Optical article comprising an electrochromic stack offering a modulation both in transmission and in reflection

Abstract

The present invention relates to an optical article comprising at least: a transparent base element having a front main face and a rear main face, at least one of said main faces being coated with a multilayered interferential sheet (MIS) comprising at least a multilayered electrochromic stack (EC stack), said multilayered EC stack comprising at least: two external layers that are a first transparent conductive electrode and a second transparent conductive electrode layer, three or more internal layers interposed between said two external layers, said internal layers comprising at least (i) a first cathodic layer, (ii) a first anodic layer and (iii) an ion conductor layer which is positioned between said (i) first cathodic layer and (ii) said first anodic layer, said EC stack being able to reversibly switch from an activated state when an electrical potential is applied to a deactivated state when the reverse electrical potential is applied, characterized in that the internal layers of said (a) multilayered EC stack comprises at least one bilayer composed of a second cathodic layer and a porous ionic diffusion layer, and wherein the multilayered interferential sheet has, in the visible region, a mean light reflection factor difference, ΔRv, higher than or equal to 60% between the activated state and the deactivated state. The invention also relates to an optical device.

Description

[0001] OPTICAL ARTICLE COMPRISING AN ELECTROCHROMIC STACK OFFERING A MODULATION BOTH IN TRANSMISSION AND IN REFLECTION

[0002] BACKGROUND OF THE INVENTION

[0003] 1. Field of the invention

[0004] The invention relates to an optical article and especially to an ophthalmic lens comprising a transparent substrate coated with a multilayer transparent interferential coating, preferably an interferential sheet (MIS) having at least one electrochromic (EC) stack, and in particular an ophthalmic lens.

[0005] 2. Description of related art

[0006] It is a common practice in the art to coat at least one main surface of a lens substrate, such as an ophthalmic lens or lens blank, with several coatings for imparting to the finished lens additional or improved optical or mechanical properties. These coatings are designated in general as functional coatings.

[0007] Thus, it is usual practice to coat at least one main surface of a lens substrate, typically made of an organic glass material, with successively, starting from the surface of the lens substrate, an impact-resistant coating (impact-resistant primer), an abrasion- and / or scratchresistant coating (hard coat), an interferential coating and, optionally, an anti-fouling top coat.

[0008] An interferential coating may be either a reflective coating (also named “mirror coating”) or an antireflective coating.

[0009] A reflective coating is usually designed so as to confer to the surface of an optical article it coats, a mean light reflection factor in the visible region R, (front face OA) that is strictly higher than 2.5 % for an angle of incidence of 15°. Reflective coatings are generally applied to a surface of an optical article so as to provide a reduction in transmitted visible, ultra-violet or infrared light (i.e.: increase the light ray reflection). They may also impart a mirror and / or coloured appearance to the optical article, which may be desirable for aesthetic purposes. Such a coating is used, for example, to provide solar spectacle lenses with a mirror effect.

[0010] An antireflective coating usually consists of a multilayer coating comprising interferential thin layers, generally an alternation of layers based on a dielectric material of high refractive index and a dielectric material of low refractive index. When deposited on a transparent substrate, the function of such a coating is to reduce its light reflection and therefore, to increase its light transmission. A substrate thus coated will consequently have its transmitted light / reflected light ratio increased, thereby improving the visibility of objects placed behind it. When it is sought to achieve a maximum antireflection effect, it is then preferable to provide both faces (front and rear faces) of the substrate with this type of coating. Hence, traditional antireflective coatings are designed and optimized to reduce reflection on the lens surface in the visible region, typically within the spectrum range of 380 nm to 780 nm. They are also designed, especially in the case of an ophthalmic lens, to prevent the formation of annoying reflections to the wearer and his interlocutors.

[0011] Other coatings such as a polarized coating, a photochromic, an electrochromic or a dyeing coating may also be applied onto one or both surfaces of the lens substrate.

[0012] Especially, electrochromism is a well-known physical phenomenon which is observed with certain classes of chemical compounds that reversibly change colour when a voltage is applied to them. The electrochromic material undergoes reversible changes in optical properties by oxidation and reduction. Indeed, the optical properties of the electrochromic material are linked to its oxidation state and thus can be manipulated by the oxidation-reduction process through the loss or gain of electrons. In general, the electrochromic material can be switched between a coloured state (named “activated state”) when an electric field is applied for a predetermined time (linked to the charging time of the electrochromic material and then there is a tint preservation during this activated state) and a colourless state (named “deactivated state” or “bleached state”) and vice versa. The required electric field for an electrochromic colour change is generally very low. As mentioned above, the colour remains even when the current has ceased to flow (the so-called “memory-effect”) and the colour change is reversible when the inverted potential is applied. For achieving this purpose, an EC stack comprises an electrochromic layer, the refractive index of said electrochromic layer being different in the activated state and in the deactivated state.

[0013] For instance, electrochromic coatings can be used in an optical article to provide certain benefits, including the blocking of certain wavelengths of visible or ultraviolet light. While such benefits can be achieved to a degree using photochromic materials, photochromic materials have certain disadvantages with respect to electrochromic materials. Indeed, electrochromic materials can be activated and deactivated when desired, whereas photochromic materials simply respond to an external stimulus, such as the degree of ambient illumination.

[0014] Until now, electrochromic optical articles, and especially electrochromic eyeglass lenses have suffered from certain limitations. These include: the inability to block light across the visible spectrum in a cosmetically pleasing manner or the inability to provide a range of contrast or blocking that is expected by consumers.

[0015] In addition, electrochromic eyeglasses have not yet gained wide acceptance on the market.

[0016] So as to try to overcome these drawbacks, several solutions have been developed in the prior art.

[0017] The document WO 2020 / 021107 describes an ophthalmic lens comprising a transparent substrate with a front main face and a rear main face, at least one of said main faces being coated with a multilayered interferential stack (IF stack), comprising at least one HI layer having a refractive index higher than or equal to 1 .55 and at least one LI layer having a refractive index lower than 1.55, characterized in that an electrochromic stack (EC stack) is part of said multilayered interferential stack or is directly deposited onto said multilayered interferential stack, so as to form a multilayered interferential coating (IF coating). Especially, the IF stack comprises a common EC stack composed of a first and a second transparent conductive electrode layer (such as tin-doped indium oxide layers, also named ITO layers), and the following layers placed between said first and a second transparent conductive electrode layers: one electrochromic layer (EC layer, such as a WO3 layer), one ion reservoir layer (IR layer, such as ZrO2 layer) and one dielectric spacer layer (DS layer, such as Ta2Os, SiO2 layer), said DS layer being placed between the EC layer and the IR layer. The applicant has discovered that such a combination of an EC stack with an interferential coating, especially an antireflective coating, enables to obtain a final interferential coating which is able to modulate the reflection as necessary and to change the reflection from an antireflective state to a mirror state or from a first mirror state to a second mirror state upon the activation of the EC stack.

[0018] However, there is still a need to increase the variation in reflection of a final interferential coating of an optical article between the activated state and the deactivated of the electrochromic stack.

[0019] The publication by B. Baloukas et al. entitled “Electrochromic interference filters fabricated from dense and porous tungsten oxide films” published by “Solar Energy Materials & Solar Cells” 95 (2011) 807-815 describes the deposition of an electrochromic interference filter onto an ITO-coated glass substrate. Especially, the best electrochromic interference filter comprises a 27-layer quarter-wave reflection filter based on a succession of layers of dense WO3 and of porous WO3. So as to obtain porous WO3 layers, these last ones were deposited at a higher pressure (here 40 mTorr) than the dense WO3 layers (here 10 mTorr). The authors determined that the refractive index difference An between this dense WO3 layer and this porous WO3 layer in the activated state is relatively low, i.e.: 0.22. In addition, the total physical thickness of this coating is very high, i.e.: around 1.55 pm and is, therefore, not adapted for an ophthalmic purpose. In addition, the resulting filters showed a reflection peak in the deactivated bleached transparent state of the WO3 which then disappeared upon colouration.

[0020] The same authors in the publication entitled “WOs / SiCh composite optical films for the fabrication of electrochromic interference filters” published by “Applied Optics”, vol.51 , No.16, June 2012 propose the deposition of another electrochromic interference filter onto ITO-coated glass substrate. This electrochromic interference filter comprises 11 layers based on the alternation of pure WO3 and (W03)o.i7(Si02)o.83 having a refractive index difference An between this pure WO3 layer and the layer made of (W03)o.i7(Si02)o.83 which is high, i.e.: 0.61. While the resulting filters were indeed active, issues during the bleaching phase were observed, as the transmission failed to completely reach its initial value. In other words, the successive clear states (“deactivated states”) are less and less transparent / colourless. This issue was ascribed to the decrease in the measured electron diffusion coefficient of the SiCh-WCh composites which resulted in a space charge limitation effect at the WCh / composite interfaces.

[0021] There is, therefore, a need to provide a novel optical article and especially an ophthalmic lens that can at least partially solve some of these problems.

[0022] There is also a need to provide a novel optical article and especially an ophthalmic lens comprising at least an electrochromic stack that is able, not only to modulate the transmission, but also the reflection, while keeping electrochromic properties and having an aesthetic appearance (i.e.: cosmetic effects).

[0023] There is also a need to provide a novel optical article and especially an ophthalmic lens comprising at least an electrochromic stack that has a suitable robustness, that is to say which is able to reversibly switch from a deactivated state (in general bleached / colourless state) when an electrical potential, such as 0.5-3.0 V is applied, to an activated state (in general darker state) a larger number times (high number of cycles).

[0024] The optical articles, such as ophthalmic lenses, described herein are provided so as to address one or more of the above problems that have led to the slow development of commercially viable electrochromic ophthalmic lenses.

[0025] SUMMARY OF THE INVENTION

[0026] An aim of this invention is indeed to provide a transparent optical article, preferably a lens and more preferably an ophthalmic lens for eyeglasses comprising an organic or mineral glass substrate bearing at least an electrochromic stack and also optionally an interferential coating, which is not only able to display a wide modulation in transmission, but also in reflection when the electrochromic stack changes from the deactivated state to the activated state, and this for a high number of cycles (activated state / deactivated state). Indeed, standard inorganic electrochromic devices, as it will be demonstrated in the experimental section below, offer a limited variation in reflection. These properties can be used in smart eyewear applications for fashion or augmented reality.

[0027] For that purpose, the Applicant developed a new and atypical structure for an optical article based at least on the combination of an electrochromic stack with a Bragg structure.

[0028] Therefore, the invention relates to an optical article comprising at least:

[0029] - a transparent base element having a front main face and a rear main face,

[0030] - at least one of said main faces being coated with a multilayered interferential sheet (MIS) comprising at least:

[0031] (a) a multilayered electrochromic stack (EC stack), said multilayered EC stack comprising at least : two external layers that are a first transparent conductive electrode and a second transparent conductive electrode layer, three or more internal layers interposed between said two external layers, said internal layers comprising at least (i) a first cathodic layer, (ii) a first anodic layer and (iii) an ion conductor layer which is positioned between said first cathodic layer (i) and (ii) said first anodic layer (ii), said EC stack being able to reversibly switch from an activated state when an electrical potential is applied to a deactivated state when the reverse electrical potential is applied, and

[0032] (b) optionally a multilayered interferential coating (IC), coated onto or below said (a) multilayered EC stack, comprising at least one LI layer having a refractive index lower than 1.55, characterized in that the internal layers of said (a) multilayered EC stack comprise at least one bilayer composed of a second cathodic layer and a porous ionic diffusion layer, said at least one bilayer being placed between said ion conductor layer (iii) and either said first cathodic layer (i) or said first anodic layer (ii), and characterized in that the multilayered interferential sheet has, in the visible region, a mean light reflection factor difference, A ?V, higher than or equal to 6.0% between the activated state and the deactivated state.

