Photochromic optical article comprising a saturated photochromic coating and a film absorbing UV radiation
View Patent ↗The invention relates to a photochromic optical article with reduced thermal dependency, comprising: (a) a transparent substrate, (b) a saturated photochromic layer having, in the activated state and at a temperature of 20° C. or greater, a relative transmission factor of less than 1% in the visible range, and (c) an anti-UV coating of plastic material at least partially covering the saturated photochromic layer, the said anti-UV coating containing at least one agent which absorbs UV radiation (anti-UV agent) and is distributed in a pattern consisting of a multitude of points, each having a surface area of less than 0.15 mm 2, the average distance between two neighboring points lying between 0.5 and 2 mm and the ratio of the overall surface area of all the points to the total surface area of the anti-UV coating being such that the relative transmission factor of the optical article in the visible range in the activated state and at 20° C. or greater is at least equal to 5%. The invention also relates to two methods for manufacturing such an optical article.
1. Photochromic optical article comprising:
(a) a transparent substrate,
(b) a saturated photochromic layer having, in the activated state and at a temperature of 20° C., a relative transmission factor of less than 1% in the visible range (Tv), and
(c) an anti-UV coating of plastic material at least partially covering the saturated photochromic layer, the said anti-UV coating containing at least one agent which absorbs UV radiation (anti-UV agent) and is distributed in a pattern consisting of a multitude of points, each having a surface area of less than 0.15 mm 2 , the average distance between two neighbouring points lying between 0.5 and 2 mm, and the ratio of the overall surface area of all the points to the total surface area of the anti-UV coating being such that the relative transmission factor of the optical article in the visible range in the activated state and at 20° C. or more, is at least equal to 5%.
2. Photochromic optical article according to claim 1 , characterized in that the relative transmission factor of the optical article in the visible range in the activated state and at 20° C. or more, is between 5% and 25%.
3. Photochromic optical article according to claim 1 , characterized in that the points which absorb UV radiation have a random distribution or an ordered distribution.
4. Photochromic optical article according to claim 1 , characterized in that the distribution of the points which absorb UV radiation is a regular distribution giving the optical article a uniform transmission to the naked eye.
5. Photochromic optical article according to claim 1 , characterized in that the distribution of the points which absorb UV radiation is denser at certain positions than at others, giving the appearance to the naked eye of a transmission gradient and/or a plurality of separate zones having different transmissions.
6. Photochromic optical article according to claim 1 , characterized in that it is an ophthalmic lens.
7. Method for manufacturing a photochromic article according to claim 1 , characterized in that it comprises the following steps:
depositing a photochromic layer, saturated at 20° C. or more, on a transparent substrate,
manufacturing a film of plastic material containing at least one anti-UV agent distributed in a pattern consisting of a multitude of points, each having a surface area of less than 0.15 mm 2 the average distance between two neighbouring points lying between 0.5 and 2 mm and the ratio of the overall surface area of all the points to the total surface area of the anti-UV coating being such that the relative transmission factor of the optical article in the visible range in the activated state and at 20° C. or more, is at least equal to 5%, and
applying the film of plastic material thus obtained on the photochromic layer.
8. Method according to claim 7 , characterized in that step of manufacturing the film of plastic material comprises:
bringing a transfer sheet containing at least one anti-UV agent in contact with the film of plastic material, and
heating the assembly to a sufficient temperature in order to obtain transfer of the anti-UV agent from the transfer sheet to the film of plastic material.
9. Method according to claim 8 , characterized in that the transfer sheet is impregnated uniformly with the anti-UV agent, and in that the pattern consisting of a multitude of points is formed by virtue of a mask, comprising a multitude of perforations, interposed during the heating step between the transfer sheet and the film of plastic material.
10. Method according to claim 8 , characterized in that the pattern consisting of a multitude of points is formed by printing on the transfer sheet with an ink containing the anti-UV agent, before the transfer sheet and the film of plastic material are brought in contact.
11. Method according to claim 8 , characterized in that the transfer sheet is first formed on the surface of the film of plastic material, then is printed on with an ink containing the anti-UV agent in a pattern consisting of a multitude of points.
12. Method for manufacturing a photochromic optical article according to claim 1 , characterized in that it comprises the following steps:
depositing a photochromic layer, saturated at 20° C., on a transparent substrate,
applying a film of plastic material on the photochromic layer,
introducing into the film of plastic material at least one anti-UV agent in a pattern consisting of a multitude of points, each having a surface area of less than 0.15 mm 2 the average distance between two neighbouring points lying between 0.5 and 2 mm and the ratio of the overall surface area of all the points to the total surface area of the anti-UV coating being such that the relative transmission factor of the optical article in the visible range in the activated state and at 20° C. or more, is at least equal to 5%.
13. Method according to claim 12 , characterized in that the applying the film step comprises:
bringing a transfer sheet containing at least one agent which absorbs UV radiation (anti-UV) in contact with the film of plastic material, and
heating the assembly to a sufficient temperature in order to obtain transfer of the anti-UV agent from the transfer sheet to the film of plastic material.
14. Method according to claim 13 , characterized in that the transfer sheet is impregnated uniformly with the anti-UV agent, and in that the pattern consisting of a multitude of points is formed by virtue of a mask, comprising a multitude of perforations, interposed during the heating step between the transfer sheet and the film of plastic material.
15. Method according to claim 13 , characterized in that the pattern consisting of a multitude of points is formed by printing on the transfer sheet with an ink containing the anti-UV agent, before the transfer sheet and the film of plastic material are brought in contact.
16. Method according to claim 13 , characterized in that the transfer sheet is first formed on the surface of the film of plastic material, then is subsequently printed on with an ink containing the anti-UV agent in a pattern consisting of a multitude of points.