JP3034950B2 - Method of manufacturing high quality plastic lenses for eyeglasses - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present application is related to applications 07 / 422,399 and 19 filed on Oct. 12, 1989.
It is a continuation-in-part of application 07 / 339,217 filed on April 17, 1989 and application 07 / 190,856 filed on May 6, 1988.

FIELD OF THE INVENTION The present invention relates to a method for quickly and inexpensively producing high quality spectacle lenses made of multifocal and multifocal plastics from preform lenses of a given formulation.

BACKGROUND OF THE INVENTION In the manufacture of lenses, especially spectacle lenses, it is often necessary to use plastics because they are lightweight and durable. Also, a plastic lens is a relatively economical method of correcting vision. Methods for producing plastic lenses of various formulations are already known. Applicant's U.S. Patent No. 4,873,029 and co-pending application No. 190,856 filed May 6, 1988 are hereby incorporated by reference as if fully set forth herein, Discloses a method for producing an optically high quality plastic lens.

However, other previous methods have not been a fast and economical means of producing high quality, reliable multifocal (such as bifocal, trifocal) or multifocal plastic lenses. U.S. Pat. No. 3,248,460 (the "460 patent") discloses a means for casting plastic lenses from thermoset or thermoplastic materials, but in this case, compared to fully formulated lenses. Using plastic semi-finished products with extremely small curvature as a base,
A further layer of material is cast thereon. In the '460 patent, a conventional optical gasket is used to provide a space between the plastic blank and the mold to hold the resin material in the resulting cavity. The additional layer of material changes the curvature of most of the surface of the resulting lens, thereby changing the resulting lens prescription to the required magnification. The material of the '460 patent cures with heat. However, since such a heat curing process requires heating for more than 12 hours, the formation of the lens is a long die-cutting process.

U.S. Pat. No. 3,946,982 also discloses a method of casting the entire surface of a lens with a prescription layer using a conventional optical gasket.

In the conventional industrial lens casting technology, the lens is cast, and the thickness of the finished lens is estimated,
It was necessary to use a "conventional optical gasket" to hold together the components used to create a substantially secure environment for the casting process. In most cases,
Since these conventional optical gaskets can be used only once, they have been discarded after use. Therefore, a significant number of different gaskets must be stored.

Attempts to cast lenses in-house further increased the inventory needed to produce the required conventional optical gaskets and finished lenses of various prescriptions. In one such system, all formulations cannot be prepared without stocking about 737 conventional optical gaskets and constantly replacing them after a single use. About 200 optical center movers (OCMs) must be kept on hand to move and decenter the optical center. Since these OCMs cannot be reused, they always need to be replaced. The need to store and replace a variety of conventional optical gaskets and OCM stocks has a significant impact on lens casting costs. When casting lenses in-house, these components add up to about 32% of the material costs of casting lenses using such systems.

Some have attempted to produce multifocal or multifocal plastic lenses using lamination techniques. In such techniques, the preformed part is bonded to another cured plastic prescription lens. The portion of the preform that defines the multifocal or multifocal portion of the finished lens is bonded to the prescription lens with an adhesive. However, this method is technically cumbersome and uneconomical, as a large number of preformed lenses must be stored, taking into account any possibility of changing the patient's initial correction and multifocal correction in the future. Has been demonstrated. Also, it was difficult to match the wafer with the surface of the preformed lens, so the optical quality of such lenses was questionable.

In the case of in-house lens casting, in which finished prescription lenses are cast, and to some extent, also in the case of industrial lens casting, which mainly forms semi-finished lens blanks, it is necessary to achieve the prism effect in the molding process. This method for producing prisms into plastic lenses has proven to be cumbersome. Creating a “prism” in the lens structure
This is to move the optical center of the lens from the geometric center of the lens to another position that is more desirable. This prism is used as a base-down prism for offsetting a base-up prism manufactured by a multifocal type even in the case of a multifocal lens. In the case of a multifocal lens, it is preferable to shift the optical center of the distance portion of the lens so as to be closer to the multifocal portion of the lens and to shift the optical center from the distance prescription of the lens of the spectacle wearer to the multifocal portion. To facilitate.

When casting the finished lens, the prism is cast into the lens in a manner known in the prior art. However, in the case of semi-finished lenses, creating a prism requires finishing the surface of the lens to produce the desired prismatic effect and produce an accurate optical prescription lens. This method is not suitable for manufacturing a lens quickly and inexpensively from the beginning to completion, since additional equipment and time is required to perform the surface finish.

Considering all aspects of lens manufacturing, from the liquid resin to the finished lens mounted on the frame, the conventional process is extremely complicated, time consuming and too difficult. 12-14 for curing
It took about 30 minutes to finish the hardened lens blank at the agency's laboratory, and about 30 minutes to finish the lens. Therefore, it may take 13 to 15 hours for the entire lens manufacturing process, and it is difficult to quickly prepare a prescription lens as required. This is possible if there is a stock of semi-finished products and the use of surface finishing equipment, but both of these will add significantly to the overall manufacturing costs, which will eventually be passed on to consumers.

