METHOD OF PROVIDING REFRACTIVE MICROSTRUCTURES ON A SURFACE OF A SPECTACLE LENS AND SPECTACLE LENS DESIGN

Abstract

A method of providing refractive microstructures on a surface of a spectacle lens body by an additive manufacturing process is provided, in which the refractive microstructures are formed by applying and curing a curable material. The process includes forming a layer of a first liquid or viscous curable material and an additional amount of the first curable material or an amount of a second liquid or viscous curable material at locations at which the refractive microstructures shall be formed before curing or pinning the at least one first curable material. Protrusions formed by the additional first curable material or the second curable material are levelled out by material transport processes within the liquid or viscous material in the layer of the at least one curable material. In addition, a spectacle lens with refractive microstructures is provided.

Claims

1. A method of providing refractive microstructures on a surface of a spectacle lens body in which the refractive microstructures are formed on the surface by an additive manufacturing process, in which the refractive microstructures are formed by applying at least one curable material and curing the at least one curable material, wherein the additive manufacturing process comprises: forming a layer of the at least one first liquid or a viscous curable material where for forming the refractive microstructures an additional amount of the at least one first curable material or an amount of at least one second liquid or the viscous curable material is applied at locations at which the refractive microstructures shall be formed before curing or pinning the at least one first curable material; and curing or pinning the layer of the at least one first curable material with the additional amount of the at least one first curable material or with the amount of the at least one second curable material before protrusions formed by the additional amount of the at least one first curable material or the amount of the at least one second curable material are levelled out by material transport processes within the liquid or viscous material in the layer of the at least one curable material.

2. The method as claimed in claim 1, wherein the amount of the at least one first curable material that is applied to the locations of the surface of the spectacle lens body where the refractive microstructures shall be formed is less than the amount of the at least one first curable material that is applied to other locations, and the amount of the at least one second curable material is applied to the locations where the refractive microstructures shall be formed.

3. The method as claimed in claim 1, wherein the layer of the at least one first curable material with the additional amount of the at least one first curable material or with the amount of the at least one second curable material is formed by applying, in a first step of the additive manufacturing process, a continuous base layer to the surface of the spectacle lens body by use of the at least one first curable material and then adding, in a second step of the additive manufacturing process, the additional amount of the at least one first curable material or the amount of the at least one second curable material to the base layer at the locations where the refractive microstructures shall be formed while the at least one first curable material of the base layer is not yet cured or pinned.

4. The method as claimed in claim 1, wherein for forming the refractive microstructures the amount of the at least one second curable material is applied at the locations at which the refractive microstructures shall be formed before curing or pinning and the at least one first curable material and the at least one second curable material have different refractive indices.

5. The method as claimed in claim 4, wherein a refractive index of the at least one first curable material is smaller than the refractive index of the at least one second curable material.

6. The method as claimed in claim 4, wherein the power of the refractive microstructures are at least partly determined by a degree by which the at least one first curable material and the at least one second curable material are interdiffused until the layer of the at least one first curable material with the amount of the at least one second curable material is cured or pinned.

7. The method as claimed in claim 1, wherein for forming the refractive microstructures the amount of the at least one second curable material is applied at the locations at which the refractive microstructures shall be formed before curing or pinning and the at least one first curable material and the at least one second curable material have a same refractive index.

8. The method as claimed in claim 1, wherein a cover layer of a cover layer material is applied onto the layer of the at least one first curable material with the additional amount of the at least one first curable material or with the amount of the at least one second curable material.

9. The method as claimed in claim 8, wherein the cover layer is applied after curing or pinning the layer of the at least one first curable material with the additional amount of the at least one first curable material or with the amount of the at least one second curable material.

10. The method as claimed in claim 8, wherein the power of the refractive microstructures is at least partly determined by a ratio of the refractive index of the cover layer material to the refractive index of the at least one first curable material or the at least one second curable material.

11. The method as claimed in claim 8, wherein the refractive index of the cover layer material is smaller than the refractive index of the at least one first curable material or the at least one second curable material.

12. The method as claimed in claim 1, wherein at least one of the following parameters is used for setting the power of the refractive microstructures: a time after which the curing or pinning is started; the time given for the at least one first curable material to cure or be pinned after the curing or pinning is started or the time given for the at least one first curable and the at least one second curable material to cure or be pinned after the curing or pinning is started; the additional amount of the at least one first curable material or the amount of the at least one second curable material applied at the locations where the refractive microstructures shall be formed; rheological properties of the at least one first curable material or the rheological properties of the at least one first curable and the at least one second curable material; a combination of surface energies of the at least one first curable material and the material of the spectacle lens body or the combination of surface energies of the at least one first curable material and the at least one second curable material and the material of the spectacle lens body; a combination of surface tensions of the at least one first curable material and the at least one second curable material; a convection speed of the at least one first curable material or the convection speed of the at least one first curable material and the at least one second curable material; temperature differences during the additive manufacturing process; a temperature of a nozzle arrangement during the additive manufacturing process; the temperature of the spectacle lens body during the additive manufacturing process; an atmospheric temperature during the additive manufacturing process; an atmospheric moisture during the additive manufacturing process; an atmospheric composition during the additive manufacturing process; a strength of external electric or magnetic fields present during the additive manufacturing process: a density of the at least one first curable material or the densities of the at least one first curable material and the at least one second curable material; and a chemical composition of the at least one first curable material or the chemical compositions of the at least one first curable material and the at least one second curable material.

13. The method as claimed in claim 1, wherein a surfactant is added to at least one of the at least one first curable material and the at least one second curable material.

14. The method as claimed in claim 1, wherein at least one of the at least one first curable material and the at least one second curable material has the same refractive index as the material of the spectacle lens body.

