Method of manufacturing lens

Abstract

Presented herein is a method for making an optical article comprising providing at least one lens blank and annealing the at least one lens blank in a heating apparatus. The annealing process comprises the following steps: adjusting the first temperature to the second temperature for 1-8 hours; heating the at least one lens blank in a heating device for 1 to 12 hours; and adjusting the second temperature to the first temperature for 1-8 hours.

Description

Technical Field

[0001] The present invention relates to a method of manufacturing a lens, so that during the manufacturing process, the internal stress of the lens is minimized, the birefringence is reduced and the optical stability is maintained. Background Art

[0002] The process of manufacturing an ophthalmic lens typically begins with an unfinished or semi-finished glass or plastic lens blank. As the manufacturing process proceeds, the blank is edged and formed into a lens. The lens may be coated and then cured in an oven at predetermined parameters (such as a predetermined temperature and duration). Typical parameters for manufacturing such lenses may result in compromised optical quality of the lens. For example, the lens may develop optical instabilities and undesirable internal pressures, which may compromise the fidelity of the lens structure. The methods of forming and cooling lens blanks described in the art may result in higher internal stresses in the ophthalmic lens that are likely to compromise its optical quality.

[0003] Therefore, there is a need for an improved lens manufacturing process so that the optimal properties of the lens (including internal pressure, optical quality and other properties) are not compromised.

[0004] Provided herein is a process for forming a semi-finished or finished ophthalmic lens comprising injection molding followed by annealing, using a unique set of parameters to achieve unexpected results for lenses that are substantially free of optical quality defects, free of any internal stress at ambient temperature, and without requiring excessive resources. Preferably, the lens formed by the method of the present invention is a spectacle lens, more preferably a semi-finished lens. However, the method described herein can be used to produce any finished product requiring tight optical tolerances and low stress.

[0005] The improved manufacturing process described herein includes manufacturing lenses with a unique combination of parameter sets to maintain optimal optical and non-optical lens properties, including optical stability and appropriate internal pressure. The improved process described herein is applicable to the manufacture of semi-finished single-light polycarbonate lenses for injection molding. However, this process can also be applied to other types of lens materials using annealing to improve the quality of lenses during the manufacturing process. Further, this method can be applied to any other product that needs to be bonded to the Rx lens blank, such as but not limited to products for sunglasses, virtual reality and augmented reality, or electrochromic lens products and / or any other product for annealing that may improve optical quality. The method described herein allows for an improved downstream manufacturing process, including surface treatment and bonding of the lens that occurs after the lens is injection molded and annealed. Because this method allows for more consistent quality lenses, it also allows, for example, consistent bonding between the Rx blank and the electrochromic unit. The lenses produced by the process described herein have improved optical stability, reduced birefringence, reduced residual stress, reduced warping, and improved other properties. Summary of the invention

[0006] Provided herein is a method for manufacturing an optical product, the method comprising: providing at least one lens blank; providing a heating device, wherein the heating device comprises a cavity defined by an inner surface, wherein the cavity has a first temperature; positioning the at least one lens blank inside the heating device; substantially completely sealing the heating device; annealing the at least one lens blank in the heating device for 3 hours to 28 hours, wherein the annealing comprises: adjusting the first temperature to the second temperature for 1 hour to 8 hours; heating the at least one lens blank in the heating device for 1 hour to 12 hours; adjusting the second temperature to the first temperature for 1 hour to 8 hours; unsealing the heating device; and removing the annealed at least one lens blank from the device.

[0007] The present invention also provides an optical product, wherein the optical product includes: an annealed semi-finished lens, wherein the annealed semi-finished lens is annealed by: a) heating the lens at an increasing temperature from about 30°C to about 140°C for 1 to 8 hours; b) heating the lens at about 140°C for 1 hour to 12 hours; and c) heating the lens at a decreasing temperature from about 140°C to about 30°C for 1 hour to 8 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more complete understanding of the description provided herein and the advantages thereof, reference is now made to the following brief description taken in conjunction with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0009] Figure 1 is a perspective view of a blank that can be used in the methods described herein.

[0010] Figure 2 is a schematic diagram of an exemplary embodiment of an injection molding apparatus.

[0011] Figure 3 is a schematic elevational view of an oven that may be used in the methods described herein.

