Photographic materials are based on silver halide microcry stals, which are sensitive to blue light in visible region. Spectral sensitization is used to extend their spectral sensitivity to light with longer wavelength by causing the microcrystals to adsorb sensitizing dyes, which absorb the light and inject electrons into the conduction band of the microcrystals. In this paper, recent progresses in understanding the electron-transfer process is described to give an example of the hybridization of inorganic and organic photofunctional materials (i. e., silver halide and sensitizing dyes).
The adsorption of dyes to silver halide was based on the Coulombic and van der Waals'interaction between them. The reduction and oxidation potentials of dyes given by phaseselective second harmonic volutammetry provided the most relevant measures for their electronic energy levels. The energy-gap dependence of the electron transfer was steep, and corresponded to that predicted by Marcus theory with small rearrangement energy and without inverted region. The rate constants as given by picosecond spectroscopy could characterized the electron-transfer process. The inverse process of the electron transfer has been analyzed in detail through ESR spectrum arising from the dye molecule which lost an electron.

View full abstract

Fulgides are the compounds defined as 2, 3-bismethylenesuccinic anhydrides with aromatic substituent(s) on the methylene carbon(s). Fulgides exhibit photochromism between the cyclized colored form and the open-ring less colored form. Some of the fulgides show thermally irreversible photochromism.
The study of photoph ysical aspects of fulgides as well as the following three subjects to improve them is reported: (1) enlargement of the quantum yields of photochromic reactions of fulgides by the control of steric congestion, (2) lengthening of the absorption maxima of the colored forms of fulgides by the control of electronic nature, and (3) discovery of a new type of nondestructive readout method using acid-base equilibrium.

The last one is particularly important for realizing rew ritable photon-mode optical memory. Thus, (5-dimethylaminoindolyl)fulgide, whose colored form has absorption at 780 nm (diode laser region) and which does not bleach upon irradiation with visible light, forms a protonated species, which does not have absorption at diode laser wavelength region, with trichloroacetic acid. This protonated species, in toluene, returns to a slightly yellow protonated open-ring form upon irradiation with 554 nm light. A mixture of (5-dimethylaminoindolyl)fulgide and its protonated species forms an equilibrating system. Thus, this mixture is regarded as a model of nondestructive readout system, using 780 nm light for readout, 554 nm light for erasing, and 403 nm light for writing.

View full abstract

Science and technology involved in our monolayered OPC (organic photoconductor) for electrophotographic use with positive charging are reviewd, being especially focused to its background chemistry, material design and xerographic photoelectrical properties. This OPC has many excellent characteristics which could not be attained with the currently used selenium or with the so-called doublelayered OPC for negative charging. The most important and photoelectrically active components of our monolayered OPC are a pigment with perylene structure (see Table 2, formula 1) as charge generation material (CGM), an aromatic hydrazone (Table 2, formula 3) as charge transport material (CTM), and a fluorenone derivative (Table 2, formula 4) as the quencher of the singlet excited state of the CTM. Not only this OPC has excellent electrophotographic sensitivity, stability and lifetime, but also good flexibility and plasticity, and among others this OPC is excellent to keep healthier office environment, ozone formation being extremely low with this OPC.

View full abstract

Origins of remarkable light scattering induced from a phase separated structure for polymer/(liquid crystal(LC)) composite film were discussed. It was proposed that the main origins of light scattering might be associated with 1) spatial distortion of nematic directors, 2) discontinouous change of nematic directors among LC channels, and 3) optical boundary (mismatching of refractive indices) between LC phase and matrix polymer. The phase separated structure of the composite film was formed through a spinodal decomposition. The faster the solvent evaporated, the smaller the domain size in the composite film was. With an increase in channel size of liquid crystal, the rise and decay times decreased and increased, respectively, and the threshold voltage of light switching decreased. A dielectic model expression was introduced to evaluate a magnitude of electric field applied to the liquid crystalline phases when an external electric field was applied to a composite film. It was suggested from the dielectric model calculation and also, was demonstrated experimentally that the larger electric field is effectively applied to the liquid crystalline phases by using the matrix polymer with the greater magnitude of dielectric constant and electric conductivity. Reversible and bistable electrooptic effects bing driven by dual frequencies were recognized for a smectic phase of the composite composed of liquid crystalline polymer (LCP) and LC. The response speed of bistable light switching can be remarkably enhanced by reducing the LCP fraction with keeping a stable smectic layer structure for the ternary induced smectic composite system. A rewritable optical storage effect induced by photoirradiation to a LCP/LC/(photoresponsive molecule) ternary composite system was also demonstrated.

View full abstract

It is strongly hoped to commercialize small-size solid-state lasers emitting b lue light, as they are critical to increase density of optical disks and to improve performance of laser printers dramatically. Several type of techniques to realize blue lasers have been proposed so far. Among them, frequency doubling of IR emission from diode lasers by using nonlinear optical crystals seems to be most promising from view point of early commercialization. In this report, we will briefly review typical nonlinear optical crystals and frequency doubling techniques. Then, we will focus our discussion on our blue laser, in which blue emission is obtained from a diode laser by an external resonant cavity made of a KNbO₃ crystal. Our laser is as small as 50 x 30 x 20 mm₃ in size and emits 14.6 mW in intensity with good Gaussian shape. The relative intensity noise is as low as -136 dB/Hz. These specifications are good enough to playback still pictures when used as optical pickup in laser video disks. Also, we will get very stable output for more than 5 hs by an optical feed back technique together with temperature stabilization of optical components. Finally, we will introduce direct modulation techniques, which are inevitable for some of important applications such as laser printers and writable optical disks.

