Lyotropic liquid crystal composition

Details Lyotropic liquid crystal composition Lyotropic liquid crystal composition

2002-04-01

2004-02-24

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C428S001200, C428S001310, C428S001550, C252S299010

Reexamination Certificate

active

06696113

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a lyotropic liquid crystal composition comprising silver grains, silver halide grains or optically anisotropic grains dispersed in lyotropic liquid crystal. The invention also relates to an optically anisotropic thin film comprising the grains and the lyotropic liquid crystal. The invention further relates to a process for preparation of the optically anisotropic thin film by use of the lyotropic liquid crystal composition.
BACKGROUND OF THE INVENTION
A diffraction optical device, which is produced on the basis of lithography and etching technology, has been rapidly improved according as the technology has been developed. For example, a diffraction optical device having a pitch shorter than visible wavelength has been studied. Generally, a material having a structure smaller than visible wavelength can be regarded as a homogeneous media having a certain refractive index, which depends on the structure and the refractive index of the material alone. The diffraction device having a fine pitch has an important advantage of controlling polarization. In fact, if the fine structure of the device is not the same in all directions, the device shows optical anisotropy called “structural birefringence”. Because of this character, it is theoretically possible to produce a diffraction grating showing controlled polarization. The fine diffraction device has been studied since late 1980s. The studies are described in Kikuta et al, OPTRONICS, 8(1996), 132.
A practically used polarizing element in the above technical field comprises silver grains of football shape dispersed in glass (described in Japanese Patent Publication No. 2(1990)-40619, U.S. Pat. Nos. 4,486,213 and 4,479,819). This device is prepared in the following manner. First, a glass material containing silver and halogen is subjected to heat treatment so as to deposit silver halide grains. The material is then heated and stretched to make the grains football shape, and thereby optical anisotropy is caused in the silver halide grains. Finally, the material is heated under reducing atmosphere to reduce the silver halide into silver metal.
In the thus-prepared device, the silver halide grains do not have uniform aspect ratio (ratio between the lengths of long and short axes). Further, it is difficult to fully reduce the silver halide in the glass, and consequently opaque silver halide slightly remains.
In order to solve these problems, it is proposed to produce a polarizing element through a film-forming process such as vacuum deposition or spattering process (described in Resume for Japan Electronic Information and Communication Society, autumn meeting 1990, C-212). According to the proposed process, first a metal layer is formed by vacuum deposition on a dielectric substrate such as a glass plate. On the formed layer, a dielectric layer such as a glass layer is then formed by, for example, spattering. The procedure is repeated several times to form some metal and dielectric layers piled up alternatively. The formed layered composition is heated and stretched so that the metal layers may be transformed into discontinuous islanded metal particle layers. Since each metal particle in the layers is stretched to transform into football shape, the polarization is realized.
For improving efficiency of light used in a polarizing plate, it is proposed to use a polarizing plate of light-scattering type in place of or in addition to that of light-absorbing type. The polarizing plate of light-scattering type as well as that of light-absorbing type transmits only the light component polarized parallel to the polarizing axis. However, the plate of light-scattering type does not absorb but scatters forward or backward the perpendicularly polarized component, and accordingly it improves the efficiency of light.
The polarizing plate of light-scattering type is described in Japanese Patent Provisional Publication Nos. 8(1996)-76114, 9(1997)-274108, 9(1997)-297204, Japanese Patent Publication Nos. 11(1999)-502036, 11(1999)-509014, U.S. Pat. Nos. 5,783,120, 5,825,543 and 5,867,316.
An anisotropic thin film comprising fine nickel metal rods is reported (Saito et al, Appl. Phys. Lett., 55(1989), No. 7, 607). In preparing the film, a porous alumina thin film is electrochemically formed on a cathode, and then the porosities are filled with nickel metal. The thus-formed film shows such polarizing performance that the extinction ratio is 30 dB at the wavelength of 1.3 &mgr;m.
The optical characteristics of gold colloid have been studied for a long time. For example, a monodispersive colloid of uniform fine gold rods is reported (van der Zande et al, J. Phys. Chem. B, 101(1997), 852). In preparing the colloid, a porous alumina film is formed by anode oxidation (diameter of porosity: 12 nm). In the film, gold rods are grown by electrochemical deposition from a gold solution. The alumina film is then removed to obtain the dispersive fine gold rods. The lengths of the rods are controlled in the range of 12 to 160 nm by the time for deposition. The anisotropy of the gold rods depends on the ratio of length/diameter, and accordingly the spectrum remarkably varies according to the ratio.
Gabor L. Hornyak et al. also adopt the method in which fine porosities are charged with gold to prepare various alumina films containing fine gold rods, and study the optical characters of the films containing anisotropically aligned fine gold rods having various aspect ratios (J. Phys. Chem. B, 101(1997), 1548). As a result, they confirm that Maxwell-Garnet theorem, which is a relation between colloidal particles and plasmon resonance absorption, holds for these fine gold particles.
Kikuta et al. notice an intense dispersion on effective refractive index of structural birefringence based on the above-described fine aligning structure. They suggest that this phenomenon can be utilized to produce a wide-ranging &lgr;/4 plate (Resume for Japan Appiled Physics Society, autumn meeting 1990, 26a-SP-22, 807).
Giving nonlinear optical effects, the composite material containing dispersed structural units of nanometer size (e.g., metal particles, semiconductor crystallites) has been studied to use in the field of nonlinear optics.
The term “nonlinear optical effects” means the following phenomena. When a ray having the electric field E and the frequency &ohgr; comes into the material, the electric field (E) induces alternative separation between positive and negative electric charge at the frequency &ohgr;. This alternative charge separation is called “polarization wave”. The polarization wave then functions as a wave source to cause a ray of the frequency &ohgr;, which comes out of the material. Consequently, the incident ray and the ray coming out have the same frequency. This is a normal interaction between light and matter. However, in some materials, when the incident ray having the electric field (E) and the frequency &ohgr; comes, another polarization wave is induced in proportion to the power of E. These materials are called “nonlinear optical materials”. The nonlinear optical material gives peculiar phenomena. For example, the ray coming out of the material has a frequency of twice or more as large as the incident frequency &ohgr; (namely, the color of the ray coming out is different from that of the incident ray). Further, the refractive index of the material varies according to the square of the intensity of light (electric field). These peculiar phenomena are generally called “nonlinear optical effects”. The nonlinear optical effects have been studied in view of application to wavelength conversion of lasers or optical logic devices. There is a close relation between the nonlinear optical effects and the quantum confinement. In fact, if a material comprises fine metal or semiconductor particles of nanometer size, the quanta (such as electrons, positive holes and excitons) concerned with the interaction between light and matter cannot freely behave and consequently induce the peculiar phenomena that are not observed in a n

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