Patent ID: 12208972

In the following description, corresponding similar or identical elements of the figures will be referenced by the same symbols and will not be described in all details for each figure.

The vertical direction is here the direction of a plumb line. A horizontal plane is orthogonal to this vertical direction.

The wordings top/bottom, up/down are defined by reference to the vertical direction and to the orientation of the elements described during their use.

The context of the invention is here the transport of close-to-vertical thin sheets of substrate for industrial processes such as vacuum sputtered thin films.

The wording “thin” is used here as meaning that the thickness of the sheet of substrate is smaller than its other dimensions, for example at least 100 times smaller, or at least 1000 times smaller. In other words, the thickness of the sheet of substrate is less than a hundredth or less than a thousandth of the other dimensions of the sheet of substrate.

Such thin sheet of substrate may be for example a thin glass sheet having at least a size of 1.5 by 1.0 meters, preferentially a size of at least 3.2 by 1.85 meters, more preferentially a standard size of 6 by 3.2 meters, with various thickness ranging from 1 to 10 millimeters, preferentially from 1 to 3 millimeters, preferentially from 1.5 to 2.6 millimeters, more preferentially from 1.9 to 2.3 millimeters.

However, the embodiments of the device and methods of the invention are not limited to these applications. Other types of substrate may be considered, as well as other dimensions and/or thickness. The device and methods may be used while implementing other coating methods or other types of processes of the sheet of substrate.

As represented onFIGS.3,4and17, the sheet of substrate10typically has two opposed main faces11,12linked by an edge face. As the sheet of substrate is generally quadrangular, here rectangular, the edge face comprises four parts, among which a bottom edge14, an top edge13, a leading edge15and a closing edge16. The main face12oriented towards the upper rollers will be named hereafter the back face12, whereas the opposed main face12will be named the front face11.

In the device1according to the invention, one of said main faces11,12of the sheet of substrate10is positioned along a reception plane RP of said device1, said reception plane being close to a vertical plane. Conventionally, in the following it is considered that the back face12is received in the reception plane RP.

In practice, the reception plane RP of the sheet of substrate10is as close as being vertical as possible. For stability reasons, it is not currently possible to have a perfectly vertical reception plane. Therefore, the reception plane RP is for example inclined by 2 to 3 degrees relative to the vertical direction. The inclination angle I of the reception plane relative to the vertical direction is preferably comprised between 1 and 15 degrees, preferably between 1 and 7 degrees, preferably between 1 and 5 degrees and even preferably between 1 and 3 degrees (FIG.3).

The reception plane RP is a theoretical plane corresponding to the plane where the back face12is received when the sheet of substrate10is not subject to any deformation.

The conveying device1according to the invention comprises a plurality of lower rollers20A;20B positioned side by side along a conveying direction D (FIGS.3,7-9,16), each of them being able to rotate about a lower rotation axis21(FIGS.3and16) extending perpendicularly to the conveying direction D in a conveying plane P and being arranged to receive a part of the edge face of the sheet of substrate10.

In practice, the lower rollers20A;20B are configured to receive the bottom edge14of the sheet of substrate10.

The conveying direction D corresponds to the global direction along which the sheet of substrate10is conveyed. It may be defined as the direction of the straight line going through the initial first zone of contact between the lower rollers20A;20B and the leading edge15of the sheet of substrate10when it enters the conveying device1and the last zone of contact between the lower rollers20A;20B and this leading edge15of the sheet of substrate10when it exits the conveying device1.

The conveying device1also comprises a plurality of upper rollers30A;30B, each of them being arranged to receive one of said main faces11,12of the sheet of substrate10and being able to rotate about an upper rotation axis31orthogonal to said conveying direction D (FIG.3).

Each of the lower roller20A;20B and upper roller30A;30B comprises a receiving portion adapted to receive a face of the sheet of substrate and a mounting portion adapted to rotatably mount the receiving portion on the lower or upper rotation axis21,31.

The receiving portion comprises a lateral surface22A,32A;22B,32B having a transverse sections (orthogonal to its rotation axis) of circular shape, configured to remain in contact with the corresponding face of the sheet of substrate during conveying. The lateral surface22A,32A;22B,32B may have any adapted shape such as cylindrical, frustoconical, toroidal or spherical. It may also be a more complex shape as long as it is a surface of revolution.