Therefore, it is desirable to provide a faster, more economical and simpler method for manufacturing multifocal or multifocal lenses. There is also a need to provide a method for changing the lens structure (multifocal, multifocal, prismatic, etc.) of a fast and inexpensive prescription lens, ie, a preformed prescription plastic lens. Preferably, such methods should produce lenses without the use of conventional optical gaskets.

SUMMARY OF THE INVENTION The present invention provides a multi-focal or multi-focal portion on a preformed plastic optical high quality spectacle lens,
It relates to a quick, simpler and relatively inexpensive method for producing a finished multifocal or multifocal lens. The preformed lens has a predetermined correction value (ie, curvature or prescription) at the optical center. This does not change for finished lenses. By casting optical segments or other multifocal or multifocal portions on a preformed lens, a myriad of lens structures can be completed quickly and inexpensively. Such a method reduces the number of different mold combinations that are typically required to cast multifocal and multifocal lenses. Also,
In some embodiments, the expensive and cumbersome conventional optical gaskets previously used in large quantities for in-house lens casting are also eliminated. In most inventions, lenses made in accordance with this invention need not be surface-finished to provide a suitable prescription lens, and the prism can be surface-finished to the finished lens, with the additional movement of the optical center. Eliminate stages. The method of the present invention allows the production of bifocal, multifocal and multifocal lenses, in particular, from preformed prescription lenses.

The multifocal or multifocal portion can be cast on the preformed lens alone or in combination with an additional thin resin non-prescription layer that acts as a carrier for the resin defining the multifocal or multifocal portion. Can be typed.

The method of the present invention is different from the conventional lens casting method,
Provides lenses relatively quickly and at significantly lower prices. With the method using ultraviolet curing disclosed herein, curing takes only about 5-30 minutes, no surface finish is required,
It only takes about 30 minutes extra to finish. Therefore,
The present invention provides a means to produce optical quality multifocal and multifocal lenses in less than about one hour, from the liquid resin to the finished lens mounted on the frame. The prescription lens can now be delivered on demand, so that the patient does not have to wait a long time. Since the method of the present invention does not require the use of conventional optical gaskets when casting, the preformed lens is finished to the exact frame of the customer, i.e., trimmed and tinted, and then thin. Non-formulated carrier layers and multifocal or multifocal planes can be added.

Various other advantages of the method of the present invention and the lenses made thereby are apparent from the following detailed description of certain embodiments.

BRIEF DESCRIPTION OF THE FIGURES The relative thicknesses of the various components have been greatly exaggerated for illustration purposes.

1 to 5 show the assembly of a mold according to the invention and the cutting of a preformed lens.

FIG. 6 shows a front view of a bifocal lens manufactured according to the present invention.

FIG. 7 shows the front view of the mold and the preformed lens as a dashed line, with the optical center (indicated by "+") of the preformed lens physically moving relative to the mold portion corresponding to the optical segment. And the astigmatism axis (indicated by broken line 31) determined for the particular prescription is also shown.

FIG. 8 shows a side view of a preformed lens and preformed wafer assembly according to the present invention.

FIG. 9 shows a cross section of an assembly for casting a convex surface of a lens according to the present invention.

FIG. 10 is a front view of a preformed lens used in accordance with the present invention, which eventually becomes part of the finished lens, with spacers installed to increase casting thickness.

FIG. 11 shows a cross section of an assembly for recasting a lens surface in accordance with certain methods of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The purpose of this method is to produce a finished lens having a multifocal or multifocal portion, having a mold, optically high quality resin molding material, having a predetermined lens correction value at the optical center Use preformed plastic lenses. The preformed lens contacts the mold and forms a cavity surrounding the resin molding material. Next, the resin is cured and molded with a cavity that conforms to the shape of the multifocal or multifocal portion. The lens correction value at the optical center of the completed lens is substantially the same as the predetermined lens correction value at the optical center of the preformed lens.

In addition to casting only the multifocal or multifocal portions, the methods disclosed herein can cast a thin layer of non-prescription material over some or all of the surface of the preformed lens.
These additional layers act as "carriers" for the multifocal or multifocal surface and do not affect the prescription of the preformed lens at the predetermined distance.

1 to 3 illustrate the shaping of a lens according to the method disclosed herein. The mold 13 and the preformed lens 11 form a cavity 14 containing a part of the optical resin molding material. In FIGS. 1 and 3, the cavity
14 defines a multifocal (bifocal) segment 12. In FIG. 2, the cavity 14 defines the segment 12 and the layer 16 in which the distance prescription of the preformed lens does not change. The segments and / or carrier, when cured, solidify and adhere to the preformed lens to form a finished lens.

The contact between the mold and the preformed lens may be caused by (a) after the resin molding material is placed on the preformed lens, (b) after the resin molding material is placed on the mold, or (c) by the resin molding material. Before it is applied to any of the components (ie, the resin molding compound is irrigated into the cavity formed by the mold and the preformed lens).

The purpose of which the cavity formed by the pre-formed lens and the mold is shaped, i.e. configured, is (1) corresponding to the desired shape of the multifocal or multifocal part of the finished lens
(2) Even when the surface of the preformed lens is cast into the carrier layer, the lens correction at the optical center of the completed lens is substantially the same as the lens correction predetermined at the optical center of the preformed lens ( If possible, they should be the same). This is also the case when moving the optical center of the resulting lens to properly align it with multifocal and multifocal prescription lenses, as described herein. In certain embodiments, at least one surface of the preformed lens or mold is masked before the lens contacts the mold. The cavity can also be shaped to correspond to the shape of the composite prism portion that creates a prism in the resulting lens.

