Optical article coated with an antireflection coating comprising a sub-layer partially formed under ion assistance and its manufacturing process

Abstract

The invention relates to an optical article provided with antireflection properties, comprising a substrate having at least one main surface coated with an antireflection coating comprising, starting from the substrate: a sub-layer comprising two adjacent layers formed from the same material, the sum of the thicknesses of the two adjacent layers being greater than or equal to 75 nm; and a multilayered antireflection stack comprising at least one high refractive index layer and at least one low refractive index layer, the deposition of the first of said two adjacent layers of the sub-layer having been carried out without ion assistance and the deposition of the second of said two adjacent layers of the sub-layer having been carried out under ion assistance. The invention also relates to a process for manufacturing such an optical article.

Claims

1. An optical article with antireflection properties, comprising a substrate having at least one main surface coated with an antireflection coating comprising, starting from the substrate: a sub-layer comprising two adjacent layers, the sum of the thicknesses of the two adjacent layers being greater than or equal to 75 nm; and multilayered antireflection stack comprising at least one high refractive index layer and at least one low refractive index layer, wherein the second adjacent layer of the sub-layer is directly deposited upon the first adjacent layer of the sub-layer, wherein the deposition of the first adjacent layer of the sub-layer has been carried out without ion assistance and the deposition of the second adjacent layer of the sub-layer has been carried out under ion assistance, and wherein the sub-layer is deposited on an abrasion- and/or scratch-resistant coating.

2. The article of claim 1, wherein the two adjacent layers of the sub-layer are formed from the same material.

3. The article of claim 1, wherein the thickness ratio of the sub-layer two adjacent layers to each other varies from 9:1 to 1:9.

4. The article of claim 3, wherein the thickness ratio of the sub-layer two adjacent layers to each other varies from 4:6 to 6:4.

5. The article of claim 1, wherein the sum of the thicknesses of the two adjacent layers is greater than or equal to 80 nm.

6. The article of claim 5, wherein the sum of the thicknesses of the two adjacent layers is greater than or equal to 100 nm.

7. The article of claim 6, wherein the sum of the thicknesses of the two adjacent layers is greater than or equal to 150 nm.

8. The article of claim 1, wherein the sub-layer two adjacent layers are SiO.sub.2-based layers.

9. The article of claim 8, wherein the sub-layer two adjacent layers are free of Al.sub.2O.sub.3.

10. The article of claim 8, wherein the sub-layer consists of SiO.sub.2 layers.

11. The article of claim 1, wherein the sub-layer comprises, in addition to the two adjacent layers, from one to three layers interleaved between the substrate and the first adjacent layer of the sub-layer.

12. The article of claim 1, further defined as comprising an ASTM BAYER value greater than or equal to 4.5 of the standard ASTM F 735.81.

13. The article of claim 1, wherein all the low refractive index layers of the multilayered antireflection stack comprise a mixture of SiO.sub.2 and Al.sub.2O.sub.3.

14. The article of claim 1, wherein the abrasion- and/or scratch-resistant coating is a poly(meth)acrylate or an epoxysilane based coating.

15. The article of claim 1, wherein the high refractive index layers of the multilayered stack comprise at least one of TiO.sub.2, PrTiO.sub.3, or ZrO.sub.2, or combinations thereof.

16. The article of claim 1, further defined as an ophthalmic lens.

17. The article of claim 1, wherein the sub-layer is adjacent to a high refractive index layer of said multilayered antireflection stack.

18. The article of claim 1, wherein the sum of the thicknesses of said two adjacent layers of the sub-layer is lower than 250 nm.

19. The article of claim 1, wherein the sub-layer comprises a higher layer and a lower layer adjacent to each other, the sum of the thicknesses of said two adjacent layers being greater than or equal to 75 nm, said higher layer being an SiO2-based layer.

20. The article of claim 1, wherein the thickness of the abrasion and/or scratch-resistant coating ranges from 2 to 10 m.

Description

EXAMPLES

(1) 1. General Procedures

(2) The optical articles used in the examples comprise an ORMA lens substrate from ESSILOR with a diameter of 65 mm, a power of 2.00 diopters and a thickness of 1.2 mm, coated (except example C2) with an impact-resistant primer based on a polyurethane latex comprising polyester units, cured to 90 C. for 1 hour (Witcobond 234 from BAXENDEN CHEMICALS modified through dilution to reduce the viscosity thereof, spin-coating at 1500 rpm for 10 to 15 seconds) thereafter with the abrasion-resistant and scratch-resistant coating (hard coat) disclosed in example 3 of the patent EP 0614957 (with a refractive index of 1.50), based on a GLYMO and DMDES hydrolyzate, colloidal silica and aluminium acetylacetonate, with an antireflection coating and lastly with an anti-fouling coating.

