WO2006086279A1

WO2006086279A1 - Deep inhibited photochromic articles and their method of making

Info

Publication number: WO2006086279A1
Application number: PCT/US2006/004045
Authority: WO
Inventors: Ronald C. Wiand
Original assignee: Softlight, Inc.
Priority date: 2005-02-08
Filing date: 2006-02-07
Publication date: 2006-08-17

Abstract

In accordance with the method of the present invention, an article is made by polymerizing a cross-linkable pre-polymer to a gel state to form a substrate of a partially cured polymeric matrix which is then stopped from further curing and then inhibited from further curing and infused with a photochromic moiety.

Description

DEEP INHIBITED PHOTO CHROMIC ARTICLES AND THEIR METHOD OF MAKING

Background of the Invention

The present invention relates to polymeric articles and to a method of making polymeric articles. In a preferred embodiment, the present invention relates to transparent polymeric articles and particularly to optical lenses comprising a photochromic moiety.

Although the present invention is broadly applicable to organic polymeric articles it is particularly useful in conjunction with photochromic articles such as photochromic optical lenses. Photochromic molecules and uses for photochromic molecules have been known for many years. For example, lens manufacturers have developed photochromic glass lenses and photochromic plastic lenses which have been commercially successful. Eyeglasses having photochromic lenses have been popular for many years and are both aesthetically pleasing and functional. Photochromic lenses protect eyes because they have the ability to adjust the density of their tint. They are quite transparent and can be worn during low light conditions but they darken when exposed to sunlight or UV light. It is, of course, the photochromic material which has been added to, or coated onto, the lens which changes state under different light conditions to give the lens its photochromic nature.

Although glass lenses with photochromic characteristics are advantageous, organic polymeric lenses with photochromic characteristics are even more advantageous. Such plastic lenses are relatively lighter in weight and can be thinner and more resistant to shattering than glass lenses. Although high quality plastic lenses fashioned from so called optical quality resins, are not as hard as glass, the lenses can be coated with a scratch resistant coating and are then both optically clear and scratch resistant. There remains a need, however, for improvements in incorporating photochromic molecules into plastic lenses. The photochromic molecules used in plastic lenses are relatively large in size and are difficult to incorporate into a polymerized plastic polymeric matrix. Difficulties also arise if the polymeric matrix interferes with the changing of states of the photochromic molecule.

Several different techniques are known for adding photochromic material to plastic lenses. In the "casting" technique, the photochromic material is added to a polymerizable optical quality monomer before polymerization and then the mixture is cast in a mold wherein the monomer is polymerized to provide a full body photochromic lens which is a homogeneous mixture of polymer and photochromic material throughout the lens. However, this technique encounters difficulties with regard to providing a lens having even tint or shading from the center of the lens to its edge. If the lens is an ophthalmic lens having a relatively thin optical center area and a relatively thick edge area, the thin center of the lens will have less photochromic additive and will tend to be lighter than the thicker edge.

One variation of casting technique is taught in United States Patent No. 5,882,556 which issued on March 16, 1999 to Perrott et al. for "Method of Preparing Photochromic Article." In the Perrott et al. method, a cross-linkable polymeric casting composition is subjected to a partial cure, such that the polymer reaches or exceeds its point of gelation, then the partially cured polymer is contacted with a photochromic composition, and the gelled polymer is finish cured. This method has shortcomings, for example, with respect to cracking of finished lenses, which the present invention overcomes.

Another known technique for adding photochromic material to a plastic lens is the "imbibing" technique in which a photochromic material is added to a plastic lens by first polymerizing an optical quality monomer in a mold until polymerization is substantially complete, and then contacting the lens surface with a photochromic material which is imbibed or diffused into the lens surface. This technique provides a layer of photochromic material of consistent depth and thus avoids the problem associated with a lens having a variation in thickness. For example, US. Patent 5,730,911 March 24, 1998 to Cano et al. discloses a process wherein a composition is polymerized in a mould under conditions such that at least one thin surface layer is polymerized to a degree of progression and/or cross-linking which is appreciably lower than that of the remainder of the substrate and then a photochromic substance is diffused into the thin surface layer. Imbibing techniques, however, tend to be relatively complex and expensive and also tend to be a slow processes which are capital intensive and not suitable to be economically carried out in the optical wholesale laboratories which presently surface and edge lenses for most wearers of ophthalmic glasses.