View full abstract

The activities of the inorgaic polymer catalyts responding to visible light have already been studied by the present author. In the present work, the formation of copolymers of inorganic polyfunctional material (metal alkoxide) and organic polyfunctional material (such as dichlorobenzene)has been studied. Copolymers of (Ti, Nb, 0) elements and (Ti, organic group, O) were obtained. The results of IR spectra and reflectance spectra of these subst ances obtained verified the copolymer formation. The results obrained from (Ti, Nb, 0) copolymers indicate that small amount of Nb (10-20%) mixed with Ti gives the maximum catalytic activity to photolyse 99.5% ethanol/water, using light having wavelengths longer than 480nm. This fact indicates that the formation of a molecular orbital consisting of Ti, Nb, and O as its member atoms is useful to photolyse alcohol. The results obtained from (Ti, C6 H4, 0) copolymers indicate that the role of C⁶H⁴ groups is something like a partition by w hich -[Ti(=O)-O-]_n-units are separated into many subunits with n=2, 3, and 4. The significa nces of alkoxides copolymers are summarized into two points. ( 1 ) The stable radical structure permits the use of visible light as the photo excitation source of the catalyst. ( 2 ) The low dimensional substance, thus formed, can contain small groups of -[Ti(.0)-0-]ⁿ(n=2, 3, 4) units, which may be the active center of these photosensitive molecules in the polymer material.

View full abstract

Dissociation equilibrium of bimolecular associates (dimers) of 1, 1'-diethyl-2, 2'-carbocyanine (Dye 2) was studied thermodynamically. At 25-60 °C, absorption spectra of 2 vol% aqueous ethanol solutions of Dye 2 showed only monomer and dimer bands. Spectral change with varying temperature suggested that a simple equilibrium between dye dimers and monomers existed in these solutions. From the temperature-dependence of monomer absorbance, values of dissociation constants K and dissociation enthalpy zill were estimated to be 4.3(40 °C)-12 (60 °C) x 10-5 mol. d m-3 and 10.4 kcal. mol-i, respectively. These K values are about one tenth of those for 1, 1'-diethyl-2, 2'-cyanine (Dye 1) with only one methine carbon, indicating that Dye 2 dimerizes much more readily than Dye 1. This is due to the larger size and the more nearly planar structure of Dye 2. Influences of molecular structures on dimer dissociation equilibria of some other cyanine dyes are also discussed.

View full abstract

The photopolymerization mechanism for a mixed crystal of 1, 6-di(9-carbazolyl)-2, 4-hexadiyne (DCH) and 1-(9-carbazolyl)-6-(9-anthryl)-2, 4-hexadiyne (CAH) was investigated. The mixed crystals with various compositions of DCH/CAH were prepared. The rates of photopolymerization were followed by measuring the diffuse-reflectance spectra, and exciton migration in the mixed crystal was studied by measuring the stationary and time-resolved fluorescence spectra. The initial rate of polymerization does not depend much on the CAH concentration, while the fluorescence lifetime of DCH was shortened with the increase of the CAH concentration. The results indicate that most of the excitation energy of carbazole moieties being in a vibrationally high level of the S1 state, flows in the diacetylene moieties and initiates polymerization before it goes to the relaxed S1 state of the carbazole moieties. The fluorescence spectroscopy showed that the exciton migration takes place stepwise, i. e., exciton migration occurs from carbazole moiety to anthracene moiety and from anthracene moiety to anthracene excimer site subsequently.

View full abstract

Polymers having photosensitive nitroaryl groups were synthesized by the nitration of polyacenaphthylene or by the ionic polymerization of 5-nitroacenaphthylene. The photoisomerization of trans-cinnamic acid in the presence of photosensitizers was carried out in DMF. From the results obtained, it was found that the partially nitrated polyacenaphthylene reveals an excellent photosensitizing activity compared with that having 100% photosensitizer unit and that its sensitivity depends on the content of the nitro group.

View full abstract

Pendant acyloxyimino (A0I) groups in photoresists can be photochemically changed into amino groups and by the transformation of amino groups to ammonio groups, the polarity of photoresists can be increased. In this study, effects of comonomers on polarity alteration of photoresists before and after irradiation were investigated. Copolymers of acetophenone oxime Ο-acryloyl ester (AAPO) with styrene (St) or methyl methacrylate (MMA), AAPO (45.6)-St and AAPO(50.3)-MMA, were used as copolymers bearing the pendant AOI g roups. Solubility changes before and after irradation of their films with benzophenone as a sensitizer were examined. Although their films did no dissolve in methanol before irradiation, the AAPO(45.6)-St films treated with an aqueous solution of HC1 after irradiation becam e soluble in a mixture of methanol and water (1: 1 (v/v)), and those of AAPO(50.3)-MMA similarly treated after irradiation dissolved in water. Furthermore, it was found that by the addition of a small amount of the third component, N, N-dimethylacrylamide (DMAA)to a AAPO-St copolymer a difference in polarity of terpolymer before and after irradiation became much greater than that of the AAPO-St copolymer and that the terpolymer showed very high sensitivity as the photoresist.