15. The method as claimed in claim 1, wherein at least one of the refractive index of the at least one first curable material and the refractive index of the at least one second curable material is larger than the refractive index of the material of the spectacle lens body.

16. The method as claimed in claim 1, wherein the layer of the at least one first curable material with the additional amount of the at least one first curable material or with the amount of the at least one second curable material is formed on a surface of a progressive addition lens.

17. A spectacle lens with refractive microstructures, which includes a spectacle lens body with a surface which is provided with the refractive microstructures, where the refractive microstructures are at least partly merged with a layer present on the surface, wherein the spectacle lens has been manufactured by the method of claim 1.

18. The spectacle lens as claimed in claim 17, wherein the refractive microstructures at least partly have refractive properties due to a gradient in the refractive index that is present in the refractive microstructures.

19. The spectacle lens as claimed in claim 17, wherein the refractive microstructures are covered by a cover layer.

20. The spectacle lens as claimed in claim 19, wherein the refractive index of the cover layer is smaller than the refractive index of the refractive microstructures.

21. The spectacle lens as claimed in claim 17, wherein the refractive index of the refractive microstructures is larger than the refractive index of the spectacle lens body.

22. A data set comprising at least one kind of the following kinds of data: (i) a numerical representation of the spectacle lens as claimed in claim 17 configured for the purpose of a use of the numerical representation of the spectacle lens for a manufacture of a spectacle lens as claimed in claim 17, and (ii) data containing computer-readable instructions for controlling one or more manufacturing machines in order to produce a spectacle lens as claimed in claim 17.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Further features, properties and advantages of the present disclosure will become clear from the following description in conjunction with the accompanying drawings.

[0094] FIGS. 1 to 4 schematically show steps of the first exemplary embodiment of the inventive method of providing refractive microstructures;

[0095] FIG. 5 schematically shows a second exemplary embodiment of the inventive method of providing refractive microstructures;

[0096] FIG. 6 schematically shows a third exemplary embodiment of the inventive method of providing refractive microstructures;

[0097] FIGS. 7 and 8 schematically show a fourth exemplary embodiment of the inventive method of providing refractive microstructures;

[0098] FIG. 9 shows the refractive index distribution in a layer of a first curable material and a second curable material with a refractive index that differs from the refractive index of the first curable material after curing or pinning the first curable material and the second curable material;

[0099] FIG. 10 shows a sectional view of an exemplary embodiment of a spectacle lens manufactured according to the inventive method;

[0100] FIG. 11 shows a plan view of an exemplary embodiment of a spectacle lens manufactured according to the inventive method; and

[0101] FIG. 12 shows a plan view of another exemplary embodiment of a spectacle lens manufactured according to the inventive method.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0102] A first exemplary embodiment of the inventive method of providing refractive microstructures on a surface of spectacle lens body 3 will now be described with respect to FIGS. 1 to 4. In this exemplary embodiment the power of the refractive microstructures is determined by the curvature of their surface.

[0103] As shown in FIG. 1, according to the first exemplary embodiment of the inventive method, a base layer 1 of a first curable material is applied to a surface 4 of a spectacle lens body 3 by means of an additive manufacturing process, which will be called 3D printing in the following. In such 3D printing processes 3D structures are formed by printing the structures onto a substrate by use of a polymer ink.

[0104] The 3D printing is done by means of a nozzle arrangement 8 the nozzles of which jet the curable material towards the surface 4 of a spectacle lens body 3 while the nozzle arrangement 8 and the spectacle lens body 4 move relative to each other. In the present exemplary embodiment, the nozzle arrangement 8 is part of a single print head which includes a one-dimensional array of nozzles, i.e., a line of nozzles, extending perpendicular to the direction of the relative movement between the nozzle arrangement 8 and the spectacle lens body 4. However, the print head could as well include a two-dimensional array of nozzles, e.g., two or more lines of nozzles. The lines of nozzles of the two-dimensional array may be aligned with each other in the direction of the relative movement between the nozzle arrangement 8 and the spectacle lens body 4. As an alternative, neighboring lines of nozzles may be shifted against each other in the direction perpendicular to the direction of the relative movement between the nozzle arrangement 8 and the spectacle lens body 4 by a fraction of the distance between neighboring nozzles in a line of nozzles so that a staggered arrangement of the lines nozzles is realized. By such a staggered arrangement, the resolution that is achievable in the printing process can be increased.

[0105] The polymer ink, i.e., the first curable material 6, of the present exemplary embodiment cures by polymerization of monomers and/or oligomers and by cross-linking polymer chains in the ink material. The polymerization and cross-linking is initiated by an initiator that is activated by an external stimulus which is ultraviolet (UV) radiation in the present exemplary embodiment. In other exemplary embodiments, the initiator may be activated by other means, e.g., heat or a particle beam, or an initiator is not used at all.

[0106] Suitable 3D polymer inks for use as first curable material 6 in the present exemplary embodiment are (meth)acrylate-based polymer inks typically without solvents. However, polymer inks with a small fraction of a solvent may also be used in cases where the base layer thickness is small enough such that the solvent can evaporate before the curing process. Typical materials of the spectacle lens body 3 are thermoplastics such as polycarbonate or thermosets such as CR-39. A compilation of polymers that are suitable for forming the spectacle lens body 3 is given in Table 1.