[0012] Figure 4 Depicted are several images of a lens blank after annealing using the process described herein.

[0013] Figure 5 Optical data from a lens with a base curve of 6 that has been processed using the method described herein is presented. DETAILED DESCRIPTION

[0014] In the following description, the drawings are not necessarily drawn to scale, and certain features may be shown in generalized or schematic form for the purpose of clarity and simplicity or for information purposes. In addition, although the manufacture and use of various embodiments are discussed in detail below, it should be understood that many inventive concepts that can be implemented in a variety of contexts are provided as described herein. The embodiments discussed herein are merely representative and do not limit the scope of the invention. It is also obvious to those skilled in the art that all technical features defined relative to the method can be transposed to the device alone or in combination, and conversely, all technical features relative to the device can be transposed to the method alone or in combination. In order to avoid unnecessary details for practicing the present invention, this specification may omit certain information known to those skilled in the art.

[0015] Optical lenses are typically manufactured from provided optical lens blanks (e.g., semi-finished lens blanks). "Lens blanks" are defined herein as blocks of material, such as transparent plastic or glass, that are to be machined to obtain optical lenses. As used herein, the term "lens" refers to an optical grade product. The term includes plano lenses as well as power lenses. Figure 1 An example of a lens blank 10 made of a synthetic material, such as polycarbonate, is shown. The blank 10 can be obtained by cutting it from a plate (e.g. by punching), or by cutting a rod, as is known in the art. Further, instead of simply being cut from a plate and thus having parallel planar faces as shown, the initial lens blank can be pre-formed to facilitate the forming method described herein. The lens blanks are available in standard diameters (e.g. 76 mm) and a thickness of 9 mm.

[0016] exist Figure 1In the illustrated embodiment, the lens blank 10 has a circular peripheral profile. The semi-finished lens blank 10 generally has two opposite surfaces, at least one of which is unfinished: a first blank surface 22 and a second blank surface 24 opposite to the front surface 22. The lens blank 10 further comprises a peripheral blank surface 26 connecting the first blank surface with the second blank surface. The unfinished surface of the lens blank is machined according to the wearer's prescription to provide the desired surface of the optical lens. According to a further manufacturing process, an optical lens can be obtained by machining both surfaces of the optical lens blank. An optical lens having a finished front surface and a rear surface is generally referred to as an uncut optical lens. The lens blank 10 is edged along a line in accordance with the shape of the spectacle frame of the optical lens to obtain an edged or cut optical lens. Suitable lens types can be selected from ophthalmic lenses, which can be afocal lenses, single vision lenses, semi-finished lenses, sunglass lenses, plano lenses, single-focus lenses, multifocal lenses, bifocal lenses, bifocal straight-top lenses, trifocal lenses, trifocal straight-top lenses, PAL or progressive lenses. The preferred lens type is a semi-finished lens. Optical lenses are made in various focal powers.

[0017] For the process described herein, polycarbonate ophthalmic lenses are injection molded. "Ophthalmic lenses" refers to contact lenses, intraocular lenses, spectacle lenses, etc. The injection molding process is described in U.S. Patent No. 7,922,942, which is incorporated herein by reference. Injection molding enables plastic raw materials to be directly converted into finished lenses. When manufacturing lenses, especially spectacle lenses, the use of plastics, especially thermoplastics, is often desirable due to their light weight and durability. Plastic lenses also provide relatively economical vision correction. Methods for producing plastic lenses of different prescriptions are well known.

[0018] When using injection molding to manufacture lenses, it is conventional to first heat the thermoplastic material so that it melts at a temperature above the glass transition point. While in this form, the lens material is introduced into a mold cavity of suitable size and shape formed in a mold under high pressure. The material is then allowed to cool to solidify, after which the resulting lens is removed from the mold. Typically, the material used is a thermoplastic resin, such as polymethyl methacrylate, polycarbonate, or copolymers of polycarbonate, polynorbornene, polystyrene, cyclic polyolefins and copolymers thereof, etc. "Thermoplastic material" refers to an optical grade, optically transparent thermoplastic material. "Resin" refers to at least one monofunctional monomer, one or more multifunctional monomers, and one or more initiators. Thermoplastics that may be used include, by way of example only, polycarbonates, polycarbonate / copolyester blends, diethylene glycol bis(allyl carbonate), acrylics such as PMMA, cyclic olefin copolymers, amorphous polyamides, polyesters, copolyesters, polyurethanes, polyamides, polyimides, polysulfones, copolymers of polyethylene terephthalate and polycarbonate, polyolefins, homopolymers and copolymers of diethylene glycol bis(allyl carbonate), homopolymers and copolymers of (meth)acrylic monomers, homopolymers and copolymers of thio(meth)acrylic monomers, homopolymers and copolymers of urethanes, homopolymers and copolymers of thiourethanes, homopolymers and copolymers of epoxy resins, and homopolymers and copolymers of episulfide. In a preferred embodiment, the lens material is polycarbonate.

