Patent Description:
By "functional film", what is meant is a film providing the optical article with at least one feature among a hard coat, anti-scratch properties, an antireflective coating, a polarizing film, a tint, a mirror or a filter for specific wavelengths, antishock, anti-smudge, anti-fog, self-healing, self-cleaning or antistatic properties, etc..

By "laminating" a film on an optical article, what is meant is the operation involving the deposition of a film on a surface of the optical article to be laminated. The lamination operation is usually performed by first providing the film disposed onto a carrier. The film and the carrier are then compressed onto the surface to be laminated, by applying a difference of pressure between a side of the carrier having both the film and the optical article and the other side, or by applying a force from the optical article side.

An adhesive, e.g. a pressure sensitive adhesive, is generally previously disposed on the face of the film which is intended to be pressed onto said surface so as to maintain the film on said surface.

In alternative processes, the adhesive is positioned onto the optical article prior to pressing the film onto the optical article and/or the film is pressed onto the optical article without being fixed to a carrier, but for example by applying pressure directly on the film or by using a stamp or a blown membrane or balloon.

In the field of optical article manufacturing, the film lamination process generally requires pre-processing or "thermoforming" the consumable or laminate complex, in order to shape the film with a given curvature, so as to comply with the surfaced prescription of the ophthalmic lens to be laminated, be it the convex or concave side of the lens.

However, the thermoformed curvature may differ from that of the surface it is laminating, in one or more axes and/or regions. In some cases, the thermoformed curvature is substantially spherical, whereas the curvature of the surface is aspherical, e.g. cylindrical, or progressive (referring to progressive addition lenses).

In case the thermoformed curvature differs from the surface curvature, after lamination, there will be stress within the laminate, as the film is constrained to accommodate the surface curvature by the adhesive.

This may increase the instances of delamination, visible defects and/or other imperfections in the laminated lens. <FIG> illustrates the phenomenon of delamination, consisting in a mismatch M between a film <NUM> and an optical article surface curvature <NUM> in the cross-section axis. Thus, the adhesive does not adhere the film to the surface of the optical article.

A known solution for preventing this problem is to thermoform the laminate such that the thermoformed curvature matches the optical article surface curvature as precisely as possible, e.g. by matching the curvature in more locations than just on the meridian of the laminate, or by controlling the other forming parameters, i.e. flow rate, temperature, pressure, etc..

However, this process cannot be optimized for all cases, as optical articles such as ophthalmic lenses are "freeform" surfaces and variables curvatures can be found over the surface of a given lens.

Document <CIT> discloses a polarizing optical element comprising a polarizing film and a method for making same.

Document <CIT> discloses a process for the production of a curved laminated glass pane.

Document <CIT> discloses a bi-layer adhesive for lens lamination.

An object of the disclosure is to overcome the above-mentioned drawbacks of the prior art.

To that end, the disclosure provides a method of laminating a functional film onto an optical article according to claim <NUM>.

As the film is adhered to the optical article surface at the time of heating, the heat forms the film laminate conforming to the lens surface curvature, thereby improving adhesion and preventing delamination.

In the description which follows, although making and using various embodiments are discussed in detail below, it should be appreciated that as described herein are provided many inventive concepts that may embodied in a wide variety of contexts. Embodiments discussed herein are merely representative and do not limit the scope of the disclosure. It will also be obvious to one skilled in the art that all the technical features that are defined relative to a process can be transposed, individually or in combination, to a device and conversely, all the technical features relative to a device can be transposed, individually or in combination, to a process and the technical features of the different embodiments may be exchanged or combined with the features of other embodiments.

The terms "comprise" (and any grammatical variation thereof, such as "comprises" and "comprising"), "have" (and any grammatical variation thereof, such as "has" and "having"), "contain" (and any grammatical variation thereof, such as "contains" and "containing"), and "include" (and any grammatical variation thereof such as "includes" and "including") are open-ended linking verbs. They are used to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps or components or groups thereof. As a result, a method, or a step in a method, that "comprises", "has", "contains", or "includes" one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more steps or elements.