Another technique for rendering an eyeglass lens to be photochromic is a "coating" technique. For example, one coating method involves depositing photochromic molecules onto a lens from a bipolar mixture of solvent and photochromic molecules and then heating the resultant lens and coating to the melting point of the molecules. A hard coating is then applied over the coating of photochromic molecules to protect the molecules and provide scratch resistance. This technique, however, has met with only limited success.

In short, there remains a need for further improvements in techniques or methods for providing articles such as lenses with photochromic characteristics. There is a need for a process that provides large enough spaces within a substrate to accept relatively large photochromic molecules and allow the molecules to freely change state to thereby exhibit the full range of their photochromic performance. Furthermore, there remains a need for lower cost methods which are suitable fc(^κse in articles such as planar lenses and inexpensive reading lenses as well as in relatively expensive ophthalmic lenses. There remains a need for further improvements in the longevity of the photochromic characteristic of the lenses. Presently known plastic photochromic lenses have a limited useful life. Thus, it would be desirable to have a process which provides a photochromic feature having a long useful life. It also would be desirable to have a process which provided a plastic photochromic lens which improved resistance to damage to its photochromic nature due to repeated or long exposure to heat or light. It also would be desirable to have a lens or other article with increased speed in changing from the activated to the non-activated state. The present invention provides an improved method for imparting photochromic qualities to plastic articles and provides an improved photochromic plastic article. The present invention is useful to make all sorts of photochromic articles or products, and such articles and products are within the broad scope of the invention disclosed herein. However, the present invention is particularly well suited for use in making lenses for eyeglasses. The lenses of this invention can be given a photochromic feature in a small optical laboratory without use of complex or expensive equipment or process steps to provide a photochromic lens that rapidly changes state, is resistant to damage due to heat or light, and has a long life expectancy. Further understanding of this invention will be had from the following disclosure taken in conjunction with the claims and drawing.

Brief Summary of the Invention

In accordance with the present invention, an article has a substrate comprised of a cross-linked organic polymer matrix. The polymeric matrix is relatively porous because it is not fully cured. Thus, the matrix readily accepts diffusion of a photochromic moiety therein. In a preferred embodiment, the article is transparent or semi-transparent. In a most preferred embodiment, the article is an optical lens.

In accordance with the method of the present invention, an article is made by the steps of: polymerizing a cross-linkable pre-polymer to a gel state to form a substrate of a partially cured polymeric matrix;

intervening to substantially stop further curing of said polymeric matrix;

substantially inhibiting further curing of said polymeric matrix; and infusing an effective amount of a photochromic or other desired moiety into said polymeric matrix.

In one preferred embodiment of the present invention, the method is used to make a transparent article. In another preferred embodiment of the present invention the method is used to make a lens. In a particularly preferred method, the cross-linkable pre- polymer is a cured to a gel state in a lens mold and then further curing is stopped by lowering the temperature of the polymeric matrix to or below its glass transition temperature. The polymeric matrix is then removed from the mold and substantially inhibited from further cure by exposing-the martix to oxygen. Then at least a surface region of the matrix is infused or imbibed with a photochromic moiety.

Detailed Description of the Invention

The present invention is a substrate comprised of an incompletely cured organic polymeric matrix. The substrate is obtained by a method wherein prepolymer is polymerized to a gel state and then the reaction is substantially completely stopped by, for example, quenching or lowering the temperature to at or below the glass transition temperature of the gelled polymeric matrix. Then further reaction is inhibited, for example, by exposing the polymerica matrix to oxygen. This provides a porous materical suitable for imbibing or diffusion of a moiety such as a photochromic moiety therein.