[0019] like Figure 2 , an embodiment of an injection molding machine 100 or "mold assembly" that can be used to manufacture lenses is shown. A "mold assembly" refers to one or more mold halves. A lens mold cavity 110 is provided to shape the optical lens 10. A removable concave insert 102 includes a partial forming surface 112 that shapes the convex surface of the lens. Another removable convex insert 104 is also provided. Receiving rings 116a and 116b surround the inserts and shape the side surfaces of the lens. The receiving rings meet along the parting line 106.

[0020] At the start of the injection molding cycle, the mold is closed and the lens is injection molded within the cavity. The removable female insert 102 has a partially molded surface 112 defined by a peripheral edge 114. A receiving ring surrounds the insert and meets the peripheral edge in an annular contact area 132.

[0021] In one embodiment, injection molding can be performed at a mold temperature between 260°F and 510°F, showing a 3.00 inch size, an injection speed of 0.1 inch / second, a packing pressure of 800 psi, a holding time of 100 seconds, a cooling time of 4 minutes, and a primary clamping force of 150 tons. At the end of the cooling cycle, the mold can be opened to expose the convex surface of the just-molded lens. The lens can be selected from a variety of base curves and a variety of lens types.

[0022] The mold used has the desired curvature of the front surface of the lens. The resin is placed in the mold, and then the lens blank that has been formed by the injection molding process is pressed against and pressed into the mold and allowed to rest on the resin so that the resin is pulled into the entire cavity between the mold surface and the lens surface. Once in this position, the system is then cured until the resin is sufficiently hardened. The lens blank with the resin cured to the surface is then removed, which has an outer surface corresponding to the curvature of the mold. Typically, the front part of the lens produced may have a surface with a known focal power or curvature, where the rear surface is blank or has no ophthalmic quality.

[0023] although Figure 1 A single lens blank is shown to be used in the process described herein, but multiple lens blanks 10 may also be used. The at least one lens blank 10 is placed in an oven for annealing. The annealing process described herein may be used for semi-finished (SF) Rx lenses. Figure 3 In the illustrated embodiment, the oven 18 may be a tunnel oven having a loading area 20 at its entrance end and an unloading area 21 at its exit end. Between these entrance and exit areas is a cavity into which the at least one lens blank 10 is positioned such that the at least one lens blank is positioned in a non-contacting relationship with the inner surface of the cavity. The oven 18 is configured to be completely sealed using a door (not shown) once the lens blank 10 is positioned inside the cavity. In one embodiment, the oven 18 may include additional separate heating zones inside the cavity, wherein the temperature in the various heating zones of the cavity may be appropriately adjusted throughout the process as desired. The temperature may be manually adjusted or may be adjustable via a programmable feature. In another embodiment, a programmable oven may be used instead of a tunnel oven to perform the forming and annealing steps of the process. In one embodiment, the lens blanks 10 may be positioned on a tree (not shown) that is loaded upright in pairs in coating trays that are then positioned in the oven. The lenses are positioned so that they do not come into contact with any part of the oven interior surface or with each other. In a preferred embodiment, the oven 18 is accurate to + / -1°C. Once the oven door is closed, it cannot be opened again until the process is complete. This is necessary to prevent overcompensation of heat losses when the lenses in the oven cavity are exposed to the ambient air temperature.