The finished optical lens manufactured according to such a method,
A second portion (ie, a multifocal or multifocal portion) having a first lens correction value at an optical center and distant from the optical center having a second lens correction value is provided.

A method for forming such a multifocal lens in multiple steps is also provided. The preformed lens is first cast as described above, resulting in an intermediate lens having an intermediate lens correction value in the second portion, the size of which is the magnitude of the first lens correction value and the magnitude of the second lens correction value. It is in between. This intermediate lens is then cast as described above, giving the second part a lens curvature corresponding to the second lens correction value (and the carrier, if a carrier is used).

Lenses made in accordance with the present invention also disclose the addition of multifocal optical segments that create beneficial prescription changes in the finished lens. Such a lens provides at least a third lens correction and a fourth lens correction. A third lens correction is provided by a third portion adjacent to the optical segment and is located between the optical center of the preformed lens and the center of the segment. A fourth lens correction is provided by the fourth portion inside the segment and is located between the optical center of the preformed lens and the center of the segment. As will be described in detail later, the magnitude of the third lens correction is between the magnitude of the first lens correction and the magnitude of the fourth lens correction, and the magnitude of the correction of the fourth lens is Between the magnitude of the third lens correction and the magnitude of the second lens correction, a gradual, discontinuous change in the prescription is thus obtained. This phenomenon was mainly observed when adding a flat top optical segment.

Using the method of the present invention, multifocal or multifocal portions can be added to the front lens surface or the rear lens surface, or both.

Preferably, the curvature of the lens is changed on only a small portion of the preformed lens surface to form an "optical segment." Using the method of the present invention, lenses of almost any multifocal or multifocal optical configuration can be formed, including bifocal, trifocal and multifocal lenses and the like. When manufacturing a multifocal or multifocal lens, a second lens correction value different from the distance lens correction value (at the optical center) of the preformed lens, respectively, if the preformed lens is treated according to the present invention. Or a (trifocal) optical segment having a third lens correction value. In such an embodiment, the mold includes the resulting lens,
If a carrier layer is used, it is shaped to be the same as the desired shape of the multifocal or multifocal portion of the layer. Using the method disclosed herein, it is also possible to vary the magnification of the preformed lens portion, create prisms, and produce multifocal or multifocal lenses from the preformed lens.

In the casting and curing process, to hold the mold and the preformed lens together, especially the outer peripheral clamping of the preformed lens and the outermost periphery of the mold, the conventional mold that holds the preformed lens and the mold together Optical gasket, force by weight of preformed lens when placing preformed lens on top of mold,
Alternatively, the suction force of the capillary generated by a very thin resin material film between the mold and the preformed lens may be used, or a combination thereof may be used. However, in the preferred embodiment of the present invention, it is not necessary to use a conventional optical gasket, so that a more versatile and compliant casting is possible, and a conventional optical gasket using the conventional optical gasket is used. These methods are significantly more economical than methods. The ability to cast the lens without using a conventional optical gasket further eliminates the limiting factors that limit the possible lens configuration due to the physical limitations of the conventional optical gasket.

In some of these embodiments, the molding compound is injected into the mold without using a conventional optical gasket, and the preformed lens is placed on top of the resin to allow for some amount of weight due to the weight of the preformed lens. Pressure is applied. This pressure pushes the molding material out of the mold and the thin carrier layer of the molding material causes the surface of the lens to leave the mold. The mold and preformed lens
The resin layers are held together by capillary suction, weight and / or other means. Thus, instead of using conventional optical gaskets, a thin layer of material is cast on the surface of the preformed lens, in addition to the segments or other optical surfaces defined by the mold. When a small amount of resin material is used, it is possible to cast a multifocal or multifocal portion without casting a carrier by using this method. Alternatively, the same effect can be obtained by lowering the mold on a preformed lens containing a molding material.

The method of the present invention, regardless of the method of molding the lens,
Useful for preformed "plastic" optical lenses. As used herein, a "plastic" lens is a lens formed from a high quality optical resin material. Examples of such materials include allyl diglycol carbonate (trademarks “MasterCast 1” and “MasterCast 2” by Vision Sciences of California, and “CR-39” by PPG Industries), triallyl cyanurate and triallyl phosphate. Allyl esters such as triallyl citrate and diallylphenyl phosphonate (allyli
cesters), acrylic ester
s), acrylates, methyl methacrylate, allyl methacrylate, butyl methacrylate, polycarbonates, polyesters such as styrenics, lexane, ethylene glycol maleate, and other liquid monomer / polymer materials having a high refractive index ( Such as, but not limited to, HiRi, a trademark of PPG Industries.

Using the method of the present invention, any surface (front, back, or both) of the preformed lens can be modified and a convex or concave surface can be treated. It is also possible to treat only part of the surface.

For example, as shown in FIG. 1, the curvature of the lens surface 11 can be varied over a small portion by providing an “optical segment” 12 that is substantially smaller than the preformed lens 11. These optical segments are
Often used for bifocal or trifocal vision, it can also be used for other purposes.

