FR2860303A1 - Optical lens provided with a temporary external protective coating covered with a peelable electrostatically adhered film, for protection during storage and manipulation prior to lens finishing operations - Google Patents

Abstract

An optical lens incorporates a temporary external protective coating, covering at least partially one surface of the lens and incorporating at least one outer layer mechanically degradable by friction and/or contact, with the exception of an outer layer of metal oxide and/or metal hydroxide directly in contact with an under-lying layer containing magnesium fluoride. The temporary external protective coating is covered with a peelable film adhering electrostatically to the outer layer. An independent claim is also included for the edge trimming of this optical lens.

Description

The present invention generally relates to an optical lens,

  in particular an ophthalmic lens, a main face of which has a temporary protective coating, itself coated with a peelable electrostatic film.

  An optical lens, in particular an ophthalmic lens, results from a succession of molding and / or surfacing / polishing operations which determine the geometry of the two convex and concave optical surfaces of the lens, and then appropriate surface treatments.

  The final finishing step of an ophthalmic lens is the edging operation which consists of machining the edge or the periphery of the lens so as to conform to the dimensions required to adapt the lens to the spectacle frame in which it is intended. to take place.

  The edging is generally performed on a grinder comprising diamond grinding wheels which perform the machining as defined above.

  The lens is maintained, during this operation, by locking members acting axially.

  The relative movement of the glass relative to the grinding wheel is controlled, generally numerically, to achieve the desired shape.

  As it appears, it is absolutely imperative that the lens be firmly held during this movement.

  For this, before the operation of edging, it performs a gliding operation of the lens, that is to say that it is positioned on the convex surface of the lens a holding means or glans.

  A holding pad, such as a self-adhesive pad, for example a double-sided adhesive, is disposed between the glans and the convex surface of the lens.

  The lens thus equipped is positioned on one of the aforementioned axial locking members, the second axial locking member then tightening the lens on its concave face by means of a stop, generally made of elastomer.

  During machining, a tangential torque is generated on the lens, which can cause rotation of the lens relative to the glans if the lens holding system is not effective enough.

  The proper retention of the lens depends mainly on the good adhesion to the holding pad / convex surface interface of the lens.

  The latest-generation ophthalmic lenses most often comprise an organic or inorganic outer layer which modifies the surface energy, for example hydrophobic and / or oleophobic antifouling coatings.

  It is most often fluorosilane type materials that reduce the surface energy to prevent the adherence of greasy soils that it is easier to eliminate.

  This type of surface coating can be so effective that the adhesion to the skid / convex surface interface can be impaired, which makes satisfactory smoothing operations difficult, in particular for polycarbonate lenses of which the overflow generates much greater efforts than for other materials.

  The consequence of a misbehaving operation is the pure and simple loss of the lens.

  This is why it is advantageous to deposit on the outer layer a temporary protective layer preferably, imparting a surface energy of at least 15 mJ / m 2, in particular a layer of fluorides, oxides, metal hydroxides, in particular a protective layer MgF2, as described in French Patent Application No. 0106534, or a marking ink or a resin constituting the binder of these marking inks.

  Optical lenses, in particular ophthalmic lenses, comprising, where appropriate, one or more conventional functional coatings such as a primer coating promoting the adhesion of other functional layers, an anti-abrasion coating and an anti-reflection coating, and comprising a hydrophobic and / or oleophobic surface coating, in particular an antifouling coating, itself at least partially covered by a temporary protective coating, in particular favoring the edging operation, are each stored and distributed in paper bags provided internally with a protective coating. The pouches each containing a lens can be stacked on top of each other during storage or shipping.

  It has been found that, due to friction, or even simple pressure, during the storage or handling of these lenses, including in their respective pouches, there appears to be a deterioration of the temporary protective coating, in particular coatings comprising an outer layer. in metal fluoride and especially in MgF2, which can go up to a loss of adhesion with the holding pad during the edging operation. This degradation can be assessed visually, particularly in the case of an outer layer of MgF2, by the appearance on the outer layer of temporary protection of mottling visible to the naked eye.

