OPTICAL ARTICLE WITH ANTIBACTERIAL FUNCTION

Abstract

The invention relates to an optical article, such as an ophthalmic lens, comprising a transparent substrate with a front main face and a rear main face, at least one of its main faces being coated with a multilayer interference coating, such as a mirror coating or an antireflective coating, which is the top coating of the article, wherein the outermost layer of the top coating comprises a material having antibacterial properties, or wherein the outermost layer of the top coating is a porous layer and the layer directly underneath the outermost layer of the top coating is a layer comprising a material having antibacterial properties.

Claims

1. An optical article comprising a transparent substrate with a front main face and a rear main face, at least one of its main faces being coated with a multilayer interference coating which is the top coating of the article, wherein the outermost layer of the top coating comprises a material having antibacterial properties, or wherein the outermost layer of the top coating is a porous layer and the layer directly underneath the outermost layer of the top coating is a layer comprising a material having antibacterial properties.

2. The optical article according to claim 1, wherein the layer comprising a material having antibacterial properties consists in the material having antibacterial properties.

3. The optical article according to claim 1, wherein the layer comprising a material having antibacterial properties consists in a composite material comprising at least 1vol% of the material having antibacterial properties and at most 99vol% of a matrix material.

4. The optical article according to claim 3, wherein the composite material comprises between 1vol% and 10vol% of the material having antibacterial properties and between 99vol% and 90vol% of the matrix material.

5. The optical article according to claim 3, wherein the composite material comprises at least 50vol% of the material having antibacterial properties and at most 50vol% of the matrix material.

6. The optical article according to claim 1, wherein the outermost layer of the top coating has a refractive index of at least 1.55, wherein the refractive index is expressed at 25° C. and at a wavelength of 510 nm.

7. The optical article according to claim 1, wherein the material having antibacterial properties has a refractive index of at least 1.55 wherein the refractive index is expressed at 25° C. and at a wavelength of 510 nm.

8. The optical article according to claim 1, wherein the material having antibacterial properties is chosen from Al, Ca, Co, Ni, Cu, Zn, Mo, Pd, Ag, W, their oxides and mixtures thereof.

9. The optical article according to claim 1, wherein the porous layer is mesoporous.

10. The optical article according to claim 1, wherein the porous layer comprises SiO2 or ZrO2.

11. The optical article according to claim 1, wherein the top coating is an antireflective coating.

12. The optical article according to claim 11, wherein the outermost layer of the top coating comprises the material having antibacterial properties and does not consist in metal.

13. The optical article according to claim 12, further comprising a metal layer placed directly underneath the outermost layer of the top coating. .

14. The optical article according to claim 11, wherein the outermost layer of the top coating is a porous layer and the layer comprising a material having antibacterial properties placed directly underneath the outermost layer of the top coating has a refractive index of at least 1.6.

15. The optical article according to claim 1, wherein the top coating is a mirror coating.

Description

[0062] According to the invention, a material is said to have antibacterial properties if the anti-microbial activity R of said material is greater than 2 for at least E. Coli and S. Aureus. The anti-microbial activity is evaluated by application of the Japanese International Standard (JIS) Z 2801 as follows:

[0063] The test microorganism is prepared, usually by growth in a liquid culture medium.

[0064] The suspension of test microorganism is standardized by dilution in a nutritive broth (this affords microorganisms the potential to grow during the test).

[0065] Control and test surfaces are inoculated with microorganisms, in triplicate, and then the microbial inoculum is covered with a thin, sterile film. Covering the inoculum spreads it, prevents it from evaporating, and ensures close contact with the antimicrobial surface.

[0066] Microbial concentrations are determined at “time zero” by elution followed by dilution and plating.

[0067] A control is run to verify that the neutralization/elution method effectively neutralizes the antimicrobial agent in the antimicrobial surface being tested.

[0068] Inoculated, covered control and antimicrobial test surfaces are allowed to incubate undisturbed in a humid environment for 24 hours.

[0069] After incubation, microbial concentrations are determined. The reduction of microorganisms relative to initial concentrations and the control surface is calculated.

[0070] The anti-microbial activity R is defined as: R = log(B/C), B being the average value of the number of active bacteria after 24h of exposition to the control and C being the average value of the number of active bacteria after 24h of exposition to the material being tested.

[0071] The materials having antibacterial properties preferably used in the present invention can be deposited as a layer on a substrate by physical vapor deposition under vacuum. In this way, optical articles of the invention can be produced by taking advantage of the reliability of vacuum coating methods in providing smooth and uniform coatings.

[0072] Physical vapor deposition under vacuum preferably is performed according to any of the following methods: [0073] i) by, optionally ion-beam assisted, evaporation; [0074] ii) by ion-beam sputtering; [0075] iii) by cathode sputtering; [0076] iv) by plasma-assisted chemical vapor deposition.

