GB2632019A - Transfer of a pattern to a substrate - Google Patents

Abstract

An apparatus and method are disclosed for transferring patterns carried by a web 100 of a deformable plastics material onto substrates. The apparatus comprises a nip defined between at least one nip roller 116 and a backing support 116 through which the substrates are passed simultaneously with the web and by means of which pressure is applied to effect transfer of the patterns from the web to the substrates. In the invention, a web heater (heatable roller 114) and a web tensioner (tensioning roller 110) are arranged upstream of the nip, and a control unit 120 is provided for controlling the web heater and the web tensioner in dependence upon data indicative of the lengths and widths of the patterns on the web prior to transfer, or of the patterns on the substrates after transfer, so as to ensure that, after transfer to the substrates, the patterns conform to a desired length and width. The apparatus may comprise a camera 122 and a shaft encoder associated with the nip roller, and to send control signals based on data received therefrom to set the speeds and/or torques of the tensioning roller and the temperature of the heating roller.

Description

TRANSFER OF A PATTERN TO A SUBSTRATE

FIELD

The present invention relates to the transfer of patterns from a web to substrates, such as performed in the manufacture of solar cells and circuit boards, wherein the pattern may furthermore be conductive.

BACKGROUND

There has previously been proposed by the present Applicant in EP 3826438, which is incorporated herein by reference in its entirety, a method of applying a pattern of electrical conductors to an electrically insulating substrate, which comprises providing a flexible membrane, or web, having a layer made of a conformable plastics polymer, such as a thermoplastic polymer, capable of being embossed or cast. A first surface of the membrane (or front side of the web) has a pattern of grooves formed therein, the pattern corresponding to at least a part of a desired pattern of electrical conductors to be applied to the substrate. A composition is loaded into the grooves of the first surface of the membrane, or may be otherwise deposited thereon, the composition including particles of an electrically conductive material and an adhesive. The loading is performed in filling cycles such that on completion of loading the composition substantially fills the grooves, level with the first surface of the membrane, and parts of the first surface between the grooves are substantially devoid of the composition. The membrane is next contacted with the substrate with the first surface of the membrane facing the substrate and pressure is applied to the membrane to cause the composition loaded into the grooves in the first surface of the membrane to adhere to the substrate. Last, the membrane can be separated from the substrate to transfer the composition from the grooves in the first surface of the membrane to the substrate. Energy may later be applied to sinter the electrically conductive particles, to render electrically conductive the pattern of composition transferred to the substrate from the grooves. A similar method is disclosed in EP 3491900 to the Applicant, which is incorporated herein by reference in its entirety.

In EP 3491902, which is also incorporated herein by reference in its entirety, the Applicant has further proposed an apparatus for transferring a pattern of a transferable composition, such as containing particles of an electrically conductive material and a thermally activated adhesive, from a surface of such a flexible web to a surface of a substrate. The apparatus comprises respective drive mechanisms for advancing the web and the substrate at the same time through a nip at which the surfaces of the web and the substrate are pressed against one another. A heating station is provided for heating at least one of the web and the substrate prior to, and/or during, passage through the nip, to a temperature at which the adhesive in the composition is activated when the surfaces are in contact with one another. A cooling station serves to cool the web after passage through the nip and prior to the web optionally passing through a separating device that peels the web away from the substrate to leave the pattern of composition adhered to the surface of the substrate.

When employing the above methods and apparatus to apply, for instance, conductive patterns to substrates, it has been found that the dimensions of the patterns after application to the substrates may vary. Not only can the dimensions of transferred patterns vary between different webs carrying the patterns but even patterns carried by the same web can vary in size progressively during the transfer process from the web to the substrates. The variations can be in both the length of the patterns, as measured in the direction of movement of the web through the nip and in their width as measured in the transverse direction. Such variations may be caused both by conditions during the production of the web carrying the patterns, as well as conditions during the process of transferring patterns from the web to the substrates. Such variations may result in deviations from desired nominal values exceeding tolerable divergences. In such a case, the transferred patterns having non-conform dimensions may be less able to align properly with the substrates and/or with patterns transferred to the opposite side of the same substrates.

Alternatively, or additionally, some deviations from desirable dimensions may adversely affect the appearance and/or function of the transferred pattern.

OBJECT OF THE INVENTION

The present invention seeks to mitigate the problem of size variation between patterns applied to different substrates, this problem being particularly significant when the patterns are carried by a flexible web.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides an apparatus for transferring patterns carried by a web of a deformable plastics material onto substrates, the apparatus comprising a nip defined between at least one nip roller and a backing support through which the substrates are passed simultaneously with the web and by means of which pressure is applied to effect transfer of the patterns from the web to the substrates, characterized by a web heater and a web tensioner arranged upstream of the nip, and a control unit for controlling the web heater and the web tensioner in dependence upon data indicative of the lengths and widths of the patterns on the web prior to transfer, or of the patterns on the substrates after transfer, so as to ensure that, after transfer to the substrates, the patterns conform to a desired length and width.