[0033] Indeed, thanks to its characteristics, the interferential multilayered sheet (MIS) according to the invention allows to generate a significant change in the reflective properties upon activation / deactivation. For example, such an optical article can possess antireflective properties in the clear state (i.e.: in general, in the deactivated state) which can then be activated into a selective and intense mirror-like coloured state (i.e.: in the activated state). The dynamic properties of such structures are interesting for contrast management, mirror activation upon colouration, logo activation as well as visual health purposes. Therefore, the multilayered interferential sheet according to the invention comprising an electrochromic stack combined with a Bragg structure enables to provide an optical article whose optical properties and / or the reflected colour (cosmetic effect) may change between the activated state and the deactivated state and this according to the wearer’s needs.

[0034] Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

[0035] DETAILLED DESCRIPTION OF THE INVENTION

[0036] 1. Definitions

[0037] The terms “comprise” (and any grammatical variation thereof, such as “comprises” and comprising”), “have” (and any grammatical variation thereof, such as “has” and “having”), “contain” (and any grammatical variation thereof, such as “contains” and “containing”), and “include” (and any grammatical variation thereof, such as “includes” and “including”) are open- ended linking verbs. They are used to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps or components or groups thereof. As a result, a method, or a step in a method, that “comprises,” “has,” “contains,” or “includes” one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more steps or elements.

[0038] Unless otherwise indicated, all numbers or expressions referring to quantities of ingredients, ranges, reaction conditions, etc. used herein are to be understood as modified in all instances by the term "about."

[0039] Also, unless otherwise indicated, the indication of an interval of values « from X to Y » or “between X to Y”, according to the present invention, means as including the values of X and Y.

[0040] We mean an ophthalmic article defined by, but not exclusive of corrective lenses, noncorrective lenses, contact lenses, intra-ocular lenses, magnifying lenses, protective lenses, and visors containing photochromic compounds within a coating, the lens material, a film, or any adjacent layer.

[0041] As used herein, “a base element” can consist in an optical, such as an ophthalmic, substrate or in a support film of optical quality to be fixed on an optical / ophthalmic substrate thanks to an adhesive such as a pressure-sensitive adhesive of optical quality (PSA layer) (i.e.: laminate).

[0042] As used herein, “interferential coating” means a coating, generally composed of transparent interferential thin layers and comprises at least one layer having a low refractive index which is lower than 1.55, defined as “LI layer” and / or at least one layer having a high refractive index which is equal to or higher than 1.55, defined as “HI layer”.

[0043] In the present application, when an optical lens comprises one or more coatings onto the surface thereof, the expression "to deposit a layer, a sheet or a coating onto the article" is intended to mean that a layer, a sheet or a coating is deposited onto the external (exposed) surface of the outer coating of the article, that is to say its coating that is the most distant from the substrate.

[0044] Unless otherwise indicated, a coating or a sheet, that is said to be "on" a substrate / base element or deposited "onto" a “substrate / base element” is defined as a coating or a sheet, which (i) is positioned above the substrate / base element, (ii) is not necessarily in contact with the substrate / base element, that is to say one or more intermediate coatings / sheets may be arranged between the substrate / base element and the coating or sheet in question, and (iii) does not necessarily completely cover the substrate / base element. In a preferred embodiment, the coating on a substrate / base element or deposited onto a substrate / base element is in direct contact with this substrate / base element.

[0045] When "a layer / sheet 1 is lying “under” or “below” a layer 2", it is intended to mean that layer / sheet 2 is more distant from the substrate / base element than layer 1.

[0046] By outermost layer or sheet of the interferential coating, it is meant the layer or sheet of the interferential coating which is the furthest from the substrate / base element.

[0047] By innermost layer or sheet of the interferential coating, it is meant the layer or sheet of the interferential coating which is the closest to the substrate / base element.

[0048] By inner layer of the interferential coating, it is meant any layer of the interferential coating except for the outermost layer of said interferential coating.

[0049] Also, unless stated otherwise, all thicknesses disclosed in the present application relate to physical thicknesses.

[0050] As used herein, a layer of the interferential stack / coating / sheet is defined as having a thickness higher than or equal to 1 nm. Thus, any layer having a thickness lower than 1 nm will not be considered when counting the number of layers in the reflective stack / coating / sheet. A sub-layer (having generally a physical thickness of 150 nm) is also not considered when counting the number of layers of the interferential stack / coating.

[0051] Unless otherwise specified, the refractive indexes referred to in the present application are expressed at 25 °C at a wavelength of 550 nm.

[0052] As used herein, the rear (or the inner or Concave or CC) face of the base element / substrate is intended to mean the face which, when using the article, is the nearest from the wearer’s eye. It is generally a concave face. On the contrary, the front face of the substrate / base element (or Convex or CX), is the face which, when using the article, is the most distant from the wearer’s eye. It is generally a convex face.

[0053] Also, as used herein, a “transparent substrate / base element” or “transparent interferential coating” is understood to be transparent, when the observation of an image through said substrate is perceived with no significant loss of contrast, that is, when the formation of an image through said substrate is obtained without adversely affecting the quality of the image.

[0054] According to the invention, the transmission factor in the visible range factor Tvshould be understood as defined by the international normalized definition (ISO 13666:1998 Standard) and is measured in accordance with the ISO 8980-3 Standard. It is defined in the wavelength range of from 380 nm to 780 nm for an angle of incidence lower than or equal to 15°, such as 0°.

[0055] The colorimetric coefficients of the optical article of the invention in the international colorimetric system CIE L*a*b* (1976) (such as the Chroma C* and the hue “ / ?”) are calculated between 380 nm and 780 nm, taking the standard illuminant D65 and the observer into account (angle of 0°). The observer is a “standard observer” as defined in the international colorimetric system CIE L*a*b*. Indeed, in the CIE L*a*b* space, it is possible to express not only overall variations in colour, but also in relation to one or more of the parameters L*, a* and b*. This can be used to define new parameters and to relate them to the attributes of the visual sensation. Clarity, related to luminosity, is directly represented by the value of L*. Chroma: C* =(a*2+b*2)1 / 2defines the chromaticness. The angle of hue: h = atan(b* / a*) (expressed in degrees) relates to the hue.

[0056] According to the invention, the colorimetric measurements (in reflection) of the face coated with the interferential multilayered coating / sheet of the invention (convex / front face), reflection factors Rv, hue angle h, and chroma C* in the international colorimetric CIE (L*, a*, b*) space were carried out with a spectrophotometer, such as a Zeiss spectrophotometer or a Cary 7000 spectrophotometer, taking into account the standard illuminant D65, and the standard observer 10° (for h and C*). They are provided in general for an angle of incidence of 0°, 15° or 35°.

[0057] According to the invention, the “angle of incidence (symbol 0)" is the angle formed by a ray of light incident on an ophthalmic lens surface and a normal to the surface at the point of incidence. The ray of light is for instance an illuminant light source, such as the standard illuminant D65 as defined in the international colorimetric CIE L*a*b* (1976). Generally, the angle of incidence changes from 0° (normal incidence) to 90° (grazing incidence). The usual range for angle of incidence is from 0° to 75° and is typically 0° for the present invention.

[0058] The optical characteristics comprise at least the mean light reflection factor in the visible region Rv, also named the "luminous reflectance".

[0059] Herein, the "luminous reflectance" noted Rv, is such as defined in the ISO 13666:1998 Standard, and measured in accordance with the ISO 8980-4, i.e. , this is the weighted spectral reflection average over the whole visible spectrum between 380 nm and 780 nm. Rvis usually measured for an angle of incidence lower than 17°, typically of 15°, 6° or 0°, but can be evaluated for any angle of incidence.

[0060] According to the invention, when the mean light reflection factor in the visible region Rvonto the front and / or rear main face of the optical article is strictly higher than 2.5%, this means that the multilayered interferential sheet is able to provide a mirror behaviour onto the front or rear main surface of the optical article, respectively. Especially, a “mirror behaviour” enables to provide a reduction in transmitted visible, ultra-violet and / or infrared light. In other words, an optical article having on its front main face a mirror behaviour reflects at least a part of light arriving on said surface. Said mirror behaviour increases light reflection at the article / air interface over a determined portion of the spectrum. Especially, reflection may be in the ultraviolet spectrum or in the visible spectrum or in the infrared spectrum or in the near infrared spectrum.

[0061] According to the invention, when the mean light reflection factor in the visible region Rvonto the front and / or rear main face of the optical article is equal to or lower than 2.5%, this means that the multilayered interferential coating is able to provide an antireflective behavior onto the front and / or rear main surface of the optical article respectively.

[0062] As previously mentioned, the term “robustness” of an optical article, such as an ophthalmic lens, in the present invention is defined as the ability of this lens to reach a fully bleached state (in general in the deactivated state) after several cycles of coloration / bleaching of the optical article (in other words after several cycles of activated state when an electrical potential is applied / deactivated state when the reverse electrical potential is applied), such as for instance at least 1 000 cycles, preferably 10 000 cycles and more preferably 100 000 cycles.

[0063] 2. Optical article according to the invention

[0064] As mentioned-above, the Applicant has developed a transparent optical article such as defined in the set of claims, especially an ophthalmic lens, for instance a spectacle lens, comprising a base element, such as a substrate in mineral or organic glass comprising at least an interferential multilayered sheet, said transparent optical article allowing for a combined modulation of the reflection and transmission and to do so without compromising not only the mechanical performances of the optical article, its cosmetic appearance, but also the economic and / or industrial feasibility of its manufacture.

[0065] The optical article according to the invention is preferably an ophthalmic lens, such as an ophthalmic lens for spectacles (spectacle lens), or a blank for ophthalmic lenses.

[0066] As it will be described hereafter (paragraph 3.), the optical article according to the invention can be an optical device, such as an ophthalmic device comprising further a means to provide an electrical potential, for instance an external source, such as a battery, as well as the required electronics, this means being able to be activated / deactivated (on-off button) by the consumer.

[0067] 2.1 The base element

[0068] The optical article according to the present invention comprises a transparent base element.

[0069] According to one embodiment, this base element can be a laminate, that is to say a support film of optical quality to be fixed on an optical / ophthalmic substrate thanks to an adhesive such as a pressure-sensitive adhesive of optical quality (PSA layer). Preferably, the support film is made of cellulose triacetate (TAG) and has a thickness of at least 40 microns, preferably a thickness in the range of 40 pm to 300 pm inclusive and preferably a thickness of 80 to 190 pm. Materials of the support film may be selected from the group of films made of cellulose triacetate (TAG), cellulose acetate butyrate (CAB), polycarbonate (PC), poly(ethylene terephthalate) (PET), poly(methylmethacrylate) (PMMA), urethane polymer (TPU), cyclo olefin copolymer (COG), polyester copoblock amide (like Pebax) and Polyimides. According to another embodiment (described hereafter), the base element can consist in an ophthalmic substrate of a transparent optical article, such as a lens or lens blank, and more preferably an ophthalmic lens or lens blank.

[0070] According to this embodiment, the transparent base element may be a mineral substrate, such as glass, sapphire or diamond.

