OPTICAL ARTICLE HAVING A REFLECTIVE COATING WITH HIGH ABRASION-RESISTANCE

Abstract

Disclosed is an optical article including a substrate having at least one main face coated with a reflective coating including a stack of at least one high refractive index layer having a refractive index higher than 1.55 and at least one low refractive index layer having a refractive index of 1.55 or less, in which the thicknesses of the layers in the reflective coating have been optimized according to specific design rules in order to boost the abrasion resistance of the optical article.

Claims

1-16. (canceled)

17. An optical article comprising a substrate having at least one main face coated with a reflective coating in the visible range comprising a stack of at least one high refractive index layer having a refractive index greater than 1.55 and at least one low refractive index layer having a refractive index of 1.55 or less, wherein: a) The reflective coating comprises at least four layers and The outermost low refractive index layer of the reflective coating has a thickness Tho of at least 10 nm, The outermost high refractive index layer of the reflective coating has a thickness of 75 nm or less, The penultimate low refractive index layer of the reflective coating has a thickness Thp of at least 150 nm, The penultimate high refractive index layer of the reflective coating has a thickness ranging from 5 nm to 90 nm, Tho/4+Thp≥200 nm, or b) The reflective coating has three layers and The outermost layer of the reflective coating is a low refractive index layer having a thickness of 70 nm or less, The penultimate layer of the reflective coating is a high refractive index layer having a thickness of 50 nm or less, The first layer of the reflective coating is a low refractive index layer having a thickness of at least 200 nm.

18. The optical article of claim 17, having a Bayer value determined in accordance with the ASTM F735-81 standard greater than or equal to 5.5.

19. The optical article of claim 17, wherein the reflective coating has a number of layers greater than or equal to four, and the outermost low refractive index layer has a thickness of at least 70 nm.

20. The optical article of claim 17, wherein the reflective coating has a number of layers greater than or equal to four, and the outermost low refractive index layer has a thickness ranging from 130 nm to 300 nm.

21. The optical article of claim 17, wherein the reflective coating has a number of layers greater than or equal to four, and the penultimate low refractive index layer has a thickness ranging from 175 nm to 400 nm.

22. The optical article of claim 17, wherein the reflective coating has a number of layers greater than or equal to four, and the penultimate high refractive index layer has a thickness ranging from 10 nm to 40 nm.

23. The optical article of claim 17, wherein the reflective coating has a number of layers greater than or equal to four, and the penultimate low refractive index layer is thicker than the outermost low refractive index layer.

24. The optical article of claim 17, wherein the reflective coating has three layers, and the first layer has a thickness ranging from 200 nm to 400 nm.

25. The optical article of claim 17, wherein a) The reflective coating comprises at least four layers and The outermost low refractive index layer of the reflective coating has a thickness of at least 200 nm, The outermost high refractive index layer of the reflective coating has a thickness of 40 nm or less, The penultimate low refractive index layer of the reflective coating has a thickness of at least 220 nm, The penultimate high refractive index layer of the reflective coating has a thickness ranging from 5 nm to 40 nm, or b) The reflective coating has three layers and The outermost layer of the reflective coating is a low refractive index layer having a thickness of 50 nm or less, The penultimate layer of the reflective coating is a high refractive index layer having a thickness of 50 nm or less, The first layer of the reflective coating is a low refractive index layer having a thickness of at least 250 nm.

26. The optical article of claim 17, wherein a) The reflective coating comprises at least four layers and The outermost low refractive index layer of the reflective coating has a thickness of at least 230 nm, The outermost high refractive index layer of the reflective coating has a thickness of 25 nm or less, The penultimate low refractive index layer of the reflective coating has a thickness of at least 300 nm, The penultimate high refractive index layer of the reflective coating has a thickness ranging from 5 nm to 20 nm, or b) The reflective coating has three layers and The outermost layer of the reflective coating is a low refractive index layer having a thickness of 50 nm or less, The penultimate layer of the reflective coating is a high refractive index layer having a thickness of 35 nm or less, The first layer of the reflective coating is a low refractive index layer having a thickness of at least 250 nm.

27. The optical article of claim 17, wherein the mean light reflection factor on said at least one main face in the visible region Rv is greater than or equal to 8%.