The patterns need not have the exact nominal values of the dimensions desired following transfer to the substrates. The patterns' dimensions may be within a tolerated deviation therefrom (either in absolute terms, e.g., within 100 micrometer (um), or in relative terms, e.g., within I% of ideal length and/or width). In some cases, when patterns are to be applied to both sides of a substrate, and the two patterns are to be aligned one with respect to the other, the desired length and width of the first pattern carried by a first web may depend on the length and width of the second pattern carried by a second web. In such a case, at least one of the heating and tensioning of the first and the second web can be set to ensure proper reciprocal alignment.

In some embodiments of the invention. measurements of the patterns or fiducial markings on the web are made prior to the patterns reaching the nip at which the patterns are transferred to the substrates, and during the process of transferring the patterns from the web to the substrates, the temperature and tension of the web prior to entering the nip are regulated in dependence upon the measurements.

In alternative embodiments, measurements are made of patterns that have been transferred to substrates, and during the process of transferring patterns from the web to further substrates, the temperature and tension of the web prior to entering the nip are regulated in dependence upon the measurements.

The length of the patterns can be varied by varying the tension of the web upstream of the nip but such stretching of the web may also reduce its width and therefore the width of the patterns. Heating of the web will soften the web and therefore increase its deformation during passage through the nip, causing both the width and the length of the patterns to increase with increased temperature. By correctly setting both the tension and the temperature of the web prior to reaching the nip in dependence upon measurements taken prior to the web entering the nip, and/or after exiting the nip, the invention can ensure that the patterns are stretched as necessary during the transfer to conform more accurately and consistently to a desired length and width after transfer to the substrates.

Measurements of the length and width of the patterns may be carried out at the time of manufacture of the web and encoded markings (e.g., a barcode) may be applied to the web during manufacture containing data indicative of the sizes of the patterns. In such an implementation of the invention, the control unit of the apparatus would serve to set the web temperature and tension based on the data read from the web. The encoded marking may provide information of relevance to different variations displayed along the web at a distance of unwinding, the web temperature and tension being modulated so as to be suitable at said distance.

Alternatively, or additionally, there could be detectable data markings on the web. The data markings on the web may be a measure of the length and width of the patterns on the web in a region adjacent to the markings, or may allow the actual in-line measurements of said dimensions, or they may indicate the optimum web temperature and web tension to be set by the control unit at the time of the transfer of the patterns to the substrates.

Such an approach would suffice if maintaining constant temperature and pressure during transfer of the patterns would consistently yield transferred patterns on the substrates of a constant size. However, as mentioned previously, it has been found in practice that size variations can develop progressively during the transfer of patterns from a single web. To compensate for such errors, in an alternative embodiment of the invention, the apparatus comprises sensors to take measurements indicative of the widths and lengths of the patterns on the web at the time of the transfer at a position upstream of the nip.

It will be appreciated that because the web temperature can only be changed relatively slowly, as compared to the speed at which the web may be fed to the nip (e.g., up to 1 m/sec), it is not possible to use this approach to correct for random variations in the size of the transferred patterns from one pattern to the next on the same web. However, this approach will at least reduce the progressive size changes that have experimentally been found to occur.

In some embodiments, the sensors may comprise optical sensors for determining the positions of specific markings on the web on opposite lateral sides of the web, the markings being either fiducials distinct from the (e.g., conductive) patterns or elements of the patterns, so as to provide a measurement indicative of the width of the patterns on the web.

The nip may be associated with a shaft encoder capable of measuring the movement of the web through nip. In such an embodiment, the length of web passing through the nip between detection by the optical sensors of consecutive specific markings on the web provides an indication of the length of the patterns on the web.

In some embodiments, the web heater may be a heated roller located upstream of the nip, but it would alternatively, or additionally, be possible to heat a section of the web by means of a blower or by radiation. It is further possible for at least one of the nip rollers to include a heater.

In some embodiments, the apparatus is adapted to transfer patterns to both sides of the same substrate. In such a case, the apparatus may include two separate nips, each one for transfer of a particular pattern from a respective web to a specific side. The nips can be constituted of a nip roller and a backing support or of two nip rollers aligned one with the other. Alternatively, the two patterns may be transferred to each side of the substrate from a respective web at a same nip, in which case the nip is constituted of two nip rollers, which are typically symmetrical.

The patterns that may be transferred to substrates by use of the apparatus and/or method according to the present teachings can be functional or decorative, the substrates and transferable compositions carried by the flexible web being accordingly selected and adapted to the desired end-use of the transferred patterns.

Notably, as the patterns are carried by a flexible web, the substrates to which they are to be transferred need not be exclusively rigid and flat, and flexible and/or non-flat (e.g., curved) substrates may also be used and benefit from the present teachings.

In another aspect, there is provided a method for ensuring that patterns carried by a web of a deformable plastics material conform a desired length and width following transfer to a substrate at a transfer nip, the method including a) collecting data indicative of the lengths and widths of the patterns on the web prior to transfer, or of the patterns on the substrates after transfer, and b) controlling a temperature of the web and a tension of the web upstream of, or at, the nip in dependence upon the collected data.

These, and additional benefits and features of the invention, will be better understood with reference to the following detailed description taken in conjunction with the figures and non-limiting examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further, by way of example, with reference to the accompanying drawings, where like reference numerals or characters indicate corresponding or like components. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments of the disclosure may be practiced. The figures are for the purpose of illustrative discussion and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the disclosure. For the sake of clarity and convenience of presentation, some objects depicted in the figures are not necessarily shown to scale.

