WO2010084272A1

WO2010084272A1 - Method and device for printing on ophthalmic glass

Info

Publication number: WO2010084272A1
Application number: PCT/FR2010/000062
Authority: WO
Inventors: Henri Dominico Demarchi; Giuseppe Naccarato; Khalid Zahouily
Original assignee: Tecoptique
Priority date: 2009-01-26
Filing date: 2010-01-25
Publication date: 2010-07-29
Also published as: FR2941398B1; FR2941398A1

Abstract

The invention relates to a method for printing on an ophthalmic glass (1), that comprises : forming a pattern by depositing a first photo-polymerisable ink on the surface of the ophthalmic glass (1); polymerising the first ink using a UV-visible light source (14); making an over-print on at least a portion of the pattern (21) using a second transparent ink (23).

Description

Method and device for printing on an ophthalmic lens

Technical field of the invention

The invention relates to a method of printing on an ophthalmic lens which comprises producing a pattern by depositing a first photopolymerizable ink on the surface of the ophthalmic lens followed by the polymerization of the first ink by means of a source of UV-visible light.

The invention also relates to an inkjet printing device of a pattern on an ophthalmic lens for implementing the method which comprises a printing station having at least one inkjet printing head. and a UV-visible light source which is integral with the print head.

State of the art

As shown in FIG. T, the pad printing on a naked, varnished, hydrophobic or superhydrophobic surface-coated ophthalmic lens 1 is commonly used to apply an inscription on the ophthalmic lens, in the form of a marking essential to the identification of the latter. The marking of an ophthalmic lens 1 is essentially carried out on its convex part. The marking shown in Figure 1 may be permanent or temporary. This marking includes commercial elements (logo of the manufacturer, name of the glass, advertising message etc.) but also technical elements that will allow the mounting of the glass on its mount. After marking, the temporary marking is eliminated by the optician thanks to a specific product such as an organic solvent or aqueous solutions likely to dissolve or pick up the ink used for marking. The marking of the progressive lenses generally contains at least three temporary technical marking elements which are a centering cross 3, a prism reference point (PRP) 4 and an axis 5. These three temporary marking elements 3, 4 and 5 allow the optician to quickly locate the areas of control of the ophthalmic lens 1 which are, in particular, the near vision power control center 6 (VP) and the far vision power control center 7 (VL). These temporary marking elements 3, 4 and 5 are located on a central zone 8 formed by a central band at the convex portion of the ophthalmic lens 1 (FIG. 1).

As shown in FIG. 2, for its transport, each ophthalmic lens 1 is conventionally packaged in a paper packaging bag 9 and then packaged in cartons. The vibrations produced during the transport of the ophthalmic lenses 1 under this packaging cause the friction between the packaging bag 9 and the convex part of the ophthalmic lens 1, in particular on the central zone 8. This prolonged friction frequently causes the marks to be erased progressively. located at the central zone 8 and affect the legibility of the marking.

On the other hand, it is known that an ink layer can be deposited by ink jet on a buffering plate (see DE 4020223 and DE 3820340) or directly on the buffer itself (see US 6840167). In the latter case, the pattern is printed through a print head on a flat surface of a stamp. The stamp is then applied to the object to receive the pattern to transfer the ink. Printing with a flat-shaped pad has the disadvantage that air cushions are formed between the pad and the object, and the quality of the affixed pattern is thus poor. In an attempt to remedy this, US 6,840,167 proposes to deform the flat surface of the buffer by means of a pusher element or hydraulically. However, this deformation at the back of the silicone pad causes uncontrolled deformation of the image printed on the front. This results in risks of geometric deformation and crazing patterns. The implementation of these known technologies remains complex.

In addition, obtaining a marking which adheres too strongly to the surface of the ophthalmic lens 1 or embedded in the glass 1 is unacceptable because it prevents any subsequent erasure of the primordial temporary marking to preserve and / or not affect the optical properties ophthalmic glass 1.

