MOLD”

FIELD OF THE INVENTION

Embodiments described here concern a method to produce a mold for forming objects, in particular small-sized objects such as contact lenses, and to the corresponding mold, made of monomeric or polymeric material, made by means of this method.

The forming mold of the present invention is particularly suitable to be used for making a contact lens by means of the molding technique.

BACKGROUND OF THE INVENTION

It is well known in the state of the art to make objects of various shapes and sizes by forming them in a mold suitably shaped according to the shape and size of the object to be made.

The step of producing the mold requires an engineering and development step which is usually very expensive and laborious since the study of the shape of the mold has several critical issues, and the more complex the shape of the object to be made, the greater said issues.

Forming molds known in the state of the art are generally used to make a plurality of objects, even very different from each other in materials, shape, sizes, and function. Among these, there are also some types of contact lenses, to which particular reference will be made in the following discussion.

It is also known that contact lenses, depending on the materials of which they are made, are substantially divided into soft and hard lenses. Soft contact lenses are made for example of hydrogel, silicone hydrogel or biocompatible polymers. Hard ones are usually made of gas-permeable thermoplastic materials.

It is also known that contact lenses can be classified according to their geometry, which allows to obtain different functions of the lens. For example, lenses can be spherical, if both their surfaces have a fixed curvature, aspherical or sphero-aspherical, if one or both surfaces have different centers of curvature, or toric, if the two main meridians have different radii of curvature, and suchlike.

It is also known that there are various methods for making contact lenses, depending on their type or the composition of the materials of which they are made. In particular, soft lenses can be made by centrifugation, turning or molding. With each technique lenses with different characteristics are obtained.

As far as the present invention is concerned, the production of soft contact lenses by molding provides to use a mold formed by two parts, called in jargon “male” and “female” which, when joined, define an internal concavity characterized by the shape and sizes that the lens has to have. The liquid material is put in the concavity and is then polymerized, forming a complete lens that can be removed from the mold.

The molding technique has a good reproducibility of the objects and allows to obtain smooth surfaces, even with thin thicknesses, and to make high and medium hydration lenses as well.

The methods for producing the molds can use different techniques, such as for example molding inside a metal forming matrix, having a shape correlated to that of the elements of the mold, additive printing techniques, precision machining, comprising for example turning and/or milling and suchlike.

For example, in particular, the method of molding inside a metal forming matrix provides to produce a first steel mold, worked by means of precision tools, for example by milling, and subsequently smoothed. The steel mold is subsequently used to produce the molds, made of monomeric or polymeric material, with which the contact lenses are made.

Known molds are generally single-use, inexpensive, dimensionally stable and, above all, their production process is repeatable, allowing to obtain a good dimensional accuracy of the molds.

However, known methods do not provide to produce molds which allow to obtain objects, and in particular lenses, having very complex or particular shapes.

EP2116888 shows a method to make a lens having a surface provided with a periodic structure of ridges and protuberances, which provides to work a mold so as to obtain the periodic structure. The mold obtained, however, is made of resin, which makes it not very durable, and does not allow to obtain precise structures.

There is therefore a need to perfect a method to produce forming molds and a corresponding reusable mold, which can overcome at least one of the disadvantages of the state of the art.

One purpose of the present invention is to perfect a method which allows to construct reusable molds by means of which to make objects, in particular contact lenses, having even very complex or particular shapes.

For example, it is a purpose of the present invention to allow to make on the objects, and in particular on lenses, construction or production details having even very small sizes, for example in the range of tens of micrometers.

Another purpose of the present invention is to perfect a very precise and highly repeatable method.

Furthermore, one purpose is to allow to adapt the production of the molds, made of monomeric or polymeric material, quickly and simply, to different shapes and sizes.

One purpose is also to perfect a method to produce reusable molds which is quick and efficient.

The invention also has the purpose of allowing a cleaner working process.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

In accordance with the above purposes, some embodiments described here concern a method to produce a re-usable mold for forming objects, in particular contact lenses, which overcomes the limits of the state of the art and eliminates the defects present therein. In particular, the molds in question are suitable to be re-used even for thousands of molding cycles until their wear causes them to be necessarily replaced.

