Optical: systems and elements – Having significant infrared or ultraviolet property
Patent
1990-02-13
1992-02-11
Arnold, Bruce Y.
Optical: systems and elements
Having significant infrared or ultraviolet property
359490, 252588, G02B 522
Patent
active
050879855
DESCRIPTION:
BRIEF SUMMARY
FIELD OF ART
The present invention relates to a polarizer superior in both heat and humidity resistance and polarization characteristics.
BACKGROUND ART
Heretofore, as methods for improving the heat and humidity resistance of a polarizer there have been known a method using dichroic dyes or polyenes as dichromophores (e.g. Japanese Patent Publication No. 5121/1986 and Patent Laid-Open no. 123944/1978) and a method wherein the surface of a dichromophore is coated with a hydrophobic resin (e.g. Japanese Patent Laid-Open No. 33612/1981 and 62011/1982).
Liquid crystal displays of TN and STN types utilizing polarizers have been used as display portions of watches and electronic calculators, and according to the recent tendency, liquid crystal displays are being applied to various uses such as, for examples, terminal displays of personal computers and word processors, displays mounted in automobiles and aircraft. The development of a polarizer superior in heat and humidity resistance and polarization characteristics is absolutely necessary for the attainment of high reliability and high picture quality of these display devices.
However, the foregoing conventional polarizers using dichroic dyes or polyenes are poor in polarization characteristics although they exhibit high heat and humidity resistance. Polarizers wherein the surface of dichromophore is coated with a hydrophobic resin such as polyurethane, polyether sulfone, polyester, or polyamide, are poor in the adhesion to polyvinyl alcohol-based polarizing elements and incapable of being rendered completely heat- and humidity-proof. Besides, interference color is easily developed due to birefringence of the hydrophobic resin layer, and curling is apt to occur due to contraction and expansion of the polarizing element and the resin layer. Thus, a limit has heretofore been encountered in the improvement of heat and humidity resistance and polarization characteristics.
DISCLOSURE OF THE INVENTION
It is the object of the present invention to remedy the above-mentioned problems and provide a novel polarizer superior in both heat and humidity resistance and polarization characteristics.
More specifically, the present invention is concerned with a polarizer for visible light comprising a polyvinyl alcohol-based polarizing element wherein 60% or more of dichromophore is iodine and a protective film, the said polarizing element having three absorption bands in an ultraviolet region of 210 to 400 nm and having a UA value of not less than 4.0 which value represents ultraviolet absorption characteristics.
According to the construction of the present invention there can be obtained a polarizer for visible light superior in both polarization characteristics and heat and humidity resistance. Since this polarizer is also superior in flatness, it permits the improvement in reliability and picture quality of a liquid crystal display.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing an absorption spectrum in the ultraviolet and visible wavelength region of the polarizer of the present invention;
FIG. 2 is a view showing an absorption spectrum in the ultraviolet and visible wavelength region of a polarizing element in a conventional polyvinyl alcohol/iodine polarizer; and
FIG. 3 is a view showing transmittance spectra of visible light and polarization efficiency spectra before and after the conventional polarizer is allowed to stand in a wet heat atmosphere, in which the reference numerals 11 and 21 represent a transmittance spectrum and a polarization spectrum, respectively, in the initial stage and the numerals 12 and 22 represent a transmittance spectrum and a polarization spectrum, respectively, after standing in a wet heat atmosphere.
BEST MODE FOR PRACTISING THE INVENTION
The "polyvinyl alcohol-based polarizing element" as referred to herein indicates a film as a base formed of polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl acetal, or a ethylene-vinyl acetate copolymer, and iodine adsorbed and oriented in the film. From the standpo
REFERENCES:
patent: 3780307 (1973-12-01), Saeva et al.
patent: 3806462 (1974-04-01), Bloom
patent: 4427741 (1984-01-01), Aizawa et al.
patent: 4803014 (1989-02-01), Okumura et al.
patent: 4859039 (1989-08-01), Okumura et al.
Hisaki Hisao
Kigoshi Shoji
Kitaura Koichi
Arnold Bruce Y.
Dang Hung Xuan
Toray Industries Inc.
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