Inkjet printing is another common printing technique commonly controlled by a computer, which makes it possible to print different patterns with great flexibility, and very quickly. However, this printing technique is still in its infancy in the field of eye optics as the difficulty is great to find the right compromise between good adhesion and ease of cleaning. The use of a water-based printing ink directly on the glass provides a pattern quality that does not have the expected accuracy because such ink has poor adhesion and wettability qualities on the glass. hydrophobic or superhydrophobic coating of ophthalmic lenses. Direct ink jet printing on hydrophobic or superhydrophobic glass causes wettability problems and poor adhesion to the ophthalmic lens coating. The ink fades at the slightest friction and the drops, which should form a continuous line, are found in a discontinuous line and irregular. This results in poor contrast and insufficient definition. Solvent inks remain the most widely used for printing ophthalmic lenses by pad printing. These inks contain a solvent which is removed by evaporation after deposition on the glass. The solvent therefore does not participate in the intrinsic properties of the ink and is present only temporarily in the ink.

WO2006 / 119733 discloses a method of ink jet printing from solvent ink in which the ophthalmic glass is heated prior to the deposition of the ink. The method comprises detecting, by means of an optical device, microgravures to determine their positions and. locate the print area. The ink is then deposited at the printing area of the preheated glass. This preheating promotes the solidification and the taking of the ink on the hydrophobic coating of the ophthalmic glass. The ophthalmic lens is preheated by means of a heating element, such as an infrared radiator or a hot air fan, disposed above the ophthalmic lens.

In addition to the fact that the use of solvent ink requires handling precautions because of their flammability and sometimes toxic, these solvent inks have the characteristic of drying quickly. In particular, inkjet solvent inks dry at the orifice of the nozzles of the print head as soon as they come into contact with the air. Dry ink has no influence on stationery as the nozzles are very close to the paper to be printed and the media is flat. This is not the case in optical glasses where the glass can be strongly curved. As shown in FIG. 3, the marking is made by moving the ophthalmic lens 1 relative to the fixed printing head 10, in a direction represented by a horizontal arrow in FIG. 3. The printing head 10 projects droplets of ink 11 in the form of an ink jet 12 for each successive position of the glass P ₁ , P ₂ , P ₃ , P ₄ to P _x . To obtain a good definition of the marking whatever the curvature, for example, for a low curvature C ₁ or a strong curvature C ₂ of the ophthalmic lens 1 (FIG. 3), each ink jet 12 must ideally be parallel to the other ink jets 12 obtained at the different successive positions P ₁ , P ₂ , P ₃ , P ₄ at P _x . However, in use, as shown in FIG. 4, ink residues 13 formed at the level of the nozzles of the print head 10 cause deviations Cc ₁ , α ₂ of the ink jets 12. The angles Ct ₁ and α ₂ vary according to the size of the residue 13. For a large residue deposition 13, the orifice of the nozzle can even be obstructed (P ₃ in FIG. 4). A noticeable deterioration of the quality of the printing is thus noted with the use.

More recent work has proposed the use of ultra-violet (UV) photopolymerizable inks for ophthalmic glass printing. In particular, WO2006 / 101526 discloses a method of ink jet printing on ophthalmic lenses from UV ink. Nevertheless, the adhesion of the ink droplets to the ophthalmic lens, in particular superhydrophobic glasses, is not sufficient to withstand the friction to which the ophthalmic lens is subjected in its packaging.

Furthermore, the inkjet printing process, in particular from UV ink causes difficulties in eliminating temporary marking elements. As shown in FIG. 5, the marking by inkjet printing method gives a marking in the form of juxtaposition of the ink droplets 11. The ink droplets 11 having very small diameters of the order of a few microns, their juxtaposition (without contact) gives an apparent form of continuous lines. After cleaning the ophthalmic lens 1, it is found that the elimination by conventional methods of temporary marking elements is not easy and leaves marks on the glass. As illustrated in Figure 6, during cleaning, the ink droplets 11 are dispersed and some of them remain on the ophthalmic lens 1 after cleaning. The residual ink droplets 11 form micropoints which are very difficult to identify in individual form and often forgotten during the cleaning process of the ophthalmic lens 1.