(3) Said abrasion-resistant and scratch-resistant coating was obtained by depositing and curing a composition comprising by weight, 224 parts of GLYMO, 80.5 parts of HCl 0.1 N, 120 parts of DMDES, 718 parts of 30% by weight colloidal silica in methanol, 15 parts of aluminium acetylacetonate and 44 parts of ethyl cellosolve. The composition further comprises 0.1% by weight relative to the total weight of the composition of a surfactant FLUORAD FC-430 from the 3M company.

(4) The layers of the sub-layer and of the multilayered stack of the antireflection coating were deposited without heating the substrates, by vacuum evaporation, optionally, when specified, ion-beam-assisted and/or with oxygen feeding during the deposition (evaporation source: electron gun).

(5) The SiO.sub.2/Al.sub.2O.sub.3 mixture used in the examples is L5 marketed by Merck KGaA. The antistatic layers are made from indium-tin oxide, abbreviated as ITO, available from Optron Inc.

(6) The anti-fouling coating was obtained by vacuum evaporation of the OF110 compound provided by the Optron Inc. Company (thickness: 2-5 nm).

(7) The device used for the deposition belongs to a Leybold 1104 apparatus fitted with an electron gun ESV14 (8 kV) for evaporating oxides, with a Joule effect crucible for depositing the top coat and with an End-Hall type ion gun (KRI for examples 1, 2 and C1, Commonwealth Mark II for example C2) for the preliminary phase of the substrate surface preparation with argon ions (IPC) and optionally for that of the sub-layer (example C1 only), as well as for depositing layers under ion assistance.

(8) The thickness of the layers is controlled by means of a quartz scale.

(9) 2. Procedures

(10) The process for manufacturing optical articles did comprise the introduction of the substrate coated with a primer coating (except example C2) and with an abrasion-resistant coating into a vacuum deposition chamber, a pumping operation until a secondary vacuum was reached, then an activation of the substrate surface using an argon ion beam (IPC: 2 minutes, 18 cm.sup.3/min, 3 A for examples 1, 2 and C1; 2 minutes, 13 sccm, 2.5 A for example C2), the interruption of the ion irradiation, the successive evaporation of the antireflection coating required number of layers, a deposition of the anti-fouling coating (top coat) and lastly a ventilation operation were performed.

(11) Formation of the Antireflection Coating According to the Process of the Invention (Examples 1 and 2)

(12) The process for manufacturing the antireflection coating of the invention comprises: The deposition of a bilayered SiO.sub.2 sub-layer comprising: i) the deposition onto the substrate coated of a first SiO.sub.2 layer at a rate of 1 nm/s (without ion assistance) until a thickness of 75 nm was reached (controlled by means of a quartz scale). The closure element of the electron gun is closed and the evaporation stopped; ii) the deposition onto this first layer of a second SiO.sub.2 layer at a rate of 1 nm/s under oxygen ion assistance (corresponding to 15 cm.sup.3/min-2 A). The deposition of this second layer is conducted by priming the ion gun, preferably with the selected oxygen flow rate. Once the ion beam has been formed and stabilized, the silica granulates are pre-heated again with the electron gun, and the closure element of the electron gun is opened so as to deposit 75 nm thick silica through concomitant ion bombardment. The electron gun closure element is closed, then the evaporation and the ion bombardment are stopped. The deposition of a multilayered antireflection stack comprising the deposition of the first HI layer (ZrO.sub.2) at a rate of 0.3 nm/s, the deposition of the first LI layer (SiO.sub.2/Al.sub.2O.sub.3) at a rate of 0.7 nm/s, the deposition of the second HI layer (TiO.sub.2, from pre-molten granulates) at a rate of 0.3-0.5 nm/s and under oxygen ion assistance (corresponding to 15 cm.sup.3/min-2 A for Example 1 and to 18 cm.sup.3/min-3 A for Example 2), the deposition of a third HI layer (ZrO.sub.2) at a rate of 0.30 nm/s and under oxygen ion assistance (corresponding to 15 cm.sup.3/min-2 A), the deposition of an ITO layer at a rate of 0.2-0.5 nm/s and under oxygen ion assistance (corresponding to 15 cm.sup.3/min-2 A), and lastly the deposition of the second LI layer (SiO.sub.2/Al.sub.2O.sub.3) at a rate of 1 nm/s.
Formation of the Antireflection Coating in the Comparative Examples C1 and C2