28. The optical article of claim 17, wherein the reflective coating has a number of layers lower than or equal to 10.

29. The optical article of claim 17, wherein the reflective coating has a thickness ranging from 300 nm to 1 μm.

30. The optical article of claim 17, wherein the high refractive index layers having a refractive index greater than 1.55 represent less than 20% of the thickness of the reflective coating.

31. The optical article of claim 17, wherein the high refractive index layers having a refractive index greater than 1.55 represent less than 15% of the thickness of the reflective coating.

32. The optical article of claim 17, wherein the reflective coating does not comprise any high refractive index layer having a thickness greater than or equal to 105 nm.

33. The optical article of claim 17, wherein the optical article is an ophthalmic lens.

34. The optical article of claim 17, wherein the reflective coating has at least one layer comprising Ti.sub.3O.sub.5.

Description

EXAMPLES

1. General Procedures

[0127] The articles employed in the examples comprise a 65 mm-diameter polythiourethane MR8® lens substrate (from Mitsui Toatsu Chemicals Inc., refractive index=1.59), with a power of −2.00 diopters and a thickness of 1.2 mm, coated on its convex face with the impact resistant primer coating based on a W234™ polyurethane material disclosed in the experimental part of WO 2010/109154 (modified to have a refractive index of 1.6 by addition of high refractive index colloids), the abrasion- and scratch-resistant coating (hard coat) disclosed in example 3 of EP 0614957 (modified to have a refractive index of 1.6 rather than 1.5 by adding high refractive index colloids), a reflective coating, and the antifouling coating disclosed in the experimental section of patent application WO 2010/109154, obtained by evaporation under vacuum of the Optool DSX® compound marketed by Daikin Industries (thickness: from 2 to 5 nm).

[0128] The various layers were deposited without heating the substrates, by vacuum evaporation, optionally assisted (IAD) during the deposition by a beam of oxygen and possibly argon ions, when specified (evaporation source: electron gun), and optionally under pressure regulation by supplying (passive) O.sub.2 gas into the chamber, where indicated.

[0129] The vacuum evaporation device that made it possible to deposit the various reflective layers was a Leybold LAB1100+ vacuum coater having two systems for evaporating materials, an electron gun evaporation system and a thermal evaporator (Joule-effect evaporation system), and a KRI EH 1000 F ion gun (from Kaufman & Robinson Inc.), for use in the preliminary phase of preparation of the surface of the substrate by argon ion bombardment (IPC) and in the ion-assisted deposition (IAD) of the layers.

2. Preparation of the Optical Articles

[0130] The lenses were placed on a carrousel provided with circular openings intended to accommodate the lenses to be treated, the concave side facing the evaporation sources and the ion gun.

[0131] The method for producing optical articles comprises introducing the lens substrate provided with the primer and abrasion-resistant coatings into a vacuum deposition chamber, conducting a pumping step until a high vacuum was created, followed by an ion gun conditioning step (IGC, such as disclosed in FR 2957454, 3.5×10.sup.−5 mBar as starting pressure, 140 V, 3.5 A, argon, 60 seconds), a substrate surface activation step using a bombardment with an argon ion beam (IPC) with an average pressure of 1.8×10.sup.−4 mBar (the ion gun was set to an anode current discharge of 1.7 A, 110 V, 60 seconds, gas flow: 10 sccm of argon), stopping the ionic irradiation, and then successively evaporating the required number of layers (reflection coating layers and antifouling coating) at a rate ranging from 2 to 3 nm/s (0.4 nm/s for the antifouling coating), and lastly a ventilation step. High refractive index layers were obtained by evaporating ZrO.sub.2 pellets without O.sub.2 pressure or the substoichiometric titanium oxide (“stabilized Ti.sub.3O.sub.5”) supplied by Merck.

[0132] The deposition conditions of a representative optical article (example 4) were as follows: a deposition step of a HI layer (ZrO.sub.2) under a pressure of 6.10.sup.−5 mBar, a deposition step of a LI layer (SiO.sub.2) under a pressure of 2.4×10.sup.−5 mBar, a deposition step of a HI layer (ZrO.sub.2) under a pressure of 6.1×10.sup.−5 mBar, a surface activation step of this ZrO.sub.2 layer using an argon ion beam (same treatment as IPC already conducted directly on the substrate, except for the treatment time: 30 seconds, the average pressure: 1.6×10.sup.−4 mBar and the anode tension: 125 V), a deposition step of a LI layer (SiO.sub.2) under a pressure of 1.8×10.sup.−5 mBar, and lastly a deposition step of an Optool DSX® layer. All the layers were deposited without adding gas in the vacuum chamber during deposition.

