川月 喜弘

To fabricate fine metal structure, we proposed and demonstrated a method by using interference pattern of copropagating optical vortices and lift-off process. This method can fabricate more fine structure compared with the conventional laser drawing method using Gaussian beam even if the low numerical aperture condition.

Nanoimprinting can be used to fabricate various nanostructures on materials without etching processes. We previously demonstrated that the molecular orientation of a photocrosslinkable liquid crystalline polymer (PLCP) was induced by nanoimprinting, using a process called nanoimprint graphoepitaxy. In the current study, we performed multiple nanoimprint graphoepitaxy steps on PLCP films and investigated the resulting molecular orientations. Double nanoimprint graphoepitaxy on the PLCP produced a simple 2-μm line-and-space pattern with a dot molecular orientation pattern.

Herein a mechanoresponsive luminophore containing a pyridine ring at the molecular terminal is synthesized. The chromophore powder exhibits blue photoemission in the initial state, but turns green upon mechanical grinding. The chromophore forms a complex when combined with materials containing an acid group and a halogen. Furthermore, the mechanoinduced photoluminescence color of the halogen complex changes from bluish green to yellowish green, while that of the acid complex turns from orange to red. These results demonstrate that the mechanoresponsive color shift can be tuned.

We developed a method for the design of multilevel anisotropic diffraction gratings based on a genetic algorithm. The method is used to design the multilevel anisotropic diffraction gratings based on input data that represent the output from the required grating. The validity of the proposed method was evaluated by designing a multilevel anisotropic diffraction grating using the outputs from an orthogonal circular polarization grating. The design results corresponded to the orthogonal circular polarization grating structures that were used to provide outputs to act as the input data for the process. Comparison with existing design methods shows that the proposed method can reduce the number of human processes that are required to design multilevel anisotropic diffraction gratings. Additionally, the method will be able to design complex structures without any requirement for subsequent examination by a human designer. The method can contribute to the development of optical elements by designing multilevel anisotropic diffraction gratings.

We demonstrate the homogeneous photoalignment of low-molecular-weight liquid crystals (LC) using nematic LCs (NLCs) doped with photoalignable low-molecular-weight LC materials, achieved in the absence of substrate surface treatment in-plane switching (IPS) is also shown using an IPS-mode LC cell. The exposure of the LC cells to linearly polarized (LP) light in the isotropic temperature range of the NLC composites generates homogenous NLC orientation, but exposure at room temperature results in the random orientation of the NLCs. Small amounts of photoalignable LC materials on the substrates, which have undergone axis-selective photoreaction, are found to control the NLC alignment.

We fabricated a terahertz (THz) polarization converter using a twisted nematic (TN) liquid crystal (LC) cell. Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) films coated on quartz glass substrates were used as electrode layers in the TN LC cell. The PEDOT/PSS films were rubbed unidirectionally using a rayon cloth to align the nematic LC, thereby also serving as an alignment layer. The azimuthal surface anchoring strength of the PEDOT/PSS films was measured to be 5 × 10−4 J/m2 using the Néel wall method, which is similar to that of typical polymeric alignment layers. The optical constants of the PEDOT/PSS film in the THz range were also characterized using the Drude-Smith model, and the results indicated that the PEDOT/PSS films could be used both as transparent electrodes in the THz range and as alignment layers for the LC. The electro-optical properties of the fabricated TN LC cell were also investigated using a polarized visible laser and THz time-domain spectroscopic system. In particular, the transmission spectra and polarization conversion property of the TN LC cell in the THz range were theoretically analyzed based on a stratified model that considers optical anisotropy, absorption, and multiple interference. This work substantiates the advantages of TN LC cells with rubbed PEDOT/PSS films useful for THz polarization converters with electrical tunability.

The reflectance dependences of diffraction properties in a Fabry–Perot liquid crystal polarization grating (LCPG) were investigated. The Fabry–Perot LCPG was fabricated by combining two Au films and an orthogonal circular polarization grating (OCPG). The diffraction efficiency of our device strongly depends on the thickness of the Au films while polarization conversion properties are maintained to be the same as these of the general OCPG. Our results clarify that the Fabry–Perot OCPG has the potential to function as a multibranch polarization beam splitter whose diffraction efficiencies of respective diffraction directions are controlled in different ways by changing resonance conditions.

