic structure has been studied. The transmission and reflection spectra of nematic liquid crystal infiltrated opals were measured. The wavelengths of the stop band and the reflection peak shift by the infiltration with a liquid crystal due to the higher refractive index than that of air. Moreover, the stop band and reflection peak are shifted by the change of the refractive index of the liquid crystal infiltrated into opal.
  • K Yoshino; Y Kawagishi; S Satoh; S Lee; K Nakayama; H Take; H Kajii
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 341 1289 - 1294 2000年 [査読有り]
     
    Nano-scale periodic structures of conducting polymer and carbons, which were prepared by infiltration of polymers and carbons in nano-scale interconnected periodic pores in synthetic opals made of regular array of SiO2 spheres and then removing SiO2 by etching, have been found to exhibit novel electrical and optical properties. Their electrical and optical properties in thus fabricated conducting polymer and carbon replicas change drastically upon pyrolysis due to progress of carbonization and graphitization. That is, due to the changes in periodicity, pore size, carbonization degree and crystal structure, electrical conductivity, magnetoconductance and their temperature dependences and optical reflection spectra have changed drastically. These replicas with porous nature can be infiltrated and also intercalated with various materials, resulting in also remarkable changes of properties. The synthetic opal infiltrated with conducting polymer can be electrochemically doped, with which remarkable change of optical properties have been observed due to the shift of the diffraction peak accompanying with the change in refractive index. Alkali metal intercalated carbon and graphite with nano-scale periodic structures have been also studied. The applications of these nano-scale periodic structures of conducting polymer and carbon are also discussed.
  • K Yoshino; T Nagata; K Nakayama; A Fujii; M Ozaki; M Onoda
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION C-MOLECULAR MATERIALS 12 2 143 - 151 2000年 [査読有り]
     
    Poly(p-Phenylenevinylene) derivative with azobenzene moiety in the side chains (MPA-10-PPV) has been prepared. Photochromism due to cis-trans isomerization of azobenzene was observed in this new type of conducting polymer. Optical dichroism induced upon irradiation by polarized light has been discussed in terms of reorientation of both azobenzene moiety and polymer main chain. Relatively strong photoluminescence (PL) and electroluminescence (EL) have also been observed in this new type of polymer.
  • K Yoshino; H Nambu; T Oue; Y Shimoda; Y Kawagishi; K Nakayama; S Yablonskii; S Uto; M Ozaki
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 347 339 - 353 2000年 [査読有り]
     
    Pyroelectric effect has been observed in freely suspended film (FSF) of ferroelectric liquid crystal (FLC). The temperature dependence of spontaneous polarization evaluated using this effect has been found to be nearly the same as that in the sandwich cell. In the FLC FSF no threshold has essentially been observed in the electro-optic effect. On the other hand, in transferred film (TF) the threshold exists even at extremely slow scan rate. The threshold field is found to increase with decreasing thickness of TF. In the case of TF the substrate influences strongly the electro-optic effect. The influence of the substrate was found to extend to about 200 smectic layers. Upon acoustic sound irradiation and also electric field application on FLC FSF, the mechanical vibration of the film was effectively excited. For both excitations, resonance vibrations were observed but their oscillating modes were different. The application of FLC FSF to a space electric field sensor has also been discussed. Unique electrical and optical properties of liquid crystals infiltrated in nano-scale voids of synthetic opals with three-dimensional regular array have also been observed.
  • T Oue; H Nambu; K Nakayama; M Ozaki; K Yoshino; SV Yablonskii
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 347 355 - 364 2000年 [査読有り]
     
    Electric field induced vibration of a freely suspended film (FSF) of smectic liquid crystal has been studied as a function of temperature, applied field and film thickness. By the application of a sinusoidal electric field parallel to the film, not only a fundamental but also higher harmonics of the vibration has been observed. In particular, even the fifth-harmonics of the vibration is excited in ferroelectric liquid crystal (FLC). Electric field dependences of the vibration strength for fundamental and second-harmonic components have been found to be proportional to the electric field and to the square of the electric field, respectively. Temperature dependence of each component of the vibration strength has been also measured in FLC. The fundamental component of the vibration increases steeply around the phase transition temperature from the smectic A (SmA) phase to the chiral smectic C (SmC*) phase, while the second-harmonic component has taken the maximum strength just below the phase transition temperature. When the FSF was in the SmA phase, the optical response was smaller for the thick film compared with that for the thin film. Oppositely, in the SmC* phase, the film vibration was smaller for the thin dim.
  • K Yoshino; S Satoh; Y Shimoda; Y Kawagishi; K Nakayama; M Ozaki
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 38 8B L961 - L963 1999年08月 [査読有り]
     
    The optical stop band in the transmission spectra and the peak in the reflection spectra of opals with a three-dimensional periodic structure shift drastically upon infiltration with organic materials such as liquids, liquid crystals and conducting polymers. In these infiltrated opals, the stop band and reflection peak have been confirmed to be tunable by adjusting various conditions such as temperature and applied voltage.
  • K Yoshino; Y Shimoda; Y Kawagishi; K Nakayama; M Ozaki
    APPLIED PHYSICS LETTERS 75 7 932 - 934 1999年08月 [査読有り]
     
