The invention relates to a method for manufacturing an optical element with a functional film .

Generally, such an optical element is m anufactured by a lam ination technique consisting in thermoform ing a functional film before depositing it under pressure on an optical elem ent surface which is already attached to a blocking piece. As an exam ple, the functional film may be an anti-reflective coating.

However, it has been observed that in som e cases, when comes the step of separating the optical elem ent with the film from the blocking piece, there is an important risk of film delam ination, namely a detachm ent of the film from the optical element. Such a situation is unacceptable, because the lam ination step m ust be restarted, resulting in additional costs.

A method pursuant to the invention allows the optical elem ent with the film to be satisfactory m anufactured by elim inating the risk of a film delam ination during the step of separating the optical elem ent with the film from the blocking piece.

I n order to solve this problem , the inventors have observed the lam inated optical elements before and after the step of separating the optical element with the film from the blocking piece. The inventors observed that after the lam ination step, in some cases, the film which adheres to said optical element surface is larger in some dim ension than the machined optical element.

It has been observed that when comes the step of separating the optical element with the film from the blocking piece, if parts of the film extend up to or beyond the edges of the optical elem ent, there is an im portant risk of film delam ination, namely a detachment of the film from the optical element. And this happens especially in the cases where the film is lam inated on a concave surface of the optical elem ent. One object of the invention is a method for m anufacturing an optical lens and com prising the following successive steps:

- a step of providing an optical lens attached to a blocking piece,

- a step of lam inating a functional film on a surface of said optical lens,

- a step of obtaining an assembly constituted by the blocking piece, the optical lens and the functional lam inated film ,

- a step of cutting the excess film directly on said assem bly, so as to reduce the film shape,

- a step of deblocking the optical lens with the film , and the blocking piece.

The originality of a method pursuant to the invention consists in including a step of reducing the film shape prior to the deblocking step, in order to prevent any delam ination phenomenon of the film adhering to the optical elem ent. I ndeed, the deblocking step is generally achieved by m eans of a pressurized fluid jet, and if the film protrudes from the lens in som e radial directions, said fluid jet m ay dissociate the functional film from the optical element before the end of the deblocking step. By cutting the film in excess, this one will stay in the sam e position on the optical elem ent with a hom ogeneous contact against a surface of said elem ent. Consequently, with the beforehand cutting step, the deblocking step will not have any negative influence on the functional film or adhesion layer and its position on the optical element, and the resulting piece com prising the optical element and said film will have the required quality.

It is to be noted that by lam inated a film on a lens the disclosure means the act of providing a film on one side, and a lens on the other side and affixing the film onto a surface of the lens, using an adhesive binder layer between the film and said surface.

According to the disclosure, the step of cutting the excess film happens while the optical lens is still fixed onto the blocking piece. The blocking piece in the disclosure is fixed to the lens prior to introducing the lens and blocking piece into a lam ination m achine configured for lam inating the functional film onto the lens. After the lam inating step, the film is fixed onto the lens, the lens is fixed onto the blocking piece and the blocking piece m ay be removed from the lam ination m achine in order to rem ove the lens from said lam ination machine.

A blocking piece according to the disclosure is an elem ent that is fixed with a part of the surface of the lens opposite the surface to be lam inated. The blocking piece may comprise a blocker and a binding m aterial to bind the blocker to the lens surface. The blocker is configured for cooperating at least with the lam inating machine and configured to be rem oved from the lam inating machine. The blocker may optionally be a surfacing blocker, configured for cooperating with a surfacing machine which enable to form the lens from a sem i-finished lens in a surfacing machine. The binder m ay be a metal alloy with a low-tem perature fusion point or an adhesive.

The functional film aim s to improve the optical properties of the optical element in particular by providing it with added features such as a hard coat, an anti-reflective coating or a polarizing film , anti-shock properties, a tint, a m irror or a filter for specific wavelength, anti-sm udge, anti-fog or antistatic properties, self-healing or self-cleaning properties, etc. The optical lens m ay have a curved profile including a concave surface, a convex surface or may have a planar profile. The blocking piece acts as a support for the optical element in order to m aintain said optical lens in a fixed position during the lam inating step. Once said lam inating step is com pleted it is possible to retrieve an assembly constituted by the blocking piece, the optical lens and the functional lam inated film , said three elem ents being fixed to each other. The step of cutting the film may be achieved with any m eans capable of reducing the film size, for example a laser beam or a blade. The film shape reduction may be achieved homogeneously, for exam ple in a sym metric manner, or only in particular directions where som e parts of the film extend from the optical lens edge. According to a possible characteristic, the step of cutting the film excess allows that the entire film surface is completely adhered on the lens surface, without any part of the film which overhangs the edge of the lens and that could create a drag for a pressurized fluid jet during the deblocking step. The aim of cutting the film is to maintain the dimensions of the film less or equal to the surface of the optical lens against which said film will be applied.