<FIG> shows a lamination machine <NUM> for laminating a functional film <NUM> onto an optical article <NUM>, in a lamination operation wherein the functional film <NUM> and the optical article <NUM> are in contact with each other.

The optical article may be an ophthalmic lens. Preferably, the optical article <NUM> has dimensions at least equal to the final dimensions of the ophthalmic lens. "Final" dimensions means the dimensions of the ophthalmic lens or optical article <NUM> at the end of the manufacturing process, when the ophthalmic lens or the optical article <NUM> is ready to be worn by a user or mounted in a frame. Preferably, the dimensions of the ophthalmic lens or optical article <NUM> at the time of the lamination process are greater than its final dimensions. In this latter case, the final contour of the ophthalmic lens or optical article <NUM> is obtained with a cutting or edging step.

The optical article <NUM> comprises a first face <NUM> which is intended to be laminated and a second face <NUM> which is intended to be disposed against a surfacing blocker <NUM>. The first face <NUM> is concave. Alternatively, the first face <NUM> may be of any form, e.g. convex or planar. The geometry of the first face <NUM> depends on the ophthalmic lens power desired for the optical article <NUM> when the optical article <NUM> is an ophthalmic lens.

Laminating the functional film <NUM> may provide the laminated face of the optical article <NUM> with at least one coating among a hard coat, an anti-scratch coating, an antireflective coating, a polarizing coating, a tinted coating, a mirror coating, a coating filtering a predetermined range of wavelengths, an anti-smudge coating, an anti-fog coating, an antistatic coating, a coating having self-healing and/or self-cleaning properties, etc..

The functional laminated film <NUM> may comprise a main film made of cellulose triacetate (TAC), polyethylene terephthalate (PET), polycarbonate (PC), polyvinyl alcohol (PVA), or cyclic olefin copolymer (COC). Alternatively, the functional film <NUM> may be made of a combination of these materials.

Furthermore, the functional film <NUM> may comprises a plurality of layers. These layers may be composed of different materials. These layers may also provide the optical article <NUM> with different features as described above. Preferably, these layers are superposed one above the other and have the same peripheral dimensions to form a multi-layer film with a uniform perimeter.

The functional film <NUM> may have an elongated shape. In other words, the functional film <NUM> preferably comprises a first dimension greater than a second dimension perpendicular to the first dimension. Most preferably, the functional film <NUM> has an oblong shape. Furthermore, the functional film <NUM> has dimensions at least corresponding to the final dimensions of the optical article <NUM>. Hence, the functional film <NUM> has dimensions making it possible to cover the entire surface of at least one side (also referred to herein as one "face") the final optical article <NUM>. However, the functional film <NUM> may have dimensions smaller than the optical article before the afore-mentioned step of edging i.e. the base lens. Alternatively, the functional film <NUM> may have dimensions making it possible to partly cover the surface of the final optical article <NUM>.

The functional film <NUM> may comprise an orientation axis. The orientation axis may be defined depending on at least one among a polarizing direction, an antireflective or reflective gradient, a tint gradient and an inscription positioning. The function film <NUM> may comprise an orientation indicator. In the case where the functional film <NUM> is elongated, the orientation axis may extend along or perpendicular to the extension axis of the functional film <NUM> in a predetermined manner. That greater dimension may form a visual indicator for the orientation axis.

The orientation axis is advantageously aligned with the nasal-temporal axis of the ophthalmic lens when the ophthalmic lens gets its final shape, in order to avoid misalignment defects that may otherwise occur, leading the ophthalmic lens to have portions without any functional film <NUM>. Furthermore, the orientation axis is advantageously disposed in a predetermined orientation when the functional film <NUM> has a polarization axis. In the same way, the orientation axis is advantageously disposed in a predetermined orientation and position with regard to a center point and the nasal-temporal axis of the ophthalmic lens, notably when the functional film <NUM> provides an antireflective or reflective linear or curved gradient, a tint linear or curved gradient, an inscription positioning or an optically active element.

