Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-02-10
2001-02-13
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S196000, C524S305000
Reexamination Certificate
active
06187844
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plastic lens, and more particularly to a plastic lens formed of a urethane-based resin having a UV absorptive function.
2. Description of the Prior Art
Plastic lenses have various advantages as compared with glass lenses. For example, plastic lenses have a relatively light-weight and are less vulnerable to breakage in comparison with glass lenses. Further, plastic lenses are colorable, and precision molding thereof can be easily carried out. In view of these advantages, in recent years, plastic lenses are widely used for optical lens products such as an eye-glass lens, camera lens, Fresnel lens, lenticular lens, prism and the like.
Among these plastic lenses, a plastic lens formed of a urethane-based resin has less optical distorsions and it has a high safety due to its excellent transparency and superior impact resistance, so that such a lens is preferably used as an eye-glass lens or the like.
In addition, plastic lenses to which UV absorptive function (UV absorptive power) is imparted have been proposed in order to protect the crystalline lens, the retina and the like from the injury by the UV. The UV absorptive function is imparted, for example, by forming a plastic lens using a resin material for plastic lens which has UV absorptive function in itself, or by providing a coating layer formed of an UV absorbent having UV absorptive function on the surface of the molded plastic lens.
However, in these methods, there have been problems such as yellowing of the lens and changes in the index of refraction of the lens due to the own color (yellow) of the resin material for the plastic lens or the UV absorbent. Moreover, there have also been such problems as the deterioration in the mechanical strength and the deterioration of transparency of the lens due to the addition of the UV absorbent and the addition of a color complementing agent which is added for the purpose of adjusting the yellowing to be caused by the UV absorbent.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a plastic lens which does not cause yellowing and changes in the index of refraction and the transparency as well as deterioration in the mechanical strength which are to be caused by the addition of the UV absorbent.
In order to achieve the above object, the plastic lens according to the present invention is formed using a composition for plastic lens which contains, as its main components, a resin material having a urethane-based resin component and at least one kind of UV absorbent selected from the group comprising 2-(5-methyl-2-hydroxyphenyl) benzotriazole, 2-(5-t-butyl-2-hydroxyphenyl) benzotriazole, 2-(5-t-octyl-2-hydroxyphenyl) benzotriazole, 2-(3, 5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3, 5-di-t-amyl-2-hydroxyphenyl) benzotriazole and 2-(3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole.
According to the plastic lens of the present invention described above, it is possible to avoid the yellowing of the lens due to the addition of the UV absorbent while exhibiting an excellent UV absorptive function.
Moreover, in order to achieve the above object, it is preferable that the above plastic lens composition contains as the UV absorbent a compound whose maximum absorption wavelength in a chloroform solution is less than 345 nm.
Further, it is preferable that the plastic lens composition contains as the UV absorbent a compound whose maximum absorption wavelength in the chloroform solution is not less than 345 nm.
Further, it is preferable that the total amount of addition of the UV absorbent in the plastic lens according to this invention is in the range of 0.02 to 2.0 wt % relative to 100 wt % of the resin material.
Further, it is preferable that the urethane-based resin component contains a mercapto group containing compound. In this case, it is preferred that the mercapto group containing compound includes at least either one of pentaerythritoltetrakis (3-mercaptopropionate) and 4-mercaptomethyl-3, 6-dithio-1, 8-octanedithiol.
Further, it is preferable that the urethane-based resin component contains an isocyanate group containing compound. More preferably, the isocyanate group containing compound includes at least either one of m-xylylenediisocyanate and 2, 5 (2, 6)-bicyclo [2,2,1] heptanebis-(isocyanatemethyl) norbornanediisocyanatemethyl.
In the present invention, it is also preferred that the urethane-based resin component contains a mercapto group containing compound and an isocyanate group containing compound. In this case, it is preferred that the mercapto group containing compound includes pentaerythritoltetrakis (3-mercaptopropionate), and said isocyanate group containing compound includes m-xylylenediisocyanate. Further, it is also preferred that the mercapto group containing compound includes 4-mercaptomethyl-3, 6-dithio-1, 8-octanedithiol, and said isocyanate group containing compound includes m-xylylenediisocyanate. Furthermore, It is also preferred that the mercapto group containing compound includes pentaerythritoltetrakis (3-mercaptopropionate) and 4-mercaptomethyl-3, 6-dithio-1, 8-octanedithiol, and the isocyanate group containing compound includes 2, 5 (2, 6)-bicyclo [2,2,1] heptanebis-(isocyanatemethyl) norbornanediisocyanatemethyl.
Further, it is preferable that the plastic lens composition contains 0.01 to 10 ppm of a bluing agent.
Further, it is preferable that the plastic lens according to the present invention has a spectroscopic transmissivity of not more than 10% for a radiation with wavelength of 400 nm in a lens thickness of 2 mm.
Further, it is preferable that the plastic lens according to the present invention has a yellow Index (YI value) of not more than 1.5 for a lens thickness of 2 mm.
Further, since the plastic lens according to the present invention maintains mechanical strength and high index of refraction, it is possible to use it for a wide range of applications as optical lenses such as safe and high precision eye-glass lenses.
Other objects, constitutions and advantages of the present invention will become more apparent from the following description of the invention and the Examples.
DESCRIPTION OF THE INVENTION
Hereinbelow, the plastic lens according to the present invention will be described in detail.
The feature of the plastic lens according to the present invention resides in that it is formed using a composition for plastic lens which contains, as its main components, a resin material having a urethane-based resin component, and at least one kind of UV absorbent selected from the group comprising 2-(5-methyl-2-hydroxyphenyl) benzotriazole, 2-(5-t-butyl-2-hydroxyphenyl) benzotriazole, 2-(5-t-octyl-2-hydroxyphenyl) benzotriazole, 2-(3, 5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3, 5-di-t-amyl-2-hydroxyphenyl) benzotriazole and 2-(3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole.
With this arrangement, it is possible to suppress yellowing of the lens caused by the color of the added UV absorbent while imparting UV absorptive function to the plastic lens.
In the present invention, at least one kind selected from the group comprising 2-(5-methyl-2-hydroxyphenyl) benzotriazole, 2-(5-t-butyl-2-hydroxyphenyl) benzotriazole, 2-(5-t-octyl-2-hydroxyphenyl) benzotriazole, 2-(3, 5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3, 5-di-t-amyl-2-hydroxyphenyl) benzotriazole and 2-(3, 5-di-t-butyl-2-hydroxyphenyl) benzotriazole is used as the UV absorbent.
These UV absorbents have an excellent compatibility especially with the resin material used in this invention, so that no bleed-out of the UV absorbents occurs at the time of polymerization or during the use of the lens. Therefore, there is no possibility of spoiling of the appearance of the lens, deterioration in the characteristics of the lens and degradation o
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Sanders Kriellion
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