[0071] Generally speaking, the interferential coating of the optical article according to the invention may be deposited onto any substrate, and preferably onto organic lens substrates, for example a thermoplastic or thermosetting plastic material.

[0072] Thermoplastic may be selected from, for instance: polyamides; polyimide; polysulfones; polycarbonates and copolymers thereof; poly(ethylene terephthalate) and polymethylmethacrylate (PMMA).

[0073] Thermoset materials may be selected from, for instance: cycloolefin copolymers such as ethylene / norbornene or ethylene / cyclopentadiene copolymers ; homo- and copolymers of allyl carbonates of linear or branched aliphatic or aromatic polyols, such as homopolymers of diethylene glycol bis(allyl carbonate) (OR 39®) ; homo- and copolymers of (meth)acrylic acid and esters thereof, which may be derived from bisphenol A ; polymer and copolymer of thio(meth)acrylic acid and esters thereof, polymer and copolymer of allyl esters which may be derived from Bisphenol A or phthalic acids and allyl aromatics such as styrene, polymer and copolymer of urethane and thiourethane, polymer and copolymer of epoxy, and polymer and copolymer of sulphide, disulfide and episulfide, and combinations thereof.

[0074] As used herein, a (co)polymer is intended to mean a copolymer or a polymer. As used herein, a (meth)acrylate is intended to mean an acrylate or a methacrylate. As used herein, a polycarbonate (PC) is intended to mean either homopolycarbonates or copolycarbonates and block copolycarbonates.

[0075] Homopolymers of diethylene glycol bis(allyl carbonate) (CR 39®), allylic and (meth)acrylic copolymers, having a refractive index between 1.54 and 1.58, polymer and copolymer of thiourethane, polycarbonates are preferred.

[0076] In particular, the base element recommended for the invention is a substrate selected from materials obtained by (co)polymerization of di(ethylene glycol) bis(allyl carbonate) and may correspond to the CR-39® ESSI LOR ORMA® lenses.

[0077] As it will be shown hereafter, the base element may be coated with one or more functional coatings prior to depositing the anti reflective coating of the invention. These functional coatings traditionally used in optics may be, without limitation, an impact-resistant primer layer, an abrasion-resistant coating and / or a scratch-resistant coating, a polarizing coating, a photochromic coating or a tinted coating. In the following a substrate means either a bare substrate or such a coated substrate. Preferably, the base element and the optional abrasion-resistant coating and / or a scratch-resistant coating generally coated onto said substrate have a similar / close refractive index so as to avoid fringes or cosmetic defects.

[0078] Prior to depositing the multilayered interferential sheet, the surface of said substrate is usually submitted to a physical or chemical surface activating treatment, so as to reinforce the adhesion of the antireflective coating. Such a pre-treatment is generally conducted under vacuum. It may be a bombardment with energetic and / or reactive species, for example with an ion beam (“Ion Pre-Cleaning” or “I PC”) or with an electron beam, a corona discharge treatment, an ion spallation treatment, an ultraviolet treatment or a plasma-mediated treatment under vacuum, generally using an oxygen or an argon plasma. It may also be an acid or basic treatment and / or a solvent-based treatment (water, hydrogen peroxide or any organic solvent).

[0079] 2.2 The multilayered interferential sheet

[0080] As previously mentioned, the optical article is such as defined in the set of claims and comprises a base element having a front main surface and a rear main surface and at least one multilayered interferential sheet (MIS) deposited onto the front main surface and / or the rear main surface of the base element.

[0081] In particular, the multilayered interferential sheet (MIS) comprises at least:

[0082] (a) a multilayered electrochromic stack (EC stack), and

[0083] (b) optionally a multilayered interferential coating (IC), coated onto or below said (a) multilayered EC stack, comprising at least one LI layer having a refractive index lower than 1.55.

[0084] (a) The multilayered electrochromic stack (EC stack) will be described hereafter.

[0085] According to the invention, the multilayered EC stack comprises at least:

[0086] - two external layers that are a first transparent conductive electrode layer and a second transparent conductive electrode layer,

[0087] - several internal layers interposed between said two external layers and comprising at least :

[0088] (i) a first cathodic layer,

[0089] (ii) a first anodic layer and

[0090] (iii) an ion conductor layer which is positioned between said first cathodic layer (i) and said first anodic layer (ii),

[0091] (iv) at least one bilayer composed of a second cathodic layer (also named hereafter “inner cathodic layer”) and a porous ionic diffusion layer, said at least one bilayer being placed between said ion conductor layer (iii) and either said first cathodic layer (i) or said first anodic layer (ii).

[0092] Hence, the external layers (i.e.: the first and the second transparent conductive electrode layers) do not make direct contact with one another. Especially, they are intended to be electrically connected to the external source, such as a battery, of the optical device (as it will be described below).

[0093] The EC stack according to the invention is able to reversibly switch from an activated state when an electrical potential is applied to a deactivated state when the reverse electrical potential is applied.

[0094] The Applicant has discovered that such a structure enables to provide a MIS which has, in the visible region, a mean light reflection factor difference, A ?V, higher than or equal to 6.0% between the activated state and the deactivated state.

[0095] Especially, the multilayered interferential sheet may have, in the visible region, a mean light reflection factor difference, A ?V, between the activated state and the deactivated state which is higher than or equal to 7.0%, preferably higher than or equal to 8.0%, in particular higher than or equal to 9.0% and especially higher than or equal to 10.0%.

[0096] As used herein, “a mean light reflection factor difference, AF?V, higher than or equal to 6.0% between the activated state and the deactivated state” includes the following values (%) and any intervals among them : 6.0; 6.5; 7.0; 7.5; 8.0; 8.5; 9.0; 9.5; 10.0; 10.5; 11.0; 11.5; 12.0; 12.5; 13.0; 13.5; 14.0; 14.5; 15.0; 15.5; 16.0; 16.5; 17.0; 17.5; 18.0; 18.5; 19.0; 19.5; 20.0; 20.5; 21.0; 21.5; 22.0; 22.5; etc.

[0097] Therefore, the MIS and especially the EC stack offers a wide modulation in reflection in the visible region, notably as compared to standard EC stacks.

[0098] Especially, in a known manner, standard EC stacks are composed of two external transparent conductive electrodes encapsulating two EC layers, i.e.: a cathodic layer such as WO3, an anodic layer such as NiO, which are separated by an ion conductor layer such as Ta2C>5 or a gel electrolyte (for instance, based on UCIO4 in propylene carbonate and poly(methyl methacrylate) or based on NaCIC>4 in propylene carbonate and poly(methyl methacrylate). In general, the anodic layer such as NiO is the inner layer which is the nearest from the base element among these two EC layers. Also, so as to improve the antireflective properties, a layer of SiO2 can also be deposited on top of the optical article.

[0099] As it will be shown in the experimental part below, this kind of EC stack offers to the final optical article a limited variation in reflection between the activated state and the deactivated state.

[0100] On the contrary, the EC stacks according to the invention has been designed to overcome this drawback. For that purpose, the EC stack according to the invention incorporates an interference-based film structure, also named Bragg mirror, into its internal layers. Especially, this interference-based film structure comprises at least one bilayer composed of an inner cathodic layer and a porous ionic diffusion layer.

[0101] A used herein, a Bragg mirror is an interference-based thin film structure that works according to the Bragg rule. The following formula is a simplified version:

[0102] 2dsin0 = / VA, where “d=nt” is the sum of the optical thicknesses of each layer in the periodic structure, “0” the grazing angle and “N” the order of reflection. Therefore, the reflected wavelength A directly depends on the period thickness of the Bragg structure (that is to say the physical thickness tB =tn+tL of a bilayer).

[0103] According to the invention, the Bragg structure is active thanks to the use of electrochromic thin film materials.

[0104] In particular and according to a first embodiment, so as to enhance the reflectivity, the refractive index difference An between the second / inner cathodic layer and the porous ionic diffusion layer of the bilayer in the activated state may be increased or relatively high.

[0105] Especially, this refractive index difference in the activated state, An(activated), is higher than or equal to 0.25, preferably higher than or equal to 0.26, more preferably higher than or equal to 0.27, especially higher than or equal to 0.30 and typically higher than or equal to 0.32.

[0106] As used herein, “a refractive index difference between the second / inner cathodic layer and the porous ionic diffusion layer in the activated state, An(activated) higher than or equal to 0.25” includes the following values (%) and any intervals among them :0.25; 0.26; 0.27; 0.28; 0.29; 0.30; 0.31 ; 0.32; 0.33; 0.34; 0.35; 0.36; 0.37; 0.38; 0.39; 0.40, etc.

[0107] According to the embodiment, the refractive index difference between the second / inner cathodic layer and the porous ionic diffusion layer of the bilayer in the deactivated state, An(deactivated), may be low. For instance, this refractive index difference in the deactivated state, An(deactivated), is lower than or equal to 0.10, preferably lower than or equal to 0.06 and typically lower than or equal to 0.04.

[0108] As used herein, “a refractive index difference between the second / inner cathodic layer and the porous ionic diffusion layer in the deactivated state, An(deactivated) lower than or equal to 0.10” includes the following values and any intervals among them :0.10; 0.09; 0.08; 0.07; 0.06; 0.05; 0.04; 0.03; 0.02; 0.01 ; 0.0.

[0109] Hence, here, according to the embodiment there is a refractive index matching in the deactivated state (or colourless / bleached state) and a refractive index contrast in the activated state (or coloured state) between the material(s) composing the inner cathodic layer and the material(s) composing the porous ionic diffusion layer. This refractive index matching or contrast respectively in the deactivated state or activated state enables to design periodic or aperiodic Bragg structures into the EC stack of the invention. According to the rules of quarterwave optical filters such as explained at paragraphs 0003 to 0005 of the document US2004 / 0157061), Bragg structures can display an intense and selective reflection peak.

[0110] According to a second embodiment, the refractive index contrast / difference may be higher in the deactivated state and lower in the activated state. Hence, here, there is a refractive index matching in the activated state (or colourless / bleached state) and a refractive index contrast in the deactivated state (or coloured state) between the material(s) composing the inner cathodic layer and the material(s) composing the porous ionic diffusion layer.

[0111] According to this embodiment, the refractive index difference between the second / inner cathodic layer and the porous ionic diffusion layer of the bilayer in the activated state, An(activated), may be low. For instance, this refractive index difference in the activated state, An(activated), is lower than or equal to 0.10, preferably lower than or equal to 0.06 and typically lower than or equal to 0.04.

[0112] As used herein, “a refractive index difference between the second / inner cathodic layer and the porous ionic diffusion layer in the activated state, An(activated) lower than or equal to 0.10” includes the following values and any intervals among them :0.10; 0.09; 0.08; 0.07; 0.06; 0.05; 0.04; 0.03; 0.02; 0.01 ; 0.0.

[0113] In addition, according to this second embodiment, this refractive index difference between the second / inner cathodic layer and the porous ionic diffusion layer of the bilayer in the deactivated state, An(deactivated) may be relatively high, such as higher than or equal to 0.25, preferably higher than or equal to 0.26, more preferably higher than or equal to 0.27, especially higher than or equal to 0.30, such as higher than or equal to 0.32.

[0114] As used herein, “a refractive index difference between the second / inner cathodic layer and the porous ionic diffusion layer in the deactivated state, An(deactivated) higher than or equal to 0.25” includes the following values and any intervals among them :0.25; 0.26; 0.27; 0.28; 0.29; 0.30; 0.31 ; 0.32; 0.33; 0.34; 0.35; 0.36; 0.37; 0.38; 0.39; 0.40, etc.