In the Figures: Figure 1 is similar as Figure 1 of EP 3491902 and is reproduced herein for completeness to show an apparatus for transferring patterns from a web to substrates, Figure 2 is a schematic representation of details of the web feeding apparatus in Figure 1 that have been modified in order to implement the present invention, and Figure 3 is a perspective view of part of the web feeding apparatus of Figure 2.

DETAILED DESCRIPTION OF THE DRAWINGS Overview of the Apparatus The apparatus of Figure 1 is intended to apply to opposite sides of substrates 10, drawn from a stack 12, patterns of a transferable composition that may contain particles of an electrically conducting material and an adhesive which may later be thermally and/or pressure activated. In such a case, the composition can be sintered by application of energy to render the patterns electrically conductive. Thus, in one example, the substrates 10 may be semiconductor wafers or insulating substrates onto which the apparatus applies the front and back patterns (e.g., electrodes, circuits) of the desired end-item. However, the composition may not require the application of energy to become conductive, and in some cases electrical conductivity may not be required, the pattern, for example, having other functions or being only ornamental. If the pattern is to be treated to develop its desired functional and/or esthetical effect, for instance it is to be heated to become electrically conductive, or to be fused or cured to increase adhesion to the substrate, this treatment is typically performed following transfer of the pattern to a suitable substrate.

The two patterns that may be applied to each face of a substrate are usually not the same but may need to be correctly aligned with one another and with the substrate. In the substrate drive mechanism, substrates 10 are dispensed one at a time from the stack 12 to an inspection station 60 where the upper surfaces of the substrates can be analyzed optically for defects. In the selection station 62 that follows, substrates found to be defective can be ejected. Substrates 10 without defects are advanced onto an alignment device 50 where they can, in one embodiment, also be heated by a heater 52. After being heated, if desired, and correctly positioned and oriented, the substrates 10 are fed into a nip 40 defined between two pressure rollers 22a and 22b.

While the inclusion of an inspection station 60 and a selection station 62 to detect and eject defective substrates is recommended, such stations are not essential for the operation of the apparatus, being only preferable from a quality control standpoint. Stations fulfilling similar roles downstream of the nip, and typically following the peeling of the flexible web, when performed, can optionally be further included to detect defective patterns and eliminate substrates bearing such defects.

When the apparatus does comprise stations 60 and 62 upstream of the nip, it can be desired to further include an accelerating station 64 allowing a non-defective substrate being drawn after a defective one, which was therefore ejected, to reach the nip in synchrony with the pattern(s) of the web(s). Such accelerating station 64 may therefore prevent an "empty" feeding of the web at the nip, in absence of a substrate. Such an accelerating station is, however, not essential as such empty feeding can be tolerated or mitigated by alternative means, such as adding a substrate pre-selected as flawless from a buffer of such non-defective wafers, or by any like solution.

In the present illustration, the patterns of composition that are to be transferred to the substrates are carried by two flexible webs 14a and 14b. The substances to be transferred, also termed transferrable compositions, can be located within recesses below the surface of the web (e.g., grooves) and/or on the surface of the web. The side of the web carrying the pattern of substances can be referred to as the front side of the web, whereas the opposite side of the web can be referred to as its rear side.

As can dearly be seen from Figure 1, the drive mechanisms of the two webs 14a and 14b can be mirror images of one another. To avoid repetition, reference numerals without a suffix will be used in the present description to refer generically to components of both web drive mechanisms but suffixes "a" and "b" are used in the drawings to distinguish between the upper and lower drive mechanisms.

Each web 14 is drawn from a motorized supply roll 16 by way of idler rollers 18 and a dancer 20, that can move from left to right as represented by an arrow. The web 14 then passes between the two pressure rollers 22 that define the nip 40 into which substrates are fed. Within the nip, the composition pattern on the web 14 is pressed against a surface of the substrate 10 resulting in the pattern of composition adhering to the substrate. The web then passes, in the present illustration, through a cooling station 23 and between two rollers 26 to a separating device 30. After separation from the substrates 10 by the device 30, the web is rewound on a take-up roll 32. To the extent that the flexible web is separated from the substrates, the web can be disposed of after a single use, in view of the costs of the plastics materials forming it and the methods (e.g., roll-to-roll embossing) that can be used for its manufacturing. A flexible web, if separated, can in some cases be irreversibly deformed, such deformation not affecting the patterns transferred from the separated web.

In order to ensure correct registration of the patterns of composition with the substrates, optical sensors 70 are positioned to sense the patterns on the web 14 upstream of the idler rollers 18. Any kind of optical sensor can be suitable for the present apparatus, if adapted to the pattern and/or the markings to be detected thereby. Optical sensors can be image sensors, fiber optic sensors, or contrast sensors, or any other like sensor adapted to detect an optical signal.

While the figures schematically illustrate an apparatus allowing simultaneous transfer of two patterns onto respective opposite surface of the substrate, the skilled person can readily appreciate how a similar apparatus can be prepared to transfer patterns of composition on a single substrate side. In such a case, nip 40, for instance, can be formed between a single pressure roller 22 and a backing support for substrate 10. Additionally, the transfer of two patterns onto respective opposite surfaces of a substrate need not be simultaneous, in which case the apparatus may include two separate nips, one for each web and side of the substrate.

