Lens manufacturing and annealing methods

Abstract

A method for annealing a lens made of plastic material is disclosed, as well as a method for manufacturing a lens made of plastic comprising said method for annealing, wherein said method for annealing is conducted on a lens obtained by casting or injection molding of a plastic material, prior to conducting the lens finishing steps, such as surfacing, among others.

Description

DescriptionTitle: LENS MANUFACTURING AND ANNEALING METHODSTechnical Field

[0001] This disclosure pertains to the field of lens manufacturing, in particular ophthalmic lenses, and describes a method for annealing a lens made of plastic, prior to conducting the lens finishing steps, such as blocking, cutting and surfacing, among others.Backg ound Art

[0002] Ophthalmic lenses are generally manufactured in two ways: “mass” production and “prescription” manufacture. “Mass” production is used for manufacturing the most commonly required finished lenses and for the production of semi-finished lenses, i.e. lenses whose front face is finished and whose rear face will be subsequently finished or surfaced according to the required optical correction. On the other hand, “prescription” manufacture may use semi-finished lenses (obtained previously by “mass” production) which are then subjected to finishing steps, such as surfacing and various surface treatments (coloring, anti-scratch, anti-reflection, etc.,), or may comprise direct surfacing of the two lens faces, or conducting direct polymerization followed by various surface treatment operations. Mass production is carried out on a large scale in manufacturing plants, whereas “prescription” manufacturing is effected piece by piece in finishing laboratories. A large part of the ophthalmic lenses is manufactured, therefore, using semi-finished lenses.

[0003] Semi-finished lenses made of plastic materials (organic polymers) are made by cast or injection molding and are then, subsequently, subjected to several finishing steps. The plastic materials used to produce said semi-finished lenses may be thermosetting or thermoplastic materials. Semi-finished lenses made with thermosetting materials are produced by casting and curing a polymerizable composition, whereas lenses made with thermoplastic materials are hot-formed or molded by injection (injection molding).

[0004] However, any change in the shape of a lens optical surface with respect to a target surface, as may occur during surfacing, results in optical defects such as image distortions or optical aberrations due to internal stresses in the lens. Such distortions and aberrations may lead to discarding of the final product following surfacing.

[0005] In that connection, the casting or injection molding processes generate residual stress inside the lens which results in several issues in the subsequent steps carried out to finish the lens, as seen in figure 1 B. Indeed, when surfacing a lens back surface, the stress balance is broken, and the lens tends to deform itself under the effect of residual stress inside the substrate material. Moreover, if the lens deformation occurs during the back surface generating process, the deformation present in the front lens surface may lead to wrong optics in transmission. This issue is particularly present when using an ART (Alloy Replacement Technology) blocking process during surfacing. ARTblocking allows replacing the metal alloys traditionally used for blocking which are harmful for the environment and health. However, the materials used in ART blocking are less rigid than the metal alloys previously used and allow the generation of deformation on the fixed (finished) front surface while it is fixed during surfacing.

[0006] As exemplified in figure 1 A, conventional annealing comprises a heating step which is carried out on the semi-finished lens and prior to the lens finishing steps. The purpose of the annealing process is to minimize the residual stress in the molded lens, prior to the finishing steps in order to avoid the issues previously described.

[0007] However, current annealing procedures are not able to minimize appropriately the residual stress present in the semi-finished lens, and results in that new stress builds up in the substrate again. Accordingly, there is still a need for developing a lens manufacturing process which allows minimizing adequately the residual stress generated during molding and reducing, as a result, the issues that may be generated during the lens finishing steps, in particular when using ART blocking, and provide therefore a lens with improved optics.Summary

[0008] After conducting extensive research, the present inventors have developed a novel method for annealing which overcomes some of the issues encountered in the prior art.

[0009] In that connection, one aspect of this disclosure refers to a method for annealing a lens made of plastic material, said plastic material having a glass transition temperature Tg, wherein said method comprises the following steps: submitting the lens to a temperature Ti for a period of time Pi of between 15 to 90 minutes, preferably 20 to 70 minutes, more preferably 30 to 60 minutes, wherein Tg+20sC > Ti > Tg, preferably Tg+10°C>Ti> Tg, more preferably Tg+5°C > Ti > Tg; immediately after the step of submitting the lens to a temperature Ti for a period of time Pi, cooling the lens by submitting the lens to a temperature decrease from temperature Ti down to a temperature T2 < Tg-35°C, preferably T2 < Tg-50°C, more preferably down to a temperature of 35°C, with a rate of cooling R1 below 1 ,5°C / min, preferably comprised between 0.5 and 1 .5°C / min, more preferably between 0.75 and 1 .25°C / min.

[0010] In some embodiments, the lens is a lens made by cast or injection molding of a plastic material which has not been yet submitted to edging or surfacing, or both or which has not yet been submitted to any lens finishing step. In particular, the lens may be a semi-finished lens.

[0011] In some embodiments the lens is made by casting and curing a polymerizable composition in a mold, preferably a polymerizable composition comprises a polythiol, such as a dithiol or a trithiol, and a polyisocyanate, for example an aromatic or a non-aromatic polyisocyanate, or a polythioisocyanate. Thus, in some embodiments the plastic material of the lens is a polythiouretane.

[0012] The novel annealing method disclosed herein may be used in a method for manufacturing of a lens, for example an optical lens (suitable for forming an image) such as an ophthalmic lens or a binocular lens, and, in particular, in a method for manufacturing an ophthalmic lens.

[0013] Accordingly, another aspect refers to a method for manufacturing an ophthalmic lens made of plastic material, said plastic material having a glass transition temperature Tg, wherein said method comprises the following steps: submitting a lens made of a plastic material having a glass transition temperature Tgto a temperature Ti for a period of time Pi of between 15 to 90 minutes, preferably 20 to 70 minutes, more preferably 30 to 60 minutes, wherein Tg+20sC>Ti>Tg, preferably Tg+10°C>Ti> Tg, more preferably Tg+5°C>Ti> Tg; immediately after the step of submitting the lens to a temperature Ti for a period of time Pi, cooling the lens by submitting the lens to a temperature decrease from a temperature Ti down to a temperature T2 < Tg-35°C, preferably T2 < Tg-50°C, more preferably down to a temperature of 35°C, with a rate of cooling R1 of below 1 .5°C / min, preferably comprised between 0.5 and 1 .5°C / min, more preferably between 0.75 and 1 .25°C / min; and conducting one or more ophthalmic lens finishing steps.

[0014] In some embodiments, the methods herein disclosed further comprise, prior to the step of submitting the lens to a temperature Ti for a period of time Pi, a step of submitting the lens to a temperature To for a period of time Po of between 10 to 30 minutes, preferably for 12 to 25 minutes, more preferably 15 to 20 minutes, wherein To is a temperature higher than Ti, preferably wherein To is a temperature Tg+5OsC>To>Tg+25sC, more preferably Tg+4OsC>To>Tg+3OsC.