Some embodiments described here also concern a mold made of monomeric or polymeric material for producing objects, in particular contact lenses, by means of the molding technique. The mold comprises a male element and a female element, cooperating to define a cavity able to house monomeric or polymeric material in the liquid state intended to form the object.

According to some embodiments, the male element and the female element can be made according to different technologies, all of which are known in the state of the art.

According to a first example embodiment, the male element and the female element of the mold can in turn be obtained by molding through the use of a forming matrix made of metal material. According to other versions, by way of a non-limiting example, the male element and the female element of the mold can be obtained by means of 3D printing techniques or by means of precision machining, such as for example turning or milling performed by numerical control processing centers. In these latter cases, these techniques allow to obtain male and female elements of the mold having the required specifications of size and shape, and it is not necessary to preliminarily produce the forming matrix made of metal material as above.

According to the invention, the method provides a laser processing for producing processed elements of the mold, in particular both on the male element and also on the female element, or even only on one of them, necessary to obtain the desired shapes for the object (for example contact lens), which can also be very complex or particular. According to one example embodiment, the processed elements as above are respectively recessed elements, or concave portions, for example holes or cavities, having shape and sizes mating with, or complementary to, relief elements in the form of micro-protuberances to be produced on the surface of the object, in particular of the lens. The processed elements as above can also comprise relief portions.

Laser processing preferably provides to use a femtosecond type laser, which allows to reduce the heating and deformation of the material, thus making the method very precise and highly repeatable. In fact, laser processing allows to execute a multitude of concave portions and/or relief portions uniformly distributed on a surface of the male or female element, in particular on a curved surface, be it convex or concave, or only on a part of such surface, for example a peripheral part. Furthermore, the concave portions or relief portions obtained will have reduced sizes, for example of the order of microns or millimeters. Preferably, the concave portions and/or relief portions are made transversely, more preferably perpendicularly, to the surface of the male element and or the female element. Advantageously, the concave portions and/or the relief portions are punctual, that is, they are not connected to each other. These portions can be cylindrical, truncated cone, ellipsoidal or paraboloid in shape. Their shape can be symmetrical or asymmetrical.

Advantageously, the concave portions and/or relief portions have micrometric sizes.

Laser processing also allows to prevent the production of fine powders, for example the type of fine powders usually generated by processing by means of metal tools.

The powders as above are, in fact, harmful both for human health and also for the plants themselves, in particular for the precision mechanisms, which for example can be damaged in the long run by the deposit of the powders, generally increasing the dispersion of the metrological parameters of the production process.

Advantageously, this processing allows to obtain molds by means of which to produce objects, for example lenses, with complex geometries.

For example, by means of laser processing it is possible to obtain molds that allow to produce particular elements of a few micrometers in size on the lenses.

These molds can also allow to produce any known type of lens whatsoever, for example spherical and/or toric lenses.

Preferentially, the molds are made of plastic material, for example PEEK (polyether-ether-ketone) or RADEL polyphenylsulfone (PPSU). PEEK is preferred, since it is a material that yields excellent results in laser processing, which does not deform and which has a low wear value, allowing the molds to be re-used.

Advantageously, it is therefore possible to quickly and simply adapt the production of the molds of polymeric material to different shapes and sizes, by modifying the settings of the control system of the laser processing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a three-dimensional view of a polymeric mold according to one embodiment described here; - figs. 2 and 3 are lateral plan views of two possible embodiments of a male element of the mold of fig. 1 ;

- fig. 4 is a schematic, perspective and enlarged view of concave portions of a polymeric mold according to fig. 1 ;

- fig. 5 is a schematic, perspective and enlarged view of relief portions and of concave portions of a polymeric mold according to fig. 1 ;

- fig. 6 is a front view of a contact lens obtained by means of polymeric molds according to fig. 1 ;

- fig. 6a is an enlargement of a portion of the contact lens of fig. 6;

- figs. 7a and 7b are a front view of a variant of the mold, fig. 7b being an exploded view.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS We will now refer in detail to the possible embodiments of the invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, one or more characteristics shown or described insomuch as they are part of one embodiment can be varied or adopted on, or in association with, other embodiments to produce further embodiments. It is understood that the present invention shall include all such modifications and variants.