  US Pat. No. 5,792,537 describes the protection of erasable marks printed on the surface of an optical lens during the grinding operation of this lens by masking the marks by means of an adhesive tape. The adhesive tape may be an electrostatic film such as a strongly plasticized vinyl film.

  The object of the present invention is therefore to provide an optical lens, in particular an ophthalmic lens, comprising an external protective coating which is mechanically degradable by friction and / or contact which is protected against such degradation, in particular during the storage and / or manipulation of The lens.

  According to the invention, the optical lens comprises a temporary external protective coating, at least partially covering the lens and comprising at least one mechanically degradable outer layer by friction and / or contact, with the exception of an outer metal oxide layer and / or metal hydroxide directly in contact with an underlying layer containing magnesium fluoride and is characterized in that the outer layer of the temporary outer protective coating is covered by a peelable film electrostatically adhering to the outer layer.

  According to a preferred embodiment of the invention, the outer layer is made of a material chosen from metal fluorides and mixtures thereof, metal oxides and mixtures thereof, metal hydroxides and mixtures thereof, and mixtures of two or more of these fluorides. metal oxides and hydroxides, the optical lens marking inks and the resins constituting the binder of these marking inks.

  More preferably, the outer layer of the temporary outer protective coating is a metal fluoride, a metal oxide or a metal hydroxide.

  In the present application, the term "lens" designates a mineral or organic glass lens, treated or not, depending on whether it comprises one or more coatings of various nature or that it remains bare.

  When the lens has one or more surface coatings, the term "depositing a layer on the lens" means that a layer is deposited on the outer coating of the lens.

  Surface energies are calculated according to the Owens-Wendt method described in the following reference: Owens D.K., Wendt R.G. (1969) J. Appl. POLYMER. SCI, 13, 1741-1747.

  The optical lenses of the invention generally comprise a hydrophobic and / or oleophobic surface coating and preferably comprise both a hydrophobic and / or oleophobic surface coating deposited on a mono- or multilayer anti-reflection coating.

  In fact, the hydrophobic and / or oleophobic coatings are generally applied to lenses comprising an antireflection coating, in particular made of mineral material, in order to reduce their marked tendency to stain, for example with respect to greasy deposits.

  As indicated above, the hydrophobic and / or oleophobic coatings are obtained by applying, generally on the surface of the antireflection coating, compounds which reduce the surface energy of the lens.

  Such compounds have been widely described in the prior art, for example in US-4410563, EP-0203730, EP-749021, EP-844265, EP933377.

  Silane compounds bearing fluorinated groups, in particular perfluorocarbon or perfluoropolyether group (s), are most often used.

  By way of examples, mention may be made of silazane, polysilazane or silicone compounds comprising one or more fluorinated groups such as those mentioned above.

  A known method consists in depositing on the anti-reflection coating compounds carrying fluorinated groups and Si-R groups, R representing an OH group or a precursor thereof, preferably an alkoxy group. Such compounds may perform polymerization and / or crosslinking reactions on the surface of the antireflection coating directly or after hydrolysis.

  The application of the compounds decreasing the surface energy of the glass is conventionally carried out by dipping in a solution of said compound, by centrifugation or by vapor deposition, in particular. Generally, the hydrophobic and / or oleophobic coating has a thickness of less than 10 nm, and more preferably less than 5 nm.

  The invention is preferably implemented on lenses having a hydrophobic and / or oleophobic surface coating giving a surface energy of less than 14 mJoules / m 2 and more preferably less than or equal to 12 mJ / m 2.

  The temporary protective coating will generally elevate the surface energy of the lens to a value of at least 15 mJoules / m 2.

  It may be applied to an area covering all of at least one of the two faces of the lens or only to the area intended to receive contact with the lens holding pad.