[0115] In addition, the Applicant demonstrated that the reflectivity, spectral selectivity and spectral peak position can be adjusted by refining the structures of the EC stacks (bilayer thickness, number of bilayers, index contrast, choice of the materials, etc.). Hence, periodic, aperiodic or chirped structures can be optimized to present a wider reflection peak.

[0116] Especially, according to a characteristic of the invention, in the EC stack according to the invention, the first anodic layer (ii) (such as NiO) is positioned so as to be the inner layer of the EC stack which is the farthest from the base element.

[0117] According to another characteristic of the invention, in the EC stack according to the invention, the first anodic layer (ii) is positioned so as to be the inner layer which is the nearest from the base element. This embodiment shows among the highest reflection modulation.

[0118] In particular, according to this characteristic, in the multilayered EC stack (a), the at least one bilayer is located between the ion conductor layer (iii) and the first cathodic layer (i). In general, the at least one bilayer may be positioned onto the ion conductor layer (iii), such as directly onto this ion conductor layer (iii). Therefore, according to this characteristic, the first anodic layer (ii) is placed below the at least one bilayer of the EC stack. The Applicant discovered that, surprisingly, this structure improves the mean light reflection factor difference, AF?v between the deactivated state (bleached state) and the activated state (coloured state) (i.e.: appearance of a high reflection peak in the activated state).

[0119] For instance, (a) the multilayered EC stack may comprise in the direction moving away from the base element:

[0120] - the first transparent conductive electrode layer; - the first anodic layer (ii);

[0121] - the ion conductor layer (iii);

[0122] - the at least one bilayer (iv) composed of a second / inner cathodic layer and a porous ionic diffusion layer;

[0123] - the first cathodic layer (ii), and

[0124] - the second transparent conductive electrode layer.

[0125] For instance, the first and the second transparent conductive electrode layers comprise one or several of the following components: tin-doped indium oxide (ITO), preferably composed of 90% InaOa and 10% of SnO2, aluminum- doped zinc oxide (AZO), fluorine- doped tin oxide (FTO), thin metals (Ag, Au, Cu...), graphene, carbon nanotubes. Preferably, the first and the second transparent conductive electrode layers comprise ITO (also named hereafter “dense ITO” by opposition to porous ITO), more preferably composed of 90% ln2O3 and 10% of SnO2.

[0126] Especially, the first and the second transparent conductive electrode layers (ITO layers) have a thickness ranging from 5 to 200 nm, preferably ranging from 15 to 160 nm and typically ranging from 20 to 130 nm.

[0127] According to the invention, a thickness ranging from 5 to 190 nm includes the following values (nm) and any intervals among them: 5; 10; 20; 30; 40; 50; 60; 70; 80; 90; 100; 110; 120; 130; 140; 150; 160; 170; 180; 190 and 200.

[0128] In a known manner, the first and the second transparent conductive electrode layers allow for the application of a potential and the insertion of electrons into the cathodic layer (such as WO3) and the anodic layer (NiO) (i.e: the electrochromic materials) during the colouration (activated state) and bleaching (deactivated state) phases respectively.

[0129] In general, the first conductive layer and / or the second conductive layer may have a physical thickness ranging from 10 to 200 nm, preferably from 20 to 190 nm and more preferably from 30 to 160 nm.

[0130] Generally, the first anodic layer (ii) comprises one or more of the following materials: NiO, LixNiO, COO2, CraOa, FeaO4, 1 rOa, MnOa, VO2, V2O5. In particular, the (ii) first anodic layer comprises NiO or LixNiO, preferably with x~0.5 (x being the amount of lithium intercalation).

[0131] According to an aspect of the invention, this (ii) first anodic layer has a physical thickness lower than or equal to 600 nm, preferably lower than or equal to 550 nm, especially ranging from 50 nm to 530 nm and typically ranging from 100 to 300 nm, such as ranging from 180 to 230 nm.

[0132] In particular, the (iii) ion conductor layer may comprise one or more of the following materials: TaaOs, SiC>2, ZrC>2, UPON, LiNbOa, LiTaOa, U3PO4, polymer electrolytes and comprises preferably TaaOs.

[0133] For instance, the polymer electrolytes which are suitable according to the invention comprise one or more of the following compounds: UCIO4 or NaCIO4 for instance in propylene carbonate (PC), poly(methyl methacrylate) (PMMA) and / or acetonitrile (ACN). Suitable composition of polymer electrolytes may comprise: 1M of UCIO4 in PC with 20% by weight of PMMA (relative to the total weight of the polymer electrolyte); UCIO4 : PC: PMMA: ACN at 3:7:20:70 wt.% (relative to the total weight of the polymer electrolyte); or 0.1 M of NaCIC>4 in PC with 20% by weight of PMMA (relative to the total weight of the polymer electrolyte).

[0134] In general, the optical article comprising such a polymer electrolyte is prepared according to the following method: a) depositing by sputtering on the base element, such as a glass substrate, the first external layer, such as ITO, and generally the first anodic layer, such as NiO; b) depositing by sputtering on the second external layer (such as ITO), the at least one bilayer composed of a second cathodic layer (such as WO3) and ion conductor layer, such as porous ITO, preferably said second external layer is also deposited on a base element, such as a glass substrate; c) preparing the polymer electrolyte by stirring for instance PC with LiCIO4 (1 M), then adding generally PMMA (for instance at 20% wt.%), then stirring by heating the mixture, for instance at 60°C so as to obtain a colorless gel electrolyte; d) spreading, for instance, at 60°C of the colorless gel electrolyte obtained at step c) onto the stack obtained at the end of step a) and then superimpose onto this superposing colorless gel electrolyte the stack obtained at the end of step b); step b) may be carried out before step a) and / or simultaneously.

[0135] Generally, according to an embodiment (in general when the (iii) ion conductor layer is not a polymer electrolyte), the physical thickness of this (iii) ion conductor layer is relatively thick and may be lower than or equal to 600 nm, preferably lower than or equal to 580 nm, especially ranging from 50 nm to 560 nm and typically ranging from 100 to 560 nm, such as ranging from 450 to 560 nm.

[0136] According to another embodiment (generally when the (iii) ion conductor layer is a polymer electrolyte), the polymer electrolyte may have a thicker physical thickness, which is especially higher than or equal to 100 pm, preferably higher than or equal to 120 pm and is within the range from 30 pm to 1000 pm, preferably from 100 pm to 200 pm and typically from 100 pm to 140 pm.

[0137] As used herein, “a physical thickness lower than or equal to 600 nm” (for any layers) includes the following values (nm) and any intervals among them : 600; 590, 580; 570; 560; 550; 540; 530; 520; 510; 500; 490; 480; 470; 460; 450; 440; 430; 420; 410; 400; 390; 380; 370; 360; 350; 340; 330; 320; 310; 300; 290; 280; 270; 260; 250; 240; 230; 220; 210; 200; 190; 180; 170; 160; 150; 140; 130; 120; 110; 100; 90; 80; 70; 60; 50; 40; 30.

[0138] In addition, the (ii) first cathodic layer may comprise one or more of the following materials: WO3, MoOs, Nb20s, TiC>2, V2O5 and comprises preferably WO3.

[0139] The physical thickness of this (ii) first cathodic layer may be lower than or equal to 300 nm, preferably lower than or equal to 280 nm, such as lower than or equal to 250 nm. In general, this (ii) first cathodic layer may have a physical thickness which is ranged from 40 nm to 250 nm, preferably from 50 nm to 150 nm, and typically from 60 nm to 100 nm. Also, as used herein, “a physical thickness lower than or equal to 300 nm” (for any layers) includes the following values (nm) and any intervals among them : 300; 290; 280; 270; 260; 250; 240; 230; 220; 210; 200; 190; 180; 170; 160; 150; 140; 130; 120; 110; 100; 90; 80; 70; 60; 50.

[0140] Then, the material(s) composing the at least one bilayer of the EC stack may be as follows:

[0141] - the second or inner cathodic layer may comprise the same material(s) as the one(s) described for the first cathodic layer, that is to say one or more of the following materials: WO3, MoOa, Nb2O5,TiC>2, V2O5 and comprises preferably WO3, and

[0142] - the porous ionic diffusion layer may comprise a porous tin-doped indium oxide (hereafter “porous ITO”), preferably composed of 90% ln2Os and 10% of SnO2. In general, this porous tin-doped indium oxide has a porosity higher than or equal to 0.5%, preferably higher than or equal to 2%, more preferably higher than or equal to 8% and typically higher than or equal to 12% determined by ellipsometry measurements. For instance, the porous ionic diffusion layer may have a porosity within the range from 0.5% to 20%.

[0143] As used herein, “a porosity higher than or equal to 0.5%” includes the following values (%) and any intervals among them: 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 , 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9; 2.0; 2.2; 2.4; 2.6; 2.8; 3.0; 3.2; 3.4; 3.6; 3.8; 4.0; 4.2; 4.4; 4.6; 4.8; 5.0; 5.2; 5.4; 5.6; 5.8; 6.0; 6.2; 6.4; 6.8; 7.0; 7.2; 7.4; 7.6; 7.8; 9.0; 8.2; 8.4; 8.6; 8.8; 9.0; 9.2; 9.4; 9.6; 9.8; 10.0;

[0144] 10.2; 10.4; 10.6; 10.8; 11.0; 11.2; 11.4; 11.6; 11.8; 12.0; 12.2; 12.4; 12.6; 12.8; 13.0; 13.2;

[0145] 13.4; 13.6; 13.8; 14.0; 14.2; 14.4; 14.6; 14.8; 15.0; 15.0; 15.2; 15.4; 15.6; 15.8; 16.0; 16.2;

[0146] 16.4; 16.6; 16.8; 17.0; 17.2; 17.4; 17.6; 17.8; 18.0; 18.2; 18.4; 18.6; 19.0; 19.2; 19.4; 19.6;

[0147] 19.8; 20.0.

[0148] Especially, the Applicant has discovered that the insertion of this porous ionic diffusion layer between the inner cathodic layer(s) or between the inner cathodic layer and the first cathodic layer enables not only the conduction of electrons, but also the ionic diffusion. The combination of all these properties allowing for all the cathodic layers of the EC stack according to the invention to participate in the EC activity of the optical article. In other words, the porous ionic diffusion layer permits the ionic diffusion to allow for the colouration of all WO3 layers (in general in the activated state), while being sufficiently conductive for electrons.

[0149] According to an embodiment of the invention, as a means of rendering the porous ionic diffusion layer more porous, and thus more conductive for ions, it is possible to play on the deposition pressure. In general, a higher deposition pressure leads to a more porous layer. For instance, oxides are obtained by magnetron sputtering deposition into a vacuum chamber at a pressure ranging from 1 to 20 mTorr, preferably ranges from 5 mTorr, to 15 mTorr, typically ranges from 8 mTorr to 12 mTorr, such as lOmTorr. Indeed, increasing the pressure reduces the mean free path of the sputtered atoms and increases shadowing effects. For instance, in the case of the porous ITO material, the resistivity of the formed layer was 4 to 5 times higher and the refractive index at 550 nm decreased from 2.074 to 1 .978.