TABLE-US-00001 TABLE 1 Compilation of polymers suitable for forming the spectacle lens body 3 Average Abbe refractive number Trade name Resin index n.sub.D* v.sub.D* CR-39, Poly allyl diglycol 1.500 56 CR-330, carbonate (PADC) CR-607, CR-630, RAV 700, RAV 7NG, RAV 7AT, RAV 710, RAV 713, RAV 720 RAVolution Polyurea/Polyurethane 1.500 54 Trivex Polyurea/Polyurethane 1.530 45 Panlite, Lexan, Polycarbonate (PC) 1.590 29 Makrolon MR-6 Polythiourethane 1.598 MR-8 Polythiourethane 1.598 41 MR-7 Polythiourethane 1.664 32 MR-10 Polythiourethane 1.666 32 MR-174 Polyepisulfide 1.738 32 MGC 1.76 Polyepisulfide 1.76 30 Spectralite Urethane/(Meth)acrylate 1.54

[0107] The polymer ink used as first curable material 6 forming the base layer 1 may have a refractive index that is the same as the refractive index of the material of the spectacle lens body 3. In the context of the present disclosure, refractive indices shall be considered the same if they differ from each other by not more than 5 parts per thousand, typically not more than one part per thousand. However, the first curable material 6 and the material of the spectacle lens body 3 do not need to have the same refractive index. In particular, the refractive index of the first curable material 6 may be lower than the refractive index of the material of the spectacle lens body which can be beneficial for the design of an additional anti-reflection (AR) coating. Furthermore, the first curable material 6 should also be suitable as substrate for hard coatings applied later onto the base layer 1 and refractive microstructures present in the base layer 1. In addition, the first curable material 6 must provide sufficient optical quality once it is cured. In the context of the present disclosure, a sufficient optical quality is achieved if the yellowness index (YI) of the spectacle lens with the refractive microstructures is below 3, typically below 1, and more typically below 0.5 and the haze is below 1.0% and typically below 0.5%.

[0108] A typical thickness of the base layer 1 lies in the range between 1 and 100 m, typically in the range between 5 and 50 m. In order to prevent from the formation of unwanted structures in a thin base layer, i.e., a base layer with a thickness below 20 m, random noise can be added to the pattern by which the nozzles of the nozzle arrangement 8 jet the droplets so that the droplets which shall form the base layer 1 are not printed in a regular pattern. Such an approach is called dithering. In the present exemplary embodiment, the thickness of the base layer 1 lies in the range between 15 and 50 m and may, in particular, be 45 m.

[0109] After the base layer 1 has been printed onto the surface 4 of the spectacle lens body 3 in a first pass of the print head 8, an additional amount of the first curable material 6 is applied to the still liquid base layer 1 at locations at which the refractive microstructures 5 shall be formed in a second pass of the print head 8 (the moving direction of the print head 8 is indicated by an arrow in FIG. 2). The additional amount of the first curable material 6 forms protrusions 15 from the surface of the base layer 1 which immediately after deposition start to merge with the base layer 1 due to coalescence. A short time after the droplets forming the protrusions 15 have been printed onto the base layer 1, the curvature of the protrusions 15 is high, i.e., the radius of curvature is small, and, thus, the refractive power provided by the protrusions 15 is high while, over a long time, the surface energy of the first curable material 6 causes the protrusions 15 to merge with the base layer 1. As a consequence, over a long time, the curvature of the protrusions 15 flattens, i.e., the radius of curvature increases, which reduces the power of the protrusions 15. The merging speed goes down with increasing viscosity during a pinning process or a curing process and finally stops when the material is cured. Therefore, controlling the time until the pinning or curing starts and the time given for pinning or curing the first curable material 6, i.e., the material of the base layer 1 and the protrusions 15, allows for determining the final curvature of the protrusions 15 and, thus, their refractive power. Moreover, further parameters can be used to control at least one of the merging speed and the speed of pinning or curing in the present exemplary embodiment. Those parameters include: [0110] The additional amount of the at least one first curable material 6 applied at the locations where the refractive microstructures shall be formed. [0111] The rheological properties of the at least one first curable material 6. [0112] The combination of surface energies of the at least one first curable material 6 and the material of the spectacle lens body. [0113] The convection speed of the at least one first curable material 6. [0114] Temperature differences during the additive manufacturing process. [0115] The temperature of a nozzle arrangement during the additive manufacturing process. [0116] The temperature of the spectacle lens body during the additive manufacturing process. [0117] The atmospheric temperature during the additive manufacturing process. [0118] The atmospheric moisture during the additive manufacturing process. [0119] The atmospheric composition during the additive manufacturing process. [0120] The strength of external electric or magnetic fields present during the additive manufacturing process. [0121] The density of the at least one first curable material 6. [0122] The chemical composition of the at least one first curable material 6.

[0123] In other words, the controlled merging provides a process that allows for a controlled reduction of the curvature of the protrusions 15, i.e., that increases its radius of curvature. The reduction of curvature in turn reduces the power provided by the curvature of the protrusions 15. A state in which the refractive microstructures 5 are partially merged with the base layer 1 is shown in FIG. 3.

[0124] In the present exemplary embodiment, the merging of the protrusions 15 with the base layer 1 needs to be stopped before the protrusions 15 are fully merged with the base layer 1 in order to keep the curvature of the protrusions 15 at a level that provides the desired refractive power, which is not more than 10 dpt and typically lies between 1.5 and 5.5 dpt. The time after which the protrusions 15 are fully merged with the base layer 1 depends on numerous parameters including the temperature and the thickness of the base layer 1 and on the surface tensions involved, for example.

[0125] In order to stop the merging process, any material transport is brought to a halt or considerably slowed down by pinning in the present exemplary embodiment. In the present exemplary embodiment this means that the first curable material 6, i.e., the material of the protrusions 15 and of the base layer 1, becomes cured except for a surface layer in contact with an oxygen containing atmosphere which remains uncured. In other exemplary embodiments a protective atmosphere without oxygen may be used so that the surface layer undergoes polymerization, too, and the protrusions 15 as well as the base layer 1 will be fully cured instead of being pinned.

