WO2016102996A1 - Procédé pour limiter la propagation de fissures dans un article optique - Google Patents

Procédé pour limiter la propagation de fissures dans un article optique Download PDF

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Publication number
WO2016102996A1
WO2016102996A1 PCT/IB2014/003128 IB2014003128W WO2016102996A1 WO 2016102996 A1 WO2016102996 A1 WO 2016102996A1 IB 2014003128 W IB2014003128 W IB 2014003128W WO 2016102996 A1 WO2016102996 A1 WO 2016102996A1
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Prior art keywords
coating
groove
hard coating
optical article
optical
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PCT/IB2014/003128
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English (en)
Inventor
Ker Chin Dave Ang
Jinhhao NG
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EssilorLuxottica SA
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Essilor International Compagnie Generale dOptique SA
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Priority to PCT/IB2014/003128 priority Critical patent/WO2016102996A1/fr
Publication of WO2016102996A1 publication Critical patent/WO2016102996A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings

Definitions

  • the present invention relates to the field of optical articles comprising a substrate at least coated with a hard coating.
  • this invention relates to a method for limiting the propagation of cracks in an optical article such as a photochromic lens when it has to be exposed to a heat treatment, and to an optical article, especially a photochromic lens obtained by this method.
  • crack initiation sites could be a result of a casting process, a coating process, a rough handling or a combination thereof during the production of the desired lens. Since these crack initiation sites enhance stress concentration, they are more susceptible to initiate fractures when subjected to thermal stress (e.g. during a step of coating including a heat treatment), thus resulting in cracks.
  • some materials commonly used for the upper coatings of said lens may have a low resistance to heat treatments, involving crack initiation sites and propagation of cracks during said step of heat treatment.
  • Such a step of heat treatment can be for example a tinting step which allows suitable amount of dyes to be imbibed into the surface of the substrate to achieve a pair of tinted lenses.
  • Dyeing or tinting of lenses for aesthetic and sunscreening purposes is well known to those skilled in the art.
  • Such dyeing processes include those which uniformly apply the dyes to the entire lens, when a uniform lens character is desired, or which apply the dyes having different concentrations to portions of the lens in order to provide special effects such as gradient lenses. It is also known to apply a first dye uniformly to a lens and a second dye in a non-uniform manner in order to vary the color characteristics of the lens in different portions thereof.
  • Tinted lenses are generally tinted by conventional wet tinting process which comprises at least one step of dipping the lenses in aqueous baths of dispersed dyes and various additives to promote the coloring process, the baths being maintained at a temperature of the order of 94°C.
  • Lenses can also be tinted by a dry tinting process which comprises at least one step of thermal transfer printing. Said dry tinting process relies on the sublimation of a subliming dye previously prepared on a provisional inert support. The temperature required to perform said dry tinting process is generally of between about 50°C to about 150°C.
  • all the conventional tinting processes to obtain a lens with the desired tint or gradient tint include at least one step of heat treatment which can render the lens more susceptible to the propagation of cracks when the lens comprises a coating before implementing the tinting process.
  • photochromic lenses are able to darken on exposure to specific types of light, most commonly ultraviolet (UV) radiation. Once the light source is removed, the lenses will gradually return to their clear state. Since the commercially available photochromic lenses only provide limited tints in whatsoever state (i.e. darken or clear state), a tinting step can be performed on the photochromic lenses to provide tints other than grey or brown usual tints in the darken state and/or a visible gradient tint in the clear state. However, again, cracking in the lens due to their exposure to such tinting step including a heat treatment is observed, damaging the hard coating thereby destroying the value of the lenses.
  • U.V. light-sensitive substances e.g. photochromic coating
  • UV radiation ultraviolet
  • US2006/0172136 describes the use of flexibility imparting agents such as polysiloxane resins, acrylic resins, polyester resins, polyurethane resins or rubbers, or acrylonitrile rubbers within the hard coating of an optical article in order to increase its heat resistance, thus limiting cracking in said hard coating.
  • FR 2 702 486 relates to a silane-based hard coating comprising colloidal silica and a specific aluminum catalyst, which does not crack and is easily tinted.
  • the compounds (e.g. flexibility imparting agents) or additional coatings used to limit the propagation of cracks in optical articles modify the chemical composition of the original coatings and/or of the optical articles, and thus can alter the other properties of said optical articles, such as their mechanical, photochromic, anti-reflection, anti-smudge or anti-dust properties.