The nanoimprint process is a useful technique for the fabrication of various nanostructures on functional materials without the use of any etching processes. We previously confirmed that the molecular orientation of a photo-crosslinkable liquid crystalline polymer (PLCP) was induced by nanoimprinting using a process called nanoimprint graphoepitaxy. In this work, we repeat the previous O<inf>2</inf>reactive ion etching processing and molecular orientation evaluation to examine the depth profile of the unidirectional molecular orientation that is induced by nanoimprint graphoepitaxy. The results obtained indicate that the initial PLCP film thickness affects the resulting unidirectional molecular orientation depth.

The application of a top-coating of 4-methoxy cinnamic acid (MCA) onto a photoinactive liquid crystalline polymeric film containing benzoic acid (BA) side groups (P6BAM) is shown to enable thermally stimulated, photo induced reorientation of the polymer structure. Annealing the MCA-coated P6BAM films leads to H-bond formation between BA and MCA, which also effectively smooths the film surface. Exposure to linearly polarized (LP) UV light initiates axis-selective photoreaction of the MCA groups; subsequent thermal treatment in the LC temperature range of P6BAM amplifies molecular reorientation of the BA side groups, while simultaneously eliminating the MCA molecules. Selective inkjet coating of MCA provides a facile route for the fabrication of patterned, oriented, and rewritable P6BAM films with multiple controlled alignment directions.

To fabricate two-dimensional anisotropic diffractive optical elements, the polarization drawing method using polarization-sensitive liquid-crystal polymers and a galvano scanner offers a flexible approach. This method produces an arbitrary anisotropic distribution in the polymer films by controlling the polarization state of an ultraviolet laser beam during scanning. The fabrication of two patterned anisotropic diffractive elements, which cannot be fabricated using conventional methods of polarization holography, demonstrates its efficacy. In addition, we also fabricate a liquid-crystal Fresnel lens using this method. Our approach has the potential to produce highly functionalized diffractive optical elements having complex anisotropic spatial distributions.

Polarization gratings (PGs) were fabricated by the recording of vector holograms between two orthogonally polarized vector vortex beams (VVBs). The polarization and diffraction properties of the resulting PGs were analyzed theoretically. The feasibility of the process was demonstrated experimentally using a photo-crosslinkable liquid crystal polymer film as the polarization-sensitive material. The fabricated PGs can convert homogeneously polarized laser beams into VVBs, vector beams, optical vortices, and ring-shaped optical lattices by controlling the incident beam's state of polarization. The PGs that are presented will be applicable to optical communications and optical manipulation processes as vortex generators and converters.

A tunable dichroic polarization beam splitter (tunable DPBS) simultaneously performs the follow functions: 1. Separation of a polarized incident beam into multiple pairs of orthogonally polarized beams 2. Separation of the propagation direction of two wavelength incident beams after passing through the tunable DPBS and 3. Control of both advanced polarization and wavelength separation capabilities by varying the temperature of the tunable DPBS. This novel complex optical property is realized by diffraction phenomena using a designed three-dimensional periodic structure of aligned liquid crystals in the tunable DPBS, which was fabricated quickly with precision in a one-step photoalignment using four-beam polarization interferometry. In experiments, we demonstrated that these diffraction properties are obtained by entering polarized beams of wavelengths 532 nm and 633 nm onto the tunable DPBS. These diffraction properties are described using the Jones calculus in a polarization propagation analysis. Of significance is that the aligned liquid crystal structure needed to obtain these diffraction properties was proposed based on a theoretical analysis, and these properties were then demonstrated experimentally. The tunable DPBS can perform several functions of a number of optical elements such as wave plates, polarization beam splitter, dichroic beam splitter, and tunable wavelength filter. Therefore, the tunable DPBS can contribute to greater miniaturization, sophistication, and cost reduction of optical systems used widely in applications, such as optical measurements, communications, and information processing.

