Method for manufacturing an optical article and associated optical article

Abstract

A method manufacturing an optical article, the method comprising: - providing a base substrate (10) comprising at least one optical surface (12a) and placing the base substrate (10) in a printing assembly (20), - providing a pattern (24, 26) to be printed on the base substrate (10) and determining a printing dot diameter for printing the pattern, - determining (200) a desired surface amount of primer to be deposited, based on the determined printing dot diameter, - depositing (300) a primer layer (30) by depositing a primer with the determined desired surface amount on at least part of the at least one optical surface (12a), - printing the pattern (24, 26) over the primer layer (30) with at least one inkjet printing head (22) depositing at least one dye (34), - placing the base substrate (10) in a heating assembly (40) for a predetermined migration duration, and - removing the primer layer (30).

Description

[0001] TITLE: Method for manufacturing an optical article and associated optical article

[0002] Field of the invention

[0003] The invention relates to the field of inkjet printing on a substrate to manufacture an optical article, such as an optical lens.

[0004] More specifically, the invention relates to a method for manufacturing an optical article comprising printing a pattern on at least one optical surface.

[0005] The invention also relates to an optical article manufactured through such a method.

[0006] Background of the invention

[0007] The local application of a dye to a surface of a lens, notably an ophthalmic lens, allows the application of various images or patterns on one of more of the optical surfaces of the lens in a precise and controlled manner. For example, a homogeneous coating may be applied on the whole optical surface or a part thereof, to tint the lens and apply a colour to the lens. This is useful both for reducing the transmission of light through the glass, as well as changing the aesthetic aspect of the lens and of the final article comprising the lens and constitutes an interesting alternative to tinting of the lens subtract.

[0008] Another application of dyes on a lens is to print more intricate and detailed patterns, such as scriptures and / or logo. This is useful for providing information to the user of the optical article, for example information relative to an optical correction provided by an ophthalmic lens, and also for aesthetic and branding purposes.

[0009] One known advantageous method for applying a dye to an object is inkjet printing, which offers a high degree of control on the application of dye and allows following complex printing pathways that are sometimes required for specific lenses with several different curvatures on the optical surfaces.

[0010] However, the application of a water-based dye on an optical surface of a lens, which is usually hydrophobic, requires a preliminary surface treatment to have a sufficient precision in the application and reduce diffusion of the dye. For example, the use of a plasma for surface treatment has been suggested in document WO 2011 / 122682 A1 .

[0011] Another possibility is the use of a water-based primer layer prior to the printing, said layer being removed after the printing step. An example of such a method is given in document US 2018 / 0292754 A1.

[0012] These methods can be further improved, by enhancing the control of the deposition and diffusion of the dye to achieve a desired level of homogeneity and resolution of the printed layer. Summary of the invention

[0013] An aim of the resent invention is thus to improve the control over precision and homogeneity of the pattern when depositing a dye on a substrate to form such a pattern on at least one surface of the substrate.

[0014] To this end, the invention relates to a method manufacturing an optical article, the method comprising:

[0015] - providing a base substrate comprising at least one optical surface and placing the base substrate in a printing assembly,

[0016] - providing a pattern to be printed on the base substrate and determining a printing dot diameter for printing the pattern,

[0017] - determining a desired surface amount of primer to be deposited, based on the determined printing dot diameter,

[0018] - depositing a primer layer by depositing a primer with the determined desired surface amount on at least part of the at least one optical surface,

[0019] - printing the pattern over the primer layer with at least one inkjet printing head depositing at least one dye,

[0020] - placing the base substrate in a heating assembly for a predetermined migration duration, and

[0021] - removing the primer layer.

[0022] Such a method allows to adapt the primer layer’s thickness to the desired printing dot size, to have either a fine printing dot size for detailed images, or a large printing dot size to improve homogeneity of a homogeneous layer.

[0023] The primer may be a water-based primer.

[0024] This feature improves the affinity between the dye and the primer layer and thus reduces diffusion and movement of the dye after deposition.

[0025] The water-based primer may comprise polyvinyl-alcohol.

[0026] This feature improves stability of the primer layer while keeping the primer easily removable after printing.

[0027] Depositing the primer layer may be achieved using at least one inkjet printing head.

[0028] This feature allows a fine control over the deposition of the dye, which enables the printing of precise and fine patterns as well as homogeneous layers with a same single method.