The lamination machine <NUM> comprises a film support <NUM> for receiving the functional film <NUM> to be laminated and an article support <NUM> configured to receive and position the optical article <NUM> in a predetermined orientation.

In the example of <FIG>, the functional film <NUM> is positioned on an external side of a carrier <NUM> which is intended to face and then contact the optical article <NUM>. The carrier <NUM> is fastened to the film support <NUM>, for example by means of an adhesive or by a clamping system.

The lamination machine <NUM> further comprises an actuating member <NUM> configured to move the film support <NUM> and the article support <NUM> toward each other at least until the functional film <NUM> is fully contacting the surface to be laminated. This movement is performed at least along a longitudinal lamination axis A. Preferably, the longitudinal axis A is orthogonal to the surface of the optical article <NUM> to be laminated at a central point of the optical article <NUM>, e.g. at the geometric center of one side (face) of the optical article <NUM>.

The actuating member <NUM> may further be configured to move the film support <NUM> and the article support <NUM> toward each other along a plurality of lamination axes. That movement may be linear or non-linear. The predetermined orientation provided by the article support <NUM> is preferably a predetermined angular position about the longitudinal lamination axis A.

In the example shown in <FIG>, the actuating member <NUM> is coupled to the article support <NUM> to displace the article support <NUM> toward the film support <NUM> which is fixed with regard to a frame <NUM>. Alternatively, the actuating member <NUM> may be coupled to the film support <NUM> to displace it toward the article support <NUM>. Alternatively, the actuating member <NUM> may be coupled to both the article support <NUM> and the film support <NUM>. The actuating member <NUM> is for example a cylinder having the article support <NUM> or the film support <NUM> coupled at an end thereof.

The lamination is configured to be performed at a predetermined pressure or predetermined pressure difference applied onto the optical article <NUM> received within the article support <NUM>. The predetermined pressure difference applied onto the optical article <NUM> through the functional film <NUM> may be between <NUM> MPa and <NUM> MPa, preferably between <NUM> MPa and <NUM> MPa, preferably of about <NUM> MPa. That predetermined pressure difference depends on the dimensions of the optical article <NUM>, particularly the area of the surface to be laminated.

To apply that predetermined pressure onto the optical article <NUM>, the functional film <NUM> is disposed on the carrier <NUM> which acts as a membrane. A positive difference of pressure may be applied between a first side of the carrier <NUM> and a second side of the carrier <NUM> carrying the functional film <NUM> which is pressed against the optical article <NUM>. The predetermined pressure difference corresponds to the pressure difference between the two sides of the carrier <NUM> before application of the carrier <NUM> onto the optical article <NUM>.

In the example of <FIG>, the film support <NUM> and the carrier <NUM> form a cavity <NUM> with a second side of the carrier <NUM> forming a lower wall of the cavity <NUM>.

The film support <NUM> comprises an inlet port <NUM> communicating with the cavity <NUM> to allow a pressuring device (not shown) to regulate the pressure in the cavity <NUM>.

The article support <NUM> is configured to transmit laminating forces induced by that predetermined pressure to the lamination machine <NUM> during the lamination. Hence, the article support <NUM> is configured to withstand the predetermined pressure difference applied onto the optical article <NUM>. More particularly, the article support <NUM> is configured to support the optical article <NUM> in withstanding the predetermined pressure difference applied onto most or even the whole of the surface of the optical article <NUM>.

The article support <NUM> is a blocker support. In other words, the article support <NUM> is configured to receive a blocker onto which an optical article <NUM> is fixed and preferably provide it with a forced predetermined orientation with regard to the lamination machine <NUM>.

A "blocker" is a support piece comprising at a first side a mounting face onto which an optical article <NUM> is intended to be fixed and at a second side opposite to the first side a clamping portion which is configured to cooperate with a blocker support. The blocker allows the optical article <NUM> to be well maintained during a manufacturing process, as for example surfacing, edging or lamination operations. Particularly, the blocker makes it possible to maintain the optical article <NUM> in a predetermined position and orientation. The blocker is thus the interface piece between the optical article <NUM> and the machine, here the lamination machine <NUM>.