In recent year, optical and polarization vortex (OV and PV) beams, which has phase and polarization singularities, have much-Attracted attention in various research fields due to their unique physical properties. In this presentation, we report our attempts for the vortex beam generation based on the photo-Alignment technique of functionalized liquid crystal polymers. The OV and PV beam generations are respectively demonstrated by using azo-dye-doped liquid crystal polymers and photocrosslinkable polymer liquid crystal. Our approaches realize highly functionalized vortex beam generators which are expected to evolve the photonics applications of vortex beams.

In the present presentation, we report the experimentally and theoretically investigated spatial wavefront conversion properties of an optical vortex (OV) generation system including azo-dye doped liquid crystal (ADDLC) polymer composite and vector beam illuminator, focusing on the abilities of flexibility and achromaticity. Three-dimensional anisotropic structure was induced by recording vector beam in ADDLC and it can convert a polarized Gaussian beam into polarized OVs whose topological charge is depending on the structure of anisotropy. The photo-induced anisotropic structure can be re-initialized by turning it off and changing the illuminating polarization pattern of vector beam. Numerical simulations and experimental results showed that our anisotropic structure can generate OV with broadband spectrum.

Liquid crystalline polymers (LCPs) comprised of N-benzylideneaniline (NBA) side groups with different alkylene spacer length (n = 2, 6, and 10) are synthesized and their photoinduced reorientation behavior is investigated. Photoinduced orientation of NBA side groups is observed for all LCP films when exposing to LP-365 nm light, but the out-of-plane motion is simultaneously generated. When the polarization of LP-365 nm light is changed, in-plane optical anisotropy is reversibly changed and the out-of-plane motion is restricted for a P1 (n = 2) film. In contrast, reversibility of the photoinduced in-plane orientation is not effective for P2 (n = 6) and P3 (n = 10) films, where out-of-plane motion of the mesogenic NBA side groups is generated when the total exposure energy increases.

Polarization is one of the important parameters of the light wave. Diffractive elements, which can control the polarization, have been attracted as high-performance light control device. We have implemented various studies on the formation method and the diffraction characteristics of the anisotropic diffractive element using a photoreactive material. Photocrosslinkable polymer liquid crystal (PCLC) is an attractive material that can induce anisotropy along the polarization direction of linearly polarized ultraviolet light (LPUV). Also, owing to its relatively large anchoring strength, PCLC have been used as an alignment film of low-molar-mass liquid crystal (LC). Galvanometer scanners (GS) can freely control the exposure position of the laser beam by adjusting the two mirrors, it is possible to form a highly functionalized optical element by drawing the arbitrary exposure lines to the photo-reactive material with temporally changing the polarization state of the laser beam. In this study, we report the polarization drawing method based on GS for the fabrication of anisotropic diffractive optical elements. First, the two types anisotropic diffractive optical elements were fabricated on the PCLC films. To investigate the diffraction properties of fabricated anisotropic diffractive optical elements, we used a polarized He-Ne laser beam as probe and observed diffracted lights. Diffracted beam was two-dimensionally emitted depending on the formed anisotropic optical distribution. Then we fabricated LC cell, which works as polarization dependent anisotropic Fresnel lens. The experimental investigations show that it has functions of light condensing and polarization control. From these results, high-performance light control device can be fabricated by the polarization drawing method.

The doping of a liquid crystalline (LC) photoemissive compound into a LC polymethacrylate with photoemissive side groups induces repeatable changes in the photoemission wavelength upon mechanical grinding and thermal annealing. The color changes observed in a handwritten pattern demonstrate the successful induction of anisotropic photoemission behavior in a LC composite polymeric film parallel to the grinding direction. The LC characteristics of the composite films play an important role in the directional selectivity of the polarized mechanoinduced color change.

