An optical article with improved visual comfort

Abstract

This optical article (20) comprises: a base element (1), defining a rear surface and a front surface; a rear interferential stack, deposited onto the rear surface and comprising at least two low refractive index layers and two high refractive index layers The optical article (20) has: a front reflection factor higher than 4%, defining for the front side of the optical article (20) a mirror behavior of a part of the rear interferential stack; and a rear reflection factor lower than 2.5%, defining for the rear side of the optical article (20) an antireflective behavior of another part of the rear interferential stack. The rear interferential stack comprises a light absorbing material layer sandwiched between a first multilayer coating (4, 5, 6) having a mirror behavior, closest to the base element (1) and a second multilayer coating (7, 8, 9, 10) having an antireflective behavior.

Description

[0001] AN OPTICAL ARTICLE WITH IMPROVED VISUAL COMFORT

[0002] FIELD OF THE DISCLOSURE

[0003] The present disclosure relates to an optical article with improved visual comfort.

[0004] More particularly, the present disclosure relates to an optical article having a first multilayer coating configured so as to impart to the optical article a front mirror behavior and a second multilayer coating configured so as to impart to the optical article a rear antireflective behavior.

[0005] BACKGROUND OF THE DISCLOSURE

[0006] Fashionable mirror coatings are widely applied on sunglasses. High forward reflection of visible light, i.e. reflection away from a wearer’s eye of visible light hitting the face of the lens of the sunglasses that is on the side of the scene viewed by the wearer, is desirable for mirror coatings.

[0007] However, conventional mirror coatings usually exhibit high backward reflection of visible light as well, i.e. reflection of visible light coming from the wearer’s side, transmitted through the substrate and then reflected through the mirror coating on the front surface towards the wearer’s eyes. Thus, backward reflection of visible light is annoying for the wearer, especially when a mirror with high to very high reflective properties is used.

[0008] SUMMARY OF THE INVENTION

[0009] An object of the present disclosure is to overcome the above-mentioned drawbacks of the prior art.

[0010] To that end, the present disclosure provides an optical article having a front side and a rear side, comprising:

[0011] a base element, defining a rear surface and a front surface, the rear surface of the base element coinciding with the rear side of the optical article;

[0012] a rear interferential stack, deposited onto the rear surface and comprising at least two low refractive index layers and two high refractive index layers; the optical article having:

[0013] a front reflection factor higher than 4%, defining for the front side of the optical article a mirror behavior of a part of the rear interferential stack; and a rear reflection factor lower than 2.5%, defining for the rear side of the optical article an antireflective behavior of another part of the rear interferential stack,

[0014] the rear interferential stack comprising a light absorbing material layer sandwiched between:

[0015] a first multilayer coating having a mirror behavior, closest to the base element and comprising at least one low refractive index layer and one high refractive index layer, and configured so as to impart to the optical article a front mirror behavior; and

[0016] a second multilayer coating having an antireflective behavior, comprising at least one low refractive index layer and one high refractive index layer, and configured so as to impart to the optical article a rear antireflective behavior.

[0017] Thus, wearing such an optical article, the wearer will not be dazzled by the mirror coating, as the optical article offers low backward reflection of visible light that may reach the wearer’s eyes. This consequently improves the wearer’s visual comfort while keeping the fashion aspect of the mirror coating.

[0018] Moreover, as the first multilayer coating having a mirror behavior is on the rear side of the optical article, it is protected from external oxidation and ageing as it happens with standard mirrors. Therefore, the durability of the coating is improved. Also, color in production is less subjected to color shift due to the Physical Vapor Deposition (PVD) machine dirt.

[0019] In addition, the manufacturing process of an optical article according to the present disclosure makes it possible to save costs and time. Namely, usually, a lens having mirror and antireflective behaviors requires two coating cycles: one for the antireflective coating, which may last around 30 minutes, and one for the mirror coating, which may last around 45 minutes. When manufacturing the optical article according to the disclosure, the mirror and antireflective coatings are made at the same time, during a single cycle of approximately 35-40 minutes. In an embodiment, the thickness of the light absorbing material layer is comprised between 5 nm and 30 nm.

[0020] In an embodiment, the light absorbing material layer is a metal, preferably chromium, or a metal oxide.

[0021] The presence of chromium makes it possible to improve traffic light vision, because the wearer will always see a brown color range, whatever the color of the first multilayer coating having a mirror behavior.

[0022] In an embodiment, none of the light absorbing material and preferably none of the high refractive index layers, is a noble metal of the group comprising ruthenium, rhodium, palladium, osmium, iridium, platinum, gold and silver. This makes it possible to save costs.

[0023] In an embodiment, the optical article further comprises an adhesion layer interposed between the rear surface of the base element and the part of the rear interferential stack having a mirror behavior.

[0024] In an embodiment, the adhesion layer is a metal, preferably chromium. In an embodiment, the thickness of the adhesion layer is comprised between 0.1 nm and 1 nm.

[0025] In an embodiment, the optical article further comprises a front interferential stack deposited onto the front surface of the base element.

[0026] In an embodiment, the front interferential stack covers at least partially the front surface of the base element.

[0027] In an embodiment, the front interferential stack comprises a tampoprinted pattern.

[0028] In an embodiment, the front interferential stack is configured so as to define for the optical article a front reflection factor higher than 4%.

[0029] In an embodiment, the optical article comprises a transmission factor above 8% and below 80%, preferably below 43%, more preferably below 18%.

[0030] This makes it possible to tailor the interferential coating according to the disclosure so as to define, with the associated substrate, different tints of sunglasses with different visible light mean transmission factors Tv: either from 43 to 80% (known as sunglasses of category or class 1), or from 18 to 43% (known as sunglasses of class 2), or from 8 to 18% (known as sunglasses of class 3). In an embodiment, the base element is tinted.