  • said compounds or additional coatings are required to be added in a specific part of the optical articles and/or in a specific type of coating of the optical articles, thus rendering their method of preparation not easily transposable to any type of lenses.
  • a first aim of the present invention is to provide a simple and alternative method which is able to limit the propagation of cracks in an optical article, and especially in a photochromic lens, while keeping all the functional properties of coatings.
  • a second aim of the present invention is to provide an optical article which is resistant to the propagation of cracks when it has to be submitted to a heat treatment, and especially to a tinting process.
  • a first object of the present invention is a method for preparing an optical article for a heat treatment, the optical article having an optical center (C) and comprising a substrate and at least one hard coating, said substrate being coated with said hard coating, said hard coating having a thickness (e) and edges (E),
  • said method comprises a step i 0 ) for limiting the propagation of cracks in said optical article when exposed to the heat treatment, said step i 0 ) including the on-purpose engraving of a continuous or discontinuous groove through at least said hard coating, the outline of the groove forming an open or closed shape which surrounds the optical center (C).
  • the method of the present invention is simple, economic and can be applied to any optical article comprising a substrate and at least one hard coating coated on said substrate and which is supposed to be submitted to a heat treatment.
  • the method does not impair the optical and mechanical properties of the resulting optical article and does not modify the chemical composition of the original coatings and/or of the optical article.
  • said method surprisingly leads to optical articles which have a central zone useable for making eyeglasses and protected from the propagation of cracks.
  • step i 0 Thanks to the use of step i 0 ) and thus, to the introduction of a continuous or discontinuous groove through at least said hard coating, the outline of which forming an open or closed shape which surrounds the center (C) of the optical article, the optical article is ready to be further heat treated without being damaged by the appearance and/or propagation of cracks.
  • the groove delimits two distinct domains: a first domain (I) containing the optical center (C) of the optical article and containing points positioned between the groove and the optical center (C); and a second domain (II) containing points separated from the optical center (C) by the groove, i .e., for which a direct line cannot be formed toward the optical center (C) without overlapping the groove.
  • Cracks initiation sites generally appear in the second domain (II) and the groove serves as a barrier to interrupt the propagation of cracks from said second domain to the first domain.
  • a third domain (III) may appear for some points which are not positioned between the optical center (C) and the groove and are not separated from the optical center (C) by the groove. According to the invention, as long as this third domain (III) covers less than one third of the surface of the hard coating, it is considered that the groove serves as a barrier to interrupt the propagation of cracks toward the optical center (C).
  • a further object of the present invention is an optical article obtained by the above described method, said optical article having an optical center (C) and comprising a substrate coated with at least one hard coating, said hard coating having a thickness (e) and edges (E), wherein said optical article further comprises a continuous or discontinuous groove engraved through at least said hard coating, the outline of said groove forming an open or closed shape which surrounds the optical center (C).
  • a method, or a step in a method that "comprises”, “has”, “contains”, or “includes” one or more steps or elements possessing those one or more steps or elements, but is not limited to possessing only those one or more steps or elements.
  • the phrase "to deposit a coating onto the optical article” means that a coating or layer is deposited onto the outermost coating of the optical article, i.e. the coating which is the closest to the air.
  • a coating that is "on" a side of a lens is defined as a coating that (a) is positioned over that side, (b) needs not be in contact with that side, i .e., one or more intervening coatings may be disposed between that side and the coating in question, and (c) needs not cover that side completely.
  • the phrase “outermost coating” or “outermost layer” means a coating or a layer which is the farthest from the substrate and conversely the phrase “innermost coating” of innermost layer” means a coating or a layer which is the closest to the substrate.
  • substrate means a naked substrate or a naked substrate already coated with one or several functional coatings.
  • optical article means one of an ophthalmic lens, an ocular visor, magnifying lenses and protective lenses or visors such as found in spectacles, glasses, goggles and helmets and sight optical systems.
  • ophthalmic lens is a lens which is designed to fit a spectacles frame so as to protect the eye and/or correct the sight and can be an uncorrective (also called piano or afocal lens) or a corrective ophthalmic lens.
  • Corrective lens may be a unifocal, a bifocal, a trifocal or a progressive lens.
  • the optical article prepared according to the present invention is a transparent optical article, preferably a lens or lens blank, and more preferably an ophthalmic lens or lens blank.
  • the optical article may be coated on its convex main side (front side (Cx)), concave (Cc) main side (back side), or both sides using the process of the invention.
  • lens means an organic or inorganic glass lens, comprising a lens substrate which may be coated with one or more coatings of various natures.