  More specifically, it is customary to deposit the support pad, associated with the glans, on the convex face of the lens. It is therefore possible to cover with the protective coating the whole of the convex face or, alternatively, only a central zone of the convex face, using a mask or any other appropriate technique.

  The deposit may uniformly cover the corresponding zone, that is to say it has a continuous structure, but it may also have a discontinuous structure, for example take the form of a frame.

  In this case, an intermittent deposit is formed, the surface of which remains sufficient to allow the required adhesion of the holding pad.

  Discontinuous deposits can be obtained by pad printing.

  Nevertheless, the zone covered by the outer temporary protective coating (according to the invention) must be such that the contact surface between the protective coating and the holding pad is sufficient to ensure the adhesion of the lens to the pad.

  Generally, the temporary protective coating covers at least 15%, preferably at least 20%, better at least 30%, more preferably at least 40%, and preferably the entire surface of the lens on which it is adhered the pad, that is to say generally the convex face of the lens.

  Following the deposition of the external protective coating, temporary, a lens is obtained capable of edging.

  That is to say that after overflow according to the method of the invention, the glass will have the dimensions required to properly fit into the frame that is intended for it.

  More precisely, this result is obtained when the glass, during the edging operation, undergoes a maximum offset of 2.

  Optimum fl exibility corresponds to a glass whose misalignment is less than or equal to 1.

  The temporary outer protective coating may consist of any material for raising the surface energy of the lens with hydrophobic and / or oleophobic properties and capable of being removed in a subsequent operation subsequent to the edging step.

  Of course, the material must be such that it does not permanently alter the surface properties of the hydrophobic and / or oleophobic coating and after the removal thereof, the optical and surface properties of the lens are generally identical to those that the lens possessed before the temporary protective coating was deposited.

  Preferably, the temporary outer protective coating comprises an inorganic outer layer, and particularly a fluoride or a mixture of metal fluorides, an oxide or a mixture of metal oxides or a metal hydroxide or a mixture of metal hydroxides, or a mixture of these fluorides, oxides and hydroxides.

  As an example of fluorides, mention may be made of magnesium fluoride MgF 2, lanthanum LaF 3, aluminum AIF 3 or cerium CeF 3.

  Oxides that can be used are magnesium (MgO), calcium (CaO), titanium (TiO2), aluminum (Al2O3), zirconium (ZrO2), or praseodymium (Pr2O3) oxides.

  Mixtures of alumina and praseodymium oxide are recommended.

  A particularly recommended commercial material is PASO2 from Leybold.

  As examples of metal hydroxides, there may be mentioned Mg (OH) 2, Ca (OH) 2 and Al (OH) 3, preferably Mg (OH) 2.

  The particularly preferred material is MgF 2.

  The protective layer may be deposited by any suitable conventional method.

  Generally, the antireflection, hydrophobic and / or oleophobic coatings have been deposited by evaporation in vacuum bells and it is desirable to deposit the temporary protective layer by the same technique, which makes it possible to carry out all the operations as a result, without excessive manipulation of the lenses between the steps.

  When it consists of a mineral material, the thickness of the protective coating is preferably less than or equal to 50 nm, and generally from 1 to 50 nm, and more preferably from 5 to 50 nm.

  In general, if the thickness of the protective coating is too low, there is a risk of insufficiently modifying the surface energy.

  If, on the contrary, the thickness of the protective coating is too high, in particular for essentially mineral coatings, the inventors have found that there is a risk of mechanical stresses appearing in the coating, which may be detrimental to the properties expected. .

  Preferably, and most particularly when the protective coating is deposited on an entire of one of the faces of the lens, the material has a certain degree of transparency making it possible to carry out conventional power measurements on the lens by means of a frontofocometer.

  Thus the lens according to the invention preferably has a transmission of at least 18%, preferably at least 40% according to ISO8980 / 3.