[0077] These various methods are described in the following references “Thin Film Processes” and “Thin Film Processes II”, Vossen & Kern, Ed., Academic Press, 1978 and 1991, respectively. A particularly recommended method is the evaporation under vacuum. Preferably, the deposition of each of the layers of the antireflective coating is conducted by evaporation under vacuum.

[0078] Preferably, the materials having antibacterial properties to be used in the invention adhere well on the inorganic layers generally used in multilayer interference coatings.

[0079] In some embodiments, the material having antibacterial properties to be used in the invention is a material with a high refractive index, for example its refractive index is of at least 1.55, for example of at least 1.6, for example of at least 1.7, for example of at least 1.8, for example of at least 1.9, wherein the refractive index is expressed at 25° C. and at a wavelength of 510 nm.

[0080] The materials having antibacterial properties to be used in the optical articles of the invention are preferably chosen from AI, Ca, Co, Ni, Cu, Zn, Mo, Pd, Ag, W, their oxides and mixtures thereof.

[0081] For example, the material having antibacterial properties is chosen from oxides of aluminum, such as AI2O3, oxides of copper, such as CuO or Cu2O, oxydes of zinc, such as ZnO, oxides of silver, such as AgO or Ag2O and mixtures of oxides of zinc and oxides of calcium.

[0082] For example, the material having antibacterial properties is a mixture of ZnO and CaO and the molar ratio ZnO/CaO is comprised between 2 and 0.5, preferably wherein the molar ratio ZnO/CaO is comprised between 1.2 and 0.8, more preferably wherein the molar ratio ZnO/CaO is 1.

[0083] As defined herein, an oxide is a chemical compound whose chemical formula contains at least one oxygen atom and one other element.

[0084] In JIS Z 2801, the anti-microbial activity R is measured 24 h after inoculation, the kinetics of the bactericidal activity is therefore not taken into account. Kawakami et al. (ISIJ International, Vol. 48 (2008), No. 9, pp. 1299-1304) have shown however that among the metals cited in the list above, Cu and Ag are the quickest to act in terms of antibacterial activity.

[0085] According to the invention, where the multilayer interference coating is an antireflective coating, silver or copper layers are preferentially used as the layer comprising the material having antibacterial properties in those embodiments where a porous layer is the top layer of the top coating. In these embodiments, silver or copper layers are positioned directly underneath the porous layer. In these embodiments, silver or copper layers used as the layer comprising the material having antibacterial properties preferentially have a thickness comprised between 6 nm and 20 nm, more preferably said metal layer has a thickness comprised between 7 nm and 15 nm.

[0086] The most common design of antireflective coatings involves an alternation of HI layers and LI layers, wherein the outermost layer is a LI layer. However most materials having antibacterial properties, in particular those that are not metals, are HI materials. Metals on the other hand tend to have an important extinction coefficient, meaning that they absorb in the visible and therefore limit the transmission of light through the optical article.

[0087] Most materials having antibacterial properties, which can be deposited as a layer on a substrate by physical vapor deposition under vacuum are thus unsuitable for use as the outermost layer of the antireflective coating in conventional antireflective coatings. It makes it difficult to design antireflective coatings with both good antibacterial properties and good optical properties.

[0088] The present invention provides various solutions to the problem of designing an antireflective coating with good antibacterial properties and good optical properties. Two solutions have already been disclosed herein, namely the use of composite materials for the layer comprising the material having antibacterial properties and the use of a porous layer as the outermost layer of the top coating with the layer comprising the material having antibacterial properties placed directly underneath said porous layer.

[0089] Indeed, when the layer comprising the material having antibacterial properties consists in a composite material, said composite material can have a low index of refraction and at the same time comprise a metal having antibacterial properties or a material of high refractive index having antibacterial properties.

[0090] In the case of porous layers, the solution is provided by the simple fact that the layer comprising the material having antibacterial properties is no longer the outermost layer of the antireflective coating. The porous layer can very easily be designed to be a LI layer. The presence of the pores lowers the index of the porous layer compared to the index of the material constituting the porous network. Moreover it is possible to use a low index material, for example SiO2, for the material constituting the porous network. In this way, the invention provides alternating HI and LI layers (the HI layer is the layer comprising the material having antibacterial properties) with a LI layer as the outermost layer in the antireflective coating.

[0091] Thus in one embodiment of the invention there is provided an optical article wherein the multilayer interference coating is an antireflective coating and wherein the outermost layer of the top coating is a porous layer which is a LI layer and the layer comprising a material having antibacterial properties is placed directly underneath the outermost layer of the top coating and is a HI layer, for example it has a refractive index of at least 1.6.