[0031] This makes it possible to obtain a “gradient mirror” effect, because the tinted part of the base element covers the mirror. This leads to a new product having tinting over coating, instead of conventional lenses having coating over tinting.

[0032] In an embodiment, the optical article is an ophthalmic lens.

[0033] To the same end as above, the present disclosure also provides eyewear comprising at least one optical article as succinctly described above and a holding structure adapted so as to hold the optical article facing a wearer’s eye.

[0034] As the advantages and particular characteristics of the eyewear are similar to those of the optical article, they are not repeated here.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] For a more complete understanding of the description provided herein and the advantages thereof, reference is now made to the brief descriptions below, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0037] FIG. 1 is a schematic view showing the layer structure of a non-limiting example of an optical article according to the present disclosure.

[0038] DETAILED DESCRIPTION OF EMBODIMENTS

[0039] In the description which follows, the drawing figures are not necessarily to scale and certain features may be shown in generalized or schematic form in the interest of clarity and conciseness or for informational purposes. In addition, although making and using various embodiments are discussed in detail below, it should be appreciated that as described herein are provided many inventive concepts that may be embodied in a wide variety of contexts. Embodiments discussed herein are merely representative and do not limit the scope of the disclosure. It will also be obvious to one skilled in the art that all the technical features that are defined relative to a process can be transposed, individually or in combination, to a device and conversely, all the technical features relative to a device can be transposed, individually or in combination, to a process. 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.

[0040] 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”.

[0041] Also unless otherwise indicated, the indication of an interval of values “from X to Y” or “between X and Y”, according to the present disclosure, means including the values of X and Y.

[0042] In the present disclosure, when an optical article comprises one or more coatings on its surface, the expression “to deposit a layer or a coating onto the article” is intended to mean that a layer 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.

[0043] A coating that is said to be “on” a substrate or deposited “onto” a substrate is defined as a coating which (i) is positioned above the substrate, (ii) is not necessarily in contact with the substrate, that is to say one or more intermediate coatings may be arranged between the substrate and the coating in question, and (iii) does not necessarily completely cover the substrate.

[0044] In a particular embodiment, the coating on a substrate or deposited onto a substrate is in direct contact with the substrate.

[0045] As used herein, the “back” or “rear” or “inner” face of an optical article is intended to mean the face which, when using the optical article, is the nearest from the wearer’s eye. Such back or rear or inner face is generally concave. On the contrary, the front face of the optical article is the face which, when using the optical article, is the most distant from the wearer’s eye. It is generally convex.

[0046] The colorimetric coefficients of the optical article of the disclosure in the international colorimetric system CIE L*a*b* are calculated between 380 nm and 780 nm, taking the standard illuminant D65 and the observer into account (angle of 10°). The observer is a “standard observer” as defined in the international colorimetric system CIE L*a*b*.

[0047] These colorimetric coefficients determine the color of objects and surfaces, such as an interferential coating, by measuring a set of three color coordinates (L* a* b*) in the CIELab color space. The CIELab color space is defined by the International Commission on Illumination (abbreviated CIE) in 1976, wherein L* represents the perceptual lightness and a* and b* represent the colors perceived by human vision: red, green, blue and yellow. The three color coordinates (L*, a*, b*) can be transformed in polar coordinates L* C*ab and h°, with the hue angle, or hue ho=(180 / π).arctang(b* / a*) and the chroma C2ab * = a2+ b2

[0048] The color coordinates (L* a* b*), the hue angle and chroma C*ab are defined in the CIELab 1976 color space, with an observer 10° and D65 illuminant.

[0049] The color of a surface is defined by a point having the coordinates (L*, a*, b*) in the CIELab color space, wherein a* measures the red to green shift and b* measures the yellow to blue shift. The hue angle (h) does express the color perception and the chroma C*ab value does express the chromatic purity sensation, that is to say the position on the color scale extending from black to achromatic white, i.e. white without any color tone, up to the saturated monochromatic color, having a totally pure color tone. As used herein, the perceived chromatic color does mean a color that is perceived as possessing a chromatic tone. The chromatic tone, or hue, represents the visual sensation attribute which has resulted in the usual color denominations such as blue, green, yellow, red, purple and so on.

[0050] The expression “natural light” or “visible light” includes any type of natural light, especially daylight or sunlight. Sunlight has a bright emission in the whole visible spectrum, especially in the 550 nm-620 nm wavelength range. In some embodiments, the expression “natural light” or “visible light” also includes artificial light having a large spectrum, such as light emitted by some LED devices that mimic the sun.

[0051] In the present invention, the terms “absorbing” and “absorption” of a device in a wavelength range refer to a case where the mean emission value of the device in the wavelength range is lower than 50% of the mean emission value of the device in each of the adjacent 40 nm wavelength ranges.

[0052] The transmission factor Tv or transmittance, also called relative light transmission factor in the visible spectrum, relative visible light mean transmission factor or “luminous transmission” of the system, is as defined in the standard NF EN 1836 and relates to an average in the 380-780 nm wavelength range that is weighted according to the sensitivity of the human eye at each wavelength of the range and measured under D65 illumination conditions (daylight).

[0053] The mean light reflection factor or reflectance Rv, also called luminous reflection, is as defined in the ISO 13666:1998 standard, and measured in accordance with the ISO 8980-4 standard (for an angle of incidence lower than 17°, typically of 15°), i.e. this is the weighted spectral reflection average over the whole visible spectrum between 380 and 780 nm. It may be measured for all incidence angles 9, thus defining a function Rv(6).