  • the lens naked substrate may be made of mineral glass or organic glass, preferably organic glass.
  • the organic glasses can be either thermoplastic materials such as polycarbonates, thermoplastic polyurethanes, poly(methylmethacrylates), polyacrylates, polyethylene, cyclic olefin homopolymers or copolymers, or thermosetting (cross-linked) materials such as diethylene glycol bis(allylcarbonate) polymers and copolymers (in particular CR-39® from PPG Industries), thermosetting polyurethanes, polythiourethanes, polyepoxides, polyepisulfides, poly(meth)acrylates and copolymers based substrates, such as substrates comprising (meth)acrylic polymers and copolymers derived from bisphenol-A, polythio(meth)acrylates, as well as copolymers thereof and blends thereof.
  • the substrate usually has a refractive index of between about 1.5 and about 1.74.
  • the refractive indexes to which reference is made in the present invention are expressed at 25°C for a wavelength of 550 nm.
  • hard coating means generally a “hardcoat”, i.e. an abrasion or scratch-resistant coating, such as those disclosed in US 2005/0123771, EP 0 614 957, US 4 211 823 and US 5 015 523. However it may also be a layer of same performances or composition even if deposited with another aim than for abrasion resistance.
  • a hard coating used therein means a coating that is brittle and susceptible to form cracks under stress conditions.
  • a hard coating may be an anti-shock coating, an anti-scratch coating, a primer coating or an adhesion coating, said coating having a thickness higher than about 1 ⁇ .
  • a shape which surrounds the optical center (C) means that the barycenter of the shape is in proximity of the optical center (C) of the optical article.
  • the surface of the optical article onto which the hard coating is applied may optionally be subjected to a pre-treatment step intended to improve adhesion, for example a high-frequency discharge plasma treatment, a glow discharge plasma treatment, a corona treatment, an electron beam treatment, an ion beam treatment, an acid or base treatment.
  • a pre-treatment step intended to improve adhesion for example a high-frequency discharge plasma treatment, a glow discharge plasma treatment, a corona treatment, an electron beam treatment, an ion beam treatment, an acid or base treatment.
  • Said hard coating can be any coating typically used for improving abrasion- and/or scratch-resistance of a finished optical article as compared to a same optical article but without the abrasion- and/or scratch-resistant coating.
  • Preferred abrasion- and/or scratch-resistant coatings are
  • composition for an abrasion-resistant coating disclosed in FR 2 702 486 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.
  • the hydrolyzate used is a [gamma]-glycidoxypropyltrimethoxysilane (GLYMO) and dimethyldiethoxysilane (DMDES) hydrolyzate or else a [gamma]-glycidoxypropyltrimethoxysilane (GLYMO) and triethyl orthosilicate (TEOS) hydrolyzate.
  • the hard coating may also comprise at least one layer of an antimony-containing-siloxane-based hard coating.
  • the thickness of the hard coating may usually be comprised between 1 and 10 ⁇ , and is often comprised between 1 ⁇ and 5 ⁇ .
  • edges (E) of the hard coating means the line or curve determining the limits of the surface of the hard coating or the periphery (i .e. the perimeter or the boundary) of the hard coating. In most cases, the edges (E) coincide mostly with edges of the optical article and thus, the center of the hard coating coincides roughly with the optical center (C) of the optical article.
  • the outline of the groove formed in step i 0 ) by engraving a continuous or discontinuous groove through at least the hard coating can have any shape providing that the shape surrounds the center (C) of the optical article.
  • the outline of the groove can have for example a square, a rectangular, a trapezoidal, a circular (i .e. round), an ellipse shape or a more complex shape such a free-form shape or a star shape; it can be an open shape or a closed shape.
  • the shape formed by the outline of the groove can be a part or the whole of a square, with acute or rounded angles, a rectangle, with acute or rounded angles, a trapezoid, with acute or rounded angles, a circle, an ellipse or a more complex shape such a free-form shape or a star shape.
  • the groove can be continuous or discontinuous. When it is discontinuous, it can be a discontinuous curved line made of a succession of dots or dashes or portions of curves or lines or a mix thereof, separated by spaces. Further, the groove can form one rank or two or more ranks of dots or dashes or portions of curves or lines. In case of multiple ranks, one rank may be composed of dots, dashes or portions of curves which are at least partially in front of the spaces of another rank of the groove.
  • the outline of the groove may form a closed shape or an open shape.