In the embodiments shown onFIGS.3and14, the lateral surface22A,32A;22B;32B of each of the lower and upper rollers20A,30A;20B,30B is cylindrical.

FIGS.14and15show an embodiment where the lateral surface22B of each lower roller20B is a surface of revolution generated by a curved, concave meridian. The lower rollers20B may for example have a bi-conical shape or hourglass shape.

Typically, the mounting portions of the lower and upper rollers are made of metal. The receiving portion is made of a material appropriate to the industrial process considered, for example, of a material adapted to be placed in a vacuum chamber. It can be for example made of metal or any elastic material.

During conveying, the sheet of substrate10may be subject to different kind of deformations caused by mechanical an/or thermal stresses.

It may be subject to deformations due to gravity, linked to its own weight and its inclination relative to the vertical direction.

It may also be subject to deformations due to its transport in the conveying device, resulting from vibrations and/or misalignement of the lower and/or upper rollers and/or irregularities of the surfaces of the lower or upper rollers in contact with the sheet of substrate.

These deformations are mechanical deformations, due to the conveying of the sheet of substrate itself.

Other types of deformations may be linked to the processing of the sheet of substrate performed while it is being conveyed.

For example, the process performed may cause variations of the temperature of some parts of the sheet of substrate, thereby causing thermal deformations of the sheet of substrate.

In a remarkable manner, in the device1according to the invention said plurality of upper rollers30A;30B comprises upper rollers positioned at different heights H1, H2, H3from said conveying plane P (FIG.3).

Such plurality of upper rollers30A;30B then provide lateral surfaces32A;32B in contact with the back face12of the sheet of substrate10at places situated at least 10 centimeters away from each other along the vertical direction.

Preferably, upper rollers30A;30B located at at least three different heights, preferably four different heights, even preferably five or six different heights are used.

The embodiment represented onFIGS.3and4is an example of the device1according to the invention where three rows of upper rollers are used. Each row comprises upper rollers30A mounted at the same height H1, H2, H3relative to the lower rollers on twelve upper rotation axes31.

These values are especially useful when dealing with the sheets of glass of standard size mentioned above. They should be adapted to the size of the sheet of substrate actually considered.

Preferably, the upper rollers are regularly distributed along the vertical direction of the sheet of substrate. The gap between the different heights of the upper roller is advantageously the same. However, other distributions may be considered.

In order to provide stability to the sheet of substrate10all along its transport by the conveying device1, it is advantageous to provide a similar distribution of upper rollers30A;30B along the conveying direction D.

In practice, the plurality of upper rotation axes31comprises a predetermined number of upper rotation axes31regularly spaced in order for the sheet of substrate to remain in contact with a predetermined number of upper rollers30A;30B at all time during conveying.

In the examples described here, upper rotation axes31are spaced by about 46 centimeters, so that the back face12of the sheet of substrate10is in contact with the upper rollers mounted on twelve upper rotation axes31at all time (FIG.4).

In practice, at least one of said upper rotation axis31supports at least two upper rollers30A;30B.

Preferably, each upper rotation axis31supports at least two upper rollers30A;30B.

In the examples described here, in order to achieve a satisfactory stability of the sheet of substrate, each upper rotation axis31supports a plurality of upper rollers30A;30B located at the same heights relative to the lower roller20A;20B.

In this configuration, the upper rollers30A;30B supported by different upper rotation axes31at the same height form a row of upper roller30A;30B parallel to the conveying plane P.

FIGS.3and4show the case of an embodiment with three rows of upper rollers30A, whereasFIG.14shows the case of an embodiment with five rows of upper rollers30B.

In the embodiment ofFIGS.3and4, all the upper rollers30A are identical: rigid, cylindrical, with a diameter of 50 millimeters and a height of 20 millimeters.

As shown inFIG.3, in this embodiment, the upper rotation axis31extend parallel to the reception plane P, therefore parallel to the back face12of the sheet of substrate10with no deformation.

In the embodiment ofFIG.14, the upper rollers30B are rigid, cylindrical, with a height of 20 millimeters and different diameters as described in more details hereafter.

In the case where, as illustrated for example byFIG.14and described later, the upper rollers30B of each row of upper rollers30B do not have the same diameter, it can be considered that the upper rotation axes31are not parallel to the sheet of substrate without deformation, as long as the contact areas of the lateral surfaces of the upper rollers30B with the back face12of the sheet of substrate10remains in the reception plane RP.