    Nematic liquid crystals and smectic liquid crystals can be infiltrated into a three-dimensional periodic array of interconnected nanosize voids in opal films prepared by sedimentation of SiO2 spheres of various diameters. The optical stop band in the transmission spectra of opals shifts drastically by the infiltration of liquid crystals. The stop band is also found to shift at the phase transition points with changing temperature. This effect enables the tuning of optical properties of opals as a prototype tunable photonic crystal. This phenomenon can also be used as a measurement method for the refractive index. (C) 1999 American Institute of Physics. [S0003-6951(99)01733-7].
  • Measurements of Refractive Index of Liquids and Liquid Crystals Utilizing Opals with Interconnected Three-dimensional Regular Array of Voids and Their Replicas
    Keizo Nakayama; Yuki Shimoda; Yoshiaki Kawagishi; Masanori Ozaki; Katsumi Yoshino
    Proceedings of 1999 IEEE 13th International Conference on Dielectric Liquids (ICDL'99), pp.~361-364 1999年07月 
    【工学部論文データから移行】
  • Dynamic Behavior of Silica Nanoparticles in Liquid Crystals under an AC Applied Voltage
    Sergey Lee; Keizo Nakayama; Masanori Ozaki; Katsumi Yoshino
    Proceedings of 1999 IEEE 13th International Conference on Dielectric Liquids (ICDL'99), pp.~571-574 1999年07月 
    【工学部論文データから移行】
  • SV Yablonskii; K Nakayama; S Okazaki; M Ozaki; K Yoshino; SP Palto; MY Baranovich; AS Michailov
    JOURNAL OF APPLIED PHYSICS 85 5 2556 - 2561 1999年03月 [査読有り]
     
    The pretilt angle controlled by electric field was studied by the modulation ellipsometry technique. The easy direction of compensated nematic liquid crystals was controlled by surface flexoelectric torque created by the linear coupling of the director deformation and electric field. The weak anchoring energy necessary for the occurrence of flexoelectric distortion was produced by unidirectional rubbing of the clean indium-tin-oxide covered glasses with a cotton cloth. The pretilt angle was measured as a function of electric field. Long relaxation times of the optical response (hundreds of seconds) were observed. The rubbed thin polyvinyl alcohol and polyimide aligning layers were seen to promote strong anchoring energy (>0.5 erg/cm(2)) preventing any deviation of pretilt angle and, consequently, to suppress the optical response. The probable applications of the obtained results are discussed. (C) 1999 American Institute of Physics. [S0021-8979(99)08404-2].
  • K Yoshino; K Nakayama; Y Kawagishi; S Tatsuhara; M Ozaki; AA Zakhidov
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 329 1045 - 1052 1999年 [査読有り]
     
    Liquid crystals such as nematic liquid crystals and ferroelectric smectic liquid crystals are well infiltrated in photonic crystal, synthetic opal. Dielectric and optical properties of liquid crystals have been found to exhibit remarkable change upon infiltration in the opal. Diffraction and transmission of light through opals have been found to change upon infiltration of liquid crystal in opals and also upon field application. Relaxation of dielectric response in liquid crystals infiltrated in opal shifted to higher frequency and its temperature dependence has also changed. Electro-optic effect of the opal infiltrated with liquid crystals have been also discussed. These results have been discussed in terms of interaction of liquid crystal molecule in nano-space and the inner surface of the nano-scale void in the photonic crystal, synthetic opal.
  • K Nakayama; M Ozaki; K Yoshino
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 329 741 - 747 1999年 [査読有り]
     
    The migration of SiO2 particles under the application of an ac electric field has been observed in the various phases. SiO2 particles in the Iso. and N* phases migrated in a circle. In the SmA and SmC* phases, SiO2 particles migrated along the smectic layer. This indicates that the smectic layer structure influences the migration of SiO2 particles. The migration has been examined with a monodomain, a multidomain and a planar cell. The migration was not observed in a homeotropic aligned region. The migration has been found to require the polarity reversal of the applied electric field.
  • K Nakayama; M Ozaki; K Yoshino
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 331 2133 - 2140 1999年 [査読有り]
     
    We have proposed the optical patterning in a ferroelectric liquid crystal with the N*-SmC* phase sequence and successfully demonstrated it. In a homogeneously aligned cell with a rubbing treatment, two smectic layer structures can be selected by applying an electric field during the phase transition from N* to SmC*, The pattern was recorded through the phase transition under applying a dc electric field. The partial phase transition was induced by the illumination of a laser. The influence of illumination time, i.e., the thermal conduction in a patterning process also has been investigated. This optical patterning have a erase, addition, subtraction and inversion function of binary images.
  • K Nakayama; M Ozaki; K Yoshino
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 37 9B 5379 - 5381 1998年09月 [査読有り]
     