The apparatus may include additional stations that are not shown in the figure, some being optionally off-line stations, to perform activities that can take place at a separate time and/or location, and/or be handled by different entities. For illustration, the apparatus may include a curing station to cure the transferred patterns, a furnace to sinter particles of the transferred compositions and/or to fuse the transferred patterns to their respective substrates, an over-coating station to over-coat the transferred patterns and any like post-transfer treating stations capable of bringing the transferred patterns and their respective substrates closer to an intended ready-to-use end-product. Each such station can be referred to as a finishing station whether off-line or in-line. The apparatus may include other in-line stations to facilitate any of the activities already described and further detailed hereinbel ow. For illustration, the apparatus may include a pre-coating station which may selectively or continuously apply upstream of the nip a layer of adhesive on the patterns while on the web, on selected regions of the substrates, or on both, the intermediate adhesive layer(s) so formed between the pattern and the substrate facilitating the transfer of the former to the latter at the nip.

Having given above a general description of an exemplary apparatus in which the present invention can be implemented, individual components and parts of the apparatus will now be described.

The Substrate Drive Mechanism The apparatus illustrated in the drawings is intended for use in the manufacture of solar cells or printed circuit boards where the substrate is typically rigid and has the form of a square semiconductor wafer or a rectangular insulating board. Before describing the drive mechanism in detail, it should be made clear that its design will depend in practice on the nature of the substrate, which in turn may depend on the type of patterns to be transferred thereto (e.g., functional or decorative). If, in alternative embodiments, the substrate is itself flexible, then the drive mechanism of the substrate may resemble that of the web. If the substrate is a 3D article that is only to have a (e.g., conductive) pattern applied to one side, then the substrate drive mechanism may be a conveyor passing beneath a single pressure roller 22.

In the case of the illustrated embodiment, the substrate drive mechanism includes a cassette within which a stack 12 of individual substrates 10 are stored. By means of a conveyor belt, the substrates 10 can be dispensed one at a time from the stack 12 to the inspection station 60 (e.g., for optical detection of defects) where they can be viewed from above by a camera 601. The image from the camera can be analyzed by a computer programmed to detect defects and flaws, such as cracks. The selection station 62 that follows the inspection station 60 may include, by way of example, a solenoid operated deflector that is under the control of the image analysis computer and displaces faulty substrates off the conveyor into a waste receptacle. Only substrates without defects are then allowed to pass to the next station, where they can be heated, if desired, and correctly aligned with respect to the nip and the pattern(s) to be transferred thereto. Correct positioning of the substrates with respect to the nip can be achieved by way of suitable abutments. Correct registration with respect to incoming patterns carried by a web can be achieved by way of acceleration or deceleration of the feeding of the substrate to the nip, in accordance with the distance of the pattern from the nip and of the speed of the web.

Heating and Alignment Station As its name implies, this station serves two separate functions. First, it serves to heat, when preferred, the substrate 10 to a temperature that will activate the adhesive in the composition carried by the web 14 when it comes into contact with it. The appropriate temperature will depend on the nature of the composition and the adhesive and is discussed in more detail in EP 3491900.

The heating may take different forms, depending on the temperature to be reached, and can be by conduction (the substrate coming into contact with a hot plate, that is heated by a circulating fluid, a resistive heating element or PTC resistors), by convection (blowing a heated gas onto the substrate) or by radiation (infra-red or microwave, depending on the nature of the substrate). When heating is performed by conduction, it may be desired to further include elements capable of maintaining the substrate in intimate contact with the hot plate (e.g., rollers forming a nip with the plate) to accelerate substrate heating to the desired temperature.

While heating can be performed upstream of the nip, separately heating at least one of the web and substrate surfaces due to be urged one into contact with the other, it can alternatively, and additionally, be performed at the nip. For instance, the pressure roller 22 may, in such embodiments, additionally serve as a heating roller.

The web 14 is made of a flexible material into which grooves can be formed by any of a variety of possible processes (e.g., by embossing or casting). The grooves, of which the geometry is complementary to that of the desired pattern e.g., of conductors, can be filled with a composition that contains particles of an electrically conductive material, for example of silver, and a thermally and/or pressure activatable adhesive. As mentioned, for certain types of relatively flat conductive patterns, such as back electrodes of solar cells and ground planes of PCBs' ground planes, the composition can alternatively be positioned on the surface of the web.

In the present context, it suffices to know that the web carries patterns of the composition matching at least a part of the desired patterns (e.g., of conductors) to be applied to the substrate, but the interested reader will find in EP 3491900 more detail of the type of material from which the web can be made, the manner in which the grooves can be made, and the chemical structure of the components of the composition. It should be mentioned that the composition need not itself be conductive but could become conductive once sintered, if conductive patterns are sought. Moreover, while the present description mainly refers to the transfer of a pattern intended to become conductive, the invention should not be construed as limited to this sole type of patterns. The present invention may be beneficial to the transfer of any kind of pattern (e.g., having a function other than electric conductivity or being decorative) for which maintaining the size of the transferred pattern within strict dimensions, or tolerated deviations therefrom, is important.

