Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or...
Reexamination Certificate
2001-02-20
2004-10-26
MacKey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
C425S155000, C425S174400, C425S808000
Reexamination Certificate
active
06808381
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to eyeglass lenses. More particularly, the convention relates to a lens forming composition, system and method for making photochromic, ultraviolet/visible light absorbing, and colored plastic lenses by curing the lens forming composition using activating light.
2. Description of the Relevant Art
It is conventional in the art to produce optical lenses by thermal curing techniques from the polymer of diethylene glycol bis(allyl)-carbonate (DEG-BAC). In addition, optical lenses may also be made using ultraviolet (“UV”) light curing techniques. See, for example, U.S. Pat. No. 4,728,469 to Lipscomb et al., U.S. Pat. No. 4,879,318 to Lipscomb et al., U.S. Pat. No. 5,364,256 to Lipscomb et al., U.S. Pat. No. 5,415,816 to Buazza et al., U.S. Pat. No. 5,529,728 to Buazza et al., U.S. Pat. No. 5,514,214 to Joel et al., U.S. Pat. No. 5,516,468 to Lipscomb, et al., U.S. Pat. No. 5,529,728 to Buazza et al., U.S. Pat. No. 5,689,324 to Lossman et al., U.S. Pat. No. 5,928,575 to Buazza, U.S. Pat. No. 5,976,423 to Buazza, U.S. Pat. No. 6,022,498 to Buazza et al. and U.S. patent application Ser. No. 07/425,371 filed Oct. 26, 1989, Ser. No. 08/439,691 filed May 12, 1995, Ser. No. 08/454,523 filed May 30, 1995, Ser. No. 08/453,770 filed May 30, 1995, Ser. No. 08/853,134 filed May 8, 1997, Ser. No. 08/844,557 filed Apr. 18, 1997, and Ser. No. 08/904,289 filed Jul. 31, 1997, all of which are hereby specifically incorporated by reference.
Curing of a lens by ultraviolet light tends to present certain problems that must be overcome to produce a viable lens. Such problems include yellowing of the lens, cracking of the lens or mold, optical distortions in the lens, and premature release of the lens from the mold. In addition, many of the useful ultraviolet light-curable lens forming compositions exhibit certain characteristics that increase the difficulty of a lens curing process. For example, due to the relatively rapid nature of ultraviolet light initiated reactions, it is a challenge to provide a composition that is ultraviolet light curable to form an eyeglass lens. Excessive exothermic heat tends to cause defects in the cured lens. To avoid such defects, the level of photoinitiator may be reduced to levels below what is customarily employed in the ultraviolet curing art.
While reducing the level of photoinitiator addresses some problems, it may also cause others. For instance, lowered levels of photoinitiator may cause the material in regions near an edge of the lens and proximate a gasket wall in a mold cavity to incompletely cure due to the presence of oxygen in these regions (oxygen is believed to inhibit curing of many lens forming compositions or materials). Uncured lens forming composition tends to result in lenses with “wet” edges covered by sticky uncured lens forming composition. Furthermore, uncured lens forming composition may migrate to and contaminate the optical surfaces of the lens upon demolding. The contaminated lens is then often unusable.
Uncured lens forming composition has been addressed by a variety of methods (see, e.g., the methods described in U.S. Pat. No. 5,529,728 to Buazza et al). Such methods may include removing the gasket and applying either an oxygen barrier or a photoinitiator enriched liquid to the exposed edge of the lens, and then re-irradiating the lens with a dosage of ultraviolet light sufficient to completely dry the edge of the lens prior to demolding. During such irradiation, however, higher than desirable levels of irradiation, or longer than desirable periods of irradiation, may be required. The additional ultraviolet irradiation may in some circumstances cause defects such as yellowing in the lens.
The low photoinitiator levels utilized in many ultraviolet curable lens forming compositions may produce a lens that, while fully-cured as measured by percentage of remaining double bonds, may not possess sufficient cross-link density on the lens surface to provide desirable dye absorption characteristics during the tinting process.
Various methods of increasing the surface density of such ultraviolet light curable lenses are described in U.S. Pat. No. 5,529,728 to Buazza et al. In one method, the lens is demolded and then the surfaces of the lens are exposed directly to ultraviolet light. The relatively short wavelengths (around 254 nm) provided by some ultraviolet light sources (e.g., a mercury vapor lamp) tend to cause the material to cross-link quite rapidly. An undesirable effect of this method, however, is that the lens tends to yellow as a result of such exposure. Further, any contaminants on the surface of the lens that are exposed to short wavelengths of high intensity ultraviolet light may cause tint defects.
Another method involves exposing the lens to relatively high intensity ultraviolet radiation while it is still within a mold cavity formed between glass molds. The glass molds tend to absorb the more effective short wavelengths, while transmitting wavelengths of about 365 nm. This method generally requires long exposure times and often the infrared radiation absorbed by the lens mold assembly will cause premature release of the lens from a mold member. The lens mold assembly may be heated prior to exposure to high intensity ultraviolet light, thereby reducing the amount of radiation necessary to attain a desired level of cross-link density. This method, however, is also associated with a higher rate of premature release.
It is well known in the art that a lens mold/gasket assembly may be heated to cure the lens forming composition from a liquid monomer to a solid polymer. It is also well known that such a lens may be thermally postcured by applying convective heat to the lens after the molds and gaskets have been removed from the lens.
SUMMARY OF THE INVENTION
An embodiment of an apparatus for preparing an eyeglass lens is described. The apparatus includes a coating unit and a lens curing unit. The coating unit may be configured to coat either mold members or lenses. In one embodiment, the coating unit is a spin coating unit. The lens curing unit may be configured to direct activating light toward mold members. The mold members are part of a mold assembly that may be placed within the lens curing unit.
Depending on the type of lens forming composition used, the apparatus may be used to form photochromic and non-photochromic lenses. The apparatus may be configured to allow the operation of both the coating unit and the lens curing unit substantially simultaneously.
The coating unit may be a spin coating unit. The spin coating unit may comprise a holder for holding an eyeglass lens or a mold member. The holder may be coupled to a motor that is configured to rotate the holder. An activating light source may be incorporated into a cover. The cover may be drawn over the body of the lens curing unit, covering the coating units. The activating light source, in one embodiment, is positioned, when the cover is closed, such that activating light may be applied to the mold member or lens positioned within the coating unit. An activating light source may be an ultraviolet light source, an actinic light source (e.g., a light source producing light having a wavelength between about 380 nm to 490 mn), a visible light source and/or an infra-red light source. In one embodiment, the activating light source is an ultraviolet light source.
The lens forming apparatus may include a post-cure unit. The post-cure unit may be configured to apply heat and activating light to mold assemblies or lenses disposed within the post-cure unit.
The lens forming apparatus may also include a programmable controller configured to substantially simultaneously control the operation of the coating unit, the lens curing unit and the post-cure unit. The apparatus may include a number of light probes and temperature probes disposed within the coating unit, lens curing unit, and the post-cure unit. These probes preferably relay information about the operation of the individual units to the con
Foreman John T.
Lattis Matthew C.
Powers Galen R.
Heckenberg Donald
MacKey James P.
Meyertons Eric B.
Meyertons Hood Kivlin Kowert & Goetzel P.C.
Q2100, Inc.
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