PROCESS FOR MARKING AN OPTICAL EYEGLASS

Abstract

The invention relates to a process for marking an optical eyeglass (1) equipped with a surface coating (5) comprising the following steps: A step of detreating by means of a laser beam, so as to locally detreat an area of the optical eyeglass by removing the surface coating (5) until a lower layer (7) of the eyeglass (1) is reached, which layer is located under said coating (5) and made of a material that is different from the surface coating (5), thus forming at least one the detreated zone (6, 11), A step of depositing an ink (9) in the detreated zone (6, 11) in order to form at least one inked pattern (4), so that the ink (9) adheres to the lower layer (7) present at the bottom (10) of the detreated zone (6, 11).

Claims

1. A process for marking an optical eyeglass equipped with a surface coating comprising the following steps: detreating by a laser beam, so as to locally detreat an area of the optical eyeglass by removing the surface coating until a lower layer of the eyeglass is reached, which layer is located under said coating and made of a material that is different from the surface coating, thus forming at least one detreated zone; and depositing an ink in the detreated zone in order to form at least one inked pattern, so that the ink adheres to the lower layer present at the bottom of the detreated zone.

2. The process according to claim 1, wherein the optical eyeglass includes an interference stack, of the antireflection or interference-mirror type, located between the surface coating and a substrate, said at least one detreated zone passing through the surface coating and the interference stack.

3. The process according to claim 1, wherein the detreatment step allows at least two separate detreated zones to be obtained that are arranged in at least one group forming a macroscopic pattern element.

4. The process according to claim 1, wherein the ink is deposited in excess and extends beyond said at least one detreated zone, said process furthermore comprising a step of removing the ink that has overflowed from said at least one detreated zone.

5. The process according to claim 5, wherein the removing step is carried out by an adhesive laid flat on the surface coating, said adhesive being removed and taking with it the ink that overflowed from said at least one detreated zone onto said coating.

6. The process according to claim 4, wherein the ink is hardened after deposition, by drying, polymerisation or thermosetting, and the step of removing the excess ink is carried out when said ink is still liquid or soft.

7. The process according to claim 1, wherein the detreated zones form wells that are separated from one another or at least one detreated zone forms a plurality of adjoining wells that are separated from one another by a protrusion comprising no surface coating.

8. The process according to claim 7, wherein said wells have substantially the same dimensions as those of the laser beam at a point of impact with the surface.

9. The process according to claim 1, wherein the step of depositing the ink in said at least one detreated zone is carried out by pad printing by an inking stamp.

10. The process according to claim 9, comprising a step of determining the inked pattern from a list of at least two different inked patterns, the dimensions of the inking stamp being such that said inking stamp deposits the ink so as to form a similar print for at least two inked patterns of said list.

11. The process according to claim 1, comprising a step of establishing a frame of reference of an uncut eyeglass, said step including a step of determining a position of the pattern on the eyeglass taking into account a shape of the cut eyeglass and mounting data, so as to place the pattern in a zone comprised in the outline of the cut eyeglass, the step of creating detreated zones being carried out on the as yet uncut eyeglass.

12. The process according to claim 1, wherein the step of depositing the ink is carried out by inkjet printing.

13. The process according to claim 12, wherein the detreated zones form wells that are separated from one another or at least one detreated zone forms a plurality of wells, and one single ink droplet is deposited per well.

14. The process according to claim 13, wherein the at least two adjacent wells include an ink of different colour.

15. The process according to claim 12, wherein when the detreated zone formed by a plurality of points of impact of the laser comprises a thinned zone at least one dimension of which is smaller than those of an ink droplet deposited on the material of the bottom of said thinned zone, the excess ink is absorbed by an adjacent zone of larger size or is removed with suitable removing means.

16. An apparatus for carrying out a process according to claim 1, comprising means suitable for emitting a laser beam, means able to deposit an ink and a holder able to hold the eyeglass, said holder remaining stationary throughout the duration of the marking process and said means being movable in order to be alternatively placeable level with an identified zone of the eyeglass in order to allow the eyeglass to be marked.

17. An optical eyeglass including a surface coating, at least one detreated zone in said coating, and ink that is absorbent in the visible and/or UV spectrum, present in said detreated zone.