A blocker is also known as a block, a blocking piece, a lens chuck or a surface block.

The blocker is attached or fixed to the optical article <NUM> by means of a blocking material which is preferably an ultraviolet and/or visible light curable adhesive blocking composition as disclosed in <CIT>. Alternatively, the blocking material may be plastic material including e-caprolactone, terpolymer derived from ethyl-methyl-acrylate-acrylic acid, polycarbonate, polyethylene (PET), high methacrylate resin, ethyl methacrylate resin, methacrylate copolymer resin, butyl methacrylate resin, and methyl/n-butyl methacrylate copolymer resin. In some alternatives, the blocking material may be a metal alloy with a low fusion temperature.

The laminating forces applied onto the optical article <NUM> are thus transmitted to the blocker which also transmits these laminating forces to the article support <NUM> or the blocker support. In other words, the blocker makes it possible to support the optical article <NUM> in bearing the laminating forces. Accordingly, this makes it possible to limit the risks for the laminating forces to deform or break the optical article <NUM> or part of the optical article <NUM>.

The article support <NUM> is further configured to receive the surfacing blocker <NUM> onto which the optical article <NUM> is to be disposed for lamination. In other words, the article support <NUM> is compatible with the surfacing blocker <NUM>. A "surfacing" blocker corresponds to a blocker that is configured to be received by a blocker support of a surfacing machine and to withstand forces involved by the surfacing operation, without any plastic deformation of the blocker. In other words, the surfacing blocker <NUM> is configured to transmit surfacing forces applied thereto by the optical article <NUM> to the blocker support and helps maintaining the optical article <NUM> fixed to the article support <NUM> despite such forces being applied.

Providing an article support <NUM> configured to receive the surfacing blocker <NUM> makes it possible to avoid supplementary deblocking and blocking steps when a surfacing operation is planned before or after the lamination operation. Indeed, in a manufacturing process comprising a step of surfacing and a step of lamination, avoiding a supplementary step of deblocking the optical article <NUM> from a first blocker, e.g. the surfacing blocker <NUM>, and a supplementary step of blocking the optical article <NUM> on a second blocker, e.g. a specific blocker for lamination machine, makes it possible to reduce the manufacturing process duration, defects that may appear in the lens and/or errors generated during film positioning.

Furthermore, this makes it possible to reduce the apparition of misalignment defects and allows to suitably position the orientation axis of the functional film <NUM>. Using a same blocker for surfacing and lamination steps allows the functional film <NUM> to be perfectly aligned with the referential used for surfacing and for providing the expected optical function.

The surfacing blocker <NUM> has at least one bearing surface <NUM> for the transmission of surfacing forces to a surfacing machine during a surfacing operation. The article support <NUM> comprises at least one supporting surface <NUM> configured to contact the at least one bearing surface <NUM> when the surfacing blocker <NUM> is received in the blocker support to transmit laminating forces induced by the predetermined pressure.

In an embodiment, the at least one supporting surface <NUM> is complementary shaped with regard to the at least one bearing surface <NUM>. In other words, the at least one supporting surface <NUM> is configured to be in surfacing contact with the at least one bearing surface <NUM>. A shape complementarity makes it possible to provide a more stable and precise contact between two contacting surfaces. When the surfacing blocker <NUM> comprises one bearing surface <NUM>, this bearing surface is preferably circular in shape. Preferably, the article support <NUM> comprises a plurality of supporting surfaces <NUM> configured to contact a plurality of bearing surfaces <NUM> of the blocker. In the latter case, the plurality of supporting surfaces <NUM> is complementary shaped with regard to the plurality of bearing surfaces <NUM>.

The supporting and bearing surfaces <NUM>, <NUM> may be planar, circular in shape or a combination thereof. Hence, the contacting surface between the supporting and bearing surfaces <NUM>, <NUM> may alternate between circular and planar or a combination thereof.