Object of the invention

The object of the invention is to develop a printing process on a simple ophthalmic lens to implement, to obtain a good contrast while improving the accuracy and quality of the affixed patterns.

The object of the invention is also to propose a printing process which makes it possible to obtain a marking that is easy to subsequently remove, while having good wear resistance and excellent resistance to any type of ophthalmic glass, in particular to a glass superhydrophobic.

Another object of the invention is to provide an inkjet printing device of a pattern on an ophthalmic lens for the implementation of the high-performance method and conferring a flexibility of use.

According to the invention, this object is achieved by a printing method and a printing device according to the indexed claims.

In particular, this object is achieved by the fact that an overprint is performed on at least a part of the pattern after polymerization of the first ink, said overprinting being performed with a second transparent ink. Brief description of the drawings

Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention given by way of non-limiting example and represented in the accompanying drawings, in which:

- Figure 1 shows schematically and in top view, an ophthalmic lens with a marking. - Figure 2 shows, schematically and in section, an ophthalmic lens in its packaging.

- Figures 3 and 4 show, schematically and in profile view, an ink jet printing device of an ophthalmic lens with a solvent ink. - Figures 5 and 6 show, schematically and in top view, an ophthalmic lens respectively before and after cleaning a temporary marking.

- Figures 7 to 10, 12 and 13 show, schematically and in profile view, the various steps of a printing method according to a particular embodiment of the invention.

- Figure 1 1 shows, schematically and in sectional view, a printing device according to Figure 7.

FIG. 14 represents, schematically and in section along the axis AA, a partial view of the device according to FIG. 13. FIG. 15 is a diagrammatic plan view of an ophthalmic lens during a cleaning operation.

- Figures 16 to 19 show, schematically and in profile view, the various steps of a printing method according to a particular embodiment of the invention. - Figures 20 and 21 show, schematically and in section along the axis BB, a partial view of the device according to Figure 19. Description of a preferred embodiment of the invention

Referring to FIGS. 7 to 10, an ink jet printing device of a pattern on an ophthalmic lens 1 comprises a UV-visible light source 14 and a printing station 15 having a print head. 16 to ink jet, for example of a known type drop on demand (thermal, piezoelectric or electrostatic) or by magnetic deflection.

According to a preferred embodiment, the ophthalmic lens 1 is hydrophobic or superhydrophobic and has a hydrophobic or superhydrophobic surface coating 17.

The UV-visible light source 14 is integral with the print head 16 during the movement so that the assembly can be moved along the vertical axis and / or the horizontal axis and positioned simultaneously and in a coordinated manner. The UV-visible light source 14 is also preferably located as close as possible to the print head 16, for example, at a distance from the print head 16 of between 1 and 10 mm. preferably 5 mm.

As shown in FIG. 7, the UV-visible light source 14 is placed above the ophthalmic lens 1 at a small distance d ₂ from the ophthalmic lens 1, more particularly from the top of the lens 1 (at the top of FIG. 4 ) to uniformly irradiate a portion of the surface of the glass 1 on which the ink is deposited to achieve a pattern. The fact of having a distance d ₂ as small as possible makes it possible to avoid the reflection on the ophthalmic lens 1 of the light emitted by the UV-visible light source 14. The distance d ₂ is advantageously between 1 mm and 5mm, preferably 1mm. The printing station 15 is also placed above the glass 1 at a distance d ₂ from the top of the glass 1 of between 1 mm and 5 mm. The printing station 15 and the UV-visible light source 14 are placed above the ophthalmic lens 1 at the same distance d ₂ . This short distance d ₂ reduces the risk of deflection of the ink jets 12. The ink jets 12 projected by the print head 16 for each position P _{0 to x)} of the ophthalmic lens 1 are thus perfectly parallel (FIG. ).