[0029] The at least one dye may be a water-based dye.

[0030] The pattern may comprise at least one image and / or at least one text character.

[0031] This feature allows the application of a logo and / or a text to the surface of the substrate.

[0032] The pattern may be a uniform layer extending over at least part of the optical surface. This feature allows the application of a light absorbing layer directly on the substrate, as well as aesthetic modifications.

[0033] The method may further comprise a calibrating step, during which several values of surface amount of primer are tested and resulting dye dot size values obtained through inkjet printing are measured.

[0034] This feature allows to easily determine the most efficient surface amount of primer for the desired printing dot size for the specific combination of dye, primer and substrate considered. The method may further comprise a step of drying the primer layer using a near-infrared light source and / or of drying the deposited dye using a near-infrared light source.

[0035] This feature allows to control a migration of the dye through the primer layer, to deposit on the optical surface of the substrate.

[0036] The method may further comprise a surface treatment step during which the optical surface is treated with a plasma prior to depositing the primer layer.

[0037] This feature allows to alter the surface state of the substrate through the plasma treatment to improve the adherence and stability of the dye.

[0038] The step of removing the primer layer may be carried out through a water-washing process.

[0039] This feature allows an easy and fast removal of the primer layer to leave only the printed pattern on the substrate.

[0040] The substrate may comprise a transparent organic material.

[0041] The at least one optical surface may comprise at least one curved region.

[0042] The substrate may be an optical lens or an unfinished optical lens.

[0043] The invention also relates to an optical article manufactured with a method as above.

[0044] Brief description of the drawings

[0045] Figure 1 is a schematic side view of the steps of a method according to the invention, figure 2 is a view of a first type of pattern to be printed through the method of figure 1 , and figure 3 is a view of a second type of pattern to be printed through the method of figure 1 .

[0046] Detailed description of embodiments

[0047] A method for manufacturing an optical article is described below, in reference to figure 1.

[0048] The method comprises a step 100 of providing a base substrate 10 to be printed on. The base substrate 10 is for example a lens substrate, such as an unfinished lens, and has a first optical surface 12a and a second optical surface 12b, opposite the first optical surface 12a.

[0049] In the disclosed example, a pattern is printed on the first optical surface 12a. Alternatively, a similar pattern or a different pattern can be printed on the second optical surface 12b, and patterns may be printed on both optical surfaces 12a, 12b.

[0050] The first optical surface 12a may be a back surface of the base substrate 10 located proximal to the eye of the user when the optical article is integrated in a pair of glasses, and the second optical surface 12b may be a front surface located distally from the eye of the user when the optical article is integrated in a pair of glasses. Alternatively, the second optical surface 12b may be the surface located proximal to the eye and the first optical surface 12a may be the front surface of the base lens substrate 10, located distally from the eye of the user.

[0051] The base substrate 10 may be formed in organic eyeglass, for example made of thermoplastic or thermosetting plastic. In particular, thermoplastic materials may be selected from, for instance: polyamides, polyimide, polysulfones, polycarbonates and copolymers thereof, poly(ethylene terephtalate) and polymethylmethacrylate (PMMA).

[0052] The base substrate 10 is preferably shaped to provide optical power suitable for correcting a wearer ametropia, for instance myopia or hyperopia. The base substrate 10 may be monofocal or multifocal such as a multifocal progressive lens.

[0053] The base substrate 10 may also be a semi-finished lens which means that it does not provide the final power, also called target power, of the lens that is to be manufactured from the semifinished lens. It may provide a power which is not the target power, said target power being obtained by later surfacing of the semi-finished lens.

[0054] The base substrate 10 may also be a lens which is not trimmed, which means that its peripheral shape has not been adjusted to the shape of a frame in which it will then be inserted.

[0055] In an embodiment of the method, the step 100 also comprises a surface treatment step, wherein at least one of the optical surfaces 12a, 12b is treated with a plasma 14 formed by a plasma torch 16, to improve the surface aspect.

[0056] In the example shown on figure 1 , the first optical surface 12a is treated with the plasma 14. The substrate is then placed in a printing assembly 20 comprising at least one printing head 22, and a pattern to be printed on at least one optical surface 12a of the base substrate 10 is provided.

