Patent ID: 12253652

DETAILED DESCRIPTION OF THE INVENTION

The invention therefore concerns a lens having a determined refractive index coated at least partially on at least one surface thereof with an anti-scratch lacquer layer having a refractive index η2lower than η1wherein between said lens and said anti-scratch lacquer layer a coating layer comprising at least 3 sub-layers of at least one compound selected from the group consisting of Zirconium oxide, Silicon oxide, Titanium oxide, Tantalum oxide, Iridium oxide, Silver oxide and Magnesium fluoride is present, and wherein each of said at least 3 sub-layers has a thickness of lower than or equal to 100 nm.

Preferably the lens has a refractive index in the range from 1.50 to 1.90, preferably from 1.70 to 1.90, more preferably is about 1.74.

Preferably said anti-scratch lacquer layer can also be a photochromatic lacquer or a coloured lacquer which has a refractive index lower than that one of the lens. The compounds comprised in the coating layer are Zirconium oxide, Titanium oxide, Silicon oxide, Tantalum oxide, Iridium oxide, Silver oxide and Magnesium fluoride.

Preferably, the at least 3 sub-layers are made of Zirconium oxide, Silicon oxide and Titanium oxide.

These three preferred oxides have different refractive indices.

Zirconium oxide (ZrO2) has a refractive index in the range of 2.05 to 1.95.

Silicon oxide (SiO2) has a refractive index in the range of 1.47 to 1.46.

Titanium oxide (TiO2) may be in form of rutile or anatase. If it is in form of rutile, it has a refractive index of 2.72, while in form of anatase, it has a refractive index in the range of 2.25 to 2.5.

In a preferred and advantageous embodiment of the invention, said coating layer comprises from 3 to 11 sub-layers, preferably from 7 to 9, more preferably 7, being each sub-layer made of a single compound selected from the group consisting of Zirconium oxide, Silicon oxide, Titanium oxide, Tantalum oxide, Iridium oxide, Silver oxide and Magnesium fluoride.

By means of the application/deposition of 3 layers it is possible to drastically reduce the iridescence phenomenon of a lens coated with anti-scratch lacquer. By adding further sub-layers to obtain from 4 to 11, preferably from 7 to 9, more preferably 7 sub-layers, this phenomenon is completely cancelled. In fact, the inventors believe that by adding more than 9 sub-layers, the thickness and therefore the stress on the lens are excessively increased, worsening accordingly the final characteristics of the lens itself. Since the sub-layers-forming compounds have different refractive indices, the layer comprising the at least 3 sub-layers may correspond to a combination of sub-layers having different refractive index, if the sub-layers are made of different compounds.

Preferably said at least 3 sub-layers are different and are combined to form the coating layer of the invention.

In a preferred embodiment of said coating layer the at least 3 sub-layers are present as a combination of the repetition of alternance of a sub-layer of a compound having a higher refractive index and a sub-layer of compound having a lower refractive index than the lens refractive index.

More preferably said coating layer comprises an alternance of sub-layers of compounds, even more preferably said layer comprises from 3 to 11, more preferably 7 sub-layers.

Said coating layer has at least 3 sub-layers having a thickness lower than or equal to 100 nm, more preferably from 2 to 80 nm, even more preferably from 5 to 50 nm. The thickness measurement is determined by the application/deposition technique used in the manufacture of the final lens itself. For example, the PVD (Physical Vapor Deposition) technique.

Without being bond to any theory, the inventors believe that the presence of the coating layer, made of at least 3 sub-layers, more preferably of Zr oxide, Ti oxide or Si oxide, and having a thickness lower than or equal to 100 nm, allows to drastically reduce the iridescence and therefore the formation of the Newton rings for an optical effect.

In an advantageous embodiment the at least 3 sub-layers are made of different compounds.

In a preferred embodiment of said coating layer the at least 3 sub-layers are present as a combination of the repetition of the alternance of a sub-layer of a compound with a higher refractive index and a sub-layer of a compound with a refractive index lower than the lens refractive index.

More preferably, said layer presents an alternance of sub-layers of zirconium and silicon, respectively, having a higher and lower refractive index with respect to the refractive index of the lens.

The coating layer of the invention is therefore present between the lens and the anti-scratch lacquer layer having a refractive index η2lower than η1so that the coated lens has reduced or absent iridescence and Newton's rings.

According to the invention, therefore, the coated lens can be coated at least partially, preferably completely, with an anti-scratch lacquer. In turn, the lens coated with anti-scratch lacquer can be coated with a layer of anti-reflection agent, and/or with a further coating layer with water/oil repellent properties.

Specifically, the inventors hence inserted between the lens, having a refractive index η1, and the anti-scratch lacquer, having a refractive index η2lower than a coating layer, at least partially, on at least one of the two surfaces of the lens, said coating layer comprising at least 3 sub-layers of one or more compounds selected from the group consisting of Zr oxide, Si oxide, Ti oxide, Ta oxide, Ir oxide, Ag oxide and Magnesium fluoride with application techniques which allow to obtain sub-layers having a thickness of lower than or equal to 100 nm, preferably in the range from 2 to 80 nm. In this way the inventors are able to drastically reduce or completely cancel the iridescence generated by the difference of the refractive indices determined by the materials used for the preparation of the lens coated with anti-scratch lacquer.

