Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2001-03-19
2003-03-18
Sugarman, Scott J. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S177000
Reexamination Certificate
active
06533415
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ocular lens material having hydrophilic surface and a process for preparing the same. In particular, the present invention relates to a process for easily preparing an ocular lens material having high oxygen permeability and is excellent in surface wettability to water, surface lubricity, water retention, deposit resistance and biocompatibility at the same time. More particularly, the present invention relates to an ocular lens material prepared by the above process, which has hydrophilic surface and the above excellent properties at the same time, and can be suitably used as an optical material including an ocular lens such as a contact lens, an intraocular lens or an artificial cornea, and a biocompatible material such as a medical material, a biochemical material, an engineering material or a pharmaceutical material.
In recent years, as to polymer materials, in particular, ocular lens materials, it is thought that one of the causes of various ocular diseases is lowering of hydrophilic property (wettability to tears) of the lens surface or adhering of deposit such as protein or lipid. So, to highten hydrophilic property and deposit resistance is watched.
Then, in order to improve hydrophilic property and adhering of deposit of the lens surface, which are the causes of various ocular diseases, modification of the surface of ocular lens materials has been examined.
As a method for modifying the surface of ocular lens materials, for instance, a method for improving wettability to water by plasma treatment for the surface of ocular lens materials (Japanese Examined Patent Publication No. 40293/1988) and a method for imparting hydrophilic property by graft polymerizing a hydrophilic monomer to the plasma-treated surface of ocular lens materials (Japanese Unexamined Patent Publication No. 49251/1994) have been proposed.
However, by the above methods, although hydrophilic property (wettability to tears) of the lens surface can be improved, deposit resistance of the lens cannot be sufficiently improved. In addition, biocompatibility of the obtained lens is insufficient.
The above graft polymerization method itself has been known in the field of polymer materials such as ocular lens materials. So, conventionally, various methods utilizing graft polymerization have been proposed.
For instance, a method comprising the steps of plasma irradiating a polymer substrate in the presence of inert gas, forming peroxide group on the surface of the polymer substrate by exposing the polymer substrate under an atmosphere of oxygen gas, and graft polymerizing various vinyl monomers to the peroxide group has been proposed (Japanese Unexamined Patent Publication No. 94819/1987, Japanese Unexamined Patent Publication No. 278224/1990, Japanese Unexamined Patent Publication No. 49251/1994, U.S. Pat. No. 5,805,264, Japanese Patent No. 2934965 and the like). Also, a graft polymerization method comprising a step of immersing an ocular lens material in a hydrophilic monomer solution containing an aqueous peroxides has been proposed (Japanese Unexamined Patent Publication No. 10055/2000). In accordance with these methods, graft polymerization of various monomers to the material surface can be carried out. However, in general, energy for initiating graft polymerization is thermally imparted.
When thermal graft polymerization method is employed, longer period of time for polymerization is needed. So, it is desired to shorten polymerization time. When polymerization is carried out for a long period of time, introduction of polymer chains to the inside of material is accelerated. As a result, deformation of an ocular lens material occurs. Furthermore, because it is difficult to control polymerization degree during thermal polymerization for a long period of time, the thermal polymerization method is unsuitable for preparing a uniform treated layer.
On the other hand, it is thought that introduction of a vinyl monomer having a zwitterionic group which can impart excellent water retention, deposit resistance and biocompatibility to the polymer surface is one of effective ways.
For instance, a method for graft polymerizing a monomer having a zwitterionic group to the surface of hydrogel has been proposed (U.S. Pat. No. 5,453,467). However, because thermal graft polymerization is carried out in this method, the method has the same problem as above. So, it is desired to dissolve the problem. Also, because the above hydrogel has no silicone-containing component, it is difficult to prepare an ocular lens material having high oxygen permeability.
Then, a method for graft polymerizing a monomer having a zwitterionic group to the activated surface of an ocular lens material prepared by using a silicone-containing component has been proposed (Japanese Unexamined Patent Publication No. 122779/1994 and Japanese Unexamined Patent Publication No. 72430/1995). However, because thermal graft polymerization is carried out in this method, the method has the same problem as above.
A graft polymerization method with a microwave having a wavelength of 250 to 500 nm has been proposed (Japanese Unexamined Patent Publication No. 60142/1998). However, because no monomer having a zwitterionic group is used in graft polymerization, a hydrophilic membrane formed by the method cannot impart sufficient water retention and biocompatibility.
A method for graft polymerizing a monomer having a zwitterionic group at hydroxyl group on the material surface as the initiation point by using a transition metal salt has been proposed (Japanese Unexamined Patent Publication No. 510322/1994). However, it is difficult to remove an initiator such as the transition metal salt in this method. Also, because thermal graft polymerization is carried out in this method, the method has the same problem as above.
A method for imparting hydrophilic property, comprising steps of immersing an ocular lens material in a hydrophilic monomer solution and irradiating the ocular lens material with ultraviolet-ray has been proposed (Japanese Unexamined Patent Publication No. 10054/2000). However, in the case that the ocular lens material is hydrogel, hydrophilic polymer chains are introduced to the inside of the hydrogel, so that optical property becomes bad. Also, it becomes difficult to remove the hydrophilic polymer chains from the inside of the hydrogel. In addition, in the case that the ocular lens material is a hard material, there is a problem that it is difficult to introduce the hydrophilic polymer chains to the hard material because it is very difficult to graft polymerize the hydrophilic monomers to the surface of the hard material.
In recent years, as a method for controlling molecular weight and molecular weight distribution during radical polymerization, a method comprising a step of adding a sulfur-containing compound as a chain transfer agent to a polymerization system has been reported (John Chiefari et. al., Macromolecules, 31, p5559 (1999)). Furthermore, a surface graft polymerization method using the above chain transfer agent has been reported (Tsujii Yoshinobu et. al., Polymer Preprints, Japan, 49, p1129 (2000)). In accordance with these methods, molecular weight and molecular weight distribution in the aimed polymer can be controlled by utilizing the chain transfer agent in polymerization. However, to control of molecular weight and molecular weight distribution in the polymer and to impart of hydrophilic property to the polymer surface have not been carried out at the same time. So, technical development has been desired.
On the other hand, as one of methods for introducing a monomer having a zwitterionic group to a silicone hydrogel, a method for forming inter-penetrating polymer network structure (in general, referred to as IPN structure) composed of a silicone segment and a hydrophilic segment has been proposed (International Publication No. WO99/29750). However, when the method is employed, the aimed material sometimes deforms. Accordingly, the method is unsuitable for preparing an op
Menicon Co. Ltd.
Sugarman Scott J.
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