[0015] In some embodiments, after the cooling from a temperature Ti down to a temperature T2, the method for manufacturing an ophthalmic lens herein disclosed further comprises a lens finishing step comprising surfacing or edging, or both, of the lens, wherein the surfacing preferably comprises using an alloy replacement technology for blocking the lens during surfacing.

[0016] The foregoing paragraphs have been provided by way of general introduction and are not intended to limit the scope of the following claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.Brief Description of Drawings

[0017] A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

[0018] [Fig. 1]: Fig. 1A is an illustration of a temperature vs. time profile of an annealing process carried out according to the prior art with ophthalmic lenses made of plastic materials MR7™ and MR8™ from Mitsui Chemicals, Inc prior to conducting the lens finishing steps.Fig. I B: images of MR7™ (left panel) and MR8™ (right panel) ophthalmic lenses (submitted to the annealing method illustrated in Fig. 1 A according to the prior art): [Fig. 1 B(i)] shows the residual stress present in said MR7™ (left panel) and MR8™ (right panel) ophthalmic lenses (submitted to the annealing method illustrated in Fig. 1 A according to the prior art) measured with a polariscope and with a StrainScope polarimeter (llis). For each lens a black and white image (left) and the corresponding color image (right) is shown. The presence of more differences in shade in the black and white image (left for each lens), indicate a higher residual stress in the lens. [Fig. 1 B(ii)] shows the impact of said residual stress in the MR7™ (left panel) and MR8™ (right panel) lens deformation by measuring with a Dual Lens Mapper (DLM; Automation and Robotics), the front curve deformation (in diopter) before surfacing is applied.Color and numeric scale, at the left of the images (from up to bottom) show the diopter deviation from target (diopter tolerance target of ±0.09, see table 1 ): red (+0.25 diopter deviation from target) which turns into orange and then yellow (+0.05) and then green to dark green for a value close to 0 (no deviation from target diopter), which turns to blue (-0.10), then darker blue and violet (-0.25): . Before surfacing is applied all the colors of both images left (MR7TM) and right (MR8TM) 1 B(ii) shown are green (diopter values within the diopter tolerance target of ±0.09, see table 1 ) in both lenses being darker green towards the center of the lens (diopter value closer to the target, i.e. diopter tolerance 0) and lighter towards the edge. [Fig. 1 B(iii)] shows the impact of said residual stress in the MR7™ (left panel) and MR8™ (right panel) lens deformation by measuring with a Dual Lens Mapper (DLM; Automation and Robotics) using the same color and numeric scale as in Fig. 1 B(ii): the front curve deformation (in diopter) after surfacing is applied. After surfacing, the MR7™ ophthalmic lens (left panel) shows practically only orange color evidencing diopter values above than the maximum diopter tolerance value of 0.09, with only some tints of yellow and light green at the center of the lens. On the other hand, after surfacing, the MR8™ ophthalmic lens (right panel) shows mainly red colors, evidencing diopter values well above than the maximum diopter tolerance value of 0.09, with values up to 0.25 and decreasing towards the center until values closer to the target (some yellow appearing towards the center of the lens, with a small patch of light green near the center point of the lens). [Fig. 1 B(iv)] shows the MR7™ (left panel) and MR8™ (right panel) lens front curve profile error (in diopter) after surfacing. [Fig. 1 B(v)] shows the MR7™ (left panel) and MR8™ (right panel) lens transmission error (in diopter) after surfacing using the same color and numeric scale as in Fig. 1 B(i i) : for the MR7™ ophthalmic lens (left panel) only green colors are present in the center, turning into yellow and then red towards the edges (in concentrical rings); for the MR8™ ophthalmic lens (right panel) the center of the lens remains yellow, with some concentric areas towards the edges with green colors (within the diopter tolerance of ±0.09) but which turn into orange-red colors towards the edge, reaching values even outside the scale indicated in the figure (the edges include values deviating more than 0.25 from the diopter target).

[0019] [Fig. 2] is an illustration of a temperature vs. time profile of an exemplary embodiment of the method of annealing according to the present disclosure carried out in MR7™ [Fig. 2A] and MR8™ [Fig. 2B] ophthalmic lenses from Mitsui Chemicals, Inc, prior to conducting the lens finishing steps. [Fig. 2C] : images of MR7™ (left panel) and MR8™ (right panel) ophthalmic lenses (submitted to anexemplary annealing method according to the present disclosure shown respectively is FIG. 2A and 2B). [Fig. 2C(i)] shows the residual stress present in the MR7™ and MR8™ ophthalmic lenses (submitted to an exemplary annealing method according to the present disclosure shown respectively is FIG. 2A and 2B) measured with a polariscope and a StrainScope polarimeter. For each lens a black and white image (left) and the corresponding color image (right) is shown. The lenses show less differences in shade when comparing to the prior art images of Fig. 1 B(i), illustrating a lower amount of residual stress present. [Fig. 2C(ii)] shows the impact of said residual stress in the MR7™ (left panel) and MR8™ (right panel) lens deformation by measuring with a DLM using the same color and numeric scale as in Fig. 1 B(ii): the front curve deformation before surfacing is applied. Before surfacing is applied all the colors shown are green (diopter values within the diopter tolerance target of ±0.09, see table 1 ) in both lenses, being the darker green zones (closer to the diopter target, i.e. 0 value) larger (present in both the edges and center of the lens) and more homogeneous than in the prior art MR7™ and MR8™ lens images of Fig 1 B(ii). [Fig. 2C(iii)] shows the impact of said residual stress in the MR7™ (left panel) and MR8™ (right panel) lens deformation by measuring with a DLM using the same color and numeric scale as in Fig. 1 B(ii): the front curve deformation after surfacing is applied. After surfacing is applied, the MR7™ ophthalmic lens (left panel) shows light orange (towards the edges) and yellow colors which turn green towards the center of the lens, illustrating values closer to the diopter tolerance target of ±0.09 towards the edges, and well inside the diopter tolerance target towards the center of the lens, when compared to the orange colors of the corresponding MR7™ prior art image of Fig. 1 B(iii). On the other hand, after surfacing, the MR8™ ophthalmic lens (right panel) shows only yellow colors towards the edges turning green and darker green towards the center of the lens, evidencing diopter values significantly closer to the diopter tolerance target than the corresponding MR8™ prior art image of Fig. 1 B(iii) in which red was the main color, appearing yellow only in a small zone towards the center of the lens, with a small patch of light green near the center point of the lens. [Fig. 2C(iv)] shows the MR7™ (left panel) and MR8™ (right panel) lens the lens front curve profile error after surfacing. [Fig. 2C(v)] shows the MR7™ (left panel) and MR8™ (right panel) lens transmission error after surfacing using the same color and numeric scale as in Fig. 1 B(ii): for both the MR7™ ophthalmic lens (left panel), the green colors are significantly more prominent and darker (closer to the diopter target, i.e., closer to the 0 value of the diopter tolerance target range) than in the corresponding MR7™ and MR8™ prior art images of Fig. 1 B(v), covering now almost all the lens surface in a significantly homogeneous manner.Description of Embodiments

[0020] For the lens materials used in the invention, the Tg values are close when measured according to the classical main methods known by the man skilled in the art. The Tg values of the materials mentioned in the application have been measured by DSC (Differential Scanning Calorimetry).