[0054] The mean light reflection factor Rv may be defined by the following equation:

[0055] / 378800 / ?(A). K(A). D65q)-^

[0056] R

[0057]

[0058] V~

[0059] where R(A) is the reflectance at a wavelength A, V(A) is the eye sensitivity function in the color space defined by the CIE (Commission on Illumination, in French “Commission Internationale de I’Eclairage”) in 1931 and D65(λ) is the daylight illuminant defined in the CIE S005 / E-1998 standard.

[0060] The specificity of the rear interferential coating according to the invention deposited on a rear face of a base material or substrate to constitute an optical article, is that it behaves as a mirror when viewing said article from its front face, and as an anti-reflection coating when viewing said article from its rear or back face. It therefore defines different reflection factors Rv depending on the direction of observation: a high (higher than 4%) forward reflection factor noted Rf1, and a low (lower than 2.5%) backward reflection factor, noted Rb1. Due to the visible light absorbing properties of the rear interferential coating designed specifically for this purpose, the backward reflection factor Rb1 is different from the forward reflection factor Rf 1, and more precisely, the backward reflection factor Rb1 is minimized (below 2.5%) whereas the forward reflection factor Rf1 is maximized.

[0061] To this end, the rear interferential coating according to the invention, comprises a light absorbing material layer sandwiched between:

[0062] a first multilayer coating having a mirror behavior, closest to said base element and comprising at least one low refractive index layer having a refractive index of 1.55 or less and one high refractive index layer having a refractive index higher than 1.55, and configured so as to impart to the optical article a front mirror behavior; and

[0063] a second multilayer coating having an antireflective behavior, comprising at least one low refractive index layer having a refractive index of 1.55 or less and one high refractive index layer having a refractive index higher than 1.55, and configured so as to impart to the optical article a rear antireflective behavior

[0064] the refractive indexes being expressed for a wavelength of 550 nm and is designed so as to define high reflective properties when viewing said article from its front face and antireflective properties when viewing said article from its rear face, and is called asymmetric mirror.

[0065] We will note “Rf” a total reflection factor resulting from the addition of the forward reflection factor of the rear interferential coating deposited at the rear side of the base element Rf1, and of a forward reflection factor Rf2 of a front interferential coating deposited at the front side of the base element, when present.

[0066] We will note “Rb” total reflection factor resulting from the addition of the backward reflection factor Rb1 of the rear interferential coating deposited at the rear side of the base element, and of a backward reflection factor Rb2 of the front interferential coating deposited at the front side of the base element, when present.

[0067] The interferential stacks either front or rear interferential coating used in the present invention can be designed by a traditional modeling process of optical coatings comprising modeling the successive layers based on the well-known matrix method, with specific Tv1, Rv1, Rf 1, Rb1, front and rear chroma, and / or front and rear hue targets to obtain the desired mirror effect for the interferential stack itself and / or for the whole optical article with specific base element and additional functional coatings. Thanks for the modeling process and software, a specific function for calculating backward reflection is available and it can also set a target of backward reflection Rv in addition to the forward reflection Rv, h* and C*, and other parameters.

[0068] The matrix method is well-known in the art and a description of steps thereof is provided for instance by Larouche et al. in Applied Optics, 2008, 47, 13, C219-C230.

[0069] Generally speaking, the interferential coatings of the optical article according to the disclosure, which will be referred to as “the reflective (or mirror) coating”, depending on the configuration described, may be deposited onto any substrate, such as mineral glass, piano lens, or a transparent sheet of polycarbonate to be laminated and thermoformed after coating and preferably onto organic lens substrates, for example a thermoplastic or thermosetting plastic material. Thermoplastic may be selected from, for instance: polyamides; polyimide; polysulfones; polycarbonates and copolymers thereof; poly(ethylene terephthalate) and polymethylmethacrylate (PMMA).

[0070] 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) (CR 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 phtalic 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. 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.

[0071] Homopolymers of diethylene glycol bis(al ly I carbonate) (CR39®), allylic and (meth)acrylic copolymers, having a refractive index between 1.54 and 1.58, polymer and copolymer of thiourethane, polycarbonates are preferred.

[0072] The substrate may be coated with one or more functional coatings prior to depositing the antireflective or mirror coating of the disclosure. 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.

[0073] Prior to depositing the mirror coating, 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 or mirror coating. Such 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 “IPC”) 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).

[0074] An optical article according to the disclosure comprises at least one ophthalmic lens or optical filter or optical glass or optical material suitable for human vision, e.g. at least one ophthalmic lens, or optical filter, or optical film or patch intended to be fixed on a substrate, or optical glass, or optical material intended for use in an ophthalmic instrument, for example for determining the visual acuity and / or the refraction of a subject, or any kind of safety device including a safety glass or safety wall intended to face an individual’s eye, such as a protective device, for instance safety lenses or a mask or shield.

[0075] The optical article may be implemented as eyewear equipment having a frame that surrounds at least partially one or more ophthalmic lenses. By way of non-limiting example, the optical article may be a pair of glasses, sunglasses, safety goggles, sports goggles, a contact lens, an intraocular implant, an active lens with an amplitude modulation such as a polarized lens, or with a phase modulation such as an auto-focus lens, etc.

[0076] The at least one ophthalmic lens or optical glass or optical material suitable for human vision can provide an optical function to the user i.e. the wearer of the lens.

[0077] It can for instance be a corrective lens, namely, a power lens of the spherical, cylindrical and / or addition type for an ametropic user, for treating myopia, hypermetropia, astigmatism and / or presbyopia. The lens can have a constant power, so that it provides power as a single vision lens would do, or it can be a progressive lens having variable power.

[0078] The optical article according to the disclosure has a rear side on the side of a wearer’s eye and a front side opposite to the rear side. In addition, the optical article comprises a base element or substrate, defining a rear surface on the side of a wearer’s eye and a front surface opposite to the rear surface.