When the article support <NUM> comprises a plurality of supporting surfaces <NUM>, at least one supporting surface <NUM> is at least partially oriented perpendicularly to the longitudinal lamination axis A to transmit forces extending along the longitudinal lamination axis A. Furthermore, at least one supporting surface <NUM> is at least partially perpendicular to a direction extending perpendicularly to the longitudinal lamination axis A to transmit forces extending in a direction perpendicular to the longitudinal lamination axis A. In other words, a first surface portion of the article support <NUM> is oriented perpendicularly to the longitudinal lamination axis A and a second surface portion of the article support <NUM> is oriented perpendicularly to a direction extending perpendicularly to the longitudinal lamination axis A.

The at least one supporting surface <NUM> is preferably continuous. Alternatively, the at least one supporting surface <NUM> may be discontinuous. The at least one supporting surface <NUM> may also comprise protrusions and/or recesses.

In the example of <FIG>, the article support <NUM> comprises a recess <NUM> within which a supporting surface <NUM> is formed. Particularly, the supporting surface <NUM> is a cylindrical lateral wall of the recess <NUM> and the bearing surface <NUM> is a cylindrical wall of the surfacing blocker <NUM>.

A method of laminating the functional film <NUM> onto the optical article <NUM> is described below with reference to <FIG>.

A thermoforming step <NUM> is performed so as to provide the functional film <NUM> with a predetermined target curvature based on a curvature of a face F of the optical article <NUM> on which the functional film <NUM> is to be applied.

Then, a step <NUM> of applying the functional film <NUM> onto the face F of the optical article <NUM> is performed. Step <NUM> may amount to bringing the functional film <NUM> in contact with the face F or, if an adhesive substance is present on the face F, bringing the functional film <NUM> in contact with the adhesive substance.

The following step <NUM> comprises pressing the functional film <NUM> against the face F of the optical article <NUM> so as to adhere the functional film <NUM> to the face F of the optical article <NUM>, by applying a predetermined pressure along the longitudinal lamination axis A through the actuating member <NUM>.

According to the disclosure, an additional step <NUM> is carried out after the applying step <NUM>. The additional step <NUM> comprises heating the functional film <NUM> at at least one predetermined temperature, so that the functional film <NUM> conforms to the curvature of the face F of the optical article <NUM>.

The heating is done while applying a predetermined pressure on the functional film <NUM> to press it against the face F of the optical article <NUM>.

As pressure is applied while the functional film <NUM> is heated, stresses may be relaxed in a shape that is as much as possible in conformity with the shape of the face F of the optical article <NUM>.

Moreover, the performance of the adhesion of the functional film <NUM> to the face F of the optical article <NUM> is improved, because the pressure-sensitive adhesion may be obtained more quickly as the surfaces being in contact with each other are hotter.

Besides, the heated pressure-sensitive adhesive may become softer and may thus conform more easily to any small texturing of the surface, such as traces of engraving, e.g. microcircles or other markings.

In the above-described embodiment in which the heating is done while applying a predetermined pressure on the functional film <NUM>, by way of non-limiting example, the heating may be done during step <NUM>, through pressing the functional film <NUM> against the face F of the optical article <NUM> so as to adhere the functional film <NUM> to the face F of the optical article <NUM>.

The heating may be done under approximately the same pressure as used while pressing the functional film <NUM> against the face F of the optical article <NUM>.

The heating may be carried out for a duration comprised between e.g. <NUM> and <NUM>.

In the heating step <NUM>, the heating may be carried out in accordance with a predetermined temperature profile.

In an embodiment, the heating may comprise a gradual heating phase and a subsequent cooling phase.

Optionally, a predetermined pressure may be applied to the functional film <NUM> during the cooling phase. The pressure will help settle the shape that the functional film <NUM> may take while cooling. In other words, in that case, part or all of the cooling phase is carried out while maintaining the film under pressure.

In an embodiment, the pressure is applied during the cooling phase at least until the temperature reaches <NUM> below the maximum temperature of the heating step, for example at least <NUM> below said temperature. In a further embodiment, the pressure is applied during the cooling phase at least until the temperature reaches a value below <NUM> or even below <NUM>. In a particular application of these embodiments, the temperature mentioned above may be defined as the temperature of the pressurized air that applies the pressure.