View full abstract

t Department of Applild Chemistry, Faculty of Engineering, Shizuoka University; Hamamatsu-shi 432 Japan Photochromic fulgides, e. g.4-oxazolyl type [1 3 ] and 3-furyl type fulgide (4) and (5) were synthesized. And the optical fulgide disks were prepared by spin-coating metho d, and recorded with argon ion laser emitting at 514.5 nm. Fulgide[ 3J disk (fulgide content; 6.4 w t%) exhibited high C/N ratio (47 d B) from the read-out signal because of the high absorption coefficient of colored fulgide (26000 M-lcm-'). On the other hand, fulgide (5) di sk did not show enough C/N ratio for practical use, because of the low absorption coefficient (6200114-'cm-1). Recording power was dependant upon the quantum yield, and fulgide 5 3 disk which featured high bleaching rate needed lowest recording power (5 mW). Though fulgide [3] exhibited low quantum yield for bleaching (1.8 x10-4), it was possible to record on the disk. A nd the disk showed high read-out stability and record-erase cycle fatigue resistance.

View full abstract

Indoline-spiro-benzopyran and indoline-spiro-naphthoxazine with a 3-(triethoxysilyl)propyl group on N-position of the indoline were synthesized. With or without the aid of a comatrices agent, RSi(OC₂H₅)₃, glass plates were coated with the photochromic compounds by means of the sol-gel method. The glass plates coated with the spiropyran were photochromic. Thermal stability of the colored form increased with increasing bulkiness of RSi(OC₂H₅)₃ used. When triethoxyphenylsilane (R=_C6_H5, ) was used, the thermal stability was improved by a factor of NY compared with that in ethanol. The spirooxazine glass sample produced without the comatrices agent was also photochromic, and the half-life of fading was ca.50 min.

View full abstract

Hydrogen glutarates of 1'-(2-hydroxyethyl)-3', 3'-dimethyl-6-nitro-8-(alkanoyloxymethyl)spiro[2 H-1-benzopyran-2, 2'-indoline] were prepared and they were converted to the corresponding polyion complexes by mixing their sodium salts with poly(diallyldimethylammonium chloride) in hot water. The polyion complexes were characterized by ¹H-NMR and IR spectroscopy. Photochromic films were prepared by spin-coating chloroform solutions of the polyion complexes on a Pyrex glass plate and their photochromic properties were examined in terms of the absorption maximum and the thermal stability of the colored merocyanines. It has been shown that spiropyrans (SP) are located at a less polar, hydrophobic portion of the polyion complex films and that the thermal decolation rates are analyzed as being the sum of two first-order processes. The results are interpreted in terms of nonhomogeneous steric restriction by the matrix rather than nonuniformity of micropolarity. _

View full abstract

Photochemical processes are influenced by the presence of heavy-atom substituted (e. g. Br, I) solvent, whereby intersystem crossing (T₁←S₁ ) is promoted. The net effect is to diminish reactions from the excited singlet state (S1) while reactions from the excited triplet state (T₁) may be enhanced. We have presented a study of heavy-atom solvent effects on the photochemical reactivity (photochromism) of 1, 3, 3-trimethylspiro[indoline-2, 3'-[3 H]naphth[2, 1-17][1, 4]oxazine] in cyclohexane solutions. Formation of the photochromic produc t, the merocyanine was observed to decrease as the concentration of heavy-atom solvent (haloalkane) was increased. Stern-Volmer plots of the relative quantum efficiency for merocyanine formation as measured by absorbance changes at 550 nm as a function of the heavy-atom solvent concentration yield a linear relationship. Based on this data a mechanism for the photochemical reactivity of spirooxazine in the presence of heavy-atom solvents is proposed. Further studies using various haloalkanes were performed to study the dependence of this effect on the identity of the halogen. It was found that merocyanine formation was strongly suppressed with increasing atomic weight of the halogen.

View full abstract

1-Phenoxy-5-chloroanthraquinone [17] was synthesized by Ullmann condensation of 1: 1mixture of 1, 5-dichloroanthraquinone [15] and potassium salt of phenol [16]. Ullmann condensation of [17]with potassium salt of thiophenol [18] gave 1-phenoxy-5-(phenylthio)anthraquinone [19]. Cyclization of [19] with a molten mixture of anhydrous aluminum chloride and sodium chloride afforded thioxantheno[1', 9': 4, 5, 6]benzo[kl]xanthene [ 5 ]1Similarly, cyclization of the condensation product of [17] with potassium salt of 1-naphthol [20] or 2-naphthol [22] gave 10, 18-dioxabenzo[ a ]naphtho[2, 1- j ]perylene [ 6] or 10, 18dioxabenzo[ a ]naphtho[1, 2-j]perylene [ 7]. The photooxidation of these unsymmetrical red compounds C 5 D, [6] or [7] with visible light of 541 nm gave the colorless endoperoxides [12], [13] or [14]. The photochemical and thermal properties of the endopero xides [12][13] or [14] were also investigated. t Studies on Condensed Polycyclic Aromatic Compounds Having Photochromic Properties. Tv.