[0021] As previously disclosed, the method for annealing a lens made of plastic material, said plastic material having a glass transition temperature Tg, disclosed herein comprises:submitting the lens to a temperature Ti for a period of time Pi of between 15 to 90 minutes, preferably 20 to 70 minutes, more preferably 30 to 60 minutes, wherein Tg+20sC>Ti>Tg, preferably Tg+10°C>Ti> Tg, more preferably Tg+5°C>Ti>Tg; immediately after the step of submitting the lens to the temperature Ti for a period of time Pi , cooling the lens by submitting the lens to a temperature decrease from the temperature Ti down to a temperature T2 < Tg-35°C, preferably T2 < Tg-50°C, more preferably down to a temperature of 35°C, with a rate of cooling R1 below 1 .5°C / min, preferably comprised between 0.5 and 1 .5°C / min, more preferably between 0.75 and 1 .25°C / min.

[0022] Preferred implementations of the method for annealing herein disclosed, further comprise, prior to the step of submitting the lens to the temperature Ti, a step of submitting the lens to a temperature To for a period of time Po of between 10 to 30 minutes, preferably of 12 to 25, more preferably of 15 to 20 minutes, wherein To is a temperature higher than Ti, preferably wherein To is a temperature Tg+5OsC>To>Tg+25sC, more preferably Tg+4OsC>To>Tg+3OsC.

[0023] In some embodiments of the annealing method herein disclosed To may be a temperature Tg+5OsC>To>Tg+25sC, or Tg+45sC>T0>Tg+27sC, or Tg+4OsC>To>Tg+3OsC.

[0024] In some embodiments of the annealing method herein disclosed Ti may be a temperature Tg+20sC > Ti > Tg, or Tg+20sC > Ti > Tg+0.5sC, or Tg+10°C>Ti> Tg+0.2sC, or Tg+10°C>Ti> Tg, or Tg+5°C > Ti > Tg.

[0025] In some embodiments of the annealing method herein disclosed T2 may be a temperature T2 < Tg-35°C, or T2< Tg-40°C, or T2< Tg-45°C, or T2< Tg-50°C, or T2is 35°C, or T2is room temperature TRT.

[0026] In some embodiments the rate of cooling R1 may be below 1 .5°C / min, or between 0.25 and 1 .5sC / min, or between 0.5 and 1 .5°C / min, or between 0.5 and 1 .25SC, or between 0.75 and 1 .25°C / min, or between 0.75 and 1 .5SC.

[0027] Thus, preferred aspects of this disclosure refer to a method for annealing a lens made of plastic material, said plastic material having a glass transition temperature Tg, wherein said method comprises the following steps: submitting the lens to a temperature To for a period of time Po of between 10 to 30 minutes, preferably for 12 to 25 minutes, more preferably of 15 to 20 minutes, wherein To is a temperature higher than a temperature Ti, preferably wherein To is a temperature Tg+5OsC>To>Tg+25sC, more preferably Tg+4OsC>To>Tg+3OsC, and wherein Tg+20sC>Ti>Tg, preferably Tg+10°C>Ti>Tg, more preferably Tg+5°C>Ti>Tg; submitting the lens to the temperature Ti for a period of time Pi of between 15 to 90 minutes, preferably 20 to 70 minutes, more preferably 30 to 60 minutes; and immediately after the step of submitting the lens to the temperature Ti for a period of time Pi , cooling the lens by submitting the lens to a temperature decrease from temperature Ti down to a temperature T2STg-35°C, preferably T2STg-50°C, more preferably down to a temperatureof 35°C, with a rate of cooling R1 below 1.5°C / min, preferably comprised between 0.5 and 1 .5°C / min, more preferably between 0.75 and 1 .25°C / min.

[0028] In some preferred embodiments, said lens is an ophthalmic lens, more preferably a semifinished ophthalmic lens. As herein defined, an ophthalmic lens is a lens which is designed to be used in monocles or in eyeglasses (including sunglasses, goggles and safety glasses). As defined herein, contact lenses are not ophthalmic lenses. Ophthalmic lenses are typically used to protect the eye and / or correct the sight. Ophthalmic lenses may be non-corrective ophthalmic lenses (also called piano or afocal lenses) or corrective ophthalmic lenses. A corrective lens may be a unifocal, a bifocal, a trifocal, or a progressive lens. As defined herein, ophthalmic lenses may comprise finished lenses and semi-finished lenses.

[0029] The ophthalmic lenses obtainable by the methods disclosed herein may be included in an optical article, which may include without limitation sunglasses, ski goggles, sport lenses, augmented reality and virtual reality lenses, magnifying lenses, protective lenses and visors, for example motorcycle visors and helmets.

[0030] A lens may undergo various treatment steps such as surfacing, coloring, coating and edging before being finally included in eyeglasses or in a monocle. A finished lens is ready to be included in eyeglasses or in a monocle. In some embodiments the annealing method is carried out on a lens made or obtained by casting or injection molding, and the method for annealing is carried out prior to conducting surfacing or edging or prior to both edging and surfacing or prior to conducting any lens finishing step. It is also to be understood that the methods herein disclosed may be carried out on one lens or in more than one lens simultaneously.

[0031] In some embodiments, between the step of submitting the lens to a temperature To and the step of submitting the lens to a temperature Ti, the methods disclosed herein comprise a step of cooling the lens by submitting the lens to a temperature decrease from temperature To at least down to a temperature Ti. Said cooling may be performed at a rate of cooling R0 below 10sC / min, preferably between 2 and 7sC / minute. Said cooling may be performed immediately after the step of submitting the lens to a temperature To.

[0032] Thus, in other embodiments the method for annealing a lens made of plastic material, said plastic material having a glass transition temperature Tg, comprises the following steps: submitting the lens at a temperature To for a period of time Po of between 10 to 30 minutes, preferably for 12 to 25 minutes, more preferably of 15 to 20 minutes, wherein To is a temperature higher than a temperature Ti, preferably wherein To is a temperature Tg+5OsC>To>Tg+25sC, more preferably Tg+4OsC>To>Tg+3OsC; and wherein Tg+20sC>Ti>Tg, preferably Tg+10°C>Ti>Tg, more preferably Tg+5°C>Ti>Tg; immediately after the step of submitting the lens to the temperature To for a period of time Po, cooling the lens by submitting the lens to a temperature decrease from temperature To at least down to a temperature Ti;submitting the lens to the temperature Ti for a period of time Pi of between 15 to 90 minutes, preferably 20 to 70 minutes, more preferably 30 to 60 minutes; and immediately after the step of submitting the lens to the temperature Ti for a period of time Pi , cooling the lens by submitting the lens to a temperature decrease from temperature Ti down to a temperature T2STg-35°C, preferably T2STg-50°C, more preferably down to a temperature of 35°C, with a rate of cooling R1 below 1 .5°C / min, preferably comprised between 0.5 and 1 .5°C / min, more preferably between 0.75 and 1 .25°C / min.