    Rewritable optical recording has been demonstrated in a ferroelectric liquid crystal (FLC) with the chiral nematic (N*)-chiral smectic C (SmC*) phase sequence. In a homogeneously aligned cell surface-treated for a unidirectional molecular alignment, there are two kinds of layer configurations in the SmC* phase which appears directly from the N* phase with decreasing temperature. The direction of the layer alignment can be controlled by selecting the polarity of the applied electric field at the phase transition from N* to SmC*. Due to these characteristics, by irradiating a laser beam on a spot in the FLC in the SmC* phase under a specific polarity of the applied field, the layer alignment in the irradiated spot can be switched to the desired direction. This recording of the laser spot is erasable. In this device, the subtraction function in a binary image has also been realized.
  • SV Yablonskii; K Nakayama; M Ozaki; K Yoshino
    JETP LETTERS 67 11 978 - 984 1998年06月 [査読有り]
     
    An asymmetric ac electric field with amplitude E = 10 V/mu m gives rise to a matched rotation of the normal to the smectic layers, while a sinusoidal field E = 1 V/mu m is used to study the rotation in the method of modulation total internal reflection ellipsometry, which makes it possible to probe the region of a ferroelectric liquid crystal (FLC) next to the electrode (h approximate to 0.7 mu m). It is shown that the angle of rotation of the normal to the smectic layers near the surface of the electrode varies reversibly as a function of the polarity and number of electric pulses applied, just as in the interior region. The characteristic dynamic properties of thin layers of nematic liquid crystals, such as an anomalously long relaxation time and a high-frequency relaxation process, are observed in thin FLC layers. (C) 1998 American Institute of Physics. [S0021-3640(98)01711-3].
  • Manifestation of Photoinduced Charge-Transfer Process in Electrooptical Effect on Nematic Liquid Crystal
    Journal of the Society of Electrical Engineering 7 1 58 - 60 1998年 [査読有り]
  • M Ozaki; Y Fuwa; K Nakayama; K Yoshino; T Tani; K Fujisawa
    FERROELECTRICS 214 1-2 725 - 732 1998年 [査読有り]
     
    Sign inversion of spontaneous polarization (Ps) has been studied in two types of mixture systems of ferroelectric liquid crystal (FLC). One is a binary mixture of chiral (ferroelectric) and achiral SmC liquid crystals. Although the pure FLC has a relatively large Ps and shows no anomaly in the sign of P-s, the magnitude of Ps exponentially decreases upon doping with achiral compound. Particularly, in the mixture highly doped with achiral compound, which shows extremely small Ps, the sign of Ps is inverted upon changing temperature. In this case, the inversion temperature is very sensitive to the concentration of achiral dopant. Another system is a mixture of two FLCs having opposite signs of Ps. In this mixture, the sign inversion has been observed with temperature in the concentration range in which Ps is suppressed.
  • S Uto; E Tazoh; K Nakayama; M Ozaki; K Yoshino
    FERROELECTRICS 214 1-2 717 - 724 1998年 [査読有り]
     
    Characteristic circular textures induced by alternating electric field have been observed in a freely suspended ferroelectric liquid crystal film using a polarizing microscope. There are two types of the circular textures, that is, a coaxial texture and a scroll texture. Formation process of both types of the textures is explained. In addition, a twofold and a fourfold scroll textures are observed.
  • K Nakayama; T Togo; M Ozaki; K Yoshino
    FERROELECTRICS 212 1-4 195 - 202 1998年 [査読有り]
     
    Dynamics of a smectic layer alignment in ferroelectric and antiferroelectric liquid crystals, in particular, the reversible rotation of a smectic layer alignment by application of asymmetric voltage pulses has been investigated. The direction of layer normal can be controlled by application of voltage pulses, and in other words, the optical axis of the sample is controllable by selecting the waveform of applied voltage pulses. Moreover, we observed a movement of the SiO2 particles which were doped into the sample. Although in the isotropic and nematic phases, SiO2 particles move circularly in the smectic A and chiral smectic C phases which have a layer structure, all particles move linearly along the smectic layer.
  • T Togo; K Nakayama; M Ozaki; K Yoshino
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 36 11B L1520 - L1522 1997年11月 
    The electric field-induced migration of SiO2 particles along a smectic layer has been observed in smectic liquid crystal. SiO2 particles migrate in a sandwiched planer cell of the liquid crystal upon application of an ac electric field. The trace of moved particles is dependent on the alignment of the host liquid crystal molecules. In the phase with a layer structure, such as smectic A and C phases, the particles migrate along the smectic layer, whereas they move in a circular pattern in the isotropic and nematic phases.
  • T Togo; K Nakayama; M Ozaki; K Yoshino
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 36 11B L1520 - L1522 1997年11月 [査読有り]
     
    The electric field-induced migration of SiO2 particles along a smectic layer has been observed in smectic liquid crystal. SiO2 particles migrate in a sandwiched planer cell of the liquid crystal upon application of an ac electric field. The trace of moved particles is dependent on the alignment of the host liquid crystal molecules. In the phase with a layer structure, such as smectic A and C phases, the particles migrate along the smectic layer, whereas they move in a circular pattern in the isotropic and nematic phases.
  • K Nakayama; M Ozaki; K Yoshino
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 36 9B 6122 - 6124 1997年09月 [査読有り]
     