For the present purpose, it can be briefly noted that the web is sufficiently non-elastic to maintain the contour of the grooves (and patterns) and the shape of the compositions to be transferred therefrom. On the other hand, the web has enough elasticity (e.g., stretchability) so as to facilitate registration of patterns carried thereon with the substrate by way of dancers and tensioning. Dancers may also serve as buffers until the web reaches a constant speed. As the various motorized cylinders that would be contacting the web on its path have different diameters, there can be some inertia between them until all can provide a same linear speed. The web is preferably flexible enough to conform to the surface of the substrate, so as to permit a sufficiently intimate contact for transfer of the composition lines. This capacity is associated with the presence of a thermoplastic polymer at least in a layer forming the first surface / front side of the web. It is stressed that thermosetting polymers, such as used for the preparation of dimension-wise resilient molds (such as used in intaglio plates) are not capable of such topographic conformity.

Other desirable properties can be readily understood, so as to render the web compatible with the process implemented by the apparatus (e.g., stress resistant, heat resistant, heat conductive or dissipative, and the like) and with the compositions used therein (e.g., chemically resistant, chemically inert, etc.), while being responsive to the changes in temperature and tensioning allowing for the modulation of the patterns lengths and widths according to the present teachings.

The Pressure Rollers The purpose of the pressure roller(s) 22 is to press the web 14 against the substrate. A force is applied to the pressure roller 22 to apply a compressive force at the nip 40, the magnitude of the force depending on the nature of the web, the compositions carried therein and/or thereon and the substrate, as well as on the geometry of the pattern (e.g., the depth and/or cross-sectional profile of a groove, complexity of the patterns, etc.). The speed at which the web is fed to the nip (i.e. the period of time it would be subjected to pressure) and the desired quality of transfer may also affect the magnitude of the applied force. The pressure roller may be made of any suitable material, for instance of a rubber or of steel but coated with a thin layer of a compliant material to ensure good contact over the entire surface area of the web.

Therefore, while the nip can be ideally considered as the line of contact formed between the web and a face of the substrate, in practice the presence of compressible material on the side of the nip coming into contact with the rear side of the web causes the nip to form an area of contact elongated in a direction parallel to the width of the web.

As mentioned, in some embodiments, when heating is not exclusively performed on the substrate, nor on the web upstream of the nip, the pressure roller can additionally serve as a heating cylinder. The pressure roller can furthermore be motorized to draw the web from the supply roll. When the nip is formed between two pressure rollers, as illustrated in the figure, it suffices for only one of the pressure rollers to be motorized, when desired.

It is important to ensure that when the patterns on the web 14, regardless of whether they are beneath and/or above the surface of the web, arrive at the nip 40, they be synchronized with the arrival of the substrates. The patterns of composition are spaced on the web so that blank web may pass through the nip 40 while a fresh substrate is being heated and oriented for presentation to the nip. A problem arises because the web is driven continuously whereas the presentation of substrates to the nip 40 is intermittent, hence the arrival time of the patterns at the nip may not coincide with the presence of a substrate in the nip.

To avoid this problem, web is drawn from the supply roll 16, be it by rotation of the supply roll 16 or the take-up roll 32. A sensor 70 is provided to detect the arrival of patterns at a certain position as the web comes away from the supply roll 16. If the expected arrival time of the pattern at the nip 40 does not coincide with the next arrival of a substrate 10 at the nip 40, then the movement of the dancer 20 can vary the length of the path of the web from the supply roll 16 to the nip 40, which has the effect of increasing or decreasing the time taken for the sensed pattern to reach the nip 40. Thus, controlling of the dancer 20 in dependence upon the time that a pattern is sensed by sensor 70 and the time that a substrate 10 is fed to the nip 40, it is possible to ensure correct registration between the patterns and the substrates. If patterns on opposite surfaces of a substrate are both correctly in register with the substrate, then they will also be in correct register with one another.

While any suitable alignment device 50 may be used in connection with the present invention, the Applicant has conceived various methods for timely feeding a substrate to a nip, while ensuring its proper alignment with its respective pattern. In addition to the devices disclosed in EP 3491902, the interested reader will find in EP 4049308 and WO 2022/214959 alternative methods and devices for their implementation, all said devices being capable of serving as alignment device 50.

The Cooling Station The cooling of the web 14 after it has passed through the nip 40 is carried out in the illustrated embodiment by means of conduction. An endless cooling belt 24 passes over first and second rollers 26 and is maintained in tension by an idler roller 28. In this way, the cooling belt 24 is maintained in thermal contact with the rear side of the web over the entire run extending from the pressure roller 22 to the second roller 26.

The cooling belt 24 is exposed to ambient air over the remainder of its length and may not need additional cooling. Should there be a need to cool the belt 24, a blower may be provided for blowing air onto it, the air being preferably, but not necessarily, cooled.

As an alternative, it would be possible to dispense with the cooling belt 24 and to cool the web downstream of the nip by directly blowing air onto its rear side. The air may, if necessary, be cooled, such as by means of a refrigeration circuit, to a temperature not exceeding 20°C. As a further alternative, the cooling belt can be replaced by any heatsink suitable to lower the temperature to a desired range of temperatures.