[0033] The step of submitting the lens to a temperature To, which is a temperature noticeably above the glass-transition temperature Tgof said plastic material, allows minimizing the stress preexisting in the lens (e.g. which could have built up during casting or molding of the lens).

[0034] In addition, the step of submitting the lens to a temperature Ti, with a plateau just above the glass-transition temperature Tg, ensures that the temperature inside the lens has the time to become homogeneous.

[0035] For the purposes of the present invention when referring to the expression submitting a lens to a temperature T (for example T being To or Ti) for a period of time P (for example Po or Pi), wherein said temperature T is comprised, for example, between a value Taand a value Tb (i.e. Ta<T<T ), it is to be understood that said temperature T may remain constant during said period P or may vary over time during said period P between said values Taand T but not outside said temperature range.

[0036] For submitting the lens to a certain temperature and for cooling the lens at a certain cooling rate an oven may be used. Said oven is preferably able to impose a temperature that does not vary spatially by more than + / -2°C, more preferably + / -0.5°C, in at least a volume larger than the lens (or group of lenses if more than one lenses are annealed together in the same oven). In some embodiments, the oven comprises air circulation. In some embodiments, the oven comprises an active cooling system. For example, Ovens such as Opticom SE-200WS or Thermo-Plus GPS0331 C can be used.

[0037] Moreover, the slow cooling rate R1 of the cooling step allows that the material crosses the glass-transition temperature Tgin a sufficiently slow manner at all the points of the lens and, in this manner, the stress build up upon cooling is avoided.

[0038] The method for annealing herein disclosed allows that, all the parts of the lens cross the glass-transition temperature Tgtogether and at the same rate avoiding, when said annealing method is implemented in a method for manufacturing an ophthalmic lens, unwanted deformation of the ophthalmic lens manufactured.

[0039] In particular, said annealing method allows an efficient release of the residual stress which is present inside the lens (inside the lens which has been generated during casting or injection molding) and / or generated during another annealing process to which the lens has been previously submitted.

[0040] In addition, the novel annealing method disclosed herein surprisingly results in:a better control of the front face curvature of the lens, before the lens finishing steps, in particular even before the surfacing step or the edging step; and minimal deformation of the lens when lens finishing steps, such as surfacing or edging are applied.

[0041] This, advantageously, allows to manufacture ophthalmic lenses which feature significantly reduced or no power transmission error, in particular in terms of the lens diopter, astigmatism and sphere evolution.

[0042] Some embodiments of the method for annealing herein disclosed, the temperature T2 is the room temperature TRT.

[0043] It is to be understood that when a cooling rate defined in the present disclosure, such as R0 or R1 , is lower or higher than XsC / min, it means that, at any point during said cooling, the average cooling rate on a time scale of 2 min, preferably 1 min, more preferably 30 s, even more preferably the instantaneous cooling rate is lower, respectively higher than XsC / min.

[0044] The term room temperature TRT, when used in the claims and / or the specification, refers to the average temperature of the air within the room in which the lens (or lenses) is placed when cooling (when using an oven for controlling the cooling rate, it is the room in which the oven is placed), TRT being comprised between 10sC and 35SC, preferably between 10sC and 30sC, more preferably between 15SC and 30sC, even more preferably between 15SC and 25SC.

[0045] Said method for annealing disclosed herein may be carried out on a lens made of plastic material which has been obtained by casting or injection molding. In some embodiments, the methods herein disclosed are carried out on a lens obtained by casting or injection molding, but prior to said lens being subjected to surfacing or edging or prior to both edging and surfacing or prior to any ophthalmic lens finishing steps, for example prior to being subjected to surfacing.

[0046] In this connection, the method for annealing disclosed herein may be used on lenses directly after they have been produced by cast or injection molding, or several days, or several weeks, or several months, or several years after they have been produced by cast or injection molding.

[0047] In some embodiments the method for annealing disclosed herein may be also used directly on commercially available semi-finished lenses.

[0048] Thus, another aspect of the present disclosure is, as previously described above, a method for manufacturing an ophthalmic lens made of plastic material, said plastic material having a glass transition temperature Tg, wherein said method comprises the following steps: conducting the method for annealing according to the present disclosure on a lens (such as a semi-finished lens); and conducting one or more ophthalmic lens finishing steps, for example edging or surfacing, or both.

[0049] In other words, said method for manufacturing an ophthalmic lens made of plastic material, said plastic material having a glass transition temperature Tg, comprises the following steps: submitting a lens to a temperature Ti for a period of time Pi of between 15 to 90 minutes, preferably 20 to 70 minutes, more preferably 30 to 60 minutes, wherein Tg+20sC>Ti>Tg, preferably Tg+10°C>Ti>Tg, more preferably Tg+5°C>Ti>Tg; immediately after the step of submitting the lens to a temperature Ti for a period of time Pi, cooling the lens by submitting the lens to a temperature decrease from a temperature Ti down to a temperature T2 < Tg-35°C, preferably T2 < Tg-50°C, more preferably down to a temperature of 35°C, with a rate of cooling R1 below 1 ,5°C / min, preferably comprised between 0.5 and 1 .5°C / min, more preferably between 0.75 and 1 .25°C / min; and conducting one or more ophthalmic lens finishing steps, for example edging or surfacing, or both, on the lens.

[0050] In addition, other preferred aspects of this disclosure refer to a method for manufacturing an ophthalmic lens made of plastic material, said plastic material having a glass transition temperature Tg, wherein said method comprises the following steps: obtaining a lens by cast or injection molding of a plastic material; submitting the lens to a temperature To for a period of time Po of between 10 to 30 minutes, preferably 12 to 25 minutes, more preferably 15 to 20 minutes, wherein To is a temperature higher than a temperature Ti, preferably wherein T is a temperature Tg+5OsC>To>Tg+25sC, more preferably Tg+4OsC>To>Tg+3OsC, and wherein Tg+20sC>Ti>Tg, preferably Tg+ 10°C>Ti >Tg, more preferably Tg+5°C>Ti>Tg; submitting the lens to a temperature Ti for a period of time Pi of between 15 to 90 minutes, preferably 20 to 70 minutes, more preferably 30 to 60 minutes; and immediately after the step of submitting the lens to a temperature Ti a period of time Pi , cooling the lens by submitting the lens to a temperature decrease from a temperature Ti down to a temperature T2STg-35°C, preferably T2STg-50°C, more preferably down to a temperature of 35°C, with a rate of cooling R1 below 1 .5°C / min, preferably comprised between 0.5 and 1 .5°C / min, more preferably between 0.75 and 1 .25°C / min; and conducting one or more ophthalmic lens finishing steps, for example edging or surfacing, or both.