18. The process according to claim 2, wherein the interference stack is separated from the substrate by one or more varnishes.

19. The process according to claim 9, wherein the inking stamp is dimensioned to cover at least the entirety of the pattern created by the at least one detreated zone created on the surface-of the optical eyeglass.

Description

[0041] Below, a detailed description of one preferred embodiment of a method for marking an optical eyeglass according to the invention is given with reference to the following figures:

[0042] FIG. 1A is a front view of an optical eyeglass having undergone marking by means of a process according to the invention,

[0043] FIG. 1B is a perspective view of the optical eyeglass in FIG. 1A,

[0044] FIG. 2 is a schematic cross-sectional view of an optical eyeglass illustrating a first step of a marking process according to the invention,

[0045] FIG. 3 is a schematic cross-sectional view of an optical eyeglass illustrating a second step of a marking process according to the invention,

[0046] FIG. 4 is an enlarged view of a portion of one pattern produced on an optical eyeglass by means of a marking process according to the invention, said portion being monochromatic and produced by pixelisation,

[0047] FIG. 5 is an enlarged view of a portion of one pattern produced on an optical eyeglass by means of a marking process according to the invention, said portion being multicoloured and produced by pixelisation,

[0048] With reference to FIGS. 1A and 1B, an optical eyeglass 1 has a front face 2 and a back face 3, said back face 3 being that face of the eyeglass 1 which is intended to be closest to the eye when said eyeglass 1 is fitted in a frame and the latter is being worn by an individual. A marking process according to the invention is intended to produce a distinctive pattern 4 on the front face 2 of the eyeglass 1 in order for said pattern 4 to be visible by a third person looking at the individual wearing a frame containing said marked eyeglass 1. Preferably, the pattern 4 is produced on the periphery of the eyeglass 1 in order not to disrupt the vision of the individual wearing a frame equipped with such an eyeglass 1. This pattern 4 may take any form and may for example consist of at least one number, or of at least one letter, or of a combination of numbers and/or letters. Thus, a pattern may for example be an identifiable word. It may also take the form of a logo possibly for example containing a specific graphic. A pattern 4 may be made up of one or more macroscopic elements.

[0049] Certain optical eyeglasses 1 benefit from a surface treatment, for example in order to prevent dust and/or water from settling on the front face 2 of the eyeglass 1 when an individual is wearing spectacles equipped with these eyeglasses 1. Thus, the eyeglass 1 possesses, on its front face 2, a surface coating 5 consisting of a hydrophobic and oleophobic layer.

[0050] An optical eyeglass 1 is generally marked by means of a deposition of an ink on the front face 2 of the eyeglass 1. However, the presence of such a hydrophobic and oleophobic surface coating 5 prevents the ink 9 from effectively adhering to the surface of the eyeglass 1, making the marking thereof questionable. In certain cases, a mark may seem to have been satisfactorily produced, but the presence of the surface coating 5 decreases the robustness of the pattern 4 and makes it nonpermanent, and liable to deteriorate or deform over the lifetime of the lens or over the time it is used.

[0051] The principle of a marking process according to the invention consists in removing material from the front face 2 of the eyeglass 1 until a deep layer located under the surface coating 5, and which allows the ink deposited on the surface of said eyeglass 1 to bind tightly, is reached. In other words, the surface coating 5 is removed locally and the lens is thus locally detreated of the surface coating 5.

[0052] One process according to the invention, allowing an optical eyeglass 1 equipped with a hydrophobic and oleophobic surface coating 5 to be marked, comprises the following steps: [0053] A step of detreating by means of a laser beam, so as to locally detreat a surface 2 of the optical eyeglass 1 by removing the surface coating 5 until a lower layer 7 of the eyeglass 1 is reached, which layer is located under said coating 5 and made of a material that is different from the surface coating 5, thus forming at least one detreated zone 6, 11, [0054] A step of depositing an ink 9 in the detreated zone 6, 11 in order to form at least one inked pattern 4, so that the ink 9 adheres to the lower layer 7 present at the bottom of the detreated zone 6, 11.