[0024] In one embodiment, the oven 18 further comprises a conveyor 22 for transferring the molds 11, each of which contains at least one lens blank 10 from its inlet end to its outlet end. Figure 3Schematically indicated by arrow F in . The linear speed of conveyor 22 may be 8 cm / min. During the annealing described herein, conveyor 22 is stationary. In one embodiment, the temperature in the cavity may be adjusted to a value exceeding the glass state or glass transition temperature of the composite material from which blank 10 is made. During the annealing process, the temperature in the cavity may be independently adjusted and monitored.

[0025] The lens blank 10 used herein can have a lens geometry defined by concentric curves (i.e., 6.75 diopters = 86.800 mm concavity and 86.800 mm convexity) so that the thickness of the entire lens is substantially equal. In addition to the annealing process, this geometric profile is beneficial to prevent uneven stress from being formed on the entire lens during the manufacturing process. The concentric curvature of the lens and the annealing of the lens allow for better downstream assembly of the finished ophthalmic lens product, including surface treatment and bonding processes that occur after injection molding and annealing. The key process steps and parameter combinations described herein also enable the bonding process to occur more smoothly, thereby enabling a higher lens yield. The minimized residual stress of the lens produced herein can also have better chemical resistance to any adhesive used during the bonding step of the process. In turn, this allows a wider range of adhesive options to be used in future bonding processes of the lens.

[0026] Compared to existing lens manufacturing processes, the manufacturing process disclosed herein uses different combinations of higher temperatures and temperature durations for each step. The annealing process includes providing at least one lens blank; providing a heating device, wherein the heating device includes a cavity defined by an inner surface, wherein the cavity has a first temperature; positioning the at least one lens blank inside the heating device; substantially completely sealing the heating device; annealing the at least one lens blank in the heating device for 3 hours to 28 hours, or 3 hours to 20 hours, or 3 hours to 16 hours, or 3 hours to 12 hours, or more preferably 3 hours to 8 hours.

[0027] In particular, the annealing step comprises: a) adjusting the first temperature to the second temperature for 1 hour to 8 hours, or 1 hour to 6 hours, or more preferably 1 hour to 4 hours; b) heating the at least one lens blank in a heating device for 1 hour to 12 hours, or 2 hours to 10 hours, or 2 hours to 8 hours, or 2 hours to 6 hours, more preferably 2 hours to 4 hours; and c) adjusting the second temperature to the first temperature for 1 hour to 8 hours, or 2 hours to 6 hours, or more preferably 2 hours to 4 hours; unsealing the heating device; and removing the annealed at least one lens blank from the device.

[0028] More particularly, the step of adjusting the first temperature further comprises adjusting the temperature from about 30° C. to about 140° C. The step of adjusting the second temperature further comprises adjusting the second temperature from about 140° C. to about 30° C. The step of heating the lens blank at about 140° C. comprises heating the lens blank for about 2 hours.

[0029] In particular, the annealing process involves: a) adjusting a first temperature starting at 30° C. to a second temperature of 140° C. for 2 hours; b) heating the at least one lens blank in a heating device at a temperature of 140° C. for 2 hours; and c) adjusting the temperature from 140° C. to 30° C. for 4 hours. The total time of the annealing process is 8 hours in total.

[0030] The step of providing the at least one lens blank further comprises providing at least one polycarbonate lens blank, and the step of providing the at least one lens blank further comprises providing a lens blank, wherein the lens blank has a substantially equal thickness substantially throughout the lens blank.

[0031] For the methods described herein, the optical article is selected from the group consisting of an ophthalmic device, an ophthalmic lens, a finished lens, a semi-finished (SF) lens, and an optical display.

[0032] In one aspect, after the annealing step, the process further comprises at least one of: finishing the lens, applying a hard coating to at least a portion of the at least one lens blank, and edging the optical article. Thus, the methods described herein include optical articles manufactured according to the above process.

[0033] The present invention also includes an optical article, wherein the optical article includes: an annealed semi-finished lens, wherein the annealed semi-finished lens is annealed by: a) heating the lens at an increasing temperature from about 30°C to about 140°C for 1 hour to 8 hours; b) heating the lens at about 140°C for 1 hour to 12 hours; and c) heating the lens at a decreasing temperature from about 140°C to about 30°C for 1 hour to 8 hours. In particular, the lens is annealed by: a) heating the lens at an increasing temperature from about 30°C to about 140°C for 2 hours; b) heating the lens at about 140°C for about 2 hours; and c) heating the lens at a decreasing temperature from about 140°C to about 30°C for 4 hours.