[0051] In other embodiments the method for manufacturing an ophthalmic lens made of plastic material, said plastic material having a glass transition temperature Tg, comprises the following steps: obtaining a lens by cast or injection molding of a plastic material; submitting the lens to a temperature To for a period of time Po of between 10 to 30 minutes, preferably 12 to 25 minutes, more preferably 15 to 20 minutes, wherein To is a temperature higher than a temperature Ti, preferably wherein T is a temperature Tg+5OsC>To>Tg+25sC,more preferably Tg+4OsC>To>Tg+3OsC; and wherein Tg+20sC>Ti>Tg, preferably Tg+ 10°C>Ti >Tg, more preferably Tg+5°C>Ti>Tg; immediately after the step of submitting the lens to the temperature To for a period of time Po, cooling the lens by submitting the lens to a temperature decrease from temperature To at least down to a temperature Ti; submitting the lens to a temperature Ti for a period of time Pi of between 15 to 90 minutes, preferably 20 to 70 minutes, more preferably 30 to 60 minutes; and immediately after the step of submitting the lens to a temperature Ti a period of time Pi , cooling the lens by submitting the lens to a temperature decrease from a temperature Ti down to a temperature T2STg-35°C, preferably T2STg-50°C, more preferably down to a temperature of 35°C, with a rate of cooling R1 below 1 .5°C / min, preferably comprised between 0.5 and 1 .5°C / min, more preferably between 0.75 and 1 .25°C / min; and conducting one or more ophthalmic lens finishing steps, for example edging or surfacing, or both.

[0052] The terms “lens finishing”, “lens finishing step”, “ophthalmic lens finishing step”, “finishing steps” or any variation of these terms, when in the claims and / or the specification refer to one or more processing steps being applied to the lens to provide said lens with the desired optical features, such as the ophthalmic prescription and final transmission power (diopter, astigmatism, sphere evolution, etc.) or other features (anti-scrach, anti-dust treatment, etc.), and to edging, i.e. conforming or cutting the lens to fit a frame.

[0053] According to the present disclosure, the expression “diopter”, when not referring to the unit, refers to the average curvature on the two main axis of the lens (forming a 90° angle between the two axis).

[0054] According to the present disclosure, the expression “astigmatism”, when used in the claims and / or the specification, refers to the difference between the two main curvatures of the lens (curvature on a first main axis and on a second main axis forming a 90° angle).

[0055] According to the present disclosure, the expression “sphere evolution”, when used in the claims and / or the specification, refers to the difference between the average curvature in the center of the lens and 15 mm away from the center.

[0056] According to the present disclosure, the expression “transmission power” or “power in transmission”, when used in the claims and / or the specification, refers to the magnification which takes into account the curvature of both surfaces of the lens as well as the thickness and index of the lens (in diopters).

[0057] The plastic material of the lens may be any of those adequate for use in ophthalmic lenses. For instance, the plastic material of the lens may be polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene, polystyrene maleic anhydride, polyamide, thermoplastic urethane, thermoset polyurethane, polyester, copolyesters, polysulfone, cyclic olefin copolymers (OCO), polyphenyl oxide,allyl diglycol carbonate, polythiourethane, episulfide polymers, epoxy, poly(meth)acrylates, polythiomethacrylates, or combinations thereof.

[0058] In some embodiments the lens is obtained by cast or injection molding.

[0059] Examples of preferred lens plastic materials are, among others, plastic materials obtained by casting and curing a polymerizable composition comprising polythiol(s) and polyiso(thio)cyanate(s) in a mold. In some embodiments the lens is a urethane-based lens. In some embodiments the lens comprises a mid or a high refractive index, for instance a refractive index of between 1 .54 to 1 .74.

[0060] In some embodiments the lens is made by casting and curing a polymerizable composition in a mold, in particular a polymerizable composition comprising a polythiol, such as a dithiol or a trithiol, and a polyisocyanate, for example an aromatic polyisocyanate or a non-aromatic isocyanate, or a polythioisocyanate. Thus, in some embodiments the plastic material of the lens is a polythiouretane. Polythiourethane are cross-linked polymers obtained from monomers comprising a polyisocyanate monomer, for example an aromatic polyisocyanate monomer, and a polythiol monomer. For example said monomers may comprise a diisocyanate and a trithiol. For example, the polythiourethane may be a polythiourethane with a refractive index of greater than 1 .50, in particular of from 1 .55 to 1 .8, more particularly of 1 .6 to 1 .7. In some embodiments the polythiol is 2,3-bis((2-mercaptoethyl)thio)- 1 -propanethiol, In some embodiments the polymerizable composition comprises 2,3-bis((2- mercaptoethyl)thio)-1 -propanethiol and m-xylylene diisocyanate.

[0061] In particular, the present invention may be implemented with a lens plastic material which has a high softening temperature or high glass transition temperature Tg. In some preferred implementations of the invention, this softening temperature and / or glass-transition temperature Tgof the lens plastic material may be equal or higher than 70sC, preferably higher than 75SC, more preferably higher than 80sC. In some preferred implementations the softening temperature and / or glass-transition temperature Tgof the lens plastic material is between 70sC and 140sC, preferably between 75SC and 140sC, more preferably between 80sC and 140sC. In other preferred embodiments the softening temperature and / or glass-transition temperature Tgof the lens plastic material is between 70sC and 120sC, preferably between 75SC and 120sC, more preferably between 80sC and 120sC.

[0062] Examples of commercially available materials used for making lenses which may be used in the method of annealing herein disclosed are, among others, PC (polycarbonate) such as CR39® [diethylene glycol bis(allyl carbonate)], episulfide substrate of index 1 .74, MR7™, MR8™,

[0063] The refractive index is the main factor behind the reduction of thickness of a lens. For a given lens power, the higher the refractive index, the thinner the lens. More precisely, the higher the refractive index, the greater the capacity of the material to deflect light rays, the flatter the curvatures required on the front and back surfaces of the lens to produce a given optical power and, as a result, the thinner the lens.

[0064] In some embodiments of the method for manufacturing an ophthalmic lens disclosed herein, the resulting ophthalmic lens is obtained from a semi-finished lens with two surfaces (front and back)which are opposed to one another by surfacing at least one of these surfaces. During the surfacing step, a lens thickness is reduced by removing material from at least one surface of the lens.