View full abstract

NTT Opto-Electronics Laboratories; Tokai-mura, N a ka-gun, I b a r a ki-ken 319-11 Japan In order to secure the storage density of PSHB memory by avoiding the las e r induced hole filling, we have investigated the hole-burning characteristics of a poly(methyl met h a c rylate)(PMMA) doped with chlorine derivatives that are less symmetric than tetraph e n y lporphyrin.
The absorption spectra of chlorin e6 trimethyl ester (Che₆TME) doped PMMA before and after hole-burning did not overlap. Since laser induced hole filling only occurs when t h e spectra overlap, it can be avoided by using Che6TME/PMMA. We found that the use of dye molecules without C₂ axis perpendicular to molecular plane, such as Che₆TME, ca n prevent laser induced hole filling which is enebitable in C₂ symmetric H₂ porphyrin derivatives.
Also in the systems we used here, we found that the energy transfer between guest molecules is negligible only at concentrations of less than 10-3 M. From fluorescence lifetime and other measurements, we have also noticed that decay processes as lfuore scence, internal conversion and inter system crossing compete with PSHB.

View full abstract

The photochromic property of pentafulvadiene and the derivatives is studied by means of semiempilical molecular orbital method (MOPAC-AM 1 and INDO/S), with experiments. Pentafluvadiene has been converted to a closed form by heat, then the open form has formed again by light. Absorption spectra of pentafulvadiene and the derivatives are calculated and compared with the observed spectra. Orbital correlation diagram suggests disrotatory cyclization to the closed form by light, and conrotatory cyclization by heat. Relative stabilities of open, closed cis- and trans-forms for various derivatives are estimated and discussed in connection with the substituent effect. Two types of side reactions, 8πelectrocyclization and sigmatropic hydrogen migration, are also examined by calculations. The former products show the unstable energy and the latter suggests the plausible stable products.

View full abstract

Achievable recording density of photochemical hole-burning (PHB) memory is estimated under the conditions of a readout time of 10 ns/bit and a signal-to-noise ratio of 20, both of which are required for high-density information storage. A kind of laser induced hole filling (LIHF) is the principal facor for determining the achievable recording density. When the hole interval becomes narrow, the degree of LIHF becomes prominent. This type of LIHF is a quite new phenomenon. Owing to this phenomenon, multiplicity (or hole interval) and irradiation energy for a single hole can be optimized simultaneously to maximize the recording density. The recording material studied here is metal-free sodium tetraphenyl porphyrintetrasulfonate in poly(vinyl alcohol), which is considered to have the least observable LIHF. According to the experimental data reported here and our previously reported theory, the maximum recording density is turned out to be 1.0 Gbit/cm² at 20 K. In this case, optimized irradiation energy is 29 mJ/cm²/hole and multiplicity is 130. This multiplicity corresponds to hole interval of 0.21 nm, which is about 5 times larger than the initial hole width of this recording material. On the analogy of this case, the maximum achievable recording density of current PHB materials at 4.2 K becomes a little bit less than 20 Gbit/cm2. The most important research target for PHB memory is to find out materials with less of this type-of LIHF.

View full abstract

The photochromism of amphiphilic dibromospiropyrans, 5', 7'-dibromo-8-docosanoyloxymethyl3', 3'-dimethy1-6-nitro-1'-octadecylspiro[2 H-1-benzopyran-2, 2'-indoline] BSP 1822, in polyion complexes and Langmuir-Blodgett (LB) films has been studied. The colored BSP1822 forms J-aggregate when mixed with polyion complexes between dioctadecyldimethylammonium salt of poly(styrene sulfonate) and some amphiphilic compounds such as methyl stearate. The J-aggregate is also formed in polyion complexes with other amphiphilic compounds which have melting point around 40°C. It is considered that these compounds play a role in enforcing interaction amoung chromophores and lowering the glass transition temperature.
The similar be havior was also found for the BSP1822 LB film mixed with dioctadecyldimethylammounium bromide and methyl stearate. The absorption maximum of J-aggregated BSP1 822 is 650 nm, which is 32 nm longer than that of spiropyran without bomide.
The J-aggregate exhibits exceedingly high stability in retaining its color, which is in marked contrast to the rapidly fading nonaggregated chromophore.

View full abstract

The 11-I-NMR spectra of 1, 3, 3-trimethylspiro[indoline-2, 3'-[3 H]naphtho[2, 1-b][1, 4]oxa zine]( 1 ), its 9'-hydroxy derivative (1 a), and two derivaties of 1 a, produced by the reaction with perfluoropropene trimer (1 b) and with 4-[perfluoro(2-isopropyl-1, 3-dimethy1-1-butenyl)oxy]benzoyl chroride (1 c) are compared with that of 6-niyro-1', 3', 3'-trimethylspiro[2 H-1benzopyran-2, 2'-indoline] ( 4 ), before and after UV irradiation. From the NMR differentiation of the uncolored and colored species, the colored spironaphthoxazine derivatives ascribe probably to the open zwitterionic structures owing to an electron-attracting effect and isotropic effect. Their structures are seemingly correlated to the quick response to UV irradiation and the lower sensitivity to the solvent polarity on solvatochromism. The relationship between melting behaviors of the crystals and thier thermochromism is further discussed.

