Conventionally, in general, a material having relatively high water-absorptive property, such as a material having a water content of at least 40% by weight has the advantage of being imparted flexibility by water even if its own flexibility is, as usual, not so high. However, oxygen permeability of the above material is insufficient and when water content in the material is increased, there generates a problem that bacteria widely breed and safety of the material is lowered.
Then, there is proposed a material comprising a copolymer which is prepared by combining a monomer or macromonomer capable of imparting excellent oxygen permeability to the material, such as a silicon and/or fluorine-containing monomer or macromonomer with a hydrophilic monomer capable of imparting excellent wettability (hydrophilic property) to the material, such as a hydroxyl group-containing monomer so that water content of the material becomes low, and then, by copolymerizing these together with. Although the material is surely excellent in oxygen permeability, the material is poor in flexibility, and furthermore, because compatibility of the silicon and/or fluorine-containing monomer or macromonomer with the hydrophilic monomer is remarkably poor, when these components are mixed together with, sometimes phase separation is generated and only an opaque polymer is obtained by the copolymerization. Therefore, there occurs a problem that it is difficult to use the above material as a contact lens or an intraocular lens.
Then, in order to solve the above problem, there is proposed a process for producing a soft contact lens, comprising desilylating the copolymer prepared by copolymerizing a hydroxyl group-containing hydrophilic monomer of which hydroxyl group is previously silylated with a polyorganosiloxane having a polymerizable group and a hydrophilic group on the same side chain of the molecule (Japanese Unexamined Patent Publication No. 295216/1989).
By the above process, a soft contact lens which is excellent in transparency can be produced. However, because there is necessitated a complicated step such that hydroxyl group of a hydroxyl group-containing hydrophilic monomer is previously silylated and then, the obtained copolymer is desilylated, it is desired that the step in the process is more simplified.
Also, in addition to the above process, there are proposed a process for producing a contact lens, comprising mixing a monomer composition containing a crosslinking agent with a solvent having high compatibility with the monomer composition to give a mixture, producing a formed article of polymer by molding the mixture by the static casting and removing the solvent from the formed article of polymer (Japanese Unexamined Patent Publication No. 225913/1989), a process comprising using a monomer composition containing a silicone-containing monomer and a hydrophilic monomer in the above process for producing a contact lens (Japanese Unexamined Patent Publication No. 501504/1996) and a process comprising evaporating and removing the solvent at the specific temperature in the above process for producing a contact lens (Japanese Unexamined Patent Publication No 503173/1996).
By these processes, a contact lens which is relatively good in transparency can be produced. However, when these processes are employed, there is a fear that the solvent and non-reacted monomer composition which have been used during the static casting are not completely removed, so that these remain in a contact lens.
In the meantime, as an intraocular lens material, there is proposed a material prepared by polymerizing a silicon-containing monomer capable of imparting flexibility to the material.
However, the above material has a problem that a lens from the material becomes cloud in white owing to stain such as lipid after inserting the lens into an eye because the material has a high affinity for lipid, so that optical properties are lost. Then; in order to solve the problem, it is tried to develop various processes for producing an intraocular lens material. However, a process by which the desired intraocular lens can be easily produced has not been provided yet.
As aforementioned, there has not yet been provided a process for easily producing a contact lens material and an intraocular lens material which are, in particular, excellent in transparency and furthermore have flexibility, high oxygen permeability, stain resistance, wettability, safety and the like at the same time.
The present invention has been accomplished in consideration of the above prior art, and aims at providing a process for extremely easily producing an ocular lens such as a contact lens, which is, in particular, remarkably excellent in transparency, has flexibility and high oxygen permeability, is excellent in stain resistance and wettability, and furthermore has high safety, and providing an ocular lens represented by a contact lens, which is produced by the process.