As shown in FIG. 7, the printing process on an ophthalmic lens 1 comprises a first step of positioning the ophthalmic lens 1 on a support 18. The ophthalmic lens 1 is typically held in position on the support 18 by suction thanks to a through channel 19. The ophthalmic lens 1 is then plated on the upper part of the support 18 (top figure 7).

The top of the ophthalmic lens 1 is then detected, for example, by a capacitive sensor, electronic or a laser beam in order to wedge the print head 16 of the printing station 15 at a predetermined distance d ₂ from the top of the ophthalmic lens 1 (vertical arrow in Figure 7).

As shown in FIGS. 8 and 9, a pattern is produced by depositing a first photopolymerizable ink, in the form of ink droplets 11, on the surface of the hydrophobic or superhydrophobic surface coating 17 of the ophthalmic lens 1.

The printing is not preferably performed following the curvature of the ophthalmic lens 1. The ophthalmic lens 1 is subjected to the ink jets 12 of the fixed print head 16 (Figure 8). The printing station 15 remains stationary throughout the following operations. Only the support 18 moves in a horizontal direction illustrated by an arrow in FIG. 9. The printing makes it possible to maintain a constant distance between the print head 16 and the support 18.

According to a variant not shown, the support 18 is fixed and the printing station 15 moves without following the curvature of the glass 1 in a horizontal direction.

The first ink 20 is polymerized by irradiation as soon as it is deposited on the ophthalmic lens 1, by means of the UV-visible light source 14. After the first droplets of the first ink 20 have been deposited, the support 18 moves in the horizontal direction (arrow in FIG. 9) exposing the ink deposit 20 to the radiation of the UV-visible light source 14 (FIG. 10).

As shown in FIG. 10, the UV-visible light source 14 emits light towards the surface of the ophthalmic lens 1, preferably parallel to the ink jets 12 projected by the print head 16.

The ink droplets 11 of the first irradiated P-deposited ink ₁ solidify by a photopolymerization reaction to form the desired printed pattern 21. An ultra fast ink setting is thus favored.

The operation is then repeated for the following P ₂ to P _{x positions} according to the topography of the desired pattern. These consecutive operations being fast, the ink droplets 11 do not have time to coalesce or roll. The displacement of the ophthalmic lens 1 from one position to another is rapid and, advantageously, constitutes a continuous movement.

The displacement of the support 18 is controlled by a computer according to the topography of the pattern to be printed on the ophthalmic lens 1. The inkjet printing program can take into account the deformation induced by the curvature, weak C ₁ or strong C ₂ , of the glass 1. Thus, the deformation of the image can be taken into account by the printing program according to any known method for reconstructing the topography of the transfer pattern compensating for this deformation and obtain the desired pattern on the ophthalmic lens 1.

According to one variant, the printing is not performed by digital anamorphism. By numerical anamorphism, we mean an impression that digitally distorts the geometric shapes of the patterns before printing to finally obtain conformal printed geometric shapes.

The first ink used is a photopolymerizable ink which cures under the effect of exposure to UV-visible light in the presence of air and at room temperature. The polymerization is almost instantaneous, the passage of the molecule to the polymer material taking place in a few tenths of a second under intense irradiation. This polymerization consumes, therefore, very little energy. Indeed, the first ink 20 is originally in the form of monomers and / or oligomers. The latter polymerize and crosslink by irradiation, causing solidification of the first ink 20. This produces a dry ink almost instantaneously and without spending a lot of energy. The first photopolymerizable ink is, preferably, an ultraviolet (UV) drying ink or a "dual cure" ink, ie thermal and photochemical drying. The photopolymerizable inks consist of both radical and / or cationic monomers, oligomers, a photoinitiator system, pigments and additives.