[0150] Therefore, for instance, if the inner cathodic layer is WO3, the refractive index at 550 nm of such a layer will be of 1.92 in the deactivated state (or bleached state) and of 1.65 in the activated state (or coloured state). Thus, the refractive index difference between the second / inner cathodic layer (WO3) and the porous ionic diffusion layer if this one is made of porous ITO such as described above in the activated state, An(activated), is 0.33 (i.e.: refractive indices contrast) and in the deactivated state, An(deactivated), is 0;06 (i.e.: matching of refractive indices).

[0151] In addition, the number of bilayers composed of a second / inner cathodic layer and a porous ionic diffusion layer into (a) the multilayered EC stack may be of 1 , 2, 3, 4, 5, 6, 7, etc. Advantageously, the number of bilayers is equal to 1 or 2. Indeed, a more limited number of bilayers enables to reduce the total thickness of the MIS according to the invention.

[0152] Especially, the physical thickness of each inner cathodic layer may be lower than or equal to 300 nm, preferably lower than or equal to 280 nm, such as lower than or equal to 250 nm. In general, inner cathodic layer may have a physical thickness which is ranged from 20 nm to 250 nm, preferably from 30 nm to 150 nm, and typically from 40 nm to 100 nm. Also, as used herein, “a physical thickness lower than or equal to 300 nm” (for any layers) includes the following values (nm) and any intervals among them : 300; 290; 280; 270; 260; 250; 240; 230; 220; 210; 200; 190; 180; 170; 160; 150; 140; 130; 120; 110; 100; 90; 80; 70; 60; 50; 40; 30; 20; 10; 5; etc.

[0153] In addition, the physical thickness of each porous ionic diffusion layer may be lower than or equal to 150 nm, preferably lower than or equal to 120 nm, such as lower than or equal to 100 nm. In general, inner cathodic layer may have a physical thickness which is ranged from 20 nm to 120 nm, preferably from 30 nm to 100 nm, and typically from 40 nm to 90 nm. Also, as used herein, “a physical thickness lower than or equal to 150 nm” (for any layers) includes the following values (nm) and any intervals among them: 150; 140; 130; 120; 110; 100; 90; 80; 70; 60; 50; 40; 30; 20; 10; 5; etc.

[0154] Generally, in the at least one bilayer or when the EC stack comprises two or more bilayers, at least into one bilayer, preferably into at least two bilayers and typically into all the bilayers, the second / inner cathodic layer is in direct contact with the porous ionic diffusion layer.

[0155] Also, according to a characteristic of the invention, when the EC stack comprises two or more bilayers, each second / inner cathodic layer may have a similar physical thickness (i.e.: + / - 10 nm) and each porous ionic diffusion layer may have a similar physical thickness (i.e.: + / - 10 nm).

[0156] According to another characteristic of the invention, when the EC stack comprises two or more bilayers, the structure and / or physical thickness of at least two bilayers may be different (i.e.: the material and / or the physical thickness of each inner cathodic layer and each porous ionic diffusion layer may differ from one bilayer to another).

[0157] As previously mentioned, the EC stack (a) according to the invention exhibits electrochromic properties, meaning that it reversibly changes colour upon the application of an electric potential, or reversible changes colour upon changing the magnitude of the electrical potential applied.

[0158] In general, the applied electrical potential is ranging from from 1 0 (not included) to 3 V |. For instance, an electrical potential of 3 V enables to totally switch the EC stack from a deactivated state (initial) that is generally transparent, to an activated state that is coloured.

[0159] In some embodiments, the electrochromic stack may be at least partially activated, for instance by applying half of the electrical potential. Typically, the state of colouration is controlled by the amount of time the potential is applied (i.e., the number of inserted electrons).

[0160] As mentioned above, the multilayered interferential sheet (MIS) according to the invention may also comprise (b) a multilayered interferential coating (IC).

[0161] (b) This multilayered interferential (IC) coating will be described hereafter.

[0162] In general, this (b) IC coating is preferably coated onto or below the (a) multilayered EC stack and is, in general, respectively in direct contact with the outermost layer or the innermost layer of the EC stack.

[0163] Generally, this IC coating comprises at least one LI layer having a refractive index lower than 1 .55 at 550 nm. Indeed, a layer of the IC coating is said to be a low refractive index layer (LI) when its refractive index is lower than 1.55, preferably lower than or equal to 1.50, more preferably lower than or equal to 1 .48. Said LI layer preferably has a refractive index higher than 1.36.

[0164] In particular, the LI layer of the IC coating which is the farthest from the base element has a physical thickness lower than or equal to 150 nm, preferably ranging from 20 to 140 nm, especially ranging from 40 to 110 nm. Also, as used herein, “a physical thickness lower than or equal to 150 nm” (for any layers) includes the following values (nm) and any intervals among them: 150; 140; 130; 120; 110; 100; 90; 80; 70; 60; 50; 40; 30; 20; 10; 5; etc.

[0165] Also, this IC coating may comprise one HI layer having a refractive index higher than or equal to 1.55 at 550 nm. Indeed, a layer of the IC coating is said to be a layer with a high refractive index (HI) when its refractive index is higher than or equal to 1 .55, preferably higher than or equal to 1.6, even more preferably higher than or equal to 1.90, such as 1.95 even more preferably higher than or equal to 2.00, such as 2.14.

[0166] According to a characteristic of the invention, the IC coating according to the invention may comprise at least one layer with a high refractive index (HI) and at least one layer with a low refractive index (LI), preferably two LI layers. Especially, it may comprise here a simple stack, since the layer total number in the IC coating is higher than or equal to 1 , preferably higher than or equal to 2, especially higher than or equal to 3 and advantageously lower than or equal to 7, more preferably lower than or equal to 6, even more preferably lower than or equal to 5.

[0167] Therefore, in general, the MIS (comprising both the EC stack and the optional IC coating) according to the invention comprises a layer total number higher than or equal to 7, preferably higher than or equal to 8, preferably higher than or equal to 9. The MIS according to the invention may comprise a layer total number lower than or equal to 25, preferably lower than or equal to 24, preferably lower than or equal to 20, in particular lower than or equal to 15, especially lower than or equal to 11 , in particular lower than or equal to 10.

[0168] Especially, when present, HI layers and LI layers of the optional interferential coating do not need to alternate with each other in the stack, although they also may, according to one embodiment of the invention. Thus, two HI layers (or more) may be deposited onto each other, as well as two LI layers (or more) may be deposited onto each other.

[0169] In general, the sum of physical thickness of all HI layers in the IC coating is ranging from 15 nm to 260 nm, preferably is ranging from 20 nm to 240 nm.

[0170] The HI layer is a traditional high refractive index layer that is well known in the art. It generally comprises one or more metal oxides such as, without limitation, zirconia (ZrCh), alumina (AI2O3), tantalum pentoxide (Ta2Os), praseodymium oxide (P^Ch), praseodymium titanate (PrTiCh), lanthanum oxide (La2Os), yttrium oxide (Y2O3), niobium oxide (Nb20s), titanium dioxide (TiCh) and mixtures thereof. The preferred materials include zirconia (ZrCh), tantalum pentoxide (Ta2Os). Optionally, the HI layers may further contain silica or other materials with a low refractive index, provided they have a refractive index higher than or equal to 1 .6 as indicated hereabove.

[0171] The LI layer is also well known and may comprise, without limitation, MgF2, SiO2, a mixture of silica and alumina, especially silica doped with alumina (the latter contributing to increase the antireflective coating thermal resistance), or a mixture thereof. The LI layer is preferably a layer comprising at least 80% by weight of silica, more preferably at least 90% by weight of silica, relative to the layer total weight, and even more preferably consists in a silica layer (SiCh). Optionally, the LI layers may further contain materials with a high refractive index, provided the refractive index of the resulting layer is lower than to 1 .6.

[0172] When a LI layer comprising a mixture of SiO2 and AI2O3 is used, it preferably comprises from 1 to 10%, more preferably from 1 to 8% and even more preferably from 1 to 5% by weight of AI2O3 relative to the SiO2 + AI2O3 total weight in such layer.

[0173] For example, SiO2 doped with 4% AI2O3 by weight, or less, or SiO2 doped with 8% AI2O3 may be employed. SiCh / AhOs mixtures, that are available on the market may be used, such as LIMA® marketed by the Umicore Materials AG company (refractive index n = 1.48-1.50 at 550 nm), or L5® marketed by the Merck KGaA company (refractive index n = 1.48 at 500 nm).

[0174] In general, the MIS may be deposited onto a sub-layer. It should be noted that such sub-layer does not belong to the MIS. As used herein, a sub-layer or adhesion layer is intended to mean a relatively thick coating, used in order to improve the mechanical properties such as the abrasion resistance and / or the scratch resistance of said coating and / or so as to reinforce its adhesion to the substrate or to the underlying coating.

[0175] Because of its relatively high thickness, the sub-layer does not generally take part to the anti reflective optical activity, especially when it has a refractive index close to that of the underlying substrate (which is generally the anti-abrasion and anti-scratch coating or the bare substrate).

[0176] The sub-layer should have a thickness that is sufficient for promoting the abrasion resistance of the MIS coating, but preferably not to such an extent that a light absorption could be caused, which, depending on the sub-layer nature, could significantly reduce the relative transmission factor Tv. Its thickness is generally lower than 300 nm, more preferably lower than 200 nm, and is generally higher than 90 nm, more preferably higher than 100 nm.

[0177] The sub-layer preferably comprises a SiCh-based layer, this layer comprising preferably at least 80% by weight of silica, more preferably at least 90% by weight of silica, relative to the layer total weight, and even more preferably consists in a silica layer. The thickness of such silica-based layer is generally lower than 300 nm, more preferably lower than 200 nm, and is generally higher than 90 nm, more preferably higher than 100 nm.

[0178] According to an embodiment, the MIS is not deposited onto a sub-layer such as described above.

[0179] In general, the MIS total thickness is lower than or equal to 2 pm, preferably equal to or below 1.5 pm, typically lower than or equal to 1.2 pm. As used herein, “a physical thickness lower than or equal to 2 pm or 2 000 nm” (for any layers) includes the following values (nm) and any intervals among them: 2000; 1950, 1900, 1850, 1800, 1750, 1700, 1650, 1600, 1550, 1500, 1450, 1400, 1350, 1300, 1250, 1200, 1100, 1000, 950, 900, 850; 800; 750, 700, 650, 600, etc.

[0180] (c) optical characteristics

[0181] Generally, by selecting the suitable materials and physical thicknesses for the various layers of the MIS (i.e. forming the EC stack and the optional IC coating), it is possible to obtain different optical characteristics, such as Rvand the transmission Tv.

[0182] All the Rvand Tvvalues according to the invention are measured with an angle of incidence equal to or below 17°, such as equal to or below 15° or for instance 0°.

[0183] Especially, the multilayered interferential sheet has, in the visible region, a mean light reflection factor Rvin the deactivated state (in general the bleached state) that is lower than or equal to 20%, preferably lower than or equal to 15%, in particular lower than or equal to 10% and typically lower than or equal to 9%.

[0184] As used herein, “a mean light reflection factor Rvin the deactivated state that is lower than or equal to 20%” includes the following values (%) and any intervals among them: 20; 19.5; 19.0; 18.5; 18.0; 17.0; 16.5; 16.0; 15.5; 15.0; 14.5; 14.0; 13.5; 13.0; 12.5; 12.0; 11.5; 11.0; 10.5; 10.0; 9.5; 9.0; 8.5; 8.0; 7.5; 7.0; 6.5; 6.0; 5.5; 5.0; 4.5; 4.0; 3.5; 3.0; 2.5; 2.0; 1.5; 1.0; 0.9; 0.8; 0.7; 0.6; 0.5, etc.