Moreover, in the embodiments shown here, each upper rotation axis supports the same number of upper rollers. Alternatively, upper rotation axes may support different numbers of upper rollers.

In the following, the results of different simulations are presented.

In these simulations, bending or deformation of the sheet of glass is defined as the difference between maximum and minimum out-of-plane displacements of simulated sheets of substrate.

The simulated sheet of substrate is a simulated sheet of glass10S inclined of 3 degrees relative to the vertical direction, and received by different numbers of rows of upper rollers supported by twelve upper rotation axes. The upper rollers all have a diameter of 50 millimeters and a height of 20 millimeters.

These simulations are used as a way to evaluate and compare considered cases.

All the simulation were calculated in a configuration where both simulated leading and closing edges15S,16S are not supported by upper rollers, as if they were just leaving the upper rollers located on a last upper rotation axis and about to contact the upper rollers located on the next upper rotation axis.

In practice this configuration does not happen but it allows to evaluate in a worst case scenario how the sheet will “fall” or “jump” when going from the upper rollers of one upper rotation axis to another.

FIG.1shows the result of a static finite-element simulation of the bending of a standard-size simulated glass sheet of different thickness conveyed in a state-of-the-art conveying device comprising only one row of upper rollers to receive the back face of the sheet of glass, without adding an additional frame to stabilize and protect the sheet of glass.

The single row of upper rollers comprises twelve upper rollers placed at 2.1 meters from the lower rollers.

Simulations of glass deformation show that sheets thinner than 2.6 millimeters deform too much to be safely transported on the state-of-the-art device. Deformations of more than 6 millimeters lead to buckling of the sheet of glass.

FIG.2shows a similar simulation achieved with the features of different embodiments of the device according to the invention.

The features of these embodiments are described in the following table 1.

TABLE 1Top rowheightDistanceNumberTotalrelative tobetweenof rowsnumberthe loweradjacentof upperof upperrollersrows inrollersrollersin metersmeters2242.71.43363.01.04483.00.75603.00.66723.00.5

Results presented onFIG.2show that the amplitude of the bending of the sheet of glass is considerably reduced by adding a second row of upper rollers30A, the maximum deformation for a sheet of glass of 2.6 millimeters being about 6 millimeters with only one row of upper rollers and 1.5 millimeter with two rows of upper rollers30A.

At least two upper rollers rows are required to ensure the stability of sheets of glass thinner than 2.6 mm. Four or five rows of upper rollers are preferred.

Using more than 5 rows of upper rollers provides limited improvement.

Using at least two rows of upper rollers therefore allows conveying sheets of substrate of smaller thickness than with the state-of-the-art devices, without needing to frame them, which is quicker and simpler.

Moreover, the conveying device according to the invention may be further optimized.

It is for example possible to adjust a position of each upper roller30A;30B along the upper rotation axis31by which it is supported and/or a number of upper roller30A;30B supported by each upper rotation axis31.

To this end, a further embodiment of the device according to the invention comprises upper rollers30A;30B whose position and/or number are adjustable.

More precisely, the mounting portion of each upper rollers30A;30B for example allows blocking and unblocking the upper roller30A;30B on the upper rotation axis31at an adjustable height on the upper rotation axis. In this way, each upper roller30A;30B may be mounted at different heights on the upper rotation axis31. The upper rotation axis may for example comprise a rack. The mounting portion of the upper roller30A;30B may cooperate with the upper rotation axis31by clip-on or interlocking means. These means may be motorized so that the adjustment can be done in real time during conveying the sheet of substrate. It can also be done in a preparation step before conveying the sheet of substrate.

The adjustment may also be achieved manually. It is then done in a preparation step before conveying the sheet of substrate.

Thanks to the fact that each upper roller may be unblocked and moved along the upper rotation axis, it is also possible to add or remove one or several upper rollers from the upper rotation axis. This adjustment may be achieved manually or automated. It is preferably done in a preparation step before conveying the sheet of substrate.

In another embodiment of the device according to the invention, the position of the upper rollers30A;30B is adjustable in distance relative to the reception plane RP.

To this end, the upper rotation axis31is movable relative to the reception plane RP, backwards, that is away from the reception plane, or forward, towards the reception plane. The mobility of the upper rotation axis31may be motorized so that the adjustment can be done in real time during conveying the sheet of substrate. It can also be done in a preparation step before conveying the sheet of substrate.

