Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1997-10-10
2000-03-07
Yoon, Tae
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
5262196, 526224, 526313, 5263292, 5262181, 523105, 523106, 524 95, 524104, 524110, 252586, 359722, C08F 238, C08F 404, G02B 523, C08K 535
Patent
active
060341939
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to novel photochromic transparent organic materials with high index of refraction presenting no optical distortion in solid form, a method for their preparation, and the articles made from these materials.
It is difficult to prepare such a photochromic ophthalmic lens made of plastic material. Ideally, the polymer matrix of such a lens should be crosslinked thermally, free of optical distortion in solid form and able to receive appropriate mixtures of photochromic dyes and to be crosslinked in the presence of such appropriate mixtures of photochromic dyes, for example spiroxazines and chromenes, to obtain a material which presents a high initial transmission before exposure and a high capacity for darkening after exposure, all with rapid darkening and lightening kinetics. In addition, the material should have a low thermal dependence, a high resistance to fatigue, and as high an index of refraction as possible.
Obviously, no such ideal material exists to date.
WO-A-92/05209 describes a copolymer that is free of optical distortions and is suitable for the manufacture of eyeglasses, and is obtained by a radical polymerization of a first monomer with formula I ##STR3## where a and b are whole numbers from 0 to 4, R.sub.1 and R.sub.2 =H or CH.sub.3, and R.sub.3 =--O--, --S--, --CO--, --SO.sub.2 --, --CH.sub.2 --, --CH.dbd.CH-- or ##STR4## with a second monomer, which can be styrene or a styrene derivative an, optionally, a third monomer, which can be a vinyl aromatic compound or an aromatic methacrylate, in the presence of an initiator of the peroxide type and of a chain transfer agent selected from various brominated compounds.
This copolymer could be a good polymer matrix for an ophthalmic article, such as a lens.
However, when one tries to incorporate ophthalmic dyes in the copolymerizable composition to impart ophthalmic properties to the matrix obtained after copolymerization, it can be observed that said dyes are destroyed by the peroxide initiator.
Even if the peroxide initiator is replaced by a milder radical polymerization initiator, such as a diazo compound, for example, azobisisobutyronitrile, the material obtained is still unsatisfactory, because the photochromic dyes are inhibited by the bronninated chain transfer agent used, as has been observed by the present inventors. It is also necessary to later incorporate the dyes into the matrix notably by a specific thermal diffusion method, which increases the cost price of the material and complicates its manufacturing process.
Thus, there is a need for high-performance ophthalmic materials that are easy and inexpensive to manufacture.
The present invention is intended to meet this need.
SUMMARY OF THE INVENTION
More particularly, the present invention concerns novel ophthalmic transparent organic materials presenting an index of refraction of more than 1.55, which are free of optical distortions and are prepared by radical polymerization of a polymerizable composition comprising: (I): ##STR5## where R=H or CH.sub.3, and m and n are independently 1 or 2; b) 5-20 wt % of at least one aromatic monovinyl monomer represented by the general formula (II): ##STR6## where R.sub.1 =H or CH.sub.3 c) an effective quantity of at least one dye that imparts photochromic properties to the material, selected from the groups of spiroxazines, spiropyrans and chromenes;
characterized in that the chain transfer agent is a linear alkanethiol and the radical polymerization initiator is a diazo compound.
Optionally, the polymerizable composition can contain, in addition, f) up to 10 wt % of an aromatic divinyl monomer represented by the general formula (III): ##STR7## where R.sub.1 =H or CH.sub.3.
The invention also relates to a method for the preparation of novel photochromic transparent organic materials presenting an index of refraction of more than 1.55, which are free of optical distortions, characterized in that it consists of carrying out a radical polymerization of a polymerizable composition comprising: (I): ##ST
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Henry David
Vial Jacques
Corning Incorporated
Nwaneri Angela N.
Rogalskyj Peter
Yoon Tae
LandOfFree
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