Liquid crystal grating with three-dimensionally modulated anisotropic structure is fabricated by one-step exposure of an empty glass cell whose inner walls are coated with photocrosslinkable polymer liquid crystals to four-beam polarization interference UV beams. The diffraction properties were probed with a 633 nm wavelength laser and a 532 nm wavelength laser which were the coaxial incident. The novel properties, which diffraction directions are three-dimensionally different depending on the wavelengths, are realized by the resultant liquid crystal grating. Furthermore, the resultant liquid crystal grating can be also applied to an advanced polarizing beam splitter which opposite circular polarization and linear polarizations are diffracted simultaneously. These diffraction properties were well-explained by Jones calculus. The resultant liquid crystal grating has the plural of the functions of optical elements such as wave plates, polarization beam splitter, dichroic beam splitter, Wollaston/Rochon prism, and tunable wavelength filter. Therefore, the resultant liquid crystal grating can contribute to miniaturization, sophistication, and cost reduction of optical systems using for, such as optical measurement, communication, and information processing.

This paper describes the thermally amplified photoinduced orientation behavior of H-bonded composite thin films of non-photoreactive polymethacrylate consisting of hexylene spacer groups terminated with benzoic acid (BA) moieties in the side chain (pM6BA) and various monomeric cinnamic acid (CA) derivatives. H-bonds between BAs and CAs cause all the pM6BA/CA derivatives composite films to exhibit liquid crystalline characteristics. Irradiating these films with linearly polarized UV light induces an axis-selective photoreaction of the CA derivatives, while subsequent thermal treatment induces molecular reorientation of the BA side groups, which is accompanied by sublimation of the unreacted CA derivatives. The reoriented films are applicable to an LC alignment layer.

Mechanochromic luminescence (MCL) is an isothermal change in solid-state photolumienscent (PL) color in response to mechanical stimuli. In this work, we synthesized a novel acidic dopoant for pyridine terminated MCL compound to form suitable intermolecular interactions in the complex, and explored the PL properties of the acid and luminophore complex. The complex changed its fluorescence and diffusion spectrum, and these changes reverted their initial states upon heating above their melting point, revealing the acid complex changed its PL properties with maintaining machanoresponsive behavior.

Polymethacrylates with different type of cinnamate side groups (P1, P2 and P3) were synthesized, and their photochemical and photoinduced reorientation behaviors were investigated using linearly polarized (LP) 313 nm and 365 nm light. P1 and P2 exhibited liquid crystalline (LC) characteristics, but P3 did not. Thin P1 and P2 films underwent thermally stimulated photoinduced molecular reorientation using LP 313 nm or 365 nm light and subsequent annealing, where adjusting the exposure energy and the exposing light wavelength could control the reorientation direction. Type of the cinnamate side groups, resultant photoproducts, and LC characteristics of the polymer played an important role in the thermally stimulated photoinduced molecular reorientation directions and their performances.

In this study, we investigated the spatial light modulation properties of an optical vortex (OV) generator consisting of azo-dye-doped polymer liquid crystal (ADDLC) and a vector beam illuminator, focusing on flexibility and achromaticity for generating OVs. Uniaxially aligned ADDLC forms three-dimensional photoinduced twisted anisotropic structures under vector beam illumination, and can generate high-order OVs with evennumbered topological charges that correspond to the polarization pattern of the illuminating vector beam. The induced anisotropic structure can be re-initialized by turning it off and changing the vector beam polarization distribution. Simulations showed that the OV generator also has achromatic wavefront modulation properties for the broadband spectrum, and this feature was experimentally demonstrated by using two laser sources whose wavelengths are λ = 633 nm and 780 nm, respectively.

We fabricated a vector diffraction grating using a chiral nematic liquid crystal (LC) and a holographically regulated photoalignment film. Periodic defects were observed in the grating LC cell, and the defect position was affected by the temperature of the cell. To characterize the defect position, the director distribution in the cell was estimated on the basis of the elastic continuum theory of chiral nematic LCs. The result clarified that the defect position depended on the helical pitch of the chiral nematic LC. We also investigated diffraction properties of the grating LC cell. The diffraction efficiency and polarization conversion property could be controlled by the temperature. The experimental results were well explained theoretically by considering the temperature dependence of the optical anisotropy and helical pitch of the chiral nematic LC.