  • An open shape may be for example illustrated by a shape which surrounds the optical center (C) on at least 2/3 rd of the directions or can even surround it completely.
  • the shape may be an open shape still surrounding the optical center (C) but on all directions, it may thus be an open shape such a spiral with one end of the groove forming a second rank in front or behind the other end of the groove forming a first rank.
  • the groove may have an apparent covered angle, as seen from the optical center (C), ranging from about 4/3 of Pi to about 2 Pi .
  • the apparent covered angle as used in the present description corresponds to the sum of the angular sectors formed, on the surface of the lens, by the directions which originate from the optical center (C) and head towards the edge of the lens, and which are interrupted by the groove before reaching the edge of the lens.
  • C optical center
  • the sum of the angular sectors covered by the multiple segments or portions of groove may range from 4/3 of Pi to 2 Pi.
  • the overall covered angle of the groove is evaluated by counting as if the succession of dots or dashes was a continuous groove, as long as the distance between two dots or dashes is smaller than 3 times, preferably 2 times the width of the groove.
  • the length of the groove is defined along the outline formed by the groove. Accordingly, the width of the groove is defined at any point, as the direction locally perpendicular to the outline of the groove. In case of the groove being locally a dot, the width of the groove corresponds to a diameter of the dot. In general, the width of the groove, at any point, is the smallest dimension of the groove, along the surface of the lens, without taking into account the depth of the groove.
  • the introduction of the groove according to step i 0 ) should not introduce more sites for crack initiation or regions of high stress concentration. Hence, it is proposed that the groove has a substantially round or U-shaped cross-section.
  • the groove is positioned near to the periphery (i.e. the edges) of the optical article and/or to the edges (E) of the hard coating where the sites of cracks initiation are located; and far enough from the center (C) of the optical article which is used to make an eyeglasses lens.
  • the groove is able to stop early the propagation of the cracks.
  • the method is not limited to the preparation of final optical articles with restricted dimensions.
  • the groove is positioned in an area of the optical article which is a non-disturbing area for vision of a wearer.
  • the optical article is a lens which has to be edged to fit into a frame, and the groove is positioned in part of the lens which has to be removed.
  • the groove is positioned out of an area corresponding to the part of the lens that has to fit into the frame.
  • the outline of the part of the lens that has to fit into the frame is known, called desired lens outline, and the outline of the groove may be within 3 mm from the desired lens outline, between said desired lens outline and the edges.
  • any part of the groove is farther than 1.8 mm from the optical center (C), preferably farther than 2 mm, or farther than 2.5 mm from the optical center (C).
  • the outline of the groove of the optical article can be at a mean distance from the edges (E) of the hard coating ranging from about 0.1 to about 20 mm, preferably from about 1 to about 10 mm, and for example of about 5 mm .
  • the edges (E) of the hard coating correspond to the edges of the optical article.
  • the outline of the groove can be at a constant distance from the edges (E) of the hard coating.
  • the outline of the groove has thus a shape similar to the one of the optical article.
  • its shape is a part or the whole of an ellipse or of a circle.
  • the cracks can propagate into the hard coating but also into the other coatings under the hard coating.
  • the engraving step i 0 produces a continuous or a discontinuous groove with an engraving depth (d) at least equal to the thickness (e) of the hard coating, which may itself include different coatings that are brittle and susceptible to form cracks under stress conditions.
  • the hard coating is defined as comprising at least one coating susceptible to form cracks under stress conditions and possibly be composed of multiple such coatings in vicinity with the others.
  • the engraving depth (d) can be at least equal to the thickness (e) of the hard coating, preferably greater than e, more preferably above 2e, such as between 2e and 3e, or may even reaching the substrate.
  • the engraving depth (d) is comprised between about 2 ⁇ and about 70 ⁇ , and preferably between about 3 and about 30 pm .
  • the groove is engraved through the hard coating, and also through some of the coating(s) which are between the hard coating and the substrate.
  • the groove may go through the whole of the hard coating and through the whole of a layer immediately below the hard coating.
  • the engraving step i 0 ) can for example be performed by laser.
  • the power of the laser can be adjusted to obtain a certain engraving depth (d).
  • the engraving depth (d) is approximately of 47 ⁇ when the laser power is set at 25%.
  • the person skilled in the art of marking ophthalmic lenses using a conventional laser would know how to adjust the parameters of the laser to reach the adequate depth depending on the material of the hard coating.
  • the groove may be formed using other cutting means such as diamond point.
  • step i 0 The heat treatment, for which step i 0 ) is a preparation, can be executed during a next step i).
