Compositions – Light transmission modifying compositions – Displaying color change
Reexamination Certificate
1998-01-12
2001-01-09
Tucker, Philip (Department: 1712)
Compositions
Light transmission modifying compositions
Displaying color change
C523S135000
Reexamination Certificate
active
06171525
ABSTRACT:
DESCRIPTION
The present invention relates to a process for the production of a photochromic object composed of a polymer and containing at least one spirooxazin compound.
There are two fundamentally different methods of carrying out the processes of producing photochromic objects composed of a polymer:
In the one method, first a non-photochromically tinted object is produced which is subsequently photochromically tinted “on the surface” from one or several surfaces. An example of a process realizing this method is described in DE-A-35 16 568 to which is explicitly referred for the explanation of all the terms not dealt with in more detail herein.
In the other method, the photochromic dyes are mixed into the material from which the photochromic object is produced prior to its polymerization. Processes realizing this method are described in U.S. Pat. No. 4,342,668 or EP-B-O 227 337. The process described in the latter-mentioned printed publication is the generic-forming presumption for the formulation of the introductory part of the process herein.
An element of the present invention is that the following drawbacks of the processes in which the photochromic dye or dyes are mixed in the monomer prior to polymerization and, in particular, the process known from EP-B-O 227 337 were recognized:
Comparatively high concentrations are required even to achieve relatively little darkening: For instance, the process of EP-B-O 227 337 requires employing a dye with a concentration of 1.5% relative to the weight of the monomer in order to obtain darkenings of maximumly 0.47 usually 0.25 measured in maximum of absorption—valued according to V&lgr; even only 0.2.
Moreover, in the process known from EP-B-O 227 337, only a low hardening degree of the polymer is achieved. Although this yields the apparently desired darkening and lightening very quickly, the low hardening degree however results, in addition to mechanical problems, also in relatively short durability of the dyes as well as very high temperature dependency of the darkening.
Furthermore, the process known from EP-B-O 227 337 does not permit the production of photochromic objects and, in particular, of ophthalmic lenses having a neutral grey, neutral brown or green photochromic tint.
REFERENCES:
patent: 5180524 (1993-01-01), Casilli et al.
patent: 5330686 (1994-07-01), Smith et al.
patent: 5391327 (1995-02-01), Ligas et al.
patent: 5621017 (1997-04-01), Kobayakawa et al.
patent: 5833885 (1998-11-01), Rickwood et al.
Effer Erhard
Melzig Manfred
Schuster Herbert
Zinner Herbert
Antonelli Terry Stout & Kraus LLP
Optische Werke G. Rodenstock
Tucker Philip
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