The UV-visible light source 14 emits a wavelength in adequacy with the emission spectrum of the photoinitiator system used in the formulation of the first ink 20. To facilitate the subsequent erasure of the printed pattern 21 on the ophthalmic lens 1, the intensity of the UV-visible light source is determined, advantageously, so as to weakly crosslink the portion of the first ink 20 in contact with the glass 1 and strongly the portion of the first ink 20 at the surface of the printed pattern 21. It being understood that the crosslinking of a polymer determines the mechanical characteristics of the polymer. Thus, to create a polymerization gradient within the printed pattern 21 and find a compromise between the rapid polymerization of the first ink 20 at the surface and an optimum adhesion to the glass 1, the choice of the photoinitiator system and the length of the film can be combined. wave selected from UV-C ₁ UV-B and / or UV-A. As a result, the order of exposure of the sample to the radiation influences the surface properties of the first ink 20 while facilitating the essential cleaning operation of the ophthalmic lenses 1 after the shaping steps thereof. The glass 1 may be, for example, subjected to a first UV-A irradiation and then to a second UVC and / or UV-B irradiation or vice versa.

The photopolymerization reaction of the first ink 20 is carried out at room temperature with resins containing no or very little solvent, which reduces the emission of polluting vapors. However, in order to adjust their viscosity, it is possible to add a very small amount of solvent, in specific proportions of between 1% and 10%, preferably between 1% and 7% in order to combine the advantages of the two types of solvent. photochemically and / or solvent-drying inks.

For a UV curing ink, the first ink cures by exposure to electromagnetic radiation corresponding to the visible UVA, UVB ₁ UVC of UV. The irradiation doses as well as the wavelengths are also chosen so as not to damage or degrade the properties of the hydrophobic or superhydrophobic treatment of the ophthalmic lenses 1. According to a particular embodiment, the first ink 20 is a UV ink and the UV-visible light source 14 is a UV-visible lamp. For example, a UV light generator with a quartz optical fiber light guide manufactured by Hamamatsu under the reference LC8 is used with a UV ink. The UV light intensity is preferably between 20 and 25%. The intensity is a function of the hydrophobicity of the glass 1, which is greater for hydrophobic glasses 1 than for glasses that are little or not hydrophobic. By way of example, the intensity is set at 20% for a weakly hydrophobic glass, 23% for a hydrophobic glass and 25% for a superhydrophobic glass.

As shown in FIG. 11, the UV-visible light source 14 preferably has a bar-shaped shape with a rectangular cross-section of a width and a length, respectively, of between 1 mm and 2 mm, and 50 mm. and 70mm. The rectangular cross-section of the UV-visible light source 14 preferably has a width of 1 mm and a length of 65 mm.

According to an alternative, the light line coming from the UV-visible light source 14 advantageously has a width of between 1 mm and 2 mm and a length of between 55 mm and 65 mm. The light line preferably has a width of 1 mm and a length of 65 mm. According to this particular embodiment, the UV-visible light source 14 is in the form of a strip having a rectangular cross section with a width and a length, respectively, of between 10 mm and 20 mm, and 60 mm and 70 mm.

In addition, the UV-visible light source 14 advantageously comprises a light line exit aperture 22 having a narrower slot shape in the center than at each end of said slot (at the top and at the bottom of the slot). 11), so that the narrow portion of the slot is above the central zone 8 (FIG. 11).

As illustrated in FIG. 10, for a constant speed of displacement of the support 18, the ink droplets 11 deposited at the periphery of the ophthalmic lens 1 (on the left in FIG. 10) are insolated with a lower intensity than those located in the center. of glass 1 because the distance d ₃ separating the ink droplets 11 from the UV-visible light source 14 is greater than the distance d ₂ .

The resistance of the ink droplets 11 to the ophthalmic lens 1 can be significantly improved by varying the exposure time of the ink droplets 11 to the light emitted by the UV-visible light source 14. , the crosslinking of the first ink 20 is not homogeneous depending on whether the printed pattern 21 is made in the center or on the periphery of the ophthalmic lens 1. The distance between the print head 16 and the ink droplets 11 deposited on the Ophthalmic lens 1 from the first ink 20 varies depending on the position of the ink droplets 11 on the ophthalmic lens 1 (peripheral or central) due to the curvature of the glass 1 and that the distance between the print head 16 and the support 18 remains constant.