While passing through the cooling station 23, the web 14 remains attached to the substrates 10 but as the web cools, the adhesion of the composition to the web decreases and/or conversely the adhesion of the composition to the substrate increases, such changes in relative adhesivity to respective source and target surface assisting in the subsequent separation of the web from the substrates, if and when desired. Thus, the temperatures to be reached or maintained by the cooling station may depend on the web, on the substrate and on a future action they might be jointly subjected to. When the cooling station is a heatsink, it can advantageously be controlled so that the temperature of the web and the substrate upon exit from the cooling station is adapted to the function to be performed at a downstream station.

The Separation Device The separation device 30 illustrated in the exemplary embodiment of the depicted apparatus comprises a metal plate that is bent or manufactured to define an acute angle, such as can be found in a blade. The web on its return path to the take-up roller 32 is bent over the sharp edge defined by the outer sides of the separation device. This action peels the web 14 away from the substrate 10 leaving the composition adhering to the substrate 10. A skilled person will readily appreciate that alternative separation devices, e.g., upon which the web may revolve towards the take-up roller, can satisfactorily achieve similar peeling of the web, when such separation is desired, a rod or a rotating cylinder being but examples of such alternative devices.

In some embodiments, it may be desired to maintain the web 14 attached to the substrates 10, either as a temporary protection to the patterns, until separation is made at a later time (optionally at different facilities and/or by different entities), or as a permanent casing to the patterns. In such a case, the web 14 need not be rewound by a take-up roll 32 but only drawn from the supply roll 16 by any suitable device adapted to this purpose. Moreover, when separation of the web(s) from the substrates is delayed or omitted, it may not be necessary to cool the web 14 downstream of the nip 40 or to cool it to a temperature selected to facilitate separation. Furthermore, in such a case, and in particular when the substrates are fed to the nip as separate individual units, the apparatus may include a cutting device to slit the web remaining on the substrates in the unbound margin between any desired number of adjacent substrates. The cutting device may disconnect each single substrate from the following one or may disconnect sets of two or more substrates from a following set of substrates.

An embodiment of the present invention is shown partially in Figures 2 and 3. For clarity, many components already discussed with reference to Figure 1, such as the substrate supplying device, the substrate drive mechanism and the alignment station, as well as the optional substrate inspection station, selection station and heating station, found upstream of the nip, are omitted. Likewise, for stations that may be found downstream of the nip.

Figures 2 and 3 show schematically only the part of the apparatus shown in Figure t that has been modified in order to implement the present invention. The web 100 in Figures 2 and 3 drawn from a motorized supply roll (not shown but equivalent to the roll 16 in Figure 1) in a direction shown in the region of the nip by arrow 130 passes first over a dancer 102 disposed between two guide rollers 104 and 106. The web 100 next passes over a further guide roller 108, through a tensioning nip formed between a motorized tensioning roller 110 and a rubber roller 112 which is forced against the web at a constant pressure to ensure there would be no slippage between tensioning roller 110 and the web 100 and around a heatable roller 114 before reaching the nip roller 116 at which the patterns are transferred from the web 100 to substrates. The nip roller 116 (equivalent to pressure roller 22 in Figure 1), or at least one of them (e.g., the upper one) when the nip is formed between two nip rollers as illustrated in the figures, can be motorized to drive the web 100.

The dancer 102 is equivalent to the dancer 20 in Figure 1 and its role is to serve as buffer during initial acceleration / final deceleration of the system when the linear speeds of the different rollers have yet to match one another. The dancer is also associated with a camera 118 that is used to ensure correct registration of the patterns with the substrate by accelerating or decelerating feeding of the substrate. The position of the substrates with respect to the nip can be asserted upstream of the nip by way of sensors (e.g., optical sensors) which can monitor either the edges of the substrates, fiduciary marks on the substrates, or both. Such sensors may be part of the substrate alignment device.

A control system 120 is provided to compensate for errors in the dimensions of patterns transferred substrates. As represented by dotted lines in Figure 2, the control system is electrically connected to receive data signals from cameras 122 and from a shaft encoder associated with the nip roller 116, and to send control signals to set the speeds and/or torques of the motorized tensioning roller 110 and the temperature of the heating roller 114 or alternatively, and additionally, of any other heating device disposed along the path followed by the web upstream of the nip or in the nip. For illustration, a segment of web 100 between guide roller 106 and nip roller 116, or between tensioning roller 112 and heatable roller 114, can be heated by convection or by radiation (e.g., using an infra-red heater).

As shown in Figure 2 and best seen in Figure 3, two cameras 122 can be positioned to view fiducials on opposite sides of the web as it passes over the nip roller 116. Additionally, or alternatively, cameras may be positioned to view fiducials on patterns after they have been transferred to substrates. From the detection of the position of the fiducials, deviations in the width separation of the fiducials from a desired dimension can be determined by the control system 120. Furthermore, from measurement by the shaft encoder associated with the nip roller 116 of the movement of the web 100 between sensing of consecutive fiducials, the control system 120 can ascertain deviations in the lengths of the patterns from a desired dimension.

Variations in the widths of the transferred patterns can be managed by the control system by varying the temperature provided by the heating devices upstream of the nip (e.g., of the heating roller 114), which will in turn vary the temperature of the web 100 and the degree that it (and patterns thereon) will spread when compressed against the substrate by the nip roller 116.