  • the heat treatment of step i) can be conducted at a temperature greater than 60°C, and can even be greater than about 80°C or even 90°C.
  • the heat treatment of step i) is applied during a tinting step.
  • the tinting step i) can be a wet tinting step or a dry tinting step.
  • the wet tinting step generally comprises a sub-step of dipping the optical article in an aqueous bath comprising at least a dye, said aqueous bath being maintained at a temperature of about 94°C, a sub-step of removing the optical article from the bath after a time sufficient to tint said optical article, and two sub-step of imbibing and then drying the optical article, for example in an oven at about 100°C, in particular for about an hour.
  • both faces of the optical article are put into contact with the aqueous bath, and are submitted to the heating in the oven. Accordingly, any of the faces that comprises a hard coating which is subject to crack generating may form some cracks.
  • the susceptibility to form cracks concerns especially hard coatings deposited on a material with a different thermal dilatation coefficient. It often concerns hard coating separated from the substrate by a soft coating (primer coating in some cases, adhesive coatings, matrix for containing dyes, etc.). However, some hard coatings may have thermal dilatation coefficients very different than some substrates and may generate cracks during heat treatments.
  • the groove of the invention may be applied to any of the faces of the substrate, and may be applied on both faces of the substrate. This embodiment is not limited to lenses destined to be submitted to a wet tinting step. In this embodiment, the grooves on both sides may have a similar shape, and/or their outline may be superposed; however while this is esthetically pleasant, this is not necessary.
  • the dry tinting step can for example comprise a tinting process by sublimation, such as the one developed by the company Nidek in JP2004-121434.
  • Such dry-tinting step generally comprises a sub-step of sublimating a dye from a carrier medium so as to deposit it by condensation on the lens at a temperature of about 100 to 250°C.
  • an imbibing sub-step is generally applied to enable the dye to migrate from the surface of the lens into the substrate. This imbibing sub-step takes place in an oven and often reaches temperatures of about 50°C to 150°C, generally above 80°C or above 90°C.
  • the tinting step i) can provide a uniform tint or a gradient tint on the optical article.
  • the heat treatment i), for which the step i 0 ) of the invention can be of use for preparing the lens may be another step than a tinting step.
  • the hard coating according to the invention may be deposited onto the naked substrate or onto the outermost coating of the substrate if the substrate is already coated with at least one surface coating.
  • Said at least one surface coating may be, without limitation, an impact- resistant coating, also called primer, an abrasion and/or scratch resistant coating which is different from said hard coating, a polarized coating, or a coating containing a dye, such as one or more photochromic dyes and/or one or more permanent dyes.
  • some layers may be temporary coating(s) or layer(s).
  • the impact- resistant coating which may be used in the present invention can be any coating typically used for improving impact resistance of a finished optical article. This coating generally enhances adhesion of the abrasion and/or scratch-resistant coating on the substrate of the finished optical article.
  • an impact-resistant primer coating is a coating which improves the impact resistance of the finished optical article as compared with the same optical article but without the impact-resistant primer coating.
  • Typical impact- resistant primer coatings are (meth)acrylic-based coatings and polyurethane-based coatings, in particular coatings made from a latex composition such as a poly(meth)acrylic latex, a polyurethane latex or a polyester latex.
  • the optical article used in step i 0 ) can further comprises an impact-resistant primer coating between the substrate and the hard coating, so as to obtain a substrate coated with the impact- resistant primer coating, said impact-resistant primer coating being further coated with the hard coating.
  • the coating containing a dye which may be used in the present invention can be any coating typically used for providing a matrix adapted to contain and disperse adequately a dye.
  • a dye is a photochromic dye
  • the coating containing said photochromic dye is called hereafter "photochromic coating”.
  • a photochromic dye is defined as any dye enabling a reversible change in color, i .e. a change in the absorption spectrum in the visible range of light (380-780 nm) of a finished optical article under activation by light of a given wavelength, typically UV light.
  • the optical article used in step i 0 ) can further comprise a photochromic coating between the substrate and the hard coating, so as to obtain a substrate coated with the coating containing a photochromic dye (i .e. photochromic coating), said photochromic coating being further coated with the hard coating.
  • a photochromic coating between the substrate and the hard coating, so as to obtain a substrate coated with the coating containing a photochromic dye (i .e. photochromic coating), said photochromic coating being further coated with the hard coating.
  • a polyurethane-based coating is used to serve as a matrix for containing the photochromic dye.