View full abstract

Degradation mechanism of 1, 2-bis(2, 4, 5-trimethyl-3 -thienyl)-1, 2-dicyanoethene (TECN)was studied by product analysis. When TECN was irradiated in dichloromethane with 420nm light, the closed-ring isomer with absorption maximum at 520 nm was the sole product. O n the other hand, when irradiated with 370 nm light, oxygenated products were detected. Photogeneration of such products, possibly endo-peroxide moieties on thiophene rings, caused the degradation of TECN.

View full abstract

Thin films for optical recording media made from cyanine dyes are constantly exposed to near-infrared rays used to carry recording and reading signals. After repeated and intense exposure to the high-density energy of near-infrared rays focused by lenses, cyanine dye thin films undergo severe photodegradation, and as a result, the written data is destroyed. A quencher, however, can very effectively suppresses this phenomenon.
We recently synthesized a new quencher consisting of bis[3 -methoxy-4-(2-methoxyethoxy)2'-chloro-α, β-stilbene-8ithiolato]nickel.
The photod egradation of cyanine dye thin film cause by exposure to near-infrared rays is well-controlled by this new quencher.

View full abstract

As a part of our study on the synthesis and application of the fluorine-containing fulgides and diarylethenes, we now demonstrate the synthesis of (trifluoromethyl)pyrazoles via 1, 3-dipolar cycloaddition reaction and their derivation to the fulgides.2, 2, 2-Trifluoro-1-(phenylhydrazono)ethyl bromide [1 ] cycliz ed with β-diketones or /β-keto esters [ 2 ] under alkaline conditions to give the corresponding 3-(trifluoromethyl)pyrazoles [3] (Table 1). The Stobbe reaction of 3 with diethyl isopropylidenesuccinate was influenced by the substituent at 5-position of pyrazole ring; that is, 4-acetyl group of the pyrazole having electron-withdrawing group at 5-position was eliminated, whereas 4-acetylpyrazole substituted by 5-methyl group gave the expected fulgide [ 7 ]. Photoirradiation of a hexane solution of 7 with 330 nm light caused absorption at 500 nm, which disappeared on exposure to light longer than 390 nm. According to the 11-I-NMR analysis, stereochemistry of 7 was assigned to be the Z-configuration and it was isomerized to the E-configuration and further to the ring-closed form by photoirradiation with 330 nm light. The ring-closed form reverted only to the E-configuration by irradiation with>390 nrn light.

View full abstract

The solid polymer electrolyte composed of poly[(a-hydrooligo(oxyethylene)-ω-yl methacrylate][P(MEO)OH], LiC10₄ and a spirobenzopyran derivative (SP) has been prepared, and its photoinduced change in ionic conductivity has been also investigated. SP is a well-known photochromic material. SP is isomerized to photomerocyanine (PMC-form)upon UV irradiation. PMC-form is especially stable in protic solvents. This is attributable to the formation of hydrogen bond between PMC-form and the solvent. In the IR spectra of P(MEO)OH film, the absorption assignable to the 0-H stretching vibration shifts from 3501 cm^-1to 3480 cm^-1 after UV irradiation for 2 h. This also indicates the formation of a hydrogen bond between PMC-form and the hydroxyl group in the polymer side chain.
The ionic conductivity of this film decreased upon UV irradiation and subsequently increased in the dark. This is attributed to the formation of hydrogen bond between PMC-form and P(MEO)OH by UV irradiation. Namely, this interaction acts as quasi-crosslinking po int and this causes the ionic mobility change. Therefore, it was found that the ionic conductivity can be controlled by photoisomerization of SP in the solid polymer electrolyte upon irradiation.

View full abstract

Photovoltaic Properties of two-layer organic solar cells were investiga ted. Metal phthalocyanines (MPc) and porphyrins (Por) shown in Fig.1 were employed for p-type layer.3, 4: 9.10-Bis(imidazo[1, 2-a]pyrido-fused)perylene derivatives (PTCIz) shown in Fig.2 were employed for n-type layer. The cell structure was indium-tin oxide(ITO)/n-type layer/p-type layer/Au and the cells were irradiated with white light through the ITO electrode. The thicknesses of organic layers were 500 A. Positive voltage appeared on an Au electrode under illumination in all the cells. Short-circuit current was proportional to the incident light intensity (Fig.9), and open-circuit voltage was proportional to the log (incident light intensity) (Fig.10). The photocurrent spectra reflected the absorption spectra of MPc or Por layers, indicating the occurrence of effective carrier generation in MPc or Por layers. The short-circuit current of the cells ranged between 0.89 and O.004 mA/cm2 at the incident light power of 15 mW/cm2 (Tables 1, 2 and 3). The open-circuit voltage ranged between O.7 4 and O.15 V. The fill factor ranged between O.63 and O.2 1. Short-circuit curre nt was most profoundly influenced, when chemical structures of dyes were varied. The energy conversion efficiencies of the cells using MPc and PTCIz ranged between 1.9 and 0.002%.