In other embodiments, for example, a preformed lens may be converted to a multifocal lens to provide a seamless multifocal, bifocal, or trifocal lens, or to provide a prismatic effect to the finished lens, for example. The entire surface can be modified according to the method of the invention. In these examples, in addition to the segments, as shown in FIG. 2, if necessary, the surface of the preformed lens may be recast to add a non-prescription carrier layer of resin material to provide a prescription or optical center of the finished lens. A desired lens structure can be created without changing the correction. If possible, the additional carrier layer should be very thin (0.025-0.5 mm) to cure quickly and reduce the likelihood of stress and strain in the finished lens.

The optical segment can be placed anywhere on the lens, but in normal applications it should be placed so that the disadvantageous prism effect can be prevented. Optically, the optical segment is located about 1.5 mm left or right, 3-5 mm below the optical center of a regular spectacle lens. In certain applications, such as eyeglasses for technicians looking directly above the wearer's head, the optical segment is approximately
It may be placed optically 1.5 mm left or right, 3-5 mm above. The optical segment may be at other locations as long as the optical center and the segment are correctly aligned.

The method of the present invention is also for correctly orienting the optical center of the lens with respect to the multifocal or multifocal portion. The method of the present invention can also be used to cast a correction base down prism in connection with casting a preformed lens. Suitable lens structures for obtaining the prism will be apparent to the skilled artisan. If prism formation is desired, the casting mold is shaped and positioned relative to the preformed lens to provide the required additional thickness for the finished lens. The mold and the preformed lens may be properly oriented by spacers separated by a desired distance, depending on the thickness required to produce a given prismatic effect. The spacer can be incorporated into a conventional optical gasket, if used, or can be formed on the surface of a mold or preformed lens. Other means of orienting the mold and preformed lens to produce the prism effect will be apparent to the skilled artisan.

The optical center is physically moved through the optical center 25 of the preformed lens 11 so that the desired position is just above the end of the multifocal portion for a multifocal lens, or appropriate for a multifocal lens It can be moved as shown in FIG. 7 by adjusting to a suitable molding position. Because the method of the present invention does not use a conventional optical gasket, the position of the preformed lens relative to the mold can be moved. In the conventional method using a conventional optical gasket, such movement is virtually impossible because the position of the lens cannot be moved corresponding to the mold due to the conventional optical gasket. Also, when changing the position of the preformed lens relative to the size of the mold described above, by increasing the size of the preformed lens, a larger surface of the mold contacts the preformed lens, and thus a larger finished lens. Surface can be created, creating a larger effective lens area.

Depending on the lens construction, adjustments must be made to accommodate the astigmatism of the resulting finished lens prescription. In this case, the preformed lens and the mold must rotate with respect to each other to an extent corresponding to the appropriate astigmatism axis. The preformed lens and mold need to contact each other at an appropriate angle after contact, ie, rotate. Mold preformed lens or conventional optical gasket (if used)
Can be arbitrarily and appropriately displayed on a retractor line or the like to determine the astigmatism axis. Or,
The mold and preformed lens can be assembled within or on an annular retractor that holds the assembly in place along the axis of astigmatism.

In the case of a multifocal lens, it is important that the optical center, multifocal portion and astigmatism axis of the finished lens be properly oriented relative to each other. This is achieved, for example, as shown in FIG. 7, by combining the above methods to produce an effect and align the prism with the astigmatism axis.

Generally, a preformed lens is formed by casting a layer of high quality optical resin material on at least a portion of the surface of the preformed lens. As shown, the profile of the casting is determined by the mold 13. The mold 13 has a cavity 14 formed between the lens 11 and the mold 13.
Are formed to accommodate the necessary changes in the curvature of the lens, including the multifocal or multifocal portion, such as optical segment 12, and the non-prescription carrier layer, if used. In the example shown in FIG. 1, the mold 13 is formed such that the cavity 14 defines the optical segment 12 in the required thickness and shape at the locations required to create a given lens structure. In Figure 2, the cavity
14 defines an optical segment 12 and a non-prescription carrier 16. Similarly, as shown in FIG. 9, the mold 13 can be formed such that the cavity 14 defines a new structure on the back side of the preformed lens and the surface changes to the required lens structure.

The mold may be made from any material that produces an optical quality surface when used for casting, such as crown glass or electroformed nickel. Means for making suitable molds and forming molds for use in accordance with the invention are already known in the prior art.

To cast a new lens surface, the optical resin monomer material is irrigated onto a preformed lens or mold or into a cavity and then cured. In certain embodiments, only a portion of the cavity may be filled with material to form a predetermined new surface. Suitable optical resin materials include, in particular, the materials described above. Certain materials used to "hard coat" lenses, such as those described in U.S. Pat.Nos. 4,758,448 and 4,544,572, incorporated herein by reference, are also used as resin materials. The surface of the finished lens part according to the invention is robust. The hard coat material may be mixed with other resin materials used in practicing the present invention. Further, the completed lens may be a composite material of a plastic material having a high refractive index and a material having a higher scratch resistance. However, the resin material should be selected to be further cured after being cured and adhere to the material of the preformed surface of the lens. Preferably, the resin material forms what appears to be intermolecular bonds with the preformed lens material.