  • the photochromic coating can be a polyurethane-based coating comprising a photochromic dye.
  • the thickness of the photochromic coating may be comprised between about 1 pm and about 30 ⁇ .
  • the hard coating can be deposited on the preceding coating by any appropriate technique, for example by dipping, centrifuging, spraying, sprinkling or application with a brush or roller, preferably by dipping or centrifuging. It is subsequently cured by the appropriate route (preferably thermal or UV radiation).
  • the hard coating may in itself be a double or triple layer comprising two or three layers of different materials.
  • the hard coating may comprise two layers, in particular an acrylic-based coating and a further coating such as a temporary coating or layer, said further coating being the outermost coating of the hard coating.
  • the stack of both the acrylic-based coating and the further coating e.g. a coating such as the antimony-containing-siloxane-based hard coating
  • the hard coating of the invention may be understood as the hard coating of the invention.
  • both coatings can be considered as susceptible to crack propagations; being in contact with each other, they are in the vicinity of each other, and without the method of the invention [i .e. step i 0 )], cracks are propagated through both layers simultaneously during a heat treatment.
  • the acrylic-based coating can be directly coated on a polyurethane-based coating containing a photochromic dye, used as a photochromic coating, and is thus protecting the photochromic coating.
  • the method can further comprises after step i), a step ii) of depositing at least one additional coating on said optical article and/or a step iii) of edging the optical article.
  • the present method is flexible and allows incorporation of other functional coatings onto the substrate either before step i 0 ) or after (or during) step i).
  • an additional hard coating may be deposited, and eventually an antireflective stack may be deposited on the additional hard coating after step ii) by means known to the person skilled in the art.
  • a top coat either an anti-smudge or an anti-fog coating, may be deposited on top of the a nti reflective stack.
  • the method of the invention can further comprise between steps i) and step ii), a step of stripping part of the hard coating, such as stripping the temporary layer.
  • step i 0 does not introduce additional defects during the following steps such as step ii) and/or step iii).
  • a second object of the present invention is an optical article obtained by the method as defined in the present invention, said optical article having an optical center (C) and comprising a substrate coated with at least one hard coating, said hard coating having a thickness (e) and edges (E), wherein said optical article further comprises a continuous or discontinuous groove engraved through at least said hard coating, the outline of said groove forming an open or closed shape which surrounds the optical center (C).
  • optical article, the groove, and the outline and the shape of the outline are as defined in the first object of the present invention.
  • the optical article can be submitted to any heat treatment such as a tinting step without being damaged by the appearance and/or the propagation of cracks.
  • cracks initiating at the edges (E) of the hard coating during the heat treatment see their progression toward the optical center (C) stopped by the groove. Accordingly the optical article after the heat treatment, even when cracks are formed, keeps a surface around the optical center (C) which is crack-free and which is delimited by the outline of the groove.
  • a third object of the present invention is the use of a continuous or discontinuous groove in an optical article having an optical center (C) and comprising a substrate and at least one hard coating, said substrate being coated with said hard coating, said hard coating having a thickness (e) and edges (E), the groove being engraved through at least said hard coating, the outline of said groove forming an open or closed shape which surrounds the optical center (C), to limit the propagation of cracks in said hard coating when the optical article is exposed to a heat treatment.
  • optical article, the groove, the outline of the groove and the shape of the outline are as defined in the first object of the present invention.
  • Photochromic lenses of the 6 th generation sold under the brand name of Transitions ® (Transitions VI) by Transitions Optical, Inc. were used as starting optical articles to perform the method of the present invention.
  • Each photochromic lens comprised a substrate having a refractive index ranging either of 1.60 (MR8) or 1.67 (MR7), a polyurethane-based coating (PU coating acting as a matrix for containing a photochromic dye; ie. acting as a photochromic coating) having a thickness of about 20 ⁇ and coated on the substrate, an acrylic-based coating, called first hard layer, having a thickness of about 8.5 ⁇ coated on the polyurethane-based coating, and an antimony-containing-siloxane-based hard coating, called second hard layer, having a thickness of about 2 ⁇ coated on the acrylic-based coating.
  • PU coating acting as a matrix for containing a photochromic dye ie. acting as a photochromic coating
  • first hard layer having a thickness of about 8.5 ⁇ coated on the polyurethane-based coating
  • second hard layer having a thickness of about 2 ⁇ coated on the acrylic-based coating.
  • Each photochromic lens was submitted to an engraving step i 0 ) according to the method of the present invention.