  As an alternative to the aforementioned mineral-type materials, conventional inks for the marking of progressive ophthalmic lenses, and / or the resins constituting the binder of these inks, may be used.

  In this case, it is possible to deposit much higher thicknesses than in the case of purely mineral coatings.

  The required thicknesses can then vary from 5 to 150 micrometers.

  Alkyd resins are particularly recommended.

  As indicated above, the temporary outer protective coating may be monolayer or multilayer, in particular bilayers.

  The layers may all be of a mineral nature or both of mineral and organic nature. In the latter case, preferably the organic layer is deposited on the thin mineral layer (5 to 200 nm) and can be much thicker, typically from 0.2 to 10 μm.

  As indicated above, the temporary outer protective coating is mechanically degradable by friction and / or contact. By mechanically degradable by friction and / or contact according to the invention is meant a coating which is removed after being subjected to dry wiping consisting of making 5 rounds on the wiping area with a tissue Wypall L40 of the KIMBERLY-CLARK company, maintaining a pressure of 3 kg / cm2.

  The invention is particularly useful for covering fragile temporary external protective coatings, that is, which are removed after being subjected to dry wiping consisting of performing 5 wipers on the wiping area with Wypall fabric previously. quoted by maintaining a pressure of 60 g / cm2.

  According to the invention the temporary outer protective coating is covered by a peelable film adhering electrostatically to the surface of the coating (peelable electrostatic film).

  These peelable electrostatic films are known in themselves and are flexible films made of plastic, preferably polyvinyl chloride (PVC), having a high content of plasticizer, that is to say at least 20% by weight, preferably at least 30% by weight and typically 30 to 60% by weight.

  The peelable electrostatic films according to the invention have a thickness generally ranging from 100 to 200 μm, typically of the order of 150 μm.

  A PVC peelable electrostatic film (thickness 150 μm) containing 36% by weight of plasticizer is sold by JAC under the reference STICK 87015. Another usable film marketed by the same company is that referenced under No. 87215.

  These electrostatic films are generally in the form of sheets, A4 format, in which one can cut the desired portion to ensure the protection of the coating.

  There may be provided on this portion a gripping tab extending beyond the edge of the lens to facilitate peeling of the film.

  Surprisingly, it has been found that such protective films can be removed from the surface of the lens without damaging the temporary protective coating despite the extreme sensitivity thereof to friction and contact degradations, and particularly a coating. temporary mineral nature, thickness equal to or less than 50 nm, and in particular in the case of a MgF2 coating.

  The lens according to the invention can be subjected to an entirely conventional edging operation, except that it is necessary to carry out, before the edging, the removal of the peelable electrostatic film and, in the final step, a removal operation of the protective coating. temporary.

  The temporary protective coating removal step may be carried out either in liquid medium or by dry wiping, or alternatively by successive implementation of these two means.

  The elimination step in a liquid medium is preferably carried out by a solution of soapy water or an alcohol such as isopropyl alcohol. An acidic solution may also be used, in particular a solution of orthophosphoric acid, at molarities which may vary from 0.01 to 1 N. The acidic solution may also comprise surfactants, anionic, cationic or amphoteric agents.

  The temperature at which the removal step is conducted is variable, but generally, it is carried out at room temperature.

  The elimination of temporary protective coating may also be promoted by mechanical action, preferably by use of ultrasound.

  For dry wiping elimination, a WYPALL 40 fabric marketed by Kimberly-Clark will preferably be used.

  After treatment with the liquid medium such as the acidic solution, dry wiping or a combination of both, the removal step may comprise a cleaning step with an aqueous solution of pH substantially equal to 7.

  At the end of the step of removing the temporary protective layer, the lens has optical and surface characteristics of the same order, or almost identical to those of the initial lens, in particular comprising the hydrophobic coating and / or oleophobic.