[0065] For example, one of these surfaces, a so-called front optical surface, is created directly with a final shape during manufacturing of the semi-finished lens. Thus, this surface initially has curvature values that are compatible with final optical features of the ophthalmic lens to be produced from the semi-finished lens. For example, the front optical surface may be a front convex surface in the final ophthalmic lens, and the front convex surface can be determined by the shape of the mold used for obtaining by casting or injection molding the semi-finished lens. It may be a complex surface, with mean sphere and cylinder values varying from one point to another within the front convex surface. The other surface of the semi-finished lens, or back optical surface, is temporary and intended to be surfaced later according to an ophthalmic prescription of a lens wearer. A back optical surface of the manufactured ophthalmic lens is created by a surfacing step of the temporary back surface of the semi-finished lens, which may include traditional machining and / or digital surfacing. In the resulting ophthalmic lens, the front optical surface and the back optical surface cooperate to produce the desired optical features of the lens. Digital surfacing includes the use of subject specific models allowing the back optical surface of the semi-finished lens to be machined to the specific optical demands of the subject. To this end, during the surfacing step, a lens thickness is reduced by removing material from the semi-finished lens, starting from the temporary back surface and continuing until the final back optical surface is created. Such a back optical surface reflects personal measurements and physiological data and may be prepared for a wide array of frames.

[0066] Accordingly, in some embodiments the one or more ophthalmic lens finishing steps comprise conducting surfacing.

[0067] Surfacing refers to a finishing step in which at least one face of the lens (previously mass produced), for example the rear or back face of a lens, is machined, for example in order to give the lens the required power / optical correction. Surfacing may comprise the steps of blocking of the lens, trimming, grinding, fining by generation and polishing. Traditional surfacing requires a large range of tools and only allows the generation of rear surfaces with simple geometry, either spherical or toroidal.

[0068] Digital - or direct - surfacing is generally used to produce complex rear surfaces but can also be used for any simple surface geometry. During digital surfacing the rear surface of the lens is machined using a “point by point” process and a numerically controlled machine managing the relative positions of the lens and the tool in three dimensions and with extreme precision.

[0069] The blocking process aims at blocking the lens before a machining step. It may comprise positioning and fixing a block on a surface of the lens (which is not the surface of the lens which will be cut or surfaced). Fixing the block is achieved either using an alloy, or a polymeric glue (alloy replacement technology blocking). Once the lens is “blocked” the subsequent steps of the surfacing are carried out: trimming, grinding, fining by generation and polishing.

[0070] The term “trimming” refers, according to the present disclosure, to a process in which the lens diameter is reduced by milling.

[0071] The term “grinding” refers to spiral milling of the rear face of the lens with a diamond-tipped tool to provide the lens with the appropriate thickness and curvature radii. At the end of this operation, the lens is almost in its final shape, but the surface is still very rough and only translucent.

[0072] The term “fining by generation” or “fining” refers to refining the grain of the lens surface without modifying the curvature radii. After fining, the lens has the exact thickness and the desired curvature radii; and although it is smooth, its surface is still unpolished at this stage.

[0073] The term “polishing” refers to subjecting the back surface of the lens to friction against a shaping tool, which is a duplicate of the back surface of the lens, covered with felt and sprayed with a polishing liquid containing a very fine abrasive. This operation gives the lens its final transparency.

[0074] In some embodiments, the one or more finishing steps comprise a surfacing step. In particular, in some embodiments, the method for manufacturing an ophthalmic lens disclosed herein further comprises, subsequently to cooling the lens down to a temperature T2 disclosed herein, for example subsequently to cooling the lens to TRT, surfacing a face of the lens to a required geometry, depending on the prescription for the final client.

[0075] In some embodiments, the surfacing step comprises using an alloy blocking process or an alloy replacement technology blocking (ART blocking).

[0076] Alloy blocking process comprises the use of a metal alloy. However, the use of alloy comes with several drawbacks. In particular, the alloys used often comprise non-environmentally friendly and health-hazardous heavy metals, such as cadmium and lead, which provide an alloy melting temperature of about 47SC. Other alloys comprising, for example, indium may be used, but are more expensive and feature higher meting temperatures, which require heating up to higher temperatures and are, accordingly, less cost effective.

[0077] Alloy replacement technology for blocking (ART blocking) has been developed to avoid the alloy blocking drawbacks and refers to the use of a plastic block in which a polymeric glue is used to fix the front surface (finished surface) of the lens while surfacing. However, ART blocks are less rigid than alloy blocks and allow or result in a higher deformation of the front surface of the lens during surfacing making it harder to reach the target prescription. Indeed, the residual stress results in lens deformation during the grinding and fine turning steps, consequently generating optical deviations in transmission, since the back surface is surfaced to a specific transmission target without taking into account that front surface deformation has previously occurred during the grinding and fine turning steps.

[0078] In that connection, the method for annealing and the method for manufacturing disclosed herein, comprising a step of submitting the lens to a temperature T1, with a plateau just above the glass-transition temperature Tg, during the time Pi specified in the method for annealing herein disclosed, and comprising a slow cooling rate R1 , allows minimizing the lens deformation during surfacing, whatever the blocking technology is used, alloy or ART blocking. The method for annealing herein disclosed it thus particularly useful since it allows a more efficient replacement of the alloyblocking with the ART blocking, which is safer and more environmentally friendly, while minimizing the drawbacks of using the ART blocking.

[0079] Thus, in some embodiments, the method for manufacturing disclosed herein further comprises a lens finishing step comprising surfacing one surface of the lens using an alloy replacement technology for blocking the lens.

[0080] In some embodiments, in addition to surfacing, the one or more ophthalmic lens finishing steps comprise steps of anti-scratch treatment, anti-reflective treatment, anti-smudge treatment and anti-dust treatment.

[0081] In particular, in some embodiments the methods herein disclosed comprise, in addition to surfacing, a step of applying one or more functional films or coatings on one or more surfaces of the lens prior or after surfacing. Said functional film or functional coating may be an anti-scratch film or coating, anti-reflective film or coating, anti-smudge film or coating or anti-dust film or coating.

[0082] Accordingly, the method for annealing disclosed herein may be integrated in an end to end (E2E) process for manufacturing an ophthalmic lens, wherein said end to end process comprises the steps of producing the ophthalmic lens made of plastic material, starting from casting or injection molding of said plastic material and ending with a resulting ophthalmic lens with the desired optical properties.

[0083] Turning now to the Figures and, in particular, FIG. 1 an illustration of a temperature vs. time profile of an annealing process carried out according to the prior art with semi-finished ophthalmic lenses made of MR7™ and MR8™ from Mitsui Chemicals, Inc prior to conducting the lens finishing steps. According to this conventional annealing, the temperature is maintained at a temperature To of respectively 120sC and 140sC for the MR7™ (Tg= 85SC) and MR8™ (Tg= 1 15SC) ophthalmic lenses, during about 15-20 minutes and, subsequently the lenses are cooled by submitting the lenses to a temperature decrease from To down to 60sC at a rate of cooling R0 of, respectively, about 4 to 5.5sC / minute. Table 1 below summarizes the optics of the lenses prior and after conducting surfacing using ART blocking technology and aiming at a diopter tolerance target of ±0.09 which is translated into yellow (0.00 to -0.05) and light to deep green colors (-0.05 to -0.09) in the images, whereas orange to red colors illustrate an obtained diopter error higher than +0.09 and blue-violet colors an obtained diopter error lower than -0.09.