[0092] A third solution to the technical problem above is provided by an embodiment of the optical article of the invention, wherein the multilayer interference coating is an antireflective coating and the outermost layer of the top coating comprises a material having antibacterial properties that does not consist in metal, for example the outermost layer of the top coating can consist in a metal oxide or in a mixture of metal oxides or in HI composite material, for example a HI composite material comprising at least 50 vol% of the material having antibacterial properties and at most 50 vol% of a matrix material.

[0093] Preferably, in this embodiment, the optical article of the invention further comprises a metal layer placed directly underneath the outermost layer of the top coating. Preferably, said metal layer consists in Cu, Ag, Au or mixtures thereof. Preferably, said metal layer has a thickness comprised between 6 nm and 20 nm, more preferably said metal layer has a thickness comprised between 7 nm and 15 nm.

[0094] The applicant has found that when metal layer are placed directly underneath the outermost layer of the top coating it becomes possible to obtain good antireflective properties even when said outermost layer has a high refractive index. Metal layers however should neither be too thin nor too thick. Under a certain thickness, for example 6 nm or 7 nm, it becomes difficult to deposit a continuous layer of metal. When metal layers are discontinuous, plasmon resonance modifies their optical properties and makes it more difficult to predict the properties of the coating containing said discontinuous metal layers. Over a certain thickness, the absorptive properties of the metal are detrimental to the transmission factor of the optical article.

Examples

[0095] The optical properties of the materials used in the examples are presented in table 1.

TABLE-US-00001 Material n@510 nm (refractive index) k@510 nm (extinction coefficient) SiO2 1.47 0.00 ZnO/CaO (1:1) 1.98 0.00 ZrO2 2.00 0.00 Ag 0.14 2.76 Au 0.75 1.85 Cu 1.12 2.60 AI2O3 1.66 0.00 CuO 2.55 0.66 SiO2 (99%)-Cu (1%) 1.49 0.02 SiO2 (95%)-Cu (5%) 1.57 0.13

[0096] In all following examples, Rv (defined above in the description) is evaluated for an angle of incidence of 15° and for one face of the optical article.

[0097] Calculations are performed with standard software, such as MacLeod version 10.

[0098] Table 2 presents examples of optical articles of the invention wherein the multilayer interference coating is an antireflective coating and wherein the top layer of the antireflective coating consists in a material having antibacterial properties.

[0099] Table 3 presents examples of optical articles of the invention wherein the multilayer interference coating is an antireflective coating and wherein the top layer of the antireflective coating consists in a composite material comprising a material having antibacterial properties.

[0100] Table 4 presents examples of optical articles of the invention wherein the multilayer interference coating is a mirror coating and wherein the top layer of the antireflective coating consists in a material having antibacterial properties.

[0101] For the examples in table 4, the substrate is made of CR 39® (ORMA® ophthalmic lenses, sold by the applicant) and are coated with a polyurethane latex primer coating and a polysiloxane based hard coating as in EP0614957, example 3 (Mithril® hardcoat by Essilor International). Such an association substrate - hard coat has a Rv of 4% for one face.

TABLE-US-00002 Example 1 Example 2 Substrate and hardcoat refractive index 1.5 1.6 Antireflective coating Layer 1 ZrO2 - 77 nm ZrO2 - 20 nm Layer 2 Cu - 9 nm SiO2 - 36 nm Layer 3 ZnO/CaO (1:1) -51 nm ZrO2 - 82 nm Layer 4 -- Au - 10 nm Layer 5 -- ZnO/CaO (1:1) -40 nm Properties of the article Rv 0.7% 1.1% Tv 85% 90% C* 60 9 h 309 ° 30 °

TABLE-US-00003 Example 3 Example 4 Substrate and hardcoat refractive index 1.5 1.5 Antireflective coating Layer 1 ZrO2 - 28 nm ZrO2 - 69 nm Layer 2 SiO2 - 29nm SiO2(99%)-Cu(1%) - 95 nm Layer 3 ZrO2 - 58 nm -- Layer 4 SiO2(99%)-Cu(1%) - 90 nm -- Properties of the article Rv 0.8% 0.9% Tv 95% 69% C* 10 30 h 135° 310°

TABLE-US-00004 Example 5 Example 6 Substrate and hardcoat refractive index 1.5 1.5 Mirror coating Layer 1 SiO2 - 69 nm SiO2 - 95 nm Layer 2 ZrO2 - 65 nm ZrO2 - 178 nm Layer 3 SiO2 - 101 nm SiO2 - 126 nm Layer 4 ZrO2 - 65 nm CuO - 6 nm Layer 5 AI2O3 - 18 nm -- Properties of the article Rv 22% 7% Tv 77% 78% C* 5 37 h 187° 260°