    We have studied the rearrangement of a smectic layer induced by asymmetric voltage pulses in ferroelectric and antiferroelectric liquid crystals. This layer rotation is reversible and takes place in both non-treated and rubbed cells. The optical response during layer rotation has been studied, and it is confirmed that the direction of the optical axis can be reversibly controlled by the accumulated number of applied voltage pulses.
  • K Nakayama; M Ozaki; K Yoshino
    APPLIED PHYSICS LETTERS 70 16 2117 - 2119 1997年04月 [査読有り]
     
    The smectic layer rotation of a ferroelectric liquid crystal (FLC) has been investigated by applying a de electric field. The smectic layer of FLC doped with a small amount of an ionic impurity can be rotated around the axis perpendicular to the glass plates upon application of de voltage. This smectic layer rotation is interpreted in terms of the electrohydrodynamic flow due to an ionic impurity. (C) 1997 American Institute of Physics.
  • K Yoshino; S Uto; K Myojin; K Nakayama; K Kobayashi; XH Yin; H Moritake; M Ozaki
    FERROELECTRICS 196 1-4 617 - 623 1997年 [査読有り]
     
    Nonlinear optical phenomena such as second harmonic generation (SHG) have been studied in various ferroelectric liquid crystals. SHG efficiency depends on the molecular structure of ferroelectric liquid crystal and can be controlled by applied voltage. Phase matching of SHG has been well realized in these ferroelectric liquid crystals. SHG in polymeric ferroelectric liquid crystals, ferroelectric liquid crystal-conducting polymer composites, thin ferroelectric liquid crystal films and liquid crystals which exhibit flexoelectric effect have also been discussed.
  • K Nakayama; M Ozaki; K Yoshino
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 304 339 - 343 1997年 [査読有り]
     
    A reversible rotation of smectic layer in ferroelectric and antiferroelectric chiral smectic C phases has been investigated as a function of a waveform of applied voltage pulses and cell geometry. The layer rotation is caused by applying asymmetric voltage pulses and the rotation direction depends on the waveform of pulses and the sign of spontaneous polarization. In addition, the reversible layer rotation in the smectic A phase has been observed by applying asymmetric voltage pulses and interpreted in terms of electroclinic effect. The layer rotation in the chiral smectic C phase of the ferroelectric liquid crystal doped with ionic impurity has been also found by applying DC voltage.
  • K Yoshino; Y Fuwa; K Nakayama; S Uto; H Moritake; M Ozaki
    FERROELECTRICS 197 1-4 637 - 645 1997年 [査読有り]
     
    The properties of ferroelectric and polymeric ferroelectric liquid crystals (FLC and PFLC) have been studied as functions of molecular structure, bias voltage and boundary conditions. Anomalous rotation of the smectic layer has been observed in the ferroelectric and antiferroelectric phases. The direction of the rotation is reversible with the polarity reversal of the applied voltage. The transition temperature (Tc) from smectic A to smectic C* becomes higher with decreasing thickness in free-standing FLC films. On the other hand, Tc in the free-standing PFLC film is similar to that of thick sandwich cell. Electro-optic effects in FLC and PFLC in spin-coated films, free-standing films and in sandwich cells have also been clarified.
  • Katsumi Yoshino; Sadahito Uto; Katsunori Myojin; Keizo Nakayama; Kentaro Kobayashi; Xiao Hong Yin; Hiroshi Moritake; Masanori Ozaki
    Ferroelectrics 196 1-4 297 - 303 1997年 [査読有り]
     
    Nonlinear optical phenomena such as second harmonic generation (SHG) have been studied in various ferroelectric liquid crystals. SHG efficiency depends on the molecular structure of ferroelectric liquid crystal and can be controlled by applied voltage. Phase matching of SHG has been well realized in these ferroelectric liquid crystals. SHG in polymeric ferroelectric liquid crystals, ferroelectric liquid crystal-conducting polymer composites, thin ferroelectric liquid crystal films and liquid crystals which exhibit flexoelectric effect have also been discussed.
  • K Nakayama; M Ozaki; K Yoshino
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 35 12A 6200 - 6201 1996年12月 [査読有り]
     
    Smectic layer rotation in the smectic A phase of ferroelectric and antiferroelectric liquid crystals has been observed by applying asymmetric voltage pulses. The layer rotates over the field-induced tilt angle due to the electroclinic effect. The rotation is reversible. Namely, the layer rotates in the opposite direction upon applying pulses of opposite polarity. The electroclinic effect plays an important role in this phenomenon.
  • LM Blinov; AV Kozlovsky; K Nakayama; M Ozaki; K Yoshino
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 35 10 5405 - 5410 1996年10月 [査読有り]
     
    A chiral ate-dye showing reversible trans-cis isomerization upon UV light irradiation was used as a dopant to induce ferroelectric properties in an achiral smectic C liquid crystal matrix. The kinetics of the isomerization in the smectic matrix was studied optically. The influence of the isomerization process on the ferroelectric properties of the mixture was investigated by observation of the ferroelectric switching in the smectic C phase and electroclinic response in the smectic A phase. The experimental results show that the banana-shaped cis isomers are less efficient in inducing the spontaneous polarization than their rodlike trans counterparts.
  • Hiroshi Moritake; Keizo Nakayama; Masanori Ozaki; Katsumi Yoshino
    FERROELECTRICS 178 277 - 285 1996年 [査読有り]
     
