Coating processes – Direct application of electrical – magnetic – wave – or... – Polymerization of coating utilizing direct application of...
Reexamination Certificate
2002-09-20
2004-11-02
Seidleck, James J. (Department: 1711)
Coating processes
Direct application of electrical, magnetic, wave, or...
Polymerization of coating utilizing direct application of...
C427S508000, C427S162000, C427S402000, C427S407100, C522S006000, C522S024000, C522S150000, C522S153000, C522S157000, C522S163000, C522S178000, C522S181000, C522S182000, C264S001700, C264S001320, C264S001360, C264S001380, C264S001800, C264S002600, C264S496000, C252S582000, C252S583000, C252S586000
Reexamination Certificate
active
06811830
ABSTRACT:
The present invention relates to photochromic articles including optical articles such as sunglasses, spectacles and piano lenses, windows, vehicle and aircraft transparencies, plastic film and coating. The present invention relates in particular to photochromic articles and to preparation thereof from organic polymerisable compositions.
Photochromic articles contain a photochromic dye which undergoes a reversible colour change when exposed to light of a certain wavelength particularly in the UV and visible ranges of the electromagnetic spectrum. The classes of known photochromic dyes include naphthopyrans and fulgides, spirooxazine chromenes and others.
Photochromic articles may be prepared by imbibing a transparent polymeric articles with a photochromic substance such as described in U.S. Pat. Nos. 4,286,957 and 5,130,353 or by casting the lens with an incorporated photochromic material as described in U.S. Pat. No. 4,851,471.
One problem of photochromic articles which has hindered their widespread acceptance is fatigue. Repeated exposure to light causes photochromic articles to exhibit reduced photochromic properties. Also customers who use photochromic articles particularly sunglasses prefer that the development of colour (activation) is rapid when the article is exposed to direct sun light and that the reverse process (fade) is also relatively rapid on moving from sunlight.
We have now found that the activation and fade properties are improved if the photochromic dye is incorporated into an optical article at an intermediate stage in the curing process.
Accordingly we provide a process for manufacture of a photochromic polymeric article comprising
providing a fluid polymerisable composition;
subjecting the fluid polymerisable composition to a first curing step to provide a solid article of intermediate hardness;
contacting the solid article of intermediate hardness with a photochromic substance; and
subjecting the solid article of intermediate harness to a further curing step to increase the hardness and provide a polymeric article imbibed with the photochromic substance.
The process of the invention includes partly curing a fluid polymerisable composition to form a solid article. The process may and generally will include casting of the fluid polymerisable composition using a suitable mould. The photochromic article is typically a shaped article such as a sheet, film or lens. Alternatively, though less, preferably the process may involve applying the polymerisable composition as a coating or shaping it by other means such as extrusion or other suitable methods.
The degree of curing which takes place prior to contacting the solid article with a photochromic substance will depend on the compound, the type of article and its intended application. The first curing step will generally provide a solid shaped article which preferably has sufficient integrity to allow it to maintain its shape during treatment with the photochromic substance. Where the article is cast using a mould it is preferred that the fast curing step provide sufficient hardness to allow it to be removed from the mould without being deformed. The hardness of the intermediate product will typically be governed by the mechanical handling required to prepare the article for contact with the photochromic substance and second curing stage. The final hardness will depend on the intended use of the product. In the case of lens materials the photochromic article will typically be cured to allow the lens to be worked for example by cutting and polishing for use in spectacles or other optical applications.
The first and second curing steps may be conducted by thermal curing, radiation curing or a combination thereof. The method of carrying out the first curing step on further curing step may be chosen to ensure that the first curing step does not activate full cure.
In a particularly preferred embodiment the second curing step comprises thermal curing of the polymeric composition. In this embodiment the polymerisable composition will typically include thermal polymerisation initiator and the composition is heated to a temperature to provide curing in the presence of the thermal polymerisation initiator. The further curing step will typically also be at a temperature which provides inbibition of the photochromic substance.
The extent of polymerisation which occurs before incorporating the photochromic material may be measured by the percentage of double bond conversion. The change in percentage conversion of the fluid polymerisable composition between the article of intermediate hardness and photochromic article (ie the change brought about by the further curing step) is typically in the range of from 5 to 30% and preferably 10 to 20%. The photochromic material is most preferably incorporated into a polymer having a double bond conversion of from 70 to 85% (preferably 77 to 83%) and the further curing provides a double bond conversion of at least 88% preferably at least 90% more preferably 92% and most preferably from 92 to 94%.
There are a number of known curing methods which may be used to effect the first curing step and further curing step. The appropriate technique may depend on the components of the polymerisable composition and the required properties. Radiation polymerisation, for example by electron beam, or ultraviolet radiation may be used. Where curing is produced by ultraviolet radiation the composition may include one or more compounds for initiating polymerisation in the presence of UV light or otherwise sensitising the composition to produce initiation in UV light. Preferably the first curing step involves radiation curing and the further curing step is by thermally initiated polymerisation.
Accordingly in a particularly preferred embodiment of the invention the fluid polymerisable composition is a photopolymer composition further comprising a thermal polymerisation initiator and the first curing step includes subjecting the fluid polymerisable composition to radiation curing and the further curing step comprises heating the article of intermediate hardness to temperature sufficient to provide thermal polymerisation in the presence of said thermal polymerisation initiator.
The further polymerisation step is preferably conducted at a temperature in the range of from 100 to 180° C. and more preferably in the range of from 120 to 150° C. The further curing step may include heating the article of intermediate hardness to a temperature of 80 to 120° C. to more fully react any photo-generated radials and then increasing the temperature to about 135° C. to provide thermal polymerisation.
Examples of UV initiators which may be used in the preferred embodiment include benzophenone, benzoin ethers, dimethoxy-&agr;-phenylacetophenone, diethoxyacetophenone, &agr;-hydroxy-&agr;,&agr;-dialkylacetophenones, acylphosphine oxides, salts of organic carboxylates and sulfonates, cyclic photoinitiators such as cyclic benzoin ethers and benzil ketones, Michlers ketones, ketocoumarins and combinations thereof. The preferred photoinitiators photosensitisers are selected from acylphosphine oxides, benzoin ethers and mixtures thereof. A specific example of preferred photoinitiators are 2,4,6-trimethylbenzoyidiphenylphosphine oxide (available under the trade name LUCIRIN TPO) and methylphenylglyoxylate (Vircure 55), bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide (Irgacure 819); 1-bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide and mixtures thereof.
The amount of photoinitiator used in the polymerisable composition cure system is normally less than that used to fully cure the lens composition by itself. Typically, the amount can be halved, or even less. It may be less than 0.5%. The presence of thermal initiator for the further cure step can compensate for an amount of photoinitiator less than needed to provide the desired final hardness.
In an alternative embodiment the first curing step is conducted by thermal curing at a first temperature and the further curing step is conducted at a second temperature whic
Bubner Raymond K.
Chen Fang
Gieslinski Bohdan Grzegorz
Lewis David Andrew
Toh Huan Kiak
Burns Doane , Swecker, Mathis LLP
McClendon Sanza L.
Seidleck James J.
Sola International Holdings Ltd.
LandOfFree
Photochromic article and method of preparation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Photochromic article and method of preparation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photochromic article and method of preparation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3345001