In a preferred embodiment, the same or similar resin material is used when recasting the preformed lens and the lens surface. If you use the same or similar materials,
The different expansion / shrinkage ratios of the preformed lens and the recast material can prevent new surfaces from separating or "cracking" (ie, cracking) from the preformed lens. Applicants also believe that the use of the same or similar materials can form intermolecular bonds between the new resin and the preformed lens surface.

For resin molding materials, thin coloring, anti-reflection coating,
Various additives that modify the resulting lens, such as anti-scratch coatings and UV inhibitors, may be included. The resulting lens is also subjected to treatments frequently performed on plastic lenses according to known methods, such as coloring, UV inhibitors, anti-reflection and scratch-resistant coatings.

In the ultraviolet curing, a colorant that decomposes or evaporates in the heat curing step can be used for the resin molding material. With UV curing, in most cases, the colorant can be added to the resin molding material before it is cured, so that it can be included relatively evenly in the resulting finished lens. In some cases, the colorant is retained by the resin material during the curing process, since considerable heat need not be used in the UV process. This is possible because it is not necessary to use a thermal initiator containing peroxide.

In certain embodiments, the preformed lens is masked with tape or other suitable material, for example, as shown in FIG. Masking can be used on the side of the lens that is cast according to the present invention, thus preventing casting unwanted portions of the lens surface. Alternatively, when the mask is applied to the reflective surface of the lens, the UV radiation can be restricted from reaching the resin material, thus limiting the extent to which the resin cures. The mask can be used on the mold or the preformed lens, both, or each component.

The preformed lens and mold can be separated by a spacer that maintains the required spacing between the lens and the mold, so that a recast surface of the desired thickness can be created. The spacer can be incorporated as part of a conventional optical gasket used to hold the lens and mold together, or can be used independently of a conventional optical gasket. As shown in FIG. 10, a suitable material may be placed between the lens and the mold assembly, for example, a piece of tape. The surface is about 0.4 mm thick when using carpet tape and 0.2-0.3 mm when using scotch tape. The spacer may be composed of the same or similar material as the preformed lens or resin molding material. After curing, these spacers are incorporated into the finished lens. Finally, the spacer may be part of a mold or preformed lens, such as a protrusion that projects on the surface to provide a predetermined spacing. In certain embodiments, no spacer is used and the preformed lens and mold are not separated from each other or separated by a thin carrier layer of resin molding material that is formed by capillary action when the preformed lens and mold come into contact. It may be done. Measurements of such a layer cast in accordance with the present invention resulted in a thickness of 0.025-0.05 mm. In most cases, these methods do not use conventional optical gaskets.

In some embodiments, the resin is not irrigated into the cavity unless the mold and preformed lens are assembled. In such embodiments, care must be taken to prevent air pockets from forming in the cavity as the resin material is injected into the resulting cavity via a conduit in a mold, conventional optical gasket or preformed lens. . Burrs or other artifacts resulting from the presence of such conduits or other structures can be removed when completing the lens of the upright.

After assembling the mold and the preformed lens, the resin material in the resulting cavity must be cured and adhered to the surface of the preformed lens. The resin material can be cured by a method suitable for the molding material of such a material. Most materials can be cured by exposure to heat or ultraviolet light ("UV"). Other curing methods include, but are not limited to, ultrasound, infrared, microwave, and other forms of radiation. A thermal initiator such as diisopropylperoxydicarbonate or a UV initiator such as 2-hydroxy-2-methyl-1-finyl-propan-1-one or 1-hydroxycyclohexylphenyl ketone may be used optically prior to use. Mix with resin material.

A suitable UV light source is Philips TL / 10R / U
There are light sources called VA reflection lamps, HPM high-pressure metal halide lamps, and HPR high-pressure mercury lamps. In a preferred embodiment, a UV light source (300-450 mm) is used in the curing process to fully cure the resin (about 5-30 minutes). In some cases, placing the lens to be cured on a turntable and rotating the lens through the incident radiation stream to cure uniformly maximizes the number of lenses that can be cast within a certain range be able to. Other UV light sources and conditions suitable for exposure will depend on the resin molding material used, but will be apparent to the skilled artisan.

Heat and / or UV may be applied by any means appropriate to the material from which the mold and preformed lens are made. Unlike thermal curing, UV curing requires at least one UV transmitting surface to transmit UV radiation to the resin monomer material. Although the preformed lens has one transmissive surface, molding a mold from a UV transmissive material creates an additional transmissive surface that cures more quickly and uniformly. After the application of heat, UV, or both, the initiator causes the optical resin material to polymerize and adhere to the surface of the preformed lens.

In certain embodiments of the present invention, the reflective surface of the mold surface is used to reflect ultraviolet light back from the curing lens resin material. The mold includes a reflective surface that matches the casting surface of the mold. The exposed surface of the reflecting surface is sufficiently polished so as to reflect the ultraviolet ray from the ultraviolet light source. This surface of the reflective surface may act directly as a casting surface to create an optical quality lens surface, or may be fixed below the transmissive layer, which acts as the actual casting surface of the mold.