Tunable wavelength-selective diffraction with polarization conversion is realized by the design of a liquid crystal (LC) grating containing a twisted nematic alignment structure that is fabricated by an efficient one-step photoalignment method. The diffraction efficiency strongly depends on the wavelength of the incident beam, and this property can be controlled by adjusting the birefringence of the nematic LC using a thermal control. These properties are well described by a theoretical analysis based on the Jones calculus and are experimentally demonstrated using 488, 532, and 633 nm wavelength incident polarized laser beams. The resultant LC grating has potential applications as diffractive optical elements that can simultaneously control the parameters of light such as amplitude, wavelength, and polarization.

Adjusting the free-surface condition facilely controls the in-plane and out-of-plane orientations in liquid crystalline polymer (LCP) films. Top coating with aromatic molecules onto LC polymethacrylate films with N-benzylideneaniline (NBA) or 4-methoxybiphenyl (MB) side groups (PNBAM or PMBM) and subsequent annealing generate a random planar orientation while simultaneously removing the coated aromatic molecules, whereas annealing noncoated films induces a homeotropic orientation of the mesogenic side groups. Additionally, irradiating a top-coated PNBAM film with linearly polarized (LP) 365 nm light induces an in-plane molecular reorientation of the NBA side groups without changing the orientation in the homeotropically oriented region. Changes in the surface topology of the LCP films due to the reorientation processes are investigated in detail. Inkjet coating with aromatic molecules and LP 365 nm light exposure precisely controls the in-plane and out-of-plane alignment pattern in a PNBAM film.

We investigated the photoalignment properties of a liquid crystalline composite. The composite consisted of a low molecular weight nematic liquid crystal (LC) and a photoreactive liquid crystalline polymer containing 4-(4-methoxycinnamoyloxy)biphenyl side groups. Homogeneously aligned LC composite cells were fabricated using rubbed substrates and were then exposed to a linearly polarized (LP) ultraviolet (UV) laser beam. The alignment states of the LC composites were characterized using a LP visible laser beam. The LC composite in the cell was realigned by LP UV exposure and subsequent annealing. The direction of the realignment could be controlled by the polarization direction of the LP UV beam. The relationship between the realignment direction and the rubbing strength of the substrates was also investigated. A large realignment was induced in the LC composite cell when the azimuthal anchoring strength of the rubbed substrates was relatively weak.

Polarized UV absorption and near-edge X-ray absorption fine structure (NEXAFS) spectroscopies are used to investigate the influence of film thickness on the thermally stimulated photoinduced reorientation of a polymethacrylate film comprised of 4-methoxycinnnamoylbiphenyl (MCB) side groups connected with a decylene spacer (PMCB10M) in the bulk (&gt; 10 nm), at the inner-surface (similar to 10 nm), and at the near-surface (&lt; 2 nm). Irradiation with linearly polarized (LP) UV light and subsequent annealing generate a biaxial molecular reorientation in the bulk of thick PMCB10M films, while the out-of-plane orientation is restricted in films less than 55-nm thick. In contrast, the in-plane reorientation is dominant at the near-surface regardless of the film thickness. Consequently, the roles of the rigid mesogenic MCB moieties and the flexible long decylene spacer depend on the film thickness. (C) 2016 Elsevier Ltd. All rights reserved.

A holographic liquid crystal polarization grating with a Fabry-Perot structure was developed. Because of its resonant structure, the device offers high levels of control of the diffraction properties of incident-polarized light beams, depending on the resonance conditions. The diffracted light beams are emitted in both the reflection and transmission directions, and the device thus works as a multibranch polarization grating with double optical paths, unlike a conventional polarization grating. These device features were experimentally demonstrated and were also explained theoretically.