According to a possible characteristic, the step of cutting the excess film is determined so as to obtain a minimum radial distance in a plan view between the film edge and the laminated lens surface edge which is between 0.05mm and 10mm, preferably between 0.5mm and 5mm, for example between 1mm and 3 mm with the film edge being closer to a center of the lens than the laminated lens surface edge Said otherwise, the step of cutting the excess film may be such that the film is cut smaller than the edges of the laminated lens surface. It is important to not reduce too much the film size, because said functional film must be approximately applied on the whole surface of the optical element after a future edging step used to machine the optical element to a contour adapted to fit in a predetermined frame of spectacles.

According to this embodiment of the disclosure, the step of cutting the excess film is determined so as to obtain a minimum radial distance in a plan view between the film edge and the laminated lens surface edge which is between 0.05mm and 10mm, preferably between 0.5mm and 5mm, for example between 1mm and 3 mm with the film edge being closer to a center of the lens than the laminated lens surface edge. Said otherwise, the film edge forms a closed loop which is inside a closed loop formed by the laminated lens surface edge.

According to a possible characteristic, the step of cutting the excess film is carried out with one cutting element to be chosen among a sharp edge, a laser cutter, and a blade. These examples are illustrative and are not limitative. These three cutting elements are particularly suitable for cutting a film which has been beforehand deposited on the optical element by a lam ination technique.

According to a possible characteristic, the method further comprises the following steps:

- a step of providing an assem bly support,

- a step of placing the assem bly in said assembly support, so that the film constitutes the upper part of said assem bly,

- a step of providing an arm equipped with a cutting element in a fixed position relatively to a center of the assembly support, at least one element to be chosen among the arm and the assem bly support being adapted to rotate around a central axis of the assem bly support,

- a step of rotating the at least one element relative to the central axis of the assem bly support so as to allow the cutting element to cut the excess film .

I n order to operate the cutting step in optim ized conditions, it is im portant to maintain the assem bly constituted by the optical element with the film and the blocking piece, in the same fixed position during this step, particularly to im prove the accuracy of the cut. The cutting step m ay be carried out indifferently with a fixed cutting m eans and a rotary assembly support, or with a fixed assem bly support and m oving cutting m eans. What is very important in the framework of a m ethod pursuant to the invention, is that there is a relative m ovem ent between the cutting elem ent and the assem bly support, so that this cutting element move around the film at a predeterm ined distance from the center of the assembly support.

According to a possible characteristic, the functional lam inated film com prises a m ain film m ade of Cellulose Triacetate (TAC) , polyethylene terephthalate ( PET) , polycarbonate ( PC) , Polyvinyl Alcohol ( PVA) , or Cyclic Olefin Copolym er (COC) . Films with such compositions can be easily and accurately cut, to have the suitable form and size with respect to the optical lens on which the film is deposited.

According to a possible characteristic, the functional lam inated film provides at least one feature to the lens to be chosen am ong a hard coat, an anti-reflective coating or a polarizing film , anti-shock properties, a tint, a m irror or a filter for specific wavelength, anti-sm udge, anti-fog or antistatic properties, self-healing or self-cleaning properties, alone or in com bination. These exam ples are only illustrative and are not lim itative. I n a general manner, the functional film m ay have a function of protecting the optical lens surface, or a function intended to im prove the optical properties of said optical lens. The film m ay also have these two functions.

According to a possible characteristic, the optical lens with the film is fastened to the blocking piece by m eans of a bonding m aterial, and wherein the deblocking step is carried out with at least a pressurized fluid jet intended to separate the lens with the film from the bonding m aterial. I f some parts of the film extend beyond the optical elem ent and overhang the edges of said optical element, the pressurized fluid jet m ay separate said film from the optical element, and thus the optical lens is defective and m ust be replaced.

Another object of the invention is an apparatus for achieving the cutting step of a m ethod pursuant to the invention.