Variations in length of the transferred patterns can be brought about by the control system by varying the tension in the web 100 immediately upstream of the nip roller 116. Tension control can be achieved by varying the relative speed and/or torque between the motors driving the nip roller 116 (or one of them if the nip is formed of a pair) and the tensioning roller 110.

The degree of tensioning that needs to be applied to the web will depend mutter allot on the specific web, the dimensions of the patterns to be transferred and their divergence from nominal and tolerated values, and the temperature of the web (e.g., between 20°C and 80°C).

Tolerable deviations in dimensions of patterns may depend on the pattern to be transferred and/or on the dimension being considered. For illustration, the deviation tolerated from ideal dimensions can be in absolute terms of up to 100 pm, up to 50 pm, up to 25 pm, up to 10 pm, up to 5 pm, or up to 1 pm; or in relative terms within 1% of ideal length and/or width, or within 0.5%, or within 0.25%, or within 0.1%, or within 0.05% of the nominal value. Regardless of the margins of tolerance encompassing ideal values, the present apparatus can correct deviations being up to 2-times the upper value of acceptable variation in any dimension, the apparatus being in some embodiments capable of correcting an up to 5-fold deviation, up to 10-fold deviation or up to 20-fold deviation. If, for illustration, a pattern may have a width within 10 pm of ideal width value and a length within 50 pm of ideal length value to remain satisfactory upon its intended substrate, then the apparatus is adapted to modify the widths and/or the lengths of the patterns carried by the web to be within 200 pm and/or 1000 pm of respective ideal values.

The apparatus is shown for symmetry as having two controllers 120 but it will be appreciated that in practice a single controller could be used for both webs based on data received from different cameras for each web, in the event that the apparatus is designed to transfer patterns from two different webs to opposite sides of a same substrate.

In some embodiments, the data read by the cameras 122 may be encoded data, written on the web at the time of its manufacture, indicative of either the lengths and widths of the patterns as measured at the time of their manufacture, or optimum setting for the amount of heat and tension to be applied to the web to achieve a desired consistent size of the patterns after transfer to the substrates. Such data need only be entered on one lateral side of the web and a single camera would suffice for each web.

While heat is the predominant parameter for determining widening of the patterns during the transfer and tension is the predominant parameter for determining the lengthening of the (e.g., conductive) patterns, these two adjustments are not independent of one another as heating may lengthen the patterns and tension may narrow them. The controller must therefore take both the measured length and width measurements into consideration when setting the degree of heating and the web tension The controller may contain a look-up table that will indicate the optimum heating and tensioning based on the measured widths and lengths of the patterns on the web or may use a recursive algorithm to arrive at the optimum settings.

It should be understood that the feedback loop that varies the heating and tensioning of the web during the process cannot respond sufficiently quickly to correct variations in dimensions from one pattern to the next. However, from readings taken at the commencement of a web, the controller can arrive at heating and tensioning settings for the remainder of the web and from reading taken during transfer of patterns from a web, the settings can be modified to compensate for slow long terms drifts in the measured lengths and widths of the patterns.

It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the disclosure. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Although the present disclosure has been described with respect to various specific embodiments presented thereof for the sake of illustration only, such specifically disclosed embodiments should not be considered limiting. Many other alternatives, modifications and variations of such embodiments will occur to those skilled in the art based upon Applicant's disclosure herein. Accordingly, it is intended to embrace all such alternatives, modifications and variations and to be bound only by the spirit and scope of the disclosure and any change which come within their meaning and range of equivalency.

In the description and claims of the present disclosure, each of the verbs "comprise", "include" and "have", and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of features, members, steps, components, elements or parts of the subject or subjects of the verb. Nevertheless, it is contemplated that the compositions of the present teachings also consist essentially of, or consist of, the recited components, that the methods of the present teachings also consist essentially of, or consist of, the recited process steps, and that the apparatus of the present teachings also consist essentially of, or consist of, the recited devices.

As used herein, the singular form "a", "an" and "the" include plural references and mean "at least one" or "one or more" unless the context clearly dictates otherwise. At least one of A and B is intended to mean either A or B, and may mean, in some embodiments, A and B. Positional or motional terms such as "upper", "lower", "right", "left", "bottom", "below", "lowered", "low", "top", "above", "elevated", "high", "vertical", "horizontal", "backward", "forward", "upstream" and "downstream", as well as grammatical variations thereof, may be used herein for exemplary purposes only, to illustrate the relative positioning, placement or displacement of certain components, to indicate a first and a second component in present illustrations or to do both. Such terms do not necessarily indicate that, for example, a "bottom" component is below a "top" component, as such directions, components or both may be flipped, rotated, moved in space, placed in a diagonal orientation or position, placed horizontally or vertically, or similarly modified.

Unless otherwise stated, the use of the expression "and/or" between the last two members of a list of options for selection indicates that a selection of one or more of the listed options is appropriate and may be made.