    The rotation of smectic layer in the antiferroelectric liquid crystals upon application of asymmetric voltage pulses has been observed. The influence of the cell configuration upon this layer rotation has been investigated. This layer rotation is not directly related with the interaction between liquid crystal molecules and the spacer at the liquid crystal-spacer interface. The rotation of smectic layer has been observed not only in a monodomain cell but also in a multidomain cell. This layer rotation has also been observed in ferroelectric liquid crystal as the same manner in antiferroelectric liquid crystals.
  • K Nakayama; H Moritake; M Ozaki; K Yoshino
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 34 12A L1599 - L1602 1995年12月 [査読有り]
     
    The smectic layer rotation in ferroelectric liquid crystals has been observed by applying an asymmetric waveform of electric field using both a rubbed cell and a nontreated cell. The rotation angle increases exceeding the tilt angle with increasing cycles of applied voltage. The direction of the smectic layer rotation depends on the sign of spontaneous polarization. The layer rotation should be a common phenomenon in ferroelectric and antiferroelectric liquid crystals.
  • H Moritake; K Nakayama; M Ozaki; K Yoshino
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS 263 13 - 26 1995年 [査読有り]
     
    The light scattering measurement and the polarized microscopic observation of field induced phase transition between antiferroelectric (AF) and ferroelectric (F) phases have been performed in a uniformly aligned cell. The light scattering is confirmed to be diffraction by the periodical change in refractive index in the stripe domains of AF and F phases. In F --> AF phase transition, the nucleation of AF domain occurs at interfaces between liquid crystal and spacer edges and AF domain grows away from spacers. On the other hand, in AF --> F phase transition, discrete F domains homogeneously appear and grow throughout the cell. The rotation of smectic layer is also observed under the application of an asymmetric voltage. This rotation is originated from the asymmetry of the polarity reversal of the applied voltage.
  • M OZAKI; H MORITAKE; K NAKAYAMA; K YOSHINO
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 33 11B L1620 - L1623 1994年11月 [査読有り]
     
    Smectic layer rotation in the antiferroelectric liquid crystal upon application of asymmetric pulses of electric field has been observed. Application of the electric field with sawtooth waveform of more than 10(3) cycles induces rotation of the direction of the smectic layer normal by more than 60-degrees away from the initial alignment axis even in the sample without surface treatment for a unidirectional alignment. This rotation is reversible, and the layer rotates in the opposite direction upon application of pulses of electric field with opposite polarity. This anomalous layer rotation has been tentatively interpreted to originate from the essential difference in F --> AF and AF --> F transition mechanisms.

書籍

  • High Quality Liquid Crystal Displays and Smart Devices Volume 2: Surface alignment, new technologies and smart device applications
    中山 敬三 (担当:分担執筆範囲:Chapter 37: Optical Security Devices Using UV Curable Nematic Liquid Crystals)IET:英国工学技術学会 2019年03月

