Optical article with gradient photochromism
View Patent ↗The present invention is drawn to an optical article comprising: (a) a photochromic substrate comprising at least one photochromic dye, and (b) an interference coating having a specific gradient thickness providing for a gradient reflectance. It also pertains to a process for making such an optical article.
1. An optical article comprising:
(a) a photochromic substrate having two opposite sides and comprising at least one photochromic dye, wherein said photochromic substrate has a first surface portion and a second surface portion which are located on opposite ends of the same side of said photochromic substrate,
(b) an interference coating having a gradient thickness, such that its thickness decreases from a highest thickness region located on said first surface portion to a lowest thickness region located on said second surface portion, wherein the difference between the mean reflectance factor of the highest thickness portion and the mean reflectance factor of the lowest thickness portion, in the wavelength range of from 330 to 380 nm, ranges from 15 to 80%.
2. The optical article according to claim 1 , wherein the lowest thickness ranges from 80% to 90% of the highest thickness.
3. The optical article according to claim 1 , which is an ophthalmic lens.
4. The optical article according to claim 1 , wherein the photochromic substrate is based on polycarbonate, or on a (co)polymer of diethyleneglycol bis(allylcarbonate) or on (meth)acrylic copolymers having a refractive index between 1.54 and 1.58.
5. The optical article according to claim 1 , wherein the interference coating comprises from 4 to 8 layers, comprising at least two layers with a low refractive index and at least two layers with a high refractive index which are arranged alternately.
6. The optical article according to claim 1 , wherein the optical article further includes at least one coating selected from: a primer, an anti-abrasion coating, an antistatic layer, an anti-fog topcoat and an anti-fouling topcoat.
7. The optical article according to claim 1 , wherein the interference coating has throughout its surface a mean reflectance factor, in the wavelength range of from 400 to 700 nm, which is less than 3% and preferably less than 2%.
8. The optical article according to claim 1 , wherein the thickness of the antireflection coating varies, preferably monotonously, from the highest thickness region to the lowest thickness region, along an axis which is vertical in normal conditions of use of the optical article.
9. Spectacles comprising at least one ophthalmic lens comprising:
(a) a photochromic substrate having two opposite sides and comprising at least one photochromic dye, wherein said photochromic substrate has a first surface portion and a second surface portion which are located on opposite ends of the same side of said photochromic substrate,
(b) an interference coating having a gradient thickness, such that its thickness decreases from a highest thickness region located on said first surface portion to a lowest thickness region located on said second surface portion, wherein the difference between the mean reflectance factor of the highest thickness portion and the mean reflectance factor of the lowest thickness portion, in the wavelength range of from 330 to 380 nm, ranges from 15 to 80%.