In an embodiment, the heating step <NUM> may be carried out at least partially during the pressing step <NUM>. For example, a temperature increase profile may be followed throughout the pressing step <NUM> and a temperature decrease profile may then be followed during and/or after the pressing step <NUM>.

Alternatively, the heating step <NUM> may be carried out after applying a predetermined pressure on the functional film <NUM> to press it against the face F of the optical article <NUM> for a predetermined amount of time. By way of non-limiting example, the heating step <NUM> may be carried out after the pressing step <NUM>, namely after pressing for a predetermined amount of time the functional film <NUM> against the face F of the optical article <NUM> so as to adhere it to the face F.

In any of the above embodiments, the heating may be carried out for a duration comprised between e.g. <NUM> and <NUM>.

In a particular embodiment, the heating step <NUM> may comprise using hot pressurized air flowing e.g. from a hot air shower. Pressurized air makes it possible to have a constant air flow entering the cavity <NUM>.

Besides, using pressurized air to heat the functional film <NUM> avoids using ovens. This makes it possible, not only to save time by not having to manipulate the optical article <NUM> and by not changing machines, but also to heat evenly the surface of the functional film <NUM>.

Furthermore, applying pressurized air on the functional film <NUM> and not placing the optical article <NUM> in an oven makes it possible to reduce the heat transferred to the optical article <NUM> and in particular to the face of the optical article <NUM> opposite to the face F, which is of interest if that opposite face has a hard coat and/or an antireflective stack and/or other temperature-sensitive added values.

In addition, pressurized air may be used for maintaining the functional film <NUM> under pressure during the heating in step <NUM>. The desired pressure may be obtained e.g. by monitoring the air outlet of the cavity <NUM>.

Alternatively, the heating step <NUM> may comprise using hot air blowing, or an infrared heater, or bringing the functional film <NUM> in contact with a heated fluid or solid element or any other appropriate heating technique.

By way of non-limiting example, the heating temperature may be comprised between <NUM> and <NUM> and is preferably comprised between <NUM> and <NUM>.

In a particular embodiment where an optional step <NUM> comprises providing the functional film <NUM> onto a carrier before the thermoforming step <NUM>, the heating step <NUM> may comprise heating a side of the carrier opposite to the face F of the optical article <NUM>.

In a particular embodiment, the heating step <NUM> may be performed conditionally based on a calculated minimum curvature difference between the thermoformed functional film <NUM> and the curvature of the face F of the optical article <NUM> in at least one meridian.

For example, the heating step <NUM> may be performed as long as the measured curvature difference exceeds the above-mentioned calculated minimum curvature difference. The heating step <NUM> may then be stopped when the measured curvature difference equals the calculated minimum curvature difference.

The curvature difference may be measured continuously or at given time instants, e.g. periodically.

At least one of the front and rear faces of an optical article such as an ophthalmic lens may be coated by a functional film laminated onto the optical article by implementing a method as described above.

Claim 1:
A method of laminating a functional film (<NUM>) onto an optical article (<NUM>), comprising:
thermoforming (<NUM>) said functional film (<NUM>) so as to provide said functional film (<NUM>) with a predetermined target curvature based on a curvature of a face (F) of said optical article (<NUM>) on which said functional film (<NUM>) is to be applied;
applying (<NUM>) said functional film (<NUM>) onto said face (F) of said optical article (<NUM>);
pressing (<NUM>) said functional film (<NUM>) against said face (F) of said optical article (<NUM>) so as to adhere said functional film (<NUM>) to said face (F) of said optical article (<NUM>) by a pressure sensitive adhesive;
wherein said method further comprises heating (<NUM>) said functional film (<NUM>) at at least one predetermined temperature after said applying (<NUM>), so that said functional film (<NUM>) conforms to the curvature of said face (F) of said optical article (<NUM>), wherein said heating (<NUM>) is done while applying a predetermined pressure on said functional film (<NUM>) to press it against said face (F) of said optical article (<NUM>).