According to the invention, the apparatus com prises an assem bly support intended for receiving an assem bly com prising the optical lens with the functional lam inated film and the blocking piece, and a cutting elem ent adapted to cut an excess film present on said assembly and having a surface that spread out of said optical lens, and thus having som e parts overhanging over the optical lens. This apparatus schematically com prises a support intended to receive an assem bly constituted by the optical lens with the lam inated film and the blocking piece, and a cutting elem ent adapted to cut an excess film present on this assembly. This apparatus can be used manually, or automatically with a motor intended to activate the cutting elem ent and/or to generate a movement of said cutting element relative to the assembly support or the contrary (a m ovem ent of the assembly support relative to the cutting element) . According to a possible characteristic, the cutting elem ent is one of a sharp edge, a laser cutter, and a blade. These examples are only illustrative and are not lim itative. These three cutting elements are particularly suitable for cutting a film which has been beforehand lam inated on the optical elem ent

According to a possible characteristic, the apparatus further comprises an arm equipped with a cutting elem ent, said arm being placed relatively to the assem bly support so that the cutting elem ent is placed over the film edge at a predeterm ined distance from the assem bly support center. This predeterm ined position can be calculated or measured. Once the predeterm ined position is known it becomes easy to position the arm in the suitable position so as to place the cutting element close to the edge of the optical lens, where it is suitable to cut the film . The predeterm ined distance may result from m easurem ents and/or calculations. This predeterm ined distance leads to position the cutting elem ent at a precise radial distance from the optical lens edge to ensure a clean cut of the film .

According to a possible characteristic, at least one element to be chosen among the assem bly support and the arm equipped with the cutting element, is adapted to rotate about a central axis of the assem bly support. Once the predeterm ined distance has been assessed, the cutting step can be easily achieved by a sim ple rotation of the arm or of the assem bly support to obtain a clean cut of the functional lam inated film .

According to a possible characteristic, the assem bly support is cylindrical-shaped and is designed to rotate about its revolution axis which extends in a vertical direction, and the arm extends in a horizontal direction.

According to a possible characteristic, the arm is placed above the film and the cutting elem ent acts in a vertical direction.

According to a possible characteristic, the position of the arm is adj ustable to adapt the cutting element position to the film sizes, so that said cutting element is placed above the film edge at a predeterm ined radial distance from the optical lens edge, and preferably over the surface of the optical lens.

According to a possible characteristic, the position of the arm is adj ustable to adapt the cutting elem ent position to the contour of the optical lens, so that said cutting elem ent is placed above the film edge at a predeterm ined radial distance from the optical lens edge, and preferably over the surface of the optical lens. Said position, with regard to the center of the optical lens, may thus vary depending on the shape of the lens contour. Said position m ay for example be adjusted by having had a prior reading of the contour of the optical lens edge, or by having the position of the arm be adjusted with regard to the feedback of a sensor positioned so as to acquire a position of the edge of the lens near the position of the cutting element.

A method pursuant to the invention presents the advantage to be conducted continuously, without any risk of delam ination of the film during the deblocking step. Moreover, while it includes a supplemental step consisting in cutting the excess film which overhang the edge of the optical lens, said step is achieved with an apparatus which is easy and rapid to handle and which produces a clean cut of the film .

We give hereafter a detailed description of a preferred embodim ent of a m ethod pursuant to the invention, by referring to the following figures:

Figure 1 is a perspective view of a first assembly constituted by a blocking piece, an optical element with a functional film and a carrier, Figure 2 is a perspective view of a second assembly which corresponds to the first assembly of figure 1 without the carrier,

Figure 3 is a perspective view of the second assembly of the figure 2 after a cutting step of the functional film ,

Figure 4 is a perspective view of an apparatus pursuant to the invention and intended to cut the excess film which overhang the optical lens,

Figure 5 is a perspective view of a specific area of the apparatus of figure 4 and showing an interaction between a cutting elem ent of said apparatus and the film deposited on an optical lens, Figure 6 is a perspective view of a specific area of the apparatus of figure 4 and showing a step of withdrawal m anually the functional film excess on the optical element after having been cut.

Referring to figure 1 , when a lam ination m ethod is used to deposit a functional film 1 on an optical elem ent which is generally constituted by an optical lens 2, a final first assem bly 3 com prising said optical lens 2 with said film 1 , a carrier 4 and a blocking piece 5 is obtained. To sum up a lam ination method, a m ultilayers assem bly comprising the functional film 1 , the carrier 4 and different layers placed therebetween, is beforehand thermoformed in order to adapt the form of the functional film 1 to the surface of the optical lens 2 intended to receive said functional film 1 .

