Method for hardening anti-reflective treatment layer deposited on transparent substrate and transparent substrate comprising hardened anti-reflective treatment layer

Abstract

The invention relates to a method for hardening an anti-reflective treatment layer (20) deposited on a transparent substrate comprising a top surface (22a) and a bottom surface (22b) extending away from the top surface (22a), the anti-reflection treatment (20) comprises the step of depositing at least one anti-reflection layer composed of at least one material on at least one of the top surface (22a) and the bottom surface (22b) of the transparent substrate, the hardening method comprises the step of bombarding the at least one top surface (22a) or bottom surface (22b) on which the at least one anti-reflection layer has been deposited with a single-charge and / or multi-charge ion beam (14) generated by a single-charge and / or multi-charge electron cyclotron resonance (ECR) ion source (1). The invention also relates to a transparent substrate that has undergone an anti-reflection treatment, at least one of the top surface (22a) and the bottom surface (22b) of the transparent substrate being coated with at least one anti-reflection layer consisting of at least one material in which ions are implanted.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201980006993.4, filed on September 19, 2019, with International Application No. PCT / EP2019 / 075256, entitled "Method for hardening an anti-reflective treatment layer deposited on a transparent substrate and a transparent substrate including a hardened anti-reflective treatment layer". Technical Field

[0002] This invention relates to a method for curing an anti-reflective coating deposited on a transparent substrate. More particularly, this invention relates to a method for curing an anti-reflective coating deposited on a sapphire substrate by vacuum evaporation. The invention also relates to a transparent substrate coated with a cured anti-reflective coating. Background Technology

[0003] The application of anti-reflective treatment to watch crystals dates back decades. The purpose of this treatment is to improve the legibility of the watch dial when viewed through the thus-treated crystal by the wearer. More specifically, light originating from the outside and passing through the crystal is first reflected at the interface between the air and the material forming the crystal, and then reflected a second time as it exits the crystal and travels towards the dial. After reflecting on the dial, the light passes through the crystal again and undergoes another double reflection.

[0004] It should be understood that these multiple reflections significantly hinder the legibility of information displayed on the watch dial. This is why efforts to provide watch crystals with anti-reflective treatments have been made very early on. Interest in this technology further increased when sapphire crystals first appeared. More specifically, due to the relatively high optical refractive index of sapphire glass, its re-emissions are almost doubled compared to mineral glass, resulting in significant reflections of light at the interface between the sapphire glass and air.

[0005] The watch crystal includes a top surface on the side closest to the individual wearing the watch and a bottom surface on the side closest to the dial. The anti-reflective treatment of the watch crystal includes coating at least one of the top and bottom surfaces of the watch crystal with at least one layer made of at least one material having an optical refractive index between the optical refractive index of air and the refractive index of the material used to manufacture the watch crystal.

[0006] This invention relates particularly to watch crystals, but is not limited thereto. More generally, the invention relates to all types of transparent substrates whose incident light reflectivity characteristics are being reduced. In this document, a transparent substrate is understood to be a substrate that allows light to pass through and clearly displays objects located behind it. In particular, the invention also relates to watch crystals made of sapphire, but is not limited thereto. However, the invention also relates to substrates made of any transparent material, such as mineral glass, plexiglass, or plastic materials.

[0007] In this paper, anti-reflective treatment is understood as a method that aims to alter the optical reflective properties of a transparent substrate, especially a watch mirror, with the goal of reducing the reflectivity of such a transparent substrate relative to the same untreated substrate.

[0008] The anti-reflective treatment methods described herein involve depositing at least one layer of at least one material on one of the top and bottom surfaces of a transparent substrate under vacuum. The vacuum-based anti-reflective treatment methods described herein include physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), or even atomic layer deposition (ALD).