The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

As used herein, unless otherwise stated, adjectives such as "substantially", "approximately" and "about" that modify a condition or relationship characteristic of a feature or features of an embodiment of the present technology, are to be understood to mean that the condition or characteristic is defined to within tolerances that are acceptable for operation of the embodiment for an application for which it is intended, or within variations expected from the measurement being performed and/or from the measuring instrument being used. When the term "about" and "approximately" precedes a numerical value, it is intended to indicate +/-15%, or +/-10%, or even only +/-5%, and in some instances the precise value. Furthermore, unless otherwise stated, the terms (e.g., numbers) used in this disclosure, even without such adjectives, should be construed as having tolerances which may depart from the precise meaning of the relevant term but would enable the invention or the relevant portion thereof to operate and function as described, and as understood by a person skilled in the art.

Unless otherwise stated, when the outer bounds of a range with respect to a feature of an embodiment of the present technology are noted in the disclosure, it should be understood that in the embodiment, the possible values of the feature may include the noted outer bounds as well as values in between the noted outer bounds.

To the extent necessary to understand or complete the disclosure of the present disclosure, all publications, patents, and patent applications mentioned herein, including in particular the applications of the Applicant, are expressly incorporated by reference in their entirety by reference as is fully set forth herein.

Claims (18)

1. CLAIMS1. Apparatus for transferring patterns carried by a web of a deformable plastics material onto substrates, the apparatus comprising a nip defined between at least one nip roller and a backing support through which the substrates are passed simultaneously with the web and by means of which pressure is applied to effect transfer of the patterns from the web to the substrates, characterized by a web heater and a web tensioner arranged upstream of the nip, and a control unit for controlling the web heater and the web tensioner in dependence upon data indicative of the lengths and widths of the patterns on the web prior to transfer, or of the patterns on the substrates after transfer, so as to ensure that, after transfer to the substrates, the patterns conform to a desired length and width.
2. 2. Apparatus as claimed in claim 1, comprising sensors for taking measurements indicative of the widths and lengths of the patterns on the web immediately before the transfer at a position upstream of the nip.
3. 3. Apparatus as claimed in claim 1 or claim 2, comprising sensors for taking measurements indicative of the widths and lengths of the patterns on the substrates after the transfer at the nip.
4. 4. Apparatus as claimed in claim 2 or claim 3, wherein the sensors comprise optical sensors for determining the positions of specific markings on the web on opposite sides of the web, the markings being either fiducials distinct from the patterns, or elements of the patterns, so as to provide a measurement indicative of the width of the patterns on the web or the substrates.
5. 5. Apparatus as claimed in claim 4, wherein the nip roller is associated with a shaft encoder capable of measuring the movement of the web and the substrates through the nip, the length of web passing through the nip between detection by the optical sensors of consecutive specific markings on the web being indicative of the length of the patterns on the web or the substrates.
6. 6. Apparatus as claimed in any one of claim 1 to claim 5, wherein measurements of the length and width of the patterns are carried out at the time of manufacture of the web and encoded data markings are applied to the web during manufacture containing data indicative of the sizes of the patterns, and wherein the control unit of the apparatus serves to set the web temperature and tension based on the data read from the web.
7. 7. Apparatus as claimed in claim 6, wherein the encoded data markings indicate the optimum web temperature and web tension to be set by the control unit prior to the time of the transfer of the patterns to the substrates.
8. 8. Apparatus as claimed in any one of claim 1 to claim 7, wherein the web heater is a heated roller located upstream of the nip.
9. 9. Apparatus as claimed in any one of claim 1 to claim 8, wherein at least one of the at least one nip roller includes a heater.
10. 10. Apparatus as claimed in any one of claim 1 to claim 9, wherein tension in the web is variable by control of the speed or torque of motors driving two spaced nip rollers serving to advance the web.
11. 11. Apparatus as claimed in any one of claim 1 to claim 10, wherein the backing support is a second nip roller.
12. 12. Apparatus as claimed in any one of claim 1 to claim 11, further comprising upstream of the nip at least one of: a) a substrate supplying device; b) a drive mechanism for transporting the substrates to the nip; c) a substrate inspection station; d) a substrate selection station; e) a substrate heating station; and 0 a substrate alignment device.
13. 13. Apparatus as claimed in any one of claim 1 to claim 12, further comprising downstream of the nip at least one of: i) a cooling station for cooling the web and/or the substrates whilst attached one to the other; ii) a separation device for peeling the web away from the substrates; iii) a cutting device for slitting the web between one or more substrates; and iv) a finishing station.
14. 14. Apparatus as claimed in any one of claim 1 to claim 13, wherein the patterns are carried within recesses in and/or on a first surface of the web.
15. 15. Apparatus as claimed in claim 14, wherein the web is made of one or more layers of plastics material and has at least the first surface made of a formable thermoplastic polymer.
16. 16. Apparatus as claimed in any one of claim 1 to claim 15, wherein the patterns are made of one or more transferable compositions containing particles of one or more materials and an adhesive being activatable by heat and/or by pressure.
17. 17. Apparatus as claimed in claim 16, wherein the patterns are, or can be rendered, conductive and at least part of the particles are made of an electrically conductive material.
18. 18. A method for ensuring that patterns carried by a web of a deformable plastics material conform a desired length and width following transfer to a substrate at a transfer nip, the method including a) collecting data indicative of the lengths and widths of the patterns on the web prior to transfer, or of the patterns on the substrates after transfer, and b) controlling a temperature of the web and a tension of the web upstream of, or at, the nip in dependence upon the collected data.