View full abstract

Fifteen distyrylbenzene (DSB) derivatives which were substituted by alkyl group, electronacceptor group or electron-donor group were synthesized and examined as an emitter for organic multilayer electroluminescence (EL) cells. We carefully measured the EL spectra and SEM pictures as well as the current-voltage and brightness-current characteristics. Then we conculded that it is very important for an emitting layer not to form exciplex or chargetransfer complex with hole transporting layer in addition to an ability to form a thin film. We found that 4, 4'-bis[2-(9-ethyl-3-carbazolyl)vinyl]biphenyl (BCzVBi) among those derivatives was very attractive material because we achieved the bright blue green light for the cell with BCzVBi as an emitting layer. We could obtain the luminance of 2000 cd/m² at a voltage of 7 V and the maximum EL efficiency of 1.5 1m/W for the cell with ITO/BCzVBi/2(4-t-Butylpheny1)-5-(4-biphenyly1)-1, 3, 4-oxadiazole/Mg: Ag. We also achieved the bright blue light and the high luminance of more than 100cd /m² by introducing methyl group to biphenyl unit. Therefore the distyrylbenzene derivatives should be most promising compounds as EL emitting materials in the color range from blue to green.

View full abstract

Layered photovoltaic cells using 2, 2': 5', 2": 5", 2": 51", 2"-quinquethiophene (5 T) and N, N'-bis(3, 5-dimethylphenyl)-3, 4: 9, 10-perylenebis(dicarboximide) (XPCI) were fabricated by successive vacuum deposition. The cell structures were indium tin oxide (ITO)/XPC115 T/Au and Au/XPCl/5 T/ITO. These cells showed rectification behavior in the dark. Photocurrents of the cells flowed from 5 T to XPCI through the outer circuit, being independent of the electrode. The results of the action spectra for short-circuit photocurrents suggest that photogeneration of charge carriers takes place at the interface between 5 T and XPCI. The ITO/XPCl/5 T/Au cell shows better performance characteristics than the Au/XPCl/5 T/ITO cell. The conversion efficiency of the ITO/XPCI(700Å)/5 T(650Å)/Au cell for the white light (62 mWcm^-2), irradiated through the ITO electrode, was 0.02%.

View full abstract

Photoelectric properties of organic heterojunction thin film cells composed of manganese phthalocyanine (MnPc) and monoazo dye or bisazo dye have been investigated. For comparison, single layer cells were also studied.1-(2, 5-Dichlorophenylazo)-3-phenylcarbamoyl-2-naphthol and 2, 7-bis[2-hydroxy-3-(2-chlorophenylcarbamoy1)-1-naphthylazo]-9-fluorenone were used as monoaz o and bisazo dyes, respectively. Cells were prepared by either vacuum vapor deposition (MnPc and monoazo) or casting (bisazo) method. Despite low photocurrent conversion efficiency of a monoazo cell, monoazo dye acted effectively for the photocurrent by the formation of the heterojunction with MnPc. It was found taht the preparing the thin monoazo dye layer because of increasing the photosensitivity in the heterojunction interface and optimizing of the electrode work function for the oganic photoconductors are effective for the photoelectric conversion of the cell. Photoelecttic conversion efficiency of the heterojunction cell was drastically changed when the bisazo dye was used instead of the monoazo dye.

View full abstract

Three-layered organic solar cell having a codeposited interlayer of phthalocyanine and perylene pigment sandwiched between respective pigment layers shows two times larger photocurrent compared to two-layered cells without the interlayer. This phenomenon was investigated by means of the microwave photoconductivity measurement which can directly observe the amount of photogenerated free carriers from its microwave absorption. Codeposited film of both pigments showed larger microwave photoconductivity signal compared to that for each single pigment films. Since the microwave signal is basically free from the carrier transport process, the above photocurrent enhancement is concluded to be due to the sensitization of carrier generation.

View full abstract

The behavior of electrification induced by light at the contact interface between a photopolymerizable layer and metal films was studied with the aim of developing a novel photofunctional material. Surface potentials from 10 V to 500 V were induced on the photopolymerized layer by peeling off the contact metal film after imagewise exposure, depending on the work function (3.63-5.1 eV) of the metals. The behavior of this photoinduced electrification, however, can not be accounted for by the contact charging model unlike the case that insulator films are used as contact materials.
Some experimental results suggest that this photoinduced electrification is attributed to the charge transfer involving the reaction of a metal and the radicals produced photochemically in the photosensitive layer.

View full abstract

t Present address: Research Laboratory of Resources Utilization, Tokyo Institute of Technology; 4259 Nagatsuta, Midori-ku, Yo kohama-shi 227 Japan Dainippon Ink and Chemicals, Inc.; 4472-1 Komuro, Ina-machi, Kitaada c hi-gun, Saitama 362 Japan In order to lower the viscosity of chiral dopants of cyclopropane type and to improve response time, we designed and synthesized optically active fluorocyclopropanes (1 a and 1 b)and trifluoromethylcyclopropanes (2 a and 2 b). Although 1 a, 1 b and trans-trifluoromethylcyclopropane (2 b) showed small spontaneous polarizations (Ps's), cis-trifluoromethylcyclopropane (2 a) exhibited large Ps and short response time comparable to that of cyanocyclopropane (3 c).