[0009] As understood above, the antireflective treatment techniques described herein involve depositing one or more layers of at least one material on at least one of the top and bottom surfaces of a transparent substrate under vacuum to reduce the reflectivity of such transparent substrate to incident light. In this document, "transparent substrate" is understood, in particular, to refer to mirrors, optical devices, especially ophthalmic devices such as spectacle lenses, and more generally, to any transparent device for which one seeks to reduce its reflectivity for technical and / or aesthetic reasons.

[0010] Anti-reflective layers have the advantage of reducing the light emissivity of the transparent substrate on which they are deposited. Depending on their thickness and the materials used to manufacture them, these anti-reflective layers can also alter the color of the transparent substrate.

[0011] However, a drawback of anti-reflective layers is that they are less hard than the substrate on which they are deposited and therefore less scratch-resistant. This is especially true when such anti-reflective layers are deposited on sapphire substrates, which are known to be scratched only by diamond.

[0012] To overcome this problem, some watch manufacturers have opted to apply anti-reflective treatment only to the underside of their watch crystal, the surface facing the dial, which is not entirely satisfactory. Summary of the Invention

[0013] Therefore, there is a commercial demand for an anti-reflective layer that retains its optical properties while being more rigid and thus more scratch-resistant and more resistant to impacts that may occur during transport, handling, or wearing.

[0014] For this purpose, the present invention relates to a method for hardening an antireflective treatment layer deposited on a transparent substrate, the transparent substrate including a top surface and a bottom surface extending away from the top surface, the antireflective treatment including the step of depositing at least one antireflective layer made of at least one material on at least one of the top surface and the bottom surface of the transparent substrate, the hardening method further including the step of bombarding at least one top surface or bottom surface on which the antireflective layer has been deposited with a single-charged or multi-charged ion beam generated by a single-charged or multi-charged ion source.

[0015] The single-charged or multi-charged ion source is an electron cyclotron resonance (ECR) type.

[0016] In this paper, the term "single-charged ion" is understood to refer to an ion with an ionization degree equal to 1. The term "multiple-charged ion" is understood to refer to an ion with an ionization degree greater than 1. An ion beam generated by an ion source may be formed from ions all having the same ionization degree, or from a mixture of ions having at least two different ionization degrees.

[0017] According to a preferred embodiment of the present invention:

[0018] - The transparent base is made of sapphire;

[0019] -The transparent substrate made of sapphire is the watch crystal;

[0020] - The material to be ionized is selected from the group consisting of carbon (C), oxygen (O), nitrogen (N), argon (Ar), helium (He), xenon (Xe) and neon (Ne);

[0021] - Single or multiple charged ions are accelerated at voltages in the range of 30 kV to 50 kV;

[0022] - The dose of implanted ions is 0.1-10. 16 ions / cm² up to 2.10 16 Within the range of ions / square centimeter;

[0023] - The duration of the ion implantation process shall not exceed 5 seconds;

[0024] - The one or more antireflective layers are made of silicon dioxide (SiO2) or magnesium fluoride (MgF2);

[0025] - The thickness of the anti-reflective layer does not exceed 150 nm;

[0026] -An antireflective treatment layer formed by the deposition of one or more antireflective layers has an optical refractive index of no more than 1.55;

[0027] - Prior to depositing the at least one antireflective layer, the top and / or bottom surfaces of the transparent substrate are subjected to ion bombardment;

[0028] - After anti-reflective treatment, deposit at least one additional anti-reflective layer on the top and / or bottom surfaces that have already undergone ion bombardment.

[0029] Thanks to these features, the present invention provides a method that allows an anti-reflective layer deposited on a transparent substrate, such as a sapphire crystal, to be hardened and thus made more scratch-resistant and more resistant to impacts that may be experienced during transport, handling, or wear.

[0030] More specifically, all mechanical property tests (scratch resistance and shock resistance) provided to conform to NIHS 61-30 watchmaking standard showed that the mechanical properties of these anti-reflective layers were significantly improved after being subjected to ion bombardment according to the invention. Furthermore, it has been satisfactorily noted that the optical properties of the anti-reflective layers were not affected in any way by the ion bombardment method according to the invention.