[0185] According to one embodiment, the multilayered interferential sheet has, in the visible region, a mean light reflection factor Rvin the activated state that is higher than or equal to 15%, preferably higher than or equal to 20%, in particular higher than or equal to 25% and typically higher than or equal to 30% (provided that the multilayered interferential sheet has, in the visible region, a mean light reflection factor difference, ARV, which is higher than or equal to 6.0% between the activated state and the deactivated state).

[0186] According to another embodiment of the invention, the multilayered interferential sheet has, in the visible region, a mean light reflection factor Rvin the deactivated state that is lower than or equal to 2.5%, preferably lower than or equal to 1 .5%, in particular lower than or equal to 1.2% and typically lower than or equal to 1.0%.

[0187] According to this embodiment, the multilayered interferential sheet has, in the visible region, a mean light reflection factor Rvin the activated state that is higher than or equal to 6%, preferably higher than or equal to 7%, in particular higher than or equal to 8% and typically higher than or equal to 9% (also, provided that the multilayered interferential sheet has, in the visible region, a mean light reflection factor difference, ARV, which is higher than or equal to 6.0% between the activated state and the deactivated state).

[0188] Also, as used herein, “a mean light reflection factor Rvin the activated state that is higher than or equal to 6%” includes the following values (%) and any intervals among them: 6; 6.5; 7.0; 7.5; 8.0; 8.5; 9.0; 9.5; 10.0; 10.5; 11.0; 11.5; 12.0; 12.5; 13.0; 13.5; 14.0; 14.5; 15.0; 15.5; 16.0; 16.5; 17.0; 17.5; 18.0; 18.5; 19.0; 19.5; 20.0.

[0189] In addition, the multilayered interferential sheet has, in the visible region, a transmission factor in the visible range Tvwhich is higher than or equal 60%, preferably higher than or equal to 65%, more preferably higher than or equal to 70 %, in particular higher than or equal to 75%, in the deactivated state. As used herein, “a transmission factor in the visible range Tvwhich is higher than or equal to 60%” includes the following values (%) and any intervals among them: 60; 61 ; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71 ; 72; 73; 74; 75; 76; 77; 78; 79; 80; 81 ; 82; 83; 84; 85; 86; 87; 88; 89; 90, etc.

[0190] Also, the multilayered interferential sheet has, in the visible region, a transmission factor in the visible range Tvwhich is lower than or equal 20%, preferably lower than or equal to 15%, more preferably lower than or equal to 10%, in particular lower than or equal to 8%, in the activated state. As used herein, “a transmission factor in the visible range Tvwhich is lower than or equal to 20%” includes the following values (%) and any intervals among them: 20; 19; 18; 17; 16; 15; 14; 13; 12; 11 ; 10; 9; 8; 7; 6; 5; 4; 3; 2; 1 , etc.

[0191] According to one aspect of the invention, the MIS is coloured (mirror reflection) when a certain electrical potential is applied (activated state) for a predetermined time (linked to the charging time of the EC layers) and bleached when the reversed electrical potential is applied (i.e.: deactivated state). In this embodiment the MIS may stay in the induced state (activated or deactivated) without any external potential applied to it (i.e.: tint preservation or no tint, respectively).

[0192] Hence, according to this embodiment of the invention, the MIS has:

[0193] - a mean light reflection factor in the visible region Rvlower than or equal to 2.5 %, preferably lower than or equal to 1 .5%, in particular lower than or equal to 1.2% and typically lower than or equal to 1 .0% in the deactivated state, and

[0194] - a mean light reflection factor in the visible region Rvhigher than 6.0 %, preferably higher than or equal to 7%, more preferably higher than or equal to 8 %, in particular higher than or equal to 9 %, in the activated state (provided that the multilayered interferential sheet has, in the visible region, a mean light reflection factor difference, ARV, which is higher than or equal to 6.0% between the activated state and the deactivated state).

[0195] According to this embodiment of the invention, the MIS may have:

[0196] - a transmission factor in the visible range Tvhigher than or equal to 70%, more preferably higher than or equal to 71 %, especially higher than or equal to 72% in the deactivated state and,

[0197] - a transmission factor in the visible range Tvlower than 20 %, more preferably lower than or equal to 15% and is in general lower than or equal to 10% in the activated state.

[0198] According to another aspect of the invention, the MIS coating is coloured (mirror reflection) when an electrical potential is applied and is still coloured (mirror reflection) when the inverted electrical potential is applied.

[0199] Hence, according to this aspect of the invention, the MIS has:

[0200] - a mean light reflection factor in the visible region Rvlower than or equal to 11%, preferably lower than or equal to 10%, in particular lower than or equal to 9% and typically lower than or equal to 8% in the deactivated state, and

[0201] - a mean light reflection factor in the visible region Rvhigher than 15%, preferably higher than or equal to 17%, more preferably higher than or equal to 20 %, in particular higher than or equal to 25%, in the activated state (provided that the multilayered interferential sheet has, in the visible region, a mean light reflection factor difference, ARV, which is higher than or equal to 6.0% between the activated state and the deactivated state).

[0202] According to this embodiment of the invention, the MIS may have:

[0203] - a transmission factor in the visible range Tvhigher than or equal to 60%, more preferably higher than or equal to 62%, especially higher than or equal to 67% in the deactivated state and,

[0204] - a transmission factor in the visible range Tvlower than 20 %, more preferably lower than or equal to 15% and is in general lower than or equal to 10% in the activated state. 2.3 Other functional layers

[0205] In some applications, it is preferred that the main surface of the base element be coated with one or more functional coatings improving its optical and / or mechanical properties, prior to depositing the MIS of the invention.

[0206] These functional coatings traditionally used in optics may be, without limitation, an impact-resistant primer layer, an internal abrasion-resistant coating (also named hard coat), an antistatic coating especially on the concave face of the optical article, or a stack made of two or more of such coatings.

[0207] Fig.1 shows an embodiment of an optical article according to the invention.

[0208] In general and by referring to Fig.1 , an optical article such as an ophthalmic lens 300 according to the invention comprises a base element / substrate 301 coated in succession on its front face 303 with an anti-shock primer layer 304, with an anti-abrasion and / or anti-scratch layer 305, the MIS according to the invention 306, and optionally with a hydrophobic and / or oleophobic coating (not represented). The optical article according to the invention is preferably an ophthalmic lens for a pair of spectacles (spectacle lenses), or an ophthalmic lens blank.

[0209] In addition, the back face 302 of the optical article such as ophthalmic lens substrate may be coated in succession with an anti-shock primer layer 304, with an anti-abrasion and / or anti-scratch layer 307, with a standard antireflective coating 308, and optionally with a hydrophobic and / or oleophobic coating (not represented). a) The abrasion-resistant and / or to scratch-resistant coatings

[0210] The abrasion-resistant and / or to scratch-resistant coatings are preferably hard coatings based on poly(meth)acrylates or on silanes generally comprising one or more mineral fillers intended to increase the hardness and / or the refractive index of the coating once cured.

[0211] Hard anti-abrasion and / or anti-scratch coatings are preferably prepared from compositions comprising at least one alkoxysilane and / or a hydrolyzate of the latter, for example obtained by hydrolysis with a hydrochloric acid solution and optionally condensation and / or curing catalysts.

[0212] Mention may be made, among the coatings recommended in the present invention, of coatings based on epoxysilane hydrolyzates, such as those described in the patents FR 2702486 (EP 0614957), US 4 211 823 and US 5 015 523.

[0213] A preferred composition for an anti-abrasion and / or anti-scratch coating is that disclosed in the patent FR 2 702 486 on behalf of the applicant. It comprises an epoxytrialkoxysilane and dialkyldialkoxysilane hydrolyzate, colloidal silica and a catalytic amount of aluminum-based curing catalyst, such as aluminum acetylacetonate, the remainder being essentially composed of solvents conventionally used for the formulation of such compositions. Preferably, the hydrolyzate used is a hydrolyzate of y- glycidoxypropyltrimethoxysilane (GLYMO) and dimethyldiethoxysilane (DM DES). The anti-abrasion and / or anti-scratch coating composition may be deposited on the main face of the substrate by dip coating or spin coating. It is subsequently cured by the appropriate route (preferably thermal or UV).

[0214] The thickness of the anti-abrasion and / or anti-scratch coating generally varies from 2 to 10 .m, preferably from 3 to 5 .m. b) Primer coating

[0215] It is possible, prior to the deposition of the anti-abrasion and / or anti-scratch coating, to deposit, on the base element / substrate, a primer coating which improves the impact resistance and / or the adhesion of the subsequent layers in the final product. This coating can be any impact-resistant primer layer conventionally used for articles made of transparent polymeric material, such as ophthalmic lenses.

[0216] Mention may be made, among preferred primer compositions, of compositions based on thermoplastic polyurethanes, such as those described in the Japanese patents JP 63- 141001 and JP 63-87223, poly(meth)acrylic primer compositions, such as those described in the patent US 5 015 523, compositions based on thermosetting polyurethanes, such as those described in the patent EP 0 404 111 , and compositions based on poly(meth)acrylic latexes or on latexes of polyurethane type, such as those described in the patents US 5 316 791 and EP 0 680 492.

[0217] Preferred primer compositions are polyurethane-based compositions and latex-based compositions, in particular polyurethane latexes optionally containing polyester units.

[0218] Among commercially available primer compositions suitable for the invention, mention may be made of the following: Witcobond(R) 232, Witcobond(R) 234, Witcobond(R) 240, Witcobond(R) 242, Neorez(R) R- 962, Neorez(R) R-972, Neorez(R) R-986 and Neorez(R) R- 9603.

[0219] It is also possible to use in the primer compositions blends of these latexes, in particular of polyurethane latex and poly(meth)acrylic latex.

[0220] These primer compositions may be deposited on the faces of the article by dip coating or spin coating then dried at a temperature of at least 70°C and possibly of as a high as 100°C and preferably of about 90°C, for a time of 2 minutes to 2 hours and generally of about 15 minutes, in order to form primer layers having thicknesses, post-bake, of 0.2 to 2.5 .m and preferably from 0.5 to 1 .5 .m. c) Hydrophobic coatings and / or oleophobic coatings

[0221] The optical article, such as an ophthalmic lens according to the invention may also comprise coatings, formed on the MIS and capable of modifying its surface properties, such as hydrophobic coatings and / or oleophobic coatings (anti-smudge top coat). These coatings are preferably deposited on the external layer of the UV-reflecting interference coating. They are generally less than or equal to 10 nm in thickness, preferably from 1 to 10 nm in thickness and better still from 1 to 5 nm in thickness. It is generally a question of fluorosilane or fluorosilazane coatings. They may be obtained by depositing a fluorosilane or fluorosilazane precursor preferably comprising at least two hydrolysable groups per molecule. The fluorosilane precursors preferably contain fluoropolyether groups and better still perfluoropolyether groups. These fluorosilanes are well known and are described, inter alia in patents US 5,081 ,192, US 5,763,061 , US 6,183, 872, US 5,739, 639, US 5,922,787, US 6,337,235, US 6,277,485 and EP 0933377.

[0222] One preferred hydrophobic and / or oleophobic coating composition is sold by Shin-Etsu Chemical under the denomination KP 801 M(R). Another preferred hydrophobic and / or oleophobic coating composition is sold by Daikin Industries under the denomination OPTOOL DSX(R). It is a question of a fluororesin comprising perfluoropropylene groups.