View full abstract

Amorphous thin films were prepared in the Al₂O₃-Er₂O₃ system by rf-magnetron sputtering apparatus. Also, their physical properties and reflection, absorption, and fluorescence spectra were measured. The values of density and refractive index increased gradually with an increase of Er₂O₃ content. From the AlKa emission, the average coordination number of AP+ ions in these films decreased from 5 to 4 with Er₂O₃ addition. With 6 absorption band s due to the 4 f transitions of Era+ ion, three Qt intensity parameters (t =2, 4, 6) were determined by Judd-Ofelt theory, which dominate the transition probability and quantum efficiency of optical transitions of rare earth ions. All the parameters, specificly Q, showed a larger value than those in any other conventional oxide glasses, indicating a larger radiative decay probability of the 4S_3/2→ 4I_15/2 transition, for which only the ‹U(6)›² is nonzero among three reduced matrix elements, ‹U(t)›2. The large Ω6 value can be ascribed to a large overlap integral of 4 f and 5d orbitals and a small electron density of 6 s orbital owing to a low local basicity around Er³⁺ ions in the alumina host. By exciting with 488nm radiation from Ar⁺- laser, the 550nm emission due to this transition was observed for all the samples. These results can be ascribed to the slow multiphonon decay rate, the high quantum efficiency of the 4S_3/2 level, and also high excitation efficiency of the ⁴F_7/2→⁴I_15/2 absorption.

View full abstract

Arylpyrazines and unsymmetrically substituted 2, 5-diarylpyrazines with chiral substituents were synthrsized to obtain ferroelectric liquid crystalline materials. Seven types of compounds, having long alkyl or alkoxyl group and chiral ether or ester groups, were newly synthesized starting from arylpyrazines having methoxyl or cyano group, or chlorine.
Furthermore, three types of unsymmetrically substituted 2, 5-diarylpyrazines were also prepared by a series of chemical transformation of the substituents into chiral alkoxyl or ester group. A few of the arylpyrazines showed liquid crystalline properties at low temperature and diarylpyrazines showed liquid crystalline phases over wide ranges of temperature..

View full abstract

Ferroelectric liquid crystallinity of unsymmetrically substituted arylpyrazines and diarylpyrazines with chiral substituents were investigated. The arylpyrazines with (S)-4-methylhexyloxyl group in the pyrazine ring showed chiral smectic C phase (Sc* phase) at the low temperature. The diarylpyrazines were revealed to f orm thermally stable Sc* phase over wider ranges of temperatures. Several compounds were revealed to have excellent ferroelectric liquid crystlline properties. Particularly, thermal stability of Sc* phase for compounds having long chain alkoxyl groups and (S)-2-methylbutoxycarbonyl group was increased. The properties of ferroelectric liquid crystalline phases for a ser ies of the compounds were measured. The tilt angle were about 22.5° and the spontaneous polarization was largest at the dodecyloxy group and the response touelectric field was faster than the other compounds. t Synthesisa nd FerroelectricL iquid Crystal of UnsymmetricallyD isubstituted Pyrazine sw ith Chiral Substituents

View full abstract

An effect of the kind of glass-former on the Er³⁺ upconversion fluorescence in fluoride glasses was examined in the MF_fl-BaF₂-YF_a-ErF_a system where MF_is ZrF₄, HfF₄, AIF₃, GaF₈, InF_s, ScF₃ or ZnF₂. The emission intensities of Er₃₊ upconversion fluorescence ex cited by 800 nm radiation from an A1GaAs laser diode varied remarkably with the kind of glassformer. The multiphonon relaxation rates of glasses, which were evaluated from the phonon sidebands of Eu³⁺, also changed with the kind of glass-former. Contrary to expectation, there was no correlation between the emission intensity and the multiphonon relaxation rate. It was suggested that, in fluoride glasses, a multiphonon relaxation rate is not a main factor determining the emission efficiency of Er"- upconversion fluorescence.

View full abstract

2-(Aminomethylene)-benzo[ b ]thiophen-3(2 H)-ones[2] and their sulfoxides were prepared by ring contraction of 3-bromo-4 H-1-benzothiopyran-4-one and 3-bromothiochroman-4-one, respectively, with amines. The crystal structures of typical second harmonic generation (SHG) active conpounds in this series were determined by X-ray analysis. Relationship between the structures and the SHG activities of these compounds was investigated. The structure factors of compound [2] required for SHG activities are trans-configuration between the amino group and the carbonyl group and the presence of an amino proton (NH)to form an intermolecular hydrogen bonding between the carbonyl group and the NH. On the other hand, 2-(anilinomethylene)-benzo[ b ]thiophen-3(2 H)-one 1-oxides and 1, 1-dioxides have cis-configuration and an intramolecular hydrogen bond between the carbonyl group and NH. Comparison with 2 J and its sulfoxides or sulfones shows that transformation of sulfide moiety in 2 J into sulfoxide or sulfone moiety leads to low SHG efficiency, but brings about blue shift of absorption maxima for blue-region transparency (below 400 nm).

View full abstract

Small-sized CuCl-doped glasses were prepared by the sol-gel process and the crystal growth of CuCl was investigated from XRD, TEM and optical absorption spectra. Gels synthesized by the hydrolysis of complex solution of Si, Al, and Zr-alkoxides and CuCl dissolved in CH₃CN were heated up to 900°C to form cubic CuCl crystals. The CuCl content of glasse s was 20 to 50% of that of the batch composition and the rest of the copper was dissolved in the form of Cu+ and Cu²⁺ ions in Si0₂ glasses containing Al₂O₃ or ZrO₂, respectively. The size of CuCl crystals grew in proportion to one third power of heat-treatment time and finally reached 8 nm in diameter. The Z_1.2 and Z₃exciton peaks were observable and their energy shifts were reciprocally proportional to the square of the crystal size.