With reference to the attached drawings, a mold 10 is described made of monomeric and/or polymeric material for producing contact lenses 11 by means of the molding technique.

It is understood that the mold 10 is suitable to be also used to form other small objects, other than the lenses 11 as above, such as for example components made of plastic material for hardware, for toys or for electronic components, for example for semiconductor products, making the necessary adjustments which will be clear to the person of skill in the art. The following discussion concerns, by way of a non-limiting example, contact lenses 11, but it is evident that the mold 10 in question is suitable to form many other types of objects 11, for example such as those mentioned above.

According to some embodiments and in a known manner, the mold 10 comprises a male element 12 and a female element 13.

The female element 13 is able to house the monomeric and/or polymeric material in the liquid state and to cooperate with the male element 12 to shape the polymeric material into the desired shape for the lens 11.

The female element 13 can comprise a female body 14 and one or more gripping elements 15. Such one or more gripping elements 15 can be able to allow the mold 10 to be gripped, for example by an operator or an automatic mechanical removal system.

Such one or more gripping elements 15 can also be able, during use, to facilitate the correct insertion of the male element 12, acting as centering elements for the correct positioning of this element. For example, it can allow the correct orientation in the case of bi-toric lenses, in which the two main meridians have different radii of curvature on both surfaces.

The female element 13 can have one or more strengthening parts 16 on the outside, for example a ring or segments of ring concentric with the female body 14, or ribs, or suchlike.

According to some embodiments, the female body 14 has a concavity 19.

The female body 14 can also comprise an external wall 17 and positioning means 18.

The concavity 19 can be able to contain the polymeric material in the liquid state and to form the front surface of the lens 11, defining its front curvature, where the front surface is the surface of the lens 11 which does not rest on the eyeball.

The concavity 19 has a shape correlated to that of the lens, for example having a spherical, aspherical, toric shape and suchlike.

According to some embodiments, the positioning means 18 are able to allow the correct positioning of the male element 12 with respect to the female element 13.

The positioning means 18 can have a shape at least partly mating with the shape of one or more positioning elements 20 present on the male element 12, advantageously producing a same shape coupling between the two male and female elements 12, 13.

The positioning means 18 can for example comprise a rest edge defined by the space between the concavity 19 and the external wall 17. The positioning elements 20 can abut on this rest edge 18.

In alternative embodiments, the positioning means 18 can for example comprise interlocking elements able to close onto the one or more positioning elements 20.

The positioning elements 20 can for example correspond to a raised wall. This raised wall 20 can comprise an abutment edge 30, able to abut on the positioning means 18.

The raised wall 20 can be straight or concave and/or vertical or inclined. The abutment edge 30 can be horizontal or oblique.

As further embodiment examples, not shown in the drawings, the positioning elements 20 can comprise an overhang able to cooperate with the channel defined by the space between the internal wall and the external wall 17 of the female element 13, and a recess between said overhang and a convexity 23, said recess being able to cooperate with the upper edge of the internal wall of the female element 13, abutting against it.

Alternatively, the positioning elements 20 can for example comprise recesses with which the interlocking elements of the one or more positioning elements 18 of the female element 13 can cooperate.

The male element 12 can comprise a male body 21 and one or more grips 22. These one or more grips 22 can be able to allow the male element 12 to be gripped, for example by an operator or an automatic mechanical removal system.

The male body 21 has a convexity 23, able to define the rear surface of the lens 11, defining its rear curvature, where the rear surface is the surface of the lens 11 intended to rest on the eyeball.

As shown in figs. 2 and 3, the maximum diameter DO of the convexity 23 can be variable. For example, the maximum diameter DO of the convexity can vary between 8 and 20 mm, preferably between 8.5 and 15 mm.

The external edge 26 of the convexity 23 can be configured to come into contact on its entire circumference with a corresponding external edge 27 of the concavity 19.