According to a particular embodiment, the outlet opening 22 of the light line passes less light into the center of the UV-visible light source 14. Thus, the ink droplets 11 located in the central zone 8 of the ophthalmic glass 1 are insolated during a shorter irradiation time than ink droplets 1 1 deposited outside this zone 8.

As shown diagrammatically in FIG. 11, it is also possible to adapt the speed of displacement of the support 18 as a function of the distance separating the UV-visible light source 14 and the surface of the ophthalmic lens 1, in order to irradiate the periphery patterns for a longer time. glass 1 (left and right of the glass in Figure 11) and intervene on the polymerization rate of the first ink 20.

By combining the adaptation of the speed mentioned above and the particular shape of the aperture 22 of light line output, significantly improves the strength of the printed pattern 21 on the ophthalmic lens 1 and homogeneity of the marking.

As shown in FIGS. 12 and 13, overprinting is performed on at least a portion of the pattern 21 thus obtained after polymerization of the first ink 20. The overprinting is performed with a second transparent ink 23.

The second ink 23 is an unpigmented ink selected from water-based, solvent-based, ultraviolet-drying, "dual-cure" inks and varnishes.

The second ink 23 may comprise a base identical to that of the first ink 20 in order to reduce the interactions between the first and second inks, respectively 20 and 23, and to improve the cohesion between the two inks, 20 and 23.

According to a preferred embodiment, the second ink 23 is a solvent ink. Solvent inks being easy to remove, there is surprisingly a synergy between the first and second inks, respectively 20 and 23, which provides a quality marking with good contrast and a good definition and a good hold on the glass 1 while still being easy to remove.

The characteristics of the two inks, 20 and 23, i.e., the ability of solvent inks to be easily removed and the quality of pattern definition 21 for UV inks surprisingly combine to provide a marking having improved properties.

Moreover, the quality of the overprint is not as important as for the printing of the pattern 21. In fact, the second ink 23 is transparent and does not have a function of readable marking. As a result, the presence of deviations during this overprinting operation, which are common with solvent inks, has little effect on the quality of the marking obtained by this process.

The superimposition is preferably performed on at least the entire printed pattern 21. In particular, the overprint covers the printed pattern 21 and may also extend over the entire pattern 21 and extend beyond the shape of the printed pattern 21. Nevertheless, the overlap of the overprinting will be as low as possible to avoid additional production costs. Preferably, the superimposition is superimposed exactly with the printed pattern 21 obtained by the first printing.

According to a particular embodiment shown in FIGS. 12 and 13, overprinting is a superimposition by pad printing. After polymerization of the first ink 20, the support 18 is moved, to position the ophthalmic lens 1 under a buffer unit 24. An overprint according to a conventional pad printing method is performed on the printed pattern 21, from the second ink 23 transparent. The second ink 23 is applied by means of the buffering unit 24, promoting penetration and adhesion to the ophthalmic lens 1.

As shown in FIG. 14, the printed pattern 1 by the first printing is encapsulated by the second transparent ink 23 and forms an assembly 25. The second ink 23 binds the droplets forming the printed pattern 21 and improves the adhesion of the printed pattern 21 on the surface of the glass Ophthalmic 1, especially when there is a surface coating 17, hydrophobic or superhydrophobic.

Moreover, it is surprisingly found that the overprinting of the printed pattern 21 favors the elimination of this pattern 21. Indeed, as illustrated in FIG. 15, unlike a pattern made by a single jet printing operation. In ink, the assembly has a cohesion of the first and second inks 20 and 23, respectively, which prevents the dispersion of the droplets forming the first ink 20 during the cleaning of the surface of the ophthalmic lens 1.