講演・口頭発表等

  • 液晶調光フィルムを用いた石器写真撮影時の陰影調整  [通常講演]
    中山敬三; 中村一郎; 中山満子
    2021年日本液晶学会討論会 2021年09月 ポスター発表
  • OpenCVを用いたセキュリティ素子応用に向けた液晶光学組織の分析プログラムの開発  [通常講演]
    藤原 広登; 中山 敬三
    電気材料技術懇談会若手研究発表会 2021年07月
  • 色覚異常者をサポートする液晶を用いた色弁別補助装置の正常色覚者による評価実験  [通常講演]
    中山敬三
    第29回日本MRS年次大会 2019年11月 口頭発表（一般）
  • Heilmeier型ゲストホスト液晶素子を利用した赤緑色覚異常者向け色弁別補助装置の有効性評価  [通常講演]
    中山敬三
    2019年日本液晶学会討論会 2019年09月 ポスター発表
  • Heilmeier型ゲストホスト液晶素子を利用した赤緑色覚異常者向け色弁別補助装置の評価実験  [通常講演]
    中山 敬三
    2018年日本液晶学会討論会 2018年09月 口頭発表（一般）
  • Application of Reddish Purple Guest-Host Liquid Crystal to Assist Device for Color Vision Defects  [通常講演]
    中山 敬三
    27th International Liquid Crystal Conference (ILCC2018) 2018年07月 ポスター発表
  • 非配向ナノファイバ層を有するネマチック液晶素子でのランダムテクスチャのフーリエ変換を用いた評価  [通常講演]
    中山 敬三; 森武 洋
    第27回日本MRS年次大会 2017年12月 口頭発表（一般）
  • 液晶素子を用いた色弱者向け色弁別補助デバイス  [通常講演]
    中山 敬三; 吉田 知恵子
    第30回東大阪産業展 テクノメッセ東大阪2017 2017年11月 その他
  • エレクトロスピニング法で形成した非配向ナノファイバー層による液晶素子へのランダム性の付与  [通常講演]
    中山 敬三; 森武 洋
    2017年日本液晶学会討論会 2017年09月
  • 液晶を用いた色弁別補助装置の評価実験系の構築  [通常講演]
    吉田 知恵子; 中山 敬三
    電気材料技術懇談会若手研究発表会 2017年07月 その他
  • 高分子分散型液晶とプロジェクタを用いた重畳表示による注意喚起インタフェース  [通常講演]
    下瀬 主揮; 中山 敬三
    平成29年電気学会全国大会 2017年03月 口頭発表（一般）
  • エレクトロスピニング法で得られる非配向ナノファイバーを用いたネマチック液晶の微細なランダムテクスチャ  [通常講演]
    中山 敬三; ドン・クォック・トアン; 森武 洋
    第26回日本MRS年次大会 2016年12月 口頭発表（一般）
  • 紫外線硬化型ネマチック液晶を用いた光セキュリティ素子  [招待講演]
    中山 敬三
    2016年日本液晶学会討論会 2016年09月 口頭発表（招待・特別）
  • セキュリティ素子応用に向けたパターニングされたネマチック液晶のシュリーレン組織パターンの評価  [通常講演]
    中山 敬三; 大坪順次
    応用物理学会春季学術講演会 2016年03月 口頭発表（一般）
  • 光重合した液晶の非均一構造のセキュリティデバイスへの応用  [通常講演]
    中山 敬三; 大坪 順次
    第25回日本MRS年次大会 2015年12月 口頭発表（一般）
  • セキュリティ応用のためのパターニングされた紫外線硬化型ネマチック液晶の偏光顕微鏡画像からのパターン抽出  [通常講演]
    中山 敬三; 大坪順次
    2015年日本液晶学会討論会 2015年09月 口頭発表（一般）
  • カイラルネマチック液晶の指紋状組織パターンの縞方向情報による類似度評価  [通常講演]
    中山 敬三; 大坪 順次
    2014年日本液晶学会討論会 2014年09月 ポスター発表
  • 液晶光IDタグ応用のための画像処理によるカイラルネマチック液晶における指紋状組織の縞方向抽出  [通常講演]
    中山 敬三; 大坪 順次
    第61回応用物理学会春季学術講演会 2014年03月 口頭発表（一般）
  • 熱相転移と光重合を用いてパターニングしたネマチック液晶光IDタグ  [通常講演]
    中山 敬三; 大坪 順次
    Optics & Photonics Japan 2013 2013年11月 口頭発表（一般）
  • 紫外線硬化型ネマチック液晶の水平配向セルにおけるテクスチャーのセキュリティ素子への応用  [通常講演]
    中山 敬三; 大坪 順次
    2013年日本液晶学会討論会 2013年09月 ポスター発表
  • 液晶光IDタグ作製における多重パターニング工程が与える指紋状組織への影響  [通常講演]
    中山 敬三; 大坪 順次
    第60回応用物理学会春季学術講演会 2013年03月 口頭発表（一般）
  • カイラルネマチック液晶の指紋状組織を利用した液晶光IDタグの光パターニング解像度  [通常講演]
    中山 敬三; 大坪 順次
    レーザー学会学術講演会第33回年次大会 2013年01月 口頭発表（一般）
  • Random Fingerprint Texture Serving as Optical Identifier and Scattering Medium  [通常講演]
    中山 敬三; 大坪 順次
    24th International Liquid Crystal Conference 2012年08月 ポスター発表
  • Individual differences in the evaluation of display legibility and preference  [通常講演]
    中山 敬三
    International Society for the Study of Individual Differences 2011年07月 ポスター発表
  • Preference of background texture in reading sentences with a computer monitor  [通常講演]
    中山 敬三
    the International Congress of Applied Psychology 2010 (ICAP 2010) 2010年07月 ポスター発表 Melbourne, Australia International Congress of Applied Psychology 2010
  • Assist Device for Colour Discrimination using Guest-Host Liquid Crystal for Red-Green Colour Blindness  [通常講演]
    中山 敬三
    11th Congress of the International Colour Association 2009年09月 ポスター発表 Sydney, Australia 11th Congress of the International Colour Association
  • Application of random texture in cholesteric liquid crystal for security device  [通常講演]
    中山 敬三; 大坪 順次
    2008年07月 ポスター発表 Nara, Japan 4th Japanese-Italian Workshop on Liquid Crystals

MISC

産業財産権

受賞

  • 2018年05月 レーザー学会 レーザー学会 上級会員
  • 2016年01月 電気材料技術懇談会 優秀論文賞
     紫外線硬化型液晶素子の不均一性を特徴として利用する液晶光IDタグ 
    受賞者: 中山 敬三;大坪 順次
  • 2003年 レーザー学会 第23回年次大会優秀論文発表賞
     偏光制御素子への強誘電性液晶スメクチック層回転現象の応用 JPN
  • 2003年 日本液晶学会 奨励賞（c分野）
     スメクチック層構造の回転現象の発見とその機構解明，機能応用に関する研究 JPN
  • 2002年 浜松電子工学奨励会 高柳研究奨励賞
     カイラルスメクチック液晶の層回転現象とその応用に関する研究 JPN