In one variant, the external edge 26 of the convexity 23 can be configured to come into contact on its entire circumference with a circumference having a diameter D1 smaller than the diameter of the external edge 27 of the concavity 19, for example in order to obtain lenses 11 with a diameter smaller than the maximum.

In this way, the convexity 23 and the concavity 19, by cooperating with each other, can define a cutting circumference that defines the edge 34 of the lens.

The concavity 19 and the convexity 23 are therefore able to cooperate in order to define, during use, a central portion comprised inside the circumference with diameter DO, or possibly Dl.

This central portion is able to contain the polymeric material first, and then the molded lens 11.

The convexity 23 can have a spherical, aspherical, toric shape and suchlike, depending on whether the corrective power is defined by the front surface or the rear surface of the lens 11, and depending on the type of defect that the lens 11 is intended to correct.

According to some embodiments, the convexity 23 has processed elements 24, 25 on its surface.

According to one variant not shown in the drawings, processed elements 24, 25 can also be present on the concavity 19 provided in the female element 13.

The processed elements 24, 25 may or may not be homogeneously distributed on the convexity 23 and/or concavity 19.

In an example embodiment, better visible in the enlarged detail of fig. 4, the processed elements as above are concave portions 24, configured for example as blind holes or similar cavities.

In another example embodiment, better visible in the enlarged detail of fig. 5, such processed elements comprise both concave portions 24 and also relief portions 25, configured for example as protuberances or similar surface reliefs.

In one variant, not shown, the processed elements as above can comprise only relief portions 25, such as protuberances or similar surface reliefs.

The concave portions 24 and/or relief portions 25 are able to form on the surface of the object, in particular of the molded lens 11, construction elements 28 mating in shape with the concave portions 24 and/or the relief portions 25.

With reference to figs. 6 and 6a, the concave portions 24, configured for example as holes of micrometric sizes, are able to form micro-protuberances 28 on the lens 11 configured to keep the contact lens slightly raised from the corneal surface.

For example, this raising of the lens with respect to the corneal surface, for the entirety of the lens or at least some of its portions, advantageously allows a better oxygenation of the eye, allowing the formation of micro-channels for circulation of the tear fluid and/or allowing a better movement of the lens on the eye, in particular for lenses 11 with reduced thickness.

According to one embodiment, shown in fig. 1 , the processed elements 24, 25 are distributed on the entire surface of the lens 11.

In one variant, shown in figs. 2 and 3, these processed elements 24, 25 are homogeneously distributed on a peripheral zone 29 of the convexity 23, outside a central smooth zone 35 of the latter. This central smooth zone 35 corresponds to a mating central smooth surface 36 (fig. 6) of the lens 11, intended to substantially occupy the pupillary area on the eyeball.

The central smooth zone 35 can have a diameter approximately comprised between 3 and 8 mm, preferably between 4.5 and 5.5 mm at the point of greatest radial extension.

Advantageously, thanks to the fact that this central smooth zone 35 does not have processed elements 24, 25, it is possible to prevent unwanted optical distortions and aberrations caused by the lens 11.

The processed elements 24, 25 can have lateral sizes comprised between 1 pm and 500pm, preferably between 20pm and 300pm.

The processed elements 24, 25 can have a constant or variable height. Furthermore, processed elements 24, 25 of different heights can be provided in different zones of the mold.

For example, the maximum height H2 of the processed elements can be comprised between 5pm and 25pm, preferably equal to 10pm. These processed elements are particularly suitable to produce contact lenses, since they allow to obtain protuberances of the same height, which substantially corresponds to the thickness of the tear film (usually between 8.5pm and 9.5pm). The distance D2 between the respective center of these processed elements can be comprised between 30pm and 500pm, preferably between 60pm and 140pm, more preferably equal to IOOmih.

The distance D2 between one concave portion 24 and the next can be comprised between one and four times the maximum height H2 of such concave portions 24 configured as holes of micrometric sizes, preferably comprised between one and three times the height H2.

In one embodiment, the concave portions 24 can have, in the part furthest from the surface of the lens 11 , a beveled shape in order to generate corresponding elements with a beveled or rounded shape in the lens.