  The invention also relates to a method of projecting an optical lens, in particular an ophthalmic lens comprising the following steps: taking an optical lens; remove the electrostatic peelable film to expose the mechanically degradable outer layer; disposing the optical lens in an edging device having a holding pad, so that the holding pad adheres to the mechanically degradable outer layer; proceed with the edging of the optical lens; remove the temporary protective coating; and recover the final optical lens overflowed.

2860303 He

Claims (18)

  An optical lens having a temporary outer protective coating at least partially covering a surface of the lens and comprising at least one mechanically degradable outer layer by friction and / or contact, with the exception of an outer layer of metal oxide and or metal hydroxide directly in contact with an underlying layer containing magnesium fluoride, characterized in that the temporary outer protective coating is covered by a peelable film adhering electrostatically to the outer layer.   2. Lens according to claim 1, characterized in that the outer layer is made of a material selected from metal fluorides and mixtures thereof, metal oxides and mixtures thereof, metal hydroxides and mixtures thereof, mixtures of two or more thereof. metal fluorides, oxides and hydroxides, the inks for marking ophthalmic lenses and the resins constituting the binder of these marking inks.   3. Lens according to claim 1 or 2, characterized in that the metal fluorides are chosen from MgF 2, LaF 3, AlF 3 and CeF 3, preferably MgF 2, the metal oxides are chosen from MgO, CaO, TiO 2, Al 2 O 3, ZrO 2 and Pr 2 O 3. preferably MgO, and the metal hydroxides are chosen from Mg (OH) 2, Ca (OH) 2 and Al (OH) 3, preferably Mg (OH) 2.   4. Lens according to claim 1, characterized in that the outer layer is metal fluoride, preferably MgF2.   5. Lens according to any one of the preceding claims characterized in that the temporary outer protective coating is of a mineral nature and has a thickness equal to or less than 50 nm.   6. A lens according to any one of the preceding claims characterized in that the outer layer of the temporary outer protective coating has a surface energy of at least 15 mJ / m2.   7. Lens according to any one of the preceding claims, characterized in that the temporary outer protective coating covers at least 15%, better still at least 20%, even more preferably at least 30% and preferably the entire surface of The lens.   8. Lens according to any one of the preceding claims, characterized in that the outer temporary protective coating is a multilayer coating.   9. Lens according to any one of the preceding claims, characterized in that the temporary outer protective coating has been deposited in the vapor phase.   10. The lens according to any one of the preceding claims, characterized in that the electrostatic peelable film is a flexible plastic film containing at least 20% by weight of at least one plasticizer.   11. The lens of claim 10 characterized in that the plastic film containing at least 30% by weight, preferably 30 to 60% by weight of at least one plasticizer.   12. The lens of claim 10 or 11, characterized in that the flexible plastic film is a polyvinyl chloride (PVC) film.   13. Lens according to any one of the preceding claims, characterized in that the electrostatic film has a thickness of 100 to 200 .mu.m.   A lens according to any one of the preceding claims, characterized in that the temporary outer protective coating is formed on a hydrophobic and / or oleophobic surface coating of the lens.   15. Lens according to claim 14, characterized in that the hydrophobic and / or oleophobic surface coating has a surface energy equal to or less than 14 mJ / m 2, preferably equal to or less than 12 mJ / m 2.   16. A lens according to claim 14 or 15, characterized in that the hydrophobic and / or oleophobic surface coating has a thickness of less than 10 nm, preferably less than 5 nm.   17. A lens according to any one of claims 14 to 16, characterized in that the hydrophobic and / or oleophobic surface coating is formed on an anti-reflection coating of the lens.   18. A method of projecting an optical lens comprising the steps of: taking an optical lens according to any one of the preceding claims; remove the electrostatic peelable film to expose the mechanically degradable outer layer; disposing the optical lens in an edging device having a holding pad so that the holding pad adheres to the mechanically degradable outer layer; proceed with the edging of the optical lens; remove the temporary protective coating; and recover the final optical lens overflowed.