According to another particular embodiment, the ophthalmic lens 1 is bare, that is to say without hydrophobic, superhydrophobic or anti-reflective coating, for example, a stock or semi-finished glass. The formulation of the first photopolymerizable ink is then adapted to the characteristics of the naked ophthalmic lens. In the absence of a hydrophobic or superhydrophobic surface coating, the printing process involves depositing the first ink directly on the surface of the ophthalmic lens 1.

According to another particular embodiment not shown, the overprint is an overprint by airbrushing. After polymerization of the first ink 20, an overprint according to a conventional airbrushing method is performed on the printed pattern 21, from the second transparent ink 23 forming the medium.

According to another particular embodiment shown in Figures 16 to 19, the overprint is an overprint by ink jet.

Preferably, the overprinting is performed with a second photopolymerizable and transparent ink 23. With the exception of the pigments of which the second ink 23 is devoid, the second ink 23 may be an ink identical at all points to the first ink 20. For example, the first ink 20 may be a yellow UV ink and the second ink 23 the same UV ink, without the yellow pigments.

As shown in FIG. 16, a printing device advantageously comprises a printing station 15 having a first inkjet printing head 26 and a second inkjet printing head 27. As illustrated in Figure 16, the source of UV-visible light 14 is arranged between ^'the first and second print heads, respectively 26 and 27. The first print head 26 is supplied with the first ink and the photopolymerizable 20 second print head 27 is fed with the second ink 23. Preferably, the UV-visible light source 14 is located at the same distance d- from the first and second print heads, respectively 26 and 27.

The first and second printing heads, 26 and 27 respectively, and the UV-visible light source 14 are preferably integral.

As shown in FIGS. 16 to 19, the method according to a particular embodiment comprises a step of producing a pattern 21 by depositing the first photopolymerizable ink on the surface of the ophthalmic lens 1 (FIG. 16) by means of the first print head 26.

As shown in FIG. 16, the support 18 is moved in the direction of the horizontal arrow so as to position the ink droplets 11 under the UV-visible light source 14 to allow the first ink 20 to be irradiated. medium of the UV-visible light source 14.

As shown in FIG. 17, the ink droplets 11 of the first ink 20 polymerize to form the printed pattern 21. The support 18 is then moved in the same direction (arrow on the right in FIG. position the printed pattern 21 under the second print head 27 of the printing device.

As shown in FIG. 18, the overprinting operation is performed on at least a portion of the printed pattern 21. The overprinting is performed with the second transparent ink 23. The displacement of the support 18 is then carried out in the opposite direction (horizontal arrow in FIG. 18), to position the superimposed pattern again under the UV-visible light source 14.

As shown in FIG. 20, the second ink 23 then polymerizes by insolation by means of the UV-visible light source 14.

As shown in FIG. 21, the printed pattern 21 can be covered by the overprint constituted by the second ink 23.

According to an alternative represented in FIG. 22, the superimposition can superimpose perfectly with the pattern 21.

This printing device makes it possible to implement the method described above and, in particular, has the advantage of perfectly superposing the second ink 23 on the first ink 20. The printing device according to this particular embodiment is particularly suitable for very hydrophobic and superhydrophobic ophthalmic lenses 1. It offers great flexibility of use since it does not require a generic model as for pad printing. In addition, the second print head 27 can be used to eject not only UV type inks but also any type of ink, thus giving the printing device a certain flexibility of use. In the event of a change in the nature of the hydrophobic or non-hydrophobic ophthalmic lens 1, it will be possible or not to use the second printing head 27 and / or only modify the formulation of the second transparent ink 23 instead of changing the formulation of the first ink 20. This possibility is very interesting because a lens manufacturer can have several printing machines with different colors of first ink.

This method is particularly advantageous for a pattern 21 made at the level of the sensitive areas of the convex surface of the ophthalmic lens 1, in particular at the central zone 8. It is also possible to deposit several patterns 21 on the same ophthalmic lens 1 and to superimpose only the patterns 21 located in the central zone 8, which are more stressed during their transport than the peripheral zones of the ophthalmic lens 1, not or rarely in contact with the paper forming the packaging pouch 9.