The adjustment may also be achieved manually. It is then done in a preparation step before conveying the sheet of substrate.

The mobility of the upper rotation axis may also be a passive one. The upper rotation axis31may be mounted on thin blades that buckle and move backwards, away from the reception plane, when the sheet of substrate contacts the upper rollers, and then retrieve their initial shape, bringing the upper rotation axis back in its initial position.

Alternatively, in yet another embodiment each upper roller is configured to be able to move relative to the reception plane independently from the others.

Example of use of these adjustments will be given later.

According to yet another embodiment of the device according to the invention, the lateral surface of each upper roller30A;30B is adapted to be moved away from said reception plane RP. This can of course be achieved through the mobility of the whole upper rotation axis, as described before.

However, it can also be achieved by the use of upper rollers30A;30B with lateral surface adapted to be deformed away from said reception plane RP. The lateral surface32A;32B of each upper roller30A;30B is then moved away from the reception plane RP without moving the corresponding upper rotation axis31.

To this end, upper rollers with a specific design or material are used. For example the lateral surface32A;32B of the upper rollers comprises a deformable material or a structure leading the lateral surface to buckle and move backwards when contacted.

Although the upper rollers with adjustable height and/or adjustable distance of the upper rotation axis and/or of their lateral surface to the reception plane have been here described in relation with the device1according to the present invention, comprising a plurality of rows of upper rollers, it is to be noted that these features of the device according to the invention could also be advantageously implemented in a conveying device having only one row of upper rollers.

As already mentioned, the upper rollers30B supported by the same upper rotation axis may have different diameters, as represented onFIG.14.

Preferably, the diameter of each upper roller30B is determined taking into account an expected deformation of the sheet of substrate10while it is conveyed on the device1.

Expected deformations of the sheet of substrate are either determined by simulation or actual measures performed on conveyed sheets of substrate.

The simulated or measured deformations are recorded in association with the features of the sheet of substrate (dimensions, material . . . ), the features of the device used (position/number/diameters of upper rollers . . . ) and the environmental conditions (thermal load . . . ).

More precisely, the diameter of each upper roller30B is determined to limit deformation of the sheet of substrate located near the edge of the sheet of substrate first conveyed in said device1and/or to limit deformation of the sheet of substrate linked to thermal or mechanical stress applied to the sheet of substrate while it is being conveyed.

The determination of the diameter of each upper roller30B may be for example based on simulated deformation of the sheet of substrate and on expected environmental conditions of the conveying device1, such as working temperature.

Alternatively, the determination of the diameter of each upper roller30B may take into account experimental data acquired while conveying similar sheet of substrate in similar environmental conditions, for example thanks to the use of sensors. These experimental data may comprise temperature and/or out-of-plane displacement measures at several locations on the sheet of substrate.

The experimental data and/or simulated data may be stored in a table or an abacus, in association with the appropriate settings of the device to be used.

The settings of the device comprise in particular the positions and/or number of upper rollers to be used.

Based on the expected deformation of the sheet of substrate, it is possible to determine the diameters of the upper roller in order to define a reception surface that exhibits a complex curved shape, not planar. The reception surface is then defined as the surface going through the zone of contact between each upper roller30B and the back face12of the sheet of substrate10. In the embodiment ofFIG.14, the reception surface profile corresponds to the sheet of substrate profile represented by a dash-dotted line. This reception surface being curved, it causes predetermined, controlled deformation to the sheet of substrate10received by the upper roller30B.

The diameters of the upper rollers30B are then determined in order to obtain a reception surface causing controlled deformations that will either limit or compensate the deformations expected to occur while the sheet of substrate is being conveyed.

As an example, detailed hereafter, imposing a controlled transverse deformation, along the close-to-vertical direction of the closing edge16and leading edge15of the sheet of substrate10will rigidify the sheet of substrate longitudinally, in the conveying direction D, and therefore limit longitudinal deformations.

In a further embodiment of the device1according to the invention, the upper rollers30B supported by different upper rotation axes may also have different diameters. This allows imposing a controlled longitudinal deformation of the sheet of substrate10. This will rigidify the sheet of substrate along the transverse close-to-vertical direction and therefore limit deformation along this transverse direction.