Some materials may be cured by applying a combination of heat and UV sequentially or simultaneously. For example, Applicant's Continuation Application No. 190,856, filed May 6, 1988, incorporated herein by reference, discloses resinous materials and means for curing such materials using both heat and UV. ing. Such materials include liquid monomers, thermal initiators, and photosensitive UV initiators. In this step, the lens resin material of the liquid monomer is placed in the preformed lens and mold combination and heat cured in a heated fluidized bath (preferably 150-180 ° F.) for a short period of less than 10 minutes. The heat activates the thermal initiator, causing the mixture of lens materials to gel. This gel freezes the photosensitive initiator in place throughout the lens material. In addition, this gelling state presets an optical framework required for the optical lens so that there is relatively no optical distortion or defect. Once the mixture of lens materials is sufficiently gelled, it is exposed to ultraviolet light to activate the photoinitiator and complete the polymerization or curing process to form a finished lens.

Thus, resin molding materials desirable for use in the curing step using both heat and UV include resin monomers (such as CR-39),
0.5-5.0% by weight of thermal initiator (diisopropyl peroxydica
rbonate, etc.) and 1-8% by volume of a photoinitiator (such as 2-hydroxy-2-methyl-phenyl-propan-1-one, 1-hydroxycyclohexylphenyl ketone, which reacts to ultraviolet light).

Especially in lens manufacturing processes using UV curing, a yellowing agent may remain on the finished lens or be released during aging. This coloring or "yellowing" can be reduced by adding a certain bluing agent to cure the lens material. Such bluing agents include amine hindered amine light stabilizers (HALS); optical brighteners that make yellowing or hindered phenol antioxidants. Another method is to use a photoinitiator which does not belong to the amine group and does not cause yellowing.

Also, accidental post-curing and further yellowing or discoloration can occur if the lens is unnecessarily subjected to a UV curing step or inadvertently exposed to sunlight or artificial light containing wavelengths in the UV spectrum during processing or use. It turns out that may happen. On further exposure to UV light, the UV initiator remaining in the formed plastic lens causes a subsequent curing action. As a result, the lens becomes unduly brittle,
There is a possibility that discoloration may occur in cosmetics, and the lens may be easily damaged, the normal life may be shortened, and the lens may not be commercially available.

The invention described herein coats a UV initiator on the surface of a cured lens and absorbs into the surface, preventing further action of the UV initiator and preventing the transmission of UV waves into the lens. A method of fully or completely preventing may be included. This process is described in more detail in co-pending US patent application Ser. No. 339,217, filed Apr. 17, 1989. This coating can take the form of a reflection-resistant coating, a scratch-resistant coating, any colored coating, a simple wavelength coating that is essentially transparent to prevent transmission of UV wavelengths. These UV inhibitors are known in the prior art and need not be discussed at length here. UV inhibitors allow all UV light and wavelength
It is desirable to eliminate other wavelengths below 0 nm, especially between 300 and 425 nm.

In this process step, usually after the curing step, the cured lens is immersed in a hot bath (a container with hot liquid) containing any of the above coatings, so that the entire surface of the lens is covered with the inhibitor. To the lens surface. The skilled artisan is well aware of this dipping step and the other steps of performing the above coating. The UV inhibitors can be used in solution so that the necessary coatings and inhibitors can be applied to the lens in one step, or can constitute a molding compound with the coatings described above. Some inhibitors may be absorbed into the lens material. Using other known coating methods,
UV inhibitors can be applied.

If further curing is required before treating the lens surface, the lens may be "post-cured". Post-curing can be used in conjunction with any of the above steps, but is not used for bath curing as the mold and other interfering media may affect the ability to achieve maximum hardness. For post-cure after heat / UV cure, it is desirable to separate the lens from the mold and apply UV or heat directly. This post-curing using a UV or heat source further cures the lens material if higher hardness is required. In some cases, post-curing with UV
This is done using a filter mask to allow radiation to strike the thicker surface of the lens.

The provision of an optical segment according to the invention may cause a slight but beneficial displacement of the finished lens near the end of this segment. This phenomenon was mainly seen in connection with the formation of multifocal segments with flat edges. For example, as shown in FIG. 6, if a planar preformed lens is provided with a conventional flat top 28 + 250 bifocal segment, the main prescription for this segment is +250, but the upper end of the segment may be +212. The optical center of the preformed lens is still planar, but the lens portion directly above the segment is, for example, +87. The benefit of this beneficial transition is that when the wearer's eye moves from the main prescription to the bifocal prescription, the eye can be easily moved from low to high magnification, thus requiring a significant change in the accommodation of the eye. It is thought that it will decrease. In fact, a bifocal lens having such a transition portion can perform at least four types of lens corrections, or prescriptions, at different portions of the lens. As shown in FIG. 6, the lens undergoes a first correction at the optical center 17 and a second lens correction at a second portion 18 at the center of the bifocal segment. The geometric center of the lens is shown at 30. The third lens correction is an imaginary line (dashed line) extending from the geometric center of the segment to the optical center of the lens by a third portion 19 located near the end of the segment, ie, adjacent to the second portion. It is almost done along. The fourth lens correction is made along substantially the same imaginary line by the fourth part 20 located within the segment, ie within the second part. The magnitude of the third lens correction is between the magnitudes of the first and fourth lens corrections, and the magnitude of the fourth lens correction is between the magnitudes of the second and third lens corrections. For example, as described above, the first, second, third, and fourth lens corrections are plane, +250, +87, and +212, respectively. In other multifocal lenses, a lens correction portion can be further provided for each segment.