It will be appreciated by those skilled in the art that the present invention is broadly applicable to make substrates which may be used in conjunction with many different photochromic products or articles of manufacture. Examples of products which can comprise or include substrates of this invention include but are not limited to window panes, such as window panes in homes or other energy efficient buildings or solar structures, sun roofs, windshields or lights for automobiles, signs, compact discs, digital audio discs, and plastic optical articles generally. While it is contemplated that most advantage will be taken from use of this invention in transparent or semi- transparent products, this invention can be used to make products that are not transparent, where, for example it may be desired to reduce reflection, or to darken or change the color or appearance of the product. Many different products or articles may be produced with a desirable photochromic effect. All of these products are considered to be within the broad scope of the present invention.

A preferred embodiment of this invention is a photochromic plastic optical lens. Another preferred embodiment is a photochromic eyeglass frame. A further preferred embodiment is a photochromic eyeglass frame with photochromic lenses. Where the embodiment is a lens, the lens may be an ophthalmic lens or a planar lens. Planar lenses are generally of consistent thickness. Ophthalmic lenses may be spherical or aspheric, monofocal, bifocal, trifocal, multifocal, invisible multi-focal or progressive, semifinished or finished piano blank for sunglasses and do not have a consistent thickness from center to edge. Ophthalmic lenses are relatively difficult to coat or infuse with a photochromic moiety to obtain a consistent photochromic effect. In accordance with the present invention, however, a consistent photochromic layer of consistent thickness can be provided in an ophthalmic lens. Of course, it should be noted that in some cases it may be desirable to have a gradient effect in a lens, i.e., greater darkening in a top of the lens than the bottom of the lens. This effect can also be achieved within the scope of this invention.

The products of the present invention can be made by the method of the present invention which comprises the steps of:

polymerizing a cross-linkable pre-polymer to a gel state to form a substrate of a partially cured polymeric matrix;

intervening to substantially stop further curing of said polymeric matrix;

substantially inhibiting further curing of said polymeric matrix; and

infusing an effective amount of a photochromic or other desired moiety into said polymeric matrix. In one preferred embodiment of the present invention, the method is used to make a transparent article. In another preferred embodiment of the present invention the method is used to make a lens. In a particularly preferred method, the cross-linkable pre-polymer is a cured to a gel state in a lens mold and then further curing is stopped by lowering the temperature of the polymeric matrix to or below its glass transition temperature. The polymeric matrix is then removed from the mold and substantially inhibited from further cure by exposing the martix to oxygen. Then at least a surface region of the matrix is infused or imbibed with a photochromic moiety.

As used herein, the term prepolymer includes monomelic moieties as well as oligomers, dimmers, etc. The prepolymer is polymerized and cross-linked during initial curing to form a gelled polymeric substrate. Suitable pre-polymers are well known and may be ultraviolate cross-linkable pre-polymers, radiation cross-linkable pre-polymers or thermally cross-linkable pre-polymers. Initiation of polymerization and/or cross-linking may be by ultraviolet or electron beam radiation or heat or a combination thereof.

For an optical quality lens, the present method requires an optical quality polymerizable pre-polymer having an index of refraction between 1.45 and 1.90. Suitable pre-polymers for use in making lenses are liquid and must be placed in a desired lens mold before initiation of polymerization. Examples of suitable pre-polymers include monomers, homopolymers and copolymers of polyol(allyl carbonate) monomers, homopolymers and copolymers of polyfunctional acrylate monomers, polyacrylates, poly(alkylacrylates) such as polymethylmethacrylate), cellulose acetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, poly(vinyl acetate), poly(vinyl alcohol), poly(vinyl chloride), poly(vinylidene chloride), polyurethanes, polycarbonates, poly(ethylene-terephthalate), polystyrene, copoly(styrene- methylmethacralate), copolyCstyrene-acrylonitdrile), poly(vinylbutyral), and homopolymers and copolymers of diallylidene pentaerythritol, such as copolymers with polyol(allyl carbonate) monomers, e.g. diethylene glycol bis(allyl carbonate), and acrylate monomers. Transparent copolymers and blends of the transparent polymers are suitable as matrix materials. Preferred pre-polymers are diethlene glycol Bis (allyl carbonate), (CR-39) monomer. Of course, it is contemplated that the polymerizable pre- polymer will be a composition which may comprise other components as is conventional in the art. For example, a suitable composition may include a polymerization initiator, a cross-linking agent, a UV absorber, or other additives conventionally used in the manufacture of lenses. Suitable pre-polymers, initiators, cross-linking agents, additives and other lens materials for use in the present invention are disclosed in United States Patent No. 5,882,556, March 16, 1999 to Perrott et al. which is specifically incorporated by reference herein.