The diameters of the upper rollers30B supported by different upper rotation axes31are then determined to limit deformation of the sheet of substrate located near the edge of the sheet of substrate first conveyed in said device1and/or to limit deformation of the sheet of substrate linked to thermal or mechanical stress applied to the sheet of substrate while it is being conveyed.

Although the upper rollers with different diameters on different upper rotation axes have been here described in relation with the device according to the present invention, comprising a plurality of rows of upper rollers, it is to be noted that this feature of the device according to the invention could also be advantageously implemented in a conveying device1having only one row of upper rollers.

In a further embodiment of the device1according to the invention, the lateral surface22B of each lower roller20B presents a concave shape and is movable along its lower rotation axis21. Such an embodiment is schematically shown onFIGS.16and17.

Thanks to this specific shape of the lower rollers20B, the sheet of substrate10may be continuously deformed along the conveying direction D.

In practice, while the lower roller20B is moved along its lower rotation axis21, that is, along a direction perpendicular to the conveying direction D, the lower edge14of the sheet of substrate10remains at the bottom of the concave lateral surface22B. Consequently, while the lower roller20B is moved along its lower rotation axis21, the bottom edge14of the sheet of substrate10follows this movement.

Adjusting the position of the lower roller20B along its lower rotation axis21then allows imposing a controlled longitudinal deformation of the sheet of substrate10. This will rigidify the sheet of substrate along the transverse close-to-vertical direction and therefore limit deformation along this transverse direction.

The position of the lower roller20B along its lower rotation axis21is then determined to limit deformation of the sheet of substrate located near the edge of the sheet of substrate first conveyed in said device and/or to limit deformation of the sheet of substrate linked to thermal or mechanical stress applied to the sheet of substrate while it is being conveyed.

This feature of the device according to the invention could also be advantageously implemented in a conveying device having only one row of upper rollers.

Alternatively, it is possible to consider imposing a longitudinal curvature to the sheet of substrate with continuous and synchronized displacements of upper rotation axes towards the reception plane or away from the reception plane, this displacement being applied successively to the upper rotation axes as the sheet of substrate is conveyed along the conveying direction.

In another embodiment of the device1according to the invention, additional opposed upper rollers40are positioned to contact the other main face11of the sheet of substrate10, that is, here, the front face11of the sheet of substrate10.

These additional opposed upper rollers40allow better controlling the deformation of the sheet of substrate10caused by adjusting the positions of the lower rollers. In the embodiment described here, they are placed close to the bottom edge14of the sheet of substrate10, so that they are located behind the commonly installed shield preventing sputtering materials on the conveying device.

The position, height and distance to the front face11, of the additional opposed upper rollers40are advantageously adjustable.

They are adjusted depending on the sheet of substrate thickness and expected deformation of the sheet of substrate.

These positions are preferably kept during the process. A more complex active control of the position of these additional upper rollers40can also be implemented and provide optimized settings without production interruption.

This feature of the device according to the invention could also be advantageously implemented in a conveying device having only one row of upper rollers located on the back of the sheet of substrate.

In the case where several upper and/or lower and/or additional upper rollers have an adjustable position, with motorized setup and real-time control, the device according to the invention also comprises synchronization means in order to synchronize the movements of all the rollers.

In the following, we will explain how using embodiments of the device according to the invention may ensure the stability of the sheet of substrate while it is being conveyed by limiting and/or compensating expected deformations of the sheet of substrate.

As examples, the following thermo-mechanical deformations will be taken into account:mechanical deformation of the leading edge15of the sheet of substrate10occurring while this leading edge15is conveyed between two adjacent upper rotation axes31and therefore not in contact with any upper roller30A;30B, andthermal deformation due to the environmental conditions of the conveying device, for example used in a vacuum chamber of a sputtering device.

According to the invention, embodiments of the conveying device described above may be used to implement a method for conveying a sheet of substrate, wherein the position of each upper rotation axis31is moved away from the reception plane RP of the sheet of substrate10when said sheet of substrate first arrives close to contacting the lateral surface of revolution32A;32B of the upper rollers30A;30B supported by this upper rotation axis31.

Other embodiments of the conveying device described above may be used to implement a method for conveying a sheet of substrate10wherein the position of each lower roller20B along its lower rotation axis21and/or the position of each upper rotation axis31relative to the reception plane RP is adjusted in real time to limit deformation of the sheet of substrate10located near the leading edge15of the sheet of substrate10first conveyed in said device1and/or to limit deformation of the sheet of substrate10linked to thermal or mechanical stress applied to the sheet of substrate while it is being conveyed.