However, in many cases, such a transition is undesirable and can be prevented or mitigated in several ways. At present, applicants believe that this displacement is caused by uneven curing of the segments and a thin carrier layer cast on the surface of the preformed lens. If the thickness of each portion of the newly provided surface is different, curing will occur at different rates and to different extents when exposed to UV light or other curing methods. As a result, some parts of the lens are more hardened than others, and the shrinkage and stress of the various parts of the lens are not uniform, resulting in displacement. Thus, the transition can be prevented or mitigated by any means that promotes uniform hardening of the newly cast surface.

For example, a preformed lens can be equipped with a mask that selectively transmits various levels of UV light. Thick portions of the casting surface are covered with a mask that transmits more light and thin portions are covered with a mask that transmits significantly less light.
In the example described above for the addition of a +250 bifocal segment, for example, the mask portion covering the thickest top of the segment transmits 100% of the incident UV light, and the mask covering the other portions of the segment gradually increases the entire spectrum. Decrease,
The thinnest portion accepts only 55% of the incident light, and the mask covering the rest of the preformed lens surface transmits 50%.

Another means of curing the segments and thin layers more uniformly involves shutters or apertures that open and close so that the thicker parts of the recast surface are exposed to light longer than the thinner parts, with a UV light source. To use. This can involve exposing the entire surface, gradually closing the aperture and exposing only the thick part of the surface, or exposing only the thick part of the surface and then gradually opening the aperture to expose a wider surface, Finally, it is achieved by exposing the entire surface.

Dislocations can be prevented, reduced or eliminated, especially by changing the casting procedure in several ways. First, casting the carrier layer thicker than 0.8 mm reduces the possibility of distortion. Second, the optical segments can be cast as multiple thin layers. For example, as shown in FIGS.
And the segment 21 can be cast at half the final required magnification. Next, as shown in FIG. 5, the lens is recast and provided with an additional carrier layer 22 using a mold 23 to the full thickness required for the final segment 12, and the desired optical The finished lens with the target segment is completed. Third, the desired segments can be cast and cured, and the additional layers recast using, for example, a mold of the same shape as in FIG. These layers are, for example, 0.025-0.0
It can be a thin film of 5 mm or a thick layer if spacers are used. When recasting, if a transition, distortion or defect occurs in the first casting, that part is filled. Since the recast layer is a very thin film of a resin material, displacement and other abnormalities are unlikely to occur. About the lens with distortion
It has been found that 90% can be modified by recasting the surface of the lens to provide a layer having a thickness of at least about 0.2 mm. Recasting can be repeated many times until the surface is of the desired quality, and the lens appears to add little thickness with each recast. The resulting surface has no such transitions. Fourth, the transitions can be prevented or reduced by forming optical segments whose ends are thinner than the upper flat segments. For example, a curved top or round segment may be used. Fifth, this effect can be reduced by reducing the incident UV radiation and extending the UV curing time. Finally, prepare a type that adapts to the transition,
Providing an excess of resinous material causes the shrinkage to become non-uniform and in the form of the desired transition, which can be prevented or reduced.

Using the recast method can also correct other drawbacks of the cast or broken cast lens. A defective lens can be recast with a thin, non-prescription film layer using the same shape mold to eliminate the defect, thereby reducing production losses in the manufacturing process. Recasts based on this method can be cured in an appropriate manner in a much shorter time than the first casting, due to the thin layer of film to be cured. In addition, significant savings can be made because less resin material is used and in most cases there is no need to use conventional optical gaskets.

The preformed lens can also be combined with a second preformed lens having a multifocal or multifocal portion according to the present invention. As shown in FIG. 8, the second preformed part
26 has a multifocal portion 27. The second preformed portion 26 and the preformed lens 11 contact to form a cavity 28 corresponding to a thin layer 29 of resin material. When the resin cures, the second preformed part 26 adheres to the preformed lens 11. The second preformed part, the preformed lens and the resin material are the same, but different materials may be used. The selection and use of conventional optical gaskets or molds helps to hold the second preformed part and the preformed lens in a predetermined orientation and to achieve the required thickness of the carrier layer.

Example 1 A mold was formed to define the optical segment to be a bifocal lens. The mold was constructed from crown glass, electroformed nickel, and other materials capable of casting optical quality surfaces.

Next, apply UV to master cast 1 or 2 containing thermal initiator.
Initiator (6.5% by volume of 2-hydroxy-2-methyl-
Phenyl-propan-1-one) was added to prepare the optical resin material. Next, the resin mixture was irrigated into a mold.
The front surface of the preformed lens made from master cast 1 or 2 was entirely taped except where the optical segment 12 was attached. This mask serves to prevent the resin from adhering to undesired locations on the lens surface and to block or direct UV radiation only to the parts to be cured. The mold and the masked preformed lens come in contact,
Form a cavity corresponding to the contour of the optical segment. The preformed lens was placed on the top of the mold filled with the resin material, and a slight pressure due to the weight of the preformed lens was applied to extrude the excess resin material. Because the weight of the preformed lens and the capillary action of the resin material were sufficient to hold the assembly together, there was no need to use a conventional optical gasket.