3. Testing Methods

[0133] The following test procedures were used to evaluate the optical articles prepared according to the present invention. Several samples for each system were prepared for measurements and the reported data were calculated with the average of the different samples.

[0134] Colorimetric measurements (reflective factor Rv, measured in reflection) of the face coated with the stack of the invention were carried out with a Zeiss spectrophotometer, taking into account the standard illuminant D65, and the standard observer 10°. They are provided for an angle of incidence of 15°.

[0135] Abrasion resistance was determined as disclosed in WO 2012/173596. Specifically, abrasion resistance was measured by means of the sand Bayer test, in accordance with the ASTM F735-81 standard, 1 week after production of the article.

[0136] The inventors noticed that the Bayer value of the article is decreasing after it has been manufactured. It is preferable to measure the value after stabilization, e.g., at least 1 week after it has been manufactured. In this application, the Bayer values for the examples have been measured 1 week after the articles have been manufactured.

4. Results

[0137] The structural characteristics, optical and mechanical performances of the ophthalmic lenses obtained in the examples are detailed hereunder. The thickness mentioned is the total thickness of the reflective stack.

TABLE-US-00001 Example 1 (comparative) Example 2 Example 3 Substrate + primer/hard coat Substrate + primer/hard coat Substrate + primer/hard coat ZrO.sub.2 4 nm ZrO.sub.2 8 nm ZrO.sub.2 20 nm SiO.sub.2 164 nm SiO.sub.2 260 nm SiO.sub.2 228 nm ZrO.sub.2 (a) 32 nm ZrO.sub.2 (a) 36 nm ZrO.sub.2 (a) 32 nm SiO.sub.2 176 nm SiO.sub.2 184 nm SiO.sub.2 192 nm Top coat Top coat Top coat Sand Bayer 4.8 Sand Bayer 5.5 Sand Bayer 5.8 Thickness (nm) 376 Thickness (nm) 488 Thickness (nm) 472 HI layers %  9.6% HI layers %    9% HI layers %   11% thickness thickness thickness Tho/4 + Thp 208 nm Tho/4 + Thp 306 nm Tho/4 + Thp 276 nm Example 4 Example 5 Example 6 (comparative) Substrate + primer/hard coat Substrate + primer/hard coat Substrate + primer/hard coat ZrO.sub.2 48 nm ZrO.sub.2 32 nm SiO.sub.2 184 nm SiO.sub.2 196 nm SiO.sub.2 296 nm ZrO.sub.2 (a) 12 nm ZrO.sub.2 (a) 28 nm ZrO.sub.2 (a) 32 nm SiO.sub.2 264 nm SiO.sub.2 248 nm SiO.sub.2 248 nm Top coat Top coat Top coat Sand Bayer 7.0 Sand Bayer 5.5 Sand Bayer 4.2 Thickness (nm) 508 Thickness (nm) 504 Thickness (nm) 576 HI layers % 11.8% HI layers % 11.9% HI layers %  5.6% thickness thickness thickness Tho/4 + Thp 250 nm Tho/4 + Thp 258 nm Example 7 Example 8 Example 9 Substrate + primer/hard coat Substrate + primer/hard coat Substrate + primer/hard coat SiO.sub.2 150 nm ZrO.sub.2 12 nm ZrO.sub.2 12 nm ZrO.sub.2 40 nm SiO.sub.2 300 nm SiO.sub.2 300 nm SiO.sub.2 276 ZrO.sub.2 (a) 24 nm ZrO.sub.2 (a) 24 nm ZrO.sub.2 (a) 16 nm SiO.sub.2 240 nm SiO.sub.2 240 nm SiO.sub.2 248 nm Top coat Top coat Top coat Sand Bayer 7.1 Sand Bayer 7.1 Sand Bayer 7.0 Thickness (nm) 576 Thickness (nm) 726 Thickness (nm) 580 HI layers %  6.3% HI layers %    5% HI layers %  9.7% thickness