共同研究・競争的資金等の研究課題

  • 文部科学省：科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 中山 敬三
  • 文部科学省：科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2013年04月 -2015年03月 
    代表者 : 中山 敬三
     
    研究実績を1.実験、2.コンピュータ解析の分類で以下に報告する。1.本研究では紫外線硬化型液晶を用いて液晶のランダムテクスチャの固定化およびパターニングを実現するアイディアに基づいている。まず、光重合条件が固定化された液晶テクスチャにどのような影響が生じるかを調べるため、照射強度、照射時間および重合時の温度制御が可能な露光光学系を作製した。紫外線強度および各種マスクパターンで実験を行い、紫外線が照射されていない部分への意図しない重合領域の浸みだしの照射強度依存性および書き込みパターンの形状にも依存するなどの基礎的知見が得られた。また、これまでは主にカイラルネマチック液晶の指紋状組織をランダムテクスチャとして用いて実験を行ってきたが、ネマチック液晶材料での素子作製も行った。指紋状組織よりもシュリーレン組織の方がテクスチャがシンプルであるが、異なる素子ではシュリーレン組織のパターンも異なる事が確認できた。この結果から、ネマチック液晶も光セキュリティタグへ用いることも可能であることが分かった。2.液晶のテクスチャは偏光顕微鏡で観察するため、偏光子とサンプルの配置により同一素子で得られるパターンでも明暗が変化することがある。同一素子から得られるこれらの画像同士を輝度情報のみで比較すると相関値は低くなってしまう。そこで、画像の輝度情報ではなくカイラルネマチック液晶で観察される指紋状組織の縞方向抽出のプログラム開発を行った。縞の方向抽出としてはフーリエ変換による平均的な縞方向の抽出も可能であるが、単独の各縞の長さなどの幾何学的情報も重要なことから、二値化により縞を抽出し、その後、各縞の角度を評価するプログラムを開発した。その結果、指紋状組織の角度分布などを定量的に評価することが可能となった。これは、ランダム性の評価手法の開発および認証アルゴリズムの基礎となるものである。
  • 文部科学省：科学研究費補助金(若手研究(B))
    研究期間 : 2005年 -2006年 
    代表者 : 中山 敬三
     
    端面発光型半導体レーザに外部共振器を設けた戻り光半導体レーザとゲストホスト型液晶素子を組合せ、液晶素子による戻り光量制御に伴う戻り光半導体レーザの発振状態変化を、高速デジタルオシロスコープ、光スペクトルアナライザー等で観測した。実験系は、液晶素子への印加電圧が0V、すなわち、液晶素子の透過率が最も低い状態において、戻り光半導体レーザの発振状態が安定となるよう、外部共振器長、NDフィルターを調節した。液晶素子への印加電圧を0Vから10Vで変化させることにより、用いた実験系ではレーザの出力光に対する戻り光量を0.031%〜0.076%の範囲で連続に制御できた。液晶素子の変化により戻り光量を増加させると、RFスペクトルにおいて緩和振動周波数を中心にノイズ成分の増加が観測された。それに対応し、フォトダイオードと高速デジタルオシロスコープで観測した出力光強度の時間波形においても戻り光量の増加に伴うノイズ成分の増加が観測され、標準偏差値の比較では7.6倍の変化であった。発振状態のこの変化は、液晶素子への電圧制御により可逆的に繰り返し制御が可能であった。しかしながら、光スペクトルの観測では大きな変化が生じておらず、完全なカオス状態にはなっていなかった。しかし、NDフィルターの条件を変え、液晶素子による戻り光量変化の範囲を0.11%〜0.24%にさせることにより光スペクトルの可逆的な変化が観測された。以上のことから、実験に用いた液晶素子の透過率の可変域が狭いため、液晶素子のみでは安定状態からカオス状態へ変化させることができなかったと考えられる。今後は液晶素子のセル厚、色素の吸収波長の最適化、液晶素子への反射防止膜の採用など、透過光量の制御幅を増加させる検討が必要である。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2003年 -2005年 
    代表者 : 大坪 順次; 中山 敬三
     
    半導体レーザに外部から高レベルのレーザ光を注入すると、注入されたレーザの変調帯域が著しく高帯域化することが最近明らかにされた。しかし、その詳しい特性や理論的背景については不明な点が多い。カオス通信においては、カオス振動をメッセージ埋め込みのためのキャリアとするため、高帯域変調特性を持つカオスジェネレータの開発が重要である。本研究においては、半導体レーザの変調高帯域化についての詳細な特性を調べ、その理論的な背景を確立することを一つの目的とする。さらに、本研究のもう一つの目的として、カオス秘匿通信に適した高帯域半導体レーザカオスジェネレータの開発を行う。 強光注入のある戻り光半導体レーザのレート方程式を用いたカオスジェネレータのモデルを提案し、理論的解析を行った。この結果、強光注入がないときに2.7GHzであったカオス搬送波の帯域が、強光注入により7GHzまで拡大できることが示された。実際に量子井戸構造の半導体レーザを用いたカオスジェネレータ実験おいて、3GHzのカオス搬送波を、強光注入により9GHzの帯域拡大でき、ほぼ理論どおりお帯域拡大ができることが確認できた。さらに、DFBレーザを用いた実験では、3GHzのカオス搬送波を強光注入により、14GHzまで拡大できることがわかった。DFBレーザと量子井戸レーザでは、モデルとしては同じレート方程式が使えるはずであるが、パラメータの値が異なることが考えられ、今後検討を要することがわかった。さらに、本システムを用いた数値シミュレーションにより、帯域拡大された半導体レーザカオスジェネレータを使ったカオス同期が可能であることが示された。また、このモデルを使い、強光注入がない場合のカオス搬送波のカットオフ周波数より高い信号に対して、強光注入を行ったモデルでカオス同期通信が行えることが確認された。今後の課題としては、このような帯域拡大されたカオスジェネレータを用いたカオス同期通信を実験により確かめることがあげられる。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2002年 -2003年 
    代表者 : 大坪 順次; 中山 敬三
     