[0055] The detreated zones 6, 11 in the eyeglass 1 have the shape and dimensions of the pattern 4 that it is desirable to see printed on the eyeglass 1. It is important to underline that the pattern 4 or at least one macroscopic element of said pattern 4 may be made up either of a plurality of discrete detreated zones 11 that may be likened to discrete or quasi-discrete holes 11 (in this case each detreated zone 11 may be likened to one pixel) or of a single detreated zone 6 that may be likened to a macroscopic recessed print having the shape and dimensions of the pattern 4 or of a macroscopic element of said pattern 4.

[0056] With reference to FIG. 2, each detreated zone 6, 11 is produced by means of an irradiation by a laser beam of the surface coating 5, this allowing a lower layer 7 of the eyeglass 1, which layer is located under said coating 5, to be reached, said lower layer 7 being distinct from said surface coating 5. Thus, where it is applied, the laser beam completely destroys the thickness of the surface coating 5 in the direction indicated by the arrow 12. If the optical eyeglass 1 were to include an interference stack, of the antireflection or interference-mirrored type, located under the anti-smudge coating 5, said at least one detreated zone 6, 11 would pass through said anti-smudge coating 5 and said interference stack. It is assumed in that example that only the surface coating 5 is hydrophobic and oleophobic, and that the layers 7 of the eyeglass 1 which are located under said coating 5 are neither hydrophobic nor oleophobic and are able to bind the ink 9 deposited in each detreated zone 6, 11.

[0057] Thus, the marking depth may be comprised between 0.01 m and 10 m and more particularly between 0.5 m and 5 m. In the second depth range, the bottom 10 of the detreated zone 6, 11 is present in the varnish. The detreated zone 6, 11 passes through the interference coating but does not reach the substrate. In one particular example, the marking depth is close to 1 m, or even close to 2 m.

[0058] When the detreated zone 6 is a macroscopic recessed print, the laser beam is programmed to scan the surface of the eyeglass 1 and to make a plurality of passes over the eyeglass 1, said beam removing a bit more material from the eyeglass 1 on each pass in order to reach a layer for binding the ink 9, which layer is located under the surface coating 5. The movements of the laser beam over the eyeglass 1 are programmed to produce the pattern 4 or macroscopic element of said pattern 4 to be drawn on the eyeglass 1.

[0059] With reference to FIGS. 4 and 5, according to another embodiment of a marking process according to the invention, the pattern 4 or the macroscopic element of said pattern 4 is made up of a plurality of separate discrete detreated zones 11 that may be likened to pixels. In this configuration, each detreated zone 11 is a hollow well having substantially the same dimensions as those of the laser beam, at the point of impact of the laser beam with the surface 2 of the lens 1. In other words, according to one variant embodiment of a marking process according to the invention, each well 11 is almost cylindrical, the diameter of each of said wells 11 being substantially equal to the diameter of said beam at the point of intersection of the beam with the surface 2 of the lens 1. In this example, each well 11 is gradually produced by way of a plurality of successive irradiations by the laser beam, without movement of said beam over the eyeglass 1.

[0060] According to a first preferred embodiment of a process according to the invention, the wells 11 may be organized so as to adjoin, two successive wells 11 following one directly after the other without any thickness of material arranged therebetween. The total area of surface presented by the adjoining wells 11 exhibits a certain adherence with respect to the deposited ink 9, and thus allows the latter to be effectively bound. In this configuration, it is preferable to deposit one ink 9 of a given colour to obtain a monochromatic pattern 4, because two inks of different colours would be liable to mix in these adjoining wells 11.

[0061] With reference to FIGS. 4 and 5, according to a second preferred embodiment of a process according to invention, the discrete wells 11, also identified as craters, do not adjoin and have a thickness 12 of material between them. In this configuration, since the wells 11 are separated from one another, it is possible to deposit at least two inks 17, 18 of different colours in said wells 11, because the risk of said two inks 17, 18 mixing is minimal or even zero. In an embodiment, the wells 11 are separated one from the other by a part comprising some hydrophobic and/or oleophobic surface coating 5, either apparent or under some temporary material.

[0062] According to another embodiment, the wells 11 adjoin to the extent that they are no longer individually distinct and separate from one another. They then define a macroscopic recessed print the bottom of which is smooth.