While any suitable molecular moiety may be imbibed or diffused into the polymeric matrix, especially preferred moieties are photochromic molecules. Suitable photochromic moieties are well-known in the art and include those selected from the group consisting of anthraquinones, naphtopyrans, phhalocyanines, spiro-oxazines, chromenes, pyrans including spiro-pyrans and fulgides. Suitable photochromic molecules include but are not limited to those disclosed in United States Patents Nos. 5,882,556 March 16, 1999 to Perrott et al. which is specifically incorporated by reference herein. In addition to photochromic molecules, the photochromic composition may include a non-photochromic dye if it is desired to provide^" a tint to the lens even when the photochromic molecules are not activated. UV stabilizers and antioxidants may be added to enhance the life of the lens.

One preferred embodiment of the present invention is a method for making a photochromic lens. In accordance with this method, a mold is prepared by filling it with pre-polymer liquid composition. Curing of the prepolymer is begun by heating or otherwise initiating curing as is conventional in the art and disclosed, for example, in the aforementioned United States Patent No. 5,882,556. When the pre-polymer composition has cured to its point of gelation, i.e. to a substrate having a gelatinous state, the curing is substantially stopped by, for example, quenching the mold in cold water to stop further curing of the polymer in the mold. Preferably, the partially cured polymeric matrix is cooled down to or below its glass transition temperature to stop further curing of the polymer. After the curing reaction is substantially stopped, the substrate is inhibited so that when heated to above its glass transition temperature little further curing will occur. Several different means can be employed to inhibit further curing. For example, where the reaction is a free radical reaction, the substrate can be taken out of the mold and exposed to oxygen. A suitable source of oxygen is the atmosphere. Preferably, the substrate is simultaneously inhibited and annealed by heating the substrate in the presence of air. Alternatively, inhibition can be accomplished by using diphenylamine (DPA), tert-butyl catechol (TBC), copper chloride, parabenzoquinone, butylated hydroxy toluene (BTH) or any other agent that will inhibit or block the free radical reaction. In accordance with the present invention, inhibition preferably extends throughout or substantially throughout the substrate although it is generally acceptable to have minimal or no inhibition in the center of the substrate.

The substrate is then ready to receive any desired moiety such as a photochromic moiety. Photochromic molecules can be infused or permeated into the entire substarate or into a surface layer portion of the substrate by contacting the layer with a solution of photochromic molecules. The photochromic moiety can be brought into contact with a surface or surfaces of the substrate to accomplish its permeation therein by various methods including, but not limited to, coating a solution containing the photochromic moiety onto the surface of the substrate, applying a layer of polymeric film having the photochromic moiety dissolved or suspended therein to the surface of the substrate and then heating the film near to but below the melting point of the photochromic moiety for a time sufficient to incorporate the photochromic moiety into the surface layer, or any of the methods for incorporating photochromic compounds into a surface of a host material disclosed in United States Patent No. 5,066,818 November 19, 1991 to Gemert et al. for "Photochromic Naphtopyran Compounds" which patent is specifically incorporated by reference herein.