The printing process and the device for the implementation of such a method according to the invention make it possible to solve the problems encountered in printing the specific supports that are ophthalmic lenses 1, especially those having a hydrophobic or hydrophobic surface coating. superhydrophobic. They also have the advantage of combining a use or a simple and economical implementation, and good results as to the quality of the pattern printed on the glass 1. Indeed, the rapid ink intake on the glass 1 makes it possible to perform a contrast and high definition printing, with a print quality on ophthalmic lenses 1 substantially equal to pad printing. The pattern obtained by the printing process according to the invention has excellent resistance to ophthalmic lens 1, in particular glasses 1 having a superhydrophobic coating. This advantage is advantageously combined with ease of cleaning to eliminate temporary marking elements. It thus preserves the smoothness of the marking while improving its adhesion to the glass 1 and greatly facilitating its subsequent removal.

Claims

claims

A method of printing on an ophthalmic lens (1) which comprises producing a pattern (21) by depositing a first photopolymerizable ink (20) on the surface of the ophthalmic lens (1) followed by the polymerization of the first ink (20) by means of a UV-visible light source (14), characterized in that an overprinting is performed on at least a part of the pattern (21) after polymerization of the first ink (20), said overprinting being performed with a second ink (23) transparent.

2. Method according to claim 1, characterized in that the ophthalmic lens (1) comprises a hydrophobic or superhydrophobic surface coating (17).

3. Method according to one of claims 1 and 2, characterized in that the first ink (20) is an ultraviolet drying ink.

4. Method according to one of claims 1 and 2, characterized in that the first ink (20) is a thermal drying ink and photochemical.

5. Method according to any one of claims 1 to 4, characterized in that the pattern is formed at a central zone (8) of the convex surface of the ophthalmic lens (1).

6. Method according to any one of claims 1 to 5, characterized in that the overprinting is performed on at least the entire pattern (21).

7. Method according to any one of claims 1 to 6, characterized in that the overprint is an overprint by pad printing.

8. Method according to any one of claims 1 to 6, characterized in that the overprint is an overprint by airbrushing.

9. Method according to any one of claims 1 to 6, characterized in that the overprint is an overprint by ink jet.

The method of claim 9, characterized in that the second ink (23) is a photopolymerizable ink.

11. The method of claim 10, characterized in that it comprises the following successive steps:

- producing a pattern (21) by depositing the first photopolymerizable ink (20) on the surface of the ophthalmic lens (1),

- polymerizing the first ink (20) by exposure using the UV-visible light source (14),

- superimposition on at least a part of the pattern (21), said overprinting being performed with the second ink (23) transparent and,

- polymerizing the second ink (23) by insolation by means of the UV-visible light source (14).

12. Method according to any one of claims 1 to 11, characterized in that the second ink (23) comprises a base identical to that of the first ink (20).

13. Method according to any one of claims 1 to 12, characterized in that the printing is not performed following the curvature of the ophthalmic lens (1).

14. Apparatus for ink jet printing a pattern on an ophthalmic lens (1) which comprises: a printing station (15) having at least one inkjet printing head (16),

- a UV-visible light source (14) which is integral with the print head (16), characterized in that the UV-visible light source (14) and the printing station (15) are placed above the ophthalmic lens (1) at a distance d ₂ from the top of the lens (1) of between 1 mm and 5 mm and in that the UV-visible light source (14) is located at a distance d-, of the print head (16) between 1 and 10mm.

15. Device according to claim 14, characterized in that the UV-visible light source (14) has a rectangular cross-sectional shape of a width and a length, respectively, of between 1 mm and 2 mm, and 50mm and 70mm.

Device according to one of claims 14 and 15, characterized in that the printing station (15) has a first inkjet printing head (26) and a second printing head (27). in that the UV-visible light source (14) is disposed between the first and second print heads (26, 27).

Device according to one of Claims 14 to 16, characterized in that the UV-visible light source (14) has a light-line exit aperture (22) having a narrower slot-like shape at the center. at each end of said slot.