[0126] In the present exemplary embodiment, the pinning (or the full curing) is initiated with the help of an initiator, which is a photoinitiator in the present exemplary embodiment. To activate the photoinitiator in order to start the pinning (or curing), the protrusions 15 and the base layer 1 are irradiated with ultraviolet radiation, i.e., radiation with a wavelength in the range between 10 and 400 nm. In other exemplary embodiments the initiator may be activated by a stimulus other than ultraviolet radiation, for example by light in the spectral range of visible light, by infrared radiation, by heat or by a particle beam. Moreover, exemplary embodiments are conceivable that use polymers which undergo cross-linking without the need of an initiator.

[0127] Due to the pinning (or the curing), the merging of the protrusions 15 in the base layer 1 stops. The time between printing the protrusions 15 onto the base layer 1 and stopping the merging by the pinning (or curing) determines the final topography of the refractive microstructure 5 formed by the protrusions 15. The longer the refractive protrusions 15 have finally merged with the base layer 1, i.e., the wider the protrusions 15 have spread, the lower is their optical power.

[0128] After the pinning (or curing), the curvature of the protrusions 15 and, thus, the curvature of the refractive microstructures 5 should not depend on whether they were printed at the beginning of printing the protrusions 15 or at the end of printing the protrusions 15. If the time passing between printing the first protrusions 15 and the last protrusions 15 is short compared to the time the protrusions 15 need to fully merge with the base layer 1 all protrusions 15 can be treated such as if they would start to merge at the same time. As the number of droplets of the first curable material 6 needed for printing a protrusion 15 is relatively small, a single pass of the print head 8 is enough for printing all the protrusions 15. This means that the time that passes between printing the first protrusions 15 and the last protrusions 15 can be kept short which allows for treating the protrusions 15 such as if they would start to merge at the same time.

[0129] In the present exemplary embodiment, fully curing the pinned base layer 1 with the protrusions 15, i.e., fully cross-linking the pinned base layer 1 with the protrusions, is done at a later point in time, namely after a cover layer 7 has been applied onto the base layer 1 with the protrusions 15, as it is shown in FIG. 4. However, the pinned base layer 1 with the protrusions 15 could as well be fully cured before applying the cover layer 7. The fact that a surface film of the base layer 1 with the protrusions 15 is not fully cross-linked after the pinning, helps to improve bonding between the cover layer 7 to the base layer 1 with the protrusions 15. In the present exemplary embodiment, the cover layer 7 is printed onto the base layer 1 with the protrusions 15. However, it is also possible to apply the cover layer 7 by spin coating or by means of a bonded foil. After the cover layer 7 has been applied it protects the base layer 1 with the protrusions 15.

[0130] The thickness of the cover layer 7 is chosen such that the refractive microstructures 5 realized by the protrusions 15 after curing are fully covered by the cover layer 7. To achieve this goal, the thickness of the cover layer 7 typically lies in the range between 2 and 15 times the height by which the refractive microstructures 5 formed by the protrusions 15 protrude from the base layer 1, in particular, in the range between 5 and 10 times the height by which the refractive microstructures structures 5 project over the base layer 1.

[0131] Suitable materials for the cover layer 7 are (meth)acrylate-based materials. However, instead of (meth)acrylate-based materials, other curable or setting materials could be used for the cover layer 7 if they allow layer thicknesses in the range between 1 and 100 m, in particular, in the range between 1 and 50 m. Possible materials are epoxides, epoxy-thiol systems, thiolene-based systems, urethanes, polysiloxane-based systems, etc.

[0132] Without the cover layer 7, the power provided by the refractive microstructures 5 will not only depend on their curvature but also on the refractive index difference between the first curable material 6 and air. Hence, with first curable materials having refractive indices in the range between 1.50 and 1.74 the refractive index difference would approximately lie in the range between 0.5 and 0.74. With the cover layer 7 this refractive index difference would be reduced, which would allow for higher curvatures of the refractive microstructures 5. Hence, the refractive index of the cover layer 7 may be used for compensating too large curvatures of the refractive microstructures 5.

[0133] In the present exemplary embodiment, the viscosity of the base layer 1 may be altered in order to suitably set the merging speed of the refractive microstructures 5 in the base layer 1. The viscosity may, for example, be adjusted by adjusting the temperature of the printing environment and/or the temperature of the printing material, i.e., the first curable material 6. Moreover, viscosity may be altered by pinning the first curable material 6. The degree of pinning can, for example, be adjusted by the oxygen concentration of the atmosphere in which the additive manufacturing takes place during the pinning process, by the dose of UV-radiation used for the pinning, by the initiator content, etc.

[0134] Although the same first curable material 6 is used for forming the base layer 1 and the protrusions 15 in the first exemplary embodiment described so far, it is also possible to use at least one first curable material for printing the base layer 1 and at least one second curable material 16 that differs from the at least one first curable material 6 for printing the protrusions 15. The at least one first curable material and the at least one second curable material may either have the same refractive index or different refractive indices.

[0135] In the following, a second exemplary embodiment of the inventive method will be described with respect to FIG. 5. The method of the second exemplary embodiment differs from the method of the first exemplary embodiment in that a layer 21 of the first curable material 6 and the protrusions 25 are formed in a single pass of the nozzle arrangement represented by the print head 8. The moving direction of the print head 8 is indicated by an arrow in FIG. 5.