Further understanding of the present invention will be had from the following examples. Example 1

Diethylene glycol bis(allyl carbonate) (CR39) monomer from PPG is mixed and prepolymerized for 1 minute at 5O⁰C with an aliphatic peroxy initiator diisoproypyl peroxydicarbonate. Mixing is continued for a further 12 hours while lowering the temperature to 5°C. The polymerizable mixture is introduced into a glass mold sized to produce a 70mm round by 2mm thick piano lens blank. The mold is then placed in a curing oven at a temperature of 78° C. After 12 hours the mixture reaches a gelled state and the mold is removed from the oven and placed in chilled water having a temperature of 5⁰C for 30 minutes whereupon the substrate mixture is cooled and the curing reaction is substantially stopped. The substrate is then removed from the mold and placed in an oven while exposed to the atmosphere for 12 hours at a temperature of 80⁰C. The substrate is removed from the oven and found to have good physical properties suitable for use as an optical lens and to have a porous structure with interstitial spaces well suited to absorb a molecular moiety such as a photochromic moiety. The lens has a high degree of inhibited progression of cure that is between 200 and 600 microns deep from all surfaces and the mean size of all openings in the lens are within 5 microns and + or - 5 pores per mm².

Example 2

One planar surface of the lens of Example 1 is contacted with a photochromic solution which imbibes, absorbs or infuses photochromic moieties into the porous surface layer. The photochromic solution is Reversacal Corn yellow from Keystone Aniline Corporation. The resultant lens exhibits superior Photochromic qualities. It is then treated with UV inhibitors and scratch resistant coated to enhance the life of the Photochromic effect and the scratch resistance of the treated lens

Example 3

The procedure of Example 1 is followed except that the monomer and initiator are mixed for 15 minutes at 12°C and then mixed for 14 hours while lowering the temperature of the mixture to 2⁰C. After the substrate mixture has been chilled in the water at 5⁰C, the mixture is placed in a freezer for 12 hours and then baked in the presence of oxygen (atmosphere) for 4 hours at 80°C. Then the procedures of Example 2 are followed to produce a photochromic lens.

Example 4

The procedure of Example 2 is followed except that the lens is contacted with photochromic material Reversacal Midnight Gray from Keystone Aniline Corporation.

Example 5

The procedure of Example 1 is followed except that the lens is contacted with photochromic material Reversacal Berry Red from Keystone Aniline Corporation.

Example 6

The procedure of Example 1 is followed except that the monomer and initiator are mixed for 1 minute at 40⁰C and then mixed for 14 hours while lowering the temperature of the mixture to 5⁰C. After the substrate mixture has been chilled in the water at 5⁰C, the mixture is placed in a freezer for 12 hours. Before introducing the prepolymerized monomer into the mold it is mixed with 100 ppm fo MEHQ and then baked in the presence of oxygen (atmosphere) for 16 hours gradually increasing the 70⁰C. Then the procedures of Example 2 are followed to produce a photochromic lens.

Claims

What is claimed is:

1. A substrate made by the process of

Intervening to substantially stop further curing of said polymeric matrix; and

Substantially inhibiting further curing of said polymeric matrix.

2. The substrate of claim 1 wherein an effective amount of a photochromic moiety has been infused therein.

3. The substrate of claim 2 wherein said intervening step is carried out by quenching the polymer to a temperature no greater than its glass transition temperature.

4. The substrate of claim 2 wherein said intervening is carried out by cooling said polymeric matrix.

5. The substrate as in claim 3 wherein said inhibiting is carried out by exposing said substrate to an atmospheric environment.

6. The substrate of claim 3 wherein said substrate is a planar optical lens.

7. The substrate as of claim 3 wherein said polymer is a multifunctional polycarbonate polymer.

8. The substrate of claim 1 wherein said polymer is an acrylic polymer.

9. The substrate of claim7 wherein said photochromic moiety has been infused into a surface layer of said substrate.

10. The substrate of claim 9 wherein said surface layer comprises an amount of photochromic moiety sufficient to be opaque when activated.

11. The substrate of claim 9 wherein said surface has an additional layer thereon.

12. The substrate of claim 2 wherein said substrate is a layer in a laminated article.

13. The substrate of claim 2 wherein said substrate is in operative association with an automotive vehicle.

14. The substrate of claim 2 wherein said substrate is associated with an architectural structure.

15. A method of making a transparent article comprising the steps of:

intervening to substantially stop further curing of said polymeric matrix; and

substantially inhibiting further curing of said polymeric matrix.

16. The method of claim 15 including an additional step of infusing a photochromic moiety into said article. 20. The method of claim 16 including a step of mounting said article as a lens in an eyeglass frame.