Then, this m ultilayers assem bly is lam inated on the surface of the optical lens 2, and once said m ultilayers assembly has been deposited on said optical lens 2, we obtain the first assembly 3 showed in figure 1 .

It is im portant to point out that the functional lam inated film 1 provides at least one feature to the optical lens 2 to be chosen am ong a hard coat, an anti-reflective coating or a polarizing film , anti-shock properties, a tint, a m irror or a filter for specific wavelength, self-healing or self-cleaning properties, a surface m odifier having anti-sm udge, anti-fog or antistatic properties, alone or in combination. I n a m ore general manner, such a functional film has a protection function in regard to the optical lens 2 on which it is deposited, or a supplem ental optical function intended to im prove the optical properties and/or characteristics of the optical lens 2. The functions of said functional film 1 are thus non-lim ited to the exam ples listed before, which are only illustrative and not lim itative.

The functional lam inated film 1 com prises a m ain film made of Cellulose Triacetate (TAC) , polyethylene terephthalate ( PET) , polycarbonate (PC) , Polyvinyl Alcohol ( PVA) , or Cyclic Olefin Copolym er (COC) . These are only illustrative examples which are not lim itative in the fram ework of a method pursuant to the invention.

The blocking piece 5 acts as a receptacle to receive the optical lens 2 just before the film lam ination step occurs. Such a blocking piece 5 is designed to maintain the optical lens 2 in a stable manner before the film lam ination step is achieved. On that subject the optical lens 2 is fixed in the blocking piece 5 by m eans of an adhesive m aterial.

Referring to figure 2, once the first assembly 3 has been formed after the film lam ination step, the carrier 4 which is a rigid and transparent plastic film is m anually rem oved from the first assembly 3. We finally obtain a second assem bly 6 made of the optical lens 2 with the functional lam inated film 1 and the blocking piece 5, said second assem bly constituting an independent resulting piece which can be easily handled and/or transported to finally obtain the suitable optical lens 2 with a functional film 1 having a homogeneous adherence on said optical lens 2, and having the required size with respect to the lens 2 dimensions.

I n the exam ple showed in the different figures, it is supposed that the optical lens 2 and the blocking piece 5 have a circular contour and each have a sym m etry of revolution.

Referring to figures 2 and 4, it can therefore happen that som e parts 20 of the functional film 1 extend beyond the circular edge 7 of the optical lens 2 so that they overhang over said edge.

An inventory of film patches with varying dimensions can be m aintained. However, such an inventory increases complexity and cost in m anufacturing. Further, while it should be possible, even if m ore expensive, to plan an inventory of film patches when the overhang of the film is due to choosing, prior to the surfacing step a sem i-finished lens with a diameter sm aller than a larger dim ension of the film , such is not always the case.

However, during the manufacturing of some type of lenses, the surfacing step happens to reduce the diam eter of the optical lens as com pared to the initial dimension of the sem i-finished lens. Such reduction of diameter m ay lead to the maxim um dim ension of the film being larger than the surfaced lens diam eter, or m ore precisely having part of the film overhanging above the surface lens edge, when the film is oriented and centered with the optical center of the lens.

The final diam eter after such reduction of diameter during the surfacing step depends on the prescription desired for the optical lens, ie the optical power. Accordingly, a m ultiplicity of such diam eters m ay be produced. Further such reduction of diam eter may lead to lens contour that do not have sym m etry of revolution anym ore. Accordingly, in such cases, if one desire films that mostly cover m ost of the surface of the lens, at least in one dimension, but do not have any overhang, the construction of an inventory of films patches of various dim ensions becom es highly complicated.

Such a configuration, involving a functional film 1 which extends in any direction beyond the optical lens edge 7, is not acceptable, because it m ay negatively influence the deblocking step which enable to separate the optical lens 2 with the film 1 from the blocking piece 5. I ndeed, said separating step is generally achieved by m eans of pressurized fluid jet and thus, it is possible and even probable, that said pressurized fluid jet generates a film delam ination which can lead to a film 2 removal. Consequently, the film lam ination step m ust be restarted, greatly increasing the optical lens manufacturing costs.

I n order to prevent delam ination, a m ethod of manufacturing an optical lens 2 pursuant to the invention, comprises a step of cutting the film 1 excess 20, directly on the second assem bly 6 obtained.