thickness thickness Tho/4 + Thp 360 nm Tho/4 + Thp 360 nm Tho/4 + Thp 338 nm Example 10 Example 11 Example 12 (comparative) Substrate + primer/hard coat Substrate + primer/hard coat Substrate + primer/hard coat ZrO.sub.2 48 nm SiO.sub.2 276 nm SiO.sub.2 300 nm SiO.sub.2 284 nm ZrO.sub.2 (a) 68 nm ZrO.sub.2 (a) 36 nm ZrO.sub.2 (a) 68 nm SiO.sub.2 12 nm SiO.sub.2 36 nm SiO.sub.2 132 nm Top coat Top coat Top coat Sand Bayer 5.8 Sand Bayer 8.4 Sand Bayer 3.5 Thickness (nm) 404 Thickness (nm) 372 Thickness (nm) 484 HI layers % 28.7% HI layers % 9.7% HI layers %   14% thickness thickness thickness Tho/4 + Thp 279 nm Example 13 (comparative) Example 14 (comparative) Example 15 (comparative) Substrate + primer/hard coat Substrate + primer/hard coat Substrate + primer/hard coat ZrO.sub.2 100 nm ZrO.sub.2 104 nm SiO.sub.2 100 nm SiO.sub.2 59 nm ZrO.sub.2 24 nm ZrO.sub.2 100 nm ZrO.sub.2 64 nm SiO.sub.2 52 nm SiO.sub.2 140 nm SiO.sub.2 103 nm ZrO.sub.2 (a) 82 nm ZrO.sub.2 (a) 10 nm ZrO.sub.2 (a) 30 nm SiO.sub.2 143 nm SiO.sub.2 100 nm SiO.sub.2 219 nm Top coat Top coat Top coat Sand Bayer 3.5 Sand Bayer 4.0 Sand Bayer 5.2 Thickness (nm) 301 Thickness (nm) 550 Thickness (nm) 579 HI layers % 35.2% HI layers % 38.2% HI layers % 34.2% thickness thickness thickness Tho/4 + Thp 88 nm Tho/4 + Thp 165 nm Tho/4 + Thp 158 nm Example 16 (comparative) Example 17 Example 18 (comparative) Substrate + primer/hard coat Substrate + primer/hard coat Substrate + primer/hard coat Ti3O.sub.5 6 nm Ti3O.sub.5 8 nm SiO.sub.2 59.82 nm SiO.sub.2 57.81 nm Ti3O.sub.5 7.25 nm Ti3O.sub.5 9.5 nm SiO.sub.2 (b) 150 nm SiO.sub.2 273.55 nm SiO.sub.2 135.13 nm ZrO.sub.2 (a) 17 nm Ti3O.sub.5 52.76 nm Ti3O.sub.5 25.77 nm SiO.sub.2 34 nm SiO.sub.2 12 nm SiO.sub.2 187.26 nm Top coat Top coat Top coat Sand Bayer 6.9 Sand Bayer 6.4 Sand Bayer 5.2 Thickness (nm) 201 Thickness (nm) 411.38 Thickness (nm) 423.47 HI layers %  8.5% HI layers %  16% HI layers % 10.2% thickness thickness thickness Tho/4 + Thp 276.55 nm Tho/4 + Thp 181.94 nm (a) Ionic bombardment treatment of the layer surface before depositing the next layer. (b) Oxygen supply during deposition.

[0138] Optical articles having a reflective stack with thicknesses according to the invention exhibit better abrasion resistance than comparative articles, while keeping a similar level of reflection performance. For instance, the article of example 11 exhibits a better abrasion resistance than the article of example 16, for a same color of reflected light (silver). Comparative articles, which do not comply with the rules of design mentioned in the present application, exhibit quite low Bayer values.

[0139] A comparison of examples 7 and 8 shows that adding an additional 150-nm thick layer of silica as a ground layer to a 4-layer stack has no effect on the sand Bayer performance. This could be explained by the fact that the reflective coating was already sufficiently thick (almost 600 nm thick).

[0140] Some Bayer values obtained are higher than or equal to 7, which indicates a very high level of abrasion resistance. It should be noted that a difference of 1-2 points in the Bayer values is highly significant.