  • Step i 0 was performed by using an ILS-II laser cutting and engraving machine commercialized by Laser Tools & Technics Corp.
  • a groove By controlling the power of the laser, a groove, the outline of which forming a shape surrounding the optical center (C) of the lens, was engraved through each layer of the hard coating with various engraving depths on each photochromic lens, at a distance of about 5 mm from the edges of each lens.
  • Each photochromic lens was subsequently subjected to a heat treatment at a temperature of about 145°C for about 2 hours (cf. step i) of the method of the present invention).
  • Figure 1 represents the engraving depth (in ⁇ ) as a function of the laser power (in %). The man skilled in the art, knowing that the ILS-II engraving machine was used, can easily reproduce this test, even using other engraving machines. In figure 1, it is also shown the occurrence or the absence of crack propagation.
  • Figure 2a represents a microscopic analysis of a cross section of the photochromic lens obtained after step i) when the laser power was set to 15% and figure 2b is a schematic representation of the various layers (or coatings) within the photochromic lens with their accompanying thicknesses.
  • the cracks were mostly limited within the two external layers of the photochromic lens ( ⁇ 10 ⁇ ). It is thus believed that the polyurethane-based coating is more ductile and as such is not comprised into the hard coating and hence, limits crack propagation on its own.
  • Figure 3 is a schematic representation of the method of the present invention, in particular to obtain a gradient tint on a starting optical article such as a photochromic lens.
  • the method of the present invention comprises a first step i 0 ) of engraving a groove through at least the hard coating (i .e. comprising both the first hard layer and second hard layer) of the photochromic lens described above, thus forming a shape surrounding the center (C) of the optical article.
  • the groove has a circular shape, and it is at a constant distance from the edges (E) of the hard coating.
  • the obtained photochromic lens is submitted to a conventional tinting step i) and provides a gradient tint on the optical article, followed by a step ii) of depositing an anti reflective stack and an anti-smudge layer, and an edging step iii).
  • the groove is positioned in an area of the optical article which is a non-disturbing area for vision of a wearer.
  • the lens having a diameter of about 160 mm to 180 mm, any part of the groove is farther than 30 mm from the optical center (C), which is farther than 2.5 mm,
  • Figure 4 is a schematic representation of a lens obtained after an engraving step i 0 ) and a step i) of heat treatment according to the method of the present invention.
  • Figure 4a represents the lens having crack initiation sites. After step i 0 ), a groove is engraved through at least the hard coating of said lens and then, said lens is submitted to a heat treatment i). Thanks to the use of said groove, the propagation of the cracks is completely stopped.
  • the groove is continuous and the outline of the groove forms a closed circular shape which surrounds the optical center (C) of the optical article.
  • a first domain (I) contains the optical center (C) of the optical article and points positioned between the groove and the optical center (C) and a second domain (II) contains points separated from the optical center (C) by the groove.
  • Figure 4b is a cross section of figure 4a. Indeed, the groove serves as a crack propagation barrier, in particular by creating discontinuity in the starting lens used in step i 0 ).
  • Figure 5 is a schematic representation of a lens having crack initiation sites and obtained after an engraving step i 0 ) and a step i) of heat treatment according to the method of the present invention.
  • the groove is continuous and the outline of the groove forms a closed free-form shape which surrounds the optical center (C) of the optical article.
  • the groove is discontinuous and is made of dots and dashes, and the outline of the groove forms a closed star shape which surrounds the optical center (C) of the optical article.
  • the groove is discontinuous and is made of two ranks of dashes, and the outline of the groove forms a closed rectangular shape which surrounds the optical center (C) of the optical article.
  • the groove is continuous and the outline of the groove forms an open ellipse shape that surrounds the optical center (C) of the optical article.
  • the apparent covered angle is of about 4/3 Pi ( ⁇ ) and ranges from 4/3 Pi to 2Pi.
  • a first domain (I) contains the optical center (C) and points positioned between the groove and the optical center (C);
  • a second domain (II) contains points separated from the optical center (C) by the groove
  • a third domain (III) appears for some points which are not positioned between the optical center (C) and the groove and are not separated from the optical center (C) by the groove.
  • EXAMPLE 2 A MR7 photochromic lens of the 6 th generation sold under the brand name of Transitions ® (Transitions VI) by Transitions Optical, Inc. was used as a starting optical article in the method of the present invention. It was first engraved with the ILS-II laser cutting and engraving machine described in example 1 using an engraving depth of about 46.5 ⁇ . The groove was positioned at about 5 to about 10 mm away from the edges of the photochromic lens. The groove can be however positioned even closer to the edges and its engraving depth can be controlled by adjusting the power of the laser until having about 25 ⁇ .