[0223] 2.4 Process

[0224] The various layers of the MIS and the optional sub-layer are preferably deposited by vapor deposition, under vacuum, according to any of the following methods: i) by optionally ion-beam assisted, evaporation; ii) by ion-beam sputtering; iii) by cathode sputtering; iv) by plasma-assisted chemical vapor deposition. 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.

[0225] Preferably, the deposition of each of the layers of the MIS and of the optional sub-layer is conducted by evaporation under vacuum or sputtering, preferably by magnetron sputtering.

[0226] The present invention also relates to a process for manufacturing an optical article as defined in any one of the preceding claims, comprising the following steps:

[0227] (a) providing the base element having a front main surface and a rear main surface;

[0228] (b) depositing, preferably by magnetron sputtering, onto said front main surface and / or said rear main surface in a vacuum chamber, said MIS.

[0229] Naturally, the various embodiments described above for the optical article also apply to this method of manufacturing the optical article and will not be repeated below.

[0230] 3. Optical device according to the invention

[0231] The current invention also relates to an optical device, such as an ophthalmic device, comprising:

[0232] - a frame comprising at least one housing, preferably two housings;

[0233] - at least an optical article, preferably two optical articles, such as defined above, the at least one optical article being mounted into said at least housing, preferably the two optical articles are mounted into the corresponding housings, respectively ;

[0234] - an external source, such as a battery, and

[0235] - connecting elements disposed between the transparent conductive electrode layers of the EC stack of the optical article and the external source. Fig.2 shows an optical device according to an embodiment of the invention, especially an ophthalmic device.

[0236] By referring to Fig.2, the ophthalmic device 1 comprises a frame 4 composed of at least two housings wherein are disposed, respectively, two ophthalmic lenses 3a, 3b according to the invention, each lens 3a and 3b comprising the electrochromic MIS of the invention. The ophthalmic device 1 also comprises spectacle legs 2 whose structure is capable of fixings the frame 4 to the head of the user.

[0237] Furthermore, the ophthalmic device 1 , and especially the frame 4 may comprise a control unit 16 or circuit for controlling the variation in amplitude, for example a variation in transmission in the visible spectrum of the electrochromic MIS. In particular, the control unit 16 is, for example, a miniaturized electronic control card equipped with a microcontroller which makes it possible to control the activation of the electrochromic MIS, or its deactivation, or else a transmission or reflection level of the electrochromic MIS.

[0238] In addition, the ophthalmic device 1 comprises at least an external source 13, such as a battery and connecting elements disposed between the transparent conductive electrode layers of the EC stack of the optical article and the external source 13. These elements may be mounted in the eyeglass legs 2.

[0239] As mentioned above, the two external layers of the EC stack, that is to say, the first and the second transparent conductive electrode layers do not make direct contact with one another. In general, in the optical device, they are intended to be electrically connected to the external source 13 such as a battery. For this purpose, a connecting element (also referred to as a “bus”), in particular that is metal (made of copper or of gold for example) may be deposited at the periphery of each of the transparent conductive electrodes. Each of the connecting elements partially, or completely, encircles each transparent conductive electrodes at its peripheral edge. Each of the connecting elements is in particular placed level with the peripheral edge of each of the transparent conductive electrodes and in particular generates an equipotential around each of the transparent conductive electrodes, which allows a uniform transmission to be obtained over the area of the eyeglass. In one variant of application, these lenses 3a, 3b comprising the electrochromic MIS may be informative eyeglasses, and therefore of electrically controllable and variable (optionally locally) amplitude. Other variants of application are also possible, in which variants electrochromic lenses 3a, 3b of electrically controllable and variable amplitude are employed. Generally a frame accommodates two lenses 3a, 3b, but in one possible variant the frame may accommodate only one lens (both illustrated) and have, for this purpose, for example, a wide bridge capable of housing a single lens that extends over the entire area facing the two eyes of the wearer.

[0240] The ophthalmic device 1 can include a user interface element integrated for instance into the structure or the frame 4. The user interface element can be configured to allow the user to control activation and deactivation of the electrochromic layer(s) of the MIS. The user interface element can be a switch, button, toggle, slide, touch-interface element, knob, other mechanical feature, or other electrical feature. For example, the user interface element can include a touch- sensitive region where if a user contacts said region the electrochromic element changes state from dark to transparent.

[0241] The eyeglass legs 2 may each be coupled to the eyeglass frame 4 via a hinge 5.

[0242] The basic structure of the eyeglass legs 13 and eyeglass frame 4 may refer to EP 3320390.

[0243] EXAMPLES

[0244] A) Characterization

[0245] Optical and colorimetric measurements (in reflection) of the surface of the base element (i.e.: substrate) coated on its front surface with the exemplified MIS (front face) : mean reflection factors Rv, hue angle h, chroma C* in the international colorimetric CIE (£.*, a*, b*) space were carried out with a spectrophotometer, taking into account the standard illuminant D65, and the standard observer 10° (for h and C*). They are provided for an angle of incidence of 0° for forward reflection (Cx face).

[0246] B) General procedures

[0247] The exemplified optical article, especially ophthalmic lenses, comprise a base element which is ITO-coated glass substrate commercialized by Delta Technologies (25 x 50 mm). ITO substrates were cleaned with soap and deionized water, and in isopropanol for 15 min using an ultrasonic bath.

[0248] The MIS were deposited in a vacuum chamber by radio frequency magnetron sputtering on the front main face on said substrate, while using an Ar, H2 and O2 gas mixture in a CMS-18 deposition system by Kurt J. Lesker using four 3-inch targets of ITO, NiV, Ta and W. The base pressure and the other experimental conditions are indicated in the tables below. The layers of the MIS coating were deposited without heating the substrates.

[0249] The thickness of the layers was controlled by means of time control or in situ spectroscopic ellipsometry. The spectral measurements were effected on a variable incidencespectrophotometer. In particular, a Cary 7000 equipped with a Universal Measurement Accessory (UMA) was used for measuring the transmission and reflection in the as-deposited state.

[0250] The EC properties of both materials were set in the clear and coloured states. Thus, the clear state refers to the most bleached state of the WO3 and NiO (deactivated state), while the coloured state refers to the most intense colouration of the WO3 and NiO (activated state) obtained when characterizing standalone MIS. No intermediate colouration states were considered here. Hereafter, F?v_b and Tv_b refer to the optical characteristics of the exemplified MIS in the bleached state and F?v-cand Tv-crefer to the optical characteristics of the exemplified MIS in the coloured state. C) Comparative examples

[0251] Ten comparative optical articles have been made by using the following deposition

[0252] Table 1 Table 2 below shows the structure and the optical characteristics of the comparative examples A1, A2, A3, A5 and B3.

[0253] Table 2

[0254] Hence, these comparative examples show that the standard EC stacks offer a very limited variation in reflection. The maximum reflection modulation is obtained when removing the top SiC>2 layer. Varying the bottom ITO thickness does not have a considerable impact on the optical response of the devices. Removing the constraints on the bleached state reflectance allows for a slightly higher ARV.

[0255] Table 2bis below shows the structure and the optical characteristics of the other comparative examples C1 to C5.

[0256] Table 2bis

[0257] These comparative examples C1 to C5 show that the “inverted” structure between the EC layers (first anodic layer and the first cathodic layer) do not enable to improve the ARVwhen trying to maintain the lowest possible Rv_b. C) Optical articles according to the invention

[0258] Different optical articles according to the invention have been made by using the following deposition conditions:

[0259] Table 3 According to the invention, the two external layers of the EC stack are made of “dense ITO” by opposition to the “porous ITO” used for forming the ionic diffusion layer composing the bilayer of the EC stack (the Bragg structure).

[0260] Indeed, the “dense ITO” external layers allow for the application of a potential and the insertion of electrons into the cathodic (WO3) and anodic (NiO) electrochromic (EC) materials during the colouration and bleaching phases respectively. As such, their deposition conditions were chosen to obtain highly transparent and conductive ITO films.

[0261] In the case of the Bragg mirror ITO layers, as they are inserted between EC WO3 layers, it is important that they not only allow for the conduction of electrons, but they must also allow for ionic diffusion. The combination of both these properties allowing for all WO3 layers to participate in the EC activity of the optical article. As a means of rendering the films more porous, and thus more conductive for ions, the deposition pressure was increased to 10 mTorr; While the layers’ resulting resistivity was approximately 4 to 5 times higher, their refractive index at 550 nm decreased from 2.074 to 1.978, a clear sign of a decrease in density. Assuming a Maxwell-Garnett effective medium approximation for the addition of pores in the denser ITO electrodes results in a 9% increase in porosity.

[0262] Optical properties of the materials implemented in the Bragg filters.

[0263] Table 4

[0264] C.1 Examples of optical articles according to one embodiment wherein MIS has a Rv< 2.5 % in the deactivated state and Rv> 6 % in the activated state.

[0265] The different tables below show the structure and the optical characteristics of the examples according to the invention.

[0266]

[0267] Table 5

[0268] The non-coherent electrolyte for the example F3 aims at simulating the optical response of the MIS using a much thicker polymeric electrolyte (lower risk of short circuits), which shows that the implementation of EC Bragg mirrors in such devices also presents a high reflection modulation upon colouration (ARV= 9.7%).

[0269]

[0270] Table 6

[0271] Increasing the number of bilayers in the MIS shows an increase of the main reflection peak at the wavelength of interest (550 nm) which leads to an increase in Rv_c in the coloured state. Most importantly, it is now possible to obtain large variations in reflection while maintaining a low reflection in the bleached state. Preferably, the number of bilayers will be below 3, since above 3 bilayers, no more increase of the main reflection peak is observed.

[0272] Table 7

[0273] In the examples shown above, the thicker, 3 quarter-wave WO3 layer is placed at the bottom while the thinner, 1 quarter-wave layer is placed at the top of the EC Bragg mirror.

[0274] MIS designs containing aperiodic Bragg mirrors.

[0275] Table 8

[0276] The present example aims at exploring whether allowing for a variation in the thickness of the EC Bragg mirror’s layers can improve the MIS’s performance (3 bilayer EC Bragg mirror).

[0277] Table 9

[0278] Table 10

[0279] C.2 Examples of optical articles according to one embodiment wherein MIS has a V_B— 11.0 % in the deactivated (bleached) state and Rvc 15.0 % in the activated (coloured) state.

[0280] The different tables below show the structure and the optical characteristics of the examples according to the invention.

[0281] Table 11

[0282] Table 12 Table 13

[0283] Table 14

[0284] Hence, all the exemplified MIS comprising a CE stack having a Bragg structure display both a wide modulation in transmission, but also in refection.

[0285] C.3 Example of optical articles according to one embodiment wherein MIS has a Rv_B< 13.0 % in the deactivated (bleached) state and Rv_C > 30.0 % in the activated (coloured) state.

[0286] For the following structure, the Applicant has manufactured an example, from simulation made by using the Essential Macleod software. This experiment shows that the simulated example has similar characteristics than the manufactured example.

[0287] Table 15

[0288] C.4 Example of optical articles according to one embodiment wherein the ion conductor layer (iii) comprises a gel electrolyte For the following experiments, the solid Ta2Os ion conductor layer (iii) has been replaced by a gel electrolyte.

[0289] This gel electrolyte comprises: UCIO4 in propylene carbonate (1 M) with 20% by weight of poly(methyl methacrylate).