[0031] As a result, watchmakers who have so far only applied anti-reflective coatings to the bottom surface of their crystals facing the dial, because the mechanical strength of the anti-reflective coatings was deemed insufficient to resist scratches and impacts, can now also consider applying anti-reflective coatings to the top surface of the crystal facing the wearer. This significantly improves the readability of the information displayed on the dial when viewed through the crystal.

[0032] Another object of the present invention relates to a transparent substrate subjected to an anti-reflective treatment, the transparent substrate comprising a top surface and a bottom surface extending away from the top surface, wherein at least one of the top surface and the bottom surface of the transparent substrate is coated with at least one anti-reflective layer made of at least one material, wherein ions are implanted into the at least one anti-reflective layer. Attached Figure Description

[0033] Other features and advantages of the invention will become clearer after reading the following detailed description of an embodiment of the method according to the invention with reference to the accompanying drawings. These embodiments are provided for illustrative purposes only and are not intended to limit the scope of the invention, wherein:

[0034] - Figure 1 This is a simplified diagram of a single-charged or multi-charged ion source of the ECR electron cyclotron resonance type;

[0035] - Figure 2A This is a top view of a flat sapphire crystal that has undergone anti-reflective treatment and scratch resistance testing.

[0036] - Figure 2B They are the same size and have been used. Figure 2A The same anti-reflective treatment shown in the figure, and subsequently subjected to ion bombardment according to the invention, is illustrated in the top view of the same flat sapphire crystal, the scratch resistance of which has been tested; and

[0037] - Figure 3 The hardness difference is shown between an anti-reflective treatment deposited on a sapphire crystal that has not undergone ion bombardment and the same anti-reflective treatment on the same sapphire crystal that has undergone ion implantation after bombardment. Detailed Implementation

[0038] This invention derives from a general inventive concept comprising implanting ions by bombardment into an antireflective treatment layer deposited on at least one of the top and bottom surfaces of a transparent substrate, such as a sapphire crystal. More specifically, after bombardment with ions, the antireflective treatment layer formed by one or more antireflective layers is observed to have significantly improved mechanical strength, resisting scratches and impacts that may occur during handling, transportation, or wear. Furthermore, the optical properties of the antireflective layer are not affected in any way by the ion bombardment according to the invention, allowing some watchmakers who have previously hesitated to apply antireflective treatments to the top surfaces of their crystals due to the perceived insufficient mechanical strength properties of antireflective treatments to now have their crystals treated on both the top and bottom surfaces, resulting in a significant reduction in parasitic reflections and a substantial improvement in the legibility of information displayed on the dial when viewed through the crystal. These results are quite unexpected with antireflective layers that are no more than 150 nm thick and often equal to about tens of nanometers. More specifically, the fear was that ion bombardment would weaken the antireflective layer's mechanical strength and alter its optical properties, rather than enhance it. However, this did not occur. In fact, the opposite result was observed.

[0039] The invention will now be described in conjunction with sapphire crystal. Of course, this embodiment is provided for illustrative purposes only and is not intended to limit the invention, and the invention can be applied in the same manner to all types of transparent substrates that undergo anti-reflective treatment, such as substrates made of mineral glass, plexiglass, or even plastic materials, like eyeglass lenses or lenses for optical devices such as cameras.

[0040] Similarly, the present invention will now be described in conjunction with single-charged or multi-charged ion sources of the electron cyclotron resonance (ECR) type.

[0041] ECR ion sources utilize electron cyclotron resonance to form plasma. A volume of low-pressure gas is ionized by microwaves injected at a frequency corresponding to the electron cyclotron resonance, which is defined by a magnetic field applied to a region within the volume of the gas to be ionized. The microwaves heat the free electrons present within the volume of the gas. Under thermal agitation, these free electrons collide with atoms or molecules of the gas, causing them to ionize. The resulting ions correspond to the type of gas used. The gas can be a single gas or a compound. It can also be a vapor produced from solid or liquid materials. ECR ion sources can produce monocharged ions (ions with an ionization degree equal to 1) or polycharged ions (ions with an ionization degree greater than 1).