[0034] Table 1 below describes the effect of various annealing temperatures on the optical quality of the lenses produced. As can be seen, even a few degrees can potentially cause the lenses to not be within the optimal optical specifications. This shift may be due to minor disturbances, such as, but not limited to, the oven door being opened during the process.

[0035] Table 1 6B optical evolution annealing

[0036]

[0037]

[0038] In the first column of Table 1, the temperatures at which each lens sample was annealed are listed. Each temperature listed is the peak temperature during a selected stage of the annealing process. The annealing process temperature was in the range of 140°C to 160°C.

[0039] For semi-finished single vision (SFSV) lenses having a 76 mm profile, annealing was accomplished with base curves of 2, 4, 6, and 8. However, as noted in column 2, only those polycarbonate lenses having a base curve of 6 were included in the above test data. In the above experiments, a maximum of 120 lens blanks 10 could be annealed in the oven 18 at a time. However, if a larger oven were to be used, for example, more lenses could be annealed simultaneously. The oven 18 could be appropriately sized based on the target volume of lenses to be annealed. Thus, the step of positioning the at least one lens blank within the heating apparatus includes positioning a plurality of lens blanks within the cavity.

[0040] Column 3 describes the power of the lens before annealing, expressed in diopters. Columns 4 and 5 describe the Far Vision Radius 1 (FVR1) and Far Vision Radius 2 (FVR2). The insert radius is 86.780 mm. Lenses that are as close to this target radius as possible are considered closer to ideal optical quality.

[0041] Column 6 describes the actual reading of distance vision after annealing, expressed in diopters (FV BC). Column 7 shows the deviation of distance vision, expressed in diopters (FV Deviation). Column 8 shows the difference between columns 4 and 5, or the distance cylinder (FVCycl.). As seen in A6 to A8, B6 to B8, and C8, D8, and E8, the deviation from the best optical quality is outside the range considered optically acceptable. While the annealed data in C7 to J7 and F8 to J8 are considered more ideal, or closer to the best optical quality. The annealed data in row J is considered the best because it is closest to the best optical properties and within the target standard deviation of + / - 0.06.

[0042] Figure 4is a series of images of a lens blank 10 after annealing the lens blank 10 at various temperatures ranging from about 140°C to about 160°C. Although the lens blanks 10 annealed at 145°C and 150°C may appear to have less stress indication values ​​(post-annealing) than lenses annealed at other temperatures, Table 1 demonstrates that the optical stability of the lens blanks 10 annealed at these temperatures does not meet standard optimal lens quality standards. For concentrically curved lens blanks, such as the lens blanks used in the annealing experiments described above, the temperature and duration parameters for the annealing step (such as the parameters described in Table 1) allow the lens to tolerate 0.02 diopters of deviation at least 95% of the time without compromising the optical quality of the lens. A "concentrically curved" lens is one in which the convex and concave surfaces are substantially the same and the center and edge thicknesses of the lens are substantially the same. In the first image, labeled "160C," the lens was annealed at a temperature of 160°C. During the heating of the lens, at least a portion of the lens was in contact with the cavity of the lens during the annealing process. Due to this contact relationship, defects are caused in the lens, as shown by the indentations at different points just within the perimeter of the lens. Although the lenses labeled "150C", "145C" and "144C" do not have similar defects as the "160C" lens, these lenses also do not have the best optical measurements compared to the other lenses. The lenses labeled "160C", "150C" and "145C" were annealed at temperatures above the glass transition temperature. These final lens products did not produce the best optical quality lens products. The lenses labeled "140C" and annealed at such temperatures have the best optical properties compared to the other lenses annealed in Table 1.

[0043] Tables 2 and 3 show that the polycarbonate lenses were replicated to tight insert specifications for the annealing process. The radius of the insert was 86.800 mm. All inserts were measured before the annealing process began to ensure a substantially perfect curve result. Products with high tolerance specifications (i.e., + / - 0.09 diopters) were avoided. This was also to trace back any quality issues during the bonding stage of the process and help identify the relevant insert. This table demonstrates how closely the replication was to the standard.