[0084] Using this conventional annealing, the lenses still show residual stress after cooling, as seen with a polariscope or with a StrainScope polarimeter in Fig. 1 B(i). Even if the lens shows an appropriate front curve after cooling, as seen by the green colors appearing on the DLM images in Fig. 1 B(ii), the residual stress has an impact during surfacing (using ART blocking technology) and results in front curve deformation as seen by the orange colors appearing on the DLM images in Fig. 1 B(iii) and in the lens front curve profile after surfacing in Fig. 1 B(iv). In addition, this residual stress is also translated into lens transmission error after surfacing, as seen by the yellow / orange / red colors appearing forming gradient at well-defined concentric zones of the lens after surfacing on the DLM images in Fig. 1 B(v).

[0085] In that connection, Fig. 2 illustrates how the method for annealing according to the present disclosure allows an efficient release of the residual stress which is present inside the lens (inside the lens which has been generated during casting or injection molding) and / or generated during another annealing process to which the lens has been previously submitted.

[0086] In particular, Fig. 2A and 2B provide an illustration of a temperature vs. time profile of an exemplary embodiment of the method of annealing according to the present disclosure carried out, respectively, on semi-finished lenses made of MR7™ (Fig. 2A) and MR8™ (Fig. 2B) from Mitsui Chemicals, Inc, prior to conducting the lens finishing steps. According to this exemplary method for annealing according to the present disclosure, the temperature is maintained at a temperature To of respectively 120sC and 140sC for the MR7™ (Tg= 85SC) and MR8™ (Tg= 1 15SC) semi-finished ophthalmic lenses, during about 15 minutes and, subsequently, the lenses are cooled by submitting the lenses to a temperature decrease from To down to a temperature Ti of respectively 87SC and 1 17SC, at a rate of cooling R0 of between 4.5 to 6.5sC / minute. Said temperature Ti is maintained for 30 to 60 minutes and, immediately after, the lens is cooled by submitting the lenses to a temperature decrease from Ti down to 25SC at a rate of cooling (R1 ) of between 1 and 1 ,5sC / minute.

[0087] Using this exemplary method for annealing according to the present disclosure, the residual stress is significantly reduced and minimizes significantly lens deformation (even prior to conducting any lens finishing steps) and lens transmission error after surfacing, even when using ART blocking as it is illustrated in Fig. 2C.

[0088] Indeed, the impact of the residual stress is highly reduced as seen by the lens front curve after surfacing, shown in Fig. 2C(iii), which features a low deformation impact as seen by the green and light-yellow colors present on the DLM image (instead of the dark orange colors shown in Fig.1 B(iii) when a conventional annealing according to the prior art was carried out). It is to be pointed out that a reduced deformation of the front surface of the lens obtained with the annealing method herein disclosed is obtained even before any surfacing step as is apparent from the comparison between figures 1 B(ii) and 2C(ii). Indeed, when using a conventional annealing, the lenses (MR7™ and MR8™) show after surfacing, in figure 1 B(iii), orange and red colors which represent higher values than the diopter tolerance target of 0.09. On the other hand, when using the annealing method of the invention, the lenses (MR7™ and MR8™) show after surfacing, in figure 2C(iii), yellow and light green colors within the diopter tolerance target. In addition, as shown in Fig. 2C(v), the resulting lenses (MR7™ and MR8™) feature, after surfacing, a very small transmission power error, as illustrated by the overall green colors shown on the DLM image, in opposition to the gradient appearing in the form of well-defined concentric zones when conventional annealing is used, as seen in Fig. 1 B(v). Furthermore, the optics of the resulting lens are significantly improved (diopter, astigmatism and sphere evolution) as seen in table 1 below:

[0089] Table 1 (N= number of lenses tested, Dpt.= diopter, Tol.= tolerance, Astig.= astigmatism, Sph. Evo.= sphere evolution, Avg.= average, StDev= standard deviation, Ppk and Pp= process performance indexes, respectively with or without accounting for the StDev) Dpt. Tol. ±0.09, Astig. Tol. 0.06 and Sph evolution Tol. ±0.06; Criteria: Ppk> 1 .33

[0090] According to the present disclosure, the expression “immediately after”, when used in the claims and / or the specification and when referred to one step B being carried out “immediately after” another step A, denotes that said step B is carried out subsequently to the step A, and that no other step may be carried out in between said steps A and B. In an analogous manner, the expression “immediately prior”, when referred to one step A being carried out “immediately prior” another step B, denotes that said step A precedes step B and that no other step may be carried out in between said steps A and B.

[0091] The terms “minimizing” or “reducing” or “preventing” or “avoiding” or any variation of these terms, when used in the claims and / or the specification, includes any measurable decrease or complete inhibition to achieve a desired result.

[0092] The terms “effective” or “efficient” as those terms are used in the specification and / or claims, means adequate to accomplish a desired, expected, or intended result.

[0093] The terms “a” or “an”, as used herein, are defined as one or more than one. The term “plurality”, as used herein, is defined as two or more than two. The term “another”, as used herein, is defined as at least a second or more. The terms “including” and / or “having”, as used herein, are defined as comprising (i.e., open language). Reference throughout this document to "one embodiment", “certain embodiments”, "an embodiment", “an implementation”, “an example” or similar terms means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of such phrases or in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments without limitation.

[0094] The terms “about” and “approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1 %, and most preferably, within 0.5% of the value to which the term “about” or “approximately” are referred.

[0095] In addition, the present invention also relates to the following embodiments:

[0096] Embodiment 1 : A method for annealing a lens made of plastic material, said plastic material having a glass transition temperature Tg, wherein said method comprises the following steps: submitting the lens to a temperature Ti for a period of time Pi of between 15 to 90 minutes, preferably 20 to 70 minutes, more preferably 30 to 60 minutes, wherein Tg+20sC>Ti>Tg, preferably Tg+10°C>Ti>Tg, more preferably Tg+5°C>Ti>Tg; and immediately after the step of submitting the lens for a temperature Ti for a period of time Pi, cooling the lens by submitting the lens to a temperature decrease from a temperature Ti down to a temperature T2 < Tg-35°C, preferably T2 < Tg-50°C, more preferably up to a temperature of 35°C, even more preferably down to room temperature TRT, with a rate of cooling R1 below 1 .5°C / min, preferably comprised between 0.5 and 1 .5°C / min, more preferably between 0.75 and 1 ,25°C / min.

[0097] Embodiment 2: The method according to the embodiment 1 , further comprising, prior to submitting the lens to a temperature Ti for a period of time Pi, a step of submitting the lens to a temperature To for a period of time Po of between 10 to 30 minutes, preferably 12 to 25 minutes, more preferably 15 to 20 minutes, wherein To is a temperature higher than a temperature Ti and preferably wherein To is a temperature Tg+5OsC>To>Tg+25sC, more preferably Tg+4OsC>To>Tg+3OsC.