In one embodiment, the concave portions 24 can have a tapered shape.

The lateral walls of the concave portions 24 are oriented, with respect to the convexity 23, so as to form with the latter an angle comprised between 80° and 100°, preferably between 85° and 95°, even more preferably of substantially 90°.

As another example embodiment, shown in fig. 2, the concave portions 24 can be configured as one or more radial grooves. In one variant, not shown, these concave portions 24 can also be configured as one or more concentric rings with respect to the center of the male body 21.

In another variant, not shown, the convexity 23 can also have only relief portions 25.

Advantageously, these relief portions 25 can have a height equal to the thickness of the lens, allowing to form micro-holes, made through, in the lens 11 which make the front surface and the rear surface of the lens communicating, allowing the exchange of fluids between the two surfaces and/or micro oxygenation.

Advantageously, the number of these processed elements 24, 25 can vary between 300 and 65,000, preferably between 5,000 and 20,000, more preferably between 8,000 and 15,000, thus allowing to produce lenses 11 provided with a corresponding number of construction elements 28, in a number such as to guarantee good oxygenation of the part of the eye under the lens 11.

Preferentially, the concave portions 24 have a cylindrical, truncated cone or paraboloid shape, symmetrical or asymmetrical. In particular, the concave portions 24 preferably have a base and a bottom. The diameter of the base and the bottom can be comprised between 5 and 255pm. The concave portions 24 can have a depth comprised between 5 and 25 pm, depending on the thickness of the object to be produced by means of the mold 10. More advantageously, the bottom of the concave portions 24 has a curvature, preferably a concavity, with a radius of curvature comprised between 30 and 13,000pm. In this way, a micro-pillar is formed with a top having a convex surface particularly suitable to rest on the surface of an eye.

According to some embodiments, the concave portions 24 are present in a density comprised between 6 and 50% of the surface of the affected zone of the object. For example, it can be provided to produce the concave portions 24 only on a peripheral zone of the object, in this case, the density is defined relative to the surface of the same peripheral zone of the object.

Figs. 7a and 7b show a variant of the mold 10, which in addition to the male element 12 and the female element 13 also comprises an annular support element 40. It provides a front edge 40a and a rear edge 40b, preferably parallel to each other.

The support element 40 is preferably made of plastic material, for example polypropylene, however other materials, plastic or otherwise, can be provided, as long as they are more elastically deformable compared to the material of the mold 10. In this way, the support element 40 acts in some way as a packing between the male element 12 and the female element 13, to the advantage of a better coupling between them. Another advantage of such a support element 40 is that it protects the male 12 and female 13 elements over time while the coupling and uncoupling operations are repeated. In fact, during these operations the friction occurs between the support element 40 and the female element 13, made of harder and more resistant material. This causes the support element to wear, rather than the mold 10 itself.

The support element 40 is configured to be inserted around the male body 21, in particular around a rear portion thereof. By rear portion, we mean the portion of the male body 21 in which the convexity, which then confers its shape on the internal surface of the lens 11 to be formed, is not provided.

As mentioned, the support element 40 is annular in shape, and has an internal diameter D3 suitably equal to the external diameter of the rear portion of the male body 21, in order to produce a coupling by interference.

Advantageously, the positioning element 20, in particular if it is conformed as a raised wall, also provides a second abutment edge 31, opposite the abutment edge 30 that interacts with the positioning mean 18 of the female element 13. The second abutment edge advantageously protrudes with respect to the rear portion of the male body 21. In this way, the support element 40 is inserted around the rear portion until its front edge 40a abuts against the second abutment edge 31 (fig. 7a).

The support element 40 is configured to act as a support for the male element 12 inside the female element 13. In particular, the support element 40 is configured to interfere with at least part of the internal wall of the female body 14 and thus stabilize the positioning of the male element 12.

For this purpose, it is preferable to provide that the support element 40 has an external lateral surface 40c with a truncated cone shape, so that its diameter D4 in correspondence with the front edge 40a is smaller than its diameter D5 in correspondence with the rear edge 40b. It should be noted that, in this case, the internal wall of the female body 14 has a rear portion 14a (that is, in correspondence with its aperture, opposite the cavity 19) which is also inclined, so as to couple with the external wall 40c of the support 40 element.