[0044] Table 2

[0045]

[0046]

[0047] Table 3

[0048]

[0049] Figure 5is a graph of the optical stability results of lenses using the proprietary A&R dual lens mapping system. The lenses were molded in ten different batches over a period of 18 months. Each batch produced between 600 and 1,000 lenses. Lens samples were removed from each batch once an hour in an automated process. One lens sample from each cavity was tested every hour. Four hundred (400) data points were collected for the lenses produced. Of these 400 lens data points, only 2.25% of the lenses were found to be outside of + / - 0.02 diopters.

[0050] After annealing, the at least one lens blank 10 is manually released from the oven 18. However, in another embodiment, the lens blank 10 can also be released via an automated programmable mechanism. The released blank 10 constitutes a semi-finished lens. The annealing method described herein can also be used to produce a finished lens.

[0051] After injection molding, annealing and releasing the at least one lens blank 10, the lens may be surface treated and bonded at a later stage. For the produced lens blank 10, once the prescription has been determined for the wearer, the prescriber finishes the rear face of the lens by standard surface treatment steps, which include grinding and polishing the rear face to the desired curvature. No further machining is required on the front face of the lens, as the molding process produces an optical quality lens for this surface. Once the lens is finished to the desired power and optical quality, it can be edged and placed into the frame selected by the user.

[0052] While representative methods and apparatus have been described in detail herein, those skilled in the art will recognize that various substitutions and modifications may be made without departing from the scope described and defined by the appended claims.

Claims

1. A method for manufacturing an optical product, the method comprising: providing at least one lens blank; providing a heating apparatus, wherein the heating apparatus comprises a cavity defined by an inner surface, wherein the cavity has a first temperature; positioning the at least one lens blank within the heating apparatus; substantially completely sealing the heating device; Annealing the at least one lens blank in the heating device for 3 hours to 28 hours, wherein the annealing comprises: Adjusting the first temperature to the second temperature for 1 hour to 8 hours; Heating the at least one lens blank in the heating device for 1 hour to 12 hours; adjusting the second temperature to the first temperature for 1 hour to 8 hours; unsealing the heating device; and The at least one lens blank annealed is removed from the apparatus.

2. The method of claim 1, wherein: The step of providing the at least one lens blank comprises providing at least one polycarbonate lens blank.

3. The method of claim 2, wherein: The step of providing the at least one lens blank further comprises providing a lens blank, wherein the lens blank has a substantially equal thickness over substantially the entire lens blank.

4. The method of claim 1, wherein: The step of adjusting the first temperature further comprises adjusting the temperature from about 30°C to about 140°C.

5. The method of claim 1, wherein: The step of adjusting the second temperature further comprises adjusting the second temperature from about 140°C to about 30°C.

6. The method of claim 1, wherein: The step of heating the lens blank comprises heating the lens blank for about 2 hours.

7. The method of claim 1, wherein: The step of positioning the at least one lens blank within the interior of the heating apparatus comprises positioning a plurality of lens blanks within the cavity.

8. The method of claim 7, wherein: The at least one lens blank is positioned in non-contact relationship with the interior surface of the cavity.

9. The method of claim 8, wherein: The annealing process lasted for 8 hours.

10. The method of claim 1, wherein: The optical article is selected from the group consisting of an ophthalmic device, an ophthalmic lens, a finished lens, a semi-finished (SF) lens, and an optical display.

11. The method of claim 9, wherein: After the annealing step, the process further comprises at least one of finishing the lens, applying a hard coating to at least a portion of the at least one lens blank, and edging the optical article.

12. An optical article manufactured according to the method of claim 1.

13. An optical product, wherein: The optical product comprises: An annealed semi-finished lens, wherein the annealed semi-finished lens is annealed by: a) heating the lens at an increasing temperature from about 30°C to about 140°C for 1 to 8 hours; b) heating the lens at about 140°C for 1 hour to 12 hours; and c) heating the lens at a decreasing temperature from about 140°C to about 30°C for 1 hour to 8 hours.

14. The optical article according to claim 13, wherein: The lens is annealed by: a) heating the lens at an increasing temperature from about 30°C to about 140°C for 2 hours; b) heating the lens at about 140°C for about 2 hours; and c) heating the lens at a decreasing temperature from about 140°C to about 30°C for 4 hours.

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