[0098] Embodiment 3: The method according to any of the embodiments 1 0 2, wherein between the step of submitting the lens to a temperature To for a period of time Po and the step of submitting the lens to a temperature Ti for a period of time Pi , the method comprises a step of cooling the lens by submitting the lens to a temperature decrease from a temperature To down to a temperature Ti at a rate of cooling R0 below 10sC / min, preferably between 2 and 7sC / minute.

[0099] Embodiment 4: The method according to the embodiment 3, wherein the step of cooling the lens by submitting the lens to a temperature decrease from a temperature To down to a temperature Ti is carried out immediately after the step of submitting the lens to a temperature To for a period of time Po and immediately prior to the step of submitting the lens to a temperature Ti for a period of time Pi.

[0100] Embodiment 5: The method according to any of the embodiments 1 to 4, wherein the lens is an ophthalmic lens or a binocular lens.

[0101] Embodiment 6: The method according to any of the embodiments 1 to 5, wherein the lens in an ophthalmic lens.

[0102] Embodiment 7: The method according to any of the embodiments 1 to 6, wherein the lens is a semi-finished lens.

[0103] Embodiment 8: The method according to any of the embodiments 1 to 7, wherein the lens is obtained by casting or injection molding.

[0104] Embodiment 9: The method according to any of the embodiments 1 to 8, wherein lens is made of a plastic material having a glass transition temperature Tgequal or higher than 70sC, preferably higher than 75SC, more preferably higher than 80sC.

[0105] Embodiment 10: The method according to any of the embodiments 1 to 8, wherein lens is made of a plastic material having a glass transition temperature Tgbetween 70sC and 140sC, preferably between 75SC and 140sC, more preferably between 80sC and 140sC.

[0106] Embodiment 11 : The method according to any of the embodiments 1 to 8, wherein lens is made of a plastic material having a glass transition temperature Tgbetween 70sC and 120sC, preferably between 75SC and 120sC, more preferably between 80sC and 120sC.

[0107] Embodiment 12: The method according to any of the embodiments 1 to 8, wherein the lens is made of a plastic material selected from the group consisting of polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene, polystyrene maleic anhydride, polyamide, thermoplastic urethane, thermoset polyurethane, polyester, copolyesters, polysulfone, cyclic olefin copolymers (OCO), polyphenyl oxide, allyl diglycol carbonate, polythiourethane, episulfide polymers, epoxy, poly(meth)acrylates and polythiomethacrylates, or combinations thereof.

[0108] Embodiment 13: The method according to any of the embodiments 1 to 12, wherein the lens made of plastic material is a lens obtained by casting and curing a urethane-based polymerizable composition.

[0109] Embodiment 14: The method according to the embodiment 13, wherein the polymerizable composition comprises a polythiol and a polyisocyanate or a polythioisocyanate.

[0110] Embodiment 15: The method according to the embodiment 14 wherein the polythiol is dithiol or a trithiol.

[0111] Embodiment 16: The method according to the embodiment 14 wherein the polythiol is 2,3- bis((2-mercaptoethyl)thio)-1 -propanethiol.

[0112] Embodiment 17: The method according to any of the embodiments 13 to 16, wherein the polymerizable composition comprises 2, 3-bis((2-mercaptoethyl)thio)-1 -propanethiol and m-xylylene diisocyanate.

[0113] Embodiment 18: A method for manufacturing an ophthalmic lens made of plastic material, said plastic material having a glass transition temperature Tg, wherein said method comprises the following steps: providing a lens; conducting the method for annealing according to any of the embodiments 1 to 17; and conducting one or more lens finishing steps.

[0114] Embodiment 19: The method according to the embodiment 18, wherein providing a lens comprises obtaining said lens by casting or injection molding.

[0115] Embodiment 20: The method according to any of the embodiments 18 or 19, wherein the one or more lens finishing steps comprise surfacing, edging, or surfacing and edging.

[0116] Embodiment 21 , The method according to any of the embodiments 18 to 20, wherein the one of more finishing steps comprises surfacing the lens, wherein surfacing includes the steps of blocking, trimming, grinding, fining by generation and polishing.

[0117] Embodiment 22: The method according to any of the embodiments 18 to 22, wherein the one or more lens finishing steps comprises surfacing one surface of the lens using an alloy replacement technology.

Claims

Claims

1. A method for annealing a lens made of plastic material, said plastic material having a glass transition temperature Tg, wherein said method comprises the following steps: submitting the lens to a temperature Ti for a period of time Pi of between 15 to 90 minutes, wherein Tg+20sC>Ti>Tg; immediately after the step of submitting the lens to a temperature Ti for a period of time Pi, cooling the lens by submitting the lens to a temperature decrease from temperature Ti down to a temperature T2 < Tg-35°C with a rate of cooling R1 below 1 ,5°C / min.

2. A method for manufacturing an ophthalmic lens made of plastic material, said plastic material having a glass transition temperature Tg, wherein said method comprises the following steps: submitting a lens to a temperature Ti for a period of time Pi of between 15 to 90 minutes, wherein Tg+20sC>Ti>Tg; immediately after the step of submitting the lens to a temperature Ti a period of time Pi , cooling the lens by submitting the lens to a temperature decrease from temperature Ti down to a temperature T2 < Tg-35°C with a rate of cooling R1 below 1 ,5°C / min; and conducting one or more lens finishing steps.

3. The method according to any of claims 1 or 2, wherein the lens is made by cast or injection molding.

4. The method according to any of claims 1 to 3, wherein the lens is made by casting and curing a polymerizable composition in a mold.

5. The method according to claim 4, wherein the polymerizable composition comprises a polythiol and a polyisocyanate or a polythioisocyanate.

6. The method according to any of claims 2 to 5, wherein the one or more lens finishing steps comprises edging, or surfacing, or edging and surfacing.

7. The method according to any of claims 2 to 6, wherein the one or more lens finishing steps comprises blocking one surface of the lens using an alloy replacing technology.

8. The method according to any of claims 1 to 7, wherein Tg+5°C > Ti > Tg+2°C.

9. The method according to any of claims 1 to 8, wherein Pi is a period of time of between 30 to 60 minutes.

10. The method according to any of claims 1 or 9, wherein T2 is < Tg-50sC

11. The method according to any of claims 1 to 10, wherein T2 is room temperature TRT.

12. The method according to any of claims 1 to 1 1 , wherein the cooling rate R1 is comprised between 0.5 and 1 .5°C / min.

13. The method according to any of claims 1 to 12, wherein the cooling rate R1 is comprised between 0.75 and 1 .25°C / min.

14. The method according to any of claims 1 to 13 further comprising, prior to the step of submitting the lens to a temperature Ti for a period of time Pi, a step of submitting the lens to a temperature To higher than Ti, for a period of time Po of between 10 to 30 minutes.

15. The method according to claim 14, wherein Tg+5OsC>To>Tg+25sC.

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