Obviously, it is possible to provide that the diameters D4 and D5 are the same as each other, or that the external wall 40c is cylindrical in shape.

In fig. 7a the support element 40 is shown partly inserted inside the female body 14; however, it is possible to provide that it be totally inserted inside the female body 14. More preferably, the height of the support element 40 is equal to the distance between the second abutment edge 31 and the rear edge of the female body 14, so that once the support element 40 has been inserted inside the female body 14, its rear edge 40b is substantially aligned with a rear edge 14b of the female body 14. It should be noted that this rear edge 14b of the female body 14 is provided with a transverse flange which can act as a gripping element and/or as a strengthening part 16.

In the example shown, the grip 22 is conformed as a handle that extends longitudinally from the male body 21. This allows an easy insertion of the support element 40 around the rear portion of the male body 21. Some embodiments described here also concern a method to produce a re usable mold 10 for forming objects, in particular contact lenses 11.

According to the invention, this method provides to produce processed elements 24, 25 on a surface of a male element 12 and/or of a female element 13 of the mold 10.

The male element 12 and the female element 13 as above cooperate to define a cavity able to house monomeric and/or polymeric material in the liquid state intended to form the object as above.

According to a preferred embodiment, the method provides to produce the processed elements 24, 25 by means of laser processing.

In particular, the laser processing provides to use a femtosecond laser.

The processed elements 24, 25 are mating with, or the same as, construction elements 28 to be produced on the surface of the lens 11.

The processed elements 24, 25 can be configured optionally as holes or cavities or one or more radial or annular grooves, homogeneously distributed or not.

In particular, the method provides that the processed elements 24, 25 can comprise concave portions 24 and/or relief portions 25, able to produce the relief and or concave construction elements 28 on the lens 11.

According to some embodiments, the method provides that the processed elements 24, 25 can be made only on a peripheral zone 29 of a convexity 23 of the male element 12 and/or of a concavity 19 of the female element 13, leaving a central smooth zone 35 without processed elements 24, 25. According to some variants, the processed elements can be located both on the peripheral zone 29 and also on the central zone 35.

According to possible embodiments, the method provides to obtain the male element 12 and the female element 13 by means of molding techniques within a molding matrix made of metal material with a shape and sizes complementary to those of the molds to be obtained.

In this case, it is preferable to perform a laser processing of at least one internal surface of the matrix, in particular one or more surfaces which will give a particular desired conformation to the mold 10, for example with the processed elements 24, 25. Laser processing has the same advantages as those indicated for the male element 12 of the mold 10.

For this purpose, it can be provided to produce a multitude of micro-pillars which will form the concave portions 24 of the male element 12. These micro pillars advantageously have the same shapes and sizes already indicated for the concave portions 24, and are present at the same density.

According to some variants, the method provides to obtain the male element

12 and the female element 13 of the mold 10 made of polymeric material by means of additive molding techniques or by means of precision machining, for example turning, milling or a combination thereof. In any case, regardless of the production technique of the male 12 and female

13 elements, it is provided to carry out the laser processing directly on these elements, in particular at least on the male element 12.

According to some embodiments, the method provides to produce the mold 10 in polymeric material resistant to laser, high temperatures and wear, where by material resistant to laser we mean a material suitable to be processed with laser.

For example, such polymeric material can be PEEK or RADEL polyphenlysulfone. PEEK is particularly preferred, since it is very stiff and hard, and therefore much less subject to wear.

According to some embodiments, the method provides to use adequate times to insert the material, polymeric or monomeric, into the mold 11, suitable to allow the material to fill the concave elements 24 uniformly and completely.

It is clear that modifications and/or additions of parts or steps may be made to the mold 10 of polymeric material for contact lenses 11 and to the method to produce the mold 10 as described heretofore, without departing from the field and scope of the present invention as defined by the claims.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of mold 10 and production method, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

In the following claims, the sole purpose of the references in brackets is to facilitate reading: they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.