[0063] With reference to FIG. 2, according to an embodiment of the invention, whatever the shape and size of the detreated zone 6, 11, the bottom 10 of said detreated zone 6, 11 corresponds to the deepest portion 13 of this detreated zone 6, 11, which is generally flat or approximately flat, and to a portion 14 of the side wall delimiting the detreated zone 6, 11 and originating level with said deepest portion 13.

[0064] The step of depositing the ink 9 in each detreated zone 6, 11 is advantageously but nonlimitingly carried out by means of a technique chosen from pad printing and inkjet printing.

[0065] Preferably, the ink 9 chosen for a depositing process according to the invention is an ink that is able to be set a few minutes after its deposition on the eyeglass 1. This ink 9 may for example be set by drying, thermosetting or polymerisation.

[0066] Schematically, the pad-printing technique consists in depositing, by means of an inking stamp, the ink 9 on a macroscopic pattern created in the optical eyeglass 1. Preferably, once the pattern 4 to be deposited on the eyeglass 1 is known, the inking stamp is then dimensioned to cover an area, for example a simple geometric shape, for example a parallelepipedal shape or an ovoid shape, that is slightly larger than that of said pattern 4 and that frames said pattern 4. In this way, with reference to FIG. 3, the ink 15 will then overflow from the detreated zone 6, 11. Although it is not particularly sought to deposit ink 9, 15 in excess in a process according to the invention, it may however prove to be advantageous to deposit a superabundance of ink 9, 15 because it makes it possible to ensure that the ink 9 will at least completely fill each detreated zone 6, 11. Two additional advantages are obtained thereby: [0067] It is possible to use a given stamp for two or more different or even very different patterns 4. [0068] Moreover, by means of this process, it is not necessary to achieve a high level of precision during the deposition of the ink 9, while also maintaining a high level of precision in the position of the inked mark on the lens 1.

[0069] When the ink 9 is induced to overflow from the pattern 4, a marking process according to the invention implements a step of removing the ink deposited in excess. This removing step may for example be carried out by means of an adhesive fabric or piece of paper placed on the surface of the eyeglass 1. The ink 9 that has overflowed from the detreated zone 6, 11 then attaches to the adhesive material. The removal of the adhesive material from the eyeglass 1 is accompanied by the removal of the ink 9, 15 deposited in excess that is bound to said adhesive material. This step of removing ink 9, 15 deposited in excess is advantageously carried out while the ink 9 is still liquid or soft. Specifically, if the removal is performed when the ink 9 has set, it is likely that the removal of the adhesive material will lead not only to the removal of the ink 9, 15 deposited in excess, but also to the removal of a portion of the ink 9 directly forming the pattern 4. The pattern 4 would then be damaged in some parts or even no longer be correctly visible and/or recognisable.

[0070] The pad printing method is a blanket method allowing ink 9 to be simultaneously deposited over a large area encompassing the pattern 4 to be reproduced on the eyeglass 1. Pad printing does not allow an eyeglass 1 marking pattern 4 of at least two different colours to be easily obtained because the inking stamp is assumed to carry only a single type of ink 9 of a given colour. With this technique, the pattern will generally be monochromatic.

[0071] Inkjet printing is an alternative to deposition by pad printing, but its implementation is more precise and therefore cleaner. Specifically, contrary to the deposition of ink by means of pad printing, with ink jets the deposition is carried out discretely, by means of ink droplets. Thus, for a pattern 4 made up of a single macroscopic recessed print, a plurality of droplets of ink 9 are deposited in the recessed print representative of the pattern 4, in order to completely fill said recessed print. In the case where the recessed print representative of the pattern 4 is made up of a plurality of discrete detreated zones 11 each forming a single discrete well 11, or pixel, one droplet of ink 9 is deposited in each discrete well 11. The discrete wells 11 may advantageously be dimensioned so that the volume of each droplet of ink 9 is slightly larger than the volume of one well 11 so as to guarantee that each well 11 will be completely filled by one droplet of ink 9. Alternatively, the size of the droplets may be adapted so as to have a slightly larger volume than the volume of the wells 11 used to form the pattern 4. This technique of depositing with jets of ink 9 makes it possible to easily produce patterns 4 which may be of at least two different colours 17, 18, in particular when the inkjet technique is coupled with detreated zones composed of wells 11, either adjoining, with only a small ridge separating each well 11, or fully separated. These two-colour or multicolour patterns 4 are preferably obtained when they are made up of a multiplicity of separate wells 11, in each of which ink 9, 17, 18 of a quite specific colour may be deposited. It is desirable for the discrete wells to be separate in order to prevent the two inks 17, 18, or at least two droplets of ink of different colours from mixing. With the inkjet depositing technique, it is also possible to make provision for the ink 9, 17, 18 to overflow from each well 11. A marking process according to the invention then implements a step of removing the ink 15 deposited in excess, which step is identical to that described above for the deposition of ink 9 by pad printing.