[0136] In the second exemplary embodiment, the printing nozzles of the print head 8 print different amounts of the first curable material 6 at different locations of the surface 4 of the spectacle lens body 3. At those locations of the surface 4 at which no refractive microstructures 5 shall be formed, the nozzles of the print head 8 eject a certain amount of the first curable material 6 for forming a layer 21 of the first curable material 6 while at locations at which the refractive microstructures 5 shall be formed the nozzles of the print head 8 eject a larger amount of the first curable material 6. The additional amount of the first curable material 6 that is applied to the surface 4 at the locations at which the refractive microstructures shall be formed as compared to other locations of the surface 4 leads to the formation of protrusions 25 protruding from the layer 21 of the first curable material 6. After the layer 21 with the protrusions 25 has been printed onto the surface 4 of the spectacle lens body 3 by a single pass of the print head 8, the remaining steps of the method of providing refractive microstructures 5 on the surface 4 of the spectacle lens body 3 are the same as in the first exemplary embodiment.

[0137] As in the first exemplary embodiment, the coalescing is stopped by pinning or at least partial curing using ultraviolet radiation as it has been described with respect to FIG. 3.

[0138] What has been said with respect to the nozzle arrangement and the materials used in the first exemplary embodiment applies to nozzle arrangement and the materials of the second exemplary embodiment, as well.

[0139] In the second exemplary embodiment a single print head 8 is used for printing the layer 21 and the protrusions 25 in a single pass of the print head 8. In a third exemplary embodiment of the inventive method, which is shown in FIG. 6, the nozzle arrangement is implemented as two print heads 27, 28. Each of the print heads 27, 28 may include a one-dimensional or two-dimensional array of nozzles and may have its own individual feed line 29, 30 for feeding curable material to its array of nozzles, as it is depicted in FIG. 6. However, instead of using two print heads 27, 28 it would also be possible to use a single print head with two or more arrays of nozzles.

[0140] In the third exemplary embodiment, the two print heads 27, 28 are used for printing a layer 21 of a first curable material 6 and protrusions 25 protruding from the layer 21 in a single pass of the print heads 27, 28 in FIG. 6. The direction of relative movement between the print heads 27, 28 and the spectacle lens body 3 is indicated by an arrow. During the passing over the surface 4 of the spectacle lens body 3, the first print head 27 ejects the first curable material 6 forming the layer 21 while the second print head 28 ejects the additional amount of the first curable material 6 forming the protrusions 25. After the layer 21 of the first curable material 6 with the protrusions 25 has been printed onto the surface 4 of the spectacle lens body 3 by a single pass of the print heads 27, 28, the remaining steps of the method of providing refractive microstructures 5 on the surface 4 of the spectacle lens body 3 are the same as in the first exemplary embodiment.

[0141] If the two print heads 27, 28 of the third exemplary embodiment have different feed lines 29, 30 for feeding curable material, as it is shown in FIG. 6, it is also possible to print the layer 21 by ejecting a first curable material 6 using the first print head 27 and to print the protrusions 25 by ejecting an amount of a second curable material onto the first curable material 6 using the second print head 28. In case of using more than two print heads, for example three, four, five, or even more print heads, more sophisticated combinations of curable materials may be realized if each print head has its own feed line for feeding curable material. The same could be achieved with a single print head that includes two or more arrays of nozzles and individual feed lines for the arrays of nozzles.

[0142] In the following, a fourth exemplary embodiment of the inventive method will be described with respect to FIGS. 7 and 8. Like in the second and third exemplary embodiments, a layer 31 and protrusions 35 are printed onto the surface 4 of the spectacle lens body 3 in a single printing pass using a nozzle arrangement that is implemented as two print heads 27, 28 with individual feed lines 29, 30. However, instead of being implemented as two print heads 27, 28, the nozzle arrangement could as well be implemented as a single print head that includes two or more arrays of nozzles and individual feed lines for the arrays of nozzles.

[0143] Like in the third exemplary embodiment, the direction of relative movement between the print heads 27, 28 and the spectacle lens body 3 is indicated by an arrow. The fourth exemplary embodiment differs from the second and third exemplary embodiments in the structure of the layer 31 of the first curable material 6 and in the way the refractive properties of the refractive microstructures 5 are achieved. For this purpose, a second curable material 16 with a refractive index that differs from the refractive index of the first curable material 6 by being higher than the refractive index of the first curable material 6 is used.

[0144] In the fourth exemplary embodiment the amount of the first curable material 6 that is applied to locations of the surface 4 of the spectacle lens body 3 where the refractive microstructures 5 shall be formed by using the first print head 27 is less than an amount of the first curable material 6 that is applied to other locations of the surface 4. As a consequence, the layer 31 is formed with dents 32 at those locations where the refractive microstructures 5 shall be formed. Although the dents 32 do not reach to the surface 4 of the spectacle lens body 3 in the present exemplary embodiment, there may be exemplary embodiments in which the surface 4 of the spectacle lens body 3 is exposed in the center of the dents 32. Whether or not the dimples 32 expose the surface 4 of the spectacle lens body 3, depends on the thickness of the layer 31 and the lateral dimensions of the dents 32 which, in turn, depend on the lateral dimensions of the refractive microstructures to be formed. For example, for the typical lateral dimensions of the refractive microstructures to be formed, the dents 32 might probably expose the surface 4 in case of layers 31 of the first curable material 6 with a maximum thickness up to 10 m while they will most likely not expose the surface 4 in case of layers 31 of the first curable material 6 with larger thicknesses. Typical lateral dimensions of refractive microstructures to be formed are 0.1 to 2 mm.