The deformations of the leading edge15of the sheet of substrate10occurring while this leading edge15is conveyed between two adjacent upper rotation axis31is represented schematically onFIG.7and simulated onFIG.5.

When the sheet of substrate10goes from the upper rollers30A of one upper rotation axis31to the upper rollers30A of the next upper rotation axis31, its leading edge15is temporary not supported and sag under its own weight due to gravity as illustrated byFIGS.5and7.

FIG.5is a contour map showing the out-of-plane displacements of a 2.1 millimeters thick standard size simulated sheet of glass10S supported by four rows of twelve upper rollers. The simulated sheet of glass10S has a simulated leading edge15S, a simulated closing edge16S, a simulated top edge13S and a simulated bottom edge14S, as well as simulated front face11S and back face.

The simulated deformations increase with decreasing number of upper rotation axis31as the unsupported part of the sheet of substrate10gets longer. This is highlighted by the simulation results represented onFIG.6. Regardless of the number of rows of upper rollers, the leading edge deformation is more than ten times higher with five upper rotation axes, corresponding to an unsupported length of about one meter between two adjacent upper rotation axes, as compared to the deformation simulated with twelve upper rotation axes, corresponding to an unsupported length of about 46 centimeters between two adjacent upper rotation axes.

As shown on thisFIG.7, if this deformation is not limited or compensated, the leading edge15of the sheet of substrate may collide into the upper rollers30A of the next upper rotation axis31, which may damage the sheet of substrate10. It may also cause vibrations and instabilities.

A first possibility to remove this risk is to use an embodiment of the device1according to the invention wherein the distance between the reception plane RP and each upper rotation axis31is adjustable.

Only a small amplitude of movement is necessary to remove the upper rollers from the trajectory of the leading edge15. For example, a backwards movement of about 4 millimeters, in the example ofFIG.7, is sufficient.

The movement of each upper rotation axis31is then synchronized with the advance of the sheet of substrate10along the conveying direction D. As shown onFIG.8, each upper rotation axis31is moved away from the reception plane as the leading edge15of the sheet of substrate10arrives near the lateral surface32A of the upper rollers30A of this upper rotation axis31.

When the leading edge has passed in front of the upper rotation axis31, the upper rotation axis31retrieves its initial position and the upper rollers softy contact the back face11of the sheet of substrate10(FIG.9).

A second possibility to remove this risk is to use an embodiment of the device1according to the invention wherein the lateral surface of each upper roller30A is deformable to smoothly absorb leading deformations or able to buckle away from the reception plane when initially contacted by the leading edge and retrieve its initial shape far from the leading edge.

A third possibility to remove this risk is to use an embodiment of the device1according to the invention wherein the diameters of the upper rollers mounted on the same upper rotation axis are different, in order to impose a specific shape to the sheet of substrate that will make it more rigid in longitudinal direction and limit leading edge15bending.

In other words, the deformation of the leading edge15is limited by imposing a controlled transverse deformation, along the close-to-vertical direction of the leading edge15of the sheet of substrate10that will rigidify the sheet of substrate longitudinally, in the conveying direction D, and therefore limit longitudinal deformations such as leading edge bending.

This shape can be imposed by moving upper rollers of one or several rows away from the reception plane RP, in the case where the upper rollers supported by an upper rotation axis can be moved independently from each other.

The upper rollers positions are then fixed during conveying.

Alternatively, upper rollers with different diameters can be used.

As an example of this last possibility,FIGS.10and11show the contour maps of the out-of-plane displacements of the simulated sheet of glass10S of thickness 2.1 millimeter with standard size supported by embodiments of the device having three rows of twelve upper rollers of same diameters according to the features of table 1 forFIG.10, and a similar device with upper rollers having different diameters causing a backwards translation of 4 millimeters of the zone of contact between the lateral surface of the upper rollers of the top row and the simulated back face12S of the sheet of glass10S inFIG.11.

A transverse convex shape is therefore imposed to the simulated sheet of glass10S by moving the lateral surface of the upper rollers of the top row 4 millimeters away from the reception plane.

The map ofFIG.10show that the largest deformations of the simulated sheet of glass10S are located near the simulated leading edge15S and simulated closing edge16S.