Referring to figure 3, the aim of this cutting step is to lim it the film size so that the film dim ensions be com pletely included in the optical lens dimensions. I n other words, the film size is to be equal or less than the size of the optical lens 2. Advantageously, this cutting step allows obtaining a m inim um radial distance d in a plan view between the film 1 edge and the lam inated lens surface edge which is com prised between 0.05m m and 1 0m m , preferably com prised between 0.1 m m and 5m m , for example between 0.5m m and 3 m m with the film edge being closer to a center of the lens than the lam inated lens surface edge.

Such a configuration enables a sm oother deblocking. I ndeed, during the further deblocking step, which is configured to separate the lens from the blocking piece, stress is applied on the film , the lens and the blocker. I n particular, the separating step m ay be achieved by means of pressurized fluid jet. Due to cutting the film so that the film edge is closer to a center of the lens than the lam inated lens surface edge, the edges of the film provide less drag to the pressurized fluid jet. This is even truer when the lam inated lens surface is concave. I n such case if the edge of the film is closer to the center of the lens than the edge of the lens, the edge of the film are protected from the pressurized fluid jet by the edges of the lens. I ndeed, the edges of the film are inside the concavity form ed by the concave lam inated lens surface.

Referring to figures 4, 5 and 6, the cutting step is carried out with an apparatus 10 comprising an arm 1 1 equipped with a cutting element 12, and an assembly support 13 intended to receive the second assembly 6. The cutting element 12 m ay for example be chosen am ong a sharp edge, a laser cutter, and a blade. I n a general manner, any type of cutting means works, if it is capable of cleanly cutting the functional film 1 with a certain accuracy. The arm 1 1 extends in a horizontal direction and have a first extrem ity which is linked to a vertical cylindrical rod 14 and a second extrem ity where the cutting elem ent 12 is placed. Preferably, the arm distance from a center of the assem bly support 13 is adj ustable so as to adapt the arm position, or dimension, to a specific optical lens 2 size. The assem bly support 13 is cylindrical-shaped and is positioned on a cylindrical platform 15 of the apparatus 10, so that its axis of revolution extends in a vertical direction perpendicularly to the platform surface 15. This assembly support 13 is delim ited by a circular bottom and by a cylindrical lateral wall 16 and is rotatably m ounted on the platform 15 about its axis of revolution. The assem bly support 13 may be rotated, either manually, or autom atically by means of a motor and a control device. When the assem bly support 13 is handled manually by an operator, said operator can adj ust the rotation direction in function of his need. I n this configuration, it is supposed that the assem bly support 13 is freely mounted in rotation in the two possible directions of rotation about its revolution axis. I n a same way, when a motor makes rotated the assem bly support 13, said m otor is designed to allow a rotation m ovem ent of the assembly support 13 in the two possible directions of rotation about its revolution axis. An electrical motor is particularly suitable to perform such assembly support 13 rotary m ovem ents.

Referring to figure 4, the second assembly 6 is placed inside the assem bly support 13 so that the optical lens 2 and the functional film 13 protrude above said assem bly support 13, the functional film 1 corresponding to the upper part of said second assem bly 6. I n this configuration, the functional film 1 extend in a plan which is approxim ately horizontal (the term “approxim ately” is used because the functional film is not rigorously plan) .

Referring to figure 5, the arm is then positioned with respect to the vertical rod, and its position or length is eventually adj usted so as to lead the cutting element 12 above the functional film 1 at a given radial distance“d” from the peripheral edge of the optical lens 2, inside said optical lens 2. Preferably, the cutting elem ent 12 is then above the lens surface so as to have a radial distance “d” which is directed toward the center of the lens, and having a part of the surface of the optical lens uncovered from the film on the whole contour of the optical lens. A sensor/feeler enables to autom atically adapt the position of the cutting elem ent 12 to the position of the edge of the optical lens.

The cutting elem ent 12 is then activated to contact the functional film 1 and to begin the cutting step. I n order to cut the suitable portions of the functional lam inated film 20 which extend beyond the optical lens edge, the assem bly support 13 is rotated, m anually or autom atically with a m otor.

Referring to figure 6, once the functional film parts 20 overhanging the optical lens 2 edge 7 have been cut, they have then rem oved manually from the rest of the functional film 1 which adheres homogeneously and firm ly to the optical lens 2. This operation m ay be sim ply carried out with two fingers of the hand.

When the lam inated functional film sizes have been reduced by the cutting step, the deblocking step can begin to separate the optical lens 2 with the film 1 and the blocking piece 5 without any risk of film delam ination, because the film 1 is completely included in the optical lens 2 without any part which extends beyond the optical lens edge 7.