(13) The formation of the antireflection coating comprises the step of depositing the SiO.sub.2 sub-layer onto the coated substrate at a rate of 1 nm/s, under an O.sub.2 atmosphere and a pressure of 1.5.Math.10.sup.4 mBar (example C1 only), optionally activating the sub-layer surface by means of an argon ion beam (the same treatment as IPC already performed directly on the substrate, example C1 only), stopping the ion irradiation, depositing the first HI layer (ZrO.sub.2) at a rate of 0.3 nm/s, depositing the first LI layer (SiO.sub.2/Al.sub.2O.sub.3) at a rate of 0.7 nm/s, depositing the second HI layer (TiO.sub.2 from premolten granulates) at a rate of 0.3-0.5 nm/s, under oxygen ion assistance (corresponding to 18 cm.sup.3/min-3 A for C1 and 2.5 A-120 V for C2), and optionally under an O.sub.2 atmosphere (under a pressure of 1.Math.10.sup.4 mBar, example C2 only), depositing the third HI layer (ZrO.sub.2) at a rate of 0.3 nm/s and optionally under oxygen ion assistance (corresponding to 15 cm.sup.3/min-2 A, example C1 only), depositing an ITO layer at a rate of 0.2-0.5 nm/s and under oxygen ion assistance (corresponding to 15 cm.sup.3/min-2 A for C1 and 2.5 A-120 V for C2), and lastly depositing the second LI layer (SiO.sub.2/Al.sub.2O.sub.3) at a rate of 1 nm/s.

(14) The contents of the optical articles obtained in examples 1, 2 and comparative examples C1 and C2 is detailed hereunder:

(15) TABLE-US-00001 Examples 1 and 2 Substrate + primer + hard coat (a) *SiO.sub.2 75 nm *SiO.sub.2 (c) 75 nm ZrO.sub.2 24 nm SiO.sub.2/Al.sub.2O.sub.3 23 nm TiO.sub.2 (c) 90 nm ZrO.sub.2 (c) 15 nm ITO (c) 13 nm SiO.sub.2/Al.sub.2O.sub.3 77 nm Anti-fouling coating Air Comparative example 1 (C1) Substrate + primer + hard coat (a) *SiO.sub.2 (a, b) 150 nm ZrO.sub.2 24 nm SiO.sub.2/Al.sub.2O.sub.3 30 nm TiO.sub.2 (c) 101 nm ZrO.sub.2 (c) 12 nm ITO (c) 7 nm SiO.sub.2/Al.sub.2O.sub.3 78 nm Anti-fouling coating Air Comparative example 2 (C2) Substrate + hard coat (a) *SiO.sub.2 (a, b) 150 nm ZrO.sub.2 24 nm SiO.sub.2/Al.sub.2O.sub.3 30 nm TiO.sub.2 (b, c) 101 nm ZrO.sub.2 (c) 12 nm ITO (c) 7 nm SiO.sub.2/Al.sub.2O.sub.3 78 nm Anti-fouling coating Air
(a) Treatment through ion bombardment of the layer surface prior to depositing the next layer.
(b) Oxygen supply for the deposition.
(c) Deposition of the layer under ion assistance.

3. Characterization of the Abrasion Resistance

(16) The abrasion resistance of the articles manufactured was evaluated by determining the BAYER values by means of the Bayer test (Bayer sand method) in accordance with the standard ASTM F 735.81, with a higher Bayer value meaning a higher abrasion resistance. The Bayer sand value is considered to be good when R is between 3.4 and 4.5, and to be outstanding when R is equal to or higher than 4.5.

(17) Such test consists in making simultaneously oscillate a sample glass and a reference glass with a given reciprocating motion in a tray containing an abrasive powder (about 500 g sand) with a defined particle size at a frequency of 100 cycles/minute for 2 minutes. Measurements of the sample glass before/after are compared with those of a reference glass, indeed a CR-39-based bare glass for which the BAYER value is set to 1. The Bayer sand value is RH reference glass/H sample glass.

(18) The diffusion measurements were conducted using a Hazeguard system model XL-211 manufactured by Pacific Scientific.

4. Results

(19) The results of the abrasion resistance measurements are given in Table 1 hereunder.

(20) TABLE-US-00002 TABLE 1 Bayer Test ASTM Example (BAYER SAND) 1 6.0 2 5.4 Comparative 1 4.7 Comparative 2 4.8

(21) The lenses of examples 1 and 2 have a better abrasion resistance than those of the comparative examples do.