As visible onFIG.11, the largest deformation of the simulated sheet of glass10S are then located along the simulated top edge13S of the simulated sheet of glass10S.

Corresponding profiles extracted from these simulations are shown ofFIGS.12and13.

FIG.12shows the transverse (vertical) profile of the back face of the simulated sheets of glass ofFIGS.10(× symbols) and11(+ symbols) at the middle of the length of the simulated sheet of glass. This figure shows the deformation of the simulated sheet of glass imposed by moving the lateral surface of the upper rollers away from the reception plane. The simulated top edge13S of the simulated sheet of glass10S is displaced by 5 millimeters backwards from the reception plane. The reception plane corresponds to the plane with zero deformation.

FIG.13shows the longitudinal (horizontal) profile of the back face of the simulated sheets of glass ofFIGS.10(× symbols) and11(+ symbols) at the height of the top row of upper rollers (3 meters). The position of the simulated leading edge15S is shown by the last symbol placed at longitudinal position of 3 meters, the middle of the simulated sheet being placed a zero.

This figure shows that bending of the simulated leading edge15S is reduced by 18.6%. The simulated leading edge bendings determined at different heights corresponding to the heights of the upper roller rows show reductions between 1.4 and 18.6%.

Other shapes imposed to the sheet of substrate can of course be considered within the scope of the invention, for example corrugated, convex with different row heights, concave.

Regarding the thermal deformation, the sputtering process for example generates fast and high heating of the treated surface as the sheet of glass moves in front of the cathodes of the sputtering device. Resulting thermal gradients appearing through the glass thickness can cause deformations and out-of-plane displacements towards the cathodes of several centimeters. This may bring the treated surface too close to the deposition system and affect coating homogeneity. Again, large displacements can also impact glass stability.

Thanks to the device according to the invention, thermal deformations are at least partly compensated by imposing a concave transverse shape to the sheet of glass. This concave shape is for example imposed by mounting upper rollers30B with a smaller diameter on the central rows of upper rollers30B and by adjusting their heights and number to increase the effect, as represented onFIG.14.

An embodiment of such a conveying device has the features listed in tables 2 and 3.

TABLE 2NumberTotalofnumberTopDistancerows ofofrowbetweenupperupperheight inrowsrollersrollersmetersin meter5603.150.77

TABLE 3RollerResultingdiameterrowRowinshift innumbermillimetersmillimeters17002321932224432195700

FIG.15shows the simulated out-of-plane displacements of a 2.1 mm thick standard size simulated sheet of glass with the conveying device having the features of Tables 2 and 3. In the perspective view deformations are magnified by a factor20to make obtained concave shape more visible.

This curved shape will also have the same rigidifying effect as discussed above, thus limiting leading edge collisions with upper rollers.

In this example, deflection at the center of the simulated sheet of glass is around 25 millimeters.

In practice, to prevent glass breakage, local radius of curvature imposed to the sheet of glass should not exceed about 3.5 m to keep bending stresses below 20 MPa.

Glass curvature, either imposed by the conveying device or coming from thermo-mechanical deformations, have to be kept below this limit by choosing adapted settings.

In addition, out-of-plane displacements during sputtering process coming from the combined effects of the conveying device and thermo-mechanical deformations should not exceed 30-40 millimeters to ensure deposited thin film homogeneity.

The device1and methods according to the invention allow controlling the shape of the conveyed sheet of substrate. Imposing a convex shape in transverse, longitudinal or a combination of both directions will rigidify the sheet of substrate and limit deformations. It also allows compensating thermal deformations, keep the sheet of substrate stable and in a position adapted to processing, for example ensuring homogeneity of the coating.

The methods according to the invention are computer-implemented. The invention therefore also related to a computer program product, comprising program code instructions for implementing the methods described above, when said program is executed on a computer or a processor.

It also relates to a non-transitory computer-readable medium comprising a computer program product recorded thereon and capable of being run by a processor, including program code instructions for implementing said methods.

For example, said computer program product may use a wide range of substrate deformation simulation results stored in a database. Said computer program product continuously provides the optimized settings of the device to apply depending on currently transported sheet of substrate thickness, environmental parameters such as cathodes power in sputtering processes and/or inputs from displacement sensors or thermocouples.

The different embodiments described here are part of the invention considered independently or with all combination technically possible.