The resin material was cured using 300-450 nm UV light.
Curing was continued using a Philips TL / 10R / UVA reflector lamp until complete curing for about 10-20 minutes. Next, the mold and the preformed lens were separated, and the finished lens was trimmed and finished and mounted.

Example 2 A lens was made as described in the example, but the resin material was cured using a combination of heat and UV radiation. The preformed lens and mold assembly containing the monomer resin material was placed in a water bath at about 180 ° C. for about 10-15 minutes until the resin material gelled. The assembly was then UV-coated for 10-20 minutes as described in Example 1.
To complete the cure. The finished lens was trimmed, finished and mounted.

Example 3 A lens was made and cured as described in Example 1, but the resin material was composed of the same UV initiator as mastercast 1 or 2 without thermal initiator, and the preformed lens was masked. Did not.

Example 4 A lens was made to be a multifocal optical surface and to produce the appropriate prismatic effect. The lens was made and cured as described in Example 3, but the conventional optical gasket used to hold the preformed lens and mold together required the additional thickness of the resulting lens. In order to obtain the desired prism effect, the preformed lens was formed so that the end of the lens was separated from the mold. Alternatively, an appropriately thick wedge was placed between the end of the preformed lens and the mold and separated as needed.

Example 5 A lens was made as described in Example 3. Three rectangular scotch tapes having a width of about 1 to 2 mm were attached at equal intervals to the outer end of the front surface of the preformed lens. After casting, this tape has a thickness of about 0.2m over the entire surface of the preformed lens.
m Acts as a spacer to form a thin non-formulated carrier layer.

Example 6 A lens was cast with physical movement such that the optical center of the preformed lens was correctly aligned with the optical segment of the finished lens. Types that define optical segments include:
A part of the resin molding material was filled. A preformed lens having a diameter much larger than the diameter of the mold was provided. To cast the finished lens, the optical center of the preformed lens was marked and positioned ("moved") to properly match the position of the mold corresponding to the optical segment. When adjusting the position,
Because the preformed lens had a large diameter, it covered the entire mold, but a portion of the preformed lens protruded from the mold. Next, the preformed lens was pressed lightly to separate excess resin from the resulting cavity. No conventional optical gasket was used, and the preformed lens and mold assembly were held together by capillary action of the resin material. After curing, the casting lens was released from the mold. Next, the preformed lens portion that is out of the mold and not cast with new resin is cut off and further finished, leaving a useful prescription lens surface.

Example 7 A lens was made as described in Example 3 and provided with a flat top 28 + 250 optical segment. The finished lens was observed for any of the beneficial distortions mentioned earlier. The "distorted" lens was then used as a preformed lens and recast in the same manner using the same mold. The resulting lens was observed for virtually no distortion previously observed.

Example 8 A lens was made as described in Example 3, except that the preformed lens was made of a different material than the carrier layer, from a high refractive index plastic (HiRi), and a resin material for casting the optical segments. (Master cast 1 or 2 including CR-39) is more flexible and has a different refractive index. The casting layer adhered to the surface of the preformed lens and resulted in an optical quality product.

Above, certain embodiments of the invention have been described in detail. This description should not be taken as limiting the scope of applicant's invention as defined in the claims.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-39526 (JP, A) JP-A-62-6216 (JP, A) JP-A-58-167125 (JP, A) 13870 (JP, B1)

Claims (13)

(57) [Claims] 1. A method for producing a finished lens having a multifocal or multifocal portion, comprising: providing a mold; providing a high-quality optical resin molding material; Preparing a preformed lens having a predetermined lens correction value at the center, and contacting the preformed lens with a mold to form a cavity surrounding the resin molding material with the molding surface of the preformed lens and the mold; After injecting the resin molding material into the inside, the method includes a step of compressing the resin molding material only by the weight of the preformed lens, and a step of curing the resin molding material with ultraviolet rays. It has a shape corresponding to the shape of the part, and a shape such that the lens correction value at the optical center of the completed lens is the same as the predetermined lens correction value at the optical center of the preformed lens. And which method of producing a finished lens having a multifocal or part of the multi-focal. 2. The preformed lens is a semi-finished product.
the method of. 3. The method of claim 1 wherein the preformed lens has been previously polished to a particular size and shape. 4. The method of claim 3, wherein the mold is pre-polished to a particular size and shape. 5. The method according to claim 1, wherein the resin molding material is photosensitive or colored. 6. The method of claim 1, wherein the mold is coated with a coating material that is transferred to the surface of the finished lens. 7. The method of claim 6, wherein the coating material is selected from the group consisting of a scratch resistant coating material, a reflection resistant coating material, and a hard coat material. 8. The method of claim 1, wherein the preformed lens is tinted. 9. The method of claim 1 wherein the finished lens is colored by treatment with a coloring liquid. 10. The method of claim 9, wherein the finished lens is at least partially masked prior to treatment with the coloring liquid. 11. The method of claim 1, wherein the ultraviolet light is provided by a flashing light source. 12. The method of claim 1, wherein the mold and the finished lens are separated by contacting them with a cold source. 13. A method according to claim 1 for making a lens having the step of providing a mold having a surface that reflects light rays.