In another aspect, therefore, the invention relates to a method for reducing or eliminating the iridescence phenomenon of a lens having a determined refractive index coated at least partially on at least one surface thereof with a layer of anti-scratch lacquer having a refractive index η2, lower than that of the lens itself, said method comprising the following steps:

a) Providing a lens having a determined refractive index η1;

b) Applying at least partially on at least one of the two surfaces of the lens a coating layer comprising at least 3 sub-layers of at least one compound selected from the group consisting of Zirconium oxide, Silicon oxide, Titanium oxide, Tantalum oxide, Iridium oxide, Silver oxide and Magnesium fluoride by a technique which ensures a thickness of each of said at least 3 sub-layers lower than or equal to 100 nm;
c) Applying on said coating layer obtained in step b) an anti-scratch lacquer layer having a refractive index η2lower than η1.

In step a) a lens having a refractive index is provided. Lenses, preferably common ocular optical lenses, are generally made of materials which have a refractive index on the range from 1.5 to 1.9, preferably 1.7-1.9, more preferably have a refractive index of about 1.74.

As indicated above, in order to considerably reduce the thickness of the lens, especially in presence of high dioptres or other ocular pathologies, it is felt the need to use lenses with a high refractive index. Therefore, ocular optical lenses have commonly refractive indices between 1.7 and 1.9.

In step b) the coating layer is applied at least partially on at least one surface of the lens.

More preferably, said coating layer is applied on the entire surface of the lens, i.e. 100% of at least one surface thereof.

The step b) of the coating layer application/deposition provides for the application/deposition of at least 3 sub-layers of at least one compound selected from the group consisting of Zr oxide, Si oxide, Ti oxide, Ta oxide, Ir oxide, Ag oxide and Magnesium fluoride.

In an advantageous embodiment of the invention, the application/deposition technique, which ensures a thickness of each of said at least 3 sub-layers lower than or equal to 100 nm, is a technique having a deposition precision of at least 0.5 nm of thickness, such as for example PVD (Physical Vapor Deposition).

However, other application/deposition techniques such as ALD (Atomic Layer Deposition), CVD (Chemical Vapor Deposition), PECVD (Plasma Enhanced Chemical Vapor Deposition) may be envisaged.

In a preferred and advantageous embodiment of the invention said sub-layers of at least one compound selected from the group consisting of Zirconium oxide, Silicon oxide, Ti oxide, Ta oxide, Ir oxide, Ag oxide and Magnesium fluoride are from 3 to 11, preferably 7-9, more preferably 7. Each sub-layer comprises at least one single compound selected from the group consisting of Zirconium oxide, Silicon oxide, Titanium oxide, Tantalum oxide, Iridium oxide, Silver oxide and Magnesium fluoride.

Since zirconium, silicon and titanium oxides exhibit different refractive indices, step b) can provide for the application/deposition of the layer as application/deposition phase of at least 3 sub-layers as a combination of sub-layers having different refractive indices.

In a preferred embodiment of the method of the invention the sub-layers of a compound are applied as a combination of the repetition of the alternance of a sub-layer of a compound with a higher refractive index and a sub-layer of a compound with a lower refractive index than the lens refractive index.

Among the compounds for the layer with refractive index higher than the refractive index of a common lens, can be mentioned Zirconium oxide, Titanium oxide and Tantalum oxide.

Among the compounds for the layer having lower refractive index than the refractive index of a common lens, silicon oxide and magnesium fluoride can be mentioned.

Therefore, on a surface of the lens provided in step a), there may be present sub-layers of a compound, each of which with a thickness lower than or equal to 100 nm, applied in step b) by means of an application/deposition technique having a deposition precision of 0.5 nm, preferably PVD.

For example, on an optical lens a layer comprising a zirconium oxide sub-layer having a higher refractive index than the lens refractive index can be applied, subsequently a silicon oxide sub-layer having a refractive index lower than the lens refractive index and again a Zirconium layer, having a refractive index higher than the refractive index of the lens. This combination of sub-layers can therefore be advantageously repeated 2 to 3 times, preferably 2. In step c), the anti-scratch lacquer layer having a refractive index lower than the lens refractive index can then be applied on the coating layer, thus obtaining a coated lens with reduced or null iridescence.

In the method of the invention, in step c) an anti-scratch lacquer is preferably applied in micrometre thicknesses, more preferably from 1 to 4 micrometres. The lacquer thicknesses are also determined by the application technique of the lacquer itself, for example with an immersion lacquering plant.

In a further preferred embodiment of the invention, when a lens, having a refractive index coated according to the invention with a layer of one or more compounds and with an anti-scratch lacquer having a refractive index lower than that one of the lens, is further coated with a further layer having refractive index different from the lens and from the anti-scratch lacquer, such as an anti-reflection upper coating, and/or a top coat with water/oil repellent properties on the anti-scratch lacquer layer, the invention provides for a step d) of application/deposition of said further coatings.

