Polarized ophthalmic lenses and methods for making same

Details Polarized ophthalmic lenses and methods for making same Polarized ophthalmic lenses and methods for making same

1999-09-03

2001-01-23

Vargot, Mathieu D. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Optical article shaping or treating

Light polarizing article or holographic article

C264S001700, C264S002700, C264S001320

Reexamination Certificate

active

06177032

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to polarized ophthalmic lenses and to methods for making such lenses. More particularly, the invention relates to polarized ophthalmic lenses which are produced by: (1) constructing a light polarizing sub-laminate, (2) vacuum forming the light polarizing sub-laminate into a substantially spherically-shaped shell, and (3) laminating the shell to a lens blank.
BACKGROUND OF THE INVENTION
Ophthalmic lenses incorporating light-polarizing films are well known and have been produced for some time. Such lenses are used in sunglasses, sports goggles, fashion eyewear, and the like. The lenses can be prescription lenses with a net optical power or plano lenses with no net power, including decentered plano lenses (see, for example, Houston et al., U.S. Pat. No. 5,648,832). The light polarizing film performs the important function of reducing sun glare, including sun glare from water and snow.
Unfortunately, the incorporation of light polarizing properties into ophthalmic lenses in a cost effective and efficient manner has proved to be a technical challenge, especially for plastic lenses composed of such materials as polycarbonates, allyl diglycol carbonates (ADC), and acrylics. Various proposals directed to this problem can be found in, for example, Hovey, U.S. Pat. No. 4,043,637, Kawaki et al., U.S. Pat. No. 5,051,309, Murata et al., U.S. Pat. No. 5,702,813, Bhalakia et al., U.S. Pat. No. 5,757,459, PCT Patent Publication No. WO 97/38345, and co-pending and commonly assigned U.S. patent application Ser. No. 08/637,360, filed Apr. 25, 1996, and entitled “Polarized Plastic Laminates,” the contents of all of which are incorporated herein by reference.
One method which has been used to manufacture polarized lenses involves laminating or gluing a pre-formed piece of polarized sheet to the outer convex surface of a glass or plastic lens blank which is then edged and inserted into suitable eyeglass frames. Polarized sheets for these applications have had a three layer sandwich construction, the two outer layers being cellulose acetate butyrate and the center layer being a thin polyvinyl alcohol polarizing film. The overall sheet thickness has been in the range of 0.010″-0.030″. As a result, lenses produced by this approach have generally been too thick and have not been widely used. Also, their optical properties have generally been poor as a result of the thickness of the polarized sheet.
PCT Patent Publication No. WO 97/38345, referred to above, discloses a process for producing polarized lenses by laminating polarizing sheets to or between flat sheets of plastic materials such as acrylic, styrene or polycarbonate. The laminates are then heat and pressure formed to the desired lens curvature.
Light-polarizing lenses have also been produced by placing a pre-formed piece of a thin polarizing film into a glass or metal mold which is then filled with a thermosetting plastic monomer, such as an allyl diglycol carbonate (e.g., CR-39), followed by polymerization or curing to produce a lens. In this process, the monomer surrounds and thus encapsulates the polarizing film. After removal from the mold, the lens is ground, edged and finished into a prescription or sunglass lens.
Polycarbonate lenses for all types of eyewear have recently become increasingly popular because of their ease of manufacture, light weight, and high impact and shatter resistance. The increased usage of polycarbonate lenses for eyewear has been driven both by fashion and safety concerns, especially in connection with lenses which are to be worn during sports activities.
A process has been developed for the manufacture of injection molded polarized polycarbonate lenses in which a disc of pre-formed polycarbonate polarized sheet, approximately 0.028″ thick, is placed into and in contact with the concave cavity of a polished steel mold which is then closed and injected with polycarbonate resin to form a lens. The molten polycarbonate fuses to the rear concave polycarbonate surface of the polarized sheet thus forming a lens.
Many problems exist with this process which result in high costs and low yields. For example, forming the polycarbonate polarized sheet is difficult and requires expensive tooling to obtain the correct curve to match the polished steel cavity. Moreover, the polycarbonate polarized sheet must be able to withstand the high temperatures necessary to injection mold the polycarbonate resin. Most polarized sheets or films decompose at these temperatures, which results in reduced polarizer efficiency and/or low manufacturing yields.
In addition, it is very difficult to mold polycarbonate lenses of this type without creating residual birefringence which reduces or destroys polarizing efficiency. In particular, excessive shrinkage of the molded “sandwich” produces birefringence in the finished lens, as well as optical distortion. In addition to the foregoing problems, the mold cavities needed for this process are expensive to build and require a high degree of maintenance.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of this invention to provide improved methods for producing polarized ophthalmic lenses.
More particularly, it is an object of the invention to provide simple and efficient methods for producing polarized ophthalmic lenses which methods have some and preferably all of the following properties: 1) the methods produce lenses having good polarizing efficiency, 2) the methods produce lenses having a low level of birefringence, 3) the methods produce lenses having excellent optical properties, 4) the methods can be used to produce lenses having a wide range of base curves, including high base curves, e.g., 8 or 9 base curves, 5) the methods can be used to produced optically corrected decentered lenses, including optically corrected decentered lenses having high base curves, 6) the methods can be used to produce colored lenses, 7) the methods can be used to produce lenses which include a UV absorber, 8) the methods can be used to produce thin lenses, and 9) the methods can be used to produce polycarbonate lenses.
It is also an object of the invention to provide improved polarized ophthalmic lenses having some and preferably all of the above properties.
To achieve these and other objects, the invention in accordance with certain of its aspects provides a method for producing a light polarizing sub-laminate
6
comprising:
(a) providing a sheet which comprises in order (i) a light polarizing layer
2
comprising a stretched polyvinyl alcohol film containing a polarizing dye, (ii) an isotropic support layer
1
for the light polarizing layer, and (iii) a protective removable skin
8
, e.g., an EVA-coated polyethylene sheet;
(b) treating the light polarizing layer
2
with a siloxane coupling agent, e.g., an amino-organo-silane coupling agent;
(c) laminating a polyurethane layer
3
to the treated light polarizing layer
2
; and
(d) forming at least one curved cavity, specifically, a spherically-shaped or substantially spherically-shaped cavity, in the sheet by supporting the sheet on a plate
10
having at least one opening
12
, heating the sheet, and applying a vacuum to the protective removable skin
8
to “drop” the sheet into the opening.
In accordance with others of its aspects, the invention provides a method for producing a light polarizing subassembly comprising:
(a) providing a mold having at least one concave precision mold cavity, e.g., a cavity formed by a polished glass or metal mold insert;
(b) inserting a light polarizing sub-laminate
6
having a first surface and a second surface into the precision mold cavity with the first surface contacting the concave precision mold cavity and the second surface defining a concave cavity for receiving a lens blank;
(c) inserting a lens blank
4
into the concave cavity defined by the second surface, e.g., a spherical, cylindrical, and/or aspherical lens blank; and
(d) autoclaving the light polarizing sub-laminate
6
and the lens blank to form the light polarizing subassembly

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