[0079] The rear surface of the base element coincides with the rear side of the optical article.

[0080] The base element may be tinted.

[0081] Furthermore, the optical article comprises a rear interferential stack, deposited onto the rear surface and comprising at least two low refractive index layers and at least two high refractive index layers.

[0082] The expression “high refractive index” means a refractive index typically above or equal to 1.5 and the expression “low refractive index” means a refractive index typically less than 1.5.

[0083] According to the present disclosure, the optical article has:

[0084] - a front reflection factor higher than 4%, defining for the front side of the optical article a mirror behavior of a part of the rear interferential stack; and

[0085] - a rear reflection factor lower than 2.5%, defining for the rear side of the optical article an antireflective behavior of another part of the rear interferential stack. Moreover, the rear interferential stack comprises a light absorbing material layer sandwiched between:

[0086] - a first multilayer coating having a mirror behavior, closest to the base element and comprising at least one low refractive index layer and at least one high refractive index layer, and configured so as to impart to the optical article a front mirror behavior; and

[0087] - a second multilayer coating having an antireflective behavior, farthest from the base element, comprising at least one low refractive index layer and at least one high refractive index layer, and configured so as to impart to the optical article a rear antireflective behavior. In some embodiments, the light absorbing material layer constitute the first layer of the second multilayer coating having an antireflective behavior and is in contact with the layer of the mirror part farthest from the base element. In some embodiments, the light absorbing material layer constitute the first HI layer of the second multilayer coating having an antireflective behavior.

[0088] The physical thickness of the light absorbing material layer may be comprised between 5 nm and 30 nm.

[0089] At least one of the layers of the multilayer interferential coating according to the invention is a layer comprising a visible light absorbing material, referred to as a "visible light-absorbing layer", "light-absorbing layer" or "absorbent layer", comprising a visible light absorbing material, i.e., one or more visible light absorbing compounds. Its function is to reduce transmission of visible light by absorption.

[0090] The absorbent layer may be any layer known to one skilled in the art and suitable for absorbing at least part of the visible light (380-780 nm).

[0091] Extinction coefficient k

[0092] Said layer of light absorbing material preferably has an extinction coefficient k at 550 nm higher than or equal to 0.1, 0.3 or 0.5. In one embodiment, the layer of light absorbing material has an extinction coefficient k higher than or equal to 0.1, 0.3 or 0.5 for any wavelength ranging from 400 to 800 nm. The extinction coefficient (also known as attenuation coefficient) of a particular substance, denoted k, measures the loss in energy of electromagnetic radiation traversing this medium. This is the imaginary part of the complex refractive index. The light absorbing material layer may be a metal, preferably chromium, titanium, or it may be a metal oxide, or a mixture thereof. Other light absorbing compounds may be used, e.g. other metals such as aluminum, sub-stoichiometric metal oxides such as TixOyorTiOx, where x < 2, x preferably varying from 0.2 to 1.2, such as TiO, Ti2 03 or Ti3 05 ), a sub-stoichiometric zirconium oxide (ZrOx, where x < 2, x preferably varying from 0.2 to 1.2), a sub-stoichiometric silicon oxide (SiOx, where x < 2, x preferably varying from 0.2 to 1.2, more preferably from 0.9 to 1.1, such as SiO), a sub-stoichiometric silicon nitride (SiNy, where y < 1, y preferably varying from 0.1 to 0.6), or a sub-stoichiometric silicon nitride oxide SiNxOy, where x and y are predetermined numbers such as x<1-y / 2, and y<2(1-x) and mixtures thereof.

[0093] The sub-stoichiometric materials listed above can show absorbing properties in the visible range, depending on the layer thickness, on the layers number and / or conditions used during their deposition.

[0094] In the present invention, a visible light-absorbing layer is defined as a layer which, when directly deposited as a monolayer onto the surface of a clear substrate (such as a polycarbonate substrate), reduces the luminous transmittance Tv of said clear substrate by at least 5 %, preferably at least 10 %, more preferably at least 20 %, by absorption, as compared to the same clear substrate without the layer in question. Absorption does not include reflection.

[0095] Advantageously, none of the light absorbing material and preferably none of the high refractive index layers, is a noble metal of the group comprising ruthenium, rhodium, palladium, osmium, indium, platinum, gold and silver.

[0096] As a variant, the antireflective part can contain several layers made of absorbing material, but there is a limit to the cumulative thickness of the different layers constituted by absorbing material: the total thickness of all layers constituted with absorbing material, should be comprised between 5 and 50 nm.

[0097] Indeed for example, when the total amount of the two chrome layers is more than 30-35 nm (chrome density 7.2, rate 0,5 nm / s) the final transmittance is lower than 10% (too dark for driving for example).

[0098] High refractive index layers may comprise, without limitation, one or more mineral oxides such as SiN, TiCh, ZrCh, Ta2Os, Y2O3, Ce2O3, La20s, Dy20s, Nb20s, HfCh, SC2O3, Pr2O3, AI2O3, or SisN4. High refractive index layers may also comprise above mentioned sub-stoichiometric materials when there refractive index is above 1.55.

[0099] Low refractive index layers may comprise, without limitation, SiC>2, MgF2, ZrF4, AI2O3, AIF3, chiolite (NasfAkFu]), cryolite (Na3[AIFe]), or any mixture thereof, preferably SiO2 or SiO2 doped with AI2O3 which contributes to raising the critical temperature of the stack.

[0100] The optical article may further comprise an adhesion layer interposed between the rear surface of the base element and the part of the rear interferential stack having a mirror behavior.

[0101] The adhesion layer may be a metal, preferably chromium, or SiO, or a mixture of Cr and SiO.