The invention will now be described with reference to two embodiments of the coated lens of the invention and of the method of the invention for illustrative and non-limiting purposes thereof.

EXPERIMENTAL PART

Example 1

A MR-174 lens having a refractive index of 1.74 was provided.

By means of the PVD technique, using the PVD Satis 900 DL instrument in vacuum conditions at 1.0×10−5mbar, the following oxide sub-layers were deposited in sequence, on one of the two lens surfaces in order to form the final coating layer:

Refractive IndexLensCoating Layer1.74Thickness (nm)Zirconium dioxide (ZrO2)1.95-2.0510.0Silicon dioxide (SiO2)1.46-1.4725.0Zirconium dioxide (ZrO2)1.95-2.0521.2Silicon dioxide (SiO2)1.46-1.4739.3Zirconium dioxide (ZrO2)1.95-2.0515.5Silicon dioxide (SiO2)1.46-1.4749.8Zirconium dioxide (ZrO2)1.95-2.055.0

The anti-scratch lacquer Crystal Coat MP 1154 D from SDC having a refractive index of 1.51 was then applied on the coating layer, until a final thickness of the lacquer layer of 4000.0 nm by means of the Dipping Immersion Lacquering plant from SCL.

FIG.1shows the scheme of the prepared lens with the coating layer and the anti-scratch lacquer. Specifically, the layer indicated with1is the lens, the four Zirconium oxide sub-layers of the coating layer (preferably with refractive index of 2.05) are indicated with number2, the three Silicon oxide sub-layers of the coating layer (preferably with a refractive index of 1.46) are indicated with number3, the anti-scratch lacquer layer is indicated with number4.

The lens thus coated with also the anti-scratch lacquer was evaluated for the iridescence phenomenon using a Shimadzu UV-2401 PC spectrophotometer.

At the same time, a comparison was made, i.e. the same lens coated with the same anti-scratch lacquer according to the prior art, namely not having the coating layer of the invention.

FIG.2shows the evaluation results of the interference of both coated lenses, i.e. both the one of the lens coated according to the invention (continuous line) and the one of the prior art (dashed line). As can be seen fromFIG.2, remarkable interferences appeared in the lens coated according to the prior art, while the interference was practically absent in the lens of the invention.

Since after application of the lacquer layer, a layer of material having anti-reflection properties is usually applied in order to improve the transmittance of the lens and the aesthetic effect of the lens thereof in presence of frontal illumination, an anti-reflection treatment consisting of 4 alternating layers of titanium oxide (Ti3O5) and silicon oxide (SiO2) has been applied both on the lens of the prior art and on the lens of the invention.

Above both lenses a top coat as a water/oil repellent was applied.

FIG.3shows the scheme of the lens coated according to the invention and also coated with an anti-reflection layer and a top coat.

FIG.3shows hence the scheme of the prepared lens with coating layer, anti-scratch lacquer, anti-reflection layer and top coat. Specifically, the layer indicated with1is the lens, the four Zirconium oxide sub-layers of the coating layer (preferably with refractive index of 2.05) are indicated with number2, the three Silicon oxide substrates of the coating layer (preferably with a refractive index of 1.46) are indicated with number3, the anti-scratch lacquer layer is indicated with number4, the anti-reflection layer is indicated with number5and the top layer is indicated with number6.

Specifically, the final lens structure with the coating layer of the invention was:

Refractive IndexLensThickness (nm)Coating Layer1.74/Zirconium dioxide (ZrO2)2.05-1.9510.0Silicon dioxide (SiO2)1.47-1.4625.0Zirconium dioxide (ZrO2)2.05-1.9521.2Silicon dioxide (SiO2)1.47-1.4639.3Zirconium dioxide (ZrO2)2.05-1.9515.5Silicon dioxide (SiO2)1.47-1.4649.8Zirconium dioxide (ZrO2)2.05-1.955.0Anti-scratch Lacquer Layer1.514000Anti-reflection Layer (Green)MultiCoat STDTitanium dioxide (Ti3O5)2.259.0Silicon dioxide (SiO2)1.46728.0Titanium dioxide (Ti3O5)2.25112.0Silicon dioxide (SiO2)1.46782.0Top Coat (W/O repellent)1.365.0

The comparison lens was the same lens but without the coating layer of the invention.

FIG.4shows the interference evaluation of both lenses, i.e the one of the invention (continuous line) having the coating layer and the one of the prior art as comparison (dashed line). The benefit of the treatment to reduce iridescence was thus evident fromFIG.4, where in case of the prior art lens (dashed line) the interferences were increased due to the successive further coating layers. The lens according to the invention, on the other hand, was advantageously free of interference.

The inventors noticed that the elimination of iridescence caused by the anti-scratch lacquer allowed to improve not only the final aesthetic properties of the lens, but also its transmittance properties in presence of frontal light.