[0042] The appendix to this patent application Figure 1 The diagram schematically illustrates an ECR (electron cyclotron resonance) type ion source. The ECR ion source, generally labeled 1, comprises: an injection stage 2 into which microwaves 6 and a volume of gas 4 to be ionized are injected; a magnetic confinement stage 8 into which plasma 10 is generated; and an extraction stage 12 that allows ions from the plasma 10 to be extracted and accelerated using an anode 12a and a cathode 12b therebetween, where a high voltage is applied. The ion beam 14 generated at the output of the ECR ion source 1 attacks the surface of the transparent substrate, in this case, the mirror 18, to be treated, and more or less penetrates into the anti-reflective treatment layer 20 constructed on at least one of the top surface 22a and the bottom surface 22b of the mirror 18 to be treated.

[0043] The gas to be ionized can be selected from, for example, carbon (C), oxygen (O), argon (Ar), nitrogen (N), helium (He), xenon (Xe), or neon (Ne) obtained from carbon dioxide (CO2) or methane (CH4). The ions can be of a single charge type (i.e., with an ionization degree equal to +1) or of a multi-charge type (i.e., with an ionization degree greater than +1). The ion beam generated by ECR ion source 1 can be formed from ions with all the same ionization degree, or from a mixture of ions with at least two different ionization degrees.

[0044] Single-charged or multi-charged ions are accelerated at voltages ranging from 30 kV to 50 kV, and the dose of ions to be implanted is 0.1-10 kV. 16 ions / cm² to 2.10 16 Within the range of ions per square centimeter, and the duration of ion implantation does not exceed 5 seconds.

[0045] The one or more antireflective layers are made using, for example, silicon dioxide (SiO2) or magnesium fluoride (MgF2). The silicon dioxide layer may be bonded to the magnesium fluoride layer. The thickness of these layers, considered individually, typically does not exceed 150 nm. Other materials such as oxides of titanium, tantalum, zirconium, silicon, and aluminum, as well as silicon nitride, can also be used to fabricate the antireflective layers. These antireflective layers are deposited by vacuum evaporation. Considerable vacuum deposition techniques include physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), or even atomic layer deposition (ALD).

[0046] Figure 2A This is a top view of a flat sapphire crystal 24A, which has undergone an anti-reflective treatment 26A and has been tested for scratch resistance. The anti-reflective treatment consists of a 90 μm thick magnesium fluoride layer. The test involved scratching the anti-reflective treatment 26A at a distance of 0.5 mm with a diamond engraving tool having a spherical-quadratic geometry with a radius of 5 μm. The diamond engraving tool was moved at a speed of 1 mm / min. A substantially zero force was applied at the origin O, which increased linearly at a rate of 401.88 mN / min to reach 200 mN at the endpoint of the 0.5 mm distance. It should be noted that the diamond engraving tool... Figure 2A The center is shifted from left to right.

[0047] exist Figure 2A In the diagram, the exposed sapphire crystal of the flat crystal 24A is indicated by line AA. Figure 2B The image shows items of the same size that have already undergone [a certain process / experience]. Figure 2A The same flat sapphire crystal 24A as the anti-reflective treatment 26B made of sapphire crystal 24B. However, Figure 2B The flat sapphire crystal 24B in the watch, after anti-reflective treatment, undergoes ion implantation via bombardment according to the present invention. The characteristics of the ion implantation treatment performed on the 90 μm thick magnesium fluoride (MgF2) layer are as follows:

[0048] -Type of injected ions: nitrogen;

[0049] - Ion acceleration voltage: 40kV;

[0050] - Ion implantation dose: at 0.1·10 16 ions / cm² to 0.25·10 16 Within the range of ions per square centimeter;

[0051] - Ion beam intensity: 6 mA;

[0052] -Vacuum conditions: 4.10 -6 mbar;

[0053] - Penetration depth of ions in the magnesium fluoride (MgF2) layer: approximately 50 nm.