[0102] The physical thickness of the adhesion layer may be comprised between 0.1 nm and 1 nm.

[0103] The optical article may further comprise a front interferential stack deposited onto the front surface of the base element.

[0104] The front interferential stack may cover at least partially the front surface of the base element.

[0105] The front interferential stack may be designed so as to have a mirror behavior, i.e. a front reflection factor Rf2 higher than 4%.

[0106] When the front interferential stack is a mirror stack partially covering the front surface of the base element, the rear interferential stack is also perceived from an observer view point, and both reflected colors of the front and rear interferential stacks are seen by an observer. The front interferential stack can be deposited with a gradient along the height, width or radius of the base element so as to let appear gradually the reflected color exhibited by the rear interferential stack for an observer.

[0107] The front interferential stack may comprise a tampoprinted pattern. The pattern may be of any kind, such as a periodic logo. This makes it possible to give a tridimensional effect to the optical article thanks to the superimposition of the virtual image of the pattern produced by the back mirror at the rear side of the optical article, with the pattern itself present at the front side with a lateral shift. The tridimensional effect is more visible when increasing the physical thickness of the optical article.

[0108] The front interferential stack may be configured so as to define for the optical article a front reflection factor higher than 4%.

[0109] Advantageously, the optical article may comprise a transmission factor above 8% and below 80%, preferably below 43%, more preferably below 18%.

[0110] The interferential coating(s) according to the disclosure, rear and possibly front interferential stack(s), can be tailored so as to define, with the associated (tinted or not tinted) substrate, different tints of sunglasses with different visible light mean transmission factors Tv, according to standard categories:

[0111] - above 80% (known as clear lens category),

[0112] - from 43 to 80% (known as sunglasses of category or class 1 ),

[0113] - from 18 to 43% (known as sunglasses of class 2),

[0114] - from 8 to 18% (known as sunglasses of class 3),

[0115] - below 8% (known as sunglasses of class 4).

[0116] In order to have two different categories on the same sunglass (for example, a left lens of category 2 having for example Tv = 18.1% and a right lens of category 3 having for example Tv = 17.9%), an exclusion interval of 2% is defined at both boundaries of each category: thus, for example, category 3 is not 8-18%, but 10-16%, category 2 is 20-41% and so on.

[0117] Figure 1 shows the layer structure of a non-limiting example of an optical article 20 according to the present disclosure.

[0118] The optical article 20 comprises a base element 1 or substrate that is transparent and that may be made of glass or of plastic material such as nylon. It may or may not have an optical correction.

[0119] The base element 1 is lacquered on both sides (0 and 2) by hard coatings that may have scratch-resistant properties and that may be based on organic materials, in particular polysiloxane. The hard coatings protect the base element 1 and prevent damage. The hard coating 0 is applied on the front surface of the base element 1 and is directed toward the front side of the optical article 20, which may be a convex side, while the hard coating 2 is applied on the rear surface of the base element 1 and is directed toward an eye of the wearer of the optical article 20, that is to say toward the rear side of the optical article 20, which may be a concave side.

[0120] The face of the hard coating 2 directed toward the rear side of the optical article 20 is coated with a rear interferential stack that is a thin film coating stack including Cr, SiCh and TisOs materials deposited by PVD.

[0121] Looking to the optical article 20 from the front side, one sees a high intensity mirror coating, while looking to the optical article 20 from the rear side, one sees an antireflective coating. The wearer of the optical article 20 sees in transmission a brown color, without being dazzled by the high intensity mirror coating.

[0122] The high intensity mirror part of the rear interferential stack is constituted in the example of Figure 1 by a first low refractive (LI) index layer 4 (for example SiCh), a first high refractive index (HI) layer 5 (for example TisOs) and and a second LI layer 6 (for example SiC>2), see examples 1-18 and 21 hereafter.

[0123] In some embodiments, the high intensity mirror part of the rear interferential stack could be constituted by a first HI layer 5 (for example TisOs) and a first LI layer 6 (for example SiCh) only, or by a plurality of n iterations of them, denoted (5-6)n, n being an integer higher than or equal to 1, see examples 19 and 20 hereafter, where n = 2. Moreover, an optional final HI layer 5 (for example TisOs) can be present on the last LI layer of the iteration, see examples 19 and 20. Layer 4 is a so-called “buffer layer”, chemically similar to the hard coating 2 (Si-Oxbonds), granting a continuity from the hard coating 2 to the thin film coating formed by the rear interferential stack and helping accommodating residual thermal stress of the coating.

[0124] As a variant, other materials may be used for layer 5, such as ZrCh or other high refractive index materials.

[0125] The antireflective part of the rear interferential stack is constituted in the example of Figure 1 by the light absorptive layer 7 (for example Cr) ad a first HI layer, a first LI layer 8 (for example SiC>2), an optional second HI layer 9, possibly also made of a light absorptive material (for example Cr) and an optional second LI layer 10 (for example SiCh).

[0126] In some embodiments, the antireflective part could be constituted only by the absorptive layer 7 (for example Cr) as a first HI layer and a first LI layer 8 (for example S iC>2), or by a plurality of m iterations of them, denoted (7-8)m, m being an integer higher than or equal to 1 that is not necessarily equal to n, see examples 1-21 where m = 1. The first HI absorptive layer 7 and the second HI absorptive layer 9 (when present) reduce the transmittance of the optical article when deposited on the rear side of a clear base element 1, giving it a brown color because of light absorption by Cr and at the same time, they make interference with other LI layer(s) 8 and 10 when present, forming an antireflective coating.