[0072] A marking process according to the invention is advantageously carried out by means of an apparatus comprising means able to emit a laser beam, means able to deposit an ink and a holder able to hold the eyeglass 1. In this apparatus, the holder remains stationary throughout the duration of the marking process, and said means are movable in order to be alternatively placeable level with an identified zone of the eyeglass in order to allow the eyeglass to be marked. Thus, when it is necessary to produce a detreated zone 6, 11 in the eyeglass 1, the means able to emit a laser beam are placed level with that zone of the eyeglass in which said detreated zone 6, 11 must be produced and controlled to insulate said zone. When the ink 9, 17, 18 must be deposited in a detreated zone of the eyeglass 1, the means able to emit a laser beam are withdrawn in order to make room for the means able to deposit ink 9, 17, 18 in the detreated zone 6, 11. All these operations of moving the various means back-and-forth are programmed in advance depending on the shape and dimensions of the pattern 4 to be deposited on the eyeglass. The characteristics of the pattern 4 and the one or more colours to be used constitute input data of this apparatus. The fact that the holder for the eyeglass 1 remains stationary (immobile) throughout the duration of the marking process allows a constant frame of reference to be preserved during all the operations to be carried out on the eyeglass 1, guaranteeing exactness, precision and therefore a good reproducibility for the marking.

[0073] Alternatively, this advantage may be unused and those two steps may be replaced by a step of displacing the eyeglass 1 first toward one area of the apparatus comprising the means able to emit a laser and then toward an area of the apparatus comprising the means able to deposit ink 9, 17, 18.

[0074] A mark on an optical eyeglass 1 produced by means of a process according to the invention is intended to be permanent and to last the entire lifetime of the eyeglass 1. It is not a provisional mark intended to be changed on a simple request or a mark intended to help to position the lens in an edger and intended to be removed after an edging step has been done or before mounting the lens into a frame, or at least before providing the spectacles comprising the eyeglass to its intended wearer.

[0075] The term MARK appearing on the eyeglasses in FIGS. 1A and 1B is a purely illustrative example of a pattern 4 that could be produced by means of a marking process according to the invention. This term is not associated with any particular commercial entity, and is representative of no particular trademark or logo. In this example, each letter represents one macroscopic element of the final pattern 4 to be produced.

[0076] The marking process according to the invention may be carried out for example by means of a pulsed laser emitting a beam at a wavelength of 266 nm with pulses of 1 ns duration, an energy per pulse of 20 J and a marking point area of about 20 m diameter. The energy and the number of repetitions may be adjusted depending on the number of layers of the multilayer and the nature of these layers. In one particular exemplary embodiment, the number of repetitions at each marking point is four.

[0077] According to more generic embodiments of the invention, the electromagnetic beam is emitted in pulses, and the energy per pulse is comprised in the interval 1 to 50 J and for example equal to 5 J, 10 J, 15 J or 20 J.

[0078] The detreatment can be achieved by local exposure to a focused beam of pulsed ultraviolet laser radiation having at least the following parameters: [0079] radiation of wavelength comprised in the interval 200 to 400 nm and preferably 200 to 360 nm and for example 213 nm, 266 nm or 355 nm; [0080] a pulse duration comprised in the interval 0.1 to 5 ns; and [0081] at the marking point, a beam diameter comprised in the interval 20 to 50 m.

[0082] According to one advantageous embodiment, the focused beam furthermore has at least one of the following parameters: [0083] a pulse frequency comprised between about 100 Hz and about 10 kHz; and/or [0084] a peak power comprised between about 2.5 kW and about 1 MW.