[0054] Assuming it is used for measurement Figure 2A and Figure 2B The experimental conditions for the scratch resistance of the flat mirrors 24A and 24B were the same, and it was observed that, with Figure 2A Compared to the situation shown in the figure, in Figure 2B The exposed sapphire crystal of the flat crystal 24B, indicated by line BB, appears further from the origin O, suggesting increased hardness of the anti-reflective treatment 26B due to ion bombardment. Figure 2A and Figure 2B In comparison, we also see that, compared with Figure 2A Compared to the situation in the middle, Figure 2B The scratches made by the diamond engraving tool are narrower, which means that in Figure 2B In the case shown, the anti-reflective treatment 26B exhibits significantly less peeling, and therefore, compared to Figure 2A Compared to the case shown, the anti-reflective treatment 26B is harder and therefore more scratch-resistant.

[0055] Figure 3 The diagram illustrates the difference between an anti-reflective treatment deposited on a sapphire crystal without ion bombardment (curve A) and the same anti-reflective treatment on the same sapphire crystal after ion implantation via bombardment (curve B). These hardness values, obtained by measuring the elastic modulus, highlight the evolution of the mechanical properties of the anti-reflective layer with depth. These hardness values ​​were measured using a technique known as instrument indentation (also called continuous stiffness measurement) in DMA (Dynamic Mechanical Analysis) mode.

[0056] Figure 3 The graph shows the thickness pd of the anti-reflective treatment in nanometers along the horizontal axis; the vertical axis shows the hardness H of the anti-reflective layer, in MPa. Examining this graph immediately reveals that from the surface of the anti-reflective treatment down to a depth of approximately 20 nm below that surface, the hardness of the anti-reflective treatment subjected to ion bombardment (curve B) is about 20% greater than that of the anti-reflective treatment not subjected to ion bombardment (curve A). At depths ranging from 20 nm to 40 nm from the surface of the anti-reflective treatment, the hardness difference between the ion-bombarded and un-ion-bombarded anti-reflective treatments remains around 10%, decreasing thereafter down to a depth of 50 nm. From a depth of 50 nm, the hardness curves of the ion-bombarded and un-ion-bombarded anti-reflective treatments align and remain so until a depth of 90 nm, which is... Figure 3 The chart shows the hardness measurement limits.

[0057] Of course, the present invention is not limited to the implementation of the methods described above, and those skilled in the art will conceive of various simple substitutions and modifications without departing from the scope of the invention as defined by the appended claims. In particular, the present invention discloses subjecting the surface of a transparent substrate intended to undergo antireflective treatment to ion bombardment prior to the deposition of the one or more antireflective layers. Similarly, the present invention discloses that after the one or more antireflective layers have undergone ion bombardment, at least one additional antireflective layer may be deposited on the antireflective layers thus treated by ion bombardment.

[0058] the term

[0059] 1. ECR Electron Cyclotron Resonance Ion Source

[0060] 2. Injection grade

[0061] 4. A certain volume of gas to be ionized

[0062] 6. Microwave

[0063] 8. Magnetic confinement level

[0064] 10. Plasma

[0065] 12. Extraction level

[0066] 12a. Anode

[0067] 12b. Cathode

[0068] 14. Ion beam

[0069] 18. Watch crystal

[0070] 20. Anti-reflective treatment layer

[0071] 22a. Top surface

[0072] 22b. Bottom surface

[0073] 24a, 24b. Flat watch crystal

[0074] 26a, 26b. Anti-reflective treatment

[0075] O. Origin

[0076] AA. The line indicating the exposed sapphire crystal of the flat crystal 24A.

[0077] BB. The line indicating the exposed sapphire crystal of the flat 24B crystal.