[0127] The light absorptive layer 7 is the first layer of the second multilayer coating that has an antireflective behavior, so that it can be considered that the light absorptive layer 7 is sandwiched between the first multilayer coating 4, 5, 6 that has a mirror behavior and the second multilayer coating 7, 8, 9, 10 that has an antireflective behavior.

[0128] The antireflective part can contain other layers than layer 7 of the same light absorbing material. Typically, such other layers will have a smaller thickness, for example comprised between 2.5 and 6 nm, so that they will not behave as the “central” or main absorptive layer 7.

[0129] Nevertheless, there is a limit to the cumulative thickness of the different layers constituted by absorptive material: when the total amount of the thickness of the two chromium layers is more than 30-35 nm (chromium density 7.2, rate 0.5 nm / s), the final transmittance is lower than 10%, which is too dark for a wearer of such lenses to drive, for example. Thus, the total thickness of all layers constituted by absorptive material should be comprised between 5 and 50 nm.

[0130] As a variant, other light absorbing materials may be used for layers 7 and 9, such as aluminum, titanium, copper or other metals, or metal oxides such as TixOywhere x and y are non-null integers. The advantage of chromium is that it provides a very good adhesion.

[0131] As a variant, other materials may be used for layers 4, 6, 8 and 10, such as MgF2 or other low refractive index materials.

[0132] By changing the physical thickness of layers 8, 9 and 10, it is possible to change the shape of the curve giving the reflectance as a function of the wavelength, in order to obtain an antireflective coating with different residual reflected colors such as blue, or purple, or green, etc., and / or different low Rv factors below 2.5%, such as 0.6%.

[0133] The high intensity mirror part and the absorption / antireflective part of the rear interferential stack are optically bonded together: by setting physical thicknesses of the high intensity mirror part, it is possible to obtain any reflected color (silver, gold, pink, purple, blue, green, orange, red and so on), and / or any high Rv factor above 4%, such as 18%, without changing the absorption / antireflective part. On the other hand, for any reflected color, the wearer will see, in transmission, a brown color.

[0134] The function of layer 3 of the rear interferential stack is to enhance adhesion on the surface of the assembly formed by the base element 1 and its two hard coatings 0 and 2. It does not have any optical impact, because its physical thickness is very low, typically lower than 1 nm, and it is deposited at a very low rate, typically 0.02 nm / s, in order to keep the base element 1, i.e. the lens substrate, as transparent as possible.

[0135] In the example of Figure 1, the adhesion layer 3 is made of Cr. As a variant, other materials may be used, such as SiO or proprietary mixtures such as Brown Sa1g from the company Satisloh.

[0136] The below table summarizes the different layers including optional layers, and corresponding thickness ranges of the rear interferential stack according to the disclosure. Thickness range (when layer is present) Optional adhesion layer 0.1-1 nm

[0137] (Cr for example) (3)

[0138] Optional first LI layer of the mirror part 100-230 nm

[0139] (SiO2 for example) (4)

[0140] First HI layer of the mirror part 10-210 nm

[0141] (ITOs for example) (5)

[0142] Second LI layer of the mirror part 70-260 nm

[0143] (or first when optional first LI layer is absent)

[0144] (SiO2 for example) (6)

[0145] Optional second HI layer of the mirror part 70-90 nm

[0146] (ITOs for example) (5)

[0147] Optional third LI layer of the mirror part (or second when optional first 60-80 nm

[0148] LI layer is absent)

[0149] (SiO2 for example (6)

[0150] Optional third HI layer of the mirror part 25-40 nm

[0151] (ITOs for example) (5)

[0152] Absorptive layer constituting the first HI layer of the antireflective part 5-30 nm

[0153] (Cr for example) (7)

[0154] First LI layer of the antireflective part 50-80 nm

[0155] (SiO2 for example) (8)

[0156] Optional second HI layer of the antireflective part 1-10 nm

[0157] (Could be made of absorptive material, Cr for example) (9)

[0158] Optional second LI layer of the antireflective part 30-70 nm

[0159] (SiO2 for example) (10)

[0160]

[0161] Table 1 below gives eighteen non-limiting examples (examples 1 to 18) of an optical article 20 according to the present disclosure that have various colors for the mirror part as well as for the antireflective part. The physical thicknesses of layers 3 to 10 in nanometers are listed in the table 1. These thicknesses can be optimized for various substrates, to obtain the same reflected color and mirror behavior. Mirror part color / Example 1: Example 3: Example 5: Example 6: AR part color Silver / Example 2: Example 4:

[0162] Blue Silver / Violet Gold /

[0163] Blue Gold / Violet Blue / Blue /

[0164] Blue Green Cr (3) 0.6 0.6 0.6 0.6 0.6 0.6 SiO2(4) 170 170 220 220 170 170 Ti3O5(5) 63 63 77 77 63 63 SiO2(6) 72 72 88 88 226 226 Cr (7) 20 17 20 17 20 18 SiO2(8) 60 60 60 60 60 60 Cr (9) 5 6 5 6 5 6

[0165]

[0166] SiO2(10) 50 60 50 60 40 60 Mirror part color / Example 7: Example 8: Example 9: Example 10: Example 11: Example AR part color Fuchsia / Violet Fuchsia / Green Pink / BluePink / BlueYellow / 12:

[0167] violet green Violet Yellow /

[0168] Blue Cr (3) 0.6 0.6 0.6 0.6 0.6 0.6 SiO2(4) 136 136 156 156 111 111 Ti3O5(5) 50 50 202 202 41 41 SiO2(6) 181 181 149 149 147 147 Cr (7) 28 25 20 18 20 19 SiO2(8) 60 60 60 60 60 60 Cr (9) 5 6 5 6 5 6

[0169]

[0170] SiO2(10) 37 60 40 60 40 60 Mirror part color / Example 13: Example 14: Example 15: Example 16: Example 17: Example AR part color Green Yellow / Green Yellow / Green Blue Green Blue Indigo Blue 18:

[0171] Purple Violet / Purple / Violet / Blue Indigo Blue / Green Cr (3) 0.6 0.6 0.6 0.6 0.6 0.6 SiO2(4) 187 187 - - 200 200 Ti3O5(5) 69 69 200 200 12 12 SiO2(6) 249 249 231 231 100 100 Cr (7) 20 17 26 22 27 24 SiO2(8) 60 60 60 60 60 60 Cr (9) 5 6 5 6 5 6

[0172]

[0173] SiO2(10) 40 60 40 60 40 60

[0174] Table 1 Table 2 below gives two other non-limiting examples (examples 19 and 20) of an optical article 20 according to the present disclosure that have various colors for the mirror part as well as for the antireflective part, where instead of comprising a single layer 4 and a single layer 5, the stack comprises two layers 4 alternating with three layers 5. The physical thicknesses of layers 3 to 10 in nanometers are listed in the table.

[0175] Mirror part color Example 19: Example 20:

[0176] / AR part color Orange / Red /

[0177] Violet Blue

[0178] Cr (3) 0.6 0.6

[0179] Ti3O5(5) 80 86

[0180] SiO2(6) 120 128

[0181] Ti3O5(5) 75 81

[0182] SiO2(6) 69 74

[0183] Ti3O5(5) 34 36

[0184] Cr (7) 20 25

[0185] SiO2(8) 60 60

[0186] Cr (9) 6 6

[0187]

[0188] SiO2(10) 40 40

[0189] Table 2

[0190] As described previously, other light absorbing materials than chromium may be used for layers 7 and 9, such as titanium. Table 3 below gives a non-limiting example (example 21) of an optical article 20 according to the present disclosure in which layers 7 and 9 are made of titanium. The physical thicknesses of layers 3 to 10 in nanometers are listed in the table.

[0191] Mirror part color / AR part color Ex 21: Silver / Blue

[0192] Cr (3) - SiO2(4) 170

[0193] Ti3O5(5) 63

[0194] SiO2(6) 72

[0195] Ti (7) 20

[0196] SiO2(8) 75

[0197] Ti (9) 2.5

[0198]

[0199] SiO2(10) 40

[0200] Table 3 In example 21, for the rear side, the reflectance at 0° is 0.61% and the L*a*b* coordinates are the following: L* = 5.49, a* = 21.04, b* = -4.37 and for the front side, the reflectance at 0° is 74.12%, L* = 89.05, a* = -2.65, b* = -1.33.

[0201] Table 4 below gives the following measured optical parameters for examples 1 to 21, when available: chroma at 15°, hue at 15° and reflectance Rf for the front side (at 15°) and for the rear side (at 35°), as well as transmittance Tv of the optical article 20.

[0202] The measured optical parameters illustrate the diversity

[0203] - of the front reflected colors defined by the mirror part of the rear interferential stack of the disclosure:

[0204] • chroma at 15° between 4.1 and 35.4;

[0205] • hue at 15° between 7.6° and 323.2°;

[0206] - of the rear residual reflected colors defined by the antireflective part of the rear interferential stack of the disclosure:

[0207] • chroma at 15° between 2.4 and 38.5;

[0208] • hue at 15° between 194.1° and 310.3°;

[0209] - of the front Rf factor defined by the mirror part of the rear interferential stack of the disclosure, between 6.76% and 18.07% (Generally, and preferably, the front Rf factor is above 10%, more preferably above 15%, more preferably above 20%, and / or below 40%, more preferably below 30%;

[0210] - of the rear Rb factor defined by the antireflective part of the rear interferential stack of the disclosure, between 0.61% and 2.45% (Generally, and preferably, the rear Rb factor is below 2.5%, more preferably below 2%, more preferably below 1.5%, more preferably below 1%, even more preferably below 0.5% );

[0211] - of the transmittance Tv of the optical article with a clear base element, between 10.1% and 14.3%; higher transmittance can be achieved with a thinner absorptive layer 7 (for example between 5 and 20 nm, more preferably below 18 nm, more preferably below 16 nm, more preferably below 14 nm, more preferably below 12 nm, and / or more preferably above 7 nm, more preferably above 9 nm). Front (mirror) side Rear (antireflective) side Transmittance Chroma Hue Rf Chroma Hue Rb

[0212] 15° 15° 15° 15° 15° 35°

[0213] Example 1: Silver / Blue 6.5 87.6° 17.12% 2. 4 284.5° 0.61% 11.9% Example 2: 4.1 89.1° 15.57% 13.1 300.6° 1.03% 11.8% Silver / Violet

[0214] Example 3: Gold / Blue 17.2 88.4° 18.07% 33.2 295.1° 0.78% 11.5% Example 4: Gold / Violet 17.3 88.5° 16.03% 20.7 288.9° 0.79% 10.1% Example 5: Blue / Blue 15.2 201.4° 13.54% 17.1 280.6° 0.91% 13.9% Example 6: Blue / Green? 251.1°? 5.2 278.9° 1.35% 11.1% Example 7: 26.4 323.2° 8.46% 19.8 295.5° 1.44% 11.7% Fuchsia / Violet

[0215] Example 8: 27.1 314.8° 7.10% 11.7 194.1° 2.01% 11.0% Fuchsia / Green

[0216] Example 9: Pink / Blue- 21.2 20.5° 9.87% 19.8 291.4° 1.89% 14.3% Violet

[0217] Example 10: Pink / Blue- 21.7 23.6° 9.09% 15.7 228.8° 1.17%? Green

[0218] Example 11: 31.7 7.6° 14.22% 34.4 307.3° 1.49% 12.2% Yellow / Violet

[0219] Example 12: Yellow / Blue 29.9 83.5° 13.46% 25.1 277.2° 0.78% 12.0%

[0220] Example 13: Green 25.4 109.7° 17.17% 38.5 305.1° 0.62% 11.5% Yellow / Purple