View full abstract

Nonlinear optical constants( d ) for 1-(4-nitropheny1)-pyrrole[NPRO], 2-ethyl-1-(4-nitrophenniytrl)oipmhdeanzole-[1ENIM, 2], , 4-triazol2e, 4-di[mDeMthNyT1-]1 -(4-annitdr oph3e, n 5y-dl)iicmhliodraoz-o1l-e([4D-nMitNroIp], h eny1)-1 3, , 5 2-, d i4m-teritahzyo1l-e1 [DCNT], which are similar to 3, 5-dimethyl-1-(4-nitrophtnyl)pyrazole [DMNP] in structure and have high transparency in blue light region, were calculated based on the oriented gas model. The results obtained were as follows: NPRO d ₃₃=275 pm/V; ENIM d₃₂=57 pm/V; DMNT d₃₂=67 prn/V; DMNT d₄₂=46 pm/V and DCNT ₂₁=71 pm/V. Since four compounds other than NPRO have fairly large offdiagonal d components, they are expected to be phase matchable in SHG and to be suitable materials for blue light SHG devices.

View full abstract

Second harmonic generation (SHG) from a mixed organic crystal of p-nitroaniline (p-NA)and p-dicyanobenzene (p-DCB) molecules was observed by the powder method, although each single crystal does not show the macroscopic SHG activity. The mixture showed the maximum SHG efficiency at a certain mixing ratio. This SHG activity is due to a kind of epitaxial growth of the noncentrosymmetrically aligned p-NA molecules. In this paper, a waveguide modulator of a poled polymer film doped with these mixed materials of p-NA and p-DCB was fabricated and the electrooptic coefficient r33 was measured. When the concentration of mixed materials was equal to 15 wt%, the value of r33 becomes maximum at a mixing ratio p-DCB: p-NA =O.4: 1. It was 23 times larger than the p-NA only doped film. It was found that the enhancement effect of r33 value came about when in the polymer matrix p-NA and p-DCB molecules gathered to some extent and interacted with each other. On the contrary, this enhancement effect was not observed when p-NA and p-DCB molecules were dispersed monomolecularly, and the only p-NA was found to contribute to the electrooptic effect.

View full abstract

A series of NaSbOSiO₄(NSS), ICSbOGeO₄(KSG), RbSbOGeO₄(RSG) compounds have been prepared by mechanochemical mixing (MM) route, which is a kind of technique of solid state reaction, or via a sol-gel route. They crystallize in the orthorhombic system, space group Pna 2, , Z=8. The framework structure, built up from SiO₄[Ge0₄] tetrahedra and Sb06octahedra, is isotypic with that of KTiOPO4. For both routes, preparation conditions have been optimized by studying the influence of various parameters such as calcination temperature, sintering temperature, sintering time.
According to the difference of topoch emical reactivity between MM and SG routes, the crystal phases deposited by the calcination are variant. Fine powders prepared by the SG route improve the sinterability. Within the group of alkali metal ion, K⁺ ion favours the progress of high polymerization during the hydrolysis. The microstructure of sintered bodies are very variant by the kind of compounds. The grain growth of KSG and RSG is cornparativery small with subsequent production of high dence pellets, while the sintering of NSS is very difficult.

View full abstract

Laser dye doped alumina film was prepared by sol-gel process starting with AlCl₃6 H₂O. Dyes used were Sulforhodamine 101(SR 101), Coumarin 1(C 1), 2-(1-Naphthyl)-5-phenyloxazole (a-NPO) and 2, 5-Diphenyloxazole (PPO). When the films doped with SR 101, C 1or α-NPO were irradiated wifh a N₂laser, lasers were acted. The film doped with both PPO and α-NPO exhibited energy-transfer-type laser emission. These results indicated that these doped alumina films have ability to operate as a compact dye laser.

View full abstract

To develop high SHG active materials with short cut-off wavelengths, “umbrella-shaped”tribenzamide derivatives were investigated. Crystals of these umbrella type materials are expected to show molecular columns due to van der Waals interactions. Tribenzamide ( 1)gave a powder SHG efficiency 1.5 times that of urea, and itsλis 330 nm in methanol. In the β calculation of 1 by the ab initio STO-3 G CPHF method, the β component of the direction along umbrella shaft was the largest. However in the crystal state, the component disappeared due to antiparallel alignment of packing columns. In other para-substituted tribenzamide derivatives with methyl and methoxy substituents, only two compounds showed SHG efficiency.

View full abstract

A KTP family compound, CsSbO(SiO₃)₂, have been prepared by mechanochemical mixing (MM) route or via a sol-gel route. They crystallize in the orthorhombic system, space group Pna2₁, Z=8 at 1100 °C. For both routes, preparation conditions have been optimized by s tudying the influence of various parameters such as calcination temperature, sintering temperature. The grain growth of sintered bodies is small with subsequent production of high dence pellets.

View full abstract