Claims

1. A curing method for curing an antireflective treatment layer (20) deposited on a transparent substrate, the transparent substrate comprising a top surface (22a) and a bottom surface (22b) extending away from the top surface (22a), the antireflective treatment comprising the step of depositing at least one antireflective layer made of at least one material on at least one of the top surface (22a) and the bottom surface (22b) of the transparent substrate, the curing method further comprising the step of bombarding at least one of the top surface (22a) and the bottom surface (22b) on which the at least one antireflective layer has been deposited with a single-charged and / or multi-charged electron cyclotron resonance (ECR) ion source (1), wherein the thickness of the antireflective layer does not exceed 150 nm.

2. The hardening method according to claim 1, characterized in that, The at least one anti-reflective layer is deposited by vacuum evaporation of the material.

3. The hardening method according to claim 2, characterized in that, Vacuum evaporation deposition technology is selected from physical vapor deposition, chemical vapor deposition, plasma-enhanced chemical vapor deposition, and atomic layer deposition.

4. The hardening method according to any one of claims 1-3, characterized in that, Before depositing the at least one antireflective layer, the top surface (22a) and / or bottom surface (22b) to be subjected to antireflective treatment are subjected to ion bombardment.

5. The hardening method according to any one of claims 1-4, characterized in that, At least one additional anti-reflective layer is deposited on the anti-reflective treatment layer (20) that has already undergone ion bombardment.

6. The hardening method according to any one of claims 1-5, characterized in that, The ECR ion source (1) includes an injection stage (2), into which microwaves (6) and a certain volume of gas (4) to be ionized are injected; a magnetic confinement stage (8) in which plasma (10) is generated; and an extraction stage (12) which allows ions from the plasma (10) to be extracted and accelerated by a high voltage applied therebetween an anode (12a) and a cathode (12b). The ion beam (14) generated at the output of the ECR ion source (1) strikes the surface of the transparent substrate to be treated and penetrates more or less into the anti-reflective treatment layer (20) constructed on at least one of the top surface (22a) and bottom surface (22b) of the transparent substrate to be treated.

7. The hardening method according to claim 6, characterized in that, The material to be ionized is selected from the group consisting of carbon (C), oxygen (O), nitrogen (N), argon (Ar), helium (He), xenon (Xe) and neon (Ne).

8. The hardening method according to claim 7, characterized in that, The ion can be a single-charge type with an ionization degree of +1, or a multi-charge type with an ionization degree greater than +1.

9. The hardening method according to claim 8, characterized in that, The ion beam (14) generated by the ECR ion source (1) can be formed by all ions having the same degree of ionization, or by a mixture of ions having at least two different degrees of ionization.

10. The hardening method according to any one of claims 7-9, characterized in that, The ions are accelerated at voltages ranging from 30 kV to 50 kV.

11. The hardening method according to claim 10, characterized in that, The dose of ions to be implanted is 0.1-10. 16 ions / cm² to 2.10 16 Within the range of ions per square centimeter.

12. The hardening method according to claim 11, characterized in that, The duration of the ion implantation process does not exceed 5 seconds.

13. The hardening method according to any one of claims 1-12, characterized in that, The transparent substrate is made of sapphire.

14. The hardening method according to claim 13, characterized in that, The transparent substrate is a watch mirror (18).

15. The hardening method according to any one of claims 1-14, characterized in that, The one or more antireflective layers are made of silicon dioxide (SiO2) or magnesium fluoride (MgF2).

16. A transparent substrate that has undergone anti-reflective treatment, the transparent substrate comprising a top surface (22a) and a bottom surface (22b) extending away from the top surface (22a), wherein at least one of the top surface (22a) and the bottom surface (22b) of the transparent substrate is coated with at least one anti-reflective layer made of at least one material, wherein, Ions are implanted into the at least one antireflective layer, wherein the thickness of the antireflective layer does not exceed 150 nm.

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