[0145] Using the second print head 28, the second curable material 16 is printed into the dents 32. As a consequence, at least the lower part of the amount of second curable material 16 applied into the dents 32 is laterally surrounded by the layer 31 of the first curable material 6. Since both the first curable material 6 and the second curable material 16 are still liquid, the first curable material 6 and the second curable material 16, which has a higher refractive index than the first curable material 6, start to diffuse into each other after the protrusions 35 have been formed in the dents 32. Due to this diffusion process and the different refractive indices, refractive index gradients are formed with the highest refractive indices at the locations of the centers of the dents 32 and the lowest refractive indices in the portions of the layer 31 of the first curable material 6 that are located between the dents 32. In this way the refractive microstructures 5 may be implemented as gradient index lenslets 5. The gradient index lenslets 5 are indicated in FIG. 8 by the dotted areas where higher density of the dots represents a higher refractive index. FIG. 10 shows the refractive index distribution from the left to the right in FIG. 9. In practice, the gradient index lenslets 5 would protrude slightly from the surface as the time allowed for the first curable material 6 and the second curable material 16 to diffuse into each other is finite. As a consequence, the refractive properties of the refractive microstructures 5 are still determined by a small degree by their surface geometry in addition to being determined by the index gradient.

[0146] The slope of the refractive index gradient can be adjusted by the duration of the diffusion process, by the lateral dimensions of the dents 32 and by the amount of second curable material 16 printed into the dents 32. Moreover, the slope of the gradient determines the power of the gradient index lenslets 5 so that adjusting the duration of the diffusion process allows for adjusting the power of the gradient index lenslets 5. Similar to stopping the coalescing process in the first to third exemplary embodiment, stopping the diffusion process in the present exemplary embodiment is achieved by pinning or curing the first and second curable materials 6, 16.

[0147] The use of gradient index lenslets 5 allows for forming a layer 31 with refractive microstructures 5 having a flat surface 3 or at least a surface that is flatter than a surface of a layer in which the refractive microstructures are solely based on the surface geometry of the refractive microstructures. This may be advantageous if further layers, like for example hard coating layers, transmission altering layers, antireflection layers, etc. shall be applied on top of the layer 31 with the refractive microstructures 5. In particular, the flat surface can help to increase the adhesion and long-term stability of subsequent layers. The adhesion of the subsequent layers may be further improved if the layer 31 with the refractive microstructures 5 is not fully cured but only pinned.

[0148] FIG. 10 shows a sectional view of a spectacle lens 100 which has been manufactured according to the inventive method. The spectacle lens includes a spectacle lens body 3 and a layer 1 with refractive microstructures 5 which, in the present exemplary embodiment, provide a positive power in addition to the power of the spectacle lens body 3 through the curvature of their surface protruding from the layer 1. On top of the layer 1 with the protruding refractive microstructures 5, a layer 7 is present which is thick enough to level out the protrusions of the refractive microstructures 5. By this measure, a flat surface of the cover layer 7 can be achieved which is advantageous in view of the application of further layers on top of the cover layer. In particular, the flat surface of the cover layer 7 can help to increase the adhesion and long-term stability of subsequent layers. The spectacle lens (100) may either be a single vision, bifocal or multifocal spectacle lens, or a progressive addition lens (PAL).

[0149] The thickness of the layer 1 is 45 m in the present exemplary embodiment, and the refractive microstructures 5 protrude from the layer 1 by an amount of approximately 1 m. In order to achieve a flat surface, the cover layer 7 should have a thickness of about 5 to 10 times the height by which the refractive microstructures 5 protrude from the layer 11. In the present exemplary embodiment, the thickness of the cover layer 7 is 10 m which corresponds to about 5 to 10 times the height by which the refractive microstructures 5 protrude from the layer 1. Onto the flat surface of the cover layer 7, a protective hard layer 101 is applied, and on top of the hard layer 101 an anti-reflection layer 103 is provided. Please note that also other layer systems could be provided on top of the cover layer 7, for example, layers with absorbing or reflecting properties, as they are used for sunglasses, for example.

[0150] Please note that the amount of elevation from the surface of the base layer 1 may be larger or smaller from 1 m in other exemplary embodiments and may lie in the range between 0 and 10 m depending, inter alia, on the power to be achieved with the refractive microstructures 5. An elevation of close to 0 m would mean an almost flat surface of the base layer 1 with the refractive microstructures 5. Such a flat surface can be present if the refractive properties of the refractive microstructures 5 are due to a difference or a gradient in their refractive index instead of a curvature of their surfaces. If the refractive properties of the refractive microstructures 5 are to be achieved by means of their curvature, their protrusion from the surface lies in the range between 0.2 and 10 m, and often in the range between 0.4 and 1.5 m. To achieve a flat surface of the cover layer 7 the cover layer needs to have a thickness in the range between 1 and 50 m, depending on the amount of protrusion of the refractive microstructures 5 from the base layer 1.

[0151] In the spectacle lens 100 shown in FIG. 11, the material, the protruding refractive microstructures 5 are made of, is identical with the material of the layer 1. This material has a refractive index that is the same as the refractive index of the material of the spectacle lens body 3. This means the refractive indices of the refractive microstructures 5 and the layer 1 do not differ by more than 5 parts per thousand, and typically by not more than one part per thousand, from the refractive index of the spectacle lens body 3. Typical materials that can be used as materials for the refractive microstructures 5 and the layer 1 have refractive indices between 1.30 and 1.75. Typical materials used for spectacle lens bodies have refractive indices in the range from 1.50 to 1.74. In order to provide a positive power in addition to the power of the spectacle lens body 3, the refractive microstructures 5 need to have a refractive index that is higher than the refractive index of the cover layer 7. Therefore, it is desirable to use a material with a refractive index at the upper end of the range between 1.30 and 1.75 for the layer 1 and the refractive microstructures 5 and a material with the refractive index at the lower end of the said the range for the cover layer 7. As the refractive index of the cover layer 7 is higher than the refractive index of air, steeper curvatures can be allowed for refractive microstructures having an interface to a cover layer 7 than for refractive microstructures 5 having an interface to air.