[0290] For these experiments, the following procedure has been followed: a) depositing by sputtering on a first glass substrate, the first external layer, here ITO, and the first anodic layer, here NiO; b) depositing by sputtering on the second external layer (here ITO), the at least one bilayer composed of the second cathodic layer (here WO3) and ion conductor layer (here porous ITO); for some examples, the second external layer is also deposited on a second glass substrate; c) preparing the polymer electrolyte by stirring PC with LiCIO4 (1M), then adding PMMA (at 20% wt.%), then stirring by heating the mixture at 60°C so as to obtain a colorless gel electrolyte; d) spreading at 60°C of the colorless gel electrolyte obtained at step c) onto the stack obtained at the end of step a) and then superimpose onto this superposing colorless gel electrolyte the stack obtained at the end of step b); c) optionally, depositing an IC coating onto the second glass substrate. Comparative example J7

[0291] A comparative example, which does not comprise the at least one bilayer composed of the second cathodic layer (here WO3) and ion conductor layer (here porous ITO) has also been reproduced by the Applicant.

[0292] Table 16

[0293] The Applicant has observed that the reflection decreases during coloration between the bleached state and the colored state; however, it is desirable to get a reflection which increases. Examples J8 and J9 according to the invention Table 17 illustrates the structure and optical characteristics of the two additional examples according to the invention.

[0294] Table 17

[0295] The table shows that here, the reflection is increased between the bleached state and the colored state (increase of the reflection during the coloration) and that by varying the thickness of the AR coating, the ARVmay be optimized. Examples J9 and J10 according to the invention and cycling stability

[0296] The Applicant has tested the cycling stability of two additional examples according to the invention having the following structures, determined at the last cycle of the optimized potential range.

[0297] Table 18

[0298] Especially, Fig.3 shows the transmittance at 550 nm (%) as function of time of example J10 according to the invention.

[0299] The coloration and bleaching of the devices were studied using chronoamperometry in a two-electrodes setup. The reference and working electrodes were connected to the bottom glass substrate / ITO and to the top dense ITO respectively. Both electrodes were interfaced with an Autolab PGSTAT204 potentiostat (Metrohm), controlled via the Nova software. To investigate the optical properties in real time, the transmission and reflection were measured in situ. For transmission characterization, the sample was mounted on an optical table equipped with a series of lenses to focus light from a halogen lamp onto the sample. The transmitted light was then collected by another set of lenses and directed into an optical fiber connected to a MultiSpec Pro spectrophotometer (Tec5), which recorded spectra from 400 nm to 900 nm at 0.5-second intervals. Reflection at normal incidence was similarly measured in situ using the same Tec5 instrument, with a reflection probe from Ocean Optics. The probe consisted in six fibers in the cladder for light delivery and a single 400-pm-core fiber for collecting the reflected light. A 1-mm-thick Si wafer with a known reflection spectrum, characterized at a 6° angle using our Cary 7000 spectrophotometer, served as a reference standard for reflection measurements.

[0300] The device J10 was electrochemically cycled by chronoamperometry by applying potential pulses of +2 V and -2 V during 60 s each and repeated 10 times. The transmittance at 550 nm was recorded during the cycling procedure. During the pulses at +2 V, the transmittance decreases in accordance to the coloration of the device and increases at -2 V during bleaching. In Fig. 3 the transmittance evolution over 10 cycles is stable with no visible decrease in optical contrast.

[0301] For the J11 structure, two samples were fabricated at the same time, at equidistance from the platen’s center while applying rotation for increased uniformity to assess both the transmittance and reflectance. Fig. 4 exhibits the voltage profile, the resulting cathodic and anodic currents, the Rvand the Tvthrough 50 cycles of chronoamperometry at different potential ranges. First, the performance was assessed by applying -3 V and +3 V for 60 seconds allocated for both bleaching and coloring processes (Fig. 4 (left)). However, a significant loss of reflection and transmission modulation was observed after only a few cycles, which indicated a decrease in the overall charge displacement and thus, a loss of the reflection- enhanced interference. Fig. 4 (right) shows the performance of two new samples based on the same structure, where a narrower potential window of -2.5 V and +2 V was applied. This led to an improved transmission durability, which remained stable for the first 23 cycles, while keeping a RVof 11.3% after the 50 cycles. Therefore, adjusting the applied potential leads to improved device durability. Also, according to yet another embodiment, adjusting how the potential is applied could improve the device’s durability, for example through using more complex voltage profiles, such as pulsing. Indeed, at the same voltage level, for example between 4 V and 30 V, a pulsed profile would not deteriorate an electrochromic device or would less deteriorate such device, than a corresponding continuous voltage. For example, a square wave signal defined by applied pulsed voltages between 4 V and 30 V, with the length of the pulses varied between 0.2 ms and 20 ms. An optimal pulse length could be defined for each applied potential.

[0302] Such pulsing profiles could, moreover, enhance the coloration speed compared to a continuous voltage.

Claims

CLAIMS1. An optical article comprising at least:- a transparent base element having a front main face and a rear main face,- at least one of said main faces being coated with a multilayered interferential sheet (MIS) comprising at least:(a) a multilayered electrochromic stack (EC stack), said multilayered EC stack comprising at least : two external layers that are a first transparent conductive electrode layer and a second transparent conductive electrode layer, three or more internal layers interleaved between said two external layers, said internal layers comprising at least (i) a first cathodic layer, (ii) a first anodic layer and (iii) an ion conductor layer which is positioned between said first cathodic layer (i) and said first anodic layer (ii), said EC stack being able to reversibly switch from an activated state when an electrical potential is applied for a predetermined time to a deactivated state when the reverse electrical potential is applied for a predetermined time, and(b) optionally a multilayered interferential coating (IC), coated onto or below said (a) multilayered EC stack, comprising at least one low refractive index layer (LI) having a refractive index lower than 1.55, characterized in that the internal layers of said (a) multilayered EC stack comprise at least one bilayer composed of a second cathodic layer and a porous ionic diffusion layer, said at least one bilayer being placed between said ion conductor layer (iii) and either said first cathodic layer (i) or said first anodic layer (ii), and characterized in that the multilayered interferential sheet has, in the visible region, a mean light reflection factor difference, ARV, higher than or equal to 6.0% between the activated state and the deactivated state at an angle of incidence lower than or equal to 17°.

2. The optical article according to claim 1 , wherein the refractive index difference in said at least one bilayer between the second cathodic layer and the porous ionic diffusion layer in the activated state, An(activated), is higher than or equal to 0.25, preferably higher than or equal to 0.26, more preferably higher than or equal to 0.27, especially higher than or equal to 0.30 and typically higher than or equal to 0.32.

3. The optical article according to claim 1 or 2, wherein the refractive index difference in said at least one bilayer between the second cathodic layer and the porous ionic diffusion layer in the deactivated state, An(deactivated), is lower than or equal to 0.10, preferably lower than or equal to 0.06 and typically lower than or equal to 0.04.

4. The optical article according to any one of the preceding claims, wherein the multilayered interferential sheet has, in the visible region, a mean light reflection factor difference, ARV, between the activated state and the deactivated state which is higher than orequal to 7.0%, preferably higher than or equal to 8%, in particular higher than or equal to 9% and especially higher than or equal to 10%.

5. The optical article according to any one of the preceding claims, wherein the multilayered interferential sheet has, in the visible region, a mean light reflection factor Rvin the deactivated state that is lower than or equal to 20%, preferably lower than or equal to 15%, in particular lower than or equal to 10% and typically lower than or equal to 9% at an angle of incidence lower than or equal to 17°.

6. The optical article according to any one of the preceding claims, wherein the multilayered interferential sheet has, in the visible region, a mean light reflection factor Rvin the deactivated state that is lower than or equal to 2.5%, preferably lower than or equal to 1 .5%, in particular lower than or equal to 1.2% and typically lower than or equal to 1 .0% at an angle of incidence lower than or equal to 17°.

7. The optical article according to any one of the preceding claims 1 to 5, wherein the multilayered interferential sheet has, in the visible region, a mean light reflection factor Rvin the activated state that is higher than or equal to 15%, preferably higher than or equal to 20%, in particular higher than or equal to 25% and typically higher than or equal to 30% at an angle of incidence lower than or equal to 17°.

8. The optical article according to any one of the preceding claims 1 to 6, wherein the multilayered interferential sheet has, in the visible region, a mean light reflection factor Rvin the activated state that is higher than or equal to 6%, preferably higher than or equal to 7%, in particular higher than or equal to 8% and typically higher than or equal to 9% at an angle of incidence lower than or equal to 17°.

9. The optical article according to any one of the preceding claims, wherein in (a) the multilayered EC stack, the first anodic layer (ii) is positioned so as to be the nearest to the base element.

10. The optical article according to any one of the preceding claims, wherein (a) the multilayered EC stack comprises, in the direction moving away from the base element:- the first transparent conductive electrode layer;- the first anodic layer (ii);- the ion conductor layer (iii);- the at least one bilayer composed of a second cathodic layer and a porous ionic diffusion layer;- the first cathodic layer (ii), and- the second transparent conductive electrode layer.

11. The optical article according to any one of the preceding claims, wherein (a) the multilayered EC stack:- the first and the second transparent conductive electrode layers comprise one or several of the following components: tin-doped indium oxide (ITO), preferably composed of90% ln2O3and 10% of SnC>2, aluminum- doped zinc oxide (AZO), fluorine- doped tin oxide (FTO), metals (Ag, Au, Cu...), graphene, carbon nanotubes and comprise preferably ITO;- the first anodic layer (ii) comprises one or more of the following materials: NiO, LixNiO, CoO2, Cr2O3, Fe3O4 lrC>2, MnO2, VO2, V2O5 and comprises preferably NiO;- the ion conductor layer (iii) comprises one or more of the following materials: Ta2Os, SiO2, ZrO2 UPON, LiNbOs, LiTaOs, U3PO4, polymer electrolytes, such as LiCICL or NaCICL for instance in propylene carbonate (PC), poly(methyl methacrylate) (PMMA) and / or acetonitrile (ACN) and comprises preferably Ta2Osor polymer electrolytes- the at least one bilayer wherein the second cathodic layer comprises one or more of the following materials: WO3, MoOs, Nb2Os,Ta2O5, TiO2, V2O5 and comprises preferably WO3 and the porous ionic diffusion layer comprises a porous tin-doped indium oxide (porous ITO), preferably composed of 90% ln2Os and 10% of SnO2 having a porosity within the range from 0.5% to 20% determined by ellipsometry measurements;- the first cathodic layer (ii) comprises one or more of the following materials: WO3, MoOs, Nb20s, T1O2, V2O5 and comprises preferably WO3.

12. The optical article according to any one of the preceding claims, wherein the LI layer of the (b) multilayered interferential coating (IC) comprises SiC>2.

13. The optical article according to any one of the preceding claims, wherein the multilayered interferential sheet (MIS) has a total thickness equal to or below 2 pm, preferably equal to or below 1.5 pm, typically lower than or equal to 1 .2 pm.

14. The optical article according to any one of the preceding claims, wherein said optical article is an ophthalmic lens, especially a spectacle lens.

15. An optical device, such as an ophthalmic device, comprising:- a frame comprising at least one housing, preferably two housings;- at least an optical article, preferably two optical articles, as defined in any one of the preceding claims, the at least one optical article being mounted into said at least one housing;- an external source, such as a battery, and- connecting elements disposed between the transparent conductive electrode layers of the EC stack of the optical article and the external source.

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