[0057] The method comprises a step 200 of determining a desired printing dot diameter for the pattern to be printed and a corresponding surface amount of primer to be deposited on the optical surface 12a before printing.

[0058] The pattern is formed of a plurality of dots with corresponding coordinates, forming an image. A first example of pattern 24 is shown on figure 2, which is a detailed image such as a logo to be printed on the base substrate 10. The detailed image comprises detail parts that have small transverse dimensions, and thus require a small size of printing dot to print with an inkjet device. The expression “transverse dimensions” is meant relative to the direction of the optical axis of the substrate, and thus designates any dimension in the pattern measured in a plane tangent to the first optical surface 12a.

[0059] An example of de detailed part with a small transverse dimension is a line of a drawing or text character, the small transverse dimension being the line width. In order to adequately print the pattern, the printing dot diameter must be smaller than the small transverse dimension of the detailed parts of the pattern.

[0060] A second example of pattern 26 is shown on figure 3, which is a homogeneous layer extending over at least a region 28 of the substrate 10. The homogeneous layer does not comprise fine details, and thus does not require a small printing dot size. On the opposite, a larger printing dot diameter improves the homogeneity of the layer and reduces the printing time.

[0061] For example, the region 28 extends over at least 50% of the first optical surface 12a.

[0062] Notably, when the substrate 10 is a lens which is not yet trimmed, the region 28 extends over all the parts of the substrate 10 that will not be removed during trimming.

[0063] The region 28 may be circular as shown on figure 3 or comprise one or more truncated parts in areas that will be trimmed subsequently.

[0064] A contour of the region 28 may closely follow the border of the substrate 10, or be further apart from said border.

[0065] The step 200 then comprises determining a desired surface amount of primer to be deposited, based on the determined printing dot diameter for the pattern.

[0066] Depositing a primer layer on the optical surface 12a of the substrate 10 allows the use of waterbased dyes for inkjet printing on any kind of substrate, by replacing the specific type of surface of the substrate with a common primer surface that is compatible with the dye.

[0067] The primer layer allows to maintain the drops of dye in place and prevent transverse movement of the dye or coalescence of the drops.

[0068] The primer is selected to be compatible with inkjet printing, with appropriate values of viscosity and surface tension, and a high degree of stability inside the formulation and stability along time.

[0069] Furthermore, the primer is selected for compatibility with all the envisioned substrates, so as to not produce any type of chemical reaction with the substrate.

[0070] Viscosity and surface tension of the rimer are also low enough for the primer to spread enough to form a homogeneous layer on the desired part of the first optical surface 12a.

[0071] The primer is further selected for chemical compatibility with the different dyes, and to allow a transfer of the dyes through the primer layer. In order for the dye to transfer through the primer layer, the primer has a low adherence and a low degree of reticulation.

[0072] Finally, the primer is selected to be easily cleanable without using any aggressive chemical products, solvent or mechanical tool, and preferably through a water cleaning. Thus, the primer is preferably water-based or water-soluble. The primer is preferably a water-based primer, notably an aqueous solution comprising a polymer. For example, the pattern 24 and the pattern 26, respectively shown on figure 2 and 3, have been printed with a primer that comprises an aqueous solution of polyvinyl alcohol.

[0073] The thickness of the primer layer influences the degree of diffusion of the dye through the primer layer, and therefore influences the printing dot diameter.

[0074] As the thickness of the primer layer is difficult to measure accurately and quickly, the amount of primer deposited per surface area is used as a metric for determining the appropriate primer layer.

[0075] For example, the pattern 24, shown on figure 2, has been printed with a surface amount of primer of 1 ,68 mm3of primer per square inch of surface, while the pattern 26, shown on figure 3, has been printed with a surface amount of primer of 3,36 mm3of primer per square inch of surface.

[0076] The relation between the amount of primer and the printing dot size depends on the natures of the primer and dye and is preferably be determined experimentally and accessed from a database during the step of determining the desired surface amount of primer used.

[0077] The desired surface amount of primer must be kept low enough to allow migration of the dye through the primer layer. An excessive amount of primer will result in a too thick primer layer that will not allow migration of the dye and prevent the application of the dye to the optical surface.

[0078] To this end, the method may further comprise a calibrating step, during which several values of surface amount of primer are tested and resulting ink dot size values obtained through inkjet printing are measured. The obtained data is preferably stored in a database for future use.