We explored the fabrication of ultraviolet (UV)-inactive photoaligned film by photoinduced orientation of H-bonded composites of non-photoreactive polymethacrylate consisting of hexylene spacer groups terminated with a benzoic acid (BA) moiety in its side chain (pM6BA) and low-molecular 4-methoxycinnamic acid (4MCA). The pM6BA/4MCA composite films exhibit liquid crystal characteristics owing to the presence of H-bonds between BA and 4MCA as well as between the BA groups. Exposure to linearly polarized UV light gives rise to axis-selective photoreaction of the 4MCAs, while thermal treatment induces the molecular reorientation of the BA side groups accompanied by the sublimation of unreacted 4MCA. As a result, the reoriented film is durable with respect to UV light irradiation, which may be useful for display applications.

Three-dimensional anisotropic structures were fabricated by a recording axisymmetrically polarized beam in azobenzene (azo)-dye doped liquid crystal polymer composites. Polarization and wavefront modulation properties of fabricated anisotropic structures are investigated by experimentally and theoretically analyzing the diffraction properties. Photo-induced anisotropic structures would be utilized to generate singular light waves, such as optical and polarization vortices.

Three-dimensional (3D) vector holograms have been formed in twisted-nematic (TN) azo-dye-doped polymer liquid crystal (LC) composites whose director is gradually rotated around the thickness direction in the initial state. Polarization states of diffracted beams were rotated in accordance with the twist angle, and the diffraction efficiency depended markedly on the incident angle. We confirmed that the 3D director distributions corresponded to the polarization modulation caused not only by light interference and the propagation in the LCs but also by the initial orientation of the LCs. In order to explain the observed properties a theoretical model of the periodic reorientation distribution in TN LCs was presented. The Jones matrix method is used to describe the interference of two polarized light beams in the anisotropic media. Then the finite-difference time-domain method was applied to analyze the diffraction properties of the 3D vector holograms recorded in the model medium.

<p>これまで我々のグループでは、光により配向性制御が可能な高分子液晶である光反応性高分子液晶の局所構造をTEYおよびAEY法による軟X線吸収分光により、表面近傍の分子配向を調べてきた。今回、表面からより深い領域を同時に検出するため、蛍光法による軟X線吸収分光測定装置を立ち上げ、光反応性高分子液晶の局所構造を調べた結果、分子配向の深さ方向に関する知見が得られたので報告する。</p>

Doping photosensitive N-benzylideneaniline (NBA) derivatives in a photoinactive polymethacrylate with benzoic acid (BA) side groups (P6BAM) produces a photoinduced orientation in a P6BAM film and its patterning upon exposure to linearly polarized (LP) 365-nm light and subsequent annealing. Two types of NBA derivatives are used: NBA1 containing a carboxylic acid substituent effectively generates a significant photoinduced reorientation. The H-bonds among the carboxylic acids of BA and NBA1 play an important role in the photoinduced orientation.

Liquid crystal (LC) cells with periodic alignment distributions were fabricated using chiral nematic LCs (N∗LCs), which were prepared using mixtures of a nematic LC and a chiral dopant, along with photoreactive liquid crystalline polymer (PLCP) films. Periodic structures were formed by polarization holographic recording in the PLCP films. The director distribution in each cell depended on the ratio of chiral dopant present, i.e., the inherent helical pitch of the N∗LCs. These periodic alignment structures with line defects in the LC grating cells were well explained on the basis of the elastic continuum theory of the N∗LCs and the photoalignment effect of the PLCP films. The diffraction properties of the grating LC cells were also investigated using a polarized visible laser. The observed intensity and polarization states of the diffracted beams were consistent with theoretical ones calculated using the director distribution models. Our results clarify that the diffraction properties of the grating LC cells can be controlled by the helical pitch of the N∗LCs.

Liquid crystal (LC) cells with periodic alignment distributions were fabricated using chiral nematic LCs (N∗LCs), which were prepared using mixtures of a nematic LC and a chiral dopant, along with photoreactive liquid crystalline polymer (PLCP) films. Periodic structures were formed by polarization holographic recording in the PLCP films. The director distribution in each cell depended on the ratio of chiral dopant present, i.e., the inherent helical pitch of the N∗LCs. These periodic alignment structures with line defects in the LC grating cells were well explained on the basis of the elastic continuum theory of the N∗LCs and the photoalignment effect of the PLCP films. The diffraction properties of the grating LC cells were also investigated using a polarized visible laser. The observed intensity and polarization states of the diffracted beams were consistent with theoretical ones calculated using the director distribution models. Our results clarify that the diffraction properties of the grating LC cells can be controlled by the helical pitch of the N∗LCs.