[0152] Although a particular combination of refractive indices is present in the exemplary embodiment shown in FIG. 10, other combinations of refractive indices are possible, as well. For example, as an alternative to the exemplary embodiment shown in FIG. 10, the refractive index of the refractive microstructures 5 could differ from the refractive index of the spectacle lens body 3. In particular, the refractive index of the refractive microstructures 5 could be larger than the refractive index of the spectacle lens body 3 which would reduce the steepness of curvature necessary for the refractive microstructures 5 to provide a positive power in addition to the power provided by the spectacle lens body 3. In addition, or as a further alternative, the refractive index of cover layer 7 could correspond to the refractive index of the spectacle lens body 3 or could be larger than the refractive index of the spectacle lens body 3. In case the layer 1 has the same refractive index as the spectacle lens body 3, a refractive index of the cover layer 7 that corresponds to the refractive index of the spectacle lens body 3 would prevent from unwanted refraction or Fresnel reflection at the interfaces between the spectacle lens body 3 and the layer 1 and between the layer 1 and the cover layer 7. However, in this case the refractive microstructures 5 need to have a refractive index that is higher than the refractive index of the cover layer 7 in order to provide a positive power in addition to the power of the spectacle lens body 3. In case the cover layer 7 has a refractive index that is higher than the refractive index of the spectacle lens body 3, providing an additional power in addition to the power of the spectacle lens body 3 would require complementary geometries of the base layer 1 with the refractive microstructures 5 or even inverted geometries, i.e., concave curvature such as dents or cups instead of a convex curvature. This alternative would, however, mainly be used if other powers then an additional power to the focal power provided by the spectacle lens body 3 are to be achieved. In addition, in case no cover layer 7 is present, the refractive index of the layer 1 could be smaller than that of the spectacle lens body 3 which could be beneficial if an antireflective layer is to be applied to the layer 1.

[0153] Although the refractive microstructures 5 of the spectacle lens 100 shown in FIG. 10 have refractive properties due to the geometry of the surface of protrusions over the layer 1 they could at least partly or even fully have refractive properties due to a gradient in the refractive index that is present in the refractive microstructures 5. Use of a gradient in the refractive index allows for a flatter surface of the layer 1 or even a fully flat surface of the layer 1 as compared to refractive microstructures 5 having refractive properties due to the geometry of protrusions protruding from the layer 1. However, the use of a gradient in the refractive index for providing the refractive properties of the refractive microstructures 5 requires using a second curable material having a refractive index that differs from the refractive index of the first curable material in the method of providing the refractive microstructures 5.

[0154] The refractive microstructures may have various shapes in a top view of the spectacle lens. FIG. 11, which shows a spectacle lens 110 manufactured according to the inventive method, represents a spectacle lens with refractive microstructures 5 which are formed as lenslets protruding from the layer 1 (not shown in FIG. 11). The spectacle lens body 3 is that of a progressive addition lens 110. However, it may as well be spectacle lens body 3 of a single vision, bifocal, or multifocal spectacle lens.

[0155] FIG. 12 shows another exemplary embodiment for spectacle lens 120 manufactured according to the inventive method with refractive microstructures 5. In this exemplary embodiment, the refractive microstructures 5 are provided on a spectacle lens body 3 of a single vision spectacle lens 120 and resemble rings having an approximately spherical curvature in radial direction and protrude from the layer 1 (not shown in FIG. 12). However, the refractive properties of a lenslet or ring do not need to be provided by the curvature of its surface, but may as well be provided by a difference or a gradient in the refractive index or by a combination of the curvature and the difference or the gradient in the refractive index. Depending on the material and the geometry of a lenslet, the refractive index within the lenslet may reduce or increase from the center of the lenslet towards its outer rim and, in a ring the refractive index, may reduce or increase starting from the center of the ring radially inwards and radially outwards. Other geometries of the refractive microstructures 5 in plan view of the spectacle lens 100 are conceivable for a person skilled in the art. Therefore, the geometry of the refractive microstructures 5 shall not be restricted to lenslets and ring-shaped microstructures. Although the spectacle lens body 3 of the spectacle lens 120 is that of a single vision spectacle lens, it could as well be a spectacle lens body 3 of a bifocal or multifocal lens or of a progressive addition lens.

[0156] In the following, concrete examples of the inventive method and their results will be discussed.

First Concrete Example

[0157] In the first concrete example, a pattern consisting of 3 refractive microstructures arranged in a 33 array on a 9 mm9 mm area of a glass substrate (SCHOTT D263T eco) is formed. In a first step, a (meth)acrylate-based polymer ink is used to print a fluid base layer with the thickness of 45 m onto the glass substrate in a first pass of the printing head using the print head of a standard 3D printer. The same (meth)acrylate-based polymer ink is then used to print a pattern of refractive microstructures onto the base layer in a second pass of the print head. The pattern consists of 9 microstructures arranged in a 33 array. Four of these patterns are printed in consecutive passes of the print head where each of these passes takes 12 seconds. Immediately after the last of the four patterns was printed, the four patterns are pinned by use of ultraviolet radiation with wavelengths of 365 nm and 395 nm in order to bring material flow to a halt while the substrate with the patterns is still in the printer. After that, the substrate with the patterns is taken out of the printer and cured under a nitrogen atmosphere using ultraviolet radiation having a wavelength of 365 nm.

[0158] As the pinning is performed immediately after the last pass of the print head, i.e., after the last one of the four patterns has been printed, the last pattern (fourth pattern) is pinned immediately after it has been printed while the third pattern has a waiting time of 12 seconds before pinning, the second pattern has a waiting time of 24 seconds before pinning and the first pattern has a waiting time of 36 seconds before pinning.