    高出力半導体レーザは、外部からの要因、たとえば外部光注入や電流変調などがなくても、それ自身不安定な発振となるレーザデバイスであり、ピコ秒程度での時間変動をするフィラメンテイションなどカオス的な光出力を持つレーザである。このことについての実験的検討あるいは、理論的な裏付けは乏しく、高出力半導体レーザ自身のダイナミクスを調べることが重要な研究課題でもある。本研究においては、高出力半導体レーザモデルのレート方程式を提案し、従来実験で断片的に知られていた高出力半導体レーザのパターンダイナミクスであるフィラメンテイションの構造や、レーザパラメータによるカオス分岐などの条件を理論的に明らかにした。また、この過程で、通常の狭ストライプ幅の端面発光半導体レーザ固有の現象として考えられていた低周波振動(Low Frequency Fluctuation ; LFF)が、高出力半導体レーザにおいても発生することが、実験的にはじめて確かめられた。 単体の高出力半導体レーザのコヒーレンスやビームプロファイルの整形のために、光注入によるレーザ制御などの方法が望まれる。本研究においては、レーザ自身の戻り光によって高出力半導体レーザを安定化することを試みた。通常、戻り光によって半導体レーザは一般に不安定化するが、そのような不安定状況下において、カオス的振動が全くの安定状態にジャンプするいわゆるカオスアトラクタの、共存状態が存在することを実験的に示した。カオスアトラクタ共存については、理論的な解析はあるものの、実験的にも証明できたことの価値も大きい。このとき、レーザは縦多モード発振状態から単一モードへ遷移し、さらに空間モードもブロードエリア半導体レーザ特有の双峰性ピークを持つプロファイルから単峰性パターンへと安定化された。詳細な安定化の条件は今後の課題であるが、当初の目的である高出力ブロードエリア半導体レーザのビーム制御の目標は達成された。現在、この結果はPhysical Review Eに投稿中である。
  • 文部科学省：科学研究費補助金(奨励研究(A), 若手研究(B))
    研究期間 : 2001年 -2002年 
    代表者 : 中山 敬三
     
    平成13年度は、スメクチック層回転現象の温度依存性を用いた光書込み型の実験を主に行った。しかし、温度依存性を利用する場合、試料に部分的な温度上昇を誘起するために高出力のレーザ照射を必要とする。また、レーザ照射による温度上昇を効率良く行うために、液晶材料に色素を添加する必要があった。そこで、平成14年度はガラス基板にアモルファスシリコン光伝導膜を利用した光書込みについて主に研究を行った。試料としては、カイラルスメクチック液晶の一種である強誘電性液晶を用い、市販されているチッソ株式会社CS-1024を選択した。透明電極付きガラス基板2枚で液晶材料を挟むが、片側の基板表面にはアモルファスシリコンを蒸着した。アモルファスシリコンの抵抗は通常では高い値を示すため、透明電極間に電圧を印加しても液晶には電圧がかからない状態となる。しかし、光を照射するとアモルファスシリコンの抵抗値が減少するため、光照射された領域では液晶に電圧が印加されることとなる。つまり、スメクチック層回転を誘起する非対称波形を印加しても、実際に光照射された領域のみの液晶にしか印加されず、結果的に、照射領域のみスメクチック層が回転する。実際に実験を行った結果、光照射領域のみスメクチック層回転が生じることが分かった。更に、解像度を詳細に調べたところ、スメクチック層に垂直な方向と、水平な方向とで書込み解像度に差が生じることが分かった。これはスメクチック層構造の弾性率等の物性値を反映しているものと考えられ、基礎科学的にも興味深い実験結果である。

委員歴

  • 2019年01月 - 現在   日本液晶学会   液晶学会誌編集委員
  • 2017年08月 - 2018年12月   第27回液晶国際会議   現地実行委員
  • 2014年01月 - 2015年12月   日本液晶学会   代議員
  • 2014年04月 - 2015年03月   レーザー学会   総務委員
  • 2009年04月 - 2015年03月   日本光学会   光科学及び光技術調査委員
  • 2006年04月 - 2011年03月   レーザー学会   総務委員
  • 2005年01月 - 2005年12月   日本液晶学会   理事

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