A diffractive optical element with a three-dimensional liquid crystal (LC) alignment structure for advanced control of polarized beams was fabricated by a highly efficient one-step photoalignment method. This study is of great significance because different two-dimensional continuous and complex alignment patterns can be produced on two alignment films by simultaneously irradiating an empty glass cell composed of two unaligned photocrosslinkable polymer LC films with three-beam polarized interference beam. The polarization azimuth, ellipticity, and rotation direction of the diffracted beams from the resultant LC grating widely varied depending on the two-dimensional diffracted position and the polarization states of the incident beams. These polarization diffraction properties are well explained by theoretical analysis based on Jones calculus.

We characterized the photoalignment anchoring energy of photocrosslinkable liquid crystalline polymers (PLCPs) doped in a liquid crystal (LC). PLCP-doped LC cells with homogeneous alignment were fabricated using rubbed polyimide (PI) films. The PLCPdoped LC cells were exposed to a linearly polarized ultraviolet laser beam, and were then annealed. As a result, the PLCP-doped LCs were realigned owing to the axis-selective photocrosslink reaction. We investigated the relationship between the surface anchoring strength of the rubbed PI films and the realignment direction. The result suggested that the photoalignment anchoring strength of the PLCP in the LC is higher than 4 � 102 J/m3 at the maximum. The photoalignment realized substantial realignment in the LC cell with the surface anchoring strength of 10-4 J/m2.

光応答性の4-メトキシ桂皮酸を非光反応性の側鎖型安息香酸ポリマーに分散し、光反応性を調査した。水素結合によって結合したコンポジットフィルムでは軸選択的光反応と熱増幅が観察され，桂皮酸を昇華によって除去したフィルムでは高い透明性と耐光性を得られることがわかった。

We investigate control of the photoinduced orientation of photoalignable polymeric films from polymethacrylate with 4-oxybenzaldehyde side groups (1) and monomeric 4-methoxyanilline (2) composites, where both 1 and 2 have no photoreactivity. Annealing the 1/2 composite film with various 1/2 ratio generates N-benzylideneaniline (NBA) side groups, which exhibit photoreactivity and photoinduced molecular reorientation when irradiated with linearly polarized (LP) 365 nm light. Adjusting the 1/2 mixture ratio controls the amount of NBA side group's formation, as well as the photoinduced orientation performance of the film. Analyses of the three-dimensional refractive indices reveal biaxial photoinduced reorientation for a 1/2 film saturated with NBA side groups (similar to 96%), while in-plane motion plays a major role for 1/2 films containing unreacted 4-oxybenzaldehyde side groups. Furthermore, a post-annealing procedure after exposure greatly amplifies the in-plane reorientation structure for film consisting of more than 75% NBA side groups, which exhibits LC characteristics. (C) 2015 Elsevier Ltd. All rights reserved.

Polarization holographic gratings were formed in liquid crystal (LC) cells fabricated from a mixture of low molecular weight nematic LC and a photoreactive liquid crystalline polymer (PLCP) with 4-(4-methoxycinnamoyloxy)biphenyl side groups. The diffraction properties of the gratings were analyzed using theoretical models which were determined based on the polarization patterns of the polarization holography. The results demonstrated that vector gratings comprised of periodic orientation distributions of the LC molecule were induced in the cells based on the axis-selective photoreaction of the PLCP. The vector gratings were erased by applying a sufficiently high voltage to the cells and then were reformed with no hysteresis after the voltage was removed. This phenomenon suggested that the PLCP molecules were stabilized based on the axis-selective photocrosslink reaction and that the LC molecules were aligned by the photocrosslinked PLCP. This LC composite with axis-selective photoreactivity is useful for various optical applications, because of their stability, transparency, and response to applied voltage.