  • the photochromic lens was subsequently tinted via a dry tinting step i), so as to obtain a photochromic lens U.
  • U was prepared according to the method of the invention.
  • Figure 6 represents images of U (figure 6b) and L 2 (figure 6a). As shown in Figure 6b, the groove clearly stops the propagation of the cracks in Li, whereas as shown in figure 6a, L 2 which was not prepared according to the method of the present invention displays cracks.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Eyeglasses (AREA)

Abstract

La présente invention concerne le domaine des articles optiques comprenant un substrat au moins revêtu d'un revêtement dur. En particulier, l'invention concerne un procédé pour limiter la propagation de fissures dans un article optique, tel qu'une lentille photochromique, lorsqu'il doit être exposé à un traitement thermique, et un article optique, en particulier une lentille photochromique obtenue par ce procédé.
PCT/IB2014/003128 2014-12-23 2014-12-23 Procédé pour limiter la propagation de fissures dans un article optique Ceased WO2016102996A1 (fr)

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Application Number Priority Date Filing Date Title
PCT/IB2014/003128 WO2016102996A1 (fr) 2014-12-23 2014-12-23 Procédé pour limiter la propagation de fissures dans un article optique

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Application Number Priority Date Filing Date Title
PCT/IB2014/003128 WO2016102996A1 (fr) 2014-12-23 2014-12-23 Procédé pour limiter la propagation de fissures dans un article optique

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WO2016102996A1 true WO2016102996A1 (fr) 2016-06-30

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4211823A (en) 1977-03-11 1980-07-08 Toray Industries, Inc. Tintable coatings and articles having such coatings
US5015523A (en) 1983-07-29 1991-05-14 Seiko Epson Corporation Coated synthetic resin lens
EP0614957A1 (fr) 1993-03-08 1994-09-14 ESSILOR INTERNATIONAL Compagnie Générale d'Optique Compositions de revêtement antiabrasion à base d'hydrolysats de silanes et de composés de l'alumium, et articles revêtus correspondants résistant à l'abrasion et aux chocs
JP2004121434A (ja) 2002-09-30 2004-04-22 Nidek Co Ltd 眼内レンズの着色方法及び該方法にて得られる着色眼内レンズ
US20060046015A1 (en) * 2004-08-30 2006-03-02 Fuji Photo Film Co., Ltd. Optical recording medium and cover sheet for optical recording media
US20060172136A1 (en) 2005-02-01 2006-08-03 Takashi Komori Coated member
CN201202408Y (zh) * 2008-06-04 2009-03-04 河南四方达超硬材料股份有限公司 表面刻槽的聚晶金刚石硬质合金复合片

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4211823A (en) 1977-03-11 1980-07-08 Toray Industries, Inc. Tintable coatings and articles having such coatings
US5015523A (en) 1983-07-29 1991-05-14 Seiko Epson Corporation Coated synthetic resin lens
EP0614957A1 (fr) 1993-03-08 1994-09-14 ESSILOR INTERNATIONAL Compagnie Générale d'Optique Compositions de revêtement antiabrasion à base d'hydrolysats de silanes et de composés de l'alumium, et articles revêtus correspondants résistant à l'abrasion et aux chocs
FR2702486A1 (fr) 1993-03-08 1994-09-16 Essilor Int Compositions de revêtement antiabrasion à base d'hydrolysats de silanes et de composés de l'aluminium, et articles revêtus correspondants résistants à l'abrasion et aux chocs.
US20050123771A1 (en) 1993-03-08 2005-06-09 Philippe Vaneeckhoutte Abrasion resistant coating compositions based on silane hydrolysates and aluminium compounds and corresponding abrasion and shock resistant coated articles
JP2004121434A (ja) 2002-09-30 2004-04-22 Nidek Co Ltd 眼内レンズの着色方法及び該方法にて得られる着色眼内レンズ
US20060046015A1 (en) * 2004-08-30 2006-03-02 Fuji Photo Film Co., Ltd. Optical recording medium and cover sheet for optical recording media
US20060172136A1 (en) 2005-02-01 2006-08-03 Takashi Komori Coated member
CN201202408Y (zh) * 2008-06-04 2009-03-04 河南四方达超硬材料股份有限公司 表面刻槽的聚晶金刚石硬质合金复合片

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