[0159] After the curing the refractive microstructures of the four patterns were evaluated for their diameter, for the amount of their protrusion from the base layer, for the radius of a sphere representing the best fit to the curvature of the microstructures and for the power they provide. The evaluation of the power is based on a refractive index of the (meth)acrylate-based polymer ink of 1.50. The results are compiled in the following Table 2:

TABLE-US-00002 Pattern no. 1 2 3 4 Time to pinning [s] 36 24 12 0 Diameter [mm] 1.612 1.436 1.268 1.265 Sphere radius [mm] 419 343 211 188 Elevation [m] 0.75 0.78 0.95 1.07 Nominal Power [dpt] 1.19 1.46 2.37 2.66

[0160] As can be seen from Table 2, the more time passes until pinning, the less the refractive microstructures protrude from the base layer. Likewise, the slope of the refractive microstructures and the power provided by the refractive microstructures decrease with the time that passes until pinning. On the other hand, the diameter of the sphere that represents the best fit to the curvature of the microstructures increases with time passing until pinning, as does the diameter of the refractive microstructures. This behavior is due to the coalescence of the printed refractive microstructures with the base layer over time.

[0161] Of the four patterns presented in Table 2, patterns number three and four show refractive microstructures having powers suitable for lenslets of spectacle lenses to be used for slowing down or stopping progression of myopia. The power of the refractive microstructures of the second pattern is a bit low but might still be suitable for lenslets of spectacle lenses to be used for slowing down or stopping progression of myopia while the power of the refractive microstructures of the first pattern is too low to be used as lenslets for spectacle lens which shall slow down or stop progression of myopia.

[0162] Furthermore, it could be observed that the coalescence of the refractive microstructures takes more time if the refractive microstructures within the pattern are located closer to each other. This might be due to the fact that the lateral material transport is hindered or affected by adjacent structures. Therefore, in case of refractive microstructures arranged close to each other, the time until the pinning needs to be longer than for refractive microstructures located further apart of each other.

Second Concrete Example

[0163] In the second concrete example, instead of lenslets, two concentric ring-shaped focusing structures are printed onto a base layer with the pinning starting immediately after printing the structures. The ink and the substrate used for printing the base layer and the refractive microstructures are the same as in the first concrete example. The radii of the resulting concentric inner and outer ring-shaped focusing structures after pinning and curing are 1.5 mm and 4.5 mm, respectively, and the distance between the two ring-shaped focusing structures is 3 mm. Their widths at their bases, i.e., where they merge with the base layer, are 1 mm for both ring-shaped focusing structures and they both protrude from the base layer with a height of 0.7 to 0.8 m. It has been noticed that additional, unwanted rings may develop if the thickness of the base layer is the same as in the first concrete example. However, the unwanted rings seem to disappear if the thickness of the base layer is reduced.

[0164] The cross-section of the rings has been fitted by a sphere in order to calculate the approximate value of the power the ring-shaped focusing structures provide. Evaluation of the best fit results in a power of 4.5 dpt for a refractive index of 1.50, which is well within the range that can be used for slowing down or stopping progression of myopia.

Third Concrete Example

[0165] In the third concrete example, the layer and the refractive microstructures are printed both in a single pass of the print head. In doing so, the layer is printed in a pattern with dents into which the refractive microstructures are printed. Different (meth)acrylate-based polymer inks are used for printing the layer and the refractive microstructures. The substrate is the same as in the first two exemplary embodiments. In the present concrete example, the ink used for printing the layer with the dents has a first refractive index and the ink used for printing the refractive microstructures into the dents has a second refractive index that is higher than the first refractive index. Over time, a diffusion of the ink of the layer and the ink of the refractive microstructures takes place, leading to a gradient in the refractive index with the highest refractive index at the center of the refractive microstructures and the lowest refractive index in the area between neighboring refractive microstructures.

Fourth Concrete Example

[0166] In the fourth concrete example, refractive microstructures are printed onto a curved substrate that does not have a hard coating and has a diameter of 65 mm, a center thickness of 2.0 mm, a radius of curvature of 143.5 mm, a refractive index of 1.50 and a power of 0.00 dpt. Both, lenslets and ring-shaped focusing structures were printed onto the surface of such a substrate. For printing the lenslets, the same procedure as for pattern four in the first concrete example was used and for printing ring-shaped focusing structures the same procedure as in the second concrete example was used.

[0167] In case of the ring-shaped focusing structures, two concentric ring-shaped focusing structures were printed. These ring-shaped focusing structures protrude from the base layer with a height of 2 to 2.5 m with the outer one of the two ring-shaped focusing structures protruding slightly less than the inner one and having a slightly smaller width. From a fit of spheres to the cross-section of the ring-shaped focusing structures powers of the rings between 3.4 dpt and 6.5 dpt has been determined.

[0168] In case of printing lenslets, the resulting lenslets have a diameter of 2.54 mm and an elevation of 7.24 m. From a fit of a sphere to the curvature of the lenslets the radius of curvature was determined to be 111.8 mm which results in a power of 4.5 dpt.

[0169] The fourth concrete example shows that with the inventive method lenslets and ring-shaped focusing structures can be printed on curved substrates with the lenslets and the ring-shaped focusing structures having suitable powers for slowing down or stopping progression of myopia.

[0170] The present invention has been described with respect to exemplary embodiments and concrete examples of the inventive method and the resulting spectacle lens designs. Guided by the exemplary embodiments and the concrete examples, a person skilled in the art is able to contemplate modifications of the inventive method and the inventive spectacle lens design. Therefore, the scope of the disclosure shall not be restricted by the exemplary embodiments or the concrete examples but only by the appended claims.

[0171] The term comprising (and its grammatical variations) as used herein is used in the inclusive sense of having or including and not in the exclusive sense of consisting only of. The terms a and the as used herein are understood to encompass the plural as well as the singular.

[0172] All publications, patents, and patent applications cited in this specification are herein incorporated by reference, and for any and all purposes, as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference. In the case of inconsistencies, the present disclosure will prevail.