[0085] According to one exemplary embodiment, the device is configured so that the focused beam of ultraviolet laser radiation has at least one of the following parameters: [0086] the pulse frequency is comprised between about 100 Hz and about 1 kHz; and/or [0087] the peak power is comprised between about 10 kW and about 100 kW; and/or [0088] a pulse duration comprised between about 0.5 ns and about 2 ns.

[0089] The expression peak power is here understood to mean the instantaneous power of the laser during a pulse. It is to be contrasted for example with what is referred to as effective power, which is an average of the power over time; the latter is therefore generally much lower since it is by definition zero between pulses.

[0090] According to one embodiment, the device includes a solid-state laser source configured to emit a pulsed infrared radiation beam, and a multiplier, positioned at the output of the laser source and configured to multiply a radiation frequency of the infrared beam emitted as output from the laser source, preferably by a factor comprised between three and ten.

[0091] In the context of the invention, the expression solid-state laser source is understood to mean a laser source the gain medium of which, also referred to as the active medium, is either a solid or ionic crystal or an optical fiber. Solid-state laser sources are thus different from lasers having a liquid or gaseous gain medium. In French, the term used to designate solid-state lasers is laser milieu solide.

[0092] The multiplication factor is here chosen as equal to four, but it may, generally, depending on the initial wavelength of the laser source, be a factor comprised between three and ten inclusive and preferably between three and five.

[0093] The multiplier is configured to form, by coupling to the laser source, a beam of ultraviolet laser radiation having a wavelength comprised between about 200 nm and about 300 nm, more preferably between about 208 nm and about 220 nm, for example about 213 nm or about 210 nm or about 209.4 nm or even between about 260 nm and about 270 nm, for example about 261.7 nm or about 263 nm or about 266 nm.

[0094] The laser source and the multiplier are two elements that may be separate, or contained in the same housing. If needs be, the combination of a solid-state laser and a multiplier in the same housing allows a possibly very compact device to be obtained and therefore one that is transportable and transposable at will, both on a manufacturing line and in the laboratory for example.

[0095] The laser source is for example an Nd-YAG laser and the multiplier is for example configured to quadruple the frequency of pulses output from the Nd-YAG laser.

[0096] An Nd-YAG source may principally emit a beam at the wavelength 1064 nm, thereby making it possible, with coupling to a quadrupler, i.e. a factor-four multiplier, to obtain a beam of laser radiation with a wavelength of about 266 nm, or of about 213 nm with a quintupler, i.e. a factor-five multiplier.

[0097] According to one particular exemplary embodiment, the Nd-YAG laser with a multiplier is a Crylas eco mopa UV laser (266 nm).

[0098] According to one alternative, the laser source is for example an Nd-YVO4 laser. Such a laser source for example emits radiation of a wavelength of about 1064 nm, which, coupled to a quadrupler, makes it possible to obtain laser beams of wavelength of about 266 nm, or of about 213 nm with a quintupler.

[0099] According to another alternative, the laser source is for example an Nd-YLF laser. Such a laser source for example emits radiation of a wavelength of about 1047 nm or radiation of a wavelength of about 1053 nm depending on its operating mode, which, coupled to a quadrupler, makes it possible to obtain laser beams of wavelength of about 262 nm or 263 nm, or even of about 209 nm or 210 nm with a quintupler.

[0100] Generally, the source and the multiplier are configured to emit ultraviolet radiation comprised between 10 and 120 J.

[0101] Preferably here, according to particular arrangements, the laser source is configured to emit a pulsed beam of laser radiation having an energy per pulse comprised between about 30 J and about 80 J and preferably higher than 40 J. The energy of the focused beam of ultraviolet radiation would then be comprised between about 5 J and about 65 J.

[0102] According to one preferred method of implementation, the device includes an optical assembly provided with an F-theta lens, which lens is configured to focus a beam of ultraviolet laser radiation onto a focal plane of the F-theta lens with a focused beam diameter in the focal plane of the order of about 20 m to about 50 m, 30 m for example.

[0103] The F-theta lens is for example located at the output of the optical assembly.

[0104] Here, the expression F-theta lens is understood to mean a flat field lens that by definition has a focal plane at a distance referred to as the focal length. The focal length is for example about 160 mm in one preferred exemplary implementation but may more generally be comprised between 100 mm and 200 mm.