Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Patent
1997-01-23
1999-06-08
McPherson, John A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
522 64, 522 71, 522 75, 522910, 430962, C08F 248
Patent
active
059105160
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a process for producing a photochromic cured product having excellent photochromic property, which is a cured product prepared by photopolymerization.
2. Background Art
Photochromism is a phenomenon which has come to draw attention in the last several years, and is such a reversible reaction that a certain compound quickly changes its color when irradiated with an ultraviolet-containing light such as sunlight or a light emitted from a mercury lamp and, when the light irradiation is stopped and the compound is placed in a dark room, returns the original color. Compounds having photochromism are called photochromic compounds, and photochromic compounds having various structures have heretofore been synthesized. In their structures, however, there is found no particular common skeletal structure.
Cured products showing photochromism are obtained by, for example, a process which comprises coating the above-mentioned photochromic compound on the surface of a pre-molded polymer, or a process which comprises dissolving the photochromic compound in a radical-polymerizable monomer and then subjecting the resulting solution to polymerization to cure.
As a process for polymerizing a radical-polymerizable monomer, there are generally known a thermal polymerization process and a photopolymerization process. When the photopolymerization process is used in obtaining a cured product having photochromic property, however, sufficient polymerization of a radical-polymerizable monomer can not be expected from the reasons that the photochromic compound contained in the polymerizable composition absorbs an ultraviolet light necessary for the cleavage of a polymerization initiator and that the color development of the photochromic compound by itself by light irradiation hinders the transmittance of light. Further, according to the study by the present inventors, in the case of employing a photopolymerization process, durability in photochromism of the photochromic compound is remarkably reduced when the photochromic compound is dispersed in a matrix polymer of insufficient degree of polymerization.
From such standpoints, in obtaining a photochromic cured product, the thermal polymerization process is in general use for polymerization of a radical-polymerizable monomer. The thermal polymerization process, however, requires a polymerization time of several hours and is still not satisfactory in productivity of the cured products.
Given the above background, the present invention aims at providing a process which allows easy polymerization in a short time by photopolymerization and can produce a cured product of excellent photochromic property.
DISCLOSURE OF THE INVENTION
In view of the above problem, the present inventors made an extensive study. As a result, the present inventors found that molding can be made easily in a short time and a cured product can show excellent photochromism by using, in combination, a specific photopolymerization initiator and an active energy ray having a specified emission spectrum. The present invention has been accomplished based on this finding.
That is, the present invention provides a process for producing a photochromic cured product, which comprises subjecting a photopolymerizable composition comprising an ultraviolet region and a molar extinction coefficient at 400 nm of 150 lit./(mol.multidot.cm) or more, and having, as the main spectrum, an emission spectrum of 400 nm or more, to cure the composition.
As the radical-polymerizable monomer used in the present process for production of a photochromic cured product, there can be used any monomer having a radical-polymerizable group without restriction. The radical-polymerizable group is preferably selected from an acrylate group, a methacrylate group, a vinyl group and the like.
Typical examples of the radical-polymerizable monomer preferably usable in the present invention include compounds represented by the following general formula (1), (2) or (3):
A diacrylate or dimethacr
REFERENCES:
patent: 5531940 (1996-07-01), Gupta et al.
patent: 5621017 (1997-04-01), Kobayakawa et al.
Imura Satoshi
Nishitake Toshihiro
McPherson John A.
Tokuyama Corporation
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