[0079] The method then comprises a step 300 of depositing a primer layer 30 by depositing a primer with the determined desired surface amount on at least part of first optical surface 12a, where the pattern is to be printed.

[0080] The primer layer is deposited with the printing head 22 of the printing assembly 20, with a controlled flow rate to achieve the desired surface amount of primer.

[0081] Advantageously, the method may comprise a step 400 of drying of the primer layer 30 using a near-infrared light source 32. The primer layer 30 is only partly dried to remove excessive moisture and improve the homogeneity of the primer layer.

[0082] The method then comprises a step 500 of printing the pattern over the primer layer 30 with the at least one inkjet printing head 22 depositing at least one dye to form a dye layer 34.

[0083] The method may then comprise a step 600 of drying the deposited dye layer 34 using the nearinfrared light source 32, similarly to the previous drying step 400.

[0084] The method then comprises a step 700 of placing the base substrate 10 with the primer layer 30 on the optical surface 12a and the dye layer 34 over the primer layer 30 in a heating assembly 40, for a predetermined migration duration at a predetermined migration temperature. The heating assembly is for example a dry oven.

[0085] During the migration duration, the dye layer 34 migrates through the primer layer 30 and reaches the optical surface 12a, where it is held in place by the primer layer 30 and adheres to the optical surface 12a, forming the pattern.

[0086] The method then comprises a step 800 of removing the primer layer 30, preferably through a water washing method such as with a low-pressure waterjet 38.

[0087] This allows a clean a fast removal of the primer layer 30 without damaging the cured dye layer 34 underneath.

[0088] The method finally comprises an end step 900 where the substrate 10 is obtained with the cured dye layer 34 forming the pattern on the optical surface 12a, forming the optical article.

Claims

CLAIMS1. A method for manufacturing an optical article, the method comprising:- providing a base substrate (10) comprising at least one optical surface (12a) and placing the base substrate (10) in a printing assembly (20),- providing a pattern (24, 26) to be printed on the base substrate (10) and determining a printing dot diameter for printing the pattern,- determining (200) a desired surface amount of primer to be deposited, based on the determined printing dot diameter,- depositing (300) a primer layer (30) by depositing a primer with the determined desired surface amount on at least part of the at least one optical surface (12a),- printing the pattern (24, 26) over the primer layer (30) with at least one inkjet printing head (22) depositing at least one dye (34),- placing the base substrate (10) in a heating assembly (40) for a predetermined migration duration, during which the dye (34) migrates through the primer layer (30) and reaches the optical surface (12a), where it is held in place by the primer layer (30) and adheres to the optical surface (12a), forming the pattern, and- removing the primer layer (30).

2. The method according to claim 1 , wherein the primer is a water-based primer.

3. The method according to claim 2, wherein the water-based primer comprises polyvinylalcohol.

4. The method according to any one of claims 1 to 3, wherein depositing (300) the primer layer (30) is achieved using at least one inkjet printing head (22).

5. The method according to any one of claims 1 to 4, wherein the at least one dye is a waterbased dye.

6. The method according to any one of claims 1 to 5, wherein the pattern (100) comprises at least one image and / or at least one text character.

7. The method according to any one of claims 1 to 5, wherein the pattern (200) is a uniform layer extending over at least part (28) of the optical surface (12a).

8. The method according to any one of claims 1 to 7, wherein the method further comprises a calibrating step, during which several values of surface amount of primer are tested and resulting dye dot size values obtained through inkjet printing are measured.

9. The method according to any one of claims 1 to 8, wherein the method further comprises a step (400, 600) of drying the primer layer (30) using a near-infrared light source (32) and / or of drying the deposited dye (34) using a near-infrared light source (32).

10. The method according to any one of claims 1 to 9, wherein the method further comprises a surface treatment step (100) during which the optical surface (12a) is treated with a plasma (16) prior to depositing the primer layer (30).11 . The method according to any one of claims 1 to 10, wherein the step of removing (800) the primer layer (30) is carried out through a water-washing process.

12. The method according to any one of claims 1 to 11 , wherein the substrate (10) comprises a transparent organic material.

13. The method according to any one of claims 1 to 12, wherein the at least one optical surface (12a) comprises at least one curved region.

14. An optical article manufactured with a method according to any one of the previous claims.

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