[0221] Example 14: Green 18.1 123.8° 14.76% 18.5 306.0° 0.94% 10.6% Yellow / Violet

[0222] Example 15: Green 25.4 109.7° 10.22% 38.5 289.6° 0.77% 10.6% Blue / Purple

[0223] Example 16: Green 18.1 123.8° 8.25% 18.5 269.1° 1.43% 10.6% Blue / Violet

[0224] Example 17: Indigo 16.9 267.3° 7.18% 18.1 265.7° 1.07% 11.5% Blue / Blue

[0225] Example 18: Indigo 17.2 266.6° 6.76% 6.5 213.1° 2.45% 11.7% Blue / Green

[0226] Example 19: 35.4 54.2° 11.32% 26.6 310.3° 1.80% 11.4% Orange / Violet

[0227] Example 20: Red / Blue 28.9 42.1° 8.11% 2.5 285.1° 1.41% 10.3%

[0228]

[0229] Table 4 Table 5 below gives another non-limiting example (example 22) of an optical article 20 according to the present disclosure, where the color of the mirror part is white with L* = 76, a* = -0.21 and b* = -0.26. The physical thicknesses of layers 3 to 10 in nanometers are listed in the table.

[0230] Mirror part color Example 22: White

[0231] Cr (3) - Ti3O5(5) 17

[0232] SiO2(4) 32

[0233] Ti3O5(5) 71

[0234] SiO2(6) 93

[0235] Cr (7) 20

[0236] SiO2(8) 61

[0237] Cr (9) 4

[0238]

[0239] SiO2(10) 51

[0240] Table 5

[0241] In an embodiment, the base element is tinted and said tint is reflected by the back mirror at the rear side before reaching an observer’s eye, which changes the observed reflected colors of the back mirror.

[0242] Moreover, this makes it possible to obtain a “gradient mirror” effect for an observer, since for a same height of observation, different lengths of the tinted base element are to be crossed by light rays reflected at the rear side by the back mirror towards the observer, changing the perceived color for the observer.

[0243] This leads to a new product having tinting over mirror coating, instead of conventional lenses having mirror coating over tinting.

[0244] The present disclosure also provides eyewear comprising at least one optical article 20 as described above and a holding structure adapted so as to hold the optical article 20 facing a wearer’s eye. By way of non-limiting example, the holding structure may be an eyeglasses frame.

[0245] Although representative devices have been described in detail herein, those skilled in the art will recognize that various substitutions and modifications may be made without departing from the scope of what is described and defined by the appended claims.

Claims

CLAIMS1. An optical article (20) having a front side and a rear side, comprising:a base element (1), defining a rear surface and a front surface, the rear surface of the base element (1 ) coinciding with the rear side of the optical article (20);a rear interferential stack, deposited onto said rear surface and comprising at least two low refractive index layers and two high refractive index layers; said optical article (20) having:a front reflection factor higher than 4%, defining for the front side of said optical article (20) a mirror behavior of a part of said rear interferential stack; anda rear reflection factor lower than 2.5%, defining for the rear side of said optical article (20) an antireflective behavior of another part of said rear interferential stack,said rear interferential stack comprising a light absorbing material layer sandwiched between:a first multilayer coating (4, 5, 6) having a mirror behavior, closest to said base element (1) and comprising at least one low refractive index layer and one high refractive index layer, and configured so as to impart to the optical article (20) a front mirror behavior; anda second multilayer coating (7, 8, 9, 10) having an antireflective behavior, comprising at least one low refractive index layer and one high refractive index layer, and configured so as to impart to the optical article (20) a rear antireflective behavior.

2. The optical article (20) according to claim 1, wherein the thickness of said light absorbing material layer is comprised between 5 nm and 30 nm.

3. The optical article (20) according to claim 1 or 2, wherein said light absorbing material layer is a metal, preferably chromium, or a metal oxide.

4. The optical article (20) according to claim 1, 2 or 3, wherein none of the lightabsorbing material and preferably none of the high refractive index layers, is a noble metal of the group comprising ruthenium, rhodium, palladium, osmium, iridium, platinum, gold and silver.

5. The optical article (20) according to any one of the preceding claims, wherein it further comprises an adhesion layer (3) interposed between the rear surface of said base element (1) and the part of the rear interferential stack having a mirror behavior.

6. The optical article (20) according to claim 5, wherein said adhesion layer (3) is a metal, preferably chromium.

7. The optical article (20) according to claim 5 or 6, wherein the thickness of said adhesion layer (3) is comprised between 0.1 nm and 1 nm.

8. The optical article (20) according to any one of the preceding claims, wherein it further comprises a front interferential stack deposited onto the front surface of said base element (1 ).

9. The optical article (20) according to claim 8, wherein said front interferential stack is configured so as to define for the optical article (20) a front reflection factor higher than 4%.

10. The optical article (20) according to claim 8 or 9, wherein said front interferential stack covers at least partially the front surface of said base element (1).

11. The optical device (20) according to any one of claims 8 to 10, wherein said front interferential stack comprises a tampoprinted pattern.

12. The optical article (20) according to any one of the preceding claims, comprising a transmission factor above 8% and below 80%, preferably below 43%, more preferably below 18%.

13. The optical article (20) according to any one of the preceding claims,wherein said base element (1) is tinted.

14. The optical article (20) according to any one of the preceding claims, wherein it is an ophthalmic lens.

15. Eyewear comprising at least one optical article (20) according to any one of the preceding claims.

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