Optical: systems and elements – Polarization without modulation – By relatively adjustable superimposed or in series polarizers
Patent
1995-04-28
1998-01-06
Callahan, Timothy P.
Optical: systems and elements
Polarization without modulation
By relatively adjustable superimposed or in series polarizers
359 63, 359491, G02B 530
Patent
active
057061319
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a polarizing element, a polarizing plate and a process for production thereof which are novel.
BACKGROUND ART
Polarizing elements used in liquid crystal display devices, sunglasses, goggles, etc. are produced by a process in which dichroic molecules are dissolved in or adsorbed on a high-molecular weight substance such as a poly(vinyl alcohol), and the resulting film is stretched in one direction to align the dichroic molecules. They are produced also by a process in which dichroic molecules are adsorbed on a uniaxially stretched polymer film. However, the axis of polarization of the polarizing element obtained by any of these processes is fixed in one direction, and only a flat polarizing element can be produced by these processes. For producing various display elements including liquid crystal display elements, there are requested a polarizing element having polarizing properties in optional directions to show a fine pattern and a polarizing element having a curved surface.
For this purpose, there has been proposed a process comprising subjecting the surface of glass or a polymer film to rubbing treatment, i.e., rubbing with cloth, paper or the like in one direction, and then adsorbing dichroic molecules on the surface (see J. F. Dreyer, J. Phys. Colloid Chem., p. 52, 808 (1948)). According to this process, the dichroic molecules are aligned in a direction determined by the rubbing direction. Therefore, a multi-axial polarizing element having axes of polarization in various directions can be produced as a single polarizing plate by subjecting the substrate surface to the rubbing treatment in different directions previously (see J. F. Dreyer, C. W. Ertel, Glass Industry, p. 29, 197 (1948), and Toshiaki Nose, Rumiko Yamaguchi and Susumu Sato, Collection of Papers in Japan Electronic Intelligence Society, J71-C, 1188 (1988)). However, in this production process of a polarizing element by the rubbing treatment, each of masks which can give patterns different in axis of polarization is placed on the substrate to be surface-treated, and only the area not covered with the mask is mechanically rubbed. Therefore, fine patterns different in axis of polarization cannot be drawn. In addition, such a process cannot be employed in the case of a gradation display pattern of photography, etc. or a complicated pattern. Furthermore, in the rubbing treatment of polymer surface, static electricity generated by rubbing causes adsorption of fine dust, so that the surface is soiled. Thus, a method for controlling axis of polarization precisely and finely in an optional direction has not yet been reported.
On the other hand, for producing a polarizing element or polarizing plate having a curved surface, such as sunglasses and goggles for skiing, it has been necessary to process a flat polarizing element by application of heat or force. Moreover, a polarizing element or polarizing plate of high grade has been very expensive because an operation such as encapsulation with a resin or cladding is necessary.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a polarizing element or polarizing plate which does not require stretching of a polymer film and permits drawing of a very fine polarization pattern, and a process for producing the polarizing element or polarizing plate.
The present inventors earnestly investigated for achieving the above object, and consequently found that when a photoactive molecular layer capable of easily undergoing a molecular axis change caused by linear polarized light is formed on a substrate and irradiated with linear polarized light in a wavelength range in which the molecular layer absorbs the linear polarized light, and then a dichroic molecular layer is formed on the photoactive molecular layer, dichroic molecules are anisotropically aligned.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of an equipment for forming a photoactive separate layer.
FIG. 2 is a schematic illustration of an irradia
REFERENCES:
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patent: 5251065 (1993-10-01), Uetsuki
Ichimura, Kunihiro, et al, "Photocontrol of In-plane Aslignment of a Nematic Liquid Crystal by a Photochromic Spiropyran Monolayer Absorbing Linearly Polarized Light," Chemistry Letters, 1992, pp.1063-1066.
Polymer Preprints, Japan (English Edition), vol. 42, No. 1 (1993), No. I-10-11 and No. I-10-12.
Ichimura Kunihiro
Ishizuki Norio
Toda Junji
Callahan Timothy P.
Lam T. T.
Nippon Kayaku Kabushiki Kaisha
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